[0001] This invention is directed to a process for preparing an element comprising a support
having at least two compositions thereon in arrays of interlaid microareas and to
such elements. The elements of this invention are of particular interest in photography.
[0002] It is desirable for a number of purposes to locate two or more compositions on a
support in a highly interlaid relationship. In those instances where the compositions
are divided into very small individual areas (e.g., microareas--here defined as areas
too small to be readily individually resolved by the unaided human eye), the techniques
for locating the compositions in a predetermined laterally displaced relationship
have been both tedious and complex.
[0003] A specific illustrative application for highly interlaid compositions is additive
multicolor photography wherein a multicolor filter is employed which can be comprised
of three additive primary filters that are segmented and interlaid to form the smallest
attainable discrete areas. By exposing through the multicolor filter a panchromatically
responsive imaging material, such as a panchromatically sensitized silver halide emulsion,
it is possible to form a multicolor image. For instance, a negative-working silver
halide emulsion can produce a multicolor negative image following exposure and development
when exposed and viewed through the multicolor filter. A direct-positive imaging material
will similarly produce a positive multicolor image. This approach, commercialized
under the name Dufaycolor, and variations of it are illustrated by U.K. Patent 15,027
(1912), U.S. Patents 1,003,720 and 3,138,459, and James, The Theory of the Photographic
Process, 4th Ed., Macmillan, 1977, p. 335.
[0004] U.S. Patent 1,003,720 teaches the desirability of providing segmented interlaid filters
of the smallest attainable sizes. Disadvantages were encountered in achieving proper
registration of filter segments. Lateral spreading of the materials forming the filter
segements was recognized to pose limitations, since unwanted mixing of filter materials,
even if confined to edge regions, can produce unwanted shifts in hue. Planar support
surfaces are generally employed, but in some instances filter segments were located
in grooves.
[0005] European Specification 0,014,572 disclosed that lateral spreading can be overcome
by placing the filter materials in microvessels (referred to herein as microcells).
[0006] This European specification describes photographic imaging with supports containing
arrays of microcells opening toward one major surface. In a variety of different forms
the photographic elements and components disclosed therein contain an array of microcells
in which first, second, and usually, third sets of identical microcells are interspersed
to form an interlaid pattern. In a typical form three separate sets of microcells,
each containing a different subtractive primary (i.e., yellow, magenta, or cyan) or
additive primary (i.e., blue, green, or red) imaging component, are interlaid. Preferably
each microcell of each set is positioned laterally next adjacent at least one microcell
of each of the two remaining sets. The microcells are intentionally sized so that
they are not readily individually resolved by the human eye, and the interlaid relationship
of the microcell sets further aids the eye in fusing the imaging components of the
separate sets of microcells into a multicolor image.
[0007] In one specifically preferred embodiment disclosed in the European specification,
cyan, magenta, and yellow dyes or dye precursors of alterable mobility are associated
with immobile red, green, and blue colorants, respectively, each present in one of
the first, second, and third sets of microcells. The microcells are overcoated with
a panchromatically sensitized silver halide emulsion layer. By exposing the silver
halide emulsion layer through the microcells and then developing, an additive primary
multicolor negative image can be formed by the microcellular array and the silver
halide emulsion layer while cyan, magenta, and yellow dyes can be transferred to a
receiver in an inverse relationship to imagewise exposure to form a subtractive primary
positive multicolor image.
[0008] A technique disclosed in the European specification for differentially filling microcells
to form an interlaid pattern calls for first filling the microcells of an array with
a sublimable material. The individual microcells forming a first set within the array
can then be individually addressed with a laser to sublime the material initially
occupying the first set of microcells. The emptied microcells can then be filled by
any convenient conventional technique with a first imaging component. The process
is repeated acting on a second, interlaid set of microcells and filling the second
set of emptied microcells with a second imaging component. The process can be repeated
again where a third set of interlaid microcells is to be filled, although individual
addressing of microcells is not in this instance required. This approach is suggested
to be useful in individually placing triads of additive and/or subtractive primary
materials in first, second, and.third sets of microcells, respectively.
[0009] Also, as described in copending British Patent Application No. 8129728 Specification
No. interlaid sets of microcells can be filled with differing imaging compositions
by employing a thermally destructible membrane to close one set of microcells while
another set is being filled with-or emptied of imaging material.
[0010] Additionally, as described in copending European Application No.81304574.7 Specification
No. , the microcells can be filled by differentially electrostatically charging differing
sets of microcells and using an electrographic imaging composition to fill selectively
at least a first set of microcells. In a preferred form the microcells are formed
in an organic photoconductor, the photoconductor is electrostatically charged in a
nonimagewise manner, laser scanning is employed to dissipate the electrostatic charge
from a first set of microcells, electrographic development introduces a first imaging
composition into the first set of microcells, and the process is twice repeated to
fill second and third sets of microcells with second and third imaging compositions.
[0011] U.S. Patent 3,248,208 illustrates the formation of a multicolor filter array for
additive primary imaging using a transparent lenticular support. The lenticules on
one major surface of the support are used to focus radiation in discrete areas on
the opposite surface of the support bearing a radiation-sensitive material. By removing
unexposed radiation-sensitive material and dyeing the material which remains, a first
segmented filter is formed. The procedure is then twice repeated with the support
being held in a different attitude with respect to the exposing radiation source in
each instance so that the lenticules focus the radiation in laterally displaced regions
of the opposite surface. By using different additive primary dyes in each dyeing step,
three segmented interlaid filters can be produced.
[0012] There is a need for alternative and simplified methods for preparing elements containing
two or more interlaid compositions.
[0013] This invention relates to a process for preparing an element comprising a support
in the form of a sheet or web having on one major surface thereof an array of walls
capable of defining microareas on said support, which comprises introducing a first
composition into a first set of microareas on said support, and introducing a second
composition into a second interlaid set of microareas on said support, characterized
in that radiation is directed toward said support at an acute angle with respect to
the plane of said support, said walls interrupting a portion of the radiation to create
a shadowed set of microareas while permitting exposure of an unshadowed, interlaid
set of microareas, and selectively introducing said first composition into one set
of microareas as a function of shadowing.
[0014] The invention also provides an element comprising a support in the form of a sheet
or web having on one major surface thereof a first composition present in a first
set of microareas and a second composition in a second interlaid set of microareas
and an array of walls capable of defining microareas characterised in that the extent
of the first set of microareas is capable of definition by directing radiation toward
the support at an acute angle with respect to its plane, the walls interrupting a
portion of the radiation to create shadowed and unshadowed interlaid sets of microareas,
the first set comprising either the shadowed or the unshadowed microareas.
[0015] The elements preferably used in the process of the invention comprise a support having
a first portion which is in the form of a sheet or web which forms the bottom walls
of an array of microcells and a second portion which forms the lateral walls of the
microcells. The first and second portions cooperate to form first and second interlaid
sets of the microcells of the array. The preferred support is one wherein at least
one of the sets of microcells are differentiated from the rest by at least one of
depth, size, shape and orientation, such that they are capable of being exposed to
radiation directed toward the support at an acute angle to its plane while the remaining
set(s) are shadowed by the lateral walls.
[0016] This invention can be better appreciated by reference to the detailed description
of the preferred embodiments considered in conjunction with the accompanying drawings,
in which
Figure lA is a plan view of a first support;
Figure 1B is a section taken along line lB-lB in Figure lA;
Figure 2 is a section of a pixel of an alternative form of the support;
Figure 3 is a section of a pixel of an additional form of the support;
Figure 4 is a plan view of an alternative support;
Figure 5A is a plan view of another support;
Figures 5B and 5C are sections taken along section line 5B-5B in Figure 5A showing
differing exposures;
Figure .6A is a plan view of still another support;
Figure 6B is a plan view of a support identical to that of Figure 6A, but showing
a different exposure;
Figure 7 is a plan view of an additional support;
Figure 8A is a plan view of yet another support;
Figures 8B and 8C are sections taken along section line 8B-8B in Figure 8A showing
differing exposures;
Figure 9 is a section of a further varied support;
Figure 10A is a plan of a preferred support;
Figure 10B is a section along section line 10B-10B in Figure 10A;
Figure 10C is a section along section line 10C-10C in Figure 10A;
Figures 11, 12, and 13 are plan views of alternative preferred supports;
Figure 14A is a sectional view of a color image transfer photographic element;
Figure 14B is a plan view of the support shown in Figure 14A; and
Figures 15A, 15B, 15C, and 15D are sectional views showing different stages of processing.
Figures 16A, 16B, 16C, 16D, 17, 18, 19 and 20 are supports and microcells.
[0017] The drawings are of a schematic nature for convenience of viewing. Since the individual
microareas are too small to be viewed with the unaided human eye, the microareas and
the elements in which they are contained are greatly enlarged. The depth of the microcells
and microgrooves have also been exaggerated in relation to the thickness of the supports,
the supports typically being 50 to 500 or more times greater in size than indicated
in the drawings
[0018] The process of the invention can be practiced with any support in the form of a sheet
or web which has an array of walls capable of interrupting radiation. The walls can
be an integral portion of the support or non-integral but joined thereto. The wall
array is such as to create an interlaid pattern of shadowed and unshadowed areas when
radiation is directed toward the support at an acute angle with respect to its axial
plane. Further, the dimensions of the array are chosen to restrict the size of the
individual shadowed and unshadowed areas of the interlaid pattern in at least one
direction so that they cannot be readily individually resolved by the unaided human
eye. In other words the wall array is chosen to produce an interlaid pattern of shadowed
and unshadowed microareas.
[0019] An illustrative simple support 100 is shown in Figures lA and 1B. The support has
substantially parallel first and second major surfaces 102 and 104. The support defines
a plurality of parallel microgrooves 106, which open toward the first major surface
of support. The microgrooves are defined in the support by an array of lateral walls
108 which are integrally joined to an underlying portion 110 of the support. The material
from which walls 108 and underlying portion 110 are made interrupts the radiation
referred to below.
[0020] In Figure 1-B the arrows 112 schematically designate radiation striking the support
at an acute angle 6 with respect to an axial plane 114 of the support. A portion of
the radiation strikes the bottom walls 116 of the microgrooves in unshadowed microareas
116A while another portion of the radiation strikes the lateral walls 108 and is thereby
interrupted, so that microareas 116B of the microgrooves are shadowed and do not receive
radiation, at least not to the same extent, as the unshadowed microareas.
[0021] The lines 118 define the boundary of an areas unit containing a single microgroove.
The remaining depicted area of the support is formed by area units essentially identical
to that within the boundary. Each area unit forms a pixel.
[0022] Certain features of the invention can be appreciated by reference to support 100.
First, it should be noted that the lateral walls 108 lie along half the boundaries
between adjacent microareas. Thus, if a material is contained in the microgrooves
which is capable of lateral spreading, it is restrained from spreading between microareas
over half of the boundaries therebetween. Similarly, radiation that might otherwise
be scattered between adjacent microareas is also restrained where the lateral walls
are present.
[0023] The acute angle 6 at which the radiation is directed toward the support can be varied
by repositioning either the radiation source and/or the support. As shown, the radiation
is directed parallel to the section line 1B-1B and perpendicular to the major axes
of the lateral walls 108. In this orientation the minimum angle of 8.at which the
radiation can strike the bottom walls 116 is determined by the relationship tan 8
= H/W, where H is the height of the lateral walls 108 and W is the width of the bottom
walls 116. It is therefore apparent that the proportion of the bottom walls that are
unshadowed can be controlled by varying any one or combination of e, H, or W. Further,
if the support is rotated 90° with respect to the radiation source so that the radiation
is introduced perpendicular to the section line 1B-1B, no shadows are produced. It
is therefore apparent that maximum shadowing for a given value of 0 is achieved when
radiation is introduced perpendicularly to the major axes of the lateral walls and
that the degree of shadowing can be decreased by rotating the lateral walls of the
support toward alignment with the radiation.
[0024] Figures 2 and 3 illustrate pixels of variant forms of supports generally similar
to support 100. In Figure 2 support 200 is shown having a first major surface 202
and a second major surface 204. A microgroove 206 is shown opening toward the first
major surface. The support is formed with the microgroove having inwardly sloping
walls which perform the functions of both the lateral and bottom walls of the microgrooves
106.
[0025] In Figure 3 a pixel of a support 300 is shown. The support is comprised of a first
support element 302 having a first major surface 304 and a second substantially parallel
major surface 306. Joined to the first support element is a second support element
308 which is provided in each pixel with an aperture 310. The second support element
is provided with an outer major surface 312. The walls of the second support element
forming the aperture 310 and the first major surface of the first support element
together define a microgroove. The support is comprised of repetitions of the pixel
shown.
[0026] Referring to Figure lA, it can be appreciated that if the support 100 is resolved
into two separate halves joined along the section line 1B-1B and one half is translated
with respect to the other along the axial plane 114, the support continues to respond
to angled radiation exposure substantially as described above--that is, it continues
to satisfy the essential shadowing criteria described above. The plane represented
by the section line 1B-1B thus constitutes a glide plane--herein defined as a plane
separating two support portions which can be displaced relative to each other along
the axial plane of the support without dimininishing the shadowing utility of the
support. It is further observed that the support 100 can be resolved not just into
halves, but into a large number of separate portions displaced along the axial plane
without substantially altering its shadowing utility. It is thus apparent that the
supports 100, 200, and 300 provide only simple examples of a large family of lateral
wall arrays that provide roughly similar shadowing utility.
[0027] This is specifically illustrated in Figure 4 in which support 400 is comprised of
identical support regions 400A, 400B, 400C, and 400D joined along parallel glide planes
402. In comparing supports 100 and 400, it can be seen that the two supports are identical,
except that the support regions 400A and 400C are laterally displaced with respect
to the support regions 400B and 400D. This has the result of producing walls 408 and
microareas 416A and 416B which are limited in their maximum dimension in the form
shown to the distance between glide planes 402. Thus, support 400 is superior to support
100 for applications in which less groove-like microareas are preferred. For exam-
ple, by positioning the glide planes between support regions at a spacing of 200 microns
or less and the walls within each support region at a center-to-center spacing of
400 microns or less, microareas limited in both length and width to 200 microns or
less can be readily obtained. As a result of the relative translation of adjacent
support regions, the support 400 contains no grooves, but only upstanding walls. This.illustrates
that neither microgrooves nor any other type of depressions in the support are required
for the practice of this invention. It is recognized that the support 400 can, if
desired, appear in section essentially identical to any one of supports 100, 200,
or 300.
[0028] In further comparing the microarea patterns of supports 100 and 400, it can be appreciated
that the microareas 416A and 416B are interspersed to a greater degree than the microareas
116A and 116B. The microareas 416A and 416B are interlaid along two perpendicular
axes, whereas the microareas 116A and 116B are interlaid along only one axis. The
higher degree of interlay can represent a distinct advantage for specific applications
requiring a high degree of interlay for desired optical or chemical properties.
[0029] Still further comparing the supports 100 and 400, it can be seen that the walls 408
separate the first and second microareas 416A and 416B over a boundary approximately
equal in length to that by which the walls 108 separate the microareas 116A and 116B.
However, in the support 400, because the microareas 416A and 416B are more highly
interspersed, there is a larger boundary between adjacent microareas where no walls
are present. This feature of the support 400 can, however, be readily modified in
a manner which does not diminish the shadowing utility of the support. If, for example,
additional walls are introduced along the glide planes 402 in Figure 4, it can be
seen that the walls now extend over a much larger proportion of the boundaries between
adjacent microareas. The result is to limit significantly the boundary region available
for lateral spreading between adjacent microareas.
[0030] If additional walls are provided for the support 400 along the glide planes 402,
it is apparent that a predetermined, ordered array of microcells is created, each
containing two microareas. The term "microcell" is herein defined as a cell or vessel
too small in size to be readily individually resolved with the unaided human eye.
In the geometrical form described the microcells produced on the modified support
400 are approximately square, but it is apparent that microcells of any geometric
configuration can be employed. Thus, supports exhibiting any of the microcell or microvessel
configurations disclosed in European Specification 0,014,572 can be employed in the
practice of this invention. Hence all of the microcellular supports disclosed in these
patent applications are useful in the practice of this invention. Polygonal (square,
rectangular, and hexagonal), circular, and elliptical microcell configurations have
been explicitly disclosed, although any other predetermined recurring microcell configuration
(or combination of configurations, discussed below) can be employed in the practice
of this invention.
[0031] Any predetermined, ordered array of walls capable of interrupting radiation, whether
or not microcells or microgrooves are. formed by these walls, can be employed in the
practice of this invention to produce two or more interlaid sets of contiguously adjoining
microareas (that is, microareas which over some boundary region are not separated
by lateral walls). Supports having uniformly spaced wall arrays, such as supports
100 and 400, or supports having a single repeated microcell configuration are particularly
suited for forming two or more laterally displaced contiguous sets of microareas that
are of uniform size in each individual occurrence.
[0032] Figures lA, 1B, and 4 illustrate perhaps the simplest shadowing approach of this
invention wherein the bottom walls of the supports are shown divided into two separate
interlaid sets of uniform microareas of substantially equal area by a single exposure
of the support to radiation directed toward the plane of the support at an acute angle.
Where one composition is introduced into exposed microareas and a second composition
is introduced into unexposed or shadowed microareas, an interlaid array of two separate
compositions is produced.
[0033] Supports useful as described above can also be applied to applications requiring
more than two laterally displaced compositions. For example, in Figures lA and 1B
it can be seen that by adjusting the angle of exposure e, the size of the microareas
116A exposed can be adjusted. If, for example, it is desired to place three separate
strips of equal size of three separate compositions between adjacent pairs of lateral
walls 108, the angle 0 is adjusted so that the radiation strikes only one third of
the area of each bottom wall 116. A first composition can then be selectively positioned
in the microareas corresponding to the exposed portions of the bottom walls. The angle
0 is then increased so that on a second exposure radiation strikes the area originally
struck, now containing the first composition, and a contiguous one third of each bottom
wall 116. A second composition is then selectively positioned in the microareas corresponding
to the exposed areas not occupied by the first composition. The procedure can be repeated
using radiation directed perpendicularly to the axial plane 114 to position a third
composition in a third laterally displaced set of microareas, or the third composition
can in many instances be introduced by a conventional technique for coating a single
composition, such as doctor blade coating. Although described by reference to three
compositions and a specific support, it is apparent that the procedure is generally
useful with all of the supports containing wall arrays herein described-and with more
than three compositions.
[0034] The procedure described above for positioning three or more laterally displaced compositions,
while useful with all lateral wall array patterns, relies in part on the presence
of a previously positioned composition to define a microarea resulting from a later
exposure. The areas covered by the first and second exposures overlap. This limits
the shadowing procedure described above to use with materials which allow the presence
or absence of one composition to exclude a subsequent composition, as is possible
in certain preferred embodiments of this invention. Exclusion and exhaustion effects
are discussed more specifically below.
[0035] It is possible to address uniquely two or more areas of a support according to this
invention so that no exclusion or exhaustion effect is relied upon. An approach for
uniquely addressing two separate sets of microareas with radiation while creating
a third set of microareas by shadowing is illustrated in Figures 5A, 5B, and 5C. Except
as otherwise noted below, the features bearing 500 series reference numerals are identical
to those bearing the corresponding 100 series reference numerals in Figures 1A and
1B and are not redescribed in detail.
[0036] The support 500 as illustrated differs from support 100 solely in the use of an optional
transparent underlying portion 510; however, the lateral walls 508 remain capable
of interrupting radiation. In Figure 5B radiation 512A is directed toward the axial
plane 514 at an angle 0 chosen to permit impingement of radiation only on the microareas
516A. The remaining area of each bottom wall 516 is shadowed by the lateral walls
508. Thus, exposure as shown in Figure 5B creates one set of microareas 516A in an
interlaid pattern with remaining support areas. A first composition can be selectively
positioned in the first set of microareas.
[0037] In Figure 5C the support is given a second exposure to radiation 512B at an acute
angle 0'. As shown, the radiation exposure patterns in Figures 5B and 5C are mirror
images, although the angles e and e' need not be equal, except when the microareas
516A and 516B are intended to be equal. Instead of changing the direction of radiation
between the first and second exposures, the support could alternatively be rotated
180° in the axial plane.
[0038] Radiation impinges on the bottom walls 516 only in the microareas 516B, creating
a second set of radiation exposed microareas. A second composition can be selectively
positioned in the second set of microareas. A third set of microareas 516C, not exposed
by either the first or second exposures, is created concurrently with the second set
of microareas. A third composition can be positioned in the third set of microareas,
if desired. It is to be noted that the first composition is laterally spaced from
the second microareas, and no exclusion property is required in order to position
the second composition. It is appreciated that the angles 6 and/or U' can be increased
to eliminate the microareas 516C without in any way altering the shadowing technique
described above.
[0039] Using the supports 100, 200, 300, 400, and 500 only two interlaid sets of microareas
can be uniquely addressed by shadowing techniques. By the term "uniquely addressed"
it is meant that a set of microareas is exposed to only the single radiation exposure
which defines its boundaries and no other microarea defining radiation exposure. It
is possible, however, to produce three, four, five, six, or even more sets of uniquely
addressed microareas in a single support containing microcells. For this purpose microcells
of polygonal shape are preferred. Generally the number of sets of uniquely addressed
areas that can be produced by shadowing in a single polygonal microcell is equal to
the number of its sides
[0040] An illustration of the creation of microareas in a set of polygonal microcells by
shadowing techniques of the type described above is provided in Figures 6A and 6B,
in which a detail of a support 600 containing an array of microcells 602 of a regular
hexagonal shape is shown. The support 600 in section can appear identical to the supports
shown in Figures 1B, 2, 3, or 5B. Referring first to Figure 6A, exposure of the support
600 in a direction parallel to arrow 1 at an acute angle with the axial plane of the
support exposes the bottom wall of each microcell in only diamond-shaped area 1, the
remainder of the wall of each microcell being shadowed. By changing the direction
of exposure, as indicated by arrows 2, 3, 4, 5, and 6, but not the exposure angle,
five more identical diamond-shaped exposed microareas 2, 3, 4, 5, and 6 are produced..
The six diamond-shaped microareas provided in each microcell are of equal area, since
each microcell is a regular hexagon and the angle of exposure is unchanged. It is
to be noted that none of the six microareas impinges on any other of the six diamond-shaped
microareas and therefore each is uniquely addressed by shadowing exposures. Thus,
it is possible to place up to six separate compositions in each microcell 602 without
relying upon any exclusion property.
[0041] Exposure can be terminated after the sixth exposure and the central area of each
microcell can be left unexposed, if desired. In this instance the lateral spacing
in the center of each microcell between compositions introduced into the six separate
microareas can be relied upon to prevent or reduce boundary mixing of compositions.
In an alternative form in which the central region is desired to receive material,
one or more compositions can be employed capable of wandering from the diamond-shaped
areas to cover the central portion of each microcell.
[0042] By using a combination of the procedures described above and exclusion effects, it
is possible to produce additional microareas in each hexagonal microcell 602. As shown
in Figure 6A, a microarea 7 equal in area to the diamond-shaped areas is produced
by exposing at the same acute angle in a direction indicated by arrow 7. The radiation
overlaps both the microareas 1 and 2 in exposing additional microarea 7. By using
exclusion effects a seventh composition can be located in only the microarea 7. Microareas
8, 9, 10, 11, and 12 are sequentially similarly formed by shadowing exposures along
like numbered axes.
[0043] Thus far it can be seen that 12 microareas can be formed, six of which can be uniquely
addressed and six of which depend on exclusion effects. At this point the central
portion of each hexagonal microcell remains shadowed. If desired, the central portion
of the microcell can be left shadowed and unfilled. Alternately, the central, shadowed
portion of the microcell can be filled with a single composition. For example, if
the microareas 1, 2, 3, 4, 5, and 6 receive a first composition and the microareas
7, 8, 9, 10, 11, and 12 receive a second composition, a third composition can be located
in the central, shadowed portion of each microcell, and three compositions will occupy
roughly equal areas of each microcell bottom wall.
[0044] By increasing the acute angle of exposure and relying on exclusion effects, it is
possible to form additional microareas in the central, initially shadowed portion
of each microcell. By exposing again in the direction indicated by arrow 7, but at
an increased acute angle, the microarea 13 can be formed, which is roughly equal to
the previously formed microareas. Similarly, microareas 14, 15 and 16 can be formed.
By increasing the acute angle of exposure again, microareas 17 and 18 can be formed
by exposing in the direction indicated by arrows 6 and 3, respectively. These microareas
are roughly equal to the previously formed microareas. Two triangular microareas 19
remain unexposed which, together are roughly equal to the remaining microareas. By
using shadowed microareas 19 as one microarea, 19 laterally spaced compositions can
be placed on the bottom walls of each hexagonal microcell, each composition occupying
an approximately equal area. The shown pattern is, of course, only exemplary. Shadowing
exposures can produce microareas of differing configuration, size, and number.
[0045] The ability to uniquely address a plurality of sets of microareas so that the microareas
cover an entire surface of a support, except for the areas occupied by walls, is an
obvious advantage in making maximum use of a support surface and in achieving a high
degree of interspersing of compositions. Some lateral wall patterns offer this capability
and some do not. In referring to supports 100, 200, 300, 400, and 500, it can be seen
that the wall patterns permit the creation of uniquely addressed microareas which
cover the entire support surface not occupied by the walls. It is also apparent that
microcells of square or rectangular configuration also offer this capability, since
it has already been pointed out above that any two contiguous microareas in the same
segment of the support 400 can be enclosed in a microcell without altering the shadowing
capability of the support. Upon further reflection it can be appreciated that square
and rectangular microcells are but special cases of parallelogram, e.g. lozenge (diamond-shaped),
configuration microcells and that all such microcells can be uniquely addressed over
their entire bottom wall areas. As shown in Figure 6A, the uniquely addressed areas
1 to 6 of the hexagonal micro-' cells 602 do not occupy the entire bottom surface
of the microcell; but, referring to Figure 6B, the identical support is uniquely addressed
over the entire bottom walls of the microcells by three exposures at an acute angle
with respect to the axial plane. Area 1 is addressed by exposure in a direction 1,
area 2 by exposure in a direction 2, and area 3 by exposure in a direction 3. This
demonstrates that uniquely addressing microcells over their entire bottom walls is
a function not only of the shape of the microcells, but also a function of the angle
and direction of exposure. Many microcell configurations, such as circular, elliptical,
triangular, and trapezoidal microcells cannot be uniquely addressed over their entire
bottom wall areas by shadowing techniques, regardless of the number or angle of shadowing
exposures attempted.
[0046] Supports containing microcells which are not only identical in each occurrence, but
are identically aligned in each occurrence, can be used in the invention. While the
present invention can employ supports containing any of the microcell arrangements
disclosed in European specification 0,014,572, it is additionally recognized that
advantageous results can be obtained by using supports containing identical microcells
which by their orientation can be resolved into interlaid sets that can be differentially
addressed.
[0047] This is illustrated in Figure 7, in which a support 700 is provided with a plurality
of identical microcells which appear triangular in plan. As can be readily appreciated,
however, the triangular microcells are not all similarly aligned. There are two interlaid
sets of microcells 702A and 702B. When the support is addressed by radiation at an
acute angle with respect to its axial plane, as indicated by arrow 704, radiation
strikes the bottom walls of the microcells 702A in microareas 706A and strikes the
bottom walls of the microcells 702B in microareas 706B. It is to be noted that the
microareas are equal, but differ in their orientation similarly as the microcells
in which they occur. While the triangular microcells shown are each equilateral triangles,
triangles of any desired type, including isosceles and right triangles, can be employed
with similar results.
[0048] In each of the elements heretofore described at least two sets of microareas are
contiguously adjoining, that is, they are not separated by a lateral wall over some
portion of their boundary. Thus, the advantages which lateral walls have to offer
in preventing lateral spreading either of materials or radiation are partially, but
not entirely, realized. It is not possible using any of the supports disclosed in
European Specification 0,014,572 to locate two or more compositions in two or more
interlaid sets of microareas each entirely separated from the other by lateral walls
by shadowing techniques of the type described above. The preferred supports of this
invention, however are those which offer the capability of providing two or more interlaid
sets of microareas by shadowing techniques, each of the microareas being entirely
separated from microareas of other sets by lateral walls. Specifically preferred supports
are those which allow three separate compositions to be interlaid by shadowing techniques
in separate sets of microareas each separated from the other by lateral walls.
[0049] A simple support 800 capable of providing three interlaid sets of microareas each
entirely separated from the other by lateral walls is illustrated in Figures 8A, 8B,
and 8C. Except as otherwise noted, the features bearing 800 series reference numerals
are identical to those bearing the corresponding 100 series reference numerals in
Figures lA and 1B and are not redescribed in detail.
[0050] The lateral walls 808 of the support are arranged in parallel relationship, but unlike
the lateral walls in support 100, are unequally spaced in a predetermined, ordered
manner. The widest spaced lateral wall pairs together with the connecting portion
810 form a first set of microgrooves 806A each having a bottom wall 816A. The next
widest spaced pairs of lateral walls similarly form a set of microgrooves 806B each
having a bottom wall 816B. The closest spaced pairs of lateral walls form a third
set of microgrooves 806C having a bottom wall 816C.
[0051] When the support is exposed with radiation as indicated by arrows 812A in Figure
8B, the acute angle a with respect to the axial plane 814 is chosen so that the radiation
strikes only the bottom walls 816A. The bottom walls 816A are shadowed, however, to
some degree. The extent to which the bottom walls 816A are shadowed can be reduced
significantly by performing a second exposure as described above in connection with
support 500. For example, the support can be rotated 180° and given a second exposure
at the same angle. By properly positioning the lateral walls and choosing the angle
0, it is possible to expose all of the bottom walls 816A without exposing any portion
of the bottom walls 816B and 816C. Once the bottom walls 816A have been selectively
exposed, a first composition can be selectively located in the first microgrooves
806A.
[0052] With a first composition 850 in place, as shown in Figure 8C, the support is given
a second exposure to radiation 812B at an increased acute angle φ with respect to
the axial plane. Radiation strikes the first composition in the first microgrooves
and also the bottom walls 816B of the second microgrooves 806B, but is blocked by
the narrowness of the third microgrooves 806C from striking the bottom walls 816C.
Since a portion of the bottom walls 816B remain shadowed, the support can be rotated
180° and exposed again to increase the exposure of the bottom walls 816B as a function
of exposure. The second set of microgrooves 816B can then be filled with a second
composition. A third composition can be introduced into the third microgrooves 806C
similarly as in positioning a third composition in the microareas 516C.
[0053] The area between the lines 818 forms a single pixel of the support 800. It is to
be noted that the microareas 816A, 816B, and 816C of the pixel present unequal areas.
In applications where a more nearly equal distribution of microareas is preferred,
the support can be formed so that the number of occurrences of each microarea is varied
to more closely balance the total areas presented by the separate sets of microareas.
For example, a second microarea 816C can be added to each pixel 818, thereby doubling
the area of the third set of microareas without in any way altering the shadowing
capability of the support 800 described above.
[0054] An alternative support which responds to shadowing exposures identically as the support
800, described above, but which offers the further advantage of providing three interlaid
sets of microareas that present equal areas in each individual occurrence is shown
in Figure 9. The support 900 is shown by reference to a single pixel 918, which contains
three separate microgrooves 906A, 906B, and 906C. The only difference between the
microgrooves is the depths of the bottom walls 916A, 916B, and 916C, which, as shown,
are parallel to the axial plane 914 of the support.
[0055] Shadowing exposure of the support 900 can be appreciated by reference to the arrows
912A, 912B, and 912C which strike the intersections of the bottom and lateral walls
of the microgrooves 906A, 906B, and 906C, respectively. By reference to the arrows
it can be appreciated that an exposure to radiation at an angle greater than 0, but
less than φ, will strike the bottom walls of the microgrooves 906A while leaving the
bottom walls of the microgrooves 906B and 906C entirely in shadow. After a first composition
is introduced into the microgrooves 906A, a second exposure at an angle with respect
to the axial plane of greater than φ and less than a will permit the bottom walls
916B of the microgrooves 906B to be exposed without exposing any portion of the bottom
walls 916C of the microgrooves 906C. After a second composition is introduced into
the second microgrooves, a third composition can be introduced into the third microgrooves
by any technique described herein for introducing a third composition.
[0056] It is apparent that the supports 800 and 900 can be resolved into separate segments
along glide planes similarly as the support 100 is resolved-along glide planes to
form the support 400. Further, although described by reference to parallel lateral
walls only, it is apparent that the use of the sets of microcells differing in lateral
extent, in depth, or in any combination of both can be employed in the practice of
this invention. Although described above in terms of three separate sets of microareas,
it is appreciated that any one of the three sets of microareas in the supports 800
and 900 can be omitted to allow two compositions to be interlaid substantially as
described.
[0057] Figures 10A, 10B, and 10C illustrate a preferred support 1000 for use in the practice
of this invention which is (1) capable of entirely laterally separating three different
compositions similarly as supports 800 and 900, (2) capable of providing equal composition
microareas similarly as support 900, (3) capable of additionally providing equal microcell
volumes of each composition within each pixel, (4) capable of being radiation exposed
by shadowing techniques over the entire bottom wall area of each of three separate
sets of microcells, and (5) capable of having two microcell sets uniquely addressed.
[0058] The support 1000 is comprised of substantially parallel first and second major surfaces
1002 and 1004. The support defines a first set of rectangular microcells 1006A, a
second set of rectangular microcells 1006B, and a third set of square microcells 1006C.
The microcells are defined in the support by an array of lateral walls 1008 which
are integrally joined to an underlying portion 1010 of the support.
[0059] The microcells 1006A and 1006B as shown are identical in shape, but not in orientation.
The major axis of each microcell of the first and second set is aligned with or parallel
to the major axis of microcells of the same set and perpendicular to the major axis
of each microcell of the other set. The set of square microcells is positioned so
that an edge of each square is substantially parallel to an adjacent edge of a rectangular
microcell.
[0060] The dashed lines in Figure 10A separate the support into identical pixels 1018. Each
pixel contains one rectangular microcell from each of the first and second sets and
two square microcells of the third set.
[0061] By uniformly exposing the first major surface of the support in the direction indicated
by the arrows 1012A, it is possible to expose selectively the bottom walls of the
first set of microcells 1006A while the lateral walls prevent direct impingement of
the radiation on the bottom walls of the remaining two sets of microcells. If desired
to expose entirely the bottom walls of the first set of microcells, the support can
be rotated 180° and exposed again at the same angle or the support can be exposed
again at the same angle, but with the horizontal direction component of the radiation
as shown in Figure 10A reversed. After a first composition is positioned in the first
set of microcells as a function of exposure, the bottom walls of the second set of
microcells 1006B can be selectively exposed by uniformly exposing the first major
surface of the support in the direction indicated by the arrows 1012B, and in the
opposite horizontal direction at the same acute angle similarly as in exposing the
bottom walls of the first set of microcells. The bottom walls of the first and third
sets of microcells are not exposed. A second composition can then be selectively introduced
into the second set of microcells as a function of exposure. The bottom walls of the
third set of microcells can then be exposed by addressing the first major surface
of the support in a direction perpendicular to its axial plane 1014. A third composition
can then be introduced into the third set of microcells. It is to be noted that no
exclusion property is required to introduce selectively the first and second compositions
into the first and second sets of microcells, but that in using a third, perpendicular
exposure the first and second compositions must exclude the third composition from
the first and second sets of microcells, since the third set of microcells is not
uniquely addressed, but is addressed concurrently with all the other microcells.
[0062] In considering the sequence of exposures disclosed above, certain more general parameters
of the invention will become apparent. In exposing the microcells 1006A, it is apparent
that it is their length and the height of the lateral walls which controls exposure
of the bottom walls. Exposure is entirely independent of the width of the first set
of microcells. It is therefore apparent that the width of the first set of microcells
can be varied at will from very small to very large, depending upon the size of the
microareas and the amount of the first composition desired. The width of the microcells
of the first set in the direction of arrows 1012B can even be increased to a point
where it exceeds the length of these microcells in the direction of arrows 1012A.
The widths can, of course, be variable from one microcell to the next, if desired.
The microcells 1006B of the second set can be of any desired length, but to avoid
being exposed on their bottom walls while the first set of microcells are being addressed,
the width of the second set of microcells must be no greater than half the length
of the first set of microcells. Measured in a direction parallel to the major axes
of the first set of microcells, the microcells of the third set can be up to one half
the length of the microcells of the first set without being addressed on their bottom
walls during exposure of the bottom walls of the microcells of the first set. The
microcells of the third set similarly can be up to half the length of the microcells
of the second set measured in a direction parallel to the major axes of the second
set of microcells. In the preferred form shown the first and second sets of microcells
are of equal length and the microcells of the third set are each substantially one
half the length of both the first and second sets of microcells and thus square; however,
the third set of microcells can be rectangular whether or not the first and second
sets of microcells are of equal length. As suggested above, the rectangular microcells
of the first and second sets are only an example of a general class of microcells
of parallelogram configuration. The microcells of the third set, shown to be square,
can be of either lozenge or other parallelogram configuration. Stated another way,
adjacent sides of the microcells need not be perpendicular, but to retain the functional
capabilities disclosed, opposite sides of the microcells should remain parallel. The
above discussion is limited to microcell dimensions that provide all the advantages
of the support 1000 as shown. If less than the entire bottom wall of each microcell
of the first and second set is to be addressed by radiation, then the dimensions of
the second and third sets of microcells can be increased above the one half limits
indicated.
[0063] A number of variations of the support 1000 and the shadowing technique for introducing
compositions will readily be apparent. For example, instead of giving the support
a third exposure to introduce the third composition, in many instances the third composition
can be introduced without reference to any exposure pattern, simply relying on the
first and second compositions to exclude the third composition from the first and
second sets of microcells, as has been mentioned in connection with previously discussed
supports. The support 1000 can be adapted to the use of two rather than three compositions
merely by omitting any one of the three sets of microcells without otherwise altering
the capabilties or shadowing techniques described above. It is to be noted that the
placement of the individual microcells in relation to each other is entirely a matter
of choice. For example, instead of placing pairs of square microcells side-by-side,
as shown, they can be separated by intervening rectangular microcells. Alternatively,
the square microcells can form columns and/or rows perpendicular to the columns which
are not interrupted by rectangular microcells.
[0064] In looking at the support 1000, it is apparent that it is only exemplary of a large
family of alternative support configurations capable of exhibiting some or all of
the advantages of this invention. For example, if the microcells 1006B are arranged
in an end-to-end pattern in parallel columns (this can be done by laterally displacing
the support along the horizontal dashed line in Figure 10A extending in the same direction
in the axial plane as the arrows 1012A); it is apparent that glide planes exist in
these columns. By laterally displacing the support on one side of a glide plane one-half
the length of the microcells 1006B, the second set of microcells 1006B are transformed
into a serpentine microgroove. The shadowing utility of the support is not affected,
however. In like manner, it can be appreciated that if the square microcells are arranged
in a row or column uninterrupted by rectangular microcells, glide planes exist in
these rows or columns. By translating one portion of the support on one side of a
glide plane with respect to the portion of the support on the other side, the square
microcells are converted into a serpentine microgroove, but the shadowing utility
of the support is not changed. If additional lateral walls are provided aligned with
the glide planes, the serpentine microgrooves, formed by displacing halves of the
first set of rectangular microcells, become rectangular microcells again, with two
rectangular microcells being present where only one existed prior to displacement
along the glide plane. In like manner, the serpentine microgroove formed by displacement
along a glide plane running through the square microcells is replaced by a series
of smaller rectangular microcells which are equal in length to the sides of the squares
initially present, but smaller in width. The variants of the support 1000 that can
be created by displacement along glide planes should be apparent by comparing supports
100 and 400 in light of the above description.
[0065] Figure 11 illustrates a preferred support 1100 for use in the practice of this invention
which is (1) capable of entirely separating three different compositions by intervening
lateral walls, similarly as supports 800, 900, and 1000.(2) capable of providing equal
microareas in each of three different sets, similarly as supports 900 and 1000, (3)
capable of providing equal volumes in each of three separate microcell sets, similarly
as support 1000, (4)capable of being uniquely addressed in each of three separate
sets of microcells, a capability not shared by any of the supports previously discussed,
and (5) capable of providing a more symmetrical distribution of three compositions
than the support 1000.
[0066] The support 1100 can be resolved into a plurality of pixels 1118 each containing
three identical microcells 1106 which are diamond-shaped in plan view. Each microcell
within the pixel belongs to a separate set of microcells. A first set of the microcells
is positioned so that the longest dimension of each microcell is aligned with or parallel
to a first axis 1120. A second set of microcells is similarly positioned with respect
to a second axis 1122, which intersects the first axis at a 60° angle. In like manner
a third set of microcells is similarly positioned with respect to a third axis 1124,
which intersects each of the first and second axes at an angle of 60°. If the support
1100 is viewed in section along any one of the first, second, or third axes it would
appear similar to the sectioned support shown in Figure 1B (ignoring wall structures
outside of the section plane).
[0067] If the support 1100 is uniformly exposed at an acute angle with respect to its axial
plane similarly as the support 100 in Figure 1B or the support 500 in Figure 5B in
a direction indicated by the arrow 1126, which is parallel to the first axis, the
bottom wall of each microcell of the first set can be exposed to radiation in the
microarea 1128 while the bottom walls of the second and third sets of microcells remain
entirely shadowed. If a second exposure is given at the same acute angle, but in the
opposite direction, as indicated by arrow 1130, the bottom walls of the first set
of microcells are again exposed, this time in only the microareas 1132. Again the
bottom walls of the second and third sets of microcells remain entirely shadowed.
[0068] It can thus be seen that two uniquely addressed microareas can be formed by angled
exposure of the bottom walls of the first set of microcells. After the first angled
exposure, a first composition can, if desired, be introduced as a function of exposure
so that it is selectively positioned in only the microareas 1128. After the second
exposure a second composition can be similarly selectively positioned in only the
microareas 1132. Alternatively, both the first and second exposures can occur before
any composition is introduced, and a single composition can then be introduced so
that it is selectively positioned in the microareas 1128 and 1132 only.
[0069] By analogy it is apparent that if the procedure described above is twice repeated,
the second and third sets of microcells can be similarly uniquely addressed and up
to four additional compositions placed in uniquely addressed interlaid sets of microareas.
Uniform exposure in the direction indicated by arrow 1134, but otherwise identical
to the first uniform exposure uniquely addresses microareas 1136 while leaving the
remainder of the bottom walls in shadow. A reversed exposure in the direction indicated
by arrow 1138 uniquely addresses microareas 1140 while leaving the remainder of the
bottom walls in shadow. Uniform exposure in the direction indicated by arrow 1142
uniquely addresses microareas 1144 while a reversed exposure in the direction indicated
by arrow 1146 uniquely addresses microareas 1148. Thus, six separate uniquely addressed
microareas can be produced and six separate compositions can be introduced, each selectively
positioned in a separate microarea. It is generally preferred to position three compositions
in the microcells so that a different composition lies in each set of microcells.
[0070] In looking at the support 1110, it is apparent that it is merely representative of
a family of possible supports having generally similar capabilities. For examp.le,
any one of the axes 1120, 1122, and 1124 shown in the drawings is merely one axis
arbitrarily selected for purposes of illustration from among a family of identical
parallel axes. Further, each family of axes constitutes a family of glide planes.
By relatively displacing portions of the support in the axial plane of the support
along one or up to the entire family of glide planes, essentially functionally identical
supports can be created which have differently shaped microcells, microgrooves, and/or
microareas. To avoid converting microcells into serpentine microgrooves by lateral
displacement additional lateral walls can be located along the glide planes.
[0071] To illustrate the effect of displacement along glide planes, in Figure 12 a support
1200 is shown differing from the support 1100 by lateral displacement of adjacent
portions of the support along glide planes 1220A and 1220B. This displacement converts
one set of microcells having major axes in the glide plane 1220A into serpentine microgrooves
which cross and recross this glide plane. Along the glide plane 1220B an additional
lateral wall 1208 is provided so that the one set of microcells having major axes
in the glide plane are converted by displacement and the lateral walls to triangular
microcells of approximately half the area, but twice the number, of the corresponding
diamond-shaped microcells in support 1100. The additional lateral walls 1208 can be
present along both glide planes 1220A and 1220B or omitted entirely. The first and
second sets of microcells are identical to those of support 1100. The shadowing utility
of the support 1200 is identical to that of the support 1100. Since the microcells
of the first, second, and third sets are identical and form a symmetrical pattern
in support 1100, it is apparent that identical patterns result from displacement along
glide planes aligned with the major axis of any one of the three sets of microcells.
In terms of capabilities-:and use the support 1200 is substantially the same as support
1100.
[0072] Referring again to support 1100, three axes 1152, 1154, and 1156 are present extending
through or parallel to the minor axes of the three sets of microcells. These three
axes intersect at 60° angles. Using any one of these axes as a glide plane and displacing
the portions of the support lying on either side of the glide plane in the axial plane
of the support, one set of microcells can be converted from diamond-shaped microcells
to triangular microcells of approximately half the area, but twice the number. When
this type of glide plane variation is undertaken, the result is a support that possesses
the capabilities of support 1100, except the capability of uniquely addressing the
triangular set of microareas produced by lateral displacement. The triangular microcells
can still be addressed similarly as the square microcells in the support 1000, however.
[0073] In Figure 13 an additional preferred support 1300 for use in the practice of this
invention is illustrated. The support is provided with first and second sets of diamond-shaped
microcells 1306A and 1306B. The microcells of each of the first and second sets have
major axes lying along parallel axes, while the axes of one set intersect those of
the other set at a 60° angle. A third set of microcells 1306C is rectangular in shape.
The major axes of the rectangular microcells are substantially parallel to each other
and intersect the axes of the first and second microcells at 60° angles. Thus, in
terms of microcell content the support 1300 differs from the support.1100 in substituting
for one set of diamond-shaped microcells a set of rectangular microcells. The first
and second sets of microcells can be uniquely addressed in microareas 1326, 1332,
1336, and 1340, which are identical to corresponding microareas in support 1100. The
rectangular microcells can be uniquely addressed in microareas 1344 and 1348, which
differ in shape from the corresponding uniquely addressed microareas in the support
1100. In terms of relative placement of microcells, it can be seen that the microcells
of each set form a separate column in the support 1300. Adjoining columns are shown
separated by glide planes 1320A, 1320B, and 1320C. It is apparent that any column
can be laterally displaced in the axial plane of the support without in any way affecting
the remaining columns or their function. For certain applications, such as linear
scanning, the columnar arrangement of the microcells in support 1300 is particularly
advantageous. Although the microcell pattern of support 1300 is less symmetrical than
that of support 1100, it otherwise offers all the capabilities of the support 1100.
[0074] Each of the supports 1100, 1200, and 1300 contain microareas within each microcell,
shown as shadowed areas, which cannot be uniquely addressed. These areas are shadowed
when the remaining bottom wall areas of each set of microareas is addressed with radiation
at an acute angle with respect to the axial plane of the support. In some applications
the shadowed areas can be left free of any composition. That is, one or two compositions
can be introduced into a microcell in only the uniquely exposed microareas thereof
without taking any further steps to introduce an additional composition in the remaining
microareas. If the compositions introduced in uniquely addressed microareas are not
capable of lateral spreading, the shadowed bottom wall portions remaining will have
no composition associated therewith. Where compositions capable of lateral spreading
are introduced into the uniquely addressed microareas, they can spread over the entire
bottom wall of each microcell in which they are contained. For example, if a spreadable
cyan, magenta, or yellow dye is positioned in one uniquely addressed microarea of
a microcell and a different spreadable subtractive primary dye is placed in the remaining
uniquely addressed microarea in the same microcell, one of three different additive
primary colors, depending on the combination of subtractive primaries chosen, can
be produced as the spreadable dyes wander over the entire bottom wall of the microcell.
[0075] Where compositions are introduced into the uniquely addressed microareas of the supports
1100, 1200, or 1300 and it is desired to place a composition also in the shadowed
areas remaining, this can be undertaken using techniques similar to those described
above. For example, if the bottom walls of the support are transparent and colorants
are placed in the uniquely addressed area%, it may be undesirable to have transparent
microareas as well as colored microareas. It is possible to selectively position an
additional, high density or opaque composition in all of the shadowed microareas remaining
to eliminate transparent microareas in the support. Since the lateral walls are capable
of interrupting radiation, radiation cannot penetrate these areas of the support.
Where a technique is employed for positioning the additional composition that requires
the initially shadowed microareas to be exposed to radiation, the support can be exposed
in a direction substantially perpendicular to its axial plane and the exclusion properties
of the previously positioned materials employed can be relied upon to position selectively
the additional composition in the initially shadowed microareas. Where a technique
is employed for positioning the additional composition in initially shadowed areas
that allows a material to be selectively positioned in unexposed areas, the additional
composition can be selectively positioned without relying upon any exclusion capability
by any composition previously positioned and without exposing the initially shadowed
areas to radiation.
[0076] In various embodiments described above it is suggested to expose the support substantially
perpendicularly to its axial plane where shadowing is not desired. In some instances
this can be disadvantageous, since the radiation source is fixed at a particular acute
angle for shadowing exposures and it may be inconvenient to provide a second radiation
source or relocate the radiation source used for shadowing. An alternative is possible
when the lateral walls are capable of interrupting radiation, but are not entirely
opaque. For example, if transparent lateral walls are dyed to the extent necessary
to provide shadowing, they may still be penetrable by radiation of increased intensity.
In such instances it is contemplated to give the support a first uniform exposure
at an acute angle, choosing a level of radiation intensity which permits the lateral
walls to interrupt the radiation and provide shadowing as required. Thereafter, when
exposure of the shadowed areas is required, the same radiation source at the same
acute angle can be increased in intensity and used to reexpose the support. This time
sufficient radiation penetrates the lateral walls to allow exposure of the initially
shadowed areas. Instead of altering the intensity of radiation between exposures,
a change in the wavelength or even type of radiation can be relied upon to allow shadowing
in one instance, but not another. Transparent lateral walls containing an ultraviolet
absorber can interrupt ultraviolet radiation while permitting penetration of visible
light. Similarly lateral walls which are dyed to appear visibly opaque may nevertheless
absorb little ultraviolet radiation.
[0077] In the preferred embodiments of the invention, described in connection with supports
800, 900, 1000, 1100, 1200, and 1300, one set of microareas can be entirely separated
from all other sets of microareas by lateral walls. However, because of shadowing
by the lateral walls, the entire bottom wall surface between these boundary forming
lateral walls cannot be entirely exposed at one time. In some geometrical forms of
the support, such as support 1000, the entire bottom wall surface between boundary
forming lateral walls (e.g., the entire bottom wall of a microcell) can be addressed
by a combination of two exposures if the support is rotated 180° or the second radiation
source is changed in direction. In some instances, however, this still leaves bottom
wall surfaces shadowed that are not intended to be differentiated from exposed microareas
within the same lateral wall boundary. For example, the shadowed areas shown in the
supports 1100, 1200, and 1300 can represent a significant inconvenience and limitation
where it is desired to locate three compositions, each in a different set of microcells,
so that each composition entirely covers the bottom walls of its microcell set.
[0078] In those instances where it is desired for an entire bottom wall surface bounded
by lateral walls, such as the entire bottom wall surface of a microcell, to form a
single microarea, but exposure at an acute angle casts a shadow over at least a portion
of the microarea, it is specifically contemplated to modify the support to either
spread the radiation itself or to spread whatever modifying effect the radiation produces
over the entire microarea. The specific approach for accomplishing this objective
can be varied, depending upon the specific application the support is intended to
serve.
[0079] In one such embodiment, a removable cover, preferably bearing a semitransparent reflective
coating, can be laid over the first major surface of the support to aid in reflecting,
if desired. Exposure must, of course, occur through the cover. The lateral walls can
be relied upon to prevent radiation from scattering beyond the intended boundary of
the microarea.
[0080] Where the support or at least the bottom wall portion of the support is a photoconductor,
as described in European Application No.81304574.7 cited above, a conductive layer
which is at least partially transparent can be placed selectively on the bottom wall
surfaces. Without the conductive layer present only the bottom wall portion actually
exposed to radiation are increased in conductivity, but with the conductive layer
present, if any portion of a bottom wall is struck by radiation to which the photoconductor
is responsive, the effect in terms of static charge retention is as though the entire
bottom wall had been radiation struck.
[0081] Another approach applicable to supports generally (i.e., not limited to reflective
or photoconductive supports) is to located a fluor on the bottom wall surfaces. Exposure
in one microarea stimulates emission of radiation by the fluor and causes the entire
bottom wall portion in the bounded area to be exposed to either direct or stimulated
radiation. Again, the lateral walls can be relied upon to prevent radiation scattering
beyond the intended boundary of the microarea.
[0082] In a very simple form of the invention the bottom walls of the supports can themselves
be relied upon to distribute radiation over a bottom wall surface. It is generally
recognized that even a polished transparent support will reflect some radiation. For
applications requiring very little radiation, the inherent light scattering property
of unmodified bottom walls can be sufficient to distribute a useful amount of radiation
over the entire bottom wall surface. Scattering of radiation by the bottom walls can
be significantly increased by roughening the bottom wall of the support.
[0083] The support of this invention can be applied to any application requiring two or
more compositions to be laterally related in a highly interlaid manner. The supports
are generally useful for the same purposes as those disclosed in European Specification
0,014,572, except for the unique features specifically described above, can be formed
in the same mamner using the same or similar materials.
[0084] A specific preferred photographic application of the invention can be illustrated
by reference to Figure 14A, wherein a multicolor image transfer photographic element
1400 is shown. The photographic element as shown employs support 1100 as it would
appear if sectioned along the major axis of microcells forming each of the three sets,
that is, along section line 14A-14A as shown in Figure l4B. The lateral walls 1108
of the support are capable of interrupting radiation, but the underlying portion 1110
which connects the lateral walls is substantially transparent. The first set of microcells
R contain red colorant and a cyan dye precursor. The second set of microcells G similarly
contain green colorant and a magenta dye precursor. The third set of microcells B
contain blue colorant and a yellow dye precursor. The dye precursors can each be shifted
between a mobile and an immobile form either in their dye or dye precursor forms.
A panchromatically sensitized silver halide emulsion layer 1402 overlies the first
major surface 1102 of the support. The support 1100, the contents of the microcells,
and the silver halide emulsion layer together form an image generating portion of
the photographic element.
[0085] An image-receiving portion of the photographic element is comprised of a transparent
support (or cover sheet) 1450 on which is coated a conventional dye immobilizing layer
1452. A reflection and spacing layer 1454, which is preferably white, is coated over
the immobilizing layer. A silver reception layer 1456, which contains a silver precipitating
agent, overlies the reflection and spacing layer.
[0086] In a preferred, integral construction of the photographic element the image-generating
and image-receiving portions are joined along their edges and lie in face-to-face
relationship. After imagewise exposure a processing solution is released from a rupturable
pod, not shown, integrally joined to the image-generating and receiving portions along
one edge thereof. A space 1458 is indicated between the image-generating. and receiving
portions to indicate the location of the processing solution when present after exposure.
The processing solution contains a silver halide solvent. A silver halide developing
agent is contained in either the processing solution or in a position contacted by
the processing solution upon its release from the rupturable pod. The developing agent
or agents can be incorporated in the silver halide emulsion.
[0087] The photographic element 1400 is preferably a positive-working image transfer system
and is described by reference to such a system. In such a system the silver halide
emulsion is preferably negative-working and the dye precursors are positive-working,
although a direct-positive emulsion and negative-working dye precursors also produce
a positive-working image transfer system.
[0088] The photographic element 1400 is imagewise exposed through the transparent underlying
portion of support 1100. The red, green, and blue colorants act as filters allowing
the silver halide emulsion layer to be exposed selectively to red, green, and blue
light in microareas corresponding to the like colored filters.
[0089] Upon release of processing solution between the image-forming and receiving portions
of the element, development of the exposed silver halide is initiated. Silver halide
development results in one exemplary form in a selective immobilization of the initially
mobile dye precursor present in the adjacent microcells. In a preferred form the dye
precursor is both immobilized and converted to a subtractive primary dye of a hue
complementary to the filter. The residual mobile imaging dye precursor, either in
the form of a dye or a precursor, migrates through the silver reception layer 1456
and the reflection and spacing layer 1454 to the dye immobilizing layer 1452. In passing
through the silver reception and spacing layers the mobile subtractive primary dyes
or precursors are free to and do spread laterally. Referring to Figure 14B, it can
be seen that each microcell containing a selected subtractive primary dye precursor
is substantially surrounded by microcells containing precursors of the remaining two
subtractive primary dyes. It can thus be seen that lateral spreading results in overlapping
transferred dye areas in the dye immobilizing layer of the receiver when mobile dye
or precursor is being transferred from adjacent microcells. Where three subtractive
primary dyes overlap in the receiver, black image areas are formed, and where no dye
is present, white areas are viewed due to the reflection from the spacing layer. Where
two of the subtractive primary dyes overlap at the receiver an additive primary image
area is produced. Thus, it can be seen that a positive multicolor dye image can be
formed which can be viewed through the transparent support 1450. The positive multicolor
transferred dye image so viewed is right-reading.
[0090] In the multicolor photographic element 1400 the risk of undesirable interimage effects
attributable to wandering oxidized developing agent is substantially reduced, as compared
to conventional multicolor photographic elements having superimposed color-forming
layer units since the lateral walls of the support element prevent direct lateral
migration between adjacent microcells. Nevertheless, the oxidized developing agent
in some systems can be mobile and can migrate with the mobile dye or dye precursor
toward the receiver and migrate back to an adjacent microcell. To minimize unwanted
dye or dye precursor immobilization prior to its transfer to the immobilizing layer
of the receiver it is preferred to incorporate in the silver reception layer 1456
a conventional oxidized developing agent scavenger.
[0091] Since the processing solution contains silver halide solvent, the residual silver
halide not developed in the microcells is solubilized and allowed to diffuse to the
adjacent silver reception layer. The dissolved silver is physically developed in the
silver reception layer. Solubilization and transfer of the silver halide from the
microcells operates to limit direct or chemical development of silver halide occurring
therein. It is well recognized by those skilled in the art that extended contact between
silver halide and a developing agent under development conditions (e.g., at an alkaline
pH) can result in an increase in fog levels. By solubilizing and transferring the
silver halide a mechanism is provided for terminating silver halide development in
the microcells. In this way production of oxidized developing agent is terminated
and immobilization of dye in the microcells is also terminated. Thus, a very simple
mechanism is provided for terminating silver halide development and dye immobilization.
[0092] In addition to obtaining a viewable transferred multicolor positive dye image a useful
negative multicolor dye image is obtained. In microcells where silver halide development
has occurred, an immobilized subtractive primary dye is present. This immobilized
imaging dye together with the additive primary filter offers a substantial absorption
throughout the visible spectrum, thereby providing a high neutral density to these
microcells. For example, where an immobilized cyan dye is formed in a microcell also
containing a red filter, it is apparent that the cyan dye absorbs red light while
the red filter absorbs in the blue and the green regions of the spectrum. The developed
silver present in the microcell also increases the neutral density. In microcells
in which silver halide development has not occurred, the mobile dye precursor, either
before or after conversion to a dye, has migrated to the receiver. The sole color
present then is that provided by the filter. It is a distinct advantage in reducing
minimum density to employ the silver reception layer 1456 to terminate silver halide
development as described above rather than to rely on other development termination
alternatives. If the image-generating portion of the photographic element 1400 is
separated from the image-receiving portion, it is apparent that the image-generating
portion forms in itself an additive primary multicolor negative of the exposure image.
The additive primary negative image can be used for either transmission or reflection
printing to form right-reading multicolor positive images, such as enlargements, prints,
and transparencies, by conventional photographic techniques.
[0093] The foregoing description of photographic element 1400 illustrates the use of initially
mobile subtractive primary dye precursors in addition to additive primary filter materials
in interlaid sets of microcells. In alternative multicolor image transfer photographic
elements the microcells can contain the silver halide precipitating agent. The subtractive
primary dye precursors can either be initially mobile or immobile. Further, either
mobile or immobile subtractive primary dyes capable of undergoing imagewise alterations
in mobility can be substituted for the dye precursors. In this instance it is preferred
to locate both silver halide and the subtractive primary dyes in the microcells so
that exposing radiation strikes the silver halide before the dye, thereby avoiding
competing absorption and any resulting decrease in speed. In still another variant
form preformed image dyes can be shifted in hue so that they do not compete with silver
halide in absorbing light to which silver halide is intended to respond. The dyes
can shift back to their desired image hue upon contact with processing solution. If
no additive multicolor retained image is desired, the additive primary filter materials
can be omitted from the microcells in those instances where the silver halide is present
in each set of microcells and in each set of microcells is responsive to only one
of the blue, green, and red portions of the spectrum. A variety of techniques are
known in the art for avoiding response by green and red sensitized silver halide emulsions
to blue light, such as the use of silver chlorides and chlorobromides and the use
of yellow filter materials. These techniques are also described in European Specification
0,014,572-and here incorporated by reference. When silver halide is located in the
microcells, the oxidized developing agent scavenger is preferably coated over the
microcells or can be located in the microcells above the silver halide. If no transferred
multicolor dye image is desired, the layer 1456 can be substituted for the layer 1452
so that a transferred silver image can be viewed and all subtractive primary dyes
or dye precursors can be omitted. Of course, if no transferred dye or silver image
is desired, the entire image receiving portion of the photographic element as well
as the subtractive primary dye or dye precursor can be omitted.
[0094] It is therefore apparent that a wide variety of different materials can be employed
to form interlaid sets of microcells useful in even a specific application, such as
multicolor photography. While the photographic element 1400 employs support 1100,
any of the supports described above can be substituted without altering the overall
performance of the photographic element, although some supports offer more advantages
than others, as has already been discussed.
[0095] If no transferred dye image is desired and the subtractive primary dyes or dye precursors
are omitted from the photographic element 1400, it is apparent that only immobile
primary colorants need remain in the microcells. However, as has been noted above
in connection with previously described supports, the lateral walls can be dyed to
provide one additive primary filter. It is therefore apparent that where the microcells
contain only additive primary colorants, such as red, green, and blue, the function
of one set of microcells can be performed merely by dyeing the lateral walls to provide
the corresponding additive primary color. Thus, one set of microcells can be omitted
from the support 1100 without affecting its performance. Since the microcell sets
of support 1100 are identical, except for the additive primary contained therein,
it is immaterial which set is omitted. It is apparent that for a similar application
any set of microcells can be omitted from the supports 900, 1000, or 1300. Similarly
in support 1200, either a diamond-shaped set of microcells can be removed or the microgrooves
and/or microcells formed by lateral displacement along the glide planes can be removed.
In support 1000 a distinct advantage is realized in some applications requiring unique
exposures of the microcells, since the square microcells which cannot be uniquely
exposed can be omitted, leaving only two rectangular sets of microcells, both of which
can be uniquely addressed.
[0096] In one specific, illustrative form the photographic element 1400 can contain (1)
in a first set of microcells a blue filter dye or pigment and an initially colorless,
mobile yellow dye-forming coupler, (2) in a second, interlaid set of microcells a
green filter dye or pigment and an initially colorless, mobile magenta dye-forming
coupler and (3) in a third, interlaid set of microcells a red filter dye or pigment
and an initially colorless, mobile cyan dye-forming coupler. A panchromatically sensitized
negative-working silver halide emulsion layer 1402 is coated over the microcells.
The layer 1456 contains a silver precipitating agent and an oxidized developing agent
scavenger. The reflection and spacing layer 1454 can be a conventional titanium oxide
pigment containing layer. The dye immobilizing layer 1452 contains an oxidizing agent.
[0097] The photographic element 1400 so constituted is first exposed imagewise through the
transparent underlying portion of support 1100. Thereafter a processing composition
containing a color developing agent and a silver halide solvent is released and uniformly
spread in the space 1458. In exposed areas silver halide is developed producing oxidized
color developing agent which couples with the dye forming coupler present to form
an immobile dye. The filter dye or pigment, the immobile dye formed, and the developed
silver thus together increase the optical density of the microcells which are exposed.
[0098] In areas not exposed, the undeveloped silver halide is solubilized by the silver
halide solvent and migrates to the layer 1456 where it is reduced to silver. Any oxidized
developing agent produced in reducing the silver halide to silver immediately cross-oxidizes
with the oxidized developing agent scavenger which is present with the silver precipitating
agent in the layer 1456.
[0099] At the same time mobile coupler is wandering from microcells which were not exposed.
The mobile coupler does not react with oxidized color developing agent in the layer
1456, since any oxidized color developing agent present preferentially reacts with
the oxidized developing agent scavenger. The coupler thus migrates through layer 1456
unaffected and enters reflection and spreading layer 1454. Because of the thickness
of this layer, the mobile coupler is free to wander laterally to some extent. Upon
reaching the immobilizing layer 1452, the coupler reacts with oxidized color developing
agent. The oxidized color developing agent is produced uniformly in this layer by
interaction of oxidizing agent with the color developing agent. Due to lateral diffusion
in the spreading layer, superimposed immobile yellow, magenta and cyan dye images
are formed in the immobilizing layer and can be viewed as a multicolor image through
the transparent support (or cover sheet) 1450 with the layer 1454 providing a white
reflective background. At the same time, since only filter dye or pigment remains
in the unexposed microcells, a useable additive primary negative transparency is formed
by the support 1100.
[0100] To illustrate a variant system, a photographic element as described immediately above
can be modified by substituting for the initially colorless, mobile dye forming couplers
initially mobile dye developers. The dye developers are shifted in hue, so that the
dye developer present in the microcells containing red, green, and blue filters do
not initially adsorb light in the red, green, and blue regions of the spectrum, respectively.
A dye mordant as well as an oxidant can be present in the dye immobilizing layer 1452.
Since the dye image forming material is itself a silver halide developing agent, a
conventional activator solution can be employed (preferably containing an electron
transfer agent). The remaining features can be identical to those described in the
preceding embodiment.
[0101] Upon imagewise exposure and release of the activator solution, dye developer reacts
with exposed silver halide to form an immobile subtractive primary dye which is a
complement of the additive primary filter material in the exposed microcell. Thus
the optical density of exposed microcells is increased, and a negative multicolor
additive primary image can be formed in the support 1100 by the filter materials.
Silver halide development is terminated by transfer of solubilized silver halide as
has already been described. In unexposed areas unoxidized dye developer migrates to
the immobilizing layer 1452 where it is oxidized and mordanted to form a multicolor
positive image. During processing the dye developers shift in hue so that they form
subtractive primaries complementary in hue to the additive primary filter materials
with which they are initially associated in the microcells. That is, the red, green
and blue filter material containing microcells contain dye developers which ultimately
form cyan, magenta and yellow image dyes. Hue shifts can be brought about by the higher
pH of processing, mor- danting, or by associating the image dye in the receiver with
a chelating material.
[0102] Instead of using shifted dye developers as described above, initially mobile leuco
dyes can be employed in combination with electron transfer agents to produce essentially
similar results. Since the leuco dyes are initially colorless, hue shifting does not
have to be undertaken to avoid competing light absorption during imagewise exposure.
[0103] Instead of employing initially mobile dyes or dye precursors as described above,
it is possible to employ initially immobile materials. In one specific preferred form
benzisoxazolone precursors of hydroxylamine dye-releasing compounds are employed.
Upon cross-oxidation in the microcells with oxidized electron transfer agent produced
by development of exposed silver halide, release of mobile dye is prevented. In areas
in which silver halide is not exposed and no oxidized electron transfer agent is produced
mobile dye release occurs. The dye image providing compounds are preferably initially
shifted in hue to avoid competing absorption during imagewise exposure. Mordant immobilizes
the dyes in the layer 1452. No oxidant is required in this layer in this embodiment.
Except as indicated, this element and its function is similar to the illustrative
embodiments described above.
[0104] Each of the illustrative embodiments described above employ positive-working dye
image providing compounds. To illustrate a specific embodiment employing negative-working
dye image providing compounds, a first set of microcells 1408 can contain a blue filter
dye or pigment, a silver ion complex precipitating agent, and a redox dye-releaser
containing a yellow dye.which is shifted in hue to avoid adsorption prior to processing
in the blue region of the spectrum. In like manner a second, interlaid set of microcells
contain a green filter dye or pigment, the silver precipitating agent and a redox
dye-releaser containing analogously shifted magenta dye, and a third, interlaid set
of microcells containing a red filter dye or pigment, the silver precipitating agent,
and a redox dye-releaser containing an analogously shifted cyan dye. The microcells
are overcoated with negative-working panchromatically sensitized silver halide emulsion
layer also containing an oxidized developing agent scavenger. The silver precipitating
layer 1456 shown in Figure 14 is not present. The reflection and spreading layer is
a white titanium oxide pigment layer. The dye immobilizing layer 1452 contains a mordant.
[0105] The photographic element is imagewise exposed through the transparent support 1100.
A processing solution containing an electron transfer agent and a silver halide solvent
is spread between the image-generating and the image-receiving portions of the element.
In a preferred form the pH of the processing solution causes the redox dye-releasers
to shift to their desired image-forming hues. In areas in which silver halide is exposed
oxidized electron transfer agent produced by development of exposed silver halide
immediately cross-oxidizes with the oxidized developing agent scavenger. Thus, in
microcells corresponding to exposed silver halide the redox dye-releasers remain unaltered
in their initially immobile, shifted form. In areas in which silver halide is not
exposed, silver halide solvent present in the processing solution solubilizes silver
halide allowing it to form soluble silver ion complex (e.g., AgSO
3-) capable of wandering into the underlying microcells. In the microcells physical
development of solubilized silver halide occurs producing silver and oxidized electron
transfer agent. The oxidized electron transfer agent interacts with the redox dye-releaser
to release mobile dye which is transferred to the layer 1452, shifted in hue, and
immobilized by the mordant. A multicolor positive transferred image is produced in
the layer 1452 comprised of yellow, magenta, and cyan transferred dyes. A multicolor
positive retained image is also produced, since (1) the silver density produced by
chemical development in the emulsion layer is small compared to the silver density
produced by physical development in the microcells and (2) with the image-generating
portion separated from the image-receiving portion the redox dye-releasers remaining
in their initial, immobile condition in the microcells can be uniformly reacted with
an oxidizing agent to release mobile dye which can be removed from the microcells
by washing.
[0106] To illustrate a simple technique for providing two or three sets of microareas each
having a different colorant associated therewith, any one of the supports described
above which provide two or more microareas that can be uniquely addressed can be initially
coated first with a colorant immobilizing material, such as a mordant or oxidant,
so that a thin layer that can be shadowed by the lateral walls is formed over the
entire bottom wall of the support. Next the immobilizing layer is overcoated with
a positive-working photoresist--that is, a photoresist which is selectively removable
on development in exposed areas. Again, the photoresist is coated in a thin layer
so that the lateral walls rise above the upper surface of the photoresist layer and
are therefore capable of shadowing this layer. The photoresist layer is then selectively
exposed to radiation to which it is responsive in a first set of microareas by shadowing
techniques described above. Upon development the photoresist is selectively removed
from the support in just these areas. By bringing the support into contact with a
dye containing solution, dye can be imbibed into the immobilizing layer selectively
in only those areas initially exposed. This selectively places immobilized dye in
the first set of microareas. By repeating the procedure using shadowing techniques
already described above two, three, or more interlaid displaced sets of uniquely addressed
microareas can be produced capable of acting as filters in additive multicolor photographic
applications. Either additive primary (i.e., red, green, and blue) dyes or combinations
of subtractive primary (i.e., cyan, magenta, and yellow) dyes which give an additive
primary color can be employed to form the filter colorants. Before each repetition
it is preferred to uniformly expose all bottom wall areas of the support and to remove
photoresist entirely by development. This avoids build up of overlaid photoresist
layers.
[0107] By substituting a negative-working photoresist for the positive-working photoresist,
dye can be selectively introduced into shadowed microareas instead of exposed microareas.
This is fully satisfactory where two colorants are being positioned, but this procedure
is not generally applicable to the supports described where three sets of colorants
are being positioned in three separate sets of microareas.
[0108] An alternative approach for employing negative-working photoresists is to coat a
mobile colorant initially on the support in place of the immobilizing layer described
above and then to overcoat the negative-working photoresist layer in place of the
positive-working photoresist layer described above. The negative-working photoresist
upon exposure in a first set of microareas is rendered immobile on development, so
that subsequent development removes photoresist in unexposed areas. Mobile colorant
is removed on development in only those areas where the photoresist is also removed,
leaving colorant in a first set of microareas initially exposed. By repeating the
procedure described above using previously described exposure techniques, two, three,
or more sets of colorants can be positioned in interlaid sets of microareas. The procedure
is generally applicable to the supports described which provide two or more sets of
microareas that can be uniquely addressed. Photoresists are preferably employed as
described above to form microareas that are substantially coextensive with microcells
or microgrooves.
[0109] Instead of using photoresists to form multicolor filter elements useful in additive
multicolor photography, other radiation-sensitive materials can be employed which
are capable of producing additive primary filter microareas as a function of selective
exposure and shadowing. To illustrate a simple approach, the supports 1100, 1200,
or 1300 can be coated with vacuum vapor deposited silver halide on the bottom and
lateral walls of the microcells. The advantage of using vacuum vapor deposited silver
halide is that a layer of radiation-sensitive materal can be substantially uniformly
deposited on the walls of the microcells which is quite thin in comparison to the
lateral walls of the microcells. If desired, a silver halide emulsion layer which
is sufficiently thin in relation to the lateral walls to permit shadowing can be substituted
for vacuum vapor deposited silver halide.
[0110] In use, a first shadowing exposure renders the silver halide developable on the exposed
lateral walls and in the bottom walls of the one set of microcells exposed. Development
with a color developer containing a mobile dye former, such as one or more dye-forming
couplers, produces a colorant selectively on the bottom walls of the first set of
microcells and on the exposed lateral walls. Colorant produced on the lateral walls
can be useful in enhancing their radiation interrupting capability during subsequent
exposures. A dye-forming coupler can be chosen that produces an additive primary dye
on reaction with oxidized color developing agent, or two dye-forming couplers can
be employed each of which produce a different subtractive primary dye on reaction
with oxidized color developing agent, so that their combined effect is to produce
an additive primary filter colorant. By going through the shadowing exposure procedure
already described above using different dye-forming couplers, two, three, or more
sets of laterally displaced filter segments can be produced. Bleaching and/or fixing
can be employed to reduce neutral densities attributable to silver.
[0111] It is important to note that in exposing a first set of microareas containing silver
halide and processing as described all of the silver halide in these microareas can
be developed. Thus, in subsequent processing it is immaterial whether these microareas
are again addressed by radiation. For example, in exposing a second time both the
first and second set of microareas can be addressed, but a second development produces
dye in only the second set of microareas where the silver halide in the first set
of microareas has already been exhausted in the first development step. Thus, the
use of silver halide lends itself to forming microareas of differing colors where
the configuration of the support does not lend itself to uniquely addressing each
microarea. This capability of excluding a second or subsequent material based on depletion
of an active component in a microarea is hereinafter referred to as an exhaustion
effect.
[0112] In one form of the invention it is preferred to form multicolor filter elements so
that filter colorant overlies the entire bottom wall of each microgroove or microcell.
In some support forms, such as support 1000, this can be achieved without the provision
of additional steps or materials. In other configurations some bottom wall areas receive
no exposure and no colorant, unless this result is specifically sought. For example,
in the embodiment shown in Figures 14A and 14B bottom wall areas which cannot be uniquely
addressed are not differentiated from the bottom wall areas which can be uniquely
addressed, although the techniques described above for forming three color filters
with photoresists and silver halide require some further elaboration to achieve this
result. By employing scattering and/or fluorescence, as described above, in combination
with shadowing exposure, the entire bottom wall area of each microgroove or microcell
is exposed so that filter colorant is uniformly distributed over the bottom wall.
[0113] In some applications bottom wall areas which are not uniquely addressed can remain
transparent. Where the filter colorant is not distributed over the entire bottom wall
area of each microgroove or microcell, it is generally preferred that the microareas
which cannot be uniquely addressed be rendered substantially opaque.
[0114] Using silver halide as described above, opacification can be accomplished in an illustrative
form by exposing the support perpendicularly to its axial plane after the desired
colorants have been formed in the microgrooves or microcells of each set. In a final
color development step a mixture of three different subtractive primary or two different
additive primary dye-forming couplers can be employed to produce a substantially black
colorant in the microareas not uniquely addressed. Silver produced in the final development
step can also increase neutral density in these areas. It is therefore preferred to
bleach silver from uniquely exposed areas providing additive primary filter microareas
before the final development step and to avoid bleaching after the final development
step.
[0115] Using a positive-working photoresist layer overlying a dye immobilizing layer as
described above, opacification can be accomplished by giving the support a nonshadowing
(perpendicular to the axial plane) exposure after the uniquely addressed colorant
containing filter microareas are formed. Development removes any remaining positive
photoresist. The positive-working photoresist is replaced by a negative-working photoresist
layer. Prior shadowing exposures are repeated, but without the introduction of any
colorants. Development leaves negative-working photoresist overlying and protecting
only the microareas uniquely addressed, the microareas not uniquely addressed being
open. One or a combination of dyes can then be imbibed into the immobilizing layer
in the microareas not uniquely addressed, thereby opacifying the bottom walls of the
support in microareas not occupied by the filters.
[0116] A preferred technique for positioning compositions as a function of exposure useful
with every support configuration and shadowing exposure sequence heretofore described
employs a support at least the bottom walls of which are photoconductive. This technique
can employ any of the supports described in European Application No. 81304574.7 and
is described herein by reference to an illustrative embodiment in which support 600
is provided with red, green, and blue colorants in microareas 1, 2, and 3 of each
microcell 602, as shown in Figure 6B. Additional features of the support and the procedure
for positioning colorants can be better appreciated by reference to Figures 15A to
15D A regular hexagonal array of microcells 602 are formed in a photoconductive portion
604 of the support 600 and open toward a first major surface 606. Adjacent microcells
are separated by lateral walls 608 which are dyed to increase their ability to interrupt
radiation. A substantially transparent underlying portion 610 connects the lateral
walls and forms bottom walls 616 of the microcells.
[0117] In addition to the photoconductive portion, the support is formed by a thin, transparent
conductive layer 612 and a transparent film base 614. Along at least one lateral edge
of the support, not shown, the film base and the conductive layer can extend laterally
beyond the photoconductive portion to facilitate attachment of an external conductor
to the support. A charge control barrier layer, not shown, can be interposed between
the conductive layer and the photoconductive portion. Depending on the choice of photoconductive
and conductive materials employed, electrical biasing of one polarity can result in
a charge injection from the conductive layer into the photoconductive layer rendering
it conductive. The function of the charge control barrier layer is to intercept and
trap injected charge--i.e., electrons or holes. Charge control barrier layers are
well known in the art, as illustrated by U.S. Patents 2,901,348; 3,554,742 and 3,640,708;
and German OLS 1,944,025.
[0118] Although the support is shown to be comprised of the photoconductive portion, the
conductive layer, and the film base, it is appreciated that it may be formed of only
the photoconductive portion. For instance, once the microcells are filled to the extent
desired, the conductive layer and/or film base can be stripped from the photoconductive
portion, leaving it as a separate element. Alternatively, the photoconductive portion
can form the entire support and be brought into contact, as required, with an electrode
which forms no part of the support.
[0119] In Figure 15A the support 600 is shown with the photoconductive portion 604 bearing
on its outer surface a positive electrostatic charge, applied in a nonimagewise manner
to provide a substantially uniform charge distribution. It is to be noted that the
positive charge not only covers the bottom walls 616 of the microcells, but also covers
the upper edges of the lateral walls 608. As is well understood by those skilled in
the art, the electrostatic charge can be conveniently applied by passing the support
through a corona discharge.
[0120] The next step of the process is to remove the electrostatic charge selectively from
the bottom walls of the microcells in the first set of microareas 1 without disturbing
the electrostatic charge in the other bottom wall microareas 2 and 3. This is accomplished
as shown in Figure 15B by exposing the support at an acute angle with respect to the
bottom walls, as indicated by arrows 618. Radiation is employed for exposure to which
the photoconductive portion is responsive. The radiation strikes only the first set
of microareas at the bottom walls, the remaining microareas of the bottom walls being
shadowed. The photoconductive portion of the support is thereby rendered conductive
in the exposed first set of microareas. By grounding or negatively biasing the conductive
layer 612, electrostatic charge can be conducted through the photoconductive portion
in the first set of microareas leaving the first set of microareas substantially uncharged,
as shown.
[0121] The process of the present invention allows all of the first set of microareas to
be addressed in a single exposure. Only a portion of the bottom walls of the microcells
can be addressed. Tedious alignments with individual microcells are entirely eliminated.
Only the angle of exposure and the direction of alignment of the support, neither
of which need be controlled precisely, provide the desired shadow pattern in the microcells.
[0122] To introduce a first imaging composition selectively into the first set of microcells,
a development procedure can be employed as illustrated in Figure 15C. A direct current
source 620 is connected between a development electrode 622 and the conductive layer
612 of the support so that the development electrode is positively biased with respect
to the conductive layer 612. An electrographic developer containing a carrier liquid
624 and dispersed positively charged particles 626 of an electrographic imaging composition
is interposed between the development electrode and the support 600 so that it can
enter the microcells. The positive bias on the development electrode can be viewed
as inducing a negative electrostatic charge on the bottom walls of the first set of
microareas. (See Schaffert, Electrophotography, John Wiley and Sons, New York, p.
51.) The positively charged dispersed particles of electrographic imaging composition
are therefore selectively attracted into the first set of microareas while being concurrently
repelled from the remaining microareas 2 and 3, which contain a positive electrostatic
charge. In Figure 15D a first set of microareas of the support 600 are shown covered
with a red electrographic imaging composition R.
[0123] To complete the preparation of an element containing green, red, and blue imaging
compositions in first, second, and third interlaid sets of microareas the procedure
described above can be twice repeated, except that the support is rotated 120° before
each of the second and third exposures and a different additive primary electrographic
imaging composition is employed in each instance. Although it is preferred to associate
red, green, and blue compositions with the first, second, and third sets of microareas
using the electrographic technique described above, it is appreciated that the second
and third compositions can be positioned using any of the alternative techniques previously
described.
[0124] It is to be appreciated that the description of the process of this invention by
reference to Figures 15A to 15D is merely illustrative of certain preferred embodiments.
Numerous variations will readily occur to those skilled in the art of electrophotography,
once the invention is appreciated. For example, the polarity of charge on the photoconductive
portions, electrographic imaging composition particles, and development electrode
can be reversed without the exercise of invention. The use of a development electrode
is not required. Reversal development through field fringing is known to be obtainable
for small areas, such as line copy. Further, it is possible to choose the polarity
of the electrographic imaging composition particles so that it is opposite to that
of the electrostatic charge on the photoconductive portion and therefore attracted
to the remaining charged microareas not exposed rather than the microareas which are
exposed. In such an alternative, particles are attracted to shadowed rather than exposed
microareas. Any conventional electrographic imaging composition particle size less
than the dimensions of the individual microareas can be employed. It is preferred
to employ particle sizes of less than 25 percent of the size of the microareas. Although
electrographic developers containing liquid carrier vehicles are preferred, since
smaller particle sizes compatible with the widths of the microcells are more readily
employed, any conventional electrographic development technique, such as the use of
aerosols and dry toners, can be employed. Liquid electrographic developers are particularly
preferred which require no separate fusing step to hold the electrographic imaging
composition particles in place in the microcells. A separate fusing step can be employed
where all of the components of the electrographic imaging composition are intended
to remain permanently in the microcells, as in a simple multicolor filter, such as
200 or 400, but it is preferred to avoid a separate fusing step intended to produce
a high degree of fusing where one or more materials are to be removed from the microcells.
Conventional biasing voltages are generally suitable for the practice of this process.
[0125] It is an advantage that second and subsequent electrographic imaging compositions
do not enter the set or sets of microareas which have already received an electrographic
imaging composition. This is true even if the first set of microareas is again exposed
to radiation, either intentionally or inadvertently, in rendering the photoconductive
portion conductive in the second and/or third sets of microareas. This effect is referred
to as the exclusion effect. U.S. Patent 3,748,125 discloses exclusion effects for
xerographic photoconductive surfaces. The exclusion effect observed in the practice
of this process does not appear related to any specific choice of electrographic toners
or specific compositions applied to planar photoconductive surfaces. Without wishing
to be bound by any particular theory to account for the exclusion effect observed,
it may result from photoconductive surface masking by the already deposited imaging
compositions, field gradient or fringing effects (influenced to a degree by the nonplanar
configuration of the photoconductive surface), or, most probably, some combination
of these effects.
[0126] The exclusion effect is particularly important to the use of photoconductive supports
having microareas that cannot be uniquely addressed. For example, three interlaid
sets of nonoverlapping red, green, and blue filter segments can be formed on the supports
100, 200, 300, and 400 by exposing at three angles (each successive angle being larger
than the preceding angle) and using the same general procedure described in connection
with Figures 15A through 15D. Only the first exposed microareas are uniquely addressed.
The second and third exposures overlap previously addressed sets of microareas. However,
the exclusion effect prevents any significant deposition of the second and third electrographic
imaging compositions in previously exposed and toned microareas. The exclusion effect
can be relied upon in placing one or more compositions selectively in the microareas
7 to 18 in Figure 6A; in placing one or more compositions selectively in the microareas
816B and 816C in Figure 8; in placing one or more compositions selectively in the
microareas 916B and 916C in Figure 9; and in placing the third composition in the
microcells 1006C in Figure 10. In supports 1100, 1200, and 1300 the exclusion effect
can be relied upon to selectively position an electrographic opacifying composition
in the shaded microareas that cannot be uniquely addressed. (The exhaustion effect
previously described in connection with the use of silver halide can be applied to
the same support configurations as the exclusion effect.)
[0127] By modifying according to the teachings of this invention supports having microgrooves
or microcells that can be uniquely addressed having photoconductive bottom walls that
cannot be entirely uniquely addressed, it is possible to position an electrographic
imaging composition over the entire bottom wall of each microcell or microgroove that
is uniquely, but partially addressed. This allows a fill pattern as shown in Figure
14B to be achieved, for example, even though support 1100 contains microareas, shown
in shadow in Figure 11, that cannot be uniquely addressed. It is a recognition of
this invention that uniform toning of uniquely but partially addressed microcells
or microgrooves in photoconductive supports can be achieved by positioning a thin
conductive layer on the bottom walls thereof.
[0128] If support 1100 as shown in Figure 11 is modified to provide a thin conductive layer
overlying the bottom wall of each microcell 1106, the capability of uniform toning
described above is achieved. It is, of course, important that conductivity not extend
through or over the lateral walls 1108, although this may be occasionally employed
to a limited degree for specialized imaging effects.
[0129] After uniform electrostatic charging of the support 1100 similarly as the support
600 in Figure 15A, exposure in the direction of arrow 1126, as previously described,
allows radiation to strike only the bottom wall microareas 1128 of one set of microcells.
In Figure 15B it can be seen that in the absence of a conductive bottom wall electrostatic
charge is dissipated only in the radiation struck microareas; however, with a conductive
bottom wall present, electrostatic charge is drained from the entire bottom wall of
each microcell of the exposed set. Hence a second exposure of the exposed set of microcells
in the direction of the arrow 1130, as previously described, is not required and would
normally serve no useful purpose, although it is not precluded. Toning as described
in connection with Figure 15C results in a first composition, such as a red filter
composition, being deposited uniformly over the entire bottom wall of each microcell
of the exposed set. By repeating the above-described procedure twice more, exposing
from different directions and using different compositions, an element can be produced
as shown in Figure 14B. Although the above description refers specifically to support
1100, essentially the same procedure can be applied to supports 800, 900, 1200, and
1300. The procedure can be applied to support 1000 as well, although it does not require
this technique to achieve uniform toning of each microcell set.
[0130] The extent to which different compositions are interlaid on the supports can be varied,
depending upon the requirements of the contemplated application being served. For
photographic applications, it is preferred that each microarea corresponding to one
occurrence of an interlaid composition, hereinafter referred to as composition microareas
(as opposed to shadowing microareas, which can be smaller), be sufficiently small
that it cannot be readily resolved with the unaided human eye. In this way, for example,
interlaid blue, green, and red filter segments are readily fused by the human eye
on viewing. For ease of description, the size of composition microareas formed by
microgrooves is indicated in terms of the width thereof measured perpendicularly to
one lateral wall of the microgroove. The sizes of composition microareas formed in
microcells correspond to the diameter of a circle of equal area.
[0131] Where a photographic image is to be viewed without enlargement and minimal visible
graininess is desired, composition microareas having sizes within the range of from
1 to 200 microns, preferably from 4 to 100 microns, are contemplated for use in the
practice of this invention. To the extent that visible graininess can be tolerated
for specific photographic applications, the composition microareas can be still larger
in size. Where the photographic images produced are intended for enlargement, composition
microarea sizes in the lower portion of the size ranges are preferred. It is accordingly
preferred that the composition microareas be 20 microns or less in size where enlargements
are to be made of the images produced. Where the composition microareas of the support
provide a radiation-sensitive material to perform an imaging function, the lower limit
on the size of the microareas is a func- - tion of the photographic speed desired.
As the size of the microareas is decreased, the probability of an imaging amount of
radiation striking a particular microarea on exposure is reduced. Microarea sizes
of at least 7 microns, preferably at least 8 microns, optimally at least 10 microns,
are contemplated where the microareas contain radiation-sensitive materials of camera
speed. At sizes below 7 microns, silver halide emulsions in the microareas can be
expected to show significant reductions in speed.
[0132] In some of the preferred supports described above a single composition microarea
corresponds to the entire bottom wall of a microgroove or microcell. In this instance
the sizes of the microgrooves and microcells correspond to the stated sizes of the
composition microareas. In other supports a number of laterally displaced composition
microareas can be present in a single microcell or microgroove. For these supports
the microgrooves and/or microcells can range upward in size by a multiple of the number
of composition microareas contained.
[0133] The walls can be of any height convenient for shadowing. When lateral walls form
microgrooves or microcells, the height is chosen so that the microgrooves or microcells
can be of any necessary depth to contain the compositions intended to be placed therein.
It is generally preferred that the microgrooves or microcells be sized so that they
are entirely filled, although in some forms of the invention partial filling is contemplated.
In terms of actual dimensions, the height of the microcells is chosen as a function
of the compositions to be placed therein. For example, in photographic applications
the height of the microgrooves or microcells is chosen to permit the composition contained
therein to provide a desired optical density. The height of the lateral walls can
be less than, equal to, or greater than their lateral spacing. For photographic applications
the height of the lateral walls is typically chosen to correspond to the thickness
to which the same compositions are coated on planar supports. It is generally contemplated
that the height of the lateral walls (and hence the depth of the microcells or microgrooves)
will fall within the range of from 1 to 1000 microns.- For silver halide emulsions,
dyes, and dye image forming components commonly employed in conjunction with silver
halide emulsions, it is generally preferred that the lateral walls be in the range
of from 5 to 20 microns in height.
[0134] The thickness of the lateral walls can be varied, depending upon the application
and the effect intended. It is generally preferred for the practice of this invention
that the thickness of the lateral walls range from 0.5 to 5 microns, although both
greater and lesser thicknesses are contemplated. The bottom walls for photographic
applications normally occupy at least 50 percent (preferably at least 80 percent)
of the array area. The microcells can occupy as much as 99 percent of the support
area, but more typically in the practice of this invention occupy no more than 90
percent of the support area. In the preferred support configurations shown the microcells
and microgrooves are arranged in closely packed patterns which allow the lateral walls
to occupy the least possible area. It is recognized, however, that the microcells
and microgrooves can be separated by lateral walls of substantial thickness where
this-is not objectionable to the end use contemplated. In other words, closely packed
patterns are not essential.
[0135] In some instances the supports employed in the practice of this invention are identical
to those disclosed in European Specification 0,014,572. These supports can be prepared
by any of the techniques disclosed therein. Certain preferred supports employed in
the practice of this invention are similar to those previously disclosed, but differ
in the configuration of the lateral and bottom wall patterns. The preparation techniques
of said European Specification can be readily modified to prepare these supports.
Still other supports, such as those requiring conductive bottom walls in a photoconductive
support portion, require fabrication techniques not previously known to the art.
[0136] A preferred technique for forming lateral and bottom walls in the supports is to
form a plastic deformable material as a planar element or as a coating on a relatively
nondeformable support element and then to form the lateral and bottom walls in the
relatively deformable material by embossing. An embossing tool is employed which contains
projections corresponding to the desired shape of the bottom walls. The projections
can be formed on an initially plane surface by conventional techniques, such as coating
the surface with a photoresist, imagewise exposing in a desired pattern and removing
the photoresist in the areas corresponding to the spaces between the intended projections
(which also correspond to the configuration of the lateral walls to be formed in the
support). The areas of the embossing tool surface which are not protected by photoresist
are then etched to leave the projections. Upon removal of the photoresist overlying
the projections and any desired cleaning step, such as washing with a mild acid, base
or other solvent, the embossing tool is ready for use. In a preferred form the embossing
tool is formed of a metal, such as copper, and is given a metal coating, such as by
vacuum vapor depositing chromium or silver. The metal coating results in smoother
walls being formed during embossing.
[0137] In various forms of the supports described above the portion of the support forming
the bottom walls is transparent, and the portion of the support forming the lateral
walls is either opaque or dyed to interrupt light transmission therethrough. As has
been discussed above, one technique for achieving this result is to employ different
support materials to form the bottom and lateral walls of the supports.
[0138] A preferred technique for achieving dyed lateral walls and transparent bottom walls
in a support formed of a single material is as follows: A transparent film is employed
which is initially unembossed and relatively nondeformable with an embossing tool.
One or a combination of dyes capable of imparting the desired color to the lateral
walls to be formed is dissolved in a solution capable of softening the transparent
film. The solution can be a conventional p.lasticizing solution for the film. As the
plasticizing solution migrates into the film from one major surface, it carries the
dye along with it, so that the film is both dyed and softened along one major surface.
Thereafter the film can be embossed on its softened and therefore relatively deformable
surface. This produces dyed lateral walls and transparent bottom walls in the film
support.
[0139] To position a conductive layer on each bottom wall while avoiding conductively connecting
adjacent bottom wall areas, a continuous, thin conductive layer is first formed on
a planar surface of an embossable support. Although the conductive layer can be formed
by any convenient method, it is preferred to form the conductive layer by vacuum vapor
deposition, since this permits uniform layers which are very thin to be easily formed.
Generally preferred conductive vacuum vapor depositions are metals at coverages of
from 0.5 to 50 mg/dm
2, preferably 1 to 10 mg/dm
2. The embossing procedure described above is performed on the surface bearing the
conductive layer. This results in breaking the conductive layer into discrete segments
corresponding to the bottom wall areas, thereby obviating electrical conduction across
the lateral walls between adjacent bottom walls. The use of conductive layers as described
is particularly contemplated in combination with embossable photoconductive supports.
The conductive layer can be formed of any conductive material. Where the conductive
layer remains on the support after a photographic image is produced and viewing is
through the bottom walls of the support, the conductive layer is preferably of relatively
low optical density (e.g., less than 0.5). On the other hand, if reflection viewing
is contemplated and/or the conductive layer is removed before viewing, the optical
density of the conductive layer need not be limited. Silver conductive layers are
specifically preferred, since silver can be removed before the photographic element
is viewed by well known bleaching techniques.
[0140] Although certain combinations of materials offer distinct advantages in the practice
of this invention, not all the materials employed are in and of themselves new. Once
the principles of this invention are understood by those skilled in the art, selection
of materials for practicing a number of embodiments thereof can be readily. undertaken
from a general knowledge of photographic chemistry and, particularly, from a familiarity
with the teachings in European Specification 0,014,572.
[0141] The supports can be formed of the same types of materials employed in forming conventional
photographic supports. Such supports are disclosed, for example, in Research Disclosure,
Vol. 176, December 1978, Item 17643, paragraph XVII, here incorporated by reference.
Research Disclosure and Product Licensing Index are publications of Industrial Opportunities
Ltd., Homewell, Havant Hampshire, P09 1EF, United Kingdom. Polymeric film supports
and resin coated reflective supports are particularly preferred.
[0142] Second support elements, such as 308, which define only lateral walls can be selected
from a variety of materials lacking sufficient structural strength to be employed
alone as supports. It is specifically contemplated that the second support elements
can be formed using conventional photopolymerizable or photocrosslinkable materials--e.g.,
photoresists. Exemplary conventional photoresists are disclosed in Patents 3,640,722;
3,748,132; 3,696,072; 3,748,131; 3,699,025; 3,699,025; 3,699,026; 3,737,319; 3,748,133;
3,779,989; 3,782,938 and 4,052,367. Still other useful photopolymerizable and photocrosslinkable
materials are disclosed by Kosar, Light-Sensitive Systems: Chemistry and Application
of Nonsilver Halide Photographic Processes, Chapters 4 and 5, John Wiley and Sons,
1965. It is also contemplated that the second support elements can be formed using
radiation-responsive colloid compositions, such as dichromated colloids--e.g., dichromated
gelatin, as illustrated by Chapter 2, Kosar, cited above. The second support elements
can also be formed using silver halide emulsions and processing in the presence of
transition metal ion complexes, as illustrated by U.S. Patents 3,856,524 and 3,862,855.
Once formed, the second support elements are not themselves further responsive to
exposing radiation.
[0143] It is contemplated that the second support elements can alternatively be formed of
materials commonly employed as vehicles and/or binders in radiation-sensit.ive materials.
The advantage of using vehicle or binder materials is their known compatibility with
radiation-sensitive materials that may be used to fill the microcells. The binders
and/or vehicles can be polymerized or hardened to a somewhat higher degree than when
employed in radiation-sensitive materials to ensure dimensional integrity of the lateral
walls which they form. Illustrative of specific binder and vehicle materials are those
employed in silver halide emulsions, typically gelatin, gelatin derivatives, and other
hydrophilic colloids. Specific binders and vehicles are disclosed in Research Disclosure,
Vol. 176, December 1978, Item 17643.
[0144] Any conventional photoconductive material or combination of photoconductive materials
can be employed to form the bottom walls of the supports of this invention. Suitable
photoconductive materials are disclosed, for example, in Research Disclosure, Vol.
109, May 1973, Item 10938, Paragraph IV. Photoconductive materials which in themselves
are capable of forming lateral and bottom walls can be employed alone, as in the case
of polymeric organic photoconductors which are plastically deformable. The photoconductive
material is preferably incorporated in a separate insulative binder to form a support
having a lateral wall array, as disclosed by UoS. Patent 3,561,358. Preferred photoconductive
supports and support portions can be formed as taught by Contois et al, Research Disclosure,
Vol. 108, April 1979, Item 10823. Other support portions, such as the conductive layers
and base portions, can take any conventional form, exemplary materials being disclosed
in Research Disclosure, Item 10938, cited above, Paragraphs II Supports and III Interlayers.
[0145] In a specific preferred form at least the photoconductive portion of each support
is substantially transparent. Where the photoconductive material forms a part of a
multicolor reflective photographic print, for instance, even a slight coloration is
apparent to the human eye and therefore objectionable. For such applications, preferred
photoconductive materials are those sensitive to the ultraviolet portion of the spectrum,
but not sensitized to the visible spectrum, to avoid imparting a visible minimum density.
Such photoconductive materials can be exposed by shadowing techniques described above
using ultraviolet radiation.
[0146] In certain applications, as where radiation-sensitive materials are intended to be
located on the supports, it is not practical to use ultraviolet radiation to address
the photoconductive portion, since many radiation-sensitive imaging materials exhibit
a native sensitivity in the ultraviolet region of the spectrum. For example, silver
halide possesses a native sensitivity in the near portion of the ultraviolet spectrum.
For introducing each of blue, green, and red-sensitized silver halide into separate
sets of microareas, the photoconductive portion is preferably sensitized to the red
or a longer wavelength region of the spectrum. The first and second sets of microareas
can be addressed with a red light without fogging the blue and green-sensitized silver
halides introduced into the first and second sets of microareas. Even if a third exposure
is employed, the red-sensitized silver halide introduced into the third set of microareas
is not fogged, since the red-sensitized silver halide is not introduced until after
the third exposure is completed.
[0147] Sensitization of photoconductive materials to a selected portion of the spectrum
can be undertaken employing spectral sensitizing dyes well known in the electrographic
arts, such as those disclosed in Research Disclosure, Item 10838, cited above, Paragraph
IV-C. Any minimum density imparted by spectral sensitization need not be objectionable.
For example, if the photographic image to be produced is not intended to be viewed
directly, such as a multicolor negative image used for printing a multicolor positive
image, coloration due to spectral sensitization is not objectionable, since color
correction can be introduced in printing by procedures well known to those skilled
in the art.
[0148] The light transmission, absorption, and reflection qualities of the supports can
be varied for different applications. The supports can be substantially transparent
or reflective, preferably white, as are the majority of conventional photographic
supports. In every instance, however, the lateral walls must be capable of interrupting
radiation employed for shadowing exposures. The lateral walls of supports that are
otherwise transparent can in some applications contain dyes or pigments (colorants)
to render them substantially light impenetrable. Levels of dye or pigment incorporation
can be chosen to retain the light transmission characteristics in the thinner regions
of the supports--e.g., in the bottom wall region--while rendering the supports relatively
less light penetrable in thicker region (e.g., in the lateral wall regions). The lateral
walls can contain neutral colorant or colorant combinations. Alternatively, the lateral
walls can contain radiation absorbing materials which are selective to a single region
of the electromagnetic spectrum (e.g., blue dyes). The lateral walls can contain materials
which alter radiation transmission qualities, but are not visible, such as ultraviolet
absorbers.
[0149] Where the supports are formed of conventional photographic support materials, they
can be provided with reflective and absorbing materials by techniques well known by
those skilled in the art. In addition, reflective and absorbing materials can be employed
of varied types conventionally incorporated directly in radiation-sensitive materials,
particularly in second supports formed of vehicle and/or binder materials or using
photoresists or dichromated gelatin. The incorporation of pigments of high reflection
index in vehicle materials is illustrated, for example, by U.K. Patents 504,283 and
760,775. Absorbing materials incorporated in vehicle materials are illustrated by
U.S. Patent 2,697,037; colloidal silver (e.g., Carey Lea Silver widely used as a filter
for blue light); super fine silver halide used to improve sharpness, as illustrated
by U.K. Patent 1,342,687; finely divided carbon used to improve sharpness or for antihalation
protection, as illustrated by U.S. Patent 2,327,828; filter and antihalation dyes,
such as the pyrazolone oxonol dyes of U.S. Patent 2,274,782, the solubilized diaryl
azo dyes of U.S. Patent 2,956,879, the solubilized styryl and butadienyl dyes of U.S.
Patents 3,423,207 and 3,384,487; the merocyanine dyes of U.S. Patent 2,527,583; the
merocyanine and oxonol dyes of U.S. Patents 3,486,897; 3,652,284; 3,718,472 and the
enamino hemioxonol dyes of U.S. Patent 3,976,661; and ultraviolet absorbers, such
as the cyanomethyl sulfone-derived merocyanines of U.S. Patent 3,723,154; the thiazolidones,
benzotriazoles and thiazolothiazoles of U.S. Patents 2,739,888; 3,253,921; 3,250,617
and 2,739,971; the triazoles of U.S. Patent 3,004,896 and the hemioxonols of U.S.
Patents 3,125,597 and U.S. Patent 4,045,229. The dyes and ultraviolet absorbers can
be mordanted, as illustrated by U.S. Patents 3,282,699; 3,455,693 and 3,438,779.
[0150] In those instances in which an image-bearing photographic element according to this
invention is a multicolor negative intended to be used in printing a multicolor positive
image or a multicolor positive intended for projection viewing, it is preferred that
the walls between adjacent microareas exhibit an elevated optical density and, preferably,
the walls should be substantially opaque, but the bottom walls forming the microareas
should remain substantially transparent. Where the microareas are intended to contain
radiation-sensitive material, increasing the absorption of exposing radiation by the
walls can reduce halation and resulting loss of image definition. For each of these
purposes the walls are preferably of increased optical density, but the bottom walls
forming the microareas preferably remain substantially transparent. This can be achieved
by introducing a dye selectively into the walls of the support. In general any dye
which absorbs light over at least a portion of the visible spectrum and which can
interrupt radiation employed for shadowing exposures can be employed. Preferred dyes
for projection and printing applications are of neutral density. For antihalation
purposes, the absorption of the dye at least extends over a spectral region within
which the radiation-sensitive material exhibits an absorption peak. For example, dyes
which absorb in at least the blue portion of the spectrum are useful with radiation-sensitive
silver halides. Sudan Black B and Genacryl Orange are exemplary of useful absorbing
dyes for incorporation in lateral walls of otherwise transparent supports, particularly
the photoconductive supports.
[0151] Generally any conventional combination of materials known to be useful when related
in an interlaid pattern can be selected for incorporation in the separate sets of
microareas. Virtually any known additive primary dye or pigment can, if desired, be
selected for use in the multicolor filters described above. Further, the additive
primary color can be imparted by blending two subtractive primary dyes or pigments.
Additive and subtractive primary dyes and pigments mentioned in the Color Index, Volumes
I and II, 2nd Edition, are generally useful in the practice of at least one form of
the present invention.
[0152] For photographic applications it has been recognized that the incorporation of radiation-sensitive
and/or image-forming materials in microareas has the effect of limiting lateral image
spreading. Lateral image spreading has been observed in a wide variety of conventional
photographic elements. Lateral image spread can be a product of optical phenomena,
such as scattering of exposing radiation; diffusion phenomena, such as lateral diffusion
of radiation-sensitive and/or imaging materials in the radiation-sensitive and/or
imaging layers of the photographic elements; or, most commonly, a combination of both.
Lateral image spreading is particularly common where the radiation-sensitive and/or
other imaging materials are dispersed in a vehicle or binder intended to be penetrated
by exposing radiation and/or processing fluids. While the present invention can be
practiced with conventional radiation-sensitive and image-forming materials known
to be useful in photography, it is appreciated that materials which exhibit visually
detectable lateral image spreading are particularly benefited by incorporation into
microareas according to this invention.
[0153] A variety of useful nonsilver imaging materials useful in the practice of this invention
are disclosed by Kosar, Light-Sensitive Systems:
Chemistry and Application of Nonsilver Halide Photographic Processes, John Wiley and
Sons, 1965. Generally any imaging system capable of forming a multicolor image can
be applied to the practice of this invention. It is specifically preferred to employ
in the practice of this invention, radiation-sensitive silver halide and the image
forming materials associated therewith in multicolor imaging. Exemplary materials
are described in Research Disclosure, Vol. 176, December 1978, Item 17643. Particularly
pertinent are paragraphs I. Emulsion types, III. Chemical sensitization, IV. Spectral
sensitization, VI. Antifoggants and stabilizers, IX. Vehicles, and X. Hardeners, which
set out conventional features almost always present in preferred silver halide emulsions
useful in the practice of this invention.
[0154] In the image transfer element 1400 described above, the microcells 1106 form three
separate interlaid sets each containing a differing imaging composition. Each of the
imaging compositions contains (1) one or more immobile colorants collectively capable
of producing an additive primary color and/or (2) a subtractive primary dye or dye
precursor capable of shifting between a mobile and an immobile form as a function
of silver halide development, hereinafter collectively referred to as a colorant portion.
The preparation of the photographic element 1400 is described by reference to Figures
15A to 15D, above, using at least one and preferably three separate electrographic
imaging compositions.
[0155] Preferred electrographic imaging compositions are comprised of a colorant portion,
as described above, and from 0.1 to 10 (preferably 0.3 to 3.0) parts by weight per
part of the colorant portion of a resinous portion capable of forming a particulate
dispersion with the colorant portion in a liquid carrier vehicle having a dielectric
constant of less than 3.0 and a resistivity of at least 10
10 ohm-cm. At least one of the colorant and resinous portions is chosen to impart an
electrostatic charge of a selected polarity to the particulate dispersion in the liquid
carrier.
[0156] It is specifically contemplated to incorporate the radiation-sensitive imaging materials
in the colorant portion of electrographic imaging compositions as described above.
The appropriate proportion of radiation-sensitive materials to subtractive primary
dyes and dye precursors will be apparent from conventional photographic compositions,
where mole ratios of silver halide to subtractive primary dye or dye precursor ranges
from 1 to 100:1. For example, radiation-sensitive silver halide is commonly employed
in combination with dye-forming couplers in mole ratios of from 2 to 100:1, more typically
from 3 to 60:1; however dye-forming couplers require at least two equivalents of silver
to form one equivalent of image dye, whereas other subtractive primary dyes and dye
precursors provide at least theoretically image dye in a 1:1 molar ratio with silver
halide. Radiation- sensitive silver halide is typically formed in a peptizer, such
as gelatin, and can be incorporated in the colorant portion as an emulsion, wherein
the nonsilver or vehicle portion of the emulsion can be present in any conventional
weight ratio, typically up to 2:1.
[0157] The disclosure of the patents and publications cited above provide a variety of examples
of positive and negative-working dye image providing compounds which can be employed
as subtractive dyes or dye precursors in the electrographic imaging compositions of
this invention The colorant portion of the preferred electrographic imaging compositions
is additionally comprised of at least one immobile additive primary colorant or a
combination of immobile colorants capable of collectively providing a desired additive
primary color. Unlike the subtractive primary dyes and dye precursors, the immobile
additive colorants which provide an additive primary color should remain immobile
at all times and should not wander from the microcells either before, during, or after
a photographic image is obtained. Suitable immobile colorants can be selected from
among a variety of materials, such as dyes and pigments, but are most preferably pigments,
since these can be more readily obtained in highly immobile forms. Useful immobile
colorants can be selected from the Color Index, 2nd Edition, 1956, Vols. I and II.
Useful immobile polymeric dyes are illustrated by U.S. Patent 3,743,503. Specific
preferred immobile pigments are disclosed in Research Disclosure, Vol. 109, May 1973,
Item 10938, Paragraph IX-C-2. Exemplary of preferred green, red and blue immobile
pigments are Monolite Green (trade mark) GN, Red Violet MR (trade mark) (Hoechst),
Pyrazolone Red (trade mark) (Harmon), Alkali Blue MG (trade mark) (Sherwin- Williams),
and Monolite Blue (ICI). Exemplary of useful green, red, and blue substantially immobile
dyes are Renazol Brilliant Green 6B, Red Dye R3G (Drimarene Scarlet (trade mark) (Sandoz),
and MX-G Procion Blue (trade mark). The proportions of the subtractive.primary dye
or dye precursor to the immobile additive primary colorant can be varied as desired
to achieve an intended imaging result without the exercise of invention. The proportions
will vary, depending upon the specific materials selected. For most materials ratios
of subtractive primary dye or dye precursor to immobile additive colorant in the range
of from 1:10 to 10:1, most commonly 1:2 to 2:1, are operative, although optimum color
balancing for a specific application requires individual adjustment by empirical procedures
well known to those skilled in the art.
[0158] The resinous portion which together with the colorant portion forms dispersed particles
in the liquid electrographic developer is preferably insoluble in the liquid carrier
vehicle or only slightly soluble therein. Resinous materials acting as binders appear
to form a coating around the colorants and thus facilitate dispersion in the liquid
carrier. Examples of useful resins are: alkyd resins as described in Australian Patent
254,001; acrylic resins described, for example, in U.S. Patents 3,671,646 and 3,334,047;
alkylated polymers described, for example, in U.S. Patents 3,542,681 and 3,542,682;
rosins described, for example in U.S. Patent 3,399,140; polystyrene as described,
for example in Australian Patent 253,986 and U.S. Patent 3,296,140; addition polymers
containing a polar moiety as described, for example, in U.S. Patent 3,788,995; ethyl
cellulose described in U.S. Patent 3,703,400; cellulosic polymers as described, for
example, in U.S. Patent 3,293,183; polyamides, shellac as described, for example,
in U.S. Patent 2,899,335; waxes or rubber-modified polystyrenes as described, for
example, in U.S. Patent 3,419,411; rosin-modified as described, for example, in U.S.
Patent 3,220,830; silica aerogels as described, for example, in U.S. Patent 2,877,133;
halogenated polyethylenes described, for example, in U.S. Patent 2,891,911; graft
copolymers described, for example, in U.S. Patent 3,623,986; cyclized rubbers described,
for example, in U.S. Patent 3,640,863; vinyl polymers described, for example, in U.S.
Patent 3,585,140 as well as coumarone-indene resins; ester gum resins; and polymerized
blends of certain soluble monomers, polar monomers and, if desired, insoluble monomers
as described in Belgian Patent 784,367.
[0159] In order to exhibit electrographic properties, the imaging composition must have
an electrostatic charge when dispersed as particles in a liquid carrier. The colorants
can themselves impart the desired electrostatic charge to the dispersed particles.
The colorants are selected to exhibit a single polarity of charge to ensure the lowest
possible minimum densities. The electrostatic charge polarity of the dispersed particles
can be enhanced or controlled by the selection of resinious binder materials and/or
charge control agents. Illustrative charge control agents are the polyoxyethylated
alkyl surfactants such as polyoxyethylated alkylamine, polyoxyethylene palmitate,
and polyoxyethylene stearate. Other useful materials are magnesium and heavier metal
soaps of fatty and aromatic acids as described in U.S. Patents 3,417,019; 3,032,432;
3,290,251; 3,554,946; 3,528,097 and 3,639,246. Useful metal soaps include cobalt naphthenate
magnesium naphthenate, manganese naphthenate, zinc resinate, calcium naphthenate,
zinc linoleate, aluminum resinate, isopropyltitanium stearate, aluminum stearate,
and others many of which are also described in U.S. Patent 3,259,581. Typically, the
amount of such materials used is less than 2 percent by weight based on the weight
of the imaging composition. In certain instances, the resinous binder materials per
se can function as the charge control agent as disclosed, for example in U.S. Patent
3,788,995. A dispersing aid can also be added as shown, for example, in U.S. Patent
3,135,695. This patent shows an electrographic liquid developer prepared by surrounding
or dispersing electrographic-type pigment particles with a suitable resinous binder
envelope and treating the pigment-binder combination with a small amount of an alkylaryl
compound before suspending the combination in a liquid aliphatic carrier. This type
of liquid electrographic developer is especially useful due to its relatively high
stability. Other addenda may include: a phospholipid charge stabilizing material,
e.g., lecithin, as described in U.S. Patents 3,220,830; 3,301,677; 3,301,698; 3,241,957;
3,668,126 and 3,674,693, and U.K. Patent 1,337,325; noble metal salts as described
in French Patent 1,354,520, isocyanate compounds as described in U.K. Patent 654,977,
and U.S. Patent 3,383,316; magnetic particles as described in U.S. Patent 3,155,531;
conductive materials as described in U.S. Patents 3,300,410 and 3,409,358; fatty acid
esters as described in U.S. Patent 3,692,520; manganese salts as described in U.S.
Patent 3,438,904; antistain agents as described in U.S. Patent 3,681,243; and hydroxy-stearins
as described in U.S. Patent 3,701,731.
[0160] Conventionally, the liquid carrier vehicle used in liquid electrographic developers
has a low dielectric constant less than 3.0 and a resistivity of at least 10
8 ohm-cm, preferably at least 10
11 ohm-cm. These requirements automatically eliminate water and most alcohols. However,
a number of liquids still are available to satisfy the above-noted requirements and
have been found to function as effective carrier vehicles for liquid developers. Among
the various useful liquid carrier vehicles are alkylaryl materials such as the xylenes,
benzene, alkylated benzenes and other alkylated aromatic hydrocarbons such as are
described in U.S. Patent 2,899,335. Other useful liquid carrier vehicles are various
hydrocarbons and halogenated hydrocarbons such a cyclohexane, cyclopentane, n-pentane,
n-hexane, carbon tetrachloride, fluorinated lower alkanes, such as trichloromonofluorane
and trichlorotrifluorethane, typically having a boiling range of from 2°C to 55°C.
Other useful hydrocarbon liquid carrier vehicles are the paraffinic hydrocarbons,
for example, the isoparaffinic hydrocarbon liquids having a boiling point in the range
of 145°C to 185°C (sold under the trademark Isopar by Exxon) as well as alkylated
aromatic hydrocarbons having a boiling point in the range of from 157 to 177°C (sold
under the trademark Solvesso 100 by Exxon). Various other petroleum distillates and
mixtures thereof may also be used as liquid carrier vehicles. Additional carrier liquids
which may be useful in certain situations include polysiloxane oils such as dimethyl
polysiloxane as described in U.S. Patents 3,053,688 and 3,150,976; Freon (trade mark)
carriers as described in Canadian Patent 701,875 and U.S. Patent 3,076,722; mixtures
of polar and nonpolar solvents as described in U.S. Patent 3,256,197; aqueous conductive
carriers such as described in U.S. Patent 3,486,922; nonflammable liquid carriers
such as described in U.S. Patent 3,058,914; polyhydric alcohols such as described
in U.S. Patent 3,578,593; and emulsified carriers such as described in U.S. Patents
3,068,115 and 3,507,794. Electroscopic imaging composition can be dispersed in the
liquid carrier vehicle in any convenient conventional concentration, typically in
the range of from 0.01 to 10 percent by weight based on total weight. Conventional
techniques for dispersing the electrographic imaging composition can be employed,
as disclosed, for example, in Research Disclosure, Item 10938, cited above, Paragraph
IX-E and F.
[0161] In the foregoing discussion the direction of exposure of microcells which are oblong
or elongated has been illustrated by showing the direction of exposing radiation striking
the bottom wall of each of the microcells to be aligned with its major axis--that
is, the axis along which its length is measured. It is appreciated that the direction
of angled light exposure striking the bottom wall of an elongated microcell need not
be aligned with its major axis. Departure from alignment can be tolerated to the extent
that exposure of remaining sets of microcells not intended to be exposed does not
occur. In many instances distinct advantages can be realized by controlled departures
from major axis alignment during angled exposure.
[0162] Figures 16A to 16D illustrate how advantage can be realized by varying the alignment
of exposing radiation. In Figure l6A a microcell 1106 is shown having a portion of
its bottom wall exposed over a microarea 1136 similarly as has already been discussed
in connection with support 1100 as shown in Figure 11. Microarea 1136 accounts for
only about one quarter of the total bottom wall area of the microcell. By rotating
the microcell 180° it is possible to expose a second portion of the microcell equal
in area to microarea 1136 to provide an exposure pattern of the bottom wall as shown
in Figure 11. This, however, still leaves approximately half of the bottom wall area
unexposed.
[0163] In Figure 16B the result is shown of rotating the angle of exposure with respect
to the major axis of the microcell. If the angle of exposure is shifted as indicated
by arrow 1138a, then the portion 1136a of the bottom wall of the microcell exposed
is changed. If the direction of exposure is rotated in the opposite direction in reference
to the major axis, as illustrated by arrow 1138b, then an area 1136b of the microcell
bottom wall is exposed. It can be seen that the area 1136 occupies a greater percentage
of the bottom wall area than either of the areas 1136a or 1136b. Thus, choice of alignment
with respect to the major axis of the microcell can control the proportion of the
bottom wall of the microcell exposed.
[0164] It is to be noted that the areas 1136, 1136a, and 1136b overlap in part and in part
occupy different portions of the bottom wall of the microcell. It can also be seen
that at the exposure angle chosen with respect to the axial plane of the support each
of the areas exposed extend to the minor axis 1154 bisecting the microcell. It is
possible to expose identically all of the microcells 1106 of one set in support 1100
by using three different exposures in the directions indicated by arrows 1138, 1138a,
and 1138b. In this case the bottom wall exposure of each microcell 1106 is the sum
of the individual exposures. If, instead of exposing the one set of microcells 1106
three times, the support or the exposing radiation source is rotated during exposure,
a larger proportion of the bottom wall of each microcell can be exposed.
[0165] In Figure 16D the result is shown of rotating the support during exposure between
the exposure angle positions indicated by arrows 1138a and 1138b and then duplicating
the exposure from the opposite direction so that the half of each microcell originally
entirely shadowed is also addressed. Such procedure only addresses one set of microcells,
but all three set of microcells can be uniquely addressed by repeating the procedure
twice, as has been previously described in reference to Figure 11. In Figure 16D each
microcell is shown to have been addressed over a major portion of its bottom wall,
as indicated by microarea 1156 while only microareas 1160 are not addressed by exposing
radiation. In comparing Figure 16D with Figure 11 it can be seen that rotation during
exposure can be relied upon to increase greatly the proportion of the bottom walls
uniquely addressed. While, in theory, all of the bottom walls of each set can be entirely
uniquely addressed by the procedure described above, in practice the risk of inadvertently
exposing an additional set of microcells while addressing an intended set of microcells
increases as the angle of exposure departs from the major axis. For the particular
configuration shown in Figure 16D only a 30° departure from the major axis would achieve
exposure of the entire bottom wall without exposing any additional microcell set.
[0166] In Figure 17 the support 600 described above is shown with three interlaid sets of
microcells each entirely occupied by a green, red, or blue material. In discussing
the image transfer application of Figure 14A, it has been pointed out that, when subtractive
dyes or dye precursors are employed, it is essential that overlapping of these materials
in a controlled manner occur to permit the formation of a multicolor transferred image.
In Figure 14A a spacing layer 1454 is provided for the purpose of facilitating lateral
spreading during image transfer.
[0167] In Figure 18 support 1800 according to this invention is disclosed which differs
from support 600 only in distinctive features discussed. Specifically, the support
1800 forms a plurality of identical microcells 1802 each of which correspond to three
separate microcells 602. Initially the microcells are empty. By exposing the support
at an acute angle with respect to the axial plane of the support in the direction
indicated by arrow 1804 microareas B1 forming a portion of the bottom wall of each
of the microcells are uniquely addressed. The dashed lines 1806, 1808, and 1810 together
with two sides of each microcell circumscribe each exposed microarea Bl which is uniquely
addressed.
[0168] This initial exposure, however, leaves unaddressed each microarea B2, which desirably
should receive exposure along with each microarea Bl. The microareas B2 can be addressed
by repeating the first angled exposure, but only after the direction (but not the
acute angle) of exposure has been changed as indicated by arrow 1812. After exposure
in the directions indicated by arrows 1804 and 1812, each microcell can be provided
with a suitable imaging material in microareas B1 and B2.
[0169] During the above exposures the microareas R and G of the support remain entirely
in shadow and are not addressed. These microareas can be uniquely addressed by rotating
the support and repeating the exposure sequence described above. The result is to
create in a single microcell three materials laterally related similarly as in support
600, but not separated by a lateral wall (although adjacent microcells are separated
by lateral walls). If during imaging blue, green, and red colorants occupy the correspondingly
initialed microareas each associated with yellow, magenta, and cyan mobile dyes or
dye precursors, respectively, the result, when the support is substituted in Figure
14A for support 1100, is to permit lateral spreading of the subtractive primary dyes
or dye precursors to occur in a controlled manner within each microcell. This can
permit reduction in the thickness of the spacing layer 1454. As described in European
Specification 0,014,572 it is possible to confine also the layers 1452, 1454, and
1456 within microcells in a modified form of support 1450 and thereby further control
lateral spreading of the subtractive primary dyes or dye precursors during image transfer.
[0170] In addition to providing a useful imaging advantage the exposure procedure described
in connection with Figure 18 illustrates further the advantages that can be realized
according to the present invention when more than one direction of exposure is employed
to address what is intended to constitute a single set of microareas of the final
product. In the case of support 1800 changing directions of exposure permits the use
of the entire bottom wall area of the support, whereas this could not be otherwise
readily achieved.
[0171] In the foregoing discussion of the invention microcellular supports have been described
with specific reference to supports having three interlaid sets of microcells, since
multicolor photography typically employs a triad of color-forming units. In connection
with Figure 6A it has been pointed out that many microareas can be present within
a single microcell. Hence even though only three sets of microcells are present in
a support, it is apparent that a much larger set of microareas can be created by appropriate
addressing. Still, there are applications in which it is desirable to have more than
three sets of microareas and at the same time to have the microareas entirely laterally
separated by being positioned in separate microcells. This can be achieved according
to the present invention by providing four or more interlaid sets of microcells.
[0172] The use of four interlaid sets of microcells can be appreciated by reference to Figure
19, wherein a support 1900 is illustrated. Support 1900 is generally similar to support
1000, but differs in having four rather than three sets of microcells interlaid. The
supports 1900 and 1000 also differ in the relative position of the mirocells of the
different sets. Microcells 1906A, 1906B, and 1906C are identical to microcells 1006A,
1006B, and 1006C, respectively. In addition support 1900 contains a fourth set of
microcells 1906D. The dashed line indicates the boundary of a single pixel 1918. It
can be seen that each set of microcells within the pixel presents an approximately
equal area.
[0173] The microcells 1906D can be initially uniquely addressed by employing radiation directed
in any one or each of the directions indicated by arrows 1912D. The radiation is at
an acute angle with respect to the axial plane of the support, but the angle is limited
to prevent exposure of the bottom walls of the remaining microcells. After microcells
1906D have been exposed selectively to radiation, they can be filled by techniques
heretofore described. Thereafter microcells 1906A and 1906B can be addressed identically
as microcells 1006A and 1006B by employing radiation at an acute angle with respect
to the axial plane of the support in the directions indicated by arrows 1912A and
1912B. Exposure of the microcells 1906A and 1906B can be undertaken in any sequence.
In both cases radiation will also fall within the microcells 1906D; however, since
these microcells have already been filled, either the exclusion or the exhaustion
principles described above can be relied upon to avoid contamination of microcells
1906D with unwanted material. After microcells 1906A, 1906B, and 1906D have been addressed
and filled with material, the microcells 1906C can be addressed by radiation which
is directed substantially perpendicular to the axial plane of the support. All of
the microcells of the support are thereby addressed, but the exclusion or exhaustion
principle can be relied upon to avoid unwanted con- taminatin of the remaining microcells.
From the foregoing is is apparent that the support 1900 differs from support 1000
in providing four rather than three interlaid sets of microcells, thereby permitting
the formation of four sets of microareas each coextensive with one set of microcells.
[0174] An advantageous application of the support 1900 can be illustrated by substituting
the support 1900 for the support 1100 in Figure 14A. The contents of the microareas
of the suport 1100 labeled B, G, and R can be positioned in the microcells 1906A,
1906B, and 1906C, respectively, of the support 1900. The three sets of microareas
can each contain a silver halide emulsion responsive to the blue, green, and red portions
of the spectrum, respectively, and yellow, magenta, and cyan dye or dye precursor,
respectively. The microcells 1906D of the fourth set can contain a panchromatically
sensitized silver halide emulsion of higher speed than contained in the remaining
sets of microcells and a dye or dye precursor (which can be a combination of dyes
or dye precursors, if desired) capable of producing a substantially neutral hue, preferably
black. The silver halide emulsions and the dyes or dye precursors are chosen so that
the image transfer system is positive-working--that is, a positive transferred image
is produced in the dye immobilizing layer 1452.
[0175] Upon exposure and processing a transferred multicolor dye image is produced for viewing.
Absent the fourth set of microcells 1906D areas that have received little or no exposure
will appear black and nearly black. In conventional photographic elements this results
in many details being lost in shadowed areas--particularly where the photographic
subject spans the entire gamut from brightly lighted areas to deep shadows, as occurs
in a landscape scene on a bright day. However, by providing in the fourth set of microcells
a faster silver halide emulsion which modulates the transfer of neutral dye, it is
possible to define image that would otherwise be lost in shadow. The fact that the
observable shadowed detail will be near monochromatic constitutes no disadvantage,
since the eye tends to see highly shadowed subject features monochromatically. This
is attributable to the human eye's requirement for higher levels of lighting to perceive
images in color. Thus, the fourth set of microcells and microareas in the support
1900 can be applied usefully to extending the range of image definition. There are,
of course, many other useful applications for the support 1900, the above being merely
exemplary.
[0176] Although three and four interlaid sets of microcells have been demonstrated to be
useful in the practice of this invention, it is appreciated that larger numbers of
interlaid sets of microcells each capable of providing microareas isolated from other
microareas by lateral cell walls can be provided. This can be illustrated by reference
to Figure 20, wherein a pixel of a support 2000 is shown. To avoid needless repetition
in description, the support can be viewed as containing within the pixel four areas
1018 identical to pixels 1018 in Figure 10A. In addition the pixel is comprised of
an additional area 1018A which is similar to pixel 1018 in Figure 10A, but larger
in size. It can be seen that overall the pixel shown of the support 2000 contains
four microcells2004, four microcells 2005, and eight microcells 2006. Thus, in a support
2000 comprised of a large number of repeating pixels there are six distinct interlaid
sets of microcells present.
[0177] It is possible to address the microcells 2001 and 2002 in directions indicated by
the arrows contained therein without addressing the bottom walls of the remaining
microcells. The procedure for addressing and filling these microcells is essentially
similar to the description previously provided in connection with support 1000. Once
material is in place in microcells 2001 and 2002, microcells 2003 can be addressed
in any or all of the directions indicated by the arrows therein without exposing the
bottom walls of microcells other than those of microcells 2001 and 2002. However,
since these microcells have already been addressed, exclusion or exhaustion effects
can be relied upon to prevent their contamination with unwanted materials in filling
the microcells 2003. After microcells 2003 have been addressed and filled, the procedure
for addressing microcells 2001 and 2002 is repeated, but with exposures at an increased
acute angle with respect to the axial plane of the support. This permits the bottom
walls of the microcells 2004 and 2005 to be addressed without addressing the bottom
walls of the microcells 2006. In exposing the bottom walls of microcells 2004 and
2005 the bottom walls of the microcells 2001, 2002, and 2003 are addressed, but exclusion
or exhaustion effects can be relied upon to avoid contamination of these microcells
with unwanted materials. Microcells 2006 cannot be selectively addressed by radiation.
However, exposure substantially perpendicular to the axial plane of the support allows
these microcells to be addressed concurrently with the remaining microcells. Exclusion
or exhaustion effects can be relied upon to avoid contamination of the remaining microcells
with unwanted materials. Hence, it is possible to place six different compositions
selectively in six interlaid sets of microcells using the support 2000.
[0178] The advantages by the six interlaid sets of microcells of support 2000 can be illustrated
by reference to a specific imaging application. In conventional multicolor photographic
elements it is common practice to divide blue, green, and red recording silver halide
emulsions into faster and slower layers. It has been observed that this permits higher
photographic speeds to be obtained than when only one emulsion layer is provided to
record each third of the spectrum. Further, earlier in the discussion of the invention,
it has been pointed out that silver halide contained in microcells of less than 8
microns in average diameter will exhibit a loss of speed. Thus, a choice is required
between the best possible image definition afforded by the smallest possible microcells
and the highest attainable photographic speeds.
[0179] In one application the support 2000 can contain microcells 2001, 2002, and 2003 sized
so that they are sufficiently large to exhibit no adverse effect on the speed of silver
halide emulsions contained therein. Fast blue, green, and red-sensitive silver halide
emulsions can then be located in these microcells. Alternatively, a single panchromatically
sensitized relatively fast silver halide emulsion can be associated with these three
sets of microcells and blue, green, and red filters positioned in the individual microcells,
as has been previously described. The three sets of microcells contained in the areas
1018 can now be sized to provide the best possible sharpness for the image, but attaining
the highest possible speed need not be given importance, as the microcells in the
area 1018A can be relied upon for speed. Thus, in an illustrative application, the
microcells in areas 1018A can have an average diameter in excess of 20 microns while
the microcells in areas 1018 can have an average diameter of less than 10 microns
or even less than 7 microns. The same material can be placed in the microcells of
areas 1018A and 1018. Alternatively the silver halide emulsion or emulsions employed
in the areas 1018 can be slower than employed in the areas 1018A. In one preferred
form one set of microcells in each of the areas 1018A and 1018 together form a smooth
modulated blue characteristic curve, another set of microcells in each of the areas
1018A and 1018 together form a smooth green modulated characteristic curve, and a
third set of microcells in each of the areas 1018A and 1018 together form a smooth
red modulated characteristic curve.
[0180] Use of the support 2000 can be illustrated by considering its substitution for the
support 1100 in Figure 14A. Upon exposure through transparent bottom walls of the
support the silver halide emulsion responds in each of the microareas corresponding
to the microcells 2001, 2002, and 2003 to a different one of the blue, green, and
red portions of the spectrum and modulates the transfer of a complementary subtractive
primary dye or dye precursor. In so doing, the areas 1018A impart to the photographic
element its threshold speed. This is achieved to some extent by providing relatively
larger microcells in the areas 1018A as compared to the areas 1018 and therefore relatively
lower sharpness capabilities. However, lower sharpness is relatively unimportant in
the threshold regions of exposure as compared to sharpness in the mid-region of the
exposure scale.
[0181] During exposure silver halide emulsion in light struck microareas corresponding to
each of the microcells 2004, 2005, and 2006 similarly responds to a different one
of the blue, green, and red portions of the spectrum and modulates the transfer of
a complementary subtractive primary dye or dye precursor. It is the areas 1018 that
record mid-scale exposures. Since the microcells are relatively smaller in these areas,
a relatively sharper dye image is afforded by mid-scale exposures. Thus, the advantages
of high speed and sharpness are combined by employing a combination of six interlaid
sets of microcells.
[0182] It should be noted that in many conventional multicolor photographic elements there
are three separate color-forming units to record a single third of the spectrum. It
is therefore appreciated that nine interlaid sets of microcells could be employed
to provide the advantages obtained in conventional photography by dividing the blue,
green, and red color-forming units each into three separate emulsion layer components.
Even larger numbers of interlaid microcell sets are possible.
[0183] A further advantage of the invention can be appreciated by considering that in multicolor
photography in which retained dye images are formed it is common practice to provide
more than one blue, green, and/or red recording silver halide emulsion layer to achieve
maximum efficiency in imaging. However, in multicolor image transfer photography,
it is uncommon to divide the blue, green, and red recording silver halide emulsions
among separage layers, since in so doing the advantages in imaging are offset by the
increased numbers of layers required and the increase in the diffusion paths of the
dyes. By contrast, in the present invention, the diffusion paths for the dyes using
the support 2000 as described above are not appreciably longer than the diffusion
paths when the support 1100 is employed. Hence, it is an important advantage that
the offsetting disadvantages of multicolor color-forming units encountered in multicolor
image transfer photographic elements employing superimposed silver halide emulsion
layers are not encountered in the image transfer applications of this invention.
[0184] The invention can be more specifically appreciated by reference to the following
illustrative examples (Examples 1 to 10 describe the preparation of colorants used
in the invention):
Example 1 -- Preparation of Green Pigment Concentrates
[0185] A. Nine grams of a finely divided immobile particulate green pigment, Monolite Green
GN, were mixed with 4.5 grams of a copolymer of tert-butylstyrene and lithium methacrylate
along with 85.5 grams of Solvesso 100 (trade mark). The concentration was ball-milled
for two weeks at room temperature.
[0186] B. Eight grams of a finely divided immobile particulate green pigment, Monolite Green
GN, were mixed with 8.0 of a copolymer of tert-butylstyrene, lauryl methacrylate,
lithium methacrylate, and methacrylic acid in the weight ratio of 60:36:3.6:0.4 (hereinafter
designated TBS) and 72.0 grams of Solvesso 100. The concentrate was ball-milled for
two weeks at room temperature.
Example 2 -- Preparation of Red Pigment Concentrates
[0187] Nine grams of a finely divided immobile particulate red pigment, Pyrazolone Red (Harmon),
were mixed with 9.0 grams of TBS and 81.0 grams of Solvesso 100. The concentrate was
ball-milled for two weeks at room temperature.
Example 3 -- Preparation of Blue Pigment Concentrates
[0188] Five grams of a finely divided immobile particulate blue pigment, Alkali Blue MG
(Sherwin-Williams) were mixed with 5.0 grams of TBS and 45.0 grams of Solvesso 100.
The concentrate was ball-milled for two weeks at room temperature.
Example 4 -- Preparation of Mobile Magenta
Dye-Forming Coupler Concentrate
[0189] Four and one-half grams of a mobile magenta dye-forming coupler, 1-(2-benzothiazolyl)-3-amino-5-pyrazolone,
were mixed with 4.5 grams of TBS and 40.5 grams of Solvesso 100. The concentrate was
ball-milled for two weeks at room temperature.
Example 5 -- Preparation of Mobile Cyan Dye-Forming Coupler Concentrate
[0190] The procedure of Example 4 was repeated, except a mobile cyan dye-forming coupler,
2,6-di- bromo-l,5-naphthalenediol, was substituted for the magenta dye-forming coupler.
Example 6 -- Preparation of Mobile Yellow Dye-Forming Coupler Concentrate
[0191] A mobile yellow dye-forming coupler, a-(4-earboxyphenoxy)-α-pivalyl-2,4-dichloroacet-
anilide, in the amount of 3.14 grams was mixed with 3.14 grams of TBS and 28.3 grams
of Solvesso 100
0. The concentrate was ball-milled for two weeks at room temperature.
Example 7 -- Preparation of Green Pigment and Magenta Dye-forming Coupler Containing
Electrographic Imaging Composition Dispersed in Carrier Vehicle to Form Electrographic
Developer
[0192] A green pigment concentrate of Example 1 and the magenta dye-forming coupler concentrate
of Example 4 were mixed in equal weights of 3.85 grams each with 4.55 grams of a 10
percent by weight solution of a copolymer of ethyl acrylate, ethyl methacrylate, lauryl
methacrylate, and lithium sulfoethyl- methylacrylate in the proportion 46:16:12 weight
percent in Solvesso 100. To this mixture was added Isopar G (trade mark) at the rate
of 6 ml per minute for the first 50 ml and then at the rate of 15 ml per minute until
the volume of the developer reached 500 ml. This addition was performed under ultrasonic
shear.
Example 8 -- Preparation of Red Pigment and Cyan Dye-forming Coupler Containing Electrographic
Imaging Composition Dispersed in Carrier Vehicle to Form Electrographic Developer
[0193] The procedure of Example 7 was repeated, except a red pigment concentrate of Example
2 was substituted for the green pigment concentrate of Example 1 and the cyan dye-forming
coupler concentrate of Example 5 was substituted for the magenta dye-forming coupler
concentrate of Example 4.
Example 9 -- Preparation of Blue Pigment and Yellow Dye-forming Coupler Containing
Electrographic Imaging Composition Dispersed in.Carrier Vehicle to Form Electrographic
Developer
[0194] The procedure of Example 7 was repeated, except a blue pigment concentrate of Example
3 was substituted for the green pigment concentrate of Example 1 and the yellow dye-forming
coupler concentrate of Example 6 was substituted for the magenta dye-forming coupler
concentrate of Example 4.
Example 10 -- Preparation of Photoconductive Microcellular Support
[0195] A conventional planar photoconductive element consisting of a transparent 102 micron
thick poly(ethylene terephthalate) film base coated with a transparent 0.2 micron
cuprous iodide electrically conductive layer which was in turn overcoated with a 2
micron cellulose nitrate charge control barrier layer, and an 8 micron organic photoconductive
layer, was employed as a starting material. The photoconductive element is similar
to a commercially available recording film sold under the trademark Kodak Ektavolt
SO-101. The recording film and its characteristics are generally described in A Mini-Textbook--KODAK
Products for Electrophotography, Kodak Publication No. G-95, Standard Book Number
0-87985-233-X, Eastman Kodak Company, 1979. The conductive layer and film base extend
laterally beyond the photoconductive layer along one edge to allow convenient electrical
contact with the conductive layer.
[0196] A microcellular array was thermally embossed in the photoconductive layer of the
support. The microcellular pattern was similar to that shown in Figures 10A to 10C,
except that pixels were displaced along glide planes so that the second set of microcells
1006B were out of major axis alignment by one-half of their width. That is, viewing
Figure 10A, the microcells appearing above the horizontal dashed line were all displaced
to the right one width of the microcells 1006B from the position shown. The microcells
were 25 microns deep from the wall widths between adjacent microcells being 15 microns.
The inside width of the square microcells of the third set 1006C was 125 microns.
Thermal embossing was conducted at a temperature of 82.2°C and at a pressure of 172
kPa applied to the embossing master.
Example 11 -- Introduction of Imaging Compositions into Microcells of Support
[0197] The embossed photoconductive portion of the support was given a charge of +460 volts
by being passed through a corona discharge. The conductive electrode was attached
to ground. Except as stated, the support was exposed as shown in Figure 10B. A Xenon
arc lamp was employed controlled by an electronic shutter. Light was substantially
collimated and directed at an acute angle of 12° with respect to the axial plane 1014
of the support. After exposure the support was rotated 180° in the axial plane 1014
and exposed a second time. Each exposure was for 2 seconds, and the bottom walls of
the first set of microcells 1006A received during each exposure approximately 600
ergs/cm
2 in the areas exposed. Direct light exposure of bottom wall areas were limited to
the bottom walls of the first set of microcells. The 15 microns width of the lateral
walls was sufficient to prevent light exposure of the remaining sets of microcells
through the lateral walls.
[0198] After angled exposure of the first set of microcells was completed, the microcellular
support was electrographically developed using the electrographic developer of Example
8 and a development time of 15 seconds. A development electrode biased to +200 volts
was employed.
[0199] The procedure described in the two preceding paragraphs was repeated, except that
the electrographic developer of Example 9 was employed and the exposure was as shown
in Figure 10C rather than Figure 10B. That is, the second set of microcells 1006B
were selectively addressed and filled. Thereafter the support was again recharged
to +460 volts and exposed perpendicular to the axial plane 1014 at a distance of 15.24
cm to give an exposure of approximately 1,300 ergs/cm
2 using a UVL Mineralite. Development was repeated as described above, but using the
electrographic developer of Example 7. After each development step and prior to recharging
a forced air dryer was employed to evaporate developer solvent.
Example 12 -- Preparation of Photoconductive Support Having Hexagonal Microcells
[0200] A conventional planar photoconductive element similar to that described in Example
10 was solvent embossed using an embossing master having an array of hexagonal projections
20 microns in width and approximately 7 microns high. An embossing solvent was placed
on the plate between one edge of the array of projections and a strip of pressure-
sensitive tape employed to restrain migration of the solvent away from the projections.
A sheet of the recording film was placed on the plate with the photoconductive layer
adjacent the projections, and the resulting sandwich was advanced beneath a roller
with the edge bearing the embossing solvent passing beneath the roller first. The
pressure exerted by the roller and the softening action of the embossing solvent being
spread laterally at the roller nip resulted in a hexagonal array of microcells being
formed on the photoconductive layer having lateral bottom walls corresponding to the
walls of the hexagonal projections. The embossing solvent was a roughly equal volume
mixture of methanol and dichloromethane containing 0.2 gram per 10 ml of solvent Sudan
Black B (Color Index No. 26150). As a result, the lateral walls of the microcells
were dyed black, since the dye entered the photoconductive layer along with the embossing
solvent. The bottom walls of the microcells remained substantially transparent, however.
Example 13 -- Introduction of Imaging Compositions into Hexagonal Microcells of Support
[0201] The photoconductive portion of the support embossed with hexagonal microcells was
given a charge of +460 volts by being passed through a corona discharge. The conductive
electrode was attached to ground. Except as stated, the support was not identically
exposed to light to which the photoconductive portion was responsive. The positively
charged support was exposed as shown in Figure 6B. A Xenon arc lamp was employed controlled
by an electronic shutter. Light was substantially collimated and directed at an acute
angle of 26° with respect to the axial plane of the support. Exposure was in the direction
indicated by the arrow 1 in Figure 6B. The time of exposure was 0.3 second. Only the
bottom wall areas 1 were exposed. The microcellular support was electrographically
developed using the electrographic developer of Example 9 and a development time of
10 seconds. A development electrode biased to +200 volts was employed. The developer
solvent was evaporated using heated forced air. Material was selectively deposited
in the microareas 1 of the support.
[0202] The support was rotated 120° in the axial plane with respect to the light source,
and the procedure described above was repeated, but with the substitution of the electrographic
developer of Example 7 for the developer of Example 9. After the developer solvent
was evaporated, the support was again rotated 120° so that it occupied yet a third
position with respect to the light source, and the procedure described above was again
repeated, but with the substitution of the electrographic developer of Example 8.
The result was the selective placement of material in the microareas 1, 2, and 3 as
shown in Figure 6B in each of the hexagonal microcells.
Example 14 -- Formation of Screened Multicolor Positive Using Color Image Transfer
Photographic Element
[0203] Elements of the type produced by Examples 11 and 13 were employed to form a multicolor
screened positive using additive primary pigments and a transferred multicolor negative
using subtractive primary dyes formed by the mobile couplers.
[0204] The filled microcells were overcoated with a mixed silver sulfide and silver iodide
silver precipitating agent dispersed in 2 percent by weight gelatin using a 50 micron
coating doctor blade spacing. A commercially available black-and-white photographic
paper having a panchromatically sensitized gelatino-silver chlorobromide emulsion
layer was attached along an edge to the microcellular support with the emulsion layer
of the photographic paper facing the microcell containing surface of the support.
The photographic paper was imagewise exposed through the support (and therefore through
the filters formed by the pigments in the microcells) with the elements in face-to-face
contact. After exposure, the elements were separated, but not detached, and immersed
for 3 seconds in the color developer of Table 1.
Water to 1 liter Thereafter, the elements were restored to face-to-face contact for
1 minute to permit development of the imagewise exposed silver halide and image transfer
to occur. The elements were then separated, and the silver image was bleached from
the photographic paper. A three-color negative image was formed by subtractive primary
dyes in the photographic paper while a three-color screened positive image was formed
by the additive primary filters and the transferred silver image on the microcellular
support.
Example 15 -- Formation of Transferred Multicolor Positive
[0205] Example 12 was repeated, but with a silver halide emulsion layer coated over the
filled microcells and the silver nucleating agent layer being coated on a separate
planar film support. The emulsion layer was a high-speed panchromatically sensitized
gelatino-silver halide emulsion layer coated with a 150-micron coating doctor blade
spacing. The color developer was of the composition set forth in Table II.
Both elements were immersed in the color developer for 5 seconds and thereafter held
in face-to-face contact for 2 minutes. A screened three-color negative was obtained
on the microcellular support and a transferred positive silver and multicolor positive
dye image was obtained on the planar support.