[0001] This invention relates to electrostatic printing and, more particularly, to an improved
electrostatic printing master adapted for the use of conventional silver halide photographic
techniques during preparation of the master for printing.
[0002] Electrostatic printing is well-known in the art and has been proposed as an alternative
to other printing techniques. In one method of electrostatic printing, one first prepares
a "master" that is capable of selectively holding electrostatic charges to form the
desired image. The master is exposed to a corona discharge that forms a latent electrostatic
image, and contacted with dry or liquid toner of the opposite electrostatic charge
to develop the image. The toned image is then transferred to a substrate, typically
paper, where the toner is fused to fix the image, and the master is returned for the
next printing cycle.
[0003] It has been suggested in U.S. Patent 4,069,759 that an improved electrostatic printing
master can be fabricated by dispersing a conventional silver halide photographic salt
in an insulating polymer (e.g., gelatin), and coating the dispersion on a conducting
substrate. The coating is exposed imagewise, and is developed to cause the exposed
silver halide to be reduced to metallic silver. The unexposed silver halide is then
dissolved and removed from the coating to fix the image. While the master suggested
in U.S. Patent 4,069,759 offers many advantages, and permits the use of conventional
aqueous silver halide photographic chemistry when gelatin is selected as the insulting
polymer, it has been found that gelatin is too highly sensitive to humidity to have
practical application in a typical workplace. Gelatin rapidly absorbs moisture from
the air and at moderate to high humidities no longer functions as an insulating medium,
but provides a conductive path that grounds surface charges imposed on the master
during the electrostatic printing process.
[0004] US-A-1981102 relates to binders for silver halide materials with improved mechanical
properties. The binders disclosed include polyacrylic acid, other polymeric carboxylic
acids, copolymers of carboxylic acids with styrene and the salts of these polymers.
[0005] Thus, there is a need for an improved electrostatic printing master that will offer
the advantages of being based on conventional aqueous silver halide photographic chemistry
and provide superior insulating properties under relative humidity conditions commonly
encountered during printing.
SUMMARY OF THE INVENTION
[0006] This invention provides a photosensitive composition adapted for use in preparing
an electrostatic printing master, the composition consisting essentially of a silver
halide photographic salt dispersed in an insulating polymeric binder that is swellable
in aqueous photographic processing solutions having a pH higher than approximately
8-1/2, and retains significant insulating properties under relative humidity conditions
normally encountered during the printing process. The composition has an insulation
value such that it will support an apparent macroscopic electric field of at least
five (5) volts/micron (micrometer), as measured by an electrostatic surface voltage
probe two (2) seconds following full charging of its surface that has been allowed
to equilibrate at 50% relative humidity at 20°C for an hour. Common photographic gelatin,
practically the only medium conventionally used for wet processing, holds approximately
one (1) volt/micron or less after equilibration under these test conditions. Since
the binder is swellable under pH conditions higher than approximately 8-1/2, conventional
aqueous silver halide developing solutions can be used to process the master for use
in electrostatic printing. Copolymers of acrylic or methacrylic acid having acid numbers
in the range of 70 to 160 are a preferred binder that may be selected in practicing
the invention. The silver halide/binder composition is typically coated onto a conducting
substrate, which may be mounted on a flexible support, for use as an electrostatic
master. After the master is imaged with actinic light, the master is developed to
contain a silver image using conventional aqueous silver halide developing and fixing
chemistry.
[0007] In a second embodiment, a diffusion transfer film is prepared by coating the polymeric
binder which contains development nuclei onto a conductive support, and overcoating
the binder with a conventional silver halide photographic emulsion. The photosensitive
element is exposed and then developed using conventional diffusion transfer techniques
to provide an imaged electrostatic master.
[0008] In a third embodiment the invention relates to a film comprising a conductive substrate
that bears a coating consisting essentially of a silver grain image dispersed in a
synthetic insulating polymeric binder that is swellable in aqueous solutions having
a pH higher than approximately 8-1/2, said binder being a copolymer of an unsaturated
carboxylic acid monomer and an aromatic monomer and having ionizing carboxylic acid
groups, said composition having an insulation value such that it will support an apparent
macroscopic eletric field of at least approximately five (5) volts/micron as measured
2 seconds following full charging of its surface that has been allowed to equilibrate
to 50 % relative humidity at 20°C for 1 hour.
[0009] As used herein, the term "electrostatic master" refers to the film element that will
be used for electrostatic printing, whether the film element contains silver particles
in the form of the desired image, and thus is ready for the printing process, or contains
silver halide particles that yet have to be exposed and/or developed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 is a schematic sectional view of an electrostatic printing master in which
a silver halide photographic salt is dispersed in the insulating binder to form photosensitive
layer 1.
[0011] Figure 2 shows the master of Fig. 1 in which a latent image has been formed and developed.
[0012] Figure 3 shows the master of Fig. 2 after the image has been fixed.
[0013] Figure 4 shows the master of Fig. 3 after being charged.
[0014] Figure 5 illustrates the master of Fig. 4 in which toner particles have been attracted
to the charged surface.
[0015] Figure 6 is a schematic sectional view of a second embodiment in which the photosensitive
layer 8 is a diffusion transfer film.
[0016] Figure 7 shows the embodiment of Fig. 6 in which the diffusion transfer film has
been imaged and development has commenced.
[0017] Figure 8 shows the embodiment of Fig. 7 after development is complete.
[0018] Figure 9 shows the embodiment of Fig. 8 after the photosensitive layer 8 has been
removed, at which time it is ready to be used as an electrostatic master.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The use of conventional aqueous silver halide photographic chemistry ideally serves
the requirements for the preparation of electrostatic printing masters, particularly
when high resolution is required for high-quality half-tone or continuous-tone applications.
Sharp image resolution can be obtained due to the fine grain size of silver that may
be obtained when using aqueous photographic chemistry well known in the art.
[0020] Insulting binders that may be selected in practicing the invention are "swellable"
in aqueous solutions having a pH higher than approximately 8-1/2, typically in the
range of 9 to 14, that are common to conventional aqueous developing solutions used
in silver halide photography. By "swellable" it is meant that the binder readily takes
up water, and indeed swells in this pH range similar to gelatin. When using preferred
polymers described hereinafter, swelling is accomplished by ionizing acidic groups
(usually carboxylic acid groups that are chemically bonded to the insulating binder)
by basic solutions at a pH of approximately 8.5 or higher. This characteristic permits
the aqueous developer (reducing) solution to come into intimate contact with the silver
halide. When negative working silver halide emulsions are used, the exposed silver
halide is reduced by developer solutions to metallic silver and complexing agents
dissolve the unexposed silver halide salt. When positive working silver halide emulsions
are used (e.g. those prepared by such well-known techniques as solarization or chemical
fogging) the unexposed silver halide is reduced to metallic silver and the exposed
silver halide is removed.
[0021] In the embodiment described in greater detail hereinafter in which negative working
silver halide is dispersed in the insulating binders provided by the invention, developer
above approximately pH 8.5 swells the binder and reduces exposed silver halide to
metallic silver and complexing agents, usually in a fixer solution, remove unexposed
silver halide. In the diffusion transfer embodiment where negative working photosensitive
silver halide is in an emulsion layer (usually gelatin) that is separate from the
insulating binder containing a fine dispersion of development nuclei, developer solution
having a pH above approximately 8.5 swells both the emulsion layer and insulating
binder layer provided by this invention, thereby developing the exposed silver halide
to metallic silver in the emulsion layer and dissolving the unexposed silver halide
with complexing agents ("silver solvents"). The complexed unexposed silver halide
then diffuses into the swollen binder layer wherein the silver ions are selectively
reduced to silver metal on the development nuclei.
[0022] Although the insulating binders are swellable in the developing solution, the insulating
properties do not drastically deteriorate as those of gelatin do under typical humidity
conditions encountered in the workplace. As a consequence, the binders will retain
an applied charge during electrostatic printing and it is not necessary to provide
special humidity controls or dry the master before each printing cycle, as would be
necessary using a gelatin binder.
[0023] The binders generally are characterized as being capable of supporting an apparent
macroscopic electric field of at least 5 volts per micron, and preferably at least
30 volts per micron, as measured by an electrostatic surface voltage probe two (2)
seconds following full charging of the surface after the surface has been allowed
to equilibrate, and thus absorb moisture, at 50% relative humidity and 20°C. Equilibration
for testing purposes will normally occur within approximately 60 minutes. In contrast,
gelatin is significantly inferior and exhibits an apparent macroscopic electric field
in the order of approximately one (1) volt per micron or less under this test procedure.
[0024] It has been found that synthetic polymers having an acid number of approximately
70 to 160 are particularly useful in practicing the invention. A preferred class of
polymers contains 10 to 25% by weight of acrylic or methacrylic acid to impart swellability.
The polymer typically will also contain styrene, or other aromatic monomers, that
are not compatible with water, and thus render the polymer less hydrophilic to moisture
in the air. Generally, the polymer will also contain monomers, such as appropriate
acrylic or methacrylic esters, that contribute to film clarity, flexibility, toughness,
processibility, etc. Other comonomers, such as alkenes having 2 to 12 carbon atoms,
haloolefins, vinyl acetate, vinyl ethers having 3 to 12 carbon atoms, methacrylamide,
and the like can be similarly useful.
[0025] Preferred polymers are copolymers containing styrene and acrylic or methacrylic acid
monomers, and preferably also an acrylic or methacrylic ester monomer. Polymers containing
25 to 35% by weight styrene, 10 to 25% by weight acrylic or methacrylic acid, with
the remainder comprising acrylic or methacrylic esters, are particularly preferred.
The molecular weight of the preferred copolymers will typically be in the range of
25,000 to 150,000. These polymers are compatible with silver halide dispersions, will
form reasonably durable films that have clarity, and are readily available from commercial
sources, or can be made using conventional techniques such as free radical polymerization
in suspension or emulsion. Equivalent polymers that will be useful in practicing the
invention will be readily apparent to those skilled in the art. These polymers include
acrylic acid and methacrylic acid polymers and copolymers, and include commercially
available polymers such as Carboset® 525 and Carboset® 526 manufactured by B. F. Goodrich
Company, and Joncryl® 67 manufactured by Johnson & Johnson.
[0026] A preferred class of polymers constitutes terpolymers and tetrapolymers of (1) a
styrene-type monomer, (2) and acrylate-type monomer, and (3) an unsaturated carboxyl-containing
monomer. The first component lends hardness and moisture resistance to the polymer;
the second, flexibility and plasticity to the polymer backbone; and the third, alkali-swellability.
The styrene-type monomer will typically be styrene, an alpha-substituted styrene having
a 1 to 6 carbon alkyl group, and those wherein the benzene ring has functional substituted
groups such as nitro, alkoxy, acyl, carboxy, sulpho, or halo, with simple compounds
such as styrene, alphamethyl styrene, para-methyl styrene and para-t-butyl styrene
being preferred. The acrylate-type component includes alkyl and hydroxyalkyl acrylates
and methacrylates wherein the alkyl group has from 1 to 12, preferably from 1 to 6
carbon atoms such as methyl methacrylate, ethylmethacrylate, ethyl acrylate, hydroxypropyl
methacrylate, hydroxyethyl methacrylate and hydroxyethyl acrylate, and mixtures thereof.
The unsaturated carboxyl-containing monomer will typically be a monomer having from
3 to 15 carbon atoms, preferably 3 to 6, and includes cinnamic acid, crotonic acid,
sorbic acid, itaconic acid, maleic acid, fumaric acid, or more preferably acrylic
or methacrylic acid, their corresponding half ester or the corresponding anhydride.
[0027] When this class of polymer is selected in practicing the invention, the ratio of
the three monomer components is selected such that the conductive film element has
the following properties: the silver halide, when incorporated into the conductive
film element, is processible by conventional aqueous photographic techniques; the
electrostatic master made therefrom retains applied charges in the nonsilver areas
under ambient relative humidity conditions; and the electrostatic master is flexible
and durable, but not tacky. Typical proportions used to achieve these results are
shown in Table 1:
Polymers within this class also generally offer the advantage of being insensitive
to Isopar®, the commonly used carrier employed in liquid toning systems.
[0028] Insulating polymeric binders described above are made by conventional free-radical
polymerization techniques, as illustrated in the examples. These polymers are soluble
in basic solutions and can be coated from aqueous solutions of triethylamine, ammonia,
or potassium hydroxide, and the like. These polymers are compatible with silver halide
dispersions and will form reasonably durable films that have clarity. It may be desired
to modify the binder (crosslink, harden, plasticize, adjust acidity, etc.) prior to
aqueous photographic processing, and thereby control swelling or improve durability.
Various modifying agents may be added for these purposes. Typical modifying agents
include aldehydes, multifunctional aziridines, and epoxides. The diglycidyl ether
of 1,4-butanediol is a preferred modifying agent for this class of polymers in practicing
the invention.
[0029] Equivalent polymers that achieve the balance of properties described above will be
apparent to those skilled in the art, and may be selected in practicing the invention.
[0030] The light sensitive silver halide selected for dispersion in the binder can be any
of the well-known salts used in photographic applications. Representative useful salts
include silver chloride, silver bromide, silver iodide, silver chlorobromide, silver
iodobromide, and silver chloroiodobromide, either singly or in mixtures. Precipitation
of the halide is carried out in conventional manner in gelatin. The amount of gelatin
present should be limited, or subsequently reduced by rinsing, to avoid defeating
purposes of the invention. Generally, levels of gelatin as high as 3 to 15 grams per
mole of silver can be tolerated in the electrostatic printing masters, without adverse
effect.
[0031] Grain size distribution and sensitization of the silver halide can be controlled
to adapt the silver halides for the selected class of photographic process, including
general continuous tone, X-ray, lithographic, microphotographic, direct positive,
and the like. Ordinarily, the silver salt dispersions will be sensitized with conventional
compounds such as sulfur, gold, rhodium, selenium and the like, or with organic sensitizing
dyes such as cyanine, 1,1ʹ-diethyl-4,4ʹ-cyanine iodide, methine and polymethine cyanine
dyes, kryptocyanines, merocyanines, and the like. Other additives commonly employed
in silver halide photographic compositions, may also be present if desired.
[0032] To prepare the dispersion of silver halide in the insulating polymeric binder, the
binder is conveniently first dissolved in an aqueous solution containing amines, such
as ammonia or triethyl amine. If desired, an alcohol, such as methanol, ethanol, or
isopropanol, may be added to aid in solubilizing the polymer. Ketones, such as methyl
ethyl ketone, may be used as a cosolvent. An aqueous dispersion of the silver halide
salt is then added to the dissolved binder in the desired quantities. The respective
portions of silver halide to binder will depend on details of the application, but
will generally be such that surface of the master immediately above the developed
silver will discharge significantly faster than areas devoid of silver. Weight ratios
of silver to polymeric binder in the range of 0.5:1 to 3:1 will typically provide
useful results. A preferred range is 1.7:1 to 2.3:1.
[0033] The polymeric binder containing the silver halide is usually applied to a conductive
substrate as a solution or dispersion in a carrier solvent, usually an aqueous solution
containing basic amines or sodium or potassium hydroxide as described above. The coating
procedure may be any conventional one including spraying, brushing, applying by a
roller or an immersion coater, flowing over the surface, picking up by immersion,
spin coating, air-knife coating, wire-bar coating or any other suitable means. The
film thickness can be adjusted accordingly and after drying is usually about 0.02
to about 0.3 mils (0.5-7.5 microns), preferably about 0.04 to about 0.20 mils (1.0-5.0
microns). Depending on the application, the conductive support may be a metal plate,
such as aluminum, copper, zinc, silver or the like; a conductive polymeric film; a
support such as paper, glass, synthetic resin and the like which has been coated with
a metal, metal oxide, or metal halide by vapor deposition or chemical deposition;
a support which as been coated with a conductive polymer; or a support which has been
coated with a polymeric binder containing a metal, metal oxide, metal halide, conductive
polymer, carbon, or other conductive fillers.
[0034] In addition to components described above, various conventional photographic additives,
e.g., developing agents, super additives, antifoggants, coating aids such as saponin,
alkylarylsulfonic acids or sulfoalkylsuccinic acids; plasticizers such as glycerol
or 1,5-pentanediol; antistatic agents; agents to prevent the formation of spots; antihalation
dyes; underlayers, subbing or backing layers; and the like may be added to the master
as appropriate. Positive images may be obtained by reversal processing of the silver
halide using either light fogging or a chemical fogging agent; or by using silver
halide emulsions that give direct positive images using the prefogging technique.
Direct positive emulsions have been described in Leersmaker U.S. Pat. No. 2,184,013,
Illingsworth U.S. Pat No. 3,501,307 and elsewhere.
[0035] Referring now to the drawings, Figure 1 depicts an electrostatic printing master
in which photosensitive layer
1 contains sensitized silver halide dispersed in the insulating polymeric binder in
accordance with the invention. Layer 1 is generally between 0.5 and 7.5 microns in
thickness, but the thickness can be decreased or increased for the specific intended
application. A thin layer
2 of an adhesion promoter such as gelatin, which is optional, aids adherence of the
photosensitive layer to the conducting substrate
3, which in turn is mounted on supporting substrate
4.
[0036] The master is exposed imagewise using any of the procedures commonly used with silver
halide photographic materials, such as by imaging with actinic light, a cathode ray
tube, or laser. For negative-working emulsions the latent image
5 is then developed by reducing the exposed silver halide particles to metallic silver
using a conventional aqueous developing solution, as illustrated in Figure 2. A conventional
aqueous fixing solution, such as sodium thiosulfate, is then used to remove the unexposed
silver halide particles, as illustrated in Figure 3. The developed master is then
ready for the electrostatic printing process.
[0037] Figure 4 illustrates the master of Figure 3 after it has been charged by a corona
discharge that deposited positive charges
6 on the master surface. The area of the film that contains silver
5 provides a pathway for overlying charges to pass to ground, thus forming a latent
image of charges that remain on the master surface. Alternatively, charging can be
accomplished with the use of a negative corona discharge, shielded corotron, scorotron,
radioactive source, contact electrodes such as electrically biased semiconductive
rubber rollers, and the like.
[0038] The latent image is then developed with liquid or dry toner
7 of the opposite polarity, as illustrated in Figure 5. Cascade, magnetic brush, powder
cloud, liquid, magne-dry and wetting development techniques are suitable. Representative
dry toners that may be used include Kodak Ektaprint K toner, Hitachi HI-Toner HMT-414,
Canon NP-350F toner, and Toshiba T-50P toner. Examples of suitable liquid toners are
Savin 24 toner, Canon LBP toner and James River Graphics T1818 toner. The latent image
so developed ("toned") is transferred to the usual substrate, typically paper, where
it is fixed in conventional fashion.
[0039] Figures 6 through 9 illustrate a second embodiment wherein conventional diffusion
transfer techniques such as those described in U.S. Patent 2,352,104 and 2,983,606,
are used to prepare an imaged electrostatic printing master of dispersed silver in
the insulating synthetic binder previously described. In this embodiment, the insulating
synthetic binder
9, approximately 0.25 to 3 microns in thickness, contains dispersed development nuclei,
and a photosensitive layer
8 containing silver halide salts dispersed in a hydrophilic colloid that overlays the
binder, wherein the ratio of silver to binder
9 is 1:1 to 5:1. A conductive layer
3 and substrate
4 are employed as hereinbefore described. Suitable development nuclei are well-known
in the art, and typically will be (1) a metal, such as silver, gold, and rhodium;
(2) sulfides, selenides, tellurides, polysulfides, or polyselenides of metals including
silver, zinc, chromium, gallium, iron, cadmium cobalt, nickel, manganese, lead, antimony,
bismuth, arsenic, copper, rhodium, palladium, platinum, lanthanum, and titanium; (3)
easily reducible silver salts which form silver nuclei during processing, such as
silver nitrate or silver citrate; (4) inorganic salts which react with the incoming
diffusing silver salts to form nuclei; and (5) organic compounds which (a) contain
a labile sulfur atom and which therefore lead to the formation of sulfide nuclei during
processing, including mercaptans, xanthates, thioacetamide, dithiooxamide, and dithiobiurate
or (b) are reducing agents such hydrazine derivatives or silanes and give rise to
silver nuclei when evaporated onto silicic acids or barium sulfate. Likewise the hydrophilic
colloid can be any of the substances commonly used in diffusion transfer processes,
such as gelatin, phthalated gelatin, cellulose derivatives such as carboxymethylcellulose
and hydroxymethylcellulose, and other hydrophilic high molecular weight colloidal
substances such as dextrin, soluble starch, polyvinyl alcohol, or polystyrenesulfonic
acid.
[0040] Referring to Figure 7, photosensitive layer
8 is imaged in conventional fashion to form a latent image with the sensitized silver
halide. For negative-working emulsions the photosensitive layer is then treated with
a developing agent that reduces the exposed silver halide to metallic silver, in area
10, and an aqueous solvent composition that converts silver halide in the unexposed
areas to form a soluble silver halide complex that diffuses into the binder of layer
9 where it contacts the development nuclei and is reduced to insoluble silver particles
11, forming a silver image. Layer
8 is then removed as illustrated in Figure 9, resulting in an electrostatic master
that is ready for printing in conventional manner. Developing baths for the diffusion
transfer process are well known in the art and are described, for example, in
Photographic Silver Halide Diffusion Processes by Andre Rott and Edith Weyde (Focal Press, 1972) and
Modern Photographic Processing, Vol. 2 by Grant Haist (Wiley, 1979).
[0041] Many additional embodiments will be evident to those skilled in the art. For example,
a positive-working silver halide emulsion can be used in conjunction with the diffusion
transfer coating
8 illustrated in Figures 6 through 9, and the exposed silver halide can be complexed
in aqueous solutions to diffuse into the insulating binder layer
9, where it is reduced by the development nuclei to form the desired silver image.
Similarly, a separate photosensitive film can be employed in lieu of coating
8, and brought into operative association with the insulating binder
9 before or after imaging, as in photomechanical transfer. The photosensitive silver
halide emulsion layer or coating
8, and the insulating polymeric binder layer
9 may also contain compounds commonly used in diffusion transfer systems provided that
the specific ingredient does not adversely affect insulating properties of the binder
or conductive properties of the silver-containing area
11 of the electrostatic printing master. Thus, appropriate antifogging agents, such
as tetraazaindenes and mercaptotetrazoles, coating aids, such as saponin and polyalkylene
oxides, hardening agents, such as formaldehyde and chrome alum, and plasticizers may
be employed if desired. The substrate
4 also can be transparent if the master is to be used as a phototool or for graphic
arts applications.
[0042] Various conventional methods can be selected for toning the electrostatic printing
master. If the toner particles are electrically conductive and essentially neutral,
or charged opposite of the latent image, they will adhere to the charged latent image.
If the toner is charged with the same polarity as the charged latent image, the toner
will adhere to the uncharged portion. A development electrode can be used to improve
the quality of the toned image; i.e., to facilitate uniform toning of solid image
areas having latent electrostatic charge and to prevent background toning in image
areas that contain no charge. Transfer of the toned image to the desired substrate,
typically paper, can be assisted by using a corona discharge of opposite polarity
on the opposite side of the substrate. Alternatively, toner transfer can be accomplished
with a conductive roller that is electrically biased, adhesive film and paper, and
the like. The toner image thus transferred can be fixed by a technique conventionally
known in the art. Usually, heating fixation, solvent fixation, pressure fixation and
the like are employed. If necessary, the surface of the master may be cleaned by using
a cleaning means such as a brush, cloth, a blade, a vacuum knife and the like to remove
the remaining toner image.
[0043] Electrostatic printing masters offer several advantages over those described in the
prior art. Since conventional aqueous development and fixing techniques remove byproducts
that are soluble in the solution used for those purposes, the master does not contain
byproducts that might interfer with the insulating properties of the binder or conductive
path of the developed silver image, a situation that may be encountered using the
dry silver halide development techniques described in U.S. Patent 4,069,759. Also,
the insulating property of the binders selected in accordance with the invention is
less sensitive to moisture which can interfere with the electrostatic printing process,
and thus the master can be used repetitively or after storage without the need to
heat the master to remove moisture or to undertake special humidity controls.
[0044] High resolution may be obtained using the electrostatic printing masters provided
by the invention, achieving results comparable to that obtained in high-quality lithographic,
flexographic, and letter press printing. While half-tone imaging will normally be
selected for these applications, it is possible to tailor a master for continuous
tone applications since the density of developed silver will vary with intensity of
light used to image the film, as in conventional photography.
[0045] The following examples further illustrate various embodiments of the invention, and
are not to be construed to limit it. Other embodiments will be apparent to those skilled
in the art. In the examples, all parts and percentages are by weight, and all temperatures
are in degrees Celsius, unless otherwise stated.
[0046] Unless otherwise stated, the silver halide emulsions were negative working and sensitized
with gold and sulfur-containing compounds in a conventional manner. The silver chloride
was doped with 0.13 millimoles of RhCl₃ per mole of silver.
Preparation of Polymers
[0047] The general procedure for the preparation of the polymers is illustrated by the preparation
of Polymer A [styrene/methyl methacrylate ethyl/acrylate/methacrylic acid in a 30/10/40/20
weight ratio] as given below.
[0048] To a five liter flask fitted with a high speed stirrer, a reflux condenser, an addition
funnel and a thermometer were charged 788 grams of deionized water, 5 grams of Duponol
WAQE (sodium lauryl sulfate), 35.2 grams of styrene, 11.7 grams of methyl methacrylate,
46.9 grams of ethyl acrylate, 23.4 grams of methacrylic acid, and 0.5 grams of octyl
mercaptan. The flask was purged with nitrogen and heated to 60°C and held for 15 minutes.
Ferrous ammonium sulfate, 0.02 grams, ammonium persulfate, 0.28 grams, and sodium
bisulfite, 0.28 grams, were added to the flask while the mixture was emulsified and
maintained at 69-74°C. A mixture of 316.5 grams of styrene, 105.5 grams of methyl
methacrylate, 422 grams of ethyl acrylate, 211 grams of methacrylic acid and 5.10
grams of octyl mercaptan was added to the flask over a period of 140 minutes while
a solution containing 2.06 grams of ammonium persulfate, 0.52 grams of sodium bisulfite
and 19.4 grams of Duponol WAQE in 1000 grams of deionized water was also added over
the 140 minutes. Polymerization was continued for an additional hour and the emulsion
was allowed to cool slowly to ambient temperature. A 5% calcium acetate solution was
added whereupon the polymer coagulated. It was strained from excess water, washed
and filtered repeatedly with deionized water until the filtrate became clear, and
vacuum dried. Polymers B-I were prepared in a similar manner. The polymer compositions
and acid numbers are given in the Table 2 below. The acid numbers are defined as the
milligrams of potassium hydroxide neutralized per gram of polymer as determined by
potentiometric titration.
Examples 1-11 demonstrate the charge retention of the different polymers when used
with different silver halides and at different silver halide to polymer ratios.
Examples 1-6
[0049] A solution was made from the following ingredients:
To this solution was added with stirring 12.5 grams of a 15.1% solution of a silver
chloride emulsion (AgCl grains doped with 0.13 millimoled of RhCl₃ per mole of AgCl
and with a median edge length of 0.13 to 0.17 microns) containing 3.3 grams of gelatin
per mole of silver chloride. The dispersion was coated onto a copper-clad polyester
base by doctor knife. The dried films were 2.4 microns thick and had 90 milligrams
of silver chloride per square decimeter, with a silver ion to polymer ratio of 2.8
to 1. The unexposed films were tray-processed according to the following procedure:
1 minute in a commercial lithographic developer (CUFD, E. I. du Pont de Nemours and
Company) at 32.2°C, 30 seconds in 30% sodium thiosulfate fixer and 15 seconds in 2%
acetic acid stop both at 25°C, followed by cold water washing and drying at 125°C
for 10 minutes. The processed films were mounted on a flat plate, the copper layer
connected to ground, and equilibrated at 24°C and the given relative humidity for
one hour. They were then corona charged (with a double wire corotron) at 8.2 kv. Charging
was stopped (at time =0) and the charge allowed to decay. Electrostatic voltages were
determined with the use of an electrostatic surface probe. The results, in voltages
per micron, are summarized in the Table 3 below.
Examples 7-10
[0050] A solution was made from the following ingredients:
To this solution was added with stirring 74.2 grams of the silver chloride as in Examples
1-6 but containing 33.3 grams of gelatin per mole of silver chloride. The dispersion
was coated on copper-clad polyester base as in the previous examples. The dried film
had a thickness of 4 microns with a silver weight of 80 milligrams per square decimeter.
The ratio of silver ion to binder was 1.15 to 1. Films were developed in a commercial
X-ray film developer (MXD. E. I. du Pont de Nemours and Company) and fixer (thiosulfate)
at ambient temperature. They were treated with 2% acetic acid, water-rinsed and dried
at 125°C for 10 minutes. After equilibration at 24°C and 37% relatively humidity,
the processed films were corona charged as described in the previous examples. The
results, in voltages per micron, are summarized in Table 4 below.
Example 11
[0051] Example 9 was repeated except that a silver iodobromide emulsion
with an average grain volume of 0.0185 cubic microns) containing 13.3 grams of gelatin
per mole of silver halide was substituted for the silver chloride. The dry film had
a coating thickness of 4 microns and contained 80 milligrams of silver halide per
square decimeter. The ratio of silver ion to polymer was 1.15 to 1. The film was processed
and charged as in Examples 7-10. At 24°C and 37% relative humidity, the electrostatic
voltages held per micron in the polymer areas were 80, 56, 47, and 40 volts per micron
at 2, 30, 60, and 120 seconds respectively.
[0052] Examples 12-17 demonstrate the use of different conductive substrates with two different
insulating polymers.
Example 12
[0053] Polymer J [methacrylamide/methyl methacrylic acid/ethyl acrylate/ methacrylic acid
in a 4.2/42.8/43/10 ratio] was prepared as follows: a mixture of 4.2 grams of methacrylamide,
42.8 grams methyl methacrylate, 43 grams ethyl acrylate, 10 grams methacrylic acid
and 0.1 grams VAZO 64 initiator (azobisisobutyronitrile) in 666 grams t-butanol was
heated at reflux under a nitrogen atmosphere for two hours. Another 0.1 grams of VAZO
was added, refluxing continued for two hours, two more additions made of 0.1 grams
of VAZO, and reflusing continued to a total reaction time of 8 hours. The polymer
was precipitated in cold water, rinsed with water, and dried to a white powder.
[0054] A solution was made of the following ingredients:
Polymer J |
5.0 grams |
triethylamine |
0.5 grams |
water |
35.0 grams |
To 5 grams of the polymer solution was added with stirring 9.9 grams of an ortho-sensitized
silver iodobromide emulsion as in Example 11 in which the gelatin content was 13 grams
of gelatin per mole of silver halide and the silver halide content was 11.7% The dispersion
was coated under red safelight conditions onto aluminum using a wire-wound bar to
give, after drying, a coating of 6.0 microns.
[0055] The coating was handled and processed under red safelights. Images were prepared
by contact exposure to halftone and resolution targets in a vacuum frame using a tungsten
lamp at 56 inches (lamp output = 10 foot candles 12 inches from the bulb). This example
was exposed one second, tray developed for 1 minute under nitrogen atmosphere is the
following developer:
0.01% potassium bromide
0.05% sodium sulfite
1.00% hydroxylamine hydrochloride
0.01% Dimezone-S
1.00% hydroquinone
5.40% potassium carbonate
5.40% potassium bicarbonate
deionized water
It was then fixed 2 minutes, stopped 2 minutes in 2% acetic acid, rinsed 2 minutes
in distilled water all at 26°C, blown dry, and heated 1 minutes at 125°C.
[0056] The image consists of black silver image where the coating was exposed and a white
background where unexposed. Resolution was at least 101 line pairs per millimeter.
Charge acceptance and dark decay were determined using a Monroe Model 276A static
charge analyzer. The exposed areas read initial acceptance of 8 volts which is the
same as an aluminum blank, and did not decay over 60 seconds; the unexposed areas
initially accepted 153 volts which decayed to 100 volts at 10 seconds, 92 volts at
20 seconds, 75 volts at 60 seconds. This difference in charge between the exposed
and unexposed areas is useful for electrostatic toning.
[0057] The electrostatic master was charged with a positive corona to maximum acceptance
charge while the aluminum support was electrically grounded. After a few seconds decay
the ground was disconnected and the plate immersed in a dispersion of negatively charged
black toner particles in Isopar®, a nonpolar hydrocarbon liquid having a Kauri-butanol
value of about 27, Exxon Corp. Toner was attracted to the white non-silver parts of
the image making the overall master look black. It was then rinsed gently in a tray
of Isopar®, drained, rewet with Isopar®, covered with paper, and passed under the
positive corona to assist toner transfer to paper. The image transferred normally
(toner transferred where the master was silver-free) and had 6 line pair/millimeter
resolution when the master stayed wet with Isopar® throughout.
Example 13
[0058] The procedure in Example 12 was repeated with the following exceptions: the emulsion
was coated onto copper-clad Kapton® (polyimide film, E.I. du Pont de Nemours and Company)
to achieve a thickness of 5.7 microns; and the processed film was heated for 5 minutes
at 125°C. The finished electrostatic master thus prepared was mounted on a Savin 770
copier drum and charged and toned, the image transferred to paper as in Example 12,
to obtain 100-150 copies of black toner image with resolution of 20 line pairs per
millimeter.
Example 14
[0059] Example 12 was repeated except that 9.9 grams of polymer solution was used, resulting
in a silver ion to polymer ratio of 0.58 to 1; and the dispersion was coated on copper-clad
Kapton® with a coating thickness of 5.7 microns. The subsequent treatment was the
same as in Example 13. The master appeared to charge and tone better with the higher
percent polymer (Example 14), but the image coating had a greater tendency to delaminate.
Example 15
[0060] Example 12 was repeated except that the conductive substrate used was aluminized
Mylar® (polyester film, E.I. du Pont de Nemours and Company). This resulted in an
intact image with no noticeable anchorage or quality problems.
Example 16
[0061] Polymer K was prepared in the same manner as Polymer J, but using 4.2 grams of methacrylamide,
21.8 grams methyl methacrylate, 64 grams ethyl acrylate, and 10 grams methacrylic
acid. The films were prepared, imaged, processed, charged and toned as in Example
12. Charge acceptance initially was 55 volts; at 10 seconds it was 16 volts.
Example 17
[0062] This example used the same coating and processing as Example 13 except that the image
was heated for 10 minutes at 125°C. A coating thickness of 1.8 microns was achieved.
Image areas that air dried before heating (A) were somewhat cloudy; areas that were
wet when placed in the oven (B) were transparent after heating. The black silver image
had resolution of 228 line pairs per millimeter. The charge acceptance and decay of
the image was determined on a Monroe 276A Static Charge Analyzer at various relative
humidities as shown in the Table 5 below. The data are in volts per micron.
[0063] The copper layer of the electrostatic master of Example 17 was electrically grounded
and the image positively charged with a corona under ambient conditions. After a few
seconds the grounded image was submerged in a toner bath consisting of negatively
charged toner particles in Isopar®, drained, lightly rinsed with Isopar® and the wet
image transferred to paper with the help of a negative corona behind the paper. The
toner image was positive with respect to the original image, negative with respect
to the master, and resolution was 16 line pairs per millimeter. The electrostatic
master was recharged and toned and the toner image allowed to dry. Clear adhesive
tape picked the toner off the master to give a clean positive image with respect to
the original, with resolution of 50 line pairs per millimeter.
Examples 18-24
[0064] These examples contrast the properties of films formed by dispersing a silver salt
in gelatin binders to those formed by dispersing the same silver salt in the improved
insulation media of the present invention. In all cases the silver salt used was AgCl
grains doped with 0.13 millimoles of RhCl₃ per mole of AgCl with and with a median
edge length of 0.13 to 0.17 microns. The charge retention was measured after developing
the unexposed films
(i) Films with gelatin binders
[0065] A silver chloride dispersion was prepared by adding 3610 grams of silver chloride
curds (grains doped with 0.13 millimoles of RhCl₃ per mole of AgCl and with a median
edge length of 0.13 to 0.17 microns) containing 13.3 grams of gelatin per mole of
AgCl to 3045 grams of water, adjusting the pH to 6.7 with 130 grams of 0.1 N sodium
hydroxide, heating and stirring for one hour at 45°C and adding 214 grams of solution
made up by mixing 165.2 g 0.1 N sodium hyroxide, 32.1 grams tetraazaindene stabilizer*,
and 16.7 grams water.
* tetraazaindene = 4-hydroxy-2-methyl-[1,2,4]triazole[2,3-b]pyrimidine
[0066] Gelatin was swollen in water at 20°C and then dissolved in additional water at 50°C
to give a 15 wt% solution. 295 grams of the gelatin solution was then added to 705
grams of the AgCl solution to make a net 17.63 wt% AgCl emulsion. Formaldehyde hardener
was added at a concentration of 5 grams formaldehyde per 1000 grams emulsion. The
emulsion was coated onto an indium tin oxide coated polyester substrate (surface resistivity
of about 500 ohms per square, 5 mil thick polyester base) using a lab coater. The
films were tray processed using standard reagents in the following sequence: developer,
stop, fix, stop, rinse, dry. The gelatins used and the coating thicknesses after processing
obtained are summarized in Table 6.
(ii) Films with improved polymeric binders
[0067] A solution was made from the following ingredients:
polymer |
2.00 grams |
water |
10.44 grams |
isopropanol |
3.20 grams |
potassium hydroxide |
0.30 grams |
potassium bicarbonate |
0.06 grams |
acid violet 520 dye |
0.10 grams |
To this solution was added with stirring 54 grams of AgCl curds containing 10 grams
gelatin per mole of AgCl. The dispersion was coated onto a gel-subbed indium tin oxide
coated polyester substrate (surface resistivity of about 500 ohms per square, 5 mil
thick polyester base) using a wire-wound rod. The films were processed following the
procedure described for the gelatin films. The polymers used and the coating weights
obtained are summarized in Table 6.
(iii) Determination of charge retention
[0068] Samples of the above films were mounted on an aluminum plate and electrical connection
from the conductive indium tin oxide substrate to ground was made with the use of
conductive copper tape. The films were equilibrated in a glove box at a given relative
humidity as measured with an Omega hand held hygrometer (Model RH-201) for one hour
and then corona charged with a double wire corotron, 6 kV being applied to the corotron.
Voltages were determined with the use of an electrostatic surface voltage probe. The
results are summarized in terms of volts per micron in Table 7.
[0069] Films with gelatin binders were heated to determine the effect on the electrostatic
properties. Films in Examples 18-21 were dried at 100°C for 10 minutes and then conditioned
at 48% relative humidity for 1 or 10 minutes after which electrostatic data were obtained.
These data in volts per micron are summarized below in Table 8.
(iv) Toning results
[0070] Films from Examples 18-24 were toned with liquid electrostatic toner containing carbon
black pigment in a modified Savin 870 copying machine under identical conditions,
the temperature was 19°C and the relative humidity was 48%. Time from corona charging
to toning was 15 seconds. The double wire corotron was biased at 6 kV and the development
electrode was maintained at ground potential. Transfer of the toner from the film
surface to offset enamel paper was accomplished with the use of a bias transfer roll.
Once transferred to paper, the toner was thermally fused at 100°C in an oven. Reflection
optical density measurements were made with the use of a Macbeth RD918 densitometer
and are given in the Table 9 below.
[0071] Examples 26 and 27 illustrate the use of a commercial resin as the insulating polymeric
binder.
Example 25
[0072] In 35 grams of water was dissolved 2.5 grams of Carboset® 526 (copolymer of ethyl
acrylate/methyl/methacrylate/acrylic acid in a 17/71/12 ratio, B. F. Goodrich Co.)
and 0.59 grams of triethylamine. Equal amounts of the polymer solution and silver
halide emulsion of Example 12 were blended and coated at 60 milligrams per square
decimeter on copper clad Kapton®. Exposure and development following the procedure
in Example 12 resulted in a black silver image with a clear background with good resolution.
Charging and charge decay studies as a function of relative humidity were conducted
on coatings of pure Carboset® 526 at 36.90 milligrams per square decimeter on copper
under the same conditions as Example 17. At 4 to 72% relative humidity Carboset® 526
held charge at least as well or better than Polymer J of Example 12.
Example 26
[0073] Example 25 was repeated using Carboset® 525 (copolymer of ethyl acrylate/methyl methacrylate/acrylic
acid in a 56/37/7 ratio, B. F. Goodrich, Co.). An image was produced, however it was
weaker than that of Example 26.
Example 27
[0074] A film was prepared as in Example 1 except that the AgCl emulsion contained 13.3
grams of gelatin per mole of AgCl and the final coating weight was 120 milligrams
per square decimeter. The film was exposed and processed MXD (E. I. du Pont du Nemours
and Company, Inc.) rapid access Xray film developer so as to get a variety of amounts
of silver developed. Development was determined by a Panalyzer 4000 (Panametrics,
division of Esterline Corp.). Surface resistance in the silver image areas was measured
with a Fluka 77 Multimeter (John Fluke Mfg. Co., Inc.) between two probes 1 centimeter
apart. Acceptance voltage in the silver image areas was measured on a Monroe 276A
static test meter. The results are given below in Table 10.
Example 28
[0075] Indium tin oxide coated Mylar® (polyester film) was coated with a 1.8 milligram per
square decimeter subbing of polyvinylidine chloride resin at 200 feet per minute with
a fountain air knife coater, and heat set at 170°C at 20 fpm giving a residence time
of 8 minutes. This was overcoated with a gelatin layer at 0.8-1.0 milligrams per square
decimeter at 200 fpm with a fountain air knife and heat relaxed at 145°C at 45 fpm
giving a residence time of 3.5 minutes.
[0076] A solution of Polymer E was prepared by adding to 2314 grams of water with stirring:
450 grams isopropyl alcohol (95%), 450 grams methyl ethyl ketone, and 132 grams potassium
hydroxide pellets. To this solution was added with rapid stirring 600 grams of Polymer
E; stirring was continued until it was mostly dissolved (15 minutes). To this was
added 54 grams of potassium bicarbonate. A silver chloride dispersion was prepared
by adding 3610 grams of silver halide curds (grains doped with 0.13 millimoles of
RhCl₃ per mole of AgCl and with a median edge length of 0.13 to 0.17 microns) containing
10 grams gelatin per mole of silver chloride to 2300 grams of water and adjusting
the pH to 6.7 by the addition of 130 grams of 0.1 N sodium hydroxide and 15 grams
of 0.1 N sulfuric acid. This was heated for 1 hour at 45°C and 214 grams of a solution
made up of 386 grams of 0.1 N sodium hydroxide, 75 grams of tetraazaindene stabilizer,
and 39 grams water was added. This was diluted to 25% silver chloride with 614 grams
water.
[0077] To 630 grams of the 25% AgCl solution was added slowly with stirring 247 grams of
the polymer solution (15%). Before coating 6.7 grams of EPI-REZ 5022 (diglycidyl ether
of 1,4-butanediol, Celanese Corp.) was added and coated onto the above treated indium
tin oxide Mylar® sheet at 15 milligrams per square decimeter polymer coating weight
using a lab coater at 60 fpm. This was dried for 30 seconds at 10°C, 60 seconds at
30°C, and 60 seconds at 50°C. total dry coating weight was 103 milligrams per square
decimeter.
[0078] After exposure and development as in Examples 18-24 the developed exposed silver
image had surface resistance of 50-100 ohms and acceptance voltage of 1 volt as measured
2 seconds after charging. The unexposed non-silver part of the image had an acceptance
voltage of 242 volts as measured 2 seconds after charging, 206 volts after 15 seconds,
and 190 volts after 30 seconds at 19% relative humidity. Toning in a modified Savin
870 Office Copier as described in Example 18-24 gave 5-98% dots and 150 lines per
millimeter resolution. the image transferred to paper had a D
max of 2.4 and a D
min of 0.03.
Example 29
[0079] In this example the invention is illustrated by a diffusion transfer film. To the
following solution
water |
3116 grams |
ammonium hydroxide (29%) |
84 grams |
isopropyl alcohol (95%) |
400 grams |
was added with intense stirring 400 grams of ground Polymer A. This solution was left
unstirred until polymer dissolved (overnight). To 1720 grams of the polymer solution
was added over 1 minute with rapid stirring 600 grams of a 2% solution of zinc sulfate;
then added over 5 seconds with stirring 210 grams of a 1.062% solution of sodium sulfide;
then over 30 seconds added 520 grams of 2.59% solution of acid violet 520 (antihalation
dye). This was diluted to 4% by the addition of 1250 grams of water. Before coating,
31 grams of EPI-REZ 5022 (diglycidyl ether of 1,4-butanediol) was added. The solution
was coated using a fountain air-knife at the following conditions: 200 fpm, 4 inch
air knife pressure; onto 5 mil thick Mylar® (polyester) previously sputtered with
indium-tin oxide. This was dried at 85°C. This film was subsequently heat relaxed
on a separate pass at 145°C and 45 fpm giving a residence time of 3.5 minutes at 145°C.
This was overcoated with a blue-sensitized camera speed high contrast emulsion of
AgCl
0.8Br
0.195I₀₀₅ (average grain volume = 0.01 cubic microns) dispersed 2:1 in gelatin using a
bar coater at 80 fpm. The final binder layer coating weight was 9.3 milligrams per
square decimeter; the emulsion layer was 73.6 milligrams per square decimeter. The
ratio of silver ion to polymer was 3.0 to 1. The film was exposed and developed with
very little agitation for 1 minute in Agfa CP297B (Agfa-Gaevert) diffusion transfer
developer at 28°C, agitated for 1 minute in 10% acetic acid stop solution at 28°C
removing much of the gelatin top layer, rinsed in 15°C water, and dried at room temperature.
[0080] The unexposed areas gave developed silver in the polymeric binder layer with surface
resistance of 20-35 ohms and acceptance voltage of 0 volts. The exposed areas were
silver-free in the polymeric binder layer and after charging, the acceptance electric
field at 38% relative humidity was 150 volts at 2 seconds; 104 volts at 15 seconds;
91 volts at 30 seconds. Toning in a modified Savin 870 copying machine as described
in Examples 18-24 gave 4-98% halftone dots/150 line per inch halftone. The D
max was 2.5 and the D
min was 0.01.
Examples 30-31
[0081] These examples contrast the properties of diffusion transfer films which contain
either gelatin or a styrene-acrylic tetrapolymer as the binder in the receptor layer.
(i) Diffusion transfer film with gelatin binder in the receptor layer (Example 30)
[0082] 60 grams of Rousselot Ills gelatin were added to 1360 milliliters of deionized water
and allowed to stir at room temperature with fast agitation for 20 minutes. The suspension
was heated to 52°C for 30 minutes and then cooled to 35°C. 106 milliliters of a 0.15
M zinc sulfate solution and 6 milliliters of a 0.15 M iron(II) sulfate solution were
added over a 1 minute interval. 336 milliliters of a 0.05 M sodium sulfide solution
was added through an orifice so that the addition time was approximately 2 minutes.
The following aqueous solutions were then added.
15% solution of Polystep B-27 (Stepan Chemical Co.) |
60 ml |
1.33 M formaldehyde |
40 ml |
0.264 M chromium potassium sulfate |
40 ml |
The solution was immediately coated onto the condutive side of indium tin oxide coated
Mylar® at a coating weight between 0.7 and 1.0 grams per square meter of gelatin.
[0083] An ortho sensitized camera speed high contrast emulsion of AgCl
0.7Br
0.3(average grain volume approximately 0.025 cubic microns) was coated onto the gelatin
layer at a silver coating weight of 3.1 grams per square meter. The emulsion contained
no hardener.
[0084] The multilayer film was exposed imagewise with a tungsten light and developed in
Commercial AgfA PMT developer (Type CP297B) for 60 seconds at approximately 20°C with
little agitation. The emulsion layer was then removed with pressurized water at 38°C.
The sample was washed for 2 minutes in 38°C water and dried at room temperature.
(ii) Diffusion transfer films with improved polymeric binders (Example 31)
[0085] To a solution of 4.0 grams of Polymer E and 2.5 grams of triethylamine in 80 grams
of water was added over 1 minute 6 milliliters of a 4% aqueous solution of zinc sulfate,
then over 5 seconds 19.2 milliliters of a 0.23% aqueous solution of sodium sulfide.
After stirring 5 minutes the precipitate was filtered off and the solution containing
the zinc sulfide nuclei was coated on the conductive side (surface resistivity = 500
ohms per square) of indium tin oxide coated Mylar® to give 7 milligrams per square
decimeter clean colorless polymeric receptor layer with 1% zinc sulfide nuclei. This
was heated at 125°C for 10 minutes to improve adhesion to the conductive substrate.
[0086] A blue-sensitized camera-speed high contrast conclusion of AgCl
0.80Br
0.195I
0.005 (grains of average volume of 0.01 cubic microns) dispersed 2:1 in gelatin was coated
without hardener over the polymeric receptor layer at a coating weight of 69 milligrams
per square decimeter.
[0087] The multilayer coating was exposed imagewise with light and developed in the commercial
Kodak PMT-D developer (Eastman Kodak Co., Chicago, Ill.) modified with 12.5% potassium
hydroxide and 5% potassium carbonate for 60 seconds at 28°C with little agitation.
The developed image was agitated 30 seconds in 10% acetic acid stop solution at 28°C
removing most of the top gelatin layer. The black positive diffusion transfer image
in the receptor layer remained on the conducting support and was rinsed free of gelatin
and loose silver residues with 40°C water, dried, heated 5 minutes at 125°C to clean
out volatile contaminants. The image had D
max of 3.0-3.5 and low D
min.
[0088] The receptor areas corresponding to unexposed image had 8.8 milligrams per square
decimeter finely divided black silver metal dispersed in 6.6 milligrams per square
decimeter polymer matrix. The ratio of silver to polymer of 1.34 to 1 is above the
threshold of about 1.2 and the surface resistance in silver containing areas was very
low, 5 to 14 ohms. The areas corresponding to the exposed image were fairly clean,
nearly colorless and had surface resistance of greater than 10⁷ ohms. The master was
toned on a modified Savin 870 copying machine as in Examples 18-24. With a 50 volt
development electrode potential the background of the toner image transferred to paper
(corresponding to the silver areas of the master) was completely clean of toner and
with halftone dots of 2-95%/150 line per inch halftone.
(iii) Electrostatic data
[0089] Data were obtained for the diffusion transfer films in Examples 30-31 at various
relative humidites according to the procedure described for Examples 18-24. the temperature
was 22°C in all cases. The results in volts per micron are summarized in Table 11.
[0090] The diffusion transfer film with gelatin as binder, Example 30, was heated at 100°C
for 10 minutes followed by conditioning at 48% relative humidity for 1 or 10 minutes.
The electrostatic data, in volts per micron, obtained immediately after conditioning
are given in Table 12 below.
(iv) Toning results
[0091] Films from Examples 30-31 were toned at 21°C and 43% relative humidity as in Examples
18-24 Reflection optical densities measured as in Examples 18-24 are given in the
Table 13 below.
Example 32
[0092] The solution of polymer E containing ZnS development nuclei as described for Example
31 was coated on gelatin subbed polyester film at 28 milligrams per square decimeter
giving a clear colorless coating. A piece of Kodak PMT Negative Paper was exposed
imagewise. The exposed PMT paper and receptor polymer/nuclei coating were fed into
the nip of a laminator with the paper emulsion side facing the nuclei coating and
the sheets spread apart. Kodak PMT-D developer was applied at the nip between the
sheets, the sheets were wet laminated together at 1 meter per minute under light nip
pressure, the laminate was held 30 seconds at room temperature and then the sheets
were separated to give a black positive image of D max 0.7 and D min 0.02 in the receptor
coating and a strong negative image on the PMT paper. This illustrates the well known
photomechanical transfer process and can be used to prepare a silver image in polymer
E.
1. A photosensitive composition consisting essentially of a silver halide photographic
salt dispersed in a synthetic insulating polymeric binder that is swellable in aqueous
solutions having a pH higher than approximately 8-1/2, said composition having an
insulation value such that it will support an apparent macroscopic electric field
of at least approximately five (5) volts/micrometer as measured 2 second following
full charging of its surface that has been allowed to equilibrate at 50% relative
humidity for 1 hour.
2. The composition of claim 1 wherein the binder is swellable in aqueous solutions having
a pH in the range of approximately 9 to 14 and an insulation value of at least approximately
30 volts/micrometer.
3. The composition of claim 2 wherein the binder has an acid number of approximately
70 to 160.
4. The composition of claim 3 wherein the binder is a copolymer of an aromatic monomer
and acrylic or methacrylic acid.
5. The composition of claim 4 wherein said binder is a copolymer containing 10 to 50%
by weight a styrene monomer, 5 to 50% by weight a carboxylic acid monomer, and 0 to
85% by weight an acrylate monomer.
6. The composition of claim 5 wherein said binder is a copolymer containing 25 to 35%
by weight a styrene monomer, 10 to 25% by weight a carboxylic acid monomer, and 40
to 65% by weight an acrylate monomer.
7. The composition of claim 4 having a weight ratio of silver ion to binder in the range
of approximately 0.5 to 3 parts silver per part of binder.
8. An electrostatic printer master comprising a conductive substrate that bears a coating
of a photosensitive composition according to claims 1 to 7.
9. A diffusion transfer film comprising development nuclei dispersed in a binder, wherein
the binder is a synthetic insulating polymeric binder that is swellable in aqueous
solutions having a pH higher than approximately 8-1/2 and said film has an insulation
value such that it will support an apparent macroscopic electric field of at least
approximately five (5) volts/micrometer as measured 2 second following full charging
of its surface that has been allowed to equilibrate at 50% relative humidity for 1
hour.
10. The film of claim 9 wherein the binder is swellable in aqueous solutions having a
pH in the range of approximately 9 to 14 and has an insulation value of at least approximately
30 volts/micrometer.
11. The film of claim 10 wherein the binder has an acid number of approximately 70 to
160.
12. The film of claim 11 wherein the binder is a copolymer of an aromatic monomer and
acrylic or methacrylic acid.
13. The film of claim 12 wherein said binder is a copolymer containing 10 to 50% by weight
a styrene monomer, 5 to 50% by weight a carboxylic acid monomer, and 0 to 85% by weight
an acrylate monomer.
14. The film of claim 13 wherein said binder is a copolymer containing 25 to 35% by weight
a styrene monomer, 10 to 25% by weight a carboxylic acid monomer, and 40 to 65% by
weight an acrylate monomer.
15. The film of claim 12 having a weight ratio of silver ion to binder in the range of
approximately 0.5 to 3 parts silver per part of binder.
16. A film comprising a conductive substrate that bears a coating consisting essentially
of a silver grain image dispersed in a synthetic insulating polymeric binder that
is swellable in aqueous solutions having a pH higher than approximately 8-1/2, said
binder being a copolymer of an unsaturated carboxylic acid monomer and an aromatic
monomer and having ionizing carboxylic acid groups, said composition having an insulation
value such that it will support an apparent macroscopic electric field of at least
approximately five (5) volts/micrometer as measured 2 seconds following full charging
of its surface that has been allowed to equilibrate to 50% relative humidity at 20°C
for 1 hour.
17. The film of claim 16 wherein the binder is swellable in aqueous solutions having a
pH in the range of approximately 9 to 14 and has an insulation value of at least approximately
30 volts/micrometer.
18. The film of claim 16 wherein the binder has an acid number of approximately 70 to
160.
19. The film of claims 16 wherein the binder is a copolymer of an aromatic monomer and
acrylic or methacrylic acid.
20. The film of claim 16 having a weight ratio of silver to binder in the range of approximately
0.5 to 3 parts silver per part of binder.
21. The film of claim 16 wherein said binder is a copolymer containing 10 to 50% by weight
a styrene-type monomer, 5 to 50% by weight a carboxylic acid monomer, and 0 to 85%
by weight an acrylate-type monomer.
22. The film of claim 21 wherein said binder is a copolymer containing 25 to 35% by weight
a styrene-type monomer 10 to 25% by weight as carboxylic acid monomer, and 40 to 65%
by weight an acrylate-type monomer.
23. The film of claim 21 wherein the binder is swellable in aqueous solutions having a
pH in the range of approximately 9 to 14 and has an insulation value of at least approximately
30 volts/micrometer.
24. The film of claim 23 wherein the binder has an acid number of approximately 70 to
160.
25. The film of claim 24 wherein the binder is a copolymer containing 25 to 35% by weight
a styrene-type monomer, 10 to 25% by weight a carboxylic acid monomer, and 40 to 65%
by weight an acrylate-type monomer.
1. Lichtempfindliche Zusammensetzung, bestehend im wesentlichen aus einem photographischen
Silberhalogenid-Salz, dispergiert in einem synthetischen isolierenden polymeren Bindemittel,
das in wäßrigen Lösungen mit einem höheren pH-Wert als etwa 8½ quellfähig ist, wobei
die Zusammensetzung einen solchen Isolations-Wert hat, daß sie ein scheinbares makroskopisches
elektrisches Feld von wenigstens etwa fünf Volt/Mikrometer (5 V/µm) trägt, gemessen
2 s nach der vollen Aufladung ihrer Oberfläche, die zur Äquilibrierung 1 h bei einer
relativen Luftfeuchtigkeit von 50 % belassen worden ist.
2. Zusammensetzung nach Anspruch 1, worin das Bindemittel in wäßrigen Lösungen mit einem
pH-Wert im Bereich von etwa 9 bis 14 quellfähig ist und einen Isolations-Wert von
wenigstens etwa 30 V/µm hat.
3. Zusammensetzung nach Anspruch 2, worin das Bindemittel eine Säurezahl von etwa 70
bis 160 hat.
4. Zusammensetzung nach Anspruch 3, worin das Bindemittel ein Copolymer aus einem aromatischen
Monomer und Acryl- oder Methacrylsäure ist.
5. Zusammensetzung nach Anspruch 4, worin das Bindemittel ein Copolymer ist, das 10 bis
50 Gew.-% eines Styrol-Monomers, 5 bis 50 Gew.-% eines Carbonsäure-Monomers und 0
bis 85 Gew.-% eines Acrylat-Monomers enthält.
6. Zusammensetzung nach Anspruch 5, worin das Bindemittel ein Copolymer ist, das 25 bis
35 Gew.-% eines Styrol-Monomers, 10 bis 25 Gew.-% eines Carbonsäure-Monomers und 40
bis 65 Gew.-% eines Acrylat-Monomers enthält.
7. Zusammensetzung nach Anspruch 4 mit einem Gewichts-Verhältnis Silber-Ion zu Bindemittel
im Bereich von etwa 0,5 bis 3 Teilen Silber auf 1 Teil Bindemittel.
8. Elektrostatische Druckschablone, umfassend ein leitfähiges Substrat, das eine Beschichtung
aus einer lichtempfindlichen Zusammensetzung nach den Ansprüchen 1 bis 7 trägt.
9. Diffusions-Transfer-Film, umfassend in einem Bindemittel dispergierte Entwicklungskeime,
worin das Bindemittel ein synthetisches isolierendes polymeres Bindemittel ist, das
in wäßrigen Lösungen mit einem höheren pH-Wert als etwa 8½ quellfähig ist und der
Film einen solchen Isolations-Wert hat, daß er ein scheinbares makroskopisches elektrisches
Feld von wenigstens etwa fünf Volt/Mikrometer (5 V/µm) trägt, gemessen 2 s nach der
vollen Aufladung ihrer Oberfläche, die zur Äquilibrierung 1 h bei einer relativen
Luftfeuchtigkeit von 50 % belassen worden ist.
10. Film nach Anspruch 9, worin das Bindemittel in wäßrigen Lösungen mit einem pH-Wert
im Bereich von etwa 9 bis 14 quellfähig ist und einen Isolations-Wert von wenigstens
etwa 30 V/µm hat.
11. Film nach Anspruch 10, worin das Bindemittel eine Säurezahl von etwa 70 bis 160 hat.
12. Film nach Anspruch 11, worin das Bindemittel ein Copolymer aus einem aromatischen
Monomer und Acryl- oder Methacrylsäure ist.
13. Film nach Anspruch 12, worin das Bindemittel ein Copolymer ist, das 10 bis 50 Gew.-%
eines Styrol-Monomers, 5 bis 50 Gew.-% eines Carbonsäure-Monomers und 0 bis 85 Gew.-%
eines Acrylat-Monomers enthält.
14. Film nach Anspruch 13, worin das Bindemittel ein Copolymer ist, das 25 bis 35 Gew.-%
eines Styrol-Monomers, 10 bis 25 Gew.-% eines Carbonsäure-Monomers und 40 bis 65 Gew.-%
eines Acrylat-Monomers enthält.
15. Film nach Anspruch 12 mit einem Gewichts-Verhältnis Silber-Ion zu Bindemittel im Bereich
von etwa 0,5 bis 3 Teilen Silber auf 1 Teil Bindemittel.
16. Film, umfassend ein leitfähiges Substrat, das eine Beschichtung trägt, die im wesentlichen
aus einem Silber-Korn-Bild besteht, das in einem synthetischen isolierenden polymeren
Bindemittel dispergiert ist, das in wäßrigen Lösungen mit einem höheren pH-Wert als
etwa 8½ quellfähig ist, wobei das Bindemittel ein Copolymer aus einem ungesättigten
Carbonsäure-Monomer und einem aromatischen Monomer ist und ionisierende Carbonsäure-Gruppen
hat, wobei die Zusammensetzung einen solchen Isolations-Wert hat, daß sie ein scheinbares
makroskopisches elektrisches Feld von wenigstens etwa fünf Volt/Mikrometer (5 V/µm)
trägt, gemessen 2 s nach der vollen Aufladung ihrer Oberfläche, die zur Äquilibrierung
1 h bei einer relativen Luftfeuchtigkeit von 50 % belassen worden ist.
17. Film nach Anspruch 16, worin das Bindemittel in wäßrigen Lösungen mit einem pH-Wert
im Bereich von etwa 9 bis 14 quellfähig ist und einen Isolations-Wert von wenigstens
etwa 30 V/µm hat.
18. Film nach Anspruch 16, worin das Bindemittel eine Säurezahl von etwa 70 bis 160 hat.
19. Film nach Anspruch 16, worin das Bindemittel ein Copolymer aus einem aromatischen
Monomer und Acryl- oder Methacrylsäure ist.
20. Film nach Anspruch 16 mit einem Gewichts-Verhältnis Silber zu Bindemittel im Bereich
von etwa 0,5 bis 3 Teilen Silber auf 1 Teil Bindemittel.
21. Film nach Anspruch 16, worin das Bindemittel ein Copolymer ist, das 10 bis 50 Gew.-%
eines Styrol-Monomers, 5 bis 50 Gew.-% eines Carbonsäure-Monomers und 0 bis 85 Gew.-%
eines Acrylat-Monomers enthält.
22. Film nach Anspruch 21, worin das Bindemittel ein Copolymer ist, das 25 bis 35 Gew.-%
eines Styrol-Monomers, 10 bis 25 Gew.-% eines Carbonsäure-Monomers und 40 bis 65 Gew.-%
eines Acrylat-Monomers enthält.
23. Film nach Anspruch 21, worin das Bindemittel in wäßrigen Lösungen mit einem pH-Wert
im Bereich von etwa 9 bis 14 quellfähig ist und einen Isolations-Wert von wenigstens
etwa 30 V/µm hat.
24. Film nach Anspruch 23, worin das Bindemittel eine Säurezahl von etwa 70 bis 160 hat.
25. Film nach Anspruch 24, worin das Bindemittel ein Copolymer ist, das 25 bis 35 Gew.-%
eines Styrol-Monomers, 10 bis 25 Gew.-% eines Carbonsäure-Monomers und 40 bis 65 Gew.-%
eines Acrylat-Monomers enthält.
1. Une composition photosensible constituée essentiellement d'un sel photographique du
type halogénure d'argent dispersé dans un liant polymère isolant synthétique qui est
gonflable dans des solutions aqueuses ayant un pH supérieur à environ 8,5, ladite
composition ayant un pouvoir d'isolement tel qu'elle supporte un champ électrique
macroscopique apparent d'au moins environ cinq (5) volts/micromètre tel que mesuré
2 secondes après charge complète de sa surface que l'on a laissée s'équilibrer à 50
% d'humidité relative pendant 1 heure.
2. La composition de la revendication 1, dans laquelle le liant est gonflable dans des
solutions aqueuses ayant un pH compris dans l'intervalle d'environ 9 à 14 et qui a
un pouvoir d'isolement d'au moins environ 30 volts/micromètre.
3. La composition de la revendication 2, dans laquelle le liant a un indice d'acide d'environ
70 à 160.
4. La composition de la revendication 3, dans laquelle le liant est un copolymère d'un
monomère aromatique et d'acide acrylique ou méthacrylique.
5. La composition de la revendication 4, dans laquelle ledit liant est un copolymère
contenant 10 à 50 % en poids d'un monomère styrénique, 5 à 50 % en poids d'un monomère
de type acide carboxylique et 0 à 85 % en poids d'un monomère de type acrylate.
6. La composition de la revendication 5, dans laquelle ledit liant est un copolymère
contenant 25 à 35 % en poids d'un monomère styrénique, 10 à 25 % en poids d'un monomère
de type acide carboxylique et 40 à 65 % en poids d'un monomère de type acrylate.
7. La composition de la revendication 4, ayant un rapport en poids de l'ion argent au
liant compris dans l'intervalle d'environ 0,5 à 3 parties d'argent par partie de liant.
8. Une matrice pour imprimante électrostatique, comprenant un substrat conducteur qui
porte un revêtement d'une composition photosensible selon les revendications 1 à 7.
9. Un film pour transfert par diffusion comprenant des germes de développement dispersés
dans un liant, dans lequel le liant est un liant polymère isolant synthétique qui
est gonflable dans des solutions aqueuses ayant un pH supérieur à environ 8,5, et
ledit film a un pouvoir d'isolement tel qu'il supporte un champ électrique macroscopique
apparent d'au moins environ cinq (5) volts/micromètre tel que mesuré 2 secondes après
charge complète de sa surface que l'on a laissée s'équilibrer à 50 % d'humidité relative
pendant 1 heure.
10. Le film de la revendication 9, dans lequel le liant est gonflable dans des solutions
aqueuses ayant un pH compris dans l'intervalle d'environ 9 à 14 et qui a un pouvoir
d'isolement d'au moins environ 30 volts/micromètre.
11. Le film de la revendication 10, dans lequel le liant a un indice d'acide d'environ
70 à 160.
12. Le film de la revendication 11, dans lequel le liant est un copolymère d'un monomère
aromatique et d'acide acrylique ou méthacrylique.
13. Le film de la revendication 12, dans lequel ledit liant est un copolymère contenant
10 à 50 % en poids d'un monomère styrénique, 5 à 50 % en poids d'un monomère de type
acide carboxylique et 0 à 85 % en poids d'un monomère de type acrylate.
14. Le film de la revendication 13, dans lequel ledit liant est un copolymère contenant
25 à 35 % en poids d'un monomère styrénique, 10 à 25 % en poids d'un monomère de type
acide carboxylique et 40 à 65 % en poids d'un monomère de type acrylate.
15. Le film de la revendication 12, ayant un rapport en poids de l'ion argent au liant
compris dans l'intervalle d'environ 0,5 à 3 parties d'argent par partie de liant.
16. Un film comprenant un substrat conducteur qui porte un revêtement constitué essentiellement
d'une image de grains d'argent dispersée dans un liant polymère isolant synthétique
qui est gonflable dans des solutions aqueuses ayant un pH supérieur à environ 8,5,
ledit liant étant un copolymère d'un monomère du type acide carboxylique insaturé
et d'un monomère aromatique et ayant des groupes acides carboxyliques ionisants, ladite
composition ayant un pouvoir d'isolement tel qu'elle supporte un champ électrique
macroscopique apparent d'au moins environ cinq (5) volts/micromètre tel que mesuré
2 secondes après charge complète de sa surface que l'on a laissée s'équilibrer à 50
% d'humidité relative à 20°C pendant 1 heure.
17. Le film de la revendication 16, dans lequel le liant est gonflable dans des solutions
aqueuses ayant un pH compris dans l'intervalle d'environ 9 à 14 et qui a un pouvoir
d'isolement d'au moins environ 30 volts/micromètre.
18. Le film de la revendication 16, dans lequel le liant a un indice d'acide d'environ
70 à 160.
19. Le film de la revendication 16, dans lequel le liant est un copolymère d'un monomère
aromatique et d'acide acrylique ou méthacrylique.
20. Le film de la revendication 16, ayant un rapport en poids de l'argent au liant compris
dans l'intervalle d'environ 0,5 à 3 parties d'argent par partie de liant.
21. Le film de la revendication 16, dans lequel ledit liant est un copolymère contenant
10 à 50 % en poids d'un monomère styrénique, 5 à 50 % en poids d'un monomère de type
acide carboxylique et 0 à 85 % en poids d'un monomère de type acrylate.
22. Le film de la revendication 21, dans lequel ledit liant est un copolymère contenant
25 à 35 % en poids d'un monomère styrénique, 10 à 25 % en poids d'un monomère de type
acide carboxylique et 40 à 65 % en poids d'un monomère de type acrylate.
23. Le film de la revendication 21, dans lequel le liant est gonflable dans des solutions
aqueuses ayant un pH compris dans l'intervalle d'environ 9 à 14 et qui a un pouvoir
d'isolement d'au moins environ 30 volts/micromètre.
24. Le film de la revendication 23, dans lequel le liant a un indice d'acide d'environ
70 à 160.
25. Le film de la revendication 24, dans lequel le liant est un copolymère contenant 25
à 35 % en poids d'un monomère styrénique, 10 à 25 5 en poids d'un monomère de type
acide carboxylique et 40 à 65 % en poids d'un monomère de type acrylate.