[0001] The present disclosure is related to marking and printing methods and systems, and
more specifically to methods and systems for variably marking or printing multi-component
(e.g., multi-color) data using marking or printing materials such as UV lithographic
and offset inks.
[0002] Offset lithography is a common method of printing today. (For the purposes hereof,
the terms "printing" and "marking" are interchangeable.) In a typical lithographic
process a printing plate, which may be a flat plate, the surface of a cylinder, or
belt, etc., is formed to have "image regions" formed of hydrophobic and oleophilic
material, and "non-image regions" formed of a hydrophilic material. The image regions
are regions corresponding to the areas on the final print (i.e., the target substrate)
that are occupied by a printing or marking material such as ink, whereas the non-image
regions are the regions corresponding to the areas on the final print that are not
occupied by said marking material. The hydrophilic regions accept and are readily
wetted by a water-based fluid, commonly referred to as a fountain solution (typically
consisting of water and a small amount of alcohol as well as other additives and/or
surfactants to reduce surface tension). The hydrophobic regions repel fountain solution
and accept ink, whereas the fountain solution formed over the hydrophilic regions
forms a fluid "release layer" for rejecting ink. Therefore the hydrophilic regions
of the printing plate correspond to unprinted areas, or "non-image areas", of the
final print.
[0003] The ink may be transferred directly to a substrate, such as paper, or may be applied
to an intermediate surface, such as an offset (or blanket) cylinder in an offset printing
system. The offset cylinder is covered with a conformable coating or sleeve with a
surface that can conform to the texture of the substrate, which may have surface peak-to-valley
depth somewhat greater than the surface peak-to-valley depth of the imaging plate.
Also, the surface roughness of the offset blanket cylinder helps to deliver a more
uniform layer of printing material to the substrate free of defects such as mottle.
Sufficient pressure is used to transfer the image from the offset cylinder to the
substrate. Pinching the substrate between the offset cylinder and an impression cylinder
provides this pressure.
[0004] In one variation, referred to as dry or waterless lithography or driography, the
plate cylinder is coated with a silicone rubber that is oleophobic and patterned to
form the negative of the printed image. A printing material is applied directly to
the plate cylinder, without first applying any fountain solution as in the case of
the conventional or "wet" lithography process described earlier. The printing material
includes ink that may or may not have some volatile solvent additives. The ink is
preferentially deposited on the imaging regions to form a latent image. If solvent
additives are used in the ink formulation, they preferentially diffuse towards the
surface of the silicone rubber, thus forming a release layer that rejects the printing
material. The low surface energy of the silicone rubber adds to the rejection of the
printing material. The latent image may again be transferred to a substrate, or to
an offset cylinder and thereafter to a substrate, as described above.
[0005] The above-described lithographic and offset printing techniques utilize plates which
are permanently patterned, and are therefore useful only when printing a large number
of copies of the same image (long print runs), such as magazines, newspapers, and
the like. However, they do not permit creating and printing a new pattern from one
page to the next without removing and replacing the print cylinder and/or the imaging
plate (i.e., the technique cannot accommodate true high speed variable data printing
wherein the image changes from impression to impression, for example, as in the case
of digital printing systems). Furthermore, the cost of the permanently patterned imaging
plates or cylinders is amortized over the number of copies. The cost per printed copy
is therefore higher for shorter print runs of the same image than for longer print
runs of the same image, as opposed to prints from digital printing systems.
[0006] Lithography and the so-called waterless process provide very high quality printing,
in part due to the quality and color gamut of the inks used. Furthermore, these inks
- which typically have a very high color pigment content (typically in the range of
20-70% by weight) - are very low cost compared to toners and many other types of marking
materials. Thus, while there is a desire to use the lithographic and offset inks for
printing in order to take advantage of the high quality and low cost, there is also
a desire to print variable data from page to page. Heretofore, there have been a number
of hurdles to providing variable data printing using these inks. Furthermore, there
is a desire to reduce the cost per copy for shorter print runs of the same image.
Ideally, the desire is to incur the same low cost per copy of a long offset or lithographic
print run (e.g., more than 100,000 copies), for medium print run (e.g., on the order
of 10,000 copies), and short print runs (e.g., on the order of 1,000 copies), ultimately
down to a print run length of 1 copy (i.e., true variable data printing).
[0007] One problem encountered is that offset inks have too high a viscosity (often well
above 50,000 cps) to be useful in nozzle-based inkjet systems. In addition, because
of their tacky nature, offset inks have very high surface adhesion forces relative
to electrostatic forces and are therefore almost impossible to manipulate onto or
off of a surface using electrostatics. (This is in contrast to dry or liquid toner
particles used in xerographic/electrographic systems, which have low surface adhesion
forces due to their particle shape and the use of tailored surface chemistry and special
surface additives.)
[0008] Efforts have been made to create lithographic and offset printing systems for variable
data in the past. One example is disclosed in
U.S. Patent 3,800,699, incorporated herein by reference, in which an intense energy source such as a laser
to pattern-wise evaporate a fountain solution.
[0009] In another example disclosed in
U.S. Patent 7,191,705, incorporated herein by reference, a hydrophilic coating is applied to an imaging
belt. A laser selectively heats and evaporates or decomposes regions of the hydrophilic
coating. Next a water based fountain solution is applied to these hydrophilic regions
rendering them oleophobic. Ink is then applied and selectively transfers onto the
plate only in the areas not covered by fountain solution, creating an inked pattern
that can be transferred to a substrate. Once transferred, the belt is cleaned, a new
hydrophilic coating and fountain solution are deposited, and the patterning, inking,
and printing steps are repeated, for example for printing the next batch of images.
[0010] In yet another example, a rewritable surface is utilized that can switch from hydrophilic
to hydrophobic states with the application of thermal, electrical, or optical energy.
Examples of these surfaces include so called switchable polymers and metal oxides
such as ZnO
2 and TiO
2. After changing the surface state, fountain solution selectively wets the hydrophilic
areas of the programmable surface and therefore rejects the application of ink to
these areas.
[0011] There remain a number of problems associated with these techniques. One limitation
not otherwise adequately addressed in known systems for variable data lithography
is that most such systems are able to produce only monochrome images. To the extent
that any such system provides multicolor printing, it does so with multiple complete
printing engines, one for each color, in a multiple impression process. Multiple color
printing is highly desired, and for a number reasons including cost, complexity, servicing,
size, energy consumption, and so on, a multiple print engine system is less than optimal.
[0012] Accordingly, the present disclosure is directed to systems and methods for providing
variable data lithographic and offset lithographic printing, which address the shortcomings
identified above - as well as others as will become apparent from this disclosure.
The present disclosure concerns various embodiments of a multiple color variable imaging
lithographic marking system based upon variable patterning of dampening solutions
and related methods.
[0013] In such a system, an imaging member, such as a drum, plate, belt, web, etc. is provided
with a reimageable layer. This layer has specific properties such as composition,
surface profile, and so on so as to be well suited for receipt and carrying a layer
of a dampening fluid from a dampening fluid subsystem. An optical patterning subsystem
such as a scanned, modulated laser patterns the dampening fluid layer, again with
the characteristics of the reimageable layer chosen to facilitate this patterning.
Ink is then applied at an inking subsystem such that it selectively resides in voids
formed by the patterning subsystem in the dampening fluid layer to thereby form an
inked latent image. The inked latent image is then transferred to a substrate, and
the reimageable surface cleaned so that the process may be repeated. High speed, variable
marking is thereby provided.
[0014] According to an aspect of the present disclosure, multiple inking subsystems are
provided, each with different color ink. Each inking subsystem moves independently
into and out of engagement with (i.e., proximate) the reimageable surface layer of
the imaging member. The patterning subsystem creates a first pattern in dampening
fluid, and the first inking subsystem engages with the reimageable surface to create
a first color inked latent image, as described. This first color inked latent image
is transferred to a substrate, for example at a transfer nip, and the reimageable
surface layer of the imaging member cleaned. A second pattern is created in dampening
fluid, the first inking subsystem disengages with the reimageable surface, and the
second inking subsystem engages with the reimageable surface to create a second color
inked latent image, as described. The substrate then makes another pass through the
transfer nip so as to receive the second color inked latent image over the first.
In a typical 4-color process, this pattern-engage-ink-print sequence may be repeated
4 times, once for each color. Indeed, it may be repeated more often if different color
systems are used or different printing effects are desired.
[0015] According to another aspect of the disclosure, after transferring the first color
inked latent image to the substrate, the image may be partially cured on the substrate
to reduce smear, color transfer from the substrate back to the imagining member, and
as subsequent color layers are added thereto. The partial cure may be from the back
or front (or both) of the substrate, and be by way of UV exposure, heat, or other
method appropriate to the particular ink and substrate being used. In one embodiment,
the substrate is in the form of a sheet, such as paper, which is carried on a single
drum from first to last pass. In other embodiments, other substrate handling mechanisms
are employed.
[0016] According to still another aspect of the disclosure, a reimageable portion of one
or more imaging members is provided. In one embodiment, the reimageable portion comprises
a reimageable surface, for example composed of the class of materials commonly referred
to as silicone (e.g., polydimethylsiloxane). The reimageable portion may contain or
be formed over a structural material such as a cotton-weave core or other suitable
material of sufficient tensile strength, or may be formed over a mounting layer composed
of a suitable material such as a thin sheet of metal or cotton-weave backing or other
suitable material of sufficient tensile strength. While it may be desirable for the
reimageable surface layer to be relatively thin, from the point of view of material
costs, etc., it is understood that thickness may be selected to improve other aspects
of consideration such as performance, lifetime, and manufacturability. The reimageable
portion may further comprise additional layers below the reimageable surface layer
and either above or below structural mounting layer. Silicone is a preferred outer
layer material because of its low surface energy (i.e., low "stickiness") which enhances
release of the marking material, as will be described in further detail later on in
this document. It is noted that the outer reimageable surface material may also be
made from materials other than those primarily composed of silicone, which provide
suitable low adhesion energy. Other examples of such materials include some types
of hydrofluorocarbon compounds (e.g., Teflon, Viton, etc.) with long polymer chains
of (-CF3) groups and fluorinated silicone hybrid compounds. It is known that surface
materials that display a much larger receding to advancing wetting contact angle generally
also display low adhesion energies to viscoelastic marking ink materials, and are
therefore suitable materials for an outer layer. It is understood that the above-mentioned
specific materials are representative examples only, and these examples should not
be interpreted as limiting the scope of this invention to a specific class of materials.
[0017] According to another embodiment of this aspect of the disclosure, the reimageable
surface layer or any of the underlying layers of the reimageable plate/belt/drum,
etc. may incorporate a radiation sensitive filler material that can absorb laser energy
or other highly directed energy in an efficient manner. Examples of suitable radiation
sensitive materials are, for example, microscopic (e.g., average particle size less
than 10 micrometers) to nanometer sized (e.g., average particle size less than 1000
nanometers) carbon black particles, carbon black in the form of nano particles of,
single or multi-wall nanotubes, graphene, iron oxide nano particles, nickel plated
nano particles, etc., added to the polymer in at least the near-surface region. It
is also possible that no filler material is needed if the wavelength of a laser is
chosen so to match an absorption peak of the molecules contained within the fountain
solution or the molecular chemistry of the outer surface layer. As an example, a 2.94
µm wavelength laser would be readily absorbed due to the intrinsic absorption peak
of water molecules at this wavelength.
[0018] Further according to this aspect, multiple print stages are provided, each printing
a separate color. Each print stage may comprise its own imaging member with reimageable
surface, dampening fluid subsystem, patterning subsystem, inking subsystem, partial
curing subsystem, transfer nip, and cleaning subsystem. Alternatively, two or more
of the multiple stages may share one or more of these subsystems. In a direct marking
tandem embodiment, each imaging member sequentially transfers an inked color latent
image to a substrate. In a central impression embodiment, each imaging member sequentially
transfers an inked color latent image to a central impression drum, which then transfers
the color composite image to a substrate.
[0019] It is understood that for the purposes of this invention, the terms "optical wavelengths"
or "radiation" or "light" may refer to wavelengths of electromagnetic radiation appropriate
for use in the system to accomplish patterning of the dampening solution, whether
or not these electromagnetic wavelengths are normally visible to the unaided human
eye, including, but not limited to, visible light, ultraviolet (UV), and infrared
(IR) wavelengths, micro-wave radiation, and the like.
[0020] BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In the drawings appended hereto like reference numerals denote like elements between
the various drawings. While illustrative, the drawings are not drawn to scale. In
the drawings:
[0022] Fig. 1 is a side view of a system for multi-component variable lithography according
to an embodiment of the present disclosure.
[0023] Figs. 2A and 2B are cut-away side views of a reimaging portion of an imaging drum,
plate or belt, without and with an intermediate layer, respectively, according to
an embodiment of the present disclosure in which absorptive particulates are dispersed
within a reimageable surface layer.
[0024] Fig. 3 is a cut-away side view of a reimaging portion of an imaging drum, plate or
belt according to another embodiment of the present disclosure, in which a reimageable
surface layer is tinted for optical absorption.
[0025] Fig. 4 is a cut-away side view of a reimaging portion of an imaging drum, plate or
belt according to still another embodiment of the present disclosure, in which a reimageable
surface layer it optically transparent or translucent, and is disposed over an optically
absorptive layer.
[0026] Figs. 5A and 5B are illustrations of imaging surface texture feature spacings and
feature amplitudes for the purposes of defining RSm and Ra, respectively.
[0027] Fig. 6 is a magnified cut-away side view of the reimaging portion shown in Fig. 2,
having a dampening solution applied thereover and patterned by a beam B, according
to an embodiment of the present disclosure.
[0028] Fig. 7 is a side view of an inker subsystem having a rotationally disposed metering
(forming) roller, which receives ink from a source roller, for selectively transferring
ink to a reimageable surface, according to an embodiment of the present disclosure.
[0029] Fig. 8 is a side view of an inker subsystem used to apply a uniform layer of ink
over a patterned layer of dampening solution and portions of a reimageable surface
layer exposed by the patterning of the dampening solution, according to an embodiment
of the present disclosure.
[0030] Fig. 9 is a side view of a system for multicolor variable lithography according to
another embodiment of the present disclosure.
[0031] Fig. 10 is a side view of a tandem architecture system for multi-component variable
lithography according to an embodiment of the present disclosure.
[0032] DETAILED DESCRIPTION
[0033] With reference to Fig. 1, there is shown therein a system 10 for multicolor variable
lithography according to one embodiment of the present disclosure. System 10 comprises
an imaging member 12, in this embodiment a drum, but may equivalently be a plate,
belt, web, etc., surrounded by a number of subsystems described in detail below. Imaging
member 12 applies an ink image to substrate 14 at nip 16 where substrate 14 is pinched
between imaging member 12 and an impression roller 18. A wide variety of types of
substrates, such as paper, plastic or composite sheet film, ceramic, glass, etc. may
be employed. For clarity and brevity of this explanation we assume the substrate is
paper, with the understanding that the present disclosure is not limited to that form
of substrate. For example, other substrates may include cardboard, corrugated packaging
materials, wood, ceramic tiles, fabrics (e.g., clothing, drapery, garments and the
like), transparency or plastic film, metal foils, etc. A wide latitude of marking
materials may be used including those with pigment densities greater than 10% by weight
including but not limited to metallic inks or white inks useful for packaging. For
clarity and brevity of this portion of the disclosure we generally use the term ink,
which will be understood to include the range of marking materials such as inks, pigments,
and other materials, which may be applied by systems and methods, disclosed herein.
[0034] With reference to Fig. 2, a portion of imaging member 12 is shown in cross-section.
In one embodiment, imaging member 12 comprises a thin reimageable surface layer 20
formed over a structural mounting layer 22 (for example metal, ceramic, plastic, etc.),
which together forms a reimaging portion 24 that forms a rewriteable printing blanket.
Reimaging portion 24 may further comprise additional structural layers, such as intermediate
layer 21 shown in Fig. 2B, below reimageable surface layer 20 and either above or
below structural mounting layer 22. Intermediate layer 21 may be electrically insulating
(or conducting), thermally insulating (or conducting), have variable compressibility
and durometer, and so forth. In one embodiment, intermediate layer 21 is composed
of closed cell polymer foamed sheets and woven mesh layers (for example, cotton) laminated
together with very thin layers of adhesive. Typically, blankets are optimized in terms
of compressibility and durometer using a 3-4 ply layer system that is between 1-3
mm thick with a thin top surface layer 20 designed to have optimized roughness and
surface energy properties. Reimaging portion 24 may take the form of a stand-alone
drum or web, or a flat blanket wrapped around a cylinder core 26. In another embodiment
the reimageable portion 24 is a continuous elastic sleeve placed over cylinder core
26. Flat plate, belt, web and other arrangements (which may or may not be supported
by an underlying drum configuration) are also within the scope of the present disclosure.
For the purposes of the following discussion, it will be assumed that reimageable
portion 24 is carried by cylinder core 26, although it will be understood that many
different arrangements, as discussed above, are contemplated by the present disclosure.
[0035] Reimageable surface layer 20 consists of a polymer such as polydimethylsiloxane (PDMS,
or more commonly called silicone) for example with a wear resistant filler material
such as silica to help strengthen the silicone and optimize its durometer, and may
contain catalyst particles that help to cure and cross link the silicone material.
Alternatively, silicone moisture cure (aka tin cure) silicone as opposed to catalyst
cure (aka platinum cure) silicone may be used. Returning to Fig. 2A, reimageable surface
layer 20 may optionally contain a small percentage of radiation sensitive particulate
material 27 dispersed therein that can absorb laser energy highly efficiently. In
one embodiment, radiation sensitivity may be obtained by mixing a small percentage
of carbon black, for example in the form of microscopic (e.g., of average particle
size less than 10 µm) or nanoscopic particles (e.g., of average particle size less
than 1000 nm) or nanotubes, into the polymer. Other radiation sensitive materials
that can be disposed in the silicone include graphene, iron oxide nano particles,
nickel-plated nano particles, etc.
[0036] Alternatively, reimageable surface layer 20 may be tinted or otherwise treated to
be uniformly radiation sensitive, as shown in Fig. 3. Still further, reimageable surface
layer 20 may be essentially transparent to optical energy from a source, described
further below, and the structural mounting layer or layers 22 may be absorptive of
that optical energy (e.g., layer 22 comprises a component that is at least partially
absorptive), as illustrated in Fig. 4.
[0037] Reimageable surface layer 20 should have a weak adhesion force to the ink at the
interface yet good oleophilic wetting properties with the ink, to promote uniform
(free of pinholes, beads or other defects) inking of the reimageable surface and to
promote the subsequent forward transfer lift off of the ink onto the substrate. Silicone
is one material having this property. Other materials providing this property may
alternatively be employed, such as certain blends of polyurethanes, fluorocarbons,
etc. In terms of providing adequate wetting of dampening solutions (such as water-based
fountain fluid), the silicone surface need not be hydrophilic but in fact may be hydrophobic
because wetting surfactants, such as silicone glycol copolymers, may be added to the
dampening solution to allow the dampening solution to wet the silicone surface.
[0038] It will therefore be understood that while a water-based solution is one embodiment
of a dampening solution that may be employed in the embodiments of the present disclosure,
other non-aqueous dampening solutions with low surface tension, that are oleophobic,
are vaporizable, decomposable, or otherwise selectively removable, etc. may be employed.
One such class of fluids is the class of HydroFluoroEthers (HFE), such as the Novec
brand Engineered Fluids manufactured by 3M of St. Paul, Minnesota. These fluids have
the following beneficial properties in light of the current disclosure: (1) much lower
heat of vaporization than water, which translates into lower laser power required
for a given print speed, or higher print speed for a given laser power, when an optical
laser is used to selectively vaporize the dampening solution to form the latent image;
(2) lower heat capacity, which translates into the same benefits; (3) they leave substantially
no solid residue after evaporation, which can translate into relaxed cleaning requirements
and/or improved long-term stability; (4) vapor pressure and boiling point can be engineered,
which can translate into an improved robustness of a spatially selective forced evaporation
process; (5) they have a low surface energy, as required for proper wetting of the
imaging member; and, (6) they are benign in terms of the environment and toxicity.
Additional additives may be provide to control the electrical conductivity of the
dampening solution. Other suitable alternatives include fluorinerts and other fluids
known in the art, that have all or a majority of the above properties. It is also
understood that these types of fluids may not only be used in their undiluted form,
but as a constituent in an aqueous non-aqueous solution or emulsion as well.
[0039] In addition, the surface energy of silicone may be optimized to provide good wetting
properties by controlling and specifying precise amounts of filler nano particles
in the silicone as well as the exact chemistry of the silicone material, which can
be composed of different distributions of polymer chain lengths and end group capping
chemistries. For example, it has been found that single component moisture cure silicones
that are tin catalyzed with low concentrations of silica filler have dispersive surface
energies between 24-26 dynes/cm. Certain additives may also be added to the marking
material in order to dramatically reduce the surface tension of the marking material
and improve its surface wetting properties to the silicone. These additives could
include, for example, leveling agents based on known copolymer fluoro or silicone
chemistries that also incorporate other polymer groups for easy dispersion and curing.
For example, leveling agents that can reduce ink surface tension to 21 dynes/cm.
[0040] If silicone is used as the reimageable surface layer 20, other particles 27 may also
be embedded within layer 20 to help catalyze the curing and cross linking of the silicone.
[0041] According to one embodiment, reimageable surface layer 20 has roughness on the order
of the desired dampening solution layer thickness to better trap the dampening solution
and prevents its spreading beyond the desired non-imaging region boundaries. For example,
reimageable surface layer 20 may have measured surface roughness characteristics RSm
and Ra defined as:
and
with reference to Figs. 5A and 5B wherein RSm is defined as the mean value of the
profile element width X(s) within a sample length L and Ra is related to averaged
peak to average baseline measurements over a sample length L. Thus, RSm is characteristic
of the peak-to-peak spacing and Ra is characteristic of the peak height. Such definitions
can be extended over two dimensions by using a characteristic sampling area A with
dimensions A∼L
2.
[0042] It is desirable that the peaks and valleys are somewhat randomly distributed to reduce
the possibility of Moire interference with a linescreen pattern. In addition, it is
desirable that the spatial distance between the peaks is somewhat less than the smallest
line screen dot size, for example less than 10 µm. This roughness helps the surface
to easily retain dampening solution while eliminating Moiré effects and acts to improve
inking uniformity and transfer, as described further below. In one embodiment RSm
is less than about 20 µm and the Ra is less than about 4.0 µm, and in a more specific
embodiment, RSm is less than 10 µm and the Ra is between 0.1 µm and 4.0 µm.
[0043] In addition, the reimageable surface layer 20 must be wear resistant and capable
of some flexibility (even under tension) in order to transfer ink off of its surface
onto porous or rough paper media uniformly. The reimageable surface layer 20 may be
made thick enough to achieve an appropriate elasticity and durometer and sufficient
flexibility necessary for coating ink over different media types with different levels
of roughness. Of course, systems may be designed for printing to a specific media
type, obviating the need to accommodate a variety of media types. In one embodiment
the thickness of the silicone layer forming reimageable surface layer 20 is in the
range of 0.5 µm to 4 mm.
[0044] Finally, reimageable surface layer 20 must facilitate the flow of ink onto its surface
with uniformity and without beading or dewetting. Various materials such as silicone
can be manufactured or textured to have a range of surface energies, and such energies
can be tailored with additives. Reimageable surface layer 20, while nominally having
a low value of dynamic chemical adhesion, may have a sufficient surface energy in
order to promote efficient ink wetting/affinity without ink dewetting or beading.
[0045] Returning to Fig. 1, disposed at a first location around imaging member 12 is dampening
solution subsystem 30. Dampening solution subsystem 30 generally comprises a series
of rollers (referred to as a dampening unit) for uniformly wetting the surface of
reimageable surface layer 20. It is well known that many different types and configurations
of dampening units exist. The purpose of the dampening unit is to deliver a layer
of dampening solution 32 having a uniform and controllable thickness. In one embodiment
this layer is in the range of 0.2 µm to 1.0 µm, and very uniform without pinholes.
The dampening solution 32 may be composed mainly of water, optionally with small amounts
of isopropyl alcohol or ethanol added to reduce its natural surface tension as well
as lower the evaporation energy necessary for subsequent laser patterning. In addition,
a suitable surfactant is ideally added in a small percentage by weight, which promotes
a high amount of wetting to the reimageable surface layer 20. In one embodiment, this
surfactant consists of silicone glycol copolymer families such as trisiloxane copolyol
or dimethicone copolyol compounds which readily promote even spreading and surface
tensions below 22 dynes/cm at a small percentage addition by weight. Other fluorosurfactants
are also possible surface tension reducers. Optionally dampening solution 32 may contain
a radiation sensitive dye to partially absorb laser energy in the process of patterning,
described further below.
[0046] In addition to or in substitution for chemical methods, physical/electrical methods
may be used to facilitate the wetting of dampening solution 32 over the reimageable
surface layer 20. In one example, electrostatic assist operates by way of the application
of a high electric field between the dampening roller and reimageable surface layer
20 to attract a uniform film of dampening solution 32 onto reimageable surface layer
20. The field can be created by applying a voltage between the dampening roller and
the reimageable surface layer 20 or by depositing a transient but sufficiently persisting
charge on the reimageable surface layer 20 itself. The dampening solution 32 may be
electronically conductive. Therefore, in this embodiment an insulating layer (not
shown) may be added to the dampening roller and/or under reimageable surface layer
20. Using electrostatic assist, it may be possible to reduce or eliminate the surfactant
from the dampening solution.
[0047] Following metering of dampening solution 32 onto reimageable surface layer 20 by
dampening solution subsystem 30, the thickness of the metered dampening solution may
be measured using a sensor 34 such as an in-situ non-contact laser gloss sensor or
laser contrast sensor, such as those sold by Wenglor Sensors (Beavercreek, OH). Such
a sensor can be used to automate the controls of dampening solution subsystem 30.
[0048] After applying a precise and uniform amount of dampening solution, in one embodiment
an optical patterning subsystem 36 is used to selectively form a latent image in the
dampening solution by image-wise evaporating the dampening solution layer using laser
energy, for example. It should be noted here that the reimageable surface layer 20
should ideally absorb most of the energy as close to an upper surface 28 (Fig. 2)
as possible, to minimize any energy wasted in heating the dampening solution and to
minimize lateral spreading of the heat so as to maintain high spatial resolution capability.
Alternatively, it may also be preferable to absorb most of the incident radiant (e.g.,
laser) energy within the dampening solution layer itself, for example, by including
an appropriate radiation sensitive component within the dampening solution that is
at least partially absorptive in the wavelengths of incident radiation, or alternatively
by choosing a radiation source of the appropriate wavelength that is readily absorbed
by the dampening solution (e.g., water has a peak absorption band near 2.94 micrometer
wavelength).
[0049] It will be understood that a variety of different systems and methods for delivering
energy to pattern the dampening solution over the reimageable surface may be employed
with the various system components disclosed and claimed herein. However, the particular
patterning system and method do not limit the present disclosure.
[0050] With reference to Fig. 6, which is a magnified view of a region of reimageable portion
24 having a layer of dampening solution 32 applied over reimageable surface layer
20, the application of optical patterning energy (e.g., beam B) from optical patterning
subsystem 36 results in selective evaporation of portions the layer of dampening solution
32. Evaporated dampening solution becomes part of the ambient atmosphere surrounding
system 10. This produces a pattern of dampening solution regions 38 and ink receiving
voids 40 over reimageable surface layer 20. Relative motion between imaging member
12 and optical patterning subsystem 36, for example in the direction of arrow A, permits
a process-direction patterning of the layer of dampening solution 32.
[0051] Returning to Fig. 1, following patterning of the dampening solution layer 32, one
of a series of inker subsystems 46a, 46b, 46c, 46d is used to apply a uniform layer
48 of ink, shown in Fig. 6, over the layer of dampening solution 32 and reimageable
surface layer 20. It will be understood that marking materials beyond inks (such as
non-aqueous marking material, finishing materials, surface treatments, etc.), whether
visible or non-visible, may be utilized in the embodiments disclosed herein. Thus,
while "marking material applicator" may be more general and comprehensive the term
"inker" subsystem is employed in the following descriptions for ease of reference.
Four inker subsystems are shown in Fig. 1, each corresponding with a color component
such as cyan, magenta, yellow, and black of a color system. Alternatively, system
10 may comprise additional or fewer inker subsystems as may be appropriate for alternative
color systems, printing effects, and so. Incorporation of such additional, or fewer,
inker subsystems will be readily understood by one skilled in the art from the present
disclosure. While for the purposes of this example each inker subsystem is assumed
to deposit different color ink, in variations contemplated hereby each inker subsystem
may deposit a marking material that may differ in other than (just) color. For example,
as between two such inker subsystems, one may deposit a flat finish of a color while
the other may deposit a reflective finish of that same color (possibly in a different
pattern as between the two). One may deposit standard ink, while the second deposits
magnetically readable ink. One may again deposit standard ink, while the second deposits
a uniform surface finish coat, etc. Therefore, the actual material deposited does
not per se limit the scope of the methods and systems disclosed and claimed herein.
[0052] Optionally, an air knife 44 may be directed towards reimageable surface layer 20.
Air knife 44 may control airflow over the surface layer before the inking subsystems
for the purpose of maintaining clean dry air supply, a controlled air temperature
and reducing dust contamination.
[0053] Each inker subsystem 46a, 46b, 46c, 46d may consist of a "keyless" system using an
anilox roller to meter an offset ink onto one or more forming rollers. Alternatively,
each inker subsystem 46a, 46b, 46c, 46d may consist of more traditional elements with
a series of form rollers that use electromechanical keys to determine the precise
feed rate of the ink. The general aspects of inker subsystem architecture will depend
on the application of the present disclosure, and will be well understood by one skilled
in the art.
[0054] Each inker subsystem 46a, 46b, 46c, 46d may be actuated to engage with or disengage
from reimageable surface 20. By engage, it is meant that the inker subsystem, or a
component thereof, is positioned proximate the reimageable surface such that material
carried thereby is permitted to be transferred onto the reimageable surface. This
may or may not mean physical contact between the two, depending on many factors. Similarly,
disengagement is meant the positioning of the inker subsystem, or a component thereof,
such that material carried thereby cannot readily transfer therefrom to the reimageable
surface. In the embodiment illustrated in Fig. 1, each inker subsystem may translate
on a track or armature generally radially with regard to imaging member 12. Many other
embodiments are within the scope of the present disclosure for engaging and disengaging
the inker subsystems with reimageable surface 20. One such alternative embodiment
50 is illustrated in Fig. 8. Embodiment 50 comprises an inking subsystem 52 including
a rotationally disposed metering (forming) roller 54, which receives ink from anilox
roller 56, and which selectively transfers ink to reimageable surface 20 of imaging
member 12. Form roller 54 rotates around a central axis that, in a first position
54a, is such that the surface of form roller 54 is not engaged with reimageable surface
20. The center of rotation of form roller 54 may be translated to a second position
54b, such as rotating around a center 56a of anilox roller 56, such that the surface
of form roller 54 is engaged with reimageable surface 20. In this way, ink from a
reservoir 58 is applied to reimageable surface 20 when form roller 54 is engaged with
reimageable surface 20, and is not applied to reimageable surface 20 when form roller
54 is disengaged from reimageable surface 20.
[0055] Returning to Fig. 6, in order for ink from inker subsystem 46 to initially wet over
the reimageable surface layer 20, the ink must have low enough cohesive energy to
split onto the exposed portions of the reimageable surface layer 20 (ink receiving
dampening solution voids 40) and also be hydrophobic enough to be rejected at dampening
solution regions 38. Since the dampening solution is low viscosity and oleophobic,
areas covered by dampening solution naturally reject all ink because splitting naturally
occurs in the dampening solution layer that has very low dynamic cohesive energy.
In areas without dampening solution, if the cohesive forces between the ink are sufficiently
lower than the adhesive forces between the ink and the reimageable surface layer 20,
the ink will split between these regions at the exit of the forming roller nip. The
ink employed should therefore have a relatively low viscosity in order to promote
better filling of voids 40 and better adhesion to reimageable surface layer 20. For
example, if an otherwise known UV ink is employed, and the reimageable surface layer
20 is comprised of silicone, the viscosity and viscoelasticity of the ink will likely
need to be modified slightly to lower its cohesion and thereby be able to wet the
silicone. Adding a small percentage of low molecular weight monomer or using a lower
viscosity oligomer in the ink formulation can accomplish this rheology modification.
In addition, wetting and leveling agents may be added to the ink in order to further
lower its surface tension in order to better wet the silicone surface.
[0056] In addition to this rheological consideration, it is also important that the ink
composition maintain a hydrophobic character so that it is rejected by dampening solution
regions 38. This can be maintained by choosing offset ink resins and solvents that
are hydrophobic and have non-polar chemical groups (molecules). When dampening solution
covers layer 20, the ink will then not be able to diffuse or emulsify into the dampening
solution quickly and because the dampening solution is much lower viscosity than the
ink, film splitting occurs entirely within the dampening solution layer, thereby rejecting
ink any ink from adhering to areas on layer 20 covered with an adequate amount of
dampening solution. In general, the dampening solution thickness covering layer 20
may be between 0.1 µm - 4.0 µm, and in one embodiment 0.2 µm - 2.0 µm depending upon
the exact nature of the surface texture.
[0057] In certain embodiments, a metering roller 62 may be employed with a form roller 60,
such as illustrated in Fig. 7. The thickness of the ink coated on roller 60 from a
source roller 64, such as an anilox roller, and optional roller 62 can be controlled
by adjusting the feed rate of the ink through the roller system using distribution
rollers, adjusting the pressure between feed roller, form roller 60, and form roller
62, and by using ink keys to adjust the flow off of an ink tray. Ideally, the thickness
of the ink presented to the rollers 60, 62 should be at least twice the final thickness
desired to transfer to the reimageable layer 20 as film splitting occurs. It is also
possible to use a keyless system which can control the overall ink film thickness
by using an anilox roller with uniformly formed ink carrying pits and maintaining
the temperature to achieve the desired ink viscosity. Typically, the final film thickness
may be approximately 1-2 µm.
[0058] Ideally, an optimized ink system splits onto the reimageable surface at a ratio of
approximately 50:50 (i.e., 50% remains on the ink forming rollers and 50% is transferred
to the reimageable surface at each pass). However, other splitting ratios may be acceptable
as long as the splitting ratio is well controlled. For example, for 70:30 splitting,
the ink layer over reimageable surface layer 20 is 30% of its nominal thickness when
it is present on the outer surface of the forming rollers. It is well known that reducing
an ink layer thickness reduces its ability to further split. This reduction in thickness
helps the ink to come off from the reimageable surface very cleanly with residual
background ink left behind. However, the cohesive strength or internal tack of the
ink also plays an important role.
[0059] Returning to Fig. 1, a first inker subsystem, such as subsystem 46a, is engaged with
reimageable surface 20 such that ink of a first color provided by that inker subsystem
is applied to the reimageable surface in regions of voids in the dampening fluid layer
provided thereover and thereby form an inked latent image of the first color. The
inked latent image of the first color is next transferred to substrate 14 such as
by passing substrate 14 through nip 16 between imaging member 12 and impression roller
18. Adequate pressure is applied between imaging member 12 and impression roller 18
such that the ink within voids 40 (Fig. 8) is brought into physical contact with substrate
14. Adhesion of the ink to substrate 14 and strong internal cohesion cause the ink
to separate from reimageable surface layer 20 and adhere to substrate 14. Impression
roller or other elements of nip 16 may be cooled to further enhance the transfer of
the inked latent image to substrate 14. Indeed, substrate 14 itself may be maintained
at a relatively colder temperature than the ink on imaging member 12, or locally cooled,
to assist in the ink transfer process. The ink can be transferred off of reimageable
surface layer 20 with greater than 95% efficiency as measured by mass, and can exceed
99% efficiency with system optimization.
[0060] Substrate 14 may be maintained within the system in a position such that it may readily
be reintroduced to nip 16 for successive passes, each layering a color latent ink
image thereon. More specifically, any residual ink and residual dampening solution
remaining on reimageable surface 20 after nip 16 must be removed, preferably without
scraping or wearing that surface. Much of the dampening solution can be easily and
quickly removed using an air knife 70 with sufficient airflow. Removal of remaining
ink is accomplished at cleaning subsystem 72. The application of dampening fluid and
patterning of the dampening fluid, as previously described is repeated. A new pattern
is thereby formed in the dampening fluid layer. Inker subsystem 46a is disengaged
from reimageable surface 20, and inker subsystem 46b moved to engage reimageable surface
20. A second color ink may thereby be applied to the patterned dampening fluid layer
over reimageable surface 20 to form a latent ink image of the second color. This latent
ink image of the second color is transferred to substrate 14 such as by passing substrate
14 through nip 16 between imaging member 12 and impression roller 18. One of a variety
of methods for registration of substrate 14 for receipt of the latent ink image of
the second color, description of which being beyond the scope of the present disclosure,
is employed to ensure the registration of the two latent images. This process is similarly
repeated for inker subsystems 46c and 46d.
[0061] To assist in preventing smearing, color contamination, color transfer from the substrate
back to the imagining member, and so on, following transfer of one inked color latent
image to the substrate, the image may be partially cured. The partial cure may be
from the back or front (or both) of the substrate, and be by way of UV exposure, heat,
or other source 74 appropriate to the particular ink and substrate being used. In
addition, the ink may be partially cured on reimageable surface 20 prior to transfer
to substrate 14, such as by a UV, heat, or other source 76.
[0062] In an exemplary embodiment, substrate 14 is retained on the surface of impression
roller 18 for each of the passes through nip 16. The rotation of imaging member 12
and impression roller 18 are synchronized to ensure the aforementioned registration.
Substrate 14 makes up to n revolutions (n being, for example, the number of inker
subsystems) and is then removed from the impression roller 18. According to another
embodiment 80 illustrated in Fig. 9, in place of imparting each latent color image
directly to substrate 14, they are successively applied to belt 82 (a web, plate or
other intermediate member may similarly be employed).
[0063] Other modes of indirect transferring of the ink pattern from an imaging member to
a substrate are also contemplated by this disclosure. For example, with reference
to Fig. 9, an alternate embodiment 80 of the present disclosure comprises a low mass,
relatively flexible belt or web image receiving member 82 having a reimageable surface
thereover. Similar to the embodiments described above, a dampening system 84 applies
a layer of dampening fluid 86 over the surface of image receiving member 82. One of
a variety of methods and systems may be employed to ensure that the layer of dampening
fluid is of a uniform and desired thickness. The dampening fluid layer is patterned
by a patterning subsystem 88, for example, a scanned and modulated laser source. A
plurality of inker subsystems 90a, 90b, 90c, 90d, etc., are positioned proximate but
not in a touching relationship to the reimageable surface of imaging member 82. Imaging
member 82 is relatively flexible. A plurality of engagement mechanisms 91 a, 91 b,
91 c 91 d, etc. is disposed opposite inker subsystems 90a, 90b, 90c, 90d, etc. with
imaging member 82 disposed therebetween. Each engagement mechanism 91 a, 91 b, 91
c, 91 d, etc. is individually translatable so as to deflect imaging member 82 into
engagement with a corresponding one of inker subsystems 90a, 90b, 90c, 90d, etc.,
which may apply ink thereto. Thus, for example, with engagement mechanism 91 a deflecting
imaging member 82 into engagement with inker subsystem 90a, as shown, ink of a first
color or composition may be applied to the reimageable surface of imaging member 82.
As explained above, this ink preferentially deposits in the voids formed by patterning
subsystem 88 to form an inked color latent image on the surface of imaging member
82.
[0064] The inked color latent image is transferred to substrate 92 such as by passing substrate
92 through nip 94 between imaging member 82 and impression roller 96. Partial curing
other aspects of image optimization and maintaining substrate 92 in position for successive
passes for image application may be performed.
[0065] Any residual ink and residual dampening solution remaining on the reimageable surface
of imaging member 82 after nip 94 is removed using an air knife 98 in combination
with a cleaning subsystem 100 (or other suitable cleaning methods and subsystems).
The application of dampening fluid and patterning of the dampening fluid, as previously
described, is repeated. A new pattern is thereby formed in the dampening fluid layer.
Engagement member 91 a is retracted, and engagement 91 b activated so as to deflect
the reimageable surface of imaging member 82 into engagement with inker subsystem
90b. A second color ink may thereby be applied by inker subsystem 90b to the patterned
dampening fluid layer over the reimageable surface of imaging member 82 to form a
latent ink image of the second color. This latent ink image of the second color is
transferred to substrate 92. This process is similarly repeated for inker subsystems
90c and 90d.
[0066] While the aforementioned embodiments have primarily involved multi-pass printing
according to which colors are successively applied to a patterned intermediate transfer
member and transferring that color pattern to the substrate, cleaning the intermediate
transfer member, in certain embodiments it may be desirable to successively transfer
individual color images directly to a substrate. Such may be the case, for example,
where the substrate is continuous or longer than the circumference of the impression
roller, where it is not practical to retain a substrate and reintroduce it through
a nip successive times, etc.
[0067] With reference next to Fig. 10, a tandem architecture embodiment 110 is shown for
multicolor variable data lithography directly to a substrate. According to embodiment
110, a plurality of imaging members 112a, 112b, 112c, 112d, etc., each having associated
therewith an inker subsystem 114a, 114b, 114c, 114d, etc. for example of a different
color, are arranged to engage a substrate 116 traveling in proximity thereto. Essentially
as previously discussed, each imaging member 112a, 112b, 112c, 112d comprises a reimageable
layer thereover for receiving dampening fluid from a dampening fluid subsystem 118a,
118b, 118c, 118d, etc., respectively. The dampening fluid layer over each reimageable
surface is patterned by a patterning subsystem 120a, 120b, 120c, 120d, etc., respectively.
Each of inker subsystems 114a, 114b, 114c, 114d, etc. apply a unique ink material
(e.g., different color, different ink composition, different opacity, etc.) over the
patterned dampening fluid layer to form a unique latent image over each imaging member
112a, 112b, 112c, 112d, etc. In succession, each unique latent image is applied to
substrate 116 at nips 122a, 122b, 122c, 122d, etc. Each reimageable surface may then
be cleaned at cleaning subsystem 124a, 124b, 124c, 124d, etc. Optionally, after each
imaging member 112a, 112b, 112c, 112d, etc. applies its latent image to substrate
116, the image on substrate 116 may be at least partially cured by curing subsystems
126a, 126b, 126c, etc. (such as UV curing for UV-cured inks). A full UV cure (or other
material treatment) subsystem 128 may also be provided following the last application
of ink.
[0068] While in such embodiments it has been assumed that each imaging member comprises
a reimageable substrate that is provided with its own dampening fluid layer that is
patterned and inked, in certain embodiments one or more of the imaging members may
carry a permanent image pattern that is inked and added to the intermediate or final
substrate together with an image(s) from a reimageable surface of an imaging member.
In this way, variable and non-variable print elements may be combined prior to or
onto a substrate.
[0069] A system having a single imaging cylinder, without an offset or blanket cylinder,
is shown and described herein. The reimageable surface layer is made from material
that is conformal to the roughness of print media via a high-pressure impression cylinder,
while it maintains good tensile strength necessary for high volume printing. Traditionally,
this is the role of the offset or blanket cylinder in an offset printing system. However,
requiring an offset roller implies a larger system with more component maintenance
and repair/replacement issues, and increased production cost, added energy consumption
to maintain rotational motion of the drum (or alternatively a belt, plate or the like).
Therefore, while it is contemplated by the present disclosure that an offset cylinder
may be employed in a complete printing system, such need not be the case. Rather,
the reimageable surface layer may instead be brought directly into contact with the
substrate to affect a transfer of an ink image from the reimageable surface layer
to the substrate. Component cost, repair/replacement cost, and operational energy
requirements are all thereby reduced.
[0070] It should be understood that when a first layer is referred to as being "on" or "over"
a second layer or substrate, it can be directly on the second layer or substrate,
or on an intervening layer or layers may be between the first layer and second layer
or substrate. Further, when a first layer is referred to as being "on" or "over" a
second layer or substrate, the first layer may cover the entire second layer or substrate
or a portion of the second layer or substrate.
[0071] The invention described herein, when operated according to the method described herein
meets the standard of high ink transfer efficiency, for example greater than 95% and
in some cases greater than 99% efficiency of transferring ink off of the imaging member
and onto the substrate. In addition, the disclosure teaches combining the functions
of the print cylinder with the offset cylinder wherein the rewritable imaging surface
is made from material that can be made conformal to the roughness of print media via
a high pressure impression cylinder while it maintains good tensile strength necessary
for high volume printing. Therefore, we disclose a system and method having the added
advantage of reducing the number of high inertia drum components as compared to a
typical offset printing system. The disclosed system and method may work with any
number of offset ink types but has particular utility with UV lithographic inks.
[0072] The physics of modern devices and the methods of their production are not absolutes,
but rather statistical efforts to produce a desired device and/or result. Even with
the utmost of attention being paid to repeatability of processes, the cleanliness
of manufacturing facilities, the purity of starting and processing materials, and
so forth, variations and imperfections result. Accordingly, no limitation in the description
of the present disclosure or its claims can or should be read as absolute. The limitations
of the claims are intended to define the boundaries of the present disclosure, up
to and including those limitations. To further highlight this, the term "substantially"
may occasionally be used herein in association with a claim limitation (although consideration
for variations and imperfections is not restricted to only those limitations used
with that term). While as difficult to precisely define as the limitations of the
present disclosure themselves, we intend that this term be interpreted as "to a large
extent", "as nearly as practicable", "within technical limitations", and the like.
[0073] Furthermore, while a plurality of preferred exemplary embodiments have been presented
in the foregoing detailed description, it should be understood that a vast number
of variations exist, and these preferred exemplary embodiments are merely representative
examples, and are not intended to limit the scope, applicability or configuration
of the disclosure in any way. Various of the above-disclosed and other features and
functions, or alternative thereof, may be desirably combined into many other different
systems or applications. Various presently unforeseen or unanticipated alternatives,
modifications variations, or improvements therein or thereon may be subsequently made
by those skilled in the art which are also intended to be encompassed by the claims,
below.
[0074] Therefore, the foregoing description provides those of ordinary skill in the art
with a convenient guide for implementation of the disclosure, and contemplates that
various changes in the functions and arrangements of the described embodiments may
be made without departing from the spirit and scope of the disclosure defined by the
claims thereto.
1. A marking material subsystem for a variable data lithography system, comprising:
a plurality of marking material assemblies, each marking material assembly comprising:
a marking material source;
a marking material transfer subsystem for receiving marking material from said marking
material source and applying said marking material to a surface of an imaging member;
a control mechanism for selectively engaging and disengaging each of said plurality
of marking material assemblies with a surface of said imaging member.
2. The marking material subsystem of claim 1, wherein said control mechanism controls
the engaging and disengaging of each said marking material assembly with said imaging
member such that only one of said marking material assemblies are engaged with said
surface of said imaging member at any one time.
3. The marking material subsystem of claim 1 or claim 2, wherein each said marking material
transfer subsystem comprises a marking material form roller, and further wherein said
control mechanism comprises an assembly for mechanically bringing said marking material
form roller into and out of engagement with said surface of said imaging member.
4. The marking material subsystem of claim 3, wherein said marking material form roller
is brought into and out of engagement with said surface of said imaging member by
said control mechanism while any remaining elements of said marking material subsystem
remain fixed in position relative to said imaging member.
5. The marking material subsystem of any of the preceding claims, wherein at least one
of said marking material assemblies is an inking assembly for applying ink to said
surface of said imaging member.
6. The marking material subsystem of claim 5, wherein at least two of said inking assemblies
each applies ink having different compositions, wherein typically at least one of
said marking material assemblies provides a non-visible material to said surface of
said imaging member.
7. The marking material subsystem of any of the preceding claims, further comprising
an engagement mechanism disposed so as to selectively deflect said imaging member
into engagement with said marking material transfer subsystem so as to cause said
marking material transfer subsystem to selectively apply said marking material to
said surface of said imaging member.
8. A variable data lithography system for applying a multicomponent image to a substrate,
comprising:
an imaging member comprising:
an arbitrarily reimageable surface layer, the arbitrarily reimageable surface having:
a surface roughness Ra in the range of 0.1 to 4.0 micrometers (µm);
a lateral spatial scale average distance RSm not exceeding 20 micrometers (µm);
a dampening solution subsystem for applying a layer of dampening solution to said
arbitrarily reimageable surface layer;
a patterning subsystem for selectively removing portions of the dampening solution
layer so as to produce a latent image in the dampening solution;
a marking material subsystem, comprising:
a plurality of marking material assemblies, each for applying marking material over
the arbitrarily reimageable surface layer such that said marking material selectively
occupies regions of the reimageable surface layer where dampening solution was removed
by the patterning subsystem to thereby produce a latent image of said marking material;
each marking material assembly further comprising a marking material source; and
an image transfer subsystem for transferring the inked latent image to a substrate.
9. The variable data lithographic system of claim 8, wherein the marking material subsystem
is in accordance with any of claims 1 to 7, the control mechanism being adapted to
selectively engage and disengage each of said plurality of marking material assemblies
with said arbitrarily reimageable surface layer.
10. A variable data lithography system for applying a multi-component image to a substrate,
comprising:
a plurality of marking stations, each marking station comprising:
an imaging member comprising:
an arbitrarily reimageable surface layer, the arbitrarily reimageable surface having:
a surface roughness Ra in the range of 0.1 to 4.0 micrometers (µm);
a lateral spatial scale average distance RSm not exceeding 20 micrometers (µm);
a dampening solution subsystem for applying a layer of dampening solution to said
arbitrarily reimageable surface layer;
a patterning subsystem for selectively removing portions of the dampening solution
layer so as to produce a latent image in the dampening solution;
a marking material subsystem, comprising:
a marking material assembly for applying marking material over the arbitrarily reimageable
surface layer such that said marking material selectively occupies regions of the
reimageable surface layer where dampening solution was removed by the patterning subsystem
to thereby produce a latent image of said marking material;
a marking material source; and
an image transfer subsystem for transferring the inked latent image to a substrate.
11. The variable data lithography system of claim 10, wherein at least one of said marking
stations is an inking assembly for applying ink to said substrate.
12. The variable data lithography system of claim 11, wherein a plurality of said marking
stations are each an inking assembly for providing ink to said substrate, and further
wherein each of said inking assemblies provides a different color of ink to said substrate.
13. The variable data lithography system of claim 11, wherein at least two of said inking
assemblies each applies ink having different compositions.
14. The variable data lithography system of claim 11, wherein at least one of said marking
material assemblies provides a non-visible material to said surface of said imaging
member.
15. The variable data lithography system of any of claims 10 to 14, wherein at least one
of said dampening solution subsystem and said patterning subsystem is shared by said
plurality of marking stations.