U.S. patent application number 15/442260 was filed with the patent office on 2017-06-08 for aqueous dispersible polymer inks.
This patent application is currently assigned to XEROX CORPORATION. The applicant listed for this patent is XEROX CORPORATION. Invention is credited to Marcel P. Breton, Carolyn Moorlag, Guerino Sacripante.
Application Number | 20170157918 15/442260 |
Document ID | / |
Family ID | 53275619 |
Filed Date | 2017-06-08 |
United States Patent
Application |
20170157918 |
Kind Code |
A1 |
Breton; Marcel P. ; et
al. |
June 8, 2017 |
AQUEOUS DISPERSIBLE POLYMER INKS
Abstract
An ink composition or ink concentrate for variable data
lithographic printing or ink jet printing that uses an intermediate
substrate, includes nano-particles, wherein each nano-particle is a
polymer or a polymer blend of polymers; the polymer or polymers of
the polymer blend are water dispersible at temperatures below 100
degrees Celsius; solids content of the ink composition is in an
amount of greater than 25 percent by total weight; and the ink
composition has a viscosity of about 100 centipoise to about 1,000
centipoise in the temperature range of 20 degrees Celsius to 50
degrees Celsius.
Inventors: |
Breton; Marcel P.;
(Mississauga, CA) ; Moorlag; Carolyn;
(Mississauga, CA) ; Sacripante; Guerino;
(Oakville, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XEROX CORPORATION |
Norwalk |
CT |
US |
|
|
Assignee: |
XEROX CORPORATION
NORWALK
CT
|
Family ID: |
53275619 |
Appl. No.: |
15/442260 |
Filed: |
February 24, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14139708 |
Dec 23, 2013 |
|
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15442260 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B41J 2/0057 20130101;
C08K 5/17 20130101; C09D 11/104 20130101; C09D 11/033 20130101;
C08K 5/3415 20130101; C09D 11/106 20130101; C08K 5/07 20130101;
C08K 5/41 20130101; C09D 11/102 20130101; C09D 11/037 20130101;
C08K 5/053 20130101 |
International
Class: |
B41J 2/005 20060101
B41J002/005; C09D 11/037 20060101 C09D011/037; C09D 11/033 20060101
C09D011/033; C09D 11/104 20060101 C09D011/104 |
Claims
1. An ink composition for variable data offset printing or an ink
jet printing process that uses an intermediate substrate,
comprising: nano-particles, wherein each nano-particle is a polymer
or a polymer blend of polymers, and optionally one or more mixtures
of the following: inorganic particles, silica, pigment, salts,
bioside, buffer, or humectant, wherein the polymer or the polymers
of the polymer blend are water dispersible at temperatures less
than 100 degrees Celsius, wherein the total solids content of the
ink composition is an amount in a range of about 25% or greater by
total weight of the ink composition, wherein the polymer or the
polymer blend comprises a sulfonated polyester, and wherein the ink
composition has a viscosity of about 100 centipoise to about 1,000
centipoise in the temperature range of 20 degrees Celsius to 50
degrees Celsius.
2. The ink composition of claim 1, wherein the polymer comprises a
component derived from monomers selected from the group consisting
of glycols, multifunctional glycols, alcohols, multifunctional
alcohols, acids, and salts thereof, and wherein the polymer blend
comprises a component selected from the group consisting of
carboxyl-polyester and polyester.
3. The ink composition of claim 1, wherein the polymer or the
polymers of the polymer blend contains a portion that is water
soluble in an amount less than 10%, and is soluble in a non-aqueous
liquid vehicle in an amount less than 30%, at a temperature between
20 and 50 degrees Celsius.
4. The ink composition of claim 1, wherein the polymer or the
polymers of the polymer blend are substantially soluble at
temperatures above 70 to 95 degrees Celsius.
5. The composition of claim 1, wherein the polymer or the polymer
blend has a critical phase separation temperature of about 50
degrees Celsius to about 90 degrees Celsius.
6. The ink composition of claim 1, wherein the polymer or the
polymers of the polymer blend comprises an unsaturated functional
group.
7. The ink composition of claim 1, comprising: a co-solvent, the
co-solvent having a surface tension of about 15 dynes/centimeter to
about 40 dynes/centimeter, the co-solvent being selected from the
group comprising alcohols, glycols, alkyl pyrrolidinones,
isopropanol, ketones methyl ethyl ketone, amino alcohol and
DMSO.
8. The ink composition of claim 1, wherein the nano-particles are
less than 200 nm, or mixtures of nano-particles forming bimodal or
trimodal distributions.
9. The ink composition of claim 1, further comprising: a
self-dispersing pigment of a particle size between 5 to 200 nm,
wherein the pigment is chemically modified or resin
encapsulated.
10. The ink composition of claim 1, further comprising a
self-dispersing pigment that is encapsulated by, or aggregated with
the polymer or the polymer blend, thereby forming a
nano-particle.
11. The composition of claim 9, wherein the resin that is used to
encapsulate the pigment is between 9 percent and 66 percent of the
combined weight of the pigment and the encapsulating resin.
12. The composition of claim 1, wherein the ink composition has a
viscosity of ink after loss of 0 to 80 percent of liquid vehicle is
between 10,000 centipoise and 1,000,000,000 centipoise at
temperatures between 10 degrees Celsius to about 90 degrees
Celsius.
13. The composition of claim 1, wherein the surface tension of the
ink is between 15 and 40 dynes/centimeter at 25 degrees C., or over
the temperature range between 20 to 50 degrees C.
14. The ink composition of claim 1, wherein the sulfonated
polyester is
copoly(1,2-propylene-dipropylene-terephthalate)-copoly(1,2-propylene-dipr-
opylene-5-sodiosulfoisophthalate).
15. A method of printing using high solids content inks,
comprising: providing an ink comprising water and nano-particles,
wherein each nano-particle is a polymer or a polymer blend of
polymers; and applying the ink to an intermediate transfer member,
wherein the intermediate transfer member has a surface comprising
silicone or fluorosilicone, wherein the polymer or polymers of the
polymer blend are water dispersible, wherein a solids content of
the ink is in an amount of about 5% to about 50% by weight by total
weight of the ink, and wherein the polymer or the polymer blend
comprises a sulfonated polyester, wherein the ink has a viscosity
of about 100 centipoise to about 1000 centipoise in the temperature
range of 20 degrees Celsius to 50 degrees Celsius.
16. The method of claim 15, wherein the step of the applying the
ink further comprises: applying the ink at an ink temperature above
the upper critical phase separation temperature of the polymer or
the polymer blend, the upper critical phase separation temperature
being about 30 degrees Celsius to about 50 degrees Celsius; cooling
the ink on the intermediate transfer member; and transferring the
ink from the intermediate transfer member to a printable
substrate.
17. The method of claim 16, wherein the printable substrate is an
imaging member of an ink-based digital printing system.
18. The method of claim 15, wherein a film of the ink on the
intermediate transfer member has a surface tension of about 15
dynes/centimeter to about 40 dynes/centimeter.
19. The method of claim 15, comprising: diluting the ink with water
before the step of applying, whereby the solid content of the ink
is between 5% and 25% by weight, and wherein, the step of applying
the ink to an intermediate transfer member further comprises
jetting the diluted ink from an inkjet printhead.
20. An ink composition for variable data offset printing or an ink
jet printing process that uses an intermediate substrate,
comprising: nano-particles, wherein each nano-particle is a polymer
or a polymer blend of polymers, wherein the polymer or the polymers
of the polymer blend are water dispersible at temperatures less
than 100 degrees Celsius, wherein the total solids content of the
ink composition is an amount in a range of about 4% to about 25% by
total weight of the ink composition, wherein the polymer or the
polymer blend comprises a sulfonated polyester, wherein the ink
composition has a viscosity of about 100 centipoise to about 1000
centipoise in the temperature range of 20 degrees Celsius to 50
degrees Celsius.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/139,708, filed Dec. 23, 2013 and relates to
U.S. patent application Ser. No. 14/139,690, filed Dec. 23, 2013;
U.S. patent application Ser. No. 14/139,811, filed Dec. 23, 2013,
the disclosures of which are hereby incorporated by reference
herein in their entireties.
FIELD OF DISCLOSURE
[0002] The disclosure relates to inks for printing images on
substrates such as paper, plastic, metal, or other printable
materials. In particular, the disclosure relates to aqueous
dispersible polymer inks particularly suitable for imaging or
jetting onto an intermediate substrate.
BACKGROUND
[0003] Conventional aqueous thermal ink jet or piezo aqueous inks
have been found to cause cockle, curl and/or showthrough, which is
readily apparent when printing on plain paper, particularly if the
amount of water in the ink exceeds 50% by weight. Also, printing on
non-porous substrate requires specialized ink formulations with
binders incorporated, and drying systems that often limit print
speed and increase cost per prints.
[0004] A number of approaches have been used to increase the
printing latitude of aqueous inks including the use of hydrophobic
and/or coagulating undercoat on the substrate. The use of
undercoats increases cost and complexity of the printing system and
cannot be applied universally to all types of substrates, including
plain and coated paper.
SUMMARY
[0005] There is a need for an aqueous based ink composition
designed to provide improved print quality on a variety of
substrates. There is also a need for improved inks that do not
require stirring on standing and would be able to form films with
minimum heating of the substrate onto which they are printed. In
addition, there is a need for a printing technology that achieves
excellent printing performance on a variety of substrates at a low
ink manufacturing cost.
[0006] High solids content aqueous ink comprising dispersible
polymers or blends of polymers as nano-sized particles are
provided. Water based inks lower ink costs and expand market
applications, while nano-sized particles enable high image
performance, thin image layers, and improve transferability when an
intermediate roll or belt is used. Dispersible polymers of inks in
accordance with embodiments self-coalesce to form a robust film
upon drying.
[0007] Methods of ink-based digital printing are provided. In an
embodiment, methods may include applying a thin film of the low
water content aqueous ink to an intermediate imaging member in an
ink-based digital printing system having an offset architecture.
Low water content may be defined as less than 75 percent, or less
than 60 percent, or less than 50 percent water by weight. Methods
may include applying a thin film of the low water content aqueous
ink directly to a substrate from an ink jet or piezo system.
[0008] In an embodiment an ink composition or ink concentrate for
variable data offset printing or an ink jet printing process that
uses an intermediate substrate may include a nano-particle polymer
or blend of nano-particle polymers, wherein the polymer or polymers
of the blend are water dispersible at temperatures less than 100
degrees Celsius; and the total solids content is an amount in a
range of about 25% or greater. In an embodiment, the total solids
content is an amount in a range of 25% to about 50%. In another
embodiment, the total solids content is greater than 50%. In
another embodiment, the ink is water diluted and the total solids
content is an amount in a range of about 4% to about 25%
[0009] In an embodiment, the polymer or blend comprises a component
selected from the group comprising sulfonated styrene, styrene,
sulfonated polyester, carboxyl-polyester, polyester, sulfonated
styrene, styrene, glycols, multifunctional glycols, alcohols,
multifunctional alcohols, acids, and salts. The polymer or polymers
of the polymer blend may have a molecular weight between 5000 and
20,000. In an embodiment, the polymer or polymers of the polymer
blend may contain a portion that is water soluble in an amount less
than 10%, and is soluble in a non-aqueous liquid vehicle in an
amount less than 30%, at a temperature between 20 and 50 degrees
Celsius.
[0010] In an embodiment, the nano-particle polymer or polymers of
the blend may be substantially soluble at temperatures above 70 to
95 degrees Celsius. In another embodiment, the polymer or a polymer
of the polymer blend may include an unsaturated functional group.
The unsaturated functional group may include a co-solvent, the
co-solvent having a surface tension of about 15 dynes/centimeter to
about 40 dynes/centimeter, the co-solvent being selected from the
group comprising alcohols, glycols, alkyl pyrrolidinones,
isopropanol, ketones methyl ethyl ketone, amino alcohol and
DMSO.
[0011] In an embodiment, the nano-particle polymers may be less
that 1 micron in size, or less than 500 nm, or less than 200 nm, or
less than 20 nm or mixtures of nanoparticles forming bimodal or
trimodal distributions. In an embodiment, the solids content of the
ink may include one or mixtures of the following: nano-particle
polymer resin, inorganic particles, silica, pigment, salts,
bioside, buffer, or humectant.
[0012] In an embodiment, an ink composition may include a
self-dispersing pigment of a particle size between 5 to 200 nm,
wherein the pigment is chemically modified or resin encapsulated.
The solids content may include resin encapsulating a
self-dispersing pigment forming a nano-particle polymer. In another
embodiment, the ink composition may include a surfactant. In an
embodiment, the resin that is used to encapsulate the pigment may
be between 9 percent and 66 percent of the combined weight of the
pigment and the encapsulating resin.
[0013] In an embodiment, the ink composition may have a viscosity
of ink of about 10 centipoise to about 1,000,000 centipoise in the
temperature range of 20 degrees Celsius to 50 degrees Celsius. In
another embodiment, the ink composition may have a viscosity of ink
after loss of 0 to 80 percent of liquid vehicle is between 10,000
centipoise and 1,000,000,000 centipoise at temperatures between 10
degrees Celsius to about 90 degrees Celsius.
[0014] In an embodiment, a viscosity of ink may be about 2
centipoise to about 10 centipoise in the temperature range of 20
degrees Celsius to 50 degrees Celsius. In an embodiment, the
polymer or polymer blend may have a critical phase separation
temperature of about 50 degrees Celsius to about 90 degrees
Celsius.
[0015] In an embodiment, the surface tension of the ink may be
between 15 and 40 dynes/centimeter at 25 degrees C., or over the
temperature range between 20 to 50 degrees C. In an embodiment, the
density range may be between about 0.95 to 1.3, or between 1.1 and
1.2 g/mL.
[0016] In an embodiment, methods for printing using high solids
content inks may include applying an ink having a nano-particle
polymer or blend of nano-particle polymers to an intermediate
transfer member, wherein the polymer or polymers of the blend are
water dispersible; and a solids content is in an amount of about 5%
to about 50% by weight. In methods, the intermediate transfer
member may have a surface tension of about 18 dynes/centimeter to
about 25 dynes/centimeter. In an embodiment, the intermediate
transfer member may include silicone or fluorosilicone.
[0017] In an embodiment, methods may include applying the ink at an
ink temperature above the upper critical phase separation
temperature, the upper critical phase separation temperature being
about 30 degrees Celsius to about 50 degrees Celsius; cooling the
ink on the intermediate transfer member; and transferring the ink
from the intermediate transfer member to a printable substrate. The
substrate may be an imaging member of an ink-base digital printing
system. In an embodiment, the applying may include forming a thin
film having a surface tension of about 15 dynes/centimeter to about
40 dynes/centimeter. In another embodiment, methods may include
diluting the ink with water before the applying, whereby the solid
content of the ink is less than 25% by weight or between 5% and 25%
by weight, the applying further comprising jetting the diluted ink
from an inkjet printhead.
[0018] Exemplary embodiments are described herein. It is
envisioned, however, that any system that incorporates features of
systems described herein are encompassed by the scope and spirit of
the exemplary embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 shows a side diagrammatical view of a related art
ink-based digital printing system;
[0020] FIG. 2 shows a side diagrammatical view of a related art
aqueous ink transfix printing system;
[0021] FIG. 3 shows methods for printing using high solids contents
inks in accordance with embodiments.
DETAILED DESCRIPTION
[0022] Exemplary embodiments are intended to cover all
alternatives, modifications, and equivalents as may be included
within the spirit and scope of the apparatus and systems as
described herein.
[0023] The modifier "about" used in connection with a quantity is
inclusive of the stated value and has the meaning dictated by the
context (for example, it includes at least the degree of error
associated with the measurement of the particular quantity). When
used with a specific value, it should also be considered as
disclosing that value.
[0024] Reference is made to the drawings to accommodate
understanding of inks, methods, and systems of embodiments. In the
drawing, like reference numerals are used throughout to designate
similar or identical elements.
[0025] Aqueous inks in accordance with embodiments are suitable for
ink-based digital printing using anilox roll and ink jet ink
delivery subsystems, and are also advantageously suitable for ink
jet printing generally. Aqueous inks in accordance with embodiments
are radiation curable, and may be formulated to be jettable and
used in ink jet systems that employ a heat drying subsystem.
Further, aqueous inks in accordance with embodiments are useful for
ink-based digital printing including indirect or offset
printing.
[0026] By way of example, an ink-based digital printing system with
anilox roll ink delivery subsystem for use with inks of embodiments
is described herein. U.S. patent application Ser. No. 13/095,714
("714 application"), titled "Variable Data Lithography System,"
filed on Apr. 27, 2011 by Stowe et al., which is commonly assigned,
and the disclosure of which is hereby incorporated by reference
herein in its entirety, describes an exemplary variable data
lithography system 100 for ink-based digital printing in FIG. 1. A
general description of the exemplary system 100 shown in FIG. 1 is
provided here. Additional details regarding individual components
and/or subsystems shown in the exemplary system 100 of FIG. 1 may
be found in the 714 application.
[0027] As shown in FIG. 1, the exemplary system 100 may include an
imaging member 110. The imaging member 110 in the embodiment shown
in FIG. 1 is a drum, but this exemplary depiction should not be
interpreted so as to exclude embodiments wherein the imaging member
110 includes a drum, plate or a belt, or another now known or later
developed configuration. The reimageable surface may be formed of
materials including, for example, a class of materials commonly
referred to as silicones, including polydimethylsiloxane (PDMS),
among others. For example, silicone, fluorosilicone, and/or VITON
may be used. The reimageable surface may be formed of a relatively
thin layer over a mounting layer, a thickness of the relatively
thin layer being selected to balance printing or marking
performance, durability and manufacturability.
[0028] The reimagable surface may be formed of a composite
containing reinforcing, or thermally or electrically conductive
particles, or containing particles which modify the surface energy
of the surface. The composite reimagable layer may be tuned to
enable imaging, partial removal of water, ink wettability, or other
printing requirements. Particles that may be included into a
reimagable composite surface include metal oxides, carbon black,
graphite, graphene, carbon nanotubes, and metal oxide
nanotubes.
[0029] The imaging member 110 is used to apply an ink image to an
image receiving media substrate 114 at a transfer nip 112. The
transfer nip 112 is formed by an impression roller 118, as part of
an image transfer mechanism 160, exerting pressure in the direction
of the imaging member 110. Image receiving medium substrate 114
should not be considered to be limited to any particular
composition such as, for example, paper, plastic, or composite
sheet film. The exemplary system 100 may be used for producing
images on a wide variety of image receiving media substrates. The
714 application also explains the wide latitude of marking
(printing) materials that may be used, including marking materials
with pigment densities greater than 10% by weight. As does the 714
application, this disclosure will use the term ink to refer to a
broad range of printing or marking materials to include those which
are commonly understood to be inks, pigments, and other materials
which may be applied by the exemplary system 100 to produce an
output image on the image receiving media substrate 114.
[0030] The 714 application depicts and describes details of the
imaging member 110 including the imaging member 110 being comprised
of a reimageable surface layer formed over a structural mounting
layer that may be, for example, a cylindrical core, or one or more
structural layers over a cylindrical core.
[0031] The exemplary system 100 includes a dampening fluid system
120 generally comprising a series of rollers, which may be
considered as dampening rollers or a dampening unit, for uniformly
wetting the reimageable surface of the imaging member 110 with
dampening fluid. A purpose of the dampening fluid system 120 is to
deliver a layer of dampening fluid, generally having a uniform and
controlled thickness, to the reimageable surface of the imaging
member 110. As indicated above, it is known that a dampening fluid
such as fountain solution may comprise mainly water optionally with
small amounts of isopropyl alcohol or ethanol added to reduce
surface tension as well as to lower evaporation energy necessary to
support subsequent laser patterning, as will be described in
greater detail below. Small amounts of certain surfactants may be
added to the fountain solution as well. Alternatively, other
suitable dampening fluids may be used to enhance the performance of
ink based digital lithography systems. Exemplary dampening fluids
include water, Novec 7600
(1,1,1,2,3,3-Hexafluoro-4-(1,1,2,3,3,3-hexafluoropropoxy)pentane
and has CAS#870778-34-0.), and D4 (octamethylcyclotetrasiloxane).
Other suitable dampening fluids are disclosed, by way of example,
in co-pending U.S. patent application Ser. No. 13/284,114, filed on
Oct. 28, 2011, titled "DAMPENING FLUID FOR DIGITAL LITHOGRAPHIC
PRINTING," the disclosure of which is hereby incorporated herein by
reference in its entirety.
[0032] Once the dampening fluid is metered onto the reimageable
surface of the imaging member 110, a thickness of the dampening
fluid may be measured using a sensor 125 that may provide feedback
to control the metering of the dampening fluid onto the reimageable
surface of the imaging member 110 by the dampening fluid system
120.
[0033] After a precise and uniform amount of dampening fluid is
provided by the dampening fluid system 120 on the reimageable
surface of the imaging member 110, and optical patterning subsystem
130 may be used to selectively form a latent image in the uniform
dampening fluid layer by image-wise patterning the dampening fluid
layer using, for example, laser energy. Typically, the dampening
fluid will not absorb the optical energy (IR or visible)
efficiently. The reimageable surface of the imaging member 110
should ideally absorb most of the laser energy (visible or
invisible such as IR) emitted from the optical patterning subsystem
130 close to the surface to minimize energy wasted in heating the
dampening fluid and to minimize lateral spreading of heat in order
to maintain a high spatial resolution capability. Alternatively, an
appropriate radiation sensitive component may be added to the
dampening fluid to aid in the absorption of the incident radiant
laser energy. While the optical patterning subsystem 130 is
described above as being a laser emitter, it should be understood
that a variety of different systems may be used to deliver the
optical energy to pattern the dampening fluid.
[0034] The mechanics at work in the patterning process undertaken
by the optical patterning subsystem 130 of the exemplary system 100
are described in detail with reference to FIG. 5 in the 714
application. Briefly, the application of optical patterning energy
from the optical patterning subsystem 130 results in selective
removal of portions of the layer of dampening fluid.
[0035] Following patterning of the dampening fluid layer by the
optical patterning subsystem 130, the patterned layer over the
reimageable surface of the imaging member 110 is presented to an
inker subsystem 140. The inker subsystem 140 is used to apply a
uniform layer of ink over the layer of dampening fluid and the
reimageable surface layer of the imaging member 110. The inker
subsystem 140 may use an anilox roller to meter an offset
lithographic ink onto one or more ink forming rollers that are in
contact with the reimageable surface layer of the imaging member
110. Separately, the inker subsystem 140 may include other
traditional elements such as a series of metering rollers to
provide a precise feed rate of ink to the reimageable surface. The
inker subsystem 140 may deposit the ink to the pockets representing
the imaged portions of the reimageable surface, while ink on the
unformatted portions of the dampening fluid will not adhere to
those portions.
[0036] The cohesiveness and viscosity of the ink residing in the
reimageable layer of the imaging member 110 may be modified by a
number of mechanisms. One such mechanism may involve the use of a
rheology (complex viscoelastic modulus) control subsystem 150. The
rheology control system 150 may form a partial crosslinking core of
the ink on the reimageable surface to, for example, increase ink
cohesive strength relative to the reimageable surface layer. Curing
mechanisms may include optical or photo curing, heat curing,
drying, or various forms of chemical curing. Cooling may be used to
modify rheology as well via multiple physical cooling mechanisms,
as well as via chemical cooling.
[0037] The ink is then transferred from the reimageable surface of
the imaging member 110 to a substrate of image receiving medium 114
using a transfer subsystem 160. The transfer occurs as the
substrate 114 is passed through a nip 112 between the imaging
member 110 and an impression roller 118 such that the ink within
the voids of the reimageable surface of the imaging member 110 is
brought into physical contact with the substrate 114. With the
adhesion of the ink having been modified by the rheology control
system 150, modified adhesion of the ink causes the ink to adhere
to the substrate 114 and to separate from the reimageable surface
of the imaging member 110. Careful control of the temperature and
pressure conditions at the transfer nip 112 may allow transfer
efficiencies for the ink from the reimageable surface of the
imaging member 110 to the substrate 114 to exceed 95%. While it is
possible that some dampening fluid may also wet substrate 114, the
volume of such a dampening fluid will be minimal, and will rapidly
evaporate or be absorbed by the substrate 114.
[0038] In certain offset lithographic systems, it should be
recognized that an offset roller, not shown in FIG. 1, may first
receive the ink image pattern and then transfer the ink image
pattern to a substrate according to a known indirect transfer
method. Following the transfer of the majority of the ink to the
substrate 114, any residual ink and/or residual dampening fluid
must be removed from the reimageable surface of the imaging member
110, preferably without scraping or wearing that surface. An air
knife may be employed to remove residual dampening fluid. It is
anticipated, however, that some amount of ink residue may remain.
Removal of such remaining ink residue may be accomplished through
use of some form of cleaning subsystem 170. The 714 application
describes details of such a cleaning subsystem 170 including at
least a first cleaning member such as a sticky or tacky member in
physical contact with the reimageable surface of the imaging member
110, the sticky or tacky member removing residual ink and any
remaining small amounts of surfactant compounds from the dampening
fluid of the reimageable surface of the imaging member 110. The
sticky or tacky member may then be brought into contact with a
smooth roller to which residual ink may be transferred from the
sticky or tacky member, the ink being subsequently stripped from
the smooth roller by, for example, a doctor blade.
[0039] The 714 application details other mechanisms by which
cleaning of the reimageable surface of the imaging member 110 may
be facilitated. Regardless of the cleaning mechanism, however,
cleaning of the residual ink and dampening fluid from the
reimageable surface of the imaging member 110 is essential to
preventing ghosting in the proposed system. Once cleaned, the
reimageable surface of the imaging member 110 is again presented to
the dampening fluid system 120 by which a fresh layer of dampening
fluid is supplied to the reimageable surface of the imaging member
110, and the process is repeated.
[0040] While FIG. 1 shows an exemplary printing system with which
inks of embodiments are useful, other printing methods and systems
may also benefit from use of inks in accordance with embodiments.
Inks in accordance with embodiments may be useful in related art
printing whether ink-based digital printing as disclosed above and
inkjet printing as now know or later developed, including indirect
or offset printing. For example, inks in accordance with
embodiments may be useful for printing using inkjet printing
systems and processes that use an intermediate transfer surface
such as the system shown in FIG. 2.
[0041] In particular, FIG. 2 shows a transfix aqueous ink printing
system with which inks and methods of embodiments may be
advantageously implemented. FIG. 2 shows a central imaging cylinder
201. A printhead 205, which may be an inkjet printhead suitable for
jetting aqueous ink is disposed for jetting ink directly onto a
surface of an intermediate substrate or imaging member 205.
[0042] The aqueous ink may be jetted into a dampening fluid layer
that is applied by a dampening fluid metering system 209. After
jetting the ink directly onto the imaging cylinder 201, the
cylinder may be caused to rotate and transport the jetted ink to a
drying system 211. The drying system 211 may be configured for
drying the jetted ink, thereby adjusting a viscosity of the ink in
preparation for ink transfer to another substrate. Subsequently,
the jetted and dried ink may be contact transferred at a nip 217
formed by the central imaging cylinder and a separate member. The
ink may be transferred to a substrate such as paper at the nip 217.
With inks in accordance with embodiments, the ink may be
transferred with advantageously high efficiency.
[0043] As discussed above, inks that are useful for ink-based
digital offset printing must possess physical and chemical
properties that meet the specific demands of ink-based digital
printing systems such as the system shown in FIG. 1. The ink must
be compatible with materials that it comes into contact with,
including the imaging plate and dampening fluid, and printable
substrates such as paper, metal, or plastic. The ink must also meet
all functional requirements of the subsystems as imposed by wetting
and transfer properties defined by subsystem architecture and
material sets.
[0044] Inks formulated for ink-based digital printing, or digital
offset inks, are different in many ways from other inks developed
for printing applications, including pigmented solvents, UV gel
inks, and other inks. For example, digital offset inks contain much
higher pigment and therefore have higher viscosity at room
temperature than other inks, which can make ink delivery by way of
an anilox roll or inkjet system difficult. Digital offset ink
should not cause the imaging member surface to swell and should be
compatible with dampening fluid options. Water-dilutable and
water-diluted inks in accordance with embodiments include digital
offset acrylate inks meeting such requirements.
[0045] Digital offset inks in accordance with water-containing ink
embodiments advantageously have a much lower solubility in
dampening fluid such as D4 than related art inks. Also, digital
offset inks of embodiments do not tend to swell a
silicone-containing imaging member surface layer used in ink-based
digital printing systems such as that shown in FIG. 1, which may be
a silicone, fluorosilicone, or VITON-containing imaging plate or
blanket.
[0046] The ink in accordance with embodiments is a dispersible
polymer ink having a high solids content of greater than 25
percent, for example, and a low water content of less than 75
percent. For example, an ink composition in accordance with
embodiments has a water content of less than 60%, and may include
nano-particles that are polymers and/or polymer blends. Aqueous
inks enable minimized ink manufacturing costs and are preferred by
some customers for their low toxicity and expanded market
applications, while the nano-sized particles enable high quality
image performance, thin image layers, and improve
transferability.
[0047] The percent solids in the ink composition may comprise of
one or mixtures of the following: nano-particle polymer resin,
inorganic particles, silica, pigment, salts, bioside, buffer, or
humectant. The solid loading content in the ink in embodiments may
be 25% to about 50%. In other embodiments, the ink composition may
be treated as an ink concentrate, and diluted with water to yield a
solid loading content of about 4% to about 25%, as may be preferred
if the ink is delivered to the intermediate substrate surface by
way of ink jet printing.
[0048] Dispersible nano-particle polymers of inks in accordance
with embodiments include polymers that self-coalesce to form a
robust film upon drying. Exemplary polymers include: polyester,
polystyrene, sulphonated polystyrene, sulphonated polyester,
polyurethane elastomers, and polymer mixtures.
[0049] Dispersible polymer inks require substantially no
surfactant, and substantially no dispersant in order to disperse.
Polymer inks in accordance with embodiments may contain a
nano-particle polymer, or blend of nano-particle polymers and are
water dispersible within the temperature range of 20 to 50 degrees
Celsius. The temperature range for lithographic or ink jet printing
is in this temperature range. A portion, less than 10 percent, of
the nano-particle polymer may be soluble in the ink formulation
within the temperature range of 20 to 50 degrees Celsius.
[0050] To obviate challenges imposed by jetting low water content
inks of high solid content directly onto a printable substrate as a
result of the high viscosity or need to increase jetting
temperature, the inks in accordance with embodiments may be applied
to an intermediate transfer member as a thin film. The thin film of
ink may subsequently be transferred to a printable substrate. For
example, a system as shown in FIG. 1 may be used for printing with
inks in accordance with embodiments. The inks may be substantially
or completely dried after jetting to an intermediate transfer
process, followed by application to a printable substrate. For
example, the inks may be dried using air flow, an IR heater, and/or
controlled heating of a substrate or component of the printing
system that contacts the substrate.
[0051] Inks in accordance with embodiments include low water
content inks having advantageous wetting properties when
transferred to an intermediate transfer member. In an exemplary
embodiment, the surface of the transfer member may have a critical
surface tension between about 18 dynes/cm and about 25 dynes/cm.
Exemplary surface materials may include silicone (24 dynes/cm), and
fluorosilicone (19-24 dynes/cm) or fluoroelastomer (24-34
dynes/cm). Inks in accordance with embodiments include low water
content inks having, in addition to water, at least one co-solvent
with a surface tension of between about 15 dynes/cm and about 30
dynes/cm. Exemplary co-solvents include isopropanol or similar
alcohols (22-23 dynes/cm), methyl ethyl ketone (23-25 dynes/cm),
and DMSO (25 dynes/cm). While these examples are suitable for inks
printed at room temperature, for example, other co-solvents useful
at higher temperatures may also be suitable if, for example, the
inks are heated to accelerate water evaporation on the intermediate
member or central imaging member of an ink-based digital printing
system. Other examples of co-solvents include glycols, alkyl
pyrrolidinones, and amino alcohols.
[0052] Methods of printing with inks in accordance with embodiments
having enhanced wetting/release properties may include applying low
water content ink onto an intermediate member or central imaging
member having, for example, a fluorosilicone surface. The surface
tension of the ink may be dynamically adjusted with the use of a
solid surfactant or a small concentration of a liquid
surfactant.
[0053] Examples of suitable surfactants include ionic surfactants,
anionic surfactants, cationic surfactants, nonionic surfactants,
zwitterionic surfactants, and the like, as well as mixtures
thereof. Examples of suitable surfactants include alkyl
polyethylene oxides, alkyl phenyl polyethylene oxides, polyethylene
oxide block copolymers, acetylenic polyethylene oxides,
polyethylene oxide (di)esters, polyethylene oxide amines,
protonated polyethylene oxide amines, protonated polyethylene oxide
amides, dimethicone copolyols, substituted amine oxides, and the
like, with specific examples including primary, secondary, and
tertiary amine salt compounds such as hydrochloric acid salts,
acetic acid salts of laurylamine, coconut amine, stearylamine,
rosin amine; quaternary ammonium salt type compounds such as
lauryltrimethylammonium chloride, cetyltrimethylammonium chloride,
benzyltributylammonium chloride, benzalkonium chloride, etc.;
pyridinium salty type compounds such as cetylpyridinium chloride,
cetylpyridinium bromide, etc.; nonionic surfactant such as
polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters,
acetylene alcohols, acetylene glycols; and other surfactants such
as 2-heptadecenylhydroxyethylimidazoline,
dihydroxyethylstearylamine, stearyldimethylbetaine, and
lauryldihydroxyethylbetaine; fluorosurfactants; and the like, as
well as mixtures thereof. Additional examples of nonionic
surfactants include polyacrylic acid, methalose, methyl cellulose,
ethyl cellulose, propyl cellulose, hydroxy ethyl cellulose, carboxy
methyl cellulose, polyoxyethylene cetyl ether, polyoxyethylene
lauryl ether, polyoxyethylene octyl ether, polyoxyethylene
octylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene
sorbitan monolaurate, polyoxyethylene stearyl ether,
polyoxyethylene nonylphenyl ether, dialkylphenoxy poly(ethyleneoxy)
ethanol, available from Rhone-Poulenc as IGEPAL CA-210.TM. IGEPAL
CA-520.TM., IGEPAL CA-720.TM., IGEPAL CO-890.TM., IGEPAL
CO-720.TM., IGEPAL CO-290.TM., IGEPAL CA-210.TM., ANTAROX 890.TM.,
and ANTAROX 897.TM.. Other examples of suitable nonionic
surfactants include a block copolymer of polyethylene oxide and
polypropylene oxide, including those commercially available as
SYNPERONIC.TM. PE/F, such as SYNPERONIC.TM. PE/F 108. Other
examples of suitable anionic surfactants include sulfates and
sulfonates, sodium dodecylsulfate (SDS), sodium dodecylbenzene
sulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkyl
sulfates and sulfonates, acids such as abitic acid available from
Sigma-Aldrich, NEOGEN R.TM., NEOGEN SC.TM. available from Daiichi
Kogyo Seiyaku, combinations thereof, and the like. Other examples
of suitable anionic surfactants include DOWFAX.TM. 2A1, an
alkyldiphenyloxide disulfonate from Dow Chemical Company, and/or
TAYCA POWER BN2060 from Tayca Corporation (Japan), which are
branched sodium dodecyl benzene sulfonates. Other examples of
suitable cationic surfactants, which are usually positively
charged, include alkylbenzyl dimethyl ammonium chloride, dialkyl
benzenealkyl ammonium chloride, lauryl trimethyl ammonium chloride,
alkylbenzyl methyl ammonium chloride, alkyl benzyl dimethyl
ammonium bromide, benzalkonium chloride, cetyl pyridinium bromide,
C12, C15, C17 trimethyl ammonium bromides, halide salts of
quaternized polyoxyethylalkylamines, dodecylbenzyl triethyl
ammonium chloride, MIRAPOL.TM. and ALKAQUAT.TM., available from
Alkaril Chemical Company, SANIZOL.TM. (benzalkonium chloride),
available from Kao Chemicals, and the like, as well as mixtures
thereof. Mixtures of any two or more surfactants can be used.
[0054] The optional surfactant can be present in any desired or
effective amount, in embodiments, the surfactant is present in an
amount of from about 0.01 to about 5 percent by weight, based on
the total weight of the ink composition. It should be noted that
the surfactants are named as dispersants in some cases.
[0055] Suitable surfactants and wetting or dispersing agents also
include TERGITOL TMN series available from Dow, 15-S series
available from Dow, STRODEX PK-90 available from Ashland,
superspreading Silwet surfactants such as Silwet L77 available from
Momentive Performance Materials, fluorinated surfactants available
from 3M. Suitable surfactants may include polyether modified
poly-dimethylsiloxan, BYK 333, ionic solution of polyacrylic
copolymer, BYK 381, polyether modified poly-dimethylalkylsiloxane,
BYK 307, and polyether modified poymethylalkylsiloxane available
from BYK Chemie GmbH.
[0056] Suitable surfactants may include fluorosurfactants, FC 4430
and 4432, available from 3M, and ZONYL FSN available from Du Pont,
Ltd. Suitable surfactants include DYHOL 604, from Air Products,
Surfadone LP 100, available from ISP, SURFYNOL 2502, available from
Air Products, TEGO GLIDE 410, TEGO GLIDE 100, TEGO FLOW 425, TEGO
PROTECT 5000, TEGO PROTECT 5100, TEGO TWIN 4000, TEGO WET KL 245,
TEGO WET 510, TEGOT WET 500, TEGO WET 270, TEGO WET 265, and TEGO
TWIN 4000, commercially available from Degussa AG.
[0057] Suitable surfactants may also include THETAWET FS8050,
commercially available from Innovative Chemical Technologies, BYK
347 and BYKDYNWET 800, commercially available from BYK Chemie GmbH,
DYNOL 604 and DYNOL 810, commercially available from Air Product,
SILSURF A004-AC-UP, commercially available from SILTECH, POLYFOX
136A, 156A, and 151N, available from OMNOVA, and CHEMGAURD S-764p,
commercially available from Chemgaurd Chemical.
[0058] Inks in accordance with embodiments may be configured for
enhanced robustness after transfer onto a printable substrate from
an intermediate transfer member or a direct-to-printable substrate
ink jet system, for example. In particular, inks in accordance with
embodiments may include a dissipatable nano-particle polymer or
polymer blends wherein the polymer(s) comprise one or more
unsaturated functional groups that enable photocuring of the final
transferred ink film for improved robustness. Inks in accordance
with embodiments, the nano-particle polymer or polymer blend(s) of
the ink composition may include high molecular weight water soluble
polymers. The molecular weight range of the dispersible polymers is
5000 to 20,000. For example, exemplary embodiments may include
polymers comprising a component selected from the group including
sulfonated styrene, styrene, sulfonated polyester,
carboxyl-polyester, polyester, sulfonated styrene, styrene,
glycols, multifunctional glycols, alcohols, multifunctional
alcohols, acids, and salts thereof. In embodiments, the
dissipatable polymer may be a nano-particle that is less that 1
micron in size, or less than 500 nm, or less than 200 nm, or less
than 20 nm. Other embodiments may contain dissipatable polymers as
mixtures of nano-particles forming bimodal or trimodal
distributions over the same ranges.
[0059] In an embodiment, the ink comprises a pigment that is
encapsulated by, or aggregated with the dispersible polymer. In a
preferred embodiment, the pigment is a self-dispersible pigment.
For example, suitable pigments include black pigments, white
pigments, cyan pigments, magenta pigments, yellow pigments, or the
like. Further, pigments can be organic or inorganic particles.
Suitable inorganic pigments include carbon black. However, other
inorganic pigments may be suitable such as titanium oxide, cobalt
blue (CoO--Al203), chrome yellow (PbCr04), and iron oxide. Suitable
organic pigments include, for example, azo pigments including diazo
pigments and monoazo pigments, polycyclic pigments (e.g.,
phthalocyanine pigments such as phthalocyanine blues and
phthalocyanine greens), perylene pigments, perinone pigments,
anthraquinone pigments, quinacridone pigments, dioxazine pigments,
thioindigo pigments, isoindolinone pigments, pyranthrone pigments,
and quinophthalone pigments), insoluble dye chelates (e.g., basic
dye type chelates and acidic dye type chelate), nitro pigments,
nitroso pigments, anthanthrone pigments such as PR168, and the
like.
[0060] Representative examples of phthalocyanine blues and greens
include copper phthalocyanine blue, copper phthalocyanine green,
and derivatives thereof (Pigment Blue 15, Pigment Green 7, and
Pigment Green 36). Representative examples of quinacridones include
Pigment Orange 48, Pigment Orange 49, Pigment Red 122, Pigment Red
192, Pigment Red 202, Pigment Red 206, Pigment Red 207, Pigment Red
209, Pigment Violet 19, and Pigment Violet 42. Representative
examples of anthraquinones include Pigment Red 43, Pigment Red 194,
Pigment Red 177, Pigment Red 216 and Pigment Red 226.
[0061] Representative examples of perylenes include Pigment Red
123, Pigment Red 149, Pigment Red 179, Pigment Red 190, Pigment Red
189 and Pigment Red 224. Representative examples of thioindigoids
include Pigment Red 86, Pigment Red 87, Pigment Red 88, Pigment Red
181, Pigment Red 198, Pigment Violet 36, and Pigment Violet 38.
Representative examples of heterocyclic yellows include Pigment
Yellow 1, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13,
Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 65, Pigment
Yellow 73, Pigment Yellow 74, Pigment Yellow 90, Pigment Yellow
110, Pigment Yellow 117, Pigment Yellow 120, Pigment Yellow 128,
Pigment Yellow 138, Pigment Yellow 150, Pigment Yellow 151, Pigment
Yellow 155, and Pigment Yellow 213. Such pigments are commercially
available in either powder or press cake form from a number of
sources including, BASF Corporation, Engelhard Corporation, and Sun
Chemical Corporation.
[0062] Examples of black pigments that may be used include carbon
pigments. The carbon pigment can be almost any commercially
available carbon pigment that provides acceptable optical density
and print characteristics. Carbon pigments suitable for use in
systems and methods in accordance with embodiments may include,
without limitation, carbon black, graphite, vitreous carbon,
charcoal, and combinations thereof. Such carbon pigments can be
manufactured by a variety of known methods, such as a channel
method, a contact method, a furnace method, an acetylene method, or
a thermal method, and are commercially available from such vendors
as Cabot Corporation, Columbian Chemicals Company, Evonik, and E.I.
DuPont de Nemours and Company.
[0063] Suitable carbon black pigments include, without limitation,
Cabot pigments such as MONARCH 1400, MONARCH 1300, MONARCH 1100,
MONARCH 1000, MONARCH 900, MONARCH 880, MONARCH 800, MONARCH 700,
CAB-O-JET 200, CAB-O-JET 300, REGAL, BLACK PEARLS, ELFTEX, MOGUL,
and VULCAN pigments; Columbian pigments such as RAVEN 5000, and
RAVEN 3500; Evonik pigments such as Color Black FW 200, FW 2, FW
2V, FW 1, FW18, FW S160, FW S170, Special Black 6, Special Black 5,
Special Black 4A, Special Black 4, PRINTEX U, PRINTEX 140U, PRINTEX
V, and PRINTEX 140V. The above list of pigments includes unmodified
pigment particulates, small molecule attached pigment particulates,
and polymer-dispersed pigment particulates. Other pigments can also
be selected, as well as mixtures thereof. The pigment particle size
is desired to be as small as possible to enable a stable colloidal
suspension of the particles in the liquid vehicle and to prevent
clogging of the ink channels when the ink is used in a thermal ink
jet printer or a piezoelectric ink jet printer.
[0064] The colorant can be present in the ink composition in any
desired or effective amount. In embodiments, the colorant can be
present in an amount of from about 0.05 percent to about 15
percent, or from about 0.1 percent to about 10 percent, or from
about 1 to about 5 percent by weight, based on the total weight of
the stretchable ink composition. Accordingly, inks in accordance
with embodiments enable enhanced pigment stability for intermediate
transfer and ink jet printing applications.
[0065] Inks may possess a range of viscosity between about 10
centipoise to about 1,000,000 centipoise in the temperature range
of 20 to 50 degrees C. This range of viscosity is suitable for
digital offset printing, and high solids loading ink jet printing
that may be carried out in the 10 centipoise viscosity range.
Follow depositing of ink onto an intermediate substrate, a
rheological change may be brought about by the removal of water
from the dispersible polymer ink. With a loss of about 50 to 80
percent of the liquid vehicle, the ink viscosity may be increased
by multiple orders of magnitude, to a range between 10,000 to
1,000,000,000 centipoise. With this range of higher ink viscosity,
transfer efficiency may be substantially improved to be greater
than 80%, or greater than 90%, or greater than 95%.
[0066] Additional ink properties include a surface tension that
enables wetting to an intermediate substrate and relatively
increased density compared with inks of solid content loading less
than 25%, and particularly less than 4%, for example. Surface
tension of inks is in between 15 and 40 dynes/centimeter at 25
degrees C., or over the temperature range between 20 to 50 degrees
Celsius. Ink density is dependent on the loading of solids content
and is between about 0.95 to 1.3, or between 1.1 and 1.2 g/m L.
[0067] In an embodiment, an ink composition may be configured for
ink jet printing. For example, an ink in accordance with an
embodiment may be configured for dilution and have a
water/co-solvent blend and a solid loading of about 4% to about
20%, and a viscosity in a range of 2.5 to 15 centipoise. In another
embodiment, solid loading may be about 5% to about 25%, and
preferably greater than 25%, for example, greater than 25% and less
than or equal to 50%.
[0068] The ink compositions in accordance with embodiments may
comprise a mixture of water and a water soluble or water miscible
organic component, referred to as a co-solvent, humectant, or the
like (hereinafter co-solvent) such as alcohols and alcohol
derivatives, including aliphatic alcohols, aromatic alcohols,
dials, glycol ethers, polyglycol ethers, long chain alcohols,
primary aliphatic alcohols, secondary aliphatic alcohols,
1,2-alcohols, 1,3-alcohols, 1,5-alcohols, ethylene glycol alkyl
ethers, propylene glycol alkyl ethers, methoxylated glycerol,
ethoxylated glycerol, higher homologues of polyethylene glycol
alkyl ethers, and the like, with specific examples including
ethylene glycol, propylene glycol, diethylene glycols, glycerine,
dipropylene glycols, polyethylene glycols, polypropylene glycols,
trimethylolpropane, 1,5-pentanediol, 2-methyl-1,3,-propanediol,
2-ethyl-2-hydroxymethyl-1,3-propanediol, 3-methoxybutanol,
3-methyl-1,5-pentanediol, 1,3-propanediol, 1,4-butanediol,
2,4-heptanediol, and the like; also suitable are amides, ethers,
urea, substituted ureas such as thiourea, ethylene urea, alkylurea,
alkylthiourea, dialkylurea, and dialkylthiourea, carboxylic acids
and their salts, such as 2-methylpentanoic acid,
2-ethyl-3-propylacrylic acid, 2-ethyl-hexanoic acid,
3-ethoxyproponic, acid, and the like, esters, organosulfides,
organosulfoxides, sulfones (such as sulfolane), carbitol, butyl
carbitol, cellusolve, ethers, tripropylene glycol monomethyl ether,
ether derivatives, hydroxyethers, amino alcohols, ketones,
N-methylpyrrolidinone, 2-pyrrolidinone, cyclohexylpyrrolidone,
amides, sulfoxides, lactones, polyelectrolytes, methyl
sulfonylethanol, imidazole, 1,3-dimethyl-2-imidazolidinone,
betaine, sugars, such as 1-deoxy-D-galactitol, mannitol, inositol,
and the like, substituted and unsubstituted formamides, substituted
and unsubstituted acetamides, and other water soluble or water
miscible materials, as well as mixtures thereof. In embodiments,
the co-solvent is selected from the group consisting of ethylene
glycol, N-methylpyrrolidone, methoxylated glycerol, ethoxylated
glycerol, and mixtures thereof.
[0069] When mixtures of water and water soluble or miscible organic
liquids are selected as the liquid vehicle, the water to organic
ratio ranges can be any suitable or desired ratio, in embodiments
from about 100:0 to about 30:70, or from about 97:3 to about 40:60,
or from about 95:5 to about 60:40. The non-water component of the
liquid vehicle generally serves as a humectant or co-solvent which
has a boiling point higher than that of water (100.degree. C.). The
organic component of the ink vehicle can also serve to modify ink
surface tension, modify ink viscosity, dissolve or disperse the
colorant, and/or affect the drying characteristics of the ink.
[0070] In accordance with an embodiment, an ink composition may
include a polymer that has a critical phase separation temperature
lying in a range of about 50 degrees Celsius to about 90 degrees
Celsius. When the ink composition is transferred to an intermediate
transfer member surface having a temperature above the critical
temperature, the viscosity of the ink is reduced for enhanced
wetting. The viscosity increases upon cooling to enable enhanced
transfer. The ink composition is also suitable for ink jet printing
at high temperatures.
[0071] Inks in accordance with embodiments may be printed on an
undercoat. The undercoat may comprise any suitable compounds that
may help the drying process and generate images of higher print
quality. This might for example be achieved by coagulating the
pigment and/or dissipatable polymer so as to minimize film forming
in the early stages of drying. If the ink is anionic in nature, the
undercoat may comprise polymeric materials such as
polyalkyleneimines and their derivatives such as polyethylenimine.
Polymers that contain quaternary ammonium functionalities or
divalent or trivalent metal salts are also suitable.
[0072] Additional pH controlling agents may also be included in the
undercoat composition, if desired. Examples of such pH controlling
agents suitable for undercoats of the present invention include,
but are not limited to, acids; bases, including hydroxides of
alkali metals such as lithium hydroxide, sodium hydroxide and
potassium hydroxide, phosphate salts, carbonate salts, carboxylate
salts, sulfite salts; amine salts; amines such as diethanolamine
and triethanolamine; and mixtures thereof and the like.
[0073] When present, the pH controlling agent is preferably
included in an amount of up to about 1 percent by weight, and
preferably from about 0.01 to about 1 percent by weight.
Appropriate selection of pH control agent may improve the
effectiveness of the coagulation additive. Inks in accordance with
embodiments may be formed on an undercoat resulting in coagulation
of pigment and dissipatable nano-polymer on, for example, the
intermediate transfer member or central imaging member surface that
facilitates drying. Contrarily, related art inks form films that
trap water, and reduce drying effectiveness. Ink compositions in
accordance with embodiments may be configured for forming thin
films having a critical surface tension of about 15 dynes/cm to
about 40 dynes/cm, for example.
Example
[0074] Low water content nano-particle dispersible polymer ink
compositions in accordance with embodiments were formed. First, a
sodio sulfonate polyester emulsion was formed. The emulsion
included the following components: dimethylterepthalate (388
grams), sodium dimethyl 5-sulfoisophthalate (44 grams), propanediol
(302 grams), diethylene glycol (34.2 grams), trimethylol propane (3
grams), and butyltin oxide (0.8 grams).
[0075] The components were charged in a 1 liter Parr reactor
equipped with a mechanical stirrer and distillation apparatus. The
resulting mixture was heated to 175 degrees Celsius for about one
hour. Then, the temperature was increased to 185 degrees Celsius
and the mixture heated for an additional three hours. The
temperature was then increased to 200 degrees Celsius and the
pressure reduced from atmospheric pressure to about 0.5 Torr over a
period of about two hours, during which time excess glycol was
collected in a distillation receiver.
[0076] The mixture was discharged into the bottom of the drain to
result in the product
copoly(1,2-propylene-dipropylene-terephthalate)-copoly(1,2-propylene-dipr-
o pylene-5-sodiosulfo-isophthalate). The product polyester resin
had a glass transition temperature of about 54.6.degree. C., a
number average molecular weight (M.sub.n) of 3,500 grams per mole,
and a weight average molecular weight (M.sub.w) of 9,160 as
measured by gel permeation chromatography using polystyrene as a
standard. 10 Grams of the product polyester resin was then heated
with 50 grams of water at 75 degrees Celsius for 1 hour to provide
an emulsion of sulfonated polyester particles in water with an
average size of about 50 nm.
[0077] An aqueous cyan pigment dispersion (17% in water) comprising
Dowfax surfactant was heated to 80 degrees Celsius, and added to
the dried solid sodio sulfonated polyester resin product. The
mixture was stirred for one hour at room temperature. The amount of
dispersion and resin included in each of example compositions A-E
is shown in Table 1.
TABLE-US-00001 TABLE 1 Low Water Content Dispersible Polymer Ink
Compositions Pigment Pigment Pigment and Resin and Resin Dispersion
Resin (Initial (Final Examples (Mass, g) (Mass, g) Mass, g) Mass,
g) % Pigment % Resin % Solids A 100 15 115 117.62 14.45 12.75 27.21
B 100 20 120 118.25 14.38 16.91 31.29 C 100 25 125 118.70 14.32
21.06 35.38 D 100 30 130 128.25 13.26 23.39 36.65 E 100 35 135
130.35 13.04 26.85 39.89
[0078] It was found that ink A contained about 27% solid at a
temperature of 25 degrees Celsius. Inks B-E had higher solid
content, and thus required less evaporation of water to yield
highly viscous ink. Inks containing less than 27% water were found
to have a viscosity of less than 10 centipoise and thus can be
ejected from inkjet piezo printheads, for example.
[0079] It was found that inks C-E have viscosities in the range of
100 to 1000 centipoise and thus may be delivered from an anilox
roller to yield a thin film on a digital imaging printing surface.
With removal of 20-30% of the water contained in the ink, rheology
was increased to the range of 50,000 to 500,000 cp, suitable for
transfer from an intermediate surface.
[0080] Ink compositions in accordance with embodiments are
film-forming high solid content nano-particle aqueous dispersible
polymer inks that are suitable for ink jet printing and ink based
digital printing using an intermediate transfer member or central
imaging member arranged in an offset architecture. The ink is
configured for strong adherence to a variety of substrates.
[0081] In accordance with the foregoing, inks of embodiments are
useful for printing processes including indirect printing,
ink-based digital printing, and inkjet printing. Methods of
printing using high solids content inks are shown in FIG. 3. In
particular, FIG. 3 shows methods 300 for printing using a high
solids content inks. Methods may include applying at S3001 an ink
comprising a nano-particle polymer or blend of nano-particle
polymers to an imaging member or intermediate transfer member,
wherein the polymer or polymers of the blend are water dispersible;
and solids content is in an amount of 5% by weight and 50% by
weight. The imaging member or intermediate transfer member may
preferably have a surface tension of about 18 dynes/centimeter to
about 25 dynes/centimeter. The imaging member or intermediate
transfer member may have a surface that includes silicone or
fluorosilicone. The imaging member may be constitute a component of
an ink-based digital printing system, for example. The intermediate
transfer member may constitute a component of an indirect or
transfix printing system, for example.
[0082] At S3001, the applying may include applying the ink at an
ink temperature above the upper critical phase separation
temperature, the upper critical phase separation temperature being
about 30 degrees Celsius to about 50 degrees Celsius. Further, the
applied ink may form a film may have a surface tension of about 15
dynes/centimeter to about 40 dynes/centimeter. The ink may be
jetted using a now known or later developed inkjet device, or may
be applied using, for example, an anilox roll delivery subsystem.
The inks may be diluted with water in preparation for jetting so
that a solids content of the ink is less than 25% by weight. For
example, the water dilutable inks may be produced and shipped with
a solids content of greater than 25%, and later water-diluted for
inkjet printing applications. As such, methods may include diluting
the ink with water before the applying, whereby the solid content
of the ink is less than 25% by weight or between 5% and 25% by
weight, the diluting being before the applying, the applying
further comprising jetting the diluted ink from an inkjet
printhead.
[0083] Methods may include cooling at S3005 the ink on the imaging
member or intermediate transfer member. Methods may include
transferring at S3007 the ink from the imaging member or
intermediate transfer member to a printable substrate such as
paper, cardboard, plastic, or other suitable substrates.
[0084] It will be appreciated that the above-disclosed and other
features and functions, or alternatives thereof, may be desirably
combined into many other different compositions or formulations,
systems or applications. Also, various presently unforeseen or
unanticipated alternatives, modifications, variations or
improvements therein may be subsequently made by those skilled in
the art.
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