U.S. patent application number 14/635679 was filed with the patent office on 2016-09-08 for process black ink compositions and uses thereof.
The applicant listed for this patent is XEROX CORPORATION. Invention is credited to Biby E. Abraham, C. Geoffrey Allen, Mihaela Maria Birau, Marcel P. Breton, Aurelian Valeriu Magdalinis, Carolyn Moorlag.
Application Number | 20160257829 14/635679 |
Document ID | / |
Family ID | 56739056 |
Filed Date | 2016-09-08 |
United States Patent
Application |
20160257829 |
Kind Code |
A1 |
Breton; Marcel P. ; et
al. |
September 8, 2016 |
PROCESS BLACK INK COMPOSITIONS AND USES THEREOF
Abstract
The present disclosure is directed to a process black ink
composition for digital offset printing including a cyan colorant
including a cyan pigment, a magenta colorant including a magenta
pigment and a yellow colorant including a yellow pigment, wherein
the process black ink composition includes a total amount of
pigment of at least about 15 wt %, a photo-initiator a dispersant,
and a curable ink vehicle component including at least one
component selected from a curable monomer or a curable oligomer;
wherein the process black ink composition comprises a ratio of the
cyan colorant to the yellow colorant of 0.70-0.80:1.0 and a ratio
of the magenta colorant to the yellow colorant of 0.90-0.80:1.0,
and wherein the process black ink composition does not comprise
carbon black. Methods of preparing the present process black ink
composition and using the process black ink composition are also
provided.
Inventors: |
Breton; Marcel P.;
(Mississauga, CA) ; Allen; C. Geoffrey;
(Mississauga, CA) ; Abraham; Biby E.;
(Mississauga, CA) ; Moorlag; Carolyn;
(Mississauga, CA) ; Birau; Mihaela Maria;
(Mississauga, CA) ; Magdalinis; Aurelian Valeriu;
(Aurora, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XEROX CORPORATION |
Norwalk |
CT |
US |
|
|
Family ID: |
56739056 |
Appl. No.: |
14/635679 |
Filed: |
March 2, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D 11/30 20130101;
C09D 11/107 20130101; C09D 11/40 20130101; B41M 1/06 20130101; C09D
11/101 20130101; C09D 11/037 20130101; B41J 2/14024 20130101; C09D
11/322 20130101; C09D 11/32 20130101; B41J 2/21 20130101 |
International
Class: |
C09D 11/107 20060101
C09D011/107; B41J 2/21 20060101 B41J002/21 |
Claims
1. A process black ink composition for digital offset printing
comprising: a cyan colorant comprising a cyan pigment, a magenta
colorant comprising a magenta pigment and a yellow colorant
comprising a yellow pigment, wherein the process black ink
composition comprises a total amount of pigment of at least about
15 wt %, a photo-initiator, a dispersant, and a curable ink vehicle
component comprising at least one component selected from the group
consisting of a curable monomer and a curable oligomer; wherein the
process black ink composition comprises a ratio of the cyan
colorant to the yellow colorant of 0.70-0.80:1.0 and a ratio of the
magenta colorant to the yellow colorant of 0.90-0.80:1.0, wherein
the process black ink composition does not comprise carbon black,
and wherein the process black ink further comprises a filler.
2. The process black ink composition of claim 1, wherein the
process black ink further comprises a stabilizer.
3-4. (canceled)
5. The process black ink composition of claim 1, wherein the cyan
colorant comprises Pigment Blue 15:3, the magenta colorant
comprises Pigment Red 57:1 and the yellow colorant comprises a
pigment selected from the group consisting of Pigment Yellow 14 and
Pigment Yellow 13.
6. The process black ink composition of claim 5, wherein the ratio
of the cyan colorant comprising Pigment Blue 15:3 to the yellow
colorant comprising the yellow pigment is 0.76:1 and wherein the
ratio of the magenta colorant comprising the Pigment Red 57:1 to
the yellow colorant comprising the yellow pigment is 0.80:1.0.
7. (canceled)
8. The process black ink composition of claim 1, wherein the
process black ink composition is transferable to a printable
substrate from an imaging member at an efficiency of 90% or
greater.
9. A method of preparing a process black ink composition, the
method comprising: a) providing a cyan colorant comprising a cyan
pigment, a magenta colorant comprising a magenta pigment and a
yellow colorant comprising a yellow pigment, wherein a ratio of the
cyan colorant to the yellow colorant is 0.70-0.80:1.0 and a ratio
of the magenta colorant to the yellow colorant is 0.90-0.80:1.0, b)
acoustically mixing the colorants; c) acoustically mixing a
photo-initiator; a dispersant and at least one curable ink vehicle
component selected from the group consisting of a monomer and an
oligomer with the acoustically mixed colorants to form a curable
ink mixture, d) milling the curable ink mixture formed in c) to
obtain a process black ink composition, wherein the process black
ink composition does not comprise carbon black.
10. The method of claim 9, wherein the cyan colorant comprises
Pigment Blue 15:3, the magenta colorant comprises Pigment Red 57:1
and the yellow colorant comprises a pigment selected from the group
consisting of Pigment Yellow 14 and Pigment Yellow 13.
11. The method of claim 10, wherein the ratio of the cyan colorant
comprising Pigment Blue 15:3 to the yellow colorant comprising the
yellow pigment is 0.76:1 and wherein the ratio of the magenta
colorant comprising Pigment Red 57:1 to the yellow colorant
comprising the yellow pigment is 0.80:1.0.
12. The process of claim 9, further comprising heating and stirring
the curable ink mixture formed in c) before milling.
13. The method of claim 9, wherein the curable ink mixture formed
in c) further comprises a stabilizer.
14. The method of claim 9, wherein the curable ink mixture formed
in c) further comprises a filler.
15. A method of halftone printing, the method comprising: providing
a cyan ink composition, a magenta ink composition and a yellow ink
composition, applying the cyan ink composition, the magenta ink
composition and the yellow ink composition onto a re-imagable
imaging member surface, wherein a ratio of the cyan ink composition
to the yellow ink composition is 0.70-0.80:1.0 and a ratio of the
magenta ink composition to the yellow ink composition is
0.90-0.80:1.0; forming an ink image; transferring the ink image
from the re-imagable surface of the imaging member onto a printable
substrate to form a halftone black image; wherein the halftone
black image does not comprise carbon black, wherein the cyan ink
composition comprises at least about 15% by weight of a cyan
pigment, the magenta ink composition comprises at least about 15%
by weight of a magenta pigment and the yellow ink composition
comprises at least about 15% by weight of a yellow pigment, and
wherein said cyan ink composition, said magenta ink composition and
said yellow ink composition each further comprises: a
photo-initiator, a dispersant, and a curable ink vehicle component
comprising at least one component selected from the group
consisting of a curable monomer and a curable oligomer.
16. The method of claim 15, wherein the transferring of the ink
image from the re-imagable surface of the imaging member onto a
printable substrate is at an efficiency of 90% or greater.
17. The method of claim 15, wherein the method further comprises
partially curing the cyan, magenta and yellow ink compositions
after applying the cyan, magenta and yellow ink compositions onto a
re-imagable imaging member surface
18. The method of claim 17, wherein the transferring of the ink
image from the re-imagable surface of the imaging member onto a
printable substrate is at an efficiency of 98% or greater.
19. The method of claim 15, wherein the cyan ink composition
comprises Pigment Blue 15:3, the magenta ink composition comprises
Pigment Red 57:1 and the yellow ink composition comprises a yellow
pigment selected from the group consisting of Pigment Yellow 14 and
Pigment Yellow 13.
20. The method of claim 19, wherein the ratio of the cyan ink
composition comprising the Pigment Blue 15:3 to the yellow ink
composition comprising the yellow pigment is 0.76:1 and wherein the
ratio of the magenta ink composition comprising the Pigment Red
57:1 to the yellow composition comprising the yellow pigment is
0.80:1.0.
Description
FIELD OF DISCLOSURE
[0001] The present disclosure relates to digital offset printing.
In particular, this disclosure relates to black inks suitable for
digital offset printing, among other printing applications.
BACKGROUND
[0002] Typical lithographic and offset printing techniques utilize
plates that are permanently patterned, and are, therefore, useful
only when printing a large number of copies of the same image, such
as magazines, newspapers, and the like. Variable data digital
lithography or digital offset lithographic printing has been
developed as a system that uses a non-patterned re-imaginable
surface on an imaging member (printable blanket), which is
initially uniformly coated with a dampening fluid layer. Regions of
the dampening fluid are removed by exposure to a focused radiation
source (e.g., a laser light source) to form pockets. A temporary
pattern in the dampening fluid is thereby formed over the
non-patterned re-imaginable surface. Ink applied thereover is
retained in the pockets formed by the removal of the dampening
fluid. The inked surface is then brought into contact with a
substrate, such as paper, plastic or metal, and the ink transfers
from the pockets in the dampening fluid layer to the substrate. The
dampening fluid may then be removed, a new uniform layer of
dampening fluid applied to the re-imaginable surface and the
process repeated.
[0003] In order to meet digital offset printing requirements, the
inks used with digital offset printing architectures typically
should possess many desirable physical and chemical properties. The
inks should be compatible with the materials it is in contact with,
including the printing plate, the dampening fluid, the paper and
the various rollers. The digital offset printing ink also should
meet all functional requirements for transfer and curing.
[0004] Many black inks in the art, however, pose challenges when
used with digital offset printing architecture. Such inks, usually
formulated with carbon black, broadly absorb UV radiation and are
inherently more difficult to cure than colored inks. High viscosity
carbon black inks, which are best suitable for digital offset
printing, are even more of a challenge since these printing
processes may include the addition of rheology modifiers that
further negatively impact the cure of carbon black inks. Moreover,
carbon black inks are also capable of interacting with the carbon
black containing blankets, resulting in transfer issues. High
transfer efficiency is necessary for high resolution digital
imaging. Accordingly, there remains a need in the art for black ink
formulations that may be efficaciously used with digital offset
printing,
SUMMARY
[0005] The present disclosure is directed to a process black ink
composition for digital offset printing including a cyan colorant
including a cyan pigment, a magenta colorant including a magenta
pigment and a yellow colorant including a yellow pigment, wherein
the process black ink composition includes a total amount of
pigment of at least about 15 wt %, a photo-initiator, a dispersant,
and a curable ink vehicle component including at least one
component selected from a curable monomer or a curable oligomer;
wherein the process black ink composition comprises a ratio of the
cyan colorant to the yellow colorant of 0.70-0.80:1.0 and a ratio
of the magenta colorant to the yellow colorant of 0.90-0.80:1.0,
and wherein the process black ink composition does not comprise
carbon black.
[0006] The present disclosure also provides a method of preparing a
process black ink composition, the method including a) providing a
cyan colorant comprising a cyan pigment, a magenta colorant
comprising a magenta pigment and a yellow colorant comprising a
yellow pigment, wherein a ratio of the cyan colorant to the yellow
colorant is 0.70-0.80:1.0 and a ratio of the magenta colorant to
the yellow colorant is 0.90-0.80:1.0; b) acoustically mixing the
pigments; c) acoustically mixing a photo-initiator; a dispersant
and at least one curable ink vehicle component selected from a
monomer or an oligomer with the acoustically mixed pigments to form
a curable ink mixture, d) milling the curable ink mixture formed in
c) to obtain a process black ink composition, wherein the process
black ink composition does not comprise carbon black.
[0007] Also provided herein is a method of halftone printing, the
method including providing a cyan ink composition, a magenta ink
composition and a yellow ink composition, applying the cyan ink
composition, the magenta ink composition and the yellow ink
composition onto a re-imagable imaging member surface, wherein a
ratio of the cyan ink composition to the yellow ink composition is
0.70-0.80:1.0 and a ratio of the magenta ink composition to the
yellow ink composition is 0.90-0.80:1.0; forming an ink age;
transferring the ink image from the re-imagable surface of the
imaging member onto a printable substrate to form a halftone black
image; wherein the halftone black image does not include carbon
black, wherein the cyan ink composition includes at least about 15%
by weight of a cyan pigment, the magenta ink composition includes
at least about 15% by weight of a magenta pigment and the yellow
ink composition includes at least about 15% by weight of a yellow
pigment, and wherein the cyan ink composition, the magenta ink
composition and the yellow ink composition each further includes: a
photo-initiator, a dispersant and a curable ink vehicle component
including at least one component selected from a curable monomer or
a curable oligomer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates a schematic representation of an
ink-based variable image digital printing system for use with the
present process black ink compositions.
[0009] FIG. 2 illustrates an exemplary embodiment for preparing
cyan ink as described in the Examples.
[0010] FIG. 3 illustrates an exemplary embodiment for preparing
magenta ink as described in the Examples.
[0011] FIG. 4 illustrates an exemplary embodiment for preparing
yellow ink as described in the Examples.
[0012] FIG. 5 illustrates viscosities at 35.degree. C. a cyan ink,
a magenta ink, a yellow ink and a process black ink.
[0013] FIG. 6 illustrates the effect of image thickness on the
number of double methylethyl ketone (MEK) rubs for process black
ink as described in the Examples.
DETAILED DESCRIPTION
Process Black Ink Composition
[0014] Exemplary embodiments are described in detail below in
formulation and in use. It is envisioned, however, that any system
that incorporates features of the systems and compositions, as set
forth below may be encompassed by the scope and spirit of the
exemplary embodiments.
[0015] Exemplary embodiments are intended to cover alternatives,
modifications, and equivalents as may be included within the spirit
and scope of the compositions and systems described in detail
below.
[0016] 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.
[0017] As used throughout, ranges are used as shorthand for
describing each and every value that is within the range. Any value
within the range can be selected as the terminus of the range. In
addition, all references cited herein are hereby incorporated by
referenced in their entireties. In the event of a conflict in a
definition in the present disclosure and that of a cited reference,
the present disclosure controls.
[0018] Unless otherwise specified, all percentages and amounts
expressed herein and elsewhere in the specification should be
understood to refer to percentages by weight. The amounts given are
based on the active weight of the material.
[0019] Reference is made to the drawings to accommodate
understanding of the black ink compositions, methods, and systems
of embodiments.
[0020] The present disclosure provides process black inks, which do
not contain carbon black and methods of printing using these inks.
The process black inks of the present disclosure exhibit excellent
transfer efficiency and cure performance as well as low blanket
contamination when using digital offset printing architecture. The
present black inks are formulated to contain only cyan, magenta and
yellow colorants, such as pigments and/or are prepared by mixing
cyan, magenta and yellow inks. A process black ink image may be
obtained either by: 1) using the present process black ink in a
digital offset printing architecture, or 2) using halftone printing
of cyan, magenta and yellow inks in a digital offset printing
architecture in the ratios described herein to obtain a process
black ink image. The advantages in both instances are good cure,
high transfer efficiency, and low blanket contamination. In the
case of a printed process black obtained by using the three colors,
one color station may be removed in the digital offset printing
architecture or flexibility may be increased due to the ability to
introduce a specialty ink (such as white or silver) into a 4.sup.th
ink tower of the architecture.
[0021] As used herein "process black" refers to black ink made from
a mixture of three colorants, cyan, magenta and yellow. In some
embodiments, the colorants are mixed with a curable vehicle
component that includes at least one curable monomer and/or curable
oligomer, at least one photo-initiator, optionally at least one
stabilizer and optionally at least one filler. In some embodiments,
the process black ink composition of the present disclosure does
not include carbon black.
[0022] The cyan colorant includes any desired or effective cyan
colorant including pigments, mixtures of pigments, mixtures of
pigments and dyes, and the like, provided that the cyan colorant
may be dissolved or dispersed in at least one curable monomer or at
least one curable oligomer and at least one dispersant. In specific
embodiments, the cyan colorant is a pigment.
[0023] Examples of suitable cyan pigments for use with the process
black ink composition of the present disclosure include copper
tetra(octadecyl sulfonamido) phthalocyanine, x-copper
phthalocyanine pigment listed in the Color Index (C.I.) as C.I.
74160, C. I. Pigment Blue-1, C. I. Pigment Blue-2, C. I. Pigment
Blue-3, C. I. Pigment Blue-15, C. I. Pigment Blue-15:2, C. I.
Pigment Blue-15:3, C. I. Pigment Blue-15:4, C. I. Pigment Blue-16,
C. I. Pigment Blue-22 and the like. In some embodiments, Pigment
Blue 15:3 is used, such as Hostaperm Blue B4G from Clariant
International Ltd Muttenz, Switzerland or Irgalite.RTM. Blue GLO
from Ciba Specialty Chemicals, Tarrytown, N.Y.
[0024] In some embodiments, the cyan pigment may be present in the
process black ink composition of the instant disclosure in any
desired or effective amount. For example, the cyan pigment may be
present in the instant process black ink composition in an amount
(by weight) ranging from 0%-20%, such as 0%-10%, such as 4%-5%,
e.g. 4.28% or 4.6% based upon the total weight of the present
process black ink composition.
[0025] The magenta colorant includes any desired or effective
magenta colorant including pigments, mixtures of pigments, mixtures
of pigments and dyes, and the like, provided that the magenta
colorant may be dissolved or dispersed in at least one curable
monomer or at least one curable oligomer and at least one
dispersant. In specific embodiments, the magenta colorant is a
pigment.
[0026] Examples of suitable magenta pigments for use with the
process black ink composition of the present disclosure include C.
I. Pigment Red-5, C. I. Pigment Red-7, C. I. Pigment Red-12, C. I.
Pigment Red-48, C. I. Pigment Red-48:1, C. I. Pigment Red-57, C. I.
Pigment Red-112, C. I. Pigment Red-122, C. I. Pigment Red-123, C.
I. Pigment Red-146, C. I. Pigment Red-168, C. I. Pigment Red-184,
C. I. Pigment Red-202, C. I. Pigment Red-207. In specific
embodiments, a monoazo lithol rubine pigment such as Pigment Red
57:1 having a Color Index of 15850:1 is used, such as Permanent
Rubine L5B01 from Clariant International Ltd Muttenz,
Switzerland.
[0027] In some embodiments, the magenta pigment may be present in
the process black ink composition of the instant disclosure in any
desired or effective amount. For example, the magenta pigment may
be present in the process black ink composition of the instant
disclosure in an amount (by weight) ranging from 0%-20%, such as
0%-10%, such as 4%-7%, e.g. 5.4% or 4.9%.
[0028] The yellow colorant includes any desired or effective yellow
colorant including pigments, mixtures of pigments, mixtures of
pigments and dyes, and the like, provided that the yellow colorant
may be dissolved or dispersed in at least one curable monomer or at
least one curable oligomer and at least one dispersant. In specific
embodiments, the yellow colorant is a pigment.
[0029] Examples of suitable yellow pigments for use with the
process black ink composition of the present disclosure include: C.
I. Pigment Yellow-12, C. I. Pigment Yellow-13, C. I. Pigment
Yellow-14, C. I. Pigment Yellow-16, C. I. Pigment Yellow-17, C. I.
Pigment Yellow-74, C. I. Pigment Yellow-83, C. I. Pigment
Yellow-93, C. I. Pigment Yellow-95, C. I. Pigment Yellow-97, C. I.
Pigment Yellow-98, C. I. Pigment Yellow-114, C. I. Pigment
Yellow-128, C. I. Pigment Yellow-129, C. I. Pigment Yellow-151, C.
I. Pigment Yellow-154. In specific embodiments, C. I. Pigment
Yellow 13 or C. I. Pigment Yellow 14 is used.
[0030] In some embodiments, the yellow pigment may be present in
the process black ink composition of the instant disclosure in any
desired or effective amount. For example, the yellow pigment may be
present in the process black ink composition of the instant
disclosure in an amount (by weight) ranging from 0%-20%, such as
0%-10%, such as 4%-7%, e.g. 6.1%.
[0031] In some embodiments, the total amount of pigment (cyan,
magenta and yellow pigment) in the process black ink composition of
the present disclosure is between 10 wt %-30 wt %, such as 10 wt %
to 20 wt %, such as 10 wt % to 15 wt %. In some embodiments, the
total amount of pigment in the process black ink composition of the
present disclosure is at least about 15 wt %.
[0032] In some embodiments, the ratio of cyan colorant to yellow
colorant is at least about 0.65:1 to about 0.85:1, such as about
0.70-0.80:1, such as about 0.70-0.76:1. In some embodiments, the
ratio of cyan colorant to yellow colorant is 0.70:1. In other
embodiments, the ratio of cyan colorant to yellow colorant is about
0.76:1.
[0033] In some embodiments, the ratio of cyan colorant to yellow
colorant is at least about 0.65:1 to about 0.85:1, such as about
0.70-0.80:1, such as about 0.70-0.76:1. In some embodiments, the
ratio of cyan colorant to yellow colorant is 0.70:1. In other
embodiments, the ratio of cyan colorant to yellow colorant is about
0.76:1.
[0034] In some embodiments, the ratio of magenta colorant to yellow
colorant is at least about 0.75:1 to about 0.85:1, such as about
0.80-0.90:1, such as about 0.80-0.88:1. In some embodiments, the
ratio of magenta colorant to yellow colorant is 0.88:1. In other
embodiments, the ratio of cyan colorant to yellow colorant is about
0.80:1.
[0035] For example, in specific embodiments, the carbon black-free
process black ink composition of the present disclosure includes a
cyan colorant, which is a pigment, such as Pigment Blue 15:3, a
magenta colorant, which is a pigment, such as Pigment Red 57:1 and
a yellow colorant, which is a pigment, such as Pigment Yellow 14 or
Pigment Yellow 13, wherein each of the pigments, respectively, are
used at a ratio of 0.70:0.88:1.0. In some embodiments, the ratio of
Pigment Blue 15:3:Pigment Red 57:1: Pigment Yellow 14 or Pigment
Yellow 13 is 0.76:0.80:1.0.
[0036] In some embodiments, the process black ink of the present
disclosure further comprises a vehicle including dispersants, a
curable vehicle component including curable monomers or oligomers,
photo-initiators, optionally stabilizers and optionally fillers. In
embodiments, suitable dispersants include copolymers and block
copolymers containing pigment affinic groups, such as amines,
esters, alcohols and carboxylic acids. Illustrative examples of
suitable dispersants include dispersants selected from Efka.RTM.
4008, Efka.RTM. 4009, Efka.RTM. 4047, Efka.RTM. 4520, Efka.RTM.
4010, Efka.RTM. 4015, Efka.RTM. 4020, Efka.RTM. 4050, Efka.RTM.
4055, Efka.RTM. 4080, Efka.RTM. 4300, Efka.RTM. 4330, Efka.RTM.
4400, Efka.RTM. 4401, Efka.RTM. 4403, Efka.RTM. 4406, Efka.RTM.
4800, all available from BASF, Charlotte, N.C. Disperbyk.RTM. 101,
Disperbyk.RTM. 102, Disperbyk.RTM. 107, Disperbyk.RTM. 108,
Disperbyk.RTM. 109, Disperbyk.RTM. 110, Disperbyk.RTM. 111,
Disperbyk.RTM. 112, Disperbyk.RTM. 115, Disperbyk.RTM. 162,
Disperbyk.RTM. 163, Disperbyk.RTM. 164, Disperbyk.RTM. 2001, all
available from BYK Additives & Instruments, Wesel Germany,
Solsperse.RTM. 24000 SC/GR, Solsperse.RTM. 26000, Solsperse.RTM.
32000, Solsperse.RTM. 36000, Solsperse.RTM. 39000, Solsperse.RTM.
41000, Solsperse.RTM. 71000 or Solsperse.RTM. J-180 all available
from Lubrizol Advanced Materials, Inc. Cleveland, Ohio or mixtures
or combinations thereof.
[0037] In specific embodiments, Solsperse.RTM. J-180 or
Solsperse.RTM. 32000 is used. The dispersant may be present in the
process black ink composition of the instant disclosure in an
amount of about 0% to about 20% by weight, such as about 1% to
about 10% by weight, such as about 4% to about 6% by weight.
[0038] In some embodiments, the process black ink composition of
the present disclosure includes further components, such as a
suitable curable monomer. Examples of suitable materials include
radically curable monomer compounds, such as acrylate and
methacrylate monomer compounds. Specific examples of acrylate and
methacrylate monomers include (but are not limited to) isobornyl
acrylate, isobornyl methacrylate, lauryl acrylate, lauryl
methacrylate, isodecylacrylate, isodecylmethacrylate, caprolactone
acrylate, 2-phenoxyethyl acrylate, isooctylacrylate,
isooctylmethacrylate, butyl acrylate, alkoxylated lauryl acrylate,
ethoxylated nonyl phenol acrylate, ethoxylated nonyl phenol
methacrylate, ethoxylated hydroxyethyl methacrylate, methoxy
polyethylene glycol monoacrylate, methoxy polyethylene glycol
monomethacrylate, tetrahydrofurfuryl methacrylate,
tetrahydrofurfuryl methacrylate and the like, as well as mixtures
and combinations thereof.
[0039] In specific embodiments, propoxylated trimethylolpropane
triacrylate, such as SR-501 (also known as CD501) from Sartomer Co.
is used. The monomers may be present in the process black ink
composition of the present disclosure in an amount from about 0% to
about 50% by weight, such as about 1% to about 30% by weight, such
as about 5% to about 30% by weight, such as about 5.5% to about
11.5% by weight.
[0040] In some embodiments, the process black ink composition of
the present disclosure includes a curable oligomer. Suitable
curable oligomers include, but are not limited to, acrylated
polyesters, acrylated polyethers, acrylated epoxies, urethane
acrylates, and pentaerythritol tetraacrylate. Specific examples of
suitable acrylated oligomers include, but are not limited to,
acrylated polyester oligomers, such as CN2255.RTM., CN2256.RTM.,
CN294E.RTM. (Sartomer Co.), and the like, acrylated urethane
oligomers, acrylated epoxy oligomers, such as CN2204.RTM.,
CN110.RTM. (Sartomer Co.), and the like and mixtures and
combinations thereof. The oligomers may be present in the process
black Ink composition in an amount of about 0% to about 80% by
weight, such as about 1% to about 70% by weight, such as about 4%
to about 67% by weight, based upon the total weight of the present
process black ink composition.
[0041] In some embodiments, CN294E.RTM. and CN2256.RTM. are used.
In some embodiments, CN294E.RTM. is present in the process black
ink composition in an amount of about 55% to 65% by weight. In some
embodiments, CN2256.RTM. is present in the process black Ink
composition in an amount of about 0% to 10% by weight. In some
embodiments, CN2256.RTM. is used to increase the cohesiveness (for
example, decrease the "runniness") of the process black ink
composition of the present disclosure.
[0042] In some embodiments, the present process black ink
composition includes a photo-initiator, such as a
.alpha.-hydroxyketone photo-initiator (including
.alpha.-hydroxyketone photoinitators sold under the trade name
IRGACURE.RTM. 184, IRGACURE.RTM. 500, DAROCUR.RTM. 1173, and
IRGACURE.RTM. 2959, which are manufactured by BASF),
.alpha.-aminoketone photo-initiators (including .alpha.-aminoketone
photo-initiators IRGACURE.RTM. 369, IRGACURE.RTM. 379,
IRGACURE.RTM. 907, and IRGACURE.RTM. 1300, which are manufactured
by BASF), and bisacyl phosphine photo-initiators (including bisacyl
phospine photo-initiators sold under the trade name IRGACURE.RTM.
819, IRGACURE.RTM. 819DW, and IRGACURE.RTM. 2022, which are
manufactured by BASF). Other suitable photo-initiators include
monoacylphosphine oxide and bisacylphosphine oxide, such as
2,4,6-trimethylbenzoybiphenylphosphine oxide (manufactured by BASF
under the trade name LUCIRIN.RTM. TPO);
ethyl-2,4,6-trimethylbenzoyiphenyl phosphinate (manufactured by
BASF under the trade name LUCIRIN.RTM. TPO-L); mono- and
bis-acylphosphine photoinitiators (such IRGACURE.RTM. 1700,
IRGACURE.RTM. 1800, IRGACURE.RTM. 1850, and DAROCUR.RTM. 4265,
manufactured by BASF), benzyldimethyl-ketal photo-initiators (such
as IRGACURE.RTM. 651, which are manufactured by BASF) and
oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]
(available as Esacure KIP 150 from Lamberti); and the like, as well
as mixtures and combinations thereof.
[0043] The photo-initiator may be present in the process black ink
composition of the instant disclosure in an amount of about 0% to
about 7% by weight, such as about 0% to about 5%, by weight, such
as about 1% to about 4% by weight.
[0044] In some embodiments, the process black ink composition of
the present disclosure comprises a stabilizer, such as
IRGASTAB.RTM. UV10 available from BASF or CN3216 available from
Sartomer Co. The stabilizer may be present in the process black ink
composition in an amount of about 0% to about 5% by weight, such as
from about 0.9% to about 4% by weight, such as about 1% to about 2%
by weight.
[0045] In some embodiments, the process black ink composition of
the present disclosure includes fillers. Suitable fillers may
include, but are not limited to, amorphous, diatomaceous, fumed
quartz and crystalline silica, clays, aluminum silicates, magnesium
aluminum silicates, talc, mica, delaminated clays, calcium
carbonates and silicates, gypsum, barium sulfate, zinc, calcium
zinc molybdates, zinc oxide, phosphosilicates and borosilicates of
calcium, barium and strontium, barium metaborate monohydrate, and
the like. In specific embodiments, the filler may be clays from
Southern Clay Products, Gonzales Tex., e.g. CLAYTONE.RTM. HA and
CLAYTONE.RTM. HY. In some embodiments, filler may be present in the
process black ink composition of the present disclosure in an
amount from about 0% to about 25% by weight, such as about 1% to
about 10% by weight, such as from about 1.% to about 5% by
weight.
[0046] In some embodiments, the color value of the process black
ink composition in the present disclosure is described
quantitatively using the L*, a* and b* coordinates as defined
according to CIELAB.RTM.. CIELAB.RTM. is color space described by
the International Commission on Illumination. According to the
CIELAB.RTM. definition, the brightness of L*=100 yields white and a
brightness of L*=0 yields black. In some embodiments, a targeted
level of L* for the process black ink composition in accordance
with the present disclosure ranges from about 0-40, such as from
about 15-35, such as about 20-25.
[0047] As is understood in the art, the "a*" dimension corresponds
to the amount of magenta present in the color. Positive "a*" values
indicate the presence of magenta and negative "a*" values indicate
green. In some embodiments, the a* value of the process black ink
composition according the present disclosure ranges from about 1-4,
such as about 1.5 to 3.8.
[0048] The "b*" dimension corresponds to the amount of cyan or
yellow in the color. Positive "b*" values indicate the presence of
cyan and negative "b*" values indicate the presence of yellow. In
some embodiments, the b* value of the process black ink composition
according the present disclosure ranges from about 3-4.5, such as
about 4.1-4.3.
[0049] In some embodiments, the color values of the process black
ink of the present disclosure are determined with reference to
image data and a particular color space. A difference may be
determined between the identified color values in the selected
color space and a predetermined color value for black ink in the
color space. This difference refers to a quantifiable amount
between color values that may or may not be perceptible to the
human eye. In some embodiments, the L*, a* and b* values are
assessed using a thin film of the present process black ink
composition, the thin film being disposed on a substrate and having
an optical density ranging from about 1.0 to about 2.0. In some
embodiments, the substrate is XEROX.RTM. Digital Color Elite Gloss
(DCEG) paper.
[0050] In some embodiments, the L*, a*, b* value described above
for the process black ink of the present disclosure are compared to
a Pantone.RTM. Standard for black, e.g., Pantone.RTM. Standard for
black, wherein L* is 22.07, a* is 1.57 and b* is 4.26 as described
in the Examples. As is known in the art, Pantone.RTM. is a
standardized color matching system, which uses a numbering system
for identifying colors.
[0051] The term "dE2000" indicates that the standard CIEdE2000
formula, published by the CIELAB.RTM., has been calculated to
provide a dE2000 value, which measures the color difference between
two colors. The larger the dE2000 value, the larger the color
difference. A dE2000 of 1.5 to 2 is generally considered to be at
the limit of visual perception. In some embodiments, the dE2000
value of the process black ink compositions of the present
disclosure in comparison to a Pantone.RTM. Standard is less than 3,
such as less than about 2.
[0052] In some embodiments, the viscosity of the present process
black ink composition drops at higher rates of shear velocity
similar to conventional process black ink compositions as
demonstrated in the Examples, below. In some embodiments, the
process black ink composition of the present disclosure may have a
viscosity from about 5,000 centipoise to about 3.66E+6 centipoise
at 35.degree. C. at a shear rate of 0.1 sec.sup.-1, more typically
between about 1.00E+5 to about 5.00E+6. Alternatively, the process
black ink composition of the present disclosure may have a shear
thinning index (viscosity at 40 sec.sup.-1/viscosity at 10
sec.sup.-1) at 35.degree. C. of from about 0.10 to about 0.60, more
typically about 0.60.
Methods of Preparing the Process Black Ink
[0053] The process black ink compositions of the present disclosure
can be prepared by any desired or suitable method. In some
embodiments, the cyan colorant comprising, for example, a cyan
pigment, the magenta colorant comprising, for example, a magenta
pigment and the yellow colorant, comprising, for example, a yellow
pigment in the ratios described herein may be mixed by acoustic
mixing prior to processing the remaining components, e.g.
dispersants, monomers, oligomers, photo-initiators, stabilizers and
fillers. In some embodiments, the acoustic mixing may be performed
using an acoustic mixer, which includes a closed vessel without
impellers, and which uses low-frequency, high intensity acoustic
energy to provide the desired mixing or blending of the pigments
used to prepare the process black ink composition of the present
disclosure.
[0054] Issues that may arise with the use of conventional mixers
that possess impellers include, but are not limited to, a moderate
mixing cycle; limited high-viscosity mixing capability; viscous
heating; limited filler loading capability; high shear localized
mixing; Further, conventional mixing may require contact mixing,
and thus impeller cleaning is an additional step that must be
utilized in the process.
[0055] In contrast, advantages to be found by using an acoustic
mixer include, but are not limited to, fast mixing cycle; excellent
high-viscosity mixing capability; low heat generation; high rate of
filler loading; high intensity mixing throughout the volume of
material to be mixed; non-contact, hygienic and sealed mixing.
[0056] The selected acoustic mixer in accordance with the present
disclosure provides mixing by applying a consistent shear field
throughout the entire vessel, and thus may be especially suitable
for the mixing of the pigments used to prepare the process black
ink composition of the present disclosure.
[0057] In some embodiments, a suitable acoustic mixer for use in
accordance with the present disclosure include LABRAM mixers and
RESONANTACOUSTIC.RTM. mixers, without impellers, commercially
available from RESODYN.TM. Acoustic Mixers, Inc. (Butte, Mont.).
The acoustic mixer is operated on a resonant frequency. A closely
controlled electromechanical oscillator is used to excite the mix
material. In some embodiments, the colorants including pigments are
mixed with an acoustic mixer at a frequency of from about 15 Hertz
to about 2000 Hertz, in embodiments from about 30 Hertz to about
1000 Hertz, for example about 60 Hertz. The entire system may
oscillate in resonance, allowing highly efficient energy transfer
and rapid mixing of the pigments of the present process black ink
composition.
[0058] Acoustic mixers, such as those available from RESODYN.TM.
Acoustic Mixers, Inc., apply high intensity, low frequency acoustic
energy such as to enable the shearing and extremely efficient
mixing of materials in various physical states. In embodiments,
optimum wetting of the pigment and then subsequent mixing into the
supporting vehicle, e.g. dispersants, monomers, etc. in an acoustic
mixer is done at an acceleration of from about 30 to about 110 g's,
wherein g is the acceleration of gravity and is defined as
approximately 9.81 m.sup.2/s, and at an applied percentage
intensity of from about 50 to about 100 percent intensity.
[0059] In embodiments, an acoustic mixer may handle applications
ranging from gas-liquid hydrogenations through powder blending and
coating to loaded resins with a viscosity up to about 100 million
centipoise (cP), in embodiments from about 1 million cP to about 80
million cP, consistent with viscosities of the process black ink
compositions of the present application. Compared with an
impeller-based mixer, an acoustic mixer may readily achieve good
pigment wetting within a very short time, in embodiments from about
1 minute to about 300 minutes, in other embodiments from about 2
minutes to about 60 minutes, such as about 10 minutes to 60
minutes.
[0060] In specific embodiments, the cyan colorant comprising a cyan
pigment, a magenta colorant comprising a magenta pigment and a
yellow colorant comprising a yellow pigment are wetted with an
acoustic mixer such as the RESODYN.TM. acoustic mixer from
RESODYN.TM. Acoustic Mixers, Inc.
[0061] In some embodiments, after the colorants are well blended,
the dispersant, curable monomers and/or oligomers, photo-initiators
and optionally stabilizers and optionally fillers are added to the
acoustically mixed colorants comprising pigments and the mixture is
then further subjected to acoustic mixing for about 1 minute to
about 300 minutes, in other embodiments from about 2 minutes to
about 60 minutes, such as about 10 minutes to 60 minutes. The
acoustic mixing is applied at a frequency of about 30 Hertz to
about 1000 Hertz, for example about 60 Hertz, at an acceleration of
from about 30 to about 110 g's and at an applied percentage
intensity of from about 50 to about 100 percent.
[0062] In some embodiments, after acoustic mixing, the processed
sample is then discharged into a mixing vessel, such as a metal
beaker. The vessel is heated to a temperature within the range of
from about 40.degree. C. to about 95.degree. C., or from about
55.degree. C. to about 85.degree. C., or from about 65.degree. C.
to about 80.degree. C. The homogeneous mixture then is mixed for a
period of from about 5 minutes to about 80 minutes or from about 25
to about 60 minutes, or from about 30 to about 45 minutes.
[0063] In some embodiments, the homogenous mixture is cooled to
about room temperature and then milled. In some embodiments,
milling is performed using a 3-roll ball mill, for example, in
which the homogenous mixture is passed anywhere from about 2 to
about 10 times, or from 3 to 7 times, or 5 times, typically 3 times
or more typically 2 times. The pigmented radiation curable ink
composition can be milled a sufficient number of times so that the
agglomerates that may be present are reduced to a particle size of
less than about 1 .mu.m, as measured by a BYK grind gauge, for
example, to provide a process black ink composition of the present
disclosure. In some embodiments, the particle size is reduced to
within the range of from about 0.01 to about 1 .mu.m, or from about
0.05 to about 0.9 .mu.m, or from about 0.1 to about 0.85 .mu.m.
Methods of Digital Offset Printing Using the Present Ink
Compositions
[0064] The present disclosure further provides a method of digital
offset printing, which includes applying the process black ink
composition of the present disclosure onto a re-imagable imaging
member surface, the re-imagable imaging member having dampening
fluid disposed thereon; forming an ink image; and transferring the
ink image from the re-imagable surface of the imaging member to a
printable substrate.
[0065] An exemplary digital offset printing architecture is shown
in FIG. 1. As seen in FIG. 1, an exemplary 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 plate or a belt, or another now known or later developed
configuration. The re-imagable surface 110(a) may be formed of
materials including, for example, a class of materials commonly
referred to as silicones, including fluorosilicone, among others.
The re-imagable 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.
[0066] U.S. patent application Ser. No. 13/095,714 ("714
application"), titled "Variable Data Lithography System," filed on
Apr. 27, 2011, now U.S. Publication 2012/0103212, by Timothy Stowe
et al., which is commonly assigned, and the disclosure of which is
hereby incorporated by reference in its entirety, depicts details
of the imaging member 110 including the imaging member 110 being
comprised of a re-imagable surface layer 110(a) formed over a
structural mounting layer that may be, for example, a cylindrical
core, or one or more structural layers over a cylindrical core.
[0067] 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
includes, but is not limited to, any particular composition or form
such as, for example, paper, plastic, folded paperboard, Kraft
paper, clear substrates, metallic substrates or labels. 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.
[0068] 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 re-imagable 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 re-imagable surface of the imaging
member 110. 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 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, now U.S.
Publication No. 2013/0104756 titled "Dampening Fluid For Digital
Lithographic Printing," the disclosure of which is hereby
incorporated herein by reference in its entirety.
[0069] Once the dampening fluid is metered onto the re-imagable
surface of the imaging member 110, a thickness of the dampening
fluid may be measured using a sensor (not shown) that may provide
feedback to control the metering of the dampening fluid onto the
re-imagable surface of the imaging member 110 by the dampening
fluid system 120.
[0070] After a precise and uniform amount of dampening fluid is
provided by the dampening fluid system 120 on the re-imagable
surface of the imaging member 110, an 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 re-imagable 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.
[0071] 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.
[0072] Following patterning of the dampening fluid layer by the
optical patterning subsystem 130, the patterned layer over the
re-imagable 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
re-imagable surface layer of the imaging member 110. The inker
subsystem 140 may use an anilox roller to meter an offset
lithographic ink, such as the process black ink compositions of the
present disclosure, onto one or more ink forming rollers that are
in contact with the re-imagable 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 re-imagable surface. The
inker subsystem 140 may deposit the ink to the pockets representing
the imaged portions of the re-imagable surface, while ink on the
unformatted portions of the dampening fluid will not adhere to
those portions.
[0073] The cohesiveness and viscosity of the ink residing in the
re-imagable 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 layer
of the ink on the re-imagable surface to, for example, increase ink
cohesive strength relative to the re-imagable surface layer. Curing
mechanisms may include optical or photo curing, heat curing,
drying, or various forms of chemical curing. After transfer from
the re-imagable layer to the substrate, which can be made from
paper, plastic or metal, the ink on the substrate then can be
exposed again to UV light for final curing of the ink.
[0074] In some embodiments, the process black ink composition of
the present disclosure demonstrates excellent curing performance.
For instance, in some embodiments, the process black ink
compositions of the present disclosure require more than 80, such
as more than 90, such as more than 100 double MEK rubs for an image
having an Optical Density (thickness) of less than 1.7. In other
embodiments, the process black ink compositions of the present
disclosure require more than 100, such as more than 140, such as
more than 160 double MEK rubs for an image having an optical
density (thickness) of greater than 1.7, such as 1.8 or such as
1.9. "Double MEK Rub" refers to an Evaluation for Solvent
Resistance by a Solvent Rub Test. The test method is used to
determine the degree of cure of an ink by the ink resistance to a
specified solvent. The solvent rub test usually is performed using
methyl ethyl ketone (MEK) as the solvent. The test, such as ASTM
D4752, involves rubbing the surface containing the ink with
cheesecloth soaked with MEK until failure or breakthrough of the
ink occurs. The rubs are counted as a double rub (one rub forward
and one rub backward constitutes a double rub).
[0075] Referring again to FIG. 1, the ink is transferred from the
re-imagable 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 re-imagable surface of the
imaging member 110 is brought into physical contact with the
substrate 114. With the adhesion of the ink, such as the process
black ink of the present disclosure, 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
re-imagable surface of the imaging member 110.
[0076] In some embodiments, the process black ink compositions of
the present disclosure exhibit high transfer efficiencies from the
re-imagable surface of the imaging member to the substrate. In some
embodiments, the transfer efficiency is greater than 90%, such as
greater than 95% or such as greater than 98%.
[0077] 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.
[0078] Following the transfer of the majority of the ink to the
substrate 114, any residual ink and/or residual dampening fluid may
be removed from the re-imagable surface of the imaging member 110,
typically 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
the 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 re-imagable 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 re-imagable 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.
[0079] The '714 application details other mechanisms by which
cleaning of the re-imagable 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
re-imagable surface of the imaging member 110 may be used to
prevent ghosting in the system. Once cleaned, the re-imagable
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 re-imagable surface of the imaging member
110, and the process is repeated.
Cyan, Magenta and Yellow Ink Compositions for Use in Forming a
Process Black Ink Image
[0080] In some embodiments, a process black ink image is formed by
first preparing a cyan ink composition, a magenta ink composition
and a yellow ink composition as described herein and then
superimposing the three ink compositions onto a substrate to form
an image comprising a process black color.
[0081] In some embodiments, an image may be transferred from an
imaging member to a substrate, for example, in a single process or
using a three part process, wherein 3 Images corresponding to the 3
colors can be transferred to a substrate, in which case the
substrate would travel around the rollers at nip pressure transfer
system 160 as shown in FIG. 1 three times for each transfer. The
rheology control system 150 of FIG. 1 may form a partial
crosslinking layer of the ink on the re-imagable surface, for
example, to increase ink cohesive strength relative to the
re-imagable surface layer. Curing mechanisms may Include optical or
photo curing, heat curing, drying, or various forms of chemical
curing. After transfer from the re-imagable layer to the substrate,
which can be made from, for example, paper, plastic or metal, the
ink on the substrate then can be exposed again to UV light for
final curing of the ink. The imaging member 110 of FIG. 1 may be
cleaned via cleaning subsystem 170 (FIG. 1) for subsequent image
processing as described herein.
[0082] In some embodiments, a digital offset color printer using
the above-described method for obtaining a process black ink image
includes four ink stations. While conventionally, the ink stations
include black, cyan, magenta and yellow ink stations, using the
present method, the black color station can advantageously be
replaced with another color, such as a specialty color, for example
silver, since the combination of the cyan, magenta and yellow
single color imaging systems may be used to obtain a process black
ink image on a substrate.
[0083] The cyan ink composition, the magenta ink composition and
the yellow ink composition may be formulated using a cyan colorant
including, for example, a cyan pigment, a magenta colorant
including, for example, a magenta pigment or a yellow colorant
comprising, for example, a yellow pigment. The types of cyan
colorants, magenta colorants and yellow colorants that may be used
in the cyan ink composition, the magenta ink composition and the
yellow ink composition, respectively, are as described above for
the process black ink composition.
[0084] In some embodiments, at least 15 wt %, such as at least 20
wt %, such as at least 35 wt % of cyan pigment, magenta pigment or
yellow pigment are included in the cyan ink composition, magenta
ink composition or yellow ink composition, respectively.
Dispersants, curable monomer or oligomers and optional stabilizers
and/or fillers in the types and amounts described herein for the
process black ink of the present disclosure may be added to each of
the instant cyan, magenta and yellow ink compositions.
[0085] In some embodiments, the cyan ink composition, magenta ink
composition or the yellow ink composition, respectively, is
individually formulated by adding the curable monomer and/or
oligomer, dispersants and optional stabilizers into a mixing
vessel, such as a metal beaker. The vessel is heated to a
temperature within the range of from about 40.degree. C. to about
95.degree. C. or from about 55.degree. C. to about 85.degree. C. or
from about 65.degree. C. to about 80.degree. C. In some
embodiments, the components are then mixed for a period of from
about 5 minutes to about 80 minutes or from about 25 to about 60
minutes or from about 30 to about 45 minutes.
[0086] In some embodiments, the colorant comprising, for example, a
cyan, magenta or yellow pigment and the photo-initiator(s) are then
added to the previously mixed curable vehicle components. In some
embodiments, the pigment is wetted by heating the vessel to a
temperature within a range of from about 40.degree. C. to about
95.degree. C., or from about 55.degree. C. to about 85.degree. C.
or from about 65.degree. C. to about 80.degree. C. The pigment and
curable vehicle components are then mixed for a period of from
about 5 minutes to about 90 minutes or from about 25 to about 60
minutes, or from about 30 to about 45 minutes. In some embodiments,
mixing is performed using high shear mixing, such as a Hockmeyer
high shear mixer (Hockmeyer Equipment Corporation, Elizabeth City,
N.C.), for example, at a speed from about 800-7000 rpm, such as
about 800 rpm to about 5000 rpm. In some embodiments, a filler such
as clay, is then added to the heated mixture and the components are
further mixed using high shear mixing for about 5 minutes to about
80 minutes.
[0087] In some embodiments, the mixture is then milled as described
herein to form a cyan ink composition, a magenta ink composition or
a yellow ink composition. For example, the mixture may be milled
using a 3-roll mill three times. In other embodiments, a portion of
the mixture is milled three times and a second portion is milled
only two times. The thus prepared cyan, magenta and yellow ink
compositions may then be used in combination to form a process
black ink image.
[0088] In other embodiments, the cyan ink composition, magenta ink
composition and/or the yellow ink composition are individually
formulated by adding the curable vehicle components and a colorant
including a pigment into an acoustic mixer and acoustically mixing
the components as described above. The mixture is then transferred
to a mixing vessel, such as a stainless steel beaker. The vessel is
heated to a temperature within the range of from about 40.degree.
C. to about 95.degree. C. or from about 55.degree. C. to about
85.degree. C. or from about 65.degree. C. to about 80.degree. C. In
some embodiments, the components are then mixed with an anchor
impeller for a period of from about 5 minutes to about 80 minutes
or from about 25 to about 60 minutes, or from about 30 to about 45
minutes, at a speed ranging from 500-5000 rpm, such as from 800 to
1000 rpm. In some embodiments, the mixture is then milled for up to
three passes, for example, two passes.
[0089] FIGS. 2, 3 and 4 describe exemplary ingredients and
processes for preparing a cyan ink composition, a magenta ink
composition and a yellow ink composition, respectively. These
exemplary embodiments are described in the Examples.
[0090] In order to prepare a process black image on a substrate,
such as a halftone process black image, the cyan ink composition,
magenta ink composition and yellow ink composition are provided to
the Imaging member and transferred to the substrate as described
herein in any effective proportion. For example, the relative ratio
of the cyan ink composition to the yellow ink composition is at
least about 0.65:1 to about 0.85:1, such as about 0.70-0.80:1, such
as about 0.70-0.76:1. In some embodiments, the relative ratio of
cyan ink composition to the yellow ink composition is 0.70:1. In
other embodiments, the relative ratio of cyan ink composition to
the yellow ink composition is about 0.76:1.
[0091] In some embodiments, the ratio of the magenta ink
composition to the yellow ink composition is at about 0.75:1 to
about 0.85:1, such as about 0.80-0.90:1, such as about 0.80-0.88:1.
In some embodiments, the relative ratio of magenta ink composition
to the yellow ink composition is 0.88:1. In other embodiments, the
relative ratio of magenta ink composition to the yellow ink
composition is about 0.80:1.
[0092] The process black ink composition in accordance with the
present disclosure is not limited to use in digital offset
printing. The process black ink composition disclosed herein may
also be useful in conventional offset printing or hybrid
conventional offset and digital offset printing systems.
Nonetheless, the process black ink compositions of the present
disclosure meet systems requirements that are unique to digital
offset printing systems. In particular, the present process black
ink compositions satisfy wetting and release requirements imposed
by the re-imagable imaging member of ink-based digital printing
systems. Further, the process black ink compositions of the present
disclosure are compatible with dampening fluids suitable for
ink-based digital printing, including non-aqueous dampening fluids.
The process black ink compositions of the present disclosure are
also enabled for transfer from an ink delivery system such as
anilox roll to the imaging member, e.g., re-imagable offset
plate.
[0093] The examples and other embodiments described herein are
exemplary and not intended to be limiting in describing the full
scope of compositions and methods of this disclosure. Equivalent
changes, modifications and variations of specific embodiments,
materials, compositions and methods may be made within the scope of
the present disclosure with substantially similar results.
EXAMPLES
Example 1
Preparation of Cyan, Magenta and Yellow Inks
[0094] A number of inks were formulated in order to find the
optimum ratio of cyan, magenta and yellow pigment dispersions to
formulate an optimum process black as follows.
[0095] Cyan Ink
[0096] FIG. 2 shows the process for a preparation of a cyan ink.
Based on a 400 gram total scale, dispersant, monomer, oligomers and
stabilizer as described in FIG. 2 or Table 1 were added to a 1 L
stainless steel vessel. The vessel was placed on a heating mantle,
available from IKA.RTM. Works, Inc., Wilmington, Del., equipped
with a thermocouple and stirrer apparatus (IKA.RTM.) and an anchor
impeller. The components in the vessel were stirred for about 30
minutes at about 80.degree. C. The photo-initiators were then
slowly added with stirring at about 80.degree. C. for about 15
minutes. With the vehicle base components solubilized, 60 g (15 wt.
%) of cyan pigment (Irgalite.RTM. Blue GLO, Ciba Specialty
Chemicals, Tarrytown, N.Y) were added to the vehicle and stirred.
The pigmented mixture was then allowed to stir for about 60 minutes
at 80.degree. C. The vessel containing the pigmented mixture was
then transferred to a high speed shearing mill (Hockmeyer Equipment
Corporation, Elizabeth City, N.C.) equipped with a 40 mm diameter
high shear Cowles blade, which was then stirred at 5000 RPM for
about 45 minutes. At this point, clay was slowly added to the
pigmented mixture and then re-stirred for about another 15
minutes.
[0097] The thoroughly mixed component mixture was then
qualitatively transferred to a 3-roll mill apparatus manufactured
by Kent Machine Works, Pendleton, Ind., where the material
composite paste was passed three times and then discharged into
brown glass bottles.
[0098] Magenta Ink
[0099] FIG. 3 shows the process for preparation of magenta ink. The
magenta ink was prepared using the components described in FIG. 3
or Table 1. Dispersant, monomer, oligomers and stabilizer were
first added to a 1 L stainless steel vessel and mixed as described
above for the cyan ink. The photo-initiators were then slowly added
with stirring at about 80.degree. C. for about 15 minutes. With the
curable vehicle base components solubilized, 60 g (15 wt. %) of
magenta pigment (PR L5B01, Clariant International Ltd Muttenz,
Switzerland) were added to the vehicle and stirred. The pigmented
mixture was then allowed to stir for about 90 minutes at 80.degree.
C. The vessel containing the pigmented mixture was then transferred
to a high speed shearing mill, Hockmeyer 15-65 (Hockmeyer Equipment
Corporation, Elizabeth City, N.C.) equipped with a 40 mm diameter
high shear Cowles blade, which was then stirred at 5000 RPM for
about 45 minutes. At this point, clay was slowly added to the
pigmented mixture and then re-stirred for about another 15
minutes.
[0100] The pigmented mixture was then split into a 100 gram portion
and a 300 gram portion. The 100 gram portion was passed three times
through an Erweka 3-roll mill (ERWEKA GmbH, Heusenstamm, Germany)
and then discharged into glass brown bottles. This process
simulates energy density 3 roll mill input using about 300 grams in
a 3-roll Kent mill (2 pass).
[0101] The 300 gram portion was passed through a 3-roll mill
apparatus (Kent Machine Works) at an input roll speed of 400 RPM
and then split into two 150 gram portions. One 150 gram portion was
then passed through the 3-roll Kent mill apparatus at an input roll
speed of 400 RPM and then discharged into brown glass bottles. The
second 150 gram portion was passed through the 3-roll Kent mill
apparatus at an input roll speed of 200 RPM and then discharged
into brown glass bottles.
[0102] Yellow Ink
[0103] FIG. 4 shows the process for preparation of yellow ink.
Components for the yellow ink were prepared by mixing all the
components of the yellow ink listed in Table 1, below or FIG. 4
(except for the pigment) by acoustic mixing for about 10 minutes.
The mixture was then transferred to a 1 L stainless steel vessel.
The vessel was placed on a heating mantle, available from IKA.RTM.,
equipped with a thermocouple and stirrer apparatus (IKA.RTM.) and
with an anchor impeller. 70 grams of PY13 (17.5 wt. %) was added to
the vessel and the components were stirred at 800 RPM for 60
minutes at 80.degree. C. The component mixture was then
qualitatively transferred to a 3-roll mill apparatus (Kent Machine
Works) where the material composite paste was passed through a
3-roll mill, first at an input roll speed of 400 RPM for the first
pass and then at an input roll speed of 200 RPM for the second
pass. The mixture was then discharged into brown glass bottles.
TABLE-US-00001 TABLE 1 Ink C139 M41-2 Y14 Chemical wt % wt % wt %
Pigments and Fillers Hostaperm Blue B4G (PB15:3) 15 Permanent
Rubine LSB01(PR57:1) 15 Permanent Yellow G-MX, PY14 17.40 Southern
Clay Claytone HY 2.00 2.00 1.99 Dispersants and Wetting Agents
Solsperse J-180 4.50 6.00 Solsperse 32000 4.77 Monomers Sartomer SR
501 5.49 11.27 5.77 Oligomer Sartomer CN294E 65.00 48.91 57.66
Sartomer CN2256E 8.81 4.47 Photo-initiators Irgacure 379 2.00 2.00
1.99 Irgacure 819 1.39 1.39 1.38 Esacure KIP 150 3.62 3.62 3.58
Stabilizers Sartomer CN3216 1.00 1.00 0.99 Total 100.00 100.00
100.00
Example 2
Process for Black Formulation
[0104] 5 gram samples of process black ink candidates were prepared
according to the formulations described in Table 2, below. The
components in each formulation were mixed together with a spatula
on a glass surface to obtain a homogenous mixture.
TABLE-US-00002 TABLE 2 StdOrder RunOrder Cyan Magenta Yellow 7 1
1.63 2.21 1.16 1 2 1.48 1.48 2.04 4 3 1.83 1.83 1.33 2 4 2.58 1.43
0.99 5 5 1.66 1.66 1.68 6 6 1.63 2.21 1.16 3 7 1.43 2.58 0.99
[0105] Analysis of the first seven inks led to the formulation of a
further 6 inks (Table 3). The inks in standard order 8 to 13 were
part of an iterative optimization that first looked at minimizing
the dE2000 values between a Pantone Standard (EA) and the present
inks. In a second stage, an attempt was made to minimize dE2000
values for all of the Pantone.RTM. Standards at the same time. A
final optimum Pantone.RTM. Standard Process Black was obtained
(Sample 13, in Table 3, below) by minimizing the dE2000 of the ink
with reference to Pantone.RTM. Standard Process Black to obtain a
target optical density (OD) of 1.5, while minimizing differences in
a* and b* between the 2 blacks at a target OD of 1.0. This was
found beneficial to minimize color shift often seen in process
blacks when going from a high to a low OD.
[0106] For the optimum candidate, Sample 13, the L*, a*, b* values
were 20.35, 3.82 and 4.25, respectively, at a normalized OD of 1.5
for a standard dE2000 value of 3.16 and 2.85. The target L*, a* and
b* values for Pantone.RTM. Standard Black is 22.07, 1.57 and 4.26,
respectively, as shown in Table 4, below. Accordingly, black inks
were successfully formulated. The process black ink was printed
using digital offset lithography printing architecture. The
transfer efficiency was 95% without pre-cure. Inks demonstrating
95% transfer efficiency without pre-cure display 100% transfer
efficiency with a pre-cure.
TABLE-US-00003 TABLE 3 Std Order Cyan Magenta Yellow 8 1.70 1.51
1.78 9 1.62 1.90 1.48 10 1.61 1.43 1.96 11 1.47 1.91 1.63 12 1.55
1.82 1.64 13 1.43 1.80 1.76
TABLE-US-00004 TABLE 4 Pantone .RTM. Standards L* a* b* 1 Yellow
87.49 -8.63 104.81 2 Orange 021 60.69 57.72 72.87 3 Warm Red 58.72
63.05 40.48 4 Red 032 52.66 69.08 36.48 5 Rubine Red 43.01 73.52
4.88 6 Rhodamine 50.53 78.77 -18.61 Red 7 Purple 46.56 70.18 -44.16
8 Violet 26.90 54.91 -61.72 9 Blue 072 24.39 48.09 -72.73 10 Reflex
Blue 22.76 38.32 -65.98 11 Process Blue 48.44 -22.42 -48.93 12
Green 61.65 -71.98 4.13 13 Yellow 87.49 -8.63 104.81 14 Black 22.07
1.57 4.26
Example 3
Novel, Scalable Ink Processing for Process Black Inks
[0107] Prints having different optical densities were generated and
the dE2000 values were obtained. The dE2000 values under D65
illumination are depicted in Table 5. Standard Pantone.RTM. Black
is used as the reference value. A dE2000 value of 1 or less between
two colors that are not touching one another is barely perceptible
using average printing presses, given that human vision is more
sensitive to color difference if two colors actually touch each
other. Any dE2000 value less than 3 is considered to be an
acceptable match.
TABLE-US-00005 TABLE 5 Measured Values OD dE2000 dE L* a* b* 1.43
1.3 1.1 22.39 2.31 3.51 1.57 2.82 3.78 18.4 2.39 3.84 1.618 3.58
5.02 17.24 1.86 2.91
[0108] In a separate experiment and to demonstrate a new scalable
process for mixed-pigment inks, process black ink was formulated
with a ratio of pigments corresponding to the ratio in described
for Sample 13 above. Normalized to 1, the proportions of pigments
used for the process black ink are shown in Table 6. As seen in
Table 6, the process black ink preparation (60 g) included 3.67 g
of yellow pigment, 3.24 grams of magenta pigment, 2.57 grams of
cyan pigment.
[0109] The pigments were wet by an acoustic mixing process prior to
processing with the remaining components. Mixers for acoustic
mixing operate at the mechanical resonance. At this operating
parameter, a lossless transfer of the mixer's mechanical energy
into the materials being mixed occurs by the propagation of an
acoustic pressure wave into the mixing vessel. This is achieved by
matching the mechanical operation of the mixer with the properties
and characteristics of the range of materials to be mixed. The
operating characteristics of the mixer are automatically sensed and
controlled to keep the system at the mixing condition established
to provide the best mixing performance. Resonant ACOUSTIC.RTM.
Mixers are available in three sizes: bench top pint, production
scale 5 gallon and 55 gallon systems. According to the literature,
various applications have demonstrated that the same mixing time is
required irrespective of the mix load size. This trend is
consistent for applications ranging from gas-liquid hydrogenations
through powder blending and coating to loaded resins with
viscosities up to 100,000,000 cP.
[0110] In the present example, the sample was processed in a
RESODYN.RTM. RAM for 10 minutes at 90% intensity and 60 Hz
frequency. Once the pigments were well blended, the rest of the
components were weighed in the bottle and processed for another 10
minutes at 90% intensity and 60 Hz frequency. The processed sample
was then discharged into a metal beaker and stirred with heating
using an anchor impeller for about 60 minutes at 80.degree. C. The
ink was finally passed three times though a 3-roll mill and
discharged into brown bottles.
TABLE-US-00006 TABLE 6 Density of pigment Experimental g/cm.sup.3
(generic Actual Amount of Proportion for average from Pigment in 5
g process black (g) literature) cyan 0.2150 0.271 1.65 magenta
0.2705 0.341 1.56 yellow 0.3069 0.387 1.25
Example 4
Rheological Properties of Process Black
[0111] The rheological properties of the process black were
determined under the same conditions as the cyan, magenta and
yellow ink used to determine the pigment ratios. Table 7 and FIG. 5
depict the viscosity and shear thinning index of the inks. These
data show that the process black properties are predictable from
the properties of the starting primary colors, which demonstrates
that the selection of the pigments was appropriate and that no
strong pigment-pigment interactions exist.
TABLE-US-00007 TABLE 7 Cyan, Magenta Yellow, Black, Metric C139
M41-2 Y14 K41 Viscosity (0.1 2.66E+06 2.14E+06 1.37E+07 3.66E+06
rad/sec) mPa s Viscosity (0.4 1.18E+06 9.08E+05 4.36E+06 1.44E+06
rad/sec) mPa s Viscosity (1 6.79E+05 5.39E+05 2.10E+06 8.11E+05
rad/sec) mPa s Viscosity (4 3.36E+05 2.92E+05 8.00E+05 4.01E+05
rad/sec) mPa s Viscosity (10 2.26E+05 2.11E+05 4.69E+05 2.73E+05
rad/sec) mPa s Viscosity (40 1.30E+05 1.32E+05 2.32E+05 1.59E+05
rad/sec) mPa s Viscosity (100 8.78E+04 9.18E+04 1.45E+04 1.06E+05
rad/sec) mPa s Shear Thinning 0.45 0.42 0.32 0.39 Index (0.4/0.1)
Shear Thinning 0.50 0.54 0.38 0.49 Index (4/1) Shear Thinning 0.57
0.63 0.50 0.58 Index (40/10)
Example 5
Hand Transfer of Inks onto Substrate and OD Data Analysis
[0112] Each of the inks were transferred onto XEROX.RTM. Digital
Color Elite Gloss (DCEG) paper at different densities, such that
the resultant visible optical densities ranged from about 1 to
about 2, the L* brightness of the transferred images ranged from
about 8 to about 40 after having been cured using a Fusion UV
Lighthammer L6 curing station equipped with D bulb from Heraeus
Noblelight America LLC. The applied energy doses for UVV, UVA, UVB
and UVC bands were 640, 1401, 420 and 37 mJ/cm2, respectively. The
print image dimensions were on the order of 2 cm by 3 cm.
[0113] A best fit of the L*a*b* parameters versus OD was obtained
as were L*a*b* values for all of the inks at OD=1.5 and at OD=1.0.
Three responses were selected for the final optimization. The
dE2000 between the Pantone.RTM. Standard and the process black of
the present disclosure at OD=1.5 and the a* b* values for the
Pantone.RTM. Standard versus the a* b* values of the present inks
expected at OD=1 was also assessed (data not shown). Scanning
Electron Transmission images at 10,000.times. magnification showed
a variation in thickness of the process black prints from about 1.2
to about 3.9 microns with an average thickness in uniform areas of
about 2.0 to about 2.4 microns for an average OD ranging from about
1.5 to about 1.7.
Example 6
Characterization of Ink Transfer Prints
[0114] In order to assess curing performance, a soft applicator
dipped in methylethyl ketone (MEK) solvent at room temperature was
spread evenly across (about 2 cm) each of the images on the DCEG
paper using constant pressure with fresh MEK being re-applied onto
the applicator every 5 double MEK rubs. The number of MEK double
rubs required before the paper substrate becomes visible was
recorded. These data are shown in FIG. 6.
[0115] As evident in FIG. 6, excellent curing performance was
achieved using the process black ink of the present disclosure. The
increase at higher OD is explained by the increase in image
thickness necessary to achieve high OD with the process black of
the instant disclosure. There was no significant variation in MEK
rubs when the OD was below about 1.7. Comparative data were
obtained for black inks using carbon black pigments (data not
shown). None of the MEK double rubs for carbon black-containing
inks exceeded 80.
[0116] The Examples demonstrate that it was possible to formulate a
carbon black-free process black using pigments such as PB 15:3,
PR57:1 and PY 14, where each of the pigments are used at a relative
ratio of 0.70:0.88:1.0. This deviates from the expected ratio
(where pigments are used at an equal volume ratio). Corrected for
density, the expected relative ratio is 0.76:0.8:1.0.
* * * * *