U.S. patent application number 11/070714 was filed with the patent office on 2005-09-29 for ink jet ink.
Invention is credited to Elwakil, Hamdy A., McIntyre, Patrick F..
Application Number | 20050215664 11/070714 |
Document ID | / |
Family ID | 34919514 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050215664 |
Kind Code |
A1 |
Elwakil, Hamdy A. ; et
al. |
September 29, 2005 |
Ink jet ink
Abstract
Disclosed is a non-aqueous inkjet ink containing certain
titanium dioxide slurries, an associated inkjet ink set for inkjet
printing, and a method of inkjet printing with the inkjet ink or
ink set. The solvent and mixtures of solvents used for the
dispersed titanium dioxide have a hydrogen bonding solubility
parameter of greater than about 9. The inks have improved
anti-settling properties with less pigment agglomeration and
flocculation over time such that they can be utilized to prepare a
stable inkjet ink. Also described is the use of this ink to print
on colored or transparent surfaces.
Inventors: |
Elwakil, Hamdy A.;
(Hockessin, DE) ; McIntyre, Patrick F.; (West
Chester, PA) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
34919514 |
Appl. No.: |
11/070714 |
Filed: |
March 2, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60549607 |
Mar 2, 2004 |
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Current U.S.
Class: |
523/160 ;
106/31.6; 106/31.9; 347/100; 523/161 |
Current CPC
Class: |
B32B 17/10761 20130101;
B41M 5/0064 20130101; C09D 11/36 20130101; B41M 7/0027 20130101;
D06P 5/30 20130101; B32B 17/10247 20130101; B41M 5/0047 20130101;
C03C 27/10 20130101; C09D 11/40 20130101; B32B 17/10339 20130101;
B32B 17/10688 20130101 |
Class at
Publication: |
523/160 ;
106/031.9; 106/031.6; 347/100; 523/161 |
International
Class: |
C09D 011/02; B41J
002/01; C03C 017/00 |
Claims
1. A non-aqueous inkjet ink comprising a non-aqueous liquid carrier
having dispersed therein (a) a titanium dioxide pigment and (b) at
least one dispersant for the titanium dioxide pigment, wherein: (i)
the non-aqueous liquid carrier comprises an organic solvent or a
mixture of organic solvents, (ii) the organic solvent or mixture of
organic solvents has a hydrogen bonding solubility parameter based
on Hansen solubility parameters of more than about 9, (iii) the
organic solvent or mixture of organic solvents in the non-aqueous
liquid carrier are predominantly only non-reactive organic
solvents; and (iv) the conductivity of the ink is less than about
50 .mu.mho/cm.
2. The non-aqueous inkjet ink of claim 1, wherein the organic
solvent or mixture of organic solvents has a boiling point of
greater than 120.degree. C. at 0.1 kpascals.
3. The non-aqueous inkjet ink of claim 1, wherein the organic
solvent or mixture of organic solvents is predominantly comprised
of polar solvents.
4. The non-aqueous inkjet ink of claim 1, wherein the at least one
dispersant is a combination of dispersants comprising: (1) a graft
copolymer having a weight average molecular weight of from about
4000 to about 100000, comprising from about 90% to about 50% by
weight of a polymeric backbone, and from about 10% to about 50% by
weight of macromonomer side chains attached to the backbone, the
polymeric backbone and macromonomer side chains comprising 100 wt %
of the graft copolymer, wherein: (i) the polymeric backbone is
hydrophobic in comparison to the macromonomer side chains and
comprises polymerized ethylenically unsaturated hydrophobic
monomers and, optionally, up to about 20% by weight, based on the
weight of the graft copolymer, of polymerized ethylenically
unsaturated acid monomers; and (ii) each of the macromonomer side
chains individually is a hydrophilic polymer containing acids
groups attached to the polymeric backbone at a single terminal
point, and (A) has a weight average molecular weight of from about
1000 to about 30000, and (B) comprises from about 2% to about 100%
by weight, based on the weight of the macromonomer side chain, of a
polymerized ethylenically unsaturated acid monomer, and (2) a block
copolymer of type AB, ABA or ABC wherein at least one of the blocks
in the block copolymer is an adsorbing segment, and wherein at
least one of the blocks in the block copolymer is a stabilizing
segment.
5. The non-aqueous inkjet ink of claim 1, which is white.
6. An inkjet ink set comprising a plurality of colored, pigmented
inks, at least one of which is a first non-aqueous inkjet ink
comprising a non-aqueous liquid carrier having dispersed therein
(a) a titanium dioxide pigment and (b) at least one dispersant for
the titanium dioxide pigment, wherein: (i) the non-aqueous liquid
carrier comprises an organic solvent or a mixture of organic
solvents, (ii) the organic solvent or mixture of organic solvents
has a hydrogen bonding solubility parameter based on Hansen
solubility parameters of more than about 9, (iii) the organic
solvent or mixture of organic solvents in the non-aqueous liquid
carrier are predominantly only non-reactive organic solvents; and
(iv) the conductivity of the ink is less than about 50
.mu.mho/cm.
7. The inkjet ink set of claim 6, wherein the organic solvent or
mixture of organic solvents has a boiling point of greater than
120.degree. C. at 0.1 kpascals.
8. The inkjet ink set of claim 6, wherein the organic solvent or
mixture of organic solvents in the first non-aqueous ink is
predominantly comprised of polar solvents.
9. The inkjet ink set of claim 6, wherein the at least one
dispersant in the first non-aqueous inkjet ink is a combination of
dispersants comprising: (1) a graft copolymer having a weight
average molecular weight of from about 4000 to about 100000,
comprising from about 90% to about 50% by weight of a polymeric
backbone, and from about 10% to about 50% by weight of macromonomer
side chains attached to the backbone, the polymeric backbone and
macromonomer side chains comprising 100 wt % of the graft
copolymer, wherein: (i) the polymeric backbone is hydrophobic in
comparison to the macromonomer side chains and comprises
polymerized ethylenically unsaturated hydrophobic monomers and,
optionally, up to about 20% by weight, based on the weight of the
graft copolymer, of polymerized ethylenically unsaturated acid
monomers; and (ii) each of the macromonomer side chains
individually is a hydrophilic polymer containing acids groups
attached to the polymeric backbone at a single terminal point, and
(A) has a weight average molecular weight of from about 1000 to
about 30000, and (B) comprises from about 2% to about 100% by
weight, based on the weight of the macromonomer side chain, of a
polymerized ethylenically unsaturated acid monomer, and (2) a block
copolymer of type AB, ABA or ABC wherein at least one of the blocks
in the block copolymer is an adsorbing segment, and wherein at
least one of the blocks in the block copolymer is a stabilizing
segment.
10. The inkjet ink set of claim 6, wherein the first non-aqueous
inkjet ink is white.
11. The inkjet ink set of claim 10, further comprising a cyan ink,
a magenta ink and a yellow ink.
12. The inkjet ink set of claim 10, further comprising a black
ink.
13. The inkjet ink set of claim 11, further comprising a black
ink.
14. A method for inkjet printing onto a substrate, comprising the
steps of: (1) providing a drop-on demand inkjet printer that is
responsive to digital data signals; (2) loading the printer with a
substrate to be printed; (3) loading the printer with an inkjet
ink; and (4) printing onto the substrate using the inkjet ink in
response to the digital data signals, wherein the inkjet ink is a
first non-aqueous inkjet ink comprising a non-aqueous liquid
carrier having dispersed therein (a) a titanium dioxide pigment and
(b) at least one dispersant for the titanium dioxide pigment,
wherein: (i) the non-aqueous liquid carrier comprises an organic
solvent or a mixture of organic solvents, (ii) the organic solvent
or mixture of organic solvents has a hydrogen bonding solubility
parameter based on Hansen solubility parameters of more than about
9, (iii) the organic solvent or mixture of organic solvents in the
non-aqueous liquid carrier are predominantly only non-reactive
organic solvents; and (iv) the conductivity of the ink is less than
about 50 .mu.mho/cm.
15. The method of claim 14, wherein the printer is loaded with an
inkjet ink set comprising a plurality of colored, pigmented inks,
at least one of which is the first non-aqueous inkjet ink.
16. The method of claim 14, wherein the substrate is a
thermoplastic polymer substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.119
from U.S. Provisional Application Ser. No. 60/549,607 (filed Mar.
2, 2004), the disclosure of which is incorporated by reference
herein for all purposes as if fully set forth.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This present invention pertains to a non-aqueous inkjet ink
made from titanium dioxide and an associated inkjet ink set for
inkjet printing. The invention also pertains to a method of inkjet
printing with the ink and ink set. The inks utilized herein have
improved anti-settling performance with less pigment agglomeration
and flocculation over time such that they can be utilized as a
stable inkjet ink. The white ink based on the titanium dioxide
provides new means to digitally print white ink by itself, but also
with other colors.
[0004] 2. Description of the Related Art
[0005] Inkjet printing is a non-impact printing process in which
droplets of ink are deposited on print media, such as paper or
polymeric substrates, to form the desired image. The droplets are
ejected from a printhead in response to electrical signals
generated by a microprocessor.
[0006] Colored inkjet inks comprise one or more colorants that are
dissolved (e.g., dyes) and/or dispersed (e.g., pigments and
dispersed dyes) in the ink vehicle. The ink vehicle can be aqueous
(significant amounts of water) or non-aqueous (predominantly
organic liquid), and the ink is referred to as aqueous or
non-aqueous ink accordingly.
[0007] Although aqueous ink is advantageous because water is
especially environmentally friendly, there are many applications
where aqueous ink is unsuitable and non-aqueous ink must be used.
Many, if not most of these non-aqueous ink applications involve
printed articles on hydrophobic substrates, and particularly
printed articles on polymer substrates, which will be exposed to
sunlight, and the preferred colorants in these applications are
pigments because of their well-know advantage in fade resistance
compared to dyes.
[0008] Dispersion of pigments in a non-aqueous vehicle is
substantially different than dispersion in an aqueous vehicle.
Generally, pigments that can be dispersed well in water do not
disperse well in non-aqueous solvent, and vice versa.
[0009] Also, the demands of inkjet printing are quite rigorous and
the standards of dispersion quality are high. Thus, pigments that
may be "well dispersed" for other applications are often still
inadequately dispersed for inkjet applications.
[0010] There is a need for improved pigment selection especially
for a stable white ink for inkjet inks. In particular, there is a
need for the white pigments that can be sufficiently stabilized in
inkjet compatible formulations so that the resultant ink can be
effectively jetted, even after being stored or otherwise unused for
some period of time. In addition, the ability to use a white ink to
complement other inks of an ink set can lead to improved images,
especially when lighter tones and/or higher degrees of coverage or
opacity are needed.
[0011] White inks are useful and provide good visibility when
printed on transparent and colored surfaces. White printing on
these surfaces is desirable in numerous end uses, such as the
computer industry (printed circuit boards, computer chips),
recording industry (tapes, film, etc.), packaging and automotive
coatings. White ink may be used not only to detail and add decals
to automobiles, but also to other motor vehicles, including trucks,
planes and trains, as well as bicycles, etc. White ink may also be
useful on other surfaces, such as plastics, wood, metal, glass,
textiles, polymeric films and leather for both practical and
ornamental purposes. Colored paper and cardboard can also be
effectively printed with white ink.
[0012] White ink formulations typically contain a particulate white
pigment dispersed in a solvent/resin system.
[0013] There are many patents and applications describing aspects
of using a white ink in ink jet printing. U.S. Pat. No. 4,630,076
describes a color ink jet system with an additional white ink that
is printed on top of the previously printed color dots, but does
not provide a means to produce a stable useful white ink.
[0014] U.S. 2001/0020964 describes the use of a quickly drying
white ink printed over another ink or adjacently. This use of white
ink is particularly directed to use of the white ink with the black
ink. No description of an effective ink jet white ink is
provided.
[0015] U.S. Pat. No. 5,439,514 describes an aqueous ink which has
both a colorant and a white inorganic material in the same ink.
[0016] U.S. Pat. No. 6,769,766 describes the need for a white UV
ink for ink jet printers.
[0017] WO02/096654 provides a possible solution to the problem of
the settling of the titanium dioxide by agitating the ink cartridge
by having a continuous ink-flow subsystem to inhibit settling of
solids out of suspension.
[0018] U.S. 2003/0052952 describes an inorganic phosphoric acid
treated titanium dioxide that can be slurred to obtain an aqueous
ink. Only modest ink stability is reported.
[0019] U.S. Pat. No. 6,433,038 describes an aqueous photocurable
ink that has a anatase titanium dioxide as the colorant.
[0020] U.S. 2004/0246319, EP-A-1321497, EP-A-1388578 and
WO00/049097 all describe inks that contain a polymerizable compound
and a white pigment and/or titanium dioxide.
[0021] U.S. Pat. No. 4,680,580 describes a white ink with an
inorganic white pigment, a binder resin, a solvent selected from an
alcohol, ketone, ether or acetate ester and cyclohexanone, which
are solvents for the binder and a conductive salt. This ink is
primarily effective for continuous ink jet printers.
[0022] WO04/053002 discloses an opaque ink jet ink which has
similar feature to U.S. Pat. No. 4,680,580, as it is an ink with a
conductive component and suggested for utility with continuous ink
jet printers.
[0023] Current white ink formulations are not acceptable for
numerous applications, such as commercial drop-on-demand inkjet
applications, primarily because of poor stability resulting in
pigment settling and agglomeration. Poor stability may result in
"nozzle outs" or plugging of the ink jet nozzles. For example, a
typical print head on an industrial printer has 256 nozzles, each
nozzle head having a diameter of about 50 microns in size. Large
pigment particles and agglomerates may plug the nozzles. Poor
stability also results in poor hiding, non-uniform coverage and
poor clarity in the printed surface.
[0024] White ink formulations based on inorganic white pigments,
such as titanium dioxide (TiO.sub.2), may fail because of poor
stabilization of the TiO.sub.2 pigment. Pigment agglomeration and
flocculation are often at fault in poor performance of white inks,
particularly white inkjet inks, due to settling and nozzle plugging
problems.
[0025] As a result, there is a need for a white pigmented ink
formulation for use in ink and inkjet systems that avoid the
aforementioned negative attributes. The present invention meets
these needs.
SUMMARY OF THE INVENTION
[0026] In one aspect of the present invention there is provided a
non-aqueous inkjet ink comprising a non-aqueous liquid carrier
having dispersed therein (a) a titanium dioxide pigment and (b) at
least one dispersant for the titanium dioxide pigment, wherein:
[0027] (i) the non-aqueous liquid carrier comprises an organic
solvent or a mixture of organic solvents,
[0028] (ii) the organic solvent or mixture of organic solvents has
a hydrogen bonding solubility parameter based on Hansen solubility
parameters of more than about 9,
[0029] (iii) the organic solvent or mixture of organic solvents in
the non-aqueous liquid carrier are predominantly only non-reactive
organic solvents; and
[0030] (iv) the conductivity of the ink is less than about 50
.mu.mho/cm.
[0031] These inkjet inks may further comprise a variety of optional
additives of the general type known to those of ordinary skill in
the art, as part of the titanium dioxide slurry and/or added to the
jet ink separately therefrom, such optional additives including,
for example, other dispersants, binders, humectants and rheological
modifiers.
[0032] Unexpectedly, by use of the dispersant in combination with
the non-aqueous solvent mixture with a Hansen solubility parameter
of greater than 9, settling of titanium dioxide particles is
significantly reduced. Moreover, even when settling does occur, the
settling is "soft" settling, meaning the titanium dioxide pigment
can be readily re-dispersed and rejuvenated by low shear mixing so
as not to result in plugging of inkjet printhead nozzles. Low shear
mixing includes, for example, simple shaking (e.g., by hand or
movement of the inkjet printhead), or stirring with an impeller or
mixing blades at speeds of less than about 500 rpm wherein no
grinding occurs. In contrast, "hard" settling occurs with many
titanium dioxide slurries of the prior art. For most of the
dispersant/solvent combinations, negligible soft settling is
observed.
[0033] The titanium dioxide pigment used herein is white, thus the
inkjet inks of the present invention are preferably white.
Non-white colored inks can also be made by utilizing one or more
additional colorants in the ink.
[0034] In accordance with another aspect of the present invention,
there is provided an inkjet ink set comprising a plurality of
colored, pigmented inks, at least one of which is a preferably
white inkjet ink as set forth above.
[0035] The inkjet inks of the present invention are suitable, for
example, for use in personal, business and industrial
drop-on-demand inkjet printers, and numerous other printing
applications. Furthermore, they can be used for printing a wide
variety of substrates including non-white paper, transparencies,
polymer substrates, textiles, etc.
[0036] The present invention thus also provides a method for inkjet
printing onto a substrate, comprising the steps of:
[0037] (1) providing a drop-on demand inkjet printer that is
responsive to digital data signals;
[0038] (2) loading the printer with a substrate to be printed;
[0039] (3) loading the printer with the above-mentioned inkjet ink
or inkjet ink set; and
[0040] (4) printing onto the substrate using the inkjet ink set in
response to the digital data signals.
[0041] A preferred substrate for the instant invention inkjet ink
or inkjet ink set is a thermoplastic polymer substrate.
[0042] These and other features and advantages of the present
invention will be more readily understood by those of ordinary
skill in the art from a reading of the following detailed
description. It is to be appreciated that certain features of the
invention which are, for clarity, described above and below in the
context of separate embodiments, may also be provided in
combination in a single embodiment. Conversely, various features of
the invention that are, for brevity, described in the context of a
single embodiment, may also be provided separately or in any
subcombination. In addition, references in the singular may also
include the plural (for example, "a" and "an" may refer to one, or
one or more) unless the context specifically states otherwise.
Further, reference to values stated in ranges include each and
every value within that range.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] The present invention provides a non-aqueous ink, preferably
a white ink, made from a particularly dispersed, stabilized
titanium dioxide slurry. Inks made therefrom have improved
stability to agglomeration upon storage. The ink utilizes at least
one dispersant in amounts to stabilize and keep the pigments
deflocculated over extended periods of time when the slurry is
subsequently used in an ink formulation. As a result, the ultimate
ink formulation provides desirable properties such as good hiding,
uniform coverage, selective coverage, selective opacity, good
chemical resistance and good clarity when applied to surfaces. The
non-aqueous ink is especially useful for printing on polymeric
substrates.
[0044] Titanium Dioxide Pigment
[0045] Titanium dioxide (TiO.sub.2) pigment useful in the present
invention may be in the rutile or anatase crystalline form. It is
commonly made by either a chloride process or a sulfate process. In
the chloride process, TiCl.sub.4 is oxidized to TiO.sub.2
particles. In the sulfate process, sulfuric acid and ore containing
titanium are dissolved, and the resulting solution goes through a
series of steps to yield TiO.sub.2. Both the sulfate and chloride
processes are described in greater detail in "The Pigment
Handbook", Vol. 1, 2nd Ed., John Wiley & Sons, NY (1988), the
relevant disclosure of which is incorporated by reference herein
for all purposes as if fully set forth.
[0046] The titanium dioxide particles can have a wide variety of
average particle sizes of about 1 micron or less, depending on the
desired end use application of the ink.
[0047] The titanium dioxide pigment is in and of itself white in
color.
[0048] For applications demanding high hiding or decorative
printing applications, the titanium dioxide particles preferably
have an average size of less than about 1 micron (1000 nanometers).
Preferably, the particles have an average size of from about 50 to
about 950 nanometers, more preferably from about 75 to about 750
nanometers, and still more preferably from about 100 to about 500
nanometers. These titanium dioxide particles are commonly called
pigmentary TiO.sub.2.
[0049] For applications demanding white color with some degree of
transparency, the pigment preference is "nano" titanium dioxide.
"Nano" titanium dioxide particles typically have an average size
ranging from about 10 to about 200 nanometers, preferably from
about 20 to about 150 nanometers, and more preferably from about 35
to about 75 nanometers. An ink comprising nano titanium dioxide can
provide improved chroma and transparency, while still retaining
good resistance to light fade and appropriate hue angle.
[0050] In addition, unique advantages may be realized with multiple
particle sizes, such as opaqueness and UV protection. These
multiple sizes can be achieved by adding both a pigmentary and a
nano grade of TiO.sub.2.
[0051] The titanium dioxide can be incorporated into an ink
formulation via a slurry concentrate composition. The amount of
titanium dioxide present in the slurry composition is preferably
from about 15 wt % to about 80 wt %, based on the total slurry
weight. For slurries wherein the majority of titanium dioxide
particles are of a pigmentary size, and preferably those in which
the average particle size is greater than about 200 nanometers up
to about 1 micron, the amount of titanium dioxide in the slurry is
preferably from about 50 wt % to about 75 wt %, based on the total
weight of the slurry. For slurries wherein the majority of titanium
dioxide particles are of "nano" size, and preferably those in which
the average particle size is from about 10 nanometers to about 200
nanometers, the amount of titanium dioxide in the slurry is
preferably from about 20 wt % to about 50 wt %, and more preferably
from about 25 wt % to about 35 wt %, based on the weight of the
slurry.
[0052] Alternatively, the titanium dioxide can be mixed with the
dispersants, the solvent(s) and dispersed to obtain the final ink
formulation in one step.
[0053] The titanium dioxide pigment may be substantially pure
titanium dioxide or may contain other metal oxides, such as silica,
alumina and zirconia. Other metal oxides may become incorporated
into the pigment particles, for example, by co-oxidizing or
co-precipitating titanium compounds with other metal compounds. If
co-oxidized or co-precipitated metals are present, they are
preferably present as the metal oxide in an amount from about 0.1
wt % to about 20 wt %, more preferably from about 0.5 wt % to about
5 wt %, and still more preferably from about 0.5 wt % to about 1.5
wt %, based on the total titanium dioxide pigment weight.
[0054] The titanium dioxide pigment may also bear one or more metal
oxide surface coatings. These coatings may be applied using
techniques known by those skilled in the art. Examples of metal
oxide coatings include silica, alumina, alumina-silica and
zirconia, among others. Such coatings may optionally be present in
an amount of from about 0.1 wt % to about 10 wt %, and preferably
from about 0.5 wt % to about 3 wt %, based on the total weight of
the titanium dioxide pigment.
[0055] The titanium dioxide pigment may also bear one or more
organic surface coatings, such as, for example, carboxylic acids,
silanes, siloxanes and hydrocarbon waxes, and their reaction
products with the titanium dioxide surface. The amount of organic
surface coating, when present, generally ranges from about 0.01 wt
% to about 6 wt %, preferably from about 0.1 wt % to about 3 wt %,
more preferably about 0.5 wt % to about 1.5 wt %, and still more
preferably about 1 wt %, based on the total weight of the
pigment.
[0056] Dispersants
[0057] The polymeric dispersant or dispersants provide enhanced
effects in stabilizing titanium dioxide pigment for inkjet ink and,
furthermore, provide enhanced stability in the ink formulations.
Suitable polymeric dispersants include cationic polymeric
dispersants, and mixtures of two dispersants, one of which is a
graft copolymer and another of which is a block copolymer.
[0058] If the polymeric dispersants (such as the block and graft
copolymer dispersants) contain acid functionality, they can be used
in their non-neutralized form. An option is to neutralize at least
a portion of the acid-functional groups with a base such as
ammonia, potassium hydroxide, sodium hydroxide, an amine, such as
dimethyl ethyl amine, amino methyl propanol and the like, which
forms a water-solubilizing group.
[0059] For the dispersants with amine-functional groups (cationic),
they can be converted to their salt form by adding acids, organic
chlorides, etc. An example of an added organic chloride is benzyl
chloride.
[0060] An additional dispersant is a phosphated polymer that is
different from the dispersants described above.
[0061] The inks of the present invention, and titanium dioxide
slurry used in those inks, preferably have an overall dispersant to
pigment weight ratio (D/P) of from about 0.0025:1 to about 0.25:1,
preferably from about 0.05:1 to about 0.175:1, and more preferably
from about 0.075:1 to about 0.14:1. The overall dispersant to
pigment ratio is the sum total of D/P contributions from each
dispersant present.
[0062] The dispersants to be used can be prepared by any of the
known polymer preparation processes for the relevant type of
polymer.
[0063] Note: All molecular weights referred to herein are
determined by Gel Permeation Chromatography using polystyrene as a
standard.
[0064] An example of a dispersant is a graft copolymer dispersant
preferably having a weight average molecular weight of from about
4000 to about 100000, and more preferably from about 10000 to about
40000. The graft copolymer dispersants can be block or comb
copolymers. The graft copolymer comprises from about 90% to about
50% by weight of a polymeric backbone and, correspondingly, from
about 10% to about 50% by weight of polymeric side chains attached
to the backbone (the backbone and side chains together being 100 wt
%).
[0065] The polymeric backbone is a hydrophobic (relative to the
side chains) adsorbing segment. The side chains are individually
hydrophilic (relative to the backbone) stabilizing segments. The
side chains are attached to the backbone at a single terminal
point.
[0066] Backbone
[0067] As just indicated, the backbone of the graft copolymer
dispersant is hydrophobic relative to the side chains. The backbone
comprises polymerized hydrophobic monomers such as alkyl
methacrylates and acrylates, and cycloaliphatic methacrylates and
acrylates, such as those listed hereinafter. The backbone may still
further comprise up to about 20% by weight, and preferably from
about 1% to about 10% by weight, based on the weight of the graft
copolymer, of polymerized ethylenically unsaturated acid monomers,
such as those listed hereinafter, as well as up to about 30% by
weight, based on the weight of the graft copolymer, of other
polymerized ethylenically unsaturated monomers containing
functional groups, such as those listed hereinafter.
[0068] The backbone of the graft copolymer has an affinity for the
surface of the pigment used in the slurry and anchors the copolymer
to the pigment, thus keeping the pigment dispersed and preventing
the graft copolymer from returning to the liquid phase.
[0069] Typical alkyl acrylates and methacrylates that can be used
have 1 to 12 carbon atoms, and preferably 1 to 8 carbon atoms, in
the alkyl group, and include, for example, methyl acrylate, methyl
methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate,
propyl methacrylate, isopropyl acrylate, isopropyl methacrylate,
butyl acrylate, butyl methacrylate, pentyl acrylate, pentyl
methacrylate, hexyl acrylate, hexyl methacrylate, 2-ethyl hexyl
acrylate, 2-ethyl hexyl methacrylate, nonyl acrylate, nonyl
methacrylate, lauryl acrylate, lauryl methacrylate and the like. Of
these, the methacrylates are preferred.
[0070] Cycloaliphatic acrylates and methacrylates can also be used
such as trimethylcyclohexyl acrylate, trimethylcyclohexyl
methacrylate, t-butyl cyclohexyl acrylate, isobutylcyclohexyl
methacrylate and the like. Again, methacrylates are preferred.
[0071] Examples of ethylenically unsaturated acid monomers include
methacrylic acid, acrylic acid, itaconic acid, maleic acid and the
like; and ethylenically unsaturated sulfonic and sulfinic acid and
esters thereof, such as styrene sulfonic acid, acrylamido propane
sulfonic acid, acrylamido methyl propane sulfonic acid and the
like. When used, acrylic and methacrylic acid are preferred.
[0072] Examples of functional monomers (other than the
ethylenically unsaturated acid monomers) include acrylamide,
methacrylamide, methacrylonitrile, hydroxy ethyl acrylate, hydroxy
ethyl methacrylate, t-butylamino ethyl methacrylate, diethyl amino
ethyl acrylate, diethyl amino ethyl methacrylate, nitro phenol
acrylate, nitro phenol methacrylate, phthalimido methyl acrylate
and phthalimido methacrylate.
[0073] Side Chains
[0074] The side chains of the graft copolymer are hydrophilic
(relative to the backbone) macromonomers that preferably have a
weight average molecular weight of from about 1000 to about 30000,
and more preferably from about 1500 to about 8000. The side chains
preferably comprise from about 2% to about 100% by weight, more
preferably from about 20% to about 60% by weight, based on the
weight of the macromonomer, of polymerized ethylenically
unsaturated acid monomers. The side chains are hydrophilic and keep
the pigment uniformly dispersed in the slurry and resulting
ink.
[0075] Alternatively, the side chains can have nonionic hydrophilic
groups such as condensed alkylene oxides. The side chains can be a
mixture of ionic and non-ionic groups or mixtures either in the
same side chain or in different side chains.
[0076] The macromonomer contains a single terminal ethylenically
unsaturated group, which is polymerized into the backbone of the
graft copolymer.
[0077] Methacrylic acid is preferred as the ethylenically
unsaturated acid monomer, particularly if it is the sole
constituent of the macromonomer. Other acid monomers that can be
used include ethylenically unsaturated carboxylic acids such as
acrylic acid, itaconic acid, maleic acid and the like; and
ethylenically unsaturated sulfonic and sulfinic acid and esters
thereof, such as styrene sulfonic acid, acrylamido propane sulfonic
acid, acrylamido methyl propane sulfonic acid and the like.
[0078] Up to about 80% by weight, based on the weight of the
macromonomer, of other hydrophobic polymerized ethylenically
unsaturated monomers can be present in the macromonomer, including
the alkyl acrylates and methacrylates, cycloaliphatic acrylates and
methacrylates listed above.
[0079] One preferred macromonomer contains from about 50% to about
80% by weight of polymerized methyl methacrylate, and from about
20% to about 50% by weight of polymerized methacrylic acid (100 wt
% total), and has a weight average molecular weight of from about
2000 to about 5000.
[0080] The monomers constituting the macromonomer are preferably
polymerized using a catalytic chain transfer agent that contains a
Co.sup.+2 group, i.e. a cobalt chain transfer agent, which ensures
that the resulting macromonomer only has one terminal ethylenically
unsaturated group which will polymerize with the backbone monomers
to form the graft copolymer. Typically, in the first step of the
process for preparing the macromonomer, the monomers are blended
with an inert organic solvent, which is water miscible or water
dispersible, and a cobalt chain transfer agent and heated usually
to the reflux temperature of the reaction mixture. In subsequent
steps additional monomers, cobalt chain transfer agent and a
conventional azo type polymerization catalyst (such as
2,2'-azobis(2-methylbutanenitrile), 2,2'-azobis(2,4'-dimethylpen-
tanenitrile) and 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile))
are added and polymerization is continued until a macromonomer is
formed of the desired molecular weight. After macromonomer is
formed, any solvent may be stripped off before additional
processing to make the first dispersant graft copolymer.
[0081] Preferred cobalt chain transfer agents are described in U.S.
Pat. No. 4,680,352 and U.S. Pat. No. 4,722,984 (the disclosures of
which are incorporated by reference herein for all purposes as if
fully set forth). Most preferred are pentacyanocobaltate (II),
diaquabis(borondifluorodimet- hyl-glyoximato) cobaltate (II) and
diaquabis(borondifluorophenylglyoximato- ) cobaltate (II).
Typically these chain transfer agents are used at concentrations of
from about 5 ppm to about 1000 ppm, based on the weight of the
monomers used.
[0082] Example of a Preparation of a Dispersant
[0083] The graft copolymer used in the present invention is
preferably prepared by the Special Chain Transfer (SCT) method as
described in U.S. Pat. No. 5,231,131 (the disclosure of which is
incorporated by reference herein as if fully set forth). By using
this method, 100% graft copolymer can be efficiently prepared
rather than a mixture of graft copolymer, low molecular weight
backbone polymer and copolymerized macromonomer segments, as is
generally been the case with other processes used for making graft
copolymers. However, it should be recognized that the graft
copolymer dispersant used in this invention is not restricted to
any specific preparation technology. Graft dispersants of the
structure and functionality described above made using other known
polymerization techniques will also provide benefits of this
invention and are thus contemplated to be within the scope of this
invention.
[0084] To form the graft copolymer, backbone monomers are
polymerized in the presence of solvent, polymerization catalyst and
macromonomer prepared, for example, as described above. Any of the
aforementioned azo type catalysts can be used, as can other
suitable catalysts such as peroxides and hydroperoxides. Typical of
such catalysts are di-tertiarybutyl peroxide, di-cumyl peroxide,
tertiaryamyl peroxide, cumenehydroperoxide, di(n-propyl)
peroxydicarbonate, peresters such as amyl peroxyacetate and the
like. Polymerization is continued usually at the reflux temperature
of the reaction mixture until a graft copolymer is formed of the
desired molecular weight.
[0085] Typical solvents that can be used to form the macromonomer
and/or the graft copolymer are ketones such as methyl ethyl ketone,
isobutyl ketone, ethyl amyl ketone and acetone; alcohols such as
methanol, ethanol and isopropanol; esters such as ethyl acetate;
glycols such as ethylene glycol and propylene glycol; ethers such
as tetrahydrofuran and ethylene glycol mono butyl ether; and the
like.
[0086] After the graft copolymer is formed, the acid functionality
thereon can be at least partially neutralized with an amine or an
inorganic base such as ammonium hydroxide or sodium hydroxide, and
then water is added to form a dispersion of the graft copolymer.
Typical amines that can be used include amino methyl propanol,
amino ethyl propanol, dimethyl ethyl amine, triethylamine and the
like. A preferred amine for inkjet applications is dimethyl ethyl
amine.
[0087] Typically, these dispersant graft copolymers and the other
dispersants described below are used as from about 20% to about 60%
solutions in typical solvents.
[0088] Particularly useful graft copolymers include the
following:
[0089] a graft copolymer having a backbone of polymerized methyl
acrylate and butyl acrylate, and side chains of a macromonomer
having a weight average molecular weight of from about 2000 to
about 5000, and containing from about 50% to about 80% by weight,
based on the weight of the macromonomer, of polymerized methyl
methacrylate and from about 20% to about 50% by weight, based on
the weight of the macromonomer, of polymerized methacrylic
acid;
[0090] a graft copolymer having a backbone of polymerized methyl
acrylate, butyl acrylate and acrylamido methyl propane sulfonic
acid, and side chains of the above macromonomer;
[0091] a graft copolymer having a backbone of polymerized methyl
acrylate, butyl acrylate and acrylic acid, and side chains of the
above macromonomer;
[0092] a graft copolymer having a backbone of polymerized ethyl
acrylate, and side chains of the above macromonomer;
[0093] a graft copolymer having a backbone of polymerized ethyl
acrylate, methyl acrylate and acrylic acid, and side chains of the
above macromonomer; and
[0094] a graft copolymer having a backbone of polymerized ethyl
acrylate and acrylic acid, and side chains of the above
macromonomer.
[0095] Alternative Dispersant
[0096] Another dispersant is a block copolymer of type AB, ABA or
ABC, or mixtures thereof. At least one of the blocks, A, B, or C is
an adsorbing segment. At least one of the blocks, A, B, or C is a
stabilizing segment. By "adsorbing segment" it is meant that the
segment is designed to adsorb onto the surface of a titanium
dioxide pigment, for example, by acid-base or other bonding
interactions. By "stabilizing segment" it is meant that the segment
is designed to provide a steric stabilization of the pigment
particle against flocculation in a slurry composition. Generally,
the adsorbing segments of the block copolymer are hydrophobic, in
comparison to the stabilizing segment, and are designed to adhere
to the pigment surface, while the stabilizing segments are
generally hydrophilic, in comparison to the adsorbing segment, and
are soluble in processing media, for example, media used in
finishing crude titanium dioxide pigment.
[0097] The hydrophobic adsorbing segment preferably comprises
polymerized ethylenically unsaturated hydrophobic monomers such as
are listed hereinafter, and further comprises polymerized
ethylenically unsaturated monomers having functional groups that
enhance the pigment binding force. Monomers having functional
groups are preferably present in an amount up to about 40% by
weight, based on the total weight of the adsorbing segment. For
example, monomers with acid functional groups may be incorporated
in the hydrophobic portion to bind with basic groups on the
titanium dioxide pigment surface. Monomers with amine groups may be
incorporated in the hydrophobic portion to bind with acid groups
that may be present on the titanium dioxide surface. Other monomers
that have known affinity for titanium dioxide, such as monomers
with silane groups, etc., may also be incorporated in the
hydrophobic portion.
[0098] Suitable hydrophobic monomers that can be used to form the
hydrophobic adsorbing segment include, but are not limited to,
alkyl (meth)acrylates having 1 to 12 (and preferably 1 to 8) carbon
atoms in the alkyl group (such as methyl acrylate, ethyl acrylate,
propyl acrylate, isopropyl acrylate, butyl acrylate, pentyl
acrylate, hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate,
lauryl acrylate, methyl methacrylate, ethyl methacrylate, propyl
methacrylate, isopropyl methacrylate, butyl methacrylate, pentyl
methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, nonyl
methacrylate, lauryl methacrylate and the like, and any mixtures
thereof). Cycloaliphatic (meth)acrylates can also be used (such as
trimethylcyclohexyl methacrylate, isobutylcyclohexyl methacrylate
and the like, as well as any mixtures thereof). Mixtures of any of
the above may also be used.
[0099] Suitable monomers with acid groups that can be incorporated
into the hydrophobic adsorbing segment to enhance the pigment
binding force include ethylenically unsaturated carboxylic acids
(such as acrylic acid and methacrylic acid). Methacrylic acid is
preferred, particularly if it is the sole acid constituent.
[0100] Suitable monomers with amine groups include alkylaminoalkyl
methacrylate monomers having 1 to 4 carbon atoms in the alkyl group
(such as dimethylaminoethyl methacrylate, diethylaminoethyl
methacrylate, dipropylaminoethyl methacrylate, dibutylaminoethyl
methacrylate) and the like.
[0101] As stated above, the stabilizing segment is preferably
soluble in the selected (aqueous) processing medium encountered
during crude pigment finishing and, therefore, primarily comprises
polymerized ethylenically unsaturated hydrophilic monomers.
Suitable hydrophilic monomers that can be used to form the
stabilizing segment include monomers with acid groups (such as
acrylic acid, methacrylic acid, 2-acrylamido-2-propane sulfonic
acid, and the like, as listed hereinabove). The salts of these
monomers can also be used to aid in dispersing the copolymer in the
selected aqueous processing medium. Such salts can be formed by the
addition of an amine (such as dimethyl ethyl amine or 2-amino
methyl propanol) or an inorganic base (such as ammonium hydroxide
or sodium hydroxide) to the polymer dispersant after it has been
formed. In addition to the forgoing monomers, other commonly used
hydrophobic monomers can be copolymerized into the stabilizing
portion, provided they are used at a concentration that will not
significantly change the solubility properties of the stabilizing
portion in the selected processing medium. Some useful examples
include the alkyl (meth)acrylates and other hydrophobic monomers
listed hereinabove.
[0102] The block copolymer dispersant preferably has a number
average molecular weight of from about 1000 to about 15000, and
more preferably from about 2000 to about 5000. The adsorbing
segment preferably has a number average molecular weight of from
about 1000 to about 5000, and more preferably from about 1000 to
about 3000. The stabilizing segment preferably has a number average
molecular weight of from about 1000 to about 5000, and more
preferably from about 1000 to about 3000.
[0103] The method of preparation of the second dispersant is not
critical. Block copolymer dispersants of the structure and
functionality described above made using known polymerization
techniques will provide the benefits of this invention and are thus
contemplated to be within the scope of this invention. The second
dispersant may be prepared, for example, by using the Group
Transfer Polymerization (GTP) method reported in U.S. Pat. No.
4,656,226; or the anionic polymerization method reported by Morton
in Anionic Polymerization: Principles and Practice (New York:
Academic Press, 1983) (the disclosures of which are incorporated by
reference herein for all purposes as if fully set forth).
[0104] The GTP method is preferred. An advantage of the GTP process
is the ability to make polymer dispersants with precise
architecture and low polydispersity. Typically polydispersity of
GTP polymers is between about 1.0 and about 1.25.
[0105] Phosphate-Containing Dispersant
[0106] Another optional dispersant is a phosphated polymer
dispersant comprising a hydrophilic (relative to the adsorbing
segment) stabilizing segment and a hydrophobic (relative to the
stabilizing segment) adsorbing segment. The phosphated polymer can
be a graft copolymer, a block copolymer or a random copolymer.
[0107] The adsorbing segment of the phosphated polymer mainly
comprises polymerized ethylenically unsaturated hydrophobic
monomers, such as alkyl (meth)acrylates, cycloaliphatic
(meth)acrylates and aryl (meth)acrylates, such as are listed
hereinafter. The term (meth)acrylate refers to both the acrylate
and methacrylate esters. The adsorbing segment preferably further
comprises from about 1% to about 20% by weight, and more preferably
from about 1% to about 10% by weight, based on the total weight of
the copolymer, of polymerized non-hydrophobic ethylenically
unsaturated monomers that have attached thereto a phosphate
anchoring group. It should be noted that it is not necessary that
the phosphate group be incorporated in the hydrophobic segment of
the polymer. Phosphate groups can be incorporated in the
hydrophilic segment as well.
[0108] Examples of hydrophobic monomers that can be used to form
the adsorbing segment include alkyl (meth)acrylates having 1 to 12
carbon atoms in the alkyl group, such as methyl acrylate, ethyl
acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate,
pentyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, nonyl
acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate,
propyl methacrylate, isopropyl methacrylate, butyl methacrylate,
pentyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate,
nonyl methacrylate, lauryl methacrylate and the like, and any
mixtures thereof. Cycloaliphatic (meth)acrylates can also be used
such as trimethylcyclohexyl methacrylate, isobutylcyclohexyl
methacrylate and the like, and any mixtures thereof. Mixtures of
any of the above may also be used.
[0109] The hydrophilic stabilizing segment of the phosphated
dispersant comprises polymerized ethylenically unsaturated
hydrophilic monomers. Such monomers include acid-containing
monomers, such as acrylic acid, methacrylic acid and
2-acrylamido-2-propane sulfonic acid; and non-ionic hydrophilic
monomers. Additional examples of useful acid-containing monomers
include itaconic acid, maleic acid and the like. Ethylenically
unsaturated sulfonic, sulfinic, phosphoric or phosphonic acid and
esters thereof also can be used, such as styrene sulfonic acid,
vinyl phosphonic acid and its esters, and the like. Monomers
containing acid functionality are selected, in part, on their
theoretical ability to bind to the titanium oxide particles.
Non-ionic hydrophilic monomers that are useful in the hydrophilic
stabilizing segment include monoethylenically unsaturated
poly(alkylene glycol) monomers, such as poly(ethylene glycol) mono
(meth)acrylate, poly(ethylene glycol) alkyl ethers having 1 to 4
carbon atoms in the alkyl group (such as poly(ethylene glycol)
methyl ether oligomers, supplied under the trade name Bisomer S20W
by International Specialty Chemicals), and the like; and
poly(alkoxylated) alkyl (meth)acrylates and the like. These
monomers preferably have a weight average molecular weight of from
about 200 to about 4000, and more preferably from about 200 to
about 2000. A combination of nonionic and anionic stabilizing
segments can also be favorable.
[0110] Phosphate groups can be incorporated into the adsorbing
segment or the stabilizing segment by reacting the polymer with
phosphoric acid or phosphorus pentoxide. Unreacted or residual
phosphoric acid groups are preferably neutralized with amine or
inorganic base when used for dispersing titanium dioxide pigment
into water. The remainder of the polymer may be adjusted to improve
dispersibility of the titanium dioxide pigment and make the
copolymer more compatible with other components to form a
stabilized pigment slurry.
[0111] Alternatively, phosphate groups may be incorporated into the
polymer by reaction of a phosphorus containing reactive group with
a monomer, macromonomer or polymer such that the resultant optional
dispersant is a phosphate-substituted dispersant. An example of
this strategy is forming a polymer having reactive hydroxyl groups,
for example, by forming a copolymer with hydroxy alkyl
methacrylates or acrylates, and subsequently reacting the hydroxy
groups with phosphorus pentoxide. Neutralizing phosphoric acid
groups with amine or inorganic base is preferable for aqueous
titanium dioxide slurries.
[0112] Suitable monomers with phosphate groups that can also be
used to introduce phosphate groups into the copolymer (adsorbing
segment or stabilizing segment) include ethylenically unsaturated
phosphate monomers (such as phosphorylated polyethylene glycol
(meth)acrylate, phosphorylated hydroxy ethyl (meth)acrylate, and
the like) or ethylenically unsaturated monomers containing alcohol
groups (such as hydroxy alkyl (meth)acrylate) or epoxy groups (such
as glycidyl acrylate and glycidyl (meth)acrylate) which are treated
with one or more phosphorylating agents (such as phosphoric acid or
phosphorous pentoxide) before or after polymerization to form
phosphate groups where the epoxy or alcohol groups used to be.
[0113] The phosphated copolymer dispersant preferably has a number
average molecular weight of from about 4000 to about 25000, and
more preferably from about 5000 to about 20000. The adsorbing
segment typically has a number average molecular weight of from
about 2000 to about 10000, and preferably from about 4000 to about
7000. The stabilizing segment typically has a number average
molecular weight of from about 2000 to about 15000, and preferably
from about 4000 to about 7000. The adsorbing segment typically
comprises from about 20% to about 80% by weight of the polymer, and
correspondingly the stabilizing segment typically comprises from
about 80% to about 20% by weight of the polymer (the adsorbing and
stabilizing segments being 100 wt % total).
[0114] The forgoing dispersants may be prepared by a variety of
well known solution polymerization techniques devised for a
particular structure, such as by the GTP (Group Transfer
Polymerization) method reported in previously incorporated U.S.
Pat. No. 4,656,226; by the standard anionic or the free radical
polymerization method reported in previously incorporated U.S. Pat.
No. 4,656,226; or by the SCT method reported in previously
incorporated U.S. Pat. No. 5,231,131.
[0115] The GTP method is traditionally used to form block
copolymers. Using this method, it is generally recommended to block
any acid or hydroxyl containing monomers to prevent side reactions
during polymerization. Following polymerization, the acid and
hydroxyl groups are unblocked by a reaction with alcohol or
water.
[0116] The SCT method is traditionally used to form the
macromonomer portion of a graft copolymer. Macromonomers can also
be supplied by other means.
[0117] Standard anionic polymerization is oftentimes used to form
random copolymers and may be used to prepare analogues of resins
described herein.
[0118] Commercially available suitable dispersants include
Disperbyk.RTM. 2000 and Disperbyk.RTM. 2001 (Byk Chemie, Wesel,
Germany). These are described as modified acrylate block
copolymers. The Disperbyk.RTM. 2000 has an amine value of 4 mg
KOH/gm, and the Disperbyk.RTM. 2001 has an amine value of 29 mg
KOH/gm and an acid value of 19 mg/KOH/gm.
[0119] A slurry formed from the titanium dioxide, the
dispersant(s), and the solvent or mixture of solvents with a
hydrogen bonding solubility parameter of greater than 9, is a
stable slurry. When settling does occur, the settling is "soft"
settling, meaning the titanium dioxide pigment can be readily
re-dispersed and rejuvenated by low shear mixing. The pigment is
also similarly stably dispersed when the slurry is formulated into
inks, so as not to result in plugging of ink jet nozzles. Low shear
mixing includes, for example, shaking by hand or stirring with an
impeller or mixing blades at speeds of less than about 500 rpm
wherein no grinding occurs. In contrast, "hard" settling occurs
with many titanium dioxide slurries of the prior art. By "hard
settling" it is meant the settling of titanium dioxide particles
from the slurry cannot be re-dispersed to an acceptable level for
ink jet inks.
[0120] Other dispersants described herein can be used singly in the
non-aqueous solvents (which have a hydrogen bonding solubility
parameter as described by Hansen solubility parameter) to produce
stable titanium dioxide inks.
[0121] The inventive inks do not have added salts that increase the
conductivity, which should be less than about 50 .mu.mho/cm, and
more preferably less than about 25 .mu.mho/cm. Added salts can be
detrimental to drop-on demand ink jet printer systems.
[0122] Liquid Carrier for Preparation of the Titanium Dioxide
Slurries
[0123] The titanium dioxide slurry used in this invention comprises
a non-aqueous liquid carrier. The carrier is preferably an organic
solvent or mixture of organic solvents having a hydrogen bonding
solubility parameter based on Hansen solubility parameters of more
than about 9. This combination of dispersant and solvent leads to a
peculiarly effective liquid carrier for the titanium dioxide
pigment.
[0124] Optional Additives for the Titanium Dioxide Slurry
[0125] The titanium dioxide slurry used in the present invention
may optionally comprise one or more additives that are compatible
with the end use in inkjet inks.
[0126] For example, the titanium dioxide slurry may optionally
comprise a humectant. A humectant may be considered a co-solvent.
Typically, although not always, a humectant has a higher boiling
point than the primary solvent, that is, the liquid carrier. A
humectant is generally added to prevent drying during storage.
Humectants may also help retard settling.
[0127] Humectants are especially useful additives to formulations
that have a propensity for chalking. Chalking occurs when solvent
(that is, liquid carrier for the slurries of this invention)
evaporates, pigment, especially the titanium dioxide pigment, dries
on surfaces, and sides of storage vessels and may flake off and
fall back into the slurry. Chalking can be a serious problem. For
example, if dried pigment agglomerates are introduced into an ink
jet formulation, an unacceptable level of nozzle outs may occur.
Humectants retard solvent evaporation and thereby retard
chalking.
[0128] Examples of suitable humectants for use in this invention
include polyhydric alcohols such as ethylene glycol, diethylene
glycol, propylene glycol, butylene glycol, triethylene glycol,
1,5-pentanediol and 1,2,6-hexanetriol; glycol ethers such as
dipropylene glycol monomethyl ether and propylene glycol normal
propyl ether; and others including trimethylolpropane,
trimethylolethane, glycerin, polyethylene glycol and dipropylene
glycol. Ethylene glycol is preferred.
[0129] The titanium dioxide slurry may also optionally comprise a
rheology modifier. A rheology modifier can be any known
commercially available rheology modifiers, such as Solthix.RTM.
thickeners available from Avecia. Other useful rheology modifiers
include cellulose and synthetic hectorite clays. Synthetic
hectorite has the formula:
[Mg.sub.wLi.sub.xSi.sub.8O.sub.20H.sub.4-yF.sub.z].sup.2-
[0130] wherein w=3 to 6; x=0 to 3; y=0 to 4; z=12-2-e-x, wherein
the negative lattice charge is balanced by counterions, and wherein
the counterions are selected from the group consisting of Na.sup.+,
K.sup.+, NH.sub.4.sup.+, Li.sup.+, Mg.sup.2+, Ca.sup.2+, Ba.sup.2+,
N(CH.sub.3).sub.4.sup.+, and mixtures thereof. Synthetic hectorite
clays are commercially available, for example, from Southern Clay
Products, Inc., and include Laponite.RTM.; Lucenite SWN.RTM.,
Laponite S.RTM., Laponite XL.RTM., Laponite RD.RTM. and Laponite
RDS.RTM. brands of synthetic hectorite.
[0131] Preparation of Titanium Dioxide Slurry
[0132] The titanium dioxide slurry used in this invention can be
prepared by mixing the components in a mixing vessel. Components
can be added sequentially or simultaneously in any order. The
following provides a typical process to prepare the slurry, but
should not be considered limiting. Typically, a two-step process is
used involving a first mixing step followed by a second grinding
step. The first step comprises mixing all of the ingredients, that
is, titanium dioxide pigment, dispersants, liquid carrier and any
optional additives to provide a blended "pre-mix". Mixing generally
occurs in a stirred vessel. High-speed dispersers are particularly
suitable for the mixing step. Preferably, the dispersants are
combined before introducing into the mixture of other ingredients.
The combined dispersants are typically added incrementally.
[0133] The second step comprises grinding of the pre-mix to produce
a titanium dioxide slurry. Preferably grinding occurs by media
milling although other techniques can be used. Following a grinding
step, the slurry is filtered. Filtration can be performed using any
means known in the art, and is typically accomplished by use of
standard, commercially available filters between 1 and 10 microns
in size.
[0134] After completion of the grinding or dispersing step,
additional ink vehicle components can be added to prepare the final
ink composition. Alternatively, all of the ink components can be
added at the mixing step and the dispersing step is done with
subsequent dilution.
[0135] Preparation of Inks
[0136] The inks of this invention are preferably made from the
titanium dioxide slurries described above, by conventional process
known to the art. That is, the titanium oxide slurry is processed
by routine operations to become an ink which can be successfully
jetted in an inkjet system.
[0137] Typically, in preparing an ink, all ingredients except the
pigment slurry are first mixed together. After the other
ingredients are mixed, the slurry is added. Common ingredients in
ink formulations useful with the titanium dioxide slurries include
one or more humectants, a co-solvent, one or more surfactants and
biocide.
[0138] The titanium dioxide slurry used in this invention utilizes
a dispersants in specific amounts to stabilize and keep the
pigments deflocculated over long periods of time both in slurry
form and when the slurry is subsequently used in an ink
formulation. As a result, the white ink formulation is stable and
non-flocculated or agglomerated and has other advantageous
properties when applied to surfaces as an ink. The neutralization
of the dispersants can depend on the final vehicle use in the ink,
the printed substrate etc.
[0139] Alternatively, the ink may be prepared without the
intervening step of preparing a pigment slurry. That is, the
TiO.sub.2 pigment and other ingredients of the ink can be combined
in any order and this mixture is subject to dispersing mixing. The
intensity of the mixing can range from milling using a ball mill
with or more intense dispersive mixing such as HSD, roll milling or
media milling can be used to obtain the final ink formulation.
There are no constraints on the milling media.
[0140] Ink Vehicle
[0141] The ink vehicle is non-aqueous. "Non-aqueous vehicle" refers
a vehicle that is substantially comprised of a nonaqueous solvent
or mixtures of such solvents, which solvents should predominantly
preferably be polar.
[0142] An important limitation of the vehicle is that made up of
solvent or a mixture of solvents that have a hydrogen solubility
greater than 9 based on the Hansen Solubility Parameters (See
Charles M Hansen, Solubility Parameters, CRC Press, 2000). The
solubility parameters are calculated based on the solvent(s) only;
dispersants, binders, etc. are not factored into the
calculation.
[0143] Examples of polar solvents include alcohols, esters, ketones
and ethers. Specific examples include mono- and di-alkyl ethers of
glycols and polyglycols, such as monomethyl ethers of mono-, di-
and tri-propylene glycols, and the mono-n-butyl ethers of ethylene,
diethylene and triethylene glycols and glycerol and substituted
glycerols.
[0144] Glycol ethers include ethylene glycol mono-methyl ether,
ethylene glycol mono-ethyl ether, ethylene glycol mono-propyl
ether, ethylene glycol monobutyl ether, diethylene glycol
mono-methyl ether, diethylene glycol mono-ethyl ether, diethylene
glycol mono-propyl ether, diethylene glycol mono-n-butyl ether,
triethylene glycol mono-n-butyl ether, 1-methyl-1-methoxybutanol,
propylene glycol mono-methyl ether, propylene glycol mono-ethyl
ether, propylene glycol mono-butyl ether, propylene glycol
mono-propyl ether, dipropylene glycol mono-methyl ether,
dipropylene glycol mono-ethyl ether, dipropylene glycol
mono-n-butyl ether, dipropylene glycol mono-n-propyl ether, and
dipropylene glycol mono-isopropyl ether.
[0145] Ether solvents include but are not limited to include
dioxane, dimethyl ether, diethyl ethyl, di-isopropyl ether,
tetrahydrofuran, glyme, diglyme, triglyme, and tetraglyme.
[0146] Heteroatom solvents include, but are not limited to amide
solvents including dimethylacetamide and cyclic amines such as
2-pyrolidinone, N-methyl 2-pyrolidinone, and sulfur containing
solvents including dimethyl sulfoxide and sulflone.
[0147] Polyhydroxyl solvents include ethylene glycol, diethylene
glycol, triethylene glycol, tetraethylene glycol, propylene glycol,
dipropylene glycol, trimethylol propane, butanediol, pentanediol
and hexanediol.
[0148] A further optional limitation of the solvent and mixture of
solvents is that it has a boiling point of greater than 125.degree.
C. at 0.1 kilopascals. It is routine to have ink components that
are volatile and can evaporate after the ink is jetted onto the
substrate. In the preferred application of these white inks, the
ink components can be imbibed into the substrate without adversely
affecting the resolution of the printed image.
[0149] For the instant invention no additional water should be
added; however, no extraordinary drying of the components of the
ink is required. Even when no water is deliberately added to the
non-aqueous vehicle, some adventitious water may be carried into
the formulation, but generally this will be no more than about 5%.
Preferably, the non-aqueous ink of this invention will have no more
than about 2%, and more preferably no more than about 1%, by weight
of water based on the total weight of the non-aqueous vehicle.
[0150] The amount of non-aqueous vehicle in the ink (non-solids) is
typically in the range of about 50% to about 99.8%, and preferably
about 66% to about 95%, based on total weight of the ink.
[0151] The inks of the present invention are not considered to be
UV-curable or photopolymerizable inks, as those terms are
understood by those of ordinary skill in the relevant art (see, for
example, previously incorporated U.S. 2004/0246319, EP-A-1321497,
EP-A-1388578 and WO00/49097). The non-aqueous vehicle, therefore,
should be comprised of predominantly "non-reactive" solvents.
"Non-reactive" in this context means non-photopolymerizable.
Preferably, the organic solvents of non-aqueous vehicle comprises
substantially only non-reactive solvents, and the non-aqueous
vehicle is substantially free of reactive components.
[0152] Other Ingredients
[0153] The inks may optionally contain one or more other
ingredients such as, for example, surfactants, binders,
bactericides, fungicides, algicides, sequestering agents, buffering
agents, corrosion inhibitors, light stabilizers, anti-curl agents,
thickeners, and/or other additives and adjuvants well-known in the
relevant art.
[0154] These other ingredients may be formulated into the inks and
used in accordance with this invention, to the extent that such
other ingredients do not interfere with the stability and
jettability of the ink, which may be readily determined by routine
experimentation. The inks may be adapted by these additives to the
requirements of a particular inkjet printer to provide an
appropriate balance of properties such as, for instance, viscosity
and surface tension, and/or may be used to improve various
properties or functions of the inks as needed.
[0155] The amount of each ingredient must be properly determined,
but is typically in the range of from about 0 to about 15% by
weight and more typically from about 0.1% to about 10% by weight,
based on the total weight of the ink.
[0156] Surfactants may be used and useful examples include
ethoxylated acetylene diols (e.g. Surfynols.RTM. series from Air
Products), ethoxylated primary (e.g. Neodol.RTM. series from Shell)
and secondary (e.g. Tergitol.RTM. series from Union Carbide)
alcohols, sulfosuccinates (e.g. Aerosol.RTM. series from Cytec),
organosilicones (e.g. Silwet.RTM. series from Witco) and fluoro
surfactants (e.g. Zonyl.RTM. series from DuPont). Surfactants, if
used, are typically in the amount of from about 0.01 to about 5%
and preferably from about 0.2 to about 2%, based on the total
weight of the ink.
[0157] Binders may be also used and can be soluble or dispersed
polymer(s), added to the ink to improve the adhesion of a pigment.
Examples of polymers that can be used include poly(meth)acrylates,
polyesters, polystyrene/acrylates, sulfonated polyesters,
polyurethanes, polyimides and the like. When present, soluble
polymer is advantageously used at levels of at least about 0.3%,
and preferably at least about 0.6%, based on the total weight of
the ink. Upper limits are dictated by ink viscosity or other
physical limitations.
[0158] When the substrates used with the invention are porous, such
as paper and textiles, binders can be added to reduce the
penetration of the ink into the substrates. In other words with
these additives, the ink will remain more on the surface of the
porous substrate and the opacity hiding power and other printing
parameters for the ink will be improved.
[0159] Ink Properties
[0160] Jet velocity, drop size and stability are greatly affected
by the surface tension and the viscosity of the ink. Inkjet inks
typically have a surface tension in the range of about 20 dyne/cm
to about 60 dyne/cm at 25.degree. C. Viscosity can be as high as 30
cps at 25.degree. C., but is typically somewhat lower. The inks
have physical properties compatible with a wide range of ejecting
conditions, i.e., driving frequency of the piezo element, or
ejection conditions for a thermal head, for either a drop-on-demand
device or a continuous device, and the shape and size of the
nozzle. The inks of this invention should have excellent storage
stability for long periods so as not clog to a significant extent
in an ink jet apparatus. Further, it should not alter the materials
of construction of the ink jet printing device it comes in contact
with, and be essentially odorless and non-toxic.
[0161] Although not restricted to any particular viscosity range or
printhead, the inventive inks are suited to lower viscosity
applications such as those required by higher resolution (higher
dpi) printheads that jet small droplet volumes, e.g. less than
about 20 pL. Thus the viscosity (at 25.degree. C.) of the inventive
inks can be less than about 8 cps.
[0162] The inks of this invention are sufficiently stable to be
effective inkjet inks. When tested by heating the inks for one week
at 70.degree. C., the physical parameters of particle size and
viscosity should be in normal bounds. The inks should also be
printable from the desired printing system for multiple days,
without any observable decrease in performance.
[0163] The conductivity was measured with an EC meter Model 1056
from Amber Science Inc., Eugene, Oreg.
[0164] Ink Set
[0165] Ink sets contain the ink described above and a plurality of
other inks. The non-white inks of the ink set contain other
colorants.
[0166] The additional colorant in the inks of the ink sets of the
present invention is preferably a pigment. By definition, pigments
do not form (to a significant degree) a solution in the vehicle and
must be dispersed.
[0167] Traditionally, pigments are stabilized to dispersion by
dispersing agents, such as polymeric dispersants or surfactants.
More recently, though, so-called "self-dispersible" or
"self-dispersing" pigments (hereafter "SDP(s)") have been
developed. As the name would imply, SDPs are dispersible in a
vehicle without dispersants.
[0168] A preferred black pigment is carbon black.
[0169] Other pigments for inkjet applications are also generally
well known. A representative selection of such pigments are found,
for example, in U.S. Pat. No. 5,026,427, U.S. Pat. No. 5,086,698,
U.S. Pat. No. 5,141,556, U.S. Pat. No. 5,169,436 and U.S. Pat. No.
6,160,370, the disclosures of which are incorporated by reference
herein for all purposes as if fully set forth. The exact choice of
pigment will depend upon color reproduction and print quality
requirements of the application.
[0170] Dispersants to stabilize the additional pigments to
dispersion are preferably polymeric because of their efficiency.
Examples of typical dispersants for nonaqueous pigment dispersions
include, but are not limited to, those sold under the trade names:
Disperbyk (BYK-Chemie, USA), Solsperse (Avecia) and EFKA (EFKA
Chemicals) polymeric dispersants.
[0171] Suitable pigments also include SDPs. SDPs for aqueous inks
are well known. SDPs for non-aqueous inks are also known and
include, for example, those described in U.S. Pat. No. 5,698,016,
U.S. 2001003263, U.S. 2001004871 and U.S. 20020056403, the
disclosures of which are incorporated by reference herein for all
purposes as if fully set forth. The techniques described therein
could be applied to the pigments of the present invention.
[0172] It is desirable to use small pigment particles for maximum
color strength and good jetting. The particle size may generally be
in the range of from about 0.005 micron to about 15 microns, is
typically in the range of from about 0.005 to about 1 micron, is
preferably from about 0.005 to about 0.5 micron, and is more
preferably in the range of from about 0.01 to about 0.3 micron.
[0173] The levels of pigment employed in the instant inks,
especially the non-white inks, are those levels that are typically
needed to impart the desired OD to the printed image. Typically,
the non-white pigment levels are in the range of from about 0.01 to
about 10% by weight, based on the total weight of the ink.
[0174] The ink sets containing a white ink provide significant new
breadth to printing capabilities. In one preferred embodiment, in
addition to a white ink, the ink sets also contain a cyan, magenta
and yellow ink. In addition to CMY, it may also be preferred that
the ink sets further comprise a black ink.
[0175] In another preferred embodiment, the ink sets comprise a
white ink and a black ink.
[0176] The method of printing in accordance with the invention
comprises the steps of:
[0177] (a) providing an ink jet printer that is responsive to
digital data signals;
[0178] (b) loading the printer with a substrate to be printed;
[0179] (c) loading the printer with the above-mentioned inks and/or
ink sets;
[0180] (d) printing onto the substrate using the inkjet ink set in
response to the digital data signals.
[0181] When printing on a transparent substrate, like polyvinyl
butyral, it is sometimes desirable for the image to only appear on
one side or be visible from both sides. If the image is to be
visible only on one side, the white ink could be printed first and
printed in the shape of the image and with adjustable opaqueness
such that the image would only appear from one side. The opaqueness
can be adjusted by a variety of means including changing the
titanium dioxide concentration in the ink, printing multiple times,
etc.
[0182] If the image is to be seen from both sides then the white
ink can be use to provide more flexibility to the image through the
use of white. Its inclusion in parts of the image can improve the
whiteness of image areas, and the clarity of the image. Nanograde
titanium dioxide with its better transparency may be preferred in
this application.
[0183] When printing on textiles, the white ink of this invention
can provide other benefits. Often when textiles are printed the ink
will feather into the textile giving an indistinct boundary. The
white ink could be use to print a small, imperceptible boundary to
a design and making it appear to have a distinct boundary.
[0184] The titanium dioxide white ink, since it is stable, can be
added to another ink to provide a pigmented ink with both a pigment
and a titanium dioxide pigment. While a white ink/pigmented ink
would be lighter than the pigmented ink, it would retain the
covering power and other beneficial properties of a combined ink
because of the inclusion of the white ink.
[0185] Printed Substrates
[0186] The inks and ink sets can be used to print many substrates
including paper, especially colored papers, packaging materials,
textiles and polymer substrates. The instant invention is
particularly advantageous for printing on polymeric (non-porous)
substrates such as polyvinyl butyral interlayer (including 15 and
30 mil thickness); spun bonded polyolefin (e.g. Tyvek.RTM.,
DuPont); polyvinyl chloride; polyethylene terephthalate polyester;
polyvinyl fluoride polymer, and the like.
[0187] A particularly preferred use for the ink sets of the present
invention is the decorative printing of polyvinyl butyral
interlayers used in safety or architectural glass applications,
such as disclosed in commonly owned WO2004018197 entitled
"Decorative Laminated Safety Glass", the disclosure of which is
incorporated by reference herein for all purposes as if fully set
forth.
EXAMPLES
[0188] Various abbreviations used in these Examples, as well as the
solubility parameter of certain solvents, are listed below in Table
1.
1 TABLE 1 Solubility Parameter of Solvents DPM Dipropylene glycol
methyl ether 10.3 DPMA Dipropylene glycol methyl ether 8 acetate
TPnP Tripropylene glycol propyl ether 8.1 DPnP Dipropylene glycol
propyl ether 9.2 TPM Tripropylene glycol methyl ether 8.7 PNP
Propylene glycol n-propyl ether 12 PMA Propylene glycol methyl
ether acetate DMAE Dimethyl ethylamine BzCl Benzyl chloride Cps
Centipoise NBA n-Butyl acrylate MA Methyl acrylate AA Acrylic acid
MAA Methacrylic acid MMA Methyl methacrylate NBMA n-Butyl
methacrylate GMA Glycidyl methacrylate EHMA 2-Ethylhexyl
methacrylate BzMA Benzyl methacrylate DMAEMA N,N-dimethylaminoethyl
methacrylate TBACB Tetrabutylammonium m-chlorobenzoate
[0189] Methods
[0190] Titanium dioxide slurries were prepared from titanium
dioxide pigments, dispersants, water and optional additives using a
Dispermat.RTM. High Speed Disperser (HSD), available from
VMA-Getzmann GMBH, to premix ingredients followed by media milling
using an Eiger minimill, available from Eiger Machinery, Inc.
Premixing of all slurry ingredients was performed using a Model
AE5--CEX Dispermat operated typically at 2000 rpm with an attached
60 mm Cowels blade.
[0191] Slurry premix was loaded into a 1-liter stainless steel
vessel for media milling. Slurry viscosity at a specific pigment
loading was used to assess dispersant effectiveness. The most
effective dispersant or combination of dispersants produced
slurries with the lowest viscosity. Slurry viscosity was measured
using a Brookfield viscometer and model RVTDV-II with measurements
taken at 10 and 100 spindle rpm. Viscosity units are Centipoise
(cps).
[0192] Titanium Dioxide Pigments
[0193] Commercially available titanium dioxide pigments were used.
Two alumina-coated titanium dioxide pigments were used, R700
(available from E. I. duPont de Nemours and Company, Wilmington
Del.) and RDI-S (available from Kemira Industrial Chemicals,
Helsinki, Finland). A third titanium dioxide was used, P-25
(available from Degussa, Parsippany N.J.), which is an uncoated
nano grade of titanium dioxide. Additional alumina and silica
coated pigmentary and nanograde titanium dioxides were tested,
including R-706 (available from E. I. duPont de Nemours and
Company, Wilmington Del.) and W-6042 (a silica-alumina-treated nano
grade titanium dioxide from Tayco Corporation, Osaka, Japan).
[0194] Ink Formulation and Evaluation
[0195] The inks were prepared by methods known to one skilled in
the art, unless otherwise noted. One strategy was to prepare
dispersions of the pigments (pigment slurries) and, in a separate
step, the ink components were combined and mixed together by ball
milling, media milling or other mixing means. In general, 0.8 to
1.0 micron zirconia was used for the milling. After the ink was
milled, it was filtered through a 1-micron filter paper to remove
the media. If the ink did not filter well, it was not tested in a
printer. Alternatively, all of the ink components were combined and
processed in dispersion equipment and filtered. In this case, the
final filtered ink was obtained from the dispersion step.
[0196] Printing Tests
[0197] Any printer can be used to test these white inks. Unless
otherwise noted, the examples described below were done using an
Epson 3000 ink jet printer or a Mimaki JV3 wide format printer, and
prints were made on various substrates. The white ink was used in
place of the black ink and images were produced using PhotoShop
Software. The substrates included polymeric sheets such as
polyvinyl butyral interlayer (15, 30 ml thickness), Tyvek.RTM.
JetSmart (available from E. I. duPont de Nemours and Company,
Wilmington Del.), uncoated polyvinyl chloride, Tedlar.RTM.
(available from E. I. duPont de Nemours and Company, Wilmington
Del.), polyethylene terephthalate and Surlyn.RTM. (available from
E. I. duPont de Nemours and Company, Wilmington Del.). In addition,
textiles and paper were also used as substrates. Polyurethane was
obtained from Deerfield Urethane, South Deerfield, Mass.
[0198] The jetting performance was rated GOOD if multiple prints
that were all white could be printed without noticeable decrease in
the white intensity. Images were also printed. These tests showed
the inventive ink set provided desirable gamut, transparency and
light-fastness.
[0199] Dispersant Preparation
[0200] The dispersants were used as 25% to 50% by weight solutions
in common organic solvents. The amount of dispersant listed in the
examples below was total weight of the added solution, not the
active ingredients. Where ratios of dispersants to pigments are
described, the ratio is given as active ingredients.
[0201] Dispersant 1--Graft Polymer Dispersant
[0202] Dispersant 1 was a graft polymer with a comb-like structure,
and its molecular configuration was:
nBA/MA/AA (45.5/45.5/9)//MMA/MAA (71.25/28.75)
[0203] The above representation illustrates the polymer backbone
made up 69% of the polymer (nBA/MA/AA). The notation (45.5/45.5/9)
indicates the relative weight percents of each monomer, that is,
45.5 wt % nBA, 45.5 wt % MA and 9 wt % AA. The arms, which were the
macromonomer, were 31% of the total polymer (MMA/MAA) wherein the
monomers were utilized in relative weight percent amounts of 71.25
wt % and 28.75 wt %, respectively. In this representation of the
dispersants, a double slash indicates a separation between blocks,
and a single slash indicates a random copolymer within a block.
[0204] The acid groups on the polymer were neutralized with
DMEA.
[0205] Dispersant 2--Block Copolymer Dispersants
[0206] The block dispersants were prepared using the GTP method
disclosed in previously incorporated U.S. Pat. No. 4,656,226. One
of these dispersants, Dispersant 2A, had a molecular configuration
of:
nBMA/MAA//MAA 13/5//10.
[0207] In this representation, which is different from the
representation for the graft copolymer, the notation 13/5//10
indicates a block copolymer with the respective number of monomers.
That is, one block is a random copolymer having 13 monomer units of
nBMA and 5 monomer units of MAA. The second block has 10 monomer
units of MAA.
[0208] The second block copolymer dispersant, Dispersant 2B, had a
molecular configuration of:
nBMA//MAA 13//10.
[0209] The notation 13//10 indicates 13 monomer units of nBMA and
10 monomer units of MAA in the block copolymer.
[0210] The third block copolymer dispersant, Dispersant 2C, had a
molecular configuration of:
nBMA//MMA/MAA 10//5/10.
[0211] The notation 10//5/10 indicates one block was an nBMA
polymer having 10 monomer units, and the other block was a random
copolymer having 5 monomer units of MMA and 10 monomer units of
MAA.
[0212] The fourth block copolymer dispersant, Dispersant 2D, was
prepared by the following procedure.
[0213] While flushing a flask with N.sub.2, 455.9 g THF and 18.86 g
1-methoxy-1-trimethysiloxy-2-methylpropene (methyl initiator) were
added via addition funnel. 1.9541 g mesitylene and 0.6 mL of a 1 M
solution of TBACB in acetonitrile (catalyst) were injected using
two syringes, and the first monomer feed was started. 88.4 g nBMA,
176.4 g MMA, 88.4 g EHMA, 44.2 g BzMA and 76.6 g methacrylic acid
3-(trimethoxysilyl)propyl ester (A-174, Tokyo Kasei Kogyo Co. Ltd.,
Japan), the primary components of the A block, were added via
addition funnel over a period of 60 min. The temperature was kept
below 50.degree. C. by cooling the reaction flask with an ice bath.
At 70 min. from the start, the conversion was 95% or more for all
monomers.
[0214] A second monomer feed (B block) of DMAEMA was started via
the same addition funnel at 90 min from the start. 227.0 g of this
monomer was added over a period of 30 min. The temperature rose to
58.degree. C. during this feed. In parallel with the monomer feeds,
a feed consisting of 0.6 mL TBACB in 5.0 g THF was fed to the
reaction pot over 120 min. The reaction mixture was held for 2
hours while temperature dropped to 31.4.degree. C. At this point,
93.2 g methanol was added to quench the reaction. Next, 425.4 g
solvent was stripped out in three steps and replaced with 613.6 g
PMA. The reaction mixture was cooled down to 94.4.degree. C., and
75.3 g methanol and 525.0 g butoxyethanol were added. Then 164.4 g
BzCl was added to quaternize the amino groups from the DMAEMA, and
this solution was refluxed for six hours until the amine value
decreased from an initial value of 0.656 mEq/g solution to 0.070
mEq/gram solution (equivalent to approx. 90% quaternization degree
of the amino groups in the polymer).
[0215] The resulting polymer solution had a polymer solids content
of 34.29 wt % and a calculated number average molecular weight of
about 8134 g/mol. The AB block copolymer had the following mole
ratio of constituents:
nBMA/MMA/EHMA/BzMA/A-174//DMAEMA-BzCl
10.1/28.7/4.1/7.2/5.0//23.6-21.2
[0216] wherein n-BMA/MMA/EHMA/BzMA/A-174 is the A-segment and
DMAEMA is the B-segment of the polymer.
[0217] The fifth block copolymer dispersant, Dispersant 2E, had the
following composition:
BMA/MMA/BzMA/EHMA//A-174/DMAEMA-BzCl
10.1/28.7/4.1/7.2//5.0/23.6-21.2
[0218] and was prepared in a manner similar to Dispersant 2D, but
the A-174 was added in the B block.
[0219] The sixth block copolymer dispersant, Dispersant 2F, had the
following composition:
BMA/MMA/BzMA/EHMA/MPEG550MA//DMAEMA-BzCl
10.3/29.3/4.2/7.4/3.2//24.0-21.6
[0220] and was prepared by a manner similar to Dispersant 2D except
that the reactive monomer A-174 (76.6 g) was replaced by MPEG550MA
(methyl-capped polyethylene glycol methacrylate monomer) (104.5g).
The weight of MPEG550MA used was different in order to adjust for
similar mole % of components in the final polymer.
[0221] Phosphate-Containing Dispersant--Dispersant 3
[0222] The third dispersant was a phosphated acrylic comb copolymer
containing phosphate functionality in the pigment adsorbing
backbone segment and prepared using a standard free radical
polymerization approach. The resulting phosphated copolymer had the
following composition:
nBA/MA/GMA-Phosphated (45.5/45.5/9)//Bisomer 20W
[0223] The weight ratio of the phosphated portion to the Bisomer
was 60:40.
[0224] The phosphate polymer was prepared using the macromonomer,
Bisomer 20W, available from International Specialty Chemicals, as
the stabilizing arms of the polymer. This material is a
macromonomer of poly(ethylene glycol monomethacrylate). It is
nonionic with a molecular weight (Mw) of 2000 and provided the
water-soluble functionality to the polymer. The Bisomer 20W
macromonomer, along with other ingredients, were reacted in a
vessel to form the macro branched graft copolymer.
[0225] The polymer was formed by charging a reactor equipped with a
stirrer, thermocouple, condenser and nitrogen blanket, and heating
the contents to reflux. To the reactor, the backbone monomers nBA,
GMA and MA, and the Bisomer 20W macromonomer, were added with
isopropanol as the solvent. The polymerization reaction was
initiated by feeding the initiator
2,2'-azobis(2,4-dimethylvaleronitrile) (Vazo.RTM. 52 from E. I. du
Pont de Nemours and Company, Wilmington, Del.) which was dissolved
in a solution of methyl ethyl ketone and isopropanol. The
phosphating was accomplished by an esterification of the epoxy
groups on glycidyl methacrylate with phosphoric acid
(H.sub.3PO.sub.4).
[0226] The resulting phosphated acrylic graft copolymer reached 99%
conversion, ans was 45 wt % solids in a solution of
water/isopropanol. The molecular weight of the polymer was obtained
using GPC. The polymer was methylated prior to injection into the
column. The GPC indicated a number average molecular weight of 4577
and a polydispersity of 2.64.
[0227] Binder Polymers
[0228] Binder Polymer 1 was a GTP monoblock having the following
composition:
BMA/MMA/EHMA/BzMA/A-174 18.3/52.1/13.1/7.4/9.1
[0229] and was prepared by the following procedure.
[0230] While flushing a flask with N.sub.2, 464.1 g THF and 18.90 g
1-methoxy-1-trimethysiloxy-2-methylpropene were added via addition
funnel. 2.0823 g mesitylene and 0.6 mL of a 1 M solution of TBACB
in acetonitrile were injected using two syringes and the monomer
mixture feed was started. The monomer mixture consisted of 88.1 g
nBMA, 176.3 g MMA, 88.1 g EHMA, 44.2 g BzMA and 77.6 g A-174, and
was added via addition funnel over a period of 60 min. The
temperature was kept below 50.degree. C. by cooling the reaction
flask with an ice bath. In parallel with the monomer feed, a feed
consisting of 0.6 mL TBACB in 5.0 g THF was fed to the reaction
pot. At 80 min. from the start, the conversion was 99% or more for
all monomers. At this point, 92.2 g methanol was added to quench
the reaction. Next, 423 g solvent was stripped out in three steps
and replaced with 500.2 g PMA. The reaction mixture was cooled down
to 92.2.degree. C., and 75.7 g methanol and 450.7 g butoxyethanol
were added.
[0231] The resulting polymer solution had a polymer solids content
of 29.76 wt %. GPC results: measured number average molecular
weight (Mn) 5330 g/mol, (theoretical 4449 g/mol), weight average
molecular weight (Mw) 6191 g/mol, polydispersity 1.16.
[0232] Binder 2 was a GTP monoblock having the following
composition:
BMA/MMA/EHMA/BzMA/MPEG-500MA 19.0/53.9/13.6/7.7/5.8
[0233] And was prepared in a manner similar to Binder 1 except the
reactive monomer A-174 (77.6g) was replaced by MPEG550MA (104.5 g).
The amount of MPEG550MA used was different to adjust for similar
mole % of components in the final polymer.
[0234] Binder 3 was a GTP monoblock having the following
composition:
BzMA/HEMA/ETEGMA/MAA 60/29/10/10
[0235] and was made in a manner similar to Binder 1.
Comparative Slurry Example 1
[0236] A titanium dioxide slurry premix was prepared by charging
138.45 g water, 1 g of 50% DMEA in water, 20 g of a 50:50 blend of
Dispersant 1 and Dispersant 2B (37 wt % solids), 50 g ethylene
glycol, 2 g Dehydran.RTM. 1620 and 720 g of R700 pigment into a
1-liter stainless steel vessel, and processing for 10 minutes at
2000 rpm using a Dispermat High Speed Disperser configured with a
60 mm Cowels blade. The premix was let down with 68.55 g water,
stirring at 250 rpm for 5 minutes.
[0237] The premix was then processed on an Eiger Mini Mill, model
MK II M250 VSE EXP for 15 minutes at 3250 rpm disc speed with a 480
g media charge of 0.8-1.0 mm zirconia. Grinding was continued for
30 minutes with sampling at 10, 15, 20 and 30 minutes to determine
particle size. The final product was 72 wt % solids. Results are
provided in Table 2 before and after let down
2TABLE 2 Comparative Slurry Example 1 Particle Size vs. Milling
Time Median Particle Particle size, Size Grind Time <204 nm 50%
95% 10 minutes 30.82 240.2 395.9 15 minutes 18.68 235.9 293.8 20
minutes 26.42 246.7 380.9
Comparative Ink Example 1
[0238] Comparative Ink Example 1 was prepared by diluting
Comparative Slurry Example 1 with water to obtain a titanium
dioxide slurry with 15 wt % solids. This diluted slurry was
converted into an ink with the following formulation.
3TABLE 3 Comparative Ink Example 1 Formulation Comparative Slurry 1
40 DPM 36.92 DPnP 24.61 BYK 348 0.5 Pigment solids (Wt %) 6.00
Viscosity (Cps) 7.56 Surface Tension (Dyne/Cm) 26.37 BYK 348 is a
surfactant from Byk Chemie.
[0239] This ink could be printed. The aqueous content in this ink
(>5 wt %) can lead to possible instability of the ink.
Comparative Slurry Examples 2 and 3
[0240] Comparative Slurry examples 2 and 3 were made in a manner
similar to Comparative Slurry Example 1. Table 4 lists the
compositions for the slurries
4TABLE 4 Comparative Slurry Examples 2 and 3 Comparative Slurry EX
2 3 Di Water 83.49 182.8 DMEA 50% 1.00 1.0 Dispersants 1/2B,
50%/50% 28.80 Dispersants 1/2C, 50%/50% 44.2 Ethylene Glycol 50.00
50.0 Dehydran .RTM. 1620 2.00 2.0 PnP 103.51 Dispersant 3 20.00
Ti-Pure R700 720.00 720.0 Total 1008.80 1000.0
Comparative Ink Examples 2 and 3
[0241] The inks were made in a manner similar to Comparative Ink
Example 1.
5TABLE 5 Comparative Ink Examples 2 and 3 Comparative Ink Example 2
3 Comparative Slurry Ex 2 35.0 Comparative Slurry Ex 3 35.0 DPM
48.8 48.8 DPMA 16.3 16.3 Total 100.00 100.00 Wt % Pigment 25.00
25.00 Viscosity (Cps) 6.38 NA Surface Tension (Dyne/Cm) 29.68 NA
Filterability Poor Poor Milling Time (hr) 72.0 72.0 Jettability of
the ink Not Jetted
[0242] These inks were not filterable and never were jetted. This
combination of dispersant, solvent and modest water present leads
to inconsistent results when compared with the non-aqueous inks of
the instant invention.
Slurry Example 1
[0243] Slurry Example 1 was prepared in a 100-gram batch by
charging the ingredients listed in Table 8 into a plastic jar (250
ml capacity) and following these steps:
[0244] (1) In a 250 ml plastic bottle, the solvents (s) as well as
the dispersants were added.
[0245] (2) The mixture was mixed until the dispersants dissolved
completely in the solvents.
[0246] (3) The white pigment was added slowly to the container
[0247] (4) The contents were mixed well, then the zirconium media
(0.8-1.0 mil zirconium media) was added.
[0248] (5) The plastic container was then added to a roller mill,
the speed of which was adjusted to 35 rpm.
6TABLE 6 Slurry Example 1, Composition Slurry Ex 1 Disperbyk .RTM.
2000 8.71 Dispersant 1/2B (50/50 wt %) 5.17 PnP 361.12 Ti-Pure R700
250.00 Total 625.00
Ink Example 1
[0249] Ink Example 1 was prepared using Slurry Ex 1 according to
the following composition.
7TABLE 7 Ink Ex 1 Ink Example 1 Slurry Example 1 60.00 DPnP 40.00
BYK 348 0.50 Total 100.50 % Pigment (Solid) 24.00 Viscosity (Cps)
6.79 Surface Tension (Dyne/Cm) 27.02
[0250] This ink was printed on polyvinyl butyral and the optical
properties are reported in Table 8
8TABLE 8 Ink Example 1, White Ink Printed Decorative Laminates
Number of printing Glass % Trans- passes type mission % Haze %
Clarity 1 Clear 39.4 92.2 52.4 2 Clear 29.8 97.0 40.8 3 Clear 24.7
96.2 46.9 4 Clear 20.9 95.1 52.3 5 Clear 19.2 89.2 66.5 1 Starphire
37.4 91.4 50.9 2 Starphire 27.7 96.9 39.4 3 Starphire 22.9 95.8
45.0 4 Starphire 19.4 85.3 48.4 5 Starphire 17.3 85.8 69.8
[0251] The "Clear glass" is normal glass made by the float process,
and it had a slightly green tint. The Starphire glass was the PPG
"ultra-white" glass.
[0252] Test for Whiteness and Yellowness of White Ink Printed
Substrates
[0253] The polyvinyl butyral decorative laminate used with Ink
Example 1 was tested for whiteness as measured by ASTM E 313, and
yellowness as measured by ASTM D1925. The Whiteness Index was
44.52, and the Yellowness Index was -2.2.
Ink Examples 2-4
[0254] Ink Examples 2-4 were prepared according to the following
recipes in a manner similar to Slurry Example 1/Ink Example 1.
9TABLE 9 Ink Examples 2-4 Ink Example 2 3 4 Ti-Pure R700 25.0 25.0
25.0 DPM 73.5 73.5 73.5 Dispersant 3 1.5 0.8 Dispersant 1/2C,
50%/50% 1.5 0.8 Total 100.00 100.00 100.00 Wt % Pigment 25.00 25.00
25.00 Viscosity (Cps) 7.06 7.65 11.60 Surface Tension (Dyne/Cm)
29.12 29.37 29.41 Filterability Very Good Very Good Very Good
Milling Time (hr) 18.0 18.0 18.0 Jetability of the ink Excellent
Excellent Excellent
Ink Examples 5-7
[0255] These inks were prepared according to the following recipes
in a manner similar to Slurry Example 1/Ink Example 1.
10TABLE 10 Ink Examples 5-7 5 6 7 Ti-Pure R700 25.0 25.0 25.0 TPM
6.5 PPH 6.5 DPM 58.5 58.5 65.0 Disperbyk .RTM. 2001 10.0 10.0 10.0
Total 100.0 100.0 100.0 Wt % Pigment (Solid) 25.00 25.00 25.00
Pigment/Dispersant 5 5 5 Viscosity (Cps) 7.35 8.22 6.84 Surface
Tension (Dyne/Cm) 28.96 29.78 29.10 Filterability Good Good Good
Media 0.8-1.0 Zirconium Media Milling Time (hour) 24.00 24.00 24.00
Ink Stability Good Good Good (minimum settling) Consistency of
print Moderate Good Good Jetability of the ink Excellent Excellent
Excellent
Ink Examples 8-10
[0256] These inks were prepared according to the following recipes
in a manner similar to Slurry Example 1/Ink Example 1.
11TABLE 11 Ink Examples 8-10 8 9 10 Ti-Pure R700 25.0 25.0 25.0 DPM
73.5 73.5 73.5 Dispersant 3 1.5 0.0 0.8 Dispersant 1 0.0 1.5 0.8
Total 100.0 100.0 100.0 Wt % Pigment (Solid) 25.00 25.00 25.00
Pigment/Dispersant 16.7 16.7 16.7 Viscosity (Cps) 7.06 7.65 11.6
Surface Tension (Dyne/Cm) 29.12 29.37 29.41
Ink Examples 11-22
[0257] These inks were prepared to test inks with varying
dispersants and two examples (15 and 22) with added binder. The
inks were aged for 7 days at 70.degree. C. to do an accelerated
test of ink stability. If the change in viscosity was less than
.+-.20% difference, they were judged to be stable.
12TABLE 12 Ink Examples 11-22 11 12 13 14 15 15 17 18 19 20 21 22
Ti Pure R 700 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0
20.0 20.0 P-25 Degussa (nano) 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
5.0 5.0 5.0 DPM 54.6 53.8 53.8 53.8 53.8 53.8 53.8 53.8 53.8 53.8
53.8 53.8 DPMA 18.2 17.9 17.9 17.9 17.9 17.9 17.9 17.9 17.9 17.9
17.9 17.9 Dispersant 1/2C 50:50 2.2 2.2 2.2 1.1 0.6 Dispersant 3
1.1 1.1 0.6 1.1 Disperbyk .RTM. 2001 2.2 1.1 2.2 2.2 2.2 2.2 2.2
2.2 2.2 2.2 Binder 1 1.1 Dispersant 2D 1.1 Dispersant 2E 1.1
Dispersant 2F 1.1 Binder 2 1.1 Surface Tension 28.3 28.6 28.2 28.3
28.7 28.9 27.0 27.8 28.8 22.3 29.0 28.3 (Dyne/Cm) Viscosity@ 60 rpm
9.4 7.7 5.4 5.6 4.8 5.3 5.2 5.3 4.8 5.1 5.1 5.0 (Cps) 7 Day Oven
Aged Viscosity@ 60 rpm 6.4 5.5 5.3 5.1 4.4 4.7 4.8 5.2 5.7 4.8 5.9
4.8 (Cps)
[0258] All of the tested inks were judged to be stable except that
Ink Examples 11 and 12 were only marginally stable by this
accelerated test.
Ink Examples 23-28
[0259] Inks 23-28 were similarly prepared as before to test binders
and dispersants, and two examples (24 and 25) had added binder. The
inks were aged for 7 days at 70.degree. C. to do an accelerated
test of ink stability. If the change in viscosity was less than
.+-.20% difference they were judged to be stable.
13TABLE 13 Ink Examples 23-28 23 24 25 26 27 28 Ti Pure R 700 20.00
20.00 20.00 20.00 20.00 20.00 P-25 Degussa (nano) 5.00 5.00 5.00
5.00 5.00 5.00 DPM 54.60 54.60 54.60 54.60 54.60 54.60 DPMA 18.20
18.20 18.20 18.20 18.20 18.20 Disperbyk .RTM. 2001 2.20 2.20 2.20
2.20 2.20 2.20 Binder 3 1.10 Binder 2 1.10 Dispersant 2E 1.10
Dispersant 2F 1.10 Dispersant 2D 1.10 Total 100.0 101.1 101.1 101.1
101.1 101.1 Filterability Good Good Good Good Good Good Viscosity@
60 rpm (Cps) 5.12 5.17 5.60 5.31 5.02 5.19 Surface Tension
(Dyne/Cm) 28.80 29.06 28.90 28.88 28.89 28.93 Viscosity@ 60 rpm
(Cps) After 7 5.10 4.50 5.30 5.20 5.10 4.50 days Surface Tension
(Dyne/Cm) 27.40 28.02 28.95 28.12 29.19 28.04 After 7 days Particle
Size: (microns, 50%) 0.2670 0.2592 0.2578 0.2570 0.2522 0.2760
[0260] All of these inks were judged stable based on the 70.degree.
C. accelerated aging test. These tests show the stability of the
inks with single dispersants, two dispersants and a single
dispersant with binder.
Ink Examples 28-32 and Comparative Ink Examples 4-6
[0261] These inks were prepared to demonstrate the importance of
the hydrogen solubility parameter. Ink examples 28-32 and
Comparative Ink Examples 4-6 are listed in Table 14. The calculated
hydrogen solubility parameter is listed in the table. Thus, Ink
Example 32 satisfies the limit of hydrogen solubility parameter of
greater than 9, but Comparative Inks 4, 5 and 6 do not.
14TABLE 14 Ink Examples 28-32 and Comparative Ink Examples 4-6
Calculated Particle Pigment Ink Vehicle Solubility Disper- Viscos-
Size Ink Example (pph) (pph) Parameter sant (pph) ity (Cps) (nm)
Stability 28 R700 (20) DPM (72.8) 10.3 D2001 6.7 289.4 Good P-25
(5) DPMA (0.0) (2.2) 29 R700 (20) DPM (63.5) 10.0 D2001 5.5 276.0
Good P-25 (5) DPMA (9.3) (2.2) 30 R700 (20) DPM (54.6) 9.73 D2001 5
256.2 Good P-25 (5) DPMA (18.2) (2.2) 31 R700 (20) DPM (45.5) 9.44
D2001 4.8 249.8 Good P-25 (5) DPMA (27.3) (2.2) 32 R700 (20) DPM
(36.4) 9.15 D2001 4.8 257.7 Good P-25 (5) DPMA (36.4) (2.2) Comp
R700 (20) DPM (18.2) 8.57 D2001 EEE 336.0 Poor Ink 4 P-25 (5) DPMA
(54.6) (2.2) Comp R700 (20) DPM (9.1) 8.27 D2001 EEE 343 Poor Ink 5
P-25 (5) DPMA (63.5) (2.2) Comp R700 (20) DPM (0) 8.0 D2001 EEE
494.8 Poor Ink 6 P-25 (5) DPMA (72.8) (2.2)
[0262] The ink stability observations were made by looking at the
containers of the ink and observing settling or other apparent
instability. Note that the particle size is larger for the
Comparative inks, perhaps indicating that the dispersing
effectiveness of the solvent mixture with hydrogen bonding
solubility parameter of less than 9 is poorer.
[0263] Ink Examples 30 and 31 could separately be left in an ink
cartridge for extended periods of time without degrading the
printed image. That is, a printer with these inks could be left
idle for several weeks and then restarted without concern that the
ink had settled.
[0264] Test of Settling of Inks
[0265] Another measure of the stability of the titanium dioxide
inks is to test the settling of the ink. Ink was placed in a
cylindrical glass vial 1.6 cm in diameter and 5 cm high. After 45
days the vials were observed and the amount of settling recorded.
The amount of clear liquid on top was recorded and the amount of
white ink recorded. The less % clear observed the less settling is
observed. A % clear of less than 5% is judged as very good, 5 to
10% as good, 10 to 20% as moderate. In each of these cases this was
soft settling, and simple mixing could resuspend the ink. If the
clear region was 20 to 40%, that was judged not acceptable for an
ink. Anything more than 40% was judged as severe settling.
15TABLE 15 Settling of the Inks Ink ID Clear/cm White/cm Total/cm %
Clear Ink 23 0.4 4.5 4.9 8.2 Ink 24 0.5 4.0 4.5 11.1 Ink 25 0.5 4.0
4.5 11.1 Ink 26 0.7 4.5 5.2 13.5 Ink 28 0.5 2.4 2.9 17.2 Ink 29 0.5
4.0 4.5 11.1 Ink 30 0.2 3.5 3.7 5.4 Ink 31 0.1 4.0 4.1 2.4 Ink 32
0.5 4.0 4.5 11.1 Comp Ink 4 0.5 3.5 4.0 12.5 Comp Ink 5 1.5 3.5 5.0
30.0 Comp Ink 6 2.0 2.5 4.5 44.4
[0266] Inks 23-26 are combinations of different dispersants and in
some cases additional binders. Inks 28-32 and Comparative Inks 4-6
are the inks with a variable ratio of DPM and DPMA. The Comparative
Inks 5 and 6 clearly failed a stability test, and Comparative Ink 4
was moderate in settling performance.
[0267] Tests of the inventive ink demonstrate surprising stability
for titanium dioxide inks.
[0268] Conductivity of the Inks
[0269] The conductivity of three inks were measured. For reference,
the pure solvents DPM and DPMA have conductivities of 4.36 and 4.22
.mu.mho/cm respectively.
16TABLE 16 Conductivity of the Inks Ink Example 33 34 35 Titanium
dioxide Ti-Pure Ti-Pure Ti-Pure R-700, 30% TS-6200 R706 DPM 50.8
50.8 50.8 DPMA 17.0 17.0 17.0 Viscosity 4.73 4.81 5.79 Surface
Tension 28.79 29.02 27.78 Conductivity (.mu.mho/cm) 5.14 5.00
4.37
[0270] The conductivities of the inventive inks were very low. The
lack of any added salt or any other significant amount of charged
species lead to these low values.
[0271] Printing Results on Polyvinyl Butyral and their Glass
Laminates.
[0272] Ink Example 16 was printed on a sheet of polyvinyl butyral
(PVB) using Mamiki JV3 printer. The white ink was printed alone and
in combinations with other colors in two different modes.
[0273] Mode 1: The white ink was printed first then the color
(CMYK) was printed on the top of it (overprinted). Mode 2: The
white ink at 100% coverage was printed simultaneously printed with
the other colors (CMYK).
[0274] The printed PVB was laminated according to techniques
described in previously incorporated WO04/018197. The Adhesion
(PSI) results are summarized in Table 17.
17TABLE 17 Laminated Glass Print Properties Color Alone Mode 1 Mode
2 White (50% coverage) 2920 White (100% coverage) 2511 Cyan 2285
2330 2031 Magenta 2375 2024 1881 Yellow 2247 2177 2039 Black 2589
2400 2249
[0275] The white ink did not adversely effect the adhesion
performance of the laminate. Also printing in either of the modes
still produced laminates with adhesion tests greater than 2000
psi.
* * * * *