U.S. patent application number 10/486930 was filed with the patent office on 2004-12-02 for pigment dispersion and ink composition for ink-jet.
Invention is credited to Okamoto, Naoki, Waki, Minoru, Yasuda, Izumi.
Application Number | 20040242726 10/486930 |
Document ID | / |
Family ID | 29544951 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040242726 |
Kind Code |
A1 |
Waki, Minoru ; et
al. |
December 2, 2004 |
Pigment dispersion and ink composition for ink-jet
Abstract
An aqueous pigment dispersion for ink jet having a pigment
dispersed, characterized by containing a water-soluble resin and a
resin having a urethane bond and/or an amide bond.
Inventors: |
Waki, Minoru; (Himeji-shi,
JP) ; Okamoto, Naoki; (Himeji-shi, JP) ;
Yasuda, Izumi; (Himeji-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
29544951 |
Appl. No.: |
10/486930 |
Filed: |
February 25, 2004 |
PCT Filed: |
May 16, 2003 |
PCT NO: |
PCT/JP03/06120 |
Current U.S.
Class: |
523/160 ;
106/499; 523/161 |
Current CPC
Class: |
C09D 11/322 20130101;
C09D 11/40 20130101 |
Class at
Publication: |
523/160 ;
106/499; 523/161 |
International
Class: |
C08K 005/00; C03C
017/00; C09D 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2002 |
JP |
2002-141594 |
Claims
1. A pigment dispersion for ink jet having a pigment dispersed,
which comprises a water-soluble resin and a resin having a urethane
bond and/or an amide bond.
2. The pigment dispersion according to claim 1, which is obtained
by blending the water-soluble resin with the pigment, finely
pulverizing the pigment in a kneading step and a dispersing step,
and further adding the resin having a urethane bond and/or an amide
bond thereto to cause crosslinking.
3. The pigment dispersion according to claim 1 or 2, wherein the
resin has a crosslinking rate of from 20 to 100%.
4. The pigment dispersion according to any one of claims 1 to 3,
which is a dispersion for ink jet.
5. An ink composition for ink jet having a pigment dispersed, which
comprises a water-soluble resin and a resin having a urethane bond
and/or an amide bond.
6. The ink composition for ink jet according to claim 5, which is
obtained by blending the water-soluble resin with the pigment,
finely pulverizing the pigment in a kneading step and a dispersing
step, and further adding the resin having a urethane bond and/or an
amide bond thereto to cause crosslinking.
7. The ink composition for ink jet according to claim 5 or 6,
wherein the resin has a crosslinking rate of from 20 to 100%.
8. An ink composition for ink jet, which is obtained by adding an
organic solvent to the pigment dispersion as defined in any one of
claims 1 to 3.
9. An ink jet recording method, which comprises printing by
discharging the ink composition for ink jet as defined in any one
of claims 5 to 8 from a nozzle of an ink jet printer.
10. An ink set having the ink composition for ink jet as defined in
any one of claims 5 to 8 charged into a cartridge.
Description
TECHNICAL FIELD
[0001] The present invention relates to a pigment dispersion
suitably usable for various ink compositions including use for ink
jet printing, and an ink for ink jet printing.
BACKGROUND ART
[0002] A pigment type ink using a pigment as a coloring agent has
an advantage of being excellent in light resistance and water
resistance as compared with a dye type ink using a dye as a
coloring agent. However, since a pigment is generally insoluble in
water, it is necessary to be mixed with a resin called as a
dispersant for being stably dispersed in water. Also, as compared
with a dye type ink, a pigment type ink as a dispersion is poor in
stability as a lapse of time since a pigment settles.
[0003] Also, it is pointed out that a pigment type ink generally
has a disadvantage of being poor in transparency and coloring.
Particularly, when recording on a transmission manuscript
represented as an OHP film processed for an aqueous recording
liquid, transparency is lowered and coloring is remarkably dull due
to light scattering by pigment particles.
[0004] It is required for ink jet use to be printed at a high
speed, but unlike a dye penetrated into the inside of a recording
medium, a pigment stays on a surface of a recording medium and
accordingly friction resistance of an image obtained becomes a
problem.
[0005] In order to improve transparency and coloring, it is
necessary to have pigment particles dispersed as finely as
possible. Particularly, in case of ink jet use for injecting ink
droplets from a minute nozzle, a strict dispersion stability and a
highly finely dispersed state are required in order to achieve
satisfactory performances such as color reproducibility on a
recorded material and injecting property at the time of injecting
from a nozzle at a high speed. For this purpose, various
elaborations are made. For example, an elaboration of fully
adsorbing a high molecular dispersant on a pigment or an
elaboration of firmly fixing a high molecular dispersant on a
finely dispersed pigment by means of coating a pigment with a resin
is studied.
[0006] For instance, the following proposals have been made. A
pigment and a resin are kneaded to prepare a solid colored
compound, and the compound is dispersed in a dispersing medium to
improve transparency and coloring (JP-A-11-80,633); a storage
stability of a dispersion is improved by using a pigment coated
with a cured polymer having a polar group insoluble in a dispersion
medium (JP-A-5-247,370); a pigment is coated with a resin swellable
in a dispersion medium to prevent clogging or bleeding
(JP-A-3-240,586); and an aqueous solution containing a resin, an
amine and water are stirred to fully dissolve the resin, and a
premixed pigment is subjected to dispersion treatment to stabilize
injecting by controlling a non-adsorbed resin amount to at most 2%
(JP-A-2-255,875).
[0007] In the ink jet use, it is required for improving a printing
speed to enhance permeability of an ink composition and to reduce a
drying time. However, when simply adding a general penetrant, there
is a case that the permeability can not be fully provided due to a
relationship between a pigment and other components or a case that
the penetrant damages color reproducibility, which adversely
affects on an image quality. Therefore, various proposals have been
made to solve these problems.
[0008] For example, by using an acetylene glycol type and/or
polysiloxane type surfactant as a penetrant and using an alkyl
ether derivative of a polyhydric alcohol such as ethylene glycol
monobutyl ether as an organic solvent, a satisfactory color
reproducibility is achieved (JP-A-2002-30,237); and by using an ink
containing water, a pigment, a wetting agent and a specific
polyoxyethylene alkyl ether acetate, an ink having excellent
permeability, drying property and image quality and having no
strike through is provided (JP-A-2001-254,036).
[0009] However, when preparing an ink having a high permeability
and a quick drying property, it has been found by the present
inventors that a stable dispersibility of a pigment is sometimes
spoiled by an interaction among a dispersing resin, a penetrant and
a solvent for preparing the ink.
[0010] The present inventors have intensive studied to solve these
problems. As a result of the study, it has been found that an
excellent ink for ink jet and an excellent pigment dispersion for
ink jet having a satisfactory dispersion stability can be obtained
without spoiling other performances by using a dispersion having a
combination of specific plural resins contained, particularly in
the preparation of an ink having a high permeability.
[0011] Further, it has been unexpectedly discovered that gloss of a
recorded material is improved by the present invention as compared
with a conventional pigment type ink. Particularly, it has been
found that when using a glossy paper as a medium, the improvement
of gloss is remarkable.
DISCLOSURE OF THE INVENTION
[0012] Thus, the essential features of the present invention reside
in:
[0013] (1) A pigment dispersion for ink jet having a pigment
dispersed, characterized by containing a water-soluble resin and a
resin having a urethane bond and/or an amide bond;
[0014] (2) the pigment dispersion according to the above feature
(1), which is obtained by blending the water-soluble resin with the
pigment, finely pulverizing the pigment in a kneading step and a
dispersing step, and further adding the resin having a urethane
bond and/or an amide bond thereto to cause crosslinking;
[0015] (3) the pigment dispersion according to the above feature
(1) or (2), wherein the resin has a crosslinking rate of from 20 to
100%;
[0016] (4) the pigment dispersion according to any one of the above
features (1) to (3), which is a dispersion for ink jet;
[0017] (5) an ink composition for ink jet having a pigment
dispersed, characterized by containing a water-soluble resin and a
resin having a urethane bond and/or an amide bond;
[0018] (6) the ink composition for ink jet according to the above
feature (5), which is obtained by blending the water-soluble resin
with the pigment, finely pulverizing the pigment in a kneading step
and a dispersing step, and further adding the resin having a
urethane bond and/or an amide bond thereto to cause
crosslinking;
[0019] (7) the ink composition for ink jet according to the above
feature (5) or (6), wherein the resin has a crosslinking rate of
from 20 to 100%;
[0020] (8) an ink composition for ink jet, which is obtained by
adding an organic solvent to the pigment dispersion as defined in
any one of the above features (1) to (3);
[0021] (9) an ink jet recording method, which comprises printing by
discharging the ink composition for ink jet as defined in any one
of the above features (5) to (8) from a nozzle of an ink jet
printer; and
[0022] (10) an ink set having the ink composition for ink jet as
defined in any one of the above features (5) to (8) charged into a
cartridge.
[0023] Hereinafter, the present invention is described in details.
The pigment dispersion of the present invention comprises at least
a pigment and specific two kinds of resins.
[0024] (Pigment)
[0025] The pigment used in an aqueous ink composition for ink jet
of the present invention is not specifically limited, and any of an
organic pigment and an inorganic pigment can be used.
[0026] Examples of the organic pigment include an azo pigment such
as an azolake, an insoluble monoazo pigment, an insoluble disazo
pigment, a condensed azo pigment, a chelate azo pigment or the
like; a polycyclic pigment such as a phthalocyanine pigment, a
perylene pigment, a perynone pigment, an anthraquinone pigment, a
quinacridone pigment, a dioxazine pigment, a thioindigo pigment, an
isoindolinone pigment, a quinophthalone pigment or the like; a dye
chelate such as a basic dye type chelate, an acidic dye type
chelate or the like; a nitro pigment; a nitroso pigment; and the
like.
[0027] Examples of the inorganic pigment include titanium oxide,
iron oxide, rouge, chromium oxide, Prussian blue, ultramarine blue,
molybdate orange, black iron oxide, chrome yellow, carbon black,
and the like, and they can be used respectively alone or in a
mixture of two or more.
[0028] Among them, in view of light resistance, an isoindolinone
type pigment, a quinacridone type pigment, a condensed azo type
pigment, a phthalocyanine type pigment, a quinophthalone type
pigment, an anthraquinone type pigment or carbon black is
preferably usable.
[0029] Particular examples of the above organic pigments include
pigment.cndot.yellow 1 (color index (hereinafter referred to as
"C.I.") 11680), pigment.cndot.yellow 3 (C.I. 11710),
pigment.cndot.yellow 14 (C.I. 21095), pigment.cndot.yellow 17 (C.I.
21105), pigment.cndot.yellow 42 (C.I. 77492), pigment.cndot.yellow
74 (C.I. 11741), pigment.cndot.yellow 83 (C.I. 21108),
pigment.cndot.yellow 93 (C.I. 20710), pigment.cndot.yellow 98 (C.I.
11727), pigment.cndot.yellow 109 (C.I. 56284), pigment.cndot.yellow
110 (C.I. 56280), pigment.cndot.yellow 128 (C.I. 20037),
pigment.cndot.yellow 138 (C.I. 56300), pigment.cndot.yellow 139
(C.I. 56298), pigment.cndot.yellow 147 (C.I. 60645),
pigment.cndot.yellow 154 (C.I. 11781), pigment.cndot.yellow 155,
pigment.cndot.yellow 180 (C.I. 21290), pigment.cndot.yellow 185,
pigment.cndot.orange 5 (C.I. 12075), pigment.cndot.orange 13 (C.I.
21110), pigment.cndot.orange 16 (C.I. 21160), pigment.cndot.orange
34 (C.I. 21160), pigment.cndot.orange 43 (C.I. 71105),
pigment.cndot.orange 61 (C.I. 11265), pigment.cndot.orange 71 (C.I.
561200), pigment.cndot.red 5 (C.I. 12490), pigment.cndot.red 8
(C.I. 12335), pigment.cndot.red 17 (C.I. 12390), pigment.cndot.red
22 (C.I. 12315), pigment.cndot.red 48:2 (C.I. 15865:2),
pigment.cndot.red 112 (C.I. 12370), pigment.cndot.red 122 (C.I.
73915), pigment.cndot.red 177 (C.I. 65300), pigment.cndot.red 178
(C.I. 71155), pigment.cndot.red 202 (C.I. 73907), pigment.cndot.red
254 (C.I. 56110), pigment.cndot.red 19 (C.I. 46500),
pigment.cndot.violet 23 (C.I. 51319), pigment.cndot.blue 15:1 (C.I.
74160), pigment.cndot.blue 15:3 (C.I. 74160), pigment.cndot.blue
15:4 (C.I. 74160), pigment.cndot.blue 60 (C.I. 69800),
pigment.cndot.green 7 (C.I. 74260), pigment.cndot.green 36 (C.I.
74265), and the like.
[0030] Particular examples of the above inorganic pigments include
pigment.cndot.yellow 42 (C.I. 77492), pigment-white 6 (C.I. 77891),
pigment.cndot.blue 27 (C.I. 77510), pigment.cndot.blue 29 (C.I.
77007), pigment.cndot.black 7 (C.I. 77266), and the like.
[0031] Preferable examples include pigment.cndot.yellow 74 (C.I.
11741), pigment.cndot.yellow 109 (C.I. 56284), pigment.cndot.yellow
110 (C.I. 56280), pigment.cndot.yellow 128 (C.I. 20037),
pigment.cndot.yellow 155, pigment.cndot.yellow 180 (C.I. 21290),
pigment.cndot.red 122 (C.I. 73915), pigment.cndot.red 202 (C.I.
73907), pigment.cndot.violet 19 (C.I. 46500), pigment.cndot.blue
15:1 (C.I. 74160), pigment.cndot.blue 15:3 (C.I. 74160),
pigment.cndot.blue 15:4 (C.I. 74160), pigment.cndot.blue 60 (C.I.
69800), pigment.cndot.black 7 (C.I. 77266), and the like.
[0032] In the present invention, it is preferable to use an organic
pigment in view of stability since its particle size easily becomes
small and its specific gravity is also small. Further, when
considering dispersibility, a primary particle size of a pigment is
preferably at most about 0.1 .mu.m.
[0033] (Water-Soluble Resin)
[0034] The present invention is characterized by including at least
two kinds of resins.
[0035] First resin is a water-soluble resin including various
resins usable as a dispersant which is adsorbed on a pigment and
works for improving dispersibility of the pigment.
[0036] Among them, a water-soluble resin having a hydrophobic group
and a hydrophilic group is desirable since it is excellent in
dispersing a pigment. Typical examples include a copolymer of a
hydrophobic monomer and a hydrophilic monomer, and such a copolymer
is particularly excellent in dispersing a pigment.
[0037] The term "hydrophobic monomer" means a monomer having a
hydrophobic group and the term "hydrophilic monomer" means a
monomer having a hydrophilic group, which are copolymerizable.
[0038] Examples of the hydrophobic monomer include methyl acrylate,
methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl
acrylate, n-propyl methacrylate, iso-propyl acrylate, iso-propyl
methacrylate, n-butyl acrylate, n-butyl methacrylate, sec-butyl
acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl
methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl
acrylate, n-octyl methacrylate, iso-octyl acrylate, iso-octyl
methacrylate, 2-ethylhexyl acrylate, 2-methylhexyl methacrylate,
decyl acrylate, decyl methacrylate, lauryl acrylate, lauryl
methacrylate, stearyl acrylate, stearyl methacrylate,
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate,
2-dimethylaminoethyl acrylate, 2-dimethylaminoethyl methacrylate,
2-diethylaminoethyl acrylate, 2-diethylaminoethyl methacrylate,
glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl
methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl
acrylate, phenyl methacrylate, nonylphenyl acrylate, nonylphenyl
methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl
acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl
methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol
dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol
dimethacrylate, ethylene glycol diacrylate, ethylene glycol
dimethacrylate, diethylene glycol diacrylate, diethylene glycol
dimethacrylate, triethylene glycol diacrylate, triethylene glycol
dimethacrylate, tetraethylene glycol diacrylate, tetraethylene
glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene
glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol
diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol
diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane
triacrylate, trimethylolpropane trimethacrylate, glycerol acrylate,
glycerol methacrylate, styrene, methylstyrene, vinyl toluene, and
the like.
[0039] They may be used respectively alone or in a mixture of two
or more.
[0040] A hydrophobic group contained in a hydrophobic monomer is
not specially limited, examples of which include an organic group
having an aromatic ring such as a phenyl group, a benzyl group or
the like, which may be substituted, and an alkyl group which may be
substituted, but a ring having an aromatic ring is particularly
preferable.
[0041] Examples of a hydrophilic monomer include acrylic acid,
methacrylic acid, maleic acid, itaconic acid and the like.
[0042] They may be used respectively alone or in a mixture of two
or more. A ratio of a hydrophilic monomer and a hydrophobic monomer
is not specially limited, but it is particularly preferable that a
hydrophilic monomer: hydrophobic monomer weight ratio is in a range
of from 5:95 to 40:60.
[0043] A copolymer can be obtained by copolymerizing these
hydrophobic monomers and hydrophilic monomers. Polymerization can
be carried out by a known method, but it is preferable that
copolymerization is carried out by a random copolymerization method
since a copolymer obtained by random copolymerization provides an
excellent stability as a lapse of time when a dispersion is
prepared by using the copolymer thus obtained as a dispersant.
[0044] It is particularly preferable to use an alkali-soluble resin
obtained by neutralizing the above-mentioned copolymer of a
hydrophobic monomer and a hydrophilic monomer with an alkaline
material as a neutralizer to have the polymer solubilized in an
aqueous medium.
[0045] Examples of the neutralizer include an alkali metal
hydroxide such as sodium hydroxide, potassium hydroxide or the
like, monoethanolamine, diethanolamine, triethanolamine,
monoethylamine, diethylamine, triethylamine, morpholine, ammonia,
and the like.
[0046] Preferable examples of the water-soluble resin having a
hydrophilic group and a hydrophobic group include a styrene-acrylic
acid copolymer, a styrene-methylstyrene-acrylic acid copolymer, a
styrene-acrylic acid-(meth)acrylic acid ester (a lower alkyl ester
of about C.sub.1C.sub.4, hereinafter the same) copolymer, a
methacrylic acid-(meth)acrylic acid ester copolymer, an acrylic
acid-(meth)acrylic acid ester copolymer, a styrene-methacrylic acid
copolymer, a styrene-maleic acid copolymer, a
styrene-methylstyrene-maleic acid copolymer, a
styrene-(meth)acrylic acid ester-maleic acid copolymer, a
styrene-(meth)acrylic acid ester-allylsulfonic acid copolymer, a
vinylnaphthalene-acrylic acid copolymer, a vinylnaphthalene-maleic
acid copolymer, or their sodium, potassium or ammonium salts, and
the like. They may be used respectively alone or in a mixture of
two or more.
[0047] Among them, particularly preferable examples include a
styrene-acrylic acid copolymer, a styrene-methylstyrene-acrylic
acid copolymer, a styrene-maleic acid copolymer, a methacrylic
acid-(meth)acrylic acid ester copolymer, and the like. When they
are used, a pigment dispersion having particularly excellent
dispersibility can be obtained.
[0048] Other various water-soluble resins known as a high molecular
dispersant can also be used. For example, a polyvinyl alcohol type
dispersant, a polyacrylamide type dispersant, a polyester type
dispersant, a polyacrylic acid type dispersant or the like is
known, and they may be selected from commercially available
products.
[0049] A glass transition point of the water-soluble resin is not
specially limited, but a preferable glass transition point is at
least 30.degree. C., more preferably at least 50.degree. C. When
the glass transition point is less than 30.degree. C., a dispersion
and an ink composition become poor in stability as a lapse of time.
When the glass transition point is less than 30.degree. C., a
pigment having a function partially as a dispersant does not work
when a temperature is raised, and consequently the stability as a
lapse of time becomes poor.
[0050] The glass transition point indicates a temperature zone
wherein physical properties rapidly vary by partial crystallization
or hydrogen bonding in the inside of a non-crystalline solid such
as a plastic when a temperature is lowered, and can be measured by
a thermally analyzing apparatus such as "DSC7" of Perkin Elmer Co.
It is general to carry out the thermal analysis at a temperature
gradient of 5 to 10.degree. C./min.
[0051] Particularly, a copolymer comprising a hydrophobic monomer
such as styrene or (meth)acrylic acid ester and a hydrophilic
monomer such as (meth)acrylic acid, and having a glass transition
point of at least 30.degree. C., more preferably at least
50.degree. C., is particularly excellent in dispersion
stability.
[0052] A molecular weight of a water-soluble resin is not specially
limited, but a preferable molecular weight is 2,000 to 30,000, more
preferably 2,000 to 20,000, as a weight average molecular weight
measured by GPC (gel permeation chromatography).
[0053] Also, an acid value of a water-soluble resin is preferably
from 50 to 320, more preferably from 55 to 270. The acid value is
an mg amount of KOH necessary for neutralizing 1 g of a resin.
[0054] A water-soluble resin is added in an amount of from 5 to 100
parts by weight, more preferably from 10 to 80 parts by weight, to
100 parts by weight of a pigment. If the amount of a water-soluble
resin is less than 5 parts by weight to 100 parts by weight of a
pigment, dispersibility of a pigment becomes insufficient and a
deposit is formed or a stability as a lapse of time becomes poor.
On the other hand, if the amount of a water-soluble resin exceeds
100 parts by weight, a dispersion or an ink prepared therefrom
becomes highly viscous, and an injecting performance is
lowered.
[0055] (Resin Having an Amide Bond and/or A Urethane Bond)
[0056] The present invention further employs a resin having an
amide bond and/or a urethane bond as a second resin in addition to
the above-mentioned water-soluble resins. Their examples include a
homopolymer obtained by polymerizing (meth)acrylamide,
vinylpyrrolidone or the like, a copolymer of the above illustrated
homopolymers with other vinyl monomers, a polyurethane resin, and
the like.
[0057] Among them, a polyurethane resin is particularly preferable.
The polyurethane resin is not specially limited, and a
water-soluble or water-dispersible polyurethane resin obtained by
reacting a diisocyanate compound and a diol compound is usable.
[0058] Examples of the diisocyanate compound include an alicyclic
diisocyanate compound such as hexamethylene diisocyanate,
2,2,4-trimethylhexamethylene diisocyanate, hydrogenated xylylene
diisocyanate, 1,4-cyclohexane diisocyanate,
4,4'-dicyclohexylmethane diisocyanate or the like, an arylaliphatic
diisocyanate compound such as xylylene diisocyanate,
tetramethylxylylene diisocyanate or the like, an aromatic
diisocyanate compound such as toluilene diisocyanate, phenylmethane
diisocyanate or the like, a modified material of the above
illustrated diisocyanates (such as carbodiimide, uretodion or
uretoimine-containing modified materials), and the like.
[0059] Examples of the diol compound include a diol compound
obtained by (co)polymerizing an alkylene oxide such as ethylene
oxide or propylene oxide, and a heterocyclic ether such as
tetrahydrofuran or the like. Particular examples of the diol
compound include a polyether diol such as polyethylene glycol,
polypropylene glycol, polytetramethylene ether glycol,
polyhexamethylene ether glycol or the like, a polyester diol such
as polyethylene adipate, polybutylene adipate, polyneopentyl
adipate, poly-3-methylpentyl adipate, polyethylene/butylene
adipate, polyneopentyl/hexyl adipate or the like, a polylactone
diol such as polycaprolactone diol or the like, polycarbonate diol,
and the like. Among them, at least one kind of polyether type,
polyester type and polycarbonate type diol compounds is
preferable.
[0060] Further, in addition to the above compounds, diol compounds
having an acidic group such as a carboxylic acid group, a sulfonic
acid group or the like are usable, examples of which include
dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutyric
acid and the like. Among them, dimethylolpropionic acid is
preferable.
[0061] These diol compounds may be used in a combination of two or
more kinds.
[0062] In the preparation of a polyurethane type resin, a
polyhydroxy compound having a low molecular weight may be added.
Examples of the polyhydroxy compound having a low molecular weight
includes a material usable as a starting material for polyester
diol, such as glycol, an alkylene oxide low mol adduct, a trihydric
alcohol such as glycerin, trimethylolethane or trimethylolpropane,
and their alkylene oxide low mol adducts. Also, with regard to the
urethane prepolyemr thus obtained, a chain can be extended after
neutralizing or during neutralizing an acid group derived from
dimethylolalkanoic acid or a chain can be extended with
di(tri)amine. Examples of a polyamine used in the extension of
chain include hexamethylenediamine, isophoronediamine, hydrazine,
piperazine or the like, and they may be used in a combination of
two or more.
[0063] The form of a urethane resin is not limited. Typical forms
include an emulsion type such as self-emulsified emulsion or
self-stabilized type. Particularly, among the above compounds, a
diol having an acidic group such as a carboxylic acid group, a
sulfonic acid group or the like is preferably usable, or a
polyhydroxy compound having a low molecular weight may be added, or
a urethane resin having an acidic group introduced, particularly
one having a carboxyl group, is desirable. Further, it is
preferable for improving gloss or friction resistance to crosslink
these functional groups such as a carboxyl group with the following
crosslinking treatment.
[0064] These resins further neutralized are usable, and examples of
a base used for neutralization include an alkyl amine such as butyl
amine or trimethyl amine, an alkanol amine such as monoethanol
amine, diethanol amine or triethanol amine, morpholine, ammonia,
and an inorganic base such as sodium hydroxide or the like.
[0065] Examples of a high molecular material having an amide bond
and/or a urethane bond include a polyether type polyurethane resin,
a polyester type polyurethane resin or a polycarbonate type
polyurethane resin, which are obtained by using a polyether type
diol, a polyester type diol or a polycarbonate type diol.
[0066] Also, an acid value of the high molecular compound having an
amide bond and/or a urethane bond is not specially limited, but is
preferably from 5 to 100, more preferably from 10 to 80. Preferable
examples of the high molecular compound having an amide bond and/or
a urethane bond include NeORez R-960 (manufactured by Zeneca),
NeORez R-989 (manufactured by Zeneca), NeORez-9320 (manufactured by
Zeneca), NeORad NR-440 (manufactured by Zeneca), Hydran AP-30
(manufactured by Dainippon Ink and Chemicals, Incorporated), Hydran
APX-601 (manufactured by Dainippon Ink and Chemicals,
Incorporated), Hydran SP-510 (manufactured by Dainippon Ink and
Chemicals, Incorporated), Hydran SP-97 (manufactured by Dainippon
Ink and Chemicals, Incorporated), Elastron MF-60 (manufactured by
Daiichi Kogyo Seiyaku Co., Ltd.), Elastron MF-9 (manufactured by
Daiichi Kogyo Seiyaku Co., Ltd.), M-1064 (manufactured by Daiichi
Kogyo Seiyaku Co., Ltd.), Izelax S-1020 (manufactured BY Hodogaya
Chemical Co., Ltd.), Izelax S-1040 (manufactured by Hodogaya
Chemical Co., Ltd.), Izelax S-1085C (manufactured by Hodogaya
Chemical Co., Ltd.), Izelax S-4040N (manufactured by Hodogaya
Chemical Co., Ltd.), Neotan UE-5000 (manufactured by Toagosei Co.,
Ltd.), RU-40 series (manufactured by Stal Japan), Ucoat UWS-145
(manufactured by Sanyo Chemical Industries, Ltd.), Parmarin UA-150
(manufactured by Sanyo Chemical Industries, Ltd.), WF-41 series
(manufactured by Stal Japan) and WPC-101 (manufactured by Nippon
Polyuretahne Industry Co., Ltd.).
[0067] The resin having a urethane bond and/or an amide bond is
added in an amount of from 5 to 100 parts by weight, preferably
from 10 to 80 parts by weight, to 100 parts by weight of a pigment.
If the amount of the resin is less than 5 parts by weight to 100
parts by weight of a pigment, friction resistance of a recorded
material becomes poor, and stability as a lapse of time also
becomes poor. On the other hand, if the amount of the resin exceeds
100 parts by weight, a dispersion and an ink composition become
highly viscous, and an injecting performance becomes lowered,
thereby lowering gloss.
[0068] (Resin Adsorbed to Pigment and Free Resin)
[0069] The present invention is characterized by using a
combination of the above-mentioned water-soluble resin and the
resin having an amide bond and/or a urethane bond. An adding method
is not limited, but preferably the water-soluble resin is first
added to a pigment. Thereafter, the mixture is subjected to the
following kneading step to form a dispersion having the pigment
dispersed therein, and then it is preferable to add the resin
having an amide bond and/or a urethane bond to the dispersion. It
is preferable to carry out the following crosslinking treatment
before or after adding the resin having an amide bond and/or a
urethane bond. Particularly, it is preferable to carry out the
crosslinking treatment after adding the resin having an amide bond
and/or a urethane bond. It has been found that dispersion stability
and gloss are remarkably improved by adding the resins in this
manner. This is probably because the water-soluble resin is firmly
fixed onto the pigment surface in the kneading step to achieve a
desired dispersion state, and the water-soluble resin and the resin
having an amide bond and/or a urethane bond forms a film coated on
the pigment surface by the crosslinking reaction, and the film is
more firmly fixed and stabilized. At the same time, an amount of a
free resin not adsorbed on the pigment can be reduced, and the
added resin can effectively disperse the pigment, thereby achieving
quite satisfactory dispersion stability. Also, by using a urethane
resin having an acidic group introduced as the resin having an
amide bond and/or a urethane bond, particularly one having a
carboxyl group, these carboxyl groups are crosslinked with a
functional group such as a carboxyl group contained in the
previously added water-soluble resin by a crosslinking agent in the
crosslinking step, thus more firmly bonding to the pigment. It is
more preferable to carry out the crosslinking treatment after
adding the resin having an amide bond and/or a urethane bond, but
even before adding the resin having an amide bond and/or a urethane
bond, the crosslinking treatment may be carried out after adding
the water-soluble resin and the crosslinked water-soluble resin is
firmly fixed on the pigment to improve stability.
[0070] For example, this is proved by measuring a ratio of a resin
adsorbed on a pigment and other unadsorbed free resin by the
following method. The method for measuring an amount of an
unadsorbed resin comprises precipitating a pigment and a resin
content adsorbed on the pigment by an ultra-centrifugal machine,
and then measuring an amount of a remaining resin contained in the
supernatant liquid by TOC (total organic carbon meter) or
gravimetric method (method comprising evaporating the supernatant
liquid to solid and measuring a resin amount) (JP-A-2-255,875).
[0071] A particularly suitable method in the present invention
comprises subjecting a liquid to an ultra-high speed cooling
centrifugal machine (Beckman-made) at 55,000 rpm for 5 hours to
precipitate a pigment content and a resin content adsorbed on the
pigment, thereafter taking a predetermined amount of the
supernatant liquid or taking only a resin not adsorbed by a
membrane-separating method such as an ultrafiltration method, and
then drying to solid by a vacuum dryer (60.degree. C., 24 hours).
This resin amount is calculated by percentage as a remaining resin
concentration to the charged ink.
[0072] Firstly, a satisfactory dispersion can be achieved by
dispersing a pigment at a stage of adding a water-soluble resin,
and then a resin having an amide bond and/or a urethane bond is
added to carry out crosslinking treatment, thereby firmly fixing
the both resins to the pigment. Further, when a solvent having a
high permeability is added thereto, stability is improved and
agglomeration of pigments at the time of drying is hardly caused,
and smoothness of a paper surface is improved, thus improving gloss
also.
[0073] A weight ratio of a water-soluble resin and a resin having a
urethane bond and/or an amide bond is preferably (water-soluble
resin)/(resin having a urethane bond and/or an amide bond)=1/2 to
2/1 based on respective solid contents, and particularly when
printing in a weight ratio of ranging from 1/1.5 to 1.5/1, a
printed image becomes excellent in gloss.
[0074] (Kneading Step)
[0075] In the present invention, it is preferable to first knead a
pigment and the above-mentioned water-soluble resin. The kneading
step is not specially limited and a well known step may be employed
so long as the pigment and the water-soluble resin are kneaded in
contact with each other. A solid content ratio (weight) of pigment:
water-soluble resin is preferably 95:5-65:35, more preferably
90:10-70:30. Also, depending on the state of a pigment and a
water-soluble resin, a system of being mixed with water may be
employed, and in such a case, an ordinary stirrer may be
satisfactorily used. If necessary, a pigment may be wetted with a
water-soluble resin. Generally, a resin and a water-soluble resin,
and an organic resin added optionally as desired, are charged into
a kneading apparatus, and are kneaded therein.
[0076] The organic solvent used is not specially limited, but it is
preferable to use a solvent having such a high boiling point as not
being volatilized in the kneading step in order to prevent the
pigment from splashing during the step, and it is preferable to
have the resin dissolved by using a solvent having a lower boiling
point in combination.
[0077] Examples of the solvent having a high boiling point include
polyhydric alcohols such as ethylene glycol, propylene glycol,
diethylene glycol, dipropylene glycol, polyethylene glycol or
glycerin, pyrrolidones such as N-methyl-2-pyrrolidone or
2-pyrrolidone, and the like. An amount of the solvent used is
selected depending on a combination of a pigment and a resin in
such a manner as to apply an appropriate shear to a mixture of a
pigment and a resin during the kneading operation, and the solvent
is generally added in an amount of from 20 to 100 parts by weight,
preferably from 30 to 80 parts by weight, to 100 parts by weight of
a pigment.
[0078] Examples of the organic solvent having a low boiling point
used at the time of kneading include alcohols such as methanol,
ethanol or isopropyl alcohol, and ketones such as acetone or methyl
ethyl ketone.
[0079] A kneading apparatus employed is not specially limited so
long as it provides an appropriate shear to a mixture of a pigment
and a resin in contact with each other at the time of kneading, and
may be selected from general kneading apparatuses. Typical examples
include two-roll or three-roll rollers or kneaders. The mixture of
a pigment and a water-soluble resin in a kneading apparatus is
heated by the heat of the apparatus or self-heated by a shear force
received from the kneading apparatus, thereby raising a
temperature. It is desirable that the resin becomes a molten state
at this time, and that the pigment is pulverized by the shear force
provided from the kneading apparatus and is dispersed in the resin.
The kneading temperature is adjusted to be from 25 to 200.degree.
C., preferably from 100 to 150.degree. C.
[0080] Various methods are usable as a method for preparing an ink
composition or a pigment dispersion from the kneaded product of
pigment obtained in the above kneading step, but it is preferable
to neutralize a base of the resin with alkali.
[0081] The neutralization may be carried out by adding the pigment
kneaded product to a solvent having an alkaline compound added in
water, and mixing and stirring. The alkaline compound used for
neutralization is not specially limited. Examples of the alkaline
compound include organic amines such as ammonia, monomethanol
amine, diethanol amine, triethanol amine, morpholine or
2-amino-2-methyl-1-propanol; and alkali metal salts such as sodium
hydroxide, potassium hydroxide or ammonium hydroxide.
[0082] It is most idealistic that an amount of the alkaline
compound added is such an amount as to completely neutralize a
hydrophilic group in the resin, and accordingly it is preferable to
make a neutralization rate of 80 to 150%, particularly 90 to 120%,
which is determined by an equivalent amount of the alkaline
compound added and an acid equivalent amount of the resin.
[0083] It is preferable to heat the materials at the time of
neutralizing. The heating temperature is preferably from 40 to
100.degree. C., more preferably from 60 to 90.degree. C.
[0084] The pigment kneaded product is dispersed by a dispersing
machine such as a beads mill as described below. At this time,
various additives such as a preservative, a wetting agent and the
like may be added in addition to the pigment kneaded product, water
and alkali.
[0085] (Dispersing Step)
[0086] In the present invention, it is quite preferable to finely
pulverize a pigment by carrying out a dispersing step after the
above kneading step. Dispersing means are not specially limited,
and typical examples include various mechanical methods
conventionally employed in the preparation of a pigment fine
particle dispersion, e.g. a mechanical method such as a grinding
method using a ball mill and a pulverizing method by vibration such
as an ultrasonic dispersing machine. Further, it is well known to
employ a method of using a dispersing machine called as a sand
mill, a basket mill or a pearl mill for an apparatus of obtaining
finer particles.
[0087] It is preferable in the present invention to stir the
pigment kneaded product obtained in the above kneading step with a
dispersing medium and to disperse the product by a shear force of
the dispersing medium. The dispersing medium and a dispersing
machine used herein are not specially limited, and conventionally
well known various materials may be used. As a wet type pulverizing
apparatus carrying out dispersion by pass-system or multi-system,
it is particularly preferable to employ an apparatus having an
ability of separating a dispersing medium as fine beads having a
diameter of at most 0.5 mm.
[0088] The dispersing medium is not specially limited, but its
preferable examples include ceramics; hard glass such as soda glass
beads or alkali-free beads; hard plastic beads such as polymethyl
methacrylate beads; metals such as chrome beads or stainless steel
beads; or metal compounds such as zirconia. Zirconia is
particularly preferable since it can produce satisfactorily fine
particles.
[0089] In order to sufficiently disperse a pigment and to make
finer particles, an amount of a dispersing medium loaded into a
dispersing machine is at least 65%, preferably at least 70%, and a
mixing ratio of a dispersing medium and an aqueous pigment
composition (dispersing medium/aqueous pigment composition (volume
ratio)) is at least 1/30, preferably at least 1/25, and when
considering a practical operation efficiency, the mixing ratio is
preferably at most 1/1, more preferably at most 1/2.
[0090] Further, it is preferable to operate a wet system
pulverizing apparatus having the above-mentioned dispersing machine
at a peripheral velocity of at least 5 m/s, preferably at least 7
m/s, in respect of making fine particles of a pigment.
[0091] Further, the time of operating the wet system pulverizing
apparatus is not specially limited, but may be from about 2 to 150
minutes as a residence time of dispersion.
[0092] (Dispersion State)
[0093] It is preferable that a particle size is at least 5 nm and
at most 200 nm after dispersing a pigment. Further, it is
preferable to finally make a pigment having a particle size in a
range of from 5 to 100 nm by removing coarse particles by
centrifugal treatment. If the particle size exceeds 100 nm,
separation or settling of pigments tends to occur. On the other
hand, if the particle size is smaller than 5 nm, control or light
resistance performances of particles become poor. A particularly
preferable particle size is in a range of from 5 to 80 nm.
[0094] This particle size is a dispersed particle size (volume 50%
particle size) of pigment particles actually forming a dispersion,
and Microtrac UPA (LEEDS & NORTHRUP Co.) is used as a measuring
device.
[0095] (Crosslinking Treatment)
[0096] After dispersing a pigment, it is preferable to crosslink a
resin adsorbed on the pigment with a crosslinking agent. A pigment
is finely pulverized in a kneading step and a dispersing step, and
it is preferable to crosslink a resin in a dispersion state before
or after adding a resin having a urethane bond and/or an amide
bond. A crosslinking agent crosslinkable at a low temperature of
about 0 to 100.degree. C. is preferable as a crosslinking agent,
and a crosslinking agent of completely water-soluble type or
organic solvent-containing water-soluble type polymer or oligomer
is preferable in respect of providing a uniform reaction in an
aqueous dispersion, but is not limited thereto. This crosslinking
reaction is a reaction of producing a new chemical bond bonding
high molecular materials having a chain-like structure to newly
develop a tridimensional net-like structure, and includes a case of
further crosslinking high molecular materials already having a
partially crosslinked structure and also a case of precipitating a
higher molecular material from a dissolved resin. A curing reaction
is also included in the crosslinking reaction.
[0097] Examples of the crosslinking agent include a carboxyl
group-reactive type such as a polycarbodiimide type having a
carbodiimide group in a molecule, an oxazoline type having an
oxazoline group in a molecule or an aziridine type. Further
examples include a hydroxyl group-reactive type such as a melamine
resin type of butyrated melamine or full-etherified melamine, or an
isocyanate type represented as an aqueous block isocyanate. Still
further examples include a carbonyl group-reactive type such as a
dihydrazide type.
[0098] In addition to these examples, there are illustrated an
ethyleneimine type having an active amino group such as
polyethyleneimine, aminoethyl-modified ethyleneimine or
aziridinyl-modified ethyleneimine, an aliphatic amine such as
polymethylene diamine, an aromatic amine such as
diaminodiphenylmethane, an epoxy resin type having a glycidyl ether
structure, and an aqueous oligomer such as an acryl oligomer having
a (meth)acryloyl group. Examples of the aqueous oligomer include an
oligoester (meth)acrylate mainly having an ester bond, an epoxy
(meth)acrylate having an epoxy resin as a main structure, and the
like.
[0099] They are used respective alone or in a mixture of two or
more.
[0100] Among them, a carboxyl group-reactive type is particularly
preferable since it is excellent in dispersibility in a pigment
dispersion.
[0101] A blending ratio of a crosslinking agent to a resin is
preferably 1/100-50/100 at a weight ratio (crosslinking agent/resin
(effective solid content weight ratio)). If the weight ratio is
smaller than 1/100, a crosslinking effect becomes poor and
stability of a dispersion or an ink becomes poor, and if the weight
ratio is larger than 50/100, agglomeration of pigments tends to
occur and a viscosity of the liquid becomes high.
[0102] In order to make the crosslinking reaction fully proceed,
the weight ratio should be at least 1/100, preferably at least
2/100, and in order to prevent qualities of an aqueous pigment
dispersion from lowering due to an excess amount of a crosslinking
agent, the weight ratio is at most 50/100, preferably at most
45/100, and any further improvement of the crosslinking effect can
not be expected if the weight ratio is still larger.
[0103] Also, it is possible to cause crosslinking without a
crosslinking agent. In such a case, a combination of at least two
kinds of crosslinkable functional groups must be contained in a
molecule.
[0104] Examples of a self-crosslinkable functional group include a
radical-polymerizable unsaturated functional group and a
hydrolyzable alkoxysilane group.
[0105] Examples of a combination of such radical-polyemerizable
unsaturated functional groups include preferably a combination of a
carboxyl group and an epoxy group, a combination of a carboxyl
group and a 1,3-dioxolan-2-on-4-yl group, a combination of a
hydroxyl group and a blocked isocyanate group, a combination of a
hydroxyl group and a N-alkoxymethylamide group, a combination of a
hydroxyl group and a hydrolyzable alkoxysilane group or a
combination of an amino group and an epoxy group, and a
self-crosslinkable functional group may be introduced when
copolymerizing the above-mentioned hydrophobic monomer and
hydrophilic monomer.
[0106] Temperature and time for crosslinking a resin are not
specially limited, and may be adjusted depending on kinds of a
resin and a crosslinking agent employed.
[0107] pH at the time of finishing the crosslinking reaction may be
in a range of from 7.0 to 10.0, and if pH is at most 7.0, there is
a possibility that a water-soluble resin dissolved by
naturalization tends to precipitate, and stability as a lapse of
time becomes poor.
[0108] Depending on a crosslinking reaction, there are a case of
initiating a curing reaction of a functional group at the same time
as splashing water, a solvent and an organic amine under heating
condition and a case of causing polymerization-curing by an organic
amine working as a radical-generating source. In any case,
tridimensional crosslinking proceeds to form a film firmly bonded
to a pigment, thereby improving dispersion stability, and by
producing a higher molecular material, gloss is improved.
[0109] The crosslinking treatment achieves remarkable effects of
not causing agglomeration and adsorption among pigment particles in
water, maintaining a function of a resin itself as a dispersant,
curing and stabilizing. Accordingly, it is preferable to maintain a
functional group, e.g. a polar group such as a carboxyl group,
necessary for maintaining a resin itself in a dissolved state
without completely reacting the functional group in a resin, even
after crosslinking
[0110] By carrying out such a crosslinking step of resin after
dispersing a pigment with the resin, a dispersing effect becomes
higher and an aqueous pigment dispersion having a small particle
size excellent in stability as a lapse of time can be obtained, as
compared with a case of dispersing a pigment with a previously
crosslinked resin.
[0111] As a method for fixing a resin to the surroundings of a
pigment, there is known a method of employing a precipitation
reaction with a poor solvent, but the present method of combining a
dispersing step and a crosslinking step has a merit of easily
producing fine particles.
[0112] (Gel Fraction)
[0113] A crosslinking rate of a resin in a dispersion, i.e.
so-called a gel fraction, is preferably from 20 to 100%. In order
to achieve such physical properties as alkali resistance and
solvent resistance, the gel fraction is preferably at least 30%,
more preferably at least 35%. The upper limit of the gel fraction
is 100%, and a higher gel fraction is more preferable.
[0114] The gel fraction is generally considered as a measure of a
crosslinking degree of a resin, but the gel fraction in the present
invention is calculated from a numerical value determined by
measuring an elution amount of a resin by drying an aqueous pigment
dispersion to powder and using tetrahydrofuran as a solvent.
[0115] For example, an aqueous pigment dispersion is freeze-dried
and 10 g of the obtained powder is placed in 100 ml of
tetrahydrofuran and is stirred at 60.degree. C. for 1 hour. A gel
fraction is calculated by measuring a solid content of a resin
amount eluted in tetrahydrofuran and making an elution amount at
the time of not crosslinking as "blank".
Gel fraction=(blank elution amount-elution amount after
crosslinking treatment)/blank elution amount
[0116] Also, a weight average molecular weight of a crosslinked
resin is preferably at least 30,000, more preferably at least
200,000, in respect of fully improving properties of an aimed
aqueous pigment dispersion. A larger weight average molecular
weight is more preferable.
[0117] Thus, by crosslinking a resin, a dispersion containing a
pigment and a crosslinked resin is obtained.
[0118] It is preferable to improve stability as a lapse of time by
adjusting pH of the dispersion containing a crosslinked resin to
the alkali side. It is preferable to adjust to pH of at least 8,
more preferably pH of 8.5-10.
[0119] (With Regard to Ion Exchange)
[0120] It is preferable to adjust a divalent metal ion content in
an aqueous pigment dispersion to at most 100 ppm by treating with
an ion exchange resin or the like. It is more preferable to adjust
to 50 ppm.
[0121] It is possible to use a weak acidic cation exchange resin, a
strong acidic cation exchange resin or the like as a cation
exchange resin. A well known ion exchange resin is usable, and it
is possible to use a commercially available ion exchange resin.
[0122] Contact of a dispersion and an ion exchange resin is
effected by a method of passing a dispersion through an ion
exchange-treating tower or column apparatus, or a method of simply
mechanically mixing and stirring a dispersion and an ion exchange
resin, or other optional methods. A metal ion content can be
measured by an atomic absorption photometer Z-8230 (Hitachi, Ltd.)
or an ICP analyzing apparatus SPQ9000 (Seiko Denshi Corporation),
and the numerical values in the present invention were measured by
these apparatuses.
[0123] By reducing a multi-valent metal ion content considered to
cause agglomeration, stability of a recording ink as a lapse of
time can be achieved, and by preventing agglomeration of an organic
pigment, a viscosity increase of a recording ink can be controlled,
thereby improving an injecting property of recording ink. A
multi-valent ion content in a recording ink is preferably at most
100 ppm, more preferably at most 80 ppm.
[0124] One of methods of removing multi-valent metal ions is to
treat a dispersion or a recording ink with a cation exchange resin.
The cation exchange resin (weak acidic cation exchange resin,
strong acidic cation exchange resin) used is not specially limited
so long as it removes a multi-valent metal ion, and a commercially
available cation exchange resin may be appropriately selected.
Examples of the commercially available cation exchange resin
include .left brkt-top.DIAION WK 10.right brkt-bot., .left
brkt-top.DIAION WK 11.right brkt-bot., .left brkt-top.DIAION WK
20.right brkt-bot., .left brkt-top.DIAION PA 406.right brkt-bot.,
.left brkt-top.DIAION PA 408.right brkt-bot., .left brkt-top.DIAION
PA 412.right brkt-bot., .left brkt-top.DIAION PA 416.right
brkt-bot., .left brkt-top.DIAION PA 418.right brkt-bot., .left
brkt-top.DIAION PK 208.right brkt-bot., .left brkt-top.DIAION PK
212.right brkt-bot., .left brkt-top.DIAION PK 216.right brkt-bot.,
.left brkt-top.DIAION PK 220.right brkt-bot. and .left
brkt-top.DIAION PK 228.right brkt-bot. (manufactured by Mitsubishi
Chemical Corporation), .left brkt-top.Amberlite IR-118H.right
brkt-bot., .left brkt-top.Amberlite IR-120B.right brkt-bot., .left
brkt-top.Amberlite IR-122.right brkt-bot., .left brkt-top.Amberlite
IR-124.right brkt-bot., .left brkt-top.Amberlite 252.right
brkt-bot., .left brkt-top.Amberlite 201CT.right brkt-bot., .left
brkt-top.Amberlite 200C.right brkt-bot., .left brkt-top.Amberlite
IRC-50.right brkt-bot. and .left brkt-top.Amberlite IRC-84.right
brkt-bot. (manufactured by Organo Corporation).
[0125] If necessary, the treatment may be carried out in
combination with an anion exchange resin (weak basic anion exchange
resin, medium basic anion exchange resin or strong basic anion
exchange resin) treatment. Examples of the anion exchange resin
include .left brkt-top.DIAION WA 10.right brkt-bot., .left
brkt-top.DIAION WA 11.right brkt-bot., .left brkt-top.DIAION WA
20.right brkt-bot., .left brkt-top.DIAION WA 21.right brkt-bot.,
.left brkt-top.DIAION WA 30.right brkt-bot., .left brkt-top.DIAION
PA 406.right brkt-bot., .left brkt-top.DIAION PA 408.right
brkt-bot., .left brkt-top.DIAION PA 412.right brkt-bot., .left
brkt-top.DIAION PA 416.right brkt-bot., .left brkt-top.DIAION PA
418.right brkt-bot., .left brkt-top.DIAION PA 306.right brkt-bot.,
.left brkt-top.DIAION PA 308.right brkt-bot., .left brkt-top.DIAION
PA 312.right brkt-bot., .left brkt-top.DIAION PA 316.right
brkt-bot., .left brkt-top.DIAION PA 318.right brkt-bot., .left
brkt-top.DIAION SA 10A.right brkt-bot., .left brkt-top.DIAION SA
11A.right brkt-bot., .left brkt-top.DIAION SA 12A.right brkt-bot.,
.left brkt-top.DIAION SA 20A.right brkt-bot. and .left
brkt-top.DIAION SA 21A.right brkt-bot. (manufactured by Mitsubishi
Chemical Corporation), .left brkt-top.Amberlite IRA-400T.right
brkt-bot., .left brkt-top.Amberlite IRA-430.right brkt-bot., .left
brkt-top.Amberlite IRA-458.right brkt-bot., .left
brkt-top.Amberlite IRA-458.right brkt-bot., .left
brkt-top.Amberlite IRA-900.right brkt-bot., .left
brkt-top.Amberlite IRA-904.right brkt-bot., .left
brkt-top.Amberlite IRA-938.right brkt-bot., .left
brkt-top.Amberlite IRA-958.right brkt-bot., .left
brkt-top.Amberlite IRA-410.right brkt-bot., .left
brkt-top.Amberlite IRA-411.right brkt-bot., .left
brkt-top.Amberlite IRA-91.right brkt-bot., .left brkt-top.Amberlite
IRA-68.right brkt-bot., .left brkt-top.Amberlite IRA-35.right
brkt-bot. and .left brkt-top.Amberlite IRA-93.right brkt-bot.
(manufactured by Organo Corporation).
[0126] (With Regard to Ultrafiltration)
[0127] As a method for removing impurities, an ultrafiltration
membrane is used. Generally, this means a treatment with a
separating membrane capable of removing each component from
compounds having respectively from a low molecular weight to a high
molecular weight and ionic materials in a solution by each kind of
membranes.
[0128] Examples of impurities include a material remaining at the
time of preparing a pigment, an excess component in a dispersion
liquid composition, a dispersant not adsorbed on an organic
pigment, and a contaminating component.
[0129] A molecular weight of a material separatable by an
ultrafiltration membrane varies depending on its fractional
molecular weight of the ultrafiltration membrane. For example, when
a fractional molecular weight of the ultrafiltration membrane used
in the treatment is 1000, only a material having a molecular weight
of at most 1000 is separatable from a solvent.
[0130] (Pigment Dispersion Liquid)
[0131] The pigment dispersion liquid of the present invention
contains a dispersion medium in addition to the above-described
pigment and specific resins. The dispersion medium is not specially
limited, and a dispersion medium conventionally used for a pigment
dispersion liquid can be selected. For example, water and other
aqueous medium are preferable, but other various organic solvents
may be contained. The aqueous medium used herein means water or a
water-soluble solvent compatible with water. It is particularly
preferable to use an ion-exchanged water as water, but it is not
limited thereto. A water-soluble solvent is preferably selected
from solvents used in an ink composition described below.
[0132] Other components in the pigment dispersion liquid are not
specially limited and optimally selected so long as they do not
adversely affect physical properties of the dispersion or do not
adversely affect the preparation of an ink, and may include a
solvent selected from an organic solvent used in an ink composition
for ink jet described below or an additive such as a
mildew-proofing agent to an aqueous ink composition using an
aqueous medium.
[0133] (Ink Composition for Ink Jet)
[0134] The ink composition of the present invention is an ink
composition for ink jet having a pigment dispersed, and is an ink
composition for ink jet characterized by containing a water-soluble
resin and a resin having a urethane bond and/or an amide bond.
[0135] The preparation method of the ink composition of the present
invention is not specially limited, but it is preferable to prepare
a pigment dispersion liquid by the above-mentioned method and to
remove coarse particles contained therein by centrifugal treatment,
and thereafter it is preferable to proceed with an ink-producing
step by adding an organic solvent such as a water-soluble organic
solvent.
[0136] A content of a pigment in the ink composition is preferably
at least 0.5 wt %, more preferably at least 2 wt %, in order to
satisfactorily achieve a coloring effect, and is preferably at most
25 wt %, more preferably at most 10 wt %, in order to provide an
appropriate viscosity for maintaining a satisfactory injecting
performance at the viscosity of the ink composition.
[0137] Examples of a preferable water-soluble organic solvent
include ethylene glycol, diethylene glycol, triethylene glycol,
polyethylene glycol, propylene glycol, butylene glycol,
1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin,
diglycerin, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,5-pentanediol,
1,3-dimethyl-2-imidazolidinone and the like, and they may be used
respective alone or in a mixture of two or more.
[0138] The water-soluble organic solvent is added in an amount of
from 5 to 30 wt %, preferably from 6 to 25 wt %, to an ink liquid,
and if the water-soluble organic solvent is added in an amount of
higher than the above upper limit, the ink itself becomes highly
viscous, and consequently stability and injecting performance of
the ink become poor, a blur into a paper becomes large, and a
drying speed becomes low. Particularly, it is preferable that the
viscosity is at most 20 mPa.multidot.s.
[0139] In addition to the above solvents, other water-soluble
organic solvents may be used, examples of which include methanol,
ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol,
t-butanol, trimethylolpropane, ethylene glycol monoethyl ether,
ethylene glycol monobutyl ether, and the like.
[0140] Further, the ink composition of the present invention may
contain such additives as a mildew-proofing agent, a defoaming
agent, a rust-proofing agent, an antiseptic agent and the like.
[0141] As described above, the ink composition of the present
invention is excellent particularly as an ink for ink jet. For
example, the ink composition is applicable to an ink jet recording
method characterized in that printing is carried out by injecting
the ink composition through a nozzle of an ink jet printer or an
ink jet recording method characterized in that recording is carried
out by liquid droplets formed by applying heat energy to the ink
composition. Further, the ink composition of the present invention
is applicable to an ink jet recording method characterized in that
recording is carried out by liquid droplets formed by applying a
mechanical energy to the ink composition.
[0142] (With Regard to Preparation of High Permeability)
[0143] The ink composition of the present invention is particularly
suitable for being used as an ink jet ink having a high
permeability. For example, conventionally known various methods can
be employed for raising a high permeability. For instance,
JP-A-2001-302,950 illustrates an ink composition having an improved
permeability to a recording medium and having an excellent
continuous injecting stability by containing a surfactant having an
acetylene bond. Also, it is possible to add a propylene oxide
adduct of a lower alcohol.
[0144] Further, JP-A-2002-3760 illustrates one containing a
compound of the following chemical formula (1) having an acetylene
bond, 1,5-pentanediol, and a butyl ether type solvent. 1
[0145] Further, JP-A-2002-30,237 illustrates an ink composition
containing an acetylene glycol type surfactant and/or a
polysiloxane type surfactant, an alkylether derivative of a
polyhydric alcohol, the alkyl carbon number of which is at least 3
(preferably from 3 to 6), as an organic solvent, and/or
1,2-alkanediol, as a satisfactory ink composition having an
excellent color reproducibility, a high permeability and a short
drying time.
[0146] As described in JP-A-2002-30,237, examples of an organic
solvent include ethylene glycol monobutyl ether, diethylene glycol
mono-n-propyl ether, ethylene glycol monoethyl ether, ethylene
glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl
ether, ethylene glycol mono-n-propyl ether, ethylene glycol
mono-t-butyl ether, diethylene glycol mono-n-butyl ether,
triethylene glycol mono-n-butyl ether, diethylene glycol
mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol
mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene
glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether,
dipropylene glycol mono-n-butyl ether, dipropylene glycol
mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, and
the like.
[0147] As described in JP-A-2002-30,237, examples of a
1,2-alkanediol include preferably 1,2-C.sub.1C.sub.8 alkanediol,
more preferably 1,2-C.sub.1C.sub.6 alkanediol, most preferably
1,2-hexanediol. The 1,2-alkanediol is added in an amount of from 1
to 15 wt %, preferably 2 to 10 wt %.
[0148] Preferable examples of an acetylene glycol type surfactant
include various compounds illustrated in JP-A-2002-30237. More
particular examples include Surfynol 82, 104, 440, 465, 485, TG
(manufactured by Air Products and Chemicals, Inc.), Orfin STG,
E1010 (manufactured by Nisshin Kagaku K.K.), and the like.
EXAMPLES
[0149] The present invention is further illustrated with reference
to the following Examples. In the Examples, "part" means "part by
weight", and "%" means "wt %".
Example 1
[0150] The following respective components were charged into a
pressure kneader, and were kneaded at room temperature for 10 hours
to prepare a pigment kneaded product.
1 (P.R122 (C.I. 73915) 100.0 Styrene-methylstyrene-acrylic acid
copolymer 20.0 (acid value 200, weight average molecular weight
7500, glass transition temperature 80.degree. C.) Glycerin 67.0
Isopropyl alcohol 20.0
[0151] Thereafter, 42 parts of the above obtained pigment kneaded
product, 3 parts of triethanolamine and 55 parts of ion-exchanged
water were mixed, and were stirred under heating at 95.degree. C.
for 2 hours, and were subjected to 3 pass treatment using 0.5 mm
glass beads in a sand mill to prepare a dispersion liquid.
[0152] The dispersion liquid was adjusted to pH 8.5 with sodium
hydroxide, and was subjected to centrifugal treatment at 25000 G
for 5 minutes to remove coarse particles. After removing the coarse
particles, the dispersion liquid had a solid content of 26.0%, a pH
value of 8.3 and a pigment particle size (volume 50% dispersion
size) of 75.2 nm.
[0153] 10.0 Parts of a polyester type polyurethane resin (acid
value 20, triethylamine neutralization, solid content 35%) and 5
parts of a 30% polycarbodiimide type crosslinking agent
(carbodiimide equivalent 300, completely water-soluble) were added
to the dispersion liquid, and the resultant mixture was stirred at
90.degree. C. for 5 hours to crosslink the resin in the dispersion
liquid. At the time of finishing the crosslinking reaction, pH was
7.4. Gel fraction exceeded 35%. Further, solid content
concentration was adjusted to 20 wt %. The dispersion liquid thus
prepared is referred to as "magenta dispersion". An ink composition
was prepared by using the magenta dispersion thus obtained and the
following components.
2 Component Amount (parts) Magenta dispersion (solid content 20%)
15.0 Diethylene glycol 15.0 Diethyleneglycol mono-n-propyl ether
10.0 Glycerin 4.0 Orfin STG 1.0 Antiseptic agent
(benzisothiazoline) 0.2 Ion exchanged water 54.8
[0154] The above components were stirred for 30 minutes to form an
ink composition.
[0155] (Evaluation Test)
[0156] The above obtained composition was tested to evaluate
stability as a lapse of time and injecting performance in
accordance with the following methods, and the results are shown in
the following Table 1.
[0157] (a) Test for Stability as A Lapse of Time
[0158] The ink composition was allowed to stand in a constant
temperature room at 50.degree. C. for 1 month, and presence or
absence of separation of pigment, water floating and precipitation
as well as changes in viscosity and average particle size of
pigment were observed. It was evaluated as "abnormal" when the
separation of pigment, water floating and precipitation occurred
even at a small degree or the changes in viscosity and average
particle size of pigment were caused.
[0159] As this result, normal state was expressed as
".largecircle.", and abnormal state was expressed as "X"
[0160] (b) Test for Injecting Performance
[0161] The ink composition charged into a cartridge, and 200 paper
sheets were printed at 2880.times.1440 dpi (4 pl) by using a
printer "PM-4000PX" (manufactured by Seiko Epson Corporation). The
paper sheet used was PM photographic paper<gloss>
(manufactured by Seiko Epson Corporation). It was evaluated as
"abnormal" when clogging of a nozzle or unsatisfactory printing was
caused even at a small degree.
[0162] Normal state was expressed as ".largecircle.", and abnormal
state was expressed as X
[0163] (c) Gloss
[0164] The paper sheet printed by the above injecting performance
test (b) was measured with regard to gloss on 200 mirror surface by
using a gloss meter VG2000 (manufactured by Nippon Denshoku Kogyo
K.K.).
[0165] (d) Friction Resistance
[0166] The above printed paper sheet was rubbed with a hand to
evaluate friction resistance. The results were expressed as
".largecircle." (excellent), ".DELTA." (acceptable) and "X"
(unacceptable), and are shown in the following Table 1.
Comparative Example 1
[0167] An ink composition was prepared in the same manner as in
Example 1, except that the polyester type polyurethane resin was
not added. The same evaluation tests as in Example 1 were carried
out, and the results are shown in the following Table 1.
Example 2
[0168] The following respective components were charged into a
pressure kneader, and were kneaded at room temperature for 8 hours
to prepare a pigment kneaded product.
3 (P.Y14 (C.I. 21095) 100.0 Styrene-methylstyrene-acrylic acid
copolymer 20.0 (acid value 160, weight average molecular weight
8000, glass transition temperature 75.degree. C.) Glycerin 67.0
Isopropyl alcohol 20.0
[0169] Thereafter, 42 parts of the above obtained pigment kneaded
product, 1.5 parts of KOH and 56.5 parts of ion-exchanged water
were mixed, and were stirred under heating at 80.degree. C. for 2
hours, and were subjected to 3 pass treatment using 0.5 mm glass
beads in a sand mill to prepare a dispersion liquid.
[0170] The dispersion liquid was adjusted to pH 8.5 with sodium
hydroxide, and was subjected to centrifugal treatment at 25000 G
for 5 minutes to remove coarse particles. After removing the coarse
particles, the dispersion liquid had a solid content of 26.8%, a pH
value of 8.4 and a pigment particle size (volume 50% dispersion
size) of 9.8 nm.
[0171] 4 Parts of a polycarbonate type polyurethane resin (acid
value 30, triethylamine neutralization, solid content 40%) and 2
parts of a 30% polyethyleneimine type crosslinking agent (amine
hydrogen equivalent 650, completely water-soluble) were added to
the dispersion liquid, and the resultant mixture was stirred at
90.degree. C. for 3.5 hours to crosslink the resin in the
dispersion liquid.
[0172] At the time of finishing the crosslinking reaction, pH was
7.8. Gel fraction exceeded 35%. Further, solid content
concentration was adjusted to 20 wt %. The dispersion liquid thus
prepared is referred to as "yellow dispersion". An ink composition
was prepared by using the yellow dispersion thus obtained and the
following components.
4 Component Amount (parts) Yellow dispersion (solid content 20%)
15.0 Diethylene glycol 10.0 Ethylene glycol monobutyl ether 10.0
Glycerin 7.0 Surfynol 485 0.5 Antiseptic agent (benzisothiazoline)
0.2 Ion exchanged water 57.3
[0173] The above components were stirred for 30 minutes to form an
ink composition. The evaluation test was carried out in the same
manner as in Example 1, and the results are shown in the following
Table 1.
Example 3
[0174] The following respective components were charged into a
pressure kneader, and were kneaded at room temperature for 8 hours
to prepare a pigment kneaded product.
5 (Pigment.Blue 15:3 (C.I. 74160) 100.0 Styrene-acrylic acid
copolymer 20.0 (acid value 75, weight average molecular weight
12000, glass transition temperature 70.degree. C.) Glycerin 67.0
Isopropyl alcohol 20.0
[0175] Thereafter, 42 parts of the above obtained pigment kneaded
product, 3.5 parts of triethanolamine and 54.5 parts of
ion-exchanged water were mixed, and were stirred under heating at
80.degree. C. for 2 hours, and were subjected to 3 pass treatment
using 0.5 mm glass beads in a sand mill to prepare a dispersion
liquid.
[0176] The dispersion liquid was adjusted to pH 8.5 with sodium
hydroxide, and was subjected to centrifugal treatment at 25000 G
for 5 minutes to remove coarse particles. After removing the coarse
particles, the dispersion liquid had a solid content of 25.9%, a pH
value of 8.3 and a pigment particle size (volume 50% dispersion
size) of 56.3 nm.
[0177] 40 Parts of a polyether type polyurethane resin (acid value
50, triethylamine neutralization, solid content 25%) and 8 parts of
a 20% epoxy resin (epoxy equivalent 200) were added to the
dispersion liquid, and the resultant mixture was stirred at
90.degree. C. for 5 hours to crosslink the dispersed resin in the
dispersion liquid.
[0178] At the time of finishing the crosslinking reaction, pH was
7.8. Gel fraction exceeded 35%.
[0179] Further, solid content concentration was adjusted to 20 wt
%. The dispersion liquid thus prepared is referred to as "blue
dispersion". An ink composition was prepared by using the blue
dispersion thus obtained and the following components.
6 Component Amount (parts) Blue dispersion (solid content 20%) 15.0
Ethylene glycol monoethyl ether 10.0 2-Pyrrolidone 5.0
1,2-Hexanediol 10.0 Surfynol 465 0.5 Antiseptic agent
(benzisothiazoline) 0.2 Ion exchanged water 59.3
[0180] The above components were stirred for 30 minutes to form an
ink composition. The evaluation test was carried out in the same
manner as in Example 1, and the results are shown in the following
Table 1.
Example 4
[0181] The following respective components were charged into a
pressure kneader, and were kneaded at room temperature for 12 hours
to prepare a pigment kneaded product.
7 (Pigment.Green 7 (C.I. 74260) 100.0 Ethyl
methacrylate-methacrylic acid copolymer 20.0 (acid value 120,
weight average molecular weight 15000, glass transition temperature
65.degree. C.) Glycerin 67.0 Isopropyl alcohol 20.0
[0182] Thereafter, 42 parts of the above obtained pigment kneaded
product, 2.5 parts of triethanolamine and 55.5 parts of
ion-exchanged water were mixed, and were stirred under heating at
80.degree. C. for 2 hours, and were subjected to 3 pass treatment
using 0.5 mm glass beads in a sand mill to prepare a dispersion
liquid.
[0183] The dispersion liquid was adjusted to pH 8.5 with sodium
hydroxide, and was subjected to centrifugal treatment at 25000 G
for 5 minutes to remove coarse particles. After removing the coarse
particles, the dispersion liquid had a solid content of 25.5%, a pH
value of 8.4 and a pigment particle size (volume 50% dispersion
size) of 81.1 nm.
[0184] 4 Parts of a polycarbonate type polyurethane resin (acid
value 30, triethylamine neutralization, solid content 40%) and 2
parts of a 30% polyethyleneimine type crosslinking agent (amine
hydrogen equivalent 650, completely water-soluble) were added to
the dispersion liquid, and the resultant mixture was stirred at
90.degree. C. for 2.5 hours to crosslink the resin in the
dispersion liquid.
[0185] At the time of finishing the crosslinking reaction, pH was
7.6. Gel fraction exceeded 35%. Further, solid content
concentration was adjusted to 20 wt %. The dispersion liquid thus
prepared is referred to as "green dispersion". An ink composition
was prepared by using the green dispersion thus obtained and the
following components.
8 Component Amount (parts) Green dispersion (solid content 20%)
15.0 Propylene glycol mono-n-butyl ether 15.0 2-Pyrrolidone 10.0
Isopropanol 3.0 Orfin STG 0.5 Antiseptic agent (benzisothiazoline)
0.2 Ion exchanged water 56.3
[0186] The above components were stirred for 30 minutes to form an
ink composition.
Comparative Example 2
[0187] The following respective components were charged into a
pressure kneader, and were kneaded at room temperature for 8 hours
to prepare a pigment kneaded product.
[0188] An ink composition was prepared in the same manner as in
Example 4, except that the polycarbonate type polyurethane resin
was not added. The same evaluation tests as in Example 1 were
carried out, and the results are shown in the following Table
1.
Example 5
[0189]
9 (Pigment.Red 22 (C.I. 12315) 100.0 Styrene-maleic acid copolymer
20.0 (acid value 180, weight average molecular weight 3000, glass
transition temperature 65.degree. C.) Glycerin 67.0 Isopropyl
alcohol 20.0
[0190] Thereafter, 42 parts of the above obtained pigment kneaded
product, 3.0 parts of triethanolamine and 55.0 parts of
ion-exchanged water were mixed, and were stirred under heating at
85.degree. C. for 2 hours, and were subjected to 3 pass treatment
using 0.5 mm glass beads in a sand mill to prepare a dispersion
liquid.
[0191] The dispersion liquid was adjusted to pH 8.5 with sodium
hydroxide, and was subjected to centrifugal treatment at 25000 G
for 5 minutes to remove coarse particles. After removing the coarse
particles, the dispersion liquid had a solid content of 26.0%, a pH
value of 8.4 and a pigment particle size (volume 50% dispersion
size) of 64.8 nm.
[0192] 5 Parts of a polyether type polyurethane resin (acid value
50, triethylamine neutralization, solid content 40%) and 1 part of
a 35% oxazoline type crosslinking agent (oxazoline equivalent 200)
were added to the dispersion liquid, and the resultant mixture was
stirred at 80.degree. C. for 2.5 hours to crosslink the resin in
the dispersion liquid.
[0193] At the time of finishing the crosslinking reaction, pH was
7.5. Gel fraction exceeded 35%. Further, solid content
concentration was adjusted to 20 wt %. The dispersion liquid thus
prepared is referred to as "red dispersion". An ink composition was
prepared by using the red dispersion thus obtained and the
following components.
10 Component Amount (parts) Red dispersion (solid content 20%) 15.0
Ethylene glycol 15.0 Triethylene glycol monobutyl ether 10. 0
Isopropanol 1.0 Surfynol 485 0.7 Antiseptic agent
(benzisothiazoline) 0.2 Ion exchanged water 58.1
[0194] The above components were stirred for 30 minutes to form an
ink composition.
Example 6
[0195] An ink composition was prepared in the same manner as in
Example 2, except that the polycarbodiimide type crosslinking agent
was not added. The same evaluation tests as in Example 1 were
carried out, and the results are shown in the following Table
1.
Example 7
[0196] An ink composition was prepared in the same manner as in
Example 3, except that the kneading step was not carried out. The
same evaluation tests as in Example 1 were carried out, and the
results are shown in the following Table 1.
Example 8
[0197] An ink composition was prepared in the same manner as in
Example 5, except that the centrifugal treatment of removing coarse
particles was not carried out. The same evaluation tests as in
Example 1 were carried out, and the results are shown in the
following Table 1.
11 TABLE 1 Stability as a Injecting Gloss Friction lapse of time
performance value resistance Example 1 .largecircle. .largecircle.
61.1 .largecircle. Example 2 .largecircle. .largecircle. 78.5
.largecircle. Example 3 .largecircle. .largecircle. 58.6
.largecircle. Example 4 .largecircle. .largecircle. 54.3
.largecircle. Example 5 .largecircle. .largecircle. 63.9
.largecircle. Example 6 X .largecircle. 77.9 .DELTA. Example 7
.largecircle. .largecircle. 41.2 .DELTA. Example 8 .largecircle. X
36.8 .DELTA. Comp. Ex. 1 X .largecircle. 49.6 X Comp. Ex. 2 X
.largecircle. 47.3 X
[0198] As evident from the above results, such a pigment dispersion
for ink jet having a pigment dispersed as an aqueous pigment
dispersion, characterized by containing a water-soluble resin and a
resin having a urethane bond and/or an amide bond, and an ink
composition using the same, are greatly improved in stability in a
highly permeable solvent, and have excellent friction resistance
and gloss.
INDUSTRIAL APPLICABILITY
[0199] The present invention can provide a pigment dispersion for
ink jet and an ink composition for ink jet, which are greatly
improved in stability in a highly permeable solvent and have
excellent friction resistance and gloss.
* * * * *