U.S. patent application number 11/575193 was filed with the patent office on 2008-04-24 for water-based inks for ink-jet printing.
This patent application is currently assigned to Kao Corporation. Invention is credited to Yasuhiro Doi, Yasushi Ito, Shigeki Nagashima, Nobuyuki Takizawa.
Application Number | 20080097015 11/575193 |
Document ID | / |
Family ID | 35453509 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080097015 |
Kind Code |
A1 |
Doi; Yasuhiro ; et
al. |
April 24, 2008 |
Water-Based Inks for Ink-Jet Printing
Abstract
The present invention relates to a water-based ink for ink-jet
printing which not only satisfies a high optical density but also
exhibits an excellent high lighter-fastness; a water dispersion
used for the water-based ink; and a method for producing a print
using the water-based ink. There are provided a water dispersion
for ink-jet printing comprising (i) (A-1) polymer particles
containing a colorant, (B) polymer particles and (C) the
water-insoluble organic compound, or (ii) (A-2) self-dispersible
pigment, (B) polymer particles and (C) the water-insoluble organic
compound; a water-based ink containing the water dispersion; and a
method for producing a print using the water-based ink.
Inventors: |
Doi; Yasuhiro; (Wakayama,
JP) ; Ito; Yasushi; (Wakayama, JP) ; Takizawa;
Nobuyuki; (Wakayama, JP) ; Nagashima; Shigeki;
(Wakayama, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Kao Corporation
14-10, Nihonbashi Kayabacho 1-chome
Cho-ku
JP
103-8210
|
Family ID: |
35453509 |
Appl. No.: |
11/575193 |
Filed: |
October 6, 2005 |
PCT Filed: |
October 6, 2005 |
PCT NO: |
PCT/JP05/18828 |
371 Date: |
March 13, 2007 |
Current U.S.
Class: |
524/115 ;
524/284; 524/315; 524/366 |
Current CPC
Class: |
C09D 11/32 20130101 |
Class at
Publication: |
524/115 ;
524/284; 524/315; 524/366 |
International
Class: |
C09D 11/00 20060101
C09D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 7, 2004 |
JP |
2004-295464 |
Mar 8, 2005 |
JP |
2005-064054 |
Claims
1: A water dispersion for ink-jet printing comprising (A-1) polymer
particles containing an colorant (B) polymer particles and (C) a
water-insoluble organic compound.
2: A water dispersion for ink-jet printing comprising (A-2)
self-dispersible pigment (B) polymer particles and (C) a
water-insoluble organic compound.
3: The water dispersion for ink-jet printing according to claim 1,
wherein the polymer particles (B) are self-emulsifiable polymer
particles containing a constitutional unit derived from a
salt-forming group-containing monomer.
4: The water dispersion for ink-jet printing according to claim 1,
wherein the polymer particles (B) are polymer particles produced by
emulsion-polymerizing an ethylenically unsaturated monomer in the
presence of a reactive surfactant.
5: The water dispersion for ink-jet printing according to claim 1,
wherein the water-insoluble organic compound (C) is an ester or
ether compound (f) containing two or more ester or ether bonds in a
molecule thereof, and/or an ester or ether compound (g) containing
one or more ester or ether bonds and at east one functional group
selected from the group consisting of a carboxyl group, a sulfonic
group, a phosphoric acid residue, a carbonyl group, an epoxy group
and a hydroxyl group.
6: The water dispersion for ink-jet printing according to claim 1,
wherein the water-insoluble organic compound (C) is at least one
compound selected from the group consisting of phosphoric esters,
aliphatic di- or tri-carboxylic esters and glyceryl alkyl
ethers.
7: The water dispersion for ink-jet printing according to claim 1,
wherein the water-insoluble organic compound (C) has a Log P value
of from -1 to 11.
8: The water dispersion for ink-jet printing according to claim 1,
wherein a content of the water-insoluble compound (C) in the water
dispersion is from 0.4 to 10% by weight.
9: The water dispersion for ink-jet printing according to claim 1,
wherein a weight ratio of the polymer particles (B) to the
water-insoluble organic compound (C) is from 15/1 to 1/2.
10: A water-based ink for ink-jet printing comprising the water
dispersion as defined in claim 1.
11: A method for producing a print, comprising the step of printing
images or characters with the water-based ink as defined in claim
10, on an ordinary paper by an ink-jet printing method.
12: The water dispersion for ink-jet printing according to claim 2,
wherein the polymer particles (B) are self-emulsifiable polymer
particles containing a constitutional unit derived from a
salt-forming group-containing monomer.
13: The water dispersion for ink-jet printing according to claim 2,
wherein the polymer particles (B) are polymer particles produced by
emulsion-polymerizing an ethylenically unsaturated monomer in the
presence of a reactive surfactant.
14: The water dispersion for ink-et printing according t claim 2,
wherein the water-insoluble organic compound (C) is an ester or
ether compound (f) containing two or more ester or ether bonds in a
molecule thereof, and/or an ester or ether compound (g) containing
one or more ester or ether bonds and at least one functional group
selected from the group consisting of a carboxyl group, a sulfonic
group, a phosphoric acid residue, a carbonyl group, an epoxy group
and a hydroxyl group.
15: The water dispersion for ink-jet printing according to claim 2,
wherein the water-insoluble organic compound (C) is at least one
compound selected from the group consisting of phosphoric esters,
aliphatic di- or tri-carboxylic esters and glyceryl alkyl
ethers.
16: The water dispersion for ink-jet printing according to claim 2,
wherein the water-insoluble organic compound (C) has a Log P value
of from -1 to 11.
17: The water dispersion for ink-jet printing according to claim 2,
wherein a content of the water-insoluble compound (C) in the water
dispersion is from 0.4 to 10% by weight.
18: The water dispersion for ink-jet printing according to claim 2
wherein a weight ratio of the polymer particles (B) to the
water-insoluble organic compound (C) is from 15/1 to 1/2.
19: A water-based ink for ink-jet printing comprising the water
dispersion as defined in claim 2.
20: A method for producing a print comprising the step of printing
images or characters with the water-based ink as defined in claim
19, on an ordinary paper by an ink-jet printing method.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to water-based inks for
ink-jet printing, water dispersions used for the water-based inks,
and a method for producing prints using the water-based inks.
BACKGROUND OF THE INVENTION
[0002] In ink-jet printing methods, droplets of ink are directly
projected onto a recording medium from very fine nozzles and
allowed to adhere to the recording medium, to form characters and
images. The ink-jet printing methods have been rapidly spread
because of their various advantages such as easiness of full
coloration, low costs, capability of using ordinary paper as the
recording medium, non-contact with printed images and characters,
etc.
[0003] Among such printing methods, in view of enhancing the
weather resistance and water resistance of printed images and
characters, an ink-jet printing method utilizing an ink containing
a pigment as the colorant has now come to dominate (for example,
refer to JP 2002-294105A, JP 2001-329199A, JP 8-157761A, JP
2003-183554A, JP 2004-75759A, JP 2003-138179A, JP 2003-147236A and
JP 2004-115589A).
[0004] JP 2002-294105A discloses a recording solution to which an
emulsion obtained by conducting polymerization in the presence of a
reactive surfactant is added to prevent clogging of nozzles with
pigments.
[0005] JP 2001-329199A discloses an ink composition containing a
self-dispersible pigment and polymer particles to improve a high
lighter-fastness and a rubbing resistance thereof.
[0006] JP 8-157761A discloses a water-based ink containing an oil
film-forming component which is prepared by dissolving a
water-insoluble resin therein to suppress color bleeding. JP
2003-183554A discloses a water-based ink which contains 10 to 1000
ppm of a phthalic diester and a latex in order to form images
having a good gloss. JP 2004-75759A discloses a dispersion of
colored fine particles in which a hydrophobic pigment, a
hydrophobic polymer and a high-boiling organic solvent are
micro-capsulated with an urethane group-containing resin.
[0007] JP 2003-138179A and JP 2003-147236A disclose
pigment-containing inks for ink-jet printing which contain
aliphatic acids and derivatives thereof. JP 2004-115589A discloses
a water-based ink containing a self-dispersible pigment, a resin
and an organic solvent exhibiting a solubility in water of 10% by
weight or lower.
[0008] However, these conventional inks have failed to exhibit both
a high optical density and an excellent high lighter-fastness to a
sufficient extent.
SUMMARY OF THE INVENTION
[0009] The present invention relates to a water-based ink for
ink-jet printing which not only satisfies a high optical density
but also exhibits an excellent high lighter-fastness; a water
dispersion used for the water-based ink; and a method for producing
a print (inclusive of printed matter) using the water-based
ink.
[0010] The present inventors have found that a water dispersion
containing a colorant, polymer particles and a water-insoluble
organic compound can provide a water-based ink for ink-jet printing
which exhibits a sufficient optical density as well as an excellent
high lighter-fastness.
[0011] Thus, the present invention relates to the following aspects
[1] to [4]:
[0012] [1] A water dispersion for ink-jet printing containing (A-1)
polymer particles containing a colorant, (B) polymer particles and
(C) a water-insoluble organic compound.
[0013] [2] A water dispersion for ink-jet printing containing (A-2)
self-dispersible pigment, (B) polymer particles and (C) a
water-insoluble organic compound.
[0014] [3] A water-based ink for ink-jet printing containing the
water dispersion as defined in any one of the above aspect [1] or
[2].
[0015] [4] A method for producing a print, containing the step of
printing images or characters on an ordinary paper (plain paper,
recycled paper) with the water-based ink as defined in the above
aspect [3] by an ink-jet printing method.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The water dispersion for ink-jet printing according to the
present invention includes the following water dispersions [1] or
[2]:
[0017] [1] A water dispersion for ink-jet printing containing (A-1)
polymer particles containing a colorant, (B) polymer particles and
(C) the water-insoluble organic compound.
[0018] [2] A water dispersion for ink-jet printing containing (A-2)
self-dispersible pigment, (B) polymer particles and (C) the
water-insoluble organic compound.
[0019] The respective components used in these water dispersions
are explained below.
Colorant
[0020] The colorant is not particularly limited, and there may be
used any of pigment, hydrophobic dye, and water-soluble dye such as
acid dye, reactive dye and direct dye. The colorant used in the
present invention is preferably pigment or hydrophobic dye in view
of a good water resistance, a good dispersion stability and a good
rubbing resistance. Among these colorants, to meet the recent
strong demand for a high weather resistance, preferred is the
pigment.
[0021] The pigment or hydrophobic dye used in the water-based ink
is required to be present in the form of stable fine particles
using a surfactant or a polymer. In particular, in view of
anti-bleeding property and water resistance, the pigment and/or
hydrophobic dye is preferably included in the polymer
particles.
[0022] The pigment may be either organic or inorganic. The organic
or inorganic pigment may be used in combination with an extender
pigment, if required.
[0023] Examples of the inorganic pigments include carbon blacks,
metal oxides, metal sulfides and metal chlorides. Among these
inorganic pigments, carbon blacks are preferably used for black
water-based inks. The carbon blacks may include furnace blacks,
thermal lamp blacks, acetylene blacks and channel blacks.
[0024] Examples of the organic pigments include azo pigments, diazo
pigments, phthalocyanine pigments, quinacridone pigments,
isoindolinone pigments, dioxazine pigments, perylene pigments,
perinone pigments, thioindigo pigments, anthraquinone pigments and
quinophthalone pigments.
[0025] Specific examples of the preferred organic pigments include
one or more pigments selected from the group consisting of
commercially available products marketed under the tradenames C.I.
Pigment Yellow, C.I. Pigment Red, C.I. Pigment Violet, C.I. Pigment
Blue, C.I. Pigment Green, etc., with various product numbers.
[0026] Examples of the extender pigment include silica, calcium
carbonate and talc.
[0027] The hydrophobic dyes are not particularly limited as long as
they are capable of being included in the polymer particles. To
allow the dye to efficiently become included in the polymer, the
solubility of the hydrophobic dye is preferably 2 g/L or more and
more preferably from 20 to 500 g/L as measured at 25.degree. C. on
the basis of the organic solvent used upon the production of the
polymer, such as preferably methyl ethyl ketone.
[0028] Examples of the hydrophobic dyes include oil-soluble dyes
and disperse dyes. Among these dyes, preferred are oil-soluble
dyes.
[0029] Examples of the oil-soluble dyes include one or more dyes
selected from the group consisting of commercially available
products marketed from Orient Chemical Co., Ltd., BASF AG, etc.,
under the tradenames C.I. Solvent Black, C.I. Solvent Yellow, C.I.
Solvent Red, C.I. Solvent Violet, C.I. Solvent Blue, C.I. Solvent
Green, and C.I. Solvent Orange, etc., with various product
numbers.
[0030] Examples of the disperse dyes include one or more dyes
selected from the group consisting of commercially available
products marketed under the tradenames C.I. Disperse Yellow, C.I.
Disperse Orange, C.I. Disperse Red, C.I. Disperse Violet, C.I.
Disperse Blue, C.I. Disperse Green, etc., with various product
numbers. Among these dyes, preferred are C.I. Solvent Yellow 29 and
30 for yellow colorant, C.I. Solvent Blue 70 for cyan colorant,
C.I. Solvent Red 18 and 49 for magenta colorant, and C.I. Solvent
Black 3 and 7 and nigrosine black dyes for black colorant.
[0031] The above colorants may be used alone or in the form of a
mixture containing any two or more thereof at an optional mixing
ratio.
(A-1) Polymer Particles Containing Colorant (Hereinafter
Occasionally Referred to Merely as "Colorant-Containing
Particles")
[0032] The colorant is preferably carbon black. As the carbon
black, there may be used the same carbon blacks as exemplified
previously. Examples of commercially available carbon blacks
include "MONARCH" series such as "MONARCH 1300", "MONARCH 1000",
"MONARCH 1100", "MONARCH 880" and "MONARCH 800" and "MOGUL L,
REGAL" series such as "MOGUL L, REGAL 330R" and "MOGUL L, REGAL
300R" all available from Cabot Corp.; "Color Black FW200", "Color
Black FW2", "Color Black FW1", "Color Black FW18", "Color Black
S170" and "Color Black S160" and "Printex" series such as "Printex
95", "Printex 90", "Printex 85", "Printex 80", "Printex 60",
"Printex 55", "Printex 40", "Printex L6" and "Printex P" all
available from Degusa AG.; "TOKA BLACK #830/F" available from Tokai
Carbon Co., Ltd.; and "MCF88" and "MA600" available from Mitsubishi
Chemical Corp.
[0033] In view of a good optical density, the carbon blacks have a
pH of usually from 2 to 10 and preferably from 4 to 8; a DBP oil
absorption of usually from 40 to 130 and preferably from 60 to 130;
and an average primary particle size of usually from 8 to 30 nm and
preferably from 8 to 20 nm.
[0034] The colorant-containing particles may be produced by the
following steps (1) and (2) using the below-mentioned
water-insoluble polymer:
[0035] (1) dispersing a mixture containing the water-insoluble
polymer, an organic solvent, colorant and an aqueous medium as well
as a neutralizing agent, if required, to obtain a dispersion;
and
[0036] (2) removing the organic solvent from the resultant
dispersion.
[0037] In the step (1), first, preferably, the water-insoluble
polymer is dissolved in the organic solvent, and then the colorant
and aqueous medium as well as optional components such as
neutralizing agent and surfactant, if required, are added to the
organic solvent solution under mixing to obtain a dispersion of an
oil-in-water type. The content of the colorant in the mixture is
preferably from 5 to 50% by weight. The content of the organic
solvent in the mixture is preferably from 10 to 70% by weight. The
content of the water-insoluble polymer in the mixture is preferably
from 2 to 40% by weight, and the content of the aqueous medium in
the mixture is preferably from 10 to 70% by weight. In view of
enhancing the optical density, the mixing ratio between the
colorant and the water-insoluble polymer is adjusted such that the
colorant is preferably used in an amount of from 50 to 900 parts by
weight and more preferably from 100 to 800 parts by weight on the
basis of 100 parts by weight of the water-insoluble polymer. The
order of mixing of the water-insoluble polymer and the colorant is
not particularly limited, and these components may be mixed with
each other at the same time.
[0038] When the water-insoluble polymer contains a salt-forming
group, the degree of neutralization of the polymer with the
neutralizing agent is not particularly limited. In general, the
degree of neutralization is preferably controlled such that the
finally obtained water dispersion exhibits a liquid property from
weak acidity to weak alkalinity, for example, a pH of from 4.5 to
10. The water-insoluble polymer may be previously neutralized with
the neutralizing agent before used in the above step.
[0039] Examples of the preferred organic solvents include alcohol
solvents, ketone solvents and ether solvents, i.e., the organic
solvents are preferably those having a solubility in water of from
10 to 80% by weight as measured at 20.degree. C.
[0040] Examples of the alcohol solvents include n-butanol, tertiary
butanol, isobutanol and diacetone alcohol. Examples of the ketone
solvents include acetone, methyl ethyl ketone, diethyl ketone and
methyl isobutyl ketone. Examples of the ether solvents include
dibutyl ether and dioxane. Among these solvents, preferred are
ketone solvents, and more preferred is methyl ethyl ketone.
[0041] Examples of the aqueous medium include those media
containing water as a main component, and the aqueous medium may
also contain a hydrophilic solvent such as polyhydric alcohols
which exhibits a solubility in water of 100% by weight or higher as
measured at 20.degree. C.
[0042] Examples of the surfactant include anionic surfactants,
nonionic surfactants, cationic surfactants and amphoteric
surfactants.
[0043] As the neutralizing agent, acids or bases may be used
according to the kind of the salt-forming group in the
water-insoluble polymer. Examples of the neutralizing agent include
acids such as hydrochloric acid, acetic acid, propionic acid,
phosphoric acid, sulfuric acid, lactic acid, succinic acid,
glycolic acid, gluconic acid and glyceric acid, and bases such as
lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia,
methylamine, dimethylamine, trimethylamine, ethylamine,
diethylamine, triethylamine, triethanolamine and tributylamine.
[0044] The degree of neutralization of the water-insoluble polymer
is usually from 10 to 200%, preferably from 20 to 150% and more
preferably from 50 to 150%.
[0045] When the salt-forming group is an anionic group, the degree
of neutralization thereof is calculated according to the following
formula: [weight (g) of neutralizing agent)/equivalent of
neutralizing agent]/[acid value of polymer (KOH mg/g).times.weight
(g) of polymer/(56.times.1000)].times.100
[0046] When the salt-forming group is a cationic group, the degree
of neutralization thereof is calculated according to the following
formula: [weight (g) of neutralizing agent)/equivalent of
neutralizing agent]/[amine value of polymer (HCl mg/g).times.weight
(g) of polymer/(36.5.times.1000)].times.100
[0047] The acid value or amine value may be calculated from the
respective constitutional units of the water-insoluble vinyl
polymer, or may also be determined by the method of subjecting a
solution prepared by dissolving the polymer in an appropriate
solvent such as methyl ethyl ketone to titration.
[0048] The method for dispersing the mixture in the step (1) is not
particularly limited. The water-insoluble polymer particles may be
finely divided into fine particles having a desired average
particle size only by substantial dispersion procedure. Preferably,
the mixture is first subjected to preliminary dispersion procedure,
and then to the substantial dispersion procedure by applying a
shear stress thereto so as to control the average particle size of
the water-insoluble polymer particles to a desired value.
[0049] Upon subjecting the mixture to the preliminary dispersion
procedure, there may be used ordinary mixing or stirring devices
such as anchor blades.
[0050] To apply the shear stress to the mixture in the substantial
dispersion procedure, there may be used, for example, kneading
machines such as roll mills, beads mills, kneaders and extruders,
homo-valve-type high-pressure homogenizers such as typically
"High-Pressure Homogenizer" (tradename: available from Izumi Food
Machinery Co., Ltd.) and "Mini-Labo 8.3H Model" (tradename:
available from Rannie Corp.), and chamber-type high-pressure
homogenizers such as "Micro Fluidizer" (tradename: available from
Microfluidics Inc.), "Nanomizer" (tradename: available from
Nanomizer Co., Ltd.), "Altimizer" (tradename: available from Sugino
Machine Co., Ltd.), "Genus PY" (tradename: available from Hakusui
Kagaku Co., Ltd.) and "DeBEE 2000" (tradename: Nippon BEE Co.,
Ltd.). Among these apparatuses, the high-pressure homogenizers are
preferred in view of reducing the particle size of the pigment
contained in the mixture.
[0051] In the step (2), the organic solvent is removed from the
dispersion obtained in the above step (1) by ordinary methods such
as distillation under reduced pressure to obtain a water dispersion
of the colorant-containing particles. The organic solvent is
substantially completely removed from the thus obtained water
dispersion of the CB-containing particles. The content of the
residual organic solvent in the water dispersion is preferably 0.1%
by weight or lower and more preferably 0.01% by weight or
lower.
[0052] The configuration of the thus obtained colorant-containing
particles is not particularly limited as long as the particles are
formed from at least the colorant and the water-insoluble polymer.
Examples of the configuration of the colorant-containing particles
include the particle configuration in which colorant is enclosed in
the respective water-insoluble polymer particles, the particle
configuration in which colorant is uniformly dispersed in the
respective water-insoluble polymer particles, and the particle
configuration in which colorant is exposed onto a surface of the
respective water-insoluble polymer particles.
[0053] The weight ratio between the colorant and the polymer in the
colorant-containing particles is controlled such that colorant is
preferably present in an amount of from 50 to 900 parts by weight
and more preferably from 100 to 800 parts by weight on the basis of
100 parts by weight of the polymer in view of enhancing the optical
density.
[0054] The average particle size of the colorant-containing
particles is preferably from 0.01 to 0.5 .mu.m, more preferably
from 0.02 to 0.3 .mu.m and still more preferably from 0.03 to 0.2
.mu.m in view of preventing clogging of nozzles and enhancing the
dispersion stability.
[0055] The average particle size may be measured using a laser
particle analyzing system "ELS-8000" (cumulant analysis) available
from Otsuka Denshi Co., Ltd. The measurement is conducted at a
temperature of 25.degree. C., an angle between incident light and
detector of 90.degree. and a cumulative frequency of 100 times, and
a refractive index of water (1.333) is input to the analyzing
system as a refractive index of the dispersing medium. The
concentration of the dispersion to be measured is usually about
5.times.10.sup.-3% by weight.
(A-2) Self-Dispersible Pigment
[0056] The "self-dispersible pigment" means pigment onto a surface
of which at least one anionic or cationic hydrophilic group is
bonded either directly or through the other atom group to thereby
allow the pigment to be dispersed in an aqueous medium without
using a surfactant or a resin. Examples of pigment usable for the
self-dispersible pigment include those exemplified above. The
self-dispersible pigment is preferably a self-dispersible carbon
black in view of a good dispersion stability.
[0057] Examples of the other atom group include an alkylene group
having 1 to 24 carbon atoms and preferably 1 to 12 carbon atoms, a
substituted or unsubstituted phenylene group and a substituted or
unsubstituted naphthylene group.
[0058] As the anionic hydrophilic group, any optional groups may be
used as long as they exhibit a high hydrophilic property sufficient
to allow the pigment particles to be stably dispersed in the
aqueous medium. Specific examples of the anionic hydrophilic group
include a carboxyl group (--COOM.sup.1), a sulfonic group
(--SO.sub.3M.sup.1), a phosphoric group (--PO.sub.3M.sup.1.sub.2),
--SO.sub.2NH.sub.2, --SO.sub.2NHCOR.sup.1, and dissociated ions
thereof such as --COO.sup.-, --SO.sub.3.sup.-, --PO.sub.3.sup.2-
and --PO.sub.3.sup.-M.sup.1.
[0059] In the above chemical formulas, M.sup.1 may be the same or
different. Examples of M.sup.1 include a hydrogen atom; alkali
metals such as lithium, sodium and potassium; an ammonium group;
and organic ammonium groups such as monomethyl ammonium, dimethyl
ammonium, trimethyl ammonium, monoethyl ammonium, diethyl ammonium,
triethyl ammonium, monomethanol ammonium, dimethanol ammonium and
trimethanol ammonium.
[0060] R.sup.1 is an alkyl group having 1 to 12 carbon atoms, a
substituted or unsubstituted phenyl group or a substituted or
unsubstituted naphthyl group.
[0061] Among these anionic hydrophilic groups, preferred are a
carboxyl group (--COOM.sup.1) and a sulfonic group
(--SO.sub.3M.sup.1).
[0062] Examples of the preferred cationic hydrophilic group include
quaternary ammonium groups. Among the quaternary ammonium groups,
more preferred are those groups represented by the general formula
(1): ##STR1## wherein R.sup.2, R.sup.3 and R.sup.4 are each
independently a hydrogen atom or R.sup.1 as defined above; X is an
anionic group obtained by removing a proton from a halogen atom
such as fluorine and chlorine, a carboxylic acid such as acetic
acid, propionic acid, lactic acid, glycolic acid, gluconic acid and
glyceric acid, or an alkyl sulfate having 1 to 8 carbon atoms, as
well as those group represented by the following formulae:
##STR2##
[0063] In order to render the pigment self-dispersible, a necessary
amount of the above anionic or cationic hydrophilic group may be
chemically bonded to a surface of the pigment. The hydrophilic
group may be bonded to the surface of the carbon black by any
optional known method, for example, by the methods described in
U.S. Pat. Nos. 5,571,311, 5,630,868 and 5,707,432; J. E. Johnson,
"Imaging Science and Technology's 50th Annual Conference (1997)";
Yuan Yu, "Imaging Science and Technology's 53rd Annual Conference
(2000)"; and "Polyfile", 1248 (1996).
[0064] More specifically, there may be used the method of
introducing a carboxyl group into carbon black using compounds,
e.g., acids having an oxidizing property such as nitric acid,
hydrogen peroxide, hypochlorous acid and chromic acid; the method
of introducing a sulfone group into carbon black by thermal
decomposition of persulfate compounds; and the method of
introducing the above anionic hydrophilic groups into carbon black
using diazonium compounds containing a carboxyl group, a sulfone
group or an amino group, though not limited thereto.
[0065] The content of the anionic or cationic hydrophilic group is
not particularly limited, and is preferably from 50 to 5,000
.mu.mol/g and more preferably from 100 to 3,000 .mu.mol/g per one
gram of the self-dispersible pigment.
[0066] The average particle size of the self-dispersible pigment in
the water dispersion or the water-based ink is preferably from 50
to 300 nm and more preferably from 60 to 200 nm in view of a good
dispersion stability thereof. Meanwhile, the average particle size
of the self-dispersible carbon black may be measured under the same
conditions as described above using the laser particle analyzing
system "ELS-8000" (cumulant analysis) available from Otsuka Denshi
Co., Ltd.
[0067] Examples of the commercially available anionic
self-dispersible carbon blacks include "CAB-O-JET 200" and
"CAB-O-JET 300" both available from Cabot Corp., "BONJET CW-1" and
"BONJET CW-2" both available from Orient Chemical Industries Co.,
Ltd., and "Aqua-Black 162" (carboxyl group content: about 800
.mu.mol/g) available from Tokai Carbon Co., Ltd.
[0068] These self-dispersible pigments may be used alone or in
combination of any two or more thereof at an optional mixing
ratio.
(B) Polymer Particles
[0069] In the present invention, the polymer particles are used to
enhance a optical density and a high lighter-fastness of the
water-based ink by the interrelation with the water-insoluble
organic compound.
[0070] The "polymer particles" used in the present invention mean
such polymer particles capable of being dispersed in a solvent
having an aqueous continuous phase in the presence or absence of a
surfactant to form a polymer emulsion. Among these polymer
particles, in view of a good optical density and a good high
lighter-fastness, preferred are (i) self-emulsifiable polymer
particles containing a constitutional unit derived from a
salt-forming group-containing monomer (hereinafter referred to
merely as a "self-emulsifiable polymer (i)" or "self-emulsifiable
polymer particles (i)"); and (ii) polymer particles obtained by
emulsion-polymerizing an ethylenically unsaturated monomer
(hereinafter referred to merely as "emulsion polymer (ii)" or
"emulsion polymer particles (ii)"), and in view of a good
dispersion stability and a good high lighter-fastness, preferred
polymer particles are vinyl polymer particles.
[0071] Further, in view of enhancing a gloss of the resultant
prints, more preferred are self-emulsifiable polymer particles (i).
This is because the self-emulsifiable polymer particles suppress
coagulation of the self-dispersible pigment.
[0072] In addition, in view of exhibiting a more excellent high
lighter-fastness, preferred are the polymer particles (ii) obtained
by emulsion-polymerizing an ethylenically unsaturated monomer in
the presence of a reactive surfactant. This is because the reactive
surfactant is hardly desorbed from the polymer particles even when
bringing the prints into contact with water-soluble inks such as
those used in marker pens, so that the printed images or characters
can be prevented from being dissolved out again.
[0073] From these viewpoints, the polymer particles (B) are
preferably (i) self-emulsifiable polymer particles and/or (ii)
polymer particles produced by emulsion-polymerizing an
ethylenically unsaturated monomer in the presence of a reactive
surfactant.
[0074] These polymer particles may be used alone or in the form of
a mixture of any two or more thereof.
[0075] The constitutional unit of the polymer constituting the
polymer particles (B) and the constitutional unit of the polymer
constituting the polymer particles (A-1) containing the colorant
may be the same or different.
(i) Self-Emulsifiable Polymer Particles
[0076] The "self-emulsifiable polymer particles" mean particles of
a water-insoluble polymer which is kept in an emulsified state
owing to a functional group (in particular, a basic group or a salt
thereof) of the polymer itself in the absence of a surfactant
(hereinafter referred to merely as a "self-emulsifiable polymer").
Such self-emulsifiable polymer particles may be produced by a
method of dissolving or dispersing the polymer in a solvent,
directly charging the resultant solution or dispersion into water
without adding any surfactant thereto, neutralizing a salt-forming
group contained in the polymer, stirring and mixing the resultant
mixture containing the neutralized polymer, and then removing the
solvent from the mixture to obtain an emulsion thereof.
[0077] Here, the "emulsified state" means such a condition in which
a stable emulsified or dispersed state of a mixture produced by
mixing and stirring a solution prepared by dissolving 30 g of the
water-insoluble polymer in 70 g of an organic solvent such as
methyl ethyl ketone, a neutralizing agent which is capable of
neutralizing 100% of a salt-forming group in the water-insoluble
polymer (sodium hydroxide for the anionic salt-forming group or
acetic acid for the cationic salt-forming group), and 200 g of
water with each other at 25.degree. C. for 30 min, can be confirmed
by visual observation even after the mixture is allowed to stand at
25.degree. C. for at least one week.
Water-Insoluble Polymer
[0078] The "water-insoluble polymer" means a polymer exhibiting a
solubility in water of 10 g or lower, preferably 5 g or lower and
more preferably 1 g or lower when the polymer is dried at
105.degree. C. for 2 h, and then dissolved in 100 g of water at
25.degree. C. The solubility means a solubility in water of the
water-insoluble polymer whose salt-forming groups are completely
(100%) neutralized with sodium hydroxide or acetic acid according
to kinds of the salt-forming groups to be neutralized.
[0079] The water-insoluble polymer is preferably a water-insoluble
vinyl polymer in view of a good dispersion stability and a good
high lighter-fastness. More preferred is such a water-insoluble
polymer which is produced by copolymerizing a monomer mixture
containing (a) a salt-forming group-containing monomer (hereinafter
occasionally referred to merely as a "component (a)"), and (b) a
macromer (hereinafter occasionally referred to merely as a
"component (b)") and/or (c) a hydrophobic monomer (hereinafter
occasionally referred to merely as a "component (c)") by a solution
polymerization method (the mixture of these monomers is hereinafter
occasionally referred to merely as a "monomer mixture"). The
water-insoluble polymer contains a constitutional unit derived from
the component (a), and a constitutional unit derived from the
component (b) and/or a constitutional unit derived from the
component (c).
[0080] The salt-forming group-containing monomer (a) is used for
promoting the self-emulsification and enhancing a dispersion
stability of the resultant dispersion. Examples of the salt-forming
group include a carboxyl group, a sulfonic group, a phosphoric
group, an amino group and an ammonium group.
[0081] The salt-forming group-containing monomer includes cationic
monomers and anionic monomers. Examples of the salt-forming
group-containing monomer include those described on page 5, from
column 7, line 24 to column 8, line 29 of JP 9-286939A.
[0082] Typical examples of the cationic monomers include
unsaturated amine group-containing monomers and unsaturated
ammonium salt group-containing monomers. Among these cationic
monomers, preferred are N,N-dimethylaminoethyl (meth)acrylate,
N--(N',N'-dimethylaminopropyl) (meth)acrylamide and vinyl
pyrrolidone.
[0083] Typical examples of the anionic monomers include unsaturated
carboxylic acid monomers, unsaturated sulfonic acid monomers and
unsaturated phosphoric acid monomers.
[0084] Examples of the unsaturated carboxylic acid monomers include
acrylic acid, methacrylic acid, crotonic acid, itaconic acid,
maleic acid, fumaric acid, citraconic acid and
2-methacryloyloxymethylsuccinic acid. Examples of the unsaturated
sulfonic acid monomers include styrenesulfonic acid,
2-acrylamido-2-methylpropanesulfonic acid, 3-sulfopropyl
(meth)acrylate and bis(3-sulfopropyl)itaconic ester. Examples of
the unsaturated phosphoric acid monomers include vinylphosphonic
acid, vinyl phosphate, bis(methacryloxyethyl)phosphate,
diphenyl-2-acryloyloxyethyl phosphate,
diphenyl-2-methacryloyloxyethyl phosphate and
dibutyl-2-acryloyloxyethyl phosphate.
[0085] Among the above anionic monomers, in view of a good
dispersion stability and a good ejecting stability of the resultant
inks, preferred are the unsaturated carboxylic acid monomers, and
more preferred are acrylic acid and methacrylic acid.
[0086] The macromer (b) is used for enhancing a optical density of
the resultant prints and a dispersion stability of the polymer
particles. The macromer (b) is in the form of a monomer containing
a polymerizable unsaturated group which has a number-average
molecular weight of from 500 to 100,000 and preferably from 1,000
to 10,000. The number-average molecular weight of the macromer (b)
may be measured by gel chromatography using chloroform containing 1
mmol/L of dodecyl dimethylamine as a solvent and using polystyrene
as a standard substance.
[0087] Among these macromers (b), in view of a good dispersion
stability of the polymer particles, etc., preferred are
styrene-based macromers and aromatic group-containing
(meth)acrylate-based macromers which have a polymerizable
functional group at one terminal end thereof.
[0088] Examples of the styrene-based macromer include homopolymers
of styrene-based monomers, and copolymers of the styrene-based
monomers with other monomers. Examples of the styrene-based
monomers (component b-1) include styrene, 2-methyl styrene, vinyl
toluene, ethylvinyl benzene, vinyl naphthalene and
chlorostyrene.
[0089] As the aromatic group-containing (meth)acrylate-based
macromers, there are preferably used homopolymers of an aromatic
group-containing (meth)acrylate and copolymers of the aromatic
group-containing (meth)acrylate with other monomers. Examples of
the aromatic group-containing (meth)acrylate (component b-2)
include (meth)acrylates containing an arylalkyl group having 7 to
22 carbon atoms, preferably 7 to 18 carbon atoms and more
preferably 7 to 12 carbon atoms which may have a substituent group
containing a hetero atom, and (meth)acrylates containing an aryl
group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms
and more preferably 6 to 12 carbon atoms which may have a
substituent group containing a hetero atom. Examples of the
substituent group containing a hetero atom include a halogen atom,
an ester group, an ether group and a hydroxyl group. Specific
examples of the aromatic group-containing (meth)acrylate include
benzyl (meth)acrylate, phenoxyethyl (meth)acrylate,
2-hydroxy-3-phenoxypropyl acrylate and
2-methacryloyloxyethyl-2-hydroxypropyl phthalate. Among these
aromatic group-containing (meth)acrylates, preferred is benzyl
(meth)acrylate.
[0090] The polymerizable functional group bonded to one terminal
end of these macromers is preferably an acryloyloxy group or a
methacryloyloxy group. Examples of the preferred other monomers
copolymerizable with the aromatic group-containing (meth)acrylate
include acrylonitrile.
[0091] The content of the constitutional unit derived from the
styrene-based monomer in the styrene-based macromer or the
constitutional unit derived from the aromatic group-containing
(meth)acrylate in the aromatic group-containing
(meth)acrylate-based macromer is preferably 50% by weight or higher
and more preferably 70% by weight or higher in view of enhancing an
affinity to the pigments.
[0092] The macromer (b) may further contain a side chain composed
of the other constitutional unit derived from an
organopolysiloxane, etc. Such a side chain may be produced, for
example, by copolymerizing the macromer (b) with a silicone-based
macromer having a polymerizable functional group at one terminal
end thereof which is represented by the following formula (2):
CH.sub.2.dbd.C(CH.sub.3)--COOC.sub.3H.sub.6--[Si(CH.sub.3).sub.2--O].sub.-
t--Si(CH.sub.3).sub.3 (2) wherein t is a number from 8 to 40.
[0093] The styrene-based macromer as the component (b) is
commercially available, for example, from Toagosei Co., Ltd., as
product names of AS-6(S), AN-6(S), HS-6(S), etc.
[0094] The hydrophobic monomer (c) is used for enhancing a optical
density and a high lighter-fastness. Examples of the hydrophobic
monomer include alkyl (meth)acrylates and aromatic group-containing
monomers.
[0095] The alkyl (meth)acrylates are preferably those containing an
alkyl group having 1 to 22 carbon atoms and preferably 6 to 18
carbon atoms. Examples of the alkyl (meth)acrylates include methyl
(meth)acrylate, ethyl (meth)acrylate, (iso)propyl (meth)acrylate,
(iso- or tertiary-)butyl (meth)acrylate, (iso)amyl (meth)acrylate,
cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (iso)octyl
(meth)acrylate, (iso)decyl (meth)acrylate, (iso)dodecyl
(meth)acrylate and (iso)stearyl (meth)acrylate.
[0096] Meanwhile, the terms "(iso- or tertiary-)" and "(iso)" used
herein mean both the structure in which the groups expressed by
"iso" and "tertiary" are present, and the structure in which these
groups are not present. and the term "(meth)acrylate" means
acrylate, methacrylate or both thereof.
[0097] The aromatic group-containing monomer are preferably vinyl
monomers containing an aromatic group having 6 to 22 carbon atoms
and more preferably 6 to 12 carbon atoms which may contain a
substituent group having a hetero atom. Examples of the preferred
aromatic group-containing monomer include the above styrene-based
monomer (component (b-1)), and the above aromatic group-containing
(meth)acrylate (component (b-2)). Examples of the substituent group
having a heteroatom are those exemplified above.
[0098] Among these components (c), preferred is the styrene-based
monomer (b-1), and more preferred are styrene and 2-methyl styrene.
The content of the component (b-1) in the component (c) is
preferably from 10 to 100% by weight and more preferably from 20 to
80% by weight in view of enhancing the optical density and the high
lighter-fastness.
[0099] Also, examples of the preferred aromatic group-containing
(meth)acrylate as the component b-2 include benzyl (meth)acrylate
and phenoxyethyl (meth)acrylate. The content of the component (b-2)
in the component (c) is preferably from 10 to 100% by weight and
more preferably from 20 to 80% by weight in view of enhancing the
optical density and the high lighter-fastness. Further, the
components (b-1) and (b-2) are preferably used in combination with
each other.
[0100] The monomer mixture may further contain (d) a
hydroxyl-containing monomer (hereinafter referred to merely as a
"component (d)") for enhancing the dispersion stability. The
component (d) exhibits an excellent effect of enhancing the
dispersion stability of the dispersion and improving the high
lighter-fastness for a short period of time upon printing.
[0101] Examples of the component (d) include 2-hydroxyethyl
(meth)acrylate, 3-hydroxypropyl (meth)acrylate, polyethylene glycol
(n=2 to 30 wherein n represents an average molar number of addition
of oxyalkylene groups: this definition is similarly applied to the
subsequent descriptions) (meth)acrylate, polypropylene glycol (n=2
to 30) (meth)acrylate and poly(ethylene glycol (n=1 to
15)/propylene glycol (n=1 to 15) (meth)acrylate. Among these
components (d), preferred are 2-hydroxyethyl (meth)acrylate,
polyethylene glycol mono-methacrylate and polypropylene glycol
methacrylate.
[0102] The monomer mixture may further contain (e) a monomer
(hereinafter occasionally referred to merely as a "component (e)")
represented by the following general formula (3):
CH.sub.2.dbd.C(R.sup.5)COO(R.sup.6O).sub.pR.sup.7 (3) wherein
R.sup.5 is a hydrogen atom or a lower alkyl group having 1 to 5
carbon atoms; R.sup.6 is a divalent hydrocarbon group having 1 to
30 carbon atoms which may contain a hetero atom; R.sup.7 is a
monovalent hydrocarbon group having 1 to 30 carbon atoms which may
contain a hetero atom; and p represents an average molar number of
addition, and is a number from 1 to 60 and preferably a number from
1 to 30.
[0103] The component (e) exhibits an excellent effect of enhancing
an ejecting property of the resultant water-based ink and
preventing occurrence of slippage even upon continuous
printing.
[0104] In the general formula (3), examples of the hetero atom
include a nitrogen atom, an oxygen atom, a halogen atom and a
sulfur atom.
[0105] Examples of the suitable R.sup.5 group include methyl, ethyl
and (iso)propyl.
[0106] Examples of the suitable R.sup.6O group include
oxymethylene, oxy(iso)propylene, oxytetramethylene,
oxyheptamethylene, oxyhexamethylene, and oxyalkylene groups having
2 to 7 carbon atoms which are each constituted from combination of
at least two of these groups.
[0107] Examples of the suitable R.sup.7 group include aliphatic
alkyl groups having 1 to 30 carbon atoms and preferably 1 to 20
carbon atoms, aromatic ring-containing alkyl groups having 7 to 30
carbon atoms, and hetero ring-containing alkyl groups having 4 to
30 carbon atoms.
[0108] Specific examples of the component (e) include methoxy
polyethylene glycol (p in the general formula (3): 1 to 30; this is
similarly applied to the subsequent descriptions) (meth)acrylate,
methoxy polytetramethylene glycol (p=1 to 30) (meth)acrylate,
ethoxy polyethylene glycol (p=1 to 30) (meth)acrylate, octoxy
polyethylene glycol (p=1 to 30) (meth)acrylate, polyethylene glycol
(p=1 to 30) (meth)acrylate 2-ethylhexyl ether, (iso)propoxy
polyethylene glycol (p=1 to 30) (meth)acrylate, butoxy polyethylene
glycol (p=1 to 30) (meth)acrylate, methoxy polypropylene glycol
(p=1 to 30) (meth)acrylate, and methoxy (ethylene glycol/propylene
glycol copolymer) (p=1 to 30: among which the number of ethylene
glycol constitutional units is 1 to 29) (meth)acrylate. Among these
compounds, preferred are octoxy polyethylene glycol (p=1 to 30)
(meth)acrylate and polyethylene glycol (p=1 to 30) (meth)acrylate
2-ethylhexyl ether.
[0109] Specific examples of commercially available components (d)
and (e) include polyfunctional acrylate monomers (NK Esters)
available from Shin-Nakamura Kagaku Kogyo Co., Ltd., such as
"M-40G", "M-90G" and "M-230G"; and BLEMMER Series available from
NOF Corporation, such as "PE-90", "PE-200", "PE-350", "PME-100",
"PME-200", "PME-400", "PME-1000", "PP-500", "PP-800", "PP-1000",
"AP-150", "AP-400", "AP-550", "AP-800", "50PEP-300" and
"50POEP-800B".
[0110] These components (a) to (e) are respectively used alone or
in the form of a mixture of any two or more thereof.
[0111] Upon production of the water-insoluble polymer, the contents
of the above components (a) to (e) in the monomer mixture (contents
of non-neutralized components; this definition is similarly applied
to the subsequent descriptions) or the contents of constitutional
units derived from the components (a) to (e) in the water-insoluble
polymer are as follows.
[0112] The content of the component (a) is preferably from 5 to 40%
by weight, more preferably from 5 to 30% by weight and most
preferably from 5 to 20% by weight in view of a good
self-emulsifiability of the polymer and a good dispersion stability
of the resultant polymer particles.
[0113] The content of the component (b) is preferably from 1 to 25%
by weight and more preferably from 5 to 20% by weight in view of a
good optical density as well as a good dispersion stability of the
resultant polymer particles.
[0114] The content of the component (c) is preferably from 5 to 79%
by weight and more preferably from 10 to 60% by weight in view of a
good optical density and a good high lighter-fastness. The
components (b) and (c) may be used either in combination or singly
in the monomer mixture.
[0115] The content of the component (d) is preferably from 5 to 40%
by weight and more preferably from 7 to 20% by weight in view of a
good dispersion stability of the resultant polymer particles as
well as a good high lighter-fastness.
[0116] The content of the component (e) is preferably from 5 to 50%
by weight and more preferably from 10 to 40% by weight in view of a
good dispersion stability of the resultant polymer particles.
[0117] The total content of the components (a) and (d) in the
monomer mixture is preferably from 6 to 60% by weight and more
preferably from 10 to 50% by weight in view of a good dispersion
stability of the resultant polymer particles. The total content of
the components (a) and (e) in the monomer mixture is preferably
from 6 to 75% by weight and more preferably from 13 to 50% by
weight in view of a good dispersion stability of the resultant
polymer particles. The total content of the components (a), (d) and
(e) in the monomer mixture is preferably from 6 to 60% by weight
and more preferably from 7 to 50% by weight in view of a good
dispersion stability of the resultant polymer particles.
[0118] Also, the weight ratio ((a)/[(b)+(c)]) of the component (a)
to a sum of the components (b) and (c) is preferably from 0.01 to
1, more preferably from 0.05 to 0.6 and still more preferably from
0.05 to 0.4 in view of a good high lighter-fastness, etc.
Production of Water-Insoluble Polymer
[0119] The water-insoluble polymer used in the present invention
may be produced by copolymerizing the monomer mixture by known
methods such as solution polymerization and bulk polymerization.
Among these polymerization methods, preferred is the solution
polymerization.
[0120] The solvent for the solution polymerization method is
preferably an organic polar solvent, although not limited thereto.
The organic polar solvent miscible with water may be used in the
form of a mixture with water. Examples of the organic polar
solvents include aliphatic alcohols having from 1 to 3 carbon atoms
such as methanol, ethanol and propanol; ketones such as acetone and
methyl ethyl ketone; and esters such as ethyl acetate. Among these
solvents, preferred are methanol, ethanol, acetone, methyl ethyl
ketone and mixed solvents of at least one thereof with water.
[0121] The polymerization may be carried out in the presence of a
conventionally known radical polymerization initiator, e.g., azo
compounds such as 2,2'-azobisisobutyronitrile and
2,2'-azobis(2,4-dimethylvaleronitrile), and organic peroxides such
as t-butyl peroxyoctoate and dibenzoyl oxide. The amount of the
radical polymerization initiator to be used is preferably from
0.001 to 5 mol and preferably from 0.01 to 2 mol per 1 mol of the
monomer mixture. The polymerization may also be carried out in the
presence of a conventionally known chain transfer agent, e.g.,
mercaptans such as octyl mercaptan and 2-mercapto ethanol, and
thiuram disulfides.
[0122] The polymerization conditions of the monomer mixture vary
depending upon the kinds of radical polymerization initiator,
monomers, solvent, etc., to be used, and the polymerization is
generally conducted at a temperature of preferably 30 to
100.degree. C. and more preferably 50 to 80.degree. C. The
polymerization time is preferably from 1 to 20 h. The
polymerization is preferably conducted in an atmosphere of an inert
gas such as nitrogen and argon.
[0123] After completion of the polymerization, the polymer thus
produced is isolated from the reaction solution by a known method
such as reprecipitation and removal of solvent by distillation. The
thus obtained polymer may be purified by repeated reprecipitation,
membrane separation, chromatography, extraction, etc., for removing
unreacted monomers, etc.
[0124] The weight-average molecular weight of the resultant
water-insoluble polymer is preferably from 5,000 to 500,000, more
preferably from 10,000 to 400,000 and most preferably from 10,000
to 300,000 in view of a good gloss.
[0125] Meanwhile, the weight-average molecular weight of the
polymer may be measured by gel chromatography using
dimethylformamide containing 60 mmol/L of phosphoric acid and 50
mmol/L of lithium bromide as a solvent and using polystyrene as a
standard substance.
(i) Production of Self-Emulsifiable Polymer Particles
[0126] The self-emulsifiable polymer particles (i) are preferably
produced from the above water-insoluble polymer in the form of a
water dispersion thereof through the following steps (1) and
(2):
[0127] (1) mixing and stirring a mixture containing the
water-insoluble polymer, an organic solvent, a neutralizing agent
and an aqueous medium; and
[0128] (2) removing the organic solvent from the resultant
mixture.
[0129] In the step (1), first, preferably, the water-insoluble
polymer is dissolved in the organic solvent, and then mixed with
the aqueous medium containing the neutralizing agent under stirring
to obtain a dispersion of an oil-in-water type. Thus, by adding the
water-insoluble polymer to the aqueous medium containing the
neutralizing agent, a water dispersion of the fine
self-emulsifiable polymer particles (i) exhibiting a higher storage
stability can be produced without applying a strong shear force
thereto. The method of mixing and stirring the mixture is not
particularly limited.
[0130] The organic solvent, the aqueous medium and contents thereof
as well as the neutralizing agent and the degree of neutralization
of the polymer therewith are the same as described above.
[0131] In the step (2), the organic solvent is removed from the
dispersion obtained in the above step (1) by known methods such as
distillation under reduced pressure to obtain a water dispersion of
the self-emulsifiable polymer particles (i). The organic solvent is
substantially completely removed from the thus obtained water
dispersion. The content of the residual organic solvent in the
resultant water dispersion is preferably 0.1% by weight or lower
and more preferably 0.01% by weight or lower.
[0132] The thus obtained water dispersion of the self-emulsifiable
polymer particles (i) has D50 (cumulative 50% value in frequency
distribution of scattering intensity when the cumulative percentage
is calculated sequentially from smaller particles) of preferably
500 nm or less, more preferably 300 nm or less and most preferably
200 nm or less in view of a good storage stability of the water
dispersion. In addition, the lower limit of D50 is preferably 10 nm
or more, more preferably 30 nm or more, in view of facilitated
production of the water dispersion.
[0133] The above water dispersion of the self-emulsifiable polymer
particles (i) has D90 (cumulative 90% value in frequency
distribution of scattering intensity when the cumulative percentage
is calculated sequentially from smaller particles) of preferably
2000 nm or less, more preferably 1000 nm or less and most
preferably 500 nm or less in view of reducing a content of coarse
particles in the water dispersion and enhancing a storage stability
of the water dispersion. In addition, the lower limit of D90 is
preferably 20 nm or more, more preferably 50 nm or more, in view of
facilitated production of the water dispersion.
[0134] Meanwhile, the measurements of D50 and D90 may be conducted
using the laser particle analyzing system "ELS-8000" (cumulant
analysis) available from Otsuka Denshi Co., Ltd., under the same
conditions as described above.
(ii) Emulsion Polymer Particles
[0135] The "emulsion polymer particles" mean polymer particles
obtained by emulsion-polymerizing an ethylenically unsaturated
monomer in the presence of a surfactant and/or a reactive
surfactant.
[0136] The emulsion polymer is preferably produced by
emulsion-polymerizing an ethylenically unsaturated monomer such as
the components (a) to (e) in the presence of the reactive
surfactant by ordinary methods in view of enhancing a high
lighter-fastness of the resultant water-based ink.
[0137] The content of constitutional units derived from the
components (a) in the emulsion polymer is preferably from 0.3 to
10% by weight, more preferably from 0.5 to 5% by weight and most
preferably from 0.5 to 3% by weight in view of a good dispersion
stability of the resultant polymer particles.
[0138] The content of constitutional units derived from the
components (c) in the emulsion polymer is preferably from 50 to
99.5% by weight, more preferably from 60 to 99.5% by weight and
most preferably from 70 to 99% by weight in view of a good
dispersion stability of the resultant polymer particles.
[0139] Also, the weight ratio [(a)/(c)] of the component (a) to the
components (c) is preferably from 0.003 to 0.5, more preferably
from 0.005 to 0.3 and most preferably from 0.01 to 0.1 in view of a
good storage stability, a good optical density, a good high
lighter-fastness and a good ejection property of the resultant ink,
etc.
[0140] In the above polymerization reaction, there may be used any
known polymerization initiators. Examples of the polymerization
initiators include inorganic peroxides such as hydrogen peroxide,
potassium persulfate and ammonium persulfate; organic peroxides
such as cumene hydroperoxide, diisopropylbenzene hydroperoxide and
p-menthane hydroperoxide; other organic polymerization initiators,
e.g., azo-based initiators such as azobisdiisobutyronitrile and
methoxybenzene diazomercaptonaphthalene; and redox polymerization
initiators using a peroxide or an oxidizing agent in combination
with a reducing agent such as sodium hydrogensulfite, sodium
thiosulfate, ferrous sulfate and sugar.
[0141] The surfactants used in the above emulsion polymerization
are not particularly limited, and are preferably anionic
surfactants and nonionic surfactants. Examples of the anionic
surfactants include sodium dodecylbenzenesulfonate, sodium laurate,
and ammonium salts of polyoxyethylene alkyl ether sulfates.
Examples of the nonionic surfactants include polyoxyethylene alkyl
ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan
fatty esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene
alkyl amines and polyoxyethylene alkyl amides. These surfactants
may be used alone or in the form of a mixture of any two or more
thereof.
[0142] The reactive surfactant means a surfactant containing one or
more radical-polymerizable unsaturated double bonds in a molecule
thereof. The reactive surfactant exhibits an excellent
emulsifiability for monomers and, therefore, can produce a water
dispersion having an excellent stability, resulting in enhanced
high lighter-fastness of the resultant water-based ink.
[0143] The reactive surfactant is preferably in the form of an
anionic or nonionic surfactant containing at least one hydrophobic
group such as linear or branched alkyl or alkenyl groups having 8
to 30 carbon atoms and preferably 12 to 22 carbon atoms, and at
least one hydrophilic group such as ionic groups and oxyalkylene
groups.
[0144] Examples of the alkyl groups include octyl, 2-ethylhexyl,
decyl, dodecyl, tetradecyl, hexadecyl, octadecyl and behenyl.
[0145] Examples of the alkenyl groups include oleyl and
octenyl.
[0146] Examples of the ionic groups include cationic groups such as
ammonium groups and anionic groups. Among these ionic groups,
preferred are anionic groups, and more preferred are anionic groups
such as a carboxyl group, a sulfonic group, a sulfuric group and a
phosphoric group and base-neutralized products thereof. The bases
used for neutralizing the anionic groups are the same neutralizing
agents as exemplified above.
[0147] The oxyalkylene groups preferably contain 1 to 4 carbon
atoms, and an average polymerization degree of repeating units
thereof is preferably from 1 to 100, more preferably from 4 to 80
and mot preferably from 4 to 50. Among these oxyalkylene groups,
preferred are an oxyethylene group and/or an oxypropylene
group.
[0148] When the surfactant contains two or more kinds of
oxyalkylene groups, for example, oxyethylene group and oxypropylene
group, these groups may be either block-added, random-added or
alternate-added. The terminal end group of the oxyalkylene groups
is not particularly limited, and may be a hydroxyl group or an
alkoxy group such as methoxy and ethoxy.
[0149] The reactive surfactants used in the emulsion polymerization
are preferably those surfactant having an anionic group and/or an
oxyalkylene group when the resultant emulsion polymer particles
contain a constitutional unit derived from anionic monomers, or
those surfactants having a cationic group and/or an oxyalkylene
group when the resultant emulsion polymer particles contain a
constitutional unit derived from cationic monomers, in view of
coagulation stability of the polymer particles.
[0150] Specific examples of the reactive surfactants include
sulfosuccinic ester-based surfactants represented by the following
general formulae (4) and (5) such as "LATEMUL S-120P" and "LATEMUL
S-180A" both available from Kao Corp., and "ELEMINOL JS-2"
available from Sanyo Kasei Kogyo Co., Ltd., and alkyl phenol
ether-based surfactants represented by the following general
formula (6) such as "AQUALON HS-10" and "AQUALON RN-20" both
available from Daiichi Kogyo Seiyaku Co., Ltd. ##STR3## wherein
M.sup.2 is Na, K or NH.sub.4; and R.sup.8 is an alkyl group having
8 to 18 carbon atoms. ##STR4## wherein M.sup.2 and R.sup.8 have the
same meaning as defined above. ##STR5## wherein X is H, SO.sub.3Na,
SO.sub.3K or SO.sub.3NH.sub.4; R.sup.8 has the same meaning as
defined above; and n is an integer of 1 to 200 and preferably 1 to
50.
[0151] Among these reactive surfactants, preferred are those
containing anionic groups represented by the above general formulae
(4) and (5) in view of facilitated operation of the emulsion
polymerization. These reactive surfactants may be used alone or in
the form of a mixture of any two or more thereof.
[0152] The amount of the reactive surfactant used is usually from
0.1 to 10 parts by weight, preferably from 0.1 to 5 parts by weight
and more preferably from 0.1 to 3 parts by weight on the basis of
100 parts by weight of the ethylenically unsaturated monomers other
than the reactive surfactant. When the amount of the reactive
surfactant used is 0.1 part by weight or more, the polymer
particles exhibit a good stability, resulting in an enhanced
dispersion stability of the polymer particles, whereas when the
amount of the reactive surfactant used is 10 parts by weight or
less, the resultant ink have a good high lighter-fastness.
[0153] Specific examples of the emulsion polymer include
(meth)acrylic polymers, vinyl acetate-based polymers,
styrene-butadiene-based polymers, vinyl chloride-based polymers,
styrene-(meth)acrylic polymers, butadiene-based polymers and
styrene-based polymers.
[0154] Among these emulsion polymers, preferred are (meth)acrylic
polymers, (meth)acrylic-styrene-based polymers and styrene-based
polymers, and more preferred (meth)acrylic-styrene-based polymers
obtained by copolymerizing a styrene-based monomer with an
(meth)acrylic ester.
[0155] As monomers used for synthesizing the (meth)acrylic polymers
or the (meth)acrylic-styrene-based polymers, there are preferably
used (meth)acrylic group-containing monomers among the salt-forming
group-containing monomers (a), the hydrophobic monomers (b) and the
hydroxyl-containing monomers (d) as exemplified above.
[0156] Among these monomers, preferred are (meth)acrylic esters.
Examples of the preferred (meth)acrylic esters include the above
alkyl (meth)acrylates and the above aromatic group-containing
(meth)acrylates. Specific examples of the (meth)acrylic esters
include methyl (meth)acrylate, ethyl (meth)acrylate, (iso)propyl
(meth)acrylate, (iso- or tertiary-)butyl (meth)acrylate, (iso)amyl
(meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, (iso)octyl(meth)acrylate,
(iso)decyl(meth)acrylate, (iso)dodecyl(meth)acrylate, (iso)stearyl
(meth)acrylate, 2-hydroxyethyl(meth)acrylate and
3-hydroxypropyl(meth)acrylate.
[0157] Examples of the styrene-based monomer for synthesizing the
(meth)acrylic-styrene-based polymers and the styrene-based polymers
include those exemplified above. Among these monomers, preferred
are styrene, vinyl toluene, 2-methyl styrene and chlorostyrene.
[0158] When the (meth)acrylic-styrene-based polymers are used as
the emulsion polymer, the constitutional unit derived from the
salt-forming group-containing monomers such as (meth)acrylic acid
is contained therein in an amount of 0.5 to 5% by weight and
preferably 0.5 to 3% by weight on the basis of the total weight of
the whole monomers used, in order to enhance the stability of the
water dispersion of the polymer particles. When the content of the
salt-forming group-containing monomers lies within the
above-specified range, the viscosity of the emulsion polymerization
reaction system is reduced, resulting in simple production of
stable polymer particles.
[0159] In view of a good dispersion stability of the polymer
particles as well as a good high lighter-fastness, the
constitutional unit derived from the (meth)acrylic esters is
contained therein in an amount of preferably 2 to 95% by weight and
more preferably 15 to 80% by weight, and the constitutional unit
derived from the styrene-based monomers is contained therein in an
amount of preferably 2 to 95% by weight and more preferably 15 to
80% by weight.
[0160] When the styrene-based monomer is copolymerized with the
(meth)acrylic ester, the weight ratio of [the styrene-based
monomer: the (meth)acrylic ester] is preferably from 70:30 to 10:90
and more preferably from 60:40 to 30:70. The solid content in the
obtained polymer particles is preferably from 1 to 80% and more
preferably from 10 to 70% in view of a good stability and a good
formulation property.
(ii) Production of Emulsion Polymer
[0161] The emulsion polymer particles used in the present invention
may be produced by known emulsion polymerization methods.
[0162] In view of enhancing the film-forming property and the high
lighter-fastness, the emulsion polymer preferably has a glass
transition temperature of 50.degree. C. or lower and preferably
30.degree. C. or lower. Further, the glass transition temperature
of the emulsion polymer is preferably -70.degree. C. or higher and
more preferably -40.degree. C. or higher in view of enhancing a
strength of the resultant coating film as well as the high
lighter-fastness.
[0163] In the water dispersion and the water-based ink, the D50
value of the water dispersion of the emulsion polymer particles
(ii) is not particularly limited as long as the resultant ink is
kept stable upon storage thereof. The D50 value of the water
dispersion of the emulsion polymer particles (ii) is preferably
from 5 to 300 nm and more preferably from 30 to 200 nm as measured
at 25.degree. C. using the laser particle analyzing system
"ELS-8000" (cumulant analysis) available from Otsuka Denshi Co.,
Ltd.
Water-Insoluble Organic Compound
[0164] It is considered that at least a part of the water-insoluble
organic compound used in the present invention is included in the
polymer particles (A-1) containing the colorant or the polymer
particles (B). Further, it is considered that the polymer particles
in which at least a part of the water-insoluble organic compound is
included, are enhanced in interaction therebetween, resulting in an
improved adhesion of the polymer particles to papers and,
therefore, enhanced optical density and high lighter-fastness.
[0165] In the present invention, aliphatic acids and derivatives
thereof tend to be deteriorated in the above-mentioned effects if
they are used as the water-insoluble organic compound (C).
Therefore, the aliphatic acids and derivatives thereof are
preferably excluded from the scope of the water-insoluble organic
compound (C) used in the present invention. In particular, when
using the polymer particles (A-1) containing the colorant in the
water dispersion or water-based ink, it is preferred that the
aliphatic acids and derivatives thereof are not used as the
water-insoluble organic compound (C) therein.
[0166] The aliphatic acids which are to be excluded from the scope
of the water-insoluble organic compound (C) include saturated or
unsaturated alkyl carboxylic acids having 8 to 22 carbon atoms.
Examples of the aliphatic acids include lauric acid, myristic acid,
palmitic acid, oleic acid, stearic acid and behenic acid.
[0167] The aliphatic acid derivatives which are to be excluded from
the scope of the water-insoluble organic compound (C) include
aliphatic acid monoester compounds produced from a monovalent
aliphatic acid in the form of a saturated or unsaturated alkyl
carboxylic acid and a monovalent alcohol, aliphatic acid amide
compounds produced from the above aliphatic acid and ammonia or a
lower amine having 3 or less carbon atoms, and aliphatic acid
anhydrides derived from the above aliphatic acid. More
specifically, the above aliphatic acid esters include ester
compounds produced from a saturated or unsaturated alkyl carboxylic
acid having 8 to 22 carbon atoms, and an alcohol. Examples of the
aliphatic acid esters include isotridecyl myristate, methyl
stearate, methyl oleate, methyl palmitate and methyl behenate.
Examples of the aliphatic acid amides include oleamide and
stearamide. Examples of the aliphatic acid anhydrides include oleic
anhydride. However, these compounds may be contained in the water
dispersion of the present invention as long as the object of the
present invention is not adversely affected.
[0168] The water-insoluble organic compound preferably has a
molecular weight of from 100 to 2,000 and more preferably from 100
to 1,000 in view of enhancing a optical density and a high
lighter-fastness of the resultant ink.
[0169] The solubility of the water-insoluble organic compound in
water is 5 g or lower, preferably 3 g or lower and more preferably
1 g or lower per 100 g of water as measured at 20.degree. C.
[0170] The water-insoluble organic compound preferably has a Log P
value of from -1 to 11, more preferably from 1 to 9, still more
preferably from 1.5 to 8 and most preferably from 2 to 7 for
enhancing a flexibility of the polymer.
[0171] In addition, in view of a good interaction between the
water-insoluble organic compound and the polymer particles, the
value obtained by subtracting the Log P value of the polymer of the
polymer particles (B) from the Log P value of the water-insoluble
organic compound (C) is preferably from -4 to 8, more preferably
from -2 to 6, still more preferably from -1.5 to 5 and most
preferably from -1 to 4.
[0172] Here, the "Log value" means a logarithm of a 1-octanol/water
partition coefficient of the water-insoluble organic compound, and
is expressed by a numerical value calculated according to fragment
approach using SRC's LOGKOW/KOWWIN Program of KowWin (Syracuso
Research Corporation, USA) (The KowWin Program methodology is
described in the following journal article: Meylan, W. M. and P. H.
Howard, 1995, "Atom/fragment contribution method for estimating
octanol-water partition coefficients", J. Parm. Sci., 84, pp.
83-92). The fragment approach is conducted on the basis of a
chemical structure of compounds in which the number of atoms and
the type of chemical bonds are taken into consideration. The Log P
value is in general a numerical value which is used for relative
evaluation of hydrophilic and hydrophobic properties of organic
compounds.
[0173] The water-insoluble organic compound is preferably in the
form of an ester compound, an ether compound or a sulfonamide
compound for facilitating inclusion of the water-insoluble organic
compound in the polymer particles. The water-insoluble organic
compound is more preferably an ester or ether compound (f)
containing two or more ester or ether bonds in a molecule thereof,
and/or an ester or ether compound (g) containing one or more ester
or ether bonds and at least one functional group selected from the
group consisting of a carboxyl group, a sulfonic group, a
phosphoric acid residue, a carbonyl group, an epoxy group and a
hydroxyl group in a molecule thereof. The number of the ester or
ether bonds in the compound (f) is preferably from 2 to 3; the
number of the ester or ether bonds in the compound (g) is
preferably from 1 to 3, and the number of the functional groups in
the compound (g) is preferably from 1 to 3.
[0174] Meanwhile, the phosphoric acid residue means a phosphoric
group as a remaining part of a phosphoric acid ester or ether which
is obtained by excluding the esterified or etherified moiety
therefrom.
[0175] Among these ester or ether compounds, preferred are esters
produced from a monovalent carboxylic acid or a salt thereof, and a
polyvalent alcohol; esters produced from a polyvalent acid such as
polycarboxylic acid and phosphoric acid or a salt thereof, and a
monovalent alcohol; and ethers of polyvalent alcohols, and more
preferred are those compounds having two aliphatic or aromatic
carboxylic ester groups or three phosphoric ester groups. Examples
of the salt include alkali metal salts, alkanol amine salts and
ammonium salts.
[0176] Examples of the monovalent carboxylic acid include linear or
branched aliphatic carboxylic acids having 1 to 18 carbon atoms and
preferably 2 to 10 carbon atoms, for example, linear aliphatic
carboxylic acids such as acetic acid, butyric acid, caproic acid,
caprylic acid, capric acid, lauric acid and palmitic acid, branched
aliphatic carboxylic acids such as pivalic acid, and unsaturated
aliphatic carboxylic acids such as acrylic acid and methacrylic
acid; and aromatic carboxylic acids having 6 to 12 carbon atoms
such as benzoic acid. Examples of the polyvalent acid include
aliphatic carboxylic acids having 2 to 12 carbon atoms such as
maleic acid, fumaric acid, itaconic acid, succinic acid, adipic
acid and sebacic acid; aromatic carboxylic acids having 6 to 12
carbon atoms such as phthalic acid and trimellitic acid; and
phosphoric acids.
[0177] Examples of the monovalent alcohol include linear or
branched aliphatic alcohols having 1 to 18 carbon atoms and
preferably 2 to 10 carbon atoms such as ethyl alcohol, butyl
alcohol, hexyl alcohol, octyl alcohol, decyl alcohol and dodecyl
alcohol; and aromatic alcohols having 6 to 12 carbon atoms such as
phenol. Examples of the polyvalent alcohol include those having 2
to 12 carbon atoms such as ethylene glycol, diethylene glycol,
neopentyl glycol, trimethylol propane, pentaerythritol and
glycerol. The aliphatic acids and alcohols used in the present
invention may be either saturated or unsaturated.
[0178] Specific examples of the water-insoluble organic compound
include (1) aliphatic carboxylic esters, (2) aromatic carboxylic
esters, (3) phosphoric esters, (4) cycloalkane (cycloalkene)
carboxylic esters, (5) oxyacid esters, (6) glycol esters, (7)
epoxy-based esters, (8) sulfonamides, (9) polyesters, (10) glyceryl
alkyl ethers, (11) glyceryl alkyl esters, (12) glycol alkyl ethers,
(13) glycol alkyl esters, (14) ethers or esters of trimethylol
propane, and (15) ethers or esters of pentaerythritol.
[0179] Among these compounds, in view of a good optical density and
a good high lighter-fastness, preferred are the compounds (1), (3),
(5), (8) and (10), more preferred is at least one compound selected
from the group consisting of (1) aliphatic di- or tri-carboxylic
esters, (3) phosphoric esters and (10) glyceryl alkyl ethers.
[0180] The aliphatic dicarboxylic esters (1) are preferably
compounds represented by the following general formula (7):
##STR6## wherein R.sup.11 and R.sup.12 are respectively a hydrogen
atom, a linear, branched or cyclic hydrocarbon group having 1 to 18
carbon atoms, an aralkyl group having 7 to 22 carbon atoms, an aryl
group having 6 to 22 carbon atoms or a glycol ether group having 2
to 10 carbon atoms, and R.sup.11 and R.sup.12 may be the same or
different; R.sup.13 is a divalent aliphatic hydrocarbon group
having 1 to 18 carbon atoms which may have an unsaturated group;
R.sup.11 to R.sup.13 may have a substituent group; n represents an
average molar number of addition, and is a number from 0 to 20; and
AO is an alkyleneoxy group.
[0181] R.sup.11 and R.sup.12 are preferably a linear or branched
alkyl or alkenyl group having preferably 2 to 18 carbon atoms and
more preferably 4 to 12 carbon atoms in view of enhancing a gloss
and an image clarity of the resultant prints. Specific examples of
the alkyl or alkenyl group include methyl, ethyl, propyl,
isopropyl, butyl, hexyl, 2-ethylhexyl, octyl, dodecyl and cetyl.
The definitions of R.sup.11 and R.sup.12 are similarly applied to
the below-mentioned formulae.
[0182] R.sup.13 is preferably an alkylene group or an alkenylene
group. Specific examples of the alkylene group or the alkenylene
group include an ethylene group, a propylene group, a trimethylene
group, a butylene group, a hexylene group, a 2-ethylhexylene group,
an octylene group and a dodecylene group. Among these alkylene or
alkenylene groups, preferred are alkylene groups having 2 to 15
carbon atoms, more preferred are alkylene groups having 2 to 12
carbon atoms, and most preferred are alkylene groups having 2 to 8
carbon atoms. The definition of R.sup.13 is similarly applied to
the below-mentioned formulae.
[0183] The symbol n is a number of preferably from 0 to 15, more
preferably from 0 to 12 and most preferably from 2 to 10.
[0184] AO is an alkyleneoxy group having 2 to 4 carbon atoms such
as an ethyleneoxy (EO) group, a propyleneoxy (PO) group and a
butyleneoxy (BO) group, and when n is 2 or more, a plurality of AO
groups may be the same or different. When a plurality of AO groups
are different from each other, the respective AO groups may be
either block-added or random-added.
[0185] Examples of the substituent group which may be bonded to
R.sup.11 to R.sup.13 include a halogen atom such as fluorine,
chlorine and bromine; an alkyl group having 1 to 12 carbon atoms
such as methyl, ethyl, propyl, isopropyl, isobutyl, t-butyl, hexyl
and lauryl; a cycloalkyl group such as cyclohexyl; an aryl group
such as phenyl; an alkoxy group having 1 to 12 carbon atoms such as
methoxy, ethoxy and isopropoxy; an aryloxy group such as phenyloxy;
an alkoxycarbonyl group such as methoxycarbonyl; an acyl group such
as acetyl and benzoyl; an acyloxy group such as acetyloxy; a cyano
group; a nitro group; a hydroxyl group; a carboxyl group; an oxo
group; an epoxy group; an ether group and an ester group. These
substituent groups may be bonded to R.sup.11 to R.sup.13 alone or
in combination of any two or more thereof.
[0186] Specific examples of the aliphatic dicarboxylic ester (1)
include aliphatic dibasic acid esters such as dimethyl adipate,
diethyl adipate, dibutyl adipate, diisobutyl adipate,
bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate,
bis(butyl diethylene glycol) adipate, dimethyl sebacate, diethyl
sebacate, dibutyl sebacate, bis(2-ethylhexyl) sebacate, diethyl
succinate and bis(2-ethylhexyl) azelate. Among these esters,
especially preferred are diesters of aliphatic dibasic acids having
6 to 10 carbon atoms such as diethyl adipate, dibutyl adipate,
diisobutyl adipate, bis(butyl diethylene glycol) adipate,
bis(octoxy polyethylene glycol) adipate (R.sup.11 and R.sup.12 are
both 2-ethylhexyl; AO=EO; average molar number of addition (n): 4,
6 or 8), diethyl sebacate, dibutyl sebacate and diisobutyl
sebacate. Examples of the aliphatic tricarboxylic ester include
esters of citric acid.
[0187] The aromatic carboxylic esters (2) are preferably di- or
tri-carboxylic esters represented by the following general formula
(8): ##STR7## wherein R.sup.11 and R.sup.12 have the same meaning
as defined above, and R.sup.11 and R.sup.12 may be the same or
different.
[0188] Specific examples of the aromatic carboxylic esters (2)
include phthalic esters such as dimethyl phthalate, diethyl
phthalate, di-n-butyl phthalate, diisobutyl phthalate,
bis(2-ethylhexyl) phthalate, di-n-octyl phthalate, diisodecyl
phthalate, butylbenzyl phthalate, octylbenzyl phthalate,
nonylbenzyl phthalate, stearylbenzyl phthalate, octyldecyl
phthalate, dicylcohexyl phthalate, diphenyl phthalate,
bis(dimethylcyclohexyl) phthalate, bis(t-butylcyclohexyl)phthalate
and ethylphthalylethyl glycolate; and trimellitic esters such as
dibutyl trimellitate, diisobutyl trimellitate and
tris(2-ethylhexyl) trimellitate. Among these aromatic carboxylic
esters, preferred are phthalic diesters containing an aliphatic
alcohol residue having 1 to 5 carbon atoms such as dimethyl
phthalate, diethyl phthalate, di-n-butyl phthalate and diisobutyl
phthalate; benzyl phthalates containing an alkyl group having 3 to
18 carbon atoms such as octylbenzyl phthalate and stearylbenzyl
phthalate; and trimellitic diesters containing an aliphatic alcohol
residue having 3 to 5 carbon atoms such as dibutyl trimellitate and
diisobutyl trimellitate. The aromatic carboxylic esters are
preferably in the form of an aromatic di- or tri-carboxylic
ester.
[0189] The phosphoric esters (3) are preferably compounds
represented by the following general formula (9): ##STR8## wherein
R.sup.11 and R.sup.12 have the same meaning as defined above, and
R.sup.11 and R.sup.12 may be the same or different.
[0190] Specific examples of the phosphoric esters (3) include
tributyl phosphate, tris(2-ethylhexyl) phosphate, tris(butoxyethyl)
phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl
phosphate, cresyldiphenyl phosphate and 2-ethylhexyl diphenyl
phosphate. Among these phosphoric esters, preferred are phosphoric
esters containing an alkoxyalkyl group having 5 to 9 carbon atoms
such as tris(butoxyethyl) phosphate; phosphoric esters containing
an aliphatic hydrocarbon group having 4 to 12 carbon atoms such as
tributyl phosphate; and phosphoric esters containing an aromatic
hydrocarbon group having 7 to 12 carbon atoms such as
tris(butoxyethyl) phosphate, tricresyl phosphate, trixylenyl
phosphate and cresyldiphenyl phosphate. The phosphoric esters are
preferably in the form of a phosphoric di- or tri-ester.
[0191] The cycloalkane (cycloalkene) carboxylic esters (4) are
those esters containing a cyclic hydrocarbon group having 3 to 8
carbon atoms which may have one unsaturated group, and are
preferably cyclohexane (cyclohexene) dicarboxylic esters
represented by the following general formula (10): ##STR9## wherein
R.sup.11 and R.sup.12 have the same meaning as defined above, and
R.sup.11 and R.sup.12 may be the same or different.
[0192] Specific examples of the cycloalkane (cycloalkene)
carboxylic esters (4) include cyclohexane esters such as dibutyl
1,2-cyclohexanedicarboxylate and diisononyl
1,2-cyclohexanedicarboxylate; and cyclohexene esters such as
dibutyl 3,4-cyclohexenedicarboxylate and diisononyl
3,4-cyclohexenedicarboxylate.
[0193] The oxyacid esters (5) are preferably compounds represented
by the following general formula (11): ##STR10## wherein R.sup.11,
R.sup.12 and R.sup.13 have the same meaning as defined above, and
R.sup.11 and R.sup.12 may be the same or different.
[0194] Specific examples of the oxyacid esters (5) include triethyl
acetylcitrate, tributyl acetylcitrate and methyl
acetylricinoleate.
[0195] The glycol esters (6) are preferably compounds represented
by the following general formula (12): ##STR11## wherein R.sup.11,
R.sup.12 and R.sup.13 have the same meaning as defined above, and
R.sup.11 and R.sup.12 may be the same or different.
[0196] Specific examples of the glycol esters (6) include
diethylene glycol dibenzoate and triethylene glycol di(2-ethyl
hexoate).
[0197] The epoxy-based esters (7) are preferably compounds
represented by the following general formula (13): ##STR12##
wherein R.sup.11 has the same meaning as defined above, and
R.sup.14 and R.sup.15 are each independently a hydrogen atom or a
lower alkyl group having 1 to 5 carbon atoms; and R.sup.16 is an
alkylene group having 1 to 6 carbon atoms.
[0198] Specific examples of the epoxy-based esters (7) include
butyl epoxystearate and octyl epoxystearate.
[0199] The sulfonamides (8) are preferably compounds represented by
the following general formula (14): R.sup.11--SO.sub.2NH--R.sup.12
(14) wherein R.sup.11 and R.sup.12 have the same meaning as defined
above, and R.sup.11 and R.sup.12 may be the same or different.
[0200] Specific examples of the sulfonamides (8) include o- and
p-toluene sulfonamides and N-butylbenzene sulfonamide.
[0201] The polyesters (9) are preferably compounds represented by
the following general formula (15): ##STR13##
[0202] wherein R.sup.11, R.sup.12 and R.sup.13 have the same
meaning as defined above, and R.sup.11 and R.sup.12 may be the same
or different, and a plurality of R.sup.3 groups may be the same or
different; and m is a number from 1 to 18 and preferably from 1 to
10.
[0203] Specific examples of the polyesters (9) include
poly(1,2-butanediol adipate) and poly(1,3-butanediol adipate).
[0204] Specific examples of the glyceryl alkyl ethers (10) include
glyceryl monoethers, glyceryl diethers and glyceryl triethers.
Among these glyceryl alkyl ethers, preferred are glyceryl
monoethers containing a linear or branched alkyl group having 8 to
30 carbon atoms. The alkyl group have 8 to 30 carbon atoms,
preferably 8 to 22 carbon atoms and more preferably 8 to 14 carbon
atoms.
[0205] Examples of the alkyl group include 2-ethylhexyl,
(iso)octyl, (iso)decyl, (iso)dodecyl, (iso)myristyl, (iso)cetyl,
(iso)stearyl and (iso)behenyl.
[0206] The bonding position of the alkyl group in the glyceryl
alkyl ethers is not particularly limited, and the glyceryl alkyl
ethers may be in the form of a 1-alkyl glyceryl monoether or a
2-alkyl glyceryl monoether.
[0207] Specific examples of the glyceryl alkyl esters (11) include
glyceryl monoalkyl esters, glyceryl dialkyl esters and glyceryl
trialkyl esters.
[0208] Among these glyceryl alkyl esters, preferred are glyceryl
alkyl esters of linear or branched aliphatic carboxylic acids
having 1 to 18 carbon atoms and preferably 2 to 10 carbon atoms,
for example, linear aliphatic carboxylic acids such as acetic acid,
butyric acid, caproic acid, caprylic acid, capric acid, lauric acid
and palmitic acid, and branched aliphatic carboxylic acids such as
pivalic acid. The total number of carbon atoms in the alkyl group
is preferably 6 or more and more preferably 8 or more.
[0209] Further specific examples of the glyceryl alkyl esters (11)
include glyceryl triacetate, glyceryl diacetate and glyceryl
monoacetate.
[0210] Specific examples of the glycol alkyl ethers (12) include
glycol monoalkyl ethers and glycol dialkyl ethers.
[0211] Specific examples of the glycol alkyl esters (13) include
glycol monoalkyl esters and glycol dialkyl esters.
[0212] Examples of the glycol contained in the compounds (12) and
(13) include ethylene glycol and neopentyl glycol. Examples of the
alkyl group contained in the compounds (12) and (13) include a
linear or branched alkyl group having 1 to 22 carbon atoms. The
total number of carbon atoms in the alkyl group is preferably 6 or
more and more preferably 8 or more.
[0213] The above water-insoluble organic compounds (1) to (15) may
be used alone or in the form of a mixture of any two or more
thereof.
Water Dispersion and Water-Based Ink for Ink-Jet Printing
[0214] The water dispersion of the present invention is produced by
mixing at least one material selected from the group consisting of
the above polymer particles (A-1) containing the colorant and the
self-dispersible pigment (A-2), with the polymer particles (B) and
the water-insoluble organic compound (C).
[0215] The order of mixing of the respective components is not
particularly limited. The mixing temperature is preferably from
about 5 to 50.degree. C. The components (A-1) and (A-2) may be used
in combination of two or more kinds thereof at the same time.
[0216] The water-based ink of the present invention is an ink
containing the water dispersion of the present invention and using
water as a main solvent. The water-based ink may further contain
various additives such as wetting agents, dispersants, defoaming
agents, mildew-proof agents and chelating agents, if required. The
mixing method of these respective components is not particularly
limited.
[0217] The contents of the colorant, the polymer particles (A-1)
containing the colorant, the self-dispersible pigment (A-2), the
polymer particles (B), the water-insoluble organic compound (C) and
water in the water dispersion and the water-based ink for ink-jet
printing are as follows.
[0218] The content of the colorant is preferably from 0.5 to 18% by
weight, more preferably from 1 to 10% by weight and most preferably
from 2 to 8% by weight in view of a good optical density and a good
high lighter-fastness.
[0219] The content of the polymer particles (A-1) (solid content)
containing the colorant is preferably from 1 to 20% by weight, more
preferably from 2 to 13% by weight and most preferably from 3 to
10% by weight in view of a good optical density and a good high
lighter-fastness.
[0220] The content of the self-dispersible pigment (A-2) is
preferably from 1 to 20% by weight, more preferably from 2 to 13%
by weight and most preferably from 3 to 10% by weight in view of a
good optical density and a good high lighter-fastness.
[0221] The content of the polymer particles (B) is preferably from
0.5 to 15% by weight, more preferably from 1 to 10% by weight and
most preferably from 2 to 8% by weight in view of a good high
lighter-fastness and a high optical density.
[0222] In view of a good high lighter-fastness and a high optical
density, the lower limit of the content of the water-insoluble
organic compound (C) is preferably 0.11% by weight or more, more
preferably 0.4% by weight or more, still more preferably 0.6% by
weight or more, further still more preferably 0.7% by weight,
further still more preferably 0.8% by weight and most preferably 1%
by weight or more, and the upper limit is preferably 10% by weight
or less, more preferably 5% by weight or less, still more
preferably 3% by weight or less and most preferably 2% by weight or
less. From these viewpoints, the content of the water-insoluble
organic compound (C) is preferably 0.11 to 10% by weight, more
preferably from 0.4 to 10% by weight, still more preferably from
0.6 to 5% by weight, further still more preferably from 0.7 to 5%
by weight, further still more preferably from 0.8 to 3% by weight
and most preferably from 1 to 2% by weight.
[0223] The content of water is preferably from 30 to 90% by weight
and more preferably from 40 to 80% by weight.
[0224] The mixing ratio between the polymer particles (A-1) (solid
content) containing the colorant or the self-dispersible pigment
(A-2) and the water-insoluble organic compound (C) is adjusted such
that the water-insoluble organic compound (C) is used in an amount
of preferably from 1 to 100 parts by weight, more preferably from 3
to 50 parts by weight and most preferably from 3 to 20 parts by
weight on the basis of 100 parts by weight of the polymer particles
(A-1) (solid content) containing the colorant or the
self-dispersible pigment (A-2) in view of a high optical density
and a good high lighter-fastness.
[0225] The weight ratio between the polymer particles (A-1) (solid
content) containing the colorant or the self-dispersible pigment
(A-2) and the polymer particles (B) is adjusted such that the
polymer particles (A-1) (solid content) containing the colorant and
the self-dispersible pigment (A-2) are respectively used in an
amount of from 50 to 900 parts by weight and more preferably from
100 to 800 parts by weight on the basis of 100 parts by weight of
the polymer particles (B) in view of a high optical density and a
good high lighter-fastness.
[0226] When both of the components (A-1) and (A-2) are used in the
form of a mixture thereof, the above-specified ratios are
calculated on the basis of the total amount thereof.
[0227] The weight ratio [(B)/(C)] of the polymer particles (B) to
the water-insoluble organic compound (C) is preferably from 15/1 to
1/2, more preferably from 6/1 to 1/1 and most preferably from 4/1
to 2/1 in view of a high optical density and a good high
lighter-fastness.
[0228] The surface tension of the water dispersion of the present
invention is preferably from 30 to 70 mN/m and more preferably from
35 to 68 mN/m as measured at 20.degree. C., and the surface tension
of the water-based ink of the present invention is preferably from
25 to 50 mN/m and more preferably from 27 to 45 mN/m as measured at
20.degree. C.
[0229] The viscosity of the water dispersion having a solid content
of 10 wt % is preferably from 2 to 6 mPas and more preferably from
2 to 5 mPas as measured at 20.degree. C. to produce a water-based
ink having a suitable viscosity. The viscosity of the water-based
ink is preferably from 2 to 12 mPas and more preferably from 2.5 to
10 mPas in order to maintain a good ejection property thereof. In
addition, the pH of the water-based ink of the present invention is
preferably from 4 to 10.
[0230] The water-based ink of the present invention is suitably
applicable to be used for ink-jet printing on ordinary paper
because printing images or characters on ordinary paper needs more
performance of optical density and high-lighter fastness.
[0231] The water-based ink of the present invention is suitably
applicable to a piezoelectric type ink-jet printer, though not
particularly limited thereto.
EXAMPLES
[0232] In the following production examples, examples and
comparative examples, the "part(s)" and "%" indicate "part(s) by
weight" and "% by weight", respectively, unless otherwise
specified.
Production Example 1
Production of Polymer Particles Containing an Colorant (A-1)
[0233] Twenty parts of methyl ethyl ketone and 0.03 part of a chain
transfer agent (2-mercaptoethanol) together with 10% of 200 parts
of a monomer mixture containing methacrylic acid (a)/a styrene
macromer (b) (tradename "AS-6" available from Toagosei Co.,
Ltd./styrene (c)/polyethylene glycol methacrylate 2-ethylhexyl
ether (e) ("NK Ester EH-4G" available from Shin-Nakamura Kagaku
Co., Ltd. average molar number of addition of ethyleneoxide:4) at a
mixing weight ratio of 14/15/56/25 were charged into a reaction
vessel and mixed with each other, and then the reaction vessel was
fully purged with a nitrogen gas to thereby obtain a mixed
solution.
[0234] Separately, remaining 90% of the monomer mixture was charged
into a dropping funnel, and further 0.27 part of the chain transfer
agent, 60 parts of methyl ethyl ketone and 1.2 parts of a radical
polymerization initiator (2,2'-azobis(2,4-dimethylvaleronitrile))
were added thereto and mixed with each other, and the dropping
funnel was fully purged with a nitrogen gas to thereby obtain a
mixed solution.
[0235] The mixed solution in the reaction vessel was heated to
65.degree. C. under stirring in a nitrogen atmosphere, and then the
mixed solution in the dropping funnel was gradually dropped
thereinto over 3 h. After the elapse of 2 h from completion of the
dropping, a solution prepared by dissolving 0.3 part by weight of
the radical polymerization initiator in 5 parts of methyl ethyl
ketone was added to the obtained reaction solution, and the
resultant solution was further aged at 65.degree. C. for 2 h and
further at 70.degree. C. for 2 h to obtain a polymer solution.
Next, the thus obtained polymer solution was mixed with a given
amount of methyl ethyl ketone under stirring to obtain a polymer
solution having a effective content of 50%. As a result, it was
confirmed that the weight-average molecular weight of the thus
obtained polymer was about 150,000.
[0236] Into 30 parts of the thus obtained polymer solution, were
added 60 parts of carbon black (tradename "Monarch 880" available
from Cabot Corp.), 4.3 parts of a 5 mol/L sodium hydroxide
solution, 1.2 parts of a 25% ammonia aqueous solution, 70 parts of
methyl ethyl ketone and 230 parts of ion-exchanged water, and the
obtained mixture was stirred at 20.degree. C. for 1 h using disper
blades. The thus obtained mixture was dispersed under a pressure of
150 MPa by passing through a dispersing apparatus "MICROFLUIDIZER"
(tradename) available from Microfluidics Corp., 10 times.
[0237] The resultant kneaded material was further mixed with 100
parts of ion-exchanged water, and then methyl ethyl ketone was
removed from the resultant mixture under reduced pressure at
60.degree. C., followed by removing a part of water therefrom. The
obtained mixture was filtered through a 5 .mu.m-mesh filter (acetyl
cellulose membrane; available from Fuji Photo Film Co., Ltd.) to
remove coarse particles therefrom, thereby obtaining a water
dispersion of pigment-containing particles having a solid content
of 20% by weight.
[0238] As a result, it was confirmed that the obtained
pigment-containing particles had D50 of 115 nm. Meanwhile, the
measurement of D50 was performed at 25.degree. C. using a laser
particle analyzing system "ELS-8000" (product number) available
from Otsuka Denshi Co., Ltd.
Production Example 2
Production of (B) Polymer Particles (B-1)
Self-Emulsifiable Polymer Particles
[0239] Thirty parts of the polymer solution obtained in Production
Example 1 was mixed with 40 parts of methyl ethyl ketone and 30
parts of acetone under stirring to prepare a uniform solution. The
thus obtained solution was charged into a dropping funnel, and
dropped into a reaction vessel filled with a mixture previously
prepared by mixing 4.3 parts of a 5 mol/L sodium hydroxide aqueous
solution, 1.2 parts of a 25% ammonia aqueous solution and 217.5
parts of ion-exchanged water with each other, over 30 min to
neutralize the polymer solution. Further, the mixture was stirred
for 30 min to obtain an emulsion composition. The thus obtained
emulsion composition was heated at 60.degree. C. under reduced
pressure to remove the organic solvent and ammonia together with a
part of water therefrom. The composition was further passed through
a filter having an average pore size of 5 .mu.m (available from
Nippon Pole Co., Ltd.) to remove coarse particles therefrom,
thereby obtaining a water dispersion containing the polymer
particles (B-1) in an amount of 20% as a solid content (effective
content). As a result of conducting the same measurement as in
Production Example 1, it was confirmed that the thus obtained
polymer particles (B-1) had D50 of 105 nm.
[0240] The weight-average molecular weight and the Log P value of
the monomer (Mw; Log P value): methacrylic acid (86; 0.99)/a
styrene macromer (6000; 165.72)/styrene (104; 2.89)/polyethylene
glycol methacrylate 2-ethylhexyl ether (374; 3.56)
[0241] The Log P value of the polymer of the polymer particles:
3.08
Production Example 3
Production of (B) Polymer Particles (B-2)
Emulsion Polymer Particles
[0242] A glass reactor equipped with a stirrer, a thermometer, a
reflux condenser and a nitrogen feed tube was charged with 1000 g
of ion-exchanged water, 62 g of polyoxyethylene alkyl ether sodium
sulfate as a surfactant (product name "LATEMUL E-118B" available
from Kao Corporation; effective ingredient content: 26%) and 2.4 g
of potassium persulfate, purged with nitrogen, and then placed in a
water bath to heat the contents of the reactor to 70.degree. C.
Next, 800 g of a monomer mixture containing acrylic acid
(a)/styrene (c)/methyl methacrylate (c)/butyl acrylate (c) at a
mixing weight ratio of 2/15/34/49 was dropped into the reactor over
2 h, and then the contents of the reactor were aged at 80.degree.
C. for 2 h, thereby obtaining polymer particles (B-2) having a
solid content (effective content) of 48%. As a result of conducting
the same measurement as in Production Example 1, it was confirmed
that the thus obtained polymer particles (B-2) had D50 of 120
nm.
[0243] The weight-average molecular weight and the Log P value of
the monomer (Mw; Log P value): acrylic acid (72; 0.44)/styrene
(104; 2.89)/methyl methacrylate (100; 1.28)/butyl acrylate (128;
2.20)
[0244] The Log P value of the polymer of the polymer particles:
1.91
Production Example 4
Production of (B) Polymer Particles (B-3)
Emulsion Polymer Particles Using Reactive Surfactant
[0245] The same procedure as in Production Example 2 was repeated
except for using 32 parts of a reactive surfactant "LATEMUL S-180A"
(available from Kao Corporation; effective ingredient content: 50%)
in place of polyoxyethylene alkyl ether sodium sulfate (product
name "LATEMUL E-118B" available from Kao Corporation; effective
ingredient content: 26%), thereby obtaining polymer particles (B-3)
having a solid content (effective content) of 47%. As a result of
conducting the same measurement as in Production Example 1, it was
confirmed that the thus obtained polymer particles (B-3) had D50 of
98 nm.
Examples 1 to 9 and Comparative Examples 1 to 5
[0246] An aqueous solution of a self-dispersible carbon black (CW-2
or CAB shown in Table 1), the pigment-containing particles obtained
in Production Example 1, a water dispersion containing the polymer
particles (B-1 to B-3) obtained in Production Examples 2 to 4
(solid content: 20%), dibutyl adipate (Log P value: 4.33), tributyl
phosphate (Log P value: 3.82), 5 parts of glycerol, 5 parts of
2-pyrrolidone, 2 parts of isopropyl alcohol, 1 part of "ACETYLENOL
EH" available from Kawaken Fine Chemicals Co., Ltd., and water were
prepared and mixed with each other under stirring at 25.degree. C.
to obtain a dispersion having an ink composition as shown in Table
1. The thus obtained dispersion was filtered through a 1.2
.mu.m-mesh filter to obtain a water-based ink.
[0247] The thus obtained water-based ink was evaluated with respect
to (1) optical density and (2) high lighter-fastness by the
following methods. The results are shown in Table 1.
[0248] Meanwhile, "CW-2", "CAB" and "Other Components" used in
Table 1 respectively represent the following s.
[0249] "CW-2": "BONJET CW-2" (tradename) available from Orient
Kagaku Kogyo Co., Ltd.; solid content: 15%; average particle size:
160 nm
[0250] "CAB": "CAB-O-JET 300" (tradename) available from Cabot
Corp.; solid content: 15%
[0251] "Other Components": 5 parts of glycerol, 5 parts of
2-pyrrolidone, 2 parts of isopropyl alcohol, and 1 part of
"ACETYLENOL EH" available from Kawaken Fine Chemicals Co., Ltd.
(1) Optical Density
[0252] Solid image printing was carried out on a recycled paper for
PPC available from Nippon Kakoseisi Co., Ltd., using an ink-jet
printer "Model EM930C" (piezoelectric type) available from Seiko
Epson Co., Ltd. The thus printed paper was naturally dried at room
temperature for 24 h, and then the optical density thereof was
measured by a Macbeth densitometer "RD914" (product number)
available from Gretag-Macbeth Corp. The results of the measurement
were evaluated according to the following evaluation criteria.
[Evaluation Criteria]
[0253] .largecircle.: optical density: 1.40 or more
[0254] .DELTA.: optical density: not less than 1.36 but less than
1.40
[0255] X: optical density: less than 1.36
(2) High Lighter-Fastness
[0256] Text printing was carried out on a recycled PPC paper
commercially available from Nippon Kakoseisi Co., Ltd., using the
above-mentioned printer, and after passage of 3 min and 10 min, the
extent of staining of the printed sample when traced with an
aqueous fluorescent marker "OPTEX 1" (tradename) commercially
available from Zebra Co., Ltd., was observed with naked eyes, and
the evaluation was made on the basis of the following evaluation
criteria.
[Evaluation Criteria]
[0257] .circleincircle.: No staining such as rubbed stains was
observed when traced with a fluorescent marker.
[0258] .largecircle.: Some rubbed stains were generated when traced
with a fluorescent marker, but at a level without practical
problems.
[0259] .DELTA.: Generation of rubbed stains were observed when
traced with a fluorescent marker.
[0260] X: Generation of rubbed stains were remarkably observed over
a whole surface traced with a fluorescent marker, which is
intolerable. TABLE-US-00001 TABLE 1-1 Ink composition Component (A)
colorant- Self-dispersible containing Polymer particles (B) carbon
black particles B-1 B-2 B-3 Kind Part (%) Part (%) Part (%) Part
(%) Part (%) Example 1 CW-2 47(7) -- 30(6) -- -- Example 2 CW-2
47(7) -- 30(6) -- -- Example 3 CW-2 47(7) -- -- 10(5) --
Comparative CW-2 47(7) -- 30(6) -- -- Example 1 Comparative CW-2
47(7) -- -- 6(3) -- Example 2 Comparative CW-2 47(7) -- -- -- 6(3)
Example 3 Example 4 CAB 47(7) -- -- 6(3) -- Example 5 CAB 47(7) --
-- -- 6(3) Example 6 CAB 47(7) -- -- -- 6(3) Example 7 CAB 47(7) --
-- -- 6(3) Comparative CAB 47(7) -- 30(6) -- -- Example 4 Example 8
-- -- 50(10) 20(4) -- -- Example 9 -- -- 50(10) 20(4) -- --
Comparative -- -- 50(10) 20(4) -- -- Example 5 Note: The numerical
values in parenthesis ( ) in the column "Ink composition" represent
respective effective contents of the self-dispersible carbon black,
the colorant-containing particles and the polymer particles.
[0261] TABLE-US-00002 TABLE 1-2 Ink composition Water-insoluble
organic compound Other (C) Water components Kind Part Part Part
Example 1 Dibutyl adipate 0.5 9.5 13 Example 2 Dibutyl adipate 1 9
13 Example 3 Dibutyl adipate 1 29 13 Comparative -- -- 10 13
Example 1 Comparative -- -- 34 13 Example 2 Comparative -- -- 34 13
Example 3 Example 4 Dibutyl adipate 1 33 13 Example 5 Dibutyl
adipate 1 33 13 Example 6 Tributyl phosphate 1 33 13 Example 7
Tributyl phosphate 3 31 13 Comparative -- -- 10 13 Example 4
Example 8 Dibutyl adipate 1 16 13 Example 9 Tributyl phosphate 1 16
13 Comparative -- -- 17 13 Example 5
[0262] TABLE-US-00003 TABLE 1-3 Evaluation High lighter-fastness
Optical density 3 min 10 min Example 1 .largecircle. (1.41)
.largecircle. .largecircle. Example 2 .largecircle. (1.43)
.largecircle. .largecircle. Example 3 .largecircle. (1.43)
.largecircle. .circleincircle. Comparative .DELTA. (1.36) X .DELTA.
Example 1 Comparative X (1.35) .DELTA. .DELTA. Example 2
Comparative .DELTA. (1.36) .DELTA. .largecircle. Example 3 Example
4 .largecircle. (1.42) .largecircle. .circleincircle. Example 5
.largecircle. (1.43) .circleincircle. .circleincircle. Example 6
.largecircle. (1.42) .largecircle. .circleincircle. Example 7
.largecircle. (1.41) .largecircle. .largecircle. Comparative
.DELTA. (1.37) X .DELTA. Example 4 Example 8 .largecircle. (1.40)
.circleincircle. .circleincircle. Example 9 .largecircle. (1.40)
.circleincircle. .circleincircle. Comparative .DELTA. (1.38)
.DELTA. .largecircle. Example 5 Note: The numerical values in
parenthesis ( ) in the column "Optical density" represent measured
values.
[0263] From the results shown in Table 1, it was confirmed that the
water-based inks for ink-jet printing obtained in Examples 1 to 9
were excellent in not only optical density but also high
lighter-fastness.
[0264] From the comparison between Examples 4 and 5, it was
confirmed that the water-based ink obtained in Example 5 which
contained the emulsion polymer particles (B-3) produced by using
the reactive surfactant was more excellent in high lighter-fastness
than the ink obtained in Example 4.
[0265] Further, it was confirmed that the inks obtained in Examples
1, 2 and 8 to 9 which were produced using the self-emulsifiable
polymer particles (B-1) were more excellent in gloss than the inks
obtained in Examples 3 to 7 which were produced using the emulsion
polymer particles (B-2) or (B-3).
[0266] Meanwhile, the gloss was evaluated by the following method.
That is, solid image printing was carried out on a coated paper
(photographic paper <glossy>"KA450PSK (tradename)" having a
60.degree. gloss of 41 which was available from Seiko Epson Co.,
Ltd., using the above ink-jet printer under the following printing
conditions:
[0267] Kind of Paper: Photo Printing Paper
[0268] Mode set: Photo
[0269] After allowing the printed paper to stand at 25.degree. C.
for 24 h, the 20.degree. gloss thereof was measured using a
glossmeter "HANDY GLOSSMETER" (tradename; product number: PG-1)
available from Nippon Denshoku Industries Co., Ltd.
Production Example 5
Production of Water Dispersion of Self-Dispersible Carbon Black
[0270] After mixing 300 g of a commercially available acidic carbon
black ("MA-7" (tradename) available from Mitsubishi Chemical Corp.;
primary particle size: 24 nm) with 1000 mL of water, 450 g of
sodium hypochlorite (effective chlorine concentration: 12%) was
dropped into the resultant mixture, and then the mixture was
stirred at a temperature of 100 to 105.degree. C. for 10 h. The
thus obtained slurry was filtered through "Toyo Filter Paper No. 2"
available from Advantis Co., Ltd., to separate the carbon black
particles therefrom. The thus separated carbon black particles were
fully washed with water. The resultant wet cake of carbon black was
dispersed again in 3000 mL of water, and desalted by passing
through a reverse osmosis membrane until reaching an electrical
conductivity of 0.2 .mu.s. Further, the obtained dispersion of
carbon black having a pH of 8 to 10 was concentrated to a carbon
black concentration of 10%, thereby obtaining a water dispersion
(a-1) of an anionic self-dispersible carbon black containing a
--COONa group bonded to a surface thereof. As a result, it was
confirmed that the carbon black contained in the water dispersion
had an average particle size of 130 nm and an anionic group content
of 270 .mu.mol/g, and a solid content of the water dispersion was
10%.
Production Example 6
Production of Polymer Particles
[0271] A glass reactor equipped with a stirrer, a thermometer, a
reflux condenser and a nitrogen feed tube was charged with 1000 g
of ion-exchanged water, 62 g of polyoxyethylene alkyl ether sodium
sulfate (product name "LATEMUL E-118B" available from Kao
Corporation; effective ingredient content: 26%) and 2.4 g of
potassium persulfate, purged with nitrogen, and then placed in a
water bath to heat the contents of the reactor to 70.degree. C.
Next, 800 g of a monomer mixture containing styrene/2-ethylhexyl
acrylate/acrylic acid at a mixing ratio of 49/49/2 was dropped into
the reactor over 2 h, and then the contents of the reactor were
aged at 80.degree. C. for 2 h, thereby obtaining polymer particles
(b-1) having an average particle size of 120 nm and a solid content
of 48%.
Example 10
[0272] Seventy parts of the water dispersion (a-1) containing the
self-dispersible carbon black which was obtained in Production
Example 5, 12.5 parts of the polymer particles (b-1), 1 part of
1-isodecyl glyceryl monoether (c-1) (Log P value: 3.39), 5 parts of
glycerol, 5 parts of 2-pyrrolidone, 2 parts of isopropyl alcohol, 1
part of "ACETYLENOL EH" available from Kawaken Fine Chemicals Co.,
Ltd., and 3.5 parts of water were mixed with each other to prepare
a dispersion. The thus obtained dispersion was filtered through a
1.2 .mu.m-mesh filter to obtain a water-based ink.
Comparative Example 6
[0273] The same procedure as in Example 10 was repeated except for
using ion-exchanged water in place of 1-isodecyl glyceryl monoether
(c-1), thereby obtaining a water-based ink.
Example 11
[0274] Forty five parts of a water dispersion containing the
commercially available self-dispersible carbon "CW-2", 12.5 parts
of the polymer particles (b-1), 1 part of 1-isodecyl glyceryl
monoether (c-1), 5 parts of glycerol, 5 parts of 2-pyrrolidone, 2
parts of isopropyl alcohol, 1 part of "ACETYLENOL EH" available
from Kawaken Fine Chemicals Co., Ltd., and 28.5 parts of water were
mixed with each other to prepare a dispersion. The thus obtained
dispersion was filtered through a 1.2 .mu.m-mesh filter to obtain a
water-based ink.
Comparative Example 7
[0275] The same procedure as in Example 11 was repeated except for
using ion-exchanged water in place of 1-isodecyl glyceryl monoether
(c-1), thereby obtaining a water-based ink.
Comparative Example 8
[0276] The same procedure as in Example 11 was repeated except for
using ion-exchanged water in place of the polymer particles (b-1),
thereby obtaining a water-based ink.
Experimental Example
[0277] The water-based inks obtained in Examples 10 and 11 and
Comparative Examples 6 to 8 were subjected to experiments to
evaluate the optical density, water resistance, rubbing resistance
and high lighter-fastness thereof by the following methods. The
results are shown in Table 2.
(1) Optical Density:
[0278] Measured by the same method as defined above.
(2) High Lighter-Fastness:
[0279] Measured by the same method as defined above.
(3) Water Resistance:
[0280] Solid image printing was carried out on a recycled paper for
PPC available from Nippon Kakoseisi Co., Ltd., using the above
ink-jet printer. The thus printed paper was naturally dried for 1
h, and then vertically dipped in static water for 10 s and
immediately vertically taken out therefrom. After naturally drying
the paper at room temperature, the optical density thereof was
measured. The residual rate of the optical density after the
dipping relative to optical density immediately after printing the
solid image was calculated to evaluate a water resistance of the
ink according to the following evaluation criteria.
[Evaluation Criteria]
[0281] .largecircle.: residual rate: 90% or higher
[0282] .DELTA.: residual rate: not less than 70% but less than
90%
[0283] X: residual rate: less than 70%
(4) Rubbing Resistance:
[0284] Solid image printing was carried out on t a recycled paper
for PPC available from Nippon Kakoseisi Co., Ltd., using the above
ink-jet printer and dried for one day. Then, the printed surface of
the paper was strongly rubbed with fingers to visually observe and
evaluate the degree of rubbing-off of the printed images according
to the following evaluation criteria.
[Evaluation Criteria]
[0285] .largecircle.: Substantially no rubbing-off of printed
images, and no blackish contamination of surrounding portions
[0286] .DELTA.: Slight rubbing-off of printed images as well as
slight blackish contamination of surrounding portions and
fingers
[0287] X: Considerable rubbing-off of printed images, and severe
blackish contamination of surrounding portions and fingers
TABLE-US-00004 TABLE 2-1 Ink composition Polymer particles
Component (A) (B) Component (C) Kind Part (%) Kind Part (%) Kind
Part (%) Example 10 a-1 70(7) b-1 12.5(6) c-1 1 Comparative a-1
70(7) b-1 12.5(6) -- -- Example 6 Example 11 CW-2 45(10.5) b-1
12.5(6) c-1 1 Comparative CW-2 45(10.5) b-1 12.5(6) -- -- Example 7
Comparative CW-2 45(10.5) -- -- c-1 1 Example 8 Note: The numerical
values in parenthesis ( ) in the column "Ink composition" represent
respective effective contents of the self-dispersible carbon black
and the polymer particles.
[0288] TABLE-US-00005 TABLE 2-2 Evaluation Optical Water Rubbing
density resistance resistance High lighter-fastness Kind Part (%)
Kind 3 min 10 min Example 10 .largecircle. (1.41) .largecircle.
(99) .largecircle. .largecircle. .circleincircle. Comparative X
(1.25) .largecircle. (99) .largecircle. .DELTA. .largecircle.
Example 6 Example 11 .largecircle. (1.42) .largecircle. (99)
.largecircle. .largecircle. .circleincircle. Comparative X (1.22)
.largecircle. (99) .largecircle. .DELTA. .largecircle. Example 7
Comparative .largecircle. (1.40) .DELTA. (85) X X X Example 8 Note:
The numerical values in parenthesis ( ) in the columns "Optical
density" and "Water resistance" represent measured values.
[0289] From the results shown in Table 2, it was confirmed that the
water-based inks obtained in Examples 10 and 11 were higher in
optical density and more excellent in water resistance, rubbing
resistance and high lighter-fastness as compared to those obtained
in Comparative Examples 6 to 8.
INDUSTRIAL APPLICABILITY
[0290] The water-based ink containing the water dispersion for
ink-jet printing according to the present invention not only
satisfies a high optical density but also exhibits an excellent
high lighter-fastness and, therefore, can be suitably used as a
water-based ink for ink-jet printing.
[0291] Also, the print produced by using the ink of the present
invention is excellent in optical density and high
lighter-fastness.
* * * * *