U.S. patent application number 10/918733 was filed with the patent office on 2005-02-24 for pigment dispersion and actinic radiation curable type ink jet ink composition.
This patent application is currently assigned to KONICA MINOLTA MEDICAL & GRAPHIC, INC.. Invention is credited to Watanabe, Shinya.
Application Number | 20050043437 10/918733 |
Document ID | / |
Family ID | 34056228 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050043437 |
Kind Code |
A1 |
Watanabe, Shinya |
February 24, 2005 |
Pigment dispersion and actinic radiation curable type ink jet ink
composition
Abstract
A pigment dispersion including photopolymerizable compounds and
pigments as well as an actinic radiation curable type ink jet
composition including photopolymerizable compounds,
photopolymerization initiators, and pigments are provided. The
hydrophilicity .delta.m of the surface of pigments incorporated
therein is at most 22.
Inventors: |
Watanabe, Shinya; (Tokyo,
JP) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Assignee: |
KONICA MINOLTA MEDICAL &
GRAPHIC, INC.
|
Family ID: |
34056228 |
Appl. No.: |
10/918733 |
Filed: |
August 16, 2004 |
Current U.S.
Class: |
523/160 ;
523/161 |
Current CPC
Class: |
C09D 11/101
20130101 |
Class at
Publication: |
523/160 ;
523/161 |
International
Class: |
C03C 017/00; C09D
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2003 |
JP |
JP2003-296175 |
Claims
What is claimed is:
1. A pigment dispersion comprising photopolymerizable compounds and
pigments, wherein: hydrophilicity .delta.m of the surface of
pigments incorporated therein is at most 22, which hydrophilicity
.delta.m is specifically determined based on the following steps,
pigments are floated on a definite amount of water (B ml), and
while stirring, acetone is dripped through a burette of which tip
is placed in the water so that acetone is not directly poured onto
the pigment, using amount of acetone (A ml) dripped to sink the
pigment, .delta.m is calculated based on the formula
below..delta.m=(A.multidot..delta..sub.acetone+B.multidot..delta.-
.sub.acetone)/(A+B).delta..sub.acetone=9.75(cal.sup.1/2.multidot.cm.sup.-1-
/2).delta..sub.water=23.43(cal.sup.1/2.multidot.cm.sup.-1/2)
2. A pigment dispersion of claim 1, wherein: said
photopolymerizable compounds are photopolymerizable compounds
containing an oxetane ring.
3. A pigment dispersion of claim 2, wherein: said
photopolymerizable compounds are photopolymerizable compounds
having 1-4 oxetane rings.
4. A pigment dispersion of claim 1, wherein: said
photopolymerizable compounds are epoxy compounds.
5. A pigment dispersion of claim 4, wherein: said epoxy compounds
are selected from aromatic epoxides and alictclic epoxides.
6. A pigment dispersion of claim 1, wherein: said
photopolymerizable compounds are vinyl ether compounds.
7. A pigment dispersion of claim 6, wherein: said vinyl ether
compounds are selected from divinyl ether compounds and trivinyl
compounds.
8. A pigment dispersion of claim 1 to 7, wherein: said
hydrophilicity .delta.m of the surface of pigments incorporated
therein is at most 21.5.
9. An actinic radiation curable type ink jet composition comprising
photopolymerizable compounds, photopolymerization initiators, and
pigments wherein: hydrophilicity .delta.m of the surface of
pigments incorporated therein is at most 22, which hydrophilicity
.delta.m is specifically determined based on the following steps,
pigments are floated on a definite amount of water(B ml), and while
stirring, acetone is dripped through a burette of which tip is
placed in the water so that acetone is not directly poured onto the
pigment, using amount of acetone (A ml) dripped to sink the
pigment, .delta.m is calculated based on the formula
below..delta.m=(A.multidot..delta..sub.acetone+B.multidot..delta.-
.sub.acetone)/(A+B).delta..sub.acetone=9.75(cal.sup.1/2.multidot.cm.sup.-1-
/2).delta..sub.water=23.43(cal.sup.1/2.multidot.cm.sup.-1/2)
10. An actinic radiation curable type ink jet composition of claim
9, wherein: said photopolymerizable compounds are
photopolymerizable compounds containing an oxetane ring.
11. An actinic radiation curable type ink jet composition of claim
10, wherein: said photopolymerizable compounds are
photopolymerizable compounds having 1-4 oxetane rings.
12. An actinic radiation curable type ink jet composition of claim
9, wherein: said photopolymerizable compounds are epoxy
compounds.
13. An actinic radiation curable type ink jet composition of claim
12, wherein: said epoxy compounds are selected from aromatic
epoxides and alictclic epoxides.
14. An actinic radiation curable type ink jet composition of claim
9, wherein: said photopolymerizable compounds are vinyl ether
compounds.
15. An actinic radiation curable type ink jet composition of claim
14, wherein: said vinyl ether compounds are selected from divinyl
ether compounds and trivinyl compounds.
16. An actinic radiation curable type ink jet composition of claim
9, wherein: said photopolymerization initiators are aromatic onium
salts.
17. An actinic radiation curable type ink jet composition of claim
9, wherein: said photopolymerization initiators are sulfonium salts
which generate no benzene by exposure to actinic radiation.
18. An actinic radiation curable type ink jet composition of claim
17, wherein: said sulfonium salts are sulfonium salt compounds
represented by following General Formulas (1)-(4). 27 (In above
General Formulas (1)-(4), R.sub.1-R.sub.17 each represent a
hydrogen atom or a substituent. None of R.sub.1-R.sub.3
simultaneously represent a hydrogen atom, none of R.sub.4-R.sub.7
simultaneously represent a hydrogen atom, and none of
R.sub.12-R.sub.17 simultaneously represent a hydrogen atom. X
represents a non-nucleophilic anionic residual group.)
19. An actinic radiation curable type ink jet composition of claim
9 to 18, wherein: said hydrophilicity am of the surface of pigments
incorporated therein is at most 21.5.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a novel pigment dispersion
and an actinic radiation curable type ink jet ink composition, and
in more detail to a pigment dispersion in which dispersibility of
pigments and dispersion stability are improved, and an actinic
radiation curable type ink jet ink using the same.
[0002] In recent years, ink jet recording systems have been applied
to various printing fields such as photography, various kinds of
printings, marking, and special printing such as color filters,
since they make it possible to simply and conveniently prepare
images at low cost. Specifically, by employing recording
apparatuses which eject microscopic ink droplets, and control them,
inks which result in improved range of color reproduction, as well
as exhibit improved durability and ejection suitability, and
special paper sheets of which ink absorbability, color forming
properties of colorants and surface glossiness are markedly
improved, it has become possible to result in image quality
comparable to conventional silver salt photography. Improvements in
image quality of the current ink jet recording systems have been
achieved only by the integration of ink jet recording apparatuses,
inks, and special kinds of paper.
[0003] However, in ink jet systems which necessitate special
papers, problems surface in which recording media are limited and
the cost of the recording media increases. Consequently, many
trials have been made in which recording is performed on media to
be transferred which are different from special paper sheets,
employing the ink jet systems. Listed as specific examples are a
phase variation ink jet system which employs a wax ink which is in
the form of a solid at room temperature, a solvent based ink jet
system which employs ink comprised of rapid drying organic solvents
as a major component, and an ultraviolet radiation curable type ink
jet system in which crosslinking undergoes employing ultraviolet
radiation after printing. However, at present, various problems
occur in these systems.
[0004] For example, in the phase variation ink jet system, neither
sufficient image strength nor fixability is achieved due to use of
wax as an ink. Further, in the solvent based ink jet system, the
following problems occur: unpleasant odors (being an environmental
problem) are generated due to high volatility of the ink, and heads
are clogged due to dried ink. Further, since ink penetration
properties differ depending on the employed recording media,
bleeding as well as drying is not stabilized, whereby ink bleeding
tends to result.
[0005] On the other hand, in recent years, an ultraviolet radiation
curable type ink jet system has received favorable attention due to
its relatively low unpleasant odor, rapid drying property which
makes it possible to carry out recording on non-ink absorptive
recording media, compared to the solvent based ink jet systems. For
example, Japanese Patent Publication No. 5-54667, Japanese Patent
Publication Open to Public Inspection No. 6-200204, and Japanese
Patent Publication Open to Public Inspection (under PCT
Application) No. 2000-504778 disclose ultraviolet radiation curable
type ink jet inks. In any of these methods, employed are acryl
monomers as a polymerizable compound. However, in view of a
decrease in viscosity to achieve stable ink ejection, an increase
in photo-speed, and closer adhesion to recording media, selected as
polymerizable monomers which are employed in ink are those which
irritate skin or induce allergic reactions. Consequently, they are
highly toxic to customers and operators. Further, Japanese Patent
Publication Open to Public Inspection (under PCT Application) No.
2000-504778 discloses a method in which either alkoxyacrylates or
polyalkoxyacrylates, which exhibit relatively high safety
standards, are incorporated in an amount of 80-95 percent by
weight. However, a structure, in which either monofunctional or
multifunctional monomers are incorporated in an amount of a minimum
of 80 percent by weight, results in problems in which sufficient
adhesion to recording media is not achieved, ink bleeding occurs,
and unpleasant odor due to unreacted monomers is generated with
respect to a wide range of recording media, such as highly
permeable recording media or highly wettable and easily bleeding
polyethylene terephthalate films.
[0006] Assumed as factors in which sufficient photocuring speed is
not achieved are bleeding of printed images before the ink is cured
and penetration of the ink into porous recording medium. In
addition, the aforesaid penetration has enlarged the problem of the
residual unpleasant odor due to the unreacted monomers. Considered
as methods which aid in an increase in photocuring speed are means
in which the intensity of a radiation source is increased and
exposure time is increased. However, all these methods have
resulted in an inevitable increase in cost of the integral
apparatuses.
[0007] As noted above, the radiation curable type ink jet system,
which employs ultraviolet radiation as one means of radiation,
exhibits excellent features compared to other ink jet systems.
However, in view of safety and apparatus cost, the present
radiation curable type ink jet system is inferior to the
water-based ink jet system. Consequently, urgently demanded is
development of problem-solving methods.
[0008] Listed as means to overcome the above problems is an
ultraviolet radiation curable type ink jet system employing
compounds which are cured via cationic polymerization. For example,
Japanese Patent Publication Open to Public Inspection No. 8-143806
discloses an actinic radiation curable type ink composition
employing an oxetane ring-containing compound (hereinafter referred
to as an oxetane compound). Oxetane compounds neither irritate skin
nor induce allergic reactions. Further, the oxetane compounds
exhibit features in that polymerization is not inhibited due to the
presence of oxygen in the same manner as radical polymerization of
acryl monomers, and it is also possible to cure the ink employing a
radiation source at a relatively low output. However, problems
still exist in which pigment dispersibility and dispersion
stability are inferior.
SUMMARY OF THE INVENTION
[0009] According to one embodiment of the present invention, a
pigment dispersion is provided, the dispersion includes
photopolymerizable compounds and pigments. The hydrophilicity
.delta.m of the surface of pigments incorporated therein is at most
22, which is specifically determined based on the following steps,
(1) pigments are floated on a definite amount of water (B ml), and
while stirring, acetone is dripped through a burette of which tip
is placed in the water so that acetone is not directly poured onto
the pigment, (2) using amount of acetone (A ml) dripped to sink the
pigment, .delta.m is calculated based on the formula below.
.delta.m=(A.multidot..delta..sub.acetone+B.multidot..delta..sub.acetone)/(-
A+B)
.delta..sub.acetone=9.75 (cal.sup.1/2.multidot.cm.sup.-1/2)
.delta..sub.water=23.43 (cal.sup.1/2.multidot.cm.sup.-1/2)
[0010] Another embodiment of the present invention, an actinic
radiation curable type ink jet composition including
photopolymerizable compounds, photopolymerization initiators, and
pigments. The hydrophilicity .delta.m of the surface of pigments
incorporated therein is at most 22, also.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011] The best embodiment to practice the present invention will
now be detailed. However, the present invention is not limited
thereto.
[0012] In the present invention, a pigment dispersion comprising
photopolymerizable compounds as well as pigments, or an actinic
radiation curable type ink jet composition comprising
photopolymerizable compounds, photopolymerization initiators, and
pigments is characterized in that hydrophilicity .delta.m of the
surface of pigments incorporated therein is at most 22.
[0013] Hydrophilicity .delta.m of the surface of pigments, as
described in the present invention refers to surface hydrophilicity
.delta.m which is determined by the titration method described in
Shikizai (Colorants), 73[3], 136 (2000), and is specifically
determined based on the following steps.
[0014] Pigments are floated on a definite amount of water(B ml),
and while stirring, acetone is dripped through a burette of which
tip is placed in the water so that acetone is not directly poured
onto the pigment. The amount of acetone (A ml) is recorded which is
dripped to sink the pigment, and .delta.m is calculated based on
the formula below.
.delta.m=(A.multidot..delta..sub.acetone+B.multidot..sub.acetone)/(A+B)
.delta..sub.acetone=9.75 (cal.sup.1/2.multidot.cm.sup.-1/2)
.delta..sub.water=23.43 (cal.sup.1/2.multidot.cm.sup.-1/2)
[0015] The present invention is characterized in that surface
hydrophilicity .delta.m is at most 22. The aforesaid hydrophilicity
.delta.m is preferably at most 21.5, and is more preferably
10.0-21.5. When .delta.m exceeds 22, the resulting dispersibility
is markedly degraded.
[0016] In the present invention, it is possible to set the
hydrophilicity of pigment surface at 22 or less specified by the
present invention, employing individually or in combinations a
method(s) selected from conventional surface treatment methods
known in the art, such as a pigment derivative treatment, a rosin
treatment, a polymer treatment, a surface graft treatment, or a
plasma treatment.
[0017] Pigments usable in the present invention are listed
below.
[0018] Employed may be those described below according to purposes.
Red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38,
43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4,
63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144,
146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216,
226, and 257; Pigment Violet 3, 19, 23, 29, 30, 37, 50, and 88, and
Pigment Orange 13, 16, 20, and 36. Blue or cyan pigments include
Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 17-1, 22, 27, 28,
29, 36, and 60. Yellow pigments include Pigment Yellow 1, 3, 12,
13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109,
110, 120, 128, 137, 138, 139, 151, 153, 154, 155, 157, 166, 167,
168, 180, 185, and 193. Black pigments include Pigment Black 7, 26
and 28; and white pigments include Pigment White 6, 18 and 21.
[0019] It is possible to disperse the above-mentioned pigments by
employing, for example, a ball mill, a sand mill, an attritor, a
roller mill, an agitator, a Henschel mixer, a colloid mill, an
ultrasonic homogenizer, a pearl mill, a wet type jet mill, and a
paint shaker. When pigments are dispersed, it is preferable that
dispersing agents are added. Preferably employed as dispersing
agents are polymer dispersing agents. Listed as polymer dispersing
agents are the Solsperse Series, available from Avecia, the Ajisper
Series available from Ajinomoto Fine Techno Co., the Disperbyk
Series available from BYK Chemie Co., and the Disperon Series and
the PLAAD Series both available from Kusumoto Chemicals, Ltd.
Further, employed as dispersing aids may be synergists
corresponding to each type of the pigments. The added amount of
such dispersing agents and dispersing aids is preferably 1-60 parts
by weight with respect to 100 parts by weight of the pigments. A
dispersion medium may be comprised of solvents or polymerizable
compounds. However, in the actinic radiation curable type ink
employed in the present invention, it is preferable that no
solvents are used so that ink undergoes reaction and curing
immediately after deposition. When solvents remain in cured images,
problems of degradation of image durability and VOC of remaining
solvents occur. Consequently, it is preferable that the dispersion
media are not solvents but polymerizable compounds. Of these, in
view of dispersion suitability, it is preferable to select monomers
which exhibit the lowest viscosity.
[0020] It is preferable that pigments are dispersed in such a
manner that the average diameter of pigment particles is at most
200 nm but is more preferably at most 150 nm. Further, pigments,
dispersing agents, and dispersion media are selected and dispersing
conditions and filtering conditions are suitably set so that the
maximum particle diameter is in 0.3-10 .mu.m, and is more
preferably 0.3-3 .mu.m. In the ink compositions according to the
present invention, the concentration of pigments is preferably 1-10
percent by weight with respect to the total ink.
[0021] Photopolymerizable compounds according to the present
invention will now be described.
[0022] One of the features of the pigment dispersion or actinic
radiation curable type ink jet ink compositions of the present
invention is that photopolymerizable compounds, especially
photopolymerizable compounds containing an oxetane ring are
incorporated. Employed as oxetane compounds may be any of those
known in the art, which are disclosed in Japanese Patent
Publication Open to Public Inspection Nos. 2001-220526 and
2001-310937.
[0023] In the present invention, when compounds having at least 5
oxetane rings are used, in some cases, the viscosity of the
resulting ink composition increases resulting in difficulty in
handling, and the glass transition temperature of the ink
composition also increases whereby the adherence of the resulting
cured composition becomes insufficient. Compounds having oxetane
ring(s) employed in the present invention are preferably those
having 1-4 oxetane rings.
[0024] Specific examples of compounds having oxetane ring(s)
according to the present invention will now be described; however,
the present invention is not limited thereto.
[0025] Listed as one example of compounds having one oxetane ring
is the compound represented by General Formula (A) described below:
1
[0026] In General Formula (A), R.sup.1 represents a hydrogen atom,
an alkyl group having 1-6 carbon atoms such as a methyl group, an
ethyl group, a propyl group, or a butyl group, an allyl group, an
aryl group, a furyl group, or a thienyl group. R.sup.2 represents
an alkyl group having 1-6 carbon atoms such as a methyl group, an
ethyl group, a propyl group, or a butyl group; an alkenyl group
having 2-6 carbon atoms such as a 1-propenyl group, a 2-propenyl
group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a
1-butenyl group, a 2-butenyl group, or a 3-butemnyl group; an
aromatic ring-containing group such as a phenyl group, a benzyl
group, a fluorobenzyl group, a methoxybenzyl group, or a
phenoxyethyl group; an alkylcarbonyl group having 2-6 carbon atoms
such as an ethylcarbonyl group, a propylcarbonyl group, or a
butylcarbonyl group; an alkoxycarbonyl group having 2-6 carbon
atoms such as an ethoxycarbonyl group, a propoxycarbonyl group, or
a butoxycarbonyl group; or an N-alkylcarbamoyl group having 2-6
carbon atoms such as an ethylcarbamoyl group, a propylcarbamoyl
group, a butylcarbamoyl group, or a pentylcarbamoyl group.
[0027] Listed as one example of compounds having two oxetane rings
is the compound represented by General Formula (B) described below:
2
[0028] In General Formula (B), R.sup.1 is the same group as defined
for the aforesaid General Formula (A). R.sup.2 is, for example, a
straight chain or branched alkylene group such as an ethylene
group, a propylene group, or a butylene group; a straight chain or
branched poly(alkyleneoxy) group such as a poly(ethyleneoxy) group
or a poly(propyleneoxy) group; a straight chain or branched
unsaturated hydrocarbon group such as a propenylene group, a
methylpropylene group, or a butenylene group; an alkylene group
containing a carbonyl group; an alkylene group containing a
carboxyl group; and an alkylene group containing a carbamoyl group.
Further, listed as R.sup.3 may be a multivalent group selected from
the group represented by the following General Formulas (C), (D),
and (E). 3
[0029] In General Formula (C), R.sup.4 represents a hydrogen atom,
an alkyl group having 1-4 carbon atoms such as a methyl group, an
ethyl group, a propyl group, or a butyl group, an alkoxy group
having 1-4 carbon atoms such as a methoxy group, an ethoxy group, a
propoxy group, or a butoxy group, a halogen atom such as a chlorine
atom or a bromine atom, a nitro group, a cyano group, a mercapto
group, a lower alkylcarboxyl group, a carboxyl group, or a
carbamoyl group. 4
[0030] In General Formula (D), R.sup.5 represents an oxygen atom, a
sulfur atom, a methylene group, NH, SO, SO.sub.2,
C(CF.sub.3).sub.2, or (CH.sub.3).sub.2. 5
[0031] In General Formula (E), R.sup.6 represents an alkyl group
having 1-4 carbon atoms such as a methyl group, an ethyl group, a
propyl group, or a butyl group or an aryl group, and n represents
an integer of 0-200. R.sup.7 represents an alkyl group having 1-4
carbon atoms such as a methyl group, an ethyl group, a propyl
group, or a butyl group, or an aryl group. Listed as R.sup.7 may be
a group selected from the groups represented by General Formula (F)
below. 6
[0032] In General Formula (F), R.sup.8 represents an alkyl group
having 1-4 carbon atoms such as a methyl group, an ethyl group, a
propyl group, or a butyl group or an aryl group, while m represents
an integer of 0-100.
[0033] Listed as specific examples having two oxetane rings are
those described below. 7
[0034] Exemplified Compound 1 is one in which, in aforesaid General
Formula (B), R.sup.1 is an ethyl group and R.sup.3 is a carboxyl
group. Further, Exemplified Compound 2 is one in which, in
aforesaid General Formula (B), R.sup.1 is an ethyl group and
R.sup.3 is a group represented by aforesaid General Formula (E) in
which each of R.sup.6 and R.sup.7 is a methyl group, while n is
1.
[0035] Listed as preferred compounds having two oxetane rings,
other than those described above, are the compounds represented by
General Formula (G) below. In General Formula (G), R.sup.1 is as
defined for R.sup.1 in aforesaid General Formula (A). 8
[0036] Listed as one example of compounds having 3-4 oxetane rings
is the compound represented by General Formula (H) below. 9
[0037] In General Formula (H), R.sup.1 is as defined for R.sup.1 in
aforesaid General Formula (A). Listed as R.sup.9 are, for example,
a branched alkylene group having 1-12 carbon atoms such as those
represented by A-C below, a branched poly(alkyleneoxy) group
represented by D below, or a branched polysiloxy group represented
by E below, while j is 3 or 4. 10
[0038] In aforesaid A, R.sup.10 is a lower alkyl group such as a
methyl group, an ethyl group, or a propyl group. Further, in
aforesaid D, p is an integer of 1-10.
[0039] Listed as one example of compounds having 3-4 oxetane rings
is Exemplified Compound 3. 11
[0040] In addition, listed as examples of compounds having 1-4
oxetane rings, other than those described above, are compounds
represented by General Formula (I) below. 12
[0041] In General Formula (I), R.sup.8 is as defined for R.sup.8 in
aforesaid General Formula (F). R.sup.11 is an alkyl group having
1-4 carbon atoms, such as a methyl group, an ethyl group, a propyl
group, or a butyl group, and r is 1-4.
[0042] Preferred specific examples of oxetane compounds employed in
the present invention include the compounds shown below. 13
[0043] Production methods of each of the aforesaid compounds,
having oxetane rings, are not particularly limited, and are
produced employing conventional methods. An example includes a
synthesis method of the oxetane ring from diol which is disclosed
in D. B. Pattison, J. Am. Chem. Soc., 3455, 79 (1957). Further,
listed are compounds having 2-4 oxetane rings and a high molecular
weight such as about 1,000-about 5,000. Listed as specific examples
of these compounds are the following compounds. 14
[0044] Further, it is possible to use 2-substituted oxetane
compounds in the pigment dispersion and the actinic radiation
curable type ink jet ink composition of the present invention.
Listed as 2-substituted oxetane compounds usable in the present
invention are compounds having one or more oxetane rings in the
molecule represented by General Formula (1) below. 15
[0045] wherein R.sub.1-R.sub.6 each represent a hydrogen atom or a
univalent or divalent organic group, and at least one of
R.sub.3-R.sub.6 is not a hydrogen atom.
[0046] Listed as compounds which have one oxetane ring in their
molecule may be the compounds represented by General Formulas
(2)-(5) below. 16
[0047] In General Formulas (2)-(5), Z is independently an oxygen or
sulfur atom, or a divalent hydrocarbon group which may contain an
oxygen or sulfur atom in the main chain.
[0048] R.sub.1-R.sub.6 each independently represent a hydrogen
atom, a fluorine atom, an alkyl group having 1-6 carbon atoms, such
as a methyl group, an ethyl group, a propyl group, or a butyl
group, a fluoroalkyl group having 1-6 carbon atoms, an allyl group,
an aryl group, or a thienyl group.
[0049] R.sub.7 and R.sub.8 each independently represent an alkyl
group having 1-6 carbon atoms, such as a methyl group, an ethyl
group, a propyl group, or a butyl group; an alkenyl group having
2-6 carbon atoms, such as a 1-propenyl group, a 2-propenyl group, a
2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-butenyl
group, a 2-butenyl group, or a 3-butemnyl group; an aryl group such
as a phenyl group, a benzyl group, a fluorobenzyl group, a
methoxybenzyl group, or a phenoxyethyl group; an alkylcarbonyl
group having 1-6 carbon atoms such a propylcarbonyl group, a
butylcarbonyl group, or pentylcarbonyl group; an alkoxycarbonyl
group having 1-6 carbon atoms such as an ethoxycarbonyl group, a
propoxycarbonyl group, or a butoxycarbonyl group; or an
N-alkoxycarbamoyl group having 1-6 carbon atoms, such as an
ethoxycarbamoyl group, a propoxylcarbamoyl group, or a
butylpentylcarbamoyl group.
[0050] Further, in General Formulas (2)-(4), at least one of
R.sub.3-R.sub.6 is not a hydrogen atom.
[0051] As oxetane ring containing compounds used in the present
invention, it is preferable that in aforesaid General Formulas
(2)-(5), R.sub.1 is a lower alkyl group, especially an ethyl group;
R.sub.7 and R.sub.8 are propyl groups, butyl groups, phenyl groups,
or benzyl groups; and Z is a hydrocarbon group containing neither
an oxygen atom nor a sulfur atom.
[0052] Incidentally, listed as compounds having at least two
oxetane rings in the molecule may be the compounds represented by
General Formula (6) or (7) below. 17
[0053] In General Formulas (6) and (7), m is 2, 3, or 4, and Z is
independently an oxygen atom, a sulfur atom, or a divalent
hydrocarbon group which may have an oxygen atom or a sulfur
atom.
[0054] R.sub.1-R.sub.6 each independently represent a hydrogen
atom, a fluorine atom, an alkyl group having 1-6 carbon atoms, such
as a methyl group, an ethyl group, a propyl group, or a butyl
group, an allyl group, an aryl group, or a furyl group.
[0055] In General Formula (6), at least one of R.sub.3-R.sub.6 is
not a hydrogen atom.
[0056] Further, R.sub.9 is, for example, a straight chain or
branched alkylene group having 1-12 carbon atoms, represented by
General Formula (8) below, or a straight chain or branched
poly(alkyleneoxy) group. 18
[0057] In General Formula (8), R.sub.10 represents a lower alkyl
group such as a methyl group, an ethyl group, or a propyl
group.
[0058] R.sub.9 is a multivalent group selected from the group of
General Formulas (9), (11), and (12) below. 19
[0059] In General Formula (9), n represents an integer of 1-2,000,
R.sub.11 represents an alkyl group having 1-10 carbon atoms, such
as a methyl group, an ethyl group, a propyl group, or a butyl
group, as well as a group selected from the group comprised of
General Formula (10) below. R.sub.12 represents an alkyl group
having 1-10 carbon atoms, such as a methyl group, an ethyl group, a
propyl group, or a butyl group. 20
[0060] In General formula (10), j represents an integer of 1-100,
and R.sub.13 represents an alkyl group having 1-10 carbon atoms,
such as a methyl group, an ethyl group, a propyl group, or a butyl
group. 21
[0061] In General Formula (11), R.sub.14 represents a hydrogen
atom, an alkyl group having 1-10 carbon atoms, such as a methyl
group, an ethyl group, a propyl group, or a butyl group, an alkoxy
group having 1-10 carbon atoms, a halogen atom, a nitro group, a
cyano group, a mercapto group, a lower alkylcarboxylate group, or a
carboxyl group. 22
[0062] In General Formula (12), R.sub.15 represents an oxygen atom,
a sulfur atom, NH, SO, SO.sub.2, CH.sub.2, C(CH.sub.3).sub.2 or
C(CF.sub.3).sub.2.
[0063] Preferred as oxetane compounds employed in the present
invention are those in which in aforesaid General Formulas (6) and
(7), R.sub.1 is a lower alkyl group, especially an ethyl group,
R.sub.9 is a group in which in General Formula (11), R.sub.14 is a
hydrogen atom, a hexamethylene group, a group in which in General
Formula (8), R.sub.10 is an ethyl group, a group in which in
General Formula (9), R.sub.12 is a methyl group, and a group in
which in General Formula (10), R.sub.13 is a methyl group, and Z is
a hydrocarbon group containing neither an oxygen atom nor a sulfur
atom.
[0064] Further, listed as examples of compounds having a plurality
of oxetane rings in the molecule are the compounds represented by
General Formula (13). 23
[0065] In General Formula (13), r is an integer of 25-300, R.sub.16
is an alkyl group having 25-200 carbon atoms or a trialkylsilyl
group. R.sub.1-R.sub.6 are each the same as those in General
Formula (1), R.sub.13 is the same as the one in General Formula
(10), and at least one of R.sub.3-R.sub.6 is not a hydrogen
atom.
[0066] It is possible to synthesize the compounds having oxetane
ring(s) according to the present invention, in which at least
position 2 is substituted, with reference to the publications
described below.
[0067] (1) Hu Xianming and Richard M. Lellogg, Synthesis, 533-538,
May (1995)
[0068] (2) A. O. Fitton, J. Hill, D. Ejane, and R. Miller, Synth.
12, 1140 (1987)
[0069] (3) Toshiro Imai and Shinya Nishida, Can. J. Chem. Vol. 59,
2503-2509 (1981)
[0070] (4) Nobujiro Shimizu, Shintaro Yamaoka, and Yuho Tsuno,
Bull. Chem. Soc. Jpn., 56, 3853-3854 (1983)
[0071] (5) Walter Fisher and Cyril A. Grob, Helv. Chim. Acta., 61,
2336 (1978)
[0072] (6) Chem. Ber. 102, 1850 (1968)
[0073] (7) "Heterocyclic Compounds with Three- and Four-membered
Rings", Part Two, Chapter IX, Interscience Publishers, John Wiley
& Sons, New York (1964)
[0074] (8) Bull. Chem. Soc. Jpn., 61. 1653 (1988)
[0075] (9) Pure Appl. Chem., A29 (10), 915 (1992)
[0076] (10) Pure Appl. Chem., A30 (2 & amp; 3), 189 (1993)
[0077] (11) Japanese Patent Publication Open to Public Inspection
No. 16804
[0078] (12) DE 1021858
[0079] Specific examples of compounds containing the oxetane ring,
in which position 2 is substituted, are shown below as Exemplified
Compounds 1-15. However, the present invention is not limited
thereto.
[0080] Exemplified Compound 1:
trans-3-tert-butyl-2-phenyloxetane
[0081] Exemplified Compound 2:
3,3,4,4-tetramethyl-2,2-dipenyloxetane
[0082] Exemplified Compound 3:
di[3-ethyl(2-methoxy-3-oxetanyl)]methyl ether
[0083] Exemplified Compound 4:
1,4-bis(2,3,4,4-tetramethyl-3-ethyl-oxetany- l)butane
[0084] Exemplified Compound 5:
1,4-bis(3-methyl-3-ethyloxetanyl)butane
[0085] Exemplified Compound 6:
di(3,4,4-trimethyl-3-ethyloxetanyl)methyl ether
[0086] Exemplified Compound 7:
3-(2-ethyl-hexylpxymethyl)-2,2,3,4-tetramet- yloxetane
[0087] Exemplified Compound 8:
2-(2-ethyl-hexyloxy)-2,3,3,4,4-pentamethyl-- oxetane
[0088] Exemplified Compound 9:
4,4'-bis[(2,4-dimethyl-3-ethyl-3-oxetanyl)m- ethoxy]biphenyl
[0089] Exemplified Compound 10:
1,7-bis(2,3,3,4,4-pentamethyl-oxetanyl)hep- tane
[0090] Exemplified Compound 11: oxetanyl silsesquioxane
[0091] Exemplified Compound 12: 2-methoxy-3,3-dimethyloxetane
[0092] Exemplified Compound 13: 2,2,3,3-tetramethyloxatane
[0093] Exemplified Compound 14:
2-(4-methoxyphenyl)-3,3-dimethyloxetane
[0094] Exemplified Compound 15:
di(2-(4-methoxyphenyl)-3-methyloxetane-3-i- l) ether
[0095] Further, in the present invention, employed as
photopolymerizable compounds may be any of the oxirane
group-containing compounds (hereinafter referred to as epoxy
compounds), as well as vinyl ether compounds known in the art.
[0096] Listed as epoxide compounds are aromatic epoxides as well as
aliphatic epoxides.
[0097] Preferred as aromatic epoxides are di- or polyglycidyl
ethers which are produced through the reaction of polyhydric phenol
or alkylene oxide addition products thereof, with epichlorohydrin.
For example, listed are bisphenol A, or di- or polyglycidyl ether
of alkylene oxide addition products thereof, hydrogenated bisphenol
A, or di- or polyglycidyl ethers of alkylene oxide addition product
thereof, and novolac type epoxy resins. Herein, listed as alkylene
oxides are ethylene oxide and propylene oxide.
[0098] It is possible to prepare alicyclic epoxides by epoxidizing
compounds having at least one cycloalkane ring, such as a
cyclohexane or cyclopentane ring, employing suitable oxidizing
agents such as hydrogen peroxide or peracid. Either cyclohexane
oxides or cyclopentane oxides are preferred.
[0099] Preferred as aliphatic epoxides are aliphatic polyhydric
alcohols or di- or polyglycidyl ethers of alkylene oxide addition
products thereof. Listed as representative examples thereof are
glycidyl ethers of alkylene glycol such as diglycidyl ether of
ethylene glycol, diglycidyl ether of propylene glycol, or
diglycidyl ethers of 1,6-hexandiol; polyglycidyl ethers of
polyhydric alcohols such as di- or triglycidyl ethers of glycerin
or alkylene oxide addition products thereof; and diglycidyl ethers
of polyalkylene glycol such as diglycidyl ethers of polyethylene
glycol of alkylene oxide addition products thereof. Herein, listed
as alkylene oxides are ethylene oxide and propylene oxide.
[0100] Of these epoxides, in view of rapid curing properties,
preferred are aromatic epoxides as well as alictclic epoxides, and
alicyclic epoxides are particularly preferred. In the present
invention, the aforesaid epoxies may be employed individually or in
suitable combinations of at least two types.
[0101] Further, listed as vinyl ether compounds are, for example,
di- or trivinyl ether compounds such as ethylene glycol divinyl
ether, diethylene glycol divinyl ether, triethylene glycol divinyl
ether, propylene glycol divinyl ether, dipropylene glycol divinyl
ether, butanediol divinyl ether, hexanediol divinyl ether,
cyclohexane dimethanol divinyl ether, or trimethylolpropane
trivinyl ether, and monovinyl ether compounds such as ethyl vinyl
ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl
ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether,
2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether,
n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl
ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol
monovinyl ether, or octadecyl vinyl ether.
[0102] Of these vinyl ether compounds, in view of curability,
adhesion property, and surface strength, di- or trivinyl ether
compounds are preferred, and divinyl ether compounds are
particularly preferred. In the present invention, the aforesaid
vinyl ether compounds may be employed individually or in suitable
combinations of at least two types.
[0103] The actinic radiation curable type ink jet ink composition
of the present invention comprises photopolymerization initiators.
Listed as photopolymerization initiators may be aromatic onium
salts. Listed as such aromatic onium salts may be salts of Group Va
elements in the periodic table such as phosphonium salts (e.g.,
hexafluorophosphoric acid triphenylphenacylphosphonium), salts of
Group VI elements such as sulfonium salts (e.g., tetrafluoroboric
acid triphenylsulfonium, hexafluorophosphoric acid
triphenylsulfonium, hexafluorophosphoric acid
tris(4-thiomethjoxyphenyl), sulfonium, and hexafluoroantimonic acid
triphenylsulfonium), and salts of Group VIIa elements such as
iodonium salts (e.g., diphenyliodonium chloride). U.S. Pat. Nos.
4,058,401, 4,069,055, 4,101,513, and 4,161,478 detail that such
aromatic onium salts are employed as a cationic polymerization
initiator during polymerization of epoxy compounds.
[0104] Listed as preferred photopolymerization initiators are
sulfonium salts of Group VIa elements. Of these, in view of
ultraviolet radiation curability as well as storage stability of
ultraviolet radiation curable compositions, hexafluoroantimonic
acid triarylsulfonium is preferred. Further, it is possible to use
any of the prior art photopolymerization initiators described on
pages 39-56 of Hotoporima Hando Bukku (Photopolymer Handbook)
(edited by Photopolymer Konwa Kai, published by Kogyo Chosa Kai,
1989) and compounds described in Japanese Patent Publication Open
to Public Inspection Nos. 64-13142 and 2-4804.
[0105] Further, it is preferable to use, as a photopolymerization
initiator, sulfonium salts which generate no benzene by exposure to
actinic radiation. "Generate no benzene by exposure to actinic
radiation", as described herein, means that no substantial amount
of benzene is generated, and specifically refers to the following
case. A 15 .mu.m thick image of an area of approximately 100
m.sup.2 is printed employing an ink containing onium salts (being
photolytically acid generating agents) in an amount of 5 percent by
weight in the ink composition, and the resulting ink layer,
maintained at 30.degree. C., is exposed to actinic radiation in an
amount which completely decomposes the photolytically acid
generating agents and the amount of generated benzene was
determined. In such a test, "generate no benzene by exposure to
actinic radiation" means that no benzene was generated, or the
amount of generated benzene was negligible, being at most 5 .mu.g.
Preferred as the aforesaid onium slats are sulfonium salts or
iodonium salts. Those having a substituent on the benzene ring,
which bonds to S.sup.+ or I.sup.+, satisfy the above
conditions.
[0106] Preferred as the aforesaid sulfonium salts are sulfonium
salt compounds represented by General Formulas (1)-(4), and those
having a substituent on the benzene ring, which bonds to S.sup.+,
satisfy the above conditions. 24
[0107] In above General Formulas (1)-(4), R.sub.1-R.sub.17 each
represent a hydrogen atom or a substituent. None of R.sub.1-R.sub.3
simultaneously represent a hydrogen atom, none of R.sub.4-R.sub.7
simultaneously represent a hydrogen atom, and none of
R.sub.12-R.sub.17 simultaneously represent a hydrogen atom.
[0108] Preferably listed as substituents represented by
R.sub.1-R.sub.17 may be an alkyl group such as a methyl group, an
ethyl group, a propyl group, an isopropyl group, a butyl group, an
isobutyl group, a t-butyl group, a pentyl group, or an hexyl group;
an alkoxy group such as a methoxy group, an ethoxy group, a propoxy
group, a butoxy group, a hexyloxy group, a decyloxy group, or a
dodecyloxy group; a carbonyl group such as an acetoxy group, a
propionyloxy group, a decylcarbonyloxy group, a dodecylcarbonyloxy
group, a methoxycarbonyl group, an ethoxycarbonyl group, or a
benzoyloxy group; a phenylthio group; a halogen atom such as
fluorine, chlorine, bromine, or iodine; a cyano group; a nitro
group; and a hydroxyl group.
[0109] X represents a non-nucleophilic anionic residual group.
Listed as examples of such may be a halogen atom such as F, Cl, Br,
and I, B(C.sub.6F.sub.5), R.sub.18COO, R.sub.19SO.sub.3, SbF6,
AsF.sub.6, PF.sub.6, or BF.sub.4, wherein R.sub.18 and R.sub.19
each represent an alkyl group such as a methyl group, an ethyl
group, a propyl group, or a butyl group, a halogen atom such as
fluorine, chlorine, bromine, or iodine, a nitro group, a cyano
group, an alkyl group which may be substituted with an alkoxy group
such as a methoxy group or an ethoxy group, or a phenyl group. Of
these, in view of safety, B(C.sub.6F.sub.5).sub.4 and PF.sub.6 are
preferred.
[0110] It is possible to readily synthesize the aforesaid compounds
employing methods known in the art in the same manner as for
photolytically acid generating agents, described in THE CHEMICAL
SOCIETY OF JAPAN, Vol. 71 No. 11, 1998, and "Imezingu yo Yuuki
Zairyo (Organic Materials for Imaging)", edited by Yuuki
Electronics Zairyo Kenkyu Kai, published by Bunshin Shuppan
(1993).
[0111] In the present invention, it is particularly preferable that
the sulfonium salt represented by aforesaid General Formulas
(1)-(4) is at least one of the sulfonium salts selected from
General Formulas (5)-(13), described below. X represents a
non-nucleophilic anionic residual group in the same manner as
above. 2526
[0112] Other than those described above, it is possible to use
various additives in the actinic radiation curable type ink
composition of the present invention. It is possible to add, for
example, surface active agents, leveling agents, matting agents, as
well as polyester based resins, polyurethane based resins, vinyl
based resins, acryl based resins, rubber based resins, and waxes,
all of which control physical properties of the applied layers.
Further, for the purpose of improving storage stability, it is
possibly to use any of the basic compounds known in the art. Listed
as the representative compounds are basic alkaline metal compounds,
basic alkaline earth metal compounds, and basic organic compounds
such as amines. Further, by combining radically polymerizable
monomers with initiators, it is possible to prepare a
radical-cation hybrid type ink.
[0113] In the actinic radiation curable type ink composition of the
present invention, in order to achieve the desired curing property,
it is preferable that the viscosity is 7-50 mPa.multidot.s at
25.degree. C., since ejection is stabilized independently in a
curing ambience (such as temperature and humidity).
EXAMPLES
[0114] The present invention will now be specifically described
with reference to examples, but the embodiments of the present
invention are not limited thereto.
Example 1
[0115] <<Control of .delta.m Value>>
[0116] While stirring, phthalocyaninesufonic acid was added to
purified water and mixed. Subsequently, untreated C.I. Pigment Blue
15:4 was added to the resulting solution and stirred for 30
minutes. The resulting mixture was filtered employing a suction
funnel to collect solids. The collected solids were dried at
120.degree. C. for two hours, whereby treated phthalocyanine
pigment was prepared.
[0117] The concentration of phthalocyaninesufonic acid mixed
solution was adjusted to vary the .delta.m value.
[0118] <<Preparation of Pigment Dispersions>>
1 (Preparation of Pigment Dispersion 1) Pigment 10.0 weight parts
Dispersing agent (Ajisper PB822, 1.5 weight parts polymer
dispersing agent, manufactured by Ajinomoto Fine Techno Co., Inc.)
Photopolymerizable compound: Aron 88.5 weight parts Oxetane OXT-221
(oxetane compound, manufactured by TOAGOSEI Co., Ltd.)
[0119] The above additives were mixed. Thereafter, the resulting
mixture was dispersed for two hours employing a bead mill utilizing
zirconia beads of a diameter of 0.5 mm, whereby Pigment Dispersion
1 was prepared.
[0120] (Preparation of Pigment Dispersions 2 and 3)
[0121] Pigment Dispersions 2 and 3 were prepared in the same manner
as aforesaid Pigment Dispersion 1, except that pigments having
different .delta.m values were used.
2 (Preparation of Pigment Dispersion 4) Pigment 7.0 weight parts
Dispersing agent: PLAAD ED-251 2.8 weight parts (pigment dispersing
agent, Kusunoki Kasei Co., Ltd.) Photopolymerizable compound: 90.2
weight parts VIKOFLEX 9010, epoxy compound, manufactured by ATOFINA
Chemicals Inc.)
[0122] The above additives were mixed. Thereafter, the resulting
mixture was dispersed for two hours, employing a bead mill
utilizing zirconia bead of a diameter of 0.5 mm, whereby Pigment
Dispersion 4 was prepared.
[0123] (Preparation of Pigment Dispersions 5 and 6)
[0124] Pigment Dispersions 5 and 6 were prepared in the same manner
as aforesaid Pigment Dispersion 4, except that pigments having
different .delta.m values were used.
[0125] (Preparation of Pigment Dispersions 7-11)
[0126] Pigment Dispersions 7-11 were prepared in the same manner as
aforesaid Pigment Dispersion 1, except that pigments having
different .delta.m values were used.
[0127] <<Evaluations of Pigment Dispersions>>
[0128] With regard to Pigment Dispersion 1-11, prepared as above,
the following measurements and evaluation were performed.
[0129] (Measurement of Hydrophilicity am of the Pigment
Surface)
[0130] Hydrophilicity am of the surface of pigment particles in
each pigment dispersion was determined employing the aforesaid
titration method.
[0131] (Measurement of Viscosity)
[0132] Viscosity was determined at 25.degree. C. under the
condition of a share rate of 12 (l/s) employing a viscoelasticity
measurement apparatus MCR300 (available from Nihon SiberHegner K.
K.).
[0133] (Evaluation of Dispersibility: Observation of Coarse Pigment
Particles)
[0134] Each of the pigment dispersions was applied onto a
polyethylene terephthalate film to result in a wet coating
thickness of 20 .mu.m, employing a wire bar. The resulting coating
was observed employing a hand magnifying lens (a magnification
factor of 100) to detect any presence of coarse pigment
particles.
[0135] (Evaluation of Dispersion Stability)
[0136] A specified amount of each of the pigment dispersions was
placed in a centrifugation tube. Subsequently, centrifugation was
performed for one hour under a condition of 1,600 G, employing a
centrifuge. Thereafter, the resulting pigment dispersion was
visually observed and dispersion stability was evaluated based on
the criteria below.
[0137] A: no supernatant was noted
[0138] B: some supernatant was noted, but was at a commercially
viable level
[0139] C: supernatant was clearly noted
[0140] Table 1 shows the results.
3TABLE 1 .delta.m Value Pigment of Dispersibility Dispersion
Pigment Viscosity (Coarse Dispersion No. Surface (mPa .multidot. s)
Grains) Stability Remarks 1 21.3 20 not observed A Inv. 2 20.9 20
not observed A Inv. 3 22.0 30 not observed B Inv. 4 21.3 45 not
observed A Inv. 5 20.9 45 not observed A Inv. 6 22.0 55 not
observed B Inv. 7 23.0 at least observed C Comp. 100 8 22.3 35 not
observed C Comp. 9 22.6 40 not observed C Comp. 10 22.7 30 not
observed C Comp. 11 22.7 30 not observed C Comp. Inv.; Present
Invention Comp.; Comparative Example
[0141] As can clearly be seen from the results in Table 1, pigment
dispersions of the present invention, which incorporated
photopolymerizable compounds as well as pigments and exhibited a
hydrophilicity .delta.m of at most 22, exhibited excellent
dispersibility and dispersion satiability compared to the
comparative examples.
Example 2
[0142] >>Preparation of Ink Compositions>>
4 (Preparation of Ink Composition 1) Pigment Dispersion 1 40.0
weight parts Photopolymerizable compound: Aron 27.9 weight parts
Oxetane OXT-221 (being an oxetane compound, manufactured by
TOAGOSEI Co., Ltd.) Photopolymerizable compound: 27.1 weight parts
Celloxide 2021P (being an epoxy compound, manufactured by Daicel
Chemical Industries Co., Ltd.) Photopolymerization initiator: 5.0
weight parts Adekaoptomer SP-152 (manufactured by Asahi Denka Kogyo
K.K.)
[0143] The above additives were mixed while stirring. Thereafter,
the resulting mixture was filtered employing a membrane filter,
whereby Ink Composition 1 was prepared.
[0144] (Preparation of Ink Composition 2)
[0145] Ink Composition 2 was prepared in the same manner as above
Ink Composition 1, except that Pigment Dispersion 1 was replaced
with Pigment Dispersion 2.
[0146] (Preparation of Ink Composition 3)
[0147] Ink Composition 3 was prepared in the same manner as above
Ink Composition 1, except that Pigment Dispersion 1 was replaced
with Pigment Dispersion 3.
5 (Preparation of Ink Composition 4) Pigment Dispersion 4 57.1
weight parts Photopolymerizable compound: 37.9 weight parts
VIKOFLEX 9010 (being an epoxy compound, manufactured by ATOFINA
Chemicals Inc.) Photopolymerization initiator: 5.0 weight parts
Adekaoptomer SP-152 (manufactured by Asahi Denka Kogyo K.K.)
[0148] The above additives were mixed while stirring. Thereafter,
the resulting mixture was filtered employing a membrane filter,
whereby Ink Composition 4 was prepared.
[0149] (Preparation of Ink Composition 5)
[0150] Ink Composition 5 was prepared in the same manner as above
Ink Composition 4, except that Pigment Dispersion 4 was replaced
with Pigment Dispersion 5.
[0151] (Preparation of Ink Composition 6)
[0152] Ink Composition 6 was prepared in the same manner as above
Ink Composition 4, except that Pigment Dispersion 4 was replaced
with Pigment Dispersion 6.
[0153] (Preparation of Ink Composition 7)
[0154] Ink Composition 7 was prepared in the same manner as above
Ink Composition 1, except that Pigment Dispersion 1 was replaced
with Pigment Dispersion 7.
[0155] (Preparation of Ink Composition 8)
[0156] Ink Composition 8 was prepared in the same manner as above
Ink Composition 1, except that Pigment Dispersion 1 was replaced
with Pigment Dispersion 8.
[0157] (Preparation of Ink Composition 9)
[0158] Ink Composition 9 was prepared in the same manner as above
Ink Composition 1, except that Pigment Dispersion 1 was replaced
with Pigment Dispersion 9.
[0159] (Preparation of Ink Composition 10)
[0160] Ink Composition 10 was prepared in the same manner as above
Ink Composition 1, except that Pigment Dispersion 1 was replaced
with Pigment Dispersion 10.
[0161] (Preparation of Ink Composition 11)
[0162] Ink Composition 11 was prepared in the same manner as above
Ink Composition 1, except that Pigment Dispersion 1 was replaced
with Pigment Dispersion 11.
[0163] <<Evaluation of Ink Compositions>>
[0164] With regard to Ink Compositions 1-11, employing the same
methods as for Example 1, hydrophilicity .delta.m of the pigment
surface and viscosity were determined; dispersibility was
evaluated; and coarse pigment particles were observed; and
dispersion stability was evaluated. Table 2 shows the results.
6TABLE 2 .delta.m Value Ink Pigment of Dispersibility Composition
Dispersion Pigment Viscosity (Coarse Dispersion No. No. Surface
(mPa .multidot. s) Particles) Stability Remarks 1 1 21.3 35 not A
Inv. observed 2 2 20.9 35 not A Inv. observed 3 3 22.0 45 not B
Inv. observed 4 4 21.3 45 not A Inv. observed 5 5 20.9 45 not A
Inv. observed 6 6 22.0 55 not B Inv. observed 7 7 23.0 100 or
observed C Comp. more 8 8 22.3 50 not C Comp. observed 9 9 22.6 55
not C Comp. observed 10 10 22.7 45 not C Comp. observed 11 11 22.7
45 not C Comp. observed Inv.; Present Invention Comp.; Comparative
Example
[0165] As can clearly be seen from the results in Table 2, the ink
compositions of the present invention, which comprised
photopolymerizable compounds, photopolymerization initiators, and
pigments, and exhibited a hydrophilicity .delta.m of the pigment
surface of at most 22, exhibited excellent dispersibility as well
as excellent dispersion stability compared to the comparative
examples.
* * * * *