U.S. patent application number 11/117430 was filed with the patent office on 2005-09-01 for oil based ink composition for inkjet printer.
This patent application is currently assigned to FUJI PHOTO FILM CO., LTD.. Invention is credited to Horie, Seiji, Sakasai, Yutaka.
Application Number | 20050192380 11/117430 |
Document ID | / |
Family ID | 29996492 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050192380 |
Kind Code |
A1 |
Horie, Seiji ; et
al. |
September 1, 2005 |
Oil based ink composition for inkjet printer
Abstract
An oil based ink composition for inkjet printer comprising
colored resin particles obtained by dispersion polymerization of a
monofunctional polymerizable monomer (A) and a macromonomer (M)
copolymerizable with the monomer (A) with coloring component fine
particles comprising a surface-treated coloring agent, which are
dispersed in a non-aqueous solvent having a dielectric constant of
from 1.5 to 20 and a surface tension of from 15 to 60 mN/m at
25.degree. C., as seed particles, in the presence of a dispersion
stabilizer (P) soluble in the non-aqueous solvent and a
polymerization initiator.
Inventors: |
Horie, Seiji; (Shizuoka,
JP) ; Sakasai, Yutaka; (Shzyoka, JP) |
Correspondence
Address: |
BUCHANAN INGERSOLL PC
(INCLUDING BURNS, DOANE, SWECKER & MATHIS)
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
FUJI PHOTO FILM CO., LTD.
Kanagawa
JP
|
Family ID: |
29996492 |
Appl. No.: |
11/117430 |
Filed: |
April 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11117430 |
Apr 29, 2005 |
|
|
|
10460304 |
Jun 13, 2003 |
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Current U.S.
Class: |
523/160 ;
523/161 |
Current CPC
Class: |
C09D 11/30 20130101;
G03G 9/12 20130101; C09D 11/36 20130101 |
Class at
Publication: |
523/160 ;
523/161 |
International
Class: |
C03C 017/00; C09D
011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 18, 2002 |
JP |
P. 2002-177379 |
Claims
What is claimed is:
1. A process of producing colored resin particles comprising
performing dispersion polymerization of a dispersion comprising a
monofunctional polymerizable monomer (A), a macromonomer (M)
copolymerizable with the monomer (A), coloring component fine
particles comprising a surface-treated coloring agent, which are
dispersed in a non-aqueous solvent having a dielectric constant of
from 1.5 to 20 and a surface tension of from 15 to 60 mN/m at
25.degree. C., as seed particles, and a dispersion stabilizer (P)
soluble in the non-aqueous solvent in the presence of a
polymerization initiator.
2. The process of producing colored resin particles as claimed in
claim 1, wherein the macromonomer (M) is a macromonomer having a
weight average molecular weight of from 1.times.10.sup.3 to
4.times.10.sup.4 in which a polymerizable double bond group
represented by formula (I) shown below is connected to a terminal
of the main chain of a polymer comprising a repeating unit
represented by formula (II) shown below: 44wherein V represents
--COO--, --OCO--, --(CH.sub.2).sub.m--OCO--,
--(CH.sub.2).sub.m--COO--, --O--, --CONHCOO--, --CONHCO--,
--SO.sub.2--, --CO--, --CON(Z.sup.1)--, --SO.sub.2N(Z.sup.1)-- or a
phenylene group; Z.sup.1 represents a hydrogen atom or a
hydrocarbon group; m represents an integer of from 1 to 3; a.sup.1
and a.sup.2, which may be the same or different, each represent a
hydrogen atom, a halogen atom, a cyano group, a hydrocarbon group,
--COO--Z.sup.2 or --COO--Z.sup.2 linked through a hydrocarbon
group; and Z.sup.2 represents a hydrogen atom or a hydrocarbon
group: 45wherein X.sup.0 represents a connecting group selected
from --COO--, --OCO--, --(CH.sub.2).sub.n--OCO--,
--(CH.sub.2).sub.n--COO--, --O--, --CONHCOO--, --CONHCO--,
--SO.sub.2--, --CO--, --CON(Z.sup.3)-- and --SO.sub.2N(Z.sup.3)--;
Z.sup.3 represents a hydrogen atom or a hydrocarbon group; n
represents an integer of from 1 to 3; b.sup.1 and b.sup.2, which
may be the same or different, each have the same meanings as
defined for a.sup.1 and a.sup.2 of formula (I); and Q.sup.0
represents an aliphatic group having from 1 to 22 carbon atoms.
3. The process of producing colored resin particles as claimed in
claim 1, wherein the surface-treated coloring agent is an organic
or inorganic pigment coated with a polymer.
4. The process of producing colored resin particles as claimed in
claim 1, wherein the coloring component fine particles are those
dispersed with a pigment dispersant in the non-aqueous solvent and
having an average particle diameter of from 0.01 to 1.0 .mu.m.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an oil based ink for use in
inkjet recording device, which ejects ink to form letters or images
on an ink receiving medium such as recording paper. In particular,
the invention relates to an oil based ink comprising a colored
resin particle in which a coloring component particle of
surface-treated coloring agent is further coated with a polymer, an
electrophotographic developer, and a process of producing the
colored resin particle.
BACKGROUND OF THE INVENTION
[0002] Hitherto, there have been known various inkjet recording
systems including on-demand ejection systems and continuous
ejection systems, as described, for example, in Takeshi Agui, et
al., Real Color Hard Copy, Sangyo Tosho Co., Ltd. (1993), Shin
Ohno, Non-impact Printing--Technologies and Materials-, CMC
Publishing Co., Ltd. (1986), and Takeshi Amari, Inkjet
Printers--Technologies and Materials-, published by CMC Publishing
Co., Ltd. (1998). Further, the continuous type includes
electrostatic systems (for example, Sweet type and Hertz type), and
the on-demand type includes a piezoelectric system, a shear mode
piezoelectric system, a thermal inkjet system and a recording
system called an electrostatic acceleration type. As inks to be
used in these inkjet recording systems, aqueous inks that are free
from ink clogging in an ink discharge section or an ink supply
passage, excellent in discharge stability and good in color image
quality, for example, color and gloss are ordinarily used.
[0003] As the on-demand type inkjet system using an electrostatic
force, systems called electrostatic acceleration type inkjet or
slit jet as described, for example, in Susumu Ichinose and Yuji
Ohba, Denshi Tsushin Gakkai Rombunnshi, Vol. J66-C (No. 1), p.47
(1983), Tadayoshi Ohno and Mamoru Mizuguchi, Gazo Denshi Gakkaishi,
Vol. 10 (No. 3), p.157 (1981) are known. Specific embodiments
thereof are disclosed, for example, in JP-A-56-170 (the term "JP-A"
as used herein means an "unexamined published Japanese patent
application"), JP-A-56-4467 and JP-A-57-151374. In these systems,
an ink is supplied from an ink tank into a slit-like ink chamber
having a plurality of electrodes disposed inside a slit-like
ink-holding section, and a high voltage is selectively applied to
these electrodes, thereby ejecting the ink in the vicinity of the
electrode to recording paper closely positioned to the slit-like
head.
[0004] An electrostatic system of a concentration discharge type
without using the slit-like recording head is described in
JP-A-10-138493. In this system, a plurality of individual
electrodes for allowing an electrostatic force to act on a colorant
component in ink are constituted of a control electrode substrate
composed of an insulating substrate having a through-hole formed
therein and a control electrode formed corresponding to the
through-hole and a convex ink guide arranged in the substantially
center position of the through-hole, the ink is carried on the
surface of a convex ink guide to an ink droplet ejecting position
by a surface tension, and a prescribed voltage is applied to the
control electrode to eject ink droplet to a recording medium,
thereby conducting recording.
[0005] As inks to be used for these various inkjet recording
systems, inks prepared by dissolving various water-soluble dyes in
water or a solvent composed of water and a water-soluble organic
solvent and optionally adding various additives thereto
(hereinafter referred to as "aqueous dye ink") are mainly employed.
However, in the case where printing is practically carried out
using the aqueous dye ink, many drawbacks are encountered in that
the ink blurs on recording paper depending on the kind of paper,
whereby high-quality print can not be obtained, in that a formed
recorded image is poor in water resistance and light fastness, in
that drying of ink on recording paper is so slow that streaks
occur, and in that a recorded image is deteriorated due to color
mixing (color turbidity or color unevenness occurred on the
interface when dots having different colors are printed adjacent to
each other).
[0006] For improving the water resistance and light fastness of
recorded image that are the problems of aqueous dye ink as
described above, there have been made various proposals to apply
pigment based ink comprising fine particles of a pigment dispersed
in an aqueous solvent or a non-aqueous solvent to the inkjet
recording system. For example, inks for inkjet printer comprising a
pigment dispersed in a solvent mainly composed of water are
proposed in JP-A-2-255875, JP-A-3-76767, JP-A-3-76768,
JP-A-56-147871 and JP-A-56-147868. However, there is a problem in
that since the pigment is insoluble in the medium, dispersion
stability of the ink is ordinarily poor to likely cause clogging in
a nozzle section.
[0007] On the other hand, ink comprising a pigment dispersed in a
non-polar insulating solvent (hereinafter referred to as "oil based
pigment ink") has advantages in that it is less in blur due to good
absorption on paper and in that a recorded image is good in water
resistance. For example, JP-A-57-10660 proposes oil based pigment
ink in which a pigment is pulverized with an alcoholamide
dispersant, and JP-A-57-10661 proposes oil based pigment ink in
which a pigment is pulverized with a sorbitan based dispersant.
However, such inks still have a problem in that clogging of ink in
a nozzle section is liable to occur, because it is not sufficient
to uniformly disperse the pigment particles in the state of fine
particles in the non-polar insulating solvent and the dispersion
stability thereof is inferior. In addition, there is a large defect
in that the ink is poor in scratch resistance because the pigment
itself does not have a fixing ability on recording paper.
[0008] For resolving these problems, there are proposed resin
dissolution type oil based inks using a resin soluble in a
non-polar insulating solvent as a fixing agent and a pigment
dispersant. For example, JP-A-3-234772 proposes a terpene phenol
based resin as the above-described resin. However, the proposed
resin is still insufficient with respect to dispersion stability of
pigment and is questionable in reliability as ink. Moreover, since
the resin is dissolved in the non-polar solvent, the resin does not
remain in an amount sufficient for completely fixing the pigment on
recording paper, so that water resistance and scratch resistance
are not sufficient.
[0009] Thus, for obtaining high-level scratch resistance, it is
proposed to coat pigment particles with a resin insoluble or
semi-soluble in the non-polar insulating solvent. For example,
JP-A-4-25574 proposes oil based ink comprising a pigment coated
with a resin by microencapsulation, etc. However, since it is
difficult to uniformly disperse the pigment-included resin
particles in the state of fine particle and dispersion stability
thereof is not sufficient, there is a problem in reliability as
ink.
[0010] In addition, in recent years, high image quality with
photographic image quality is attained by ordinary inkjet printers
using the aqueous dye ink. With respect to the pigment ink, for
increasing color forming property and transparency, it is required
to make pigment fine as far as possible and to keep the dispersion
state thereof stably.
[0011] However, in contrast, when the pigment is made finer,
crushing of pigment primary particles occurs simultaneously with
pulverization of the pigment. Further, since cohesive energy
simultaneously becomes large due to increase of surface energy,
re-coagulation of the pigment particles is apt to occur. As a
result, a problem occurs in that storage stability of the
pulverized pigment dispersion is damaged. As described above, with
respect to the pigment dispersion used in oil based pigment ink for
inkjet printer, pulverization at a higher level is required.
However, high-level techniques are required for dispersing pigment
in the state of fine particle, and it is very difficult to increase
the dispersion stability thereof. Therefore, it is the actual
situation that oil based pigment ink capable of meeting the
above-described requirements is hardly available.
[0012] Moreover, in the case where such oil based pigment ink is
used for an electrostatic inkjet printer or as an
electrophotographic liquid developer, control of charge polarity
and stability of the charge with the lapse of time are required.
However, since it is very difficult to control the polarity on the
pigment surface, it is the actual situation that oil based pigment
ink capable of meeting the above-described requirements is hardly
available. The electrophotographic liquid developer using a
non-aqueous solvent is ordinarily produced by pulverizing a mixture
comprising an aliphatic hydrocarbon solvent, a coloring agent, a
fixing resin and a dispersant, and optionally added various
additives in a ball mill or an attritor, etc. Various methods for
the production thereof have been proposed. On the other hand,
JP-A-63-174070 discloses a colored liquid developer comprising as a
coloring agent, a polymer latex dyed with a dye, wherein the
polymer latex is obtained by polymerization of styrene or an
acrylic monomer in a non-aqueous solvent. However, the method of
using a dye as the coloring agent has defects in that preparation
of a black liquid developer is difficult, in that an image density
is low because of the dye system, and in that light fading occurs.
As an example using a pigment as the coloring agent, JP-B-62-3859
(the term "JP-B" as used herein means an "examined Japanese patent
publication") proposes an electrophotographic liquid developer
containing a pigment and as a fixing resin, a resin obtained by
reacting a natural resin-modified thermosetting resin with a long
chain alkyl group-containing monomer. Although the effect for
improving dispersion stability of coloring agent is found, the
electrophotographic liquid developer is still insufficient in the
dispersion stability. Thus, with respect to the electrophotographic
liquid developer using a pigment as the coloring agent, sufficient
dispersion stability as well as scratch resistance have been
desired. In addition, since pigments are different in a charge
polarity depending on the kinds thereof, it has been desired to
make the charge polarity of pigment particle clear and to prevent
change of the charge polarity with the lapse of time.
SUMMARY OF THE INVENTION
[0013] Therefore, an object of the invention is to provide an oil
based ink for inkjet printer in which a pigment is uniformly
dispersed in the state of fine particle and dispersion stability of
the pigment dispersion is excellent, and which has high discharge
stability free from the occurrence of clogging in a nozzle
section.
[0014] Another object of the invention is to provide an oil based
ink for inkjet printer, which has excellent drying property on
recording paper, excellent water resistance and light fastness of
recorded image, and high-level scratch resistance.
[0015] A further object of the invention is to provide an oil based
ink for electrostatic inkjet printer, which is excellent not only
in dispersion stability and scratch resistance but also in control
of charge polarity and stability of charge with the lapse of
time.
[0016] A still further object of the invention is to provide an
electrophotographic liquid developer, which is excellent not only
in dispersion stability and scratch resistance but also in control
of charge polarity and stability of charge with the lapse of
time.
[0017] A still further object of the invention is to provide a
production process for obtaining ink for inkjet printer comprising
resin particles including a pigment uniformly dispersed in the
state of fine particle.
[0018] Other objects of the invention will become apparent from the
following description.
[0019] It has been found that the above-described objects can be
attained by the following constructions.
[0020] (1) An oil based ink composition for inkjet printer
comprising colored resin particles obtained by dispersion
polymerization of a monofunctional polymerizable monomer (A) and a
macromonomer (M) copolymerizable with the monomer (A) with coloring
component fine particles comprising a surface-treated coloring
agent, which are dispersed in a non-aqueous solvent having a
dielectric constant of from 1.5 to 20 and a surface tension of from
15 to 60 mN/m at 25.degree. C., as seed particles, in the presence
of a dispersion stabilizer (P) soluble in the non-aqueous solvent
and a polymerization initiator.
[0021] (2) The oil based ink composition for inkjet printer as
described in item (1) above, wherein the macromonomer (M) is a
macromonomer having a weight average molecular weight of from
1.times.10.sup.3 to 4.times.10.sup.4 in which a polymerizable
double bond group represented by formula (I) shown below is
connected to a terminal of the main chain of a polymer comprising a
repeating unit represented by formula (II) shown below. 1
[0022] In formula (I), V represents --COO--, --OCO--,
--(CH.sub.2).sub.m--OCO--, --(CH.sub.2).sub.m--COO--, --O--,
--CONHCOO--, --CONHCO--, --SO.sub.2--, --CO--, --CON(Z.sup.1)--,
--SO.sub.2N(Z.sup.1)-- or a phenylene group (hereinafter, the
phenyl group is represented by "--Ph--" and the "--Ph--" includes a
1,2-phenylene group, a 1,3-phenylene group and a 1,4-phenylene
group). Z.sup.1 represents a hydrogen atom or a hydrocarbon group,
and m represents an integer of from 1 to 3.
[0023] a.sup.1 and a.sup.2, which may be the same or different,
each represent a hydrogen atom, a halogen atom, a cyano group, a
hydrocarbon group, --COO--Z.sup.2 or --COO--Z.sup.2 linked through
a hydrocarbon group, in which Z.sup.2 represents a hydrogen atom or
a hydrocarbon group. 2
[0024] In formula (II), X.sup.0 represents a connecting group
selected from --COO--, --OCO--, --(CH.sub.2).sub.n--OCO--,
--(CH.sub.2).sub.n--COO- --, --O--, --CONHCOO--, --CONHCO--,
--SO.sub.2--, --CO--, --CON(Z.sup.3)-- and --SO.sub.2N(Z.sup.3)--,
in which Z.sup.3 represents a hydrogen atom or a hydrocarbon group,
and n represents an integer of from 1 to 3. b.sup.1 and b.sup.2,
which may be the same or different, each have the same meanings as
defined for a.sup.1 and a.sup.2 of formula (I). Q.sup.0 represents
an aliphatic group having from 1 to 22 carbon atoms.
[0025] (3) The oil based ink composition for inkjet printer as
described in item (1) above, wherein the surface-treated coloring
agent is an organic or inorganic pigment coated with a polymer.
[0026] (4) The oil based ink composition for inkjet printer as
described in item (1) above, wherein the coloring component fine
particles are those dispersed with a pigment dispersant in the
non-aqueous solvent and having an average particle diameter of from
0.01 to 1.0 .mu.m.
[0027] (5) An electrophotographic liquid developer comprising
colored resin particles obtained by dispersion polymerization of a
monofunctional polymerizable monomer (A) and a macromonomer (M)
copolymerizable with the monomer (A) with coloring component fine
particles comprising a surface-treated coloring agent, which are
dispersed in a non-aqueous solvent having a volume resistivity of
10.sup.9.OMEGA.cm or more, as seed particles, in the presence of a
dispersion stabilizer (P) soluble in the non-aqueous solvent and a
polymerization initiator.
[0028] (6) The electrophotographic liquid developer as described in
item (5) above, wherein the macromonomer (M) is a macromonomer
having a weight average molecular weight of from 1.times.10.sup.3
to 4.times.10.sup.4 in which a polymerizable double bond group
represented by formula (I) described in item (2) above is connected
to a terminal of the main chain of a polymer comprising a repeating
unit represented by formula (II) described in item (2) above.
[0029] (7) The electrophotographic liquid developer as described in
item (5) above, wherein the surface-treated coloring agent is an
organic or inorganic pigment coated with a polymer.
[0030] (8) The electrophotographic liquid developer as described in
item (5) above, wherein the coloring component fine particles are
those dispersed with a pigment dispersant in the non-aqueous
solvent and having an average particle diameter of from 0.01 to 1.0
.mu.m.
[0031] (9) A process of producing colored resin particles
comprising performing dispersion polymerization of a dispersion
comprising a monofunctional polymerizable monomer (A), a
macromonomer (M) copolymerizable with the monomer (A), coloring
component fine particles comprising a surface-treated coloring
agent, which are dispersed in a non-aqueous solvent having a
dielectric constant of from 1.5 to 20 and a surface tension of from
15 to 60 mN/m at 25.degree. C., as seed particles, and a dispersion
stabilizer (P) soluble in the non-aqueous solvent in the presence
of a polymerization initiator.
[0032] (10) The process of producing colored resin particles as
described in item (9) above, wherein the macromonomer (M) is a
macromonomer having a weight average molecular weight of from
1.times.10.sup.3 to 4.times.10.sup.4 in which a polymerizable
double bond group represented by formula (I) described in item (2)
above is connected to a terminal of the main chain of a polymer
comprising a repeating unit represented by formula (II) described
in item (2) above.
[0033] (11) The process of producing colored resin particles as
described in item (9) above, wherein the surface-treated coloring
agent is an organic or inorganic pigment coated with a polymer.
[0034] (12) The process of producing colored resin particles as
described in item (9) above, wherein the coloring component fine
particles are those dispersed with a pigment dispersant in the
non-aqueous solvent and having an average particle diameter of from
0.01 to 1.0 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a sectional view of an inkjet head including an
ejection electrode corresponding to a recording dot.
[0036] FIG. 2 is a front view showing a construction of ejection
electrode plates of a line scanning type multi-channel inkjet
head.
DETAILED DESCRIPTION OF THE INVENTION
[0037] The invention will be described below in detail.
[0038] A non-aqueous dispersion medium that is used in the oil
based ink composition for inkjet printer according to the invention
is a non-polar insulating solvent and preferably has a dielectric
constant of from 1.5 to 20 and a surface tension of from 15 to 60
mN/m at 25.degree. C. Also, a non-aqueous dispersion medium that is
used in the electrophotographic liquid developer according to the
invention preferably has a volume resistivity of 10.sup.9 .OMEGA.cm
or more. Characteristics further desired include that toxicity is
low, that flammability is low and that odor is low.
[0039] The non-aqueous dispersion media include straight chain or
branched aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic
hydrocarbons, petroleum naphthas and halogen-substituted products
thereof. Examples thereof include hexane, octane, isooctane,
decane, isodecane, decalin, nonane, dodecane, isododecane, Isopar
E, Isopar G, Isopar H and Isopar L (manufactured by Exxon), Solutol
(manufactured by Phillips Oil), IP Solvent (manufactured by
Idemitsu Petrochemical Co., Ltd.), and peptroleum naphthas
including S.B.R., Shellsol 70 and Shellsol 71 (manufactured by
Shell Petrochemical) and Vegasol (manufactured by Mobil Oil). The
solvents can be used individually or in combination.
[0040] The hydrocarbon solvents are preferably high-purity
isoparaffinic hydrocarbons having a boiling point in the range of
from 150 to 350.degree. C. Examples of commercially available
products include Isopar G, Isopar H, Isopar L, Isopar M and Isopar
V (trade names, manufactured by Exxon Chemical), Norpar 12, Norpar
13 and Norpar 15 (trade names, manufactured by Exxon Chemical), IP
Solvent 1620 and IP Solvent 2028 (trade names, manufactured by
Idemitsu Petrochemical Co., Ltd.), Isosol 300 and Isosol 400 (trade
names, manufactured by Nippon Pertochemicals), and Amsco OMS and
Amsco 460 solvents (trade names, manufactured by American Mineral
Spirits Corp.). These products are composed of an aliphatic
saturated hydrocarbon having an extremely high purity, and have a
viscosity at 25.degree. C. of 3 cSt or less, a surface tension at
25.degree. C. of from 22.5 to 28.0 mN/m, and a volume resistivity
at 25.degree. C. of 10.sup.10 .OMEGA..multidot.cm or more. Further,
these products have characteristics such that they are stable due
to low reactivity and are safe due to low toxicity and that their
odors are low.
[0041] The halogen-substituted hydrocarbon solvents include
fluorocarbon solvents. Examples thereof include perfluoroalkanes
represented by C.sub.nF.sub.2n+2, for example, C.sub.7F.sub.16 and
C.sub.8F.sub.18 (for example, Fluorinert PF5080 and Fluoriner
PF5070 (trade names, manufactured by Sumitomo 3M)), fluorine based
inert liquids (for example, Fluorinert FC Series (trade names,
manufactured by Sumitomo 3M)), fluorocarbons (for example, Krytox
GPL Series (trade names, manufactured by DuPont Japan Ltd.)),
fleons (for example, HCFC-141b (a trade name, manufactured by
Daikin Industries, Ltd.), and iodinated fluorocarbons for example,
F(CF.sub.2).sub.4CH.sub.2CH.sub.2I and F(CF.sub.2).sub.6I (for
example, I-1420 and I-1600 (trade names, manufactured by Daikin
Fine Chemical Laboratory, Ltd.).
[0042] As the non-aqueous solvent that is used in the invention,
higher fatty acid esters and silicone oils can also be used.
Specific examples of the silicone oil include low-viscosity
synthetic dimethylpolysiolxanes, which are commercially available,
for example, KF96L (a trade name, manufactured by Shin-Etsu
Silicone) and SH200 (a trade name, manufactured by Dow Corning
Toray Silicone).
[0043] The silicone oils are not limited to these specific
examples. As the dimethylpolysiloxanes, those having a very broad
viscosity range are available depending on the molecular weight,
but those having a viscosity at 25.degree. C. in the range of from
1 to 20 cSt are preferably used. Similar to the isoparaffinic
hydrocarbons, the dimethylpolysiloxanes have a volume resistivity
at 25.degree. C. of 10.sup.10.OMEGA..multidot.cm or more and have
characteristics, for example, high stability, high safety and
odorlessness. Further, the dimethylpolysiloxanes are characterized
by a low surface tension, i.e., the surface tension is from 18 to
21 mN/m at 25.degree. C.
[0044] Examples of solvents that can be used together with the
above-described organic solvents include alcohols (for example,
methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and
fluorinated alcohol), ketones (for example, acetone, methyl ethyl
ketone and cyclohexanone), carboxylic acid esters (for example,
methyl acetate, ethyl acetate, propyl acetate, butyl acetate,
methyl propionate and ethyl propionate), ethers (for example,
diethyl ether, dipropyl ether, tetrahydrofuran, and dioxane), and
halogenated hydrocarbons (for example, methylene dichloride,
chloroform, carbon tetrachloride, dichloroethane and
methylchloroform).
[0045] Now, the surface-treated coloring component of the invention
will be described below in detail.
[0046] The surface-treated coloring component of the invention
(hereinafter also referred simply to as "coloring component"
sometimes) is prepared by surface treatment of a coloring agent.
The coloring agent is not particularly limited and includes any
ordinarily commercially available organic pigments and inorganic
pigments.
[0047] Examples of coloring agents that exhibit yellow color
include mono-azo pigments, for example, C.I. Pigment Yellow 1 (Fast
Yellow G, etc.) and C.I. Pigment Yellow 74; dis-azo pigments, for
example, C.I. Pigment Yellow 12 (Disazo Yellow AAA, etc.) and C.I.
Pigment Yellow 17; non-benzidine based azo pigments, for example,
C.I. Pigment Yellow 180; azo lake pigments, for example, C.I.
Pigment Yellow 100 (Tartrazine Yellow Lake, etc.); condensed azo
pigments, for example, C.I. Pigment Yellow 95 (Condensed Azo Yellow
GR, etc.); acidic dye lake pigments, for example, C.I. Pigment
Yellow 115 (Quinoline Yellow Lake, etc.); basic dye lake pigments,
for example, C.I. Pigment Yellow 18 (Thioflavin Lake, etc.);
anthraquinone based pigments, for example, Flavanthrone Yellow
(Y-24); isoindolinone pigments, for example, Isoindolinone Yellow
3RLT (Y-110); quinophthalone pigments, for example, Quinophthalone
Yellow (Y-138); isoindoline pigments, for example, Isoindoline
Yellow (Y-139); nitroso pigments, for example, C.I. Pigment Yellow
153 (Nickel Nitroso Yellow, etc.); and metal complex azomethine
pigments, for example, C. I. Pigment Yellow 117 (copper Azomethine
Yellow, etc.).
[0048] Examples of coloring agents that exhibit magenta color
include mono-azo pigments, for example, C.I. Pigment Red 3
(Toluidine Red, etc.); dis-azo pigments, for example, C.I. Pigment
Red 38 (Pyrazolone Red B, etc.); azo lake pigments, for example,
C.I. Pigment Red 53:1 (Lake Red C, etc.) and C.I. Pigment Red 57:1
(Brilliant Carmine 6B); condensed azo pigments, for example, C.I.
Pigment Red 144 (Condensed Azo Lake BR, etc.); acidic dye lake
pigments, for example, C.I. Pigment Red 174 (Phloxine B Lake,
etc.); basic dye lake pigments, for example, C.I. Pigment Red 81
(Rhodamine 6G' Lake, etc.); anthraquinone based pigments, for
example, C.I. Pigment Red 177 (Dianthraquinonyl Red, etc.);
thioindigo pigments, for example, C.I. Pigment Red 88 (for example,
Thioindigo Bordeaux, etc.); perinone pigments, for example, C.I.
Pigment Red 194 (Perinone Red, etc.); perylene pigments, for
example, C.I. Pigment Red 149 (Perylene Scarlet, etc.);
quinacridone pigments, for example, C.I. Pigment Red 122
(Quinacridone Magenta, etc.); isoindolinone pigments, for example,
C.I. Pigment Red 180 (Isoindolinone Red 2BLT, etc.); and arizalin
lake pigments, for example, C.I. Pigment Red 83 (Madder Lake,
etc.).
[0049] Examples of pigments that exhibit cyan color include dis-azo
pigments, for example, C.I. Pigment Blue 25 (Dianisidine Blue,
etc.); phthalocyanine pigments, for example, C.I. Pigment Blue 15
(Phthalocyanine Blue, etc.); acidic dye lake pigments, for example,
C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); basic dye lake
pigments, for example, C.I. Pigment Blue 1 (Victoria Pure Blue BO
Lake, etc.); anthraquinone based pigments, for example, C.I.
Pigment Blue 60 (Indanthrone Blue, etc.); and alkali blue pigments,
for example, C.I. Pigment Blue 18 (Alkali Blue V-5:1).
[0050] Examples of pigments that exhibit black color include
organic pigments, for example, aniline black based pigments such as
BK-1 (Aniline Black), iron oxide pigments, and carbon black
pigments, for example, furnace black, lamp black, acetylene black
and channel black.
[0051] Also, metallic powders are employable for attaining color
reproduction, for example, gold, silver or copper color.
[0052] The surface treatment methods of coloring agent are
described in Pigment Dispersing Technologies, Chapter 5, Gijutsu
Joho Kyokai Co., Ltd., and examples thereof include rosin
treatment, polymer treatment, grafting treatment and plasma
treatment.
[0053] The "rosin treatment" as referred to herein includes a
method in which a pigment and rosin are mechanically kneaded to
treat the surface of the pigment with rosin and a method in which
after adding an alkaline aqueous solution of rosin to an aqueous
slurry of a pigment, an alkaline earth metal salt or an acid is
added to the mixture to deposit a sparingly soluble salt or free
acid of rosin on the surfaces of pigment particles. In the rosin
treatment, the rosin is ordinarily used in an amount of from
several % to about 20%. The rosin treatment brings about the
following large effects: (1) fine and highly transparent pigment is
obtained due to the effect for preventing crystal growth of the
pigment; (2) mechanical dispersion is easy conducted because of
small cohesive forth of particle in drying; and (3) wetting
property to an oil based vehicle is improved by increasing
oleophilicity on the pigment surface. In particular, the rosin
treatment is widely used in the field of printing inks.
[0054] The "grafting treatment" as referred to herein is to conduct
a grafting reaction of functional group (for example, a hydroxy
group, a carboxy group or an amino group) present on the surfaces
of inorganic fine particle, for example, carbon black, silica or
titanium oxide, or organic pigment with a polymer. The grafting
reaction of the polymer to the pigment surface includes (1) a
method in which a vinyl monomer is polymerized in the presence of
pigment fine particles using a polymerization initiator and the
growing of polymer formed in the system is terminated at the
functional group on the pigment fine particle surface, (2) a method
in which a graft chain is grown from a polymerization initiating
group introduced on the pigment fine particle surface and (3) a
method of a polymer reaction between the functional group on the
pigment fine particle surface and a terminal functional group of
the polymer.
[0055] The "plasma treatment" as referred to herein is to conduct
modification of the pigment powder surface with low-temperature
plasma or thermal plasma. Specific examples of the treatment of the
pigment surface with low-temperature plasma include (1)
modification by plasma irradiation with a non-polymerizable gas,
for example, oxygen or nitrogen, (2) modification by formation of
plasma polymerized film using a polymerizable gas and (3)
modification by a two-stage plasma initiation graft polymerization
reaction comprising a first stage for forming an active species on
the pigment surface by plasma irradiation and a second stage for
bringing the active species into contact with a monomer to proceed
graft polymerization as the post reaction.
[0056] From the viewpoints that dispersibility of the coloring
agent is enhanced and that the dispersed coloring component as seed
particle is subjected to dispersion polymerization in a non-aqueous
solvent, the following polymer treatments are preferred.
[0057] Representative examples of the polymer treatment include a
chemical method of utilizing an in-situ polymerization method as
described in Pigment Dispersing Technologies, page 99, et seq.,
Gijutsu Joho Kyokai Co., Ltd., a method of utilizing a phase
separation method (coacervation), and a method of conducting
treatment by a mechanical force during pigment dispersion.
[0058] The in-situ polymerization method includes a method in which
a system of pigment and polymer is dispersed and then subjected to
suspension polymerization, a method in which a pigment is dispersed
in an aqueous system in the presence of a dispersant and to the
dispersion are added a polar polymer, a vinyl based polymer and a
polyfunctional crosslinking polymer to undergo polymerization and a
method in which a dispersion of a monomer and a pigment is
subjected to bulk polymerization and then to suspension
polymerization or emulsion polymerization, thereby thoroughly
achieving adsorption onto the pigment. The phase separation method
(coacervation) includes a method in which a pigment is dispersed in
a polymer solution, and the solubility of the polymer is reduced by
an appropriate method to deposit the polymer from the solution
system on the pigment particle. This method is characterized in
that the polymer can be selected from a wide range, in comparison
with the chemical method (in-situ polymerization method). There are
widely used a method in which a nonsolvent is added to a resin
solution having a pigment dispersed therein to deposit the resin on
the pigment surface and a method in which a pigment is finely
dispersed in a water-soluble polymer or water-soluble resin
solution, then the pH is adjusted to deposit the polymer or resin
on the pigment surface, inclusive of the rosin treatment. When a
pigment is dispersed in an acid solution of an acid-soluble
nitrogen-containing acrylic resin and then the pH thereof is
increased to insolubilize the polymer on the pigment surface,
effects, for example, prevention of coagulation and improvements in
fluidity, gloss and coloring power are recognized in paint and
printing ink. As an example of the method of polymer treatment by a
mechanical force, a method wherein a polymer and a pigment are
previously mixed such that the pigment content is from 5 to 95%,
the mixture is kneaded by a kneader, three rolls, etc. while
heating, and the kneaded mixture is then pulverized by a pin mill,
etc. A method called flushing resin treatment is also included in
the mechanical polymer treatment method.
[0059] As the resin that is used in the polymer treatment, resins
capable of not only enhancing dispersibility of a pigment in a
non-aqueous solvent but also imparting heat dispersion stability
during dispersion polymerization in-the non-aqueous solvent using
the dispersed coloring component fine particles as seed particles
are preferred. Resins that are conventionally used in liquid
developers can also be used.
[0060] As the resin, resins having a segment solvating with a
solvent, a segment hardly solvating with a solvent and a polar
group-containing segment for the purposes of adsorbing on a
coloring agent and having a function of well dispersing the
coloring agent in a non-aqueous solvent are preferably used.
Examples of the monomer that solvates with a solvent after
polymerization include lauryl methacrylate, stearyl methacrylate,
2-ethylhexyl methacrylate and cetyl methacrylate. Examples of the
monomer that hardly solvates with a solvent after polymerization
include methyl methacrylate, ethyl methacrylate, isopropyl
methacrylate, styrene and vinyltoluene. Examples of the polar
group-containing monomer include an acid group-containing monomers,
for example, acrylic acid, methacrylic acid, itaconic acid, fumaric
acid, maleic acid, styrenesulfonic acid and an alkali metal salt
thereof and a basic group-containing monomer, for example,
dimethylamonoethyl methacrylate, diethylaminoethyl methacrylate,
vinylpyridine, vinylpyrrolidone, vinylpiperidine and
vinyllactam.
[0061] Specific examples of the resin for use in the polymer
treatment include olefin polymers and copolymers (for example,
polyethylene, polypropylene, polyisobutylene, ethylene-vinyl
acetate copolymers, ethylene-acrylate copolymers,
ethylene-methacrylate copolymers, and ethylene-methacrylic acid
copolymers), polymers and copolymers of styrene or derivatives
thereof (for example, butadiene-styrene copolymers,
isoprene-styrene copolymers, styrene-methacrylate copolymers, and
styrene-acrylate copolymers), acrylic acid ester polymers and
copolymers, methacrylic acid ester polymers and copolymers,
itaconic acid diester polymers and copolymers, maleic anhydride
copolymers, rosin resins, hydrogenated rosin resins, petroleum
resins, hydrogenated petroleum resins, maleic acid resins, terpene
resins, hydrogenated terpene resins, chroman-indene resins,
cyclized rubber-methacrylic acid ester copolymers and cyclized
rubber-acrylic acid ester copolymers.
[0062] In the invention, a weight ratio of the coloring agent to
the resin to be used in the polymer treatment is preferably in the
range of from 95/5 to 5/95, and more preferably from 80/20 to
10/90.
[0063] Further, as the surface-treated coloring component,
ordinarily commercially available processed pigment can be used.
Specific examples of the commercially available processed pigment
include Microlith pigments manufactured by Ciba Specialty
Chemicals. Preferred examples of the processed pigment include
Microlith-T pigment in which pigment is coated with a rosin ester
resin.
[0064] In the invention, the above-described surface-treated
coloring component is dispersed in the state of fine particles in a
non-aqueous solvent to obtain coloring component fine particles,
which are used as seed particles in the subsequent dispersion
polymerization. First of all, the dispersion step of the coloring
component is described.
[0065] In the dispersion step, in order to disperse the coloring
component in the state of fine particles and to stabilize the
dispersion in the non-aqueous solvent, it is preferred to use a
pigment dispersant.
[0066] As the pigment dispersant for dispersing the surface-treated
coloring component in the state of fine particles in a non-aqueous
dispersion medium, which can be used in the invention, conventional
pigment dispersants applied to the non-aqueous dispersion medium
are used. Any pigment dispersants can be used so far as they are
compatible with the above-described non-polar insulating solvent
and can stably disperse the coloring component in the state of fine
particles.
[0067] Specific examples of pigment dispersant include nonionic
surfactants, for example, sorbitan fatty acid esters (e.g.,
sorbitan monooleate, sorbitan monolaurate, sorbitan sesquioleate
and sorbitan trioelate), polyoxyethylene sorbitan fatty acid esters
(e.g., polyoxyethylene sorbitan monostearate and polyoxyethylene
sorbitan monooleate), polyethylene glycol fatty acid esters (e.g.,
polyethylene glycol monostearate and polyethylene glycol
diisostearate), polyoxyethylene alkylphenyl ethers (e.g.,
polyoxyethylene nonylphenyl ether and polyoxyethylene octylphenyl
ether), and aliphatic diethanolamides. Further, as high-molecular
dispersants, high-molecular compounds having a molecular weight of
1,000 or more are preferable. Examples thereof include
styrene-maleic acid resins, styrene-acrylic resins, rosins,
BYK-160, BYK-162, BYK-164 and BYK-182 (urethane based
high-molecular compounds manufactured by BYK-Chemie), EFKA-47 and
LP-4050 (urethane based dispersants manufactured by EFKA),
Solsperse 24000 (polyester based high-molecular compound
manufactured by Zeneca PLC), and Solsperse 17000 (aliphatic
diethanolamide based high-molecular compound manufactured by Zeneca
PLC).
[0068] Other examples of the high-molecular pigment dispersant
include random copolymers comprising a monomer that solvates with a
solvent (for example, lauryl methacrylate, stearyl methacrylate,
2-ethylhexyl methacrylate and cetyl methacrylate), a monomer that
hardly solvates with a solvent (for example, methyl methacrylate,
ethyl methacrylate, isopropyl methacrylate, styrene and
vinyltoluene) and a polar group-containing monomer, and the graft
copolymers described in JP-A-3-188469. Examples of the polar
group-containing monomer include an acid group-containing monomer,
for example, acrylic acid, methacrylic acid, itaconic acid, fumaric
acid, maleic acid, styrene sufonic acid and an alkali metal salt
thereof, and a basic group-containing monomer, for example,
dimethylamonoethyl methacrylate, diethylaminoethyl methacrylate,
vinylpyridine, vinylpyrrolidone, vinylpiperidine and vinyllactam.
In addition, styrene-butadiene copolymers and the block copolymers
of styrene and a long chain alkyl methacrylate as described in
JP-A-60-10263 are enumerated. Preferred examples of the pigment
dispersant include the graft copolymers described in
JP-A-3-188469.
[0069] The amount of the pigment dispersant used is preferably from
0.1 to 300 parts by weight based on 100 parts by weight of the
surface-treated coloring agent. When the amount of pigment
dispersant added is less than 0.1 parts by weight, the effect for
dispersing the coloring agent is low, and hence, such is not
preferred. On the other hand, even when it exceeds 300 parts by
weight, no further improving effect is obtained.
[0070] A method of using the pigment dispersant in the dispersion
of the surface-treated coloring agent (coloring component) in the
non-aqueous dispersion medium includes the following methods, and
any of these methods can achieve the desired effects.
[0071] 1. A coloring component composition obtained by previously
mixing the surface-treated coloring agent with the pigment
dispersant is added and dispersed in the non-aqueous solvent.
[0072] 2. The surface-treated coloring agent and the pigment
dispersant are individually added and dispersed in the non-aqueous
solvent.
[0073] 3. Dispersions previously obtained by individually
dispersing the surface-treated coloring agent and the pigment
dispersant in the non-aqueous solvent are mixed with each
other.
[0074] 4. The surface-treated coloring agent is dispersed in the
non-aqueous solvent and then the pigment dispersant is added to the
resulting coloring component dispersion.
[0075] The above-described surface-treated coloring agent (coloring
component) is mixed or dispersed in the non-aqueous solvent to
prepare coloring component fine particles, preferably in the
presence of the pigment dispersant. A machine used for conducting
the mixing or dispersion in the non-aqueous solvent includes, for
example, a dissolver, a high-speed mixer, a homomixer, a kneader, a
ball mill, a roll mill, a sand mill and an attritor. The coloring
component (for example, processed pigment) has an average particle
size in the range of from 0.01 to 10 .mu.m. The coloring component
obtained by such a dispersing step preferably has an average
particle size ranging from 0.01 to 1.0 .mu.m.
[0076] Now, a step in which a monofunctional polymerizable monomer
(A) and a macromonomer (M) are added to the dispersed coloring
component fine particles as seed particles to conduct dispersion
polymerization will be described below.
[0077] A polymerization system comprising the coloring component
fine particles, as seed particles, dispersed in the non-aqueous
solvent, a monofunctional polymerizable monomer (A), a macromonomer
(M) and a dispersion stabilizer (P) is polymerized in the presence
of a polymerization initiator to obtain colored resin particles
having the coloring agent included therein according to the
invention.
[0078] The colored resin particle according to the invention is a
particle having a two-layer structure composed of a core layer
comprising the coloring component fine particle, which is a seed
particle, and a shell layer present outside the core layer. The
shell layer insoluble in the non-aqueous solvent is formed by
copolymerization of the monomer (A) and the macromonomer (M).
[0079] It is preferred that the monofunctional polymerizable
monomer (A) is a polymerizable monomer that is soluble in the
non-aqueous solvent but becomes insoluble in the non-aqueous
solvent upon polymerization.
[0080] Specific examples of the monomer (A) include polymerizable
monomers represented by the following formula (III): 3
[0081] In formula (III), V.sup.1 represents --COO--, --OCO--,
--CH.sub.2OCO--, --CH.sub.2COO--, --O--, --CONHCOO--, --CONHOCO--,
--SO.sub.2--, --CON(Z.sup.11)--, --SO.sub.2N(Z.sup.11)-- or a
phenylene group (hereinafter also referred to as "--Ph--"
sometimes; the phenylene group includes a 1,2-phenylene group, a
1,3-phenylene group and a 1,4-phenylene group). Z.sup.11 represents
a hydrogen atom or an aliphatic group having from 1 to 8 carbon
atoms, which may be substituted (for example, a methyl group, an
ethyl group, a propyl group, a butyl group, a 2-chloroethyl group,
a 2-bromoethyl group, a 2-cyanoethyl group, a 2-hydroxyethyl group,
a benzyl group, a chlorobenzyl group, a methylbenzyl group, a
methoxybenzyl group, a phenethyl group, a 3-phenylpropyl group, a
dimethylbenzyl group, a fluorobenzyl group, a 2-methoxyethyl group
or a 3-methoxypropyl group).
[0082] T.sup.1 represents a hydrogen atom or an aliphatic group
having from 1 to 6 carbon atoms, which may be substituted (for
example, a methyl group, an ethyl group, a propyl group, a butyl
group, a 2-chloroethyl group, a 2,2-dichloroethyl group, a
2,2,2-trifluoroethyl group, a 2-bromoethyl group, a 2-hydroxyethyl
group, a 2-hydroxypropyl group, a 2,3-dihydroxypropyl group, a
2-hydroxy-3-chloropropyl group, a 2-cyanoethyl group, a
3-cyanopropyl group, a 2-nitroethyl group, a 2-methoxyethyl group,
a 2-methanesulfonylethyl group, a 2-ethoxyethyl group, a
3-bromopropyl group, a 4-hydroxybutyl group, a 2-furfurylethyl
group, a 2-thienylethyl group, a 2-carboxyethyl group, a
3-carboxypropyl group, a 4-carboxybutyl group, a
2-carboxyamidoethyl group, a 3-sulfonamidopropyl group, a
2-N-methylcarboxyamidoethyl group, a cyclopentyl group, a
chlorocyclohexyl group or a dichlorohexyl group).
[0083] c.sup.1 and c.sup.2, which may be the same or different,
each preferably represent a hydrogen atom, a halogen atom (for
example, a chlorine atom or a bromine atom), a cyano group, an
alkyl group having from 1 to 3 carbon atoms (for example, a methyl
group, an ethyl group or a propyl group), --COO--Z.sup.12, or
--CH.sub.2--COO--Z.sup.12, wherein Z.sup.12 represents a hydrogen
atom or an hydrocarbon group having not more than 10 carbon atoms,
which may be substituted (for example, an alkyl group, an alkenyl
group, an aralkyl group or an aryl group).
[0084] Specific examples of the monofunctional polymerizable
monomer (A) include a vinyl ester or allyl ester of an aliphatic
carboxylic acid having from 1 to 6 carbon atoms (for example,
acetic acid, propionic acid, butyric acid, monochloroacetic acid or
trifluoropropionic acid); an alkyl ester or alkyl amide having from
1 to 32 carbon atoms, which may be substituted, of an unsaturated
carboxylic acid (for example, acrylic acid, methacrylic acid,
crotonic acid, itaconic acid or maleic acid) (examples of the alkyl
group include a methyl group, an ethyl group, a propyl group, a
butyl group, a 2-chloroethyl group, a 2-bromoethyl group, a
2-hydroxyethyl group, a 2-cyanoethyl group, a 2-nitroethyl group, a
2-methoxyethyl group, a 2-methanesulfonylethyl group, a
2-benzenesulfonylethyl group, a 2-carboxyethyl group, a
4-carboxybutyl group, a 3-chloropropyl group, a
2-hydroxy-3-chloropropyl group, a 2-furfurylethyl group, a
2-thienylethyl group, a 2-carboxyamidoethyl group, a decyl group, a
dodecyl group, a tridecyl group, a tetradecyl group, a hexadecyl
group, an octadecyl group, a docosyl group, a dodecenyl group, a
hexadecenyl group, an oleyl group, an linoleyl group or a docosenyl
group); a styrene derivative (for example, styrene, vinyltoluene,
.alpha.-methylstyrene, vinylnaphthalene, chlorostyrene,
dichlorostyrene, bromostyrene, vinylbenznecarboxylic acid,
vinylbenzenesulfonic acid, chloromethylstyrene,
hydroxymethylstyrene, methoxymethylstyrene, vinylbenzenecarboxamide
or vinylbenzenesulfonamide)- ; an unsaturated carboxylic acid (for
example, acrylic acid, methacrylic acid, crotonic acid, maleic acid
or itaconic acid); a cyclic acid anhydride of maleic acid or
itaconic acid; acrylonitrile; methacrylonitrile; and a
polymerizable double bond group-containing heterocyclic compound
(specifically, the compounds described in Kobunshi Gakkai ed.,
Polymer Data Handbook--Fundamental Edition-, pages 175 to 184,
Baifukan Co., Ltd. (1986), for example, N-vinylpyridine,
N-vinylimidazole, N-vinylpyrrolidone, vinylthiophene,
vinyltetrahydrofuran, vinyloxazoline, vinylthiazole or
N-vinylmorpholine).
[0085] The monofunctional polymerizable monomer (A) is preferably
selected from those described above.
[0086] In the invention, other monomer components that are
copolymerizable with the monofunctional polymerizable monomer (A)
may be used together.
[0087] Examples of the other copolymerizable monomer component
include a basic monomer (B) containing an amino group represented
by formula: --N(R.sup.1) (R.sup.2). By using the copolymerizable
amino group-containing basic monomer (B) as a copolymerization
component together with the monofunctional polymerizable monomer
(A) in the colored resin particles of the invention, the surfaces
of the particles themselves exhibit positive charges, thereby
enhancing dispersion stability of the particles dispersed in the
non-aqueous solvent. It is assumed that this is caused by charge
repulsion effects generated when the particles come close to each
other.
[0088] In the above formula, R.sup.1 and R.sup.2, which may be the
same or different, each preferably represent a hydrogen atom, an
alkyl group having from 1 to 22 carbon atoms, which may be
substituted (for example, a methyl group, an ethyl group, a propyl
group, a butyl group, a hexyl group, a heptyl group, an octyl
group, a nonyl group, a decyl group, a dodecyl group, a tridecyl
group, a tetradecyl group, a hexadecyl group, an octadecyl group,
an eicosyl group, a docosyl group, a 2-chloroethyl group, a
2-bromoethyl group, a 2-cyanoethyl group, a 2-methoxycarbonylethyl
group, a 2-methoxyethyl group or a 3-bromopropyl group), an alkenyl
group having from 4 to 18 carbon atoms, which may be substituted
(for example, a 2-methyl-1-propenyl group, a 2-butenyl group, a
2-pentenyl group, a 3-methyl-2-pentenyl group, a 1-pentenyl group,
a 1-hexenyl group, a 2-hexenyl group, a 4-methyl-2-hexenyl group, a
decenyl group, a dodecenyl group, a tridecenyl group, a hexadecenyl
group, an octadecenyl group or a linoleyl group), an aralkyl group
having from 7 to 12 carbon atoms, which may be substituted (for
example, a benzyl group, a phenethyl group, a 3-phenylpropyl group,
a naphthylmethyl group, a 2-naphthylethyl group, a chlorobenzyl
group, a bromobenzyl group, a methylbenzyl group, an ethylbenzyl
group, a methoxybenzyl group, a dimethylbenzyl group or a
dimethoxybenzyl group), an alicyclic group having from 5 to 8
carbon atoms, which may be substituted (for example, a cyclohexyl
group, a 2-cyclohexylethyl group or a 2-cyclopentylethyl group), or
an aromatic group having from 6 to 12 carbon atoms, which may be
substituted (for example, a phenyl group, a naphthyl group, a tolyl
group, a xylyl group, a propylphenyl group, a butylphenyl group, an
octylphenyl group, a dodecylphenyl group, a methoxyphenyl group, an
ethoxyphenyl group, a butoxyphenyl group, a decyloxyphenyl group, a
chlorophenyl group, a dichlorophenyl group, a bromophenyl group, a
cyanophenyl group, an acetylphenyl group, a methoxycarbonylphenyl
group, an ethoxycarbonylphenyl group, a butoxycarbonylphenyl group,
an acetamidophenyl group, a propionamidophenyl group or a
dodecyloylamidophenyl group).
[0089] Further, R.sup.1 and R.sup.2 may be combined with each other
to form a ring, and specifically represent together a ring-forming
organic reside that may contain a hetero atom (for example, an
oxygen atom, a nitrogen atom or a sulfur atom). Examples of the
cyclic amino group formed include a morpholino group, a piperidino
group, a pyridinyl group, an imidazolyl group and a quinolyl group.
A plurality of the amino groups may be included in a molecule of
the basic monomer.
[0090] The basic monomer (B) is preferably used in an amount of
from 1 to 45% by weight, and more preferably from 3 to 30% by
weight based on the total amount of the polymerizable monomer
(A).
[0091] Specific examples of the basic monomer (B) are set forth
below, but the invention should not be construed as being limited
thereto. In the following examples, d.sup.1 represents --H,
--CH.sub.3, --Cl or --CN; p.sub.1 represents an integer of from 2
to 12; d.sup.2 represents --H or --CH.sub.3; and p.sub.2 represents
an integer of from 2 to 4. 45
[0092] Now, the macromonomer (M) for use in the invention is
described in detail below.
[0093] The macromonomer (M) for use in the invention is preferably
a macromonomer having a weight average molecular weight of from
1.times.10.sup.3 to 4.times.10.sup.4 in which a polymerizable
double bond group represented by formula (I) described above is
connected to a terminal of the main chain of a polymer comprising a
repeating unit represented by formula (II) described above.
[0094] In formula (I), V represents --COO--, --OCO--,
--(CH.sub.2).sub.m--OCO--, --(CH.sub.2).sub.m--COO--, --O--,
--CONHCOO--, --CONHCO--, --SO.sub.2--, --CO--, --CON(Z.sup.1)--,
--SO.sub.2N(Z.sup.1)-- or a phenylene group (hereinafter, the
phenyl group is represented by "--Ph--" and the "--Ph--" includes a
1,2-phenylene group, a 1,3-phenylene group and a 1,4-phenylene
group). Z.sup.1 represents a hydrogen atom or a hydrocarbon group,
and m represents an integer of from 1 to 3.
[0095] a.sup.1 and a.sup.2, which may be the same or different,
each represent a hydrogen atom, a halogen atom, a cyano group, a
hydrocarbon group, --COO--Z.sup.2 or --COO--Z.sup.2 linked through
a hydrocarbon group, in which Z.sup.2 represents a hydrogen atom or
a hydrocarbon group which may be substituted.
[0096] In formula (II), X.sup.0 represents a connecting group
selected from --COO--, --OCO--, --(CH.sub.2).sub.n--OCO--,
--(CH.sub.2).sub.n--COO- --, --O--, --CONHCOO--, --CONHCO--,
--SO.sub.2--, --CO--, --CON(Z.sup.3)-- and --SO.sub.2N(Z.sup.3)--.
Z.sup.3 represents a hydrogen atom or a hydrocarbon group, and n
represents an integer of from 1 to 3.
[0097] b.sup.1 and b.sup.2, which may be the same or different,
each have the same meanings as defined for a.sup.1 and a.sup.2 of
formula (I). Q.sup.0 represents an aliphatic group having from 1 to
22 carbon atoms.
[0098] The aliphatic group having from 1 to 22 carbon atoms
represented by Q.sup.0 may have a substituent containing a fluorine
atom and/or a silicon atom.
[0099] In formula (I), Z.sup.1 included in the group represented by
V represents a hydrocarbon atom, as well as a hydrogen atom.
Preferred examples of the hydrocarbon group include an alkyl group
having from 1 to 22 carbon atoms, which may be substituted (for
example, a methyl group, an ethyl group, a propyl group, a butyl
group, a heptyl group, a hexyl group, an octyl group, a decyl
group, a dodecyl group, a tridecyl group, a tetradecyl group, a
hexadecyl group, an octadecyl group, a 2-chloroethyl group, a
2-bromoethyl group, a 2-cyanoethyl group, a 2-methoxycarbonylethyl
group, a 2-methoxyethyl group or a 2-bromopropyl group), an alkenyl
group having from 4 to 18 carbon atoms, which may be substituted
(for example, a 2-methyl-1-propenyl group, a 2-butenyl group, a
2-pentenyl group, a 3-methyl-2-pentenyl group, a 1-pentenyl group,
a 1-hexenyl group, a 2-hexenyl group or a 4-methyl-2-hexenyl
group), an aralkyl group having from 7 to 12 carbon atoms, which
may be substituted (for example, a benzyl group, a phenethyl group,
a 3-phenylpropyl group, a naphthylmethyl group, a 2-naphthylethyl
group, a chlorobenzyl group, a bromobenzyl group, a methylbenzyl
group, an ethylbenzyl group, a methoxybenzyl group, a
dimethylbenzyl group or a dimethoxybenzyl group), an alicyclic
group having from 5 to 8 carbon atoms, which may be substituted
(for example, a cyclohexyl group, a 2-cyclohexylethyl group or a
2-cyclopentylethyl group), an aromatic group having from 6 to 12
carbon atoms, which may be substituted (for example, a phenyl
group, a naphthyl group, a tolyl group, a xylyl group, a
propylphenyl group, a butylphenyl group, an octylphenyl group, a
dodecylphenyl group, a methoxyphenyl group, an ethoxyphenyl group,
a butoxyphenyl group, a decyloxyphenyl group, a chlorophenyl group,
a dichlorophenyl group, a bromophenyl group, a cyanophenyl group,
an acetylphenyl group, a methoxycarbonylphenyl group, an
ethoxycarbonylphenyl group, a butoxycarbonylphenyl group, an
acetamidophenyl group, a propionamidophenyl group or a
dodecyloylamidophenyl group), and a group of a bridged hydrocarbon
having from 5 to 18 carbon atoms (for example, bicyclo[1.1.0]
butane, bicyclo[3.2.1]octane, bicyclo[5.2.0]nonane,
bicyclo[4.3.2]undecane or adamantane).
[0100] When V represents --Ph--, the benzene ring may have a
substituent. Examples of the substituent include a halogen atom
(for example, a chlorine atom or a bromine atom) and an alkyl group
(for example, a methyl group, an ethyl group, a propyl group, a
butyl group, a chloromethyl group or a methoxymethyl group).
[0101] a.sup.1 and a.sup.2, which may be the same or different,
each preferably represent a hydrogen atom, a halogen atom (for
example, a chlorine atom or a bromine atom), a cyano group, an
alkyl group having from 1 to 3 carbon atoms (for example, a methyl
group, an ethyl group or a propyl group), --COO--Z.sup.2 or
--CH.sub.2COO--Z.sup.2 (wherein Z.sup.2 represents a hydrogen atom
or an alkyl group having from 1 to 18 carbon atoms, an alkenyl
group, an aralkyl group, an alicyclic group or an aryl group, which
may be substituted, and specific examples thereof include those
described for Z.sup.1 described above).
[0102] In formula (II), X.sup.0 represents a connecting group
selected from --COO--, --OCO--, --(CH.sub.2).sub.n--OCO--,
--(CH.sub.2).sub.n--COO- --, --O--, --CONHCOO--, --CONHCO--,
--SO.sub.2--, --CO--, --CON(Z.sup.3)-- and --SO.sub.2N(Z.sup.3)--.
Z.sup.3 represents a hydrogen atom or a hydrocarbon group, and
specific examples thereof include those described for Z.sup.1
described above. n represents an integer of from 1 to 3.
[0103] Q.sup.0 represents an aliphatic group having from 1 to 22
carbon atoms, and specific examples thereof include those of the
alkyl group for Z.sup.1 described above.
[0104] The aliphatic group having from 1 to 22 carbon atoms
represented by Q.sup.0 may have a substituent containing a fluorine
atom and/or a silicon atom. Examples of the substituent containing
a fluorine atom include the following monovalent or divalent
organic residues: --C.sub.p(F).sub.2p+1 (p represents an integer of
from 1 to 22), --CFH.sub.2, --CFHCl, --CFCl.sub.2, --CF.sub.2Cl,
--(CF.sub.2).sub.qCF.su- b.2H (q represents 0 or an integer of from
1 to 17), --CF.sub.2--, --CFH-- and --CFCl--.
[0105] The organic residues containing a fluorine atom may be used
in combination. In such cases, they may be combined with each other
directly or through other connecting group. The connecting group
includes a divalent organic residue, for example, a divalent
aliphatic residue or divalent aromatic residue that may contain a
connecting group selected from --O--, --S--, --N(g.sup.1)--,
--CO--, --SO--, --SO.sub.2--, --COO--, --OCO--, --CONHCO--,
--NHCONH--, --CON(g.sup.1)-- and --SO.sub.2N(g.sup.1)-- and an
organic group composed of a combination of these divalent groups.
g.sup.1 represents an alkyl group having from 1 to 3 carbon
atoms.
[0106] Examples of the substituent containing a silicon atom
preferably include a residue containing a siloxane structure (or a
silyloxy structure) or a silyl group.
[0107] b.sup.1 and b.sup.2, which may be the same or different,
each have the same meanings as defined for a.sup.1 and a.sup.2 of
formula (I) described above. Preferred examples of b.sup.1 and
b.sup.2 are also same as those described for a.sup.1 and a.sup.2
above.
[0108] More preferred group for a.sup.1 or a.sup.2 of formula (I)
and b.sup.1 or b.sup.2 of formula (II) is a hydrogen atom or a
methyl group.
[0109] It is desirable that the polymer having the repeating unit
represented by formula (II) can solvate with the non-aqueous
dispersing medium in view of dispersion stability of the colored
resin particles. From this point of view, Q.sup.0 preferably
represents an aliphatic group having from 6 to 22 carbon atoms.
Preferred examples of the polymer having the repeating unit
represented by formula (II) include polyhexyl acrylate, polyhexyl
methacrylate, polylauryl acrylate, polylauryl methacrylate,
polystearyl acrylate, polystearylmethacrylate, poly-2-ethylhexyl
acrylate, poly-2-ethylhexyl methacrylate and polycetyl
methacrylate, but the invention should not be construed as being
limited thereto.
[0110] Specific examples of the repeating unit represented by
formula (II) wherein Q.sup.0 represents an aliphatic group having
from 1 to 22 carbon atoms, which includes a substituent containing
a fluorine atom and/or a silicon atom, are set forth below, but the
invention should not be construed as being limited thereto.
678910111213
[0111] Of the macromonomers (M) according to the invention, those
represented by the following formula (IV) are preferred. 14
[0112] In formula (IV), a.sup.1, a.sup.2, b.sup.1, b.sup.2 and V
have the same meanings as defined for those in the formulae (I) and
(II), respectively.
[0113] W represents --X.sup.0--Q.sup.0 in formula (II) and X.sup.0
and Q.sup.0 each have the meanings as defined in formula (II).
[0114] W.sup.1 represents a single bond, an individual connecting
group selected from --C(Z.sup.6) (Z.sup.7)-- (wherein Z.sup.6 and
Z.sup.7 each represent a hydrogen atom, a halogen atom (for
example, a fluorine atom, a chlorine atom or a bromine atom), a
cyano group or a hydroxy group), --(CH.dbd.CH)--, a cyclohexylene
group (hereinafter, the cyclohexylene group is represented by
"--Cy--" and the "--Cy--" includes a 1,2-cyclohexylene group, a
1,3-cyclohexylene group and a 1,4-cyclohexylene group), --Ph--,
--O--, --S--, --C(.dbd.O)--, --N(Z.sup.8)--, --COO--, --SO--,
--CON(Z.sup.8)--, --SON(Z.sup.8)--, --NHCOO--, --NHCONH-- and
--Si(Z.sup.8) (Z.sup.9)-- (wherein Z.sup.8 and Z.sup.9 each
represent a hydrogen atom or a hydrocarbon group having the same
meaning as defined for Z.sup.1 described above), or a connecting
group constituted by an appropriate combination of two or more
thereof.
[0115] In the formulae (I), (II) and (IV), particularly preferred
examples of X.sup.0, V, a.sup.1, a.sup.2, b.sup.1 and b.sup.2, are
shown below, respectively.
[0116] X.sup.0 includes one or more connecting groups selected from
--COO--, --OCO--, --O--, --CH.sub.2COO-- and --CH.sub.2OCO--; V
includes all the groups described above (provided that Z.sup.1
represents a hydrogen atom); and a.sup.1, a.sup.2, b.sup.1 and
b.sup.2 include a hydrogen atom and a methyl group,
respectively.
[0117] Specific examples of the moiety represented by
CH(a.sup.1).dbd.C(a.sup.2)--V--W.sup.1-- in the macromonomer of
formula (IV) are set forth below, but the invention should not be
construed as being limited thereto.
[0118] In the following examples, j represents an integer of from 1
to 12, k represents an integer of from 2 to 12, and a represents
--H or --CH.sub.3. 1516171819202122
[0119] The macromonomer (M) of the invention can be produced by
conventionally known synthesis methods. Examples thereof include
(1) a method using ionic polymerization in which various reagents
are reacted with a terminal of a living polymer obtained by anionic
polymerization or cationic polymerization to form a macromonomer;
(2) a method using radical polymerization in which various reagents
are reacted with an oligomer having a terminal reactive group
obtained by radical polymerization using a polymerization initiator
and/or chain transfer agent containing a reactive group, for
example, a carboxy group, a hydroxy group or an amino group in the
molecule thereof, thereby forming a macromonomer; and (3) a method
using polyaddition condensation in which a polymerizable double
bond group is introduced into an oligomer obtained by a
polyaddition or polycondensation reaction, in the same manner as in
the above-described radical polymerization method.
[0120] Specifically, the macromonomer can be synthesized according
to methods described, for example, in P. Dreyfuss and R. P. Quirk,
Encycl. Polym. Sci. Eng., Vol. 7, page 551 (1987), P. F. Rempp and
E. Franta, Adv. Polym. Sci., Vol. 58, page 1 (1984), V. Percec,
Appl. Polym. Sci., Vol. 285, page 95 (1984), R. Asami and M.
Takagi, Makromol. Chem. Suppl., Vol. 12, page 163 (1985), P. Rempp
et al., Makromol. Chem. Suppl., Vol. 8, page 3 (1987), Yusuke
Kawakami, Kagaku Kogyo, Vol. 38, page 56 (1987), Tatsuya Yamashita,
Kobunshi, Vol. 31, page 988 (1982), Shiro Kobayashi, Kobunshi, Vol.
30, page 625 (1981), Toshinobu Higashimura, Nippon Setchaku
Kyokaishi, Vol.18, page 536(1982), Koichi Ito, Kobunshi Kako,
Vol.35, page 262 (1986), and Takashiro Azuma and Takashi Tsuda,
Kino Zairyo, Vol. 1987, No. 10, page 5, and the literature
references and patents cited therein.
[0121] The resin insoluble in the non-aqueous solvent, which
constitutes a shell layer of the colored resin particle for use in
the ink composition of the invention, has preferably a glass
transition point ranging from 0 to 80.degree. C. or a softening
point ranging from 40 to 100.degree. C., and more preferably a
glass transition point ranging from 10 to 70.degree. C. or a
softening point ranging from 45 to 80.degree. C. The monomer (A)
and the macromonomer (M), and if desired, the monomer (B) can be
appropriately selected so as to form a polymer exhibiting such
thermal properties.
[0122] In order to prepare a stable resin dispersion of polymer
particles that are formed by polymerization of the monomers in a
non-aqueous solvent and insoluble in the non-aqueous solvent, the
polymerization is performed in the presence of a dispersion
stabilizer (P) in the invention.
[0123] Now, the dispersion stabilizer (P) is described in detail
below.
[0124] It is preferred that the dispersion stabilizer (P) has a
segment that solvates with the non-aqueous solvent and a segment
that hardly solvates with the non-aqueous solvent and is liable to
associate with or adsorb on the resin particles formed by the
polymerization. The dispersion stabilizers (P) are described in
detail, for example, in K. J. Barrett, Dispersion Polymerization in
Organic Media, Chapter 3, "The Design and Synthesis of Dispersants
for Dispersion Polymerization in Organic Media", John Willy &
Sons. Examples of the monomer that solvates with the solvent
include lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl
methacrylate and cetyl methacrylate. Examples of the monomer that
hardly solvates with the solvent and is liable to adsorb on the
resin particles after the polymerization include methyl
methacrylate, ethyl methacrylate, isopropyl methacrylate, styrene
and vinyltoluene.
[0125] Further, various known amphipathic resins that are used in
liquid developers can be used as the dispersion stabilizer (P).
Specific examples thereof include the graft copolymer type
dispersion stabilizers (P) as described in JP-A-4-350669 and
JP-A-5-188657, the block copolymer type dispersion stabilizers (P)
as described in JP-A-6-95436, non-aqueous solvent-soluble random
copolymer type dispersion stabilizers (P) containing graft groups
as described in JP-A-11-43638, the partially crosslinked polymer
type dispersion stabilizers (P) as described in JP-A-10-316917, and
the partially crosslinked polymer type dispersion stabilizers (P)
containing a graft group at the terminal of the main chain thereof
as described in JP-A-10-316920. However, the dispersion stabilizer
(P) should not be construed as being limited thereto.
[0126] Preferred examples of the dispersion stabilizer (P) include
the graft copolymers shown below as described in JP-A-4-350669 and
JP-A-5-188657. Specifically, graft copolymers comprising at least
one macromonomer (MM) having a weight average molecular weight of
from 1.times.10.sup.3 to 1.times.10.sup.5, which has a
polymerizable double bond group represented by formula (VI) shown
below connected to the terminal of the main chain of a polymer
containing at least one polymer component represented by formula
(Va) or (Vb) shown below, and at least one monomer represented by
formula (VII) shown below are preferred. 23
[0127] In formula (Va), f.sup.1, f.sup.2, X.sup.1 and Q.sup.1 have
the same meanings as defined for b.sup.1, b.sup.2, X.sup.0 and
Q.sup.0 in formula (II) described above, respectively.
[0128] In formula (Vb), Q represents --CN or an unsubstituted or
substituted phenyl group. Examples of the substituent include a
halogen atom, an alkoxy group or --COOZ.sup.4 (wherein Z.sup.4
represents an alkyl group, an aralkyl group or an aryl group).
f.sup.1 and f.sup.2 have the same meanings as defined for b.sup.1
and b.sup.2 in formula (II) described above, respectively.
[0129] In formula (VI), V has the same meaning as defined for V in
formula (I). g.sup.1 and g.sup.2, which may be the same or
different, each have the same meanings as defined for b.sup.1 and
b.sup.2 in formula (II) described above, respectively.
[0130] In formula (VII), X.sup.2 has the same meaning as defined
for V.sup.1 in formula (III). Q.sup.2 represents a hydrogen atom,
an aliphatic group having from 1 to 22 carbon atoms or an aromatic
group having from 6 to 12 carbon atoms. h.sup.1 and h.sup.2, which
may be the same or different, each have the same meanings as
defined for a.sup.1 and a.sup.2 in formula (I).
[0131] However, in the case where the graft copolymer comprises the
polymer component represented by formula (Va) and the monomer
represented by formula (VII), at least one of Q.sup.1 and Q.sup.2
represents an aliphatic group having from 4 to 22 carbon atoms.
Further, in the case where the graft copolymer comprises the
polymer component represented by formula (Vb) and the monomer
represented by formula (VII), Q.sup.2 represents an aliphatic group
having from 4 to 22 carbon atoms.
[0132] Specific preferred examples of the macromonomer (MM) for use
in the graft copolymer type dispersion stabilizer (P) include the
specific preferred examples described above for the macromonomer
(M) copolymerizable with the monomer (A).
[0133] For the preparation of the colored resin particles having a
coloring agent included therein for use in the invention, a method
is employed wherein a polymerization system comprising the
monofunctional polymerizable monomer (A), the macromonomer (M) and
the dispersion stabilizer (P) added to a non-aqueous solvent
containing seed particles (coloring component fine particles)
prepared by finely dispersing the surface-treated coloring agent
(coloring component) is polymerized in the presence of a
polymerization initiator, for example, benzoyl peroxide,
azobis(2,4-dimethylvaleronitrile),
azobis(4-methoxy-2,4-dimethylvaleronit- rile),
azobisisobutyronitrile or butyllithium can be employed.
[0134] Specifically, in order to add the polymerizable monomers
(including the monomer (A), the macromonomer (M) and optionally the
monomer (B)), the dispersion stabilizer (P) and the polymerization
initiator to the non-aqueous solvent containing the seed particles
prepared by finely dispersing the surface treated coloring agent,
there are various methods including, for example, the following
methods:
[0135] (1) A method in which a solution prepared by mixing and
dissolving the polymerizable monomers, the dispersion stabilizer
(P) and the polymerization initiator in the non-aqueous solvent is
added dropwise, collectively or dividedly to a non-aqueous solvent
containing the seed particles prepared by finely dispersing the
coloring component.
[0136] (2) A method in which a solution containing the dispersion
stabilizer (P) dissolved therein is added to the non-aqueous
solvent containing the seed particles prepared by finely dispersing
the coloring component, then are added thereto dropwise,
collectively or dividedly the polymerizable monomers and the
polymerization initiator.
[0137] (3) A method in which a part of a solution prepared by
mixing and dissolving the polymerizable monomers, the dispersion
stabilizer (P) and the polymerization initiator in the non-aqueous
solvent is added to the non-aqueous solvent containing the seed
particles prepared by finely dispersing the coloring component to
conduct dispersion polymerization, and then the remaining mixture
of the polymerizable monomers, the dispersion stabilizer (P) and
the polymerization initiator is then appropriately added.
[0138] (4) A method in which a part of the polymerizable monomers
is added to the non-aqueous solvent containing seed particles
prepared by finely dispersing the coloring component to promote
absorption of the polymerizable monomers on the seed particles, and
then the remaining polymerizable monomers, the dispersion
stabilizer (P) and the polymerization initiator are added dropwise,
collectively or dividedly.
[0139] A proportion of the seed particle (coloring component fine
particle) to the total amount of the polymerizable monomers
(including monomer (A), macromonomer (M) and optionally, monomer
(B)) is preferably from 5/95 to 95/5 by weight, and more preferably
from 10/90 to 80/20 by weight. An amount of the total polymerizable
monomers used is from about 5 to 80 parts by weight, and preferably
from 10 to 50 parts by weight based on 100 parts by weight of the
non-aqueous solvent. An amount of the soluble dispersion stabilizer
(P) is from 1 to 100 parts by weight, and preferably from 3 to 50
parts by weight based on 100 parts by weight of the total monomers.
An amount of the polymerization initiator is suitably from 0.1 to
5% by mole based on the total monomers. Moreover, the
polymerization temperature is approximately from 20 to 180.degree.
C., and preferably from 30 to 120.degree. C. The reaction time is
preferably from 1 to 15 hours.
[0140] In the case where an aromatic hydrocarbon, for example,
toluene or xylene remains in the non-aqueous solvent used for the
reaction, in the case where the above-described polar solvent, for
example, alcohol, ketone, ether or ester is used together, or in
the case where the monomer to be subjected to granulation
polymerization remains unreacted, it is preferred to remove such a
material by distillation with heating over a boiling point of such
a material or vacuum distillation.
[0141] The thus prepared non-aqueous dispersion of colored resin
particles having a coloring agent included therein is excellent in
that the coloring agent is uniformly dispersed in the state of fine
particle and in its dispersion stability do that it can provide an
oil based ink for inkjet printer, which is free from clogging in a
nozzle section and has high discharge stability. Further, the
resulting ink is excellent in drying property on recording paper
and water resistance and light fastness of recorded images, and has
high-level scratch resistance. In addition, it is possible to
easily obtain colored resin particles containing a coloring agent
included therein uniformly dispersed in the state of fine particles
in the non-aqueous solvent. Accordingly, the invention provides an
oil based ink for inkjet printer excellent in control of charge
polarity and stability of charge with the lapse of time, and an
inexpensive production process thereof. Further, the invention is
characterized in that a function, for example, fixing property or
charge property can be imparted to the colored resin particles
containing a coloring agent included therein by appropriately
selecting the polymerizable monomer.
[0142] In the following embodiments, usefulness of the ink
composition of the invention will be described using an oil based
ink for inkjet printer. As the inkjet printer, a printer of
piezoelectric system or a printer of electrostatic system is
employed by way of illustration. However, it should be noted that
the invention is not limited to such a system, and can also be
applied to inkjet printers of thermal system and slit jet system as
represented by NTT.
[0143] An inkjet printer of electrostatic system is described in
detail below.
[0144] FIGS. 1 and 2 are schematic views showing an embodiment of a
discharge head. FIG. 1 is a view of an inkjet head and particularly
shows a cross-section of an ejection electrode corresponding to a
recording dot. In FIG. 1, ink 100 is supplied between a head plate
102 and an ejection electrode plate 103 through an ink supply
passage 112 connected to a head block 101 from a circulation
mechanism 111 including a pump and recovered in the ink circulation
mechanism 111 through an ink recovery passage 113 formed in the
head block 101. The ejection electrode plate 103 is constructed of
an insulating plate 104 having a through-hole 107 and an ejection
electrode 109 formed around the through-hole 107 toward a recording
medium. On the other hand, a convex ink guide 108 is disposed
approximately in the center of the through-hole 107 on the head
plate 102. The convex ink guide 108 is made of an insulating
member, for example, a plastic resin or ceramics. Each convex ink
guide is disposed at the line spacing and pitch so that the center
thereof corresponds to the center of each through-hole 107, and
kept on the head plate 102 by the prescribed method. Each convex
ink guide 108 has a shape such that a tip of flat plate having a
constant thickness is cut out into a triangular or trapezoidal
shape, and the tip section thereof forms an ink droplet ejecting
position 110. Each convex ink guide 108 may form a slit-like groove
from its tip section, and ink supply into the ink ejecting position
110 is smoothly conducted by capillarity of the slit, thereby
enabling to enhance the recording frequency. Further, an
appropriate surface of the ink guide may have conductivity, if
desired. In this case, by making the conductive portion in an
electrically floating state, it is possible to effectively form an
electrical field at the ink ejecting position by applying a low
voltage to the ejection electrode. Each convex ink guide 108
protrudes approximately vertically from the corresponding
through-hole by a prescribed distance in the direction of ink
droplet ejection. A recording medium 121, for example, recording
paper is placed toward the tip of the convex ink guide 108, and a
counter electrode 122 functioning also as a role of a platen
guiding the recording medium 121 is disposed on the back surface of
the recording medium 121 in relation to the head plate 102. Also, a
migration electrode 140 is formed in the bottom portion of a space
formed by the head plate 102 and the ejection electrode plate 103.
By applying a prescribed voltage to the migration electrode 140,
the charged particles in the ink are subjected to electrophoresis
in the direction of ejecting position in the ink guide, thereby
enabling to enhance responsibility of ejection.
[0145] A specific constructional embodiment of the ejection
electrode plate 103 in a line scanning type multi-channel inkjet
head is described with reference to FIG. 2. FIG. 2 is a view of the
ejection electrode plate seeing from the side of the recording
medium 121, in which a plurality of ejection electrodes are aligned
in two lines in an array form in the main scanning direction, the
through-hole 107 is formed in the center of each ejection
electrode, and the individual ejection electrode 109 is formed
around the through-hole 107. In this embodiment, the inner diameter
of the ejection electrode 109 is larger than the diameter of the
through-hole 107, but it may be equal to the diameter of the
through-hole 107. The insulating plate 104 is made of polyimide
having a thickness of from about 25 to 200 .mu.m, the ejection
electrode 109 is made of a copper foil having a thickness of from
about 10 to 100 .mu.m, and the inner diameter of the though-hole
107 is from about 50 to 250 .mu.m.
[0146] Recording action of an inkjet recording device of
electrostatic system is described below. An embodiment where
positively charged ink is used is described, but the invention
should not be construed as being limited thereto. At the time of
recording, the ink 100 supplied from the ink circulation mechanism
111 through the ink supply passage 112 is supplied into the ink
ejecting position 110 of the tip of the convex ink guide 108
through the through-hole 107, and a part of the ink 100 is
recovered in the ink circulation mechanism 11 through the ink
recovery passage 113. A voltage of, e.g., +1.5 kV as a continuous
bias is applied to the ejection electrode from a bias voltage
source 123, and when turning on, a pulse voltage of, e.g., +500 V
as a signal voltage corresponding to an image signal from a signal
voltage source 124 is superimposed to the ejection electrode 109.
Further, during this period of time, a voltage of +1.8 kV is
applied to the migration electrode 140. On the other hand, the
counter electrode 122 provided on the back side of the recording
medium 121 is set up at a ground voltage of 0 V as shown in FIG. 1.
If desired, the side of the recording medium 121 may be charged,
for example, at -1.5 kV, for applying a bias voltage. In such a
case, an insulating layer is provided on the surface of the counter
electrode 122, the recording medium is charged by a corona
discharger, a scorotron charger, a solid ion generator, etc., the
ejection electrode 109 is, for example, grounded, and when turning
on, a pulse voltage of, e.g., +500 V as a signal voltage
corresponding to an image signal from the signal voltage source 124
is superimposed to the ejection electrode 109. Further, during this
period of time, a voltage of +200 V is applied to the migration
electrode 140. When the ejection electrode 109 is in the turn-on
state (in the state where 500 V is applied), and a voltage of 2 kV
in total (the pulse voltage of 500 V is superimposed to the bias
voltage of 1.5 kV) is applied, an ink droplet 115 is ejected from
the ink ejecting position 110 of the tip of the convex electrode
108, drawn in the direction of the counter electrode 122, and
reaches the recording medium 121 to form an image.
[0147] For precisely controlling flight of the ink droplet after
ejection to enhance dot placement accuracy on the recording medium,
there are often taken measures, for example, provision of an
intermediate electrode between the ejection electrode and the
recording medium and provision of a guard electrode for suppressing
electric field interference between the ejection electrodes. In
this embodiment, as a matter of course, such measures are suitably
employed, if desired. Further, a porous body may be provided
between the head plate 102 and the ejection electrode plate 103. In
this case, not only influence by a change of ink inner pressure due
to movement of the inkjet head, etc. can be prevented, but also ink
supply into the through-hole 107 after ejection of the ink droplet
can be rapidly achieved. Accordingly, ejection of the ink droplet
115 is stabilized, whereby a good image having a uniform density
can be recorded at a high speed on the recording medium 121.
[0148] The invention will be described in more detail below with
reference to the following examples, but the invention should not
be construed as being limited thereto.
[0149] Preparation examples of the macromonomer (M) according to
the invention are described below.
PREPARATION EXAMPLE 1 OF MACROMONOMER: MACROMONOMER (M-1)
[0150] A mixed solution of 100 g of octadecyl methacrylate, 2 g of
thioglycolic acid and 200 g of toluene was heated to a temperature
of 75.degree. C. with stirring under a nitrogen gas stream. To the
solution was added 1.5 g of 2,2'-azobis(isobutyronitrile)
(abbreviated as AIBN), followed by reacting for 4 hours. Then, 0.5
g of AIBN was added thereto, followed by reacting for 3 hours, and
further 0.3 g of AIBN was added thereto, followed by reacting for 3
hours. The reaction solution was cooled to room temperature, and
2.8 g of 2-hydoxyethyl methacrylate was added thereto. A mixed
solution of 4.5 g of dicyclohexylcarbodiimide (abbreviated as DCC)
and 10 g of methylene chloride was added dropwise thereto over a
period of one hour. Then, 0.1 g of 4-dimethylaminopyridine and 0.1
g of tert-butylhydroquinone were added to the reaction solution,
followed by stirring for 4 hours.
[0151] The crystals deposited were removed by filtration, and the
filtrate was reprecipitated in 2 liters of methanol. The resulting
white solid was collected by decantation, dissolved in 300 ml of
tetrahydrofuran, and reprecipitated again in 3 liters of methanol.
The resulting white powder was collected by decantation and dried
under a reduced pressure to obtain Macromonomer (M-1) having a
weight average molecular weight of 12,100 in a yield of 93.2 g. The
weight average molecular weight (Mw) was measured by a GPC method
and calculated in terms of polystyrene (hereinafter the same).
24
PREPARATION EXAMPLES 2 TO 17 OF MACROMONOMER: MACROMONOMERS (M-2)
TO (M-17)
[0152] Macromonomers (M-2) to (M-17) shown in Tables A and B below
were prepared in the same manner as in Preparation Example 1 of
Macromonomer except that a methacrylate monomer (corresponding to
octadecyl methacrylate), a chain transfer agent (corresponding to
thioglycolic acid), an initiator (corresponding to AIBN) and an
unsaturated carboxylic acid ester (corresponding to 2-hydoxyethyl
methacrylate) were changed to the corresponding compounds,
respectively. The weight average molecular weight of each
macromonomer obtained was in a range of from 4,600 to 31,000.
1TABLE A Preparation Macromonomer Example of Weight Average
Macromonomer Molecular Weight) Chemical Structure of Macromonomer 2
M-2 (Mw = 12,600) 25 3 M-3 (Mw = 11,800) 26 4 M-4 (Mw = 16,500) 27
5 M-5 (Mw = 4,600) 28 6 M-6 (Mw = 9,800) 29 7 M-7 (Mw = 13,000) 30
8 M-8 (Mw = 14,400) 31 9 M-9 (Mw = 28,300) 32 10 M-10 (Mw = 21,400)
33
[0153]
2TABLE B 34 Preparation Example of Macro- mono- Macro- mer (M)
monomer (M) --X-- 11 M-11 35 12 M-12 36 13 M-13 37 14 M-14 38 15
M-15 39 16 M-16 40 17 M-17 41
[0154] Specific examples of the dispersion stabilizer (P) of graft
copolymer type for use in the invention are set forth below, but
the invention should not be construed as being limited thereto.
[0155] Dispersion Stabilizer (P-1)
[0156] Styrene/Macromonomer (M-1)=50/50 (wt/wt)
[0157] Weight average molecular weight: 43,000 42
3TABLE C Specific Weight Average Example of Monomer Molecular
Weight Dispersion (Corresponding Monomer/Macro- of Dispersion
Stabilizer to Styrene) Macromonomer monomer (wt/wt) Stabilizer
(.times.10.sup.4) P-2 Styrene M-1 30/70 2.8 P-3 Styrene M-1 70/30
3.8 P-4 Styrene M-2 30/70 3.9 P-5 Styrene M-2 50/50 4.0 P-6 Styrene
M-3 50/50 4.6 P-7 Styrene M-4 30/70 10.1 P-8 Styrene M-6 50/50 8.2
P-9 Styrene M-8 10/90 3.3 P-10 MMA M-1 30/70 5.5 P-11 MMA M-1 10/90
4.7 P-12 MMA M-2 20/80 5.0 P-13 MMA M-7 30/70 5.6 P-14 Styrene M-10
50/50 3.6 P-15 Styrene M-10 70/30 3.2 * MMA: Methyl
methacrylate
[0158]
4TABLE D Specific Example of Dispersion Monomer/Macro- Stabilizer
Monomer Macromonomer monomer (wt/wt) P-16 SMA AS-6 80/20 P-17 LMA
AS-6 50/50 P-18 2EHMA AS-6 70/30 P-19 2EHMA AS-6 50/50 P-20 SMA
AA-6 90/10 P-21 2EHMA AA-6 90/10 P-22 BMA AA-6 70/30 P-23 SMA AA-2
90/10 P-24 2EHMA AA-2 90/10 P-25 2EHMA AA-2 80/20 * SMA: Stearyl
methacrylate LMA: Lauryl methacrylate 2EHMA: 2-Ethylhexyl
methacrylate BMA: Butyl methacrylate AS-6, AA-6 and AA-2 are each a
methacryloyl group-terminated macromonomer manufactured by Toagosei
Co., Ltd. AS-6 is a styrene based macromonomer (number average
molecular weight: 6,000), and AA-6 and AA-2 are methyl methacrylate
based macromonomers having number average molecular weights of
6,000 and 2,000, respectively.
[0159] The dispersion stabilizers shown in Table D each had a
weight average molecular weight of from about 40,000 to 80,000.
EXAMPLE 1
<Preparation of Pigment Dispersion>
[0160] A 20% solution prepared by dissolving Dispersion Stabilizer
(P-1) described above in Isopar H by heating was used as a pigment
dispersant. A mixture of 88.25 parts by weight of the pigment
dispersant solution, 17.65 parts by weight of rosin ester
resin-treated Microlith Black C-T (manufactured by Ciba Specialty
Chemicals) as a black processed pigment and 29.4 parts by weight of
Isopar H was blended together with 250 parts by weight of glass
beads in a paint shaker (manufactured by Toyo Seiki Co., Ltd.) for
30 minutes. After separating the glass beads by filtration, the
mixture was dispersed for 3 hours in a high-speed dispersion
kneading machine (Dynomill KDL, trade name) at a rotation number of
3,000 rpm. Glass beads (MK-3GX) were used as media. The volume
average particle size of pigment particles in the resulting
dispersion was measured by ultra-centrifugal automatic particle
size distribution analyzer (CAPA700 manufactured by Horiba, Ltd.).
As a result, it was found that the pigment particles were well
dispersed to 0.17 .mu.m.
<Preparation of Colored Resin Particles>
[0161] In a four-necked flask was charged 85.8 g of the filtrate of
the processed pigment dispersion (solid content: 23.3%) obtained by
separating the glass beads upon filtration, and it was heated with
stirring in a nitrogen gas stream at a temperature of 80.degree. C.
for 3 hours.
[0162] Then, a solution prepared by adding 1.1 g of
2,2'-azobis(2,4-dimethylvaleronitrile) to a mixed solution of 8 g
of Dispersion Stabilizer (P-1) described above as powder, 16.0 g of
methyl methacrylate, 22.0 g of methyl acrylate, 2.0 g of
Macromonomer (M-1) described above and 120 g of Isopar H as a feed
solution was dropwise added at a dropping rate of 2.5 ml/min to the
processed pigment dispersion, followed by reacting for 3 hours.
About 20 minutes after the initiation of the dropwise addition,
heat generation occurred, and the temperature of the reaction
mixture rose by about 5.degree. C. After the reaction for 3 hours,
the temperature was elevated to 90.degree. C., and the reaction
mixture was stirred for 2 hours to distill off the unreacted
monomers. After cooling, the reaction mixture was filtered through
a 200-mesh nylon cloth, and the resulting black resin particle
dispersion had a polymerization rate of 98% and an average volume
particle size of 0.26 .mu.m. The black resin particle dispersion
exhibited a good dispersion state even after preservation by
standing for one month.
[0163] The black resin particle dispersion was observed by a field
emission scanning electron microscope (S-800 Model manufactured by
Hitachi, Ltd.). As a result, it was found that the Microlith Black
pigment particle of about 100 nm grew to spherical resin particle
of about 180 nm after the dispersion polymerization and that the
monomers were absorbed on the seed pigment particles and
polymerized.
[0164] In addition, the black resin particle dispersion was
observed by a transmission scanning electron microscope. As a
result, it was recognized that the seed pigment particle was
incorporated into the spherical colored resin particle of about 180
nm after the dispersion polymerization.
[0165] In the light of these results, it can be seen that the
colored resin particles formed by seed dispersion polymerization
according to the invention have the rosin ester resin-treated
pigment incorporated therein.
<Preparation of Ink Composition (IJ-1)>
[0166] The above-described colored resin particle dispersion was
once concentrated by solvent distillation and then diluted with
Isopar G to prepare Ink Composition (IJ-1) having a viscosity of 13
cp (measured at a temperature of 25.degree. C. using an E type
viscometer, hereinafter the same) and a surface tension of 23 mN/m
(measured at a temperature of 25.degree. C. using an automatic
surface tensiometer manufactured by Kyowa Interface Science Co.,
Ltd., hereinafter the same).
[0167] Ink Composition (IJ-1) was charged in a color facsimile
(SAIYUKI UX-E1CL manufactured by Sharp Corporation) as an inkjet
recording device, and an image was drawn on an exclusive use paper
of inkjet paper high-grade manufactured by Fuji Photo Film Co.,
Ltd. As a result, the discharge was stably conducted without
causing nozzle clogging. The resulting image was good and clear
without blur and the image density thereof was 1.8. Further, a full
solid pattern was printed, and after drying the print, the solid
portion thereof was rubbed by fingers. As a result, staining on the
fingers was not visually observed at all, so that it was found that
the scratch resistance was extremely excellent. The ink composition
was free from precipitation and coagulation and extremely good in
dispersibility even after preservation for 6 months at room
temperature, and it could be continuously used for printing for one
month to provide prints having excellent clearness.
EXAMPLE 2
<Preparation of Pigment Dispersion>
[0168] A mixture of 100 parts by weight of Carbon Black #30
(manufactured by Mitsubishi Chemical Corporation) as a black
pigment and 200 parts by weight of a ethylene/stearyl acrylate
copolymer (molar ratio: 95/5) was previously pulverized and well
mixed in a trio blender, and then melt-kneaded in a three-roll mill
heated at 120.degree. C. for 20 minutes. The kneaded pigment
mixture was further pulverized in a pin mill.
[0169] A mixture of 10 parts by weight of the resulting kneaded
pigment mixture, 65 parts by weight of Isopar G, 25 parts by weight
of a 20 wt % solution prepared by dissolving Dispersion Stabilizer
(P-5) described above as a pigment dispersant in Isopar G by
heating was blended together with 250 parts by weight of glass
beads (3G-X) in a paint shaker (manufactured by Toyo Seiki Co.,
Ltd.) for 60 minutes. After separating the glass beads by
filtration, the mixture was dispersed for 3 hours in a high-speed
dispersion kneading machine (Dynomill KDL, trade name) at a
rotation number of 3,000 rpm. Glass beads (MK-3GX) were used as
media. The volume average particle size of pigment particles in the
resulting dispersion was measured by ultra-centrifugal automatic
particle size distribution analyzer (CAPA700 manufactured by
Horiba, Ltd.). As a result, it was found that the pigment particles
were well dispersed to 0.18 .mu.m.
<Preparation of Colored Resin Particles>
[0170] In a four-necked flask was charged 230.8 g of the filtrate
of the pigment dispersion (solid content: 13.0%) obtained by
separating the glass beads upon filtration, and it was heated with
stirring in a nitrogen gas stream at a temperature of 75.degree. C.
for one hour. Then, a solution prepared by adding 0.6 g of
2,2'-azobis(2,4-dimethylvaleronitr- ile) to a mixed solution of 4 g
of Dispersion Stabilizer (P-1) as powder, 5.8 g of methyl
methacrylate, 13.2 g of methyl acrylate, 1.0 g of Macromonomer
(M-2) described above and 120 g of Isopar H as a feed solution was
added dropwise to the pigment dispersion for one hour, followed by
reacting for 3 hours. About 15 minutes after the initiation of the
dropwise addition, heat generation occurred, and the temperature of
the reaction mixture rose by about 4.degree. C. After the reaction
for 3 hours, the temperature was elevated to 90.degree. C., and the
reaction mixture was stirred for 2 hours while increasing the flow
rate of nitrogen to distill off the unreacted monomers. The
resulting black resin particle dispersion had a polymerization rate
of 95.5% and an average volume particle size of 0.23 .mu.m. The
black resin particle dispersion exhibited a good dispersion state
even after preservation by standing for one month.
<Preparation of Ink Composition (IJ-2)>
[0171] The above-described colored resin particle dispersion was
once concentrated by solvent distillation and then diluted with
Isobar G to prepare Ink Composition (IJ-2) having a viscosity of 13
cp and a surface tension of 23 mN/m.
[0172] Ink Composition (IJ-2) was provided for printing in the same
manner as in Example 1 using a color facsimile (SAIYUKI UX-E1CL
manufactured by Sharp Corporation). As a result, clear prints of
good quality without blur were obtained. Also, the scratch
resistance was examined in the same manner as in Example 1, and it
was found that staining on fingers was not visually observed at
all, so that the scratch resistance was extremely excellent. Even
after preservation for 6 months at room temperature, the ink
composition was free from precipitation and coagulation and good in
dispersibility.
EXAMPLE 3
<Preparation of Pigment Dispersion>
[0173] A mixture of 10 parts by weight of Carbon Black #100
(manufactured by Mitsubishi Chemical Corporation) as a black
pigment and 100 parts by weight of water were stirred in a flusher,
and to the mixture was added 60 parts by weight of a 33% toluene
solution of a styrene/vinyl toluene/lauryl methacrylate copolymer
(molar ratio: 40/58/2) as a resin for polymer treatment, followed
by stirring in the flusher. Then, the system was heated and reduced
in pressure to remove the moisture and solvent, thereby obtaining a
black block product having a moisture content of 1% by weight. The
black block product was dried in vacuo to completely remove the
moisture and then pulverized in a sample mill to obtain black
powder of from 0.01 to 0.1 mm.
[0174] The dispersion of pigment was carried out in the same manner
as in Example 2, except for using the black powder described above
in place of the kneaded pigment mixture. A black pigment dispersion
obtained after separating the glass beads upon filtration had good
dispersibility and a volume average particle size thereof was 0.15
.mu.m.
<Preparation of Colored Resin Particles>
[0175] The dispersion polymerization was carried out in the same
manner as in Example 2 except that the filtrate of the pigment
dispersion (solid content: 13.0%) obtained by separating the glass
beads upon filtration was used and that Macromonomer (M-3)
described above was used in place of Macromonomer (M-2). The
resulting black resin particle dispersion had a polymerization rate
of 97.0% and an average volume particle size of 0.20 .mu.m. The
resulting black resin particle dispersion exhibited a good
dispersion state even after preservation by standing for one
month.
<Preparation of Ink Composition (IJ-3)>
[0176] The above-described colored resin particle dispersion was
adjusted so as to have a viscosity of 13 cp and a surface tension
of 23 mN/m, whereby Ink Composition (IJ-3) was prepared.
[0177] Ink Composition (IJ-3) was provided for printing in the same
manner as in Example 1 using a color facsimile (SAIYUKI UX-E1CL
manufactured by Sharp Corporation). As a result, clear prints of
good quality without blur were obtained. Also, the scratch
resistance was examined in the same manner as in Example 1, and it
was found that staining on fingers was not visually observed at
all, so that the scratch resistance was extremely excellent. Even
after preservation for 6 momths at room temperature, the ink
composition was free from precipitation and coagulation and good in
dispersibility.
COMPARATIVE EXAMPLE 1
<Preparation of Comparative Pigment Dispersion>
[0178] A mixture of 5 parts by weight of Alkali Blue as a blue
pigment, which had not been subjected to the surface treatment
according to the invention, 5 parts by weight of a lauryl
methacrylate/acrylic acid copolymer (composition ratio: 95/5 by
weight) as a pigment dispersant and 90 parts by weight of Isopar H
was blended together with 250 parts by weight of glass beads in a
paint shaker (manufactured by Toyo Seiki Co., Ltd.) for30 minutes.
After separating the glass beads by filtration, the mixture was
dispersed for 3 hours in a high-speed dispersion kneading machine
(Dynomill KDL, trade name) at a rotation number of 3,000 rpm. The
volume average particle size of pigment particles in the resulting
dispersion was measured by ultra-centrifugal automatic particle
size distribution analyzer (CAPA700 manufactured by Horiba, Ltd.).
As a result, it was found that the pigment particles were well
dispersed to 0.13 .mu.m.
<Preparation of Comparative Colored Resin Particles>
[0179] In a four-necked flask was charged 208.3 of the filtrate of
the pigment dispersion (solids content: 9.6%) obtained by
separating the glass beads upon filtration, and it was heated with
stirring in a nitrogen gas stream at a temperature of 80.degree. C.
for 3 hours. Then, a solution prepared by adding 1.1 g of
2,2'-azobis (2,4-dimethylvaleronitrile) to a mixed solution of 8 g
of Dispersion Stabilizer (P-1), 16.0 g of methyl methacrylate, 22.0
g of methyl acrylate, 2 g of Macromonomer (M-1) and 120 g of Isopar
H as a feed solution was dropwise added at a dropping rate of 2.5
ml/min to the pigment dispersion, followed by reacting for 3 hours.
About 15 minutes after the initiation of the dropwise addition,
heat generation occurred, and the temperature of the reaction
mixture rose by about 5.degree. C. Coarse particles adhered to the
inner wall surface of the flask, and after the reaction, a large
amount of precipitate was found in the bottom of the flask. The
colored resin particles could not be provided for the subsequent
preparation of ink composition because of the formation of coarse
particles and precipitate.
[0180] It was understood from the results of Examples 1 to 3 and
Comparative Example 1 that since the polymer-treated coloring agent
according to the invention is made in the state of fine particles
and has good dispersibility, the seed dispersion polymerization
proceeds well, and the colored resin particles containing the
polymer-treated coloring agent therein formed by the seed
dispersion polymerization have good ink characteristics, for
example, clear printed image quality, extremely excellent scratch
resistance and good long-term dispersibility.
EXAMPLE 4
<Preparation of Pigment Dispersion>
[0181] A mixture of 100 parts by weight of Carbon Black #30
(manufactured by Mitsubishi Chemical Corporation) as a black
pigment and 200 parts by weight of a methyl methacrylate/stearyl
methacrylate copolymer (molar ratio: 9/1) was previously pulverized
and well mixed in a trio blender, and then melt-kneaded in a
three-roll mill heated at 120.degree. C. for 20 minutes. The
kneaded pigment mixture was further pulverized in a pin mill.
[0182] A mixture of 10 parts by weight of the resulting kneaded
pigment mixture, 65 parts by weight of Isopar G, 25 parts by weight
of a 20 wt % solution prepared by dissolving Solprene 1205
(styrene/butadiene copolymer, manufactured by Asahi Kasei
Corporation) as a pigment dispersant in Isopar G by heating was
blended together with 250 parts by weight of glass beads (3G-X) in
a paint shaker (manufactured by Toyo Seiki Co., Ltd.) for60
minutes. After separating the glass beads by filtration, the
mixture was dispersed for 3 hours in a high-speed dispersion
kneading machine (Dynomill KDL, trade name) at a rotation number of
3,000 rpm. Glass beads (MK-3GX) were used as media. The volume
average particle size of pigment particles in the resulting
dispersion was measured by ultra-centrifugal automatic particle
size distribution analyzer (CAPA700 manufactured by Horiba, Ltd.).
As a result, it was found that the pigment particles were well
dispersed to 0.21 .mu.m.
<Preparation of Colored Resin Particles>
[0183] In a four-necked flask was charged 214.3 g of the filtrate
of the pigment dispersion (solid content: 14.0%) obtained by
separating the glass beads upon filtration, and it was heated with
stirring in a nitrogen gas stream at a temperature of 50.degree. C.
for one hour. Then, a solution prepared by adding 0.7 g of
2,2'-azobis(4-methoxy-2,4-dimethyl- valeronitrile) to a mixed
solution of 2 g of Dispersion Stabilizer (P-1) as powder, 19.6 g of
methyl acrylate, 0.4 g of Macromonomer (M-1) and 80 g of Isopar H
as a feed solution was added dropwise to the processed pigment
dispersion for one hour, followed by reacting for 3 hours. About 20
minutes after the initiation of the dropwise addition, heat
generation occurred, and the temperature of the reaction mixture
rose by about 5.degree. C. After the reaction for 3 hours, the
temperature was elevated from 50.degree. C. to 80.degree. C., and
the reaction mixture was stirred for 2 hours while increasing the
flow rate of nitrogen to distill off the unreacted monomers. After
cooling, the reaction mixture was filtered through a 200-mesh nylon
cloth, and the resulting black resin particle dispersion had a
polymerization rate of 98% and an average volume particle size of
0.26 .mu.m. The black resin particle dispersion exhibited a good
dispersion state even after preservation by standing for one
month.
<Preparation of Ink Composition (IJ-4)>
[0184] The above-described colored resin particle dispersion was
once concentrated by solvent distillation and then diluted with
Isobar G to prepare Ink Composition (IJ-4) having a viscosity of 13
cp and a surface tension of 23 mN/m.
[0185] Ink Composition (IJ-4) was provided for printing in the same
manner as in Example 1 using a color facsimile (SAIYUKI UX-E1CL
manufactured by Sharp Corporation). As a result, clear prints of
good quality without blur were obtained. Also, the scratch
resistance was examined in the same manner as in Example 1, and it
was found that staining on fingers was not visually observed at
all, so that the scratch resistance was extremely excellent. Even
after preservation for 6 months at room temperature, the ink
composition was free from precipitation and coagulation and good in
dispersibility.
COMPARATIVE EXAMPLE 4
<Preparation of Comparative Ink Composition (IJR-1)>
[0186] Comparative Ink Composition (IJR-1) was prepared in the same
manner as in the preparation of Ink Composition (IJ-4) except that
the pigment dispersion of seed particles prepared in Example 4 was
used in place of the colored resin particles of Example 4. The
comparative ink composition (IJR-1) had a viscosity of 12 cp and a
surface tension of 23 mN/m.
[0187] Comparative Ink Composition (IJR-1) was provided for
printing in the same manner as in Example 1 using a color facsimile
(SAIYUKI UX-E1CL manufactured by Sharp Corporation). As a result,
clear prints without blur were obtained. However, when the solid
image portion was rubbed by fingers, the image portion was easily
removed. Thus, it was found that the scratch resistance was
extremely poor. In order to obtain the printed image portion free
from the removal by rubbing with fingers, it was recognized that
the printed recording material must be fixed upon heating at
120.degree. C. or higher.
[0188] It can be understood from the results of Ink Composition
(IJ-4) of the invention and Comparative Ink Composition (IJR-1)
that the colored resin particles coated with a low-softening resin
prepared by the seed dispersion polymerization using the
polymer-treated pigment as seed particles in the invention exhibit
good ink characteristics, for example, clear printed image quality,
ease of fixing, extremely excellent scratch resistance and good
long-term dispersibility.
EXAMPLE 5
<Preparation of Pigment Dispersion>
[0189] The pigment dispersion was carried out in the same manner as
in Example 1 except that a yellow pigment (Microlith Yellow 3R-T
manufactured by Ciba Specialty Chemicals) was used in place of the
black pigment (Microlith Black C-T Ciba Specialty Chemicals). A
yellow pigment dispersion obtained after separating the glass beads
upon filtration had good dispersibility and a volume average
particle size thereof was 0.22 .mu.m.
<Preparation of Colored Resin Particles>
[0190] In a four-necked flask was charged 100 g of the yellow
pigment dispersion (solid content: 20.0%) and it was heated with
stirring in a nitrogen gas stream at a temperature of 80.degree. C.
for 2 hours. Then, the same procedures as in Example 1 were carried
out except that a solution prepared by adding 0.56 g of
2,2'-azobis(2,4-dimethylvaleronitri- le) to a mixed solution of 6 g
of Dispersion Stabilizer (P-5) as powder, 8.0 g of methyl
methacrylate, 13.2 g of methyl acrylate, 1.0 g of Macromonomer
(M-3) described above and 80 g of Isopar H as a feed solution was
dropwise added at a dropping rate of 2.0 ml/min to the pigment
dispersion, followed by reacting for 3 hours. The temperature of
the reaction mixture rose by about 4.degree. C. The resulting
yellow resin particle dispersion had a polymerization rate of 97%
and an average volume particle size of 0.30 .mu.m and exhibited a
good dispersion state even after preservation by standing for one
month.
<Preparation of Ink Composition (IJ-5)>
[0191] The yellow resin particle dispersion was diluted with Isopar
G to make the content of the resin particles 6.0%. Then,
octadecene/semi-maleic acid octadecylamide copolymer as a charge
control agent was added in an amount of 0.01 g per liter of Isopar
G to prepare Ink Composition (IJ-5).
[0192] Measurement of the charge amount of Ink Composition (IJ-5)
was conducted using a development characteristic measurement device
(measuring the initial value of voltage change with time, which is
induced on the back surface of an electrode to which a voltage of
500 V is applied) as described in JP-B-64-696. Ink Composition
(IJ-5) exhibited the distinct positive charge property such that
the entire charge was 256 mV and the charge of yellow resin
particle was 220 mV. Further, it was found that Ink Composition
(IJ-5) was substantially free from change in the charge amount and
extremely stable even after preservation for one month. It was also
recognized that the charge amount could be easily adjusted by the
amount of charge control agent used.
COMPARATIVE EXAMPLE 5
<Preparation of Comparative Ink Composition (IJR-2)>
[0193] Comparative Ink Composition (IJR-2) was prepared in the same
manner as in the preparation of Ink Composition (IJ-5) of Example 5
except for using the yellow pigment dispersion of seed particles
itself. The charge amount of Comparative Ink Composition (IJR-2)
was measured in the same manner as in Example 5. As a result, it
was found that Comparative Ink Composition (IJR-2) was negatively
charged, and the entire charge was 95 mV and the charge of yellow
pigment particle was 15 mV.
[0194] It can be understood from the results of Example 5 and
Comparative Example 5 that although the yellow pigment (Microlith
Yellow 3R-T) in Comparative Ink Composition (IJR-2) as the seed
particle is originally negatively charged, the colored resin
particles coated with the resin by the seed dispersion
polymerization in Ink Composition (IJ-5) according to the invention
exhibit the distinct positive polarity and that the charge amount
thereof can be easily adjusted by the amount of charge control
agent. Specifically, it can be seen that by coating the pigment
surface with the resin by the seed dispersion polymerization, the
charge polarity (by appropriately selecting the charge control
agent) and the charge amount can be freely adjusted, regardless of
the original charge polarity of pigment.
<Image Drawing Property>
[0195] An inkjet device equipped with 64-channel (100 dpi)
electrostatic inkjet heads each having the structure as shown in
FIG. 1 was used, and Ink Composition (IJ-5) was charged in an ink
tank thereof. After removing dusts on the surface of coated
recording paper as a recording medium by air pump suction, the
discharge heads were moved to a drawing position toward the coated
recording paper and the ink was discharged at a drawing resolution
of 600 dpi to draw an image. The drawing was conducted while
changing dot areas at 16 stages in the dot size ranging from 15
.mu.m to 60 .mu.m by means of regulating the pulse voltage. The
image obtained was clear and of good quality having the
satisfactory density without blur. The discharge stability from ink
head was good, no clogging occurred, and dot-form printing could be
stably conducted in the image drawing. Further, the scratch
resistance was examined in the same manner as in Example 1. As a
result, staining on fingers was not visually observed at all, so
that it was noted that the scratch resistance was extremely
excellent. Even after preservation for 6 months at room
temperature, Ink Composition (IJ-5) was free from precipitation and
coagulation and good in dispersibility.
[0196] On the other hand, using Comparative Ink Composition
(IJR-2), image drawing was conducted in the same manner as above
but changing the pulse voltage applied to the head to a negative
polarity. As a result, the image obtained exhibited severe blur and
low density. Further, since discharge failure occurred during the
image drawing, lack of images were observed, and thus satisfactory
image was not obtained.
[0197] It can be understood from these results that since the
pigment resin particles coated with the resin by the seed
dispersion polymerization in Ink Composition (IJ-5) according to
the invention exhibit the distinct positive property and have the
sufficient charge amount, Ink Composition (IJ-5) has good ink
characteristics, for example, clear printed image quality, good
discharge stability, extremely excellent scratch resistance and
good long-term dispersibility in case of using in the electrostatic
inkjet device.
EXAMPLES 7 TO 20
<Preparation of Pigment Dispersion>
[0198] The pigment dispersion was carried out in the same manner as
in Example 1 except that Dispersion Stabilizer (P-21) was used as a
pigment dispersant in an amount of 50 wt % based on the processed
pigment in place of Dispersion Stabilizer (P-1) and that a blue
processed pigment (Microlith Blue 4G-T manufactured by Ciba
Specialty Chemicals) in place of the black processed pigment
(Microlith Black C-T). A pigment dispersion obtained after
separating the glass beads upon filtration had good dispersibility
and a volume average particle size thereof was 0.16 .mu.m. Using
the blue pigment dispersion, the seed dispersion polymerization was
conducted to prepare colored resin particles and Ink Compositions
(IJ-7) to (IJ-20) as described below.
<Preparation of Colored Resin Particles>
[0199] The same reaction operations as in Example 1 were followed
except that 157.5 g of the blue processed pigment dispersion (solid
content: 19.1%) was used and that a solution containing 8 g of a
dispersion stabilizer (P) as powder and 40 g of the polymerizable
monomer(s) including a macromonomer (M) as shown in Table E below,
80 g of Isopar G and 1% by mole, based on the polymerizable
monomer(s), of 2,2'-azobis(2,4-dimethylvaleronitrile) was added
dropwise as a feed solution over a period of 2 hours. The
temperature of each of the reaction mixtures rose by about 3 to
8.degree. C. The resulting blue particle resin dispersions 7 to 20
had a polymerization rate of from about 90 to 98% and an average
volume particle size of from 0.20 to 0.28 .mu.m, respectively.
Further, each of the blue particle dispersions 7 to 20 exhibited a
good dispersion state even after preservation by standing for one
month.
5 TABLE E Polymerizable Monomer Component Dispersion Example (A)
(A) (M) and (B) Stabilizer 7 Methyl methacrylate: 20.0 g Methyl
acrylate: 18.0 g Macromonomer (M-3): 2.0 g P-4 8 Methyl
methacrylate: 23.0 g Ethyl acrylate: 15.0 g Macromonomer (M-3): 2.0
g P-10 9 Methyl methacrylate: 29.0 g Butyl acrylate: 9.0 g
Macromonomer (M-3): 2.0 g P-15 10 Ethyl methacrylate: 25.0 g Methyl
acrylate: 13.0 g Macromonomer (M-6): 2.0 g P-6 11 Methyl
methacrylate: 20.0 g Methyl acrylate: 18.0 g Macromonomer (M-7):
2.0 g P-12 12 Methyl methacrylate: 20.0 g Methyl acrylate: 18.0 g
Macromonomer (M-11): 2.0 g P-13 13 Methyl methacrylate: 20.0 g
Methyl acrylate: 18.0 g Macromonomer (M-15): 2.0 g P-19 14 Methyl
methacrylate: 18.0 g Methyl acrylate: 18.0 g DMAEMA: 2.0 g P-21
Macromonomer (M-1): 2.0 g 15 Methyl methacrylate: 17.0 g Methyl
acrylate: 17.0 g DMAEMA: 4.0 g P-24 Macromonomer (M-1): 2.0 g 16
Methyl methacrylate: 18.5 g Methyl acrylate: 18.5 g DEAPMA: 2.0 g
P-2 Macromonomer (M-1): 2.0 g 17 Methyl methacrylate: 18.5 g Methyl
acrylate: 18.5 g DEAEMA: 2.0 g P-16 Macromonomer (M-1): 2.0 g 18 --
Methyl acrylate: 38.0 g Macromonomer (M-2): 2.0 g P-1 19 Methyl
methacrylate: 18.1 g Methyl acrylate: 15.5 g Macromonomer (M-2):
2.0 g P-12 Styrene: 4.4 g 20 Methyl methacrylate: 18.0 g Methyl
acrylate: 18.0 g Macromonomer (M-2): 2.0 g P-2 Vinyl toluene: 2.0 g
DMAEMA: 2-(dimethylamine)ethyl methacrylate DEAEMA:
2-(diethylamine)ethyl methacrylate DEAPMA: 2-(diethylamine)propyl
methacrylate
<Preparation of Ink Compositions (IJ-7) to (IJ-20)>
[0200] The above-described colored resin particle dispersions were
each adjusted so as to have a viscosity of from 12 to 14 cp and a
surface tension of from 22 to 24 mN/m to prepare Ink Compositions
(IJ-7) to (IJ-20).
[0201] Each of Ink Compositions (IJ-7) to (IJ-20) was provided for
printing in the same manner as in Example 1 using a color facsimile
(SAIYUKI UX-E1CL manufactured by Sharp Corporation). As a result,
clear prints of good quality having a satisfactory density without
blur were obtained. Further, the staining on fingers was not
visually observed at all, so that it was noted that the scratch
resistance was extremely excellent. Even after preservation for 6
months at room temperature, Ink Compositions (IJ-7) to (IJ-20) were
free from precipitation and coagulation and good in
dispersibility.
EXAMPLE 21
<Preparation of Pigment Dispersion and Colored Resin
Particles>
[0202] Colored resin particles were prepared by the seed dispersion
polymerization shown below using the blue processed pigment
dispersion of Example 7.
[0203] The same reaction operations as in Example 1 were followed
except that 157.5 g the blue processed pigment dispersion (solid
content: 19.1%) was used and that a solution of 8 g of Dispersion
Stabilizer (P-26) having the structure shown below as powder, 19.0
g of ethyl methacrylate, 19.0 g of methyl acrylate, 2.0 g of
Macromonomer (M-1), 80 g of Isobar G and 1% by mole, based on the
polymerizable monomers, of 2,2'-azobis(2,4-dimethylvaleronitrile)
was added dropwise as a feed solution over a period of 2 hours. The
temperature of the reaction mixture rose by about 4.degree. C. The
resulting blue resin particle dispersion 21 had a polymerization
rate of about 93% and an average volume particle size of 0.25
.mu.m. Further, the blue resin particle dispersion 21 exhibited a
good dispersion state even after preservation by standing for one
month.
(Preparation of Dispersion Stabilizer (P-26))
[0204] A mixture of 70 g of octadecyl methacrylate and 2.0 g of
benzyl N,N-diethyldithiocarbamate was sealed in a vessel in a
nitrogen gas stream and heated at a temperature of 60.degree. C.
The mixture was subjected to polymerization upon irradiation with
light emitting from a 400-W high pressure mercury vapor lamp at a
distance of 10 cm through a glass filter for 10 hours. To the
mixture were added 30 g of styrene monomer and 180 g of methyl
ethyl ketone, and after purging with nitrogen, the mixture was
again irradiated with light for 10 hours. The resulting reaction
mixture was reprecipitated in 3 liters of methanol, and the
precipitate was collected and dried in vacuo to obtain Dispersion
Stabilizer (P-26) having a weight average molecular weight of
90,000 in a yield of 78.0 g.
Dispersion Stabilizer (P-26)
[0205] 43
<Preparation of Ink Composition (IJ-21)>
[0206] The above-described colored resin particle dispersion was
adjusted so as to have a viscosity of 12 cp and a surface tension
of 24 mN/m to prepare Ink Composition (IJ-21).
[0207] Ink Composition (IJ-21) was provided for printing in the
same manner as in Example 1 using a color facsimile (SAIYUKI
UX-E1CL manufactured by Sharp Corporation). As a result, it was
found that Ink Composition (IJ-21) provided clear prints of good
quality having a satisfactory density without blur. Further, the
staining on fingers was not visually observed at all, so that that
the scratch resistance was extremely excellent. Even after
preservation for 6 months at room temperature, Ink Composition
(IJ-21) was free from precipitation and coagulation and good in
dispersibility.
EXAMPLE 22
[0208] Ink Composition (IJ-5) obtained in Example 5 was used as an
electrophotographic liquid developer, and printing test was
conducted using a wet type copying machine (DT-2500 manufactured by
Ricoh Co., Ltd). As a result, an image having a sufficient image
density and good fixing property was obtained.
[0209] Further, the electrophotographic liquid developer exhibited
an extremely small change in the charge with the lapse of time and
was excellent in redispersibility and storage stability.
[0210] According to the ink composition of the invention, which
contains pigment-containing resin particles obtained by seed
dispersion polymerization of polymerizable monomers including the
macromonomer (M) with a polymer-treated pigment as a seed particle
in a non-aqueous solvent, an oil based ink for inkjet printer in
which the pigment is uniformly dispersed in the state of fine
particle and dispersion stability of the pigment dispersion is
excellent can be obtained. Further, an oil based ink for inkjet
printer having high discharge stability without the occurrence of
clogging in a nozzle section can be obtained. Moreover, an oil
based ink for inkjet printer having excellent drying property on
recording paper, excellent water resistance and light fastness of
recorded image, and high-level scratch resistance can be obtained.
Also, an oil based ink for use in an electrostatic inkjet printer
or an electrophotographic liquid developer, which is excellent not
only in dispersion stability and scratch resistance but also in
control of charge polarity and charge stability with the lapse of
time can be obtained. In addition, according to the invention, a
process of producing an oil based ink for inkjet printer, which
comprises resin particles having the above-described
characteristics and containing a pigment therein uniformly
dispersed in the state of fine particle is provided.
[0211] The entire disclosure of each and every foreign patent
application from which the benefit of foreign priority has been
claimed in the present application is incorporated herein by
reference, as if fully set forth herein.
[0212] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope
thereof.
* * * * *