JP2002241649A - Water-based ink for inkjet - Google Patents

Abstract

(57) Abstract: An aqueous ink using a hydrophobic dye (microcapsule type dye) encapsulated in a hydrophilic resin as a colorant,
Furthermore, in aqueous inks using both microcapsule type dyes and pigments, excellent long-term storage stability, without changing dischargeability after long-term storage, an inkjet water-based ink capable of obtaining images with excellent water resistance Provision of ink. SOLUTION: In an ink containing at least a hydrophobic dye, an aqueous organic substance, and water encapsulated in a hydrophilic resin, the absolute value of the zeta potential is 30 mV or more, and the aqueous ink for inkjet is further encapsulated in at least the hydrophilic resin. An aqueous ink for inkjet, wherein the absolute value of the zeta potential is 30 mV or more in the ink containing a hydrophobic dye, a pigment, an aqueous organic substance, and water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink for ink-jet printing, and more particularly to a water-based ink having a hydrophobic dye encapsulated in a hydrophilic resin, which has excellent long-term storage stability and excellent water resistance. Water-based ink for ink-jet printing.

[0002]

2. Description of the Related Art Many conventional water-based inks for ink-jet inks have an excellent storage stability due to the use of an aqueous dye as a colorant, but have a problem that formed images are poor in water resistance. Was. On the other hand, there is a proposal to use a pigment as a colorant in order to improve water resistance (see JP-A-8-125306, JP-A-9-272831, JP-A-10-110112, etc.). In the case of a pigment ink, since the pigment is in a dispersed state, there is a problem that the coloring property and the storage stability are inferior to the dye ink. Further, in order to improve the water resistance of an image and achieve high color development, a proposal has been made to use a microcapsule type dye as a coloring agent for an aqueous ink for inkjet (Japanese Patent Application Laid-Open Nos. 8-67847 and 8-253728). Publications, etc.). However, even when a microcapsule type dye is used, there is a problem that the storage stability of the ink is inferior to that of the dye ink.

[0003]

Accordingly, an object of the present invention is to provide an ink using a hydrophobic dye (hereinafter also referred to as a microcapsule type dye) encapsulated in a hydrophilic resin as a colorant, It is an object of the present invention to provide a water-based inkjet ink which is excellent in long-term storage stability and in which an image having excellent water resistance is obtained in an ink using both a capsule type dye and a pigment. In particular, it is an object of the present invention to provide a water-based ink for inkjet that can stably eject ink without causing a change in ejection property after long-term storage.

[0004]

The above object is achieved by the present invention described below. That is, the present invention provides an ink containing at least a hydrophobic dye, an aqueous organic substance, and water encapsulated in a hydrophilic resin having an absolute value of zeta potential of 30 mV.
The absolute value of the zeta potential is 30 mV or more in the ink jet aqueous ink characterized by the above, and further, in an ink containing at least a hydrophobic dye, a pigment, an aqueous organic substance, and water encapsulated in a hydrophilic resin. A water-based ink for ink-jet printing, characterized in that:

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to embodiments of the present invention. The present inventors have conducted intensive studies to solve the above problems, and as a result, when measuring the zeta potential in an aqueous inkjet ink using a hydrophobic dye encapsulated in a hydrophilic resin, the absolute value of the zeta potential was The present inventors have found that an ink having a voltage of 30 mV or more has excellent storage stability at high temperatures, and have reached the present invention. Hereinafter, each material constituting the aqueous inkjet ink of the present invention will be described.

[0006] The aqueous ink jet ink of the present invention comprises:
As a coloring agent, at least a hydrophobic dye encapsulated in a hydrophilic resin is used. First, the microcapsule type dye will be described. Since the microcapsule type dye used in the present invention is composed of a hydrophilic resin, it is stably dispersed in an excellent state in an aqueous medium comprising an aqueous organic substance and water. As a result, the hydrophobic dye, which is a colorant encapsulated in the hydrophilic resin, is well dispersed in the ink, so that a high storage stability of the ink is realized, and the ejection property after long-term storage is improved. There is no change in.
Further, since a hydrophobic dye is used as a colorant, the formed image has high water resistance. Furthermore, the aqueous inkjet ink of the present invention is configured so that the absolute value of the zeta potential thereof is 30 mV or more, so that the dispersion state of the microcapsule-type dye in the ink is favorably maintained even at high temperatures. Than conventional inks using microcapsule type dyes as colorants,
Further, the storage stability is excellent, and it is possible to effectively suppress the change in the ejection property that tends to occur after long-term storage.

As the hydrophilic resin used in the present invention, the following anionic or cationic resins having a hydrophilic group are suitable so that they can be dispersed in an aqueous medium in a favorable state. In particular, it is preferable to use a resin having a weight average molecular weight of 1,000 to 60,000. Specific examples of the anionic resin include hydrophobic monomers such as styrene, a styrene derivative, vinyl naphthalene, a derivative of vinyl naphthalene, an alkyl ester of acrylic acid, and an alkyl ester of methacrylic acid; Unsaturated carboxylic acids and their aliphatic alcohol esters, acrylic acid, methacrylic acid,
Copolymers composed of hydrophilic monomers such as maleic acid, fumaric acid, itaconic acid and derivatives thereof, and salts thereof.

The cationic resin includes, for example, a copolymer comprising a monomer containing an unsaturated group-containing tertiary amine or an unsaturated group-containing ammonium salt. Specific examples of these monomers include, for example, monovinylpyridines such as vinylpyridine and 2-methyl-5-vinylpyridine, and dialkylamino such as N, N-dimethylaminostyrene and N, N-dimethylaminomethylstyrene. Group-containing styrenes, dialkylamino group-containing acrylates such as N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, etc. Dialkylamino group-containing methacrylates,
N, N-dimethylaminoethyl vinyl ether, N, N
Dialkylamino group-containing vinyl ethers such as -diethylaminoethyl vinyl ether, N- (N ', N'-dimethylaminoethyl) acrylamide, N- (N',
Acrylamides containing a dialkylamino group such as N′-diethylaminoethyl) acrylamide, N- (N ′,
N'-dimethylaminoethyl) methacrylamide, N-
Examples thereof include methacrylamides having a dialkylamino group such as (N ′, N′-diethylaminoethyl) methacrylamide, and quaternized products thereof.

The hydrophobic dye used as a colorant in the present invention can be used without any particular limitation as long as it is a hydrophobic dye that can be encapsulated in a favorable state in a hydrophilic resin composed of the above-mentioned raw materials. For example, oil dyes, disperse dyes, direct dyes, acid dyes, basic dyes and the like can be mentioned. Among these, it is preferable to use an oily dye and a disperse dye as described below from the viewpoint of encapsulation in a hydrophilic resin.

Specifically, oil-soluble dyes include, for example, C.I. I. Solvent Yellow 1, 2, 3, 13, 1
9, 22, 29, 36, 37, 38, 39, 40, 4
3, 44, 45, 47, 62, 63, 71, 76, 8
1, 85, 86, etc .; I. Solvent Red 8,2
7, 35, 36, 37, 38, 39, 40, 58, 6
0, 65, 69, 81, 86, 89, 91, 92, 9
7, 99, 100, 109, 118, 119, 122
Etc .; I. Solvent Blue 14, 24, 26, 3
4, 37, 38, 39, 42, 43, 45, 48, 5
2, 53, 55, 59, 67, etc .; I. Solvent Black 3, 5, 7, 8, 14, 17, 19, 20, 2
2, 24, 26, 27, 28, 29, 43, 45, and the like, but are not limited thereto.

The disperse dyes include, for example, C.I. I.
Disperse Yellow 5, 42, 54, 64, 79, 8
2, 83, 93, 99, 100, 119, 122, 12
4, 126, 160, 184: 1, 186, 198, 1
C. 99, 204, 211, 224 and 237; I. Disperse Orange 13, 29, 31: 1, 33, 4
9, 54, 55, 66, 73, 118, 119 and 16
3; I. Disperse Red 54, 72, 73, 8
6, 88, 91, 92, 93, 111, 126, 12
7, 134, 135, 143, 145, 152, 15
3, 154, 159, 164, 167: 1, 177, 1
79, 181, 204, 206, 207, 221, 23
9, 240, 258, 277, 278, 283, 28
8, 311, 323, 343, 348, 356 and 36
2; I. Disperse Violet 26, 33, 7
7; I. Disperse Blue 56, 60, 73, 7
9, 79: 1, 87, 87: 1, 113, 128, 14
3, 148, 154, 158, 165, 165: 1, 1
65: 2, 176, 183, 185, 197, 198,
201, 214, 224, 225, 257, 266, 2
67, 287, 354, 358, 365 and 368;
C. I. Disperse Green 6: 1 and 9, but are not limited thereto.

The hydrophobic dye encapsulated in the hydrophilic resin used in the aqueous inkjet ink of the present invention is generally prepared by a phase inversion emulsification method, an interfacial polymerization method, or an in-situ method.
It can be produced by a microencapsulation method such as a polymerization method and a coacervation method. When the phase inversion emulsification method is specifically described, as a first step, a hydrophobic dye and a hydrophilic resin are put in an organic solvent and dissolved, and the hydrophobic dye is mixed into the resin. In the second step, by mixing with an excess of water in the presence of an acid or base to neutralize the solution, the solubility of the hydrophilic resin in the organic solvent is reduced, and the hydrophilic resin in which the hydrophobic dye is mixed To a water system to form microcapsules. Further, as a third step, the organic solvent is removed to obtain a microcapsule dispersion. In the examples of the present invention described below, microcapsule type dyes are produced by this phase inversion emulsification method, but the present invention is not limited to this.

When the encapsulation is carried out using the phase inversion emulsification method, the organic solvent used in the first step includes, for example,
Ketone organic solvents such as methyl ethyl ketone and acetone,
Alcohol organic solvents such as methanol, ethanol, and isopropyl alcohol; ether organic solvents such as diethyl ether, dibutyl ether, tetrahydrofuran, and ethylene glycol monoethyl ether; ester organic solvents such as ethyl acetate; and aromatics such as benzene, xylene, and toluene Group organic solvents, and chlorinated organic solvents such as chloroform and methylene chloride. These solvents are:
Species or a mixture of two or more can be used. In particular,
Preferred organic solvents that can be used in the above-described phase inversion emulsification method include one or a combination of two or more selected from ketone-based organic solvents and alcohol-based organic solvents.

Next, a known acid or base can be used as a neutralizing agent used in the second step when encapsulation is carried out using the phase inversion emulsification method. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as acetic acid, lactic acid, succinic acid, glycolic acid, and gluconic acid. or,
Examples of the base include sodium hydroxide, potassium hydroxide, trimethylamine, triethanolamine and the like. However, the present invention is not limited to these.

The aqueous ink jet ink of the present invention comprises:
As the colorant, a microcapsule-type dye in which the hydrophobic dye obtained by the above method is encapsulated in a hydrophilic resin is used. Another form of the aqueous inkjet ink of the present invention includes a colorant. As an agent, a pigment is used together with a microcapsule type dye. Even in the case of such a configuration, if the ink is configured so that the absolute value of the zeta potential is 30 mV or more, the microcapsule type dye and pigment in the ink can be stored in a good state for a long period of time in a stable state. The aqueous ink for inkjet is excellent in stability and can provide an image excellent in water resistance. In particular, a water-based ink for ink jet, which is a water-based ink having microcapsule-type dyes and pigments and which does not change its ejection properties even after long-term storage, can be obtained.

As the pigment used at this time, conventionally known carbon blacks and organic pigments can be used. Particularly preferred as the anionic pigment is surface-modified carbon black, such as acidic carbon black. The acidic carbon black can be generally obtained by grafting a functional group or a molecule containing a functional group to the surface of the carbon black by a physical treatment such as vacuum plasma or a chemical treatment. The functional group suitable for the present invention is a carbonyl group, a carboxyl group, a hydroxyl group, or a sulfone group. These functional groups to be grafted to one carbon black particle may be single or plural. As the cationic pigment, it is particularly preferable to use a self-dispersible carbon black in which at least one kind of cationic hydrophilic group is bonded to the surface of the carbon black directly or via another atomic group.

The aqueous ink for ink-jet recording of the present invention comprises:
As a colorant, having a hydrophobic dye encapsulated in at least the hydrophilic resin described above, in another form, having such a microcapsule type dye and a pigment as described above,
Further, it has an aqueous organic substance and water as an aqueous medium for dispersing them.

The following three groups can be used as the aqueous organic substance that can be used in the aqueous ink jet ink of the present invention, and any of these can be used in an appropriate combination. Here, those belonging to the third group include a first group of solvents having high moisture retention, hardly evaporating, and having excellent hydrophilicity;
A second group of solvents that are organic and have good wettability to hydrophobic surfaces and are also evaporatively dry; a third group of solvents (monohydric alcohols) that have moderate wettability and low viscosity is there.

Specifically, the solvents belonging to the first group include, for example, ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, glycerin, 1,2,4-butanetriol,
2,6-hexanetriol, 1,2,5-pentanetriol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dimethyl sulfoxide, diacetone alcohol, glycerin monoallyl ether, propylene Glycol, butylene glycol,
Polyethylene glycol 300, thiodiglycol, N
-Methyl-2-pyrrolidone, 2-pyrrolidone, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, sulfolane, trimethylolpropane, trimethylolethane, neopentyl glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl Ether, ethylene glycol monoisopropyl ether, ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether,
Dipropylene glycol monomethyl ether, β-dihydroxyethyl urea, urea, acetonylacetone,
Pentaerythritol, 1,4-cyclohexanediol and the like can be mentioned.

The solvents belonging to the second group include hexylene glycol, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monophenyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, and diethylene glycol. Monoisobutyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopro Diether glycol, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, glycerin monoacetate, glycerin diacetate, glycerin triacetate, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, cyclohexanol, 1,2-cyclohexanediol, 1-butanol, 3-methyl-1,5-pentanediol, 3-
Hexene-2,5-diol, 2,3-butanediol, 1,5-pentanediol, 2,4-pentanediol, 2,5-hexanediol, and the like.

Further, the solvents belonging to the third group include ethanol, n-propanol, 2-propanol, 1-methoxy-2-propanol, furfuryl alcohol, tetrahydrofurfuryl alcohol and the like. The total amount of the water-soluble organic solvent as described above is approximately 5% of the total weight of the ink.
It is preferable to use it in the range of ４０40% by weight. In addition to the above-described materials, the aqueous inkjet ink of the present invention may optionally contain a surfactant, a preservative, an antioxidant, an antifoaming agent, a fungicide, a pH adjuster, and the like. is there.

[0022]

Next, the present invention will be described in more detail with reference to examples and comparative examples of the present invention. First, microcapsule dispersions 1 to 5 used in Examples and Comparative Examples of the present invention were produced by the following method. Such a microcapsule dispersion liquid is obtained by dispersing a microcapsule type dye in a state where a hydrophobic resin is encapsulated in a hydrophilic resin in water. All parts described below are parts by weight.

[0023] First, the above composition was kneaded with a paint shaker for 10 hours to obtain 240 parts of a mill base solution. Next, 250 parts of pure water was added to 240 parts of the obtained mill base solution with stirring, and then triethanolamine was added dropwise to neutralize.
Next, acetone and methyl ethyl ketone were distilled off using a rotary evaporator, and further concentrated. afterwards,
The concentrated liquid was filtered with a 2 micron filter paper to obtain a 15 wt% (solid content) microcapsule dispersion liquid 1.

[0024] First, the above composition was kneaded with a paint shaker for 10 hours to obtain 240 parts of a mill base solution. Next, 250 parts of pure water was added to 240 parts of the obtained mill base solution with stirring, and then triethanolamine was added dropwise to neutralize.
Next, acetone and methyl ethyl ketone were distilled off using a rotary evaporator, and further concentrated. Then 2
The solution was filtered through a micron filter paper to obtain a microcapsule dispersion liquid 2 of 20 wt% (solid content).

[0025] The above composition was kneaded with a paint shaker for 10 hours to obtain 240 parts of a mill base solution. Next, 250 parts of pure water was added to 240 parts of the obtained mill base solution with stirring, and then triethanolamine was added dropwise to neutralize. Furthermore,
Acetone and methyl ethyl ketone were distilled off using a rotary evaporator, and further concentrated. Thereafter, the mixture was filtered through a filter paper of 2 microns to obtain a microcapsule dispersion liquid 3 of 15 wt% (solid content).

[0026] The above composition was kneaded with a paint shaker for 10 hours to obtain 240 parts of a mill base solution. Next, 250 parts of pure water was added to 240 parts of the obtained mill base solution with stirring, and then triethanolamine was added dropwise to neutralize. Furthermore,
Acetone and methyl ethyl ketone were distilled off using a rotary evaporator, and further concentrated. Thereafter, the solution was filtered through a filter paper of 2 microns to obtain a microcapsule dispersion liquid 4 of 15 wt% (solid content).

<Production of Microcapsule Dispersion Liquid 5> The following materials were mixed and dissolved.・ C. I. Solvent Black 35 parts ・ Styrene-N, N-dimethylaminoethyl methacrylate copolymer (Mw = 40,000) 20 parts ・ Methyl ethyl ketone 30 parts ・ Glass beads (0.2 micron) 60 parts Paint the above composition The mixture was kneaded with a shaker for 10 hours to obtain 55 parts of a mill base solution. In 55 parts of mill base solution,
After adding 60 parts of pure water with stirring, acetic acid was added dropwise to neutralize. Further, using a rotary evaporator, methyl ethyl ketone was distilled off, and further concentrated. Thereafter, the solution was filtered through a filter paper of 2 microns to obtain a microcapsule dispersion liquid 5 of 20 wt% (solid content).

Microcapsule dispersion 1 obtained above
Using Examples 1 to 4, inks of Examples 1 to 4 and Comparative Examples 1 and 2 containing pigments having the following compositions were prepared. The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink and the zeta potential of the obtained ink were measured by the following methods. The results are shown in Table 1.

(Measurement of zeta potential)
After dilution with pure water to 0 times and sonication for 3 minutes,
eta Plus (Brook Haven Inst)
measurements (manufactured by the Company, Inc.). that time,
The measurement temperature was 25 ° C., and an appropriate pH value was measured using a pH adjuster as necessary.

(Average Particle Size of Dispersion)
After dilution with pure water by a factor of 0 and sonication for 3 minutes, measurement was performed using ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) using a dynamic light scattering method.

[0031] The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink and the zeta potential of the obtained ink were measured in the same manner as in Example 1, and the results are shown in Table 1.

[0032] The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink and the zeta potential of the obtained ink were measured in the same manner as in Example 1, and the results are shown in Table 1.

[0033] The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink and the zeta potential of the obtained ink were measured in the same manner as in Example 1, and the results are shown in Table 1.

[0034] The above composition was mixed well to obtain an ink of this comparative example. The average particle size of the dispersion contained in the ink and the zeta potential of the obtained ink were measured in the same manner as in Example 1, and the results are shown in Table 1.

[0035] The above composition was mixed well to obtain an ink of this comparative example. The average particle size of the dispersion contained in the ink and the zeta potential of the obtained ink were measured in the same manner as in Example 1, and the results are shown in Table 1.

<Evaluation Method> Using the inks of Examples 1 to 4 and Comparative Examples 1 and 2 obtained above, images were formed using BJC-430J manufactured by Canon as a printing machine.
The obtained images were evaluated for each ink according to the following evaluation methods and evaluation criteria. The results are shown in Table 1.

(Water resistance) A printed matter for evaluating water resistance was placed on a table having an inclination angle of 45 °, and 150 μl of tap water was dropped with a micropipette to visually evaluate the occurrence of bleeding. The evaluation was performed according to the following criteria. ：: No bleeding occurred on the printed matter 30 minutes after printing. D: Bleeding occurred on printed matter 30 minutes after printing.

(Long-term storage test) Each ink was stored in a thermostat at 60 ° C for 30 days, and an image was formed using the ink before and after storage. Using the obtained images, the following items were evaluated, and evaluated according to the following criteria.

[Physical stability after storage] ：: The average particle size and viscosity of the dispersion in the ink are not changed. X: The average particle size and viscosity of the dispersion in the ink are not changed.

[Print Density Difference] The image density of 100% solid printed matter obtained by each ink before and after storage was measured using a Macbeth densitometer (manufactured by Macbeth). The print density difference before and after storage (OD difference = initial print density−
The print density after storage was determined, and the results are shown in Table 1.

[Ejection stability] A4 size 100% solid printing is performed, the amount of ink consumed at that time is compared before and after storage, and the change in the amount of ejection (ejection amount change = ink consumption after storage / initial ink consumption) Amount) was calculated. The results are shown in Table 1.

[0042]

As is clear from Table 1 above, it was found that the comparative example in which the absolute value of the zeta potential of the ink was smaller than 30 mV was inferior in long-term storage stability. It was also found that in Comparative Example 2 where the absolute value of the zeta potential of the ink was as small as 5 mV, the water resistance of the image was poor. Furthermore,
In this case, it was found that the ejection property changed after long-term storage. On the other hand, in the case of the ink of the embodiment in which the absolute value of the zeta potential of the ink is larger than 30 mV, the water resistance of the image and the long-term storage stability of the ink are excellent. It was found that the composition was suitable for aqueous ink-jet inks without any change in properties.

Further, using the microcapsule dispersions 1 to 5 obtained above, aqueous inks of Examples 5 to 9 and Comparative Examples 3 and 4 having the following compositions containing no pigment as a coloring agent were produced, respectively. <Example 5>-55% by weight of microcapsule dispersion liquid-10% by weight of glycerin-35% by weight of pure water The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink, and the zeta potential of the obtained ink were measured by the same method as in Example 1,
The results are shown in Table 2. The ink was evaluated by the same evaluation method and standard as in Example 1. The results are shown in Table 2. As a result, in the case of the ink of this embodiment,
Excellent image water resistance, long-term storage stability of ink, and
It was found that the ejection property did not change even after long-term storage.

[0045] The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink, and the zeta potential of the obtained ink were measured by the same method as in Example 1,
The results are shown in Table 2. The ink was evaluated by the same evaluation method and standard as in Example 1. The results are shown in Table 2. As a result, in the case of the ink of this embodiment,
Excellent image water resistance, long-term storage stability of ink, and
It was found that the ejection property did not change even after long-term storage.

Example 7 Microcapsule Dispersion 2 80% by weight Glycerin 10% by weight Pure water 10% by weight The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink, and the zeta potential of the obtained ink were measured by the same method as in Example 1,
The results are shown in Table 2. The ink was evaluated by the same evaluation method and standard as in Example 1. The results are shown in Table 2. As a result, in the case of the ink of this embodiment,
Excellent image water resistance, long-term storage stability of ink, and
It was found that the ejection property did not change even after long-term storage.

Example 8 Microcapsule Dispersion Liquid 3 35% by weight Glycerin 10% by weight Pure water 55% by weight The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink, and the zeta potential of the obtained ink were measured by the same method as in Example 1,
The results are shown in Table 2. The ink was evaluated by the same evaluation method and standard as in Example 1. The results are shown in Table 2. As a result, in the case of the ink of this embodiment,
Excellent image water resistance, long-term storage stability of ink, and
It was found that the ejection property did not change even after long-term storage.

Example 9 Microcapsule dispersion 5 80 wt% Glycerin 10 wt% Pure water 10 wt% The above composition was mixed well to obtain an ink of this example. The average particle size of the dispersion contained in the ink, and the zeta potential of the obtained ink were measured by the same method as in Example 1,
The results are shown in Table 2. The ink was evaluated by the same evaluation method and standard as in Example 1. The results are shown in Table 2. As a result, in the case of the ink of this embodiment,
Excellent image water resistance, long-term storage stability of ink, and
It was found that the ejection property did not change even after long-term storage.

Comparative Example 3 Microcapsule dispersion 1 55 wt% Glycerin 10 wt% Sodium benzenesulfonate 1 wt% Pure water 34 wt% The above composition was mixed well to obtain an ink of this comparative example. The average particle size of the dispersion contained in the ink, and the zeta potential of the obtained ink were measured by the same method as in Example 1,
The results are shown in Table 2. The ink was evaluated by the same evaluation method and standard as in Example 1. The results are shown in Table 2. As is clear from Table 2, in the case of this comparative example in which the absolute value of the zeta potential of the ink is smaller than 30 mV, even if the ink uses a hydrophobic dye encapsulated in a hydrophilic resin as a coloring agent, It was found that the long-term storage stability was poor.

Comparative Example 4 Microcapsule dispersion liquid 4 35 wt% Glycerin 10 wt% Pure water 55 wt% The above composition was mixed well to obtain an ink of this comparative example. The average particle size of the dispersion contained in the ink, and the zeta potential of the obtained ink were measured by the same method as in Example 1,
The results are shown in Table 2. The ink was evaluated by the same evaluation method and standard as in Example 1. The results are shown in Table 2. As is clear from Table 2, it was found that in the case of this comparative example, in which the absolute value of the zeta potential of the ink was 5 mV, which was considerably smaller than 30 mV, the long-term storage stability and the water resistance were poor. Further, it was also found that the ejection property changed after long-term storage.

[0051]

[0052]

As described above, according to the present invention, a formed image is excellent in water resistance, and even after long-term storage, a stable image can be formed without inferior physical properties and ejection properties of the ink. An aqueous ink jet ink is provided.

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Claims (4)

[Claims] 1. An aqueous ink jet ink characterized by having an absolute value of zeta potential of 30 mV or more in an ink containing at least a hydrophobic dye, an aqueous organic substance, and water encapsulated in a hydrophilic resin. 2. An ink-jet aqueous ink comprising an ink containing at least a hydrophobic dye, a pigment, an aqueous organic substance, and water encapsulated in a hydrophilic resin, wherein the absolute value of the zeta potential is 30 mV or more. 3. The aqueous ink for inkjet according to claim 2, wherein the pigment is a surface-modified pigment. 4. The ratio of the hydrophilic resin and the hydrophobic dye is as follows: hydrophobic dye / (hydrophilic resin + hydrophobic dye) × 100 = 10
The aqueous ink for inkjet according to claim 1 or 2, which is 80 wt%.