JP2000351931A - Ink composition for ink-jet printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink composition capable of providing clear images of suppressed blur even in the case of printing on plain papers, by including a coloring agent comprising particles having electric charge and a specific resin emulsion in an aqueous medium. SOLUTION: This ink composition is obtained by including (B) a coloring agent comprising particles having electric charge and (c) a resin emulsion having the electric charge with the identical polarity to that of the component B, in (A) an aqueous medium. Preferably, the component B comprises pigment particles each having a particle diameter of 50-200 nm, in particular, comprises carbon black having functional group. The component C is desirable to be such one as to contain a thermoplastic resin with a glass-transition temperature of >=35 deg.C and a minimum temperature for film formation of <=20 deg.C. The component C is pref. such one as to be selected from an acrylic resin emulsion, a vinyl acetate-based rein emulsion, vinyl chloride-based resin emulsion, styrene- acrylic resin emulsion, and styrene-based resin emulsion.

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 used for water-based writing utensils, recorders, and pen plotters, and more particularly to a water-based ink suitable for ink-jet recording. The present invention relates to a water-soluble ink composition.

[0002]

2. Description of the Related Art In recent years, ink jet printers have become popular due to their advantages such as low noise and low running cost, and color printers capable of printing on plain paper have also been put on the market. Aqueous dye ink compositions containing a black dye have been mainly used as recording liquids for ink jet printers. In recent years, an aqueous pigment ink composition using a pigment such as carbon black to impart light resistance and water resistance to a recorded image has attracted attention. However, it is difficult to satisfy all of various reliability such as image color reproducibility, water resistance, abrasion resistance, light resistance, image drying property, image bleeding, and ejection.

As a method of suppressing image bleeding and improving the water resistance and abrasion resistance, an ink composition is disclosed in Japanese Patent Application Laid-Open No. Hei 4-18462 for the purpose of securing fixability to a recording medium by adding a resin emulsion. Is disclosed.
However, in this prior art, the particle size of the resin emulsion is 50 n in order to improve the ejection stability of the ink.
m or less, it is necessary that the emulsion particles penetrate deep into the recording medium after printing, resulting in insufficient coating strength on the surface,
When the concentration of the resin emulsion was increased in order to obtain a coating strength, the viscosity was increased and the printing characteristics were impaired.

On the other hand, Japanese Patent Application Laid-Open No. Hei 10-168368 discloses a method of adding particles having a charge opposite to that of a colorant particle, landing on a recording medium, and then restraining each other's movement by these attractive forces to suppress bleeding. Proposed. In this case, at the time of ink ejection, since the ink viscosity is designed to be reduced by the shear speed, it is necessary not only to precisely control the attraction between the particles but also to considerably limit the ink ejection mechanism. There are drawbacks.

Further, Japanese Patent Application Laid-Open No. 8-283636,
JP-A-10-110126, JP-A-10-152
No. 640 discloses an ink containing a thermoplastic resin component in an ink, and printing is performed by discharging ink droplets onto a recording medium heated to a temperature higher than the softening point of the thermoplastic resin, thereby preventing bleeding. It has been proposed to obtain images.
However, heating the recording medium is not preferable because not only the device becomes complicated, but also the energy consumption increases.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to
(1) When used for ink jet recording, in which a recording liquid is applied by applying vibration or thermal energy to generate droplets, a clear image with suppressed image bleeding can be obtained even when printing on plain paper, and An object of the present invention is to provide an aqueous pigment ink composition from which an image having excellent water resistance and weather resistance can be obtained.
(2) Another object of the present invention is to provide a recording method for favorably forming an image using the ink composition. (3) Furthermore, high-frequency driving provides excellent ejection stability and ejection responsiveness,
Another object of the present invention is to provide a recording method and a recorded material using highly safe ink.

[0007]

Means for Solving the Problems As a result of diligent studies by the present inventors, the object of the above (1) is to provide an ink composition containing at least a coloring agent and a resin emulsion in an aqueous medium of the present invention. An ink composition, wherein the colorant is a charged particle, and the resin emulsion has a charge of the same polarity as the colorant ", (2)
"The ink composition according to the above (1), wherein the colorant is a pigment particle having a particle diameter of 50 nm to 200 nm", (3) "the colorant substantially contains a surfactant. The ink composition according to the above (1) or (2), wherein the ink composition is a self-dispersible pigment particle containing no pigment particles.
(4) “The resin emulsion is made of a thermoplastic resin, and the glass transition temperature (Tg) of the resin is 35 ° C. or more,
And (5) a particle diameter of the resin emulsion, wherein the minimum film forming temperature (MFT) is 20 ° C. or lower. The ink composition according to any one of the above (1) to (4), which has a thickness of 50 nm to 300 nm, and (6) that the resin emulsion contains substantially no surfactant. The ink composition according to any one of the above (1) to (5), which is a self-dispersing emulsion ", (7)" wherein the resin emulsion is an acrylic resin emulsion or a vinyl acetate resin. (1) to (6), which are selected from emulsions, vinyl chloride emulsions, styrene-acrylic resin emulsions, and styrene emulsions.
Ink composition according to any one of the above items. In addition, the problems (2) and (3) described in (8) of the present invention relate to an inkjet method for performing printing by discharging droplets of an ink composition from a recording head and attaching the droplets to a recording medium. An ink-jet recording method, wherein the ink composition according to any one of the above items (1) to (7) is used as an ink composition;
(9) The present invention has been found to be achieved by a "recorded matter obtained by the recording method described in the above item (8)".

[0008]

DETAILED DESCRIPTION OF THE INVENTION The pigment used as a coloring material in the present invention has a charge in the ink (in water) and can be dispersed in fine particles. Either one adsorbing an ionic surfactant may be used, and there is no particular limitation. Carbon black having a functional group is preferably used. Carbon black as a raw material used in the present invention has a primary particle size of 4
It has a thickness of 0 nm or less, preferably 30 nm or less, and more preferably 30 to 10 nm. If the primary particle diameter is 40 nm or more, the original carbon black itself has a low coloring power, and the optical density (reflection density) of the recorded matter decreases. In the present invention, a positive or negative charge is provided in water by chemically bonding a specific functional group to the surface of such a raw material carbon black, and the charge is used to stabilize the dispersion of fine particles.

Further, wet oxidation may be performed in water using hypohalous acid and / or a salt thereof. Specific examples of the hypohalous acid and / or its salt include sodium hypochlorite and potassium hypochlorite, and sodium hypochlorite is particularly preferred from the viewpoint of reactivity. In the oxidation reaction, carbon black and a hypohalite (for example, sodium hypochlorite) are charged in an appropriate amount of water, and the reaction is carried out for 5 hours or more, preferably for about 10 to 15 hours, at 50 ° C. or more, and preferably for 95 to 10 hours.
Perform by stirring at 5 ° C. At that time, it is preferable that the carbon black is oxidized in a finely dispersed state.

The particle size of the finely dispersed carbon black in the aqueous pigment ink composition of the present invention is 50 to 200 n.
m, particularly preferably 75 to 150 nm. If the particle size of the carbon black is 50 nm or less, the recorded matter becomes transparent and a sufficient optical density cannot be obtained. Also,
If it exceeds 200 nm, sedimentation of carbon black is likely to occur.

In general, fine dispersion is carried out by an operation of wet grinding in an aqueous medium for 3 to 10 hours using a mill medium and a grinding apparatus. As a mill medium, glass beads, zirconia beads, magnetic beads and the like are used. Examples of the pulverizer include a ball mill, an attritor, a Fouro jet mixer, an impeller mill, a colloidal mill, and a sand mill (for example, a bead mill, a sand glider, a super mill, an agitator mill, a Dyno mill (trade name)) and the like.

The pigment preferably used in the present invention can be obtained, for example, by the method described in JP-A-8-3498. It is also possible to use commercially available pigments as the above-mentioned pigments. Preferred examples thereof include Cbot Specialty Chemicals, Inc.
AB-O-JET 200, 300, IJX-181, 1
57 and 164 and MicroJet CW1 or 2 manufactured by Orient Chemical Industries, Ltd.

As the pigment of the present invention, a color pigment may be used. Examples of color pigments include CI Pigment Yellow as the pigment used for the yellow ink.
1, CI Pigment Yellow 2, CI Pigment Yellow 3,
CIPigment Yellow 13, CIPigment Yellow 16,
Pigments used as CI Pigment Yellow 83 and magenta ink include CI Pigment Red 5 and CI Pigment
t Red 7, CI Pigment Red 12, CI Pigment Red 4
8 (Ca), CI Pigment Red 48 (Mn), CI Pigment
Red 57 (Ca), CI Pigment Red 112, CI Pigmen
t Red 122, pigments used as cyan inks include CI Pigment Blue 1, CI Pigment Blue 2, C.I.
I. Pigment Blue 3, CI Pigment Blue 15: 3, CI
Pigment Blue 16, CI Pigment Blue 22, CIVat B
lue 4, CIVat Blue 6, and the like.

The aqueous pigment ink composition of the present invention contains a resin emulsion having a charge having the same polarity as that of the pigment. The resin emulsion used in the present invention has a Tg
Is 35 ° C or higher and the minimum film formation temperature (MFT) is 20 ° C
It is as follows. The resin component of the dispersed phase is not particularly limited as long as it satisfies the above-mentioned conditions, but preferred examples include an acrylic resin, a vinyl acetate resin, a styrene-butadiene resin, a vinyl chloride resin, and an acrylic resin. Hydrophobic resins such as styrene resins, butadiene resins, and styrene resins are exemplified. The particle size of the resin emulsion is in the range of 50 to 300 nm, more preferably 50 to 300 nm.
The size is in the range of 200 nm.

These resin emulsions can be obtained by mixing the resin particles with water, if necessary, together with a surfactant. More preferably, the resin monomer is directly synthesized by a conventionally known emulsion polymerization method. This is also advantageous. As the emulsion polymerization method, for example, in an aqueous medium, if necessary, in the presence of an emulsifier, a polymerization initiator, a chain transfer agent, a chelating agent, a pH adjuster, and the like, the polymerizable monomer is usually at 30 to 100 ° C. The polymerization reaction may be performed at a temperature for about 1 to 30 hours. For example, an emulsion of an acrylic resin or a styrene-acrylic resin can be obtained by polymerizing a polymerizable monomer such as a (meth) acrylate, or a (meth) acrylate and styrene together with a polymerization initiator in water. it can.

The charge of the resin emulsion is provided by any one or a combination of an ionic functional group contained in the monomer, an initiator fragment of a polymerization initiator, and an ionic surfactant. Examples of the monomer containing an ionic functional group include, for example, sodium styrene sulfonate, sodium allyl alkyl sulfonate, alkyl allyl sulfosuccinate, polyoxyethylene alkyl allyl glycerin ether sulfate, polyoxyethylene alkyl phenol allyl glycerin ether sulfate, dimethylaminoethyl (Meth) acrylate, diethylaminoethyl (meth) acrylate and the like.

If necessary, an emulsifier can be used.
Examples include anionic surfactants such as higher alcohol sulfate sodium salt, alkylbenzene sulfonate sodium salt, dialkyl succinate sodium sulfonate, sodium alkyldiphenyl ether disulfonate, and cationic surfactants such as lauryl trimethyl ammonium chloride. . These surfactants are usually 0 to 100 parts by weight of the polymerizable monomer.
It is used in an amount of 1 part by weight. In the present invention, it is preferable that the amount used is as small as possible from the viewpoint of preventing foaming.

Examples of the polymerization initiator include water-soluble persulfates such as sodium persulfate, hydrogen peroxide, azo compounds, peroxides and the like generally used in emulsion polymerization. These polymerization initiators can be used by dissolving them in water, a polymerizable compound or a solvent. In the present invention, a water-soluble persulfate such as sodium persulfate is preferably used as the polymerization initiator. These polymerization initiators add a sulfuric acid group to the produced resin and impart a charge to the resin emulsion. The polymerization initiator as described above is generally used in an amount of 0.1 to 3 parts by weight based on 100 parts by weight of the polymerizable monomer.

In the emulsion polymerization, a reducing agent may be used together with the polymerization initiator. Examples of such a reducing agent include sodium pyrobisulfite, sodium hydrogen sulfite, sodium thiosulfate, L-ascorbic acid and salts thereof, and sodium formaldehyde sulfoxylate.

The following compounds are used as the chain transfer agent. Halogenated hydrocarbons such as chloroform and bromoform; mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, n-octyl mercaptan; xanthogens such as dimethyl xanthogen disulfide, diisopropyl xanthogen disulfide; Kind,
Unsaturated cyclic hydrocarbon compounds such as 9,10-dihydroanthracene, 1,4-dihydronaphthalene, indene, and 1,4-cyclohexadiene; and unsaturated heterocyclic compounds such as xanthene and 2,5-dihydrofuran. . The chain transfer agent is generally used in an amount of 0 to 5 parts by weight based on 100 parts by weight of the monomer.

Examples of the chelating agent include glycine,
Alanine, ethylenediaminetetraacetic acid and the like can be mentioned. p
Examples of the H adjustor include sodium carbonate, potassium carbonate, sodium hydrogen carbonate, ammonia and the like.

The emulsion polymerization carried out in an aqueous medium as described above may be carried out in the presence of a small amount of an organic solvent, if necessary. For example, methyl ethyl ketone, acetone, trichlorotrifluoroethane, methyl isobutyl ketone,
Organic solvents such as dimethyl sulfoxide, toluene, dibutyl phthalate, methylpyrrolidone, ethyl acetate, alcohols, cellosolves, carbinols and the like can be used. This organic solvent is used within a range that does not impair workability, disaster prevention safety, environmental safety and manufacturing safety. Specifically, 5 parts by weight or less based on 100 parts by weight of the polymerizable monomer is specifically used. It can be used in quantity. Emulsion polymerization performed in the coexistence of each component as described above can be performed by a known method such as a batch method, a semi-continuous method, and a continuous method.

The ink composition according to the present invention comprises at least the above pigment, the above resin emulsion and water. The amount of the pigment added to the ink composition is preferably 2 to 15% by weight, more preferably about 4 to 10% by weight.
The addition amount of the resin emulsion is preferably 1 to 30% by weight as a resin component, and more preferably about 3 to 20% by weight. The aqueous pigment ink composition of the present invention may contain a water-miscible organic solvent, if necessary. In addition, water, a water-miscible organic solvent, and a mixture thereof are referred to as an aqueous medium in this specification.

Hereinafter, the ink composition will be described. According to a preferred embodiment of the present invention, the ink composition according to the present invention preferably contains a glycol in order to prevent nozzle clogging of the ink jet recording head. As the glycols, water-soluble glycols are preferable, and examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol having a molecular weight of 600 or less, and 1,3-propylene. Glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, mesoerythritol, pentaerythritol and the like.

Further, thiodiglycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, propylene glycol, dipropylene glycol are used as components for effectively preventing clogging of other nozzles. , Tripropylene glycol, neopentyl glycol, 2-methyl-2,4-pentanediol, trimethylolpropane, trimethylolethane and the like. The amount of the component for preventing clogging may be appropriately determined within a range in which clogging is prevented. In the case of glycols, 3 to 25% by weight is used.
The degree is preferred.

According to a preferred embodiment of the present invention, the ink composition according to the present invention improves the solubility of glycol ethers having low solubility in water, and further improves the permeability to a recording medium such as paper, or To prevent nozzle clogging, other water-soluble organic solvents may be included. Preferred examples of the water-soluble organic solvent include ethanol, methanol, butanol, propanol, alkyl alcohols having 1 to 4 carbon atoms such as isopropanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,
Ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-
iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-
Butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-
n-propyl ether, propylene glycol mono-i
glycol ethers such as so-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, formamide,
Acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane and the like can be mentioned. The addition amount is preferably about 5 to 60% by weight based on the total amount of the ink composition.

The ink composition according to the present invention can also contain an alkyl ether carboxylate surfactant if necessary. Examples of the alkyl ether carboxylate surfactant include ECT-3NE manufactured by Nikko Chemicals Co., Ltd.
X, ECTD-3NEX, ECTD-6NEX, ECT
-3, ECT-7, AKYPO RLM 45 NV (C
HEM-Y), AKYPO RLM45 (CHEM-
Y), AKYPO RLM100NV (CHEM-
Y), AKYPO RLM100 (CHEM-Y) or the like can be used. In particular, ECTD-3NEX and EC
Using TD-6NEX shows good recording quality.

The addition amount of these alkyl ether carboxylate surfactants is preferably about 0.1 to 5% by weight of the ink composition, more preferably 0.5 to 1.5% by weight. The alkyl ether carboxylate in the above range further reduces bleeding. According to a preferred embodiment of the present invention,
The ink composition according to the present invention can comprise other surfactants to control its permeability. The surfactant preferably has good compatibility with the ink composition, and among the surfactants, those having high permeability and high stability are preferable. Preferred specific examples thereof include amphoteric surfactants and nonionic surfactants.

Examples of the amphoteric surfactant include betaine lauryldimethylaminoacetate, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, coconut oil fatty acid amidopropyldimethylaminoacetate betaine, polyoctylpolyaminoethylglycine and other imidazolines. Derivatives. As nonionic surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether,
Polyoxyethylene alkyl ethers, ethers such as polyoxyalkylene alkyl ethers, polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, Sorbitan sesquiolate,
Examples include ester-based surfactants such as polyoxyethylene monooleate and polyoxyethylene stearate, and fluorine-containing surfactants such as fluorine alkyl esters and perfluoroalkyl carboxylate.

According to a preferred embodiment of the present invention, the ink composition according to the present invention may comprise a saccharide. Addition of sugar effectively prevents nozzle clogging of the ink jet recording head. The saccharide may be any of a monosaccharide and a polysaccharide, and specific examples thereof include glucose, mannose, fructose, ribose, xylose, arabinose, lactose, galactose, aldonic acid, glucitolose, maltose, cellobiose, sucrose, trehalose, In addition to maltotriose and the like, alginic acid and salts thereof, cyclodextrins, and celluloses can be mentioned. The addition amount is preferably about 1% to 10%, more preferably 3 to 7%.

According to a preferred embodiment of the present invention, the ink composition according to the present invention comprises a preservative, a fungicide, a pH adjuster, a dye dissolving aid, or an antioxidant for improving its properties. , A conductivity adjuster, a surface tension adjuster, an oxygen absorber and the like.

Preferred examples of the preservative and the fungicide include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate and 1,2-dibenziso. Thiazolin-3-one (ICI
Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN).

Examples of pH adjusters, dye dissolution aids, and antioxidants include amines such as diethanolamine, triethanolamine, propanolamine, and morpholine, and modified products thereof, potassium hydroxide, sodium hydroxide, and the like. Inorganic salts such as lithium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide (such as tetramethylammonium), potassium carbonate, sodium carbonate, carbonates such as lithium carbonate, and other phosphates, and N-methyl-2-
L-ascorbic acid and salts thereof, such as ureas such as pyrrolidone, urea, thiourea, and tetramethylurea; allohanates such as allohanate and methyl allohanate; burettes such as burette, dimethyl buret, and tetramethyl buret; And the like.

Further, the ink composition according to the present invention can contain an antioxidant and an ultraviolet absorber. Examples of those commercial products include Tinu from Ciba Geigy.
Vin 328, 900, 1130, 384, 292, 1
23, 144, 622, 770, 292, Irgaco
r252, 153, Irganox 1010, 107
6, 1035 and MD1024.

Further, the ink composition according to the present invention may comprise a viscosity modifier. Specific examples thereof include rosins, alginic acids, polyvinyl alcohol,
Examples include hydroxypropylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, polyacrylate, polyvinylpyrrolidone, and gum arabic.

[0036]

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these. The amounts (%) of each component described in Examples and Comparative Examples are on a weight basis. [Synthesis of resin emulsion]

Emulsion 1 Styrene 22% Butyl acrylate 7% Sodium styrene sulfonate 1% Potassium persulfate 0.2% Deionized water

Emulsion 2 Styrene 22% 2-ethylhexyl methacrylate 5% Dimethylaminoethyl methacrylate 5% AIBA 1% Deionized water

Emulsion 3 Styrene 30% Sodium dodecyl sulfate 1% Potassium persulfate 0.1% Deionized water

Emulsion 4 Ethyl methacrylate 30% Tween 80 2% Potassium persulfate 0.1% Deionized water

Emulsion 5 Styrene 25% Sodium styrenesulfonate 5% Sodium dodecylbenzenesulfonate 2% Potassium persulfate 0.1% Remaining ion-exchanged water The above composition was stirred at 70 ° C. for 12 hours under a nitrogen stream to obtain a resin. I got an emulsion.

[Characteristics of Emulsion] <Minimum film forming temperature (MFT)> A resin emulsion was thinly applied on a glass plate and dried by applying a temperature gradient. The temperature at the boundary where the thin film was formed was defined as the minimum film formation temperature (MFT). <Glass transition point (Tg)> Measured by differential thermal analysis DSC. <Particle size> Measured by a transmission electron microscope TEM. The results are shown in Table 1.

[0043]

[Table 1]

[Preparation of Ink Composition] Example 1 An ink composition having the following formulation was prepared and adjusted with a 10% aqueous solution of lithium hydroxide so as to have a pH of 9.
The ink composition was obtained by filtration with a membrane filter having an average pore diameter of 0.8 μm. Sulfone group-added type carbon black 5% by weight (as carbon amount) (Cabot Specialty Chemicals, Inc.) Glycerin 5% by weight Diethylene glycol 15% by weight 2-ethyl-1,3-hexanediol 2% by weight 2-pyrrolidone 2% by weight % Emulsion 16% by weight (as solid) Deionized water

Example 2 An ink composition was prepared according to the following formulation and using the same method as in Example 1. Quaternary ammonium group-added type carbon black 5% by weight (as carbon amount) (Cabot Specialty Chemicals, Inc.) Glycerin 5% by weight Diethylene glycol 15% by weight 2-ethyl-1,3-hexanediol 2.5% by weight 2 -Pyrrolidone 2% by weight sodium alginate NSPLL 0.15% by weight (manufactured by Kibun Food Chemifa Co., Ltd.) Emulsion 2 5% by weight (as solid content)

Comparative Example 1 An ink having the same composition as in Example 1 was prepared except that the emulsion 1 used in the example 1 was replaced with the emulsion 2. Comparative Example 2 An ink having the same composition as in Example 1 was prepared, except that Emulsion 3 was used instead of Emulsion 1 used in Example 1. Comparative Example 3 An ink having the same composition as in Example 1 was prepared, except that Emulsion 4 was used instead of Emulsion 1 used in Example 1. Comparative Example 4 An ink having the same composition as in Example 1 was prepared, except that Emulsion 5 was used instead of Emulsion 1 used in Example 1.

[Printing Test] An ink jet printer IPSiO was prepared using the inks prepared in Examples and Comparative Examples.
Printing was performed on plain paper using JET 300 (manufactured by Ricoh Co., Ltd.).

[Evaluation Method] <Ejection Stability> After confirming that the ink was ejected from all the nozzles, 10 test patterns were continuously printed, and the ink ejection from all the nozzles during or after printing was examined. ：: No discharge failure Δ: 1 to 5 non-discharge nozzles ×: 5 or more non-discharge nozzles <Friction resistance of printed image> Printed material was pressed with an eraser (Lion, # 501). Rubbing 5 times at a pressure of 50 g, and measuring the print density before and after the test with a spectrophotometer (X-Rite,
# 938) and evaluated as a residual ratio. <Water resistance> One drop of water was dropped on the printed image, and the image was air-dried. After that, bleeding of the image (flow of ink) was visually judged and evaluated in three steps. A: good with almost no bleeding B: slightly bleeding C: large bleeding The results are shown in Table 2.

[0049]

[Table 2]

[0050]

As apparent from the detailed and concrete description, the ink composition according to the first aspect of the present invention has the following features.
Since the colorant particles and the resin emulsion particles have the same polarity of charge, they are kept stable without agglomeration due to electrostatic repulsion, and the viscosity of the ink composition increases significantly even when the particle concentration becomes relatively high. Without this, an effect is obtained that clogging of the discharge nozzle is significantly reduced. The ink composition according to claim 2 has a pigment particle diameter of 5%.
Since it is as small as 0 nm to 200 nm, a high concentration and a clear color tone can be obtained with a small amount of addition, and further, there is an effect that ejection failure due to clogging or the like does not occur. Further, the ink composition according to the third aspect is a self-dispersion type pigment particle in which the colorant is substantially free of a surfactant. Can be maintained, and the ink composition has a low foaming property, and does not adversely affect the ejection. Further, the ink composition according to claim 4 is a resin emulsion.
Since the TF is 20 ° C. or less, after forming a print image on a recording medium, a resin film of the resin emulsion is formed on the surface of the print image even when the print image is naturally dried without using a special heating means. For protection, a printed image is bright and an image having excellent wear resistance is obtained. In addition, since Tg is 35 ° C. or higher and is in a glassy state in use, the emulsion does not coagulate due to heat or pressure received at the time of discharge, and does not adhere and deposit on a thin film resistor or a diaphragm for a long time. The effect is that stable ejection can be obtained over a wide range. The ink composition according to claim 5 has a particle size of the resin emulsion of 50.
Because it is relatively large, such as ~ 300 nm, even when plain paper is used as a recording medium, after printing, it does not penetrate deep into the fibers of the paper, remains relatively on the surface, and even when the amount of the resin emulsion added is small. A film is efficiently formed on the printed image surface, and the object of the present invention is achieved. Also,
When compared at the same solid content concentration of the resin emulsion, the viscosity is lower than that of the microemulsion, the increase in the viscosity of the ink composition due to the addition of the resin emulsion is small, and there is an effect that the ink ejection performance characteristics are not impaired. Further, in the ink composition according to claim 6, since the resin emulsion does not contain a surfactant, the ink composition itself does not contain unnecessary (excess) surfactant,
Bubbling of the ink is suppressed, and there is no ejection failure due to entrainment of bubbles in the print head, and stable ejection properties can be obtained. Further, since a surfactant is not contained in the resin film formed on the surface of the printed image, an effect that a printed image having high water resistance can be obtained is obtained. Further, the ink composition according to claim 7 is formed because the resin emulsion is selected from an acrylic resin emulsion, a vinyl acetate resin emulsion, a vinyl chloride emulsion, a styrene-acrylic resin emulsion, and a styrene emulsion. The resulting film becomes a hydrophobic resin film, and the printed image has high water resistance, and the film has high transparency, high smoothness, gives a clearer color tone, and has an extremely excellent effect of being inexpensive. . Still further, the recording method according to claim 8,
The ejection stability is excellent by high frequency driving, a good image can be obtained without heating, and the printed matter according to the ninth aspect has an extremely excellent effect that it is a recorded matter having excellent fixability and no bleeding.

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Claims (9)

[Claims] 1. An ink composition comprising at least a colorant and a resin emulsion in an aqueous medium, wherein the colorant is charged particles, and the resin emulsion has a charge of the same polarity as the colorant. An ink composition comprising: 2. The colorant has a particle size of 50 nm to 200 nm.
The ink composition according to claim 1, which is a pigment particle of nm. 3. The ink composition according to claim 1, wherein the colorant is a self-dispersion type pigment particle substantially containing no surfactant. 4. The resin emulsion according to claim 1, wherein the resin emulsion has a glass transition temperature (Tg) of 35 ° C. or higher and a minimum film forming temperature (MFT) of 20 ° C. or lower. The ink composition according to claim 1. 5. The particle size of the resin emulsion is 50.
The ink composition according to any one of claims 1 to 4, wherein the thickness is from 300 nm to 300 nm. 6. The ink composition according to claim 1, wherein the resin emulsion is a self-dispersion emulsion containing substantially no surfactant. 7. The resin emulsion according to claim 1, wherein the resin emulsion is selected from an acrylic resin emulsion, a vinyl acetate resin emulsion, a vinyl chloride emulsion, a styrene-acryl resin emulsion, and a styrene emulsion. The ink composition according to any one of the above. 8. An ink jet method in which droplets of an ink composition are ejected from a recording head and the droplets are attached to a recording medium to perform printing, wherein the ink composition is used as an ink composition.
8. An ink jet recording method, comprising using the ink composition according to any one of items 1 to 7. 9. A recorded matter obtained by the recording method according to claim 8.