JP2002030235A - Aqueous pigment set for ink jet and method for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous pigment set used for ink jet and capable of giving images having excellent gloss, images not having a rough feeling, and images having excellent abrasion resistance, and to provide a method for ink jet recording using the pigment ink. SOLUTION: This water-based pigment ink set used for ink jet and using two different ink compositions having the same color but having different colorant concentrations, characterized in that the two ink compositions have a pigment and thermoplastic resin particles, respectively, in an aqueous medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment ink set for ink jet (hereinafter, also simply referred to as an ink set).
More particularly, the invention relates to an aqueous inkjet pigment ink set and an inkjet recording method using the pigment ink. More specifically, the present invention relates to a water-based inkjet pigment ink set capable of obtaining an image having high gloss, an image without a feeling of roughness, and an image having excellent scratch resistance on a recording medium, and an inkjet recording method using the pigment ink. is there.

[0002]

2. Description of the Related Art An ink jet recording method is capable of recording a high-definition image with a relatively simple apparatus, and is rapidly developing in various fields. 2. Description of the Related Art Printers adopting an ink jet recording system are manufactured in a wide range of fields, and the types of inks are also diversified according to the usage.

Conventionally, dyes have been used as colorants as inks for ink-jet recording. However, inks using pigments have been proposed because of poor light resistance and scratch resistance of printed matter.

[0004] However, prints made with pigment ink have been pointed out to have disadvantages such as poor glossiness and transparency on a recording medium (hereinafter also referred to as recording medium), and these defects have been pointed out by pigments in the ink. Attempts have been made to overcome this by controlling the particle size.

[0005] For example, Japanese Patent Application Laid-Open Nos. 1-24979, 4-220473, 7-331147, and 8-1
JP-A-51546 discloses a pigment ink in which a specific amount of particles is present in a certain particle size range, in which the pigment particle diameter of the pigment ink is reduced. However, since the printed pigment exists in an agglomerated state on the recording medium, control of the particle diameter of the pigment ink alone is not sufficient, and the above-mentioned disadvantages cannot be solved.

On the other hand, as a technique for simultaneously improving glossiness, water resistance and scratch resistance, addition of a resin to a pigment ink is disclosed in JP-A-6-116522 and the like. Since the polymer is a conductive polymer, there has been a problem in ejection stability such as increase in ink viscosity and decap property.
Also, Japanese Patent Publication No. Sho 62-1426 and Japanese Patent Application Laid-Open No. 55-1576
No. 68, JP-A-3-160068 and 4-18427
Japanese Patent Laid-Open Publication No. H08-27139 proposes a relatively low-viscosity ink or an ink with improved ejection characteristics by adding a water-insoluble resin emulsion to a pigment ink, but is still insufficient in head clogging and ink dispersion stability. The above disadvantages have not been solved.

Even if such a resin emulsion is added to the ink, the pigment after printing does not penetrate and diffuse into the recording medium, but only exists on the surface of the recording medium. It was a matter of nature.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water-based pigment ink set for ink jet which can provide a glossy image, an image free of roughness and an image excellent in abrasion resistance on a recording medium. An object of the present invention is to provide an ink jet recording method using the pigment ink.

[0009]

The above object of the present invention is attained by the following constitutions.

[0010] 1. An ink-jet aqueous pigment ink set using two ink compositions having the same color but different colorant concentrations, wherein the two ink compositions have a pigment and thermoplastic resin fine particles in an aqueous medium. Water-based pigment ink set.

2. The same color but different colorant concentration 2
The concentration ratio (light ink / dark ink) of the aqueous pigment ink set for inkjet using two ink compositions is 0.5
2. The aqueous pigment ink set for inkjet according to the item 1, wherein the aqueous pigment ink set is from 0.1 to 0.1.

3. The water-based inkjet pigment ink according to 1 or 2, wherein the average particle size of the pigment in the ink composition is 10 nm to 200 nm, and the average particle size of the fine thermoplastic resin particles is 10 nm to 200 nm. set.

4. In the aqueous pigment ink set for inkjet using the ink composition having the different concentration,
The content of the pigment in the dark ink is P mass%, the content of the thermoplastic resin fine particles is B mass%, the content of the pigment in the light color ink is p mass%, and the content of the thermoplastic resin fine particles is b mass%. Wherein the following formula 1 is satisfied:
4. The aqueous pigment ink set for inkjet according to any one of items 3 to 3.

Equation 1 P / B ≧ p / b In the inkjet aqueous pigment ink set using the ink compositions having different concentrations, the ratio of the surface tension (γa) of the dark color ink to the surface tension (γb) of the light color ink is 1.2 ≦ γa / γb ≦ 0.8. The aqueous pigment ink set for inkjet according to any one of the above items 1 to 4, wherein

6. In the aqueous pigment ink set for inkjet using the ink composition, the glass transition temperature of the thermoplastic resin fine particles is from 50 ° C to 150 ° C, the aqueous inkjet ink according to any one of the above items 1 to 5, Pigment ink set.

[7] 7. An ink jet recording method for printing the ink composition of the aqueous pigment ink set for ink jet according to any one of 1 to 6 on a recording medium, comprising a step of heating at a temperature equal to or higher than the glass transition temperature of the thermoplastic resin fine particles. An ink jet recording method characterized by the following.

8. 8. The ink jet recording method according to the above item 7, wherein the recording medium is heated in advance at a temperature equal to or higher than the glass transition temperature of the plastic resin fine particles.

9. 8. The ink jet recording method according to the item 7, further comprising a step of heating the ink droplets at a temperature equal to or higher than a glass transition temperature of the thermoplastic resin fine particles after attaching the ink droplets to the recording medium.

Hereinafter, the present invention will be described in more detail. A pigment is used as a colorant in the ink composition of the present invention (hereinafter, also simply referred to as ink). As the pigment, conventionally known organic and inorganic pigments can be used.

For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelated azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthaloni pigments Dye lakes such as polycyclic pigments such as basic dye lakes and acid dye lakes; organic pigments such as nitro pigments, nitroso pigments, aniline black and daylight fluorescent pigments; and inorganic pigments such as carbon black. . In addition, any pigment that is not described in the color index can be used as long as it can be dispersed in water.

Preferred examples of the yellow pigment include:
C. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I.
I. Pigment Yellow 15, C.I. I. Pigment Yellow 17, C.I. I. Pigment yellow 73, C.I. I.
Pigment yellow 74, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment Yellow 180.

Preferred examples of the magenta pigment include:
C. I. Pigment Red 2, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I.
Pigment Red 184, C.I. I. Pigment Red 2
02.

Preferred examples of the cyan pigment include C.I.
I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I.
I. Pigment Blue 16, C.I. I. Pigment Blue 60.

Preferred examples of the black pigment include carbon black. The pigment of the present invention is preferably 0.01 to 10% by mass, more preferably 0.3 to 8% by mass, based on the total mass of the ink composition.

Examples of the pigment dispersant preferably used in the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, and the like.
Activator such as polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivative, vinyl Block copolymers having two or more monomers selected from naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, random copolymers Examples thereof include polymers and salts thereof.

As a method for dispersing the pigment, various types such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker may be used alone or in an appropriate combination. it can.

The pigment of the present invention has an average particle size of 10 nm to 50 nm.
It is preferably 0 nm, more preferably 10 nm to 200 nm. If the average particle diameter of the pigment exceeds 500 nm, the glossiness of the image recorded on the medium will be significantly deteriorated, and the transparency will be significantly deteriorated. Further, there is a problem that clogging is likely to occur in terms of ink dischargeability. When the average particle size of the pigment is less than 10 nm, the stability of the pigment dispersion is likely to deteriorate, and the storage stability of the ink is likely to deteriorate. The average particle size of the pigment is measured by light scattering, electrophoresis,
It can be determined by a commercially available particle size measuring device using a laser Doppler method or the like.

It should be noted that, during the preparation of the ink, it is possible to mix (mix and stir) the pigment in the form of an aqueous dispersion (solid content: 5 to 50% by mass) with other ink compositions from the viewpoint of the dispersion stability of the pigment. preferable.

The thermoplastic resin of the present invention includes styrene-acrylate copolymer, polyacrylate, polymethacrylate, polystyrene, polyethylacrylate, styrene-butadiene copolymer, butadiene copolymer. Coalescing, acrylonitrile-butadiene copolymer, cross-linked acrylic resin, cross-linked styrene resin,
Fluororesin, vinylidene fluoride, polyolefin resin,
Polyurethane resin, styrene-methacrylic acid ester copolymer, polystyrene, styrene-acrylamide copolymer, n-isobutyl acrylate, acrylonitrile, vinyl acetate, acrylamide, polyvinyl acetal, rosin resin, polyethylene, vinylidene chloride resin, vinyl acetate resin , Ethylene-vinyl acetate copolymer,
A vinyl acetate-acrylic copolymer or a vinyl chloride resin is exemplified.

The glass transition temperature of the thermoplastic resin of the present invention is preferably 50 to 150 ° C., more preferably 6 to 150 ° C.
0 ° C to 100 ° C. If the glass transition temperature is lower than 50 ° C., the preservability in the ink and the head is poor, and if it exceeds 150 ° C., the fixability on the recording medium is degraded.

Commercial products of the thermoplastic resin of the present invention include:
Nipol 2507 (styrene butadiene resin, Tg58
° C, average particle size 70 nm, Zeon Corporation), Nipol LX
303 (styrene butadiene resin, Tg 100 ° C., average particle size 160 nm, Zeon Corporation), Nipol LX416
(Styrene butadiene resin, Tg 50 ° C, average particle size 11
0 nm, Zeon Corporation), AE121 (acrylic resin,
Tg 58 ° C, average particle size 90 nm, JSR), AE14
0 (acrylic resin, Tg 53 ° C., average particle size 80 nm, J
SR Co., Ltd.), AE173 (acrylic resin, Tg 60 ° C., average particle size 80 nm, JSR Co., Ltd.), Takerak W-6015
(Urethane resin, Tg 85 ° C., average particle size 80 nm, Takeda Pharmaceutical Co., Ltd.), Takelac W-405 (Urethane resin, Tg
135 ° C., average particle size 80 nm, Takeda Pharmaceutical Co., Ltd., Mile Clogel E-1002 (styrene-acrylic resin, Tg
Approx. 60 ° C. Average particle size 100 nm Nippon Paint Co., Ltd., Mile Clogel E-5002 (Styrene-acrylic resin, Tg) Approx.
About 80 ° C, average particle size 100 nm, Daicel Chemical), Iodozol AD53 (acrylic resin, Tg 80 ° C, average particle size 80 nm, NCS Japan), Iodozol GD86B (styrene-acrylic resin, Tg 60 ° C, average particle size 90 nm)
Japan NCS).

The amount of the thermoplastic resin of the present invention is preferably 0.1 to 20% by mass, more preferably 1 to 18% by mass, based on the total mass of the ink composition.

The ink of the present invention may contain a water-soluble organic solvent if necessary. Examples of preferably used water-soluble organic solvents include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol,
Tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc., polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexane) Diol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol) Monobutyl ether, professional Lene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amine (For example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine , Tetramethylpro Amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, -Oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (eg, dimethyl sulfoxide), sulfones (eg, sulfolane), urea,
Acetonitrile, acetone and the like can be mentioned.

The ink of the present invention may contain a surfactant, if necessary. Surfactants preferably used in the ink of the present invention include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl allyl ethers. , Acetylene glycols, polyoxyethylene
Examples include nonionic surfactants such as polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used. Further, acetylene glycols are preferred.

The above-mentioned dispersant for pigments may be added to the ink. The addition amount of the surfactant is 0.05% by mass to 5% by mass based on the total mass of the ink composition.

The ink of the present invention may further contain a preservative, a fungicide, an antifoaming agent, a humectant, a pH adjuster, a viscosity adjuster, and the like, if necessary. When a humectant is contained, saccharides are preferred, and examples of saccharides include monosaccharides, disaccharides,
Oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides are mentioned, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucosyl, sorbitol, maltose, cellobiose, lactose, sucrose, trehalose. , Maltotriose and the like.

The ink of the present invention uses an ink set using two inks of the same color but different colorant concentrations in order to express a gradation that changes continuously and smoothly over a wide density range. At this time, the density ratio (light ink / dark ink) of both is preferably 0.5 to 0.1.

Further, when a smooth gradation is expressed by using dark ink and light ink, printing is performed by mixing dark ink and light ink, and gloss and scratch resistance are maintained in a wide density range. Is the content of the pigment in the dark ink as P mass%, the content of the thermoplastic resin fine particles B mass%, the content of the pigment in the light color ink as p mass%, and the content of the thermoplastic resin fine particles b mass% When it is, it is preferred that P / B ≧ p / b.

In the ink compositions of the present invention having different densities, the surface tension (γ
a) and the surface tension (γb) of the light-colored ink is 1.2 ≦
Preferably, γa / γb ≦ 0.8, and more preferably, 1.1 ≦ γa / γb ≦ 0.9.

In order to express smooth gradation over a wide range of densities and maintain glossiness and abrasion resistance over a wide range of densities, it is preferable that the surface tensions of inks having different densities be as uniform as possible.

The ink composition of the present invention can be used in any ink-jet recording method. In the invention of claims 7 and 8 of the present invention, the recording medium is heated to form the ink composition on the recording medium. It is characterized by being used in an inkjet recording method for fixing. In this heating step, an ink droplet is ejected from a print head to a pre-heated recording medium to form an ink image, or an ink droplet is ejected from the print head to a recording medium to form an ink image. Then, a heating step of heating the recording medium may be performed.

In the heating step in this case, it is necessary to sufficiently fix the ink composition of the present invention adhered to the recording medium, which is contained in the ink composition of the present invention.
The heating temperature of the present invention is required to be equal to or higher than the glass transition temperature of the thermoplastic resin fine particles because the thermoplastic resin fine particles are achieved by being fixed on the recording medium by the heat energy applied in the heating step. It is.

In the ink jet recording method of the present invention, one or more of the above ink compositions of the present invention can be used. In particular, the color ink jet recording of the present invention carried out using an ink composition of at least two colors. In the method, it is preferable to use two or more colors of the ink composition of the present invention.

That is, the above-mentioned yellow ink composition,
A color inkjet that forms a red image, a green image, and a blue image using an ink set that combines a magenta ink composition, a cyan ink composition, and a black ink composition, and superimposes three color (yellow, magenta, and cyan) ink images A recording method and a color ink jet recording method in which a black image is further superimposed with a black ink composition are preferred. Further, a color ink jet recording method of forming various images using at least one selected from a blue ink, a green ink and a red ink in addition to the above-described inks of the respective colors is also a more preferable embodiment of the present invention.

[0045]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

[Preparation of Pigment Dispersion] (Preparation of Yellow Dispersion 1) I. Pigment Yellow 74 20% by mass Styrene-acrylic acid copolymer (molecular weight 10,000, acid value 120) 12% by mass Diethylene glycol 15% by mass Deionized water Remaining amount is mixed, and 0.3 mm zirconia beads are mixed at a volume ratio of 6%.
A 0% -filled horizontal bead mill (Ashizawa Co., Ltd., System Zeta Mini) was used to disperse the yellow pigment dispersion 1
I got The average particle size of the obtained yellow pigment is 112 nm.
Met.

(Preparation of Magenta Dispersion 1) I. Pigment Red 122 25% by mass Joncryl 61 (acrylic-styrene resin, manufactured by Johnson) (solid content) 18% by mass Diethylene glycol 15% by mass Deionized water remaining amount is mixed, and zirconia beads of 0.3 mm are mixed in volume ratio. 6
A 0% -filled horizontal bead mill (Ashizawa Co., Ltd., System Zeta Mini) was used to disperse the magenta pigment dispersion 1
I got The average particle size of the obtained magenta pigment is 105 nm.
Met.

(Preparation of Cyan Dispersion 1) I. Pigment Blue 15: 3 25% by mass Joncryl 61 (acrylic-styrene-based resin, manufactured by Johnson) (solid content) 15% by mass Glycerin 10% by mass Deionized water The remaining amount is mixed, and the volume of 0.3 mm zirconia beads is mixed. 6 at a rate
The mixture was dispersed using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Corporation) filled with 0% to obtain a cyan pigment dispersion 1. The average particle size of the obtained cyan pigment was 87 nm.

(Preparation of Black Dispersion 1) Carbon black 20% by mass Styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150) 10% by mass Glycerin 10% by mass 0.3 mm zirconia beads in a volume ratio of 6
A 0% -filled horizontal bead mill (Ashizawa Co., Ltd., System Zeta Mini) was used to disperse the black pigment dispersion 1
I got The average particle size of the obtained black pigment was 75 nm.

[Preparation of Ink Composition] (Yellow Dark Ink 1) Yellow Dispersion 1 15% by mass Acrylic emulsion 10% by mass (Iodozol AD53 Tg 80 ° C. Average particle size 80 nm NCS Japan) Ethylene glycol 20% by mass Diethylene glycol 10% by mass Maltitol 5% by mass Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass Deionized water remaining amount Mix and stir the above composition, filter with a 1 μm filter,
An aqueous pigment ink of the present invention was produced. The average particle size of the pigment in the ink is 120 nm, and the surface tension γa is 36 mN.
/ M.

(Yellow light ink 1) Yellow dispersion 1 3% by mass Acrylic emulsion 10% by mass (Iodozol AD53 Tg 80 ° C. Average particle size 80 nm NCS Japan) Ethylene glycol 25% by mass Diethylene glycol 10% by mass Maltitol 10% by mass Surface activity Agent (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass of ion-exchanged water The remaining composition is mixed and stirred, and filtered with a 1 μm filter.
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 118 nm, and the surface tension γb was 37 mN / m.

(Magenta Dark Ink 1) Magenta Dispersion 1 15 mass% Styrene-acryl emulsion 10 mass% (Microgel E-1002 Tg about 60 ° C. Average particle size 100 nm Nippon Paint Co., Ltd.) Ethylene glycol 20 mass% Diethylene glycol 10 mass % Maltitol 5% by mass Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass Deionized water Remaining amount The above composition was mixed and stirred, and filtered with a 1 μm filter.
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 113 nm, and the surface tension γa was 35 mN / m.

(Magenta pale ink 1) Magenta dispersion 1 3% by mass Acrylic emulsion 8% by mass (Microgel E-1002 Tg about 60 ° C. Average particle size 100 nm Nippon Paint Co., Ltd.) Ethylene glycol 25% by mass Diethylene glycol 10% by mass Multi Toll 10% by mass Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass Deionized water remaining amount
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 110 nm, and the surface tension γb was 37 mN / m.

(Cyan Concentrated Ink 1) Cyan Dispersion 1 10% by mass Styrene-acryl emulsion 10% by mass (Iodozol GD86B Tg 60 ° C. Average particle size 90 nm NCS Japan) Ethylene glycol 20% by mass Diethylene glycol 10% by mass Maltitol 5% by mass Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass Deionized water Remaining amount The above composition was mixed and stirred, and filtered with a 1 μm filter.
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 95 nm, and the surface tension γa was 36 mN / m.

(Cyan light ink 1) Cyan dispersion 1 2% by mass Acrylic emulsion 10% by mass (Iodozol GD86B Tg 60 ° C. Average particle size 90 nm NCS Japan) Ethylene glycol 25% by mass Diethylene glycol 10% by mass Maltitol 10% by mass Surface activity Agent (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.2% by mass of ion-exchanged water The remaining composition is mixed and stirred, and filtered with a 1 μm filter.
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 92 nm, and the surface tension γb was 33 mN / m.

(Dark Black Ink 1) Black Dispersion 1 10% by mass Acrylic emulsion 8% by mass (Iodozol GD86B Tg 60 ° C. Average particle size 90 nm NCS Japan) Ethylene glycol 20% by mass Diethylene glycol 10% by mass Maltitol 5% by mass Surface activity Agent (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass of ion-exchanged water The remaining composition is mixed and stirred, and filtered with a 1 μm filter.
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 85 nm, and the surface tension γa was 35 mN / m.

(Black Light Ink 1) Black Dispersion 1 2% by mass Acrylic emulsion 8% by mass (Iodozol GD86B Tg 60 ° C. Average particle size 90 nm NCS Japan) Ethylene glycol 25% by mass Diethylene glycol 10% by mass Maltitol 10% by mass Surface activity Agent (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass of ion-exchanged water The remaining composition is mixed and stirred, and filtered with a 1 μm filter.
An aqueous pigment ink of the present invention was produced. The average particle size of the pigment in the ink is 89 nm, and the surface tension γa is 36 mN /
m.

(Comparative Black Dark Ink 1) Black Dispersion 1 10% by mass Acrylic emulsion 10% by mass (Iodozol GD86B Tg 60 ° C. Average particle size 90 nm NCS Japan) Ethylene glycol 20% by mass Diethylene glycol 10% by mass Maltitol 5% by mass Interface Activator (Na dioctyl sulfosuccinate: manufactured by Kao Corporation) 0.5% by mass Deionized water Remaining amount The above composition is mixed and stirred, and filtered with a 1 μm filter.
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 82 nm, and the surface tension γa was 28 mN / m.

(Comparative Black Deep Ink 2) Black Dispersion 1 15% by mass Ethylene glycol 25% by mass Diethylene glycol 10% by mass Maltitol 5% by mass Deionized water remaining amount The above compositions were mixed and stirred, and filtered with a 1 μm filter.
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 85 nm, and the surface tension γa was 45 mN / m.

(Comparative Black Light Ink 1) Black Dispersion 1 3% by mass Ethylene glycol 20% by mass Diethylene glycol 10% by mass Maltitol 5% by mass Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass Ion Exchange water remaining amount Mix and stir the above composition, filter through a 1 μm filter,
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 90 nm, and the surface tension γb was 36 mN / m.

(Comparative Black Dark Ink 2) Black Dispersion 1 2% by mass Ethylene glycol 25% by mass Diethylene glycol 10% by mass Maltitol 5% by mass Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.3% by mass Ion Exchange water remaining amount Mix and stir the above composition, filter through a 1 μm filter,
An aqueous pigment ink of the present invention was produced.

The average particle size of the pigment in the ink was 88 nm, and the surface tension γb was 32 mN / m.

(Printing test) Printing was performed using PM670C (Seiko Epson Corporation) at a recording density of 720 dpi.
(Dpi represents the number of dots per 2.54 cm) and printed with a glossy film dedicated to the print mode. Printing was performed using an optical densitometer with a maximum density of about 1.5 and a minimum density of about 0.25 in a pattern in which there were five levels of density gradation without bias from low density to high density.

The ink was refilled with a cyan light and dark cartridge in the present invention or the comparative dark and light ink set. When only the dark ink was compared with the dark ink alone, printing was performed by refilling the cartridge with the black ink. At this time, the pattern printed by refilling the dark and light inks is in a state where dark and light inks are mixed. The recording medium to be printed was thick Photoket QP paper manufactured by Konica Corporation.

(Heating Step) When printing the dark and light ink set of yellow and magenta of the present invention, the recording medium was heated in a 90 ° C. oven and then printed by a printer. At this time, the recording medium was heated with a drier from under the recording medium so that the temperature did not decrease during printing.

In the case of the dark and light ink set of cyan and black of the present invention and the comparative ink, after printing, the recording medium was subjected to a heat treatment by an apparatus in which a heating and fixing unit of a copying machine (u-box4345AF manufactured by Konica) was improved. At this time, the temperature of the recording medium surface was adjusted to 110 ° C.

(Evaluation of Glossiness) The evaluation sample image was reflected by an image clarity measuring device ICM-1DP (manufactured by Suga Test Machine Co., Ltd.).
The image clarity (gloss value C value%) at 0 ° and 2 mm of the optical comb was measured. The evaluation was performed according to the following criteria.

：: Gloss value C value% of 60% or more Δ: Gloss value C value% of 50 to less than 60% ×: Gloss value C value of less than% 50 (evaluation of roughness) The graininess such as sticking was observed and evaluated according to the following criteria.

：: No roughness in the entire density range. Δ: Roughness only in the low density range. ×: Roughness in the middle to low density range. (Evaluation of abrasion resistance) Density of evaluation sample 5 When the third density portion in the step was rubbed 10 times with an eraser (manufactured by MONO Tombow Pencil), the presence or absence of stains on the printed portion was visually determined.

：: Stain on the printed part is not observed. Δ: Stain on the printed part is slightly observed. △: Stain on the printed part is clearly observed. The above evaluation results are shown in Table 1.

[0080]

[Table 1]

[0081]

The aqueous pigment ink set for inkjet and the inkjet recording method using the pigment ink according to the present invention provide an image having excellent glossiness, an image having no roughness and an image having excellent scratch resistance on a recording medium. And has an excellent effect.

Claims (9)

[Claims] 1. An ink-jet aqueous pigment ink set using two ink compositions having the same color but different colorant concentrations, wherein the two ink compositions have a pigment and thermoplastic resin particles in an aqueous medium. A water-based pigment ink set for ink-jet, characterized by the following. 2. A concentration ratio (light ink / dark ink) of an aqueous pigment ink set for inkjet using two ink compositions having the same color but different colorant concentrations is 0.5 to 2.
The aqueous pigment ink set for inkjet according to claim 1, wherein the value is 0.1. 3. The ink composition according to claim 1, wherein the pigment has an average particle diameter of 10 nm to 200 nm, and the thermoplastic resin particles have an average particle diameter of 10 nm to 200 nm. Water-based pigment ink set for inkjet. 4. A light-color ink, wherein the pigment content in the dark ink is P mass%, and the content of the thermoplastic resin fine particles is B mass% in the ink-jet aqueous pigment ink set using the ink compositions having different concentrations. The following formula 1 is satisfied when the content of the pigment is p mass% and the content of the thermoplastic resin fine particles is b mass%.
4. The aqueous pigment ink set for inkjet according to any one of items 3 to 3. Formula 1 P / B ≧ p / b 5. The aqueous pigment ink set for inkjet using the ink compositions having different concentrations, wherein the ratio of the surface tension (γa) of the dark color ink to the surface tension (γb) of the light color ink is 1.2 ≦ γa / The aqueous pigment ink set for inkjet according to any one of claims 1 to 4, wherein? b? 0.8. 6. The aqueous pigment ink set for inkjet using the ink composition, wherein the glass transition temperature of the fine thermoplastic resin particles is 50 ° C. to 150 ° C. 2. The aqueous pigment ink set for inkjet according to item 1. 7. An ink jet recording method for printing the ink composition of the aqueous pigment ink set for ink jet according to any one of claims 1 to 6 on a recording medium, wherein the temperature is equal to or higher than the glass transition temperature of the fine thermoplastic resin particles. An ink jet recording method, comprising a step of heating with (i). 8. The ink jet recording method according to claim 7, wherein the recording medium is heated in advance at a temperature equal to or higher than the glass transition temperature of the plastic resin fine particles. 9. The ink-jet recording method according to claim 7, further comprising a step of heating the ink droplet at a temperature equal to or higher than the glass transition temperature of the thermoplastic resin fine particles after attaching the ink droplet to the recording medium.