JP2001254036A - Ink and recording method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink which has characteristics especially required of an ink for ink jet recording, is excellent in penetrating properties and dryability, and has been improved in image quality and strike through and to provide an excellent recording method using the ink. SOLUTION: This ink is a water-base ink which contains water, a pigment, and a wetting agent and further contains, based on the total wt. of the ink, 0.01-5 wt.% polyoxyethylene alkyl ether acetic acid salt represented by formula (I): R1-O-(CH2CH2O)m-CH2COOM (wherein R1 is an optionally branched 6-14C alkyl; m is a natural number of 3-12; and M is an alkali metal ion, a quaternary ammonium, a quaternary phosphonium or an alkanolamine) and 0.1-10 wt.% 2-ethyl-1,3-hexanediol.

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 suitable for ink jet recording such as an on-demand method such as a piezo method and a thermal method and a continuous ejection method such as a charge control method, and in particular, excellent characteristics as a color ink for so-called plain paper. A water-based ink composition, comprising:
It is also used as an aqueous ink for recorders and pen plotters.

[0002]

2. Description of the Related Art In recent years, ink-jet recording systems have rapidly spread in recent years due to their advantages of small size, low cost, low running cost, and low noise, and include electrophotographic transfer paper, printing paper, typewriter paper, and wire. Dot printer paper, word processor paper, letter paper,
Ink jet printers capable of printing on various types of non-coated plain paper such as report paper have also been put on the market.

[0003] In these ink jet printers, various proposals have been made to improve the drying property of the ink so as to obtain higher quality images.

However, the color reproducibility of an image, water resistance,
It is difficult to satisfy all of light fastness, image drying property, image bleeding and ejection reliability. In particular, in the case of a color printer, even if the image quality is not deteriorated in the single-color printing portion of yellow, magenta, and cyan, the image quality is likely to be deteriorated in a portion where two colors of red, green, and blue are overlapped. In particular, when drying is performed without using a fixing device, since the drying property is improved by increasing the permeability as disclosed in Japanese Patent Application Laid-Open No. 55-29546, the paper greatly bleeds on the paper.

Japanese Patent Publication No. 60-23793 discloses that dialkyl sulfosuccinate as a surfactant improves drying properties and causes less image deterioration. However, the pixel diameter of paper is remarkably different, and the image density decreases. There is a problem that the activator is decomposed on the alkali side and the activating effect is lost during storage. In addition, Japanese Patent Publication No. 58-6
No. 752 discloses a quick-drying ink with less bleeding by improving the permeability by using a surfactant which is an ethylene oxide adduct having an acetylene bond. However, inks using direct dyes such as DBK168 and inks using pigments such as carbon black, depending on the colorant, have a problem that the drying speed is not improved due to the hydrophobic interaction with the colorant. Also, in order to improve the drying speed, JP-A-8-113439 proposes an ink containing a dye and a water-soluble glycol ether. JP-A-10-95941 discloses a pigment and a diethylene glycol mono-oxide. An ink composition comprising a glycol ether such as n-butyl ether and water has been proposed.
However, in order to improve the drying speed, it is necessary to add a large amount of glycol ethers, which is not preferable in terms of ink odor and safety. Further, depending on the colorant, similar to the above-described surfactant having an acetylene bond,
A hydrophobic interaction occurs between the colorant and the glycol ether, and the drying speed is not improved, and a sufficient effect cannot be obtained.

Japanese Patent Application Laid-Open No. Sho 56-57862 discloses an ink to which a strong basic substance is added.
Rosin-sized acidic paper has an effect, but has no effect on paper using an alkyl ketene dimer or alkenyl sulfosuccinic acid as a sizing agent. In addition, even with acidic paper, there is no effect in the two-color overlapping portion.

JP-A-1-203483 discloses a recording liquid characterized by containing a polyhydric alcohol derivative and pectin. This recording liquid is prepared by adding pectin as a thickener to reduce bleeding. However, since pectin is nonionic having a hydroxyl group as a hydrophilic group, there is a problem in that the pectin lacks ejection stability after printing is stopped. Japanese Patent Application Laid-Open No. 2-36276 discloses 2-propanol as a component for improving frequency response and fixability, but has problems in safety such as toxicity and flammability.

Accordingly, the applicant of the present invention has disclosed Japanese Patent Application Laid-Open No. Hei 6-157959.
In order to enhance the permeability, Japanese Patent Application Laid-Open Publication No. H11-264, proposes an aqueous ink containing 2-ethyl-1,3-hexanediol and a recording method using the same.

This makes it possible to provide an aqueous ink recording composition which satisfies various properties as an ink-jet ink, has excellent permeability and drying properties, and has improved image quality deterioration. It was possible to provide a recording method for favorably forming an image, to provide a high-frequency drive ejection stability with a small amount of addition, and to provide a recording method using highly safe ink. .

However, even with an aqueous ink containing 2-ethyl-1,3-hexanediol, the image density is not yet sufficient, and clogging with an ink jet head, storage stability of the ink, and problems in use in double-sided printing. Even with strike-through, sufficient quality could not be obtained simply by adding 2-ethyl-1,3-hexanediol.

In general, conventional inks having high drying properties have the disadvantage that while penetrating the paper in the thickness direction of the paper, penetration through the paper is increased while improving the permeability to the paper. . From the viewpoint of the development of ink jet printers and paper consumption as an environmental problem, it is clear that double-sided printing is indispensable, and there is a need for a water-based ink capable of performing double-sided printing with little strikethrough.

As described above, even today, the ink-jet ink satisfies various characteristics as an ink-jet ink, and has excellent permeability and drying properties.
There is still a need for aqueous inkjet inks with improved image quality and strikethrough.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to provide an ink and a recording method which overcome the above-mentioned problems of the prior art. .

[0014]

Means for Solving the Problems The constitution of the present invention for solving the above problems is an ink and a recording method as described in claims 1 to 11.

In the present invention, in order to enhance the permeability to paper, a polyoxyethylene alkyl ether acetate represented by the following formula (I) is added in an amount of 0.01 to 5% by weight based on the total amount of the ink, and By adding ethyl-1,3-hexanediol in an amount of 0.1 to 10% by weight based on the total amount of the ink, it is possible to improve the wettability between the ink and the paper surface and to increase the penetration rate into the paper. Further, the inventors have found that image deterioration is extremely small as compared with conventionally known inks having increased permeability. Further, by using a pigment as a colorant, water resistance and light resistance are improved, and further, strike-through (hereinafter, simply referred to as strike-through) in which ink is removed from a layer of the recording medium and exudes to the back surface can be prevented. . Since the pigment is not dissolved in the ink but is dispersed therein, when printed by inkjet, it is harder to enter the recording medium than the liquid component of the ink in the recording medium and stays near the surface of the recording medium. It is fast but can prevent strikethrough. Further, the ink of the present invention has a feature that the penetration speed is substantially the same regardless of the pigment.

R 1 -O— (CH ₂ CH ₂ O) _m —CH ₂ COOM (I) (wherein, R 1 is an alkyl group having 6 to 14 carbon atoms and may be branched, and m is a natural number of 3 to 12) , M represents an alkali metal ion, a quaternary ammonium, a quaternary phosphonium, or an alkanolamine.)

Specific examples of the compound represented by formula (I) are shown below in free acid form.

[0018]

Embedded image And the like, but are not limited thereto.
These may be used alone or as a mixture of two or more. Commercially available surfactants containing the present compound as a main component include ECTD3NEX available from Nikko Chemicals Co., Ltd. (in the general formula, R1:
Tridecyl group, m: 3, M: Na), ECT3 (R1:
Tridecyl group, m: 3, M: H), ECTD6NEX
Surfactants such as (R1: tridecyl group, m: 6, M: Na) can also be used.

By using an alkali metal ion, quaternary ammonium, quaternary phosphonium or alkanolamine as a counter ion of the compound represented by the formula (I), excellent dissolution stability is exhibited. Further, when sodium, lithium and / or a quaternary ammonium, quaternary phosphonium, or alkanolamine cation represented by the following general formula (2) is used as a counter ion, the dissolution stability is further increased, which is more preferable.

[0020]

Embedded image (In the formula, Y represents nitrogen or phosphorus, and R _{1 to} R ₄ each represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, or a halogenated alkyl group.)

For example, in the case of a lithium salt, the reaction is carried out by adding lithium hydroxide, and the fourth compound represented by the general formula (2)
The quaternary ammonium, phosphonium and alkanolamine cations are specifically prepared by adding the following hydroxides.

[0022]

Embedded image

When the amount of the polyoxyethylene alkyl ether acetate is less than 0.01% by weight based on the total amount of the ink, the improvement in permeability becomes insufficient. It does not stably dissolve, causing problems in the storage stability of the ink and the stability of jetting by ink jet. Similarly, if the addition amount of 2-ethyl-1,3-hexanediol is less than 0.1% by weight with respect to the total amount of the ink, the improvement in permeability is insufficient, and if the addition amount is more than 10% by weight, It does not stably dissolve in the ink, causing problems in the storage stability of the ink and the jetting stability of the ink jet.

The mixing of polyoxyethylene alkyl ether acetate and 2-ethyl-1,3-hexanediol exhibits a synergistic effect, and achieves high permeability with a small amount of addition compared to ink containing each alone. Therefore, there is an advantage that the solvent smell is small as compared with a conventional ink having a high permeability by adding a large amount of ethers of a polyhydric alcohol or the like.

The present applicant has also found that the surface tension of the ink, particularly the dynamic surface tension in a short time period of 1 second or less after the surface is formed, is an index indicating the permeability to paper. Dynamic surface tension is a measurement of the surface tension of a solvent molecule or a penetrant molecule in the process of adsorbing to a surface, and after a sufficient time, is measured in a state where the above-mentioned molecules and the like have been completely adsorbed to the surface. The value is often different from the static surface tension. As a measuring method, any method can be used as long as it can measure a dynamic surface tension of 1 second or less by a conventionally known method described in JP-A-63-31237, etc., and particularly, the maximum bubble pressure method is preferable. . The maximum bubble pressure method is a method in which a capillary is placed vertically in a liquid, and the dynamic surface tension is obtained by measuring the maximum pressure required to discharge air generated by blowing air.

The present inventors used a BP-2 bubble pressure dynamic surface tensiometer manufactured by Cruz at 25 ° C. for a surface age of 10 ms to 1 for various ink formulations.
As a result of measuring the dynamic surface tension in the 000 ms region, polyoxyethylene alkyl ether acetate and 2-ethyl-
In an ink containing 1,3-hexanediol, the dynamic surface tension at a Surface Age of 50 ms was 40 mN /
m, particularly preferably 35 mN / m or less, not only high permeability can be obtained, but also storage stability of the ink,
The present inventors have found that the jetting stability in ink jet is also excellent, and have reached the present invention. In addition, the reduction in image density and the strike-through, which have been problems with the conventional penetrating type ink having increased permeability, are very small, and at the same time, a whisker-like bleeding phenomenon (referred to as feathering) seen at an image edge portion. Reduced.

Further, in a recording method such as a so-called bubble or thermal method in which thermal energy is applied to the ink to eject the ink as droplets from the fine holes to perform recording, conventionally, 2-propanol is used to obtain the ejection stability. Is added, but by adding 2-ethyl-1,3-hexanediol instead, the wettability to the thermal element is improved, and the ejection stability and frequency stability can be obtained even with a small amount of addition. Thus, safety issues associated with the use of 2-propanol are also improved.

Further, it has been found that when 2-pyrrolidone is added to the ink, an excellent effect of improving image density and preventing strikethrough is obtained. This is because, by containing 2-pyrrolidone, the ink easily wets and spreads on the paper surface, and the permeation in the thickness direction of the paper is relatively suppressed, so that the colorant easily stays near the paper surface. Is assumed. The amount of 2-pyrrolidone added is
Preferably it is 0.05% by weight to 8% by weight, more preferably 0.5% by weight to 4% by weight.

Further, the ink of the present invention contains 5% by weight to 50% by weight of a wetting agent for the purpose of preventing clogging due to drying of the ink and improving the dissolution stability of the ink of the present invention, so that the ink jet head can be used. The nozzles are designed to prevent clogging even if moisture in the ink evaporates, and to perform normal printing.Even if clogging occurs, normal cleaning can be restored by a simple cleaning operation. I found it. As the wetting agent, a low-volatile water-soluble organic solvent is preferable. The low-volatile water-soluble organic solvent acts as a dissolution aid for the polyoxyethylene alkyl ether acetate and 2-ethyl-1,3-hexanediol of the present invention, thereby further improving the storage stability and jetting stability of the ink. Can be increased.

The low volatile water-soluble organic solvents include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerin, 1,2,6- Polyhydric alcohols such as hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol and petriol;
Polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; ethylene glycol monophenyl ether; Polyhydric alcohol aryl ethers such as ethylene glycol monobenzyl ether; 2-pyrrolidone, N
-Methyl-2-pyrrolidone, N-hydroxyethyl-2
-Pyrrolidone, 1,3-dimethylimidazolidinone,
nitrogen-containing heterocyclic compounds such as ε-caprolactam and γ-butyrolactone; formamide, N-methylformamide,
Amides such as N, N-dimethylformamide; amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine and triethylamine; sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol; propylene carbonate; And ethylene. These solvents are used alone or in combination with water.

In particular, glycerin and diethylene glycol may be used alone or in combination from the viewpoints of compatibility with polyoxyethylene alkyl ether acetate and 2-ethyl-1,3-hexanediol, integrity, and price. It is suitable.

The amount of the low volatile water-soluble organic solvent added to the ink composition is from 5% by weight to 50% by weight as described above.
And preferably 8 to 30% by weight. If it is less than 5% by weight, the effect of suppressing water evaporation in the ink is insufficient, and depending on the contents of polyoxyethylene alkyl ether acetate and 2-ethyl-1,3-hexanediol in the ink, a dissolution aid is used. Is insufficient, and the storage stability and the ejection stability of the ink are impaired. Conversely, if more than 50% by weight is added, there is a problem that the jetting stability in the ink jet is deteriorated due to an increase in viscosity.

A surfactant may be further added to the ink of the present invention. Examples of the surfactant include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium laurate, and ammonium salts of polyoxyethylene alkyl ether sulfate;
Cationic surfactants such as quaternary ammonium salts, amphoteric surfactants such as imidazoline derivatives, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester,
Nonionic surfactants such as polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyethoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide additives of acetylene alcohol, and fluorine-based surfactants And the like.

The addition amount of these surfactants in the ink composition is from 0.01% by weight to 5.0% by weight, preferably from 0.5% by weight to 3% by weight. If the amount is less than 0.01% by weight, the effect of the addition is not obtained. If the amount is more than 5.0% by weight, the permeability to the recording medium becomes unnecessarily high, and there is a problem that the image density is reduced and strikethrough occurs.

Further, a penetrant can be further added for the purpose of adjusting the physical properties of the ink such as the surface tension. Specific examples of the penetrant include polyhydric alcohols such as diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, and tetraethylene glycol chlorophenyl ether. Examples thereof include alkyl and aryl ethers, and lower alcohols such as ethanol and 2-propanol, but are not limited thereto as long as they can be dissolved in ink and adjusted to desired physical properties.

As the pigment used as the coloring material, inorganic pigments and organic pigments can be used without any particular limitation. Inorganic pigments include titanium oxide and iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon produced by known methods such as a contact method, a furnace method, and a thermal method. Black can be used. Also, as an organic pigment,
Azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelated azo pigments, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, Thioindigo pigments, isoindolinone pigments, quinoflurone pigments, etc., dye chelates (eg, basic dye chelates, acidic dye chelates, etc.), nitro pigments, nitroso pigments, aniline black and the like can be used.

Among these pigments, those having good affinity for water are preferably used. The amount of the pigment added as a coloring agent in the ink composition is preferably about 0.5 to 25% by weight, more preferably about 2 to 15% by weight.

Specific examples of the pigment preferably used in the present invention include furnace black,
Carbon blacks (CI pigment black 7) such as lamp black, acetylene black and channel black; metals such as copper, iron (CI pigment black 11) and titanium oxide; aniline black (CI) And organic pigments such as CI Pigment Black 1). Further, for color, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 3
4, 35, 37, 42 (yellow iron oxide), 53, 55, 8
1,83,95,97,98,100,101,10
4, 408, 109, 110, 117, 120, 13
8, 150, 153, C.I. I. Pigment Orange 5,
13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31,
38, 48: 2, 48: 2 (Permanent Red 2B
(Ca)), 48: 3, 48: 4, 49: 1, 52:
2, 53: 1, 57: 1 (Brilliant Carmine 6
B), 60: 1, 63: 1, 63: 2, 64: 1, 8
1, 83, 88, 101 (Bengara), 104, 10
5, 106, 108 (cadmium red), 112, 1
14, 122 (quinacridone magenta), 123, 14
6, 149, 166, 168, 170, 172, 17
7, 178, 179, 185, 190, 193, 20
9, 219, C.I. I. Pigment Violet 1 (rhodamine lake), 3, 5: 1, 16, 19, 23, 3
8, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3 (phthalocyanine blue), 16, 17: 1, 56, 60, 6
3, C.I. I. Pigment Green 1, 4, 7, 8, 1
0, 17, 18, 36, etc.

Other pigments (for example, carbon) whose surface is treated with a resin or the like to make it dispersible in water,
A processed pigment or the like which can be dispersed in water by adding a functional group such as a sulfone group or a carboxyl group to the surface of a pigment (for example, carbon) can be used.

The pigment may be contained in microcapsules so that the pigment can be dispersed in water.

According to a preferred embodiment of the present invention, it is preferable that the pigment in the ink has an average particle diameter in a range of 50 nm to 200 nm. Here, the average particle size means a value of 50% by volume cumulative percentage. Volume cumulative percentage 5
To measure the value of 0%, for example, a laser beam is radiated to particles undergoing Brownian motion in the ink, and the frequency (light frequency) of light (backscattered light) returning from the particles changes. A method called a dynamic light scattering method (Doppler scattered light analysis) for obtaining a particle diameter from an amount can be used. When the average particle size is 50 nm or less, the effect of preventing strike-through is small, and when the average particle size is 200 nm or more, the ink has poor dispersion stability,
During storage, the particle size becomes large due to aggregation or the like, and the ejection stability is poor.

The pigment is preferably added to the ink as a pigment dispersion obtained by dispersing the pigment in an aqueous medium with a dispersant. As a preferred dispersant, a known dispersion used for preparing a conventionally known pigment dispersion can be used. Examples of the dispersant include the following.

Polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic ester copolymer, acrylic acid-alkyl acrylate copolymer, styrene-acrylic acid copolymer, styrene Methacrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methyl Styrene-acrylic acid copolymer-alkyl acrylate copolymer, styrene-
Maleic acid copolymer, vinylnaphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-
Examples include fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer and the like.

These copolymers have a weight average molecular weight of 3,
It is preferably from 000 to 50,000, more preferably from 5,000 to 30,000, and most preferably from 7,0.
00 to 15,000. The addition amount of the dispersant may be appropriately added within a range in which the pigment is stably dispersed and other effects of the present invention are not lost. As a dispersant, 1: 0.06-
A range of 1: 3 is preferred, more preferably 1: 0.12.
The range is 5 to 1: 3.

More preferably, the dispersant in the ink has a carboxyl group bonded thereto. When a carboxyl group is bonded to the dispersant, not only the dispersion stability is improved, but also high quality printing quality is obtained, and the water resistance of the recording medium after printing is further improved. Further, an effect of preventing the above strike-through is obtained. In particular, a pigment dispersed with a dispersant having a carboxyl group bonded thereto,
When 2-ethyl-1,3-hexanediol is used in combination, a sufficient drying speed can be obtained even when printing is performed on a recording medium having a relatively large size, such as plain paper, and strikethrough occurs. The effect of being small is obtained. This is because the dissociation constant of the carboxylic acid is small compared to other acid groups, so that after the pigment adheres to the recording medium, the pH value of the ink decreases, and polyvalent metals such as calcium existing near the surface of the recording medium. It is presumed that the solubility of the dispersant itself decreases due to interaction with ions and the like, and the dispersant itself and the pigment aggregate.

As another form, a form in which the pigment in the ink is surface-modified and a carboxyl group is directly bonded to the pigment and dispersed in water is also preferable. Again, because the pigment is surface-modified and the carboxyl groups are bonded, not only the dispersion stability is improved, but also high-quality printing quality is obtained, and the water resistance of the recording medium after printing is further improved. . In addition, since this type of ink has excellent re-dispersibility after drying, printing is paused for a long time, and even if the water in the ink near the nozzles of the inkjet head evaporates, clogging does not occur and a simple cleaning operation is easily performed. Printing can be performed.

The pigment for black ink used in these is preferably carbon black. As a black ink, carbon black is excellent in color tone, excellent in water resistance, light resistance, dispersion stability, and inexpensive.

The ink of the present invention contains the above-mentioned coloring agent, wetting agent,
Conventionally known additives other than the surfactant can be added.

For example, a resin emulsion may be added to the aqueous ink of the present invention. The resin emulsion that can be used in the present invention means an emulsion in which the continuous phase is water and the dispersed phase is the following resin component. Examples of the resin component of the dispersed phase include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acryl-styrene resins, butadiene resins, and styrene resins. This resin is preferably a polymer having both a hydrophilic part and a hydrophobic part. The particle size of these resin components is not particularly limited as long as an emulsion is formed, but is preferably about 150 nm or less, more preferably about 5 to 100 nm.

These resin emulsions can be obtained by mixing resin particles with water, if necessary, together with a surfactant.

Commercially available resin emulsions include Microgel E-1002 and E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd.),
Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.), Boncoat 5454
(Styrene-acrylic resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.), SAE-1014 (styrene-acrylic resin emulsion, manufactured by Zeon Corporation), Sibinol SK-200 (acrylic resin emulsion, Seiden Chemical Co., Ltd.) Manufactured). The ink used in the present invention is a resin emulsion,
Preferably, the resin component is contained in an amount of 0.1 to 40% by weight of the ink, more preferably 1 to 25% by weight.
Range.

The resin emulsion has the property of thickening and aggregating, has the effect of suppressing the penetration of the coloring component, and has the effect of promoting the fixation to the recording material. Further, depending on the type of the resin emulsion, a film is formed on the recording material, which has the effect of improving the abrasion resistance of the printed matter.

Further, the ink composition may contain sugar. Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, Lactose, sucrose, trehalose, maltotriose and the like. Here, the polysaccharide means a saccharide in a broad sense, and is used to include substances widely existing in nature such as α-cyclodextrin and cellulose.

The derivatives of these saccharides include reducing sugars of the aforementioned saccharides (for example, sugar alcohols (formula H
OCH ₂ (CHOH) _n CH ₂ OH (where n represents an integer of 2 to 5). ), Oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thioacids and the like. In particular, sugar alcohols are preferred, and specific examples include maltitol and sorbitol.

The content of these saccharides is suitably in the range of 0.1 to 40% by weight, preferably 0.5 to 30% by weight of the ink composition.

In addition, sodium alginate may be contained. Sodium alginate is a substance contained only in brown algae, and is a hydrophilic polymer electrolyte that mainly exists as a cell membrane or intercellular substance. Chemically, it is a polymer of D-Mannuronic acid [M] having β-1,4 bond and L-Guluronic acid [G] having α-1,4 bond. There are effects such as a thickening action, a stabilizing action, a dispersing action, a gelling action, and a film forming action. When added to an ink-jet ink, bleeding between different colors (color bleed) can be improved by viscosity change due to pH, precipitation by salts, and gelation with polyvalent cations.

As preservatives and fungicides, sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1
-Sodium oxide, sodium benzoate, sodium pentachlorophenol and the like can be used in the present invention.

As the pH adjuster, any substance can be used as long as it can adjust the pH to a desired value without adversely affecting the prepared ink.

Examples thereof include amines such as diethanolamine and triethanolamine; hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide; quaternary ammonium hydroxide; Examples include quaternary phosphonium hydroxides, carbonates of alkali metals such as lithium carbonate, sodium carbonate and potassium carbonate.

Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate and sodium uramil diacetate.

As the rust inhibitor, for example, acid sulfite,
Examples include sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

In addition, a water-soluble ultraviolet absorber and a water-soluble infrared absorber can be added according to the purpose.

The viscosity of the ink is preferably 8 mPa · s or less. If it is larger than 8 mPa · s, sufficient discharge cannot be performed by the ink jet, and a problem of image failure occurs.

The recording medium preferably contains pulp fiber as a main component and has a size of 10 s or more and an air permeability of 5 to 50 s. When printing is performed on such a recording medium with the ink of the present invention, even if printing is performed on both sides of the recording medium by the inkjet recording method, the image on the back surface does not hinder image recognition. The sizing degree referred to here is a test method for sekighito sizing degree of paper JIS P812.
2-76, What is air permeability? Air permeability test method JI for paper and paperboard
Performed according to SP8117-80. Size degree is 10s
If it is smaller, the ink penetrates to the back side and causes strike-through, and if the air permeability is smaller than 5 s, the ink penetrates to the back side and strike-through occurs. Although there is no problem, the cost is increased because the filler is added more than necessary. Also, when this recording medium is used in an electrophotographic copying machine or printer, the amount of paper transferred to the photoreceptor or fixing roller will cause deterioration of the image quality or cause a failure. It must be a burden for consumers to use properly. As a result, it can be handled in the same way as various uncoated plain papers such as electrophotographic transfer paper, printing paper, typewriter paper, wire dot printer paper, word processor paper, letter paper, report paper, etc. There is no need to separate it from plain paper. In addition, the production can be basically performed with the existing paper machine, and the capital investment can be minimized. Further, it can be commonly used for applications of these other recording methods.

As the material of the pulp fiber used in the present invention, any material that does not affect the ink jet process can be used irrespective of the type of pulp and the treatment method. Further, non-wood pulp (kenaf, flax, bamboo, seaweed, etc.) or waste paper pulp may be used or may be mainly used. Preferably L
It is a chemical pulp represented by BKP and NBKP. Papermaking of these pulp is carried out by a conventional method using a known sizing agent, filler, and other papermaking aids as required, as with ordinary plain paper.

As the sizing agent, rosin size, AKD,
Examples include sodium chloride, potassium chloride, styrene-maleic acid copolymer, quaternary ammonium salt, alnickel succinic anhydride, petroleum resin size, epichlorohidone, cationic starch, acrylamide and the like. Examples of the filler include clay, calcium carbonate, talc, titanium dioxide, synthetic silica and the like. Further, a paper strength enhancer, a retention enhancer, a fixing agent, a dye, and other papermaking auxiliaries are added.

The ejection amount per droplet ejected from the recording head is 25 pl or less, and the pixel area is 3000 μm ^2.
It is preferable that it is above. 3 with a discharge amount of 25 pl or less
When a pixel area of 2,000 μm ² or more is obtained, it indicates that the ink penetrates in the lateral direction rather than the depth direction of the recording medium as compared with the conventional ink, and therefore, it is possible to absorb the ink in the middle of the recording medium layer. It is possible to prevent the ink from penetrating to the back surface, prevent strike-through, and leave a colorant pigment near the surface of the recording medium, so that the image density is high.

If it is 25 pl or more, ink penetrates to the back surface of the recording medium and strike-through occurs. If the pixel area is 3000 μm ² or less, when a solid image is formed, the filling between dots is poor and a good solid image is formed. Can not get.

[0069]

(Examples) Examples of the present invention and comparative examples are shown below, but the present invention is not limited to these. The amounts (%) of the components described in the examples are on a weight basis.

Example 1 First, carbon black was dispersed using a bead mill according to the following dispersion liquid formulation. The resulting aqueous dispersion was mixed and stirred according to the following ink formulation, and then adjusted to a pH of 8.5 with a 10% aqueous solution of lithium hydroxide. Thereafter, the mixture was filtered through a membrane filter having an average pore diameter of 0.8 μm to obtain an ink composition.

Pigment dispersion 1 Carbon black (average particle size: 104 nm) 15% by weight Styrene-acrylate-methacrylic acid diethanolamine salt copolymer 3% by weight Deionized water Remaining ink composition 1 Pigment dispersion 1 33.3% by weight Diethylene glycol 15% by weight Glycerin 5% by weight Compound (1-1) 0.3% by weight 2-ethyl-1,3-hexanediol 3% by weight 2-pyrrolidone 2% by weight

Example 2 A pigment dispersion 2 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 2 was obtained using the dispersion.

Pigment dispersion 2 Carbon black (average particle size: 104 nm) 15% by weight Styrene-acrylate-diethanolamine methacrylate copolymer 3% by weight Deionized water Remaining ink composition 2 Pigment dispersion 2 33.3% by weight Diethylene glycol 13% by weight Glycerin 6.5% by weight Compound (1-1) 0.3% by weight 2-ethyl-1,3-hexanediol 1% by weight 2-pyrrolidone 2% by weight fluorinated alkyl ester; nonionic surfactant 0 0.3% by weight of ion-exchanged water

Example 3 A pigment dispersion 3 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 3 was obtained using the dispersion.

Pigment dispersion 3 Carbon black (average particle diameter 99 nm) 15% by weight Formalin condensate of naphthalene sulfonate 3% by weight Ion-exchanged water Ink composition 3 Pigment dispersion 3 33.3% by weight Diethylene glycol 15% by weight % Glycerin 5% by weight Compound (1-3) 0.3% by weight 2-ethyl-1,3-hexanediol 3% by weight fluorinated alkyl ester; nonionic surfactant 0.3% by weight Deionized water remaining amount

Example 4 A pigment dispersion 4 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 4 was obtained using the dispersion.

Pigment dispersion 4 C.I. I. Pigment Yellow 13 (average particle size: 117 nm) 15% by weight Styrene-acrylate-diethanolamine methacrylate salt copolymer 3% by weight Deionized water Residual ink composition 4 Pigment dispersion 4 33.3% by weight Polyethylene glycol (molecular weight 200) 5% by weight Ethylene glycol 6.5% by weight Compound (1-2) 0.05% by weight 2-ethyl-1,3-hexanediol 5% by weight 2-pyrrolidone 2% by weight Deionized water

Example 5 A pigment dispersion 5 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 5 was obtained using the dispersion.

Pigment dispersion 5 C.I. I. Pigment Yellow 74 (average particle size: 96 nm) 15% by weight Formalin condensate of naphthalene sulfonate 3% by weight Deionized water Remaining ink composition 5 Pigment dispersion 5 33.3% by weight Polyethylene glycol (molecular weight 200) 6.5 5% by weight of ethylene glycol 5% by weight of compound (1-2) 0.05% by weight of 2-ethyl-1,3-hexanediol 5% by weight of ethylene oxide (40% by weight) added polyethylene propylene glycol with a molecular weight of 3000 (nonionic surfactant) 3 Wt% ion exchange water

Example 6 A pigment dispersion 6 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 6 was obtained using the dispersion.

Pigment dispersion 6 C.I. I. Pigment Red 122 (average particle size: 120 nm) 15% by weight Styrene-acrylate-diethanolamine salt methacrylate copolymer 3% by weight Deionized water Remaining ink composition 6 Pigment dispersion 6 33.3% by weight Glycerin 5% by weight Ethylene glycol 5% by weight Compound (1-5) 0.5% by weight 2-ethyl-1,3-hexanediol 3% by weight 2-pyrrolidone 2% by weight Deionized water

Example 7 A pigment dispersion 7 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 7 was obtained using the dispersion.

Pigment dispersion 7 C.I. I. Pigment Red 57: 1 (average particle size 115 nm) 15% by weight Formalin condensate of naphthalene sulfonate 3% by weight Deionized water Residual ink composition 7 Pigment dispersion 7 33.3% by weight Glycerin 5% by weight Ethylene glycol 8 % By weight Compound (1-5) 0.5% by weight 2-ethyl-1,3-hexanediol 3% by weight 2-pyrrolidone 2% by weight Sodium dodecylbenzenesulfonate (anionic surfactant) 2% by weight Deionized water Remaining amount

Example 8 A pigment dispersion 8 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 8 was obtained using the dispersion.

Pigment dispersion 8 C.I. I. Pigment Blue 15: 3 (average particle size 123 nm) 15% by weight Styrene-acrylate-diethanolamine methacrylate copolymer 3% by weight Ion-exchanged water Remaining ink composition 8 Pigment dispersion 8 33.3% by weight Glycerin 10% by weight 1,5-pentanediol 6.5% by weight Compound (1-4) 1.0% by weight 2-ethyl-1,3-hexanediol 2% by weight Deionized water

Example 9 A pigment dispersion 9 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 9 was obtained using the dispersion.

Pigment dispersion 9 C.I. I. Pigment Blue 56 (average particle size: 138 nm) 15% by weight Formalin condensate of naphthalene sulfonate 3% by weight Deionized water Residual ink composition 9 Pigment dispersion 9 33.3% by weight Glycerin 10% by weight 1,5-pentane Diol 6.5% by weight Compound (1-4) 1.0% by weight 2-Ethyl-1,3-hexanediol 1.5% by weight Deionized water Remaining amount

Example 10 An ink composition 10 was obtained in the same manner as in Example 1 except that the following composition was used.

Ink composition 10 Carboxyl group-bonded type carbon black solid content 16.4 wt% dispersion Average particle size 128 nm 33.3 wt% Diethylene glycol 12 wt% Glycerin 4.5 wt% Compound (1-1) 1 wt% 2-ethyl-1,3-hexanediol 2% by weight 2-pyrrolidone 2% by weight Deionized water

Example 11 The procedure of Example 1 was repeated, except that the following composition was used.
A composition 11 was obtained. Ink composition 11 Carboxyl group-bonded carbon black solid content 16.4 wt% dispersion Average particle size 128 nm 33.3 wt% Diethylene glycol 12 wt% Glycerin 4.5 wt% Compound (1-1) 1 wt% 2-ethyl-1,3 -Hexanediol 2% by weight 2-Pyrrolidone 2% by weight Ethylene oxytoluene (40% by weight) -added polyfluoropropylene glycol Molecular weight 3000 (Nonionic surfactant) 0.3% by weight Ion exchange water Remaining

Example 12 An ink composition 12 was obtained in the same manner as in Example 1 except that the following composition was used.

Ink composition 12 Sulfonate group-bonded carbon black solid content 18% by weight Dispersion solution Average particle size 132nm 33.3% by weight Diethylene glycol 10% by weight Glycerin 6% by weight Compound (1-1) 1% by weight 2-ethyl -1,3-hexanediol 2% by weight 2-pyrrolidone 2% by weight

Example 13 An ink composition 13 was obtained in the same manner as in Example 1 except that the following composition was used.

Ink composition 13 Sulfonate group-bonded carbon black solid content 18% by weight Dispersion Average particle size 132 nm 33.3% by weight Diethylene glycol 10% by weight Glycerin 6% by weight Compound (1-1) 1% by weight 2-ethyl -1,3-hexanediol 2% by weight 2-pyrrolidone 2% by weight Sodium dodecylbenzenesulfonate (anionic surfactant) 1% by weight Deionized water

Example 14 A pigment dispersion 10 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 14 was obtained using the dispersion.

Pigment dispersion 10 Carbon black (average particle diameter 53 nm) 15% by weight Styrene-acrylate-diethanolamine methacrylate copolymer 3% by weight Ion exchange water Remaining ink composition 14 Pigment dispersion 10 33.3% by weight Diethylene glycol 23% by weight Glycerin 7.5% by weight Compound (1-6) 0.01% by weight 2-ethyl-1,3-hexanediol 10% by weight Deionized water

Example 15 A pigment dispersion 11 was prepared in the same manner as in Example 1 except that the following composition was used, and an ink composition 15 was obtained using the dispersion.

Pigment dispersion liquid 11 Carbon black (average particle size: 196 nm) 15% by weight Styrene-acrylate-methacrylic acid diethanolamine salt copolymer 3% by weight Ion exchange water Residual ink composition 15 Pigment dispersion liquid 11 33.3% by weight 1,5-pentanediol 5% by weight N-methyl-2-pyrrolidone 2% by weight Compound (1-3) 5% by weight 2-ethyl-1,3-hexanediol 0.1% by weight Deionized water

Comparative Example 1 The same amount of C.I. I. An ink composition 16 was prepared in the same manner as in Example 1 except that the ink composition contained Direct Black 168.

Comparative Example 2 The same amount of C.I. I. An ink composition 17 was produced in the same manner as in Example 2 except that the ink composition contained Direct Black 168.

Comparative Example 3 The same amount of C.I. I. An ink composition 18 was prepared in the same manner as in Example 4 except that Direct Yellow 142 was included.

Comparative Example 4 The same amount of C.I. I. Except for containing Direct Red 227, in the same manner as in Example 6,
Ink composition 19 was prepared.

Comparative Example 5 The same amount of C.I. I. Except for containing Direct Blue 199, in the same manner as in Example 8,
Ink composition 20 was prepared.

Comparative Example 6 An ink composition 21 was prepared in the same manner as in Example 1 except that the same amount of ion-exchanged water was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 7 An ink composition 22 was prepared in the same manner as in Example 2 except that the same amount of ion-exchanged water was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 8 An ink composition 23 was prepared in the same manner as in Example 4 except that the same amount of ion-exchanged water was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 9 An ink composition 24 was prepared in the same manner as in Example 6 except that the same amount of ion-exchanged water was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 10 An ink composition 25 was prepared in the same manner as in Example 8, except that the same amount of ion-exchanged water was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 11 An ink composition 26 was prepared in the same manner as in Example 1 except that the same amount of diethylene glycol monobutyl ether was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 12 An ink composition 27 was prepared in the same manner as in Example 2 except that the same amount of diethylene glycol monobutyl ether was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 13 Instead of 2-ethyl-1,3-hexanediol, 1
An ink composition 28 was prepared in the same manner as in Example 1 except that the composition contained 0% by weight of diethylene glycol monobutyl ether.

Comparative Example 14 An ink composition 29 was prepared in the same manner as in Example 4 except that the same amount of diethylene glycol monobutyl ether was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 15 An ink composition 30 was prepared in the same manner as in Example 6, except that the same amount of diethylene glycol monobutyl ether was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 16 An ink composition 31 was prepared in the same manner as in Example 8, except that the same amount of diethylene glycol monobutyl ether was used instead of 2-ethyl-1,3-hexanediol.

Comparative Example 17 Except for containing 3% by weight of Surfynol 465 (Shin-Etsu Chemical: acetylene glycol-based surfactant) instead of compound (1-1) and 2-ethyl-1,3-hexanediol Was prepared in the same manner as in Example 10.
2 was produced.

Comparative Example 18 The procedure of Example 1 was repeated, except that the same amount of 2-ethyl-2-methyl-1,3-propanediol was used instead of 2-ethyl-1,3-hexanediol. Ink composition 33 was produced.

Comparative Example 19 An ink was prepared in the same manner as in Example 2 except that the same amount of 3,3-dimethyl-1,2-butanediol was used instead of 2-ethyl-1,3-hexanediol. Composition 34
Was prepared.

Comparative Example 20 An ink was prepared in the same manner as in Example 4 except that the same amount of 2,4-dimethyl-2,4-pentanediol was used instead of 2-ethyl-1,3-hexanediol. Composition 3
5 was produced.

Comparative Example 21 An ink was prepared in the same manner as in Example 6 except that the same amount of 2,2-diethyl-1,3-propanediol was used instead of 2-ethyl-1,3-hexanediol. Composition 3
No. 6 was produced.

Comparative Example 22 An ink was prepared in the same manner as in Example 8 except that the same amount of 2,5-dimethyl-2,5-hexanediol was used instead of 2-ethyl-1,3-hexanediol. Composition 3
7 was produced.

Next, the following tests were performed on the inks described in the above Examples and Comparative Examples. Table 1 shows the results.

1) Measurement of Dynamic Surface Tension of Ink Surface Age 10 ms to 100 at 25 ° C. using a BP-2 bubble pressure dynamic surface tensiometer manufactured by Cruz.
The dynamic surface tension in the 0 ms area was measured, and Surface Age 50
The surface tension γ at (ms) was determined.

2) Sharpness of Image 720 × 720 dp using My Paper (size 12 s, air permeability 16 s) manufactured by NBS Ricoh Co., Ltd. as a recording medium
Printing is performed with a piezo-type inkjet printer having a resolution of i and discharging from a recording head at a discharge amount of 23 pl per droplet. After drying, image bleeding, color tone, and density are visually observed and reflected color spectral colorimetrically. Totally determined by a total meter (manufactured by X-Rite).

3) Drying property of image The image after printing the solid image on the recording medium is 0.1 kg / cm ^2.
The pressure was applied to the filter paper to measure the time until the ink did not transfer to the filter paper. When all of the papers were dried within 3 seconds, it was judged as ○, 3 to 20 seconds as Δ, and 20 seconds or more as ×.

4) Through-through A reflection type color spectrophotometer (X-Rite) was used as a recording medium.
The solid image was formed such that the density of each ink color measured by the method described in the above was 1.0. This image was visually observed from the back side, and when the colorant of the solid image was removed to the back side and the level could not be used for double-sided printing, x, the colorant of the solid image was not removed to the back side, but the solid image and the white background If the boundary of the part is clear and there is a problem when using it for double-sided printing, △, if the boundary between the solid image and the white background is almost unclear and there is no problem even when used for double-sided printing, When the boundary of the white portion was completely unclear and there was no problem even when used for double-sided printing, it was judged as ◎.

5) Abrasion The image formed with each ink on the recording medium was rubbed with a finger, a cloth, an eraser, and a marking pen 30 seconds after printing, and the state of the rubbing was visually observed. Was evaluated as x when there was no occurrence, and as o when there was no occurrence.

6) Pixel area (μm ² ) A dot image with an area ratio of 5% was formed so that each dot was printed apart, and measured with a dot analyzer.

7) Embedding of Image When the solid image is uniformly colored with the ink even after observing the solid image after drying and observing the enlarged image, 拡 大 indicates that the recording medium is uniformly uniform with the ink as long as it is visually observed. ○ if colored, × if uneven coloring such that the background can be seen visually
And

8) Storage Property With the ink set in the ink jet printer,
It was left at 60 ° C. for 7 days, and thereafter, it was evaluated as “good” if it could be recovered by one cleaning operation of a conventionally known ink jet printer, and if it could be recovered from 2 to 5 times, and “x” if it could not be recovered even after 5 times.

9) Water resistance The solid image formed with each ink on a recording medium was immersed in ion exchanged water at 30 ° C. for 60 seconds, and then 0.1 kg / cm ^2.
Press the filter paper with the pressure of. Colorant does not transfer to filter paper,
When there was no bleeding of the image, the colorant was slightly transferred to the filter paper. However, when there was no bleeding of the image, ○ was given. When the colorant was transferred to the filter paper and bleeding of the image occurred, x was given.

10) Light fastness A solid image formed with each ink on a recording medium was subjected to a dry bulb temperature of 5 using an Atlas weatherometer (xenon arc type, borosilicate / borosilicate filter).
0 ° C., humidity 50% RH, black panel temperature 63 ° C., irradiance 0.35 W / m ² (at 340 nm), 24 hours in all lighting modes (radiation energy at 340 nm of about 34
J / m ² ), and the fading rate was determined from the image density before and after the irradiation by the following equation. Light fading rate [%] = ((image density before light irradiation processing) − (image density after light irradiation processing)) / (image density before light irradiation processing) × 100 When the fading rate is 10% or more ×: 5 to 10%, Δ: 5% or less.

Examples 16 to 25 Using the inks described in Examples 1, 4, 6, and 8, printing was evaluated on the following recording media. Evaluation items are as described above. Example 16: Xerox Corporation; Xerox Paper R
(Size 8s, air permeability 20s) Example 17: AUSTRALIAN PAPER (Australia); REFLE
X (size 25 s, air permeability 4 s) Example 18: NBS Ricoh; NBS copy print paper 9
0K (size degree 60 s, air permeability 68 s) Example 19: manufactured by Canon Inc .; PB paper (size degree 21
s, air permeability 8 s) Example 20: NBS Ricoh; NBS copy printing paper 4
5K (size 11 s, air permeability 45 s) Example 21: Honshu Paper Co., Ltd .; Yamayuri (size 12
s, air permeability 21 s) Example 22: Ricoh; paper source PPC paper type S
(Size 22 s, air permeability 13 s) Example 23: Xerox Corporation; P paper (size 24
s, air permeability 19 s) Example 24: Xerox Corporation; Multi Ace (size degree 25 s, air permeability 17 s) Example 25: Xerox Corporation; Xerox 4024
Paper (size 32s, air permeability 21s)

Example 26: The ink jet printer was changed to a thermal type ink jet printer having a resolution of 720 × 720 dpi and discharging from a recording head at a discharge rate of 20 pl per droplet, and using the ink described in Example 1. And printed on My Paper (size 12s, air permeability 16s) manufactured by NBS Ricoh;
7) was evaluated.

Example 27 Evaluations 1) to 7) were performed in the same manner as in Example 26, except that the ink jet printer was changed to a thermal type ink jet printer that discharges from the recording head at a discharge amount of 30 pl per droplet. .

[0135]

[Table 1]

[0136]

As described above, according to the present invention,
By using a pigment as a coloring agent and adding a predetermined weight% of polyoxyethylene alkyl ether acetate having a predetermined structure and 2-ethyl-1,3-hexanediol, the wettability to the paper surface is improved, and the ink is used as an inkjet ink. It is possible to provide an aqueous ink composition which satisfies various characteristics, has high permeability and good drying property, has excellent image quality such as strike-through or image bleeding, and has improved image quality deterioration.

According to the present invention, Surface Ag measured at 25 ° C. by the maximum bubble pressure method with the above-described configuration.
e By using an ink whose surface tension at 50 ms is 40 mN / m or less, it shows good wettability even with various so-called plain papers, and has high permeability and image quality regardless of the type of paper. The water-based ink having excellent water resistance can be provided.

According to the present invention, by further adding 2-pyrrolidone, the paper surface is more easily wetted,
It is possible to provide a water-based ink composition in which permeation in the thickness direction of paper is relatively suppressed, image density is improved, and strikethrough is prevented.

According to the present invention, strike-through is further prevented by using a pigment having a predetermined particle size as a colorant.
An ink composition having improved dispersion stability can be provided.

According to the present invention, by using a dispersant having a carboxyl group bonded thereto as a pigment dispersant or a pigment having a carboxyl group bonded to the surface by modifying the pigment surface, strike-through is further prevented. An aqueous ink composition having improved water resistance can be provided.

According to the present invention, the use of carbon black as a black ink pigment provides excellent color tone,
It is possible to provide an inexpensive ink which is excellent in water resistance, light extinction property and dispersion stability and is inexpensive.

According to the present invention, there is provided a recording method which can uniformly exhibit good wettability even with various kinds of so-called plain paper and can form a color image having high permeability and excellent image quality regardless of the type of paper. Can be provided.

According to the present invention, in a recording method such as a so-called bubble or thermal method in which thermal energy is applied to ink to eject the ink as droplets from micro holes to perform recording, 2-ethyl-1,3-ethyl is used. By adding hexanediol, it is possible to provide a recording method in which the wettability to a thermal element is improved and the ejection stability and the frequency stability can be obtained with a small amount of addition.

By combining the ink of the present invention with a recording medium containing pulp fibers as a main component and having a size of 10S or more and an air permeability of 5 to 50S, the ink has excellent permeability, high image density, and strikethrough. It is possible to provide a recording method capable of forming a very small and very good image.

According to the present invention, by setting the ejection amount per droplet ejected from the recording head and the pixel area to predetermined values, it is possible to absorb ink halfway through the recording medium layer. Thus, it is possible to provide a recording method in which ink does not penetrate and an image with few strikethroughs suitable for double-sided printing can be formed, ink penetrates in the horizontal direction, and the solid image has good filling between dots, and has a high image density.

As described above, according to the present invention, it is possible to stably record a high-quality color image on plain paper, and it is possible to record at a high speed because of extremely high ink permeability. Since it is difficult for strikethrough to occur, double-sided printing on a recording medium is enabled, and this has the effect of promoting the further spread of inkjet color printers.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hitoshi Arita 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Akihiko Goto 1-3-6 Nakamagome, Ota-ku, Tokyo Share Inside Ricoh Company (72) Inventor Tomoko Sekine 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Masaji Murakami 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company F-term (Reference) 2C056 EA05 FC01 2H086 BA03 BA55 BA59 BA60 BA62 4J039 AE07 BA04 BA12 BC07 BC12 BC16 BC19 BC50 BC75 BE01 BE22 CA06 EA01 EA42 EA43 EA46 GA24

Claims (11)

[Claims] 1. A polyoxyethylene alkyl ether acetate represented by the following general formula (I) containing water, a pigment and a wetting agent, and 0.01 to 5% by weight based on the total weight of the ink.
An aqueous ink containing 0.1 to 10% by weight of 2-ethyl-1,3-hexanediol based on the total weight of the ink. _{R1-O- (CH 2 CH 2} O) m -CH 2 COOM ... (I) ( wherein, R1 is optionally branched alkyl group having 6 to 14 carbon atoms, m is a natural number of 3 to 12, M is Represents an alkali metal ion, quaternary ammonium, quaternary phosphonium, or alkanolamine.) 2. The aqueous ink according to claim 1, wherein the surface tension measured at 25 ° C. at a surface age of 50 ms by the maximum bubble pressure method is 40 mN / m or less. 3. The aqueous ink according to claim 1, which contains 2-pyrrolidone. 4. The pigment has an average particle size of 50 nm to 200 nm.
The aqueous ink according to any one of claims 1 to 3, wherein the aqueous ink has a range of nm. 5. The aqueous ink according to claim 1, wherein the pigment is dispersed in water by a dispersant, and a carboxyl group is bonded to the dispersant. 6. The aqueous ink according to claim 1, wherein the pigment is surface-modified, a carboxyl group is bonded, and the pigment is dispersed in water. 7. The aqueous ink according to claim 1, wherein the pigment is carbon black. 8. The water-based ink according to claim 1, which has a different color tone, is discharged as droplets from fine discharge ports.
A recording method characterized by forming a color image on a recording medium by flying. 9. An ink-jet recording method for recording on a recording medium by applying thermal energy to the ink to discharge the ink as droplets from micropores, wherein the aqueous ink according to claim 1 is used. A recording method characterized in that: 10. A recording medium comprising pulp fibers as a main component,
The size degree is 10S or more and the air permeability is 5S to 50S.
Or the recording method according to 9. 11. The ejection amount per one ejection from the recording head is 25 pl or less, and the pixel area is 3000 μm.
The recording method according to claim 8, characterized in that m ² or more.