JPH101629A - Water-color ink and ink jet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-color ink excellent in drying characteristics of printed image on plain paper, inhibiting bleeding of a printed material and strike-throughs of printed ink by containing a water-soluble coloring agent, water, a wetting agent, and a specific polymer compound. SOLUTION: This water-color ink is obtained by containing the coloring agent which disperses or dissolves in water, the wetting agent and polymer compounds of formula I [M is sodium, lithium, a quaternary ammonium or a quaternary phosphonium or an alkanol imine of formula II (X is N, P; R1 -R4 are each H, a 1-4C alkyl, hydroxylalkyl, etc.); x:y=25:75-75:25], having surface tension of <=50mN/m, suitable for ink jet recording, excellent in storage stability and discharging reliability after idle period of printing.

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, and more particularly to a water-based ink suitable for ink-jet recording, particularly a water-based ink exhibiting excellent characteristics for forming a color image on a so-called plain paper. The present invention relates to an inkjet recording method used.

[0002]

2. Description of the Related Art Inkjet printers have become widespread due to the advantages of low noise and low running cost, and color printers capable of printing on plain paper have also been put on the market. In recent years, in particular, the speed of color ink jet printers has been increased, and accordingly, there has been a demand for aqueous inks for ink jet recording that can dry images printed on recording paper such as plain paper quickly and obtain clear printed images. ing.

Conventionally, a surfactant has been added as a component of an aqueous ink in order to improve the drying property of a printed image. The role of the surfactant is to lower the surface tension of the water-based ink and increase the permeability of the water-based ink to the recording paper, thereby improving the drying property of the printed image.

[0004] However, if the permeability of the water-based ink into the recording paper is increased by using a surfactant, there is a problem that image bleeding occurs depending on the type of the recording paper and the sharpness of the image is reduced. In particular, in the case of a color ink jet printer, image bleeding occurs in the overlapped portion of two colors of red, green, and blue, and the sharpness of the image is degraded, even if there is no image bleeding in a single color printing portion of yellow, magenta, and cyan. There is a problem that it is easy to do.

Japanese Patent Publication No. 60-23793 discloses that a dialkyl sulfosuccinic acid is used as a surfactant to improve the drying property and reduce the deterioration of image quality. There is a problem that the pixel diameter in a printed image is significantly different and the image density is reduced, and when the pH of the aqueous ink is on the alkaline side, the surfactant is decomposed and the effect of the surfactant during storage of the aqueous ink is reduced. There is a disadvantage that it disappears. JP-A-56-57862 and the like disclose an aqueous ink to which a strongly basic substance is added to improve the drying property of a printed image. There is a drawback that recording paper using an alkyl ketene dimer or alkenyl sulfosuccinic acid as a sizing agent has no effect, and even an acidic paper has no effect on a printed image in a two-color overlapping portion. Also, Japanese Patent Laid-Open No. 1-2
Japanese Patent No. 03483 discloses an aqueous ink containing a polyhydric alcohol derivative and pectin, which adds pectin as a thickener to prevent bleeding. Pectin converts hydroxyl groups to hydrophilic groups. However, since it is nonionic, its solubility in water is poor, and there is a drawback in that the ejection reliability after printing pause and the storage stability of the aqueous ink are lacking.

Japanese Patent Application Laid-Open No. 6-240188 discloses a wrinkle by absorbing and drying an aqueous ink using an aqueous ink containing an alkylamine oxide as a surfactant and sodium alginate and 1,5 pentanediol as a water-soluble polymer. It is disclosed that the occurrence of cockling), the bleeding of the boundary of the color overlap portion, the bleeding of characters, etc. are improved. However, the occurrence of strikethrough of the water-based ink lowers the image density and lowers the sharpness of the image. In addition, if the dye is not a dye having poor water resistance, there is a drawback that the ejection reliability after printing pause is lacking.

Japanese Patent Application Laid-Open No. 6-92008 discloses that the drying property of printed images and image bleeding are improved by using an aqueous ink containing an acetylene alcohol-based surfactant and an alkylene glycol. However, there is a disadvantage that strikethrough of the aqueous ink cannot be sufficiently prevented.

Japanese Unexamined Patent Publication No. Hei 6-136306 discloses a water-based ink having a styrene-acrylic acid copolymer and excellent in permeability, particularly a fixed-head type ink-jet printer having sufficient discharge reliability. There was a problem that the property could not be obtained.

[0009]

In the conventional water-based ink for ink-jet recording, if the permeability of the water-based ink is increased to improve the drying property of the printed image, bleeding of the printed image occurs and the sharpness of the image deteriorates. In addition, if the bleeding of the printed image is prevented, the pixel diameter of the printed image changes and the image density is reduced, or the density of the printed image is reduced due to the occurrence of strikethrough of the aqueous ink, resulting in a lack of sharpness of the image. ,
In addition, there is a problem that the ejection reliability after printing suspension and the storage stability of the water-based ink are lacking, and it is difficult to obtain a water-based ink for ink-jet recording having excellent characteristics suitable for high-speed operation of a color ink-jet printer or the like. Was.

Accordingly, a first object of the present invention is to solve such problems, and in particular, to improve the drying property of an image printed on plain paper, and to prevent the occurrence of bleeding of a printed image and the occurrence of strike-through of ink. It is an object of the present invention to provide a water-based ink suitable for ink-jet recording that can obtain a small and clear printed image.

A second object of the present invention is to provide the above-mentioned water-based ink which is further excellent in the storage stability of the ink and the discharge reliability after printing is stopped.

A third object of the present invention is to provide an ink jet recording method which can cope with high speed operation and can obtain a clear printed image.

[0013]

SUMMARY OF THE INVENTION The object of the present invention is to provide a water-based ink having a surface tension of 50 mN / m or less containing a colorant dispersed or dissolved in water, water and a wetting agent as main components, and having at least the following general formula: Molecular weight of 80 shown in (1)
This is achieved by an aqueous ink characterized by containing 000 to 250,000 polymer compounds.

[0014]

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(Wherein, M represents an alkali metal, quaternary ammonium, quaternary phosphonium, or alkanolamine. X and y represent structural unit ratios, and x: y = 25: 75)
75:25. )

The high molecular compound represented by the general formula (1) is a hydrophilic high molecular compound obtained from vinylpyrrolidone and acrylic acid. Compared with sodium acrylate that has been added for, especially alkaline and stable water solubility, and also has a large ability to solubilize the dye that is a colorant, while having excellent discharge reliability of aqueous ink, Further, it is characterized by precipitation by divalent and trivalent inorganic salts such as calcium chloride and aluminum sulfate present in recording paper such as plain paper, thereby causing strikethrough and image bleeding on recording paper such as plain paper. The present inventors have found that a clear printed image with few occurrences of blemishes can be formed, and have reached the present invention.

In addition, although sodium acrylate has a remarkable adhesion of decomposition products to the thermal element (so-called kogation) and lacks ejection reliability, the polymer compound represented by the general formula (1) copolymerizes vinylpyrrolidone. This has also improved this point. In particular, the structural unit ratio x: y between the vinylpyrrolidone moiety and the acrylic acid moiety in the polymer compound represented by the general formula (1) is preferably from 25:75 to 75:25. When x exceeds this, the effect of preventing image bleeding is reduced.

That is, according to the present invention, a water-based ink containing a colorant that is dispersed or dissolved in water, water and a wetting agent as main components and having a surface tension of 50 mN / m or less is represented by the general formula (1). By containing a high molecular weight compound having a molecular weight of 80,000 to 250,000, it has particularly high permeability to plain paper, excellent drying property of printed images, can cope with high-speed printing, decreases image density due to strikethrough, and blurs images. It is possible to obtain a water-based ink suitable for ink-jet recording, which can form a clear printed image with less occurrence of ink droplets and has excellent ejection reliability.

The surface tension in the present invention is an index indicating the permeability of a liquid to paper, and is a dynamic surface tension in a short time of 1 second or less after the surface of the liquid is formed.
This is a value measured using a my-type hanging plate type surface tensiometer. Aqueous ink having a surface tension of 50 mN / m or less, especially 4
It is preferable that the aqueous ink having a molecular weight of 0 mN / m or less contains the polymer compound having a molecular weight of 80,000 to 250,000 represented by the above general formula (1), whereby more excellent drying properties can be obtained.

The amount of the polymer compound represented by the general formula (1) depends on the molecular weight distribution, but it is generally preferable to use from 0.01% by weight to 1% by weight of the aqueous ink. . If the amount is less than 0.01% by weight, the effect of preventing strike-through or image bleeding is insufficient. If the amount exceeds 1% by weight, the viscosity of the water-based ink becomes too high, and it becomes difficult to discharge at room temperature, which is excessive. It is not preferable because it requires energy.

In the polymer compound represented by the general formula (1), the counter ion M is sodium, lithium or a quaternary ammonium or a quaternary ammonium represented by the following general formula (2).
By using a quaternary phosphonium or alkanolamine cation, the dissolution stability of the polymer compound is improved, whereby an aqueous ink having more excellent storage stability and ejection reliability can be obtained. In particular, it is possible to improve reliability in ink jet recording in which ejection is performed by applying thermal energy.

[0022]

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(Wherein X is nitrogen or phosphorus, R ₁ , R ₂ ,
R ₃ and R ₄ are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
Represents a hydroxyalkyl group or a halogenated alkyl group. )

In the present invention, the surface tension of the aqueous ink can be reduced to 50 mN / m or less by adding a surfactant as conventionally known. By adding a polyoxyethylene alkyl ether acetate represented by (3) and / or a dialkyl sulfosuccinate represented by the following general formula (4) to reduce the surface tension to 50 mN / m or less,
The wettability between the aqueous ink and the recording paper is improved, the permeability of the aqueous ink is further increased, and the drying property of a printed image can be further improved. In addition, a polymer compound represented by the above general formula (1) is used. As a result, it is possible to form a clear printed image with further reduced image density due to strikethrough or the like, and less occurrence of image bleeding. It is estimated that the occurrence of image bleeding and the like is further reduced because the water-based ink is thickened by protons supplied from the surface of the recording paper.

[0025]

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Wherein R ₅ is a branched alkyl group having 6 to 14 carbon atoms, R ₆ is a branched alkyl group having 5 to 7 carbon atoms, M is an alkali metal, quaternary ammonium,
Represents a phosphonium or alkanolamine, and m represents an integer of 3 to 12. )

The amount of the anionic surfactant represented by the general formula (3) or (4) may be in the range of 0.
It is preferably used in the range of 0.05 to 10% by weight.
If the amount is less than 05% by weight, the permeability becomes insufficient and bleeding occurs at the boundary of the two-color overlapping portion, and the amount becomes 10% by weight.
If it exceeds, the surfactant itself is likely to precipitate at low temperatures,
In addition, a dye serving as a colorant may be deposited, resulting in poor discharge reliability. The counter ion M in the anionic surfactant represented by the general formula (3) or (4) may be sodium, lithium or a fourth ion represented by the following general formula (2).
By using a quaternary ammonium, quaternary phosphonium or alkanolamine cation, the solubility stability of the surfactant is improved, thereby obtaining a water-based ink having more excellent storage stability and ejection reliability especially at low temperatures. Can be. Further, reliability can be improved particularly in ink jet recording in which ejection is performed by applying thermal energy.

[0028]

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(Wherein X is nitrogen or phosphorus, R ₁ , R ₂ ,
R ₃ and R ₄ are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
Represents a hydroxyalkyl group or a halogenated alkyl group. )

When the specific examples of the anionic surfactant represented by the general formula (3) or (4) are shown in free acid form, for example, those shown in the following Table 1 or Table 2 can be mentioned.

[0031]

[Table 1]

[0032]

[Table 2]

In the polymer compound represented by the general formula (1) or the anionic surfactant represented by the general formula (3) or (4) in the present invention, the counter ion is an alkali metal ion, a quaternary ammonium, In order to obtain a quaternary phosphonium or alkanolamine ion, for example, a hydroxide of an alkali metal such as lithium hydroxide is added, and a quaternary ammonium, phosphonium,
Regarding the alkanolamine ion, for example, see Table 3 below.
May be added.

[0034]

[Table 3]

In the present invention, the counter ion of the polymer compound represented by the general formula (1) or the anionic surfactant represented by the general formula (3) or (4) is all sodium, lithium or It does not need to be a quaternary ammonium, quaternary phosphonium or alkanolamine cation represented by the formula (2), and can be mixed with other alkali ions. The amount of ions of sodium, lithium, quaternary ammonium, quaternary phosphonium or alkanolamine cation represented by the general formula (2) is at least 30 mol%, more preferably at least 50 mol%, per unit mol. It is preferable to add so as to be at least mol%.

In the present invention, a nonionic surfactant, in particular, a polyoxyethylene alkyl phenyl ether represented by the following formula (5) and / or an acetylene glycol-based surfactant represented by the following formula (6): By adding an agent to reduce the surface tension to 50 mN / m or less and using the polymer compound represented by the general formula (1), the wettability between the aqueous ink and the recording paper is improved, and the permeability of the aqueous ink is improved. Can be further improved, and the dryness of the printed image can be further improved, and a clear printed image can be formed in which the reduction in image density due to strikethrough or the occurrence of image bleeding is further reduced.

[0037]

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Further, by adding urea or a urea derivative such as hydroxyethyl urea or dihydroxyethyl urea together with these surfactants, the interaction between the colorant dye and the nonionic surfactant is reduced, and By relaxing the association, it is possible to obtain a water-based ink which further enhances the permeability, further improves the drying property of a printed image, and is excellent in long-term storage properties and ejection reliability. The amount of the urea or urea derivative to be added may be set at 0.
It is preferable to use it in the range of 1% by weight to 5% by weight.
If the amount is less than 0.1% by weight, the effect of the addition is not obtained. If the amount is more than 5% by weight, a change in viscosity at the time of water evaporation is affected, and the discharge reliability may be deteriorated.

In order to adjust the surface tension of the aqueous ink of the present invention, in addition to the above surfactants, for example, diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl Alkyl and aryl ethers of polyhydric alcohols such as ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, and tetraethylene glycol chlorophenyl ether, fluorine surfactants, and lower alcohols such as ethanol and 2-propanol may be added. Often, diethylene glycol monobutyl ether is particularly preferred.

The water-based ink of the present invention contains a wetting agent for the purpose of preventing drying of the water-based ink or improving the dissolution stability of the polymer represented by the general formula (1). Has been added.

Examples of the humectant include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5 pentanediol, 1,6 hexanediol, glycerol, 1,2,6-hexanetriol,
Polyhydric alcohols such as 1,2,4-butanetriol, 1,2,3-butanetriol and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,
Polyhydric alcohol alkyl ethers such as diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monophenyl ether,
Polyhydric alcohol aryl ethers such as ethylene glycol monobenzyl ether, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, etc. Nitrogen heterocyclic compound, formamide, N
Amides such as -methylformamide, N, N-dimethylformamide, amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine and triethylamine; sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol; Propylene carbonate, ethylene carbonate,
γ-butyrolactone and the like can be mentioned, and these can be used alone or in combination.

Of these, particularly preferred are diethylene glycol, thiodiethanol, polyethylene glycol 200 to 600, triethylene glycol, glycerol, 1,2,6-hexanetriol, 1,2,
4-butanetriol, petriol, 1,5-pentanediol, N-methyl-2-pyrrolidone, N-hydroxyethylpyrrolidone, 2-pyrrolidone, and 1,3 dimethylimidazolidinone. The solubility of the polymer compound represented by the formula (1) can be improved, and ejection failure due to moisture evaporation can be more effectively prevented.

The coloring material used in the present invention is a dye classified into an acid dye, a direct dye, a basic dye, a reactive dye and an edible dye in a color index and having excellent water resistance and light resistance. preferable.

Specific examples of these dyes include acid dyes and edible dyes such as C.I. I. Acid Yellow 17,2
3, 42, 44, 79, 142, C.I. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 3
7, 42, 52, 82, 87, 89, 92, 97, 10
6,111,114,115,134,186,24
9, 254, 289, C.I. I. Acid Blue 9,2
9, 45, 92, 249, C.I. I. Acid Black 1, 2, 7, 24, 26, 94, C.I. I. Food yellow 3, 4, C.I. I. Food red 7, 9, 14, C.I.
I. Food blacks 1 and 2 are C.I. I. Direct Yellow 1,12,24,26,3
3,44,50,86,120,132,142,14
4, C.I. I. Direct Red 1,4,9,13,1
7, 20, 28, 31, 39, 80, 81, 83, 8
9,225,227, C.I. I. Direct orange 2
6, 29, 62, 102, C.I. I. Direct Blue 1,2,6,15,22,25,71,76,79,8
6,87,90,98,163,165,199,20
2, C.I. I. Direct Black 19, 22, 32, 3
8, 51, 56, 71, 74, 75, 77, 154, 1
68, 171 and the like as C.I. I. Basic Yellow 1, 2, 11, 13, 14, 15, 19,
21,23,24,25,28,29,32,36,4
0, 41, 45, 49, 51, 53, 63, 64, 6
5, 67, 70, 73, 77, 87, 91, C.I. 1. basic. Red 2,12,13,14,15,18,
22, 23, 24, 27, 29, 35, 36, 38, 3
9, 46, 49, 51, 52, 54, 59, 68, 6
9, 70, 73, 78, 82, 102, 104, 10
9, 112, C.I. I. Basic Blue 1,3,5
7, 9, 21, 22, 26, 35, 41, 45, 47,
54, 62, 65, 66, 67, 69, 75, 77, 7
8,89,92,93,105,117,120,12
2,124,129,137,141,147,15
5, C.I. I. Basic Black 2, 8 and the like, and C.I. I. Reactive Black 3,4
7, 11, 12, 17, C.I. I. Reactive yellow 1,5,11,13,14,20,21,22,25,
40, 47, 51, 55, 65, 67, C.I. I. Reactive Red 1,14,17,25,26,32,3
7,44,46,55,60,66,74,79,9
6,97, C.I. I. Reactive Blue 1,2,7,1
4,15,23,32,35,38,41,63,8
0, 95 and the like. Particularly, acid dyes and direct dyes are preferred.

Further, a dye newly developed for ink jet can of course be used.
et Fast B1ack 2, Projet Fast
Magenta 2, Projet Fast Yellow
ow 2, Projet Fast Cyan 2 (registered trade name, manufactured by Zeneca Corporation). Further, as a pigment used as a coloring material, azo-based, phthalocyanine-based, anthraquinone-based, quinacridone-based, dioxazine-based, indigo-based, thioindigo-based organic pigments,
Perylene, isoindolenone, aniline black,
Azomethine-based, rhodamine B lake pigment, carbon black, etc., and inorganic pigments include iron oxide, titanium oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, navy blue, cadmium red, chrome yellow, metal powder, etc. Can be

A hydrophilic polymer may be added as a pigment dispersant. Examples of the hydrophilic polymer include natural gums such as gum arabic, gum tragan, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, and the like.
Plant macromolecules such as quince seed starch, alginic acid, carrageenan, seaweed macromolecules such as agar, gelatin,
Animal macromolecules such as casein, albumin, collagen, shellac and the like, microbial macromolecules such as xanthene gum, dextran, etc. -Based polymers, starch-based polymers such as sodium starch glycolate and sodium starch phosphate; seaweed-based polymers such as sodium alginate and propylene glycol alginate; and purely synthesized systems include polyvinyl alcohol, polyvinylpyrrolidone, and polyvinylmethyl. Vinyl polymers such as ether, non-crosslinked polyacrylamide, polyacrylic acid and alkali metal salts thereof, acrylic resins such as water-soluble styrene acrylic resin, water-soluble styrene polymer Formic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic acid resin, polyvinylpyrrolidone, polyvinyl alcohol, alkali metal salt of β-naphthalenesulfonic acid formalin condensate, cationic functional groups such as quaternary ammonium and amino groups And a polymer compound having a salt of the above in the side chain.

The aqueous ink of the present invention may further contain conventionally known additives. For example, as a preservative / antifungal agent, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol and the like can be used.

As the pH adjuster, any substance can be used as long as it can adjust the pH to 7 or more without affecting the prepared aqueous 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, and quaternary ammonium hydroxide. Grade phosphonium hydroxide, or carbonates of alkali metals such as lithium carbonate, sodium carbonate and potassium carbonate.

As the chelating reagent, for example, sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate and the like can be used. Salt, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite and the like can be used. In addition, a water-soluble ultraviolet absorber or a water-soluble infrared absorber can be added according to the purpose.

Further, in the aqueous ink of the present invention,
By adjusting the pH to 6 or more, especially 6 or more and 11 or less, the storage stability of the aqueous ink is further improved, and the precipitation of precipitates and changes in physical properties such as surface tension and viscosity even after long-term storage. And a clear printed image can always be obtained. However, when the pH is 9 or more, the activator of (4) is likely to undergo a change in physical properties due to decomposition during storage, so that when (4) is used, the pH is preferably 6 to 9.

By using the aqueous ink of the present invention,
Excellent drying properties for plain paper and coated paper for inkjet,
In addition, it is possible to form a clear printed image with less occurrence of bleeding or strike-through, and it is possible to perform inkjet recording excellent in color reproducibility of a color image. In addition, inkjet recording with excellent color reproducibility of a color image can be performed on a film for an overhead projector.

Many ordinary papers such as copy paper and tag paper generally used in offices have a pH of 5 to 6, and the aqueous ink of the present invention can be applied to these recording materials by heat energy or mechanical energy. By causing the droplets to fly as fine droplets by the energy and to adhere to the recording material, it is possible to stably form a clear printed image which is excellent in drying property and has little occurrence of bleeding or strike-through.

In particular, by forming a print image on so-called plain paper having a Stighit sizing degree of 3 seconds or more by the above-described method, a high-quality, high-resolution print image can be obtained. More specifically, the formation of a printed image is performed, for example, by applying the aqueous ink of the present invention to a fine ejection port having a diameter of 20 to 60 μm by applying thermal energy or mechanical energy to the aqueous ink.
This is performed by flying at a speed of 5 to 20 m / s as a droplet of 0 ng to 160 ng and attaching the droplet to a recording material.

[0054]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. Example 1 A composition having the following formulation was stirred and dissolved at 60 ° C., allowed to cool at room temperature, and then adjusted to a pH of 8.5 with a 10% aqueous solution of lithium hydroxide. The aqueous ink 1 was obtained by filtration with a Teflon filter. Projet Fast B1ack 2 (manufactured by Zeneca) 3% by weight Glycerol 5% by weight N-hydroxyethylpyrrolidone 5% by weight Polymer compound free acid type of the general formula (1) (x: y = 75: 25, molecular weight 250,000) 0 0.1% by weight Surfactant of the specific example (3-1) 0.8% by weight Sodium dehydroacetate 0.2% by weight Deionized water

Example 2 The following composition was used, and the pH was adjusted with sodium hydroxide.
8, the aqueous ink 2 was prepared in the same manner as in Example 1.
I got Projet Fast Magenta 2 (Zeneca) 1.5% by weight Direct Red 227 0.5% by weight 1,2,6-Hexanetriol 4% by weight 1,5-pentanediol 8% by weight The above specific example (4-1) ) Surfactant 1.2% by weight 0.8% by weight of 25% aqueous solution of the specific example (2-1) Polymer compound free acid type of the general formula (1) (x: y = 50: 50, molecular weight) 250,000) 0.2% by weight 2-pyridinethiol-1-oxide sodium 0.2% by weight Deionized water

Example 3 Using the following composition, the pH was adjusted to 8.5 with lithium hydroxide.
Aqueous ink 3 was obtained in the same manner as in Example 1 except that the adjustment was made as follows. Projet Fast Cyan 2 (manufactured by Zeneca) 1% by weight C.I. I. Direct Blue 199 1.2% by weight Diethylene glycol 5% by weight Glycerol 5% by weight Polymer compound free acid type of the general formula (1) (x: y = 25: 75, molecular weight 250,000) 0.1% by weight The general formula ( 5) Surfactant (R ₇ : C ₉ H ₁₉ , k: 12) 2% by weight 0.2% by weight of 25% aqueous solution of the specific example (2-3) 0.2% by weight sodium dehydroacetate Deionized water Remaining amount

Example 4 Using the following composition, the pH was adjusted to 7.5 with lithium hydroxide.
Aqueous ink 4 was obtained in the same manner as in Example 1 except that the adjustment was made as follows. Projet Fast Yellow 2 (manufactured by Zeneca) 1.2% by weight Ethylene glycol 5% by weight Glycerol 2% by weight 1,5-pentanediol 10% by weight Surfactant of the general formula (6) (m, n = 20) 0 0.8% by weight 25% aqueous solution of the specific example (2-4) 2% by weight Polymer compound free acid type of the general formula (1) (X: Y = 75: 25, molecular weight 80000) 0.2% by weight Benzo 0.2% by weight sodium ion deionized water

Example 5 Using the following composition, the pH was adjusted to 7.0 with sodium hydroxide.
8, the aqueous ink 5 was prepared in the same manner as in Example 1.
I got C. I. Direct Black 168 4% by weight Triethylene glycol 5% by weight Petriol 10% by weight Activator of specific example (3-5) 2% by weight 25% aqueous solution of specific example (2-2) 1.5% by weight Polymer compound free acid form of 1) (x: y = 50: 50, molecular weight: 80,000) 0.2% by weight 2-pyridinethiol-1-oxide sodium 0.2% by weight Deionized water

Example 6 Using the following composition, the pH was adjusted to 8.0 with lithium hydroxide.
A water-based ink 6 was obtained in the same manner as in Example 1 except that the adjustment was made as follows. C. I. Food black 2 1.5% by weight C.I. I. Direct black 154 0.5% by weight Propylene glycol 8% by weight Glycerol 7% by weight Surfactant of the general formula (6) (m + n = 15) 1% by weight Surfactant of the general formula (6) (m, n = 0) 1% by weight 25% aqueous solution of the specific example (2-7) 2% by weight Sodium dehydroacetate 0.2% by weight Polymer compound free acid type of the general formula (1) (x: y = 25: 75, molecular weight 80000) 0.3% by weight Urea 2% by weight Deionized water

Example 7 Using the following composition, the pH was adjusted to 8.0 with lithium hydroxide.
A water-based ink 7 was obtained in the same manner as in Example 1 except that the adjustment was made as follows. C. I. Direct Red 9 1.8% by weight C.I. I. Acid Red 289 0.5% by weight N-methyl-2-pyrrolidone 8% by weight 1,5-pentanediol 8% by weight Surfactant of the specific example (3-4) 0.8% by weight The general formula (1) High molecular compound free acid form (x: y = 25: 75, molecular weight 80000) 0.2% by weight Sodium benzoate 0.1% by weight Urea 1% by weight Ion-exchanged water

Example 8 Using the following composition, the pH was adjusted to 7.5 with lithium hydroxide.
A water-based ink 8 was obtained in the same manner as in Example 1 except that the adjustment was made as follows. C. I. Direct Blue 199 2.0% by weight C.I. I. Acid Blue 249 0.5% by weight Thiodiethanol 5% by weight Glycerol 10% by weight Surfactant (R ₇ : C ₁₀ H ₂₁ , k: 12) of the above general formula (5) 1.5% by weight of the above general formula (1) )) Polymer free acid form (x: y = 25: 75, molecular weight 80000) 0.4% by weight Sodium benzoate 0.1% by weight Deionized water

Example 9 Using the following composition, the pH was adjusted to 8.0 with lithium hydroxide.
Aqueous ink 9 was obtained in the same manner as in Example 1 except that the adjustment was carried out. C. I. Direct Yellow 142 1.5% by weight C.I. I. Acid Red 23 1.0% by weight 2-Pyrrolidone 5.0% by weight Glycerol 15.0% by weight Surfactant (m + n = 40) of the general formula (6) 1.0% by weight The specific example (3-2) Surfactant 1.0% by weight Free acid type of polymer compound of general formula (1) (x: y = 25: 75, particle size: 80000) 0.2% by weight Sodium pentachlorophenol 0.2% by weight Ion Exchange water level

Comparative Example 1 An aqueous ink 10 was obtained in the same manner as in Example 1 except that the polymer compound of the general formula (1) was omitted.

Comparative Example 2 Example 2 was repeated except that polyvinyl alcohol was used in place of the polymer compound of the general formula (1), and that the surfactant in the specific example (4-1) was changed to dodecylbenzenesulfonic acid. A water-based ink 11 was obtained in the same manner as in 2.

Comparative Example 3 In Example 3, sodium polyacrylate was used in place of the polymer compound of the general formula (1), and the pH of the aqueous ink was changed to 4. except for the 25% aqueous solution of the specific example (2-3). A water-based ink 12 was obtained in the same manner as in Example 3, except that the ink was set to 5.

Comparative Example 4 Example 3 was repeated except that a styrene-acrylic acid copolymer was used in place of the polymer compound of the general formula (1).
In the same manner as in the above, an aqueous ink 13 was obtained.

Comparative Example 5 An aqueous ink 14 was obtained in the same manner as in Example 4 except that sodium alginate was used instead of the polymer compound of the general formula (1).

Comparative Example 6 In Example 6, a styrene-acrylic acid copolymer was used in place of the polymer compound of the general formula (1).
Remove the 25% aqueous solution of 7) and adjust the pH to 8 with potassium hydroxide.
Aqueous ink 15 in the same manner as in Example 6 except that
I got

Comparative Example 7 An aqueous ink 16 was obtained in the same manner as in Example 7 except that the polymer compound of the general formula (1) and urea were omitted.

Comparative Example 8 An aqueous ink 17 was obtained in the same manner as in Example 8, except that pectin was used instead of the polymer compound of the general formula (1).

Comparative Example 9 Example 9 was the same as Example 9 except that the polymer compound of the general formula (1) was replaced with a vinyl acetate polymer and the surfactant of the specific example (3-2) was omitted. And aqueous ink 18
I got

Next, Example 1 obtained as described above was used.
The following tests were performed using the aqueous inks of Comparative Examples 1 to 9 and Comparative Examples 1 to 9. Table 4 shows the results. 1) Clarity of image Nozzle diameter of thermal inkjet system 30 μm, 60
An inkjet printer having a nozzle of 0 dpi,
And nozzle diameter 2 using laminated PZT for pressurizing the liquid chamber flow path
Using an ink jet printer having a nozzle of 7 μm and 600 dpi, printing was performed on three types of recording paper, commercially available recycled paper, woodfree paper and bond paper, using each aqueous ink. For each printed image, blurring at the boundary of the two-color overlapped portion, image blurring, color tone, image density, and strike-through were comprehensively visually judged and evaluated according to the following criteria. …: All characteristics were excellent. Δ: One of the characteristics was not satisfied. X: Two characteristics of blurring at the boundary of the two-color overlapped portion and image blurring were not satisfied.

2) Drying of Image A filter paper was applied to the printed image according to the above 1) at a pressure of 30 g / cm ² , after 2 seconds, after 4 seconds, after 6 seconds, after 8 seconds, after 10 seconds.
After 12 seconds, the time until the pressing ink was not transferred to the filter paper was measured. 10 for any of the three types of recording paper
Ink stopped transferring to filter paper within 2 seconds (dry)
In this case, the evaluation was evaluated as ○, when the ink did not transfer to the filter paper (dry) in 11 seconds or more and less than 40 seconds, and evaluated as x when the ink did not transfer to the filter paper (dry) in 40 seconds or more.

3) Storage stability Each aqueous ink was placed in a polyethylene container and stored at -20 ° C.
The solution was stored for 3 months under the conditions of ° C, 20 ° C, and 70 ° C, and the surface tension, viscosity, and the presence or absence of precipitates after storage were examined. No change in physical properties, etc., regardless of the conditions of storage, was marked as ○, and any change in physical properties was recognized as い ず れ.
The sample having a precipitate was evaluated as x.

4) Reliability at the time of pause of printing During the operation of a piezo-type inkjet printer having four heads each having a diameter of 30 μm and 128 nozzles using each aqueous ink, printing was paused for a certain period of time without capping. When printing was restarted without cleaning, the ejection time was shifted or the pause time until the weight of the ejected droplets changed was measured, and the reliability was evaluated according to the following criteria. . …: Good injection stability was always shown. Δ: A change in the ejection direction or a significant change in the weight of the discharged droplet occurred within 600 seconds or less. ×: clogging occurred within 600 seconds or less.

5) Water resistance of image The printed image sample obtained in 1) was immersed in water at 30 ° C. for 1 minute, and the change in image density before and after immersion was measured with a Macbeth densitometer. Water resistance (% fading) was determined. Fading rate (%) = [1− (image density after processing / image density before processing)] × 100 Any of the three types of recording paper having a recording density of less than 20% is evaluated as ○, 20% or more and less than 30%. Was evaluated as Δ, and 30% or more was evaluated as x.

[0077]

[Table 4]

As is clear from Table 4, by using the aqueous ink of the present invention for ink-jet recording, it is possible to obtain a clear printed image which is excellent in image drying properties and has less occurrence of image bleeding and ink strike-through. Can be. Further, the aqueous ink of the present invention is excellent in storage stability and ejection reliability after printing is stopped.

[0079]

According to the present invention, in particular, an ink-jet ink which is excellent in drying property of an image printed on plain paper, has less bleeding of the printed image and less occurrence of ink strike-through, and can obtain a clear printed image. An aqueous ink suitable for recording can be obtained.

Further, according to the present invention, it is possible to obtain the above-mentioned water-based ink which is further excellent in the storage stability of the ink and the discharge reliability after printing is stopped.

Further, according to the present invention, it is possible to cope with high speed,
In addition, it is possible to perform ink jet recording in which a clear printed image is obtained.

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[Table 1]

[Table 2]

[Table 3]

[Table 4]

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Ikuko Yamada 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (8)

[Claims] 1. An aqueous ink having a surface tension of 50 mN / m or less containing a coloring agent dispersed in or dissolved in water, a water and a wetting agent as main components and having a molecular weight of at least 80,000 to 250,000 represented by the following general formula (1). A water-based ink containing a polymer compound. Wherein M represents an alkali metal ion, a quaternary ammonium, a quaternary phosphonium, or an alkanolamine ion. X and y represent structural unit ratios, and x: y = 2.
5:75 to 75:25. ) 2. The counter ion M in the polymer compound represented by the general formula (1) is sodium, lithium or a quaternary ammonium, quaternary phosphonium or alkanolamine cation represented by the following general formula (2). The aqueous ink according to claim 1, wherein: Wherein X is nitrogen or phosphorus, R ₁ , R ₂ , R ₃
And R ₄ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group or a halogenated alkyl group. ) 3. A surfactant comprising a polyoxyethylene alkyl ether acetate represented by the following general formula (3) and / or a dialkyl sulfosuccinate represented by the following general formula (4): Claim 1 or 2
The aqueous ink as described in the above. Wherein R ₅ is a branched alkyl group having 6 to 14 carbon atoms, R ₆ is a branched alkyl group having 5 to 7 carbon atoms, M is an alkali metal, quaternary ammonium, Represents a quaternary phosphonium or an alkanolamine, m is 3 to
Represents an integer of 12. ) 4. The surfactant represented by the general formula (3) or (4), wherein the counter ion M is sodium, lithium or a quaternary ammonium, quaternary phosphonium or alkanolamine represented by the following general formula (2) The aqueous ink according to claim 3, which is a cation. Wherein X is nitrogen or phosphorus, R ₁ , R ₂ , R ₃
And R ₄ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group or a halogenated alkyl group. ) 5. The composition according to claim 1, wherein the surfactant comprises a compound represented by the following general formula (5) and / or a compound represented by the following general formula (6). The aqueous ink as described in the above. Wherein R ₇ is an alkyl group having 6 to 14 carbon atoms which may be branched, k represents an integer of 5 to 12, and m and n represent 0
Represents an integer of ~ 40. ) 6. The aqueous ink according to claim 5, comprising urea or a urea derivative. 7. The aqueous ink according to claim 1, wherein the pH is 6 or more and 11 or less. 8. The method of claim 1, 2, 3, 4, 5, 6, or 7.
An image is formed by causing the aqueous ink described in the above item to fly as fine droplets by thermal energy or mechanical energy, and attaching the droplet to a recording material having a Steckigt size of 3 seconds or more. Ink jet recording method.