JP5771922B2 - Water-based ink - Google Patents

Description

  In the aqueous ink containing a water-soluble resin, the present invention improves the storage stability (precipitation) of the ink, and does not impair the glossiness of the printed matter, and provides a high-quality printed image that has both abrasion resistance and repellency resistance. The present invention relates to a novel water-based ink that can be provided.

  In recent years, responses to environmental problems have been sought in various fields, and recording materials and inking materials used for printers, printing machines, markers, writing instruments and the like have been required to be desolvated and water-based. For example, non-water-absorbing recording media such as polyvinyl chloride sheets are used in a wide range of applications, such as outdoor postings that require long-term weather resistance and printed matters that require adhesion to curved objects. In some fields, solvent ink is mainly used, but there is also a demand for water-based ink here. There are a plurality of methods for printing on a non-water-absorbing recording medium. However, an inkjet recording method is known as a method that does not require preparation of a plate, has a short time to finish, and is suitable for the production of a small variety of products.

  In heat-fixable water-based inks containing pigments, water-soluble resins, organic solvents specified by solubility parameters, and water, water spots with reduced occurrence of spots when printed on non-absorptive or absorbent recording media Ink is disclosed, and the detailed description includes pyrrolidone as an example of a rub resistance improver for vinyl chloride, and even better presents an organic solvent defined by a solubility parameter (for example, a patent) Reference 1).

  However, a water-soluble organic solvent is added to promote wettability and penetrability to the recording medium, and in an aqueous ink containing a water-soluble resin for the purpose of fixing and protecting the image surface, it is intended to satisfy each function. In some cases, the amount of organic solvent used is increased, and the amount of water-soluble resin used may be limited due to the influence thereof. In particular, in a mixed solvent system of water and a water-soluble organic solvent, in order for the water-soluble resin to be stably present in the ink, consideration must be given to the combination and amount of the solvent, and the function of the water-soluble resin can be reduced. In order to achieve sufficient expression, it is necessary to distribute a relatively large amount of the water-soluble organic solvent. However, in a water-based ink containing a large amount of an organic solvent, the water-soluble resin is precipitated, or the glossiness of the formed image, the adhesion to the recording medium, or the abrasion resistance is reduced.

JP 2008-260820 A

  The present invention has been made in view of the above problems, and its purpose is to increase the degree of freedom in the amount of water-soluble organic solvent added and the amount of water-soluble resin to be used, thereby precipitating the water-soluble resin in the ink. It is an object of the present invention to provide a water-based ink that can be stably present without adhesion, improve adhesion to a recording medium, and obtain a high-quality printed image excellent in glossiness, abrasion resistance, and repellency resistance.

  The above object of the present invention is achieved by the following configurations.

  1. In a water-based ink containing at least water, a coloring material, a water-soluble resin, and a water-soluble organic solvent, the water-soluble organic solvent contains a β-alkoxypropionamide represented by the following general formula (1). A characteristic water-based ink.

[Wherein, R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms, and R ₂ and R ₃ are each a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms. R ₂ and R ₃ may be the same or different. ]
2. 2. The water-based ink as described in 1 above, wherein the water-soluble resin is at least one resin selected from an acrylic resin, a polyamide resin, a polyvinyl alcohol resin, and a polyurethane resin.

  3. 3. The water-based ink as described in 1 or 2 above, wherein the water-soluble resin is an amine neutralized resin.

  4). 2. The water-based ink as described in 1 above, wherein the water-soluble resin is a water-soluble resin A having the following characteristics.

  Water-soluble resin A: Acid value is 50 mgKOH / g or more and 130 mgKOH / g or less, glass transition temperature (Tg) is 30 ° C. or more and 100 ° C. or less, and weight average molecular weight (Mw) is 20,000 or more, 8 A copolymer resin synthesized from at least methyl methacrylate, an alkyl acrylate ester or an alkyl methacrylate ester, and a monomer containing an acid monomer as a monomer, and the methyl methacrylate and the alkyl acrylate ester; The total mass with the methacrylic acid alkyl ester is 80% or more and 95% or less with respect to the total monomer mass constituting the copolymer resin.

  According to the present invention, the degree of freedom of the use amount of the water-soluble organic solvent is expanded, the water-soluble resin can be stably dissolved in the ink, and the addition amount of the water-soluble resin is increased accordingly, and the adhesion to the recording medium is increased. It was possible to provide a water-based ink having good properties and capable of obtaining a high-quality printed image excellent in gloss, rubbing resistance and repellency resistance.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventors have found that the water-soluble organic solvent containing at least water, a coloring material, a water-soluble resin, and a water-soluble organic solvent has the general formula (1) as the water-soluble organic solvent. The water-based ink characterized in that it contains β-alkoxypropionamides represented by the formula (1) provides a high-quality image with excellent adhesion to the recording medium and excellent glossiness, abrasion resistance and repellency resistance. As a result, it has been found that the water-based ink can be realized, and the present invention has been achieved.

  In the water-based ink of the present invention, by containing the β-alkoxypropionamide represented by the general formula (1), it can have both functions of wetting and penetrating into the recording medium. The degree of freedom regarding the choice of the water-soluble organic solvent to be used and the amount of use can be expanded, so that the water-soluble resin can be stably dissolved in the water-based ink, and the relative amount of the water-soluble resin added can be increased. As a result, it was possible to obtain a high-quality image having excellent adhesion to a recording medium and excellent glossiness, abrasion resistance and repellency resistance.

  More specifically, the water-based ink has excellent adhesion to the recording medium, glossiness, and resistance to recording media whose surface is used for signing, such as resin recording media, and coated paper with poor water absorption, such as printing paper. Investigation was repeated for the purpose of forming a high-quality image excellent in rubbing and repellency. The recording medium having a resin surface in the present invention specifically means a resin plate such as polystyrene or acrylonitrile-butadiene-styrene copolymer (ABS resin), or a plastic film such as vinyl chloride or polyethylene terephthalate (PET). Or the thing which stuck these plastic films on the surface of base materials, such as paper, etc., and the surface to record is a recording medium which cannot permeate | transmit water easily.

  By adding the β-alkoxypropionamide represented by the general formula (1) to the water-based ink with respect to the recording medium having such characteristics, adhesion to the recording medium, glossiness, The present inventors have found that a high-quality image with improved abrasion resistance and cissing resistance can be formed.

[Β-alkoxypropionamides]
First, the β-alkoxypropionamides represented by the general formula (1) contained in the aqueous ink of the present invention will be described.

  The β-alkoxypropionamides represented by the general formula (1) according to the present invention have an effect as an organic solvent having a low surface tension, reduce the surface tension of the inkjet ink, It is effective in preventing penetration. Furthermore, the β-alkoxypropionamides represented by the general formula (1) have a high solubility in the resin component constituting the recording medium so that the landed ink droplets penetrate into the recording medium containing the resin component. Therefore, drying after printing is accelerated, and the resin component of the recording medium is dissolved or swollen by β-alkoxypropionamides represented by the general formula (1). Since the ink solvent enters the recording medium and is integrated with the recording medium, the adhesion of the formed image is increased, and the adhesion to the recording medium, the abrasion resistance, and the repellency resistance are improved.

  Furthermore, by using β-alkoxypropionamides, the amount of water-soluble organic solvent added can be reduced as compared with the conventional amount. As a result, the total amount of organic solvent in the water-based ink is reduced, and conversely the ratio of water Can be set high, it was possible to prevent precipitation of the water-soluble resin and obtain an image with high glossiness.

  Further, as an incidental effect, since the drying property is increased by the permeation of the ink, the deterioration of the image quality generated at the time of image recording by an ink jet method such as liquid contact or color bleeding caused by the ink staying on the surface of the recording medium is also improved.

In the general formula (1), R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms, and R ₂ and R ₃ are each a hydrogen atom, or a straight chain having 1 to 4 carbon atoms or It represents a branched alkyl group, and R ₂ and R ₃ may be the same or different.

By selecting the groups defined above as R ₁ , R ₂ , and R ₃ , the solubility and penetration ability of the resin component of β-alkoxypropionamides can be maintained and the compatibility with water can be increased. it can.

R ₁ is preferably a methyl group, an ethyl group or an n-butyl group, and preferred R ₂ and R ₃ are a methyl group or an ethyl group.

  The addition amount of the β-alkoxypropionamide represented by the general formula (1) to the aqueous ink is preferably 0.1% by mass or more and less than 40% by mass with respect to the total mass of the ink.

  Specific production methods of β-alkoxypropionamides represented by the general formula (1) according to the present invention are described in, for example, Japanese Patent Application Laid-Open No. 2009-185079 and International Publication No. 2008/102615. In addition, it is commercially available from Idemitsu Kosan Co., Ltd. under the trade name Ecamide.

[Other water-soluble organic solvents]
Next, water-soluble organic solvents other than the β-alkoxypropionamides represented by the general formula (1) that can be applied to the water-based ink of the present invention will be described.

  In the present invention, by adding a water-soluble organic solvent having a low surface tension together with β-alkoxypropionamides, absorption of recording media made of various hydrophobic resins including soft vinyl chloride sheets and printing paper can be absorbed. Even on a slow paper support, ink mixing can be suppressed and a high-quality printed image can be obtained.

  In particular, it is preferable to add glycol ethers or 1,2-alkanediols. Specifically, it is preferable to use a water-soluble organic solvent having the following low surface tension.

  Examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl. Examples include ether.

  Examples of 1,2-alkanediols include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and the like.

  It is also preferable to add a solvent that can dissolve, soften, or swell a recording medium such as vinyl chloride from the viewpoint of further improving the adhesiveness and abrasion resistance of the image.

  Examples of such solvents include cyclic solvents containing nitrogen or sulfur atoms, cyclic ester solvents, lactic acid esters, alkylene glycol diethers, alkylene glycol monoether monoesters, and dimethyl sulfoxide.

  Specific examples of preferred solvents include cyclic amide compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, Examples thereof include methyl caprolactam and 2-azacyclooctanone, and preferred specific examples of the cyclic solvent containing a sulfur atom are preferably cyclic 5- to 7-membered rings such as sulfolane.

  Preferable specific examples of the cyclic ester solvent include γ-butyrolactone and ε-caprolactone, and examples of the lactic acid ester include butyl lactate and ethyl lactate.

  Preferable specific examples of the alkylene glycol diether include diethylene glycol diethyl ether, and a preferable specific example of the alkylene glycol monoether monoester includes diethylene glycol monoethyl monoacetate.

  In addition, alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol) , Dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine) , Morpholine, N-ethylmorpholine, ethylenediamine, diethylenedia , Triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (for example, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), etc. It is done.

[Color material]
Next, the color material contained in the water-based ink of the present invention will be described.

  Examples of the color material applicable in the present invention include water-soluble dyes such as acid dyes, direct dyes and basic dyes, various pigments, disperse dyes containing colored polymers / waxes, and oil-soluble dyes. In particular, the use of a pigment is preferable from the viewpoint of image durability.

  As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, phthalocyanine pigment, perylene and perylene pigment, anthraquinone pigment, quinacridone pigment, dioxazine pigment, thioindigo pigment, isoindolinone pigment, quinophthalone pigment, etc. Examples include polycyclic pigments, dye lakes such as basic dye lakes, and acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as carbon black.

  Preferred specific organic pigments are exemplified below.

  Examples of pigments for magenta, red and violet include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 8, C.I. I. Pigment red 12, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 17, C.I. I. Pigment red 22, C.I. I. Pigment red 23, C.I. I. Pigment red 41, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 112, C.I. I. Pigment red 114, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 146, C.I. I. Pigment red 148, C.I. I. Pigment red 149, C.I. I. Pigment red 150, C.I. I. Pigment red 166, C.I. I. Pigment red 170, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 220, C.I. I. Pigment red 202, C.I. I. Pigment red 222, C.I. I. Pigment red 238, C.I. I. Pigment red 245, C.I. I. Pigment red 258, C.I. I. Pigment red 282, C.I. I. Pigment violet 19, C.I. I. And CI Pigment Violet 23.

  Examples of pigments for orange or yellow and brown include C.I. I. Pigment orange 13, C.I. I. Pigment orange 16, C.I. I. Pigment orange 31, C.I. I. Pigment orange 34, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 43, C.I. I. Pigment yellow 55, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 81, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 139, C.I. I. Pigment yellow 147, C.I. I. Pigment yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 153, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 175, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 181, C.I. I. Pigment yellow 185, C.I. I. Pigment yellow 194, C.I. I. Pigment yellow 199, C.I. I. Pigment yellow 213, C.I. I. Pigment Brown 22 and the like.

  Examples of pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 15: 5, C.I. I. Pigment blue 16, C.I. I. Pigment blue 29, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  As a pigment for black, in addition to carbon black, C.I. I. Pigment black 5, C.I. I. Pigment black 7 and the like.

  In addition to titanium oxide, C.I. I. Pigment white 6 and the like. The present invention is not limited to these.

(Pigment dispersion)
In order to maintain a stable dispersion state in the water-based ink, the above pigment is subjected to various kinds of processing to prepare a pigment dispersion.

  The dispersion is not particularly limited as long as it can be stably dispersed in an aqueous system. A pigment dispersion dispersed with a polymer dispersion resin, a capsule pigment coated with a water-insoluble resin, a pigment surface is modified, and a dispersion resin is not used. Can also be selected from dispersible self-dispersing pigments.

  When a pigment dispersion dispersed with a polymer dispersion resin is used, a water-soluble resin can be used. As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer are preferably used. Styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer It is a water-soluble resin such as.

  Further, as the pigment dispersion resin, the copolymer resin may be used for dispersion.

  As a pigment dispersion method, for example, various types such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used.

  From the viewpoint of removing the coarse particles of the pigment dispersion and making the particle size distribution of the pigment particles uniform, it is also preferable to use a centrifugal separator or a filter.

  Further, a capsule pigment coated with a water-insoluble resin may be used as the pigment. The water-insoluble resin is a resin that is insoluble in water in a weakly acidic to weakly basic range, and is preferably a resin having a solubility of 2% or less in an aqueous solution having a pH of 4 to 10.

  The water-insoluble resin is preferably acrylic, styrene-acrylic, acrylonitrile-acrylic, vinyl acetate, vinyl acetate-acrylic, vinyl acetate-vinyl chloride, polyurethane, silicon-acrylic, acrylic silicon, Listed are polyester resins and epoxy resins.

  As the molecular weight of the dispersion resin or the water-insoluble resin, those having an average molecular weight of 3000 to 500,000 can be preferably used, and more preferably 7000 to 200,000 can be used.

  The dispersion resin or the water-insoluble resin preferably has a Tg of about -30 ° C to 100 ° C, more preferably about -10 ° C to 80 ° C.

  The mass ratio of the pigment and the resin in which the pigment is dispersed can be selected preferably in the range of 100/150 or more and 100/30 or less in the pigment / resin ratio. Particularly, the image durability, injection stability, and ink storage stability are in the range of 100/100 or more and 100/40 or less.

  The average particle diameter of the pigment particles coated with the water-insoluble resin is preferably about 80 to 200 nm from the viewpoint of ink storage stability and color development.

  As a method for coating the pigment with the water-insoluble resin, various known methods can be used. Preferably, the water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and further an acidic group in the resin with a base component. A production method is preferred in which after partially or completely neutralizing, pigment and ion exchange water are added and dispersed, then the organic solvent is removed, and water is added if necessary. Alternatively, a method in which a pigment is dispersed using a polymerizable surfactant, a monomer is supplied thereto, and coating is performed while polymerization is also preferable.

  Further, as the self-dispersing pigment, a surface-treated commercial product can be used, and preferable self-dispersing pigments include, for example, CABO-JET200, CABO-JET300 (manufactured by Cabot Corporation), Bonjet CW1 (Orient Chemical Industries, Ltd. And the like).

(Water-soluble resin)
The water-based ink of the present invention contains at least a water-soluble resin. The water-soluble resin that can be used in the present invention functions as a binder when a pigment is used as a coloring material, has adhesiveness with a non-absorbing recording medium such as vinyl chloride, There is a function to improve water resistance. In addition, a function of forming an image with high gloss and high optical density is also required. Therefore, the water-soluble resin itself has high transparency in the coating film and is compatible with the pigment or the pigment dispersion resin. It is also necessary.

  The water-soluble resin applicable to the water-based ink of the present invention is not particularly limited, and is an acrylic resin, polystyrene-acrylic resin, polyacrylonitrile-acrylic resin, vinyl acetate-acrylic resin, polyvinyl alcohol resin, polyurethane resin. , Polyamide resins, polyester resins, polyolefin resins, and the like. Among them, at least one resin selected from acrylic resins, polyamide resins, polyvinyl alcohol resins, and polyurethane resins is preferable. In particular, a water-soluble resin which is an acrylic copolymer resin is preferable.

  As is well known, acrylic copolymer resins can be freely selected and designed from a wide variety of monomers, are easily polymerized, and can be produced at low cost, and are therefore suitable for the present invention. In particular, as described above, an acrylic copolymer resin having a high degree of design freedom is suitable for responding to a large number of requirements required for addition to water-based inks. It is particularly preferable to use the water-soluble resin A provided.

(Water-soluble resin A)
<Acid value of water-soluble resin A>
In the water-soluble resin A according to the present invention, the acid value is 50 mgKOH / g or more and 130 mgKOH / g or less. If the acid value is 50 mgKOH / g or more, the resin has high water solubility and is easily dissolved, and if the acid value is 130 mgKOH / g or less, it is preferable from the viewpoint of obtaining high glossiness.

[Measurement method of acid value]
The acid value of the water-soluble resin referred to in the present invention can be determined according to the following method.

  10 g of the resin is weighed into a 300 ml Erlenmeyer flask, and about 50 ml of a mixed solvent of ethanol: benzene = 1: 2 is added to dissolve the resin. Next, using a phenolphthalein indicator, titration was performed with a 0.1 mol / L potassium hydroxide ethanol solution that was standardized in advance, and the acid amount was determined from the amount of the potassium hydroxide ethanol solution used for the titration according to the following formula (1). The value (mgKOH / g) can be determined. Depending on the type of resin, one that does not dissolve in about 50 ml of a mixed solvent of ethanol: benzene = 1: 2 is a solvent type that dissolves either 50 ml of ethanol or about 50 ml of a mixed solvent of ethanol / pure water = 1: 1. Select the other and perform the titration with the same operation.

Formula (1)
A = (B × f × 5.611) / S
In the formula, A is the acid value of the resin (mgKOH / g), B is the amount of 0.1 mol / L potassium hydroxide ethanol solution used for titration (ml), and f is the 0.1 mol / liter potassium hydroxide ethanol solution. Factor, S is the mass of the resin (g), 5.611 is the formula weight of potassium hydroxide (56.11 / 10).

<Glass transition temperature of water-soluble resin A>
In the water-soluble resin A according to the present invention, the glass transition temperature (Tg) is 30 ° C. or higher and 100 ° C. or lower. If Tg is 30 ° C. or higher, the abrasion resistance is sufficient, and the occurrence of blocking can also be suppressed. If Tg is 100 ° C. or lower, desired abrasion resistance can be obtained. This is believed to prevent the dried film from becoming too hard and brittle.

<Weight average molecular weight of water-soluble resin A>
The water-soluble resin A according to the present invention has a weight average molecular weight (Mw) of 20,000 or more and 80,000 or less. This is because if the weight average molecular weight is 20,000 or more, the rubbing resistance is good, and if it is 80,000 or less, the maintainability of the ink is excellent. Further, the weight average molecular weight of the water-soluble resin A is preferably 25,000 or more and 70,000 or less.

<Monomer composition of water-soluble resin A>
The water-soluble resin A according to the present invention is a copolymer resin synthesized from a monomer containing at least methyl methacrylate, an alkyl acrylate ester or an alkyl methacrylate ester, and an acid monomer as monomers. The total mass of the acid alkyl ester and the methacrylic acid alkyl ester is 80% or more and 95% or less with respect to the total monomer mass constituting the copolymer resin.

(Amine neutralized resin)
The water-soluble resin according to the present invention can be used by neutralizing all or part of the acid component contained in the resin with a base. As the neutralizing base, alkali metal-containing bases (for example, NaOH, KOH, etc.), amines (for example, alkanolamines, alkylamines, etc.) or ammonia can be used. The resin is preferably an amine neutralized resin.

  The amount of the neutralizing base added depends on the amount of the acid monomer contained in the copolymer resin, but if it is too small, the effect of neutralization of the copolymer resin cannot be obtained. Since there are problems such as discoloration and odor, the content is preferably 0.2% by mass or more and 2.0% by mass or less of the total mass of the ink.

  The water-soluble resin according to the present invention may be added before the color material is dispersed or may be added after the color material is dispersed during the preparation of the water-based ink. It is preferable.

  The water-soluble resin is preferably added in an amount of 1% by mass to 15% by mass in the aqueous ink. More preferably, it is 3 mass% to 10 mass%.

  In the water-based ink of the present invention, water-dispersed polymer fine particles composed of the same resin as described above can be used together with the water-soluble resin.

[Other additives]
In addition to the water-based ink of the present invention, a fixing resin, a surfactant, an antifungal agent, an antirust agent, an antifoaming agent, a viscosity adjusting agent, a penetrating agent, a pH adjusting agent, urea as an anti-drying agent, if necessary. Thiourea, ethyleneurea and the like can be added, and it is particularly preferable to add a surfactant because image durability and image quality are further improved.

[Surfactant]
Next, the surfactant applicable to the present invention will be described.

  Surfactants that can be used in the ink of the present invention include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers , Nonionic surfactants such as acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, silicone-based and fluorine-based surfactants In particular, silicone-based or fluorine-based surfactants are preferable. Surfactants can be used alone or in combination.

  By adding a silicone-based or fluorine-based surfactant, it is possible to further suppress ink mixing on recording media made of various hydrophobic resins such as vinyl chloride sheets and recording media that absorb slowly such as printing paper. And high-quality printed images can be obtained. The surfactant is particularly preferably used in combination with the low surface tension water-soluble organic solvent.

  The silicone-based surfactant is preferably a polyether-modified polysiloxane compound, and examples thereof include KF-351A and KF-642 manufactured by Shin-Etsu Chemical Co., and BYK345, BYK347, and BYK348 manufactured by Big Chemie.

  The fluorine-based surfactant means a compound in which a part or all of the surfactant is substituted with fluorine in place of hydrogen bonded to carbon of the hydrophobic group of a normal surfactant. Of these, those having a perfluoroalkyl group in the molecule are preferred.

  Among the fluorosurfactants, some are from DIC under the trade name Megafac F and from Asahi Glass under the trade name Surflon, Minnesota Mining and Manufacturing Company Under the trade name Fluorad FC from the company, under the trade name Monflor from Imperial Chemical Industry, and under the trade name Zonyls from EI Dupont Nemeras & Company, Also, the product name of Licobet VPF is available from Farbeberke-Hoechst and the name of footage is available from Neos.

  The addition amount of the surfactant is preferably 0.1% by mass or more and less than 2.0% by mass with respect to the total mass of the ink.

  The surface tension of the ink is preferably 15 mN / m or more and less than 35 mN / m, because the surface energy of the ink is lower than that of ordinary paper and the recording medium made of resin does not get wet and whitening does not occur. .

[Preservatives and antifungal agents]
In order to maintain the long-term storage stability of the ink, an antiseptic and an antifungal agent may be added to the ink. Examples of the antiseptic / antifungal agent include aromatic halogen compounds (for example, Preventol CMK), methylene dithiocyanate, halogen-containing nitrogen sulfur compounds, 1,2-benzisothiazolin-3-one (for example, PROXEL GXL), and the like. It is done. The present invention is not limited to these.

  In image formation using the water-based ink of the present invention, in order to form an image with higher image quality and higher image durability and to be able to cope with higher-speed image formation conditions, the recording medium is kept at 35 ° C. As described above, it is preferable to print while heating to a temperature of less than 100 ° C. When the temperature is 35 ° C. or higher, the effect of heating is sufficiently exhibited, and when the temperature is 100 ° C. or lower, it is possible to eliminate the influence of the recording medium being deformed and wavy.

  In addition, it is more preferable that after printing with heating, the print is further dried by heating at 55 ° C. or more and less than 100 ° C. in order to promote ink drying and enhance image durability.

[Application field of water-based ink]
The water-based ink of the present invention is a water-based ink that can be widely used from a paint, a water-based paint, a paper coating agent, a film coating material, etc. to a recording material, and in particular, a writing instrument, a marker, a marking pen, etc. Therefore, it can be suitably used as an ink recording material used in various printing machines, ink jet printers, ferroelectric printers and the like.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Preparation of ink>
(Preparation of cyan pigment dispersion)
20 parts of Floren TG-750W (solid content 40%, manufactured by Evonik Degussa) was added to 65 parts of ion-exchanged water as a pigment dispersant. To this solution, C.I. I. 15 parts of Pigment Blue 15: 3 was added and premixed, and then dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads to obtain a cyan pigment dispersion having a pigment solid content of 15%. It was.

[Preparation of Ink C-1]
5 parts of β-hydroxypropionamide 3-methoxy-N, N-dimethylpropionamide (hereinafter referred to as A-1), 5 parts of dipropylene glycol monopropyl ether (DPGPE), and dipropylene glycol Add 10 parts of monomethyl ether (DPGME) to 20 parts of ion-exchanged water, and add 17 parts of Jonkrill JDX-6500 (BASF acrylic resin solid content 29.5%) as a water-soluble resin. The mixture was stirred and adjusted with ion-exchanged water so that the total amount became 80 parts.

  Next, 20 parts of the cyan pigment dispersion prepared above was added and stirred, and then filtered through a 0.8 μm filter to obtain cyan ink C-1.

[Preparation of inks C-2 to C-12]
In the preparation of the ink C-1, the types of β-alkoxypropionamides (not added), the types and contents of organic solvents, and the contents of water-soluble resins were changed as shown in Table 1. Similarly, inks C-2 to C-12 were prepared.

  In addition, the specific compounds of β-alkoxypropionamides, organic solvents, water-soluble resins, and surfactants described in abbreviated terms in Table 1 are as follows.

<* 1: β-alkoxypropionamides>
A-1: 3-methoxy-N, N-dimethylpropionamide A-2: 3-butoxy-N, N-dimethylpropionamide <Organic solvent 1, 2, 3>
HDO: 1,2-hexanediol DPGME: Dipropylene glycol monomethyl ether DPGPE: Dipropylene glycol monopropyl ether NMP: N-methyl-2-pyrrolidinone 2-PDN: 2-pyrrolidinone <Water-soluble resin>
JDX: John Kuril JDX-6500 (BASF acrylic resin)
<Surfactant>
F-100: Aftergent 100 (manufactured by Neos)

<Evaluation of ink>
Each ink prepared as described above was evaluated according to the following method. The surface tension measured by the plate method for each ink was all in the range of 15 to 35 mN / m, and the ink viscosity was all in the range of 5 to 19 mPa · s.

[Evaluation of precipitation resistance]
After each 7.0 g of the prepared ink was put in a petri dish having a diameter of 5 cm, the ink was left for 72 hours in an environment at 25 ° C., and the presence or absence of precipitation of the water-soluble resin during that period was observed with a microscope. The precipitation resistance of was evaluated.

○: No precipitation was observed even after standing for 72 hours. Δ: Slight precipitation was observed between 24 hours and less than 72 hours. X: Precipitation was observed in less than 24 hours. In the above-mentioned evaluation rank, it was judged that it was practically preferable if it was ○.

[Evaluation of gloss]
A soft vinyl chloride sheet MD5 (manufactured by Metamark) was used as a recording medium, applied with a wire bar so that the amount of ink applied was about 16 g / m ² and dried, and the 20 ° gloss was measured. The glossiness was measured using a variable angle glossiness meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd., and the glossiness was measured according to the following criteria.

A: 20 degree gloss is 100% or more B: 20 degree gloss is 85% or more and less than 100% Δ: 20 degree gloss is 70% or more and less than 85% ×: 20 The glossiness is less than 70%. In the evaluation rank, ◎ and ◯ were judged to be practically preferable.

[Evaluation of abrasion resistance]
The image created by the gloss evaluation was rubbed with dry cotton (Kanakin No. 3) under a load of 200 g, and the rub resistance was evaluated according to the following criteria.

A: The image does not change even after rubbing 30 times or more. ○: Some scratches remain in the stage of rubbing in the range of 11 times or more and 29 times or less, but the image density is not affected. Δ: 5 times or more and 10 times or less The image density decreases while rubbing in the range of ×: The image density decreases while rubbing 4 times or less. In the evaluation rank, ◎ and ○ were judged to be practically preferable.

  Table 2 shows the evaluation results obtained as described above.

  As is clear from the results shown in Table 2, it can be seen that the water-based ink of the present invention is superior in all properties of precipitation resistance, gloss and abrasion resistance to the comparative example.

Example 2
<Preparation of ink>
Ink C-2 was prepared in the same manner as in inks C-2, C-6, and C-10 prepared in Example 1, except that the water-soluble resin JDX used in each ink was changed to each water-soluble resin shown in Table 3. -13 to C-15, C-16 to C-18, and C-19 to C-21 were prepared.

  In addition, the detail of each water-soluble resin described with the abbreviation in Table 3 is as follows.

(Water-soluble resin)
JDX: Jonkrill JDX-6500 (manufactured by BASF, acrylic resin)
K300: COFFLOCK K-300 (made by Showa Polymer Co., Ltd., polyamide resin)
GOH: GOHSENOL (Nippon GOHSEI, polyvinyl alcohol resin)
EL: Elastrone (Daiichi Kogyo Seiyaku, urethane resin)
<Evaluation of ink>
In the evaluation of the ink described in Example 1, precipitation resistance, gloss and abrasion resistance were the same except that the recording medium used for the evaluation was changed to Tokuhishi Art Double Side N (manufactured by Mitsubishi Paper Industries Co., Ltd.). Evaluation was performed and the obtained results are shown in Table 4.

  As is apparent from the results shown in Table 4, it can be seen that the ink of the present invention containing various water-soluble resins is superior in all properties of precipitation, gloss and abrasion resistance to the comparative example. .

Example 3
<Preparation of ink>
Inks C-22 and C were prepared in the same manner as in ink C-2 prepared in Example 1, except that water-soluble resin JDX was changed to water-soluble resins P-1 and P-2 prepared by the following method, respectively. -23 in the same manner as in ink C-6 prepared in Example 1, except that the water-soluble resin JDX was changed to water-soluble resins P-1 and P-2 prepared by the following methods, respectively. C-24 and C-25 were prepared.

(Synthesis of water-soluble resin P-1: amine neutralized resin)
50 g of methyl ethyl ketone was added to a flask equipped with a dropping funnel, a nitrogen introducer, a reflux condenser, a thermometer and a stirrer, and heated to 75 ° C. while bubbling nitrogen.

  There, monomers (9 parts by weight of methacrylic acid, 78 parts by weight of methyl methacrylate, 6.5 parts by weight of n-butyl acrylate and 6.5 parts by weight of 2-ethylhexyl acrylate), 50 g of methyl ethyl ketone, initiator (AIBN: A mixture of 2,2'-azobisisobutyronitrile (500 mg) was dropped from a dropping funnel over 3 hours. It heated and refluxed for 6 hours after dripping. After allowing to cool, the mixture was heated under reduced pressure to distill off methyl ethyl ketone to obtain a copolymer resin.

  The polymer residue was dissolved in a solution in which dimethylaminoethanol corresponding to 1.05 mol of acrylic acid added as a monomer was dissolved in 450 ml of ion-exchanged water.

  An aqueous solution of water-soluble resin P-1 having a hydrophobic monomer having a solid content of 20% as a polymerization component was obtained by adjusting with ion-exchanged water.

(Synthesis of water-soluble resin P-2: water-soluble resin A)
186 parts of 2-propanol was placed in a flask equipped with a dropping funnel, a reflux tube, a nitrogen introduction tube, a thermometer, and a stirring device, and the mixture was heated to reflux while bubbling nitrogen. A monomer solution in which 0.5 part of an initiator (AIBN) was dissolved in a mixed liquid of 76 parts of methyl methacrylate, 13 parts of 2-ethylhexyl acrylate, and 11 parts of methacrylic acid was dropped from the dropping funnel over 2 hours. After dropping, the mixture was further heated and refluxed for 5 hours and then allowed to cool, and 2-propanol was distilled off under reduced pressure to obtain a water-soluble resin P-2 as a copolymer resin. Add 207.8 parts of ion-exchanged water and 12.2 parts of N, N-dimethylaminoethanol as a neutralizing base to 20 parts of water-soluble resin P-2, and heat and stir at 70 ° C. to dissolve the resin. An aqueous solution of water-soluble resin P-2 having a solid content of 20% was obtained. The amount of N, N-dimethylaminoethanol is an amount corresponding to 1.05 times the number of chemical equivalents of the acid equivalents of the acid groups of the water-soluble resin P-2.

<Evaluation of ink>
In the same manner as the ink evaluation described in Example 1, evaluation of precipitation resistance, gloss and abrasion resistance, and evaluation of image repelling resistance were performed according to the following methods.

(Evaluation of image repelling resistance)
As a recording medium, a soft vinyl chloride sheet MD5 (manufactured by Metamark) was coated with a wire bar so that the amount of ink applied was about 11 g / m ² and dried, and the coated surface was visually observed and repelled with a microscope. The presence or absence was observed, and image repellency resistance was evaluated according to the following criteria.

◎: No repelling is observed even with a microscope. ○: Although it cannot be recognized visually, a slight repelling is observed when observed with a microscope. △: Slight repelling is observed visually. In the above evaluation rank where cissing is observed in the entire image, it was judged that ◎ and ○ were practically preferable.

  Table 6 shows the results obtained as described above.

  As is apparent from the results shown in Table 6, it can be seen that the ink of the present invention satisfies all the characteristics of precipitation resistance, gloss, abrasion resistance and image repelling resistance.

Example 4
[Evaluation of ejection stability]
Each ink prepared in Examples 1 to 3 was loaded into an ink jet printer, and the ejection stability was evaluated. Using a printing apparatus equipped with a piezo-type inkjet head (720 dpi, appropriate amount of liquid 16 pl, “dpi” represents the number of todds per 2.54 cm), ink was introduced into one head, and A4 size was continuously used. After 10 solid images were created, they were left in an environment of 25 ° C. and 55% RH for 60 minutes, and then images were created again. The image quality of the obtained solid images was visually observed, and in accordance with the following criteria: The discharge stability was evaluated.

◎: Image defects are not observed at all, and the image is uniform. ○: Slight blurring is observed in the image writing portion (2 mm or less). △: Image defects caused by defective ink ejection (streaks). Occurrence of failure) is slightly observed. X: Generation of strong image defect (streak failure) due to ink ejection failure is recognized. In the evaluation rank, ◎ and ○ are judged to be practically preferable.

  Table 7 shows the results obtained as described above.

  As is apparent from the results shown in Table 7, it can be seen that the ink of the present invention can provide stable ejection performance even with an inkjet printer.

Claims (3)

In a water-based ink containing at least water, a coloring material, a water-soluble resin, and a water-soluble organic solvent, the water-soluble organic solvent is 3-methoxy-N, N-dimethylpropionamide, and the water-soluble resin is used as a monomer. A copolymer resin synthesized from a monomer containing at least methyl methacrylate, alkyl acrylate ester or alkyl methacrylate ester, and an acid monomer, and the total mass of methyl methacrylate, alkyl acrylate ester and alkyl methacrylate ester Is a water-based ink, characterized in that it is 80% or more and 95% or less with respect to the total monomer mass constituting the copolymer resin. The water-based ink according to claim 1, wherein the water-soluble resin is an amine neutralized resin. The water-soluble resin, characterized in that a water-soluble resin A having the properties described below, an aqueous ink according to claim 1 or 2.
Water-soluble resin A: Acid value is 50 mgKOH / g or more and 130 mgKOH / g or less, glass transition temperature (Tg) is 30 ° C. or more and 100 ° C. or less, and weight average molecular weight (Mw) is 20,000 or more, 8 A copolymer resin synthesized from at least methyl methacrylate, an alkyl acrylate ester or an alkyl methacrylate ester, and a monomer containing an acid monomer, and the methyl methacrylate and the alkyl acrylate ester. The total mass of methacrylic acid alkyl ester is 80% or more and 95% or less with respect to the total monomer mass constituting the copolymer resin.