JP2007099917A - Ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inkjet recording ink having excellent storage stability and ejection stability, while achieving good color development on plain paper or glossy paper and high gloss on glossy paper and having high light resistance. <P>SOLUTION: The ink contains water and a pigment dispersed therein using a polymer having an acid number of 50-120 mgKOH/g and a weight-average molecular weight of 20,000-120,000, and containing ≥50 wt.% benzyl acrylate and ≤15 wt.% (meth)acrylic acid polymerized as a constitutional component of the polymer. At least C.I. Pigment Yellow 138 is used as the pigment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink for ink jet recording, which has excellent storage stability and ejection stability, has both high colorability on plain paper and glossy paper and high glossiness on glossy paper, and also has good light resistance. .

  Many conventional inks for ink jet recording use dyes as coloring materials, but those using pigments have recently started to spread. In recent years, it has become increasingly popular to create so-called photographic image recordings using an ink-jet recording apparatus and post them indoors and outdoors. Is advantageous in that printed images having various weather resistance such as light resistance, gas resistance, and water resistance can be obtained as compared with dyes used as coloring materials.

  In the ink using a pigment, as a means for dispersing the pigment in water, a method using a surfactant (see Patent Document 1) and a method using a dispersion polymer having a hydrophobic part and a hydrophilic part (see Patent Document 2) are known. ing. Also, a method of coating the surface of the pigment with a polymer has been studied, and examples thereof include a method using a phase inversion emulsification reaction or an acid precipitation method (see Patent Document 3).

  However, in any case, as a method of dispersing the pigment, since a polymer containing styrene as a main constituent is used, the fixability is not so good, and there is a problem that yellowing is easily caused by long-term storage of the printed matter. In addition, in the normal case, when a substance having a hydrophilic part and a hydrophobic part such as a surfactant or glycol ether is present, adsorption / desorption tends to occur and storage stability is inferior, but conventional water-based inks reduce bleeding on paper. Therefore, a substance having a hydrophilic part and a hydrophobic part such as a surfactant or glycol ether is necessary. Ink not using these substances has insufficient permeability to paper, and in order to perform uniform printing, However, there is a problem that the print image is liable to be reduced.

  Further, for example, additives for improving the print quality (acetylene glycol, acetylene alcohol, silicon surfactant, di (tri) ethylene glycol monobutyl ether or 1,2-alkylene glycol or a mixture thereof) to the conventional dispersion Long-term storage stability cannot be obtained, and in the case of pigment inks, the re-solubility is poor, so that the ink dries and easily becomes clogged with the nozzles of the ink-jet head, and the adhesion used for the substances constituting the head A material such as an agent is attacked to lower the adhesive strength, leading to a decrease in ejection reliability. In the worst case, there is a problem that ejection becomes impossible.

  In addition, the pigment dispersed by the general dispersant as described above has a high viscosity because the residual dispersant remains in the ink system, and the dispersant does not contribute sufficiently to the dispersion and is detached from the pigment. There was a problem that it would end up. When the viscosity is increased, the amount of the coloring material such as pigment is limited, and there is a problem that sufficient print quality cannot be obtained particularly on plain paper.

  Pigment inks are superior to dye inks in various weather resistances such as light resistance, gas resistance, and water resistance. In yellow inks, C.I. I. Pigment Yellow 74 or the like has a problem that its ability is inferior to cyan or magenta in terms of light resistance. On the other hand, examples of yellow pigments excellent in light resistance include C.I. I. Pigment Yellow 138 has been conventionally known, but it was not suitable for use in inks for ink jet recording because of its low color developability and poor storage stability as an ink.

  Therefore, an ink for ink jet recording using a yellow pigment aims to achieve various characteristics such as light resistance, print quality, and storage stability. I. As a means for suitably using CI Pigment Yellow 138 for inks for inkjet recording, water resistance, light resistance, hue, and storage stability are improved by coating the pigment with an organic polymer compound having a neutralized anionic group. Method of improving (Patent Document 4), Method of obtaining printed material having clear and high-quality image and excellent light resistance by combining with recording medium having ink receiving layer with specific coating (Patent Document 5), pigment By changing the miniaturization conditions in production, C.I. I. Conventionally, a method of making Pigment Yellow 138 into a special crystal type and making it suitable for inkjet having excellent transparency and sharpness (Patent Document 6) has been conventionally performed.

Japanese Patent Laid-Open No. 01-301760 Japanese Patent Laid-Open No. 06-306317 Japanese Patent Laid-Open No. 10-140065 Japanese Patent Laid-Open No. 11-172180 JP 11-228888 A JP 2002-105351 A

  However, in any of the methods, although the light resistance of the recorded matter is good, the color developability, particularly the color developability on plain paper is not sufficient. In addition, glossiness on glossy paper cannot be ensured, and the printing quality is not satisfactory. As described above, an ink for ink jet recording using a yellow pigment as a coloring material has not yet been found to have both light resistance and printing quality.

  In the inkjet recording ink of the present invention, water, at least 50% by weight of benzyl acrylate and 15% by weight or less (meth) acrylic acid are polymerized as a polymer component, and an acid value of 50 to 120 mgKOH / g is obtained. An ink containing a pigment dispersed using a polymer having a weight average molecular weight of 20,000 to 120,000, wherein at least C.I. I. Pigment Yellow 138 is used.

  The ink for inkjet recording of the present invention is excellent in storage stability and ejection stability in an ink mainly composed of a yellow pigment, and has high colorability on plain paper and glossy paper and high glossiness on glossy paper. In addition, there is an effect of providing an ink for inkjet recording that can obtain a recorded matter having excellent light resistance.

  The ink for ink-jet recording of the present invention is excellent in storage stability and ejection stability, has high color development on plain paper and glossy paper, has fixing properties in addition to sufficient gloss on glossy paper, This is a result of intensive studies in view of demands for characteristics such as excellent ink ejection stability and light resistance.

  In the ink for inkjet recording of the present invention, water, at least 50% by weight or more of benzyl acrylate as a polymer component, and 15% by weight or less of (meth) acrylic acid are polymerized, and an acid value of 50 to 120 mgKOH / g. And a pigment dispersed using a polymer having a weight average molecular weight of 20,000 to 120,000.

  In the present invention, a polymer in which 50% by weight or more of benzyl acrylate and 15% by weight or less of (meth) acrylic acid are polymerized is preferable. When benzyl acrylate is less than 50% by weight, the fixability is lowered, so the preferred range is 50% by weight or more, but the case of less than 50% by weight is not denied. The benzyl acrylate is preferably 50% by weight or more, more preferably 60% by weight or more, and still more preferably 70% by weight or more. Polymerization with 15% by weight or less of (meth) acrylic acid is preferred. If it exceeds 15% by weight, the color developability of the ink-jet ink on plain paper tends to be lowered, but polymerization exceeding 15% by weight is not denied, and is shown as a more preferable range, and a more preferable range is 10% by weight. % Or less. When methacrylic acid and acrylic acid are compared, it is more preferable to use acrylic acid from the viewpoint of fixability.

  The polymer used for dispersion of the pigment in the present invention is a commercially available styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, polyethylene glycol ( A combination of one or more selected from a (meth) acrylate- (meth) acrylic acid copolymer, a vinyl acetate-maleic acid copolymer, a styrene-maleic acid copolymer, and the like can also be used. However, it is preferable that at least 80% or more is a polymer obtained by copolymerization of acrylate and acrylic acid. Examples of the acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl carbitol acrylate, phenol EO-modified acrylate, N-vinyl pyrrolidone, Commercially available acrylates such as isobornyl acrylate, benzyl acrylate, paracumylphenol EO-modified acrylate, and 2-hydroxyethyl-3-phenoxypropyl acrylate can be used. Further, ω-carboxy-polycaprolactone monoacrylate, phthalic acid monohydroxyethyl acrylate, acrylic acid dimer or the like can be used instead of acrylic acid.

  Moreover, it is preferable that the dispersion method using the polymer used by this invention is the phase inversion emulsification in water so that a polymer may cover a pigment. By using the phase inversion emulsification method, the ink becomes stable and the color developability of plain paper is improved.

  In the present invention, the polymer in which the pigment is dispersed preferably has a weight average molecular weight of 20,000 to 200,000. If the weight average molecular weight is less than 20,000, the long-term storage stability, thermal stability and fixability as an ink-jet ink will deteriorate, and if it exceeds 200,000, the viscosity as an ink-jet ink will increase and the dispersion stability will tend to deteriorate. There is also a tendency for the discharge stability to decrease.

  As a method for polymerizing the polymer of the present invention, an alcohol solvent, a ketone solvent, an ether solvent, or a glycol ether solvent can be used as a solvent. However, since it is an aqueous pigment dispersion, it is necessary to be able to remove the above-mentioned solvent later. Therefore, the following can be used as such a solvent. Examples of the alcohol solvent include methanol, ethanol, isopropanol, 1-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Furthermore, examples of the glycol ethers include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, and butyl cellosolve.

  Moreover, as a radical polymerization initiator for polymerizing a polymer, t-butyl peroxy (2-ethylhexanoate), di-t-butyl peroxide, t-butyl peroxybenzoate, t-butyl peroxyoct Organic peroxides such as ate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisbutyrate, 2, Azo compounds such as 2′-azobis (2-methylbutyronitrile), potassium persulfate, sodium persulfate, and the like can be used, but are not limited to these, and start other than the above as long as radical polymerization is possible. An agent can also be used. As for the usage-amount of a radical polymerization initiator, 0.01-5 mol% is preferable with respect to the monomer used in the case of superposition | polymerization. The polymerization temperature is not particularly limited, but is usually in the range of 30 to 100 ° C, and preferably in the range of 40 to 90 ° C. When the polymerization temperature is too low, it is necessary to take a long time for the polymerization of the monomer, and in some cases, the polymerization rate may decrease and a large amount of monomer may remain.

  Moreover, although the polymer in this invention has a carboxyl group, it is preferable to contain triethanolamine and / or tripropanolamine as the counter ion. By using triethanolamine and / or tripropanolamine, ink clogging hardly occurs even in a dry state.

  From the viewpoint of light resistance, the yellow pigment used in the present invention is C.I. I. Pigment yellow 138 is preferably used. C. I. By using Pigment Yellow 138 in combination with the above-mentioned polymer, it is possible to obtain a recorded matter that exhibits high color development on both plain paper and glossy paper, exhibits high gloss on glossy paper, and is excellent in light resistance. Is possible.

  In the present invention, C.I. I. It is also preferable to further use Pigment Yellow 74. C. I. Pigment yellow 138 and C.I. I. By using together with Pigment Yellow 74, the effect of improving the color developability of plain paper can be obtained.

  In the present invention, C.I. I. Pigment yellow 138 and C.I. I. When using together with pigment yellow 74, it is preferable that the content rate is the range of 20: 1-1:10 in conversion of a weight. C. I. When the content ratio of Pigment Yellow 74 is less than 20: 1, C.I. I. The effect of adding Pigment Yellow 74 cannot be obtained. On the other hand, if it exceeds 1:10, the light resistance is reduced, so it is desirable to use in the range of 20: 1 to 1:10.

  In the present invention, the addition amount as a pigment is preferably 0.5 to 30%, more preferably 1.0 to 12%. If the addition amount is less than this, the print density cannot be ensured, and if the addition amount is more than this, the viscosity of the ink increases or structural viscosity is generated in the viscosity characteristics, and the ejection stability of the ink from the ink jet head tends to deteriorate. .

  In the present invention, the yellow pigment has an average particle diameter of 20 to 110 nm and is dispersed using a polymer having an acid value of 50 to 120 mgKOH / g, so that storage stability and ejection stability are improved. It is preferable from the viewpoint of providing an ink for ink jet recording which is excellent and has both high color developability on plain paper and glossy paper and high gloss on glossy paper. When the average particle size is less than 20 nm, the light resistance deteriorates. When the average particle size exceeds 110 nm, the color developability on plain paper decreases. Further, when the acid value is less than 50 mgKOH / g, the dispersion becomes unstable, and when the acid value exceeds 120 mgKOH / g, the color developability on plain paper decreases.

  In the present invention, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7, One or more selected from the alkylene oxide adduct of 9-tetramethyl-5-decyne-4,7-diol and the alkylene oxide adduct of 3,6-dimethyl-4-octyne-3,6-diol in the ink It is preferable to contain. By using the pigment dispersion of the present invention and further using these, the ejection stability of the ink for ink jet recording is improved, and bleeding when printed on plain paper is reduced. The content is preferably in the range of 0.05 to 1 weight with respect to the total amount of ink. If it is less than 0.05% by weight, bleeding on plain paper increases, and if it exceeds 1% by weight, the storage stability as an ink for ink jet recording deteriorates and long-term storage becomes difficult. More preferably, it is 0.1 to 0.7% by weight.

  2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5 -An alkylene oxide adduct of decyne-4,7-diol is commercially available, Surfinol 104, Surfinol 82, Surfinol 2502, Surfinol 420, Surfinol 440, Surfinol 465, Surfinol manufactured by Nissin Chemical Co., Ltd. 485, acetylenol EOO, acetylenol E40, acetylenol E100 manufactured by Kawaken Fine Chemical Co., Ltd. and the like.

  In the present invention, it is preferable to further comprise 1,2-alkylene glycol. Among the 1,2-alkylene glycols, 1,2-hexanediol and 4-methyl-1,2-pentanediol are particularly preferable. By using the pigment dispersion of the present invention and further using these, the ejection stability of the ink jet ink is used. And the bleeding when printed on plain paper is reduced.

  Further, in the present invention, 1 selected from di (tri) ethylene glycol monobutyl ether, (di) propylene glycol monobutyl ether, di (tri) ethylene glycol monopentyl ether and di (tri) ethylene glycol monohexyl ether Preferably it comprises more than seeds. By using the pigment dispersion of the present invention and further using these glycol ethers, bleeding when printed on plain paper by the inkjet method is further reduced, and the printing quality is improved.

  In the present invention, it is also preferable that 2-butyl-2-ethyl-1,3-propanediol is contained, and the pigment dispersion of the present invention is used to prepare 2-butyl-2-ethyl-1, By further using 3-propanediol, glossiness on glossy paper is improved, and color developability on plain paper is improved.

  Similarly, in order to make inkjet clogging difficult to occur, it is preferable to include one or more selected from glycerin, trimethylolethane, trimethylolpropane, tetrasaccharide, pentasaccharide and hexasaccharide.

  In the present invention, a dispersant, a surface tension adjusting agent or a penetrating agent (surfactant), a wetting and drying preventing agent, an antiseptic, a bactericidal agent, a pH adjusting agent, a rust preventing agent, a moisturizing agent and other additives are added as necessary. An agent may be used. These may be used alone or in combination of two or more.

  Next, as a method for producing the ink for ink jet recording of the present invention, for example, the polymer composition for ink for ink jet recording of the present invention, an aqueous medium, an alkali such as sodium hydroxide is emulsified by high speed stirring, and a pigment is further added. And the like, and a method of strongly dispersing with a disper or the like. Further, if necessary, a method of dispersing with a three-roll mill or the like, dispersing the obtained pigment slurry to a predetermined particle size with a high-pressure disperser or the like, and then removing the organic solvent or the like from the obtained pigment dispersion Etc. may be performed.

  The high-pressure disperser is not particularly limited, and examples thereof include a microfluidizer (Microfluidics), an optimizer (Sugino Machine), a wet jet mill (Genus), and a nanomizer (Nanomizer).

  The pressure at the time of dispersing with the above-described high-pressure disperser may be any as long as it can reach the desired pigment particle diameter, but is preferably 100 MPa to 300 MPa. If it is less than 100 MPa, the dispersed particle size tends to be large, and it takes time to disperse, and unless the number of passes is extremely increased, a stable dispersion is difficult to obtain, which is not economical. Moreover, when it exceeds 300 MPa, it is easy to become overdispersed, and it is difficult to obtain the stability of the dispersion. If the desired pigment particle diameter cannot be reached, the dispersion may be carried out by increasing the number of dispersions or increasing the pressure within the aforementioned pressure range.

  Further, in the method for producing an ink for ink jet recording of the present invention, an alkali solution is added to the above-described polymer composition for ink for ink jet recording which has been polymerized and heated, and then the solvent is removed, and ion exchange water or the like. A polymer composition solution for ink jet recording ink substituted with may be used.

  Further, the solvent for the ink for ink-jet recording described above after polymerization is removed by distillation under reduced pressure, the solid matter of the polymer for ink-jet recording obtained is crushed, and ion-exchanged water, an alkali solution, etc. are added and heated. The polymer solution for ink for ink jet recording obtained by dissolving may be used. In this case, thereafter, it is not necessary to remove the organic solvent and the like from the obtained pigment dispersion.

  Examples of the alkali used in the aforementioned alkaline solution include tertiary alkyl alkanolamines such as triethanolamine and tripropanolamine, and inorganic bases such as sodium hydroxide, potassium hydroxide and lithium hydroxide.

(Example)
The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples, and various modifications can be made without departing from the gist of the present invention.

  The inside of a 2000 ml separable flask equipped with a stirrer, a reflux tube, a thermometer, and a dropping funnel was purged with nitrogen, and then 200.0 parts by weight of diethylene glycol monomethyl ether was placed in the separable flask and heated to 80 ° C. while stirring. . Next, 200.0 parts by weight of diethylene glycol monomethyl ether, 483.0 parts by weight of benzyl acrylate, 50.4 parts by weight of acrylic acid, and 4.8 parts by weight of t-butylperoxy (2-ethylhexanoate) are placed in the dropping funnel. The reaction was conducted dropwise at 80 ° C. over 4 hours in a separable flask. After completion of dropping, the mixture was kept at 80 ° C. for 1 hour, 0.8 parts by weight of t-butylperoxy (2-ethylhexanoate) was added, and the reaction was further carried out at 80 ° C. for 1 hour. Thereafter, diethylene glycol monomethyl ether was removed by distillation under reduced pressure. Then, 600.0 parts by weight of methyl ethyl ketone was added to obtain a polymer composition solution having a resin solid content of 50%. After taking a part of the polymer composition solution thus obtained and drying for 1 hour in an oven at 105 ° C., the acid value of the solid of the polymer composition obtained is 65 mgKOH / g, The weight average molecular weight was 34,000.

  Next, 3.0 parts by weight of a 30% aqueous sodium hydroxide solution is added to 120.0 parts by weight of the polymer composition solution thus prepared, and the mixture is stirred for 5 minutes with a high-speed disper, and further PALIOTOL Yellow D0960 ( CI Pigment Yellow 138 (manufactured by BASF) was added in an amount of 480.0 parts by weight, and the mixture was stirred with a high-speed disper for 1 hour to obtain a pigment-dispersed slurry. Then, the pigment dispersion slurry was continuously dispersed 10 times at a pressure of 200 MPa with an ultrahigh pressure homogenizer (Microfluidizer, manufactured by Mizuho Kogyo Co., Ltd.) to obtain a pigment dispersion.

  Further, methyl ethyl ketone and a part of water were distilled off from the pigment dispersion thus obtained by vacuum distillation using an evaporator, and centrifuged at 5000 rpm for 30 minutes using a centrifuge (05P-21, manufactured by Hitachi, Ltd.). Then, ion-exchanged water was added so that the pigment concentration was 15% by weight to prepare a pigment dispersion. This was subjected to pressure filtration using a 2.5 μm membrane filter (manufactured by Advantech), and then an ink for ink jet recording of ink composition example 1 shown in Table 3 was prepared.

  The inkjet of Composition Example 2 shown in Table 3 was carried out in the same manner as in Example 1, except that 13.2 parts by weight of methacrylic acid and 36.5 parts by weight of acrylic acid were used instead of 50.4 parts by weight of acrylic acid. A recording ink was prepared. Moreover, after taking a part of polymer composition solution and drying for 1 hour with a 105 degreeC high heat dryer, the acid value of the solid substance of the obtained polymer composition is 60 mgKOH / g, and a weight average molecular weight is 32000. Met.

  The same procedure as in Example 1 was conducted except that 42.6 parts by weight of acrylic acid was used instead of 50.4 parts by weight of acrylic acid, and an ink jet recording ink of Composition Example 3 shown in Table 3 was produced. Moreover, after taking a part of polymer composition solution and drying for 1 hour with a 105 degreeC high temperature dryer, the acid value of the solid substance of the obtained polymer composition is 55 mgKOH / g, and a weight average molecular weight is 48000. Met.

  PALIOTOL Yellow D0960 instead of 480.0 parts by weight PALIOTOL Yellow D0960 456.0 parts by weight, Fast Yellow 7413-A (C.I.PY74; manufactured by Sanyo Dye Co., Ltd.) 24.0 parts by weight In the same manner as in Example 1, an inkjet recording ink of Composition Example 4 shown in Table 3 was prepared.

  Example of composition shown in Table 3 except that PALIOTOL Yellow D0960 was replaced with 480.0 parts by weight, and PALIOTOL Yellow D0960 was 320.0 parts by weight and Fast Yellow 7413-A was 160.0 parts by weight. Inkjet recording ink No. 5 was prepared.

  Instead of 50.4 parts by weight of acrylic acid, 77.5 parts by weight of acrylic acid, 480.0 parts by weight of PALIOTOL Yellow D0960 instead of 480.0 parts by weight, 48.0 parts by weight of PALIOTOL Yellow D0960, 432.0 parts by weight of Fast Yellow 7413-A Except for the parts, the same procedure as in Example 1 was performed to prepare an ink for inkjet recording of Composition Example 6 shown in Table 3. Further, after taking a part of the polymer composition solution and drying it for 1 hour with a high-temperature dryer at 105 ° C., the solid value of the polymer composition obtained was 100 mg KOH / g, and the weight average molecular weight was 29000. Met.

  Instead of 50.4 parts by weight of acrylic acid, 93.0 parts by weight of acrylic acid is used. Instead of 480.0 parts by weight of PALIOTOL Yellow D0960, 30.0 parts by weight of PALIOTOL Yellow D0960, 450.0 parts by weight of Fast Yellow 7413-A Except for the parts, the same procedure as in Example 1 was performed to prepare an ink for inkjet recording of Composition Example 7 shown in Table 3. Moreover, after taking a part of polymer composition solution and drying for 1 hour with a 105 degreeC high heat dryer, the acid value of the solid substance of the obtained polymer composition is 120 mgKOH / g, and the weight average molecular weight is 34000. Met.

(Comparative Example 1)
An ink for inkjet recording of Composition Example 8 shown in Table 4 was prepared in the same manner as in Example 1 except that 100.8 parts by weight of acrylic acid was used instead of 50.4 parts by weight of acrylic acid. Further, after taking a part of the polymer composition solution and drying it for 1 hour with an oven at 105 ° C., the solid value of the polymer composition obtained was 130 mgKOH / g, and the weight average molecular weight was 29000. Met.

(Comparative Example 2)
An ink for inkjet recording of Composition Example 9 shown in Table 4 was prepared in the same manner as in Example 1 except that 116.3 parts by weight of acrylic acid was used instead of 50.4 parts by weight of acrylic acid. Moreover, after taking a part of polymer composition solution and drying for 1 hour with a 105 degreeC high temperature drier, the acid value of the solid substance of the obtained polymer composition is 150 mgKOH / g, and the weight average molecular weight is 34000. Met.

(Comparative Example 3)
An ink for inkjet recording of Composition Example 10 shown in Table 4 was prepared in the same manner as in Example 3 except that 155.0 parts by weight of acrylic acid was used instead of 42.6 parts by weight of acrylic acid. Moreover, after taking a part of polymer composition solution and drying for 1 hour with a 105 degreeC high temperature dryer, the acid value of the solid substance of the obtained polymer composition is 200 mgKOH / g, and a weight average molecular weight is 29000. Met.

(Comparative Example 4)
The same as Example 4 except that 19.2 parts by weight of t-butylperoxy (2-ethylhexanoate) was used instead of 4.8 parts by weight of t-butylperoxy (2-ethylhexanoate). Then, an ink for inkjet recording of Composition Example 11 shown in Table 4 was prepared. Further, after taking a part of the polymer composition solution and drying it for 1 hour with a high-temperature dryer at 105 ° C., the solid value of the polymer composition obtained was 65 mgKOH / g, and the weight average molecular weight was 10,000. Met.

(Comparative Example 5)
The same as Example 5 except that instead of 4.8 parts by weight of t-butylperoxy (2-ethylhexanoate), 14.2 parts by weight of t-butylperoxy (2-ethylhexanoate) was used. The ink for inkjet recording of the composition example 12 shown in Table 4 was produced. Moreover, after taking a part of polymer composition solution and drying for 1 hour with a 105 degreeC high heat dryer, the acid value of the solid substance of the obtained polymer composition is 60 mgKOH / g, and a weight average molecular weight is 18000. Met.

(Comparative Example 6)
The same as Example 6 except that instead of 4.8 parts by weight of t-butylperoxy (2-ethylhexanoate), 2.3 parts by weight of t-butylperoxy (2-ethylhexanoate) was used. The ink for inkjet recording of the composition example 13 shown in Table 4 was produced. Moreover, after taking a part of polymer composition solution and drying for 1 hour with a 105 degreeC high heat dryer, the acid value of the solid substance of the obtained polymer composition is 65 mgKOH / g, and a weight average molecular weight is 140000. Met.

(Comparative Example 7)
An ink for inkjet recording of Composition Example 14 shown in Table 4 was prepared in the same manner as in Example 7 except that 93.3 parts by weight of acrylic acid was used and 23.3 parts by weight of acrylic acid was used. Moreover, after taking a part of polymer composition solution and drying for 1 hour with a 105 degreeC high heat dryer, the acid value of the solid substance of the obtained polymer composition is 30 mgKOH / g, and the weight average molecular weight is 33000. Met.

(Evaluation test 1: Evaluation of color development on plain paper)
The ink according to Examples 1 to 7 and Comparative Examples 1 to 7 was solid-printed on XeroxP paper (manufactured by Fuji Xerox Co., Ltd.) using an inkjet printer (EM-930C, manufactured by Seiko Epson Corporation) to obtain a test specimen. (Print mode is paper: plain paper, print quality: super fine, color correction: none, print direction: bidirectional). And OD (Optical Density) of each color was measured using GRETAGMACBETH SPECTROSCAN SP50 (made by Gretag) (measurement conditions were light source: D50, viewing angle: 2 degrees). The results are shown in Tables 1 and 2 as OD values.

(Evaluation test 2: Evaluation of glossiness)
The ink according to Examples 1 to 7 and Comparative Examples 1 to 7 was solid-printed on an EPSON photographic paper (manufactured by Seiko Epson Corporation) with an inkjet printer (EM-930C) to obtain a test specimen (printing mode is paper: Photo print paper, print quality: photo, color correction: none, print direction: bidirectional). The 20-degree gloss of this specimen was measured with a gloss meter (HG-268, manufactured by Suga Test Instruments Co., Ltd., V type company). The results are shown in Tables 1 and 2.

(Evaluation Test 3: Evaluation of Dispersibility)
The average particle diameter of the particles in the ink according to Examples 1 to 7 and Comparative Examples 1 to 7 was measured with a laser particle size analyzer (Zeta Sizer 3000, manufactured by Malvern). The results are shown in Tables 1 and 2.

(Evaluation Test 4: Evaluation of Storage Stability)
The initial viscosity of the ink pigment dispersions according to Examples 1 to 7 and Comparative Examples 1 to 7 and the viscosity after standing at 70 ° C. for 1 week were measured with a rolling ball viscometer (AMVn, manufactured by Anton Paar). did. The results are shown in Tables 1 and 2 as storage stability: viscosity (mPa · s) / initial viscosity (mPa · s) after standing at 70 ° C. for 1 week.

  Tables 1 and 2 also show the monomer composition, the polymerization initiator and the pigment, and the inkjet ink composition used when the ink was produced.

(Evaluation Test 5: Evaluation of Light Resistance)
The inks according to Examples 1 to 7 and Comparative Examples 1 to 7 were applied to EPSON photographic paper with an inkjet printer (EM-930C) so as to be in the range of OD (Optical Density) = 0.9 to 1.1. Were adjusted, and solid printing was performed to obtain a test specimen (printing mode: paper: photo print paper, print quality: photo, color correction: none, print direction: bidirectional). After leaving these specimens in a room temperature room for 3 days, using a xenon weather meter (XL-75S; manufactured by Suga Test Instruments Co., Ltd.), 24 ° C. 60% RH; BPT (black panel temperature) 40 ° C .; Light exposure treatment for 720 hours was performed under the condition of illuminance of 34 W / m ² at 400 nm.

About the test body before and behind the said light exposure process, OD was measured using GRETAGMACBETH SPECTROSCAN SP50, and optical density residual ratio (ROD) was calculated | required by following Formula. The results are shown in Table 3 and Table 4.
ROD (%) = (D / D ₀ ) × 100
D: OD after light exposure treatment
D ₀ : OD before light exposure treatment

In addition, the symbol shown in Table 1-Table 4 is as follows.
BZA: benzyl acrylate AA: acrylic acid MAA: methacrylic acid BPEH: t-butylperoxy (2-ethylhexanoate)
PY138 C.I. I. Pigment Yellow 138 (Kinophthalone)
PY74: C.I. I. Pigment Yellow 74 (Condensed Azo Pigment)
DEGmBE: diethylene glycol monobutyl ether TEGmBE: triethylene glycol monobutyl ether PGmBE: propylene glycol monobutyl ether DPGmBE: dipropylene glycol monobutyl ether BEPD: 2-butyl-2-ethyl-1,3-propanediol 1,2-HD: 1, 2-Hexanediol TMP: Trimethylolpropane

  As can be seen from the results shown in Tables 1 to 4, when the inks for ink jet recording according to Examples 1 to 7 are used, the results of all the tests are good, but according to Comparative Examples 1 to 7 Ink jet recording ink cannot obtain good results in any one or more of the evaluation tests.

Claims (7)

  Water and at least 50% by weight of benzyl acrylate and 15% by weight or less (meth) acrylic acid as a polymer component are polymerized, and have a weight average molecular weight of 20,000 to 120,000 having an acid value of 50 to 120 mgKOH / g. An ink containing a pigment dispersed using a polymer, wherein the pigment includes at least C.I. I. Ink for inkjet recording, comprising Pigment Yellow 138.   As the pigment, C.I. I. The ink for inkjet recording according to claim 1, comprising Pigment Yellow 74.   C. I. Pigment yellow 138 and C.I. I. The ink for inkjet recording according to claim 2, wherein the content ratio of Pigment Yellow 74 is in a range of 20: 1 to 1:10 in terms of weight.   At least 0.05% by weight to 1% by weight of 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4, The ink for inkjet recording according to any one of claims 1 to 3, comprising at least one selected from alkylene oxide adducts of 7-diol.   The ink for inkjet recording according to any one of claims 1 to 4, comprising 1,2-alkylene glycol.   The ink for inkjet recording according to any one of claims 1 to 5, comprising one or more selected from di (tri) ethylene glycol monobutyl ether and (di) propylene glycol monobutyl ether.   The ink for inkjet recording according to any one of claims 1 to 6, comprising 2-butyl-2-ethyl-1,3-propanediol.