JP2009280670A - Inkjet ink and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink which can prevent bleeding, beading and feathering , and also prevent curling and cockling on a printing paper and a regular paper, and to provide an inkjet recording method. <P>SOLUTION: The inkjet ink includes at least a coloring material, water, a water-soluble solvent and a water-soluble polymeric compound, wherein one water-soluble polymeric compound includes acrylamide having a sulfo group expressed by general formula (1) as a monomer component. In the formula, R<SP>1</SP>represents a hydrogen atom or a 1-4C alkyl group; R<SP>2</SP>represents a 1-6C alkylene group; and M represents a counter salt. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a recording material with good feathering and low curl for plain paper media, and no beading or bleeding on media with low ink absorption or ink absorption. The present invention relates to an ink-jet ink and an ink-jet recording method that give an image with a low image quality.

  In recent years, inkjet recording methods are capable of recording high-definition images with a relatively simple apparatus, and have been rapidly developed in various fields. In addition, there are various uses, and a recording medium or ink suitable for each purpose is used. In particular, in recent years, the recording speed has been greatly improved, and printers having performance capable of withstanding light printing applications have been developed.

  However, the demand for printing on printing paper and plain paper in light printing is still high, and there is a high demand for high-speed and clear printing of characters in inkjet recording.

  However, a problem with inkjet recording is that only ink with a relatively low viscosity can be emitted from the inkjet head, so when recording on printing paper with low ink absorbency, the bleed mixes between different colors. And a phenomenon called beading in which the shades of colors appear as rosary between single colors occur, causing image quality to deteriorate. Further, in recording on plain paper having a high ink absorption speed, a phenomenon called feathering in which irregular bleeding occurs along the fiber of the paper occurs, which also causes a reduction in image quality. On the other hand, inkjet ink usually contains water as a main component, so both printing paper and plain paper undergo curling phenomenon when dried after printing, and a phenomenon called cockling in which the recording medium undulates, resulting in deterioration of quality. It is the cause.

  Various methods have been proposed to prevent this. A temperature-sensitive polymer whose viscosity changes depending on the temperature is put in the ink so that the ink has temperature sensitivity, and the temperature of the inkjet head and the temperature of the recording medium are made different, so that the viscosity is low at the time of emission and recording is performed. There is an attempt of a temperature-sensitive thickening type water-based ink which attempts to prevent bleeding, beading, and feathering while ensuring high light emission properties when landing on a medium. For example, Patent Document 1 proposes a temperature-sensitive thickening type water-based ink containing a high-molecular substance that is thermoreversibly converted to a temperature-sensitive gel at a transition temperature or higher and becomes water-insoluble by drying. Patent Document 2 proposes to use a temperature-sensitive colored polymer obtained by reacting a temperature-sensitive polymer anion having a lower critical solution temperature (LCST) with a dye. Patent Document 3 proposes an ink-jet ink containing a dispersion having a temperature-sensitive polymer.

  However, since the proposed temperature-sensitive ink has temperature sensitivity only in a region where the water content is high, curling and cockling cannot be prevented even though bleeding, beading and feathering can be prevented.

  On the other hand, Patent Document 4 states that the high water content is the cause of curling, and the water content is less than 50% by mass and the water-soluble organic solvent has an SP value of 9.0 or more and less than 12.0. An ink containing 30% by mass or more of the ink mass has been proposed. In fact, when this ink is used, curling can be prevented, but conversely, since the viscosity when the ink lands on the recording medium is as low as that at the time of emission, bleeding, beading, and feathering cannot be prevented.

For this reason, there has been a demand for an ink that can prevent curling and cockling as well as preventing bleeding, beading, and feathering by changing the viscosity with temperature in a region where the water content is low.
JP 09-012947 A JP 2001-114820 A JP 2006-16499 A JP 2007-091905 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to prevent bleed, beading, feathering, and curling and cockling with respect to printing paper and plain paper. An inkjet recording method is provided.

The above object of the present invention is achieved by the following configurations.
1. In an inkjet ink containing at least a coloring material, water, a water-soluble solvent, and a water-soluble polymer compound, one of the water-soluble polymer compounds is a monomer component of acrylamide having a sulfo group represented by the following general formula (1) An ink-jet ink comprising a water-soluble polymer compound as described above.

(In the formula, R ¹ represents a hydrogen atom and a C1-C4 alkyl group, R ² represents a C1-C6 alkylene group, and M represents a counter salt.)
2. The inkjet ink as described in 1 above, wherein b / a is 10 or more, where a is a viscosity at 2.70 ° C. and b is a viscosity at 30 ° C.
3. 3. The inkjet ink according to 1 or 2, wherein the water-soluble solvent is 40% by mass or more of the inkjet ink.
4). 4. The inkjet ink according to any one of 1 to 3, wherein at least one of the water-soluble solvents is a compound represented by the following general formula (2).

Formula (2) RO (AO) _n H
(In the formula, R represents a C1 to C6 alkyl group, A represents an ethylene oxide group or a propylene oxide group, and n represents a natural number of 1 to 3.)
5. One of the water-soluble polymer compounds having a sulfo group-containing acrylamide as a monomer component is a copolymer with a monomer having a nonionic ethylenically unsaturated bond. The inkjet ink according to item 1.
6). The content of the water-soluble polymer containing acrylamide having a sulfo group as a monomer component is 0.5 to 10% by mass of the ink-jet ink, according to any one of 1 to 5 above. Inkjet ink.
7). 7. An ink jet recording method, wherein the ink jet ink according to any one of 1 to 6 is recorded using an ink jet printer having a heated head.

  According to the present invention, it is possible to provide an ink-jet ink and an ink-jet recording method which prevent bleeding, beading and feathering as well as curling and cockling with respect to printing paper and plain paper.

  As a result of intensive studies in view of the above problems, the present inventors have found that, in an inkjet ink containing a colorant, water, a water-soluble solvent, and a water-soluble polymer compound, one of the water-soluble polymer compounds contains a sulfo group. Ink jet ink, which is a water-soluble polymer compound containing acrylamide as a monomer component, can prevent ink from bleeding, beading, feathering, and curling and cockling against printing paper and plain paper. I found out.

  Further, as a preferable property of the ink-jet ink, b / a is 10 or more when the water-soluble solvent is contained in an amount of 40% by mass or more, the viscosity at 70 ° C. is a, and the viscosity at 30 ° C. is b. More preferably, the water-soluble solvent is ejected from a heated head using an inkjet ink which is a compound represented by the general formula (2), and is recorded on a recording medium at room temperature. It has been found that an ink jet recording method can be obtained that prevents bleeding, beading, and feathering, and curling and cockling of the main paper and plain paper.

  The ink of the present invention is a temperature-sensitive thickening type ink, but can increase the amount of water-soluble organic solvent. Therefore, printing paper, plain paper bleed and beading obtained with conventional temperature-sensitive thickening type water-based inks can be used. In addition to the effect of preventing feathering, it is also possible to prevent curling and cockling.

  Conventionally, water-soluble polymers containing acrylamide having a sulfo group as a monomer component have already been known as a thickener that can be widely used in cosmetics and the like from 100% water to a mixture of alcohol and water with a low water content. It was. On the other hand, the water-soluble polymer of acrylamide having a sulfo group has a partially identical structure to polyisopropylacrylamide, which is famous as a temperature-sensitive polymer. There was no literature that showed the temperature sensitivity of acrylamide itself. Therefore, when the change in viscosity of a water-soluble polymer containing acrylamide having a sulfo group as a monomer component in a mixed solvent of a number of solvents and water was measured with temperature, even in a region where the content of the water-soluble solvent was high, It has been found that when it contains a water-sensitive solvent of 40% by mass or more and further contains an alkylene glycol alkyl ether in the water-soluble solvent, the viscosity is greatly changed. Furthermore, when copolymerized with acrylamide having a sulfo group and a monomer having a nonionic ethylenically unsaturated bond, the ratio of the monomer having a nonionic ethylenically unsaturated bond, or having a nonionic ethylenically unsaturated bond It has been found that as the hydrophobicity of the monomer increases, the viscosity change with temperature increases, and the effect of preventing bleeding, beading and feathering is further improved. The reason for this is that the sulfo group of the water-soluble polymer containing acrylamide having a sulfo group as a monomer component acts to dissolve the water-soluble polymer by strongly interacting with water up to a region where the water content is low. Is considered to be more hydrophobic by interacting with a hydroxyl group of water at low temperatures and interacting with a water-soluble solvent instead of water at high temperatures. Especially when the water-soluble solvent has one hydroxyl group on the hydrophobic group such as alkylene glycol monoalkyl ether, it becomes more hydrophobic as a result of the interaction with water-soluble polymer containing acrylamide having sulfo group as a monomer component at high temperature. As a result of this, microemulsion is considered to cause a larger viscosity change.

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

[Water-soluble polymer compound]
The water-soluble polymer compound used in the present invention is preferably a water-soluble polymer compound having acrylamide having a sulfo group represented by the general formula (1) as a monomer component.

In the general formula (1), R ¹ represents a hydrogen atom, an unsubstituted or substituted C1-C4 alkyl group (methyl group, ethyl group, propyl group, butyl group), preferably a hydrogen atom or a methyl group. .

R ² represents a C1-C6 unsubstituted or substituted alkylene group (methylene group, ethylene group, propylene group, butylene group, hexylene group).

  Specific examples of the acrylamide monomer having a sulfo group include 2- (meth) acrylamide-2-methylpropanesulfonate, (meth) acrylamide-2-ethylsulfonate, and (meth) acrylamide-3-propanesulfonate. , (Meth) acrylamide-4-butanesulfonate, and the like. Examples of the counter salt represented by M include a monovalent cation and a divalent cation. Specifically, examples of the monovalent cation include an ammonium cation, an organic ammonium cation, a sodium ion, a potassium ion, and a lithium ion. Examples of the divalent cation include calcium ions. Preferably it is a monovalent cation.

(Copolymer component)
The water-soluble polymer compound used in the present invention may be a homopolymer of an acrylamide monomer having a sulfo group, but various monomers may be used from the viewpoints of ink storage stability, water resistance of the obtained image, and improved adhesion. It is preferable to use the copolymer as a copolymer.

  Monomers that may be copolymerized include monomers having an anionic ethylenically unsaturated bond represented by acrylic acid, methacrylic acid, itaconic acid, styrene sulfonic acid, vinyl sulfonic acid, and salts thereof, styrene, and acrylic acid. Examples thereof include a monomer having a nonionic ethylenically unsaturated bond typified by an ester and the like, and a monomer having a cationic ethylenically unsaturated bond such as N, N-dimethylaminoethyl (meth) acrylate. However, since the interaction with the sulfo group of acrylamide having a sulfo group is reduced and the viscosity is lowered by increasing the temperature, the absolute value of the viscosity is small, which is more preferable as an inkjet ink. It is preferable to copolymerize with a monomer having a saturated bond.

  Examples of the nonionic ethylenically unsaturated bond monomer include compounds having at least one styrene group, acrylic group, methacryl group, allyl group, crotonic acid group, maleic acid group, and itaconic acid group in the molecule. A compound having at least one acrylic group or methacryl group in the molecule is preferable.

  Examples of the compound having a styrene group include styrene and styrene sulfonic acid.

  Examples of compounds having an acryl group and a methacryl group (hereinafter referred to as “(meth) acryl group” together) include (meth) acrylamide, 2-hydroxy (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, vinylpyrrolidone, hydroxyalkyl (meth) acrylate such as 1,4-butanediol mono (meth) acrylate; polyoxyethylene (meth) acrylate, polyoxyethylene polyoxypropylene (meth) acrylate Alkyl polyoxyethylene (meth) acrylate, alkyl polyoxyethylene polyoxypropylene (meth) acrylate, and the like.

  Alternatively, a surfactant monomer having a polymerizable group can also be used. Specifically, Aqualon RN-10, Aqualon RN-20, Aqualon RN-30, Aqualon RN-50 from Daiichi Kogyo Seiyaku Co., Ltd. Genapol-O-150-methacrylate from Clariant, Genapal-T -070-methacrylate, Genapal-LA-250-methacrylate, Genapal-Behenyl-020-methacrylate, and the like.

  The copolymerization ratio is not particularly limited, but if too many acrylamides have a sulfo group, the ink storage stability, the water resistance of the obtained image, and the adhesiveness deteriorate, and the monomer has a nonionic ethylenically unsaturated bond. If the amount is too large, the thickening due to temperature change is lost, so the ratio of the acrylamide having a sulfo group / the monomer having an ethylenically unsaturated bond is preferably 40/60 to 97/3.

  The molecular weight of the water-soluble polymer compound used in the present invention is not particularly limited, but is preferably 7000 to 100,000 in order to preferably enjoy the effects of the present invention as an inkjet ink. If it is less than 7000, the solvent composition range showing the temperature-sensitive thickening range becomes wide, but the magnitude of thickening decreases. When the molecular weight exceeds 100,000, the thickening level increases, but the solvent composition range showing the temperature-sensitive thickening range becomes narrow, making it difficult to prepare an ink.

[How to determine the solvent composition of temperature-sensitive thick ink-jet ink]
Preferred properties of the inkjet ink of the present invention (hereinafter also simply referred to as ink) are inks having a b / a of 10 or more, where a is a viscosity at 70 ° C. and b is a viscosity at 30 ° C.

  As a method for measuring the viscosity, a rotary type, a vibration type, or a thin tube type can be used, but a rotary type is preferred because it can be easily measured. The present invention was measured under the conditions of CP75-1 (plate diameter 75 mm), temperature change −10 ° C./min, shear rate 1/10 s using MCR300 manufactured by Paar PHYSICA.

  FIG. 1 is a conceptual diagram showing the relationship between the solvent ratio and the viscosity ratio, and shows that the viscosity ratio is 10 times or more in the range of the solvent ratio of 25 to 45.

(Water-soluble solvent)
Examples of the water-soluble solvent used in the present invention include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-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, triethanol) Amine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenedia , Diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), Heterocycles (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) and the like It is done.

  As the water-soluble solvent used in the present invention, a compound represented by the general formula (2) (alkylene glycol alkyl ether) is preferable.

  In General formula (2), R represents a C1-C6 alkyl group, A represents an ethylene oxide group or a propylene oxide group, and n represents a natural number of 1 to 3. Examples of the alkylene glycol alkyl ether include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol monomethyl ether, monoethyl ether, monobutyl ether, and the like.

  In the present invention, in order to prevent curling and cockling, at least 40% by mass of the water-soluble solvent is preferably used.

[Surfactant]
A surfactant can be used in the ink of the present invention.

  Preferred surfactants include anionic surfactants, nonionic surfactants, and cationic surfactants.

  Anionic surfactants include alkyl sulfates, alkyl ester sulfates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, fatty acid salts, and the like. Agents.

  Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene alkyl phenyl ethers, acetylene glycols, polyoxyethylene-polyoxypropylene block copolymers and the like nonionic surfactants, glycerin esters, sorbitan esters. And activators such as polyoxyethylene fatty acid amides and amine oxides.

  Examples of the cationic surfactant include cationic surfactants such as alkylamine salts and quaternary ammonium salts.

[Color material]
As the coloring material used in the ink of the present invention, various known dyes or pigments can be used. It is preferable to use a pigment from the viewpoint of image storability.

(dye)
There is no restriction | limiting in particular as dye which can be used by this invention, Water-soluble dyes, such as an acid dye, a direct dye, and a reactive dye, a disperse dye, etc. are mentioned. Of these, anionic dyes are preferred.

  Examples of water-soluble dyes that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, and the like. The compounds are shown below. However, it is not limited to these exemplified compounds.

<C. I. Acid Yellow>
1, 3, 11, 17, 18, 19, 23, 25, 36, 38, 40, 42, 44, 49, 59, 61, 65, 67, 72, 73, 79, 99, 104, 110, 114, 116, 118, 121, 127, 129, 135, 137, 141, 143, 151, 155, 158, 159, 169, 176, 184, 193, 200, 204, 207, 215, 219, 220, 230, 232, 235, 241, 242, 246
<C. I. Acid Orange>
3, 7, 8, 10, 19, 24, 51, 56, 67, 74, 80, 86, 87, 88, 89, 94, 95, 107, 108, 116, 122, 127, 140, 142, 144, 149, 152, 156, 162, 166, 168
<C. I. Acid Red>
88, 97, 106, 111, 114, 118, 119, 127, 131, 138, 143, 145, 151, 183, 195, 198, 211, 215, 217, 225, 226, 249, 251, 254, 256, 257, 260, 261, 265, 266, 274, 276, 277, 289, 296, 299, 315, 318, 336, 337, 357, 359, 361, 362, 364, 366, 399, 407, 415
<C. I. Acid Violet>
17, 19, 21, 42, 43, 47, 48, 49, 54, 66, 78, 90, 97, 102, 109, 126
<C. I. Acid Blue>
1, 7, 9, 15, 23, 25, 40, 62, 72, 74, 80, 83, 90, 92, 103, 104, 112, 113, 114, 120, 127, 128, 129, 138, 140, 142, 156, 158, 171, 182, 185, 193, 199, 201, 203, 204, 205, 207, 209, 220, 221, 224, 225, 229, 230, 239, 249, 258, 260, 264, 278, 279, 280, 284, 290, 296, 298, 300, 317, 324, 333, 335, 338, 342, 350
<C. I. Acid Green>
9, 12, 16, 19, 20, 25, 27, 28, 40, 43, 56, 73, 81, 84, 104, 108, 109
<C. I. Acid Brown>
2, 4, 13, 14, 19, 28, 44, 123, 224, 226, 227, 248, 282, 283, 289, 294, 297, 298, 301, 355, 357, 413
<C. I. Acid Black>
1, 2, 3, 24, 26, 31, 50, 52, 58, 60, 63, 107, 109, 112, 119, 132, 140, 155, 172, 187, 188, 194, 207, 222
<C. I. Direct yellow>
8, 9, 10, 11, 12, 22, 27, 28, 39, 44, 50, 58, 79, 86, 87, 98, 105, 106, 130, 132, 137, 142, 147, 153
<C. I. Direct orange>
6, 26, 27, 34, 39, 40, 46, 102, 105, 107, 118
<C. I. Direct Red>
2, 4, 9, 23, 24, 31, 54, 62, 69, 79, 80, 81, 83, 84, 89, 95, 212, 224, 225, 226, 227, 239, 242, 243, 254
<C. I. Direct Violet>
9, 35, 51, 66, 94, 95
<C. I. Direct Blue>
1, 15, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 160, 168, 189, 192, 193, 199, 200, 201, 202, 203, 218, 225, 229, 237, 244, 248, 251, 270, 273, 274, 290, 291
<C. I. Direct Green>
26, 28, 59, 80, 85
<C. I. Direct Brown>
44, 106, 115, 195, 209, 210, 222, 223
<C. I. Direct Black>
17, 19, 22, 32, 51, 62, 108, 112, 113, 117, 118, 132, 146, 154, 159, 169
<C. I. Basic Yellow>
1, 2, 11, 13, 15, 19, 21, 28, 29, 32, 36, 40, 41, 45, 51, 63, 67, 70, 73, 91
<C. I. Basic Orange>
2, 21, 22
<C. I. Basic Red>
1, 2, 12, 13, 14, 15, 18, 23, 24, 27, 29, 35, 36, 39, 46, 51, 52, 69, 70, 73, 82, 109
<C. I. Basic Violet>
1, 3, 7, 10, 11, 15, 16, 21, 27, 39
<C. I. Basic Blue>
1, 3, 7, 9, 21, 22, 26, 41, 45, 47, 52, 54, 65, 69, 75, 77, 92, 100, 105, 117, 124, 129, 147, 151
<C. I. Basic Green>
1, 4
<C. I. Basic Brown>
1
<C. I. Reactive Yellow>
2, 3, 7, 15, 17, 18, 22, 23, 24, 25, 27, 37, 39, 42, 57, 69, 76, 81, 84, 85, 86, 87, 92, 95, 102, 105, 111, 125, 135, 136, 137, 142, 143, 145, 151, 160, 161, 165, 167, 168, 175, 176
<C. I. Reactive Orange>
1, 4, 5, 7, 11, 12, 13, 15, 16, 20, 30, 35, 56, 64, 67, 69, 70, 72, 74, 82, 84, 86, 87, 91, 92, 93, 95, 107
<C. I. Reactive Red>
2, 3, 5, 8, 11, 21, 22, 23, 24, 28, 29, 31, 33, 35, 43, 45, 49, 55, 56, 58, 65, 66, 78, 83, 84, 106, 111, 112, 113, 114, 116, 120, 123, 124, 128, 130, 136, 141, 147, 158, 159, 171, 174, 180, 183, 184, 187, 190, 193, 194, 195, 198, 218, 220, 222, 223, 228, 235
<C. I. Reactive Violet>
1, 2, 4, 5, 6, 22, 23, 33, 36, 38
<C. I. Reactive Blue>
2, 3, 4, 5, 7, 13, 14, 15, 19, 21, 25, 27, 28, 29, 38, 39, 41, 49, 50, 52, 63, 69, 71, 72, 77, 79, 89, 104, 109, 112, 113, 114, 116, 119, 120, 122, 137, 140, 143, 147, 160, 161, 162, 163, 168, 171, 176, 182, 184, 191, 194, 195, 198, 203, 204, 207, 209, 211, 214, 220, 221, 222, 231, 235, 236
<C. I. Reactive Green>
8, 12, 15, 19, 21
<C. I. Reactive Brown>
2, 7, 9, 10, 11, 17, 18, 19, 21, 23, 31, 37, 43, 46
<C. I. Reactive Black>
5, 8, 13, 14, 31, 34, 39
<C. I. Food Black>
1,2.

(Pigment)
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 lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Examples include cyclic pigments, dye lakes such as basic dye type lakes and acid dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black and daylight fluorescent pigments, and inorganic pigments such as carbon black. Pigments are preferred.

  Specific organic pigments are exemplified below.

  Examples of pigments for magenta or red 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 15, C.I. I. Pigment red 16, 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 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the orange or yellow pigment include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, 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 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. And CI Pigment Yellow 138.

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

(Dispersant)
As the water-soluble polymer dispersant for stably dispersing the pigment in the ink, the following water-soluble resin can be used, which is preferable from the viewpoint of ejection stability.

  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.

  The content of the water-soluble resin with respect to the total amount of the ink is preferably 0.1 to 10% by mass, and more preferably 0.3 to 5% by mass.

  Two or more of these water-soluble resins can be used in combination.

(Anionic pigment)
The form of the anionic pigment used in the present invention is preferably a pigment in which the pigment is dispersed with an anionic polymer dispersant or an anion-modified self-dispersing pigment from the viewpoint of dispersion stability.

(Anionic polymer dispersant)
An anionic polymer dispersant refers to a dispersant having an anionic group obtained by neutralizing an acidic group in a molecule with a basic compound. Examples of the basic compound used at this time include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamine, and alkanolamine. In the present invention, amines are particularly preferable. .

  The anionic polymer dispersant preferably used in the present invention is not particularly limited as long as the molecular weight is 1000 or more. For example, polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, and acrylic acid-acrylonitrile copolymers , Acrylic resins such as potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer Styrene-acrylic resins such as styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, Styrene-maleic acid copolymer, styrene-maleic anhydride Acid copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, and vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer Polymers, vinyl acetate copolymers such as vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, and copolymers or resins such as salts thereof are, for example, carboxylic acid, sulfonic acid or phosphonic acid. Includes homopolymers, copolymers and terpolymers with acid functionality.

  Monomers that give acid functionality include, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, mesaconic acid, fumaric acid, citraconic acid, vinyl acetic acid, acrylic oxypropionic acid, vinyl sulfonic acid Styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, allyl sulfonic acid, allyl phosphonic acid, vinyl phosphonic acid and vinyl sulfonic acid.

(Self-dispersing pigment)
The anion-modified self-dispersing pigment preferably used in the present invention refers to a pigment having an anionic group on the surface and capable of being dispersed without a dispersant. An anionic self-dispersing pigment is a pigment in which an acidic group is modified on the pigment, and this is neutralized with a basic compound to form an anionic group that can be dispersed in water without a dispersant.

  Pigment particles having acidic groups on the surface are pigments directly modified with acidic groups on the surface of the pigment particles, or organic substances having organic pigment mother nuclei, or those having acidic groups bonded via a joint. Say.

  Examples of the acidic group (also referred to as polar group) include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a boric acid group, and a hydroxyl group, preferably a sulfonic acid group and a carboxylic acid group, and more preferably a sulfonic acid group. It is a group.

  Acid group modifiers include sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt, sulfamic acid and other treatments containing sulfur atoms, and the pigment particle surface is oxidized. Carboxylating agents such as sodium hypochlorite and potassium hypochlorite that introduce carboxylic acid groups can be mentioned. Among them, a sulfonating agent such as sulfur trioxide, sulfonated pyridine salt or sulfamic acid, or a carboxylating agent is preferable.

  Examples of basic compounds that neutralize acidic groups include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamines, and alkanolamines. In the present invention, amines are used. Is particularly preferred.

  Examples of a method for obtaining pigment particles having a polar group on the surface include, for example, International Publication No. 97/48769 pamphlet, JP-A Nos. 10-110129, 11-246807, 11-57458, and 11-189739. By oxidizing the pigment particle surface described in JP-A-11-323232, JP-A-2000-265094, etc. with an appropriate oxidizing agent, at least a part of the pigment surface is referred to as a sulfonic acid group or a salt thereof. And a method of introducing a polar group.

  Specifically, it is prepared by oxidizing carbon black with concentrated nitric acid, or in the case of color pigments by oxidizing with sulfamic acid, sulfonated pyridine salt, amidosulfuric acid, etc. in sulfolane or N-methyl-2-pyrrolidone. Can do. A pigment dispersion can be obtained by removing and purifying a substance that has been excessively oxidized by these reactions and has become water-soluble. Moreover, when a sulfonic acid group is introduced to the surface by oxidation, the acidic group may be neutralized with a basic compound as necessary.

  As other methods, a method of adsorbing the pigment derivatives described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. on the pigment particle surface by a treatment such as milling, Examples include a method of dissolving the pigments described in JP-A Nos. 2002-179777 and 2002-201401 together with a pigment derivative in a solvent and then crystallization in a poor solvent. Pigment particles having a polar group can be obtained.

(Pigment particle size)
The average particle size of the pigment dispersion used in the ink of the present invention is preferably 500 nm or less, more preferably 200 nm or less, preferably 10 to 200 nm, more preferably 10 to 150 nm. If the average particle size of the pigment dispersion exceeds 500 nm, the dispersion becomes unstable, and even if the average particle size of the pigment dispersion is less than 10 nm, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink Tend to deteriorate.

  The particle size of the pigment dispersion can be measured by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. It is also possible to obtain a particle image with a transmission electron microscope on at least 100 particles and perform statistical processing on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). Is possible.

(Pigment dispersion method)
Examples of dispersion means that can be used in the present invention include various dispersions such as a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, and high-pressure homogenizer. A machine can be used. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.

(Polymer fine particles)
In the present invention, polymer fine particles may be added in order to improve fixability. The fixing fine polymer particles that can be used in the present invention are not particularly limited, and examples thereof include styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylate copolymer, polyurethane, and silicon-acrylic. Examples thereof include latex such as a copolymer and an acrylic-modified fluororesin. The latex may be obtained by dispersing polymer particles using an emulsifier, or may be dispersed without using an emulsifier. A surfactant is often used as an emulsifier, but a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a single group having a solubilizing group). It is also preferable to use a polymer obtained from a monomer and a monomer having an insoluble part.

  In the ink of the present invention, soap-free latex may be used. Soap-free latex is a latex that does not use an emulsifier and a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a solubilizing group) A polymer obtained from a monomer having a water-soluble monomer and a monomer having an insoluble part) as an emulsifier.

  In recent years, there are latexes in which core-shell type polymer particles with different compositions at the center and outer edges of the particles are dispersed, in addition to latexes in which the polymer particles are uniform throughout. A type of latex can also be preferably used.

  The average particle diameter of the fixing fine polymer particles in the present invention can be measured by light scattering, and is preferably 10 to 300 nm, and more preferably 10 to 200 nm. If the average particle diameter of the fixing fine polymer particles by light scattering exceeds 300 nm, the glossiness of the image is deteriorated, and if it is less than 10 nm, the water resistance and scratch resistance become insufficient.

  The fixing fine polymer particles used in the present invention have a glass transition point of -20 to 80 ° C, preferably -10 to 60 ° C. If the glass transition point is too low, the scratching property is improved, but conversely, if the images are left on top of each other, adhesion occurs and the image portion is peeled off. Further, if the glass transition point is too high, the scratch resistance is poor.

  From the viewpoint of fixability, the total amount of polymer fine particles having groups that generate hydrogen bonds with water molecules and release water by a water-soluble solvent and fixing polymer fine particles is preferably 3 to 30% by mass. If the amount is less than 3% by mass, a printed matter with insufficient rubbing properties and high fastness cannot be obtained. If the amount is more than 30% by mass, the ink viscosity before drying is too high and it is difficult to emit from the head.

(Other additives)
In the ink of the present invention, in addition to the above description, if necessary, the output stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performance improvement objectives are known. Various additives such as a viscosity modifier, a specific resistance modifier, a film forming agent, an ultraviolet absorber, an antioxidant, a fading inhibitor, an antifungal agent, a rust inhibitor, etc. can be appropriately selected and used. Oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476; -74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. be able to.

[Inkjet recording method]
In the ink jet recording method of the present invention, recording is performed using an ink jet printer in which the above ink is used and the head is heated. It is preferable that the ink is heated and emitted with a viscosity of 10 to 300 mPa · s. If it is less than 10 mPa · s, the fluidity of the ink during recording is too high, and the sharpness of the image deteriorates. If it exceeds 300 mPa · s, the ink viscosity is too high and it becomes difficult to emit from the head. The ink jet printer is not particularly limited as long as the head can be heated.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these. In addition, although the display of "part" is used in an Example, unless otherwise indicated, "mass part" is represented.

<Production of ink>
(Preparation of polymer A)
A mixture of 9.6 g (75 mmol) of butyl acrylate, 46.7 g (225 mmol) of 2-acrylamido-2-methylpropanesulfonic acid, 14.3 g of aqueous ammonia and 500 g of t-butanol was heated at 90 ° C., and then azoisobutyro 0.75 g of nitrile was added and stirred. The resulting white precipitate was filtered, washed, and dried to obtain 52 g of polymer A (water-soluble polymer compound).

(Preparation of polymer B)
A mixture of 2.8 g (15 mmol) of 2-ethylhexyl acrylate, 59.0 g (285 mmol) of 2-acrylamido-2-methylpropanesulfonic acid, 18.2 g of aqueous ammonia and 500 g of t-butanol was heated at 90 ° C. 0.75 g of butyronitrile was added and stirred. The resulting white precipitate was filtered, washed, and dried to obtain 58 g of polymer B (water-soluble polymer compound).

(Production of polymer C)
A mixture of 50.4 g (45 mmol) of dodecyloxypolyethylene oxide (20) acrylate, 52.7 g (255 mmol) of 2-acrylamido-2-methylpropanesulfonic acid, 16.2 g of aqueous ammonia and 700 g of t-butanol was heated at 90 ° C. Thereafter, 0.75 g of azoisobutyronitrile was added and stirred. After reacting for 3 hours, the mixture was concentrated to obtain 98 g of polymer C (water-soluble polymer compound).

(Preparation of polymer D)
A mixture of 9.6 g (75 mmol) of butyl acrylate, 25.4 g (225 mmol) of isopropylacrylamide, 14.3 g of aqueous ammonia and 500 g of t-butanol was heated at 90 ° C., and then 0.75 g of azoisobutyronitrile was added and stirred. did. The resulting white precipitate was filtered, washed, and dried to obtain 33 g of polymer D (water-soluble polymer compound).

(Preparation of ink 1)
C. I. Pigment Blue 15: 3 3 parts Tripropylene glycol monomethyl ether (TPGME) 70 parts Polymer A 5 parts Water 30 parts Using a sand grinder filled with 50% by volume of 1.5 mm zirconia beads with the above additives. Dispersion was carried out while heating to ℃. After dispersion, ink 1 was prepared by filtering with a 5 μm felter. In addition, the difference between the mass before dispersion and the mass after dispersion was regarded as evaporation by water, and a reduced amount of water was added to prepare a predetermined concentration.

(Preparation of ink 2 to ink 16)
Inks 2 to 16 were prepared in the same manner except that the TPGME, the amount of water, and the polymer type were changed as shown in Table 1.

(Preparation of ink 17)
A cyan ink described in JP-A-2006-016499, Example 1 was produced.

<Evaluation of ink>
(Measurement of viscosity)
About each ink, it measured on 80 degreeC to 10 degreeC temperature-fall conditions on condition of temperature change -10 degreeC / min and shear rate 1/10 s using MCR300 and plate CP75-1 by Paar PHYSICA.

(Print evaluation)
Nozzle diameter 25 μm, drive frequency 12 kHz, nozzle number 128, nozzle density 180 dpi (dpi represents the number of dots per 2.54 cm), a piezo head with a heating device is mounted, and the maximum recording density is 720 × 720 dpi. An on-demand inkjet printer was prepared. While heating the head to 70 ° C., a cyan image, a solid image, a nine-level gradation image with a density of 0 to 80%, and a line drawing image were created on art paper and plain paper at room temperature. When the head was not heated, the ink was thickened in the head and could not be ejected.

(Evaluation of beading)
The above-prepared dots of each gradation of each cyan were observed with a loupe, and the image uniformity was evaluated according to the following criteria.

◎: The dot shape is maintained for each gradation ○: The dot shape is maintained up to a density of 60%, but some dots are deformed at a density of 70 to 80% △: The dots are up to a density of 40% Although the shape is maintained, some dots are deformed at a density of 50 to 80%. X: The dot shape is not maintained in the entire region.

(Evaluation of curl)
The A4 solid image was left on a horizontal table for one day under an environment of 23 ° C. and 55% relative humidity. The heights of the four corners were measured, and the average value was curled (in mm). Evaluation was made according to the following criteria.

◯: The curl value is less than 0 to 5 mm. Δ: The curl value is less than 5 to 10 mm. ×: The curl value is 10 mm or more.

(Evaluation of feathering)
The cyan line drawing images created above were observed with a magnifying glass and evaluated according to the following criteria.

◎: Thin lines are reproduced without blurring due to bleeding ○: Lines are not thickened due to bleeding, but less than 5 spots, ink bleeding along the paper fiber is observed Δ: Lines are thickened due to bleeding No, but less than 10 spots, ink bleeding along the paper fiber is observed. ×: Line thickness due to bleeding is severe. Table 2 shows the results of viscosity measurement and curl and feathering evaluation.

  From the table, it can be seen that the print sample using the ink of the present invention is prevented from beading and feathering and curl is prevented as compared with the print sample using the comparative ink.

Example 2
(Preparation of ink set of the present invention)
In preparation of ink 1 of Example 1, C.I. I. Pigment Blue 15: 3, carbon black, C.I. I. Pigment red 122, C.I. I. Instead of Pigment Yellow 74, black ink, magenta ink, and yellow ink were prepared, and these were combined to obtain the ink set of the present invention.

(Production of comparative ink set)
An ink set described in JP-A-2006-016499 and Example 1 was produced.

(Evaluation)
A4 output image of high-definition color digital standard image data “N5 bicycle” (issued in December 1995) using the ink set of the present invention and the comparative ink set using the ink jet printer used in Example 1. Obtained.

(Bleed evaluation)
The boundary between black and cyan was visually observed with a magnifying glass and evaluated according to the following criteria.

◯: Both black and cyan have a dot shape. Δ: Either black or cyan has a slightly broken dot shape. X: Either black or cyan has a broken dot shape.

(Evaluation of curl)
The image was evaluated in the same manner as in Example 1.

(Evaluation of cockling)
The printed matter was dried for 10 minutes in an environmental chamber at 23 ° C. and 55% humidity, and then the size of cockling was measured at 10 locations in A4 plain paper, and the difference between the maximum and minimum values was obtained. At this time, the limit target value for quality maintenance was set to 0.2 mm, and cockling beyond that was not allowed. Table 3 shows the evaluation results.

  From the table, it can be seen that the print sample using the ink (ink set) having the configuration defined in the present invention is prevented from bleeding and curling and cockling compared to the print sample using the comparative ink. I understand.

It is a conceptual diagram which shows the relationship between a solvent ratio and a viscosity ratio.

Claims (7)

In an inkjet ink containing at least a coloring material, water, a water-soluble solvent, and a water-soluble polymer compound, one of the water-soluble polymer compounds is a monomer component of acrylamide having a sulfo group represented by the following general formula (1) An ink-jet ink comprising a water-soluble polymer compound as described above.

(In the formula, R ¹ represents a hydrogen atom and a C1-C4 alkyl group, R ² represents a C1-C6 alkylene group, and M represents a counter salt.) The inkjet ink according to claim 1, wherein b / a is 10 or more, where a is a viscosity at 70 ° C and b is a viscosity at 30 ° C. The ink-jet ink according to claim 1, wherein the water-soluble solvent is 40% by mass or more of the ink-jet ink. The inkjet ink according to any one of claims 1 to 3, wherein at least one of the water-soluble solvents is a compound represented by the following general formula (2).
Formula (2) RO (AO) _n H
(In the formula, R represents a C1 to C6 alkyl group, A represents an ethylene oxide group or a propylene oxide group, and n represents a natural number of 1 to 3.) One of the water-soluble high molecular compounds which have the acrylamide which has the said sulfo group as a monomer component is a copolymer with the monomer which has a nonionic ethylenically unsaturated bond, Any one of Claims 1-4 characterized by the above-mentioned. The inkjet ink of Claim 1. The content of the water-soluble polymer containing acrylamide having a sulfo group as a monomer component is 0.5 to 10% by mass of the ink-jet ink. Inkjet ink. 7. An ink jet recording method comprising: recording the ink jet ink according to claim 1 using an ink jet printer having a heated head.

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