JPH1046084A - Water-based pigment ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject ink excellent in pigment dispersion stability and dryability, thus useful for ink jet printing use, comprising a pigment, (meth) acrylic acid derivative copolymer, aliphatic monohydric alcohol, water-soluble solvent and water. SOLUTION: This water-based pigment ink excellent in pigment dispersibility and ink dryability comprises (A) a pigment such as carbon black, (B) a copolymer from a (meth)acrylic acid derivative of formula I (R1 and R2 are each H or a lower alkyl; (m1 ) is an integer of 0-2; AO is a 2-3C oxyalkylene; (n) is an integer of 1-300; X is H or a lower alkyl) and a monomer of formula II [R3 to R5 are each H, a lower alkyl or a group of the formula (CH2 )m2 COOM2 (M2 is H, an alkali metal, alkaline earth metal, ammonium or amine; (m2 ) is an integer of 0-2); M1 is the same kind as M2 ], (C) an aliphatic monohydric alcohol (e.g. ethyl alcohol), (D) a water-soluble solvent (e.g. diethylene glycol), and water as aqueous medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment ink excellent in pigment dispersion stability and ink drying property (quick drying property), and more particularly to an aqueous pigment ink suitable for ink jet recording.

[0002]

2. Description of the Related Art Dye inks and pigment inks are mainly used as water-based inks conventionally used. Of these inks, pigment inks are known to have excellent water and light fastness of printed images as compared to dye inks, but have insufficient pigment dispersion stability.

[0003] For example, as a water-based pigment ink, a water-based pigment ink having excellent coating and writing surface leveling properties comprising a pigment, a binder, a surfactant, and water has been known (JP-A-59-199780). . However, such water-based pigment inks still have insufficient dispersion stability of the pigment, particularly when stored for a long period of time. In particular, the low dispersion stability of the pigment is a major problem that causes clogging of the head when such an aqueous pigment ink is used as an ink for inkjet recording.
In addition, the water-based pigment ink is not sufficiently dry when printed on a member to be recorded because water is used as a medium. For example, when printing is performed by an inkjet recording method, particularly high-speed printing is performed. In such a case, or when printing is performed on a film such as an OHP sheet or a metal, ink dripping occurs, and there is still room for improvement.

Japanese Patent Application Laid-Open No. 4-110363 discloses that ethanol and isopropyl alcohol are blended for the purpose of improving the ejection stability during printing by an ink jet recording method. Does not mention the drying properties of the ink.

Accordingly, an object of the present invention is to provide a water-based pigment ink excellent in pigment dispersion stability and ink drying property (quick drying property). Another object of the present invention is to provide a water-based pigment ink particularly suitable as an ink for inkjet recording.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that an aqueous pigment ink which can achieve the above object can be obtained by using a specific copolymer in combination with an aliphatic monohydric alcohol. Was found.

[0007] The present invention has been made based on the above-mentioned findings, and provides an aqueous pigment ink containing a pigment, a copolymer of a (meth) acrylic acid derivative, an aliphatic monohydric alcohol, a water-soluble solvent and water. The above object has been achieved by providing.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The water-based pigment ink of the present invention contains a pigment, a specific copolymer, an aliphatic monohydric alcohol,
It contains a water-soluble solvent and water as essential components.

The specific copolymer used in the water-based pigment ink of the present invention is a copolymer of a (meth) acrylic acid derivative and is used as a polymer dispersant. Since this polymer dispersant has a good affinity for the pigment,
This is preferable because the long-term storage stability of the ink is improved for the reasons described below. The copolymer of the (meth) acrylic acid derivative may be one in which only acrylic acid or methacrylic acid or a derivative thereof is used as a copolymer component, or may be a copolymer of acrylic acid or methacrylic acid or a derivative thereof. And a polymerizable monomer may be used as a copolymerization component. As the derivatives of (meth) acrylic acid, alkali metal salts, alkaline earth metal salts, ammonium salts or amine salts and esters thereof, and hydrogen atoms bonded to the double bond carbon may have various functional groups (for example, carboxyl group and carboxyalkyl group). (For example, maleic acid, itaconic acid, citraconic acid, and fumaric acid). These can be used alone or in combination of two or more. In particular, a derivative of (meth) acrylic acid capable of introducing a side chain having a chain length sufficient to exhibit steric hindrance into the copolymer is preferable.

Particularly preferred copolymers of the (meth) acrylic acid derivative include a monomer (a) represented by the following general formula (A) and a monomer (a) represented by the following general formula (B). And a copolymer obtained by polymerizing the monomer (b) [hereinafter, this copolymer is referred to as “copolymer (I)”].

[0011]

Embedded image

The copolymer (I) is described in detail below.
In the general formula (A), R ₁ and R ₂ represent a hydrogen atom or a lower alkyl group (preferably C 1 to C
3), which may be the same or different. In particular, it is preferred that both R ₁ and R ₂ are hydrogen atoms, or that R ₁ is a hydrogen atom and R ₂ is a methyl group. m ₁ is, 0-2
And preferably 0 or 1. AO represents an oxyalkylene group having 2 to 3 carbon atoms (that is, an oxyethylene group or an oxypropylene group), and is preferably an oxyethylene group. n represents an integer of 1 to 300, preferably an integer of 2 to 150, more preferably 4 to
It is an integer of 130. If n is 0, the dispersion stability cannot be sufficiently exhibited, and if n exceeds 300, the viscosity of the ink increases, which may adversely affect the ejection behavior, for example, when used in an ink jet printer. X represents a hydrogen atom or a lower alkyl group (preferably C1 to C5), and is preferably a hydrogen atom, a methyl group or an ethyl group.

Specific examples of preferred compounds represented by the above general formula (A) include methoxy polyethylene glycol, methoxy polyethylene polypropylene glycol, ethoxy polyethylene glycol, ethoxy polyethylene polypropylene glycol, propoxy polyethylene glycol, and propoxy polyethylene polypropylene glycol. Ethylene oxide, propylene oxide to esterified product of dealkylated (oxidized) reactant of acrylic acid, methacrylic acid or fatty acid, or to dehydrogenated (oxidized) reactant of acrylic acid, methacrylic acid or fatty acid Adducts. In the compound represented by the general formula (A),
When both ethylene oxide and propylene oxide are added, any of random addition, block addition, alternate addition and the like can be used. In this case, the addition molar ratio between ethylene oxide and propylene oxide (the former: the latter) is preferably from 10:90 to 90:10, and more preferably from 10:90 to 60:40.

The compound represented by the above general formula (B) includes unsaturated monocarboxylic acids and salts thereof, and unsaturated dicarboxylic acids and salts thereof. Specifically, acrylic acid, methacrylic acid and crotonic acid and metal salts thereof, and maleic acid which is an unsaturated dicarboxylic acid monomer,
Examples include itaconic acid, citraconic acid and fumaric acid and their alkali metal salts, alkaline earth metal salts, ammonium salts and amine salts, and their acid anhydrides, maleic anhydride, itaconic anhydride and citraconic anhydride.

In the copolymer (I), the molar ratio of the monomers (a) and (b) [monomer (a) / monomer (b)] is 0.1 / 100 to 100. / 100, more preferably 1/100 to 70/100. If the ratio of the monomer (a) is smaller than this, the dispersion storage stability is impaired. If the ratio of the monomer (a) is larger than this, the solubility in water is reduced and the dispersibility is reduced. There is a risk of doing so. That is, it is preferable that the molar ratio of the monomers (a) and (b) is within the above range, since the monomer functions as a polymer dispersant having excellent dispersibility and excellent storage stability.

In the copolymer (I), another copolymerizable monomer may be further used as a copolymer component as long as the function as a polymer dispersant is not impaired. The monomer includes (meth) acrylonitrile, (meth)
Acrylamide, styrene, styrene sulfonic acid and the like can be mentioned.

The copolymerization mode of the above monomers (a) and (b) can be random copolymerization, block copolymerization, alternating copolymerization, or graft copolymerization. There is no particular limitation as long as the function of the polymer dispersant (I) is not impaired.

When the copolymer (I) has a high molecular weight, the viscosity of the copolymer (I) is increased and the handleability is poor. Weight average molecular weight of 5000 to 20
It is preferably 10,000, and more preferably 5000 to 70,000.

In particular, among the above copolymers (I), from the viewpoint of dispersibility and storage stability of the dispersion, preferably 1 to 300, more preferably 2 to 150 oxyalkylene groups per molecule are used. More preferably, 4 to 130 polyalkylene glycol monoester monomers (particularly, a polyalkylene glycol ester of (meth) acrylic acid or an alkoxypolyalkylene glycol ester) and a (meth) acrylic acid monomer are introduced. It is desirable to use a copolymer obtained by polymerization.

The method for preparing the copolymer (I) is not particularly limited as long as the function of the copolymer (I) as a polymer dispersant is not impaired, and a conventionally known preparation method is used.
Specific examples of the preparation method include the method described in JP-A-7-223852, column 4, line 42 to column 5, line 11.

In the water-based pigment ink of the present invention, the reason why the dispersibility of the pigment is particularly improved by using a copolymer of a (meth) acrylic acid derivative, particularly the above-mentioned copolymer (I), is not clear. It is presumed to be as follows. That is, in the ink, the copolymer (I) is charged in a state where a charged site (for example, a carbonyl site) in the molecule is adsorbed on the pigment surface and a side chain polyoxyalkylene group is directed outward. Surrounds the surface of the pigment. Since the polyoxyalkylene group has a long chain length and high steric hindrance, aggregation between the pigments is inhibited by the polyoxyalkylene group. As a result, it is considered that the dispersibility and the storage stability of the pigment are improved. Since the steric hindrance caused by the polyoxyalkylene group is particularly noticeable when the pH of the aqueous pigment ink of the present invention is high, the pH of the aqueous pigment ink of the present invention may be set to a high range as described later. preferable.

The copolymer of the (meth) acrylic acid derivative is contained in the aqueous pigment ink of the present invention in an amount of 0.05 to 10% by weight.
It is preferred to be blended. If the compounding amount of the copolymer of the (meth) acrylic acid derivative is less than 0.05% by weight, the compounding amount does not reach a sufficient amount to stabilize the pigment, so that storage stability may be lacking, and 10% by weight. %, The dispersibility and storage stability are not further improved, and the viscosity of the ink may be increased. The compounding amount of the copolymer of the (meth) acrylic acid derivative is more preferably from 0.1 to 7% by weight, further preferably from 0.5 to 5% by weight, and more preferably from 0.5 to 3% by weight. % Is most preferred.

As the aliphatic monohydric alcohol used in the water-based pigment ink of the present invention, those having appropriate volatility and azeotropic properties with water, preferably those having a saturated vapor pressure at 25 ° C. of 20 to 300 mmHg. Examples thereof include lower alcohols such as ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, methyl alcohol, allyl alcohol, s-butyl alcohol and t-butyl alcohol. One or more of these aliphatic monohydric alcohols are used. In particular, from the viewpoint of reducing the viscosity of the ink, one or more selected from the group consisting of ethyl alcohol, 1-propyl alcohol and 2-propyl alcohol are preferably used, and 1-propyl alcohol is particularly preferably used. By blending the aliphatic monohydric alcohol, the drying property of the ink, particularly the drying property of the ink when printed on a film or metal such as an OHP sheet, is improved,
Ink dripping is effectively prevented.

It is preferable that the aliphatic monohydric alcohol is incorporated in the aqueous pigment ink of the present invention in an amount of 1 to 15% by weight. If the amount of the aliphatic monohydric alcohol is less than 1% by weight, a desired quick-drying property may not be obtained when printing on a film such as an OHP sheet or glossy paper or a metal surface, and 15% by weight. If it exceeds, the dispersion stability of the pigment is impaired, and stable inkjet recording may not be performed when used as an inkjet recording ink. The aliphatic monohydric alcohol is more preferably blended in an amount of 2 to 10% by weight, most preferably 2.5 to 8% by weight.

By blending the above aliphatic monohydric alcohol in the water-based pigment ink of the present invention, the drying property (quick drying property) of the ink, particularly the drying property of the ink when printing on a film such as an OHP sheet or a metal, is improved. The reason is not clear, but is presumed to be as follows. That is, the aliphatic monohydric alcohol has an appropriate volatility, and additionally has a property of azeotroping with water. As a result, the ink dries quickly enough even when printed on a recording member with poor ink permeability, such as a film or metal. As described above, since the drying property of the ink is caused by the moderate volatility of the aliphatic monohydric alcohol and the azeotropic property with respect to water, the water-based pigment ink of the present invention is particularly useful when the ink is used in an inkjet recording method. Drying property is further improved.

In the present invention, the copolymer of the (meth) acrylic acid derivative and the aliphatic monohydric alcohol are
It is preferable to use the copolymer of the (meth) acrylic acid derivative: the aliphatic monohydric alcohol = 1: 10 to 1: 1 by weight. If the copolymer of the (meth) acrylic acid derivative is less than the above weight ratio, the dispersion stability of the pigment may be impaired. If the copolymer of the (meth) acrylic acid derivative is more than the above weight ratio, The desired quick-drying property cannot be obtained, and dripping may occur when recording on a film or a metal surface. The copolymer of the above (meth) acrylic acid derivative and the above aliphatic monohydric alcohol are mixed with the copolymer of the (meth) acrylic acid derivative: the aliphatic monohydric alcohol = 1: 9 to 1:
More preferably, it is used in a weight ratio of 1: 1: 8 to 1:
Most preferably, it is used in a weight ratio of 1.

Next, in the water-based pigment ink of the present invention,
The essential components other than the (meth) acrylic acid derivative copolymer and the aliphatic monohydric alcohol will be described. The pigment used in the water-based pigment ink of the present invention is not particularly limited in its kind, and includes, for example, carbon black;
C. I. Pigment Yellow 1, 5, 12, 14, 1
7, 24, 42, 53, 83, 95, 97, 98 and 1
00; I. Pigment Red 1, 3, 4, 5, 1
7, 22, 31, 48, 49, 53, 63, 64, 8
1: 1, 88 and 101; I. Pigment Blue 1, 15, 16, 27, 28, 29, 56, 60 and 6
3 and; I. Pigment Black 1 and 11 can be used, and carbon black is particularly preferable. The pigment is preferably blended in the water-based pigment ink of the present invention in an amount of 1 to 15% by weight.
More preferably, it is added at 0% by weight. If the amount of the pigment is less than 1% by weight, the printing density is insufficient and
Even if it is used in an amount exceeding 5% by weight, the print density cannot be significantly improved, so it is preferable to be within the above range. Also,
The pigment has an average particle size of 0.05 to 3 μm from the viewpoint of improving the storage stability of the ink, and further improving the intermittent ejection property particularly when used as an inkjet recording ink.
And more preferably 0.05 to 1 μm.

When color printing is performed by the subtractive color mixture method using the water-based pigment ink of the present invention, black, yellow,
It is preferable to use a water-based pigment ink set including four types of inks (black ink, yellow ink, magenta ink, and cyan ink) containing magenta and cyan pigments. In this case, carbon black is used as a black pigment, and C.I. I. Pigment Yellow 17 and 83,
As a magenta pigment, C.I. I. Pigment Red 48:
3, 83 and 122, and C.I. I. Pigment Blue 15: 3 is preferred because color reproducibility is improved.

The water-soluble solvent used in the water-based pigment ink of the present invention is not particularly limited as long as it has a function as a wetting agent or a humectant. Examples thereof include ethylene glycol, propylene glycol, diethylene glycol, and triethylene glycol. Glycols such as glycol, tetraethylene glycol and polyethylene glycol; glycerin; diethylene glycol diethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol , Ethyl carbitol acetate, diethyl carbitol, triethylene glycol monomethyl ether, triethyl Ethers of polyhydric alcohols such as tylene glycol monoethyl ether and propylene glycol monomethyl ether, acetates; thiodiglycol; N-methyl-2-pyrrolidone; 1,3-dimethylimidazolidinone; triethanolamine; formamide; One or two or more of nitrogen-containing compounds such as dimethylformamide and dimethylsulfoxide can be used. These water-soluble solvents are preferably contained in the water-based pigment ink of the present invention in an amount of 0.1 to 30% by weight, more preferably 0.1 to 15% by weight.

In the water-based pigment ink of the present invention (particularly when used as an ink jet recording ink), water is used as a medium, and is preferably contained in an amount of 70 to 98% by weight, more preferably 85 to 95% by weight. More preferably,

In addition to the above-mentioned essential components, the water-based pigment ink of the present invention may optionally contain various components as described below.

In the water-based pigment ink of the present invention, it is preferable to use a dispersibility improver together with the copolymer of the (meth) acrylic acid derivative used as a polymer dispersant. As the dispersibility improver, an anionic surfactant,
Various surfactants such as a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant can be used. The surfactant is contained in the aqueous pigment ink of the present invention in a total amount of 0.1%.
It is preferable that the content is 0.1 to 10% by weight.
-10% by weight, more preferably 0.05% by weight.
-5% by weight, particularly preferably 0.1-5% by weight.
Most preferably, it is blended by weight.

Examples of the above-mentioned anionic surfactant include alkyl benzene sulfonate, alkyl naphthalene sulfonate, alkane or olefin sulfonate, alkyl sulfate, polyoxyethylene alkyl or alkyl aryl ether sulfate, alkyl phosphate. , An alkyl diphenyl ether disulfonate, an ether carboxylate, an alkyl sulfosuccinate, an α-sulfofatty acid ester, and a surfactant selected from the group consisting of a fatty acid salt, a condensate of a higher fatty acid and an amino acid, a naphthenate, and the like. Can be used. Anionic surfactants preferably used include alkyl benzene sulfonates (especially linear alkyl), alkanes or olefin sulfonates (especially secondary alkane sulfonates, α-olefin sulfonates), alkyl sulfates Polyoxyethylene alkyl or alkyl aryl ether sulfate (especially polyoxyethylene alkyl ether sulfate), alkyl phosphate (especially monoalkyl), ether carboxylate, alkyl sulfosuccinate, α-sulfofatty acid ester And surfactants selected from the group consisting of fatty acid salts, and particularly preferred are alkylbenzene sulfonates (especially those of linear alkyl), polyoxyethylene alkyl or alkylaryl ether sulfates Ester salts (especially polyoxyethylene alkyl ether sulfate salts), and alkyl sulfate salts. These can be used alone or in combination of two or more.

As the above-mentioned cationic surfactant, aliphatic amine salts, quaternary ammonium salts, sulfonium salts, phosphonium salts and the like can be used. These can be used alone or in combination of two or more.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, sorbitan fatty acid ester,
A surfactant selected from the group consisting of polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester and alkyl (poly) glycoxide can be used. Nonionic surfactants preferably used are surfactants selected from polyoxyethylene alkyl ethers and polyoxyethylene alkyl aryl ethers. These can be used alone or in combination of two or more.

As the amphoteric surfactant, amino acid type compounds, betaine type compounds and the like can be used.

In particular, when the above surfactant is used,
An anionic surfactant is used, or an anionic surfactant and a nonionic surfactant are used in combination, and the amount of each is 0.01 to 5% by weight (particularly 0.01 to 4% by weight,
In particular, 0.05 to 3% by weight), and the mixing ratio of both is anionic surfactant: nonionic surfactant = 10
It can be used in a weight ratio of 0: 1 to 1: 100 (especially 90: 1 to 1:70, especially 70: 1 to 1:50), and the print density of the printed image and the long-term storage It is preferable from the viewpoint of improving dispersion stability.

When an anionic surfactant is used as the surfactant, the blend ratio of the (meth) acrylic acid derivative copolymer and the anionic surfactant is the same as that of the (meth) acrylic acid. It is preferable to use the copolymer of the acid derivative and the anionic surfactant in a weight ratio of 1: 2 to 30: 1. If the amount of the copolymer of the (meth) acrylic acid derivative exceeds the above range, the wettability of the copolymer of the (meth) acrylic acid derivative with the pigment may be insufficient, and the dispersibility may decrease. . On the other hand, if the amount of the anionic surfactant is more than the above range, the foaming property of the ink is increased and the handleability may be poor. The mixing ratio of the two is more preferably 1: 1 to 15: 1, that is, the copolymer of the (meth) acrylic acid derivative: the anionic surfactant, and more preferably 1: 1 to 10: 1. preferable.

In the water-based pigment ink of the present invention, polypropylene glycol is used in order to balance the improvement of the permeability of the ink into the recording paper and the prevention of strikethrough (ink seepage to the back side of the recording paper). It is preferable to mix them. Polypropylene glycol has a molecular weight of 400
It is preferably from 3,000 to 3,000, and more preferably from 400 to 2,000. The polypropylene glycol is preferably incorporated in the water-based pigment ink of the present invention in an amount of 0.01 to 3% by weight, more preferably 0.01 to 1% by weight.

Further, the water-based pigment ink of the present invention has a molecular weight of 400 to 3 in order to improve the intermittent ejection property particularly when used as an ink for ink jet recording.
A polyethylene glycol disulfate salt of 500 (particularly, 400 to 2,000) can be blended.
The polyethylene glycol disulfate salt is preferably incorporated in the aqueous pigment ink of the present invention in an amount of 0.01 to 3% by weight, more preferably 0.01 to 1% by weight.

Similarly, in order to improve the intermittent ejection property,
Sugars can be blended in the aqueous pigment ink of the present invention. As the saccharide, D-glucose, fructose,
It is preferable to use one or more of maltose and saccharose, and it is particularly preferable to use saccharose. The saccharide is preferably contained in the water-based pigment ink of the present invention in an amount of 0.1 to 5% by weight, more preferably 0.1 to 3% by weight. In particular, when the blending amount of the saccharide is related to the blending amount of the copolymer of the (meth) acrylic acid derivative, the blending ratio of both is such that the copolymer of the (meth) acrylic acid derivative: the saccharide = 20: By adjusting so as to be in the range of 1 to 1: 3, the intermittent ejection property is further improved.

Similarly, a nitrogen-containing heterocyclic compound such as N-methyl-2-pyrrolidone or 1,3-dimethyl-2-imidazolidinone is added to the aqueous pigment ink of the present invention to improve the intermittent ejection property. It can also be blended. The nitrogen-containing heterocyclic compound is preferably incorporated in the aqueous pigment ink of the present invention in an amount of 0.01 to 10% by weight, more preferably 0.1 to 5% by weight.

Similarly, an aprotic polar solvent can be added to the aqueous pigment ink of the present invention in order to improve the intermittent ejection property. As the aprotic polar solvent, it is preferable to use one or more of dimethyl sulfoxide and sulfolane. The aprotic polar solvent is preferably incorporated in the aqueous pigment ink of the present invention in an amount of 0.01 to 10% by weight, and more preferably 0.1 to 10% by weight.
-5% by weight.

The polyethylene glycol disulfate salt, saccharide, nitrogen-containing heterocyclic compound, and aprotic polar solvent capable of improving the intermittent ejection property are used in combination with a pigment having an average particle diameter of 0.05 to 3 μm. Thereby, the intermittent ejection property is further improved.

Further, in the water-based pigment ink of the present invention, in order to improve the fixing property of the ink, an acrylic-based pigment ink is used.
It is preferable to mix emulsions such as aqueous urethane, styrene-butadiene, and polyester. In particular, it is preferable to mix an acrylic-urethane copolymer emulsion. As the emulsion, it is particularly preferable to use an acryl-urethane block copolymer (a copolymer in which urethane is grafted on a side chain of an acrylic main chain). The weight average molecular weight of the copolymer in the emulsion is from 10,000 to 3,000
00, preferably 20000 to 250,000
Is more preferable. The emulsion has a solid content of 0.01 to 1 in the aqueous pigment ink of the present invention.
It is preferably added at 0% by weight, more preferably 0.05 to 5% by weight.

Similarly, in order to improve the fixability of the ink, the water-based pigment ink of the present invention has a weight average molecular weight of 800.
Polyethyleneimine of up to 300,000 may be blended. As the polyethyleneimine, it is preferable to use one or more of polyethyleneimine grafted to the side chain of the main chain composed of an acrylic chain, polyethyleneimine subjected to hydroxylation treatment, and polyethyleneimine zwitterionized. It is particularly preferable to use hydroxylated polyethyleneimine. The polyethyleneimine is present in the aqueous pigment ink of the present invention in an amount of 0.01%.
-10% by weight, preferably 0.05-5%
More preferably, it is blended by weight.

In the aqueous pigment ink of the present invention, if necessary, an antifoaming agent such as a silicone compound, a fungicide such as a chloromethylphenol compound, a chelating agent such as EDTA, and an oxygen absorbing agent such as a sulfite may be used. Etc. can also be blended.

The water-based pigment ink of the present invention preferably has a pH of 9.5 to 13.0, from the viewpoint that the print density of a printed image, particularly the black print density, can be improved.
More preferably, it is 0 to 12.0. In order to keep the pH within the above range, a pH adjuster, for example, amino alcohol may be added to the aqueous pigment ink of the present invention. As the amino alcohol, it is preferable to use monoethanolamine (for example, 2-aminoethanol), triethanolamine, or the like.

The method for preparing the water-based pigment ink of the present invention by mixing the above-mentioned components is not particularly limited, and is prepared using a conventionally known apparatus, for example, a ball mill, a sand mill, an attritor, a basket mill, a roll mill or the like. can do. In preparing the water-based pigment ink of the present invention, it is preferable to remove coarse particles. For example, the ink obtained by blending the above components is centrifuged (2500 G, 20 minutes) with a centrifuge to remove particles of preferably 2 μm or more, more preferably 1 μm or more. This is preferable because ink without clogging can be obtained.

The water-based pigment ink of the present invention is used as an ink for ordinary writing implements such as a fountain pen, a ball-point pen, a magic pen, and a felt-tip pen, and is particularly suitably used as an ink for ink-jet recording. When the water-based pigment ink of the present invention is used as an inkjet recording ink,
If the printer uses the inkjet recording method,
It can be used in any printer. For example, a thermal jet recording type printer that performs recording using thermal energy from a heater or the like of a heating resistance element disposed in a printer head, and a piezoelectric element recording that performs recording using a piezoelectric element disposed in the printer head Any type of printer can be used.

[0051]

The following examples illustrate the effectiveness of the present invention. However, the scope of the present invention is not limited to such an embodiment. In the following examples, "parts" and "%" represent parts by weight and% by weight, respectively, unless otherwise specified.

Example 1-15 parts of pigment A-2 parts of polymer dispersant A-3 parts of aliphatic monohydric alcohol A-1 part of diethylene glycol-0.5 part of 2-aminoethanol-water remaining (78.5) Part) The above components were dispersed in a sand mill for 4 hours to obtain Dispersion A. Next, the dispersion A and the following components were diluted with a dissolver so as to have the following mixing ratio. -33.3 parts of dispersion liquid A-1.3 parts of polymer dispersant A-2 parts of aliphatic monohydric alcohol A-0.7 parts of diethylene glycol-0.3 parts of 2-aminoethanol-The remaining part of water (62.4 parts) ) After blending the above components, centrifuge (2500)
G, 20 minutes) to remove coarse particles to obtain an aqueous pigment ink. The storage stability and drying property of this water-based pigment ink were measured according to the following [measurement method]. Table 3 shows the results. In the above components, pigment A, polymer dispersant A
The details of the aliphatic monohydric alcohol A are as shown in Table 2.

[Measurement method] Storage stability The obtained ink was stored at 60 ° C for 120 hours, and then stored for 25 hours.
The ink was centrifuged at 00 G for 20 minutes, and the solid content concentration (wt%) of the ink after the centrifugation was measured. In the same manner, the solid content concentration (w of the ink stored at room temperature (25 ° C., 120 hours)
t%). The measured value was substituted into the following formula (I) to calculate the change in the solid content (%) of the ink. The storage stability of the ink was evaluated from the calculated solid content change value of the ink according to the following criteria.

[0054]

(Equation 1)

Evaluation Criteria 0 ≦ Ink Solids Concentration Change ≦ 3... ◎ 3 <Ink Solids Concentration Change ≦ 5 ... ○ 5 <Ink Solids Concentration Change ≦ 10 ... 1010 <Ink Change in solid concentration

[0056] After drying the resulting ink was filled in the ink cartridge, the Canon ink jet printer BJ-10vLite (thermal jet ink jet printer) to the ink cartridge, and Epson inkjet printer MJ-500C (piezoelectric ink JIT printer ), And for each printer, 2c
A black square of mx 2 cm was printed on recycled paper for PPC [manufactured by Nippon Kaishi Paper Co., Ltd.]. The printed surface (the portion on which the square was printed) was rubbed with a cotton swab, and the drying time of the ink was evaluated based on the following criteria, using the time when the cotton swab was not stained as the drying time.

Evaluation criteria Drying time is less than 1 minute .... ○ Drying time is more than 1 minute to less than 2 minutes. △ Drying time is more than 2 minutes ..... ×

Examples 2 to 5 and Comparative Example 1 An aqueous system was prepared in the same manner as in Example 1 except that the types and amounts of the pigment, the polymer dispersant and the aliphatic monohydric alcohol were as shown in Table 1, respectively. A pigment ink was obtained. The same measurement as in Example 1 was performed for the obtained water-based pigment ink. Table 3 shows the results.
Shown in The details of the pigment, polymer dispersant and aliphatic monohydric alcohol used in Examples 2 to 5 and Comparative Example 1 are as shown in Table 2.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

[Table 3]

As is evident from the results shown in Table 3, the water-based pigment ink of the present invention (Examples 1 to 5) using a copolymer of a (meth) acrylic acid derivative and an aliphatic monohydric alcohol in combination was used. Compared with the ink of Comparative Example 1 using a polymer dispersant other than the copolymer of the (meth) acrylic acid derivative, the dispersion stability of the printed image under long-term storage and the drying property of the ink are excellent. You can see that. In particular, Examples 2 and 4 using 1-propyl alcohol were particularly excellent in the drying property of the ink.

[0063]

According to the present invention, there is provided a water-based pigment ink having excellent pigment dispersion stability and ink drying property (quick drying property), particularly excellent in ink drying property when printing on a film such as an OHP sheet or a metal. can get. Further, according to the present invention, a water-based pigment ink particularly suitable as an ink for inkjet recording can be obtained.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hideki Yanagi 2606, Kabashi-cho, Akaga-cho, Haga-gun, Tochigi Prefecture (72) Inventor Shoichi Suzuki 2606, Akabane-Akabane, Kaiga-cho, Haga-gun, Tochigi (72) Inventor Yoshiaki Tsujii 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Pref. (72) Inventor Kenji Aida 2606 Kabane-cho, Akabane-cho, Haga-gun, Tochigi Pref.

Claims (6)

[Claims] 1. A water-based pigment ink comprising a pigment, a copolymer of a (meth) acrylic acid derivative, an aliphatic monohydric alcohol, a water-soluble solvent, and water. 2. The copolymer of the (meth) acrylic acid derivative and the aliphatic monohydric alcohol, the copolymer of the (meth) acrylic acid derivative: the aliphatic monohydric alcohol = 1:
The water-based pigment ink according to claim 1, which is used in a weight ratio of 10 to 1: 1. 3. The content of the aliphatic monohydric alcohol is:
The aqueous pigment ink according to claim 1, wherein the amount is 1 to 15% by weight. 4. The method according to claim 1, wherein the aliphatic monohydric alcohol is one or more selected from the group consisting of ethyl alcohol, 1-propyl alcohol and 2-propyl alcohol. Water-based pigment ink. 5. The copolymer of the (meth) acrylic acid derivative comprises a monomer (a) represented by the following general formula (A) and a monomer (a) represented by the following general formula (B): 3. The aqueous pigment ink according to claim 1, which is a copolymer obtained by polymerizing b). Embedded image 6. The aqueous pigment ink according to claim 1, which is an ink jet recording ink.