JPH1046090A - Aqueous pigment ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject ink comprising a pigment, a dispersing comprising an alkyleneoxide-addition reacted (meth)acrylic acid derivative copolymer, an aminoakcohol and water, and good in the quality of printed letters, dispersion stability for a long period and extrusion stability. SOLUTION: This aqueous pigment ink comprises (A) a pigment such as carbon black, (B) a polymer dispersant comprising the copolymer of an alkyleneoxide-addition reacted (meth)acrylic acid derivative of formula I [R1 , R2 are each H, 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, a lower alkyl] with a monomer of formula II R3 -R5 are each H, a lower alkyl, a group of the formula: (CH2 )m2 COOM2 [M2 is H, an alkali metal, an alkaline earth metal, ammonium amine; (m2 ) is an integer of 0-2]}, (C) am aminoalcohol such as 2-aminoethanol, and (D) water. The objective aqueous pigment ink is excellent in printed letter quality, dispersion stability under long-term storage, and extrusion stability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based pigment ink, and more particularly to a water-based pigment ink excellent in print quality of a printed image and dispersion stability during long-term storage. The present invention relates to a water-based pigment ink having excellent ejection stability when used.

[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 resistance and light fastness of printed images as compared with dye inks, but are insufficient in print density of printed images.

[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). . Japanese Patent Application Laid-Open No. 4-110363 discloses that in order to improve the long-term storage stability of an aqueous pigment ink, a pH adjuster such as diethanolamine or triethanolamine is blended and the pH of the ink is increased.
It describes that H is adjusted to 7 to 10.

[0004] However, the water-based pigment inks described in the above publications still have an insufficient print density of a printed image,
In addition, the pigment has poor dispersion stability, especially dispersion stability under long-term storage. In particular, the low dispersion stability of the pigment causes clogging of the head when using such an aqueous pigment ink as an ink for ink jet recording, and causes a reduction in ejection stability.

Accordingly, an object of the present invention is to provide a water-based pigment ink which is excellent in print quality of a print image and dispersion stability during long-term storage. The object of the present invention is
In particular, it is an object of the present invention to provide a water-based pigment ink having excellent ejection stability when used 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 capable of achieving the above object can be obtained by using a specific polymer dispersant in combination with an amino alcohol. I learned.

The present invention has been made based on the above findings, and is characterized by comprising a pigment, a polymer dispersant comprising a copolymer of an alkylene oxide-added (meth) acrylic acid derivative, an amino alcohol and water. The above object has been achieved by providing a pigment ink.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The water-based pigment ink of the present invention contains a pigment, a specific polymer dispersant, an amino alcohol and water as essential components as described above, and alkylene oxide is added as the specific polymer dispersant. A polymer dispersant comprising a copolymer of a (meth) acrylic acid derivative and an amino alcohol are used in combination.
Hereinafter, each of the above components constituting the water-based pigment ink of the present invention will be described.

The above-mentioned copolymer of an alkylene oxide-added (meth) acrylic acid derivative used as a polymer dispersant may be one in which only an alkylene oxide-added (meth) acrylic acid derivative is used as a copolymer component. Alternatively, an alkylene oxide-added (meth) acrylic acid derivative and a polymerizable monomer may be used as a copolymer component. As the alkylene oxide-added (meth) acrylic acid derivative, (meth)
Alkylene oxide adducts of acrylic acid, compounds in which the hydrogen atom bonded to the double bond carbon in the alkylene oxide adduct has been replaced with various functional groups (eg, carboxyl group or carboxyalkyl group) (eg, alkylene oxide-added maleic acid, Alkylene oxide-added itaconic acid, alkylene oxide-added citraconic acid and alkylene oxide-added fumaric acid).

Particularly preferred copolymers of the alkylene oxide-added (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 resulting 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 to set the molar ratio of the monomers (a) and (b) within such a range, since a polymer dispersant having excellent dispersibility and excellent storage stability can be obtained.

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 improved by using a copolymer of an alkylene oxide-added (meth) acrylic acid derivative, particularly the above-mentioned copolymer (I), as a polymer dispersant. Is not clear, but 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. To set the pH in the aqueous pigment ink of the present invention,
Amino alcohol is used as described below. That is, in the water-based pigment ink of the present invention, the storage stability of the ink is improved by using the copolymer of the alkylene oxide-added (meth) acrylic acid derivative and the amino alcohol in combination. The reason that the steric hindrance by the polyoxyalkylene group is remarkably expressed in a high pH region is that the molecular chain of the polyoxyalkylene group in a entangled state in a low pH region increases as the pH increases. It is presumed that the entanglement is released and the entanglement is extended.

The above-mentioned copolymer of the alkylene oxide-added (meth) acrylic acid derivative used as the polymer dispersant 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. When the blending amount of the copolymer is 0.1.
If the amount is less than 05% by weight, the compounding amount is not sufficient to sufficiently stabilize the pigment, so that storage stability may be lacking. If the amount exceeds 10% by weight, dispersibility and storage stability may not be further improved. Since the viscosity of the ink may be increased, the viscosity is preferably set in the above range. The blending amount of the copolymer is more preferably 0.1 to 4% by weight, and even more preferably 0.5 to 3% by weight.

The amino alcohol used in combination with the above-mentioned copolymer of the alkylene oxide-added (meth) acrylic acid derivative is blended for improving the storage stability of the ink as described above. In addition to this, the use of the amino alcohol improves the print quality of a printed image, particularly the black print density, and greatly reduces the bleeding of the print.Further, the aqueous pigment ink of the present invention is used for inkjet recording. When used as ink, ejection stability is improved.

As the amino alcohol, it is preferable to use monoethanolamine such as 2-aminoethanol or triethanolamine. These amino alcohols can be used alone or in combination of two or more.

The pH of the aqueous pigment ink of the present invention is preferably 9.5 to 13.3.
The amount is preferably 0, more preferably more than 10.0 to 12.0, more preferably more than 10.0 to 11.0. By blending the amino alcohol so that the pH falls within such a range, the storage stability of the ink is further improved, and the print quality of the printed image, particularly the black print density, is further improved, and the printing bleeding is reduced. Greatly reduced. . In particular, when the water-based pigment ink of the present invention is used as an inkjet recording ink, the ejection stability is improved.

Next, in the water-based pigment ink of the present invention,
The essential components other than the polymer dispersant and the amino alcohol will be described. The type of the pigment used in the aqueous pigment ink of the present invention is not particularly limited, and examples thereof include carbon black; I. Pigment Yellow 1, 5, 12, 14, 17, 24, 42, 53, 83,
95, 97, 98 and 100; I. Pigment Red 1, 3, 4, 5, 17, 22, 31, 48, 49,
53, 63, 64, 81: 1, 88 and 101;
I. Pigment Blue 1, 15, 16, 27, 28,
C. 29, 56, 60 and 63; I. Pigment Black 1 and 11 can be used, and carbon black is particularly preferable. The pigment is
It is preferably contained in the aqueous pigment ink of the present invention in an amount of 1 to 15% by weight, more preferably 2 to 10% by weight. If the amount of the pigment is less than 1% by weight, the print density is insufficient, and even if the pigment is used in excess of 15% by weight, the print density cannot be significantly improved. . The average particle diameter of the pigment is preferably 0.05 to 3 μm, more preferably 0.05 to 1 μm, from the viewpoint of improving the storage stability of the ink.

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.

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 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 preferably added in an amount of from 0.05 to 10% by weight.
More preferably, it is blended at 5% 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, etc. 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,
Either an anionic surfactant or a combination of an anionic surfactant and a nonionic surfactant is used, and the amount of each is 0.01 to 5% by weight (particularly 0.01 to 3% by weight,
In particular, 0.05 to 2% 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 mixing ratio of the polymer dispersant and the anionic surfactant is such that the polymer dispersant and the anionic surfactant are mixed. = 1: 2 to 30: 1 by weight. If the amount of the polymer dispersant exceeds the above range, the wettability of the polymer dispersant with the pigment may be insufficient, and the dispersibility may be reduced. on the other hand,
If the amount of the anionic surfactant exceeds the above range, the foaming property of the ink increases and the handleability may be poor. The compounding ratio of the two is more preferably the polymer dispersant: the anionic surfactant = 1: 1 to 15: 1, and further preferably 1: 1 to 10: 1.

The water-based pigment ink of the present invention preferably contains a water-soluble solvent. The type of the water-soluble solvent is not particularly limited as long as it has a function as a humectant or a humectant. For example, ethylene glycol, propylene glycol, diethylene glycol,
Glycols such as triethylene 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,
Ethers and acetates of polyhydric alcohols such as triethylene glycol monoethyl ether and propylene glycol monomethyl ether; thiodiglycol;
-Methyl-2-pyrrolidone; 1,3-dimethylimidazolidinone; formamide; one or more of nitrogen-containing compounds such as dimethylformamide and dimethylsulfoxide. 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, polypropylene glycol is used in order to balance the improvement in 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, in order to improve the drying property of the ink, it is preferable to mix an aliphatic monohydric alcohol with the aqueous pigment ink of the present invention. As the aliphatic monohydric alcohol, it is preferable to use one or more of ethyl alcohol, 1-propyl alcohol, and 2-propyl alcohol, and it is particularly preferable to use 1-propyl alcohol. The aliphatic monohydric alcohol 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 8% by weight. In particular, in relation to the amount of the aliphatic monohydric alcohol and the amount of the polymer dispersant, the compounding ratio of the both is such that the polymer dispersant: the aliphatic monohydric alcohol = 1: 10.
By adjusting the ratio to １1: 1, the drying property of the ink is further improved.

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 compounding amount of the saccharide is related to the compounding amount of the polymer dispersant, the compounding ratio of both is such that the polymer dispersant: the saccharide = 20: 1 to 1: 3.
The intermittent ejection property is further improved by adjusting such that.

Similarly, in order to further improve the intermittent ejection property, 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. 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 and nitrogen-containing heterocyclic compound which can further improve the intermittent ejection property can be used in combination with the above-mentioned pigment having an average particle size of 0.05 to 3 μm to provide an intermittent ejection property. Even better.

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 preferable to use an acryl-urethane block copolymer (a copolymer in which urethane is grafted on a side chain of a main chain composed of an acrylic chain). The weight average molecular weight of the copolymer in the emulsion is 10,000 to 300,000
And more preferably 20,000 to 250,000. The emulsion is preferably contained in the aqueous pigment ink of the present invention in a solid content concentration of 0.01 to 10% 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 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 such as a ball mill, a sand mill, an attritor, a basket mill, and a roll mill. 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 instruments such as a fountain pen, a ball-point pen, a magic pen, and a felt-tip pen, and is particularly preferably 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.

[0050]

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

Example 1 Pigment A 15 parts Polymer dispersant A 2 parts Diethylene glycol 5 parts 2-aminoethanol 1 part Water remaining (77 parts) The above components were dispersed in a sand mill for 4 hours and dispersed. Liquid A was used. 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 A-0.5 parts of polymer dispersant A-2.0 parts of diethylene glycol-0.5 parts of 2-aminoethanol-water remainder (63.7 parts) After mixing the above components, centrifugation Centrifuge with a separator (2500
G, 20 minutes) to remove coarse particles to obtain an aqueous pigment ink. Storage stability, print density,
Print bleeding and ejection stability were measured according to the following [measurement method]. Table 3 shows the results. Table 3 also shows the pH of the obtained water-based pigment ink (the pH was measured at 20 ° C. using a pH meter equipped with a glass electrode). Further, in the above components, the details of the pigment A and the polymer dispersant 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.

[0053]

(Equation 1)

Evaluation Criteria 0 ≦ Ink Solid Content Concentration ≦ 3... ◎ 3 <Ink Solid Content Concentration ≦ 5... 5 <Ink Ink Solid Content Concentration ≦ 10... Change in solid concentration

A thermal jet printer (BJ-10L manufactured by Canon Inc.) in which a heater for a heating resistance element is provided on a print density printer head.
item), and an ink jet printer in which a piezoelectric element is arranged in a printer head (MJ-11 manufactured by Epson)
00C), solid printing is performed on recycled paper for PPC [manufactured by Nippon Kaishi Paper Co., Ltd.], and after leaving for one hour or more, the optical character density of the solid printing portion is measured with a Macbeth densitometer RD918 (manufactured by Macbeth). It was measured.

[0056] by using the printing bleeding above each printer, and print 10 characters of "hawk" of 8 points to the PPC for recycled paper, it was evaluated by observing the following criteria the collapse of the character by visual observation.

Evaluation criteria : None of the 10 pieces are crushed ........ ○ 8 or more pieces are not crushed ..... △ 3 or more pieces are crushed ..... ×

Ejection Stability Using each of the printers described above, the print quality of continuous printing of 20 solid patterns (20 cm × 20 cm) on PPC recycled paper (A4) was examined and evaluated according to the following criteria.

Evaluation criteria : No blurring in continuous printing of 20 sheets.... Occurrence of blurring in continuous printing of 20 sheets.

Examples 2 to 4 and Comparative Examples 1 and 2 Example 1 was repeated except that the types and amounts of pigment and polymer dispersant and the amount of 2-aminoethanol were as shown in Table 1, respectively. In the same manner as in the above, an aqueous pigment ink was obtained. The same measurement as in Example 1 was performed for the obtained water-based pigment ink. The results are shown in Table 3 together with the pH of the ink.
The details of the pigment and the polymer dispersant used in Examples 2 to 4 and Comparative Examples 1 and 2 are as shown in Table 2.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

[Table 3]

As is clear from the results shown in Table 3, the water-based pigment inks of the present invention (Examples 1 to 4) using a specific polymer dispersant and an amino alcohol in combination have the polymer dispersant of the present invention. It can be seen that the print quality of the printed image is higher than that of the aqueous pigment ink of Comparative Example 1, which is not used, the dispersion stability during long-term storage is excellent, and the ejection stability is high. In particular, the aqueous pigment inks of Examples 1 and 2, which are black inks, have a high print density, and particularly the aqueous pigment ink of Example 2 having a high pH has an extremely high print density. In addition, it can be seen that the aqueous pigment ink of the present invention (Examples 1 to 4) has less bleeding after printing than the aqueous pigment ink of Comparative Example 2 in which no amino alcohol is used. In addition, it can be seen that the water-based pigment ink of the present invention can provide good results in any of the ink jet recording methods in which recording is performed using thermal energy and a piezoelectric element.

[0065]

According to the present invention, a water-based pigment ink having high print quality of a printed image and excellent dispersion stability under long-term storage can be obtained. Further, according to the present invention, a water-based pigment ink excellent in ejection stability, particularly when used as an ink for inkjet recording, can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideki Yanagi 2606, Kabashi-cho, Akaga-cho, Haga-gun, Tochigi Prefecture (72) Inventor Shigemi Wakabayashi 2606, Kabaka-cho, Akaba-cho, Haga-gun, Tochigi Prefecture, Kao Corporation ( 72) Inventor Yoshiaki Tsujii 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Pref. (72) Inventor Kenji Aida 2606 Kabashi-cho, Akabane-cho, Haga-gun, Tochigi Pref.

Claims (5)

[Claims] 1. A pigment, alkylene oxide addition (meth)
An aqueous pigment ink comprising a polymer dispersant comprising a copolymer of an acrylic acid derivative, an amino alcohol and water. 2. The aqueous pigment ink according to claim 1, wherein the pH is 9.5 to 13.0. 3. The aqueous pigment ink according to claim 1, wherein the amino alcohol is 2-aminoethanol or triethanolamine. 4. The polymer dispersant according to the following general formula (A)
And a copolymer obtained by polymerizing a monomer (b) represented by the following general formula (B):
The aqueous pigment ink according to claim 1. Embedded image 5. The aqueous pigment ink according to claim 1, which is an ink for inkjet recording.