JPH1060352A - Aqueous pigment ink - Google Patents

Abstract

(57) [Problem] To provide an aqueous pigment ink having improved fixability of a pigment to a recording member, particularly a film such as an OHP sheet. SOLUTION: The aqueous pigment ink of the present invention is characterized by containing a pigment, a polymer dispersant, polyethyleneimine having a weight average molecular weight of 800 to 300,000, a water-soluble solvent and water.

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 having excellent pigment dispersion stability and improved pigment fixability.

[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 pigment dispersion stability and fixability to recording members.

[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 use OHP as a recording member.
When a film such as a sheet is used, there is a problem that the fixability of the pigment is not sufficient.

Accordingly, it is an object of the present invention to provide a water-based pigment ink having improved fixability of a pigment to a recording member, particularly a film such as an OHP sheet.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that an aqueous system which can achieve the above object can be achieved by using a combination of a polymer dispersant and polyethyleneimine having a weight average molecular weight within a specific range. It has been found that a pigment ink can be obtained.

[0006] The present invention has been made based on the above findings, and has a pigment, a polymer dispersant, and a weight average molecular weight of 800 to 3.
The above object has been achieved by providing an aqueous pigment ink comprising 0000 polyethyleneimine, a water-soluble solvent and water.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The water-based pigment ink of the present invention is characterized in that it contains a pigment, a polymer dispersant, polyethyleneimine having a weight average molecular weight within a specific range, a water-soluble solvent, and water as essential components as described above. It is assumed that.

[0008] The polyethyleneimine has a weight average molecular weight of 800 to 300,000. If the weight average molecular weight is less than 800, the fixability of the pigment to a film such as an OHP sheet will not be improved, and if it exceeds 300,000, the viscosity of the ink will increase and the ink will be poor in handleability. Also,
The polyethyleneimine has a weight average molecular weight of 100
0 to 100000, preferably 1500 to 50
More preferably, 000. The addition of the polyethyleneimine improves the fixability of the pigment to a recording member, particularly a film such as an OHP sheet. The method for producing the above polyethyleneimine is not particularly limited, and can be obtained by a known polymerization method, for example, by the following [1] to [3]. That is, [1] ring-opening polymerization of ethyleneimine using carbon dioxide, hydrochloric acid, hydrobromic acid or the like as a catalyst. [2] Polycondensation of ethylene chloride and ethylenediamine. [3] Oxazolidone-2 is heated.

The above weight average molecular weight is 800-3000.
Examples of the polyethyleneimine (hereinafter, simply referred to as “polyethyleneimine”) are polyethyleneimine grafted to a side chain of an acrylic main chain, hydroxylated polyethyleneimine, and zwitterionized polyethyleneimine. Is preferably used. These polyethyleneimines are used alone or in combination of two or more.

The polyethyleneimine grafted on the side chain of the main chain composed of the acrylic chain is, for example, polyacrylic acid is converted to polyacrylic acid chloride with thionyl chloride, and the polyacrylic acid chloride and the polyethyleneimine are combined. It is synthesized by a method such as complete reaction.

The above-mentioned hydroxylated polyethyleneimine is prepared, for example, by converting polyacrylic acid into an acid chloride with thionyl chloride, reacting the excess polyacrylic acid with the polyethyleneimine, and then adding an excess of the acid chloride. Is synthesized by a method of hydrolyzing the compound to convert it into an acid.

The amphoteric ionized polyethyleneimine may be prepared, for example, by converting polyacrylic acid into polyacrylic acid chloride with thionyl chloride, and reacting the polyacrylic acid chloride with a part of the polyethyleneimine. Synthesized.

[0013] Of these polyethylene imines, from the viewpoint of the ability to disperse pigments, hydroxylated polyethylene imine is particularly preferred.

The above-mentioned polyethyleneimine is preferably incorporated in the aqueous pigment ink of the present invention in an amount of 0.01 to 10% by weight, from the viewpoint of a balance between the basic physical properties of the ink and the improvement of fixability. It is more preferable that the content is from 0.5 to 5% by weight.

It is presumed that the reason why the fixability of the pigment to a recording member, particularly a film such as an OHP sheet, is improved by blending the polyethyleneimine in the aqueous pigment ink of the present invention is as follows. That is, since the polyethyleneimine has tackiness, it acts as a binder for binding the pigment and the recording member on the recording member. As a result, the pigment is sufficiently fixed even when printing is performed on a recording member having poor ink permeability such as a film. As described above, since the fixing property of the pigment is caused by the tackiness of the polyethyleneimine,
Particularly when the water-based pigment ink of the present invention is used in an ink jet recording method in which recording is performed using thermal energy, the fixability of the pigment is further improved.

As the polymer dispersant used in the water-based pigment ink of the present invention, a polymer dispersant capable of improving the dispersibility of the pigment in the ink is used. Examples of the polymer dispersant include gelatin, proteins such as casein, natural gums such as gum arabic, glucoxides such as saponin, alkyl cellulose, carboxyalkyl cellulose, cellulose derivatives such as hydroxyalkyl cellulose, lignin sulfonate, shellac and the like. Natural polymer, polyacrylate, styrene-acrylic acid copolymer salt, vinylnaphthalene-acrylic acid copolymer salt, styrene-maleic acid copolymer salt, vinylnaphthalene-maleic acid copolymer salt, β-naphthalene Anionic polymers such as sodium salt of sulfonic acid formalin condensate and polyphosphoric acid, and nonionic polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyalkylene glycol can be used. These can be used alone or in combination of two or more.

In particular, it is preferable to use a copolymer of a (meth) acrylic acid derivative as the polymer dispersant, since the dispersibility of the pigment is further improved and the long-term storage stability of the ink is improved. 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.
Alternatively, acrylic acid or methacrylic acid or a derivative thereof and a polymerizable monomer may be used as a copolymer component. Derivatives of (meth) acrylic acid include alkali metal salts, alkaline earth metal salts, ammonium salts or amine salts and esters thereof,
And compounds (for example, maleic acid, itaconic acid, citraconic acid and fumaric acid) in which a hydrogen atom bonded to a double bond carbon is substituted with various functional groups (for example, carboxyl group or carboxyalkyl group). 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 examples of the copolymer 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)”].

[0019]

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.

Examples of the compound represented by the general formula (B) include 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 / 100-100. / 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 its 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 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), as a polymer dispersant is not clear. However, it is inferred that: 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 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 is
Is preferably set to a high region.

The above-mentioned polymer dispersant is preferably incorporated in the aqueous pigment ink of the present invention in an amount of 0.05 to 10% by weight. If the compounding amount of the polymer dispersant is less than 0.05% by weight, the compounding amount does not reach a level sufficient to stabilize the pigment, so that storage stability may be lacking. In addition, the storage stability may not be further improved, and the viscosity of the ink may be increased. The compounding amount of the polymer dispersant is more preferably from 0.1 to 4% by weight, and even more preferably from 0.5 to 3% by weight.

Next, in the water-based pigment ink of the present invention,
The essential components other than the polyethyleneimine and the polymer dispersant 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, 8
3, 95, 97, 98 and 100; I. Pigment Red 1, 3, 4, 5, 17, 22, 31, 48, 4
9, 53, 63, 64, 81: 1, 88 and 101;
C. I. Pigment Blue 1, 15, 16, 27, 2
8, 29, 56, 60 and 63; I. Pigment Black 1 and 11 can be used, and carbon black is particularly preferable. The pigment is preferably incorporated 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. . Further, the pigment preferably 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 ink for inkjet recording. ,
More preferably, the thickness is 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 humectant. For example, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, etc. 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 for ink jet recording), 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 preferable that the content is 0.1 to 10% by weight.
More preferably, it is blended in an amount of about 5% by weight.

Examples of the anionic surfactant include alkyl benzene sulfonate, alkyl naphthalene sulfonate, alkane or olefin sulfonate, alkyl sulfate, polyoxyethylene alkyl or alkyl aryl ether sulfate, and 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 cationic surfactant, an aliphatic amine salt, a quaternary ammonium salt, a sulfonium salt, a phosphonium salt 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 to the pigment may be insufficient and the dispersibility may be reduced. 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 the polymer dispersant: the anionic surfactant = 1: 1 to 15: 1, and 1: 1.
More preferably, the ratio is from 10 to 10: 1.

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, 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.

Furthermore, the water-based pigment ink of the present invention has a molecular weight of 400 to 3 particularly in order to improve the intermittent ejection property when used as an ink jet recording ink.
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 the two is such that the polymer dispersant: the saccharide = 20: 1 to 1: 5.
The intermittent ejection property is further improved by adjusting such that.

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, it is preferable to blend an acrylic-urethane copolymer emulsion in order to further improve the fixing property of the ink. As the emulsion, it is preferable to use an acryl-urethane block copolymer (a copolymer in which a polyurethane polymer is bonded to a polyacrylic acid polymer). The weight average molecular weight of the copolymer in the emulsion is preferably from 10,000 to 300,000, and more preferably from 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.

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 of improving the print density of a printed image, particularly the black print density.
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 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 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 It can be used for any of printers of the thermal jet recording type, and is particularly preferably used for a printer of the thermal jet recording type which performs recording using thermal energy.

[0055]

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 Pigment A 15 parts Polymer dispersant A 2 parts Diethylene glycol 7 parts Water 76 parts 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 A-0.3 parts of polymer dispersant A-3 parts of polyethyleneimine A-1.7 parts of diethylene glycol-0.7 parts of 2-aminoethanol-60.9 parts of water After that, centrifugation was performed using a centrifuge (2500
G, 20 minutes) to remove coarse particles to obtain an aqueous pigment ink. The storage stability and fixability of the pigment of this water-based pigment ink were measured according to the following [measurement method]. Table 3 shows the results. The details of the pigment A, the polymer dispersant A and the polyethylene imine A in the above components are as shown in Table 2.

[Measurement method] Storage stability After the obtained ink was stored at 60 ° C for 120 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.

[0058]

(Equation 1)

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

Pigment fixability A thermal jet printer (BJ-10V manufactured by Canon Inc.) in which a heater for a heating resistor element is provided on a printer head.
Lite), and an ink jet printer in which a piezoelectric element is disposed in a printer head (MJ-5 manufactured by Epson)
Using 00C), solid printing was performed on an ink-jet OHP sheet, and after drying, the solid printed portion was checked for the degree of fixing of the ink when rubbed with rubber, and the fixing property of the pigment was evaluated based on the following criteria. Evaluation criteria x: Ink falls when rubbed with poppy rubber.・ ・ ・: The ink does not fall even if it is rubbed with brush rubber, but it falls down with nails. ◎ ・ ・ ・ The ink does not fall even if it is rubbed with brush rubber or scratched with nails.

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

[0062]

[Table 1]

[0063]

[Table 2]

[0064]

[Table 3]

As is evident from the results shown in Table 3, the water-based pigment inks of the present invention (Examples 1 to 5) using a combination of a polymer dispersant and a polyethyleneimine having a weight average molecular weight within a specific range were obtained. It can be seen that, compared with the ink of Comparative Example 1 in which no polymer dispersant was used, the fixability of the pigment of the printed image was excellent. Further, as a polymer dispersant, a copolymer of a specific (meth) acrylic acid derivative was used, and the copolymer of the (meth) acrylic acid derivative and the above-mentioned polyethyleneimine were used in combination with Examples 1, 2, 4 and It can be seen that the water-based pigment ink No. 5 also has excellent storage stability under long-term storage. In particular, it can be seen that the aqueous pigment ink of the present invention has good pigment fixability in an inkjet recording method in which recording is performed using thermal energy.

[0066]

According to the present invention, a recording member, in particular, OH
An aqueous pigment ink having improved fixability of the pigment to a film such as a P sheet can be obtained.

Continuing on the front page (72) Inventor Hideki Yanagi 2606, Kabashi-cho, Akaga-cho, Haga-gun, Tochigi In-house research laboratory (72) Inventor Shoichi Suzuki 2606, Akabane, Akabane-cho, Haga-gun, Tochigi prefecture In-house researcher of Kao Corporation (72) Inventor: Shigemi Wakabayashi 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Pref. In the Kao Corporation Research Institute

Claims (7)

[Claims] An aqueous pigment ink comprising a pigment, a polymer dispersant, polyethyleneimine having a weight average molecular weight of 800 to 300,000, a water-soluble solvent and water. 2. The aqueous pigment ink according to claim 1, wherein the polyethyleneimine is a polyethyleneimine grafted on a side chain of a main chain composed of an acrylic chain. 3. The water-based pigment ink according to claim 1, wherein the polyethyleneimine is a polyethyleneimine that has been subjected to a hydroxylation treatment. 4. The aqueous pigment ink according to claim 1, wherein the polyethyleneimine is zwitterionized polyethyleneimine. 5. The aqueous pigment ink according to claim 1, wherein the polymer dispersant is a copolymer of a (meth) acrylic acid derivative. 6. 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 5. Embedded image 7. The aqueous pigment ink according to claim 1, which is an ink jet recording ink.