JP2003238846A - Water-base ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-base ink which can impart high print density to a printed matter, more precisely, an ink for an inkjet printer, which is excellent in delivery stability and exhibits sufficient rate of delivery in high-frequency printing. <P>SOLUTION: The water-base ink contains an aqueous dispersion of polymer particles comprising a polymer having an ionic group, hardly soluble in water, and having a water-insoluble coloring agent incorporated therein, wherein the polymer hardly soluble in water has a content of components with a molecular weight of 50,000 or higher of 2% or less. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous ink. More specifically, it relates to a water-based ink that can be suitably used in an inkjet recording system.

[0002]

2. Description of the Related Art The ink jet recording system is a recording system in which ink droplets are ejected directly from a very fine nozzle onto a recording member and adhered thereto to obtain characters and images. According to this method, not only has the advantage that the device used is low in noise and has good operability, but it also has the advantage that colorization is easy and plain paper can be used as a recording member. Widely used in recent years.

Inks for ink jet printers generally include water-based inks and organic solvent-based inks, and water-based inks are usually used except for industrial printers. A water-soluble dye or pigment is used as a colorant for the water-based ink.

Water-soluble dye-based inks are used for personal and office use because of their high color reproducibility and printing reliability. Further, the pigment-based ink is excellent in image fastness such as light resistance and gas resistance, and the printing is clear.

The pigment-based ink generally contains a dispersion in which a pigment is dispersed in water with a water-soluble dispersant such as a surfactant or a polymer dispersant. But in this dispersion,
It has drawbacks in long-term storage stability, reliability such as clogging, and glossiness when printed on glossy film.

In order to solve this drawback, a dispersion containing polymer particles in which a pigment is encapsulated with a poorly water-soluble polymer (JP 2000-191967 A) or an oil-soluble dye is encapsulated with a poorly water-soluble polymer, Inks in which polymer particles are dispersed in water (JP-A-9-241565 and JP-A-9-15)
7565, etc.) has been proposed.

However, when an ink containing a dispersion containing polymer particles in which a pigment is encapsulated with a poorly water-soluble polymer is used for ink jet recording,
Distortion occurs in the ejection direction of the ink droplets, the landing accuracy is poor, the ejection speed of the ink droplets is low, and a sufficient ejection amount cannot be obtained. Further, when high frequency printing is performed, the ejection speed becomes low, and ejection failure is likely to occur. Further, even in the case of an ink in which a hydrophobic dye such as an oil-soluble dye is encapsulated with a poorly water-soluble polymer and polymer particles are dispersed in water, there are similar drawbacks.

The cause of these drawbacks is that the viscosity of the water-based ink is high, but if the viscosity of the water-based ink is reduced, the robustness of printing after printing may be reduced.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water-based ink capable of imparting a high print density to a printed matter. More specifically, it is an object of the present invention to provide an ink for an inkjet printer, which has excellent ejection stability and exhibits a sufficient ejection speed during high-frequency printing.

[0010]

The present invention comprises an aqueous dispersion of polymer particles comprising a poorly water-soluble polymer having an ionic group and a water-insoluble coloring agent, and has a molecular weight of 50,000 or more in the poorly water-soluble polymer. Content of 2
% Of water-based ink.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As used herein, a "water-insoluble polymer having an ionic group" (hereinafter, simply referred to as "water-insoluble polymer") means 50 mol% or more of ionic groups present in the polymer. When the polymer is neutralized, the solubility of the polymer in water at 25 ° C. is 1% by weight or less.

The "water-insoluble colorant" referred to in the present specification
Means that the solubility in water at 25 ° C is 1% by weight or less. Typical examples thereof include hydrophobic dyes and pigments.

Examples of poorly water-soluble polymers include poorly water-soluble vinyl polymers, polyester polymers and polyurethane polymers having an ionic group. Among these poorly water-soluble polymers, a poorly water-soluble vinyl polymer having an ionic group is preferable.

In the poorly water-soluble polymer, examples of the "ionic group" include a carboxylic acid group, a sulfonic acid group and a phosphoric acid group.

A typical example of the poorly water-soluble vinyl polymer is a copolymer of a water-soluble vinyl monomer and a poorly water-soluble vinyl monomer.

"Water-soluble vinyl monomer" as used herein
Means that the solubility in water at 25 ° C is 1% by weight or more.

Specific examples of the water-soluble vinyl monomer include:
Ionic group-containing vinyl monomer, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth)
A hydroxyl group-containing vinyl monomer such as acrylate, formula (I): CH ₂ ═C (R ¹ ) COO (R ² O) _p R ³ (I) (In the formula, R ¹ is a hydrogen atom or a lower one having 1 to 3 carbon atoms. Alkyl group, R ² has 1 to 8 carbon atoms which may have a hetero atom.
30 divalent hydrocarbon groups, R ³ is a monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hydrogen atom or a hetero atom,
and p represents a number from 1 to 60). In addition, the "(meth) acry" as used in this specification means "acry" or "methacry".

As the ionic group-containing vinyl monomer,
Examples include cationic vinyl monomers and anionic vinyl monomers. As a typical example of a vinyl monomer containing an ionic group, JP-A-9-286939, page 5, column 7, line 24 to column 8,
Examples include those listed in line 29.

Specific examples of the cationic vinyl monomer include unsaturated tertiary amine-containing vinyl monomers and unsaturated ammonium salt-containing vinyl monomers. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ', N'-dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferable.

Representative examples of the anionic vinyl monomer include unsaturated vinyl carboxylate monomer, unsaturated vinyl vinyl sulfonate monomer, unsaturated vinyl vinyl phosphate monomer and the like. Of these, unsaturated vinyl carboxylate monomers such as (meth) acrylic acid are preferred.

The term "poorly water-soluble vinyl monomer" as used herein means one having a solubility in water at 25 ° C. of less than 1% by weight.

Specific examples of the poorly water-soluble vinyl monomer include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate,
(Iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (Meth) acrylic acid esters in which the ester moiety such as (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate has 1 to 30 carbon atoms; styrene, vinyl Styrene-based monomers such as toluene, 2-methylstyrene, chlorostyrene;

Formula (II): X (Y) _q Si (R ⁴ ) _3-r (Z) _r (II) (wherein X is a polymerizable unsaturated group, Y is a divalent linking group,
R ⁴ is independently a hydrogen atom, a lower alkyl group, an aryl group or an alkoxy group, Z is a residue of a monovalent siloxane polymer having a number average molecular weight of 500 or more, q is 0 or 1, r is 1 to 3 Represents a whole number), a styrene-based macromer having a polymerizable functional group such as an acryloyloxy group or a methacryloyloxy group at one end, and an alkyl (meth) acrylate-based macromer. These poorly water-soluble vinyl monomers may be used alone or in admixture of two or more.

The above "(iso or tertiary)"
And “(iso)” means both when these groups are present and when they are not, and when these groups are not present, normal is indicated.

The weight ratio of the water-insoluble vinyl monomer unit and the water-insoluble vinyl monomer unit constituting the water-insoluble polymer (water-soluble vinyl monomer unit: water-insoluble vinyl monomer unit, hereinafter referred to as "water-insoluble monomer ratio") is ,
From the viewpoint of storage stability of the water dispersion, it is preferably 3: 97-.
70:30.

A representative example of the poorly water-soluble vinyl polymer is a poorly water-soluble vinyl polymer composed of one or more vinyl monomers selected from the group consisting of styrene, (meth) acrylic acid and (meth) acrylic acid ester.

When the water-insoluble colorant is a pigment and the poorly water-soluble polymer is an anionic type, the poorly water-soluble monomer ratio is 1 in terms of storage stability and ejection reliability of the dispersion.
It is more preferably 5:85 to 50:50.

When the water-insoluble colorant is a pigment and the poorly water-soluble polymer is a cationic system, the ratio of the poorly water-soluble monomer is 2 from the viewpoint of storage stability of the dispersion and ejection reliability.
5:75 to 70:30 is more preferable.

When the water-insoluble colorant is a hydrophobic dye and the poorly water-soluble polymer is an anionic type, the poorly water-soluble monomer ratio is 3: 97-from the viewpoint of storage stability and ejection reliability of the dispersion. More preferably, it is 45:55.

When the water-insoluble colorant is a hydrophobic dye and the poorly water-soluble polymer is a cationic type, the poorly water-soluble monomer ratio is 5:95 to 40 from the viewpoint of storage stability and ejection reliability of the dispersion. : 60 is more preferable.

When the water-insoluble colorant is a pigment and the sparingly water-soluble polymer is an anionic polymer, the acid value of the sparingly water-soluble polymer is 150 to 260 from the viewpoint of stability and ejection reliability of the dispersion. Is preferred.

When the water-insoluble colorant is a pigment and the poorly water-soluble polymer is a cationic type, the total amine value of the poorly water-soluble polymer is 30 to 230 from the viewpoint of stability and ejection reliability of the dispersion. Is preferred.

When the water-insoluble colorant is a hydrophobic dye and the sparingly water-soluble polymer is an anionic polymer, the acid value of the sparingly water-soluble polymer is 12 to 200 from the viewpoint of stability and ejection reliability of the dispersion. Is preferred.

When the water-insoluble colorant is a hydrophobic dye and the poorly water-soluble polymer is a cationic type, the total amine value of the poorly water-soluble polymer is from 10 to 230, which improves stability and ejection reliability of the dispersion. It is preferable from the viewpoint.

The poorly water-soluble vinyl polymer is produced by the bulk polymerization method,
It is produced by polymerizing by a known polymerization method such as a solution polymerization method, a suspension polymerization method and an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.

The solvent used in the solution polymerization method is preferably a polar organic solvent, or a water-miscible organic solvent can be mixed with water.

Examples of the polar organic solvent include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol and propanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate. Among these, methanol, ethanol, acetone, methyl ethyl ketone or a mixed solution of these and water is preferable.

A radical polymerization initiator can be used in the polymerization. As the radical polymerization initiator,
2,2'-azobisisobutyronitrile, 2,2'-azobis
(2,4-dimethylvaleronitrile), dimethyl-2,2'-azobisbutyrate, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (1-cyclohexanecarbonitrile) Azo compounds such as are suitable. It is also possible to use an organic peroxide such as t-butyl peroxyoctoate, di-t-butyl peroxide, dibenzoyl oxide.

The amount of the radical polymerization initiator is preferably 0.001 to 5 mol%, particularly 0.01 to 2 mol% based on the total amount of vinyl monomers.

A polymerization chain transfer agent may be added during the polymerization. Specific examples of the polymerization chain transfer agent include:
Octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan, mercaptoethanol and other mercaptans; dimethylxanthogen disulfide, diisopropylxanthogen disulfide and other xanthogen disulfides; tetramethylthiuram disulfide, tetrabutylthiuram disulfide and the like Thiuram disulfides; halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide; hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexylthioglycolate, terbinolene, α-terpinene, γ-terpinene, dipentene, α-methylstyrene dimer, 9,10-dihydroanthracene, 1,4-dihydronaphthalene, indene, 1,4-cyclohexene Unsaturated cyclic hydrocarbon compounds such as xadiene; unsaturated heterocyclic compounds such as 2,5-dihydrofuran and the like can be mentioned, and these can be used alone or in combination of two or more kinds.

The polymerization conditions will differ depending on the type of radical polymerization initiator, monomer, solvent used, etc.
The polymerization temperature is 30 to 100 ° C, preferably 50 to 80 ° C, and the polymerization time is 1 to 20 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas.

The weight-average molecular weight of the poorly water-soluble polymer (measured by the method described in Production Examples 1 to 4 described later) is the durability of the ink after printing and the stability of the dispersion (determined by the method described in Examples described later). From the viewpoint of (measurement), it is preferably 3000 to 30000, and more preferably 5000 to 20000.

The sparingly water-soluble polymer obtained by radical polymerization generally has a distribution in molecular weight. Therefore, when the molecular weight is determined from the viewpoints of the durability of the ink after printing and the stability of the dispersion, the poorly water-soluble polymer constituting the polymer particles contained in the water-based ink of the present invention contains a component having a molecular weight of 50,000 or more ( Hereinafter referred to as "high molecular weight component"). If the amount of this high molecular weight component is large, the viscosity of the aqueous dispersion becomes high, the viscosity of the water-based ink becomes high, and the water-based ink is hindered from being ejected or deposited at the tip of the orifice to bend the water-based ink ejection direction. In addition, in the bubble jet (registered trademark) system, the heater portion is burnt and the discharge pressure is reduced. Therefore, if such high molecular weight components are removed, the viscosity of the water-based ink is reduced, the deposits at the tip of the orifice are eliminated, and the heater does not burn, so that the ejection stability is improved. The content of the high molecular weight component in the poorly water-soluble polymer (measured by the method described in Examples described later) is 2% from these viewpoints.
It is preferably 1% or less, more preferably 0.5% or less. Since components other than the high molecular weight component are not removed, the durability of the ink after printing and the stability of the dispersion become good.

Removal of this high molecular weight component is carried out by dialysis membrane treatment,
It can be separated by membrane treatment such as ultrafiltration membrane treatment, gel filtration treatment, chromatographic treatment such as adsorption chromatography treatment. These methods can be selected according to the properties of the sample. Among these methods, the membrane treatment is preferable and the ultrafiltration membrane treatment is more preferable from the viewpoint of efficiency and cost.

The hydrophobic dye can be used without particular limitation as long as it is a dye that can be contained in the polymer particles. Examples thereof include oil dyes and disperse dyes.

The oily dye is not particularly limited, but for example, CI Solvent Black 3, 7,
27, 29, 34; CI Solvent Yellow 14, 16, 29, 5
6, 82; CI Solvent Red 1, 3, 8, 18, 24, 2
7, 43, 51, 72, 73; CI Solvent Violet
3; CI solvent blue 2, 11, 70; CI solvent green 3, 7; CI solvent orange 2 and the like.

The disperse dye is not particularly limited, but preferred examples include CI Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 11
9, 122, 124, 126, 160, 184: 1, 186, 198, 19
9, 204, 224, 237; CI Disperse Orange 1
3, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119, 1
63; CI Disperse Red 54, 60, 72, 73, 86, 8
8, 91, 93, 111, 126, 127, 134, 135, 143, 145
, 152, 153, 154, 159, 164, 167: 1, 177, 181
, 204, 206, 207, 221, 239, 240, 258, 277
, 278, 283, 311, 323, 343, 348, 356, 362
CI Dispers Violet 33; CI Dispers Blue 56, 60, 73, 87, 113, 128, 143, 148
, 154, 158, 165, 165: 1, 165: 2, 176, 183, 1
85, 197, 198, 201, 214, 224, 225, 257, 266
, 267, 287, 354, 358, 365, 368; CI Disperse Green 6: 1, 9 and the like.

The hydrophobic dye is contained in the organic solvent in an amount of 2 g / L or more, preferably from the viewpoint of efficiently containing it in the polymer particles.
It is desirable to dissolve 20 to 500 g / L.

An aqueous dispersion of polymer particles containing a hydrophobic dye can be produced by a known emulsification method.
For example, a poorly water-soluble polymer and a hydrophobic dye are dissolved in an organic solvent, a neutralizing agent is added as necessary to ionize the salt-forming group in the poorly water-soluble polymer, and water is added to this,
It can be obtained by carrying out emulsification using an ultrasonic emulsifier, if necessary, and distilling off the organic solvent to invert the phase to an aqueous system.

As the pigment, both known inorganic pigments and organic pigments can be used. If necessary, an extender pigment may be used in combination therewith. Examples of the inorganic pigment include carbon black, metal oxides, metal sulfides, metal chlorides and the like, and carbon black is particularly preferable for black aqueous inks. Examples of carbon black include furnace black, lamp black, acetylene black, channel black and the like. Examples of organic pigments include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthoraquinone pigments, and quinophthalone pigments. Examples of extender pigments include silica, calcium carbonate, talc and the like.

The amount of water-insoluble colorant in the polymer particles is
In terms of print density and ease of inclusion in polymer particles,
It is preferably 20 to 400 parts by weight, more preferably 40 to 250 parts by weight, based on 100 parts by weight of the solid content of the poorly water-soluble polymer.

The content of the water-insoluble colorant in the water-based ink is not particularly limited as long as a sufficient print density can be obtained. Usually, the content is 2 from the viewpoint of providing a sufficient ejection speed and imparting sufficient printing density and drying resistance.
It is desirable that the content is -10% by weight, preferably 4-8% by weight.

As a method for obtaining an aqueous dispersion of polymer particles containing a pigment, a sparingly water-soluble polymer is dissolved in an organic solvent, a pigment, water, a neutralizing agent and, if necessary, a surfactant are added and kneaded to obtain a paste. After that, a method is preferred in which the paste is diluted with water as necessary and the organic solvent is distilled off to form an aqueous system.

50 mol% of ionic groups of poorly water-soluble polymer
When it is neutralized and self-dispersed in water without using a water-insoluble colorant, the average particle size of the polymer particles is 0.1-100 μm.
The water-insoluble polymer having m is highly adsorbable to the water-insoluble colorant, and the content of the water-insoluble polymer that does not adsorb to the water-insoluble colorant when formed into a coloring material tends to decrease in the water-based ink, which is preferable. . The average particle size of the polymer particles is preferably 0.1 to 50 μm, more preferably 0.1 to 50 μm.
~ 10 μm.

The water-based ink of the present invention preferably contains a water-soluble organic solvent. When a water-soluble organic solvent is contained, there is an advantage that it is excellent in drying resistance.

The water-soluble organic solvent referred to in the present specification means 25 ° C.
Refers to an organic solvent having a solubility in water of 1% by weight or more.

Examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, glycerin, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, trimethylolpropane and trimethylolethane. Polyhydric alcohols such as, 2-pyrrolidone, γ-butyrolactam, urea, nitrogen-containing cyclic compounds such as ethylene urea, acetamide, nitrogen-containing acyclic compounds such as N-monomethylacetamide and the like, these are each independently. Alternatively, two or more kinds can be mixed and used. Of these, diethylene glycol, glycerin and 2-pyrrolidone are preferred.

The content of the water-soluble organic solvent in the water-based ink is not particularly limited, but is usually preferably about 5 to 30% by weight from the viewpoint of drying resistance.

If necessary, the water-based ink of the present invention may contain a surfactant and a pH within a range that does not impair the object of the present invention.
Additives for ink such as a regulator and a preservative can be contained.

The water-based ink of the present invention contains a balance amount of water in the balance so that the desired amount of each of the above components is contained.

[0061]

EXAMPLES Production Examples 1 to 4 [Polymerization Step] After a dropping funnel and a Dimroth cooling pipe were attached to a reaction vessel and nitrogen gas replacement was sufficiently performed, 20 parts by weight of methyl ethyl ketone in the reaction vessel and the initial portion of Table 1 were used. The vinyl monomer and polymerization chain transfer agent shown in the charging monomer column are charged, and the dropping funnel contains the vinyl monomer and polymerization chain transfer agent shown in the dropping monomer column of Table 1, 80 parts by weight of methyl ethyl ketone and 2,2'-azobis (2,4- Dimethyl valeronitrile) 1.2 parts by weight was charged.

Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. with stirring, and the mixed solution in the dropping funnel was gradually added dropwise over 3 hours. After 2 hours at 65 ° C from the end of the dropping, a solution of 0.3 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) in 5 parts by weight of methyl ethyl ketone was added, and further at 65 ° C for 2 hours, 70 ° C. Aged for 2 hours, and finally add 395 parts by weight of methyl ethyl ketone,
A copolymer solution of wt% was obtained.

A part of the obtained copolymer solution was added to 0.02 MPa.
It was dried under reduced pressure at 105 ° C. for 2 hours and the solvent was removed to obtain a copolymer. The weight average molecular weight of the obtained copolymer was measured by gel permeation chromatography using polystyrene as a standard substance and chloroform containing 1 mmol / L of dodecyldimethylamine as a solvent. The results are shown in Table 1. The content of components having a molecular weight of 50,000 or more (hereinafter referred to as "content of high molecular weight component") was determined by the method described in Examples. The results are shown in Table 2.
Shown in.

[Dispersion Step] Next, 5 parts by weight of the obtained copolymer was dissolved in 25 parts by weight of methyl ethyl ketone, and 6 parts by weight of 1N aqueous sodium hydroxide solution was added as a neutralizing agent to the solution to prepare a copolymer. Part of the mixture was neutralized, 5 parts by weight of pigment was further added, and the mixture was kneaded with a bead mill.

To the obtained kneaded product, 30 parts by weight of ion-exchanged water was added, and after stirring, the organic solvent was removed at 60 ° C. under a reduced pressure of 0.02 MPa, and a part of water was removed to give a solid product. An aqueous dispersion of pigment-containing vinyl polymer particles having a concentration of 20% by weight was obtained.

Production Example 5 [Polymerization Step] A copolymer solution was obtained in the same manner as in Production Examples 1 to 4 using the monomers and polymerization chain transfer agents shown in Table 1.
The weight average molecular weight and the content of high molecular weight components of the copolymers obtained in the same manner as in Production Examples 1 to 4 were measured. The results are shown in Tables 1 and 2, respectively.

[Dispersion Step] To 5 parts by weight of the obtained copolymer, 25 parts by weight of methyl ethyl ketone and 5 parts by weight of the hydrophobic dye shown in Table 1 were added and completely dissolved to give 6 parts by weight of a 1N aqueous sodium hydroxide solution. Is added to neutralize a part of the salt-forming groups of the copolymer, 300 parts by weight of ion-exchanged water is added thereto,
After stirring, the mixture was emulsified for 30 minutes using a Microfluidizer (manufactured by Microfluidizer).

The organic solvent was removed from the obtained emulsion at 60 ° C. under reduced pressure, and a part of water was removed to obtain an aqueous dispersion of dye-containing vinyl polymer particles having a solid content concentration of 20% by weight. Obtained.

Production Examples 6 to 10 [Purification step] 200 parts by weight of 2-butanone was added to 50 parts by weight of the copolymer solution obtained in the polymerization steps of Production Examples 1 to 5, and a vibrating membrane separator VSEP (NEW LOGIC (Made by INTERNATIONAL INC.)
Purified by. The purification method used was continuous solvent diafiltration (diafiltration), and the purification membrane used was an ultrafiltration membrane (fluorine resin) with a molecular weight cutoff of 50,000. Content of the high molecular weight component of the purified copolymer (hereinafter, referred to as "purified copolymer") obtained by drying the obtained purified copolymer solution in the same manner as in Production Examples 1 to 4. Was measured by gel permeation chromatography, and the results are shown in Table 2.

[Dispersion Step] The obtained purified copolymer was dispersed in the same manner as in the dispersion step of Production Examples 1 to 5, and Production Example 1 to
Aqueous dispersions of pigment- or dye-containing polymer particles having a solid content concentration of 20% by weight were prepared in Production Examples 6 to 10 corresponding to Example 5.

The names shown in Table 1 mean the following. Styrene macromer A: Toagosei Co., Ltd., trade name: AN
-6 (styrene-acrylonitrile copolymer macromer, styrene content: 75% by weight, number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group)

Styrene macromer B: Toagosei Co., Ltd.
Product name: AS-6 (styrene homopolymer macromer, number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group)

Silicone macromer: manufactured by Chisso Co.,
Product name: FM-0711, formula (IIa): CH ₂ = C (CH ₃ ) -COOC ₃ H _6- [Si (CH ₃ ) ₂ -O] _d -CH ₃ (IIa) (where d is a number) A compound represented by a number that satisfies the average molecular weight of 1000)

Poorly water-soluble monomer ratio: Weight ratio of water-soluble vinyl monomer unit and sparingly water-soluble vinyl monomer unit

[0075]

[Table 1]

Examples 1-5 and Comparative Examples 1-5 40 parts by weight of an aqueous dispersion of the pigment- or dye-containing vinyl polymer particles obtained in Production Examples 1-10, 5 parts by weight of glycerin, urea
10 parts by weight, acetylene glycol / polyethylene oxide adduct [Kawaken Fine Chemicals Co., Ltd., trade name:
1 part by weight of acetylenol EH] and 44 parts by weight of ion-exchanged water were mixed, and the resulting mixture was fitted with a 0.5 μm filter [acetyl cellulose membrane, outer diameter: 2.5 cm, Fuji Photo Film Co., Ltd.]. A 25 mL needleless syringe (manufactured by Terumo Corp.) was used for filtration to remove coarse particles, and Examples 1 to 5 and Production Examples 1 to 5 corresponding to Production Examples 6 to 10, respectively.
To obtain the water-based inks of Comparative Examples 1 to 5.

The physical properties of the copolymers and water dispersions obtained in Production Examples 1-10 and the water-based inks obtained in Examples 1-5 and Comparative Examples 1-5 were evaluated by the following methods. The results are shown in Table 2. The ejection stability is evaluated by the ejection amount, the landing accuracy, and the ejection speed ratio.

(1) Content of high molecular weight component In the gel permeation chromatogram obtained to measure the weight average molecular weight of the copolymer, the ratio (%) of the area of the high molecular weight component having a molecular weight of 50,000 or more to the total area.
Is the content (%) of the high molecular weight component.

(2) Average particle size of polymer particles The average particle size of the polymer particles is ELS-80 manufactured by Otsuka Electronics Co., Ltd.
It was determined by cumulant analysis using 00. The measurement conditions are a temperature of 25 ° C, an angle of 90 ° between the incident light and the detector, and the number of integrations.
It was 100 times, and the refractive index (1.333) of water as the dispersion solvent was input. As the standard substance, Uniform Microparticles (particle size 204 nm) manufactured by Seradyn was used.

(3) Viscosity of water dispersion The solid content of the water dispersion of polymer particles is adjusted to 20% by weight,
Rotational E-type viscometer RE-80L (manufactured by Toki Sangyo Co., Ltd., product number: 1 ° 34 ′ × R24 standard rotor) was measured at a temperature of 20 ° C.

(4) Discharge amount Canon Inc., trade name: Bubble Jet Printer
Fill the F-870 ink cartridge with water-based ink and
Print a 3 cm × 3 cm square on the P sheet. This is washed with water and the discharged water-based ink is collected, diluted 10,000 times and the absorbance is measured. A calibration curve is prepared in advance, and the ejection amount is calculated from it. The same evaluation is performed with genuine ink manufactured by Canon Inc. using the same head, and the ratio (%) of the ejection amount of the water-based ink to the ejection amount of the genuine ink is evaluated.

(5) Impact Accuracy Canon Inc., trade name: Bubble Jet Printer
Fill the F-870 ink cartridge with water-based ink, perform head cleaning 3 times, and print the nozzle check pattern. If there are no problems such as misalignment of prints and marks, a rating of ○ is given, and if there is, a rating of x is given.

(6) Discharge speed ratio and f Toku Canon Co., Ltd., trade name: Bubble Jet Printer
The print head of F-870 was modified so that it could be removed, and printing was performed under a microscope to observe the discharge state and
Examples 1 to 5 for the ejection speed of genuine ink at (10 Hz)
Also, the ratio of the ejection speeds of the water-based inks obtained in Comparative Examples 1 to 5 (hereinafter referred to as “ejection speed ratio”) (%) is measured. The ejection frequency is changed by changing the print pattern to obtain the frequency dependence (f characteristic) of the ejection speed. When the discharge speed does not change from 10Hz to 10kHz, it is evaluated as ○, and when the discharge speed is decreased, it is evaluated as ×.

(7) Printing density Bubble jet printer (model number: Desk Jet-720C) manufactured by HEWLETT PACKARD, which is commercially available
After solid printing on a commercially available copy paper using, and leaving it at 25 ° C. for 1 hour, the print density is measured with a Macbeth densitometer (manufactured by Macbeth, product number: RD910).

[0085]

[Table 2]

From the results shown in Table 2, all the water-based inks obtained in the respective examples have low viscosity and excellent ejection stability, and provide sufficient ejection speed even in high frequency printing,
It can be seen that the water-based ink exhibits high printing density.

[0087]

EFFECTS OF THE INVENTION The water-based ink of the present invention is excellent in ejection stability, provides a sufficient ejection speed in high frequency printing, and exhibits a high printing density on a printed matter.

Claims (5)

[Claims] 1. A water-insoluble dispersion of polymer particles, comprising a water-insoluble colorant in a water-insoluble polymer having an ionic group, and having a molecular weight of 5 in the water-insoluble polymer.
A water-based ink containing 2% or less of a component of 0000 or more. 2. The water-based ink according to claim 1, wherein the poorly water-soluble polymer having an ionic group is a poorly water-soluble vinyl polymer having an ionic group. 3. A water-insoluble polymer having an ionic group is obtained by polymerizing a water-soluble vinyl monomer and a monomer mixture containing a water-insoluble vinyl monomer, and the weight ratio of the water-soluble vinyl monomer unit to the water-insoluble vinyl monomer unit ( The water-based ink according to claim 1 or 2, wherein the water-soluble vinyl monomer unit: poorly water-soluble vinyl monomer unit) is 3:97 to 70:30. 4. The water-based ink according to claim 1, wherein the poorly water-soluble polymer has been subjected to a film treatment. 5. An average particle size of the polymer particles in an aqueous dispersion of polymer particles of a poorly water-soluble polymer having an ionic group, in which 50 mol% of the ionic group is neutralized, is 0.1 to 100.
The water-based ink according to any one of claims 1 to 4, which has a thickness of μm.