JP2003138176A - Water-based ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide water-based ink excellent in jetting stability and having sufficient jetting speed in high frequency printing and imparting high printing concentration to printed matters. SOLUTION: This water-based ink comprises water dispersion of polymer particles obtained by adding water-insoluble coloring agent to a slightly water- soluble polymer having an ionic group. The ink has 0.01-2 wt.% total content of a water-soluble polymer content and a self-dispersing polymer content in the water-based ink.

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 An ink jet recording system is a recording system in which characters and images are obtained by directly ejecting and adhering ink droplets onto a recording member from a very fine nozzle. 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,
When the ejection speed of ink droplets is low and high-frequency ejection is performed, ejection failure occurs, distortion occurs in the ejection direction of ink droplets, landing accuracy is poor, and a sufficient ejection amount cannot be obtained. There is a defect in the ejection stability. 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.

As a technique similar to these, the content of the water-soluble resin component in the ink is specified (Japanese Patent Publication No.
-019361), the content of the resin-dissolving component in the ink of the film-forming resin is specified (JP-A-10-292143), and the like. However, the former is a pigment in which a water-soluble resin is dispersed, which is basically different from the present invention.
The latter has a drawback that the self-dispersing polymer is not removed because the dissolved component is removed by the acid precipitation method.

[0009]

DISCLOSURE OF THE INVENTION The present invention has excellent ejection stability and exhibits a sufficient ejection speed during high-frequency printing.
An object of the present invention is to provide an aqueous ink capable of imparting a high print density to a printed matter.

[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. The present invention relates to an aqueous ink in which the total content of the content and the content of the self-dispersing polymer is 0.01 to 2% by weight.

[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).

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. Among these, unsaturated vinyl carboxylate monomers such as acrylic acid and methacrylic acid are preferable.

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 of (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate has 1 to 30 carbon atoms; styrene, vinyl toluene, 2-methyl styrene, styrene monomers such as chlorostyrene; formula (II): X (Y) q Si (R 4) 3-r (Z) r (II) ( wherein, X is a polymerizable unsaturated A saturated 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 terms (iso or tertiary) and (iso) mean both cases where these groups are present and cases where they are not present. When these groups are not present, normal is used. Indicates.

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.

Representative examples of poorly water-soluble vinyl polymers include poorly water-soluble vinyl polymers composed of one or more vinyl monomers selected from the group consisting of styrene, (meth) acrylic acid and (meth) acrylic acid esters.

When the water-insoluble colorant is a pigment and the poorly water-soluble polymer is an anionic type, the ratio of the poorly water-soluble monomer is 1 from the viewpoint 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 type, the ratio of the poorly water-soluble monomer is 2 from the viewpoint of storage stability and ejection reliability of the dispersion.
5:75 to 70:30 is more preferable.

When the water-insoluble colorant is a hydrophobic dye and the sparingly water-soluble polymer is an anionic polymer, the sparingly water-soluble monomer ratio is 3:97 to 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 sparingly water-soluble polymer is a cationic type, the sparingly 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 from 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, it is necessary that the total amine value of the poorly water-soluble polymer is 10 to 230 to improve the 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, and a water-miscible organic solvent may 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 vary 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 vinyl polymer (measured by the method described in Production Examples 1 to 4 described later) is good in terms of dischargeability, prevention of charring of the printer head, durability of ink after printing and stability of dispersion. From a sex perspective, 3000-200000
Is preferable, and more preferably 5000 to 10000.

The hydrophobic dye can be used without particular limitation as long as it 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 encapsulating 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 polymer and a hydrophobic dye are dissolved in an organic solvent, a neutralizing agent is added as necessary to ionize a salt-forming group in the polymer, water is added to this, and then an ultrasonic emulsifier is added if necessary. It can be obtained by emulsifying using, the organic solvent is distilled off, and the phase is converted into 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,
20 to 400 parts by weight is preferable to 100 parts by weight of the solid content of the 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 to 10% by weight, preferably 4 to 8% by weight from the viewpoint of providing a sufficient ejection speed in high frequency printing, and imparting sufficient printing density and drying resistance. desirable. Since the ejection speed of printing generally decreases at high frequencies, the frequency dependence of the ejection speed (f
Special characteristics are taken, and if the discharge speed does not change from low frequency (100Hz) to 10kHz, it has sufficient discharge speed even at high frequency.

As a method for obtaining an aqueous dispersion of polymer particles containing a pigment, the polymer is dissolved in an organic solvent,
A preferred method is to add a pigment, water, a neutralizing agent and, if necessary, a surfactant and knead to form a paste, and then dilute the paste as necessary with water and distill off the organic solvent to prepare an aqueous system.

The obtained aqueous dispersion contains a water-soluble polymer produced in the course of polymerization and a self-dispersing polymer which is self-dispersed without being adsorbed by a water-insoluble coloring agent such as a pigment.

In the present specification, the self-dispersing polymer means the solid content of the filtration residue obtained by filtering the supernatant of the aqueous ink after centrifugation with a filter having a pore size of 0.2 μm.

The content of the self-dispersing polymer is
It is the solid content of the filtration residue in the water-based ink.

In the present invention, the water-soluble polymer is contained in the supernatant of the water-based ink after centrifugation, together with the self-dispersing polymer and the ink additive described later. The solid content of the supernatant is the total content of the water-soluble polymer and the self-dispersing polymer and the additive for ink.

When determining the content of the additive for ink, the content of the water-soluble polymer is calculated from the solid content of the supernatant and the solid content of the filtration residue and the content of the ink additive. It is calculated by subtracting. When the content of the additive for ink is not required, is the content of the water-soluble polymer determined by the calibration curve method from the peak area of the water-soluble polymer in the chromatogram of the aqueous GPC of the supernatant liquid,
Or, it is required by the preparative method.

The content of the water-soluble polymer and the content of the self-dispersing polymer are specifically described in Examples 1 to 5 and Comparative Example 1.
It is determined by a method using a centrifuge or a centrifuge of equivalent performance as shown in FIGS. When the content of the water-soluble polymer is high, the ink viscosity becomes high, which causes ejection failure. On the other hand, when the content of the self-dispersing polymer is large, a film is formed at the tip of the orifice and the ink flow path, which causes clogging, ink supply failure, and ejection failure. Therefore, it is desirable that the content of such a polymer in the water-based ink is low.

The content of the water-soluble polymer and the content of the self-dispersing polymer in the water-based ink are preferably 0.01% by weight or more, and more preferably 0.05% by weight or more, from the viewpoint of fixability.

The content of the water-soluble polymer is preferably 2% by weight or less, more preferably 1% by weight or less, from the viewpoints of ejection stability, sufficient ejection speed in high frequency printing and high printing density. . Considering the above points, the content of the water-soluble polymer in the water-based ink is preferably 0.
It is from 1 to 2% by weight, more preferably from 0.05 to 1% by weight.

The content of the self-dispersing polymer is preferably 1% by weight or less, more preferably 0.5% by weight or less, from the viewpoint of ejection stability, sufficient ejection speed in high frequency printing and high printing density. is there. Considering the above points,
The content of the self-dispersing polymer in the water-based ink is preferably 0.01 to 1% by weight, more preferably 0.05 to 0.5% by weight.

The total content of the water-soluble polymer and the content of the self-dispersing polymer in the water-based ink is 0.01 to 2% by weight, preferably 0.1 in consideration of the above points.
~ 1% by weight.

Examples of methods for removing the water-soluble polymer and the self-dispersing polymer include dialysis, membrane treatment such as ultrafiltration, centrifugation treatment, gel filtration treatment and the like. It can be selected according to the property. Among these methods, the membrane treatment and the centrifugation treatment are preferable from the viewpoint of efficiency and cost.

Centrifugation is sometimes used to remove coarse particles, not to remove water-soluble polymers and self-dispersing polymers. In this case, centrifugation is performed under the condition that only coarse particles settle and other polymer particles do not settle.

50 mol% of ionic groups of poorly water-soluble polymer
When the polymer is neutralized and self-dispersed in water without using a water-insoluble colorant, the polymer having an average particle size of 0.1 μm or more has a high adsorbability to the water-insoluble colorant and is a coloring material. It is preferable because the content of the water-soluble polymer and the self-dispersing polymer which are not adsorbed to the water-insoluble colorant when converted into the water-based ink tends to decrease.

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 alone. 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.

[0070]

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 weight% copolymer solution was obtained.

A part of the obtained copolymer solution was put under reduced pressure to
The copolymer was isolated by drying at 105 ° C. for 2 hours and removing the solvent. 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. [Dispersion step] Next, 5 parts by weight of the obtained copolymer was dissolved in 25 parts by weight of methyl ethyl ketone, and a neutralizing agent therein (6 parts by weight of 1N aqueous sodium hydroxide solution in Production Examples 1 to 3 and 5) was prepared. In Example 4, 50% glycolic acid aqueous solution (18.2 parts by weight) was added to neutralize a part of the copolymer, 5 parts by weight of pigment was further added, and the mixture was kneaded by a bead mill.

To the resulting kneaded product, 125 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. 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 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 of the copolymer was measured in the same manner as in Production Examples 1 to 4. The results are shown in Table 1. [Dispersion step] To 25 parts by weight of the obtained copolymer, 250 parts by weight of methyl ethyl ketone and 25 parts by weight of the hydrophobic dye shown in Table 1 were added and completely dissolved, and 10 parts by weight of 1N aqueous sodium hydroxide solution was added. A part of the salt-forming groups of the copolymer was neutralized, 1250 parts by weight of ion-exchanged water was added thereto, and the mixture was stirred and then emulsified for 30 minutes using a Microfluidizer (manufactured by Microfluidizer Co., Ltd.).

From the obtained emulsion, the organic solvent was removed 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 8 [Purification step] An aqueous dispersion of the pigment-containing vinyl polymer particles obtained in Production Example 1 or 2 or an aqueous dispersion of the dye-containing vinyl polymer particles obtained in Production Example 5 was used as a vibrating membrane. It was purified by a separation device VSEP (manufactured by NEW LOGIC INTERNATIONAL INC.). Purification was performed by continuous hydrodiafiltration (diafiltration), and an ultrafiltration membrane (polyether sulfone) having a molecular weight cutoff of 4000 was used as the purification membrane.

The purified solution thus obtained was heated under reduced pressure to remove a part of water, and the solid content of Production Example 6, Production Example 7 and Production Example 8 corresponding to Production Example 1, Production Example 2 and Production Example 5, respectively. Concentration
An aqueous dispersion of 20% by weight of pigment or dye-containing polymer particles was obtained. Production Examples 9 to 10 [Purification step] The pigment water dispersion obtained in Production Example 3 or 4 was used in a centrifuge [Hitachi Koki Co., Ltd., trade name: compact ultracentrifuge himac CS150GXL]. , Rotation speed 150,000r / m
The dispersion was completely settled under the condition of in (1,050,000 g) × 6 h. The dispersion and the supernatant liquid are filtered through the filter having a pore size of 0.2 μm, the filtration residue is washed with 100 g of ion-exchanged water, and again,
Ion-exchanged water was added to the filtration residue filtered by the filter and redispersed, and an aqueous dispersion of pigment-containing vinyl polymer particles having a solid content concentration of 20% by weight in Production Example 9 or 10 corresponding to Production Example 3 or 4, respectively. Got

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: manufactured by Toagosei Co., Ltd., trade name: AS
-6 (styrene homopolymer macromer, number average molecular weight: 600
0, polymerizable functional group: methacryloyloxy group) Silicone macromer: manufactured by Chisso Corporation, trade name: FM-0
711 [Number average molecular weight: 1000, Formula (IIa): CH ₂ = C (CH ₃ ) -COOC ₃ H _6- [Si (CH ₃ ) ₂ -O] _d -CH ₃ (IIa) (where, d is A compound represented by a number of 8 to 40)] Water-insoluble monomer ratio: Weight ratio of water-soluble vinyl monomer unit to water-insoluble vinyl monomer unit

[0077]

[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 deionized water were mixed, and the resulting mixture was equipped with a 1.2 μm filter [acetyl cellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.]. A 25 mL needle-free 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.

With respect to the obtained water-based inks of Examples 1 to 5 and Comparative Examples 1 to 5, the total content of the water-soluble polymer and the content of the self-dispersing polymer, the content of the water-soluble polymer, and the self-dispersion content The dispersible polymer content was determined by the following method. The results are shown in Table 2. [Measurement method of total content of water-soluble polymer and self-dispersing polymer, content of water-soluble polymer and content of self-dispersing polymer] Centrifuge [Hitachi Koki after weighing aqueous ink Co., Ltd., trade name, small ultracentrifuge for reactor separation, himac CD150GXL], rotation speed 150,000 r / min (1,05
Centrifuge under the condition of 0,000 g) x 6 h.

The supernatant after centrifugation was separated into No. 1, No. 2 and N
Divide into 3 pieces of o.3, and after drying the supernatant of No. 1 under reduced pressure,
Weigh and calculate the content of the water-soluble polymer, the content of the self-dispersing polymer, and the solid content, which is the sum of the additives for the ink.

The filter residue obtained by filtering the No. 2 supernatant with a filter having a pore size of 0.2 μm (Fuji Photo Film Co., Ltd., trade name: Disk Capsule CALC20 2.5CMD) was dried under reduced pressure, and then weighed. The solid content, which is the content of the self-dispersing polymer, is calculated.

The water-based GPC of the No. 3 supernatant was measured and the content of the water-soluble polymer in the No. 3 supernatant was determined by the calibration curve method.

The content of the water-soluble polymer and the content of the self-dispersing polymer in the supernatant are calculated from the measurement results of the solid content in each of the No. 1, No. 2 and No. 3 supernatants.

The physical properties of 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. (1) Discharge rate Made by Canon Inc., product 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. (2) Impact accuracy Canon Inc. product 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. (3) Discharge speed and f Toku Canon Co., Ltd., product 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)
And the ejection speed ratio (%) of the water-based inks obtained in Comparative Examples 1 to 5 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 ×. (4) Printing density Bubble jet printer (model number: Desk Jet-720C) manufactured by HEWLETT PACKARD, which is commercially available
Using, a solid copy is printed on a commercially available copy paper, left at 25 ° C. for 1 hour, and 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 of the water-based inks obtained in the respective examples have excellent ejection stability, provide a sufficient ejection speed even in high frequency printing, and exhibit high printing density. It can be seen that it is a water-based ink that does.

[0087]

The water-based ink of the present invention is excellent in ejection stability, has no deviation of the printed matter, and provides a sufficient ejection speed in high frequency printing, and the printed matter exhibits a high printing density. .

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C056 FC01 FC02                 2H086 BA01 BA53 BA55 BA59 BA60                       BA62                 4J039 AD00 AD03 AD09 AD10 AD20                       AE04 AE06 BE01 BE07 BE08                       CA06 EA44 GA24

Claims (5)

[Claims] 1. An aqueous dispersion of polymer particles comprising a poorly water-soluble polymer having an ionic group and a water-insoluble coloring agent, wherein the content of the water-soluble polymer in the aqueous ink and the self-dispersing polymer A water-based ink having a total content of 0.01 to 2% by weight. 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. The poorly water-soluble polymer having an ionic group comprises a water-soluble vinyl monomer and a poorly water-soluble vinyl monomer, and the weight ratio of the water-soluble vinyl monomer unit and the poorly water-soluble vinyl monomer unit (water-soluble vinyl monomer unit: water The water-based ink according to claim 1 or 2, wherein the soluble vinyl monomer unit) is 3:97 to 70:30. 4. The water-based ink according to claim 1, wherein the aqueous dispersion of polymer particles has been subjected to a membrane treatment or a centrifugal separation treatment. 5. The average particle size of the poorly water-soluble polymer having an ionic group 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. The water-based ink according to claim 1, which is a polymer having a diameter of 0.1 μm or more.