JP2003138173A - Water-based ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based ink imparting a high print density, and having excellent jetting stability, abrasion resistance and marker resistance. SOLUTION: This water-based ink contains a water dispersion of polymer particles including a water-insoluble coloring matter in a polymer slightly soluble in water and having an ionic group. The content of the water-soluble component in the polymer slightly soluble in the water in an unneutralized state is <=30 wt.%.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, inks for ink jet printers include water-based inks and organic solvent-based inks, but water-based inks are usually used except for those used in industrial printers.

As the water-based ink, a dye-based ink using a water-soluble dye or a pigment-based ink using a pigment is mainly used.

Dye-based inks are used personally or in the office because they have high color reproducibility and printing reliability. On the other hand, the pigment-based ink is excellent in image storability such as light resistance and gas resistance and clearness of printing,
It is used as an ink for industrial printers such as wide format printers.

However, in recent years, pigment-based inks have been used for printers for office use from the viewpoint of image storability.

The pigment-based ink generally contains an aqueous dispersion in which the pigment is dispersed with a water-soluble dispersant such as a surfactant or a polymer dispersant, but the ink using the aqueous dispersion has storage stability. However, there is a drawback in terms of reliability such as clogging.

As a coloring material for eliminating the above-mentioned drawbacks, a coloring material containing a pigment in a water-insoluble polymer has been proposed (Japanese Patent Laid-Open No. 2000-191967).

However, when an ink containing this coloring material is used for ink jet recording, the ejection speed of ink droplets is low, and when ejected at a high frequency,
There are drawbacks in terms of ejection stability, such as ejection failure and moreover, the ejection direction of the ink droplets bends, resulting in poor landing accuracy and inability to secure a sufficient ejection amount. It is considered that these drawbacks are caused by difficulty in achieving both redispersibility of the coloring material and reduction of viscosity. Here, "redispersibility" means that the dried aggregate of the coloring material is restored to the dispersed state by contacting with water.

As a water-based ink for solving the above-mentioned drawbacks, a water-based ink containing an aqueous dispersion in which an oil-soluble dye is contained in a water-insoluble polymer and dispersed in water has been proposed (JP-A-9-157565). Gazette).

However, when the water-based ink is used as the ink for ink jet recording, there is a defect in the marker resistance.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a water-based ink which imparts high print density and is excellent in ejection stability, scratch resistance and marker resistance.

[0012]

The present invention relates to an aqueous ink containing an aqueous dispersion of polymer particles, which comprises a poorly water-soluble polymer having an ionic group and a water-insoluble coloring agent. The present invention relates to a water-based ink in which the content of the water-soluble component of the poorly water-soluble polymer in a Japanese state is 30% by weight or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The "water-insoluble colorant" as used herein refers to a colorant having a solubility in water of 1% by weight or less. Examples of water-insoluble colorants include hydrophobic dyes and pigments.

The hydrophobic dye is not particularly limited as long as it can be contained in polymer particles. Examples of hydrophobic dyes include oil dyes and disperse dyes. Solubility of the hydrophobic dye, from the viewpoint of efficiently containing in the polymer particles, to the organic solvent,
It is preferably 2 g / L or more, and more preferably 20 to 500 g / L.

The oil 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 pigment may be either an inorganic pigment or an organic pigment. If necessary, they can be used in combination with an extender pigment.

Examples of the inorganic pigment include carbon black, metal oxides, metal sulfides, metal chlorides and the like. Among these, carbon black is particularly preferable for black water-based ink. Examples of carbon black include furnace black, thermal 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, anthraquinone pigments, and quinophthalone pigments.

Examples of extender pigments include silica, calcium carbonate, talc and the like.

Examples of the poorly water-soluble polymer having an ionic group include a poorly water-soluble vinyl polymer, a poorly water-soluble polyester polymer, and a poorly water-soluble polyurethane polymer. Of these, sparingly water-soluble vinyl polymers are preferred.

The sparingly water-soluble vinyl polymer can be obtained by copolymerizing a water-soluble vinyl monomer and a sparingly water-soluble vinyl monomer.

The water-soluble vinyl monomer and the poorly water-soluble vinyl monomer are those having a solubility in water at 25 ° C. of 1% by weight or more and less than 1% by weight, respectively.

As the water-soluble vinyl monomer, for example,
Ionic group-containing vinyl monomers such as cationic vinyl monomers and anionic vinyl monomers, hydroxyl group-containing vinyl monomers such as 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) 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 alkyl group having 1 to 3 carbon atoms, and R ² is a carbon which may have a hetero atom. Number 1
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). The ionic group of the poorly water-soluble polymer having an ionic group is derived from the ionic group of the ionic group-containing monomer.

As examples of the cationic vinyl monomer and the anionic vinyl monomer, JP-A-9-286939 5
Examples thereof include those described on page 7, column 24 line to column 8, line 29.

Representative 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 anionic vinyl monomers include unsaturated vinyl vinyl carboxylate monomers, unsaturated vinyl vinyl sulfonate monomers, and unsaturated vinyl vinyl phosphate monomers. Among these, unsaturated vinyl carboxylate monomers such as acrylic acid and methacrylic acid are preferable.

As the poorly water-soluble vinyl monomer, 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, (Meth) acrylic acid esters such as (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate; styrene, vinyltoluene, Examples thereof include styrene-based monomers such as 2-methylstyrene and chlorostyrene, and these can be used alone or in admixture of two or more. The above (iso or tertiary) and (iso) mean both cases where these groups are present and cases where they are not present, and when these groups are not present, normal is shown.

As the poorly water-soluble vinyl monomer,
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 having 1 to 3 carbon atoms, an aryl group having 6 to 9 carbon atoms, or 1 to 4 carbon atoms.
3, 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
Represents an integer of 1 to 3), a styrene-based macromer having a polymerizable functional group such as an acryloyloxy group or a methacryloyloxy group at one end, and a macromer such as an alkyl (meth) acrylate-based macromer. To be

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 among the polar organic solvents, 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. Also, t-butyl peroxyoctoate, di-t-butyl peroxide,
It is also possible to use organic peroxides such as dibenzoyl oxide.

The amount of the polymerization initiator is 0.001 to 5 mol, preferably 0.01 to 2 per 1 mol of the total amount of vinyl monomers.
Molar is preferred.

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 Sajien; 2,5-dihydrofuran unsaturated heterocyclic compounds such as, and the like. These may be used alone or in combination of two or more.

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 vinyl polymer (measured by the method described in Production Examples 1 to 4 described later) is used for ejection stability, prevention of charring of a printer head, durability of ink after printing, and dispersion. From the viewpoint of stability, it is preferably 3000 to 20000, more preferably 5000 to 100000.

In the water-insoluble vinyl polymer thus obtained, the content of the water-soluble vinyl monomer unit in the total weight of the water-soluble vinyl monomer unit and the water-insoluble vinyl monomer unit (% by weight; hereinafter referred to as "water-soluble monomer content"). Is preferably 3 to 70% by weight from the viewpoint of the stability of the dispersion.

When the water-insoluble colorant is a pigment and the poorly water-soluble polymer is anionic, the water-soluble monomer content is 15 in terms of dispersion stability and ejection reliability.
˜65 wt% is more preferred, and 50-65 wt% is even more preferred.

When the water-insoluble colorant is a pigment and the poorly water-soluble polymer is cationic, the water-soluble monomer content is 25% from the viewpoint of dispersion stability and ejection stability.
˜70% by weight is more preferred.

When the water-insoluble colorant is a hydrophobic dye and the poorly water-soluble polymer is anionic, the water-soluble monomer content is 3 to 45% by weight from the viewpoint of the stability of the dispersion and the ejection stability. Is more preferable.

When the water-insoluble colorant is a hydrophobic dye and the poorly water-soluble polymer is cationic, the water-soluble monomer content is 5 to 5 from the viewpoint of stability of the dispersion and ejection stability. 40% by weight is more preferred.

When the water-insoluble colorant is a pigment and the poorly water-soluble polymer is anionic, the acid value of the poorly water-soluble polymer is determined from the viewpoints of stability of the dispersion and ejection reliability.
160 to 260 is preferable.

When the water-insoluble colorant is a pigment and the poorly water-soluble polymer is cationic, the total amine value of the poorly water-soluble polymer is preferably 30 to 230.

When the water-insoluble colorant is a hydrophobic dye and the poorly water-soluble polymer is anionic, the acid value of the poorly water-soluble polymer is preferably 12 to 200.

When the water-insoluble colorant is a hydrophobic dye and the poorly water-soluble polymer is cationic, the total poor amine value of the poorly water-soluble polymer is preferably 10 to 230.

When the vinyl monomers are randomly copolymerized, a water-soluble component is produced by copolymerizing a portion of the water-soluble vinyl monomer with a higher content than the charged. When the amount of this water-soluble component is large, the viscosity of the water-based ink becomes high, and the ejection stability is impaired. Therefore, if this water-soluble component is removed, the viscosity of the ink is reduced and the ejection stability is improved. As a means to reduce the amount of water-soluble components, it is possible to use a poorly water-soluble vinyl monomer in the composition of the polymer to reduce the amount of the water-soluble vinyl monomer, but in this case, the content of the poorly water-soluble vinyl monomer is higher than the content. The amount of components copolymerized with
This component has a poor redispersibility, is deposited and deposited at the tip of the orifice of the printer, and impairs the ejection of droplets of the water-based ink, which causes a problem of ejection failure.

The content of the water-soluble component in the poorly water-soluble polymer in the unneutralized state is 30% by weight from the viewpoint of ejection stability.
It is below, preferably 25% by weight or less, and more preferably 13% by weight or less. Further, even when printed on a recording medium having a low ink permeability such as a glossy film, it is preferably 0.6% by weight or more, more preferably 3% by weight or more from the viewpoint of improving scratch resistance. From these viewpoints, the content of the water-soluble component in the poorly water-soluble polymer is preferably 0.6 to 25% by weight, more preferably 3 to 13% by weight. The content of the water-soluble component is measured by the measuring method shown in the examples.

As a method for removing the water-soluble component, a poorly water-soluble polymer is dissolved in a water-soluble organic solvent such as acetone, methyl ethyl ketone, ethanol and the like, and the solution is dropped into water to reprecipitate the water-insoluble component, Examples include a method of dissolving a poorly water-soluble polymer in a water-insoluble organic solvent such as toluene and extracting a water-soluble component from the solution with water.

A method similar to these is described in, for example, Japanese Patent Publication No. 8-
It is described in Japanese Patent Application Laid-Open No. 019361 and Japanese Patent Application Laid-Open No. 10-292143.

However, the method disclosed in the former publication is essentially different from the above-mentioned method for removing a water-soluble component from a poorly water-soluble polymer because the polymer used is a water-soluble polymer. Further, the method disclosed in the latter publication is a method of limiting the dissolved polymer component by a reprecipitation step, but since the lipophilic component in the polymer is also removed together with the dissolved polymer component, the storage stability of the ink is improved. It has the disadvantage of being inferior.

On the other hand, in the above-mentioned reprecipitation method and water extraction method for removing water-soluble components, the steps are simple and the water-soluble components can be removed. There is an advantage that characteristics such as ink ejection stability and storage stability are excellent.

When the obtained poorly water-soluble polymer itself has high self-dispersibility in water, polymer particles containing no colorant increase in the dispersing step, which is not preferable. Therefore, the self-dispersing property is low to some extent, the particle size of the self-dispersing polymer particles is not too small, specifically, 50 mol% of the ionic groups are neutralized without using the water-insoluble coloring agent, The average particle size of the polymer particles in the aqueous dispersion of the polymer particles of the poorly water-soluble polymer having a group is 0.1 to 1 μm.
Is preferable from the viewpoint of dispersion stability of the aqueous dispersion of polymer particles. The method for measuring the average particle size of the self-dispersing polymer particles will be shown in Examples.

An aqueous dispersion of polymer particles obtained by incorporating a water-insoluble coloring agent in a poorly water-soluble polymer can be produced by a known emulsification method.

For example, when a water-insoluble dye is used as the hydrophobic dye, the sparingly water-soluble polymer and the water-insoluble dye are dissolved in an organic solvent, and a neutralizing agent is added if necessary to ionize the salt-forming group in the sparingly water-soluble polymer. Then, after adding water to this, emulsification is performed using an ultrasonic emulsifier, if necessary,
An aqueous dispersion of polymer particles can be obtained by distilling off the organic solvent and inversion into an aqueous system.

When a pigment is used as the hydrophobic dye, a poorly water-soluble polymer is dissolved in an organic solvent to prepare a pigment,
After kneading water, a neutralizing agent and a surfactant as necessary to form a paste, the paste is diluted with water as necessary,
By distilling off the organic solvent, an aqueous dispersion of polymer particles can be obtained.

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

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 preferably 2 to 10% by weight, more preferably 4 to 8% by weight from the viewpoint of imparting sufficient print density and drying resistance.

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 may have a solubility in water at 25 ° C. of 1% by weight or more. Examples thereof include ethylene glycol, diethylene glycol, glycerin, propylene glycol, 1,3-butanediol,
Polyhydric alcohols such as 1,4-butanediol, 1,5-pentanediol, trimethylolpropane, and trimethylolethane, 2-pyrrolidone, γ-butyrolactam, urea,
Nitrogen-containing cyclic compounds such as ethylene urea, acetamide, N-
Examples thereof include nitrogen-containing acyclic compounds such as monomethylacetamide, and these can be used alone or in admixture of two or more. 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 usually about 5 to 30% by weight is preferable from the viewpoint of drying resistance.

If necessary, the water-based ink of the present invention may contain additives such as a surfactant, a pH adjuster and an antiseptic, within the range not impairing the object of the present invention.

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

[0064]

[Examples] Production Examples 1 to 4 and 11 [Polymerization step] A reaction funnel was equipped with a dropping funnel and a Dimroth cooling tube, and after nitrogen gas was sufficiently replaced, 20 parts by weight of methyl ethyl ketone, vinyl monomer and The polymerization chain transfer agent was charged as shown in the column of initial charge of Table 1, and the dropping funnel was charged with vinyl monomer and polymerization chain transfer agent, 80 parts by weight of methyl ethyl ketone and 2,2'-azobis as shown in the column of drop monomer of Table 1. 1.2 parts by weight of (2,4-dimethylvaleronitrile) was charged to obtain a mixed solution.

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 crude polymer solution (polymer content: 50% by weight) was obtained.

[Dispersion Step] A part of the obtained crude polymer solution was dried at 105 ° C. for 2 hours under reduced pressure of 0.02 MPa to remove methyl ethyl ketone to obtain a crude polymer dried product.
The dried material is polystyrene as a standard substance and 1 as a solvent.
The weight average molecular weight was measured by gel permeation chromatography using chloroform containing mmol / L dodecyldimethylamine. The results are shown in Table 1.

5 parts by weight of the dried product was added to methyl ethyl ketone.
It is dissolved in 25 parts by weight, and a neutralizing agent (Production Examples 1 to 3 and
In 11, 6 parts by weight of 1N-sodium hydroxide aqueous solution, and in Production Example 4, 50% by weight aqueous solution of glycolic acid 18.2 parts by weight) was added to neutralize a part of the copolymer, and 5 parts by weight of pigment was further added. Kneaded

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 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 crude polymer solution was obtained in the same manner as in Production Examples 1 to 4 and 11 using the vinyl monomer and the polymerization chain transfer agent shown in Table 1.

[Dispersion Step] The weight average molecular weight of the dried crude polymer obtained in the same manner as in Production Examples 1 to 4 and 11 was determined in the same manner as in Production Examples 1 to 4 and 11. The results are shown in Table 1. To 5 parts by weight of the dried product, 50 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, and 0.8 part by weight of a 1N-potassium hydroxide aqueous solution was added to form a salt-forming group of a poorly water-soluble polymer. Part of the water was neutralized, 250 parts by weight of deionized water was added to this, and the mixture was stirred and then used with a Microfluidizer (manufactured by Microfluidizer).
Emulsified for 30 minutes.

From the obtained emulsion, a reduced pressure of 0.02 MPa, 60
The mixture was concentrated by removing the organic solvent at 0 ° C and further removing a part of water to obtain an aqueous dispersion of dye-containing vinyl polymer particles having a solid content concentration of 20% by weight.

Production Examples 6 to 10 The crude polymer solutions obtained in the [polymerization step] of Production Examples 1 to 5 were subjected to the next purification step.

[Purification Step] 50 parts by weight of the crude polymer solution obtained in the polymerization step of Production Examples 1 to 5 was dropped into 1000 parts by weight of ion-exchanged water to precipitate the crude polymer, and the mixture was stirred at 25 ° C. for 3 hours. Then, the water-soluble component in the crude polymer was dissolved in ion-exchanged water and removed. The precipitate was collected by filtration to give 0.02
It was dried under reduced pressure of MPa at 60 ° C. for 2 hours to obtain a purified polymer (referred to as “purified polymer A” in Production Examples 6 to 10), that is, a non-neutralized poorly water-soluble polymer after purification.

[Dispersion Step] The dispersion step was performed in the same manner as in Production Examples 1 to 5 except that the purified polymer A obtained in the purification step was used in place of the crude polymer dried product in the dispersion step in Production Examples 1 to 5, Aqueous dispersions of pigment- or dye-containing vinyl polymer particles of Production Examples 6 to 10 were obtained.

[Content of Water-Soluble Component] Of the water-soluble components in the crude polymer, the content of the water-soluble component removed by the purification step in the crude polymer is S1 (wt%), which is not removed by the purification step. The content of the water-soluble component with respect to the crude polymer is S2 (% by weight), and the purified polymer A
Assuming that the content of the water-soluble component therein is S3 (% by weight), there is a relation of the following expression (1). The content of the water-soluble component in the crude polymer is S1 + S2.

[0076] S3 / 100 = (S2 / 100) / [1- (S1 / 100)] (1)

[0077]   That is, S3 = S2 / (100−S2) (2)

Part of the ion-exchanged water in which the water-soluble component was dissolved was dried under reduced pressure of 0.02 MPa at 60 ° C. for 2 hours under reduced pressure, and the weight of the recovered solid content and the weight of the crude polymer used for purification were compared. From the above, S1 (% by weight) was calculated.

Since the crude polymer is not completely dissolved in the methyl ethyl ketone used in the purification step, some water-soluble components are not removed even in the purification step. Since it is completely dissolved in acetone, the water-soluble polymer can be removed by using acetone. 50 parts of purified polymer A was dissolved in 40 parts by weight of acetone to obtain a purified polymer A solution 50
By weight, 1000 parts by weight of ion-exchanged water was added dropwise to precipitate the purified polymer A, and the purified polymer A was stirred at 25 ° C. for 3 hours to dissolve and remove the water-soluble component in the purified polymer A in the ion-exchanged water. The precipitate was collected by filtration, and under reduced pressure of 0.02 MPa,
The polymer was dried at 60 ° C. for 2 hours to obtain a purified polymer B.

10 parts by weight of the purified polymer B was dissolved in 40 parts by weight of acetone, and 50 parts by weight of the obtained purified polymer B solution was added.
The purified polymer B was precipitated by dropping into 1000 parts by weight of ion-exchanged water and stirred at 25 ° C. for 3 hours to dissolve and remove the water-soluble component in the purified polymer B in the ion-exchanged water. The precipitate was collected by filtration and dried under reduced pressure of 0.02 MPa at 60 ° C. for 2 hours to obtain a purified polymer C.

When the purified polymer A, the purified polymer B and the purified polymer C were obtained, a part of the ion-exchanged water for three times in which the water-soluble component was dissolved was dried under reduced pressure of 0.02 MPa at 60 ° C. for 2 hours, Weight of recovered solids and purified polymer A
S3 (% by weight) was calculated from the weight and.

By modifying the equation (2), S2 = S3 * (10
0-S1). S2 was calculated by substituting the above S1 and S3 into this equation. S1 and S2 were added to determine the content of the water-soluble component in the crude polymer, and the results are shown in Production Examples 1 to 5 in Table 2, which is the content of the water-soluble component in the purified polymer A S3.
Are shown in Production Examples 6 to 10 in Table 2.

[Average particle size of self-dispersing polymer particles] A 10 wt% methyl ethyl ketone solution of the purified polymer A obtained in Production Examples 6 to 10 was prepared, and 5 parts by weight of the polymer solution was mixed with 25 parts by weight of ion-exchanged water. In addition, an aqueous solution of sodium hydroxide or glycol is added in addition to neutralize the ionic groups in the polymer by 50%. Using an ultrasonic homogenizer, disperse for 15 minutes at an output of 200 μA, remove the organic solvent at 60 ° C. under reduced pressure, and further remove a part of the water.
An aqueous dispersion of vinyl polymer particles having a solid content concentration of 20% by weight was obtained. The average particle size of the polymer particles was measured by a light scattering type particle size distribution analyzer [manufactured by Otsuka Electronics Co., Ltd., product number: ELS-8000].

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, compound represented by formula (III)) EO 9 moles, EO 23 moles: ethyl oxide addition moles 9 moles, 23 moles, respectively

CH ₂ = C (CH ₃ ) -COOC ₃ H _6- [Si (CH ₃ ) _2- O] _d -Si (CH ₃ ) ₃ (III) (where d is a number from 8 to 40) Show)

[0086]

[Table 1]

[0087]

[Table 2]

Examples 1-5 40 parts by weight of an aqueous dispersion of the pigment- or dye-containing vinyl polymer particles obtained in Production Examples 6-10, 5 parts by weight of glycerin, urea
10 parts by weight, acetylene glycol / polyethylene oxide adduct (Kawaken Fine Chemical 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.]. Coarse particles were removed by filtering with a 25 mL syringe without a needle (manufactured by Terumo Corp.) to obtain aqueous inks of Examples 1 to 5 corresponding to Production Examples 6 to 10, respectively.

Comparative Examples 1 to 6 Similar to Examples 1 to 5 except that the water dispersions obtained in Production Examples 1 to 5 or 11 were used instead of Production Examples 6 to 10. And manufacturing examples 1 to 5 or 11 respectively
To obtain the water-based inks of Comparative Examples 1 to 6.

The physical properties of the water-based inks obtained in Examples 1 to 5 and Comparative Examples 1 to 6 were evaluated by the following methods.
The results are shown in Table 3.

(1) Water Dispersion Viscosity The water dispersions of Production Examples 1 to 11 were measured with a rotary E-type viscometer [manufactured by Toki Sangyo Co., Ltd., product number: “RE-80L”, temperature 20 ° C., Table 3
It was shown to.

(2) Printing density Bubble jet printer (model number: Desk Jet-720C) manufactured by Hewlett-Packard (HEWLETT PACKARD)
Was used, solid printing was performed on a commercially available copy paper, left at 25 ° C. for 1 hour, and the printing density was measured with a Macbeth densitometer (manufactured by Macbeth, product number: RD914).

(3) Discharging stability Canon Inc., trade name: Bubble Jet Printer
Fill the F-870 ink cartridge with ink and print a 3 cm × 3 cm square on the OHP sheet. Wash this with water and collect the ejected ink, dilute it 10,000 times and measure the absorbance. A calibration curve is prepared in advance, and the ejection amount is calculated from it. The same evaluation is performed using Canon genuine ink with the same head, and the ratio [water-based ink ejection rate / genuine ink ejection rate x 100 (%)] is used for evaluation.

(4) Impact Accuracy Canon Inc., trade name: Bubble Jet Printer
Fill the ink cartridge of F-870 with ink, perform head cleaning 3 times, and print the nozzle check pattern. ○, if there is no problem with printing deviation
If there is, mark it as x.

(5) Discharge rate retention rate and frequency dependence Canon brand, bubble jet printer
Modified so that the print head of F-870 can be removed, and
Then, printing is performed under a microscope, the ejection state is observed, the ejection speed is measured, and the retention rate is shown as a ratio (%) to the genuine product. Retention rate (%) = ejection speed of water-based ink /
Genuine ink ejection speed x 100

By changing the print pattern and the discharge frequency,
The frequency dependence (f characteristic) of the discharge speed is taken. Low frequency (10
(Hz) to 10 kHz, if the discharge speed does not decrease, mark ○; if the discharge speed decreases, mark ×.

(6) Scratch resistance Using the above printer, solid printing was performed on a commercially available copy paper, dried at 25 ° C. for 24 hours, and then the printed surface was strongly rubbed with a finger. The print quality was evaluated based on the following evaluation criteria.

[Evaluation Criteria] ◯: Almost no print is printed and the surrounding area is not stained. Δ: The print is slightly scraped, the surroundings are slightly soiled, and the fingers are also slightly soiled. ×: The print was considerably scraped off, the surroundings were considerably badly soiled, and the fingers were considerably soiled.

(7) Marker resistance Using the above printer, text was printed on commercially available copy paper, and after 6 hours at 25 ° C, the degree of stain on the printed sample was visually observed when tracing with a commercially available aqueous highlighter pen. Then, the evaluation was made based on the following evaluation criteria.

[Evaluation Criteria] A: There is no stain such as tailing even when tracing with a highlighter pen. ○: Traces with a highlighter pen, but there is no problem in practical use. ×: When traced with a highlighter pen, tailing occurs and the stain is severe.

[0101]

[Table 3]

From the results shown in Table 3, each of the water-based inks obtained in the respective examples gives a high print density, ejection stability, landing accuracy, retention rate of ejection speed, frequency dependency, It can be seen that it is also excellent in scratch resistance and marker resistance.

[0103]

The water-based ink of the present invention has a high printing density and is excellent in ejection stability, landing accuracy, ejection velocity retention, frequency dependence, scratch resistance and marker resistance.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C056 EA13 FC01 FC02                 2H086 BA53 BA55 BA59 BA60                 4J039 AD03 AD10 AD23 AE04 AE06                       BA04 BA16 BA21 BA26 BE01                       BE07 BE08 CA03 CA06 EA36                       EA41 EA46 GA24

Claims (4)

[Claims] 1. A water-based ink comprising an aqueous dispersion of polymer particles comprising a poorly water-soluble polymer having an ionic group and a water-insoluble colorant, wherein the poorly water-soluble polymer is in an unneutralized state. A water-based ink containing 30% by weight or less of a water-soluble component. 2. The water-based ink according to claim 1, wherein the polymer of the poorly water-soluble polymer having an ionic group is a poorly water-soluble vinyl polymer. 3. The content of the water-soluble vinyl monomer unit in the total weight of the water-soluble vinyl monomer unit and the poorly water-soluble vinyl monomer unit constituting the poorly water-soluble polymer having an ionic group is 3 to 70% by weight. Claim 1 or 2
The water-based ink described. 4. The 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 has been neutralized, is 0.1 μm or more. 3) The water-based ink according to any one of 3) to 3).