JP2003082024A - Method for producing polymer emulsion and ink composition comprising the same - Google Patents

Abstract

(57) [Problem] To provide a method for producing a polymer emulsion which improves the printing stability and the ejection stability of an ink composition. SOLUTION: Water, a monomer, an emulsifier, and a polymerization initiator are mixed to carry out an emulsion polymerization reaction, and thereafter, a monovalent inorganic hydroxide is added to adjust to a desired pH. Can be achieved by:

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polymer emulsion, particularly a method for producing a polymer emulsion used in an ink composition.

2. Background Art Ink jet recording is an ink from a fine nozzle and ejected as droplets, a method of recording characters or figures on a recording medium surface. As the ink for inkjet recording, those obtained by dissolving various water-soluble dyes in an aqueous medium are generally used. There is also provided an ink in which a pigment is dispersed in an aqueous medium. The ink in which the pigment is dispersed in the aqueous medium has a feature that it is superior in water resistance and light resistance as compared with the water-soluble dye.

On the other hand, when an ink containing a pigment is printed on a recording medium and the pigment as a colorant is not sufficiently fixed on the recording medium, the image portion may be rubbed by an external force and the image portion may be soiled. there were. Therefore, in the ink containing the pigment, the pigment as the colorant is required to be firmly fixed to the recording medium and to be excellent in scratch resistance.

Conventionally, in order to improve the fixability of a pigment as a colorant onto a recording medium, it has been proposed to add a resin to an ink composition. For example, in JP-B-62-1426, an ink in which a pigment and a resin emulsion are dispersed in water is disclosed, and in JP-A-55-157668, the pigment is dispersed in a water-insoluble resin emulsion dispersion.
In JP-A 1-217088, it is disclosed in JP-A-3-600 that an emulsion having a specific film-forming temperature is used.
No. 68 and Japanese Patent Laid-Open No. 18462/1992 similarly disclose an ink using a resin emulsion.
Further, JP-A-8-259869 discusses the use of core-shell type resin particles composed of a core portion and a shell portion surrounding the core portion for an inkjet recording ink.

However, in the case of an ink composition containing such a resin emulsion, it is observed that the viscosity of the ink composition becomes high in some cases, making it unsuitable for an ink jet recording method. It was Further, the ink jet recording head is designed so that the nozzle plate is subjected to a water repellent treatment so that ink droplets can fly more easily than the nozzles. However, an ink composition using a resin emulsion composed of polymer fine particles having a general polymer structure, which is commercially available for paints and adhesives, as an additive tends to wet the nozzle plate very much. As a result, flight deflection of ink droplets and ink ejection failure were observed. Further, in order to obtain quick-drying properties of the printed matter, a surfactant such as a glycol ether or an acetylene glycol-based surfactant may be contained in the ink as a penetrant. However, when these penetrants are mixed with a certain type of resin emulsion, the polymer fine particles constituting the resin emulsion swell, and as a result, the ejection stability of the ink and the long-term storage stability may be lacking.

Furthermore, the resin emulsion contains water and
It is produced by mixing an emulsifier and a polymerization initiator and causing a polymerization reaction under appropriate conditions. Since the resin emulsion produced generally exhibits an acidic value, viscosity increase or aggregation may occur in itself. Therefore, conventionally, ammonia water is added to the produced resin emulsion to adjust the pH,
It was trying to stabilize itself. However, when the resin emulsion neutralized with aqueous ammonia was stored for a long period of time, a decrease in pH and an increase in viscosity were observed. When the ink composition using this resin emulsion was also stored for a long period of time, a decrease in pH and an increase in viscosity were observed, which sometimes affected ejection stability.

[0007]

SUMMARY OF THE INVENTION The present inventor has now prepared a method for producing a polymer emulsion containing fine polymer particles, in which water, a monomer, an emulsifier and a polymerization initiator are mixed to carry out an emulsion polymerization reaction, and After that, by adding a monovalent inorganic hydroxide to adjust the pH value in the neutral to alkaline range, it is possible to produce a polymer emulsion with improved storage stability, the finding that, Obtained. Further, the present inventor has improved the storage stability, clogging reliability, and ejection stability of the ink composition by adding the polymer emulsion produced by the present invention to the ink composition, and It was also found that the image of the printed matter printed with the product is excellent in robustness and scratch resistance. The present invention is based on these findings.

Therefore, the present invention provides a method for producing a polymer emulsion containing fine polymer particles, which can improve the fixability of a pigment printed on a recording medium and realize an image having excellent scratch resistance. Has an aim.

Accordingly, the method for producing a polymer emulsion containing fine polymer particles according to the present invention comprises:
Mixing a monomer, an emulsifier, and a polymerization initiator to carry out an emulsion polymerization reaction, and then adding a monovalent inorganic hydroxide to adjust the pH value to a neutral to alkaline range. It includes that.

According to another aspect of the present invention, an ink composition is provided, the ink composition comprising a pigment, a polymer emulsion, water, and a water-soluble organic solvent. Thus, the polymer emulsion is produced by the production method according to the present invention.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Definitions "Polymer emulsion" means an aqueous dispersion in which the continuous phase is water and the dispersed particles are polymeric microparticles.
"Polymer emulsion" is sometimes referred to as resin emulsion. “Polymer fine particles” means fine particles of a polymer component. Specific examples of the polymer component constituting the polymer particles include, for example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid ester- (meth) acrylic acid copolymer, poly (meth) acrylic acid. Ester, styrene-butadiene copolymer, polybutadiene, acrylonitrile-butadiene copolymer, chloroprene copolymer, polyolefin, polystyrene, polyvinyl acetate, polyamide, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic acid ester copolymer , A method for producing a polymer emulsion such as polyurethane, etc. a) Monomer In the present invention, an unsaturated vinyl monomer is preferably used as the monomer. Specific examples of unsaturated vinyl monomers include acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl cyanide compound monomers, halogenated compounds generally used in emulsion polymerization. Monomers,
Examples thereof include olefin monomers and diene monomers. Specific examples thereof include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, Acrylic esters such as octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate; methyl methacrylate, ethyl methacrylate,
Isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, Methacrylic acid esters such as glycidyl methacrylate; vinyl esters such as vinyl acetate; vinyl cyan compounds such as acrylonitrile and methacrylonitrile; halogenated monomers such as vinylidene chloride and vinyl chloride; styrene, 2-methylstyrene, Vinyltoluene, t-butylstyrene, chlorostyrene, vinyl aniso Le, aromatic vinyl monomers such as vinyl naphthalene, ethylene, propylene, isopropylene, olefins and the like; butadiene, dienes such as chloroprene; vinyl ethers, vinyl ketones, vinyl monomers such as vinyl pyrrolidone. For the monomer having no carboxyl group, it is essential to use an unsaturated vinyl monomer having a carboxyl group, but preferable examples thereof include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, The use of methacrylic acid is preferred.

In the present invention, the molecule derived from the above monomer is preferably provided with a structure in which the molecule is crosslinked by a crosslinkable monomer having two or more polymerizable double bonds. Examples of the crosslinkable monomer having two or more polymerizable double bonds include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,
3-butylene glycol diacrylate, 1,6-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2'- Bis (4-acryloxyproproxyphenyl) propane,
Diacrylate compounds such as 2,2′-bis (4-acryloxydiethoxyphenyl) propane; triacrylate compounds such as trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate; ditrimethylol tetraacrylate , Tetramethylolmethane tetraacrylate, tetraacrylate compounds such as pentaerythritol tetraacrylate; hexaacrylate compounds such as dipentaerythritol hexaacrylate;
Ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate,
1,4-butylene glycol dimethacrylate, 1,6
-Hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate,
Dimethacrylate compounds such as 2,2′-bis (4-methacryloxydiethoxyphenyl) propane; trimethacrylate compounds such as trimethylolpropane trimethacrylate and trimethylolethanetrimethacrylate; methylenebisacrylamide and divinylbenzene.

Furthermore, printing stability can be further improved by adding acrylamides or hydroxyl group-containing monomers in addition to the above monomers. Specific examples of acrylamides include acrylamide and N, N′-dimethylacrylamide. In addition, specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate, and these are used as one kind or a mixture of two or more kinds. be able to.

B) Emulsifier, Polymerization Initiator, Other Components Specific examples of emulsifiers include anionic surfactants such as alkylallyl sulfonates or sulfates, alkyl sulfonates or sulfates, and dialkyl sulfosuccinates.
Examples thereof include nonionic surfactants such as polyoxyethylene nonyl phenyl ether, polyoxyethylene stearic acid ester, polyoxyethylene alkyl allyl ether, and sorbitan monolauric acid ester. Further, in the present invention, the “emulsifier” also includes a protective colloid. Specific examples of the protective colloid include polyvinyl alcohol, polyvinylpyrrolidone, gum arabic, tragacanth gum, gelatin and the like.

Examples of the polymerization initiator include potassium persulfate and ammonium persulfate. Examples of other components include polymerization regulators, chain transfer agents, and molecular weight modifiers.

C) Emulsion Polymerization and Reaction Conditions The polymer fine particles can be produced by mixing a monomer, an emulsifier, a polymerization initiator and other optional components and carrying out an emulsion polymerization reaction. The addition amount of these components can be appropriately determined. The emulsion polymerization reaction temperature is 60 to 90 ° C, preferably about 70 to 80 ° C.

The polymer fine particles having a core-shell structure described below are produced by a known method, generally by multistage emulsion polymerization or the like. For example, Japanese Patent Laid-Open No. 4-76
It can be manufactured by the method disclosed in Japanese Patent Publication No. 004. Specific examples of the unsaturated vinyl monomer used for the polymerization may be the same as those mentioned above.

The introduction of the epoxy group into the core is an unsaturated vinyl monomer having an epoxy group,
Glycidyl acrylate, glycidyl methacrylate,
A method of copolymerizing allyl glycidyl ether or the like with another unsaturated vinyl monomer, or a method of polymerizing one or more unsaturated vinyl monomers to simultaneously add an epoxy compound to prepare core particles to form a composite, and the like. To be The former method is preferably used in terms of easiness of polymerization, polymerization stability and the like.

D) pH Adjustment In the present invention, the polymer emulsion obtained by the above-mentioned emulsion polymerization has a pH value adjusted to a neutral to alkaline range by adding a monovalent inorganic hydroxide. It will be done.

Specific examples of the monovalent inorganic hydroxide used in the present invention include monovalent metal hydroxides, preferably alkali metal hydroxides. Among the alkali metal hydroxides, one or a mixture of two or more selected from the group consisting of lithium hydroxide (LiOH), sodium hydroxide (NaOH), and potassium hydroxide (KOH) is particularly preferable.

The pH value is adjusted to a neutral to alkaline range, preferably in the range of about 7 to 10, more preferably in the range of about 7 to 9. Therefore, the addition amount of the monovalent inorganic hydroxide should be the same as that of the polymer emulsion described above.
It may be added within the range of the H value.

E) Manufacturing Method The manufacturing method of the polymer emulsion is outlined below. Charge water, emulsifier, add polymerization initiator, stirrer adjusted to a predetermined temperature, reflux condenser,
The emulsified monomer is added to a reaction vessel equipped with a dropping device, a thermometer, etc., and reacted to obtain a polymer emulsion. To this, a monovalent inorganic hydroxide is added so as to have a desired pH. This produces the polymer emulsion according to the invention.

Polymer Emulsion The polymer emulsion produced according to the present invention has a ratio of fine polymer particles to water of about 1: 1 to 4,
The range is preferably about 1: 1 to 3. In addition, according to a preferred embodiment of the present invention, the polymer fine particles preferably include a polymer component having both a hydrophilic portion and a hydrophobic portion. The weight average molecular weight of the polymer particles is
It is about 10,000 or more. The average particle size of the polymer fine particles is preferably about 400 nm or less, more preferably about 10 to 200 nm, further preferably 50 to 200.
It is about nm.

According to a preferred embodiment of the present invention, the glass transition point of the polymer particles is about 30 ° C. or lower, preferably 2
It is preferably about 5 ° C. or lower, more preferably about 20 ° C. or lower.

According to a preferred embodiment of the present invention, the minimum film forming temperature of the polymer emulsion is about 30 ° C. or lower, preferably about room temperature (about 25 ° C.) or lower, more preferably about 20 ° C. or lower. preferable. If film formation of polymer particles can be performed at 30 ° C or lower, film formation on the printed surface will automatically proceed at room temperature or below without heating and drying the printed recording medium, and the pigment will firmly adhere to the recording medium. It is preferable because it can be fixed on. Here, the "minimum film formation temperature" is a continuous film that is transparent when a polymer emulsion obtained by dispersing polymer fine particles in water is thinly cast on a metal plate such as aluminum and the temperature is raised. Is the lowest temperature at which It becomes a white powder in the temperature range below the minimum film formation temperature.

The term "film-forming property" means that when polymer particles are dispersed in water to form a polymer emulsion, the water component which is the continuous phase of this polymer emulsion is evaporated to form a polymer film. Means that. The ink composition containing the polymer fine particles is
When water or an aqueous organic solvent is removed from around the polymer microparticles, a polymer film is similarly formed.

According to a preferred embodiment of the present invention, the polymer fine particles preferably have a carboxyl group on the surface thereof and further have high cohesiveness with the divalent metal salt.

Specifically, the polymer fine particles are the fine particles.
3 volume of polymer emulsion with 0.1% by weight
And 1 volume of an aqueous solution of a divalent metal salt having a concentration of 1 mol / l
When contacted, the transmittance of light with a wavelength of 700 nm is the initial value
50% of the time is 1 × 10 ^FourSeconds or less (preferably 1
× 10^ThreeSeconds or less, more preferably 1 × 10^TwoAnd less)
It has cohesiveness with such a divalent metal salt.
The polymer particles aggregate when they come into contact with divalent metal ions.
This creates a floating substance and reduces the clarity of the solution. Raw of this float
The amount of light is measured by the light transmittance. Where divalent metal
Ion is Ca ²⁺, Cu²⁺, Ni²⁺, Mg²⁺, Z
n²⁺, Ba²⁺And an anion that forms a salt with it
Cl is^-, NO^3-, I^-, Br^-, ClO^3-
And CH _ThreeCOO^-Can be given. Such high tension
Collectivity means that the polymer particles have a relatively large amount of
It is considered to be caused by having a voxyl group.
A polymer having a large amount of carboxyl groups on its surface as described above.
The ink composition containing fine limmer particles is treated to be water repellent.
The nozzle plate of the inkjet recording head
Not compatible. Therefore, conventionally, the resin-containing
The ink composition requires more than the nozzle plate for the ink composition.
Liquid, which results in ink droplet flight deflection and ejection failure.
The occurrence of goodness was a problem. However, in the present invention
An ink composition comprising a polymer emulsion according to
The advantage of being able to effectively prevent such problems
Have. It also has a relatively large amount of carboxyl groups
The use of polymer microparticles gives better abrasion and dissolution resistance.
Achieve drug properties. Furthermore, this polymer particle surface
Due to its high hydrophilicity, the ink composition has excellent storage stability
It also has the advantage of being obtained.

According to a preferred embodiment of the present invention, a polymer emulsion in which polymer particles are dispersed in water at a concentration of 10% by weight has a contact angle of 70 ° on a tetrafluoroethylene resin (Teflon: registered trademark) plate. It is preferably about 80 ° or more, more preferably about 80 ° or more. Further, the surface tension of the polymer emulsion in which the polymer fine particles are dispersed in water at a concentration of 35% by weight is 40 × 10 ⁻³ N / m.
(40 dyne / cm, 20 ° C.)), preferably 5
It is preferably about 0 × 10 ⁻³ N / m or more. By using the polymer fine particles as described above, in the ink jet recording method, flight bending can be further prevented, and good printing becomes possible.

According to another preferred embodiment of the present invention, the polymer fine particles contain 1 to 10% by weight of a structure derived from an unsaturated vinyl monomer having a carboxyl group, and have two polymerizable double bonds. It is preferable that it has a structure crosslinked by the above-mentioned crosslinkable monomer and contains 0.2 to 4% by weight of a structure derived from the crosslinkable monomer. By using a crosslinkable polymer which is three-dimensionally crosslinked by copolymerizing crosslinkable monomers having two or more, more preferably three or more polymerizable double bonds during the polymerization, the nozzle plate surface can be formed by the ink composition. Further, it becomes harder to get wet, the flight bending can be further prevented, and the ejection stability can be further improved.

In the present invention, polymer particles having a single particle structure can be used. On the other hand, in the present invention, it is also possible to use polymer fine particles having a core-shell structure composed of a core part and a shell part surrounding the core part. In the present invention, the “core shell structure” means
It means "a form in which two or more polymers having different compositions are present in the particles in a phase-separated state". Therefore, not only the shell portion completely covers the core portion, but also the shell portion may partially cover the core portion. Further, a part of the shell polymer may form a domain or the like in the core particle. Further, it may have a multilayer structure of three or more layers including one or more layers having different compositions between the core portion and the shell portion.

According to a preferred embodiment of the present invention, it is preferable that the core part is made of a polymer having an epoxy group and the shell part is made of a polymer having a carboxyl group. The epoxy group and the carboxyl group have the property of reacting with each other, but these two groups are present separately in the core part and the shell part. Due to the decrease in water or the water-soluble organic solvent, the polymer particles are united with each other and deformed by the pressure associated with the film formation. As a result, the epoxy group of the core part and the carboxyl group of the shell part are bonded to each other to form a network structure. This has the advantage that a stronger coating can be formed. The amount of unsaturated vinyl monomer having an epoxy group is 1 to 10% by weight.
Is preferred. The reaction between a part of the epoxy group and the carboxyl group before film formation is allowed in the present invention as long as the film forming ability is not lost. In the present invention, the property of allowing a reactive functional group to coexist in such a polymer fine particle and reacting those groups during film formation to form a network structure without adding a curing agent is "self-crosslinking". Call.

Ink Composition The ink composition of the present invention comprises a pigment, a polymer emulsion, water, and a water-soluble organic solvent, and the polymer emulsion is produced by the above-mentioned production method. It is characterized by being a polymer emulsion. The ink composition according to the present invention,
It is used in a recording method using an ink composition. Examples of the recording method using the ink composition include an inkjet recording method, a recording method using a writing instrument such as a pen, and various other printing methods. In particular, the ink composition according to the present invention is preferably used in an inkjet recording method.

A ) Polymer Emulsion As the polymer emulsion, the polymer emulsion produced by the production method according to the present invention described above is used.
The addition amount of the polymer emulsion can be appropriately determined depending on the addition amount of the polymer fine particles constituting the polymer emulsion to the ink composition. Therefore, the addition amount of the polymer fine particles is 0.1 with respect to the total amount of the ink composition.
-30% by weight, preferably 5-30% by weight.

B) Pigment The ink composition of the present invention uses a pigment as a colorant. The pigment is a colorant excellent in light resistance and water resistance.

The pigment is not particularly limited, and both inorganic pigments and organic pigments can be used. As the inorganic pigment, in addition to titanium oxide and iron oxide, a contact method,
Carbon black manufactured by a known method such as a furnest method or a thermal method can be used.
The organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinofuraron pigments, etc.), dye chelates (eg, basic dye type chelates, acid dye type chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc. can be used.

Specific examples of carbon black include No. 1 manufactured by Mitsubishi Chemical. 2300, No. 900, MCF88,
No. 33, No. 40, No. 45, No. 52, M
A7, MA8, MA100, No2200B, etc. are Raven 5750, 5250 and 5 manufactured by Colombia.
000, 3500, 1255, 700, etc. are Regal 400R, 330R, 660R, MogulL, 700, Monarch manufactured by Cabot Corporation.
800, 880, 900, 1000, 110
0, 1300, 1400, etc. are C made by Degussa.
color Black FW1, same FW2, same FW2
V, same FW18, same FW200, Color Bla
ck S150, S160, S170, Print
ex 35, same U, same V, same 140U, Special
Black 6, the same 5, the same 4A, the same 4 and the like.

As the pigment used as the yellow ink, C.I. I. Pigment Yellow 1 (Hansa Yellow), 2,3 (Hansa Yellow 10G), 4,5 (Hansa Yellow 5G), 6,7,10,11,12,13,1
4, 16, 17, 24 (flavantron yellow), 3
4,35,37,53,55,65,73,74,7
5,81,83,93,94,95,97,98,9
9,108 (Anthrapyrimidine Yellow), 109,1
10, 113, 117 (copper complex salt pigment), 120, 124,
128,129,133 (quinophthalone), 138,13
9 (isoindolinone), 147, 151, 153 (nickel complex pigment), 154, 167, 172, 180 and the like.

Examples of pigments used as magenta ink include C.I. I. Pigment Red 1 (Para Red),
2,3 (Toluidine Red), 4,5 (lTR Red),
6,7,8,9,10,11,12,14,15,1
6, 17, 18, 19, 21, 22, 23, 30, 3
1, 32, 37, 38 (pyrazolone red), 40, 4
1,42,88 (Thioindigo), 112 (Naphthol A
S type), 114 (naphthol AS type), 122 (dimethylquinacridone), 123, 144, 146, 149, 15
0,166,168 (Ant Antron Orange), 17
0 (Naphthol AS system), 171,175,176,17
7,178,179 (Beryl Maroon), 185,18
7,209 (Dichloroquinacridone), 219,224
(Berylene type), 245 (naphthol AS yarn), or C.I.
I. Pigment Violet 19 (Quinacridone), 23
(Dioxazine violet), 32, 33, 36, 3
8, 43, 50 and the like can be mentioned.

Pigments used as cyan ink include C.I. I. Pigment Blue 15, 15: 1, 15:
2,15: 3,16 (Metal-free phthalocyanine), 18 (Alkali blue toner), 25,60 (Thren blue), 6
5 (Violantrone), 66 (Indigo) and the like can be mentioned.

As organic pigments used in color inks other than magenta, cyan or yellow inks, C.I. I. Pigment Green 7 (Phthalocyanine Green), 10 (Green Gold), 36, 37; C.I. I. Pigment Brown 3, 5, 25, 26; or C.I. I. Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16,
24, 34, 36, 38, 40, 43, 63 and the like.

The amount of the pigment added is preferably about 0.1 to 25% by weight, more preferably 1% by weight based on the total amount of the ink composition.
It is about 15% by weight. The particle size of the pigment is 10μ
m or less, and more preferably 0.1 μm or less.

Surface-treated pigment In one of the preferred embodiments of the present invention, it is preferable to use a pigment that can be dispersed in water without a dispersant.
Such a pigment is made dispersible in water without a dispersant by a surface treatment such that at least one functional group of a carbonyl group, a carboxyl group, a hydroxyl group, or a sulfone group or a salt thereof is bonded to the surface of the pigment. There are some. Specifically, for example, a functional group or a molecule containing a functional group is attached to the surface of carbon black by physical treatment such as vacuum plasma or chemical treatment (for example, oxidation treatment with hypochlorous acid or sulfonic acid). It can be obtained by grafting. In the present invention, one kind or two or more kinds of functional groups may be grafted on one carbon black particle. The kind and degree of the functional group to be grafted may be appropriately determined in consideration of the dispersion stability in the ink, the color density, the drying property on the front surface of the inkjet head, and the like.

The above-mentioned pigment preferably used in the present invention can be obtained, for example, by the method described in JP-A-8-3498. The carbon black treated by the method described in this publication has a high surface active hydrogen content of 1.5 to 2.5 mmol / g. As a result, it disperses very well in water. It is also possible to use a commercially available product as the above-mentioned pigment, and as a preferred example, Microjet CW manufactured by Orient Chemical Industry Co., Ltd.
1 or 2.

According to a further preferred embodiment of the present invention, those treated to have a hydrophilic group on the surface are preferred. The pigment having a hydrophilic group on its surface is obtained by treating the surface of pigment particles with a hydrophilic group-providing agent. The pigment constituting the pigment particles having a hydrophilic group on the surface is not particularly limited as long as it is a pigment that does not dissolve in the hydrophilic group-providing agent,
The above-mentioned pigments may be used, and carbon black and organic pigments are preferable.

Sulfonation treatment In the sulfonation treatment, a sulfonation agent is used as a hydrophilic group-imparting agent to form a sulfonic acid group (--SO ₂ O) on the surface of the pigment particles.
H) and / or sulfinic acid group (-RSO ₂ H: R refers to a treatment for imparting an alkyl group of C ₁ -C _12, or a phenyl group and its derivatives).

As the sulfonating agent, a treating agent containing sulfur is preferably mentioned. Specific examples of such treating agents include sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid,
Examples thereof include fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt, and sulfamic acid. Among them, sulfonating agents such as sulfur trioxide, sulfonated pyridine salt, and sulfamic acid are preferred, and these are one kind or two or more kinds. It can be used as a mixture.

Further, sulfur trioxide will be described later together with a solvent capable of forming a complex with it, for example, a basic solvent such as N, N-dimethylformamide dioxane, pyridine, triethylamine and trimethylamine, nitromethane, acetonitrile and the like. Depending on the mixed solvent with the solvent,
It is useful to use it in the form of a complex. In particular, it is preferable to use a complex of sulfur trioxide with a tertiary amine for surface treatment of pigment particles (sulfonation in this case). The complex of sulfur trioxide can suppress the reaction of sulfur trioxide as an acid, and as a result, the surface of the pigment can be treated without decomposing or degrading the pigment itself.

When sulfuric acid, fuming sulfuric acid, chlorosulfuric acid, fluorosulfuric acid or the like is used alone as the sulfonating agent, it is necessary to suppress the reaction so that the pigment particles are not dissolved. Examples of the suppressing means include adjusting the kind and the amount of the solvent to be described later.

The solvent used in the reaction is preferably one that does not react with the sulfonating agent and does not dissolve the pigment,
Specific examples thereof include sulfolane, N-methyl-2-pyrrolidone, dimethylacetamide, quinoline, hexamethylphosphoric triamide, chloroform, dichloroethane, tetrachloroethane, tetrachloroethylene,
Examples include dichloromethane, nitromethane, nitrobenzene, liquid sulfur dioxide, carbon disulfide, trichlorofluoromethane and the like.

As a specific example of the sulfonation treatment of the pigment surface, pigment particles are dispersed in a solvent, a treating agent containing sulfur is added to the dispersion, and the mixture is heated at 60 to 200 ° C. for 3 to 10 It may be performed by stirring for a time. Specifically, the pigment particles and the solvent are preliminarily subjected to high speed shear dispersion with a high speed mixer or the like, or impact dispersion with a bead mill, a jet mill or the like to form a slurry (dispersion liquid). Then, after shifting to gentle stirring, a treatment agent containing sulfur is added to introduce a hydrophilic group onto the surface of the pigment particle. Then, heat treatment is performed to remove the solvent and the residual sulfur-containing treatment agent from the pigment particle slurry. This removal can be done by washing with water,
It is carried out by repeating ultrafiltration, reverse osmosis, etc., centrifugation, filtration, etc.

According to a preferred embodiment of the present invention, it is preferable that the sulfonic acid group and / or sulfinic acid group provided on the pigment surface by the sulfonation treatment is further alkali-treated with an alkali compound. This treatment, the surface of the pigment, as a hydrophilic group, a sulfonic acid anion group (-SO ₃ ^-) and / or sulfinic acid anion group (-
RSO ₂ : R can be a C _{1 to} C ₁₂ alkyl group or a phenyl group and its derivative).

As the alkaline compound, it is
If the cation is converted to an alkali metal ion or
Chemical formula R₁R₂R₃R_FourN⁺(In the above formula, R₁, R₂, R₃And
And R _FourMay be the same or different, and are hydrogen atom, alkyl
Group, hydroxyalkyl group or halogenated alkyl group
, Which is a monovalent ion represented by
It As a preferable specific example thereof, lithium ion (L
i⁺), Potassium ion (K⁺), Sodium ion (N
a⁺), Ammonium ion (NH_Four ⁺), And Trieta
Alkanolamine cations such as anolamine cations
There is one that becomes.

As the alkaline compound, a hydroxide anion is preferably used as an anion when itself ionized, and specific examples thereof include ammonia and alkanolamines (monoethanolamine, diethanolamine, N, N-butyl). Ethanolamine, triethanolamine, propanolamine, aminomethylpropanol, 2-aminoisopropanol, etc.) and monovalent alkali metal hydroxides (LiOH, NaOH, KOH).

The amount of the alkali compound added is preferably equal to or more than the neutralization equivalent of the hydrophilic group imparted by treating the surface of the pigment particles. Further, when the alkaline compound is a volatile one such as ammonia or alkanolamine, it is preferable to add 1.5 times or more of the neutralization equivalent.

The alkalization treatment can be carried out by putting the above-mentioned pigment particles chemically bonded to the surface of the hydrophilic group in an alkali compound and shaking the mixture with a paint shaker or the like.

Carboxylation Treatment The carboxylation treatment is a treatment for imparting a carboxylic acid group (—COOH) to the surface of pigment particles by utilizing a carboxylating agent as a hydrophilic group-imparting agent. Specific examples of the carboxylating agent include sodium hypochlorite and potassium hypochlorite, and these treating agents cleave some bonds on the surface of the pigment particles, such as C = C and C-C. Then, it is oxidized and carboxylated.

On the other hand, in addition to the chemical treatment, the present invention also includes a treatment method such as plasma treatment for imparting carboxylic acid groups to the pigment surface by physical oxidation. In the above-mentioned carboxylation treatment, a quinone group or the like may be introduced although the amount is small.

The following is an example of a specific method for carboxylating the surface of the pigment. The pigment particles are preliminarily shear-dispersed in an aqueous medium with a high-speed mixer or the like, or impact-dispersed with a bead mill, a jet mill or the like to obtain a slurry (dispersion liquid). Next, an appropriate amount of sodium hypochlorite (carboxylating agent) having an effective halogen concentration of 10 to 30% is mixed and heated to 60 to 80 ° C.
The stirring is performed for about 10 hours, preferably 10 hours or more. Then, the solvent and the residual carboxylating agent are removed from the slurry of the surface-treated pigment particles by heat treatment. If necessary, washing with water, ultrafiltration, reverse osmosis, etc., centrifugation, filtration, etc. are repeated to obtain the desired surface-treated pigment.

According to a preferred embodiment of the present invention, it is preferable that the carboxylic acid group provided on the pigment surface by the carboxylation treatment is further alkali-treated with an alkali compound. By this treatment, a carboxylate anion group (—COO ⁻ ) can be provided as a hydrophilic group on the surface of the pigment. In this case, the kind of the alkaline compound and the treatment method with the alkaline compound may be the same as described above.

The average particle diameter of the pigment particles having the hydrophilic group on the surface thereof can be adjusted to 150 nm or less by treating the surface of the pigment. Preferably, the average particle size is 20 nm
It can be ˜80 nm.

Dispersant According to another preferred embodiment of the present invention, the pigment (including the above-mentioned surface-treated pigment) is preferably added to the ink as a pigment dispersion liquid dispersed in an aqueous medium with a dispersant. Specific examples of the dispersant used for preparing the pigment dispersion include polymer dispersants and surfactants.

Preferred examples of the polymer dispersant include natural polymers, and specific examples thereof include proteins such as glue, gelatin, casein and albumin; natural gums such as gum arabic and tragacanth; savonin and the like. Glucosides; alginic acid and alginic acid derivatives such as alginic acid propylene glycol ester, alginic acid triethanolamine, and alginic acid ammonium; methyl cellulose, carboxymethyl cellulose,
Examples thereof include cellulose derivatives such as hydroxyethyl cellulose and ethyl hydroxycellulose. Furthermore, a synthetic polymer is mentioned as a preferable example of the polymer dispersant, and specific examples thereof include polyvinyl alcohols,
Acrylics such as polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer Resin: Styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α
-Methylstyrene-acrylic acid copolymer, styrene-α
-Styrene-acrylic resin such as methylstyrene-acrylic acid-acrylic acid ester copolymer; styrene-maleic acid copolymer, styrene-maleic anhydride copolymer,
Vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, and vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl-ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate Examples thereof include vinyl acetate copolymers such as crotonic acid copolymers and vinyl acetate-acrylic acid copolymers and salts thereof. Among these, a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group, and a polymer composed of a monomer having both a hydrophobic group and a hydrophilic group in the molecular structure are preferable. Examples of the above salts include lithium hydroxide, sodium hydroxide, monovalent inorganic hydroxides such as potassium hydroxide, diethylamine, ammonia, ethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, Examples thereof include salts with triethanolamine, diethanolamine, aminomethylpropanol, morpholine and the like. The weight average molecular weight of these copolymers is preferably 3,000 to 30,000, more preferably 5,000 to 15,000.

Specific examples of the surfactant preferable as the dispersant include alkane sulfonate, a-olefin sulfonate (AOS), alkylbenzene sulfonate (ABS), alkylnaphthalene sulfonate and acylmethyl taurine. Salt, sulfonic acid type such as dialkylsulfosuccinate; alkyl sulfate ether ether salt, sulfated oil,
Sulfated olefin, polyoxyethylene alkyl ether sulfuric acid ester salt, polyoxyethylene alkylphenyl ether sulfuric acid ester salt and other sulfuric acid ester type; fatty acid salt (soap), alkyl sarcosine salt and other carboxylic acid type; alkyl phosphoric acid ester salt, Anionic surfactants represented by phosphate ester types such as polyoxyethylene alkyl ether phosphate ester salts, polyoxyethylene alkylphenyl ether phosphate ester salts, and monoglycerite phosphate ester salts; Zwitterionic surfactants represented by pyridinium-type salts such as diamine salts; amino-acid types such as alkylamino acid salts; betaine-types such as alkyldimethylbetaine; and polyoxyethylene alkyl ethers and polyoxyethylene alkynes. Phenyl ethers, polyoxyethylene alkyl esters, ethylene oxide addition type such as polyoxyethylene alkylamide; glycerol alkyl esters, sorbitan alkyl esters, polyol ester type, such as sugar alkyl ester; polyol ether type, such as a polyhydric alcohol alkyl ethers;
Alkanol amide type such as alkanol amine fatty acid amide;

The amount of these dispersants added is preferably in the range of 1 to 50% by weight, more preferably 5 to 50% by weight, based on the pigment.
It is in the range of 30% by weight.

C) Water-Soluble Organic Solvent The ink composition of the present invention contains water and a water-soluble organic solvent as main components.

According to a preferred embodiment of the present invention, the ink composition used in the present invention preferably contains a wetting agent composed of a high boiling point organic solvent as the water-soluble organic solvent.
Preferred examples of the high boiling point organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,
2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane,
Polyhydric alcohols such as trimethylol propane; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene Alkyl ethers of polyhydric alcohols such as glycol monobutyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, triethanolamine and the like can be mentioned.

Among these, it is preferable to use a water-soluble organic solvent having a boiling point of 180 ° C. or higher. Use of a water-soluble organic solvent having a boiling point of 180 ° C. or higher brings about water retention and wettability of the ink composition. As a result, even when the ink composition is stored for a long period of time, there is no aggregation of the pigment or increase in viscosity, and excellent storage stability can be realized. Further, it is possible to realize an ink composition that maintains fluidity and redispersibility for a long time even when left in an open state (a state in which it is exposed to air at room temperature). Further, in the inkjet recording method, nozzle clogging does not occur during printing or upon restarting after printing is interrupted, and high ejection stability can be obtained.

Examples of the water-soluble organic solvent having a boiling point of 180 ° C. or higher include ethylene glycol (boiling point: 197 ° C .; boiling point in parentheses below) and propylene glycol (187
C.), diethylene glycol (245.degree. C.), pentamethylene glycol (242.degree. C.), trimethylene glycol (214.degree. C.), 2-butene-1,4-diol (235.
C.), 2-ethyl-1,3-hexanediol (243
C.), 2-methyl-2,4-pentanediol (197
C), N-methyl-2-pyrrolidone (202 C), 1,
3-Dimethyl-2-imidazolidinone (257-260
℃), 2-pyrrolidone (245 ℃), glycerin (29
0 ° C.), tripropylene glycol monomethyl ether (243 ° C.), dipropylene glycol monoethyl glycol (198 ° C.), dipropylene glycol monomethyl ether (190 ° C.), dipropylene glycol (2
32 ° C), triethylene glycol monomethyl ether (249 ° C), tetraethylene glycol (327
C.), triethylene glycol (288.degree. C.), diethylene glycol monobutyl ether (230.degree. C.), diethylene glycol monoethyl ether (202.degree. C.), diethylene glycol monomethyl ether (194.degree. C.). Those having a boiling point of 200 ° C. or higher are preferable.
These can be used alone or in combination of two or more.

The amount of the high boiling point organic solvent added is preferably 0.01 to 50% by weight, based on the total amount of the ink composition.
More preferably, it is 0.1 to 40% by weight.

In the present invention, a low boiling point organic solvent may be included. Specific preferred examples thereof include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, sec-butanol and t.
Examples include ert-butanol, iso-butanol, n-pentanol and the like. Particularly, monohydric alcohols are preferable. The addition amount of the low boiling point organic solvent is 0.5 to 0.5 with respect to the ink composition.
The range is preferably 10% by weight, more preferably 0.5 to
It is in the range of 6% by weight.

D) Penetrant or Wetting Agent Penetrant According to a preferred embodiment of the present invention, the ink composition preferably further comprises a penetrant. Although some of the above water-soluble organic solvents can function as penetrants,
In the present invention, the following are preferably used as the penetrant.

Specific examples of penetrants include 1,2-alkyl diols, glycol ethers, acetylene glycol-based surfactants, and acetylene alcohol-based surfactants. These are one kind or a mixture of two or more kinds. It may be.

Preferred specific examples of the 1,2-alkyldiol include 1,2-hexanediol and 1,2-hexanediol.
Mention may be made of pentanediol.

Specific examples of glycol ethers include dialkylene glycol monobutyl ether, dialkylene glycol monopentyl ether, dialkylene glycol monohexyl ether, trialkylene glycol monobutyl ether, trialkylene glycol monopentyl ether, trialkylene glycol monohexyl ether. , Tetraalkylene glycol monobutyl ether, tetraalkylene glycol monopentyl ether, and tetraalkylene glycol monohexyl ether. More preferred specific examples include diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, triethylene glycol monobutyl ether, triethylene glycol monohexyl ether, triethylene glycol monopentyl ether, tetraethylene glycol monobutyl ether, tetraethylene glycol. Examples include monopentyl ether and tetraethylene glycol monohexyl ether.

The amount of 1,2-alkylene glycol or glycol ether added is preferably 1 to 20% by weight, more preferably 1 to 20% by weight, based on the total weight of the ink composition.
It is 10% by weight.

The addition of the acetylene glycol-based surfactant and the acetylene alcohol-based surfactant can enhance the penetrability of the ink composition into the recording medium, and can be expected to print with less bleeding on various recording media. Specific examples of the acetylene glycol-based surfactant and the acetylene alcohol-based surfactant include compounds represented by the following formula (I).

[Chemical 1] [In the above formula, 0 ≦ m + n ≦ 50, R ¹ , R ² , R ³ , and R ⁴ are independently an alkyl group (preferably an alkyl group having 6 or less carbon atoms)]

Among the compounds represented by the above formula (I), 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 3,6-dimethyl-4-octyne are particularly preferable. -3,6-diol, 3,5-dimethyl-1-hexyne-3-ol and the like can be mentioned. It is also possible to use a commercially available product as the acetylene glycol-based surfactant represented by the above formula (I), and specific examples thereof include Surfynol 104, 82, 465, 485, or TG.
(Both available from Air Products and Chemicals. Inc.), Olfine STG, Olfine E1010
(The above are product names manufactured by Nisshin Chemical Co., Ltd.). The addition amount of the acetylene glycol-based surfactant and the acetylene alcohol-based surfactant is about 0.01 to 10% by weight based on the total amount of the ink composition, and more preferably 0.
1 to 5.0% by weight, more preferably 0.5
It is about 2.0% by weight.

In the present invention, other surfactants can be used as the penetrant. Specific examples of such a surfactant include anionic surfactants (for example, sodium dodecylbenzenesulfonate, sodium laurate, ammonium salt of polyoxyethylene alkyl ether sulfate, etc.), nonionic surfactants (for example, Oxyethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, etc., amphoteric surfactant (eg, N, N- Dimethyl-N-alkyl-
N-carboxymethylammonium betaine, N, N-
Dialkylaminoalkylene carboxylate, N, N, N
-Trialkyl-N-sulfoalkylene ammonium betaine, N, N-dialkyl-N, N-bispolyoxyethylene ammonium sulfate ester betaine, 2-alkyl-1-carboxymethyl-1-hydroxyethyl imidazolinium betaine) Can be mentioned. These can be used alone or in combination of two or more.

The amount of these surfactants added is in the range of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, and more preferably 0.5 to 10% by weight, based on the ink composition.
It is in the range of 2% by weight.

Wetting Agent According to a preferred embodiment of the present invention, the ink composition preferably further comprises a wetting agent. Although some of the above-mentioned water-soluble organic solvents can function as a wetting agent, the following are preferably used as the wetting agent in the present invention.

In the present invention, the wetting agent is preferably a water-soluble organic solvent having a boiling point of 180 ° C. or higher and having water absorbability and water retention. In the present invention, a particularly preferable wetting agent is glycerin (boiling point:
290 ° C), trimethylene glycol (boiling point: 210
℃). The addition amount of the wetting agent is preferably in the range of 5 to 30% by weight, more preferably 10 to 20% by weight, based on the total weight of the ink composition for inkjet recording.

In the present invention, a tertiary amine can be used as a wetting agent. Examples of tertiary amines include trimethylamine, triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, triisopropenolamine, butyldiethanolamine and the like. These may be used alone or in combination of two or more. The addition amount of these tertiary amines is in the range of about 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, based on the total amount of the ink composition.
It is about the range.

According to another preferred embodiment of the present invention, the ink composition preferably comprises a solid wetting agent. In the present invention, the solid wetting agent has a water retention function, and
A water-soluble substance that is solid at room temperature (25 ° C). In the present invention, specific examples of particularly preferable wetting agents are sugars, sugar alcohols, hyaluronate, trimethylolpropane, and 1,2,6-hexanetriol. Examples of sugars include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol. , (Sorbit), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, polysaccharides means sugars in a broad sense, alginic acid, α-cyclodextrin,
It is meant to include substances widely existing in nature such as cellulose. In addition, examples of derivatives of these sugars include reducing sugars of the above-mentioned sugars (for example, sugar alcohol (general formula HOCH ₂ (CHOH) _n CH ₂ OH (here, n
= An integer of 2 to 5)), oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thiosugars, etc.). Sugar alcohol is particularly preferable, and specific examples thereof include maltitol, sorbitol, xylitol and the like. As the hyaluronate, a commercially available 1% aqueous solution of sodium hyaluronate (molecular weight: 350,000) can be used. These solid wetting agents may be used alone or in combination of two or more. When two or more kinds are mixed and used, a preferable combination is two or more kinds selected from the group consisting of sugars, sugar alcohols, hyaluronate, trimethylolpropane, and 1,2,6-hexanetriol. ..

The amount of the solid wetting agent added is preferably 3 to 20% by weight, more preferably 3 to 10% by weight, based on the total weight of the ink composition.

E) pH adjusting agent The ink composition according to the present invention may further contain a pH adjusting agent. The pH adjuster is added for the purpose of keeping physical properties such as viscosity of the ink composition stable for a long period of time.
Specific examples of the pH adjuster are monovalent inorganic hydroxides, more preferably alkyl metal hydroxides,
Among them, potassium hydroxide, sodium hydroxide and lithium hydroxide are preferable. The addition amount of the pH adjustor may be appropriately determined so that the pH value of the ink composition is in the range of 7.5 to 8.5.

F) Other components The ink composition according to the present invention contains an antiseptic agent, if necessary.
It may further contain additives such as an antifungal agent, an antioxidant, a surface tension adjusting agent, and a nozzle clogging preventing agent. Examples of the preservatives and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, and 1,2-dibenzisothiazolin-3-one ( ICI Proxel C
RL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

Production of Ink Composition The ink composition according to the present invention can be produced by dispersing and mixing the above components by a suitable method. Prepare a pigment dispersion liquid in which the pigment is uniformly dispersed, using an appropriate disperser (eg, ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer, jet mill, ong mill, etc.) . Next, a polymer emulsion, a water-soluble organic solvent, a penetrating agent, a wetting agent, p
An H solution, an antiseptic agent, an antifungal agent, etc. are added and sufficiently stirred to prepare an ink solution. After sufficient stirring, filtration or centrifugation is performed to remove coarse particles and foreign matter that may cause clogging to produce the intended ink composition.

Recording Medium In the present invention, a recording medium having absorptivity for an ink composition such as paper and having an ink receiving layer are preferably used. Furthermore, when a heating step is provided after printing, a recording medium that is substantially non-absorbent with respect to the ink composition is also used. Specific examples of the recording medium include plain paper, recycled paper, high-quality paper, recording paper such as dedicated paper for inkjet recording; polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polysulfone, ABS resin, polyvinyl chloride, etc. as a base material. Plastic sheet; brass, iron, aluminum, SU
Recording medium with metal coating such as S or copper on metal surface or non-metal substrate by vapor deposition method; recording medium with water repellent treatment using paper as substrate; water repellent on fiber surface such as cloth Examples of the recording medium include a recording medium that has been subjected to a treatment and the like;

[0090]

The present invention will be described with reference to the following examples.
The present invention is not limited to the contents of this embodiment.

Preparation of Polymer Emulsion A A polymer emulsion containing fine polymer particles as dispersed particles was prepared by the following method. Further, various properties of the obtained polymer emulsion were measured by the following methods.

Preparation In a flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, under a nitrogen atmosphere, 0.5 parts by weight of potassium persulfate and 80 parts by weight of pure water were added, dissolved and stirred. ,
The internal temperature was heated to 70 ° C. On the other hand, the respective components shown in the following Table A1 and Table A2 (in the tables A1 and A2, the units of numerical values represent parts by weight) were mixed and stirred to prepare an emulsion. Add this emulsion into the flask using a dropping funnel.
The mixture was gradually added dropwise over time to carry out an emulsion polymerization reaction. A part of the obtained polymer emulsion was added with KOH, NaOH,
And LiOH (example) and ammonia (comparative example) to the rest, solid content 40% by weight, p
It was in the form of a polymer emulsion prepared in H8. The obtained polymer emulsion had a minimum film forming temperature of about 20 ° C. and an average particle size of 150 nm.

Measurement of Minimum Film Forming Temperature A Measurement was carried out using a minimum film forming temperature measuring device. When the temperature gradient on the aluminum sample plate reached equilibrium, the polymer emulsion was thinly spread and dried. When the sample plate is observed after the completion of drying, a transparent continuous film is formed in the temperature range above the minimum film formation temperature, but it becomes a white powder in the temperature range below the minimum film formation temperature. The temperature at this boundary was measured as the minimum film formation temperature.

Measurement of Contact Angle A The measurement was carried out at 25 ° C. using a contact angle measuring device. One drop of the polymer emulsion prepared so that the polymer particles are 10% by weight is dropped onto a tetrafluoroethylene resin (Teflon: registered trademark) plate having a smooth surface, and the contact angle at that time is measured by a method of reading with a microscope. I went.

Measurement of Surface Tension A A polymer emulsion prepared so that the polymer fine particles contained 35% by weight was subjected to a fully automatic equilibrium electro surface tension Didiomatic ESB-IV type (manufactured by Kyowa Kagaku Co., Ltd.) at 25 ° C. Used to make measurements.

Of the half-life in the reaction with divalent metal ions
Measurement A 3 ml of a polymer emulsion prepared so that the polymer fine particles would be 0.1% by weight was put into a spectrophotometer cell without bubbles and set in a sample chamber of the spectrophotometer. 1 mol / l magnesium chloride aqueous solution in the cell 1
At the same time as the addition of ml, the change with time of the transmittance at a wavelength of 700 nm was measured. The time at which the transmittance for a predetermined time was 50% with respect to the initial transmittance was determined.

Measurement of Average Particle Size A The average particle size is measured by Laser Doppler system particle size distribution measuring instrument Microtrac UPA15 manufactured by Leeds & Northrop Co.
It was measured using 0.

Preparation of Ink Composition A The ink composition was prepared by subjecting each of the components shown in the following Tables A3 to A6 (wherein the units of numerical values represent% by weight) to the following operations. Prepared. First, a pigment, a dispersant and water were mixed and dispersed for 2 hours with a sand mill (Yasukawa Seisakusho: zirconia as filler (diameter 1 mm, filling rate 60%)). After that, coarse particles were removed by a centrifuge to prepare an aqueous dispersion of the pigment. On the other hand, the polymer emulsion and other components were mixed and stirred at room temperature for 20 minutes to obtain a stirred product. The aqueous dispersion of the above pigment was gradually added dropwise to this stirred product, and the mixture was stirred for another 20 minutes. This is 5μ
m membrane filter to obtain an ink composition.

Evaluation Test A Evaluation Test A of Polymer Emulsion 50 ml of the polymer emulsion prepared above was placed in a polypropylene container at room temperature (about 20 ° C.). afterwards,
After standing at 60 ° C for 4 weeks, the polymer emulsion p
H and viscosity were examined and evaluated according to the following criteria.
The results were as shown in Table 1 or Table 2 below. In Tables A1 and A2, MFT represents the minimum film formation temperature of the polymer emulsion, and γ represents the surface tension. Evaluation A: There was no change in pH and viscosity as compared with the initial values. Evaluation B: The pH was decreased by 10% and the viscosity was increased by 10% as compared with the initial value. Evaluation C: pH decreased by 20% or more as compared with the initial value,
The viscosity has increased by more than 20%.

Ink Composition Evaluation Test A The following ink evaluation test was performed on the above ink composition. The printing methods in Evaluations A2 and A3 were as follows. Inkjet printer MJ-7
00C (manufactured by Seiko Epson Corporation) was used to print characters on the following papers. Ink ejection amount is 0.0
The density was 7 μg / dot and the density was 360 dpi. The printing test paper used was as follows. The result of each evaluation is
The results are shown in Tables A3 to A6 below. Xerox P Paper (Xerox Co., Ltd.) Xerox 4024 Paper (Xerox Co., Ltd.) Xerox R Paper (Xerox Co., Ltd .: Recycled Paper) Yamayuri Paper (Honshu Paper Co., Ltd .: Recycled Paper)

Evaluation A1: Storage stability 50 ml of the ink composition prepared above was placed in a polypropylene container at room temperature (about 20 ° C.). Then, after leaving at 60 ° C. for 4 weeks, the pH and viscosity of the polymer emulsion were examined and evaluated according to the following criteria. Evaluation A: There was no change in pH and viscosity as compared with the initial values. Evaluation B: The pH was decreased by 10% and the viscosity was increased by 10% as compared with the initial value. Evaluation C: pH decreased by 20% or more as compared with the initial value,
The viscosity has increased by more than 20%.

Evaluation A2: Clogging Reliability The printer was filled with the ink composition, and alphanumeric characters were printed continuously for 10 minutes. After that, stop the printer, and without cap, in an environment of temperature 40 ° C and humidity 25%, 1
Left for a week. After leaving, the alphanumeric characters were printed again, and the number of recovery operations required until the print quality equivalent to that before leaving was obtained was examined and evaluated according to the following criteria. Evaluation A: Print quality equivalent to that at the initial stage was obtained by the returning operation 0 to 2 times. Evaluation B: Print quality equivalent to that at the initial stage was obtained after 3 to 5 recovery operations. Evaluation C: The print quality equivalent to that at the initial stage was not obtained after the returning operation was performed 6 times or more.

Evaluation A3: Ejection Stability A printer is filled with an ink composition, and alphanumeric characters are continuously printed to observe missing dots and ink scattering.
The number of recording sheets on which dot omission and ink scattering occurred was examined and evaluated according to the following criteria. Evaluation A: Less than 1,000 sheets. Evaluation B: 1,000 or more and 5,000 or less. Evaluation C: 5,000 sheets were exceeded.

[0104]

[Table 1]

[0105]

[Table 2]

[0106]

[Table 3]

[0107]

[Table 4]

[0108]

[Table 5]

[0109]

[Table 6]

Preparation of Polymer Emulsion B An aqueous emulsion containing polymer particles as dispersed particles was prepared by the following method. Further, the characteristics of the obtained aqueous emulsion were measured by the following methods.

Measurement of Minimum Film Forming Temperature B Measurement was carried out using a minimum film forming temperature measuring device. When the temperature gradient on the aluminum sample plate reached equilibrium, the aqueous emulsion was thinly spread and dried. When the sample plate is observed after the completion of drying, a transparent continuous film is formed in the temperature range above the minimum film formation temperature, but it becomes a white powder in the temperature range below the minimum film formation temperature. The temperature at this boundary was measured as the minimum film formation temperature.

Measurement of Contact Angle B The measurement was carried out at 25 ° C. using a contact angle measuring device. 10% by weight
One drop of the aqueous emulsion prepared in (1) was dropped onto a tetrafluoroethylene resin (Teflon: registered trademark) plate having a smooth surface,
The contact angle at that time was measured by a microscope.

Measurement of surface tension B The solid content of the aqueous emulsion was adjusted to 35% by weight, and
The measurement was carried out at 0 ° C. using a fully-automatic equilibrium electro surface tension Didiomatic ESB-IV type (manufactured by Kyowa Kagaku Co., Ltd.).

Of the half-life in the reaction with divalent metal ions
Measurement B 3 ml of an aqueous emulsion prepared so that the polymer fine particles became 0.1% by weight was put into a spectrophotometer cell without bubbles, and set in the sample chamber of the spectrophotometer.
1 ml of 1 mol / l magnesium chloride aqueous solution in the cell
At the same time as was dropped, the time change of the transmittance at a wavelength of 700 nm was measured. The time at which the transmittance for a predetermined time was 50% with respect to the initial transmittance was determined.

Measurement of Average Particle Size B The average particle size is measured by Laser Doppler system particle size distribution analyzer Microtrac UPA15 manufactured by Leeds & Northrop Co.
It was measured using 0.

Polymer Emulsion B1 A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and 4 g of sodium lauryl sulfate, stirred under a nitrogen atmosphere and heated to 70 ° C. While maintaining the temperature at 70 ° C., 2 g of potassium persulfate as a polymerization initiator was added and dissolved. Ion-exchanged water 450 g, sodium lauryl sulfate 3 g,
20 g of acrylamide, 435 g of styrene, 475 g of butyl acrylate, 30 g of methacrylic acid, and 2 g of ethylene glycol dimethacrylate were added with stirring to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 3 hours. After completion of dropping, aging was carried out at the same temperature for 3 hours. The obtained polymer emulsion of polymer fine particles B1 was cooled to room temperature, and then ion-exchanged water and potassium hydroxide were added to prepare a solid content of 35% by weight and a pH of 8. The obtained polymer emulsion of polymer fine particles has a minimum film forming temperature of 22 ° C. and a surface tension of 53 × 10 ⁻³ N.
/ M (53 dyne / cm), the contact angle was 83 °, the average particle size was 100 nm, and the half-life in the reaction with Mg ²⁺ ions was 150 seconds.

Polymer emulsion B2 A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and 4 g of sodium lauryl sulfate, and the mixture was stirred under a nitrogen atmosphere and heated to 70 ° C. While maintaining the temperature at 70 ° C., 2 g of potassium persulfate as a polymerization initiator was added and dissolved. Ion-exchanged water 450 g, sodium lauryl sulfate 3 g,
20 g of acrylamide, 435 g of styrene, 475 g of butyl acrylate, 30 g of methacrylic acid, and 40 g of ethylene glycol dimethacrylate were added with stirring to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 3 hours. After completion of dropping, aging was carried out at the same temperature for 3 hours. After the obtained polymer emulsion was cooled to room temperature, ion-exchanged water and sodium hydroxide were added to prepare a solid content of 35% by weight and a pH of 8. The minimum emulsion temperature of the obtained aqueous emulsion of polymer fine particles B2 is 2
2 ° C., surface tension 57 × 10 ⁻³ N / m (57 dyne /
cm), the contact angle is 95 °, the average particle size is 102 nm, and M
The half-life in the reaction with g ²⁺ ions was 90 seconds.

Polymer Emulsion B3 A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and 4 g of sodium lauryl sulfate, stirred under a nitrogen atmosphere and heated to 70 ° C. While maintaining the temperature at 70 ° C., 2 g of potassium persulfate as a polymerization initiator was added and dissolved. Ion-exchanged water 450 g, sodium lauryl sulfate 3 g,
20 g of acrylamide, 435 g of styrene, 475 g of butyl acrylate, 30 g of methacrylic acid, and 10 g of ethylene glycol dimethacrylate were added with stirring to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 3 hours. After completion of dropping, aging was carried out at the same temperature for 3 hours. After the obtained polymer emulsion was cooled to room temperature, ion-exchanged water and sodium hydroxide were added to prepare a solid content of 35% by weight and a pH of 8. The polymer emulsion of the obtained polymer fine particles B3 had a minimum film forming temperature of 22 ° C. and a surface tension of 54 × 10 ⁻³ N / m (54 dyne).
/ Cm), the contact angle is 85 °, the average particle size is 101 nm,
The half-life in the reaction with Mg ²⁺ ions was 134 seconds.

Polymer Emulsion B4 A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and 4 g of sodium lauryl sulfate, stirred under a nitrogen atmosphere and heated to 70 ° C. While maintaining the temperature at 70 ° C., 2 g of potassium persulfate as a polymerization initiator was added and dissolved. Ion-exchanged water (450 g), sodium lauryl sulfate (3 g), acrylamide (20 g), styrene (435 g), butyl acrylate (475 g), methacrylic acid (30 g), and tetraethylene glycol dimethacrylate (10 g) were added with stirring to prepare an emulsion, which was continuously prepared in a reaction vessel. Over 3 hours. After completion of dropping, aging was carried out at the same temperature for 3 hours. After the obtained polymer emulsion was cooled to room temperature, ion-exchanged water and sodium hydroxide were added to prepare a solid content of 35% by weight and a pH of 8. The polymer emulsion of the obtained polymer fine particles has a minimum film formation temperature of 22.
℃, surface tension 51 × 10 ^-3 N / m (51 dyne / c
m), the contact angle was 80 °, the average particle size was 190 nm, and the half-life in the reaction with Mg ²⁺ ions was 3860 seconds.

Polymer Emulsion B5 A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water, and the mixture was stirred under an elementary atmosphere and heated to 70 ° C., and the internal temperature was brought to 70 ° C. While holding, 2 g of potassium persulfate as a polymerization initiator was added and dissolved. 70 g of ion-exchanged water, 1.0 g of sodium lauryl sulfate, 53 g of styrene, 59 g of butyl acrylate, 48 g of glycidyl methacrylate, and t-dodecyl mercaptan 0.16 as a molecular weight modifier.
g was added with stirring to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 1 hour. After completion of dropping, aging was carried out for 1 hour. Subsequently, 70 g of ion-exchanged water, 1.0 g of sodium lauryl sulfate, 1 g of acrylamide, 79 g of styrene, and 80% of butyl acrylate were previously prepared.
g, and 0.16 g of t-dodecyl mercaptan were added with stirring to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 1 hour. After completion of dropping, aging was carried out at the same temperature for 1 hour. Then, an aqueous solution in which 2 g of ammonium persulfate was dissolved in 20 g of ion-exchanged water as a polymerization initiator was added into the reaction vessel. Further, 300 g of ion-exchanged water, 2 g of sodium lauryl sulfate, 16 g of acrylamide, 298 g of styrene, and 2 parts of butyl acrylate were previously prepared.
An emulsion was prepared by adding 97 g, methacrylic acid 29 g, ethylene glycol dimethacrylate 10 g, and t-dodecyl mercaptan 0.65 g with stirring. This emulsion was continuously dropped into the reaction vessel over 3 hours. After completion of dropping, aging was carried out at the same temperature for time. After cooling the obtained polymer emulsion to room temperature, ion-exchanged water and potassium hydroxide were added to solid content 35% by weight, pH 8
Was prepared. The obtained polymer emulsion of polymer fine particles B5 had a core-shell structure and an average particle size of 90 n.
m polymer particles, the minimum film formation temperature is 24 ° C,
Surface tension is 58 × 10 ^-3 N / m (58 dyne / c
m), contact angle is 108 °, average particle size is 90 nm, Mg
The half-life in the reaction with ²⁺ ions was 10 seconds.

Polymer Emulsion B6 A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water, stirred under a nitrogen atmosphere and heated to 70 ° C., and the internal temperature was brought to 70 ° C. While holding, 2 g of potassium persulfate as a polymerization initiator was added and dissolved. 70 g of ion-exchanged water, 0.5 g of sodium lauryl sulfate, 53 g of styrene, 59 g of butyl acrylate, 48 g of glycidyl methacrylate, and 0.16 of t-dodecyl mercaptan as a molecular weight modifier.
An emulsion was prepared by stirring g. This emulsion was continuously dropped into the reaction vessel over 1 hour. After completion of dropping, aging was carried out at the same temperature for 1 hour. Subsequently, 70 g of ion-exchanged water, 0.5 g of sodium lauryl sulfate, 1 g of acrylamide, 79 g of styrene, and 80% of butyl acrylate were previously prepared.
g and 0.16 g of t-dodecyl mercaptan were stirred to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 1 hour. After the end of dropping, 1 at the same temperature
Aged for time. Then, an aqueous solution in which 2 g of ammonium persulfate was dissolved in 20 g of ion-exchanged water as a polymerization initiator was added into the reaction vessel. Furthermore, ion-exchanged water 3
00 g, sodium lauryl sulfate 2 g, acrylamide 16 g, styrene 298 g, butyl acrylate 297
g, 29 g of methacrylic acid, 10 g of tetraethylene glycol dimethacrylate, and 0.65 g of t-dodecyl mercaptan were added with stirring to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 3 hours.
After completion of dropping, aging was carried out for 3 hours at the same temperature. The obtained polymer emulsion of polymer fine particles was cooled to room temperature, and ion-exchanged water and potassium hydroxide were added to adjust the solid content to 35% by weight and pH to 8. The polymer emulsion of the obtained polymer fine particles B6 was one in which the polymer fine particles had a core-shell structure. The polymer emulsion has a minimum film formation temperature of 24 ° C and a surface tension of 55 x 1
0 ^-3 N / m (55 dyne / cm), contact angle is 92 °,
The average particle size was 180 nm, and the half-life in reaction with Mg ²⁺ ions was 3620 seconds.

Polymer Emulsion B7 (Comparative Example) 400 g of ion-exchanged water and 4 g of sodium lauryl sulfate were charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer, and the mixture was stirred under a nitrogen atmosphere and heated to 70 ° C. The mixture was heated and the internal temperature was maintained at 70 ° C., and 1 g of potassium persulfate as a polymerization initiator was added and dissolved. To 300 g of ion-exchanged water and 3 g of sodium lauryl sulfate, 470 g of butyl acrylate and 30 g of methacrylic acid were added in advance with stirring to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 3 hours. After completion of dropping, aging was carried out at the same temperature for 3 hours. After cooling the obtained polymer emulsion of polymer fine particles to room temperature, ion-exchanged water and ammonia are added to obtain a solid content of 35% by weight and pH.
8 was prepared. The obtained polymer emulsion of polymer fine particles B7 had a minimum film formation temperature of 5 ° C. and an average particle size of 1
It was 80 nm.

Polymer Emulsion B8 (Comparative Example) A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and 4 g of sodium lauryl sulfate, and the mixture was stirred under a nitrogen atmosphere and heated to 70 ° C. The mixture was warmed, the internal temperature was kept at 70 ° C., and 2 g of potassium persulfate as a polymerization initiator was added and dissolved. An emulsion was prepared in advance by adding 450 g of ion-exchanged water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 435 g of styrene, 475 g of butyl acrylate, 30 g of methacrylic acid and 60 g of ethylene glycol dimethacrylate under stirring. This emulsion is continuously added to the reaction vessel for 3 times.
It dripped over time. After completion of dropping, aging was carried out at the same temperature for 3 hours. The obtained polymer emulsion of polymer fine particles B8 was cooled to room temperature, and ion-exchanged water and ammonia were added to adjust the solid content to 35% by weight and pH to 8.

Polymer Emulsion B9 (Comparative Example) 900 g of ion-exchanged water and 4 g of sodium lauryl sulfate were charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer, and the mixture was stirred under a nitrogen atmosphere and heated to 70 ° C. After heating and maintaining the internal temperature at 70 ° C., 2 g of potassium persulfate was added as a polymerization initiator, and after dissolution, 450 g of ion-exchanged water, 3 g of sodium lauryl sulfate and 435 g of styrene, 475 g of butyl acrylate and 3 g of methacrylic acid were previously added. An emulsion was prepared by adding with stirring. This emulsion was continuously dropped into the reaction vessel over 3 hours. After completion of dropping, aging was carried out at the same temperature for 3 hours. After cooling the polymer emulsion of the obtained polymer fine particles to room temperature, ion-exchanged water and ammonia are added to obtain a solid content of 3
It was adjusted to 5% by weight and pH 8. The polymer emulsion of the obtained polymer fine particles B9 has a minimum film formation temperature of 12
℃, surface tension 37 × 10 ^-3 N / m (37 dyne / c
m), the contact angle was 60 °, and the average particle size was 150 nm.

Polymer Emulsion B10 (Comparative Example) 300 g of ion-exchanged water and 4 g of sodium lauryl sulfate were charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer, and the mixture was stirred under a nitrogen atmosphere and heated to 70 ° C. Warm and maintain the internal temperature at 70 ° C., add 1 g of potassium persulfate as a polymerization initiator, and after dissolution, 100 g of ion-exchanged water and 0.3 g of sodium lauryl sulfate in advance.
Further, 260 g of styrene, 47.5 g of butyl acrylate and 2 g of methacrylic acid were added to 2 g of acrylamide under stirring to prepare an emulsion. This emulsion was continuously dropped into the reaction vessel over 3 hours. After completion of dropping, aging was carried out at the same temperature for 3 hours. The obtained polymer emulsion of polymer fine particles was cooled to room temperature, and ion-exchanged water and ammonia were added to adjust the solid content to 35% by weight and pH to 8. The polymer emulsion of the obtained polymer fine particles B10 had a minimum film formation temperature of 75 ° C. and an average particle diameter of 120 n.
It was m.

Preparation B for imparting hydrophilic groups to the surface of pigment B Black pigment B1 300 g of commercially available acidic carbon black "MA-100 (manufactured by Mitsubishi Chemical Corporation)" was thoroughly mixed with 1000 ml of water,
Sodium hypochlorite (effective chlorine concentration 12%) 450
g was added dropwise, and the mixture was stirred at 80 ° C. for 15 hours. The resulting slurry was designated as Toyo Filter Paper No. It was repeatedly washed with ion-exchanged water while being filtered with 2. As a guide for the completion of washing with water, when the 0.1N silver nitrate aqueous solution was added to the ion-exchanged water that had passed through the filter paper, the washing was carried out until the white turbidity disappeared. This pigment slurry was redispersed in 2500 ml of water, desalted with a reverse osmosis membrane until the electric conductivity was 0.2 microsiemens or less, and further concentrated to a pigment concentration of about 15% by weight. The surface-treated pigment dispersion obtained is acid-treated (acidified with hydrochloric acid),
It was concentrated, dried and pulverized to give a powder. The surface active hydrogen content of this powder of surface-treated carbon black was measured by the method described below. The result is 2.8 mmol
/ G.

15 parts of black pigment B2 carbon black (“MA-7” manufactured by Mitsubishi Chemical Co., Ltd.) were mixed in 200 parts of sulfolane, and a bead packing ratio of 7 was obtained using an Eiger motor mill M250 type (manufactured by Eiger Japan).
It is dispersed for 1 hour under the conditions of 0% and a rotation speed of 5000 rpm, the dispersed mixture of the pigment paste and the solvent is transferred to an evaporator, and the pressure is reduced to 30 mmHg or less while
After heating to ℃ to distill off the water contained in the system as much as possible, the temperature was controlled to 150 ℃. Then sulfur trioxide 2
After adding 5 parts and reacting for 6 hours, after completion of the reaction, the mixture was washed several times with excess sulfolane, poured into water and filtered to obtain a black pigment. The amount of hydrophilic groups introduced into the obtained black pigment was 120 × 10 ⁻⁶ equivalent per 1 g of the pigment.

Cyan Pigment B Phthalocyanine Pigment (CI Pigment Blue 15:
3) 20 parts of quinoline and 500 parts of quinoline were mixed and dispersed in an Eiger motor mill M250 type (manufactured by Eiger Japan Co., Ltd.) for 2 hours under the conditions of a bead filling rate of 70% and a rotation speed of 5000 rpm, and the dispersed pigment paste and solvent were mixed. Transfer the solution to an evaporator and reduce the pressure to 30 mmHg or less, and
After heating to 0 ° C. and distilling off water contained in the system as much as possible, the temperature was controlled to 160 ° C. Then, 20 parts of a sulfonated pyridine complex was added and reacted for 8 hours. After the reaction was completed, the mixture was washed several times with excess quinoline, poured into water, and filtered to obtain a cyan pigment having a hydrophilic group on the surface. The amount of the hydrophilic group introduced in the obtained cyan pigment was the same as that of Pigment 1
It was 40 × 10 ⁻⁶ equivalent per g.

Yellow Pigment B In the above-mentioned cyan pigment B, “phthalocyanine pigment
(CI Pigment Blue 15: 3) 20 parts "to" isoindolinone pigment (CI Pigment Yellow 110) "
A yellow pigment having a hydrophilic group on its surface was obtained by the same treatment method except that "20 parts" was used. The amount of hydrophilic groups introduced into the obtained yellow pigment was 45 × per 1 g of the pigment.
It was 10 ^-6 equivalent.

Magenta Pigment B In the above cyan pigment B, “phthalocyanine pigment
(CI pigment blue 15: 3) 20 parts "to" isoindolinone pigment (CI pigment red 122) 2
A magenta pigment having a hydrophilic group on its surface was obtained by the same treatment method except that "0 part" was used. The amount of hydrophilic groups introduced into the obtained yellow pigment was 60 × 1 per 1 g of the pigment.
0 ^-6 it was equivalent.

Quantification of hydrophilic group introduction amount B The “ quantity of hydrophilic group introduction on the surface of the pigment particle” was determined by the following method.

1) A hydrophilic group is removed by a carboxylating agent.
In case of introduction Manual quantification was carried out using the Tuiser method. Diazomethane was dissolved in a suitable solvent, and this was added dropwise to replace all active hydrogen on the pigment particle surface with methyl groups. Then, hydroiodic acid having a specific gravity of 1.7 was added and heated to vaporize the methyl group as methyl iodide. This methyl iodide gas was trapped with a silver nitrate solution to precipitate as methyl iodide silver. The amount of the original methyl group, that is, the amount of active hydrogen was measured from the weight of this silver iodide.

2) Introduction of hydrophilic group by sulfonating agent
In that case, the pigment particles whose surfaces were treated with the sulfonating agent were treated by the oxygen flask combustion method and absorbed in a 0.3% hydrogen peroxide aqueous solution. After that, sulfate ion (divalent) was quantified by ion chromatography (Dionex Co .; 2000i),
This value was converted to a sulfonic acid group and shown as an equivalent weight per 1 g of the pigment.

Ink Composition Preparation B Based on the composition shown in Table B1, ink compositions of Examples B1 to B6 and ink compositions of Comparative Examples B1 to B6 were prepared. To prepare the ink, water and the penetrant, the wetting agent, the solid wetting agent, and other additives shown in Table B1 were added in a predetermined amount, mixed and dissolved,
This was gradually added to a polymer emulsion having a predetermined amount of fine polymer particles as dispersed particles under stirring. The thus obtained mixed liquid was gradually added dropwise to the dispersion liquid of the pigment having the hydrophilic group on the surface obtained above and sufficiently stirred. This was filtered with a 5 μm membrane filter to obtain an ink composition. In Table B1, the addition amount of the polymer particles was calculated from the solid content concentration of the polymer emulsion containing the polymer particles as dispersed particles.

[0135]

[Table 7]

Ink Composition Evaluation Test B The following ink evaluation tests were conducted on the ink compositions prepared in Table B1. Inkjet printer P
It was performed using M-980C (manufactured by Seiko Epson Corporation). The following printing test sheets were used. The evaluation results were as shown in Table B2. Xerox P paper (manufactured by Xerox Co., Ltd.) Ricopy 6200 paper (manufactured by Ricoh Co., Ltd.) Xerox 4024 paper (manufactured by Xerox Co., Ltd.) Neenah Bond paper (manufactured by Kimberley Clark Co.) Xerox R paper (manufactured by Xerox Co., Ltd.) Yamayuri paper (Recycled paper manufactured by Honshu Paper Co., Ltd.)

Evaluation B1: Scratch resistance (over) resistance (line marker resistance)
After the printed matter is naturally dried for 24 hours, the printed characters are rubbed with a writing pressure of 4.9 × 10 ⁵ N / m ² using a yellow aqueous highlighter ZEBRA PEN2 (trademark) manufactured by Zebra Co. Was visually observed, and the results were evaluated according to the following criteria. Evaluation A: No stain was generated even if rubbed twice. Evaluation B: Staining did not occur until rubbing once, but some rubbing occurred in the paper after rubbing twice. Evaluation C: There was a paper sheet that was stained by rubbing once.

Evaluation B2: Clogging reliability Alphanumeric characters were printed continuously for 10 minutes. After that, the printer is stopped, the temperature is 40 ° C, the humidity is 2 without removing the cap.
The printer was left for one week in a 5% environment. After leaving, the alphanumeric characters were printed again, the number of returning operations required until the print quality equivalent to that before leaving was obtained was examined, and the number of times was evaluated according to the following criteria. Evaluation A: 0 to 2 times. Evaluation B: 3 to 5 times. Evaluation C: It was 6 times or more.

Evaluation B3: Ejection stability The ink composition was applied to an inkjet printer EM-900.
With C (manufactured by Seiko Epson Corporation), a 1 mm ruled line pattern (see FIG. 1) was printed on superfine paper (manufactured by Seiko Epson Corporation) 1000 sheets at a time. The ejection stability of the ink from the recording head was evaluated according to the following criteria. Evaluation A: No bending of the ruled line occurred through 1000 sheets. Evaluation B: Bending of the ruled line occasionally occurred through 1000 sheets, and the cleaning operation was required less than 5 times to normally print the ruled line. Evaluation C: Bentness of the ruled line was frequently generated through 1000 sheets, and the cleaning operation was required 5 times or more to normally print the ruled line.

Evaluation B4: Print quality (bleeding) The printed matter printed with the ink composition was dried, and then the bleeding on the characters of the printed matter was evaluated according to the following criteria. Evaluation A: Slight whisker-like bleeding occurred on some papers, but the other papers were clear printed images. Evaluation B: Whiskers-like bleeding occurred on all the papers. Evaluation C: Bleeding occurred so that the outline of the character was not clear.

Evaluation B5: Printing Density The ink composition was applied to an inkjet printer EM-900.
C (manufactured by Seiko Epson Corporation), high quality plain paper KA
Solid printing was performed on 4250NP (manufactured by Seiko Epson Corporation). The density of the printed portion of the printed matter was measured and evaluated using a spectrophotometer (GRETAG SPM-50 manufactured by Gretag Macbeth Co., Ltd.), and the obtained results were evaluated according to the criteria shown below. Evaluation A: The OD value of the black ink is 1.4 or more,
In addition, the OD value of the color ink was 1.2 or more. Evaluation B: The OD value of the black ink was 1.3 or more and less than 1.4, and the OD value of the color inks was 1.15 or more and less than 1.2. Evaluation C: Black ink OD value: less than 1.3,
In addition, the OD value of the color ink was less than 1.15.

Evaluation B6: Storage stability The ink composition was placed in a glass bottle in an amount of 50 cc, and the bottle was tightly stoppered.
It was left for 2 weeks at ℃. After that, the change in viscosity and the presence or absence of foreign matter (sediment) were examined, and the results were evaluated according to the following criteria. Evaluation A: No generation of foreign matter and no change in viscosity. Evaluation B: No foreign matter is generated, but the viscosity is slight (1.0 cp
less than s). Evaluation C: No foreign matter was generated, but the viscosity was changed. Evaluation D: Foreign matter was generated.

Evaluation B7: Quick-drying The ink composition was applied on an Xerox P paper with an ink jet printer MJ-930C (manufactured by Seiko Epson Corporation) to a thickness of 10 mm.
Solid printing was performed on the area of × 10 mm with 100% duty, 10 seconds later, a new same paper was placed on the printed portion, a weight of 300 g was put on it, left for 10 seconds and then removed. Ink was adhered to the latter paper. The results were evaluated according to the following criteria. Evaluation A: No ink adhered. Evaluation B: Ink adhered.

[0144]

[Table 8]

[Brief description of drawings]

FIG. 1 shows a ruled line pattern for measuring the ejection stability of an inkjet recording ink.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08F 14/04 C08F 18/08 4J100 18/08 20/02 20/02 36/04 36/04 220/06 220/06 220/20 220/20 246/00 246/00 C09D 11/00 C09D 11/00 C09C 1/48 // C09C 1/48 3/00 3/00 C08F 220: 06 (C08F 246/00 220: 20 220: 06 B41J 3/04 101Y 220: 20) F-term (reference) 2C056 EA13 FC01 2H086 BA02 BA53 BA55 BA59 BA60 BA62 4J011 KA04 KA10 KA15 KB14 4J037 AA02 CA05 CA14 CA19 CA20 CB21 EE02 EE11 EE19 EE43EE01 EE22 EE22 EE22 EE22 EE22 AD03 AD08 AD09 AD10 AD11 AD15 AE04 AE08 BA04 BA14 BA29 BC09 BC13 BE01 BE12 BE22 BE30 CA06 EA19 GA24 4J100 AA02P AA03P AB00P AB02P AB04P AB07P AB08P AB16R AC03P AC04P AE02P AF10P AG04P AJ02Q AJ09Q AL03P AL04P AL05P AL08P AL10P AL11P AL62R AL63R AL6 6R AL67R AM02P AM24R AQ08P AS02P AS07P BA02R BA03R BA05P BA08R BC04P BC43P BC45R CA03 CA31 EA07 FA20 HA31 HB39 HG12 JA07

Claims (28)

[Claims] 1. A method for producing a polymer emulsion containing fine polymer particles, which comprises mixing water, a monomer, an emulsifier, and a polymerization initiator to cause an emulsion polymerization reaction, and then monovalent inorganic water. A method comprising adding an oxide to adjust the pH value in the neutral to alkaline range. 2. The method according to claim 1, wherein the monovalent inorganic hydroxide is an alkali metal hydroxide. 3. The method according to claim 2, wherein the alkali metal hydroxide is one or a mixture of two or more selected from the group consisting of lithium hydroxide, sodium hydroxide and potassium hydroxide. 4. The p value so that the pH value is in the range of 7-9.
The method according to claim 1, wherein the H value is adjusted. 5. The polymer fine particles have a structure derived from an unsaturated vinyl monomer having a carboxyl group of 1 to 10.
%, And has a structure crosslinked by a crosslinkable monomer having two or more polymerizable double bonds, and contains 0.2 to 4% by weight of a structure derived from the crosslinkable monomer. The method according to any one of claims 1 to 4, wherein: 6. The polymer fine particles having a film-forming property, having a carboxyl group on the surface thereof, and having 3% by volume of a polymer emulsion having 0.1% by weight of the polymer fine particles and a concentration of 1 mol / l. When brought into contact with 1 volume of an aqueous solution of a divalent metal salt, the reactivity with a divalent metal salt is set so that the time at which the transmittance of light having a wavelength of 700 nm becomes 50% of the initial value is 1 × 10 ⁴ seconds or less. It has, Claims 1-5
The method according to any one of 1. 7. A polymer emulsion produced by the method according to any one of claims 1 to 6. 8. A pigment, a polymer emulsion, water,
An ink composition comprising a water-soluble organic solvent, wherein the polymer emulsion is as described in claim 7. 9. The addition amount of polymer fine particles constituting the polymer emulsion is 0.
The ink composition according to claim 8, which is 01 to 30% by weight. 10. The ink composition according to claim 8, wherein the pigment is a pigment having a hydrophilic group on its surface. 11. The pigment constituting the pigment having a hydrophilic group on its surface is carbon black or an organic pigment.
The ink composition according to claim 10. 12. The hydrophilic group of the pigment having a hydrophilic group on the surface is a sulfonic acid group (—SO ₂ OH) and / or a sulfinic acid group (—RSO ₂ H: R is C ₁ -C ₁₂ alkyl). Group or a phenyl group and derivatives thereof),
The ink composition according to item 1. 13. The hydrophilic group of the pigment having a hydrophilic group on the surface is a sulfonate anion group (—SO ₃ ^— ) and / or a sulfinate anion group (—RSO ₂ : R is C _{1 to} C ₁₂ ). An alkyl group or a phenyl group and its derivatives),
The ink composition according to claim 10. 14. The hydrophilic group of the pigment particles is a carboxylic acid group (—CO ₂ H) and / or a carboxylic acid anion group (—).
CO ₂ ^-) a is, the ink composition according to claim 10. 15. The ink composition according to any one of claims 8 to 14, further comprising a penetrant or a wetting agent. 16. The penetrant is one or more selected from the group consisting of 1,2-alkyldiols, glycol ethers, acetylene glycol-based surfactants and acetylene alcohol-based surfactants.
The ink composition according to claim 15. 17. The 1,2-alkyldiol is 1,
The ink composition according to claim 16, which is 2-hexanediol or 1,2-pentanediol. 18. The glycol ether is dialkylene glycol monobutyl ether, dialkylene glycol monopentyl ether, dialkylene glycol monohexyl ether, trialkylene glycol monobutyl ether, trialkylene glycol monopentyl ether, trialkylene glycol monohexyl ether, The ink composition according to claim 16, which is one or more selected from the group consisting of tetraalkylene glycol monobutyl ether, tetraalkylene glycol monopentyl ether, and tetraalkylene glycol monohexyl ether. 19. The ink composition according to claim 15, wherein the wetting agent is glycerin or trimethylene glycol. 20. The ink composition according to claim 15, wherein the amount of the wetting agent added is 10 to 20% by weight based on the total amount of the ink composition. 21. The ink composition according to claim 15, wherein the wetting agent is a solid wetting agent. 22. The amount of the solid wetting agent added is in the range of 3 to 20% by weight based on the total amount of the ink composition.
The ink composition according to 1. 23. The ink composition according to claim 21, wherein the solid wetting agent is a water-soluble substance which has a water-retaining function and is solid at room temperature (25 ° C.). 24. The solid humectant is one or more selected from the group consisting of sugars, sugar alcohols, hyaluronate, trimethylolpropane, and 1,2,6-hexanetriol. , Claims 21 to 2
The ink composition according to any one of 3 above. 25. The pH adjusting agent further comprises one or more selected from the group consisting of potassium hydroxide, sodium hydroxide and lithium hydroxide. The ink composition according to item 1. 26. A recording method for depositing an ink composition and printing on a recording medium, wherein the ink composition according to any one of claims 8 to 25 is used. 27. The method according to claim 26, wherein the recording method is an inkjet recording method in which droplets of an ink composition are ejected and the droplets are attached to a recording medium to perform printing. 28. A recorded matter printed by the recording method according to claim 26 or 27.