JP2011088977A - Method for manufacturing ink composition for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an ink composition, whereby the ink composition for inkjet recording excellent in shelf stability, discharge stability and recovery from clogging can be obtained. <P>SOLUTION: The method is for manufacturing the ink composition for inkjet recording comprising at least a pigment, a dispersant for dispersing the pigment, a polymer, a penetrant and water. The method comprises steps of: preparing a pigment dispersion by subjecting a mixture comprising at least the pigment, the dispersant for dispersing the pigment, the penetrant and water to a dispersion treatment; and adding the polymer to the pigment dispersion. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

Background of the Invention

FIELD OF THE INVENTION The present invention relates to a method for producing an ink composition for ink jet recording, and more specifically, an ink composition for ink jet recording having excellent storage stability and excellent ejection stability and clogging recovery properties. The present invention relates to a method for producing an ink composition.

BACKGROUND ART Pigments are used as colorants for ink jet recording inks because of their excellent fastness such as water resistance and light resistance. Since the pigment has poor solubility in water, a dispersing agent such as a surfactant or a polymer is added to the ink to improve the dispersion stability of the pigment. As the dispersant, a resin having both a hydrophobic part and a hydrophilic part, for example, a styrene-acrylic copolymer resin is generally used.

  In addition, ink used for ink jet recording has various prints such as no bleeding, good dryness, uniform printing on various recording media, and no mixing of adjacent colors in multicolor printing. Quality is required. In order to improve the printing quality, various additives are usually added to the ink. For example, glycol ethers such as diethylene glycol monobutyl ether are added to the ink in order to improve the permeability to the recording medium and reduce bleeding (US Pat. No. 5,156,675: Patent Document 1). An acetylene glycol surfactant is added (US Pat. No. 5,183,502: Patent Document 2), or both are added (US Pat. No. 5,196,056). Patent Document 3).

  However, in the ink to which the pigment dispersant is added, if the above surfactants or glycol ethers are present in the ink, the dispersion resin is likely to be adsorbed and desorbed from the pigment, and the storage stability of the ink is insufficient. There was a case. Further, when the dispersant detached from the pigment remains in the ink, the ink viscosity increases, and the ink ejection stability and clogging recovery ability may be insufficient.

US Pat. No. 5,156,675 US Pat. No. 5,183,502 US Pat. No. 5,196,056

  In the process of preparing a pigment dispersion, the present inventors have recently prepared a pigment dispersion by subjecting a mixed liquid in which a penetrant is added in addition to a pigment and a dispersant for dispersing the pigment and water to a dispersion treatment. Then, by preparing an ink composition by adding a specific polymer, an ink composition having improved ink storage stability and excellent ejection stability and clogging recovery can be produced. , And got the knowledge. The present invention is based on such knowledge.

  Accordingly, an object of the present invention is to provide a method for producing an ink composition, from which an ink composition for inkjet recording having excellent storage stability and excellent ejection stability and clogging recovery properties can be obtained.

The method according to the present invention is a method for producing an ink composition for ink jet recording, comprising at least a pigment, a dispersant for dispersing the pigment, a polymer, a penetrant, and water,
At least a pigment, a dispersant for dispersing the pigment, a penetrant, and water are subjected to a dispersion treatment in a mixed liquid state to prepare a pigment dispersion,
Adding the polymer to the pigment dispersion.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the ink composition for inkjet recording which is excellent in storage stability, and is excellent also in discharge stability and clogging recoverability can be provided.

Detailed description of the invention

  The method according to the present invention includes a step of preparing a pigment dispersion by subjecting at least a pigment, a dispersant for dispersing the pigment, a penetrant, and water to a dispersion treatment in a mixed solution state, and adding a polymer to the pigment dispersion. Including a two-stage process. Hereinafter, each step will be described.

<Pigment dispersion preparation process>
The pigment dispersion can be prepared by mixing at least a pigment, a dispersant for dispersing the pigment, a penetrant, and water, and subjecting the mixture to a dispersion treatment. A conventionally known method can be applied to the mixing and dispersion treatment. For example, a pigment, a dispersant and water are mixed with an appropriate dispersing machine (for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator mill, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a jet mill, an ang mill, etc.) A uniform pigment dispersion can be prepared. In the dispersion treatment, an organic solvent may be added and kneaded as necessary. In this step, the dispersant is firmly fixed on the surface of the pigment, and since the penetrant is added in the step of preparing the pigment dispersion, the pigment particles are easily compatible with the aqueous medium (water) and the aqueous medium. Dispersion efficiency is improved by increasing the contact resistance between the pigment particles inside and between the pigment and the dispersion medium. As a result, the shearing conditions of the apparatus used for the dispersion treatment can be relaxed (the shear force applied from the apparatus to the pigment dispersion can be reduced), and the time required for the dispersion treatment can be shortened.
The obtained pigment dispersion is preferably filtered using a filter such as a membrane filter or a mesh filter to remove coarse particles.

  The amount of penetrant added in the dispersion treatment step is preferably in the range of 1/50 to 2 times in terms of weight with respect to the pigment. If the amount of penetrant added is less than 1/50, a sufficient dispersion treatment effect may not be obtained. On the other hand, when added in a large amount (for example, several times the pigment), the ink prepared to a desired pigment concentration using this pigment dispersion has a surface tension that is unnecessarily lowered and spreads in the vicinity of the inkjet head. Therefore, it becomes difficult to ensure stable discharge characteristics.

<Polymer addition process>
An ink composition is produced by adding a heat-treated polymer to the pigment dispersion obtained above. The polymer may be added to the pigment dispersion by dispersing or dissolving the heat-treated polymer in water. The water in which the polymer is dispersed or dissolved may contain additives contained in conventional ink compositions.

Hereinafter, each component constituting the ink composition will be described.
<Polymer>
The polymer added to the pigment dispersion is obtained by copolymerizing 50% by mass or more of benzyl acrylate and 15% by mass or less of (meth) acrylic acid. When benzyl acrylate is 50% by mass or more, fixability is improved. More preferably, it is 60 mass% or more, More preferably, it is 70 mass% or more. Further, polymerization with 15% by mass or less of (meth) acrylic acid is preferable, but when it is 15% by mass or less, the color developability of the inkjet ink on plain paper is improved. A more preferable range is 10% by mass or less.

  As (meth) acrylic acid, it is more preferable to use acrylic acid than methacrylic acid from the viewpoint of fixability. Moreover, as (meth) acrylic acid, it is more preferable to use a mixture of methacrylic acid and acrylic acid.

  The acid value of this polymer needs to be in the range of 50 to 200 mg KOH / g. Dispersion becomes unstable at an acid value of less than 50 mg KOH / g. Furthermore, when the acid value exceeds 200 mgKOH / g, the color developability on plain paper decreases. A more preferable acid value is 55 mgKOH / g to 180 mgKOH / g. In addition, in this specification, an acid value means the milligram number of potassium hydroxide required in order to neutralize the free fatty acid contained in 1g of polymers. The acid value of the polymer can be adjusted as appropriate by adjusting the ratio of monomer components constituting the polymer.

  Further, the above polymer needs to have a weight average molecular weight in the range of 20,000 to 120,000. If the weight average molecular weight is less than 20,000, the long-term storage stability, thermal stability and fixability as an inkjet ink tend to deteriorate, and if it exceeds 120,000, the viscosity as an inkjet ink increases. Dispersion stability tends to deteriorate, and discharge stability tends to decrease. A preferable range of the weight average molecular weight is 22,000 to 119,000.

  Moreover, in this invention, it is preferable that the ratio of the weight average molecular weight of a polymer and a number average molecular weight is the range of 1-3. By using a polymer within this range, the long-term storage stability and ejection stability of the ink composition can be further improved. A more preferable ratio is 1.5 to 2.6. In the present specification, the weight average molecular weight and the number average molecular weight are values measured by gel permeation chromatography using polystyrene as a standard substance.

  As a method for polymerizing the polymer, an alcohol solvent, a ketone solvent, an ether solvent, or a glycol ether solvent can be used as a solvent. However, since it is an aqueous pigment dispersion, the solvent is required to be removable later. As such a solvent, the following can be used. That is, examples of the alcohol solvent include methanol, ethanol, isopropanol, 1-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone. Examples of ether solvents include dibutyl ether, tetrahydrofuran, dioxane and the like. Examples of the glycol ether solvent include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, and butyl cellosolve.

  As radical polymerization initiators for polymerizing polymers, t-butyl peroxy (2-ethylhexanoate), di-t-butyl peroxide, t-butyl peroxybenzoate, t-butyl peroxy octoate, etc. Organic peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisbutyrate, 2,2 ′ -Azo compounds such as azobis (2-methylbutyronitrile), potassium persulfate, sodium persulfate, and the like can be used, but the invention is not limited to them. It can also be used. The amount of radical polymerization initiator used is preferably 0.01 mol% or more and 5 mol% or less with respect to the monomer used in the polymerization. The polymerization temperature is not particularly limited, but is usually in the range of 30 to 100 ° C, and preferably in the range of 40 to 90 ° C. When the polymerization temperature is too low, it is necessary to take a long time for the polymerization of the monomer, and in some cases, the polymerization rate may decrease and a large amount of monomer may remain.

<Pigment dispersant>
As the dispersant for dispersing the pigment, a polymer resin generally used in conventional ink compositions can be used, and specifically, a copolymer resin of a hydrophobic monomer and a hydrophilic monomer can be mentioned. It is done. These copolymer resins are adsorbed on the pigment to improve dispersibility.

  Specific examples of the hydrophobic monomer in the copolymer resin include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, n- Butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, iso- Octyl acrylate, iso-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, Sil acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl acrylate, 2 -Dimethylaminoethyl methacrylate, 2-diethylaminoethyl acrylate, 2-diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, phenyl methacrylate, nonyl phenyl acrylate, noni Phenyl methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butane Diol diacrylate, 1,4-butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetra Ethylene glycol dimethacrylate, polyethylene glycol di Acrylate, polyethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylol Mention may be made of methylolpropane trimethacrylate, glycerol acrylate, glycerol methacrylate, styrene, methylstyrene, vinyltoluene and the like. You may use these individually or in mixture of 2 or more types.

  Specific examples of the hydrophilic monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like.

  From the standpoint that the copolymer resin of the hydrophobic monomer and the hydrophilic monomer can form a color image having both glossiness of the color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Styrene- (meth) acrylic acid copolymer resin, styrene-methylstyrene- (meth) acrylic acid copolymer resin, or styrene-maleic acid copolymer resin, (meth) acrylic acid- (meth) acrylic acid ester copolymer resin, Alternatively, it is preferably at least one of styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer resin.

  The copolymer resin may be a resin (styrene-acrylic acid resin) containing a polymer obtained by reacting styrene with acrylic acid or an ester of acrylic acid. Alternatively, the copolymer resin may be an acrylic acid-based water-soluble resin. Alternatively, a salt such as sodium, potassium, or ammonium may be used.

  The content of these copolymer resins is 100 parts by weight of pigment from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition, and formation of a color image having further excellent glossiness. On the other hand, it is preferably 10 to 50 parts by mass, and more preferably 10 to 35 parts by mass.

  In the embodiment of the present invention, the pigment dispersant was copolymerized mainly with 8 to 98% by mass of cyclohexyl acrylate and / or benzyl acrylate, 1 to 31 methacrylic acid, and 1 to 25 acrylic acid. A resin having an acid value of 10 to 200 mg KOH / g is used. By using these pigment dispersants in combination with the above polymers, in addition to glossiness and bronzing prevention of color images, ejection stability, clogging prevention, color stability and high image quality comparable to silver salts are achieved. can do.

  The content of cyclohexyl acrylate and / or benzyl acrylate can be appropriately set depending on the type and combination of pigments and aqueous media used in ink jet recording ink, but is preferably 30 to 95% by mass, and more preferably 50 It is -90 mass%.

  As content of methacrylic acid, Preferably it is 3-25 mass%, More preferably, it is 5-20 mass%. As content of acrylic acid, Preferably it is 2-23 mass%, More preferably, it is 3-20 mass%.

  The acid value of the dispersion resin is preferably 20 to 150 mgKOH / g, more preferably 30 to 150 mgKOH / g. When the acid value is less than 10 mgKOH / g, pigment dispersion becomes difficult and stability is deteriorated. On the other hand, when it exceeds 200 mgKOH / g, the hydrophilicity becomes strong and the weather resistance and the OD value (optical density) for plain paper are lowered. To do.

  The dispersion resin is preferably polymerized with 20% by mass or less of (meth) acrylate having a long-chain alkyl group. Preferably it is 1-20 mass%, More preferably, it is 5-20 mass%. The (meth) acrylate having a long-chain alkyl group is not particularly limited, and examples include stearyl acrylate, stearyl methacrylate, lauryl acrylate, lauryl methacrylate, and n-dodecyl methacrylate. These may be used alone or in combination of two or more. As said long chain alkyl group, a C10-C18 linear alkyl group etc. are mentioned, for example. Preferably, it is a C12-18 alkyl group.

Moreover, it is preferable that the said dispersion resin is polymerized by 20 mass% or less of (meth) acrylate which has an amino group further. Preferably it is 1-20 mass%, More preferably, it is 3-20 mass%.
The (meth) acrylate having an amino group is not particularly limited, and examples thereof include 2- (dimethylamino) ethyl methacrylate, 2- (diethylamino) ethyl methacrylate, 2- (dimethylamino) ethyl acrylate, and morpholinoethyl acrylate. . These may be used alone or in combination of two or more.

Moreover, it is preferable that the dispersion resin is further polymerized with a hydroxyl group-containing (meth) acrylate at 20% by mass or less. Preferably it is 1-20 mass%, More preferably, it is 3-20 mass%.
The (meth) acrylate having a hydroxyl group is not particularly limited, and examples thereof include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate. These may be used alone or in combination of two or more.

  The dispersion resin preferably has a weight average molecular weight of 5,000 to 150,000. More preferably, it is 5,000-100,000. If the weight average molecular weight is less than 5,000, the fixability as an ink-jet ink may be deteriorated. On the other hand, if it exceeds 150,000, the viscosity as an ink-jet ink is increased and the stability may be further lowered. There is.

  Further, the molecular weight distribution (weight average molecular weight / number average molecular weight) is preferably 2 to 8. For example, those having a weight average molecular weight of 5,000 and those having a weight average molecular weight of 100,000 may be used in combination. Two or more types may be used in combination.

  The manufacturing method of the said dispersing agent is not restrict | limited in particular, It can carry out by a well-known method. For example, as a method for adding the monomer at the time of polymerization, the monomers may be charged all at the beginning of the reaction, or at least one may be added to the reaction system continuously or intermittently. The polymerization is preferably performed in the presence of a radical polymerization initiator and / or a catalyst.

  As the solvent used in the polymerization, an alcohol solvent, a ketone solvent, an ether solvent, or a glycol ether solvent is preferable.

  Examples of the alcohol solvent include methanol, ethanol, isopropanol, 1-butanol, tertiary butanol, isobutanol, diacetone alcohol, and the like.

  Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone.

  Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like.

  Examples of the glycol ethers include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, and butyl cellosolve.

  Examples of the radical polymerization initiator include organic peroxides such as t-butyl peroxy (2-ethylhexanoate), di-t-butyl peroxide, t-butyl peroxybenzoate, and t-butyl peroxy octoate. 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisbutyrate, 2,2′-azobis (2- Azo compounds such as methylbutyronitrile are preferred.

  As the usage-amount of the said radical polymerization initiator, 0.01 mol% or more and 5 mol% or less are preferable with respect to the monomer used in the case of superposition | polymerization.

  The polymerization temperature is not particularly limited, but is usually in the range of 30 to 100 ° C, and preferably in the range of 40 to 90 ° C. When the polymerization temperature is too low, the polymerization rate of the monomer may decrease.

  In the present invention, as a pigment dispersant, styrene- (meth) acrylic acid copolymer resin, styrene-methylstyrene- (meth) acrylic acid copolymer resin, styrene-maleic acid copolymer resin, (meth) acrylic acid- A copolymer resin selected from the group consisting of (meth) acrylic acid ester copolymer resins and styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer resins (hereinafter sometimes referred to simply as copolymer resins). And urethane resin. By using these pigment dispersants in combination with the above polymers, in addition to glossiness and bronzing prevention of color images, ejection stability, clogging prevention, color stability and high image quality comparable to silver salts are achieved. can do.

  The weight ratio of the copolymer resin and the urethane resin is preferably 1/2 to 2/1, and more preferably 1 / 1.5 to 1.5 / 1. By adding both resins in this range, it is possible to form an image having even more excellent gloss and bronzing prevention, and to maintain the storage stability of the ink.

  The copolymer resin may be a resin (styrene-acrylic acid resin) containing a polymer obtained by reacting styrene with acrylic acid or an ester of acrylic acid. Alternatively, the copolymer resin may be an acrylic acid-based water-soluble resin. Alternatively, a salt such as sodium, potassium, or ammonium may be used.

  The urethane resin has a urethane bond and / or an amide bond, from the viewpoint of achieving a color image having excellent glossiness while being compatible with glossiness of color images, prevention of bronzing, and storage stability of the ink composition, A resin having an acidic group is preferable.

  The urethane resin is a resin containing a polymer obtained by reacting a diisocyanate compound and a diol compound.

  Examples of the diisocyanate compound include aromatic aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, and modified products thereof. .

  Examples of the diol compound include polyethers such as polyethylene glycol and polypropylene glycol, polyesters such as polyethylene abido and polybutylene abates, and polycarbonates.

  The urethane resin preferably has a carboxyl group.

  The weight ratio of the solid content of the pigment to the solid content other than the pigment (the former / the latter) is compatible with the glossiness of the color image, the prevention of bronzing, and the storage stability of the ink composition, and is further excellent in glossiness. From the viewpoint of forming a color image, it is preferably 100/20 to 100/80.

  The content of the copolymer resin is 100 parts by mass of the pigment from the viewpoint of achieving a color image having excellent glossiness while being compatible with glossiness of the color image, prevention of bronzing, and storage stability of the ink composition. On the other hand, it is preferably 10 to 50 parts by mass, and more preferably 10 to 35 parts by mass.

  The content of the urethane resin is compatible with 100 parts by mass of the pigment from the viewpoint of achieving a color image with excellent glossiness, prevention of bronze, and storage stability of the ink composition and at the same time forming a more glossy color image. The amount is preferably 10 to 40 parts by mass, and more preferably 10 to 35 parts by mass.

  The total amount of the copolymer resin and the urethane resin is used so as to be 90 parts by mass or less (more preferably 70 parts by mass or less) with respect to 100 parts by mass of the pigment. In addition, the ink composition is preferable because it can achieve both the storage stability of the ink composition and can form a color image with more excellent gloss.

  The acid value of the copolymer resin is preferably 50 to 320 from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image having further excellent glossiness. Yes, more preferably 100-250.

  The acid value of the urethane resin is preferably 10 to 300 from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition, and forming a color image having further excellent glossiness. More preferably, it is 20-100.

  The weight-average molecular weight (Mw) of the copolymer resin is preferably from the viewpoint of achieving a color image having a glossy color image, prevention of bronzing, and storage stability of the ink composition, and an excellent glossiness. It is 2,000-30,000, More preferably, it is 2,000-20,000.

  From the viewpoint that the weight average molecular weight (Mw) before crosslinking of the urethane resin can form a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Preferably it is 100-200,000, More preferably, it is 1000-50,000.

  The glass transition temperature (Tg; measured according to JIS K6900) of the copolymer resin is a viewpoint capable of forming a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Is preferably 30 ° C. or higher, and more preferably 50 to 130 ° C.

  The glass transition temperature (Tg; measured in accordance with JIS K6900) of the urethane resin is from the viewpoint that both color image glossiness, prevention of bronzing, and storage stability of the ink composition can be achieved, and a color image with even higher glossiness can be formed. Is preferably −50 to 200 ° C., and more preferably −50 to 100 ° C.

  The copolymer resin may be adsorbed to the pigment in the ink composition or in the pigment dispersion, or may be free. The gloss of the color image, prevention of bronzing, and storage stability of the ink composition From the viewpoint of being able to form a color image that is more excellent in glossiness and at the same time, the maximum particle size of the copolymer resin is preferably 0.3 μm or less, and the average particle size is more preferably 0.2 μm or less. More preferably, it is 0.1 μm or less.

  The urethane resin is dispersed in fine particles in the ink composition or in the pigment dispersion, and is adsorbed on the pigment. The glossiness of the color image, prevention of bronzing, and the ink composition From the viewpoint of achieving storage stability and forming a color image with further excellent glossiness, the maximum particle size of the urethane resin is preferably 0.3 μm or less, and the average particle size is more preferably 0.2 μm or less. In particular, the thickness is more preferably 0.1 μm or less. The average particle diameter is an average value of the dispersion diameter (cumulative 50% diameter) as the particles actually formed in the dispersion liquid. For example, Microtrac UPA (Microtrac Inc.) is used. Can be measured.

  Furthermore, in the present invention, the epoxy resin having a glycidyl ether skeleton or the resin having an oxazoline group is added as a crosslinking agent, so that glossiness of a color image, prevention of bronzing, and storage stability of the ink composition are achieved. It is particularly preferable from the viewpoint of achieving a color image that is compatible with the properties and further excellent in glossiness.

  The crosslinking agent is preferably a resin that reacts with a carboxyl group (carboxyl group attack type resin) from the viewpoint of further improving dispersibility. For example, a polycarbodiimide type having a carbodiimide group in the molecule, an oxazoline type having an oxazoline group in the molecule, an aziridine type and the like can be mentioned.

  The amount of the crosslinking agent added is such that the copolymer resin and the urethane can be formed from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition as well as formation of a color image having further excellent glossiness. The gel fraction is preferably 20% or more, more preferably 35% or more, based on the total carboxy groups of the resin.

  In addition, the amount of the crosslinking agent added is effective solid weight from the viewpoint of achieving color image glossiness, bronzing prevention, and storage stability of the ink composition, and capable of forming a color image having further excellent glossiness. The ratio (that is, the amount of the crosslinking agent / the total amount of the copolymer resin and the urethane resin) is preferably an amount that is 0.5 / 100 to 50/100, more preferably 0.5 / 100 to 40 /. The amount is 100.

  The weight average molecular weight (Mw) of the urethane resin reacted with the crosslinking agent is a viewpoint capable of forming a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Is preferably 10,000 or more, and more preferably 30,000 or more.

  In the present invention, a surfactant may be used as a dispersant in addition to the polymer dispersant described above. Such surfactants include fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, sulfosuccinate esters, naphthenates, liquid fats. Anionic surfactants such as oil sulfate esters and alkyl allyl sulfonates; Cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts and phosphoniums; polyoxyethylene alkyl ethers and polyoxyethylene alkyls Nonionic surfactants such as esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters and the like can be mentioned. It goes without saying that the surfactant described above also functions as a surfactant by being added to the ink composition.

<Penetration agent>
What can be used as the wetting agent is not particularly limited as long as it has the effect of increasing the dispersion efficiency as described above, and particularly preferable ones include acetylene glycols and acetylene alcohols. , Glycol ethers, alkylene glycols and the like. In addition, lower alcohols and nonionic surfactants can be used, and other alcohols, water-soluble organic solvents, anionic, cationic and amphoteric surfactants, saccharides, etc., alone or in combination And can be used.

  Specific examples of acetylene glycols and acetylene alcohols that can be used as a wetting agent include compounds represented by the following formulas (I) and (II).

  Specific product names include, for example, Surfinol TG, Surfinol 104, Surfinol 420, Surfinol 440, Surfinol 465, Surfinol 485, Surfinol 61, Surfinol 82 (all of which are manufactured by Air Products) Alternatively, acetylinol EH, acetylinol EL, acetylinol EO (all of which are manufactured by Kawaken Fine Chemical Co., Ltd.) can be used.

  Moreover, it is preferable that the addition amount (total amount) in the dispersion step of acetylene glycols and / or acetylene alcohols is in the range of 1/50 or more and twice or less in terms of weight with respect to the pigment. If the addition amount is less than 1/50, a sufficient dispersion treatment effect may not be obtained. On the other hand, when added in a large amount (for example, several times the pigment), the ink prepared to a desired pigment concentration using this pigment dispersion has a surface tension that is unnecessarily lowered and spreads in the vicinity of the inkjet head. Therefore, it becomes difficult to ensure stable discharge characteristics.

  When it is desired to minimize the amount of wetting agent mixed into the ink using this pigment dispersion or to suppress the permeability of the ink, it is preferable to use acetylene alcohols having a low molecular weight as the wetting agent. For example, when the Surfynol 61 is used as a wetting agent, the dispersion can be volatilized by heating after the dispersion step to minimize the remaining amount.

  Examples of glycol ethers that can be suitably used as a wetting agent include diethylene glycol mono (alkyl having 4 to 8 carbon atoms) ether, triethylene glycol mono (alkyl having 4 to 8 carbon atoms) ether, propylene glycol mono (3 to 6 carbon atoms). Alkyl) ether, propylene glycol mono (C 3-6 alkyl) ether, and the like. Specific examples include diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, propylene glycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether. Specific examples of glycol ethers that can be used include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl. Ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol , Propylene glycol monomethyl ether, propylene Glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n -Propyl ether, dipropylene glycol mono-iso-propyl ether and the like.

  Examples of alkylene glycols that can be used as a wetting agent include 1,2- (alkyl having 4 to 10 carbon atoms) diol, 1,3- (alkyl having 4 to 10 carbon atoms) diol, and 1,5- (carbon having 4 to 4 carbon atoms). 10 alkyl) diol and 1,6- (C4-10 alkyl) diol. Specific examples include 1,2-pentanediol, 1,2-hexanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and the like.

  The glycol ethers and / or alkylene glycols have the effect as a wetting agent and also have the characteristics as a solubilizing agent. That is, among the above-mentioned acetylene glycols, when using a compound having low solubility in water alone, the solubility of acetylene glycols is increased by adding glycol ethers in combination, and the amount added is increased. Can be increased. Furthermore, since the glycol ethers and / or alkylene glycols have a bactericidal and antibacterial effect, they can suppress the generation of microorganisms and fungi when mixed in dispersions and inks. it can. Therefore, by adding a certain amount or more (several percent or more in terms of weight) as a wetting agent in the dispersion step, the generation of these microorganisms can be suppressed without newly adding a bactericidal agent or a preservative.

  Specific examples of other wetting agents include, for example, lower alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, t-butyl alcohol, 1-pentanol, 2 -Pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, t-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol.

  Nonionic surfactants include fluorine copolymer, silicone copolymer, acrylic acid copolymer, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene secondary alcohol ether, poly Oxyethylene sterol ether, polyoxyethylene lauryl ether, polyoxyethylene lanolin derivative, ethylene oxide derivative of alkylphenol formalin condensate, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropylene alkyl ether, fatty acid of polyoxyethylene compound Ester type, polyethylene oxide condensation type polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbita Fatty acid esters, propylene glycol fatty acid esters, sucrose fatty acid esters, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, and alkyl amine oxide, and the like.

  Further, specific examples of other wetting agents will be described. Examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, hexylene glycol, Examples thereof include thiodiglycol, glycerin, 1,2,6-hexanetriol. Alcohols include 1-hexanol, 2-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol , 2-octanol, 2-ethyl-1-hexanol, 1-nonanol, 3,5,5-trimethyl-1-hexanol, 1-decanol and the like.

  Examples of anionic surfactants include higher fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, and naphthalene sulfonate salts (Na, K). , Li, Ca), formalin polycondensates, condensates of higher fatty acids and amino acids, dialkyl sulfosuccinates, alkyl sulfosuccinates, naphthenates, alkyl ether carboxylates, acylated peptides, α-olefin sulfonic acids Salt, N-acylmethyl taurine, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate sodium salt, polyoxyethylene alkyl phenyl ether ammonium sulfate salt, monoglycal Fate, alkyl ether phosphate ester salt, alkyl phosphate ester salt and the like can be mentioned.

  Examples of the cationic surfactant include aliphatic amine salts, quaternary ammonium salts, sulfonium salts, and phosphonium salts. Examples of amphoteric surfactants include carboxybetaine type, aminocarboxylate, lecithin and the like. Examples of the saccharide include glucose, mannose, fructose, ribose, xylose, arabinose, lactose, galactose, maltitol, sorbitol, gluconolactone, maltose and the like. The specific examples of the wetting agent that can be used in the present invention have been described above, but the present invention is not limited thereto.

<Pigment>
As the pigment added when preparing the pigment dispersion, carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black are particularly preferable for black ink. Metal pigments such as copper oxide, iron oxide (CI pigment black 11) and titanium oxide, and organic pigments such as aniline black (CI pigment black 1) can also be used.

  For color ink, C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 12 (Disazo Yellow AAA), 13, 14, 17, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 74, 81, 83 (Disazo Yellow HR), 93, 94, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 153, 155, 180, 185, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B (Ca)), 48 : 3 (Permanent Red 2B (Sr)), 48: 4 (Permanent Red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G rake), 83, 88, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (Quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 202, 206, 09,219, C. I. Pigment violet 19, 23, C.I. I. Pigment orange 36, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 1, 56 , 60, 63, C.I. I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc. can be used. Thus, various pigments can be used as the colorant.

  In an embodiment of the present invention, the polymer and C.I. I. It is preferable to use in combination with Pigment Red 170. The polymer and C.I. I. By combining with Pigment Red 170, storage stability, ejection stability, and clogging recovery can be further improved.

  In another embodiment of the present invention, the polymer and C.I. I. It is preferable to use in combination with Pigment Green 36. The polymer and C.I. I. By combining with Pigment Green 36, storage stability, ejection stability, and clogging recovery can be further improved.

  The pigment content in the ink composition is preferably 0.5 to 30% by mass. If the content is less than this, the print density cannot be secured, and if the content is more than this, the viscosity of the ink increases and structural viscosity is generated in the viscosity characteristics, and the ejection stability of the ink from the inkjet head tends to deteriorate. .

  Before the pigment is mixed and dispersed together with the dispersant, the pigment particle size may be refined and uniformed by untreated or kneading treatment. At that time, it is preferable to neutralize the pigment by adding an alkaline compound. After adding the copolymer resin, using a bead mill or a collision-type jet pulverizer, a dispersion step of dispersing the pigment, and in some cases, a urethane resin and a cross-linking agent are added, and a post-processing step of cross-linking treatment, It is preferable to contain.

  After the pretreatment step and before the dispersion step, it is preferable to perform neutralization treatment by adding an alkaline compound to the pigment.

  In the dispersion step, the dispersion treatment is preferably performed by a bead mill or a collision type jet pulverizer as described above. The bead mill may be either a miniaturizable type or a normal type. The dispersion treatment conditions are adjusted as appropriate, and the dispersion treatment is performed until the copolymer resin has the preferred particle size. In the dispersion treatment, an organic solvent may be added and kneaded as necessary. By this step, the copolymer resin is firmly fixed on the surface of the pigment.

  After the dispersion step, it is preferable to go through an impurity removal step by ion exchange treatment or ultrafiltration treatment, followed by a post-treatment step. Ion exchange treatment can remove ionic substances such as cations and anions (divalent metal ions, etc.), and by ultra-treatment, impurities dissolved substances (residual substances during pigment synthesis, excess components in dispersion composition) , Resin not adsorbed on the organic pigment, contamination components, etc.) can be removed. In the ion exchange treatment, a known ion exchange resin is used. The ultratreatment uses a known ultrafiltration membrane and may be either a normal type or a double capacity up type.

  In the post-treatment step, by adding a urethane resin and a crosslinking agent to cause a crosslinking reaction, the copolymer resin and the urethane resin are crosslinked by the crosslinking agent and coat the surface of the pigment (encapsulation). Improves stability, lowers viscosity, and improves adhesion, and stabilizes the pigment dispersion.

<Water and other ingredients>
The ink composition obtained by the production method of the present invention contains water as a main solvent. As the water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. In addition, the use of water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold or bacteria can be prevented when the ink composition is stored for a long period of time.

  The ink composition may contain a pH adjuster. The pH adjusting agent may be added during the addition of the polymer or after the addition of the polymer. Specific examples of pH adjusters include hydroxides of alkali metals such as lithium hydroxide, potassium hydroxide and sodium hydroxide, amines such as ammonia, triethanolamine, tripropanolamine, diethanolamine and monoethanolamine. More preferred are those selected from the group consisting of triethanolamine, tripropanolamine, and mixtures thereof.

  In the present invention, the ink composition is prepared so as to have a pH of 8.0 to 11. By adjusting the pH of the ink composition in such a range, a more excellent gloss feeling can be realized. In order to bring the ink composition to a pH in the above range, it can be suitably adjusted by using the above pH adjuster.

  In addition, the ink composition is compatible with water and stably dissolves the pigment, the pigment dispersant, the above-described polymer, and the above-described pH adjuster and various components described later that are contained in the ink composition. Or it is preferable to contain the water-soluble organic solvent hold | maintained disperse | distributed. The water-soluble organic solvent may be added in the step of preparing the pigment dispersion, or may be added during the addition of the polymer or after the addition of the polymer.

  As a water-soluble organic solvent, the solubility of glycol ethers having low solubility in water and other components is improved, the permeability to a recording medium (for example, paper) is improved, and nozzle clogging is prevented. As the function can be expected, the above-described penetrant may be used. That is, the penetrant added during the preparation of the pigment dispersion can also be added during the preparation of the ink composition to adjust the final addition amount. Preferred water-soluble organic solvents to be added during the preparation of the ink composition include alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol and isopropanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene Glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n- Butyl ether, diethylene glycol mono-n-butyl ether, triethylene Recall mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, Propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether , Propylene glycol mono-n-butyl ether, dipropylene glycol mono-n-butyl ether Glycol ethers such as, formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan, acetin, diacetin, triacetin, sulfolane, and mixtures thereof.

  In the present invention, among the water-soluble organic solvents described above, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, diethylene glycol monopentyl ether, triethylene glycol monopentyl ether, diethylene glycol monohexyl Ether or triethylene glycol monohexyl ether is more preferable. By using the above-mentioned polymer and polymer dispersant together with these glycol ethers, bleeding can be further reduced and printing quality is improved.

  In the present invention, glycols can be added as a water-soluble organic solvent in order to suppress drying of the ink in front of the nozzles of the recording head. Examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, and propylene glycol. , Dipropylene glycol, tripropylene glycol, polyethylene glycol having a molecular weight of 2000 or less, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol 1,2-hexanediol, 1,6-hexanediol, glycerin, mesoerythritol, pentaerythritol and the like.

  In the present invention, it is preferable that 2-butyl-2-ethyl-1,3-propanediol is contained. By using the above polymer and polymer dispersant in combination with 2-butyl-2-ethyl-1,3-propanediol, glossiness is improved when glossy paper is used as a recording medium, and plain paper is used. Even if it is used, the color developability is improved.

  Furthermore, saccharides can be used for the same purpose. Examples include monosaccharides and polysaccharides, in addition to glucose, mannose, fructose, ribose, xylose, arabinose, lactose, galactose, aldonic acid, glucitol, maltose, cellobiose, sucrose, trehalose, maltotriose, etc. Alginic acid and its salts, cyclodextrins, and celluloses can be used. The addition amount may be appropriately determined, but is preferably 0.05% by mass or more and 30% by mass or less. By being in the above range, even when the ink composition is dried at the tip of the head, the clogging can be easily recovered, and the viscosity of the ink composition capable of stable printing can be easily realized. Can do. According to a preferred embodiment of the present invention, more preferable addition amount of glucose, mannose, fructose, ribose, xylose, arabinose, lactose, galactose, aldonic acid, glucitolose, maltose, cellobiose, sucrose, trehalose, maltotriose is 3-20. % By mass. In addition, since addition of alginic acid, its salt, and cellulose tends to increase the viscosity of the ink composition, attention must be paid to the addition amount.

  In the present invention, a surfactant is preferably contained in order to control the permeability. The surfactant to be added is preferably compatible with other components in the ink composition. Further, a surfactant having high penetrability and stability is preferable. As the surfactant, amphoteric surfactants and nonionic surfactants are preferably used.

  Preferred examples of amphoteric surfactants include lauryl dimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine and others Examples include imidazoline derivatives.

  Preferred examples of nonionic surfactants include acetylene glycol surfactants, acetylene alcohol surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl. Ethers such as allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene oleic acid, polyoxyethylene oleic acid ester, polyoxyethylene distearic acid ester , Sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxye Examples include ester surfactants such as lenmonooleate and polyoxyethylene stearate, silicon surfactants such as dimethylpolysiloxane, fluorine-containing surfactants such as other fluorine alkyl esters and perfluoroalkyl carboxylates, and the like. In particular, acetylene glycol surfactants and acetylene alcohol surfactants are preferred. When these surfactants are added to the ink composition, they are preferable because they have a low foaming property and an excellent antifoaming function. Specific examples of the acetylene glycol surfactant and the acetylene alcohol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne- 3,6-diol, 3,5-dimethyl-1-hexyne-3ol, etc. are available, but are also commercially available. For example, Surfynol 104, 82, 465, 485, TG of Air Products Examples include Olfin STG and Olphine E1010 manufactured by Nissin Chemical.

  The addition amount of the surfactant is preferably 0.01% by mass or more and 3% by mass or less with respect to the total amount of the ink composition, and the more preferable upper limit value is 2.0% by mass, and the preferable lower limit value is 0.05% by mass.

  In the present invention, among the surfactants described above, acetylene glycols and / or acetylene alcohols are preferably used. By using these surfactants, bleeding is further reduced and printing quality is improved. In the present invention, acetylene glycols and / or acetylene alcohols added in the above-described pigment dispersion preparation step may be added as a surfactant during the preparation of the ink composition. 7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4,7-diol alkylene oxide adducts, 2,4-dimethyl- One or more selected from alkylene oxide adducts of 5-decyn-4-ol and 2,4-dimethyl-5-decyn-4-ol can be preferably used. These acetylene glycols and / or acetylene alcohols are available as E series such as Olfin 104 series and Olphine E1010 manufactured by Air Products (UK), Surfinol 465 or Surfinol 61 manufactured by Nisshin Chemical. Addition of these improves the drying property of printing, and enables high-speed printing.

  In the present invention, 1,2-alkylene glycol and acetylene glycol surfactants and / or acetylene alcohol surfactants, glycol ethers and acetylene glycol surfactants and / or acetylene alcohol surfactants are used. By using a plurality, the bleeding is further reduced.

  In addition, a pH buffer, an antioxidant, an ultraviolet absorber, an antiseptic or antifungal agent, a chelating agent, and the like may be added. Specific examples of the pH buffering agent include collidine, imidazole, phosphoric acid, 3- (N-morpholino) propanesulfonic acid, tris (hydroxymethyl) aminomethane, boric acid and the like.

  Specific examples of the antioxidant or ultraviolet absorber include allophanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret, L-ascorbic acid and its salts, etc., manufactured by Ciba Geigy Examples include Tinuvin 328, 900, 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035, MD1024, or lanthanide oxides.

  Specific examples of preservatives or fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazoline-3- ON (Avecia's Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like. Specific examples of the chelating agent include ethylenediaminetetraacetic acid (EDTA).

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited to these.

<Preparation of pigment dispersion>
As a pigment, C.I. I. 20 parts by mass of Pigment Green 36, 3 parts by mass of a styrene-methylstyrene-acrylic acid copolymer (acid value 160, weight average molecular weight 8000, glass transition temperature 75 ° C.), 15 parts by mass of glycerin, and isopropyl alcohol 4 parts by mass and 1.25 parts by mass of Surfynol 104 (produced by Air Products) as a penetrant were charged in a pressure kneader and kneaded at room temperature for 10 hours to prepare a pigment kneaded product.

  Next, 42 parts by mass of the pigment kneaded product, 3 parts by mass of triethanolamine as a neutralizing agent, and 55 parts by mass of ion-exchanged water were charged into a stirrer, and the mixture was superheated at 95 ° C. for 2 hours, before pigment dispersion. An adjustment liquid was prepared. This pre-pigment dispersion adjustment liquid was successively charged into a bead mill capable of making fine particles (having the ability to produce 50 nm organic pigment fine particles) and subjected to a 3-pass treatment to prepare a post-pigment dispersion preparation. The obtained pigment-dispersed preparation was adjusted to pH 8.5 with sodium hydroxide, centrifuged at 25000 G for 5 minutes to remove coarse particles, and a re-adjusted product was prepared after pigment dispersion.

  Next, 100 parts by mass of the obtained re-adjusted product after dispersion, 10 parts by mass of a polyester-based polyurethane resin (solid content 30%, acid value 50, triethylamine neutralization), and 20% glycidyl ether as a crosslinking agent are used as a skeleton. An epoxy resin (epoxy equivalent 200, acid value 50, triethylamine neutralized) 8 parts by mass was charged into a stirrer and stirred at 90 ° C. for 5 hours to crosslink the resin in the dispersion to obtain a crosslinked preparation. . Next, a pigment dispersion was obtained by adjusting with ion-exchanged water and potassium hydroxide so that the pigment solid content concentration was 10% and the pH was about 9.

  The obtained pigment dispersion was about 15 parts of styrene-methylstyrene-acrylic acid copolymer and about 15 parts of polyester polyurethane resin with respect to 100 parts of pigment.

<Preparation of polymer>
The inside of a 2000 ml separable flask equipped with a stirrer, a reflux tube, a thermometer and a dropping funnel was purged with nitrogen, and then diethylene glycol monomethyl ether was charged into the 200.0 parts by mass flask and heated to 80 ° C. while stirring. . Next, in the dropping funnel, 200.0 parts by mass of diethylene glycol monomethyl ether, 483.0 parts by mass of benzyl acrylate, 16.4 parts by mass of methacrylic acid, 13.9 parts by mass of acrylic acid, 7.6 parts by mass of oxy (2-ethylhexanoate) was added and dropped into the flask at 80 ° C. over 4 hours to react the monomer. After completion of the dropwise addition, the mixture was kept at 80 ° C. for 1 hour, then 0.8 parts by mass of t-butylperoxy (2-ethylhexanoate) was added, and further reacted at 80 ° C. for 1 hour. Thereafter, diethylene glycol monomethyl ether was removed by distillation under reduced pressure. Subsequently, 600.0 parts by mass of methyl ethyl ketone was added to the flask to obtain a polymer solution having a resin solid content of 50%.

  A part of the obtained polymer solution was sampled and dried for 1 hour with a high-temperature dryer at 105 ° C., and then the acid value of the obtained polymer was measured to be 55 mgKOH / g. Moreover, when the molecular weight of the polymer was measured, the weight average molecular weight (Mw) was 22,000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was 1.92.

<Preparation of ink composition>
Using the polymer solution (solid content 50%) obtained as described above and each pigment dispersion, each component was added according to the composition shown in Table 2 below so that the total amount was 100 parts by mass, and the mixture was stirred for 2 hours. did. Then, the ink composition of Examples 1-40 and Comparative Examples 1 and 2 was obtained by filtering with a membrane filter (trade name, manufactured by Nippon Millipore Limited) having a pore size of about 1.2 μm. In the table, DEGmBE represents diethylene glycol monobutyl ether, TEGmBE represents triethylene glycol monobutyl ether, PGmBE represents propylene glycol monobutyl ether, DPGmBE represents dipropylene glycol monobutyl ether, and BEPD represents 2-butyl-2 -Represents ethyl-1,3-propanediol. Moreover, all the numbers in the table indicate the blending ratio based on weight.

<Evaluation of storage stability>
The viscosity immediately after the preparation of each ink composition (initial viscosity) and the viscosity after the ink composition was allowed to stand in an environment of 70 ° C. for 2 weeks were measured using a rolling ball viscometer (AMVn, manufactured by Anton Paar). It measured using.

  From the measurement results, the value of viscosity (mPa / s) / initial viscosity (mPa / s) after standing for 2 weeks was calculated. The evaluation results were as shown in Table 3 below.

<Evaluation of ejection stability>
Using an inkjet printer (PM930c, manufactured by Seiko Epson Corporation), in an atmosphere of 35 ° C. and humidity of 35% RH, an A4 version of Xerox P (trade name, manufactured by Fuji Xerox Co., Ltd.) is used as a Microsoft Word document (character size). 11, standard, MSP Gothic) was printed at 500 pages at a rate of 4000 characters / page. The evaluation criteria were as follows.
AA: No printing disorder A: There is printing disorder at one place B: There is printing disorder at 2-3 places C: There is printing disorder at 4-5 places D: There are printing disorders at 6 places or more Evaluation results Was as shown in Table 3 below.

<Evaluation of clogging recovery ability>
After continuously printing for 10 minutes using an ink jet printer (EM930c, manufactured by Seiko Epson Corporation) and confirming that ink is ejected normally from all nozzles, the ink cartridge is removed, and the recording head is attached to the head cap. The sample was left in a 50 ° C. environment for 3 months. After leaving, the cleaning operation was repeated until all nozzles ejected at the same level as the initial stage, and the ease of recovery was evaluated according to the following criteria.
A: Recovered to the same level as the initial level after 3 or fewer cleaning operations B: Recovered to the same level as the initial level after 4 to 5 cleaning operations C: Recovered to the same level as the initial level after 10 or fewer cleaning operations D: Performing the cleaning operation Also, all the nozzles were clogged and did not discharge. The evaluation results were as shown in Table 3 below.

Claims (7)

A method for producing an ink composition for ink jet recording, comprising at least a pigment, a dispersant for dispersing the pigment, a polymer, a penetrant, and water,
At least a pigment, a dispersant for dispersing the pigment, a penetrant, and water are subjected to a dispersion treatment in a mixed liquid state to prepare a pigment dispersion,
Adding the polymer to the pigment dispersion.   The method according to claim 1, wherein the penetrant is at least one selected from the group consisting of acetylene glycols, acetylene alcohols, polyorganosiloxanes, glycol ethers, and alkylene glycols.   The method according to claim 1 or 2, wherein a penetrant 1/50 to 2 times in terms of weight is added to the pigment dispersion in terms of weight.   The polymer comprises at least 50% by mass of benzyl acrylate and 15% by mass or less (meth) acrylic acid as monomer components, and the acid value thereof is in the range of 50 to 200 mgKOH / g, The method as described in any one of Claims 1-3 whose weight average molecular weights are 20,000-120,000.   The dispersant is styrene- (meth) acrylic acid copolymer resin, styrene-methylstyrene- (meth) acrylic acid copolymer resin or styrene-maleic acid copolymer resin, (meth) acrylic acid- (meth) acrylic ester. The copolymer resin selected from the group consisting of a copolymer resin and a styrene- (meth) acrylic acid- (meth) acrylic ester copolymer resin, and a urethane resin. The method according to claim 1.   The method as described in any one of Claims 1-5 whose weight ratio of the copolymer resin of said dispersing agent and urethane resin is 1 / 2-2 / 1.   The ink composition for inkjet recording obtained by the method as described in any one of Claims 1-6.