JP2012046680A - Nonaqueous ink composition for ink jet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous pigment ink for inkjet which is excellent in wiping durability and image density.SOLUTION: The nonaqueous ink composition of inkjet recording at least includes (A) a pigment, (B) an alkyl (meth)acrylate copolymer having an acidic group, (C) an organic solvent, and (D) a basic compound, wherein (B) the alkyl (meth)acrylate copolymer having the acidic group is an acrylic polymer which includes an alkyl (meth)acrylate unit which has an at least 12C alkyl group, an (meth)acrylate unit which has a urethane group, and a (meth)acrylate unit which has the acidic group.

Description

The present invention relates to a non-aqueous ink composition for ink jet and a pigment dispersant for non-aqueous ink jet ink, and in particular, a non-aqueous ink composition for ink jet and a pigment dispersion excellent in wiping durability and capable of obtaining a high image density. It relates to the agent.

Color materials for inks used in ink jet recording systems are roughly classified into those using pigments and those using dyes. Ink with pigments as color materials because of its excellent weather resistance and water resistance. Tend to increase.

From the viewpoint of the solvent, the ink is large, and it is roughly classified into an aqueous type and a non-aqueous type. However, the non-aqueous ink is suitable for high-speed printing because of its dryness and no cockling as compared with the aqueous type.

Non-aqueous ink pigment dispersants can be broadly divided into solvent-soluble types and solvent-dispersed types, but in the case of inks that use solvent-soluble pigment dispersants, pigment dispersion Since the agent has high affinity with not only the pigment but also the solvent, the pigment tends to be easily drawn into the recording medium when the solvent penetrates into the recording medium after landing. As a result, the image density is lowered and the showthrough is likely to occur.

Therefore, as a non-aqueous ink composition using a pigment dispersant of a type dispersed in a solvent, the pigment (pigment dispersant) and an organic solvent are included, and the pigment dispersant has an alkyl group having 12 or more carbon atoms (meth). An acrylic polymer comprising an acrylate unit and a (meth) acrylate unit having a urethane group, wherein the acrylic polymer reacts with an alkyl (meth) acrylate having an alkyl group having 12 or more carbon atoms and an amino group. There has been proposed a non-aqueous ink composition which is a copolymer of a monomer mixture containing a reactive (meth) acrylate having a functional group that can be obtained (Patent Document 1).

JP 2010-001452 A

With the non-aqueous ink composition, a high image density can be obtained, but the wiping durability against the nozzle plate is insufficient.

According to the study by the present inventors, the reason why the wiping durability of the nozzle plate deteriorates is that the pigment in the ink adhering to the nozzle plate becomes an abrasive, and the ink repellent film on the nozzle plate is removed by the wiping operation for head cleaning. It turns out that it is to be.
It was found that the deterioration of the wiping durability was remarkable particularly with carbon black among the pigments.

An object of the present invention is to provide a non-aqueous ink composition that is further improved in terms of wiping durability while ensuring a high image density.

According to one aspect of the present invention, there is provided a non-aqueous ink composition for inkjet recording, comprising at least (A) a pigment, (B) an alkyl (meth) acrylate copolymer having an acidic group, and (C). A non-aqueous ink composition comprising an organic solvent and (D) a basic compound,
The alkyl (meth) acrylate copolymer having an acidic group (B) has an alkyl (meth) acrylate unit having an alkyl group having 12 or more carbon atoms, a (meth) acrylate unit having a urethane group, and an acidic group. There is provided a non-aqueous ink composition that is an acrylic polymer comprising (meth) acrylate units.

According to another aspect of the present invention, an alkyl (meth) acrylate unit having an alkyl group having 12 or more carbon atoms, a (meth) acrylate unit having a urethane group, and a (meth) acrylate unit having an acidic group, A pigment dispersant for a non-aqueous ink composition is provided, wherein the acidic group of the alkyl (meth) acrylate copolymer having an acidic group is neutralized with a basic compound. The

The reason why the wiping durability is improved with the non-aqueous ink composition for inkjet is not clear, but (B) an alkyl (meth) acrylate having an acidic group in a state where the acidic group is neutralized with a basic compound. By adsorbing the copolymer to the pigment surface, the contact between the pigment and the nozzle plate is suppressed, the ink repellent film on the nozzle plate is hardly scraped by the pigment, and it is presumed that the wiping durability is improved. It is presumed that the alkyl (meth) acrylate copolymer having an acidic group has a large steric hindrance by binding a basic compound and further suppresses the contact between the pigment and the nozzle plate.

The non-aqueous ink composition for inkjet according to the present invention (hereinafter sometimes simply referred to as “ink composition”) comprises (A) a pigment, (B) an alkyl (meth) acrylate copolymer having an acidic group, and (C The combination of the organic solvent and the basic compound (D) can form a high density image and improve the wiping resistance to the nozzle plate.

<(A) Pigment>
The (A) pigment used in the present invention may be arbitrary. Preferably, a pigment for black ink is used in that the effect of the present invention is more remarkable. Examples of such pigments include carbon blacks such as furnace black, lamp black, acetylene black and channel black; metals or metal oxides such as copper, iron and titanium oxide; organic pigments such as orthonitroaniline black. it can. These may be used alone or in any mixture. In that the resulting higher print density, dibutyl phthalate as measured according to JIS K6221 (DBP) oil absorption is 80cm ³ / 100g~140cm ³ / 100g, and the nitrogen adsorption specific surface area measured in accordance with JIS K6217 is 100 m ² / g A carbon black pigment of ˜200 m ² / g is preferred.

The average particle diameter of the pigment is preferably 300 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less from the viewpoint of ejection stability and storage stability. Here, the average particle diameter of the pigment can be measured with a dynamic light scattering particle size distribution analyzer LB-500 (manufactured by Horiba, Ltd.) or the like.

The content of the pigment in the ink composition is usually 0.1 to 20% by weight, preferably 1 to 15% by weight from the viewpoint of printing density and ink viscosity, and preferably 5 to 10% by weight. Even more preferred. When the amount is less than 0.1% by weight, it is difficult to achieve a sufficient image density, and when it is more than 20% by weight, it is difficult to ensure ejection stability and storage stability.

<(B) Alkyl (meth) acrylate copolymer having acidic group>
The alkyl (meth) acrylate copolymer having an acidic group (B) used in the present invention is an alkyl (meth) acrylate unit having an alkyl group having 12 or more carbon atoms, a (meth) acrylate unit having a urethane group, An acrylic polymer containing an acidic group-containing (meth) acrylate unit, (B1) an alkyl (meth) acrylate having an alkyl group having 12 or more carbon atoms, and (B2) a functional group capable of reacting with an amino group. In a copolymer of a monomer mixture containing a reactive (meth) acrylate and (B3) an acidic group-containing (meth) acrylate, the functional group capable of reacting with the amino group, an amino alcohol, and a polyvalent isocyanate compound Those in which the urethane group is introduced by reaction are preferred. The urethane base is considered to be excellent in affinity with the pigment (A) because of its high polarity.

Examples of the (B1) alkyl (meth) acrylate having an alkyl group having 12 or more carbon atoms include lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, and isolauryl (meth) acrylate. And iso (meth) stearyl acrylate. By providing the alkyl group having 12 or more carbon atoms, it is excellent in affinity with (C) an organic solvent.

The (B1) alkyl (meth) acrylate having an alkyl group having 12 or more carbon atoms is preferably contained in an amount of 30% by weight or more based on the total weight of the monomer (weight of the trunk polymer), more preferably 40 to 95. % By weight, most preferably 50-90% by weight.

In the reactive (meth) acrylate having a functional group capable of reacting with the (B2) amino group, examples of the functional group capable of reacting with the amino group include a glycidyl group, a vinyl group, and a (meth) acryloyl group. Of these, a glycidyl group is preferred.

Examples of the reactive (meth) acrylate having a functional group capable of reacting with the (B2) amino group include glycidyl (meth) acrylate, glycidyl ether of hydroxyalkyl (meth) acrylate, such as 4-hydroxybutyl acrylate glycidyl ether, 3 , 4-epoxycyclohexylmethyl (meth) acrylate, etc., among which glycidyl methacrylate is preferred.

The (B2) reactive (meth) acrylate having a functional group capable of reacting with an amino group is preferably contained in an amount of 1 to 30% by weight of the total monomer weight (trunk polymer weight), more preferably 3 to 25% by weight, most preferably 10 to 20% by weight.

Examples of the acidic group in the (B3) (meth) acrylate having an acidic group include a carboxyl group, a phosphoric acid group, a phosphate ester group, and a sulfone group, and among these, a carboxyl group is preferable.

Examples of the (B3) (meth) acrylate having an acidic group include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid. Among these, methacrylic acid is preferable.

The (B3) (meth) acrylate having an acidic group is preferably contained in an amount of 0.1 to 15% by weight, more preferably 0.3 to 10% by weight, based on the total amount of monomers (total amount of trunk polymer). Most preferably, it is 1 to 5% by weight. When the amount is less than 0.1% by weight, sufficient wiping durability is difficult to be secured, and when it is more than 15% by weight, storage stability is difficult to be secured.

In the first stage reaction in the preparation of (B) an alkyl (meth) acrylate copolymer having an acidic group, (B1) an alkyl (meth) acrylate having an alkyl group having 12 or more carbon atoms, Second-stage reaction is performed by performing radical polymerization using the (B2) reactive (meth) acrylate having a functional group capable of reacting with an amino group and the (B3) (meth) acrylate having an acidic group. The compound having a functional group capable of reacting with an amino group and an alcoholic hydroxyl group is reacted with the copolymer obtained in the first stage, and the alcoholic hydroxyl group and the polyvalent isocyanate compound are reacted in the third stage reaction. It can obtain by making it react.

Further, as a comonomer, a β-diketone group (—C (═O) —C—C (═O) —) or a β-keto acid ester group (—C (═O) —C—C (═O) OR, When (meth) acrylate having R is a hydrocarbon group, it is possible to prepare an ink having a lower viscosity. Thereby, when selecting the solvent of an ink, the restriction | limiting based on the viscosity value of the solvent itself decreases, and the choice range of a non-aqueous solvent can be expanded. In addition, when blending a fixing resin or an additive as necessary, the allowable range of ink viscosity increase by the blended components is widened, and the degree of freedom of ink formulation can be expanded. Further, the β-diketone group or β-keto ester group suppresses the aggregation of the pigment, thereby suppressing the back-through and simultaneously improving the printing density.

Examples of the (meth) acrylate having a β-diketone group or β-keto acid ester group include acetoacetoxyalkyl (meth) acrylate such as acetoacetoxyethyl (meth) acrylate, hexadione (meth) acrylate, acetoacetoxyethyl (meth) acrylamide And acetoacetoxyalkyl (meth) acrylamide. These may be used alone or in combination of two or more.

The amount of the (meth) acrylate having a β-diketone group or β-keto acid ester group is preferably 3 to 30% by mass, more preferably 5 to 20% by mass in the monomer mixture.

In addition, examples of the comonomer include styrene monomers such as styrene and α-methylstyrene; vinyl ether polymers such as vinyl acetate, vinyl benzoate, and butyl vinyl ether; maleate ester, fumarate ester, acrylonitrile, methacrylonitrile, α -Olefin etc. are mentioned. Further, alkyl (meth) acrylates having an alkyl chain length of less than 12 carbons such as 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, tert-octyl (meth) acrylate, and the like can also be used. These can be used alone or in combination of two or more.

Each of the above monomers can be easily polymerized by known radical copolymerization. The reaction system is preferably carried out by solution polymerization or dispersion polymerization.
In this case, in order to make the molecular weight of the acrylic polymer after polymerization within the above-mentioned preferred range, it is effective to use a chain transfer agent in combination during the polymerization. Examples of the chain transfer agent include thiols such as n-butyl mercaptan, lauryl mercaptan, stearyl mercaptan, and cyclohexyl mercaptan.

Examples of the polymerization initiator include azo compounds such as AIBN (azobisisobutyronitrile), t-butylperoxybenzoate, t-butylperoxy-2-ethylhexanoate (Perbutyl O, manufactured by NOF Corporation), etc. Known thermal polymerization initiators such as peroxides can be used. In addition, a photopolymerization initiator that generates radicals upon irradiation with active energy rays can be used.
As a polymerization solvent used for solution polymerization, for example, a petroleum solvent (aroma free (AF) system) or the like can be used. As the polymerization solvent, it is preferable to select one or more kinds of solvents (described later) that can be used as they are as a non-aqueous solvent for the ink.
In the polymerization reaction, other commonly used polymerization inhibitors, polymerization accelerators, dispersants and the like can also be added to the reaction system.

Next, in the obtained copolymer (trunk polymer), a urethane group is introduced by a reaction between a compound having a functional group capable of reacting with an amino group and an alcoholic hydroxyl group and a polyvalent isocyanate compound. As the compound having a functional group capable of reacting with an amino group and an alcoholic hydroxyl group, an amino alcohol is preferably used. The reactive (meth) acrylate in which the amino group of the amino alcohol has a functional group capable of reacting with the amino group reacts with and binds to the functional group capable of reacting with the amino group. Then, the hydroxyl group of the amino alcohol, isocyanate ester group of the polyvalent isocyanate compound ^{(R 1 N = C = O} ) is an addition reaction with R-OH, a urethane group (urethane bond) (carbamic acid ^ester: R 1 NHCOOR ) Is obtained.
Here, R- represents an amino alcohol moiety bonded to the functional group of the trunk polymer.
By the above, the urethane group which acts as a pigment adsorption group is introduced with respect to the trunk polymer which does not have pigment adsorption ability.

Examples of amino alcohols include monomethylethanolamine, diethanolamine, and diisopropanolamine. Among them, since the number of urethane groups formed by providing two alcoholic hydroxyl groups can be increased, dialkanolamines represented by the general formula (HOR) ₂ NH (R is a divalent hydrocarbon group) (2 Secondary alkanolamine). These amino alcohols can also be used in combination of multiple types.

This amino alcohol is 0.05 to 1 from the viewpoint of introducing an appropriate amount of urethane group to the functional group capable of reacting with the amino group of the reactive (meth) acrylate having a functional group capable of reacting with the amino group. It is preferable to make it react by molar equivalent, and it is more preferable to make it react by 0.1-1 molar equivalent. When the amino alcohol is less than 1 molar equivalent, an unreacted functional group remains in the reactive (meth) acrylate having a functional group capable of reacting with an amino group, but the remaining functional group serves as an adsorption group for the pigment. It is thought to act.

Examples of the polyvalent isocyanate compound include polyvalent isocyanates having an alicyclic group such as a cycloalkylene group or an aromatic group such as an arylene group, such as 1,6-diisocyanatohexane, 1,3-bis (isocyanate). Methyl) benzene, 1,3-bis (isocyanatomethyl) cyclohexane, 1,5-naphthalene diisocyanate, and mixtures thereof. The isocyanate compound is preferably reacted in an equivalent amount (0.98 to 1.02 molar equivalent) with respect to the alcoholic hydroxyl group so as not to leave an unreacted alcoholic hydroxyl group.

  In this way, for the copolymer part (trunk polymer) soluble in the solvent, it is unnecessary for the solvent based on the amino alcohol bonded to the reactive (meth) acrylate having a functional group capable of reacting with the amino group. A urethane side chain part (graft part) is formed, which forms a dispersed particle nucleus. This process ultimately forms a copolymer wrapped in a shell structure (backbone polymer) that can be solvated in the solvent.

In the above reaction, it is also preferable to add a polyhydric alcohol and react the polyhydric alcohol with the polyvalent isocyanate compound. By adding a polyhydric alcohol, formation of a urethane group is repeated, and a polyurethane side chain (branched polymer) that becomes a more polar side chain can be obtained.
Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, dipropylene glycol, 1,3 propanediol, polyethylene glycol, polypropylene glycol and the like, and a plurality of types can be used.
The polyhydric alcohol is preferably reacted at 0 to 20 molar equivalents with respect to amino alcohol, more preferably at 1 to 10 molar equivalents.

  The mass ratio of the copolymer part (trunk polymer) and the introduced urethane base part (branch or branch polymer) in the acrylic polymer is preferably 60:40 to 99: 1, and 70:30 to 99: 1 is more preferable. The mass of the copolymer part in the acrylic polymer is the total mass of the monomers used in the copolymerization, and the mass of the introduced urethane base is the mass of the amino alcohol and polyvalent isocyanate compound used in the reaction, When polyhydric alcohol is used, this is the total mass added.

  The urethane base has a structure represented by, for example, the following formulas (1), (2), (3), or a combination thereof. That is, the urethane base part comprises two urethane bonds, and constitutes a crosslinked part in which both ends are bonded to a poly (meth) acrylate chain represented by the formula (4) via an amino alcohol or polyhydric alcohol residue.

Formula (1)
(In Formula (1), R ¹ is an alkylene group having 2 to 10 carbon atoms, R ² is a divalent hydrocarbon group having 6 to 16 carbon atoms, k is 0 or 1, and m is 1 or 2) , N is 0 or 1.)

Formula (2)
(In the formula (2), R ³ is an alkylene group or oxyalkylene group having 2 to 20 carbon atoms.)

Formula (3)

Formula (4)

The urethane group part is contained in 1 to 40% by weight, preferably 1 to 30% by weight, more preferably 5 to 20% by weight in the alkyl (meth) acrylate copolymer having an acidic group (B). The weight of the urethane base is the total weight of amino alcohol, polyhydric alcohol and isocyanate compound used in the reaction.

(B) The alkyl (meth) acrylate copolymer having an acidic group has a weight average molecular weight measured by GPC of 5000 to 50,000, preferably 8000 to 30,000. If the molecular weight is less than the lower limit, the storage stability of the ink composition tends to deteriorate. If the molecular weight exceeds the upper limit, the viscosity of the ink composition is high and the inkjet ejection stability is high. Tend to get worse. The average particle size measured by dynamic light scattering method _{(D 50)} is 50 to 300 nm, preferably 70 to 200 nm,.

The content of the alkyl (meth) acrylate copolymer having an acidic group (B) in the ink composition is preferably 0.1 to 20% by weight, more preferably 2 to 15% by weight or more. Preferably, it is more preferably 3 to 10% by weight. When the amount is less than 0.1% by weight, it is difficult to ensure sufficient pigment dispersibility. When the amount is more than 20% by weight, not only the viscosity of the ink is increased, but also storage stability in a high temperature environment may be deteriorated. .

<(C) Organic solvent>
The organic solvent used in the present invention may be either a nonpolar solvent or a polar solvent, but is preferably composed of 30 to 70% by weight of a nonpolar solvent and 70 to 30% by weight of a polar solvent. More preferably, it is composed of a weight percent non-polar solvent and 60-40 weight percent polar solvent. The organic solvent is preferably an organic solvent having 12 to 30 carbon atoms. An organic solvent having less than 12 carbon atoms is not preferable from the viewpoint of safety because it easily volatilizes. Those having a 50% distillation point of 150 ° C. or higher are preferably used. The 50% distillation point means a temperature at which 50% by weight of a solvent is volatilized, which is measured according to JIS K0066 “Testing method for distillation of chemical products”. More preferably, those having a 50% distillation point of 160 ° C. or higher, most preferably 230 ° C. or higher are used. Many organic solvents having 30 or more carbon atoms have a high viscosity and are difficult to eject, which is not preferable.

  Examples of the organic solvent include nonpolar organic solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents, and polar solvents such as ester solvents and alcohol solvents. .

Examples of the aliphatic hydrocarbon solvent and alicyclic hydrocarbon solvent include, for example, “Teclean N-16, Teclean N-20, Teclean N-22, Nisseki Naphthezol L, Nissho Naphthezol M, manufactured by Nippon Petroleum Corporation. Nisseki Naphthezol H, No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent H, Nisseki Isosol 300, Nisseki Isosol 400, AF-4, AF-5, AF-6, AF-7 ", manufactured by Exxon “Isopar (Isopar) G, IsoparH, IsoparL, IsoparM, ExxsolD40, ExxsolD80, ExxsolD100, ExxsolD130, ExxsolD140” and the like. Examples of the aromatic hydrocarbon solvent include “Nisseki Clean Sol G” (alkylbenzene) manufactured by Nippon Petroleum Co., Ltd., “Solvesso 200” manufactured by Exxon, and the like.

Examples of ester solvents include methyl laurate, isopropyl laurate, hexyl laurate, isopropyl myristate, isopropyl palmitate, isooctyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, methyl linoleate, Isobutyl linoleate, ethyl linoleate, isopropyl isostearate, soybean oil methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, propylene glycol monocaprate, tri-2-ethyl Examples include trimethylolpropane hexanoate and glyceryl tri-2-ethylhexanoate. Preferably, ester solvents such as isopropyl isostearate, isooctyl palmitate, and hexyl laurate are used.

Examples of the alcohol solvent include isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol and the like.

The content of the organic solvent in the ink composition is usually 60 to 99% by weight, preferably 70 to 95% by weight, and more preferably 80 to 90% by weight.

<(D) Basic compound>
Although the basic compound used by this invention will not be specifically limited if it is an oil-soluble amine compound which can neutralize the acidic group of (B), An alkylamine is mentioned typically. Such an alkylamine is a compound containing one amino group in one molecule and 1 to 3 alkyl groups bonded to the amino group, that is, any of primary, secondary and tertiary amine compounds. The alkyl group is preferably a long chain alkyl group having 8 or more carbon atoms.

The content of the basic compound in the ink composition is usually 0.001 to 10% by weight, preferably 0.01 to 1% by weight from the viewpoint of printing density and ink viscosity, The content is more preferably 0.5% by weight, and a content that can be neutralized by 0.1 to 2 molar equivalents with respect to the acidic group (B) is preferred.

  Specific examples of the alkylamine include dioctylamine, dilaurylmethylamine, trioctylamine, dimethyllaurylamine, dimethylmyristylamine, dimethylpalmitylamine and the like. The molecular weight of the alkylamine is preferably 150 to 800.

<Optional component>
The ink of the present invention can contain an arbitrary component as long as the effects of the present invention are not impaired. For example, as resins other than the component (B), acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, rosin resins, rosin ester resins, ethylene-vinyl acetate resins, petroleum resins, coumarone Indene resin, terpene phenol resin, phenol resin, urethane resin, melamine resin, urea resin, epoxy resin, cellulose resin, vinyl acetate resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral resin, Maleic acid resin, fumaric acid resin, hydroxyl group-containing carboxylic acid ester, salt of long chain polyaminoamide and high molecular weight acid ester, salt of high molecular weight polycarboxylic acid, salt of long chain polyaminoamide and polar acid ester, high molecular weight unsaturated acid Ester, polymer copolymer, modified polyurethane, modified polyacrylate, polyester It contains teller ester type anionic activator, naphthalenesulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonylphenyl ether, polyester polyamine, stearylamine acetate, etc. Can do.

  A nozzle clogging preventive agent, an antioxidant, a conductivity adjusting agent, a viscosity adjusting agent, a surface tension adjusting agent, an oxygen absorbent and the like can be appropriately added. These types are not particularly limited, and those used in the field can be used.

  The ink composition of the present invention is added to a disperser such as a bead mill, the component (A), a mixture of the component (B) and the component (C), and the component (D) and an additional component for adjusting the viscosity of the ink composition. The component (C), an optional component as desired, is added all at once or divided and stirred and mixed, and if desired, it is obtained by filtering with a membrane filter or the like.

  The suitable range of the viscosity of the ink varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, and the like, but in general, it is preferably 5 to 30 mPa · s at 23 ° C., and preferably 5 to 15 mPa · s. Is more preferable, and is most preferably about 10 mPa · s. Here, the viscosity represents a value at 10 Pa when the shear stress is increased from 0 Pa at a rate of 0.1 Pa / s at 23 ° C.

The ink jet recording apparatus to which the ink composition of the present invention is applied may be of any system such as a piezo system, an electrostatic system, or a thermal system. When an ink jet recording apparatus is used, it is preferable that ink according to the present invention is ejected from an ink jet head based on a digital signal, and the ejected ink droplets are attached to a recording medium.

<(B) Preparation of alkyl (meth) acrylate copolymer having acidic group>
In a 300 ml four-necked flask, 70.4 g of AF-4 (naphthenic solvent; manufactured by Shin Nippon Oil Co., Ltd.) was placed, and the temperature was raised to 110 ° C. with aeration of nitrogen gas and stirring. Next, while maintaining the temperature at 110 ° C., the mixture shown in Table 1 was put into the four-necked flask, and 16.7 g of AF-4 and 4 g of perbutyl O (t-butylperoxy 2-ethylhexano) were added thereto. A mixture of Eight; manufactured by NOF Corporation was added dropwise over 3 hours. Thereafter, 0.2 g of perbutyl O was added after 1 hour and 2 hours while maintaining at 110 ° C. Further, aging was performed at 110 ° C. for 1 hour and diluted with 12.9 g of AF-4 to obtain a colorless and transparent copolymer solution having a solid content of 50% as a trunk polymer.

A 500 mL four-necked flask is charged with 100 g of the above trunk polymer (solid content 50 g), 84.3 g of IPIS (isopropyl isostearate, manufactured by Nikko Chemicals), 0.86 g of propylene glycol, and 1.05 g of diethanolamine, and nitrogen gas. The temperature was raised to 110 ° C. with aeration and stirring. While maintaining at 110 ° C. for 1 hour, the glycidyl group of the copolymer was reacted with diethanolamine. To the obtained reaction product, 0.08 g of dibutyltin dilaurate was added, and 3.84 g of Takenate 600 (1,3-bis (isocyanatomethyl) cyclohexane, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) and 34.56 g of The IPIS mixture was added dropwise over 1 hour. After the dropwise addition, the temperature was raised to 120 ° C., reacted for 6 hours, cooled, and 83.01 g of AF-4 (naphthenic solvent; manufactured by Shin Nippon Oil Co., Ltd.) was added. A non-aqueous dispersion was obtained. The urethane base part of the obtained copolymer was about 10% by weight of the copolymer.

<Examples 1-4, Comparative Examples 1-4>
In accordance with the formulation shown in Table 3, each component is put in a glass container, and 80 g of zirconia beads (φ0.5 mm) are put in this container, and run for 2 hours at a frequency of 60 Hz using a rocking mill (RM05S type manufactured by Seiwa Giken). A product was prepared. In Tables 3 and 4, the details of the product indicated by the trade name are as follows.
MA-100: carbon black, DBP oil absorption of 100 cm ^3/100 g, the nitrogen adsorption specific surface area 110m ² / g, manufactured by Mitsubishi Chemical Corporation S28000 (Solsperse 28000): Polyamide-based dispersing agent, Lubrizol Corporation DOA: dioctylamine, Wako Pure Chemical Industrial Co., Ltd. TOA: Trioctylamine, Wako Pure Chemical Industries, Ltd. AF-4: Naphthenic solvent, Nippon Oil Co., Ltd. IPIS: Ester solvent, Nikko Chemicals Co., Ltd. Lisonol 16SP: Alcohol solvent, higher alcohol industrial stock Made by company

  The obtained ink composition was evaluated by the following method. The results are shown in Table 3.

<Evaluation of image density and show-through>
Each ink composition is loaded into an inkjet printer “HC5500” (trade name: manufactured by Riso Kagaku Kogyo Co., Ltd.) and 1 dot 30 pL is applied to plain paper (ideal paper thin mouth (product name: manufactured by Oki Kagaku Kogyo Co., Ltd.)). A solid image of 300 dpi × 300 dpi was formed with a droplet amount, and the OD values of the front and back surfaces of the obtained solid image were measured using an optical densitometer (RD920, manufactured by Macbeth Co., Ltd.) and evaluated according to the following criteria. A high OD value on the front surface is preferable because an image density is high, and a low OD value on the back surface is less likely to show through.
Image density (Table OD)
A: 1.15 or more, B: 1.08 or more and less than 1.15, C: less than 1.08 show-through (back OD)
A: Less than 0.29, B: 0.29 or more to less than 0.35, C: 0.35 or more

<Evaluation of wiping durability>
After the ejection stability test, the head cleaning was performed a predetermined number of times by normal cleaning for head maintenance, and the ink repellency of the portion in contact with the wiping blade was visually evaluated.
A: Ink repellency was maintained at all the portions where the wiping blade was in contact.
B: The ink repellency of the part where the wiping blade contacted was lowered.
C: The ink repellency of all the portions that were in contact with the wiping blade was lowered.

<Evaluation of storage stability>
Each ink was put in a sealed container and allowed to stand in an environment of 70 ° C. for 4 weeks. Then, a change in the viscosity of the ink was measured, and the measurement result was evaluated as follows.
Viscosity change rate:
[(Viscosity after 4 weeks × 100) / (initial value of viscosity)] − 100 (%)
A: Absolute value of viscosity change rate is less than 5% B: Absolute value of viscosity change rate is 5% or more and less than 10% C: Absolute value of viscosity change rate is 10% or more

<Evaluation of ejection stability>
Using an inkjet printer “HC5500” (trade name: manufactured by Riso Kagaku Kogyo Co., Ltd.), 100 continuous 7-drop solid images of about 51 mm in the main scanning direction (for 600 nozzles) × 260 mm in the sub-scanning direction were printed continuously. . Non-printed parts due to non-ejection of ink are observed as white streaks. Depending on how many of these white streaks occur in 100 printed materials (equivalent to 60,000 nozzles in total), the ejection stability can be improved. Evaluation was performed as follows.
A: 0
B: 1 or more and less than 5 C: 5 or more

As shown in Table 3, the wiping durability was poor in Comparative Example 1 and Comparative Example 2 using an alkyl (meth) acrylate copolymer having no acidic group as a dispersant. In Comparative Example 3 using a comb-type polyamide dispersant having a plurality of side chains composed of polyester chains, the wiping durability was poor, and the image density and show-through were also poor. Even when an alkyl (meth) acrylate copolymer having an acidic group was used as a dispersant, the wiping durability was poor in Comparative Example 4 containing no basic compound.
On the other hand, in the example containing the ink composition of the present invention, although the storage stability was slightly inferior in Example 4 in which the amount of acrylic acid in the trunk polymer raw material was large, the image density, wiping durability and storage stability were low. Both were excellent.

  The non-aqueous ink composition for inkjet of the present invention has excellent wiping durability and can form a high density image.

Claims (10)

A non-aqueous ink composition for inkjet recording, comprising at least (A) a pigment,
(B) an alkyl (meth) acrylate copolymer having an acidic group;
(C) an organic solvent;
(D) a basic compound;
A non-aqueous ink composition comprising:
The alkyl (meth) acrylate copolymer having an acidic group (B) has an alkyl (meth) acrylate unit having an alkyl group having 12 or more carbon atoms,
A (meth) acrylate unit having a urethane group;
A (meth) acrylate unit having an acidic group;
A non-aqueous ink composition, which is an acrylic polymer comprising The alkyl (meth) acrylate copolymer having an acidic group (B) is (B1) an alkyl (meth) acrylate having an alkyl group having 12 or more carbon atoms,
(B2) a reactive (meth) acrylate having a functional group capable of reacting with an amino group;
(B3) a (meth) acrylate having an acidic group;
In the copolymer of the monomer mixture containing, the urethane group is introduced by the reaction of the functional group capable of reacting with the amino group, the amino alcohol and the polyvalent isocyanate compound, and the acrylic polymer in the copolymer 2. The non-aqueous ink composition according to claim 1, wherein a mass ratio between the copolymer part and the introduced urethane base part is 60:40 to 99: 1. 3. The monomer mixture contains 1 to 30% by weight of (B2) reactive (meth) acrylate having a functional group capable of reacting with an amino group. The non-aqueous ink composition as described. 4. The non-aqueous ink composition according to claim 1, wherein (B3) (meth) acrylate having an acidic group is 1 to 5% by weight in the monomer mixture. The non-aqueous ink composition according to claim 1, wherein the monomer mixture further contains a monomer having a β-diketone group or a β-keto acid ester group. The non-aqueous ink composition according to claim 1, wherein the functional group capable of reacting with the amino group is a glycidyl group. The non-aqueous ink composition according to claim 1, wherein the acidic group is a carboxyl group. The non-aqueous ink composition according to claim 1, wherein the acidic group is neutralized with 0.1 to 2 molar equivalents of (D) a basic compound. The organic solvent (C) is an organic solvent having 12 to 30 carbon atoms, and is composed of 30 to 70% by weight of a nonpolar solvent and 70 to 30% by weight of a polar solvent. The non-aqueous ink composition according to any one of the above. An alkyl (meth) acrylate unit having an alkyl group having 12 or more carbon atoms;
A (meth) acrylate unit having a urethane group;
A (meth) acrylate unit having an acidic group;
A pigment dispersant for a non-aqueous ink composition, wherein the acidic group of the alkyl (meth) acrylate copolymer having an acidic group is neutralized with a basic compound.