JP2010168583A - Nonaqueous inkjet ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous inkjet ink composition having excellent ink ejection stability, which does not clog a nozzle of a printer head portion when used for printing by an inkjet printer, thereby enabling achievement of a printed matter having excellent print quality. <P>SOLUTION: The nonaqueous inkjet ink composition includes a pigment, a resin, a pigment dispersing agent, an organic solvent, and an imidazole compound, wherein the imidazole compound is an imidazole, 2-methylimidazole, benzimidazole, or 2-ethyl-4-methylimidazole and the content of the imidazole compound is 0.01-5.0 mass% in the ink composition, the pigment dispersing agent has two or more amide groups in one molecule and is a polyester polyamide resin having a number average molecular weight of 700-15,000, and the organic solvent is a glycol ether and γ-butyrolactone. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous ink-jet ink composition, and more specifically, ink ejection that does not cause clogging of nozzles of a printer head portion when printing with an ink-jet printer and that can provide a print with excellent print quality. The present invention relates to a non-aqueous ink jet ink composition having excellent stability.

  Conventionally, many pigment ink compositions for ink jet printing using various solvents have been proposed. However, when a printed material is produced with an ink jet printer using such a pigment ink composition, nozzles of the ink jet printer are clogged. As a result, a printed matter that is not preferable in terms of print quality may be obtained, or even if a printed matter is produced using such a pigment ink composition, the color may not always be sufficiently developed.

  In particular, when an organic solvent, an acidic or basic pigment, an additive, or the like having a strong dissolving power is used in the ink composition, they easily corrode the nozzle portion of the printer head, which may cause nozzle clogging. there were.

  Patent Document 1 discloses a technique for preventing corrosion of an electrode installed in a piezo element by containing an ethanolamine compound in an ink composition. However, when these corrosion inhibitors are added to the ink, the dispersion stability of the ink is not good because the pigments and resins dispersed in the ink during long-term storage aggregate and cause nozzle clogging. It was.

Japanese Patent Laid-Open No. 2005-23099

  An object of the present invention is to solve the above-described problems. By preventing corrosion of the ink jet printer head, nozzle clogging does not occur, and the ink dispersion stability is excellent. Another object is to provide a non-aqueous ink jet ink composition.

  As a result of intensive studies to achieve the above object, the present inventors have found that an excellent non-aqueous inkjet ink composition can be obtained by containing an imidazole compound in the ink composition. It came to be completed.

That is, according to the present invention, in a non-aqueous ink jet ink composition containing a pigment, a resin, a pigment dispersant, an organic solvent, and an imidazole compound,
The imidazole compound is imidazole, 2-methylimidazole, benzimidazole or 2-ethyl-4-methylimidazole;
The content of the imidazole compound is 0.01 to 5.0% by mass in the ink composition,
The pigment dispersant is a polyester polyamide resin having two or more amide groups in one molecule and having a number average molecular weight of 700 to 15000,
There is provided a non-aqueous ink jet ink composition, wherein the organic solvent is a glycol ether and γ-butyrolactone.

  By using the non-aqueous ink jet ink composition of the present invention, by preventing corrosion of the ink jet printer head portion, nozzle clogging does not occur, and an ink composition excellent in ink dispersion stability can be provided. .

  The non-aqueous ink jet ink composition of the present invention will be specifically described below.

  The non-aqueous ink jet ink composition of the present invention contains a pigment, a resin, a pigment dispersant, an organic solvent, and further needs to use an imidazole compound.

  Hereinafter, each component of the non-aqueous ink jet ink composition of the present invention will be described.

  Examples of the pigment used in the non-aqueous ink jet ink composition of the present invention include the following.

Pigment Yellow 12, 13, 14, 17, 20, 24, 31, 55, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153 (Nitron type nickel complex yellow), 154, 155, 166, 168, 180, 181, 185
Pigment Orange 16, 36, 38, 43, 51, 55, 59, 61, 64, 65, 71
Pigment Red 9, 48, 49, 52, 53, 57, 97, 122 (Quinacridone Magenta), 123, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 244, 254
Pigment violet 19 (quinacridone violet), 23, 29, 30, 32, 37, 40, 50
Pigment Blue 15 (phthalocyanine blue), 15: 1, 15: 3, 15: 4, 15: 6, 22, 30, 64, 80
Pigment Green 7 (chlorinated phthalocyanine green), 36 (brominated phthalocyanine green)
Pigment Brown 23, 25, 26
Pigment black 7 (carbon black), 26, 27, 28
Titanium oxide, iron oxide, ultramarine, yellow lead, zinc sulfide, cobalt blue, barium sulfate, calcium carbonate

  Here, as the titanium oxide, titanium dioxide which is usually used for paints and the like can be used, and the crystal system may be either anatase type or rutile type, but considering the weather resistance, the rutile type is preferred. preferable.

  The blending amount of the pigment can be arbitrarily determined depending on the kind of the pigment to be used, but is usually 0.1 to 20% by mass, preferably 0.5 to 10% by mass with respect to the mass of the ink composition. is there. The content in the case of titanium oxide is preferably 1.0 to 20.0 mass%, more preferably 3.0 to 15.0 mass%, based on the mass of the ink composition. When the content is less than 1.0% by mass, the concealability of the printed matter on the base is lowered. When the content exceeds 20.0% by mass, titanium dioxide tends to settle and nozzle clogging is likely to occur. The average particle diameter of the pigment is preferably 50 to 400 nm, more preferably 80 to 300 nm. In the case of titanium dioxide, 100 to 400 nm is preferable, and 150 to 300 nm is more preferable. If it is larger than 400 nm, the pigment tends to settle and nozzle clogging tends to occur. When the thickness is less than 50 nm, the inconvenience of lowering the concealment property to the base tends to occur.

  The non-aqueous ink jet ink composition of the present invention contains a resin as a binder in the same manner as a normal ink composition. Such a resin may be a resin for binders commonly used in ordinary ink compositions, and is not particularly limited, but includes any of polyester resins, acrylic resins, and vinyl chloride resins. This is preferable because the adhesion to the substrate is improved.

  As the polyester resin, both saturated polyester resin and unsaturated polyester resin can be used. The polyester resin is obtained by a condensation reaction between a polybasic acid and a polyhydric alcohol. As a polybasic acid used for a polyester resin, the following are mentioned, for example.

Aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 9,10-anthracenedicarboxylic acid, diphenic acid;
aromatic oxycarboxylic acids such as p-oxybenzoic acid and p- (hydroxyethoxy) benzoic acid;
Aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid;
Aliphatic unsaturated polycarboxylic acids such as fumaric acid, maleic acid, itaconic acid, mesaconic acid, cyclohexene dicarboxylic acid, dimer acid, trimer acid and tetramer acid;
Alicyclic dicarboxylic acids such as hexahydrophthalic acid and tetrahydrophthalic acid;
Multivalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid

  In addition, a monobasic acid may be used in combination with the polybasic acid. Examples of monobasic acids include benzoic acid, chlorobenzoic acid, bromobenzoic acid, parahydroxybenzoic acid, t-butylbenzoic acid, naphthalenecarboxylic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, salicylic acid, and thiosalicylic acid. , Phenylacetic acid, naphthalenecarboxylic acid, anthracenecarboxylic acid, t-butylnaphthalenecarboxylic acid, cyclohexylaminocarbonylbenzoic acid, and the like.

  Examples of the polyhydric alcohols used in the polyester resin include the following.

Ethylene glycol, propylene glycol, 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol Aliphatic diols such as 2,2,4-trimethyl-1,3-pentanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol;
Aliphatic polyhydric alcohols such as triols and tetraols such as trimethylolethane, trimethylolpropane, glycerin and pentaerythritol;
Alicyclic polyhydric alcohols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, spiroglycol, bisphenol A, hydrogenated bisphenol A, tricyclodecanediol, tricyclodecane dimethanol;
Aromatic polyhydric alcohols such as para-xylene glycol, meta-xylene glycol, ortho-xylene glycol and 1,4-phenylene glycol

  In addition, a monohydric alcohol may be used in combination with the polyhydric alcohol.

  The number average molecular weight of the polyester resin used in the present invention is preferably in the range of 1000 to 50000, and more preferably in the range of 2000 to 20000. When the number average molecular weight of the polyester resin is less than 1000, the evaluation of ethanol resistance of the ink print film is inferior, and when it is more than 50000, the ink stringing phenomenon is likely to occur, and the ink discharge property is not stable. This is not preferable.

  As an acrylic resin, what copolymerized the radically polymerizable monomer normally used can be used. Examples of the radical polymerizable monomer include the following.

Acrylic esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate;
Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate;
Aromatic vinyls such as styrene, vinyltoluene, α-methylstyrene;
Vinyl esters such as vinyl acetate and vinyl propionate;
Heterocyclic vinyl compounds such as vinylpyrrolidone;
Vinyl halides such as vinyl chloride, vinylidene chloride and vinylidene fluoride;
Vinyl ethers such as ethyl vinyl ether and isobutyl vinyl ether;
Α-olefins such as ethylene and propylene

  In addition, a polymerizable monomer containing a functional group such as an acid or a base can be used for the synthesis of the acrylic resin. As a functional group containing monomer, the following are mentioned, for example.

Carboxyl group-containing monomers such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, mono n-butyl maleate, mono n-butyl fumarate, mono n-butyl itaconic acid, crotonic acid;
(Meth) acrylic acid 2-hydroxyethyl, (meth) acrylic acid 2-hydroxypropyl, (meth) acrylic acid 3-hydroxypropyl, (meth) acrylic acid 4-hydroxybutyl, acrylic acid (2-hydroxymethyl) ethyl, (2-hydroxymethyl) butyl acrylate, (4-hydroxymethylcyclohexyl) methyl (meth) acrylate, glycerol mono (meth) acrylate, 2- (meth) acryloyloxyethyl 2-hydroxypropyl phthalate, 2-hydroxy-3 -Hydroxyl group-containing (meth) acrylic acid esters such as phenoxypropyl (meth) acrylate;
Amide group-containing monomers such as acrylamide, methacrylamide, maleic acid amide, diacetone acrylamide;
Glycidyl group-containing monomers such as glycidyl methacrylate and allyl glycidyl ether;
Cyano group-containing monomers such as acrylonitrile and methacrylonitrile;
Dienes such as butadiene and isoprene;
Hydroxyl-containing allyl compounds such as allyl alcohol and 2-hydroxyethyl allyl ether;
Tertiary amino group-containing monomers such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate;
Vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltris (β-methoxyethoxy) silane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinyldimethylmethoxysilane, vinyldimethylethoxysilane, 3-methacryloxy Alkoxysilyl group-containing monomers such as propyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane

  In addition, monomers having two or more unsaturated bonds in one molecule such as diallyl phthalate, divinylbenzene, allyl acrylate, and trimethylolpropane trimethacrylate can be used. These monomers may be used alone or in combination of two or more.

  Various vinyl chloride resins can be used, and examples thereof include copolymer resins of vinyl chloride and other monomers such as vinyl acetate, vinylidene chloride, acrylic and maleic acid. A preferable vinyl chloride resin is a vinyl chloride / vinyl acetate copolymer resin obtained by copolymerizing vinyl chloride and vinyl acetate, and a copolymer resin having a molecular weight of 30,000 or less is particularly preferable.

  There is no restriction | limiting in particular as resin other than the above, Any resin used for a normal ink composition can be used. For example, epoxy resin, phenol resin, novolak resin, rosin modified phenol resin, amino resin such as melamine, benzoguanamine, polyamide resin, cellulose diacetate, cellulose triacetate, nitrocellulose, cellulose nitrate, cellulose propionate, cellulose acetate butyrate, etc. Examples thereof include cellulose ester resins, cellulose ether resins such as methyl cellulose, ethyl cellulose, benzyl cellulose, trityl cellulose, cyanethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, and aminoethyl cellulose. These resins can be used in combination.

  The content of the resin used in the non-aqueous ink jet ink composition of the present invention is preferably 1 to 20% by mass and more preferably 1 to 10% by mass with respect to the mass of the ink composition. If the resin content is less than 1% by mass, the adhesion to the substrate may be insufficient, and if it is more than 20% by mass, the viscosity of the ink composition becomes high and the ejection properties become unstable. Inconvenience may occur, which is not preferable.

  The non-aqueous ink jet ink composition of the present invention uses a pigment dispersant in order to improve the dispersibility of the pigment.

  The pigment dispersant is not particularly limited as long as it is used for the purpose of dispersing a pigment in this technical field. For example, a polyamide resin, a hydroxyl group-containing carboxylic acid ester, a long-chain polyaminoamide, and a salt of a high molecular weight acid ester , Salt of long chain polyaminoamide and high molecular weight polycarboxylic acid, salt of long chain polyaminoamide and polar acid ester, high molecular weight unsaturated acid ester, modified polyurethane, modified polyacrylate, polyether ester type anionic active agent, naphthalene sulfone Acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonylphenyl ether, stearylamine acetate and the like can be used.

  In the non-aqueous ink jet ink composition of the present invention, it is preferable to use a polyester polyamide resin having two or more amide groups in one molecule and a number average molecular weight of 700 to 15000 as a pigment dispersant. . The blending amount of the pigment dispersant varies depending on the type of pigment to be used, but is usually preferably 0.1 to 15% by mass, and more preferably 0.5 to 10% by mass with respect to the mass of the ink composition. It is preferable to further improve the pigment dispersibility.

  The polyester polyamide resin is produced by reacting an acid-terminated polyester resin with a polyamine compound having two or more amino groups in one molecule. For example, Sol sparse 32000, Sol sparse 32500, Sol sparse 32600, Sol sparse 33500, Sol sparse 34750, Sol sparse 35100, Sol sparse 37500, etc. manufactured by Lubrizol, BYK9077 made by BYK Chemie, etc. can be mentioned.

  In addition, when the number of amide groups of the polyester polyamide resin is less than 2 in one molecule, the pigment dispersibility is lowered, which is not preferable. Further, when the number average molecular weight is less than 700, the pigment dispersibility is lowered, and when the number average molecular weight exceeds 15,000, the dispersibility in the ink is lowered, which is not preferable.

  The non-aqueous ink-jet ink composition of the present invention uses an organic solvent used for ordinary solvent-based inks.

  As an organic solvent, the following are mentioned, for example.

Alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tridecyl alcohol, cyclohexyl alcohol, 2-methylcyclohexyl alcohol;
Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, glycerin;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, Diethylene glycol dibutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, Lopylene glycol dimethyl ether, dipropylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol diethyl ether, ethylene glycol monomethyl acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monomethyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol mono Ethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, diethylene glycol monoethyl acetate, diethylene glycol monobutyl acetate, triethylene glycol Glycol ethers such as monomethyl ether;
Esters such as ethyl acetate, isopropylene acetate, n-butyl acetate, methyl lactate, ethyl lactate, butyl lactate;
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, diacetone alcohol;
Other nitrogen-containing compounds such as toluene, xylene, acetonitrile, γ-butyrolactone, γ-valerolactone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone

  From these, various solvents are selected from the viewpoints of compatibility with the characteristics of the head nozzle during printing, safety, and drying properties, and a plurality of solvents can be mixed and used as necessary.

  The non-aqueous ink jet ink composition of the present invention contains glycol ethers and γ-butyrolactone as organic solvents. Among the glycol ethers, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether Ethyl ether acetate and diethylene glycol monobutyl ether acetate are preferred because they are excellent in ink redissolvability at the printer head portion, and ink adhesion to non-absorbent substrates such as plastics and drying properties.

  By containing the imidazole compound, the non-aqueous ink-jet ink composition of the present invention does not cause clogging of the nozzles of the printer head when printing with an ink-jet printer, and a printed matter with excellent print quality can be obtained.

  The nozzles of the printer head that come into contact with the ink may be corroded by chemical action due to organic solvents, pigments, or the like in the ink, which may cause nozzle clogging. By containing the imidazole compound in the ink, it is possible to prevent nozzle corrosion that causes nozzle clogging and ink dot bending, and to obtain further excellent dispersion stability.

  Examples of the imidazole compound include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, benzimidazole, 2-phenyl-benzimidazole, 2-mercaptomethylbenzimidazole, 2-phenylimidazole, and 2-phenyl-4. -Methylimidazole, 1-benzyl-2-methylimidazole, naphthimidazole, 1-cyanoethyl-2-methylimidazole, 1-aminoethyl-2-methylimidazole, 2,4-diamino-6- (2-undecyl-1- Imidazolylethyl) -1,3,5-triazine, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and the like, particularly imidazole, 2-methylimidazole, benzimidazole and 2-ethyl-4-methylimid. Tetrazole is preferred because of excellent corrosion prevention of the head portion.

  The imidazole compounds may be used singly or in combination, but the total amount of imidazole compounds is preferably 0.01 to 5.0% by mass with respect to the mass of the ink composition, and 0.05 to It is more preferable that it is 3.0 mass%, and it is still more preferable that it is 0.1-1.0 mass% further.

  If the content of the imidazole compound is less than 0.01% by mass, clogging of the nozzle tends to occur, and if it exceeds 5.0% by mass, the ink may be thickened due to pigment aggregation, which is not preferable.

  About the water extract of the non-aqueous ink jet ink composition of the present invention, the pH is 6.0 to 10.0, and the printed matter with excellent print quality can be obtained without clogging the nozzles during printing. Since it is obtained, it is preferable. If the pH of the water extract is less than 6.0, the printer head is likely to corrode and cause nozzle clogging or ink dot bending. If the pH is greater than 10.0, Inconvenience such as thickening may occur, which is not preferable. The pH of this water extract is more preferably 6.5 to 8.5.

  The measuring method of pH is as follows. For the water extract of the ink composition, 1 g of the ink composition is added to 100 g of distilled water and stirred well. After standing still for a while, the water extract is measured with a pH meter.

  Further, the pH of the water extract of the ink composition can be adjusted to pH 6.0 to 10.0 by adjusting the amount of the imidazole compound blended in the ink composition.

  The non-aqueous ink jet ink composition of the present invention may be used in combination with additives such as dyes, surface conditioners, UV absorbers, light stabilizers, antioxidants, and plasticizers depending on applications.

  The non-aqueous ink jet ink composition of the present invention can be used in various ink jet printers. Examples of such an ink jet printer include a method of ejecting an ink composition by a charge control method and an ink on demand method.

  The non-aqueous ink jet ink composition of the present invention can be suitably applied particularly to printing by a large ink jet printer using a large format, for example, printing of an ink jet printer for the purpose of printing on an outdoor article such as a sign display. . Further, the contrast is clear in color graphic printing and video recording drawing, and the reproducibility of the image is remarkably improved.

  The printed surface (ink composition) after inkjet printing is dried at room temperature to several hundred degrees C to form a dry film. In addition, about the base material used as the object of printing by this invention, if it does not deform | transform or change in quality on the conditions which dry a printing surface (ink composition), it will not restrict | limit in particular. Examples of such a substrate include metal, glass, and plastic, and more specifically, a paper whose surface is coated with a resin, a plastic sheet, a film, and the like.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Hereinafter, both “parts” and “%” are based on mass.

<Examples 1-32 and Comparative Examples 1-6>
Ink compositions of Examples 1 to 32 and Comparative Examples 1 to 6 were prepared by kneading the mixtures shown in Tables 1 to 4 in corresponding amounts (parts by mass) with a sand mill for 3 hours, respectively.

As pigments:
As carbon black, Monarch 1000 (manufactured by Cabot Corporation);
As a quinacridone magenta pigment, FASTOGEN Super Magenta RG (Dainippon Ink Co., Ltd.);
As phthalocyanine blue, Irgarite Blue 8700 (manufactured by Ciba Specialty Chemicals);
E4GN-GT (manufactured by LANXESS) as a nickel complex yellow pigment;
TR92 (manufactured by TIOXIDE) as titanium oxide;
Each was used.

As resin:
Byron GK810 (manufactured by Toyobo Co., Ltd., number average molecular weight = 6000, Tg = 46 ° C., acid value = 5 mgKOH / g, hydroxyl value = 19 mgKOH / g) as a polyester resin;
As an acrylic resin, Dianal MB2660 (manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight = 65000, Tg = 52 ° C., acid value = 3 mgKOH / g);
As vinyl chloride resin, Solvain CL (manufactured by Nissin Chemical Co., Ltd., vinyl chloride-vinyl acetate copolymer, number average molecular weight = 25000, Tg = 70 ° C.);
Each was used.

As imidazole:
Imidazole (trade name: IZ, manufactured by Nippon Synthetic Chemical);
2-methylimidazole (trade name: 2MI, manufactured by Nippon Synthetic Chemical);
Benzimidazole (trade name: benzimidazole, manufactured by Aldrich); and 2-ethyl-4-methylimidazole (trade name: 2-ethyl-4-methylimidazole, manufactured by Tokyo Chemical Industry Co., Ltd.);
Were used respectively.

As pigment dispersant:
As polyester polyamide resin A, Solsperse 32000 (manufactured by Lubrizol Corp., solid content concentration 100%, number average molecular weight = 1500);
As the polyester polyamide resin B, BYK9077 (manufactured by Big Chemie, solid content concentration 99%, number average molecular weight = 1400);
Each was used.

  As a rust preventive agent, diisopropyl ammonium nitrite (trade name: VERZONE CRYSTAL # 150, manufactured by Daiwa Kasei Laboratories) was used.

  With respect to the obtained ink compositions of Examples 1 to 32 and Comparative Examples 1 to 6, the viscosity, the average particle diameter, the pH of the water extract, the dispersion stability and the nozzle discharge stability were tested by the following methods, respectively. , Measured and evaluated according to the following criteria.

<Viscosity measurement>
The viscosity of each ink composition was measured at 20 ° C. using a B-type viscometer.

<Average particle size measurement>
The particle diameter of the pigment of each ink composition was determined by measuring the average particle size (D50) using a laser diffraction particle size distribution analyzer (“SALD-7000” manufactured by Shimadzu Corporation).

<PH of water extract>
The pH of the water extract of each ink composition was dropped by adding 1 g of the ink composition to 100 g of distilled water using a separatory funnel, and mixed and stirred. After standing for a while, the water extract (lower layer part) was taken out. Then, it was measured at 20 ° C. with a pH meter.

<Dispersion stability>
Each ink composition was stored in a sealed container at 60 ° C. for 1 month, then removed, its viscosity and particle size were measured as described above, and each change before and after the test was evaluated according to the following criteria. .

A: Changes in viscosity and particle size are both within ± 5%.
◯: At least one of changes in viscosity and particle diameter exceeds ± 5% and within ± 10%.
X: Change in viscosity and particle diameter, at least one of which exceeds ± 10%.

<Nozzle discharge stability>
An image was continuously printed on a vinyl chloride base material for 8 hours using an inkjet printer for large format, then stopped for 1 week in an environment of a temperature of 40 ° C. and a humidity of 65%, and again printed continuously for 1 hour. The print state before and after the stop was visually observed, the percentage of the print state reproduced after the stop with respect to the print state before the stop was calculated, and evaluated according to the following criteria.

A: Correct printing can be performed at a predetermined position with 90% or more of the printed dots.
○: The printed dots can be correctly printed at a predetermined position with 80% or more and less than 90%.
(Triangle | delta): The dot curvature generate | occur | produces in 20% or more and less than 70% among the printed dots.
×: Dot bending occurs when 70% or more of the printed dots.

  The measurement results and evaluation results were as shown in Tables 1 to 4.

  As is clear from the data shown in Tables 1 to 3, the ink compositions of Examples 1 to 32 of the present invention gave good evaluation results for each test item, and inks with good printing were obtained.

  On the other hand, as apparent from the data shown in Table 4, the ink compositions of Comparative Examples 1 to 6 were clogged with nozzles, resulting in poor printing. In Comparative Example 6 using diisopropyl ammonium nitrite which is a corrosion inhibitor such as metal, the dispersion stability was poor.

Claims (5)

In the non-aqueous inkjet ink composition containing a pigment, a resin, a pigment dispersant, an organic solvent, and an imidazole compound,
The imidazole compound is imidazole, 2-methylimidazole, benzimidazole or 2-ethyl-4-methylimidazole;
The content of the imidazole compound is 0.01 to 5.0% by mass in the ink composition,
The pigment dispersant is a polyester polyamide resin having two or more amide groups in one molecule and having a number average molecular weight of 700 to 15000,
A non-aqueous inkjet ink composition, wherein the organic solvent is a glycol ether and γ-butyrolactone.   2. The non-aqueous inkjet ink composition according to claim 1, wherein the pH of the water extract of the non-aqueous inkjet ink composition is 6.0 to 10.0.   The non-aqueous inkjet ink composition according to claim 1 or 2, wherein the pigment is titanium oxide, and the content of the titanium oxide is 1.0 to 20.0 mass% in the ink composition.   The volume average particle diameter of the pigment is 50 to 400 nm. The non-aqueous ink jet ink composition according to any one of claims 1 to 3.   The non-aqueous ink jet ink composition according to claim 1, wherein the resin contains any one of a polyester resin, an acrylic resin, and a vinyl chloride resin.