JP2006045450A - Inkjet ink and method for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink which has excellent ink dispersion stability, curl resistance, strike-through resistance and dryness, and has double face printing suitability for plain paper, and to provide an inkjet recording method using the inkjet ink. <P>SOLUTION: This inkjet ink is characterized by containing a compound represented by the general formula (1) (X<SB>1</SB>is an oxygen atom or NR<SB>2</SB>; X<SB>2</SB>is an oxygen atom, NR<SB>3</SB>or CH<SB>2</SB>; R<SB>1</SB>is H or a 1 to 4C alkyl; R<SB>2</SB>and R<SB>3</SB>are each a 1 to 4C alkyl) in an amount of ≥20 mass%, and containing a pigment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel inkjet ink and inkjet recording method.

  In recent years, the ink jet recording system can create images easily and inexpensively, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, ink jet recording devices that emit and control fine dots, ink with improved color reproduction gamut, durability, and emission suitability, ink absorbency, coloring material color development, surface gloss, etc. are dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper.

  However, in an inkjet image recording system that requires dedicated paper, there are problems in that the recording media that can be used are limited and the cost of the recording media is increased.

  On the other hand, in the office, there is an increasing need for a system capable of performing full color printing at high speed without being restricted by a recording medium (for example, plain paper, coated paper, art paper, plain paper double-sided printing, etc.).

  As for the composition of inkjet ink, it can print at high speed, has good character reproducibility on plain paper, and shows through when printing (a phenomenon in which the printed ink passes through the recording medium and the image appears on the back), feathering Various studies have been made from the viewpoints of no occurrence of image bleeding, rapid penetration into paper, and quick drying.

  As one of the methods, a so-called water-based ink-jet ink having a water content of 50% by mass or more is widely used as an ink-jet ink. An electrophotographic copy paper using such a water-based ink-jet ink is widely used. When recording images on plain paper such as high-quality paper and medium-quality paper, in addition to problems caused by penetrability such as image back-through and feathering, curling and cockling of the recorded plain paper is a major problem. Become.

  In order to solve the above problems, an ink jet recording method using an ink having improved penetrability by specifying a wetting time and an absorption coefficient for a recording medium in the Bristow method has been disclosed (for example, see Patent Document 1). However, in this method, since the colorant in the ink also penetrates into the plain paper at the same time, the image density is lowered and the ink shows through, which is not suitable for double-sided printing. Have

  Further, an inkjet ink containing a specific amide compound, pyridine derivative, imidazoline compound or urea compound as an anti-curl agent is disclosed (for example, see Patent Document 2). However, this method attempts to prevent curling by adding an anti-curling agent, but does not prevent cockling immediately after printing, and its effect is insufficient. In addition, with the drying of the ink liquid, there is a problem that clogging is likely to occur at the nozzle portion of the recording head.

  Further, as a method for improving the curl, an inkjet recording method supplement is proposed in which a solution containing water is applied to the back side of the image printing surface to optimize the curl balance (see, for example, Patent Document 3). . However, this method has the disadvantages that it does not have double-sided recording suitability, and the strength of plain paper decreases with the increase in the amount of ink and curl balance liquid attached to plain paper, and jamming or the like tends to occur during transportation. there were.

  Further, solvent-based inks that can perform printing at high speed instead of water-based inkjet inks have been studied. That is, by using an oil-based ink (solvent ink jet ink) that contains a volatile solvent and has improved drying properties, even when printing on plain paper, the penetration into the recording medium is fast and the drying time is short. High-speed printing is possible without curling or the like. However, solvent-based inks have high penetrability into plain paper media, resulting in poor character reproducibility and back-through on recording media, which is a major obstacle especially when printing on both sides of plain paper. It was.

In addition, an inkjet ink containing an N-alkyl-substituted derivative of ethylene urea has been disclosed (for example, see Patent Document 4). In the examples described in the patent document, an inkjet ink containing 60% by mass of 1,3-dimethyl-2-imidazolidine is disclosed. However, since the colorant used is a water-soluble dye, It can be said that the show-through is large and the suitability for double-sided printing is extremely insufficient. Further, a nitrogen-containing heterocyclic compound selected from an oxidized self-dispersing pigment, an acetylenic diol surfactant, 1,3-dimethyl-2-imidazolidine, N-methyl-2-pyrrolidinone and 2-pyrrolidinone And an ink-jet ink containing a preservative (see, for example, Patent Document 5). However, there is no suggestion regarding a preferable content of the nitrogen-containing heterocyclic compound in the patent document, and an inkjet ink containing 4.5 to 9% by mass of N-methyl-2-pyrrolidone is disclosed in Examples. However, in the present situation, the added amount presented therein has not led to curling resistance, cockling resistance, and suppression of back-through.
JP 10-316915 A JP 9-176538 A JP-A-10-272828 JP-A-55-71768 International Publication No. 00/58411 Pamphlet

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to provide an inkjet ink having excellent ink dispersion stability, excellent curling properties, anti-through-through resistance and drying properties, and suitable for double-sided printing on plain paper and the like. An ink jet recording method using the method is provided.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
An ink-jet ink comprising 20% by mass or more of a compound represented by the following general formula (1) and a pigment.

[Wherein, X ₁ represents an oxygen atom or NR ₂ , and X ₂ represents an oxygen atom, NR ₃ or CH ₂ . R ₁ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ each represents an alkyl group having 1 to 4 carbon atoms. ]
(Claim 2)
The inkjet ink according to claim 1, wherein the content of the compound represented by the general formula (1) is 40% by mass or more.

(Claim 3)
The inkjet ink according to claim 1, wherein the content of the compound represented by the general formula (1) is 50% by mass or more.

(Claim 4)
The compound represented by the general formula (1) is at least one selected from ethylene carbonate, propylene carbonate and 1,3-dimethyl-2-imidazolidinone. The inkjet ink of Claim 1.

(Claim 5)
An ink-jet ink comprising an aprotic solvent having a relative dielectric constant of 30 or more and 20% by mass or more and a pigment.

(Claim 6)
The inkjet ink according to claim 5, wherein the content of the aprotic solvent having a relative dielectric constant of 30 or more is 40% by mass or more.

(Claim 7)
The inkjet ink according to claim 5, wherein the content of the aprotic solvent having a relative dielectric constant of 30 or more is 50% by mass or more.

(Claim 8)
8. The inkjet ink according to claim 5, wherein at least one of the aprotic solvents having a relative dielectric constant of 30 or more is a compound represented by the general formula (1). .

(Claim 9)
The ink content according to claim 1, wherein the water content is 10% by mass or more and less than 50% by mass.

(Claim 10)
10. The inkjet ink according to claim 1, wherein the surface tension is 40 mN / m or less.

(Claim 11)
The ink-jet ink according to claim 1, wherein the pigment is dispersed by an anionic polymer dispersant.

(Claim 12)
The inkjet ink according to any one of claims 1 to 10, wherein at least one of the pigments is a self-dispersing pigment.

(Claim 13)
An inkjet recording method, comprising: discharging the inkjet ink according to any one of claims 1 to 12 from an inkjet recording head, and printing on plain paper.

(Claim 14)
An inkjet recording method, comprising: discharging the inkjet ink according to any one of claims 1 to 12 from an inkjet recording head, and printing on both surfaces of a recording medium.

  According to the present invention, it is possible to provide an ink-jet ink having excellent ink dispersion stability, curl suitability, anti-through-through resistance and drying property, and suitable for double-sided printing on plain paper, and an ink jet recording method using the same. .

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventor has 1) an inkjet ink containing 20% by mass or more of the compound represented by the general formula (1), and 2) a relative dielectric. Ink-jet ink containing 20% by mass or more of an aprotic solvent having a rate of 30 or more and having a pigment has excellent dispersion stability of the ink, excellent curling ability, resistance to back-through and drying, and both sides of plain paper As soon as an ink-jet ink having printability can be realized, the present invention has been achieved.

  As described above, demand for double-sided printing on plain paper is increasing, especially in offices, especially in the case of ink-jet printing. When classified broadly about suitability for double-sided printing, there is no curling or cockling on the printed surface, and the printed image is on the back side. It is mentioned that it does not come out. The former is related to the transportability during backside printing, and the latter is related to the visibility of the backside image.

  In the present invention, by containing 20% by mass or more of the compound represented by the general formula (1) or an aprotic solvent having a relative dielectric constant of 30 or more in the ink, the curling property is excellent and cockling resistance is improved. It was found that it can be improved.

  The mechanism for achieving the above characteristics of the ink having the configuration defined in the present invention is not clear, but by containing a certain amount of aprotic compound in the ink, for example, the interaction with the cellulose fibers constituting plain paper can be achieved. It is estimated that curling and cockling were suppressed due to the decrease. Furthermore, the effect becomes more remarkable by making content of water less than 50 mass%. Furthermore, it has been found that the use of a pigment as a coloring material suppresses show-through. In a medium containing a certain amount or more of the compound represented by the general formula (1) according to the present invention or an aprotic solvent having a relative dielectric constant of 30 or more, the pigment strongly adsorbs to the cellulose fiber, and the surface It is presumed that the color material is localized in the vicinity.

  Details of the present invention will be described below.

  The inkjet ink of the present invention is characterized by containing 20% by mass or more of the compound represented by the general formula (1), and the content is preferably 20% by mass or more and less than 90% by mass, more preferably 40%. It is at least 50% by mass and less than 90% by mass.

In the general formula (1), X ₁ represents an oxygen atom or NR ₂ , and X ₂ represents an oxygen atom, NR ₃ or CH ₂ . R ₁ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ each represents an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group.

  Examples of the compound represented by the general formula (1) according to the present invention include ethylene carbonate, propylene carbonate, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, N-methyl-2-pyrrolidinone and the like. Can be mentioned. These compounds may be used alone, or a plurality of compounds may be used in combination, and the effect of the present invention can be obtained if the total addition amount relative to the total amount of ink is 20% by mass or more.

  In the inkjet ink of the present invention, the compound represented by the general formula (1) according to the present invention is preferably ethylene carbonate, propylene carbonate or 1,3-dimethyl-2-imidazolidinone, and more preferably 1 , 3-dimethyl-2-imidazolidinone.

  The inkjet ink of the present invention is characterized by containing an aprotic solvent having a relative dielectric constant of 30 or more in an amount of 20% by mass or more, and the content is preferably 20% by mass or more and less than 90% by mass, more preferably Is 40% by mass or more and less than 90% by mass, more preferably 50% by mass or more and less than 90% by mass.

The relative dielectric constant referred to in the present invention is a relative dielectric constant with respect to vacuum, and can be measured with a commercially available measuring device such as a dielectric constant measuring device HP E5050A HEWRET PACKARD according to ASTM-150. In addition, values are described in “Chemical Handbook 4th revised edition (II)” Maruzen Co., Ltd., “Solvent Handbook 1st edition” (Kodansha Scientific) Aprotic with a relative dielectric constant of 30 or more according to the present invention Examples of the solvent include propylene carbonate (69), 1,3-dimethyl-2-imidazolidinone (38), γ-butyrolactone (39), N-methyl-2-pyrrolidinone (32), dimethyl sulfoxide (49) N, N-dimethylformamide (37), N, N-dimethylacetamide (38) and the like. The numerical value in parentheses represents the relative dielectric constant. These solvents may be used alone or in combination with a plurality of solvents, and the effect of the present invention can be obtained if the total addition amount relative to the total amount of ink is 20% by mass or more.

  In the inkjet ink of the present invention, the aprotic solvent having a relative dielectric constant of 30 or more according to the present invention is more preferably a compound represented by the general formula (1).

  One characteristic of the inkjet ink of the present invention is that a pigment is used as a coloring material.

  As the pigment that can be used in the present invention, conventionally known pigments can be used without particular limitation, and any of water-dispersible pigments, solvent-dispersible pigments, and the like can be used, for example, organic pigments such as insoluble pigments and lake pigments, An inorganic pigment such as carbon black can be preferably used.

  The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

In addition to the above, when red, green, blue and intermediate colors are required, the following pigments are preferably used alone or in combination. I. Pigment Red 209, 224, 177, 194;
C. I. Pigment Orange 43;
C. I. Vat Violet 3;
C. I. Pigment Violet 19, 23, 37;
C. I. Pigment Green 36, 7;
C. I. Pigment Blue 15: 6;
Etc. are used.

Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment Black 7 and the like can be mentioned. The pigment used in the present invention is preferably used after being dispersed by a dispersing machine together with a dispersant and other necessary additives according to various desired purposes. As the disperser, conventionally known ball mills, sand mills, attritors, roll mills, agitators, Henschel mixers, colloid mills, ultrasonic homogenizers, pearl mills, wet jet mills, paint shakers and the like can be used.

  In the present invention, the pigment is preferably a pigment dispersed with an anionic polymer dispersing agent or an anionic self-dispersing pigment from the viewpoint of suppression of showthrough.

  The anionic polymer dispersant refers to a dispersant having an anionic group obtained by neutralizing an acidic group in a molecule with a basic compound. Examples of the basic compound used at this time include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamine, and alkanolamine. In the present invention, amines are particularly preferable. .

  The polymer dispersant used in the present invention is preferably an anionic dispersant having a molecular weight of 1000 or more, that is, an anionic polymer dispersant, and is not particularly limited as long as the molecular weight is 1000 or more. For example, polyvinyl alcohol , Polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic ester copolymer, acrylic acid-acrylic ester copolymer, etc. Acrylic resin, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α- Methylstyrene-acrylic acid-acrylic acid ester copolymer, etc. Styrene-acrylic resin, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, and vinyl acetate-ethylene copolymer, Vinyl acetate copolymers such as vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, and salts thereof These copolymers or resins include, for example, homopolymers, copolymers and terpolymers having carboxylic acid, sulfonic acid or phosphonic acid functionality. Monomers that give acid functionality are, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, mesaconic acid, fumaric acid, citraconic acid, vinyl acetic acid, acryloxypropionic acid, vinyl sulfonic acid, Styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid, allylphosphonic acid, vinylphosphonic acid and vinylsulfonic acid.

  The average particle size of the pigment dispersion used in the ink of the present invention is preferably 10 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less. When the average particle size of the pigment dispersion exceeds 200 nm, the dispersion becomes unstable. In addition, even when the average particle size of the pigment dispersion is less than 10 nm, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. It is also possible to obtain a particle image with a transmission electron microscope on at least 100 particles and perform statistical processing on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). Is possible.

  The self-dispersing pigment according to the present invention refers to a pigment that can be dispersed without a dispersant, preferably pigment particles having a polar group on the surface, and more preferably an anionic self-dispersing pigment. An anionic self-dispersing pigment refers to a pigment in which an acidic group is modified and neutralized with a basic compound, thereby making the anionic group dispersible in water without a dispersant.

  The pigment particle having an acidic group on the surface means a pigment directly modified with an acidic group on the surface of the pigment particle, or an organic substance having an organic pigment mother nucleus and having an acidic group bonded directly or through a joint. .

  Examples of the acidic group (also referred to as polar group) include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a boric acid group, and a hydroxyl group, preferably a sulfonic acid group and a carboxylic acid group, and more preferably a sulfone group. It is an acid group.

  Acid group modifiers include sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt, sulfamic acid and other treatments containing sulfur atoms, and the pigment particle surface is oxidized. Carboxylating agents such as sodium hypochlorite and potassium hypochlorite that introduce carboxylic acid groups can be mentioned. Among them, a sulfonating agent such as sulfur trioxide, sulfonated pyridine salt or sulfamic acid, or a carboxylating agent is preferable. Examples of basic compounds that neutralize acidic groups include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamines, and alkanolamines. In the present invention, amines are used. Is particularly preferred.

  By using a pigment having an anionic group, the strike-through is suppressed by inhibiting the water molecules adsorbed on the cellulose and the anionic group from interacting with each other and inhibiting the pigment from penetrating into the paper together with the ink solvent. However, the present invention is not limited to this reasoning.

  Examples of a method for obtaining pigment particles having a polar group on the surface include WO97 / 48769, JP-A-10-110129, JP-A-11-246807, JP-A-11-57458, and 11-189739. No. 1, JP-A-11-323232, JP-A 2000-265094, etc., by causing the surface of the pigment particles to be treated with an appropriate oxidizing agent, so that at least a part of the pigment surface has a polarity such as a sulfonic acid group or its salt The method of introduce | transducing group is mentioned. Specifically, it is prepared by oxidizing carbon black with concentrated nitric acid, or in the case of color pigments by oxidizing with sulfamic acid, sulfonated pyridine salt, amide sulfuric acid, etc. in sulfolane or N-methyl-2-pyrrolidone. can do. In these reactions, the pigment dispersion can be obtained by removing and purifying the substance that has been excessively oxidized and becomes water-soluble. Moreover, when a sulfonic acid group is introduced onto the surface by oxidation, the acidic group may be neutralized with a basic compound as necessary.

  Other methods include a method of adsorbing pigment derivatives described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. on the surface of pigment particles by a treatment such as milling, and the like. Examples include a method of dissolving the pigment described in 377068, 2001-1495, and 2001-234966 in a solvent together with a pigment derivative and then crystallizing in a poor solvent. Pigment particles having groups can be obtained.

  In the present invention, the polar group may be free or in a salt state, or may have a counter salt. Examples of the counter salt include inorganic salts (lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium) and organic salts (triethylammonium, diethylammonium, pyridinium, triethanolammonium, etc.), preferably 1 A counter salt having a valence.

  In the inkjet ink of the present invention, the compound represented by the general formula (1) according to the present invention or an aprotic solvent having a relative dielectric constant of 30 or more, and a water content of 10% by mass or more, It is preferable to prescribe | regulate to less than 50 mass%. When the water content in the ink-jet ink is less than 10% by mass, the back-through and text bleeding increase, and when it is 50% by mass or more, curling tends to occur.

  Usually, the surface tension of the inkjet ink is in the range of 37 mN / m to 55 mN / m. However, in the inkjet ink of the present invention, the surface tension is preferably 40 mN / m or less, more preferably 25 to 35 mN / m. is there. By setting the surface tension range as defined above, an ink-jet ink having good permeability and better drying properties when image recording is performed using plain paper. As a result, when printing on plain paper, the ink is suitable for high-speed printing with the necessary penetrability and dryness, and at the same time, no set-off or show-through. The surface tension is measured by a Wilhelmy surface tension meter in an environment with a relative humidity of 55% and 23 ° C.

  Next, other components of the inkjet ink of the present invention will be described.

  In the ink-jet ink of the present invention, a surfactant can be used. As the surfactant used in the present invention, any of cationic, anionic, amphoteric and nonionic can be used. The addition amount of the surfactant is preferably set as appropriate so that the surface tension of the ink-jet ink of the present invention is 40 mN / m or less as described above.

  Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like.

  Examples of the anionic surfactant include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acyl glutamate, acylated peptide, alkyl sulfonate, Alkylbenzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol sulfate, secondary higher alcohol Sulfate ester, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate, monoglyculate, fatty acid alkylolamide sulfate, alkyl ether phosphate ester, alkyl phosphate ester Examples include tellurium salts.

  Examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like.

  Nonionic activators include polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene glycerin fatty acid ester, Oxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid alkanolamide, polyoxyethylene Fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide, acetyl Glycol, acetylene alcohol, and the like.

  The ink-jet ink of the present invention contains the compound represented by the general formula (1) according to the present invention or an aprotic solvent having a relative dielectric constant of 30 or more and does not interfere with the object effects of the present invention. A known organic solvent can be used in combination as the ink solvent.

  The organic solvent used as the ink solvent in the inkjet ink of the present invention is selected from the following water-soluble organic solvents. Alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, Triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether , Ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol mono Ethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol dimethyl ether, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, -Methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (for example, formamide , N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3 -Dimethyl-2-imidazolidinone etc.), sulfoxides (eg dimethyl sulfoxide etc.), sulfones (eg sulfolane etc.), sulfonates (eg sodium 1-butanesulfonate) Salt), urea, acetonitrile, acetone and the like.

  In the ink-jet ink of the present invention, the total content of calcium ions, magnesium ions and iron ions, which are polyvalent metal ions of the ink, is preferably 10 ppm or less, more preferably 0.1 to 5 ppm, Most preferably, it is 0.1-1 ppm.

  By setting the content of polyvalent metal ions in the inkjet ink to the amount specified above, an ink having high dispersion stability can be obtained. The polyvalent metal ion according to the present invention is contained in sulfates, chlorides, nitrates, acetates, organic ammonium salts, EDTA salts and the like.

  In addition to the above description, the inkjet ink of the present invention is publicly known depending on the purpose of improving the emission stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Various additives, such as viscosity modifiers, specific resistance regulators, film forming agents, UV absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust inhibitors, etc. can be appropriately selected and used, For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376. , Whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771 and JP-A-4-219266. An agent etc. can be mentioned.

When forming an image by ejecting the ink-jet ink of the present invention, the ink-jet head used may be an on-demand system or a continuous system. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, thermal ink jet) Mold, bubble jet (registered trademark) mold, etc.)
Any discharge method may be used.

  In the image forming method using the ink-jet ink of the present invention, for example, the ink jet ink is ejected as droplets from the ink-jet head based on the digital signal and attached to the ink receiver by using a printer or the like loaded with the ink-jet ink. An ink jet print in which an ink jet recording image is formed on the image recording medium is obtained.

  As the inkjet image recording medium, for example, any of plain paper, coated paper, cast coated paper, glossy paper, glossy film, and OHP film can be used. For example, a recording medium coated with a recording liquid receiving layer having a so-called void layer in which a porous layer is formed may be used, but plain paper typified by office paper such as copy paper is inexpensive. In addition, the recording medium used in the inkjet ink of the present invention is preferable because the ink characteristics can be sufficiently exhibited (printing quality is good, there is no show-through, and wrinkles and curls are small after printing).

  The plain paper is preferably 80 to 200 [mu] m uncoated paper belonging to a part of uncoated paper, special printing paper and information paper. Examples of the plain paper of the present invention include high-grade printing paper, intermediate-grade printing paper, low-grade printing paper, thin printing paper, fine-coating printing paper, special printing paper such as colored fine-quality paper, foam paper, PPC paper, and other information paper. Specifically, there are the following papers and various modified / processed papers using them, but the present invention is not particularly limited to these.

  High quality paper and colored high quality paper, recycled paper, copy paper / colored paper, OCR paper, carbonless paper / colored paper, synthetic paper such as YUPO 60, 80, 110 microns, YUPO COAT 70, 90 microns, etc. Coated paper 90kg, Foam mat paper 70, 90, 110kg, Foamed PET 38 microns, Mitsuori-kun (above, Kobayashi recording paper), OK fine paper, New OK fine paper, Sunflower, Phoenix, OK Royal White, Export fine paper ( NPP, NCP, NWP, Royal White) OK Book Paper, OK Cream Book Paper, Cream Premium Paper, OK Map Paper, OK Ishikari, Cucumber, OK Foam, OKH, NIP-N (above, Shin Oji Paper), Gold Wang, Toko, export quality paper, special demand quality paper, book paper, book paper L, light cream book paper, trilogy subject Paper, continuous slip paper, high quality NIP paper, silver ring, gold yang, gold yang (W), bridge, capital, silver ring book, harp, harp cream, SK color, securities paper, opera cream, opera, KYP medical record, silvia HN, Excellent Foam, NPI Foam DX (Nippon Paper), Pearl, Kinryo, Uscream fine paper, Special Book Paper, Super Book Paper, Book Paper, Diamond Foam, Inkjet Foam (Mitsubishi Paper), Carpet V, carpet SW, white elephant, luxury publication paper, cream carpet, cream white elephant, securities / voucher paper, book paper, map paper, copy paper, HNF (above, Hokuetsu), phone book cover, Book paper, cream shiorai, cream shiorai medium luff, cream shiorai large luff, DSK (above, Daishowa Paper), Sendai MP fine paper Jinjiang, Thunderbird fine, hanging paper, colored paper base, dictionary paper, cream book, white book, cream fine paper, map paper, continuous slip paper (above, Chuetsu Pulp), OP gold cherry (chuetsu), gold sand, reference book paper, Replacement certificate paper (white), form printing paper, KRF, white foam, color foam, (K) NIP, fine PPC, Kishu inkjet paper (made by Kishu Paper), Taiou, Bright Foam, Kant, Kant White, Dante, CM paper, Dante Comic, Heine, paperback book, Heine S, New AD paper, Utrilo Excel, Excel Super A, Kant Excel, Excel Super B, Dante Excel, Heine Excel, Excel Super C, Excel Super D, AD Excel, Excel Super E, New Bright Foam, New Bright NI P (above Daio Paper), Sun Ring, Moon Ring, Cloud Pass, Galaxy, Baiyun, Weiss, Moon Ring Ace, Baiyun Ace, Cloud Pass Ace (above Nippon Paper Industries), Taiou, Bright Foam, Bright Nip (above) Nagoya Pulp), Peony A, Gold Pigeon, Special Peony, White Peony A, White Peony C, Silver Pigeon, Super White Peony A, Light Cream White Peony, Special Medium Quality Paper, White Pigeon, Super Medium Quality Paper, Blue Pigeon, Red Pigeon, Gold Pigeon M Snow Vision, Snow Vision, Gold Pigeon Snow Vision, White Pigeon M, Super DX, Hamanasu O, Red Pigeon M, HK Super Printing Paper (above Honshu Paper), Stalinden (A / AW), Star Elm, Star Maple, Star Laurel, Star Poplar, MOP, Star Cherry I, Cherry I Super, Cherry II Super, Star Cherry III, Star Cherry IV, Cherry III Super, Cherry IV Sue Over (more than made Marusumiseishi), SHF (more than manufactured by Toyo pulp), TRP (all manufactured by Tokai pulp), Konica copy paper NR-A100 (manufactured by Konica Minolta Business Technologies, Inc.).

  In the ink jet recording method of the present invention, printing is performed on both surfaces of a recording medium using the ink jet ink of the present invention.

  Examples of the recording medium include high-quality paper and color high-quality paper, inkjet plain paper and special paper, recycled paper, and slip paper. Usually, paper having a film thickness of 80 to 200 μm widely used as plain paper is particularly preferable for the purpose of the present invention.

  The ink-jet ink of the present invention can be printed on plain paper at a high speed as described above, has excellent permeability and dryness, and unlike ordinary ink, even when printed on plain paper, curls, etc. It does not occur, has good character reproducibility, does not cause a phenomenon such as so-called show-through, which is a phenomenon that the ink is removed from the back of the recording medium and can be seen from the back, and has no show-through even immediately after printing. In addition, since the ink-jet ink is excellent in drying property, particularly when performing double-sided printing, the object effect of the present invention can be exhibited.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<< Preparation of pigment dispersion >>
[Preparation of Yellow Pigment Dispersion Y1]
A mixture composed of the following additives was put in a container together with zirconia beads having a diameter of 1 mm, sealed, and dispersed for 2 hours with a paint shaker, and then the zirconia beads were removed to prepare a yellow pigment dispersion Y1.

Polymer dispersing agent obtained by copolymerizing styrene, methacrylic acid, octyl methacrylate and hydroxyethyl methacrylate (mass ratio = 10/40/20/30) 5 parts by mass Pigment: C.I. I. Pigment Yellow 128 15 parts by mass Water 80 parts by mass [Preparation of Magenta Pigment Dispersion M1]
In the preparation of the yellow pigment dispersion Y1, C.I. I. Instead of CI Pigment Yellow 128, C.I. I. A magenta pigment dispersion M1 was prepared in the same manner except that CI Pigment Red 122 was used.

[Preparation of Cyan Pigment Dispersion C1]
In the preparation of the yellow pigment dispersion Y1, C.I. I. Instead of CI Pigment Yellow 128, C.I. I. A cyan pigment dispersion C1 was prepared in the same manner except that CI Pigment Blue 15: 3 was used.

[Preparation of Black Pigment Dispersion K1]
In the preparation of the yellow pigment dispersion Y1, C.I. I. Instead of CI Pigment Yellow 128, C.I. I. A black pigment dispersion C1 was prepared in the same manner except that CI Pigment Black 7 was used.

[Preparation of Black Pigment Dispersion K2]
Cab-O-Jet-300 (a pigment concentration of 15% by mass manufactured by Cabot) was used as a self-dispersing pigment, and this was designated as black pigment dispersion K2.

<Preparation of ink>
[Preparation of Ink 1]
The following additives were mixed and stirred well. Next, this mixed liquid was subjected to filtration and membrane deaeration treatment using a hollow fiber membrane to prepare ink 1.

Compound 1: γ-butyrolactone 22 parts by mass Compound 2: diethylene glycol 15 parts by mass Magenta pigment dispersion M1 3 parts by mass in terms of pigment solid content Antifungal agent: Proxel GXL (manufactured by Avicia) 0.2 parts by mass Water Total amount is 100 parts by mass Part amount [Preparation of inks 2 to 18]
Inks 2 to 18 were prepared in the same manner as in the preparation of the ink 1 except that the composition of each additive was changed as shown in Table 1.

  The details of each abbreviation described in Table 1 are as follows.

(solvent)
γ-BR: γ-butyrolactone (* 1, * 2)
DMI: 1,3-dimethyl-2-imidazolidinone (* 1, * 2)
NMP: N-methyl-2-pyrrolidinone (* 1, * 2)
DMSO: Dimethyl sulfoxide (* 1, * 2)
DMAA: N, N-dimethylacetamide (* 1, * 2)
DMFA: N, N-dimethylformamide (* 1, * 2)
Ethylene carbonate (* 1)
Propylene carbonate (* 1, * 2)
DPGME: Dipropylene glycol monomethyl ether TEGBE: Triethylene glycol monomethyl ether TEGBE: Triethylene glycol monobutyl ether EGdME: Ethylene glycol dimethyl ether (relative dielectric constant 5.5)
DEG: Diethylene glycol 1,2-HDO: 1,2-hexanediol Gly: glycerin In each of the above solvents, * 1 is a compound corresponding to the general formula (1) according to the present invention, and * 2 is related to the present invention. It is a compound corresponding to an aprotic solvent having a relative dielectric constant of 30 or more.

(Surfactant)
E1010: Olfine E1010 (manufactured by Nissin Chemical Co., acetylenediol ethylene oxide (10 mol) addition product)
(dye)
Black dye K1: Food Black 2

<Measurement and evaluation of ink characteristic values>
(Measurement of viscosity)
The viscosity of each ink prepared above at 25 ° C. was measured using MODEL DD-1 manufactured by Yamaichi Electronics.

(Measurement of surface tension)
The surface tension at 25 ° C. of each ink prepared above was measured by a platinum plate method using a surface tension meter (manufactured by Kyowa Interface Science: CBVP-Z).

(Evaluation of ink dispersion stability)
After each ink was stored in a glass bottle, it was stored in an environment at 60 ° C. for 1 week, the change in viscosity before and after storage was measured, and the dispersion stability of the ink was evaluated according to the following criteria.

○: Change width of ink viscosity after storage is less than ± 10% of ink viscosity before storage ×: Change width of ink viscosity after storage is ± 10% or more of ink viscosity before storage << Inkjet Image formation >>
A piezo-type head with a nozzle diameter of 23 μm, 128 nozzles per color, and a nozzle density of 90 dpi (dpi represents 1 inch, that is, the number of dots per 2.54 cm) is mounted, recording density 1440 dpi × 1440 dpi, 1 drop Each of the produced ink-jet inks is set in an on-demand type ink-jet printer set to have a droplet volume of 6 pl, and plain paper (Konica copy paper NR-A100 (manufactured by Konica Minolta Business Technology Co., Ltd.) is used as a recording medium. )) Was set on a paper feed tray, and a solid image of 10 cm × 10 cm was printed.

  The following evaluation was performed for each of the image recording samples thus prepared.

<Evaluation of image recording sample>
(Evaluation of strikethrough resistance)
The back side of the sample printed on the plain paper (Konica copy paper NR-A100) was visually observed and evaluated for see-through resistance according to the following criteria.

A: No ink bleed or show-through on the back side B: No ink bleed or show-through on the back side is a permissible quality C: No ink bleed or show-through on the back side Slightly recognized, but not of concern when printing on the back side D: Ink bleed or back-through on the back side is quite acceptable and unacceptable quality for back-side printing E: Clear ink bleed or back-through on the back side Is recognized and is unsuitable for backside printing (evaluation of curl resistance)
For a sample printed with a solid area of 10 cm × 10 cm, the curl was measured by leaving it in the environment for 3 minutes after printing, and the curl resistance was evaluated according to the following criteria for each curl when each image was output. went.

A: No curl B: Slightly curled C: Some expansion and contraction is observed, weak curl is generated but is not a quality that is a problem in practical use D: Large shrinkage, obvious curl generated E: Quality that poses practical problems E: High shrinkage, strong curl, and quality that poses practical problems (Dryability evaluation)
Is there any transfer of ink from the solid print part on the back side of the white background of the overlapped sample for the printed sample that is printed 200 sheets of the above solid print image continuously and overlaid on the discharge tray? The dryness was evaluated according to the following criteria.

A: No transfer of ink to the other back of the sample was observed. B: Slight ink transfer was observed. C: Weak ink transfer was observed. D: Clear ink transfer was observed. Vigorous ink transfer was observed (evaluation of duplex printing suitability)
Immediately after the set-off evaluation, 200 sheets of the above-described solid print image evaluated for the set-off were set again on the paper feed tray of the inkjet printer so that the reverse side would be the print surface. Were continuously printed, and during printing or after printing, visual inspection was conducted for the presence or absence of conveyance failure or contamination of the printer conveyance section, and the double-sided printing suitability was evaluated according to the following criteria.

A: No conveyance failure or contamination of the printer conveyance unit was observed. B: No conveyance failure was observed, and no contamination of the printer conveyance unit was observed. C: No conveyance failure was observed, and the printer conveyance unit was not recognized. Slight contamination was observed, but it was not a problem for practical use.

D: Conveyance failure occurred during continuous printing, and contamination was observed in the printer transport section E: Conveyance failure occurred frequently during continuous printing, and considerable contamination was observed in the printer transport portion The results obtained as described above are shown in Table 2.

  As is apparent from the results shown in Table 2, the ink of the present invention (pigment ink) having the configuration defined in the present invention is superior in dispersion stability of the ink to the comparative example and is printed using plain paper. In this case, it can be seen that the film has excellent resistance to see-through, curl resistance, drying property and suitability for double-sided printing.

Claims (14)

An ink-jet ink comprising 20% by mass or more of a compound represented by the following general formula (1) and a pigment.

[Wherein, X ₁ represents an oxygen atom or NR ₂ , and X ₂ represents an oxygen atom, NR ₃ or CH ₂ . R ₁ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ each represents an alkyl group having 1 to 4 carbon atoms. ] The inkjet ink according to claim 1, wherein the content of the compound represented by the general formula (1) is 40% by mass or more. The inkjet ink according to claim 1, wherein the content of the compound represented by the general formula (1) is 50% by mass or more. The compound represented by the general formula (1) is at least one selected from ethylene carbonate, propylene carbonate and 1,3-dimethyl-2-imidazolidinone. The inkjet ink of Claim 1. An ink-jet ink comprising an aprotic solvent having a relative dielectric constant of 30 or more and 20% by mass or more and a pigment. The inkjet ink according to claim 5, wherein the content of the aprotic solvent having a relative dielectric constant of 30 or more is 40% by mass or more. The inkjet ink according to claim 5, wherein the content of the aprotic solvent having a relative dielectric constant of 30 or more is 50% by mass or more. 8. The inkjet ink according to claim 5, wherein at least one of the aprotic solvents having a relative dielectric constant of 30 or more is a compound represented by the general formula (1). . The ink content according to claim 1, wherein the water content is 10% by mass or more and less than 50% by mass. 10. The inkjet ink according to claim 1, wherein the surface tension is 40 mN / m or less. The ink-jet ink according to claim 1, wherein the pigment is dispersed by an anionic polymer dispersant. The inkjet ink according to any one of claims 1 to 10, wherein at least one of the pigments is a self-dispersing pigment. An inkjet recording method, comprising: discharging the inkjet ink according to any one of claims 1 to 12 from an inkjet recording head, and printing on plain paper. An inkjet recording method, comprising: discharging the inkjet ink according to any one of claims 1 to 12 from an inkjet recording head, and printing on both surfaces of a recording medium.