JP2010142965A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare satisfactory printed matter of high clearness and sharpness, free from grain-like feeling and bleeding, even in single path printing, when using an image forming method by an inkjet recording system. <P>SOLUTION: This image forming method uses ink containing at least 20% or more to 90% or less of water, ink-soluble resin and a pigment, and uses the inkjet recording system of forming an image by a single path, and the ink-soluble resin is a resin containing an acidic group neutralized with ammonia. The method applies a treating liquid aggregating or thickening an ink component, on a printing coated paper sheet, ejects thereafter the ink, and makes the printing coated paper sheet heated within a range of 40°C or higher to 60°C or lower when ejecting the ink. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming method using an ink jet recording method, and in particular, an ink jet recording in which an image is formed by ejecting ink after applying a treatment liquid capable of aggregating or thickening ink components onto a coated paper for printing. The present invention relates to a high-quality image forming method using the method.

  In recent years, the inkjet recording method can be easily and inexpensively produced images, 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, etc.).

  For example, with respect to the inkjet recording method for plain paper, printing can be performed at high speed, character reproducibility is good, and the back side of printing (a phenomenon in which the printed ink passes through the recording medium and the image appears on the back side), feathering, Various studies have been made from the viewpoint of no occurrence of image blurring.

  As one of the methods, water-based ink-jet inks are widely used as ink-jet inks, but such water-based ink-jet inks are used to make plain paper such as electrophotographic copy paper, high-quality paper, and medium-quality paper. When image recording is performed, there is a problem that curling and cockling (a phenomenon in which the paper surface gets wet and undulates) occurs on the image-recorded plain paper.

  On the other hand, when printed materials such as leaflets, brochures, and flyers, which are usually produced by offset printing, are produced by inkjet recording, printing and printing can be reduced. Printing can be performed on demand. For this reason, there is a demand for an offset printing alternative machine using an inkjet system as a printing machine capable of performing small lot and on-demand printing.

  Usually, the coated paper for printing used for offset printing is provided with a coating layer made of a binder such as a white pigment and starch on the front and back surfaces to enhance smoothness and gloss.

  When an image is formed on such paper using water-based ink-jet ink, the coating paper for printing absorbs the ink slowly, and the wettability of the ink-jet ink and the surface of the coating layer causes the coating for printing. There was a problem that inks gathered together on the surface of the paper, resulting in uneven printing of spots.

  On the other hand, a high-speed printing speed is required as a printing machine capable of performing small lot and on-demand printing. One method for achieving high speed printing is a single pass line head inkjet system. Inkjet heads with a length longer than the width of the printing range are called line heads. A single-pass line head inkjet means that all dots are formed when paper passes once under the line head in synchronization with paper feed. Called the system.

  On the other hand, the conventional method scans by moving the print head perpendicularly to the medium conveyance direction, and repeats a plurality of passes according to the scan width to form dots and create an image. This method is called a multi-pass or scan type.

  The scan type ink jet recording method prints by repeating the paper feed and scan operation for the scan width, whereas the line type ink jet recording device does not require the scan operation and prints in synchronization with the paper feed. Suitable for high-speed printing.

  When printing on coated paper for printing with single-pass printing, dots are absorbed and contacted with adjacent dots before drying or fixing. A good image cannot be obtained. Compared with this liquid, the dot shape changes due to the connection between droplets, and density unevenness occurs due to the liquid coming closer to the surface tension in the connected droplets and in the high density area where the printing rate is high. Deteriorate the state of the image in one step. In particular, the latter occurrence of density unevenness presents a spot having a size of about 0.1 mm to several mm. Therefore, if no countermeasure is taken, significant image deterioration occurs.

  Further, the change in dot shape due to ink contact occurs in a very short time after contact, so it is extremely difficult to completely suppress the occurrence. Even when the density unevenness is completely suppressed, the change in the dot shape reduces the sharpness of the extracted characters, and more than 50% particularly when printing a print pattern that has been subjected to image processing by the error dispersion method. The image is as if the high-density shadow area was flattened. This is due to the fact that the ink around the white dots in the error diffusion image in the high density portion is shifted and the white dots are randomly filled.

  There has been proposed a method (for example, see Patent Document 1) in which the ink is heated by adding a resin neutralized with an amine to heat the medium.

  However, this method is insufficient to improve image quality in single-pass printing, although the mixing of inks (hereinafter referred to as bleed) and the liquid is improved to some extent even in non-absorbent media due to heating and the presence of a specific solvent. Met.

  Further, a method of applying a treatment liquid before image formation (for example, see Patent Documents 2 to 7) is disclosed. In the method using these treatment liquids, when the amount of treatment liquid is increased, the cohesiveness is increased and the image is improved, but it is highly glossy like the coated paper for printing which is an application according to the present invention, and When this method is used for a recording medium having poor absorbability, it has been a big problem to cause deterioration of glossiness and cockling. When the processing solution is reduced to prevent cockling, the cohesiveness is lowered, and the effect of improving the image quality particularly in single pass becomes insufficient.

  The problem to be solved by the present invention is that, when printing is performed on a coated paper for printing by this single pass printing, the sharpness is reduced due to the fact that the shape is not maintained by connecting dots, and between the inks The deterioration of the graininess due to the gathering of density unevenness can be suppressed, and the ink bleed between colors (hereinafter referred to as bleed) that occurs when printing on a slightly absorbent medium at high speed. And an image forming method having good gloss and dischargeability.

  The improvement in sharpness cannot be improved even when an image is formed while heating the media with an ink containing an amine-neutralized resin. This is because the thickening behavior due to the presence of the amine neutralizing resin is not fast enough to suppress dot deformation in a single pass, and the thickening is performed from the dot surface. This is considered to be because there is not enough force to hold down the deformation of the ink when the ink comes into contact.

  In addition, when an image is formed on a substrate that has been pre-coated with a treatment liquid that agglomerates ink, the agglutination reaction is fast, but the agglomeration reaction occurs from below, and the treatment agent hardens to the top only after diffusing in the dots. Since the liquid above the dots spreads wet, contacts with the liquid flowing from the top of the adjacent dots, and spreads greatly wet, the effect of suppressing the reduction in sharpness is low. When the amount of the processing liquid is increased, image disturbance due to the flow of the processing liquid, cockling deterioration due to the increase in the liquid amount, and the like occur.

When the printing method using the treatment liquid and the heating of the medium are used together, the evaporation of the treatment liquid is promoted by the heating of the medium after the application of the treatment system, and the aggregation effect of the treatment liquid is impaired. For this reason, it is preferable to apply ink immediately after application of the treatment liquid. In the case of the scan-type printing method, due to the configuration of the apparatus, it takes a long time before the ink is applied after the treatment liquid is applied. This causes great deterioration in cohesiveness, and particularly when a processing liquid is applied to a substrate with poor absorption, the liquid composition changes with the drying and evaporation of the liquid, and the processing liquid itself exhibits repellency, causing deterioration in image quality. . Furthermore, due to the multi-pass injection configuration, the time from when the treatment liquid is applied until the ink lands on the media varies greatly depending on the dot, so the cohesiveness of the ink varies from dot to dot and makes the dots non-uniform. In some cases, this may lead to degradation of image quality. On the other hand, in the case of single pass, due to the configuration of the device, the dots land immediately after application of the treatment liquid, and the landing time for each dot is so small that it does not become a problem. When used in combination, it can be said that single-pass printing is superior.
JP 2008-208153 A Japanese Patent Laid-Open No. 6-092009 JP-A-6-099576 JP-A-6-128514 JP 7-001837 A Japanese Unexamined Patent Publication No. 6-057192 JP-A-8-020161

  In the image forming method based on the ink jet recording method, even when printed on a slightly absorbent medium such as coated paper for printing by single-pass printing, gloss is not impaired, sharpness is high, and there is no graininess or blurring. The purpose is to produce a printed material.

  The problem to be solved by the present invention is achieved by the following means.

  1. In an image forming method using an ink jet recording method in which an ink containing at least 20% to 90% water, an ink-soluble resin, and a pigment is used to form an image in a single pass, the ink-soluble resin is contained by ammonia. A resin having a hydrated acid group, and after applying a treatment liquid capable of aggregating or thickening the ink component onto a printing paper, the ink is discharged, and further, printing is performed when the ink is discharged. An image forming method, wherein the use paper is heated to 40 ° C. or more and 60 ° C. or less.

2. ^2. The image forming method as described in 1 above, wherein the amount of the treatment liquid applied is 0.5 ml / m ² or more and 7 ml / m ² or less.

  3. 3. The image forming method as described in 1 or 2 above, wherein the treatment liquid contains a polyvalent metal salt.

  4). 4. The image forming method according to any one of 1 to 3, wherein the processing liquid is an aqueous solution of an organic acid, and the pKa is smaller than 4.5.

  5. 5. The image forming method according to any one of 1 to 4, wherein the processing liquid contains a resin having a positive charge.

  When the image forming method according to the inkjet recording method of the present invention is used, even when printed on a slightly absorbent medium such as coated paper for printing by single pass printing, gloss is not impaired, sharpness is high, and graininess It was found that it was possible to produce a good print without blurring.

  In the image forming method of the present invention, the ink dot can be solidified from the bottom of the dot by reaction with the processing liquid and from the top of the dot by the thickening effect of the resin by evaporation of ammonia so as to surround the dot. Even in a high-speed printing form such as pass printing, it is believed that an image with sufficiently low density unevenness, little graininess, sharpness, and almost complete suppression of bleeding between colors could be obtained. Since the dots are hardened so as to wrap only the surface without hardening the dots, it is possible to fix the dots more efficiently than when the dots are solidified. I guess you can get. Further, since the entire dot is not cured, it is assumed that the gloss is not impaired even if printing is performed on paper having low absorbability such as coated paper for printing.

  In general, when a large amount of processing liquid is used, cockling is deteriorated and gloss of the coated paper for printing is caused. However, according to the image forming method of the present invention, each image can be improved with a small amount of processing liquid. Obtainable.

  The present invention is an invention for water-based ink-jet inks. In the present invention, water-based ink is intended to contain water as a main solvent, and is an electrode that is dispersed by chance or as an additive in oil-based inks and alcohol-based inks. A small amount of water is not implied, and specifically, 20% or more of water is included in the ink.

  The resin having an acid group neutralized by ammonia in the present invention is a resin having an acid group such as a carboxylic acid or a sulfonic acid group in the resin and using ammonia for neutralization of the resin.

  By using ammonia as an acid group counter, the ammonia quickly evaporates due to the heat of the coated paper and the resin's solubility decreases, so a film is formed on the dot surface, preventing ink outflow and image quality. The present inventor presumes that it will be effective for improvement.

  Specific examples of the resin include acrylic resins, styrene acrylic resins, acrylonitrile-acrylic resins, vinyl acetate acrylic resins, polyurethane resins, and polyester resins.

  A monomer having an acid group may be polymerized to obtain such a resin. Examples of such monomers include radical copolymerization of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and styrene acid derivatives. Moreover, you may copolymerize with another monomer as needed.

  The molecular weight of the resin is preferably 3000 or more from the viewpoint of the effect of improving the image quality according to the present invention, and preferably 30000 or less, more preferably 10,000 or more and 20000 or less from the viewpoints of injection property and viscosity. Moreover, it is preferable that an acid value is 60-300.

  The fact that the resin neutralized with ammonia is dissolved in the ink means a water-soluble resin that is not adsorbed to the pigment in the ink, and a GPC is used to obtain a supernatant obtained by centrifuging the ink at 30000 rpm for 2 hours. The amount of ink-dissolving resin can be measured.

  The amount of the ink-soluble resin of the present invention varies depending on the polymerization degree of the resin, but is preferably 2 to 10%, more preferably 3 to 6% of the total ink mass. If the amount of the resin is small, the effect of the present invention cannot be obtained, and conversely, if it is large, the ink jetting property and storage stability are abnormal.

  These resins are preferably added separately from the resin for dispersing the pigment. That is, it is preferably added later to the stable pigment dispersion. If the ammonia-neutralized resin is present in a large amount dissolved in the solvent in the ink, good results can be obtained in terms of gloss and ink maintainability.

  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. I. Pigment Orange; 43, C.I. I. Vat Violet; 3, C.I. I. Pigment Violet; 19, 23, 37, C.I. I. Pigment Green; 36, 7, C.I. 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.

  The pigment used in the present invention is preferably used after being dispersed by a disperser together with a dispersant and other necessary additives according to various desired purposes. As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used.

  The average particle size of the pigment dispersion used in the ink of the present invention is preferably 10 nm to 200 nm, more preferably 10 nm to 100 nm, and still more preferably 10 nm to 50 nm. If the average particle size of the pigment dispersion exceeds 100 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.

  In addition to the resin neutralized with ammonia, a resin may be further included for various purposes. These resins may be contained in a plurality or in a copolymer, and may be dispersed in an emulsion state. In the case of dispersing in an emulsion state, the particle diameter is preferably 300 nm or less from the viewpoint of not impairing the jetting property by inkjet. In the case of a soluble polymer, the composition and molecular weight are not particularly limited. However, since a polymer having a higher degree of polymerization tends to deteriorate injection properties, the molecular weight is preferably 50,000 or less, although it depends on the composition of the polymer.

  The solvent for the ink that dissolves and disperses the solute preferably contains a solvent component that dissolves in water in addition to water for the purpose of improving ejection properties and adjusting ink physical properties. As long as the effects of the present invention are not impaired, the type of the solvent is not particularly limited. For example, glycerin, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, decaglyceryl, 1,4-butanediol, 1, 3-butanediol, 1,2,6-hexanetriol, 2-pyrrolidinone, dimethylimidazolidinone, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl Ether, triethylene glycol No ethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene Glycol monopropyl ether, diethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol Tylene glycol dibutyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, tripropylene glycol dibutyl ether, 3-methyl-2,4-pentanediol, diethylene glycol monoethyl ether acetate, 1,2 -Hexanediol, 1,2-pentanediol, 1,2-butanediol, and the like.

  The ink of the present invention preferably contains an activator for improving dischargeability and wettability. As the surfactant to be used, any of cationic, anionic, amphoteric and nonionic can be used. Specific examples of the surfactant used are not particularly limited. For example, examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, and 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, alkyl benzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher grade Alcohol sulfate, secondary higher alcohol sulfate, alkyl Amphoteric surface activity such as ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkylphenyl ether sulfate, monoglyculate, fatty acid alkylolamide sulfate, alkyl ether phosphate, alkyl phosphate As the agent, carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine, etc. As nonionic active agents, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether , Polyoxyethylene lanolin derivatives polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene glycerin fatty acid ester, polyoxyethylene 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, Examples include alkylamine oxide, acetylene glycol, and acetylene alcohol. Further, from the viewpoint of lowering the surface tension, it is preferable that some of these surfactants are substituted with fluorine atoms or silicon atoms.

  These surfactants and solvents may be used alone or in combination.

  The ink of the present invention may further contain additives for various purposes. Various known additives such as polysaccharides, viscosity modifiers, specific resistance modifiers, depending on the purpose of improving the emission stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances , Film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust inhibitors, etc. can be appropriately selected and used, for example, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil Oil droplet fine particles such as JP-A-57-74193, 57-87988 and 62-261476, JP-A-57-74192, 57-87989, 60-72785. No. 61-146591, JP-A-1-95091, JP-A-3-13376, etc., and JP-A-59-42993, JP-A-5 No. -52689, 62-280069 JP, mention may be made of a fluorescent brightening agent that is described in the 61-242871 Patent and 4-219266.

  The treatment liquid capable of aggregating or thickening the ink component in the present invention refers to a liquid having a component that acts on the solid content in the ink to insolubilize it.

  For example, a liquid containing a polyvalent metal salt or the like is brought into contact with ink, thereby blocking an anionic group in the pigment or resin and causing aggregation and precipitation. Although depending on the selection of the pigment or resin in the ink, examples of the treatment liquid having such an agglomeration mechanism include acidic liquids and cationic resin solutions in addition to the polyvalent metal salt solution.

  As the polyvalent metal salt, a metal salt having a valence of 2 or more can be used. As the type of salt, known salts such as carbonate, sulfate, nitric acid, hydrochloric acid, organic acid, boric acid and phosphoric acid can be used. It is also preferable to adjust the pH to dissolve the polyvalent metal salt as necessary. Particularly preferred salts from the viewpoints of performance and handling of the present invention include calcium nitrate, calcium chloride, aluminum nitrate, aluminum chloride and the like.

  When an acidic liquid is used as the treatment liquid, the acid of the pH adjusting agent that makes the treatment liquid acidic is not particularly limited, but considering that it causes a reaction with the carboxylic acid group in the ink, pKa Is preferably an acid lower than 4.5. Considering the quality of the final printed matter (yellowing of the printed matter, image storability, etc.), an organic acid is preferable to an inorganic acid. Examples of the acid of the pH adjuster include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, carbonic acid, an organic compound having a carboxylic acid group, an organic compound having a sulfonic acid group, and an organic compound having a phosphoric acid group. Particularly preferably, citric acid, isocitric acid, oxalic acid, maleic acid, fumaric acid, malonic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, citric acid, 2-pyrrolidone-5-carboxylic acid Examples thereof include acids, benzoic acid, benzoic acid derivatives, salicylic acid, ascorbic acid, malic acid, benzenesulfonic acid, benzenesulfonic acid derivatives, pyrpinic acid, and oxaloacetic acid.

  Although there is no restriction | limiting in particular as cationic resin, Since the high effect is acquired with little addition amount of resin which has quaternary amine, it is preferable. As the group imparting cationicity to the resin, it is preferable to have a nitrogenous cation or a metallic cation in the resin. Examples thereof include polyallylamine, polyamine, cation-modified acrylic resin, cation-modified methacrylic resin, cation-modified vinyl resin, cationic urethane resin, and copolymers thereof.

  As an agent to be contained in these treatment liquids, it is preferable to dissolve a polyvalent metal salt, an organic acid having a pKa of less than 4.5, a quaternary amine resin, or the like. These exhibit high cohesiveness with a small addition amount. It is preferable that these components that cause aggregation are contained in the treatment liquid by adjusting an appropriate amount with respect to the amount of ink or treatment liquid attached.

  The treatment liquid preferably contains a compound that adjusts the liquid physical properties such as a solvent and an activator, if necessary, in addition to the component that aggregates or thickens the solid content in the ink.

  Solvents that can be contained in the treatment liquid include water, glycerin, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol. , Decaglyceryl, 1,4-butanediol, 1,3-butanediol, 1,2,6-hexanetriol, 2-pyrrolidinone, dimethylimidazolidinone, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol Nomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene Glycol monoethyl ether, dipropylene glycol monopropyl ether, diethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monomethyl ether Diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, tripropylene glycol dibutyl ether, 3-methyl-2,4-pentanediol, diethylene glycol monoethyl ether acetate, Examples include 1,2-hexanediol, 1,2-pentanediol, 1,2-butanediol, and the like.

  In order to make the liquid properties convenient for the coating method of the treatment liquid, it is preferable to use one or a plurality of them in combination. In particular, it is preferable that a part of the solvent contains water from the viewpoints of coating property, drying property, image quality, safety and the like.

  If necessary, the treatment liquid preferably contains an activator. As the surfactant to be used, any of cationic, anionic, amphoteric and nonionic can be used. For example, the activator exemplified as the activator that can be used in the ink of the present invention can be similarly used for the treatment liquid.

  Further, the treatment liquid may contain additives for various purposes. For example, polysaccharides, viscosity modifiers, specific resistance modifiers, film forming agents, ultraviolet absorbers, antioxidants, fading inhibitors, antifungal agents, rust preventives, etc. can be appropriately selected and used. Examples thereof include oil droplet fine particles such as paraffin, dioctyl phthalate, tricresyl phosphate, and silicone oil, ultraviolet absorbers, anti-fading agents, and fluorescent brighteners.

  Any known method may be used as a treatment liquid coating method. Specific coating methods include roller coating, inkjet coating, curtain coating, and spray coating. The roller method is preferable in terms of a coating method with a small amount of liquid. In order to limit the application location and the amount of treatment liquid applied according to the image printing rate and paper type, the treatment liquid application method by the ink jet method is preferred.

The amount of treatment liquid applied is not particularly limited, but if the amount is too large, cockling, image distortion due to the flow of treatment liquid, degradation of gloss, etc. may occur. In order to obtain high image quality, the amount of attached processing solution is preferably ^{0.5~7ml / m 2, 1.5~4ml / m} 2 is more preferable.

The printing paper for use in the present invention refers to a slightly water-absorbent coated paper having a coating layer made of a binder such as a white pigment and starch. The coated paper for printing that exhibits the effects of the present invention has a transfer amount of 0.05 ml of water adjusted with an activator or the like so that the surface tension is 20 mN / m or more and 40 mN / m or less. it is preferable for exerting the effects of the present invention is / m ² or more 6 ml / m ² or less is coated paper for printing.

  In the present invention, the surface temperature of the printing application paper is heated to 40 ° C. or more and 60 ° C. or less when ink is ejected. When the temperature is lower than 40 ° C., the image quality improvement effect of the present invention cannot be obtained. Therefore, the apparatus for performing the image forming method of the present invention is equipped with a heater for heating the recording medium. preferable.

  About the heating method of printing application paper, you may heat a printing coated paper from the back surface. Also preferred is a method of heating the surface with infrared rays just before the print-coated paper is conveyed under the head. The type of the heater is not particularly limited, and it is preferable to select and use a necessary method from known methods such as an infrared heater, heating wire, UV lamp, gas, hot air dryer, etc. Temperature is preferable from the viewpoint of safety and energy efficiency.

  In the inkjet ink recording method of the present invention, printing is performed on the coated coated paper by ejecting ink as droplets from the inkjet head based on digital signals by a printer or the like loaded with inkjet ink.

  When forming an image by ejecting the ink of the present invention, the ink jet head to be 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) Any ejection method such as a mold, a bubble jet (registered trademark) mold, or the like may be used.

  Among them, in the ink jet recording method of the present invention, it is preferable to use a piezo ink jet recording head having a nozzle diameter of 30 μm or less.

  The ink jet recording method of the present invention is a single pass type ink jet recording method. The single-pass ink jet recording method is an ink jet recording method in which when a medium passes under one ink jet head unit, ink droplets are applied to all pixels where dots are to be formed in one pass.

  As means for achieving the single-pass ink jet recording method, it is preferable to use a line head ink jet head.

  The line head type ink jet head refers to an ink jet head having a length equal to or greater than the width of the printing range. As a line head type ink jet head, one head may be larger than the width of the printing range, or a configuration in which a plurality of heads are combined to exceed the width of the printing range as disclosed in Japanese Patent Application Laid-Open No. 2007-320278. May be.

  A plurality of line head type ink jet heads can be used for one color. In this case, the heads of the same color are preferably adjacent to each other. When the heads are separated from each other in the same color, the time from the application of the treatment liquid to the landing of the ink varies within the same color, causing dot disproportionation and image quality degradation.

  As the order of colors to be arranged, when an image is composed of yellow, cyan, magenta, and black, it is preferable to arrange the head for discharging yellow last. Although it depends on the aggregation property of the ink for each color, it is more preferable to discharge in the order of black, cyan, magenta, and yellow. This is because, since the cohesiveness is reduced due to drying and evaporation of the treatment liquid as time elapses after the treatment liquid is applied, it is preferable to dispose a light head that is less susceptible to image quality deterioration at the rear of the conveyance.

  Specific examples of preferable apparatuses for achieving the image forming method of the present invention are shown below.

  In FIG. 1, 11 is a head unit. Reference numerals 111 to 114 denote heads, and the nozzle pitch of each head is 360 dpi. The nozzle holes 15 of the head 111 and the head 112, and the head 113 and the head 114, respectively, are arranged alternately as shown in FIG.

  This is an apparatus that outputs an image for the head width when the paper passes under the head unit 11 by the transport mechanism 12.

  An infrared heater 13 is attached to warm the paper in advance. A treatment liquid application roller 14 is attached immediately before the head so that the amount of the treatment liquid can be variably applied according to the type of paper and the target amount.

  In order to increase the printing width, it is preferable to use a line head unit in which the heads are alternately arranged as shown in FIG.

  FIG. 4 shows a comparative scanning printer. The medium 44 is transported in the transport direction by the transport roller 45. The head unit 41 includes heads 411 to 414, is attached to the carriage 42, and is scanned in a direction perpendicular to the conveyance direction of the medium 44. Heating by the heater 43 is possible from the back side.

Preparation of Pigment Dispersion Magenta Pigment Dispersion 3 parts by weight of Joncryl 678 (manufactured by BASF), 1.3 parts by weight of dimethylaminoethanol, and 80.7 parts by weight of ion-exchanged water were dissolved by stirring with heating and mixing. . In this solution, C.I. I. After 15 parts by mass of Pigment Red 122 was added and premixed, the mixture was dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads to obtain a magenta pigment dispersion having a pigment solid content of 15%.

Cyan Pigment Dispersion As a pigment dispersant, 3 parts by mass of Joncryl 678 (manufactured by BASF) 1.3 parts by mass of dimethylaminoethanol and 80.7 parts by mass of ion-exchanged water were heated and stirred and mixed to dissolve. In this solution, C.I. I. After adding 15 parts by weight of Pigment Blue 15: 3 and premixing, the mixture was dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads to obtain a cyan pigment dispersion having a pigment solid content of 15%. .

Preparation of Ink 1-M The materials described below, except for the magenta pigment dispersion, were mixed in the amounts shown and sufficiently stirred, and then 33 parts by mass of the magenta pigment dispersion was added with stirring.

  After sufficiently stirring, the mixture was filtered through a # 3500 mesh metal filter, degassed with a hollow fiber membrane, and ink 1-M was prepared. JDX6500 is an acrylic resin neutralized with ammonia.

<Ink 1-M composition>
Magenta pigment dispersion 33 parts by weight JDX6500 (manufactured by BASF) 10 parts by weight Activator E1010 0.5 parts by weight Propylene glycol 15 parts by weight TEGBE 5 parts by weight Glycerin 25 parts by weight Water remaining In the same manner as ink 1-M, the following composition Ink 1-C was produced.

<Ink 1-C composition>
Cyan Pigment Dispersion 33 parts by weight JDX6500 (manufactured by BASF) 10 parts by weight Activator E1010 0.5 parts by weight Propylene glycol 15 parts by weight TEGBE 5 parts by weight Glycerin 25 parts by weight Water remaining In the same manner as ink 1-M, the following composition Ink 2-M and Ink 3-C were respectively prepared.

<Ink 2-M composition>
Magenta pigment dispersion 33 parts by mass Activator E1010 0.5 part by mass Propylene glycol 15 parts by mass TEGBE 5 parts by mass Glycerin 35 parts by mass Water remainder <Ink 3-C composition>
Cyan pigment dispersion 33 parts by weight Activator E1010 0.5 part by weight Propylene glycol 15 parts by weight TEGBE 5 parts by weight Glycerin 35 parts by weight Water remainder Ink 1-C and ink 1-M are used as ink set A, and ink 2- C and ink 2-M were used as ink set B. Ink set A contains JDX6500 (manufactured by BASF) as an ammonia neutralizing resin, and ink set B contains no ammonia neutralizing resin.

Preparation of treatment liquid After the following components were mixed and sufficiently stirred, the mixture liquid was filtered through a # 3500 mesh metal filter, deaerated with a hollow fiber membrane, and treatment liquid 1 was prepared.

<Processing liquid 1>
Calcium nitrate 5 parts by mass Glycerin 30 parts by mass Diethylene glycol monobutyl ether 15 parts by mass Polyalkylene glycol lauryl ether 1 part by mass Water remainder In the same manner as in the treatment liquid 1, the following components were mixed to prepare treatment liquids 2 to 6, respectively.

<Processing liquid 2>
Maleic acid (pKa 1.75) 5 parts by mass Glycerin 30 parts by mass Diethylene glycol monobutyl ether 15 parts by mass Polyalkylene glycol lauryl ether 1 part by mass Water remainder <Treatment liquid 3>
Citric acid (pKa 3.15) 8 parts by mass Glycerin 30 parts by mass Diethylene glycol monobutyl ether 15 parts by mass Polyalkylene glycol lauryl ether 1 part by mass Water remainder <Treatment liquid 4>
Calcium nitrate 12 parts by mass Glycerin 30 parts by mass Diethylene glycol monobutyl ether 15 parts by mass Polyalkylene glycol lauryl ether 1 part by mass Water remainder <Treatment liquid 5>
PAS-21-Cl (Nitto Boseki Co., Ltd.): Secondary polyamine resin 10 parts by mass Glycerin 30 parts by mass Diethylene glycol monobutyl ether 15 parts by mass Polyalkylene glycol lauryl ether 1 part by mass Water remainder <Treatment liquid 6>
HAS-H-1L (Nitto Boseki Co., Ltd.): Quaternary polyamine resin 5 parts by mass Glycerin 30 parts by mass Diethylene glycol monobutyl ether 15 parts by mass Polyalkylene glycol lauryl ether 1 part by mass Water Remaining The printing conditions are as follows.

  An apparatus having the configuration shown in FIG. 1 was used.

Printing resolution: 720 dpi x 720 dpi
Printing was performed with a 360 dpi 16 pl head arranged so that the nozzles of each head were arranged alternately.

Printing paper: SA Kanofuji, Mirror Coat Platinum (both Oji Paper Co., Ltd.)
Output image: Natural image and patch image with a printing rate of 0 to 100% Paper transport speed: 300 mm / s
Printing was performed by the image forming method described in Table 1 below. Regarding the temperature of the media, the temperature of the media surface immediately before the head was measured with a non-contact type infrared thermometer.

[Evaluation]
<Evaluation of sharpness>
A: The dot shape remains in a solid patch of 100 to 50%. B: When observed with a microscope, the dots are partially connected to each other, but there is almost no problem in the appearance image. In some cases, the ink pool is conspicuous depending on the state of error diffusion. ×: There is a place where the white portion is completely buried in the high density portion. In the halftone area, dots are connected and there is a graininess larger than the printing resolution.

<Evaluation from liquid>
○: There is no density unevenness or dots are not connected. Δ: There is almost no problem with a completely solid part, but there is a slight density distribution in a narrow solid part formed by densely connecting several dots. Even in the solid portion, density unevenness is observed. Or, there is a clear density distribution in a narrow solid portion formed by connecting several dots densely.

<Evaluation of bleed>
◎: Bleed does not occur. ○: When 100% solid portion is covered with 100% solid, the outflow of ink is smaller than 0.02 mm. △: When 100% solid portion is covered with 100% solid, The outflow is in the range of greater than 0.02 mm and less than or equal to 0.05 mm. X: When 100% solid is covered on the 100% solid part, the outflow of ink is greater than 0.05 mm.

<Evaluation of gloss>
◎: There is no significant decrease in gloss ○: I don't care about the difference in gloss from the non-printed area in SA Kanfuji, but there is a clear decrease in gloss in the non-printed part in Mirror Coat Platinum △: In SA Kanfuji A drop in gloss is felt ×: The printed part appears rough.

<Evaluation of cockling>
A: No cockling occurs. O: Some cockling occurs but almost disappears due to drying. Δ: Some cockling occurs. X: The cockling is severely rubbed.

Comparative Example 8
Using the scan type printer shown in FIG. 4, ink was introduced into the heads 413 and 414, and the same image was produced by an interleave method.

Printing conditions are: Print resolution: 720 dpi x 720 dpi
(360 dpi 16 pl bidirectional printing)
Printing paper: SA Kanofuji, Mirror Coat Platinum Output image: Natural image and patch image with 0 to 100% coverage.

  Printing was performed under the same printing conditions as in Example 4.

Comparative Example 9
The same image was produced by the interleaving method while applying the treatment liquid using the inkjet head 415 using the scan type printer shown in FIG.

Printing conditions are: Print resolution: 720 dpi x 720 dpi
(360 dpi 16 pl one-way printing)
Printing paper: SA Kanofuji, Mirror Coat Platinum Output image: Natural image and patch image with 0 to 100% coverage.

Preheating, treatment liquid type, and ink set are the same as in Example 4. However, since it was applied from an inkjet head, it was uniformly applied without pixel defects, and thus a treatment liquid of 12.9 ml / m ² was attached.

Comparative Example 10
The printing method was the same as in Comparative Example 9, except that the treatment liquid was printed at a printing rate of 40%. At this time, the amount of the treatment liquid is 5.2 ml / m ² .

  Table 2 shows the results of evaluation of printed matter in each image forming method.

  Since Comparative Examples 8 to 10 are scan type printers, the printing speed is slower than the printer configuration of the example, the time from application of the treatment liquid to printing is misaligned, sharpness, and there is a problem of bleeding from the liquid. There was also a low gloss performance. In Comparative Example 9, the amount of the treatment liquid was large and a cockling problem occurred.

  According to the printing method of the present invention, it is possible to produce a high-quality printed product without cockling by a single pass.

It is an example of the single pass type | mold inkjet printer used for this invention. The head unit which arranged the nozzle alternately is shown. The head unit in which the heads for increasing the print width are arranged alternately is shown. It is an example of a scanning ink jet printer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Head unit 111-114 Head 12 Conveyance mechanism 13 Infrared heater 14 Roller for process liquid application 15 Nozzle hole 41 Head unit 411-414 Head 42 Carriage 43 Heater 44 Media 45 Conveyance roller

Claims (5)

In an image forming method using an ink jet recording method in which an ink containing at least 20% to 90% water, an ink-soluble resin, and a pigment is used to form an image in a single pass, the ink-soluble resin is contained by ammonia. A resin having a hydrated acid group, and after applying a treatment liquid capable of aggregating or thickening the ink component onto a printing paper, the ink is discharged, and further, printing is performed when the ink is discharged. An image forming method, wherein the use paper is heated to 40 ° C. or more and 60 ° C. or less. ^2. The image forming method according to claim 1, wherein the amount of the treatment liquid applied is 0.5 ml / m ² or more and 7 ml / m ² or less. The image forming method according to claim 1, wherein the processing liquid contains a polyvalent metal salt. The image forming method according to claim 1, wherein the processing liquid is an aqueous solution of an organic acid, and the pKa is less than 4.5. The image forming method according to claim 1, wherein the processing liquid contains a resin having a positive charge.

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