JP5581041B2 - Inkjet recording treatment liquid, inkjet recording method and inkjet recording apparatus using the treatment liquid - Google Patents

Description

  The present invention relates to a processing liquid for ink jet recording that can be used in an ink jet recording method for forming an image on a recording medium by ejecting ink toward a recording medium such as paper, an ink jet recording method using the processing liquid, and ink jet recording. Relates to the device.

  Conventionally, for example, based on image information transmitted from another device, ink containing at least water and a colorant is ejected toward a recording medium such as PPC paper from an ink ejection port (nozzle) of an inkjet recording head. Thus, an ink jet recording apparatus that forms an image by attaching ink to the recording medium is known. The ink jet recording apparatus generally includes a transport belt for transporting a recording medium and an ink jet recording head disposed to face the transport belt. An image is formed on the recording medium by ejecting ink from a plurality of ink ejection openings arranged in the ink jet recording head toward the recording medium while the recording medium is conveyed by traveling of the conveying belt. The recording medium on which the ink is adhered and the image is formed is discharged from the conveyance belt by the discharge roller.

  In such an ink jet recording apparatus, in order to perform large-scale high-speed printing such as 150 sheets / minute, in addition to increasing the driving frequency of the recording head for ejecting ink, the width is equal to or greater than the width of the recording medium. It has been proposed to use a long line-type ink jet recording head having a length of. That is, instead of a serial type recording head that ejects ink while scanning the recording head in a direction perpendicular to the conveyance direction of the recording medium, a long line type recording head is attached to the apparatus main body so as to extend in the width direction of the recording medium. Ink is discharged simultaneously over the entire width of the recording medium while being fixed. As a result, a significantly faster processing is realized as compared with the serial type recording head.

  However, when the high speed processing of the ink jet recording apparatus is achieved, the time from when the ink is ejected to the recording medium until the discharge roller comes into contact with the recording medium is shortened. There is a high possibility that ink contacts with the recording medium and adheres to the roller surface. As a result, the density of the image formed on the recording medium is reduced, the image is chipped or disturbed, and the recording medium is wound around the roller.

  Further, the ink adhering to the roller surface may be transferred to a non-printing portion of the recording medium (a portion of the recording medium to which no ink is attached: for example, a peripheral edge or a side edge portion of the recording medium) to contaminate the recording medium. In the case of continuous printing on a plurality of recording media, there is a problem that the ink adhering to the roller surface is transferred to a subsequent recording medium like a print and contaminates the plurality of recording media.

  In order to cope with this problem, it is conceivable to apply the techniques disclosed in Patent Documents 1 and 2. That is, after the ink is attached to the recording medium, an overcoat liquid (treatment liquid) containing a polymer capable of forming a transparent film is attached. As a result, it is expected that the surface of the ink adhering to the recording medium is covered with the polymer film of the overcoat liquid to suppress the ink adhering to the discharge roller surface.

JP 2002-144551 A (paragraph 0014) JP2003-53942A (paragraph 0027)

  However, general acrylic emulsions and urethane emulsions listed as polymers of the overcoat liquid disclosed in Patent Documents 1 and 2 are, as will be apparent from Examples described later, a resin film-forming property. Inferior to drying, ink adhesion to the surface of the discharge roller could not be sufficiently suppressed. This tendency is particularly remarkable in high-speed printing such as 150 sheets / minute.

  The present invention addresses the above-described problems in the ink jet recording method in which after the ink is deposited on the recording medium, a treatment liquid (overcoat liquid) for coating the ink with a resin film is deposited. It is an object of the present invention to provide a treatment liquid that can sufficiently suppress the adhesion of ink to the surface of the discharge roller even in high-speed printing at 150 sheets / minute.

  That is, one aspect of the present invention is a treatment liquid used in an ink jet recording method in which a treatment liquid for coating an ink on a recording medium and then coating the ink with a resin film is attached to the recording medium, and the glass transition Inkjet recording treatment comprising a graft copolymer and / or block copolymer emulsion of an acrylic resin having a temperature of -5 ° C or higher and lower than 30 ° C and a urethane resin having a glass transition temperature of 30 ° C or higher and 50 ° C or lower It is a liquid.

  According to this treatment liquid for ink jet recording, excellent film-forming properties are secured by an acrylic resin having a glass transition temperature of −5 ° C. or higher and lower than 30 ° C. and relatively low, and the glass transition temperature is 30 ° C. or higher and 50 ° C. or lower. Excellent drying properties (quick drying) are ensured by a relatively high urethane resin. By covering the surface of the ink previously attached to the recording medium with a film of such a graft copolymer of acrylic resin and urethane resin and / or block copolymer, the ink adheres sufficiently to the surface of the discharge roller. To be suppressed.

  In addition, since a graft copolymer and / or block copolymer of an acrylic resin and a urethane resin forms a transparent film, gloss is imparted to the image by this transparent resin film, and an image with excellent cosmetic properties can be obtained. There are also benefits to be gained. Furthermore, there is an advantage that flexibility and impact resistance are imparted to the resin film by the urethane resin.

  The content of the copolymer contained in the emulsion in the entire treatment liquid is preferably 3 to 5% by mass. If the resin content is excessively small, the effect of covering the ink adhering to the recording medium and the effect of suppressing the adhesion of ink to the surface of the discharge roller tend to be insufficient. When the content of the resin is excessively large, a good balance between the film forming property and the drying property is lost, and only the film forming property is relatively improved, and the quick drying property tends to be relatively lowered.

  Another aspect of the present invention is an ink jet recording method in which an ink is attached to a recording medium, and then a treatment liquid for coating the ink with a resin film is attached to the recording medium, the glass transition temperature being −5. An inkjet recording method using a treatment liquid containing a graft copolymer and / or an emulsion of a block copolymer of an acrylic resin having a glass transition temperature of 30 ° C. or higher and a glass transition temperature of 30 ° C. or higher and 50 ° C. or lower. is there.

  According to still another aspect of the present invention, there is provided an ink jet recording apparatus in which an ink is attached to a recording medium and then a treatment liquid for coating the ink with a resin film is attached to the recording medium. An ink adhering unit for adhering ink to the recording medium and a treatment liquid adhering unit for adhering the processing liquid to the recording medium are arranged in this order from the upstream side in the conveying direction of the recording medium on the conveyance path, The treatment liquid adhesion means is a graft copolymer and / or block copolymer of an acrylic resin having a glass transition temperature of −5 ° C. or higher and lower than 30 ° C. and a urethane resin having a glass transition temperature of 30 ° C. or higher and 50 ° C. or lower. This is an ink jet recording apparatus using a treatment liquid containing the emulsion.

  Even with these ink jet recording methods or ink jet recording apparatuses, excellent film-forming properties are ensured by an acrylic resin having a glass transition temperature of −5 ° C. or higher and lower than 30 ° C., and a glass transition temperature of 30 ° C. or higher and 50 Excellent drying properties (rapid drying properties) are ensured by a urethane resin having a relatively high temperature of ℃ or less, and the recording medium is first coated with a coating of such an acrylic resin and urethane resin and / or a block copolymer. By covering the surface of the ink adhering to the ink, the adhesion of the ink to the surface of the discharge roller is sufficiently suppressed. In addition, there is an advantage that gloss is imparted to the image by the transparent resin coating and an image excellent in cosmetics can be obtained, and there is an advantage that flexibility and impact resistance are imparted to the resin coating by the urethane resin.

  The ink adhering means of the ink jet recording apparatus is preferably a line type ink jet recording head. This is because large-scale high-speed printing such as 150 sheets / minute can be easily realized, and even in this case, the adhesion of ink to the surface of the discharge roller is sufficiently suppressed.

  The treatment liquid according to the present invention has an excellent film-forming property and an excellent drying property because the resin film covering the surface of the ink attached to the recording medium is obtained by using a copolymer of two kinds of resins having different glass transition temperatures. (Fast drying) is provided, and ink adhesion to the discharge roller surface can be sufficiently suppressed.

It is a schematic block diagram of the inkjet recording device suitable for performing the inkjet recording method which concerns on this invention. FIG. 2 is an enlarged vertical cross-sectional view of a dot forming portion provided in an ink jet recording head of the ink jet recording apparatus.

[Overcoat solution]
The overcoat liquid (treatment liquid) for ink jet recording according to the present invention is for covering the surface of the ink previously attached to the recording medium with a resin film. As a basic configuration, an acrylic resin and a urethane resin are used. Contains emulsions of graft copolymers and / or block copolymers. The glass transition temperature of the acrylic resin is −5 ° C. or higher and lower than 30 ° C. The glass transition temperature of the urethane resin is 30 ° C. or more and 50 ° C. or less. In that case, it is preferable that content in the whole overcoat liquid of the said copolymer contained in the said emulsion is 3-5 mass%.

  The water used as the solvent in the overcoat solution of the present invention is preferably ion exchange water. And the graft copolymer and / or block copolymer of an acrylic resin and a urethane resin are included as a polymer in water, and it is set as an emulsion, and is set as the overcoat liquid of this invention. Alternatively, the copolymer emulsion may be diluted with water to form the overcoat liquid of the present invention. The average particle diameter of the polymer particles in the emulsion is, for example, preferably about 50 to 500 μm, and more preferably about 80 to 300 μm from the viewpoint of film-forming properties.

  In the overcoat liquid of the present invention, a graft copolymer and / or block copolymer of an acrylic resin and a urethane resin is used. Thereby, the resin film which has both the characteristic of an acrylic resin and the characteristic of a urethane resin is obtained reliably.

  In that case, the glass transition temperature of the acrylic resin is −5 ° C. or more and less than 30 ° C. Excellent film-forming properties are ensured by an acrylic resin having a glass transition temperature of -5 ° C or higher and lower than 30 ° C. From such a viewpoint, the glass transition temperature of the acrylic resin is more preferably −3 ° C. or higher, and further preferably −1 ° C. or higher. Moreover, More preferably, it is 27 degrees C or less, More preferably, it is 25 degrees C or less. If the glass transition temperature of the acrylic resin is too low, the film may be formed with a relatively large amount of water, and the quick drying property may be reduced. If the glass transition temperature of the acrylic resin is excessively high, the film forming property may be insufficient.

  Acrylic resins include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, cyclohexyl acrylate, benzyl acrylate, ethylene glycol acrylate, 2-ethylhexyl acrylate, acrylic Lauryl acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, ethylene glycol methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate Homopolymers (homopolymers) or copolymers (copolymers) of acrylic monomers such as

  On the other hand, the glass transition temperature of the urethane resin is 30 ° C. or higher and 50 ° C. or lower. Excellent drying properties (rapid drying properties) are ensured by a urethane resin having a glass transition temperature of 30 ° C. or higher and 50 ° C. or lower and relatively high. From such a viewpoint, the glass transition temperature of the urethane resin is more preferably 33 ° C. or higher, and further preferably 35 ° C. or higher. Further, it is more preferably 47 ° C. or lower, and further preferably 45 ° C. or lower. If the glass transition temperature of the urethane resin is too low, the quick drying property may be insufficient. If the glass transition temperature of the urethane resin is excessively high, the film forming property may be lowered.

  As the urethane resin, in general, a compound composed of an isocyanate compound and a polyol compound can be used without any particular limitation. Examples of the isocyanate compound include tolylene diisocyanate and diphenylmethane diisocyanate, and examples of the polyol compound include polyester polyol. Here, the polyester polyol is a resin composition in which 1,4-butanediol, 1,6-hexanediol or the like is added to an ester such as ethylene glycol or propylene glycol of an acid such as adipic acid or sebacic acid. .

  The urethane resin that can be used in the present invention is not particularly limited. For example, a water-soluble or water-dispersible polyurethane resin obtained by reacting a diisocyanate compound as the isocyanate compound with a diol compound as the polyol compound. Can be used.

  Examples of the diisocyanate compound include alicyclic diisocyanate compounds such as hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, and 4,4-dicyclohexylmethane diisocyanate. Araliphatic diisocyanate compounds such as xylylene diisocyanate and tetramethylxylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, or modified products of these diisocyanate compounds (carbodiimide, uretdione, uretoimine-containing modified products, etc.) Etc. As needed, you may use 1 type of these diisocyanate compounds, or may use 2 or more types together.

  Examples of the diol compound include alkylene oxides such as ethylene oxide and propylene oxide, and diol compounds obtained by (co) polymerizing a heterocyclic ether such as tetrahydrofuran, and specific examples of such diol compounds. For example, polyether diols such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyethylene adipate, polybutylene adipate, polyneopentyl adipate, poly-3-methylpentyl adipate, polyethylene / Polyester diols such as butylene adipate, polyneopentyl / hexyl adipate, polylactone diols such as polycaprolactone diol, or polyca Boneto based diol. Among these, one or more of a polyether diol, a polyester diol, and a polycarbonate diol are preferable. In addition to the above, diol compounds having an acidic group such as a carboxylic acid group and a sulfonic acid group can also be used, and specific examples thereof include dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutyric acid and the like. Of these, dimethylolpropionic acid is preferred. As needed, 1 type of these diol compounds may be used, or 2 or more types may be used together.

  The glass transition temperature of the acrylic resin or the glass transition temperature of the urethane resin can be adjusted, for example, by selecting the type of each monomer, the number of monomer types, the molecular weight, or the like.

  In the overcoat liquid of the present invention, the discharge roller is formed by coating the surface of the ink previously attached to the recording medium with a film of such a graft copolymer of acrylic resin and urethane resin and / or a block copolymer. (Reference numeral 8: see FIG. 1) Adhesion of ink to the surface is sufficiently suppressed.

  In the overcoat solution of the present invention, since the graft copolymer and / or block copolymer of acrylic resin and urethane resin forms a transparent film, gloss is imparted to the image by this transparent resin film, and the cosmetic property is improved. There is also an advantage that an excellent image can be obtained. Furthermore, there is an advantage that flexibility and impact resistance are imparted to the resin film by the urethane resin.

  Examples of the emulsion of a graft copolymer of an acrylic resin and a urethane resin that can be used in the overcoat liquid of the present invention include “WBR-202U” and “WBR-321U” manufactured by Taisei Fine Chemical Co., Ltd.

  In the overcoat liquid of the present invention, the content of the copolymer (that is, polymer or resin) contained in the emulsion in the entire overcoat liquid is preferably 3 to 5% by mass. If the resin content is excessively small, the effect of covering the ink adhering to the recording medium and the effect of suppressing the adhesion of ink to the surface of the discharge roller tend to be insufficient. When the content of the resin is excessively large, a good balance between the film forming property and the drying property is lost, and only the film forming property is relatively improved, and the quick drying property tends to be relatively lowered.

  In the overcoat liquid of the present invention, the mass ratio of the acrylic resin and the urethane resin of the copolymer contained in the emulsion is generally preferably 5: 5. For example, importance is attached to either the film forming property or the quick drying property. Depending on the situation, it may be arbitrarily changed within the range of 1: 9 to 9: 1, more preferably 3: 7 to 7: 3.

  In the overcoat liquid of the present invention, the molecular weight of the copolymer acrylic resin is preferably about 80,000 to 120,000, for example, from the viewpoint of film forming properties. On the other hand, the molecular weight of the urethane resin of the copolymer is preferably about 10,000 to 20,000, for example, from the viewpoint of quick drying.

  In the overcoat liquid of the present invention, the polymer contained in the emulsion, that is, the graft copolymer and / or block copolymer of acrylic resin and urethane resin may be a core-shell type polymer. The core-shell type polymer refers to a polymer in which different resin components exist in the central part (core part) and the outer shell part (shell part) in the same micelle. In that case, in the core part, the glass transition temperature of the acrylic resin is −5 ° C. or higher and lower than 30 ° C., and the glass transition temperature of the urethane resin is 30 ° C. or higher and 50 ° C. or lower. In the case of such a core-shell type polymer, for example, an acrylic resin in which an emulsifying group is incorporated exists around the graft copolymer and / or block copolymer of acrylic resin and urethane resin, and this acrylic resin is a micelle. The polymer itself acts as an emulsifier and exhibits a soap-free self-emulsifying core-shell structure. Such a core-shell type polymer emulsion can be produced by a known seed emulsion polymerization method, a multi-stage emulsion polymerization method, or the like. The mass ratio of the core part to the shell part is generally preferably 2: 8 to 8: 2, and more preferably 3: 7 to 7: 3.

  The overcoat liquid of the present invention may contain various additives such as a wetting agent, a leveling agent, an antifoaming agent, a viscosity adjusting agent, a pH adjusting agent, and an antiseptic as necessary. Further, in order to protect the resin film formed on the recording medium and coated with ink, or to promote the release of the resin film from the discharge roller, waxes such as polyethylene wax may be contained.

  Examples of the wetting agent or viscosity modifier include ethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, diethylene glycol monomethyl ether, ethylene glycol monomethyl ether, triethylene glycol, hexylene glycol, octanediol, thiodi Glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl -1,3-butanediol, 2,4-pentanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol trimethylolpropane, 2-methyl-1,3-propanediol, Ethylene glycol, propylene glycol, 1,3-butanediol, ethylene glycol, polyethylene glycol, glycerine, 2-pyrrolidone, and the like. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the leveling agent include nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene / polyoxypropylene block copolymers. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the antifoaming agent include silicon-based emulsions, polyether-based modified silicon emulsions, and polyolefin-polyether-modified emulsions. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of these additives in the overcoat solution varies depending on the type and the like, and is, for example, in the range of 0.1 to 20% by mass in the overcoat solution.

  The overcoat liquid of the present invention can be prepared by sufficiently stirring the above raw materials using, for example, a propeller-type stirrer, mixing, and then filtering.

The amount of adhesion of the overcoat liquid of the present invention to the recording medium may be changed according to the content of the copolymer (polymer) in the overcoat liquid, etc., for example, the content of the resin in the overcoat liquid is When it is in the range of 3 to 5% by mass, the overcoat solution is in the range of 0.1 to 2.0 mg, preferably in the range of 0.3 to 1.5 mg, more preferably 0, per cm ² of the recording medium. Deposit within the range of 5-1.2 mg. If the amount of the overcoat liquid adhering is too small, the effect of covering the ink adhering to the recording medium, and the effect of suppressing the ink adhering to the discharge roller surface, tends to be insufficient. If the amount of overcoat liquid attached is excessively large, cockling (a phenomenon in which the surface of the recording medium becomes wavy with the overcoat liquid) or curl (the recording medium becomes bent by the overcoat liquid). Phenomenon).

[ink]
As the ink that can be used in the present invention, an ink jet recording ink that has been conventionally used in an ink jet recording method and an ink jet recording apparatus can be used without any particular limitation. Such an ink contains at least water and a colorant. In addition, various additives such as polymer dispersing agents, wetting agents, leveling agents, antifoaming agents, viscosity adjusting agents, pH adjusting agents, preservatives, etc., for dispersing pigments as coloring agents are included as necessary. May be.

  As the colorant that can be used in the present invention, a conventionally well-known and widely used pigment can be used without particular limitation. Examples of pigments that can be used in the present invention include insoluble azo pigments, soluble azo pigments, phthalocyanine blue, isoindolinone, quinacridone, dioxazine violet, and organic pigments such as verinone and betalin, and inorganic pigments such as carbon black and titanium dioxide. Colorant pigment components, or extender pigments such as white clay, talc, clay, diatomaceous earth, calcium carbonate, barium sulfate, titanium oxide, alumina white, silica, kaolin, and aluminum hydroxide.

  More specifically, as a pigment for yellow (Y) ink, C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 12 (Disazo Yellow AAA), 13, 14, 17, 23, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 74, 81, 83 (Disazo Yellow HR), 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153 and the like. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the pigment for magenta (M) ink include C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B (Ca)), 48 : 3 (Permanent Red 2B (Sr)), 48: 4 (Permanent Red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G lake), 83, 88, 92, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (Dimethylquinacridone), 123,146,149,166,168,170,172,177,178,179,185,190,193,209,2 9, and the like. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the pigment for cyan (C) ink include C.I. I. Pigment Blue 1, 2, 15 (copper phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 1, 56, 60, 63 and the like. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of black (K) ink pigments include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black, and aniline black (CI pigment black 1). Examples thereof include organic pigments, metal oxides such as copper oxide, iron oxide (CI Pigment Black 11), and titanium oxide. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of these pigments in the ink varies depending on the type and purpose of use. For example, the coloring power and the viscosity of the ink (the higher the pigment content, the higher the viscosity of the ink and the ink jet In the ink, it is 0.1 to 20% by mass, more preferably 1 to 10% by mass, and further preferably 3 to 7% by mass.

  The average particle size of the pigment particles is preferably 30 to 300 nm, more preferably 50 to 150 nm, and even more preferably about 100 nm. The average particle size of the pigment particles is, for example, a dynamic light scattering type particle size distribution measuring device (“LB-550” manufactured by Horiba Ltd.), a particle size distribution measuring device (“Zeta Sizer Nano” manufactured by Sysmex Corporation), etc. Can be measured.

  Examples of the polymer dispersant that can be used in the present invention include styrene-acrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer, styrene-maleic acid copolymer, styrene-maleic acid-alkyl acrylate. Ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid Water-soluble resins such as copolymers are listed. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of these polymer dispersants in the ink is generally 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, and still more preferably 1.0 to 6% by mass.

  Examples of the wetting agent or viscosity modifier include ethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, diethylene glycol monomethyl ether, ethylene glycol monomethyl ether, triethylene glycol, hexylene glycol, octanediol, thiodi Glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl -1,3-butanediol, 2,4-pentanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol trimethylolpropane, 2-methyl-1,3-propanediol, Ethylene glycol, propylene glycol, 1,3-butanediol, ethylene glycol, polyethylene glycol, glycerine, 2-pyrrolidone, and the like. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the leveling agent include nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene / polyoxypropylene block copolymers. As needed, these may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of these additives in the ink varies depending on the type and the like, and is, for example, in the range of 0.1 to 20% by mass in the ink.

  The ink that can be used in the present invention is obtained by using the above raw materials, for example, a wet type media disperser, a propeller type stirrer, etc. A shaker or the like can also be used), and after sufficient stirring, mixing and dispersing, it can be prepared by centrifugation or filtration.

  As the wet type media type disperser, for example, even when zirconia beads having a media diameter of 0.2 to 1.0 mm are used, a wet type disperser having a mechanism for giving optimum dispersion energy to each medium is preferable. For example, “Nano Glen Mill” manufactured by Asada Tekko Co., Ltd., “MSC Mill” manufactured by Mitsui Mining Co., Ltd., “Dyno Mill” manufactured by Shinmaru Enterprises Co., Ltd. and the like can be preferably used. Then, the liquid after the dispersion treatment is centrifuged to remove coarse particles such as foreign matters and dust, and the fine particles are removed by filtration to finally obtain ink.

  In order to prepare the ink, a high-concentration pigment dispersion liquid (a liquid having a pigment concentration several times the pigment concentration in the ink) may be prepared in advance.

[Inkjet recording apparatus]
Next, an example of a specific configuration of an ink jet recording apparatus suitable for performing the ink jet recording method of the present invention using the overcoat liquid of the present invention will be described.

  As shown in FIG. 1, an ink jet recording apparatus 1 according to this embodiment is an ink jet printer that forms an image on a recording medium using ink for ink jet recording based on image information transmitted from another device.

  The ink jet recording apparatus 1 includes a paper storage unit that stores recording media X such as PPC paper in a stacked state in a paper feeding cassette (not shown). The recording medium X is fed one by one from the uppermost one by the rotation of the paper feed roller 2 and is supplied to the paper transport unit by the transport roller pairs 3.

  The paper transport unit includes an endless transport belt 7 that is horizontally wound between a pair of rollers. The recording medium X supplied by the conveying roller pairs 3... 3 is conveyed to the image forming unit with the recording surface facing upward by the traveling of the conveying belt 7.

  The image forming unit is a long line type ink jet recording head 5 (ink adhering means) having a length equal to or greater than the width of the recording medium X conveyed by the conveying belt 7 above the conveying belt 7. It has. The recording head 5 is fixed to the main body of the inkjet recording apparatus 1 over a direction orthogonal to the conveyance direction of the recording medium X. As will be described later, the recording head 5 has a large number of ink discharge ports (nozzles) of the dot forming portion arranged on the lower surface facing the conveyance belt 7 or the recording medium X, and ink is simultaneously applied over the entire width of the recording medium X. By discharging all at once, an image can be formed on the recording medium X at high speed. The recording head 5 is arranged such that the distance between the lower surface (nozzle surface) of the recording head 5 and the recording medium X on the conveying belt 7 is about 1 mm.

  A recording medium detection sensor 4 for detecting the leading end of the recording medium X conveyed by the conveying belt 7 is provided above the conveying belt 7 and upstream of the inkjet recording head 5 in the conveying direction of the recording medium X. Yes. An ink discharge command is output to the inkjet recording head 5 with reference to the detection time of the sensor 4. Further, an overcoat liquid discharge command is output to the overcoat liquid discharge head 6 described below.

  Above the transport belt 7, an overcoat liquid discharge head 6 (overcoat liquid adhering means) is provided downstream of the inkjet recording head 5 in the transport direction of the recording medium X. The overcoat liquid discharge head 6 is for containing the overcoat liquid and discharging the overcoat liquid onto the recording medium X to adhere thereto, and has substantially the same configuration as the ink jet recording head 5. That is, the overcoat liquid discharge head 6 is a long line type head having a length equal to or longer than the width of the recording medium X conveyed by the conveyance belt 7. The overcoat liquid discharge head 6 is fixed to the main body of the inkjet recording apparatus 1 over a direction orthogonal to the conveyance direction of the recording medium X. The overcoat liquid discharge head 6 has a large number of overcoat liquid discharge ports (nozzles) arranged on the lower surface facing the conveyance belt 7 or the recording medium X, and the overcoat liquid is simultaneously spread over the entire width of the recording medium X. The overcoat liquid can be adhered to the recording medium X at a high speed. The overcoat liquid discharge head 6 is disposed such that the distance between the lower surface (nozzle surface) and the recording medium X on the transport belt 7 is about 1 mm.

  While being transported by the transport belt 7, the recording medium X to which ink has been deposited by the ink jet recording head 5 and then the overcoat liquid has been deposited by the overcoat liquid discharge head 6 is subsequently transported by the transport belt 7. Then, the paper is transferred to the pair of upper and lower discharge rollers 8 and 8 at the end of the conveyor belt 7 and discharged from the conveyor belt 7. If the ink is not sufficiently dried when the overcoat liquid is not attached, the ink adheres to the surface of the discharge roller 8.

  FIG. 2 is an enlarged longitudinal sectional view showing one of the dot forming portions 50 arranged in a large number on the ink jet recording head 5 of the ink jet recording apparatus 1. Since the overcoat liquid discharge head 6 has the same configuration in accordance with this, the description thereof is omitted.

  The recording head 5 is a long line-type inkjet recording head 5 that extends in a direction orthogonal to the conveyance direction of the recording medium X. Although not shown in detail, the recording head 5 has a structure in which three sub heads (divided heads) are sequentially connected in a direction orthogonal to the conveyance direction of the recording medium X. Each sub-head has four trapezoidal discharge port collecting areas on the lower surface (nozzle surface) in the direction perpendicular to the conveyance direction of the recording medium X (the upper and lower bases of the trapezoid are in order). (Arranged so that they are alternately reversed). In each discharge port assembly area, the dot forming section 50 and the nozzles (ink discharge ports) 53 shown in FIG. 2 are arranged in four rows in the transport direction of the recording medium X. By setting the pitch between adjacent nozzles 53, 53 in the same row to 150 dpi, and shifting the position of the nozzle 53 between adjacent rows by a quarter pitch in the direction orthogonal to the conveyance direction of the recording medium X, 600 dpi is obtained. Image formation is realized. Since the number of dot forming sections 50 and nozzles 53 per row is 166, 664 nozzles 53 are arranged in one discharge port assembly area (four rows). Therefore, 7968 (664 × 4 × 3) nozzles 53 are provided in the entire recording head 5.

  The dot forming unit 50 includes an oval pressurizing chamber 52 in plan view, and one end of the pressurizing chamber 52 is connected to a nozzle 53 formed on the lower surface of the recording head 5 via a nozzle channel 54. The other end portion communicates with the common ink supply path 56 via the throttle path 55. The nozzle 53 has an inverted truncated cone shape in which the diameter of the upper opening 53b is larger than the diameter of the lower opening 53a.

  The dot forming unit 50 includes a first substrate 51a in which a pressurizing chamber 52 is formed, a second substrate 51b in which an upper portion 54a of a nozzle channel 54 and a throttle passage 55 are formed, a lower portion 54b of the nozzle channel 54, and ink. The third substrate 51c in which the common supply path 56 is formed and the fourth substrate 51d in which the nozzle 53 is formed are stacked. A substrate 51 of the recording head 5 is provided by the laminated first to fourth substrates 51a to 51d.

  A piezoelectric actuator AC having a configuration in which a thin plate-like piezoelectric element 58 having a common electrode 57 therein and an individual electrode 59 corresponding to the pressurizing chamber 52 of each dot forming unit 50 are stacked on the upper surface of the substrate 51. It has been. By driving the piezoelectric actuator AC, a pressure wave is transmitted to the ink in the pressurizing chamber 52, and the ink in the nozzle channel 54 and the nozzle 53 is vibrated by the pressure wave, so that the ink flows from the lower opening 53a of the nozzle 53. The ink is discharged toward the recording medium X.

Here, an example of a preferable specific numerical value regarding the specification of the dot forming portion 50 is shown below.
・ Area of pressurizing chamber 52: 0.2 mm ²
・ Pressure chamber 52 width: 200 μm
-Depth of pressurizing chamber 52: 100 μm
・ Length of nozzle 53: 30 μm
The radius of the lower opening 53a of the nozzle 53: 10 μm
-Diameter of nozzle channel 54: 200 μm
・ Length of nozzle channel 54: 800 μm
-Diameter of throttle passage 55: 30 μm
・ Length of throttle passage 55: 40 μm

  The ink jet recording apparatus 1 illustrated in FIG. 1 has a single recording head 5 and forms an image in a single color. However, the present invention is not limited to this. For example, Y (yellow) ink, M ( A plurality of (four) recording heads 5 may be arranged in the conveyance direction of the recording medium X for each of magenta ink, C (cyan) ink, and K (black) ink, and an image may be formed in full color.

  Further, the ink jet recording apparatus 1 may be provided with a serial type recording head (what the recording head scans) instead of the line type recording head as long as desired high speed processing is realized.

  Since the ink adhering means of the ink jet recording apparatus 1 is the line type ink jet recording head 5, a large amount of high speed printing such as 150 sheets / min can be easily realized. Even in that case, ink adhesion to the surface of the discharge roller 8 is sufficiently suppressed.

[Inkjet recording method]
Using the inkjet recording apparatus 1 configured as described above, ink is stored in the recording head 5 and the overcoat liquid of the present invention is stored in the ejection head 6, so that the recording medium X is conveyed by the conveying belt 7. Then, ink is ejected from the recording head 5 to adhere to the recording surface of the recording medium X, and then an overcoat liquid for coating the recording surface of the recording medium X with a polymer film is overcoated liquid. An ink jet recording method in which the ink is ejected from the ejection head 6 and adhered thereto can be executed.

  The ink jet recording method of the present invention includes an ink attaching step for attaching ink to the recording medium X, and an overcoat liquid attaching step for attaching an overcoat liquid to the recording medium X to which ink is attached after the ink attaching step. As long as it has, it is not necessary to use the ink jet recording apparatus 1 configured as described above. Further, instead of using the overcoat liquid discharge head 6, as another aspect of the overcoat liquid adhesion means, the overcoat liquid can be applied and adhered to the recording medium X using, for example, a roll coater. However, since the overcoat liquid adhering means of the ink jet recording apparatus 1 is a long line type overcoat liquid discharge head 6 having the same configuration as the line type ink jet recording head 5, for example, 150 sheets / min. In this case, it is possible to sufficiently prevent the ink from adhering to the surface of the discharge roller 8.

  EXAMPLES Hereinafter, although the Example of this invention is given with a comparative example and this invention is demonstrated further more concretely, this invention is not limited by a following example.

[Preparation of overcoat solution]
With the composition shown in Table 1, overcoat liquids (treatment liquids) of Examples 1-2 and Comparative Examples 1-4 were prepared. That is, adding raw materials to ion-exchanged water, using a propeller type stirrer “Polymix Stirrer PX-SR90E” manufactured by Central Science Trading Co., Ltd., sufficiently stirring at room temperature for 30 minutes at a rotation speed of 500 rpm, After mixing, pressure-filtering was performed with a filter having a pore diameter of 5 μm to remove fine particles, thereby obtaining an overcoat liquid for inkjet recording.

Each raw material shown in Table 1 is as follows.
Emulsion A: Acrylic urethane emulsion (graft copolymer of acrylic resin and urethane resin) manufactured by Taisei Fine Chemical Co., Ltd. “WBR-202U” (see Table 2)
Emulsion B: Acrylic urethane emulsion (graft copolymer of acrylic resin and urethane resin) manufactured by Taisei Fine Chemical Co., Ltd. “WBR-321U” (see Table 2)
Emulsion C: Acrylic urethane emulsion (graft copolymer of acrylic resin and urethane resin) manufactured by Taisei Fine Chemical Co., Ltd. “WBR-031U” (see Table 2)
Emulsion D: Acrylic emulsion “Jonkrill 734” manufactured by BASF (see Table 3)
Emulsion E: Urethane emulsion “WBR-2018” manufactured by Taisei Fine Chemical Co., Ltd. (see Table 3)
Emulsion F: urethane emulsion “WBR-2019” manufactured by Taisei Fine Chemical Co., Ltd. (see Table 3)
Leveling agent: “Surfinol 465” manufactured by Air Products
・ Polyethylene wax: Chemipearl manufactured by Mitsui Chemicals
Antifoaming agent: polyether modified silicone emulsion “Deformer 1312” manufactured by San Nopco

[Preparing ink]
A “Photo Black ICBK39A” manufactured by Seiko Epson Corporation was prepared.

[Evaluation test]
The ink was stored in the recording head 5 of the ink jet recording apparatus 1 (Kyocera Mita's experimental machine) having the structure shown in FIGS. 1 and 2, and the overcoat liquid was stored in the overcoat liquid discharge head 6. Excess liquid coming out from the lower surfaces of the nozzles of the heads 5 and 6 was scraped off with a wipe blade. The heads 5 and 6 were fixed by adjusting the positions of the heads 5 and 6 so that the distance between the nozzle surfaces of the heads 5 and 6 and the recording medium X on the conveying belt 7 was 1 mm. A4 size PPC paper (“F938” manufactured by Fuji Xerox Co., Ltd.) was used as the recording medium X, and the drive frequency was 20 kHz (printing speed: 150 sheets / min) in a normal temperature and humidity environment with a temperature of 20 ° C. and a humidity of 65%. , The ink is uniformly applied from the recording head 5 to the area of 30 mm × 30 mm with the maximum density, and then the overcoat liquid is uniformly applied to the same area from the ejection head 6 in an amount of 0.8 mg per cm ^{2 of the} recording medium. 10 sheets were continuously printed after being adhered.

(Ink smear evaluation)
Visually check whether ink and / or overcoat liquid has adhered to the surface of the discharge roller 8 and whether ink has adhered to the non-printing portion of the recording medium X, and evaluated according to the following criteria: did. The results are shown in Table 4. In Table 4, the reference examples are those in which no overcoat solution was used.
◯: There is no ink stain on the surface of the discharge roller 8 or the non-printing portion of the recording medium X.
Δ: The surface of the discharge roller 8 is stained with ink, but the non-printing portion of the recording medium X is not stained with ink.
X: Ink stains exist on the surface of the discharge roller 8 and on the non-printing portion of the recording medium X.

(Gloss evaluation)
Using a gloss meter “Gloss Checker IG-320” manufactured by HORIBA, Ltd., the glossiness of the printing part and the non-printing part of the recording medium X were measured, and the difference was determined and evaluated according to the following criteria. . The results are shown in Table 4.
○: The difference in glossiness is 10 or more.
(Triangle | delta): The difference in glossiness is less than 10 and 5 or more.
X: The difference in glossiness is less than 5.

  As is apparent from Table 4, in Examples 1 and 2, although the printing speed is 150 sheets / minute, the surface of the discharge roller 8 and the non-printing portion of the recording medium X can be used. There was no ink stain. This is because the overcoat liquids of Examples 1 and 2 are graft copolymers of an acrylic resin having a glass transition temperature of −5 ° C. or higher and lower than 30 ° C. and a urethane resin having a glass transition temperature of 30 ° C. or higher and 50 ° C. or lower. As a result of containing an emulsion containing a polymer as a polymer, the resin film has excellent film-forming properties and drying properties, and the ink attached to the recording medium is sufficiently covered with the resin film in a short time, and the surface of the ink discharge roller 8 It is considered that the adhesion to the surface was sufficiently suppressed. In addition, Examples 1 and 2 were good results in terms of gloss.

  On the other hand, all of Comparative Examples 1 to 4 were inferior in ink stain evaluation. This is because even when the polymer is a copolymer of an acrylic resin and a urethane resin, the glass transition temperature of the acrylic resin is excessively high (Comparative Example 1), the case where the polymer is only an acrylic resin (Comparative Example 2), and urethane. In the case of resin only (Comparative Examples 3 and 4), the resin film is inferior in film forming property and drying property, and the ink adhering to the recording medium is not sufficiently covered with the resin film, and the ink is discharged onto the surface of the discharge roller 8. It is considered that the adhesion was not sufficiently suppressed.

  As described above in detail with reference to specific examples, the present invention is a high-speed process in an ink jet recording method and an ink jet recording apparatus in which a recording medium to which ink is attached and information is recorded is discharged by a discharge roller. The ink has a remarkable advantage that it can solve the problem that the ink that has been dried shortly and is insufficiently dried adheres to the discharge roller and the non-printing part of the recording medium and causes contamination. Is.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 5 Line type inkjet recording head (ink adhesion means)
6 Overcoat liquid discharge head (overcoat liquid adhesion means)
7 Conveying belt 8 Discharge roller X Recording medium

Claims (5)

After the ink adhered to the recording medium, ink jet recording said ink at least deposited so the ink that is adhered to the recording medium processing liquid for coating with a resin film, you cover the ink with resin in the treatment solution A processing solution used in the method,
Inkjet recording containing an emulsion of a graft copolymer and / or a block copolymer of an acrylic resin having a glass transition temperature of −5 ° C. or higher and lower than 30 ° C. and a urethane resin having a glass transition temperature of 30 ° C. or higher and 50 ° C. or lower. Treatment liquid.   The treatment liquid for inkjet recording according to claim 1, wherein the content of the copolymer contained in the emulsion in the whole treatment liquid is 3 to 5 mass%. After the ink adhered to the recording medium, ink jet recording said ink at least deposited so the ink that is adhered to the recording medium processing liquid for coating with a resin film, you cover the ink with resin in the treatment solution A method,
Treatment liquid containing emulsion of graft copolymer and / or block copolymer of acrylic resin having glass transition temperature of -5 ° C or higher and lower than 30 ° C and urethane resin having glass transition temperature of 30 ° C or higher and 50 ° C or lower An ink jet recording method using After the ink adhered to the recording medium, ink jet recording said ink at least deposited so the ink that is adhered to the recording medium processing liquid for coating with a resin film, you cover the ink with resin in the treatment solution A device,
An ink adhering unit for adhering ink to the recording medium and a processing liquid adhering unit for adhering the processing liquid to the recording medium are arranged in this order from the upstream side in the conveying direction of the recording medium on the recording medium conveying path. Arranged,
The treatment liquid adhesion means is a graft copolymer and / or block copolymer of an acrylic resin having a glass transition temperature of −5 ° C. or higher and lower than 30 ° C. and a urethane resin having a glass transition temperature of 30 ° C. or higher and 50 ° C. or lower. An ink jet recording apparatus using a treatment liquid containing the emulsion.   The ink jet recording apparatus according to claim 4, wherein the ink adhering means is a line type ink jet recording head.

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