JP2012153052A - Coating agent for forming inkjet ink reception layer, recording medium using the same, and printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating agent for forming an inkjet ink reception layer which is excellent in water resistance, sppresses whited-out and white streaks of an image, has a good drying property of an ink, and has an excellent image forming property.SOLUTION: The coating agent for forming the inkjet ink reception layer contains a crosslinked vinyl emulsion prepared by emulsion-polymerizing a monomer mixture including a monomer (A) having two or more ethylenically unsaturated groups, a monomer (B) having a carboxyl group and one ethylenically unsaturated group, and a monomer (C) having a 1-12C hydrophobic group and one ethylenically unsaturated group.

Description

  The present invention relates to a coating agent for forming an ink receiving layer for forming an image using an inkjet ink.

Inkjet printing generates little noise, enables high-speed printing and multicolor printing, and has been rapidly spreading in recent years. As a recording medium for receiving inkjet ink, conventionally, a recording medium provided with an ink receiving layer on the surface of a substrate such as paper or plastic film has been used.
Also, with the recent increase in awareness of environmental protection, so-called water-based inks that do not contain organic solvents or that contain a small amount even if they are included have come to be used preferably.

  The ink receiving layer is required not only to absorb and dry ink quickly, but also to have excellent ink fixability, color development, sharpness, and image gradation. Furthermore, for printed matter obtained by ink jet printing on a recording medium, it is required that the durability of the image is excellent, particularly when water-based ink is used.

The ink jet printing method is a recording method in which ink droplets are ejected from very fine nozzles and ink dots are deposited on a recording medium to obtain characters and images. Due to the displacement of the dot position and volume, a dot dropout (a state where no ink dot exists at a position where the ink dot should exist) may occur on the recording medium.
Dot missing is particularly a problem in solid printing in which a printing area is filled with dots, and white spots and white streaks are generated in a printed image, and a high-definition image cannot be obtained.

  As a means for preventing the white spots and white stripes, there is a method of increasing the number of dots per unit area. However, this method imparts an excessive amount of ink to the recording medium, which may cause deterioration of the ink drying property and image quality, and is not preferable in terms of running cost.

  No printing technology has yet been provided that can provide a print image with a small amount of ink and with few white spots and white streaks.

  In order to provide a printed image with excellent water resistance and with as little ink as possible, with few white spots and white streaks, the ink dots on the surface of the substrate do not bleed in contact with ink dots of other colors In addition, it is necessary to form an ink receiving layer that spreads moderately and does not peel off the fixed ink dots.

  That is, a receiving layer in which the hydrophilicity of the ink is good and spreads moderately and the hydrophobic part in which the ink does not spread excessively and develops water resistance after drying are balanced and uniformly arranged on the substrate surface. It is necessary to form. Simply mixing a hydrophilic component and a hydrophobic component cannot provide an ink-receiving layer from which a high-definition image formed by multicolor ink dots can be obtained.

  Inkjet inks that contain pigments as colorants are used when durability as printed matter is required. In the pigment ink, since the pigment is insoluble in the solvent, the pigment dispersion resin is used to stabilize the dispersion in the solvent in order to maintain the pigment dispersion in the ink.

  In general, anionic pigment dispersion resins are often used. For example, an inkjet ink containing such an anionic pigment dispersion resin is used to form an image on a receiving layer made of a cationic compound. When formed, the pigment aggregates on the surface of the receiving layer, the ink dots do not spread sufficiently, and it is difficult to provide a printed image with few white spots and white streaks.

  On the other hand, in Patent Documents 1 to 3, paper sizing may be performed in the papermaking process. As the surface sizing agent, anionic compounds such as styrene-maleic acid copolymer and carboxyl group-containing acrylic resin are used. Has been proposed. Since these have a carboxyl group that works predominately in ink wetting, absorption, and drying properties, they have the effect of spreading the ink dots. However, these have a drawback of poor water resistance.

  On the other hand, in patent documents 4-5, the inkjet recording medium which formed the surface coat layer containing the acrylic resin emulsion which has a specific glass transition temperature and a particle diameter on a base material, and the specific minimum film-forming temperature and particle diameter. A recording medium on which a coating layer containing water-dispersible resin particles is formed has been proposed. However, these do not contain a carboxyl group that is superior in ink wetting, absorption, and drying properties as an essential component, and have the disadvantage that a printed image with few white spots and white streaks cannot be provided.

JP 2009-161885 A Japanese Patent No. 3854165 JP 2001-232932 A Japanese Patent No. 3721651 Japanese Patent No. 3950688

  The present invention provides a coating agent for forming an ink-jet ink receiving layer having excellent image forming properties, which is excellent in water resistance, suppresses white spots and white streaks in images, and has good ink drying properties. Is an issue.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following coating agent for forming an inkjet ink receiving layer, and have completed the present invention.

  One embodiment of the present invention is a monomer (A) having two or more ethylenically unsaturated groups, a monomer (B) having a carboxyl group and one ethylenically unsaturated group, and C 1-12. An ink-jet ink receiving layer comprising a cross-linked vinyl emulsion obtained by emulsion polymerization of a monomer mixture containing a monomer (C) having a hydrophobic group and one ethylenically unsaturated group The present invention relates to a coating agent for formation.

In a total of 100% by weight of the monomers to be subjected to emulsion polymerization, the proportion of the monomer (A) is 0.1 to 5% by weight, and the proportion of the monomer (B) is 20 to 80% by weight. It is preferable that the acid value of the resin particles of the cross-linked vinyl emulsion is 100 to 500 mgKOH / g.

  It is preferable that the glass transition temperature of the resin particle of the said crosslinked vinyl-type emulsion is 0-100 degreeC.

  It is preferable that the volume average particle diameter of the resin particles of the cross-linked vinyl emulsion is 10 to 500 nm.

  It is preferable that the cross-linked vinyl emulsion has a viscosity of 0.1 to 300 mPa · s at a solid content concentration of 10% by weight.

  It is preferable that the monomer used for emulsion polymerization does not contain an ethylenically unsaturated monomer having a cationic functional group.

The SP value of the resin particles of the cross-linked vinyl emulsion is 3.9 to 6.8 (J · cm ⁻³ ) ^1/2 by the Fedor method, and the resin particles of the pre-cross-linked vinyl emulsion are Macintosh. -It is preferable that the surface tension by Sugden method is 22-35 * 10 < ^-3 > (N / m).

  Another embodiment of the present invention relates to an image forming recording medium in which an ink jet ink receiving layer formed from the above ink jet ink receiving layer forming coating agent is provided on at least one surface of a substrate.

  Furthermore, one embodiment of the present invention relates to a printed matter in which an image is formed by inkjet ink on the above-described image forming recording medium.

  The inkjet ink comprises a pigment dispersion resin, the pigment dispersion resin comprising an aromatic ethylenically unsaturated monomer (m1), a carboxyl group-containing ethylenically unsaturated monomer, a neutralized product or a metal salt thereof, And a copolymer comprising two components of at least one monomer (m2) selected from the group consisting of an acid anhydride group-containing ethylenically unsaturated monomer or a half ester thereof.

  Further, one embodiment of the present invention is a monomer having a monomer (A) having two or more ethylenically unsaturated groups, a carboxyl group, and one ethylenically unsaturated group on at least one surface of the substrate. A crosslinked vinyl emulsion obtained by emulsion polymerization of a monomer mixture containing a monomer (B) and a monomer (C) having a hydrophobic group having 1 to 12 carbon atoms and one ethylenically unsaturated group A first step of forming an inkjet ink receiving layer using the coating agent for forming an inkjet ink receiving layer, and a second step of forming an image with the inkjet ink on the inkjet ink receiving layer, The present invention relates to a method for producing printed matter.

  The inkjet ink comprises a pigment dispersion resin, the pigment dispersion resin comprising an aromatic ethylenically unsaturated monomer (m1), a carboxyl group-containing ethylenically unsaturated monomer, a neutralized product or a metal salt thereof, And a copolymer comprising two components of at least one monomer (m2) selected from the group consisting of an acid anhydride group-containing ethylenically unsaturated monomer or a half ester thereof.

  According to one embodiment of the present invention, it is possible to provide a print recording medium having excellent image forming properties that is excellent in water resistance, suppresses white spots and white streaks in an image, and has good ink drying properties. it can.

  The cross-linked vinyl emulsion that is the main component of the coating agent for forming an inkjet ink receiving layer of the present invention is a monomer (A) having two or more ethylenically unsaturated groups, a carboxyl group and one ethylenically unsaturated group. And a monomer mixture containing a monomer (B) having a group and a monomer (C) having a hydrophobic group having 1 to 12 carbon atoms and one ethylenically unsaturated group. .

  First, the ethylenically unsaturated monomer constituting the pre-crosslinked vinyl emulsion that is the main component of the coating agent for forming the ink-jet ink receiving layer of the present invention will be described.

  Here, an ethylenically unsaturated monomer, that is, a monomer having an ethylenically unsaturated group is mainly referred to as a so-called vinyl compound having an α, β-unsaturated double bond, and (meth) It includes a (meth) acrylic acid ester-based monomer having an acryloyl group, a (meth) allyl group, or another monomer having a vinyl group.

  In addition, when expressed as “(meth) acrylic acid”, “(meth) acrylate”, “(meth) allyl”, and “(meth) acryloyl”, “acrylic acid and / or methacrylic acid”, “Acrylate and / or methacrylate”, “allyl and / or methallyl”, and “acryloyl and / or methacryloyl” shall be indicated.

The monomer (A) having two or more ethylenically unsaturated groups used in the present invention introduces a crosslinked structure inside acrylic emulsion particles obtained by an emulsion polymerization method.
The monomer (A) is not limited to the following examples. For example, ethylene oxide-modified phosphoric acid poly (ethylene oxide-modified phosphoric acid di (meth) acrylate) or ethylene oxide-modified phosphoric acid tri (meth) acrylate is used. (Meth) acrylates;
Ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tri Propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, poly (ethylene glycol-propylene glycol) di (meth) acrylate, poly (ethylene glycol-tetramethylene glycol) di (meth) acrylate, poly (propylene glycol- Tetramethylene glycol) di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, 1,3-butanediol di (Meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, or 2-ethyl, 2-butyl-propanediol di ( (Poly) alkylene glycol di (meth) acrylates such as (meth) acrylate;
Poly (meth) acrylates of triols such as trimethylolpropane (tri) (meth) acrylate or glycerol (tri) (meth) acrylate;
Polyol poly (meth) acrylates such as pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyester polyol poly (meth) acrylate, polyurethane polyol poly (meth) acrylate, or polycarbonate polyol poly (meth) acrylate ;
Poly (meth) acrylic acid metal salts such as zinc di (meth) acrylate;
Dienes such as butadiene, isoprene or chloroprene;
Divinyl compounds such as divinylbenzene;
Diallyl compounds such as diallyl phthalate and monomers having two different types of ethylenically unsaturated groups such as allyl (meth) acrylate, dicyclopentenyl (meth) acrylate, vinyl (meth) acrylate, vinyl crotonate And the like. From the viewpoint of water resistance and emulsion particle stability, divinylbenzene or diallyl phthalate is preferred. These monomers may use only 1 type and may use 2 or more types together.

  In the present invention, the content of the monomer (A) is preferably from 0.1 to 5% by weight in a total of 100% by weight of the monomers to be subjected to emulsion polymerization, from the viewpoint of water resistance and emulsion particle stability. 0.1 to 4% by weight is more preferable.

The monomer (B) having a carboxyl group and one ethylenically unsaturated group used in the present invention increases the wettability between the receiving layer and the ink and absorbs the ink quickly. Used for the purpose of drying the surface.
In order to form a high-definition image with inkjet ink, it is important to control the affinity between the inkjet ink and the surface of the ink receiving layer to form ink dots having a preferable dot diameter and color density. When the ink droplet comes into contact with the surface of the ink receiving layer, the ink dot spreads appropriately, quickly absorbs and dries, whereby ink dots having a preferable dot diameter and color density can be formed. In the present invention, by using the monomer (B) having a carboxyl group and one ethylenically unsaturated group, the above effects are remarkably improved. Although this mechanism is not clear, the electrical affinity of the functional groups of the pigment dispersion resin and additives contained in the ink, the carboxyl group of the emulsion resin contained in the ink receiving layer, and the hydrophilicity of the ink By combining with a solvent, ink dots having a preferable dot diameter and color density can be formed.
Specific examples of the monomer (B) are not limited to the following examples. For example, acrylic acid, acrylic acid dimer, methacrylic acid, crotonic acid, itaconic acid, itaconic anhydride, maleic acid, maleic anhydride, Fumaric acid, citraconic acid, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxypropyl phthalate, 2- (meth) acryloyloxyethyl hexahydrophthalate, 2- (meth) acryloyloxypropyl hexahydrophthalate, Examples thereof include ethylenically unsaturated carboxylic acids such as ethylene oxide-modified succinic acid (meth) acrylate, β-carboxyethyl (meth) acrylate, or ω-carboxypolycaprolactone (meth) acrylate, and anhydrides and salts thereof. Among these, acrylic acid, methacrylic acid, crotonic acid, itaconic acid or maleic acid is preferable from the viewpoint of copolymerization. These monomers may use only 1 type and may use 2 or more types together.

  In the present invention, the content of the monomer (B) is 20 to 80% by weight in a total of 100% by weight of the monomers to be subjected to emulsion polymerization from the viewpoint of spreading of ink dots on the receiving layer and water resistance. Preferably, it is 25 to 80% by weight. If it is 20% by weight or more, the ink wetting property and the ink absorption / drying property are excellent, and the ink dots are sufficiently spread on the receiving layer, so that no whitening or white streaking occurs. In the case of multicolor printing, there is no problem that ink droplets of different colors come into contact with each other and bleeding between colors occurs. On the other hand, if it is 80% by weight or less, the water resistance is sufficient.

The monomer (C) having a hydrophobic group having 1 to 12 carbon atoms and one ethylenically unsaturated group used in the present invention is intended to improve the water resistance of the receiving layer and the ink bleeding resistance. Used in
Here, in this invention, the monomer which has one ethylenically unsaturated group, a carboxyl group, and a C1-C12 hydrophobic group shall be handled as a monomer (B).
In addition, the hydrophobic group here refers to a hydrocarbon group having 1 to 12 carbon atoms that has low polarity and is not easily compatible with water.
Specific examples of the monomer (C) are not limited to the following examples. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n -Chain alkyls such as butyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, or lauryl (meth) acrylate ) Acrylate;
Cyclic alkyl (meth) acrylate monomers such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, or dicyclopentanyl (meth) acrylate;
Aromatic (meth) acrylates such as benzyl (meth) acrylate; and
Styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, 4-t-butoxystyrene, 4-t-butoxy- α-methylstyrene, 4- (2-ethyl-2-propoxy) styrene, 4- (2-ethyl-2-propoxy) -α-methylstyrene, 4- (1-ethoxyethoxy) styrene, 4- (1- And aromatic vinyl monomers such as ethoxyethoxy) -α-methylstyrene, 1-butylstyrene and 1-chloro-4-isopropenylbenzene. Of these, aromatic monomers are preferable from the viewpoint of water resistance, and α-methylstyrene and styrene are more preferable.
These monomers may use only 1 type and may use 2 or more types together. An ethylenically unsaturated monomer having a hydrophobic group having more than 12 carbon atoms is not preferred because of poor copolymerization.
The content of the monomer (C) is preferably 19.9 to 79.9% by weight, out of a total of 100% by weight of the monomers to be subjected to emulsion polymerization, from the viewpoint of the balance between image forming properties and water resistance. More preferred is ˜79.9% by weight.

In the present invention, monomers other than the monomers (A) to (C) are optionally added to adjust the copolymerizability, compatibility with other components, film forming properties, and coating film properties. Can be copolymerized.
Examples of such monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-acrylic acid. Leuoxyethyl-2-hydroxyethyl (meth) phthalate;
Diethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate;
Polytetramethylene glycol mono (meth) acrylate, poly (ethylene glycol-propylene glycol) mono (meth) acrylate, poly (ethylene glycol-tetramethylene glycol) mono (meth) acrylate, poly (propylene glycol-tetramethylene glycol) mono ( (Meth) acrylates having hydroxyl groups such as meth) acrylate or glycerol (meth) acrylate;
2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, diethylene glycol monomethyl ether (meth) acrylate, diethylene glycol monoethyl ether (meta ) Acrylate, triethylene glycol monomethyl ether (meth) acrylate, triethylene glycol monoethyl ether (meth) acrylate, diethylene glycol mono-2-ethylhexyl ether (meth) acrylate, dipropylene glycol monomethyl ether (meth) acrylate, tripropylene glycol monomethyl Ether (meth) acrylate, tripropylene glycol monoethyl ether (meth) acrylate , Polyethylene glycol monolauryl ether (meth) acrylate, or having an ether structure such as polyethylene glycol monostearyl ether (meth) acrylate (meth) acrylates;
Glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, 3,2-glycidoxyethyl (meth) acrylate, 3,4-epoxycyclohexyl (meth) acrylate, 3,4-epoxybutyl (meth) acrylate, or 4 , (Meth) acrylates having an epoxy group such as 5-epoxypentyl (meth) acrylate;
Vinylsilanes such as vinyltris (β-methoxyethoxy) silane, vinylethoxysilane, or vinyltrimethoxysilane;
(meth) acryloyloxysilanes such as γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, or γ- (meth) acryloyloxypropyldimethoxymethylsilane;
Fluoroalkyl (meth) acrylates such as trifluoroethyl (meth) acrylate, octafluoropentyl (meth) acrylate, perfluorooctyl (meth) acrylate, or tetrafluoropropyl (meth) acrylate;
(Meth) acryloyloxy-modified polydimethylsiloxanes (silicone macromers); and acrylonitrile, but are not limited to these monomers. These monomers may use only 1 type and may use 2 or more types together.

In the present invention, it is preferable that the monomer to be subjected to emulsion polymerization does not contain an ethylenically unsaturated monomer having a cationic functional group. When an ethylenically unsaturated monomer having a cationic functional group is copolymerized, it interacts with a functional group contained in an ink pigment dispersion resin or an additive, and the ink aggregates on the surface of the ink receiving layer. In some cases, the spread of ink dots may be hindered. In addition, an acid-base bond may be formed with the carboxyl group of the monomer (B), resulting in blurring during the polymerization of the emulsion or extreme thickening.
Specific examples of the ethylenically unsaturated monomer having a cationic functional group include (meth) acrylamides such as (meth) acrylamide, N-methylol (meth) acrylamide, and N-butoxymethyl (meth) acrylamide. Is mentioned.

  The cross-linked vinyl emulsion of the present invention is synthesized by a conventionally known emulsion polymerization method. In the emulsion polymerization method, since the polymerization reaction of the polymer proceeds in water or water containing a hydrophilic organic solvent, when the hydrophobic and hydrophilic monomers are copolymerized, the central part of the emulsion particles is hydrophobic. High, and the surface portion of the particle has a highly hydrophilic structure.

  That is, the central part of the emulsion particles has high water resistance, and furthermore, a cross-linked structure is introduced by copolymerizing the monomer (A) having two or more ethylenically unsaturated groups in one molecule, thereby further improving the water resistance. Can increase the sex.

  The cross-linked vinyl emulsion of the present invention has a hydrophobic part in which a cross-linked structure is introduced inside the emulsion particles, and has a carboxyl group which is a hydrophilic group on the surface of the emulsion particles. Therefore, when it becomes a coating film, the emulsion particle | grains inside is bridge | crosslinked and hydrophobicity becomes high. Therefore, when printed, it has a structure that hardly swells with respect to water or a hydrophilic solvent contained in the ink, and the particle surface has a structure in which a plurality of carboxyl groups exist and the particles are associated with each other. The interaction with the ink is large, and it works preferentially on the wettability of the ink, but the water resistance is not lowered. Thus, since the structure of an anionic hydrophilic part and a hydrophobic part can be formed, the dot of an ink can be expanded moderately and a high-definition image can be provided, without impairing water resistance.

  In the present invention, a surfactant can be used in the emulsion polymerization. Surfactants include anionic and nonionic surfactants, and conventionally known ones such as a reactive surfactant having an ethylenically unsaturated group and a non-reactive surfactant having no ethylenically unsaturated group are used. Can be used arbitrarily.

Examples of the anionic reactive surfactant having an ethylenically unsaturated group include alkyl ethers (commercially available products include, for example, Aqualon KH-05, KH-10, KH-20, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Adeka Soap SR-10N, SR-20N manufactured by ADEKA Corporation, LATEMUL PD-104 manufactured by Kao Corporation, etc.);
Sulfosuccinic acid esters (for example, LATEMUL S-120, S-120A, S-180P, S-180A, Sanyo Chemical Co., Ltd., Elemiol JS-2, etc., manufactured by Kao Corporation);
Alkylphenyl ethers or alkylphenyl esters (commercially available products include, for example, Aqualon H-2855A, H-3855B, H-3855C, H-3856, HS-05, HS-10, HS, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. -20, HS-30, ADEKA Corporation ADEKA rear soap SDX-222, SDX-223, SDX-232, SDX-233, SDX-259, SE-10N, SE-20N, etc.);
(Meth) acrylate sulfates (commercially available products include, for example, Anxox MS-60 and MS-2N manufactured by Nippon Emulsifier Co., Ltd., Eleminol RS-30 manufactured by Sanyo Chemical Industries, Ltd.); and phosphate esters (commercially available) Examples of the product include H-3330PL manufactured by Daiichi Kogyo Seiyaku Co., Ltd. and Adeka Soap PP-70 manufactured by ADEKA Co., Ltd.).

Nonionic reactive surfactants that can be used in the present invention include, for example, alkyl ethers (commercially available products such as Adeka Soap ER-10, ER-20, ER-30, and ER manufactured by ADEKA Corporation). -40, LATEMUL PD-420, PD-430, PD-450, etc. manufactured by Kao Corporation);
Alkyl phenyl ethers or alkyl phenyl esters (commercially available products include, for example, Aqualon RN-10, RN-20, RN-30, RN-50, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Adeka Soap NE- manufactured by ADEKA Corporation. 10, NE-20, NE-30, NE-40, etc.); and (meth) acrylate sulfates (commercially available products include, for example, RMA-564, RMA-568, RMA-1114, etc., manufactured by Nippon Emulsifier Co., Ltd.) Is mentioned.

Examples of non-reactive nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether or polyoxyethylene stearyl ether;
Polyoxyethylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether or polyoxyethylene nonylphenyl ether;
Sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, or sorbitan trioleate;
Polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate;
Polyoxyethylene higher fatty acid esters such as polyoxyethylene monolaurate or polyoxyethylene monostearate;
Examples include glycerol higher fatty acid esters such as oleic acid monoglyceride or stearic acid monoglyceride; and polyoxyethylene / polyoxypropylene / block copolymer or polyoxyethylene distyrenated phenyl ether.

Examples of non-reactive anionic surfactants include higher fatty acid salts such as sodium oleate;
Alkylaryl sulfonates such as sodium dodecylbenzenesulfonate;
Alkyl sulfate salts such as sodium lauryl sulfate;
Polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate;
Polyoxyethylene alkylaryl ether sulfate salts such as sodium polyoxyethylene nonylphenyl ether sulfate;
Examples thereof include alkyl sulfosuccinic acid ester salts such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, or sodium polyoxyethylene lauryl sulfosuccinate and derivatives thereof; and polyoxyethylene distyrenated phenyl ether sulfates.

  These surfactants may be used alone or in combination of two or more.

The amount of the surfactant used in the present invention is not necessarily limited, and can be appropriately selected according to the physical properties required when the already crosslinked vinyl emulsion is finally used as a composition for forming an ink receiving layer. . For example, the surfactant is usually preferably 0.1 to 30 parts by weight, more preferably 0.3 to 20 parts by weight with respect to 100 parts by weight of the total of ethylenically unsaturated monomers, More preferably, it is in the range of 0.5 to 10 parts by weight.
When the surfactant is 0.1 parts by weight or more, the polymerization stability and mechanical stability are good. On the other hand, if it is 30 parts by weight or less, the resulting recording medium has excellent water resistance.

In the emulsion polymerization for obtaining the cross-linked vinyl emulsion of the present invention, a water-soluble protective colloid can be used in combination. Examples of the water-soluble protective colloid include polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, or modified polyvinyl alcohol;
Examples thereof include cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, or carboxymethyl cellulose salt; and natural polysaccharides such as guar gum. These can be used either alone or in a combination of a plurality of types. The amount of the water-soluble protective colloid used is 0.1 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the total amount of ethylenically unsaturated monomers.

In obtaining the cross-linked vinyl emulsion of the present invention, a polymerization initiator can be used. The polymerization initiator is not particularly limited as long as it has the ability to initiate radical polymerization, and known oil-soluble polymerization initiators and water-soluble polymerization initiators can be used.
The oil-soluble polymerization initiator is not particularly limited, and examples thereof include benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy (2-ethylhexanoate), and tert-butyl peroxide. Organic peroxides such as oxy-3,5,5-trimethylhexanoate or di-tert-butyl peroxide; and 2,2′-azobisisobutyronitrile, 2,2′-azobis-2, Mention may be made of azobis compounds such as 4-dimethylvaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), or 1,1′-azobis-cyclohexane-1-carbonitrile.
These may use only 1 type and may use 2 or more types together. These polymerization initiators are preferably used in an amount of 0.1 to 10.0 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated monomer.

In the present invention, a water-soluble polymerization initiator is preferably used. For example, ammonium persulfate, potassium persulfate, hydrogen peroxide, or 2,2′-azobis (2-methylpropionamidine) dihydrochloride is conventionally known. Can be preferably used.
Moreover, when performing emulsion polymerization, a reducing agent can be used together with a polymerization initiator if desired. Thereby, it becomes easy to accelerate the emulsion polymerization rate or to perform the emulsion polymerization at a low temperature. Examples of such reducing agents include reducing organic compounds such as metal salts such as ascorbic acid, ersorbic acid, tartaric acid, citric acid, glucose, or formaldehyde sulfoxylate,
Reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, or sodium metabisulfite,
Examples thereof include ferrous chloride, Rongalite, or thiourea dioxide.

  These reducing agents are preferably used in an amount of 0.05 to 5.0 parts by weight based on 100 parts by weight of the total of ethylenically unsaturated monomers. In addition, it can superpose | polymerize also by a photochemical reaction, radiation irradiation, etc. irrespective of an above described polymerization initiator. The polymerization temperature is not less than the half-life temperature of each polymerization initiator. For example, in the case of a peroxide-based polymerization initiator, it may be usually about 70 ° C. The polymerization time is not particularly limited, but is usually 2 to 24 hours.

  In the present invention, the aqueous medium used in the emulsion polymerization includes water, and a hydrophilic organic solvent can also be used as long as the object of the present invention is not impaired.

  Further, if necessary, a buffering agent and a chain transfer agent can be used. Examples of the buffer include sodium acetate, sodium citrate, and sodium bicarbonate. Examples of chain transfer agents include mercaptans such as octyl mercaptan, 2-ethylhexyl thioglycolate, octyl thioglycolate, stearyl mercaptan, lauryl mercaptan, and t-dodecyl mercaptan.

In the present invention, all or part of the acidic functional group of the monomer (B) having a carboxyl group and one ethylenically unsaturated group can be neutralized with a basic compound before or after polymerization. .
As a neutralizing agent, ammonia; alkylamines such as trimethylamine, triethylamine, or butylamine; alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine, or aminomethylpropanol; or a base such as morpholine is used. can do.

In the present invention, the acid value of the resin particles of the already crosslinked vinyl emulsion can be adjusted by the composition of the ethylenically unsaturated monomer used for polymerization, but is preferably 100 to 500 mg KOH / g. When it is 100 mgKOH / g or more, the ink has excellent wettability and ink absorption and drying properties, and the ink dots are sufficiently spread on the receiving layer, so that whitening and white stripes are less likely to occur. Further, in the case of multicolor printing, ink droplets of different colors do not come into contact with each other and bleeding between colors does not occur. When it is 500 mgKOH / g or less, the water resistance is excellent.
In addition, the acid value here is a value measured by the following operation.
<Method for measuring acid value>
About 1 g of a sample is accurately weighed in a stoppered Erlenmeyer flask, and 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution is added and dissolved. To this, phenolphthalein test solution is added as an indicator, held for 30 seconds, and then titrated with a 0.1N alcoholic potassium hydroxide solution until the solution becomes light red.

The acid value (mgKOH / g) is determined by the following equation as the value of the resin in the dry state.
Acid value (mgKOH / g) = {(5.611 × a × F) / S} / (Nonvolatile content concentration / 100)
Where S: Amount of sample collected (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml)
F: Potency of 0.1N alcoholic potassium hydroxide solution

In the present invention, the glass transition temperature (Tg) of the resin particles of the already cross-linked vinyl emulsion can be adjusted by the composition of the ethylenically unsaturated monomer to be subjected to polymerization, but is preferably 0 to 70 ° C. . When the temperature is 0 ° C. or higher, blocking (refers to a state in which the printed surface and the back surface of the base material are fused and cannot be easily peeled off) does not occur when the printed material is laminated. When it is 70 ° C. or lower, the texture of the printed matter is excellent.
The glass transition temperature here is a value that can be calculated by the Fox method.
Here, the Fox method (T.G. Fox, Phys. Rev., 86, 652 (1952)) is a method for estimating the Tg of a copolymer from the Tg of each homopolymer represented by the following formula. is there.

1 / Tg = W ₁ / Tg ₁ + W ₂ / Tg ₂ +... + W _n / Tg _n
Wherein, Tg is the glass transition temperature of the copolymer (absolute temperature _{display), Tg 1, Tg 2 ···} Tg n is the glass transition temperature of the homopolymer of each monomer component (absolute display), W ₁ , W ₂ ... W _n represents the weight fraction of each monomer component. ]

The volume average particle size of the cross-linked vinyl emulsion of the present invention can be adjusted by the composition of the ethylenically unsaturated monomer used for polymerization, the type and amount of the surfactant used during polymerization, the polymerization operation, etc. From the viewpoint of particle stability, the thickness is preferably 40 to 400 nm, more preferably 40 to 250 nm. In consideration of the stability of the particles, the coarse particles exceeding 1 μm are preferably 5% by weight or less. In addition, the volume average particle diameter in the present invention is measured by a dynamic light scattering method, and more specifically is a value measured by the following operation.
<Measurement method of volume average particle diameter>
The already cross-linked vinyl emulsion is diluted with water 200 to 1000 times according to the solid content concentration. About 5 ml of the diluted solution is injected into a cell of a measuring apparatus [Microtrack manufactured by Nikkiso Co., Ltd.], and the measurement is performed after inputting the solvent (water in the present invention) and the refractive index condition of the resin according to the sample. The peak of the volume particle size distribution data (histogram) obtained at this time is defined as the volume average particle size of the present invention.

In the present invention, the viscosity of a cross-linked vinyl emulsion at a solid content concentration of 10% by weight depends on the composition of the ethylenically unsaturated monomer used for polymerization, the type and amount of surfactant used during polymerization, the polymerization operation, and the like. Although it can adjust, it is preferable that it is 0.1-300 mPa * s. If the viscosity at a solid content concentration of 10% by weight is 300 mPa · s or less, there is no need to dilute and apply when forming the inkjet ink receiving layer.
The viscosity here is a value that can be measured by the following operation.
<Measurement method of viscosity of emulsion>
A sample adjusted to a solid content concentration of 10% by weight was taken in a glass bottle, and the viscosity after 1 minute was measured with a vibrating viscometer (VM-10A manufactured by Seconic Corporation).

In the present invention, the SP value [R. F. Fedor, Polym. Eng. Sci. , 14 (2) 147 (1974)] can be adjusted by the composition of the ethylenically unsaturated monomer to be used for the polymerization, but it is 3.9 to 6.8 (J · cm ⁻³ ) ^1/2 . It is preferably 4.9 to 5.9 (J · cm ⁻³ ) ^1/2 . If it is 3.9 (J · cm ⁻³ ) ^1/2 or more, ink wetting and ink absorption and drying properties are excellent, and the ink dots spread sufficiently on the receiving layer, resulting in whitening and white streaks. Does not occur. The ink droplets of different colors do not come into contact with each other and bleeding between colors does not occur. If it is 6.8 (J · cm ⁻³ ) ^1/2 or less, the water resistance is sufficient.

In the present invention, the surface tension of resin particles of a cross-linked vinyl emulsion by the Macleod-Sugden method [Maclead, Trans, Faraday Soc. , 19, 38 (1923)] can be adjusted by the composition of the ethylenically unsaturated monomer used for polymerization, but is preferably 22 to 35 × 10 ⁻³ (N / m). If it is 22 × 10 ⁻³ (N / m) or more, the ink has excellent wettability and ink absorption / drying properties, and the ink dots will spread sufficiently on the receiving layer, and no whitening or white streaks will occur. The ink droplets of different colors do not come into contact with each other and bleeding between colors does not occur. When it is 35 × 10 ⁻³ (N / m) or less, the water resistance is excellent.

  When the ink jet ink receiving layer of the present invention forms an image using the ink composition described later, the surface tension value of the receiving layer surface is close to the value of the dynamic surface tension of the ink composition. It is important to be. When the surface tension value on the surface of the receiving layer is close to the value of the dynamic surface tension of the ink composition to be used, the ink dots on the receiving layer spread appropriately and a high-definition image can be obtained.

  Thus, the SP value and the surface tension value of the resin particles of the already cross-linked vinyl emulsion are the criteria for judging the compatibility (interaction) with the ink composition, and the quality of the image changes depending on these values. Therefore, in order to obtain a high-detail image, these numerical values are very important.

The coating agent for forming an ink-jet ink receiving layer in the present invention is composed of one of the aforementioned crosslinked vinyl emulsions or a combination of two or more. In particular, from the viewpoint of the balance between image formability and water resistance, the copolymer (X) using an aromatic monomer as the monomer (C) and the aromatic as the monomer (C) It is preferable to use together with the copolymer (Y) which uses only monomers other than. Here, in the copolymer (X), an aromatic monomer and a non-aromatic monomer may be used in combination as the monomer (C).
In the copolymer (X), the aromatic monomer (C) is preferably 1 to 79.9% by weight, more preferably 1%, in a total of 100% by weight of the monomers to be subjected to emulsion polymerization. -50% by weight is included. Further, the non-aromatic monomer (C) is preferably contained in an amount of 0 to 78.9% by weight, more preferably 0 to 75% by weight.
Moreover, you may mix | blend a film-forming auxiliary, an antifoamer, a leveling agent, an antiseptic | preservative, a pH adjuster, a viscosity adjuster, or another compound as needed. About these additives, it can select arbitrarily from a conventionally well-known compound according to the objective.

The film-forming aid is responsible for the temporary plasticizing function that helps the formation of the coating film, and evaporates relatively quickly after the coating film is formed to improve the strength of the coating film. An organic solvent of 110 to 200 ° C. is preferably used.
Specifically, propylene glycol monobutyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol monobutyl ether, diethylene glycol diethyl ether, dipropylene glycol monopropyl ether, carbitol, butyl carbitol, dibutyl carbitol, or benzyl Alcohol etc. are mentioned. Among these, ethylene glycol monobutyl ether and propylene glycol monobutyl ether are particularly preferable because they have a high film forming auxiliary effect in a small amount. These film forming aids are preferably contained in an amount of 0.5 to 15% by weight in the coating agent for forming the ink jet ink receiving layer.

  The viscosity modifier may be used in an amount of 1 to 100 parts by weight with respect to 100 parts by weight of the already cross-linked vinyl emulsion. Examples of the viscosity modifier include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (and its salt), oxidized starch, phosphorylated starch, and casein.

  The coating agent for forming an ink-jet ink receiving layer of the present invention may be composed of an already crosslinked vinyl emulsion alone or may be used in combination with an inorganic filler such as colloidal silica or silica.

  The colloidal silica may be blended later in the cross-linked vinyl emulsion of the present invention, or an aqueous dispersion of colloidal silica may be blended in the aqueous medium when the cross-linked vinyl emulsion is synthesized.

  Moreover, the coating agent for forming an ink-jet ink receiving layer of the present invention may contain an aqueous glossy resin in order to impart gloss to the ink receiving layer. Specifically, Jonkrill 52J, Jonkrill 62J, Jonkrill 70J, Jonkrill 7667 manufactured by BASF, Luciden 400SF manufactured by Nippon Polymer Co., Ltd., Emmapoly SG-5157 manufactured by Gifcellac are listed.

  The coating agent for forming an ink-jet ink receiving layer of the present invention may further contain a crosslinking agent, for example, methylolated melamine, methylolated urea, methylolated hydroxypropylene urea, polyfunctional isocyanate compound, or polyfunctional epoxy. Compounds and the like.

Examples of the base material on which the coating agent for forming the ink-jet ink receiving layer of the present invention is coated include high-quality paper, medium-quality paper, coated paper, art paper, glossy paper, newspaper paper, various information papers, various special papers, paperboard, etc. Or a film made of a plastic such as polyethylene terephthalate, diacetate, triacetate, cellophane, celluloid, polycarbonate, polyimide, polyvinyl chloride, polyvinylidene chloride, polyacrylate, polyethylene, or polypropylene can be used.
The surface of the substrate may be a smooth surface, an uneven surface, or transparent, translucent, or opaque.
Further, two or more of these substrates may be bonded to each other. Furthermore, a peeling adhesive layer or the like may be provided on the opposite side of the printing surface, or an adhesive layer or the like may be provided on the printing surface after printing.

The coating agent for forming an inkjet ink receiving layer of the present invention can be applied to the substrate by a known method, for example, a roll coating method, a blade coating method, an air knife coating method, a gate roll coating method, a bar coating method. , Size press method, spray coating method, die coating method, lip coating method, comma coating method, spin coating method, gravure coating method, curtain coating method and the like.
There is no restriction | limiting in particular in a drying method, The thing using hot air drying, infrared rays, and the pressure reduction method is mentioned. As drying conditions, although depending on the film forming property of the coating agent for forming an ink-jet ink receiving layer, the coating amount, or the selected additive, hot air heating of about 60 to 180 ° C. or about 20 to 60 ° C. is usually sufficient. Infrared heating may be used.

  By the coating, an ink-jet ink receiving layer is formed on the substrate, and an image-forming recording medium can be obtained. By performing printing with inkjet ink on the recording medium, a printed matter on which an image is formed can be preferably obtained.

In addition, the inkjet ink receiving layer may be provided only on one side of the substrate, or may be provided on both sides.
Furthermore, if necessary, a super calendering treatment or a casting treatment can be performed for smoothing the ink receiving layer, improving gloss, or improving surface strength.
Moreover, the ink jet ink receiving layer forming coating agent of the present invention can be filled in an ink cartridge of an ink jet printer, and can be printed by the ink jet method simultaneously with or prior to the printing ink.

The coating amount of the ink-jet ink receiving layer of the present invention, as dry weight, preferably from 0.2 to 50 g / m ^2, more preferably from 0.5 to 30 g / m ^2. When the coating amount is 0.2 g / m ² or more, the color developability of the ink is excellent as compared with the case where the ink receiving layer is not provided. On the other hand, when it is 50 g / m ² or less, the occurrence of curling can be suppressed.

  Examples of the ink when performing inkjet recording on the image forming recording medium of the present invention described above include, for example, water-based ink, solvent-based ink, solid ink (hot melt ink), UV curable ink, and EB curable ink. And other radiation-curable inks. From the viewpoint of the environment and durability of the printed matter, it is preferable to use a water-based pigment ink.

A preferable configuration for the ink will be described below.
The inkjet ink comprises a pigment dispersion resin, the pigment dispersion resin comprising an aromatic ethylenically unsaturated monomer (m1), a carboxyl group-containing ethylenically unsaturated monomer, a neutralized product or a metal salt thereof, Or it is preferable that it is a copolymer which consists of two components with the at least 1 sort (s) of monomer (m2) chosen from the group which consists of an acid anhydride group containing ethylenically unsaturated monomer or its half ester.

  When such a pigment dispersion resin is used, the affinity between the ink-jet ink and the ink receiving layer surface is appropriately controlled, and the ink dots spread appropriately, which is beneficial in terms of reproducibility of high-definition images. Moreover, it is also beneficial in terms of storage stability of the ink itself.

  Examples of the aromatic ethylenically unsaturated monomer (m1) constituting the pigment dispersion resin include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, 4-t-butoxystyrene, 4-t-butoxy-α-methylstyrene, 4- (2-ethyl-2-propoxy) styrene, 4- (2-ethyl-2- Propoxy) -α-methylstyrene, 4- (1-ethoxyethoxy) styrene, 4- (1-ethoxyethoxy) -α-methylstyrene, 1-butylstyrene, 1-chloro-4-isopropenylbenzene and the like. However, it is not particularly limited to these. These may use only 1 type or may use multiple types together.

At least one selected from the group consisting of carboxyl group-containing ethylenically unsaturated monomers constituting the pigment dispersion resin, neutralized products or metal salts thereof, and acid anhydride group-containing ethylenically unsaturated monomers or half esters thereof Examples of the monomer (m2) include acrylic acid, methacrylic acid, 2-carboxyethyl (meth) acrylate, 2-carboxypropyl (meth) acrylate, 3-carboxypropyl (meth) acrylate, ( (Meth) acrylic acid 4-carboxybutyl, (meth) acrylic acid dimer, maleic acid, fumaric acid, monomethylmaleic acid, monomethylfumaric acid, aconitic acid, sorbic acid, cinnamic acid, α-chlorosorbic acid, glutaconic acid, citracone Acid, mesaconic acid, itaconic acid, tiglic acid, angelic acid, senecioic acid, croton , Isoccrotonic acid, mucobromic acid, mucochloric acid, sorbic acid, muconic acid, aconitic acid, penicillic acid, gellanic acid, citronellic acid, or ω-carboxypolycaprolactone mono (meth) acrylate, etc. Carboxyl group-containing fats such as polylactone type (meth) acrylic acid ester having a carboxyl group or alkylene oxide addition type succinic acid (meth) acrylate having a carboxyl group at the terminal where alkylene oxide such as ethylene oxide or propylene oxide is repeatedly added Group ethylenically unsaturated carboxylic acids;
For example, 2- (meth) acryloyloxyethyl hexahydrophthalate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxypropyl phthalate, 2- (meth) acryloyloxybutyl phthalate, 2- (Meth) acryloyloxyhexyl phthalate, 2- (meth) acryloyloxyoctyl phthalate, 2- (meth) acryloyloxydecyl phthalate, 2-vinylbenzoic acid, 3-vinylbenzoic acid, 4-vinylbenzoic acid, 4 -Ethylenically unsaturated carboxylic acids having a carboxyl group-containing alicyclic ring or aromatic ring such as isopropenylbenzenecarboxylic acid, cinnamic acid, 7-amino-3-vinyl-3-cephem-4-carboxylic acid;
And these neutralized products, metal salts, acid anhydrides, acid ester half-esterified products, and the like, are not particularly limited thereto. These may use only 1 type or may use multiple types together.

  The pigment dispersion resin can be synthesized by a conventionally known solution polymerization method, emulsion polymerization method, suspension polymerization method, bulk polymerization method, or the like.

  Examples of commercially available pigment-dispersed resins include styrene-acrylic acid resins (John Krill series) manufactured by BASF (Johnson Polymer).

  Conventionally known pigments can be used as pigments contained in water-based pigment inks.

Examples of the black pigment contained in the aqueous pigment ink include carbon black produced by the furnace method and the channel method. For example, these carbon blacks have a primary particle diameter of 11 to 40 nm, a specific surface area by BET method of 50 to 400 m ² / g, a volatile content of 0.5 to 10% by mass, a pH value of 2 to 10 and the like. Those having characteristics are preferred. The following are mentioned as a commercial item which has such a characteristic. For example, no. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (manufactured by Mitsubishi Chemical), RAVEN1255 (manufactured by Colombian Carbon), REGAL330R, 400R, 660R, MOGUL L, ELFTEX415 (manufactured by Cabot) ), Nexex90, Nipex150T, Nipex 160IQ, Nipex 170IQ, Nipex 75, Printex 85, Printex 95, Printex 90, Printex 35, Printex U (manufactured by Evonik Degussa), etc., which can be preferably used.

  Examples of the yellow pigment contained in the water-based pigment ink include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213 and the like.

  Examples of the magenta pigment contained in the water-based pigment ink include C.I. I. Pigment Red 5, 7, 9, 12, 31, 48, 49, 52, 53, 57, 97, 112, 122, 147, 149, 150, 168, 177, 178, 179, 202, 206, 207, 209, 238, 242, 254, 255, 269, C.I. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50 and the like.

  Examples of cyan pigments contained in water-based pigment inks include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 16, 22, C.I. I. Vat Blue 4, 6 etc. are mentioned.

  As the pigment contained in the water-based pigment ink, pigments other than those described above, self-dispersing pigments, and the like can also be used. These pigments may be used alone or in combination of two or more in each color ink.

  The content of the pigment contained in the water-based pigment ink is in the range of 0.1 to 20% by weight, more preferably 0.1 to 12% by weight in the ink.

  A suitable medium contained in the ink is a mixed solvent of water and a water-soluble solvent. As water, ion-exchanged water (deionized water) is used instead of general water containing various ions. preferable.

  As the water-soluble solvent used by mixing with water, glycol ethers and diols are preferable, and (poly) alkylene glycol monoalkyl ether and alkanediol having 3 to 6 carbon atoms are particularly effective. These solvents penetrate the paper very quickly. Penetration is fast even for substrates with low solvent absorption such as coated paper and art paper. Therefore, drying at the time of printing is fast and accurate printing can be realized. Moreover, since the boiling point is high, the function as a moisturizing agent is sufficient.

  Specific examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, triethylene Glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene Glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, and the like.

  Specific examples of diols include 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, Examples include 1,2-hexanediol, 1,6-hexanediol, and 2-methyl-2,4-pentanediol.

  Of these, the most effective are diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-hexanediol. 2-methyl-2,4-pentanediol.

  These solvents may be used alone or in combination.

  Further, depending on the type of substrate to be printed, water-soluble nitrogen-containing complex such as 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, N-methyloxazolidinone, N-ethyloxazolidinone and the like is used for the purpose of improving the solubility. Ring compounds can also be added.

  The content of the water-soluble organic solvent as described above in the ink is generally in the range of 3% by mass to 60% by mass, more preferably 3% by mass to 50% by mass of the total mass of the ink. Range. The water content is in the range of 10% by mass to 90% by mass, more preferably 30% by mass to 80% by mass, based on the total mass of the ink.

The water-based pigment ink can also contain an aqueous emulsion.
By containing an aqueous emulsion, it is possible to improve the resistance of the printed coating film without significantly increasing the ink viscosity. Thereby, water resistance, solvent resistance, scratch resistance and the like are improved. Even if a water-soluble resin is added, the durability can be expected to improve to some extent, but the viscosity of the ink tends to increase. In the case of inkjet ink, there is a suitable range for the viscosity at which ink can be ejected from the nozzle, and if the viscosity is too high, it may become impossible to eject the ink, so it is important to suppress the increase in viscosity.

  The content of the aqueous emulsion as described above in the ink is preferably in the range of 2 to 30% by weight, more preferably in the range of 3 to 20% by weight based on the solid content concentration of the emulsion.

  Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, “part” represents “part by weight”, and “%” represents “% by weight”.

<Synthesis of cross-linked vinyl emulsion>
(Synthesis Example 1)
In a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, 136.2 parts of ion exchange water, 1.6 parts of a 24% aqueous solution of RA-9607 (manufactured by Nippon Emulsifier Co., Ltd.) as a surfactant, and As a buffer, 0.13 parts of sodium bicarbonate was charged.
Separately, 0.5 part of diallyl phthalate, 40 parts of methacrylic acid, 30 parts of ethyl acrylate, 29.5 parts of butyl acrylate, 80 parts of ion-exchanged water, and a 24% strength aqueous solution of RA-9607 as a surfactant. 4 parts were mixed to prepare a pre-emulsion.
Next, 5% of the pre-emulsion was added to the reaction vessel. After raising the internal temperature of the reaction vessel to 75 ° C. and sufficiently purging with nitrogen, 6% of 6% aqueous solution of potassium persulfate (that is, 0.6 part) was added to initiate polymerization.
After maintaining the reaction system at 75 ° C. for 5 minutes, the remaining pre-emulsion and the remaining 5% strength aqueous solution of potassium persulfate (ie, 5.4 parts) are maintained for 2 hours while maintaining the internal temperature at 75-80 ° C. The mixture was added dropwise, and stirring was further continued for 2 hours. After confirming that the polymerization rate exceeded 98% by solid content concentration measurement, the temperature was cooled to 30 ° C. A vinyl emulsion was obtained by adjusting the solid content concentration to 30% with ion-exchanged water. In addition, solid content density | concentration was calculated | required with the residue after drying with 150 degreeC-20 minutes in a hot air oven.

(Synthesis Examples 2 to 25)
The monomer compositions shown in Table 1 were synthesized in the same manner as in Synthesis Example 1, and vinyl emulsions of Synthesis Examples 2 to 25 were obtained.

About the vinyl-type emulsion obtained by the synthesis examples 1-25, the acid value, glass transition temperature (Tg), volume average particle diameter, viscosity, SP value, and surface tension were measured with the following method. The results are shown in Table 1.
<Acid value>
About 1 g of vinyl-based emulsion was accurately weighed in a stoppered Erlenmeyer flask, and dissolved by adding 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution. To this was added a phenolphthalein test solution as an indicator, which was held for 30 seconds, and then titrated with a 0.1N alcoholic potassium hydroxide solution until the solution turned light red.

The acid value (mgKOH / g) was determined by the following equation as the value of the resin in the dry state.
Acid value (mgKOH / g) = {(5.611 × a × F) / S} / (Nonvolatile content concentration / 100)
Where S: Amount of sample collected (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml)
F: Potency of 0.1N alcoholic potassium hydroxide solution <Tg>
The glass transition temperature of the vinyl emulsion was determined by calculation using the Fox method (TG Fox, Phys. Rev., 86, 652 (1952)).
<Volume average particle diameter>
The vinyl emulsion was diluted with water 200 to 1000 times. About 5 ml of the diluted solution was poured into a cell of a measuring apparatus [Microtrack manufactured by Nikkiso Co., Ltd.], and after measuring the refractive index conditions of water and resin, measurement was performed. At this time, the peak of the obtained volume particle size distribution data (histogram) was taken as the volume average particle size.
<Viscosity>
In a glass bottle, adjust by adding ion-exchanged water so that the solid content concentration of the vinyl emulsion is 10% by weight, and measure the viscosity after 1 minute with a vibration viscometer (VM-10A manufactured by Seconic). did.
<SP value>
The SP value of the resin particles of the already crosslinked vinyl emulsion was determined by the Fedor method. Specifically, R.I. F. Fedor, Polym. Eng. Sci. , 14 (2) 147 (1974).
<Surface tension>
The surface tension of the resin particles of the already crosslinked vinyl emulsion was determined by the Macleod-Sugden method. Specifically, McLead, Trans, Faraday Soc. , 19, 38 (1923).

<Adjustment of inkjet ink>
15 parts of cyan pigment (“Lionol Blue 7351” manufactured by Toyo Ink Manufacturing Co., Ltd.), acrylic resin pigment dispersant [“John Crill 680” manufactured by BASF (Johnson Polymer) (content: styrene-acrylic acid copolymer)] 1.5 parts, 5.0 parts of glycerin and 78.5 parts of ion exchange water were dispersed in a sand mill for 2 hours to obtain an aqueous pigment dispersion.
The following components including the obtained pigment dispersion were stirred and mixed with a disper, and then filtered through a nitrocellulose membrane filter having a pore size of 0.45 μm to obtain a blue ink composition.
-20 parts of pigment dispersion
-Glycerin 10 parts
-1,3-propanediol 5 parts
-Acrylic resin emulsion 2.3 parts (Nippon Polymer "F-157", solid content concentration 40%)
-Ion exchange water 62.7 parts

<Preparation of coating agent for forming inkjet ink receiving layer, creation of printed matter>
Example 1
To 100 parts of the vinyl emulsion obtained in Synthesis Example 1, 200 parts of ion-exchanged water was blended to prepare a coating agent for forming an inkjet ink receiving layer having a solid content concentration of 10%. This coating agent was applied to coated paper [Oji Paper Co., Ltd., OK Top Coat Plus] with a wire bar No. 2 and dried in a hot air oven at 60 ° C. for 2 minutes to produce a recording medium having an inkjet ink receiving layer laminated thereon.

Next, the above blue ink composition was filled in a cartridge of an ink jet printer (“PM-750C” manufactured by Epson Corporation), pattern printing was performed, and a printed matter for evaluation was produced.
(Examples 2 to 17, Examples 21 to 24, Comparative Examples 1 to 4)
A printed matter for evaluation was produced in the same manner as in Example 1, except that the emulsion of Synthesis Example 1 was changed to the emulsion shown in Table 2.
(Examples 18 to 20)
A printed matter for evaluation was produced in the same manner as in Example 1, except that the emulsion of Synthesis Example 1 was changed to the emulsion mixture shown in Table 2 (the numbers are the weight ratio of the solid content).

  Table 2 shows the evaluation results of white spots / white stripes, drying properties, and water resistance. A specific evaluation method will be described below.

<White spots / white stripes>
In a solid printing part with a printing rate of 100%, it is visually evaluated, and x is clearly white spots and white lines are generated, x is slightly white spots and white lines are generated, and white and white lines are white. Those without streaks were marked with ○. In particular, “A” indicates that there is no white spot or white streak and there is no density unevenness and a uniform solid print portion is obtained.

<Drying>
Immediately after printing, press the copy paper with a finger against a solid print section with a printing rate of 200%. If there is a color transition, cross x. If there is a slight color transition, Δ. The ones that were not possible were marked with ○

<Water resistance>
Drop a drop of water with a dropper on a solid printing part with a printing rate of 100%, wipe off the water with tissue paper after 1 minute, and visually evaluate it. △ was assigned and ◯ was not changed. In particular, among those that did not change visually, those that did not change visually even when rubbed 5 times with a cotton swab wetted with water were rated as ◎.

As shown in Table 2, according to the coating agent for forming the ink image-receiving layer of Examples 1 to 24 of the present invention, there are almost no white stripes or white spots, and the drying property and water resistance are excellent.
Especially, according to the coating agent for ink image-receiving layer formation in Examples 9, 18 to 21, 23 and 24 using the monomer having an aromatic group as the monomer (C), the water resistance is very excellent.
Further, among these, an emulsion using an aromatic monomer as the monomer (C) and an emulsion using only a monomer other than the aromatic monomer as the monomer (C) are used in combination. According to Examples 18-20, it is very excellent in the white stripe / white spot test.
On the other hand, according to the coating agent for forming an ink image-receiving layer of Comparative Example 1 that does not use the monomer (A), the water resistance is very poor.
In addition, according to the coating agent for forming an ink image-receiving layer of Comparative Examples 2 and 4 in which the monomer (B) is not used, white streaks and white spots are often generated.
Furthermore, according to the coating agent for forming an ink image-receiving layer of Comparative Example 3 in which the monomer (C) is not used, white streaks and white spots are frequently generated and the drying property is inferior.

Claims (13)

  Monomer (A) having two or more ethylenically unsaturated groups, monomer (B) having a carboxyl group and one ethylenically unsaturated group, and a hydrophobic group having 1 to 12 carbon atoms and one ethylene A coating agent for forming an ink-jet ink receiving layer, comprising a cross-linked vinyl emulsion obtained by emulsion polymerization of a monomer mixture containing a monomer (C) having a polymerizable unsaturated group.   In a total of 100% by weight of the monomers to be subjected to emulsion polymerization, the proportion of the monomer (A) is 0.1 to 5% by weight, and the proportion of the monomer (B) is 20 to 80% by weight. The coating agent for forming an inkjet ink receiving layer according to claim 1.   The coating agent for forming an ink-jet ink receiving layer according to claim 1 or 2, wherein the acid value of the resin particles of the cross-linked vinyl emulsion is 100 to 500 mgKOH / g.   The coating agent for forming an ink-jet ink receiving layer according to any one of claims 1 to 3, wherein the glass transition temperature of the resin particles of the already crosslinked vinyl emulsion is 0 to 100 ° C.   The coating agent for forming an ink-jet ink receiving layer according to any one of claims 1 to 4, wherein the volume average particle diameter of resin particles of the crosslinked vinyl emulsion is 10 to 500 nm.   The coating agent for forming an ink-jet ink receiving layer according to any one of claims 1 to 5, wherein the already crosslinked vinyl emulsion has a viscosity of 0.1 to 300 mPa · s at a solid content concentration of 10% by weight.   The coating agent for forming an inkjet ink receiving layer according to any one of claims 1 to 6, wherein the monomer to be subjected to emulsion polymerization does not contain an ethylenically unsaturated monomer having a cationic functional group. The SP value of the resin particles of the cross-linked vinyl emulsion is 3.9 to 6.8 (J · cm ⁻³ ) ^1/2 by the Fedor method, and the resin particles of the pre-cross-linked vinyl emulsion are Macintosh. The coating agent for forming an ink-jet ink receiving layer according to any one of claims 1 to 7, wherein the surface tension according to the Sugden method is 22 to 35 x ^10-3 (N / m).   An image-forming recording medium comprising an ink-jet ink receiving layer formed from the coating agent for forming an ink-jet ink receiving layer according to claim 1 on at least one surface of a substrate.   A printed matter obtained by forming an image with an inkjet ink on the image-forming recording medium according to claim 9.   The inkjet ink comprises a pigment dispersion resin, the pigment dispersion resin comprising an aromatic ethylenically unsaturated monomer (m1), a carboxyl group-containing ethylenically unsaturated monomer, a neutralized product or a metal salt thereof, And at least one monomer (m2) selected from the group consisting of an acid anhydride group-containing ethylenically unsaturated monomer or a half ester thereof, and a copolymer comprising two components. Item 11. A printed matter according to item 10. Monomer (A) having two or more ethylenically unsaturated groups, monomer (B) having a carboxyl group and one ethylenically unsaturated group, and carbon number 1 on at least one surface of the substrate Coating agent for forming an ink-jet ink receiving layer comprising a cross-linked vinyl emulsion, which is obtained by emulsion polymerization of a monomer mixture containing a monomer (C) having a hydrophobic group of -12 and one ethylenically unsaturated group A first step of forming an ink jet ink receiving layer using the ink jet; and a second step of forming an image with the ink jet ink on the ink jet ink receiving layer;
A method for producing a printed material, comprising:   The inkjet ink comprises a pigment dispersion resin, the pigment dispersion resin comprising an aromatic ethylenically unsaturated monomer (m1), a carboxyl group-containing ethylenically unsaturated monomer, a neutralized product or a metal salt thereof, And at least one monomer (m2) selected from the group consisting of an acid anhydride group-containing ethylenically unsaturated monomer or a half ester thereof, and a copolymer comprising two components. Item 13. A method for producing a printed material according to Item 12.