JP2006044041A - Inkjet recording sheet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet, which is suitable for inkjet recording, more concretely, excellent in producibility, water resistance of an ink accepting layer, especially its film water resistance under environment exposed with ultraviolet rays and the ink absorbency of which is improved, and its manufacturing method. <P>SOLUTION: In the inkjet recording sheet having at least two layers including fine inorganic particles and a hydrophilic binder on a support, the mean degree of polymerization of the hydrophilic binder included in the farthest layer A from the support is higher than that of the hydrophilic binder included in at least one layer B locating nearer than the layer A to the support side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel inkjet recording paper and a method for manufacturing the same.

  Ink-jet recording is a method in which micro droplets of ink are ejected according to various operating principles and deposited on a recording sheet such as paper to record images and characters. In recent years, it has rapidly spread in various fields such as various printers, facsimiles, computer terminals, and the like.

  The recording paper used in this ink jet recording system has a high density of printed dots, a bright and vivid color tone, and ink does not run out or bleed even when printed dots overlap quickly. In addition, it is generally required that the horizontal spread of the printed dots is not larger than necessary, and the periphery is smooth and unblurred.

  In order to improve these properties, an ink jet recording sheet having a porous structure in the ink receiving layer has been developed and put into practical use. The ink jet recording sheet is excellent in ink absorbency by having a porous structure and having voids.

  Furthermore, the storability of the printed image has been remarkably improved in recent years. In general, the image quality and the image storability are rapidly approaching the quality of silver salt photographs.

  By the way, in the ink jet recording sheet having a porous structure in the ink receiving layer, the ink receiving layer is generally bonded with a hydrophilic binder such as polyvinyl alcohol using inorganic fine particles such as silica and alumina in the porous. Thus, a film is formed. Further, in order to quickly absorb ink, the hydrophilic binder contains only about a fraction of the inorganic fine particles by mass ratio.

  Therefore, when water droplets are scattered on the surface of the ink receiving layer, and as a more severe example, when exposed to rainwater outdoors, the binding force of the hydrophilic binder weakens and the receiving layer cracks or is severe It is known that a situation occurs in which the film peels off from the support. In addition, since resins such as polyvinyl alcohol may be photodegraded by ultraviolet rays, for example, when exposure to ultraviolet rays and water exposure occur alternately, the deterioration rate of the film may be further increased. It becomes.

  In response to the above problems, an inkjet recording paper having an ink receiving layer containing inorganic fine particles and a polyvinyl alcohol having a polymerization degree of 4000 or more is disclosed, and an improvement in crack resistance during coating and drying is mentioned as one of the effects ( For example, see Patent Document 1.)

  Certainly, the polyvinyl alcohol having a high degree of polymerization has an effect of improving cracks, but on the other hand, an unfavorable situation occurs in terms of production efficiency. That is, in general, polyvinyl alcohol having a high degree of polymerization has a higher viscosity of the coating solution than that having a low degree of polymerization, and thus it is often necessary to dilute the coating solution. Therefore, in order to apply a certain solid content, the amount of water increases, and the drying load in the production process increases. For this reason, the production efficiency is lowered, for example, the application speed must be reduced, or a measure such as capital investment is required to increase the drying capacity, and the energy consumption required for production increases.

  On the other hand, an inkjet recording paper containing at least one layer of colloidal silica and polyvinyl alcohol having a saponification degree of 95% or more and a polymerization degree of 1100 or less is disclosed (for example, see Patent Document 2). Patent Document 2 describes that when a plurality of layers are provided on a support, the degree of polymerization of the binder resin in each layer may be different. However, the purpose of the colloidal silica-containing layer is to express gloss, and its position is mainly placed farthest from the support, and is different from the configuration intended by the present invention.

Furthermore, an inkjet recording material having an ink receiving layer containing polyvinyl alcohol with different average polymerization degrees and containing a curing agent is disclosed (for example, see Patent Document 3), but the average polymerization degrees are different in the same layer. This is a method of applying polyvinyl alcohol, which is clearly different from the present invention.
Japanese Patent Laid-Open No. 7-117334 JP-A-9-123588 JP 2001-150805 A

  The present invention has been made in view of the above-mentioned problems, and an object thereof is related to an ink jet recording paper suitable for ink jet recording and a method for producing the same. More specifically, the present invention is excellent in production suitability and water resistance of an ink receiving layer, in particular, ultraviolet light. Provided are an ink jet recording paper having excellent water resistance in an exposed environment and improved ink absorbability, and a method for producing the same.

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

(Claim 1)
In the ink jet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on the support, the average degree of polymerization of the hydrophilic binder contained in the layer A located farthest from the support is An ink jet recording paper, wherein the average degree of polymerization of the hydrophilic binder contained in at least one layer B located on the support side from the layer A is higher.

(Claim 2)
In the ink jet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on the support, the average degree of polymerization of the hydrophilic binder contained in the layer A located farthest from the support is It is higher than the average degree of polymerization of the hydrophilic binder contained in at least one layer B located on the support side from the layer A, and the average degree of polymerization of the hydrophilic binder contained in the layer B is 1900 or less. Inkjet recording paper, characterized in that there is.

(Claim 3)
The inkjet recording paper according to claim 1 or 2, wherein an average polymerization degree of the hydrophilic binder contained in the layer A is 2800 or more.

(Claim 4)
The average polymerization degree of the hydrophilic binder contained in the layer A is higher than the average polymerization degree of the hydrophilic binder contained in all the layers containing the inorganic fine particles and the hydrophilic binder located on the support side from the layer A. The inkjet recording paper according to any one of claims 1 to 3.

(Claim 5)
The layer A and the layer that is located closer to the support than the layer A and contains a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A are other cationic organic resins for the hydrophilic binder. The ink jet recording paper according to claim 1, wherein the mass ratio of the ink jet recording paper is 20% or less.

(Claim 6)
The layer containing the hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A, which is located on the support side from the layer A and the layer A, is ionized by 70% by mass or more of the hydrophilic binder. It is a radiation curable resin, and after apply | coating this layer on a support body, the hydrophilic binder of this layer is hardened by ionizing radiation irradiation, The one of Claims 1-5 characterized by the above-mentioned. Inkjet recording paper.

(Claim 7)
The layer containing the hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A, which is located on the support side from the layer A and the layer A, has 70% by mass or more of the hydrophilic binder. The inkjet recording paper according to claim 1, which is a water-soluble resin having at least one functional group selected from a group, a sulfoxyl group, an acetoacetyl group, and a reactive ketone group. .

(Claim 8)
The inkjet recording paper according to any one of claims 1 to 7, wherein the inorganic fine particles are at least one selected from gas phase method silica, alumina, boehmite, and pseudoboehmite.

(Claim 9)
In a method for producing an inkjet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on a support, it is contained in a coating solution used for forming layer A that is located farthest from the support. The average polymerization degree of the hydrophilic binder is higher than the average polymerization degree of the hydrophilic binder contained in the coating liquid used for forming at least one layer B located on the support side from the layer A. Ink jet recording paper manufacturing method.

(Claim 10)
In a method for producing an inkjet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on a support, it is contained in a coating solution used for forming layer A that is located farthest from the support. The average degree of polymerization of the hydrophilic binder is higher than the average degree of polymerization of the hydrophilic binder contained in the coating liquid used for forming at least one layer B located on the support side of the layer A, and the layer B The average polymerization degree of the hydrophilic binder contained in 1900 is 1900 or less, The manufacturing method of the inkjet recording paper characterized by the above-mentioned.

(Claim 11)
The method for producing an inkjet recording paper according to claim 9 or 10, wherein the average degree of polymerization of the hydrophilic binder contained in the coating liquid used for forming the layer A is 2800 or more.

(Claim 12)
Coating having an average degree of polymerization of the hydrophilic binder contained in the coating liquid used for forming the layer A is used for forming all layers containing the inorganic fine particles and the hydrophilic binder located on the support side from the layer A. The method for producing an inkjet recording paper according to any one of claims 9 to 11, wherein the average degree of polymerization of the hydrophilic binder contained in the liquid is higher.

(Claim 13)
The layer A and the layer that is located closer to the support than the layer A and contains a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A are other cationic organic resins for the hydrophilic binder. The method for producing an inkjet recording paper according to claim 9, wherein a mass ratio of the ink jet recording paper is 20% or less.

(Claim 14)
The layer formed on the support side of the layer A and the layer A and formed of a coating solution containing a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A is a hydrophilic binder. 70 mass% or more of the above is an ionizing radiation curable resin, and after coating the layer on the support, the hydrophilic binder of the layer is cured by irradiation with ionizing radiation. The manufacturing method of the inkjet recording paper of any one.

(Claim 15)
The layer formed on the support side of the layer A and the layer A and formed of a coating solution containing a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A is a hydrophilic binder. 70% by mass or more of the water-soluble resin having at least one functional group selected from a carboxyl group, a sulfoxyl group, an acetoacetyl group and a reactive ketone group. The manufacturing method of the inkjet recording paper as described in a term.

(Claim 16)
The method for producing an inkjet recording paper according to any one of claims 9 to 15, wherein the inorganic fine particles are at least one selected from gas phase method silica, alumina, boehmite, and pseudoboehmite.

  According to the present invention, the present invention relates to an inkjet recording paper suitable for inkjet recording and a method for producing the same, and in particular, is excellent in production suitability, excellent in water resistance of the ink receiving layer, particularly excellent in water resistance in an environment exposed to ultraviolet rays, In addition, it is possible to provide an ink jet recording paper having improved ink absorbability and a method for producing the same.

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

  As a result of intensive studies in view of the above problems, the present inventors have found that an inkjet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on a support, 1) a position farthest from the support The average degree of polymerization of the hydrophilic binder contained in the layer A in the layer is higher than the average degree of polymerization of the hydrophilic binder contained in at least one layer B located on the support side of the layer A. Or 2) the average degree of polymerization of the hydrophilic binder contained in the layer A located farthest from the support is hydrophilic in at least one layer B located on the support side from the layer A When composed of two or more layers by adopting a constitution in which the degree of polymerization is higher than the average degree of polymerization of the binder and the average degree of polymerization of the hydrophilic binder contained in the layer B is 1900 or less. In particular, the application of a hydrophilic binder with a high degree of polymerization, which has a great influence on the viscosity of the coating solution, should be limited to a specific layer, and the average polymerization degree balance of each hydrophilic binder used between the layers should be the optimum condition. By applying a hydrophilic binder having the highest average degree of polymerization to the layer A that is located farthest from the support, while realizing a highly productive coating without using an excessively high viscosity coating solution, It has been found that an ink jet recording sheet having excellent water resistance of the ink receiving layer, particularly excellent film water resistance in an environment exposed to ultraviolet rays, and improved ink absorbability can be realized.

  Details of the present invention will be described below.

  The inkjet recording paper of the present invention (hereinafter also simply referred to as recording paper) has two or more porous layers (hereinafter also referred to as ink receiving layers) containing at least inorganic fine particles and a hydrophilic binder, Among these layers, the average degree of polymerization of the hydrophilic binder contained in layer A that is farthest from the support (hereinafter referred to as average degree of polymerization A) is at least one of the layers located below layer A. One characteristic is that it is higher than the average degree of polymerization of the hydrophilic binder contained in the layer (layer B) (hereinafter referred to as average degree of polymerization B), and the average degree of polymerization A of the hydrophilic binder contained in layer A The difference in polymerization degree from the average polymerization degree B of the hydrophilic binder contained in the layer B is not particularly limited as long as A> B, but AB is preferably 500 or more, more preferably 500 to 3000. , Particularly preferably It is a 00-2500.

  Further, the average degree of polymerization A of the hydrophilic binder contained in the layer A is not particularly limited, but the use of a hydrophilic polymer having an average degree of polymerization of 2800 or more can exhibit the intended effects of the present invention. It is preferable from a viewpoint, More preferably, it is 2800-5000, More preferably, it is 2800-4000. Further, the average degree of polymerization B of the hydrophilic binder contained in the layer B is not particularly limited, but the use of a hydrophilic polymer having an average degree of polymerization of 1900 or less can exhibit the intended effects of the present invention. It is preferable from a viewpoint, More preferably, it is 500-1900, More preferably, it is 1000-1900.

  Furthermore, in the ink jet recording paper of the present invention having three or more porous layers containing inorganic fine particles and a hydrophilic binder, the average of the hydrophilic binder contained in the layer A located farthest from the support It is preferable from the viewpoint that the degree of polymerization A is higher than the average degree of polymerization of each hydrophilic binder contained in all layers below the layer A, so that the objective effects of the present invention can be exhibited.

  Details of the present invention will be described below.

  The ink jet recording paper of the present invention has a porous ink receiving layer containing at least two layers of inorganic fine particles and a hydrophilic binder.

  First, the hydrophilic binder constituting the ink receiving layer will be described.

  In the present invention, as the hydrophilic binder that can be used in the ink receiving layer, a conventionally known hydrophilic resin can be used as long as it satisfies the average degree of polymerization specified in the present invention. Examples thereof include ethylene oxide, polyacrylamide, and polyvinyl alcohol. Among them, polyvinyl alcohol is particularly preferable.

  Polyvinyl alcohol has an interaction with inorganic fine particles, which will be described later, has a particularly high holding power for inorganic fine particles, and is a polymer with relatively small humidity dependency such as hygroscopicity, and shrinkage stress during coating and drying. Is relatively small, the suitability for cracking during coating and drying, which is the subject of the present invention, is excellent. Examples of the polybilyl alcohol preferably used in the present invention include, in addition to ordinary polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate, modified polyvinyl alcohol having a terminal cation modified, anion-modified polyvinyl alcohol having an anionic group, and the like. Polyvinyl alcohol is also included. As polyvinyl alcohol obtained by hydrolysis of vinyl acetate, polyvinyl alcohol having a higher average degree of polymerization is used for layer A according to the present invention, and polyvinyl alcohol having a lower average degree of polymerization is used for layer B according to the present invention. It is preferable.

  The average degree of polymerization referred to in the present invention can be determined from the viscosity of the polymer solution in the previous stage for modifying the crosslinkable group. For example, when polyvinyl alcohol is used as the hydrophilic binder, the degree of polymerization can be determined according to the method described in JIS K-6726.

  In addition, when the layer A or the layer B according to the present invention contains two or more hydrophilic binders, the average degree of polymerization of the hydrophilic binder in the layer is defined by the following formula.

That is, the average degree of polymerization of each of the plurality of hydrophilic binders contained in the layer is M ₁ , M ₂ , M ₃ ,..., M _n , and the respective mass ratios are T ₁ , T ₂ , T _3. ,..., when the T _n,
Average degree of polymerization = M ₁ × T ₁ + M ₂ × T ₂ + M ₃ × T ₃ +... + M _n × T _n
Represented by

  The saponification degree is preferably 70 to 100%, particularly preferably 90 to 100%. Examples of the cation-modified polyvinyl alcohol have primary to tertiary amino groups and quaternary ammonium groups in the main chain or side chain of the polyvinyl alcohol as described in JP-A-61-110483. Polyvinyl alcohol, which is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  In the present invention, the above-mentioned hydrophilic binder is preferably cured by a hardener, and the hardener is generally a compound having a group capable of reacting with the hydrophilic binder or a different group possessed by the hydrophilic binder. It is a compound that promotes the reaction between them, and is appropriately selected according to the type of the hydrophilic binder.

As the hardening agent, a conventionally known crosslinking agent can be used, and inorganic crosslinking agents (for example, chromium compounds, aluminum compounds, zirconium compounds, boric acids, etc.) and organic crosslinking agents (for example, epoxy crosslinking agents). , Isocyanate crosslinking agents, aldehyde crosslinking agents, N-methylol crosslinking agents, acryloyl crosslinking agents, vinyl sulfone crosslinking agents, active halogen crosslinking agents, carbodiimide crosslinking agents, ethyleneimino crosslinking agents, etc.) can do.
Specific examples include, for example, epoxy hardeners (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl-4- Glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde hardeners (formaldehyde, glioxal, etc.), active halogen hardeners (2,4-dichloro-4-hydroxy-1,3) , 5-s-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), boric acid, its salts, borax, aluminum alum, etc. Can be mentioned.

  When polyvinyl alcohol or cation-modified polyvinyl alcohol is used as the hydrophilic binder, inorganic hardeners and epoxy hardeners such as compounds containing Group 3 and 4 elements, especially boric acids, aluminum compounds, zirconium compounds, etc. Agents are preferred. Most preferred is a hardener selected from boric acid or a salt thereof.

  As boric acid or a salt thereof, oxygen acid having a boron atom as a central atom and a salt thereof are shown. Specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, octaboric acid Or a salt thereof.

  The amount of the hardener used varies depending on the type of hydrophilic binder, the type of hardener, the type of inorganic fine particles, the ratio to the hydrophilic binder, etc., but usually 5 to 500 mg, preferably 10 to 10 g per hydrophilic binder. 300 mg.

  Two or more hardeners may be used in combination. Moreover, it may be mixed and applied to a coating solution containing an ink receiving layer, or a solution containing a hardener without containing a porous substance may be supplied after being coated and dried. Preferably, simultaneously with application of the ink receiving layer or after application of the ink receiving layer and before the layer exhibits a reduced drying rate, an overcoat solution containing a hardener and not containing a porous material is overcoated, It is preferable to supply a hardener because the risk of aggregation of the porous material is reduced and production efficiency is good.

  In the ink jet recording paper of the present invention, each of the layers containing the hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A, located on the support side from the layer A and the layer A according to the present invention, respectively. The mass ratio of the other cationic organic resin to the hydrophilic binder is preferably 20% or less from the viewpoint of more effectively achieving the object effect of the present invention, and more preferably 0 to 20%. The content of the cationic organic resin referred to in the present invention includes an organic cationic polymer used as a mordant described later.

  Examples of the cationic organic resin applicable to the present invention include a cationic polymer having a primary to tertiary amino group and a quaternary ammonium base. As the cationic polymer, a known polymer can be used, for example, polyethyleneimine, polyallylamine and a modified product thereof, dicyandiamide polyalkylene polyamine, a condensate of dialkylamine and epichlorohydrin, polyvinylamine, polyvinylpyridine, Polyvinyl imidazole, diallyldimethylammonium salt condensate, polyacrylic acid ester quaternized product, etc., but the discoloration with time and deterioration of light resistance are small, and the mordanting ability of the dye is sufficiently high. A homopolymer of a monomer having a quaternary ammonium base or a copolymer with one or more other monomers capable of copolymerization, JP-A-10-193976, JP-A-10-217601, JP-A-11-20300 What is described in the publication, etc. Amine-modified products, monomethyl ammonium chloride is preferred. As the polyallylamine-modified product, one obtained by adding acrylonitrile, chloromethylstyrene or the like is known.

  In the ink jet recording paper of the present invention, the layer A according to the present invention and a layer that is located closer to the support than the layer A and contains a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A. In addition, 70% by mass or more of the hydrophilic binder contained in each is composed of an ionizing radiation curable resin, and after coating the layer on a support, the hydrophilic binder of the layer may be cured by irradiation with ionizing radiation. preferable.

  In the present invention, the ionizing radiation curable resin used as the hydrophilic binder of the ink-receiving layer is a water-soluble resin that undergoes a reaction and undergoes a crosslinking reaction upon irradiation with ionizing radiation such as ultraviolet rays and electron beams. It is a resin that is water-soluble before but becomes substantially water-insoluble after the crosslinking reaction and forms a water-resistant film. A water-resistant resin refers to a resin having a mass residue of 80% or more when immersed in warm water at 80 ° C. for 5 minutes. However, such a compound is a resin that has hydrophilicity after the crosslinking reaction and maintains sufficient affinity with ink.

  Examples of such resins include saponified polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or derivatives of the above hydrophilic resins, and these It is at least one selected from the group consisting of copolymers, or a hydrophilic resin modified with a modifying group such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, or a photodepolymerization type It is.

  Among these, a resin modified with a photodimerization type or photopolymerization type modification group is preferable from the viewpoint of sensitivity or stability of the resin itself. As the photodimerization type photosensitive resin, a diazo type, a cinnamoyl group, a stilbazonium group, or a stilquinolium group is preferably used, and a resin that is dyed with a water-soluble dye such as an anionic dye after photodimerization is preferable.

  Examples of such resins include resins having a cationic group such as a primary amino group or a quaternary ammonium group, such as JP-A-56-67309, JP-A-60-129742, JP-A-60-252341, and JP-A-62-283339. And photosensitive resins (compositions) described in JP-A-1-198615, etc., resins that become cationic after curing, such as azide groups that become amino groups by curing treatment, for example, JP-A 56-56 Photosensitive resin (composition) described in publications such as 67309.

  Specifically, for example, in the polyvinyl alcohol structure described in JP-A-56-67309,

A photosensitive resin having

  In particular, a 2-azido-5-nitrophenylcarbonyloxyethylene structure represented by Chemical Formula 1 or

The resin composition which has 4-azido-3-nitrophenyl carbonyloxyethylene structure represented by these is preferable.

  Specific examples of the resin are described in Examples 1 and 2 in the official gazette, and the constituent components of the resin and the use ratio thereof are described on page 2 of the official gazette.

  The photosensitive resin described in JP-A-60-129742 has the following partial structure in a polyvinyl alcohol structure.

In the formula, R ₁ represents an alkyl group having 1 to 4 carbon atoms, and A ⁻ represents an anion.

  As the photopolymerization type modifying group, for example, a resin described in JP-A No. 2000-181062 is preferable from the viewpoint of reactivity.

In the formula, R ₂ represents a hydrogen atom or a methyl group, n represents 1 or 2, Y represents an aromatic ring or a single bond, and X represents the following bond.

_{- (CH 2) m -COO -} , - O-
In the formula, m represents an integer of 0 to 6.

  In the present invention, it is also preferable to add a photoinitiator or a sensitizer. These compounds may be dissolved or dispersed in a solvent, or may be chemically bonded to the photosensitive resin.

  There is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A conventionally well-known thing can be used.

  The photoinitiator and photosensitizer to be applied are not particularly limited, but as an example, benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4 ′ Benzophenones such as dimethylaminobenzophenone, thioxanthone, thioxanthone such as 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, isopropoxychlorothioxanthone, anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone, chloroanthraquinone, acetophenone , Benzoin ethers such as benzoin methyl ether, 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexylphenyl , 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (m-methoxyphenyl) imidazole dimer, 2- (o-fluoro Phenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer, 2- (p-methoxyphenyl) -4,5-diphenylimidazole dimer 2-di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4,5-diphenylimidazole dimer 2,4,5-triarylimidazole 2 , Benzyldimethyl ketal, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [ -(Methylthio) phenyl] -2-morpholino-1-propanone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2- Hydroxy-2-methyl-1-propan-1-one, phenanthrenequinone, 9,10-phenanthrenequinone, benzoins such as methylbenzoin and ethylbenzoin, 9-phenylacridine, 1,7-bis (9,9 ' -Acridinyl) acridine derivatives such as heptane, bisacylphosphine oxide, and mixtures thereof, and the like may be used alone or in combination.

  In particular, water-soluble 1- [4- (2-hydroxyethoxy) -phenyl]-(2-hydroxy) -2-methyl-1-propan-1-one, 4- (2-hydroxyethoxy) -phenyl- ( Water-soluble initiators such as 2-hydroxy-2-propyl) ketone, thioxanthone ammonium salt, and benzophenone ammonium salt are preferable from the viewpoint of crosslink efficiency because of excellent mixing properties.

  In addition, when using a sensitizer, the usage-amount is adjusted in the range of 0.2-10 mass% with respect to the ionizing radiation hardening type resin in a coating liquid, Preferably it is about 0.5-5 mass%. Is desirable.

  In addition to these initiators, accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like. You may mix about 0.05-3 mass% with respect to the ionizing radiation-curable resin in a coating composition.

  In the above, the base polyvinyl alcohol may partially contain unsaponified acetyl groups, and the content of acetyl groups is preferably less than 30%. The saponification degree is preferably 70 to 100%, particularly preferably 90 to 100%.

  The cation-modified polyvinyl alcohol is a polyvinyl alcohol having a primary to tertiary amino group or a quaternary ammonium group in the main chain or side chain of the polyvinyl alcohol, and an ethylenically unsaturated monomer having a cationic group. It can be obtained by saponifying a copolymer of a monomer and vinyl acetate.

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxyethyl-trimethylammonium chloride, trimethyl- (methacrylamidopropyl) ammonium chloride, N- (1,1 -Dimethyl-3-dimethylaminopropyl) acrylamide and the like.

  Compared with the method in which water-soluble resin and inorganic fine particles are mixed with a crosslinking agent to increase the viscosity of the coating solution and set, and the coating film is dried as it is to form a void layer, ionizing radiation curable resin is irradiated with ionizing radiation. The network structure formed by cross-linking includes a cross-link at a long distance, which is different from a three-dimensional structure at a relatively short distance formed by using a cross-linking agent, and therefore has a structure that can easily hold many fine particles. It is considered that a uniform film can be formed with a smaller amount of binder, that is, it can be used where the ratio of fine particles to hydrophilic binder is smaller. In addition, the coating film formed with respect to the conventional hydrophilic binder is strong and strong against bending, etc. In addition, after forming the inkjet recording paper, the recording layer before printing or printing by handling the inkjet recording paper It is considered that an ink jet recording paper having a porous material layer having a void having little resistance to stress due to bending or the like even after printing or printing is obtained with little cracking or peeling.

  When an ionizing radiation curable resin is used as a binder, the suitable degree of polymerization can be appropriately selected within a range that satisfies the requirements defined in the present invention.

  In the present invention, when a hydrophilic solvent is present, irradiation with the ionizing radiation is performed, and the ionizing radiation curable resin present in the coating layer is cross-linked and then dried to obtain a porous material having voids. An ink jet recording paper composed of layers is obtained. Curing by ionizing radiation irradiation of the ionizing radiation curable resin according to the present invention may be performed immediately after coating until the end of drying, but preferably immediately after coating and before the coating layer exhibits a reduced drying rate. It is.

  Examples of ionizing radiation include electron beams, ultraviolet rays, alpha rays, beta rays, gamma rays, and X-rays. Since alpha rays, beta rays, gamma rays and X-rays are accompanied by problems such as danger to the human body, electron beams and ultraviolet rays which are easy to handle and are widely used industrially are preferably used. In the invention, the ionizing radiation curable resin is preferably a compound that is cured by ultraviolet rays.

  In addition, when the hydrophilic resin is cross-linked by an electron beam, the inorganic fine particles generally have a higher specific gravity than the hydrophilic binder or solvent water, so the electron beam irradiation amount is excessively supplied to the hydrophilic binder or solvent. Moisture in the coating film instantaneously evaporates to form bubbles, roughens the coating surface, and the irradiation dose is insufficient for the deep part of the coating film, resulting in a gradient in the crosslinking density, resulting in a hard film only on the surface. As a result, there is a problem that the curl resistance may be significantly impaired, and there is a problem that the effect is hindered when the oxygen concentration of the atmosphere is high at the time of electron beam irradiation, and substitution is performed in the irradiation zone with an inert gas such as nitrogen or helium. It is more preferable to use ultraviolet rays because it is necessary to keep the oxygen concentration to about 400 ppm or less, and it has an unfavorable aspect in terms of process suitability.

  When using an electron beam, it is desirable to adjust the amount of the electron beam to be irradiated within a range of about 0.1 to 20 Mrad. If it is less than 0.1 Mrad, a sufficient irradiation effect cannot be obtained, and irradiation exceeding 20 Mrad is not preferable because it may deteriorate the support, particularly paper or some plastics. As the electron beam irradiation method, for example, a scanning method, a curtain beam method, a broad beam method, etc. are adopted, and the acceleration voltage when irradiating an electron beam can be changed as appropriate depending on the specific gravity and film thickness of the coating film. A voltage of about 20 to 300 kV is appropriate.

  In particular, in the production process, it is preferable to use ultraviolet rays that are relatively easy to handle and can be easily installed.

For example, a low-pressure, medium-pressure, high-pressure mercury lamp, metal halide lamp or the like having an operating pressure of several hundred Pa to 1,000,000 Pa is used as an ultraviolet light source, but a high-pressure mercury lamp or a metal halide lamp is preferable from the viewpoint of wavelength distribution of the light source. A metal halide lamp is more preferable. It is preferable to provide a filter that cuts light having a wavelength of 300 nm or less. As the output of the lamp 400W～30kW, as the illuminance ^{10mW / cm 2 ~10kW / cm 2} , preferably from 0.1mJ / cm ² ~1J / cm ² as irradiation ^{energy, 50mJ / cm 2 ~100mJ / cm} 2 is More preferred.

When the light source wavelength includes ultraviolet rays of 300 nm or less or when the irradiation energy exceeds 1 J / cm, the base of the ionizing radiation crosslinkable resin or various coexisting additives are decomposed by ionizing radiation, and the present invention. In addition to not being able to obtain the above effect, there is a possibility of causing problems such as odor derived from the decomposition product, which is not preferable. When the irradiation energy is less than 0.1 mJ / cm ² , the crosslinking efficiency is insufficient and the effect of the present invention cannot be obtained sufficiently.

Illuminance is preferably 1mW / cm ² ~1W / cm ² at the time of ultraviolet irradiation, 100~200mW / cm ² is more preferable. When the illuminance is 1 W / cm ² or less, the surface curability of the coating film is improved, and the film is cured to a deep portion and a uniformly crosslinked film is obtained. In that case, the hardness of the film in the depth direction is also uniform, and curling or the like hardly occurs, which is preferable. If the illuminance is 10 mW / cm ² or more, it is preferable because non-uniformity of crosslinking is avoided by scattering in the film and the effects of the present invention are obtained.

When giving the same integrated light quantity (mJ / cm ² ), the preferable range of illuminance is due to the change in the light transmittance. When the concentration distribution of the generated cross-linking reactive species is different due to the transmittance of ultraviolet rays, and the ultraviolet illuminance is high, a high concentration of cross-linking reactive species is generated on the surface layer, and a hard and dense film is formed on the surface of the coating film. When the illuminance is in a preferable range, the degree of cross-linking of the surface layer is low and light permeability in the deep direction is high, so that gentle cross-linking is uniformly formed in the deep direction. If the illuminance is too low, it takes a long time to give the necessary integrated illuminance, which is not only disadvantageous in terms of equipment introduction, but also because the amount of absolute light due to scattering of ultraviolet rays by the coating film is insufficient. Absent.

  In the present invention, ionizing radiation is irradiated in a state where the coating layer contains a hydrophilic solvent, and after irradiating with ionizing radiation, the coating film is dried to evaporate an aqueous solvent mainly composed of water. However, when irradiating with ionizing radiation, the aqueous solvent may be partially or largely evaporated.

  Further, in the ink jet recording paper of the present invention, each of the layer A and the layer that is located closer to the support than the layer A and contains a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A, It is preferable that 70% by mass or more of the hydrophilic binder is a water-soluble resin having at least one functional group selected from a carboxyl group, a sulfoxyl group, an acetoacetyl group, and a reactive ketone group.

  These water-soluble resins are obtained, for example, by polymerization of monomers each having a carboxyl group, a sulfoxyl group, an acetoacetyl group, and a ketone group. Moreover, you may provide these functional groups in water-soluble resin by polymer reaction.

  Examples of the binder used for the preparation of each of the water-soluble resins include polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, and polyvinyl alcohol. Among them, polyvinyl alcohol is particularly preferable.

  These water-soluble resins preferably have a modification rate of 0.05 mol% to 40 mol% due to the above functional groups. If the modification rate is too low, it is difficult to obtain the effect of having the functional group, and if the modification rate is too high, the water solubility is lowered and it is not suitable for the use of the present invention.

  The saponification degree of these resins is preferably 70% or more, more preferably 90 to 100%. The average degree of polymerization is preferably 300 or more, and particularly preferably an average degree of polymerization of 1000 to 5000.

  When these water-soluble resins are used, it is preferable to use a compound that forms a crosslink by reaction with a functional group, a so-called crosslinker. Examples of the crosslinking agent include aldehydes, amino resins, amine compounds, hydrazine compounds, hydrazide compounds, epoxy compounds, isocyanate compounds, and polyvalent metal salts.

  Specific examples of the compound include, but are not limited to, the following.

  Formaldehyde, acetaldehyde, glyoxal, methylated methylol melamine or partially etherified product of butylated methylol melamine, ethylenediamine, triethylenediamine, polyethylenediamine, m-xylylenediamine, hydrazine, carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, adipine Acid dihydrazide, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, polyisocyanate, ethylene glycol, propylene glycol, polyethylene glycol, glycerin.

  The amount of the crosslinking agent added to the modified polyvinyl alcohol varies depending on its purpose and type, but is preferably 0.1 to 20% by mass.

  The crosslinking agent may be used by mixing with a coating solution containing modified polyvinyl alcohol and inorganic fine particles, or after coating the coating solution, supplying a solution containing the crosslinking agent to the inkjet recording paper. Also good.

  Each layer according to the present invention contains inorganic fine particles together with the hydrophilic binder to form a void structure.

  Examples of such inorganic fine particles include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, White inorganic pigments such as hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. Can be mentioned. Moreover, each may be used independently and multiple types may be used together.

  In the present invention, from the viewpoint of obtaining a high-quality print on an inkjet recording paper, the inorganic fine particles are preferably fine particle silica, alumina, boehmite, or pseudoboehmite synthesized by a vapor phase method, and among them, synthesized by a vapor phase method. Particulate silica is particularly preferred. The silica synthesized by this vapor phase method may have a surface modified with Al. The Al content of vapor-phase process silica whose surface is modified with Al is preferably 0.05 to 5% by mass with respect to silica.

  The inorganic fine particles may have any particle diameter, but the average particle diameter is preferably 4 μm or less. If it is 4 micrometers or less, glossiness and coloring property are favorable, Furthermore, 0.1 micrometer or less is preferable. The lower limit of the particle size is not particularly limited. In particular, in the case of the above-mentioned vapor phase method silica, the average primary particle size is preferably 30 nm or less for obtaining a structure having a large porosity, and 3-10 nm is particularly preferred for enhancing the transparency of the film.

  The average particle size of the inorganic fine particles is obtained as a simple average value (number average) by observing the cross section and surface of the porous material layer with an electron microscope and determining the particle size of 100 arbitrary particles. Here, each particle size is expressed by a diameter assuming a circle equal to the projected area.

  Further, the degree of dispersion of the fine particles is preferably 0.5 or less from the viewpoint of glossiness and color developability. If it is 0.5 or less, the gloss and the density during printing are good. In particular, 0.3 or less is preferable. Here, the dispersity of the fine particles is obtained by observing the fine particles of the porous material layer with an electron microscope in the same manner as obtaining the average particle size, and dividing the standard deviation by the average particle size. The above average particle diameter refers to the particle diameter of particles forming independent particles in the porous material layer when observed with an electron microscope. The content of the fine particles in the water-soluble coating solution is 5 to 40% by mass, and particularly preferably 7 to 30% by mass. As the vapor phase silica fine particles, those dispersed with the aforementioned cationic resin can also be used.

  In the inkjet recording paper of the present invention, the ratio of the inorganic fine particles to the binder in the void layer is preferably 2 to 50 times in terms of mass ratio. If the mass ratio is 2 times or more, the void ratio of the void layer is good, a sufficient void volume can be easily obtained, and excessive binder can be prevented from swelling and closing the void during ink jet recording. On the other hand, when this ratio is 50 times or less, it is preferable that cracks do not easily occur when the ink absorbing layer is applied as a thick film. A particularly preferable ratio of the inorganic fine particles to the hydrophilic binder is 2.5 to 20 times, and 5 to 15 times is more preferable from the viewpoint of resistance to breakage of the dry coating film.

In order to obtain a void layer having a high porosity, the specific surface area measured by the BET method is preferably 100 m ² / g or more. The BET method referred to in the present invention is a method for measuring the specific surface area by a method for determining the surface area per 1 g from the gas phase adsorption isotherm.

The void layer according to the present invention preferably has a capacity of 15 to 40 ml / m ² per unit area of the coating film. This capacity is defined by the volume of bubbles generated when a coating film of a unit area is immersed in water, or the volume of water that the coating film can absorb.

  In the present invention, a compound containing an aluminum atom can be suitably used as a mordant. The compound containing an aluminum atom may be any of a single salt and double salt of an inorganic acid or an organic acid, an organic metal compound, a metal complex, etc., but a polyaluminum chloride compound, a polyaluminum sulfate compound, a polyaluminum sulfate silicate Particularly preferred are compounds.

The polyaluminum chloride compound is represented by the general formula [Al ₂ (OH) _n Cl _6-n ] m, [Al (OH) ₃ ] n · AlCl ₃ , for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ (OH) ₃₄ ] ⁵⁺ and other basic and highly positively charged polynuclear condensed ions (polymeric) as active ingredients, It is a polyaluminum chloride containing stably.

Examples of commercially available products of polyaluminum chloride include polyaluminum hydroxide (Paho) manufactured by Asada Chemical Co., Ltd., polyaluminum chloride (PAC) manufactured by Taki Chemical Co., Ltd., and Pukeram manufactured by Riken Green Co., Ltd. WT. The polyaluminum sulfate compound is represented by the general formula [Al ₂ (OH) _n (SO ₄ ) _{6-n / 2} ] m (provided that 0 <n <6). As a commercially available product, Asada Examples include basic aluminum sulfate (AHS) manufactured by Chemical Co., Ltd. As a commercial item of a polysulfuric acid aluminum silicate compound, PASS made from Nippon Light Metal Co., Ltd. is mentioned.

  Various additives can be added to the water-soluble coating liquid forming the porous material layer. Such additives include, for example, cationic mordants, crosslinking agents, surfactants (cations, nonions, anions, amphoterics), white color tone modifiers, fluorescent whitening agents, antifungal agents, viscosity modifiers, low boiling points. Organic solvents, high-boiling organic solvents, latex emulsions, anti-fading agents, UV absorbers, polyvalent metal compounds (water-soluble or water-insoluble), matting agents, silicone oils, etc., among which cationic mordants are printing It is preferable for improving water resistance and moisture resistance later. As the cationic mordant, a cationic polymer having the same primary to tertiary amino groups and quaternary ammonium bases as those of the above-described cationic organic resin is preferable.

  As the cationic polymer, a known polymer can be used, for example, polyethyleneimine, polyallylamine and a modified product thereof, dicyandiamide polyalkylene polyamine, a condensate of dialkylamine and epichlorohydrin, polyvinylamine, polyvinylpyridine, Polyvinyl imidazole, diallyldimethylammonium salt condensate, polyacrylic acid ester quaternized product, etc., but the discoloration with time and deterioration of light resistance are small, and the mordanting ability of the dye is sufficiently high. A homopolymer of a monomer having a quaternary ammonium base or a copolymer with one or more other monomers capable of copolymerization, JP-A-10-193976, JP-A-10-217601, JP-A-11-20300 What is described in the publication, etc. Amine-modified product is preferred. As the polyallylamine-modified product, one obtained by adding acrylonitrile, chloromethylstyrene or the like is known.

  These mordants may be mixed and applied to a porous substance-containing coating solution that forms the ink receiving layer, or may be independently applied as a separate solution. As in the case of the above hardener, it is preferable to overcoat the base material having the porous material layer with a separate liquid simultaneously with or after the application of the porous material layer. In this case, you may mix and add with a hardener.

  In the present invention, a polyvalent metal compound can be added to the ink receiving layer.

Examples of the polyvalent metal compound include sulfates such as Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Zr ²⁺ , Ni ²⁺ , and Al ³⁺ , chlorides, nitrates, and acetates. In addition, inorganic polymer compounds such as basic polyaluminum hydroxide and zirconyl acetate are also included as examples of preferable water-soluble polyvalent metal compounds. Many of these water-soluble compounds generally have a function of improving light resistance and improving bleeding and water resistance. These water-soluble polyvalent metal ions are generally used in a range of 0.05 to 20 mmol, preferably 0.1 to 10 mmol, per 1 m ^{2 of} recording paper.

  The ink jet recording paper of the present invention preferably contains a compound represented by the following general formula (1).

General formula (1)
R ₁ R ₂ N—Y—NR ₃ R ₄
In the general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom, a substituted or unsubstituted aliphatic group, or a substituted or unsubstituted aromatic group. Y represents a divalent organic group.

In the general formula (1), R ₁ , R ₂ , R ₃ and R ₄ are each a hydrogen atom, a substituted or unsubstituted aliphatic group, or a substituted or unsubstituted aromatic group, which are connected to each other. A ring may be formed. R ₁ , R ₂ or R ₃ , R ₄ is preferably a hydrogen atom.

  Examples of the substituent of the aliphatic group or aromatic group include linear, branched or cyclic alkyl groups, aralkyl groups, alkoxy groups, alkylsulfonyl groups, arylsulfonyl groups, ureido groups, aryl groups, arylthio groups, alkylthio groups, An alkylsulfoxy group, arylsulfoxy group, alkylsulfonyl group, arylsulfonyl group, aryloxy group, carbamoyl group, sulfamoyl group, amino group, hydroxy group, hydroxyalkyl group, halogen atom, sulfonic acid group, or carboxylic acid group And so on.

  The organic group for Y represents a divalent linking group such as a substituted or unsubstituted alkylene group or an arylene group. These organic groups may contain one or more hetero atoms such as oxygen, nitrogen and sulfur atoms, and the nitrogen atoms may have a substituent such as an alkyl group.

  As the substituent of the group represented by Y, linear, branched or cyclic alkyl group, aralkyl group, alkoxy group, alkylsulfonyl group, arylsulfonyl group, ureido group, aryl group, arylthio group, alkylthio group, alkyl Sulfoxy group, arylsulfoxy group, alkylsulfonyl group, arylsulfonyl group, aryloxy group, carbamoyl group, sulfamoyl group, amino group, hydroxy group, hydroxyalkyl group, halogen atom, sulfonic acid group, carboxylic acid group, etc. Can be mentioned.

  In the general formula (1), Y is preferably represented by the following general formula (2).

General formula (2)
-NHCO-X-CONH-
In the general formula (2), X is a divalent organic group and represents a divalent linking group such as a substituted or unsubstituted alkylene group or an arylene group. These organic groups may contain one or more hetero atoms such as oxygen, nitrogen and sulfur atoms, and the nitrogen atoms may have a substituent such as an alkyl group.

  As the substituent of the group represented by Y, linear, branched or cyclic alkyl group, aralkyl group, alkoxy group, alkylsulfonyl group, arylsulfonyl group, ureido group, aryl group, arylthio group, alkylthio group, alkyl Sulfoxy group, arylsulfoxy group, alkylsulfonyl group, arylsulfonyl group, aryloxy group, carbamoyl group, sulfamoyl group, amino group, hydroxy group, hydroxyalkyl group, halogen atom, sulfonic acid group, carboxylic acid group, etc. Can be mentioned.

  Although the specific example of a compound represented by General formula (1) below is shown, it is not limited to these.

1-1: 1,3-diaminopropane 1-2: 1,6-diaminohexane 1-3: 1,10-diaminodecane 1-4: N, N-dibutyl-1,2-diaminoethane 1-5: N, N-dibutyl-1,3-diaminopropane 1-6: N, N, N ′, N′-tetramethyl-1,3-propanediamine 1-7: N, N, N ′, N′-tetra Methyl-1,6-hexanediamine 1-8: Triethylenetetramine 1-9: Tris (dimethylamino) methane 1-10: 3,3-diamino-N-methyldipropylamine 1-11: 4,4-diamino Diphenylamine 1-12: m-xylylenediamine 1-13: adipic acid dihydrazide Among the compounds 1-1 to 1-13 exemplified above, compound 1-13 (adipic acid dihydrazide) is particularly preferable.

The content of the compound represented by the general formula (1) according to the present invention is preferably 0.1 mmol to 10 mmol, more preferably 0.5 to 5 mmol per 1 m ^{2 of} recording paper.

  As the support used in the ink jet recording paper of the present invention, a water-absorbing support (for example, paper) or a non-water-absorbing support can be used. From the viewpoint of obtaining a higher-quality print, non-water-absorbing support. An ionic support is preferred.

  Examples of the non-water-absorbing support preferably used include, for example, polyester film, diacetate film, triatesate film, polyolefin film, acrylic film, polycarbonate film, polyvinyl chloride film, polyimide film, cellophane, A transparent or opaque film made of a material such as celluloid, or a resin-coated paper in which both surfaces of a base paper are coated with a polyolefin resin coating layer, so-called RC paper, or the like is used.

  When applying the water-soluble coating solution on the support, the support is subjected to corona discharge treatment, subbing treatment or the like for the purpose of increasing the adhesive strength between the surface and the coating layer. Is preferred. Furthermore, the inkjet recording paper of the present invention may be a colored support.

  The support preferably used in the present invention is a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both sides of paper are laminated with a polyolefin resin.

  Hereinafter, a paper support laminated with polyethylene, which is the most preferred representative of polyolefin, will be described.

  The base paper used for the paper support is made from wood pulp as a main raw material and, if necessary, paper making using synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester in addition to wood pulp. As wood pulp, for example, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, NUKP can be used, but more LBKP, NBSP, LBSP, NDP, LDP with more short fibers are used. Is preferred. However, the ratio of LBSP or LDP is preferably 10% by mass or more and 70% by mass or less.

  The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful.

  In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added.

  The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is a 24 mesh residual mass% defined by JIS-P-8207, and 42 The sum of the mesh residual mass% is preferably 30 to 70 mass%. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less.

The basis weight of the base paper is preferably 30 to 250 g, particularly preferably 50 to 200 g. The thickness of the base paper is preferably 40 to 250 μm. The base paper can be given a high smoothness by subjecting it to a calendar process at the paper making stage or after paper making. The density of the base paper is generally 0.7 to 1.2 g / cm ³ (according to the method defined in JIS-P-8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS-P-8143. A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, the same sizing agents that can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS-P-8113.

  The polyethylene covering the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, etc. can also be used.

  The polyethylene layer on the coating layer side preferably has an improved opacity and whiteness by adding rutile or anatase type titanium oxide to the polyethylene, as is widely done in photographic paper. The titanium oxide content is 1 to 20% by mass, preferably 2 to 15% by mass, based on polyethylene.

  The polyethylene-coated paper can be used as glossy paper, or when the polyethylene is melt-extruded and coated on the surface of the base paper, a matte surface or silk-like surface obtained by ordinary photographic photographic paper by performing a so-called molding process Those having a fine grain surface can also be used in the present invention.

  The amount of polyethylene used on the front and back of the base paper is selected so as to optimize the film thickness of the aqueous coating composition and the curl at low and high humidity after providing the back layer, but the aqueous coating according to the present invention The polyethylene layer on the side on which the composition is applied is preferably 20 to 40 μm, and the back layer side is preferably in the range of 10 to 30 μm.

  Furthermore, the polyethylene-coated paper support preferably has the following characteristics.

1) Tensile strength: strength specified by JIS-P-8113, preferably 20-300N in the vertical direction and 10-200N in the horizontal direction 2) Tear strength: as defined by JIS-P-8116 The longitudinal direction is preferably 0.1 to 2N and the lateral direction is preferably 0.2 to 2N. 3) Compression elastic modulus: ≧ 1030 N / cm ²
4) Surface Beck smoothness: 500 seconds or longer is preferable as a glossy surface under the conditions specified in JIS-P-8119, but it may be less than this for so-called molded products. 5) Back surface Beck smoothness: JIS- 100 to 800 seconds are preferable under the conditions specified in P-8119. 6) Opacity: Transmittance of light in the visible range is 20% or less, particularly 15% under the measurement conditions of linear light incidence / diffuse light transmission conditions. The following is preferable. An undercoat layer is preferably provided on the ink-receiving layer side of the support for the purpose of improving the adhesion to the ink-receiving layer. The binder for the undercoat layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, or a latex polymer having a Tg of −30 to 60 ° C. These binders are used in the range of 0.001 to ² g per 1 m ^{2 of} recording paper. In the undercoat layer, a small amount of a conventionally known antistatic agent such as a cationic polymer can be contained for the purpose of antistatic.

  A back layer can also be provided on the surface of the support opposite to the ink receiving layer side for the purpose of improving slipperiness and charging characteristics. The binder for the back layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, a latex polymer having a Tg of −30 to 60 ° C., an antistatic agent such as a cationic polymer, various surfactants, A matting agent having an average particle diameter of about 0.5 to 20 μm can also be added. The thickness of the back layer is generally 0.1 to 1 μm, but in the case where the back layer is provided for preventing curling, it is generally in the range of 1 to 20 μm. Further, the back layer may be composed of two or more layers.

  In coating the undercoat layer and the back layer, it is preferable to use a surface treatment such as corona treatment or plasma treatment on the surface of the support in combination.

  In the present invention, the coating method of each layer on the support such as an ink receiving layer can be appropriately selected from known methods, for example, gravure coating method, roll coating method, rod bar coating method, air knife coating method, A spray coating method, an extrusion coating method, a curtain coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used.

  In the present invention, when there are two or more ink receiving layers, it is preferable to apply all the layers simultaneously from the viewpoint of reducing the production cost.

In the ink jet recording paper of the present invention having the above structure, the surface of the ink jet recording paper is measured by the method described in JIS-Z-8722, and the chromaticity index a ^* , b ^* defined in JIS-Z-8730 is measured ^. Are preferably -2 to +4, or -11 to 0. More preferably, the chromaticity indices a ^* and b ^* are −2 to +4 and −11 to −5. The chromaticity of the recording surface side surface of the recording paper depends on its use and preference, but in general, in the case of printing paper, it is generally measured by the method specified in JIS-Z-8722. However, it seems that a ^* and b ^* when expressed in JIS-Z-8730 are preferably −2 to +2 and −4 to +4, respectively. However, according to the study by the present inventors, in order to obtain a high-quality image having a so-called silver salt photograph texture on an inkjet recording paper, the chromaticity of the recording paper recording surface side is the above-mentioned conventional one. The range is not always sufficient.

If b ^* is greater than 0, the image, particularly the white to light color image portion, is weakened even if the hue of the white background is within the allowable range. A decrease in sharpness can be felt.

In the recording paper of the present invention, it is necessary for the surface chromaticity to be relatively blue, that is, b ^* is −11 to 0 in order to obtain a clear image, and b ^* is − If it is 11-5, a still higher clear feeling will be acquired and it is preferable.

When b ^* is smaller than -11, the white background becomes bluish and uncomfortable, and the entire image is bluish, so that the state becomes a so-called cyan fog. It will decline.

The lightness index L ^* of the recording surface side surface of the inkjet recording paper of the present invention is preferably 90 or more, and more preferably 95 or more. Here, the lightness index L ^* is measured by the method described in JIS-Z-8722, and is displayed by the method defined in JIS-Z-8730.

In the present invention, as one of the methods for achieving a ^* and b ^* defined above, it is preferable to add a fluorescent whitening agent to the ink absorbing layer.

  The fluorescent whitening agent that can be used in the present invention has, as its basic chemical structure, a diaminostilmene, imidazole, thiazole, oxazole, triazole, oxadiazole, thiadiazole, coumarin, Examples include phthalimide, pyrazoline, pyrene, imidazolone, benzidine, diaminocarbazole, oxacyanine, methine, pyridine, anthrapyridazine, distyryl, and carbostyryl. Specific examples are shown below, but the present invention is not limited thereto.

  As an imidazole fluorescent whitening agent,

  As thiazole fluorescent whitening agent,

  As an oxazole fluorescent whitening agent,

  As a triazole fluorescent whitening agent,

  As a coumarin type fluorescent whitening agent,

  As naphthalimide type fluorescent whitening agent,

  As a pyrazoline fluorescent whitening agent,

  Other fluorescent brighteners include

Etc.

  Commercially available fluorescent brighteners include C.I. I. Fluorescent St. Brightner 226, C.I. I. Fluorescent St. Brightner 363, C.I. I. Fluorescent Brightening Agent 52, C.I. I. Fluorescent Brightening Agent 135, Mika White ACR, Mika White ATN, Kayphor 3BS, Blankophor (manufactured by Bayer), Hostalux (manufactured by Hoechst), Palani, Ultrapho (manufactured by BASF), Uvitex (manufactured by Ciba Geigy) , Whiteex (manufactured by Sumitomo Chemical Co., Ltd.) and the like. The manufacturing method of the optical brightener used for this invention does not have a restriction | limiting in particular, It can manufacture by a conventionally well-known method.

  Although there is no restriction | limiting in particular as content of a fluorescent whitening agent, 0.1-20 mass% of solid content contained in a surface layer is preferable. If the amount is less than 0.1% by mass, the effect on the white background is small. If the amount exceeds 20% by mass, the ink absorbability decreases, the coating failure occurs, and the fluorescent whitening agent itself is colored. Becomes noticeable and is not preferable.

  The film surface pH of the recording surface of the inkjet recording paper of the present invention is preferably 3.5 to 9. When the film surface pH is less than 3.5, so-called bronzing, in which the dye is deposited and the gloss is changed to a metallic state during ink jet recording, is likely to occur. On the other hand, if the film surface pH exceeds 9, the effect of preventing bleeding is reduced. The measurement of the film surface pH of the recording surface is described in J. Org. TAPPI paper pulp test method no. According to the method described in 49, it is measured after 30 seconds using distilled water. The film surface pH of the recording surface can be set to a predetermined range by overcoating an appropriate pH adjusting agent after forming the recording surface. As the pH adjuster, an appropriate aqueous solution of acid or alkali can be used. In this case, the type and concentration of the acid or alkali to be used can be appropriately selected depending on the pH range to be adjusted.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “%” represents mass% unless otherwise specified.

Example 1
<Preparation of ink receiving layer coating solution>
[Preparation of Ink Receptive Layer Coating Liquid 1]
In 150 ml of pure water, 1.2 ml of a nonionic acrylic polymer type dispersant (solid content: 40%, SD-10 manufactured by Toa Gosei Co., Ltd.) was dissolved, and the pH was adjusted to 11.0 with sodium hydroxide. To this, 435 g of a 23% aqueous dispersion of silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 7 nm was added and dispersed with a high-speed homogenizer to obtain a dispersion of vapor phase silica. .

  Next, 280 ml of an 8% aqueous solution of polyvinyl alcohol (Kuraray PVA217, polymerization degree 1700), 78.4 ml of a 25% solution of the following cationic polymer-1 and 0.7 g of borax were added to this dispersion. . Finally, pure water was added so that the total volume became 1000 ml to prepare a translucent ink-receiving layer coating solution 1.

[Preparation of ink receiving layer coating solution 2]
In the preparation of the ink receiving layer coating solution 1, the polyvinyl alcohol (PVA217) is changed to Kuraray polyvinyl alcohol (PVA224) having a polymerization degree of 2400, and the viscosity at 40 ° C. is the same as that of the ink receiving layer coating solution 1. Therefore, an ink receiving layer coating solution 2 was prepared in the same manner except that the total volume was changed to 1240 ml.

[Preparation of ink receiving layer coating solution 3]
In the preparation of the ink receiving layer coating liquid 1, the polyvinyl alcohol (PVA217) is changed to Kuraray polyvinyl alcohol (PVA235) having a polymerization degree of 3500, and the viscosity at 40 ° C. is the same as that of the ink receiving layer coating liquid 1. Therefore, an ink receiving layer coating solution 3 was prepared in the same manner except that the total volume was changed to 1380 ml.

[Preparation of Ink Receptive Layer Coating Liquid 4]
Ink receiving layer coating solution 4 was prepared in the same manner as in the preparation of ink receiving layer coating solution 1, except that the amount of cationic polymer-1 added was changed to 29.4 ml.

[Preparation of ink receiving layer coating solution 5]
Ink-receiving layer coating solution 5 was prepared in the same manner as in the preparation of ink-receiving layer coating solution 3, except that the amount of cationic polymer-1 added was changed to 29.4 ml.

[Preparation of Ink Receptive Layer Coating Liquid 6]
In 150 ml of pure water, 1.2 ml of a nonionic acrylic polymer type dispersant (solid content 40%, SD-10 manufactured by Toa Gosei) was dissolved, and the pH was adjusted to 11.0 with sodium hydroxide. Here, 435 g of a 23% aqueous dispersion of silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 7 nm was added and dispersed with a high-speed homogenizer to obtain a dispersion of vapor phase silica. .

  Next, an ionizing radiation-curable polyvinyl alcohol derivative aqueous solution having a stilbazolium group introduced therein and adjusted to a concentration of 8% (manufactured by Toyo Gosei Co., Ltd .: SPP-SHR main chain PVA polymerization degree 1700, saponification degree 88) %) And 280 ml of a 25% solution of the cationic polymer-1 are gradually added with stirring, and finally pure water is added so that the total volume of the liquid becomes 1000 ml. A coating solution 6 was prepared.

[Preparation of ink receiving layer coating solution 7]
In the preparation of the ink-receiving layer coating solution 6, the polymerization volume of the ionizing radiation curable polyvinyl alcohol was changed to 3000, and the total volume was changed to 1400 ml to match the viscosity of the ink-receiving layer coating solution 1 at 40 ° C. Thus, an ink receiving layer coating solution 7 was prepared.

<Production of recording paper>
[Production of Sample 101: Comparative Example]
The first layer, the second layer, and the third layer are formed from the side close to the support, the ink receiving layer coating solution 3 is used as the coating solution for the first to third layers, and the following betaine is used for the coating solution for the third layer. 3 ml of 5% solution of type surfactant-1 (* 1) was added and filtered with the following filter.

<filter>
1st layer-2nd layer: Two-stage structure of Toyo Filter Paper Co., Ltd. TCP10 Third layer: Two-stage structure of Toyo Filter Paper Co., Ltd. TCP30 * 1) Betaine type surfactant-1:
C ₈ H ₁₇ SO ₂ NH (CH ₂ ) ₃ N ⁺ (CH ₃ ) ₂ CH ₂ COO ⁻
Each coating solution prepared as described above was coated with polyethylene on both sides of a base paper having a basis weight of 170 g / m ² (containing 8% anatase-type titanium oxide in the polyethylene layer on the recording surface side. 05G / m ² of gelatin subbing layer, Tg is a latex polymer of approximately 80 ° C. on a recording surface on a back layer) containing 0.2 g / m ² on the opposite side, the first layer (62 .mu.m), Simultaneous coating was performed in the order of the second layer (62 μm) and the third layer (62 μm). In addition, the numerical value in a parenthesis is a wet film thickness.

  Each coating solution was applied by a slide curtain coating method at 40 ° C., and after cooling for 10 seconds in a cooling zone maintained at 5 ° C. immediately after coating, the coating solution was dried by passing through a drying zone at 50 ° C. The coating and drying speeds were adjusted as appropriate so that the time required for drying could be minimized. After drying, the humidity was adjusted at 25 ° C. and a relative humidity of 50% to obtain a sample 101 composed of three ink receiving layers.

[Production of Sample 102: Comparative Example]
In the preparation of the sample 101, the third layer coating solution was changed to the ink receiving layer coating solution 1 prepared above, and 3 ml of 5% betaine surfactant-1 was added to the third layer. Similarly, a sample 102 was obtained. However, the wet film thickness at the time of application was 45 μm for the first layer, 62 μm for the second layer, and 62 μm for the third layer so that the amount of silica applied to the sample 101 and each layer was the same. Further, the coating and drying speeds were adjusted as appropriate so that the time required for drying could be minimized as the drying load varied due to the change in wet film thickness. The coating speed was 110 when the coating speed of the sample 101 was 100.

[Preparation of Sample 103: Present Invention]
A sample 103 was obtained in the same manner as in the preparation of the sample 101 except that the coating liquid for the second layer was changed to the ink receiving layer coating liquid 2 prepared above. However, the wet film thickness at the time of application was 62 μm for the first layer, 56 μm for the second layer, and 62 μm for the third layer so that the amount of silica applied to the sample 101 and each layer was the same. Further, the coating and drying speeds were adjusted as appropriate so that the time required for drying could be minimized as the drying load varied due to the change in wet film thickness. The coating speed was 104 when the coating speed of the sample 101 was 100.

[Preparation of Sample 104: Present Invention]
A sample 104 was obtained in the same manner as in the preparation of the sample 101 except that the coating solution for the second layer was changed to the ink receiving layer coating solution 1 prepared above. However, the wet film thickness at the time of application was 62 μm for the first layer, 45 μm for the second layer, and 62 μm for the third layer so that the amount of silica applied to the sample 101 and each layer was the same. Further, the coating and drying speeds were adjusted as appropriate so that the time required for drying could be minimized as the drying load varied due to the change in wet film thickness. The coating speed was 110 when the coating speed of the sample 101 was 100.

[Production of Sample 105: Present Invention]
A sample 105 was obtained in the same manner as in the preparation of the sample 101 except that the coating liquid for the first layer and the second layer was changed to the ink receiving layer coating liquid 1 prepared above. However, the wet film thickness at the time of application was 62 μm for the first layer, 45 μm for the second layer, and 45 μm for the third layer so that the amount of silica applied to the sample 101 and each layer was the same. Further, the coating and drying speeds were adjusted as appropriate so that the time required for drying could be minimized as the drying load varied due to the change in wet film thickness. The coating speed was 125 when the coating speed of sample 101 was 100.

[Production of Sample 106: Present Invention]
In the preparation of the sample 105, the coating solution for the third layer was changed to the ink receiving layer coating solution 2 prepared above, and 3 ml of 5% betaine surfactant-1 was added to the third layer. Similarly, a sample 106 was obtained. However, the wet film thickness at the time of application was 56 μm for the first layer, 45 μm for the second layer, and 45 μm for the third layer so that the amount of silica applied to the sample 101 and each layer was the same. Further, the coating and drying speeds were adjusted as appropriate so that the time required for drying could be minimized as the drying load varied due to the change in wet film thickness. The coating speed was 128 when the coating speed of the sample 101 was 100.

[Preparation of Sample 107: Present Invention]
In the preparation of the sample 105, the first layer and second layer coating liquids are respectively used as the ink receiving layer coating liquid 4, and the third layer coating liquid is used as the ink receiving layer coating liquid 5, and betaine is added to the third layer coating liquid. Sample 107 was obtained in the same manner except that 3 ml of 5% liquid of type surfactant-1 was added.

[Preparation of Sample 108: Present Invention]
The coating liquid for the first layer and the second layer is the ink receiving layer coating liquid 6, the coating liquid for the third layer is the ink receiving layer coating liquid 7, and betaine surfactant-1 is added to the third layer coating liquid. 3 ml of 5% solution was added and filtered through a filter having the same structure as described above.

  Next, on the polyethylene-coated paper, the first layer (45 μm), the second layer (45 μm), and the third layer (63 μm) were simultaneously applied so that the silica coating amount of each layer was the same as that of the sample 101. .

Then, after irradiating 40 mJ / cm ² of ultraviolet energy with a metal halide lamp having a dominant wavelength at 365 nm, and passing through a drying zone at 50 ° C. in the same manner as Sample 101, drying was performed at 25 ° C. and relative humidity. The sample 108 was obtained by adjusting the humidity at 50%. The coating and drying rates were adjusted as appropriate so that the time required for drying could be minimized as the drying load varied due to changes in wet film thickness. The coating speed was 125 when the coating speed of sample 101 was 100.

<Evaluation of recording paper>
About each sample produced by the above, the weather resistance evaluation and the relative application | coating speed | rate were calculated | required according to the method as described below.

[Evaluation of weather resistance]
Each sample was irradiated for 80 hours at an irradiation illuminance of 48 W / m ² in an environment of 23 ° C. and 60% relative humidity using a xenon weatherometer, and then each sample was put into pure water at 25 ° C. After dipping for 2 minutes, the operation of drying with hot air at 50 ° C. was repeated 10 times, and the presence or absence of cracking of the coating layer on the recording paper surface was visually evaluated, and the weather resistance was evaluated according to the following criteria. It was.

◎: No cracks observed, the same state as before immersion evaluation ○: Compared with the surface state before immersion evaluation, the glossiness is slightly deteriorated, but there is no problem in practice △: Cracked part is observed, surface Image quality is clearly degraded ×: Cracks are generated over the entire surface [Relative coating speed]
The coating speed was displayed as a relative coating speed when the coating speed when the sample 101 was coated and dried under optimum conditions was set to 100. A larger value means higher productivity per unit time and less energy consumption for drying.

  The results obtained as described above are shown in Table 1.

  As is apparent from the results shown in Table 1, the samples 103 to 108, which are ink jet recording papers having the configuration defined in the present invention, have higher productivity and comparable weather resistance to the sample 101 which is a comparative example. It turns out that it has sex. In addition, the sample 102 as a comparative example has good characteristics in productivity, but is inferior in weather resistance.

  Further, comparing the samples 105 and 106 of the present invention, the sample 105 in which the degree of polymerization of the third layer binder farthest from the support has a degree of polymerization of 3000 or more has excellent weather resistance with almost no loss of productivity. I understand that. In addition, comparing the samples 105 and 107 of the present invention, the sample 107 having a low content of the cationic polymer, and the sample 108 using the ionizing radiation curable binder in the comparison of the samples 105 and 108 of the present invention are more It turns out that it has the outstanding weather resistance.

Example 2
<Preparation of ink receiving layer coating solution>
[Preparation of Ink Receptive Layer Coating Liquid 8]
In 150 ml of pure water, 1.2 ml of a nonionic acrylic polymer type dispersant (solid content 40%, SD-10 manufactured by Toa Gosei) was dissolved, and the pH was adjusted to 11.0 with sodium hydroxide. To this, 385 g of a 23% aqueous dispersion of silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 7 nm was added and dispersed with a high-speed homogenizer to obtain a dispersion of vapor phase silica. .

  Next, 320 ml of an 8% aqueous solution of polyvinyl alcohol (Kuraray PVA217, polymerization degree 1700), 89.6 ml of a 25% solution of cationic polymer-1 and 0.75 g of borax were added to this dispersion. Finally, pure water was added so that the total volume became 1000 ml, and a translucent ink receiving layer coating solution 8 was obtained.

[Preparation of Ink Receptive Layer Coating Liquid 9]
An ink receiving layer coating solution 9 was prepared in the same manner as in the preparation of the ink receiving layer coating solution 8 except that polyvinyl alcohol (PVA 217) was changed to Kuraray polyvinyl alcohol (PVA 210) having a polymerization degree of 1000.

[Preparation of ink receiving layer coating solution 10]
In 150 ml of pure water, 1.2 ml of a nonionic acrylic polymer type dispersant (solid content 40%, SD-10 manufactured by Toa Gosei) was dissolved, and the pH was adjusted to 11.0 with sodium hydroxide. To this, 385 g of a 23% aqueous dispersion of silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 7 nm was added and dispersed with a high-speed homogenizer to obtain a dispersion of vapor phase silica. .

  Next, 320 ml of an 8% aqueous solution of acetoacetyl-modified polyvinyl alcohol (Nippon Gosei Z320, polymerization degree 1700) and 89.6 ml of a 25% solution of cationic polymer-1 were added to this dispersion. Finally, pure water was added so that the total volume became 1000 ml to obtain a translucent ink receiving layer coating solution 10.

[Preparation of ink receiving layer coating solution 11]
In the preparation of the ink-receiving layer coating solution 10, the ink-receiving layer coating solution was similarly changed except that the acetoacetyl-modified polyvinyl alcohol (Nippon Gosei Z320, degree of polymerization 1700) was changed to Nihon Gosei Z220 with a degree of polymerization of 1000. 11 was prepared.

<Production of recording paper>
[Production of Sample 201]
The first layer, the second layer, and the third layer are formed from the side close to the support, and the ink receiving layer coating liquid 9 prepared above is used as the coating liquid for the first layer and the second layer, and the coating liquid for the third layer is used as described above. Using the prepared ink receiving layer coating solution 8, 3 ml of a 5% solution of betaine surfactant-1 (supra) was added to the third layer coating solution, followed by filtration with the following filter.

<filter>
First layer to the second layer: Toyo Roshi Co. TCP10 two-stage third layer: Toyo filter paper each coating solution prepared by two-stage or more manufactured TCP30 Ltd., base paper both surfaces of a basis weight of 170 g / m ² Coated with polyethylene (containing 8% anatase-type titanium oxide in the polyethylene layer on the recording surface side. 0.05 g / m ² gelatin subbing layer on the same side, Tg of about 80 ° C. on the other side) The first layer (45 μm), the second layer (45 μm), and the third layer (45 μm) are applied simultaneously in this order on the recording surface side (with a back layer containing 0.2 g / m ² of latex polymer). went. In addition, the numerical value in a parenthesis is a wet film thickness.

  Each coating solution was applied by a slide curtain coating method at 40 ° C., and after cooling for 10 seconds in a cooling zone maintained at 5 ° C. immediately after coating, the coating solution was dried by passing through a drying zone at 50 ° C. The coating and drying speeds were adjusted as appropriate so that the time required for drying could be minimized. After drying, the humidity was adjusted at 25 ° C. and a relative humidity of 50% to obtain a sample 201 composed of three ink receiving layers.

[Preparation of Sample 202]
The first layer, the second layer, and the third layer are formed from the side close to the support, and the ink receiving layer coating liquid 11 prepared above is used as the coating liquid for the first layer and the second layer, and the ink prepared above is used for the third layer. The receiving layer coating solution 10 was used. Further, 3 ml of 5% solution of betaine surfactant-1 was added to the ink receiving layer coating solution 10 and filtered through the filter having the above-described configuration.

  After adding and mixing 0.8 g of adipic acid dihydrazide immediately before coating to each coating solution prepared as described above, coating and drying were performed in the same manner as Sample 201 to obtain Sample 202.

<Evaluation of recording paper>
About each sample produced by the above, the weather resistance evaluation and the relative application | coating speed | rate were calculated | required according to the method as described below.

[Evaluation of weather resistance]
Each sample was irradiated for 80 hours at an irradiation illuminance of 48 W / m ² in an environment of 23 ° C. and 60% relative humidity using a xenon weatherometer, and then each sample was put into pure water at 25 ° C. After dipping for 2 minutes, the operation of drying with hot air at 50 ° C. was repeated 5 times, and the presence or absence of cracks in the coating layer on the recording paper surface was visually evaluated, and the weather resistance was evaluated according to the following criteria. It was.

◎: No cracks observed, the same state as before immersion evaluation ○: Compared with the surface state before immersion evaluation, the glossiness is slightly deteriorated, but there is no problem in practice △: Cracked part is observed, surface Image quality is clearly degraded ×: Cracks are generated over the entire surface [Relative coating speed]
The coating speed is displayed as a relative coating speed when the coating speed when the sample 201 is coated and dried under the optimum conditions is 100.

  The results obtained as described above are shown in Table 2.

  As apparent from the results shown in Table 2, by using acetoacetyl-modified polyvinyl alcohol as the hydrophilic binder, more excellent weather resistance could be obtained.

Example 3
<Preparation of ink receiving layer coating solution>
[Preparation of ink receiving layer coating solution 12]
In the preparation of the ink-receiving layer coating liquid 7 described in Example 1, the average particle size of primary particles is about 30 nm instead of silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) where the average particle size of primary particles is about 7 nm. In the same manner, except that γ-alumina (synthesized by the method described in JP-A-10-231120) was used and the solid content of γ-alumina was added so as to be the same as that of the ink-receiving layer coating solution 7. A receiving layer coating solution 12 was prepared.

[Preparation of ink receiving layer coating solution 13]
In the preparation of the ink-receiving layer coating liquid 7 described in Example 1, the average particle size of primary particles is about 18 instead of silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) where the average particle size of primary particles is about 7 nm. Ink-receiving layer coating solution in the same manner except that -25 nm colloidal silica (Snowtex PS-M manufactured by Nissan Chemical Industries, Ltd.) is used and the solid content of colloidal silica is the same as that of ink-receiving layer coating solution 7. 13 was prepared.

<Production of recording paper>
[Preparation of Sample 301]
A sample 301 was prepared in the same manner as in the preparation of the sample 108 described in Example 1, except that the third layer ink receiving layer coating solution 7 was changed to the ink receiving layer coating solution 12 prepared above.

[Preparation of Sample 302]
A sample 302 was prepared in the same manner as in the preparation of the sample 108 described in Example 1, except that the third layer ink receiving layer coating solution 7 was changed to the ink receiving layer coating solution 13 prepared above.

<Evaluation of recording paper>
For each of the samples prepared as described above and the sample 108 prepared in Example 1, the weather resistance was evaluated in the same manner as in the method described in Example 1, and the ink absorptivity evaluation and relative coating speed were determined according to the method described below. Asked.

[Evaluation of ink absorbency]
Using an ink jet printer PM950C manufactured by Seiko Epson Corporation, a gray solid image having a reflection density of about 1.0 is printed on the ink receiving layer coating surface side of each sample using a genuine ink, and the ink overflow state of the image The ink absorptivity was evaluated according to the following criteria.

◎: Ink overflow location is not recognized ○: Ink overflow location is slightly recognized, but there is no problem in practice △: Ink overflow is recognized and image quality is clearly deteriorated ×: Ink overflow is almost the entire surface [Relative application speed]
The coating speed was displayed as a relative coating speed when the coating speed when the sample 108 was coated and dried under the optimum conditions was 100.

  The results obtained as described above are shown in Table 3.

  As is apparent from the results shown in Table 3, the samples 108 and 301 using vapor phase method silica or alumina as the inorganic fine particles of the ink receiving layer are superior to the sample 302 using colloidal silica as the inorganic fine particles. It can be seen that it has both weather resistance and ink absorption.

Claims (16)

In the ink jet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on the support, the average degree of polymerization of the hydrophilic binder contained in the layer A located farthest from the support is An ink jet recording paper, wherein the average polymerization degree of the hydrophilic binder contained in at least one layer B located on the support side from the layer A is higher. In the ink jet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on the support, the average degree of polymerization of the hydrophilic binder contained in the layer A located farthest from the support is It is higher than the average degree of polymerization of the hydrophilic binder contained in at least one layer B located on the support side from the layer A, and the average degree of polymerization of the hydrophilic binder contained in the layer B is 1900 or less. An ink jet recording paper characterized by being. The inkjet recording paper according to claim 1 or 2, wherein an average degree of polymerization of the hydrophilic binder contained in the layer A is 2800 or more. The average polymerization degree of the hydrophilic binder contained in the layer A is higher than the average polymerization degree of the hydrophilic binder contained in all the layers containing the inorganic fine particles and the hydrophilic binder located on the support side from the layer A. The inkjet recording paper according to any one of claims 1 to 3. The layer A and the layer that is located closer to the support than the layer A and contains a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A are other cationic organic resins for the hydrophilic binder. The ink jet recording paper according to claim 1, wherein a mass ratio of the ink jet recording paper is 20% or less. The layer containing a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A, which is located on the support side from the layer A and the layer A, is ionized in an amount of 70% by mass or more of the hydrophilic binder. It is a radiation curable resin, and after apply | coating this layer on a support body, the hydrophilic binder of this layer is hardened by ionizing radiation irradiation, The one of Claims 1-5 characterized by the above-mentioned. Inkjet recording paper. The layer containing the hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A, which is located on the support side from the layer A and the layer A, has a carboxyl content of 70% by mass or more of the hydrophilic binder. The inkjet recording paper according to claim 1, which is a water-soluble resin having at least one functional group selected from a group, a sulfoxyl group, an acetoacetyl group, and a reactive ketone group. . The inkjet recording paper according to any one of claims 1 to 7, wherein the inorganic fine particles are at least one selected from gas phase method silica, alumina, boehmite, and pseudoboehmite. In a method for producing an inkjet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on a support, it is contained in a coating solution used for forming layer A that is located farthest from the support. The average polymerization degree of the hydrophilic binder is higher than the average polymerization degree of the hydrophilic binder contained in the coating liquid used for forming at least one layer B located on the support side from the layer A. Ink jet recording paper manufacturing method. In a method for producing an inkjet recording paper having at least two layers containing inorganic fine particles and a hydrophilic binder on a support, it is contained in a coating solution used for forming layer A that is located farthest from the support. The average degree of polymerization of the hydrophilic binder is higher than the average degree of polymerization of the hydrophilic binder contained in the coating liquid used for forming at least one layer B located on the support side of the layer A, and the layer B The average polymerization degree of the hydrophilic binder contained in 1900 is 1900 or less, The manufacturing method of the inkjet recording paper characterized by the above-mentioned. The method for producing an inkjet recording paper according to claim 9 or 10, wherein an average degree of polymerization of the hydrophilic binder contained in the coating liquid used for forming the layer A is 2800 or more. Coating having an average degree of polymerization of the hydrophilic binder contained in the coating liquid used for forming the layer A is used for forming all layers containing the inorganic fine particles and the hydrophilic binder located on the support side from the layer A. The method for producing an inkjet recording paper according to any one of claims 9 to 11, wherein the average degree of polymerization of the hydrophilic binder contained in the liquid is higher. The layer A and the layer containing a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A, located on the support side from the layer A, are other cationic organic resins for the hydrophilic binder. The method for producing an ink jet recording paper according to claim 9, wherein the mass ratio of the ink jet recording paper is 20% or less. The layer formed on the support side of the layer A and the layer A and formed of a coating liquid containing a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A is a hydrophilic binder. 70 mass% or more of the above is an ionizing radiation curable resin, and after coating the layer on the support, the hydrophilic binder of the layer is cured by irradiation with ionizing radiation. The manufacturing method of the inkjet recording paper of any one. The layer formed on the support side of the layer A and the layer A and formed of a coating liquid containing a hydrophilic binder having a lower average polymerization degree than the hydrophilic binder contained in the layer A is a hydrophilic binder. 70% by mass or more of the water-soluble resin having at least one functional group selected from a carboxyl group, a sulfoxyl group, an acetoacetyl group and a reactive ketone group. The manufacturing method of the inkjet recording paper as described in a term. The method for producing an inkjet recording paper according to any one of claims 9 to 15, wherein the inorganic fine particles are at least one selected from gas phase method silica, alumina, boehmite, and pseudoboehmite.