JP2005088215A - Inkjet recording sheet and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet which is improved in handling flexibility of a recording material and is excellent in image quality characteristics without deteriorating ink receiving performances and a film-forming property at production. <P>SOLUTION: The inkjet recording sheet has on a support an ink receiving layer containing at least two or more layers of porous substances and at least one layer of a hydrophilic binder thereof is hardened by ionizing radiation and a hardener. The recording sheet is characterized in that the ink receiving layer most distant from the support contains an ionizing radiation-curable resin as a hydrophilic binder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a recording material suitable for ink jet recording, and more particularly to an ink jet recording sheet having improved recording material handling flexibility without impairing film-forming properties during production.

  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.

  Furthermore, in recent years, many attempts have been made to bring the image quality obtained by color ink jet recording close to the level of silver salt photography.

  As an example of a recording medium capable of obtaining a high image quality, there is one having a swelling type ink receiving layer mainly composed of a hydrophilic binder on a support, whereby a texture close to that of a silver salt photograph can be obtained.

  However, on the other hand, the speed of ink jet recording is increasing. Also, in order to improve image quality, it is necessary to make the ink droplets small so that each dot cannot be identified with the naked eye, or to lower the dot reflection density especially in the highlight area to identify the dot. In order to make it difficult, it has been practiced to use an ink with a low dye concentration. For this reason, the amount of ink ejected tends to increase. Accordingly, recording papers are increasingly required to have high ink absorption and quick drying.

  In order to cope with this situation, a void-type recording medium capable of obtaining a fast absorption rate by having an ink receiving layer comprising a porous void layer having a small amount of a hydrophilic binder and a hardener and a large amount of fine-particle silica, Widely used as a high-quality inkjet recording material. Polyvinyl alcohol is generally used as the hydrophilic binder of the void-type recording medium, and boric acid or a salt thereof has been used as the hardener.

  However, a void-type recording medium such as the upper air has a weak ink receiving layer. For example, when the recording medium is rolled or folded while the air is dry, the ink receiving layer cracks and cracks. It has been found that there is a problem that the gloss is lowered and the appearance is deteriorated, and in a severe case, the strip is peeled off.

  In view of such circumstances, attempts have been made to improve the situation. For example, it is described that the amount of polyvinyl alcohol, which is a binder contained in an ink receiving layer, and boric acid, or a salt thereof, which is a hardener, is regulated to improve the brittleness of a recording material (for example, patents). Reference 1).

  However, in general, the quantity ratio between the binder and its hardener must be set in consideration of not only fragility but also other performance such as ink absorbability and film-forming property. Further, for example, the fragility changes depending on the amount ratio of the binder and the silica fine particles, but this also has to settle down to the performance level currently used in the market due to the relationship with other performances. That is, it has been considered that there is a limit to improvement in the conventional technology category.

  On the other hand, there is a description of an ink jet recording medium in which bendability is improved by applying pressure to the recording paper with a linear pressurizing jig to give a delimited region (see, for example, Patent Documents 2 and 3). These inventions are, for example, for facilitating folding when being put in an envelope, and have different purposes and applications from the present invention.

  Therefore, it is considered that there are not sufficient techniques for improving the vulnerability and flexibility considered as important performance items when handling the inkjet recording medium.

  On the other hand, in the present invention, it has been found that an ionizing radiation curable resin is used as a means for achieving the above, but an ink jet recording medium using the resin as a binder for an ink receiving layer is described in the following patent publications and the like. There is.

  There is a description of an ink jet recording material using an ionizing radiation curable resin, and an effect of improving the adhesion of the coating layer to the substrate is described (for example, see Patent Document 4). However, there is no mention of cracking, lowering of glossiness, and peeling of the ink receiving layer due to rolling. Further, there is no specific description about the multilayer structure material, and the effect of the present invention is not foreseen.

  Although there is a description of an ink jet recording material using an ionizing radiation curable resin (see, for example, Patent Document 5), the base paper is impregnated with the resin to improve cockling, curling properties, and ink absorption. Thus, the present invention is completely different from the present invention in terms of contents, embodiments, and effects.

  Although there is a description of an inkjet recording paper that uses an electron beam curable resin (see, for example, Patent Document 6), the present invention is different from the present invention in terms of aspect and effect, and the present invention cannot be foreseen. Further, the resin is limited to electron beam irradiation, and the recording material is limited to cast coated paper.

  There is a description of an inkjet recording material using an electron beam curable resin having one or more layers (see, for example, Patent Document 7), and there is a description of cracking improvement effect during production. There is no description about the effect on the above, and there is no description about the effect of the present invention in a multilayer structure material, so the present invention is not foreseen.

That is, the multilayered inkjet recording material of the present invention using an ionizing radiation curable resin has not been known so far and has not been foreseen.
JP 2002-225427 A (Claims, pages 2 to 3) JP-A-9-295454 (Claims, pages 2 to 4) Japanese Patent Laid-Open No. 10-6638 (Claims, pages 2 to 4) Japanese Patent Laid-Open No. 7-40649 (Pages 2 and 3, Examples) JP-A-8-169174 (pages 2 and 3) JP-A-9-71035 (Pages 2 and 3, Examples) JP 2002-160439 A (pages 2 to 5, examples)

  An object of the present invention is to provide an ink jet recording sheet that improves the handling flexibility of a recording material and further has excellent image quality characteristics without impairing ink receiving performance and film-forming properties during production.

The above object of the present invention can be achieved by the following configuration.
(Claim 1)
Inkjet recording having an ink receiving layer containing at least two layers of porous material on a support, and at least one hydrophilic binder of the ink receiving layer being cured by ionizing radiation and a hardener An ink jet recording sheet, wherein the ink receiving layer located farthest from the support contains an ionizing radiation curable resin as a hydrophilic binder.
(Claim 2)
2. The ink jet recording sheet according to claim 1, wherein the ionizing radiation curable resin is a compound that is cured by ultraviolet rays.
(Claim 3)
The ink jet recording sheet according to claim 1 or 2, wherein the ionizing radiation curable resin is a resin modified with a photodimerization type or photopolymerization type modification group.
(Claim 4)
The ink-jet recording sheet according to any one of claims 1 to 3, wherein the ink-receiving layer is coated on a support, and then the hydrophilic binder of the ink-receiving layer is cured by ionizing radiation irradiation and a hardening agent. A method for producing an inkjet recording sheet.

  According to the present invention, it is possible to provide an ink jet recording sheet having improved recording material handling flexibility and excellent image quality characteristics without impairing ink receiving performance and film-forming property during production.

  The present invention will be described in more detail. 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 water-soluble resin that 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.

  In the present invention, the ionizing radiation curable resin used as a binder for 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. A resin that is water-soluble but substantially water-insoluble after the crosslinking reaction.

  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 upon curing, such as JP-A-56-67309 Photosensitive resin (composition) described in publications such as No. 1 and the like.

  Specifically, for example, a photosensitive resin described in JP-A-56-67309 is incorporated in a polyvinyl alcohol structure.

2-azido-5-nitrophenylcarbonyloxyethylene structure represented by:

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

  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. Thioxanthones such as thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, and isopropoxychlorothioxanthone. Anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone and chloroanthraquinone. Acetophenones. Benzoin ethers such as benzoin methyl ether. 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di ( m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -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 -2,4,5-triarylimidazole dimer of diphenylimidazole dimer, benzyldimethyl ketal, 2-benzyl-2-dimethyl Amino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (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, acridine derivatives such as 1,7-bis (9,9′-acridinyl) 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 0.2-10 mass% with respect to the ionizing-radiation-curable resin in a coating composition, Preferably it adjusts in the range of 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 degree of polymerization is preferably 1800 or more. 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-acrylamide-2,2-dimethylethyl) ammonium chloride, trimethyl- (3-acrylamide-3,3-dimethylpropyl) ammonium chloride, N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxyethyl-trimethylammonium chloride, trimethyl- (methacrylamidepropyl) ammonium chloride, N- (1,1- And dimethyl-3-dimethylaminopropyl) acrylamide.

  Compared with the method in which water-soluble resin and inorganic fine particles (porous substance) 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 The network structure formed by cross-linking by ionizing radiation contains many fine particles because it includes cross-linking at a long distance, which is different from the three-dimensional structure at a relatively short distance formed by using a cross-linking agent. It is considered that the structure is easy to form, and 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 the 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 ionizing radiation curable resin is used as a binder, the suitable degree of polymerization is 1000-5000.

  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 sheet comprising a layer is obtained. Curing by ionizing radiation irradiation of the ionizing radiation curable resin of 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 rate of drying. is there.

  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 that are easy to handle and are widely used industrially are preferably used.

  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 and the like having an operating pressure of several hundred Pa to one million Pa are used as the ultraviolet light source, but a high pressure mercury lamp and a metal halide lamp are preferable from the viewpoint of wavelength distribution of the light source, A metal halide lamp is more preferable. Moreover, 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.

  In the present invention, the hydrophilic resin other than the ionizing radiation curable resin used as a binder for a coating layer such as an ink-receiving layer on a support is not particularly limited, and may be a hydrophilic resin that can be used as a conventionally known hydrophilic binder. Can be used.

  As the conventionally known hydrophilic binder, for example, gelatin, polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, polyvinyl alcohol and the like can be used, and polyvinyl alcohol is particularly preferable. Polyvinyl alcohol has an interaction with inorganic fine particles, has a particularly high holding power to inorganic fine particles, and is a polymer with relatively small humidity dependency such as hygroscopicity, and has a comparative shrinkage stress during coating and drying. Therefore, 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 hydrolyzing vinyl acetate, those having an average degree of polymerization of 300 or more are preferably used, and those having an average degree of polymerization of 1000 to 5000 are particularly preferably used. 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.

  The ratio of the fine particles to the hydrophilic binder in the porous material layer is preferably 2 to 50 times in terms of mass ratio. If the mass ratio is 2 times or more, the porosity of the porous material layer is good, it is easy to obtain a sufficient void volume, and an excessive hydrophilic 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 porous material layer is applied as a thick film. In particular, the ratio of the fine particles to the hydrophilic binder is preferably 2.5 to 20 times, and more preferably 5 to 15 times from the viewpoint of cracking of the dried coating film.

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 unit volume of the coating film is put on water, or the volume of water that the coating film can absorb.

  When the hydrophilic binder is cured with a hardener, the water resistance of the ink receiving layer is further improved, and since the swelling of the hydrophilic binder during ink jet recording is suppressed, the ink absorption rate is improved.

  The hardener is generally a compound having a group capable of reacting with the hydrophilic binder or a compound that promotes the reaction between different groups of the hydrophilic binder, and is appropriately selected depending on the type of the hydrophilic binder. Select and use.

  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 polymer. 300 mg.

  Two or more hardeners may be used in combination. In addition, it may be mixed and applied to a coating solution containing an ink receiving layer, but after coating film formation and drying, a solution containing a hardener without containing a porous substance may be overcoated and supplied. This is preferable because the risk of aggregation of the substance is reduced. In the case of overcoating, the application timing is preferably simultaneously with the application of the ink receiving layer or after the ink receiving layer is applied, but before the layer exhibits a reduced drying rate.

  In particular, the present inventors have described that the cross-linked form of the ionizing radiation curable resin described in the present invention may be different from the conventionally known form of the hardener, so that the ink jet recording having a multilayer structure is particularly preferred. In the sheet for use, it is thought that by combining the cross-linking method with ionizing radiation, which seems to have different characteristics, and the cross-linking method with the hardener for each layer, it is possible to draw out each suitable characteristic, and the present invention has been achieved. .

  An ink jet recording sheet having an ink receiving layer containing at least two porous materials of the present invention and having the binder of the ink receiving layer cured by ionizing radiation and a hardener is most distant from the support. The ink receiving layer located in the position contains an ionizing radiation curable resin as a binder. That is, since the binder of the ink receiving layer existing on the surface side is considered to have more robust and flexible characteristics in terms of film properties as described above, the film surface is resistant to rounding and bending in a low humidity environment. It is considered that the cracks accompanying the cracking of the ink and the removal of the porous fine particles in the ink receiving layer can be improved. Furthermore, a binder containing an ionizing radiation curable resin is excellent in film-forming properties at the time of production, and is effective against cracks that cause problems during drying.

  The mass ratio of the ionizing radiation curable resin contained in the ink receiving layer located farthest from the support to the total amount of binder contained in the layer is preferably 50% or more, and more preferably 80% or more. When the ratio of the ionizing radiation curable resin is small, the effect on flexibility becomes poor.

  The film surface pH of the recording surface of the ink jet recording sheet 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. Am. 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.

  In the present invention, inorganic fine particles and organic fine particles can be used as the porous material used in the ink receiving layer. In particular, it is easy to obtain a smaller particle size, and a high gloss recording paper is prepared. Inorganic fine particles are preferable because a high-density printed image can be obtained.

  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 alumina, pseudoboehmite, colloidal silica, or fine particle silica synthesized by a gas phase method, and fine particles synthesized by a gas phase method. 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 a cationic resin are preferably used.

  As the cationic resin, a cationic polymer having a primary to tertiary amino group and a quaternary ammonium base 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 products, monomethyl ammonium chloride is preferred. As the polyallylamine-modified product, one obtained by adding acrylonitrile, chloromethylstyrene or the like is known.

  As this dispersion treatment method, various conventionally known dispersers such as a high-speed rotary disperser, a medium stirring disperser (ball mill, sand mill, etc.), an ultrasonic disperser, a colloid mill disperser, a roll mill disperser, and a high pressure disperser are used. Although it can be used, in the present invention, an ultrasonic disperser or a high-pressure disperser is preferably used from the viewpoint of efficient dispersion.

  An ultrasonic disperser is usually dispersed by concentrating energy at a solid-liquid interface by irradiating ultrasonic waves of 20 to 25 kHz, and is dispersed very efficiently, but a large amount of dispersion is prepared. It is not very suitable when necessary.

  On the other hand, the high-pressure disperser is equipped with one or two homogeneous valves at the outlet of a high-pressure pump having three or five pistons, the gap of which can be adjusted by screws or hydraulic pressure. The liquid medium fed by the high-pressure pump is squeezed by the homogeneous valve and pressure is applied, and a relatively coarse dispersion is pulverized at the moment of passing through the homogeneous valve.

This dispersion treatment method is particularly preferable when a large amount of liquid is produced because a large amount of liquid can be dispersed continuously. The pressure applied to the homogeneous valve is usually 50 to 1000 kg / cm ² and the dispersion can be done in one pass or repeated many times.

  Two or more kinds of the above dispersion processing methods can be used in combination.

  In preparing the above dispersion, various additives can be added and adjusted.

  For example, various nonionic or cationic surfactants (anionic surfactants are not preferred for forming aggregates), antifoaming agents, nonionic hydrophilic polymers (polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide) , Polyacrylamide, various sugars, gelatin, pullulan, etc.), nonionic or cationic latex dispersion, water-miscible organic solvent (ethyl acetate, methanol, ethanol, isopropanol, n-propanol, acetone, etc.), inorganic salts, A pH adjuster can be used in a timely manner as required.

  The pH in preparing the cationic dispersion can vary widely depending on the type of inorganic fine particles, the type of cationic polymer, various additives, etc., but generally the pH is 1-8, 7 is preferred.

  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. 7) Whiteness: Hunter whiteness as defined in JIS-P-8123, preferably 90% or more. Further, when measured by JIS-Z-8722 (non-fluorescent) and JIS-Z-8717 (containing fluorescent agent) and displayed by the color display method defined in JIS-Z-8730, L ^* = 90 to 98, a ^* = − 5 to +5, b ^* = − 10 to +5 are preferable.

An undercoat layer is preferably provided on the ink-receiving layer side of the support for the purpose of improving 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.

  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 a primary to tertiary amino group and a quaternary ammonium base 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.

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, there are two or more ink receiving layers, but it is preferable to apply all the ink receiving layers simultaneously from the viewpoint of reducing the production cost.
When recording an image using the ink jet recording sheet of the present invention, a water-based ink is preferably used, which may be a water-based dye ink or a water-based pigment ink, but a water-based pigment ink is preferable.

  Here, the water-based dye ink and the water-based pigment ink are recording liquids having the following colorant, liquid medium, and other additives. Examples of the colorant include water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes or food dyes known in the ink-jet recording field, organic pigments such as azo pigments, phthalocyanine pigments, dye lakes, and carbon black. Aqueous pigments such as inorganic pigments can be used. Other water-based ink additives include, for example, water-soluble organic solvents (propanol, hexanol, ethylene glycol, diethylene glycol, glycerin, hexanediol, urea, etc.), surfactants, water-soluble polymers, preservatives, viscosity modifiers, pH adjusters. An agent etc. can be mentioned.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. In the examples, “%” represents mass% unless otherwise specified.

Example 1
(Preparation of Comparative Sample 101)
(Preparation of coating solution A)
1.2 ml of a nonionic acrylic polymer type dispersant (solid content 40%, SD-10 manufactured by Toa Gosei Co., Ltd.) was dissolved in 150 ml of pure water and adjusted to pH 11 with sodium hydroxide. 400 g of a 25% aqueous dispersion of silica (QS-20 manufactured by Tokuyama) having an average primary particle size of about 12 nm was added thereto and dispersed with a high-speed homogenizer.

  Next, 280 ml of a 7% aqueous solution of polyvinyl alcohol (Kuraray PVA235) and 0.7 g of borax were added to the dispersion. Finally, pure water was added so that the total volume became 1000 ml, and a translucent coating solution was obtained.

Recording surface side on a paper support (thickness 260 μm, containing 6% anatase titanium dioxide in the polyethylene layer on the recording surface side) coated with polyethylene on both sides of a base paper having a basis weight of 170 g / m ² using the coating liquid A Two layers are applied so that the wet film pressure is 90 μm each, and after cooling at 8 ° C. for 10 seconds, it is dried with 30 ° C. air for 60 seconds, 50 ° C. air for 60 seconds, and 70 ° C. air for 60 seconds. After that, humidity was adjusted at 25 ° C. and a relative humidity of 50% to obtain an ink jet recording sheet 101.

(Preparation of Comparative Sample 102)
The coating solution for the first layer was changed to the following coating solution B, and the binder for the first layer was changed to an ionizing radiation curable resin.

(Preparation of coating solution B)
1.2 ml of a nonionic acrylic polymer type dispersant (solid content 40%, SD-10 manufactured by Toa Gosei Co., Ltd.) was dissolved in 150 ml of pure water and adjusted to pH 11 with sodium hydroxide. 400 g of a 25% aqueous dispersion of silica (QS-20 manufactured by Tokuyama) having an average primary particle size of about 12 nm was added thereto and dispersed with a high-speed homogenizer.

  Next, an ionizing radiation-curable polyvinyl alcohol derivative aqueous solution having a stilbazolium group introduced therein and adjusted to a concentration of 10% (Toyo Gosei Kogyo Co., Ltd .: SPP-SHR main chain PVA polymerization degree 2300, saponification degree) 88%) 196 ml was added. Finally, pure water was added so that the total volume became 1000 ml, to obtain a translucent coating solution.

The coating liquid A was applied for the second layer, and the coating liquid B was applied for the first layer, and the coating was performed in the same manner as the preparation of the sample 101. After the application, a metal halide lamp having a dominant wavelength at 365 nm was irradiated with 40 mJ / cm ² of ultraviolet energy, and then cooled at 8 ° C. for 10 seconds. Then, after drying for 60 seconds with a wind of 30 ° C., 60 seconds with a wind of 50 ° C., and 60 seconds with a wind of 70 ° C., the humidity was adjusted at 25 ° C. and a relative humidity of 50% to obtain an ink jet recording sheet 102.

(Preparation of sample 103 of the present invention)
Using the coating liquid A for the first layer and the coating liquid B for the second layer, coating was performed in the same manner as the preparation of the sample 102, and an ink jet recording sheet 103 was obtained.

(Preparation of Sample 104 of the Present Invention)
Except having changed the coating liquid of the 2nd layer into the following coating liquid C, it apply | coated similarly to preparation of the sample 103, and the sheet | seat 104 for inkjet recording was obtained.

(Preparation of coating solution C)
1.2 ml of a nonionic acrylic polymer type dispersant (solid content 40%, SD-10 manufactured by Toa Gosei Co., Ltd.) was dissolved in 150 ml of pure water and adjusted to pH 11 with sodium hydroxide. 400 g of a 25% aqueous dispersion of silica (QS-20 manufactured by Tokuyama) having an average primary particle size of about 12 nm was added thereto and dispersed with a high-speed homogenizer.

  Next, an ionizing radiation-curable polyvinyl alcohol derivative aqueous solution having a stilbazolium group introduced therein and adjusted to a concentration of 10% (Toyo Gosei Kogyo Co., Ltd .: SPP-SHR main chain PVA polymerization degree 2300, saponification degree) 88%) 137 ml, polyvinyl alcohol (Kuraray PVA235) 7% aqueous solution 84 ml and borax 0.7 g were added. Finally, pure water was added so that the total volume became 1000 ml, and a translucent coating solution was obtained.

(Production of Sample 105 of the Present Invention)
An ink jet recording sheet 105 was obtained in the same manner as the preparation of the sample 103 except that the coating solution for the second layer was changed to the following coating solution D.

(Preparation of coating solution D)
1.2 ml of a nonionic acrylic polymer type dispersant (solid content 40%, SD-10 manufactured by Toa Gosei Co., Ltd.) was dissolved in 150 ml of pure water and adjusted to pH 11 with sodium hydroxide. 400 g of a 25% aqueous dispersion of silica (QS-20 manufactured by Tokuyama) having an average primary particle size of about 12 nm was added thereto and dispersed with a high-speed homogenizer.

  Next, an ionizing radiation-curable polyvinyl alcohol derivative aqueous solution having a stilbazolium group introduced therein and adjusted to a concentration of 10% (Toyo Gosei Kogyo Co., Ltd .: SPP-SHR main chain PVA polymerization degree 2300, saponification degree) 88%) 78 ml, polyvinyl alcohol (Kuraray PVA235) 7% aqueous solution 168 ml and borax 0.7 g were added. Finally, pure water was added so that the total volume became 1000 ml, and a translucent coating solution was obtained.

  Each recording sheet produced as described above was evaluated for film surface properties during production and flexibility of the ink receiving layer in accordance with the method described below.

  Film surface properties: The occurrence of cracks on the film surface after sample preparation was visually evaluated using a comparative sample 101 as a reference (reference point 3) and evaluated in five stages of 1 to 5 points. 1 is the most cracked and 5 is the best.

  Flexibility of ink receiving layer: Each sample was conditioned at 23 ° C. and 20% relative humidity for 24 hours, and then wound around a cylindrical stainless steel cap having diameters of 10 mm, 20 mm, 30 mm, and 40 mm, respectively, and the ink receiving layer cracked. The order of the bars was examined visually to determine the order between the samples. If the comparative sample 101 is a reference (reference point 3) and the crack is cracked by a cylinder having a diameter larger than that of the sample 101, the evaluation point is small, and if it is good, the evaluation point is high.

  From the results shown in Table 1, it can be seen that the inkjet recording sheet of the present invention has improved flexibility during handling without losing the crack resistance during production. Further, the higher the mass ratio of the ionizing radiation curable resin contained in the second layer, which is the ink receiving layer farthest from the support, to the total hydrophilic binder of the layer, that is, 40% to 70%, It can also be seen that 100% is more preferable than 70%.

Claims (4)

Inkjet recording having an ink receiving layer containing at least two layers of porous material on a support, and at least one hydrophilic binder of the ink receiving layer being cured by ionizing radiation and a hardener An ink jet recording sheet, wherein the ink receiving layer located farthest from the support contains an ionizing radiation curable resin as a hydrophilic binder. 2. The ink jet recording sheet according to claim 1, wherein the ionizing radiation curable resin is a compound that is cured by ultraviolet rays. The ink jet recording sheet according to claim 1 or 2, wherein the ionizing radiation curable resin is a resin modified with a photodimerization type or photopolymerization type modification group. The ink-jet recording sheet according to any one of claims 1 to 3, wherein the ink-receiving layer is coated on a support, and then the hydrophilic binder of the ink-receiving layer is cured by ionizing radiation irradiation and a hardening agent. A method for producing an inkjet recording sheet.