JP2007130965A - Manufacturing method for inkjet recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method which enables the inexpensive manufacture of high-gloss inkjet recording paper having a porous ink absorbing layer with improved ink absorbency. <P>SOLUTION: This manufacturing method is used for manufacturing the inkjet recording paper in which a porous layer, containing inorganic particulates and a hydrophilic polymer crosslinked by ionizing radiation, is provided on a substrate. The manufacturing method for the inkjet recording paper is characterized in that the ionizing radiation is emitted on condition that the volume ratio of the hydrophilic polymer, crosslinked by the ionizing radiation, to the inorganic particulates is in the range of 15-33%, and immediately after coating and/or within the time when the moisture content of a coated film is in the range of 190-450%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an ink jet recording paper (hereinafter, also simply referred to as a recording paper), and more particularly to a method for manufacturing an ink jet recording paper having excellent ink absorbability, high gloss and no coating failure.

  In recent years, in the ink jet recording system, image quality has been improved rapidly, and the image quality is approaching that of silver halide photography. As a means for achieving such a silver salt photographic image quality by the ink jet recording method, rapid technical improvement is also being made on the ink jet recording paper to be used.

  As an ink receiving layer generally used for ink jet recording paper, for example, an ink jet recording paper used as an ink receiving layer by applying a hydrophilic resin such as gelatin or polyvinyl alcohol as an ink absorbing layer on a support having high smoothness. It has been known. This type of recording paper is a method of absorbing ink by utilizing the swelling property of resin, and is called a swelling type ink jet recording paper.

  This swelling type ink receiving layer is composed of a water-soluble resin, so that it is difficult to dry the ink after printing, the image and film are weak against moisture and poor in water resistance, and the resin swells. Ink absorbs slowly, and the printing surface does not dry for a while after printing, which makes it unsuitable for high-speed printing.

  For swelling ink jet recording paper of a type that absorbs ink by utilizing the swelling property of the water-based resin, for example, inorganic fine particles as in Patent Document 1 and a relatively small amount of hydrophilic resin are used to form voids between the fine particles. There is an ink jet recording paper having an ink absorption layer formed of a porous layer having a high porosity. A void-type ink jet recording paper provided with a porous layer having such minute voids as an ink absorbing layer has a relatively high ink absorbability and quick-drying property, and the one closest to the silver salt photographic image quality is obtained. Is one of the methods.

  In particular, when a non-water-absorbing support is used as the support, there is no cockling (wrinkles) after printing as seen on a water-absorbing support, and a high smooth surface can be maintained, resulting in higher quality print printing. Can be obtained.

  In the case of recording paper using such a non-water-absorbing support, since it is necessary to absorb all of the ink ejected from the printer with the ink receiving layer, the ink receiving layer requires a large amount of coating, In many cases, the coating was relatively thick.

  In general, as a method of applying and drying a coating liquid on a support, there are methods of drying by applying hot air to the surface of the coated coating liquid, or heating and drying with infrared rays or the like. However, when a thick film is applied as described above, convection due to the wind pressure of the hot air or the heat of the coating liquid occurs, the coating liquid flows and the coating layer becomes non-uniform, or drying shrinkage occurs. The coating layer may be cracked or cracked due to stress.

  In order to solve the above problem, for example, as disclosed in Patent Document 2, a method of adding a crosslinking agent to a coating solution of polyvinyl alcohol and inorganic fine particles to increase the strength of the coating film has been proposed.

  However, since boric acid is water-soluble, the porous layer to which boric acid is added is not very strong in water resistance, and a large amount of water is printed on the print surface due to exposure to wind and rain during outdoor exhibitions. When it takes a long time, the boric acid and the binder in the porous layer are eluted, resulting in a problem that the strength of the film is lowered and the printed surface is cracked or the gloss is lowered.

  Furthermore, in this crack prevention method, a crosslinking agent such as boric acid is added to the coating solution, and the amount of the binder resin relative to the inorganic fine particles is relatively large, and the molecular weight of the binder resin needs to be increased. For this reason, even if the solid content concentration of the coating solution is low, the viscosity tends to increase. Therefore, it is necessary to dilute the coating solution to a viscosity at which coating is possible. There was also a problem that the manufacturing cost was high.

  In addition, crosslinking agents other than boric acid that are generally used for hydrophilic resins, such as epoxy compounds, aldehyde compounds, active halogen compounds, active vinyl compounds, and the like, all of which are more than boric acid. The crosslinking reactivity was poor, and there was little effect on cracks and cracks due to drying shrinkage of the coating layer.

  On the other hand, in Patent Documents 3 and 4, after applying a coating liquid mainly composed of an inorganic sol and an ionizing radiation curable monomer / oligomer, and then irradiating with ionizing radiation to cure the compound, A method of forming an ink receiving layer by drying a coating film has been proposed. In this method, since the monomer / oligomer is used as the binder resin, the viscosity of the coating solution is lowered, and the coating solution can be concentrated, so that the drying load is considered to be reduced.

However, in general, ionizing radiation curable monomers / oligomers and the like have a relatively low molecular weight and strong skin irritation, and there are concerns about adverse effects on printing quality due to unreacted components and safety. There was a fault that there were many. Furthermore, since most of the compounds on the market have low hydrophilicity, they are not suitable for water-based coating generally used for coating an ink-jet receiving layer, and there is a problem that the range of material selection is naturally extremely narrow.
JP 10-119423 A JP-A-10-175364 Japanese Patent Laid-Open No. 9-263038 Japanese Patent No. 3333338

  An object of the present invention is to provide a manufacturing method for manufacturing a high-gloss inkjet recording paper having a porous ink absorbing layer with improved ink absorbability at low cost.

  The above-mentioned subject is achieved by the following composition and manufacturing method.

  1. A method for producing an ink jet recording paper, wherein a porous film containing a hydrophilic polymer compound and inorganic fine particles that are crosslinked by ionizing radiation is applied on a support to form a coating film, and then the coating film is irradiated with ionizing radiation. Irradiating with ionizing radiation when the volume ratio of the hydrophilic polymer compound crosslinked by ionizing radiation to the inorganic fine particles is 15% or more and 33% or less and the moisture content of the coating film is 190% or more and 450% or less. A method for producing an ink jet recording paper characterized by the above.

  2. Irradiating with ionizing radiation when the volume ratio of the hydrophilic polymer compound crosslinked by ionizing radiation to the inorganic fine particles is 18% or more and 30% or less and the moisture content of the coating film is 190% or more and 350% or less. 2. The method for producing an inkjet recording paper as described in 1 above.

  3. 3. The method for producing an ink jet recording paper according to 1 or 2, wherein the inorganic fine particles are silica, alumina, or alumina hydrate having an average particle diameter of 0.005 to 0.4 μm.

  4). 4. The method for producing an ink jet recording paper according to any one of 1 to 3, wherein the hydrophilic polymer compound that is cross-linked by ionizing radiation is a nonionic compound.

  5. 5. The inkjet recording according to any one of 1 to 4, wherein the hydrophilic polymer compound that is cross-linked by ionizing radiation is a saponified polyvinyl acetate containing a structural unit represented by the following general formula (1): Paper manufacturing method.

[Wherein, R ₁ represents a hydrogen atom or a Me group, X represents — (CH ₂ ) _m —CO—O— or —O—, Y represents an aromatic ring or a single bond, and n represents 1 or 2 and m represents an integer of 0-6. ]
6). 6. The method for producing an inkjet recording paper as described in 5 above, wherein the degree of polymerization of the saponified polyvinyl acetate crosslinked by ionizing radiation is 500 to 4000.

  7). 7. The method for producing an inkjet recording paper according to any one of 1 to 6 above, comprising at least one water-soluble photoinitiator.

  8). 8. The method for producing an inkjet recording paper according to any one of 1 to 7, wherein the support is non-water-absorbing.

9. 9. The method for producing an inkjet recording paper according to any one of 1 to 8, wherein the ionizing radiation to be irradiated is ultraviolet rays having an irradiation energy of 1 to 300 mJ / cm ^{2 at} a wavelength of 350 nm.

  10. A method for producing an ink jet recording paper, wherein a porous film containing a hydrophilic polymer compound and inorganic fine particles that are crosslinked by ionizing radiation is applied on a support to form a coating film, and then the coating film is irradiated with ionizing radiation. In the above, the volume ratio of the hydrophilic polymer compound that is crosslinked by ionizing radiation to the inorganic fine particles is 15% or more and 33% or less, and immediately after coating, and the moisture content of the coated film is 190% or more and 450% or less. Each of which is irradiated at least once.

  11. The volume ratio of the hydrophilic polymer compound that is crosslinked by ionizing radiation to the inorganic fine particles is 18% or more and 30% or less, and the ionizing radiation is applied immediately after coating and while the moisture content of the coating film is 190% or more and 350% or less. 11. The method for producing an ink jet recording paper as described in 10 above, wherein the irradiation is performed at least once.

  12 12. The method for producing an inkjet recording paper according to any one of 10 or 11, wherein the inorganic fine particles are silica, alumina, or alumina hydrate having an average particle diameter of 0.005 to 0.4 μm.

  13. 13. The method for producing an inkjet recording paper according to any one of 10 to 12, wherein the hydrophilic polymer compound that is cross-linked by ionizing radiation is a nonionic compound.

  14 14. The inkjet recording according to any one of 10 to 13, wherein the hydrophilic polymer compound that is cross-linked by ionizing radiation is a saponified polyvinyl acetate containing the structural unit represented by the general formula (1). Paper manufacturing method.

  15. 15. The method for producing an inkjet recording paper as described in 14 above, wherein the degree of polymerization of the saponified polyvinyl acetate crosslinked by ionizing radiation is 500 to 4000.

  16. 16. The method for producing an ink jet recording paper according to any one of 10 to 15, wherein the method contains at least one water-soluble photoinitiator.

  17. 17. The method for producing an inkjet recording paper according to any one of 10 to 16, wherein the support is non-absorbable.

18. 18. The method for producing an ink jet recording paper according to any one of the above items 10 to 17, wherein the ionizing radiation to be irradiated is ultraviolet rays, and the total irradiation energy at a wavelength of 350 nm is 1 to 300 mJ / cm ^2. .

  According to the present invention, it was possible to provide a manufacturing method for manufacturing a high-gloss inkjet recording paper having a porous ink absorbing layer with improved ink absorbability at low cost.

  Hereinafter, the present invention will be described in detail.

  The hydrophilic polymer compound that is cross-linked by ionizing radiation used in the ink receiving layer of the present invention is a water-soluble resin that undergoes a cross-linking reaction by reacting with ionizing radiation such as ultraviolet rays and electron beams. The resin is water-soluble before the reaction, but becomes substantially water-insoluble after the crosslinking reaction. Such a resin is hydrophilic even 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 modifying group, those having a diazo group, a cinnamoyl group, a stilbazonium group or a stilquinolium group introduced are preferable, and a resin 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 Nos. 62-283339, 1-198615, and 60-252341. Photosensitive resins (compositions) described in JP-A-56-67309, JP-A-60-129742, etc., resins that become cationic after curing, such as azide groups that become amino groups by curing treatment, such as Examples thereof include photosensitive resins (compositions) described in JP-A-56-67309. Specifically, for example, the following can be listed.

  The photosensitive resin described in JP-A No. 56-67309 includes a 2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following formula (2) in the polyvinyl alcohol structure or the following formula (3). It is a resin composition which has 4-azido-3-nitrophenyl carbonyloxyethylene structure represented by these.

  Specific examples of the photosensitive resin, the constituent components of the resin, and the use ratio thereof are described in the publication.

  On the other hand, JP-A-60-129742 discloses a resin composition having a structure represented by the following formula (4) or the following formula (5) in a polyvinyl alcohol structure as a photosensitive resin.

  As the photopolymerizable modifying group, for example, a resin having a structure represented by the following general formula (1) disclosed in JP-A No. 2000-181062 is preferable from the viewpoint of reactivity.

In the formula, R ₁ represents a hydrogen atom or a Me group, X represents — (CH ₂ ) _m —CO—O— or —O—, Y represents an aromatic ring or a single bond, and n represents 1 or 2 And m represents an integer of 0-6.

  In the hydrophilic polymer compound according to the present invention, the degree of polymerization and the crosslink density affect the strength and flexibility at the time of film formation. If the degree of polymerization is too low or the number of crosslinking-modified groups is too large, cracking and drying during coating and drying will occur. Failure such as breakage of the paint film will occur. In addition, when the degree of polymerization is high, the viscosity of the coating solution increases and it becomes difficult to apply, so it is necessary to dilute the coating solution, which imposes a drying load and makes high-speed drying difficult and increases the manufacturing cost. End up. Therefore, the degree of polymerization is preferably 500 to 4000, and particularly when the degree of polymerization is 1000 to 2000, which is a relatively low degree of polymerization, the suppression of cracks, which is an effect of the present invention, becomes remarkable. Moreover, it is preferable that the modification | denaturation rate of the ionizing radiation reaction crosslinking group with respect to a segment is 4 mol% or less, More preferably, it is 0.01-2 mol%.

  In addition, in this invention, you may use together a conventionally well-known hydrophilic resin in the range which does not impair the objective effect of this invention. Examples of known hydrophilic resins include gelatin, polyvinyl pyrrolidone, pullulan, polyvinyl alcohol or derivatives thereof, polyethylene glycol, hydroxyethyl cellulose, dextran, dextrin, and water-soluble polyvinyl butyral.

  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, 2,4-di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4, 2,4,5-triarylimidazole dimer of 5-diphenylimidazole dimer, benzyldimethyl ketal, 2-benzyl-2-dimethyl Ruamino-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. 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- (2-hydroxy Water-soluble initiators such as 2-propyl) ketone, thioxanthone ammonium salt, and benzophenone ammonium salt are preferable from the viewpoint of cross-linking efficiency because of excellent mixing properties.

  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.

  The ink receiving layer having a porous layer of the present invention contains inorganic fine particles. Examples of inorganic fine particles used in the ink receiving layer include light calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotal Site, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, boehmite, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide and the like.

  These inorganic fine particles may be used in a state of being uniformly dispersed as primary particles, or may be used in a state of being dispersed by forming secondary agglomerated particles.

  The average particle size of the inorganic fine particles is preferably 0.005 to 0.4 μm from the viewpoint of gloss of the ink receiving layer. The average particle size of the inorganic fine particles referred to here is obtained as a simple average value (number average value) by observing the cross section and surface of the void layer with a scanning electron microscope and determining the particle size of a plurality of arbitrary particles. Can do. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

  In the present invention, silica, alumina, or alumina hydrate is particularly preferable from the viewpoint of forming fine voids, and an average particle diameter of 0.01 to 0.4 μm is particularly preferable in terms of gloss of the ink receiving layer of inkjet recording paper. Pseudoboehmite which is silica or alumina synthesized by the gas phase method and alumina hydrate is preferable.

The amount of inorganic fine particles used in the ink receiving layer depends on the type of inorganic fine particles, but is usually 5 to 30 g, preferably 10 to 25 g, per 1 m ^{2 of} inkjet recording paper.

  In the porous layer according to the present invention, the ratio of the hydrophilic polymer compound that is crosslinked by ionizing radiation to the inorganic fine particles is determined by the viscosity of the coating solution, the porosity of the porous layer, and cracks during coating and drying. The smaller the ratio of the hydrophilic polymer compound adhering to the high porosity skeleton formed of inorganic fine particles, the easier it is to crack, and the higher the hydrophilicity to the volume of the inorganic fine particles, regardless of the specific gravity of the inorganic fine particles. The smaller the volume of the molecular compound, the easier it is to crack. On the other hand, when the ratio of the hydrophilic polymer compound increases, the hydrophilic polymer compound fills the voids and the substantial porosity decreases, or the hydrophilicity is relatively higher than other solid contents. The ratio of the polymer compound in the coating liquid increases, and the viscosity of the coating liquid itself increases, resulting in an increase in the drying load accompanying dilution of the coating liquid and an increase in manufacturing cost.

  From these viewpoints, the ratio of the hydrophilic polymer compound to the inorganic fine particles is preferably 15 to 33% by volume. A volume ratio of 33% or less is preferable because the porosity of the porous layer is good, a sufficient void volume can be easily obtained, and the viscosity of the coating solution is reduced. If this ratio is 15% or more and the moisture content of the coating film is irradiated between 190% and 450%, ionizing radiation is preferable because cracks are less likely to occur when the porous layer is applied as a thick film. . More preferably, it is a production method of irradiating ionizing radiation while the ratio is 18% or more and 30% or less and the moisture content of the coating film is 190% or more and 350% or less, and particularly preferably the ratio is 20% or more and 28%. It is as follows.

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. The term “capacity” as used herein refers to the volume of bubbles generated when a unit volume of the coating film is put on water, the volume of water that can be absorbed by the coating film, or the recording paper finally obtained. It is defined as the amount of liquid transfer when the contact time is 2 seconds as measured by the liquid absorbency test method (Bristow method) for paper and paperboard specified in TAPPI 51.

  Various additives can be added to the water-soluble coating liquid for forming the ink receiving layer and the ink absorbing layer according to the present invention. Such additives include, for example, cationic mordants, polyvalent metal compounds, surfactants (eg, cations, nonions, anions, amphoteric surfactants), white background tone modifiers, fluorescent whitening agents, antifungals as mordants. Agents, viscosity modifiers, low-boiling organic solvents, high-boiling organic solvents, latex emulsions, anti-fading agents, ultraviolet absorbers, matting agents, silicone oils and the like.

  As the cationic mordant, a polymer mordant having a primary to tertiary amino group and a quaternary ammonium base is used, but there is little discoloration or deterioration of light resistance during long-term storage, and the mordant ability of the dye is sufficiently high. Therefore, a polymer mordant having a quaternary ammonium base is preferable. A preferred polymer mordant is obtained as a homopolymer of a monomer having the quaternary ammonium base, a copolymer with another monomer, or a condensation polymer.

  Examples of the polyvalent metal compound include metal salts such as aluminum, calcium, magnesium, zinc, iron, zirconium, tin, and lead. Of these, compounds composed of magnesium, aluminum, zirconium, calcium and zinc are preferred because they are colorless. Further, a water-soluble inorganic polymer such as polyaluminum chloride may be used as a salt of water-soluble polyvalent metal ions.

  The use amount of the cationic polymer or the water-soluble polyvalent metal compound is preferably 15% by mass or less, more preferably 12% or less by mass ratio with respect to the inorganic fine particles in order to suppress deterioration of ink absorbability.

  As a method for adding a cationic polymer or a water-soluble polyvalent metal compound, in addition to a method of directly adding to a coating liquid and coating, a cationic resin or a water-soluble polyvalent metal compound can be added after coating and drying of a recording medium. A method of overcoating with an aqueous solution and drying may also be used.

  The support used for the ink jet recording paper of the present invention is preferably a non-water-absorbing support from the viewpoint of obtaining a higher quality print.

  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, Examples thereof include 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 or the like, so-called RC paper.

  In applying the water-soluble coating solution on the support, the surface of 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. It is preferable. Further, 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 non-water-absorbing paper support laminated with polyethylene, which is the most preferred polyolefin resin, will be described.

  The base paper used for the paper support is made from wood pulp as the main raw material, and if necessary, synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester is added to the 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 30-70 mass% of sum with the mass% of a mesh remainder is preferable. 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.

  In addition, the polyethylene layer on the side where the ink receiving layer is applied is obtained by adding rutile or anatase type titanium oxide to polyethylene and improving opacity and whiteness, as is widely done in photographic paper. Is preferred. The titanium oxide content is 1 to 20% by mass, preferably 2 to 15% by mass, based on polyethylene.

  Polyethylene-coated paper can be used as glossy paper. Also, when polyethylene is melt-extruded onto the surface of the base paper and coated, so-called typing treatment is used to produce matte surfaces, silks, etc. What formed the fine surface can also be used by this 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, the low humidity after providing the back layer, or the curl under high humidity. The polyethylene layer on the surface side to which the aqueous coating composition is applied is preferably in the range of 20 to 40 μm, and the back layer coating surface side is 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 specified 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 can be provided on the ink-receiving layer surface 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 may be provided on the surface of the support opposite to the ink receiving layer surface 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, and an average. A matting agent having a particle size 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 the production of the ink jet recording paper of the present invention, the coating method used when coating the ink-receiving layer coating liquid on the support can be appropriately selected from known methods, such as a gravure coating method, Roll coating method, rod bar coating method, air knife coating method, spray coating method, extrusion coating method, curtain coating method or extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used. It is done.

  The porous layer according to the recording paper of the present invention may be a single layer or may be composed of two or more layers. When the porous layer is composed of two or more layers, the structures of the ink absorbing layers are the same as each other. Or different. Moreover, when it comprises by two or more layers, it is preferable from a viewpoint of productivity improvement that it is the method of apply | coating all the structural layers simultaneously.

  In one manufacturing method of the ink jet recording paper of the present invention, a porous layer containing a hydrophilic polymer compound and inorganic fine particles that are cross-linked by ionizing radiation is applied to form a coating film, and then drying is started. The ink receiving layer is formed by irradiating with ionizing radiation and then further drying. Further, in another manufacturing method, immediately after forming the coating film by applying the porous layer, the ionizing radiation is irradiated and then drying is started. Then, the ionizing radiation is irradiated again during the drying, and then further dried. An ink receiving layer is formed.

  The reason why the above production method is an effective means for cracking during production even when a hydrophilic polymer compound having a relatively low degree of polymerization that is cross-linked by ionizing radiation is used is considered as follows.

  At the time of application and drying, when the moisture content of the coating film at the initial stage of drying is high, the film shrinks and becomes constant rate drying with drying, but when the moisture content decreases as drying progresses to some extent, Reduced rate drying with no shrinkage of the film with respect to drying. The formation of voids begins before and after the moisture content at which the rate of drying is switched, and the energy of drying shrinkage is accumulated as internal stress, and cracking occurs when the internal stress exceeds the strength of the coating film. In order to prevent such cracks, the strength of the film may be increased so as to counter the accumulated internal stress. For this purpose, the binder resin is generally cross-linked, and the binder resin is increased in amount or increased in molecular weight.

  When a hydrophilic polymer that crosslinks with ionizing radiation is used as a binder resin, it is necessary to bring the crosslinkable groups close to a reactable distance upon irradiation with ionizing radiation. It is considered that the greater the amount, the higher the crosslinking efficiency and the more the cracks are suppressed. Therefore, the higher the concentration of the binder resin in the coating solution, the more advantageous for crosslinking, that is, cracking. On the other hand, when the coating solution is concentrated, the viscosity increases and coating becomes impossible.

  In order to solve this contradiction, after coating, the coating solution may be cross-linked after drying and concentrating to a certain extent, whereby the viscosity at the time of coating is kept low, and the density of the crosslinking group at the time of irradiation with ionizing radiation is high. It is considered that the crosslinking efficiency was increased and cracking was suppressed.

  However, if the coating film is dried too much before being irradiated with ionizing radiation, the coating film is dried at a reduced rate before crosslinking, and internal stress is accumulated, and cracking occurs before irradiation with ionizing radiation.

  The amount of internal stress accumulated and the amount of cross-linking necessary to prevent cracking differ depending on the amount of inorganic fine particles and the degree of polymerization of the binder resin, so the coating solution to be irradiated with ionizing radiation that is optimal for cracking prevention is dried. Although the state differs, if the coating film is dried until the moisture content of the coating film is 450% or less and then irradiated with ionizing radiation, the crosslinking density of the coating solution becomes sufficiently high to increase the crosslinking efficiency, and cracks are suppressed. The Further, if the ionizing radiation is irradiated in a state where the moisture content of the coating film is 190% or more, the internal stress that causes cracking in the coating film is not accumulated, and it is not cracked before the ionizing radiation is irradiated.

  If ionizing radiation is irradiated in this region, even if the volume ratio of the hydrophilic polymer compound cross-linked by the ionizing radiation to the inorganic fine particles is relatively small such as 35% or less, the hydrophilic polymer cross-linked by the ionizing radiation. Even if the degree of polymerization of the compound is 1000-2000, cracking of the coating film is suppressed, the coating liquid also has a low viscosity at a high solid content concentration, and the drying load is reduced, resulting in an increase in production efficiency. Moreover, since the amount of the binder resin relative to the inorganic fine particles is small, the amount of the binder resin that fills the voids formed is small, the void diameter and void ratio are increased, and the ink absorption speed during printing is increased, and The ink absorption amount is also increased, and mottle and beading during high-speed printing can be suppressed.

  Furthermore, it is more preferable to irradiate ionizing radiation while the moisture content of the coating film is 190% or more and 350% or less.

  In addition, the moisture content of a coating film is calculated from the mass in the middle of drying after application | coating, and the mass of the applied solid content, and can be computed from the following formula | equation.

  In another production method of the present invention, immediately after the porous layer is applied and the coating film is formed, the ionizing radiation is irradiated and then drying is started. Then, the ionizing radiation is irradiated again during the drying, and then further drying is performed. In this case, the drying process is preferably performed at the same moisture content of the coating film as described above.

  The term “immediately after application” refers to the period from when the coating liquid is applied to the support until before substantial drying is started by a heater or hot air.

  If the drying air is strong during drying, the drying time can be shortened. However, a part of the coating film may be moved by the drying air and blown unevenness, which is a streak-like failure, may occur. On the other hand, if ionizing radiation is irradiated immediately after coating, some of the cross-linking groups are cross-linked, and the coating film thickens and gels. Is less likely to occur. As a result, drying with stronger drying air is possible, and the drying time is shortened to increase production efficiency.

  Examples of the ionizing radiation in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X-rays. In view of the widespread use of electron beam, ultraviolet rays or ultraviolet rays are preferable.

  Examples of the electron beam irradiation method include a scanning method, a curtain beam method, and a broad beam method. The curtain beam method is preferable from the viewpoint of processing capability. The acceleration voltage of the electron beam can be changed as appropriate depending on the specific gravity and film thickness of the coating film, but 20 kV to 300 kV is appropriate. The irradiation amount of the electron beam is preferably in the range of 0.1 to 20 mRad.

  As the ultraviolet light source, for example, a low pressure, medium pressure, high pressure mercury lamp, metal halide lamp or the like having an operating pressure of 100 Pa to 100 kPa is used. From the viewpoint of the wavelength distribution of the light source, a high pressure mercury lamp and a metal halide lamp are preferable. More preferred.

In particular, when the wavelength of the light source includes ultraviolet rays of 250 nm or less, or when the irradiation energy exceeds 100 J / cm ² , the core of the ionizing radiation crosslinkable resin or various coexisting additives is decomposed by ionizing radiation. In addition to not being able to obtain the effects of the present invention, there is a possibility that problems such as odor derived from the decomposition products may occur. On the contrary, 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 sufficiently obtained. Therefore, it is preferable to provide a filter that cuts off light having a wavelength of 250 nm or less as the light source. The output of the lamp is preferably 100 W to 30 kW, and the illuminance is preferably 1 mW / cm ^{2 to} 10 kW / cm ² . It is more preferably preferably 1mJ / cm ² ~300mJ / cm ² at a wavelength of 350 nm, it is 1mJ / cm ² ~100mJ / cm ² as the sum of the irradiation energy.

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.

  When irradiation with ionizing radiation is performed immediately after application and during drying, the distribution of irradiation energy immediately after application and during drying is the amount of irradiation energy that gels to the extent that the coating film is not blown by dry air. Rather, the more the remaining amount of the crosslinking group or photoinitiator at the time of irradiation during drying, the higher the final crosslinking efficiency, which is advantageous in suppressing cracking. Therefore, it is preferable that the irradiation energy immediately after coating is less than the irradiation energy during drying, and the irradiation energy immediately after coating is more preferably in the range of 0.5% to 20% of the irradiation energy during drying.

  The drying method may be drying by a known method such as heating with an oven or heater, or drying by blowing warm air like a dryer, but if the temperature is too high, the water will boil and the film surface will be rough, or The support may be deformed by heat. On the other hand, if the film surface temperature is too low, it takes a long time to dry and the production efficiency is lowered. Therefore, the condition of the film surface temperature in the range of 10 to 80 ° C. is preferable, and it is more preferable to blow with a wind of 20 ° C. or more from the viewpoint of shortening the drying time and obtaining a uniform film surface.

  When recording an image using the ink jet recording paper of the present invention, a recording method using water-based ink is preferably used.

  The water-based ink is a recording liquid having the following colorant, liquid medium, and other additives. As the colorant, water-soluble dyes or water-dispersible pigments such as direct dyes, acid dyes, basic dyes, reactive dyes or food dyes known for inkjet can be used.

  Examples of water-based ink solvents include water and various water-soluble organic solvents, for example, alcohols such as methyl alcohol, isopropyl alcohol, butyl alcohol, tert-butyl alcohol, and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; acetone , Ketones such as diacetone alcohol or ketone alcohols; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6 -Polyhydric alcohols such as hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, glycerin, triethanolamine , Ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether. Of these, polyhydric alcohols such as diethylene glycol, triethanolamine and glycerin, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether are preferable.

  Examples of other water-based ink additives include pH adjusters, metal sequestering agents, fungicides, viscosity modifiers, surface tension adjusters, wetting agents, surfactants and rust inhibitors.

  In order to improve the wettability with respect to the recording paper, the water-based ink liquid usually has a surface tension within a range of 0.025 to 0.06 N / m, preferably 0.03 to 0.05 N / m at 20 ° C. It is preferable to have. The pH of the ink is preferably 5 to 10, particularly preferably 6 to 9.

  Hereinafter, although an example is given and the effect of the present invention is explained, the present invention is not limited to these examples. In the examples, “%” represents mass% unless otherwise specified.

(Preparation of polymer compound crosslinked by ionizing radiation)
With reference to JP-A No. 2000-181062, p- (3-methacryloxy-2-hydroxypropyloxy) benzaldehyde is reacted with polyvinyl alcohol having a polymerization degree of 1700 and a saponification degree of 99.8%. An aqueous solution of a UV-polymerizable polyvinyl alcohol derivative having a structure (crosslinking group modification rate 1 mol%, solid content concentration 10%, solid content specific gravity 0.98 g / cm ³ ) was prepared.

Example 1
(Preparation of recording paper 1-1)
Gas phase method silica (specific gravity 2) having an average primary particle diameter of 12 nm and a specific surface area of 200 m ² / g measured by BET method in 700 ml of 1% ethanol aqueous solution adjusted to pH 3.5 with nitric acid using a high-speed stirring disperser. 0.2 g / cm ³ ) 190 g was gradually added and dispersed. Next, 76 g of a 25% aqueous solution of the following cationic polymer was added to this liquid, the pH was adjusted to 4.0 with a 10% aqueous sodium acetate solution, and the average secondary particle size of the inorganic fine particles in the dispersion was further 0.3 μm or less with a sand mill. Finally, pure water was added to finish 1000 g.

  While stirring this dispersion at 40 ° C., 288 g of the aqueous solution of the UV-polymerizable polyvinyl alcohol derivative and 0.8 g of a photopolymerization initiator (Kayacure QTX manufactured by Nippon Kayaku Co., Ltd.) were gradually added while stirring, and 1350 g of pure water was added. The coating liquid was prepared. In addition, the average secondary particle diameter of the inorganic fine particles in the dispersion is a value measured by diluting the dispersion 10 times and using a dynamic light scattering particle diameter measuring apparatus Zatasizer Nano-S (manufactured by Malvern). It is.

The coating liquid prepared above was coated with polyethylene on both sides of a base paper having a thickness of 170 g / m ² (containing 8% by mass of anatase-type titanium oxide in polyethylene on the ink receiving layer side; 0 on the ink receiving layer side). .05 g / m ² gelatin undercoat layer, latex polymer with Tg of about 80 ° C. on the opposite side as back layer 0.2 g / m ² ), coated at 40 ° C. with wet coat thickness of 120 μm by bar coater Then, it is dried in a hot air oven at 60 ° C. adjusted so that the wind speed of the coating surface is 8 m / sec until the moisture content of the coating film becomes 240%, and immediately after that, the energy amount is measured with a metal halide lamp having a main wavelength of 365 nm. Was irradiated with 40 mJ / cm ² of ultraviolet rays. This sample was completely dried in the oven to obtain inkjet recording paper 1-1. The volume ratio of the hydrophilic polymer compound crosslinked by ionizing radiation to the inorganic fine particles (volume of hydrophilic polymer compound crosslinked by ionizing radiation / volume of the inorganic fine particles) is the BP ratio (%) and the surface of the recording paper. Table 1 shows the average secondary particle diameter determined by observation with an electron microscope.

(Preparation of recording sheets 1-2 to 1-12)
In the production of the recording paper 1-1, the BP ratio and the moisture content of the coating film at the time of ultraviolet irradiation were changed as shown in Table 1 to produce recording papers 1-2 to 1-12. The recording sheets 1-4 and 1-9 were cracked on the film surface immediately before the moisture content reached 180% during drying before irradiating with ultraviolet rays, but were irradiated with ultraviolet rays as they were and then dried. Recording paper was produced.

(Preparation of recording paper 1-13)
In the production of the recording paper 1-1, a coating solution was prepared by changing the BP ratio as shown in Table 1, but the coating was not possible due to the high viscosity.

(Evaluation of each characteristic of recording paper)
Each recording paper produced as described above was evaluated by the methods described below. The results are shown in Table 1.

[Evaluation of crack resistance]
The surface of the ink receiving layer of each recording sheet prepared above was observed with a magnifying glass, and the number of cracks on the film surface generated in 100 cm ² was counted, which was used as a measure of crack resistance.

◎: 3 or less ○: 10 or less △: 20 or less ×: 21 or more [Glossiness Evaluation]
The 60 ° gloss was measured using a variable angle gloss meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd.

A: Glossiness is 30% or more B: Glossiness is 25% or more and less than 30% B: Glossiness is 20% or more and less than 25% X: Glossiness is less than 20% [Evaluation of ink absorbency]
Blue solid printing was performed with an Seiko Epson inkjet printer, PM950C, and the occurrence of madras in the image portion was visually evaluated according to the following evaluation criteria. When the ink absorption speed is low, the occurrence of spotting becomes large.

〔Evaluation criteria〕
◎: There is no madara ○: Slightly madara is observed when the image surface is observed △: Madara is observed even if observed 15 cm away from the image surface ×: Madara is observed even if observed 30 cm away from the image surface Be

  As is apparent from Table 1, the recording paper of the present invention satisfies both glossiness and high ink absorptivity at the same time, and it is difficult to cause cracks during production. On the other hand, the recording paper of the comparative example was inferior in production suitability, such as being cracked during production.

(Example 2)
(Preparation of recording paper 2-1)
Gas phase method silica (specific gravity 2) having an average primary particle diameter of 12 nm and a specific surface area of 200 m ² / g measured by BET method in 700 ml of 1% ethanol aqueous solution adjusted to pH 3.5 with nitric acid using a high-speed stirring disperser. 0.2 g / cm ³ ) 190 g was gradually added and dispersed. Next, 76 g of a 25% aqueous solution of the cationic polymer (1) was added to this liquid, the pH was adjusted to 4.0 with a 10% aqueous sodium acetate solution, and the average secondary particle size of the inorganic fine particles in the dispersion was further increased by a sand mill. The dispersion was dispersed so as to be 0.3 μm or less, and finally, pure water was added to finish 1000 g.

  While stirring this dispersion at 40 ° C., 288 g of the aqueous solution of the UV-polymerizable polyvinyl alcohol derivative and 0.8 g of a photopolymerization initiator (Kayacure QTX manufactured by Nippon Kayaku Co., Ltd.) were gradually added while stirring, and 1350 g of pure water was added. The coating liquid was prepared. In addition, the average secondary particle diameter of the inorganic fine particles in the dispersion is a value measured by diluting the dispersion 10 times and using a dynamic light scattering particle diameter measuring apparatus Zatasizer Nano-S (manufactured by Malvern). It is.

The coating liquid prepared above was coated with polyethylene on both sides of a base paper having a thickness of 170 g / m ² (containing 8% by mass of anatase-type titanium oxide in polyethylene on the ink receiving layer side; 0 on the ink receiving layer side). .05 g / m ² gelatin undercoat layer and latex polymer with Tg of about 80 ° C. on the opposite side as a back layer 0.2 g / m ² ) at 40 ° C. with a bar coater at a wet film thickness of 130 μm Then, immediately after coating, a metal halide lamp having a dominant wavelength at 365 nm was irradiated with ultraviolet rays having an energy amount of ² mJ / cm ² . Then, it is dried until the moisture content of the coating film becomes 260% in a hot air oven at 60 ° C. adjusted so that the wind speed of the coated surface becomes 20 m / sec, and then irradiated again with ultraviolet rays having an energy amount of 22 mJ / cm ^2. Then, it was completely dried in the oven to obtain ink jet recording paper 2-1. The volume ratio of the hydrophilic polymer compound crosslinked by ionizing radiation to the inorganic fine particles (volume of hydrophilic polymer compound crosslinked by ionizing radiation / volume of the inorganic fine particles) is the BP ratio (%) and the surface of the recording paper. Table 2 shows the average secondary particle diameter determined by observation with an electron microscope.

(Preparation of recording sheets 2-2 to 2-20)
In the production of the recording paper 2-1, the BP ratio, the ultraviolet irradiation energy immediately after coating, the moisture content of the coating film during the ultraviolet irradiation during drying, and the irradiation energy were changed as shown in Table 2, respectively. 2-2 to 2-20 were produced. The recording sheets 2-6 and 2-17 were cracked on the film surface immediately before the moisture content reached 180% during drying before irradiating with ultraviolet rays, but were irradiated with ultraviolet rays as they were and then dried. Recording paper was produced. Recording papers 2-7, 2-14 and 2-19 were prepared without being irradiated with ultraviolet rays immediately after application, and recording paper 2-10 was irradiated with ultraviolet rays immediately after application, and was in the middle of drying. Recording paper was produced without ultraviolet irradiation.

(Preparation of recording paper 2-21)
In the production of the recording paper 2-1, a coating solution was prepared by changing the BP ratio as shown in Table 2, but the coating was not possible due to the high viscosity.

(Evaluation of each characteristic of recording paper)
Each recording paper produced as described above was evaluated by the methods described below. The results are shown in Table 2.

[Evaluation of crack resistance]
The surface of the ink receiving layer of each recording paper prepared above was observed with a magnifying glass, and the number of film surface cracks occurring in 100 cm 2 was counted, and this was used as a measure of crack resistance.

◎: 3 or less ○: 10 or less △: 20 or less ×: 21 or more [Glossiness Evaluation]
The 60 ° gloss was measured using a variable angle gloss meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd.

◎: Glossiness is 30% or more ○: Glossiness is 25% or more and less than 30% △: Glossiness is 20% or more and less than 25% X: Glossiness is less than 20% [Evaluation of blown unevenness (blown rough)]
A neutral gray color with a reflection density of 1.0 is printed on each recording sheet with a Seiko Epson inkjet printer, PM950C, and the printing surface is visually observed to check the unevenness of the ink receiving layer according to the following evaluation criteria. evaluated.

◎: No unevenness △: Slight unevenness is observed when paying attention to solid printing ×: Unevenness is clearly seen with solid printing [Evaluation of ink absorbency]
Blue solid printing was performed with an Seiko Epson inkjet printer, PM950C, and the occurrence of madras in the image portion was visually evaluated according to the following evaluation criteria. When the ink absorption speed is low, the occurrence of spotting becomes large.

〔Evaluation criteria〕
◎: No madara ○: Slight madara is observed when the image surface is closely observed △: Madara is observed even if observed 15 cm away from the image surface ×: Madara is observed even if observed 30 cm away from the image surface Be

  As is apparent from Table 2, it can be seen that the recording paper of the present invention satisfies both glossiness and high ink absorbency at the same time, and is less likely to cause unevenness and cracks when blown during production. On the other hand, the recording paper of the comparative example was inferior in production suitability because it was blown at the time of manufacture, causing unevenness or cracking.

Claims (18)

A method for producing an ink jet recording paper, wherein a porous film containing a hydrophilic polymer compound and inorganic fine particles that are crosslinked by ionizing radiation is applied on a support to form a coating film, and then the coating film is irradiated with ionizing radiation. Irradiating with ionizing radiation when the volume ratio of the hydrophilic polymer compound crosslinked by ionizing radiation to the inorganic fine particles is 15% or more and 33% or less and the moisture content of the coating film is 190% or more and 450% or less. A method for producing an ink jet recording paper characterized by the above. Irradiating with ionizing radiation when the volume ratio of the hydrophilic polymer compound crosslinked by ionizing radiation to the inorganic fine particles is 18% or more and 30% or less and the moisture content of the coating film is 190% or more and 350% or less. The method for producing an inkjet recording paper according to claim 1. The method for producing an inkjet recording paper according to claim 1 or 2, wherein the inorganic fine particles are silica, alumina, or alumina hydrate having an average particle diameter of 0.005 to 0.4 µm. The method for producing an inkjet recording paper according to any one of claims 1 to 3, wherein the hydrophilic polymer compound that is cross-linked by ionizing radiation is a nonionic compound. The inkjet according to any one of claims 1 to 4, wherein the hydrophilic polymer compound crosslinked by ionizing radiation is a saponified polyvinyl acetate containing a structural unit represented by the following general formula (1). Recording paper manufacturing method.

[Wherein, R ₁ represents a hydrogen atom or a Me group, X represents — (CH ₂ ) _m —COO— or —O—, Y represents an aromatic ring or a single bond, and n represents 1 or 2. Yes, m represents an integer of 0-6. ] 6. The method for producing an inkjet recording paper according to claim 5, wherein the degree of polymerization of the saponified polyvinyl acetate crosslinked by ionizing radiation is 500 to 4000. The method for producing an inkjet recording paper according to claim 1, comprising at least one water-soluble photoinitiator. The method for producing an inkjet recording paper according to claim 1, wherein the support is non-water-absorbing. The method for producing an inkjet recording paper according to any one of claims 1 to 8, wherein the ionizing radiation to be irradiated is an ultraviolet ray having an irradiation energy of 1 to 300 mJ / cm ^{2 at} a wavelength of 350 nm. A method for producing an ink jet recording paper, wherein a porous film containing a hydrophilic polymer compound and inorganic fine particles that are crosslinked by ionizing radiation is applied on a support to form a coating film, and then the coating film is irradiated with ionizing radiation. In the above, the volume ratio of the hydrophilic polymer compound that is crosslinked by ionizing radiation to the inorganic fine particles is 15% or more and 33% or less, and immediately after coating, and the moisture content of the coated film is 190% or more and 450% or less. Each of which is irradiated at least once. The volume ratio of the hydrophilic polymer compound that is crosslinked by ionizing radiation to the inorganic fine particles is 18% or more and 30% or less, and the ionizing radiation is applied immediately after coating and while the moisture content of the coating film is 190% or more and 350% or less. The method for producing an inkjet recording paper according to claim 10, wherein the irradiation is performed at least once. The method for producing an inkjet recording paper according to any one of claims 10 and 11, wherein the inorganic fine particles are silica, alumina, or alumina hydrate having an average particle diameter of 0.005 to 0.4 µm. The method for producing an inkjet recording paper according to any one of claims 10 to 12, wherein the hydrophilic polymer compound that is cross-linked by ionizing radiation is a nonionic compound. 14. The inkjet according to claim 10, wherein the hydrophilic polymer compound that is cross-linked by ionizing radiation is a saponified polyvinyl acetate containing a structural unit represented by the general formula (1). Recording paper manufacturing method. The method for producing an ink jet recording paper according to claim 14, wherein the degree of polymerization of the polyvinyl acetate saponified product crosslinked by ionizing radiation is 500 to 4000. The method for producing an inkjet recording paper according to any one of claims 10 to 15, comprising at least one water-soluble photoinitiator. The method for producing an ink jet recording paper according to any one of claims 10 to 16, wherein the support is non-absorbable. 18. The inkjet recording paper according to claim 10, wherein the ionizing radiation to be irradiated is ultraviolet rays, and the total irradiation energy at a wavelength of 350 nm is 1 to 300 mJ / cm ^2. Method.