JP2007069414A - Inkjet recording paper and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording paper which is excellent in cockling resistance, has no possibility of peeling off after preserving a printed image, and has high glossiness and good image copying properties. <P>SOLUTION: The inkjet recording paper is characterized by laminating an undercoating layer comprising a resin prepared by curing a photo-polymerizable oligomer with ultraviolet rays and an ink absorbing layer on at least one face of a substrate having cellulose pulp as a main component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  In recent years, in the ink jet recording system, image quality has been improved rapidly, and approaching silver salt photography. As a means for achieving such a photographic image quality by ink jet recording, technical improvement is rapidly attempted for the ink jet recording paper used.

  As for the support used for the ink jet recording paper, a water-absorbing support such as paper and a non-water-absorbing support such as polyester film and resin-coated paper are generally known.

  The former water-absorbing support, such as plain paper, fine paper, or a porous substrate such as coated paper or cast-coated paper, has the advantage of having high ink absorption capability because the support itself can absorb ink. Further, there is a problem that wrinkles are generated (also referred to as cockling) during production or printing due to the water absorption of the support. In addition, when a dye is used as an ink coloring material, it is difficult to obtain a high-quality print such that the dye penetrates into the support and the maximum density is difficult to obtain and a clear image is difficult to obtain. Furthermore, there is a problem that the print surface is easily scratched by the ink jet recording head due to cockling during printing. In response to the above problem, for example, a method of improving cockling by providing an intermediate layer made of an adhesive and a pigment having a glass transition point of 30 to 60 ° C. between a plain paper substrate and an ink absorbing layer has been proposed. However, the effect is still insufficient and further improvement is required.

  On the other hand, the latter non-water-absorbing support does not have the above-described problems and has an advantage that a high-quality print can be obtained. Examples of the non-water-absorbing support include a plastic resin film support or a support in which both surfaces of paper are covered with a plastic resin film. In particular, the latter is useful in that a high-quality print can be easily obtained. A typical example is a support in which both sides of paper are coated with a polyolefin resin, and porous ink absorption is provided on this support. By providing the layer, it was possible to realize a high gloss photo quality (for example, see Patent Document 2).

  As an example of an ink jet recording paper using another non-absorbing support, an example in which a resin coating layer obtained by curing an unsaturated organic compound by electron beam irradiation is provided on at least one side of the paper and an ink absorption layer is further laminated is shown. (See Patent Document 3).

Further, a technique is disclosed in which a water-dispersible emulsion is coated and dried on a base paper and calendered to heat and smooth the water-dispersible emulsion, thereby improving the surface gloss of the support (for example, (See Patent Document 4).
Japanese Patent Laid-Open No. 5-85035 Japanese Patent No. 3321700 JP-A-9-193533 JP 2004-347722 A

  However, there is a method for improving cockling by an invention in which an intermediate layer composed of an adhesive and a pigment having a glass transition point of 30 to 60 ° C. is provided between the plain paper substrate and the ink absorbing layer described in Patent Document 1. Although proposed, the effect is still inadequate and further improvements are needed.

  Moreover, the inkjet recording paper using the support body which coat | covered both surfaces of the paper of patent document 2 with the polyolefin resin is expensive to manufacture a support body, and implement | achieves the inkjet recording paper used more easily. There were limits. In addition, it is possible to obtain a high-quality printed image due to the high glossiness and high smoothness of the support, but when the printed matter is posted on a tape, particularly after storage at high temperature and high humidity. It has been found that there is a problem that the recording paper is peeled off when the tape is peeled off.

  On the other hand, an ink jet recording paper in which an ink absorbing layer having fine particles and a hydrophilic polymer is laminated on a paper support provided with a resin coating layer obtained by curing an unsaturated organic compound described in Patent Document 3 by electron beam irradiation, Such a film peeling problem is slightly improved, but it is not sufficient. Further, as a new problem, it has been found that gloss and image clarity are completely insufficient, and cracks are likely to occur.

  Further, the technique for improving the surface glossiness of a support by heating and forming a water-dispersible emulsion on a base paper described in Patent Document 4 is a method for producing a water-dispersible emulsion coating solution itself because it is an aqueous coating solution. It has been found that cockling resistance is reduced due to, for example, breaking of hydrogen bonds of paper fibers with water, and only a support having a limit in recovery of cockling resistance can be obtained even after calendering. Furthermore, since the water-dispersible emulsion is softened into a rubber-like shape by heating and forming a film by calendering at a temperature higher than Tg, there is a problem in that it is transferred to a calender roll and soils the roll surface. found.

  Therefore, the present invention has been made in view of the above problems, and its purpose is excellent in cockling resistance, does not cause peeling after storing a printed image, and has high gloss, good image clarity, and cracking. It is an object of the present invention to provide an ink jet recording medium and a method for manufacturing the same.

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

  (1) An ink jet comprising an undercoat layer containing a resin obtained by curing a photopolymerizable oligomer with ultraviolet rays and an ink absorbing layer on at least one surface of a support mainly composed of cellulose pulp. Recording sheet.

  (2) The inkjet recording paper as described in (1) above, wherein the photopolymerizable oligomer is a radical photopolymerizable polyfunctional acrylate.

  (3) The inkjet recording paper as described in (1) or (2) above, wherein the photopolymerizable oligomer is urethane acrylate.

  (4) Any one of (1) to (3), wherein the ink absorbing layer contains a hydrophilic polymer, and the hydrophilic polymer is a compound formed by crosslinking with ionizing radiation. The inkjet recording paper as described in the item.

  (5) The ink jet recording sheet described in any one of (1) to (4), wherein the ink absorbing layer is a void type ink absorbing layer.

  (6) An undercoat layer mainly composed of a resin obtained by curing a photopolymerizable oligomer with ultraviolet rays was applied to at least one surface of a support mainly composed of cellulose pulp, and the surface was calendered. Thereafter, an ink absorbing layer is laminated, and a method for producing an ink jet recording paper.

  (7) The method for producing an ink jet recording paper according to (6), wherein the photopolymerizable oligomer is a radical polymerization type polyfunctional acrylate.

  (8) The method for producing an inkjet recording paper according to (6) or (7), wherein the photopolymerizable oligomer is urethane acrylate.

  (9) Any one of (6) to (8), wherein the ink absorbing layer contains a hydrophilic polymer, and the hydrophilic polymer is a compound formed by crosslinking with ionizing radiation. The manufacturing method of the inkjet recording paper as described in a term.

  (10) The method for producing an inkjet recording paper according to any one of (6) to (9), wherein the ink absorption layer is a void-type ink absorption layer.

  According to the present invention, it is possible to provide an inkjet recording paper that is excellent in cockling resistance, does not cause peeling after storage of a printed image, has high glossiness, good image clarity, and does not crack, and a method for producing the same.

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

  As a result of intensive studies in view of the above problems, the present inventor 1) an undercoat containing a resin obtained by curing a photopolymerizable oligomer with ultraviolet light on at least one surface of a support mainly composed of cellulose pulp. An ink jet recording paper characterized by laminating a layer and an ink absorbing layer, or 2) a resin obtained by curing a photopolymerizable oligomer with ultraviolet rays on at least one surface of a support mainly composed of cellulose pulp. The ink-jet recording paper manufacturing method is characterized by applying an undercoat layer as a component, calendering the surface, and then laminating an ink-absorbing layer. Inkjet recording paper that does not cause peeling, has high glossiness, good image clarity, and does not crack, and a method for producing the same It is up to, which led to the present invention.

  That is, as described above, the method described in Patent Document 1 is still insufficient as an effect of improving cockling, and further improvement is required. However, the ink jet recording paper of the present invention or the ink jet recording is required. The paper manufacturing method solves this problem, and can provide an ink jet recording paper that does not cause cockling and a method for manufacturing the same.

  In addition, the inkjet recording paper described in Patent Document 2 can obtain a high-quality print image due to the high glossiness and high smoothness of the support, but this is expensive to manufacture. In addition, when the printed matter is posted on a tape, there is a problem that the recording paper is peeled off when the tape is peeled off after being stored under high temperature and high humidity. It was found that this phenomenon was caused not by the layer itself but by the peeling of the paper of the support or the interface between the paper and the polyethylene resin layer, and these problems were solved by the inkjet recording paper of the present invention or the method of manufacturing the inkjet recording paper. The present invention has been completed to solve the problem.

  Moreover, in the inkjet recording paper described in the above-mentioned Patent Document 3, the phenomenon that the interface between the paper of the support and the resin coating layer is peeled off is somewhat improved, but it is not sufficient, and as a new problem beyond that, It was found that the gloss and image clarity were completely insufficient, and cracking was likely to occur. This is because when high-energy ionizing radiation such as an electron beam is applied to a paper support provided with a resin coating layer, moisture in the paper support is instantaneously evaporated to form bubbles, resulting in a smooth surface of the resin coating layer. It is easy to deteriorate property and to produce a pinhole in the resin coating layer. When there is a pinhole, when the coating liquid for the ink absorption layer provided on the pinhole is applied, the coating liquid penetrates into the pinhole. As a result, the pushed-out air becomes a bubble nucleus and the ink absorption layer is cracked. The present inventors thought that this was the cause, and completed the present invention to solve these problems.

  Furthermore, the support in which the surface glossiness is improved by heating and forming a water-dispersible emulsion on the base paper described in Patent Document 4 is supported because the water-dispersible emulsion coating liquid itself is an aqueous coating liquid. Cockling resistance is reduced due to, for example, breaking hydrogen bonds of paper fibers with water at the time of body production, and only a support that has a limit in recovery of cockling resistance can be obtained even after calendering. I understood. Furthermore, since the water-dispersible emulsion is softened in a rubber-like form to heat and form a film by calendering at a temperature higher than Tg, there is a problem that it is transferred to a calender roll and the roll surface is soiled. The present invention has been completed to solve these problems.

  In response to the above problems, the inkjet recording paper of the present invention and the method for producing the same cause the phenomenon of instantaneous evaporation of moisture in the paper support by using ultraviolet rays that are lower in energy than electron beams. In other words, the above-described problems of gloss, image clarity, and cracks have been solved.

  The support mainly composed of cellulose pulp, which can be exemplified by plain paper and fine paper, is coated with the photopolymerizable oligomer of the present invention or a photopolymerizable oligomer solution (preferably a non-aqueous solution), etc., and is cured by ultraviolet rays. Therefore, it is considered that the undercoat layer can be formed without affecting the bonding of the paper fibers of the support, and thus the cockling resistance at the time of production can be satisfied. Further, by providing the base material mainly composed of cellulose pulp with the undercoat layer according to the present invention, it is possible to prevent cockling that is likely to occur when the ink absorbing layer is formed and during printing. I believe that.

  In particular, in the present invention, the solvent used in the coating solution for forming the undercoat layer is preferably a non-aqueous solvent in terms of preventing the occurrence of cockling during production. Further, it is preferable to form the undercoat layer by irradiating with ultraviolet rays at the same time or within a short time when the undercoat layer forming coating solution is applied.

  Details of the present invention will be described below.

  In the inkjet recording paper of the present invention, an undercoat layer containing a resin obtained by curing a photopolymerizable oligomer with ultraviolet rays and an ink absorbing layer are laminated on at least one surface of a support mainly composed of cellulose pulp. It is characterized by that.

  The photopolymerizable oligomer according to the present invention is a polymer having about 2 to 20 repeating units of a monomer and having 2 to 6 double bond reactive groups, and is also called a prepolymer. It is preferable that the polyfunctional acrylates or photocationic polymerization type oligomers are used. In particular, the photo radical polymerization type polyfunctional acrylates are not easily affected by humidity and temperature during UV curing, and can be stably used for inkjet recording paper. It is preferably used because it can be provided.

  As the photo radical polymerization type polyfunctional acrylates, the following compounds are known (reference: “photocuring technology” technical information association, p3-5).

For example,
(1) Bisphenol type epoxy resin or epoxy acrylates,
(2) urethane acrylates,
(3) polyester acrylates,
(4) polyether acrylates,
(5) Reactive polyacrylates synthesized by reacting side chain epoxy groups with acrylic acid,
(6) Acid-modified epoxy acrylates having a carboxyl group,
(7) Acid-modified reactive polyacrylates having a carboxyl group,
Etc.

  Urethane acrylates are particularly preferably used as the photopolymerizable oligomer in terms of further improving the adhesion between the support mainly composed of cellulose pulp and the undercoat layer, which is one of the objects of the present invention.

  Urethane acrylate is a resin obtained by reacting a polyhydric isocyanate such as tolylene diisocyanate and a hydroxyl group-containing acrylic ester such as 2-hydroxyethyl acrylate, and further a polyhydric alcohol as necessary. As a specific example, Polyester (ethylene glycol, adipic acid), tolylene diisocyanate, 2-hydroxyethyl acrylate, polyether (polyethylene glycol), tolylene diisocyanate, 2-hydroxyethyl methacrylate, hydroxyethylphthalyl methacrylate, xylene diisocyanate, 1,2-polybutadiene Glycol, tolylene diisocyanate, 2-hydroxyethyl methacrylate, trimethylolpropane, propylene glycol, tolylene diisocyanate Etc. Installation Methods Installation Guide 2-hydroxyethyl acrylate.

  In the preparation of the coating solution containing the photopolymerizable oligomer according to the present invention, various reactive monomers can be used in combination for the purpose of adjusting the viscosity of the coating solution.

  The reactive monomer that can be used in the present invention includes, for example, a photopolymerizable monomer. If the viscosity of the coating liquid composed of the photopolymerizable oligomer alone is too high, the viscosity of the coating liquid can be reduced by reducing the viscosity. The main purpose of the adjustment is to adjust, but this makes it possible to provide a highly smooth ink jet recording sheet with higher smoothness by leveling the surface on which the undercoat layer is applied.

  Furthermore, by reacting and curing itself, the film strength of the undercoat layer can be increased and the flexibility can be controlled.

  Specific examples of the reactive monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, cellosolve (meth) acrylate, methyl cellosolve (meth) acrylate, butyl cellosolve (meth) acrylate, carbitol (meth) ) Acrylate, methyl carbitol (meth) acrylate, butyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, dicyclopentadienyloxyethyl (meth) acrylate, vinyl acetate , N-vinylpyrrolidone, tetraethylene glycol mono (meth) acrylate, polybutylene glycol mono (meth) acrylate, polycaprolactone mono (meth) acrylate, phenylglycol Monofunctional unsaturated compounds such as diether (meth) acrylic acid adducts and polyethylene glycol di (meth) acrylate, polybutylene glycol di (meth) acrylate, polycaprolactone di (meth) acrylate, 1,6-hexanediol di Bifunctional unsaturated compounds such as (meth) acrylate and neoventyl glycol di (meth) acrylate are exemplified.

  Of these, polyfunctional acrylates having two or more functional groups are preferable in terms of contributing to improvement in film strength by curing, and having no skin irritation or odor, and in particular, bifunctional acrylates are excellent in viscosity reducing ability. Since the volumetric shrinkage ratio is relatively small, it can be preferably used from the viewpoint that an undercoat layer excellent in adhesion to the support or the ink absorbing layer can be formed. Particularly preferred in these respects are bifunctional acrylates of polyhydric alcohols such as polyethylene glycol diacrylate.

  Moreover, in preparation of the coating liquid containing the photopolymerizable oligomer which concerns on this invention, in order to adjust the viscosity of a coating liquid, various solvents can also be used together.

  As the solvent used here, it is preferable to use an organic solvent so as not to swell the cellulose in the support and cause curling, and therefore the coating solution for the undercoat layer of the present invention may contain substantially no water. preferable.

  Examples of the organic solvent include ester solvents such as ethyl acetate and butyl acetate, aromatic solvents such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene, isononanoic acid, isomyristic acid, hexadecanoic acid, Higher fatty acid solvents such as isopartic acid, oleic acid and isostearic acid, ester solvents, alcohol solvents such as methanol, ethanol, isopropanol and t-butyl alcohol, phenol solvents such as phenol and parachlorophenol, dimethylformamide, Amide solvents such as dimethylacetamide and dimethyl sulfoxide, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, ether solvents such as ethylene glycol monobutyl ether, chloroform, dichloromethane and dichloromethane Halogenated hydrocarbon solvents such as ethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, cellosolve solvents such as ethyl cellosolve and butyl cellosolve, sulfoxide solvents, pyridine, triethylamine, 2-pyrrolidone, N-methyl-2-pyrrolidone , Acetonitrile, butyronitrile, carbon disulfide, tetrahydrofuran and the like can be used. You may use these 1 type or in mixture of 2 or more types. Particularly preferred organic solvents include ester solvents such as ethyl acetate.

  Various organic solvents such as those mentioned above can be used, but organic solvents that change the hydrogen bonding properties in paper substrates such as ethylene glycol, diene glycol, triethylene glycol, and glycerin rather deteriorate the curl characteristics. It is better not to use because of concern.

  When the photopolymerizable oligomer according to the present invention is cured by ultraviolet rays, it is preferable that a photopolymerization initiator and a photosensitizer coexist. These compounds may be dissolved or dispersed in a solvent, or may be chemically bonded to the photopolymerizable oligomer.

  The photopolymerization initiator and photosensitizer that can be used in the present invention are not particularly limited, and conventionally known ones can be used. Examples of photopolymerization initiators and photosensitizers include benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone, etc. Benzophenones; thioxanthones such as thiooxaton, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, isopropoxychlorothioxanthone; anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone, chloroanthraquinone; acetophenones; benzoin methyl ether, etc. 2,4,6-trihalomethyltriazines; 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) Nyl) -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, 2,4,5-triarylimidazole dimer of 2- (2,4-dimethoxyphenyl) -4,5-diphenylimidazole dimer, benzyldimethyl ketal 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) pheny ] -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, ethylbenzoin, 9-phenylacridine, 1,7-bis (9,9'-acridinyl) heptane, etc. Acridine derivatives, bisacylphosphine oxides, and mixtures thereof, and the like may be used alone or in combination.

  Of the above compounds, acetophenones are preferred in terms of good radical production efficiency.

  The amount of the compound added is generally 0.5 to 20% by mass, preferably 2 to 10% by mass, based on the photopolymerizable oligomer.

  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.

  Although there is no restriction | limiting in particular as the film thickness of the undercoat which concerns on this invention, It is about 0.5-10 micrometers in general, If it is 0.5 micrometer or more, the penetration effect of water will be remarkable and will suppress generation | occurrence | production of cockling. Can do. Moreover, if it is 10 micrometers or less, generation | occurrence | production of the curl at the time of handling an inkjet recording paper in various temperature / humidity environment can be prevented effectively.

  It is preferable because the gloss can be remarkably improved by subjecting the undercoat layer to calendar treatment simultaneously with or after the formation of the undercoat layer according to the present invention.

  Examples of the calendar process applicable to the present invention include a super calendar, gloss calendar, machine calendar, and soft calendar. In the calendering process, the support provided with the undercoat layer is subjected to pressure by applying a nip (gap) between the metal roll and another roll, pressure treatment by shearing force, and heat treatment by heat. It improves surface gloss. As the metal roll, a roll made of steel or the like is generally used as a protective layer by spraying nickel, chromium, ceramic or the like, and the surface is polished so as to have a specular gloss. As another roll combined with the metal roll, a metal roll, an elastic roll, or the like is used, but an elastic roll is preferable in terms of uniformity of gloss on the surface of the resin-containing layer. As the elastic roll, a roll obtained by winding cotton, wool, pulp or the like around an iron core and performing high-pressure processing and polishing, a synthetic resin roll such as a urethane resin, an epoxy resin, or a polyimide resin, an aramid fiber roll, or the like is used.

  In the surface smoothing treatment according to the present invention, the linear pressure at the nip between the metal roll and other rolls during the calendar treatment is preferably 1 kN / cm or more and 5 kN / cm or less. When the linear pressure at the nip is 1 kN / cm or more, remarkable surface smoothness is recognized. Moreover, if it is 5 kN / cm or less, implementation on an apparatus is also easy.

  Further, the preferable nip linear pressure varies depending on the processing speed, but it is preferable to perform processing at a processing speed of 20 m / min or more per nip. Although there is no upper limit on the processing speed, 500 m / min or less is preferable from the viewpoint of quality stability and operability.

  Next, a support mainly composed of cellulose pulp used for the ink jet recording paper of the present invention will be described.

  As a raw material of a support mainly composed of cellulose pulp according to the present invention, chemical pulp such as LBKP and NBKP, mechanical pulp such as GP, CGP, RMP, TMP, CTMP, CMP and PGW, waste paper pulp such as DIP, Those made mainly of wood pulp such as can be used. In addition, various fibrous materials such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as raw materials as necessary.

  Various conventionally known additives such as a sizing agent, pigment, paper strength enhancer, fixing agent, fluorescent whitening agent, wet paper strength agent, and cationizing agent may be added to the paper base as necessary. it can. Higher fatty acids, alkyl ketene dimers, etc. as sizing agents, calcium carbonate, talc, titanium oxide, etc. as pigments, starch, polyacrylamide, polyvinyl alcohol, etc. as paper strength enhancing agents, sulfate bands, cationics as fixing agents However, the present invention is not limited to this.

  The paper base material can be manufactured by mixing various fibrous materials such as wood pulp and various additives and using various paper machines such as a long net paper machine, a circular net paper machine, and a twin wire paper machine. Further, if necessary, a size press treatment with starch, polyvinyl alcohol, or the like, a various coating treatment, or a calendar treatment can be performed at the paper making stage or after paper making.

  Next, the ink absorbing layer according to the present invention will be described.

  As the ink absorbing layer of the ink jet recording paper of the present invention, either a swelling ink absorbing layer or a void ink absorbing layer can be used, but a void ink absorbing layer having a void structure is preferable.

  The swelling type ink absorbing layer is mainly composed of a hydrophilic resin, and absorbs ink when the hydrophilic resin swells. As this hydrophilic resin, crosslinked gelatin is preferably used, but other hydrophilic polymers can also be used. For example, polyvinyl alcohol, gelatin derivatives, graft polymers of gelatin and other polymers, proteins such as albumin and casein; cellulose derivatives such as hydroxyethyl cellulose, carboxymethyl cellulose, cellulose sulfate, etc .; sodium alginate, cellulose sulfate, dextrin, Sugar derivatives such as dextran and dextran sulfate; various synthetic hydrophilic polymers such as poly-N-vinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinylimidazole, polyvinylpyrazole and the like or copolymers It is possible to use a crosslinked product of As gelatin, acid-processed gelatin may be used in combination with lime-processed gelatin, and gelatin hydrolyzate and gelatin enzyme-decomposed product can also be used. These hydrophilic resins may be used alone or in a plurality of types.

  Next, an ink absorbing layer having a void structure preferably applied to the ink jet recording paper of the present invention will be described.

  Examples of the void-type ink absorbing layer include those that form voids from inorganic fine particles and an organic binder, those that form voids from phase separation of polymers, and those that form voids from organic fine particles and organic binders.

  In the present invention, it is particularly preferable from the viewpoint of ink absorption speed that a void type ink absorbing layer is formed with a void from inorganic fine particles and an organic binder. For water-based ink recording, a hydrophilic binder is preferable as the organic binder.

  Examples of inorganic fine particles preferably used for forming the voids of the ink absorbing layer include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, and zinc oxide. , Zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. A white inorganic pigment etc. can be mentioned.

  The average secondary particle size of the inorganic fine particles is determined by observing the particles themselves or the particles appearing on the cross section or surface of the ink absorbing layer with an electron microscope, measuring the particle size of 1000 arbitrary particles, and calculating the simple average value (number Average). Here, the particle size of each particle is represented by the diameter when a circle equal to the projected area is assumed.

  In the present invention, it is preferable to use solid fine particles selected from silica and alumina or alumina hydrate as the inorganic fine particles.

  As silica that can be preferably used in the present invention, silica synthesized by an ordinary wet method, colloidal silica, silica synthesized by a gas phase method, or the like is preferably used, but as fine particle silica particularly preferably used in the present invention. Is preferably colloidal silica or fine-particle silica synthesized by a gas phase method. Among them, fine-particle silica synthesized by a gas phase method not only provides high porosity, but is also used for the purpose of immobilizing a dye. When added to the polymer, coarse aggregates are hardly formed, which is preferable. Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as amorphous particles, spherical particles, and acicular particles can be used.

  The inorganic fine particles are preferably in a state where the fine particle dispersion before mixing with the cationic polymer is dispersed to the primary particles.

  In the present invention, the ink absorbing layer contains an organic binder, preferably a hydrophilic binder. Examples of the hydrophilic binder that can be used in the present invention include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color ginnan (κ, ι, λ, etc.), agar , Pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. Two or more of these hydrophilic binders can be used in combination. It is also one of preferred embodiments to use an organic binder resin that is crosslinked or polymerized by ionizing radiation.

  The hydrophilic binder preferably used in the present invention is polyvinyl alcohol.

  The polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal and anion-modified polyvinyl alcohol having an anionic group. Accor is also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably has an average degree of polymerization of 1,500 to 5,000. The degree of saponification is preferably 70 to 100%, particularly preferably 80 to 99.5%.

  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.

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

  The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Anion-modified polyvinyl alcohol is, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-2060888, as described in JP-A-61-237681 and JP-A-63-330779, Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, and described in JP-A-8-25595. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol. Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification.

The addition amount of the inorganic fine particles used in the ink absorbing layer is required ink absorption capacity, the porosity of the ink absorbing layer, the kind of inorganic pigments, depends largely on the type of hydrophilic binders, in general, the recording medium 1 m ² Usually, it is 5-30 g, preferably 10-25 g.

  The ratio of the inorganic fine particles and the organic binder used in the ink absorbing layer is usually 2: 1 to 20: 1 by mass ratio, and particularly preferably 3: 1 to 10: 1.

Further, it may contain a cationic water-soluble polymer having a quaternary ammonium base in the molecule, and is usually used in the range of 0.1 to 10 g, preferably 0.2 to 5 g per 1 m ^{2 of} the ink jet recording medium. .

In the ink absorbing layer, the total amount of voids (void volume) is preferably 20 ml or more per 1 m ² of recording paper. When the void volume is less than 20 ml / m ² , the ink absorbency is good when the amount of ink at the time of printing is small, but when the amount of ink increases, the ink is not completely absorbed and the image quality deteriorates, Problems such as delay in drying are likely to occur.

  In the ink absorbing layer having ink holding capacity, the void volume relative to the solid content volume is referred to as a void ratio. In the present invention, it is preferable to set the porosity to 50% or more because the voids can be efficiently formed without unnecessarily increasing the film thickness.

  In the inkjet recording paper of the present invention, the hydrophilic binder contains a polymer compound in which a hydrophilic polymer compound having a plurality of side chains in the main chain is irradiated with ionizing radiation and crosslinked between the side chains. It is preferable that the effect of the present invention can be further enhanced.

  In the present invention, the hydrophilic polymer compound having a plurality of side chains in the main chain is a polymer compound that is cross-linked between the side chains when irradiated with ionizing radiation. The main chain is (a) a saponified product of polyvinyl acetate, (b) polyvinyl acetal, (c) polyethylene oxide, (d) polyalkylene oxide, (e) polyvinyl pyrrolidone, (f) polyacrylamide, (g) hydroxy Selected from ethylcellulose, (h) methylcellulose, (i) hydroxypropylcellulose, (j) at least one derivative of (a) to (i), and a copolymer containing (k) (a) to (j) Consists of at least one kind.

  These hydrophilic polymer compounds are preferably resins that are less soluble in water after crosslinking by irradiation with ionizing radiation such as ultraviolet rays and electron beams than before crosslinking.

  The side chain is preferably composed of at least one modifying group selected from a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, and a photodepolymerization type. It is preferable to obtain by modifying at least one main chain selected from k).

  The hydrophilic polymer compound having a plurality of side chains in the main chain used in the present invention is substantially free of a polymerization initiator, a polymerization inhibitor and the like for crosslinking, and unreacted free radicals are generated after irradiation with ionizing radiation. Since it can suppress, it can suppress that the crackability of a coating film deteriorates with time. The network structure of the porous layer containing a binder containing a polymer compound in which the hydrophilic polymer compound having a plurality of side chains in the main chain of the present invention is irradiated with ionizing radiation and the side chains are cross-linked is as follows. Ionizing radiation to porous network structures formed by crosslinking using only a crosslinking agent, hydrophilic polymer compounds that do not have multiple side chains in the main chain, or hydrophilic polymer compounds with a low degree of polymerization Unlike a three-dimensional structure at a relatively short distance, such as a porous network structure formed by cross-linking by irradiation, it contains a long distance cross-link, so it is easy to hold many inorganic fine particles It has a structure, and a uniform film can be formed with a smaller amount of binder, that is, with a smaller ratio of binder to inorganic fine particles.

  Thus, the smaller the binder ratio to the inorganic fine particles, the higher the porosity of the ink absorption layer, and the easier it is to hold the ink (it becomes easier to absorb the ink), so that the ink overflow can be suppressed and the drying is quicker. The coating film formed is strong and resistant to bending, etc., and there is little cracking or peeling off of the recording layer before printing or printing after forming the ink jet recording paper, and it is also bent after printing or printing. An ink jet recording sheet having a void-type ink absorbing layer that is highly resistant to stress can be obtained.

  Therefore, it is possible to obtain an ink jet recording paper having a high ink absorbability, improved water resistance, and having a fast ink drying rate with less cracking and cracking.

  The hydrophilic polymer compound having a plurality of side chains in the main chain is preferably a photodimerized diazo type or a compound into which a cinnamoyl group, a stilbazonium group or a stilquinolium group is introduced. Further, a resin dyed with a water-soluble dye such as an anionic dye after photocrosslinking is preferred. 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. Photosensitive resins (compositions) described in publications such as JP-A-283339 and JP-A-1-198615, resins having a group such as an azide group that becomes an amino group and becomes cationic by a curing treatment, for example, The photosensitive resin (composition) described in gazettes, such as Kaisho 56-67309, is mentioned.

  Specifically, for example, in the polyvinyl alcohol structure described in JP-A-56-67309, the following formula (I)

2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following formula (II)

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

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

  Also. The photosensitive resin described in JP-A-60-129742 has the following formula (III) or (IV) in a polyvinyl alcohol structure.

It is a polyvinyl alcohol-type resin which has a structural unit shown by these. In the formula, R ₁ represents an alkyl group having 1 to 4 carbon atoms, and A ₋ represents an anion. These are structural units having a styrylpyridinium (stilbazolium) structure or a styrylquinolinium structure produced by reacting polyvinyl alcohol or partially saponified polyvinyl acetate with a styrylpyridinium salt or styrylquinolinium salt having a formyl group. The production method is described in detail in JP-A-60-129742, and can be easily produced with reference to this.

  The ratio of the styrylpyridinium group or styrylquinolinium group in the polyvinyl alcohol having a styrylpyridinium group or styrylquinolinium group is 0.2 to 10.0 mol% per vinyl alcohol unit. Is preferred. By setting it as 10.0 mol% or less, the solubility to a coating liquid can be improved. Moreover, the intensity | strength after bridge | crosslinking can be improved by setting it as 0.2 mol% or more.

  In the above, the base polyvinyl alcohol may partially contain unsaponified acetyl groups, and the content of acetyl groups is preferably less than 30%. The saponification degree is preferably 70 to 100%, particularly preferably 90 to 100%. Further, the degree of polymerization is preferably about 300 to 3000, more preferably 400 or more. By setting the degree of polymerization to 300 or more, the irradiation time of radiation for the crosslinking reaction can be shortened, and productivity can be improved. Further, when the degree of polymerization is 3000 or less, an increase in viscosity can be suppressed, and handling becomes easy.

  As the binder, a hydrophilic resin such as gelatin, polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, or polyvinyl alcohol may be used in combination with the hydrophilic polymer compound having a plurality of side chains in the main chain.

  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 examples include benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4. Benzophenones such as' -dimethylaminobenzophenone, thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, thioxanthones such as chlorothioxanthone, isopropoxychlorothioxanthone, anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone, chloroanthraquinone, Acetophenones, benzoin ethers such as benzoin methyl ether, 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexylphen Ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (m-methoxyphenyl) imidazole dimer, 2- (o-fluoro) Phenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer, 2- (p-methoxyphenyl) -4,5-diphenylimidazole dimer 2,4-di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4,5-diphenylimidazole dimer 2,4,5-triarylimidazole Dimer, benzyldimethyl ketal, 2-benzyl-2-dimethylamino-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, 1,7-bis (9, 9'-acridinyl) heptane and other acridine derivatives, bisacylphosphine oxides, and mixtures thereof. The above 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. When ultraviolet rays are used as ionizing radiation, examples of sensitizers include thioxanthone, benzoin, benzoin alkyl ether xanthone, dimethylxanthone, benzophenone, N, N, N ′, N′-tetraethyl-4,4 ′. -Sensitizers such as diaminobenzophenone and 1,1-dichloroacetophenone are preferred.

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

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

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

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

  After the ink absorbing layer containing the binder is applied, the coating film is irradiated with ionizing radiation, for example, ultraviolet rays (such as a mercury lamp or a metal halide lamp). By irradiation with this ionizing radiation, a cross-linking reaction is caused between the side chains of the hydrophilic polymer compound, the viscosity of the aqueous coating film is increased, and fluidization is prevented (so-called setting) to form a uniform coating film. be able to. After the ionizing radiation irradiation, the coating film is dried to obtain an ink jet recording sheet on which a uniform void-type ink absorbing layer mainly containing a hydrophilic binder and fine particles is formed on a support.

  In the present invention, after irradiating with ionizing radiation, it is preferable to dry the coating film and evaporate an aqueous solvent mainly composed of water contained in the coating film. A part or most of the aqueous solvent may be evaporated, but it is preferable to irradiate ionizing radiation in a state where the coating film contains a hydrophilic solvent, and it is more preferable to irradiate ionizing radiation immediately after coating. . As a result, it is possible to form a porous layer by drying the coating film while suppressing fluidization of the coating film by a cross-linking reaction between the side chains of the hydrophilic polymer compound in the coating film. An ink jet recording paper having a void type ink absorbing layer can be obtained.

  Examples of ionizing radiation include electron beams, ultraviolet rays, alpha rays, beta rays, gamma rays, and X-rays, which have little influence on the human body, are easy to handle, and are widely used industrially. Electron beams and ultraviolet rays are preferably used.

  When an electron beam is used as the ionizing radiation, it is desirable to adjust the amount of the electron beam to be irradiated within a range of about 0.1 to 20 Mrad. By setting it to 0.1 Mrad or more, a sufficient irradiation effect can be obtained, and by setting it to 20 Mrad or more, it is possible to suppress deterioration of 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, or the like is adopted, and the acceleration voltage when the electron beam is irradiated is preferably about 100 to 300 kV. In addition, the electron beam irradiation method has an advantage that productivity is higher than that of ultraviolet irradiation, there is no problem of odor or coloring due to addition of a sensitizer, and a uniform cross-linked structure is easily obtained.

The hydrophilic polymer compound having a plurality of side chains in the main chain preferably used in the present invention, in particular, can be exposed to, for example, ultraviolet rays and can easily undergo a crosslinking reaction without adding the above sensitizers. As the light source, an ultraviolet lamp (for example, a low pressure, medium pressure, high pressure mercury lamp having an operating pressure of 0.5 kPa to 1 MPa), a xenon lamp, a tungsten lamp, a halogen lamp, or the like is used, and about 5000 to 8000 μW / cm ^2. An ultraviolet ray having an intensity of 1 is preferably irradiated. As the amount of energy required for curing, a range of 0.02 to 20 kJ / cm ² is used.

  In addition, in the ink jet recording paper of the present invention, as a method of forming voids by polymer phase separation, (1) after applying a solution obtained by dissolving a polymer in a good solvent on the ink absorption layer, Wet phase inversion method in which voids are formed by overcoating a poor solvent, (2) A polymer, a good solvent for this polymer, and a coating solution having a boiling point higher than that of the good solvent and containing the poor solvent for the polymer Then, there is a dry phase inversion method in which microphase separation is caused by evaporating the solvent and drying to form voids.

  Examples of the polymer include olefin polymers, vinyl polymers, acrylic polymers, styrene polymers, polyesters, polyamides, polycarbonates, polyurethanes, polysulfones, polymers derived from epoxides, and cellulose derivatives.

  Organic fine particles used in the void-type ink absorbing layer composed of organic fine particles and an organic binder include polymethyl methacrylate, polyfunctional methacrylate polymer, polyamide, polystyrene, polyvinyl chloride, chloroprene rubber, nitrile rubber, styrene-butadiene. For example, rubber.

  Moreover, as an organic binder, the same thing as the space | gap type ink absorption layer which consists of inorganic fine particles and an organic binder can be used.

In the ink absorption layer according to the present invention, a cationic polymer can be used as a fixing agent for dye ink and a dispersion aid for fine particles. Examples of cationic polymers include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin-dialkylamine addition polymer, diallyldimethylammonium chloride polymerization things, diallyl dimethyl ammonium chloride-SO ₂ copolymer, polyvinyl imidazole, polyvinyl pyrrolidone, vinyl imidazole copolymers, polyvinyl pyridine, polyamidine, chitosan, cationized starch, vinylbenzyltrimethylammonium chloride polymers, (2-methacryloyloxy-oxy Ethyl) trimethylammonium chloride polymer, dimethylaminoethyl methacrylate DOO polymer, and the like. Examples include the cationic polymers described in Chemical Industry Times, August 15 and 25, 1998, and polymer dye fixing agents described in “Introduction to Polymer Drugs” issued by Sanyo Chemical Industries, Ltd.

  In addition to the above cationic polymer, nonionic or anionic ones such as polyacrylic acid can be used as the dispersant for the inorganic fine particles. In this case, the fixing agent for the dye ink can be applied by overcoating the cationic polymer or the polyvalent metal salt after applying the ink absorbing layer.

  Various additives other than those described above can be used in the ink absorbing layer of the ink jet recording paper of the present invention and other layers provided as necessary. For example, organic latex fine particles such as polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, or melamine resin , Anionic, cationic, nonionic and amphoteric surfactants, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and JP-A-3-13376, etc., JP-A-59-42993, 59- Nos. 52689, 62-280069, 61-242871, and JP-A-4-2192. Optical brighteners described in No. 6 etc., pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, preservatives, thickeners, antistatic Various known additives such as an agent and a matting agent can also be contained.

  The ink absorbing layer may be composed of two or more layers. In this case, the structures of the ink absorbing layers may be the same or different from each other.

  In the present invention, the coating method for providing the undercoat layer or ink absorbing layer according to the present invention on the support can be appropriately selected from known methods. For example, gravure coating method, roll coating method, rod A bar coating method, an 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 can also be used.

  In the recording paper of the present invention, in order to suppress the curl balance, it is preferable to provide a backcoat layer on the surface opposite to the ink absorbing layer with the support interposed therebetween, thereby suppressing the occurrence of curling. Prevents the edge of the inkjet printer from getting in contact with the recording head.

  Examples of the material constituting the back coat layer include water-dispersible emulsions, water-soluble resins, fine particles, and organic solvent-based resins. The constituent material of the back coat layer is the same as the layer containing the resin and fine particles soluble in the organic solvent formed between the ink absorbing layer and the paper base, and the viewpoint that the curl balance is easily achieved To preferred. In this case, it is preferable to change the thickness of the undercoat layer on the front and back sides in consideration of the shrinkage stress of the ink absorbing layer. Alternatively, a paper base material on which a back coat layer such as a resin layer is previously coated on one side may be used, and the undercoat layer and the ink absorbing layer of the present invention may be formed on the opposite side. For example, if the undercoat layer and the ink absorbing layer according to the present invention are formed on the non-cast coated side of general cast coated paper, the cast coat layer becomes the back coat layer. If necessary, a matting agent or an antistatic agent can be added to the backcoat layer, and the coating method can be applied in the same manner as the ink absorbing layer.

  The back coat layer may be applied before forming the undercoat layer or the ink absorbing layer on the front surface, or may be applied after the ink absorbing layer is applied.

  When forming an image using the ink jet recording paper of the present invention, an ink jet ink can be used, and among them, a water-based dye ink containing a water-soluble dye, water, an organic solvent and the like is preferably used.

  Examples of water-soluble dyes that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, and the like. Examples of the compound include dyes exemplified in JP-A No. 2002-264490.

  The organic solvent contained in the ink that can be used in the present invention is not particularly limited, but is preferably a water-soluble organic solvent, and specifically, alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol). Secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, Butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (for example, Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol Monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene Recall dimethyl ether), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, Polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclics (eg, 2-pyrrolidone, N-methyl) -2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (for example, dimethyl ester) Til sulfoxide and the like), sulfones (for example, sulfolane and the like), sulfonates (for example, 1-butanesulfonic acid sodium salt and the like), urea, acetonitrile, acetone and the like.

  Various surfactants can be used in the ink according to the present invention. The surfactant that can be used in the present invention is not particularly limited, but examples thereof include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxy Nonionic surfactants such as ethylene alkylallyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

  In the ink of the present invention, a polymer surfactant can also be used. For example, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-acrylic acid. Alkyl ester copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid A copolymer, a vinyl naphthalene-maleic acid copolymer, etc. can be mentioned.

  In addition to the above description, the ink according to the present invention is publicly known depending on the purpose of improving the emission stability, the compatibility with the print head and the ink cartridge, the storage stability, the image storage stability, and other various performances as necessary. Various additives, such as viscosity modifiers, specific resistance modifiers, film forming agents, ultraviolet absorbers, antioxidants, fading inhibitors, antifungal agents, rust inhibitors, etc. can be appropriately selected and used, For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, 57-74192, 57-87989, 60-72785, 61-14659, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. Can be mentioned.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Preparation of coating solution for undercoat layer >>
[Preparation of coating solution A for undercoat layer]
Urethane acrylate oligomer (R-1213 manufactured by Daiichi Kogyo Seiyaku) 53 parts Polyethylene glycol diacrylate (PE-200 manufactured by Daiichi Kogyo Seiyaku) 43 parts Photopolymerization initiator (Irgacure 184 manufactured by Ciba Specialty Chemicals) 4 parts Each of the above additives Were mixed with stirring at room temperature to prepare an undercoat layer coating solution A.

[Preparation of coating liquid B for undercoat layer]
In the preparation of the coating liquid A for the undercoat layer, the urethane acrylate oligomer (R-1213 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was changed to an epoxy acrylate oligomer (Arakawa Chemical Beam Set AQ-9) in the same manner. Undercoat layer coating solution B was prepared.

[Preparation of coating liquid C for undercoat layer]
An undercoat layer coating solution C was prepared in the same manner as in the preparation of the undercoat layer coating solution A except that the photopolymerization initiator was removed.

<< Preparation of Silica Dispersion S-1 >>
Gas phase method in which the average particle size of primary particles uniformly dispersed in advance in 150 g of 10% aqueous cationic polymer P-1 solution (containing 10% n-propanol and 2% by mass of ethanol) is about 7 nm. 435 g of a silica dispersion (pH 2.6, containing 0.5% ethanol) containing 23% silica (produced by Nippon Aerosil Co., Ltd .; Aerosil 300), 3.6 g boric acid and 0.8 g borax at 3000 rpm at room temperature Added with stirring.

Subsequently, it disperse | distributed by the pressure of ₃ kN / cm < ₂ > with the high-pressure homogenizer by Sanwa Kogyo Co., Ltd., the whole quantity was finished with a pure water so that a silica content might be 18%, and silica dispersion liquid S-1 was obtained. The obtained silica dispersion S-1 was filtered using a TCP-10 type filter manufactured by Advantex Toyo. The average secondary particle size of the silica fine particles was measured and found to be 39 nm. The average secondary particle size is a value measured by diluting the silica dispersion by a factor of 50 and using a dynamic light scattering type particle size measuring device Zeta Sizer 1000HS (manufactured by Malvern).

<Preparation of ink absorbing layer coating solution>
[Preparation of coating liquid A for ink absorbing layer]
While stirring 500 g of the above silica dispersion S-1 at 40 ° C., 263 g of an 8% aqueous solution of polyvinyl alcohol having a polymerization degree of 3500 (PVA235 manufactured by Kuraray Co., Ltd.) was gradually added, and finally the total amount was finished to 1000 g with pure water, Ink absorbing layer coating liquid A was prepared.

[Preparation of Ink Absorbing Layer Coating Liquid B]
In the preparation of the ink absorbing layer coating liquid A, the polyvinyl alcohol used was changed to the following modified polyvinyl alcohol aqueous solution, and the same except that 6 ml of a 10% by mass isopropanol solution of a photopolymerization initiator (Irgacure 2959 manufactured by Ciba Specialty Chemicals) was added. Thus, an ink absorbing layer coating liquid B was prepared.

<Modified polyvinyl alcohol aqueous solution>
With reference to the method described in JP-A No. 2000-181062, pH (3-methacryloxy-2-hydroxypropyloxy) benzaldehyde is reacted with polyvinyl alcohol having a polymerization degree of 1700 and a saponification degree of 98%, and the crosslinking group modification rate An aqueous solution of a UV-polymerizable polyvinyl alcohol derivative having a concentration of 1 mol% and a solid content concentration of 8% was prepared.

<Production of recording paper>
[Preparation of recording paper 1]
Apply an undercoat layer coating solution A to high-quality paper (made by Nihon Daishowa Paperboard Co., Ltd.) using an applicator so that the wet film thickness is 10 μm, and continuously apply a metal halide lamp having a main wavelength of 365 nm. The resin layer A was formed by irradiating with ultraviolet rays under the condition that the amount of energy used was 200 mJ / cm ² . Further, the non-water-absorbing support 1 was prepared by providing the resin layer A in the same manner on the back surface on the side where the resin layer A was provided.

  Next, the ink-absorbing layer coating liquid A is applied to one surface of the non-water-absorbing support 1 using a slide hopper so that the wet film thickness is 180 μm, cooled to 5 ° C., and stepwise from 20 to 65 ° C. The recording paper 1 was produced by sequentially drying with a wind of varying temperature.

[Preparation of recording paper 2]
In the production of the recording paper 1, using a calender device provided with a metal roll on the surface of the formed resin layer A, a calendar treatment is performed at a surface temperature of the metal roll of 60 ° C., a linear pressure of 3.0 kN / cm, and a speed of 20 m / sec. After that, the recording paper 2 was prepared in the same manner except that the ink absorbing layer coating liquid A was applied and dried.

[Preparation of recording paper 3]
Using the non-water-absorbing support 1 used in the preparation of the recording paper 1, the ink absorbing layer coating liquid B is applied to one side of the recording paper 1 using a slide hopper so that the wet film thickness becomes 180 μm. A metal halide lamp having a dominant wavelength of 365 nm was used to irradiate ultraviolet rays under the condition that the energy amount was 30 mJ / cm ^2, and then sequentially dried with a wind whose temperature was changed stepwise from 20 to 65 ° C. Was made.

[Preparation of recording paper 4]
A recording paper 4 was produced in the same manner as in the production of the recording paper 1 except that the resin layer B was formed by changing the undercoat layer coating liquid A to the undercoat layer coating liquid B.

[Preparation of recording paper 5]
Apply a urethane acrylate oligomer (Daiichi Kogyo Seiyaku Co., Ltd., R-1213) to high-quality paper (Shiraoi Nippon Daishowa Paperboard Co., Ltd.) using an applicator so that the wet film thickness is 10 μm. A resin layer C was formed by using a metal halide lamp having a dominant wavelength of 365 nm and irradiating with ultraviolet rays under an energy amount of 200 mJ / cm ² . Furthermore, the resin layer C was similarly provided on the back surface on the side where the resin layer C was provided. The surface of the formed resin layer C is calendered using a calender device equipped with a metal roll at a surface temperature of the metal roll of 60 ° C., a linear pressure of 3.0 kN / cm, and a speed of 20 m / sec. 2 was produced.

  Next, the ink absorbing layer coating liquid A is applied to one surface of the non-water-absorbing support 2 using a slide hopper so that the wet film thickness becomes 180 μm, cooled to 5 ° C., and stepwise from 20 to 65 ° C. The recording paper 5 was produced by sequentially drying with wind of varying temperature.

[Preparation of recording paper 6]
The coating solution C for the undercoat layer was applied to high-quality paper (manufactured by Nihon Daishowa Paperboard Co., Ltd.) using an applicator so that the wet film thickness was 10 μm, and the acceleration voltage was 175 kV and the absorbed dose from the back side of the coated side. Resin layer D was formed by irradiation with an electron beam under the condition of 2 Mrad. Furthermore, the resin layer D was similarly provided on the back surface on the side where the resin layer D was provided, and the non-water-absorbing support 3 was produced.

  Next, the ink absorbing layer coating liquid A is applied to one surface of the non-water-absorbing support 3 using a slide hopper so that the wet film thickness becomes 180 μm, cooled to 5 ° C., and stepwise from 20 to 65 ° C. The recording paper 6 was produced by sequentially drying with a wind of varying temperature.

[Preparation of recording paper 7]
On both sides of a base paper with a basis weight of 170 g / m ² , a water-dispersible emulsion (T-XP163, manufactured by Starlight PMC, Tg = 50 ° C.) is adjusted to a wire bar by adjusting the solid content to 5 g / m ^2. After applying and drying, a surface smoothing treatment (also called calendering treatment) is performed using a calender apparatus equipped with a metal roll at a surface temperature of the metal roll of 70 ° C., a linear pressure of 2 kN / cm, and a speed of 20 m / min. The non-water-absorbing support 4 was produced by forming the resin layer E. Next, the ink absorbing layer coating liquid A is applied to one surface of the non-water-absorbing support 4 using a slide hopper so that the wet film thickness becomes 180 μm, cooled to 5 ° C., and then stepped to 20 to 65 ° C. The recording paper 7 was produced by sequentially drying in a wind with a changed angle.

<Evaluation of recording paper>
The following evaluations were performed on each of the recording sheets produced.

[Evaluation of cockling resistance 1: Printed part]
Using an ink jet printer PM-G800 (manufactured by Seiko Epson Corporation), a black solid image is printed on each recording medium and left at 25 ° C., and then the formed black solid image surface is visually observed, according to the following criteria: The cockling resistance was evaluated. If the evaluation rank was Δ or more, it was determined that the quality had no practical problem.

◎: Waviness on the surface is not known and the aesthetic appearance is not impaired. ○: Slight undulation is observed on the surface, but the glossiness is not impaired. △: The surface undulation is small and the aesthetic appearance is not impaired. Swelling is observed greatly and the appearance is impaired [Evaluation of cockling resistance 2: Non-printing part]
The unprinted white portion of each recording paper was visually observed, and cockling resistance was evaluated according to the following criteria. If the evaluation rank was Δ or more, it was determined that the quality had no practical problem.

◎: Waviness on the surface is not known and the aesthetic appearance is not impaired. ○: Slight undulation is observed on the surface, but the glossiness is not impaired. △: The surface undulation is small and the aesthetic appearance is not impaired. Swell is observed greatly, and the beauty is impaired [Evaluation of Glossiness]
Glossiness is relative to the gloss on the ink absorbing layer side of each recording paper with silver salt photograph color paper (Konica Minolta Photo Imaging Color Paper Glossy Type QA Paper Glossy Type QA Paper). Glossiness was evaluated.

◎: Glossiness equivalent to or better than silver halide photography ○: Glossiness slightly inferior to silver halide photography, but in practically no problem △: Glossy compared to silver salt photography Although the feeling is inferior, a certain degree of gloss is felt. ×: The glossiness is clearly inferior to that of silver halide photographs.
The C value of each recording paper was measured for image clarity (C value%) at a reflection of 60 degrees and an optical comb of 2 mm using an image clarity measuring device ICM-1DP (manufactured by Suga Test Instruments Co., Ltd.).

A: The C value is 60% or more and the image clarity is good. O: The C value is 45 to 60% and the image clarity is slightly inferior, but there is no practical problem. X: The C value is less than 45%. Insufficient image clarity [Evaluation of crack resistance]
For each recording paper 100 cm ² , the ink absorption layer coating surface side was observed with a magnifying glass, the number of cracks having a size of 5 μm or more was counted, and failure resistance (crack resistance) was evaluated according to the following criteria. The acceptable limit level in terms of image quality is indicated by Δ, and the quality outside the practically acceptable range is indicated by ×.

○: Number of occurrence of cracks is 3 or less Δ: Number of occurrence of cracks is 4 to 9 ×: Number of occurrence of cracks is 10 or more [Evaluation of image clarity]
Using the method described in JIS H8866-2, the C value in an optical comb with a reflection of 45 ° and 2.0 mm was measured with a Suga Test Instruments Co., Ltd. image clarity measuring device, and the evaluation of the image clarity was performed according to the following criteria. went.

◎: C value is 60 or more ○: C value is 50 or more and less than 60 Δ: C value is 40 or less and less than 50 ×: C value is less than 40 [Evaluation of film resistance]
Using an inkjet printer PM-G800 (manufactured by Seiko Epson Corporation), a black solid image is printed on each recording medium, and a cellophane tape is pasted on the surface of the formed black solid image under an environment of 40 ° C. and 80% RH. The film was peeled off when the cellophane tape was peeled off after storage for 1 week, and the film resistance was evaluated according to the following criteria.

◎: Solid image was not peeled at all ○: Solid image was almost free from peeling Δ: Part of the solid image was finely peeled, but it was a quality acceptable for practical use ×: Solid image Table 1 shows the results obtained with the above-mentioned quality in which the peeling is observed in a considerable area of the part and the quality is not practical.

  As is clear from the results shown in Table 1, the ink jet recording paper having the structure defined in the present invention or the ink jet recording paper manufactured according to the method defined in the present invention has a cockling resistance and glossiness compared to the comparative example. It can be seen that it is excellent in image clarity, crack resistance and film resistance.

Claims (10)

An ink jet recording paper comprising an undercoat layer containing a resin obtained by curing a photopolymerizable oligomer with ultraviolet rays and an ink absorbing layer on at least one surface of a support mainly composed of cellulose pulp. 2. The inkjet recording paper according to claim 1, wherein the photopolymerizable oligomer is a radical polymerization type polyfunctional acrylate. The inkjet recording paper according to claim 1, wherein the photopolymerizable oligomer is a urethane acrylate. The inkjet recording according to any one of claims 1 to 3, wherein the ink absorbing layer contains a hydrophilic polymer, and the hydrophilic polymer is a compound formed by crosslinking with ionizing radiation. Paper. The inkjet recording paper according to claim 1, wherein the ink absorption layer is a void-type ink absorption layer. An undercoat layer mainly composed of a resin obtained by curing a photopolymerizable oligomer with ultraviolet rays is applied to at least one surface of a support mainly composed of cellulose pulp, and a calender treatment is applied to the surface. A method for producing an inkjet recording paper, comprising laminating an absorption layer. The method for producing an inkjet recording paper according to claim 6, wherein the photopolymerizable oligomer is a radical polymerization type polyfunctional acrylate. The method for producing an inkjet recording paper according to claim 6 or 7, wherein the photopolymerizable oligomer is urethane acrylate. The ink jet recording according to any one of claims 6 to 8, wherein the ink absorbing layer contains a hydrophilic polymer, and the hydrophilic polymer is a compound formed by crosslinking with ionizing radiation. Paper manufacturing method. The method for producing an ink jet recording paper according to claim 6, wherein the ink absorbing layer is a void type ink absorbing layer.