JP2010162759A - Inkjet recording medium - Google Patents

Abstract

To provide an ink jet recording medium capable of recording an image having excellent ink absorbability, high density and excellent scratch resistance.
SOLUTION: An ink receiving layer containing vapor-phase process silica and polymer particles having a primary average particle diameter of 5 to 50 nm and a glass transition temperature of 80 ° C. or higher are sequentially formed on a base material from the base material side. Including a surface layer.
[Selection figure] None

Description

  The present invention relates to an ink jet recording medium having an ink receiving layer for receiving ink.

  In recent years, various methods have been proposed as an image recording method for recording an image. In any case, there is a high demand for the quality of recorded matter, such as image quality. For example, as an ink jet recording method, a method using an ink jet recording medium in which a recording layer that receives ink has a porous structure has been put into practical use.

  As an example, an ink jet recording medium has been proposed in which a recording layer containing inorganic pigment particles and a water-soluble binder and having a high porosity is provided on a support. Since this has a porous structure, it is excellent in the quick-drying property of the ink. Thus, while high ink absorptivity is important as one of the recording characteristics, the image density tends to decrease, and it is desirable that the image has scratch resistance after recording. It is.

  As a technique relating to ink jet recording, an ink jet recording medium having a gloss layer on an ink receiving layer and containing the polymer dispersion having a predetermined average particle diameter and glass transition temperature as an pigment component and an adhesive is disclosed. (See, for example, Patent Document 1), and is said to be excellent in ink absorbability and tape peel strength.

Also disclosed is an inkjet recording paper provided with a porous layer containing organic fine particles having a glass transition temperature of 70 ° C. or higher and an average particle diameter of 100 nm or less as a surface layer (see, for example, Patent Document 2).
JP 2008-207409 A Japanese Patent Laid-Open No. 2004-1412

  However, in terms of the absorption characteristics of the landed ink and the scratch resistance and density of the image after recording, it has not yet been possible to secure recording performance that can be adapted to the recent increase in recording speed.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet recording medium capable of recording an image having excellent ink absorbability, high density and excellent scratch resistance, and achieving the object. Let it be an issue.

Specific means for achieving the above object are as follows.
<1> On the base material, in order from the base material side, an ink receiving layer containing vapor-phase process silica, and polymer particles having a primary average particle diameter of 5 to 50 nm and a glass transition temperature of 80 ° C. or higher are included. An ink jet recording medium having a surface layer.
<2> The inkjet recording medium according to <1>, wherein the polymer particles are irregularly shaped particles having a concavo-convex shape on a surface.

<3> The inkjet recording medium according to <1> or <2>, wherein the ink receiving layer further contains a polyaluminum chloride compound.
<4> The above-mentioned <1> to <3>, wherein the surface layer has a solid content (dry coating amount of the coating liquid for forming the surface layer) of 0.5 to 4.0 g / m ^2. The inkjet recording medium according to any one of the above.
<5> The <1> to the above, wherein the polymer particles are at least one kind of particles selected from a (meth) acrylate-based polymer, a styrene- (meth) acrylate-based polymer, and a polystyrene-based polymer. <4> The inkjet recording medium according to any one of <4>.

  ADVANTAGE OF THE INVENTION According to this invention, the ink jet recording medium which can record the image which was excellent in ink absorptivity, and was excellent in abrasion resistance with high density | concentration can be provided.

Hereinafter, the ink jet recording medium of the present invention will be described in detail.
The ink jet recording medium of the present invention has a base material, an ink receiving layer containing vapor-phase-process silica in order from the base material side, a primary average particle diameter of 5 to 50 nm, and a glass transition temperature (Tg; hereinafter, “ And a surface layer containing polymer particles having a temperature of 80 ° C. or higher. In the ink jet recording medium of the present invention, another layer may be further provided on the substrate as necessary.

  In the present invention, a surface layer is provided on the ink receiving layer, and this surface layer is constituted by using polymer particles having a primary average particle diameter of 5 to 50 nm and a glass transition temperature of 80 ° C. or higher. In addition, compared to the case where there is no surface layer on the ink receiving layer or the case where the ink receiving layer is composed of inorganic particles other than vapor phase method silica, a better ink absorbability can be obtained, and the image density is high, In addition, an image having excellent scratch resistance can be recorded.

~ Surface layer ~
The ink jet recording medium of the present invention has a surface layer on the ink receiving layer on the substrate. The surface layer comprises at least one polymer particle having a primary average particle diameter of 5 to 50 nm and a glass transition temperature of 80 ° C. or higher (hereinafter also referred to as “polymer particle in the present invention”). As needed, it can comprise using another component.

<Polymer particles>
The polymer particles in the present invention can be selected from resin particles having a primary average particle diameter of 5 to 50 nm and a glass transition temperature (Tg) of 80 ° C. or higher. Examples of the resin forming the resin particles include (meth) acrylate polymers (preferably a polymer or copolymer obtained by polymerizing one or more monomers selected from acrylic acid esters and methacrylic acid esters), styrene. -(Meth) acrylate polymer (preferably a copolymer obtained by copolymerizing styrene and one or more monomers selected from acrylic acid ester and methacrylic acid ester), polystyrene polymer, styrene-maleic anhydride Copolymer, SBR polymer (styrene / butadiene copolymer), MBR polymer (methyl methacrylate / butadiene copolymer), epoxy polymer (epoxy / acrylic modified copolymer), urethane Polymer, EVA polymer (ethylene / vinyl acetate copolymer), o Fin-based polymers, polyvinyl chloride polymers, chlorinated polypropylene-based polymers, polyethylene-based polymers, vinylidene chloride polymers, melamine-based polymers, urea based polymers, silicone-modified acrylic polymers, mention may be made of fluorine / acrylic polymer.

  Among them, a polymer obtained by polymerizing an ethylenically unsaturated monomer is preferable from the viewpoint of easy formation of fine particles, and is a (meth) acrylate polymer, a styrene- (meth) acrylate polymer, or a polystyrene polymer. A polymer is more preferred.

The primary average particle diameter of the polymer particles in the present invention is in the range of 5 to 50 nm. If the primary average particle size is less than 5 nm, it is difficult to produce, and even if used, there are too few voids between the particles, resulting in a decrease in ink absorbability, poor dryness and image quality after recording, and abrasion resistance. The nature is also reduced. On the other hand, if the primary average particle diameter exceeds 50 nm, the surface unevenness becomes excessively large, and the image density and glossiness decrease.
Among these, the primary average particle diameter is preferably in the range of 5 to 35 nm, more preferably in the range of 10 to 35 nm from the viewpoint of increasing the ink absorbency, scratch resistance, and image density while increasing the gloss. .

Here, the “primary average particle diameter” is measured by the following method through observation with an electron microscope. That is,
The polymer particles are diluted to 5% by mass with ion-exchanged water, 5 μl is placed on a metal mesh and dried, and then dried by passing 1 μl of ion-exchanged water 10 times, followed by vacuum drying. Sample particles put in the machine all day and night are prepared, 50 sample particles are observed with a transmission electron microscope, and the maximum diameter of each particle is measured. The average value of the maximum diameters of these particles is determined and used as the primary average particle diameter.

The glass transition temperature (Tg) of the polymer particles in the present invention is 80 ° C. or higher. When the glass transition temperature is less than 80 ° C., the polymer particles are fused to each other during drying at the time of layer formation, the voids between the particles are reduced, and ink absorbability and scratch resistance are reduced.
Tg is preferably in the range of 80 ° C. to 150 ° C., more preferably in the range of 80 ° C. to 120 ° C., and particularly preferably in the range of 90 ° C. to 115 ° C. in terms of improving ink absorbability and image scratch resistance. .

  The glass transition temperature (Tg) refers to an intermediate glass transition temperature measured by differential scanning calorimetry (JIS K7121).

  From the viewpoint of the Tg, it is preferable to use methyl methacrylate or styrene as the ethylenically unsaturated monomer used for forming the polymer particles.

The particle shape of the polymer particles in the present invention may be either spherical or irregular. As for the particle shape of the polymer particles, the amount of voids between particles is larger than that of true spherical particles, and from the viewpoint of obtaining better ink absorbability and scratch resistance, the particle surface has unevenness with different distances from the center to the surface. A deformed particle having a shape is preferable, and a deformed particle having one or more protrusion shapes on the particle surface is more preferable.
As the shape of the irregularly shaped particle having one or more protrusion shapes on the particle surface, particle shapes such as confetti shape, daruma shape, squid octopus shape, raspberry shape and the like are preferably mentioned.

The polymer particles in the present invention can be prepared by a known method.
Specifically, an emulsion polymerization method in which emulsion polymerization is performed in the presence of a surfactant is an example of a method for producing a polymer obtained by polymerizing an ethylenically unsaturated monomer. As the emulsion polymerization method, a method of batch polymerization and a method of polymerization while continuously supplying each component can be applied. The polymerization is usually carried out at 30 to 85 ° C. with stirring. In the emulsion polymerization, a polymerization initiator is preferably used, and persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, azo compounds, and the like are used. Moreover, the redox initiator by using these together with a reducing agent can also be used.
Examples of the surfactant include anionic surfactants, nonionic surfactants, cationic surfactants, and copolymerizable emulsifiers, which can be used alone or in combination of two or more. The amount of the surfactant is not particularly limited.

  Moreover, the average particle diameter of the polymer particles obtained by emulsion polymerization can be controlled by increasing or decreasing the amount of the emulsifier. In the case of emulsion polymerization using an emulsifier, the particle size of the polymer particles is decreased by increasing the amount of the emulsifier, and polymer particles having a primary average particle size of 5 to 50 nm are obtained by increasing the amount of the emulsifier. The emulsion of polymer particles prepared by emulsion polymerization can be used as it is.

  Examples of the ethylenically unsaturated monomer include (meth) acrylate (eg, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, etc. , As well as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate Carbon of alkyl moiety, such as relate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate An unsubstituted alkyl methacrylate having 1 to 12), vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, ethylene, propylene, butylene, isobutylene, and the like, and hydroxyl-containing (meth) acrylates ( Examples: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate , 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, etc.) (meth) acrylates substituted with polar groups (eg 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate) Glycidyl methacrylate, etc.), unsaturated carboxylic acids (eg acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, acrylic anhydride, methacrylic anhydride, maleic anhydride, itaconic anhydride, fumaric anhydride, etc.),

Aromatic vinyls (eg, styrene, 2-methylstyrene, t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, divinylbenzene, etc.), amides (eg, acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide, N-isopropylacrylamide, N-methylolmethacrylamide, N-methylolacrylamide, diacetoneacrylamide and maleic acid amide), vinyl Esters (eg, vinyl acetate, vinyl propionate, etc.), vinylidene halides (eg, vinylidene chloride, vinylidene fluoride, etc.), vinyl chloride, vinyl ether, vinyl ketone, vinylamide, chloroprene Ethylene, propylene, isoprene, butadiene, chloroprene, vinyl pyrrolidone, allyl glycidyl ether, acrylonitrile, methacrylonitrile, etc., as well as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, Neopentyl glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, Tripropylene glycol diacri Polypropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, tetramethylolmethane tetraacrylate, allyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate Saturated (meth) acrylate, isopropenyl-α, α-dimethylbenzyl isocyanate, allyl mercaptan, etc., and 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H-benzotriazole, 2- (2 ′ -Hydroxy-5′-methacryloyloxyphenyl) -benzotriazole, 2-hydroxy-4- (2-methacryloyloxy) ethoxybenzopheno , 2- (2'-hydroxy-5'-methacryloyloxy phenyl) -5-chloro-benzotriazole, etc., can be mentioned.
These ethylenically unsaturated monomers can be used alone or in combination of two or more.

For example, seed emulsion polymerization or seed dispersion polymerization, that is, firstly spherical polymer particles are prepared, and then different types of monomers are swollen therein to form the polymer particles. The monomer is swollen in the vicinity of the particle surface by free radical polymerization in the inside or by copolymerizing a polyfunctional monomer with spherical polymer particles, and free radical polymerization is performed with a water-soluble initiator. Can be produced. This method is described in detail in “Creation of irregularly shaped polymer fine particles” by Masayoshi Okubo, Polymer 50 Vol. September, 696-700 (2003).
In the present invention, a form using methyl methacrylate and styrene as the ethylenically unsaturated monomer is preferable. In this case, for example, polymethyl methacrylate (PMMA) is produced by an emulsion polymerization method, and the PMMA particles are seeded. It is generated by forming a convex portion on the surface by seed emulsion polymerization of styrene.

  As the polymer particles in the present invention, spherical particles and irregularly shaped particles having one or more protrusion shapes on the particle surface may be used alone, or a mixture of both may be used.

  Among the above, the polymer particles in the present invention have one or more protrusion shapes on the particle surface and a primary average particle diameter of 10 to 35 nm from the viewpoints of ink absorbability, image scratch resistance and density improvement effect. In addition, (meth) acrylic irregularly shaped particles having a Tg of 80 to 120 ° C. are preferred.

The polymer particles in the present invention may be used alone or in combination of two or more.
As content in the surface layer of the polymer particle in this invention, 40-100 mass% is preferable with respect to the total solid of a surface layer, and 50-90 mass% is more preferable. When the content is 40% by mass or more, the ink absorbency is good, and it is suitable for recording an image having a high concentration and excellent scratch resistance. When the content is 90% by mass or less, the coating strength is high. It is advantageous.

<Binder component>
In the surface layer, in addition to the polymer particles in the present invention, a binder component can be used as necessary.
Examples of the binder component include polyvinyl alcohol, polyvinyl acetal, oxidized starch, etherified starch, carboxymethyl cellulose, hydroxyethyl cellulose, casein, gelatin, soy protein, polyethylene imide resin, polyvinyl pyrohydrin resin, polyacrylic acid or the like Copolymer, Maleic anhydride copolymer, Acrylamide resin, Acrylate ester resin, Polyamide resin, Polyurethane resin, Polyester resin, Polyvinyl butyral resin, Alkyd resin, Epoxy resin, Epichlorohydrin resin, Urea Acrylic resin, melamine resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic acid ester, methacrylic acid ester polymer or copolymer Polymer latices, ethylene - resins of the vinyl polymer latexes such as vinyl acetate copolymer.

  Further, the thickness of the surface layer in the present invention is preferably in the range of 0.2 to 5 [mu] m from the viewpoint of obtaining high ink absorbability and enhancing the scratch resistance and density of the image.

  In addition to the above, the surface layer in the present invention includes a mold release agent, a dispersant, a thickener, an antiseptic, an antifoaming agent, a coloring dye, a coloring pigment, a fluorescent whitening agent, a water-proofing agent, a leveling agent, Additives such as antioxidants and ultraviolet absorbers can be used as necessary.

~ Ink receiving layer ~
The ink jet recording medium of the present invention has at least one ink receiving layer between the surface layer and a substrate described later. The ink receiving layer in the present invention contains at least gas phase method silica, and preferably further contains a water-soluble resin. In addition, the ink receiving layer can be further constituted by using a nitrogen-containing organic cationic polymer, a crosslinking agent, a mordant, a water-soluble polyvalent metal salt, and other components as necessary.

<Gas phase silica>
The ink receiving layer in the present invention contains vapor phase method silica as inorganic fine particles. Vapor phase silica forms a porous structure when an ink receiving layer is formed, and improves ink absorption performance. In particular, when vapor phase silica is used, the surface layer having the above-described structure is provided, so that the ink absorbability is improved compared to the case where other inorganic particles such as wet silica are used. The concentration can be improved effectively.

  When the solid content in the ink-receiving layer is 50% by mass or more, more preferably more than 60% by mass, the vapor-phase process silica can form a more favorable porous structure and can improve the ink absorbability. More preferable in terms. The solid content in the ink-receiving layer of the vapor phase silica is an amount calculated based on components other than water in the composition constituting the ink-receiving layer.

  The average primary particle size of the vapor phase silica is preferably 2 μm or less, more preferably 200 nm or less, further preferably 30 nm or less, further preferably 20 nm or less, and particularly preferably 10 nm or less. Among these, 3 to 10 nm is most preferable. In particular, when the average primary particle size is 30 nm or less, it is easy to form a porous structure having a large porosity, which is effective in ink absorption characteristics.

The silica fine particles generally include wet method particles and dry method (gas phase method) particles depending on the production method. Among these methods, the vapor phase method is a method by high-temperature vapor phase hydrolysis of silicon halide (flame hydrolysis method), and silica sand and coke are heated and reduced and vaporized by an arc in an electric furnace and oxidized with air. A method of obtaining anhydrous silica by a method (arc method) is the mainstream, and “gas phase method silica” means silica (anhydrous silica particles) synthesized by a gas phase method. In the present invention, particularly when vapor phase silica is used, the ink absorbency is high, and the image density and scratch resistance are excellent.
In the wet method, the mainstream is a method in which active silica is produced by acid decomposition of silicate, and this is appropriately polymerized and coagulated and precipitated to obtain hydrous silica.

Vapor phase silica is different from hydrous silica in terms of the density of silanol groups on the surface, the presence or absence of vacancies, etc., and exhibits different properties, but is suitable for forming a three-dimensional structure with a high porosity. The reason for this is not clear, but in the case of hydrous silica, the density of silanol groups on the fine particle surface is high at 5 to 8 / nm ² , and the silica fine particles tend to aggregate (aggregate) easily. In the case of the method silica, the density of silanol groups on the surface of the fine particles is 2 to 3 / nm ² , so that it is sparse soft agglomeration (flocculate), resulting in a structure with a high porosity. Is done.
Vapor phase silica has a particularly large specific surface area, so ink absorption and retention efficiency is high, and since the refractive index is low, transparency can be imparted to the receiving layer by dispersing to an appropriate particle size. It is characterized by high color density and good color development.

  The content of the vapor phase silica in the ink receiving layer is preferably in the range of 50 to 90% by mass with respect to the total solid content.

  Further, in addition to the vapor phase method silica, other inorganic particles may be included as necessary within a range not impairing the effects of the present invention. Preferably, the proportion of vapor-phase method silica in all particles when other inorganic particles are used in combination is preferably 30% by mass or more.

<Water-soluble resin>
The ink receiving layer in the invention may contain at least one water-soluble resin.
Examples of water-soluble resins include polyvinyl alcohol resins that are resins having a hydroxy group as a hydrophilic structural unit [polyvinyl alcohol (PVA), acetoacetyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl. Alcohol, polyvinyl acetal, etc.], cellulose resins [methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, etc.], Chitins, chitosans, starches, resins with ether bonds [polyethylene oxide (PEO), polyp Pyrene oxide (PPO), polyethylene glycol (PEG), poly ether (PVE)], and resins having carbamoyl groups [polyacrylamide (PAAM), polyvinyl pyrrolidone (PVP), polyacrylic acid hydrazide, etc.] and the like.
Moreover, the polyacrylic acid salt which has a carboxyl group as a dissociable group, maleic acid resin, alginate, gelatins, etc. can be mentioned.

Among the above, the water-soluble resin is preferably at least one selected from polyvinyl alcohol resins, cellulose resins, resins having an ether bond, resins having a carbamoyl group, resins having a carboxyl group, and gelatins. Polyvinyl alcohol (PVA) resin is preferable.
Examples of the polyvinyl alcohol include Japanese Patent Publication No. 4-52786, Japanese Patent Publication No. 5-67432, Japanese Patent Publication No. 7-29479, Japanese Patent No. 2537827, Japanese Patent Publication No. 7-57553, Japanese Patent No. 2502998, and Japanese Patent No. 3053231. JP-A-63-176173, JP-A-2604367, JP-A-7-276787, JP-A-9-207425, JP-A-11-58941, JP-A-2000-135858, JP-A-2001-205924, JP 2001-287444, JP 62-278080, JP 9-39373, JP 2750433, JP 2000-158801, JP 2001-213045, JP 2001-328345, JP 8 -324105, JP-A-11-348417, JP-A58-18168 JP, 10-259213, JP 2001-72711, JP 2002-103805, JP 2000-63427, JP 2002-308928, JP 2001-205919, JP 2002-264489. Etc. are mentioned.
Examples of water-soluble resins other than polyvinyl alcohol resins include compounds described in JP-A No. 11-165461, [0011] to [0012], JP-A Nos. 2001-205919, and 2002-26489. The described compounds are also included.

The water-soluble resins may be used alone or in combination of two or more.
The content of the water-soluble resin in the ink receiving layer is preferably 9 to 40% by mass and more preferably 12 to 33% by mass with respect to the total solid content.

  The water-soluble resin contained together with the vapor phase method silica may be a single material or a mixed system of a plurality of materials. From the viewpoint of maintaining transparency, the type of water-soluble resin to be combined with the vapor phase silica is important. When vapor phase silica is used, the water-soluble resin is preferably a polyvinyl alcohol resin, more preferably a polyvinyl alcohol resin having a saponification degree of 70 to 100%, and a polyvinyl alcohol resin having a saponification degree of 80 to 99.5%. Is particularly preferred.

  Polyvinyl alcohol resin has a hydroxyl group in its structural unit, but since this hydroxyl group and the surface silanol group of gas phase method silica form a hydrogen bond, tertiary particles having secondary particles of gas phase method silica as network chain units. It becomes easy to form the original network structure. By forming this three-dimensional network structure, it is considered that a porous ink receiving layer having a high porosity and sufficient strength is formed. In ink jet recording, the porous ink receiving layer obtained as described above can absorb ink rapidly by a capillary phenomenon, and can form dots with good roundness without ink bleeding.

  Moreover, you may use the said other water-soluble resin together with polyvinyl alcohol-type resin. When another water-soluble resin is used in combination with the polyvinyl alcohol resin, the content of the polyvinyl alcohol resin in the total water-soluble resin is preferably 50% by mass or more, and more preferably 70% by mass or more.

-Content ratio of vapor phase silica and water-soluble resin-
By optimizing the mass content ratio [PB ratio (x: y)] of the vapor phase silica (x) and the water-soluble resin (y), the film structure and film strength of the ink receiving layer can be further improved. Is possible.
As the mass content ratio [PB ratio (x: y)], the decrease in film strength and cracking during drying caused by the PB ratio being too large are prevented, and the PB ratio is too small, The ratio of 1.5: 1 to 10: 1 is preferable from the viewpoint of preventing the gap from being easily blocked by the resin and preventing the ink absorbency from being lowered due to the decrease in the porosity.
Since stress may be applied to the recording medium when passing through the conveyance system of the ink jet printer, the ink receiving layer needs to have sufficient film strength. Further, when cutting into a sheet shape, the ink receiving layer needs to have sufficient film strength in order to prevent the ink receiving layer from cracking or peeling off. Considering these cases, the PB ratio is more preferably 5: 1 or less, and more preferably 2: 1 or more from the viewpoint of ensuring high-speed ink absorbability with an inkjet printer.

For example, a coating solution in which gas phase method silica particles having an average primary particle size of 20 nm or less and a water-soluble resin are completely dispersed in an aqueous solution at a mass ratio (x: y) of 2: 1 to 5: 1 is formed on the substrate. When the coating layer is dried, a three-dimensional network structure is formed in which secondary particles of vapor phase method silica are used as a network chain, the average pore diameter is 30 nm or less, the porosity is 50 to 80%, A translucent porous film having a pore specific volume of 0.5 ml / g or more and a specific surface area of 100 m ² / g or more can be easily formed.

<Nitrogen-containing organic cationic polymer>
The ink receiving layer in the invention contains at least one nitrogen-containing organic cationic polymer. By using the nitrogen-containing organic cationic polymer, it is possible to favorably disperse the vapor phase method silica and to suppress bleeding of the recorded image.

  The nitrogen-containing organic cationic polymer is not particularly limited, but a polymer having a primary to tertiary amino group or a quaternary ammonium base is suitable, for example, a primary to tertiary amino group and Obtained as a homopolymer of the salt or a monomer having a quaternary ammonium base (nitrogen-containing organic cation monomer), or a copolymer or condensation polymer of the nitrogen-containing organic cation monomer and another monomer. Are preferred. These nitrogen-containing organic cationic polymers can be used in any form of water-soluble polymer or water-dispersible latex particles.

Examples of the nitrogen-containing organic cation monomer include trimethyl-p-vinylbenzylammonium chloride, trimethyl-m-vinylbenzylammonium chloride, triethyl-p-vinylbenzylammonium chloride, triethyl-m-vinylbenzylammonium chloride, N, N -Dimethyl-N-ethyl-Np-vinylbenzylammonium chloride, N, N-diethyl-N-methyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-Nn-propyl-Np -Vinylbenzylammonium chloride, N, N-dimethyl-Nn-octyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N-benzyl-Np-vinylbenzylammonium chloride, N, N- Ethyl-N-benzyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N- (4-methyl) benzyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N-phenyl-N -P-vinylbenzylammonium chloride;
Trimethyl-p-vinylbenzylammonium bromide, trimethyl-m-vinylbenzylammonium bromide, trimethyl-p-vinylbenzylammonium sulfonate, trimethyl-m-vinylbenzylammonium sulfonate, trimethyl-p-vinylbenzylammonium acetate, trimethyl-m-vinyl Benzylammonium acetate, N, N, N-triethyl-N-2- (4-vinylphenyl) ethylammonium chloride, N, N, N-triethyl-N-2- (3-vinylphenyl) ethylammonium chloride, N, N-diethyl-N-methyl-N-2- (4-vinylphenyl) ethylammonium chloride, N, N-diethyl-N-methyl-N-2- (4-vinylphenyl) ethylammonium chloride Tate;
N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N- Methyl chloride, ethyl chloride, methyl bromide of dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide , Quaternized products of ethyl bromide, methyl iodide or ethyl iodide, or sulfonates, alkyl sulfonates, acetates or alkyl carboxylates substituted with their anions.

  Specific examples of the compound include monomethyl diallylammonium chloride, trimethyl-2- (methacryloyloxy) ethylammonium chloride, triethyl-2- (methacryloyloxy) ethylammonium chloride, trimethyl-2- (acryloyloxy) ethylammonium chloride, Triethyl-2- (acryloyloxy) ethylammonium chloride, trimethyl-3- (methacryloyloxy) propylammonium chloride, triethyl-3- (methacryloyloxy) propylammonium chloride, trimethyl-2- (methacryloylamino) ethylammonium chloride, triethyl- 2- (methacryloylamino) ethylammonium chloride, trimethyl-2- (acryloylua) C) ethylammonium chloride, triethyl-2- (acryloylamino) ethylammonium chloride, trimethyl-3- (methacryloylamino) propylammonium chloride, triethyl-3- (methacryloylamino) propylammonium chloride, trimethyl-3- (acryloylamino) Propyl ammonium chloride, triethyl-3- (acryloylamino) propyl ammonium chloride, N, N-dimethyl-N-ethyl-2- (methacryloyloxy) ethylammonium chloride, N, N-diethyl-N-methyl-2- (methacryloyl) Oxy) ethylammonium chloride, N, N-dimethyl-N-ethyl-3- (acryloylamino) propylammonium chloride, trimethyl-2 (Methacryloyloxy) ethyl ammonium bromide, it may be mentioned trimethyl-3- (acryloylamino) propyl ammonium bromide, trimethyl-2- (methacryloyloxy) ethyl ammonium sulfonate, trimethyl-3- (acryloylamino) propylammonium acetate. In addition, examples of copolymerizable monomers include N-vinylimidazole and N-vinyl-2-methylimidazole. Further, it is also possible to use a polymer unit such as N-vinylacetamide or N-vinylformamide, which is converted into a vinylamine unit by hydrolysis after polymerization and a salt thereof.

  Examples of the other monomer that can be copolymerized (or polycondensed) with the nitrogen-containing organic cation monomer include primary to tertiary amino groups and salts thereof, or basic such as quaternary ammonium base. Or the monomer which does not contain a cationic part, does not show interaction with the dye in an inkjet ink, or interaction is substantially small is mentioned. For example, (meth) acrylic acid alkyl ester; (meth) acrylic acid cycloalkyl ester such as cyclohexyl (meth) acrylic acid; (meth) acrylic acid aryl ester such as phenyl (meth) acrylate; benzyl (meth) acrylic acid Aralkyl esters of styrene; vinyl aromatics such as styrene, vinyl toluene and α-methyl styrene; vinyl esters such as vinyl acetate, vinyl propionate and vinyl versatate; allyl esters such as allyl acetate; vinylidene chloride, vinyl chloride, etc. Halogen-containing monomers, vinyl cyanides such as (meth) acrylonitrile, olefins such as ethylene and propylene, and the like.

  The (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid alkyl ester having 1 to 18 carbon atoms in the alkyl moiety, specifically, for example, methyl (meth) acrylate or ethyl (meth) acrylate. Propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, (meth) Examples include octyl acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and hydroxyethyl methacrylate are preferable. The other monomers can also be used alone or in combination of two or more.

Among the nitrogen-containing organic cationic polymers, from the viewpoint of suppressing bleeding, cationic polyurethanes and cationic polymers described in JP-A No. 2004-167784 are preferable, and cationic polyurethanes are more preferable. Examples of commercial products of cationic polyurethane include “Superflex 650”, “F-8564D”, “F-8570D” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., “Neofix IJ” manufactured by Nikka Chemical Co., Ltd. -150 "and the like.
Further, from the viewpoint of dispersion of the vapor phase silica, polydiallyldimethylammonium chloride and polymethacryloyloxyethyl-β-hydroxyethyldimethylammonium chloride derivatives are preferable, and polydiallyldimethylammonium chloride is more preferable. As a commercially available product, “Chemistat 7005” manufactured by Sanyo Chemical Industries, Ltd. can be mentioned.

  The nitrogen-containing organic cationic polymer is also preferably a polymer obtained from a cationic emulsion in the first liquid described later.

<Crosslinking agent>
The ink receiving layer in the invention preferably contains at least one crosslinking agent that crosslinks the water-soluble resin. It is preferable that the ink receiving layer is a porous layer in which the vapor phase silica and the water-soluble resin are used in combination, and further cured by a cross-linking reaction between the cross-linking agent and the water-soluble resin.

Boron compounds are preferred for crosslinking of water-soluble resins, particularly polyvinyl alcohol. Examples of the boron compound include borax, boric acid, borates (for example, orthoborate, InBO ₃ , ScBO ₃ , YBO ₃ , LaBO ₃ , Mg ₃ (BO ₃ ) ₂ , Co ₃ (BO ₃ ) ₂ , two Borate (eg, Mg ₂ B ₂ O ₅ , Co ₂ B ₂ O ₅ ), metaborate (eg, LiBO ₂ , Ca (BO ₂ ) ₂ , NaBO ₂ , KBO ₂ ), tetraborate (eg, Na ₂ B ₄ O ₇ · 10H ₂ O), pentaborate (for example, KB ₅ O ₈ · 4H ₂ O, Ca ₂ B ₆ O ₁₁ · 7H ₂ O, CsB ₅ O ₅ ), etc. Of these, borax, boric acid, and borate are preferable, and boric acid is particularly preferable in that a crosslinking reaction can be promptly caused.

As the cross-linking agent, the following compounds other than the boron compound can also be used.
For example, aldehyde compounds such as formaldehyde, glyoxal and glutaraldehyde; ketone compounds such as diacetyl and cyclopentanedione; bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1,3,5- Active halogen compounds such as triazine and 2,4-dichloro-6-S-triazine sodium salt; divinylsulfonic acid, 1,3-vinylsulfonyl-2-propanol, N, N′-ethylenebis (vinylsulfonylacetamide) ), Active vinyl compounds such as 1,3,5-triacryloyl-hexahydro-S-triazine; N-methylol compounds such as dimethylolurea and methyloldimethylhydantoin; melamine resins (for example, methylolmelamine, alkylated methylolmelamine) Epoxy resin; 1,6- Isocyanate compounds such as hexamethylene diisocyanate; Aziridine compounds described in US Pat. Nos. 3,017,280 and 2,983,611; Carboximide compounds described in US Pat. No. 3,100,704; Glycerol triglycidyl ether, etc. Epoxy-based compounds; ethyleneimino-based compounds such as 1,6-hexamethylene-N, N′-bisethyleneurea; halogenated carboxaldehyde-based compounds such as mucochloric acid and mucophenoxycyclolic acid; 2,3-dihydroxydioxane and the like Dioxane compounds: titanium lactate, aluminum sulfate, chromium alum, potash alum, metal-containing compounds such as zirconyl acetate and chromium acetate, polyamine compounds such as tetraethylenepentamine, hydrazide compounds such as adipic acid dihydrazide, o A low molecule or polymer containing two or more xazoline groups can be used.

A crosslinking agent may be used individually by 1 type, and may be used in combination of 2 or more type.
The content of the crosslinking agent in the ink receiving layer is preferably 1 to 50% by mass, more preferably 5 to 40% by mass with respect to the water-soluble resin.

<Water-soluble polyvalent metal salt>
The ink receiving layer in the invention can contain at least one water-soluble polyvalent metal salt as a mordant.

  The water-soluble polyvalent metal salt is preferably a divalent or higher metal compound. Examples of the divalent or higher metal compound further include water-soluble salts of metals selected from calcium, barium, manganese, copper, cobalt, nickel, aluminum, iron, zinc, zirconium, chromium, tungsten, and molybdenum. . Specific examples include calcium acetate, calcium chloride, calcium formate, calcium sulfate, calcium butyrate, barium acetate, barium sulfate, barium phosphate, barium oxalate, barium naphthoresorcin carboxylate, barium butyrate, manganese chloride, manganese acetate , Manganese formate dihydrate, manganese ammonium sulfate hexahydrate, cupric chloride, ammonium copper (II) chloride dihydrate, copper sulfate, copper (II) butyrate, copper oxalate, copper phthalate, citric acid Copper, copper gluconate, naphthenic copper, cobalt chloride, cobalt thiocyanate, cobalt sulfate, cobalt acetate (II), cobalt naphthenate, nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, Nickel ammonium sulfate hexahydrate, nickel amidosulfate tetrahydrate, sulfamate Kell, nickel 2-ethylhexanoate, aluminum sulfate, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate, aluminum acetate, aluminum lactate, basic aluminum thioglycolate, Ferrous bromide, ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, iron (III) citrate, iron (III) lactate trihydrate, iron triammonium trioxalate ( III) Trihydrate, zinc bromide, zinc chloride, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, zinc lactate, zirconium acetate, zirconium tetrachloride, zirconium chloride, zirconium chloride octahydrate, hydroxy chloride Zirconium, chromium acetate, chromium sulfate, sodium phosphotungstate, sodium tungsten citrate, 2 tungstophosphoric acid n hydrate, 12 tungstosilicic acid 26 hydrate, molybdenum chloride, 12 molybdophosphoric acid n hydrate, etc., aluminum alum, basic polyaluminum hydroxide, zinc phenolsulfonate, zinc ammonium acetate, Zinc ammonium carbonate.

  Two or more water-soluble polyvalent metal salts may be used in combination. In the present invention, the water solubility in the water-soluble polyvalent metal salt means that 1% by mass or more is dissolved in 20 ° C. water.

  Among water-soluble polyvalent metal salts, an aluminum compound or a compound composed of a group 4A metal (for example, zirconium or titanium) in the periodic table is preferable, and an aluminum compound is more preferable. Particularly preferred is a water-soluble aluminum compound. Examples of the water-soluble aluminum compound include inorganic salts such as aluminum chloride or a hydrate thereof, aluminum sulfate or a hydrate thereof, and ammonium alum. Furthermore, a basic polyaluminum hydroxide compound (also referred to as basic polyaluminum chloride or polyaluminum chloride) which is an inorganic aluminum-containing cationic polymer is suitable.

The basic polyaluminum hydroxide compound is represented by the following formula 1, formula 2 or formula 3, and, for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [ It is a water-soluble polyaluminum hydroxide containing a basic and high-molecular polynuclear condensed ion stably such as Al ₁₃ (OH) ₃₄ ] ⁵⁺ , [Al ₂₁ (OH) ₆₀ ] ³⁺ , and the like.
[Al ₂ (OH) _n Cl _6-n ] _m (Formula 1)
[Al (OH) ₃ ] _n AlCl ₃ (Formula 2)
Al _n (OH) _m Cl _{(3 nm)} [0 <m <3n] (Formula 3)

  As these compounds, Taki Chemical Co., Ltd. named polyaluminum chloride (PAC) as a water treatment agent, Asada Chemical Co., Ltd. named polyaluminum hydroxide (Paho), and Riken Co., Ltd. There is the name of HAP-25 from Green, the name of Alphain 83 from Daimei Chemical Co., Ltd., and other manufacturers that have been put on the market for similar purposes. it can.

  As the water-soluble compound containing the Group 4A element of the periodic table, a water-soluble compound containing titanium or zirconium is more preferable. Examples of the water-soluble compound containing titanium include titanium chloride, titanium sulfate, titanium tetrachloride, tetraisopropyl titanate, titanium acetylacetonate, and titanium lactate. Examples of water-soluble compounds containing zirconium include zirconium acetate, zirconium chloride, hydroxy zirconium chloride, zirconium nitrate, basic zirconium carbonate, zirconium hydroxide, zirconium lactate, zirconium carbonate / ammonium, zirconium carbonate / potassium, zirconium sulfate, zirconium fluoride. Compounds and the like.

  The content of the water-soluble polyvalent metal salt in the ink receiving layer is preferably in the range of 0.1 to 10% by mass and more preferably in the range of 0.5 to 8% by mass with respect to the vapor phase silica.

<Magnesium salt>
In addition to the above water-soluble polyvalent metal salt, a magnesium salt can also be used for the ink receiving layer in the invention. By containing a magnesium salt, ozone resistance can be improved.
Examples of the magnesium salt include magnesium acetate, magnesium oxalate, magnesium sulfate, magnesium chloride hexahydrate, and magnesium citrate nonahydrate. Of these, magnesium chloride hexahydrate is preferred. Examples of commercially available products include “White Nigari NS” and “Mag Chloride (Special Name) NS” manufactured by Naikai Shigyo Co., Ltd.

<Other ingredients>
In addition to the above components, the ink receiving layer in the invention may contain other components such as a nitrogen-containing organic cationic polymer, a water-soluble polyvalent metal salt, a mordant other than a magnesium salt, and various surfactants.
As other components, the components described in paragraph Nos. 0088 to 0117 of JP-A No. 2005-14593, the components described in paragraph Nos. 0138 to 0155 of JP-A No. 2006-321176, etc. may be appropriately selected and used. it can.

~Base material~
The ink jet recording medium of the present invention includes a base material as a support for supporting the ink receiving layer and the surface layer.

  As the substrate, any of a transparent substrate made of a transparent material such as plastic and an opaque substrate made of an opaque material such as paper can be used. In order to take advantage of the transparency of the ink receiving layer, it is preferable to use a transparent substrate or a highly glossy opaque substrate. In addition, a read-only optical disk such as a CD-ROM or DVD-ROM, a write-once optical disk such as a CD-R or DVD-R, or a rewritable optical disk may be used as a base material to provide an ink receiving layer on the label surface side. it can.

  As a material that can be used for the transparent substrate, a material that is transparent and can withstand radiant heat when used in an OHP or a backlight display is preferable. Examples of the material include polyesters such as polyethylene terephthalate (PET); polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide and the like. Of these, polyesters are preferable, and polyethylene terephthalate is particularly preferable. Although there is no restriction | limiting in particular as thickness of a transparent base material, 50-200 micrometers is preferable at the point which is easy to handle.

As the highly glossy opaque base material, one having a glossiness of 40% or more on the surface on which the ink receiving layer is provided is preferable. The glossiness is a value determined according to the method described in JIS P-8142 (75-degree specular gloss test method for paper and paperboard). Specifically, for example, high gloss paper substrates such as art paper, coated paper, cast coated paper, baryta paper used for a silver salt photographic support, etc .; polyesters such as polyethylene terephthalate (PET), Nitrocellulose, cellulose acetate, cellulose esters such as cellulose acetate butyrate, polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide, and other plastic films are made opaque by adding white pigments etc. (surface calendering is applied) A polyolefin coating layer containing or not containing a white pigment is provided on the surface of a highly glossy film or a highly glossy film containing various paper substrates, transparent substrates or white pigments. The obtained base material etc. are mentioned.
A white pigment-containing foamed polyester film (for example, foamed PET containing polyolefin fine particles and forming voids by stretching) can also be suitably exemplified. Furthermore, resin-coated paper used for silver salt photographic printing paper is also suitable.
Although there is no restriction | limiting in particular also about the thickness of an opaque base material, 50-300 micrometers is preferable at the point of handleability.

  Further, the surface of the substrate may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment or the like in order to improve wettability and adhesion.

Next, the base paper used for the resin-coated paper will be described in detail.
As the base paper, wood pulp is used as a main raw material, and paper is made using synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester in addition to wood pulp as necessary. As the above-mentioned wood pulp, 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. preferable. However, the ratio of LBSP and / 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% and a 42 mesh residual as defined in JIS P-8207. 30 to 70% of the sum with the mass% of 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, and 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 calendering at the paper making stage or after paper making. The density of the base paper is generally 0.7 to 1.2 g / m ₂ (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, a sizing agent similar to the size 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) and / or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, etc. can also be used. In particular, the polyethylene layer on the side on which the ink receiving layer is formed is obtained by adding rutile or anatase type titanium oxide, fluorescent whitening agent, ultramarine to polyethylene, as is widely done in photographic paper. Those having improved whiteness and hue are preferred. Here, as a titanium oxide content, about 3-20 mass% is preferable with respect to polyethylene, and 4-13 mass% is more preferable. Although the thickness of a polyethylene layer does not have limitation in particular, 10-50 micrometers is suitable for both front and back layers. Further, an undercoat layer can be provided on the polyethylene layer in order to provide adhesion to the ink receiving layer. As the undercoat layer, aqueous polyester, gelatin and PVA are preferable. Moreover, as thickness of this undercoat layer, 0.01-5 micrometers is preferable.
Polyethylene-coated paper can be used as glossy paper, or when it is coated by melt-extruding polyethylene onto the surface of the base paper, a matte or silky surface that can be obtained with ordinary photographic printing paper by performing a so-called molding process. Can also be used.

  The substrate can also be provided with a backcoat layer. This backcoat layer is composed of white pigments (inorganic pigments such as light calcium carbonate, heavy calcium carbonate, kaolin, talc and calcium sulfate, and organic pigments such as polyethylene and melamine resin). ), Aqueous binders (water-soluble polymers such as styrene / acrylate copolymers, polyvinyl alcohol, gelatin, and polyvinylpyrrolidone), and other components (antifoaming agents, antifoaming agents, dyes, fluorescent whitening agents, Antiseptics, water-proofing agents, etc.).

  The ink jet recording medium of the present invention may further have an ink solvent absorption layer, an intermediate layer, and the like in addition to the ink receiving layer and the surface layer. Further, an undercoat layer may be provided on the base material for the purpose of improving the adhesion between the ink receiving layer and the base material and appropriately adjusting the electric resistance value.

  A polymer fine particle dispersion may be added to a constituent layer (for example, an ink receiving layer, a surface layer, or a back coat layer) of the ink jet recording medium of the present invention. This polymer fine particle dispersion is used for the purpose of improving film properties such as dimensional stabilization, curling prevention, adhesion prevention, and film cracking prevention. The polymer fine particle dispersion is described in JP-A-62-245258 and JP-A-10-228076. If a polymer fine particle dispersion having a low glass transition temperature (40 ° C. or lower) is added to the layer containing the mordant, cracking and curling of the layer can be prevented. Further, even when a polymer fine particle dispersion having a high glass transition temperature is added to the back layer, curling can be prevented.

  The ink receiving layer and the surface layer may be provided only on one side of the base material, or may be provided on both sides of the base material for a desired purpose such as preventing deformation such as curling. When the ink receiving layer is provided only on one side of the base material when used in OHP or the like, an antireflection film can be provided on the opposite surface or both surfaces for the purpose of enhancing light transmittance.

  Also, by applying boric acid or boron compound to the surface of the substrate on the side where the ink receiving layer is provided and forming the ink receiving layer thereon, the glossiness and surface smoothness of the ink receiving layer are further increased. In addition, it is possible to further suppress bleeding of the image over time in a high temperature and high humidity environment.

≪Inkjet recording medium manufacturing method≫
The ink jet recording medium of the present invention is constituted by providing at least an ink receiving layer and a surface layer in order from the base material side on the base material. A method of forming a surface layer by coating or the like after forming an ink receiving layer; b) coating by simultaneously applying a coating solution for forming an ink receiving layer and a coating solution for forming a surface layer on a substrate; It can be manufactured by the method to do.

~ Formation of ink receiving layer ~
The ink receiving layer can be suitably formed by the following first and second modes.
The first form of forming the ink receiving layer includes a step of applying a first liquid containing at least gas phase method silica on a substrate to form an application layer, and (1) the first At the same time when one liquid is applied, or (2) either during the drying of the coating layer formed by applying the first liquid and before the coating layer exhibits reduced drying, A step of applying a second liquid containing a compound and performing crosslinking and curing of the coating layer to form an ink receiving layer in which the coating layer is crosslinked and cured.

  In addition, the second form of forming the ink receiving layer includes a step of applying a first liquid containing vapor-phase-processed silica on a substrate to form a coating layer, and the formed coating layer. In this embodiment, the ink receiving layer is formed by providing a step of cooling so as to lower by 5 ° C. or more with respect to the temperature of the first liquid at the time of coating and a step of drying the cooled coating layer.

<Coating layer formation process>
In the first and second embodiments, a step of forming a coating layer by applying a first liquid containing vapor phase silica on a substrate (hereinafter also referred to as a “coating layer forming step”). Have. Application | coating of a 1st liquid can be performed using well-known coating apparatuses, such as an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater, for example.
The wet coating amount of the first solution is preferably ^{50~200ml / m 2, 75~150ml / m} 2 is more preferable. Moreover, as a solid content application quantity of 1st liquid, 5-25 g / m < ² > is preferable and 10-18 g / m < ² > is more preferable.

  The first liquid can further contain other components such as a water-soluble resin, a crosslinking agent, a mordant, a dispersant, and a surfactant. Moreover, in application | coating of a 1st liquid, it is also preferable to apply, after carrying out in-line mixing of the liquid containing water-soluble polyvalent metal salt (preferably basic polyaluminum chloride compound) as stated above.

  The first liquid is preferably acidic, and the pH is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. When the pH of the first liquid is 5.0 or less, for example, the crosslinking reaction of the water-soluble resin by the crosslinking agent (particularly the boron compound) in the first liquid can be more sufficiently suppressed.

The first liquid containing vapor-phase process silica can be prepared, for example, as follows. That is,
Vapor phase silica fine particles and a dispersant are added to water (for example, silica fine particles in water are 10 to 20% by mass), and a high-speed rotating wet colloid mill (for example, “Clearmix” manufactured by M Technique Co., Ltd.) ), For example, under high speed rotation conditions of 10,000 rpm (preferably 5000-20000 rpm), for example, for 20 minutes (preferably 10-30 minutes), and thereafter, a crosslinking agent (for example, boric acid) and polyvinyl alcohol (PVA) ) An aqueous solution (for example, PVA having a mass of about 1/3 of the above-mentioned vapor phase silica) is added, and a water-soluble polyvalent metal salt (for example, a basic polyaluminum hydroxide compound) is further added. Can be prepared by carrying out dispersion under the same rotation conditions. The water-soluble polyvalent metal salt may be added by in-line mixing immediately before application.
Moreover, a liquid-liquid collision type disperser (for example, an optimizer manufactured by Sugino Machine Co., Ltd.) can also be used for the dispersion.
The obtained coating liquid is in a uniform sol state, and a porous ink receiving layer having a three-dimensional network structure can be formed by applying the coating liquid onto a substrate by the following coating method and drying it.

In addition, preparation of an aqueous dispersion composed of vapor phase silica and a dispersant may be carried out by preparing a vapor phase silica aqueous dispersion in advance and adding the aqueous dispersion to the aqueous dispersant solution. May be added to the vapor phase silica aqueous dispersion or may be mixed at the same time. Further, the vapor phase silica may be added to the dispersant aqueous solution as described above in a powder state, not as a vapor phase silica aqueous dispersion.
After mixing said vapor phase silica and a dispersing agent, the mixed liquid is refined using a disperser, whereby an aqueous dispersion having an average particle diameter of 50 to 300 nm can be obtained. As a disperser used for obtaining the aqueous dispersion, various kinds of conventionally known dispersers such as a high-speed rotary disperser, a medium agitating disperser (ball mill, sand mill, etc.), an ultrasonic disperser, a colloid mill disperser, and a high pressure disperser. Although a disperser can be used, a stirrer-type disperser, a colloid mill disperser, or a high-pressure disperser is preferable from the viewpoint of efficiently dispersing the formed fine particles.

  As the solvent, water, an organic solvent, or a mixed solvent thereof can be used. Examples of the organic solvent that can be used for this coating include alcohols such as methanol, ethanol, n-propanol, i-propanol, and methoxypropanol, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, acetonitrile, ethyl acetate, and toluene. It is done.

  In addition, a chaotic polymer can be used as the dispersant. Examples of the chaotic polymer include mordant examples described in paragraph numbers 0138 to 0148 of JP-A No. 2006-321176. It is also preferable to use a silane coupling agent as the dispersant. The amount of the dispersant added to the vapor phase silica is preferably 0.1% by mass to 30% by mass, and more preferably 1% by mass to 10% by mass.

<Crosslinking curing process>
In the first embodiment, for the coating layer formed in the coating layer forming step,
(1) At the same time as the first liquid is applied, or (2) during the drying of the coating layer formed by applying the first liquid, before the coating layer exhibits reduced-rate drying,
In any of the cases, there is a step of applying a second liquid containing a basic compound and crosslinking and curing the coating layer (hereinafter also referred to as “crosslinking and curing step”).

  As a method of applying the second liquid at the same time as “(1) Applying the first liquid”, a mode in which the first liquid and the second liquid are simultaneously applied in order from the substrate side is preferable. The simultaneous multilayer coating can be performed using a known coating apparatus such as an extrusion die coater or a curtain flow coater.

The method of applying the second liquid before “(2) during the drying of the coating layer formed by applying the first liquid and before the coating layer exhibits reduced-rate drying” is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-2005. The so-called Wet-On-Wet method (WOW method) described in paragraph Nos. 0016 to 0037 of Japanese Patent No. 14593 is preferable. In the present invention, after the first liquid is applied to the substrate to form the coating layer, (i) the coating is performed during the drying of the formed coating layer and before the coating layer exhibits reduced-rate drying. A method of applying the second liquid on the layer, (ii) a method of spraying the second liquid on the coating layer by spraying, or (iii) immersing the substrate on which the coating layer is formed in the second liquid It can be done by the method to do.
In the above (i), examples of the application method for applying the second liquid include curtain flow coaters, extrusion die coaters, air doctor coaters, bread coaters, rod coaters, knife coaters, squeeze coaters, reverse roll coaters, and bar coaters. A known coating method such as the above can be used. However, it is preferable to use a method in which the coater does not directly contact an already formed coating layer, such as an extrusion die coater, a curtain flow coater, a bar coater or the like.

  The term “before the coating layer comes to show reduced-rate drying” usually refers to a process for several minutes immediately after the application of the coating liquid for forming the ink receiving layer (first liquid). This shows the phenomenon of “constant rate drying” in which the content of the solvent (dispersion medium) in the applied layer decreases in proportion to time. About the time which shows this "constant rate drying", it describes in chemical engineering handbook (pages 707-712, Maruzen Co., Ltd. issue, October 25, 1980), for example.

  As a condition for drying until the coating layer exhibits reduced-rate drying, it is generally performed at 40 to 180 ° C. for 0.5 to 10 minutes (preferably 0.5 to 5 minutes). The drying time varies depending on the coating amount, but usually the above range is appropriate.

Next, the said 2nd liquid in a bridge | crosslinking hardening process is demonstrated.
The second liquid contains at least one basic compound. Examples of basic compounds include weak acid ammonium salts, weak acid alkali metal salts (eg, lithium carbonate, sodium carbonate, potassium carbonate, lithium acetate, sodium acetate, potassium acetate, etc.), weak acid alkaline earth metal salts (eg, , Magnesium carbonate, barium carbonate, magnesium acetate, barium acetate, etc.), hydroxyammonium, primary to tertiary amines (eg, triethylamine, tripropylamine, tributylamine, trihexylamine, dibutylamine, butylamine, etc.), primary to tertiary Aniline (eg, diethylaniline, dibutylaniline, ethylaniline, aniline, etc.), optionally substituted pyridine (eg, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 4- (2-hydroxy) Ethyl) -ami Pyridine, and the like), and the like.

  In addition to the basic compound, other basic substances and / or salts thereof may be used in combination with the basic compound. Examples of other basic substances include ammonia, primary amines such as ethylamine and polyallylamine, secondary amines such as dimethylamine, tertiary amines such as N-ethyl-N-methylbutylamine, and alkali metals. And alkaline earth metal hydroxides.

  Of these, ammonium salts of weak acids are particularly preferred. The weak acid is an inorganic acid or an organic acid described in Chemical Handbook Fundamentals II (Maruzen Co., Ltd.) or the like and has an pKa of 2 or more. Examples of the weak acid ammonium salt include ammonium carbonate, ammonium hydrogen carbonate, ammonium borate, ammonium acetate, and ammonium carbamate. However, it is not limited to these. Among these, ammonium carbonate, ammonium hydrogen carbonate, and ammonium carbamate are preferable, and are effective in that ink bleeding can be reduced without remaining in the layer after drying. In addition, a basic compound can use 2 or more types together.

  As content in the 2nd liquid of the said basic compound (especially ammonium salt of weak acid), 0.5-10 mass% is preferable with respect to the total mass (a solvent is included) of 2nd liquid, More preferably, 1 ˜5 mass%. When the content of the basic compound (particularly the ammonium salt of the weak acid) is particularly in the above range, a sufficient degree of curing can be obtained, and the ammonia concentration becomes too high without impairing the working environment.

A mode in which the second liquid contains at least one metal compound is preferable.
As the metal compound contained in the second liquid, those that are stable under basic conditions can be used without limitation, and any of the water-soluble polyvalent metal salts, metal complex compounds, inorganic oligomers, or inorganic polymers described above can be used. There may be. For example, zirconium compounds and compounds listed as inorganic mordants in paragraph numbers 0100 to 0101 in JP-A-2005-14593 are suitable. Examples of the metal complex compound include metal complexes described in “Chemistry Review No. 32 (1981)” edited by the Chemical Society of Japan, “Coordination Chemistry Review”, Vol. 84, pages 85-277. (1988) and JP-A-2-182701, transition metal complexes containing a transition metal such as ruthenium can be used.

  Among the above, zirconium compounds and zinc compounds are preferable, and zirconium compounds are particularly preferable. Zirconium compounds include, for example, ammonium zirconium carbonate, ammonium zirconium nitrate, potassium zirconium carbonate, ammonium zirconium citrate, zirconyl stearate, zirconyl octylate, zirconyl nitrate, zirconium oxychloride, and zirconium zirconium hydroxy chloride. Zirconium ammonium is preferred. In the second liquid, two or more metal compounds (preferably containing a zirconium compound) may be used in combination.

  As content in the 2nd liquid of the said metal compound (especially zirconium compound), 0.05-5 mass% is preferable with respect to the total mass (a solvent is included) of a 2nd liquid, More preferably, it is 0.1-0.1%. 2% by mass. By setting the content of the metal compound (especially zirconium compound) in the above range, the coating layer can be sufficiently hardened, and the mordanting ability is lowered and sufficient print density cannot be obtained or beading occurs. The concentration of the basic compound such as ammonia is not too high, and the working environment is not deteriorated. Two or more metal compounds can be used in combination, and when other mordant components to be described later are used in combination with a metal compound other than the metal compound, the total amount is within the above range and does not impair the effects of the present invention. It can be contained in a range.

  From the viewpoint of image density and ozone resistance, the second liquid preferably contains the above-described magnesium salt as a metal compound. As the magnesium salt, magnesium chloride is particularly preferred. In this case, the addition amount of the magnesium salt is preferably 0.1 to 1% by mass, and more preferably 0.15 to 0.5% by mass with respect to the total mass of the second liquid.

The second liquid may contain a crosslinking agent and other mordant components as necessary.
The second liquid can be used as an alkaline solution to promote hardening of the coating layer, and is preferably adjusted to pH 7.1 or higher, more preferably pH 8.0 or higher, particularly preferably pH 9.0 or higher. is there. When the pH is 7.1 or more, the crosslinking reaction of the water-soluble resin that may be contained in the first liquid can be further promoted, and bronzing and cracking of the ink receiving layer can be more effectively suppressed.

  The second liquid is, for example, ion-exchanged water, a metal compound (for example, zirconia compound; for example, 1 to 5%) and a basic compound (for example, ammonium carbonate; for example, 1 to 5%), and paraffin as necessary. It can be prepared by adding toluenesulfonic acid (for example, 0.5 to 3%) and stirring sufficiently. In addition, all "%" of each composition means solid content mass%. Moreover, water, an organic solvent, or these mixed solvents can be used for the solvent used for preparation of a 2nd liquid. Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol, i-propanol and methoxypropanol, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, acetonitrile, ethyl acetate and toluene.

  On the other hand, the second liquid preferably has a small content of inorganic particles such as silica particles, and the content of the inorganic particles is preferably 50% by mass or less based on the total solid content of the second liquid. It is desirable not to include inorganic particles.

<Cooling and drying process>
In the second embodiment, the step of cooling the coating layer formed in the coating layer forming step so as to decrease by 5 ° C. or more with respect to the temperature of the first liquid at the time of coating (hereinafter referred to as “cooling step”). And a step of drying the cooled coating layer (hereinafter also referred to as “drying step”).

As a method for cooling the coating layer in the cooling step, a method of cooling the substrate on which the coating layer is formed in a cooling zone maintained at 0 to 10 ° C. for 5 to 30 seconds is preferable. In a cooling process, it is preferable to cool so that it may fall 0-10 degreeC, and it is more preferable to cool so that it may fall 0-5 degreeC or more. Here, the temperature of the coating layer is measured by measuring the temperature of the film surface.
Moreover, drying in a drying process can be performed by, for example, applying drying air. The temperature of the drying air at this time is preferably 30 to 80 ° C.

~ Formation of surface layer ~
The surface layer provided on the ink receiving layer formed as described above is applied by applying a preparation liquid (for example, coating solution) for forming a surface layer containing at least the polymer particles in the present invention on the ink receiving layer. Can be formed.

  When the surface layer is formed by coating, for example, coating is performed using a known coating apparatus such as an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater, etc. be able to.

The amount to impart preparation liquid for surface layer formation (e.g., coating liquid) (e.g., coating amount) is preferably from 5 to 100 ml / ^{m 2} in moisture deposition volume, more preferably 10-50 ml / ^{m 2,} also, preferably 0.5 to 4.0 g / ^{m 2} in solid coating amount, 0.5 to 2.5 g / ^{m 2} is more preferable.

≪Inkjet recording method≫
There is no particular limitation on the recording method by the ink jet method for recording an image on the ink jet recording medium of the present invention, and a known method, for example, a charge control method in which ink is ejected using electrostatic attraction, a piezoelectric method, and the like. A drop-on-demand method (pressure pulse method) that uses the vibration pressure of the element, an acoustic ink jet method that discharges ink using radiation pressure by irradiating the ink with an electrical signal converted into an acoustic beam, and heating the ink A thermal ink jet method or the like that uses bubbles to form bubbles can be used. The ink jet recording method includes a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent. A method using ink is included.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

Example 1
<Preparation of base material>
Wood pulp consisting of 100 parts of LBKP is beaten to 300 ml Canadian freeness with a double disc refiner, 0.5 parts of epoxidized behenamide, 1.0 part of anionic polyacrylamide, 0.1 part of polyamide polyamine epichlorohydrin, 0.5 part of cationic polyacrylamide All the parts were added at an absolutely dry mass ratio to the pulp, and weighed with a long net paper machine to make a base paper of 170 g / m ² .

In order to adjust the surface size of the obtained base paper, 0.04% of a fluorescent whitening agent (“Whiteex BB” manufactured by Sumitomo Chemical Co., Ltd.) was added to a 4% aqueous solution of polyvinyl alcohol, and this was converted to an absolute dry weight. The base paper was impregnated so as to be 0.5 g / m ² , dried, and then subjected to calendar treatment to obtain a base paper adjusted to a density of 1.05.

After the corona discharge treatment was performed on the wire surface (back surface) side of the obtained base paper, high-density polyethylene was coated to a thickness of 19 μm using a melt extruder to form a resin layer composed of a mat surface. (Hereinafter, this resin layer surface is referred to as “back surface”). The back side resin layer is further subjected to a corona discharge treatment, and thereafter, as an antistatic agent, aluminum oxide (“Alumina Sol 100” manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (“Snow manufactured by Nissan Chemical Industries, Ltd.”) are used. Tex O ") the mass ratio of 1: a dispersion dispersed in water at 2, dry weight was coated to a 0.2 g / m ^2.

  Furthermore, after the corona discharge treatment is applied to the felt surface (surface) side where the resin layer is not provided, anatase-type titanium dioxide 10%, a trace amount of ultramarine blue, and a fluorescent whitening agent 0.01% (vs. polyethylene) Low-density polyethylene containing MFR (melt flow rate) 3.8 is melt-extruded to a thickness of 29 μm using a melt extruder, and a high-gloss thermoplastic resin layer is formed on the surface side of the base paper. (Hereinafter, this highly glossy surface is referred to as a “front surface”) to form a substrate (support).

<Preparation of inkjet recording medium>
-Preparation of coating liquid A (first liquid) for ink receiving layer-
Among various components in the following composition, first, (1) gas phase method silica fine particles, (2) ion-exchanged water, (3) Charol DC-902P, and (4) ZA-30 are mixed, and a bead mill (KD-P Then, the obtained dispersion was heated to 45 ° C. and held for 20 hours. Thereafter, (5) an aqueous boric acid solution, (6) a dimethylamine / epichlorohydrin / polyalkylenepolyamine polycondensate, (7) a polyvinyl alcohol solution, (8) Superflex 650 and (9) ethanol water at 30 ° C. In addition, an ink receiving layer coating solution A (first solution) was prepared.

<Composition>
(1) Gas phase method silica fine particles: 100 parts (AEROSlL300SF75, manufactured by Nippon Aerosil Co., Ltd.)
(2) Ion-exchanged water: 555 parts (3) Charol DC-902P (51.5 mass% aqueous solution): 8.7 parts (dispersant; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
(4) Zirconyl acetate (50% by mass aqueous solution) 2.7 parts (ZA-30, manufactured by Daiichi Rare Element Chemical Co., Ltd.)
(5) 7.5% by mass aqueous solution of boric acid (crosslinking agent) 50 parts (6) Dimethylamine / epichlorohydrin / polyalkylene polyamine polycondensate (50% aqueous solution) 0.77 parts (SC- 505, made by Hymo Co., Ltd.)
(7) Polyvinyl alcohol (water-soluble resin) solution ... 290 parts
<Composition of polyvinyl alcohol solution>
Polyvinyl alcohol: 20.3 parts (PVA-235 (saponification degree 88%, polymerization degree 3500), manufactured by Kuraray Co., Ltd.)
・ Diethylene glycol monobutyl ether: 6.0 parts (Butisenol 20P, manufactured by Kyowa Hakko Co., Ltd.)
・ Ion-exchanged water: 263.7 parts (8) Superflex 650: 25 parts (cation-modified polyurethane, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
(9) Ethanol water (ethanol content: 59 mass%) 75 parts

-Preparation of basic solution B (second solution)-
Various components in the following composition were mixed and stirred to prepare a basic solution B.
<Composition>
(1) Boric acid: 0.65 parts (2) Zirconyl ammonium carbonate (13% by mass aqueous solution): 2.5 parts (Zircosol AC-7, manufactured by Daiichi Rare Element Chemical Co., Ltd.)
(3) Ammonium carbonate (first grade: manufactured by Kanto Chemical Co., Ltd.) ··· 4.0 parts (4) Ion exchange water ··· 92.85 parts (5) Emulgen 109P ··· 0.6 parts (Polyoxy Ethylene lauryl ether; manufactured by Kao Corporation

-Preparation of polyvalent metal salt aqueous solution C for in-line blending-
Various components in the following composition were mixed and stirred to prepare an aqueous polyvalent metal salt solution C for in-line blending.
<Composition>
(1) Alphain 83 ... 20.0 parts (polyaluminum chloride; manufactured by Daimei Chemical Industry Co., Ltd.)
(2) Emulgen 109P ... 4.4 parts (Polyoxyethylene lauryl ether; manufactured by Kao Corporation)
(3) Ion exchange water: 75.6 parts

-Preparation of surface layer coating solution 1-
Polysol OLZ-1790 (manufactured by Showa High Polymer Co., Ltd .; cationic polymer particles (polymethyl methacrylate-polystyrene irregular shaped particles), primary average particle size: 33 nm, differential scanning calorimetry (DSC; the same applies hereinafter) Tg: 110 ° C.) was mixed in water so that the solid concentration was 10% by mass and PVA-235 was 1% by mass in solid content to prepare a coating solution 1 for the surface layer.

-Preparation of inkjet recording sheet-
After the corona discharge treatment was performed on the front surface of the base material obtained above, the ink receiving layer coating liquid A (first liquid) that was allowed to flow to a coating amount of 173 ml / m ² was added to the polyvalent for in-line blending. A metal salt aqueous solution C was mixed in-line at a rate of 10.8 ml / m ² to prepare an ink-receiving layer coating solution A-2, which was applied to the front side with a slide bead coater. Then, it was dried with a hot air dryer at 80 ° C. (wind speed 3 to 8 m / sec) until the solid content concentration of the coating layer became 20%. During this period, the coating layer exhibited constant rate drying. Then, before showing the rate-decreasing drying, the base material provided with the coating layer is immersed in the basic solution B (second liquid) for 3 seconds, and 13 g / m ² is adhered on the coating layer. Dry at 10 ° C. for 10 minutes.
In this way, an ink receiving layer having a dry film thickness of 32 μm was formed.

Subsequently, the surface layer coating solution 1 is further applied on the formed ink receiving layer with a slide bead coater so that the dry coating amount (solid content coating amount) is 2.0 g / m ² . The surface layer was laminated by drying.

  As described above, an ink jet recording sheet was prepared in which an ink receiving layer and a surface layer were provided in this order on a substrate.

(Example 2)
In Example 1, Polyzol OLZ-1790 was converted to Polyzol OLZ-1808 (manufactured by Showa High Polymer Co., Ltd .; anionic polymer particles (polymethyl methacrylate-polystyrene irregularly shaped particles), primary average particle size: 32 nm, by DSC. An ink jet recording sheet was produced in the same manner as in Example 1 except that Tg was changed to 110 ° C.

(Example 3)
In Example 1, except that polyzol OLZ-1790 was replaced with fine particles not containing styrene in the course of preparing the polyzol OLZ-1790 dispersion (non-shaped particles, primary average particle size: 16 nm, DSC Tg: 100 ° C.). In the same manner as in Example 1, an inkjet recording sheet was produced.

Example 4
In Example 1, except that the dry coating amount (solid content coating amount) of the surface layer coating solution 1 was changed from 2.0 g / m ² to 0.6 g / m ² , the same as in Example 1, An ink jet recording sheet was prepared.

(Example 5)
In Example 1, except that the dry coating amount (solid content coating amount) of the surface layer coating liquid 1 was changed from 2.0 g / m ² to 3.5 g / m ² , the same as in Example 1, An ink jet recording sheet was prepared.

(Comparative Example 1)
-Preparation of coating solution D for ink receiving layer-
100 parts of synthetic silica (Mizukasil P-78A, manufactured by Mizusawa Chemical Co., Ltd.) in terms of solid content, 50 parts of polyvinyl alcohol (JF-17L, Showa Polymer Co., Ltd.) as an adhesive, and ink fixing agent As a mixture, 20 parts of a cationic resin (Polyfix 700, manufactured by Showa Polymer Co., Ltd.) was mixed to prepare a coating liquid D for ink receiving layer having a solid content concentration of 15% by mass.

-Preparation of surface layer coating solution 2-
Polysol OLZ-1790 (manufactured by Showa High Polymer Co., Ltd .; cationic polymer particles (polymethyl methacrylate-polystyrene irregular shaped particles), primary average particle size: 33 nm, differential scanning calorimetry (DSC; the same applies hereinafter) Tg: 110 ° C.) in terms of solid content and 10 parts of polyvinyl alcohol (JF-17L, manufactured by Nihon Vinegar Bipovar Co., Ltd.) as an adhesive are mixed, and the surface layer coating solution 2 having a solid content concentration of 15% by mass Was prepared.

-Preparation of inkjet recording sheet-
On the base material obtained in Example 1, the ink receiving layer coating solution D was applied using a bar coater so that the dry coating amount was 5 g / m ^2, and dried at 100 ° C. for 30 seconds. Formed. Subsequently, the surface layer coating solution 2 was further coated on the formed ink receiving layer using a bar coater so that the dry coating amount was 20 g / m ² . Thereafter, the coated substrate was passed through a mirror roll maintained at a surface temperature of 70 ° C. while being pressed at a linear pressure of 15 kg / cm to obtain a comparative inkjet recording sheet.

(Comparative Example 2)
A comparative inkjet recording sheet was prepared in the same manner as in Example 1 except that the surface layer was not laminated on the formed ink receiving layer in Example 1.

(Evaluation)
The following evaluation was performed about the sheet | seat for inkjet recording produced in each of said Example and comparative example. The evaluation results are shown in Table 1 below.

-1. Image density
After the inkjet recording sheet is stored in an environment of 25 ° C. and 50% RH for 24 hours, a black solid image is recorded at a maximum density using a printer PM-A700 manufactured by Seiko Epson Corporation, and the ink is recorded at 25 ° C. and 50% RH. And stored for 24 hours in the environment. Thereafter, the density of the black solid image was measured with X-rite 310 (manufactured by X-rite) and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: The density was 2.5 or more.
B: The concentration was 2.4 or more and less than 2.5.
C: The concentration was 2.3 or more and less than 2.4.
D: The concentration was 2.2 or more and less than 2.3.

-2. Ink absorption
Ink jet printer PX-G930 (manufactured by Seiko Epson Corporation) applies cyan (C), magenta (M), yellow (Y), and black (K) inks to the maximum ink discharge amount for the ink jet recording sheet. And a solid image was recorded. Immediately after recording, Xerox paper C2 (manufactured by Fuji Xerox Co., Ltd.) was overlaid on the solid image, and the degree of ink transferred to the Xerox paper after peeling off was visually observed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: There was no transcription.
B: Slight transfer was observed.
C: Transfer was observed and was in an unacceptable range for practical use.
D: The transfer amount was large.

-3. Scratch resistance
Each inkjet recording sheet was cut into A4 size, and two sheet test pieces obtained by cutting were placed on a horizontal and flat test table. At this time, the sheet test pieces are overlapped so that the surface of the ink receiving layer of the lower sheet test piece close to the test table and the base material surface of the upper sheet test piece are in contact with each other. While applying a load of 500 g / A4 size on the upper upper sheet test piece, the lower sheet test piece is pulled out at a speed of 1 cm / sec to be the surface of the surface layer of the lower sheet test piece. The scratches were evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: Generation | occurrence | production of the damage | wound was not recognized.
B: Although a thin crack was attached, it was within a practically acceptable range.
C: Scratches were observed, and the scratches remained after recording, and were practically unacceptable.
D: Scratches were conspicuous, and the scratches were conspicuous even after recording.

  As shown in Table 1, in the examples, the ink absorbency was good, the image after recording had a high density, and the scratch resistance was also excellent. On the other hand, in Comparative Example 1 using wet silica, the ink absorptivity and the image density are extremely low, and when no polymer particles are given (Comparative Example 2), the ink absorptivity and the image density can be obtained. The image rubbing performance was significantly reduced.

Claims (5)

  On the base material, in order from the base material side, an ink receiving layer containing vapor-phase process silica, and a surface layer containing polymer particles having a primary average particle diameter of 5 to 50 nm and a glass transition temperature of 80 ° C. or higher, An ink jet recording medium comprising:   The ink jet recording medium according to claim 1, wherein the polymer particles are irregularly shaped particles having a concavo-convex shape on a surface thereof.   3. The ink jet recording medium according to claim 1, wherein the ink receiving layer further contains a polyaluminum chloride compound. The surface layer, the ink-jet recording medium according to any one of claims 1 to 3, wherein the solid content is 0.5 to 4.0 g / ^{m 2.}   The said polymer particle is at least 1 sort (s) of particle | grains selected from a (meth) acrylate type polymer, a styrene- (meth) acrylate type polymer, and a polystyrene type polymer, Any one of Claims 1-4 characterized by the above-mentioned. 2. An ink jet recording medium according to item 1.