JP2007268924A - Inkjet recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording material which is excellent in an ink absorbency. <P>SOLUTION: The inkjet recording material which provides a plurality of ink acceptance layers on a support comprises an ink acceptance layer which is made by coating and drying an upper coating layer coating liquid containing a porous inorganic pigment, a binder and an alkali viscosity increase type emulsion of 0.09-2.4 pts. to 100 pts. of a porous inorganic pigment and having a pH of more than 3 and less than 7 after an undercoating layer made of a porous inorganic pigment and a binder on the support and having a surface pH of 7 or more to 13 or less is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording material excellent in printing density and ink absorbability.

  As a recording material used in the inkjet recording method, a porous ink receiving layer comprising a pigment such as amorphous silica and a hydrophilic binder such as polyvinyl alcohol is provided on a support called ordinary paper or inkjet recording paper. Such recording materials are generally known. Although dye inks are widely used as inks for ink jet printers because of their excellent color developability, they have the disadvantage of being inferior in weather resistance and image storage stability.

  In order to improve the weather resistance and image storage stability, a pigment ink is used. It is known that the pigment ink has little light deterioration and does not re-dissolve with water, so that the weather resistance and the image storage stability are improved as compared with the dye type ink. However, since the color material pigment in the ink is insoluble in the solvent unlike the dye, it is necessary to stably disperse the color material pigment in the ink, and the ratio of the color material pigment in the ink cannot be easily increased. In addition, the coloring efficiency is not high like dye ink, and it is difficult to obtain a clear color.

  Therefore, the demand for ink jet recording materials is inevitably increasing. In order to improve the color developability and fixability of the pigment ink, it has been proposed that the pigment used in the ink receiving layer is alumina hydrate (see, for example, Patent Document 1). Although this method improves the color developability and fixability of the pigment ink, there is a problem that the ink absorbability is insufficient even when a paper support having high absorbency is used.

  In addition, as an ink jet recording material having both color developability and ink absorptivity for pigment ink, a first ink receiving layer containing vapor phase silica, boric acid or borate, and polyvinyl alcohol on a non-absorbing support. It has been proposed to sequentially laminate a second ink-receiving layer containing alumina or alumina hydrate, boric acid or borate, and polyvinyl alcohol (see, for example, Patent Document 2). Although the ink absorbency was improved by this method, it was still insufficient.

  In addition, these ink receiving layers are generally obtained after the coating liquid is applied to the support by various methods and dried, and the coating liquid has a viscosity suitable for each coating method. is required. In general, water-soluble polymers such as starch derivatives, cellulose derivatives, and polyvinyl alcohol are added to the ink-receiving layer, which improves the viscosity of the coating solution, but is one factor that greatly reduces the ink absorbability. It was.

  As a method for obtaining high ink absorbency while maintaining the color developability of the ink-jet recording paper for pigment ink, a coating layer containing ultrafine particles such as alumina is applied on the outermost surface of the recording paper, and the layer below it is coated. Although a method including gas phase method silica or the like is shown (for example, Patent Document 3). In this method, the pigment that contributes to color development is kept in the uppermost layer, and only the dispersion solvent of the pigment ink penetrates into the coating layer to fix the ink.

Although the printing density is surely improved by the above method, the ink receiving layer must be made so that the specific surface area of vapor phase method silica or the like used in the lower layer infiltrated with the dispersion solvent is not smaller than the specific surface area of alumina used in the outermost layer. The method of reducing the specific surface area is not preferable in terms of improving ink absorbability. In addition, if the dry coating amount is increased with the above-described configuration in order to further improve the ink absorbability, there is a disadvantage that cracks are generated and the print density is lowered as a result.
JP 2002-79748 A JP 2002-225423 A JP 2004-174875 A

  An object of the present invention is to provide an ink jet recording material having excellent print density and ink absorbability.

  As a result of intensive studies to achieve the above object, the present inventor has obtained a surface comprising a porous inorganic pigment and a binder on a support in an ink jet recording material comprising a plurality of ink receiving layers on the support. After forming an undercoat layer having a pH of 7 or more and 13 or less, the coating liquid contains 0.09 to 2.4 parts of a porous inorganic pigment, a binder, and an alkali-thickened emulsion with respect to 100 parts of the porous inorganic pigment. Is achieved by an ink jet recording material characterized by having an ink receiving layer formed by applying and drying an overcoat layer coating solution of 3 or more and less than 7.

  When the ink jet recording material of the present invention is used, an ink jet recording material excellent in print density and ink absorbability can be obtained.

  Hereinafter, the ink jet recording material excellent in printing density and ink absorbency of the present invention will be described in detail.

  In the ink jet recording material of the present invention, after forming an undercoat layer containing a porous inorganic pigment and a binder on the support so that the surface pH after coating and drying is 7 or more and 13 or less, the porous inorganic pigment, the binder, The alkali thickening type emulsion is contained in 0.09 to 0.24 parts with respect to 100 parts of the porous inorganic pigment, and the pH is 3 or more and less than 7, preferably 3.5 or more and 6.5 or less, more preferably 3.5 or more. An ink receiving layer composed of a plurality of layers is formed by applying and drying a coating liquid of 6 or less topcoat layers.

  In the present invention, when an overcoat layer containing an alkali-thickened emulsion is applied on an undercoat layer having a surface pH of 7 or more and 13 or less, the overcoat layer coating liquid thickens at the interface with the undercoat layer, It is thought that the penetration of the constituent components of the overcoat layer into the undercoat layer is suppressed and the ink absorbency is improved.

  When a thickener that is not an alkali thickening emulsion is added to the topcoat layer to increase the viscosity, the penetration of porous inorganic pigment in the topcoat layer into the undercoat layer is suppressed, but it is already thickened at the coater head. Therefore, proper coating cannot be performed.

  The surface pH in the present invention is a surface pH measured according to Method A (coating method) of the “surface pH test method for paper and paperboard” defined by the Japan Paper Pulp Technology Association.

  The undercoat layer according to the present invention will be described in more detail.

  The undercoat layer according to the present invention contains a porous inorganic pigment and a binder, and has a surface pH before application of the overcoat layer of 7 or more and 13 or less. The role of the undercoat layer in the present invention is to contribute to ink absorbability and when the overcoat layer containing an alkali-thickened emulsion comes into contact with the undercoat layer, it effectively increases the viscosity of the overcoat layer coating solution and absorbs ink. It contributes to sex.

  If the surface pH immediately before the application of the undercoat layer is less than 7, it may not be possible to efficiently increase the viscosity when it comes into contact with the overcoat layer, and as a result, no improvement in ink absorbency may be observed. On the other hand, if it exceeds 13, the surface pH of the overcoat layer becomes high, so that the ink fixability may be impaired.

  From the viewpoint of improving ink absorbability, a porous inorganic pigment needs to be added to the undercoat layer.

  As the porous inorganic pigment added to the undercoat layer, one or more known white inorganic pigments can be used. For example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic non White porous inorganic pigments such as crystalline silica, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide can be used. Among these, it is desirable to use porous wet method silica and dry method silica.

  Porous amorphous silica includes a wet method and a gas phase method depending on the production method. As the wet process silica, (1) silica sol obtained through metathesis by an acid of sodium silicate or ion exchange resin membrane, or (2) colloidal silica obtained by heating and aging this silica sol, (3) gelling the silica sol, By changing the production conditions, silica gel that became three-dimensional secondary particles in which primary particles of several μm to 10 μm were bonded to siloxane, and (4) silica gel, sodium silicate, sodium aluminate, etc. were heated and produced. There are synthetic silicic acid compounds mainly composed of silicic acid such as those obtained.

  Wet silica is classified into precipitation method silica, gel method silica, and sol method silica depending on the production method. In the present invention, precipitation method and gel method silica are preferably used. Precipitated silica is produced by reacting sodium silicate and sulfuric acid under alkaline conditions, and the silica particles that have grown are agglomerated and settled, and are then commercialized through filtration, washing, drying, pulverization, and classification steps. The silica secondary particles produced by this method become loosely agglomerated particles and particles that are relatively easy to grind. Gel silica is produced by reacting sodium silicate and sulfuric acid under acidic conditions. In this case, the small silica particles dissolve during ripening and reprecipitate so that the primary particles are bonded to each other between the primary particles of the large particles, so that the clear primary particles disappear and a relatively hard agglomeration having an internal void structure Form particles. For this reason, precipitated silica and gel silica are preferably used in order to make a large contribution to the ink absorbability.

  The average secondary particle diameter of the porous inorganic pigment used in the undercoat layer is 1 μm or more and 5 μm or less. Preferably they are 1 micrometer or more and 4 micrometers or less, Most preferably, they are 1.2 micrometers or more and 3 micrometers or less. In addition, the average secondary particle diameter as used in the field of this invention is obtained by measuring a dilute dispersion liquid with a Coulter counter type particle size distribution measuring apparatus (aperture size 50 μm). When the average secondary particle diameter of the porous inorganic pigment is smaller than 1 μm, the porous inorganic pigment or the like in the undercoat layer on the air-permeable paper support has a large drop, and when the overcoat layer coating liquid is applied, It becomes easy to crack. Further, if the average secondary particle diameter of the porous inorganic pigment is larger than 5 μm, the gap between the pigment particles becomes too large, and the undercoat layer cannot sufficiently suppress the drop of the binder component or the like in the overcoat layer. The overcoat layer may crack.

  The binder to be blended in the undercoat layer is not particularly limited, and generally known water-soluble polymers and synthetic resin latex can be used. Examples include starch derivatives such as oxidized starch, etherified starch, and phosphate esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein, gelatin, soybean protein, polyvinyl alcohol or derivatives thereof; polyvinyl pyrrolidone, maleic anhydride resin, Conjugated diene copolymer latex such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer; Acrylic polymer latex such as polymer or copolymer of acrylate ester and methacrylate ester; ethylene-vinyl acetate Vinyl-based polymer latex such as copolymer; or functional group-modified polymer latex with functional group-containing monomers such as carboxy groups of these various polymers; or those cationized using cationic groups on these various polymers , Mosquito Polymerized in cationic surfactant with cationic surfactant, polymerized under cationic polyvinyl alcohol and distributed on the polymer surface, polymerized in suspension dispersion of cationic colloidal particles The particles are distributed on the polymer surface; aqueous binders such as thermosetting synthetic resins such as melamine resins and urea resins; polymers or copolymers of acrylic acid esters and methacrylic acid esters such as polymethyl methacrylate Synthetic resin binders such as polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, alkyd resins, and the like.

  The amount of the binder to be added to the undercoat layer is 5 to 70 parts by mass, preferably 10 to 100 parts by mass of the total of the porous inorganic pigments in terms of coating layer strength, cracks in the coating layer, and ink absorbability. -50 mass parts.

  As the pH adjusting agent for the undercoat layer, an undercoat is used using amines such as ammonia and monoethanolamine, alkali metals such as sodium and potassium, or magnesium, calcium and alkaline earth metal hydroxides alone or in combination. It is added so that the surface pH after application and drying of the layer is 7 or more and 13 or less.

  After the undercoat layer is applied on the paper support and dried, the surface pH of the undercoat layer may decrease. Although the cause of this is not clear, it is presumed to be due to migration of components contained in the paper support or the undercoat layer. For this reason, it is necessary to note that the surface pH of the undercoat layer is 7 or more and 13 or less when the undercoat layer is applied and then the overcoat layer is applied after standing.

There are no particular restrictions on the coating amount of the undercoat layer, considering that the undercoat layer contributes to ink absorption 2 to 20 g / m ^2, preferably of 4~12g / m ² A range is desirable. If the coating amount is less than ² g / m ² , when the overcoating layer is applied, although the viscosity increases, the undercoating layer coating amount is too small, and as a result, the ink absorbability is greatly reduced. Further, even if the coating exceeds 20 g / m ² , the effect of further improving the ink absorbability may not be observed.

  Next, the topcoat layer according to the present invention will be described in detail.

  As the alkali thickened emulsion, which is an essential component of the topcoat layer according to the present invention, an alkali thickened emulsion having an effect of thickening at pH 7 to 13 can be used.

  As the resin for the alkali thickener emulsion, a resin obtained by emulsion polymerization or interfacial polymerization in the presence of an anionic surfactant with monomers such as sodium polyacrylate and methacrylic acid ester is used. Any material that thickens can be used. As these alkali thickening emulsions, various grades such as SN thickener 926 and SN thickener 923 are marketed by San Nopco, and L-275, L-29K and L-821 are marketed by NSC Japan. It is possible to obtain.

  About the addition amount of the alkali thickening type emulsion added to the overcoat layer of this invention, it is necessary to be 0.09-2.4 mass parts with respect to 100 mass parts of porous inorganic pigments. When the addition amount is less than 0.09 parts by mass, the thickening effect is reduced, so that the ink absorbability is difficult to improve. When the addition amount exceeds 2.4 parts by mass, the ink absorbency is difficult to improve.

  The alkali-thickened emulsion added to the overcoat layer preferably has a viscosity of 10 mPa · s or more, preferably 50 mPa · s or more, at 25 ° C. in a 2% by mass aqueous solution completely neutralized with sodium hydroxide. If the viscosity is less than 10 mPa · s, the effect of increasing the viscosity when applied on the undercoat layer is small, so that it is difficult to improve the ink absorbability.

  It is necessary to add a porous inorganic pigment to the overcoat layer in order to improve ink absorbability. As the porous inorganic pigment used in the overcoat layer of the present invention, one or more inorganic porous white pigments can be used. For example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic non Examples thereof include white inorganic pigments such as crystalline silica, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, and magnesium hydroxide. Among these, porous synthetic amorphous silica, porous calcium carbonate, porous magnesium carbonate, porous alumina and the like are mentioned from the balance of ink absorbability, and particularly porous synthetic amorphous silica or porous alumina, These are preferably used in a mixed form.

  The porous synthetic amorphous silica used for the overcoat layer is preferably a wet method silica such as a gel method silica and a precipitation method silica, or a gas phase method silica in consideration of ink absorbability.

  The average secondary particle diameter of the porous synthetic amorphous silica used for the overcoat layer is preferably 500 nm or less.

  As a specific method for obtaining wet-process silica fine particles having an average secondary particle diameter of 500 nm or less that is desirably used for the overcoat layer, silica particles and a cationic compound are first mixed in water (whichever comes first) Or may be mixed with each of the dispersions or aqueous solutions of the dispersion device such as a sawtooth blade type disperser, a propeller blade type disperser, or a rotor stator type disperser. At least one is used to obtain a preliminary dispersion. If necessary, an appropriate low boiling point solvent may be added. The higher the solid content concentration of the silica pre-dispersion, the higher the concentration. However, since the dispersion becomes impossible when the concentration is too high, the preferred range is 15 to 40% by mass, and more preferably 20 to 35% by mass. Next, by applying a stronger mechanical means, a wet process silica fine particle dispersion having an average secondary particle diameter of 500 nm or less is obtained. As a mechanical means, a known method can be adopted, for example, a media mill such as a ball mill, a bead mill, a sand grinder, a high pressure homogenizer, a pressure disperser such as an ultra high pressure homogenizer, an ultrasonic disperser, a thin film swirl disperser, etc. Can be used.

Vapor phase silica desirably used for the overcoat layer is also called dry silica, and is generally produced by flame hydrolysis. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone or in place of silicon tetrachloride. It can be used in a mixed state with silicon. The average dispersed particle size of the vapor phase silica is preferably in the range of 10 to 500 nm, and particularly preferably from 15 nm to 30 nm from the viewpoint of ink absorbability and cracks. Further, the specific surface area by the BET method is preferably 30 m ² / g or more and 300 m ² / g or less, particularly preferably 40 m ² / g or more and 150 m ² / g or less from the viewpoint of cracking of the coating layer of the overcoat layer and ink absorbability. preferable. The average primary particle diameter as used in the present invention is an average particle diameter obtained by observing the diameter of a circle equal to the projected area of each of 100 primary particles existing within a certain area by observation of fine particles with an electron microscope. The BET method referred to in the present invention is one of the powder surface area measurement methods by the vapor phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from the adsorption isotherm. is there. Usually, nitrogen gas is often used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. The most prominent expression for expressing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller formula, called the BET formula, which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  As the cationic compound used for the dispersion of the gas phase method silica and the wet method silica, a cationic polymer or a water-soluble metal compound can be used. As the cationic polymer, polyethyleneimine, polydiallylamine, polyallylamine, alkylamine polymer, JP-A-59-20696, 59-33176, 59-33177, 59-155888, 60-11389 No. 60-49990, No. 60-83882, No. 60-109894, No. 62-198493, No. 63-49478, No. 63-115780, No. 63-280681, JP-A-1-40371. No. 6-234268, No. 7-125411, No. 10-193376, and the like, and polymers having a primary to tertiary amino group and a quaternary ammonium base are preferably used. In particular, diallylamine derivatives are preferably used as the cationic polymer. In terms of dispersibility and dispersion viscosity, the molecular weight of these cationic polymers is preferably about 2,000 to 100,000, and particularly preferably about 2,000 to 30,000.

  Examples of the water-soluble metal compound include water-soluble polyvalent metal salts, and among them, a compound made of aluminum or a Group 4A metal (for example, zirconium or titanium) of the periodic table is preferable. Particularly preferred is a water-soluble aluminum compound. As a water-soluble aluminum compound, for example, as an inorganic salt, aluminum chloride or a hydrate thereof, aluminum sulfate or a hydrate thereof, ammonium alum and the like are known. Furthermore, a basic polyaluminum hydroxide compound which is an inorganic aluminum-containing cationic polymer is known and preferably used.

When porous alumina is used for the overcoat layer, the alumina used can be represented by the chemical formula Al ₂ O ₃ .nH ₂ O, and the average secondary particle size of the alumina hydrate is preferably 500 nm or less. In particular, the thickness is desirably 50 to 200 nm.

  Alumina hydrates are classified into gypsite, vialite, norstrandite, boehmite, boehmite gel (pseudoboehmite), diaspore, amorphous amorphous, etc., depending on the composition and crystal form. In particular, when the value of n in the above chemical formula is 1, it represents boehmite-structured alumina hydrate, and when n is more than 1 and less than 3, it represents pseudoboehmite-structured alumina hydrate, and n is 3 The above represents an alumina hydrate having an amorphous structure. The shape of the alumina hydrate may be any of a flat plate shape, a fiber shape, a spherical shape, a needle shape, a rod shape, and the like, and a preferable shape is a flat plate shape from the viewpoint of ink absorbability.

  The alumina hydrate used in the overcoat layer can be produced by a known method such as hydrolysis of aluminum alkoxide such as aluminum isopropoxide, neutralization of aluminum salt with alkali, hydrolysis of aluminate. The physical properties of alumina hydrate, such as particle size, pore size, pore volume, and specific surface area, should be controlled by conditions such as precipitation temperature, aging temperature, aging time, solution pH, solution concentration, and coexisting compounds. Can do.

  As methods for obtaining alumina hydrate from alkoxide, JP-A-57-88074, JP-A-62-56321, JP-A-4-275717, JP-A-6-64918, JP-A-7-10535, and JP-A-7-267633. This is disclosed as a method for hydrolyzing aluminum alkoxide in Japanese Patent Publication No. 2,656,321. These aluminum alkoxides include isopropoxide, 2-butoxide and the like.

  In order to stabilize the dispersion of alumina hydrate, various acids are usually added to the dispersion. Examples of such acids include nitric acid, hydrochloric acid, hydrobromic acid, acetic acid, formic acid, ferric chloride, aluminum chloride and the like, but the present invention is not limited thereto.

  The pH of the overcoat layer coating solution is 3 or more and less than 7, preferably 3.5 or more and 6.5 or less in order to prevent thickening at the coating solution stage and to increase the viscosity efficiently when contacting the undercoat layer. More preferably, it is necessary to adjust to 3.5 or more and 6 or less.

  When the coating solution pH of the topcoat layer is less than 3, the alkali-thickened emulsion in the topcoat layer solution is difficult to neutralize when coming into contact with the undercoat layer, and the topcoat layer coating solution is difficult to thicken. As a result, ink absorbability may be difficult to improve.

  When the coating solution pH of the overcoat layer is 7 or more, the viscosity of the overcoat layer coating solution is increased before coming into contact with the undercoat layer, but it is difficult to drop into the undercoat layer of the porous inorganic pigment in the overcoat layer. Application may be difficult.

  In order to adjust the coating solution pH of the overcoat layer to 3 or more, but less than 7, preferably 3.5 or more and 6.5 or less, more preferably 3.5 or more and 6 or less, inorganic acids and sulfonic acids, carboxylic acids, sulfines Organic acids such as acids, phenols, enols, thiols, acid imides, oximes, and sulfonamides can be used alone or in combination of two or more, but inorganic acids with strong acidity are used. It is preferable from the viewpoint of increasing the concentration of the coating liquid and thus improving the productivity of the ink jet recording material.

  For the overcoat layer, a hydrophilic binder that maintains the properties as a film and has high transparency and high ink permeability is used. Examples of the hydrophilic binder include starch derivatives such as oxidized starch, etherified starch and phosphate esterified starch; cellulose derivatives such as methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose; polyvinyl alcohol derivatives such as polyvinyl alcohol and silanol-modified polyvinyl alcohol Casein, gelatin and modified products thereof, soy protein, pullulan, gum arabic, Karaya gum, albumin and other natural polymer resins or derivatives thereof, vinyl polymers such as polyacrylamide and polyvinylpyrrolidone, alginic acid, polyethyleneimine, polypropylene glycol, Examples thereof include polyethylene glycol, maleic anhydride or a copolymer thereof, and these can be used alone or in combination. The present invention is not limited to, et al. Polyvinyl alcohol derivatives such as polyvinyl alcohol or silanol-modified polyvinyl alcohol are preferred from the viewpoints of adhesive strength, film formability, and the like. Among the polyvinyl alcohols, polyvinyl alcohol having a saponification degree of 80% or more, more preferably 88% or more and less than 96%, is particularly preferable among polyvinyl alcohols in terms of adjustment of the coating liquid viscosity and film formability. Of polyvinyl alcohol. The average degree of polymerization is preferably 2,000 or more, particularly preferably 3,000 or more.

  The blending amount of these hydrophilic binders is preferably 8 to 30% by mass, and preferably 10 to 25% by mass in terms of the total dry solid content in the topcoat layer, from the viewpoint of cracking of the ink receiving layer and ink absorbability. It is particularly preferred.

The dry coating amount of the top coating layer is not particularly limited, but the range of the dry coating amount is 3 to 16 g / m ² , more preferably 5 to 12 g in terms of ink absorbency and cracking of the coating layer. / M ² .

  The overcoat layer may further contain a cationic compound for the purpose of improving the fixability and water resistance of the ink. As the cationic compound, the compounds exemplified as the cationic compound used for dispersion of the gas phase method silica and the wet method silica can be used. Of these, the use of basic polyaluminum hydroxide is preferred because the ink-receiving layer is unlikely to crack and the color of the pigment ink is good.

The basic polyaluminum hydroxide compound has a main component represented by the following general formula 1, 2, or 3, for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [ It is a water-soluble polyaluminum hydroxide that stably contains a basic and high-molecular polynuclear condensed ion 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 _(3n-m) where 0 <m <3n Formula 3

  These are water treatment agents from Taki Chemical Co., Ltd. under the name of polyaluminum chloride (PAC), from Asada Chemical Co., Ltd. under the name of polyaluminum hydroxide (Paho), and from Riken Green Co., Ltd. It is marketed under the name of Purachem WT and from other manufacturers for the same purpose, and various grades can be easily obtained.

  In the present invention, even when a coating layer comprising a porous inorganic pigment and a binder (hereinafter referred to as the uppermost layer) is provided on the top coat layer, the effect of improving the ink absorbency by adding the alkali thickening emulsion is It is remarkable.

  The uppermost layer is provided in the case where the required white paper gloss or print gloss cannot be obtained only by the undercoat layer or the top coat layer, or when a higher print density or absorbency is required. A binder for efficiently fixing the pigment and the overcoat layer is contained.

  As the binder used for the uppermost layer, those similar to those used in the undercoat layer and the overcoat layer can be used.

  The porous inorganic pigment used in the uppermost layer is not particularly limited as in the case of the topcoat layer and the undercoat layer, and a generally known white pigment can be used. Here, when alumina is used as the uppermost pigment, a recording material having a high gloss value can be easily obtained.

  A wetting agent may be added to the undercoat layer, the topcoat layer, and the uppermost layer according to the present invention, if necessary. Wetting agents include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2- Hexanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, polyhydric alcohols such as thioglycol and hexylene glycol, lactams such as 2-pyrrolidone and ε-caprolactam, Examples include ureas such as urea and thiourea.

  Further, the undercoat layer, the overcoat layer, and the uppermost layer according to the present invention may further include a surfactant, a hardener, a coloring pigment, a coloring dye, a fixing agent such as an ink dye, an ultraviolet absorber, an antioxidant, Various known additives such as a porous inorganic pigment dispersant, an antifoaming agent, and a pH adjusting agent can also be added.

  The application method of the undercoat layer, the overcoat layer, and the uppermost layer constituting the inkjet recording material of the present invention is not particularly limited, and a known application method can be used. For example, a coating method in which application and metallization stages such as a slide lip method, a pre-metaling method such as a curtain method, an extrusion method, an air knife method, a roll coating method, and a rod bar coating method are divided.

  The ink jet recording material according to the present invention uses a gas-permeable paper support as a support. Examples of the air-permeable paper support in the present invention include chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP, and wood pulps such as waste paper pulp such as DIP, and conventionally known ones. The main component is a pigment, and a binder, a sizing agent, a fixing agent, a yield improver, a cationizing agent, a paper strength enhancer and the like are mixed using one or more additives, and a long net paper machine, circular net paper machine, It is a base paper manufactured by various apparatuses such as a twin-wire paper machine, and the base paper may be further subjected to size press with starch, polyvinyl alcohol, or the like.

  In the present invention, a sheet provided with an undercoat layer on a gas-permeable paper support may be provided with an overcoat layer or an uppermost layer in the present invention without calendering or calendering, or after providing an overcoat layer or an uppermost layer, For the purpose of flattening or controlling the air permeability, a calendar device such as a machine calendar, a TG calendar, or a soft calendar can be used, or a glossy surface can be formed using a known cast coating method.

  Various back coat layers can be coated on the paper support in the present invention for writing property, antistatic property, transportability and anticurl property. In the backcoat layer, an inorganic antistatic agent, an organic antistatic agent, a hydrophilic binder, latex, an inorganic or organic pigment, a curing agent, a surfactant, and the like can be used in appropriate combination.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” and “%” indicate parts by mass and mass% unless otherwise specified.

(Inkjet recording material 1)
On the following support 1, the following undercoat layer 1 was coated and dried with an air knife coater so that the dry coating amount was 10 g / m ² . The surface pH of the undercoat layer after drying was 12. On the undercoat layer thus obtained, the following overcoat layer 1 was applied with an air knife coater so that the dry coating amount was 10 g / m ² and dried to obtain an inkjet recording material 1.
<Support 1>
100 parts of wood pulp comprising 70 parts of LBKP with a freeness of 450 ml CSF and 30 parts of NBKP with a freeness of 450 ml CSF, 5 parts of a pigment having a light calcium carbonate / heavy calcium carbonate / talc ratio of 30/35/35, a commercially available alkyl ketene dimer 0.1 parts, 0.03 parts of commercially available cationic acrylamide, 1.0 part of commercially available cationized starch, and 0.5 parts of sulfuric acid band were prepared and supported using a long net paper machine at a basis weight of 105 g / m ^2. Body 1 was obtained.
<Undercoat layer 1>
100 parts of gel silica (P78D, manufactured by Mizusawa Chemical Co., Ltd.) is dispersed in 400 parts of water using a homogenizer, and 350 parts of an aqueous solution of 10% polyvinyl alcohol (R1130, manufactured by Kuraray Co., Ltd.) and wetting agent (Nopco Wet) 50, manufactured by San Nopco Co., Ltd.) and 0.3 part of a 25% aqueous sodium hydroxide solution were added to prepare an undercoat layer 1 having a solid content concentration of 16%.
<Topcoat layer 1>
To 400 parts of water, 8 parts of 50% dimethyldiallylammonium chloride homopolymer (molecular weight 9,000) and 100 parts of vapor phase silica (average primary particle diameter 20 nm, specific surface area 90 m ² / g by BET method) are added, and sawed A preliminary dispersion was prepared using a toothed blade type disperser. The obtained preliminary dispersion was treated with a high-pressure homogenizer to obtain a silica dispersion. 500 parts of silica dispersion thus obtained, 10 parts of 4% boric acid aqueous solution, 250 parts of 8% polyvinyl alcohol (saponification degree 88%, average polymerization degree 3500), 30% alkali thickening emulsion (SN thickener 926, San Nopco) Company Co., Ltd.) 0.3 parts (0.09 parts in terms of solid content) were mixed and prepared with water so that the solid content concentration was 15.0% to prepare the topcoat layer 1. The coating solution pH of the topcoat layer 1 was 4.3.

(Inkjet recording material 2)
The following undercoat layer 2 was used as an undercoat layer, and an inkjet recording material 2 was obtained in the same manner as the inkjet recording material 1 except that the surface pH of the undercoat layer was 7.5.
<Undercoat layer 2>
Undercoat layer 2 was obtained in the same manner as undercoat layer 1 except that the amount of water in which the gel silica was dispersed was 395 parts and the amount of 25% aqueous sodium hydroxide added was 0.8 parts.

(Inkjet recording material 3)
The ink jet recording material 3 is obtained in the same manner as the ink jet recording material 1 except that the undercoat layer 2 is used as the undercoat layer, the surface pH is 7.5, and the following overcoat layer 2 is used as the overcoat layer. It was.
<Topcoat layer 2>
The topcoat layer 2 is the same as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco Co., Ltd.) is 0.6 parts (0.18 parts in terms of solid content). Got. The coating solution pH of the topcoat layer 2 was 4.3.

(Inkjet recording material 4)
An ink jet recording material 4 was obtained in the same manner as the ink jet recording material 1 except that the top coat layer 2 was used as the top coat layer.

(Inkjet recording material 5)
An inkjet recording material 5 was obtained in the same manner as the inkjet recording material 1 except that the following topcoat layer 3 was used as the topcoat layer.
<Topcoat layer 3>
The topcoat layer 3 is formed in the same manner as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco Co., Ltd.) is 3.0 parts (0.9 parts in terms of solid content). Obtained. The coating solution pH of the topcoat layer 3 was 4.3.

(Inkjet recording material 6)
An inkjet recording material 6 was obtained in the same manner as the inkjet recording material 1 except that the following topcoat layer 4 was used as the topcoat layer.
<Topcoat layer 4>
The topcoat layer 4 is formed in the same manner as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (SN thickener 923, manufactured by San Nopco Co., Ltd.) is 3.0 parts (0.9 parts in terms of solid content). Obtained. The coating solution pH of the topcoat layer 4 was 4.3.

(Inkjet recording material 7)
An inkjet recording material 7 was obtained by the same method as the inkjet recording material 1 except that the following topcoat layer 5 was used as the topcoat layer.
<Topcoat layer 5>
The topcoat layer 5 is the same as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (L-821, manufactured by NSC Japan, Inc.) is 3.0 parts (0.9 parts in terms of solid content). Got. The coating solution pH of the topcoat layer 5 was 4.3.

(Inkjet recording material 8)
An inkjet recording material 8 was obtained by the same method as the inkjet recording material 1 except that the following topcoat layer 6 was used as the topcoat layer.
<Topcoat layer 6>
The topcoat layer 6 was prepared in the same manner as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (L-29K, manufactured by Nippon NSC Co., Ltd.) was 3.0 parts (0.9 parts in terms of solid content). Got. The coating solution pH of the topcoat layer 6 was 4.3.

(Inkjet recording material 9)
An inkjet recording material 9 was obtained in the same manner as the inkjet recording material 1 except that the following topcoat layer 7 was used as the topcoat layer.
<Topcoat layer 7>
The topcoat layer 7 was prepared in the same manner as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (L-275, manufactured by NSC Japan) was 3.0 parts (0.9 parts in terms of solid content). Got. The coating solution pH of the topcoat layer 7 was 4.3.

(Inkjet recording material 10)
An inkjet recording material 10 was obtained in the same manner as the inkjet recording material 1 except that the following topcoat layer 8 was used as the topcoat layer.
<Overcoat layer 8>
A topcoat layer 8 was obtained in the same manner as the topcoat layer 1 except that the addition amount of a 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco Co., Ltd.) was 5 parts (1.5 parts in terms of solid content). . The coating solution pH of the topcoat layer 8 was 4.3.

(Inkjet recording material 11)
An inkjet recording material 11 was obtained in the same manner as the inkjet recording material 1 except that the topcoat layer 9 was used as the topcoat layer.
<Topcoat layer 9>
The topcoat layer 9 was obtained in the same manner as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco) was 6 parts (1.8 parts in terms of solid content). . The coating solution pH of the topcoat layer 9 was 4.3.

(Inkjet recording material 12)
An inkjet recording material 12 was obtained by the same method as the inkjet recording material 1 except that the following topcoat layer 10 was used as the topcoat layer.
<Topcoat layer 10>
A topcoat layer 10 was obtained in the same manner as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco Co., Ltd.) was 8 parts (2.4 parts in terms of solid content). . The coating solution pH of the topcoat layer 10 was 4.3.

(Inkjet recording material 13)
An inkjet recording material 13 was obtained in the same manner as the inkjet recording material 5 except that the following topcoat layer 11 was used as the topcoat layer.
<Topcoat layer 11>
To 200 parts of water, 4 parts of 50% dimethyldiallylammonium chloride homopolymer (molecular weight 9,000) and 50 parts of vapor phase silica (average primary particle diameter 20 nm, specific surface area 90 m ² / g by BET method) are added, and sawed A preliminary dispersion was prepared using a toothed blade type disperser. The obtained preliminary dispersion was treated with a high-pressure homogenizer to obtain a silica dispersion. 250 parts of the silica dispersion thus obtained, 250 parts of a commercially available 20% colloidal silica dispersion (Snowtex AK, manufactured by Nissan Chemical Industries, Ltd.), 4 parts of a 4% boric acid aqueous solution, 8% polyvinyl alcohol (saponification degree 88%) , Average polymerization degree 3500) 250 parts, 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco Co., Ltd.) 3.0 parts (0.9 parts in terms of solid content) were mixed, and the solid content concentration was 15.0. The topcoat layer 11 was prepared by preparing with water so as to be in a percentage. The coating solution pH of the topcoat layer 11 was 4.3.

(Inkjet recording material 14)
An inkjet recording material 14 was obtained in the same manner as the inkjet recording material 5 except that the following topcoat layer 12 was used as the topcoat layer.
<Topcoat layer 12>
To 200 parts of water, 4 parts of 50% dimethyldiallylammonium chloride homopolymer (molecular weight 9,000) and 50 parts of vapor phase silica (average primary particle diameter 20 nm, specific surface area 90 m ² / g by BET method) are added, and sawed A preliminary dispersion was prepared using a toothed blade type disperser. The obtained preliminary dispersion was treated with a high-pressure homogenizer to obtain a silica dispersion. After adding 250 parts of the silica dispersion thus obtained, 200 parts of water, 50 parts of commercially available gel silica (P78D, manufactured by Mizusawa Chemical Co., Ltd.) and 10 parts of 4% boric acid aqueous solution and thoroughly dispersing, 8% polyvinyl 250 parts alcohol (saponification degree 88%, average polymerization degree 3500) 250 parts, 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco Co.) 3.0 parts (0.9 parts in terms of solid content) are mixed. The top coat layer 12 was prepared with water so as to have a solid content concentration of 15.0%. The coating solution pH of the topcoat layer 12 was 4.3.

(Inkjet recording material 15)
An inkjet recording material 15 was obtained by the same method as the inkjet recording material 5 except that the following topcoat layer 13 was used as the topcoat layer.
<Topcoat layer 13>
To 200 parts of water, 4 parts of 50% dimethyldiallylammonium chloride homopolymer (molecular weight 9,000) and 50 parts of vapor phase silica (average primary particle diameter 20 nm, specific surface area 90 m ² / g by BET method) are added, and sawed A preliminary dispersion was prepared using a toothed blade type disperser. The obtained preliminary dispersion was treated with a high-pressure homogenizer to obtain a silica dispersion. In addition, 1 part of 60% nitric acid and 50 parts of alumina hydrate having a pseudo boehmite structure (average primary particle size 15 nm, specific surface area 160 m ² / g by BET method) are added to 200 parts of water, and a sawtooth blade type dispersion is added. Alumina hydrate dispersion was prepared using a machine. The average secondary particle diameter of the alumina hydrate fine particles obtained by measurement with a laser diffraction / scattering particle size distribution analyzer was 150 nm. 250 parts of silica dispersion thus obtained, 250 parts of alumina hydrate dispersion, 4% boric acid aqueous solution, 8% polyvinyl alcohol (saponification degree 88%, average polymerization degree 3500) 250 parts, 30% alkali thickening emulsion (Thickener 926, manufactured by San Nopco Co., Ltd.) 3.0 parts (0.9 parts in terms of solid content) were mixed and prepared with water so that the solid content concentration was 15.0% to prepare the topcoat layer 13. . The coating solution pH of the topcoat layer 13 was 4.3.

(Inkjet recording material 16)
An ink jet recording material 16 was obtained in the same manner as the ink jet recording material 5 except that the undercoat layer 1 was applied in a dry coating amount of 2 g / m ² and the top coat layer 3 was applied as an overcoat layer.

(Inkjet recording material 17)
An ink jet recording material 17 was obtained in the same manner as the ink jet recording material 5 except that the undercoat layer 1 was applied in a dry coating amount of 22 g / m ² and the top coat layer 3 was applied as an overcoat layer.

(Inkjet recording material 18)
An ink jet recording material 18 was obtained in the same manner as the ink jet recording material 5 except that the top coat layer 3 was applied as a dry coating amount of 3 g / m ² as the top coat layer.

(Inkjet recording material 19)
An ink jet recording material 19 was obtained in the same manner as the ink jet recording material 5 except that the dry coating amount of the undercoat layer 1 was 1.5 g / m ² and the top coat layer 3 was used as the top coat layer.

(Inkjet recording material 20)
An ink jet recording material 20 was obtained in the same manner as the ink jet recording material 5 except that the top coat layer 3 was applied as a dry coat amount of 2.0 g / m ² as the top coat layer.

(Inkjet recording material 21)
The ink jet recording material 21 was prepared in the same manner as the ink jet recording material 1 except that the undercoat layer 3 shown below was used as the undercoat layer, the surface pH of the undercoat layer was 6.0, and the top coat layer 14 shown below was used. Obtained.
<Undercoat layer 3>
Undercoat layer 3 was prepared in the same manner as undercoat layer 1 except that the amount of water in which the silica gel was dispersed was 395 parts and no aqueous sodium hydroxide solution was added.
<Topcoat layer 14>
A topcoat layer 14 was prepared in the same manner as the topcoat layer 1 except that the alkali thickening emulsion was not added. The coating solution pH of the topcoat layer 14 was 4.3.

(Inkjet recording material 22)
An ink jet recording material 22 was obtained in the same manner as the ink jet recording material 1 except that the undercoat layer 2 was used as the undercoat layer, the surface pH of the undercoat layer was 7.5, and the top coat layer 14 was used. .

(Inkjet recording material 23)
An inkjet recording material 23 was obtained in the same manner as the inkjet recording material 1 except that the topcoat layer 14 was used as the topcoat layer.

(Inkjet recording material 24)
The undercoat layer 3 is coated on a paper support, the surface pH of the undercoat layer is 6.0, and the overcoat layer 2 is used as the overcoat layer. Inkjet recording material 24 was obtained.

(Inkjet recording material 25)
The undercoat layer 3 is coated on a paper support, the surface pH of the undercoat layer is 6.0, and the topcoat layer 3 is used as the overcoat layer in the same manner as the ink jet recording material 1 Inkjet recording material 25 was obtained.

(Inkjet recording material 26)
An inkjet recording material 26 was obtained in the same manner as the inkjet recording material 1 except that the following topcoat layer 15 was applied as the topcoat layer.
<Topcoat layer 15>
The topcoat layer 15 was formed in the same manner as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (SN926, manufactured by San Nopco Co., Ltd.) was 8.33 parts (2.5 parts in terms of solid content). Obtained. The coating solution pH of the topcoat layer 15 was 4.3.

(Inkjet recording material 27)
An ink jet recording material 27 was obtained by the same method as the ink jet recording material 1 except that the following top coat layer 16 was applied as the top coat layer.
<Topcoat layer 16>
The topcoat layer was prepared in the same manner as the topcoat layer 1 except that the addition amount of 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco Co., Ltd.) was 0.267 parts (0.08 parts in terms of solid content). 16 was obtained. The coating solution pH of the topcoat layer 16 was 4.3.

(Inkjet recording material 28)
An inkjet recording material 28 was obtained in the same manner as the inkjet recording material 5 except that the following topcoat layer 17 was applied as the topcoat layer.
<Topcoat layer 17>
The top coat layer except that the addition amount of 30% alkali thickening emulsion (SN thickener 926, manufactured by San Nopco Co., Ltd.) was 3 parts (0.9 parts in terms of solid content) and the 60% nitric acid aqueous solution was 2.0 parts. The topcoat layer 17 was obtained in the same manner as in Example 1. The coating solution pH of the topcoat layer 17 was 2.8.

(Inkjet recording material 29)
An inkjet recording material 29 was obtained in the same manner as the inkjet recording material 5 except that the undercoat layer 4 shown below was applied as the undercoat layer and the above-described overcoat layer 3 was applied as the overcoat layer.
<Undercoat layer 4>
Undercoat layer 4 was obtained in the same manner as undercoat layer 1 except that the amount of 25% aqueous sodium hydroxide solution added was 12 parts.

<Ink absorbability>
After cutting each inkjet recording material into A4 size, printing was performed with an inkjet printer (W6400 manufactured by Canon Inc.), and the state of unevenness in the solid portion was observed and evaluated according to the following criteria. If the ink absorptivity is low, unevenness is easily noticeable.
A: There is no unevenness.
○: Unevenness can be recognized slightly (allowable limit).
Δ: Unevenness can be clearly recognized.
X: Unevenness is strongly generated.

<Print density>
After cutting each inkjet recording material into A4 size, printing was performed with an inkjet printer (W6400, manufactured by Canon Inc.), and then the printing density of a cyan 100% portion was measured with SpectroEye manufactured by Gretag-Macbeth. This is an acceptable level at a print density of 1.4 or higher.

  The printing density and ink absorbability of the recording material produced as described above were evaluated. The results are shown in Table 1.

  As is clear from the above results, in the recording material of the present invention, when the surface pH of the undercoat layer is 7 or more and 13 or less, an alkali thickening emulsion outside the present invention is added to the overcoat layer. When the liquid pH is 3 or more and less than 7, an ink jet recording material having high ink absorbability can be obtained. When the addition amount of the alkali thickening emulsion exceeds 2.5 parts, cracks occurred in the topcoat layer, and the printing density was lowered.

  The uppermost layer was further coated on the top coat layer to obtain the following ink jet recording material.

(Inkjet recording material 30)
On the inkjet recording material 5, the following uppermost layer 1 was coated with an air knife coater so that the dry coating amount was 10 g / m ² and dried to obtain an inkjet recording material 30.
<Preparation of top layer 1>
To 400 parts of water, 2 parts of 60% nitric acid and 100 parts of alumina hydrate having a pseudo boehmite structure (average primary particle diameter 15 nm, specific surface area 160 m ² / g by BET method) are added, and a sawtooth blade type disperser Was used to prepare an alumina hydrate dispersion. 500 parts of the resulting alumina hydrate dispersion, 5 parts of 4% boric acid aqueous solution, and 100 parts of 8% polyvinyl alcohol (saponification degree 88%, average polymerization degree 3500) were mixed, and the solid content concentration was 17.0 with water. % Top layer 1 was prepared.

(Preparation of inkjet recording material 31)
An ink jet recording material 31 was obtained in the same manner as the ink jet recording material 30 except that the following uppermost layer 2 was coated on the ink jet recording material 5.
<Preparation of top layer 2>
100 parts of commercially available gel method silica (P78D, manufactured by Mizusawa Chemical Co., Ltd.) was added to 400 parts of water, and a gel method silica dispersion was prepared using a sawtooth blade type disperser. 500 parts of the gel silica dispersion thus obtained, 5 parts of 4% boric acid aqueous solution and 100 parts of 8% polyvinyl alcohol (saponification degree 88%, average polymerization degree 3500) are mixed, and the solid content concentration is 15.5% with water. To obtain the uppermost layer 2.

(Inkjet recording material 32)
An ink jet recording material 32 was obtained in the same manner as the ink jet recording material 30 except that the following uppermost layer 3 was coated on the ink jet recording material 5.
<Preparation of top layer 3>
To 400 parts of water, 8 parts of 50% dimethyldiallylammonium chloride homopolymer (molecular weight 9,000) and 100 parts of vapor phase silica (average primary particle diameter 20 nm, specific surface area 90 m ² / g by BET method) are added, and sawed A preliminary dispersion was prepared using a toothed blade type disperser. The obtained preliminary dispersion was treated with a high-pressure homogenizer to obtain a silica dispersion. 500 parts of silica dispersion thus obtained, 5 parts of 4% boric acid aqueous solution, 100 parts of 8% polyvinyl alcohol (saponification degree 88%, average polymerization degree 3500), prepared with water to a solid content concentration of 15.5% Thus, the uppermost layer 3 was obtained.

<Preparation of Inkjet Recording Material 33>
An ink jet recording material 33 was obtained in the same manner as the ink jet recording material 30 except that the uppermost layer 1 was coated on the ink jet recording material 23.

  The recording material produced as described above was evaluated for ink absorbability. The results are shown in Table 2. The ink absorptivity was evaluated in the same manner as in Table 1.

  As apparent from the above results, in the recording material of the present invention, an overcoat layer containing an alkali thickener is applied on an undercoat layer having a surface pH of 7 or more and 13 or less, and then an uppermost layer is provided thereon. In this case, the ink absorbency is improved.

Claims (1)

  In an inkjet recording material in which a plurality of ink receiving layers are provided on a support, a porous inorganic pigment is formed on the support after an undercoat layer composed of a porous inorganic pigment and a binder and having a surface pH of 7 to 13 is formed. Ink formed by applying and drying a topcoat layer coating solution having a coating solution pH of 3 or more and less than 7 and containing 0.09 to 2.4 parts of binder, alkali thickening emulsion to 100 parts of porous inorganic pigment An ink jet recording material comprising a receiving layer.