JP2002321449A - Medium to be ink-jet-recorded and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a medium to be ink-jet-recorded, which has a high gloss, a high ink absorbency and excellent image coloring properties and develops a few corrugation after recording, and its manufacturing method. SOLUTION: In the medium to be ink-jet-recorded, in which a primer coating layer including an alkaline-earth metal salt and an adhesive is provided on a base paper and, in addition, an ink accepting layer including ultrafine inorganic particles is coated on the primer coating layer, a barrier layer including a pigment and the adhesive is provided between the base paper and the primer coating layer. The preferable alkaline-earth metal is calcium carbonate. Further, the preferable ultrafine inorganic particle is amorphous synthetic silica by the vapor phase method. In addition, the ink accepting layer is provided after being coated with the primer coating layer and then subjected to a hot calendaring treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording medium and a method for manufacturing the same, and more particularly, to a medium having high gloss, high absorbency, excellent image coloration, and having a wavy shape after recording. The present invention relates to a small number of inkjet recording media.

[0002]

2. Description of the Related Art In an ink jet recording system, fine droplets of ink are made to fly and adhere to a recording medium such as paper by various operating principles to record images, characters, and the like. It has features such as noise, easy multi-coloring, great flexibility in recording patterns, and no need for development-fixing, and it is rapidly spreading in various applications as a recording device for various figures and color images including kanji. . Further, an image formed by the multi-color ink jet system can obtain a record comparable to multi-color printing by a plate making system or printing by a color photographic system. Further, in applications requiring only a small number of copies, it is being widely applied to the field of full-color image recording because it is cheaper than photographic printing.

[0003] Further, with diversification of uses, they are increasingly used for large-format posters, POP art, drafting applications, and the like. In these applications, the high sharpness of the ink jet can be utilized and excellent color can be obtained, so that a good image can be obtained, and the advertising effect is large. Application to these is because it is possible to easily obtain an image with excellent image reproducibility and color reproducibility such as sharpness and color at the level of a personal computer. I have.

[0004] Diversification has been applied to the appearance of ink jet recording media, in addition to the conventional matte or matte appearance of plain paper and matte paper, as well as art paper, coated paper, cast coated paper, and photographic printing. An appearance having gloss similar to paper or the like is required. This is because ink jet recording is capable of reproducing image quality comparable to printing or photography, and is required to have a similar appearance.

Therefore, as an ink jet recording medium having a glossy surface, a cast-coated paper obtained by performing a cast finish while the coating layer is in a wet state is disclosed in Japanese Patent Laid-Open No. 6-3 / 1994.
Although disclosed in Japanese Patent No. 20857 and the like, the surface gloss is extremely low as compared with silver halide photographic printing paper, and the texture of silver halide photographs cannot be obtained.

[0006] As an ink jet recording medium having improved surface glossiness, a medium having an ink receiving layer made of a resin on a support has been proposed. Examples of resins used in such applications include, for example, JP-A-57-381.
Nos. 85, 62-184879 and the like, polyvinylpyrrolidone, vinylpyrrolidone-vinyl acetate copolymer, JP-A-60-168651, JP-A-60-171143, and JP-A-61-134290. A resin composition mainly comprising polyvinyl alcohol disclosed in JP-A-60-234879; a copolymer of vinyl alcohol and olefin or styrene and maleic anhydride disclosed in JP-A-60-234879;
No. 9, JP-A 61-181679, a cross-linked product of polyethylene oxide and isocyanate, a mixture of carboxymethyl cellulose and polyethylene oxide disclosed in JP-A-61-181679,
377, a polymer obtained by grafting methacrylamide to polyvinyl alcohol; an acrylic polymer having a carboxyl group disclosed in JP-A-62-220383;
No. 82, etc., polyvinyl acetal polymers disclosed in JP-A-4-282282 and JP-A-4-282282.
Various ink-absorbing polymers such as a crosslinkable acrylic polymer disclosed in Japanese Patent No. 5650 are disclosed.
Also, JP-A-4-282282 and JP-A-4-2856.
No. 50 discloses an ink jet recording medium in which a polymer matrix composed of a crosslinkable polymer and an absorbing polymer are used in combination. However, the ink-receiving layer made of these resins has the drawback that although it has high surface gloss, it has a low absorption rate and a small absorption capacity, as compared with an ink-receiving layer made of fine pigment particles such as silica.

Inkjet recording media using alumina hydrate (cationic alumina hydrate) have recently been proposed as an inkjet recording medium having a high ink absorption rate and improved surface gloss. For example, JP
JP-A-232990, JP-A-60-245588, JP-B-3-24906, JP-A-6-1990
JP-A Nos. 35 and 7-82694 disclose an ink jet recording medium in which fine pseudo-boehmite-type alumina hydrate is coated on the surface of a support together with a water-soluble adhesive. However, an ink jet recording medium using pseudo-boehmite-type alumina hydrate has very high surface gloss, but has a small pore volume, and is therefore described in, for example, JP-A-5-24335. In addition, the ink absorption capacity per unit coating application amount is small, and a thick film coating is necessary to obtain a sufficient ink absorption capacity.

Further, for example, JP-A-10-203006 and JP-A-8-174992 disclose that the primary particle diameter is 3
An ink jet recording medium mainly using a synthetic silica prepared by a gas phase method having a thickness of 30 nm to 30 nm is disclosed. Also in this case, in order to obtain a sufficient absorption capacity, 30 μm
The above film thickness is required. Further, JP-A-11-4
No. 8602 discloses a hydrophilic adhesive and a first ink-absorbing layer containing solid fine particles in a mass ratio of 0.5 to 2.5 times the hydrophilic adhesive and a dry film thickness of 5 to 30 μm. In addition, an ink jet recording medium provided with a void layer containing fine particles having an average particle diameter of 100 nm or less is disclosed. However, in this configuration, in order to obtain sufficient ink absorbency, it is necessary to increase the thickness of the void layer, and if the thickness is increased, defects such as cracks are generated.
It was necessary to increase the amount of adhesive in the ink absorbing layer.

On the other hand, an ink jet recording apparatus is inexpensive and can easily obtain an image having excellent image reproducibility and color reproducibility such as sharpness and color at a personal computer level. Has changed from a special recording device used by a specific person to a general-purpose recording device, and since the quality of the image is comparable to that of printed matter and photographs, it is possible to create a self-made picture postcard or digital It is also being used as a photo printer. In such applications, the amount of ink to be ejected is large, and the ink solvent reaching the base paper causes the recording medium after recording to undulate, resulting in a problem of poor appearance. Therefore, at present, securing these characteristics is a necessary condition of the inkjet recording apparatus and the inkjet recording medium.

Therefore, the ink jet recording medium provided with anti-waving after recording contains non-wood fibers,
Further, a recording medium having a surface coated or impregnated with a cationic substance is disclosed in JP-A-8-179546 or the like. However, since the medium is plain paper, its surface gloss is extremely low.
It does not provide glossiness.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording medium having high gloss, high ink absorption, excellent image coloration, and excellent appearance with little ripple after image recording. Is to provide a way.

[0012]

According to the present invention, an undercoat layer containing a salt of an alkaline earth metal and an adhesive is provided on a base paper mainly composed of natural pulp, and an inorganic ultrafine particle is contained thereon. An ink jet recording medium provided with an ink receiving layer, wherein a barrier layer containing a pigment and an adhesive is provided between the base paper and the undercoat layer.

Preferably, the pigment contained in the barrier layer is kaolin and / or an organic pigment.

Preferably, the alkaline earth metal is calcium or magnesium, and more preferably, the salt of the alkaline earth metal is a carbonate.

It is preferable that the inorganic ultrafine particles are an amorphous synthetic silica or alumina compound obtained by a gas phase method.

It is preferable that the undercoat layer contains an adhesive having a mass ratio of 0.05 to 0.8 times the alkaline earth metal salt.

Further, the base paper mainly composed of natural pulp is
A barrier layer containing a pigment and an adhesive is provided, and after that, an undercoat layer containing a salt of an alkaline earth metal and an adhesive is provided, and then subjected to a heat calendering treatment, and contains at least inorganic ultrafine particles. This is a method for producing an ink jet recording medium in which an ink receiving layer coating liquid is applied.

In the method for producing an ink jet recording medium, the inorganic ultrafine particles are amorphous synthetic silica or alumina hydrate obtained by a gas phase method, and the pH of the ink receiving layer coating liquid is 5.0 or less. Some are preferred embodiments.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ink jet recording medium of the present invention and a method for manufacturing the same will be described in detail.
The ink jet recording medium of the present invention is an ink jet recording medium in which an undercoat layer is provided on a base paper mainly composed of natural pulp, and an ink receiving layer containing inorganic ultrafine particles is provided thereon. And a barrier layer containing a pigment and an adhesive between the undercoat layer and the undercoat layer.

In the barrier layer of the present invention, pigments such as kaolin, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, aluminum silicate, synthetic amorphous silica, alumina, alumina hydrate, aluminum hydroxide, Halloy site and the like. Examples of the organic pigment include polystyrene resin, styrene-acrylic resin, acrylic resin, polyethylene resin, vinyl acetate copolymerized polyolefin resin, polypropylene resin, polyacetal resin, chlorinated polyether resin, and polyvinyl chloride resin. . Among these, kaolin, polystyrene resin, acrylic resin or styrene-acryl resin is preferable, and one or more of these pigments can be appropriately selected and used in combination.

The barrier layer used in the present invention contains a water-soluble or water-dispersible polymer compound as an adhesive.
For example, examples of the water-soluble polymer compound include cellulose binders such as methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and hydroxyethylcellulose, starch and modified products thereof, gelatin and modified products thereof, casein, pullulan, gum arabic, and albumin. Natural polymer resins or derivatives thereof, polyvinyl alcohol and modified products thereof, polyacrylamide, vinyl polymers such as polyvinylpyrrolidone, polyethyleneimine, polypropylene glycol, polyethylene glycol, and maleic anhydride or a copolymer thereof. . Examples of the water-dispersible polymer compound include latexes and emulsions such as styrene-butadiene copolymer, styrene-acryl copolymer, methyl methacrylate-butadiene copolymer, and ethylene-vinyl acetate copolymer. . Among these, a styrene-butadiene copolymer is preferable.

Other additives include cationic dye fixing agents, pigment dispersants, thickeners, flow improvers, viscosity stabilizers, pH adjusters, surfactants, defoamers, foam inhibitors, Release agents, foaming agents, penetrants, coloring dyes, coloring pigments, optical brighteners, ultraviolet absorbers, antioxidants, leveling agents, preservatives, anti-binders, water-proofing agents, wet paper strength agents, drying A paper strength enhancer and the like can be appropriately added as long as the object of the present invention is not impaired.

The dry thickness of the barrier layer containing the pigment used in the present invention is preferably 3 μm or more and 20 μm or less. More preferably, it is in the range of 5 μm or more and 15 μm or less. If the dry film thickness is less than 3 μm, the effects desired by the present invention will not be exhibited. If the dry film thickness is too large, not only the production will be difficult but also the effects will be saturated and the economy will be poor.

When providing the barrier layer, the method of coating is not particularly limited, and a known coating method can be used. For example, air knife coater, curtain coater, slide lip coater, die coater, blade coater, gate roll coater, bar coater, rod coater, roll coater, bill blade coater,
It can be coated on the base paper by various devices such as a short dwell blade coater and a size press.

The applied barrier layer may be smoothed by calendering. Gloss calendar, super calendar,
A soft calendar is exemplified.

As the base paper used in the present invention, generally used paper can be used. As the pulp constituting the base paper, natural pulp may be used as a main component, and recycled pulp, synthetic pulp and the like may be mixed and used. As the natural pulp, bleached chemical pulp such as pulp usually used for papermaking, that is, softwood kraft pulp, hardwood kraft pulp, softwood sulphite pulp, hardwood sulphite pulp and the like can be used. Further, mechanical pulp having high whiteness may be used. Further, non-wood pulp manufactured from grass fibers such as straw, esparto, bagasse, and kenaf, bast fibers such as hemp, mulberry, ganpi, mitsumata, and cotton, may be used. Of these, bleached chemical pulp, such as softwood kraft pulp, hardwood kraft pulp, softwood sulphite pulp, and hardwood sulphite pulp, which is usually most frequently used industrially, is particularly preferred.

The pulp is usually beaten by a beater such as a double disc refiner in order to improve the papermaking properties and various properties of the paper such as strength, smoothness and uniformity of formation. Beating degree is 250ml ~ 550ml in Canadian Standard Freeness
Can be selected according to the purpose within the usual range.

The beaten pulp slurry is made by a paper machine such as a fourdrinier paper machine, a twin wire paper machine, or a round net paper machine. At this time, in the present invention, the pulp slurry usually used in papermaking is used. Various additives such as a dispersing aid, a dry paper strength enhancer, a wet paper strength enhancer, a filler, a sizing agent, and a fixing agent can all be added as needed. Further, if necessary, a pH adjuster, a dye, a colored pigment, an optical brightener and the like can be added.

The dispersing aids include, for example, polyethylene oxide, polyacrylamide, smelt, and the like. The paper strength enhancers include, for example, vegetable gums, starches, anionic paper strength enhancers such as carboxy-modified polyvinyl alcohol, cationized starch, and the like. Cationic polyacrylamide, a cationic paper strength enhancer such as polyamide polyamine epichlorohydrin resin, as a filler, for example, clay, kaolin,
Talc, heavy calcium carbonate, light calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, magnesium hydroxide, etc., as sizing agents, for example, higher fatty acid salts, rosin, rosin derivatives such as maleated rosin, dialkyl ketene dimer, Alkenyl or alkyl succinates, epoxidized fatty acid amides, polysaccharide esters and the like, as fixing agents, for example, polyvalent metal salts such as aluminum sulfate and aluminum chloride, cationized starch, and cationic polymers such as polyamide polyamine epichlorohydrin resin. Hydrochloric acid, caustic soda, sodium carbonate, and the like are used as pH adjusters.

The base paper used in the present invention is prepared by coating a liquid containing various additives including a water-soluble polymer additive with a tab size, a size press, a gate roll coater or a film transfer coater. It is also possible to work.

Examples of the above-mentioned water-soluble polymer additives include starch derivatives such as starch, cationized starch, oxidized starch, etherified starch and phosphate esterified starch; polyvinyl alcohol derivatives such as polyvinyl alcohol and carboxy-modified polyvinyl alcohol; Carboxymethyl cellulose,
Hydroxymethyl cellulose, hydroxyethyl cellulose, cellulose derivatives such as cellulose sulfate,
Gelatin, casein, water-soluble natural polymers such as soy protein,
Sodium polyacrylate, sodium salt of styrene-maleic anhydride copolymer, water-soluble polymer such as maleic anhydride resin such as sodium polystyrene sulfonate, and aqueous polymer such as thermosetting synthetic resin such as melamine resin and urea resin Adhesives and the like are used. In addition, petroleum resin emulsions, ammonium salts of styrene-maleic anhydride copolymer alkyl esters, alkyl ketene dimer emulsions, styrene-butadiene copolymers, ethylene-vinyl acetate copolymers are used as sizing agents. Examples include dispersions of polymers, polyethylene, polyvinylidene chloride and the like. Other additives include an inorganic electrolyte such as sodium chloride, calcium chloride, and boa nitrate as antistatic agents, glycerin and polyethylene glycol as hygroscopic substances, and clay, kaolin, talc, barium sulfate, and oxidized as pigments. Titanium or the like is used as a pH adjusting agent such as hydrochloric acid, caustic soda, or sodium carbonate, and other additives such as a dye, a fluorescent whitening agent, an antioxidant, and an ultraviolet absorber can be used in combination.

The base paper used in the present invention preferably has good surface smoothness, such as being compressed by applying pressure during or after papermaking with a calendar or the like.
0 to 250 g / m ² is preferred.

The undercoat layer of the present invention contains a salt of an alkaline earth metal. The alkaline earth metal referred to in the present invention is a general term for beryllium, calcium, magnesium, strontium, barium, and radium. Examples of the alkaline earth metal salts include carbonates, silicates, borates,
Examples thereof include hydrochlorides, sulfates, and organic acid salts. Since the coating liquid for the undercoat layer is often aqueous, weak acid salts having low solubility are preferred. Particularly preferred are calcium carbonate and magnesium carbonate.

The undercoat layer containing a salt of an alkaline earth metal used in the present invention contains an adhesive. The adhesive preferably contains 0.05 to 0.8 times the mass of the alkaline earth metal salt. More preferably, it is in the range of 0.05 times or more and 0.4 times or less. If the adhesive has a mass ratio of less than 0.05 with respect to the alkaline earth metal salt, the adhesive strength will be insufficient, and peeling will occur between the barrier layer and the ink receiving layer. On the other hand, if the mass ratio of the adhesive to the salt of the alkaline earth metal is more than 0.8 times, the absorbability is reduced, which is not preferable.

Examples of the adhesive contained in the undercoat layer include cellulosic adhesives such as methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose and hydroxyethylcellulose, starch and its modified products, gelatin and its modified products, casein,
Natural polymer resins such as pullulan, gum arabic, and albumin or derivatives thereof, polyvinyl alcohol and modified products thereof, styrene-butadiene copolymer, styrene-acryl copolymer, methyl methacrylate-butadiene copolymer, ethylene-acetic acid Examples include latexes and emulsions such as vinyl copolymers, vinyl polymers such as polyacrylamide and polyvinylpyrrolidone, polyethyleneimine, polypropylene glycol, polyethylene glycol, and maleic anhydride or a copolymer thereof. Preferably, it is a copolymer type emulsion.

Further, other additives include cationic dye fixing agents, pigment dispersants, thickeners, flow improvers, viscosity stabilizers, pH adjusters, surfactants, defoamers, foam inhibitors, Release agents, foaming agents, penetrants, coloring dyes, coloring pigments, white inorganic pigments, white organic pigments, fluorescent brighteners, ultraviolet absorbers, antioxidants, leveling agents, preservatives, anti-binders, waterproofing agents ,
A wet paper strength enhancer, a dry paper strength enhancer and the like can be appropriately added within a range not to impair the object of the present invention.

When providing the undercoat layer, the method of coating is not particularly limited, and a known coating method can be used. For example, air knife coater, curtain coater, slide lip coater, die coater, blade coater, gate roll coater, bar coater, rod coater, roll coater, bill blade coater,
The coating can be performed on the base paper coated with the barrier layer by various devices such as a short dwell blade coater and a size press.

The applied undercoat layer may be smoothed by calendering. As the calendar processing device at that time, a gloss calendar, a super calendar, a soft calendar, and the like can be given. In particular, a heat calendering treatment for performing a smoothing treatment while applying heat is preferably used.

The coating amount of the undercoat layer is not particularly limited.
If the amount is too small, the effect of the undercoat layer does not appear. If the amount is too large, not only is the production difficult, but the effect is saturated and the economy is poor. Therefore, the preferable range is 5 g / m ² or more and 30 g.
/ M ² or less.

The ink jet recording medium of the present invention is provided with an ink receiving layer containing inorganic ultrafine particles on the undercoat layer.

The inorganic ultrafine particles in the ink jet recording medium of the present invention have a primary particle diameter of 100 nm or less,
In addition, it refers to inorganic fine particles having a secondary particle diameter of 400 nm or less.
For example, JP-A-1-97678 and JP-A-2-2755.
No. 10, No. 3-281383, No. 3-285
Nos. 814, 3-285815, 4-92
183, 4-267180, 4-27
Pseudo-boehmite sol which is an alumina hydrate disclosed in, for example, JP-A-5917 / 1994, JP-A-60-219083, JP-A-61-19389, and JP-A-61-188183.
JP-A-63-178074, JP-A-5-51
No. 470, colloidal silica, etc.
JP-B-4-19037, JP-A-62-28678
7, a silica / alumina hybrid sol described in JP-A-10-119423 and JP-A-10-119423.
-217601, silica sol obtained by dispersing fumed silica with a high-speed homogenizer, smectite clay such as hectite and montmorillonite (JP-A-7-81210), zirconia sol,
Representative examples include chromia sol, yttria sol, ceria sol, iron oxide sol, zircon sol, antimony oxide sol, and the like.

Among these inorganic ultrafine particles, fumed silica ultrafine particles and alumina compounds (alumina hydrate or aluminum oxide ultrafine particles) can be preferably used.

The silica fine particles are made of SiO ₂ 93 on a dry basis.
%, About 5% or less of Al ₂ O _{3 and} about 5% or less of Na ₂ O.
There is amorphous silica such as silica gel and fine powder silica.
Methods for producing amorphous silica fine particles include a liquid phase method, a pulverized solid phase method, a crystallization solid phase method, and a gas phase method. What is the liquid phase method?
This is a method for producing fine particles in which a silicate compound or the like existing in a liquid is precipitated in a solid state by a chemical change or a physical change. The pulverized solid phase method is a method for mechanically pulverizing silica solids, and the crystallization solid phase method is a method for producing fine particles utilizing melting, phase transition of a solid, or the like. The gas phase method is a method for producing fine particles by thermal decomposition of vapor of a volatile metal compound, heating and evaporation of raw materials, cooling and condensation of generated gas phase species.

The silica fine particles used in the present invention are amorphous silica fine particles synthesized by a gas phase method among the above. Among them, ultrafine silica having an average primary particle diameter of 3 nm to 50 nm is preferable. Particularly preferred primary particle size is 5n
m to 30 nm. Further, the secondary particle diameter in which these are connected is preferably 10 nm to 400 nm. Aerosil (Texa) corresponds to a commercially available product as amorphous silica fine particles synthesized by the gas phase method.

The fumed silica used in the present invention is obtained by adding silica fine particles having the above-mentioned primary particle size to water and dispersing the same with a high-speed homogenizer or the like so that the average secondary particle size is 400 nm or less.
Preferably, it is dispersed to 200 nm or less.

The alumina hydrate used in the present invention can be represented by the following general formula. Al ₂ O ₃ .nH ₂ O alumina hydrate is classified into gypsite, vialite, norstrandite, boehmite, boehmite gel (pseudo boehmite), diaspore, amorphous amorphous, etc. according to the difference in composition and crystal form. You. Among them, in the above formula, when the value of n is 1, it represents an alumina hydrate having a boehmite structure, and when n is more than 1 and less than 3, it represents an alumina hydrate having a pseudo-boehmite structure; When it is 3 or more, it represents an alumina hydrate having an amorphous structure. In particular, alumina hydrates preferred for the present invention are those having a pseudo-boehmite structure in which at least n is more than 1 and less than 3.

The shape of the alumina hydrate used in the present invention may be any of a flat plate shape, a fibrous shape, a needle shape, a spherical shape, a rod shape and the like, and a preferable shape is a flat plate shape from the viewpoint of ink absorption. The plate-like alumina hydrate has an average aspect ratio of 3
-8, preferably an average aspect ratio of 3-6. Aspect ratio is the "diameter" of the particle "thickness"
It is expressed by the ratio of Here, the diameter of the particle means the diameter of a circle equal to the projected area of the particle when the alumina hydrate is observed with an electron microscope. When the aspect ratio is smaller than the above range, the pore size distribution of the ink receiving layer becomes narrow, and the ink absorbency decreases. On the other hand, when the aspect ratio exceeds the above range, it becomes difficult to prepare alumina hydrate by aligning the particles.

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

As a method for obtaining an alumina hydrate from an alkoxide, JP-A-57-88074, JP-A-57-88074, and
No. 56321, JP-A-4-275917, JP-A-6-64918, JP-A-7-10535,
-267633, U.S. Pat. No. 2,656,321
Patent Document 1 discloses a method for hydrolyzing aluminum alkoxide. These aluminum alkoxides include isopropoxide, 2-butoxide and the like.

Further, Japanese Patent Application Laid-Open No. 54-116398,
JP-A-55-23034, JP-A-55-27824 and JP-A-56-120508 disclose a method using an aluminum inorganic salt or a hydrate thereof as a raw material. Examples of the raw material include inorganic salts such as aluminum chloride, aluminum nitrate, aluminum sulfate, polyaluminum chloride, ammonium alum, sodium aluminate, potassium aluminate, and aluminum hydroxide, and hydrates thereof.

As still another method, Japanese Patent Application Laid-Open No. 56-120
Japanese Patent Publication No. 508 discloses a method of growing crystals of alumina hydrate by alternately changing the pH from an acidic side to a basic side. Japanese Patent Publication No. 4-33728 discloses an alumina water obtained from an inorganic salt of aluminum. A method is disclosed in which a hydrate is mixed with alumina obtained by a Bayer method, and the alumina is rehydrated.

The ink jet recording medium of the present invention includes:
Commercially available alumina hydrate can also be suitably used. An example is described below, but the present invention is not limited to this. For example, as the alumina hydrate, Cataloid AS-1, Cataloid AS-2, Cataloid AS-
Alumina sol 100, alumina sol 200, alumina sol 520 (overall, manufactured by Nissan Chemical Industries), M-200 (overall, manufactured by Mizusawa Chemical Industries), aluminum sol 10, aluminum sol 20, aluminum sol 132, aluminum sol 132S , Aluminum sol SH5, aluminum sol CS
A55, aluminum sol SV102, aluminum sol SB52
(Above, manufactured by Kawaken Fine Chemical).

As the ultrafine particles of aluminum oxide (hereinafter, alumina) used in the present invention, γ-type alumina fine particles which are γ-type crystals are preferably used. When crystallographically classifying γ-type crystals, they can be further divided into γ groups and δ groups. Fine particles having a crystal form of the δ group are more preferable.

The γ-type alumina fine particles can reduce the average particle diameter of the primary particles to about 10 nm, but generally, the primary particles have a secondary aggregation form (hereinafter, referred to as secondary particles). Once formed, the particle size increases from thousands to tens of thousands of nm. Use of such gamma-alumina fine particles having a large particle diameter, although having good printability and absorbability of the ink receiving layer, lacks transparency and easily causes coating film defects. The average particle size of the primary particles is preferably less than 80 nm. When secondary particles composed of primary particles of 80 nm or more are used, fragility is increased and coating film defects are very likely to occur.

In order to obtain γ-type alumina fine particle sol, usually, γ-type alumina crystals, which are secondary particles of several thousand to several tens of thousands nm, are averaged by a pulverizing means such as a bead mill, an ultrasonic homogenizer, and a high-pressure homogenizer. Particle size 2
Pulverization is performed until ultrafine particles having a diameter of not more than 00 nm, preferably not more than 100 nm are obtained. When the average particle size exceeds 200 nm, the ink absorbency increases, but the coating is brittle and the transparency decreases. As the pulverizing means, a method using an ultrasonic homogenizer or a high-pressure homogenizer is preferable.In other pulverizing methods such as a bead mill, since the γ-type alumina crystal is a hard crystal, foreign matter is easily mixed in from the pulverizing container, and the transparency is high. Causes a decrease in the number of defects and the generation of defects. γ-type alumina fine particles have excellent ink absorbency, good print quality such as drying property and ink fixing property, and are made into ultra fine particles, so that even if they are contained in the ink receiving layer at a high ratio, they have excellent transparency. Medium can be obtained.

Γ-type alumina fine particles are commercially available as δ-type alumina fine particles.
It can be obtained as aluminum oxide C (manufactured by Nippon Aerosil Co., Ltd.) belonging to the group, AKP-G015 (manufactured by Sumitomo Chemical Co., Ltd.) belonging to the γ group, and the like.

A water-soluble or water-insoluble polymer compound may be added as an adhesive for the inorganic ultrafine particles used in the present invention. The polymer compound used in the present invention is a compound having an affinity for ink as a component of the ink receiving layer. For example, as the water-soluble polymer compound, methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, cellulose-based adhesives such as hydroxyethylcellulose, starch and its modified products, gelatin and its modified products, casein, pullulan, gum arabic, and Natural polymer resins such as albumin or derivatives thereof, polyvinyl alcohol and modified products thereof, styrene-butadiene copolymer, styrene-acryl copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl acetate copolymer, etc. Latexes and emulsions, vinyl polymers such as polyacrylamide and polyvinylpyrrolidone, polyethyleneimine, polypropylene glycol, polyethylene glycol, and maleic anhydride or copolymers thereof Like the body or the like.
Preferably, it is polyvinyl alcohol.

Examples of the water-insoluble polymer compound include alcohols such as ethanol and 2-propanol, and water-insoluble adhesives that are soluble in a mixed solvent of these alcohols and water. It is particularly preferable because it is converted. Examples of such a water-insoluble adhesive include acetal resins such as vinylpyrrolidone / vinyl acetate copolymer, polyvinyl butyral, and polyvinyl formal. In particular, the degree of acetalization is in the range of 5 mol% to 20 mol%. The acetal resin is preferable because it can contain a little water and can easily disperse the inorganic ultrafine particles.

These polymer compounds may be used alone or in combination of two or more.
It is preferable to add 0% by mass or less. More preferably, 5 mass% or more and 30 mass% or less are added. If the amount is less than the above range, the strength of the coating film will be weak, and if it exceeds the range, the ink absorbency will be reduced.

The method for applying the coating liquid in the present invention is as follows.
E-bar coating, curtain coating, extrusion coating,
Various coating methods such as roll coating, air knife coating, gravure coating, and rod bar coating can be adopted.

In the present invention, the layer constitution of the ink receiving layer may be a single layer or a laminated layer. In the case of a laminated structure, all layers may be layers having the same composition, or may be a laminated structure with a layer composed of other components.

The coating amount of the ink receiving layer containing the inorganic ultrafine particles of the present invention is required to be 5 g / m ² or more in terms of solid content.
It is 0 g / m ² or more and 30 g / m ² or less. More preferably 1
It is 0 g / m ² or more and 20 g / m ² or less. Although it depends on the amount of voids and the like, the thickness is preferably 10 μm or more and 30 μm or less.

As a means for drying after coating, a general known method can be used and is not limited. For example,
There are a method of transporting the heated air generated by the heat source into the heated heater, and a method of passing the air near the heat source such as a heater.

Further, a coating liquid for forming an ink receiving layer containing the inorganic ultrafine particles of the present invention and, if necessary, an adhesive may contain, if necessary, a surfactant, an inorganic pigment, a coloring dye, a coloring pigment, and an ink. Dye fixing agent (cationic resin), UV absorber, antioxidant, pigment dispersant, defoamer, leveling agent, preservative, fluorescent brightener, viscosity stabilizer, pH adjuster, hardener, etc. Various known additives can be added.

In the present invention, a barrier layer is provided on a base paper, an undercoat layer containing an alkaline earth metal salt and an adhesive is provided thereon, and an ink receiving layer containing inorganic ultrafine particles is further provided thereon. Accordingly, it is possible to obtain an ink jet recording medium having high gloss, high absorptivity, excellent image color properties, no problem in the adhesiveness of the ink receiving layer, and little ripple after recording. Why this combination
It is not clear whether an ink jet recording medium having high glossiness and high absorbency and having less ripple after recording can be obtained. In order to obtain high gloss, it is necessary that the ink receiving layer does not penetrate into the undercoat layer during coating of the ink receiving layer, but is leveled to form a highly smooth surface and dried. In order to obtain high absorbency, not only the ink receiving layer but also the undercoat layer must contribute to absorption. However, if the undercoat layer has too high absorptivity, the ink receiving layer is coated when the ink receiving layer is applied. The liquid infiltrates the undercoat layer, causing a contradiction that high gloss cannot be obtained.

As in the present invention, when the pigment in the undercoat layer is a salt of an alkaline earth metal and the coating liquid for the ink receiving layer is acidic, when the ink receiving layer is coated, It is thought that the salt of the acid and the alkaline earth metal causes a shock, and the inorganic ultrafine particles do not seep into the undercoat layer and form an interface. During or after drying, the salt of the alkaline earth metal in the boundary surface or in the undercoat layer is gradually dissolved or deformed by moisture or acid in the ink receiving layer, forming an absorption path, thereby forming the undercoat layer. It is considered that the absorptivity is linked to the voids of the ink receiving layer, thereby enhancing the absorptivity. Therefore, it is necessary that the ink receiving layer coating liquid is acidic. The pH of the coating liquid for the ink receiving layer is preferably 5.0 or less, particularly preferably 4.0 or less. The pH of the ink receiving layer coating liquid is 5.
If it exceeds 0, the interaction with the salt of the alkaline earth metal is weakened, and the ink absorbency tends to slightly decrease. In addition, the effect is not exhibited in the alkaline region.

In addition, it is considered that the waving is generally caused by swelling and stress relaxation of the pulp constituting the base paper when moisture penetrates into the base paper, and unevenness locally generated when the pulp is dried again remains. In the present invention, as described above, the interaction between the undercoat layer and the ink receiving layer increases the ink absorbency, reduces the penetration of moisture into the base paper, and reduces the alkaline earth metal between the undercoat layer and the base paper. By providing a barrier layer containing a pigment not having a salt as a main component, the barrier layer does not cause dissolution or deformation of the ink-receiving layer due to acid, and further has a synergistic effect of suppressing permeation into the base paper. It is presumed that the ripple after recording is small.

Therefore, it is considered that the lower the water absorption on the side where the barrier layer is provided on the base paper, the more the permeation of water into the base paper is suppressed, and the occurrence of waving is less likely. Specifically, the water absorption (contact time 30 seconds) by the Cobb method specified in JIS P 8140 is preferably 25 g / m ² or less. In order to adjust the water absorption by the Cobb method, it is easy to adjust the addition amount of the internal sizing agent in addition to providing the barrier layer. Furthermore, not only internal sizing agent but also external sizing agent (given by size press etc.)
Can also be adjusted depending on the type and amount of application.

[0069]

The present invention will be described below with reference to examples. The present invention is not limited to the embodiments. All parts and percentages in the following are based on mass.

<Preparation of base paper> A 1: 1 mixture of bleached hardwood kraft pulp (LBKP, whiteness 90%) and softwood bleached sulphite pulp (NBSP, whiteness 90%) was beaten to 300 ml with Canadian Standard Freeness. Then, a pulp slurry was prepared. 0.5 mass% of alkyl ketene dimer to pulp as a sizing agent, 1.0 mass% of polyacrylamide to pulp as a paper strength enhancer, 2.0 mass% of cationized starch to pulp, polyamide epichlorohydrin Resin to pulp
5% by mass was added and diluted with water to obtain a 1% slurry. The slurry was subjected to papermaking using a fourdrinier paper machine so as to have a basis weight of 150 g / m ² to prepare a paper substrate.

<Barrier Layer Coating Solution A> 100 parts by mass of high-white primary kaolin (UW-90: manufactured by Engelhard Co.), and a styrene-butadiene copolymer latex (Luckstar DS226, manufactured by Dainippon Ink) as an adhesive ) Was mixed with water at 20 parts by mass of solid content to prepare a barrier layer coating solution A having a solid content concentration of 45%.

<Barrier Layer Coating Solution B> Organic pigment (L880)
1; 100 parts by mass of polystyrene resin manufactured by Asahi Kasei Kogyo Co., Ltd .; styrene-butadiene copolymer latex (Luckstar DS226, manufactured by Dainippon Ink) as an adhesive; A barrier layer coating liquid B having a concentration of 45% was prepared.

<Barrier Layer Coating Solution C> 60 parts by mass of high-white primary kaolin (UW-90: manufactured by Engelhard Co.), 40 parts by mass of organic pigment (L8801; polystyrene resin manufactured by Asahi Kasei Kogyo Co., Ltd.), used as an adhesive A styrene butadiene copolymer latex (Luckstar DS226, manufactured by Dainippon Ink and Chemicals, Inc.) was mixed with 20 parts by mass of water in water to prepare a barrier layer coating liquid C having a solids concentration of 45%.

<Barrier Layer Coating Solution D> Heavy Calcium Carbonate (Carbital 90: manufactured by ECC International) 1
20 parts by mass of styrene-butadiene copolymer latex (Luckstar DS226, manufactured by Dainippon Ink) as an adhesive were mixed with water in an amount of 20 parts by mass in water, and a barrier layer coating liquid D having a solid concentration of 45% was mixed. Was prepared.

<Undercoat Layer Coating Solutions A1 to A8> Light calcium carbonate (Tamapearl 22) is used as a salt of an alkaline earth metal.
2H: 100 parts by mass of Okutama Industry Co., Ltd .; styrene butadiene copolymer latex (Luckstar DS226, manufactured by Dainippon Ink) as an adhesive 3 parts by mass, 5 parts by mass, 10 parts by mass, 15 parts by mass Parts by mass, 20 parts by mass, 40 parts by mass, 80 parts by mass, and 100 parts by mass are mixed with water, and each of the undercoat layer coating liquids A1 to A8 has a solid content concentration of 45%.
Was prepared.

<Undercoat Layer Coating Solution B> Heavy calcium carbonate (Carbital 90: ECC) is used as a salt of an alkaline earth metal.
International Co., Ltd.) 100 parts by mass, styrene-butadiene copolymer latex (Luckstar DS226, manufactured by Dainippon Ink Co., Ltd.) as an adhesive, and 20 parts by mass of a solid content mixed with water to give an undercoat layer having a solid content concentration of 45% Coating liquid B
Was prepared.

<Coating solution C for undercoat layer> 100 parts by mass of magnesium carbonate (spherical magnesium carbonate: manufactured by Kamishima Chemical Industry Co., Ltd.) as a salt of an alkaline earth metal, and a styrene-butadiene copolymer latex (Luckster DS2) as an adhesive
26, manufactured by Dainippon Ink Co., Ltd.) was mixed with 20 parts by weight of solids in water to prepare an undercoat layer coating liquid C having a solids concentration of 45%.

<Undercoat layer coating liquid D> 100 parts by mass of barium sulfate (precipitable barium sulfate D-2: manufactured by Barite Industry Co., Ltd.) as a salt of an alkaline earth metal, and a styrene butadiene copolymer latex (rack) as an adhesive Star DS2
26, manufactured by Dainippon Ink Co., Ltd.) in an amount of 20 parts by mass of solid content in water to prepare an undercoat layer coating liquid D having a solid content concentration of 45%.

<Undercoat layer coating solution E> 100 parts by mass of synthetic amorphous silica (Fine Seal X37B: manufactured by Tokuyama Corporation), polyvinyl alcohol (PVA11) as an adhesive
7: Kuraray Co., Ltd.) was dissolved and mixed with 20 parts by mass of solid content in water to prepare an undercoat layer coating solution E having a solid concentration of 20%.

<Ink receiving layer coating liquid A> Primary particle diameter 7n
m of gas phase ultrafine silica (AEROSIL300: manufactured by Nippon Aerosil Co., Ltd.) and a dispersant (Sharol DC
902P: Daiichi Kogyo Seiyaku Co., Ltd.) was dispersed in 500 g of ion-exchanged water with a stirrer, and the secondary particle diameter was 200 nm.
The following dispersion was obtained. Further, 15 parts of a 10% by mass aqueous solution of polyvinyl alcohol (PVA105: manufactured by Kuraray Co., Ltd.) was mixed with 100 parts of the silica dispersion of the gas phase method ultrafine particles, and water was added. Working fluid A was used. The pH of the ink receiving layer coating liquid A was 3.8.

<Synthesis of Alumina Hydrate> Ion-exchanged water 1
200 g and isopropyl alcohol 900 g were charged into a 3 L reactor and heated to 75 ° C. 408 g of aluminum isopropoxide were added, and 75 g for 24 hours, followed by 9 g
Hydrolysis was performed at 5 ° C. for 10 hours. After hydrolysis, acetic acid 2
4 g was added and the mixture was stirred at 95 ° C. for 48 hours. Next, the mixture was concentrated so that the solid content became 15% by mass to obtain a dispersion liquid of white ultrafine alumina hydrate. The sol was dried at room temperature and measured for X-ray diffraction, which showed a pseudo-boehmite structure. Further, the average particle size was measured with a transmission electron microscope, and was 30 nm, which was a tabular ultrafine alumina hydrate having an aspect ratio of 6.0. Further, the average pore radius, the pore volume and the BET were determined by the nitrogen adsorption / desorption method.
The specific surface area was measured to be 7.1 nm and 0.1 nm, respectively.
65 ml / g and 200 m ² / g.

<Ink receiving layer coating liquid B> 15% by mass
Is dispersed using a homomixer so that the secondary particle diameter is 400 nm or less. Further, 10% by mass of 100 parts by mass of this alumina hydrate dispersion is dispersed. Polyvinyl alcohol (PVA10
5: Kuraray Co., Ltd.) 15 parts of an aqueous solution were mixed. This mixed solution was concentrated by an evaporator so as to have a solid content concentration of 15% to obtain an ink receiving layer coating liquid B. The pH of the ink receiving layer coating liquid B was 4.5.

<Ink-receiving layer coating liquid C> As γ-type alumina crystal powder of δ group as alumina ultra-fine particles,
Aerosil aluminum oxide C having a primary particle diameter of 13 nm
600 g (manufactured by Nippon Aerosil Co., Ltd.) was placed in 2400 g of ion-exchanged water using a homomixer and the secondary particle diameter was 10
The slurry was dispersed so as to be 0 nm or less to prepare a 20% by mass slurry-like viscous liquid. Using this 20 mass% γ-type alumina dispersion, 10 parts
% By mass of polyvinyl alcohol (PVA23 manufactured by Kuraray Co., Ltd.)
5) 30 parts of the aqueous solution were mixed. Add solid to solid content 1
The ink receiving layer coating liquid C was 5%. The pH of the ink receiving layer coating liquid was 5.0.

<Ink receiving layer coating liquid D> Primary particle diameter 7n
m of gas phase ultrafine silica (AEROSIL300: manufactured by Nippon Aerosil Co., Ltd.) and a dispersant (Sharol DC
902P: Daiichi Kogyo Seiyaku Co., Ltd.) was dispersed in 500 g of ion-exchanged water with a stirrer, and the secondary particle diameter was 200 nm.
The following dispersion was obtained. Further, 15 parts of a 10% by mass aqueous solution of polyvinyl alcohol (PVA105: manufactured by Kuraray Co., Ltd.) was mixed with 100 parts of the silica dispersion liquid of the gas phase method ultrafine particles, and the pH was adjusted to 5.5 by adding sodium hydroxide. Then, water was added to obtain an ink receiving layer coating liquid D having a solid content of 15%.

<Ink receiving layer coating liquid E> Synthetic amorphous silica having a secondary particle diameter of 3.7 μm (fine seal X-37B: B manufactured by Tokuyama Corporation) which does not correspond to the inorganic ultrafine particles of the present invention
100 parts of an ET specific surface area of 270 m ² / g), 15 parts of polyvinyl alcohol (PVA105: manufactured by Kuraray Co., Ltd.) and 20 parts of a cationic dye fixing agent (Smileds Resin 1001: manufactured by Sumitomo Chemical Co., Ltd.) are dissolved and mixed in water, and the solid content is An ink receiving layer coating liquid E having a concentration of 15% was used. P of ink receiving layer coating liquid E
H was 5.3.

Examples 1 to 19 The coating liquid for the barrier layer shown in Table 1 was applied on a base paper by a bar coater so as to have a dry coating thickness shown in Table 1, and then dried. In addition, the undercoat layer coating liquid shown in Table 1 was coated with a bar coater so as to have a dry coating amount of 10 g / m ^2, and dried, and then subjected to a heat calendering treatment (temperature 100 ° C., nip pressure 15
0 kg / cm). Then, the coating liquid for the ink receiving layer shown in Table 1 was dried with a bar coater at a dry coating amount of 15 g /
After coating to dryness of m ² , Examples 1 to 19 were obtained.

Example 20 A barrier layer coating solution shown in Table 1 was coated on a base paper by a bar coater so as to have a dry coating amount shown in Table 1, and then dried.
A calender treatment (nip pressure 150 kg / cm) was performed. The undercoat layer coating liquid shown in Table 1 was further coated thereon by a bar coater so as to have a dry coating amount of 10 g / m ² , and then dried, and subjected to a heat calendering treatment (temperature: 100 ° C., nip pressure: 1).
50 kg / cm). Further, the ink receiving layer coating liquid shown in Table 1 was applied thereon by a bar coater so as to have a dry coating amount of 15 g / m ² , and then dried to obtain Example 20.

Example 21 On a base paper, a barrier layer coating solution shown in Table 1 was applied to a bar coater.
After coating to dry coating thickness as shown in Table 1, dry
Was. In addition, the undercoat layer coating liquid shown in Table 1 was applied to a bar coater.
-Dry coating amount 10 g / m^TwoAfter coating to dry
Dried. On top of this, apply the ink receiving layer coating liquid shown in Table 1
-Dry coating amount 15g / m by coater ^TwoTo be
After coating, the mixture was dried to obtain Example 21.

Example 22 A barrier layer coating solution shown in Table 1 was coated on a base paper by a bar coater so as to have a dry coating amount shown in Table 1, and then dried.
A calender treatment (nip pressure 150 kg / cm) was performed. The undercoat layer coating liquid described in Table 1 was further applied thereon by a bar coater so as to have a dry coating amount of 10 g / m ² and then dried. On top of this, the ink receiving layer coating liquid shown in Table 1 was applied by a bar coater so as to have a dry coating amount of 15 g / m ² , and then dried to obtain Example 22.

Comparative Examples 1 to 4 The coating liquid for the barrier layer shown in Table 1 was coated on a base paper by a bar coater so as to have a dry coating amount shown in Table 1, and then dried. In addition, the undercoat layer coating liquid shown in Table 1 was coated with a bar coater so as to have a dry coating amount of 10 g / m ^2, and dried, and then subjected to a heat calendering treatment (temperature 100 ° C., nip pressure 15
0 kg / cm). Further, the coating liquid for the ink receiving layer shown in Table 1 was dried with a bar coater to a dry coating amount of 15 g.
/ M ² and dried after drying to obtain Comparative Examples 1 to 4.

The ink jet recording media prepared in Examples and Comparative Examples were evaluated by the following evaluation methods, and the results are shown in Table 1.

<Evaluation of ink absorptivity> Evaluation of ink absorptivity was carried out using an ink jet recording apparatus Epson Corp.
Using M9000, a heavy-color rectangular pattern was printed with cyan ink, magenta ink, and yellow ink. When the amount of ink to be overlapped is 100% for each color, 300% is set, when all inks are 90% are set to 270%, and similarly, 240%, 21%
Rectangular patterns of 0%, 180%, and 150% were created and printed. The boundary between the printed pattern and the unprinted portion was visually evaluated according to the following criteria. ◎: 300% printing does not show any afterburning ○: 270% printing does not show any afterburning Δ: 210% printing does not show any afterburning ×: 180% printing shows no afterburning Good ink absorption Are the evaluations of ◎ to △.

<Evaluation of Image Color> Canon BJC-42
Solid printing of magenta and cyan was performed using 0J. The color was visually evaluated as follows. A: The color is good and the image looks clear. ：: The color looks good. Δ: The color looks slightly dull, but there is no practical problem. ×: The color is rough and dull. Those having no practical problem are evaluated from ◎ to △.

<Evaluation of glossiness of blank paper> Example 12 was evaluated as standard (（), and 高 い was higher than that of Example 12 by visual observation. Poor was rated as x.

<Rippling after Image Recording> Rippling after image recording is performed by drawing a high-definition photographic image with a wide range of hue and lightness, leaving it for one day, and visually checking the ripple on the recording surface after drying. The evaluation was made in four steps as shown below. ◎: Very good undulation after image recording. 良好: Good undulation after image recording. が: Some undulation after image recording, but no practical problem. ×: Poor undulation after image recording. No practical problem. Those are ◎ ~ △.

<Evaluation of Adhesive Property> After making a grid-shaped cut at intervals of 5 mm in the vertical and horizontal directions from the recording surface side with a cutter knife,
An adhesive tape was applied to the recording surface, peeled off, and the number of peeled ink receiving layers per 100 grids was determined. ◎: The number of peeling is less than 5 ：: The number of peeling is less than 6 to 9 △: The number of peeling is 10 to 30 ×: The number of peeling is 31 or more ◎ and ○ show good adhesiveness, and △ But there is no practical problem.

[0097]

[Table 1]

As shown in Table 1, the amount of dry coating was 3 g / m on the base paper.
^More than 20 g / m ² or less of a barrier layer is provided, the upper alkaline earth Metal salts, 0.8 times or less of the adhesive 0.05 times or more in a mass ratio relative to the alkaline earth metal salts In Examples 1 to 22 in which an undercoating layer containing the inorganic fine particles was further provided and an ink receiving layer containing the inorganic ultrafine particles was provided, all of the visual white paper gloss, image color, ink absorption, and waving were excellent in a well-balanced manner. Things have been obtained. However, when the barrier layer is not applied (Comparative Example 4), the waving is inferior, which is not preferable. When the undercoat layer was not applied (Comparative Example 3), the glossiness of white paper and the ink absorption were poor, and when the undercoat layer did not contain an alkaline earth metal salt (Comparative Example 2), the glossiness of white paper was poor. Furthermore, the pigment in the ink receiving layer is not ultrafine particles (Comparative Example 1)
And the glossiness of blank paper is inferior. Further, performing a thermal calendering treatment is a preferable production method because the visual white paper gloss is improved.

[0099]

As described above, according to the present invention,
It is possible to provide a high-gloss inkjet recording medium having excellent ink absorbency and image colorability, good adhesion of the ink receiving layer, and no ripple after recording.

Continued on front page F-term (reference) 2C056 FC06 2H086 BA01 BA15 BA21 BA31 BA33 BA35 BA36 BA41 4D075 AE03 CA13 CA35 CB04 DA04 DB18 DB20 DB31 DC27 EA05 EA25 EA43 EB07 EB12 EB15 EB19 EB55 EB56 EC02 EC03 EC11

Claims (8)

[Claims] An undercoat layer containing a salt of an alkaline earth metal and an adhesive is provided on a base paper mainly composed of natural pulp,
An ink jet recording medium comprising an ink receiving layer containing inorganic ultrafine particles provided thereon, wherein a barrier layer containing a pigment and an adhesive is provided between the base paper and the undercoat layer. Recording medium. 2. The ink jet recording medium according to claim 1, wherein the pigment contained in the barrier layer is kaolin and / or an organic pigment. 3. The ink jet recording medium according to claim 1, wherein said alkaline earth metal is calcium or magnesium. 4. The ink jet recording medium according to claim 1, wherein the salt of the alkaline earth metal is a carbonate. 5. The ink-jet recording medium according to claim 1, wherein said inorganic ultrafine particles are an amorphous synthetic silica or an alumina compound obtained by a gas phase method. 6. The method according to claim 1, wherein the undercoat layer contains an adhesive having a mass ratio of 0.05 to 0.8 times the alkaline earth metal salt. Item 10. The ink jet recording medium according to item 1. 7. A base paper containing natural pulp as a main component is provided with a barrier layer containing a pigment and an adhesive, and an undercoat layer containing a salt of an alkaline earth metal and an adhesive is provided thereon.
A method for producing an ink jet recording medium, comprising applying a coating liquid for an ink receiving layer containing at least inorganic ultrafine particles after a heat calendering treatment. 8. The method according to claim 7, wherein the inorganic ultrafine particles are amorphous synthetic silica or an alumina compound obtained by a gas phase method, and the pH of the ink receiving layer coating liquid is 5.0 or less. The method for producing an ink jet recording medium according to the above.