JP2002200838A - Ink jet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording medium which shows high luster, high ink absorption and outstanding image color effect, and is free from a handling problem. SOLUTION: In the ink jet recording medium of such a structure that an undercoat layer containing a salt of an alkaline earth metal is formed on a support and an ink receiving layer coating liquid containing an inorganic ultrafine particle is formed on the undercoat layer, a backing coat layer is formed on the opposite side of the support having an ink receiving layer. The alkaline earth metal is preferably calcium or magnesium carbonate. In addition, the more preferable form of the inorganic ultrafine particle is an amorphous synthetic silica or an alumina compound by a gas phase process. Besides, it is preferable that the thickness of the backing coat layer be 5-30 μm and that the backing coat layer contain an inorganic pigment and/or a spherical organic pigment.

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 more particularly, to an undercoat layer provided on a support, and a coating liquid for an ink receiving layer containing inorganic ultrafine particles. The present invention relates to an ink-jet recording medium having a high glossiness, a high absorptivity, and excellent image color, and having improved curl suitability and transportability.

[0002]

2. Description of the Related Art Ink-jet recording is a method in which fine droplets of ink are made to fly on a recording medium such as paper by various operating principles to record images and characters. It has features such as noise, easy multi-coloring, great flexibility in recording patterns, and no need for development-fixing.
It is rapidly spreading in various uses as a recording device for various figures and color images including kanji. Furthermore, the image formed by the multi-color ink jet method is compared with the multi-color printing by the plate making method and the printing by the color photographic method,
It is possible to obtain comparable records. In addition, in applications requiring a small number of copies, it is being widely applied to the field of full-color image recording because it is less expensive than the photographic technique.

[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] Due to the high performance and diversification of applications of these ink jet recording apparatuses, the characteristics and requirements required for the ink jet recording medium have been considerably increased. In particular, in a recording device that claims high definition of an image or a recording device capable of large-format printing, the amount of ink used to form an image is considerably increased, and an ink receiving layer for absorbing the ink is used. Is improving.

[0005] The diversification of applications is also applied to the appearance of ink jet recording media. In addition to the conventional matte or low gloss appearance of plain paper and matte paper, art paper, coated paper, cast paper, There is a demand for an appearance having gloss similar to that of coated paper, photographic paper and the like. 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 JP-A-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.

On the other hand, as an ink jet recording medium having improved surface glossiness, there is proposed an ink jet recording medium provided with an ink receiving layer made of a resin on a support. Examples of resins used in such applications include, for example, JP-A-57-381.
Nos. 85 and 62-184879, polyvinylpyrrolidone and vinylpyrrolidone-vinyl acetate copolymer disclosed in JP-A-60-168651, JP-A-60-171143 and JP-A-61-134290. JP-A-60-234879 discloses a resin composition containing polyvinyl alcohol as a main component, a copolymer of vinyl alcohol and an olefin or styrene and maleic anhydride as disclosed in JP-A-60-234879. A crosslinked product of polyethylene oxide and isocyanate as disclosed in JP-A-61-74879, a mixture of carboxymethyl cellulose and polyethylene oxide as disclosed in JP-A-61-181679, No. 61-132377. Grafting of methacrylic acid amide to alcohol polymer, JP 62-220383
Acrylic polymers having a carboxyl group as disclosed in JP-A-4-214382, polyvinyl acetal-based polymers as disclosed in JP-A-4-214382, JP-A-4-282282, JP-A-4-28565.
Various ink-absorbing polymers, such as a crosslinkable acrylic polymer as disclosed in Japanese Patent Publication No. 0, No. 0, 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 ink jet recording medium having a high ink absorption rate and enhanced surface gloss. For example, JP
-232990, 60-245588,
JP-B-3-24906, JP-A-6-199035
JP-A-7-82694 discloses 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 is small, and 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 0.5 to 2.5 times the solid fine particles in a weight ratio to 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 absorption layer of
This first ink absorbing layer does not contribute to the improvement of the ink absorbing property.

[0010] On the other hand, there has been a proposal for improving the sharpness of an image by devising a support provided with an ink receiving layer. For example, Japanese Patent Application Laid-Open No. 62-162588 discloses a whiteness of 90
An ink jet recording sheet having a sheet whiteness of 90% or more, comprising bleached pulp of at least 90% and an absorbent filler is disclosed. However, although sufficient whiteness and absorptivity can be obtained by this method, a high-quality glossy image cannot be obtained. JP-A-11-129613 discloses a recording paper provided with a layer containing solid fine particles having a fluorescent whitening effect. However, this method requires a step of providing a layer containing a special component and a special component in the ink-receiving layer, which complicates the production process and is not preferable.

Japanese Patent Application Laid-Open Nos. 4-204727 and 4-296745 disclose resin-coated photographic supports having improved whiteness. However, these technologies have the purpose of making photographic printing paper, and since the paper is covered with resin, the ink absorption capacity is small, and in order to obtain sufficient ink absorption capacity, it is necessary to apply a thick film of the ink receiving layer. is there. In JP-A-2000-33771, polyvinyl alcohol, polyvinylpyrrolidone and vinyl acetate-butyl acrylate copolymer are used as a base paper having a layer containing barium sulfate and thermoplastic hollow fine beads on at least one surface. An ink jet recording material support coated with an ink receiving layer is disclosed.
However, since the ink receiving layer is made of a resin, the surface glossiness can be obtained, but the absorption rate is low and the amount of absorption is small as compared with the ink receiving layer made of fine pigment particles such as silica.

The ink jet recording medium is also required to have a property of preventing curling (curl suitability). The occurrence of curl is caused by a difference in expansion and contraction of the front surface and the back surface of the recording medium with respect to changes in temperature and humidity. For example, in a low humidity environment, the front surface is larger than the shrinkage of the back surface. Then, the edge of the recording sheet warps toward the front side.

The lack of curl aptitude is not only a problem that paper cannot be fed or ejected in the ink jet recording apparatus (conveyability), but also a problem that a recording medium comes into contact with a head in the ink jet recording apparatus due to curl. Also occur. From this, an attempt to ensure curl aptitude using a polyethylene terephthalate film as a support,
JP-A-61-2351846 and JP-A-62-28
No. 2967 and the like. However, the effect can hardly be obtained for an ink jet recording medium provided with a liquid-permeable coating layer or a water-absorbing coating layer on a paper support.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording medium having high gloss, high absorptivity, excellent image color, and improved curl suitability and transportability. .

[0015]

SUMMARY OF THE INVENTION The present invention provides a method for manufacturing a semiconductor device comprising the steps of:
In an ink jet recording medium obtained by applying an undercoat layer containing a salt of an alkaline earth metal and applying a coating liquid for an ink receiving layer containing inorganic ultrafine particles, a support opposite to the support having the ink receiving layer This is an inkjet recording medium provided with a backing layer on its surface.

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

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

It is more preferable that the ink receiving layer coating liquid containing the inorganic ultrafine particles has a pH of 5 or less.

The thickness of the backing layer is 5 μm or more and 30 μm or more.
m or less, and it is a more preferred embodiment that the backing layer contains an inorganic pigment and / or a spherical organic pigment.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ink jet recording medium of the present invention will be described below in detail.

In the present invention, the backcoat layer refers to a layer containing a polymer resin or a polymer resin and an inorganic pigment and / or an organic pigment and provided on the opposite side of a support of the ink receiving layer.

Examples of the polymer resin used in the backing layer include polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, casein,
Gelatin, soy protein, silyl-modified polyvinyl alcohol, etc .; conjugated diene copolymer latex such as maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer; polymers of acrylate and methacrylate Or an acrylic polymer latex such as a copolymer, a polymer or a copolymer of acrylic acid and methacrylic acid; a vinyl polymer latex such as an ethylene-vinyl acetate copolymer; or a carboxyl group of these various polymers. Functional group-modified polymer latex with functional group-containing monomer; aqueous adhesive such as thermosetting synthetic resin such as melamine resin and urea resin; polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer , Polyvinyl butyral, alkyd tree Synthetic resin-based adhesive and the like can be mentioned,
Used in one or more types.

It is preferable to use one or more known white pigments for the backcoat layer. 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-crystalline Crystalline silica, colloidal silica, colloidal alumina,
White inorganic pigments such as pseudo-boehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrohaloysite, magnesium carbonate, magnesium hydroxide, styrene-based plastic pigment, acrylic-based plastic pigment, polyethylene fine particles, microcapsules, urea resin, melamine resin, etc. Organic pigments. Among these organic pigments, various plastic pigments or spherical fine particles such as polyethylene fine particles are preferably used.

In the backing layer, other additives such as inorganic or organic antistatic agents, hardeners, pigment dispersants, thickeners, flow improvers, defoamers, defoamers, release agents Agent, foaming agent,
Penetrants, coloring dyes, coloring pigments, fluorescent whitening agents, ultraviolet absorbers, antioxidants, preservatives, anti-binders, waterproofing agents, wet paper strength agents, dry paper strength agents, surfactants, etc. The backing layer may have the function of an ink receiving layer substantially.

The coating amount of the backing layer varies depending on the coating amount on the ink receiving layer side, but is 5 μm to 30 μm in thickness.
It is good to provide so that it becomes. If it is less than 5 μm, the curl suppressing effect is not sufficient, and if it exceeds 30 μm, the curling is suppressed too much and a trouble occurs.

By providing a backing layer as described above,
By preventing the curl by balancing the expansion and contraction of the undercoat layer and the ink receiving layer, the paper cannot be fed or ejected in the ink jet recording apparatus, or the curl causes the recording medium to reach the head in the ink jet recording apparatus. This makes it possible to avoid the problem that the recording medium becomes dirty due to the contact.

The support used in the present invention is not particularly limited as long as the undercoat layer and the ink receiving layer can be coated, but paper is preferably used. As the pulp constituting the paper preferably used, natural pulp, recycled pulp, synthetic pulp, etc. may be used alone or in combination of two or more. 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 with a beater such as a double disc refiner in order to improve paper properties and various properties of the paper such as strength, smoothness, uniformity of formation and the like. Beating degree is 250ml ~ 550ml in Canadian Standard Freeness
It can be selected according to the purpose within the usual range of the degree.

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. In this case, in the present invention, the pulp slurry usually used for 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, a fluorescent whitening agent 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, anionic paper strength enhancers such as vegetable gum, starch, 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 paper support preferably used in the present invention is prepared by coating a solution 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 apply with.

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. Dispersions of polymers, polyethylene, polyvinylidene chloride and the like can be mentioned. 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 paper support preferably used in the present invention preferably has good surface smoothness, for example, by applying pressure with a calender or the like during or after papermaking, and has good surface smoothness, according to JIS-P-8119. The measured Beck's smoothness is preferably 50 seconds or more, particularly preferably 100 seconds or more. The basis weight is 150 to 300 g / m ^2.
Is preferred.

The ink jet recording medium of the present invention is an ink jet recording medium comprising an undercoat layer on the support and 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,
And 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, for example, colloidal silica described in JP-B-4-19037, JP-A-62-28.
Silica / alumina hybrid sol described in US Pat. No. 6,787,687, and fumed silica as described in JP-A-10-119423 and JP-A-10-217601 are dispersed by a high-speed homogenizer. Silica sol and other smectite clays such as hectite and montmorillonite (JP-A-7-81210)
Publication), zirconia sol, 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 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 finely divided 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, among the above, amorphous silica fine particles synthesized by a gas phase method. 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 particles 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 plate shape, a fiber shape, a needle shape, a spherical shape and a rod shape, and the preferred shape is a plate shape from the viewpoint of ink absorbability. 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, Japanese Patent Application Laid-Open No.
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
No. 508, a method in which the pH is alternately changed from an acidic side to a basic side to grow alumina hydrate crystals, and aluminum as described in Japanese Patent Publication No. 4-33728. There is also a method of mixing alumina hydrate obtained from an inorganic salt of the above with alumina obtained by the Bayer method, and rehydrating the alumina.

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-
3 (manufactured by Catalyst Chemical Industry), alumina sol 100, alumina sol 200, alumina sol 520 (manufactured by Nissan Chemical Industry), M-200 (manufactured by Mizusawa Chemical Industry), aluminum sol 10, aluminum sol 20, aluminum sol 132, aluminum sol 132S, Aluminum sol SH5, Aluminum sol CSA
55, aluminum sol SV102, and aluminum sol SB52 (all manufactured by Kawaken Fine Chemical).

As the ultrafine aluminum oxide particles used in the present invention, γ-type aluminum oxide fine particles that 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 alumina of the γ-type crystal fine particles can reduce the average particle diameter of the primary particles to about 10 nm.
(Hereinafter referred to as “secondary particles”), and the particle diameter increases from several thousand to tens of thousands of nm. When such γ-type alumina crystal fine particles having such a large particle diameter are used, the printability and the absorbability of the ink receiving layer are good, but the ink lacks transparency and the coating film defects are liable to occur. 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.

To obtain a γ-type alumina crystal fine particle sol,
Normally, ultrafine particles having an average particle diameter of 200 nm or less, preferably 100 nm or less, are obtained by milling γ-type alumina crystals, which are secondary particles of several thousands to tens of thousands of nm, using a bead mill, an ultrasonic homogenizer, or a high-pressure homogenizer. Crush until it becomes 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 crystal fine particles are excellent in ink absorbency, good in printing quality such as drying property and ink fixing property, and are excellent in transparency by making them ultra-fine particles even if they are contained in the ink receiving layer at a high ratio. A recording medium can be obtained.

The γ-type alumina crystal fine particles are commercially available as aluminum oxide C belonging to δ group (manufactured by Nippon Aerosil Co., Ltd.) and AKP-G01 belonging to γ group.
5 (manufactured by Sumitomo Chemical Co., Ltd.).

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 compounds 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 an acetal resin such as a 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 particularly preferable because it can contain water to some extent and can easily disperse the inorganic ultrafine particles.

These polymer compounds may be used alone or in combination of two or more.
0% by weight or less is added. Preferably, 5% by weight or more 3
0% by weight or less is added. If the amount is less than the above range, the strength of the coating film becomes weak, and if it is too large, the ink absorbency decreases.

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

In the present invention, the ink receiving layer may have a single layer structure or a multilayer structure. 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 or more per unit square meter in terms of solid content. 10g or more 3
0 g or less. Particularly preferably, it is 10 g or more and 20 g or less per unit square meter. Although it depends on the amount of voids, the thickness is particularly preferably from 10 μm to 30 μm.

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, the coating liquid for forming the 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.

The pH of the coating liquid for forming the ink receiving layer is preferably acidic (pH 5 or less), and particularly preferably pH 4 or less. The present invention provides an undercoat layer containing an alkaline earth metal salt and an adhesive, and by providing an ink receiving layer containing inorganic ultrafine particles thereon,
An inkjet recording medium having high gloss, high absorptivity and excellent image color is obtained. Why this combination
It is not clear whether high gloss and high absorption 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 application of the ink receiving layer, but is leveled to form a clean 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, when coating the ink receiving layer, the acid and the salt of the alkaline earth metal in the ink receiving layer cause a shock, and It is considered that the ultrafine particles do not penetrate into the undercoat layer and form an interface. During or after drying, the salt of the alkaline earth metal in the interface or the undercoat layer is gradually dissolved or deformed by moisture or acid in the ink receiving layer to form an absorption path, thereby making the undercoat layer absorbable. It is thought that is linked to the voids in the ink receiving layer, thereby enhancing the absorbency.

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 having a weight ratio of 0.05 to 0.8 times the alkaline earth metal salt. Is preferred. More preferably 0.05 times or more.
The range is four times or less. When the weight ratio of the adhesive to the alkaline earth metal salt is less than 0.05, the adhesive strength becomes insufficient, and peeling occurs between the support and the ink receiving layer. On the other hand, if the weight ratio of the adhesive to the alkaline earth metal salt is more than 0.8 times, the absorptivity is lowered, 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. An emulsion of a styrene-butadiene copolymer or an acrylic copolymer is preferred.

Further, other additives include cationic dye fixing agents, pigment dispersants, thickeners, flow improvers, viscosity stabilizers, pH adjusters, surfactants, defoamers, defoamers, 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 support 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 there much difficulty in production, but the effect is saturated.
Therefore, a preferable range is 5 g / m ² or more and 30 g / m ² or less.

[0067]

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 by weight.

<Preparation of Support> 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% by weight of alkyl ketene dimer to pulp as a sizing agent, 1.0% by weight of pulp to polyacrylamide as a paper strength enhancer, 2.0% by weight of pulp to cationized starch, polyamide epichlorohydrin Resin to pulp
5% by weight was added and diluted with water to obtain a 1% slurry. Thereafter, the stock slurry is formed into a web by a Fourdrinier paper machine, subjected to a three-stage wet press in a wet part, treated with a smoothing roll, and then treated with a smoothing roll in the middle of a subsequent drying part.
Pressing of the column was performed. Then, during the drying, a size press solution of 5% by weight of carboxy-modified polyvinyl alcohol was subjected to a size press of 20 g / m ² to dry the base paper so that the finally obtained base paper water content was 8% by weight in absolute dry water. The paper support was produced by calendering to obtain a paper weight of 170 g / m ² . The Beck smoothness of the paper support was 110 seconds.

<Undercoat layer coating liquid 1> 100 parts of light calcium carbonate (Tamapearl 222H, manufactured by Okutama Kogyo Co., Ltd.) as a salt of an alkaline earth metal, and a styrene-butadiene copolymer latex (Luckstar DS226,
(Dai Nippon Ink Co., Ltd.) was mixed at 15 parts by solid content to prepare an undercoat layer coating liquid 1 having a solid concentration of 45%.

<Undercoat Layer Coating Solution 2> Heavy calcium carbonate (Carbital 90: ECC) is used as an alkaline earth metal salt.
International Co., Ltd.) 100 parts, styrene-butadiene copolymer latex (Luckstar D) as an adhesive
S226, manufactured by Dainippon Ink Co., Ltd.)
An undercoat layer coating liquid 2 having a solid content of 45% was prepared.

<Undercoat Layer Coating Solution 3> 100 parts of magnesium carbonate (spherical magnesium carbonate: manufactured by Kamishima Chemical Co., Ltd.) as a salt of an alkaline earth metal, and a styrene-butadiene copolymer latex (Luckstar DS22) as an adhesive
6, Dai Nippon Ink Co., Ltd.) 20 parts of solids were mixed to prepare a coating liquid 3 for an undercoat layer having a solids concentration of 45%.

<Undercoat layer coating liquid 4> 100 parts 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 (Luckster) as an adhesive DS22
6, Dai Nippon Ink Co., Ltd.) 20 parts of solids were mixed to prepare an undercoat layer coating liquid 4 having a solids concentration of 45%.

<Undercoat layer coating liquid 5> 100 parts of synthetic amorphous silica (Fine Seal X37B: manufactured by Tokuyama Corporation)
20 parts of polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) was dissolved and mixed as an adhesive to prepare an undercoat layer coating liquid 5 having a solid concentration of 20%.

<Coating Liquid A for Ink Receiving Layer> A coating composition for the ink receiving layer is 100-particle silica having a primary particle diameter of 7 nm (AEROSIL 300: manufactured by Nippon Aerosil Co., Ltd.).
g and a dispersant (Shalol DC902P: 3 g, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were dispersed in 500 g of ion-exchanged water with a stirrer, and 10% by weight of polyvinyl alcohol (PVA10).
5: Kuraray Co., Ltd.) 15 parts of an aqueous solution were mixed, and water was added to obtain a coating solution A having a solid content of 11%. The pH of the coating solution 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 concentration became 15% by weight 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> Using the above 15% by weight dispersion of ultrafine alumina hydrate, 10 parts by weight of polyvinyl alcohol (100 parts by weight) was added to 100 parts of the alumina hydrate dispersion. 15 parts of PVA105 (Kuraray) aqueous solution was mixed. After mixing, the mixture was uniformly dispersed in a homomixer at 10,000 rpm for 10 minutes. The dispersion was concentrated by an evaporator to a solid concentration of 11% to obtain a coating liquid B. The pH of the coating solution B was 4.5.

<Ink-Receiving Layer Coating Liquid C> The coating composition for the ink-receiving layer is a fine particle of alumina, γ-type alumina crystal powder of the δ group, which is aerosil aluminum oxide C having a primary particle diameter of 13 nm (Nippon Aerosil Co., Ltd.). 6)
00 g was dispersed in 2400 g of ion-exchanged water with a stirrer to prepare a 20% by weight slurry-like viscous liquid. Using this 20 wt% γ-type alumina dispersion, 30 parts of a 10 wt% aqueous solution of polyvinyl alcohol (Kuraray PVA235) was mixed with 100 parts of the alumina dispersion. After mixing, the mixture was uniformly dispersed in a homomixer at 10,000 rpm for 10 minutes. The dispersion liquid was concentrated by an evaporator so as to have a solid content concentration of 11% to obtain a coating liquid C. The pH of the coating solution was 5.0.

<Ink-receiving layer coating liquid D> The coating composition for the ink-receiving layer is a vapor-phase method ultrafine silica having a primary particle diameter of 7 nm (AEROSIL300: manufactured by Nippon Aerosil Co., Ltd.).
g and a dispersant (Shalol DC902P: 3 g, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were dispersed in 500 g of ion-exchanged water with a stirrer, and 10% by weight of polyvinyl alcohol (PVA10).
5: Kuraray Co., Ltd.), 15 parts of an aqueous solution were mixed, sodium hydroxide was added to adjust the pH to 5.5, and water was added to obtain a coating liquid D having a solid content of 11%.

<Ink receiving layer coating liquid E> The coating composition of the ink receiving layer is a synthetic amorphous having a secondary particle diameter of 3.7 μm and a BET specific surface area of 270 m ² / g which does not correspond to the inorganic ultrafine particles of the present invention. Porous silica (Fine Seal X-37B: manufactured by Tokuyama Corporation) 100 parts, polyvinyl alcohol (PVA10
5: Kuraray Co., Ltd.) and cationic dye fixing agent (Smirez Resin 1001: Sumitomo Chemical Co., Ltd.) 20 parts were mixed, and water was added to prepare a coating solution E having a solid content of 15%. The pH of the coating solution E was 5.3.

<Coating solution a for backing layer> The coating composition for the backing layer was composed of 50 parts of commercially available secondary kaolin and 50 parts of commercially available heavy calcium carbonate, 10 parts of commercially available styrene-butadiene latex, 5 parts of oxidized starch was prepared at a solids concentration of 50% to prepare a backing layer coating liquid a.

<Backing layer coating solution b> The coating composition for the backing layer was prepared by mixing 100 parts of a spherical organic pigment, 10 parts of a commercially available styrene-butadiene latex, and 5 parts of a commercially available oxidized starch with a solid content of 50%. To prepare a backing layer coating solution b.

<Coating liquid for backing layer c> The coating composition for the backing layer was composed of 50 parts of a spherical organic pigment, 50 parts of a commercially available heavy calcium carbonate, and a commercially available styrene-butadiene latex 1
0 parts and 5 parts of a commercially available oxidized starch were prepared at a solid content concentration of 50% to prepare a backing layer coating liquid c.

<Backcoat Coating Solution d> The coating composition for the backcoat layer is a commercially available styrene-butadiene latex 10
And 10 parts of a commercially available oxidized starch at a solid concentration of 50% to prepare a backing layer coating liquid d.

Example 1 An undercoat layer coating solution 1 was applied on the paper support prepared above with an air knife coater so as to have a dry solid content of 15 g / m ² . Next, on the undercoat layer, the ink receiving layer coating liquid A was dried with a curtain coater to a dry solid content of 15%.
g / m ² and dried. Further, the backing layer coating solution c was applied to the opposite side of the support provided with the ink receiving layer by a blade coater so as to have a dry solid content of 10 g / m ² and dried to obtain a recording medium of Example 1. . The thickness of the backing layer was 10 μm.

Comparative Example 1 A recording medium of Comparative Example 1 was prepared in the same manner as in Example 1 except that no backing layer was provided.

Example 2 A recording medium of Example 2 was prepared in the same manner as in Example 1 except that the undercoat layer coating liquid 1 was replaced by the undercoat layer coating liquid 2.

Example 3 A recording medium of Example 3 was prepared in the same manner as in Example 1 except that the undercoat layer coating liquid 1 was replaced by the undercoat layer coating liquid 3.

Example 4 A recording medium of Example 4 was prepared in the same manner as in Example 1 except that the undercoat layer coating liquid 1 was changed to the undercoat layer coating liquid 4.

Comparative Example 2 A recording medium of Comparative Example 2 was prepared in the same manner as in Example 2 except that no backing layer was provided.

Comparative Example 3 A recording medium of Comparative Example 3 was prepared in the same manner as in Example 3 except that no backing layer was provided.

Comparative Example 4 A recording medium of Comparative Example 4 was prepared in the same manner as in Example 4 except that no backing layer was provided.

Example 5 A recording medium of Example 5 was prepared in the same manner as in Example 1 except that the coating liquid A for the ink receiving layer was changed to the coating liquid B for the ink receiving layer.

Example 6 A recording medium of Example 6 was prepared in the same manner as in Example 1 except that the ink receiving layer coating liquid A was replaced with the ink receiving layer coating liquid C.

Example 7 A recording medium of Example 7 was prepared in the same manner as in Example 1, except that the ink receiving layer coating liquid A was replaced with the ink receiving layer coating liquid D.

Comparative Example 5 Comparative Example 5 was carried out in the same manner as in Example 1 except that the ink receiving layer coating liquid A was replaced with the ink receiving layer coating liquid E and no backing layer was provided. Recording medium.

Examples 8 to 12 In Example 1, the coating amount of the backcoat layer coating liquid c was
Example 4 except that 3, 5, 15, 25, and 35 g / m ² were used.
In the same manner as in the above, recording media of Examples 8 to 12 were obtained. The thickness of the backing layer is 3, 5, 16, 27, and 33 μ, respectively.
m.

Example 13 A recording medium of Example 13 was produced in the same manner as in Example 1, except that the backcoat layer coating liquid c was changed to the backcoat layer coating liquid a.

Example 14 A recording medium of Example 14 was prepared in the same manner as in Example 1, except that the backcoat layer coating liquid c was changed to the backcoat layer coating liquid b.

Example 15 A recording medium of Example 15 was produced in the same manner as in Example 1 except that the coating liquid c for the backcoat layer was changed to the coating liquid d for the backcoat layer.

<Evaluation of ink absorptivity> Evaluation of ink absorptivity was carried out using an ink-jet recording apparatus, Epson Corporation.
Using M9000, a heavy-color rectangular pattern was printed with cyan ink, magenta ink, and yellow ink. When the amount of ink to be superimposed is 100% for each color, 300% is used, when 90% is used for all colors, 270% is used.
Rectangular patterns of 0%, 180%, and 150% were created and printed. The bleeding state of the ink at 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. ×: The color is rough and dull. The evaluation of ◎ to ○ indicates good image color.

<Evaluation of glossiness of blank paper> Example 1 was standard (○)
The level was inferior to that of Example 1 by visual observation, but had no problem in practical use.

<Evaluation of Curl Suitability> Curl suitability was determined at 23 ° C.
After leaving the samples (A4 size) of Examples and Comparative Examples under the environmental condition of 50% RH, the samples were placed on a table, and the curl height at four corners of one sample was measured. When a plus sign is given to a change in curl toward the ink receiving layer surface side and a minus sign is given to a change in curl toward the back coating layer side, the lack of curl aptitude, which is a problem, is not within ± 10 [mm]. is there. When the value is within the range of ± 8 [mm], it is indicated by “○”.
A case outside the range of ± 10 [mm] was evaluated as x.

<Evaluation of transportability>
% (RH)
4 size), and then put it on the sheet feeder of an Epson inkjet printer (PM750C).
Zero sheets were set, and continuous printing was performed. The print test was performed 5 times, when no double feed occurred, when two or less double feeds occurred, when two or less double feeds occurred, or when three or more double feeds occurred or insertion was defective. It evaluated as x. ○ and Δ show good transportability.

[0105]

[Table 1] 記録 Recording media Ink image Blank paper Transportability Curl Absorption Chromaticity Gloss Suitability ─────────────────────────────────── Example 1 ◎ ◎ ○ ○ ○ Comparative Example 1 ◎ ◎ ○ × × Example 2 ○ ◎ ○ ○ ○ Example 3 ◎ ◎ ○ ○ ○ Example 4 △ ◎ △ ○ ○ Comparative Example 2 ○ ◎ ○ × × Comparative Example 3 ◎ ◎ ○ × × Comparative Example 4 △ ◎ △ × × Example 5 ◎ ◎ ○ ○ ○ Example 6 ○ ◎ ○ ○ ○ Example 7 △ ◎ ○ ○ ○ Comparative Example 5 ○ △ × × × Example 8 ◎ ◎ ○ ○ △ Example 9 ◎ ◎ ○ ○ ○ ○ Example 10 ◎ ◎ ○ ○ ○ Example 11 ◎ ◎ ○ ○ ○ Example 12 ◎ ◎ ○ ○ △ Example 13 ◎ ◎ ○ ○ ○ Example 14 ◎ ◎ ○ ○ ○ Example 15 ◎ ◎ ○ ○ △ ○ ― ――― -----------------------------

From Table 1, it can be seen that the alkaline earth metal salt, the alkaline earth metal salt, and the undercoating layer containing an adhesive are
In Examples 1 to 15 in which the ink receiving layer containing the inorganic ultrafine particles was provided and the backing layer was provided, all of the visual white paper gloss, image colorability, ink absorption, transportability and curl aptitude were excellent in a well-balanced manner. Things have been obtained. But,
In Comparative Examples 1 to 5 where no backing layer was provided, the transportability and the curl suitability were poor, and there was a problem in handling. Examples 1 to 5 in which the backing layer was provided in a thickness of 5 μm to 30 μm
7, 9 to 11, and 13 to 15 are excellent in curl aptitude.
Further, it can be seen that the case where the backcoat layer contains an inorganic pigment and / or a spherical organic pigment is more excellent in transportability than Example 15 which does not contain a pigment.

[0107]

As described above, according to the present invention,
It is possible to provide an ink jet recording medium having high gloss, excellent ink absorbency and image colorability, and having no problem in handling such as transportability and curl aptitude.

 ──────────────────────────────────────────────────続 き Continued on front page F-term (reference) 2C056 EA05 FC06 2H086 BA12 BA15 BA24 BA31 BA32 BA34 BA41

Claims (8)

[Claims] 1. An ink jet recording medium comprising a support, on which an undercoat layer containing a salt of an alkaline earth metal is provided, and a coating liquid for an ink receiving layer containing ultrafine inorganic particles is applied thereon. An ink jet recording medium comprising a backing layer provided on the opposite side of the support having the ink receiving layer. 2. The ink jet recording medium according to claim 1, wherein said alkaline earth metal is calcium or magnesium. 3. The ink jet recording medium according to claim 1, wherein the salt of the alkaline earth metal is a carbonate. 4. The ink-jet recording medium according to claim 1, wherein the inorganic ultrafine particles are amorphous synthetic silica prepared by a gas phase method. 5. The inkjet recording medium according to claim 1, wherein said inorganic ultrafine particles are an alumina compound. 6. The ink receiving layer coating liquid containing the inorganic ultrafine particles has a pH of 5 or less.
The inkjet recording medium according to any one of the above. 7. The thickness of the backing layer is 5 μm or more and 30 μm or more.
The inkjet recording medium according to claim 1, wherein: 8. The ink jet recording medium according to claim 8, wherein said back coat layer contains an inorganic pigment and / or a spherical organic pigment.