JP2011062966A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which is excellent in handling easiness to the sticky surface of a pasted album etc., paper dust proofness, conveyance scratch resistance during continuous printing under stacked pieces of the medium, and further, a superb surface glossiness. <P>SOLUTION: This inkjet recording medium includes an air permeable support, a porous ink receiving layer formed on one of the surfaces of the air permeable support, and a porous back coat layer formed on the other surface of the air permeable support. The porous ink receiving layer and the porous back coat layer come to the uppermost surface layer of the inkjet recording medium respectively, and the porous back coat layer contains a colloidal silica particle of non-spherical shape, the solids concentration of an acrylic emulsion and a hydrophilic binder. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inkjet recording medium.

  The ink jet recording method is a method for recording images, characters, and the like by causing ink to fly by various operating principles and depositing the ink on a recording medium. As a recording medium used in the ink jet recording system, there is an ink jet recording medium having a porous ink receiving layer formed of an inorganic pigment such as silica or alumina hydrate on a substrate.

  In recent years, ink jet recording media have increased opportunities to be pasted on a glued album after printing and stored for a long time. At this time, an easy handling property (peeling property) that can be easily peeled off from the adhesive surface of the glued album is required.

  In addition, when continuous printing is performed with a large number of recording media set in a printer at the same time, it is possible to suppress conveyance scratches caused by rubbing the printing surface and back surface of the recording medium during conveyance of the recording medium (conveyance resistance) Scratch resistance) is demanded.

  As recording media with improved conveyance scratch resistance, there are recording media described in Patent Documents 1, 2, and 3.

JP 2004-209653 A JP 2004-209654 A Japanese Patent Laid-Open No. 2002-200845

  The recording media described in Patent Documents 1, 2, and 3 exhibit a certain degree of effect with respect to easy handling and conveyance scratch resistance against the above-mentioned glued album. However, the ease of handling and transport scratch resistance of a recording medium that is also excellent in gloss may not yet be satisfactory.

  An object of the present invention is an ink jet having excellent handling properties for adhesive surfaces such as glued albums, powder falling, and excellent transport scratch resistance during continuous printing with a large number of sheets stacked, and also has excellent surface gloss. It is to provide a recording medium.

  As a result of repeated studies to achieve the above object, the present inventors have found the following present invention. That is, according to the present invention, there is provided a gas-permeable support, a porous ink-receiving layer on one side of the gas-permeable support, and a porous backcoat layer on the other side of the gas-permeable support. An ink jet recording medium, wherein the porous ink receiving layer and the porous backcoat layer are outermost layers, respectively, and the porous backcoat layer is formed of non-spherical colloidal silica particles and an acrylic emulsion solid. An ink jet recording medium is provided, which contains a portion and a hydrophilic binder.

  According to the present invention, an ink jet having excellent handling properties for powdery albums and other adhesive surfaces, powder fall, and resistance to transport scratches during continuous printing with a large number of sheets stacked, and also excellent surface gloss. A recording medium can be provided.

<< Inkjet recording medium >>
The inkjet recording medium of the present invention comprises a gas-permeable support, a porous ink receiving layer on one side of the gas-permeable support, and a porous backcoat layer on the other side of the gas-permeable support. And have. The porous ink-receiving layer and the porous backcoat layer are the outermost layers, respectively, and the porous backcoat layer comprises non-spherical colloidal silica particles, an acrylic emulsion solid content, and hydrophilicity. Containing a binder. Hereinafter, the one surface may be referred to as a printing surface and the other surface as a back surface.

  With the above configuration, it has excellent high-speed absorbability of ink, can easily achieve excellent handling properties for adhesive surfaces such as glued albums, etc., and has excellent surface gloss by gloss treatment such as rewet cast A recording medium having the same can be obtained.

  By providing a porous ink-receiving layer on the outermost surface of one side (printing surface) of the air-permeable support, it is possible to achieve excellent high-speed absorption of ink. In addition, by having a porous back coat layer on the outermost surface of the other side (back side) and making the back coat layer a layer composed of non-spherical colloidal silica particles, solid content of acrylic emulsion and a hydrophilic binder The following can be achieved. That is, it is possible to achieve excellent ease of handling for adhesive surfaces such as glued albums, and to improve transport scratch resistance during continuous printing with a large number of sheets stacked. At the same time, the porous ink-receiving layer can be subjected to gloss treatment such as rewet cast, and excellent surface gloss can be achieved.

  The back surface of the recording medium having air permeability is usually the base paper itself or a surface provided with a coating layer such as an undercoat layer on the base paper, but these may be in a state where the paper fibers are exposed. Or it is a surface which has a certain amount of porosity. Therefore, the ink receiving layer (printing surface) can be made highly glossy by gloss treatment such as rewet cast. On the other hand, when the back side is pasted on the adhesive surface such as an album with glue, a part of the adhesive easily penetrates into the fine holes, and the contact area with the adhesive increases, so it can adhere strongly. Yes, it may be difficult to peel from the adhesive surface. For this reason, if it is forcibly peeled off, a part of the paper fiber or the coating layer may be peeled off from the adhesive surface.

  The present invention has a porous backcoat layer on at least the outermost surface (back surface), and the backcoat layer is composed of a dispersoid of non-spherical colloidal silica, a solid content of an acrylic emulsion, and a hydrophilic binder. Is a layer. This not only has excellent ease of handling on the adhesive surface, it also has excellent transport scratch resistance during continuous printing with a large number of sheets stacked, and air permeability that allows gloss processing such as rewet cast on the printed surface. The back surface which has can be formed.

  In the present invention, the air resistance of the recording medium is preferably 6000 seconds or less, and more preferably 5500 seconds or less.

<Porous backcoat layer>
(Non-spherical colloidal silica particles)
The recording medium of the present invention contains non-spherical colloidal silica particles, that is, solids of non-spherical colloidal silica, as inorganic fine particles of the porous back coat layer, and uses the non-spherical colloidal silica to form the back coat layer. . Applying (coating) and drying a porous backcoat layer-forming coating solution containing non-spherical colloidal silica on the back surface of the air-permeable support (or other layers if it has other layers) A porous back coat layer containing a solid content of non-spherical colloidal silica can be obtained. Even with ordinary monodispersed spherical colloidal silica, it is possible to obtain an easy handling effect on an adhesive surface such as a glued album. However, in the case of monodispersed spherical colloidal silica, the layer is formed in a state where the particles are closely packed, so that the layer becomes nonporous, and the air permeability of the recording medium that is necessary when performing gloss treatment by the rewet cast method or the like later. Is insufficient. When other types of silica, such as gas phase method silica or wet gel method silica, are used, the surface smoothness is inferior and the conveyance scratch resistance at the time of continuous printing with a large number of sheets stacked may be inferior.

  While general colloidal silica particles are in a monodispersed state, non-spherical colloidal silica particles used in the present invention are secondary agglomerated particles in which spherical primary particles are linked in a chain. Examples of the secondary aggregation form of the secondary aggregated particles include a pearl necklace shape and a tuft-like shape connected in a three-dimensional network. Examples of the non-spherical colloidal silica having pearl necklace-like secondary agglomerated particles include Snowtex PS-M (trade name) and Snowtex PS-MO (trade name) manufactured by Nissan Chemical Industries, Ltd. Further, as non-spherical colloidal silica having tufted secondary aggregated particles having a three-dimensional network structure, Snowtex UP (trade name), Snowtex HS-M-20 (trade name), Snowtex O manufactured by Nissan Chemical Industries, Ltd. -UP (trade name) and the like.

  The non-spherical colloidal silica used in the present invention can be obtained by various known methods. In the present invention, any non-spherical colloidal silica obtained by any method can be preferably used if the silica particles in the non-spherical colloidal silica are non-spherical. The non-spherical colloidal silica used in the present invention is preferably an acidic sol. Usually, colloidal silica sol including non-spherical colloidal silica is an alkaline sol because it is synthesized in an alkaline atmosphere. However, when the sol is acidic, aggregation of the hydrophilic binder hardly occurs as compared with the alkaline sol, and the surface of the coating film becomes smoother. For this reason, when the non-spherical colloidal silica is an acidic sol, a porous back coat layer excellent in conveyance scratch resistance at the time of continuous printing with a large number of sheets can be formed. The acidic sol is known in various ways, such as a method of making an alkaline sol acidic by treating it with a cation exchange resin, a method of acidifying with an acid such as hydrochloric acid or nitric acid, a method of removing and purifying alkali by ultrafiltration or the like. What was obtained by this method can be used. Examples of the non-spherical colloidal silica of acidic sol include Snowtex PS-MO (trade name) manufactured by Nissan Chemical Industries, Ltd. If necessary, spherical colloidal silica can be mixed with non-spherical colloidal silica to such an extent that the air permeability of the recording medium is not lost.

(Acrylic emulsion)
The porous back coat layer used in the present invention contains a solid content of an acrylic emulsion. A porous backcoat layer-forming coating solution containing an acrylic emulsion is applied (coated) to the back surface of the air-permeable support (or other layers if the back surface has other layers) and dried, and then acrylic It can be set as the porous back coat layer containing the solid content of an emulsion. In the present invention, by using an acrylic emulsion, the removability of the porous back coat layer to an adhesive surface such as a glued album is greatly improved, and excellent ease of handling is achieved. In addition, conveyance scratch resistance is improved by imparting appropriate slipperiness. Emulsions other than acrylic emulsions, such as polyethylene, polystyrene, polypropylene, polyvinyl acetate, styrene-butadiene rubber, polyurethane, polyvinyl chloride, ethylene-vinyl acetate copolymer, etc., ensure sufficient handling on the adhesive surface. I can't do it.

Examples of the acrylic emulsion used in the present invention include a polymer emulsion of (meth) acrylic acid ester, and a polymer emulsion of acrylic acid ester monomer is preferable. Specifically, the polymer emulsion is preferably an acrylic acid alkyl ester such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate.
The acrylic emulsion may be an emulsion of a copolymer of two or more monomers. The copolymer monomers include (meth) acrylic acid ester monomers, acrylic acids, vinyl esters, olefins, styrenes, crotons, itacones, maleic acids, fumaric acids, acrylamides, allyl compounds, vinyl ethers. , Vinyl ketones, vinyl heterocycles, glycidyl esters, unsaturated nitriles, polyfunctional monomers and various unsaturated acids in combination with (meth) acrylic acid ester monomers Can be used. The composition ratio of the (meth) acrylic acid ester monomer in the case of the copolymer is preferably 50% or more and 100% or less in terms of a molar ratio with respect to all monomers used in the copolymer. A preferable acrylic emulsion has a Tg (glass transition point) of -20 ° C or higher and 120 ° C or lower. More preferably, it is 0 degreeC or more and 80 degrees C or less.
The acrylic emulsion used in the present invention includes ST-200 (trade name) manufactured by Nippon Shokubai Co., Ltd., Boncoat CF6140 and CP6190 (trade name) manufactured by Dainippon Ink Co., Ltd., and Polysol manufactured by Showa Polymer Co., Ltd. OLZ-1298 (trade name) or the like can be used. As the copolymer emulsion in the acrylic emulsion, Grosdale 292-S (trade name) manufactured by Mitsui Chemicals, Inc., which is a styrene-acrylic copolymer emulsion, can be used.
It is preferable that the non-spherical colloidal silica particles (solid content) in the porous back coat layer and the mass ratio of the solid content of the acrylic emulsion are mixed in the range of 100: 10 to 100: 100. More preferably, it is 100: 20-100: 80. When the amount of the acrylic emulsion solid content is 10% by mass or more based on the solid content of the non-spherical colloidal silica, it is possible to achieve excellent ease of handling for an adhesive surface such as a glued album. Further, when the acrylic emulsion solid content is 100% by mass or less with respect to the non-spherical colloidal silica solid content, it is possible to excellently prevent the air permeability of the porous back coat layer from being lost. When the content is 100% by mass or less, the glossiness is particularly improved in the gloss treatment step (step C) of the porous ink receiving layer described later.

(Hydrophilic binder)
Further, the hydrophilic binder for forming a porous back coat layer used in the present invention is a material capable of binding the non-spherical colloidal silica and forming a film, and impairs the effects of the present invention. As long as it is not in the range, it can be used without any particular limitation. For example, starch derivatives such as oxidized starch, etherified starch and phosphate esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein, gelatin, polyvinyl alcohol and derivatives thereof; polyvinyl pyrrolidone, polyethylene oxide, polypropylene oxide, polyethylene glycol , Polyvinyl ether, polyacrylamide, polyacrylate, maleic resin, alginate, polyallylamine, polyethyleneimine, epoxidized polyamide, polyvinylpyridine and the like. Among these, polyvinyl alcohol is particularly preferable from the viewpoints of water resistance, film strength, cracking prevention, and curl adjusting function. The hydrophilic binder can be used alone or in combination, and if necessary, a hydrophilic binder crosslinking agent such as a boron compound (for example, boric acid and borate described later) can be added. Is also possible.

  In addition, as a hydrophilic binder used for this invention, PVA117 and PVA235 (brand name) by Kuraray Co., Ltd. which are polyvinyl alcohol, Alcox R-40 (brand name) by Meisei Chemical Co., Ltd. which is polyethylene oxide, etc. Can be used.

  The hydrophilic binder content in the porous back coat layer is less than the non-spherical colloidal silica solid content in order to prevent deterioration of film strength and cracking during drying due to its low content. The content is preferably 5% by mass or more and 50% by mass or less.

<Porous ink receiving layer>
The material for forming the porous ink receiving layer used in the present invention will be described. The porous ink receiving layer can contain a pigment and a binder, and can be formed by applying a coating liquid containing them.

(Pigment)
The pigment is particularly preferably an alumina hydrate in terms of dye fixing properties, transparency, printing density, color developability, and gloss, but the following pigments can also be used. Examples of inorganic pigments include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, and magnesium hydroxide. . Examples of organic pigments include styrene plastic pigments, acrylic plastic pigments, polyethylene particles, microcapsule particles, urea resin particles, and melamine resin particles. In the porous ink receiving layer used in the present invention, one selected from these pigments or a combination of two or more selected as necessary can be used.

As the alumina hydrate that can be used in the present invention, for example, those represented by the following general formula (X) can be preferably used.
Al ₂ O ₃ − _n (OH) _2n · mH ₂ O (X)
In the above formula, n represents any of 0, 1, 2, and 3, and m represents a number of 0 to 10, preferably 0 to 5. However, m and n are not 0 at the same time. Since mH ₂ O often represents a detachable aqueous phase that does not participate in the formation of a crystal lattice, m can take an integer or a non-integer value. Further, when the alumina hydrate is heated, m may be zero. As for the crystal structure of alumina hydrate, it changes from amorphous, kibsite-type, boehmite-type aluminum hydroxide to γ, σ, η, θ, α-type aluminum oxide depending on the heat treatment temperature. It is known. Any of these crystal structures can be used in the present invention. Suitable alumina hydrates are alumina hydrates showing a boehmite structure or an amorphous state by analysis by X-ray diffraction method, and in particular, JP-A-7-232473, JP-A-8-132731, Examples thereof include alumina hydrates described in JP-A-9-66664, JP-A-9-76628, and the like. Moreover, as a commercial item, alumina hydrates, such as Dispersal HP13 (brand name) by Sasol, can be used.

The alumina hydrate is adjusted in pore properties in the production process, but in order to satisfy the preferred BET specific surface area and pore volume of the porous ink receiving layer described later, the pore volume is 0.3 ml. It is preferable to use alumina hydrate that is not less than / g and not more than 1.3 ml / g. More preferred is an alumina hydrate of 0.5 ml / g or more and 1.2 ml / g or less. Alumina hydrate having a pore volume of 0.3 ml / g or more and 1.3 ml / g or less is more suitable for making the pore volume of the porous ink receiving layer within a preferable range described later. Further, it is preferable to use an alumina hydrate having a BET specific surface area measured by the BET method of 50 m ² / g to 350 m ² / g, more preferably 100 m ² / g to 250 m ² / g. It is a thing. Alumina hydrate having a BET specific surface area of 50 m ² / g or more and 350 m ² / g or less is more suitable for bringing the BET specific surface area of the porous ink receiving layer into a preferable range described later. The BET method is a method for measuring the surface area of a powder by a gas phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm. Usually, nitrogen gas is often used as the adsorbed gas, and the method of measuring the amount of adsorption from the pressure or volume change of the gas to be adsorbed is most often used. The most prominent expression for representing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller equation, called the BET equation, which is widely used for determining the specific surface area. The adsorption amount is obtained based on the BET formula, and the BET specific surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  Moreover, the shape of the alumina hydrate suitable for the present invention is preferably a flat plate having an average aspect ratio of 3 to 10 and an aspect ratio of the flat surface of 0.6 to 1.0. The aspect ratio can be obtained by the method described in Japanese Patent Publication No. 5-16015. The aspect ratio is expressed as the ratio of the “diameter” to the “thickness” of the particles. Here, the “diameter” indicates the diameter of a circle having an area equal to the projected area of the particles when the alumina hydrate is observed with a microscope or an electron microscope. The aspect ratio of the flat plate surface is the ratio of the diameter indicating the minimum value to the diameter indicating the maximum value of the flat plate surface when the particles are observed with a microscope in the same manner as the aspect ratio. When an alumina hydrate having an average aspect ratio of 3 or more and 10 or less is used, it can be excellently prevented that the pore distribution range of the formed porous ink receiving layer is narrowed. Moreover, when using a thing with an average aspect-ratio of 10 or less, it can prevent excellently that it becomes difficult to arrange | equalize and manufacture the particle diameter of an alumina hydrate. Similarly, when the aspect ratio is 0.6 or more and 1.0 or less, it is possible to excellently prevent the pore size distribution of the porous ink receiving layer from becoming narrow.

  Reference: Rocek J. et al. It is generally known that some of the alumina hydrates are ciliated and not shaped as described in "Applied Catalysis", 1991, Vol. 74, p29-36. ing. According to the knowledge of the present inventors, even with the same alumina hydrate, the plate-like alumina hydrate has better dispersibility than the cilia-like one. Further, in the case of ciliated alumina hydrate, there is a tendency to orient in parallel to the surface of the undercoat layer during coating, and the formed pores may be small, which makes the porous ink The ink absorption of the receiving layer may be reduced. On the other hand, when using a plate-like alumina hydrate, the tendency to be oriented by coating is small, so that the pore size of the formed porous ink receiving layer and the ink absorbency are reduced. The impact is small.

  As the pigment of the porous ink receiving layer, a non-flat plate such as silica may be used. However, in order to increase the gloss, it is preferable to use a flat alumina hydrate from the above.

(binder)
The binder that can be used in the porous ink-receiving layer and the coating liquid used in the present invention is a material capable of binding the pigment and forming a film, and has the effects of the present invention. If it is the range which is not impaired, there will be no restriction | limiting in particular and it can utilize. For example, starch derivatives such as oxidized starch, etherified starch and phosphate esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein, gelatin, polyvinyl alcohol and derivatives thereof; polyvinyl pyrrolidone, polyethylene oxide, polypropylene oxide, polyethylene glycol And polyvinyl ether, polyacrylamide, polyacrylate, maleic acid resin, alginate, polyallylamine, polyethyleneimine, epoxidized polyamide, polyvinylpyridine and the like. The above binders can be used alone or in combination.
The binder content in the porous ink receiving layer is preferably 5% by mass or more and 50% by mass or less with respect to the pigment in the porous ink receiving layer. When the content of the binder is 5% by mass or more, it is excellently prevented that cracks are easily generated in the porous ink receiving layer, and the mechanical strength of the porous ink receiving layer is reduced, and the powder It can be excellently prevented that the fall easily occurs. On the other hand, when the amount is 50% by mass or less, it is possible to excellently prevent a decrease in ink absorptivity (for example, overflow of ink and occurrence of bleeding in an image) and a decrease in adsorbability of ink dye. Furthermore, in order to obtain excellent ink absorbency even under high temperature and high humidity, the binder content in the porous ink receiving layer is set to 5% by mass or more based on the pigment in the porous ink receiving layer. More preferably, it is 20 mass% or less.

(Boric acid and borate)
Incorporation of at least one selected from the group consisting of boric acid and borate in the material for forming the porous ink receiving layer is extremely effective in forming the porous ink receiving layer. Examples of the boric acid include not only orthoboric acid (H ₃ BO ₃ ) but also metaboric acid and hypoboric acid. The borate is preferably a water-soluble salt of boric acid. Specifically, for example, sodium salt of boric acid (Na ₂ B ₄ O ₇ · 10H ₂ O, NaBO ₂ · 4H ₂ O etc.) and, potassium salt _{(K 2 B 4 O 7 ·} 5H 2 O, alkali metal salts such KBO _2, etc.), an ammonium salt of boric acid _{(NH 4 B 4 O 9 ·} 3H 2 O, NH 4 BO 2 , etc. ), Alkaline earth metal salts such as magnesium salts and calcium salts of boric acid.

  It is preferable to use orthoboric acid from the viewpoint of the temporal stability of the coating solution and the effect of suppressing the occurrence of cracks. The amount used can be appropriately selected depending on production conditions and the like, but is 1.0% by mass or more in terms of the total solid content of boric acid and borate with respect to the binder in the porous ink receiving layer. It is preferable that it is 15.0 mass% or less. When the total use amount of the boric acid and borate is 15.0% by mass or less, it is possible to excellently prevent the temporal stability of the coating liquid from being lowered. Generally, when producing an inkjet recording medium, the coating liquid is used for a long time. If the total amount of the boric acid and borate used is 15.0% by mass or less, when the coating solution is used for a long time, the increase in the viscosity of the coating solution and the generation of gelled product are excellently prevented. be able to. Furthermore, it is not necessary to frequently change the coating liquid or clean the coater head, and it is possible to excellently prevent the productivity from being significantly lowered. Furthermore, when the total amount of boric acid and borate used is 15.0% by mass or less, when forming a porous ink receiving layer, a point-like surface (cast surface) defect is likely to occur. It is excellently prevented, and a particularly uniform and good gloss surface can be obtained.

(Pore radius, pore volume and BET specific surface area of porous ink receiving layer)
The porous ink-receiving layer formed as described above preferably has a pore property satisfying the following conditions in order to particularly improve the high-speed absorbability of the ink. First, the pore size distribution of the porous ink receiving layer preferably has a peak at least at a pore radius of 5 nm to 20 nm. The peak means a maximum peak. When the pore radius has a peak at 5 nm or more, the high-speed absorbability of the ink is excellently prevented, and when it has a peak at 20 nm or less, it has excellent performance in terms of color development and resolution. Obtainable. In addition, the pore volume of the porous ink receiving layer is preferably 0.1 cm ³ / g or more and 1.0 cm ³ / g or less. That is, when the pore volume is 0.1 cm ³ / g, excellent ink absorption performance can be obtained, and a porous ink receiving layer with excellent ink absorption can be obtained, resulting in ink overflow and bleeding in the image. Can be prevented excellently. On the other hand, in the case of 10 cm ³ / g or less, it is possible to excellently prevent the porous ink receiving layer from being easily cracked or powdered. The BET specific surface area of the porous ink receiving layer is preferably 20 m ² / g or more and 450 m ² / g or less. When it is 20 m ² / g or more, excellent gloss can be obtained, and haze is prevented from increasing (transparency is lowered), and the image appears to have a white haze. Can be excellently prevented. Furthermore, in this case, not only can the color developability of the dye be excellently prevented, but also the decrease in the adsorptivity of the dye in the ink can be excellently prevented. On the other hand, in the case of 450 m ² / g or less, it is possible to excellently prevent the porous ink receiving layer from being easily cracked. The pore volume and the BET specific surface area are determined by a nitrogen adsorption / desorption method.

<Air-permeable support>
As the air-permeable support used in the present invention, an air-permeable support made of an opaque material such as paper can be used. In particular, when a fibrous support, that is, a gas-permeable support made of paper, is used, a silver ink is formed by forming a porous ink receiving layer on the support and then performing a gloss treatment such as casting. It is preferable because high surface gloss comparable to that of a system photograph can be obtained.

  For air-permeable support made of paper, coated with art paper, coated paper, cast coated paper, etc., with a size press of starch, polyvinyl alcohol, etc. on the base paper, or with a coat layer on the base paper Paper is also included.

When paper is used as the air-permeable support, the coating layer having a thickness that completely covers the cellulose pulp fibers and texture of the paper (base paper) is at least one of the porous ink receiving layer and the porous backcoat layer. It is preferable that it is provided as an undercoat layer. When the fibers and texture are completely covered, it is excellent in preventing the occurrence of uneven coating (such as streak-like defects) due to the fibers and texture when the porous ink receiving layer is applied. Can do. In addition, the presence of cellulose pulp fibers in the porous ink receiving layer or in the vicinity of or on the surface of the porous ink receiving layer is excellently prevented, and particularly good and homogeneous when the surface of the recording medium is cast. A simple cast surface, that is, a photo-like high gloss surface can be easily obtained. In order to cover the cellulose pulp of the air-permeable support made of paper, the dry coating amount of the coat layer is preferably 10 g / m ² or more, more preferably 13 g / m ² or more.

In the case of using an air-permeable support made of paper, the Steecht sizing degree of the air-permeable support is 100 seconds to 400 seconds, the Beck smoothness is 100 seconds to 500 seconds, and the underwater elongation is 1.2%. It is preferable to set it to 2.5% or less. In order to obtain a recording medium having the same texture and high quality as silver halide photography, the basis weight of the air-permeable support made of paper is 160 g / m ² or more and 230 g / m ² or less, and Gurley stiffness (J. Tappi No. 40. Longitudinal) is preferably 7 mN or more and 15 mN or less.

<Inkjet recording medium manufacturing method>
Further, the recording medium of the present invention can be produced by a method for producing a recording medium having the following steps (A) and (B), and (C) as necessary.
(Process A) A porous ink-receiving layer-forming coating liquid containing at least a pigment, a binder, and a dispersion medium is applied on one surface of a gas-permeable support to form a porous ink-receiving layer (image recording). Layer).
(Step B) Applying a coating liquid for forming a porous back coat layer containing non-spherical colloidal silica, an acrylic emulsion and a hydrophilic binder to the surface of the air-permeable support on the side opposite to the image recording layer. Forming a porous backcoat layer;
(Step C) A step of glossing the porous ink receiving layer.

  Further, if necessary, a porous layer made of another material is formed between the back coat layer formed using the porous back coat layer forming coating solution and the air-permeable support. It is also possible to provide a process between the process A and the process B. Hereinafter, the porous layer made of the other material may be referred to as other porous layer in distinction from the porous ink receiving layer and the porous backcoat layer.

Hereinafter, the production method will be described in more detail with reference to preferred embodiments.
The recording medium of the present invention can be manufactured through the following steps in sequence.

(1) Surface treatment step of air-permeable support In the recording medium of the present invention, paper can be used as it is as an air-permeable support, but as described above, an undercoat layer such as a porous ink-receiving layer is formed on the paper. Those provided, surface-treated and having a surface-treated layer on paper, or those having both of these layers on paper can also be used. The undercoat layer and the surface treatment layer can be provided on one side or both sides of the air-permeable support, respectively.

  A surface treatment process for providing a surface treatment layer on the air-permeable support will be described below. In addition, this surface treatment process can be suitably performed before the process A.

First, a surface treatment liquid (precoat liquid) is applied to the air-permeable support.
The surface treatment step of the air-permeable support is a step of applying a pre-coating liquid containing a crosslinking agent that cures by causing a crosslinking reaction with the hydrophilic binder in the porous ink receiving layer to the air-permeable support. It can be done according to. The application of the crosslinking agent is preferable from the viewpoint of suppressing cracks in the drying process of the porous ink receiving layer. Examples of the crosslinking agent include one or more selected from the group consisting of boric acid and borate.

In the surface treatment process, the surface of the base material is not dried after the surface treatment liquid is applied to the air-permeable support, and the surface of the base material is maintained in a certain wet state (coating liquid state or thickened state). It is preferable to perform the step (step A) of applying the coating liquid for forming a porous ink receiving layer.
The surface treatment liquid that can be used in the present invention is preferably an aqueous solution containing the crosslinking agent, and more preferably contains 1% by mass or more and 10% by mass of the crosslinking agent. Further, in order to improve the wettability of the surface treatment liquid, a surfactant, alcohol, or the like may be added to the surface treatment liquid to adjust the surface tension and water absorption.
The coating amount of the surface treatment liquid in the surface treatment step is preferably a total solid basis of boric acid and borate is 0.05 g / m ² or more 3.0 g / m ² or less.

(2) Porous ink receiving layer forming step (step A)
Next, a porous ink-receiving layer-forming coating solution containing at least a pigment, a binder, and a dispersion medium is applied onto a gas-permeable support appropriately subjected to surface treatment and the like, and dried to obtain a porous material. An ink-receiving layer can be formed.

  The coating liquid for forming a porous ink-receiving layer can be a coating liquid containing at least alumina hydrate, a binder, a dispersion medium, and, if necessary, a crosslinking agent. An example of the dispersion medium is water. For the preparation of the coating liquid for the porous ink receiving layer, it is preferable to use a mixing apparatus. By using this apparatus, a mixture obtained by mixing at least one selected from the group consisting of boric acid and borate as a crosslinking agent with an alumina hydrate dispersion, and a polyvinyl alcohol aqueous solution as a binder Can be mixed immediately before coating to form a coating solution. In this way, the increase in the viscosity of the coating solution and the gelation that occur during the manufacturing process can be particularly reduced, so that the production efficiency can be particularly improved. The solid content concentration of the alumina hydrate in the alumina hydrate dispersion used above is preferably 10% by mass or more and 30% by mass or less. In the case of 30% by mass or less, the viscosity of the alumina hydrate dispersion and the viscosity of the porous ink receiving layer are excellently prevented, and the coatability is particularly good.

  In the coating liquid for forming a porous ink receiving layer, for example, formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, malonic acid, succinic acid, adipic acid, maleic acid, malic acid, tartaric acid, Organic acids such as citric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, pimelic acid, suberic acid, inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, and These salts can be added as appropriate.

  Other coating liquid additives include pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, penetrating agents, colored pigments, colored dyes, fluorescent whitening agents, Ultraviolet absorbers, antioxidants, antiseptics, antifungal agents, water resistance agents, dye fixing agents, curing agents, weathering materials and the like can be appropriately contained as necessary.

The porous ink receiving layer of the inkjet recording medium of the present invention may contain a colorant deterioration preventing agent. The colorant deterioration preventing agent refers to a compound that, when present together with a dye in the porous ink receiving layer, protects the dye from factors that deteriorate the dye, such as gas and light, and improves the weather resistance of the dye. To tell.
General examples of the colorant deterioration inhibitor include hindered amine compounds, hindered phenol compounds, benzophenone compounds, benzotriazole compounds, thiourea compounds, thiuram compounds, phosphite compounds, and the like. . As the color material deterioration preventing agent, a hindered amine compound is particularly preferably used, but is not limited thereto.

  The content of the hindered amine compound in the porous ink receiving layer is preferably 0.5% by mass or more and 10% by mass or less based on the pigment solid content in the porous ink receiving layer. By setting the content to 0.5% by mass or more, an excellent discoloration suppressing effect can be obtained. Further, by setting the content to 10% by mass or less, it is possible to excellently prevent a decrease in ink absorbency.

  The colorant deterioration preventing agent that can be used in the present invention is added to the porous ink receiving layer by overcoating the prepared porous ink receiving layer with a prepared solution dissolved in a solvent. It is preferable to do. The solvent that dissolves the colorant deterioration preventing agent may be any solvent as long as the colorant deterioration preventing agent can be dissolved, and various solvents such as an organic solvent can be used. Examples of the organic solvent include, but are not limited to, esters such as ethyl acetate and butyl acetate, ketones such as methyl isobutyl ketone, methyl ethyl ketone and acetone, ethers such as diethyl ether and ethyl methyl ether, isopropanol, Examples include alcohols such as methanol and ethanol.

  The step of overcoating the porous ink receiving layer with the colorant deterioration preventing agent-containing liquid may be before or after any step as long as it is after the formation of the porous ink receiving layer. However, when overcoating is performed in such a manner that the coating member is in contact with the surface of the porous ink receiving layer, it is preferable to perform overcoating before the gloss treatment step (step C) of the porous ink receiving layer. . Thereby, it is possible to excellently prevent the porous ink receiving layer surface from being damaged in the overcoat process.

The dry coating amount of the porous ink receiving layer is preferably 20 g / m ² or more and 40 g / m ² or less. In the case of 20 g / m ² or more, excellent ink absorption is achieved even when using a printer in which a plurality of light-color inks are added in addition to black ink in addition to the three colors of cyan, magenta, and yellow. Sex can be obtained. That is, in the case of 20 g / m ² or more, it is excellent in preventing the occurrence of ink overflow, excellent in preventing bleeding, and excellent in reducing the print density by diffusing the ink dye to the substrate. Can be prevented. On the other hand, when it is 40 g / m ² or less, the occurrence of cracks can be excellently prevented. Furthermore, when the amount is more than 30 g / m ² , a porous ink receiving layer exhibiting excellent ink absorbency even under a high temperature and high humidity environment is more preferable. Further, when the dry coating amount is 40 g / m ² or less, it is preferable that uneven coating of the porous ink receiving layer hardly occurs, and a porous ink receiving layer having a stable thickness can be produced.

(3) Porous back coat layer forming step (step B)
The porous backcoat layer forming step is a method of applying a porous backcoat layer forming coating liquid to the surface (back surface) opposite to the image recording layer of the gas-permeable support. This is a step of forming a conductive backcoat layer. The coating liquid for forming the porous backcoat layer can contain non-spherical colloidal silica, an acrylic emulsion and a hydrophilic binder, and is the opposite surface to the surface (printing surface) on which the porous ink receiving layer is formed. (Back side) can be applied. Dry coating amount of the backcoat layer is preferably made to be 2 g / m ² or more 25 g / m ² or less. In the case of ² g / m ² or more, the effects of the porous back coat layer such as excellent easy handling property to adhesive surfaces such as glued albums and imparting conveyance scratch resistance can be easily expressed. Further, at a dry coating amount of 25 g / m ² or less, it is possible to excellently prevent a decrease in production efficiency due to the coating amount.
Moreover, it is also possible to provide another porous layer between the said backcoat layer and the said air-permeable support body as needed. Examples of the other porous layers include layers having the same composition as the porous ink receiving layer used in the present invention, and porous layers using the following pigments and binders. Examples of inorganic pigments used in other porous layers include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, Examples of organic pigments such as colloidal silica, alumina, and magnesium hydroxide include styrene plastic pigments, acrylic plastic pigments, polyethylene particles, microcapsule particles, urea resin particles, and melamine resin particles. One selected from these pigments or a combination of two or more selected as necessary can be used. The binder used for the other porous layer is a material capable of binding the pigments listed above to form a film and not impairing the effects of the present invention. It can be used without any particular limitation.

(4) Glossing process of porous ink receiving layer (process C)
After the porous ink receiving layer is formed on the gas-permeable support, a glossy surface can be formed on the surface of the porous ink receiving layer by a casting method. That is, the gloss treatment step (step C) of the porous ink receiving layer may be performed subsequent to step B, or may be performed subsequent to step A and before step B. Step C will be described. The casting method is a wet or plastic porous ink-receiving layer that is pressure-bonded to a film or a heated mirror-like drum (cast drum) surface, and dried in the pressure-bonded state. In this method, the film surface or mirror surface is copied onto the surface of the porous ink receiving layer. There are three typical methods among the casting methods: a direct method, a rewet method (indirect method), and a coagulation method. Any of these casting methods can be used, but the rewet casting method is more preferable. By using this rewet cast method, high glossiness of the surface of the porous ink receiving layer can be easily obtained. Moreover, when using a highly air-permeable support, a highly glossy surface can be easily obtained by using a film casting method.

  The surface treatment liquid used in the surface treatment step of the air-permeable support, the porous ink receiving layer formation step (step A), the porous back coat layer formation step (step B), and the coating of each coating solution In order to obtain an appropriate coating amount, the following various coating apparatuses can be appropriately selected and used. As the coating device, for example, various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, curtain coaters, gravure coaters, coaters using extrusion methods, coaters using slide hopper methods, sizes A press etc. are mentioned, It can coat by an on machine and an off machine. At the time of coating, for the purpose of adjusting the viscosity of each coating solution, each coating solution may be heated, or the coater head can be heated.

  The following method is preferable as the method for supplying the coating liquid used in the porous ink receiving layer forming step (step A) to the coating apparatus. The method is to mix pigments and binders from separate lines using a continuous mixing device such as a static mixer to form a coating liquid, and send the coating liquid to an online coating head for coating. Is the method. This supply method is excellent in preventing cracks during coating and drying, and in the case where a crosslinking agent is added to the coating liquid in order to particularly increase the binding strength of the porous ink receiving layer, Since it becomes easy to thicken at the time of liquid preparation and liquid feeding, it can use especially preferable. The static mixer refers to a structure in which a mixing unit is housed in a hollow cylindrical frame. In the mixing unit, a plurality of elements are connected in the longitudinal direction, and one element has a shape that is twisted, for example, 180 degrees in the circumferential direction as the plate body is advanced in the longitudinal direction. The twisting directions of adjacent elements are opposite to each other. In this case, the coating liquid is uniformly mixed by each element while flowing in the frame.

  Moreover, the following dryer etc. can be suitably selected and used for the drying after application | coating of the said surface treatment liquid and each coating liquid. Examples of the dryer include a straight-air tunnel dryer, an arch dryer, an air loop dryer, a hot air dryer such as a sine curve air float dryer, a dryer using infrared rays, a heated dryer, a microwave, and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to these examples.

  First, methods for measuring various physical property values used in the present invention will be described.

<Stick human sizing degree>
The measurement object was cut into A4 size, and two of them were left to stand for 2 hours or more under conditions of an air temperature of 23 ° C. and a relative humidity of 50%. Thereafter, in accordance with JIS P8122, the degree of steecht size was measured for each sheet, and the average value of the two sheets was obtained.

<Beck smoothness>
After leaving five A4-sized objects to be measured in the same state as in the above-mentioned measurement of the Steecht sizing degree, the Beck smoothness is measured for each sheet according to JIS P8119. The average value was obtained.

<Gurley stiffness>
After five A4-sized objects to be measured are left in the same state as in the measurement of the Steecht sizing degree, Tappi No. According to 40, the Gurley stiffness in the longitudinal direction was measured for each sheet, and the average value of the five sheets was obtained.

<Air permeability resistance>
After leaving two A4-sized objects to be measured in the same state as in the above-mentioned measurement of steecht degree, the air resistance is measured for each piece according to the Gurley test method of JIS P8117. The average value of two values was determined.

<BET specific surface area, pore volume>
The alumina hydrate used for the porous ink receiving layer is sufficiently heated and degassed, and then measured with an apparatus using a nitrogen adsorption / desorption method (trade name, Autosorb 1 manufactured by Cantachrome Co., Ltd.) to hydrate the alumina. The BET specific surface area and pore volume of the product were calculated. The BET specific surface area was calculated using the method of Brunauer et al. (See J. Am. Chem. Soc., 60, 309, 1938). The pore volume was calculated using the method of Barrett et al. (See J. Am. Chem. Soc., 73, 373, 1951).

<Glossiness>
According to JIS Z8741, a specular gloss of 20 degrees on the printing surface of a recording medium was measured using a gloss meter (trade name: VG2000, manufactured by Nippon Denshoku Industries Co., Ltd.), and based on the following criteria: Rank.

Rank criterion A: 15% or more,
B: 8% or more and less than 15%,
C: Less than 8%.

(Production Example 1 of Support)
A support was prepared under the following conditions. First, a paper stock having the following composition was prepared with water so that the solid content concentration was 3% by mass.

(Paper composition)
-Pulp 100 parts by mass (freezing degree 450 ml CSF (Canadian Standard Freeness), hardwood bleached kraft pulp (LBKP) (80 parts by mass),
And freezing kraft pulp (NBKP) (20 parts by mass)) having a freeness of 480 ml CSF.
-Cationized starch 0.60 mass part.
-Heavy calcium carbonate 10 mass parts.
-Light calcium carbonate 15 mass parts.
-Alkyl ketene dimer 0.10 mass part.
-Cationic polyacrylamide 0.030 mass part.

Next, the stock was made with a long paper machine, subjected to a three-stage wet press, and dried with a multi-cylinder dryer. Thereafter, an aqueous oxidized starch solution was impregnated with a size press device so that the coating amount was 1.0 g / m ^2, and after drying, machine calendering was performed. As a result, a base paper having a basis weight of 155 g / m ² , a Steecht sizing degree of 100 seconds, an air resistance of 50 seconds, a Beck smoothness of 30 seconds, and a Gurley stiffness of 11.0 mN was obtained. Next, an undercoat layer was formed on both sides of the base paper obtained above as follows. First, 100 parts by mass of kaolin (trade name: Ultra White 90, manufactured by Engelhard) / zinc oxide / aluminum hydroxide having a mass ratio of 65/10/25, and a commercially available polyacrylic acid-based dispersant 0. A slurry having a solid concentration of 70% by mass consisting of 1 part by mass and water was prepared. To this slurry, 7 parts by mass of a commercially available styrene-butadiene latex was added, and the solid content concentration was adjusted to 60% by mass using water to prepare an undercoat layer forming coating solution. Next, this coating solution was applied to both surfaces of the base paper A with a blade coater so that the dry coating amount was 15 g / m ² and dried. Thereafter, machine calender finishing was performed (linear pressure 150 kgf / cm (1471 N / cm)), basis weight 185 g / m ² , Steecht sizing degree 300 seconds, air resistance 3,000 seconds, Beck smoothness 200 seconds, Gurley A support 1 with an undercoat layer, which is a gas-permeable support having a stiffness of 11.5 mN, was obtained.

(Production Example 2 of Support)
25 g / m of a resin composition comprising low density polyethylene (70 parts by mass), high density polyethylene (20 parts by mass) and titanium oxide (10 parts by mass) on the base paper obtained in Production Example 1 of the support. ² applied. Subsequently, a resin-coated non-permeable support made by applying 25 g / m ^{2 of a} resin composition comprising high-density polyethylene (50 parts by mass) and low-density polyethylene (50 parts by mass) to the back surface of the base paper. A support 2 was obtained.

<Recording Medium Production Example 1 (Example 1)>
(Surface treatment process of air-permeable support)
The following surface treatment was performed on the undercoat layer on the surface of the support 1 obtained above where the porous ink-receiving layer is provided. First, a surface treatment liquid having the following composition heated to 30 ° C. was applied with an air knife coater to a wet coating amount of 16 g / m ² (the coating amount when dried was 0.8 g / in terms of solid content of sodium tetraborate). m ² ) so that it was applied at 30 m / min.
-Surface treatment solution sodium tetraborate: 5 g
And isopropanol: 0.15 g,
Ion exchange water was added to adjust the total amount to 100 g.

(Porous ink receiving layer forming step (step A))
Next, a porous ink receiving layer was formed. After the surface treatment liquid is applied in the surface treatment step, that is, as soon as the surface treatment liquid is impregnated in the undercoat layer, the porous ink receiving layer forming coating liquid is provided on the surface on which the porous ink receiving layer is provided. It was applied to. Subsequently, the applied surface treatment liquid and the coating liquid for forming a porous ink receiving layer were simultaneously dried to form a surface treatment layer and a porous ink receiving layer. In this case, the coating liquid for forming the porous ink-receiving layer, the coating method, and the like are as follows.

Dispersal HP13 (trade name, manufactured by Sasol Co., Ltd.) as alumina hydrate I was dispersed in water (preferably pure water as a measure against dust with respect to alumina) so that the solid concentration was 5% by mass, and then to this Hydrochloric acid was added, the pH value was adjusted to 4, and the mixture was stirred for a while. Thereafter, the dispersion was heated to 95 ° C. while stirring and held at that temperature for 4 hours. Then, while maintaining this temperature, the pH value was adjusted to 10 with caustic soda and stirred for 10 hours, and then the temperature of this dispersion was returned to room temperature, and the pH value was adjusted to 7-8. Further, desalting was performed, followed by addition of acetic acid and peptization to obtain a colloidal sol containing alumina hydrate II. When the alumina hydrate II obtained by drying this colloidal sol was measured by X-ray diffraction, it showed a boehmite structure (pseudo boehmite). At this time, the alumina hydrate II had a BET specific surface area of 143 g / m ² and a pore volume of 0.8 cm ³ / g.

On the other hand, polyvinyl alcohol PVA117 (trade name, manufactured by Kuraray Co., Ltd.) was dissolved in ion-exchanged water to obtain an aqueous solution having a solid content concentration of 9% by mass. Then, the colloidal sol containing alumina hydrate II having the boehmite structure prepared above was concentrated to prepare an alumina hydrate dispersion having a solid content concentration of 22.5% by mass of alumina hydrate II. 3 mass% boric acid aqueous solution was added to the dispersion liquid so that it might become 0.50 mass% in conversion of boric acid solid content with respect to solid content of alumina hydrate II. Thereafter, the obtained boric acid-containing alumina hydrate dispersion and the prepared polyvinyl alcohol aqueous solution were mixed with a static mixer so that the ratio of the alumina hydrate II solid content to the polyvinyl alcohol solid content was 100: 9. This was used as a coating liquid for a porous ink receiving layer. Immediately thereafter, this was applied to the surface of the support 1 on which the porous ink receiving layer was provided at 30 m / min so that the dry coating amount was 35 g / m ² with a die coater. Then, the surface treatment liquid and the porous ink receiving layer coating liquid were dried at 170 ° C. to form the surface treatment layer and the porous ink receiving layer. When the pore size distribution of the formed porous ink receiving layer was measured, the peak of the pore size distribution was about 9 nm in terms of the pore radius.

(Porous back coat layer forming step (step B))
Next, a coating solution for forming a porous backcoat layer is applied onto the undercoat layer on the opposite side (back side) of the support 1 on which the porous ink-receiving layer is provided, and dried to be porous. A backcoat layer was formed. In this case, the preparation of the coating liquid for forming the porous backcoat layer, the coating method, and the like are as follows. Non-spherical colloidal silica, an aqueous dispersion sol (trade name: Snowtex PS-MO, manufactured by Nissan Chemical Industries, Ltd., pH 3.0, solid content concentration 18.0 mass% sol), acrylic emulsion (trade name: ST -200, manufactured by Nippon Shokubai Co., Ltd., MFT (minimum film forming temperature) 56 ° C., solid content concentration 40.0% by mass), so that the solid content ratio of non-spherical colloidal silica and acrylic emulsion is 100: 30. Mixed. Next, an aqueous polyvinyl alcohol solution (trade name: PVA117, manufactured by Kuraray Co., Ltd., solid content concentration: 9.0% by mass) is mixed with the liquid mixture using a static mixer to obtain a non-spherical colloidal silica solid content and a polyvinyl alcohol solid content. The mixture was mixed so that the ratio was 100: 20. This was used as the coating liquid for the porous backcoat layer. Immediately thereafter, this was coated with a die coater at a rate of 30 m / min so that the dry coating amount was 20 g / m ^2, and the undercoat of the opposite surface (back surface) provided with the porous ink receiving layer of the support 1 was applied. Coated on the layer. And it dried at 170 degreeC and formed the porous backcoat layer.

(Glossy treatment process of porous ink receiving layer (process C))
Next, the surface of the porous ink receiving layer formed as described above was subjected to a gloss treatment by a rewet cast coater to obtain the recording medium 1 of the present invention.

<Recording Medium Production Example 2 (Example 2)>
The non-spherical colloidal silica contained in the porous backcoat layer forming coating solution used for the recording medium 1 is replaced with another non-spherical colloidal silica (trade name: Snowtex PS-M, manufactured by Nissan Chemical Industries, Ltd., pH 9. 8, solid content concentration 20.0 mass% sol). Otherwise, the recording medium 2 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 3 (Example 3)>
The non-spherical colloidal silica contained in the coating liquid for forming the porous back coat layer used in the recording medium 1 is replaced with another non-spherical colloidal silica (trade name: Snowtex HS-M-20, manufactured by Nissan Chemical Industries, Ltd., pH 7.0, solid content concentration 20.5 mass% sol). Otherwise, the recording medium 3 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 4 (Example 4)>
The nonspherical colloidal silica contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 is replaced with another nonspherical colloidal silica (trade name: Snowtex O-UP, manufactured by Nissan Chemical Industries, Ltd., pH 2. 9 and a solid content concentration of 15.6% by mass sol). Otherwise, the recording medium 4 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 5 (Comparative Example 1)>
A colloidal sol containing the above-mentioned alumina hydrate II used for the non-spherical colloidal silica contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 in the porous ink-receiving layer of the recording medium 1 A recording medium 5 was obtained in the same manner as the recording medium 1 except that

<Recording Medium Production Example 6 (Comparative Example 2)>
Non-spherical colloidal silica contained in the coating liquid for forming a porous backcoat layer used in the recording medium 1 was converted into spherical colloidal silica (trade name: Snowtex O, manufactured by Nissan Chemical Industries, Ltd., pH 3.1, solid content concentration). 20.2% by mass sol). Otherwise, the recording medium 6 was obtained in the same manner as the recording medium 1. The solid content ratio between the spherical colloidal silica and the acrylic emulsion and the solid content ratio between the spherical colloidal silica and the polyvinyl alcohol are the same as those in the recording medium 1 using non-spherical colloidal silica. Further, as in the case of the recording medium 6, the solid content ratio of the following example in which the component in the coating liquid for forming the porous backcoat layer was changed to another component not corresponding to the present invention is The ratio was the same as the solid content ratio of the recording medium 1 before the change.

<Recording Medium Production Example 7 (Comparative Example 3)>
Non-spherical colloidal silica contained in the coating liquid for forming a porous backcoat layer used in the recording medium 1 was converted into spherical colloidal silica (trade name: Snowtex 30, Nissan Chemical Industries, Ltd., pH 9.8, solid content concentration). 30.2% by mass sol). Otherwise, the recording medium 7 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 8 (Comparative Example 4)>
Non-spherical colloidal silica contained in the coating liquid for forming a porous back coat layer used in the recording medium 1 is made of spherical colloidal alumina (trade name: alumina sol 520, manufactured by Nissan Chemical Industries, Ltd., pH 4.2, solid content concentration). 20.5% by mass). Otherwise, the recording medium 8 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 9 (Comparative Example 5)>
The same procedure as for the recording medium 1 except that the non-spherical colloidal silica contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 was replaced with a vapor phase silica aqueous dispersion prepared by the following method. Thus, a recording medium 9 was obtained.

(Method for adjusting vapor phase silica aqueous dispersion)
A nitric acid aqueous solution having a pH of 3.0 by adding nitric acid to pure water was stirred with a homomixer (trade name: TK homomixer MARK II2.5 type, manufactured by Tokushu Kika Kogyo Co., Ltd.) under a rotation condition of 3000 rpm. Gas phase method silica (trade name: Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.) is added little by little to the agitated aqueous solution so that the solid content concentration is 9.5% by mass, and as it is after the addition is completed. Dispersed for 30 minutes. Next, the gas phase method silica dispersion is filtered with a cartridge filter (trade name: TCP-30S, average pore size 30 μm, manufactured by Advantech Co., Ltd.), and a gas phase method silica water dispersion sol having a solid content concentration of 9.3 mass% is obtained. Prepared.

<Recording Medium Production Example 10 (Comparative Example 6)>
The same as the recording medium 1 except that the non-spherical colloidal silica contained in the coating liquid for forming the porous back coat layer used in the recording medium 1 was replaced with a wet gel silica aqueous dispersion prepared by the following method. Thus, the recording medium 10 was obtained.

(Method for adjusting wet gel method silica aqueous dispersion)
While stirring pure water with the above-mentioned homomixer at a rotation speed of 1500 rpm, a small amount of wet gel silica (trade name: Cylysia SY370P, manufactured by Fuji Silysia Chemical Co., Ltd.) so that the solid content concentration becomes 15.0% by mass. After each addition, the mixture was dispersed as it was for 30 minutes. Next, the gas phase method silica dispersion was filtered through the cartridge filter to prepare a wet gel method silica aqueous dispersion.

<Recording Medium Production Example 11 (Example 5)>
The acrylic emulsion contained in the coating liquid for forming a porous backcoat layer used in the recording medium 1 is replaced with another acrylic emulsion (trade name: Boncoat CF6140, manufactured by Dainippon Ink Co., Ltd., MFT 20 ° C., solid content concentration 47. 5% by mass). Otherwise, the recording medium 11 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 12 (Example 6)>
The acrylic emulsion contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 is replaced with another acrylic emulsion (trade name: Boncoat CP6190, manufactured by Dainippon Ink Co., Ltd., MFT 50 ° C., solid content concentration 40. 3% by mass). Otherwise, the recording medium 12 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 13 (Example 7)>
The acrylic emulsion contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 is replaced with another acrylic emulsion (trade name: Polysol OLZ-1298, manufactured by Showa Polymer Co., Ltd., MFT 66 ° C., solid content concentration 35.1% by mass). Otherwise, the recording medium 13 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 14 (Example 8)>
The acrylic emulsion contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 was converted into a styrene-acrylic copolymer emulsion (trade name: Grosdale 292-S, manufactured by Mitsui Chemicals, MFT 80 ° C., The solid content concentration was changed to 48.3% by mass). Otherwise, the recording medium 14 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 15 (Comparative Example 7)>
The acrylic emulsion contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 was replaced with a polyurethane emulsion (trade name: Hydran HW930, MFT 0 ° C., solid content concentration 50.8% by mass). A recording medium 15 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 16 (Comparative Example 8)>
The acrylic emulsion in the coating liquid for forming the porous backcoat layer used for the recording medium 1 was replaced with a styrene-butadiene copolymer emulsion. The styrene-butadiene copolymer emulsion used was trade name: Smartex PA3305, manufactured by Nippon A & L Co., Ltd., glass transition temperature 85 ° C., solid content concentration 48.4% by mass. Otherwise, the recording medium 16 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 17 (Comparative Example 9)>
The acrylic emulsion contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 is a polyethylene emulsion (trade name: Hitech E-1000, manufactured by Toho Chemical Co., Ltd., melting point 138 ° C., solid content concentration 34. 8% by mass). Otherwise, the recording medium 17 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 18 (Comparative Example 10)>
The acrylic emulsion contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 was converted into a polyvinyl chloride emulsion (trade name: 601 manufactured by Nissin Chemical Industry Co., Ltd., MFT 50 ° C., solid content concentration 42. 3% by mass). Otherwise, the recording medium 18 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 19 (Comparative Example 11)>
The acrylic emulsion contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 is made of an ethylene-vinyl acetate copolymer (trade name: SUMIKAFLEX 305HQ, manufactured by Sumitomo Chemical Co., Ltd., MFT 0 ° C., solid The partial concentration was changed to 50.0% by mass). Otherwise, the recording medium 19 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 20 (Example 9)>
The hydrophilic binder contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 was replaced with another polyvinyl alcohol (trade name: PVA235, manufactured by Kuraray Co., Ltd., solid content concentration: 9% by mass). Except for this, the recording medium 20 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 21 (Example 10)>
The hydrophilic binder contained in the coating liquid for forming the porous backcoat layer used in the recording medium 1 is polyethylene oxide (trade name: Alcox R-40, manufactured by Meisei Chemical Co., Ltd., solid content concentration 8% by mass). A recording medium 21 was obtained in the same manner as the recording medium 1 except that

<Recording Medium Production Example 22 (Comparative Example 12)>
A recording medium 22 was obtained in the same manner as the recording medium 1 except that the hydrophilic binder contained in the coating liquid for forming a porous backcoat layer used for the recording medium 1 was not mixed.

<Recording Medium Production Example 23 (Comparative Example 13)>
Ethylene-vinyl acetate copolymer (trade name: SUMIKAFLEX 305HQ, manufactured by Sumitomo Chemical Co., Ltd.) is used as the hydrophilic binder in the coating liquid for forming the porous backcoat layer used in the recording medium 1. , MFT 0 ° C., solid content concentration 50.0 mass%). Otherwise, the recording medium 23 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 24 (Comparative Example 14)>
The hydrophilic binder in the coating liquid for forming the porous backcoat layer used for the recording medium 1 was replaced with a styrene-butadiene copolymer emulsion which is a non-hydrophilic binder. The styrene-butadiene copolymer emulsion used was trade name: Smartex PA3305, manufactured by Nippon A & L Co., Ltd., glass transition temperature 85 ° C., solid content concentration 48.4% by mass. Otherwise, the recording medium 24 was obtained in the same manner as the recording medium 1.

<Recording Medium Production Example 25 (Comparative Example 15)>
A recording medium 25 was obtained in the same manner as the recording medium 1 except that the air-permeable support 1 used for the recording medium 1 was replaced with the support 2 which was a non-air-permeable support.

<Recording Medium Production Example 26 (Example 11)>
A recording medium 26 was obtained in the same manner as the recording medium 1 except that the particle size of the alumina hydrate II used for the recording medium 1 was adjusted. As a result of measuring the pore size distribution of the porous ink receiving layer of the obtained recording medium 26, it was confirmed that there were maximum peaks in the pore radius of about 13 to 15 nm and about 20 nm.

<Recording Medium Production Example 27 (Example 12)>
Others different from the surface treatment layer and the porous backcoat layer on the undercoat layer on the opposite surface (back surface) provided with the porous ink-receiving layer of the support 1 used in the recording medium 1 by the following method Two layers of porous layers were provided. Subsequently, a recording medium 27 was obtained in the same manner as the recording medium 1 except that one porous back coat layer was provided as the outermost layer on the porous layer and a total of three layers were provided on the undercoat layer.

(Other porous layer and porous back coat layer forming method)
The same surface treatment liquid as that used in the production of the recording medium 1 is applied on the undercoat layer on the opposite surface (back surface) provided with the porous ink-receiving layer of the support 1 used in the production of the recording medium 1. It applied similarly with the air knife coater. Further, after the surface treatment liquid is applied in the surface treatment step, that is, as soon as the undercoat layer is impregnated with the undercoat layer, the same application as the coating liquid for forming the porous ink receiving layer used for the recording medium 1 is used. The liquid was applied with a die coater at a rate of 30 m / min so that the dry coating amount was 20 g / m ² . And it dried at 170 degreeC and the other porous layer (layer of the same composition as the porous ink receiving layer of the recording medium 1) different from a surface treatment layer and a porous backcoat layer was formed.

Next, on the porous layer, the same coating liquid for the porous back coat layer as that used for the production of the recording medium 1 is dried to 3 g / m ² with a die coater. It was applied at 50 m / min. Then, the film was dried at 170 ° C. to form a porous back coat layer, whereby a recording medium 27 was obtained.

<Recording Medium Production Example 28 (Example 13)>
A recording medium 28 was obtained in the same manner as the recording medium 27 except that the dry coating amount of the porous backcoat layer used for the recording medium 27 was 1 g / m ² .

<Examples 1-13, Comparative Examples 1-15>
The recording media 1 to 28 obtained as described above were evaluated as described below, and the results are shown in Table 1.

<Evaluation method>
1) Easy handling to the adhesive surface of glued album (glue album peelability)
In the following procedure, a peel test from the adhesive surface was performed on the back surface of each recording medium, and then visually evaluated based on the following evaluation criteria.
As an album with glue for evaluation, an album with a Fuji Color anniversary-free glue (trade name: NF-20L) was used.
1. Each recording medium is cut into 2.5 cm × 8 cm to produce test pieces for evaluation.
2. Place the cut evaluation specimen on the adhesive surface of the glued album with the back side down, and rub it once with your index finger.
3. Cover the glued album film and rub it once from the top, bottom, left, and right to prevent air from entering.
Wait for 4 or 5 seconds.
5. Peel off the film and peel off the test piece.

Evaluation criteria A: It was able to peel well, without sticking.
B: Although some sticking was seen, it was able to peel favorable.
C: A part of the test piece was stuck a little, but the stuck area was less than a quarter of the test piece.
D: A part of the test piece was stuck over an area of one quarter or more of the test piece.

2) Scratch resistance during multi-stack conveyance Using an inkjet printer 990i (trade name) manufactured by Canon Inc. on the surface (porous ink receiving layer (printing surface) side) of the recording medium cut to A4 size. A black solid image was created in professional photo paper mode (default setting). The recording medium is transported in a state of being stacked with the surface (printing surface) facing upward, and the scratch resistance of the lower recording medium of the two recording media is visually evaluated based on the following evaluation criteria. did.

Evaluation criteria A: Scratch marks are hardly seen and good.
B: 1 to 3 rubbing marks can be seen but acceptable level
C: 4 or more and 9 or less scratches are seen,
D: Ten or more scratches are seen.

3) Powder fall Each recording medium was evaluated using a Gakushin type friction tester type II (trade name, manufactured by Tester Sangyo Co., Ltd.) defined in JIS-L0849. Black rusha paper was attached to a friction piece of a testing machine on which a 300 g weight was placed, and set on a vibrating table so that the printing surface of each recording medium as a sample piece was up. After rubbing this printed surface and the frictional element with black Rash paper 20 times, the black reflection density of the Rash paper rubbing part (test part) and the other part is measured by X-Rite. It was measured with 310TR (trade name) manufactured by the manufacturer. From the reflection density difference, the black density residual ratio was obtained according to the following formula and evaluated based on the following evaluation criteria.

Evaluation criteria A: residual rate is 95% or more,
B: The residual rate is 90% or more and less than 95%,
C: Residual rate is 80% or more and less than 90%,
D: Residual rate is 60% or more and less than 80%.

  Residual rate (%) = [1-{(reflection density other than test part−reflection density of test part) / reflection density other than test part}] × 100

  As shown in Table 1, the recording media of Examples 1 to 13 have a high glossiness, and are excellent in both peelability from the glued album, scratching property during multi-stack conveyance, and powder falling. On the other hand, in Comparative Example 1 in which the pigment of the porous back coat layer is alumina hydrate, Comparative Example 5 in which gas phase method silica is used, and Comparative Example 6 in which wet type gel method silica is used, any of these items is not satisfactory. It is enough. Further, in Comparative Examples 2, 3, 4, and 15, the air resistance of the recording medium was 10,000 seconds or more, and compared with the recording media of Examples 1 to 13, the gloss treatment was performed. The glossiness of the porous ink receiving layer was not sufficient. Comparative Examples 2 and 3 used spherical colloidal silica particles instead of non-spherical colloidal silica, Comparative Example 4 used spherical colloidal alumina particles, and Comparative Example 15 used a non-permeable support.

  On the other hand, in Comparative Examples 7 to 11 in which another polymer emulsion such as polyurethane or styrene-butadiene copolymer is used instead of the acrylic emulsion, either peelability from a glued album or abrasion resistance during multi-load transport But that was not enough.

  Furthermore, the comparative example 12 which did not use a hydrophilic binder and the comparative examples 13 and 14 which were another water-insoluble polymer binder were inferior to Examples 1-13 in powder-off.

Claims (2)

An ink jet recording medium comprising a gas-permeable support, a porous ink receiving layer on one surface of the gas-permeable support, and a porous backcoat layer on the other surface of the gas-permeable support. And
The porous ink receiving layer and the porous backcoat layer are the outermost layers, respectively, and the porous backcoat layer comprises non-spherical colloidal silica particles, a solid content of an acrylic emulsion, a hydrophilic binder, An ink jet recording medium comprising:   The inkjet recording medium according to claim 1, wherein the air permeability resistance is 6000 seconds or less.