JP2007030200A - Inkjet recording medium and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which shows excellence in the quality of inkjet recording whichever of a dye ink and a pigment ink is used, and which has high pigment ink recording characteristics by reducing microcracks in the surface thereof, in particular, and has the same feel of gloss as a film photo. <P>SOLUTION: In the inkjet recording medium, a smoothing layer containing a pigment (A) comprising colloidal silica which has a primary particle diameter of 10-50 nm and wherein the ratio of a secondary particle diameter to the primary particle diameter is 1.5-2.5, and a binder (B), is provided on at least one side of a substrate, and an upper layer of an ink accepting layer is provided directly on the smoothing layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording medium suitably used for ink jet recording and a manufacturing method thereof, and more particularly to an ink jet recording medium suitable for ink jet recording using either a dye ink or a pigment ink and a manufacturing method thereof.

In general, the ink jet recording method uses a variety of mechanisms to eject ink droplets and deposit them on the recording paper to form dots and perform recording. However, compared with the dot impact type recording method, noise is generated. In addition, there is an advantage that full color is easy and high-speed printing is possible.
Conventionally, water-based dye ink has been mainly used in the ink jet recording system. Although this water-based dye ink uses a low molecular weight dye as a colorant, it has good color developability, but it easily bleeds due to adhesion of water or the like, or is exposed to light or gas for a long time due to the structure of the colorant. Discoloration, discoloration, and there are problems with the storability of recorded images and image fastness.

Therefore, in order to improve the problems of dye ink and improve water resistance and light resistance, inks using pigments as colorants are disclosed in, for example, Patent Documents 1 to 3, and are put into practical use. However, the pigment ink has problems such as lower printing density than the dye ink and poor uniformity of the solid printing portion. In particular, when there is a microcrack on the surface of the inkjet recording medium, the solid printing portion. The color loss is remarkable.
In addition, if a large amount of pigment ink is ejected to enhance color development, the colorant accumulates on the surface of the recording medium, resulting in a decrease in friction resistance, resulting in smearing of printed matter, or absorption of the solvent in the ink due to the accumulation of colorant. May interfere.

As described above, in recent years, both dyes and pigments have been used as inks for ink jet recording, and in order to cope with this, recording media suitable for both dye inks and pigment inks are required. Therefore, for example, Patent Document 4 discloses a technique in which an ink receiving layer includes an adhesive composed of inorganic fine particles and a vinyl chloride-vinyl acetate copolymer, and imparts recording properties for both dye ink and pigment ink. Yes.
On the other hand, recently, high-definition digital video (camera), scanners and personal computers have become popular, and the image data has also been refined. However, the performance of inkjet printers has made these image data as high as silver halide photographs. Opportunities to output (hard copy) are increasing. As a result, in addition to the glossiness of silver salt photographs, ink-jet recording media have a high ink drying speed, high print density, no ink overflow or bleeding, and no paper wavy due to ink absorption. Such characteristics are required.

In order to satisfy these characteristics, for example, Patent Document 5 proposes a technique for producing a recording medium by a cast coating method. In the cast coating method, an ink-receiving layer composed of a pigment mainly composed of synthetic silica and a binder is applied, and while the coating layer is in an undried wet state, the heated mirror-finished surface is applied. The layer is pressure-bonded to copy the mirror surface and simultaneously dried to obtain a high-gloss cast-coated paper.
Further, Patent Document 6 proposes a technique of providing a gloss layer containing pearl necklace-like colloidal silica on an ink receiving layer without using a cast coating method.

JP-A-11-20306 JP 2000-79752 A JP 2003-145916 A Japanese Patent Laid-Open No. 2001-270238 Japanese Patent Laid-Open No. 2-27487 JP 2000-108505 A

However, in the case of the technique described in Patent Document 4, both the print recording characteristics such as the print density and the ink absorbability cannot be satisfied, and it is difficult to obtain a high gloss recording medium. In the case of the technique described in Patent Document 5, the glossiness of the ink receiving layer is not yet sufficient, and the glossiness equivalent to that of a silver salt photograph has not been obtained. Furthermore, although the technique described in Patent Document 6 is suitable for dye inks, printing with pigment ink has drawbacks such as missing an image or contaminating a blank paper portion when the print portion is touched by hand. It was.
Therefore, the object of the present invention is that the ink jet recording quality is good regardless of whether the dye ink or the pigment ink is used, and in particular, by reducing microcracks on the surface of the ink jet recording medium, it has high pigment ink recording characteristics, An object of the present invention is to provide an ink jet recording medium having glossiness similar to that of a silver salt photograph.

  The present inventor provided a smoothing layer containing a specific colloidal silica as a pigment, and provided an ink receiving layer upper layer directly thereon, the ink jet recording quality was good and high glossiness was obtained using either dye ink or pigment ink. And found that an ink jet recording medium can be obtained. Further, the present inventor, in the upper layer of the ink receiving layer, shows a polymer compound (C) and fine particles (D) exhibiting hydrophilicity in a temperature region below the temperature sensitive point and hydrophobic in a temperature region exceeding the temperature sensitive point. ) And the above-described properties are further increased.

  Therefore, the inkjet recording medium of the present invention has a primary particle diameter of 10 to 50 nm and a ratio of the secondary particle diameter to the primary particle diameter of 1.5 to 2.5 on at least one surface of the support. A smoothing layer containing a pigment (A) containing colloidal silica and a binder (B) is provided, and an ink receiving layer upper layer is provided immediately above the smoothing layer, and further the ink receiving layer upper layer In the coating solution that forms the polymer, the polymer compound (C) and the fine particles (D) that are hydrophilic in the temperature range below the temperature sensitive point and hydrophobic in the temperature range above the temperature sensitive point are included. Is preferred.

  The method for producing an ink jet recording medium of the present invention comprises a pigment (A) containing colloidal silica having a primary particle size of 10 to 50 nm and a ratio of the secondary particle size to the primary particle size of 1.5 to 2.5. And a coating solution containing the binder (B) is provided to provide a coating layer, and the coating layer in a wet state is pressed against a heated mirror surface and dried to provide a smoothing layer. Further, a coating liquid for forming an upper layer of the ink receiving layer is applied directly on the smoothing layer to provide a coating layer, and a heated mirror surface is pressure-bonded to the wet coating layer and dried. In addition, an upper layer of the ink receiving layer is provided.

  According to the ink jet recording medium of the present invention, a high-quality recorded image can be obtained using either a dye-type ink or a pigment-type ink, and glossiness similar to that of a silver salt photograph can be obtained.

The support used for producing the ink jet recording medium of the present invention is not particularly limited as long as it has air permeability, and may be transparent or opaque. In the present invention, for example, paper such as high-quality paper, photographic paper base paper, drawing paper, image paper, art paper, coated paper, cast coated paper, craft paper, non-woven fabric, and the like can be appropriately used depending on the application. . From the viewpoint of operability, the preferable air permeability is 1,000 seconds or less, and from the viewpoint of coatability, the Steecht sizing degree is desirably 5 seconds or more.

  The pulp constituting the support includes chemical pulp (such as bleached or unbleached kraft pulp of softwood, bleached or unbleached kraft pulp of hardwood, etc.), mechanical pulp (such as ground pulp, thermomechanical pulp, chemithermomechanical pulp, etc.) It is possible to use black pulp or the like alone or in admixture at any ratio. This base paper is blended with additives such as a sizing agent, a paper strength enhancer, a filler, an antistatic agent, a fluorescent whitening agent, and a dye generally used in papermaking. Further, a surface sizing agent, a surface paper strength agent, a fluorescent brightening agent, an antistatic agent, a dye, an anchor agent, and the like may be applied on the surface.

The support is preferably one having good surface smoothness which is compressed by applying pressure with a calendar or the like during or after paper making, and the Beck smoothness measured by JIS-P-8119 is 200 seconds or more. Is particularly preferred. The basis weight is preferably 30 to 250 g / m ² .
Various back coat layers can be coated on the support in the present invention for antistatic properties, transport properties, curl prevention properties, writing properties, gluing properties, and the like. In the backcoat layer, an inorganic antistatic agent, an organic antistatic agent, a hydrophilic binder, latex, a crosslinking agent, a pigment, a lubricant, a surfactant, and the like can be added in an appropriate combination.

The coating layer of the present invention may be provided only on one side of the support, or may be provided on both sides of the support for the purpose of suppressing deformation such as double-sided recording or curling.
As the pigment for the smoothing layer, a pigment (A) containing a specific colloidal silica is used.
The colloidal silica used in the present invention has a shape in which a plurality of spherical primary particles are bonded when the dispersion state is observed with a microscope, and this is referred to as “peanut shape” for convenience. When single spherical colloidal silica with no primary particles is used, ink absorbency is inferior, but when peanut-shaped colloidal silica is used, glossiness, ink color developability (image sharpness), ink absorbency Can be satisfied together.

The peanut-like colloidal silica is synthesized by sol-gel method using alkoxysilane as a raw material, and the primary particle size (BET method particle size) and secondary particle size (dynamic light scattering method particle size) can be controlled according to the synthesis conditions. preferable. An example of such colloidal silica is Quartron: trade name, manufactured by Fuso Chemical Industries. In addition, the colloidal silica of the present invention does not include colloidal particles obtained by subdividing an aggregate in which primary particles are aggregated by mechanical means.
The peanut-like colloidal silica has a ratio of the secondary particle diameter to the primary particle diameter of the colloidal silica (secondary particle diameter / primary particle diameter) of 1.5 to 2.5. When colloidal silica having a particle size ratio within this range is used, high image quality can be obtained both when a dye ink is used and when a pigment ink is used.

  Furthermore, the primary particle diameter of peanut-like colloidal silica is 10 to 50 nm, and the particularly preferable primary particle diameter is 13 to 40 nm. When the primary particle diameter is less than 10 nm, the transparency is high, but the voids between the particles are impaired and the ink absorbability is lowered. On the other hand, when the diameter is larger than 50 nm, the voids between the particles are good, but the opacity increases, so that the color developability at the time of ink jet recording is lowered. In particular, when printing is performed with an ink jet printer using a pigment ink containing colored particles having a particle diameter of 50 to 150 nm in the ink, the ink coloring property is greatly reduced.

In addition, in the said peanut-shaped colloidal silica, 1.8-2.5 are mentioned as an example of the average value of the connection number of a primary particle. This value is the same value as the above ratio.
In the present invention, other pigments such as aluminum hydroxide, alumina sol, pseudoboehmite and the like (alumina of α-type crystal, alumina of θ-type crystal) Synthetic silica, kaolin, talc, calcium carbonate, titanium dioxide, clay, zinc oxide and the like, and plastic beads and fine particles (D) described later may be used in combination.

  As the pigment for the smoothing layer of the present invention, it is preferable to use plastic beads in combination for the purpose of imparting smoothness and improving ink absorbability. As the plastic beads, styrene beads, crosslinked styrene beads, benzoguanamine beads, melamine beads, acrylic beads, PMMA beads, acrylic-styrene beads, polycarbonate beads, polyethylene beads, vinyl chloride beads and the like are used. The particle diameter of these plastic beads is preferably 0.05 to 12.0 μm. From the viewpoint of smoothness, 0.05 to 2.0 μm is more preferable. Specifically, these plastic beads are “Ropeke HP-91”, “Ropeke OP-62”, “Ropeke OP-84J” (trade name, manufactured by Rohm and Haas Japan Co., Ltd.), “Chemical S- 650, Chemipearl S-100, Chemipearl V-100, Chemipearl W-100, Chemipearl W-500, Chemipearl WF-640, Chemipearl W-950, Chemipearl W-100 (Mitsui Chemicals, Inc .: trade name) and the like.

(Binder for smoothing layer (B))
As the binder (B), one or more kinds of polymer compounds capable of forming a film can be used. For example, as the binder (B), polyvinyl alcohol, polyvinyl pyrrolidone, starches such as oxidized starch and esterified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, water-soluble resins such as casein, gelatin, soybean protein, Urethane resins, styrene-acrylic resins, styrene-butadiene resins, acrylic resins, vinyl acetate resins, vinyl chloride resins, urea resins, alkyd resins, and derivatives thereof can be used alone or in combination.

  The blending amount of the binder (B) is preferably 3 to 30 parts by mass with respect to 100 parts by mass of the total pigment of the smoothing layer, but is particularly limited as long as the required coating layer strength is obtained. It is not a thing. The polymer compound used as the binder (B) is preferably aqueous. “Aqueous” means that the resin is dissolved or dispersed and stabilized in water or a medium composed of water and a small amount of an organic solvent. These binders (B) are dissolved or dispersed as particles in the coating liquid, but after coating and drying, they become pigment binders (B) and form a smoothing layer. When an organic solvent is used as the medium, it is preferable that the mixing ratio is less than 50% by mass, preferably less than 10% by mass, and the flash point of the coating liquid is high.

The binder (B) preferably contains polyvinyl alcohol. When polyvinyl alcohol is used as the binder (B), ink absorbability and color developability are particularly improved, and when an ink receiving layer is provided by a cast coating method described later, an ink jet recording medium having a high gloss feeling Can be obtained. It is preferable that 50-100 mass% of polyvinyl alcohol is contained with respect to all the binders (B) of a smoothing layer.
The smoothing layer contains the above-described pigment and binder (B), but other components such as a thickener, an antifoaming agent, an antifoaming agent, a pigment dispersant, a release agent, a foaming agent, and pH adjustment. Agent, surface sizing agent, coloring dye, coloring pigment, fluorescent dye, ultraviolet absorber, antioxidant, light stabilizer, preservative, water resistance agent, dye fixing agent, surfactant, wet paper strength enhancer, water retention An agent, a cationic polymer electrolyte, and the like can be appropriately added within a range not impairing the effects of the present invention.

As a method of applying a coating liquid for forming a smoothing layer on a support or an ink receiving layer lower layer, and a method of applying a coating liquid for forming an ink receiving layer upper layer on a smoothing layer, a blade coater, Known coating machines such as air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, bar coater, gravure coater, gate roll coater, short dwell coater, etc. were used on-machine or off-machine. It can be used by appropriately selecting from the coating methods.

The coating amount of the smoothing layer can be arbitrarily adjusted as long as the surface of the support or the ink receiving layer is uniformly covered and sufficient smoothness can be obtained. In order to reduce this, the smoothing layer needs to be homogeneous and sufficiently smooth, and for that purpose, it is preferably 5 to ²⁰ g / m ² in terms of solid content per one side, and the lower layer of the ink receiving layer is formed. In order to make the smoothing layer also have the role of the ink receiving layer without providing it, it is preferably 10 to 25 g / m ² .
The coating amount of the upper layer of the ink receiving layer needs to be a coating amount sufficient for fixing the dye ink and the pigment ink, and for that purpose, it should be 5 to ²⁰ g / m ² in terms of solid content per side. Preferably, in order to suppress microcracks in the upper layer of the ink receiving layer, it is more preferably 5 to 15 g / m ² in terms of solid content.

  In the present invention, the smoothing layer is preferably formed by a cast coating method to impart high smoothness. Here, the cast coating method is a method in which a coated surface in a wet state after coating is pressed onto a heated finished surface and dried. The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressed onto a mirror-finished heating drum while the coating layer is wet, and (2) a wet coating layer is once dried. Alternatively, it is semi-dried and then swollen and plasticized with a rewetting liquid, and is pressed onto a mirror-finished heated drum and dried (rewetting method). (3) The wet coating layer is made into a gel state by coagulation treatment. There are generally known three types: a gelled cast method (coagulation method) in which a heated drum having a mirror finish is pressed and dried.

  In the case of the above (2) and (3), after applying the coating liquid to be the smoothing layer to the support, the processing liquid has the action of coagulating the binder (particularly the aqueous binder) in the coating liquid. Is applied to the coating layer to wet the coating layer. And a smoothing layer is formed by press-bonding the wet coating layer to a heated mirror-finished surface and drying, and gloss is imparted to the surface. The coating layer when applying the coagulation treatment liquid may be wet or dry. The former corresponds to the method (3) and the latter corresponds to the method (2). In particular, the method (3) is easy to copy the mirror-finished surface on the surface of the smoothing layer and can reduce fine irregularities on the surface of the coating layer, so that the upper layer of the ink receiving layer is formed on the obtained smoothing layer. When it is applied, it becomes easy to give glossiness similar to that of a silver salt photograph. Examples of the method for applying the treatment liquid include, but are not limited to, a roll, a spray, and a curtain method.

When the gelling cast method (method (3)) is used, when polyvinyl alcohol is used as the aqueous binder, it is preferable to use a liquid containing boric acid and borate as the coagulation treatment liquid. By mixing and using boric acid and borate, it becomes easy to make the hardness at the time of coagulation moderate, and it is possible to impart a good gloss to the smoothing layer.
When casein is used as the aqueous adhesive, the aqueous solution containing various salts such as calcium, zinc, magnesium, etc. such as formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid, etc. is used as the coagulation treatment liquid. It is done.
Moreover, a release agent can be added to the coating liquid and / or coagulation liquid for the ink receiving layer as necessary. The melting point of the release agent is preferably 90 to 150 ° C, and particularly preferably 95 to 120 ° C. In the above temperature range, since the melting point of the release agent is almost equal to the temperature of the mirror finish surface, the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above characteristics, but it is preferable to use a polyethylene wax emulsion.

Examples of the mirror-finished solid material include metals such as stainless steel, glass, polyacryl, polyethylene terephthalate, silicone resin, fluororesin, etc., but metals such as stainless steel are used in terms of surface smoothness. Presently the most excellent and preferably used, and preferred shapes are cylindrical, flat and the like, but cylindrical is preferably used.
Examples of the method of heating the mirror surface (drum) include steam, heating wire, induction heating coil, and the like, which can be heated to a predetermined temperature. A coating equipment having a coating device and a mirror drum for applying an ink receiving layer or the like on a support is usually referred to as a cast coater.
Any of the above methods (1), (2), and (3) may be used to form the smoothing layer of the present invention.

In the present invention, it is preferable to impart high gloss by forming the upper layer of the ink receiving layer by a cast coating method.
In particular, in the formation of the upper layer of the ink receiving layer of the present invention, it is preferable to use the methods (1) and (3). In the case where the coating liquid that forms the upper layer of the ink receiving layer contains a polymer compound (C) that exhibits hydrophilicity in a temperature region below the temperature sensitive point and exhibits hydrophobicity in a temperature region that exceeds the temperature sensitive point, After coating the coating liquid to form a coating layer, the coating layer is hydrophilized by cooling below the temperature sensitive point of the polymer compound (C), and the coating liquid gels. By using this, the same effect as the gelled cast method can be obtained.

  The manufacturing apparatus according to the present invention is a means for pressure-bonding the coating layer to a heated mirror-finished solid surface after the coating liquid for forming the smoothing layer is applied, in a wet state, which will be described later in the present invention. A coating solution containing an emulsion of the polymer compound (C) to be applied on the smoothing layer at a temperature exceeding the temperature sensitive point of the polymer emulsion; A manufacturing apparatus comprising means for cooling to a temperature below the warm point, means for pressure-bonding the coating layer to a heated mirror-finished solid surface in a wet state, and means for drying the coating layer Preferably there is.

  As one aspect of the ink jet recording medium of the present invention, a plurality of coating layers can be formed on a support, such as an ink receiving layer lower layer, a smoothing layer, and an ink receiving layer upper layer directly thereon. Also, providing a layer having adhesiveness and other various functions between the support and the smoothing layer, or between the support and the ink receiving layer lower layer, providing a gloss layer on the ink receiving layer upper layer, It is possible to further provide a backcoat layer having ink absorptivity, writing property, printer printability and other various functions on the side opposite to the surface on which the ink receiving layer is provided. A plurality of coating layers may be performed by simultaneous multilayer coating. The simultaneous multilayer coating can be performed, for example, by a coating method using an extrusion die coater or a curtain flow coater. An extrusion die coater is more preferable for the purpose of avoiding mixing or coalescence of a plurality of coating layers.

  When using an extrusion die coater, a plurality of coating solutions discharged at the same time are layered near the extrusion die coater discharge port, i.e., just before moving onto the support, and in that state, a multilayer coating is applied on the support. Is done. When performing the simultaneous multi-layer coating, in order to avoid mixing of a plurality of coating liquids, a barrier layer liquid (intermediate layer liquid) may be interposed between the coating layers and the coating layers simultaneously. it can. The barrier layer liquid can be selected without particular limitation as long as it is difficult to mix with the upper and lower coating layers, but a liquid having thixotropic properties is preferably used. Examples of the liquid preferably used include aqueous solutions of polymers such as hydroxypropylmethylcellulose, methylcellulose, hydroxyethylmethylcellulose, polyvinylpyrrolidone, and gelatin.

As means for cooling the coating layer, known means such as natural cooling, a cold air blower, a blower, and a refrigerator can be used. A blower or a cool air blower is preferably used, and the temperature of the wind changes variously depending on the temperature sensitive point of the polymer emulsion of the present invention, preferably a temperature below the temperature sensitive point, and a temperature 5 ° C. or more lower than the temperature sensitive point. More preferred is a temperature that is 10 ° C. or more lower than the temperature sensitive point. When natural cooling is performed, it is preferable to set the temperature sensing point higher by 10 ° C. than the environmental temperature.
As means for drying the coating layer, known drying means such as a hot air dryer, a steam heating dryer, a far-infrared dryer and the like can be used. A hot air dryer is preferably used, and examples thereof include a drum dryer, an air cap dryer, an air foil dryer, an air conditioner dryer, and combinations thereof. The drying temperature varies depending on the type of dryer, but the temperature inside the dryer is 50 to 200 ° C, preferably 100 to 150 ° C.

In the recording medium of the present invention, the coating amount of the entire coating layer including the ink receiving layer lower layer, the smoothing layer, and the ink receiving layer upper layer is preferably 5 to 50 g / m ² in terms of solid content. More preferably, it is 10-40 g / m < ² >. If the coating amount is less than 5 g / m ² , the effect is small from the viewpoint of color developability, and if it exceeds 50 g / m ² , the ink-receiving layer may fall off. In addition, as thickness of the whole coating layer, 5-50 micrometers is preferable and 10-40 micrometers is still more preferable.
The polymer compound (C) used in the present invention exhibits hydrophilicity in the temperature range below the temperature sensitive point and exhibits hydrophobicity in the temperature range above the temperature sensitive point. A homopolymer polymer of a monomer (main monomer (M)) or a copolymer polymer compound of two or more main monomers (M) from which a polymer compound exhibiting a change in hydrophobicity is obtained; A monomer (submonomer (N)) that can react with the main monomer (M) to produce a polymer compound and that does not give a polymer compound exhibiting the temperature responsiveness by homopolymerization; It is a copolymerized polymer compound. The main monomer (M) and the submonomer (N) can be used alone or in combination of two or more.
A polymer compound having high temperature responsiveness can be obtained by homopolymerization, but by performing the copolymerization, a polymer compound having a temperature sensitive point different from that of the homopolymer polymer compound can be obtained, or a homopolymer polymer A film forming property different from that of the compound can be obtained.

  As the main monomer (M), N-alkyl or N-alkylene-substituted (meth) acrylamide derivatives (here, (meth) acryl is a simple notation of methacryl (or methacryl) or acryl), vinyl Specific examples include N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-cyclopropyl (meth) acrylamide, N-methyl (meth) acrylamide, N, N-, and the like. Diethylacrylamide, N, N-dimethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-methyl-Nn-propylacrylamide, N-methyl-N-isopropylacrylamide, N- (meth) acryloylpyrrolidine N- (meth) acryloylpiperidine, -Tetrahydrofurfuryl (meth) acrylamide, N-methoxypropyl (meth) acrylamide, N-ethoxypropyl (meth) acrylamide, N-isopropoxypropyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N- (2 , 2-dimethoxyethyl) -N-methylacrylamide, N-methoxyethyl (meth) acrylamide, N- (meth) acryloylmorpholine and the like. From the viewpoint of film formability, N-isopropylacrylamide, Nn-propylacrylamide, N, N-diethylacrylamide, and N-acryloylmorpholine are preferable.

Examples of the auxiliary monomer (N) include lipophilic vinyl compounds, hydrophilic vinyl compounds, and ionic vinyl compounds. Specifically, lipophilic vinyl compounds include methyl (meth) acrylate and ethyl (meth) acrylate. , N-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, glycidyl methacrylate, styrene, α-methylstyrene, ethylene, isoprene, butadiene, vinyl acetate, vinyl chloride, and the like. As the hydrophilic vinyl compound, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, N-methyl (meth) acrylamide, N-methylol acrylamide, diacetone acrylamide, methylene bisacrylamide, 2-methyl 5-vinylpyridine, N-vinyl-2-pyrrolidone, N-acryloylpyrrolidine, acrylonitrile and the like can be mentioned. Examples of ionic vinyl compounds include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, butene. Carboxylic acid group-containing monomers such as tricarboxylic acid, monoethyl maleate, monomethyl maleate, monoethyl itaconate, monomethyl itaconate, 2-acrylamido-2-methyl-propanesulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, (meth) acrylic Examples include sulfonic acid group-containing monomers such as sulfonic acid, and amino group-containing monomers such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate. In particular, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, styrene, 2-hydroxypropyl (meth) acrylate, acrylamide, methacrylamide, diacetone acrylamide, and methylene bisacrylamide are preferably used. It is done.

The copolymerization ratio of the main monomer (M) and the submonomer (N) is within a range in which the obtained copolymer polymer compound exhibits temperature responsiveness in which hydrophilicity and hydrophobicity reversibly change at a certain temperature as a boundary. It is decided in. That is, when the proportion of the submonomer (N) is too large, the copolymeric polymer compound obtained does not exhibit the temperature responsiveness.
That is, the copolymerization ratio of the main monomer (M) and the submonomer (N) depends on the combination of the monomer species used, but the ratio of the submonomer (N) in the resulting polymer compound is preferably 50% by mass or less. More preferably, it is 30 mass% or less. Moreover, 0.01 mass% or more is preferable in order that the addition effect of a submonomer (N) may be expressed better.

  In the present invention, the “temperature sensitive point” of the polymer compound (C) is a temperature at which its hydrophilicity-hydrophobicity changes, and “temperature responsiveness” indicates the change in the hydrophilicity-hydrophobicity. Means nature. In the present invention, the term “hydrophilic” means that the polymer compound (C) in a system in which the polymer compound (C) and water coexist is more stable in a state compatible with water than in a phase separated state. In the system in which the polymer compound (C) and water coexist, the term “hydrophobic” means that the polymer compound (C) is in a state in which the polymer compound (C) is phase-separated with water rather than in a state in which the polymer compound (C) is in solution. Means stable.

  The change in hydrophilicity-hydrophobicity is, for example, an abrupt viscosity change accompanying a temperature change in a system in which the polymer compound (C) and water coexist, or transparency in a system in which the polymer compound (C) and water coexist. It appears as a sudden change in the solubility of the polymer compound (C) in water. That is, the viscosity when the temperature of the system in which the polymer compound (C) and water coexist is gradually lowered from the temperature range where the polymer compound (C) exhibits hydrophobicity (temperature exceeding the temperature sensitive point). The polymer compound (C) obtained as a transition point at which the temperature-viscosity curve obtained by measurement changes abruptly or in a temperature range where the polymer compound (C) exhibits hydrophobicity (temperature exceeding the temperature sensitive point) The temperature sensitive point of the polymer compound (C) can be determined as the temperature at which the dispersion begins to become transparent or gel when the aqueous dispersion is gradually cooled.

When the polymer compound (C) of the present invention is used in the production of an ink jet recording medium, the use of a dye ink having an anion group in ink jet recording is often more durable than a dye ink having a cationic group. Is preferable because of high. Therefore, it is preferable to add a cationic compound such as a cationic polymer or cationic particles to the coating liquid for inkjet recording medium for the purpose of fixing the dye ink having an anionic group to the recording medium. Although it is more preferable that the polymer compound (C) is cationic or nonionic from the viewpoint of easiness, the polymer compound (C) is not limited to this, and the polymer compound (C) may be anionic or amphoteric. Good. The cationic polymer compound (C) can be obtained, for example, by including an ethylenically unsaturated monomer having a cationic group as a submonomer (N) used in the polymerization. It is preferable to use an ethylenically unsaturated monomer having a cationic group as the secondary monomer (N). The ethylenically unsaturated monomers having a cationic group can be used alone or in combination of two or more. In particular, from the viewpoint of the degree of fading that occurs when a printed material printed using an inkjet printer is exposed to sunlight or fluorescent light, and the polymer compound (C) When used in the state, from the viewpoint of colloidal stability of the polymer emulsion, the ethylenically unsaturated monomer having a cationic group preferably contains a tertiary amino group and / or a quaternary ammonium base.
The polymer compound (C) containing a tertiary amino group and / or a quaternary ammonium base contains, for example, a main monomer (M) and a tertiary amino group and / or a quaternary ammonium base as a submonomer (N). It is obtained by copolymerizing with a monomer. The main monomer (M) and submonomer (N) (including monomers containing a tertiary amino group and / or a quaternary ammonium base) can be used alone or in combination of two or more.

The tertiary amino group or quaternary ammonium base-containing monomer is not particularly limited as long as it has a structure containing a tertiary amino group or quaternary ammonium base in the monomer, but vinyloxyethyltrimethylammonium chloride, 2, 3-dimethyl-1-vinylimidazolinium chloride, trimethyl- (3- (meth) acrylamide-3,3-dimethylpropyl) ammonium chloride, trimethyl- (3-methacrylamidopropyl) ammonium chloride, trimethyl- (3-acrylamide) Propyl) ammonium chloride, N- (1,1-dimethyl-3-dimethylaminopropyl) (meth) acrylamide and its quaternary ammonium salt, trimethyl- (3- (meth) acrylamide) ammonium chloride, 1- Nyl-2-methyl-imidazole, 1-vinyl-2-ethyl-imidazole, 1-vinyl-2-phenyl-imidazole, 1-vinyl-2,4,5-trimethyl-imidazole, N, N-dimethylaminopropyl ( Meth) acrylate and quaternary ammonium salt thereof, N, N-dimethylaminoethyl (meth) acrylate and quaternary ammonium salt thereof, N, N-diethylaminoethyl (meth) acrylate and quaternary ammonium salt thereof, t-butylaminoethyl (Meth) acrylate and its quaternary ammonium salt, N- (3-dimethylaminopropyl) methacrylamide and its quaternary ammonium salt, N- (3-dimethylaminopropyl) acrylamide and its quaternary ammonium salt, N- (3 -Diethylaminopropyl) meta Rilamide and its quaternary ammonium salt, N- (3-diethylaminopropyl) acrylamide and its quaternary ammonium salt, o-, m-, p-aminostyrene and its quaternary ammonium salt, o-, m-, p-vinyl Benzylamine and its quaternary ammonium salt, N- (vinylbenzyl) pyrrolidone, N- (vinylbenzyl) piperidine, N-vinylimidazole and its quaternary ammonium salt, 2-methyl-1-vinylimidazole and its quaternary ammonium salt N-vinylpyrrolidone and its quaternary ammonium salt, N, N′-divinylethyleneurea and its quaternary ammonium salt, α- or β-vinylpyridine and its quaternary ammonium salt, α- or β-vinylpiperidine and its Quaternary ammonium salt, 2-, or 4 -Vinylquinoline and its quaternary ammonium salt are exemplified. In particular, a methyl chloride quaternary compound of N, N-dimethylaminopropyl methacrylate, N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl (meth) acrylamide is preferably used.
The copolymerization ratio of the main monomer (M) and the secondary monomer (N) containing a tertiary amino group and / or quaternary ammonium base-containing monomer is such that the resulting copolymeric polymer compound is hydrophilic with respect to the temperature sensitive point. The hydrophobicity is determined within a range exhibiting temperature responsiveness that reversibly changes.

The content of the tertiary amino group and / or quaternary ammonium base-containing monomer unit in the polymer compound (C) used in the present invention is not particularly limited within the range of the above conditions. 0.01 mass% or more is preferable from the viewpoint of ease, and 50 mass% or less is preferable from the viewpoint of film formability. More preferably, it is 0.1-30 mass%.
Furthermore, it is more preferable to use a quaternary ammonium group-containing monomer rather than a tertiary amino group-containing monomer from the viewpoint of the degree of fading that occurs when the printed material is exposed to sunlight or fluorescent light.
Furthermore, the inclusion of both a tertiary amino group and / or quaternary ammonium base-containing monomer and the anion group-containing monomer is due to the ease of preparation of the coating liquid described above and the polymer emulsion of the present invention. From the viewpoint of both the film formability of the resulting coating layer, it is particularly preferable that the anion group-containing monomer is a carboxylic acid group-containing monomer such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid. .

The glass transition point of the polymer compound (C) used in the present invention is not particularly limited, but the glass transition point is preferably −50 to 150 ° C. from the viewpoints of film formability and flexibility of the obtained recording medium, etc. Is preferably −50 to 30 ° C. from the viewpoint of imparting flexibility to the obtained recording medium.
The anionic polymer compound (C) can be obtained, for example, by including an ethylenically unsaturated monomer having an anionic group as a submonomer (N) used in the polymerization. It is preferable to use an ethylenically unsaturated monomer having an anionic group as the secondary monomer (N). The ethylenically unsaturated monomers having an anionic group can be used alone or in combination of two or more.

  Examples of the ethylenically unsaturated monomer having an anionic group include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, butenetricarboxylic acid, monoethyl maleate, monomethyl maleate, monoethyl itaconate, and itaconic acid. Examples thereof include carboxylic acid group-containing monomers such as monomethyl, and sulfonic acid group-containing monomers such as 2-acrylamido-2-methyl-propanesulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, and (meth) acryl sulfonic acid. In particular, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid are preferably used from the standpoint of stability such that aggregates are less likely to occur when the coating liquid is blended.

In the present invention, from the viewpoint of surface glossiness of the resulting ink jet recording paper, the polymer compound (C) preferably forms a polymer emulsion in the coating solution before coating. Therefore, when producing the polymer compound (C), it is preferable to carry out the polymerization reaction in an aqueous solvent in a temperature range exceeding the temperature sensitive point of the polymer compound (C). Since the polymer compound (C) exhibits hydrophobicity and forms an emulsion in the temperature region, a widely known polymer emulsion production technique can be used in the temperature region. Specifically, a surfactant is dissolved in water, and the copolymerization monomer component such as the main monomer (M) and the submonomer (N) is added and emulsified, and a radical polymerization initiator is added and emulsified by a reaction by batch charging. In addition to the method of performing polymerization, there may be mentioned a method of supplying the above copolymerization component or radical polymerization initiator to the reaction system by a method such as continuous dropping or divided addition.
In producing a polymer emulsion, it is preferable to use a surfactant.
The polymer emulsion may be any of anionic, cationic, nonionic, and amphoteric.

When the polymer compound (C) is an anionic emulsion, an anionic surfactant and / or a nonionic surfactant is used. For example, fatty acid soap, alkyl sulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl aryl sulfate, p-styrene sulfonate, alkyl naphthalene sulfonate, naphthalene sulfonate, formalin heavy Condensate, higher fatty acid and amino acid condensate, dialkylsulfosuccinate ester salt, naphthenate salt, alkyl ether carboxylate, acylated peptide, α-olefin sulfonate, N-acylmethyl taurine, alkyl ether sulfate, Anionic surfactants such as secondary higher alcohol ethoxy sulfates, polyoxyethylene alkylphenyl ether sulfates, monoglyculates, alkyl ether phosphate salts, alkyl phosphate salts and the like can be mentioned. Examples of the nonionic surfactant include polyoxyethylene alkyl aryl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene sorbitan fatty acid ester, oxyethylene oxypropylene block copolymer, polyglycerin fatty acid ester and the like.

When the polymer compound (C) is a cationic emulsion, a cationic surfactant and / or a nonionic surfactant is used. For example, examples of the cationic surfactant include laurylamine hydrochloride, alkylbenzyldimethylammonium chloride, lauryltrimethylammonium chloride, alkylammonium hydroxide, and polyoxyethylene alkylamine. Nonionic surfactants include Examples thereof include polyoxyethylene alkyl aryl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene sorbitan fatty acid ester, oxyethylene oxypropylene block copolymer, polyglycerin fatty acid ester and the like.
When the polymer compound (C) is a nonionic emulsion, a nonionic surfactant is used. Examples of the nonionic surfactant include polyoxyethylene alkyl aryl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene sorbitan fatty acid ester, oxyethylene oxypropylene block copolymer, polyglycerin fatty acid ester and the like.

In the case where the polymer compound (C) is an amphoteric emulsion, it is preferable to use an amphoteric surfactant from the viewpoint of stability against a change in pH of the polymer emulsion. When the emulsion of the molecular compound (C) is cationic, a cationic surfactant can be used, and when the emulsion of the polymer compound (C) is anionic in the coating liquid of the present invention An anionic surfactant can be used. Examples of amphoteric surfactants include carboxybetaine type, aminocarboxylate, and lecithin.
The amount of these surfactants used is preferably 0.05 to 50 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the resin solid content of the polymer compound (C) emulsion. It is.
In this invention, the said surfactant can also be used individually by 1 type, and can also use 2 or more types together.

  By using a “surfactant having a reactive group” during emulsion polymerization of the polymer compound (C) of the present invention, the amount of non-reactive surfactant used can be reduced by printing on the resulting recording medium. It is preferable from the viewpoint of the water resistance of the image. The surfactant having a reactive group is generally called a reactive surfactant, and examples thereof include a compound having a hydrophobic group, a hydrophilic group and a reactive group in the molecule. Examples of the reactive group include carbon-carbon double bonds such as (meth) allyl group, 1-propenyl group, 2-methyl-1-propenyl group, isopropenyl group, vinyl group and (meth) acryloyl group. The functional group which has is mentioned.

  Examples of the reactive surfactant having an anionic property include those having a structure such as a sulfonate group, a sulfate ester base, a carboxylate group, and a phosphate group. Examples of vinyl monomers having a sulfonate group include allyl sulfone. Acid, 2-methylallylsulfonic acid, vinylsulfonic acid, 4-vinylbenzenesulfonic acid, 2- (meth) acryloyloxyethanesulfonic acid, 3- (meth) acryloyloxypropanesulfonic acid, 2-acrylamido-2-methylpropane Examples thereof include those obtained by neutralizing various sulfonic acid group-containing vinyl monomers such as sulfonic acid with various basic compounds.

Examples of the basic compound include lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, ethylamine, n-butylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, tri-n-butylamine, diethanolamine, 2-dimethylamine. Aminoethyl alcohol, tetramethylammonium hydroxide, tetra-n-butylammonium hydroxide, etc. are mentioned. Examples of the vinyl monomer containing a sulfate ester base include those obtained by neutralizing vinyl monomers containing a sulfate ester group such as sulfate of allyl alcohol with the various basic compounds. Examples of vinyl monomers containing phosphate groups include those obtained by neutralizing phosphate group-containing vinyl monomers such as mono {2- (meth) acryloyloxyethyl} acid phosphate with the various basic compounds. Can be mentioned.

Examples of the reactive surfactant having an anionic property containing an allyl group (CH ₂ ═C (—R) —CH ₂ —) (where R is an alkyl group) include, for example, sulfuric acid of polyoxyethylene allyl glycidyl nonyl phenyl ether Examples of commercially available products include “Adekaria Soap SE-10N” series (trademark: manufactured by Asahi Denka Kogyo Co., Ltd.), “Eleminol JS-2” (trademark: manufactured by Sanyo Chemical Industries, Ltd.). "Latemul S-180 or S-180A" (trademark: manufactured by Kao Corporation), "H3390A" and "H3390B" (trademark: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the like.

As the reactive surfactant having an anionic property containing a (meth) acryloyl group (CH ₂ ═C (—R) —C (═O) —O—) (where R is an alkyl group), for example, a commercially available product Examples thereof include “Eleminol RS-30” series (trademark: manufactured by Sanyo Chemical Industries, Ltd.), “Antox MS-60” series (trademark: manufactured by Nippon Emulsifier Co., Ltd.), and the like. Examples of the reactive surfactant having an anionic property containing a propenyl group (CH ₃ —CH═CH—) include ammonium sulfate ester of polyoxyethylene nonylpropenyl phenyl ether, and commercially available products include “ There are Aqualon HS-10 "series and Aqualon BC series (trademark: Daiichi Kogyo Seiyaku Co., Ltd.).

  Examples of the reactive surfactant having a cationic property include cationic vinyl monomers containing a structure having a cationic property such as an amine base. Examples of vinyl monomers having an amine base include neutralizing amino group-containing vinyl monomers such as allylamine, N, N-dimethylallylamine, N, N-diethylallylamine, and N, N-diethylaminopropyl vinyl ether with various acidic compounds. What can be obtained by this. Examples of the acidic compound include hydrochloric acid, formic acid, acetic acid, lauric acid and the like. Examples of commercially available reactive surfactants having cationic properties include "RF-751" (trademark: manufactured by Nippon Emulsifier Co., Ltd.) and "Blemmer QA" (trademark: manufactured by Nippon Oil & Fats Co., Ltd.).

Examples of nonionic reactive surfactants include various polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene higher fatty acid esters, and polyoxyethylene-polyoxypropylene block copolymers. Examples thereof include vinyl ethers having an ether chain in the side chain, monomers of allyl ethers or (meth) acrylic acid esters. Examples of the nonionic reactive surfactant containing an allyl group (CH ₂ ═C (—R) —CH ₂ —) (where R is an alkyl group) include polyoxyethylene allyl glycidyl nonyl phenyl ether. Examples of commercially available products include the “ADEKA rear soap NE” series (Asahi Denka Co., Ltd.). As a nonionic reactive surfactant containing a (meth) acryloyl group (CH ₂ ═C (—R) —C (═O) —O—) (where R is an alkyl group), as a commercially available product, “ RMA-560 "series (manufactured by Nippon Emulsifier Co., Ltd.)," Blenmer PE "series (manufactured by Nippon Oil & Fats Co., Ltd.) and the like. As a nonionic reactive surfactant containing a propenyl group (CH ₃ —CH═CH—), for example, polyoxyethylene nonylpropenyl phenyl ether can be mentioned, and as a commercial product, “AQUALON RN series” ( Daiichi Kogyo Seiyaku Co., Ltd. product name).

The amount of these reactive surfactants used is preferably 0.05 to 100 parts by weight, more preferably 1 to 50 parts by weight, based on 100 parts by weight of the emulsion resin solid content of the polymer compound (C). Part.
In the present invention, one of the reactive surfactants can be used alone, or two or more of the reactive surfactants can be used together. Further, the reactive surfactant is used in combination with the surfactant having no reactivity. You can also

  When the emulsion of the polymer compound (C) of the present invention is used for the production of an ink jet recording medium, the use of a dye ink having an anion group in ink jet recording is often compared with a dye ink having a cationic group. It is preferable because of high light durability. For this reason, it is preferable to add a cationic compound such as a cationic polymer or cationic particles to the coating liquid for inkjet recording media for the purpose of fixing the dye ink having the anionic group. From the viewpoint, it is more preferable to use a cationic surfactant or a nonionic surfactant in the emulsion of the polymer compound (C).

  In particular, when particles having a main component of silica (silicon oxide) such as dry silica and a cationic polymer are used as the fine particles (D) to be described later, the coating liquid can be easily prepared. From the viewpoint, it is preferable that the emulsion of the polymer compound (C) contains a cationic surfactant. The reason for this is not clear, but when the emulsion of the polymer compound (C) of the present invention contains only a nonionic surfactant, fine particles mainly composed of silica are aggregated to adjust the coating liquid. Although not easy, it was found that the inclusion of a cationic surfactant makes it difficult to form aggregates.

  The average particle size of the emulsion particles of the polymer compound (C) of the present invention is not particularly limited, but is 10 to 10 from the viewpoint of the film forming property of the upper layer of the ink receiving layer and the production efficiency of the emulsion of the polymer compound (C). The thing of 200 nm is preferable, More preferably, it is 10-100 nm. When the emulsion of the polymer compound (C) of the present invention is used in the production of an ink jet recording medium, it is particularly preferably 100 nm or less from the viewpoints of transparency and color developability of the upper layer of the ink receiving layer. The average particle size referred to here is the number average particle size of the emulsion of the polymer compound (C) measured by the dynamic light scattering method in the temperature range where the polymer compound (C) exhibits hydrophobicity.

  In the coating liquid before coating of the coating liquid for forming the upper layer of the ink receiving layer of the present invention, a core part comprising particles (E) and a shell containing the polymer compound (C) around the core part It is preferable from the viewpoint of film formability to contain particles formed by the part. The particles (E) forming the core part may be organic polymer compounds or inorganic fine particles. From the viewpoint of flexibility of the finally obtained coating film, the organic polymer compound is More preferably, inorganic fine particles are more preferable from the viewpoints of the size of the void volume of the upper layer of the finally obtained ink receiving layer, ink absorbability, and the like. Here, the periphery of the core portion means a peripheral portion of a range that moves in the medium together with the core portion.

  The polymer emulsion formed by the core part composed of the particles (E) and the shell part containing the polymer compound (C) around the core part is composed of the particles (E) as the core part in the first stage. After the synthesis by reaction, or after preparing separately prepared particles (E) to be a core part into the reaction system, it can be produced by a reaction similar to the above-described method for synthesizing the emulsion of the polymer compound (C). it can. In the present invention, the particles (E) may be any of anionic, cationic, nonionic and amphoteric, but it is more preferable that the polymer compound (C) is cationic as described above. Therefore, when polymerizing a polymer emulsion containing the polymer compound (C) in the shell part, the particles (E) are more preferably cationic from the viewpoint of polymerization stability.

The ratio (core / shell ratio (mass ratio)) between the core portion composed of the particles (E) and the shell portion containing the polymer compound (C) around the core portion is not particularly limited. The range of 1/10 to 10/1 is preferable from the viewpoint of the coating film strength and ink absorbability of the coating layer to be obtained.
When the particle (E) is an organic polymer compound, for example, conventionally known poly (meth) acrylate-based, polyvinyl acetate-based, vinyl acetate-acrylic obtained by radical polymerization, anionic polymerization, cationic polymerization, etc. in an aqueous medium , Ethylene vinyl acetate, silicone, polybutadiene, styrene butadiene, NBR, polyvinyl chloride, chlorinated polypropylene, polyethylene, polystyrene, vinylidene chloride, polystyrene- (meth) acrylate, styrene Copolymers such as maleic anhydride, three-dimensional cross-linked resins, etc., including silicone-modified acrylic, fluorine-acrylic, acrylic silicone, epoxy-acrylic, etc. Two or more kinds can be contained. Here, the (meth) acrylate type is simply a methacrylate type (or methacrylate type) or acrylate type. In particular, an ink in which an organic polymer compound classified into a poly (meth) acrylate (acrylic polymer compound) and / or polystyrene- (meth) acrylate (styrene-acrylic polymer compound) is finally obtained. It is preferably used from the viewpoints of transparency of the upper layer of the receiving layer, light yellowing resistance, and storage stability of the resulting recording medium.

  The particles (E) in the case of an organic polymer compound are preferably obtained as a polymer emulsion, and can be obtained by using a widely known production technique of a polymer emulsion. In addition to the method of dissolving the above-mentioned surfactant, emulsifying by adding the monomer components described later, adding a radical polymerization initiator and performing emulsion polymerization by a batch charging reaction, the reaction system can be applied by methods such as continuous dripping and divided addition. And a method of supplying the above copolymerization component and radical polymerization initiator to the reaction system.

  As a monomer (monomer (L)) for obtaining particles (E) in the case of an organic polymer compound, one or more of ethylenically unsaturated monomers can be used in combination. (Meth) acrylic acid esters, (meth) acrylamide monomers, vinyl cyanides, and the like. Examples of (meth) acrylic acid esters include (meth) alkyl groups having 1 to 18 carbon atoms. Acrylic acid alkyl ester, (meth) acrylic acid hydroxyalkyl ester having 1 to 18 carbon atoms in the alkyl part, (poly) oxyethylene (meth) acrylate having 1 to 100 ethylene oxide groups, number of propylene oxide groups Of 1 to 100 (poly) oxypropylene (meth) acrylates and 1 to 100 ethylene oxide groups Poly) oxyethylene di (meth) acrylate.

  Specific examples of (meth) acrylic acid alkyl esters having 1 to 18 carbon atoms in the alkyl portion include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. Examples include 2-ethylhexyl acid, cyclohexyl (meth) acrylate, methyl cyclohexyl (meth) acrylate, dodecyl (meth) acrylate, and the like. Specific examples of the hydroxyalkyl ester of (meth) acrylic acid having 1 to 18 carbon atoms in the alkyl part include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylic acid 2 -Hydroxycyclohexyl, dodecyl (meth) acrylate, and the like.

Specific examples of the (poly) oxyethylene (meth) acrylate having 1 to 100 ethylene oxide groups include (meth) acrylic acid ethylene glycol, methoxy (meth) acrylic acid ethylene glycol, (meth) acrylic acid diethylene glycol, Examples include methoxy (meth) acrylic acid diethylene glycol, (meth) acrylic acid tetraethylene glycol, and methoxy (meth) acrylic acid tetraethylene glycol. Specific examples of the (poly) oxypropylene (meth) acrylate having 1 to 100 propylene oxide groups include propylene glycol (meth) acrylate, propylene glycol methoxy (meth) acrylate, and dipropylene (meth) acrylate. Examples thereof include glycol, methoxy (meth) acrylic acid dipropylene glycol, (meth) acrylic acid tetrapropylene glycol, and methoxy (meth) acrylic acid tetrapropylene glycol.

  Specific examples of (poly) oxyethylene di (meth) acrylate having 1 to 100 ethylene oxide groups include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and methoxy (meth) acrylic acid. Examples include diethylene glycol and tetraethylene glycol di (meth) acrylate. Examples of (meth) acrylamide monomers include (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, and diacetone acrylamide. Examples of vinyl cyanides include (meta) ) Acrylonitrile and the like.

  Specific examples other than the above include, for example, olefins such as ethylene, propylene and isobutylene, dienes such as butadiene, haloolefins such as vinyl chloride and vinylidene chloride, vinyl acetate, vinyl propionate, vinyl n-butyrate, and benzoate. Carboxylic acid vinyl esters such as vinyl acid, vinyl tert-butylbenzoate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl versatic acid, vinyl laurate, carboxylic acids such as isopropenyl acetate and isopropenyl propionate Isopropenyl esters, ethyl vinyl ether, isobutyl vinyl ether, vinyl ethers such as cyclohexyl vinyl ether, styrene derivatives such as styrene and methylstyrene, aromatic vinyl compounds such as vinyl toluene, allyl acetate, allyl benzoate, etc. Allyl esters such as allyl esters, allyl ethyl ether, allyl glycidyl ether, allyl phenyl ether, γ- (meth) acryloxypropyltrimethoxysilane, vinylmethyldiethoxysilane, vinylmethyldimethoxysilane, vinyldimethylethoxysilane, Vinyldimethylmethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6 , 6-pentamethylpiperidine, perfluoromethyl (meth) acrylate, perfluoropropyl (meth) acrylate, perfluoropropylmethyl (meth) acrylate, vinyl pyrrolidone, trimethylolpropane tri (meth) ) Acrylate, glycidyl (meth) acrylate, 2,3-cyclohexene oxide (meth) acrylate, allyl (meth) acrylate, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate, methyl Carboxylic acid groups such as propanesulfonic acid acrylamide, divinylbenzene, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, butenetricarboxylic acid, monoethyl maleate, monomethyl maleate, monoethyl itaconate, monomethyl itaconate -Containing monomers, sulfonic acid group-containing monomers such as 2-acrylamido-2-methyl-propanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, (meth) acrylsulfonic acid, N, N-dimethylaminoethyl ( Data) acrylate, N, amino group-containing monomers such as N- diethylaminoethyl (meth) acrylate. Here, (meth) acryl is a simple description of methacryl (or methacryl) or acryl.

From the viewpoint of film formability of the coating layer obtained using the polymer emulsion of the present invention, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, butenetricarboxylic acid, monoethyl maleate, maleic acid Carboxylic acid group-containing monomers such as monomethyl, monoethyl itaconate and monomethyl itaconate, and sulfonic acid group-containing monomers such as 2-acrylamido-2-methyl-propanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid and (meth) acrylsulfonic acid It is preferable to use an anion group-containing monomer such as carboxylic acid group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid.

  The glass transition point of the particles (E) in the case of an organic polymer compound is not particularly limited, but the glass transition point is preferably −50 to 150 ° C. from the viewpoint of film formability, and generally to the recording medium obtained. From the viewpoint of imparting flexibility, -50 to 30 ° C is preferable. However, when the emulsion of the polymer compound (C) of the present invention is used for the production of an ink jet recording medium, when emphasizing the ink absorbability of the obtained ink jet recording medium, 30 to 130 ° C. is preferable, and the ink jet obtained When importance is attached to the flexibility of the recording medium and the transparency of the upper layer of the ink receiving layer, the glass transition point is preferably -50 to 30 ° C.

  The number average particle diameter of the particles (E) in the case of an organic polymer compound is not particularly limited, but is 3 to 150 nm from the viewpoint of the film forming property of the upper layer of the ink receiving layer and the production efficiency of the emulsion of the polymer compound (C). Are preferably used, and more preferably 10 to 100 nm. However, when the emulsion of the polymer compound (C) of the present invention is used for the production of an ink jet recording medium, from the viewpoints of transparency of the ink receiving layer upper layer, color developability and production efficiency of the polymer emulsion, The thing of 100 nm is used preferably, More preferably, it is 5-70 nm, Most preferably, it is 10-50 nm. The number average particle size referred to here is a number average particle size measured by a dynamic light scattering method.

  When the particles (E) forming the core part are inorganic fine particles, examples of the particles (E) include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, and titanium dioxide. , Zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, dry silica, alumina, colloidal alumina, pseudoboehmite-based alumina , Aluminum hydroxide, zeolite, magnesium hydroxide, and other metal oxides such as zirconium, titanium, tantalum, niobium, tin and tungsten, and metal phosphates such as aluminum, vanadium, zirconium and tungsten, etc. Part of And those obtained by substituting the elements, can also be used those obtained by modifying the surface by modifying with an organic material. Among these inorganic fine particles, one kind may be used alone, or two or more kinds may be used. In particular, it is preferable to use colloidal silica or dry silica as the particles (E).

  The use of colloidal silica or dry silica is preferable because good image quality can be obtained when printing on the resulting recording medium. It does not specifically limit as colloidal silica, Cationic colloidal silica obtained by methods, such as reacting polyvalent metal compounds, such as normal anionic colloidal silica and aluminum ion, is used. The dry silica is not particularly limited, but vapor phase silica synthesized by burning silicon tetrachloride with hydrogen and oxygen is preferably used. The dry method silica may be used as it is, or a surface modified with a silane coupling agent or the like.

Further, when the emulsion of the polymer compound (C) of the present invention is used for producing an ink jet recording medium, it is preferable to use alumina sol or pseudo boehmite-based alumina fine particles as the particles (E). By using alumina sol and pseudo boehmite-based alumina fine particles, it is possible to easily obtain a cationic polymer emulsion, improve image quality when printed on the resulting ink jet recording medium, and impart water resistance of the image. Can do.
The particles (E) forming the core part may be used as primary particles or in a state where secondary particles are formed. In addition, any particle diameter of the particles (E) forming the core part can be used, but the optical density (color density) of the printed part after printing is increased, and gloss similar to that of a silver salt photograph is obtained. For the purpose, particles (E) forming a core part having a number average particle diameter of primary particles of 200 nm or less are preferably used, more preferably 50 nm or less. The lower limit of the particle diameter of the particles (E) forming the core part is not particularly limited, but is desirably a number average particle diameter of about 3 nm or more from the viewpoint of productivity.

In the present invention, it is preferable to include a hydrophilic binder in the coating liquid from the viewpoint of the surface gloss of the upper layer of the ink receiving layer obtained and the color developability when printed using an ink jet printer.
Examples of the hydrophilic binder used in the present invention include gelatin or gelatin derivatives, polyvinyl pyrrolidone, pullulan, polyvinyl alcohol or derivatives thereof, polyethylene glycol, carboxymethyl cellulose, hydroxyethyl cellulose, dextran, dextrin, polyacrylic acid and salts thereof, agar, κ-carrageenan, λ-carrageenan, ι-carrageenan, xanthene gum, locust bean gum, alginic acid, gum arabic, pullulan, polyalkylene oxide copolymer described in JP-A-7-195826 and 7-9757 Polymer, water-soluble polyvinyl butyral, or vinyl monomers having a carboxyl group or a sulfonic acid group described in JP-A-62-245260, or these Mention may be made of the polymers of the copolymers having repeat vinyl monomers. These hydrophilic binders may be used alone or in combination of two or more.

A preferred hydrophilic binder is polyvinyl alcohol or a derivative thereof, gelatin or a gelatin derivative, and particularly preferred is polyvinyl alcohol.
As the polyvinyl alcohol preferably used in the present invention, those having an average degree of polymerization of 300 to 4000 are preferably used. Particularly, those having an average degree of polymerization of 1000 or more have good viscosity increase at the time of coating, and can be obtained. It is preferable because the film strength of the work layer is good. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, particularly preferably 80 to 100%.

When using polyvinyl alcohol, it is particularly preferable to use dry silica as fine particles (D) described later. Polyvinyl alcohol has a hydroxyl group in its structural unit, but this hydroxyl group and the silanol group on the surface of the silica fine particle form a hydrogen bond, and it is easy to form a three-dimensional network structure in which the secondary particle of the silica fine particle is a chain unit. To do. By forming the above three-dimensional network structure, a porous structure having a high porosity can be formed, and a coating layer having good ink absorbability can be obtained. Furthermore, thickening due to cooling immediately after coating is also improved by the formation of hydrogen bonds between the hydroxyl groups of polyvinyl alcohol and the silanol groups on the surface of the silica fine particles.
The ratio of the hydrophilic binder to the fine particles (D) is approximately 1:15 to 1: 1 by mass ratio, preferably 1:10 to 1: 2.

In order to obtain the ink jet recording medium of the present invention without deteriorating the high porosity of the coating layer, the hydrophilic binder is preferably hardened with a hardener.
The hardener is generally a compound having a group capable of reacting with the hydrophilic binder or a compound that promotes the reaction between different groups of the hydrophilic binder, and is appropriately selected depending on the type of the hydrophilic binder. Select and use.
Specific examples of the hardener include, for example, epoxy hardeners (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N- Diglycidyl 4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde hardeners (formaldehyde, glioxal, etc.), active halogen hardeners (2,4-dichloro-4-hydroxy-1, 3,5-s-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), boric acid and its salts, borax, aluminum alum, etc. Is mentioned.

When polyvinyl alcohol is used as a particularly preferred hydrophilic binder, from the viewpoint of the coating strength of the coating layer, at least one hardener selected from boric acid and its salts and / or epoxy hardeners is used. It is preferable to use it, and boric acid and / or borax are most preferable from the viewpoint of coating liquid thickening (gelation) immediately after coating.
The amount of the hardener used varies depending on the type of hydrophilic binder, the type of hardener, the type of inorganic fine particles, the ratio to the hydrophilic binder, and the like, but is generally 1 to 200 mg, preferably 5 mg, per 1 g of the hydrophilic binder. ~ 100 mg.

  When gelatin is used as the hydrophilic binder, the following compounds known as gelatin hardeners can be used as hardeners. For example, aldehyde compounds such as formaldehyde, glyoxal and glutaraldehyde, ketone compounds such as diacetyl and cyclopentanedione, bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1,3,5- Active halogen compounds such as triazine, 2,4-dichloro-6-S-triazine sodium salt, divinylsulfonic acid, 1,3-vinylsulfonyl-2-propanol, N, N′-ethylenebis (vinylsulfonylacetamide) ), Active vinyl compounds such as 1,3,5-triacryloyl-hexahydro-S-triazine, N-methylol compounds such as dimethylolurea and methyloldimethylhydantoin, isocyanate compounds such as 1,6-hexamethylene diisocyanate, US patent specification 301728 Aziridin compounds described in U.S. Patent No. 2,983,611, carboximide compounds described in U.S. Pat. No. 3,100,704, epoxy compounds such as glycerol triglycidyl ether, 1,6-hexamethylene -Ethyleneimino compounds such as -N, N'-bisethyleneurea, halogenated carboxaldehyde compounds such as mucochloric acid and mucophenoxycyclolic acid, dioxane compounds such as 2,3-dihydroxydioxane, chromium alum, potash Examples of such materials include zirconium, zirconium sulfate, and chromium acetate. In addition, the said hardening agent may be single 1 type, or may combine 2 or more types.

  The above hardener is preferably used by dissolving the hardener in water and / or an organic solvent from the viewpoint of ease of adjustment of the coating liquid, stability, and the like. As a density | concentration of the hardener in a hardener solution, 0.05-20 mass% is preferable with respect to the mass of a hardener solution, and 1-10 mass% is especially preferable. As a solvent constituting the hardener solution, water is generally used, and an aqueous mixed solvent containing an organic solvent miscible with water may be used. The organic solvent can be arbitrarily used as long as it can dissolve the hardener, and examples thereof include alcohols such as methanol, ethanol, isopropyl alcohol and glycerin; ketones such as acetone and methyl ethyl ketone; methyl acetate and ethyl acetate. An ester such as toluene; an aromatic solvent such as toluene; an ether such as tetrahydrofuran; and a halogenated carbon-based solvent such as dichloromethane.

  The upper layer of the ink receiving layer of the present invention may contain a polymer compound (F) that does not change in hydrophilicity or hydrophobicity due to temperature change in a system in which the polymer compound and water coexist. The polymer compound (F) is, for example, one or more monomers (monomer (L)) for obtaining particles (E) in the case of the above-mentioned submonomer (N) or organic polymer compound It is obtained by polymerizing in combination. Further, one or more of the main monomers (M) are contained within a composition that does not show a change in hydrophilicity / hydrophobicity due to a temperature change in a system in which the polymer compound (C) and water coexist. You can also The hydrophilicity or hydrophobicity of the polymer compound (F) is changed depending on whether the temperature of the system in which the polymer compound (C) and water coexist is changed gradually, or the liquid state becomes transparent or gel. Changes such as turbidity or cloudiness are visually confirmed.

When the polymer compound (F) is obtained by copolymerization of the submonomer (N) and the main monomer (M), the copolymerization ratio of the submonomer (N) and the main monomer (M) depends on the combination of the monomer species used. Although it depends, the proportion of the main monomer (M) is preferably 50% by mass or less, and more preferably 30% by mass or less. The polymer compound (F) can be contained in the polymer emulsion using the same polymerization method as that for the polymer compound (C) or the particles (E) made of an organic polymer. The polymer compound (F) may be hydrophilic or hydrophobic. When the polymer compound (F) is hydrophilic, it is preferable because better film formability can be obtained. When the polymer compound (F) is hydrophobic, a coating liquid having a higher solid content concentration can be obtained with a low viscosity, and the coating layer can be dried more efficiently and economically.

  Monomers used for obtaining the polymer compound (F) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, diacetone acrylamide, acrylic acid, methacrylic acid, and itaconic acid. , Fumaric acid, maleic acid, crotonic acid, butenetricarboxylic acid, monoethyl maleate, monomethyl maleate, monoethyl itaconate, monomethyl itaconate, 2-acrylamido-2-methyl-propanesulfonic acid, styrene sulfonic acid, (meth) acrylic Preferred examples include sulfonic acid, vinyl sulfonic acid, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, styrene, and 2-hydroxypropyl (meth) acrylate. And the like.

  From the viewpoint of the film formability of the coating layer obtained using the polymer emulsion of the present invention, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, butenetricarboxylic acid, monoethyl maleate, Carboxylic acid group-containing monomers such as monomethyl maleate, monoethyl itaconate and monomethyl itaconate, sulfonic acid groups such as 2-acrylamido-2-methyl-propane sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid and (meth) acryl sulfonic acid It is preferable to use an anion group-containing monomer such as a containing monomer, and it is particularly preferable to use a carboxylic acid group-containing monomer such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid.

From the viewpoint of easy preparation of the coating liquid of the present invention, it is more preferable that the polymer compound (F) is cationic or nonionic. The cationic polymer compound (F) can be obtained, for example, by including an ethylenically unsaturated monomer having a cationic group as a part of the submonomer (N) used for polymerization. The ethylenically unsaturated monomers having a cationic group can be used alone or in combination of two or more. In particular, the colloidal stability of the polymer emulsion obtained from the viewpoint of the degree of fading that occurs when a printed matter printed with an inkjet printer is exposed to sunlight or fluorescent light. From the viewpoint, the ethylenically unsaturated monomer having the cationic group preferably contains a tertiary amino group and / or a quaternary ammonium base. Examples and preferred examples of the tertiary amino group or quaternary ammonium base-containing monomer are the same as those of the polymer compound (C).
Furthermore, the inclusion of a tertiary amino group and / or quaternary ammonium base-containing monomer and the anion group-containing monomer can be obtained using the above-described ease of preparation of the coating liquid and the polymer emulsion of the present invention. From the viewpoint of both the film formability of the coating layer to be formed, it is particularly preferable that the anion group-containing monomer is a carboxylic acid group-containing monomer such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid.

The glass transition point of the polymer compound (F) used in the present invention is not particularly limited, but the glass transition point is preferably −50 to 150 ° C. from the viewpoints of film formability and flexibility of the obtained recording medium. When emphasizing the ink absorbability of the ink jet recording medium, 30 to 130 ° C. is preferable. When emphasizing the flexibility of the resulting ink jet recording medium and the transparency of the upper layer of the ink receiving layer, the glass transition point is −50 to 30 ° C is preferred.
The ratio of the polymer compound (F) contained in the solid content of the polymer emulsion of the present invention is not particularly limited, but from the viewpoint of the effect of changing the viscosity caused by the change in hydrophilicity and hydrophobicity of the polymer compound (C). 70 mass% or less is preferable and 40 mass% or less is more preferable.
When polymerizing the polymer compound (C), it is preferable to polymerize in the presence of polyvinyl alcohol or a polyvinyl alcohol derivative from the viewpoint of the film forming property and film forming strength of the upper layer of the ink receiving layer of the finally obtained recording medium. .

  The polyvinyl alcohol and / or polyvinyl alcohol derivative used for the polymerization of the polymer compound (C) of the present invention is not particularly limited, but as the polyvinyl alcohol, polyvinyl alcohol having a saponification degree of 96% to 100% generally called fully saponified polyvinyl alcohol is used. Examples of the alcohol include polyvinyl alcohol having a saponification degree of 76% to 95% generally called partially saponified polyvinyl alcohol, and examples of the polyvinyl alcohol derivative include silanol-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, mercapto group-containing polyvinyl alcohol, and keto group. Examples thereof include polyvinyl alcohol. One kind of polyvinyl alcohol and / or polyvinyl alcohol derivative may be used, or a plurality of kinds may be mixed and used. The polymerization degree of the polyvinyl alcohol and the polyvinyl alcohol derivative is not particularly limited, but those having a polymerization degree of 300 to 4000 are preferably used.

The use ratio of the main monomer (M) and the submonomer (N), polyvinyl alcohol and / or polyvinyl alcohol derivative is determined within the range in which the obtained polymer compound (C) exhibits temperature responsiveness. The content of polyvinyl alcohol or polyvinyl alcohol derivative in C) is not particularly limited within the range of the conditions, but from the viewpoint of water resistance of the coating film of the finally obtained recording medium, it is 0.1 to 50 mass. % Is preferably used, and more preferably 0.5 to 20% by mass.
Using a polymer emulsion containing a polymer compound (C) obtained by polymerization in the presence of polyvinyl alcohol or a polyvinyl alcohol derivative, the film formability of the upper layer of the ink receiving layer of the ink jet recording medium finally obtained, From the viewpoint of film strength, it is preferable to add a crosslinking agent capable of crosslinking polyvinyl alcohol or a polyvinyl alcohol derivative to the coating solution.

As the crosslinking agent, from the viewpoint crosslinking reaction is rapid, boron compounds are preferable, for example, borax, boric acid, borates (eg, _{orthoborate, InBO 3, ScBO 3, YBO} 3, LaBO 3, Mg _{3 (BO 3) 2, Co} 3 (BO 3) 2, diborate salts _{(e.g., Mg 2 B2O 5, Co 2} B 2 O 5), metaborate _{(eg, LiBO 2, Ca (BO 2} ) 2 , NaBO ₂ , KBO ₂ ), tetraborate (eg, Na ₂ B4O ₇ · 10H ₂ O), pentaborate (eg, KB ₅ O ₈ · 4H ₂ O, Ca ₂ B ₆ O ₁₁ · 7H ₂₎ O, CsB ₅ O ₅ ), glyoxal, melamine / formaldehyde (eg, methylol melamine, alkylated methylol melamine), methylol urea, resol resin, polyisocyanate, epoxy resin, etc. Borax, boric acid, and borate are preferable from the viewpoint of causing a crosslinking reaction.
The amount of boric acid or a salt thereof used is selected from a wide range depending on other components in the coating liquid, for example, the concentration and pH of inorganic fine particles, polyvinyl alcohol or polyvinyl alcohol derivatives, and is generally about polyvinyl alcohol. It is preferable that it is 1-60 mass%, and 5-40 mass% is still more preferable.

In addition to the polyvinyl alcohol or polyvinyl alcohol derivative, polyvinyl acetal, cellulose resin (methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, etc.), chitins, chitosans, starch, polyethylene oxide which is a resin having an ether bond, polypropylene Water-soluble resins such as oxide, polyethylene glycol, polyvinyl ether, amide group or polyacrylamide, polyvinyl pyrrolidone, polyacrylate, maleic acid resin, alginate, and gelatin having a amide bond can also be used. Polyvinyl alcohol or polyvinyl alcohol derivatives are most preferably used.

It is preferable from the viewpoint of coating strength and water resistance of the coating layer of the ink jet recording medium that the coating liquid for the recording medium contains a crosslinking agent capable of crosslinking the emulsion of the polymer compound (C) of the present invention.
In particular, it is industrially desirable that the crosslinking reaction does not proceed in the coating solution before coating, but the crosslinking reaction proceeds after coating. The reaction is preferably a reaction of a carbonyl group with a hydrazine group or a semicarbazide group. That is, it is preferable to polymerize a polymer emulsion having a carbonyl group and use a hydrazine derivative having a hydrazine group and / or a semicarbazide group as a crosslinking agent.

The carbonyl group can be contained in the polymer compound (C), can be contained in the particles (E), and further can be contained in the polymer compound (F). The polymer compound (C) containing a carbonyl group is obtained, for example, by copolymerizing a main monomer (M) and a submonomer (N) containing a monomer containing a carbonyl group. The main monomer (M) and the submonomer (N) containing a monomer containing a carbonyl group can be used alone or in combination of two or more. As for the copolymerization ratio of the main monomer (M) and the submonomer (N) containing the carbonyl group-containing monomer, the hydrophilicity and hydrophobicity of the obtained copolymeric polymer compound change reversibly at the temperature sensitive point. It is determined within a range exhibiting temperature responsiveness.
The content of the carbonyl group-containing monomer unit in the polymer compound (C) is not particularly limited, but is preferably 0.01 to 50% by mass, more preferably 0.1 to 20% by mass from the viewpoint of film formability. .

  For example, when the particle (E) is made of an organic polymer compound, the particle (E) containing the carbonyl group contains a monomer and a carbonyl group for obtaining the particle (E) in the case of the above-described organic polymer compound. It can be obtained by copolymerizing with the contained monomer. The monomer for obtaining the particles (E) in the case of the above organic polymer compound and the monomer containing a carbonyl group can be used alone or in combination of two or more. The content of the carbonyl group-containing monomer unit in the particles (E) is not particularly limited, but is preferably 0.01 to 50% by mass, more preferably 0.1 to 20% by mass from the viewpoint of film forming properties.

  The polymer compound (F) containing a carbonyl group is obtained, for example, by copolymerizing a monomer for obtaining the polymer compound (F) and a monomer containing a carbonyl group. The monomer for obtaining the polymer compound (F) and the monomer containing a carbonyl group may be used alone or in combination of two or more. The content of the carbonyl group-containing monomer unit in the polymer compound (F) is not particularly limited, but is preferably 0.01 to 50% by mass, more preferably 0.1 to 20% by mass from the viewpoint of film forming properties. .

  The carbonyl group-containing monomer is not particularly limited as long as it has a structure containing a keto group or an aldo group, but acrolein, diacetone acrylamide, diacetone methacrylamide, formylstyrene, vinyl methyl ketone, vinyl ethyl Examples include ketones, vinyl isobutyl ketone, acryloxyalkylpropanals, methacryloxyalkylpropanals, diacetone acrylate, diacetone methacrylate, acetonitrile acrylate, 2-hydroxypropyl acrylate acetyl acetate, butanediol acrylate acetyl acetate, and the like.

When the polymer compound (C), particle (E), or polymer compound (F) of the present invention contains a carbonyl group, at least two crosslinking agents are used in the coating liquid used for producing the ink jet recording medium. It is preferable to use a hydrazine derivative having a hydrazine group and / or a semicarbazide group from the viewpoints of water resistance and strength of the resulting coating film. The hydrazine derivative is added to the coating solution containing the carbonyl group-containing polymer compound (C), particle (E), or polymer compound (F) of the present invention, mixed, coated, and dried. By doing so, it is possible to obtain a coating layer containing a compound having a molecular structure in which a carbonyl group site is crosslinked by a hydrazine derivative.

  The hydrazine derivative is not particularly limited as long as it is a compound having at least two hydrazine groups and / or semicarbazide groups. Among these compounds, carbohydrazide, isophthalic acid dihydrazide, malonic acid dihydrazide, amber Acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, polyacrylic acid hydrazide, ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, Examples include butylene-1,4-dihydrazine and hydrated hydrazine, and examples of the compound having a semicarbazide group include products obtained by the reaction of a polyisocyanate compound and the hydrazine compound. That. As the hydrazine derivative, a compound having a semicarbazide group is preferable because the resulting recording medium has high water resistance. Although content of this hydrazine derivative is not specifically limited, 0.01-10 times mole amount is preferably used with respect to the carbonyl group containing monomer unit in the obtained polymer emulsion.

  The temperature sensitive point can be lowered by adding an alcohol such as ethyl alcohol to the emulsion of the polymer compound (C) of the present invention. That is, when the temperature sensitive point is room temperature or outside air temperature, by adding alcohols, the polymer compound (C) emulsion can be kept in the emulsion state at room temperature or outside air temperature. The transport and storage of the emulsion of compound (C) can be carried out very easily and economically, which is preferable. Although there is no restriction | limiting in particular as alcohol, Ethyl alcohol, methyl alcohol, n-propyl alcohol, n-butyl alcohol, isopropyl alcohol, n-pentyl alcohol, n-hexyl alcohol, ethylene glycol, propylene glycol, glycerol etc. are mentioned. However, methyl alcohol, ethyl alcohol, and isopropyl alcohol are preferably used from the viewpoint of effects. These alcohols can also be used independently and can also be used in combination of 2 or more types. In the case of ethanol, the alcohol is preferably added in an amount of usually 5 to 200 parts by mass with respect to 100 parts by mass of water in the polymer emulsion.

Including the fine particles (D) in the coating solution for the upper layer of the ink receiving layer of the present invention is preferable from the viewpoint of ink absorbability of the resulting recording medium. The fine particles (D) may be organic compounds or inorganic compounds.
When the fine particle (D) is an organic compound, for example, a conventionally known poly (meth) acrylate type, polyvinyl acetate type, vinyl acetate-acrylic type obtained by radical polymerization, anionic polymerization, cationic polymerization in an aqueous medium, Ethylene vinyl acetate, silicone, polybutadiene, styrene butadiene, NBR, polyvinyl chloride, chlorinated polypropylene, polyethylene, polystyrene, vinylidene chloride, polystyrene- (meth) acrylate, styrene-anhydrous malee Examples include acid-based copolymers, three-dimensional crosslinked resins, and silicone-modified acrylic, fluorine-acrylic, acrylic silicone, and epoxy-acrylic modified copolymers. The above can be contained. Here, the (meth) acrylate type is simply a methacrylate type (or methacrylate type) or acrylate type. In particular, an ink in which an organic polymer compound classified into a poly (meth) acrylate (acrylic polymer compound) and / or polystyrene- (meth) acrylate (styrene-acrylic polymer compound) is finally obtained. It is preferably used from the viewpoints of transparency of the upper layer of the receiving layer, light yellowing resistance, and storage stability of the resulting recording medium.

  The fine particles (D) in the case of an organic polymer compound are preferably obtained as a polymer emulsion, and can be obtained by using a widely known production technique of a polymer emulsion. In addition to the method of dissolving the above-mentioned surfactant, emulsifying by adding the monomer components described later, adding a radical polymerization initiator and performing emulsion polymerization by a batch charging reaction, the reaction system can be applied by methods such as continuous dripping and divided addition. And a method of supplying the above copolymerization component and radical polymerization initiator to the reaction system.

  As a monomer for obtaining fine particles (D) in the case of an organic polymer compound, one or more of ethylenically unsaturated monomers can be used in combination, and specifically, (meth) Acrylic acid esters, (meth) acrylamide monomers, vinyl cyanides and the like. Examples of (meth) acrylic acid esters include (meth) acrylic acid alkyl esters having 1 to 18 carbon atoms in the alkyl portion, alkyls (Meth) acrylic acid hydroxyalkyl ester having 1 to 18 carbon atoms, (poly) oxyethylene (meth) acrylate having 1 to 100 ethylene oxide groups, and 1 to 100 propylene oxide groups (Poly) oxypropylene (meth) acrylate, (poly) oxye having 1 to 100 ethylene oxide groups Di (meth) acrylate.

  Specific examples of (meth) acrylic acid alkyl esters having 1 to 18 carbon atoms in the alkyl portion include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. Examples include 2-ethylhexyl acid, cyclohexyl (meth) acrylate, methyl cyclohexyl (meth) acrylate, dodecyl (meth) acrylate, and the like. Specific examples of the hydroxyalkyl ester of (meth) acrylic acid having 1 to 18 carbon atoms in the alkyl part include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylic acid 2 -Hydroxycyclohexyl, dodecyl (meth) acrylate, and the like.

  Specific examples of the (poly) oxyethylene (meth) acrylate having 1 to 100 ethylene oxide groups include (meth) acrylic acid ethylene glycol, methoxy (meth) acrylic acid ethylene glycol, (meth) acrylic acid diethylene glycol, Examples include methoxy (meth) acrylic acid diethylene glycol, (meth) acrylic acid tetraethylene glycol, and methoxy (meth) acrylic acid tetraethylene glycol. Specific examples of the (poly) oxypropylene (meth) acrylate having 1 to 100 propylene oxide groups include propylene glycol (meth) acrylate, propylene glycol methoxy (meth) acrylate, and dipropylene (meth) acrylate. Examples thereof include glycol, methoxy (meth) acrylic acid dipropylene glycol, (meth) acrylic acid tetrapropylene glycol, and methoxy (meth) acrylic acid tetrapropylene glycol.

  Specific examples of (poly) oxyethylene di (meth) acrylate having 1 to 100 ethylene oxide groups include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and methoxy (meth) acrylic acid. Examples include diethylene glycol and tetraethylene glycol di (meth) acrylate. Examples of (meth) acrylamide monomers include (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, and diacetone acrylamide. Examples of vinyl cyanides include (meta) ) Acrylonitrile and the like.

Specific examples other than the above include, for example, olefins such as ethylene, propylene and isobutylene, dienes such as butadiene, haloolefins such as vinyl chloride and vinylidene chloride, vinyl acetate, vinyl propionate, vinyl n-butyrate, Carboxylic acid vinyl esters such as vinyl benzoate, p-t-butyl vinyl benzoate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl versatate, vinyl laurate, etc. Carboxyl such as isopropenyl acetate and isopropenyl propionate Acid isopropenyl esters, ethyl vinyl ether, isobutyl vinyl ether, vinyl ethers such as cyclohexyl vinyl ether, styrene derivatives such as styrene and methyl styrene, aromatic vinyl compounds such as vinyl toluene, allyl acetate, allyl benzoate Allyl esters, allyl ethyl ether, allyl glycidyl ether, allyl phenyl ether and other allyl ethers, γ- (meth) acryloxypropyltrimethoxysilane, vinylmethyldiethoxysilane, vinylmethyldimethoxysilane, vinyldimethylethoxysilane , Vinyldimethylmethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2, 6,6-pentamethylpiperidine, perfluoromethyl (meth) acrylate, perfluoropropyl (meth) acrylate, perfluoropropylmethyl (meth) acrylate, vinyl pyrrolidone, trimethylolpropane tri (me Acrylate), glycidyl (meth) acrylate, 2,3-cyclohexene oxide (meth) acrylate, allyl (meth) acrylate, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate, Examples include methyl propane sulfonic acid acrylamide and divinyl benzene. Here, (meth) acryl is a simple description of methacryl (or methacryl) or acryl.

  The glass transition point of the fine particles (D) in the case of an organic polymer compound is not particularly limited, but the glass transition point is preferably −50 to 150 ° C. from the viewpoint of film formability, and generally to the obtained recording medium. From the viewpoint of imparting flexibility, -50 to 30 ° C is preferable. However, in the case of the emulsion of the polymer compound (C) of the present invention, when emphasizing the ink absorbability of the resulting ink jet recording medium, it is preferably 30 to 130 ° C. The flexibility of the ink jet recording medium obtained and the ink receiving layer When importance is attached to the transparency of the upper layer, the glass transition point is preferably -50 to 30 ° C.

  When the fine particles (D) are inorganic compounds, for example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, Zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, dry silica, alumina, colloidal alumina, pseudo boehmite alumina, aluminum hydroxide, zeolite, magnesium hydroxide, Other examples include metal oxides such as zirconium, titanium, tantalum, niobium, tin, and tungsten, and metal phosphates such as aluminum, vanadium, zirconium, and tungsten. A part of the inorganic compound is substituted with another element. Things or organic It can also be used in those who modify the surface by modifying. Among these inorganic fine particles, one type may be used alone, or two or more types may be used.

  In particular, it is preferable to use colloidal silica or dry silica as the fine particles (D). By using colloidal silica or dry silica, the image quality when printed on the resulting recording medium is improved, and gloss can be imparted. It does not specifically limit as colloidal silica, Cationic colloidal silica obtained by methods, such as reacting polyvalent metal compounds, such as normal anionic colloidal silica and aluminum ion, is used. The dry silica is not particularly limited, but vapor phase silica synthesized by burning silicon tetrachloride with hydrogen and oxygen is preferably used. The dry method silica may be used as it is, or a surface modified with a silane coupling agent or the like.

Moreover, it is preferable to use alumina sol or pseudo boehmite type alumina fine particles as the fine particles (D) of the present invention. By using alumina sol and pseudo boehmite-based alumina fine particles, the image quality when printed on the resulting ink jet recording medium is improved, and the water resistance of the image can be imparted.
The fine particles (D) used in the present invention may be used as primary particles or in a state in which secondary particles are formed. Any particle diameter of the fine particles (D) can be used, but primary particles are used for the purpose of increasing the optical density (color density) of the printed part after printing and obtaining a gloss similar to silver salt photography. Fine particles (D) having a number average particle diameter of 200 nm or less are preferably used, more preferably those having a number average particle diameter of 100 nm or less, and still more preferably 50 nm or less.

Although the minimum of the particle diameter of microparticles | fine-particles (D) is not specifically limited, From a viewpoint of the manufacturing efficiency of microparticles | fine-particles (D), it is desirable that it is a number average particle diameter of about 3 nm or more. The number average particle size referred to here is a number average particle size measured by a dynamic light scattering method.
And (a) a step of producing a composite by using a metal oxide and / or a precursor thereof as a metal source as a fine particle (D), and (b) the composite. The difference between the converted specific surface area SL obtained from the number average particle diameter DL measured by the dynamic light scattering method and the nitrogen adsorption specific surface area SB by the BET method (SB-SL) ) Is more preferably 250 m ² / g or more from the viewpoint of ink absorbability of the resulting coating layer. Here, “porous” means that pores are shown in the pore distribution determined by the nitrogen adsorption method. Here, the converted specific surface area SL (m ² / g) calculated from the average particle diameter DL measured by the dynamic light scattering method assumes that the particles are spherical, and SL = 6 × 10 ³ / density ( g / cm ³ ) × DL (nm). The difference between this value and the nitrogen adsorption specific surface area SB by the BET method (SB-SL) is 250 m ² / g or more indicates that the particles are extremely porous. It is particularly preferable to use the ink jet recording medium from the viewpoint of ink absorbability.

Any particle size of the porous material can be used, but in order to obtain a recording medium having a smooth surface, those having a DL of 10 μm or less are usually used, preferably those having a particle size of 1 μm or less. Furthermore, in the production of an inkjet recording medium, fine particles (D) having a DL of 300 nm or less are used for the purpose of increasing the optical density (color density) of the printed portion after printing and obtaining a gloss similar to that of a silver salt photograph. It is preferably used, more preferably 150 nm or less.
The lower limit of the particle size of the porous material is not particularly limited, but a number average particle size of about 10 nm or more is desirable from the viewpoint of production efficiency of the porous material.

  The metal source used in the synthesis of the porous material is a metal oxide and / or a precursor thereof, and as the metal species, silicon, an alkaline earth metal such as group 2 magnesium or calcium, zinc, group 3 aluminum Gallium, rare earth, etc., Group 4 titanium, zirconium, etc., Group 5 phosphorus, vanadium, Group 7 manganese, tellurium, etc., Group 8 iron, cobalt and the like. Examples of the precursor include inorganic salts such as nitrates and hydrochlorides of these metals, organic acid salts such as acetates and naphthenates, organic metal salts such as alkylaluminums, alkoxides, and hydroxides. It is not limited to this as long as it can be synthesized by a method.

  When silicon is selected as the metal, an alkoxide such as tetraethoxysilane or activated silica can be preferably used as the metal source. The active silica can be prepared by extraction from water glass with an organic solvent or ion exchange of the water glass. Use of inexpensive water glass as a raw material is preferable from the viewpoint of industrial use. In particular, when water glass is prepared by bringing it into contact with an H + type cation exchanger, it is industrially preferable to use No. 3 water glass that has a low Na content and is inexpensive. As the cation exchanger, for example, a sulfonated polystyrene divinylbenzene-based strong acid exchange resin (for example, Amberlite IR-120B: trade name, manufactured by Rohm & Haas Co., Ltd.) is preferable, but is not particularly limited thereto.

If aluminum is selected as the metal, the metal source is preferably an alkali aluminate,
Specifically, sodium aluminate, potassium aluminate, lithium aluminate, primary ammonium aluminate, guanidine aluminate, or the like can be used.
The template is not particularly limited as long as it has an interaction with a metal source compound. However, when a nonionic surfactant is used, a template removing step, which will be described later, is used to produce the porous material. The template can be easily removed using water or a mixed solvent of water and an organic solvent.

Examples of the nonionic surfactant, the structural formula _{HO (C 2 H 4 O)} a- (C 3 H 6 O) b- (C 2 H 4 O) cH ( where, a, c are the 10 to 110, b represents 30 to 70), or a structural formula R (OCH ₂ CH ₂ ) _n OH (where R represents an alkyl group having 12 to 20 carbon atoms, and n represents 2 to 30). What is shown is preferred. Specifically, “Pluronic P103”, “Pluronic P123”, “Pluronic P85” (manufactured by Asahi Denka Kogyo Co., Ltd., surfactant: trade name), polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, poly Examples thereof include oxyethylene stearyl ether.
In order to change the pore diameter of the porous material, as an organic auxiliary, an aromatic hydrocarbon having 6 to 20 carbon atoms, an alicyclic hydrocarbon having 5 to 20 carbon atoms, an aliphatic carbonization having 3 to 16 carbon atoms Hydrogen and their amines and halogen substituents such as toluene, trimethylbenzene, triisopropylbenzene and the like can be added.

Below, the manufacturing method of this porous substance is demonstrated.
The reaction between the metal source and the template can be carried out, for example, by stirring and mixing a metal source dissolved or dispersed in a solvent and a template dissolved or dispersed in a solvent, but is not limited thereto. Absent. As the solvent, either water or a mixed solvent of water and an organic solvent may be used, and as the organic solvent, alcohols are preferable. As alcohols, lower alcohols such as ethanol and methanol are preferred.
The composition used for these reactions varies depending on the template, the metal source, and the solvent, but it is necessary to select a range in which aggregation, precipitation, etc. occur and the particle size does not increase. In order to prevent aggregation and precipitation of particles, an alkali such as NaOH or a stabilizer such as low molecular weight polyvinyl alcohol may be added.

For example, when using active silica as the metal source, “Pluronic P103” as the template, and water as the solvent, the following composition can be used. The mass ratio of P103 / SiO ₂ is preferably 0.01 to 30, more preferably 0.1 to 5. The mass ratio of organic assistant / P103 is preferably 0.02 to 100, more preferably 0.05 to 35. The mass ratio of water / P103 during the reaction is preferably in the range of 10 to 1000, more preferably 20 to 500. As a stabilizer, NaOH may be added in a range of 1 × 10 ^{−4 to} 0.15 as a mass ratio of NaOH / SiO ₂ .

When the porous material contains silicon and aluminum, the element ratio of Al / Si is preferably 0.003 to 0.1, and more preferably 0.005 to 0.05.
Although the reaction proceeds easily even at room temperature, it can be carried out under heating up to 100 ° C., if necessary. The reaction time is 0.5 to 100 hours, preferably 3 to 50 hours. The pH during the reaction is preferably in the range of 2 to 13, more preferably 4 to 12, and an alkali such as NaOH or an acid such as hydrochloric acid or sulfuric acid may be added to control the pH.

After the production of the composite, a step of denaturing by heating to 40 to 95 ° C. in the presence of alkali aluminate can also be performed. When the composite contains silicon, by performing this step, a sol that is stable even when acidified or added with a cationic substance and can withstand long-term storage can be produced. As the alkali aluminate to be used, sodium aluminate, potassium aluminate, lithium aluminate, ammonium ammonium aluminate, guanidine aluminate and the like can be used, and sodium aluminate is preferable. The denaturing step may be performed before or after removing the template from the complex.

  Hereinafter, the modification method will be described taking the case before the template removal as an example. After producing the composite, an alkali aluminate solution is added to the reaction solution. The addition is performed with stirring at 0-80 ° C, preferably 5-40 ° C. Although the density | concentration of the aluminate alkali to add is not specifically limited, It is preferable to use at 1-20 mass%. The amount to be added is preferably 0.003 to 0.1, more preferably 0.005 to 0.05, as the element ratio of Al / Si. It is preferable to heat at 40-95 degreeC after addition, and it is more preferable to heat at 60-80 degreeC. When heating at 40 ° C. or lower, when a sol is prepared, it is easily gelled when it is acidified, and sufficient stability cannot be obtained.

  Next, a template removal method will be described. A porous material is obtained by adding a solvent such as alcohol to the obtained reaction solution and removing the template from the composite using an ultrafiltration device or the like. At this time, an alkali such as NaOH or a stabilizer such as low molecular weight polyvinyl alcohol may be added to prevent aggregation of particles. The solvent used for the removal is not particularly limited as long as it dissolves the template, and alcohols that are easy to handle and have high dissolving power are preferable. As alcohols, lower alcohols such as methanol and ethanol are preferred. The removal temperature varies depending on the solvent and template used, but is preferably 20 to 80 ° C. The removed template can be reused by removing the solvent. Further, the obtained composite is separated by filtration, washed with water, dried, and then the contained template is contacted with a solvent such as a supercritical fluid or alcohol, or removed by a method such as baking. A porous material may be obtained. The baking temperature is not less than the temperature at which the template disappears, and generally not less than 500 ° C. The firing time is appropriately set in relation to the temperature, but is about 30 minutes to 6 hours. As a removal method, a method of stirring and mixing the solvent and the composite, a method of packing the composite into a column or the like and circulating the solvent can be used.

  The coating liquid for forming the upper layer of the ink receiving layer of the present invention is preferably prepared and used at a temperature exceeding the temperature sensitive point of the polymer emulsion of the polymer compound (C). That is, the coating liquid of the present invention has a relatively low viscosity at a temperature exceeding the temperature sensitive point, but the coating liquid is rapidly reduced by cooling the coating liquid to a temperature below the temperature sensitive point. To thicken (or gel). The thickening occurs when the polymer compound (C) changes from hydrophobic to hydrophilic. That is, the coating liquid of the present invention is formed on a support at a temperature exceeding the temperature sensitive point, and then rapidly cooled to a temperature below the temperature sensitive point, thereby forming a relatively low viscosity coating liquid. Can be fixed as it is by subsequent thickening (or gelation), and can maintain good coating uniformity even in the cast coating process. Obtainable.

  The coating solution for forming the upper layer of the ink receiving layer of the present invention is applied to the support at a temperature exceeding the temperature sensitive point of the emulsion of the polymer compound (C) (that is, the temperature at which the polymer compound (C) is hydrophobic). In the case of coating, the coating solution is applied to the support at a temperature lower than the temperature sensitive point (that is, the polymer compound (C) is hydrophilic) or in place of the polymer emulsion of the present invention. Compared with the case where other water-soluble polymer such as polyvinyl alcohol is used, the coating solution has a lower viscosity and a coating solution having a higher concentration can be obtained. That is, the time and energy required for drying can be saved, and a recording medium can be obtained more economically. Furthermore, when a coating liquid having a temperature exceeding the temperature sensitive point of the polymer compound (C) is applied to the support, the resulting coating layer has a high porosity and good ink absorbability, and ink jet recording. This is particularly useful when used as a medium. The reason for this is not clear, but the polymer compound (C) is hydrophobized in the coating liquid to form a polymer emulsion, which can penetrate into the fine voids effective for ink absorption and fill the voids. Since it is small, it is estimated that good ink absorbability can be expressed.

  The coating liquid for forming the upper layer of the ink receiving layer of the present invention has a relatively low viscosity at a temperature exceeding the temperature sensitive point of the emulsion of the polymer compound (C), but the coating liquid is below the temperature sensitive point. The coating liquid rapidly thickens (or gels) by cooling to the temperature of The thickening occurs when the polymer compound (C) changes from hydrophobic to hydrophilic. The cooling temperature after coating is preferably 5 ° C. or more lower than the temperature sensitive point, more preferably 10 ° C. or more, from the viewpoint of film formability and transparency of the resulting coating layer.

Furthermore, when the emulsion of the polymer compound (C) used in the present invention forms a polymer emulsion in the coating liquid before coating, the recording medium obtained using the recording medium coating liquid is: Compared with the recording medium obtained when the emulsion is not emulsified, that is, when the polymer compound (C) forms an agglomerated or coarse lump in the recording medium coating solution, it is more homogeneous and good coating. The coating film of a layer can be obtained and is preferable.
When the emulsion of the polymer compound (C) forms an emulsion in the coating solution before coating, the recording medium obtained using the coating solution is used instead of the emulsion of the polymer compound (C). In addition, surface smoothness and surface gloss compared to recording media obtained using a coating solution containing an emulsion made of a polymer compound that does not have temperature responsiveness (hydrophilicity and hydrophobicity do not change) And a good recording medium excellent in ink absorbability can be obtained.

The solvent used in the recording medium coating liquid of the present invention is not particularly limited, but water-soluble solvents such as alcohols, ketones and esters and / or water are preferably used. Furthermore, a pigment dispersant, a thickener, a flow regulator, a defoaming agent, a defoaming agent, a release agent, a foaming agent, a colorant, and the like can be blended in the coating liquid as necessary.
It is also preferred that the coating liquid for the upper layer of the ink receiving layer of the present invention comprises the emulsion of the polymer compound (C) of the present invention and at least two kinds of fine particles (D), one of which is colloidal silica. By containing colloidal silica, film formability is improved. Examples of colloidal silica include ordinary spherical colloidal silica, colloidal silica connected and / or branched in a rosary shape, and colloidal silica connected and / or branched in a rosary shape is preferably used.

  In the present invention, when colloidal silica having a shape connected and / or branched in a bead shape is used as the fine particles (D), it is preferable because not only the film forming property but also the ink absorbability are improved. Colloidal silica having a shape connected and / or branched in a bead shape is one having a long chain structure in which spherical colloidal silica is connected in a bead shape, and one in which the connected silica is branched or bent. For example, primary particles of spherical silica can be obtained by interposing particles between particles through interposition of divalent or higher metal ions. The size of the colloidal silica is not particularly limited, but the number average particle diameter measured by a dynamic light scattering method is preferably 20 to 400 nm, and more preferably 20 to 200 nm. Specifically, "Snowtex UP", "Snowtex OUP", "Snowtex PS-M", "Snowtex PSL", "Snowtex PS-S", "Snowtex PS-SO" (Nissan Chemical Industry ( Co., Ltd .: trade name) etc. are illustrated.

The primary particle size of the colloidal silica used in the present invention is not particularly limited, but those having an average particle size measured by the BET method of 4 to 100 nm are preferably used. Although the usage-amount of the colloidal silica of this invention is not specifically limited, 1-900 mass parts is used preferably with respect to 100 mass parts of microparticles | fine-particles (D) other than colloidal silica, and 5-200 mass parts is used more preferably.
It is also preferred that the coating liquid for the upper layer of the ink receiving layer of the present invention comprises the emulsion of the polymer compound (C) of the present invention and at least two kinds of fine particles (D), one of which is dry silica. Inclusion of dry silica improves ink absorbability. The dry silica used in the present invention is not particularly limited, but gas phase method silica synthesized by burning silicon tetrachloride, methyltrichlorosilane, trichlorosilane or the like with hydrogen and oxygen is preferably used. Specific examples include “Aerosil” (manufactured by Nippon Aerosil Co., Ltd .: trade name), “Leolo Seal” (manufactured by Tokuyama Corporation: trade name), and the like. The dry method silica may be used as it is, or the surface of which may be modified with a silane coupling agent or the like, or may contain a part of aluminum oxide or the like.

The primary particle diameter of dry silica used in the present invention is not particularly limited, but those having an average particle diameter measured by the BET method of 4 to 50 nm are preferably used. Although the usage-amount of the dry silica of this invention is not specifically limited, 1-900 mass parts is used preferably with respect to 100 mass parts of microparticles | fine-particles (D) other than dry silica, and 5-200 mass parts is used more preferably.
The content of the polymer emulsion of the present invention in the coating layer is not particularly limited, but in each coating layer containing the polymer emulsion of the present invention, the film formability and the coating liquid are cooled. From the viewpoint of thickening, 1% by mass or more of the solid content of the coating layer is preferable, and from the viewpoint of ink absorbability of the coating layer, the content is preferably 60% by mass or less, and preferably 2 to 30% by mass. Particularly preferred.

  In the present invention, at the time of producing the ink jet recording medium, at least one of the ink receiving layers preferably contains a cationic polymer (G). By containing the cationic polymer (G), the water resistance of the printed portion is improved. The cationic polymer (G) is not particularly limited as long as it exhibits a cationic property, but at least one of primary amine, secondary amine, tertiary amine substituents and salts thereof, and quaternary ammonium salt substituents. Those containing seeds are preferably used. Examples include dimethyldiallylammonium chloride polymer, dimethyldiallylammonium chloride-acrylamide copolymer, alkylamine polymer, polyamine dicyan polymer, polyallylamine hydrochloride, and the like. The molecular weight of the cationic polymer (G) is not particularly limited, but those having a weight average molecular weight of 1,000 to 200,000 are preferably used. Although the usage-amount of a cationic polymer (G) is not specifically limited, 0.1-200 mass parts is preferable with respect to 100 mass parts of polymer emulsion from a water resistant viewpoint of a coating film, and 10-100 mass parts is more. Preferably used. Furthermore, it is preferable to use a cationic polymer (G) having only a quaternary ammonium substituent from the viewpoint of the degree of fading that occurs when the printed matter is exposed to sunlight or fluorescent light.

  In the present invention, at the time of producing the inkjet recording medium, it is preferable that at least one of the coating layers contains an ultraviolet absorber, a hindered amine light stabilizer, a singlet oxygen quencher, and an antioxidant. By containing this substance, the light resistance of the printed part is improved. Although it does not specifically limit as an ultraviolet absorber, A benzotriazole type | system | group, a benzophenone type | system | group, a titanium oxide, a cerium oxide, a zinc oxide etc. are used preferably. The hindered amine light stabilizer is not particularly limited, but the N atom of the piperidine ring is N—R (R is a hydrogen atom, alkyl group, benzyl group, allyl group, acetyl group, alkoxyl group, cyclohexyl group, benzyloxy group, etc.) Are preferably used. The singlet oxygen quencher is not particularly limited, but aniline derivatives, organonickel-based, spirochroman-based, and spiroindane-based are preferably used. Although it does not specifically limit as antioxidant, A phenol type, hydroquinone type, organic sulfur type, phosphorus type, and amine type are used preferably. The amount of the substance used is preferably 0.0001 to 20 parts by mass with respect to 100 parts by mass of the ink receiving layer in the ink receiving layer containing the substance.

In the present invention, at the time of manufacturing the ink jet recording medium, it is preferable that at least one of the ink receiving layers contains an alkaline earth metal compound. Light resistance improves by containing an alkaline-earth metal compound. As alkaline earth metal compounds, oxides, halides and hydroxides of magnesium, calcium and barium are preferably used. The method for incorporating the alkaline earth metal compound into the ink receiving layer is not particularly limited. It may be added to the coating solution, or after the ink receiving layer is formed, the ink receiving layer may be impregnated with an aqueous solution of an alkaline earth metal compound. In the ink receiving layer containing the alkaline earth metal compound, the content of the alkaline earth metal compound is preferably 0.5 to 20 parts by mass in terms of oxide with respect to 100 parts by mass of the solid content in the ink receiving layer. .

In the present invention, it is preferable that the coating layer contains a thiocyanic acid compound because ozone resistance and light resistance can be improved. Examples of the thiocyanate compound include ammonium thiocyanate, zinc thiocyanate, calcium thiocyanate, potassium thiocyanate, sodium thiocyanate, magnesium thiocyanate, aluminum thiocyanate, lithium thiocyanate, silver thiocyanate, chloromethyl thiocyanate, and thiocyanate. Cobalt, copper thiocyanate, lead thiocyanate, barium thiocyanate, benzyl thiocyanate, and the like, and ammonium thiocyanate, zinc thiocyanate, and calcium thiocyanate are preferable in terms of further improving ozone resistance and light resistance. Particularly preferred are ammonium acid and zinc thiocyanate.
As content of said thiocyanic acid compound, 0.3-10 mass% is preferable with respect to the total solid of a coating layer, and 0.5-8 mass% is further more preferable. When the content is in the range of 0.3 to 10% by mass, it is preferable in terms of ozone resistance, water resistance, and aging blur (a phenomenon in which bleeding occurs due to the printing portion being passed for a long time). Moreover, the said thiocyanic acid compound may be used individually by 1 type, and may use 2 or more types together.

  The recording medium of the present invention is useful for recording using an ink composition containing a water-soluble dye, an oil-soluble dye, an aqueous pigment, an oily pigment and the like. Examples of the recording method include an ink jet recording method in which printing is performed by ejecting fine droplets of the ink composition to attach the ink composition to the surface of the recording medium, and printing is performed by coloring the ink composition by heating. Examples include thermal recording to be performed, gravure printing, offset printing, various other printing methods, recording with a writing instrument such as a pen, and the like. In particular, the recording medium of the present invention is preferably used for printing by an inkjet recording method. That is, the pigment (A) containing the colloidal silica of the present invention, the binder (B), the polymer compound (C), the fine particles (D), and the method for producing the recording medium of the present invention are also recorded and printed by the above recording method. It is useful when producing a preferable recording medium, and particularly useful for producing an inkjet recording medium.

Hereinafter, the present invention will be more specifically invented with reference to examples and the like, but the present invention is not limited to these examples and the like.
In the examples, “parts” and “%” mean “parts by mass” and “mass%” unless otherwise specified.
About the cast coat paper for inkjet recording obtained by each Example and each comparative example, the microcrack, intensity | strength, glossiness, and inkjet recording quality were evaluated with the following method.
(1) Microcracks Microcracks on the cast coated paper surface (the upper surface of the ink receiving layer) were observed with a 200-fold optical microscope and evaluated according to the following criteria.
○: 3 cracks or less in 4 mm square viewing angle on average of 4 fields of view Δ: 20 cracks or less in 4 mm square viewing angle on average of 4 fields of view ×: 21 cracks in 4 mm square viewing angle on average of 4 fields of view more than

(2) Strength The strength of the cast coated paper surface was cut with a cutter, and the degree of paper dust generation at that time was visually evaluated.
○: Paper dust is hardly generated.
Δ: Some generation of paper dust is observed.
X: A lot of paper dust is generated.
(3) Glossiness The glossiness of the cast coated paper surface (ink receiving layer surface) was visually observed and evaluated according to the following criteria.
○: Highly transparent glossy △: Cloudy glossy ×: Low glossiness or uneven coating

(4) Inkjet recording quality Each of dye ink and pigment ink was evaluated. When dye ink was used, a predetermined pattern was recorded by an ink jet printer (PM-G800: trade name, manufactured by Epson Corporation), and evaluated according to the following criteria. In the case of pigment ink, the same evaluation was performed using an inkjet printer (PX-G900: trade name of Epson Corporation).
(5) Ink absorbability (bleeding)
The blur at the boundary of the solid print of red and green was visually evaluated.
○: The color boundary portion is clearly separated Δ: The color boundary portion has a slight blur ×: The color boundary portion has a large blur (6) Vividness The vividness of a predetermined recorded image Was visually evaluated.
○: Vivid △: Slightly inferior x: Invisible

The particle diameter of colloidal silica was determined by the following method.
(7) Measurement of primary particle size of colloidal silica The specific surface area was determined by a nitrogen adsorption method, and calculated from the following formula (1).
Specific surface area = 4πr ² / ((4πr ³ /3)×2.2)(1)
(2.2: True specific gravity of silica (unit: g / cm ³ ))
(R: primary particle size (nm))
(8) Secondary particle size measurement of colloidal silica
Measurement was performed using ZETASIZER 3000HSA manufactured by MALVERN INSTRUMENTS.

[Example 1]
(Manufacture of support)
To a pulp slurry consisting of 100 parts hardwood bleached kraft pulp (L-BKP) with a beating degree of 285 ml, 10 parts of talc, 1.0 part of aluminum sulfate, 0.1 part of a synthetic sizing agent, and 0.02 part by weight of a yield improver. Added. Using this slurry, a base paper was made with a paper machine. In addition, starch was applied to both sides of the base paper at the time of paper making so that the solid content per side was 1.5 g / m ² to obtain a support having a basis weight of 170 g / m ² .

(Formation of lower layer of ink receiving layer)
The following coating solution A was applied to one side of this support using a blade coater so that the coating amount was 23 g / m ^2, and air-dried at 140 ° C. to form an ink-receiving layer lower layer.
Coating liquid A: As a pigment, 100 parts of synthetic silica (AZ-400: trade name of Tosoh Silica Co., Ltd.), 50 parts of polyvinyl alcohol (PVA230: trade name of Kuraray Co., Ltd.), 3 parts of boric acid , 10 parts of styrene beads (PL-30: Nippon Zeon brand name) and 5 parts of sizing agent (Polymaron 360: trade name of Arakawa Chemical Co., Ltd.) were prepared to prepare a 15% aqueous coating solution. .
Fine seal X-37: 100 parts by Tokuyama Corporation, latex (LX438)
C: 5 parts by Sumitomo Chemical Co., Ltd. (trade name), 5 parts polyvinyl alcohol (PVA117: trade name by Kuraray Co., Ltd.), sizing agent (Polymarlon 360: trade name by Arakawa Chemical Industries, Ltd.) 5 An aqueous coating solution having a concentration of 20% was prepared.

(Formation of smoothing layer)
Next, the following coating solution B is applied onto the lower layer of the ink receiving layer using a roll coater so that the coating amount is 8 g / m ^2. C was solidified, and then the coated layer was pressure-bonded to the heated mirror-finished surface via a press roll to copy the mirror surface to form a smoothing layer.
Coating liquid B: 100 parts of colloidal silica (PL1: trade name manufactured by Fuso Chemical Industry Co., Ltd.) having an average primary particle size of 14 nm as a pigment, and polyvinyl alcohol A (Kuraray 224: manufactured by Kuraray Co., Ltd.) having a polymerization degree of 2400 as a binder. Product name) and polyvinyl alcohol B having a polymerization degree of 2600 (MA26GP: trade name manufactured by Shin-Etsu Chemical Co., Ltd.) in total 10 parts (mixing mass ratio is 1: 1), cationic polyurethane (F8570D2: Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts of a product name), 3 parts of an ink fixing agent (Saftmer ST3300: manufactured by Mitsubishi Chemical Industries) and 0.2 part of an antifoaming agent were blended to prepare a coating solution having a concentration of 28%.
Coagulating liquid C: A coagulating liquid was prepared by blending a total concentration of borax and boric acid of 4% and a release agent (FL-48C: manufactured by Toho Chemical Co., Ltd.) 0.2%. The blending mass ratio of borax and boric acid was 1, and the total concentration was a value obtained by converting borax into Na ₂ B ₄ O ₇ and boric acid with H ₃ BO ₃ .

(Formation of upper layer of ink receiving layer)
Next, the following coating liquid D is applied onto the smoothing layer using a roll coater so that the coating amount is 8 g / m ^2, and cold air of 10 ° C. is applied while the coating layer is in a wet state. Then, the coating layer was pressure-bonded to the heated mirror-finished surface via a press roll, and the mirror surface was copied to form an upper layer of the ink receiving layer.
Coating liquid D: Water is added to dry silica (manufactured by Nippon Aerosil Co., Ltd., A300: trade name, hereinafter referred to as A300) to a solid content of 18% by mass, and dispersed using an ultrasonic disperser. After that, 20% by mass aqueous solution of cationic polymer (Asahi Denka Kogyo Co., Ltd., Adekathioace DM-20A: trade name) was added so that the dry silica / cationic polymer = 100/5 (dry mass ratio). Then, it was again dispersed using an ultrasonic disperser. To this dispersion, polymer compound 1 obtained in Preparation Example 1 below was added at 50 ° C. in a ratio of A300 / polymer compound 2 = 100/25 (dry mass ratio), and a coating solution having a concentration% was added. It was adjusted.

  Preparation Example 1: 360 parts of water was added to a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a thermometer, and the inside of the reaction vessel was brought to 80 ° C. Next, 25 parts of 25% aqueous solution of “Coatamine 86W” (manufactured by Kao Corporation, cationic surfactant: trade name), “Emulgen 1135S-70” (manufactured by Kao Corporation, nonionic surfactant: commodity No.) 70% aqueous solution and N, N-dimethylaminopropylacrylamide methyl chloride quaternary salt 70% aqueous solution 4 parts were added into the reactor. Further, 8 parts of a 5% aqueous solution of 2,2′-azobis (2-methylpropionamidine) dibasic acid salt was charged into the reactor, and after 5 minutes, 9 parts of methyl methacrylate, 9 parts of butyl acrylate, A mixture of 9 parts of styrene, 2 parts of diacetone acrylamide and 2 parts of 2-hydroxyethyl methacrylate was continuously added to the reactor over 30 minutes. The addition was performed while keeping the inside of the reaction vessel at 80 ° C.

The number average particle size of the emulsion at this stage was 11 nm. Subsequently, 290 parts of N-isopropylacrylamide, 10 parts of diacetone acrylamide, 0.5 parts of methylenebisacrylamide, 5 parts of 70% aqueous solution of methyl quaternary salt of N, N-dimethylaminopropylacrylamide methyl chloride, “Cotamine 86W 10 parts of a 25% aqueous solution, 15 parts of a 25% aqueous solution of “Blemmer QA” (manufactured by NOF Corporation, cationic reactive surfactant: trade name) and 2,2′-azobis (2-methylpropionamidine) ) A solution in which 11 parts of a 5% dibasic acid solution was dissolved was added to the reaction vessel, and the addition was completed over 5 hours. The liquid temperature in the reaction vessel was kept at 80 ° C. during the addition and 1 hour after the addition was completed, and then cooled to 50 ° C., and 1000 parts of a 60% aqueous solution of ethanol was gradually added into the reaction vessel. After completion of the addition of the ethanol aqueous solution, the emulsion was cooled to room temperature to form an emulsion having a resin solid content of 11% and a number average particle size of 100 nm, and a polymer compound 1 having a temperature sensitive point of 30 ° C. was obtained.

[Example 2]
Ink for ink jet recording was carried out in the same manner as in Example 1, except that in the coating liquid B, colloidal silica having an average primary particle size of 23 nm (PL2: trade name manufactured by Fuso Chemical Co., Ltd.) was blended instead of the colloidal silica. Coated paper was obtained.
Example 3
Ink for ink jet recording was carried out in the same manner as in Example 1, except that in the coating liquid B, colloidal silica having an average primary particle size of 35 nm (PL3: trade name manufactured by Fuso Chemical Co., Ltd.) was blended instead of the colloidal silica. Coated paper was obtained.

Example 4
Example except that the ink receiving layer lower layer using the coating liquid A was not formed and the coating liquid B was directly coated on a base paper having a basis weight of 170 g / m ² so that the coating amount was 20 g / m ^2. In the same manner as in No. 1, a cast coated paper for ink jet recording was obtained.
Example 5
After coating the coating liquid B, cast coated paper for inkjet recording was obtained in exactly the same manner as in Example 1, except that the smoothing layer was formed by blowing and drying at 140 ° C.
Example 6
After coating the coating liquid B, cast coated paper for inkjet recording was obtained in exactly the same manner as in Example 4 except that a smoothing layer was formed by blowing and drying at 140 ° C.

Example 7
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the following coating liquid E was used in place of the coating liquid D.
Coating liquid E: Water is added to dry silica (manufactured by Nippon Aerosil Co., Ltd., A300: trade name) to a solid content of 18% by mass and dispersed using an ultrasonic disperser, and then the cationic polymer (Asahi Denka Kogyo Co., Ltd., Adeka thioace DM-20A: trade name) A 20% by mass aqueous solution was added so as to be dry silica / cationic polymer = 100/5 (dry mass ratio), and then again ultrasonic. Dispersion was performed using a disperser. A 15% aqueous solution of polyvinyl alcohol (PVA230: trade name of Kuraray Co., Ltd.) was added to the dispersion at a rate of A300 / PVA230 = 100/25 (dry mass ratio) at a concentration of 18%. The coating solution was adjusted.
About the cast coated paper for inkjet recording obtained in each Example and the comparative example, the operativity at the time of cast coating, glossiness, and inkjet recording quality were evaluated with the following method.

[Comparative Example 1]
Ink jet recording was carried out in the same manner as in Example 1 except that the smoothing layer using the coating liquid B was not formed and the coating liquid D was directly applied onto the lower layer of the ink receiving layer using the coating liquid A. A cast coated paper was obtained.
[Comparative Example 2]
Ink for ink jet recording was carried out in the same manner as in Example 1, except that in the coating liquid B, colloidal silica having an average primary particle size of 52 nm (PL5: trade name manufactured by Fuso Chemical Co., Ltd.) was blended in place of the colloidal silica. Coated paper was obtained.

[Comparative Example 3]
Ink coating for ink jet recording was carried out in the same manner as in Example 1 except that in the coating liquid B, colloidal silica having an average primary particle size of 70 nm (PL7: trade name manufactured by Fuso Chemical Industries) was blended instead of the colloidal silica. Coated paper was obtained.
[Comparative Example 4]
Example in which coating liquid B was replaced with spherical colloidal silica having a mean primary particle diameter of 15 nm (Snowtex AK: trade name, non-agglomerated silica manufactured by Nissan Chemical Industries, Ltd.) instead of colloidal silica. In the same manner as in No. 1, a cast coated paper for ink jet recording was obtained.
The obtained results are shown in Table 1.

As is clear from Table 1, in each example, the microcrack, the strength is good, and the ink jet recording quality is good regardless of whether the dye ink or the pigment ink is used. was gotten.
On the other hand, in the case of Comparative Example 1 in which a smoothing layer using colloidal silica was not formed, and spherical colloidal silica having a ratio of secondary particle diameter to primary particle diameter of less than 1.5 (secondary particles exist without agglomeration) In the case of Comparative Example 4 in which the primary particle size = secondary particle size was used for the smoothing layer for convenience, many microcracks in the upper layer of the ink receiving layer were generated, and vividness when recording by inkjet Decreased. In the case of Comparative Example 4, the ink absorbability was also lowered. In the case of Comparative Examples 2 and 3 where the primary particle diameter of colloidal silica exceeded 50 nm, the vividness when recorded by inkjet was lowered.

  The ink jet recording medium according to the present invention is preferably used for printing by an ink jet recording method using an ink composition containing a water-soluble dye, an oil-soluble dye, an aqueous pigment, an oily pigment and the like.

Claims (7)

  A pigment (A) containing colloidal silica having a primary particle diameter of 10 to 50 nm and a ratio of the secondary particle diameter to the primary particle diameter of 1.5 to 2.5 is formed on at least one surface of the support. An ink jet recording medium comprising: a smoothing layer containing an adhesive (B); and an ink receiving layer upper layer provided directly on the smoothing layer.   In the coating liquid forming the upper layer of the ink receiving layer, the polymer compound (C) and the fine particles (D) exhibiting hydrophilicity in a temperature region below the temperature sensitive point and hydrophobic in a temperature region exceeding the temperature sensitive point, The ink jet recording medium according to claim 1, comprising:   At least one coated ink-receiving layer lower layer is provided on at least one surface of the support, a smoothing layer is provided thereon, and an ink-receiving layer upper layer is provided immediately thereon, so that at least three layers are provided. The inkjet recording medium according to claim 1, wherein the inkjet recording medium has a structure.   A coating solution for forming a smoothing layer according to claim 1 is applied to provide a coating layer, and the coating layer in a wet state is pressed onto a heated mirror surface and dried to provide a smoothing layer. The method for producing an ink jet recording medium according to any one of claims 1 to 3.   The coating liquid which forms the smoothing layer of Claim 1 is applied, a coating layer is provided, this coating layer in a wet state is pressure-bonded to a heated mirror surface and dried, and the resulting smoothing A coating solution for forming the upper layer of the ink receiving layer is applied immediately above the layer to provide a coating layer, and the coated layer in a wet state is pressed onto a heated mirror surface and dried to provide an upper layer of the ink receiving layer. The method for producing an ink jet recording medium according to claim 1, wherein   An inkjet recording medium manufactured by the manufacturing method according to claim 4.   An ink jet recording medium manufactured by the manufacturing method according to claim 5.