JPH1094754A - Recording medium and manufacturing method thereof - Google Patents

Abstract

[PROBLEMS] To provide a recording medium in which a porous layer made of alumina hydrate is formed on a base material with a coating solution that is stable over time, and that the ink receiving layer is thin, inexpensive and of high quality. Recording media having high glossiness, and methods for producing them. A recording medium having, on a substrate, a porous layer containing alumina hydrate particles and nonionic or cationic water-insoluble resin particles having an average particle size of 0.005 to 0.1 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium, and more particularly to a recording medium for ink jet and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, overhead projectors have become the mainstream in place of conventional slide projectors for presentations at various academic meetings and conferences. Also in the field of printing, transparent printed matter has been demanded for various publications, packaging and the like. Printing and printing on these transparent films requires special considerations in terms of printing speed and drying compared to printing on general paper because the film itself, which is the base material, has no absorbency. .

On the other hand, JP-A-2-276670 and JP-A-4
JP-A-320877 reports that a recording sheet in which an ink receiving layer made of alumina hydrate is provided on a transparent, non-absorbing base material can be suitably used as a recording medium. This recording sheet is provided with a layer made of porous alumina hydrate that mainly absorbs and fixes the dye in the ink on a transparent substrate such as polyethylene terephthalate (hereinafter referred to as PET). This porous alumina hydrate layer is formed by applying an alumina sol composed of boehmite crystal particles and a coating liquid composed of a polyvinyl alcohol-based binder to a substrate, followed by drying.

[0004] However, a coating solution comprising an alumina sol and a polyvinyl alcohol-based binder tends to increase in viscosity with time, and particularly in the case of a coating solution having a high solid content, the handling properties are poor, and the coating operation and the like are difficult. there were. In addition, when the coating liquid is kept at a high temperature to suppress a rise in viscosity, particularly during continuous coating work, gelation and agglomerates accumulate in local areas of the coater head of the coating machine due to evaporation. There is a problem that the accumulated matter causes the appearance defect of the recording sheet.

[0005] The ink-receiving layer made of the above-mentioned alumina hydrate can be formed on a paper base material. In particular, by using a method such as cast coating or calendering, it has a smooth surface. Glossy paper with high gloss can be obtained. However, in order to enhance the ink absorbency and color reproducibility of this glossy paper, the thickness of the ink receiving layer must be 20 μm or more, which is sufficient in the glossy paper market where low price is required. Did not. This is because the transfer speed of the ink between the ink receiving layer and the paper substrate is low, and it is necessary to absorb most of the ink only by the ink receiving layer.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording medium having excellent image quality by using an alumina coating liquid which is stable over time and can be continuously worked. In addition, the present invention provides a high ink transfer rate between the ink receiving layer and the base material, a high ink absorption, a high color density, and a high glossiness even when the thickness of the ink receiving layer is 15 μm or less, and even 10 μm or less. It is an object of the present invention to provide a high-quality recording medium, particularly high-quality glossy paper.

[0007]

According to the present invention, there is provided a porous material comprising alumina hydrate particles and nonionic or cationic water-insoluble resin particles having an average particle diameter of 0.005 to 0.1 μm on a substrate. Recording medium characterized by having a recording layer.

[0008] In the present invention, the alumina hydrate particles are:
When a porous layer is formed by coating on the surface of a recording medium, any material can be used as long as it can effectively absorb the solvent and the like in the ink, but boehmite (AlOOH)
Is particularly preferred. The secondary aggregation diameter is preferably 100 to 200 nm in order to form a transparent porous alumina hydrate layer and to obtain a recorded matter having a high color density.

In the present invention, the alumina hydrate particles in the porous layer are preferably formed from alumina sol, and particularly preferably the sol particles are boehmite.
In addition, nonionic or cationic water-insoluble resin particles having an average particle diameter of 0.005 to 0.1 μm are preferably mixed with the alumina sol as an aqueous dispersion. The mixture has excellent dispersibility and low viscosity. When this mixture is applied on a substrate, a highly transparent porous layer can be formed. At this time, the resin particles function as a binder.

[0010] Alternatively, the mixed liquid may be aggregated to form aggregated particles, and the aggregated particles may be coated on a substrate to form a porous layer. At this time, it is preferable that the aggregated particles be coated on a substrate together with an organic binder different from the resin particles. By forming the porous layer with the aggregated particles, the transfer speed of the ink from the porous layer to the base material is increased, and when the base material itself has ink absorbency, the thickness of the coating layer is 15 μm or less. However, it is possible to obtain a recording medium having good ink absorbability and high dye fixability.
Further, the thickness of the coating layer can be set to 10 μm or less. Here, as a substrate having ink absorbability, high-quality paper for printing paper, high-quality foam paper for information paper, PPC paper,
Or paper or the like having the same ink absorbency as these is preferable.

In the case of forming aggregated particles, it is preferable that the mixture of the alumina sol and the dispersion of the water-insoluble resin particles be rapidly dried by spray drying. Agglomerated particles obtained by rapid drying preferably have an average particle size of 1 to 20 μm. When the thickness is less than 1 μm, the transfer speed of the ink from the porous layer to the paper substrate becomes slow, and the ink absorbency of the recording medium when the thickness of the porous layer is reduced may be insufficient. On the other hand, if it exceeds 20 μm, irregularities are likely to be formed on the surface of the recording medium, and the glossiness may be lowered, which is not preferable. More preferably, it is 1 to 15 μm.

In the spray drying, a spray dryer is used. In order to keep the particle size of the aggregated particles within the above range, it is preferable to use a spray dryer of a pressurized two-fluid nozzle system.

The agglomerated particles are then dispersed in water. At this time, according to the present invention, since the aggregated particles themselves have water resistance, the aggregated particles are dispersed in water while maintaining the aggregated state. Further, it is preferable that an organic binder is added to this aqueous dispersion to form a coating liquid.

Examples of the organic binder include polyvinyl alcohol and modified products thereof, starch and modified products thereof, S
Water-soluble polymers such as BR latex (styrene-butadiene copolymer rubber latex), NBR latex (acrylonitrile-butadiene copolymer rubber latex), carboxycellulose, and polyvinylpyrrolidone can be used. The amount of the organic binder used is preferably about 5 to 50% by weight of the alumina hydrate particles forming the aggregated particles contained in the coating liquid. When the amount of the binder used is less than 5% by weight, the layer strength may be insufficient. On the other hand, when the amount is more than 50% by weight, the ink absorption or the dye adsorption may be insufficient.

It is preferable that the recording medium having the porous layer formed by applying the above-mentioned coating solution on a substrate has a 60 ° specular glossiness of 30% or more specified in JIS Z8741. More preferably, the 60 ° specular gloss is 40% or more. In particular, when the base material is paper, it can be used as glossy paper.

As a method for obtaining a recording medium having such a high glossiness, the above-mentioned coating solution is applied to the surface of a substrate, a mold having a smooth surface is pressed against the coating layer, dried, and then the mold is peeled off. Thereby, a coating layer is formed on the base material. The mold having a smooth surface is preferably peeled off after drying until the amount of water in the coating layer is preferably 100 to 450% by weight with respect to the solid content. For a mold with a smooth surface, 5
Preferably, the mold is heated to 0 to 150 ° C., and a mold having a smooth surface is brought into close contact with the coating layer at a linear pressure of 2 to 50 kg / cm,
After drying, the mold is preferably peeled off.

The embossing on the surface on which the coating layer is formed can be performed not only in a batch system but also in a continuous system using, for example, a rotating roll as a smooth surface mold. The application and the embossing of the coating liquid can be continued to perform the continuous operation.

The above-mentioned high gloss recording medium is prepared by applying a coating solution to the surface of a smooth mold, pressing a substrate against the surface on which the coating layer is formed, and drying the substrate to form an alumina hydrate layer. Is formed, then the mold is peeled off, and the alumina hydrate layer is transferred and transferred from the mold to the substrate. As a material of the mold, a plastic such as PET or polycarbonate, a metal, or the like can be employed without particular limitation.

In the present invention, the average particle size is 0.005 to 0.5.
The content of the nonionic or cationic water-insoluble resin particles of 1 μm is preferably 2 to 50% by weight in terms of solid content based on the alumina hydrate particles. If it exceeds 50% by weight, the ink absorption of the porous layer may be impaired, which is not preferred. If the content is less than 2% by weight, the mechanical strength becomes insufficient when used as a binder, and when the aggregated particles are formed, the aggregated state of the aggregated particles cannot be maintained when the aggregated particles are dispersed in water. On the other hand, if the thickness of the porous layer is reduced, the ink absorbency of the recording medium may be insufficient. Particularly, when it is used as a binder, it is more preferably 5 to 50% by weight, and when it forms aggregated particles, it is 2 to 35% by weight.

The resin particles in the present invention must be nonionic particles having no charge on the surface or cationic resin particles having a positive charge on the surface. Especially,
The cationic type is preferred. These nonionic or cationic resin particles form a stable aqueous dispersion under acidic conditions of pH 8 or less, preferably pH 6 or less.

In the present invention, specifically, a polymer composed of a cationic acrylic polymer (the acrylic polymer includes a methacrylic polymer in the present invention) is preferably used.
The cationic resin particles have groups such as amines and quaternary ammoniums, and a positive charge is obtained by ionization of these groups. Among such cationic acrylic polymers, those having a molecular weight of 10,000 or more are preferred from the viewpoint of the water resistance and weather resistance of the alumina hydrate layer.
In the case of an anionic acrylic polymer composed of an acrylate or the like, aggregation of alumina hydrate may occur due to electrostatic reasons, and a stable coating liquid may not be obtained. Also,
In the case of a general nonionic acrylic polymer composed of an acrylic ester such as an alkyl acrylate, the mechanical strength of the polymer itself is sufficient, but the adhesion between the alumina hydrate layer and a base material such as PET. It may be inferior in sex.

In particular, composite-type resin particles having a core / shell structure are preferred from the viewpoint of the mechanical strength of the porous layer and the adhesiveness to the substrate. The core portion is preferably made of a polymer having an acrylic acid ester such as an alkyl acrylate as a polymerized unit. The shell part is, for example, N,
Having acrylic acid derivatives such as acrylates or acrylamides having a tertiary amino group such as N-dimethylaminoethyl acrylate or N, N-dimethyl-N'-acryloyl-propane-1,3-diamine as polymerized units. It is preferable that the polymer be composed of a polymer obtained by cationizing the polymer. A polymer having a cationic acrylic acid derivative having a quaternary ammonium cation or the like as a polymerization unit may be used. In the present invention, the water-insoluble resin particles are 5
It is preferably used in the form of an aqueous dispersion of up to 50% by weight.

The average particle size of the resin particles in the present invention is:
It is 0.005 to 0.1 μm. If the average particle size is larger than the above range, the porous layer becomes opaque, and the recording medium does not become transparent even if the substrate is transparent. Further, even when the substrate is opaque, there may be a problem that a high-quality image that does not impair the texture of the substrate cannot be obtained. Conversely, if the average particle size is smaller than the above range, the mechanical strength becomes insufficient particularly when used as a binder. Preferably 0.01 to 0.0
5 μm.

In the present invention, when a porous layer is formed substantially from alumina hydrate particles and nonionic or cationic water-insoluble resin particles having an average particle diameter of 0.005 to 0.1 μm, the fineness of the porous layer is reduced. The pore structure has a radius of substantially 1-20 n
m. Further, when the pore volume is 0.3 to 1.2 ml / g, it is preferable because it has sufficient absorbency and the porous layer also has transparency. At this time, if the substrate is transparent, a transparent recording medium can be obtained. Even when the substrate is opaque, a high-quality image that does not impair the texture of the substrate can be obtained. The measurement of the pore size distribution in the present specification is based on the nitrogen adsorption / desorption method.

Desirably, in addition to these physical properties, the alumina hydrate layer preferably has an average pore radius of 4.5 to 9.0 nm, and more preferably has an average pore radius of ± 1 nm. Is preferably 50% or more of the total pore volume, particularly from the viewpoint of achieving both fixing property and transparency of the dye.

In the present invention, the average particle diameter is 0.005 to 0.005.
0.1 μm nonionic or cationic water-insoluble resin particles are used as a binder, and a coating liquid composed of the resin particles and alumina hydrate particles is kept at a normal temperature of 5 to 35 ° C. after being prepared. . Since this coating liquid has a small change in viscosity with time and is stable, long-term continuous application is possible with the coating liquid set. In addition, the coating liquid may contain a binder and other additional components as required, in addition to the resin particles.

In the method of applying the coating liquid, it is preferable that the coating liquid is applied onto the substrate by using a bar coater, a rod coater, a blade coater, a comma coater, a roll coater, a die coater, an air knife coater, a floating knife coater or the like. The thickness of the coating layer can be appropriately selected depending on the specifications of each printer and the like, the type of ink and its solvent used for recording, the amount of ink, and the like.

In the present invention, the porous layer may be a single layer containing alumina hydrate and water-insoluble resin particles. However, in order to improve the scratch resistance of the surface, alumina hydrate and water-insoluble resin are used. A silica layer formed by applying a silica sol may be provided on the layer containing particles. When the thickness of the layer containing alumina hydrate and the water-insoluble resin particles is small, a surface layer made of alumina hydrate may be provided to optimize the dot diameter formed by inkjet printing. it can. Here, the surface layer made of alumina hydrate may be the same as or different from the layer containing alumina hydrate and water-insoluble resin particles in the present invention. If necessary, a substance having water repellency or hydrophilicity can be mixed in the surface layer made of silica or alumina hydrate.

In the present invention, the mechanism by which the increase in the viscosity of the mixed solution of the alumina sol and the aqueous dispersion of the nonionic or cationic water-insoluble resin particles is suppressed to be stable is not clearly understood. It seems that the viscosity is appropriately adjusted by the interaction of the water-insoluble resin with the alumina sol.

Further, although the structure of the porous alumina hydrate layer obtained after applying and drying the coating liquid substantially consisting of the above mixed liquid is not clearly understood, resin particles having a small average particle diameter are used. In particular, by reducing the average particle diameter of the resin particles compared to the secondary aggregation diameter of the alumina hydrate particles, an appropriate porous layer is formed, and a transparent alumina hydrate layer is obtained. Conceivable.

When a thin porous layer is formed on an ink-absorptive base material by a coating liquid composed of agglomerated particles formed from the above mixed liquid, the porous layer having large pores is formed. As a result, the transfer speed of the ink from the porous layer to the base material is increased. On the other hand, since the aggregated particles are particles in which alumina hydrate particles are uniformly dispersed, it is considered that the fixing property of the dye is high and the color reproducibility is excellent. The recording medium of the present invention is a recording medium particularly suitable for an ink jet printer.

[0032]

EXAMPLES Examples and comparative examples of the present invention will be described below. In the following, the solid concentration of the alumina sol is 14
It refers to the concentration calculated based on the solid matter dried at 0 ° C. to a constant weight. In Examples 6 to 10, the glossiness was measured at an angle of 60 ° using a gloss meter 300A manufactured by Nippon Denshoku Co., Ltd.

The water resistance of the agglomerated particles in Examples 6 to 10 was evaluated by the rate at which the agglomerated state of the agglomerated particles was maintained when the agglomerated particles were exposed to water.
Specifically, the agglomeration rate as defined below was used as an evaluation criterion.

2 g of the dried aggregated particles were placed in a 100 cc centrifuge tube, and 50 g of water was further added and stirred to disperse the aggregated particles in water. 2000 rpm
After centrifugation for 5 minutes at, the supernatant was removed and the remaining sediment was dried, and the ratio of the weight of the dried sediment to the weight of the initially dried aggregated particles was expressed as a percentage. Was taken as the agglomeration rate. That is, agglomeration rate (%)
= (Sediment weight / 2) x 100.

Example 1 (Example) A precipitate obtained by hydrolyzing aluminum isopropoxide is peptized to obtain alumina hydrate particles having an average secondary aggregate diameter of 170 nm.
An alumina sol containing 9% by weight was obtained. Next, 95 g of an aqueous dispersion of a cationic acrylic resin particle having a solid content concentration of 30% by weight (Acryt UW-129EX manufactured by Taisei Kako Co., average particle size 0.01 μm) was added to 500 g of the alumina sol.
Was added and mixed by stirring to obtain a coating liquid. The viscosity of this coating solution was 45 cP at 20 ° C., and no increase in viscosity was observed even after holding for 12 hours. Next, this coating solution was applied on a transparent PET having a thickness of 100 μm by a bar coater and dried to obtain a transparent recording sheet having a porous alumina hydrate layer.

Example 2 (Comparative Example) An aqueous dispersion of anionic acryl / urethane resin particles having a solid content of 40% by weight (Acryt WEM-141 manufactured by Taisei Kako, average particle size) was added to 500 g of the same alumina sol as in Example 1. Diameter 0.1μm) 7
1.3 g was added and mixed by stirring. Immediately after the completion of the addition, a gel-like aggregate precipitated, and a stable coating liquid was not obtained.

Example 3 (Comparative Example) An aqueous dispersion of cationic acrylic resin particles having a solid content of 39.5% by weight (Boncoat SFC-241 manufactured by Dainippon Ink and Chemicals, Inc.) was added to 500 g of the same alumina sol as in Example 1. , Average particle size 0.2μ
m) 72.2 g was added and mixed with stirring to obtain a coating liquid. The viscosity of this coating solution at 5 ° C. was 52.5 cP. After holding for 8 hours, the viscosity was stable with almost no increase. Next, in the same manner as in Example 1, this coating solution was applied on a transparent PET having a thickness of 100 μm using a bar coater and dried to obtain a recording sheet having a porous alumina hydrate layer. This recording sheet was white and did not become transparent.

Example 4 (Example) A precipitate obtained by hydrolyzing aluminum isopropoxide is peptized to obtain alumina hydrate particles having an average secondary aggregate diameter of 190 nm.
An alumina sol containing 0% by weight was obtained. Next, 120 g of the same aqueous dispersion of the cationic acrylic resin as in Example 1 was added to 600 g of the alumina sol, followed by stirring and mixing to obtain a coating liquid. The viscosity of this coating solution was 43 cP at 23 ° C. Then, a 100 μm-thick PE was coated with a bar coater.
This coating solution was applied on T and dried to obtain a recording sheet having a porous alumina hydrate layer having a thickness of 30 μm.

The recording sheet was placed outdoors, and an exposure test was performed under sunlight, wind and rain. Three months after the exposure, the porous alumina hydrate layer maintained the same form as immediately after application and drying, and no deterioration of the recording sheet was observed.

Example 5 (Comparative Example) 600 g of the same alumina sol as in Example 4 was heated to 55 ° C., and polyvinyl alcohol (PVA-124 manufactured by Kuraray Co., Ltd.) was added at 11% by weight to the alumina hydrate particles. Add water, stir and mix,
A coating liquid having a solid content of 16.5% by weight was obtained. The viscosity of this coating solution was 52 cP at 55 ° C. Using this coating liquid, a recording sheet having a porous alumina hydrate layer having a thickness of 30 μm was obtained in the same manner as in Example 4.

When the same exposure test as in Example 4 was performed on this recording sheet, cracks were formed on the entire surface of the porous alumina hydrate layer after one month, and three months after the exposure, the PET was converted to an alumina hydrate layer. Peeled off.

Example 6 (Example) To 100 parts by weight (solid content) of the same alumina sol as in Example 4, 5 parts by weight (solid content) of the same aqueous dispersion of the cationic acrylic resin as in Example 1 were added. Water was added to prepare a preparation having a solid concentration of 10% by weight. The prepared liquid was rapidly dried using a pressurized two-fluid nozzle type spray dryer (Papyrus GB22, manufactured by Yamato Scientific Co., Ltd.) to obtain dried aggregated particles. At this time, the average particle diameter of the aggregated particles was 6 μm, and the agglomeration rate was 90%.

Next, 20 parts by weight of the agglomerated particles were added to 80 parts by weight of water while stirring and dispersed completely, and polyvinyl alcohol (MA26G, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a binder.
P) was added so as to be 10% by weight based on the aggregated particles,
Further, water was added to obtain a coating liquid having a solid concentration of 16.5% by weight. The coating liquid was applied on a base material made of high-quality paper having a basis weight of 157 g / m ^{2 using} a bar coater so that the dry coating amount was 8 g / m ² . The water content immediately after coating was 506% by weight based on the solid content in the coating layer. This was dried to reduce the water content to 300%.

A mold having a mirror surface heated to 90 ° C. was adhered to the coating layer at a linear pressure of 10 to 20 kg / cm, dried, and then the mirror surface was peeled off to obtain a coated paper. The thickness of the coating layer of this coated paper was 10 μm, and the 60 ° specular gloss was 42%.

Example 7 (Example) An average particle diameter of 6 μm and a coagulation were obtained in the same manner as in Example 6, except that the amount of the aqueous dispersion of the cationic acrylic resin was changed to 10 parts by weight (solid content). Aggregated particles having a rate of 94% were obtained. Example 6 using the aggregated particles
In the same manner as described above, a coated paper having a coating layer thickness of 10 μm and a 60 ° specular gloss of 40% was obtained.

Example 8 (Example) A coating liquid having a solid content of 16.5% by weight was prepared in the same manner as in Example 4 except that polyvinyl alcohol was added so as to be 11% by weight based on the aggregated particles. Obtained. This coating solution was applied on a PET film having a thickness of 100 μm using a bar coater so that the dry coating amount was 8 g / m ² . The water content immediately after coating was 506% by weight based on the solid content in the coating layer. This was dried to reduce the water content to 370% by weight.

The surface on which the coating layer was formed had a basis weight of 128 g.
After adhering high quality paper / m ² , the coating layer was dried until the water content of the coating layer became 5% by weight or less based on the solid content, and the PET film was peeled off. The coated layer completely transferred to the paper, and a coated paper was obtained. The thickness of the coating layer of this coated paper is 10 μm, 6
The 0 ° specular gloss was 41%.

Example 9 (Comparative Example) Aggregated particles in the same manner as in Example 6 except that only alumina sol was used without using a cationic acrylic resin and water was added so as to have a solid concentration of 10% by weight. I got The average particle size of the aggregated particles is 6μ.
m, the aggregation rate was 0%. Using the aggregated particles, a coated paper having a coating layer thickness of 10 μm and a 60 ° specular gloss of 43% was obtained in the same manner as in Example 6.

Example 10 (Comparative Example) Agglomerated particles were obtained in the same manner as in Example 7, except that the same dispersion as in Example 3 was used as the aqueous dispersion of the cationic acrylic resin. The average particle size of the aggregated particles was 6 μm, and the aggregation rate was 54%. Using the aggregated particles, the thickness of the coating layer was set to 10 μm in the same manner as in Example 6.
m, 60 ° Coated paper having a specular gloss of 42% was obtained.

With respect to the coated papers obtained in Examples 6 to 10, an ink jet printer (MJ5 manufactured by Seiko Epson Corporation) was used.
00C), a test pattern was printed. From the printed sheet, the ink absorbency and the degree of beading were evaluated relative to each other on a scale of 1 to 5 (1: worst, 5: best). The color densities of cyan and magenta were measured with a color densitometer (manufactured by Gretag, SPM1002).
Table 1 shows the results.

[0051]

[Table 1]

[0052]

The recording medium of the present invention has a high ink absorbency, provides a recorded matter having a high color density, and is excellent in water resistance. Further, according to the present invention, a recording medium can be formed by an alumina sol coating liquid having excellent stability over time and having a stable viscosity even when held for a long period of time, which facilitates handling, coating, and especially continuous coating. it can. Further, a recording medium having high glossiness, particularly excellent glossy paper, having excellent ink absorption and adhesion can be provided even if the thickness of the coating layer is thin, using a substrate having ink absorption. Therefore, inexpensive and high-quality glossy paper can be provided. In particular, by using a cationic acrylic polymer for the resin particles of the binder, an effect of suppressing the bleeding of the dye in the recording ink is also recognized.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 133/04 C09D 133/04

Claims (8)

[Claims] 1. A porous layer comprising alumina hydrate particles and nonionic or cationic water-insoluble resin particles having an average particle diameter of 0.005 to 0.1 μm on a substrate. Recording medium. 2. The recording medium according to claim 1, wherein the content of the water-insoluble resin particles is 2 to 50% by weight of the alumina hydrate particles. 3. The recording medium according to claim 1, wherein a 60 ° specular glossiness specified in JIS Z8741 is 30% or more. 4. The porous layer substantially comprises alumina hydrate particles and nonionic or cationic water-insoluble resin particles having an average particle size of 0.005 to 0.1 μm. The pore structure is substantially composed of pores having a radius of 1 to 20 nm, and the pore volume is 0.3 to 1.2 ml / g.
Or the recording medium according to 2. 5. An alumina sol having an average particle size of 0.005 to 0.5.
A method for producing a recording medium, comprising applying a coating liquid containing 1 μm of an aqueous dispersion of nonionic or cationic water-insoluble resin particles to a substrate. 6. The method for producing a recording medium according to claim 5, wherein the coating liquid contains agglomerated particles obtained by mixing alumina sol and nonionic or cationic water-insoluble resin particles and drying the mixture rapidly. 7. A coating layer is formed on a substrate by applying a coating liquid on a substrate, pressing a mold having a smooth surface against the coating layer, drying the mold, and removing the mold. Item 7. The method for producing a recording medium according to Item 6. 8. A coating liquid is applied to the surface of a mold having a smooth surface,
7. The method for producing a recording medium according to claim 6, wherein after the substrate is brought into close contact with the coating layer and dried, the smooth mold is released and the coating layer is transferred onto the substrate.