JP2011190130A - Method for producing silica dispersion liquid and method for producing inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a silica dispersion liquid which allows a coating liquid to be excellent in coating aptitude and prevents the coating liquid from getting highly viscous when the coating liquid for an ink receptive layer of an inkjet recording medium is prepared. <P>SOLUTION: The method for producing the silica dispersion liquid includes: a previous dispersion step of preliminarily dispersing a liquid including silica obtained by a gas phase method and a dispersant; a microdispersion step of micro-dispersing another liquid containing the preliminarily-dispersed liquid so that the amount of the dispersant is 40-74 mass% of the saturation adsorbed amount (mass) of the silica obtained by the gas phase method; and a heat treatment step of heat-treating the micro-dispersed liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a silica dispersion and a method for producing an ink jet recording medium.

In recent years, with the rapid development of the information technology industry, various information processing systems have been developed, and recording methods and recording apparatuses suitable for the information processing systems have been developed and put into practical use.
Among these recording methods, the inkjet recording method is capable of recording on a variety of recording materials, has advantages such as being relatively inexpensive and compact in hardware (device), and excellent in quietness. It has also been widely used for so-called home use.

In addition, with the recent increase in resolution of inkjet printers, it has become possible to obtain so-called photographic-like high-quality recorded matter. With the progress of such hardware (devices), recording for inkjet recording has become possible. Various seats have been developed.
The characteristics required for this recording sheet for ink jet recording are generally (1) fast drying (high ink absorption speed), and (2) ink dot diameter is appropriate and uniform. (No blurring), (3) good graininess, (4) high dot roundness, (5) high color density, (6) high chroma (dullness) (7) The water resistance, light resistance, and ozone resistance of the print portion are good, (8) the whiteness of the recording sheet is high, and (9) the storage stability of the recording sheet is good ( Does not cause yellowing coloring even after long-term storage, does not blur images after long-term storage (good aging blur), and (10) is difficult to deform and has good dimensional stability (curl is sufficiently small) (11) Good hard running performance, etc. That.
Furthermore, in the use of photo glossy paper used for the purpose of obtaining so-called photographic-like high-quality recorded matter, in addition to the above properties, gloss, surface smoothness, photographic paper-like texture similar to silver salt photography, etc. Is also required.

  In recent years, an ink jet recording medium containing fine inorganic pigment particles and a water-soluble resin and having a porous structure having a high porosity in an ink receiving layer has been developed and put into practical use for the purpose of improving the various properties described above. . Since such an ink jet recording medium has a porous structure, it has excellent high ink receptivity (fast drying property) capable of forming a high resolution image and high gloss.

  Usually, an ink jet recording medium is produced by applying an ink receiving layer coating liquid to a support. The ink-receiving layer coating liquid is prepared by predispersing an aqueous liquid containing fine particles and a cationic polymer, and further finely pulverizing the fine particles to prepare a finely divided dispersion liquid, to which a water-soluble resin or a crosslinking agent or the like is added. Manufactured. However, the ink-receiving layer coating solution produced in this way often has a high viscosity and sometimes loses coating suitability and filtration suitability.

As a method for improving the above properties, a dispersion is disclosed in which a liquid containing fine particles and a cationic polymer is pre-dispersed and / or heat-treated at a temperature higher than room temperature after being atomized so that the fine particle dispersion does not increase in viscosity. (For example, refer to Patent Document 1).
In addition, it contains fine particles, a binder, and a dispersant that have high glossiness, a large ink absorption capacity, and no defects such as application lines and cracks on the coated surface, and 75% of the saturated adsorption amount of the dispersant. A method for producing an inkjet recording paper that is dispersed in the presence of a dispersant of ˜125 mass% is disclosed (for example, see Patent Document 2).

JP 2004-43628 A JP 2004-276363 A

However, although Patent Documents 1 and 2 describe that the viscosity of the coating liquid, coating lines, cracks, and the like are improved, it is not necessarily sufficient in terms of the coating suitability of the coating liquid and the image density of the inkjet recording medium. There wasn't.
The present invention provides a method for producing a silica dispersion capable of producing the coating liquid excellent in coating suitability when the coating liquid for an ink receiving layer of an ink jet recording medium is prepared, and in which the coating liquid does not increase in viscosity. It is an object to solve this object.
Another object of the present invention is to provide a method for manufacturing an ink jet recording medium capable of realizing a high image density, and to solve the object.

<1>
A pre-dispersing step of pre-dispersing a liquid containing vapor phase silica and a dispersing agent;
A fine dispersion step of finely dispersing the dispersion obtained by the pre-dispersion as a liquid containing a dispersant of 40% by mass to 74% by mass with respect to the saturated adsorption amount (mass) of the vapor phase method silica;
A heat treatment step of heat-treating the finely dispersed dispersion;
A method for producing a silica dispersion having:
<2>
The pre-dispersing step is the method for producing a silica dispersion according to <1>, in which the zirconium compound is added after the dispersion obtained by pre-dispersing is cooled to 25 ° C. or lower.
<3>
The said heat processing process is a manufacturing method of the silica dispersion as described in <1> or <2> which heat-processes at the temperature of 30-80 degreeC for 1 hour or more.
<4>
The method for producing a silica dispersion according to <2> or <3>, wherein the addition amount of the zirconium compound is 1 to 10% by mass with respect to the total mass of the vapor phase method silica.
<5>
<1>-<4> The coating liquid preparation process which mixes the silica dispersion manufactured by the manufacturing method of the silica dispersion of any one of <4>, and water-soluble resin, and a support, and support An ink receiving layer forming step of forming an ink receiving layer by applying the coating liquid on a body.
<6>
The ink receiving layer forming step includes (1) simultaneously with the application of the coating liquid, or (2) during the drying of the coating layer formed by the coating of the coating liquid, and before the coating layer exhibits reduced-rate drying. <5> The method for producing an ink jet recording medium according to <5>, wherein a liquid containing a basic compound is applied at any of the times, and the coating layer is crosslinked and cured to form an ink receiving layer.

According to the present invention, when a coating liquid for an ink-receiving layer of an ink jet recording medium is prepared, a method for producing a silica dispersion that can produce the coating liquid with excellent coating suitability and does not increase the viscosity of the coating liquid. Can be provided.
Another object of the present invention is to provide a method for manufacturing an inkjet recording medium capable of realizing a high image density, and to solve the object.

≪Method for producing silica dispersion≫
The method for producing a silica dispersion of the present invention includes a pre-dispersing step of pre-dispersing a liquid containing vapor phase silica and a dispersant,
A fine dispersion step of finely dispersing the dispersion obtained by pre-dispersion as a liquid containing a dispersant of 40% by mass to 74% by mass with respect to the saturated adsorption amount (mass) of the vapor phase silica;
A heat treatment step of heating the finely dispersed dispersion;
In addition, other processes can be provided as necessary.
The method for producing a silica dispersion of the present invention is, in particular, finely dispersed as a liquid containing a dispersant of 40% by mass or more and 74% by mass or less with respect to the saturated adsorption amount (mass) of vapor phase method silica, and a finely dispersed liquid By adopting a constitution in which heat treatment is performed, when an ink-receiving layer coating solution for an ink jet recording medium is prepared, a silica dispersion in which the coating solution does not increase in viscosity can be obtained.
The silica dispersion obtained above can be used in a method for producing an inkjet recording medium having an ink receiving layer on a support described later.

[Pre-dispersion process]
The pre-dispersion step is a step of performing a dispersion treatment before fine dispersion in order to make the vapor phase method silica conform to the solvent. In this step, a liquid containing vapor phase silica (gas phase silica dispersion) may be prepared in advance, and the dispersion may be added to a liquid containing a dispersant (dispersant solution). It may be added to the phase method silica dispersion, or both solutions may be mixed at the same time, or the gas phase method silica and the dispersant may be divided into small amounts and mixed in the solvent. Among them, it is particularly preferable to mix the gas phase method silica and the dispersant into the solvent in small portions.
The amount of the dispersant added during the pre-dispersion may be the total amount of the dispersant, or only a part of the dispersant may be added and the remaining dispersant added during the fine dispersion described later. It is preferred to add the entire amount of dispersant.
When the total amount of the dispersant is added, the amount of the dispersant added during the pre-dispersion is 40% by mass or more and 74% by mass or less with respect to the saturated adsorption amount (mass) of the vapor phase method silica.

Further, according to the method for producing a silica dispersion of the present invention, adding a zirconium compound to a dispersion (predispersion) containing the vapor phase silica obtained by pre-dispersing and a dispersant (pre-dispersion) is described below. It is preferable from the viewpoint of improving the viscosity of the layer forming coating solution and the image density of the ink jet recording medium.
Furthermore, from the viewpoint of improving image density, the method for producing a silica dispersion of the present invention preferably adds the zirconium compound after cooling the pre-dispersion to 25 ° C. or less, from the viewpoint of the cooling time of the pre-dispersion. Addition at a temperature of 15 ° C. to 25 ° C. is more preferable.

A known dispersion method can be used for the pre-dispersion step, and a known dispersion apparatus can be used.
What is necessary is just to select suitably about dispersion conditions, such as a rotation or the stirring speed at the time of dispersion | distribution processing, and processing time, with a composition, the dispersion apparatus to be used, etc.
For example, for pre-dispersion, vapor phase silica and a dispersant are added to a solvent (for example, 10 to 20% by mass of silica fine particles in water), and KDL-PILOT manufactured by Shinmaru Enterprises Co., Ltd. is used. And a dispersion method.

(Gas phase method silica)
The liquid to be predispersed is configured to contain at least one kind of vapor phase silica.
The vapor phase method is a method by high-temperature vapor phase hydrolysis of silicon halide (flame hydrolysis method), a method in which silica sand and coke are heated and reduced and vaporized by an arc in an electric furnace and oxidized with air (arc). The method of obtaining anhydrous silica by the method) is the mainstream, and “gas phase method silica” means silica (anhydrous silica fine particles) synthesized by the gas phase method.
Vapor phase silica is different from hydrous silica in terms of the density of silanol groups on the surface, the presence or absence of vacancies, etc., and exhibits different properties, but is suitable for forming a three-dimensional structure with a high porosity. The reason for this is not clear, but in the case of hydrous silica, the density of silanol groups on the surface of the fine particles is high at 5 to 8 / nm ² , and the silica fine particles tend to aggregate closely (aggregate). In the case of the method silica, the density of silanol groups on the surface of the fine particles is 2 to 3 / nm ² , so that it is sparse soft aggregation (flocculate), and as a result, it is assumed that the structure has a high porosity. Is done.

  Vapor phase silica has a particularly large specific surface area, so it has high ink absorption and retention efficiency, and has a low refractive index, so that it can impart transparency to the ink receiving layer by dispersing it to an appropriate particle size. It is characterized by high color density and good color development. The transparency of the ink receiving layer is not only for applications that require transparency, such as OHP, but also for high color density and good color development gloss even when applied to recording media such as photo glossy paper. Is important.

The average primary particle diameter of the vapor phase silica is preferably 30 nm or less, more preferably 20 nm or less, particularly preferably 10 nm or less, and most preferably 3 to 10 nm. Since the vapor phase silica is easily adhered to each other by hydrogen bonding with a silanol group, a structure having a large porosity can be formed when the average primary particle size is 30 nm or less, and ink absorption characteristics are effectively improved. Can be improved.
The content of the vapor phase method silica is preferably 10 to 30% by mass, and more preferably 13 to 25% by mass with respect to the total mass of the pre-dispersion liquid.
The content of the vapor phase silica in the ink receiving layer described later is preferably 50 to 90% by mass, more preferably 60 to 80% by mass with respect to the total solid content of the ink receiving layer.

(Dispersant)
In the present invention, the predispersed liquid contains at least one dispersant.
As the dispersant, a cationic polymer is preferable from the viewpoints of change of the silica dispersion over time, suppression of increase in viscosity of the coating liquid for forming the ink receiving layer, and improvement of image density.
As the cationic polymer, a polymer having a primary to tertiary amino group or a quaternary ammonium base as a cationic group is preferably used.
As the cationic polymer, a homopolymer of a monomer having a primary to tertiary amino group and a salt thereof, or a quaternary ammonium base (cationic monomer), the cationic monomer and another monomer (hereinafter, Those obtained as a copolymer or condensation polymer with "non-cationic monomer") are preferred. These polymers can be used in any form of water-soluble polymer or water-dispersible latex particles.

  Examples of the monomer (cationic monomer) include trimethyl-p-vinylbenzylammonium chloride, trimethyl-m-vinylbenzylammonium chloride, triethyl-p-vinylbenzylammonium chloride, triethyl-m-vinylbenzylammonium chloride, N , N-dimethyl-N-ethyl-Np-vinylbenzylammonium chloride, N, N-diethyl-N-methyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-Nn-propyl-N -P-vinylbenzylammonium chloride, N, N-dimethyl-Nn-octyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N-benzyl-Np-vinylbenzylammonium chloride, N, N- Ethyl-N-benzyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N- (4-methyl) benzyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N-phenyl-N -P-vinylbenzylammonium chloride;

  Trimethyl-p-vinylbenzylammonium bromide, trimethyl-m-vinylbenzylammonium bromide, trimethyl-p-vinylbenzylammonium sulfonate, trimethyl-m-vinylbenzylammonium sulfonate, trimethyl-p-vinylbenzylammonium acetate, trimethyl-m-vinyl Benzylammonium acetate, N, N, N-triethyl-N-2- (4-vinylphenyl) ethylammonium chloride, N, N, N-triethyl-N-2- (3-vinylphenyl) ethylammonium chloride, N, N-diethyl-N-methyl-N-2- (4-vinylphenyl) ethylammonium chloride, N, N-diethyl-N-methyl-N-2- (4-vinylphenyl) ethylammonium chloride Tate;

  N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N- Methyl chloride, ethyl chloride, methyl bromide of dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide , Quaternized products of ethyl bromide, methyl iodide or ethyl iodide, or sulfonates, alkyl sulfonates, acetates or alkyl carboxylates substituted with their anions.

  Specifically, for example, monomethyl diallyl ammonium chloride, trimethyl-2- (methacryloyloxy) ethylammonium chloride, triethyl-2- (methacryloyloxy) ethylammonium chloride, trimethyl-2- (acryloyloxy) ethylammonium chloride, triethyl- 2- (acryloyloxy) ethylammonium chloride, trimethyl-3- (methacryloyloxy) propylammonium chloride, triethyl-3- (methacryloyloxy) propylammonium chloride, trimethyl-2- (methacryloylamino) ethylammonium chloride, triethyl-2- (Methacryloylamino) ethylammonium chloride, trimethyl-2- (acryloylamino) ethyl Ammonium chloride, triethyl-2- (acryloylamino) ethylammonium chloride, trimethyl-3- (methacryloylamino) propylammonium chloride, triethyl-3- (methacryloylamino) propylammonium chloride, trimethyl-3- (acryloylamino) propylammonium chloride Triethyl-3- (acryloylamino) propylammonium chloride;

N, N-dimethyl-N-ethyl-2- (methacryloyloxy) ethylammonium chloride, N, N-diethyl-N-methyl-2- (methacryloyloxy) ethylammonium chloride, N, N-dimethyl-N-ethyl- 3- (acryloylamino) propylammonium chloride, trimethyl-2- (methacryloyloxy) ethylammonium bromide, trimethyl-3- (acryloylamino) propylammonium bromide, trimethyl-2- (methacryloyloxy) ethylammonium sulfonate, trimethyl-3- And (acryloylamino) propylammonium acetate.
In addition, examples of copolymerizable monomers include N-vinylimidazole and N-vinyl-2-methylimidazole.

In addition, allylamine, diallylamine, its derivatives, salts and the like can be used. Examples of such compounds include allylamine, allylamine hydrochloride, allylamine acetate, allylamine sulfate, diallylamine, diallylamine hydrochloride, diallylamine acetate, diallylamine sulfate, diallylmethylamine and salts thereof (for example, Hydrochloride, acetate, sulfate, etc.), diallylethylamine and salts thereof (for example, hydrochloride, acetate, sulfate, etc.), diallyldimethylammonium salt (chloride, acetic acid as counter anions of the salt) Ion sulfate ions, etc.). In addition, since these allylamines and diallylamine derivatives are inferior in polymerizability in the amine form, they are generally polymerized in the form of a salt and desalted as required.
In addition, a unit such as N-vinylacetamide, N-vinylformamide or the like, which is converted into a vinylamine unit by hydrolysis after polymerization, and a salt thereof can also be used.

The non-cationic monomer does not include a basic or cationic moiety such as a primary to tertiary amino group and a salt thereof, or a quaternary ammonium base, and does not show an interaction with a dye in an inkjet ink. Or the monomer which interaction is substantially small is said.
Examples of the non-cationic monomer include (meth) acrylic acid alkyl ester; (meth) acrylic acid cycloalkyl ester such as cyclohexyl (meth) acrylate; (meth) acrylic acid aryl ester such as phenyl (meth) acrylate; Aralkyl esters such as (meth) benzyl acrylate; Aromatic vinyls such as styrene, vinyl toluene and α-methylstyrene; Vinyl esters such as vinyl acetate, vinyl propionate and vinyl versatic acid; Allyl esters such as allyl acetate Halogen-containing monomers such as vinylidene chloride and vinyl chloride; vinyl cyanide such as (meth) acrylonitrile; olefins such as ethylene and propylene; and the like.

The (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid alkyl ester having 1 to 18 carbon atoms in the alkyl moiety, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) Propyl acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, Examples include 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like.
Of these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and hydroxyethyl methacrylate are preferable.
The non-cationic monomers can also be used alone or in combination of two or more.

Further, as the cationic polymer, polydiallyldimethylammonium chloride, polymethacryloyloxyethyl-β-hydroxyethyldimethylammonium chloride, polyethyleneimine, polyallylamine and derivatives thereof, polyamide-polyamine resin, cationized starch, dicyandiamide formalin condensate, dimethyl- 2-hydroxypropylammonium salt polymer, polyamidine, polyvinylamine, dicyan diamide-formalin polycondensate dicyan-based chaotic resin, dicyanamide-diethylenetriamine polycondensate-typified polyamine-based chaotic resin, epichlorohydrin-dimethylamine addition polymerization , Dimethyldialin ammonium chloride-SO ₂ copolymer, diallylamine salt-SO ₂ copolymer, A (meth) acrylate-containing polymer having a quaternary ammonium base-substituted alkyl group in the ester portion, a styryl polymer having a quaternary ammonium base-substituted alkyl group, and the like can also be mentioned as preferable examples.

  Specific examples of the cationic polymer include JP-A Nos. 48-28325, 54-74430, 54-124726, 55-22766, 55-142339, 60-23850, and 60. -23851, 60-23852, 60-23853, 60-57836, 60-60643, 60-118834, 60-122940, 60-122941, 60-122294 No. 60-235134, JP-A-1-161236, U.S. Pat.Nos. 2,484,430, 2,548,564, 3,148,061, 3,309,690, 4,115,124, 4,124,386, 4,193,800, 4,273,853, JP 4282305, JP 4450224, JP-A-1-1612. No. 6, No. 10-81064, No. 10-119423, No. 10-157277, No. 10-217601, No. 11-348409, JP-A No. 2001-138621, No. 2000-43401, No. 2000-212235 No. 2000-309157, No. 2001-96897, No. 2001-138627, JP-A-11-91242, No.8-2087, No.8-2090, No.8-2091, No.8-2093 8-1744992, 11-192777, JP-A-2001-301314, JP-B-5-35162, JP-A-5-35163, JP-A-5-35164, JP-A-5-88846, JP-A-7-118333. , JP 2000-344990, JP 2648847, 2616677, etc. Such as and the like. Among them, polyallylamine and derivatives thereof are preferable, and diallyldimethyl cation polymer is preferable in terms of structure.

  As the polyallylamine or a derivative thereof, various known allylamine polymers and derivatives thereof can be used. Examples of such derivatives include salts of polyallylamine and acids (acids include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid, methanesulfonic acid, toluenesulfonic acid, acetic acid, propionic acid, cinnamic acid, (meth) Organic acids such as acrylic acid, or combinations thereof, or salts of only a part of allylamine), derivatives of polyallylamine by polymer reaction, copolymers of polyallylamine and other copolymerizable monomers Specific examples of the monomer include (meth) acrylic acid esters, styrenes, (meth) acrylamides, acrylonitrile, vinyl esters and the like.

  Specific examples of polyallylamine and derivatives thereof include JP-B-62-31722, JP-B-2-14364, JP-B-63-43402, JP-A-63-43403, JP-A-63-45721, and JP-A-63-29881. Japanese Patent Publication No. 1-26362, No. 2-56365, No. 2-57084, No. 4-41686, No. 6-2780, No. 6-45649, No. 6-15592, No. 4-68622, Patents No. 3199227, No. 3008369, JP-A-10-330427, JP-A-11-21321, JP-A-2000-281728, JP-A-2001-106636, JP-A-62-256801, JP-A-7-173286, 7-213897, 9-235318, 9-302026, 11-21321, WO99 / 2190 No., No. WO99 / 19,372, JP-A-5-140213, compounds described in JP Kohyo No. 11-506488, and the like.

Among the above, the dispersant in the present invention is more preferably a diallyldialkyl cationic polymer, and more preferably a diallyldimethyl cationic polymer.
In addition, the dispersant in the present invention is preferably a cationic polymer having a weight average molecular weight of 60000 or less, and particularly preferably a cationic polymer having 40000 or less, from the viewpoint of improving dispersibility, particularly preventing thickening.

(Zirconium compound)
The zirconium compound used in the present invention is not particularly limited, and various compounds can be used.
Examples of the zirconium compound used in the present invention include hydroxy zirconyl chloride, zirconyl chloride, zirconyl nitrate, zirconyl acetate, zirconyl ammonium carbonate, basic zirconium carbonate, zirconium hydroxide, zirconium carbonate / potassium, zirconium sulfate, zirconium fluoride compound. Etc.
Among these zirconium compounds, one or more selected from hydroxy zirconyl chloride, zirconyl chloride, zirconyl nitrate, zirconyl acetate, and zirconyl ammonium carbonate are preferable, and hydroxy zirconyl chloride and zirconyl acetate are preferable from the viewpoint of suppressing thickening of the silica dispersion. Are more preferable, and hydroxy zirconyl chloride and zirconyl acetate are particularly preferable.
The addition amount of the zirconium compound is from the viewpoint of the change over time of the silica dispersion, the suppression of the increase in the viscosity of the coating liquid for forming the ink receiving layer, and the improvement of the image density of the inkjet recording medium with respect to the total mass of the vapor phase method silica. 1-10 mass% is preferable, 1-7 mass% is more preferable, and 1-5 mass% is especially preferable.

(solvent)
Examples of the solvent that can be used in the pre-dispersion liquid in the present invention include water, an organic solvent, and a mixed solvent thereof. Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol, i-propanol and methoxypropanol, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, acetonitrile, ethyl acetate and toluene.

[Fine dispersion process]
In the fine dispersion step, the dispersion obtained by pre-dispersing in the pre-dispersion step is a liquid containing 40% by mass or more and 74% by mass or less of a dispersant with respect to the saturated adsorption amount (mass) of the vapor phase method silica. This is a fine dispersion step, and the pre-dispersion liquid can be further atomized.
In the present invention, “atomization” means that the pre-dispersed dispersion is atomized by a disperser so that the ratio of coarse particles having a volume average particle diameter of 5 μm or more is 5% or less. The volume average particle size is a value obtained by measuring the liquid after atomization with a particle size measuring instrument (for example, LA910 manufactured by HORIBA).
The amount of dispersant added at the time of fine dispersion is the amount excluding the amount of dispersant added at the time of pre-dispersion. 40 wt% or more and 74 wt% or less with respect to (mass), and if it is less than 40 wt%, the viscosity of the coating liquid for forming an ink-receiving layer obtained using a silica dispersion increases, and the coating suitability deteriorates. . On the other hand, if it exceeds 74% by mass, the image density of the ink jet recording medium produced using the silica dispersion after fine dispersion of silica is low, and a performance change is caused such that it further decreases with time.
The total amount of the dispersant added at the time of fine dispersion as a liquid containing the dispersant is from the viewpoint of change with time of the silica dispersion, suppression of increase in the viscosity of the coating liquid for forming the ink receiving layer, and improvement in image density of the ink jet recording medium. 45 mass% or more and 74 mass% or less are preferable, 55 mass% or more and 74 mass% or less are more preferable, and 55 mass% or more and 70 mass% or less are especially preferable.

As a disperser used for fine dispersion, various conventionally known dispersers such as a high-speed rotary disperser, a medium stirring disperser (ball mill, sand mill, etc.), an ultrasonic disperser, a colloid mill disperser, and a high-pressure disperser can be used. However, from the standpoint of efficiently dispersing the formed fine particles, a medium stirring type disperser, a colloid mill disperser or a high pressure disperser is preferable.
The fine dispersion is preferably performed within 7 days after pre-dispersion from the viewpoint of suppressing reaggregation of the vapor-phase process silica, and more preferably within 2 days from the viewpoint of cost and productivity.
The amount of the dispersing agent for fine dispersion is determined by adding the remaining dispersing agent when the dispersing agent is added in portions during pre-dispersion.

  The fine dispersion liquid (atomization dispersion liquid) in the present invention contains the above-mentioned vapor phase silica, a dispersant, and preferably a zirconium compound, and the components contained in the fine dispersion liquid are ink receiving of an ink jet recording medium. It is a component of the layer and can further contain other components.

(Other ingredients)
-Fine particles-
Fine particles other than gas phase method silica may be added within a range not impairing the effects of the present invention.
Either organic fine particles or inorganic fine particles may be used, but inorganic fine particles are preferred from the viewpoint of ink absorbability and image stability.

  Examples of preferable organic fine particles include polymer fine particles obtained by, for example, emulsion polymerization, microemulsion polymerization, soap-free polymerization, seed polymerization, dispersion polymerization, suspension polymerization, and the like. Specifically, polyethylene, polypropylene, Examples include polystyrene, polyacrylate, polyamide, silicon resin, phenol resin, natural polymer powder, latex or emulsion polymer fine particles, and the like.

  Examples of the inorganic fine particles include colloidal silica, titanium dioxide, barium sulfate, calcium silicate, zeolite, kaolinite, halloysite, mica, talc, calcium carbonate, magnesium carbonate, calcium sulfate, pseudoboehmite, zinc oxide, zinc hydroxide, Examples thereof include alumina, aluminum silicate, calcium silicate, magnesium silicate, zirconium oxide, zirconium hydroxide, cerium oxide, lanthanum oxide, and yttrium oxide. Among these, colloidal silica, alumina fine particles, or pseudoboehmite is preferable from the viewpoint of forming a good porous structure.

Alumina hydrate is preferable because it absorbs and fixes ink well, and pseudoboehmite (Al ₂ O ₃ .nH ₂ O) is particularly preferable. Alumina hydrates can be used in various forms, but it is preferable to use sol boehmite as a raw material because a smooth layer can be easily obtained.

About the pore structure of pseudo boehmite, the average pore radius is preferably 1 to 25 nm, and more preferably 2 to 10 nm. The pore volume is preferably 0.3 to 2.0 cc / g, more preferably 0.5 to 1.5 cc / g. Here, the pore radius and pore volume are measured by a nitrogen adsorption / desorption method, and can be measured by, for example, a gas adsorption / desorption analyzer (for example, trade name “Omni Soap 369” manufactured by Coulter). .
Among alumina fine particles, vapor-phase method alumina fine particles are preferable because of their large specific surface area. The average primary particle size of the vapor phase alumina is 50 nm or less, and more preferably 20 nm or less.
Furthermore, colloidal silica having an average primary particle size of 50 nm or less is also preferable.
That is, the inorganic fine particles that may be used in the present invention are preferably colloidal silica, alumina fine particles, and pseudoboehmite.

  When the above-mentioned fine particles are used in an ink jet recording medium, for example, JP-A-10-81064, JP-A-10-119423, JP-A-10-157277, JP-A-10-217601, JP-A-11-348409, JP-A-2001-138621. No. 2000-43401 No. 2000-2111235 No. 2000-309157 No. 2001-96897 No. 2001-138627 No. 11-91242 No. 8-2087 No. 8-2090 No. 8-2091, 8-2093, 8-174992, 11-192777, JP-A-2001-301314, and the like can also be preferably used.

<Heat treatment process>
The heat treatment step is a step of heating the finely dispersed dispersion.
By performing the heat treatment, thickening of the silica dispersion can be effectively suppressed.
The heat treatment after fine dispersion is preferably 30 ° C. to 80 ° C., more preferably 35 ° C. to 60 ° C., from the viewpoint of suppressing increase in viscosity due to re-aggregation and water evaporation. The heating time depends on the heating temperature and the like, and it is necessary to lengthen the heating time at a temperature close to room temperature. When the heat treatment is performed at 30 ° C. to 80 ° C., the heating time is preferably 1 to 40 hours, more preferably 1 to 20 hours, and further preferably 5 to 15 hours. When the heat treatment is performed at 35 ° C. to 60 ° C., the heating time is preferably 1 to 20 hours, and more preferably 5 to 15 hours.
From the viewpoint of suppressing the increase in viscosity of the silica dispersion after the heat treatment, it is preferable that the time required for preparing the ink-receiving layer-forming coating liquid is within 2 days.

≪Inkjet recording medium manufacturing method≫
Next, the manufacturing method of the inkjet recording medium of this invention is demonstrated.
The method for producing an ink jet recording medium of the present invention is a method for producing an ink jet recording medium having an ink receiving layer comprising at least one layer on a support, wherein the ink forms at least one ink receiving layer on the support. A receiving layer forming step.
The method for producing an inkjet recording medium of the present invention comprises a step of preparing a coating liquid by mixing the silica dispersion produced by the method for producing a silica dispersion of the present invention and a water-soluble resin (coating liquid preparation step), And a step of forming an ink receiving layer by applying the coating liquid on a support (ink receiving layer forming step).
The method for producing an ink jet recording medium of the present invention is the ink jet recording medium having an ink receiving layer having an excellent image density by using the coating liquid having high viscosity suppressed and having excellent coating suitability by adopting the above configuration. Can be manufactured.

Further, the ink receiving layer forming step of the method for producing an ink jet recording medium of the present invention includes (1) applying the coating liquid, or (2) during the drying of the ink receiving layer formed by applying the coating liquid. Preferably, the ink receiving layer further includes a curing step of applying a liquid containing a basic compound and crosslinking and curing the ink receiving layer at any time before the ink receiving layer exhibits reduced-rate drying.
In addition to the above steps, the method for producing an ink jet recording medium of the present invention may further include other steps as necessary.
Hereinafter, a method for producing the ink jet recording medium of the present invention will be described.

[Coating solution preparation process]
The method for producing an ink jet recording medium of the present invention includes a coating liquid preparation step of preparing a coating liquid by mixing the silica dispersion produced by the method for producing a silica dispersion of the present invention and a water-soluble resin.
The coating liquid is preferably prepared by adding a water-soluble resin as an aqueous solution to the silica dispersion from the viewpoint that the change in physical properties (viscosity) of the coating liquid is small and the coating liquid is excellent in stability over time.

In the present invention, the coating liquid (hereinafter sometimes referred to as “ink receiving layer forming coating liquid”) can be prepared, for example, as follows. That is,
An aqueous solution of a water-soluble resin (for example, a water-soluble resin having a mass of about 1/3 of the vapor phase silica) is added to the silica dispersion obtained by the method for producing a silica dispersion of the present invention. Can be prepared.
The obtained coating liquid is in a uniform sol state, and a porous ink-receiving layer having a three-dimensional network structure can be formed by coating this on a support by the following coating method and drying it.

  In the present invention, in order to obtain a coating liquid and a liquid containing a basic compound, the disperser described in the section of silica dispersion can be used.

  A pH adjuster, a dispersant, a surfactant, an antifoaming agent, an antistatic agent, and the like can be further added to the aqueous solution of the water-soluble resin as necessary.

<Coating solution>
The coating liquid in the present invention further comprises at least a water-soluble resin in the silica dispersion and, if necessary, other components.
The constituent components of the silica dispersion used in the coating solution are the same as those described in the method for producing a silica dispersion, and preferred examples are also the same.

(Water-soluble resin)
The coating liquid includes at least one water-soluble resin.
The water-soluble resin is not particularly limited and can be used. For example, a polyvinyl alcohol resin that is a resin having a hydroxy group as a hydrophilic structural unit [polyvinyl alcohol (PVA), acetoacetyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, polyvinyl acetal, etc.) , Cellulose resins [methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, etc.], chitins, chitosans, Starch, resin having an ether bond [polyethylene oxide (PEO), polypropylene oxide ( PO), polyethylene glycol (PEG), poly ether (PVE)], and resins having carbamoyl groups [polyacrylamide (PAAM), polyvinyl pyrrolidone (PVP), polyacrylic acid hydrazide, etc.] and the like.
Moreover, the polyacrylic acid salt which has a carboxyl group as a dissociable group, maleic acid resin, alginate, gelatins, etc. can be mentioned.

Among these, polyvinyl alcohol resin is particularly preferable. Examples of the polyvinyl alcohol include Japanese Patent Publication No. 4-52786, Japanese Patent Publication No. 5-67432, Japanese Patent Publication No. 7-29479, Japanese Patent No. 2537827, Japanese Patent Publication No. 7-57553, Japanese Patent No. 2502998, and Japanese Patent No. 3053231. JP-A-63-176173, JP-A-2604367, JP-A-7-276787, JP-A-9-207425, JP-A-11-58941, JP-A-2000-135858, JP-A-2001-205924, JP 2001-287444, JP 62-278080, JP 9-39373, JP 2750433, JP 2000-18801, JP 2001-213045, JP 2001-328345, JP 8 -324105, JP-A-11-348417, etc. It is below.
Examples of the water-soluble resin other than the polyvinyl alcohol resin include compounds described in “0011” to “0014” of JP-A No. 11-165461.
These water-soluble resins may be used alone or in combination of two or more.

  As content of water-soluble resin, 9-40 mass% is preferable with respect to the total solid content mass of an ink receiving layer, and 12-33 mass% is more preferable.

The vapor phase silica (hereinafter also referred to as silica fine particles) and the water-soluble resin, which mainly constitute the ink receiving layer, may be a single material or a mixed system of a plurality of materials. Good.
From the viewpoint of maintaining transparency, the type of water-soluble resin to be combined with the vapor phase method silica is important. In the vapor phase silica, the water-soluble resin is preferably a polyvinyl alcohol resin, more preferably a polyvinyl alcohol resin having a saponification degree of 70 to 100%, and a polyvinyl alcohol having a saponification degree of 80 to 99.5%. Alcohol resins are particularly preferred.

The polyvinyl alcohol-based resin has a hydroxyl group in its structural unit. Since this hydroxyl group and the surface silanol group of the vapor phase silica form a hydrogen bond, secondary particles of the vapor phase silica are formed as network chain units. It is easy to form a three-dimensional network structure. By forming this three-dimensional network structure, it is considered that an ink receiving layer having a porous structure with a high porosity and sufficient strength is formed.
In ink jet recording, the porous ink receiving layer obtained as described above can absorb ink rapidly by a capillary phenomenon, and can form dots with good roundness without ink bleeding.

  In addition, the polyvinyl alcohol resin may be used in combination with the other water-soluble resin. When the other water-soluble resin and the polyvinyl alcohol resin are used in combination, the content of the polyvinyl alcohol resin in the total water-soluble resin is preferably 50% by mass or more, and more preferably 70% by mass or more.

-Content ratio of gas phase method silica and water-soluble resin-
The mass content ratio [PB ratio (x / y)] of the vapor phase method silica (x) and the water-soluble resin (y) greatly affects the film structure and film strength of the ink receiving layer. That is, as the mass content ratio [PB ratio] increases, the porosity, pore volume, and surface area (per unit mass) increase, but the density and strength tend to decrease.

  In the ink receiving layer, the mass content ratio [PB ratio (x / y)] prevents a decrease in film strength and cracks during drying caused by the PB ratio being too large, and the PB ratio is From the viewpoint of preventing the ink absorbability from being lowered by decreasing the void ratio, the void is easily blocked by the resin, and is preferably 1.5 to 10.

  Since stress may be applied to the ink jet recording medium when passing through the transport system of the ink jet printer, the ink receiving layer needs to have sufficient film strength. Further, when cutting into a sheet shape, the ink receiving layer needs to have sufficient film strength in order to prevent cracking or peeling of the ink receiving layer. Considering these cases, the mass ratio (x / y) is more preferably 5 or less, while it is more preferably 2 or more from the viewpoint of ensuring high-speed ink absorbency in an inkjet printer.

For example, a coating solution in which vapor-phase method silica fine particles having an average primary particle size of 20 nm or less and a water-soluble resin are completely dispersed in an aqueous solution at a mass ratio (x / y) of 2 to 5 is applied onto a support. When the ink receiving layer is dried, a three-dimensional network structure is formed in which the secondary particles of silica fine particles are network chains, the average pore diameter is 25 nm or less, the porosity is 50 to 80%, and the pore specific volume is 0. A translucent porous film having a surface area of 5 ml / g or more and a specific surface area of 100 m ² / g or more can be easily formed.

(Crosslinking agent)
The coating liquid in the present invention may contain a crosslinking agent capable of crosslinking the water-soluble resin. By containing the crosslinking agent, a porous ink receiving layer cured by a crosslinking reaction of the water-soluble resin can be obtained.

As the cross-linking agent, a suitable one may be appropriately selected in relation to the water-soluble resin contained in the ink-receiving layer. Among them, a boron compound is preferable in that the cross-linking reaction is rapid, and examples thereof include borax and boric acid. , borates (eg, _{orthoborate, InBO 3, ScBO 3, YBO} 3, LaBO 3, Mg 3 (BO 3) 2, Co 3 (BO 3) 2, two borates _(e.g., Mg ₂ B _{2 O 5} , Co ₂ B ₂ O ₅ ), metaborate (eg, LiBO ₂ , Ca (BO ₂ ) ₂ , NaBO ₂ , KBO ₂ ), tetraborate (eg, Na ₂ B ₄ O ₇ · 10H ₂ O), five borate _{(e.g., KB 5 O 8 · 4H 2} O, CsB 5 O 5) can be cited, six borate _{(e.g., Ca 2 B 6 O 11 ·} 7H 2 O) and the like. Among them, rapidly crosslinked Cause a reaction In that it is, borax, boric acid, borate are preferable, and boric acid is particularly preferred, it is most preferable to use in combination with polyvinyl alcohol can be water-soluble resin added thereto.

As the crosslinking agent for the water-soluble resin, in addition to the boron compound, the following compounds can also be mentioned as suitable ones.
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 and 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; melamine resins (for example, methylolmelamine, alkylated methylolmelamine) ;Epoxy resin;

  Isocyanate compounds such as 1,6-hexamethylene diisocyanate; Aziridine compounds described in US Pat. Nos. 3,017,280 and 2,983,611; Carboximide compounds described in US Pat. No. 3,100,704; Glycerol triglycidyl Epoxy compounds such as ether; Ethyleneimino compounds such as 1,6-hexamethylene-N, N′-bisethyleneurea; Halogenated carboxaldehyde compounds such as mucochloric acid and mucophenoxycyclolic acid; 2,3-dihydroxy Dioxane compounds such as dioxane; metal-containing compounds such as titanium lactate, aluminum sulfate, chromium alum, potash alum, chromium acetate, polyamine compounds such as tetraethylenepentamine, hydrazide compounds such as adipic acid dihydrazide, oxazoline groups It is a small molecule or polymer or the like containing two or more.

Furthermore, as the crosslinking agent for the water-soluble resin in the present invention, polyvalent metal compounds listed below are also preferable. By using a polyvalent metal compound, not only acts as a cross-linking agent, but ozone resistance, image blurring, and glossiness can be further improved.
The polyvalent metal compound is preferably water-soluble, for example, calcium acetate, calcium chloride, calcium formate, calcium sulfate, barium acetate, barium sulfate, barium phosphate, manganese chloride, manganese acetate, manganese formate dihydrate. , Ammonium manganese sulfate hexahydrate, cupric chloride, ammonium copper (II) chloride dihydrate, copper sulfate, cobalt chloride, cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate Japanese, nickel acetate tetrahydrate, nickel ammonium sulfate hexahydrate, nickel amidosulfate tetrahydrate, aluminum sulfate, aluminum alum, aluminum sulfite, aluminum thiosulfate, aluminum nitrate nonahydrate, aluminum chloride hexahydrate Japanese, ferrous bromide, ferrous chloride, ferric chloride, ferrous sulfate Ferric sulfate, zinc phenolsulfonate, zinc bromide, zinc chloride, zinc nitrate hexahydrate, zinc sulfate, titanium tetrachloride, tetraisopropyl titanate, titanium acetylacetonate, titanium lactate, chromium acetate, chromium sulfate, sulfuric acid Magnesium, magnesium chloride hexahydrate, magnesium citrate nonahydrate, sodium phosphotungstate, sodium tungsten citrate, 12 tungstophosphoric acid n hydrate, 12 tungstosilicic acid 26 hydrate, molybdenum chloride, 12 molybdenum Phosphoric acid n hydrate, gallium nitrate, germanium nitrate, strontium nitrate, yttrium acetate, yttrium chloride, yttrium nitrate, indium nitrate, lanthanum nitrate, lanthanum chloride, lanthanum acetate, lanthanum benzoate, cerium chloride, cerium sulfate, cerium octylate Praseodymium nitrate, neodymium nitrate, samarium, europium nitrate, gadolinium nitrate, dysprosium nitrate, erbium nitrate, ytterbium nitrate, hafnium chloride, and bismuth nitrate.

  Among these, aluminum-containing compounds (water-soluble aluminum compounds) such as aluminum sulfate, aluminum alum, aluminum sulfite, aluminum thiosulfate, aluminum nitrate nonahydrate, aluminum chloride hexahydrate; and titanium tetrachloride, tetraisopropyl titanate Titanium-containing compounds such as titanium acetylacetonate and titanium lactate are preferred.

  Of the compounds listed above, boron compounds are particularly preferred as the crosslinking agent in the present invention.

  In this invention, it is preferable that the said crosslinking agent is contained 5-50 mass% with respect to the said water-soluble resin, and it is more preferable that 8-30 mass% is contained. When the content of the cross-linking agent is within the above range, the water-soluble resin is effectively cross-linked to increase the hardness of the ink receiving layer, prevent cracks and the like, and obtain excellent scratch resistance. It is possible to effectively suppress the secondary particle size change of the vapor phase silica before and after the application, and as a result, it is possible to obtain an excellent recorded image with high image density and little hue change.

  In addition, although said crosslinking agent may be used individually by 1 type or in combination of 2 or more types, from the viewpoint of further improving ozone resistance, image blurring, and glossiness while acting as a suitable crosslinking agent. It is preferable to contain at least 0.1% by mass of the polyvalent metal compound with respect to the water-soluble resin, more preferably 0.5% by mass or more, and particularly preferably 1.0% by mass or more. preferable. Further, although not particularly limited, the upper limit of the content of the polyvalent metal compound is preferably 50% by mass or less from the viewpoints of image density, ink absorbability, curling of the recording medium, and the like.

  In the present invention, the cross-linking agent may be added to the coating liquid and / or the coating liquid for forming the adjacent layer of the ink-receiving layer when forming the ink-receiving layer, or the cross-linking agent may be added in advance. A cross-linking agent is applied to the ink-receiving layer by coating the above-described coating liquid on a support coated with the coating liquid, or by applying a cross-linking agent-free coating liquid and drying the cross-linking solution after drying. Can be supplied. Preferably, from the viewpoint of production efficiency, it is preferable to add a crosslinking agent to the coating solution or the coating solution for forming the adjacent layer, and supply the crosslinking agent simultaneously with the formation of the ink receiving layer. In particular, it is preferably contained in the coating liquid from the viewpoint of improving the image density and glossiness of the image. Moreover, as a density | concentration of the crosslinking agent in a coating liquid, 0.05-10 mass% is preferable and 0.1-7 mass% is more preferable.

  For example, the crosslinking agent can be suitably applied as follows. Here, a boron compound will be described as an example. That is, when the ink receiving layer is a cross-linked and cured layer coated with a coating liquid, the cross-linking and curing is performed simultaneously with (1) forming the ink receiving layer by applying the coating liquid and (2) applying the coating liquid. Applying a liquid containing a basic compound to the ink receiving layer at any time during the drying of the ink receiving layer formed by coating and before the ink receiving layer exhibits a reduced rate of drying. Is done. The boron compound that is a cross-linking agent may be contained in any of the above coating solutions or solutions, and may be contained in both the coating solution and the solution.

(solvent)
The solvent that can be used for the coating solution is the same as the solvent described in the pre-dispersion liquid.

(Other ingredients)
In addition to the above components, the coating liquid in the present invention may contain other additives as necessary, for example, surfactants, mordants, and ultraviolet rays described in JP-A-2003-335043, paragraphs [0062] to [0079]. Absorber, antioxidant, fluorescent brightener, monomer, polymerization initiator, polymerization inhibitor, anti-bleeding agent, preservative, viscosity stabilizer, antifoaming agent, antistatic agent, matting agent, anti-curl agent, water resistance An agent etc. can be comprised.

-Surfactant-
In the present invention, the coating solution preferably contains a surfactant. As the surfactant, any of cationic, anionic, nonionic, amphoteric, fluorine and silicon surfactants can be used.
Examples of the nonionic surfactant include polyoxyalkylene alkyl ethers and polyoxyalkylene alkyl phenyl ethers (for example, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene Ethylene nonylphenyl ether) and the like, and among these, polyoxyalkylene alkyl ethers are preferable. The nonionic surfactant can be used in coating solutions and solutions. Moreover, the said nonionic surfactant may be used independently and may use 2 or more types together.

  In the present invention, the surfactant content is preferably 0.001 to 2.0 mass%, more preferably 0.01 to 1.0 mass%, based on the total mass of the coating solution.

-Mordant-
In the present invention, in order to improve the water resistance and aging resistance of the formed image, the coating liquid for forming the ink receiving layer can contain at least one mordant.
As the mordant, a cationic polymer (cationic mordant) or an inorganic mordant is preferable as the organic mordant, and the mordant is present in the ink receiving layer so that it can interact with the liquid ink having the anionic dye as an ink. It acts to stabilize the ink and improve water resistance and aging resistance. The organic mordant and the inorganic mordant may be used alone or in combination with the organic mordant and the inorganic mordant.

Examples of the organic mordant include organic mordants described in paragraph numbers [0045] to [0058] of JP-A-2003-335043.
As the organic mordant in the present invention, polyallylamine having a weight average molecular weight of 100,000 or less and derivatives thereof are particularly preferable from the viewpoint of preventing bleeding with time.

  Examples of the inorganic mordant include water-soluble polyvalent metal salts. Specific examples of the inorganic mordant include inorganic mordants described in paragraph numbers [0059] to [0060] of JP-A-2003-335043.

As the inorganic mordant, an aluminum-containing compound, a titanium-containing compound, a zirconium-containing compound, and a metal compound (salt or complex) of Group IIIB of the Periodic Table of Elements are preferable.
Particularly preferred are aluminum-containing compounds and zirconium-containing compounds. Water-soluble aluminum compounds (aluminum sulfate, aluminum alum, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate, etc.), water-soluble zirconium compounds (zirconyl acetate, zirconyl sulfate) Zirconium ammonium carbonate, zirconyl nitrate, zirconium oxychloride, zirconium zirconium hydroxy, etc.) are preferred. Polyaluminum chloride is particularly preferable.
The inorganic mordant may be used alone or in combination. When used in combination, it preferably contains at least an aluminum-containing compound or a zirconium-containing compound. Further, it is preferable to use an aluminum-containing compound and a zirconium-containing compound in combination.
Mordant amount contained in the ink receiving layer in the present invention is preferably from ^{0.01g / m 2 ~5g / m 2} , 0.1g / m 2 ~3g / m 2 is more preferable.

[Ink-receiving layer forming step]
The method for producing an inkjet recording medium of the present invention includes a step of forming an ink receiving layer by applying the coating liquid on a support (hereinafter also referred to as “ink receiving layer forming step”). In the ink receptive layer forming step, the coating solution is applied on a support, but another coating solution may be further applied on the coating solution as necessary.

  The form for applying the coating solution is not particularly limited. For example, known coating apparatuses such as an extrusion die coater, an air doctor coater, a blade coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, and a bar coater. Can be used. Furthermore, other coating solutions used as necessary can be applied in the same manner.

As a moisture application quantity of a coating liquid, 50-200 ml / m < ² > is preferable and 75-150 ml / m < ² > is more preferable. Moreover, as a solid content application quantity of a coating liquid, 5-25 g / m < ² > is preferable and 10-18 g / m < ² > is more preferable.

[Cooling process and drying process]
The method for producing an ink jet recording medium of the present invention includes a step of cooling the ink receiving layer formed in the ink receiving layer forming step and a step of drying the ink receiving layer (hereinafter also referred to as “drying step”). May further be included.
As a method of cooling the ink receiving layer, the support on which the ink receiving layer is formed is cooled for 5 to 30 seconds in a cooling zone maintained at 0 to 10 ° C., and the cooling temperature of the ink receiving layer is 0. A method of setting the temperature to ˜20 ° C. is preferable.
Here, the temperature of the ink receiving layer is measured by measuring the temperature of the film surface.

[Curing process]
The method for producing an ink jet recording medium of the present invention includes (1) the application of the coating liquid, or (2) the drying of the ink receiving layer formed by the application of the coating liquid and the reduction of the ink receiving layer. At any time before showing the rate drying, it may further include a step of applying a liquid containing a basic compound and crosslinking and curing the ink receiving layer (hereinafter also referred to as “curing step”). preferable.

As a method of applying the “(1) at least simultaneously with the application of the coating solution” and the “liquid containing a basic compound”, the coating solution, (other coating solutions as necessary), and “basic compound” A form in which the “liquid containing” is simultaneously applied (multilayer application) so as to be in this order from the support side is preferable.
The simultaneous coating (multilayer coating) can be performed using a known coating apparatus such as an extrusion die coater or a curtain flow coater.

A method of applying a “liquid containing a basic compound” to the “(2) at least during the drying of the ink receiving layer formed by applying the coating liquid and before the ink receiving layer exhibits reduced-rate drying” Is a method called “Wet-On-Wet method” or “WOW method”. Details of the “Wet-On-Wet method” are described, for example, in paragraph numbers [0016] to [0037] of JP-A-2005-14593.
In the present invention, the above-mentioned coating liquid (and other coating liquids as required) is applied simultaneously (simultaneous multilayer coating) or one layer at a time so that the ink receiving layer is formed in this order from the support side. (I) A “liquid containing a basic compound” is further applied on the ink receiving layer after the formation and before the ink receiving layer is in the middle of drying, and before the ink receiving layer exhibits reduced-rate drying. A method, (ii) a method of spraying a “liquid containing a basic compound” by spraying or the like, and (iii) a method of immersing the support on which the ink receiving layer is formed in a “liquid containing a basic compound”. Can be mentioned.

<Liquid containing basic compound>
Here, the “liquid containing a basic compound” in the curing step will be described.
~ Basic compounds ~
The “liquid containing a basic compound” in the present invention contains at least one basic compound.
Basic compounds include ammonium salts of weak acids, alkali metal salts of weak acids (eg, lithium carbonate, sodium carbonate, potassium carbonate, lithium acetate, sodium acetate, potassium acetate, etc.), alkaline earth metal salts of weak acids (eg, carbonate Magnesium, barium carbonate, magnesium acetate, barium acetate, etc.), hydroxyammonium, primary to tertiary amines (eg, triethylamine, tripropylamine, tributylamine, trihexylamine, dibutylamine, butylamine, etc.), primary to tertiary anilines ( For example, diethyl aniline, dibutyl aniline, ethyl aniline, aniline, etc.), optionally substituted pyridine (for example, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 4- (2-hydroxyethyl) -Aminopyrid Etc.), and the like.

  In addition to the basic compound, other basic substances and / or salts thereof may be used in combination with the basic compound. Examples of other basic substances include ammonia, primary amines such as ethylamine and polyallylamine, secondary amines such as dimethylamine, tertiary amines such as N-ethyl-N-methylbutylamine, and alkali metals. And alkaline earth metal hydroxides.

Of these, ammonium salts of weak acids are particularly preferred. The weak acid is an inorganic acid or an organic acid described in Chemical Handbook Fundamentals II (Maruzen Co., Ltd.) or the like and having an pKa of 2 or more. Examples of the weak acid ammonium salt include ammonium carbonate, ammonium hydrogen carbonate, ammonium borate, ammonium acetate, and ammonium carbamate. However, it is not limited to these. Among these, ammonium carbonate, ammonium hydrogen carbonate, and ammonium carbamate are preferable, and are effective in that ink bleeding can be reduced without remaining in the layer after drying.
In addition, a basic compound can use 2 or more types together.

  The content of the basic compound (particularly the ammonium salt of a weak acid) in the “liquid containing the basic compound” is 0.5 to 0.5% relative to the total mass (including the solvent) of the “liquid containing the basic compound”. 10 mass% is preferable, More preferably, it is 1-5 mass%. When the content of the basic compound (particularly the ammonium salt of the weak acid) is particularly in the above range, a sufficient degree of curing can be obtained, and the ammonia concentration becomes too high without impairing the working environment.

The “liquid containing a basic compound” can contain the cross-linking agent and the mordant component as necessary.
The “liquid containing a basic compound” can promote dura mater by being used as an alkaline solution, and is preferably adjusted to pH 7.1 or more, more preferably pH 8.0 or more, and particularly preferably pH 9.0. That's it. When the pH is 7.1 or more, the crosslinking reaction of the binder that may be contained in the second coating solution and / or the third coating solution can be further promoted, and bronzing and cracking of the ink receiving layer can be further prevented. It can be effectively suppressed.

  In addition, water, an organic solvent, or a mixed solvent thereof can be used as a solvent used for preparing the “liquid containing a basic compound”. Examples of the organic solvent that can be used for coating include alcohols such as methanol, ethanol, n-propanol, i-propanol, and methoxypropanol, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, acetonitrile, ethyl acetate, and toluene. .

  In the above (i), as a coating method for applying the “liquid containing a basic compound”, for example, curtain flow coater, extrusion die coater, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, reverse A known coating method such as a roll coater or a bar coater can be used. However, it is preferable to use a method in which the coater does not directly contact the already formed ink receiving layer, such as an extrusion die coater, a curtain flow coater, or a bar coater.

  In the curing process, “before the ink receiving layer starts to decrease in drying” usually means a process for several minutes immediately after the application of the coating liquid (and other coating liquid if necessary). The phenomenon of “constant rate drying” in which the content of the solvent (dispersion medium) in the applied ink receiving layer decreases in proportion to time is shown. About the time which shows this "constant rate drying", it describes in chemical engineering handbook (pages 707-712, Maruzen Co., Ltd. issue, October 25, 1980), for example.

  The above-mentioned conditions for “drying until the ink receiving layer shows reduced-rate drying” are generally performed at 40 to 180 ° C. for 0.5 to 10 minutes (preferably 0.5 to 5 minutes). . The drying time naturally varies depending on the coating amount, but usually the above range is appropriate.

-Other processes-
After the ink receiving layer is formed on the support, the ink receiving layer is subjected to, for example, super calender, gloss calender, etc., and is subjected to calender treatment through the roll nip under heat and pressure, so that surface smoothness, glossiness, It is possible to improve transparency and coating strength. However, since the calendering process may cause a decrease in the porosity (that is, the ink absorbability may be decreased), it is necessary to set a condition in which the decrease in the porosity is small.

As roll temperature in the case of performing a calendar process, 30-150 degreeC is preferable and 40-100 degreeC is more preferable.
Moreover, as a linear pressure between rolls at the time of a calendar process, 50-400 kg / cm is preferable and 100-200 kg / cm is more preferable.

In the case of ink jet recording, the thickness of the ink receiving layer needs to have an absorption capacity sufficient to absorb all of the droplets, and therefore needs to be determined in relation to the porosity in the layer. For example, if the ink amount is 8 nL / mm ² and the porosity is 60%, a film having a layer thickness of about 15 μm or more is required.
Considering this point, in the case of ink jet recording, the layer thickness of the ink receiving layer is preferably 10 to 50 μm.

The pore diameter of the ink receiving layer is preferably 0.005 to 0.025 μm, more preferably 0.01 to 0.025 μm in terms of average pore diameter.
The porosity and pore median diameter can be measured using a mercury porosimeter (trade name “Bore Sizer 9320-PC2” manufactured by Shimadzu Corporation).

In addition, the ink receiving layer is preferably excellent in transparency, as a guide, the haze value when the ink receiving layer is formed on a transparent film support is preferably 30% or less, More preferably, it is 20% or less.
The haze value can be measured using a haze meter (HGM-2DP: Suga Test Instruments Co., Ltd.).

  A polymer fine particle dispersion may be added to a constituent layer (for example, an ink receiving layer or a back layer) of the inkjet recording medium obtained by the production method of the present invention. This polymer fine particle dispersion is used for the purpose of improving film properties such as dimensional stabilization, curling prevention, adhesion prevention, and film cracking prevention. The polymer fine particle dispersion is described in JP-A Nos. 62-245258, 62-1316648, and 62-110066. If a polymer fine particle dispersion having a low glass transition temperature (40 ° C. or lower) is added to the layer containing the mordant, cracking and curling of the layer can be prevented. Further, even when a polymer fine particle dispersion having a high glass transition temperature is added to the back layer, curling can be prevented.

<Support>
As the support for the ink jet recording medium in the present invention, either a transparent support made of a transparent material such as plastic or an opaque support made of an opaque material such as paper can be used. In order to make use of the transparency of the ink receiving layer, it is preferable to use a transparent support or a highly glossy opaque support.

The material that can be used for the transparent support is preferably a material that is transparent and can withstand radiant heat when used in an OHP or a backlight display. Examples of the material include polyesters such as polyethylene terephthalate (PET); polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide and the like. Of these, polyesters are preferable, and polyethylene terephthalate is particularly preferable.
Although there is no restriction | limiting in particular as thickness of the said transparent support body, 50-200 micrometers is preferable at the point which is easy to handle.

  As the highly glossy opaque support, one having a glossiness of 40% or more on the surface on which the ink receiving layer is provided is preferable. The glossiness is a value determined according to the method described in JIS P-8142 (75-degree specular gloss test method for paper and paperboard). Specifically, for example, the support described in paragraph numbers [0083] to [0094] of JP-A No. 2003-335043 can be mentioned.

  A back coat layer can also be provided on the support, and examples of components that can be added to the back coat layer include white pigments, aqueous binders, and other components. For example, paragraph numbers in JP-A-2003-335043 [0095] The components described in [0096] can be mentioned.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the examples, “parts” and “%” represent “parts by mass” and “mass%” unless otherwise specified, and “average molecular weight” and “degree of polymerization” are “mass average molecular weight” and “mass”. It represents “average degree of polymerization”.

Example 1
<Production of support>
A 1: 1 mixture of hardwood bleached kraft pulp (LBKP) and softwood bleached sulfite pulp (NBSP) was beaten to 300 ml with Canadian Standard Freeness (CSF) to prepare a pulp slurry. As a sizing agent, alkylketene dimer is 0.5% to pulp, polyacrylamide is 1.0% to pulp, and cationized starch is 2.0% to pulp. Polyamide epichlorohydrin resin is 0 to pulp. 0.5% was added and diluted with water to make a 1% slurry. This slurry was made with a long paper machine to a basis weight of 170 g / m ² , dried and conditioned to obtain a base paper for polyolefin resin-coated paper as a support.

A polyethylene resin composition in which 10 parts of anatase-type titanium is uniformly dispersed in 100 parts of low-density polyethylene having a density of 0.918 g / cm ³ is melted at 320 ° C. and then thickened at 200 m / min. Extrusion coating was carried out to a thickness of 35 μm, and extrusion coating was carried out using a cooling roll that had been processed with a finely roughened surface. Melted at similarly 320 ° C. The blend resin composition of the low density polyethylene resin 30 parts of a density 0.962 g / cm 70 parts high density polyethylene resin of ³ and a density 0.918 g / cm ³ on the other surface, the thickness Extrusion-coating to a thickness of 30 μm and extrusion-coating using a roughing cooling roll to form a back surface.
The front surface of the polyolefin resin-coated paper is subjected to high-frequency corona discharge treatment, and then an undercoat layer coating solution in which each component is added to water so as to have the following composition is coated with a gelatin coating amount of 50 mg / m ² (about 0.05 μm ) To obtain a support.

"Composition of undercoat layer coating solution"
(1) Lime-processed gelatin 100 parts (2) Sulfosuccinic acid-2-ethylhexyl ester salt 2 parts (3) Chrome alum 10 parts

<Preparation of silica fine dispersion>
-Preparation of silica pre-dispersion A-
Using Conti-TDS (a suction-type dispersion stirrer, manufactured by Dalton Co., Ltd.), components having the following composition were mixed and pre-dispersed. The liquid after pre-dispersion is cooled to 25 ° C., and 0.54 parts of ZA-30 (manufactured by Daiichi Rare Element Chemical Co., Ltd., zirconyl acetate, 50% by weight solid content liquid) is added and preliminarily added. A dispersion was obtained.

"Composition of silica pre-dispersion"
(1) Ion-exchanged water 39.87 parts (2) Aerosil 300 (primary particle diameter 7 nm) 10.00 parts (Evonik Degussa Co., Ltd., vapor phase method silica fine particles)
(3) Charol DC-902P (51.5% solution) 0.78 parts (Daiichi Kogyo Seiyaku Co., Ltd., dispersant)

-Silica fine dispersion A-
The silica pre-dispersion was finely dispersed using a liquid-liquid collision type disperser (Ultimizer, manufactured by Sugino Machine Co., Ltd.) (dispersion condition pressure: 100 MPa). The liquid after fine dispersion was stored in a 45 ° C. constant temperature and humidity chamber (manufactured by Espoc Co., Ltd.) for 10 hours and subjected to heat treatment to obtain a fine dispersion. Got.

<Polyvinyl alcohol solution A>
(1) PVA235 22 parts (Kuraray Co., Ltd., degree of saponification 88.0 mol%, degree of polymerization 3500)
(2) Ion-exchanged water 290 parts (3) Diethylene glycol monobutyl ether 3.4 parts (Kyowa Hakko Chemical Co., Ltd., Butisenol 20P)
(4) 0.4 parts of polyoxyethylene lauryl ether (surfactant) (manufactured by Kao Corporation, Emulgen 109P)

<Preparation of inkjet recording medium>
(Formation of ink receiving layer)
After the corona discharge treatment was performed on the front surface of the support prepared as described above, an in-line liquid having the following composition was applied to the front surface with respect to 132 g / m ² of the ink receiving layer forming coating liquid having the following composition. A coating solution obtained by in-line mixing at a speed of 0.1 g / m ² was applied using an extrusion die coater to form an ink receiving layer.

“Composition of coating solution for forming ink receiving layer”
(1) Silica fine dispersion A 107 parts (2) Ion-exchanged water 11.4 parts (3) Boric acid (7.5% solution) 10.2 parts (4) SC-506 (6.0% solution) 0 .16 parts (manufactured by Haimo Co., Ltd.)
(5) Polyvinyl alcohol solution A 60.5 parts (6) Superflex 650 (25% solution) 3.1 parts (Daiichi Kogyo Seiyaku Co., Ltd., cationic polyurethane)
(7) Emulgen 109% (10% solution) 1.3 parts (manufactured by Kao Corporation, polyoxyethylene lauryl ether, surfactant)
(8) Ethanol (59% aqueous solution) 16.8 parts

"Inline liquid"
(1) Polyaluminum chloride aqueous solution 2.5 parts (manufactured by Daimei Chemical Co., Ltd., solid content concentration 23%, alpha-in 83, basicity 83%)
(2) 7.5 parts of ion exchange water

The ink receiving layer formed by coating was dried with a hot air drier at 80 ° C. (wind speed 3 to 8 m / sec) until the solid content concentration of the ink receiving layer reached 36% by mass. During this time, the ink receiving layer showed constant drying. Immediately after that, it was immersed in a liquid containing a basic compound having the following composition for 3 seconds to adhere 13 g / m ² to the ink receiving layer, and further dried at 72 ° C. for 10 minutes (drying process). An ink receiving layer was formed on one side of the support. The ink receiving layer had a thickness of 27 μm.

"Composition of liquid containing basic compound"
(1) Boric acid 0.65 parts (2) Ammonium carbonate (1st grade: manufactured by Kanto Chemical Co., Ltd.) 5.0 parts (3) Ion-exchanged water 88.35 parts (4) Emulgen 109% (10% solution) 6.0 parts (manufactured by Kao Corporation, polyoxyethylene lauryl ether, surfactant)

<Performance evaluation>
―Measurement of saturated adsorption amount of dispersant―
The saturated adsorption amount of the dispersant was measured by preparing a silica dispersion in which the addition amount of the dispersant was changed and measuring the adsorption amount of the dispersant. The amount of the dispersant adsorbed was measured at 25 ° C., and the dispersion was centrifuged at 80,000 rpm for 30 minutes (Opta XL-100K Ultracentrifuge, manufactured by Beckman Coulter, Inc.), and the silica contained in the supernatant was not yet removed. The adsorbent dispersant was separated, and it was freeze-dried for 24 hours (freeze dryer FDU-540, manufactured by EYALA Co., Ltd.) to remove moisture, and N-methyl was measured by NMR measurement (manufactured by VARIAN Co., Ltd., MERCURY). The peak intensity (3.2 ppm) was measured. Using the dispersant as a standard sample, the amount of adsorption of the dispersant adsorbed on the silica was calculated from the peak intensity comparison of N-methyl with the dispersant.

―Image density―
Using the ink for Frontier Dry Minilab DL410 (manufactured by Fuji Film Co., Ltd.), a black solid image with the highest density was printed on the inkjet recording medium obtained above in an environment of 25 ° C. and 60% RH. The image density of the obtained image was measured using a spectrophotometer Spectrolino (manufactured by Gretag Macbeth) under the conditions of a viewing angle of 2 °, a light source F8, and no filter. Based on the image density of Example 1, evaluation was performed based on the following formula. The higher the numerical value, the larger the numerical value, the higher the image density.
Image density (%) = (1− (Sample image density) / (Image density of Example 1)) × 100

―Viscosity of coating solution―
The viscosity of the coating liquid for forming an ink receiving layer prepared as described above was measured using a B-type viscometer at a liquid temperature of 35 ° C. after 24 hours from the preparation.

-Performance change of silica dispersion over time-
After the silica fine dispersion obtained above was stored at a liquid temperature of 30 ° C. for 7 days, a coating liquid for forming an ink receiving layer was prepared, and an ink jet recording medium was obtained by the method described above. The difference in image density of the ink jet recording medium before and after storage of the silica fine dispersion for 7 days was evaluated.

(Example 2)
In Example 1, it carried out similarly to Example 1 except having changed the amount of Charol DC-902P addition of a silica pre-dispersion liquid from 0.78 part to 0.73 part, and evaluated similarly.

(Example 3)
In Example 2, silica was changed from Aerosil 300 to Aerosil 300SV (primary particle diameter 7 nm, manufactured by Nippon Aerosil Co., Ltd., vapor phase silica fine particles), and the same evaluation was performed as in Example 1.

Example 4
In Example 1, it carried out similarly to Example 1 except having changed the amount of Charol DC-902P addition amount of a silica dispersion from 0.78 part to 0.57 part, and evaluated similarly.

(Example 5)
In Example 1, it carried out similarly to Example 1 except having changed the amount of Charol DC-902P addition of a silica dispersion liquid from 0.78 part to 0.47 part, and evaluated similarly.

(Example 6)
In Example 1, it carried out similarly to Example 1 except having added ZA-30 with respect to the silica pre-dispersion liquid of 45 degreeC, and evaluated similarly.

(Example 7)
In Example 1, it carried out similarly to Example 1 except having added ZA-30 with respect to the silica pre-dispersion liquid of 15 degreeC, and evaluated similarly.

(Example 8)
In Example 1, it carried out similarly to Example 1 except having added ZA-30 with respect to the silica pre-dispersion liquid of 30 degreeC, and evaluated similarly.

Example 9
In Example 1, it carried out similarly to Example 1 except having changed the addition amount of ZA-30 into 0.8 mass% with respect to the gaseous-phase-method silica, and evaluated similarly.

(Example 10)
In Example 1, it carried out similarly to Example 1 except having changed the addition amount of ZA-30 into 5.4 mass% with respect to the gaseous-phase-method silica, and evaluated similarly.

(Example 11)
In Example 1, it carried out similarly to Example 1 except having changed the addition amount of ZA-30 into 7.2 mass% with respect to the gaseous-phase-method silica, and evaluated similarly.

(Example 12)
In Example 1, it carried out similarly to Example 1 except having changed the addition amount of ZA-30 into 10.3 mass% with respect to the gaseous-phase-method silica, and evaluated similarly.

(Comparative Example 1)
In Example 6, it carried out similarly to Example 1 except having changed the amount of addition of Charol DC-902P of a silica dispersion from 0.78 part to 0.98 part, and evaluated similarly.

(Comparative Example 2)
In Example 6, it carried out similarly to Example 1 except having changed the amount of Charol DC-902P addition amount of a silica dispersion from 0.78 part to 0.39 part, and evaluated similarly.

(Comparative Example 3)
In Example 6, it carried out similarly to Example 1 except not implementing the heat processing after fine dispersion, and evaluated similarly.

(Comparative Example 4)
In Comparative Example 1, evaluation was performed in the same manner as in Example 1 except that the heat treatment after fine dispersion was not performed.

(Comparative Example 5)
In Example 6, evaluation was performed in the same manner as in Example 6 except that ZA-30 was not added to the silica predispersion.

  As apparent from Table 1 above, in the examples having the configuration of the present invention, the performance change of the silica dispersion liquid is small, the increase in the viscosity of the ink receiving layer coating liquid is suppressed, and the obtained image density is high. I understand.

Claims (6)

A pre-dispersing step of pre-dispersing a liquid containing a vapor-phase process silica and a dispersant, and a dispersion obtained by the pre-dispersion is 40% by mass or more and 74% by mass with respect to the saturated adsorption amount (mass) of the vapor-phase process silica %. A method for producing a silica dispersion, comprising: a fine dispersion step of finely dispersing as a liquid containing no more than% dispersing agent; and a heat treatment step of heat-treating the dispersion liquid after fine dispersion. The method for producing a silica dispersion according to claim 1, wherein in the pre-dispersing step, the zirconium compound is added after the dispersion obtained by pre-dispersing is cooled to 25 ° C or lower. The said heat processing process is a manufacturing method of the silica dispersion liquid of Claim 1 or Claim 2 which heat-processes at the temperature of 30-80 degreeC for 1 hour or more. The method for producing a silica dispersion according to claim 2 or 3, wherein the addition amount of the zirconium compound is 1 to 10% by mass with respect to the total mass of the vapor phase method silica. A coating liquid preparation step of preparing a coating liquid by mixing a silica dispersion produced by the method for producing a silica dispersion according to any one of claims 1 to 4 and a water-soluble resin, and support An ink receiving layer forming step of forming an ink receiving layer by applying the coating liquid on a body. The ink receiving layer forming step includes (1) simultaneously with the application of the coating liquid, or (2) during the drying of the coating layer formed by the coating of the coating liquid, and before the coating layer exhibits reduced-rate drying. 6. The method for producing an ink jet recording medium according to claim 5, wherein a liquid containing a basic compound is applied at any of the steps, and the coating layer is crosslinked and cured to form an ink receiving layer.