JP2009208293A - Manufacturing method of inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an inkjet recording medium having two or more ink receiving layers which can control wrinkles caused by its contraction. <P>SOLUTION: The method for manufacturing the inkjet recording medium, wherein a gas phase method silica layer coating liquid and pseudo-boehmite layer coating liquid are applied on the support body with both its base paper sides covered by polyolefin resin, includes the process of forming the gas phase method silica layer and uppermost-layered pseudo-boehmite layer by applying the pseudo-boehmite liquid in a way it can be adjacent to the coating layer (1) at the same time as the coating layer is formed by applying the gas phase silica layer, or (2) in the middle of drying the coating layer formed by applying the gas phase method silica layer and before the coating layer shows the falling-drying rate, or (3) after drying the coating layer formed by applying the gas phase method silica layer, the difference in pH between the gas phase method silica layer coating liquid and the pseudo-boehmite layer coating liquid being 0.7 or less, and the gas phase method silica layer coating liquid including water-soluble basic chemical compound. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an inkjet recording medium.

  With the rapid development of the information technology industry in recent years, various information processing systems have been developed, and recording methods and recording apparatuses suitable for each information processing system have been put into practical use. Among these, the ink jet recording method is widely used because it can record on various recording materials, the hardware (device) is relatively inexpensive and compact, and has excellent quietness. ing. In the recording using the ink jet recording method, it has become possible to obtain a so-called photographic-like high quality recorded matter.

  In general, recording materials for ink-jet recording are (1) fast-drying (high ink absorption speed), (2) proper and uniform dot diameter (no bleeding), and (3) granular (4) High roundness of dots, (5) High color density, (6) High saturation (no dullness), (7) Water resistance of image area (8) High whiteness, (9) High storage stability (no yellowing coloring or bleeding of images after long-term storage), (10) It is required to have properties such as being hard to deform and having good dimensional stability (low curl) and (11) good hard running performance.

In view of the above, in recent years, an ink jet recording medium (ink jet recording material) in which an ink receiving layer has a porous structure has been put into practical use and various studies have been made.
In relation to the above, assuming that the ink has a high gloss and good ink absorbability, the inorganic fine particles of the ink receiving layer close to the support are vapor-phase-process silica having at least two ink receiving layers. An ink jet recording material containing alumina hydrate is disclosed in the far ink receiving layer (see, for example, Patent Documents 1 to 3).
JP 2002-321445 A JP 2003-165269 A JP 2003-191633 A

However, Patent Documents 1 to 3 are inferior in terms of bronze and ink absorbability, and have problems due to inferior bronzing and smoothness.

An object of the present invention is to provide a method for producing an ink jet recording medium in which wrinkles due to shrinkage of the ink jet recording medium having two or more ink receiving layers can be suppressed.

<1> A method for producing an inkjet recording medium, wherein a gas phase method silica layer coating solution and a pseudo boehmite layer coating solution are coated on a support on which both surfaces of a base paper are coated with a polyolefin resin,
(1) At the same time when the gas phase silica layer coating solution is applied to form a coating layer,
(2) During the drying of the coating layer formed by applying the gas-phase silica layer coating solution and before the coating layer exhibits reduced-rate drying, or (3) Applying the gas-phase silica layer coating solution After drying the coating layer formed by
Any one of the above, including the step of applying the pseudo boehmite layer coating solution so as to be adjacent to the coating layer to form a vapor phase silica layer and an uppermost pseudo boehmite layer, the vapor phase silica layer An ink jet recording medium characterized in that the pH difference between the coating solution and the pseudo boehmite layer coating solution is less than 0.7, and the pH of the gas phase method silica layer coating solution is adjusted with a water-soluble basic compound. Production method.

<2> The method for producing an ink jet recording medium according to <1>, wherein the water-soluble basic compound is a compound having a guanidino group.
<3> The method for producing an ink jet recording medium according to <2>, wherein the compound having a guanidino group is arginine.
<4> In any one of the above items <1> to <3>, wherein the mass ratio of the pseudo boehmite coating amount (A) and the vapor phase silica coating amount (B) is A / B <1 The manufacturing method of the inkjet recording medium of description.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the inkjet recording medium which can suppress effectively the wrinkle by shrinkage | contraction of the inkjet recording medium which has two or more ink receiving layers can be provided.

Hereafter, the manufacturing method of the inkjet recording medium of this invention is demonstrated in detail.
The method for producing an ink jet recording medium of the present invention is a method for producing an ink jet recording medium in which a gas phase method silica layer coating solution and a pseudo boehmite layer coating solution are coated on a support having both surfaces of a base paper coated with a polyolefin resin. And
(1) At the same time when the gas phase silica layer coating solution is applied to form a coating layer,
(2) During the drying of the coating layer formed by applying the gas-phase silica layer coating solution and before the coating layer exhibits reduced-rate drying, or (3) Applying the gas-phase silica layer coating solution After drying the coating layer formed in any of the following,
Applying the pseudo boehmite layer coating solution so as to be adjacent to the coating layer to form a vapor phase silica layer and an uppermost pseudo boehmite layer;
The pH difference between the gas phase method silica layer coating solution and the pseudo boehmite layer coating solution is less than 0.7, and
PH adjustment of the gas phase method silica layer coating solution is performed with a water-soluble basic compound.
The gas phase method silica layer and the pseudo boehmite layer formed using the gas phase method silica layer coating solution and the pseudo boehmite layer coating solution are collectively referred to as an “ink receiving layer”.
By making the method for producing an ink jet recording medium of the present invention, wrinkles due to shrinkage of the ink jet recording medium having two or more ink receiving layers (gas phase method silica layer and pseudoboehmite layer) are effectively suppressed. obtain.

<Preparation of gas phase method silica layer coating solution and pseudo boehmite layer coating solution>
In the present invention, the method for preparing the gas phase method silica layer coating solution and the pseudo boehmite layer coating solution is not particularly limited, and a known method of mixing and stirring each component contained in each coating solution can be used. .
From the viewpoint of suppressing the coating result more effectively, in the preparation of the gas phase method silica layer coating solution or the pseudo boehmite layer coating solution, first, a fine particle dispersion (gas phase method silica dispersion or pseudo boehmite-like alumina hydrate is used. (Dispersion liquid) is prepared, and then the prepared fine particle dispersion liquid and other components are mixed.
At this time, a form in which the fine particle dispersion and other components are kept warm at the same temperature and mixed while keeping the temperature is preferable. The specific temperature is preferably 15 to 45 ° C. and more preferably 20 to 40 ° C. in the preparation of the gas phase method silica layer coating solution. In the preparation of the pseudo boehmite layer coating solution, 40 to 70 ° C is preferable, and 45 to 60 ° C is more preferable.
The mass ratio of the pseudo boehmite (A) in the pseudo boehmite layer coating solution to the gas phase method silica (B) in the gas phase method silica layer coating solution is A / B <1, which also indicates the smoothness of the coated product. It is preferable in terms of improvement. Furthermore, A / B is more preferably A / B <0.8, and more preferably A / B <0.6.
It is preferable that A / B is less than 1, that is, A is smaller than B, since the smoothness of the coated product is improved and the image clarity is improved.

<PH of gas phase method silica layer coating solution and pseudo boehmite layer coating solution>
In the present invention, the pH difference between the vapor phase method silica layer coating solution and the pseudo boehmite layer coating solution needs to be less than 0.7. Thus, by setting the pH difference between the gas phase method silica layer coating solution and the pseudo boehmite layer coating solution, the ink receiving layer (gas layer) formed by coating the gas phase method silica layer coating solution and the pseudo boehmite coating solution is set. The wrinkle due to the shrinkage of the ink jet recording medium having the phase method silica layer and the pseudo boehmite layer) is remarkably suppressed.
In the pH difference, the pH value of the vapor phase silica layer coating solution is preferably the same as or less than the pH value of the pseudo boehmite layer coating solution.
The pH difference is preferably from 0 to less than 0.7, more preferably from 0 to less than 0.5, and particularly preferably from 0 to less than 0.3.
Among the above, the pH of the vapor phase silica layer coating solution is preferably 3.5 to 5.5, more preferably 3.8 to 5.2, from the viewpoint of suppressing the shrinkage of the recording medium. 0.0 to 5.0 is particularly preferable.
Further, the pH value of the pseudo boehmite layer coating solution is preferably 4.0 to 5.5, more preferably 4.3 to 5.2, and particularly preferably 4.5 to 5.0 from the viewpoint of suppressing bronzing.

<Application of gas phase method silica layer coating solution and pseudo boehmite layer coating solution>
In the present invention, the vapor phase silica layer coating solution and the pseudo boehmite layer coating solution are applied as follows:
(1) At the same time as applying the gas phase silica layer coating solution to form a coating layer (simultaneous multilayer coating),
(2) During the drying of the coating layer formed by applying the gas-phase silica layer coating solution and before the coating layer exhibits reduced-rate drying (sequential coating), or (3) Application of the gas-phase silica layer After drying the coating layer formed by applying the liquid (sequential coating), either
It is necessary to apply a pseudo boehmite layer coating solution.
By passing through this step, the pseudo boehmite layer coating solution can be applied so as to be adjacent to the gas phase method silica layer, and the gas phase method silica layer and the uppermost pseudo boehmite layer can be formed.

The simultaneous multi-layer coating is a method in which a gas phase method silica layer coating solution and a pseudo boehmite layer coating solution are applied simultaneously without providing a drying step.
In the above (2), “before the coating layer exhibits reduced-rate drying” usually refers to a process for several minutes immediately after coating of the coating solution. During this period, the solvent (dispersion medium) in the coated coating layer is used. ) Shows a phenomenon of “constant rate drying” in which the content of) decreases in proportion to time. About the time which shows this "constant rate drying", it describes in chemical engineering handbook (p.707-712, Maruzen Co., Ltd. issue, October 25, 1980), for example.

  The application can be performed by a known application method. Examples thereof include a slide bead method, a curtain method, an extrusion method, an air knife method, a roll coating method, and a Ked bar coating method.

Among the above, from the viewpoint of suppressing mixing of each component in each coating liquid and from the viewpoint of production efficiency, simultaneous multilayer coating is preferable, and among these, simultaneous multilayer coating using a slide bead method, a curtain method, etc. is more preferable. .
In the simultaneous multi-layer coating, it is preferable to apply each coating solution while keeping the temperature warm. As temperature of each coating liquid at this time, 35-55 degreeC is preferable and 40-50 degreeC is more preferable.

<Dry>
The coating film (ink receiving layer) formed by the coating can be dried by a known method.
The drying temperature depends on the heat resistance of the support, but is preferably in the range of 10 to 100 ° C, more preferably 20 to 80 ° C.
In addition, after the application, after the ink receiving layer is sufficiently dried, the pore volume of the ink receiving layer can be increased by performing a heat treatment within a range that does not adversely affect the support, thereby improving the ink absorbability. Further, the water resistance of the ink receiving layer can be improved. The temperature for the heat treatment depends on the heat resistance of the support, but is preferably 30 to 80 ° C, more preferably 40 to 60 ° C.

<Gas phase method silica layer and pseudo boehmite layer (ink receiving layer)>
In the method for producing an inkjet recording medium of the present invention, a vapor phase silica layer coating solution and a pseudo boehmite layer coating solution are laminated in this order from the support side, and a vapor phase silica layer and a pseudo boehmite layer (hereinafter, generic name) are formed on the support. (Also referred to as an “ink receiving layer”).
The formed ink receiving layer is in a state in which a laminated structure composed of at least two layers can be clearly recognized, such as a layer obtained by a gas phase method silica layer coating solution and a layer obtained by a pseudo boehmite layer coating solution. Alternatively, the interface between the layers may be mixed and the laminated structure may not be clearly recognized.
The total thickness of the formed ink receiving layer is not particularly limited, but is preferably 20 to 60 μm and more preferably 30 to 50 μm from the viewpoint of ink absorbability.

  Hereinafter, each component in the ink receiving layer or the ink receiving layer coating solution will be described, and then the support will be described.

<Gas phase silica layer coating solution>
The gas phase method silica layer coating liquid in the present invention is a coating solution for coating and forming a gas phase method silica layer as an ink receiving layer on a support, and includes at least gas phase method silica and a water-soluble basic compound. Further, other components can be used as necessary.

-Gas phase method silica-
The gas phase method silica layer coating solution contains at least one type of gas phase method silica. By using vapor phase silica, a structure having a large porosity can be formed when a film (layer) is formed, the absorption characteristics of the liquid can be improved effectively, and the gloss is high and high. It is possible to record an image with a high density.

  In the present invention, the primary particle diameter of the vapor-phase process silica can be used without any particular limitation, but in particular, the primary particle diameter is preferably 20 nm or less from the viewpoint of increasing gloss and image density. The range of 15 nm is more preferable, and the range of 5 to 10 nm is particularly preferable.

  The “primary particle diameter” in the present invention is an average particle diameter calculated by measuring the particle size distribution of inorganic fine particles by observation with a transmission electron microscope.

  Here, the vapor phase silica is a particle obtained by a dry method (vapor phase method) with respect to a wet method particle (hydrous silica). The gas phase method is mainly a method by high-temperature gas 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. This is a method of obtaining anhydrous silica by (arc method).

Vapor phase silica is different from hydrous silica in the density of silanol groups on the surface, the presence or absence of vacancies, etc., and exhibits different properties.For example, when forming a film, it forms a three-dimensional structure with high porosity. Suitable for 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 5 to 8 / nm ² and many silica fine particles tend to aggregate tightly, whereas in the case of vapor phase method silica, Since the density of silanol groups is 2 to 3 / nm ² and is small, it becomes a loose soft aggregation (flocculate), and as a result, it is estimated that the structure has a high porosity.

  Since vapor phase silica has a particularly large specific surface area, when a film is formed using a preparation liquid containing vapor phase silica, the formed film has high liquid absorption and retention efficiency. Since the refractive index is low, it is possible to impart transparency to the film by dispersing to an appropriate particle size. For example, when an image is formed by applying colored ink, a high color density and good color developability can be obtained. Can do. The transparency of the film is important not only for applications that require transparency, such as OHP, but also for obtaining high color density and good color development gloss even when applied to recording sheets such as photo glossy paper. It is.

  For the vapor phase silica layer coating solution, for example, a fine particle dispersion containing vapor phase silica is prepared in advance, and other components such as a hydrophilic binder and a crosslinking agent are added to the prepared silica dispersion as necessary. Can be prepared. By applying (preferably coating) this gas phase method silica layer coating solution onto a support, an ink jet recording medium having a gas phase method silica layer on the support can be produced.

-Water-soluble basic compound-
The gas phase method silica layer coating solution is preferably adjusted with a water-soluble basic compound. The pH adjustment here means adjustment of pH determined as appropriate in relation to the pseudo boehmite layer coating solution.
The water-soluble basic compound is not particularly limited as long as it can raise the pH value.
Among the above, a water-soluble amino acid having no odor is preferable, and from the viewpoint of the performance of the coated product, an amino acid having a guanidino group is more preferable as an amino acid, and arginine is most preferable.
By using the water-soluble basic compound as the water-soluble amino acid, further the amino acid having a guanidino group, and further arginine, wrinkles due to shrinkage of an ink jet recording medium having two or more ink receiving layers are remarkably suppressed. be able to.
In addition to the above, examples of the water-soluble basic compound include volatile bases such as ammonia, ammonium salts of weak acids, alkali metal salts of weak acids (for example, lithium carbonate, sodium carbonate, potassium carbonate, lithium acetate, acetic acid). Sodium, potassium acetate, etc.), alkaline earth metal salts of weak acids (eg, magnesium carbonate, barium carbonate, magnesium acetate, barium acetate, etc.), hydroxyammonium, primary to tertiary amines (eg, triethylamine, tripropylamine, tributylamine) , Trihexylamine, dibutylamine, butylamine, etc.), primary to tertiary anilines (eg, diethylaniline, dibutylaniline, ethylaniline, aniline, etc.), optionally substituted pyridines (eg, 2-aminopyridine, 3-aminopyridine, 4 Aminopyridine, 4- (2-hydroxyethyl) - or an amino pyridine), and the like.

  Furthermore, examples of the basic substance as the water-soluble basic compound include primary amines such as ammonia, ethylamine and polyallylamine, secondary amines such as dimethylamine, and N-ethyl-N-methylbutylamine. Tertiary amines, alkali metal and alkaline earth metal hydroxides, and the like.

The weak acid is an inorganic acid or an organic acid described in Chemical Handbook Fundamentals II (Maruzen Co., Ltd.) or the like and has 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.
A water-soluble basic compound may be used individually by 1 type, or may be used in combination of 2 or more type.
The content of the water-soluble basic compound in the gas phase method silica layer coating solution may include an amount capable of adjusting the pH, and is not particularly limited.

<Pseudo boehmite layer coating solution>
-Pseudo boehmite-like alumina hydrate-
The pseudo boehmite layer coating liquid in the present invention contains at least one pseudo boehmite-like alumina hydrate. By including pseudo-boehmite-like alumina hydrate in the pseudo-boehmite layer coating liquid in the present invention, the pseudo-boehmite layer formed by applying this coating liquid has a larger amount of hydrophilic binder than gas phase method silica or the like. The transparency after ink absorption can be greatly improved, and an image with an overwhelming high density can be recorded. Further, the ink absorbability and the absorption speed can be improved.

The pseudo-boehmite-like alumina hydrate is represented by a constitutional formula of Al ₂ O ₃ .nH ₂ O (1 <n <3), and refers to an alumina hydrate when n is greater than 1 and less than 3.
Hereinafter, pseudoboehmite-like alumina hydrate is also simply referred to as “alumina hydrate” or “pseudoboehmite”.

The alumina hydrate may be crystalline or amorphous, and the shape thereof may be any one of an indeterminate shape, a spherical shape, a plate shape, etc., or a combination of a plurality. May be.
As an average primary particle diameter of the said alumina hydrate, 3-30 nm is preferable and 3-20 nm is more preferable. The aspect ratio of the alumina hydrate is preferably 2 or more.

  As the pre-alumina hydrate, usually, a secondary particle crystal of several thousand to several tens of thousands nm can be preferably used after being pulverized to about 50 to 300 nm by an ultrasonic wave, a high-pressure homogenizer, a counter collision type jet pulverizer or the like.

  For dispersion of the alumina hydrate of the present invention, an acid such as lactic acid, acetic acid, formic acid, nitric acid, hydrochloric acid, hydrobromic acid, aluminum chloride may be used.

In the present invention, the average primary particle diameter of the alumina hydrate is obtained by observing the diameter of a circle equal to the projected area of each of 100 particles existing in a certain area by electron microscope observation of the dispersed particles. be able to. In addition, you may use a commercial item manufacturer nominal value for an average primary particle diameter.
In the case of spindle-shaped particles, the average particle diameter is obtained by averaging the major axis and the minor axis. The average thickness of the plate-like alumina hydrate is obtained by observing the cut surface of the sheet coated with the alumina hydrate on the film, and the aspect ratio of the alumina hydrate is obtained as the ratio of the average particle diameter to the average thickness. be able to. The average secondary particle size of the alumina hydrate can be measured with a laser diffraction / scattering particle size distribution analyzer using a dilute dispersion.
In addition, the average primary particle diameter and average secondary particle diameter of the vapor phase method silica fine particles to be described later can also be determined by the same method as for alumina hydrate.

  The average pore radius of the alumina hydrate is preferably 1 to 10 nm, and particularly preferably 2 to 7 nm, from the viewpoint of improving the ink absorption rate of the ink receiving layer. When the average pore radius is within the above range, the ink absorptivity is good, the fixing of the dye in the ink is good, and the occurrence of image bleeding can be avoided.

The pore volume of the alumina hydrate is preferably in the range of 0.1 to 0.8 ml / g, particularly in the range of 0.4 to 0.6 ml / g from the viewpoint of improving the ink absorption capacity of the ink receiving layer. A range is preferred. When the pore volume of the ink receiving layer is within the above range, it is possible to avoid the occurrence of cracks and powder falling in the ink receiving layer, and the ink absorption is improved. The pore volume at a pore radius of 2 nm to 10 nm is preferably 0.1 ml / g or more. Within this range, the adsorption of the dye in the ink becomes good. Further, the solvent absorption amount per unit area of the ink receiving layer is preferably 5 ml / m ² or more, and particularly preferably 10 ml / m ² or more. When the solvent absorption amount per unit area is within the above range, it is possible to prevent ink overflow particularly when multicolor printing is performed.

In order for the alumina hydrate to sufficiently absorb and fix the dye in the ink, the BET specific surface area of the alumina hydrate is preferably in the range of 70 to 300 m ² / g. When the BET specific surface area is within the above range, the alumina hydrate can be dispersed well, the pore size distribution is not deviated, the fixing efficiency of the dye in the ink is improved, and image bleeding can be avoided.

In order to increase the concentration of the alumina hydrate dispersion, the number of surface hydroxyl groups of the alumina hydrate is preferably 10 ²⁰ / g or more. When the number of surface hydroxyl groups is small, the alumina hydrate tends to aggregate and it is difficult to increase the concentration of the dispersion.

  The alumina hydrate can be produced by a known method such as hydrolysis of aluminum alkoxide such as aluminum isopropoxide, neutralization of aluminum salt with alkali, hydrolysis of aluminate. The particle size, pore size, pore volume, specific surface area, number of surface hydroxyl groups, etc. of the alumina hydrate can be controlled by the precipitation temperature, aging time, solution pH, solution concentration, coexisting salts and the like.

  For example, JP-A-57-88074, JP-A-62-56321, JP-A-4-275717, JP-A-6-64918, JP-A-7-10535, JP-A-7-267633, U.S. Pat. No. 2,656,321. No., Am. Ceramic Soc. Bull. , 54, 289 (1975), etc. disclose a method for hydrolyzing aluminum alkoxide. These aluminum alkoxides include isopropoxide, propoxide, 2-butoxide and the like. By this method, a highly pure alumina hydrate can be obtained.

  In addition, as a method for obtaining alumina hydrate, as disclosed in JP-A Nos. 54-116398, 55-23034, 55-27824, 56-120508, etc., aluminum Generally, a method for obtaining an inorganic salt or a hydrate thereof as a raw material. Examples of these inorganic salts include inorganic salts such as aluminum chloride, aluminum nitrate, aluminum sulfate, polyaluminum chloride, ammonium alum, sodium aluminate, potassium aluminate, aluminum hydroxide, and hydrates of these inorganic salts. Etc.

  Specifically, for example, an alumina hydrate is obtained by a neutralization reaction between an aqueous solution of an acidic aluminum salt such as aluminum sulfate, aluminum nitrate, or aluminum chloride and a basic aqueous solution such as sodium aluminate, sodium hydroxide, or aqueous ammonia. Can be manufactured. In this case, it is common to mix within a range where the amount of alumina hydrate produced in the liquid does not exceed 5% by mass, and to react under conditions of pH 6 to 10 and temperature 20 to 100 ° C. Further, as described in JP-A-56-120508, a method for growing alumina hydrate crystals by alternately changing the pH to the acid side and the base side, aluminum described in JP-B-4-33728 It can also be produced by a method of rehydrating alumina by mixing alumina hydrate obtained from the inorganic salt and alumina obtained by the Bayer method.

Further, from the viewpoint of print density, the total amount of the pseudo boehmite alumina hydrate of pseudo-boehmite layer pseudo-boehmite layer formed by the coating solution is preferably ^{3~20g / m 2, 5~15g / m} 2 Is more preferable.
From the viewpoint of raw material cost, the total amount of pseudo boehmite-like alumina hydrate in the pseudo boehmite layer formed by the pseudo boehmite layer coating solution is preferably more than 3 g / m ² and not more than 20 g / m ^2. preferably from / ^{m 2,} greater 15 g / ^{m 2,} 15 g / ^{m 2} exceed 5 g / ^{m 2} is more preferred.
Further, from the viewpoint of coexistence of crack suppression and ink absorbency improvement, the content of the pseudo boehmite-like alumina hydrate in the coating liquid is preferably 80 to 100% by mass with respect to the total solid content of the coating liquid. 90-100 mass% is more preferable.

  The pH of the pseudo boehmite layer coating solution can be adjusted using the water-soluble basic compound of the gas phase method silica layer coating solution and a known pH adjusting agent.

<Other ingredients>
In addition to the above, the gas phase method silica layer coating solution and pseudoboehmite coating solution may contain the following other components as necessary.

-Hydrophilic binder-
The gas phase method silica layer coating solution preferably contains at least one hydrophilic binder. The gas phase method silica layer for receiving ink preferably has a porous structure, and can be formed into a porous structure by using a hydrophilic binder together with the gas phase method silica.

Examples of the hydrophilic binder include 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, resins having an ether bond [polyethylene oxide (PEO), Polypropylene oxide (PPO), 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.

From the viewpoint of ink absorptivity when forming a vapor phase silica layer, among the hydrophilic binders, polyvinyl alcohol resins, cellulose resins, resins having ether bonds, resins having a galvamoyl group, having carboxy groups It is more preferable to contain at least one selected from resins and gelatins.
Among these, polyvinyl alcohol (PVA) is particularly preferable.

  The saponification degree of polyvinyl alcohol (PVA) is preferably 90% or less, more preferably 75 to 90 mol%, still more preferably 77 to 90 mol%, particularly preferably 80 to 90 mol%, from the viewpoint of color density. It is.

  Moreover, as a polymerization degree of polyvinyl alcohol (PVA), from a viewpoint of obtaining sufficient film | membrane intensity | strength, 1400-5000 are preferable and 2300-4000 are more preferable. Polyvinyl alcohol having a polymerization degree of less than 1400 and a polymerization degree of 1400 or more may be used in combination.

The content of the hydrophilic binder in the gas phase method silica layer coating solution is to prevent a decrease in film strength and cracking during drying due to an insufficient hydrophilic binder content when the gas phase method silica layer is applied and formed. In addition, it is included in the gas phase method silica layer coating liquid from the viewpoint of preventing the void from being easily blocked by the resin due to the excessive content and preventing the ink absorbability from being decreased due to the decrease in the porosity. 5-40 mass% is preferable with respect to the total solid content, and 10-30 mass% is more preferable.
The vapor phase silica fine particles and the hydrophilic binder may each be a single material or a mixed system of a plurality of materials.

  In addition to unmodified polyvinyl alcohol (PVA), the polyvinyl alcohol includes cation-modified PVA, anion-modified PVA, silanol-modified PVA, and other polyvinyl alcohol derivatives. Polyvinyl alcohol may be used alone or in combination of two or more.

The PVA has a hydroxyl group in its structural unit, and this hydroxyl group and the silanol group on the surface of the silica fine particle form a hydrogen bond, and it is easy to form a three-dimensional network structure in which the secondary particle of the silica fine particle is a chain unit. To do. It is considered that an ink receiving layer having a porous structure with a high porosity can be formed by forming such a three-dimensional network structure.
In the ink jet recording medium obtained by the present invention, the porous vapor-phase silica layer obtained as described above absorbs ink rapidly by capillary action and has good roundness without ink bleeding. Can be formed.

<Crosslinking agent>
The gas phase method silica layer coating solution or pseudoboehmite layer coating solution in the present invention can contain each independently at least one crosslinking agent that crosslinks the hydrophilic binder. By containing a cross-linking agent, the hydrophilic binder can be cross-linked and hardened.
Thus, the film strength, film formability, and water resistance of the pseudo boehmite layer formed using the vapor phase method silica layer or the pseudo boehmite-like alumina hydrate can be improved.
The content of the crosslinking agent in the gas phase method silica layer coating solution is preferably less than 3% by mass with respect to the gas phase method silica in the gas phase method silica layer coating solution, and is 0% by mass (that is, the gas phase method). A form in which the silica layer coating solution does not contain a crosslinking agent is more preferred.
Similarly, when the cross-linking agent is contained in the pseudo-boehmite coating solution, the content of the cross-linking agent is preferably less than 3% by mass with respect to the pseudo-boehmite alumina hydrate in the pseudo-boehmite coating solution. When the content is 3% by mass or more, the coating defect may be deteriorated. From the viewpoint of the coating defect, the pseudo boehmite layer coating solution preferably does not contain a crosslinking agent.

  The crosslinking agent can be used as an aqueous solution in which one or more of them are dissolved in an aqueous solvent. As the aqueous solvent, water such as pure or ion-exchanged water, or a mixed solvent of water and an organic solvent soluble in the water can be used, and details will be described later.

What is necessary is just to select a suitable crosslinking agent suitably in relation to the hydrophilic binder contained in the said vapor phase method silica layer or pseudo-boehmite layer. Especially, when PVA is contained, boric acid and / or its salt are preferable at the point that a crosslinking reaction is quick. As boric acid, for example, orthoboric acid, metaboric acid, hypoboric acid and the like can be used. As the boric acid salt, these soluble salts (sodium salt, potassium salt, ammonium salt, etc.) are preferable. ₂ B ₄ O ₇ · 10H ₂ O, NaBO ₂ · 4H ₂ 0, K ₂ B ₄ O ₇ · 5H ₂ O, NH ₄ HB ₄ O ₇ · 3H ₂ O, NH ₄ BO _{2 and the} like. However, the present invention is not limited to these.

When gelatin is used together with PVA as a hydrophilic binder, the following compounds other than boric acid and its salts can also be used as a crosslinking agent.
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; 1,6- Isocyanate compounds such as hexamethylene diisocyanate; Aziridine compounds described in US Pat. Nos. 3,017,280 and 2998611; Carboximide compounds described in US Pat. No. 3,100,704; Epoxys such as glycerol triglycidyl ether Compounds; ethyleneimino compounds such as 1,6-hexamethylene-N, N′-bisethyleneurea; halogenated carboxaldehyde compounds such as mucochloric acid and mucophenoxycyclolic acid; dioxane such as 2,3-dihydroxydioxane Compounds: titanium lactate, aluminum sulfate, chromium alum, potash alum, metal-containing compounds such as zirconyl acetate and chromium acetate, polyamine compounds such as tetraethylenepentamine, hydrazide compounds such as adipic acid dihydrazide, oxazo A low molecule or polymer containing two or more phosphorus groups.

Crosslinking agents may be used alone or in combination of two or more.
The content of the crosslinking agent in the ink receiving layer (gas phase method silica layer or pseudoboehmite layer) is preferably 5 to 40 parts by mass, and 15 to 35 parts by mass with respect to 100 parts by mass of the total amount of the hydrophilic binder. More preferred. When the content of the crosslinking agent is within the above range, it is effective for preventing cracks and the like.
In the case of using boric acid and / or salts thereof, the total amount of boric acid and / or salt thereof _is preferably 5 to 40 mass% with respect to PVA in H 3 BO ₃ in terms, more preferably 15 to 35 wt% It is. By making the total amount within the above range, it is possible to improve film formability and water resistance while suppressing an increase in viscosity of the coating solution to be prepared.

Further, from the viewpoint of improving ink absorption and suppressing cracking, the content of the crosslinking agent in the ink receiving layer (gas phase method silica layer or pseudo boehmite layer) is preferably 0.2 to 3.0 g / m ^2. 0.4 to 1.5 g / m ² is more preferable.
Moreover, from a viewpoint of suppressing a coating defect more, as content of the crosslinking agent in a pseudo boehmite layer, 2-8 mass% is preferable with respect to pseudo boehmite-like alumina hydrate, and 3-6 mass% is more. preferable.

-Cationic compounds-
The ink-receiving layer coating liquid in the invention preferably contains a cationic compound for the purpose of improving water resistance. Examples of the cationic compound include a cationic polymer and a water-soluble metal compound. When the cationic polymer is used in combination with the vapor phase silica, the transparency tends to decrease, and the water-soluble metal compound improves the transparency. This is presumed to suppress fine cracks generated in the ink receiving layer.

  Examples of the cationic polymer include polyethyleneimine, polydiallylamine, polyallylamine, JP-A-59-20696, 59-33176, 59-33177, 59-1555088, 60-11389, and 60. -49990, 60-83882, 60-109894, 62-198493, 63-49478, 63-115780, 63-280681, JP-A-1-40371, 6- Polymers having a primary to tertiary amino group and a quaternary ammonium base described in JP-A Nos. 234268, 7-125411, and 10-193976 are preferably used. The molecular weight of these cationic polymers is preferably about 5,000 to 100,000.

  The amount of these cationic polymers used is 1 to 10% by mass, preferably 2 to 7% by mass, based on the inorganic fine particles.

  Examples of the water-soluble metal compound include water-soluble polyvalent metal salts. Examples include water-soluble salts of metals selected from calcium, barium, manganese, copper, cobalt, nickel, aluminum, iron, zinc, zirconium, chromium, magnesium, tungsten, and molybdenum. Specifically, for example, calcium acetate, calcium chloride, calcium formate, calcium sulfate, barium acetate, barium sulfate, barium phosphate, manganese chloride, manganese acetate, manganese formate dihydrate, manganese ammonium sulfate hexahydrate, chloride Cupric, ammonium copper (II) chloride dihydrate, copper sulfate, cobalt chloride, cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, sulfuric acid Nickel ammonium hexahydrate, nickel amidosulfate tetrahydrate, aluminum sulfate, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate, ferrous bromide, chloride Ferrous, ferric chloride, ferrous sulfate, ferric sulfate, zinc phenolsulfonate, odor Zinc, zinc chloride, zinc nitrate hexahydrate, zinc sulfate, zirconium acetate, zirconium chloride, chlorinated zirconium oxide octahydrate, hydroxy zirconium chloride, chromium acetate, chromium sulfate, magnesium sulfate, magnesium chloride hexahydrate, citrate Examples include magnesium nitrate nonahydrate, sodium phosphotungstate, sodium tungsten citrate, 12 tungstophosphoric acid n hydrate, 12 tungstophosphoric acid 26 hydrate, molybdenum chloride, 12 molybdophosphoric acid n hydrate, and the like. . Among them, a zirconium-based compound having a high effect of improving transparency and water resistance is preferable.

Examples of the cationic compound include a basic polyaluminum hydroxide compound that is an inorganic aluminum-containing cationic polymer. The basic polyaluminum hydroxide compound has a main component represented by the following general formula 1, 2 or 3, for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ (OH) ₃₄ ] ⁵⁺ , [Al ₂₁ (OH) ₆₀ ] ³⁺ , and the like are water-soluble polyaluminum hydroxides that stably contain basic and high-molecular polynuclear condensed ions.

_{[Al 2 (OH) n Cl} 6-n] m ··· Formula 1
[Al (OH) ₃ ] _n AlCl ₃ Formula 2
Al _n (OH) _m Cl _(3n-m) , 0 <m <3n Formula 3

  These are water treatment agents from Taki Chemical Co., Ltd. under the name of polyaluminum chloride (PAC), from Asada Chemical Co., Ltd. under the name of polyaluminum hydroxide (Paho), and from Riken Green Co., Ltd. It is marketed under the name of Purachem WT and from other manufacturers for the same purpose, and various grades can be easily obtained. In the present invention, these commercially available products can be used as they are, but there are also products having an inappropriately low pH, and in that case, the pH can be appropriately adjusted and used.

In the present invention, the content of each ink receiving layer of the water-soluble metal ^{compound, 0.1g / m 2 ~10g / m} 2, and preferably from ^{0.2g / m 2 ~5g / m 2} .

  Two or more of the above cationic compounds can be used in combination. For example, a cationic polymer and a water-soluble metal compound may be used in combination.

  The ink receiving layer in the present invention preferably contains various oil droplets in order to improve the brittleness of the film. Such oil droplets have a hydrophobicity of 0.01% by mass or less in water at room temperature. High-boiling organic solvents (for example, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil) and polymer particles (for example, styrene, butyl acrylate, divinylbenzene, butyl methacrylate, hydroxyethyl methacrylate, etc.) One or more kinds of polymerized particles) can be contained. Such oil droplets can be preferably used in the range of 10 to 50% by mass relative to the hydrophilic binder.

-Hardener-
In the present invention, a hardening agent other than the above crosslinking agent can be added to the ink receiving layer for the purpose of improving water resistance and dot reproducibility. Specific examples of the hardener include aldehyde compounds such as formaldehyde and glutaraldehyde, ketone compounds such as diacetyl and chloropentanedione, bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1 , 3,5 triazine, a compound having a reactive halogen as described in US Pat. No. 3,288,775, divinyl sulfone, a compound having a reactive olefin as described in US Pat. No. 3,635,718, N-methylol compounds as described in Japanese Patent No. 2,732,316, isocyanates as described in US Pat. No. 3,103,437, US Pat. Nos. 3,017,280 and 2,983,611 described Aziridines such as carbodiimide compounds as described in US Pat. No. 3,100,704, Such epoxy compounds described No. 3,091,537, such as halogen carboxy aldehydes mucochloric acid, such as dioxane derivatives of dihydroxy dioxane, chromium alum, there is a zirconium sulfate and the like. Preferably, by using an organic titanium compound in combination with boric acid or borate, the thixotropic coefficient can be increased without greatly increasing the viscosity.

  In the present invention, in addition to the surfactant and the hardener, the ink receiving layer further includes a coloring dye, a coloring pigment, an ink dye fixing agent, an ultraviolet absorber, an antioxidant, a pigment dispersant, and an antifoaming agent. , Various known additives such as leveling agents, preservatives, optical brighteners, viscosity stabilizers, and pH adjusters may be added.

<Support>
As the support in the present invention, a resin-coated paper in which both sides of a base paper are coated with a polyolefin resin is used.
Although there is no limitation in particular as thickness of a support body, 50-250 micrometers is preferable.

(Base paper)
Examples of the base paper include virgin pulp such as chemical pulp such as LBKP, NBKP, LBSP, NBSP, LUKP, NUKP, LUSP, and NUSP, and mechanical pulp such as GP and TMP, recycled paper from newspapers, magazines, and office paper Paper made using pulp can be used.

The base paper has at least one white pigment having an average particle size of 0.3 to 10 μm as a filler, for example, calcium carbonate, magnesium carbonate, talc, kaolin, silica, alumina, titanium dioxide, barium sulfate, etc. Is used in an amount of 2 to 30% by mass, preferably 4 to 30% by mass. If the average particle size of the white pigment is 0.3 μm or more, the yield can be further improved, and if the average particle size of the white pigment is 10 μm or less, the texture of the paper can be further improved.
In particular, a white pigment having a whiteness degree defined by JIS-M8016 of 88% or more is preferably used. If the white pigment content is 2% by mass or more, a white base paper can be obtained, and if the white pigment content is 30% by mass or less, the strength of the base paper can be further improved. Dirt can be further suppressed.
Various sizing agents, paper strength enhancing agents, antistatic agents, fluorescent whitening agents, dyes and the like generally used in papermaking are blended with the base paper.

  Further, a surface sizing agent, a surface paper strengthening agent, a fluorescent whitening agent, an antistatic agent, a dye, an anchor agent, and the like may be applied to the base paper.

  The thickness of the base paper is preferably 70 to 200 μm. The thickness is adjusted by applying pressure on the paper during paper making or after paper making and compressing it.

  As the support in the present invention, a resin-coated paper obtained by coating a base paper with a polyolefin (polyethylene, polypropylene, etc.) resin is used.

The resin-coated paper refers to one obtained by coating both surfaces of the above-mentioned base paper with resin.
As the resin, low density polyethylene, density 0.94~0.96g / cm ³ density polyethylene having a density of 0.91~0.93g / cm ^3, medium density polyethylene of medium density, polypropylene, polybutene, Various density and melt viscosity index (melt index) such as polyolefin resins such as homopolymers of olefins such as polypentene or copolymers of two or more olefins such as ethylene-propylene copolymers and mixtures thereof Can be used alone or in combination. In particular, from the viewpoint of handling, it is preferable to contain 50% by mass or more of low density polyethylene having a density of 0.91 to 0.93 g / cm ³ in particular, based on the total resin solid content of the resin coating layer.

  Further, in the resin coating layer on the side where the ink receiving layer is provided on at least the resin-coated paper, white particles such as titanium dioxide, barium sulfate, zinc oxide, calcium carbonate, magnesium carbonate having an average particle diameter of 0.1 to 1 μm. At least one pigment can be contained in an amount of 5 to 20% by mass, preferably 7 to 15% by mass, based on the solid content of the total resin. A white pigment having an average particle size of less than 0.1 μm has a hiding effect, and if it is greater than 1 μm, the surface properties of the resin layer deteriorate. In particular, a white pigment having a whiteness degree defined by JIS-M8016 of 88% or more is preferably used. By setting the white pigment to 5% by mass or more based on the solid content of the resin, sufficient opacity of the resin-coated paper can be obtained even when the thickness of the base paper is thin. Moreover, by setting it as 20 mass% or less, the nonuniformity by the generation | occurrence | production of a crack etc. on the surface of a resin layer is suppressed, and intensity | strength can be maintained. Other additives include fatty acid amides such as stearic acid amide and arachidic acid amide, fatty acid metal salts such as zinc stearate, calcium stearate, aluminum stearate and magnesium stearate, antioxidants such as Irganox 1010 and Irganox 1076, Various additives such as blue pigments and dyes such as cobalt blue, ultramarine blue, cecilian blue, and phthalocyanine blue, magenta pigments and dyes such as cobalt violet, fast violet, and manganese purple, fluorescent whitening agents, and UV absorbers are appropriately used. Add in combination.

  The main production method of the resin-coated paper is produced by a so-called extrusion coating method in which a thermoplastic resin is cast on a traveling base paper in a heated and melted state, and the base paper is coated with the resin. Further, before the resin is coated on the base paper, the base paper is preferably subjected to an activation treatment such as corona discharge treatment or flame treatment. The resin coating layer on the back surface is usually a matte surface, and an active treatment such as a corona discharge treatment or a flame treatment can be applied to the front surface or both the front and back surfaces as necessary.

  The front side resin layer on which the ink receiving layer of the resin-coated paper is formed is obtained by mainly heating and melting a thermoplastic resin on one side of the base paper with an extruder, extruding it into a film between the base paper and a cooling roll, pressing and cooling. Manufactured. At this time, the cooling roll is used to form the surface shape of the resin coating layer, and the surface of the resin layer is molded into a mirror surface, a fine rough surface, or a patterned silk or mat shape depending on the shape of the cooling roll surface. can do.

  The back side resin layer opposite to the front side resin layer of the resin-coated paper can also be produced by heating and melting the resin with an extruder, extruding it into a film between the base paper and a cooling roll, pressing and cooling. At this time, preferably, from the viewpoint of transportability in the printer, the cooling roll is preferably a finely roughened surface or patterned depending on the shape of the cooling roll surface so that Ra specified in JIS-B-0601 is 0.8 to 5 μm. For example, it is preferable to mold the material into a silky shape or a mat shape.

  The method of providing the resin coating layer on the base paper includes the method of irradiating the electron beam after applying the electron beam curable resin, in addition to extruding the heated molten resin, and drying after applying the coating solution of the polyolefin resin emulsion. And a method of performing a surface smoothing treatment. In any case, a resin-coated paper applicable to the present invention can be obtained by performing molding with a hot roll having irregularities.

An undercoat layer may be provided on the front side surface of the resin-coated paper in order to improve adhesion. The undercoat layer is applied and dried in advance on the surface of the resin layer of the support before the ink receiving layer is applied. The undercoat layer is a layer mainly comprising a water-soluble polymer capable of forming a film, a polymer latex or the like, and preferably a water-soluble polymer such as gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, or water-soluble cellulose is used. Preferably it is formed using gelatin. 10-500 mg / m < ² > is preferable and, as for the adhesion amount of a water-soluble polymer, 20-300 mg / m < ² > is more preferable. The undercoat layer preferably further contains a surfactant or a hardener. Moreover, it is preferable to perform a corona discharge treatment before forming the undercoat layer (by coating or the like) on the resin-coated paper.

  The present invention will be described more specifically with reference to the following examples. The scope of the present invention is not limited to the specific examples shown below. Unless otherwise specified, “part” and “%” are based on mass.

[Example 1]
(Preparation of polyolefin resin-coated paper 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 to prepare a pulp slurry.
As a sizing agent, alkyl ketene dimer is 0.5% by weight of pulp, polyacrylamide is 1.0% by weight of pulp, and cationized starch is 2.0% by weight of pulp, and polyamide epichlorohydrin resin is used as a sizing agent. 0.5% by weight of pulp 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 polyolefin resin-coated paper base paper.
A polyethylene resin composition in which 10% by weight of anatase-type titanium is uniformly dispersed with respect to 100% by weight of low density polyethylene having a density of 0.918 g / cm ³ is melted at 320 ° C. at 320 ° C. The film was extrusion coated to a thickness of 35 μm per minute, and extrusion coated using a cooling roll with a finely roughened surface.
On the other side, 70 parts by weight of a high density polyethylene resin having a density of 0.962 g / cm ³ and 30 parts by weight of a low density polyethylene resin having a density of 0.918 were similarly melted at 320 ° C. to obtain a thickness. Extrusion coating was carried out to a thickness of 30 μm, and extrusion coating was performed using a cooling roll having a rough surface.

The polyolefin resin-coated paper surface was subjected to a high-frequency corona discharge treatment, and then an undercoat layer having the following composition was applied and dried so that gelatin was 50 mg / m ² to prepare a support.

-Undercoat layer-
Lime-processed gelatin 100 parts Sulfosuccinic acid-2-ethylhexyl ester salt 2 parts Chromium alum 10 parts

(Preparation of pigment dispersion)
-Preparation of alumina white dispersion-
40.2 kg of ion-exchanged water is added to a suction disperser CONTI-TDS (manufactured by Dalton Co., Ltd.), and while stirring at the maximum rotational speed, 20.2 kg of Cataloid AP-5 (manufactured by Catalytic Chemical Industry, pseudoboehmite alumina primary particle size) 8 nm) was added little by little to obtain a pseudo boehmite white coarse dispersion. The dispersion time at this time was 35 minutes.
The pseudo-boehmite white coarse dispersion was finely dispersed with a high-pressure disperser (Ultimizer HJP25005 manufactured by Sugino Machine Co., Ltd.) to obtain a transparent pseudo-boehmite dispersion having a solid content concentration of 32%. The pressure at this time was 100 MPa, and the discharge rate was 600 g / min. The particle size of the pseudo boehmite dispersion at this time was 0.050 μm.

-Preparation of vapor phase silica dispersion-
First, 16704 g of ion-exchanged water, 266 g of a dispersant aqueous solution (Charol DC902P, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 250 g of an arginine aqueous solution (concentration: 8%) were first stirred with a dissolver, and gas phase silica (Aerosil 300; manufactured by Nippon Aerosil) was added thereto. 3046 g was added and stirred for 10 minutes.
This gas phase silica crude dispersion was finely dispersed with a high-pressure disperser (Ultimizer HJP25005 manufactured by Sugino Machine Co., Ltd.) to obtain a gas phase silica dispersion having a solid content concentration of 15%. The pressure at this time was 100 MPa, and the discharge rate was 600 g / min.

(Preparation of inkjet recording sheet)
-Preparation of pseudo boehmite layer (upper layer) coating solution-
2500 g of prepared pseudo boehmite alumina dispersion, 1062.5 g of ion-exchanged water, polyvinyl alcohol (PVA235 manufactured by Kuraray Co., Ltd., degree of saponification 88%, degree of polymerization 3500) 1104 g, 10% surfactant aqueous solution (Swanol AM2150 manufactured by Nikko Chemical) 6.8 g of each liquid was kept at 50 ° C. and then mixed to obtain a pseudo boehmite layer coating liquid.

-Preparation of gas phase method silica layer (lower layer) coating solution-
1784.5 g of the vapor phase silica dispersion prepared above, 190 g of ion exchange water, 158.4 g of 7.5% boric acid aqueous solution, 140 g of alcohol aqueous solution (59% AP-7; manufactured by Nippon Alcohol Sales Co., Ltd.), polyvinyl alcohol 7 % Aqueous solution (PVA235, saponification degree 88%, polymerization degree 3500; manufactured by Kuraray Co., Ltd.) 934.8 g, 10% surfactant aqueous solution (Nikko Chemical's Swanol AM2150) 22.8 g, and each liquid was kept at 30 ° C. After mixing, a gas phase method silica layer coating solution was obtained.

Each of the upper layer coating solution and the lower layer coating solution is kept at 50 ° C., and 188 g of a 7.5% boric acid aqueous solution kept warm in the upper layer solution is added in-line, and then simultaneously applied to the support by a slide bead coating device, and the film surface temperature is Was set and dried for 2 minutes so that the temperature became 20 ° C., and then dried at 80 ° C. for 10 minutes to obtain an ink jet recording sheet.
The pseudo boehmite coating amount at this time was 8 g / m ² , and the vapor phase method silica coating amount was 14.6 g.

[Example 2]
An inkjet recording sheet was prepared in the same manner as in Example 1 except that 16704 g of ion-exchanged water was changed to 16854 g and 250 g of the arginine aqueous solution was changed to 100 g in preparation of the vapor phase silica dispersion of Example 1.

[Example 3]
An inkjet recording sheet was prepared in the same manner as in Example 1, except that 16704 g of ion-exchanged water was changed to 16904 g and 250 g of the arginine aqueous solution was changed to 50 g in preparation of the vapor phase silica dispersion of Example 1.

[Examples 4 and 5]
In the production of the ink jet recording medium of Example 1, the same procedure was performed except that the lower layer liquid and the upper layer liquid were used so that the solid content coating amounts of pseudoboehmite and gas phase method silica were the coating amounts shown in Table 1. Thus, an inkjet recording sheet was produced.

[Example 6]
An inkjet recording sheet was prepared in the same manner except that the preparation of the vapor phase silica dispersion of Example 1 was changed as follows.
-Preparation of vapor phase silica dispersion-
First, 16874 g of ion-exchanged water, 266 g of a dispersant aqueous solution (Charol DC902P, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 80 g of an aqueous ammonia solution (concentration: 2.5%) were first stirred with a dissolver, and gas phase silica (Aerosil 300; manufactured by Nippon Aerosil Co., Ltd.) was stirred there. ) Was added and stirred for 10 minutes.
This crude gas phase silica dispersion was finely dispersed with a high-pressure disperser (Ultimizer HJP25005, manufactured by Sugino Machine Co., Ltd.) to obtain a transparent gas phase silica dispersion having a solid content concentration of 15%. The pressure at this time was 100 MPa, and the discharge rate was 600 g / min.

[Comparative Example 1]
An inkjet recording sheet was prepared in the same manner as in Example 1 except that ion-exchanged water was used instead of using the arginine aqueous solution in the production of the vapor phase silica dispersion of Example 1.

(Evaluation)
The following evaluation was performed about the sheet | seat for inkjet recording obtained by the Example and the comparative example. The evaluation results are shown in Table 1.

-1. Shrinkage
The case where the shrinkage wrinkles at both ends of the coated surface of the ink jet recording sheet could be observed visually was rated as x, and the case where the shrinkage wrinkles could not be observed was marked as o.

-2. Print density
Using an inkjet printer PM-A820 (Seiko Epson), solid printing of yellow (Y), magenta (M), cyan (C), and black (Bk) on each of the inkjet recording sheets obtained above. Went.
Yellow (Y), magenta (M), cyan (C), and black (Bk) solid image density using Gretag Spectrolino SPM-50, with a viewing angle of 2 °, light source D50, and no filter Measured.

  As is clear from Table 1, it was found that the comparative example having a pH difference of 0.9 was inferior because shrinkage wrinkles could be observed. On the other hand, no shrinkage wrinkles were observed in any of the examples with a small pH difference.

Claims (4)

A method for producing an ink jet recording medium in which a gas phase method silica layer coating solution and a pseudo boehmite layer coating solution are coated on a support on which both surfaces of a base paper are coated with a polyolefin resin,
(1) At the same time when the gas phase method silica layer coating solution is applied to form a coating layer,
(2) During the drying of the coating layer formed by applying the gas phase method silica layer coating solution, and before the coating layer exhibits reduced rate drying, or (3) Applying the gas phase silica layer coating solution After drying the coating layer formed in the
Any one of the above, including the step of applying the pseudo boehmite layer coating solution so as to be adjacent to the coating layer to form a vapor phase silica layer and an uppermost pseudo boehmite layer, the vapor phase silica layer An ink jet recording medium characterized in that the pH difference between the coating solution and the pseudo boehmite layer coating solution is less than 0.7, and the pH of the gas phase method silica layer coating solution is adjusted with a water-soluble basic compound. Production method.   The method for producing an ink jet recording medium according to claim 1, wherein the water-soluble basic compound is a compound having a guanidino group.   The method for producing an ink jet recording medium according to claim 2, wherein the compound having a guanidino group is arginine.   The ink jet recording according to any one of claims 1 to 3, wherein the mass ratio of the pseudo boehmite coating amount (A) and the vapor phase silica coating amount (B) is A / B <1. A method for manufacturing a medium.