JP2005178189A - Method for producing inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an inkjet recording sheet which is greatly improved in cracking of an ink receiving layer and exhibits excellent glossiness, ink absorption, image quality and long-term storage stability. <P>SOLUTION: In the method for producing an inkjet recording sheet having at least two layers of ink receiving layers containing inorganic fine particles and a binder on a support, at least one layer of an inside ink receiving layer containing inorganic fine particles and a binder is formed on the support, and an aqueous solution containing a cationic compound is coated on the inside ink receiving layer to form a water coating layer. Then, at least one layer of an outside ink receiving layer containing inorganic fine particles and a binder is formed on the water coating layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing an ink jet recording sheet having an ink receiving layer containing inorganic fine particles and a binder on a support.

The ink jet recording method that forms an image by ejecting liquid ink from a fine nozzle onto a recording body has low noise during recording, easy colorization, high-speed recording, and other printing It is widely used in terminal printers, facsimiles, plotters, form printing, and the like because it is less expensive than the apparatus.
In recent years, due to the rapid spread of printers, high definition and high speed, and the advent of digital cameras, advanced characteristics have also been demanded on the recording medium side. That is, there is a strong demand for the realization of a recording medium having both image quality and storage stability comparable to silver salt photographs excellent in ink absorption, recording density, water resistance and storage stability.

  In order to improve the ink absorptivity, recording density, image quality, etc. of the recording medium, for example, a method has been proposed in which inorganic fine particles such as amorphous silica are provided on a support together with a binder as an ink receiving layer (for example, patents). Reference 1-8). In order to improve the gloss and image quality of the recording material, a method using synthetic silica fine particles in the ink receiving layer has been proposed.

  Furthermore, a method of adding at least one of metal oxides such as phosphotungstic acid, phosphomolybdic acid, and chromic chloride, metal chloride, and tannic acid, hindered phenols, in order to improve image storability A method of adding an antioxidant such as a method, a method of adding a hindered amine, a method of adding a UV absorber such as benzophenone, benzotriazole or phenylsalicylic acid, a method of adding a thiourea compound, 2-mercaptobenzo Method of adding a specific mercapto compound such as thiazole, 2-mercaptobenzimidazole, method of adding dithiocarbamate, thiuram salt, thiocyanate or thiocyanate, method of adding basic polyaluminum hydroxide, acidification Addition of zirconium-based active inorganic polymer Etc., a method of adding various additives have been proposed.

In order to improve the recording density and the water resistance of the image, a method of incorporating a cationic polymer or a basic latex in the ink receiving layer has been proposed. Examples of the cationic polymer include quaternary ammonium type polymers such as polydiallyldimethylammonium chloride, secondary amine type polymers such as polydiallylamine, primary amine type polymers such as polyallylamine salts and polyamidine salts, or polyalkylene polyamine dicyandiamide hydrochloride. Condensed cationic polymers such as salt condensates have been proposed (see, for example, Patent Documents 9 to 13).
JP-A-55-51583 JP-A-56-157 JP-A-57-107879 JP-A-57-107880 JP 59-230787 A JP-A-62-183382 Japanese Patent Laid-Open No. Sho 62-184879 Japanese Patent Laid-Open No. 64-11877 JP 60-83882 A JP-A-61-61887 JP-A-62-238783 JP-A-8-39927 JP-A-60-49990

  However, the ink jet recording sheet obtained by using these techniques has a high printing density when a full-color ink jet recording image is formed, and is excellent in the water resistance and light resistance of the image. In particular, the storage stability (heat resistance and humidity) under high temperature and high humidity was insufficient. Further, if the ink absorbability is increased, the surface of the ink receiving layer is likely to be cracked. For this reason, the gloss of the sheet is lowered and the image quality of the formed image is deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an ink jet recording sheet, in which the cracks of the ink receiving layer are significantly improved and the gloss, ink absorbability, image quality, and long-term storage are all excellent.

  The present inventors can solve these problems by forming an ink-receiving layer from a plurality of layers and applying a water solution layer containing a cationic compound between the layers to form a water-coating layer. As a result, the present invention has been completed.

The present invention includes the following embodiments.
[1] In the method for producing an ink jet recording sheet having at least two ink receiving layers containing inorganic fine particles and a binder on a support, at least one layer containing inorganic fine particles and a binder is provided on the support. After forming the inner ink receiving layer, an aqueous solution containing a cationic compound is coated on the inner ink receiving layer to form a water coating layer, and then inorganic fine particles and a binder are coated on the water coating layer. A method for producing an ink jet recording sheet, comprising forming at least one outer ink receiving layer.
[2] The method for producing an inkjet recording sheet according to [1], wherein the aqueous solution containing the cationic compound further contains a crosslinking agent.
[3] The method for producing an inkjet recording sheet according to [2], wherein the crosslinking agent is a boron compound.
[4] The inkjet recording according to any one of [1] to [3], wherein the cationic compound is at least one selected from the group consisting of a cationic polymer, a water-soluble aluminum compound, and a water-soluble zirconium compound. Sheet manufacturing method.
[5] The method for producing an ink jet recording sheet according to any one of [1] to [4], wherein the content of the cationic compound in the water-coating layer is 0.01 to 10 g / m ² .
[6] The cationic polymer is represented by the following general formula (1) or (2):

〔式中、ｍ、ｎはそれぞれ独立に０または１〜４の整数を表し、Ｘは酸残基を表す。〕
で表される少なくとも１種の構成単位（ａ１）と、下記一般式（３）、（４）、（５）または（６）：

[Wherein, m and n each independently represents 0 or an integer of 1 to 4, and X represents an acid residue. ]
And at least one structural unit (a1) represented by the following general formula (3), (4), (5) or (6):

〔式中、Ｒ^１〜Ｒ^８はそれぞれ独立に水素原子または炭素数１〜４のアルキル基を表し、Ｙ、Ｚはそれぞれ独立の酸残基を表す。〕
で表される少なくとも１種の構成単位（ａ２）とを含むポリマー（Ａ）である［１］〜［５］のいずれか１項に記載のインクジェット記録シートの製造方法。

[Wherein, R ^{1 to} R ⁸ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Y and Z each represents an independent acid residue. ]
The method for producing an inkjet recording sheet according to any one of [1] to [5], which is a polymer (A) including at least one type of structural unit (a2) represented by:

  According to the present invention, there is provided a method for producing an ink jet recording sheet, in which the crack of the ink receiving layer is greatly improved, and all of glossiness, ink absorbability, image quality, and long-term storage are excellent.

Hereinafter, the present invention will be described in more detail.
The method for producing an inkjet recording sheet of the present invention is a method of forming at least two ink-receiving layers containing inorganic fine particles and a binder on a support,
After forming at least one inner ink receiving layer containing inorganic fine particles and a binder on the support (inner ink receiving layer forming step), an aqueous solution containing a cationic compound is applied onto the inner ink receiving layer. Forming a water coating layer (water coating layer forming step), and forming at least one outer ink receiving layer containing inorganic fine particles and a binder on the water coating layer (outer ink receiving layer forming step) It is characterized by being performed.

Hereinafter, each step will be described.
"Inner ink receiving layer formation process"
In this step, first, at least one inner ink receiving layer containing inorganic fine particles and a binder is formed on a support.
≪Support body≫
As the support, a known ink jet recording paper can be appropriately used.
More specifically, as a support, for example, paper (acid paper, neutral paper, etc.), synthetic paper, plastic film, a support coated with plastic on one or both sides of paper (RC paper), one side of paper or The thing etc. which bonded together the nonwoven fabric or the plastic film through the adhesive agent on both surfaces are mentioned.
Examples of the plastic film include polyolefin resins such as polyester and polypropylene, and films such as nylon.

Among these, in order to obtain a clear image at a higher density, it is preferable to use a water-resistant support that does not allow ink liquid to penetrate into the support.
As the water-resistant support, a support in which both sides of the paper are coated with a polyolefin resin is preferably used because a recorded image is close to photographic quality and a high-quality image can be obtained at low cost.

  Although there is no restriction | limiting in particular as thickness of a support body, For example, 100-400 micrometers is preferable.

≪Inner ink receiving layer≫
<Inorganic fine particles>
Examples of the inorganic fine particle material to be contained in the ink receiving layer include zeolite, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, zinc sulfide, and zinc carbonate. , Satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, amorphous silica, aluminum hydroxide, alumina, alumina hydrate, aluminosilicate, boehmite, pseudo-boehmite, etc. Various publicly known inorganic fine particles are appropriately used. In particular, amorphous silica, aluminosilicate, aluminum and alumina hydrate are preferable from the viewpoint of ink absorbability, and silica is particularly preferable. Further, the same inorganic fine particles used for the outer ink receiving layer described later can be used.

<Binder>
Examples of binders incorporated in the inner ink receiving layer include starch derivatives such as oxidized starch and etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, proteins such as casein, gelatin and soybean protein, and complete (partial) Ken. Polyvinyl alcohol, silicon-modified polyvinyl alcohol, polyvinyl alcohols such as acetoacetyl group-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, salts of styrene-maleic anhydride copolymer, styrene-butadiene latex, acrylic latex, polyester polyurethane Aqueous adhesives such as latex and vinyl acetate latex, or polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copoly Chromatography, polyvinyl butyral, and an organic solvent-soluble resins such as alkyd resin. These binders may be used alone or in combination.

  Among these binders, polyvinyl alcohols are preferable because they have high transparency and water resistance, are nonionic and can be mixed with various materials, and further have a relatively low swellability around room temperature. In addition, there is an advantage that the ink does not swell and block the voids at the initial permeation of the ink.

  Among the polyvinyl alcohols, completely (partially) saponified polyvinyl alcohol, cation-modified polyvinyl alcohol or silicon-modified polyvinyl alcohol is particularly preferably used.

As the complete (partially) saponified polyvinyl alcohol, a partially saponified polyvinyl alcohol or a completely saponified polyvinyl alcohol having a saponification degree of 80% or more, particularly 95% or more is preferable. 000 is preferable, and 500 to 5,000 is more preferable.
The reason why a portion having a saponification degree of 80% or more or a completely saponified polyvinyl alcohol is preferable is that it has excellent water resistance. The reason why the average degree of polymerization is preferably 200 to 5,000 is that when a polymer having a degree of polymerization in this range is used, the viscosity is excellent in water resistance and easy to handle.

  The cation-modified polyvinyl alcohol is preferably polyvinyl alcohol having a primary, secondary, or tertiary amino group or a quaternary ammonium base in the main chain or side chain of the polyvinyl alcohol.

  The binder is used in an amount of preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass with respect to 100 parts by mass of the inorganic fine particles.

<Cationic compound>
If necessary, various known cationic compounds as described later can also be used.

<Other ingredients>
In the present invention, it is preferable to use a crosslinking agent as described later together with the binder. Thereby, generation | occurrence | production of a crack can be reduced and ink absorptivity, glossiness, an image quality, etc. improve further.
The cross-linking agent may be blended in the coating liquid for forming the ink receiving layer, or the cross-linking agent solution may be applied before the ink receiving layer is applied or after the ink receiving layer is applied.
The coating amount of the crosslinking agent, preferably ^{0.01~1.0g / m 2, 0.05~0.5g / m} 2 is more preferable. If it is less than 0.01 g / m ² , the effect of preventing cracking will be low, and if it exceeds 1.0 g / m ² , the ink receiving layer may be broken due to strong shrinkage during drying or ink absorbability may be reduced. There is.

  In the ink receiving layer, various known pigment dispersants, thickeners, antioxidants, light stabilizers, water-soluble metal salts, fluidity modifiers, antifoaming agents, antifoaming agents, release agents In addition, a foaming agent, a penetrating agent, a coloring dye, a coloring pigment, a fluorescent brightening agent, an antiseptic, an antibacterial agent and the like can be appropriately added.

≪Formation of inner ink receiving layer≫
The inner ink receiving layer is formed by applying and drying the inner ink receiving layer coating liquid containing the various components described above on at least one surface of the support.
The coating amount of the inner ink receiving layer coating liquid is preferably ² to 50 g / m ² in terms of dry mass, and more preferably ³ to 30 g / m ² . Incidentally, when the coating amount is within this range, the recording image quality and the coating film strength are excellent.
The ink receiving layer coating liquid can be applied by a coating method such as a bar coater, a blade coater, an air knife coater, a gravure coater, a die coater, or a curtain coater.
In the present invention, the inner ink receiving layer may be a single layer or may be composed of at least two layers.

"Water coating layer formation process"
Next, an aqueous solution containing a cationic compound is applied onto the inner ink-receiving layer formed as described above to form a water-coating layer.

<Cationic compound>
As the cationic compound used in the present invention, various publicly known cationic compounds in the field of inkjet recording sheets such as a cationic polymer, a water-soluble aluminum compound, a water-soluble zirconium compound, and a water-soluble titanium compound are appropriately used. . In particular, from the viewpoint of water resistance, a cationic polymer, a water-soluble aluminum compound and a water-soluble zirconium compound are preferably used, and among these, a cationic polymer is preferably used.
These cationic compounds may be used alone or in combination of two or more.

As the cationic polymer, for example, a primary amine type cation having a primary amine salt such as monoallylamine salt, vinylamine salt, N-vinylacrylamidine salt, dicyandiamide / formalin polycondensate, dicyandiamide / polyethyleneamine polycondensate as a structural unit. Polymer, secondary amine type cationic polymer having a secondary amine salt such as diallylamine salt, ethyleneimine salt as a structural unit, tertiary amine type cationic polymer having a tertiary amine salt such as diallylmethylamine salt as a structural unit, diallyldimethyl Quaternary ammonia such as ammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acrylamidopropyltrimethylammonium chloride, dimethylamine / epichlorohydrin polycondensate Quaternary ammonium type cationic polymers having a ium salt as a constituent unit thereof.
Examples of the water-soluble aluminum compound include basic aluminum chloride, basic aluminum sulfate, and basic fatty acid aluminum.
Examples of the water-soluble zirconium compound include zirconyl chloride, basic zirconyl chloride, zirconyl nitrate, and fatty acid zirconyl.
Specific examples of fatty acids in basic fatty acid aluminum, fatty acid zirconyl and the like include, for example, formic acid, acetic acid, propionic acid, butanoic acid, glycolic acid, 3-hydroxypropionic acid, 4-hydroxybutanoic acid, glycine, β-alanine 4-aminobutanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid and the like, among which acetic acid is particularly preferable.

As a coating amount of a cationic compound, 0.01-10 g / m < ² > is preferable, More preferably, it is 0.05-5 g / m < ² >. When used in this range, the image quality and the image storability are excellent.

  In the present invention, in particular, at least one structural unit (a1) represented by at least the general formula (1) or (2) and the general formula (3), (4), (5) or (6) The polymer (hereinafter referred to as polymer (A)) containing at least one structural unit (a2) represented by By using the aqueous solution containing this polymer (A), the crack of the ink receiving layer is greatly improved. Also, the glossiness and ink absorbability of the ink receiving layer are improved. Further, the image quality of the image formed on the ink receiving layer and its long-term storage stability are improved.

In the general formulas (1) and (2), m and n each independently represent 0 or an integer of 1 to 4, preferably 1.
In general formulas (3) to (6), R ^{1 to} R ⁸ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ^{1 to} R ⁸ are preferably all hydrogen atoms from the viewpoint of easy availability of the monomer and resistance to cracking.
In the general formulas (2), (4), and (6), X, Y, and Z each represent an independent acid residue, and the acid (HX, HY, HZ, HW) may be an inorganic acid or an organic acid. As specific examples, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, pyrophosphoric acid, metaphosphoric acid and the like as inorganic acids, formic acid, acetic acid, propionic acid, methanesulfonic acid, p-toluenesulfonic acid as organic acids Etc. Among these acids, hydrochloric acid, sulfuric acid, and methanesulfonic acid are particularly preferable because they are effective for image preservation.

Specific examples of the structural unit (a1) represented by the general formula (1) or (2) include a primary amine having a vinyl alkyl group such as vinylamine, allylamine, vinylethylamine, vinylbutylamine, or an acid salt thereof. And the structural unit.
Specific examples of the structural unit (a2) represented by the general formula (3), (4), (5) or (6) include diallylamine, di (2-methylallyl) amine, di (2-ethylallyl) amine and the like. And a structural unit having a secondary amine having two vinylalkyl groups or an acid salt thereof as a monomer.
In particular, a cationic polymer in which the structural unit (a1) is a structural unit having allylamine or its acid salt as a monomer and the structural unit (a2) is a structural unit having diallylamine or its acid salt as a monomer provides high image quality. It is preferable because it has excellent storage stability such as heat and humidity resistance, light resistance and ozone resistance.

  In the polymer (A), the molar ratio of the structural unit (a1) to the structural unit (a2) is preferably 0.1: 1 to 10: 1, more preferably 0.5: 1 to 5: 1. By setting the molar ratio within this range, the ink receiving layer has particularly high image quality and excellent long-term image preservation.

The polymer (A) can further have a structural unit (a3) other than the structural units (1) to (6) described above.
As the structural unit (a3), structural units having various known ethylenically unsaturated compounds copolymerizable with the monomers of the structural units (1) to (6) as monomers can be used.
Specific examples of the structural unit (a3) include, for example, acrylamide, methacrylamide, N-methylacrylamide, N, N-dimethylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, diacetone acrylamide, N-methylolacrylamide, N , N-dimethylacrylamide, N, N-dimethylaminopropylacrylamide, acroylmorpholine, N-vinylpyrrolidone, hydroxyethyl acrylate, hydroxyethyl methacrylate, methoxyethyl acrylate, vinyl acetate, N-vinylformamide, acrylonitrile, acrylic Examples thereof include structural units having acid, methyl acrylate, ethyl acrylate and the like as monomers.

  In order to exert the effect of the present invention more, the total amount of the structural unit (a1) and the structural unit (a2) in the polymer (A) is preferably 50% by mass or more of the polymer (A).

  The molecular weight of the polymer (A) used in the present invention is preferably 5,000 to 500,000, more preferably 10,000 to 200,000. Within this range, the image quality is good, the storage stability such as light resistance and heat and humidity resistance, the ink absorbability are excellent, and the cracks are also improved.

<Crosslinking agent>
In this invention, it is more preferable from a viewpoint of crack control to use a crosslinking agent together in the aqueous solution containing the said cationic compound.
Specific examples of the crosslinking agent include, for example, boron compounds such as boric acid, borax, borate, glyoxal, melamine / formaldehyde, glutaraldehyde, methylol urea, polyisocyanate compound, epoxy compound, aziridine compound, carbodiimide compound, dihydrazide A compound, an aluminum compound, a zirconium compound, etc. are mentioned. Of these, boron compounds are preferable, and borax is particularly preferable.

  In the present invention, it is particularly preferable to apply an aqueous solution containing borax together with the polymer (A). By applying a mixed liquid of borax and polymer (A), the heat and humidity resistance of the image is particularly high, and the cracking suppressing effect is high. Furthermore, since the pH of the mixed solution is adjusted to 7.0 to 10.0, preferably 7.5 to 9.0 with an alkali such as sodium hydroxide, it is more effective for cracking. preferable.

When formulating a crosslinking agent, the coating amount of the crosslinking agent, preferably ^{0.01~3.0g / m 2, 0.05~2.0g / m} 2 is more preferable. If it is less than 0.01 g / m ² , the effect of preventing cracking will be low, and if it exceeds 3.0 g / m ² , there is a risk that the ink receiving layer will crack due to strong shrinkage during drying or the ink absorbability may be reduced. There is.
Moreover, as mass ratio of a crosslinking agent and a polymer (A), 20: 1 to 1:20 are preferable and 10: 1 to 1:10 are more preferable. By setting the mass ratio within this range, an inkjet recording sheet excellent in cracking, aging resistance and ink absorbability can be obtained.

<Formation of water coating layer>
Application of the aqueous solution containing the cationic compound can be performed by a bar coater, a blade coater, a rod blade coater, an air knife coater, a gravure coater, a die coater, or a curtain coater. In particular, a bar coater and a rod blade coater are preferably used.

"Outer ink receiving layer formation process"
Next, at least one outer ink receiving layer containing inorganic fine particles and a binder is formed on the water coating layer.
The outer ink receiving layer is formed while the water-coating layer is in a wet state.

≪Outside ink receiving layer≫
<Inorganic fine particles>
As the material of the inorganic fine particles to be contained in the outer ink receiving layer, various inorganic fine particles known and used in the general coated paper field similar to the inner ink receiving layer are appropriately used.

In the present invention, the average primary particle diameter of the inorganic fine particles contained in the outer ink receiving layer is preferably 30 nm or less. By containing inorganic fine particles having an average primary particle diameter of 30 nm or less, an ink receiving layer having high transparency and excellent print density, gloss, ink absorbability and the like can be obtained. The average primary particle diameter of the inorganic fine particles is more preferably 3 to 15 nm.
In addition, the primary particle diameter as used in the field of this invention is a particle diameter (Martin diameter) observed with the electron microscope (SEM and TEM).

  When the inorganic fine particles are aggregated particles (secondary particles) in which primary particles are aggregated, the average secondary particle diameter is not particularly limited, but is preferably 0.05 to 1.0 μm, more preferably 0.05 to 0.5 μm.

The inorganic fine particles preferably have a specific surface area of 100 m ² / g or more by the BET method. Although there is no upper limit to the specific surface area by the BET method, it is preferably about 1000 m ² / g or less. More preferably, it is 200-400 m < ² > / g.
The BET method referred to in the present invention is one of powder surface measurement methods by a gas phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm.

  The amount of the inorganic fine particles used in the ink receiving layer is preferably about 20 to 95% by mass, more preferably about 30 to 90% by mass with respect to the solid content of the ink receiving layer. In this range, there is no possibility that the coating strength of the ink receiving layer is lowered, the ink absorbability and the ink drying property are excellent, and a higher image quality is obtained.

In the present invention, as described above, silica is preferably used as the inorganic fine particles. Silica is roughly classified into natural silica obtained by pulverizing natural silica such as quartz and synthetic silica produced by synthesis. Synthetic silica is broadly classified into vapor-phase silica and wet silica. In the present invention, the wet method fine silica described later is preferably used among the vapor phase method silica and the wet method silica because high ink absorbability, transparency, and gloss can be obtained.
Vapor phase silica is also called a dry method as opposed to a wet method, and is made by a flame hydrolysis method. Specifically, it is made by burning silicon tetrachloride with hydrogen and oxygen. In place of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane may be used alone or mixed with silicon tetrachloride. Vapor phase method silica is commercially available as a powder having a very low bulk density.
When the aqueous dispersion of vapor phase silica is dried, it becomes porous silica gel, and the pore volume of the gel by the BET method is generally 1.2 to 1.6 ml / g. This pore volume is convenient for absorbing ink. However, cracks tend to occur during drying, and it is not easy to produce an ink receiving layer free of cracks.

As the wet method silica, silica by a precipitation method and silica by a gel method are known.
For example, as disclosed in JP-A-55-116613, the precipitated silica is produced by adding a mineral acid stepwise to an alkali silicate aqueous solution and filtering the precipitated silica.
The gel method silica is obtained by mixing a mineral acid with an alkali silicate solution, gelling, washing, and pulverizing.
Precipitated silica and gel silica are formed by combining primary particles of silica to form secondary particles, and there are many voids between the primary particles and between the secondary particles. In addition to being large, the property of scattering light is small, so a high printing density can be obtained.

  Further, as a wet process silica by a slightly special production method, for example, active silicic acid is condensed as described in US Pat. No. 2,574,902, JP-A No. 2001-354408, JP-A No. 2002-145609. There is fine silica (hereinafter, referred to as wet method fine silica) produced. Here, the active silicic acid refers to an aqueous silicic acid solution having a pH of 4 or less obtained by ion-exchange treatment of an aqueous alkali metal silicate solution with a hydrogen cation exchange resin, for example.

The wet method fine silica described in US Pat. No. 2,574,902 prepares an aqueous solution of active silicate by treating a diluted aqueous solution of sodium silicate with a cation exchange resin to remove sodium ions. Part of the solution is stabilized by adding alkali to polymerize to form a liquid in which silica seed particles are dispersed (seed liquid), and the remaining portion of the active silicic acid aqueous solution (feed liquid) is maintained while maintaining alkaline conditions. It is produced by gradually adding silica to polymerize silicic acid and growing colloidal silica particles.
This fine silica has a feature that it has a diameter of 3 nm to several hundreds nm, does not undergo secondary aggregation, and has a very narrow particle size distribution. Usually, a product of 7 nm to 100 nm, which is called colloidal silica, is commercially available as an aqueous dispersion, and when used for an ink receiving layer, a receiving layer having extremely high gloss and high transparency can be obtained.

On the other hand, the wet method fine silica described in JP 2001-354408 A is
"In a specific surface area by the BET method of 300m ² / g~1000m ² / g, and a liquid silica fine pore volume is 0.4ml / g~2.0ml / g are dispersed in colloidal seed solution, the BET method characterized in that after adding an alkali to the seed solution, silica fine particles are grown by adding a small amount of at least one feed solution selected from an active silicic acid aqueous solution and an alkoxysilane to the seed solution. specific surface area according to the 100m ² / g~400m ² / g, average secondary particle diameter of 20 nm to 300 nm, and the silica fine silica particles of the pore volume of 0.5ml / g~2.0ml / g is dispersed colloidally method of manufacturing a fine particle dispersion. ", or" a specific surface area by BET method is at 300m ² / g~1000m ² / g, a pore volume of 0.4 ml / g to 2 A liquid in which silica fine particles of 0 ml / g are colloidally dispersed is used as a seed liquid, and a mixture of at least one feed liquid selected from active silicic acid aqueous solution and alkoxysilane and alkali is added to the seed liquid little by little. or, or is characterized by growing silica particles added simultaneously in small portions the feed solution and the alkali, the specific surface area by BET method of 100m ² / g~400m ² / g, average secondary particle diameter 20nm~ A method for producing a silica fine particle dispersion in which silica fine particles having a pore volume of 300 nm and a pore volume of 0.5 ml / g to 2.0 ml / g are colloidally dispersed.
The silica fine particles obtained by

Moreover, the wet method fine silica described in JP-A-2002-145609 is,
“A suspension containing an agglomerate of silica fine particles is formed by heating an aqueous solution containing at least one selected from activated silicic acid and alkoxysilane, and then the suspension is activated in the presence of alkali. Silica fine particle dispersion characterized in that at least one selected from an aqueous solution containing silicic acid and alkoxysilane is added little by little to grow silica fine particles in the suspension, and then the suspension is wet pulverized Liquid manufacturing method. "
The silica fine particles obtained by

  The wet method fine silica disclosed in Japanese Patent Application Laid-Open Nos. 2001-354408 and 2002-145609 is a silica having both the advantages of precipitation method silica and gel method silica and the advantages of colloidal silica. This silica is a secondary particle in which primary particles of silica (for example, the colloidal silica described above) are bonded, and it is easy to adjust the secondary particle diameter to be equal to or less than the wavelength of light. It is most preferably used in the present invention because an ink-receiving layer having excellent resistance can be easily produced. Hereinafter, these wet process fine silicas are referred to as secondary fine silicas.

Among these, in particular, the secondary fine silica obtained by the condensation method disclosed in JP-A-2001-354408 is directly related to the average secondary particle diameter (20 nm to 300 nm) and fineness, regardless of mechanical means. Since secondary fine silica having a pore volume (0.5 ml / g to 2.0 ml / g) can be produced and the particle size distribution is narrow, the transparency and gloss of the resulting ink receiving layer are good, which is preferable for the present invention. Can be used.
In the condensation method disclosed in JP-A-2001-354408, as the active silicic acid, for example, an aqueous silicic acid solution having a pH of 4 or less obtained by ion-exchange treatment of an aqueous alkali metal silicate solution with a hydrogen cation exchange resin. (Activated silicic acid aqueous solution) is preferably used.
The active silicic acid aqueous solution is preferably 1 to 6% by mass as SiO ₂ concentration, more preferably 2 to 5% by mass, and preferably pH 2 to 4.
The alkali metal silicate may be a commercially available industrial product, and more preferably a sodium water glass having a SiO ₂ / M ₂ O (where M represents an alkali metal atom) molar ratio of about 2 to 4. It is preferable to use it.
As a method for condensing active silicic acid, the above active silicic acid aqueous solution is dropped into hot water, or the active silicic acid aqueous solution is heated to produce seed particles, before the dispersion is precipitated or gelled. the seed particles are stabilized by adding an alkali, then the preferred in terms of SiO ₂ with respect to SiO ₂ 1 mole contained in the seed particles of the active silicic acid solution while maintaining the stable state 0.001 The seed particles are preferably grown at a rate of mol / min to grow the primary particles of the seed particles.

Moreover, it is preferable that the wet method fine silica has a specific surface area by BET method of 100 to 400 m ² / g and a pore volume of 0.5 to 2.0 ml / g. Fine silica in this range has a very good balance of cracks in the ink receiving layer, ink absorbency, and gloss.

Further, in the outer ink receiving layer, a silica-cationic material obtained by pulverizing silica-cationic compound aggregate particles obtained by previously mixing and aggregating the above-described silica and a cationic compound to an average particle size of 0.7 μm or less. Compound aggregate fine particles are preferably used.
By using the silica-cationic compound aggregate fine particles, the ink receiving layer can be made into a porous layer having good transparency, ink absorbability, ink color development, weather resistance and the like.

  The silica-cationic compound aggregate fine particles are a silica colloid particle solution composed of secondary particles substantially formed by aggregation of primary particles. In the case of silica sol in which primary particles are monodispersed (for example: general commercially available colloidal silica), the porous layer obtained by applying to the base material becomes relatively dense, and it is easy to lose transparency. In order to provide ink absorbency, a high coating amount is inevitable. However, when the coating amount is high, the coating film tends to crack, and the coating process tends to be complicated. Of course, primary particles may be partially contained in the silica colloid particle solution.

  Silica-cationic compound aggregated fine particles can be obtained by applying a strong force to a mixture of silica and a cationic compound by mechanical means. That is, it can be obtained by a breaking down method (a method of subdividing a bulk material). The silica-cationic compound aggregate fine particles may be a slurry. Examples of the mechanical means include ultrasonic, high-speed rotary mill, roller mill, container drive medium mill, medium agitation mill, jet mill, cracker, sand grinder and the like.

  The average particle diameter of the silica-cationic compound aggregate fine particles (substantially secondary particles) is 0.7 μm or less, preferably 10 to 300 nm, more preferably 20 to 200 nm. When silica-cationic compound aggregate fine particles having an average particle diameter exceeding 0.7 μm are used, the transparency is remarkably lost, the print density is remarkably lowered, and an ink jet recording sheet having high gloss after printing cannot be obtained. There is a fear. On the other hand, if silica colloidal particles having an extremely small average particle diameter are used, there is a possibility that a sufficient ink absorption rate cannot be obtained.

  The silica constituting the silica-cationic compound aggregate fine particles preferably has an average primary particle diameter of 3 nm to 40 nm. If it is less than 3 nm, the gap between the primary particles becomes extremely small, and the ability to absorb the solvent and ink in the ink is remarkably lowered. On the other hand, if it exceeds 40 nm, the aggregated secondary particles become large and the transparency of the ink receiving layer may be lowered.

  As the cationic compound used in the silica-cationic compound aggregate fine particles, various known cationic compounds generally used in ink jet paper can be used, for example, monoallylamine salt, vinylamine salt, N-vinylacrylamidine salt. A primary amine type cationic polymer having a primary amine salt such as dicyandiamide / formalin polycondensate or dicyandiamide / polyethyleneamine polycondensate as a structural unit, or a secondary amine salt such as diallylamine salt or ethyleneimine salt as a structural unit Secondary amine type cationic polymer, tertiary amine type cationic polymer having a tertiary amine salt such as diallylmethylamine salt as a structural unit, diallyldimethylammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride Aluminum such as quaternary ammonium type cationic polymer, basic polyaluminum chloride, basic polyfatty acid aluminum, etc. having quaternary ammonium salts such as lide, (meth) acrylamidopropyltrimethylammonium chloride, dimethylamine / epichlorohydrin polycondensate Examples thereof include zirconyl compounds such as compounds, zirconyl chloride, basic zirconyl chloride and fatty acid zirconyl. In addition, as addition amount of a cationic compound, it is adjusted in the range of 1-30 mass parts with respect to 100 mass parts of amorphous silica, More preferably, it is 5-20 mass parts.

  The outer ink receiving layer may be a single layer or multiple layers. When the outer ink receiving layer is composed only of a layer containing silica-cationic compound aggregate fine particles, color development, print density, glossiness and transparency are the best. Of course, a layer containing silica-cationic compound aggregate fine particles may be provided in the upper layer, and another ink receiving layer may be provided in the lower layer. In order to maintain gloss and shine after printing, it is preferable that the coating amount of the layer mainly composed of silica colloidal particles is adjusted in the range of 50 to 100% with respect to the entire outer ink receiving layer. Even if it is less than 50%, a certain gloss can be obtained. However, in the embodiment in which the layer containing the silica-cationic compound aggregate fine particles is 50 to 100%, gloss and shine like those of photographs can be obtained.

<Binder>
The kind and content of the binder used for the outer ink receiving layer are the same as those for the inner ink receiving layer.

  In the present invention, when silica-cationic compound aggregate fine particles are used as the inorganic fine particles, PVA is most effective as a binder from the viewpoint of dispersion suitability and paint stability. In particular, in order to obtain dispersibility and ink absorbability, PVA having a polymerization degree of 2000 or more is preferably used. The degree of polymerization of PVA is more preferably 2000 to 5000. In order to obtain water resistance, PVA having a saponification degree of 95% or more is effective.

  The solid mass ratio of the silica-cationic compound aggregate fine particles and the binder is not particularly limited, but is adjusted to a range of 100/5 to 100/100, preferably 100/10 to 100/60. If the amount of the binder added is large, the pores between the particles may be small, and a sufficient ink absorption rate may not be obtained, while if the binder is small, the coating layer will crack and become unusable. Sometimes it becomes.

<Cationic compound>
Also in the outer ink receiving layer, various known cationic polymers described in the section of the water-coating layer can be used as necessary.

<Other ingredients>
In the present invention, it is preferable to use a crosslinking agent as described above together with the binder. Thereby, generation | occurrence | production of a crack can further be reduced and ink absorptivity, glossiness, an image quality, etc. improve further.
The cross-linking agent may be blended in the coating liquid for forming the ink receiving layer, or the cross-linking agent solution may be applied before the ink receiving layer is applied or after the ink receiving layer is applied.
The coating amount of the crosslinking agent, preferably ^{0.01~1.0g / m 2, 0.05~0.5g / m} 2 is more preferable. If it is less than 0.01 g / m ² , the effect of preventing cracking will be low, and if it exceeds 1.0 g / m ² , the ink receiving layer may be broken due to strong shrinkage during drying or ink absorbability may be reduced. There is.

  In the present invention, in order to further improve the heat and humidity resistance, the ink receiving layer contains an aluminum compound such as basic aluminum chloride, basic aluminum sulfate, and basic fatty acid aluminum, or zirconyl chloride, basic zirconyl chloride, zirconyl nitrate, fatty acid. Zirconium compounds such as zirconyl can also be contained. Specific examples of fatty acids in basic fatty acid aluminum, fatty acid zirconyl and the like include, for example, formic acid, acetic acid, propionic acid, butanoic acid, glycolic acid, 3-hydroxypropionic acid, 4-hydroxybutanoic acid, glycine, β-alanine 4-aminobutanoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid and the like, among which acetic acid is particularly preferable.

  In the present invention, various known compounds used for the purpose of improving storage stability such as light resistance and gas resistance, such as phenolic antioxidants, hindered amine light stabilizers, benzotriazole ultraviolet absorbers, sulfur compounds It is also possible to use a water-soluble metal salt or the like.

  In the ink receiving layer, various known pigment dispersants, thickeners, fluidity modifiers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, coloring dyes, coloring pigments, fluorescence Brightening agents, preservatives, antifungal agents and the like can be added as appropriate.

≪Formation of outer ink receiving layer≫
The outer ink receiving layer is formed by coating and drying the outer ink receiving layer coating liquid containing the various components described above on the water-coating layer formed as described above.

The coating amount of the outer ink receiving layer is preferably ² to 50 g / m ² , more preferably ³ to 30 g / m ² in terms of dry mass. When the coating amount is within this range, the recording image quality and the coating film strength are excellent. When the coating amount is small, it is difficult to obtain a uniform coating film. When the coating amount is large, the effect is saturated, and cracks tend to occur in the coating film. For example, in order to obtain a high coating amount of 15 g / m ² or more, a method by thickening and increasing the concentration of the coating liquid can be used, and it is realized by two or more coatings.
The coating liquid for the outer ink receiving layer can be applied by a coating method such as a bar coater, a blade coater, an air knife coater, a gravure coater, a die coater, or a curtain coater.
In the present invention, the outer ink receiving layer may be a single layer or may be composed of at least two layers.

In addition, after the application of the coating liquid for the outer ink receiving layer, a casting process is performed while the coating layer is in a wet state, and the outer ink receiving layer is directly cast-processed, whereby ink jet recording with higher surface glossiness is achieved. It can also be used as a sheet.
As a method for the casting treatment, there are a wet method, a gelation method, and a rewet method. In the wet method, while the coated layer is in a wet state, the coated layer is pressed against the heated mirror drum surface to perform a high gloss finish. In the gelation method, the coating layer is brought into contact with the gelling agent bath while the coating layer is in a wet state, and the coating layer in the gelled state is pressed against the surface of the heated drum to perform a high gloss finish. It is. In the rewetting method, a wet coating layer is once dried and then brought into contact with a wetting liquid again, and then pressed against the surface of a heated drum to perform a high gloss finish.
When the outer ink receiving layer is cast, it is preferable that a release agent is blended in the outer ink receiving layer. As the release agent, various publicly known release agents generally used in the coated paper field can be used.

  Further, for the purpose of imparting high gloss after the formation of the outer ink receiving layer, it is possible to provide surface smoothness through the roll nip under pressure with, for example, a super calender, gloss calender, or soft calender.

"Other configurations"
In the present invention, a cast gloss layer may be further provided on the outer ink receiving layer. Thereby, it can be set as the inkjet recording sheet with higher surface glossiness.
The gloss layer is configured to contain a pigment and / or a resin.
The gloss layer is preferably porous or liquid-permeable so long as it does not impair the gloss so that the ink can pass or absorb quickly.

Examples of the pigment used in the gloss layer include those similar to the inorganic fine particles used in the outer ink receiving layer. However, in terms of gloss, transparency, and ink absorbability, colloidal silica, amorphous silica, alumina, alumino Silicate, zeolite, synthetic smectite and the like are preferable.
These pigments are desirably contained in the gloss layer in an amount of 10 to 95% by mass.
The average particle diameter of the pigment (in the case of aggregated particles, the diameter of the aggregated particles) is preferably 0.001 to 1 μm, and more preferably 0.005 to 0.5 μm. When the particle diameter is in this range, excellent ink absorbability, gloss and print density can be obtained.

  Examples of resins used for the gloss layer include water-soluble binders (for example, polyvinyl alcohols such as polyvinyl alcohol, cation-modified polyvinyl alcohol, and silyl-modified polyvinyl alcohol, casein, soy protein, synthetic proteins, starch, cellulose such as carboxymethyl cellulose and methyl cellulose). Derivatives), styrene-butadiene copolymers, conjugated diene polymer latexes such as methyl methacrylate-butadiene copolymers, and water-dispersible resins such as vinyl copolymer latexes such as styrene-vinyl acetate copolymers, aqueous acrylics Various resins (adhesives) commonly used in the field of coated paper, such as resins, water-based polyurethane resins and water-based polyester resins, can be used alone or in combination.

  It is preferable that a release agent is further blended in the glossy layer. As the release agent, various publicly known release agents generally used in the coated paper field can be used.

  In addition, the glossy layer should contain the above-mentioned cationic compound to increase the print density and improve the water resistance, and add various auxiliary agents to improve the light resistance and gas resistance. Is also possible.

The gloss layer is formed by coating the coating liquid for the gloss layer containing the above-mentioned various components on the outer ink receiving layer to form a coating layer, casting the coating layer, and drying the coating layer. Is done.
The coating amount of the glossy layer coating liquid is preferably 0.1 to 30 g / ^{m 2} by dry weight, 0.2 to 10 g / ^{m 2} is more preferable. When the coating amount is within this range, the gloss, ink drying property and recording density are excellent.
The coating of the gloss layer coating liquid and the casting treatment can be performed in the same manner as described for the outer ink receiving layer.
The drying temperature of the gloss layer is also important. If the drying temperature is too high, film formation proceeds too much, resulting in a decrease in surface porosity. As a result, the ink absorption rate decreases, and conversely if the drying temperature is too low, the gloss tends to be poor and the productivity also decreases. The drying temperature is preferably 50 to 150 ° C, more preferably 70 to 120 ° C.

  In the present invention, an intermediate layer is provided between the support and the ink receiving layer, a protective layer is provided on the back surface (the surface on which the ink receiving layer is not formed) of the support, and the back surface is further adhered to the back surface. It can be processed, and various known techniques in the field of inkjet recording sheet production can be added.

The liquid ink for forming a recorded image on the ink jet recording sheet of the present invention is a recording liquid composed of a colorant, a liquid medium, and other optional additives, and any commercially available liquid ink for ink jet recording is used. Can be used.
Examples of the colorant include various water-soluble dyes such as direct dyes, acid dyes, and reactive dyes, carbon black finely divided around 100 nm, and surface-treated with a resin, a surfactant, and the like, organic pigments, and the like.
The liquid medium includes water alone or a combination of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent include monohydric alcohols such as ethyl alcohol and isopropyl alcohol, polyhydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, and glycerin, and polyvalent alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether. And lower alkyl ethers of alcohols.
Examples of the additive include a pH adjuster, a metal sequestering agent, an antifungal agent, a viscosity adjuster, a surface tension adjuster, a surfactant, and a rust preventive agent.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” respectively indicate parts by mass and mass% unless otherwise specified.

Example 1
(Preparation of coating liquid A for ink receiving layer)
Gas phase method silica (trade name: Aerosil 300, average particle size of primary particles 7 nm, specific surface area 300 m ² / g by BET method, manufactured by Nippon Aerosil Co., Ltd.), N-vinylacrylamidine hydrochloride / acrylamide co-polymer After adding 50 parts of 30% aqueous solution (molar ratio 2: 1, molecular weight about 20,000) and 850 parts of ion-exchanged water and dispersing with a stirrer, the mixture was processed using a wet ultrafine atomizer Nanomizer. Next, 360 parts of 5% aqueous solution of polyvinyl alcohol (trade name: PVA-145, manufactured by Kuraray Co., Ltd., saponification degree 99%, average polymerization degree 4,500) and a small amount of antifoaming agent, dispersing agent and water were added. An ink receiving layer coating solution A having a solid content concentration of 8% was obtained.

(Preparation of coating liquid B for ink receiving layer)
Wet process synthetic amorphous silica 20% dispersion (trade name: Silojet 703A, manufactured by Grace Devison) 500 parts, polyvinyl alcohol (trade name: PVA-145, manufactured by Kuraray Co., Ltd.) 400% 5% aqueous solution and A small amount of an antifoaming agent, a dispersing agent and water were added to obtain a coating liquid B for ink receiving layer having a solid content concentration of 15%.

(Creation of inkjet recording sheet)
On a paper support (thickness 240 μm, polyethylene resin containing 15% by mass of anatase-type titanium dioxide) on both sides of a 180 g / m ² base paper, 20 g of coating solution B for ink receiving layer in solid content The ink receiving layer B was provided by applying and drying with a wire bar so as to be / m ² . Next, 20 g / m ^{2 of} borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) aqueous solution (1: 4 mixture, concentration 3.75%) was applied, The ink receiving layer A was formed by applying and drying the ink receiving layer coating liquid A with a wire bar so that the solid content was 7 g / m ² , thereby preparing an ink jet recording sheet.

Examples 2-14
In Example 1, except that the following compounds were used in place of the allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight of about 20,000) in Example 1, for inkjet recording. Created a sheet.
Example 2: Allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 1: 1, molecular weight about 70,000)
Example 3: Allylamine / diallylamine copolymer (molar ratio 4: 1, molecular weight about 20,000)
Example 4: Allylamine / diallylamine copolymer (molar ratio 1: 1, molecular weight about 70,000)
Example 5: Allylamine methanesulfonate / diallylamine methanesulfonate copolymer (molar ratio 1: 1, molecular weight about 50,000)
Example 6: Vinylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 1: 1, molecular weight about 50,000)
Example 7: N-vinylacrylamidine hydrochloride / acrylamide copolymer (molar ratio 2: 1, molecular weight about 20,000)
Example 8: Polyallylamine hydrochloride (molecular weight about 60,000)
Example 9: Polydiallyldimethylammonium chloride (molecular weight about 50,000)
Example 10: Dicyandiamide / polyethyleneamine polycondensate (molecular weight about 10,000)
Example 11: Basic polyaluminum chloride Example 12: Basic polyaluminum acetate Example 13: Zirconyl acetate Example 14: Basic zirconyl chloride

Example 15
In Example 1, borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) instead of an aqueous solution (1: 4 mixed solution, concentration 3.75%), zirconyl carbonate An inkjet recording sheet was prepared in the same manner as in Example 1 except that an aqueous ammonium solution (concentration: 3.0%) was used.

Example 16
In Example 1, borax instead of borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) aqueous solution (1: 4 mixture, concentration 3.75%) -Allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) An aqueous solution (1: 3 mixture, concentration 3.0%) was used in the same manner as in Example 1 An ink jet recording sheet was prepared.

Example 17
In Example 1, a borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight of about 20,000) in an aqueous solution (1: 4 mixture, concentration 3.75%, pH 7.5) Instead, borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) in aqueous solution (1: 4 mixture, concentration 3.75%, pH 8.5 adjusted with sodium hydroxide) An ink jet recording sheet was prepared in the same manner as in Example 1 except that the coating amount of the outer ink receiving layer was 10 g / m ² in terms of solid content.

Example 18
In Example 17, borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) in aqueous solution (1: 4 mixture, concentration 3.75%, pH 8 with sodium hydroxide) .5 prepared product) instead of borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) aqueous solution (1: 6 mixture, concentration 5.25%, hydroxylated) An ink jet recording sheet was prepared in the same manner as in Example 1 except that the pH was adjusted to 8.5 with sodium.

Example 19
In Example 1, instead of N-vinylacrylamidine hydrochloride / acrylamide copolymer (molar ratio 2: 1, molecular weight about 20,000), diallyldimethylammonium chloride / acrylamide copolymer (molar ratio 8: 1, molecular weight). An ink jet recording sheet was prepared in the same manner as in Example 1 except that about 200,000) was used.

Example 20
In Example 1, a borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight of about 20,000) in an aqueous solution (1: 4 mixture, concentration 3.75%, pH 7.5) Instead of Example 1 except that an aqueous solution of boric acid-allylamine hydrochloride / diallylamine hydrochloride (molar ratio 4: 1, molecular weight about 20,000) in water (1: 4 mixture, concentration 3.75%) was used. In the same manner, an inkjet recording sheet was prepared.

Example 21
In Example 1, a borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight of about 20,000) in an aqueous solution (1: 4 mixture, concentration 3.75%, pH 7.5) Instead, an inkjet recording sheet was prepared in the same manner as in Example 1 except that an allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) aqueous solution (concentration: 3.0%) was used. Created.

Example 22
(Preparation of silica fine particle dispersion)
Distilled water was added to a sodium silicate solution having a SiO ₂ concentration of 30% by mass and SiO ₂ / Na ₂ O (molar ratio) of 3.1 (manufactured by Tokuyama Corp., No. 3 sodium silicate) to obtain a SiO ₂ concentration of 4.0. After preparing a mass% dilute sodium silicate aqueous solution, an active silicic acid aqueous solution was prepared through a column filled with hydrogen-type cation exchange resin (manufactured by Mitsubishi Chemical Corporation, Diaion SK-1BH). Distilled water (500 g) was charged into a 5 liter glass reaction vessel equipped with a reflux condenser, a stirrer, and a thermometer, heated to 100 ° C., and kept at 100 ° C., the active silicic acid aqueous solution prepared earlier was 1.5 g / 450 g was added at a rate of minutes to prepare a seed solution. The average secondary particle diameter of the seed particle aggregate in the seed solution was 184 nm.
Subsequently, after stabilizing by adding 0.9 g of 28% ammonia aqueous solution, 550 g of active silicic acid aqueous solution was further added at 100 ° C. at a rate of 1.5 g / min. After completion of the addition, the mixture was heated to reflux at 100 ° C. for 9 hours and then concentrated to obtain a 10% by mass silica fine particle dispersion. The silica fine particles had an average primary particle diameter of 11 nm, an average secondary particle diameter of 130 nm, a specific surface area of 257 m ² / g, and a pore volume of 1.01 ml / g.

(Preparation of coating liquid C for ink receiving layer)
To 1000 parts of the 10% by mass silica fine particle dispersion obtained earlier, 50 parts of a 30% aqueous solution of N-vinylacrylamidine hydrochloride / acrylamide copolymer (molar ratio 2: 1, molecular weight about 20,000) and ion-exchanged water 850 After adding a part and disperse | distributing with a stirring apparatus, it processed using the wet super atomizer nanomizer. Next, 360 parts of 5% aqueous solution of polyvinyl alcohol (trade name: PVA-145, manufactured by Kuraray Co., Ltd., saponification degree 99%, average polymerization degree 4,500) and a small amount of antifoaming agent, dispersing agent and water were added. An ink receiving layer coating solution C having a solid content concentration of 8% was obtained.

(Creation of inkjet recording sheet)
On a paper support (thickness 240 μm, polyethylene resin containing 15% by mass of anatase-type titanium dioxide) on both sides of a 180 g / m ² base paper, 20 g of coating solution B for ink receiving layer in solid content The ink receiving layer B was provided by applying and drying with a wire bar so as to be / m ² . Next, 20 g / m ^{2 of} borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) aqueous solution (1: 4 mixture, concentration 3.75%) was applied, The ink receiving layer C was provided by coating and drying the ink receiving layer coating liquid C with a wire bar so that the solid content was 7 g / m ² , thereby preparing an ink jet recording sheet.

Example 23
In Example 1, high-quality paper of 200 g / m ² instead of a paper support (thickness 240 μm, polyethylene resin containing 15% by mass of anatase-type titanium dioxide) coated on both sides of a 180 g / m ² base paper with polyethylene resin. An ink jet recording sheet was prepared in the same manner as in Example 1 except that was used.

Comparative Example 1
In Example 19, borax instead of borax-allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) aqueous solution (1: 4 mixture, concentration 3.75%) An ink jet recording sheet was prepared in the same manner as in Example 1 except that the aqueous solution (concentration: 0.75%) was used.

Comparative Example 2
(Preparation of coating liquid D for ink receiving layer)
Wet process synthetic amorphous silica 20% dispersion (trade name: Silojet 703A, manufactured by Grace Devison) 500 parts, allylamine hydrochloride / diallylamine hydrochloride copolymer (molar ratio 4: 1, molecular weight about 20,000) 40 A 25% aqueous solution and 25 parts of ion-exchanged water were added and dispersed with a stirrer, and then treated with a wet ultrafine atomizer Nanomizer. Next, 400 parts of a 5% aqueous solution of polyvinyl alcohol (trade name: PVA-145, manufactured by Kuraray Co., Ltd.) and a small amount of an antifoaming agent, a dispersing agent and water were added, and a coating solution for an ink receiving layer having a solid content concentration of 15%. D was obtained.

(Creation of inkjet recording sheet)
On a paper support (thickness 240 μm, polyethylene resin containing 15% by mass of anatase-type titanium dioxide) on both sides of a 180 g / m ² base paper, 20 g of ink receiving layer coating solution D in solid content The ink receiving layer D was provided by applying and drying with a wire bar so as to be / m ² . Next, after applying 20 g / m ^{2 of an} aqueous borax solution (concentration: 3.0%), the ink receiving layer coating liquid A was applied and dried with a wire bar so that the solid content was 7 g / m ^2. Layer A was provided to produce an inkjet recording sheet.

(Evaluation methods)
For the ink jet recording sheets obtained in Examples 1 to 23 and Comparative Examples 1 and 2, using an Epson ink jet printer PM-950C, an ISO-400 image (“high-definition color digital standard image data ISO / JIS-SCID”, p13). , Image name: portrait, issued by the Japanese Standards Association) and solid printing was performed so that the optical density of the composite black was 1.0. The obtained inkjet recording sheet and its image were evaluated as follows, and the results are shown in Table 1.

[Glossy]
The glossiness of the coated surface of the inkjet recording sheet in the unprinted part was evaluated by visual observation.
(Evaluation criteria)
◎: Gloss is very high and good ○: Gloss is high and good △: Gloss is slightly inferior ×: Gloss is almost absent

〔crack〕
The cracked state of the inkjet recording sheet coated surface of the unprinted part was evaluated by visual observation.
(Evaluation criteria)
◎: No cracks are observed ○: Some cracks are observed but there is no problem △: Cracks are observed and there are practical problems ×: There are many cracks

[Ink absorbency]
The obtained ISO-400 image was visually observed to evaluate ink absorbency.
(Evaluation criteria)
◎: Image collapse due to ink overflow is not observed at all ○: Image collapse due to ink overflow is slightly observed, but at a level that is not a problem for practical use Δ: Image collapse due to ink overflow is observed with practical problem × : Significant ink overflow

〔image quality〕
The image quality of the obtained ISO-400 image was evaluated by visual observation.
(Evaluation criteria)
◎: Image quality is very good ○: Image quality is good and practically no problem △: Image quality is inferior and practically problematic ×: Image quality is very inferior

The long-term storage stability was evaluated by the following heat and humidity resistance and water resistance.
[Heat resistance]
Immediately after printing, the obtained ISO-400 image and composite black solid print image were stored in a constant temperature and humidity chamber at 30 ° C. and 85% relative humidity for 72 hours, and the level of heat and humidity resistance was visually observed and evaluated.
(Evaluation criteria)
A: Occurrence of blurring and discoloration over time is good, and it is good. ○: Slight blurring and discoloration over time are observed, but there is no practical problem at all. Δ: Bending over time and discoloration are observed. X which is a problem level in practical use x: A blurring with time is remarkably recognized, and a discoloration is also remarkable.

〔water resistant〕
The obtained ISO-400 image and the composite black solid print image are immersed in water at 25 ° C. for 24 hours, and then superposed on high-quality paper for 10 minutes to visually observe the level of water resistance such as discoloration and color transfer. Observed and evaluated.
(Evaluation criteria)
A: No change in color or color transfer of the image is observed and good. ○: Slight change color and color transfer are observed, but there is no problem in practical use. Δ: Change color and color transfer are observed. X, which is a practically problematic level, x: Discoloration and color transfer are remarkable.

  As is apparent from Table 1, the ink jet recording sheets of Examples 1 to 23 (invention) are excellent in gloss, cracks, ink absorbency, and image quality, and are subject to aging blurring and discoloration even under high humidity. The recording sheet was hardly seen and excellent in water resistance.

INDUSTRIAL APPLICABILITY The present invention can be used for producing an ink jet recording sheet having at least two ink receiving layers containing inorganic fine particles and a binder on a support.

Claims (6)

  In the method for producing an ink jet recording sheet having at least two ink receiving layers containing inorganic fine particles and a binder on a support, at least one inner ink receiving containing inorganic fine particles and a binder is provided on the support. After forming the layer, an aqueous solution containing a cationic compound is applied onto the inner ink receiving layer to form a water-coating layer, and then at least the inorganic fine particles and the binder are contained on the water-coating layer. A method for producing an ink jet recording sheet, comprising forming one outer ink receiving layer.   The method for producing an inkjet recording sheet according to claim 1, wherein the aqueous solution containing the cationic compound further contains a crosslinking agent.   The method for producing an inkjet recording sheet according to claim 2, wherein the crosslinking agent is a boron compound.   The method for producing an inkjet recording sheet according to any one of claims 1 to 3, wherein the cationic compound is at least one selected from the group consisting of a cationic polymer, a water-soluble aluminum compound, and a water-soluble zirconium compound. . The method for producing an ink jet recording sheet according to claim 1, wherein the content of the cationic compound in the water-coating layer is 0.01 to 10 g / m ² . The cationic compound is represented by the following general formula (1) or (2):

[Wherein, m and n each independently represents 0 or an integer of 1 to 4, and X represents an acid residue. ]
And at least one structural unit (a1) represented by the following general formula (3), (4), (5) or (6):

[Wherein, R ^{1 to} R ⁸ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Y and Z each represents an independent acid residue. ]
The method for producing an inkjet recording sheet according to any one of claims 1 to 5, which is a polymer (A) containing at least one type of structural unit (a2) represented by formula (1).