JP2021084340A - Inkjet recording material - Google Patents

Abstract

To provide an inkjet recording material that can reduce environmental load during its production and has excellent gloss and stain removability.SOLUTION: An inkjet recording material has, on a support, an ink receiving layer predominantly composed of inorganic fine particles with an average secondary particle size of 500 nm or less, and a surface layer that is more farther from the support than the ink receiving layer and contains hydrophobic colloidal silicas.SELECTED DRAWING: None

Description

The present invention relates to an inkjet recording material that can reduce the environmental load during production and has excellent glossiness and stain removal property.

As a recording material used in the inkjet recording method, an inkjet recording material having a porous ink receiving layer containing a pigment such as amorphous silica and a water-soluble binder such as polyvinyl alcohol on a support is known. In recent years, a recording material having a photo-like luster using ultrafine particles such as vapor phase silica or wet silica pulverized to about several hundred nm has become known as a pigment.

However, while these porous ink receiving layers can quickly absorb water-based ink, even if an unintended colored liquid adheres, the speed of penetration thereof makes it possible to wipe off the colored liquid. There was a problem that was left. For this reason, there is a demand for an inkjet recording material having a hydrophobic surface having excellent stain removal properties, which can easily wipe off colored marks while having high color development and image sharpness when printed with water-based ink. It was.

As a study for making the surface of an inkjet recording material hydrophobic, for example, Patent Document 1 discloses an ink jet recording acceptance composition containing an aqueous cationic resin and hydrophobic silica, and Patent Documents 2 to 4 describe a pigment. A method of providing a water-repellent layer containing hydrophobic silica fine particles on an ink receiving layer containing a binder is disclosed. However, in Patent Documents 2 to 4, an organic solvent such as alcohol is used as a dispersion medium for hydrophobic silica during the production of recording materials, and it is possible to cope with the environmental load due to the generation of volatile organic compounds and to make the coating liquid flammable. It is necessary to take measures under the Fire Service Act due to the cause, or measures under the Occupational Safety and Health Law due to the harmfulness of organic solvents. On the other hand, when the coating liquid is composed of an aqueous mixed solvent in which the amount of organic solvent is reduced and water is added, the affinity between the hydrophobic silica and the dispersion medium is low and the dispersion of the hydrophobic silica is insufficient. It is difficult to develop the gloss of the surface, and it is difficult to apply it to a recording material for photographic output, which requires a highly glossy surface.

Japanese Unexamined Patent Publication No. 2003-191602 Japanese Unexamined Patent Publication No. 2012-196922 Japanese Unexamined Patent Publication No. 2019-18431 JP-A-2019-116008

An object of the present invention is to provide an inkjet recording material which can reduce the environmental load during production and has excellent glossiness and stain removal property.

The above object of the present invention is basically achieved by the following invention.
An inkjet recording material having an ink receiving layer mainly containing inorganic fine particles having an average secondary particle size of 500 nm or less on the support and a surface layer containing hydrophobic colloidal silica on the side farther from the support from the ink receiving layer. ..

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an inkjet recording material which can reduce the environmental load during production and has excellent glossiness and stain removal property.

The inkjet recording material of the present invention contains an ink receiving layer mainly containing inorganic fine particles having an average secondary particle size of 500 nm or less on a support, and hydrophobic colloidal silica on a side farther from the support than the ink receiving layer. It has a surface layer containing it. The inkjet recording material using hydrophobic silica is excellent in removing colored marks (stain removing property) due to the hydrophobicity of the surface, but it is necessary to use an organic solvent as a dispersion medium of hydrophobic silica at the time of production. It was necessary to deal with volatile organic compounds generated during manufacturing, and if the coating liquid was a dangerous substance under the Fire Service Law or an organic solvent under the Industrial Safety and Health Law, it was necessary to take measures in terms of equipment and operation. .. As a result of diligent studies in the present invention, it has been found that by using hydrophobic colloidal silica for the surface layer, an inkjet recording material capable of satisfying stain removal property and gloss while suppressing the use of an organic solvent can be obtained. It was. Hereinafter, the inkjet recording material of the present invention will be described in detail.

In the present invention, the ink receiving layer mainly contains inorganic fine particles having an average secondary particle size of 500 nm or less. Here, the content as a main component means that the inorganic fine particles are contained in an amount of 50% by mass or more, preferably 60 to 96% by mass, based on the total solid content of the ink receiving layer. As the inorganic fine particles contained in the ink receiving layer, hydrophilic inorganic fine particles are preferable, and examples thereof include various known inorganic fine particles such as amorphous synthetic silica, alumina, alumina hydrate, calcium carbonate, magnesium carbonate, and titanium dioxide. However, amorphous synthetic silica, alumina or alumina hydrate is preferable in terms of obtaining high print density and excellent image sharpness.

Amorphous synthetic silica can be roughly classified into wet method silica, vapor phase method silica, and others depending on the production method. Wet silica gel is further classified into sedimentation silica gel, gel silica gel, and sol silica gel according to the production method. Sedimentation method Silica is produced by reacting sodium silicate and sulfuric acid under alkaline conditions, and the silica particles that have grown particles are aggregated and settled, and then commercialized through the steps of filtration, washing with water, drying, crushing and classification. As the sedimentation method silica, for example, it is commercially available from Tosoh Silica Co., Ltd. as Nip Seal (registered trademark). Gel method silica is produced by reacting sodium silicate and sulfuric acid under acidic conditions. During aging, the fine particles dissolve and reprecipitate to bond other primary particles to each other, so that the clear primary particles disappear and form relatively hard aggregated particles with an internal void structure. As the gel method silica, for example, it is commercially available from Tosoh Silica Co., Ltd. as Nipgel (registered trademark). The sol method silica is also called colloidal silica, and is obtained by heat-aging silica sol obtained through compound decomposition with acid of sodium silicate or through an ion exchange resin layer. For example, as Snowtex (registered trademark) from Nissan Chemical Co., Ltd. It is commercially available.

Vapor phase silica is also called a dry method as opposed to a wet method, and is generally produced by a flame hydrolysis method. Specifically, a method of burning silicon tetrachloride together with hydrogen and oxygen is generally known, but instead of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane can also be used alone or silicon tetrachloride. Can be used in a mixed state with. Vapor phase silica is commercially available from Aerosil Japan Co., Ltd. as AEROSIL® and Tokuyama Corporation as Leolosil®.

Gas phase silica can be preferably used for the ink receiving layer of the inkjet recording material of the present invention. The average primary particle size of the vapor phase silica contained in the ink receiving layer is preferably 30 nm or less, more preferably the average primary particle size is 3 to 15 nm and the specific surface area by the BET method is 200 m ² / g or more, and the average primary particle size is 200 m 2 / g or more. It is particularly preferable that the particle size is 3 to 10 nm and the specific surface area by the BET method is 250 to 500 m ^{2 / g.} The average primary particle diameter referred to in the present invention is the average value obtained by using the diameter of a circle equal to the projected area of each of the 100 primary particles existing in a certain area as the particle diameter by electron microscope observation of the fine particles. Is. The BET method referred to in the present invention is one of the methods for measuring the surface area of powder by the vapor phase adsorption method, and is a method for determining the total surface area of a 1 g sample from the adsorption isotherm, that is, the specific surface area. Nitrogen gas is usually used as the adsorbed gas, and the method of measuring the adsorbed amount from the pressure or volume change of the adsorbed gas is most often used. The most prominent ones for expressing the isotherms of multimolecular adsorption are the Brunauer, Emmett, and Teller equations, which are called BET equations and are widely used for surface area determination. The amount of adsorption is determined based on the BET formula, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

As the vapor phase method silica, those dispersed in the presence of a cationic compound can be preferably used. As the vapor phase silica used in the present invention, one dispersed with an average secondary particle diameter of 500 nm or less is used, but more preferably 10 to 300 nm. As a dispersion method, vapor phase silica and a dispersion medium are premixed by ordinary propeller stirring, turbine type stirring, homomixer type stirring, etc., and then a media mill such as a ball mill, a bead mill, a sand grinder, a high pressure homogenizer, and an ultrahigh pressure are used. It is preferable to perform dispersion using a pressure type disperser such as a homogenizer, an ultrasonic disperser, a thin film swirl type disperser, or the like. The average secondary particle size referred to in the present invention refers to a particle size distribution meter of a laser scattering type (for example, LA920 manufactured by HORIBA, Ltd.) measured as a number median diameter.

In the present invention, wet silica can also be preferably used. As the wet silica contained in the ink receiving layer, sedimented silica or gel silica is preferable, and sedimented silica is particularly preferable. The wet method silica used in the present invention needs to have an average secondary particle size of 500 nm or less, more preferably in the range of 20 to 300 nm. The average primary particle size of the wet silica used in the present invention is preferably 50 nm or less, and more preferably 3 to 40 nm.

As the wet method silica, those dispersed and pulverized in the presence of a cationic compound can be preferably used. As the pulverization method, a wet dispersion method in which silica dispersed in an aqueous medium is mechanically pulverized can be preferably used. A preferred method for pulverizing the wet method silica used in the present invention will be described. First, silica particles and a cationic compound are mixed in a dispersion medium mainly composed of water, and at least one of a disperser such as a sawtooth blade type disperser, a propeller blade type disperser, or a rotor stator type disperser is used. To obtain a silica pre-dispersion solution. If necessary, an appropriate low boiling point solvent or the like may be added to the aqueous dispersion medium. The silica pre-dispersion liquid preferably has a high solid content concentration, but if the concentration is too high, it becomes impossible to disperse. Therefore, the preferable range is 15 to 40% by mass, more preferably 20 to 35% by mass. Next, it is preferable to pulverize the silica particles by applying the silica predisperse to a mechanical means having a stronger shearing force. Known methods can be adopted as the mechanical means, for example, media mills such as ball mills, bead mills and sand grinders, pressure homogenizers such as high pressure homogenizers, pressure dispersers such as ultrahigh pressure homogenizers, ultrasonic dispersers and thin film swirl dispersers. Can be used.

As the cationic compound used for dispersing or pulverizing the vapor phase silica and the wet silica, a cationic polymer can be preferably used. Examples of the cationic polymer include polyethyleneimine, polyallylamine, polyallylamine, and alkylamine polymers, JP-A-59-20696, JP-A-59-33176, JP-A-59-333177, JP-A. 59-155588, 60-11389, 60-49990, 60-83882, 60-109894, 62-198493. , JP-A-63-49478, JP-A-63-115780, JP-A-63-280681, JP-A-1-40371, JP-A-6-234268, JP-A-7-125411. The polymer having a 1st to 3rd amino group and a quaternary ammonium base described in Japanese Patent Application Laid-Open No. 10-193776 and the like is preferably used. In particular, a diallylamine derivative is preferably used as the cationic polymer. In terms of dispersibility and viscosity of the dispersion liquid, the mass average molecular weight of these cationic polymers is preferably about 2000 to 100,000, and particularly preferably about 2000 to 30,000.

As the alumina contained in the ink receiving layer, γ-alumina, which is a γ-type crystal of aluminum oxide, is preferable, and δ group crystals are particularly preferable. γ-Alumina can reduce the size of primary particles to about 10 nm, but usually secondary particle crystals with a diameter of several thousand to tens of thousands nm are crushed by ultrasonic waves, a high-pressure homogenizer, a counter-collision jet crusher, or the like. Can be used. In the present invention, alumina having an average secondary particle size of 500 nm or less can be used, but those in the range of 20 to 300 nm are more preferable.

The alumina hydrate contained in the ink receiving layer is _{represented by the constitutive equation of Al 2} O ₃ , nH ₂ O (n = 1 to 3). The alumina hydrate used in the present invention can be obtained by a known production method such as hydrolysis of aluminum alkoxide such as aluminum isopropoxide, neutralization of aluminum salt with alkali, and hydrolysis of aluminate. The alumina hydrate used in the present invention also needs to have an average secondary particle size of 500 nm or less, more preferably 20 to 300 nm.

As the above-mentioned alumina and alumina hydrate used in the present invention, those dispersed with known dispersants such as acetic acid, lactic acid, formic acid and nitric acid are preferably used.

It is also possible to use two or more kinds of inorganic fine particles together from the above-mentioned inorganic fine particles. For example, the combined use of finely pulverized wet silica and vapor phase silica, the combined use of finely pulverized wet silica and alumina or alumina hydrate, and the combined use of vapor phase silica and alumina or alumina hydrate can be mentioned. Be done.

The ink receiving layer of the present invention preferably contains a water-soluble binder. As the water-soluble binder, polyvinyl alcohol, polyethylene glycol, starch, dextrin, carboxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid ester type and derivatives thereof are used, and among them, completely saponified or partially saponified polyvinyl alcohol is preferable. In particular, those having a degree of saponification of 80% or more are particularly preferable. The average degree of polymerization of polyvinyl alcohol is preferably 500 to 6000, more preferably 1000 to 5000.

The polyvinyl alcohol includes, in addition to general polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, and derivatives of other polyvinyl alcohols. One type of polyvinyl alcohol may be used alone, or two or more types may be used in combination.

The content of the water-soluble binder in the ink receiving layer is preferably 3 to 40% by mass, more preferably 5 to 30% by mass, based on the total amount of the inorganic fine particles.

The ink receiving layer preferably contains a cross-linking agent in addition to the above-mentioned water-soluble binder. As the cross-linking agent, known cross-linking agents for water-soluble binders can be used, but when polyvinyl alcohol is used as the water-soluble binder, boric acid or borate salt is particularly preferable. When polyvinyl alcohol contains a highly active modifying group, a known cross-linking agent may be used depending on the modifying group. The amount of the cross-linking agent added is preferably 0.1 to 40% by mass, more preferably 0.5 to 30% by mass, based on the water-soluble binder.

In the present invention, the ink receiving layer may further contain a cationic polymer similar to that used for cationization of the above-mentioned amorphous synthetic silica as an additive. Further, the ink receiving layer may contain a water-soluble polyvalent metal compound in order to improve water resistance and the like. As the water-soluble polyvalent metal compound, a water-soluble aluminum compound can be preferably used.

As the water-soluble aluminum compound, for example, aluminum chloride or its hydrate, aluminum sulfate or its hydrate, ammonium alum and the like are known as inorganic salts. Further, a basic polyaluminum hydroxide compound, which is an inorganic aluminum-containing cationic polymer, is known.

Among these water-soluble aluminum compounds, those that can be stably added to the coating liquid forming the ink receiving layer are preferable, and basic polyaluminum hydroxide compounds are preferably used. The main components of this compound are represented by the following formulas 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 ] A water-soluble polyaluminum hydroxide that stably contains polynuclear condensed ions of a basic polymer such as ^3+.

[Al ₂ (OH) _n Cl _6-n ] _m ... Equation 1
[Al (OH) ₃ ] _n AlCl ₃ ... Equation 2
Al _n (OH) _m Cl _(3n−m) 0 <m <3n ・ ・ Equation 3

These products are called polyaluminum chloride (PAC) from Taki Chemical Co., Ltd. as a water treatment agent, polyaluminum hydroxide (Paho) from Asada Chemical Co., Ltd., and RIKEN Co., Ltd. It is marketed under the name of Purachem WT from Green and for the same purpose from other manufacturers, and various grades are easily available.

The content of the water-soluble polyvalent metal compound described above is preferably in the range of 0.1 to 10% by mass with respect to the inorganic fine particles contained in the ink receiving layer.

The ink receiving layer is further known as a coloring dye, a coloring pigment, an ultraviolet absorber, an antioxidant, a pigment dispersant, a defoaming agent, a leveling agent, a preservative, a fluorescent whitening agent, a viscosity stabilizer, a pH adjuster and the like. Various additives can also be added.

Further, by incorporating a thioether compound, a carbohydrazide and a derivative thereof in the ink receiving layer, the storage stability after printing can be improved.

The carbohydrazide derivative used in the present invention may be a compound having one or more carbohydrazide structures in the same molecule, or a polymer having a carbohydrazide structure in the main chain or side chain. ..

Examples of the thioether compound used in the present invention include an aromatic thioether compound in which an aromatic group is bonded to both sides of a sulfur atom, an aliphatic thioether compound having an alkyl group at both ends sandwiching the sulfur atom, and the like. Among these, an aliphatic thioether compound having a hydrophilic group is particularly preferable.

In the present invention, the dry coating amount of the ink receiving layer is preferably 10 to 60 g / m 2, and when the support is a non-absorbent support such as resin-coated paper, the dry coating amount is 20 to 20 to ^{60 g / m 2.} It is preferably 60 g / m ^2.

In the present invention, the coating method of the ink receiving layer is not particularly limited, and a known coating method can be used. For example, there are a slide bead method, a curtain method, an extrusion method, an air knife method, a roll coating method, a rod bar coating method and the like.

Next, the surface layer will be described. In the present invention, the surface layer contains hydrophobic colloidal silica. Colloidal silica is a colloidal solution in which amorphous silica particles are dispersed in an aqueous solution in a monodispersed state of primary particles. The method for producing colloidal silica is not particularly limited, and can be produced by a known method as described above. For example, (1) a water glass method in which an alkali metal silicate such as sodium silicate is used as a raw material and condensed in an aqueous solution to grow particles, and (2) an alkoxysilane such as tetraethoxysilane is used as a raw material and water in water such as alcohol is used. Examples thereof include an alkoxysilane method in which a condensation reaction is carried out in water containing an organic solvent to grow the mixture. The hydrophobic colloidal silica used in the present invention is obtained by substituting the hydrogen atom of the −OH group on the surface of the colloidal silica particles with a highly hydrophobic functional group, and specific examples of the hydrophobic functional group used for the substitution include. Examples thereof include a trimethylsilyl group, a dimethylsilyl group, an octylsilyl group and a group having a siloxane bond (for example, a dimethylpolysiloxane group). In the present invention, a trimethylsilyl group and an octylsilyl group are preferable, and a trimethylsilyl group is particularly preferable, from the viewpoint of stain removing property and ink acceptability.

The average primary particle size of the hydrophobic colloidal silica used in the present invention is preferably in the range of 10 to 150 nm, more preferably in the range of 30 to 100 nm, from the viewpoint of the glossiness and surface strength of the obtained recording material. Further, as long as it is a hydrophobic colloidal silica having an average primary particle size in the above range, two or more kinds can be used in combination. In general, hydrophobic silica having a highly hydrophobic substituent has lower dispersibility in a hydrophilic solvent and forms a higher-order aggregated structure, but hydrophobic colloidal silica has a relatively small specific surface area with respect to particle size, and particles. Dispersion uniformity is high even in a hydrophilic solvent because the diameter distribution is sharp and there is little variation in particle size. The dispersion uniformity can be evaluated by a particle size distribution meter, and a particle size distribution meter based on a dynamic light scattering method (for example, PAR-III manufactured by Otsuka Electronics Co., Ltd.) can be preferably used for measuring these submicron particles.

Hydrophobic colloidal silica is sold as, for example, TG-C series by Cabot Corporation and QSG series by Shin-Etsu Chemical Co., Ltd., and these can be obtained and used.

Hydrophobic colloidal silica is preferably subjected to a dispersion treatment. A known method can be used as a mechanical means for the dispersion treatment, but a method of dispersing with an ultrasonic disperser can be preferably used. As the dispersion medium used for the dispersion treatment, a mixture of a hydrophilic organic solvent and water is preferable, and a mixture of alcohol and water having 3 or less carbon atoms is more preferable. For alcohols having 3 or less carbon atoms, an aqueous solution having a content concentration of less than 60% can be treated as a non-dangerous substance if certain conditions such as the content of other third components are satisfied. The mixing ratio of the hydrophilic organic solvent and water is preferably 80:20 to 40:60, particularly preferably 60:40 to 50:50. From the viewpoint of reducing the environmental load, it is preferable that the mixing ratio of water is high, but if it is too high, the dispersibility of the hydrophobic colloidal silica deteriorates. The content of the hydrophobic silica in the surface layer is preferably in the range of 0.01 to 2 g / ^{m 2,} the range of 0.1 to 1 g / ^{m 2} is more preferable.

In the present invention, the surface layer preferably contains a resin emulsion as a binder for hydrophobic colloidal silica. In the present invention, the resin emulsion refers to a dispersion in which a substantially water-insoluble thermoplastic polymer compound is dispersed in water or an organic solvent, for example, vinyl acetate polymer, ethylene-vinyl acetate copolymer, acrylic. Acid ester polymers, styrene-acrylic acid ester copolymers, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, isoprene copolymers, chloroprene copolymers, urethane-based polymers, and polymers thereof. Examples thereof include dispersions of synthetic polymer compounds such as copolymers in which two or more kinds of constituent monomers are randomly, grafted, or blocked. Of these, acrylic acid ester polymers, styrene-acrylic acid ester copolymers, urethane-based polymers, and copolymers thereof are preferable. Further, these resin emulsions may be used alone or in combination of two or more of them.

The average particle size of the resin emulsion is preferably larger than the average pore size of the ink receiving layer. If the average particle size of the resin emulsion is smaller than the average pore size of the ink receiving layer, the resin emulsion falls into the void portion of the ink receiving layer at the stage of coating the surface layer, and the coating layer strength of the obtained surface layer becomes high. May decrease. The content of the resin emulsion is preferably 3 to 150% by mass, more preferably 5 to 100% by mass, based on the hydrophobic colloidal silica. If the amount is less than the above range, the binding performance of the hydrophobic colloidal silica particles cannot be sufficiently obtained and the particles are likely to fall off, and if the amount is more than the above range, the contribution of the hydrophobic colloidal silica becomes small and the dirt removing performance is reduced.

In addition to the hydrophobic colloidal silica and the binder resin, the surface layer can further contain various known additives described in the section of the ink receiving layer.

As a coating method used for coating the surface layer, a slide bead method, a curtain method, an extrusion method, a slot die method, a gravure roll method, an air knife method, a blade coating method, a rod bar coating method and the like are preferable.

The support contained in the inkjet recording material of the present invention includes films such as polyethylene, polypropylene, polyvinyl chloride, diacetate resin, triacetate resin, cellophane, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, and non-polyethylene resin coated paper. Examples thereof include absorbent supports, high-quality papers, art papers, coated papers and the like. Among them, the non-absorbent support is preferable in that high gloss can be obtained, but on the other hand, it does not absorb the solvent component in the ink. A porous ink receiving layer having excellent ink absorbency is preferably provided on such a non-absorbent support, and the present invention is particularly useful for an inkjet recording material having such a structure. The thickness of these supports is preferably about 50 to 300 μm.

When a film or polyolefin resin-coated paper that is a non-absorbent support is used, an activation treatment such as a corona discharge treatment or a flame treatment can be performed on the surface on which the ink receiving layer is provided.

When a film or polyolefin resin-coated paper is used as the support, the support is preferably a support having an undercoat layer mainly composed of a natural polymer compound or a synthetic resin on the surface on which the ink receiving layer is provided. A support having an undercoat layer mainly composed of gelatin is preferable.

There is no particular restriction on the coating amount of the undercoat layer is preferably in the range of 0.005~2.0g / ^{m 2} in solid coating amount, more preferably in the range of 0.01 to 1.0 g / ^{m 2,} The range of 0.02 to 0.5 g / m ² is particularly preferable.

On the support in the present invention, various backcoat layers can be applied to the surface opposite to the surface on which the ink receiving layer is provided for antistatic, improved transportability, curl prevention, and the like. The backcoat layer may contain an appropriate combination of an inorganic and organic antistatic agent, a hydrophilic binder, a latex, a curing agent, a pigment, a surfactant and the like.

Hereinafter, the present invention will be described in detail with reference to Examples, but the content of the present invention is not limited to the Examples. Unless otherwise specified, parts and% are based on mass.

(Example 1)
<Preparation of polyolefin resin coated paper>
A 1: 1 mixture of hardwood bleached kraft pulp (LBKP) and hardwood bleached sulfite pulp (LBSP) was beaten with Canadian standard freeness to 300 ml to prepare a pulp slurry. Alkylketen dimer as a sizing agent is 0.5% against pulp, polyacrylamide is 1.0% against pulp as a strength agent, cationized starch is 2.0% against pulp, and polyamide epichlorohydrin resin is 0 against pulp. 5.5% was added and diluted with water to obtain a 0.2% slurry. This slurry was made with a long net paper machine so as to have a basis weight of 170 g / m ² , and dried and humidity-controlled to obtain a base paper for a polyolefin resin-coated paper. A polyethylene resin composition in which 10% anatase-type titanium dioxide is uniformly dispersed in a low-density polyethylene resin having a density of 0.918 g / cm ^{3 is melted at 320 ° C. on the extracted base paper to a thickness of 35 μm.} The surface was extruded and coated using a cooling roll with a slightly roughened surface. Melted at similarly 320 ° C. The blend resin composition of the low density polyethylene resin 30 parts of a density 0.962 g / cm 70 parts high density polyethylene resin of ³ and a density 0.918 g / cm ³ on the other surface, the thickness It was extruded and coated to a size of 30 μm, and extruded and coated using a cooling roll with a roughened surface to form a back surface.

After applying a high-frequency corona discharge treatment to the surface of the polyolefin resin-coated paper, the undercoat layer having the following composition was applied and dried so ^{that the gelatin content was 50 mg / m 2 to prepare a support.}

<Underlay layer>
Lime-treated gelatin 100 parts Sulfosuccinic acid 2-ethylhexyl ester salt 2 parts Chromium bright 10 parts

A slide bead coater so ^{that the dry coating amount of the ink receiving layer coating liquid 1 having the following composition is 25 g / m 2 on} the surface provided with the undercoat layer of the polyolefin resin coated paper (thickness 235 μm) produced as described above. Was applied with. Then, after cooling at 10 ° C. for 20 seconds, it was dried by blowing heated air at 30 to 55 ° C. Further, as a result of evaluating the void structure of this ink receiving layer with the specific surface area pore distribution measuring device SA3100 manufactured by Beckman Coulter, the average pore diameter was 34 nm. Further, the surface layer coating liquid 1 having the following composition was applied by a coating apparatus using a diagonal gravure roll, and was dried by blowing warm air at 45 ° C. to obtain an inkjet recording material of Example 1. The wet coating amount of the surface layer coating liquid was set to 20 ml / m ^{2 (0.3 g / m 2} as the solid content coating amount) by adjusting the rotation speed of the diagonal gravure roll.

<Preparation of vapor phase silica dispersion>
After preparing a preliminary dispersion by adding 4 parts of dimethyldiallyl ammonium chloride homopolymer (molecular weight 9000) and 100 parts of hydrophilic vapor phase silica (average primary particle size 7 nm, specific surface area 300 m ^{2 / g by BET method) to water.} , High-pressure homogenizer treatment was performed to prepare a vapor phase method silica dispersion having a solid content concentration of 20%. The average secondary particle size of the vapor phase silica was 135 nm.

<Ink receiving layer coating liquid 1>
Gas phase method silica dispersion liquid (as solid content of vapor phase method silica) 100 parts boric acid 4 parts polyvinyl alcohol (sakenization degree 88%, average degree of polymerization 3500) 23 parts so that the solid content concentration of the coating liquid is 13% Adjusted with water.

<Preparation of Hydrophobic Silica Dispersion Liquid 1>
After preparing a preliminary dispersion by adding hydrophobic colloidal silica (QSG-80, manufactured by Shinetsu Chemical Industry Co., Ltd., average primary particle size 80 nm) having a trimethylsilyl group to a 50% aqueous ethanol solution so as to have a solid content concentration of 2%. , The hydrophobic silica dispersion 1 was prepared by ultrasonic dispersion treatment.

<Surface layer coating liquid 1>
Hydrophobic silica dispersion 1 (as solid content of hydrophobic silica) 100 parts Acrylic acid ester polymer emulsion (as solid content) 20 parts (average particle size 60 nm)
A 50% aqueous ethanol solution was added so that the solid content concentration of the coating liquid was 1%.

(Example 2)
An inkjet recording material of Example 2 was obtained in the same manner as in Example 1 except that the surface layer coating liquid 1 of Example 1 was replaced with the following surface layer coating liquid 2.

<Preparation of Hydrophobic Silica Dispersion Liquid 2>
After preparing a preliminary dispersion by adding hydrophobic colloidal silica (QSG-30, manufactured by Shinetsu Chemical Industry Co., Ltd., average primary particle size 30 nm) having a trimethylsilyl group to a 50% aqueous ethanol solution so as to have a solid content concentration of 2%. , The hydrophobic silica dispersion 2 was prepared by ultrasonic dispersion treatment.

<Surface layer coating liquid 2>
Hydrophobic silica dispersion 2 (as solid content of hydrophobic silica) 100 parts Acrylic acid ester polymer emulsion (as solid content) 20 parts (average particle size 60 nm)
A 50% aqueous ethanol solution was added so that the solid content concentration of the coating liquid was 1%.

(Example 3)
The inkjet recording material of Example 3 was obtained in the same manner as in Example 1 except that the surface layer coating liquid 1 of Example 1 was replaced with the following surface layer coating liquid 3.

<Preparation of Hydrophobic Silica Dispersion Liquid 3>
Hydrophobic colloidal silica having a trimethylsilyl group (TG-C110, manufactured by Cabot Corporation, average primary particle size 110 nm) is added to a 50% aqueous ethanol solution so as to have a solid content concentration of 2% to prepare a preliminary dispersion, and then ultrasonically dispersed. The treatment was performed to prepare a hydrophobic silica dispersion liquid 3.

<Surface layer coating liquid 3>
Hydrophobic silica dispersion 3 (as solid content of hydrophobic silica) 100 parts Acrylic acid ester polymer emulsion (as solid content) 20 parts (average particle size 60 nm)
A 50% aqueous ethanol solution was added so that the solid content concentration of the coating liquid was 1%.

(Example 4)
The inkjet recording material of Example 4 was obtained in the same manner as in Example 1 except that the surface layer coating liquid 1 of Example 1 was replaced with the following surface layer coating liquid 4.

<Preparation of Hydrophobic Silica Dispersion Liquid 4>
Hydrophobic colloidal silica (TG-C390, manufactured by Cabot Corporation, average primary particle size 65 nm) having an octylsilyl group is added to a 50% aqueous ethanol solution so that the solid content concentration is 2%, and then ultrasonic waves are prepared. The hydrophobic silica dispersion 4 was prepared by dispersion treatment.

<Surface layer coating liquid 4>
Hydrophobic silica dispersion 4 (as solid content of hydrophobic silica) 100 parts Acrylic acid ester polymer emulsion (as solid content) 20 parts (average particle size 60 nm)
A 50% aqueous ethanol solution was added so that the solid content concentration of the coating liquid was 1%.

(Comparative Example 1)
An inkjet recording material of Comparative Example 1 was obtained in the same manner as in Example 1 except that the surface layer coating liquid 1 of Example 1 was replaced with the following surface layer coating liquid 5.

<Preparation of Hydrophobic Silica Dispersion Liquid 5>
Hydrophobic vapor phase silica (AEROSIL RX-200, manufactured by Nippon Aerosil Co., Ltd.) is added to a 50% aqueous ethanol solution to prepare a preliminary dispersion, and then ultrasonically dispersed to make it hydrophobic. A sex silica dispersion 5 was prepared.

<Surface layer coating liquid 5>
Hydrophobic silica dispersion 5 (as solid content of hydrophobic silica) 100 parts Acrylic acid ester polymer emulsion (as solid content) 20 parts (average particle size 60 nm)
A 50% aqueous ethanol solution was added so that the solid content concentration of the coating liquid was 1%.

(Comparative Example 2)
An inkjet recording material of Comparative Example 2 was obtained in the same manner as in Example 1 except that the surface layer coating liquid 1 of Example 1 was replaced with the following surface layer coating liquid 6.

<Preparation of Hydrophobic Silica Dispersion Liquid 6>
Hydrophobic vapor phase silica (AEROSIL R-974, manufactured by Nippon Aerosil Co., Ltd.) is added to a 50% aqueous ethanol solution to prepare a preliminary dispersion, and then ultrasonically dispersed to make it hydrophobic. A sex silica dispersion 6 was prepared.

<Surface layer coating liquid 6>
Hydrophobic silica dispersion 6 (as solid content of hydrophobic silica) 100 parts Acrylic acid ester polymer emulsion (as solid content) 20 parts (average particle size 60 nm)
A 50% aqueous ethanol solution was added so that the solid content concentration of the coating liquid was 1%.

The following evaluations were performed on the hydrophobic silica dispersions (hydrophobic silica dispersions 1 to 6) of Examples 1 to 4 and Comparative Examples 1 and 2 prepared as described above, and the inkjet recording material. The results are shown in Table 1.

<Silica dispersibility>
The average particle size Dw of each hydrophobic silica dispersion was determined using a particle size distribution meter (PAR-III, manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method. Further, the hydrophobic silica dispersions 1'to 6'in which the dispersion medium contained in the hydrophobic silica dispersions 1 to 6 was changed to 100% ethanol were prepared, and the average particle size De was determined in the same manner as described above. The ratio Dw / De was used as an index of silica dispersibility in a water-diluted solvent, and was evaluated according to the following criteria.
◯: Dw / De is less than 1.5. Good dispersibility even in water-diluted solvent.
X: Dw / De is 1.5 or more. Poor dispersibility in water-diluted solvent.

<Glossy>
Using a gloss meter (GM-26D type, manufactured by Murakami Color Technology Research Institute Co., Ltd.), the 75-degree mirror gloss of the unprinted portion of each inkjet recording material was measured by the method of JIS-Z-8741 and described as follows. Evaluated by criteria.
⊚: The glossiness is 50 or more, and there is a high glossiness.
◯: The glossiness is 40 or more and less than 50, and a glossy feeling is recognized.
Δ: The glossiness is 30 or more and less than 40, and the glossiness is slightly low.
X: The glossiness is less than 30, and the glossiness is insufficient for glossy paper.

<Dirt removal property>
As a model substance for colored stains, 1 ml of a 1% blue No. 1 dye aqueous solution was dropped on the surface of each inkjet recording material, wiped off after 5 seconds, and the degree of coloring marks remaining on the inkjet recording material was visually observed. Evaluated by criteria.
◯: No coloring marks remain.
Δ: Slightly colored marks remain.
X: Coloring marks are clearly left.

From the results in Table 1, it can be seen that the inkjet recording material of the present invention can reduce the environmental load by suppressing the use of an organic solvent during production, and is excellent in glossiness and stain removal property.

Claims (1)

An inkjet recording material having an ink receiving layer mainly containing inorganic fine particles having an average secondary particle size of 500 nm or less on the support and a surface layer containing hydrophobic colloidal silica on the side farther from the support from the ink receiving layer. ..