JP2020062798A - Inkjet recording material - Google Patents

Abstract

To provide an inkjet recording material having excellent coating layer strength, image sharpness, and a contamination removing property.SOLUTION: An inkjet recording material has an ink reception layer containing inorganic fine particles as main constituent on a supporting body, and a surface layer containing hydrophobic silica and a polyvinyl acetal resin on the ink reception layer.SELECTED DRAWING: None

Description

  The present invention relates to an inkjet recording material excellent in coating layer strength, image sharpness, and stain removability.

  As a recording material used in the inkjet recording system, an inkjet recording material having a porous ink receiving layer made of 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, which uses ultrafine particles such as vapor phase silica or wet silica pulverized to about several hundred nm as a pigment, has been known.

  However, while these porous ink-receiving layers can absorb water-based ink quickly, even when an unintended colored liquid adheres, the penetration speed of the permeation of the colored liquid makes it difficult to remove the colored mark even if the liquid is wiped off. There was a problem that remained. Therefore, there is a demand for an inkjet recording material having a hydrophobic surface, which has a high image sharpness when printed with a water-based ink and is capable of easily wiping colored stains and which is excellent in stain removability.

  Studies on making a surface hydrophobic in an inkjet recording material have already been tried, and for example, Patent Document 1 discloses an inkjet recording receiving composition containing an aqueous cationic resin and hydrophobic silica, and Patent Document 2 discloses: A method of providing a water repellent layer containing hydrophobic silica fine particles on an ink receiving layer containing a pigment and a binder is disclosed. However, in these conventional techniques, it is not possible to obtain a surface layer having excellent image sharpness and sufficient coating layer strength when printed with a water-based ink, and there has been a demand for improvement.

  On the other hand, Patent Document 3 discloses an ink jet recording sheet containing hydrophobic silica and a hydrophobic thermoplastic resin, which can improve stain resistance when used outdoors when exposed to rain or the like. Although it was reported, it was still not sufficiently satisfactory in terms of the sharpness of the obtained image.

JP, 2003-191602, A JP2012-196922A JP, 2007-276167, A

  An object of the present invention is to provide an inkjet recording material excellent in coating layer strength, image sharpness, and stain removability.

The above problems of the present invention are basically achieved by the following inventions.
An ink jet recording material having an ink receiving layer containing inorganic fine particles as a main component on a support, and a surface layer containing hydrophobic silica and a polyvinyl acetal resin on the ink receiving layer.

  According to the present invention, it is possible to provide an inkjet recording material having excellent coating layer strength, image sharpness, and stain removability.

  The inkjet recording material of the present invention is characterized in that it has an ink receiving layer mainly containing inorganic fine particles on a support and a surface layer containing hydrophobic silica and a polyvinyl acetal resin on the ink receiving layer. Ink jet recording materials using hydrophobic silica have been known so far, but none of them satisfy both the removal property of unintended coloring marks (removal property of stains) and the image sharpness when printed with a water-based ink. It was In the present invention, as a result of intensive studies focusing on the printing performance with the water-based ink, the ink jet recording material having the above-mentioned constitution, the coating layer strength and stain removability, and the image sharpness when printed with the water-based ink. It has been found that an inkjet recording material satisfying all requirements can be obtained. 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. The term "mainly contained" as used herein 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. The inorganic fine particles contained in the ink receiving layer are preferably hydrophilic inorganic fine particles, and examples thereof include various known fine particles such as amorphous synthetic silica, alumina, alumina hydrate, calcium carbonate, magnesium carbonate, and titanium dioxide. Amorphous synthetic silica, alumina, or alumina hydrate is preferable in that high printing density and excellent image sharpness can be obtained.

  Amorphous synthetic silica can be roughly classified into wet process silica, vapor phase process silica, and others depending on the manufacturing method. Wet method silica is further classified into precipitation method silica, gel method silica and sol method silica according to the production method. Precipitated silica is produced by reacting sodium silicate and sulfuric acid under alkaline conditions, and the silica particles that have grown are aggregated / precipitated, and then commercialized through steps of filtration, washing with water, drying, pulverization / classification. The precipitated silica is commercially available, for example, from Tosoh Silica Co., Ltd. as Nipseal (registered trademark). The gel method silica is produced by reacting sodium silicate and sulfuric acid under acidic conditions. During the aging, the fine particles are dissolved and re-precipitated so as to bond the other primary particles to each other, so that the distinct primary particles disappear and relatively hard agglomerated particles having an internal void structure are formed. For example, it is commercially available as Nip Gel (registered trademark) from Tosoh Silica Co., Ltd. The sol method silica is also called colloidal silica, and is obtained by heating and aging a silica sol obtained through metathesis of sodium silicate with an acid or the like or through an ion exchange resin layer. For example, from Nissan Chemical Co., Ltd., as Snowtex (registered trademark) 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 with hydrogen and oxygen is generally known, but instead of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane may be used alone or in the form of silicon tetrachloride. It can be used as a mixture with. Vapor grown silica is commercially available from Nippon Aerosil Co., Ltd. as AEROSIL (registered trademark) and Tokuyama Corporation as Reorosil (registered trademark).

For the ink receiving layer of the ink jet recording material of the present invention, vapor phase method silica can be preferably used. The vapor phase silica contained in the ink receiving layer preferably has an average primary particle size of 30 nm or less, more preferably an average primary particle size of 3 to 15 nm, and a BET specific surface area of 200 m ² / g or more. Those having a particle diameter of 3 to 10 nm and a specific surface area by the BET method of 250 to 500 m ² / g are particularly preferable. The average primary particle diameter in the present invention is an average value obtained by observing fine particles by an electron microscope, using the diameter of a circle equal to the projected area of each of 100 primary particles in a certain area as the particle diameter. Is. The BET method referred to in the present invention is one of the surface area measurement methods for powders by the vapor phase adsorption method, and is a method for obtaining the total surface area of 1 g of a sample, that is, the specific surface area, from the adsorption isotherm. Usually, nitrogen gas is often used as the adsorbed gas, and the most commonly used method is to measure the adsorbed amount from the pressure or volume change of the adsorbed gas. The most prominent one for expressing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller equation, which is called the BET equation and is widely used for determining the surface area. The adsorption amount is calculated 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 silica, those dispersed in the presence of a cationic compound can be preferably used. The average secondary particle diameter of the vapor phase silica is preferably 500 nm or less, more preferably 10 to 300 nm. As the dispersion method, ordinary propeller stirring, turbine-type stirring, homomixer-type stirring and the like are used to premix the vapor phase silica and the dispersion medium, and then a ball mill, a bead mill, a media mill such as a sand grinder, a high pressure homogenizer, and an ultrahigh pressure. Dispersion is preferably performed using a pressure-type disperser such as a homogenizer, an ultrasonic disperser, and a thin film swirl-type disperser. The average secondary particle diameter as referred to in the present invention refers to that measured as the number median diameter using a laser scattering type particle size distribution meter (for example, LA920 manufactured by Horiba Ltd.).

  In the present invention, wet process silica can also be preferably used. The wet method silica contained in the ink receiving layer is preferably precipitated silica or gel silica, and particularly preferably precipitated silica. The wet-process silica used in the present invention is preferably a wet-process silica having an average primary particle size of 50 nm or less, preferably 3 to 40 nm, and an average secondary particle size of 500 nm or less, and having an average secondary particle size of Wet silica having a thickness of 20 to 300 nm is more preferable.

  As the wet method silica, those obtained by dispersing and pulverizing 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 process silica used in the present invention will be described. First, silica particles and a cationic compound are mixed in a dispersion medium composed mainly of water, and at least one of a dispersing device such as a saw-tooth blade type disperser, a propeller blade type disperser, or a rotor stator type disperser is used. Use to obtain a silica predispersion. If necessary, an appropriate low boiling point solvent or the like may be added to the aqueous dispersion medium. The silica solid dispersion preferably has a high solid content concentration, but if the concentration is too high, dispersion becomes impossible. Next, the silica pre-dispersion liquid is preferably subjected to mechanical means having a stronger shearing force to grind the silica particles. As the mechanical means, a known method can be adopted, for example, a ball mill, a bead mill, a media mill such as a sand grinder, a high pressure homogenizer, a pressure type disperser such as an ultrahigh pressure homogenizer, an ultrasonic disperser, and a thin film swirling disperser. Can be used.

  A cationic polymer can be preferably used as the cationic compound used for dispersing or pulverizing the vapor phase silica and the wet method silica. Examples of the cationic polymer include polyethyleneimine, polydiallylamine, polyallylamine, alkylamine polymers, JP-A-59-20696, JP-A-59-33176, JP-A-59-33177, and JP-A-59-33177. 59-155088, JP-A-60-11389, JP-A-60-49990, JP-A-60-83882, JP-A-60-109894, and JP-A-62-198493. , JP-A-63-49478, JP-A-63-115780, JP-A-63-280681, JP-A-1-40371, JP-A-6-234268, and JP-A-7-125411. Polymers having a primary to tertiary amino group and a quaternary ammonium base described in JP-A-10-193776 and the like are It used Mashiku. Particularly, a diallylamine derivative is preferably used as the cationic polymer. From the viewpoint of dispersibility and dispersion viscosity, the weight 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 crystal is particularly preferable. With γ-alumina, primary particles can be reduced to about 10 nm, but usually secondary particle crystals of several thousands to tens of thousands nm are pulverized by ultrasonic waves, a high pressure homogenizer, an opposed collision type jet pulverizer, or the like. Can be used. The average secondary particle diameter of alumina is preferably 500 nm or less, more preferably 20 to 300 nm.

The alumina hydrate contained in the ink receiving layer is represented by a constitutive formula of Al ₂ O ₃ .nH ₂ O (n = 1 to 3). The alumina hydrate used in the present invention can be obtained by known production methods such as hydrolysis of aluminum alkoxide such as aluminum isopropoxide, neutralization of aluminum salt with alkali, and hydrolysis of aluminate. The average secondary particle diameter of the alumina hydrate used in the present invention is preferably 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 by a known dispersant such as acetic acid, lactic acid, formic acid and nitric acid are preferably used.

  Two or more kinds of inorganic fine particles may be used in combination from the above-mentioned inorganic fine particles. For example, a combination of finely pulverized wet method silica and vapor phase method silica, a combination of finely pulverized wet method silica and alumina or an alumina hydrate, a combination of vapor phase method silica and alumina or an alumina hydrate may be mentioned. To be

  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-based or derivatives thereof are used, but among them, fully saponified or partially saponified polyvinyl alcohol is preferable. Particularly preferably, the saponification degree is 80% or more. 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 other polyvinyl alcohol derivatives. The polyvinyl alcohol may be used alone or in combination of two or more.

  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 crosslinking agent in addition to the above water-soluble binder. As the cross-linking agent, those known as 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 is particularly preferable. When the polyvinyl alcohol contains a highly active modifying group, a known crosslinking agent may be used depending on the modifying group. The addition amount of the crosslinking agent 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, as an additive, the same cationic polymer as that used for the cationization of the above-mentioned amorphous synthetic silica. Further, the ink receiving layer may contain a water-soluble polyvalent metal compound for improving water resistance and the like. A water-soluble aluminum compound can be preferably used as the water-soluble polyvalent metal compound.

  Known examples of water-soluble aluminum compounds include inorganic salts such as aluminum chloride or its hydrate, aluminum sulfate or its hydrate, and ammonium alum. Further, a basic polyaluminum hydroxide compound which is an inorganic aluminum-containing cationic polymer is known.

Among these water-soluble aluminum compounds, those which can be stably added to the coating liquid for forming the ink receiving layer are preferable, and the basic polyaluminum hydroxide compound is preferably used. The main component of this compound is represented by the following formula 1, 2 or 3, and for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ (OH) ₃₄ ] ⁵⁺ , It is a water-soluble polyaluminum hydroxide that stably contains basic and polymeric polynuclear condensed ions such as [Al ₂₁ (OH) ₆₀ ] ³⁺ .

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

  These are water treatment agents under the name of Poly Aluminum Chloride (PAC) from Taki Chemical Co., Ltd., under the name of Poly Aluminum Hydroxide (Paho) from Asada Chemical Co., Ltd., and RIKEN Co., Ltd. It is commercially available from Green under the name Purachem WT and from other manufacturers for the same purpose, and various grades are easily available.

  The content of the above water-soluble polyvalent metal compound 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, an antiseptic, a fluorescent brightening agent, a viscosity stabilizer, a pH adjusting agent, etc. Various additives can also be added.

  Further, the ink-receiving layer may contain a thioether compound, carbohydrazide and its derivative to improve the storage stability after printing.

  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 molecular main chain or side chain. .

  Examples of the thioether compound used in the present invention include an aromatic thioether compound having an aromatic group bonded to both sides of a sulfur atom, and an aliphatic thioether compound having an alkyl group at both ends sandwiching a sulfur atom. Of 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. 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 silica and polyvinyl acetal resin. Hydrophobic silica is obtained by subjecting the surface of amorphous silica to hydrophobicity-imparting treatment. For example, paraffin wax, carnauba wax, amide wax, polyethylene wax, and other waxes are used as hydrophobicity-imparting treatments. Hydrolysis by covering the -OH group on the surface of crystalline silica, or by adding an organic silicon compound such as tetramethylsilane, vinyltrichlorosilane, vinyltrimethoxysilane, epoxy group-containing silane, dimethyldichlorosilane or an amino group-containing organic compound. A method of denaturing the same is known. The obtained hydrophobic silica is one in which the —OH group on the surface of amorphous silica is chemically reacted with an organic silicon compound or the like, and has a hydrophobic group such as an alkyl group on the particle surface. Therefore, it exhibits high hydrophobicity.

  As the above-mentioned hydrophobic silica, AEROSIL R972, R974, R976, RX200, RX300, RY200, RY300, R104, and R106 from Nippon Aerosil Co., Ltd. are HDK from Asahi Kasei Wacker Silicone Co., Ltd. (Registered trademark) H15, H18, H20, H30 and the like are commercially available, and these are obtained by subjecting vapor phase silica to a hydrophobic treatment. As other hydrophobic silica, Silophobic (registered trademark) 100, 200, 704, 507, 505 and the like are commercially available from Fuji Silysia Chemical Ltd., and these are wet-process silica. It has been subjected to a hydrophobicity-imparting treatment. These hydrophobic silicas can be used alone or in combination of two or more. As the hydrophobic silica used in the present invention, from the viewpoint of obtaining an inkjet recording material that is particularly excellent in coating layer strength and image sharpness, hydrophobic silica obtained by subjecting the surface of vapor-phase method silica to hydrophobic treatment is preferable. .

The hydrophobic silica may be subjected to a dispersion treatment. A known method can be used as a mechanical means for the dispersion treatment, but the method used for dispersing the vapor phase method silica or the wet method silica in the ink receiving layer is preferably used. 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 contains a polyvinyl acetal resin as a binder resin of hydrophobic silica. Among the water-insoluble resins, the polyvinyl acetal resin has a high binder ability for inorganic pigments, and the resulting surface layer has excellent coating layer strength and appropriate flexibility. Further, the film after drying is transparent and has excellent water resistance, and when printed with an aqueous ink, an image having excellent image sharpness can be obtained. The polyvinyl acetal resin can be obtained by reacting polyvinyl alcohol with an aldehyde to form an acetal. For this acetalization, a known method such as a precipitation method, a dissolution method, a homogeneous method, a heterogeneous method can be used. It is also possible to use polyvinyl acetate as a raw material and perform saponification and acetalization in parallel to obtain a polyvinyl acetal resin.

  The polyvinyl alcohol used for the acetalization preferably has a saponification degree of 75 to 99% and an average degree of polymerization of 500 to 3500, but is not limited to this range. Further, those having different degrees of saponification or average degree of polymerization may be mixed and used. Furthermore, a derivative obtained by suitably introducing various functional groups into them can also be used.

  Examples of the aldehyde used for acetalization include aliphatic saturated aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isopropylaldehyde and isobutyraldehyde: aromatic aldehydes such as benzaldehyde, benzylaldehyde and salicylaldehyde: heterocyclic aldehydes such as furfural : Aliphatic unsaturated aldehydes such as acrolein, crotonaldehyde, propiolaldehyde, hexenal, heptenal, etc. Aldehydes are mentioned. As these aldehydes, butyraldehyde, isobutyraldehyde and isopropylaldehyde are preferable, and butyraldehyde is particularly preferable.

  The degree of acetalization of the polyvinyl acetal resin is preferably 30 mol% or more, more preferably 50 mol% or more. When the degree of acetalization is 30 mol% or more, the hydrophobicity is improved and the stain removability is enhanced. The average molecular weight is preferably 30,000 or more, more preferably 60,000 or more. The polyvinyl acetal resin described above is commercially available, for example, S-REC (registered trademark) from Sekisui Chemical Co., Ltd., Mobital (registered trademark) from Kuraray Co., Ltd., and the like.

  The content of the polyvinyl acetal resin in the surface layer is preferably 15 to 500% by mass, more preferably 50 to 300% by mass based on the content of the hydrophobic silica. If the amount is less than the above range, the binding performance of the hydrophobic silica particles is not sufficiently obtained and is likely to fall off, and if the amount is more than, the contribution of the hydrophobic silica becomes small, and the coloring accompanying the adhesion of the coloring liquid such as a beverage is colored. The dirt removal performance may be reduced.

  In addition to the hydrophobic silica and the polyvinyl acetal 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 ink jet recording material of the present invention includes polyethylene, polypropylene, polyvinyl chloride, diacetate resin, triacetate resin, cellophane, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, etc. Examples of the absorbent support include high-quality paper, art paper, and coated paper. Among them, the non-absorptive support is preferable in that high gloss is obtained, but on the other hand, it does not absorb the solvent component in the ink. A porous ink receiving layer having excellent ink absorbability is preferably provided on such a non-absorbent support, and the present invention is particularly useful for an inkjet recording material having such a constitution. The thickness of these supports is preferably about 50 to 300 μm.

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

  When a film or a 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 a subbing 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.

  The support of the present invention may be coated with various back coat layers on the surface opposite to the surface on which the ink receiving layer is provided for the purpose of preventing electrification, improving transportability and preventing curling. The backcoat layer may contain an inorganic and organic antistatic agent, a hydrophilic binder, a latex, a curing agent, a pigment, a surfactant and the like in an appropriate combination.

  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. Parts and% are based on mass.

(Example 1)
<Production of polyolefin resin coated paper>
A 1: 1 mixture of a hardwood bleached kraft pulp (LBKP) and a hardwood bleached sulfite pulp (LBSP) was beaten to 300 ml with Canadian standard freeness to prepare a pulp slurry. Alkyl ketene dimer as a sizing agent to pulp 0.5%, polyacrylamide as a strength agent to pulp 1.0%, cationized starch to pulp 2.0%, polyamide epichlorohydrin resin to pulp 0% 0.5% was added and diluted with water to give a 0.2% slurry. This slurry was made into a paper by a Fourdrinier paper machine so as to have a basis weight of 170 g / m ² , dried and conditioned to obtain a base paper for a polyolefin resin-coated paper. A polyethylene resin composition in which 10% anatase-type titanium is uniformly dispersed in a low-density polyethylene resin having a density of 0.918 g / cm ³ is melted at 320 ° C. into a paper-made base paper to have a thickness of 35 μm. Extrusion coating was carried out as described above, and the surface was extrusion coated using a cooling roller having a finely roughened surface. Melted at similarly 320 ° C. The blend resin composition of the low density polyethylene resin 30 parts of a density 0.962 g / cm 70 parts high density polyethylene resin of ³ and a density 0.918 g / cm ³ on the other surface, the thickness It was extrusion coated to a thickness of 30 μm and was extrusion coated using a roughened cooling roll to obtain the back surface.

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

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

On the surface of the polyolefin resin-coated paper prepared as described above, on which the undercoat layer was provided, the ink receiving layer coating liquid 1 having the following composition was applied by a slide bead coater so that the dry coating amount was 25 g / m ² . Then, after cooling at 10 ° C. for 20 seconds, heated air at 30 to 55 ° C. was blown to dry. After drying, the water content of the ink receiving layer was 5% by mass. The average pore diameter was 34 nm as a result of evaluating the void structure of the ink receiving layer with a specific surface area pore distribution measuring device SA3100 manufactured by Beckman Coulter. Further, the surface layer coating liquid 1 having the following composition was coated by a coating device using a diagonal gravure roll and 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 adjusted to 20 ml / m ² by adjusting the rotation speed of the oblique gravure roll.

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

<Ink receiving layer coating liquid 1>
Gas phase method silica dispersion (as solid content of gas phase method silica) 100 parts Boric acid 4 parts Polyvinyl alcohol (saponification degree 88%, average degree of polymerization 3500) 23 parts So that the solid content concentration of the coating solution is 13% Adjusted with water.

<Preparation of Hydrophobic Silica Dispersion 1>
Hydrophobic silica (Syrohobic 100, manufactured by Fuji Silysia Chemical Ltd.) was added to ethanol so as to have a solid content concentration of 20% to prepare a preliminary dispersion liquid, which was then subjected to ultrasonic dispersion treatment to obtain a hydrophobic silica dispersion liquid 1. Was produced.

<Surface layer coating liquid 1>
Hydrophobic silica dispersion 1 (as solid content of hydrophobic silica) 100 parts Polyvinyl acetal resin acetalized with butyraldehyde (ESREC BH-3, manufactured by Sekisui Chemical Co., Ltd.) (as resin solid content) 200 parts Ethanol was added so that the solid content concentration of the liquid was 2%.

(Example 2)
An ink jet 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 changed to the following surface layer coating liquid 2.

<Preparation of hydrophobic silica dispersion 2>
Hydrophobic silica (AEROSIL RX-200, manufactured by Nippon Aerosil Co., Ltd.) was added to ethanol to give a solid content concentration of 20% to prepare a preliminary dispersion liquid, which was then ultrasonically dispersed to prepare a hydrophobic silica dispersion liquid 2. It was made.

<Surface layer coating liquid 2>
Hydrophobic silica dispersion 2 (as solid content of hydrophobic silica) 100 parts S-REC BH-3 (as resin solid content) 200 parts Ethanol was added so that the solid content concentration of the coating solution was 2%.

(Comparative Example 1)
Comparative Example in which the surface layer coating liquid 1 prepared so that the solid content concentration was 10% was applied to the surface provided with the undercoat layer of the polyolefin resin-coated paper so that the dry coating amount was 25 g / m ^2. Inkjet recording material 1 was obtained.

(Comparative example 2)
An ink jet 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 changed to the following surface layer coating liquid 3.

<Preparation of Hydrophilic Silica Dispersion 1>
Hydrophilic silica (AEROSIL 200, manufactured by Nippon Aerosil Co., Ltd.) was added to ethanol so as to have a solid content concentration of 20% to prepare a preliminary dispersion liquid, which was then ultrasonically dispersed to prepare a hydrophilic silica dispersion liquid 1. .

<Surface layer coating liquid 3>
Hydrophilic Silica Dispersion Liquid 1 (as solid content of hydrophilic silica) 100 parts S-REC BH-3 (as resin solid content) 200 parts Ethanol was added so that the solid content concentration of the coating solution was 2%.

(Comparative example 3)
An inkjet recording material of Comparative Example 3 was obtained in the same manner as in Example 1 except that the surface layer coating liquid 1 of Example 1 was changed to the following surface layer coating liquid 4.

<Surface layer coating liquid 4>
Hydrophobic silica (AEROSIL RX-200) 3 parts Tetraethoxysilane 10.3 parts 1N nitric acid 1 part Water 8.8 parts Ethanol 76.9 parts

  The following evaluations were performed on the ink jet recording material produced as described above. The results are shown in Table 1.

<Coating strength>
As an evaluation showing the degree of removal of the coating layer, a cellophane tape (manufactured by Nichiban Co., Ltd.) was attached to the surface of the ink jet recording material obtained as described above, and a coating layer (surface layer The area of) was visually observed, and the coating layer strength was evaluated according to the following criteria.
4: Almost no coating layer was transferred, and coating layer strength was good.
3: Most of the coating layers are not transferred and the coating layer strength is practically no problem.
2: A large part of the coating layer is transferred, and there is a problem in the coating layer strength.
1: Almost all of the coating layer is transferred, and there is a serious problem in coating strength.

<Image sharpness>
A predetermined evaluation image is printed on the ink jet recording material obtained as described above by a commercially available water-based ink jet printer (PIXUS (registered trademark) XK-70 manufactured by Canon Inc.), and each color of black, cyan, magenta, and yellow is printed. Sensory evaluation was performed based on the following criteria, using the sharpness in detail of the blank characters arranged in the solid image area and the level of blurring between color boundaries as criteria.
4: Extremely sharp, and no bleeding was observed at the intercolor boundary.
Although inferior to 3: 4, the level of sharpness and bleeding is practically no problem.
2: Poor sharpness and bleeding were observed, and there was a problem in practical use.
1: The sharpness is extremely low, the image is blurred, and it is not practical.

<Removal of dirt>
As a model substance for colored stain, 1 mL of 1% blue dye No. 1 aqueous solution was dropped on the surface of the recording material, and after 5 seconds, it was wiped off, and the degree of the colored mark remaining on the recording material was visually observed and evaluated according to the following criteria .
3: No coloring marks remain.
2: A slight coloring mark remains.
1: Clearly colored traces remain.

  From the results in Table 1, it is understood that the inkjet recording material of the present invention has excellent coating layer strength and image sharpness, and has high stain removability.

Claims (1)

  An ink jet recording material having an ink receiving layer containing inorganic fine particles as a main component on a support, and a surface layer containing hydrophobic silica and a polyvinyl acetal resin on the ink receiving layer.