JP2021117404A - Inkjet recording adhesive label - Google Patents

Abstract

To provide an inkjet recording adhesive label which allows a recording surface and an adhesive layer in contact with each other when rolled to be easily separated without using a release paper, which offers superior uniformity of printed images.SOLUTION: An inkjet recording adhesive label is provided, comprising an ink-receiving layer and a release layer containing hydrophobic silica disposed on the ink-receiving layer, both provided on a first surface of a support material, and an adhesive layer provided on the other surface of the support material.SELECTED DRAWING: None

Description

The present invention relates to an adhesive label for inkjet recording, in which the recording surface and the adhesive layer in contact with each other in a rolled state can be easily peeled off without using a release paper, and the printed image has excellent uniformity. Is.

Adhesive labels for inkjet recording are rapidly becoming widespread in recent years because they can be easily made full-color and high-speed, and can be printed in small lots. Generally, the adhesive label is configured by providing an adhesive layer on a support on the back surface side having no ink receiving layer and a release paper on the adhesive layer. Release paper is no longer needed after the label is attached to the adherend, but it is difficult to dispose of it because it cannot be recycled pulp with ordinary waste paper collection equipment. Further, since the product thickness is increased by the amount of the release paper, the roll diameter per unit length is increased in the state of being rolled into a roll shape, and therefore improvement in handling is required.

In order to solve the problem caused by having the release paper, it is generally practiced to eliminate the need for the release paper by providing a release layer on the surface of the recording layer. However, especially in the case of an adhesive label for inkjet recording having an ink receiving layer having excellent ink absorption, since the ink receiving layer on the recording surface is bulky and porous, the release agent is applied to the surface of the ink receiving layer as it is. However, the release agent is absorbed into the ink receiving layer, and sufficient peeling performance cannot be obtained. In addition, when a large amount of mold release agent is applied in order to exhibit the mold release performance, the voids in the ink receiving layer are filled and the ink absorbability is impaired, and the surface becomes strongly hydrophobic and the landed ink. Since it hinders the spread of the ink, problems such as deterioration of image quality occur.

In order to solve the above problem, an adhesive label for inkjet recording using a compound selected from a long-chain alkyl group-containing polyvinyl alcohol, a long-chain alkyl group-containing aminoalkyd resin, and a long-chain alkyl group-containing polyethyleneimine as a mold release agent has been proposed. (Patent Document 1). However, in the case of a glossy type ink receiving layer having a small void diameter, a decrease in ink absorbability is still a problem. On the other hand, an adhesive label for inkjet recording using a mixture of a styrene polymer and a silicone release agent or a mixture of a styrene polymer and a perfluoro release agent has been proposed as a release agent (Patent). Document 2). However, the adhesive label for inkjet recording of Patent Document 2 is intended for output with non-water-based ink, and when an image is printed with general water-based ink, the ink is repelled and the image cannot be formed.

On the other hand, an adhesive label for inkjet recording has been proposed in which the surface of the ink receiving layer is coated so that the release layer containing the silicone resin has a coverage of 20 to 70% (Patent Document 3). However, it is difficult to uniformly surface-cover the release layer with the above-mentioned coverage rate, and uneven ink absorption and deterioration of image quality occur locally in a part of the continuous layer, so that a particularly high-quality image is printed. It is a problem when doing so. Further, an adhesive label for inkjet recording has been proposed in which peeling portions thicker than the thickness of the adhesive layer are discretely provided on the surface of the ink receiving layer (Patent Document 4). However, even if the peeling portions are provided discretely, the peeling portions have poor ink absorbing ability, and therefore, they are inferior in terms of image uniformity, especially when printing a high-quality image.

Japanese Unexamined Patent Publication No. 2001-139900 Japanese Unexamined Patent Publication No. 2005-29718 Japanese Unexamined Patent Publication No. 2014-195994 JP-A-2019-199504

The present invention provides an adhesive label for inkjet recording, in which the recording surface and the adhesive layer in contact with each other in a rolled state can be easily peeled off without using a release paper, and the printed image has excellent uniformity. The task is to do.

The above object of the present invention is basically achieved by the following invention.
For inkjet recording, which has an ink receiving layer on one surface of the support and a release layer containing hydrophobic silica on the ink receiving layer, and has an adhesive layer on the other surface of the support. Adhesive label.

INDUSTRIAL APPLICABILITY The present invention provides an adhesive label for inkjet recording, in which the recording surface and the adhesive layer in contact with each other in a rolled state can be easily peeled off without using a release paper, and the printed image has excellent uniformity. can do.

The adhesive label for inkjet recording of the present invention has a release layer containing hydrophobic silica on the ink receiving layer. The surface of the release layer serves as the recording surface. Generally, when the release layer is provided on the ink receiving layer, the release performance is deteriorated due to the release agent being absorbed into the ink receiving layer, and the release agent fills the voids in the ink receiving layer. Deterioration of ink absorbability and further deterioration of image uniformity are problems. However, as a result of diligent studies in the present invention, ink absorption is achieved by providing a release layer containing hydrophobic silica on the ink receiving layer. It has been found that it is possible to obtain good mold release performance while having high image uniformity without impairing the properties. Hereinafter, the adhesive label for inkjet recording of the present invention will be described in detail.

In the present invention, the ink receiving layer preferably contains mainly inorganic fine particles having an average secondary particle size of 500 nm or less from the viewpoint of obtaining good color development. 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. Precipitation 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.

Gas 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 from the viewpoint of color development, 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. Is more preferable, and those having an average primary particle size 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 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. Further, 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 obtaining 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 described above, the vapor phase silica used in the present invention is preferably dispersed with an average secondary particle size of 500 nm or less from the viewpoint of color development, but more preferably in the range of 10 to 300 nm. As a method for dispersing the vapor phase silica, the vapor phase silica and the 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, or a sand grinder, It is preferable to perform dispersion using a pressure-type disperser such as a high-pressure homogenizer or an ultra-high-pressure homogenizer, an ultrasonic disperser, a thin-film swirling 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, precipitated silica or gel silica is preferable from the viewpoint of color development, and precipitated silica is particularly preferable. The wet method silica used in the present invention preferably has an average secondary particle size of 500 nm or less, more preferably 20 to 300 nm, from the viewpoint of color development. 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 solution preferably has a high solid content concentration, but if the concentration is too high, dispersion becomes impossible. Therefore, the preferred 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 pre-dispersion liquid 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. From the viewpoint of dispersibility and stability of the dispersion liquid viscosity, the mass average 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, from the viewpoint of color development, it is preferable to use alumina having an average secondary particle size of 500 nm or less, and more preferably alumina having an average secondary particle size in the range of 20 to 300 nm.

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 preferably has an average secondary particle size of 500 nm or less, more preferably 20 to 300 nm, from the viewpoint of color development.

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 saponification degree 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 smaller the content of the water-soluble binder in the ink receiving layer, the larger the void volume in the ink receiving layer and the higher the ink absorbency. However, if it is too small, the ink receiving layer becomes fragile and surface defects such as cracks are formed. 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. By containing the cross-linking agent, the occurrence of surface defects such as cracks can be suppressed, and the ink absorbability is also improved. 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 Industry 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 carbhydrazide 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. ..

The thioether compound used in the present invention includes an aromatic thioether compound in which aromatic groups are bonded to both sides of a sulfur atom, an aliphatic thioether compound having alkyl groups 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 coating amount of the ink receiving layer after drying ^{is preferably 10 to 60 g / m 2} , and when the support is a non-absorbent support such as resin-coated paper, the coating after drying is applied. The amount is preferably 20 to 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 release layer will be described. In the present invention, the release layer contains hydrophobic silica. Hydrophobic silica is obtained by subjecting the surface of amorphous silica to a hydrophobic treatment, and the hydrophobic treatment is not performed by waxes such as paraffin wax, carnauba wax, amide wax, and polyethylene wax. A method of covering the -OH group on the surface of crystalline silica, or adding an organosilicon compound such as tetramethylsilane, vinyltrichlorosilane, vinyltrimethoxysilane, epoxy group-containing silane, or dimethyldichlorosilane, or an amino group-containing organic compound for hydrolysis. A method of denatured by such as is known. The obtained hydrophobic silica exhibits high hydrophobicity because the −OH group on the surface of the amorphous silica chemically reacts with an organosilicon compound or the like and has a hydrophobic group on the particle surface. In the present invention, by using the voids formed by the hydrophobic silica as the ink flow path, it is possible to impart releasability to the recording surface of the adhesive label without impairing the ink absorbency. Specific examples of the hydrophobic group include a trimethylsilyl group, a dimethylsilyl group, an octylsilyl group, a group having a siloxane bond (for example, a dimethylpolysiloxane group) and the like. In the present invention, a trimethylsilyl group and an octylsilyl group are preferable from the viewpoint of releasability and ink acceptability.

As the above-mentioned hydrophobic silica, AEROSIL (registered trademark) R972, R974, R976, RX200, RX300, RY200, RY300, R104, R106, etc. from Nippon Aerosil Co., Ltd. are available from Asahi Kasei Wacker Silicone. HDK (registered trademark) H15, H18, H20, H30, etc. from Fuji Silysia Chemical Ltd., and Silohobic (registered trademark) 100, 200, 704, 507, 507 from Fuji Silysia Chemical Ltd. 505 and the like, TG-C series from Cabot Corporation, and QSG series from Shin-Etsu Chemical Ltd. are commercially available and are easily available.

Hydrophobic 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. The content of the hydrophobic silica in the release 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 release layer preferably contains a resin emulsion or a polyvinyl acetal resin as a binder for hydrophobic 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 release layer, and the coating layer of the obtained release layer is obtained. The strength 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 silica. If the amount is less than the above range, the binding performance of the hydrophobic silica particles cannot be sufficiently obtained and the particles are likely to fall off. Ink absorbability may decrease due to the decrease.

A polyvinyl acetal resin can also be preferably used as a binder for hydrophobic silica. Among the water-insoluble resins, the polyvinyl acetal resin has a high binder ability against inorganic pigments, and the obtained ink receiving 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 a water-based 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 acetalize it. For this acetalization, known methods such as a precipitation method, a dissolution method, a uniform method, and a non-uniform method can be used. It is also possible to obtain a polyvinyl acetal resin by using polyvinyl acetate as a raw material and performing saponification and acetalization in parallel.

The polyvinyl alcohol used for acetalization is preferably one having a saponification degree of 75 to 99% and a degree of polymerization of 500 to 3500, but is not limited to this range. Further, those having different saponification degrees or degree of polymerization may be mixed and used. Furthermore, derivatives 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, butylaldehyde, isopropylaldehyde and isobutylaldehyde: aromatic aldehydes such as benzaldehyde, benzylaldehyde and salicylaldehyde: heterocyclic aldehydes such as furfural. : Acrolein, crotonaldehyde, propiolaldehyde, hexenal, heptenal and other aliphatic unsaturated aldehydes: glyoxal, succindialdehyde, glutaaldehyde, adiposialdehyde, piperindialdehyde, suberindialdehyde, sebacindialdehyde and other aliphatic dialdehydes. Aldehydes can be mentioned. As these aldehydes, butyraldehyde, isobutyraldehyde, and isopropylaldehyde are preferable, and butyraldehyde is particularly preferable. A polyvinyl acetal resin acetalized with butyraldehyde is known as a polyvinyl butyral resin.

The degree of acetalization of the polyvinyl acetal resin (degree of butyralization in the case of polyvinyl butyral resin) is preferably 30 mol% or more, more preferably 50 mol% or more. By setting the degree of acetalization to 30 mol% or more, the hydrophobicity is improved and the releasability is enhanced. The average molecular weight is preferably 30,000 or more, more preferably 60,000 or more. As the polyvinyl acetal resin described above, for example, Sekisui Chemical Co., Ltd. sells Eslek (registered trademark), Kuraray Co., Ltd. sells Mobital (registered trademark), and the like, and they are easily available.

The content of the polyvinyl acetal resin 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 cannot be sufficiently obtained and the particles are likely to fall off. Ink absorbency may decrease due to the decrease in the amount of ink.

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

As a coating method used for coating the release 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 of the adhesive label for inkjet recording of the present invention includes films such as polyethylene, polypropylene, polyvinyl chloride, diacetate resin, triacetate resin, cellophane, acrylic resin, polyethylene terephthalate, and polyethylene naphthalate, and an inorganic filler in polypropylene resin. Non-absorbent support such as synthetic paper (for example, YUPO (registered trademark), YUPO Corporation), polyolefin resin coated paper, etc., high-quality paper, etc. Examples thereof include absorbent supports such as art paper and coated paper. 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} of the coating amount after drying, more preferably in the range of 0.01 to 1.0 g / ^{m 2} , 0.02-0.5 g / m ² is particularly preferred.

The pressure-sensitive adhesive layer of the present invention is provided on a surface opposite to the surface on which the ink receiving layer of the support is provided. The pressure-sensitive adhesive used for the pressure-sensitive adhesive layer is not particularly limited, and various pressure-sensitive adhesives such as solvent-type pressure-sensitive adhesives, emulsion-type pressure-sensitive adhesives, and hot-melt-type pressure-sensitive adhesives can be used. Coating amount after drying of the adhesive layer is preferably ^{5~50g / m 2, 10~30g / m} 2 is more preferable. If the coating amount after drying ^{is less than 5 g / m 2} , sufficient adhesive strength cannot be obtained when used as a label, while if ^{it exceeds 50 g / m 2} , the adhesive strength is saturated.

The application method used for applying the adhesive layer is Mayer bar coater, kiss roll coater, lip coater, direct roll coater, offset roll coater, gravure roll coater, reverse roll coater, rod coater, blade coater, comma direct coater, comma. A reverse coater, an air knife coater, a slit die coater and the like are suitable. Further, the adhesive is not applied to the surface of the support on which the ink receiving layer is provided, but is once applied to the process paper, and after drying, the adhesive is applied to the surface of the support on which the ink receiving layer is provided. It is also possible to apply the pressure-sensitive adhesive layer by transferring to the ink and then peeling off the process paper.

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)
On synthetic paper FGS80 (thickness 80 μm) manufactured by Yupo Corporation, the ink receiving layer coating solution 1 having the following composition was coated with a slide bead coater so that ^{the coating amount after drying was 25 g / m 2.} 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 release layer coating liquid 1 having the following composition was applied by a coating device using a diagonal gravure roll, and was dried by blowing warm air at 45 ° C. The wet coating amount of the release layer coating liquid was set to 20 ml / m ^{2 (0.3 g / m 2} as the coating amount after drying) by adjusting the rotation speed of the diagonal gravure roll. Next, a commercially available water-based acrylic resin type (emulsion type) adhesive (BPW6441, manufactured by Toyochem Co., Ltd.) was applied to the surface of the support on the side where the ink receiving layer was not applied, and the applied amount after drying was 18 g / m ² . It was applied with a gap roll and dried to form an adhesive layer, and an adhesive label for inkjet recording of Example 1 was obtained.

<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 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 (saponification 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 Solution 1>
Hydrophobic colloidal silica (QSG-80, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) having a trimethylsilyl group is added to ethanol to prepare a pre-dispersion liquid, and then ultrasonically dispersed to make it hydrophobic. Silica dispersion 1 was prepared.

<Release 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)

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

<Preparation of Hydrophobic Silica Dispersion Solution 2>
Hydrophobic vapor phase silica (AEROSIL RX-200, manufactured by Nippon Aerosil Co., Ltd.) having a trimethylsilyl group is added to ethanol to prepare a pre-dispersion solution, which is then subjected to ultrasonic dispersion treatment. Hydrophobic silica dispersion 2 was prepared.

<Release layer coating liquid 2>
Hydrophobic silica dispersion 2 (as solid content of hydrophobic silica) 100 parts Polyvinyl butyral resin (degree of butyralization 65 mol%)
(Eslek BH-3, manufactured by Sekisui Chemical Co., Ltd.) 200 copies (as resin solid content)

(Example 3)
An inkjet recording adhesive label of Example 3 was obtained in the same manner as in Example 1 except that the release layer coating liquid 1 of Example 1 was replaced with the following release layer coating liquid 3.

<Preparation of Hydrophobic Silica Dispersion Solution 3>
Hydrophobic gel method silica (Silohobic 100, manufactured by Fuji Silysia Chemical Ltd.) having a dimethylpolysiloxane group is added to ethanol to prepare a pre-dispersion liquid, and then ultrasonic dispersion treatment is performed. The hydrophobic silica dispersion 3 was prepared.

<Release layer coating liquid 3>
Hydrophobic silica dispersion 3 (as solid content of hydrophobic silica) 100 parts Polyvinyl butyral resin (degree of butyralization 65 mol%)
(Eslek BH-3, manufactured by Sekisui Chemical Co., Ltd.) 200 copies (as resin solid content)

(Example 4)
An adhesive label for inkjet recording of Example 4 was obtained in the same manner as in Example 1 except that the release layer coating liquid 1 of Example 1 was replaced with the following release layer coating liquid 4.

<Preparation of Hydrophobic Silica Dispersion Solution 4>
Hydrophobic colloidal silica (TG-C390, manufactured by Cabot Corporation) having an octylsilyl group is added to ethanol to prepare a preliminary dispersion, and then ultrasonically dispersed to prepare a hydrophobic silica dispersion. 4 was prepared.

<Release 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)

(Comparative Example 1)
Comparative Example in the same manner as in Example 1 except that the release layer coating liquid 1 of Example 1 was replaced with the following release layer coating liquid 5 and ^{coated and dried so that the coating amount after drying was 3 g / m 2.} An adhesive label for inkjet recording of 1 was obtained.

<Release layer coating liquid 5>
Water was added to a solution of polyvinyl alcohol containing a long-chain alkyl group (Resem K-256, manufactured by Chukyo Oil & Fat Co., Ltd.) so that the solid content concentration was 15%.

(Comparative Example 2)
For inkjet recording of Comparative Example 2 in the same manner as in Example 1 except that the release layer coating liquid 1 of Example 1 was replaced with the following release layer coating liquid 6 and coated so that the thickness after drying was 3 μm. Obtained an adhesive label.

<Release layer coating liquid 6>
Polystyrene (GPPS, manufactured by PS Japan Corporation) 94.5 parts Titanium dioxide (Typake (registered trademark) CR-90, manufactured by Ishihara Sangyo Co., Ltd.) 5.0 parts Stearic acid amide 0.5 parts Solid content of coating liquid Toluene was added to a concentration of 15%.

(Comparative Example 3)
The release layer coating liquid 1 of Example 1 was replaced with the following release layer coating liquid 7, ^{and the coating was applied so that the coating amount after drying was 3 g / m 2,} and the comparison was carried out in the same manner as in Example 1 except that the coating was dried. An adhesive label for inkjet recording of Example 3 was obtained.

<Release layer coating liquid 7>
Silicone resin emulsion (KM-3951, manufactured by Shin-Etsu Chemical Co., Ltd.) 47.6 parts Silicone resin curing catalyst (CAT-PM-10A, manufactured by Shin-Etsu Chemical Co., Ltd.) 2.4 parts Water 50.0 parts

(Comparative Example 4)
An inkjet recording adhesive label of Comparative Example 4 was obtained in the same manner as in Example 1 except that the release layer coating liquid 1 was not applied in Example 1.

The following evaluation was performed on the adhesive label for inkjet recording produced as described above. The results are shown in Table 1.

<Image uniformity>
Perform solid printing of cyan, magenta, yellow, and black with a commercially available water-based inkjet printer (EP-881A, manufactured by Seiko Epson Corporation), observe the uniformity (graininess and unevenness) of the solid image part, and use the following criteria. Sensory evaluation was performed.
⊚: Image uniformity is very high.
◯: The uniformity of the image is inferior to that of “◎”, but there is no problem in practical use.
Δ: The uniformity of the image is inferior to that of “◯”, which is a practical problem.
X: The uniformity of the image is inferior to that of “Δ”, and the unevenness is remarkable.

<Easy peeling>
After winding the adhesive label for inkjet recording in a roll shape so that the adhesive layer surface is in contact with the recording surface (the release layer surface in Examples 1 to 4 and Comparative Examples 1 to 3 and the ink receiving layer surface in Comparative Example 4). The state of the recording surface after peeling when peeled again was visually observed and evaluated according to the following criteria.
◯: No peeling marks remain.
Δ: A slight peeling mark remains.
X: Peeling marks are clearly left or do not peel off cleanly.

From the results shown in Table 1, the adhesive label for inkjet recording of the present invention can be easily peeled off from the recording surface in contact with the adhesive layer in a rolled state without using a release paper, and the printed image can be easily peeled off. It can be seen that the uniformity is excellent.

Claims (1)

For inkjet recording, which has an ink receiving layer on one surface of the support and a release layer containing hydrophobic silica on the ink receiving layer, and has an adhesive layer on the other surface of the support. Adhesive label.