JP2006169354A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet satisfying the adoptability of indirect dry electrophotoghraphic printers. <P>SOLUTION: The pressure-sensitive adhesive sheet has an adhesive layer on at least one side of the surface substrate. The adhesive layers are bonded with each other by applying pressure on the adhesive layers facing with each other. The bonded adhesive layers are peelable. The surface substrate has a base paper sheet and a coated layer containing a pigment and a binder resin as the main components and formed at least on one side of the base paper sheet. The surface of the layer has specific glossiness and smoothness. The surface substrate has a specific air permeability. The adhesive layer contains at least one kind of the adhesives such as an acrylic-modified natural rubber. The constitutional ingredients of the pressure-sensitive adhesive sheet includes a fine particle filler, an organic polymer compound and a resin whose minimum film-formation temperature is ≥90°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is an electrophotographic transfer paper for use in an indirect dry electrophotographic full-color copying machine and printer, and various postcards such as a tri-fold or a bi-fold postcard in which an adhesive layer is further provided on the coating layer. The present invention relates to a pressure-sensitive adhesive sheet used in a system.

Along with the revision of the Postal Law, a postcard system having a confidential property by folding a sheet on which necessary information is recorded into two or three is put into practical use and has become widespread. The adhesive layer provided on the postcard base sheet having such confidentiality is not adhesive at room temperature and normal pressure, and is pressed to about 500 kg / cm ² with the adhesive layers facing each other. A pressure-sensitive adhesive sheet (hereinafter, also referred to as a confidential postcard paper, which is a representative example) having an adhesive layer that exhibits adhesiveness and can be re-peeled after adhesion is used.

  As described in Japanese Patent Application Laid-Open No. 7-276858 (Patent Document 1), the confidential postcard paper is offset printed with a form printer as a postcard on the surface of the adhesive layer, and then the address, personal information, etc. The secret information is printed with a laser printer, folded so that the adhesive layers face each other so that the secret information cannot be seen from the outside, and pressure-laminated with a dry sealer to form a confidential postcard. The confidential postcard allows the recipient to see the information by peeling off the adhesive layer as it was, and once peeled off, the surface of the adhesive layer is not adhesive at room temperature and normal pressure. It is a postcard that must not be.

  On the other hand, in recent years, copying machines and printers have been developed in color, high speed, and high image quality. In particular, in the field of on-demand publications, it is relatively easy to handle a small number of copies, so there is a tendency to produce publications that have been produced by printing methods with color copiers and color printers. For this purpose, application of coated paper having high white paper gloss is being studied.

The coated paper has usually been produced by applying a pigment having an average particle diameter of 2 microns or less on each side of a base paper by 10 g / m ² or more using various coaters and then smoothing the surface by calendering. These coated papers are usually used in the field of commercial printing. However, these coated papers are applied to electrophotographic copying machines and printers instead of ordinary PPC paper and printer paper. Increasing cases are increasing the sharpness. Therefore, by using a color copier or color printer and a pressure-sensitive adhesive sheet provided with an adhesive layer on the coated paper, it becomes possible to print standard items and print personal information in one step. It is considered economically advantageous.

  However, when such a pressure-sensitive adhesive sheet having a coating layer and an adhesive layer is applied to an electrophotographic copying machine or printer, there arises a problem that blisters are generated when the toner image is heated and fixed. The blister is a water vapor generated by heating water inside the toner image when the toner image is heated and fixed, and the water vapor pressure inside the paper rises. When this water vapor is discharged out of the paper, for some reason, the discharge does not go smoothly.If the internal bond strength of the paper is weak, this water vapor will rapidly expand inside the paper layer and cause local blistering. Occurs (hereinafter referred to as paper blister).

  Also, when the toner layer is formed into a film by the heat of the fixing roll with respect to the above paper blister, if the air permeability of the coating layer is low, the air existing in the toner layer breaks through the filmed toner layer. Then, a crater is generated in the image portion. Fine blisters and through-holes are generated in the pressure-sensitive adhesive sheet to lower the quality (hereinafter referred to as toner blister). This toner blister becomes a serious defect of the image. As described above, since the pressure-sensitive adhesive sheet has a coating layer and an adhesive layer, it is difficult to secure a sufficient water vapor discharge path. Furthermore, if there is a color toner image, paper blisters and toner blisters are likely to occur. In particular, in the case of coated paper having a high glossiness, a calendar process is required to increase the glossiness, and the coating layer density increases, so that paper blisters and toner blisters are likely to occur.

  Furthermore, the blister phenomenon is more likely to occur during double-sided printing than during single-sided printing. The reason is that since the toner adheres to the surface of the adhesive layer during single-sided printing, the water vapor generated in the double-sided printing is less likely to be discharged than during single-sided printing. This is a pressure-sensitive adhesive sheet that uses conventional coated paper for printing with high white paper gloss or coated paper for electrophotography as a base sheet, and blistering during single-sided printing is slight or non-occurring. However, blistering occurs during double-sided printing.

Up to now, for improving blistering of electrophotographic coated paper, a method of adjusting the center line average roughness of the coating layer surface to 2.0 μm or less and the air permeability to 4,000 seconds or less (JP-A-62-2). 198876 (Patent Document 2) and the smoothness and air permeability of the base paper for coating, and the coating amount of the coating layer containing the organic pigment is regulated to set the air permeability to 4,000 seconds. The following adjustment methods (Japanese Patent Laid-Open No. 5-241366 (Patent Document 3)) and the like have been proposed. In addition, air permeability is Japan Tappi No. This is a measurement of the time in seconds that 10 ml of air pressurized to 0.1 kg / cm ² permeates through the paper according to the Oken type air permeability test method (method according to JIS P8117) specified in 5. .

  Further, it is proposed to improve toner blocking on a pressure-sensitive adhesive sheet by an electrophotographic printer by specifying the air permeability and moisture of confidential postcard paper (Japanese Patent Laid-Open No. 2002-169320 (Patent Document 4)). However, the problem of paper blisters and toner blisters when a pressure-sensitive adhesive sheet having a coating layer and an adhesive layer is used in an electrophotographic color copying machine or color printer is not disclosed or suggested. Currently.

Japanese Patent Laid-Open No. 7-276858 (2nd page) JP-A 62-198876 (Claim 1) JP-A-5-241366 (Claim 1) JP 2002-169320 A (Claims 1 to 14)

  An object of the present invention is to provide a pressure-sensitive adhesive sheet that satisfies the suitability of an indirect dry electrophotographic printer, and in which generation of paper blisters and toner blisters is effectively suppressed.

  As a result of intensive studies to solve the above problems, the present inventors have found that a surface base material provided with a coating layer having a specific range of glossiness, smoothness, and air permeability has an acrylic modified natural nature. Rubber, methyl methacrylate modified natural rubber, acrylic ester copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer / acrylic ester copolymer composite resin, styrene-butadiene copolymer resin , Including at least one adhesive selected from acrylonitrile-butadiene copolymer resin, vinyl chloride resin, and vinylidene chloride resin, further containing a fine particle filler, an organic polymer compound, and a resin having a minimum film forming temperature of 90 ° C. or more. It has been found that the blending effectively suppresses the generation of paper blisters and toner blisters.

  The present invention provides a pressure-sensitive adhesive sheet that does not generate paper blisters or toner blisters when printed with an indirect dry electrophotographic printer by providing an adhesive layer containing a specific adhesive on a specific surface substrate. It is provided and includes the following inventions.

[1] It has an adhesive layer on at least one surface of the surface base material, and the adhesive layer can be bonded by performing a high pressure treatment with the adhesive layers facing each other, and after bonding, the adhesive layer In the pressure-sensitive adhesive sheet that can be peeled off, the surface substrate has a base paper and a coating layer formed on at least one surface thereof and containing a pigment and a binder resin as main components, The surface of the layer has a glossiness of 50% or more, a smoothness of 2,000 seconds or less, the air permeability of the surface base material is 7,000 seconds or less, and the adhesive layer is an acrylic modified natural Rubber, methyl methacrylate modified natural rubber, acrylic ester copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer / acrylic ester copolymer composite resin, styrene-butadiene copolymer A resin containing at least one adhesive selected from fat, acrylonitrile-butadiene copolymer resin, vinyl chloride resin, and vinylidene chloride resin, a fine particle filler, an organic polymer compound, and a resin having a minimum film forming temperature of 90 ° C or higher. A pressure-sensitive adhesive sheet, characterized by being a constituent component.

[2] The pressure-sensitive adhesive sheet according to [1], wherein the density of the surface substrate is 1.10 g / cm ³ or less and the internal bond strength of the base paper is 0.2 kJ / m ² or more.

[3] The adhesive is at least one selected from methyl methacrylate-modified natural rubber, acrylate copolymer resin, ethylene-vinyl acetate copolymer / acrylate copolymer composite resin [1] Thru | or [2] pressure sensitive adhesive sheet.

[4] Kaolin particles in which the pigment constituting the coating layer has an average particle diameter of 0.3 to 1.5 μm and satisfies the following formula (1): 5 ≦ L / W ≦ 50 (1)
[However, in formula (1), L represents the major axis of the kaolin particles, and W represents the minor axis of the kaolin particles],
And the binder resin constituting the coating layer is (A) a copolymer having a glass transition temperature of 10 to 60 ° C. and having a single structure, and (B) a synthetic polymer compound having a core-shell structure The pressure-sensitive adhesive sheet according to any one of [1] to [3], which is at least one selected from

  The pressure-sensitive adhesive sheet of the present invention is not only excellent in suitability for indirect dry electrophotographic printers (paper blister resistance and toner blister resistance), but also has a good balance with adhesion suitability and is extremely suitable for applications such as confidential postcard paper. Is suitable.

In the pressure-sensitive adhesive sheet of the present invention, the adhesive layer provided on at least one surface of the surface base material does not show adhesiveness at normal temperature and normal pressure before pressing, and the adhesive layers are made to face each other. In such a state, it can be bonded by applying a pressure treatment to about 500 kg / cm ² , and the bonding surface can be peeled by hand (this surface is also referred to as a re-peeling surface). It has an adhesive layer having a characteristic that it does not adhere even if the adhesive layers are stacked and pressure-bonded by hand.

  The pressure-sensitive adhesive sheet of the present invention has (I) a structure having an adhesive layer having removability (hereinafter also referred to as a re-peeling surface) on only one surface of the surface substrate, and (II) the surface substrate. Configuration with adhesive layer (removable surface) having removability on both sides, (III) Removable adhesive layer (removable surface) is provided on one side of the surface substrate, and removability is provided on the other surface A pressure-sensitive adhesive sheet having a surface having no surface (permanently bonded surface).

Pressure-sensitive adhesive sheet of the present invention, re-peeling surface, the permanent adhesive surface of both normal temperature, do not exhibit adhesiveness at normal pressure, by pressure laminating to ² about 300kg / cm ² ~700kg / cm in the dry sealer Although it adheres, such an adhesive layer adjusts adhesive force with the compounding quantity etc. of an adhesive agent and a fine particle filler. For example, after providing information that requires secrecy on the re-peeling surface, the sheet is folded so that the information is hidden, or another sheet is stacked so that the re-peelable adhesive layers face each other. By applying pressure treatment, it is used as a laminated sheet having information inside (for example, a confidential postcard, a lottery, etc.).

As a result of intensive studies to achieve the above object, the present inventors have a base paper and a coating layer formed on at least one surface thereof and containing a pigment and a binder resin as main components, By making the surface of the coating layer have a glossiness of 50% or more, a smoothness of 2,000 seconds or less, and the air permeability of the surface base material is 7,000 seconds or less, It has been found that the adhesion between the coating layer and the adhesive layer can be improved. In a preferred embodiment, the pigment in the coating layer has an average particle size of 0.3 to 1.5 μm and satisfies the following formula (2): 5 ≦ L / W ≦ 50 (2)
[Wherein L represents the major axis of the kaolin particles and W represents the minor axis of the kaolin particles], and the binder resin has (A) a glass transition temperature of 10 to 60 ° C. And a copolymer having a single structure and (B) a synthetic polymer compound having a core-shell structure (hereinafter also referred to as “core-shell structure polymer compound”).

  The lower the smoothness of the coating layer surface, the better the adhesion between the coating layer surface and the adhesive layer. And transfer of toner to the opposite surface is reduced. In the present invention, when (A) a single structure copolymer having a glass transition temperature of 10 to 60 ° C. and / or (B) a core-shell structure polymer compound is blended in the coating layer. It was confirmed that the adhesion between the base paper and the coating layer and between the coating layer and the adhesive layer was good, and it was effective in preventing the adhesive layer from falling off when the pressure-sensitive adhesive sheet was peeled off again. In the present invention, the core-shell structure polymer compound is composed of a core portion made of a single polymer or a copolymer and a shell portion surrounding the core portion and made of a single polymer or a copolymer. Copolymer. The single structure copolymer is a copolymer which is composed of a copolymer of two or more comonomers and does not have a composite structure such as a core-shell structure.

  In the coating layer of the present invention, the single structure copolymer (A) having a glass transition temperature of 10 to 60 ° C., preferably 15 to 50 ° C., suitably used as a binder resin is, for example, a styrene-butadiene copolymer. It is selected from a polymer, an acrylic ester copolymer, a styrene-acrylic ester copolymer, a vinyl acetate copolymer, an ethylene-vinyl acetate copolymer, and the like.

The core-shell structure polymer compound (B) used in the present invention has the following formulas (3) and (4):
Tg1 <Tg2 (3)
−10 ° C. <Tg2 <100 ° C. (4)
[In the formulas (3) and (4), Tg1 represents the glass transition temperature of the core portion in the core-shell structure polymer compound (B), and Tg2 represents the glass transition temperature of the shell portion. ] Is preferable. That is, in this preferred embodiment, the glass transition temperature Tg2 of the shell portion is higher than the glass transition temperature Tg1 of the core portion, and the glass transition temperature of the shell portion is in the range of higher than −10 ° C. and lower than 100 ° C. For this reason, the surface of the film formed of the core-shell structure polymer compound is formed by a shell portion having a glass transition temperature Tg2. After the coating layer is formed, the (Tg1) core portion having a low glass transition temperature is sandwiched by the shell portion having a high glass transition temperature (Tg2), and exhibits high flexibility, flexibility and elasticity at room temperature. When the external pressure is removed, the polymer compound core part in the coating film is easily deformed with respect to the external pressure, and returns to the original shape and exhibits high cushioning properties. Therefore, the coating layer and the adhesive layer are brought into close contact with each other by pressing with a dry sealer, and exhibit good adhesion and re-peelability. Incidentally, when the glass transition temperature Tg2 of the shell part of the core-shell structure polymer compound (B) is 100 ° C. or more, the film formability may be insufficient. On the other hand, when the glass transition temperature Tg2 of the shell portion is −10 ° C. or lower, the resulting coating film is sticky and blocking may easily occur. The glass transition temperature Tg2 of the shell part is more preferably in the range of 0 ° C to 75 ° C. In particular, the glass transition temperature Tg2 of the shell part is preferably 5 ° C. or more higher than the glass transition temperature Tg1 of the core. When this temperature difference is less than 5 ° C., the cushioning property of the coating layer becomes insufficient, and when the pressure-sensitive adhesive sheet is peeled again, the effect of preventing the adhesive layer from falling off may be insufficient. The core-shell structured polymer compound (B) used in the present invention is available as a core-shell type copolymer latex, and the latex preferably has an average particle size of 40 to 300 nm. When the average particle diameter is larger than 300 nm, the strength of the coating film may be insufficient. Moreover, it is preferable that the gel fraction with respect to toluene of a core-shell structure high molecular compound (B) is 30% or more. If the gel fraction is less than 30%, the coating strength of the resulting coating layer may become unstable.

  Next, a method for producing a latex of the core-shell structure polymer compound (B) will be described. The method for producing the latex of the core-shell structure polymer compound (B) is disclosed in JP-A-62-117897, JP-A-7-324112, JP-A-9-31141 and the like. For example, an aliphatic conjugated diene monomer and at least one monomer that is different from this and copolymerizable therewith are emulsion-polymerized to prepare a core-forming copolymer. Monomers copolymerizable with the core-forming monomer in the presence of a copolymer latex, such as aliphatic conjugated diene monomers, aromatic vinyl monomers, and ethylenically unsaturated monomers When at least one carboxylic acid monomer is emulsion-polymerized, a shell part-forming polymer (or copolymer) copolymerized with the core part-forming copolymer is formed, and a core-shell structure polymer compound (B ) Latex is obtained. The heterogeneous monomer for forming the core may be selected from an aliphatic conjugated diene monomer, an aromatic vinyl monomer, and an ethylenically unsaturated carboxylic acid monomer.

  Representative examples of the aliphatic conjugated diene monomer used for forming the core part and the shell part include butadiene, isoprene, 2-chloro-1,3-butadiene and the like. On the other hand, among the monomers copolymerizable with the aliphatic conjugated diene monomer, the aliphatic conjugated diene monomer is, for example, butadiene, isoprene, 2-chloro-1,3-butadiene, and the like, and is aromatic. Examples of the vinyl monomer include styrene, methyl styrene, vinyl toluene, and chlorostyrene. Examples of the ethylenically unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid. is there.

  In the production of the core-shell structure polymer compound (B), the emulsion polymerization of the monomer is performed using an emulsifier, a polymerization initiator, a molecular weight regulator and the like in an aqueous medium according to a conventional emulsion polymerization method. As the emulsifier, an anionic emulsifier, a nonionic emulsifier, an amphoteric emulsifier and the like can be used alone or in combination of two or more thereof.

  As for the polymerization method, similarly to seed polymerization, the core copolymer is preliminarily polymerized in one polymerization system, and a predetermined amount is transferred to another polymerization system, and in the presence, the monomer for shell formation is polymerized. Or the core-forming monomer and the shell-forming monomer in the same polymerization vessel, and the multi-stage core copolymer and the shell copolymer are polymerized sequentially in the same polymerization vessel. Methods are taken.

  In the latex of the core-shell structure polymer (B), a core copolymer component having a low glass transition temperature Tg1 and a shell copolymer component having a high glass transition temperature Tg2 are present in the same latex. As a result, the desired film performance can be obtained. That is, in the present invention, when the core-shell structure polymer compound latex is used as a binder resin for a coating layer, the polymer compound contained in the binder resin component of the coating layer has a glass transition temperature in its core portion. Therefore, it is considered that the coating layer and the adhesive layer are brought into close contact with each other by pressing with a dry sealer and exhibit good adhesion suitability and re-peelability.

  In order to improve the adhesion between the coating layer and the adhesive layer, the present inventors have further intensively studied the relationship between the smoothness and adhesion of the coating layer surface, and as a result, the pigment contained in the coating layer. As a main component, the aspect ratio defined as the ratio of the plane major axis L to the minor axis W of the pigment particles is in the range of 5 to 50, preferably in the range of 5 to 15, and the average particle size is 0.3. Use of kaolin particles in the range of ~ 1.5 μm, preferably in the range of 0.3 to 1.2 μm, preferably 30 parts by mass or more, preferably 35 parts by mass or more in 100 parts by mass of the total pigment By containing it in an amount, a coating layer with high gloss, low smoothness and low air permeability was obtained, and the adhesion between the coating layer and the adhesive layer was successfully improved. Incidentally, even if the average particle diameter of the kaolin particles is 0.3 to 1.5 μm, when the aspect ratio is less than 5, it is difficult to obtain appropriate smoothness and air permeability in the obtained coating layer, When the pressure-sensitive adhesive sheet is peeled again, the adhesive layer may fall off. On the other hand, when the aspect ratio exceeds 50, the glossiness of the obtained coating layer is sufficiently high, but the air permeability is also high, so that paper blisters and toner blisters may be generated.

  The reason why kaolin used in the present invention is effective for forming a coating layer with high gloss, low smoothness and low air permeability is that the aspect ratio of kaolin particles is in the range of 5 to 50, and is generally used. Compared with delaminated kaolin with an aspect ratio exceeding 50, the ratio of the minor axis is a relatively large shape, and the average particle size is as small as 0.3 to 1.5 μm, and the particle size distribution is uniform. This is presumed to be because the gap between the laminated pigments does not form a dense structure.

  When the average particle diameter of the pigment having an aspect ratio in the range of 5 to 50 is smaller than 0.3 μm, the glossiness of the obtained coating layer tends to be high, but the air permeability is remarkably lowered. On the other hand, when the average particle diameter is larger than 1.5 μm, the glossiness of the obtained coating layer is difficult to increase, and a desired glossiness cannot be obtained. As for the particle size distribution, the distribution frequency of particles having a particle size of 0.3 to 1.5 μm is preferably 65% or more.

  In the present invention, the content of kaolin used as the main component of the pigment in the coating layer is preferably 30 parts by mass or more with respect to 100 parts by mass of the total pigment in the coating layer. More preferably, it is within the range of parts. If it is less than 30 mass parts, there exists a possibility that the air permeability of the obtained coating layer may become inadequate.

  In the present invention, the pulp constituting the base paper is not particularly limited in its production method and type. For example, chemical pulp such as KP, mechanical pulp such as SGP, RGP, BCTMP and CTMP, waste paper pulp such as deinked pulp, and non-wood pulp such as kenaf, bamboo, straw, hemp, etc. In addition, organic synthetic fibers such as polyamide fibers and polyester fibers, recycled fibers such as polynosic fibers, and inorganic fibers such as glass fibers, ceramic fibers, and carbon fibers can also be used. In addition, it is preferable to use chlorine free pulp, such as ECF pulp and TCF pulp, as the pulp used for the base paper.

  Moreover, the base paper may contain a filler as required. As the filler, various pigments generally used for fine paper can be used, such as kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, zinc oxide, alumina, magnesium carbonate, magnesium oxide, Mineral pigments such as silica, white carbon, bentonite, zeolite, sericite and smectite, as well as fine hollow particles, solid particles and polystyrene resins, urea resins, melamine resins, acrylic resins and vinylidene chloride resins Examples thereof include organic pigments such as through-hole particles.

  In addition to the pulp fiber and filler, various anionic, nonionic, and cationic properties that have been used in the past are included in the stock when the base paper is made, as long as the desired effects of the present invention are not impaired. Alternatively, various additive agents for papermaking, such as amphoteric yield improvers, freeness improvers and internal sizing agents, can be appropriately selected and used as necessary. Furthermore, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

In addition, since toner is fixed by heat treatment, moisture in the surface base material rapidly expands during processing, and blisters occur in the image area, but the interlayer strength of the surface base material is controlled within a desired range. It was considered to respond by doing. In the present invention. TAPPI No. It is desirable to use a base paper having an interlayer strength measured according to 54-93 of 0.20 kJ / m ² or more, preferably 0.25 kJ / m ² or more.

  As a method for improving the internal bond strength of the base paper, for example, the type of pulp (highly soft conifer), the bond between fibers is increased by proceeding beating, a paper strength agent (polyamide, polyacrylamide, polyamine compound, etc.), Addition of wet paper strength enhancer (polyamide, epoxy resin, melamine resin, etc.) and water-based resin (polyvinyl alcohol, fluorine resin, acrylic resin, styrene resin, acrylic-styrene copolymer resin, polyamide resin, urethane resin, epoxy resin) Etc.) impregnation, coating, laminating processing, laminating, etc., which are appropriately selected according to the purpose.

  There is no particular limitation on the paper making method of the base paper. For example, an acidic paper making method in which the paper making pH is around 4.5, an alkaline filler such as calcium carbonate is contained as a main component, and the paper making pH is from about 6 to about the paper making pH. All paper making methods such as neutral paper making method with 9 weak alkalinity can be applied, and long paper machine, twin wire paper machine, round net paper machine, Yankee paper machine etc. are used as appropriate can do.

  As the pigment used in the coating layer according to the present invention, in addition to the above kaolin, for example, heavy calcium carbonate, light calcium carbonate, aspect ratio (L / W) and / or average particle diameter are used in the present invention. Kaolin, calcined kaolin, delaminated kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, particulate calcium silicate, particulate carbonate Magnesium, fine particulate light calcium carbonate, white carbon, bentonite, zeolite, mineral pigments such as sericite and smectite, and polystyrene resins, styrene-acrylic copolymer resins, urea resins, melamine resins, acrylic resins, Vinylidene chloride resin Fine benzoguanamine resin hollow particles type, it is possible to use dense solid particle type and the through-hole particles organic pigments also include one or two or more among these may be used suitably selected.

  In addition to the core-shell structure polymer compound (B) and the single structure copolymer (A), the binder resin contained in the coating layer of the present invention may include the copolymer ( A) and the core-shell structure polymer compound (B) may contain one or more of water-soluble and / or water-dispersible polymer compounds different from each other, for example, cationic starch, amphoteric starch, Natural or semi-synthetic products such as oxidized starch, enzyme-modified starch, thermochemically modified starch, starch such as esterified starch, etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, gelatin, casein, soy protein, natural rubber, etc. Molecular compounds, polydienes such as polyisoprene and polybutadiene, polyalkenes such as polybutene, polyisobutylene, polypropylene and polyethylene, Vinyl polymers and copolymers such as revinyl halide, polyvinyl acetate, polystyrene, poly (meth) acrylic acid, poly (meth) acrylic ester, polyvinyl alcohol, poly (meth) acrylamide, polymethyl vinyl ether, styrene -Synthetic rubber latex such as butadiene copolymer, methyl methacrylate-butadiene copolymer, chloroprene rubber, polyurethane resin, polyester resin, polyamide resin, olefin-maleic anhydride resin, melamine resin, etc. Examples include synthetic resins. Among these, one or more kinds are appropriately selected and used according to the purpose.

  The blending ratio of the total binder resin including the polymer compound (B) having a core-shell structure and / or the single structure copolymer (A) in the coating liquid of the present invention is 100 parts by mass of pigment ( It is preferable that it exists in the range of 2-25 mass parts (solid part) with respect to a solid part. If the total blending ratio of the binder resin is less than 2 parts by mass, the coating film strength of the coating layer becomes insufficient, and the coating layer may be peeled off and deposited on the drum when the printer is fed, which may cause damage to the transfer drum. There is. On the other hand, if the blending ratio of the total binder resin exceeds 25 parts by mass, the air permeability of the coating layer is remarkably lowered, and the paper blister and toner blister prevention properties may be insufficient. In the coating layer of the present invention, the content of the core-shell structure polymer compound (B) and / or the single structure copolymer (A) in the binder resin is also 2 to 100 parts by mass of the binder. It is preferably 25 parts by mass.

  In this coating layer, in addition to these pigments and binder resins, various auxiliary agents such as emulsifiers, pH regulators, viscosity modifiers, softeners, gloss imparting agents, waxes, dispersants, flow modifiers, At least one kind of stabilizer, antistatic agent, cross-linking agent, sizing agent, fluorescent brightening agent, colorant, ultraviolet absorber, antifoaming agent, water-resistant agent, plasticizer, lubricant, preservative, fragrance, etc. is required May be included as appropriate.

The coating amount of the coating layer of the present invention is preferably 6 to ²⁰ g / m ² , more preferably 7 to 15 g / m ² . If the coating amount is less than 6 g / m ² , the unevenness on the surface of the base paper cannot be sufficiently covered and the smoothness cannot be optimized, so that the adhesive layer acceptability of the obtained coating layer may be insufficient. There is. On the other hand, when the coating amount exceeds 20 g / m ² , the operability such as poor drying properties during coating is deteriorated and the production cost may be increased.

  As a coating method for forming a coating layer, generally, a conventional coating apparatus such as a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater, a slot die coater, a gravure coater, a channel is used. Coating apparatuses such as plex coaters, brush coaters, two rolls, metering blade type size press coaters, bill blade coaters, short dwell coaters, and gate roll coaters can be appropriately used.

  The pressure-sensitive adhesive sheet of the present invention is obtained by providing an adhesive layer on the coating layer. As the adhesive layer, an adhesive, a fine particle filler, an organic polymer compound, a minimum film-forming temperature of 90 ° C. The above resin is an essential constituent.

  The adhesive used in the pressure-sensitive adhesive sheet of the present invention is a material that imparts an appropriate peeling force to the pressure-bonded postcard, and is an acrylic modified natural rubber, a methyl methacrylate modified natural rubber, an acrylate copolymer resin, Ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer / acrylic ester copolymer composite resin, styrene-butadiene copolymer resin, acrylonitrile-butadiene copolymer resin, vinyl chloride resin, vinylidene chloride Preferred examples include polymer resins such as resins.

  Next, the mixing ratio of the adhesive in the adhesive layer is preferably such that the solid content is about 15 to 60% by mass. If the amount is less than 15% by mass, the adhesive strength of the adhesive may be too weak. If the amount exceeds 60% by mass, the fine particle filler in the adhesive layer may be covered and the toner fixability may be reduced. is there.

  The pressure-sensitive adhesive sheet of the present invention comprises at least one selected from organic polymer compounds having a glass transition temperature of −30 to 50 ° C. and a gel fraction with respect to toluene of 30% by mass or more in the adhesive layer. It is preferable to make it into a component. Here, the organic polymer compound is a material for imparting surface strength in the case of indirect dry electrophotographic printer printing. If the glass transition temperature is less than −30 ° C., the adhesive layer becomes too soft and blocking may occur. On the other hand, when the glass transition temperature exceeds 50 ° C., the adhesive layer becomes hard and the adhesiveness may be lost. The glass transition temperature is preferably -20 to 45 ° C, more preferably -15 to 30 ° C. Further, if the gel fraction is less than 30% by mass, problems such as drum contamination may occur.

On the other hand, a gel fraction becomes like this. Preferably it is 34-99 mass%, More preferably, it is 40-99 mass%. Here, the gel fraction with respect to toluene is a value obtained by the following method. That is, it is formed on a Teflon (registered trademark) sheet so that the film thickness of the organic polymer compound is 0.3 to 0.5 mm (after drying). Drying conditions are 50 ° C. and 24 hours. Next, the film prepared under the above conditions was cut into 3 cm square, immersed in toluene for 24 hours, dried at 105 ° C. for 3 hours to completely evaporate the solvent, and the mass change before and after immersion was measured. To obtain the gel fraction.
Gel fraction (%) = {mass after immersion (g) / mass before immersion (g)} × 100

  Although it does not specifically limit as an organic polymer compound, A styrene-butadiene copolymer, a styrene-butadiene-acrylic acid ester copolymer, a (meth) acrylic acid ester copolymer, an ethylene-vinyl acetate copolymer, an ethylene- Examples include vinyl acetate-vinyl chloride copolymer, polyvinyl alcohol (partially saponified, completely saponified), and modified polyvinyl alcohol (partially saponified, completely saponified). These may be used singly or in combination of two or more, but are preferably a styrene-butadiene copolymer, an ethylene-vinyl acetate copolymer, and a partially saponified polyvinyl alcohol, which have excellent affinity with the adhesive component.

  The blending ratio of the organic polymer compound in the adhesive layer of the pressure-sensitive adhesive sheet of the present invention is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the adhesive. If it is less than 1 part by mass, the coating strength of the adhesive layer becomes too weak, and the printer printability may be deteriorated. If the amount exceeds 100 parts by mass, the toner fixing property, paper blister, and toner blister may be deteriorated, and the adhesive force may be further reduced.

  For the adhesive layer, carboxymethylcellulose, casein, dextrin, vinyl acetate resin, starch such as oxidized starch (gelatinized), polyethylene oxide, polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylic acid, polyacrylamide, urethane A polymer or the like may be used in combination. As a result, the suitability for electrophotography may be improved.

  As the fine particle filler contained in the adhesive layer of the pressure-sensitive adhesive sheet of the present invention, inorganic and organic pigments can be used. For example, silica, colloidal silica, zinc oxide, titanium oxide, zeolite, calcium carbonate, clay, aluminum oxide, starch (non-gelatinized), alumina, γ-alumina, plastic pigment, polyethylene resin, polypropylene resin, fluorine resin Etc. Among them, silica, starch and the like are suitable for controlling the adhesive force and are preferably used.

  Starch is used as a spacer for the purpose of preventing blocking. Silica is preferable because it has excellent ink acceptability and suitability for electrophotographic printing. It also has an effect of preventing a decrease in adhesive strength. The fluorine-based resin has a high effect of preventing toner bleeding. Titanium oxide has a high hiding effect, and the hiding effect is further enhanced by mixing with silica. The particle size of the inorganic or organic pigment is preferably about 0.1 to 30 μm. The fine particle filler has an effect of adhering to the adhesive layer surface under pressure and adjusting so as not to adhere after peeling.

  In the adhesive layer of the pressure-sensitive adhesive sheet of the present invention, it is necessary to blend a resin having a minimum film forming temperature of 90 ° C. or higher in order to suppress the generation of paper blisters and toner blisters. The type of resin having a minimum film-forming temperature of 90 ° C. or higher is not particularly limited, but a protective colloid acrylic copolymer emulsion is preferred, and an acrylic acid ester monomer and other monomers are copolymerized using a protective colloid. The thing which was done is mentioned. Examples of other monomers used for the copolymerization include various unsaturated monomers such as styrene and methyl methacrylate. Examples of the protective colloid include styrene-maleic anhydride copolymer and isobutylene-maleic anhydride copolymer. The reason why a resin having a minimum film forming temperature of 90 ° C. or higher is used is that it is considered that the resin does not form a film when dried and does not form a film, and the blister resistance is improved.

  The blending ratio of the resin having a minimum film forming temperature of 90 ° C. or higher in the adhesive layer of the pressure-sensitive adhesive sheet of the present invention is preferably 5 to 70 parts by mass with respect to 100 parts by mass of the adhesive. If it is less than 5 parts by mass, the film-forming property of the adhesive layer coating film becomes too good, and the effect of improving the blister resistance may be poor. If it exceeds 70 parts by mass, the adhesive layer coating film becomes too hard and the adhesive strength may be reduced.

  For the adhesive layer, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, penetrating agents, coloring dyes, UV absorbers, antistatic agents, deodorants An appropriate amount of an agent, a cationic, nonionic or amphoteric surfactant, an antioxidant, an antiseptic, a water-proofing agent and the like can be blended.

When applying the adhesive layer to the surface of the surface substrate, the application method is not particularly limited, but various blade coaters, roll coaters, air knife coaters, bar coaters, gravure coaters, die coaters, curtain coaters, etc. Used. Among these, an air knife coater, a bar coater, a gravure coater, a blade coater, a die coater and the like are preferable. The coating amount is in the range of ^{2 to} 30 g / m ² , but preferably in the range of ^{3 to} 15 g / m ² .

In the winding after the adhesive layer is applied, the JAPAN TAPPI paper pulp test method no. It is preferable that the winding hardness deviation specified by the 37-81 method is 5 kgf · m or less. If the maximum value of the winding hardness deviation exceeds 5 kgf · m, unnecessary paper deformation will occur when high-speed printing is performed with an indirect dry electrophotographic printer, the paper dimensions will be different on the left and right, and wrinkles will occur. Or print misalignment may occur.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” shown in the examples are parts by mass and mass%.

Example 1
[Manufacture of base paper]
LBKP (CSF freeness 550 ml) in 100 parts by mass of pulp slurry, 0.2 parts by mass of polyacrylamide resin (trade name: PS194-7, manufactured by Arakawa Chemical Co., Ltd.) as a paper strength agent, and polyamide epichlorohydrin as a wet strength agent -Based resin (trade name: WS570, manufactured by Nippon PMC Co., Ltd.) 0.2 parts by mass and sulfuric acid band 1 part are added, and the mixture is diluted with white water to obtain a paper material having a pH of 5.3 and a solid content of 1.1%. Was prepared. This stock is subjected to a long paper machine to make a paper, and the obtained wet paper is supplied with a size press liquid containing oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) at a concentration of 6%. The coating weight is 2 g / m ² by dry mass, dried, and further smoothed using a machine calendar so that the Beck smoothness is 50 seconds, and the basis weight is 83 g / m ^2. An m ² base paper was produced.

[Preparation of coating solution]
80 parts by weight of structural kaolin (trade name: Astraplus, manufactured by Imeris) and 20 parts by weight of heavy calcium carbonate (trade name: Hydrocurve 90, manufactured by Bihoku Powder Chemical Co., Ltd.) 0.2 parts by mass (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) was added, and the mixture was dispersed in water using a Coreless disperser to prepare a pigment slurry. To this pigment slurry, 3.0 parts by mass of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) and a styrene-butadiene-based core-shell structure polymer compound <Tg1: −10 ° C., Tg2: + 28 ° C.> (trade name) : S2524, manufactured by JSR) 12 parts by mass were added and stirred, and water was further added to prepare a coating solution having a solid content concentration of 60%.

[Formation of coating layer]
The obtained coating liquid is coated on both sides of the base paper using a blade coater so that the dry coating mass per side is 11 g / m ² , dried, and composed of a metal roll and an elastic roll. The surface of the coating layer is surface-treated so that the glossiness at an incident / light-receiving angle of 75 degrees according to JIS Z8741 is 70%, and a surface substrate having a basis weight of 105 g / m ² is obtained. Obtained.

[Manufacture of pressure-sensitive adhesive sheet]
A re-peeling surface coating material having the following composition was applied to one side of the surface base material with a Mayer bar at 8 g / m ² (solid content) and dried with a hot air dryer at a temperature of 120 ° C. for 1 minute. A pressure-bonding sheet was produced. Subsequently, the same coating material was applied in the same manner as described above to the opposite surface of the surface base material to which the re-peeling surface coating material was applied, thereby preparing the pressure-sensitive adhesive sheet of the present invention.

<Manufacture of resin with minimum film-forming temperature of 90 ° C or higher>
Using a styrene-maleic anhydride copolymer as a protective colloid, 70% by mass of styrene and 30% by mass of butyl acrylate are mixed and polymerized by the monomer oil droplet dropping method, and the minimum film forming temperature at a solid content concentration of 50%. A styrene-acrylic resin emulsion at 100 ° C. was obtained.
<Re-peeling surface coating composition>
Acrylic modified natural rubber adhesive (trade name: Flutite FB-06-OJB, manufactured by Mitsui & Co. Solvent Coating Co., Ltd.) 38 parts by mass, styrene-butadiene copolymer binder (trade name: 0696, glass transition point -12 ° C, Styrene-acrylic resin having a mass fraction of 100 ° C., manufactured by JSR, 2 parts by mass of a gel fraction with respect to toluene (80% by mass), partially saponified polyvinyl alcohol (trade name: PVA235, manufactured by Kuraray Co., Ltd.) 5 parts by mass, silica (trade name: Mizukasil P-526, manufactured by Mizusawa Chemical Co., Ltd.) 14.2 parts by mass, kaolin (trade name: HG-90, manufactured by JM HUBER) 7.5 parts by mass, starch 20 parts by mass of particles (trade name: beach snow, manufactured by Samejima Starch Co., Ltd.), 8 parts by mass of starch particles (trade name: AS-225, manufactured by Chiba Milling Co., Ltd.), dispersant (trade name: Emargue A-60, manufactured by Kao Corporation) 0.4 parts by mass, lubricant (trade name: DEF-727K, manufactured by Nissin Chemical Laboratory) 3 parts by mass, antifoaming agent (trade name: SN deformer 777, manufactured by San Nopco) 0 .3 parts by weight, 0.2 parts by weight of a wetting agent (trade name: Neocor SW-C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

(Example 2)
[Manufacture of base paper]
LBKP (CSF freeness 550 ml) in 100 parts by mass of pulp slurry, 0.3 parts by mass of polyacrylamide resin (trade name: PS194-7, manufactured by Arakawa Chemical Co., Ltd.) as a paper strength agent, and polyamide / epichlorohydrin as a wet strength agent -Based resin (trade name: WS570, manufactured by Nippon PMC) 0.3 parts by weight and 1 part by weight of a sulfuric acid band are added, and the mixture is diluted with white water to have a pH of 5.3 and a solid content concentration of 1.1%. The material was prepared. This stock is made into a paper web machine and made into paper, and the resulting wet paper is coated with a size press liquid containing oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) at a concentration of 6%. Was applied and dried so as to have a dry weight of 2 g / m ² . Subsequently, this was smoothed by a machine calendar so that the Beck smoothness was 50 seconds, and a base paper having a basis weight of 113 g / m ² was produced.

[Preparation of coating solution]
100 parts by weight of kaolin (trade name: Kao gloss, manufactured by Imeris), 0.2 parts by weight of sodium polyacrylate (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) as a dispersant are added, and a coreless disperser is used. A pigment slurry was prepared. To this pigment slurry, 3.0 parts by mass of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene-based core-shell structure polymer compound <Tg1: −10 ° C., Tg2: + 28 ° C.> (trade name) : S2524, manufactured by JSR) 12 parts by mass were added and stirred, and water was further added to prepare a coating solution having a solid content concentration of 60%.

[Formation of coating layer]
The obtained coating liquid was applied to both sides of the base paper using a blade coater so that the dry mass per side was 11 g / m ² and passed through a pressure nip composed of a metal roll and an elastic roll. The surface base material with a basis weight of 135 g / m ² was obtained by adjusting the gloss of the coating layer surface so that the glossiness at an incident / light receiving angle of 75 degrees based on JIS Z8741 was 70%.

[Manufacture of pressure-sensitive adhesive sheet]
A re-peeling surface coating material having the following composition was applied to one side of the surface base material with a Mayer bar at 8 g / m ² (solid content) and dried with a hot air dryer at a temperature of 120 ° C. for 1 minute. A pressure-bonding sheet was produced.

<Re-peeling surface coating composition>
39 parts by mass of ethylene-vinyl acetate copolymer / acrylic ester copolymer composite resin adhesive (trade name: Ricabond AP120-7, manufactured by Chuo Rika Kogyo Co., Ltd.), styrene-butadiene copolymer binder (trade name: 0696) 2 parts by mass, glass transition point -12 ° C, manufactured by JSR, gel fraction 80% by mass with respect to toluene, 6 parts by mass of partially saponified polyvinyl alcohol (trade name: PVA235, manufactured by Kuraray), minimum film-forming temperature 100 ° C 6 parts by mass of styrene-acrylic resin, 28 parts by mass of silica (trade name: Mizukasil P-526, manufactured by Mizusawa Chemical Co., Ltd.), 5 parts by mass of silica (trade name: Mizukasil P-603, manufactured by Mizusawa Chemical Co., Ltd.), Starch particles (trade name: AS-225, manufactured by Chiba Flour Mills) 8 parts by mass, dispersant (trade name: Emulgen A-60, manufactured by Kao Corporation) 0.4 parts by mass, lubricant ( Product name: DEF-727K, manufactured by Nissin Chemical Laboratory) 3 parts by mass, antifoaming agent (trade name: SN deformer 777, manufactured by San Nopco) 0.3 part by mass, wetting agent (trade name: Neocor SW-C, (Daiichi Kogyo Seiyaku Co., Ltd.) 0.2 parts by mass.

(Comparative Example 1)
[Manufacture of base paper]
Add 100 parts by mass of LBKP (CSF freeness 550 ml) to a pulp slurry of 1.5 parts by mass of rosin emulsion sizing agent, 0.5 parts by mass of cationized starch and 2 parts by mass of sulfuric acid band, and dilute the mixture with white water. A paper stock having a pH of 5.3 and a solid content concentration of 1.1% was prepared. This stock is made into a paper web machine and made into paper, and the resulting wet paper is coated with a size press liquid containing oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) at a concentration of 6%. Was applied and dried such that the dry weight was 0.5 g / m ² . Subsequently, this was smoothed by a machine calendar so that the Beck smoothness was 40 seconds, and a base paper having a basis weight of 113 g / m ² was produced.

[Preparation of coating solution]
10 parts by weight of structural kaolin (trade name: Astraplus, manufactured by Imeris), 90 parts by weight of heavy calcium carbonate (trade name: Hydrocurve 90, manufactured by Bihoku Powdered Industries), sodium polyacrylate (as a dispersant) (Product name: Aron A-9, manufactured by Toa Gosei Co., Ltd.) 0.2 parts by mass was added, and a pigment slurry was prepared using a Coreless disperser. In this pigment slurry, 3.0 parts by mass of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene single structure polymer compound <Tg: −10 ° C.> (trade name: G1176, manufactured by Asahi Kasei Co., Ltd.) ) 10 parts by mass was added and stirred, and further water was added to prepare a coating solution having a solid concentration of 60%.

[Formation of coating layer]
The obtained coating liquid was applied to both sides of the base paper using a blade coater so that the dry mass per side was 11 g / m ² and passed through a pressure nip composed of a metal roll and an elastic roll. The surface base material with a basis weight of 135 g / m ² was obtained by adjusting the gloss of the coating layer surface so that the glossiness at an incident / light receiving angle of 75 degrees based on JIS Z8741 was 70%.

[Manufacture of pressure-sensitive adhesive sheet]
A re-peeling surface coating material having the following composition was applied to one side of the surface base material with a Mayer bar at 8 g / m ² (solid content) and dried with a hot air dryer at a temperature of 120 ° C. for 1 minute. A pressure-bonding sheet was produced.

<Re-peeling surface coating composition>
Acrylic modified natural rubber-based adhesive (trade name: Flutite FB-06-OJB, manufactured by Mitsui & Co. Solvent Coating Co.) 43 parts by mass, styrene-butadiene copolymer binder (trade name: 0696, glass transition point -12 ° C, 2 parts by mass, gel fraction 80% by mass with respect to toluene, manufactured by JSR, 0.3 parts by mass of partially saponified polyvinyl alcohol (trade name: PVA235, manufactured by Kuraray Co., Ltd.), silica (trade name: Mizukacil P-526, Mizusawa Chemical) 14.2 parts by mass of Kogyo Co., Ltd., 7.5 parts by mass of kaolin (trade name: HG-90, manufactured by JM HUBER), 20 parts by mass of starch particles (trade name: Snow at the beach, manufactured by Takashima Starch Co., Ltd.) Parts, starch particles (trade name: AS-225, manufactured by Chiba Flour Mills) 8 parts by weight, dispersant (trade name: Emulgen A-60, manufactured by Kao Corporation) 0.4 parts by weight, lubricant (trade name: DEF) -727K, manufactured by Nissin Chemical Laboratory) 3 parts by mass, antifoaming agent (trade name: SN deformer 777, manufactured by San Nopco) 0.3 part by mass, wetting agent (trade name: Neocor SW-C, Daiichi Kogyo Seiyaku) 0.2 parts by mass)

<Evaluation method>
(1) Measurement of average particle diameter and particle size distribution of pigment: Measured using Cedygraph 5100; V3.07.

  (2) Measurement of aspect ratio of pigment and observation of shape: The aspect ratio was measured and the shape was observed by enlarging the image to 15,000 times with an electron microscope.

  (3) Measurement of glossiness of surface substrate: Glossiness was measured under the conditions of an incident angle and a light receiving angle of 75 degrees using GLOSS METER MODEL GM-26D manufactured by Murakami Color Research Laboratory.

  (4) Measurement of internal bond strength of base paper: JAPAN TAPPI Paper Pulp Test Method No. According to 54-93, an internal bond tester (model No. 2085-D, manufactured by Kumagai Riki Kogyo Co., Ltd.) was used for measurement.

  (5) Measurement of air permeability of surface base material: Measured with Oken type air permeability meter.

(6) Paper Blister Evaluation: Paper blister evaluation of the pressure sensitive adhesive sheet was performed using two indirect dry electrophotographic type IPSIO CX3000 manufactured by Ricoh under two environments of 28 ° C., 85% RH and 20 ° C., 65% RH. Carried out. The copy manuscript has a halftone dot area ratio of 100% for cyan, magenta, and yellow, and the images for single-sided printing and double-sided printing are placed at the same position on the front and back of the paper. Went. The fed sample was printed on one side immediately after opening the package, left for 1 minute, and then printed on both sides.
○: Paper blisters are not recognized at all Δ: Paper blisters are slightly generated, but there is no practical problem ×: Paper blisters are generated

(7) Toner blister evaluation: The sample of (6) was evaluated according to the following evaluation criteria.
○: No toner blister is observed Δ: Some toner blisters are generated, but there is no practical problem ×: Toner blisters are generated

(8) Adhesiveness of re-peeling surface: Using a dry sealer (model 6860, manufactured by Toppan Forms), the obtained tri-fold post card sample was cut into a size where the normal post card was connected to the tri-leaf, and then re-peeled. Z-folded so that the faces would face each other, adjusted for humidity for 24 hours under a temperature and humidity condition of 23 ° C. and 50%, and then passed through a press roll with a roll gap set to 240 μm to produce a confidential postcard. . The obtained confidential postcard was evaluated by T-type peeling to evaluate the adhesive strength.
○: Adhesive strength is sufficient and good Δ: Adhesive strength is slightly low, but at a level that is not problematic in practical use ×: Adhesive strength is low, causing peeling, and practically problematic level

(9) Removability of re-peeled surface: The confidential postcard prepared in (8) was re-peeled by T-type peeling, and the peeled state and the peeled surface state were evaluated.
○: Smooth re-peeling and good Δ: Adhesive strength is strong but practically no problem ×: Adhesive strength is too strong, causing substrate breakage and causing practical problems

(10) Comprehensive evaluation: Comprehensive evaluation as confidential postcard paper was performed.
◎: Excellent as a confidential postcard paper ○: Excellent as a confidential postcard paper △: There is a slight problem as a confidential postcard paper, but there is no problem in practical use ×: There is a problem as a confidential postcard paper, practical use It is a level that can not be done

  From Table 1, the pressure-sensitive adhesive sheets of the present invention of Examples 1 and 2 are free of paper blisters or toner blisters when full-color printing is performed using an indirect dry electrophotographic full-color printer. It became clear that it was excellent also in the property. On the other hand, in Comparative Example 1, a paper blister or a toner blister occurs because the base paper does not contain a wet paper strength enhancer and the adhesive layer does not contain a resin having a minimum film forming temperature of 90 ° C. or higher. However, it could not be used as a confidential postcard.

  According to the present invention, a pressure-sensitive adhesive sheet can be obtained which is suitable for full-color printers for indirect dry electrophotography, in particular, paper blisters and toner blisters, and at the same time satisfies the adhesiveness when used as confidential postcard paper.

Claims (3)

  It has an adhesive layer on at least one surface of the surface substrate, and the adhesive layer can be bonded by applying high pressure with the adhesive layers facing each other, and can be peeled off between the adhesive layers after bonding In the pressure-sensitive adhesive sheet, the surface substrate has a base paper and a coating layer formed on at least one surface thereof and containing a pigment and a binder resin as main components, and the surface of the coating layer Is glossiness of 50% or more, smoothness of 2,000 seconds or less, air permeability of the surface base material is 7,000 seconds or less, and the adhesive layer is made of acrylic modified natural rubber, methyl Methacrylate-modified natural rubber, acrylic ester copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer / acrylic ester copolymer composite resin, styrene-butadiene copolymer resin, Consists of at least one adhesive selected from rilonitrile-butadiene copolymer resin, vinyl chloride resin, and vinylidene chloride resin, a fine particle filler, an organic polymer compound, and a resin having a minimum film forming temperature of 90 ° C. or more. A pressure-sensitive adhesive sheet characterized by ^{2. The} pressure-sensitive adhesive sheet according to claim 1, wherein the density of the surface substrate is 1.10 g / cm ³ or less and the internal bond strength of the base paper is 0.20 kJ / m ² or more. Kaolin particles in which the pigment constituting the coating layer has an average particle diameter of 0.3 to 1.5 μm and satisfies the following formula (1): 5 ≦ L / W ≦ 50 (1)
[However, in formula (1), L represents the major axis of the kaolin particles, and W represents the minor axis of the kaolin particles],
And the binder resin constituting the coating layer is (A) a copolymer having a glass transition temperature of 10 to 60 ° C. and having a single structure, and (B) a synthetic polymer compound having a core-shell structure The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet is at least one selected from the group consisting of: