JP2006193721A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet satisfying fitness of an indirect and dry electron photographic type printer. <P>SOLUTION: The pressure-sensitive adhesive sheet has an adhesive layer on at least one face of a base surface material. The adhesive layers can be adhered by treating them with strong force in a state in which the adhesive layers are facing to each other and the adhesive layers are released between the adhesive layers after adhesion. In the pressure-sensitive adhesive layer, the base surface material comprises base paper and a coated layer comprising a pigment and a binder resin as main components on at least on one side of the same, the surface of the coated layer has predetermined luster and surface flatness and the base surface material has predetermined air permeability. The sheet is prepared by installing a drawing printed/a letter printed layer on the surface of the coated layer, subsequently coating an adhesive composition comprising a (meth)acryloyl group-containing radiation-curing component (A), a (meth)acrylic copolymer (B) having a predetermined weight average molecular weight and Tg and/or a photoinitiator (C) on the drawing printed/the letter printed layer and forming the adhesive layer by hardening with radiation to form the adhesive layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a sheet used for electrophotography, ink jet, and offset printing, and further comprises a tri-fold or an adhesive layer on which a printing / printing layer and an adhesive layer are sequentially provided on the coating layer. The present invention relates to a pressure-sensitive adhesive sheet used for various postcard systems such as a folded paper postcard.

  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 such a friendly postcard base sheet has no adhesiveness at room temperature and normal pressure, and it is applied at a rate of about 1.1 to 50 kg / cm with the adhesive layers facing each other. Pressure-sensitive adhesive sheet having an adhesive layer that exhibits adhesiveness by heat treatment and / or heat treatment at 50 to 150 ° C. and can be re-peeled after bonding (hereinafter, a typical example of a confidential postcard) Paper).

  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, printers of various systems (electrophotography, ink jet) are becoming more colored, faster, and higher in image quality. In particular, in the field of on-demand publications, it is relatively easy to handle variable information from a small number of copies or a single copy unit. Especially, the variable information section (individual addresses, items preferred by customers) Information, invoice fees, etc.), the publications that have been produced by printing methods so far have been prominently produced by printers of various methods (electrophotographic method, ink jet method), and high glossiness for this application. The application of coated paper with

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, but there are cases in which this coated paper is applied to printers of various systems (electrophotographic system, ink jet system) to increase the sharpness of images. It is increasing. Therefore, a fixed information printing / printing layer by a color printer or offset printing on the coated paper, and variable information on the back surface by a color printer, an adhesive layer is sequentially provided on the printing / printing layer, and the fixed information printing / printing layer. By using the pressure-sensitive adhesive sheet, it is possible to perform printing of standard items and printing of personal information in one step, which is considered to be economically advantageous.

  However, when such a coated paper having a high white paper gloss 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 the water vapor is discharged out of the paper and is not smoothly discharged for some reason, the water vapor rapidly expands inside the paper layer to generate local blisters (hereinafter referred to as paper blister). .

  In addition, when the high-pressure steam generated from the paper blister is to be discharged to the outside of the paper through the gap inside the coating layer, if there is a toner image on the steam discharge path, it breaks through the toner image portion. In some cases, fine blisters or through-holes are generated in the coated paper to lower the quality (hereinafter referred to as toner blister). This toner blister becomes a serious defect of the image. Since the coated paper has a coating layer as described above, a sufficient water vapor discharge path is not ensured. Furthermore, if there is a toner image, paper blisters and toner blisters are likely to occur. In particular, in the case of coated paper having a high glossiness, calendering is required to increase glossiness, and the coating layer density is increased, 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 for this is that the toner adheres to the surface of the coating layer during single-sided printing, so that the water vapor generated during double-sided printing is less likely to be discharged than during single-sided printing. Even if it is a conventional coated paper for printing or electrophotographic coated paper with high white paper glossiness, blistering occurs during double-sided printing even if the blistering during single-sided printing is slight or does not occur End up.

  On the other hand, when applied to inkjet printers (especially line head high-speed printers equipped with drying equipment), especially for coated papers with high glossiness, calendering is required to increase gloss, Since the layer density is increased, the ink absorptivity of the coating layer is remarkably reduced, which causes bleeding and smearing of the printed portion.

  Also, when applied to offset printing, if the coating layer has good air permeability as described above, piling occurs due to ink tack, and blanket contamination is likely to occur.

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 4000 seconds or less (Japanese Patent Laid-Open No. 62-198876). Gazette (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 adjust the air permeability to 4000 seconds or less. A method (JP-A-5-241366 (Patent Document 3)) has 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. .

  However, these electrophotographic coated papers are less susceptible to paper blisters and toner blisters during single-sided printing, but cannot prevent paper blisters and toner blisters during double-sided printing. The reason is that during one-sided printing, it becomes difficult to discharge water vapor from the toner image surface, but since water vapor is discharged from the opposite surface, blisters are unlikely to occur. This is probably because the water vapor is not discharged smoothly due to the air permeability of these electrophotographic coated papers.

  Further, by using an acrylic UV curable varnish composition as an adhesive, a releasable adhesive processed paper (Japanese Patent Application Laid-Open No. 11-349854 (Patent Document 4) excellent in glossing effect on the printed surface and removable adhesiveness. )) Is proposed, but there is no disclosure or suggestion of paper blisters or toner blisters when pressure sensitive adhesive sheets with coating layers are used in electrophotographic color copiers or color printers. is the current situation.

Japanese Patent Laid-Open No. 7-276858 (2nd page) JP-A 62-198876 (Claim 1) JP-A-5-241366 (Claim 1) JP-A-11-349854 (Claims 1 to 4)

  The object of the present invention is to effectively suppress the occurrence of paper blisters and toner blisters in electrophotography, ink absorbency in inkjet, and blanket stains in offset printing, which are suitable for each type of printer and offset printing. It is to provide a pressure-sensitive adhesive sheet.

  As a result of diligent research to solve the above problems, the present inventors have conducted indirect dry electron on a surface substrate provided with a coating layer having a specific range of glossiness, smoothness, and air permeability. A pressure-sensitive adhesive sheet that effectively suppresses the generation of paper blisters and toner blisters by providing a photographic / printing layer using a photographic method, and further providing a radiation-curable acrylic resin layer having a specific composition, molecular weight, and glass transition temperature. It was found that can be obtained.

  The present invention provides a specific adhesive layer when printing / printing on a specific substrate sheet by an electrophotographic method, an inkjet method and an offset method, thereby generating paper blisters and toner blisters, The present invention provides a pressure-sensitive adhesive sheet that does not cause blanket stains in offset printing, 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 and a smoothness of 2,000 seconds or less, the air permeability of the surface base material is 7,000 seconds or less, and printing / printing on the surface of the coating layer After providing the layer, at least one radiation curable component (A) selected from a radiation curable monomer having a (meth) acryloyl group and an oligomer having a (meth) acryloyl group, a weight average molecular weight of 10, 000-100,000, moth It comprises a (meth) acrylic copolymer (B) having a transition temperature of −60 to 20 ° C. and / or a photopolymerization initiator (C), and is a radiation curable component (A) or (meth) acrylic. An adhesive composition in which the copolymer (B) and / or the photopolymerization initiator (C) are compatible with each other is coated on the printing / printing layer and cured with radiation to form the adhesive layer. A pressure-sensitive adhesive sheet characterized by

[2] The pressure-sensitive adhesive sheet according to [1], wherein the adhesive layer is transparent.

[3] Pressure sensitivity of [1] or [2] wherein the blending ratio of the (meth) acrylic copolymer (B) is 5 to 80 parts by mass with respect to 100 parts by mass in total of the radiation curable component (A). Adhesive sheet.

[4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], 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.

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

  The pressure-sensitive adhesive sheet of the present invention is suitable for each type of printer and offset printing, especially the occurrence of paper blisters and toner blisters in electrophotography, ink absorbency in inkjet, and the occurrence of blanket stains in offset printing. And is well suited for applications such as confidential postcard paper.

  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. Can be bonded by applying pressure treatment to about 10-50 kg / cm / or pressure of 1.1-10 kg / cm and heat treatment of 50-150 ° C., and the bonding surface is It has an adhesive layer that can be peeled by hand (this surface is also referred to as a re-peeling surface), but once peeled, it has the property that it does not adhere even if the adhesive layers are stacked and pressed 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).

  The pressure-sensitive adhesive sheet of the present invention shows no adhesiveness at normal temperature and normal pressure on both the re-peeling surface and the permanent adhesive surface, and is about 1.1 to 50 kg / cm and / or 50 to 150 ° C. with a sealer or the like. Adhesion is achieved by laminating and pressure bonding by heating to a certain degree, and such an adhesive layer adjusts the adhesive force by the adhesive composition, molecular weight, glass transition temperature, curing rate, and the like. For example, after providing information that requires secrecy on the coating layer that becomes the re-peeling surface, an adhesive is provided, and the sheet is folded so that the information is hidden, or another sheet is superimposed, and the re-peelability By applying pressure and / or heat treatment so that the adhesive layers face each other, they are 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 and the air permeability of the coated paper is 7000 seconds or less, the coating layer has printability and printability and is coated. It has been found that the adhesion between the layer and the printing / printing 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 (1):
5 ≦ L / W ≦ 50 (1)
[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.

  In the present invention, in the coating layer, (A) a single-structure copolymer having a glass transition temperature of 10 to 60 ° C. and / or (B) a synthetic polymer compound having a core-shell structure (hereinafter, When a binder resin containing “core-shell structure polymer compound”) was blended, it was confirmed that the adhesion between the base paper and the coating layer and between the coating layer and the printing / printing layer was good. In the present invention, the core-shell structure polymer compound (B) is a fine ball-shaped core portion composed of a single polymer or copolymer, and surrounds the core portion, and is a single polymer or copolymer. It is a copolymer comprised by the shell part which consists of. The single structure copolymer (A) 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., used as a binder resin is, for example, a styrene-butadiene copolymer. , 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 (2) and (3):
Tg1 <Tg2 (2)
−10 ° C. <Tg2 <100 ° C. (3)
[In the formulas (2) and (3), 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 part is higher than the glass transition temperature Tg1 of the core part, and the glass transition temperature of the shell part is higher than −10 ° C. and within a range of less 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. The polymer compound core part in the coating film is easily deformed with respect to the external pressure, and when the external pressure is removed, it returns to the original shape and exhibits high cushioning properties. Therefore, the coating layer and the print / print layer are brought into close contact with each other by pressing in the printer, and exhibit good toner adhesion and toner transferability. 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. If this temperature difference is less than 5 ° C., the cushioning property of the coating layer becomes insufficient, and the toner adhesion and toner transfer property 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 obtained coating layer at -20 to 80 ° C 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 the 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 size of the pigment having an aspect ratio in the range of 5 to 50 is smaller than 0.3 μm, the resulting coating layer tends to have high gloss, but the air permeability may be significantly reduced. On the other hand, when the average particle diameter is larger than 1.5 μm, it is difficult to obtain a high gloss on the resulting coating layer, and the desired glossiness may not 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 pulps, such as ECF pulp and TCF pulp, as a pulp used for a 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, when making the base paper, in addition to pulp fibers and fillers, various anionic, nonionic, cationic, or other conventionally used materials may be used in the stock, as long as the desired effects of the present invention are not impaired. Various papermaking internal additives such as amphoteric yield improver, drainage improver, paper strength enhancer, wet paper strength enhancer and internal additive sizing agent 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.

  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 blending ratio is less than 2 parts by mass, the coating film strength of the coating layer becomes insufficient, and the coating layer peels off and accumulates on the drum when the printer is fed, which may cause damage to the transfer drum. On the other hand, if it exceeds 25 parts by mass, the air permeability of the coating layer is remarkably lowered, and the prevention of paper blisters and toner blisters 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 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 acceptability of the obtained coating layer may be insufficient. is there. On the other hand, if it exceeds 20 g / m ² , the operability such as poor drying at the time of coating is lowered, 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 printed on the coating layer by, for example, full-color printing and printing of standard information and variable information using an indirect dry electrophotographic printer (IPSIO CX3000) manufactured by Ricoh, and further an adhesive. This adhesive layer is formed from an adhesive composition that is excellent in compatibility with the radiation curable monomer and oligomer having a (meth) acryloyl group, and has the inherent gloss and resistance to adhesive. Able to give adhesion and re-peelability by pressurization and / or heating without deteriorating blocking property and water resistance, without impairing the curing properties of the adhesive, and exhibiting stable re-peelability It is.

  The adhesive composition used for the pressure-sensitive adhesive sheet of the present invention comprises at least one radiation curable component (A) selected from radiation curable monomers and oligomers having a (meth) acryloyl group, and a weight average. The radiation curable component comprising a (meth) acrylic copolymer (B) and / or a photopolymerization initiator (C) having a molecular weight of 10,000 to 100,000 and a glass transition temperature of −60 to + 20 ° C. The (A), (meth) acrylic copolymer (B) and / or photopolymerization initiator (C) are compatible with each other. In the adhesive composition, it is preferable that the component (A), the component (B) and / or the component (C) are not only mutually compatible, but also are in a transparent solution state as a whole. The blending ratio of the (meth) acrylic copolymer (B) is preferably 5 to 80 parts by mass with respect to a total of 100 parts by mass of the radiation curable component (A).

<Radiation curable component (A)>
Examples of radiation curable monomers having a (meth) acryloyl group include alcohols such as ethylene glycol, dipropylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, trimethylolpropane, and pentaerythritol ( Examples include those obtained by esterifying (meth) acrylic acid, those obtained by esterifying allyl alcohol to phthalic acid, maleic acid, isocyanuric acid, or the like, or those obtained by esterifying glycidyl (meth) acrylate.

  Examples of radiation curable oligomers having a (meth) acryloyl group include monofunctional, bifunctional and polyfunctional urethane acrylate oligomers, polyester acrylate oligomers, epoxy acrylate oligomers, polyether acrylate oligomers, and silicone acrylate oligomers. An oligomer etc. are mentioned.

<(Meth) acrylic copolymer (B)>
The (meth) acrylic copolymer (B) is obtained by polymerizing a monomer component composed of an acrylic acid alkyl ester or a methacrylic acid alkyl ester using an organic solvent as a polymerization solvent.

  Examples of the acrylic acid alkyl ester or methacrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, n-decyl (meth) acrylate and glycol di (meth) acrylate, such as ethylene glycol di (meth) acrylate, Examples include butylene glycol di (meth) acrylate and 1,6-hexanediol di (meth) acrylate.

  When producing the (meth) acrylic copolymer (B), an ethylenically unsaturated monomer copolymerizable with the (meth) acrylic acid ester, for example, acrylic acid, methacrylic acid, itaconic acid, etc. Carboxylic acid-containing ethylenically unsaturated monomers and hydroxyalkyl (meth) acrylates such as 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and alkyl Amino (meth) acrylates such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate and glycidyl (meth) acrylate, (meth) acrylonitrile, (meth A) Ethylenically unsaturated monomer having a functional group as such Riruamido, vinyl acetate, vinyl propionate, styrene, can be copolymerized α- methyl styrene.

  As the polymerization solvent for the (meth) acrylic copolymer (B), various organic solvents can be used. For example, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i Alcohols such as butyl alcohol, cellosolve acetate, methyl cellosolve, ethyl cellosolve, n-butyl cellosolve, i-butyl cellosolve, cellosolves such as n-propyl cellosolve, propylene glycol-n-butyl ether, propylene glycol methyl ether, propylene glycol phenyl ether , Propylene glycol ethers such as dipropylene glycol methyl ether and propylene glycol methyl ether acetate, toluene, ethyl acetate, butyl acetate, acetone, methyl ethyl Ketones, aromatic (petroleum fractions) solvents, phthalate ester plasticizers, such as alkyl phosphates. In preparing the adhesive composition, the (meth) acrylic copolymer (B) solution dissolved in the solvent may be blended as it is, and in that case, the solvent is finally removed from the composition. May be.

  The (meth) acrylic copolymer (B) synthesized as described above can find particularly effective use in a specific molecular weight range and a specific glass transition temperature range.

  The weight average molecular weight of the (meth) acrylic copolymer (B) is required to be 10,000 to 100,000, preferably 20,000 to 50,000. If this component (B) has a weight average molecular weight of less than 10,000, the cohesive force is insufficient, the adhesive force is low, and appropriate removability and adhesiveness are not exhibited. Further, when the weight average molecular weight of this component (B) exceeds 100,000, the compatibility with the radiation curable component (A) decreases. In such a case, it is necessary to use a large amount of a diluent for blending the component (B) into the radiation curable component (A), which causes a decrease in the curing rate and surface gloss due to radiation, and a solvent. The problem of hygiene and fire-fighting law due to the deterioration of the work environment due to

  Next, the glass transition temperature of the (meth) acrylic copolymer (B) needs to be in the range of −60 to 20 ° C., preferably −50 to 10 ° C. When the glass transition temperature is lower than −60 ° C., this component (B) has a strong stickiness and does not have sufficient adhesive strength. Moreover, when this component (B) has a glass transition temperature higher than 20 degreeC, re-peelability may not be acquired.

  The glass transition temperature referred to in the present invention is, for example, a polymer chain in an amorphous region as described in Manabu Seneo, Kimio Kurita, Shoichiro Yano, Takashi Sawaguchi “Basic Polymer Science” (Kyoritsu Publishing Co., Ltd.) In the case of a copolymer, this is the glass transition temperature calculated by the Fox equation described on pages 131 to 132 of the same document. That is, the glass transition temperature of the copolymer is calculated by the following formula.

In the above formula, Tg is the glass transition temperature of the copolymer and is calculated in terms of absolute temperature. Tg ₁ , Tg ₂ ,..., Tgn are the glass transition temperatures of the respective homopolymers ₁ , ₂ ,..., _N of the components 1, 2,. Is calculated. W ₁ , W ₂ ,..., W _n are weight fractions of specific monomers in the copolymer component.

  The above (meth) acrylic copolymer (B) has good compatibility with the radiation curable component (A), and an adhesive composition in which this component (B) is uniformly dissolved is obtained. Can do.

  The blending ratio of the (meth) acrylic copolymer (B) to the radiation curable component (A) is not particularly limited, but a particularly preferable range is 100 parts by mass in total of the radiation curable component (A). On the other hand, it is 5-80 mass parts. If the blending ratio is less than 5 parts by mass, the adhesive composition may not be provided with sufficient re-peelability or may have poor adhesion. Further, when this exceeds 80 parts by mass, the resulting adhesive composition has a strong stickiness and lowers the original gloss of the adhesive, the adhesiveness is too strong at the time of peeling, and paper breakage occurs. The blocking resistance of the coated paper may be inferior. In addition, the said mixture ratio (mass part) of this component (B) means the quantity of only a copolymer component, and does not contain the solvent etc. which were used for superposition | polymerization.

  Since the (meth) acrylic copolymer (B) of the present invention is uniformly mixed with other components in the composition to form a solution state, the coating surface has excellent gloss and is in a normal living environment. In the atmosphere, blocking resistance is given. As physical conditions at the time of bonding, the adhesive composition surfaces coated and cured on the paper surface are combined with each other, for example, a linear pressure of about 10 to 50 kg / cm, or about 0.1 to 10 kg / cm When a combination of pressurization by linear pressure and heating at a temperature of 50 to 150 ° C. is used, component (B) exudes to the surface to form an adhesive layer, and the releasability between the adhesive layer surfaces Adhesion becomes possible. The adhesive strength between the adhesive layer surfaces can be appropriately adjusted by selecting the physical conditions and changing the blending ratio of the component (B), glass transition temperature and average molecular weight. It is weaker than the adhesive strength, and it can give moderate peelability without damaging the surface at the time of peeling.

<Photopolymerization initiator (C)>
The adhesive composition is blended with a photopolymerization initiator as required. For example, benzoin such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin butyl ether, 2-allyl benzoin, 2-chlorobenzoin, benzophenone Benzophenones such as p-methylbenzophenone and p-chlorobenzophenone, diethoxyacetophenone, hydroxyacetophenone (1-hydroxy-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, etc.), α -Acetophenone type such as aminoacetophenone, thioxanthone type such as 2-methylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, azo type such as azobisisobutyronitrile, anthraquino , 2-chloro anthraquinone, quinone and the like combinations thereof, such as phenanthrene and the like. Examples of the photopolymerization initiator (C) include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 2-dimethylaminoethylbenzoate, N, N-dimethylaminoethyl methacrylate-N-methyldiethanolamine, and the like. By adding a sensitizer, the sensitivity of ultraviolet rays can be increased.

  As described above, the adhesive composition according to the present invention is a radiation comprising a radiation curable monomer or oligomer having a (meth) acryloyl group that can be cured by radiation after being applied to the surface of paper with various coating machines. A curable component (A), a (meth) acrylic copolymer (B) and a photopolymerization initiator (C) that generates radicals upon irradiation are blended as necessary, and the components (A) and (B ) And component (C) are mutually compatible. If necessary, additives such as a sensitizer, a leveling agent, a colorant, a wax, an antifoaming agent, a release agent, an antiwear agent, and an organic solvent are added to the adhesive composition, and the required physical properties are added. Can also be given. These additives are preferably dissolved uniformly in the composition from the viewpoint of ensuring superior surface gloss, coating stability, etc., but some may be effective in a dispersed state. The turbidity or separation of the adhesive composition of the present invention due to the dispersion of the agent is different from the uniform compatibility of the present invention and can be used without affecting the physical properties.

When the adhesive layer is applied to the surface of the surface substrate, the coating method is not particularly limited, but a roll coater, bar coater, gravure coater, die coater, curtain coater, flexo coater, sheet-fed printing inline varnish. A coater or the like is used. Among them, a gravure coater, a flexo coater, a sheet-fed printing inline varnish coater and the like are preferable. The coating amount is in the range of 2 to 30 g / m ^2, preferably in the range of 3 to 15 g / m ^2.

  The pressure-sensitive adhesive sheet coated with the adhesive layer in this manner is a layer that is appropriately cured by irradiating radiation such as ultraviolet rays, electron beams, α rays, β rays, and γ rays. .

In the winding after the adhesive layer coating, 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 printing 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 weight and sulfuric acid band 1 part by weight 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 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 80 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) 10 parts by mass was 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 coating mass per side was 12.5 g / m ² , dried, and then with a metal roll and an elastic roll. The paper is passed through the configured pressure nip, and the surface of the coating layer is surface-treated so that the glossiness at an incident / light-receiving angle of 75 degrees based on JIS Z8741 is 70%, and a surface basis having a basis weight of 105 g / m ² I got the material. Furthermore, fixed information and variable information were printed and printed on the surface base material using a printer and an offset printer of each method.

[Manufacture of pressure-sensitive adhesive sheet]
On one side of the surface base material, a removable adhesive having the following composition was applied with a gravure coater at 8 g / m ² (solid content), and a conveyor type ultraviolet irradiation machine (high pressure mercury lamp 80 W / cm ² ), Ultraviolet irradiation was performed at a conveyor speed at which the integrated light amount was 60 mJ / cm ² to produce a pressure-sensitive adhesive sheet. Subsequently, the same releasable adhesive was applied to the opposite surface of the surface base material coated with the releasable adhesive in the same manner as described above to prepare the pressure-sensitive adhesive sheet of the present invention.

<Removable adhesive>
[Production of intermediate product]
Epoxy acrylate oligomer (trade name: Lipoxy SP-1509, Showa Polymer Co., Ltd.) 40 parts by mass, tripropylene glycol diacrylate 40 parts by mass, dipentaerythritol hexaacrylate (trade name: Aronix M-400, manufactured by Toagosei Co., Ltd.) 20 parts by mass, 5 parts by mass of hydroxycyclohexyl phenyl ketone (trade name: Irgacure 184, manufactured by Ciba-Geigy) and 0.1 part by mass of methoquinone were mixed and stirred to obtain an intermediate product.

[Production of removable adhesive]
A 500 ml reaction vessel equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, and a reflux condenser is charged with 50 parts by weight of butyl acrylate, 50 parts by weight of 2-ethylhexyl methacrylate, 100 parts by weight of ethyl cellosolve as a polymerization solvent, and azobisiso as a polymerization initiator. Add 6 parts by mass of butyronitrile, polymerize at 80 ° C. for 6 hours in a nitrogen gas stream, and contain 50% by mass of a transparent and viscous resin component ((meth) acrylic copolymer used in the present invention). A resin solution was obtained. The obtained resin had a glass transition temperature of −35 ° C. and a weight average molecular weight of 11,000.
Next, the resin solution was added in an amount of 12 parts by mass (of which 105.1 parts by mass of the intermediate product (100 parts by mass of the UV-curable monomer and oligomer having a (meth) acryloyl group)). The solid content was 6 parts by mass) to obtain an ultraviolet curable adhesive composition in a transparent solution state.

(Example 2)
[Manufacture of base paper]
85 parts by mass of LBKP (CSF freeness 550 ml), 15 parts by mass of NBKP (CSF freeness 550 ml), and 0.3 parts by mass of a polyacrylamide resin (trade name: PS194-7, manufactured by Arakawa Chemical Co., Ltd.) as a paper strength agent As a wet paper strength enhancer, 0.3 part by mass of a polyamide / epichlorohydrin resin (trade name: WS570, manufactured by Japan PMC) and 1 part by mass of a sulfuric acid band were added, and the mixture was diluted with white water to pH 5.3. A paper stock having 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 so that the dry mass was 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 110 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) 15 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 resulting coating liquid was applied to both sides of the base paper using a blade coater so that the dry mass per side was 12.5 g / m ^2, and a pressure nip composed of a metal roll and an elastic roll The surface base material having a basis weight of 135 g / m ² was obtained by adjusting the glossiness at an incident / light-receiving angle of 75 ° based on JIS Z8741 on the surface of the coating layer to 70%. Furthermore, fixed information and variable information were printed and printed on the surface base material using an indirect dry electrophotographic full color printer (IPSIO CX3000) manufactured by Ricoh.

[Manufacture of pressure-sensitive adhesive sheet]
On one side of the surface base material, a removable adhesive having the following composition was applied with a gravure coater at 8 g / m ² (solid content), and a conveyor type ultraviolet irradiation machine (high pressure mercury lamp 80 W / cm ² ), Ultraviolet irradiation was performed at a conveyor speed at which the integrated light amount was 60 mJ / cm ² to produce a pressure-sensitive adhesive sheet.

<Removable adhesive>
[Production of intermediate product]
Urethane acrylate oligomer (trade name: KAYARADUX-2031, manufactured by Nippon Kayaku Co., Ltd.) 10 parts by weight, tripropylene glycol diacrylate 50 parts by weight, trimethylolpropane triacrylate (trade name: Aronix M-309, manufactured by Toagosei Co., Ltd.) 40 Part by mass, 5 parts by mass of hydroxycyclohexyl phenyl ketone (trade name: Irgacure 184, manufactured by Ciba-Geigy) and 0.1 part by mass of methoquinone were mixed and stirred to obtain an intermediate product.

[Production of removable adhesive]
In a 500 ml reaction vessel equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, and a reflux condenser, 10 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of 2-hydroxyethyl acrylate, 50 parts by mass of butyl methacrylate, 10 parts by mass of acrylic acid, polymerization 100 parts by mass of isopropyl alcohol as a solvent and 1 part by mass of azobisisobutyronitrile as a polymerization initiator are added and polymerized at 82 ° C. under reflux of isopropyl alcohol in a nitrogen gas stream for 6 hours to obtain a transparent and viscous resin component ( A resin solution containing 50% by mass of (meth) acrylic copolymer used in the present invention was obtained. The obtained resin had a glass transition temperature of 0 ° C. and a weight average molecular weight of 50,000.
Next, the resin solution was added in an amount of 60 parts by mass with respect to 105.1 parts by mass of the intermediate product (of which 100 parts by mass of the ultraviolet curable monomer and oligomer having a (meth) acryloyl group). The solid content was 30 parts by mass) to obtain a UV-curable adhesive composition in a transparent solution state.

(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 80 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 solution was coated on both sides of the base paper using a blade coater so that the dry mass per side was 12 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%. Furthermore, fixed information and variable information were printed and printed on the surface base material using an indirect dry electrophotographic full color printer (IPSIO CX3000) manufactured by Ricoh.

[Manufacture of pressure-sensitive adhesive sheet]
On one side of the surface base material, a removable adhesive having the following composition was applied with a gravure coater at 8 g / m ² (solid content), and a conveyor type ultraviolet irradiation machine (high pressure mercury lamp 80 W / cm ² ), Ultraviolet irradiation was performed at a conveyor speed at which the integrated light amount was 60 mJ / cm ² to produce a pressure-sensitive adhesive sheet.

<Removable adhesive>
Only the intermediate product used in Example 1 was used as a releasable adhesive.

(Comparative Example 2)
A pressure-sensitive adhesive sheet was produced in the same manner as in Comparative Example 1 except that only the resin component obtained in Example 1 ((meth) acrylic copolymer used in the present invention) was used as a removable adhesive.

<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 coated paper: Measured with Oken type air permeability measuring device.

(6) Paper Blister Evaluation: Paper blister evaluation of pressure-sensitive adhesive sheets was conducted in two environments of 28 ° C., 85% RH and 23 ° C., 50% RH using an indirect dry electrophotographic type IPSIO CX3000 manufactured by Ricoh. did. 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) Inkjet ink absorptivity (IJ absorptivity) evaluation: Monochrome printing is performed with a commercially available inkjet printer PM-800C (Epson), and a high quality paper is applied to the printing portion immediately after that to evaluate ink transfer.
○: Ink does not transfer to high-quality paper at all Δ: Ink moves slightly to high-quality paper, but there is no practical problem ×: A lot of ink has transferred to high-quality paper

(9) Offset printing evaluation: Printing was performed under the following conditions, and offset printing evaluation was performed based on the stain of the blanket after printing.
Printer: Miyakoshi MVF18B type UV ink T & K TOKA RMC
Environment: 23 ° C-50% RH
Printing speed: 100 to 120 m / min
Printing length: 6000m
Drying conditions: UV drying Irradiation amount 160 w / cm

(Blanket dirt evaluation)
The stain on the blanket after printing 6000 m was evaluated according to the following evaluation criteria.
○: Dirt is not seen. The quality is also excellent.
Δ: Some dirt is observed. There is no problem in practical use.
X: Dirt is frequently observed. There are practical problems.

(10) Adhesiveness of re-peeling surface: Using a dry sealer (model 6860, manufactured by Toppan Forms), the obtained tri-fold postcard sample is cut into an appropriate size so that the re-peeling surfaces face each other. Z-folded and conditioned for 24 hours under the temperature and humidity conditions of 23 ° C. and 50% RH, and then passed through a press roll with a roll gap set to 240 μm and pressed to prepare a confidential postcard. The obtained confidential postcard was cut into a width of 25 mm, and the adhesive strength was subjected to sensory evaluation by T-type peeling (peeling speed 300 mm / min).
○: 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

(11) Re-peelability of re-peeled surface: The confidential postcard prepared in (10) was re-peeled by T-type peeling, and the peeled state and the peeled surface state were evaluated.
○: Removable smoothly and good with no unevenness or gloss unevenness on the peeled surface. Δ: Strong adhesion, does not peel smoothly, and unevenness or uneven glossiness is observed on the peeled surface, but there is no practical problem. X: Adhesive strength is too strong, it does not peel off smoothly, unevenness of the peeled surface and uneven gloss are generated, and the substrate is destroyed, causing a practical problem.

(12) 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 paper blisters when full-color printing is performed using an indirect dry electrophotographic full-color printer, and even when printing is performed by inkjet printing or offset printing. In addition, it was revealed that toner blisters were not generated, and adhesion and removability were excellent. On the other hand, in Comparative Example 1, since the wet paper strength enhancer is not blended in the base paper and the (meth) acrylic copolymer is not blended in the adhesive layer, the occurrence of paper blisters and toner blisters occurs. In many cases, the adhesive strength was very low.
In Comparative Example 2, since the wet paper strength enhancer is not blended in the base paper and the radiation curable component is not blended in the adhesive layer, there are many occurrences of paper blisters and toner blisters, and the adhesive strength is very high. The re-peelability was poor.

  The pressure-sensitive adhesive sheet according to the present invention is suitable for indirect dry electrophotographic full-color printers, in particular, paper blisters and toner blisters are not generated, and at the same time satisfies the adhesiveness when used as confidential postcard paper.

Claims (5)

  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 Has a glossiness of 50% or more, a smoothness of 2,000 seconds or less, an air permeability of the surface base material of 7,000 seconds or less, and a print / print layer provided on the surface of the coating layer. Then, at least one radiation curable component (A) selected from a radiation curable monomer having a (meth) acryloyl group and an oligomer having a (meth) acryloyl group, and a weight average molecular weight of 10,000 to 100 1,000, glass rolling It comprises a (meth) acrylic copolymer (B) having a temperature of −60 to 20 ° C. and / or a photopolymerization initiator (C), and is a radiation curable component (A) or (meth) acrylic copolymer. The adhesive composition in which the blend (B) and / or the photopolymerization initiator (C) are compatible with each other was applied on the print / print layer and cured with radiation to form the adhesive layer. A pressure-sensitive adhesive sheet.   2. The pressure-sensitive adhesive sheet according to claim 1, wherein the adhesive layer is transparent.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the blending ratio of the (meth) acrylic copolymer (B) is 5 to 80 parts by mass with respect to 100 parts by mass of the radiation curable component (A). The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, 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 has an average particle size 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 at least one selected from (D) a copolymer having a glass transition temperature of 10 to 60 ° C. and having a single structure, and (E) a synthetic polymer compound having a core-shell structure. The pressure-sensitive adhesive sheet according to claim 1, which is a seed.