JP2006028706A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensitive adhesive sheet excellent in printing aptitude for various printers, having a high concealing property for printed personal information, also not only excellent in offset printing aptitude but also having a good balance with adhesive power and equipped with characteristics as a confidential postcard. <P>SOLUTION: This pressure sensitive adhesive sheet having the adhesive layer at least on one of the surfaces of a substrate sheet, capable of bonding the adhesive layers by firmly compressing them in the state of facing each other and peeling off between the adhesive layers after bonding is provided by containing 3-20 pts. mass titanium dioxide of which particle surfaces are covered by SiO<SB>2</SB>and/or Al<SB>2</SB>O<SB>3</SB>, as a filler constituting the substrate sheet based on 100 pts mass pulp, having the adhesive layer consisting of the adhesive, the fine particle filler and a binder resin as its constituting components, and having ≥90.0 % opacity of the pressure sensitive adhesive sheet measured in accordance with the JIS P-8149. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure-sensitive adhesive sheet used in various postcard systems such as tri-fold or bi-fold postcards.

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 JP-A-7-276858, the confidential postcard paper is printed with a fixed item as a postcard on the surface of the adhesive layer, and then the information desired to be kept secret such as address and personal information is printed on the same layer with a laser printer. It is printed and folded so that the adhesive layers face each other so that confidential information cannot be seen from the outside, and is pressed and 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.

  When recording information on the confidential postcard paper, a dot printer method, an electrophotographic method, an ink jet method, or the like is used. On the other hand, it is essential that the recorded information is not visible in the superimposed state. Therefore, in order to ensure this concealment property, it is known to perform concealment printing (background pattern printing) on the printed surface or the back surface of the information recording surface.

  In the case of performing the above-described concealing printing (background pattern printing), the number of steps increases, so that not only the cost increases but also the appearance is poor. In order to avoid this problem, it has been proposed to use recycled paper containing 20 to 100% of used paper in the base sheet (Patent Document 1, Patent Document 2), but fixing printing ink and toner. However, the use of waste paper is not so popular at present. Also, in the ordinary printing paper field, a large amount of filler has been added to the base sheet in order to improve concealment. However, if this technology is applied to confidential postcard paper as it is, the recipient can record information. When peeling to see the surface, there is a concern that the base sheet itself is torn. In order to prevent this, it is necessary to limit the blending amount of the filler. If the basis weight is increased in order to compensate for this, there is a possibility that the weight determined by the Postal Code may be exceeded.

Japanese Patent Laid-Open No. 11-161180 (Claim 1, second page (0007) to (0008) column) JP-A-2004-122451 (Claim 1, second page (0009) to (0010) column)

  The object of the present invention is not only excellent in printability of various printers, high concealment of printed personal information, and excellent in offset printability, but also has a good balance with adhesive strength and has characteristics as confidential postcard paper. It is to provide a pressure-sensitive adhesive sheet.

  As a result of diligent research to solve the above problems, the present inventors have formulated a specific amount of titanium dioxide pigment with a specific surface coating as a filler constituting the base sheet, and the adhesive layer has The present inventors have found that confidential postcard paper having excellent concealability can be efficiently produced by using an adhesive, a fine particle filler, a binder resin and the like as constituent components.

The present invention includes the following aspects.
(1) It has an adhesive layer on at least one surface of the base sheet, and the adhesive layer can be adhered by subjecting the adhesive layers to high pressure in a state where the adhesive layers are opposed to each other. In a pressure-sensitive adhesive sheet that can be peeled between adhesive layers, as a filler constituting the base sheet, titanium dioxide having a filler particle surface coated with SiO ₂ and / or Al ₂ O ₃ is used as 100 mass of pulp. 3 to 20 parts by mass with respect to parts, and the adhesive layer is composed of an adhesive, a fine particle filler, a binder resin, and the pressure sensitive adhesive sheet is measured according to JIS P-8149. A pressure-sensitive adhesive sheet having a transparency of 90.0% or more.
(2) The pressure-sensitive adhesive sheet according to (1), wherein the titanium dioxide has an average particle size of 0.1 to 0.5 μm.
(3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein 0.1 to 20 parts by mass of titanium dioxide is contained in the adhesive layer with respect to 100 parts by mass of the adhesive.

  The pressure-sensitive adhesive sheet of the present invention is excellent in various printer printability, has high concealment of printed personal information, and not only excellent in offset printability, but also has a good balance with adhesive force, such as confidential postcard paper. Very suitable for the application.

In the pressure-sensitive adhesive sheet of the present invention, the adhesive layer provided on at least one surface of the base material sheet does not exhibit adhesiveness at normal temperature and normal pressure before pressing, and the adhesive layers are opposed to each other. In this state, the adhesive layer can be bonded by applying a pressure treatment to about 500 kg / cm ² , and the bonding surface has an adhesive layer (this surface is also referred to as a re-peeling surface) that can be peeled by hand. The adhesive surfaces of the adhesive layers have the property that once the adhesive layers are peeled off, the adhesive layers are overlapped with each other and do not adhere even when pressed by hand.

  The pressure-sensitive adhesive sheet of the present invention includes (1) a configuration in which an adhesive layer having removability (hereinafter also referred to as a re-peeling surface) is formed only on one side of a base sheet, (2) a base sheet A configuration in which a releasable adhesive layer (removable surface) is formed on both sides of the substrate, (3) a releasable adhesive layer (removable surface) is provided on one side of the base sheet, and the other surface It includes a case where the layer structure is such as a structure in which a non-removable adhesive layer (permanently bonded surface) is formed.

Both the re-peeling surface and the permanent bonding surface of the pressure-sensitive adhesive sheet of the present invention do not show adhesiveness at normal temperature and normal pressure, and are about 500 kg / cm ² (300 kg / cm ^{2 to} 700 kg / cm ² ) with a dry sealer or the like. The adhesive layer is bonded by pressure lamination, and the adhesive force of such an adhesive layer is adjusted by the blending amount of the adhesive and the 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 performing the pressure treatment, a laminated sheet having information inside (for example, a confidential postcard, a lottery, etc.) can be obtained.

  The pressure-sensitive adhesive sheet of the present invention contains a specific amount of a titanium dioxide pigment with a specific surface coating as a filler constituting the base sheet, and the adhesive layer contains an adhesive, a fine particle filler, a binder resin, and the like. It is a constituent component.

The pressure-sensitive adhesive sheet of the present invention must have an opacity of 90.0% or more measured according to JIS P-8149. If the opacity is less than 90.0%, there is a risk that confidential information about the individual can be seen from the outside, which is not suitable as a confidential postcard paper. In order to achieve concealment as this confidential postcard paper, the base sheet used in the present invention is usually softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), ECF. Pulp for papermaking such as pulp, TCF pulp, etc., 300-600 ml C.I. S. F. Beaten into this, fillers such as titanium dioxide, clay, kaolin, calcium carbonate, paper strength enhancers such as urea resin, starch, polyvinyl alcohol, polyacrylamide, melamine resin, urea resin, dialdehyde starch, polyamide, polyamine, Add wet paper strength enhancers such as epichlorohydrin resin and polyethyleneimine resin, sizing agents such as rosin sizing agents, alkyl ketene dimer sizing agents, fluorescent whitening agents, colored dyes / pigments, fixing agents, etc. based on the conventional method using a known papermaking machine, such as a net paper machine or Fourdrinier paper machine, are produced by paper making in the usual basis weight 40~150g / m ^2, the particle surface as a filler SiO ₂ and Titanium dioxide coated with Al ₂ O ₃ is an essential material. Further, the crystal form of titanium dioxide used in the present invention is not particularly limited, but the rutile type is preferred because of excellent hiding power and coloring power. In addition, the compounding quantity of titanium dioxide is 3-20 mass parts with respect to 100 mass parts of pulp. By the way, if the amount of titanium dioxide is less than 3 parts by mass, the confidential postcard paper has poor concealment, and if it exceeds 20 parts by mass, the strength of the base sheet becomes too weak and peels off for viewing personal information. When it does, the problem that a base material sheet will tear arises.

  Moreover, the average particle diameter of titanium dioxide is 0.1-0.5 micrometer, Preferably it is 0.15-0.35 micrometer, More preferably, it is 0.2-0.3 micrometer. When the average particle diameter is less than 0.1 μm or more than 0.5 μm, the hiding power or whiteness of the coating film decreases, which is not preferable.

  The particle size distribution of the titanium dioxide used in the present invention is 7.0 in terms of mass percentage of coarse particles of 0.6 μm or more in the particle size distribution obtained by measuring natural sedimentation in an aqueous suspension by a specific gravity balance method. The content is preferably at most mass%, more preferably at most 6.0 mass%. The particle size distribution of titanium dioxide can be adjusted by pulverization and classification. However, if the coarse particles of 0.6 μm or more exceed 7.0% by mass, the suspension stability decreases, which is not preferable. The particle size distribution can be measured by, for example, an automatic particle size distribution measuring instrument “SA-2 type” manufactured by Shimadzu Corporation.

  The titanium dioxide particles used in the present invention are first coated with a silicon oxide or hydroxide at a high density to form a chemically stable surface coating layer. That is, an aqueous solution of a silicate such as sodium silicate is added to an aqueous suspension of titanium dioxide, and the coating is carried out by gradually lowering the pH to 40 or less at 40 to 100 ° C. over 20 to 360 minutes. More preferably, the coating is performed by gradually lowering the pH to 60 or less at 60 to 90 ° C. over 60 to 360 minutes.

According to the above, the surface of the titanium dioxide particles should be coated with silicon as SiO ₂ in an amount of 1.0 to 10.0% by mass with respect to titanium dioxide, more preferably 2.0 to 8.0% by mass. Let In the above, if the temperature is less than 40 ° C. or the coating time is less than 20 minutes, the dehydration condensation due to the siloxane bond becomes insufficient, so that a chemically stable and high-density surface coating layer can be obtained. First, it is suitable for the purpose of the present invention. Even if the temperature exceeds 100 ° C. or the coating time exceeds 360 minutes, the dehydration condensation described above hardly proceeds any more, so the conditions are meaningless and uneconomical. Therefore, the temperature and time are limited to the above ranges. In order to completely coat a predetermined amount of silicon oxide or hydroxide, it is desirable to lower the pH to 6 or less.

In order to obtain the concealability and whiteness aimed by the present invention, it is preferable that the surface coating of SiO ₂ is 1.0% by mass or more with respect to titanium dioxide. When the surface is coated in excess of 10.0% by mass as SiO ₂ , the titanium dioxide content is insufficient, and the hiding power or whiteness of the coating film is reduced. Therefore, the coating amount of silicon is preferably in the range of 1.0 to 10.0 wt% with respect to titanium dioxide as SiO _2.

  In the present invention, it is preferable that high-density coating is performed by further coating aluminum oxide or hydroxide on the silicon coating formed on the titanium dioxide particles by the treatment. Therefore, a solution of aluminum salt such as aluminum chloride, nitrate, sulfate or sodium aluminate is added to the titanium dioxide particle suspension coated with silicon, and the pH is adjusted with an acidic solution or a basic solution. Cover.

Examples of the acidic solution used in the present invention include hydrochloric acid, nitric acid, sulfuric acid and the like, and examples of the basic solution include sodium hydroxide and potassium hydroxide. By this method, an amount of 0.5 to 5.0% by mass with respect to titanium dioxide is coated as Al ₂ O ₃ . More preferably, an amount of 1.0 to 5.0% by mass is coated. If the precipitation amount is less than 0.5% by mass, the agglomeration property as a pigment powder cannot be suppressed, and if it exceeds 5.0% by mass, the titanium dioxide content is insufficient, so that the coating film is concealed. The above range is preferred because the strength or whiteness decreases.

The specific surface area of the pigment powder by the nitrogen adsorption BET method of titanium dioxide coated with SiO ₂ and / or Al ₂ O ₃ by the above method is in the range of 10 to 25 m ² / g.

The reason why titanium dioxide coated with SiO ₂ and / or Al ₂ O ₃ is used in the present invention is not only to improve the concealment property of personal information, but also to fix printing when printing personal information by an ink jet method. This is because the property and the printing water resistance are improved, and the elution of the cationic resin into the fountain solution during offset printing can be effectively prevented.

  It is preferable that the compounding quantity of the titanium dioxide used by this invention contains 0.1-20 mass parts of titanium dioxide with respect to 100 mass parts of adhesive agents.

  In the present invention, the adhesive layer is composed of an adhesive, a fine particle filler, a binder resin, and the like. The adhesive used for the pressure-sensitive adhesive sheet of the present invention may be any adhesive that can be used to develop the adhesive force between the adhesive layers. For example, natural rubber, modified natural rubber, styrene-butadiene rubber, acrylonitrile- Examples thereof include synthetic rubbers such as butadiene rubber, ethylene-vinyl acetate copolymer resins, acrylate copolymer resins, ethylene-vinyl acetate / acrylate ester composite resins, vinyl chloride resins, and vinylidene chloride resins.

  As an adhesive compounding quantity in the adhesive layer of a re-peeling surface, solid content mass is about 20-60 mass%. When the amount is less than 20% by mass, the strength of the adhesive layer is weakened. As an adhesive compounding quantity in the adhesive layer of a permanent surface, solid content mass is about 40-70 mass%. Incidentally, if it is less than 40% by mass, it exhibits removability, and if it exceeds 70% by mass, blocking tends to occur.

  It does not specifically limit as binder resin used for this invention, It is used in order to express the adhesive force of a base material sheet and an adhesive bond layer. For example, styrene-butadiene copolymer resin, styrene-butadiene-methyl methacrylate copolymer resin, ethylene-vinyl acetate copolymer resin, acrylate copolymer resin, polyvinyl alcohol, modified polyvinyl alcohol, etc. Partially saponified polyvinyl alcohol is preferred. Furthermore, acid-modified polyvinyl alcohol obtained by partially saponifying a copolymer of a vinyl ester and a monomer selected from olefinically unsaturated dicarboxylic acids and / or derivatives thereof is more preferable. An appropriate range of the saponification degree of the partially saponified polyvinyl alcohol is preferably 90 mol% or less. If the degree of saponification exceeds 90 mol%, the wet strength is reduced, and printing defects due to blanket piling, blanket stains, turn bar stains, etc. occur during offset printing. Also, the viscosity of the paint increases due to an increase in hydrogen bonding due to an increase in hydroxyl groups. The increase in the viscosity causes poor coating and slows down the coating efficiency when the coating material needs to be diluted, resulting in poor production efficiency. Moreover, 3000 or less is preferable as a suitable range of the polymerization degree of partially saponified polyvinyl alcohol. If the degree of polymerization exceeds 3000, the adhesive layer becomes too hard, so that the adhesive strength is lowered and the viscosity of the paint is also increased. More preferably, the degree of saponification is 80 mol% or less, and there is no lower limit to the degree of saponification, but it may be about 60 mol%. Regarding the degree of polymerization, it is 1000 or less, more preferably 800 or less, still more preferably 500 or less.

  For the adhesive layer, carboxymethylcellulose, casein, dextrin, starch (gelatinized), modified starch (gelatinized), polyethylene oxide, polyvinylpyrrolidone, polyvinylmethylether, polyacrylic acid, polyacrylamide, urethane A hydrophilic polymer such as a polymer may be used in combination with a binder resin.

  Although the compounding quantity of the binder resin of this invention is not specifically limited, The range of 50-100 mass parts is preferable with respect to 100 mass parts of adhesive agents. If the blending amount is less than 50 parts by mass, the wet strength becomes too weak, the offset printing suitability may be deteriorated, and the non-transferability of non-impact print printing may be deteriorated. On the other hand, if the blending amount exceeds 100 parts by mass, the ink drying property and printing density of non-impact printing may be lowered, and the adhesive force may be lowered.

  As the fine particle filler contained in the adhesive layer, inorganic and organic pigments can be used. Examples thereof include titanium dioxide, zinc oxide, zeolite, calcium carbonate, clay, aluminum oxide, starch (non-gelatinized), silica, colloidal silica, alumina, γ-alumina, plastic pigment, fluorine resin, and the like. Among them, starch, silica 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 is excellent in ink acceptability and improves printability and non-impact printability. It also has an anti-blocking effect. The fluorine-based resin is highly effective in preventing ink bleeding. Titanium dioxide has a high hiding effect, and the hiding effect is further enhanced by mixing with silica. Therefore, when the concealability improving effect by titanium dioxide blended in the base sheet is insufficient, it is effective to blend titanium dioxide and silica in the adhesive layer. The particle size of the inorganic or organic pigment is preferably about 0.1 to 50 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.

  As for the compounding quantity of the fine particle filler contained in the adhesive bond layer of this invention, 20-50 mass% of the whole adhesive bond layer is preferable. If the blending amount is less than 20% by mass, the drying property of the ink used in the non-impact printer may be insufficient, and if it exceeds 50% by mass, the binder resin can fix the fine particle filler to the adhesive layer. Therefore, the offset printability may be deteriorated.

  The adhesive layer has a cationic group and / or a compound having a functional group that can be a cationic group, a pigment dispersant, a thickener, a fluidity improver, an antifoaming agent, a foam suppressant, a lubricant, a penetrating agent, An appropriate amount of a coloring dye, an ultraviolet absorber, an antistatic agent, a cationic, nonionic or amphoteric surfactant, an antioxidant, a preservative, a water-proofing agent, and the like can be blended.

  In particular, when printing personal information on the confidential postcard paper of the present invention using an inkjet printer, it is preferable to mix a compound having a cationic group and / or a functional group capable of forming a cationic group in the adhesive layer, For example, a cationic compound having a primary amino group or an addition salt thereof as a functional group, a cationic compound having a secondary amino group or an addition salt thereof, a cationic compound having a tertiary amino group or an addition salt thereof, or a quaternary ammonium And a cationic compound having a group, (meth) acrylic acid pyridylalkyl esters and pyridinium salts thereof, N-substituted pyridinium salts of (meth) acrylic acid pyridylalkyl esters, vinylpyridines and pyridinium salts thereof, and the like.

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

  In the winding after the adhesive layer coating, the JAPAN TAPPI paper pulp test method No. It is preferable that the deviation of the winding hardness specified in the 37-81 method is 5 kgf · m or less. If the maximum value of the winding hardness deviation exceeds 5 kgf · m, when the adhesive layer is applied, unnecessary paper deformation occurs, and the paper dimensions differ between the left and right. Printing at a high speed (150 m / min) using a printing machine may cause problems such as wrinkles and misregistration.

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

Example 1
Suspension obtained by suspending 30 kg of rutile-type titanium dioxide pigment with an average primary particle diameter of 0.25 μm and no surface coating layer in 100 L of water and wet-grinding with a sand mill for 60 minutes is sufficiently stirred. While heating to 60 ° C., 15 g of 100 g / L sodium silicate aqueous solution was added as SiO ₂ , and the pH was adjusted to 3 using 240 g of diluted sulfuric acid for 240 minutes. Stir for another 60 minutes, cool to 30 ° C., adjust pH to 9 with 300 g / L dilute aqueous sodium hydroxide solution, add 3.6 g of 250 g / L aqueous sodium aluminate as Al ₂ O ₃ and dilute sulfuric acid simultaneously. Then, it was added over 180 minutes while maintaining pH 9. Subsequently, the mixture was stirred for 60 minutes, adjusted to pH 7 with dilute sulfuric acid for 10 minutes, further stirred for 60 minutes, filtered, washed, dried at 110 ° C., and then dry-pulverized with a steam mill. In this way, titanium dioxide coated with SiO ₂ and Al ₂ O ₃ was obtained.

100 ml of hardwood bleached kraft pulp (LBKP) is 420 ml C.I. S. F. , Rosin sizing agent 0.2 parts by weight, paper strength enhancer 0.8 parts by weight, titanium dioxide coated with SiO ₂ and Al ₂ O ₃ 6.0 parts by weight, talc 2.0 parts by weight, sulfuric acid A paper stock is prepared by adding 1.2 parts by mass of a band, and a high-quality paper having a basis weight of 115 g / m ² is made using a long net paper machine, and a base sheet is prepared by adjusting the thickness to 140 μm with a calendar. Obtained.
On one side of the substrate sheet, a re-peeling surface coating having the following composition was applied at 8 g / m ² per solid with a Mayer bar, and dried for 1 minute at a temperature of 120 ° C. with a hot air dryer. Subsequently, the same coating material was applied in the same manner as described above to the opposite surface of the base material sheet coated with the re-peeling surface coating material, to obtain a pressure-sensitive adhesive sheet of the present invention.
"Re-peeling surface coating composition"
Blending amount
40 parts by mass of an ethylene-vinyl acetate copolymer resin / ethyl acrylate composite resin adhesive (trade name: OLY3817-2, manufactured by Showa Polymer Co., Ltd.)
4 parts by mass of a copolymer of diallylamine hydrochloride, which is a resin containing a hydrochloride of a secondary amino group, and acrylamide (trade name: Sumirez Resin 1001, manufactured by Sumitomo Chemical Co., Ltd.)
10 parts by mass of silyl-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.)
Styrene-Butidiene Rubber (trade name: Nippon Lx-416, manufactured by Nippon Zeon Co., Ltd.) 5 mass silica (trade name: Mizukasil P-526, manufactured by Mizusawa Chemical Co., Ltd.) 36 parts by mass,
0.4 parts by mass of a dispersant (trade name: Emulgen A-60, manufactured by Kao Corporation)
3 parts by mass of lubricant (trade name: DEF-704TF, manufactured by Nissin Chemical Laboratory),
Defoaming agent (SN deformer 480, manufactured by San Nopco) 0.6 parts by mass

Example 2
100 ml of hardwood bleached kraft pulp (LBKP) in 400 ml C.I. S. F. Titanium dioxide coated with 0.15 parts by mass of rosin sizing agent, 0.8 parts by mass of paper strength enhancer, and SiO ₂ and Al ₂ O ₃ (trade name: TITON R-21, manufactured by Sakai Chemical Industry Co., Ltd.) (Average particle size 0.3 μm) 8.0 parts by mass, 2.0 parts by mass of talc, and 1.6 parts by mass of sulfuric acid band were added to prepare a paper stock, and a basis weight of 115 g / m using a long net paper machine. m ² fine paper was made and adjusted to a thickness of 140 μm with a calendar to obtain a base sheet.
On one side of the substrate sheet, a re-peeling surface coating having the following composition was applied at 8 g / m ² per solid with a Mayer bar, and dried for 1 minute at a temperature of 120 ° C. with a hot air dryer. Subsequently, the same coating material is applied to the opposite surface of the base material sheet coated with the re-peeling surface coating material in the same manner as described above to produce the pressure-sensitive adhesive sheet (confidential postcard paper for tri-fold postcard) of the present invention. did.
"Re-peeling surface coating composition"
Compounding amount Methyl methacrylate grafted natural rubber adhesive (trade name: Flutite FB672IJ, manufactured by Mitsui & Co. Solvent Coating Co., Ltd.) 39 parts by mass,
14 parts by mass of a quaternary cationic resin, dimethylamine-epichlorohydrin polycondensate (trade name: Jetfix 70, manufactured by Satorita Chemical Co., Ltd.)
Partially saponified maleic acid-modified polyvinyl alcohol (trade name: DR0415, manufactured by Denki Kagaku Kogyo Co., Ltd.) 9 parts by mass,
34 parts by mass of silica (trade name: Nipgel AY-603, manufactured by Tosoh Silica)
0.4 parts by mass of a dispersant (trade name: Emulgen A-60, manufactured by Kao Corporation)
1 part by mass of lubricant (trade name: DEF-704TF, manufactured by Nissin Chemical Laboratory),
1 part by mass of an antifoaming agent (trade name: SN deformer 480, manufactured by San Nopco).

Example 3
100 ml of hardwood bleached kraft pulp (LBKP) in 400 ml C.I. S. F. Titanium dioxide coated with 0.15 parts by mass of rosin sizing agent, 0.8 parts by mass of paper strength enhancer, and SiO ₂ and Al ₂ O ₃ (trade name: TITON R-21, manufactured by Sakai Chemical Industry Co., Ltd.) (Average particle diameter 0.3 μm) 3.5 parts by mass, 6.5 parts by mass of talc, and 1.6 parts by mass of sulfuric acid band were added to prepare a paper stock, and a basis weight of 115 g / m using a long net paper machine. m ² fine paper was made and adjusted to a thickness of 140 μm with a calendar to obtain a base sheet.
On one side of the substrate sheet, a re-peeling surface coating having the following composition was applied at 8 g / m ² per solid with a Mayer bar, and dried for 1 minute at a temperature of 120 ° C. with a hot air dryer. Subsequently, the same coating material is applied to the opposite surface of the base material sheet coated with the re-peeling surface coating material in the same manner as described above to produce the pressure-sensitive adhesive sheet (confidential postcard paper for tri-fold postcard) of the present invention. did.
"Re-peeling surface coating composition"
Compounding amount Methyl methacrylate grafted natural rubber adhesive (trade name: Flutite FB672IJ, manufactured by Mitsui & Co. Solvent Coating Co., Ltd.) 39 parts by mass,
14 parts by mass of a quaternary cationic resin, dimethylamine-epichlorohydrin polycondensate (trade name: Jetfix 70, manufactured by Satorita Chemical Co., Ltd.)
Partially saponified maleic acid-modified polyvinyl alcohol (trade name: DR0415, manufactured by Denki Kagaku Kogyo Co., Ltd.) 9 parts by mass,
29 parts by mass of silica (trade name: Nipgel AY-603, manufactured by Tosoh Silica)
6 parts by mass of titanium dioxide coated with SiO ₂ and Al ₂ O ₃ (trade name: TITON R-21, manufactured by Sakai Chemical Industry Co., Ltd.)
0.4 parts by mass of a dispersant (trade name: Emulgen A-60, manufactured by Kao Corporation)
1 part by mass of lubricant (trade name: DEF-704TF, manufactured by Nissin Chemical Laboratory),
1 part by mass of an antifoaming agent (trade name: SN deformer 480, manufactured by San Nopco).

Example 4
A pressure-sensitive adhesive sheet (confidential postcard paper for tri-fold postcard) of the present invention was obtained in the same manner as in Example 2 except that the composition for re-peeling surface was changed to the following composition.
"Re-peeling surface coating composition"
80 parts by weight of methyl methacrylate grafted natural rubber adhesive (trade name: Flutite FB-520, manufactured by Mitsui & Co. Solvent Coating Co., Ltd.)
20 parts by mass of titanium dioxide (trade name: Taipei W-10, manufactured by Ishihara Sangyo Co., Ltd.)
20 parts by weight of wheat starch (trade name: AS-225, manufactured by Chiba Starch)
40 parts by mass of silica (trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Co., Ltd.)
18 parts by mass of a styrene-butadiene copolymer binder (trade name: 0696, manufactured by JSR)
12 parts by mass of dimethylamine-epichlorohydrin polycondensate (trade name: Jetfix 70, manufactured by Satorita Chemical Co., Ltd.), which is a quaternary cationic resin,
Magnesium sulfate (trade name: Magnesium sulfate, manufactured by Tomita Pharmaceutical Co., Ltd.) 8 parts by mass,
3 parts by mass of fluorine fine particles (trade name: Hydrosser SST3, manufactured by Shamrock)
0.4 parts by mass of a dispersant (trade name: Emulgen A-60, manufactured by Kao Corporation)
1 part by mass of lubricant (trade name: DEF-704TF, manufactured by Nissin Chemical Laboratory),
1 part by mass of an antifoaming agent (trade name: SN deformer 480, manufactured by San Nopco).

Example 5
100 ml of hardwood bleached kraft pulp (LBKP) in 400 ml C.I. S. F. Titanium dioxide coated with 0.15 parts by mass of rosin sizing agent, 0.8 parts by mass of paper strength enhancer, and SiO ₂ and Al ₂ O ₃ (trade name: TITON R-21, manufactured by Sakai Chemical Industry Co., Ltd.) (Average particle diameter 0.3 μm) 16.0 parts by mass, 2.0 parts by mass of talc and 1.6 parts by mass of sulfuric acid band were added to prepare a paper stock, and a basis weight of 115 g / m using a long net paper machine. m ² fine paper was made and adjusted to a thickness of 140 μm with a calendar to obtain a base sheet.
On one side of the substrate sheet, a re-peeling surface coating having the following composition was applied at 8 g / m ² per solid with a Mayer bar, and dried for 1 minute at a temperature of 120 ° C. with a hot air dryer. Subsequently, the same coating material is applied to the opposite surface of the base material sheet coated with the re-peeling surface coating material in the same manner as described above to produce the pressure-sensitive adhesive sheet (confidential postcard paper for tri-fold postcard) of the present invention. did.
"Re-peeling surface coating composition"
Compounding amount Methyl methacrylate grafted natural rubber adhesive (trade name: Flutite FB672IJ, manufactured by Mitsui & Co. Solvent Coating Co., Ltd.) 39 parts by mass,
14 parts by mass of a quaternary cationic resin, dimethylamine-epichlorohydrin polycondensate (trade name: Jetfix 70, manufactured by Satorita Chemical Co., Ltd.)
Partially saponified maleic acid-modified polyvinyl alcohol (trade name: DR0415, manufactured by Denki Kagaku Kogyo Co., Ltd.) 9 parts by mass,
33.5 parts by mass of silica (trade name: Nipgel AY-603, manufactured by Tosoh Silica)
1.2 parts by mass of titanium dioxide coated with SiO ₂ and Al ₂ O ₃ (trade name: TITON R-21, manufactured by Sakai Chemical Industry Co., Ltd.)
0.4 parts by mass of a dispersant (trade name: Emulgen A-60, manufactured by Kao Corporation)
1 part by mass of lubricant (trade name: DEF-704TF, manufactured by Nissin Chemical Laboratory),
1 part by mass of an antifoaming agent (trade name: SN deformer 480, manufactured by San Nopco).

Example 6
Suspend 30 kg of rutile titanium dioxide (Titanium (4) Oxide, manufactured by Wako Pure Chemical Industries, Ltd.) without a surface coating layer in 100 L of water and wet pulverize with a sand mill for 30 minutes. The mixture was heated to 60 ° C. with stirring, 15 L of 100 g / L sodium silicate aqueous solution was added as SiO ₂ , and the pH was adjusted to 3 using 240 g of diluted sulfuric acid for 240 minutes. Stir for another 60 minutes, cool to 30 ° C., adjust pH to 9 with 300 g / L dilute aqueous sodium hydroxide solution, add 3.6 g of 250 g / L aqueous sodium aluminate as Al ₂ O ₃ and dilute sulfuric acid simultaneously. Then, it was added over 180 minutes while maintaining pH 9. Subsequently, the mixture was stirred for 60 minutes, adjusted to pH 7 with dilute sulfuric acid for 10 minutes, further stirred for 60 minutes, filtered, washed, dried at 110 ° C., and then dry-pulverized with a steam mill. In this way, titanium dioxide coated with SiO ₂ and Al ₂ O ₃ was obtained. (Average particle size 0.6μm)
A pressure-sensitive adhesive sheet (a trifold postcard confidential postcard paper) of the present invention was obtained in the same manner as in Example 2 except that the above titanium dioxide was used as a filler constituting the base sheet.

Example 7
Suspension obtained by suspending 30 kg of rutile-type titanium dioxide (trade name: Titanium (4) Oxide, manufactured by Wako Pure Chemical Industries, Ltd.) having no surface coating layer in 100 L of water and wet-grinding with a sand mill for 120 minutes Was heated to 60 ° C. with sufficient stirring, 15 g of 100 g / L sodium silicate aqueous solution was added as SiO ₂ , and the pH was adjusted to 3 using 240 g of diluted sulfuric acid for 240 minutes. Stir for another 60 minutes, cool to 30 ° C., adjust pH to 9 with 300 g / L dilute aqueous sodium hydroxide solution, add 3.6 g of 250 g / L aqueous sodium aluminate as Al ₂ O ₃ and dilute sulfuric acid simultaneously. Then, it was added over 180 minutes while maintaining pH 9. Subsequently, the mixture was stirred for 60 minutes, adjusted to pH 7 with dilute sulfuric acid for 10 minutes, further stirred for 60 minutes, filtered, washed, dried at 110 ° C., and then dry-pulverized with a steam mill. In this way, titanium dioxide coated with SiO ₂ and Al ₂ O ₃ was obtained. (Average particle size 0.18 μm)
A pressure-sensitive adhesive sheet (a trifold postcard confidential postcard paper) of the present invention was obtained in the same manner as in Example 2 except that the above titanium dioxide was used as a filler constituting the base sheet.

Comparative Example 1
100 ml of hardwood bleached kraft pulp (LBKP) is 420 ml C.I. S. F. Beaten to 0.2 parts by weight of rosin sizing agent, 0.8 parts by weight of paper strength enhancer, 10.0 parts by weight of rutile titanium dioxide having an average primary particle size of 0.25 μm and no surface coating layer, A paper stock is prepared by adding 1.2 parts by mass of a sulfuric acid band, and a high-quality paper having a basis weight of 115 g / m ² is made using a long net paper machine, and adjusted to a thickness of 140 μm with a calender to form a base sheet Got.
On one side of the substrate sheet, a re-peeling surface coating having the following composition was applied at 8 g / m ² per solid with a Mayer bar, and dried for 1 minute at a temperature of 120 ° C. with a hot air dryer. Subsequently, the same coating material was applied in the same manner as described above to the opposite surface of the base material sheet coated with the re-peeling surface coating material, to obtain a pressure-sensitive adhesive sheet of the present invention.
"Re-peeling surface coating composition"
Formulated amount of methyl methacrylate grafted natural rubber adhesive (trade name: Flutite FB672IJ, manufactured by Mitsui & Co. Solvent Coating Co., Ltd.) 37 parts by mass,
10 parts by mass of a copolymer of diallylamine hydrochloride, which is a resin containing a hydrochloride of a secondary amino group, and acrylamide (trade name: Sumirez Resin 1001, manufactured by Sumitomo Chemical Co., Ltd.)
13 parts by mass of partially saponified polyvinyl alcohol (trade name: PVA210, manufactured by Kuraray Co., Ltd.)
36 parts by mass of silica (trade name: Fine Seal X-60, manufactured by Tokuyama Corporation),
0.4 parts by mass of a dispersant (trade name: Emulgen A-60, manufactured by Kao Corporation)
3 parts by mass of lubricant (trade name: DEF-704TF, manufactured by Nissin Chemical Laboratory),
Defoaming agent (trade name: SN deformer 480, manufactured by San Nopco) 0.6 parts by mass.

Comparative Example 2
20 parts by weight of softwood bleached kraft pulp (NBKP) and 80 parts by weight of hardwood bleached kraft pulp (LBKP) at 430 ml C.I. S. F. And rosin sizing agent (trade name: Size Pine E, manufactured by Arakawa Chemical Co., Ltd.) 0.3 parts by weight, wet paper strength enhancer (trade name: WS-500, manufactured by Seiko PMC) 0.8 parts by weight Then, 1.0 mass part of titanium dioxide coated with SiO ₂ and Al ₂ O ₃ (trade name: TITON R-21, manufactured by Sakai Chemical Industry Co., Ltd.) and 3.5 parts by mass of sulfuric acid band were added to prepare a paper stock. Then, a fine paper having a basis weight of 114 g / m ² was made using a long paper machine and adjusted to a thickness of 135 μm with a calendar to obtain a base sheet. The resulting base sheet was coated with a re-peeling surface coating composition having the following composition on both sides at a coating amount of 7.0 g / m ² to obtain a pressure-sensitive adhesive sheet.
"Re-peeling surface coating composition"
100 parts by mass of methyl methacrylate grafted natural rubber adhesive (trade name: Flutite FB672IJ, manufactured by Mitsui & Co. Solvent Coating Co., Ltd.)
30 parts by mass of silica (trade name: Snowtex, manufactured by Nissan Chemical Industries, Ltd.)
150 parts by weight of wheat starch (trade name: AS-225, manufactured by Chiba Starch)
6 parts by mass of a copolymer of diallylamine hydrochloride, which is a resin containing a hydrochloride of a secondary amino group, and acrylamide (trade name: Sumirez Resin 1001, manufactured by Sumitomo Chemical Co., Ltd.)

Comparative Example 3
20 parts by weight of softwood bleached kraft pulp (NBKP) and 80 parts by weight of hardwood bleached kraft pulp (LBKP) at 430 ml C.I. S. F. And rosin sizing agent (trade name: Size Pine E, manufactured by Arakawa Chemical Co., Ltd.) 0.3 parts by weight, wet paper strength enhancer (trade name: WS-500, manufactured by Seiko PMC) 0.8 parts by weight 22.0 parts by mass of titanium dioxide coated with SiO ₂ and Al ₂ O ₃ (trade name: TITON R-21, manufactured by Sakai Chemical Industry Co., Ltd.) and 3.5 parts by mass of sulfuric acid band were added to prepare a paper stock. Then, a fine paper having a basis weight of 114 g / m ² was made using a long paper machine and adjusted to a thickness of 135 μm with a calendar to obtain a base sheet. The resulting base sheet was coated with a re-peeling surface coating composition having the following composition on both sides at a coating amount of 7.0 g / m ² to obtain a pressure-sensitive adhesive sheet.
"Re-peeling surface coating composition"
100 parts by mass of methyl methacrylate grafted natural rubber adhesive (trade name: Flutite FB672IJ, manufactured by Mitsui & Co. Solvent Coating Co., Ltd.)
30 parts by mass of silica (trade name: Snowtex, manufactured by Nissan Chemical Industries, Ltd.)
150 parts by weight of wheat starch (trade name: AS-225, manufactured by Chiba Starch)
6 parts by mass of a copolymer of diallylamine hydrochloride, which is a resin containing a hydrochloride of a secondary amino group, and acrylamide (trade name: Sumirez Resin 1001, manufactured by Sumitomo Chemical Co., Ltd.)

Comparative Example 4
100 ml of hardwood bleached kraft pulp (LBKP) in 400 ml C.I. S. F. The rosin sizing agent (trade name: Size Pine E, manufactured by Arakawa Chemical Industry Co., Ltd.) was 0.7 parts by mass, and the wet paper strength enhancer (trade name: WS-500, manufactured by Seiko PMC Co., Ltd.) was 0.8. Mass parts, 8 parts by mass of talc, and 1.5 parts by mass of sulfuric acid band are added to prepare a stock, and a fine paper with a basis weight of 114 g / m ² is made using a long net paper machine, and the thickness is measured with a calendar. The substrate sheet was obtained by adjusting to 135 μm. A re-peeling surface coating material having the following composition was applied to both surfaces of the obtained base material sheet at a coating amount of 8.0 g / m ² to obtain a pressure-sensitive adhesive sheet.
A pressure-sensitive adhesive sheet (confidential postcard paper for tri-fold postcard) of the present invention was obtained in the same manner as in Comparative Example 2 except that the following composition was used as the re-peeling surface paint.
"Re-peeling surface coating composition"
Blending amount Methyl methacrylate grafted natural rubber adhesive (trade name: Flutite FB-06OJ, manufactured by Mitsui Fuller) 60 parts by mass,
30 parts by mass of silica (trade name: Fine Seal X-45, manufactured by Tokuyama Corporation),
30 parts by weight of wheat starch (trade name: AS-225, manufactured by Chiba Starch)
20 parts by mass of zeolite (trade name: Toyo Builder, manufactured by Tosoh Corporation),
10 parts by mass of polyvinyl alcohol (trade name: PVA-217, manufactured by Kuraray Co., Ltd.)
12 parts by mass of a copolymer of diallylamine hydrochloride, which is a resin containing a hydrochloride of a secondary amino group, and acrylamide (trade name: Sumirez resin 1001, manufactured by Sumitomo Chemical Co., Ltd.).

〔Evaluation methods〕
Ink drying property evaluation: Yellow, magenta, cyan, and black were printed using an inkjet printer MC-830 (manufactured by Seiko Epson Corporation), and the ink flow condition when the printed portion was immediately rubbed with a finger was visually evaluated.
◎: No ink flow and excellent ○: Little ink flow △: Slight ink flow is observed, but there is no practical problem ×: There is an ink flow, there is a practical problem

Evaluation of water resistance of printing: Yellow, magenta, cyan, and black are printed on a re-peeling surface using an inkjet printer MC-830 (manufactured by Seiko Epson Corporation), and ink bleeding is visually evaluated when immersed in water for 2 minutes. did.
A: There is no blur and is excellent. B: Little blur is observed. B: Slight blur is observed, but there is no practical problem. X: There is a blur and there is a practical problem.

Print density evaluation: Black was printed on the re-peeling surface using an inkjet printer MC-830 (manufactured by Seiko Epson Corporation), and visually evaluated.
◎: Print density is very dark and excellent ◯: Print density is high △: Print density is slightly light, but there is no practical problem ×: Print density is light and practical problem

Wet strength (offset printing suitability): When printing with a predetermined hardness (tack 8) ink on a pressure-sensitive adhesive sheet sample immediately after water is printed with a molton roll using an RI tester (manufactured by Ishikawajima Industrial Machinery Co., Ltd.) The peeling of the adhesive layer was visually evaluated.
◎: No peeling at all and very good ○: Little peeling △: There is some peeling, but there is no practical problem ×: There is severe peeling, there is a practical problem

Re-peelability of the re-peeled surface: Using a dry sealer (6860, manufactured by Toppan Foams), the obtained tri-fold postcard sample was cut to an appropriate size and Z-folded so that the re-peeled surfaces face each other Then, after adjusting the temperature and humidity conditions of 23 ° C. and 50% RH for 24 hours, a press post with a roll gap set to 200 μm was passed through and pressed to prepare a confidential postcard. The obtained confidential postcard was peeled off again 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 at a level where there is no practical problem ×: The strength of the base material is weak, the base material breaks down, and is a level causing practical problems

Adhesiveness of re-peeling surface: Using a dry sealer (6860, manufactured by Toppan Foams), the obtained tri-fold postcard sample was cut to an appropriate size and Z-folded so that the re-peeling surfaces face each other After adjusting the temperature and humidity conditions of 23 ° C. and 50% RH for 24 hours, a press post with a roll gap set to 200 μm was passed through and pressed to prepare a confidential postcard. The adhesive strength of the obtained confidential postcard was evaluated by T-type peeling.
○: 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

(7) Opacity: The opacity of the pressure-sensitive adhesive sheet and the substrate sheet was measured according to JIS P-8149 using a spectral whiteness colorimeter (SC-10WN, manufactured by Suga Test Instruments Co., Ltd.).

Dispersion stability of titanium dioxide: The dispersion stability was evaluated from the sedimentation state of titanium dioxide fine particles.
○: No settling and excellent dispersion stability Δ: Slightly settled, but at a level that is not a problem for practical use ×: Severe settling is at a level that causes a problem for practical use

(9) 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

From Table 1, the pressure-sensitive adhesive sheets of the present invention of Examples 1 to 7 are made to conceal personal information by blending a specific amount of titanium dioxide with a specific surface coating as a filler constituting the base sheet. It is very excellent, and there is no problem with wet strength, which is an index of ink-jet ink drying property, printing water resistance, printing density, and offset printing suitability, and it has excellent adhesion and removability. In particular, in Examples 4 and 5 in which a relatively large amount of titanium dioxide was blended in the adhesive layer, the concealability was excellent. Further, the particle diameter of titanium dioxide affects the dispersion stability, so it is preferable to make it within an appropriate range. On the other hand, in Comparative Examples 1 and 4, titanium dioxide with a specific surface coating is not used as a filler constituting the base sheet, and the pressure-sensitive adhesive sheet has low opacity and personal information can be seen from the outside. End up. Moreover, when there are too few compounding quantities of titanium dioxide, it is inferior to concealment property, and when there are too many compounding quantities of titanium dioxide, the intensity | strength of a base material sheet will become weak too much and it will become impossible to peel again.

Claims (3)

It has an adhesive layer on at least one surface of the base sheet, and the adhesive layer can be bonded by performing a high pressure treatment with the adhesive layers facing each other. In the pressure-sensitive adhesive sheet that can be peeled off, titanium dioxide in which the filler particle surface is coated with SiO ₂ and / or Al ₂ O ₃ is used as a filler constituting the base sheet, with respect to 100 parts by mass of the pulp. 3 to 20 parts by mass, and the adhesive layer has an adhesive, a fine particle filler, and a binder resin as constituents, and the opacity of the pressure-sensitive adhesive sheet measured according to JIS P-8149 is 90. A pressure-sensitive adhesive sheet characterized by being 0% or more.   The pressure-sensitive adhesive sheet according to claim 1, wherein the titanium dioxide has an average particle size of 0.1 to 0.5 µm. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein 0.1 to 20 parts by mass of titanium dioxide is contained in the adhesive layer with respect to 100 parts by mass of the adhesive.