JP2005074699A - Information hiding sheet excellent in hiding performance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet which is an information hiding sheet having spread surfaces that are stuck together temporarily, but can be peeled off easily as occasion demands, and through which hidden information can not be seen. <P>SOLUTION: A sticking layer 6 for bearing the hidden information which does not stick superposed surfaces of the sheet 2 together in an ordinary state, but sticks them together peelably by bringing them into face-to-face contact with each other and by applying a prescribed pressure thereto, is formed in a prescribed part of the surfaces to be superposed, and a hiding layer 7 for preventing the hidden information 5 from being read by seeing it through from outside is formed in a prescribed part of the side opposite to the surfaces to be superposed, while visible information is written on the hiding layer 7 as occasion demands. In the information hiding sheet 1 thus constituted, the sticking layer 6 and the hiding layer 7 are formed with a prescribed amount of high-refractive-index titanium oxide particles compounded therein. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an information concealment sheet having excellent concealment performance. More specifically, the present invention relates to an information concealment sheet, a folding sheet having a facing surface that can be easily peeled off as needed, but can be easily peeled off if necessary. The present invention relates to an information concealment sheet excellent in concealment performance of various information such as personal information such as postcards, notices, cards, etc., or print information, print information, and the like.

  In recent years, with the revision of the Postal Law, postcard systems with confidentiality have been put into practical use and are widely used. This confidential postcard system can be used for various kinds of wrapping, such as folding personal information, postcards that contain various information such as print information and print information, or stacking them together. In the mating mode, the information is peelably bonded and the information is concealed and then mailed, and the recipient peels the overlapping surface again to read the concealment information.

As an information-carrying sheet used in a postcard system, for example, an adhesive composition comprising an adhesive base on a superposed surface of a base sheet and a fine particle filler exhibiting non-affinity for the adhesive base One having an adhesive layer made of a material is known (for example, Patent Document 1).
However, in the conventional sheet for carrying information, there is an incident that privacy information or personal information, etc. that is concealed and carried, is read through the outside of the sheet by another person before the recipient peels off the overlapping surface. Occurred. Therefore, various measures for preventing sheet see-through have been proposed.

  For example, there are a method for improving the opacity of the paper itself by adding a filler (white pigment) to a base sheet such as paper, and a method for forming an opaque layer (hiding layer) on the paper (for example, Patent Documents 2 and 3). However, the concealing effect (prevention of see-through effect) is not sufficient, and the concealment information can be seen through when the light is applied from the back side.

Therefore, methods have been proposed in which a specific color camouflage pattern is provided on the paper and the concealment information of the same color as the specific color is carried or a concealment film is attached to the paper. In the latter case, a concealment label prepared separately is attached, which complicates the processing process and increases costs, and restricts the original free use of the sheet carrying concealment information. This is not preferable.
JP-A-4-59395 JP-A-4-62129 JP 2000-309184 A

  The purpose of the present invention is to solve the conventional problems and to bond the peelable postcards in which the concealment information is written in various manners of superposition such as folding, cutting or overlapping each other. It is possible to hide the concealment information through the watermark, and the recipient can read the concealment information by peeling the overlapped surface again. The concealment effect (prevention of see-through effect) is high and inexpensive. It is to provide an information concealment sheet used for carrying concealment information.

According to a first aspect of the present invention for solving the problem, the overlapping is performed by applying a predetermined pressure by bringing the overlapping surfaces into contact with each other without contacting the predetermined portions of the overlapping surfaces of the sheets in a normal state. A concealment information carrying adhesive layer that adheres the mating surfaces to each other in a peelable manner is formed, and a concealment layer that prevents the concealment information from being read from the outside through a predetermined portion on the opposite surface of the overlapping surface is formed. In the information concealment sheet for filling in the visible information on the concealment layer according to
The adhesive layer and the concealing layer are information concealment sheets excellent in concealment performance, characterized in that they are formed by blending a predetermined amount of high refractive index titanium oxide fine particles.

  According to a second aspect of the present invention, in the information concealment sheet according to the first aspect, the concealment layer makes the concealment layers come into contact with each other by applying a predetermined pressure by bringing the concealment layers into contact with each other. It is formed using a pressure adhesive.

  Claim 3 of the present invention is the information hiding sheet according to claim 1 or claim 2, wherein the adhesive layer and the pressure-sensitive adhesive have a high refractive index titanium oxide with respect to 100 parts by mass of the adhesive base material (solid content). 5 to 50 parts by mass of fine particles are blended.

A fourth aspect of the present invention is the information hiding sheet according to any one of the first to third aspects, wherein the coloring material has a lightness L ^{* of} 0 to 50 in a predetermined amount in the adhesive layer and / or the pressure sensitive adhesive. It is characterized by blending.

  According to a fifth aspect of the present invention, in the information hiding sheet according to any one of the first to fourth aspects, the colorant is a black or blue dark dye or pigment.

  A sixth aspect of the present invention is the information hiding sheet according to any one of the first to fifth aspects, wherein the adhesive base is a natural rubber-based aqueous emulsion type adhesive base.

The information concealment sheet having excellent concealment performance according to claim 1 of the present invention does not adhere to a predetermined portion of the overlapping surface of the sheet in a normal state, but applies the predetermined pressure by bringing the overlapping surfaces into contact with each other. , Forming a concealing information carrying adhesive layer for releasably adhering the overlapping surfaces, and forming a concealing layer for preventing the concealing information from being read from the outside through a predetermined portion on the opposite surface of the overlapping surface In the information concealment sheet in which visible information is entered on the concealment layer as necessary, the adhesive layer and the concealment layer are formed by blending a predetermined amount of high refractive index titanium oxide fine particles. ,
A concealment effect (prevention of see-through) that can be peeled off in a superposition manner so that the concealment information cannot be seen through from the outside, and the recipient can read the concealment information by peeling the overlap surface again. The information hiding sheet is highly effective, has good visibility of the information entered on the hiding layer, and is inexpensive.
The information concealment sheet of the present invention is a folding sheet having a facing surface that is temporarily bonded, but can be easily peeled off as necessary, a superposed sheet, for example, a postcard having a confidential property such as an information concealment sheet, a notice, It can be used as a concealment sheet for personal information such as cards or various information such as print information and print information.

  In the information hiding sheet according to claim 2 of the present invention, the hiding layer uses a pressure sensitive adhesive that firmly bonds the overlapping surfaces by bringing the hiding layers into contact with each other and applying a predetermined pressure. Since it is formed, when applied to a W-fold type information concealment sheet that performs a new type of folding, which will be described later, the concealing layer and the adhesive surface are formed using the pressure-sensitive adhesive on the opposite surface of the overlapping surface. It can be formed at the same time, and visible information such as an address can be formed on the concealing layer, and the adhesive surfaces can be brought into contact with each other and given a predetermined pressure to firmly bond the overlapping surfaces to each other. The further effect that it is possible is acquired.

  Claim 3 of the present invention is the information hiding sheet according to claim 1 or claim 2, wherein the adhesive layer and the pressure-sensitive adhesive have a high refractive index titanium oxide with respect to 100 parts by mass of the adhesive base material (solid content). Since 5 to 50 parts by mass of the fine particles are blended, a stable and good concealing effect (through prevention effect) can be obtained, and the information written on the concealing layer can be further improved in visibility.

A fourth aspect of the present invention is the information hiding sheet according to any one of the first to third aspects, wherein the coloring material has a lightness L ^{* of} 0 to 50 in a predetermined amount in the adhesive layer and / or the pressure sensitive adhesive. Thus, a better concealing effect (prevention of see-through effect) can be obtained, and an additional effect that the visibility of information written on the concealing layer is not impaired can be obtained.

  According to a fifth aspect of the present invention, in the information concealment sheet according to any one of the first to fourth aspects, since the color material is a black or blue dark dye or pigment, the concealment is performed with a small amount. The further effect that an effect (a prevention effect of see-through) is obtained is obtained.

  Claim 6 of the present invention is the information hiding sheet according to any one of claims 1 to 5, wherein the adhesive base is a natural rubber-based aqueous emulsion type adhesive base. Is easy to adjust the coating amount and excellent in suitability for coating on the surface of the base sheet.Because the solvent is water, it is harmless to the human body and is not flammable. The further effect that it is not necessary is obtained.

Hereinafter, embodiments of the present invention will be described in detail.
The adhesive layer for supporting information concealment of the information concealment sheet of the present invention is formed by using a pressure-sensitive adhesive composition that does not adhere in a normal state, adheres by pressure, and can be peeled off when necessary. A preferable adhesive base is not particularly limited and may be any of a solvent system using an organic solvent, an aqueous system using water as a medium, a system cured by radiation such as ultraviolet rays, and a heat curing system. However, if a water-based, particularly natural rubber-based aqueous emulsion type adhesive base is used instead of a solvent system that uses an organic solvent as the adhesive base, the coating sheet has low volatility, and the coating amount can be easily adjusted. In addition to being excellent in applicability to water, it is harmless to the human body because the solvent is water, is not flammable, and does not require exposure equipment or the like in the coating process or drying process.

The concealing layer of the information concealing sheet of the present invention is not particularly limited and may use any system such as a solvent system using an organic solvent, an aqueous system using water as a medium, a system cured by radiation such as ultraviolet rays, or a heat curing system. It is not a thing. However, it is preferable to use a natural rubber-based aqueous emulsion type system for the above reasons.
When the concealing layer is formed using a pressure sensitive adhesive that adheres the concealing layers to each other and applies a predetermined pressure so as to firmly bond the overlapping surfaces, a new type of folding method described later is applied. When applied to a foldable information concealment sheet, the concealing layer and the adhesive surface can be formed simultaneously on the opposite surface of the overlapping surface using the pressure-sensitive adhesive, and the visible information such as an address is visible on the concealment layer. In addition, the overlapping surfaces can be firmly bonded to each other by applying the predetermined pressure by bringing the bonding surfaces into contact with each other.

The natural rubber-based aqueous emulsion type adhesive base and the natural rubber-based aqueous emulsion type system can be arbitrarily selected from, for example, those conventionally conventionally used as bases for natural rubber-based pressure-sensitive adhesives. Examples of such a latex include natural rubber-based latex, modified rubber such as acid latex, depolymerized latex, vulcanized latex, or grafted natural rubber latex, and these natural rubber latexes. Examples thereof include styrene-rich SBR latex, polystyrene emulsion, and a mixture containing one or more styrene / acrylic copolymer emulsions in an appropriate amount.
Among natural rubber latexes, natural rubber latex obtained by graft copolymerization of methyl methacrylate with natural rubber, especially styrene and methyl methacrylate, especially in terms of blocking resistance, heat resistance, and abrasion resistance. Natural rubber latex obtained by graft copolymerization of

  The natural rubber latex preferably used in the pressure-sensitive adhesive composition used in the present invention, for example, obtained by graft copolymerization of methyl methacrylate with natural rubber is, for example, 10 to 40 methyl methacrylate with respect to 100 parts by mass of natural rubber. About one part by mass is graft copolymerized.

In order to obtain an excellent concealing effect (prevention of see-through effect), the adhesive layer and the concealing layer are made of a predetermined amount of high refractive index titanium oxide fine particles (refractive index example, anatase type; 2.52, rutile type; 2.71). It is important to blend and form. Silica fine particles (refractive index example, 1.45 to 1.47), calcium carbonate fine particles (refractive index example, 1.48 to 1.68), kaolin fine particles (refractive index example, 1.55 to 1.57). The fine particles such as) are not without the concealing effect, but the refractive index is lower than that of the high refractive index titanium oxide fine particles, so in order to obtain an excellent concealing effect (prevention of see-through effect), the amount must be increased. If the blending amount increases, the adhesiveness decreases, and in the worst case, there is a possibility that the concealment information may be read by another person by peeling before the recipient peels the overlapping surface again.
The high refractive index titanium oxide fine particles may be anatase type, rutile type, or a mixture thereof. Of these, the rutile type is preferable because it has a high refractive index.

As an example of a commercial product of the above-described high refractive index titanium oxide fine particles that can be preferably used in the present invention, sulfuric acid method titanium oxide (rutile type) [trade name: Tyco R-780, manufactured by Ishihara Sangyo Co., Ltd., TiO ₂ 88%, Specific gravity 4.0, specific surface area 17m ² / g, average particle diameter (measured by single particle diameter with electron microscope) 0.24μm, appropriate water content such as Al and Si to improve the affinity with the medium And surface-treated with an oxide].

  It is preferable to blend 5 to 50 parts by mass of high refractive index titanium oxide fine particles with respect to 100 parts by mass of the adhesive layer and the adhesive base material (solid content) of the pressure sensitive adhesive. If it is less than 5 parts by mass, the concealability may be inferior. If it exceeds 50 parts by mass, the adhesion may be inferior, and a stable and good concealing effect (prevention of see-through effect) within the above range can be obtained. The information entered in is highly visible.

The pressure-sensitive adhesive composition and pressure-sensitive adhesive used in the present invention are blended with a particulate filler which has no or very little affinity with the adhesive base and is difficult to dissolve in the adhesive base. It is better to use something.
Examples of the fine filler include various starch-based, fine spherical acrylic resin, fine spherical methacrylic resin, fine spherical polyethylene, silica, spherical alumina, glass powder, shirasu balloon, natural zeolite, synthetic zeolite, calcium carbonate, activated clay, etc. Is mentioned. These fine particle fillers may be used alone or in combination of two or more. A fine particle filler having an average particle diameter of 1 to 20 μm can be preferably used in the present invention.

  The pressure-sensitive adhesive light composition and pressure-sensitive adhesive of the present invention include additives commonly used in pressure-sensitive adhesives as desired, for example, tackifiers, viscosity modifiers, anti-aging agents, stabilizers, and colorants. Etc. can be added.

In the present invention, it is preferable to blend a predetermined amount of a colorant having a lightness L ^{* of} 0 to 50 in the adhesive layer and / or the pressure-sensitive adhesive. The hue and saturation of the color material are not particularly limited. If the lightness L ^* of the adhesive layer or the concealing layer is less than 35, the visibility of various information may be impaired. Conversely, if it exceeds 88, the concealing effect (prevention effect) may be impaired. The lightness L ^* of the adhesive layer or the hiding layer is preferably in the range of 35 to 88.
High visibility means that information such as an address can be easily read, and information that the recipient is concealed can be easily read.
Colorant lightness L ^* exceeds 50, since the lightness L ^* becomes much amount to obtain an adhesive layer or hiding layer of 35 to 88, there is a possibility that adequate adhesive strength and moderate peel strength is impaired .

The color material used in the present invention is not particularly limited as long as it is a color material that can provide a high concealing effect (through-through effect) without impairing the visibility of various information such as print information and print information. However, black and blue-based dark dyes or pigments are inexpensive and easily available, hardly transmit light, and have a lightness L ^* of 35 to 88 even in a small amount. Since a layer can be obtained and the hiding effect (prevention of see-through effect) is high, it can be preferably used.

  Specific examples of black and blue dark dyes or pigments include, for example, carbon black, phthalocyanine blue, cobalt phthalocyanine, dyed lake pigment, bitumen, complex oxide pigment, dioxazine violet, insoluble azo pigment, vinyl sulfone. Type reactive dyes, disperse dyes, vat dyes, basic dyes, cationic dyes, oil-soluble dyes, direct dyes, acid dyes and the like.

Although the compounding amount of the color material used in the present invention is not particularly limited, the color material is added in an amount of 0.001 to 0.1 with respect to the entire pressure-sensitive adhesive composition (solid content) or the pressure-sensitive adhesive (solid content). By blending in mass%, a high concealment effect (prevention of see-through effect) can be surely obtained without impairing properties such as application suitability and releasable adhesion.
If the blending amount of the color material is less than the lower limit value, the concealing effect (prevention of see-through effect) may be inferior. Therefore, it is preferable to be within the above range.

  The pressure-sensitive adhesive composition and pressure-sensitive adhesive used in the present invention can be applied to the substrate sheet surface by an application means such as a gravure coater, flexo, air knife coater, bar coater or the like. And in the form of various overlays such as bi-fold, tri-fold, cut-over, W-fold, or superposition of separate bodies, a spread surface that is temporarily bonded but can be easily peeled off as needed It can be suitably used for postcards, various forms, notices, various cards, and the like.

Next, as a base sheet, synthetic paper or synthetic films such as polyethylene, polyethylene terephthalate, polypropylene, and vinyl chloride can be used in addition to ordinary paper. When these synthetic films are used, the surface of the base sheet is preferably subjected to surface treatment such as mat treatment or corona treatment. The amount of the pressure-sensitive adhesive composition of the present invention and the pressure-sensitive adhesive applied to the base sheet surface is 1 to 30 g / m ² , preferably 3 in order to maintain the adhesiveness and peelability of the adhesive layer. ˜20 g / m ² , more preferably 5 to 15 g / m ² .
Furthermore, blocking resistance can be further improved by pressing the formed peelable adhesive layer with a pressure roller at about 1 to 10 kg / cm ² .

  Next, the structure of the sheet of the present invention will be described in detail with reference to the accompanying drawings. Here, FIG. 1 is a developed front view of a tri-fold postcard of the present invention, FIG. 2 is a developed rear view of the postcard, FIG. 3 is a cross-sectional view taken along the line XX of FIG. FIG. 5 is a developed front view of the folded bi-fold postcard of the present invention, FIG. 6 is a developed rear view of the postcard, FIG. 7 is an explanatory diagram of the state of folding the postcard of FIG. 5, and FIG. 9 is a developed view of the surface of the partially folded postcard, FIG. 9 is a developed view of the back surface of the postcard, FIG. 10 is an explanatory view of the state of folding the postcard of FIG. 8, and FIG. FIG. 11B is a development view, and FIG. 11B is an explanatory diagram of a state when the W-fold type crimping postcard of FIG.

  First, the tri-fold postcard 1 shown in FIGS. 1 to 3 is composed of a base sheet 2 having a size three times the standard postcard size, and is divided into three regions by folding lines 3a and 3b. A concealing layer 7 is formed on the surface of the left partition area A, and address information printing 4 such as a zip code, address and address is displayed on the concealment layer 7 on the partition areas B and C of the base sheet 2. A pressure-sensitive adhesive composition is applied to the entire front surface and the entire back surfaces of the partition regions A and B to form a peelable adhesive layer 6. A concealment information print 5 is printed on the adhesive layer 6 on the back surface of the left partition region A, the front and back surfaces of the central partition region B, and the front surface of the right partition region C. A layer 7 is formed, and visible information 4 is formed on the concealment layer 7. As shown in FIG. 4, the tri-fold postcard 1 configured in this way is formed by folding the overlapping surface of each section into a Z shape at the fold lines 3a and 3b to bring the adhesive layers into contact with each other. By applying pressure with a sealer, the adhesive layer 6 is activated and bonded.

  Next, the bi-fold postcard 11 shown in FIGS. 5 and 6 is composed of a base sheet 2 having a size twice as large as the standard postcard size, and is divided into two regions D and E by a fold line 3 at the center. Is. A concealing layer 7 is formed on the surfaces of the left partition regions D and E. On the concealing layer 7, destination information printing 4 such as a zip code, address, and address and visible information 4 are displayed on the base sheet 2. A pressure-sensitive adhesive composition is applied to the entire back surfaces of the partition regions D and E, and a peelable adhesive layer 6 is formed. A concealment information print 5 is printed on the adhesive layer 6 on the back of the partition regions D and E. As shown in FIG. 7, the bi-fold postcard 11 configured in this way is folded and pressed at the fold line 3 so that the adhesive layers on the back surfaces of the left and right compartments are in contact with each other as in the case of the above-described tri-fold postcard. The adhesive layer 6 is activated and bonded.

  Further, the partially folded postcard 21 shown in FIGS. 8 and 9 is composed of a base sheet 2 having a size 1.5 times the standard postcard size, and is divided into two left and right regions F and G having different sizes depending on the folding line 3. It is to be partitioned. On the surface of the left partition area F, destination information printing 4 such as a postal code, a destination name, and an address is formed, and a corresponding part of the partition area F overlapped when the partition area G is folded at the folding line 3. A concealing layer 7 is formed on the front surface and on the entire surface of the partition region G, and the entire back surface of the partition region G of the base sheet 2 and the partition region overlapped when the partition region G is folded at the fold line 3. A pressure-sensitive adhesive composition is applied to a part of the back surface corresponding to F to form a peelable adhesive layer 6. A concealment information print 5 is printed on the adhesive layer 6 on the back surface of the partition area F that is overlapped when the back surface of the right partition area G and the partition area G are folded at the folding line 3. As shown in FIG. 10, the partially folded postcard 21 configured in this manner is folded and pressed at the folding line 3 so that the adhesive layers on the back surfaces of the left and right compartments are in contact with each other, as in the case of the above-described folded bicard. Thus, the adhesive layer 6 is activated and bonded.

  11 (a) and 11 (b) is composed of a base sheet 2 having a size four times the standard postcard size, and is divided into four regions by folding lines 3a, 3b, and 3c. Is. A concealing layer 7 is formed on the surface of the partition regions H, I, J, and K using a pressure-sensitive adhesive that can firmly bond the concealment layers to each other. The pressure sensitive adhesive composition is applied to the destination information print 4 and the visible information 4 such as the postal code, the address, and the address, and to the entire back surface of the partition regions H, I, J, and K of the base sheet 2. Thus, a peelable adhesive layer 6 (not shown) is formed. A concealing information print 5 (not shown) is printed on the adhesive layer 6. As shown in FIG. 11 (b), the W-fold crimping postcard 31 configured in this manner is formed by folding the overlapping surface of each section into a W-shape along the fold lines 3a, 3b, and 3c so that the adhesive layers face each other. While contacting and concealing the concealing layers 7 (adhesive surfaces) of the partition regions I and J, and pressurizing with a dry sealer in this state, the adhesive layer 6 is activated and releasably adhered, The concealing layers 7 (adhesion surfaces) of the partition area I and the partition area J are firmly and permanently bonded to each other so that the partition area I and the partition area J cannot be peeled off.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
(Preparation of pressure-sensitive adhesive composition for forming an adhesive layer for supporting concealment information)
Graft polymerization of 25 parts by mass of styrene and MMA (methyl methacrylate) was performed on 100 parts by mass (solid content) of natural rubber (NR) by a known method to prepare an aqueous latex of styrene MMA copolymer having a solid content of 49%.
Silica fine particles (product name: Nippon E200 (manufactured by Nippon Silica Kogyo Co., Ltd.)) are previously solidified in ion-exchanged water with respect to 120 parts by mass (solid content: 58.8 parts by mass) of the aqueous styrene MMA copolymer latex prepared above. The dispersion dispersed in 16% by mass was stirred and mixed so as to be 55.1 parts by mass (silica solid content: 8.8 parts by mass). 29.4 parts by mass (starch) of a dispersion in which a commercially available starch (trade name: ACTISIZE CWH (manufactured by Rocket)) having an average particle size of 20 μm is previously dispersed in ion-exchanged water at a solid content of 50% by mass in this mixed solution. The mixture was stirred and mixed so that the solid content was 14.7 parts by mass.
In this mixed solution, 35.3 parts by mass (titanium oxide solid content) of titanium oxide fine particles (trade name: R-780 (manufactured by Ishihara Sangyo Co., Ltd.)) previously dispersed in ion exchange water at a solid content of 50% by mass. 17.6 parts by mass).
Add 0.20 parts by mass of black dye (trade name: DF Black CC (manufactured by Sumitomo Chemical Co., Ltd.)) (lightness L ^* = 16) to this mixed solution, and sufficiently stir to form a concealed information carrying adhesive layer. A pressure sensitive adhesive composition was obtained.

(Preparation of pressure-sensitive adhesive that firmly bonds the concealment layers)
Graft polymerization of 25 parts by mass of styrene and MMA (methyl methacrylate) was performed on 100 parts by mass (solid content) of natural rubber (NR) by a known method to prepare an aqueous latex of styrene MMA copolymer having a solid content of 49%.
Silica fine particles (trade name: Nippil E200 (manufactured by Nippon Silica Kogyo Co., Ltd.)) are previously charged in ion-exchanged water with respect to 145.8 parts by mass (solid content: 71.4 parts by mass) of the aqueous styrene MMA copolymer latex prepared above. The dispersion liquid having a solid content of 16% by mass was stirred and mixed so as to be 44.6 parts by mass (silica solid content: 7.1 parts by mass). 28.6 parts by mass (starch) of a dispersion in which a commercially available starch (trade name: ACTISIZE CWH (manufactured by Rocket)) having an average particle size of 20 μm is previously dispersed in ion-exchanged water at a solid content of 50% by mass in this mixed solution. The mixture was stirred and mixed so that the solid content was 14.3 parts by mass.
14.3 parts by mass (titanium oxide solids content) of a dispersion in which titanium oxide fine particles (trade name: R-780 (manufactured by Ishihara Sangyo Co., Ltd.)) were previously dispersed in ion-exchanged water at a solid content of 50% by mass in this mixed solution. 7.1 parts by mass).
0.12 parts by mass of black dye (trade name: DF Black CC (manufactured by Sumitomo Chemical Co., Ltd.)) (lightness L ^* = 16) is added to this mixed solution, and the mixture is sufficiently stirred to firmly bond the concealing layers to each other. A pressure sensitive adhesive was prepared.

(Creation of information hiding sheet sample for hiding and adhesive strength measurement)
On the surface of water-resistant recycled paper (trade name: FPWS-P77R 70 kg continuous quantity (manufactured by Nippon Paper Industries Co., Ltd.)), the pressure sensitive adhesive composition for forming the concealing information-carrying adhesive layer is 6 g / m ² using a wire bar. After coating so as to be (solid content), it was put in an oven set at 105 ° C. for 60 seconds and dried to form a concealment information carrying adhesive layer (sometimes referred to as concealment surface). And after applying the pressure sensitive adhesive which makes the said concealment layer adhere firmly to the back surface of the water-resistant recycled paper so that it may become 6 g / m < ² > (solid content) using a wire bar, it carries out similarly. It dried and formed the concealment layer (it may be called an address surface), and obtained the information concealment sheet sample for a test.
Using the obtained test information hiding sheet sample, (1) hiding properties and (2) adhesive strength were evaluated by the following test methods, and the results are shown in Table 1.

(Test method):
(1) Concealment Characters (MS Gothic 11 points) randomly selected by a laser printer (model name: LP9600S, manufactured by Seiko Epson) are printed on the adhesive layer (concealed surface) (L ^* = 23). The sample is cut into a width of 210 mm and a length of 296 mm. The printed adhesive layer is turned inside and folded in two, and a pressure of 7 MPa is applied and crimped to obtain an evaluation sample. The obtained sample was placed on a desk, and the visibility of concealed characters was evaluated according to the following criteria in that state.
◎: Not visible at all ○: Not visible at all (no problem in practical use)
△: The contents can be visually recognized to some extent if you look closely (practical problems)
×: Readable

(2) (Adhesive strength)
A sample is prepared by cutting to a width of 100 mm and a length of 270 mm, folding the sample into two with the adhesive layer (concealed surface) of the sample inside, applying a pressure of 7 MPa, and bonding the adhesive layers (concealed surfaces) to each other. The peel adhesive strength was measured by 90 ° T-type peel using an autograph AGS50 (manufactured by Shimadzu Corp.) according to the test method JISK6854.
Similarly, a sample was prepared by cutting to a width of 100 mm and a length of 270 mm, bent into two with the concealing layer (addressed surface) of the sample inside, and subjected to pressure bonding by applying a load of 7 MPa, and the concealing layer (addressed) The adhesive strength between the surfaces) was measured by 90 ° T-type peeling using an autograph AGS50 (manufactured by Shimadzu Corporation) in accordance with the test method JISK6854.

  The concealed surface was operated in the same manner as in Example 1, and the address surface was tested in the same manner as in Example 1 except that the titanium oxide fine particles used in Example 1 were changed to 14.2 parts by mass of solid content. A cover sheet sample was made. And it evaluated similarly to Example 1 and shows a result in Table 1.

  The concealed surface was operated in the same manner as in Example 1, and the address surface was tested in the same manner as in Example 1 except that the titanium oxide fine particles used in Example 1 were changed to 21.3 parts by mass. A cover sheet sample was made. And it evaluated similarly to Example 1 and shows a result in Table 1.

  The concealed surface was operated in the same manner as in Example 1, and the address surface was tested in the same manner as in Example 1 except that the titanium oxide fine particles used in Example 1 were changed to 28.4 parts by weight of solid content. A cover sheet sample was made. And it evaluated similarly to Example 1 and shows a result in Table 1.

Comparative Example 1

The concealing surface was operated in the same manner as in Example 1, and the addressing surface was operated in the same manner as in Example 1 except that the titanium oxide fine particles used in Example 1 were not used. .
The evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 2

The concealing surface was operated in the same manner as in Example 1 except that the titanium oxide fine particles used in Example 1 were made to have a solid content of 10.65 parts by mass, and the addressing surface did not use the titanium oxide fine particles used in Example 1. A test information hiding sheet sample was prepared in the same manner as in Example 1 except for the above.
Then, evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 3

The concealed surface was operated in the same manner except that the titanium oxide fine particles used in Example 1 were not used, and the address surface was operated in the same manner as in Example 1 except that the titanium oxide fine particles used in Example 1 were not used. A test information hiding sheet sample was made.
The evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 4

The concealing surface was operated in the same manner as in Example 1 except that the titanium oxide fine particles used in Example 1 were made to have a solid content of 28.4 parts by mass, and the addressing surface did not use the titanium oxide fine particles used in Example 1. Except that, a test information hiding sheet sample was prepared in the same manner as in Example 1.
The evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 5

The concealing surface does not use the fine titanium oxide particles used in Example 1, but instead kaolin (trade name: HYDRACOTE-A (manufactured by Nissei Kyoben Co., Ltd.)) is previously dispersed in ion-exchanged water to a solid content of 50% by mass. Except that the dispersion was stirred and mixed so as to be 14.3 parts by mass (7.1 parts by mass of kaolin solid content), and the destination surface was the titanium oxide used in Example 1. A test information hiding sheet sample was prepared in the same manner as in Example 1 except that the fine particles were not used and the content of kaolin solid content was 7.1 parts by mass.
The evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 6

The concealing surface does not use the titanium oxide fine particles used in Example 1, but instead of a dispersion in which calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd.) is dispersed in ion-exchanged water at a solid content of 50% by mass in advance. The same operation as in Example 1 was performed except that the mixture was stirred and mixed so as to be 3 parts by mass (calcium carbonate solid content: 7.1 parts by mass), and the address surface did not use the titanium oxide fine particles used in Example 1, Instead, a test information hiding sheet sample was prepared in the same manner as in Example 1 except that the solid content of calcium carbonate was 7.1 parts by mass.
The evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

From Table 1, the information concealment sheets of Examples 1 to 4 are excellent in concealability, and the adhesive layers (concealed surfaces) can be releasably adhered, and the concealment layers (address surfaces) can be firmly adhered and re-peeled. Since it disappears, it turns out that it is applicable also to a W-fold type | mold crimping postcard.
On the other hand, from Table 2, the information concealment sheets of Comparative Examples 1 to 6 are all inferior in concealment property, and the concealment layers (address surfaces) are firmly adhered and cannot be re-peeled, but the adhesive layer (containment surface) Some of them can be releasably bonded (Comparative Example 1), but the adhesive strength is poor and they may open before the recipient receives (Comparative Examples 2, 4, 6). It can be seen that there are some which are too strong and cannot be peeled off (Comparative Examples 3 and 5).

  The information concealment sheet of the present invention is detachably bonded in an overlapping manner so that the concealment information cannot be seen from the outside, and the recipient can read the concealment information by peeling the overlapping surface again. Is an information concealment sheet that has high concealing effect (prevention of see-through effect), good visibility of information entered on the concealment layer, and is inexpensive, and is temporarily bonded, but can be easily peeled off if necessary Folding sheets with facing sides that can be spread, overlapping sheets, for example, personal information such as confidential postcards such as information concealment sheets, notices, and cards, or concealment sheets for various information such as print information and print information Since it can be used, the industrial utility value is high.

The surface expansion | deployment figure of the trifold postcard of this invention. The back surface expanded view of the postcard of FIG. XX sectional drawing of FIG. The state explanatory view at the time of folding the postcard of FIG. The surface expansion | deployment figure of the bifold postcard of this invention. FIG. 6 is a rear development view of the postcard of FIG. 5. The state explanatory view at the time of folding the postcard of FIG. The surface expanded view of the partial bifold postcard of this invention. The back surface expanded view of the postcard of FIG. The state explanatory view at the time of folding the postcard of FIG. (A) is a surface development view of a new type of W-fold type crimping postcard, and (b) is a state explanatory diagram when folding the (W) type W-folding crimped postcard.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tri-fold postcard 11 Double-fold postcard 21 Partially double-fold postcard 31 W-fold type | mold crimping postcard 2 Base sheet 3, 3a, 3b, 3c Folding line 4 Visible information, such as an address 5 Concealment information printing 6 For peeling concealment information support Adhesive layer 7 Hiding layer

Claims (6)

Concealment information carrying adhesion that does not adhere to a predetermined portion of the overlapping surface of the sheet in a normal state, but allows the overlapping surfaces to contact each other and apply a predetermined pressure so that the overlapping surfaces can be peeled off. Forming a layer, forming a concealment layer on the predetermined surface on the opposite side of the overlapping surface so that the concealment information cannot be read through the outside, and enter visible information on the concealment layer as necessary In the information concealment sheet
An information hiding sheet having excellent hiding performance, wherein the adhesive layer and the hiding layer are formed by blending a predetermined amount of high refractive index titanium oxide fine particles. The said concealing layer is formed using the pressure sensitive adhesive which adhere | attaches the concealing layers and gives the predetermined | prescribed pressure, and adheres the overlapping surfaces firmly. Information hiding sheet of description. The high refractive index titanium oxide fine particles are mixed in an amount of 5 to 50 parts by mass with respect to 100 parts by mass of the adhesive layer and the adhesive base material (solid content) of the pressure-sensitive adhesive. Information hiding sheet. The information concealment sheet according to any one of claims 1 to 3, wherein a predetermined amount of a colorant having a lightness L ^{* of} 0 to 50 is blended in the adhesive layer and / or the pressure-sensitive adhesive. The information hiding sheet according to any one of claims 1 to 4, wherein the coloring material is a black or blue dark dye or pigment. The information concealment sheet according to any one of claims 1 to 5, wherein the adhesive base is a natural rubber-based aqueous emulsion type adhesive base.

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