JPS58209588A - Transfer sheet for preparation of secret document - Google Patents

Abstract

PURPOSE:To obtain a transfer sheet free of discoloration by a method in which micro capsules having core materials formed by dissolving and dispersing a developer or a colorless dye in a solvent are printed or coated on the back of a supporter. CONSTITUTION:Micro capsules having core materials formed by dissolving or dispersing 5-50wt% an electron-accepting developer or 2-20wt% an electron donative colorless dye in a non-volatile solvent are printed or coated on the back of a supporter to form a transfer type recording layer for usual papers. By this, an objective transfer sheet is obtained. The transfer sheet thus obtained is overlapped on an usual paper and a pressure printing is applied to the uncoated surface of the transfer sheet to obtain a latent picture consisting of the developer or colorless dye, transferred to the surface of the usual paper. A solution of the colorless dye or the developer in a volatile solvent is then sprayed onto the laten picture to cause it to be colored, thereby permitting it to be distinguished as a colorless print picture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to secret document 1 "Complete Transfer Sheet" which can obtain a latent image made of an electron-accepting color developer or an electron-donating colorless dye transferred onto a plain paper surface. It is.

In the past, there was something called falsification when creating secret documents. This is when you write pictures or letters on plain paper with a specific solution and let it dry, it becomes difficult to see after writing, but if you burn the plain paper with fire, the pictures or letters will reappear (for example, chloride powder). There are blue colors caused by rut, black colors caused by carbonization of cellulose caused by dilute sulfuric acid, and dark brown colors caused by squeezed orange juice.

However, the roasted waistcoat shows discoloration even before it is roasted, and does not meet the intended requirements.

On the other hand, Japanese Unexamined Patent Publication No. 56-75659 discloses a secret document recording medium that produces a magnetic latent image on a magnetic TK notebook. In this method, pressure-sensitive paper, a magnetic recording sheet, and a high magnetic permeability material are sequentially laminated, and a magnetic latent image is obtained by pressing the pressure-sensitive paper with a magnetic pen. This method has the advantage that magnetic recording can be performed while viewing a visible image using pressure-sensitive paper during recording, but it is complicated by the use of a magnetic pen and magnetic powder.

As a result of research to solve the above-mentioned drawbacks, the present inventors have developed microcapsules whose core material is an electron-accepting color developer or an electron-donating colorless dye dissolved or dispersed in a non-volatile solvent. Coated paper with a plain paper transfer type recording layer printed or coated on the back side of the support is pressed against plain paper, and an electron-accepting chicken coloring agent or an electron-donating coloring agent is transferred to the plain paper surface. To provide a transfer sheet for producing secret documents that can obtain a latent image made of colorless dye.

An object of the present invention is to overlap the above-mentioned transfer sheet for creating secret documents with plain paper and perform pressure printing from the non-coated surface of the transfer sheet using pen pressure from a ballpoint pen or the like, and to simultaneously print on the non-coated surface of the transfer sheet. The microcapsules on the coated surface are destroyed, and a nonvolatile solvent in which an electron-accepting color developer or an electron-donating colorless dye is dissolved or dispersed is transferred onto the plain paper surface to obtain a latent image. The obtained latent image is colored by spraying a solution of an electron-donating colorless dye or an electron-accepting color developer dissolved in a volatile organic solvent, and can be identified as a colored printed image. However, unless the colorless dye solution or the blood-tinting agent is sprayed, a@ cannot be visually identified.

For the electron-accepting color developer used in the present invention, dissolving or dispersing 5 to 50 percent by weight in a nonvolatile solvent and microcapsulating it as a core material is good for transferability to plain paper, and has been known for a long time. 20 to 40 double stitch percentage is preferred.

The reason for the above definition is that if the density is lower than the specified range, the density of the fQ printed image will be low, and if it is higher than the range, the viscosity of the core material will increase, resulting in a disadvantage of poor transferability.

The colorless electron-donating dye used in the present invention can be dissolved and dispersed in a non-volatile solvent at 2 to 20 percent by weight and then micro-encapsulated as a core material for better transferability onto plain paper. Approximately 5 to 15 percent above weight.

By the way, the electron-accepting color developer-owned microcapsules used in the present invention can be produced using various microencapsulation methods, such as the complex core method, the industry method, the 1 nsitu method, and the spray method. dry method,
It can be used as appropriate, such as in-liquid curing method.

The method for coating or printing on plain paper depends on the microcapsules formed, for example, in the case of an aqueous dispersion of microcapsules, aqueous coating using an air knife coater, dehydration and substituting an organic solvent, or powder coating. According to the present invention, it is possible to select a method as appropriate, such as a method of gravure printing or flexible printing with an organic solvent as body capsules, or a method of powdering the microcapsules and mixing them with waxes for hot melt printing. Electron-accepting color developers used in E' include substituted phenols, phenol-formalin condensates,
Phenolic color developers and their metal salts such as alkyl-substituted phenol-formalin condensates and aryl-substituted phenol-formalin condensates, benzoic acid, chlorobenzoic acid, toluic acid, salicylic acid, 5-tert-butylsalicylic acid, 3.5- Di-tert-butylsalicylic acid, 3.5-
Salicylic acid-based graying agents such as di(α-methylbenzyl)salicylic acid and metal salts thereof can be used alone or in combination.

As the nonvolatile solvent used in the present invention, alkylnaphthalene, chlorinated paraffin, diarylethane, alkyldiphenyl, aromatic ester, aliphatic ester, etc. can be used alone or in combination.

Examples of the electron-donating colorless dyes that can be used in the present invention include 3,3-bis(p-dimethylaminophenyl)-6-dimethylamino-7thallide, 33-bis(p-dimethylaminophenyl)phthalide, , 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-:3-(2-methylindol-3-yl)
Phthalide, 3-(p-dimethylaminophenyl)-3-
(2-phenylindol-3-yl)tutaride, 33
-Triarylmethane compounds such as bis(9-ethylcarbasol-3-yl)-5-dimethylaminophthalide. 4. Dimethylmethane compounds such as 4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoauramine, N-2,4,5-11J 00 phenylleucoauramine, rhodamine B-ani linolactam, 3-dimethylamine-7-medoxyfluorane, 5-diethylaminol-chlorofluorane,
3-diethylamito-6,8-dimethylfluorane,
3-diethylamino-7-methylaminofluorane, 6
fudiethylaminofluorane, 3-diethylamino-
Gysante such as 7-cybenzylaminofluorane, 3-genalamino-chloroethylmethylaminofluorane, Ik-based compounds, thiazine-based compounds such as benzoylleucomethylene blue, p-nitrobenzylleucomethylene blue, 3-methyl-spirodi Color formers such as spiro compounds such as naphthopyran, 3-ethyl-spirodinaphthopyran, 33'-dichlorospirodinaphthopyran, and 3-glopyru-spirodibenzopyran can be used alone or in combination.

Electron-accepting color developer-containing microphone according to the present invention [In addition to cocapsules or electron-donating colorless dyes, stilts, binders, dispersants, etc. can be added as appropriate, but the additives are limited to these exemplified additives. It is clear that it is not a thing.

Although paper is mainly used as the support for forming the recording layer according to the present invention, various nonwoven fabrics, Zolastra, Tsukufilm, synthetic paper, metal foil, etc., or composite sheets made by combining these may also be used. In particular, it is desirable to use an embossed sheet as a latent image during transfer.

Hereinafter, the present invention will be specifically explained by giving one example. Note that "parts" and percentages indicate parts by weight and percentages by weight, respectively.

Example Microcapsules containing para-phenyl-phenol-formalized 7JfLJ fat were prepared as follows.

10% aqueous solution of ethylene-maleic anhydride copolymer
0 parts of urea, 1 part of resorcinol, and 200 parts of water were prepared into a mixed solution, and the pH was adjusted to 3.5 using a 20% aqueous sodium hydroxide solution.

60 parts of para-phenyl-phenol-formalin resin was dissolved in 140 parts of Hysol 5ASN-296C diarylethane solvent (manufactured by Nippon Petrochemical Co., Ltd.) to prepare a color developer solution. This color developer solution is emulsified and dispersed in the above mixed aqueous solution,
When the oil droplets reached a size of 5 to 6 μm, 25 parts of a 37% formalin aqueous solution was added, and the temperature of the system was maintained at 55 C while stirring. After reacting for 2 hours, the system was cooled and the pH of the system was adjusted to 9.5 to complete encapsulation.

48 parts of para-phenyl-phenol-formalin resin-containing capsules (as solid content) prepared as above, 120 parts of wheat starch, and 200 parts of 10% oxidized starch were added to the coating liquid so that the solid content was 20%. Water was added and mixed and stirred to obtain an aqueous dispersion coating liquid. This aqueous dispersion coating liquid has a basis weight of 4
A Mayer bar was applied to 8μ'' base paper-F at a density of 69/rl.

The obtained transfer sheet for creating secret documents was stacked with the coated side facing the embossed plain paper, and printing was performed on the non-coated side of the transfer sheet using a ballpoint pen. After printing, the printed image could not be identified on the embossed transfer portion on the plain paper.

Next, desensitizing Chenoka (product name: Mitsubishi NC), which is used for so-called desensitizing ink for pressure-sensitive paper, was applied to the transfer area by dissolving a blue-based colorless dye in a solvent and placing it in a cylinder together with chlorofluorocarbon gas.
When I sprayed R desensitization checker (manufactured by San-ai Paper Co., Ltd.), I was able to discern a clear printed image with a blue color.

Claims (1)

[Claims] A plain paper transfer type recording layer comprising microcapsules whose core material is an electron-accepting color developer or an electron-donating colorless dye dissolved or dispersed in a non-volatile solvent, printed or coated on the back side of a support. A transfer sheet for creating secret documents that can obtain a latent image made of an electron-accepting color developer or an electron-donating colorless dye transferred to the surface of the plain paper by stacking coated paper and plain paper and pressing them together. .