JPH0348037B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a secret document preparation method for obtaining a latent image made of an electron-accepting color developer transferred onto a plain paper surface. Traditionally, creating secret documents involved exposing them. This is when you write pictures or letters on plain paper with a specific solution and let it dry. After the writing, it becomes difficult to see, but when you burn the plain paper with fire, the pictures and letters will reappear. For example, it is caused by the blue color caused by cobalt chloride. Color development, blackening due to carbonization of cellulose with dilute sulfuric acid, and blackish brown due to squeezed orange juice. However, this roasted product shows discoloration even before it is roasted, and does not meet the intended requirements. On the other hand, JP-A-56-75658 discloses a recording medium for producing secret documents which obtains a magnetic latent image on a magnetic recording sheet. 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. The present inventors conducted research to solve the above-mentioned drawbacks, and as a result, the present inventors discovered that the present invention is composed of an electron-accepting color developer and waxes, and has an electron-accepting color developer of 5 to 50% by weight based on the waxes. dissolve or disperse the agent,
By overlaying and pressing the transfer sheet for secret document creation, which has a plain paper transfer type recording layer printed on the back side of the support by hot-melt printing, with the plain paper, the electron-accepting manifestation transferred to the plain paper surface can be seen. This invention provides a method for creating a secret document that obtains a latent image made of colorants. 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. A wax layer containing an electron-accepting color developer on the coated surface is transferred onto a plain paper surface to obtain a latent image. The obtained latent image is colored by spraying a solution of an electron-donating colorless dye dissolved in a volatile organic solvent, and can be identified as a colored printed image. However, the latent image cannot be visually discerned unless the colorless dye solution is sprayed. The plain paper transfer type recording layer of the present invention is composed of an electron-accepting color developer and waxes. The color developer is dissolved or dispersed in the waxes in an amount of 5 to 50% by weight, so that it can be transferred to the plain paper surface extremely efficiently. It can be transferred. More preferably, it is 10 to 30 weight percent. Outside the range specified above, that is, below 5% by weight, there is a drawback that when the volatile solvent of the electron-donating colorless dye is sprayed, it does not exhibit sufficient color density and is difficult to identify. On the other hand, if it exceeds 50% by weight, it is not preferable because the developer becomes too plastic after dissolving in the wax and is cooled, resulting in the developer itself becoming sticky, or in the case of dispersion, the dispersion stability is poor. The waxes used in the present invention include animal-based waxes such as beeswax, spermaceti wax, Chinese wax, and lanolin, plant-based waxes such as candelilla wax, carnauba wax, wood wax, rice wax, and sugarcane wax, and montan waxes. Tsukusu,
Mineral waxes such as ozokerite, ceresin, and lignite waxes, petroleum waxes such as paraffin waxes and microcrystalline waxes, modified waxes such as montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives, and caster waxes. Hydrogenated waxes such as wax and opal wax, low molecular weight polyethylene and its derivatives, synthetic waxes such as acra wax and distearyl ketone, caproic acid amide, caprylic acid amide, pelargonic acid amide, capric acid amide, lauric acid amide, tridecylic acid Fatty acid amide waxes such as amide, myristamide, ethylene bisstearamide, caproleic acid amide, myristoleic acid amide, oleic acid amide, elaidic acid amide, linoleic acid amide, erucic acid amide, ricinoleic acid amide, linoleic acid amide Examples include those selected from unsaturated fatty acid amides such as. And these can be used alone or in combination. Regarding the exemplified waxes, those that dissolve the color developer can be used as a dissolving system, and those that do not dissolve can be used as a dispersing system, as appropriate. The color developer used in the present invention includes acid clay, activated clay, inorganic acidic substances such as kaolin, bentonite, and attapulgide, substituted phenols, phenol-formalin condensates, alkyl-substituted phenol-formalin condensates, and aryl-substituted phenol-formalin. Phenolic color developers such as condensates and their metal salts, benzoic acid, chlorobenzoic acid, toluic acid, salicylic acid, 5-tert-butylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,
Salicylic acid color developers such as 5-di(α-methylbenzyl)salicylic acid and metal salts thereof can be used alone or in combination. The colorless dyes used in the present invention include, for example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-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
Triarylmethane-based compounds such as -dimethylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 3,3-bis(9-ethylcarbazol-3-yl)-5-dimethylaminophthalide, etc. Compound. Dimethylmethane compounds such as 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenylleucoauramine, rhodamine B-anilinolactam , 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6,8-dimethylfluorane, 3-
diethylamino-7-methylaminofluorane,
3,7-diethylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3
- xanthene compounds such as diethylamino-chloroethylmethylaminofluorane, thiazine compounds such as benzoylleucomethylene blue and p-nitrobenzylleucomethylene blue, 3-methyl-spirodinaphthopyran, 3-ethyl-spirodinaphthopyran, 3 , 3'-dichlorospirodinaphthopyran, 3-propyl-spirodibenzopyran, and other spiro compounds can be used alone or in combination. The transfer sheet for producing secret documents according to the present invention can be obtained by printing on a part or the entire surface of a support using a hot-melt printer commonly used for reverse carbon printing. In addition to the waxes and color developer according to the present invention, nonvolatile solvents, pigments, binders, surfactants, and the like may be appropriately added to improve pressure sensitivity, whiteness, adhesion, and stability. However, it is clear that the additives are not limited to these exemplified additives. As the recording layer according to the present invention, paper is mainly used, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of a combination of these may also be used. In particular, it is preferable to use an embossed sheet as a latent image during transfer. Hereinafter, the present invention will be specifically explained with reference to Examples. Note that "parts" indicate parts by weight. Example 1 30 parts of p-phenyl-phenol powder with a melting point of 78
℃ erucic acid amide (trade name Diamond L-
200 (manufactured by Nippon Kasei Co., Ltd.) was dissolved under heat, and this was printed solidly on a base paper with a basis weight of 40 g/m ² using a hot-melt printing machine at a coating weight of 8 g/m ² . . The solid printed side of the obtained transfer sheet was stacked facing the embossed plain paper, and a ballpoint pen was used to print on the non-printed side of the transfer sheet. After printing,
The printed image on the embossed plain paper could not be identified. Subsequently, when an acetone solution containing 10% by weight of crystal violet lactone was sprayed onto the transfer area, a clear printed image with a blue color could be discerned. Examples 2 to 7 and Comparative Examples 1 to 3 Melting point 80°C in place of erucic acid amide in Example 1
lauric acid amide (trade name: Diamond Y,
(manufactured by Nippon Kasei Co., Ltd.), and the same experiment was conducted using the combinations with the color developer shown in the weight percentages shown in Table 1.

[Table] ◎＞○＞△＞×
Example 8 30 parts of finely powdered zinc 3,5-di-tert-butylsalicylate was uniformly dispersed in 70 parts of paraffin wax having a softening point of 70°C when heated, and this was dispersed with a basis weight of 40°C.
Solid printing was performed using a hot-melt printing machine on a base paper of 8 g/m ² at a coating weight of 8 g/m ² . The solid printed surface of the obtained transfer sheet was stacked facing the embossed plain paper, and a ballpoint pen was used to print on the non-printed surface of the transfer sheet. After printing, the printed image could not be identified on the embossed transfer portion on the plain paper. Next, we applied a desensitizing checker (product name: Mitsubishi NCR paper desensitizing checker), which is used for pressure-sensitive paper desensitizing ink, in which a blue colorless dye was dissolved in a solvent and placed in a cylinder together with chlorofluorocarbon gas. , manufactured by Mitsubishi Paper Mills Co., Ltd.), a clear blue printed image could be discerned.

Claims (1)

[Claims] 1 Consists of an electron-accepting color developer and waxes,
5 to 50% by weight of an electron-accepting color developer is dissolved or dispersed in the wax, and this is printed on the back side of the support by hot melt printing to have a plain paper transfer type recording layer. A secret document creation method that obtains a latent image made of an electron-receptive color developer transferred onto the plain paper surface by stacking and pressing a transfer sheet for secret document creation and plain paper.