JPH022437B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a transfer sheet for creating secret documents that can obtain a latent image made of a heat-sensitive recording material 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. As a result of research to solve the above-mentioned drawbacks, the present inventors have discovered that a colorless dye is coated on the back side of the support, an electron-accepting color developer that develops color when heated together with the dye, and a total amount of the dye and color developer. A coated paper coated with a transfer-type heat-sensitive recording layer consisting of three components of waxes having a weight percent of 100 to 700% of To provide a transfer sheet for creating secret documents that can transfer a latent image onto a plain paper surface. 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 heat-sensitive recording layer on the coated surface is transferred onto the plain paper surface to obtain a latent image. The obtained latent image can be colored by a heating means such as a dryer or lighter and can be identified as a colored printed image, but the latent image cannot be visually identified unless a heating means is used. The transfer type heat-sensitive recording layer of the present invention is composed of three components: a colorless dye, an electron-accepting color developer, and a wax, and the total amount of the two components is 100 to 700% by weight relative to the colorless dye and the color developer. By mixing and dispersing a certain amount of wax, it is possible to transfer the image onto plain paper very efficiently. By the way, some thermal paper that is currently widely available has the three components of the present invention as its main components, but when the ratio of waxes specified above is used, it becomes pressure sensitive and there is a risk that scum will not form on the thermal head. Accumulating,
This does not meet the desired requirements for thermal paper, such as a decrease in print density. However, waxes of 100 to 700 weight percent, which are not suitable for thermal paper, can facilitate transfer to plain paper, which is the object of the present invention. Outside the specified range, there was no transferability below the lower limit of 100% by weight, and the portion of plain paper that appeared to be printed was unreadable even when heating means was applied. On the other hand, above the upper limit of 700% by weight, transferability is possible, but when a heating means is added, the color reaction between the colorless dye and the color developer is too low to be read due to the dilution effect of waxes. . The waxes used in the present invention include animal-based waxes such as mitsuro, spermaceti wax, Chinese wax, and lanolin; plant-based waxes such as candelilla wax, carnauba wax, wood wax, rice wax, and sugarcane wax; Montan wax,
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. Desirably, among the above waxes, an amide wax and other waxes are used in combination. The above-mentioned waxes are preferably used in an emulsion type or after being dispersed in a characteristic manner together with an aqueous dispersant using a ball mill, an attritor, or the like. However, the colorless dye and color developer described later may be dissolved in the same or different waxes, and then finely dispersed using the above-mentioned means. The colorless dye and color developer which are other components of the present invention are illustrated below. For colorless dyes, for example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl) phenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3-(p- dimethylaminophenyl)-3-(2-phenylindole-
Triarylmethane compounds such as 3-yl)phthalide and 3,3-bis(9-ethylcarbazol-3-yl)-5-dimethylaminophthalide.
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-
xanthene compounds such as diethylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, and 3-diethylamino-chloroethylmethylaminofluorane; thiazine compounds such as benzoylleucomethylene blue and p-nitrobenzylleucomethylene blue; 3 -Methyl-spirodinaphthopyran, 3-ethyl-spirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran,
Coloring agents such as spiro compounds such as 3-propyl-spirodibenzopyran can be used alone or in combination. Regarding color developers, examples of organic acids include boric acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, benzoic acid, stearic acid, gallic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, 0- Mention may be made of hydroxybenzoic acid, m-hydroxybenzoic acid, and 2-hydroxy-p-toluic acid. In addition, phenolic substances include 3,5-xylenol, thymol, p-tert-butylphenol, 4-hydroxyphenol, and methyl-4-
Hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechol, resorcinol, hydroquinone, 4-tert
-Octylcatechol, 4,4'-sec-butylidenephenol, 2,2-dihydroxydiphenyl, 2,2-methylenebis(4-methyl-6-
tert-butylphenol), 2,2-bis(4'-hydroxyphenyl)propane (also known as bisphenol A), 4,4'-isopropylidene-bis(2-
tert-butylphenol), 4,4'-sec-butylidene diphenol, pyrogallol, phloroglucin, and phloroglucin carboxylic acid. The transfer sheet for producing confidential documents according to the present invention can be produced by coating the entire surface of the support using a general coater such as an air knife coater as an aqueous dispersion coating solution, or by coating the support using flexographic printing or the like. You can choose any way you want to print on a part of the image. When preparing the coating solution according to the present invention, binders, pigments, desensitizers, etc. can be added as appropriate depending on various coaters and printing machines. However, it is clear that the additives are not limited to these exemplified additives. As the support for forming the coating layer according to the present invention, paper is mainly used, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., composite sheets of combinations of these, and sheets embossed with each of these can also be used. . Hereinafter, the present invention will be specifically explained with reference to Examples. Note that "parts" indicate parts by weight. Example 1 Various dispersions were prepared as follows. (1) Dispersion A A dispersion obtained by pulverizing and dispersing 150 parts of 3-diethylamino-6-methyl-7-phenylaminofluorane together with 150 parts of 5% hydroxyethyl cellulose and 150 parts of water in a ball mill for 24 hours. (2) Dispersion B A dispersion obtained by pulverizing and dispersing 150 parts of bisphenol A in a ball mill for 24 hours together with 150 parts of 5% hydroxyethyl cellulose and 150 parts of water. (3) Dispersion C A dispersion obtained by pulverizing and dispersing 150 parts of stearamide with 300 parts of 5% hydroxyethyl cellulose and 210 parts of water in a ball mill for 72 hours. A coating solution was prepared as follows using the dispersion prepared above. However, it was expressed as dry weight. Dispersion A 3 parts by weight Dispersion B 15 parts by weight Dispersion C 27 parts by weight Here, Dispersion C is the total amount of Dispersions A and B.
Equivalent to 150% by weight. Apply the prepared coating solution onto base paper with a basis weight of 40 g/ ^m2 .
A transfer sheet having ^a colorless coating layer was obtained by applying the coating using a Mayer bar so as to give a colorless coating layer. The coated side of the resulting transfer sheet was stacked facing the embossed plain paper, and a ballpoint pen was used to print on the non-coated side of the transfer sheet. The printed image could not be identified on the transfer portion on the plain paper that was embossed after printing. Subsequently, when the transfer area was heated with a dryer, a clear printed image of black color could be discerned. Examples 2 to 6 and Comparative Examples 1 to 2 Example 1 was prepared by changing the weight of each dispersion liquid in Example 1.
I conducted an experiment in the same way. The results are summarized in Table 1.

[Table] Examples 7 to 10 and Comparative Examples 3 to 4 Among the various dispersions of Example 1, Dispersion C was used as a paraffin wax emulsion (Mobilcer C:
An experiment was carried out in the same manner as in Example 1 except that the same amount of dispersion liquid (manufactured by Mobil Oil) was used in combination (referred to as dispersion C'). The results are summarized in Table 2.

【table】

Claims (1)

[Claims] 1. Transfer-type heat-sensitive material consisting of three components on the back side of a support: a colorless dye, an electron-accepting color developer that develops color when heated with the dye, and a wax having 100 to 700 percent by weight of the total amount of the dye and color developer. A coated paper coated with a recording layer, characterized in that a latent image can be transferred to the plain paper surface by stacking the coated side of the coated paper on plain paper and pressing from the non-coated side. Transfer sheet for document creation.