JPH0356193B2 - - 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 an ultraviolet absorber on a plain paper surface that is distinguishable under a fluorescent inspection lamp in a dark place, and a recording method thereof. It is something.

In the past, the creation of secret documents involved exposure. If you write pictures or letters on plain paper with a specific solution and let it dry, it becomes difficult to identify after writing, but when you heat the plain paper, the pictures or letters will appear again.For example, blue coloring caused by cobalt chloride, Blackening occurs due to carbonization of cellulose with dilute sulfuric acid, and blackish brown coloring occurs due to squeezed orange juice.

However, this method of roasting cannot meet the intended requirements because discoloration occurs even before roasting.

On the other hand, JP-A-56-75658 discloses a recording medium for producing secret documents that produces a magnetic latent image on a magnetic recording sheet. This has the advantage that pressure-sensitive paper, a magnetic recording sheet, and a high magnetic permeability material are sequentially laminated, and magnetic recording can be performed while viewing a visible image using the pressure-sensitive paper with a magnetic pen. There is complexity.

As a result of research to solve the above-mentioned drawbacks, the present inventor has discovered that a plain paper transfer type film containing microcapsules containing a solution of an ultraviolet absorber dissolved in a non-volatile vehicle and waxes on a support. To provide a transfer sheet for creating secret documents, which is coated with a recording layer.

Furthermore, there is provided a recording method for a transfer sheet for creating secret documents, which comprises coating a support with a plain paper transfer type recording layer comprising microcapsules containing a solution of an ultraviolet absorber dissolved in a non-volatile vehicle and waxes. In this method, by overlapping the plain paper transfer type recording layer side and plain paper and printing under pressure from the non-plain paper transfer type recording layer side, a latent image of the ultraviolet absorber is formed on the plain paper surface, and it is possible to print in a dark place. The present invention provides a recording method for a transfer sheet for creating secret documents in which the latent image can be identified under a fluorescent inspection lamp.

It is an object of the present invention to provide a method for printing on the non-coated surface of the transfer sheet when the above-mentioned transfer sheet for creating secret documents and plain paper are overlapped and pressure printing is performed on the non-coated surface of the transfer sheet using pen pressure from a ballpoint pen or the like. At the same time, the microcapsules (hereinafter referred to as UV absorber-containing capsules) containing a solution of the UV absorber dissolved in a non-volatile vehicle on the coated surface are destroyed, and the UV absorber is transferred to the plain paper surface. It is used to obtain a latent image on plain paper. The obtained latent image is indistinguishable during normal handling, that is, in a visible state, and can only be confirmed by using a fluorescent inspection lamp.

That is, a transfer sheet for creating a secret document is required by the provider of the sheet, and when used by a user without any prior knowledge, the user will not notice the latent image printed under pressure on the plain paper surface. This is because the latent image cannot be visually identified. on the other hand,
The donor can read the latent image in a dark room using a fluorescent inspection light. As a result, confidential documents can be protected from being known to others.

By the way, various microencapsulation methods such as complex coacervation method, interfacial polymerization method, and
Depending on the properties of the UV absorber itself, it can be used depending on the properties of the UV absorber itself, such as in-situ method, spray drying method, and liquid curing method.
There are no difficulties.

In the combination of ultraviolet absorber capsules and waxes, which are components of the plain paper transfer type recording layer of the present invention,
The use of waxes has the advantage of being able to transfer ultraviolet absorbers to the surface of plain paper very efficiently. For efficient transfer, the amount of wax used is preferably 5 to 100 percent by weight based on the solid content of the capsule.

The ultraviolet absorbers of the present invention include, for example, 2,4-dihydroxybenzophenone, 2-hydroxy-4
-methoxybenzophenone, 2-hydroxy-4
-n-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,
2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4 -Methoxy-2'-carboxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-4-oxybenzylbenzophenone, 2-hydroxy-4-chlorobenzophenone, 2 -Hydroxy-5-chloro-benzophenone, 2-hydroxy-4-methoxy-4-methylbenzophenone, 2-hydroxy-4-n-
Heptoxybenzophenone, 2-hydroxy-
3,6-dichloro-4-methoxybenzophenone, 2-hydroxy, 3,6-dichloro-4-ethoxybenzophenone, 2-hydroxy-4-
(2-hydroxy-3-methylacryloxy)
Benzophenone UV absorbers such as propoxybenzophenone; 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-
Hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-4' -octoxyphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-tert-butyl) -5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5-
methoxyphenyl)benzotriazole, 2-
(2'-hydroxy-5-ethoxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-tertiary-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tertiary) Benzotriazole UV absorbers such as -amyl phenyl) benzotriazole; phenyl salicylate, p-octylphenyl salicylate, p-tert-butylphenyl salicylate, carboxyphenyl salicylate, methyl phenyl salicylate, dodecyl phenyl salicylate, etc. Salicylic acid phenyl ester ultraviolet absorber; 2-ethylhexyl-2-cyano-3,
Examples include cyanoacrylate ultraviolet absorbers such as 3'-diphenyl acrylate and ethyl-2-cyano-3,3'-diphenyl acrylate. Among these exemplified ultraviolet absorbers, those that are visible because they are colored can be used by coloring the background of plain paper to which they are transferred in the same color. Regarding the UV absorber, nonvolatile oils such as vegetable oil, animal oil, mineral oil, synthetic oil, etc. can be used as the vehicle, and the amount of the UV absorber is 0.2 to 10% by weight dissolved in the vehicle. Preferably it is 0.5 to 5 weight percent. Waxes used in combination with UV absorbers 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 wax. Mineral waxes such as tux, 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; Hydrogenated waxes such as castor 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, Fatty acid amide waxes such as tridecylic acid amide, myristic acid amide, ethylene bisstearic acid amide, caproleic acid amide, myristoleic acid amide, oleic acid amide, elaidic acid amide, linoleic acid amide, erucic acid amide, ricinoleic acid amide, linolenic acid amide Examples include those selected from unsaturated fatty acid amides such as acid amides. And these can be used alone or in combination.

The transfer sheet for creating secret documents according to the present invention can be produced by coating the entire surface of the support with a general coater such as an air knife coater as an aqueous dispersion coating solution, or by spray-drying microcapsules, etc. After drying, if necessary, mix uniformly with powdered microcapsules at the melting temperature of wax to form a coating solution, and print on a part of the support using an ordinary carbon printing machine. You can choose to.

When preparing the coating liquid according to the present invention, a liquid property improver can be added depending on various coaters and printing machines. Examples include thickeners that keep the viscosity constant and surfactants that improve dispersibility, but it is clear that they are not limited to these.

Paper is mainly used as the support for forming the coating layer according to the present invention, but various nonwoven plastic films, synthetic papers, metal foils, composite sheets of combinations of these, and sheets embossed with each of these may also be used.

Hereinafter, the present invention will be specifically explained with reference to Examples. Note that "parts" indicate parts by weight.

Example 1 Microcapsules containing an ultraviolet absorber were prepared as follows.

100 parts of a 10% aqueous solution of ethylene/maleic anhydride copolymer, 10 parts of urea, 1 part of resorcinol, and 200 parts of water
A mixed solution was prepared, and the pH was adjusted to 8.5 using a 20% aqueous sodium hydroxide solution. Add 1.4 parts of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole [trade name: TINUVIN P, manufactured by CIBA-GEIGY] to 140 parts of Hysol SAS N-296 [diarylethane solvent, manufactured by Nippon Petrochemical Co., Ltd.]. This was dissolved to obtain an ultraviolet absorber solution. This ultraviolet absorber solution is emulsified and dispersed in the above mixed aqueous solution to form oil droplets of 5 to 6 μm.
After that, 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, it was cooled and the pH of the system was brought to 9.5, completing the encapsulation. Mix and stir 50 parts of the ultraviolet absorber-containing capsules (as solid content) prepared as above, 45 parts of 45% paraffin wax emulsion, 25 parts of wheat starch, and 50 parts of 48% SBR latex, and add water. In addition, a water dispersion coating solution with a solid content of 20% was prepared. This coating solution was applied onto a base paper having a basis weight of 48 g/m ² using a Mayer bar to give a coating weight of 6 g/m ² .

The coated side of the obtained transfer sheet for creating secret documents was placed opposite to plain paper, and pressure printing was performed using a ballpoint pen from the non-coated side. When the printed portion of the plain paper was visually observed, no printed portion could be identified.

Next, when the printed area was illuminated with a fluorescent inspection lamp (manufactured by Tokyo Kogaku Kikai Co., Ltd., model F1-3L) in a dark room, a dark red printed image with clear contrast due to the absorption of fluorescence was confirmed. We were able to.

Example 2 In place of the ultraviolet absorber 2-(2'-hydroxy-5'-methylphenyl)benzotriazole in the ultraviolet absorber-containing capsule prepared in Example 1, a benzophenone ultraviolet absorber 2,4-dihydroxybenzophenone was used. Encapsulation and coating were carried out in the same manner except that [trade name: SUMITOBU 100, manufactured by Sumitomo Chemical Industries, Ltd.] was used.

The coated surface of the obtained transfer sheet for creating secret documents was slightly reddish.

On the other hand, the plain paper had a similar reddish background. When pressurized printing was performed in the same manner as in Example 1, it was impossible to visually identify the image, but it was possible to confirm the identification of a clear printed image on the red plain paper using a fluorescent inspection lamp in a dark room.

Claims (1)

[Scope of Claims] 1. For producing secret documents, which is made by coating on a support a plain paper transfer type recording layer containing waxes and microcapsules containing a solution of an ultraviolet absorber dissolved in a non-volatile vehicle. Transfer sheet. 2. In a recording method for a transfer sheet for creating secret documents, which comprises coating a plain paper transfer type recording layer comprising waxes and microcapsules containing a solution of an ultraviolet absorber dissolved in a non-volatile vehicle on a support. By overlapping the plain paper transfer type recording layer side and plain paper and printing under pressure from the non-plain paper transfer type recording layer side, a latent image of the ultraviolet absorber is formed on the plain paper surface, and the fluorescence in the dark room is A recording method for a transfer sheet for creating secret documents in which the latent image is identified under an inspection light.