JPH10329457A - Sheet with confidential information - Google Patents

Abstract

(57) [Summary] [Problem] To provide a sheet such as a postcard or a greeting card having confidential information which is printed in an invisible state so as not to be seen by a person and which can be visualized by a simple means. SOLUTION: The secret information 3 is formed by printing mainly composed of a hot-melt wax and / or a thermoplastic resin containing microcapsules encapsulating a thermosetting agent transferred from the heat-sensitive transfer layer of the heat-sensitive transfer ribbon to the surface of the base material 2. Sheet 1 applied in an invisible state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet, such as a postcard or a greeting card, provided with secret information using a special heat-sensitive transfer ribbon using a thermosensitive agent which develops, decolors or discolors due to a change in temperature.

[0002]

2. Description of the Related Art With the development of word processors and personal computers, thermal transfer ribbons for thermal printers, which have become widespread at present, refer to hot melt wax and / or thermoplastic resin containing colored dyes and pigments. This thermal transfer ribbon has a thermal transfer layer which is melted by a thermal head of a thermal printer, and the thermal transfer layer is partially transferred to a sheet surface to apply information.

[0003]

The information printed on such a thermal transfer ribbon is colored by the color of the dye or pigment contained in the thermal transfer layer. Therefore, as a matter of course, it is not possible to use this to print, in an invisible state, secret information that is not desired to be seen by a person, for example, on a sheet surface such as a postcard or a greeting card. Alternatively, even if the printed portion of the sheet is made the same color as that of the thermal transfer ribbon to make the information invisible, there is no means for the recipient to visualize the information.

Accordingly, an object of the present invention is to provide a sheet such as a postcard or a greeting card having confidential information which is printed in an invisible state so as not to be seen by a person and which can be visualized by a simple means. And

[0005]

Means for Solving the Problems Conventionally, a temperature indicator which realizes color development / decoloration or discoloration due to a temperature change has been put into practical use as a temperature indicator ink which is encapsulated in microcapsules and mixed with an ink vehicle. For example, it is used for temperature indicator cards, mugs, T-shirts, and the like.

Accordingly, the present inventors have paid attention to the function of a temperature indicator that changes color, decolors, or changes color due to temperature change, particularly, a temperature indicator that is colorless at normal temperature but develops color by heating or cooling. The above object can be achieved by printing secret information on a base material surface of a sheet with a thermal transfer ribbon having a thermal transfer layer in which a microcapsule encapsulating is contained in a hot melt wax and / or a thermoplastic resin. We have now found the present invention.

That is, the sheet having the secret information of the present invention is mainly composed of a heat-melted wax and / or a thermoplastic resin containing microcapsules encapsulating a heat transfer agent transferred from the heat-sensitive transfer layer of the heat-sensitive transfer ribbon to the substrate surface. The secret information is provided in an invisible state by the printing.

[0008] Particularly preferably, the sheet having the secret information of the present invention is characterized in that the above-mentioned temperature indicator is colorless at room temperature, but is colored by heating or cooling.

Alternatively, the sheet having the secret information according to the present invention is a sheet in which the temperature indicator shows a specific color at normal temperature and changes its color by heating or cooling, and at least a print area of the secret information is formed with the specific color. It is characterized by having the same color.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on preferred embodiments. FIG. 1 is a perspective view of a sheet 1 having secret information of the present invention configured as a greeting card, which is provided with predetermined information 4 printed on a surface of a base material 2 using a conventional thermal transfer ribbon. At the same time, the secret information 3 printed with a heat-sensitive transfer ribbon having a heat-sensitive transfer layer in which a microcapsule encapsulating a thermostat is contained in a hot-melt wax and / or a thermoplastic resin is applied in a colorless and invisible state at room temperature. Be done.

FIG. 2 is a perspective view of a sheet 11 having secret information according to the present invention, which is formed as a postcard. The sheet 11 has predetermined information printed on a surface of a base material 12 with a conventional heat-sensitive transfer ribbon. 14 and the secret information 13 printed with a heat-sensitive transfer ribbon having a heat-sensitive transfer layer in which the thermosetting wax-containing microcapsules are contained in the heat-melting wax and / or the thermoplastic resin is obtained at room temperature. The printing is performed in an invisible state on a printing area P having the same color as the printing color.

[0012] The sheet having the secret information of the present invention comprises a heat transfer ribbon having a heat transfer layer in which a microcapsule encapsulating a thermosetting agent is contained in a hot-melt wax and / or a thermoplastic resin. Is formed.

Hereinafter, the hot-melt wax and / or thermoplastic resin constituting the heat-sensitive transfer layer of the special heat-sensitive transfer ribbon related to the present invention, and the microcapsules enclosing the temperature-inducing agent will be described in detail. The melting point of the hot melt wax is 60-
It can be suitably selected from paraffin wax, caunabal wax, montan wax, petroleum wax, shellac wax, synthetic oxidized wax and derivatives thereof, fatty acid ester wax, hydrogenated wax and the like at about 150 ° C. On the other hand, as the thermoplastic resin, those appropriately selected from polyethylene, polyvinyl acetate, polyvinyl chloride, polystyrene, polyacrylate, and the like having a melting point or softening point of about 60 to 150 ° C. can be suitably used. The hot-melt wax and the thermoplastic resin can be used alone or as a mixture, but most preferably a hot-melt wax having excellent transition properties is used.

The temperature indicator in the present invention is a thermochromic material which reversibly develops, discolors or discolors in response to a temperature change. Examples of such a thermochromic material include metamocolor, condensed aromatic ring-substituted ethylene derivatives, There are liquid crystals. Metamocolor is composed of an electron donating organic compound, an electron accepting compound, and a polar organic compound. The electron donating organic compound determines the color of the color,
For example, 3,6-dimethoxyfluoran (yellow), 3-cyclohexylamino-6-chlorofluoran (orange), 3
-Diethylamino-6-methyl-7-chlorofluoran (red), 3-diethylaminobenzfluoran, (peach)
Rhodamine B lactam (red), crystal violet lactone (blue), 3-diethylamino-7-dibenzylaminofluoran (green), 3-diethylamino-6-methyl-7-anilinofluoran (black) and the like. .

The electron-accepting compound determines color density, and usually includes gallic acid propyl ester. Further, the polar organic compound determines the discoloration temperature, and examples thereof include higher alcohols such as n-octyl alcohol, n-densyl alcohol-lauryl alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol. The discoloration temperature can be adjusted to about -40 to 40 by appropriately mixing these alcohols.
It can be arbitrarily selected within the range of 50 ° C.

The condensed aromatic ring-substituted ethylene derivative is, for example, a spiropyran compound such as di-α, β-naphthoisospiropyran, benzo-β-naphthoisospiropyran, 3-alkyl-di-β-naphthospiropyran. And anthrone-based compounds such as bianthrone, dixanthylene, and xanthylideneanthrone. Particularly preferred are spiropyran-based compounds, which include a cooling discoloration type and a heating discoloration type, which change from colorless to colored at a specific temperature, and change reversibly.

Further, the liquid crystal is preferably a cholesteric liquid crystal which can be used as a thermochromic material, which is a derivative of cholesterin, and has a very small helical deformation energy in its molecular arrangement, and the helical pitch changes easily with temperature. This pitch change is considered as an optical color change. The discoloration temperature can be appropriately selected depending on the type and the mixing ratio.

When the temperature indicator is selected to emit a specific color at room temperature, the printing area formed by solid printing or copy-forgery-inhibited pattern printing in the same color as the specific color is applied to the base material surface so that the secret information is invisible. Become. However, it is most preferable to select and prepare a temperature indicator which is colorless at room temperature and develops a color by heating or cooling. A suitable temperature indicator satisfying these conditions is a spiropyran compound.

The method of microencapsulation of the temperature indicator may be a conventional one in a conventional microencapsulation method, and is not particularly limited. For example, an interfacial polymerization method, an in-situ method, a coacervation method, an orifice method and the like can be used. A preferred example of microencapsulation is as follows. A warming agent is added to an acidic aqueous solution of a styrene-maleic anhydride copolymer, followed by high-speed stirring to emulsify or disperse. On the other hand, an alkali is added to a mixed solution of formalin and melamine to adjust the pH to 8 to 10, and then heated to about 50 to 100 ° C to prepare an aqueous solution of a melamine-formaldehyde precondensate composed of methylolated melamine. Next, the aqueous solution of the melamine-formaldehyde precondensate is added to an emulsion or dispersion containing the styrene-maleic anhydride copolymer and a temperature indicator, and the mixture is stirred at about 40 to 90 ° C. for 30 minutes to 4 hours while stirring. Then, a wall film made of a melamine resin is formed around the temperature indicator to obtain an aqueous solution of microcapsules containing the temperature indicator.

As a method for removing water from the thus obtained aqueous solution of microcapsules encapsulating a thermosetting agent and incorporating the microcapsules encapsulating a thermostat into hot melt wax and / or a thermoplastic resin, an aqueous solution of microcapsules encapsulating a thermostat is used. The microcapsule powder is dried by a dry spray method, and the obtained microcapsule powder is generally kneaded with a predetermined hot-melt wax or a thermoplastic resin, or a mixture thereof. Add a lower alcohol such as glycols to the oil (add oils such as spindle oil if necessary)
It is preferable to use a vacuum dehydration method to vaporize water and then mix it with hot melt wax.

According to this method, since the powdering step is not performed, the capsules do not bind to each other to form enlarged particles,
In addition, since the physical properties such as elasticity and strength at the time of capsule formation are not impaired, the heat-sensitive transfer layer can be suitably formed on the substrate surface by a special coating machine or an offset printing machine. The content of the microcapsules containing the thermosetting agent in the heat-sensitive transfer layer depends on the coloring density.
%, Preferably 10 to 60%, more preferably 20 to 60%.
About 50% is good.

This heat-sensitive transfer layer is provided on the substrate surface by a coating machine or a printing machine, and is formed as a heat-sensitive transfer ribbon for a thermal printer. The application amount of the thermal transfer layer is the same as that of the conventional thermal transfer ribbon, and may be 1 to 10 g per square meter of the substrate. The thus-obtained thermal transfer ribbon is usually housed in a cassette like a conventional thermal transfer ribbon, and used for printer printing in the same manner as the conventional one.

When the recipient visualizes the confidential information applied to the substrate surface with such a special thermal transfer ribbon,
It is only necessary to give a temperature change according to the color development / decolorization of the temperature indicator, the discoloration temperature, for example, put the sheet in the refrigerator and cool it, or blow the hot air of the dryer and heat it to turn the secret information from colorless. Visualization can be achieved by causing a color to develop or a color change to produce a contrast with the color of the print area.

[0024]

According to the sheet having the secret information of the present invention, the secret information which is not desired to be seen by a person can be obtained by printing mainly composed of the hot-melt wax and / or the thermoplastic resin containing the microcapsules enclosing the thermosetting agent. This is performed in an invisible state, and has an effect that the recipient can visualize it by simple means.

[Brief description of the drawings]

FIG. 1 is a perspective view of a sheet having secret information of the present invention configured as a greeting card.

FIG. 2 is a perspective view of a sheet having secret information of the present invention configured as a postcard.

[Explanation of symbols]

 1, 11 Sheet having secret information of the present invention 2, 12 Base material 3, 13 Secret information 4, 14 Predetermined information P Print area

Claims (3)

[Claims] 1. A printing method mainly comprising a hot-melt wax and / or a thermoplastic resin containing microcapsules encapsulating a thermosetting agent transferred from a heat-sensitive transfer layer of a heat-sensitive transfer ribbon to a substrate surface, so that secret information is invisible. A seat that has been decorated. 2. The sheet according to claim 1, wherein the temperature indicator is colorless at room temperature but develops a color by heating or cooling. 3. The sheet according to claim 1, wherein the temperature indicator shows a specific color at normal temperature, changes color by heating or cooling, and at least a print area of the secret information has the same color as the specific color.