JPH02187389A - Heat transfer sheet with reversible heat-sensitive recording layer - Google Patents

Abstract

PURPOSE:To obtain a picture having an excellent contrast on visual sensing by reflected light by forming a reversible heat-sensitive recording layer by laminating a heat-sensitive layer depending upon a temperature and capable of being brought to a transparent state or a cloudy state and a reflecting layer having specific reflecting characteristics and further combining the thermal recording layer and a heat seal layer. CONSTITUTION:A heat-sensitive layer 2, which is adjoined to a supporter 1 and into which an organic low molecular substance 5 is dispersed, a reflecting layer 3 and a heat seal layer 4 are shaped successively. A thermal transfer sheet with a reversible thermal recording layer is positioned so that the surface of the heat seal layer 4 of the sheet is brought into contact onto a body to be transferred 6, and thermocompression-bonded by a hot plate 7 from the supporter 1 side. The supporter 1 is peeled from an interface with the heat-sensitive layer 2, thus forming the reversible heat-sensitive recording layer onto the body to be transferred. The heat-sensitive layer 2 functions as the disperse system of a resin and the organic low molecular substance, and a heating temperature is selected, thus making the refractive index of the organic low molecular substance uniform to or differ from that of the resin, then changing transparency.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a thermal transfer method in which a heat-sensitive recording layer capable of recording and erasing an image reversibly by heating means can be provided at any location on a transfer target. The present invention relates to a sheet, and the heat-sensitive recording layer relates to a thermal transfer sheet that can also be used in a thermal printer.

<Prior art> In recent years, new recording materials have been proposed that can record and erase images reversibly by changing heating temperatures and that have image fixability at room temperature (Japanese Patent Application Laid-Open No. Publication No. 55-154198).

This recording material has a heat-sensitive layer in which a low-molecular-weight organic substance such as behenic acid is dispersed in a resin such as polyester resin or vinyl chloride resin, and the transparency of the heat-sensitive layer changes by selecting the heating temperature. It is something. moreover,
This recording material can stably maintain a transparent state or a cloudy state even when cooled to room temperature after heating, and can reversibly maintain these states. That is, if this recording material is in a cloudy state, for example, it becomes transparent when it is heated to a specific temperature T and then cooled to room temperature. Next, after heating this transparent state above Tz (T+ <Tz),
It has the property of becoming cloudy again when cooled to room temperature.

However, with this recording material itself, a white image is formed on a colorless transparent background or a transparent image is formed on a white background, so it is difficult to see when viewed with reflected light. Therefore, for the purpose of improving the contrast, a reversible heat-sensitive recording material has been proposed in which a heat-sensitive layer using this reversible heat-recording material is combined with a colored support or a colored layer (Japanese Patent Laid-Open No. 62-257883). Publication, JP-A-63-3937
Public No. 7 @).

However, these images still lacked sufficient contrast and were not satisfactory. Furthermore, the conventional techniques are only concerned with reversible thermosensitive recording materials, and are not intended to provide a function for reversible thermosensitive recording at any arbitrary location on the transfer material.

<Problems to be Solved by the Invention> The present invention solves the above-mentioned problems of the prior art, and provides a reversible thermosensitive recording layer that can provide an image with excellent contrast when viewed with reflected light. An object of the present invention is to provide a thermal transfer sheet with a reversible thermosensitive recording layer that can be easily provided at any location.

Means for Solving the Problems> The present invention provides a reversible sensitive layer by laminating a heat-sensitive layer that can become transparent or cloudy depending on the temperature as shown below, and a reflective layer having specific reflective properties. The above object could be achieved by combining the thermal recording layer with a thermal adhesive layer.

That is, the present invention provides, on a support, at least (a) a heat-sensitive layer consisting of a dispersion system of a resin and an organic low-molecular substance and whose transparency changes reversibly depending on the heating temperature, and ('b) a metal thin film or A reflective layer made of metal foil and (c
) A thermal transfer sheet with a reversible thermosensitive recording layer, in which a thermal adhesive layer and are sequentially laminated.

In the above-mentioned thermal transfer sheet with a reversible thermosensitive recording layer, the most effective effect is obtained when the reflective layer has a specular reflectance of 35% or more in the wavelength range of 500 to 600 r+m.

<Function> To explain the present invention with reference to the drawings, the thermal transfer sheet with a reversible thermosensitive recording layer of the present invention has a support 1 as shown in FIG.
It has a basic structure in which a heat-sensitive layer 2 in which an organic low-molecular substance 5 is dispersed, a reflective layer 3, and a heat adhesive layer 4 are successively provided adjacent to the film.

Further, an example of a method of providing a reversible thermosensitive recording layer on a transfer target using the thermal transfer sheet with a reversible thermosensitive recording layer of the present invention will be explained with reference to FIG.

As shown in FIG. 2 (1), the surface of the thermal adhesive layer 4 of the thermal transfer sheet with a reversible heat recording layer is placed in contact with the transfer target 6, and the thermal pressure is bonded from the support 1 side with a hot plate 7. .

Next, as shown in FIG. 2(2), by peeling the support 1 from the interface with the heat-sensitive layer 2, a reversible heat-sensitive recording layer is provided on the transfer target.

The heat-sensitive layer 2 constituting the present invention is a dispersion system of a resin and an organic low-molecular substance, and by selecting the heating temperature, the refractive index of the organic low-molecular substance can be made equal to the refractive index of the resin.
Alternatively, the transparency may change due to different colors.

That is, in FIG. 3, when the organic low-molecular substance is in a cloudy state beforehand at a temperature T0 or lower and is heated from that state to a temperature T1 (A) and then cooled to a temperature T0 or lower (B), the refractive index of the organic low-molecular substance changes to that of the resin. The refractive index is almost equal to that of the transparent state. Furthermore, when this transparent state is heated to a temperature of T2 or higher (C) and then cooled to a temperature of T0 or lower (D), the refractive index of the organic low-molecular substance is different from the refractive index of the resin, causing light scattering and turning into a cloudy state. Become. Therefore, the heat-sensitive layer can undergo these state changes repeatedly.

Here, the temperature T2 is substantially the melting point or freezing point of the organic low-molecular substance.

The resin used for the heat-sensitive layer is preferably one that has good transparency, excellent mechanical strength, and good film-forming properties. Specific examples include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acrylate copolymer. , polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer, polyester resin, polyamide resin, acrylic resin, silicone resin, and the like. Among these, particularly preferred are vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, and polyester resin.

Organic low molecular substances include alkanols, alkanediols, halogenalkanols or halogenalkanediols, alkylamines, alkanes, alkenes, alkynes, halogenalkanes, halogenalkenes, halogenalkynes, cycloalkanes, cycloalkenes, cycloalkynes, saturated or unsaturated Mono- or dicarboxylic acids or their esters, amides, or ammonium salts, saturated or unsaturated halogenated fatty acids or their esters, amides, or ammonium salts, acrylic carboxylic acids or their esters, amides.

or ammonium salts, halogenallylcarboxylic acids or their esters, amides, or ammonium salts;
Thioalcohol, thiocarboxylic acid or ester, amide, or ammonium salt thereof, carboxylic acid ester of thioalcohol, and the number of carbon atoms is 10 to 40.
Examples of the molecular weight include those of 100 to 700. Particularly preferred are higher fatty acids such as lauric acid, palmitic acid, stearic acid, arachidic acid, and behenic acid having a melting point in the range of 50 to 150°C, or their esters, amides, and ammonium salts.

The mixing ratio of the resin and the organic low molecular weight substance is preferably in the range of 5 parts to 200 parts, more preferably 10 parts to 100 parts, based on 100 parts of the resin by weight. When the amount is less than 5 parts, the heat-sensitive layer becomes less cloudy, making it difficult to obtain contrast.

Moreover, if the amount is more than 200 parts, the film-forming properties of the heat-sensitive layer will deteriorate. The thickness of the heat-sensitive layer is preferably in the range of 5 to 50 microns, more preferably 10 to 30 microns. When it is thinner than 5 μm, contrast is difficult to obtain because the heat-sensitive layer becomes less cloudy. Moreover, if it is thicker than 50 μm, the sensitivity of the heat-sensitive layer decreases.

The reflective layer constituting the present invention has a thickness of 500 to 600 nm.
A metal thin film or metal foil having a specular reflectance in the wavelength range of 35% or more can be used, preferably 50% or more, and more preferably 70% or more in the 400-700 nm wavelength range. The specular reflectance here is based on the integrating sphere reflectance measurement method using a spectrophotometer, and is calculated by (total reflectance) -
This is obtained from the relationship (diffuse reflectance)=(specular reflectance). Moreover, the wavelength range of 500 to 600 nm means the region where the visibility with respect to brightness is the highest. The role of the reflective layer constituting the thermal transfer sheet with a reversible thermosensitive recording layer of the present invention will be explained with reference to FIG. Figure 4 shows the transferred object 6.
On top of that, there is a thermal adhesive layer 4, a reflective layer 3, and a cloudy thermosensitive layer 2a (
This shows a layer structure in which a transparent heat-sensitive layer 2b (left side) and a transparent heat-sensitive layer 2b (right side) are sequentially provided. When a light ray R1 obliquely enters the cloudy heat-sensitive layer 2a, the light is scattered by the organic low-molecular substance 5a, and a part of the light ray R2 enters the eye E in front. Further, some of the other light rays R3 are specularly reflected by the reflective layer 3, and then similarly scattered by the organic low-molecular substance 5a and enter the eye E. On the other hand, the light rays R, / obliquely incident on the transparent heat-sensitive layer 2b do not cause light scattering by the organic low-molecular substance 5b. Therefore, as a result of being specularly reflected by the reflective layer 3, R3' does not enter itself. In this way, when the specular reflectance of the reflective layer 3 is large, the difference in the amount of light entering the eye E from the cloudy heat-sensitive layer 2a and the transparent heat-sensitive layer 2b becomes large, and as a result, the contrast becomes high. It is. On the other hand, there are two cases when the specular reflectance of the reflective layer 3 is small. That is, there are cases where the total reflectance itself is small because the light absorption of the reflective layer 3 is large, and cases where the diffuse reflectance is also large even if the total reflectance is large. In the former case, the amount of light R1 reflected by the reflective layer 3 decreases, and as a result, the amount of light entering the eye E from the cloudy heat-sensitive layer 2a decreases. Furthermore, in the latter case, the number of light rays reflected from the reflective layer 3 toward the front increases, and as a result, the amount of light entering the transparent heat-sensitive layer 2b increases. That is, in either case, the difference in the amount of light entering the heat-sensitive layer from the cloudy state and the transparent state is reduced. Although FIG. 4 describes the positional relationship between the oblique incident light beam and the front eye on the recording medium, the same explanation as above can be made even if the positional relationship is reversed.

Materials for the reflective layer include aluminum, tin, silver, zinc, magnesium, chromium, nickel, rhodium, copper,
Suitable are foils made of metals such as gold or platinum formed into a thin film layer by vacuum evaporation, ion blasting, sputtering, electroless plating, etc., or mirror-finished metals made of these metals by rolling. Its thickness is
In the case of metal thin film layers from the viewpoint of reflection characteristics and mechanical strength,
It is in the range of about 0.01 to 5 μm, preferably 0.03 to 1 μm, and in the case of metal foil, it is in the range of about 1 to 50 μm, preferably 5 to 30 μm.

As the thermal adhesive layer constituting the present invention, a heat-melting or heat-softening resin, a B-stage thermosetting resin, or the like is used. This thermal adhesive layer is for making it possible to easily provide the reversible thermosensitive recording layer consisting of the above-mentioned thermosensitive layer and reflective layer at any desired location on the transfer object. Specific examples include polyester resin, polyamide resin, polyurethane resin, polystyrene resin, vinyl chloride-vinyl acetate copolymer resin, acrylic resin, polyvinyl butyral resin, ethylene-vinyl acetate copolymer resin, polyolefin resin, nitrile rubber, and styrene. - Butadiene rubber, isoprene rubber, epoxy resin, phenol resin, etc. may be used alone or in combination of two or more. The thickness of the thermal adhesive layer is preferably in the range of 1 to 30 μm in order to obtain good adhesion to the transfer target.

As the support constituting the present invention, any support can be used as long as it can be peeled off from the heat-sensitive layer after being thermally bonded. Specific examples include polyester, polycarbonate, acetate, polyimide, polypropylene, various films made of fluorine, synthetic paper, and paper base materials treated with resin. The thickness of the support is not particularly limited, but from the viewpoint of ease of handling when manufacturing the thermal transfer sheet with a reversible thermosensitive recording layer of the present invention or when thermally adhering it to a transfer target, the thickness is 3.5 mm. ~100μ
A range of m is preferred.

Although each layer constituting the present invention has been explained above,
The thermal transfer sheet with a reversible thermosensitive recording layer of the present invention can be provided with the following layers as necessary. For example, in order to improve the releasability of the thermosensitive layer from the support, a release agent layer such as silicone resin or fluororesin may be provided between the eyebrows. In addition, when recording is performed on the surface of the heat-sensitive layer with a thermal head etc. after transfer to the transfer target, in order to improve the heat resistance of the heat-sensitive layer, polymethacrylate resin or silicone is used between the support and the heat-sensitive layer in advance. A heat-resistant protective layer containing a resin such as a resin, a polycarbonate resin, a thermosetting acrylic resin, an alkyd resin, a melamine resin, or a photocurable epoxy-acrylate resin as a main component may be provided. Furthermore, in order to improve the adhesion between the heat-sensitive layer and the reflective layer, a resin layer of polyester resin, vinyl chloride resin, polyamide resin, acrylic resin, polyvinyl butyral resin, or the like may be provided between the eyebrows.

Examples of the method for producing the thermal transfer sheet with a reversible thermosensitive recording layer of the present invention include the following methods. That is, the above organic low-molecular substance and resin are mixed in a suitable organic solvent such as tetrahydrofuran, and then mixed with a stirrer, a paint shaker,
Dissolve it with a dispenser to create a heat-sensitive layer paint.

This paint is applied onto a support using a wire bar or reverse roll method, and then dried with hot air to form a heat-sensitive layer.

Next, a reflective layer such as a metal thin film is provided on this heat-sensitive layer by the method described above. Thereafter, in order to provide a thermal adhesive layer, a paint consisting of the above-mentioned hot-melting or thermo-softening resin and a suitable solvent is prepared, and the hot-melting resin is laminated on the reflective layer by a solvent coating method, or by a true melt coating method. In this way, the thermal transfer sheet with a reversible thermosensitive recording layer of the present invention can be produced.

The thus obtained thermal transfer sheet with a reversible thermosensitive recording layer of the present invention is cut into a tape shape or other desired shape, and then cut from paper, synthetic paper, or plastic by the method explained in FIG. A reversible thermosensitive recording layer can be provided at any location on a transfer object such as a sheet or card.

<Example> 0 Hereinafter, the present invention will be specifically explained with reference to Examples.

still. All parts and percentages of ingredients listed in the examples are based on weight.

Example 1 [Formation of heat-sensitive layer] -Resin: 80 parts of vinyl chloride-vinyl acetate copolymer resin (manufactured by Block Chemical Industry Co., Ltd., trade name: SURETSUK C) -Organic low-molecular substance:
Behenic acid 20 parts Solvent: Tetrahydrofuran 400 parts The above mixture was dissolved in a paint shaker for 1 hour while heating, and then coated on a 12 μm thick polyester film support using a wire bar. A heat-sensitive layer was formed by drying at °C. In this case, the coating thickness of the heat-sensitive layer after drying is 20 μm.
(Formation of reflective layer) Approximately 1000 A1 was coated on the above heat-sensitive layer by vacuum evaporation method.
A reflective layer consisting of an aluminum vapor-deposited film was formed.

[Formation of thermal adhesive layer]

・Thermofusible resin: Boryamide resin, melting point 80-90℃ 15 parts (
Manufactured by Nippon Rilsan Co., Ltd., product name: Bratabond) I-103T
^15) ・Solvent: 85 parts of isopropyl alcohol After dissolving the above mixed solution with a stirrer, it is coated on the above reflective layer with a wire bar and dried at 100°C to obtain the reversible coating of the present invention. A thermal transfer sheet with a thermosensitive recording layer was prepared. The coating thickness of the thermal adhesive layer after drying was 5 μm.

Example 2 [Formation of heat-sensitive layer] A heat-sensitive layer was formed on the support in the same manner as in Example 1.

[Formation of reflective layer]

A reflective layer was formed on the above heat-sensitive layer in the same manner as in Example 1, using tin instead of aluminum.

[Formation of thermal adhesive layer]

A thermal adhesive layer similar to that in Example 1 was provided on the above reflective layer to produce a thermal transfer sheet with a reversible thermosensitive recording layer of the present invention.

Example 3 [Formation of heat-sensitive layer] A heat-sensitive layer was formed on the support in the same manner as in Example 1.

[Formation of reflective layer]

A toluene-methyl ethyl ketone mixed solution of polyester resin (manufactured by Toyobo Co., Ltd., Byron 300) was applied onto the mirror-finished surface of 15 μm thick aluminum foil (manufactured by Nippon Seifuku Co., Ltd., trade name: Nila Puff Foil) until the dry coating thickness was 5 μm. It was painted like this. By the dry lamination method, a reflective layer was formed by laminating it with the above heat-sensitive layer.

[Formation of thermal adhesive layer]

・Thermofusible resin: Ethylene-vinyl acetate copolymer resin, softening point 85°C 10 parts (manufactured by DuPont Mitsui Polychemicals, trade name: Evaflex 210) ・Solvent: 90 parts of toluene Dissolve the above mixture with a stirrer Thereafter, a thermal adhesive layer was provided on the reflective layer in the same manner as in Example 1 to produce a thermal transfer sheet with a reversible thermosensitive recording layer of the present invention.

Example 4 [Formation of heat-sensitive layer] A heat-sensitive layer was formed on the support in the same manner as in Example 1.

[Formation of reflective layer]

Instead of aluminum foil, a reflective layer was formed in the same manner as in Example 3 using 18 μm thick copper foil (manufactured by Mitsui Kinzoku Kogyo Co., Ltd., trade name: BSH foil) so that the mirror-finished surface was on the heat-sensitive layer side. .

[Formation of thermal adhesive layer]

・Thermofusible resin: Polyester resin, melting point 83°C 10 parts (manufactured by Nippon Gosei Kagaku Kogyo, trade name Polyester-5P-170) ・Solvent Nidioxane 90 parts Using the above mixed solution, apply it on the above reflective layer. A thermal adhesive layer similar to that of Example 3 was provided to produce a thermal transfer sheet with a reversible thermosensitive recording layer of the present invention.

Example 5 [Formation of heat-sensitive layer] - Resin: 80 parts of polyester resin (manufactured by Toyobo Co., Ltd., trade name: Vylon 200) - 20 parts of organic low-molecular substance nistearic acid - Solvent: 400 parts of tetrahydrofuran The above mixed solution After dissolving for 1 hour in a paint shaker while heating, it was coated on a 12 μm thick polyester film support using a wire bar and dried at 100° C. to form a 20 μm thick heat-sensitive layer.

[Formation of reflective layer]

A reflective layer similar to that in Example 1 was formed on the above heat-sensitive layer.

[Formation of thermal adhesive layer]

A thermal adhesive layer similar to that in Example 1 was provided on the above reflective layer to provide a thermal transfer film with a reversible thermosensitive recording layer of the present invention. A heat-sensitive layer was provided, and on the heat-sensitive layer, 100 parts of aluminum paste (solid content 50%) and polyester resin (manufactured by Toyobo Co., Ltd., trade name: Vylon 200) were added.
0 parts of toluene and 350 parts of toluene-methyl ethyl ketone was coated so that the coating thickness after drying was 5 μm to form a reflective layer. A comparative thermal transfer sheet with a reversible thermosensitive recording layer was prepared by providing an adhesive layer.

Comparative Example 2 A heat-sensitive layer similar to that in Example 1 was provided on a support made of a 12 μm thick polyester film, and a polyester resin (manufactured by Toyobo Co., Ltd., trade name: Vylon 200) was placed on the heat-sensitive layer.
A mixed solution consisting of 80 parts of carbon black, 20 parts of carbon black, and 400 parts of toluene-methyl ethyl ketone was applied so that the coating thickness after drying was 5 μm to form a reflective layer. A thermal transfer sheet with a reversible thermosensitive recording layer for comparison was prepared by providing a thermal adhesive layer similar to that in Example 1.

The thermal transfer sheets with reversible thermosensitive recording layers of each of the above Examples and Comparative Examples were cut into strips of 5×10 CIm, and
A polyester film with a thickness of μm and an art film with a thickness of about 170 μm were each used as transfer objects and were bonded by thermocompression using a hot roll at a temperature of 110°C and a linear pressure of 3 kg/Cl11, and then the support was peeled off and removed. It was possible to partially transfer and provide a reversible fever recording layer onto the transfer body.

When provided on the object to be transferred, both heat-sensitive layers were in a cloudy state at room temperature.

Those using Examples 1 to 4 and Comparative Examples 1 to 2 were 70
When heated to 80° C. and then cooled to room temperature, the heat-sensitive layer changed to a transparent state, and when heated again to 80° C. or higher and cooled, it returned to a cloudy state. Further, in the sample using Example 5, when heated to 60°C and then cooled to room temperature, the cloudy state changed to a transparent state, and when heated again to 70°C or higher and cooled, the state returned to the cloudy state.

Furthermore, after making the heat-sensitive layer transparent, using a thermal head, printing density: 8 dots/dragon, printing energy: 0
．． When printing under the condition of 5 mJ/dot, a cloudy image was obtained. When these images were processed under the above heating conditions and cooled, they were able to return to a transparent state again. In this way, the reversible thermosensitive recording layers obtained from Examples 1 to 5 and Comparative Examples 1 to 2 were able to repeatedly write and erase images.

Furthermore, when writing was performed using the thermal head, the contrast between the image area and the non-image area was visually evaluated. The results are shown in Table 1.

Table 1 The contrast criteria were as follows.

◎: Very good ○: Good △: Slightly bad The reversible thermosensitive recording layer can be easily provided at any location, and images can be written and erased repeatedly by selecting the heating temperature using a thermal printer, etc., and when viewed with reflected light, You can get excellent contrast.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the basic structure of the thermal transfer sheet with a reversible thermosensitive recording layer of the present invention, and FIG. 3 is a cross-sectional view schematically explaining the method of providing a thermal recording layer. FIG. 3 is an explanatory diagram of the recording principle in the thermal layer of the thermal transfer sheet with a reversible thermosensitive recording layer of the present invention. FIG. FIG. 2 is a cross-sectional view schematically illustrating the reflection characteristics of a reversible thermosensitive recording layer formed on a transfer target using a recording layer-attached thermal transfer sheet. DESCRIPTION OF SYMBOLS 1...Support, 2...Thermosensitive layer, 3...Reflection layer, 4
... Thermal adhesive layer, 5 ... Organic low-molecular substance, 6 ... Transferred object, 7 ... Hot plate agent Patent attorney Takeuchi 9 Figure 1 Figure 3 To Ti Taka Onhama

Claims (1)

[Scope of Claims] On a support, at least (a) a heat-sensitive layer consisting of a dispersion system of a resin and an organic low-molecular substance and whose transparency changes reversibly depending on the heating temperature, and (b) a metal thin film or A thermal transfer sheet with a reversible thermosensitive recording layer, characterized in that a reflective layer made of metal foil and (c) a thermal adhesive layer are sequentially laminated.