JPH07290839A - Thermally rev ersible recording medium - Google Patents

Abstract

PURPOSE:To provide a thermally reversible recording medium capable of sufficiently enhancing the contrast between a recording part and a non-recording part even when reflection type recording or transmission recording is performed. CONSTITUTION:A thermally reversible recording medium has a transparent support 21, the thermally reversible recording.display layers 22, 23 formed on both surfaces of the support 21 and composed of a matrix material and one of saturated carboxylic acid and a derivative thereof and the transparent protective layers 24, 25 formed on the respective recording.display layers 22, 23. In this case, since two recording.display layers 22, 23 are formed, the thickness of the whole of the recording.display layers 22, 23 can be made twice. Therefore, the contrast between a recording part and a non-recording part can be enhanced by the quantity corresponding thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoreversible recording medium capable of repeatedly recording and erasing visual information by heating means such as a thermal head.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording method in which an image is formed by using a heat-generating recording element, a heat-generating recording element is low in price, and a recording process is simple, so that a FAX, a printer or the like is used. It is widely used in the recording device. For example, in a recording apparatus in which a heat-generating recording element is used to directly write on thermal paper, the thermal paper is a colorless dye (leuco dye) that is an electron donor and a developer (phenolic acidic substance) that is an electron acceptor. It is formed by the above, and writing can be performed by the color reaction between the two. Then, a heat-sensitive layer for assisting the color development reaction is formed on the heat-sensitive paper.

When heat energy from a heat-generating recording element is applied to the heat-sensitive paper, the colorless dye and the color developer are dissolved in a portion where the heat energy is applied to cause a color reaction. Therefore, a density difference can be generated between a colored portion and a non-colored portion, so that a character, an image or the like can be recognized by the density difference (Japanese Patent Publication No. 45-14).
039).

However, in the case of directly writing on the thermal paper, recording and erasing cannot be repeated. Therefore, a recording device using a thermoreversible recording medium has been provided. FIG. 2 is a sectional view of a conventional thermoreversible recording medium. As shown in the figure, the thermoreversible recording medium comprises a support 11 made of transparent plastic, and the support 11
A thermoreversible recording / display layer 12 formed on the above, and a transparent protective layer 13 formed on the recording / display layer 12. The recording / display layer 12 reversibly becomes transparent or cloudy by being heated or cooled, and maintains the transparent or cloudy state at room temperature.

Therefore, recording and erasing can be repeated by using the thermoreversible recording medium. When performing reflection type recording, the recording section is made cloudy and the non-recording section is made transparent. When transmissive recording is made, the recording section is made transparent and the non-recording section is set. Make it cloudy. Moreover, since the thermoreversible recording medium has a resolution equivalent to that of general-purpose thermal paper, not only can characters and figures be recorded,
You can also record the barcode.

Then, in order to increase the contrast between the recording portion and the non-recording portion, the support 11 and the recording / display layer 1 are provided.
A colored layer (not shown) may be formed as a base between the two. In this case, various colors can be used for the colored layer, but a black or silver colored layer is used in order to obtain a recording state as when printing on plain paper.

[0007]

However, in the above-mentioned conventional thermoreversible recording medium, recording is performed by utilizing the scattering of light. Therefore, in the case of reflection type recording, the cloudy portion is generated. Is inferior in whiteness to plain paper, and when performing transmissive recording, it is not possible to sufficiently block light by the cloudy portion. Therefore, the contrast between the recorded portion and the non-recorded portion cannot be sufficiently increased.

Therefore, in the case of reflection type recording, a colored layer is formed as a base to increase the contrast. For example, using a black colored layer is visually pleasing. Further, a silver-colored film that has been subjected to aluminum vapor deposition or the like can be used as a base. However, in this case, not only the appearance is largely different from the case of printing on plain paper, but also it becomes difficult to form a colored layer.

On the other hand, when performing transmissive recording, there is no method for increasing the contrast between the recording portion and the non-recording portion.
The present invention solves the above-mentioned problems of the conventional thermoreversible recording medium, and provides a sufficiently high contrast between the recording portion and the non-recording portion in both reflective recording and transmissive recording. It is an object of the present invention to provide a thermoreversible recording medium that can be used.

[0010]

Therefore, in the thermoreversible recording medium of the present invention, a transparent support and a matrix material and one of a saturated carboxylic acid and its derivative are formed on both sides of the support. And a transparent protective layer formed on each recording / display layer.

[0011]

According to the present invention, in a thermoreversible recording medium, a thermoreversible recording medium comprising a transparent support and a matrix material and one of a saturated carboxylic acid and its derivative formed on both sides of the support is used. It has a recording / display layer and a transparent protective layer formed on each recording / display layer.

In this case, since the two recording / display layers are formed, the film thickness of the entire recording / display layer can be doubled. Moreover, since the thickness of one recording / display layer can be reduced, it becomes technically easy to make the thickness of each recording / display layer uniform.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a sectional view of a thermoreversible recording medium in an example of the present invention. As shown in the figure, the thermoreversible recording medium comprises a support 21 made of transparent plastic, thermoreversible recording / display layers 22 and 23 formed on both sides of the support 21, and recording / displaying. Transparent protective layers 24, 25 formed on the layers 22, 23. The recording / display layers 22 and 23 reversibly become transparent or cloudy by being heated or cooled, and maintain transparent or cloudy at room temperature.

Therefore, recording and erasing can be repeated by using the thermoreversible recording medium. When reflective recording is performed, the recording portion is made cloudy and the non-recording portion is made transparent. When transmissive recording is performed, the recording portion is made transparent and the non-recording portion is made transparent. Make it cloudy. In this embodiment, the support 21 is made of transparent PE having a thickness of 75 μm.
T film was used. As the support 21, transparent glass, transparent synthetic paper, or the like can be used.

In the recording / display layers 22 and 23, S-REC KS-1 (trade name, manufactured by Sekisui Chemical Co., Ltd.) is used as polyvinyl acetal constituting the matrix material.
Praiophen 5030 (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) was used as the phenol resin, and behenic acid was used as the saturated carboxylic acid and its derivative. Then, 5 parts by weight of S-REC KS-1, 5 parts by weight of Priofen 5030 and 3 parts by weight of behenic acid were dissolved in 50 parts by weight of tetrahydrofuran (THF) to prepare a coating solution of the thermoreversible recording material. . Next, the coating solution was coated on the support 21 by a bar coating method. Then, the coating solution was applied such that the film thickness after drying was 10 to 20 [μm].

By increasing the thickness of the recording / display layers 22 and 23, the contrast between the recording portion and the non-recording portion can be increased. However, it becomes technically difficult to make the film thickness uniform as the film thickness is increased, and even if the film thickness is doubled, the contrast between the recording portion and the non-recording portion cannot be doubled. Therefore, in this embodiment, the recording / display layers 22 and 23 are formed on both surfaces of the support 21 to double the actual film thickness. Therefore,
The contrast between the recording portion and the non-recording portion can be increased accordingly.

If a colored layer is formed as a base on one of the protective layers 24 and 25, the contrast between the recorded portion and the non-recorded portion can be further increased. The protective layers 24 and 25 were formed by the following method. That is,
First, 1 part by weight of 2-hydroxyethyl acrylate,
1 part by weight of 2,6-tolylene diisocyanate and 1 part by weight of 1,6-hexanediol are mixed using a roll mill, and the mixed solution is left standing for 24 hours. Then 1,6-
A mixture of hexanediol diacrylate and ethyl acetate in equal amounts is added to the mixed solution so that the mixed solution has a viscosity of 10 [cSt]. Then, 5% (by weight) of isobutyl benzoin ether is added to the mixture in a dark place, and the mixture is stirred (stirred) and allowed to stand for about 1 hour to form a protective layer coating solution.

Then, the protective layer coating liquid is applied onto the samples of the recording / display layers 22 and 23 by a bar coating method, and the samples are heated at 80 ° C. for 1 minute to evaporate the solvent. Next, 2 [kW] for the sample
Ultraviolet rays of 100 [mJ] per unit area were irradiated with a (80 [W / cm]) high-pressure mercury lamp to cure the applied protective layer coating liquid.

Next, the thermoreversible recording media of Examples 1 to 3 in which the recording / display layers 22 and 23 are formed with different thicknesses will be described. (Example 1) In this case, the recording / display layers 22 and 23 were made of polyvinyl acetal, S-REC KS-1.
(Trade name, manufactured by Sekisui Chemical Co., Ltd.), PRIOFEN 5030 (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) as a phenol resin, and behenic acid as a saturated carboxylic acid and its derivative.

Then, 5 parts by weight of S-REC KS-1,
A coating solution of the thermoreversible recording material was prepared by dissolving 5 parts by weight of Priofen 5030 and 3 parts by weight of behenic acid in 50 parts by weight of tetrahydrofuran. Next, the coating solution was applied to both sides of the support 21 by a bar coating method so that the film thickness after drying was 5 [μm].
Therefore, the total film thickness of the recording / display layers 22 and 23 is 10
[Μm].

The protective layers 24 and 25 were formed on the recording / display layers 22 and 23 by the following method. That is, first, 1 part by weight of 2-hydroxyethyl acrylate, 1 part by weight of 2,6-tolylene diisocyanate,
Parts by weight of 1,6-hexanediol are mixed using a roll mill, and the mixed solution is allowed to stand for 24 hours. Then 1,6
A mixture of hexanediol diacrylate and ethyl acetate mixed in equal amounts is added to the mixed solution so that the mixed solution has a viscosity of 10 [cSt]. Then, 5% (by weight) of isobutyl benzoin ether was added to the mixed solution in a dark place, and the mixture was stirred and allowed to stand for about 1 hour to give a protective layer coating solution.

Then, the protective layer coating liquid was applied onto the samples of the recording / display layers 22 and 23 by a bar coating method. Next, the sample is heated to 80 ° C. for 1 hour.
After heating for 1 minute to evaporate the solvent, 2 [kW] (80
[W / cm]) high-pressure mercury lamp was used to irradiate the sample with ultraviolet rays of 100 [mJ] per unit area to cure the applied protective layer coating solution. (Example 2) In this case, the coating solution was coated on both surfaces of the support 21 so that the film thickness after drying was 7.5 [μm]. Therefore, the total film thickness of the recording / display layers 22 and 23 is 15 [μm].

The protective layers 24 and 25 were formed on the recording / display layers 22 and 23 in the same manner as in Example 1. (Example 3) In this case, the coating solution was coated on both surfaces of the support 21 so that the film thickness after drying was 10 [μm]. Therefore, the total film thickness of the recording / display layers 22 and 23 is 20 [μm].

The protective layers 24 and 25 were formed on the recording / display layers 22 and 23 in the same manner as in Example 1. The samples of the finished products of Examples 1 to 3 were made cloudy and transparent, and the reflection density (O
D) was measured, and the contrast between the recorded portion and the non-recorded portion was calculated based on the reflection density value. In measuring the reflection density, a substrate having a reflection density of 1.83 was used as a base. The contrast between the recorded area and the non-recorded area was evaluated by the value obtained by subtracting the reflection density in the cloudy state from the reflection density in the transparent state.

The evaluation results are shown in FIGS. 3 and 4 and Table 1. FIG. 3 is a characteristic diagram of a cloudy state in an example of the present invention,
FIG. 4 is a characteristic diagram of a transparent state in the embodiment of the present invention. In the figure, the horizontal axis represents the recording / display layers 22 and 23.
And the reflection density is plotted on the vertical axis. In the figure,
The circles show the characteristics of the comparative example, and the circles show the characteristics of each of Examples 1 to 3. In the comparative example, only one recording / display layer 12 is formed as shown in FIG.

As can be seen from FIG. 3, when the reflection densities of Examples 1 to 3 and the reflection density of the comparative example in the cloudy state are compared with each other having the same film thickness, Examples 1 to 3 are compared.
It can be seen that the reflection densities up to are lower than the reflection densities of the comparative examples, and are clouded. Further, as can be seen from FIG. 4, when the reflection densities of Examples 1 to 3 and the reflection density of the comparative example in the transparent state are compared between those having the same film thickness, the reflection densities of Examples 1 to 3 are compared. There is almost no difference from the reflection density of the example.

Therefore, as shown in Table 1, when the contrast between the recording portion and the non-recording portion is evaluated by the value obtained by subtracting the reflection density in the cloudy state from the reflection density in the transparent state, Examples 1 to 3 are It is higher than that of the comparative example.

[0028]

[Table 1]

Since the recording / display layers 22 and 23 (FIG. 1) also function as support members, the thickness of the support 21 can be reduced. As a result, the recording / display layer 2
Since 2 and 23 are arranged at positions close to each other, not only can the quality of the recorded image be improved, but also when the heating and cooling are repeated for recording and erasing, the support 21 The heat transfer can be improved as much as the film thickness is reduced.

The recording / display layer 2 is provided on both sides of the support 21.
Since the layers 23 and 23 and the protective layers 24 and 25 are provided, it is possible to prevent warping of the thermoreversible recording medium. It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0031]

As described above in detail, according to the present invention, in a thermoreversible recording medium, a transparent support and a matrix material, a saturated carboxylic acid and a derivative thereof formed on both sides of the support are provided. And a thermoreversible recording / display layer, and a transparent protective layer formed on each recording / display layer.

In this case, since the two recording / display layers are formed, the film thickness of the entire recording / display layer can be doubled. Therefore, the contrast between the recording portion and the non-recording portion can be increased correspondingly.

[Brief description of drawings]

FIG. 1 is a sectional view of a thermoreversible recording medium in an example of the present invention.

FIG. 2 is a cross-sectional view of a conventional thermoreversible recording medium.

FIG. 3 is a characteristic diagram of a cloudy state in an example of the present invention.

FIG. 4 is a characteristic diagram of a transparent state in the example of the present invention.

[Explanation of symbols]

 21 Supports 22 and 23 Recording / display layers 24 and 25 Protective layers

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoichi Nishioka 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (2)

[Claims] 1. A (a) transparent support, and (b) a thermoreversible recording / display layer formed on both sides of the support and comprising a matrix material and one of a saturated carboxylic acid and a derivative thereof. (C) A thermoreversible recording medium having a transparent protective layer formed on each recording / display layer. 2. The thermoreversible recording medium according to claim 1, wherein a colored layer is formed on one of the protective layers.