JPH07112579A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To provide a reversible thermal recording material enhanced in visual contrast, reduced in irreversible color development and not becoming high in residual density even when the development and erasure of a color are repeated. CONSTITUTION:In a reversible thermal recording-material wherein a-recording layer based on a leuco dye, a coupling/tone-reducing agent and a binder is provided on a support, the coupling/tonereducing agent is a complex salt of bis(p-hydroxyphenyl) acetate and a alkoxypropylamine (having a 8 or more C alkoxy group). As alkoxypropylamine, 3-dodecyloxypropylamine is especially pref.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording material used for image formation, and more particularly to a reversible thermosensitive recording material with less irreversible color development.

[0002]

2. Description of the Related Art Reversible thermosensitive recording materials have hitherto been disclosed in JP-A-58-191190, JP-A-60-193691, JP-A-3666666 and JP-A-54-119377.
JP, JP 63-41186, U.S. Pat.No. 4,0
28,118, JP-A-50-81157, JP-A-50-105555
It is disclosed in Japanese Patent Publication No. WO 90/11898 and the like.

However, among the above publications, US Pat. No. 4,028,118, JP-A-50-81157 and JP-A-
In the method disclosed in Japanese Patent Application Laid-Open No. 50-105555, the image formed varies depending on the temperature, and the image formation was insufficient. Further, those described in JP-A-58-191190, JP-A-60-193691 and U.S. Pat.No. 3,666,525 have a recording layer comprising a leuco dye, a color developer and a binder. It is provided by adding a low vapor pressure solvent or a heat melting substance as needed, and its color development is performed by using thermal energy, and decolorization is performed by water, water vapor or some organic solvent. It is a thing. Since this method uses water vapor or an organic solvent for erasing, the mechanism becomes extremely complicated when an erasing mechanism is incorporated into a device such as a printer, and it is not intended due to moisture in the air. There were drawbacks such as discoloration.

Recording and erasing can be performed as intended by only coloring and erasing by controlling the thermal energy. Such techniques are disclosed in JP-A-54-119377 and JP-A-63-39.
As described in JP-A No. 377 and JP-A No. 63-41186, it has a heat-sensitive layer mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material, It has a function of reversibly changing the light diffusivity of the heat-sensitive layer by energy for image formation and erasure, and a function of both coloring and decoloring together with a leuco dye as described in WO 90/11898. Some have a heat-sensitive layer containing a molecule or a complex salt as a color-developing agent, and perform coloring and decoloring by a reversible reaction of a leuco dye.

In the former case, since the image is formed by changing the diffusion state of light, the contrast of the obtained image by visual observation is extremely low, and it is impossible to obtain a color image. Further, the latter forms an image with a dye, so the contrast of the image by visual observation is high, and various color images can be obtained by changing the leuco dye to be blended, but part of it does not disappear during color development. Produces irreversible color development,
There is a problem that the residual density becomes higher as the coloring and decoloring are repeated.

[0006]

As described above, the conventional techniques have problems such as low visual contrast and high residual density due to repeated coloring and decoloring.

The object of the present invention is to solve the problems of the above-mentioned prior art, to provide a high contrast, less irreversible color development, and a reversible color which does not increase the residual density even after repeated color development and decolorization. To provide a heat-sensitive recording material.

[0008]

The above-mentioned object is to provide a reversible thermosensitive recording material having a recording layer containing a leuco dye, a color-developing color-reducing agent and a binder as a main component on a support. This can be achieved by using a reversible heat-sensitive recording material, which is a complex salt of (p-hydroxyphenyl) acetic acid and alkoxypropylamine (wherein the alkoxy group has 8 or more carbon atoms).

As the above alkoxypropylamine, 3-dodecyloxypropylamine is particularly preferable.

The above leuco dyes may be those conventionally used in conventional thermal papers such as crystal violet lactone and 3-indolino-3-p.
-Dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 2- (2
-Fluorophenylamino) -6-diethylaminofluorane, 2- (2-fluorophenylamino) -6-di-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5- Methyl-7-t-butylfluorane, 3-diethylamino-6
-Methyl-7-p-butylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 3-pyrrolidino-6 -Methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-N-methylcyclohexylamino-6-methyl-7
-Anilinofluorane, 3-N-ethylbenzylamino-
6-methyl-7-anilinofluorane and the like can be mentioned.

As the binder, any water-soluble resin such as polyvinyl alcohol, gelatin, casein, acrylic resin, polyester resin, cellulose derivative, vinyl resin, styrene resin or the like can be used as long as it is a film-forming resin. can do. In addition, various additives may be added as necessary.

[0012]

When recording is performed on the reversible thermosensitive recording material of the present invention by using a thermal printer or the like, the portion to be printed is heated for an extremely short time, and at that time, the leuco dye and the color-developing / reducing agent chemically react with each other to make visible An image is formed by producing a dye having absorption in a region (color reaction).

Next, when this is heated for several seconds with a hot plate, a hot roll or the like, the dye forming the image reacts with the color-developing and reducing agent to return to the leuco dye again (decoloring reaction).

During the color development reaction, a slight but irreversible color development reaction occurs together with the above reversible color development reaction, and a product of the above irreversible color development reaction is generated by repeating color development and decolorization. Accumulate and increase residual concentration. This is due to the thermal decomposition that occurs immediately after melting in the color-developing / reducing agent, and therefore the above-described irreversible color-developing reaction does not occur in the color-reducing / degrading agent having a high thermal decomposition temperature.

In this respect, the above-mentioned color developing and reducing agent of the present invention has a sufficiently high thermal decomposition temperature, so that there is no irreversible color development, and even if the color development and the color erasing are repeated many times, the residual concentration hardly increases. .

[0016]

EXAMPLES The effects of the reversible thermosensitive recording material of the present invention will be specifically described below with reference to examples.

First, solutions A and B having the following compositions were prepared.

Liquid A 2-Amino-3-methyl-6-dibutylaminofluorane: 6 parts Acrylic resin (Dianal BR-106, manufactured by Mitsubishi Rayon Co., Ltd.): 3 parts Toluene: 21 parts Liquid B: Color reducing agent: 9 parts Acrylic resin (Dianal BR-106 manufactured by Mitsubishi Rayon Co., Ltd.) ... 3 parts Toluene ... 38 parts As a developer / color-reducing agent in the above-mentioned component B, No. 1 in Table 1
The complex salts shown in ~ 12 were used. The above liquids A and B were pulverized and dispersed by a ball mill for 20 hours respectively, and then sufficiently mixed at a ratio of 1 part of the liquid A to 3 parts of the liquid B to prepare a recording layer coating liquid. The solution was dried on a white processed polyester film with a thickness of 50 μm using a bar coater to give a dry weight of 8
A reversible thermosensitive recording sheet having no background coating was prepared by applying the solution so that the coating amount was g / m ² and drying.

Table 1 shows the decomposition temperature of each of the developing and reducing agents used,
The values of the color-developing density, the decoloring density and the residual density of the sheet obtained as described above are shown together. Here, each number in the table indicates a value measured under the following conditions.

Decomposition temperature: A temperature at which the weight of each of the color-reducing agents is measured by a thermobalance (TG / DTA 220 manufactured by Seiko Denshi Kogyo Co., Ltd.) and the weight is rapidly reduced.

Color density: The reflection optical density of the printed portion when printed using a thermal printer (AP-850 manufactured by Seiko Epson) (measured by Macbeth reflection densitometer RD-918).

Decoloring density: The reflection optical density of the decolored portion of the print when the color is erased through a heating roll heated to 110 ° C. after the above printing.

Residual density: The reflection optical density of the decolored portion of the print after the above printing and erasing are repeated 50 times.

[0024]

[Table 1]

Nos. 1 to 6 in Table 1 are examples of reversible thermosensitive recording sheets using the color-developing / reducing agent of the present invention.
It can be seen that there is almost no increase in the reflection optical density in the print-erased portion even after repeated repetitions.

Of these, the alkoxy group has 10 carbon atoms.
If it is smaller than this (No. 1-2), the decolorization density is high and it is difficult to erase. When the number of carbon atoms in the alkoxy group is greater than 14 (No. 4 to 6), the color density is low. From this result, it is understood that the best characteristics are exhibited when the carbon number is 12 (No. 3). Nos. 7 to 8 are examples in which the same organic acid as No. 1 to 6 and a complex salt of a linear alkylamine were used. The decoloring density and residual density were low, but the coloring density was low. . Also, No. 9
-10 is an example of the case where a complex salt of gallic acid and alkoxypropylamine is used as a color-developing agent. The coloring density is relatively high, but the erasing density is high and the residual density is considerably high. Further, Nos. 11 to 12 are examples in which a complex salt of gallic acid and a linear alkylamine was used as a color-developing / reducing agent. The color density was high and the color density was low, but the residual density was considerably high.

From the above results, it is clear that the reversible thermosensitive recording sheet of the present invention using No. 1 to 6 developing and reducing agents is more obvious than the reversible thermosensitive recording sheet using No. 7 to 12 developing and reducing agents. It can be seen that it has excellent characteristics.

The residual concentration is high when gallic acid is the organic acid that forms the complex salt that serves as the color-developing agent, but is almost the same as the initial decoloring concentration when bis (p-hydroxyphenyl) acetic acid. . This is because the decomposition temperature of the latter is high and the amount of irreversible color development is small.

The leuco dye and the resin exhibit the characteristics similar to those in the above case even if the leuco dye and the resin other than the above are used, and the combination is not limited to the above. Also, the support is
The material is not limited to a sheet-like material such as paper or polyester film, and can be formed into various shapes if an appropriate device for printing and erasing is used.

[0030]

As described above, by using a reversible thermosensitive recording material as the material of the constitution of the present invention, the problems of the prior art can be solved and irreversible color development is reduced.
It was possible to provide a reversible thermosensitive recording material in which the residual density does not increase even after repeated coloring and erasing.

In recent years, a large amount of paper consumption such as OA has become a problem from the standpoint of the rapid increase of urban garbage and the protection of the global environment. However, the widespread use of the reversible thermosensitive recording material of the present invention reduces the usage of paper. Is expected to be an effective means of.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroshi Uchiyama 3819 Noborito, Tama-ku, Kawasaki-shi, Kanagawa Sliontech Co., Ltd. (72) Daiji Sugiuchi, No. 3819 Noboto, Tama-ku, Kawasaki, Kanagawa (72) ) Inventor Kazuyoshi Yatsuka 3819 Noborito, Tama-ku, Kawasaki City, Kanagawa Prefecture

Claims (2)

[Claims] 1. A reversible thermosensitive recording material having a recording layer containing a leuco dye, a color-developing color-reducing agent and a binder as a main component on a support, wherein the color-developing color-reducing agent is bis (p-hydroxyphenyl).
A reversible heat-sensitive recording material, which is a complex salt of acetic acid and alkoxypropylamine (having 8 or more carbon atoms in the alkoxy group). 2. The reversible thermosensitive recording material according to claim 1, wherein the alkoxypropylamine is 3-dodecyloxypropylamine.