JPH04247984A - Reversible thermal coloring composition and thermal recording material using the composition - Google Patents

Abstract

PURPOSE:To enhance a density contrast between a color developed state and a discharged state by adding a special additive to a reversible thermal coloring composition consisting of leuco dye and the 6-0-acyl drivative of ascorbic acid or araboascorbic acid. CONSTITUTION:A reversible thermal coloring composition consists of leuco dye and the 6-0-acyl derivative of ascorbic acid or araboascorbic acid and higher fatty acid. This composition is supported using a support to manufacture a reversible thermal recording material. The composition is used in the area of a thermal recording medium, a thermal recording material, display material, an electronic blackboard, etc.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversibly thermochromic composition and a heat-sensitive recording material using the same.

0002

[Prior art and its problems] JP-A-63-176368
According to Publication No. 4, leuco dye and ascorbic acid-6-
Heat-sensitive recording materials made of O-acyl derivatives have been proposed. In this heat-sensitive recording material, color can be developed by heating at a high temperature of 90°C or higher, and the color formed by this heating can be decolored by heating at a lower temperature. be.

However, in the case of such heat-sensitive recording materials,
Even in the decolorized state caused by heating the coloring body, some coloring still remains, resulting in the problem that the density contrast between the colored state and the decolored state is insufficient.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible thermochromic composition that solves the above-mentioned problems found in the prior art, and a heat-sensitive recording material using the composition.

[0005]

[Means for Solving the Problems] As a result of intensive research aimed at solving the above problems, the present inventors discovered that the problems could be solved by adding higher fatty acids, and completed the present invention. reached.

That is, according to the present invention, there is provided a reversible thermochromic composition comprising a leuco dye, a 6-O-acyl derivative of ascorbic acid or araboascorbic acid, and a higher fatty acid, and a thermosensitive recording material using the same. is provided.

As the leuco dye, conventionally known ones such as triarylmethane compounds and fluoran compounds can be used.

Specific examples of leuco dyes include crystal violet lactone, 3-dipropylamino-7-chlorofluorane, 3-cyclohexylamino-
6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-N,N-n-propyl, n-butylamino-7-aminofluorane, 3-butylamino-7-t- Butylfluorane, 3-butylamino-7-N,N-methylphenylfluorane, 3-octylamino-7-anilinofluorane, 3-hexadecaamino-7-methylaminofluorane, 3-pyrrolidino-7 -dibenzylaminofluorane, 3-dibutylamino-7-o-chloroanilinofluorane, 3-dibutylamino-7-p-3-acetylanilinofluorane, 3
-pyrrolidino-7-o-toluidinofluorane, 3-N
, N-cyclohexyl, n-butylamino-7-p-acetylaminofluorane, 3-octylamino-7-(
2,4-dinitroanilino)fluorane, 3-N,N-
Examples include n-butyl, n-propyl-7-m-acetylanilinofluorane, and 3-diethylamino-6-chloro-7-anilinofluorane.

In the present invention, ascorbic acid-6-O-acyl derivatives are used as the color developer. Also used are araboascorbic acid-6-O-acyl derivatives, which are equivalents of ascorbic acid. Acyl derivatives include aliphatic and aromatic derivatives. Examples of 6-O-acyl derivatives of ascorbic acid and araboascorbic acid include acetylated products, propylonylated products, butylylated products, palmitoylated products, myristoylated products, stearoylated products, oleoylated products, beheniroylated products, benzoylated products, toluoylated products, etc. can be mentioned.

[0010] In the present invention, higher fatty acids are used as auxiliary ingredients. Higher fatty acids usually have a carbon number of 1
Two or more saturated or unsaturated carboxylic acids are used. Further, the higher fatty acid may be a polyhydric carboxylic acid. Specific examples of such substances include lauric acid, myristic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, melisic acid, tetradecyldicarboxylic acid, hexadecyldicarboxylic acid,
Octadecyl dicarboxylic acid, eicosyl dicarboxylic acid,
Examples include hexacosyldicarboxylic acid.

The proportion of the 6-O-acyl derivative of ascorbic acid or araboascorbic acid used is 0.5 to 4 parts by weight, preferably 2 to 3.5 parts by weight, per 1 part by weight of the leuco dye. The proportion of the fatty acid used is 1 to 10 parts by weight, preferably 2 to 5 parts by weight, per 1 part by weight of the leuco dye.

In the heat-sensitive recording material of the present invention, a thermochromic composition comprising a leuco dye, a 6-O-acyl derivative of ascorbic acid or arabo-ascorbic acid, and a higher fatty acid is applied to a suitable support such as paper or film. It can be obtained by supporting it as a recording layer on top. In this case, the composition is used in the form of a solution or dispersion, and a polymeric binder is usually added to the composition in order to bind it to the support.

An appropriate polymer binder is used depending on whether the composition is an aqueous dispersion system or a solvent solution system. Specific examples of polymer binders include vinyl chloride-vinyl acetate copolymer, vinyl acetate-maleic acid copolymer, vinyl chloride-acrylate copolymer, vinylidene chloride-acrylonitrile copolymer, and vinyl chloride in the solvent solution system. Examples include -vinyl acetate-maleic acid copolymer, polyester, polystyrene, polyphenol, silicone, perfluoroacrylic resin, and the like. Further, in an aqueous dispersion system, starch, methyl or ethyl cellulose, polyvinyl alcohol, etc. can be mentioned.

Among the above polymer binders, polyester, polystyrene, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, etc. are particularly preferred.

[0015] Furthermore, fillers such as calcium carbonate, calcium oxide, and silica, and modifiers such as metal soaps, surfactants, and plasticizers may also be added to the composition. Further, it is desirable to form an overcoat protective layer on the recording layer formed on the support for the purpose of improving the durability of the recording layer, for example, to prevent scum from adhering to the thermal head or from sticking.

[0016]

Effects of the Invention The thermochromic composition of the present invention can be colored by heating it to a high temperature, and the colored body formed by this heating does not fade even if it is kept at room temperature. It has memory properties.

On the other hand, the colored body formed by this heating can be decolored by heating it at a temperature lower than the heating temperature, and this decolored state can be maintained even at room temperature. In the present invention, by using higher fatty acids in combination, it is possible to improve the density contrast between the decolored state and the colored state. Then, by heating this decolored composition, it can be colored again, and the coloring and decoloring can be repeated.

The composition of the present invention can be used in a wide range of applications such as heat-sensitive recording media, heat-sensitive recording materials, heat-sensitive display materials, heat-sensitive recording labels, and electronic blackboards. The composition of the present invention can be advantageously applied as a rewritable recording medium by utilizing its record erasability.

[0019]

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that all parts and percentages shown below are based on weight.

Comparative Example 1 1 part of 3-dibutylamino-7-O-chloroanilinofluorane, 1.1 parts of 6-O-stearoyl ascorbic acid
14.0 parts of vinyl chloride-vinyl acetate copolymer was dissolved in 46 parts of tetrahydrofuran, coated on a 25 μm thick polyester film using a wire bar, and dried to form a recording layer with a coating weight of 2.7 g/m2. A nearly white recording sheet was obtained.

Example 1 An almost white recording sheet having a recording layer with a coating weight of 3.0 g/m 2 was obtained in the same manner as in Comparative Example 1 except that 3.0 parts of behenic acid was added.

Comparative Example 2 3-Cyclohexylamino-6-chlorofluorane 1.
0 parts, L-ascorbic acid-6-O-palmitoyl 1.
4 parts, 14.0 parts of polystyrene and 4 parts of tetrahydrofuran.
Comparative Example 1 by dissolving in a solvent of 1.0 parts and 5.0 parts of toluene.
A slightly orange recording sheet with a coating amount of 2.9 g/m2 was obtained in the same manner as above.

Example 2 In Comparative Example 2, 2.4 parts of eicosyldicarboxylic acid,
A slightly orange recording sheet with a coating weight of 3.4 g/m2 was obtained in the same manner except that 0.6 part of stearic acid was added.

Comparative Example 3 1.0 parts of 3-diethylamino-6-methyl-7-chlorofluorane, 3.0 parts of L-ascorbic acid-6-O-myristoyl, 20% polyvinyl alcohol aqueous solution.
0 parts and 12.0 parts of water were dispersed in a ball mill for 48 hours, and this was applied onto a 25 μm thick polyester film using a wire bar, and dried at 70°C to form a 12 μm thick polyester film.
A white recording sheet was obtained having a recording layer of .

Example 3 A white recording sheet having a recording layer having a thickness of 14 μm was obtained in the same manner as in Comparative Example 3 except that 3.0 parts of behenic acid was added.

Comparative Example 4 A sheet having a 15 μm thick recording layer was obtained in the same manner as in Comparative Example 3 except that crystal violet lactone was used as the leuco dye.

Example 4 A sheet having a recording layer having a thickness of 16 μm was obtained in the same manner as in Comparative Example 4 except that 3.0 parts of behenic acid was added.

The recording sheet prepared above is heated for 1 minute in a dryer adjusted to a high temperature (color development temperature), the colored sheet is taken out and allowed to cool, and the color density is measured using a Macbeth densitometer. Next, this recording sheet is heated for 1 minute in a dryer adjusted to a low temperature (erasing temperature), and the decolored sheet is taken out and left to cool, and the residual density after decoloring is measured in the same manner. The results are shown in Table 1.

[0029]

[Table 1]

From the above results, it can be seen that the density contrast between the decolored state and the colored state of the products of the present invention is good in all cases. It was confirmed that the recording sheets of each example had reproducibility of coloring and decoloring by repeated heating, and could be used as temperature-dependent reversible thermosensitive recording materials.

Claims (2)

[Claims] 1. A reversible thermochromic composition comprising a leuco dye, a 6-O-acyl derivative of ascorbic acid or araboascorbic acid, and a higher fatty acid. 2. A reversible heat-sensitive recording material comprising the composition of claim 1 supported on a support.