JPH02117890A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance thermal response properties under a minute quantity of energy and enhance plasticizer resistance and oil resistance of recorded images by incorporating at least one 5,6-di-O-acylascorbic acid or erythorbic acid derivative as a color developer. CONSTITUTION:A thermal recording material can be produced by a method wherein a colorless or light-colored leuco dye as a thermal color former, a color developer for developing the dye into a color when being heated, a binder and, optionally, various additives are dissolved or dispersed in an aqueous dis persed liquid or in a solvent such as methyl alcohol, ethyl alcohol and benzene, and the resultant solution or dispersed liquid is applied to a support such as a paper, a plastic film and a synthetic paper, followed by drying. At least one 5,6-di-O-acylascorbic acid or erythorbic acid derivative of formula (I), wherein n is an integer of 0 to 21, is incorporated as the color developer. The leuco dye and the color developer are used in a weight ratio of 1:(0.5-2), preferably, 1:(1-1.7).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material using a leuco dye as a color former and a color developer that develops color when heat is applied.

[Prior art]

Thermosensitive recording materials that utilize a color reaction between a leuco dye and a color developer are widely known (for example, Japanese Patent Application Laid-Open No. 1986-30
No. 437, JP-A-48-51644, JP-A-51-5
No. 947). In recent years, with the development of society, recording speeds have increased and the applications of these recording materials have become more diverse.
In particular, there is an increasing demand for high reliability for organic solvents and plasticizers. Therefore, there is a strong desire to develop recording materials that can meet this requirement. Therefore, from this point of view, various sensitizers are used to increase speed, overcoating methods using water-soluble polymers for high reliability, low melting point color developers, etc.
For example, Utility Model Publication No. 59-9909), various methods have been proposed. However, it is still insufficient to record images with high reliability in high-speed recording, where only a small amount of heat is supplied by short-time pulses.There are advantages and disadvantages, and it is still not satisfactory for practical purposes. - [Purpose] An object of the present invention is to provide a new heat-sensitive recording material that has excellent fastness of recorded images, particularly stability against discoloration and decolorization caused by organic solvents and plasticizers, and has excellent high-speed recording characteristics. .

〔composition〕

The present invention relates to a heat-sensitive recording material containing a colorless or light-colored leuco dye as a heat-sensitive color forming agent and a color developer that develops color from the leuco dye by heating, and a 5゜6-dye compound represented by the following general formula as the color developer. It is characterized by containing at least one type of -0-acylascorbic acid or erythorbic acid derivative.

Examples of the color developer are shown in Table 1.

Table 1 The ratio of leuco dye to color developer used in the present invention is usually 1:0.5 to 2, preferably 1:1 to 1.7 by weight.

As the binder, any binder commonly used in this field can be used. Examples include starch, cellulose derivatives such as methyl or ethyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinylpyrrolidone, polyvinyl alcohol, polyacrylamide, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, Vinyl chloride copolymers such as vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride acrylate copolymer; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer Polymers, vinylidene chloride copolymers such as vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylate-methacrylate copolymers, silicone resins, epoxy resins, and the like. These may be used alone or in combination of two or more. In particular, polyvinyl alcohol is suitable for use in an aqueous dispersion system, and vinyl chloride-vinyl acetate copolymer is suitable for use after being dissolved in a solvent. Further, fillers such as calcium carbonate, titanium oxide, silica, talc, and surfactants can be added to the heat-sensitive recording layer.

The heat-sensitive recording material of the present invention is prepared by adding a leuco dye, a color developer of the present invention, a binder, and various additives as desired on a support such as paper, plastic film, or synthetic paper, and adding a dispersion using water or methyl alcohol. It can be produced by dissolving or dispersing it in a solvent such as ethyl alcohol, benzene, toluene, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, tetrahydrofuran, etc., coating it on a support, and drying it. The coating amount of the heat-sensitive recording layer is 0.5 to 5 g/m2, preferably 2 to 4 g/rr
l' is used.

As the leuco dyes that can be used, any of those conventionally used for pressure-sensitive paper and thermal paper can be used. For example, triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based ones are preferably used. be done. Specific examples of these leuco dyes are shown below.

3.3-bis(p-dimethylaminophenyl)-phthalide 3.3-bis(p-dimethylaminophenyl)-6-dilactone) 3.3-bis(p-dimethylaminophenyl)-6-diethylaminophenyl3. 3-bis(P-dimethylaminophenyl)-6-chlorophthalide 3.3-bis(P-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran.

3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-7-chlorofluoran 3-diethylamino-7-methylfluoran 3-diethylamino-7
,8-Benzfluoran 3-diethylamino-6-methyl-7-chlorofluoran 3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluoran 3-pyrrolidino-6- Methyl-7-anilinofluorane 2- (N-(3'-trifluoromethylphenyl)amino)-6-dinithylaminofluorane 2- (3,6-bis(diethylamino)-9-(o-
3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran 3-diethylamino-7-(o-chloroanilino)fluoran 3-dibutylamino-7-(o-chloroanilino) Fluoran 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluoran 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran 3-diethylamino-6-methyl-7-anilinofluoran 3-(N,N-diethylamino)-5 -methyl-7-(
N,N-dibenzylamino)fluoranebenzoylleucomethylene blue6'-chloro-8'-methoxy-benzoindolino-pyrylospirane6'-furomo3'-methoxy-benzoindolino-pyrylospirane3-(2'-hydroxy- 4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'- Nitrophenyl)
Phthalide 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)
Phthalide 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide [Example] Example 1 (1) (Liquid A ) ・Water 65〃(B liquid) ・Calcium carbonate 10〃・
5% aqueous solution of methylcellulose 20 tt
The above-mentioned liquid and liquid B are sufficiently dispersed and mixed to prepare a heat-sensitive coloring layer liquid, and coated with a wire bar at a coating amount of 3 to 4 g/rrr on high-quality paper weighing 50 g/rrr. A recording sheet (A) was created.

(2) 5,6-di-0-myristoyl ascorbic acid in place of 5,6-di-0-docosanoyl ascorbic acid in Example 1 (solution B).
... (Liquid E) (3) 5,6-di-0-balmitoyl ascorbic acid.
... (Liquid C) (4) 5.6-di-O-stearylascorbic acid...
・Thermal recording sheets (B), (C), and (D) were prepared in the same manner as above except that (liquid E) was used.

Comparative Example Thermal recording was carried out in the same manner as in Example 1, except that 5,6-di-O-docosanoyl ascorbic acid in Example (1) (Liquid E) was deleted and Liquid E was used that contained 35 parts of bisphenol A. A sheet (E) was created.

Each of the heat-sensitive recording sheets obtained as described above was printed at high speed using a G-3 facsimile machine [Liftex 3300 (Ricoh)], plasticizer resistance and oil resistance tests were performed, and the image density was measured using a Macbeth densitometer RD-514. The results measured are shown in Table 2.

Example 2 3-N,N-diethylamino-7-chlorofluoran 3 parts by weight
5. A thermosensitive coloring solution was prepared by dissolving 6-di-0-stearylascorbic acid 7 and vinyl acetate-vinyl chloride copolymer 15 in 80 parts of tetrahydrofuran and applying it to a 25 μm thick polyester film using a wire bar. A white heat-sensitive recording film was obtained by adjusting the coating amount to 2.5 to 3.0 g/-. When this heat-sensitive recording film was printed at 105° C. using a thermal head, a clear red image was obtained. The image density was measured with a Macbeth densitometer RD-514 and showed an image density of 0.68.

〔effect〕

(1) Excellent thermal response, especially to small amounts of energy, and the recorded images obtained are organic solvents and plasticizers.

Excellent resistance to plasticizers such as oil and oil.

(2) Even if the obtained recorded image is stored over time, the image density does not decrease and the image contrast does not deteriorate.

Patent applicant: Rico Co., Ltd.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material containing a colorless or light-colored leuco dye as a heat-sensitive coloring agent and a color developer that causes the leuco dye to develop color by heating, wherein the color developer is represented by the following general formula 5. , 6-di-O-acylascorbic acid or erythorbic acid derivative. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (n: indicates an integer from 0 to 21)