JPS618389A - Thermal recording material - Google Patents

Abstract

PURPOSE:To contrive higher preservability, by incorporating a specified tyrosine derivative into a recording layer of a thermal recording material. CONSTITUTION:A dye precursor is dispersed in an aqueous solution of a binder by a ball mill. On the other hand, a color developer and a tyrosine derivative of the formula, wherein R1 is subst. or unsubst. alkyl and R2 is aryl, are dispersed in an aqueous solution of a binder by a ball mill. The dispersed liquids are mixed with each other, and other desired additives are added thereto, followed by agtating to prepare a coating liquid. The coating liquid is applied to a base, followed by drying. Accordingly, preservability characteristics can be enhanced without degrading color forming properties.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material with excellent storage stability of colored images.

A heat-sensitive recording material generally has a heat-sensitive recording layer on a support, the main components of which are an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting developer. A dye precursor and a color developer instantaneously react with each other by heating with a laser beam, etc., and a recorded image is obtained. There is. These heat-sensitive recording materials have the advantages of being able to record with relatively simple equipment, being easy to maintain, and producing no noise, and are suitable for measurement recorders, facsimile machines, printers, and computer terminals. It is used in a wide range of fields, including automatic ticket vending machines, labels, and train tickets.

The basic performances required of thermosensitive recording materials include sufficient color image density and sensitivity, and no deterioration of color images over time. In addition, in recent years, heat-sensitive recording materials have become widely used, and hair styling products,
The stability of images due to the adhesion of oily substances such as creams and oils and fats contained in sweat on the skin (grease resistance), and the fact that images do not deteriorate even if water adheres to them (image water resistance), etc. Thermosensitive recording materials with excellent storage stability have become desired.

The present inventors investigated various branching agents, that is, image stabilizers, in order to obtain heat-sensitive recording materials with excellent image storage stability. As a result, the present inventors found that they react with normally colorless or light-colored dye precursors during heating, and the dye precursor By incorporating a tyrosine derivative represented by the following general formula into the recording medium of a heat-sensitive recording material containing a color developer that develops color, a heat-sensitive recording material with excellent storage properties can be obtained. did it.

General formula (However, in the formula, R1 represents an optionally substituted alkyl group and R2 represents an aryl group.) Tyrosine for obtaining a tyrosine derivative exists in natural protein chambers and has no safety problems. The substance jClDL, L, and D forms can all be used.

Examples of the tyrosine derivatives represented by the above general formula used in the present invention include N-benzenesulfonyltyrosine ethyl ester, N-p-chlorobenzenesulfonyltyrosine methyl ester, N-p-methylbenzenesulfonyltyrosine ethyl ester, N-0- Methylbenzenesulfonidityrosine ethyl ester, N-(2,5-
Dimethylbenzenesulfonyl) tyrosine ethyl ester, N-benzenesulfonyltyrosine benzyl ester%
N-p-) luenesulfonyltyrosine ethyl ester,
etc., but are not limited to these.

The image stabilizer used in the present invention is preferably used in an amount of 10 to 250% by weight based on the dye precursor. A particularly preferred range is 25-200%. If it is less than 10% by weight, the effect will be small, and if it is more than 250% by weight, the dilution effect will be greater (which will adversely affect the image density and be economically disadvantageous).

The main components used in the heat-sensitive recording material of the present invention will be specifically explained, but the present invention is not limited to these substances unless it goes beyond the gist of the present invention.

Examples of the dye precursor include triphenylmethane-based, fluoran-based, diphenylmethane-based, thiazine-based, and subiropifune-based compounds. For example, crystal violet lactone, 3-diethylamino-7-methylfluorane, 3-diethylamino-6-chloro-7-methylfluorane, 6-diethylamino-6-methyl-chlorofluorane, 6-dinithylamino-7-anilino Fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 6-cyptylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-7-
(6-Chloroanilino)fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-
Ethyl-p-)iso)-6-methyl-7-anirithufluorane, 3-(N-methylcyclohexylamino)
Examples include -3-methyl-7-anilinofluoran, 6-biperidi/-5-1f-7-anilifluorane, and the like.

As the color developer, acidic substances generally used in thermal paper can be used, such as phenol, p-t-butylphenol, p-phenylphenol, naphthol, p-hydroxyacetophenone, and 2゜2'-dihydroxydiphenol. , 4.4'-inzoloceridene (2-1-butylphenol), 4.4'-inzolopylidene diphenol, 4.4'-cyclohexylidene diphenol, novolac type phenol resin, benzoic acid, pt- Examples include butylbenzoic acid, p-hydroxybenzoic acid, p-hydroxybenzoic acid pencil ester, p-hydroxybenzoic acid methyl ester, and the like.

As binders, starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified a&! J-vinyl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, etc., water-soluble pyridine, styrene-citadiene copolymer, acrylonitrile-citadiene copolymer, methyl acrylate-detazoene Examples include latex-based water-insoluble binders such as copolymers.

Examples of the pigment include cinnabar earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like.

In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide, and castor wax are used to prevent head wear and stickiness. Examples include dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, surfactants, and fluorescent dyes.

Paper is mainly used as the support for the heat-sensitive recording material according to the present invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of combinations of these can also be used as desired.

Hereinafter, the present invention will be explained in more detail by way of examples.
The present invention is not limited to this example.

Example 1 20 g of 3-diethylamino-6-methyl-tuanilinofluorane was dissolved in 60 l of an aqueous solution of 2-tivolivinyl alcohol!
The mixture was dispersed in a ball mill for 24 hours. On the other hand, benzyl p-hydroxybenzoate 50+! i'5N-p-) luenesulfonyltyrosine ethyl ester20. 2% F
It was dispersed for 24 hours in a ball mill with polyvinyl alcohol aqueous solution 21011.

These dispersions were mixed, 100 g of a 50-g dispersion of calcium carbonate was added, and a 20-g dispersion of zinc stearate 50.9'112% polyvinyl alcohol aqueous solution 2
50# and 230I of water were added and mixed to prepare a coating liquid.

Next, this coating liquid was applied to a base paper having a basis weight of 5011/m'' so that the amount of the dye precursor was 0.5 g/m<2>, dried, and treated with a supercalender to obtain a heat-sensitive recording material.

Comparative Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that N-hydroxymethylstearic acid amide was used instead of N-p-)luenesulfonyltyrosine ethyl ester in Example 1.

Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that N-p-)luenesulfonyltyrosine ethyl ester in Example i was removed.

The heat-sensitive recording materials obtained in Example 1 and Comparative Examples 1 and 2 were evaluated by conducting the following tests.

Test using a thermal facsimile tester with an applied pulse width of 2.0
Printed under the conditions of 16.00 volts and 16.00 volts.
After obtaining a colored image, the following storage test was conducted. The results are shown in Table 1. Note that the density of the colored image was measured using a Macbeth densitometer RD514.

a) Color image density was measured.

b) Heat resistance test: The image density was measured after storage at 60° C. for 24 hours, and the image survival rate was determined.

C) Humid and heat resistance test: After being stored for 24 hours in an environment of 40° C. and 90% relative humidity, the image density was measured and the image survival rate was determined.

d) Grease resistance test: After strongly pressing the image area with the pad of a finger and leaving it at room temperature for 3 months, the image density was measured and the image survival rate was determined.

e) Water resistance test: The image density was measured after immersion in 3 liters of water for 24 hours, and the image survival rate was determined.

Table 1 From Table 1, it can be seen that the tyrosine derivative according to the present invention does not inhibit color development (and significantly improves various storage properties).

Claims (1)

[Scope of Claims] A heat-sensitive recording material containing a normally colorless or light-colored dye precursor and a color developer that reacts with the dye precursor when heated to develop a color, which contains a tyrosine derivative represented by the following general formula. A heat-sensitive recording material characterized by: General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, in the formula, R_1 represents an alkyl group that may be substituted, and R_2 represents an aryl group.)