JPS6067192A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having excellent heat response characteristic and image preservability, wherein two specified organic compounds are jointly used in a thermal recording layer comprising a dye precursor and a color developer as main constituents. CONSTITUTION:(A) A compound of the formula, wherein R is aralkyl, e.g., dibenzyl phthalate or diphenethyl terephthalate, and (B) 1,1,3-tris(3-t-butyl-4- hydroxy-6-methylphenyl)butane are incorporated in the thermal recording layer in a weight ratio of about 0.1:1-3:1. Namely, a coating liquid consisting of a normally colorless (light-colored) dye precursor, e.g., crystal violet lactone, a color developer for developing the color of the dye precursor when being heated, e.g., benzyl hydroxybenzoate, the compounds A and B, a binder, e.g., starch, and other additives is applied to a base, followed by drying to provide a recording layer, thereby obtaining a thermal recording material.

Description

Detailed Description of the Invention The invention relates to a heat-sensitive recording material with excellent storage stability and thermal response. A heat-sensitive recording material generally includes an electron-donating, usually colorless or light-colored dye precursor on a support. The dye precursor and the developer react instantly when heated with a thermal head, thermal pen, laser source, etc. However, it is possible to obtain a recorded image and is disclosed in Japanese Patent Publication No. 43-4160 and Japanese Patent Publication No. 45-14039. 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. It is used in a wide range of fields such as terminals, labels, and automatic ticket vending machines such as train tickets.

The basic performance required of heat-sensitive recording materials includes sufficient color image density and sensitivity, and no deterioration of color images over time. As the speed of the apparatus itself increases, it is desired to develop a recording material that can cope with the increase in speed, that is, a heat-sensitive recording material that has excellent thermal responsiveness and can obtain high-density colored images with low thermal energy. Furthermore, as heat-sensitive recording materials became widely used, properties such as image stability (grease resistance) due to the adhesion of oily substances such as hair products, hand creams, and oils and fats contained in skin sweat were also required. However, there is a growing demand for heat-sensitive recording materials that have sufficient thermal response and storage stability.In order to obtain high-density colored images, various additives have not been added to the recording layer in the past. There are known ways to do this. For example, Japanese Patent Publication No. 43-4160 contains urea, phthalic anhydride, acetanilide, etc., Japanese Patent Publication No. 48-19231 contains natural and natural waxes such as beeswax, carnalaba wax, paraffin wax, and Japanese Patent Publication No. 49-17748. The issue discloses a method of adding salicylic acid, phthalic acid monobenzyl ester, etc. However, the heat response is poor and sufficient UK
Even if daytime density IIfIi1 images are obtained, there are drawbacks such as poor storage stability and deterioration over time, and the present inventors have not been able to obtain satisfactory results. As a result of various studies on additives in order to obtain heat-sensitive recording materials with excellent storage stability, we found that heat-sensitive recording materials containing a color developer that reacts with normally colorless or light-colored dye precursors during heating to cause the dye precursors to develop color. ,
In the recording layer of the heat-sensitive recording material, a compound represented by the following general formula [1.1.3-tris(3-t-butyl-4
By containing (hydroxy-6-methylphenyl)butane, a heat-sensitive recording material excellent in various properties could be obtained.

(However, R represents an aralkyl group.) The 1,1,3-)lis(3-t-butyl-4-hydroxy-6-methylphenyl)butane used in the present invention is
As already shown in Japanese Patent Application No. 57-112106, the storage stability of colored images has been improved, but the thermal responsiveness has been insufficient. However, by incorporating the compound represented by the above general formula (1) into the recording layer, the thermal response is significantly improved, a high-density colored image is obtained, and the storage stability is further improved, and the synergistic effect of the combined use is I discovered something.

Compounds represented by the above general formula used in the present invention include, for example, phthalic acid dibenzyl ester, isophthalic acid dibenzyl ester, terephthalic acid dibenzyl ester, terephthalic acid diphenethyl ester, etc. The mixing ratio of the compound represented by the above general formula (1) and 1.1.3-tris(3-t-butyl-4-hydroxy-6-methylphenyl)butane used for is 0.1 by weight: In the range of 1 to 3:1, the ratio is 0.3
It is in the range of L1 to 2:1.

The main components used in the non-inventive heat-sensitive recording material will be explained in detail, but unless it goes beyond the gist of the non-invention, it does not add to the non-invention.As dye precursors, triphenylmethane, fluoran etc. Examples include diphenylmethane-based, thiazine-based, and spiropyran-based compounds.

For example, crystal violet lactone, 3-diethylamino-twomethylfluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-ani Linofluorane, 3-diethylamino-7-(2-/OOanilino)fluorane, 3-dibutylamino-7-(2-chloroanilino)fluorane, 3-diethylamino-7-(3-chloroanilino)fluorane, 3-diethylamino- 6-Methyl-7-anilinofluorane, 3-(N-ethyl-p-4luidino)
-6-methyl-7-anilinofluorane, 3-(N-methylsituhexylamino)-3-methyl-7-anilinofluorane, 3-piperidino-3=methyl-7-anilinofluorane, etc. be.

As the color developer, acidic substances generally used in thermal paper are used, such as phenol, P-t-butylphenol, p-phenylphenol, naphthol, p-hydroxyacetophenone, and 2.2'- Dihydroxydiphenol, 4゜4I-isopropylidene (2-t-butylphenol L4,4'-isopropylidene diphenol, 4,4'-cyclohexylidene diphenol, novolac type phenol resin, benzoic acid, p-1-butylbenzoin) Acid, p-hydroxybenzoic acid, p-troxybenzoic acid benzylnis fA (, p-hydroxybenzoic acid methyl ester, etc.).

As a binder, water-soluble binders such as hamidane, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride co'M@ body, ethylene/maleic anhydride copolymer, etc. -, styrene-butadiene copolymer, acrylonitrile-butadiene co-X itself, methyl acrylate-butadiene copolymer, and other latex-based water-soluble binders.

Examples of pigments include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, and urea-formalin IQI.

17) Others: Higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, paraffin oxide, etc. for the purpose of preventing head wear and sticking.
Waxes such as polyethylene, polyethylene oxide, stearamide, castor wax, dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, surfactants, fluorescent dyes, etc. Can be mentioned.

Paper is mainly used as the support for the heat-sensitive recording material according to the invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or multiple sheets made of a combination of these may 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 3-diethylamino-6-methyl-7-anilinofluorane 20I was dispersed with a 2% polyvinyl alcohol aqueous solution 609 in a ball mill for 24 hours.Meanwhile, benzyl p-hydroxybenzoate 509.1,1.3- ) squirrel (3
-t-butyl-4-hydroxy-6-meth-ruphenyl)butane 20F, dibenzyl terephthalate #20
The mixture was dispersed in a ball mill for 24 hours with 270 g of a 2% gt polyvinyl alcohol aqueous solution.

These dispersions were mixed, 50% calcium carbonate dispersion 1009 was added, 20% zinc stearate dispersion 5op, xz% polyvinyl alcohol water bath g, 2
50#, water 160I was added and mixed to form a coating solution.Next, this coating solution was applied to base paper with a basis weight of 5011// so that the amount of dye precursor was 0.511/I11' and dried. The material was treated with a supercalender to obtain a heat-sensitive recording material.

Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that isophthalic acid dibenzyl ester was used instead of terephthalic acid dibenzyl ester.

Comparative Example 1 1.1.3-)lis(3-t-butyl-4-) of Example 1
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the (6-methylphenyl)butane and terephthalic acid dibenzyl ester of Example 1 were removed. Comparative Example 2 The terephthalic acid dibenzyl ester of Example 1 was removed. Except for this, a thermosensitive material was obtained in the same manner as in Example 1.

Comparative Example 3 1.1.3-)lis(3-t-butyl-4-) of Example 1
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that hydroxy-6-methylphenyl)butane was omitted.

The heat-sensitive recording materials obtained in Examples 1 and 2 and North Wall Example 1.2.3 were evaluated by conducting the following tests.

Test Printing was performed using a heat-sensitive facsimile tester under the conditions of an applied pulse width of 1.8 milliseconds and an applied voltage of 16.00 volts, and the colored image was subjected to the storage test shown below. The results are shown in Table 1. The density of the coloring group is Macbeth #meter R.
It was measured using D514.

a) Colored image density was measured. b) Heat resistance test; Under an environment of 60'C [Image density was measured after storage for 24 hours, and image residual and σ rate were calculated. ◎ C) Humid heat resistance test; 40t After storing for 24 hours in an environment with relative humidity of 90%, 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, it was left at room temperature for 2 days, and II! Ii consideration level was measured and the image survival rate was determined.

Table-1 From Table-1, 1.1. a-tris (3-t-
When 6≦butane (butyl-4-hydroxy-6-methylphenyl) is added alone, the storage stability is good, but the heat response is insufficient, and the color density is insufficient. When the ester is added alone, the color development is good, but the storage stability is insufficient. However, when both are added at the same time, the thermal response is improved,
It can be seen that the color density is improved synergistically.
The same thing can be said when using isophthalic acid dibenzyl ester, which is also found to improve storage stability due to a synergistic effect.

Claims (1)

[Scope of Claims] A heat-sensitive recording material containing a normally colorless to light-colored dye precursor and a color developer that reacts with the dye precursor upon heating to develop a color, in the recording layer of the heat-sensitive recording material, A compound represented by the following general formula [1.1.3-) lis(3-
A heat-sensitive recording material containing 1-butyl-4-hydroxy-6-methylphenyl)butane. (However, 几 indicates an aralkyl group.)