JPH033600B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material with excellent storage stability and thermal responsiveness. Heat-sensitive recording materials generally have 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. By heating with light etc., the dye precursor and developer react instantly,
This allows recorded images to be obtained, and is designated as Special Publication No. 43-4160.
It is disclosed in Japanese Patent Publication No. 14039/1983. Such 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 automatic ticket vending machines, labels, and ticket vending machines. The basic performances required of a heat-sensitive recording material include sufficient color image density and sensitivity, and no deterioration of color images over time.
In addition, in recent years, the speed of print recording has been increasing, and as the speed of recording devices themselves has increased, we have also developed recording materials that can cope with this, that is, heat-sensitive recording materials with excellent thermal responsiveness that can produce high-density colored images with low thermal energy. is desired. 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. Therefore, there has been a demand for a heat-sensitive recording material that satisfies thermal responsiveness and storage stability. Conventionally, methods have been known in which various additives are contained in a recording agent layer in order to obtain a colored image with high density. For example, urea, phthalic anhydride, acetanilide, etc. are listed in Japanese Patent Publication No. 43-4160;
The issue includes natural and synthetic waxes such as beeswax, carnauba wax, and paraffin wax.
No. 17748 discloses a method of adding salicylic acid, phthalic acid monobenzyl ester, etc. However, they have disadvantages such as poor thermal response and failure to obtain sufficient density, and even if high density images are obtained, poor storage stability and deterioration over time, so that no satisfactory product has been obtained. The present inventors investigated various additives in order to obtain a heat-sensitive recording material with excellent heat responsiveness and image storage stability. As a result, they reacted with a normally colorless or light-colored dye precursor upon heating, causing the dye precursor to develop color. In a heat-sensitive recording material containing a color developer, a compound represented by the following general formula [] and 1,1,3-tris(3-t-butyl-4-hydroxy- By containing 6-methylphenyl)butane, a heat-sensitive recording material with excellent properties could be obtained. (However, R represents an aralkyl group.) 1,1,3-tris(3-
Although t-butyl-4-hydroxy-6-methylphenyl) butane improves the storage stability of colored images, as already shown in Japanese Patent Application No. 112106/1982, its thermal responsiveness was insufficient. However, by incorporating the compound represented by the above general formula [] 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 there is a synergistic effect when used in combination. I discovered that. Examples of the compound represented by the above general formula [] used in the present invention include phthalic acid dibenzyl ester, isophthalic acid dibenzyl ester, terephthalic acid dibenzyl ester, and terephthalic acid diphenethyl ester. The mixing ratio of the compound represented by the above general formula [] and 1,1,3-tris(3-t-butyl-4-hydroxy-6-methylphenyl)butane used in the present invention is 0.1:1 to 1 by weight. In the range of 3:1,
Preferably it is in the range of 0.3:0 to 2:1. 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 thereto unless it exceeds the gist of the present invention. As a dye precursor, triphenylmethane type,
Examples include fluoran-based, diphenylmethane-based, thiazine-based, and spiropyran-based compounds. For example, crystal violet lactone, 3-diethylamino-7-methylfluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7 -anilinofluorane, 3-diethylamino-7-(2-
chloroanilino)fluoran, 3-dibutylamino-7-(2-chloroanilino)fluoran, 3
-diethylamino-7-(3-chloroanilino)
Fluoran, 3-diethylamino-6-methyl-
7-anilinofluorane, 3-(N-ethyl-P
-toluidino)-6-methyl-7-anilinofluorane, 3-(N-methylcitalohexylamino)
-3-methyl-7-anilinofluorane, 3-piperidino-3-methyl-7-anilinofluorane, and the like. As the color developer, acidic substances generally used for thermal paper can be used, such as phenol, p-t
-butylphenol, p-phenylphenol,
naphthol, p-hydroxyacetophenone,
2,2'-dihydroxydiphenol, 4,4'-isopropylidene (2-t-butylphenol),
4,4'-isopropylidenediphenol, 4,
Examples include 4'-cyclohexylidene diphenol, novolac type phenolic resin, benzoic acid, pt-butylbenzoic acid, p-hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid methyl ester, and the like. As binders, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol,
Styrene-maleic anhydride copolymer, ethylene/
Examples include water-soluble binders such as maleic anhydride copolymers, and latex-based water-insoluble binders such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and methyl acrylate-butadiene copolymers. Examples of pigments include diatomaceous 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, paraffin,
Waxes such as paraffin oxide, polyethylene, polyethylene oxide, stearamide, castor wax, dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, surfactants, and fluorescent Examples include 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 may also be used as desired. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 20 g of 3-diethylamino-6-methyl-7-anilinofluorane and 60 g of a 2% aqueous polyvinyl alcohol solution were dispersed in a ball mill for 24 hours. On the other hand, 50 g of benzyl p-hydroxybenzoate, 1,
20 g of 1,3-tris(3-t-butyl-4-hydroxy-6-methylphenyl)butane and 20 g of dibenzyl terephthalate were dispersed in a ball mill for 24 hours with 270 g of a 2% aqueous polyvinyl alcohol solution. These dispersions were mixed, 100 g of a 50% dispersion of calcium carbonate was added, 50 g of a 20% dispersion of zinc stearate, 250 g of a 12% aqueous polyvinyl alcohol solution, and 160 g of water were mixed and stirred to obtain a coating liquid. . Next, this coating liquid was applied to a base paper having a basis weight of 50 g/m ² so that the amount of the dye precursor was 0.5 g/m ² and dried, and 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 Thermal recording was carried out in the same manner as in Example 1 except that 1,1,3-tris(3-t-butyl-4-hydroxy-6-methylphenyl)butane and terephthalic acid dibenzyl ester were removed. I got the material. Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that dibenzyl terephthalate in Example 1 was omitted. Comparative Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 1,1,3-tris(3-t-butyl-4-hydroxy-6-methylphenyl)butane in Example 1 was removed. The heat-sensitive recording materials obtained in Examples 1 and 2 and Comparative Examples 1, 2, and 3 were evaluated by conducting the following tests. Test The applied pulse width was measured using a heat-sensitive facsimile tester.
After printing was performed for 1.8 milliseconds and an applied voltage of 16.00 volts to obtain 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: After storing in an environment at 60°C for 24 hours, the image density was measured and the image survival rate was determined. Image survival rate (%) = Image density after test / Image density before test × 100 (c) Humid heat resistance test: After storing for 24 hours in an environment of 40°C and 90% relative humidity, the image density was measured, and the image density was measured. The survival rate was calculated. (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 the image density was measured to determine the image survival rate.

[Table] From Table 1, when 1,1,3-tris(3-t-butyl-4-hydroxy-6-methylphenyl)butane is added alone as an additive, the storage stability is good, but the thermal response is poor. It is sufficient, and the color density is insufficient. In addition, when terephthalic acid dibenzyl ester is added alone, the color density is good, but
Insufficient in terms of storage stability. However, it can be seen that when both are added at the same time, the thermal response is improved and the color density is synergistically improved. Furthermore, it can be seen that the preservability is similarly improved due to a synergistic effect. The same thing can be said when using isophthalic acid dibenzyl ester.

Claims (1)

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