JPH0436878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with improved color development. Heat-sensitive recording materials using an electron-donating colorless dye and an electron-accepting compound are disclosed in Japanese Patent Publications No. 14039-1982, Japanese Patent Publication No. 4160-43-1972, and the like. The minimum performance that such a heat-sensitive recording material should have is (1) sufficient color density and color development sensitivity, (2) no fogging (color development phenomenon during storage before use), and (3) Although there are some issues such as sufficient fastness of the colored body after color development, there is currently no product that completely satisfies these requirements. In recent years, with the increase in speed of thermal recording systems, research has been conducted particularly on the above (1). Specific examples of electron-accepting compounds in heat-sensitive recording materials include phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters. Phenol compounds are particularly preferred because their melting points are near the desired recording temperature. For example, it is described in detail in Japanese Patent Publication No. 45-14039, Japanese Patent Publication No. 51-29830, etc. Specifically, 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, methyl-4-hydroxybenzoate, 2,2′-dihydroxybiphenol Neil, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 4,4'-isopropylidene bis(2-methylphenol), 4,
Examples include 4'-isobutylidene diphenol bis-4-hydroxyphenyl sulfone. However, these phenol compounds cannot necessarily be said to be satisfactory materials for heat-sensitive recording materials. That is, they have drawbacks such as insufficient color density when these phenol compounds are combined with electron-donating colorless dyes. Therefore, an object of the present invention is to provide a heat-sensitive recording material which has sufficient color density when used in combination with an electron-donating colorless dye and which satisfies other requirements. The object of the present invention has been achieved by a heat-sensitive recording material characterized by containing an electron-donating colorless dye and an electron-accepting compound represented by the following general formula () or (). In the above formula, R ₁ represents an aralkyl group, and R ₂ represents an alkylene group. The characteristics of the electron-accepting compound according to the present invention include the following. (1) In combination with an electron-donating colorless dye, it provides a highly concentrated colored image. (2) The color image is stable, and there is extremely little fading due to aging, humidity, light, etc. (3) Stable with almost no sublimation. Next, specific examples of the electron-accepting compound according to the present invention will be shown, but the present invention is not limited thereto. 1 4-N-Benzylcarbamoylphenol 2 N,N'-bis-(p-hydroxybenzoyl)-1,3-diaminopropane 3 N,N'-bis-(p-hydroxybenzoyl)-1,2-diaminopropane As the electron-donating colorless dye used in the present invention, triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds, etc. are used. To illustrate some of these, triarylmethane compounds include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e., crystal violet lactone);
3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3
-(1,3-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3
-(2-methylindol-3-yl)phthalide, etc. Diphenylmethane compounds include:
There are 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenylleucoauramine, and xanthene compounds include rhodamine-B. -anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine B (p-chloroanilino)lactam, 2-
Dibenzylamino-6-diethylaminofluorane, 2-anilino-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6
-cyclohexylmethylaminofluorane, 2-
o-chloroanilino-6-diethylaminofluorane, 2-m-chloroanilino-6-diethylaminofluorane, 2-(3,4-dichloroanilino)-6-diethylaminofluorane, 2-octylamino-6-diethylaminofluorane ,2
-dihexylamino-6-diethylaminofluorane, 2-m-trichloromethylanilino-6-
6-diethylaminofluoran, 2-butylamino-3-chloro-6-diethylaminofluoran, 2-ethoxyethylamino-3-chloro-6
-diethylaminofluorane, 2-anilino-3
-Chloro-6-diethylaminofluorane, 2-
Diphenylamino-6-diethylaminofluorane, 2-anilino-3-methyl-6-diphenylaminofluorane, 2-phenyl-6-diethylaminofluorane, etc. Thiazine compounds include benzoylleucomethylene blue, p-nitrobenzyl There are leucomethylene blue, etc., and spiro-based compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, and 3-benzylspiro-dinaphthopyran.
Examples include methyl-naphtho-(3-methoxy-benzo)-spiropyran and 3-propyl-spiro-dibenzopyran. These may be used alone or in combination. Next, a specific example of the method for producing a heat-sensitive recording material according to the present invention will be described. The most common manufacturing method for heat-sensitive recording materials is
The above-mentioned colorless electron-donating dye and electron-accepting compound are each separately dispersed in a 1 to 10% by weight water-soluble polymer solution using a ball mill, sand mill, etc., and then mixed. talc,
A coating liquid is created by adding an inorganic pigment such as calcium carbonate. A paraffin wax emulsion, a latex binder, a sensitivity improver, a metal soap, an ultraviolet absorber, etc. can be added to this as required. Coating fluids are most commonly applied onto base paper. Generally, the coating amount is 2 to 10 g/m ² in terms of solid content, with the lower limit determined by the concentration during color development by heating, and the upper limit determined mainly by economic constraints. Examples will be shown below, but the present invention is not limited only to these examples. Example 2-anilino-3-, an electron-donating colorless dye
10g of chloro-6-diethylaminofluorane 5
% polyvinyl alcohol (Sapon value 99%, degree of polymerization
1000) Dispersed with 100g of an aqueous solution in a ball mill overnight. On the other hand, 20g or 10g of the electron-accepting compounds (phenols) shown in Table 1 were dispersed with 200g or 100g of a 5% polyvinyl alcohol aqueous solution in a ball mill overnight, and after mixing both dispersions, 20g of kaolin (diyodiakaolin) was added. Add and disperse well, and then add paraffin wax emulsion 50% dispersion (Chukyo Yushi Cellosol #428)
5 g was added to prepare a coating liquid. The coating solution was applied onto base paper with a basis weight of 50 g/m ² so that the coating amount of the electron-donating colorless dye was 0.5 g/m ² , and after drying at 60°C for 1 minute, a linear pressure of 60 KgW/cm was applied.
A coated paper was obtained by supercalendering. The coated paper is heated at 150℃/1 using a thermal head.
The color was developed by heating for seconds, and the color density was determined. Comparative Sample A similar test was conducted using exactly the same formulation as that used in the Examples except that only the electron-accepting compound was replaced with a compound other than the present invention shown in Table 1. The results are also shown in Table 1. It can be seen from Table 1 that the recording material according to the invention clearly has a high sensitivity. 【table】

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material characterized by containing an electron-donating colorless dye and an electron-accepting compound represented by the following general formula () or (). In the above formula, R ₁ represents an aralkyl group, and R ₂ represents an alkylene group.