JPH0375355B2 - - 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) The coloring body must have sufficient fastness after coloring, but there are currently no products that completely satisfy these requirements. Particularly in recent years, as thermal recording systems have become faster, research on the above (1) has been intensively conducted. One way to do this is to raise the melting point of the electron-accepting compound itself from 60 to 100°C. However, it is difficult to control the melting point of phenolic compounds, which are currently the most widely used electron-accepting compounds, and the phenolic compounds themselves are expensive and impractical. Other methods include the combined use of organic acids and phenolic compounds as electron-accepting substances, as described in Japanese Patent Publications No. 49-17748 and No. 51-39567;
Alternatively, it is described that a polyvalent metal salt of a compound having an alcoholic hydroxyl group is used. Furthermore, Japanese Patent Publication No. 51-29945 describes the use of a copolymer of hydroxyethyl cellulose and maleic anhydride. Also, Japanese Patent Publication No. 51-27599 and Japanese Patent Publication No. 48-19231
The issue states that waxes are added. Furthermore, JP-A-49-34842, JP-A-49-115554
No., JP-A-50-149353, JP-A-52-106746,
JP-A-53-5636, JP-A-53-11036, JP-A-Sho
No. 53-48751 and JP-A-56-72996, etc., disclose thioacetanilide, phthalonitrile, acetamide, di-β-naphthyl-p-phenylenediamine, fatty acid amide, acetoacetanilide, diphenylamine, benzamide, carbazole, etc. or 2,3-di-m-
It has been described that thermofusible substances such as tolylbutane, 4,4'-dimethylbiphenyl, or carboxylic acid esters such as dimethyl isophthalate, diphenyl phthalate, dimethyl terephthalate, etc. are added as sensitizers. However, heat-sensitive recording materials produced using these methods are insufficient in color density and color sensitivity. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heat-sensitive recording material which has sufficient color density and color sensitivity and 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, an electron-accepting compound, and a naphthoic acid derivative represented by the following general formula (). In the above formula, R represents an alkoxy group, an aralkyloxy group, an aryloxy group, an alkylamino group, a dialkylamino group, an alkylarylamino group, or an arylamino group. In the above general formula, the naphthalene ring is an alkyl group,
It may be substituted with an aralkyl group or a hydroxy group. However, N-substituted hydroxynaphthoic acid amide compounds and methyl ester, ethyl ester, or phenyl ester of O-hydroxynaphthoic acid are excluded from the naphthoic acid derivatives. Among the above naphthoic acid derivatives, those having a melting point of 40°C to 150°C are preferred, particularly 50°C to 120°C.
It is preferable to have a melting point of . The heat-sensitive recording material containing the naphthoic acid derivative represented by the general formula () according to the present invention has sufficient coloring density and coloring sensitivity, and has little deterioration in coloring sensitivity over time and fog, and has good fastness of the coloring material after coloring. It is enough. Next, specific examples of naphthoic acid derivatives according to the present invention will be shown, but the present invention is not limited thereto. (1) β-naphthoic acid phenyl ester (2) β-naphthoic acid p-cresyl ester (3) β-naphthoic acid p-chlorophenyl ester (4) 2-hydroxy-3-naphthoic acid benzyl ester (5 ) N-β-naphthylcarbonylaniline (6) N-β-naphthylcarbonylbutylamine, etc. Examples of electron-donating colorless dyes used in the present invention include triarylmethane compounds, diphenylmethane compounds, xanthene compounds, and 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., and diphenylmethane compounds include:
4,4'-bis-dimethylaminobenzhydrin bendiether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenylleucoauramine, etc., 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-trifluoromethylanilino-6-
Diethylaminofluorane, 2-butylamino-
3-chloro-6-diethylaminofluorane, 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-diethylaminofluoran, etc. Thiazine compounds include benzoylleucomethylene blue, p-nitrobenzylleucomethylene blue, etc. The compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-
Examples include methyl-naphtho-(3-methoxy-benzo)spiropyran and 3-propyl-spiro-dibenzopyran. These may be used alone or in combination. Examples of electron-accepting compounds include phenol compounds, organic acids or their metal salts, and oxybenzoic acid esters. Phenol compounds in particular have melting points near the desired recording temperature, so it is necessary to use low-melting-point compounds. However, it is often used because it requires only a small amount, such as
It is described in detail in No. 14039, Special Publication No. 51-29830, etc. Specifically, 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, methyl-4-hydroxybenzoate,
2,2'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 4,4'-isopropylidene bis(2-methylphenol), 1,1-bis- (3-
Examples include chloro-4-hydroxyphenyl)cyclohexane, 1,1-bis-(3-chloro-4-hydroxyphenyl)-2-ethylbutane, and 4,4'-secondary isobutylidene diphenol. The heat-sensitive recording material according to the present invention has the general formula ()
It contains one or more types of naphthoic acid derivatives represented by the formula below, and a specific example of its production method will be described next. 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 1-10% by weight water-soluble polymer solution using a ball mill, sand mill, etc., and then mixed. , talc, calcium carbonate, and other inorganic pigments are added to create a coating liquid. If necessary, a paraffin wax emulsion, a latex binder, a sensitivity improver, a metal soap, an ultraviolet absorber, etc. can be added thereto. Coating fluids are most commonly applied onto base paper. Generally, the coating amount is 2 to 10 g/m ² as a solid content, with the lower limit determined by the density 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 (1) Preparation of Samples 1 to 3 5g of the electron-donating colorless point shown in Table 1 was
% polyvinyl alcohol (Saponity number: 99%, degree of polymerization: 1000) and 50 g of an aqueous solution was dispersed overnight in a ball mill. On the other hand, 20 g of the electron-accepting compounds (phenols) shown in Table 1 were similarly dispersed in a ball mill with 200 g of a 5% polyvinyl alcohol aqueous solution, and then 20 g of the naphthoic acid derivatives shown in Table 1 were dispersed in a 5% polyvinyl alcohol aqueous solution. Dispersed all day and night in a ball mill,
After mixing these three types of dispersions, 20g of kaolin (diyodia kaolin) was added and dispersed well, and then 50g of paraffin wax emulsion was added.
% dispersion (Chukyo Yushi Cellosol #428) was added to prepare a coating liquid. The coating liquid was applied onto a base paper having a basis weight of 50 g/m ² so that the solid content was 6 g/m ² ,
After drying at 60° C. for 1 minute, a coated paper was obtained by supercalendering at a linear pressure of 60 KgW/cm. Coated paper is heated by facsimile
Color was developed by heating at 35 mJ/cm ² and the color density was determined. The results are shown in Table 1. (2) Preparation of Comparative Samples 1 to 2 A similar test was conducted using exactly the same formulation as that used to prepare Samples 1 to 5, using only the naphthoic acid derivative and replacing the compounds 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. Furthermore, when the fog density in Table 1 exceeds 0.13, the commercial value is significantly reduced. From this point of view as well, it was found that the electron-accepting compound of the present invention provides an extremely excellent heat-sensitive recording sheet. 【table】

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material characterized by containing an electron-donating colorless dye, an electron-accepting compound, and a naphthoic acid derivative represented by the following general formula (). In the above formula, R is an alkoxy group, an aralxyloxyl group, an aryloxy group, an alkylamino group,
Represents a dialkylamino group, an alkylarylamino group, or an arylamino group. In the above general formula, the naphthalene ring is an alkyl group,
It may be substituted with an aralkyl group or a hydroxy group. However, N-substituted hydroxynaphthoic acid amide compounds and methyl ester, ethyl ester, or phenyl ester of O-hydroxynaphthoic acid are excluded from the naphthoic acid derivatives.