JPH0427584A - heat sensitive recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with excellent thermal responsiveness.

[Conventional technology]

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. By heating with laser light etc., the dye precursor and the color developer react instantaneously 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. It is used in a wide range of fields, including ticket vending machines. Particularly in the field of facsimile, the demand for heat-sensitive methods is increasing significantly, and along with this, efforts are being made to increase speed, miniaturize devices, and lower prices in order to reduce transmission costs. As a result, the amount of energy applied for image printing has been steadily decreasing in recent devices. Therefore, there has been a strong demand for the development of highly sensitive heat-sensitive recording materials with high thermal responsiveness that can cope with such higher speed and lower energy facsimiles. In high-speed recording, it is necessary to use the small amount of thermal energy released from the thermal head in an extremely short period of time (usually less than 1 millisecond) for the color reaction to form a high-density color image. be. As a means to achieve the above objective, it is proposed to use a thermofusible substance with a relatively low melting point as a color development accelerator or sensitizer together with a dye precursor and an electron-accepting compound that causes the dye precursor to develop color. has been done. For example, JP-A-57
-64593, JP-A-58-87094 disclose naphthol derivatives, JP-A-57-64592, JP-A-57-185187, JP-A-57-191089,
JP-A-58-110289, JP-A-59-15393
The patent publication discloses naphthoic acid derivatives in JP-A-58-7249.
No. 9 and JP-A-58-87088 propose the use of ether and ester derivatives of phenolic compounds. However, the heat-sensitive recording materials produced using these methods are still insufficient in terms of thermal response, color development sensitivity, etc.

[Purpose of the invention]

An object of the present invention is to obtain a heat-sensitive recording material that has excellent thermal responsiveness and high color development sensitivity.

[Structure of the invention]

In a heat-sensitive recording material containing a normally colorless or light-colored dye precursor and an electron-accepting compound (color developer) that reacts with the dye precursor upon heating to develop a color, a compound represented by the following general formula, that is, dithio By containing an acetal compound, it was possible to obtain a heat-sensitive recording material with excellent thermal responsiveness and high color development sensitivity. General formula (wherein, R represents an aralkyl or aryloxyalkyl group, and may have a substituent (for example, an alkyl, alkoxy, halogen atom, etc.) on these aromatic rings. On the other hand, Z7 and Z2 are an alkyl group and may be different from each other.) Specific examples of the compounds of the present invention include those listed in the following formulas, but the present invention is not limited thereto. Me SEt Also, for use in heat-sensitive recording materials, the melting point is 60°C to 160°C.
℃ range is practically preferable. Note that the compound of the present invention can be easily synthesized by a known method, and can also be easily purified. For example, as shown below, a known method for synthesizing dithioacetals involves reacting a carbonyl compound such as an aldehyde or ketone, such as P-methylbenzyloxybenzaldehyde, with a thiol, such as methyl mercaptan or a derivative thereof, usually using an acid catalyst. Dithioacetals can be obtained. Moreover, many methods other than these are known. Next, a specific method for producing the heat-sensitive recording material according to the present invention will be described. The heat-sensitive recording material according to the present invention generally has a heat-sensitive recording layer mainly composed of an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting compound on a support, and can be used with a heat head, a heat pen, or a laser beam. By heating the dye precursor with an electron-accepting compound, a recorded image is obtained by instantaneous reaction between the dye precursor and the electron-accepting compound.
It is disclosed in Publication No. 39 and the like. Further, pigments, sensitizers, antioxidants, anti-sticking agents and the like are added to the heat-sensitive recording layer as necessary. The dye precursor used in the heat-sensitive recording material according to the present invention is not particularly limited as long as it is generally used in pressure-sensitive recording paper or heat-sensitive recording paper. Specific examples include (1) triarylmethane compounds 3.3-bis(p-dimethylaminophenyl) 6-dimethylaminophthalide (crystal violet lactone), 3.3-bis(p-dimethylaminophenyl) )
Phthalide, 3-(p~dimethylaminophenyl)-3
-(1,2-dimethylindol-3-yl)phthalide, 3-(pdimethylaminophenyl')-3-(2-methylindol-3-yl)phthalide, 3-(p-
dimethylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 3,3-bis(1,2
-dimethylindol-3-yl) to 5-dimethylaminophthalide, 3.3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide,
3.3-bis(9-ethylcarbazol-3-yl)
-5-dimethylaminophthalide, 3.3-bis(2-phenylindol-3-yl)-5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1
-Methylpyrrol-2-yl)-6-dimethylaminophthalide, etc., (2) diphenylmethane compounds 4.4° -bis-dimethylaminophenylbenzhydryl benzyl ether, N-halophenylleucoauramine, N-2 , 4,5-trichlorophenylleucoolamine, etc., (3) xanthine compound Rhodamine B anilinolactam, Rhodamine B-p-
Chloroanilinolactam, 3-diethylamino-7-
Dibenzylaminofluorane, 3-diethylamino-7
-Octylaminofluorane, 3-diethylamino-
7-phenylfluorane, 3-diethylamino-7-
Chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino 7
-(3,4-dichloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran,
3-diethylamino-6-methyl-7-anilinofluorane, 3-(N~ethyl-N-1lyl)amino-
6-Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-(
N-ethyl-N-tolyl)amino-6-methyl-7-phenethylfluorane, 3-diethylamino-7(4
-nitroanilino)fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-(N
-Methyl-N-propyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-anilinofluorane,
3-(N-methyl-N-cyclohexyl)amino-6-
Methyl-7-anilinofluorane, 3-(N-ethyl-N-tetrahydrofuryl)amino-6-methyl 7-anilinofluorane, etc., (4) Thiazine compounds benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, etc. , (5) Spiro-based compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3°-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho-(3-methoxy Examples include benzo) spiropyran, 3-propylspirobenzopyran, etc., and these can be used alone or in combination of two or more. The color developer is not particularly limited as long as it is an acidic substance commonly used in thermal paper. For example, polyvalent metal salts such as phenol derivatives, aromatic carboxylic acid derivatives, N, N'diarylthiourea derivatives, and zinc salts of organic compounds can be used. Particularly preferred are phenol derivatives, such as p-phenylphenol, p-hydroxyacetophenone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and 4-hydroxy-4'-isopropoxydiphenylsulfone. Hydroxy-4'-benzenesulfonyloxydiphenylsulfone, 1
．． 1-bis(p-hydroxyphenyl)propane, 1.
1-bis(p-hydroxyphenyl)pentane, 1,1
-bis(p-hydroxyphenyl)hexane, 1,1-
Bis(p-hydroxyphenyl)cyclohexane, 2.
2-bis(p-hydroxyphenyl)propane, 2.2
Bis(p-hydroxyphenyl)hexane, 1゜1-bis(p-hydroxyphenyl)-2-ethylhexane,
2,2-bis(3-chloro-4-hydroxyphenyl)
Propane, 1,1-bis(p-hydroxyphenyl)-1
-phenylethane, 1,3-di[2-(p-hydroxyphenyl)2-propyl]benzene, 1,3-di[
2(3,4-dihydroxyphenyl)-2-propyl]
Benzene, 1,4-di[2-(p-hydroxyphenyl)-2-propyl]benzene, 4°4°-dihydroxydiphenyl ether, 4.4'dihydroxydiphenyl sulfone, 3.3'dichloro-4,4° -dihydroxydiphenylsulfone, 3,3°-diallyl-4,4
゛ -dihydroxydiphenyl sulfone, 3. 3'
-dichloro-4,4'-dihydroxydiphenyl sulfide, 2.2-bis(4-hydroxyphenyl)methyl acetate, 2.2-bis(4-hydroxyphenyl)butyl acetate, 4.4°-thiobis(2-t -butyl-5-
methylphenol), benzyl p-hydroxybenzoate, chlorobenzyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, benzyl gallate, stearyl gallate, salicylanilide, 5-chlorosalicylanilide, and the like. Binders used in heat-sensitive recording materials include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein,
Alkali salts of polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylic amide/acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer , water-soluble adhesives such as alkali salts of ethylene/maleic anhydride copolymers, polyvinyl acetate, polyurethane, polyacrylic esters, styrene/butadiene copolymers, acrylonitrile/butadiene copolymers, methyl acrylate/butadiene copolymers Examples include polymers and latexes such as ethylene/vinyl acetate copolymers. In addition, N-
Waxes such as hydroxymethylstearamide, stearamide and palmitic acid amide, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2-bis(3 -methylphenoxy)
Ethane, 2.2°-bis(4-methoxyphenoxy)
Polyether compounds such as diethyl ether and bis(4-methoxyphenyl) ether, carbonic acid or oxalic acid diester derivatives such as diphenyl carbonate, dibenzyl oxalate, and bis(p-methylbenzyl) oxalate ester may be added together. I can do it. Examples of the pigment 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, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide, and castor wax are used to prevent head wear and stickiness, as well as dioctyl sulfosuccinate. Dispersants such as sodium chloride, ultraviolet absorbers such as benzophenone and benzotriazole, and surfactants, fluorescent dyes, and the like are added as necessary. As the support used in the present invention, paper is mainly used, but nonwoven fabric, plastic film, synthetic paper, metal foil, etc., or a composite sheet of a combination of these can also be used as desired. In addition, in the production of heat-sensitive recording materials, an overcoat layer is provided to protect the heat-sensitive recording layer, and an undercoat layer consisting of a single layer or multiple layers of pigment or resin is provided between the heat-sensitive recording layer and the support. Various known techniques can be used. The amount of coating on the heat-sensitive recording layer is determined by the amount of dye precursor and color developer, which are color forming components, and is usually 0.1 to 1.0 g.
/A is appropriate. The color developer is added in an amount of 5 to 400% by weight based on the dye precursor, with a particularly preferable addition amount of 20 to 300% by weight. The compound of the present invention is added in an amount of 5 to 400% by weight, with a particularly preferable addition amount of 20 to 300% by weight.

EXAMPLES Next, the present invention will be explained in more detail by way of examples. Note that all parts and percentages shown below are based on weight. Example 1 Preparation of heat-sensitive recording material (A) Preparation of heat-sensitive coating liquid Dye precursor 3-dibutylamino-6-methyl-7
- 35 parts of anilinofluorane and 80 parts of a 2.5% polyvinyl alcohol aqueous solution were ground in a ball mill for 24 hours to obtain a dye dispersion. Next, 40 parts of 2,2-bis(p-hydroxyphenyl)propane and 60 parts of a 2.5% polyvinyl alcohol aqueous solution were ground in a ball mill for 24 hours to obtain a color developer dispersion. 50 parts of the compound represented by formula [2] was ground with 120 parts of a 2.5% polyvinyl alcohol aqueous solution in a ball mill for 24 hours to obtain a dispersion of the compound of the present invention. After mixing the above three types of dispersions, the following were added and mixed well while stirring to prepare a heat-sensitive coating liquid. 50% calcium carbonate dispersion 100 parts 40% zinc stearate dispersion 25 parts 10% polyvinyl alcohol aqueous solution 185 parts water
280 copies (B) Preparation of heat-sensitive coated paper A coating liquid consisting of the following composition is smeared on base paper with a basis weight of 40 g/ryf to a solid content of 9 g/rrf, and dried to create heat-sensitive coated paper. did. Calcined kaolin 100 parts Styrene-butadiene latex 50% aqueous dispersion 24 parts water
200 copies (C) Preparation of heat-sensitive recording material The heat-sensitive coating liquid prepared in (A) was smeared on the surface of the heat-sensitive coating paper prepared in (B) so that the solid content coating amount was 4 g/rd, and dried. A heat-sensitive recording material was prepared. Example 2 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the compound represented by formula [2] in Example 1 was changed to the compound represented by formula [4]. Example 3 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the compound represented by formula [2] in Example 1 was changed to a compound represented by formula [5]. Comparative Example 1 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the compound represented by formula [2] in Example 1 was removed. Comparative Example 2 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the compound represented by formula [2] in Example 1 was changed to N-hydroxymethylstearamide. (Evaluation) The heat-sensitive recording materials obtained in Examples 1 to 3 and Comparative Example 1.2 were calendered so that the Bekk smoothness of the heat-sensitive coated surface was 400 to 500 seconds, and then subjected to a facsimile testing machine manufactured by Taishiki Denki. A printing test was conducted using TH-PMD. Dot density 8 dots/1111n, head resistance 185Ω
A thermal head with a head voltage of 12V and a pulse width of 0. Printing was carried out by applying current at 6 and 0.9 milliseconds, and the color density was measured using a Macbeth RD-918 reflection densitometer.

【Effect of the invention】

As is clear from the examples, by incorporating the compound of the present invention, it was possible to obtain a heat-sensitive recording material with excellent thermal responsiveness, high optical density with the same applied energy, and high color development sensitivity.

Claims (1)

[Scope of Claims] A heat-sensitive recording material containing a normally colorless or light-colored dye precursor and an electron-accepting compound that reacts with the dye precursor upon heating to cause the dye precursor to develop color, which contains a compound represented by the following general formula. A heat-sensitive recording material characterized by: General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, R represents an aralkyl or aryloxyalkyl group, and may have a substituent on these aromatic rings. On the other hand, Z_1 and Z_2 are alkyl groups , and each may be different from each other.)