JPH0414636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material containing a specific color developer. Thermosensitive recording materials are usually manufactured by coating a colorless or light-colored colorless dye and a developer in a separated state together with a binder and other additives on the surface of a base paper. Then, in the recording device, when a heat generating element such as a thermal head or a hot pen comes into contact with this recording medium, the dye and the color developer react to develop a color such as black, and the recording is performed. Conventionally, phenolic color developers have been used as color developers, such as bisphenol A,
4,4'-cyclohexylidene diphenol, p-
Hydroxybenzoic acid esters and the like have been used, but when these phenols are used, they have the disadvantage of causing color unevenness or discoloration during storage. As a result of intensive studies to eliminate these drawbacks, the inventors of the present invention discovered that a specific dihydroxy compound exhibits excellent effects as a color developer, and arrived at the present invention. That is, the present invention provides a heat-sensitive recording material containing a color-forming substance that is usually colorless to light and a dihydroxy compound represented by the following general formula () or (). (In the formula, X represents _-CH2- , _-CH2CH2- , _-S- or -0-, and R represents an alkyl group.) In the above general formulas () and (), R represents Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, octyl, 2-
Examples include ethylhexyl, decyl, dodecyl, octadecyl, benzyl, 4-chlorobenzyl, 4-methylbenzyl and the like. Therefore, the above general formula () used in the present invention
Or, as a compound represented by (), 3,4-
Dihydroxythiophene-2,5-dicarboxylic acid, 3,4-dihydroxyfuran-2,5-dicarboxylic acid, 2,3-dihydroxy-1,3-cyclopentadiene-1,4-dicarboxylic acid, 2,3
-dihydroxy-1,3-cyclohexadiene-
Examples include dimethyl, diethyl, dibutyl, dioctyl or dibenzyl esters of 1,4-dicarboxylic acid or 2,5-dihydroxy-1,3-cyclohexadiene-1,4-dicarboxylic acid. It goes without saying that the dihydroxy compound of the present invention can be used alone as a color developer for heat-sensitive recording materials, but depending on the application and required performance, it may be used as a color developer such as p-octylphenol, p-octylphenol, or p-octylphenol.
-t-butylphenol, p-phenylphenol, bisphenol A, 1,1-bis(p-hydroxyphenyl)butane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate,
Benzyl p-hydroxybenzoate, 3,5-di-
t-Butylsalicylic acid, 4,4'-cyclohexylidene diphenol, p-hydroxyphenoxide, α-naphthol, β-naphthol, p-hydroxyacetophenone, p-t-octylcatechol, 2,2'-hydroxy biphenyl, 2,2-
Bis(m-methyl-p-hydroxyphenyl)propane, 2,2-bis(m,m'-dimethyl-p
It can also be used in combination with phenols such as -hydroxyphenyl)propane or organic acids. Various dyes are well known as the usually colorless to light-colored color-forming substance used in the present invention, and there are no particular limitations as long as they are used in general pressure-sensitive recording paper or heat-sensitive recording paper. To give specific examples, (1) triarylmethane compounds; for example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone), 3-(p-dimethylaminophenyl), phenyl)-3-(1,2-dimethyl-3
-indolyl) phthalide, 3-(p-dimethylaminophenyl)-3-(2-phenyl-3-indolyl) phthalide, 3,3-bis(9-ethyl-3
-carbazolyl)-5-dimethylaminophthalide,
3,3-bis(2-phenyl-3-indolyl)
-5-dimethylaminophthalide, etc., (2) diphenylmethane compounds; for example, 4,4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenylleukoolamine, N-2,4,5-
(3) xanthene compounds such as trichlorophenyl leukoolamine; e.g. rhodamine-β-anilinolactam, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-
(2-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-anilifluoran,
3-diethylamino-6-chloro-7-(β-ethoxyethylamino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-
Ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-cyclohexylmethylanilino-6-methyl-7-anilinofluorane, 3-
(4) Thiazine compounds such as diethylamino-6-chloro-7-γ-chloropropylaminofluorane; for example, benzoylleucomethylene blue, p
−Nitrobenzoylleucomethylene blue, etc. (5)
Spiro compounds; for example, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3
Examples include -benzylspirodinaphthopyran, 3-methylnaphtho(3-methoxybenzo)spiropyran, etc., and several types of these dyes may be used in combination. The aforementioned color developer and color-forming colorless dye are atomized using a grinder such as a ball mill, attritor, or sand grinder, or a suitable emulsifying device, and various additive materials are added depending on the purpose to form a coating liquid. This coating liquid usually contains polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, starches, styrene-maleic anhydride copolymer,
Binders such as vinyl acetate-maleic anhydride copolymer and styrene-butadiene copolymer, and fillers such as kaolin, diatomaceous earth, talc, titanium dioxide, calcium carbonate, magnesium carbonate, and aluminum hydroxide are blended. In addition, metal soaps, waxes, light stabilizers, waterproofing agents, dispersants, antifoaming agents, etc. can be used. By applying this coating liquid to paper and various films, the desired heat-sensitive recording material can be obtained. The type and amount of the dihydroxy compound used in the present invention and the type and amount of other components are determined according to the required performance and recording suitability, and are not particularly limited. 1 to 10 parts of the dihydroxy compound are used. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 20 g of 3-diethylamino-6-chloro-7-anilinofluorane was ground in a ball mill with 100 g of a 10% polyvinyl alcohol aqueous solution to obtain a dye dispersion (liquid A). Similarly, 20 g of the color developer (see Table 1) was ground in a ball mill with 100 g of a 10% polyvinyl alcohol aqueous solution to obtain a color developer dispersant (liquid B). Mix liquid A and liquid B at a ratio of 3:10 to make a mixed solution.
A coating liquid was obtained by adding and dispersing 50 g of calcium carbonate to 200 g. This coating liquid was applied to a base paper of 50g/ ^m2 with a solid content of 6g/m2.
It was applied to a coating amount of m ² and dried. Using the obtained thermal paper, after printing with a commercially available thermal facsimile machine NEFAX-3000 (manufactured by NEC Corporation),
Temperature 50℃, humidity 90% and temperature 70℃, dry condition 2
The sample was stored under the following conditions for 24 hours, the density of the printed area of the sample after storage was measured, and the residual rate of the density of the printed area after storage was determined from the following formula. Residual rate (%) = Concentration after storage / Concentration before storage × 100 The results are shown in Table 1. The concentration was measured using a Macbeth densitometer model RD-514. 【table】

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material characterized by containing a normally colorless to light-colored color-forming substance and a dihydroxy compound represented by the following general formula () or (). (In the formula, X represents _-CH2- , _-CH2CH2- , _-S- or -0-, and R represents an alkyl group.)