JPH0437798B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Application of the Invention) The present invention relates to a heat-sensitive recording sheet, and more particularly to a heat-sensitive recording sheet that has excellent storage stability and thermal responsiveness. (Prior Art) A thermosensitive recording sheet is a device that records images by utilizing physical and chemical changes in substances caused by thermal energy, and a large number of processes are being studied. So-called wax-type thermal recording paper has been known for a long time as a paper that takes advantage of the physical changes in substances caused by heat, and is used for electrocardiograms and the like. In addition, various types of coloring mechanisms have been proposed that utilize chemical changes caused by heat, but a two-component coloring type thermosensitive recording sheet is particularly representative. A two-component color-forming thermosensitive recording sheet is produced by dispersing two types of heat-reactive compounds in the form of fine particles, mixing them with a binder, etc. so that the two types of heat-reactive compounds are separated by the binder, etc., and forming a support. One or both of them are melted and brought into contact with each other by heating, and the coloring reaction that occurs is used to obtain records. These two types of heat-reactive compounds are
Generally, they are called electron-donating compounds and electron-accepting compounds. These two-component color-forming thermosensitive recording sheets have many advantages as recording sheets, such as (1) primary color development and no need for development, (2) paper quality similar to ordinary paper, and (3) ease of handling. In particular, those using colorless dyes as electron-donating compounds have further advantages such as (4) high color density, and (5) ease of producing thermosensitive recording papers of various color hues, and have great utility value. Therefore, it is most commonly used as a heat-sensitive recording material. In particular, the use of heat-sensitive recording sheets in the fields of facsimiles, recorders, and printers has been remarkable in recent years. As its use in the field of facsimile has spread, recording speeds have been increased, but heat-sensitive recording sheets also require short heat pulses, i.e., color development in response to low thermal energy, i.e., thermal responsiveness. There is a strong demand for improvement. On the other hand, since thermosensitive recording sheets are primary color-developing, they have the disadvantage that a reaction between an electron-donating colorless dye and an electron-accepting compound occurs not only by heat but also by a solvent or the like. This is because all of these heat-sensitive recording materials are organic substances, have high solubility in solvents, and therefore react in the solvent. In response to this, conventional efforts have been made to further provide a solvent-resistant protective layer on the heat-sensitive coloring layer, but these efforts have many drawbacks, such as the manufacturing process being complicated. (Object of the Invention) Therefore, an object of the present invention is to obtain a photosensitive recording sheet which has excellent thermal responsiveness and is less likely to develop color due to solvents and the like. (Structure of the Invention) The object of the present invention is to use 1,4-bis(P-hydroxycumyl)benzene as an electron-accepting compound of a heat-sensitive recording sheet, and to use 1,4-bis(P-hydroxycumyl)benzene as a thermofusible substance represented by the following general formula This is achieved by containing at least one kind of material. R ₅ NHCONH ₂ R ₆ CONH−R ₇ (In the formula, R ₁ to _{R 4} each represent a phenyl group, a benzyl group, and a lower alkyl or halogen substituted product thereof, and R ₅ and R ₆ each represent the number of carbon atoms.
_R7 represents an alkyl group of 12 or more and 24 or less, and a phenyl group. ) 1,4-bis(P-hydroxycumyl)benzene used in the present invention is obtained, for example, by subjecting diisopropenylbenzene to a Friedel-Crafts reaction with 2 molar equivalents of phenol in the presence of an acid catalyst. The crystals are white needle-shaped crystals with a melting point of 145°C. 1,4-bis(P-hydroxycumyl)benzene has low solubility in solvents such as alcohols, ketones, and benzene derivatives, and provides sufficient thermal responsiveness when used in combination with the above thermofusible substances. Surprisingly, only 1,4-bis(P-hydroxycumyl)benzene satisfies both at the same time, whereas 1,3-bis(P-hydroxycumyl)benzene or 1,2
-Bis(P-hydroxycumyl)benzene cannot be obtained. The compounds of the general formula ~ used in the present invention are:
The melting point is preferably 70°C or higher and 150°C or lower,
More preferably, the melting point is 80°C or higher and 130°C or lower. Further, when the phenyl group or benzyl group represented by R ₁ to R ₄ in the general formula is substituted with a lower alkyl group, the number of carbon atoms is 1 or more and 8 or less, preferably 1 or more and 3 or less. When substituted with halogen, preferred is chlorine or fluorine. Specifically, benzyl P-benzyloxybenzoate (mp. 119°C), β-naphthol benzyl ether (mp. 105°C), N-phenyl stearic acid amide (mp. 96°C), enyl ester (mp. 92℃), β-naphthol (P-chlorobenzyl) ether (mp. 115℃), β-naphthol (P-methylbenzyl ether (mp. 96℃),
Examples include α-naphthol benzyl ether (mp. 76°C). The colorless to light-colored electron-donating dyes used in the present invention include triarylmethane compounds, diphenylmethane compounds, xanthene compounds,
Examples include thiazine compounds and spiropyran compounds. Some examples of these are 3,3
-bis-(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e. crystal violet lactone) 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl) -3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindole-3-
yl) phthalide, 3-(p-dimethylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 3,3-bis-(1,2-dimethylindol-3-yl)-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-methylpyrrole-
2-yl)-6-dimethyl-aminophthalide 3-
Diethylamino-7-methoxyfluorane, 3-
Diethylamino-6-methoxyfluorane, 3-
Diethylamino-7-dibenzylaminofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tolylamino-6-methyl-7-anilinofluorane, 3
-N-methyl-N-tolylamino-6-methyl-
7-anilinofluorane, 3-piperidino-6-
Methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane,
3-N-cyclohexyl-N-methylamino-6
-Methyl-7-anilinofluorane, 3-piperazino-6-methyl-7-(p-methylanilino)
Fluoran, 3-diethylamino-7-(o-chloroanilino)fluorane, 3-diethylamino-7-butylaminofluorane, 3-diethylamino-7-diphenethylaminofluorane, 3,
7-bis(methyltolylamino)fluorane, 3
-piperidino-7-phenethylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino-7,8-benzofluorane, and the like. These may be used alone or in combination for the purpose of color tone adjustment. A water-soluble binder is added to the recording layer of the heat-sensitive recording paper of the present invention, and these binders are preferably compounds that dissolve 5% or more in water at 25°C. Specifically, methylcellulose, carboxylic Methylcellulose, hydroxyethylcellulose, starches, gelatin, gum arabic,
Casein, styrene-maleic anhydride copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and the like. Furthermore, if necessary, a pigment, a water-insoluble binder, a metal soap, etc. may be added to the recording layer of the heat-sensitive recording paper of the present invention. As the pigment, zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, waxite, kaolin, aluminum hydroxide, etc. are used. As the water-insoluble binder, synthetic rubber latex or synthetic resin emulsion is generally used, such as styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, vinyl acetate emulsion, etc. . As the metal soap, higher fatty acid metal salts are used, and emulsions of zinc stearate, calcium stearate, aluminum stearate, etc. are used. (Examples of the Invention) Examples will be shown below, but the present invention is not limited thereto. Example 1 20g of 2-anilino-3-chloro-6-diethylaminofluorane at 5% as an electron-donating dye
A.
Make it into a liquid. 1,4-bis(P-hydroxycumyl)benzene 60g 5% polyvinyl alcohol aqueous solution 600g,
The mixture was dispersed overnight with 60 g of benzyl P-benzyloxybenzoate to obtain liquid B. Calcined kaolin (Engelhard)
Disperse 100 g of Ansilex 90) with 100 g of 1% sodium hexametaphosphate solution using a homogenizer to obtain Solution C. Mix liquid A, liquid B, and liquid C to make a 30% dispersion of zinc stearate (Chukyo Yushi Hydrin Z-7)
Add 60g to make a heat-sensitive coating liquid. This has a basis weight of 50g/m ²
It was applied with a Mayer bar to a dry coating amount of 5 g/m ² on high-quality paper with
It was finished so that it would be a second (Betsuku). Examples 2 to 5 The same procedure as in Example 1 was conducted except that the thermofusible substances listed in Table 1 were used. Comparative Examples 1 to 3 2,2-bis(P
Example 1 was carried out in exactly the same manner as in Example 1, except that -hydroxyphenyl)propane, benzyl 4-hydroxybenzoate, and 1,3-bis(P-hydroxycumyl)benzene were used. Comparative Example 4 In Example 1, the thermofusible substance benzyl P-benzyloxybenzoate was not used, but twice the amount of 1,4-bis(P-hydroxycumyl)benzene was used. Thermal response is Fujitsu Ltd. high-speed facsimile FF-
2000 and a copy of the Institute of Image Electronics Engineers Test Chart No. 3, the density was measured using a Macbeth Co., Ltd. RD-918 model densitometer. On the other hand, solvent resistance was evaluated by impregnating paper with ethanol, toluene, and methyl cellosolve, and superimposing them on the colored surface of the resulting heat-sensitive recording sheet, and evaluating the degree of fog in three stages: good, fair, and poor. Ivy. The results are shown in Table 1, and it can be seen that the present invention is very effective.

[Table] Benzyl

[Table] Notes ○: Good, △: Fair, ×: Failed

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording sheet containing a colorless to light-colored electron-donating colorless dye, an electron-accepting compound that reacts with the colorless dye when heated, and a thermofusible substance, which has an electron-accepting property. A heat-sensitive recording sheet characterized by containing 1,4-bis(P-hydroxycumyl)benzene as a compound and at least one compound selected from the following general formulas I to V as a heat-fusible substance. R ₅ NHCONH ₂ R ₆ CONH-R ₇ In the formula, R ₁ to _{R 4} each represent a phenyl group, a benzyl group, and a lower alkyl or halogen substituted product thereof, and R ₅ and R ₆ each have 12 or more carbon atoms.
24 or less alkyl group, and R ₇ represents a phenyl group.