JPH0339472B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive material, and particularly to a heat-sensitive recording material with improved thermal responsiveness. 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 developer react instantly,
This allows recorded images to be obtained, and is designated as Special Publication No. 43-4160.
It is disclosed in Japanese Patent Publication No. 14039/1983. 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 heat distribution applications, such as in automatic ticket vending machines, labels, and ticket vending machines. Particularly in facsimile, the demand for heat-sensitive methods is increasing rapidly, and speeds are being increased to reduce transmission costs. In response to such increased speed of facsimile, there has been a demand for higher sensitivity of heat-sensitive recording materials. High-speed facsimile can print standard A4 documents.
Since reception and transmission take 10 to 20 seconds, the current flowing through the facsimile's thermal head is repeated over a very short period of time, less than a few milliseconds, and the generated thermal energy is transferred to the thermosensitive recording sheet, causing an image-forming reaction. It is something that allows you to do the following. In order to carry out an image forming reaction using thermal energy transmitted in such a short time, it is necessary to use a heat-sensitive recording material with excellent thermal responsiveness. In order to improve thermal responsiveness, it is necessary to improve the compatibility between the color developer and the dye precursor. A sensitizer is used for this purpose if necessary. When the sensitizer itself melts due to the transferred thermal energy, it dissolves or encapsulates nearby dye precursors and color developers to promote the color reaction, so the thermal responsiveness of the sensitizer increases. Improving the compatibility with dye precursors and color developers is also one method for increasing the sensitivity of heat-sensitive recording materials. As such a method, waxes are used in JP-A-48-19231, JP-A-49-34842 and JP-A-Sho.
No. 50-149353, JP-A-52-106746, JP-A-53-
5636, etc., nitrogen-containing compounds, carboxylic acid esters, etc. are described in JP-A-57-64593, JP-A-58-
No. 87094 discloses naphthol derivatives,
-64592, JP-A-57-185187, JP-A-57-
No. 191089 and JP-A-58-110289 disclose the addition of naphthoic acid derivatives. However, the heat-sensitive recording materials produced using these methods are still unsatisfactory in terms of color density and color sensitivity. The present inventors investigated various sensitizers in order to obtain a heat-sensitive recording material with even higher sensitivity. As a result, the present inventors developed a color developer that reacts with normally colorless or light-colored dye precursors when heated to develop color from the dye precursors. By incorporating a fumaric acid derivative represented by the following general formula as a sensitizer into a heat-sensitive recording material containing the general formula (In the formula, R represents a substituted or unsubstituted phenyl group or a substituted or unsubstituted aralkyl group.) A highly sensitive heat-sensitive recording material with excellent thermal responsiveness could be obtained. Fumaric acid derivatives according to the invention include dibenzyl fumarate, bis(4-chlorobenzyl) fumarate, bis(4-methylbenzyl) fumarate, bis(3-chlorobenzyl) fumarate, bis(3-methyl fumarate). benzyl), bis(2-chlorobenzyl) fumarate, bis(2-methylbenzyl) fumarate, bis(α-phenethyl) fumarate, bis(β-phenethyl) fumarate, bis(4-bromobenzyl) fumarate , bis(3,5-dimethylbenzyl) fumarate, bis(3,4-dimethylbenzyl) fumarate, bis(2,4-dichlorobenzyl) fumarate, diphenyl fumarate, bis(4-methylphenyl) fumarate, Bis(3-methylphenyl) fumarate, bis(2-methylphenyl) fumarate, bis(4-chlorophenyl) fumarate, bis(3-chlorophenyl) fumarate, bis(3,4-dimethylphenyl) fumarate, fumar bis(3,5-dimethylphenyl) acid, bis(3,5-dimethylphenyl) fumarate
-methyl-4-chlorophenyl), bis(4-bromophenyl) fumarate, and the like, but are not limited to these. The fumaric acid derivative according to the present invention is usually added in an amount of 5% by weight or more based on the color developer. The preferred amount is 10~
400% by weight, particularly preferably 20 to 300% by weight. If the amount added is less than 5% by weight, the effect of improving sensitivity will not be sufficient, and if the amount added is more than 400% by weight, it may be economically disadvantageous. The main components used in the heat-sensitive recording material of the present invention will be specifically explained below, but it goes without saying that components other than those described below may also be used in the present invention. As a dye precursor, triphenylmethane type,
Examples include fluoran-based, diphenylmethane-based, thiazine-based, and spiropyran-based compounds. For example, crystal violet lactone, 3-diethylamino-7-methylfluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7 -anilinofluorane, 3-diethylamino-7-(2-
chloroanilino)fluoran, 3-dibutylamino-7-(2-chloroanilino)fluoran, 3
-diethylamino-7-(3-chloroanilino)
Fluoran, 3-diethylamino-6-methyl-
7-anilinofluorane, 3-(N-ethyl-p
-toluidino)-6-methyl-7-anilinofluorane, 3-(N-methylcyclohexylamino)
-3-methyl-7-anilinofluorane, 3-piperidino-3-methyl-7-anilinofluorane, and the like. As the color developer, acidic substances generally used for thermal paper can be used, such as phenol, p-t
-butylphenol, p-phenylphenol,
naphthol, p-hydroxyacetophenone,
2,2'-dihydroxydiphenol, 4,4'-isopropylidene (2-t-butylphenol),
4,4'-isopropylidenediphenol, 4,
Examples include 4'-cyclohexylidene diphenol, novolac type phenolic resin, benzoic acid, pt-butylbenzoic acid, p-hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid methyl ester, and the like. As binders, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol,
Styrene-maleic anhydride copolymer, ethylene-
Examples include water-soluble binders such as maleic anhydride copolymers, and latex-based water-insoluble binders such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and methyl acrylate-butadiene copolymers. Examples of pigments 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, paraffin,
Waxes such as paraffin oxide, polyethylene, polyethylene oxide, stearamide, and castor wax, dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, and surfactants and fireflies. Examples include photodyes. Paper is mainly used as the support for the heat-sensitive recording material according to the present invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of combinations of these may also be used as desired. EXAMPLES Hereinafter, the present invention will be explained in more detail by way of Examples, but the present invention is not limited to these Examples. Example 1 10 g of 3-diethylamino-6-methyl-7-anilinofluorane was dispersed in a ball mill for 24 hours with 30 g of a 2% polyvinyl alcohol aqueous solution. On the other hand, add 25 g of 2,2-(bis(4-hydroxyphenyl)propane) to 75 g of a 2% aqueous polyvinyl alcohol solution.
24 hours in a ball mill, and further dispersed in a ball mill with 10 g of bis(3-methylphenyl fumarate) and 30 g of a 2% polyvinyl alcohol aqueous solution.
Dispersed for 24 hours. After mixing these three types of dispersions, add 80 g of a 50% dispersion of calcium carbonate, then add 25 g of a 20% dispersion of zinc stearate, 180 g of a 10% aqueous polyvinyl alcohol solution, and 75 g of water, stir thoroughly, and apply the coating solution. And so. The coating liquid was applied to a base paper having a basis weight of 55 g/m ² so that the solid content was 6 g/m ² and dried, followed by processing with a super calender to obtain a heat-sensitive recording material. Examples 2 to 5 Heat-sensitive recording materials were obtained in the same manner as in Example 1, except that the following fumaric acid derivatives were used instead of bis(3-methylphenyl) fumarate used in Example 1. Example 2 Diphenyl fumarate Example 3 Dibenzyl fumarate Example 4 Bis(4-methylbenzyl) fumarate Example 5 Bis(4-chlorobenzyl) fumarate Comparative example Bis(3-methylbenzyl fumarate) used in Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that methylphenyl) was omitted. The heat-sensitive recording materials obtained in Examples 1 to 5 and Comparative Examples were evaluated by conducting the following tests. The results are shown in Table 1. Test 1 Heat-sensitive facsimile tester [manufactured by Matsushita Electronic Components Co., Ltd.]
Printing was performed using a Macbeth densitometer to print under the conditions of applied pulse widths of 1.5, 2.0, and 2.5 milliseconds and applied voltage of 16.00 volts.
Measured using RD514.

[Table] It can be seen from the table that by adding the fumaric acid derivative according to the present invention, a heat-sensitive recording material with excellent heat responsiveness can be obtained.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material containing a normally colorless or light-colored dye precursor and a color developer that reacts with the dye precursor when heated to develop a color, in which a fumaric acid derivative represented by the following general formula is used. A heat-sensitive recording material characterized by containing: general formula (In the formula, R represents a substituted or unsubstituted phenyl group, a substituted or unsubstituted aralkyl group)