JPS6127285A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enable to obtain a thermal recording material with excellent heat response characteristics and high sensitivity, by incorporating a specified sulfide compound as a sensitizer for a color developer for developing the color of a dye precursor. CONSTITUTION:The thermal recording material comprising a colorless or light- colored dye precursor and a color developer for developing the color of the dye precursor by reacting therewith when being heated comprises a compound of formula I, wherein R is subst. or unsubst. aralkyl, as a sensitizer. For example, aqueous solutions of polyvinyl alcohol are added respectively to 3-diethylamino-6- methyl-7-anilinofluoran used as the color former, 2,2-bis(4'-hydroxyphenyl)propane used as the color developer and beta-benzylthionaphthalene used as the sensitizer, and the resultant three mixtures are individually dispersed for 24hr by ball mills. Three dispersed liquids thus obtained are mixed with each other, then a dispersed liquid of calcium carbonate, a dispersed liquid of zinc stearate, an aqueous solution of polyvinyl alcohol and water are added to the mixture, followed by sufficient agitation to produce a coating liquid. The coating liquid is applied to a raw paper, and is dried, followed by a supercalendering treatment to obtain the desired thermal recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a highly sensitive heat-sensitive recording material with excellent thermal responsiveness.

(B) Conventional heat-sensitive recording materials generally have 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. When heated with a head, heat vent, laser source, etc., the Eri dye precursor and color developer react instantaneously, and a recorded image is obtained. has been disclosed. Such a heat-sensitive recording material allows recording to be obtained using a relatively simple device and is easy to maintain.

It has the advantage of not producing any expansion noise, and is used in a wide range of fields, including measurement recorders, facsimiles, printers, computer terminals, labels, and automatic ticket vending machines. Particularly in the field of facsimile, demand for heat-sensitive methods is rapidly increasing, 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 machines can receive and send an A4 standard $ document in 10 to 20 seconds, so the current that flows through the facsimile's thermal head is repeated over a very short period of less than a few milliseconds, and the heat generated by this is extremely short. All of the energy is transmitted to the heat-sensitive recording sheet to carry out the image forming reaction.

In order to carry out the image forming reaction 7 with thermal energy transmitted in such a short time, it is essential that the thermosensitive recording material has excellent thermal responsiveness. In order to achieve heat-responsive gelling, the compatibility between the color developer and the dye precursor must be improved. A sensitizer is used for this purpose if necessary. When the sensitizer itself melts due to the transferred thermal energy, it dissolves or encapsulates the nearby dye precursor and color developer and promotes the entire coloring reaction, so the thermal responsiveness of the sensitizer increases. Alternatively, improving the compatibility with dye precursors and color developers is one way to increase the sensitivity of heat-sensitive recording materials.

As such a method, Japanese Patent Application Laid-open No. 48-19231 discloses wax-like grapes, JP-A No. 49-34842, JP-A No. 5
No. 0-149353, JP-A-52-10112746, JP-A-53-5636, etc. disclose nitrogen-containing compounds,
Carbo/acid nisdel etc., JP-A-57-64593,
JP-A-58-87094 discloses naphthol derivatives, 4'? 1'-1 No. 1983-64592, JP-A No. 1983-
No. 185187; JP-A-57-191089 and JP-A-58-110289 disclose the addition of naphthoic acid dichloromethane r.

However, the heat-sensitive recording materials produced using these methods are still unsatisfactory in terms of color density and color sensitivity.

(0) Purpose of the Invention The present inventors have investigated various sensitizers with the aim of creating a highly sensitive heat-sensitive recording material with further excellent heat responsiveness.

υ) Structure of the invention In a heat-sensitive recording material containing a color developer 2 which reacts with a normally colorless or light-colored dye precursor upon heating to cause the dye precursor to develop color, a sulfide compound t represented by the following general formula is used as a sensitizer. By @M, a highly sensitive heat-sensitive recording material with excellent heat responsiveness could be obtained.

Ichiki style (However, R represents a substituted or unsubstituted aralkyl group.

) Specific examples of the above general formula include the following derivatives.

β-be/dilthionaphthalene a-be/dilthionaphthalene β-(p-chlorobenzyl)thionaphthalene β-(m-
chlorobenzyl) thionaphthalene β-(0-chlorobenzyl) thionaphthalene β-(p-methylbenzyl) thionaphthalene β-(m-methylbenzyl) thionaphthalene/
β-(0-methylbenzyl)thionaphthalene/β-(p-
ethylbenzyl)thionaphthalene/β-(2,4-dichlorobenzyl)thionaphthale/β-(3,4-dichlorobenzyl)thionaphthale/β-(p-methoxybenzyl)
Thionaphthalene/β-(p-nitrobenzyl)thionaphthale/β-(α-phenethyl)thionaphthalene/β-(β-
7 enethyl) thionaphthalene β-be/zhydryl thionaphthalene β-(α-naphthylmethyl) thionaphthalene/The sensitizer according to the present invention is usually used in a ratio of 5% to the color developer.

Added in an amount of 1 or more. Preferred amount is 10-400% by weight
and particularly preferably 20-300% by weight. If the amount added is less than 5% by weight, the effect of improving sensitivity will not be sufficient (but if the amount 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 are not limited thereto.

The dye precursor is triphenylmethane.

Examples include fluorane-based, diphenylmethane-based, thiazino-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)fluorane, 3-dibutylamino-7-
(2-chloroanilino)fluoran, 3-diethylamine-7-(3-chloroanilino)fluoran, 3-diethylamine-6-methyl-7-anilinofluoran, 3
-(N-ethyl-p-toluidino)-6-methyl-7-
Anilinofluorane, 3-(N-methylcyclohexylamino)-3-methyl-7-aniline fluorane/, 3
-piperidino-3-methyl-7-anilinofluorane and the like.

As the color developer, hostile substances generally used in thermal paper can be used. For example, phenol, pt-butylphenol, p-phenylphenol, naphthol, p-hydroxyacetophenone, 2゜2'-dihydroxydiphenol, 4,4'-isopropylidene (2-t-butylphenol), 4,4'-isoglopylidene diphenol, 4-4'-cyclohexylidene diphenol, novolak type phenol resin, benzoic acid, pt-butylbenzoin Examples include p-hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid M methyl ester, and the like.

Examples of binders include de/guns, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, etc. Examples include water-soluble binders, latex-based water bath binders such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and methyl acrylate-butadiene copolymers.

Examples of M materials include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, acid ratio titanium, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin wood, and the like.

In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, and paraphytes are used for purposes such as head wear prevention and steering wheel locking prevention.

Waxes such as paraffin oxide, polyethylene, polyethylene oxide/stearamide, castor wax, dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, surfactants, and fireflies. Examples include original dyes.

Paper is mainly used as the support for the heat-sensitive recording material of the present invention, but various types of nonwoven fabrics, glass films, synthetic papers, metal foils, etc., or composite sheets made of a combination of these materials may also be used. Can be used arbitrarily.

(E) Example The present invention will be explained in more detail by way of examples.

Example 1 3-diethylamino-6-methyl-7-anilinofluorane 1ofk2 was dispersed in a ball mill with 30f of an aqueous solution for 24 hours. On the other hand, 2,2-his(4'-hydroxyphenyl)propane was dispersed in a ball mill for 24 hours with 2-5th 2% polyvinyl alcohol aqueous solution 752, and then further dispersed in a ball mill with β-benzylthionaphthalene 73 5fk 2% polyvinyl alcohol water bath solution 1059. Dispersed for 24 hours.

After mixing these three types of dispersions, 5% of calcium carbonate was added.
140 ft of the 0% dispersion were added, and further 251 ft of the 20% zinc stearate dispersion, 2402 ml of the 12-tiboripinyl alcohol water bath solution, and 180 ft of the water were added and thoroughly stirred to prepare a coating liquid.

Apply the coating liquid to a basis weight of 4 9 f/n? The mixture was coated on base paper at a solid coating amount of 8.5 hours, dried, and treated with a supercalender to obtain a heat-sensitive recording material.

Example 2 β-benzylthionaphthalene in Example 1 was replaced with β-
(p-chloroy/zyl)thionaphthalene? A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the material was used.

Comparative Example 1 In place of β-benzylthionaphthalene in Example 1, N-
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that hydroxymethyl stearamide was used.

The heat-sensitive recording materials obtained in Example 1.2 and Comparative Example 1 were evaluated by conducting the tests shown below. The results are shown in Table 1.

Test 1 Application pulse width: 1.0, 1.5, 2.0 milliseconds using a heat-sensitive facsimile tester [manufactured by Matsushita Electronic Components].

The applied voltage was 16.00 V, and the density of the resulting colored image was measured using a Macbeth densitometer H, D514.

Test 2 The density of the unprinted area after being stored in a 60°C environment for 24 hours was measured in the same manner as Test 1.

Table 1 (G) Effects of the Invention As shown in Table 1, by using the sulfide compound of the present invention, a highly sensitive heat-sensitive recording material with excellent thermal responsiveness could be obtained.

-492

Claims (1)

[Scope of Claims] A heat-sensitive recording material containing a color developer that reacts with a normally colorless or light-colored dye precursor upon heating to cause the dye precursor to develop color, containing a compound represented by the following general formula. Features of heat-sensitive recording material. General formula▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R represents a substituted or unsubstituted aralkyl group.)