JPS60260383A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance heat response characteristics and color forming property, by providing a thermal recording material comprising a colorless or light-colored dye precursor, a color developer for developing the color of the dye precursor by reacting therewith when being heated, and a specified sensitizer. CONSTITUTION:A thermal recording layer 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 is provided on a base such as a paper, a non-woven fabric, a plastic film and a metallic foil to obtain the thermal recording material. In this case, at least one compound of formula I or II, wherein each of R1 and R6 is alkoxyl or aralkoxyl, and each of R2-R5 and R7-R9 is hydrogen, alkoxyl or aralkoxyl, with the proviso that all of R2-R5 and R7- R9 are not simultaneously hydrogen, must be incorporated in the thermal recording layer as a sensitizer.

Description

DETAILED DESCRIPTION OF THE INVENTION (4) Field of Industrial Application The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with improved color development.

(B) A heat-sensitive recording layer containing a conventional color developer as a main component, in which the dye precursor and the color developer are heated by a thermal head, a thermal pen, a laser beam, etc. It reacts instantaneously and can obtain recorded images.
It is disclosed in Publication No. 4039 and the like. Such heat-sensitive recording materials have the advantages of being able to record with relatively simple equipment, being easy to maintain, and not generating noise.
Measuring recorder, facsimile, printer, computer
It is used in a wide range of fields, including computer terminals, labels, and automatic ticket vending machines for passenger tickets. Particularly in the field of facsimile, the demand for heat-sensitive methods is rapidly increasing, and speeds are increasing in order to reduce transmission costs. In response to the increase in speed of facsimile, there has been a demand for higher sensitivity of heat-sensitive recording materials and materials.

Since high-speed facsimile machines accept standard A4 documents in 10 to 20 seconds, 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 thermal energy generated by this is extremely short. is transmitted to a heat-sensitive recording sheet to cause an image-forming reaction.

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. Compatibility with 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 has the function of dissolving or encapsulating the nearby dye precursor and color developer and promoting the color reaction. Improving the thermal responsiveness or the compatibility with dye precursors and color developers is also one method for making heat-sensitive recording materials highly sensitive.

As such a method, waxes are described in Japanese Patent Application Laid-Open No. 49-34842 and Japanese Patent Application Laid-Open No. 5
0-149353, JP-A-52-106746, JP-A-53-5636, etc., contain nitrogen-containing compounds, carboxylic acid esters, etc., and JP-A-57-64593, JP-A-58-87094 The publications include naphthol derivatives, JP-A-57-64592, JP-A-57-185187, q! jgU No. 57-191089, JP-A-58-1
Publication No. 10289 discloses 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.

(0) Purpose of the Invention The present inventors investigated various sensitizers with the aim of obtaining a heat-sensitive recording material with even higher sensitivity.

(b) In the groove bottom of the invention, in the heat-sensitive recording material containing a monochromatic agent that reacts with a normally colorless or light-colored dye precursor upon heating to cause the dye precursor to develop a color, the sensitizer is expressed by the following general formula (1): Alternatively, by containing the dihydroxynaphthalene derivative shown in (6), a highly sensitive heat-sensitive recording material with excellent heat responsiveness could be obtained.

There isn't. ) Specific examples of general formula (I) include 1,5-dimethoxynaphthalene, 1,6-diethoxynaphthalene, 1,7-diethoxynaphthalene, 1,5-diisoamyloxynaphthalene, etc. Specific examples of formula (6) include 2,3-dimethoxynaphthalene, 2,7-dimethoxynaphthalene, 2,6-diethoxynaphthalene, and 2,7-dimethoxynaphthalene.
Examples include diethoxynaphthalene, 2.6-dimethoxynaphthalene, 2.7-diisoamyloxynaphthalene, 2.7-dibenzyl oxynaphthalene, etc. The sensitizer according to the present invention is usually 5% by weight based on the color developer. The preferred amount added is 10-400% by weight,
20-300gg% is preferable for the load ◇ Addition amount is 5-fold fi
If it is less than 400% by weight, the sensitivity improvement effect will not be sufficient, and if it is added more than 400% by weight, it may be economically disadvantageous. The dye precursors include, but are not limited to, triphenylmethane, fluoran, diphenylmethane, thiazine, spiropyra/
Examples include system 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-aniso , nofluorane, 3-diethylamino-7-, C2-chloroanilino)fluorane, 3-
Dibutylamino-7-(2-chloroanilino)fluoran, 3-diethylamine-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-pibe IJ di/-3-methyl-7
- Anilitus fluorane, etc.

As the color developer, acidic substances generally used in thermal paper can be used, such as phenol, p-t-7" methylphenol, p-phenylphenol, naphthol, p-hydroxyacetophenone, and 2,21-dihydroxydihydroxydiphenol. Phenol, 4゜4-inpropylidene (2-t-butylphenol), 4,4-ingropylidene diphenol, 4-4'-cyclohexylidene diphenol, novolak type phenol resin, benzoic acid, pt-butylbenzoin Examples of binders include starches, hydroxyethylcellulose, methylcellulose, carboquine methylcellulose, gelatin, Water-soluble binders such as casein, polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate
Latex-based water-insoluble binders such as butadiene copolymers, etc. Pigments include cane earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, and urea. - Examples include formalin resin.

- In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearic acid amide,
Examples include waxes such as castor wax, acid splitting agents such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, surfactants, and fluorescent dyes.

Paper is mainly used as the support for the heat-sensitive recording material of the present invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, and composite sheets made of combinations of these may also be used as desired.

(Trout) The present invention will be explained in more detail by way of examples.
Also, I used a ball mill for 24FRf. On the other hand, 2.
2-bis(hydroxyphenyl)proban 25.9t
- 24 hours in a ball mill with 2% polyvinyl alcohol aqueous solution 75F, and then add 2,3-dimethoxynaphthalene 109 to 2% polyvinyl alcohol aqueous solution 3
It was milled with 0I in a ball mill for 24 hours. After mixing 1 g of these three types of molecules, 50% of calcium carbonate
l! Add 1g80g and further add 20g of zinc stearate.
% dispersion 92519.10% polyvinyl alcohol aqueous solution 180 i water 751 were added and sufficiently stirred to obtain a coating liquid.

The coating liquid was applied to a base paper with a basis weight of 55 g and 7 m'' as a solid coating amount of 6.
It was coated and dried to a thickness of 117 m'', and treated with a super calendar to obtain a heat-sensitive recording material.

Examples 2 to 5 In place of 2,3-dimethoxynaphthalene in Example 1, 2,7-dimethoxynaphthalene (Example 2),
1.5-dimethoxynaphthalene C implementation 9AJ3), 2
．． 7-dibenzyloxynaphthalene (Example 4), 1.
Thermal recording materials of Examples 2 to 5 were obtained in the same manner as in Example 1 except that 5-diynamyloxynaphthalene (Example 5) was used.' Comparative Example 1 2,3-Dimethoxynaphthalene of Example 1 A heat-sensitive recording material was prepared in the same manner as in Example 1 except that.

The heat-sensitive recording materials obtained in Examples 1 to 5 and Comparative Example 1 were evaluated by conducting the following tests.

The results are shown in Table 1.

Test 1 Using a heat-sensitive facsimile tester (manufactured by Matsushita Electronic Components Co., Ltd.), the pulse width was 1.0.1.5.2.0 milliseconds.
Printing was performed under the conditions of applied voltage i6:oov, and the color density of the resulting colored image was measured using a Macbeth densitometer RD514.

Test 2 The density of the vermilion printed area was measured in the same manner as Test 1 after being stored for 24 hours at 40° C. and 90% relative humidity.

Table 1 (F) Effects of the invention - Yoo, Eyo1, Axis, Yoyo, -E, ゎ ゛ or (2)
By using the compound shown in , it was possible to obtain a heat-sensitive recording material with excellent heat responsiveness.

Claims (1)

[Claims] In a heat-sensitive recording material containing a normally colorless or light-colored dye precursor and a color developer that reacts with the dye precursor upon heating to develop a color, at least one of the compounds represented by the following general formula (1) or (6) is used. There is no heat-sensitive recording material characterized by containing 1)