JPS61149395A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having excellent heat response characteristics and high sensitivity, by incorporating a specified sulfur-containing compound, in a thermal recording material comprising a normally colorless or light-colored dye precursor and a color developer for developing the color of the dye precursor by reacting therewith when being heated. CONSTITUTION:A sulfur-containing compound of the general formula, wherein R1 is 2-8C alkylene and R2 is subst. or unsubst. aryl, is incorporated in the thermal recording material, whereby a thermal recording material having excellent heat response characteristics and high sensitivity can be obtained. The sensitizer is ordinarily used in an amount of not less than 5wt% based on the amount of the color developer, preferably, 10-400wt%. The color developer may be an acidic substance, e.g., phenol or p-t-butylphenol. Diatomaceous earth, talc, kaolin or the like is used as a pigment. A base of the thermal recording material is a paper, a nonwoven fabric, a plastic film, a synthetic paper, a metallic foil or a composite sheet thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application The present invention relates to a highly sensitive heat-sensitive recording material that is thermally responsive.

However, conventional heat-sensitive recording materials generally have a gold film on a support as a heat-sensitive recording layer, the main components of which are a colorless or light-colored dye precursor with a range-donating property and a color developer with a single-child-accepting property. , by heating with a thermal head, thermal pen, laser beam, etc., a dye precursor and a color developer react instantaneously and a recorded image is obtained, and is disclosed in Japanese Patent Publication No. 43-4160 and Japanese Patent Publication No. 45-14039. etc. are disclosed. Such heat-sensitive recording materials have the advantage of being able to record with relatively simple equipment, are easy to maintain, and do not generate noise. Viewer terminal, label, US military Tsutomu, etc.! It is used in a wide range of fields such as xb vending machines. Particularly in facsimile, the demand for heat-sensitive methods is increasing, and speeds are being increased to reduce transmission costs. A of this kind of facsimile
In response to the trend toward higher speeds, there has been a growing demand for higher sensitivity in heat-sensitive recording materials.

Since high-speed facsimile machines can receive and send a standard A4 document 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 heat generated by this is extremely short. It transmits energy to the 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. 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 has the function of accelerating the color development reaction by encapsulating the nearby dye precursor and color developer. Improving responsiveness or compatibility with dye precursors and coloring agents is also one method of increasing the sensitivity of heat-sensitive recording materials.

As such a method, Japanese Patent Application Laid-Open No. 48-19231 discloses waxes, %
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 visiting conductors, JP-A-57-64592, JP-A-57-185187, JP-A-57-191089, JP-A-58-1102.
Publication No. 89 discloses that the entire t-unafthoic acid derivative is added.

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

(C) Purpose of the Invention The present inventors further investigated various sensitizers for the purpose of obtaining a highly sensitive heat-sensitive recording material with excellent heat responsiveness.

(To) Structure of the Invention In a heat-sensitive recording material containing a monochromatic agent that reacts with a normally colorless or light-colored dye precursor to give the dye precursor a uniform color, a sulfur-containing agent represented by the following general formula is used as a sensitizer. By incorporating the compound, it was possible to obtain a heat-sensitive recording material with high sensitivity and poor thermal response.

(However, R1 is an alkylene group having 2 to 8 carbon atoms, R
2 represents a Vt-substituted or unsubstituted aryl group. ) Specific examples of the above general formula include compounds represented by the following formula.

These compounds can be easily obtained by known methods.

For example, these compounds can be obtained by treating the corresponding aryl mercaptan and dicarboxylic acid dichloride in the presence of a neutralizing agent (base). This reaction formula is expressed by the following formula.

(However, R1 is an alkylene group having 2 to 8 carbon atoms, R
2 represents a substituted or unsubstituted aryl group tl-. ) In the reaction of the above formula, if the neutralizing agent decomposes the dicarboxylic acid dichloride, the neutralizing agent and the aryl mercaptan k
It is desirable to prepare a cutting edge for the ly, reaction system, and then add dicarbonate or dichloride to this.

Note that examples of the neutralizing agent used in this reaction include caustic soda, caustic potash, sodium carbonate, potassium carbonate, sodium acetate, potassium acetate, trimethylamine, triethylamine, and pyridine.

When the neutralizing agent is solid, it may be used in the form of a solution such as a water bath solution. In addition, as a solvent for this reaction, acetone, methyl ethyl ketone, ether, ethyl acetate, dioxane,
Tetrahydrofuran, benzene, toluene, xine/,
Use of hexane, hegetane, octane, cyclohexane, water, etc. is preferable to one without a solvent. In addition,
As an auxiliary solvent, alcohols such as methanol and ethanol may be added in addition to the above-mentioned solvents.

The sensitizer 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 ta1t-400% by weight, particularly preferably 20-300% by weight. Addition amount is 5
If it is less than 400% by weight, the sensitivity improvement effect will not be sufficient, and if more than 400 μm is added, it may be disadvantageous in terms of cutting.

The main components used in the heat-sensitive recording material of the present invention will be specifically explained below, but the present invention is not exhaustive.

As a dye precursor, triphenylmethane type, full secondary
Examples include ion-based, diphenylmethane-based, thiazine-based, and spiropyran-based compounds. For example, crystal violet lactone, 3-diethylamino-7-methylfluora/, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-ani Linofluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-dibutylamino-7-[2-chloroanilino]fluoran, 3-diethylamino-7-
(3-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 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 in thermal paper can be used, such as phenol, p'-t-butylphenol, p-phenylphenol, naphthol, p-hydroxyacetophenone, and 2゜2'-dihydroxydiphenol. , 4.4'-isopropylidene (2-1-butylphenol), 4.4'-ingropylidene diphenol, 4-4'-cyclohexylidene diphenol, novolak type phenol resin, benzoic acid, pt-butylbenzoin Examples include acids, p-hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, and p-hydroxybenzoic acid methyl ester.

Examples of binders include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, water bath binders such as styrene-maleic anhydride copolymer, ethylene-maleic anhydride coelectrolyte, and styrene. -Butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-
Latex-based water-bathable binders such as butadiene copolymers are included.

Examples of the pigment include cinnabar 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, waxes such as paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearic acid amide, and castor wax are used to prevent head wear and stickiness. , dispersants such as sodium dioctyl sulfosuccinate, ultraviolet light absorbers such as benzophenone and benzotriazole, surfactants, fluorescent dyes, and the like.

Paper is mainly used as a support for the heat-sensitive recording material according to the invention, but any type of non-woven oak fabric, plastic film, synthetic paper, metal foil, etc., or a composite sheet of a combination of these can be used. .

(E) Synthesis Examples and Examples The present invention will be explained in more detail by synthesis examples and examples.

(Preparation of Compound (11) 12.6 f of phenylmercaptan was added to 200 g of total acetone.Meanwhile, Caustic Nuda 52 was dissolved in 10 f of water, and this was added to the above A7Tone bath solution.While stirring the system, adipine Added 9.7 ff of acid dichloride. After 4 minutes, benzene and water were added to the system to dissolve the solid and separate the liquid. 1 N
After washing with a caustic soda water bath and then a sodium bicarbonate water bath, it was dried over anhydrous potassium carbonate. Remove the solvent and treat the residue with cyclohexane to obtain crude crystals of the target product 1.
7rt-obtain+. This was re-M crystallized with 1 sod of cyclohexane to obtain crystal 12.3F of the target product.

m,p,=81-82℃ 1,R,spect'tv y'c=0=1710
cm-'mass spectrum #CFD method) m/e =
Preparation of 330 (Compound (2)) Phenylmercaptan was added to 12.0 ff of acetone at 2°O. To this was added 159' of a 33% aqueous solution of caustic soda.While stirring the system, 7.8' of conolic acid dichloride was added.
It was dropped into r'. The formation of black and colored colored components was observed in the system. Add benzene and water to the reaction mixture, separate the liquid, and make the M layer t.
, water, hydrogen carbonate), IJum aqueous solution, zNHct water bath solution, and sodium hydrogen carbonate ice-melting solution. After drying with anhydrous potassium carbonate, the hot medium was distilled off. The residue was dissolved in benzene, n-hexane was added thereto, and the coloring component, i.e., piffl oil, was removed by slipping it onto paper.

Thereafter, the bath IM was plotted, and the residue was treated with a mixed solvent of benzene and n-hexane to obtain 3.3f of crude crystals of the target product. This was recrystallized with a mixed solvent of 15 Wt of benzene and 45 Tnt of hexane to crystallize 1. I got Of.

m, p, =89.5-90℃ 1, kL, spectrum 'C=0±1700o+s-'
11.0ft of β-naphthylmercaptan was used instead of phenylmercagtan, and 9.0ft of adipic acid dichloride was used.
The target product 8 was prepared in the same manner as in Synthesis Example 1 except that 02 was used.
11 I got busy.

m, p, 124-127℃ engineering, concentration, spectrum 4〉o= 1700cm -1 (
Preparation of compound (4)] The desired product was obtained in the same manner as in Synthesis Example 1, except that 14.7f't of parachlorophenylmercagutan was used instead of phenylmercaptan, and 8.52f't of adipic acid dichloride was used. Ta.

m, p, = 128.5-131.5°C 1, ya spectrum) '6 = = 0 = = 1700 cm -' (Example) 3-diethylamino-6-methyl-7-anilinofluorane 10f' ( l-2% polyvinyl alcohol water soluble g3
The liquid was separated for 24 hours using a ball mill with 0f. -10,000, 2 tons
2-His(4'-hydroxyphenyl)propane 25
ft 2% polyvinyl alcohol water bath solution 75F and dispersed in a ball mill for 24 hours, and further compound (1) obtained in Synthesis Example 1 35fk 2% polyvinyl alcohol water f & 1o
It was dispersed for 24 hours in a ball mill with st. After mixing these three dispersions, 50% calcium carbonate dispersion 1402 was added, followed by 20% stearic acid*lead dispersion fi25F, and 12% polyvinyl alcohol water dispersion 240.
2. Added 18 liters of water (li) and stirred thoroughly to prepare a coating liquid.

Painting? ! - 8.5t/n as the amount of solids applied to base paper of 49 f/n1' lid? The mixture was coated and dried, and treated with a super calendar to obtain a heat-sensitive recording material T-.

(Comparison?ll) A heat-sensitive recording material was obtained in the same manner as in the example except that N-hydroxymethylstearic acid amide was used as the compound used in the example (1).

The heat-sensitive recording materials obtained in Examples and Comparative Examples were evaluated by conducting the tests shown below. The results are shown in the table.

Trial yR1 Thermal facsimile trial MfLbAt: Matsushita Kako parts @ mounting]
Applied pulse width: 1.0.1.5.2.0 milliseconds, applied voltage 16. Each image was marked without OOV, and the density of the obtained colored image was measured using a gold Macbeth dosimeter D514.

Test 2 The unprinted area (JJi degree) after being stored for one month
(added 04).

Effects of the Invention By using the sulfur-containing compound shown in the table above, a heat-sensitive recording material that is sensitive to heat response and has good storage stability in unprinted areas can be produced. I was able to get it.

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 sulfur-containing compound represented by the following general formula: A heat-sensitive recording material characterized by: General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, R_1 is an alkylene group with 2 to 8 carbon atoms,
R_2 represents a substituted or unsubstituted aryl group. )