JPS6395982A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance thermal response characteristics, by providing a thermal recording layer comprising a colorless or light-colored dye precursor, a color developer for color-developing the dye precursor by reacting therewith when being heated and a sensitizer of a specified general formula, on a base. CONSTITUTION:A colorless or light-colored dye precursor, a color developer for color-developing the dye precursor by reacting therewith when being heated and a sensitizer of formula I (wherein R is a lower alkyl) are mixed, are ground, and are dissolved in a solvent to prepare a coating liquid. The coating liquid is applied to a base such as a paper, a nonwoven fabric and a plastic film, followed by drying to obtain a thermal recording material. The dye precursor may be a compound based on triphenylmethane, fluoran or the like, and the color developer may be a phenol derivative, an aromatic carboxylic acid derivative, an N,N'-diarylthiourea derivative or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a highly sensitive heat-sensitive recording material which has a thermoresponsive property.

(B) Prior art 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. By heating with a head, thermal pen, laser source, etc., the dye precursor and the color developer react instantaneously and a recorded image is obtained. etc. are disclosed. Such a heat-sensitive recording material has a figurative m1
It has the advantages of being able to obtain records using standard equipment, being easy to maintain, and producing no noise. Suitable for a wide range of fields such as
It is used. 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.

Since high-speed facsimiles can receive and send standard A4 documents in a few seconds to 20 seconds, the current that flows through the facsimile thermal head is repeated over a very short period of time, less than a few milliseconds, and the thermal energy generated by this is reduced. It is transmitted to the heat-sensitive recording sheet and causes 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 dissolving or encapsulating the nearby dye precursor and color developer and promoting the color reaction. Improving the responsiveness or the compatibility with dye precursors and color developers is one way to make heat-sensitive recording materials highly sensitive.

As such a method, waxes are used in JP-A-48-19231, JP-A-49-34842 and JP-A-5
No. 0-149353, JP-A-52-106746, JP-A-53-5636, etc. contain nitrogen-containing compounds, carboxylic acid esters, etc., JP-A-57-64593, JP-A-58-87094, etc. The publications include naphthol derivatives, such as JP-A-57-64592, JP-A-57-185187, JP-A-57-191089, and JP-A-58-1102.
Publication No. 89 discloses a derivative of solacetic acid, which is disclosed in Japanese Patent Application Laid-open No. 57-14.
No. 8688, JP-A-57-182483, JP-A-58
-112788 and JP-A No. 58-162379 disclose benzoic acid ester derivatives;
Publication No. 3 describes parabenzyl biphenyl in JP-A-60-
No. 56588 discloses the addition of diphenoxyethanes.

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

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

(D) Constituent structure of the invention In 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, a compound represented by the following general formula is used as a sensitizer. By containing P, a highly sensitive heat-sensitive recording material with excellent thermal responsiveness could be obtained.

Specific examples of the compound represented by the general formula (wherein R represents a lower alkyl group) are shown below.

Compounds of the above general formula can be easily obtained by known methods.

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 10 to 400% by weight,
In particular, 20 to 300% by weight is preferred. Addition amount is 5% by weight
If the amount is less than 4%, the sensitivity improvement effect will not be sufficient, and if more than 4% is added, it may be economically disadvantageous, and the amount of thermofusible material will increase, resulting in a dilution effect, resulting in insufficient color development and healing. I can't get the degree.

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

Examples of the dye precursor include triphenylmethane-based, fluoran-based, diphenylmethane-based, thiazine-based, and spiropyran-based compounds. For example, 3,3-bis(p-
dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-diethylamine -6-methyl-7-chlorofluorane, 3-diethylamino-7
-Chlorofluorane, 3-(N-cyclohexylamino)-7-methylfluorane, 3-diethylamino-7-
Methylfluorane, 3-diethylamino-6-chloro-
7-methylfluorane, 3-diethylamine-7-anilinofluorane, 3-dietheramino-6-methyl-7
-dibenzylaminofluorane, 3-(N-ethyl-N
-p-toluidino)-7-anilinofluorane, 3-diethylamine-7-(0-chloroanilino)fluorane, 3-dibutylamino-7-(0-chloroanilino)fluorane, 3-diethylamine-6-methyl-7- Anilinofluorane, 3-(N-ether-N-p-1luidino)-6-methyl-7-anilinofluorane, 3-(N
-Methyl-N-cyclohexylamino)-6-methyl-
7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-7
-(m-)lifluoromethylanilino)fluorane, 3
-(N-ethyl-N-impentylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-6
-Methyl-7-(p-phenetidine)fluoran, 3-
Examples include dibutylamino-7-(0-fluoroanilino)fluoran.

As a color developer, acidic O type commonly used for thermal paper,
That is, electron-accepting compounds are used, particularly phenol derivatives, aromatic carboxylic acid derivatives, N,N'-diarylthiourea derivatives, and polyvalent metal compounds such as zinc.

Among the above-mentioned phenol derivatives, particularly preferred color developers are bisphenols in which one of the hydroxyl groups may be substituted, as represented by the following structural formula.

represents. R1 represents a hydroxyl group, a lower alkoxy group, hydrogen, a lower alkyl group, or a nitrogen group. R2 and R3 represent hydrogen, a lower alkyl group, a lower alkenyl group, or a halogen. R4 and R5 represent hydrogen, a lower alkyl group, or a lower alkoxycarbonyl group. R4 and R5 may be combined to form a ring. ) Specific examples of compounds represented by the above structural formula include 2.2-bis(4-hydroxyphenyl)propane, 2.
．． 2-bis(4-hydroxyphenyl)butane, 1.1
-bis(4-hydroxyphenyl)cyclohexane, 2
．． 2-bis(4-hydroxyphenyl)pentane, 2.
2-bis(4-hydroxyphenyl)hexane, 2.2
-methyl bis(4-hydroxyphenyl)acetate, 2.2
-bis(4-hydroxyphenyl)ethyl acetate, 2.2
-His(4-hydroxyphenyl)butyl acetate, bis(
4-hydroxyphenyl) sulfone, bis(4-hydroxyphenyl) sulfoxide, bis(4-hydroxyphenyl) sulfide, 4-hydroxy-47-itugloviroxydiphenyl sulfone, 4-hydroxy-4'
-methyldiphenylsulfone, 4-hydroxy-47-
Chlorodiphenylsulfone, 2.2-? "S(a-t-
Butyl-4-hydroxyphenyl)propane, 2.2-
Bis(3-chloro-4-hydroxyphenyl)propane, bis(3-7ly-4-hydroxyphenyl)sulfone, bis(3-t-7'thyl-4-hydroxy-8-methylphenyl)sulfide, 4-hydroxy Examples include diphenyl sulfone.

Specific examples of other preferred color developers include benzyl 4-hydroxybenzoate, 1,7-bis(4-hydroxyphenylthio)-3,5
-Dioxahebutane, N,pQ/-bis(3-chlorophenyl)thiourea, zinc thiocyanate, N,N'-bis(3-trifluoromethylphenyl)l
- Ourea, lauryl gallate, stearyl gallate, behenyl gallate, zinc hydroxynaphthoate, zinc oxide, salicylanilide, dimethyl 4-hydroxyphthalate, metal salts such as zinc of 5-t-butylsalicylic acid, 6-hydroxy -2,3-naphthalene dicarboxylic acid dimethyl, 4
-Methyl hydroxybenzoate, 4-hydroxybenzoic acid, benzyl 2.4-dihydroxybenzoate, benzyl 3.4-dihydroxybenzoate, 4-t-butyl izoic acid, 5-chlorosalicylanilide, 4-hydroxysaccharide Isopropyl zoate, 2-phenoxyethyl 4-hydroxybenzoate, benzoic acid, novolak phenolic resin, 2,2'-dihydroxybiphenyl, 1-naphthol, 2-naphthol, bis(2-hydroxy-5-chlorophenyl)methane ,
1.1-bis(2-hydroxy-5-methylphenyl)
Dodecane, 4-phenylphenol, 4-t-butylphenol, phenol, 1.5-bis(3-hydroxyphenoxy)pentane,
1.2-bis(3-hydroxyphenoxy)ethane, 1
．． 2-bis(4-hydroxyphenoxy)ethane, 1-
(2,4-dihydroxyphenyl)-1-phenylethane, stearyl 4-hydroxybenzoate, 1.1-bis(4-hydroxyphenyl)-1-phenylethane, 3-(2-phenoxyethoxy)phenol, etc. be.

Examples of binders include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, water-soluble binders such as styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, and styrene. -Butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-
Examples include latex-based water-soluble binders such as 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, waxes such as higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide, and castor wax are used to prevent head wear and stickiness. Examples include dispersants 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 according to the present invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of combinations of these can also be used as desired.

(E) Synthesis Examples and Examples The present invention will be explained in more detail with reference to Synthesis Examples and Examples. However, the present invention is not limited to the following synthesis examples and examples.

Synthesis Example 1 Synthesis of Compound (1) 4.4'-dihydroxydiphenyl ether 10°12
(dissolved in 50 g of acetone and hydroxylated to 35.6%)
An aqueous solution of Jum was added. Dimethyl sulfate 14. (L was added dropwise over 6 minutes. After stirring for 5 hours, toluene and water were added to separate the layers. The organic layer was hydroxylated.) Washed with an aqueous IJ solution, dried over anhydrous potassium carbonate, and removed the solvent. Distilled away.

The residue was treated with ethanol to obtain crystals of the desired product.

This was further recrystallized from ethanol to obtain the desired product 8.9f.

m, p, = 101.0-102.5°C Synthesis Example 2 Synthesis of Compound 4.4'-dihydroxydiphenyl ether 10°1f
was dissolved in 50 g of acetone, and a 34.2% aqueous sodium hydroxide solution was added. While stirring this system, diethyl sulfate 1
7.4F was added dropwise. Thereafter, the system was heated and stirred and kept under reflux conditions for 6 hours. After cooling, toluene and water were added to separate the layers. The organic layer was washed with an aqueous sodium hydroxide solution, dried over anhydrous potassium carbonate, and the solvent was distilled off. The residue was treated with ethanol to obtain crystals of the target product. This was further recrystallized from ethanol to obtain the desired product 9.9f.

m, p, = 89.5 to 90.5°C Example 1 3-(N-4j-N-(soventylamino)-6-methyl-7-anilite fluorane 201 was dispersed with 1 tivolivinyl alcohol aqueous solution 802 in a ball mill. did.

On the other hand, 50f of 2,2-bis(4-hydroxyphenyl)propane was dispersed in a ball mill with an aqueous solution of 1 tibolyvinyl alcohol, and 5(l) of compound (1) was similarly dispersed with 200f of an aqueous solution of 1 tibolyvinyl alcohol.

After mixing these three types of dispersions, 4
0% dispersion 1257″ff: Added and further added 25% zinc stearate dispersion 407.10% polyvinyl alcohol aqueous solution 3002 and stirred thoroughly to prepare a coating solution.The coating solution was coated on base paper with a basis weight of 49. 6 f/n as solid content coating amount
? It was coated, dried, and treated with a supercalender to obtain a heat-sensitive recording material.

Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 50f of compound (2) was used in place of 50f of compound (1) used in example 1.

Comparative Example Compound (1) used in Example 1 50 r of N
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that -hydroxymethyl stearamide 501 was used.

A facsimile machine FACOM FAX-6210 manufactured by Fujitsu ■ was applied to the heat-sensitive recording materials obtained in Evaluation Example 1.2 and Comparative Example.
The optical density of the image printed using Macbeth D
-514.

The results were tabulated.

As shown in Table (F) Effects of the Invention, by using the sensitizer of the present invention, a highly sensitive heat-sensitive recording material with excellent thermal responsiveness can be obtained.

Procedure Nefu Seisho (self-motivated) October 6, 1986

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 ▲ Numerical formula, chemical formula, table, etc. ▼ (However, R represents a lower alkyl group.)