JPS62152782A - 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 compound as a sensitizer. CONSTITUTION:A compound of the general formula, wherein R is a substd. or unsubstd. aryl or a substd. or unsubstd. aralkyl, is incorporated into 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 the therewith when being heated. The sensitizer is ordinarily used in an amount of not less than 5wt% based on the amount of the color developer. The amount of the sensitizer is preferably 10-400wt%, particularly, 20-300wt%. The color developer may be an acidic substance, namely, an electron-acceptive compound which is usually used for thermal recording papers. Particularly, a phenol derivative or an aromatic carboxylic acid derivative is used as the color developer. Among phenol derivatives, preferred is a phenol derivative having at least one phenolic hydroxyl group, and more preferred is a phenol derivative which is unsubstd. in both or one of the two ortho-positions with respect to the phenolic hydroxyl group.

Description

[Detailed description of the invention] (A) Industrial application field The present invention relates to a highly sensitive recording material with excellent thermal responsiveness.

(B) Conventional technology 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 color developer. By heating with a head, a thermal pen, a laser beam, etc., the dye precursor and developer react instantaneously and a recorded image is obtained. Disclosed. Such 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 fields, including automatic ticket vending machines, labels, and train tickets. 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 facsimile machines 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 transferred to a thermosensor. The information is transmitted to the recording sheet and an image forming reaction is performed.

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 increase the thermal reactivity, 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-5
0-149353, JP-A No. 52-106746, JP-A-53-5636, etc., contain nitrogen-containing compounds, carboxylic acid esters, etc. The publications include naphthol derivatives, JP-A-57-64592, JP-A-57-185187@
, JP-A-57-191089, JP-A-58-1102
No. 89 discloses naphthoic acid derivatives in JP-A-57-14.
No. 8688, JP-A-57-182483, JP-A-58
No. 112788 and JP-A-58-162379 disclose the addition of benzoic acid ester derivatives.

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 have investigated various sensitizers with the aim of obtaining a highly sensitive heat-sensitive recording material with excellent heat responsiveness.

(D) 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 this, a highly sensitive heat-sensitive recording material with excellent thermal responsiveness could be obtained.

General formula (wherein R represents either a substituted or unsubstituted aryl group or a substituted or unsubstituted aralkyl group) Specific examples of compounds represented by the above general formula include those shown below. .

(Leaving space below) Compound (1) Compound (2) Compound (3) Compound (4) Compound (5) Compound (6) Compound (7) Compound (8) The compound of the above general formula can be prepared by a known method. easily obtained.

The sensitizer according to the present invention is usually added in an amount of 5% or more based on the color developer. The preferred amount is 10-400% by weight;
Particularly preferred is 20-300% by weight. Addition amount is 5% by weight
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 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-diethylamine-7
-Chlorofluorane, 3-(N-cyclohexylamino)-7-methylfluorane, 3-diethylamino-7-
Methylfluorane, 3-diethylamine-6-chloro-
7-methylfluorane, 3-diethylamine-7-anilinofluorane, 3-diethylamine-6-methyl-7
-dibenzylaminofluorane, 3-(N-ethyl-N
-p-toluidino)-7-anilinofluorane, 3-diethylamino-7-(0-chloroanilino)fluoran, 3-dibutylamino-7-(O-chloroanilino)fluoran, 3-diethylamine-6-methyl-7- Anilinofluorane, 3-(N-ethyl-N-p-toluidino)-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-trifluoromethylanilino)fluorane, 3
-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluorane, 3-diethylamine-6
-Methyl-7-(p-7enetidino)fluoran, 3-
Examples include dibutylamino-7-(O-fluoroanilino)fluoran.

As a color developer, acidic substances commonly used in thermal paper,
That is, electron-accepting compounds are used, particularly phenol derivatives and aromatic carbon H conductors. Preferred compounds among the phenol derivatives are those having at least one phenolic hydroxyl group, and more preferably phenol derivatives in which both or one of the ortho positions of the phenolic hydroxyl group are unsubstituted. For example, phenol, p-t-butylphenol, p-phenylphenol, 1-naphthol, 2-naphthol, p-hydroxyacetophenone, 2,2'-dihydroxybiphenyl, 4,4'-impulpylidenediphenol, 4,4'
-isono°11pylidene diphenol, 4°4'-isopropylidene bis(2-1-butylphenol), 4,
4'-isopropylidene bis(2-lylolophenol)
, 4.4'-cyclohexylidene diphenol, 2.
2-bis(4-hydroxyphenyl)butane, 2,2-
Bis(4-hydroxyphenyl)pentane, 2,2-bis(4-hydroxyphenyl)hexane, diphenol acetic acid methyl ester, bis(4-hydroxyphenyl)
Sulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropyloxydiphenylsulfone, bis(4-hydroxyphenyl)
Sulfide, 4,4'-thiobis(2-butyl-5
-methyl)phenol, 7-bis(4-hydroxyphenylthio)-3,5-dioxyhebutane, novolac type phenol resin, etc.; examples of aromatic carboxylic acid derivatives include benzoic acid, p-t-butyl benzoic acid,
p-hydroxybenzoic acid, p-hydroxybenzoic acid methyl ester, p-hydroxybenzoic acid isopropyl ester, p-hydroxybenzoic acid benzyl ester, gallic acid lauryl ester, gallic acid stearyl ester,
salicylanilide, 5-chlorosalicylanilide, 5-
Examples include metal salts of t-butylsalicylic acid such as zinc, metal salts of hydroxynaphthoic acid such as zinc, and the like.

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, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as 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 dioctyl sodium sulfosuccinate, ultraviolet absorbers such as benzophenone type and benzo 1-lyazole type, 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) 7.03 ml of thiophenol was added to 40 ml of acetone, and 11.3 cJ of a 28.3% aqueous sodium hydroxide solution was added thereto. Silicyl chloride 11. 'l acetone 20r
nl and added dropwise with stirring. - After continued stirring, benzene and water were added to separate the layers, and the organic layer was washed with an aqueous sodium bicarbonate solution and dried over anhydrous potassium carbonate. The solvent was distilled off and the residue was treated with n-hexane to obtain 1q of the desired product. This was recrystallized from n-hexane and further recrystallized from ethanol to obtain the desired product 6.0y.

m, p, = 88.5 to 91.5 °C Mass spectrum (FD method > m/e = 240 Example 1 3-diethylamino-6-methyl-7-anilinofluorane 20y in 1% polyvinyl alcohol aqueous solution 809 On the other hand, 4,4'-isopropylidenediphenol 509 was dispersed in a ball mill with 200 g of a 1% polyvinyl alcohol aqueous solution, and coarsely dispersed.
Compound (1) 50 mg was similarly dispersed together with 1% polyvinyl alcohol aqueous solution 2009.

After mixing these three types of dispersions, 4
A 0% dispersion 1253 was added, and 40 g of a 25% zinc stearate dispersion and 285tj of a 10.5% polyvinyl alcohol aqueous solution were added and sufficiently stirred to prepare a coating liquid. The coating liquid was applied to a base paper with a basis weight of 55 g/Td at a solid content of 67
/'rIt, dried, and treated with a supercalender to obtain a heat-sensitive recording material.

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

The facsimile IIFAcOMFAX-62 manufactured by Fujitsu@J was added to the heat-sensitive recording materials obtained in Evaluation Example 1 and Comparative Examples 1 and 2.
The optical density of the colored image obtained by printing using 1G was measured using Macbeth RD-514. The results were tabulated.

(Left below) (F) As shown in the effect table of the invention, by using the sensitizer according to the invention, it is possible to produce a heat-sensitive recording material with excellent thermal responsiveness.

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 either a substituted or unsubstituted aryl group or a substituted or unsubstituted aralkyl group.)