JPS6253876A - 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 in a thermal recording material which comprises 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. CONSTITUTION:A compound of formula 1, wherein R is an alkyl, halogen, alkoxy, acyloxy or acyl, and n is 0, 1 or 2, is incorporated as a sensitizer, 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 a color developer, preferably, 10-400wt%. If the amount of the sensitizer is less than 5wt%, a sensitivity-enhancing effect is insufficient, whereas an addition of more than 400wt% of the sensitizer is inadvantageous on an economical basis.

Description

DETAILED DESCRIPTION OF THE INVENTION (^) Industrial Application Field The present invention relates to a highly sensitive heat-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 thermal head, a thermal pen, a laser beam, etc., the dye precursor and color developer react instantaneously and a recorded image is obtained. has been 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, the 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's thermal head is repeated over a very short period of time, less than a few milliseconds, and the thermal energy generated by this is absorbed. 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 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-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, such as JP-A-57-64592, JP-A-57-185187, JP-A-57-191089, and JP-A-58-1102.
89＠Publication describes 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 (where R is an alkyl group, halogen, alkoxy group 1,
Represents an acyloxy group or an acyl group. n represents an integer of 0.1.2. ) Specific examples of the compound represented by the above general formula include those shown below.

Compound (1) m, p, = 98-99°C Compound (2) m, p, = 103-104°C m, p, = 76°C Compound (4) m, p, = 91-92°C Compound (5 ) m, p, = 84-85°C Compound (6) m, p, = 95°C Compound (7) m, p, = 106°C Compound (8) m, p, = 111°C Compound (9) m, p , = 121-122°C Compound (10) m, p, = 73°C Compound (11) m, p, = 99°C Compound (12) m, p, = 90°C Compounds of the above general formula can be easily prepared by known methods. can be obtained.

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 10-400% 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-diethylamino -6-methyl-7-chlorofluorane, 3-diethylamino-7
-Chlorofluorane, 3-(N-cyclohexylamino)-7-methylfluorane, 3-diethylamino-7-
Methylfluorane, 3-diethylamino-6-chloro-
7-Methylfluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-6-methyl-7
-dibenzylaminofluorane, 3-(N-ethyl-N
-p-toluidino)-7-anilinofluorane, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-dibutylamino-7-(0-chloroanilino)fluorane, 3-diethylamino-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-diethylamino-6
-Methyl-7-(p-phenetidine)fluorane, 3-
Examples include dibutylamino-7-(0-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 carboxylic acid derivatives. Among the phenol derivatives, preferred compounds include at least 1
The compound is a compound having at least one phenolic hydroxyl group, and is more preferably a phenol derivative in which both or one of the ortho positions of the phenolic hydroxyl group is unsubstituted. For example, phenol, pt-butylphenol, p-phenylphenol, 1-naphthol, 2-naphthol, p-hydroxyacetophenone, 2,2'-dihydroxyphenyl, 4,4'-isopurpylidenediphenol, 4. 4
'-isopropylidene diphenol, 4°4'-isopropylidene bis(2-t-butylphenol), 4.
4'-isopropylidene bis(2-chlorophenol)
, 4.4'-cyclohexylidene diphenol, 2,
2-bis(4-hydroxyphenyl)butane, 2,2-
Bis(4-hydroxyphenyl)pentane, 2,2-bis(4-hydroxyphenyl)hexadi, 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(2-1-butyl-5
-Methyl)phenol, 1,7-bis(4-hydroxyphenylthio)-3,5-dioxyhebutane, novolac type phenol resin, etc.Aromatic carbon W1 derivatives include, for example, benzoic acid, p- t-Butylbenzoic 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, metal salts such as zinc of 5-t-butylsalicylic acid, metal salts such as zinc of hydroxynaphthoic acid, and the like.

Examples of the binder include starches, hydroxyethylcellulose, methylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, water-soluble binders such as styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, and styrene-maleic anhydride copolymer. Examples include latex-based water-soluble binders such as butadiene copolymer, acrylonitrile-butadiene copolymer, and methyl acrylate-butadiene copolymer.

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. , 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) 6.9 g of para-cresol was dissolved in 40 rn1 of acetone, and 9.4 g of a 34% aqueous sodium hydroxide solution was added thereto. 11.2g of cinnamic acid chloride in 20rr of acetone
A solution dissolved in IIl was added dropwise over 10 minutes with stirring, and after continued stirring for 7 minutes, benzene and water were added to separate the layers. The organic layer was washed with an aqueous sodium bicarbonate solution, dried over anhydrous potassium carbonate, and the solvent was distilled off. The residue was treated with n-hexane to obtain crystals of the target product, which were recrystallized from n-hexane.
11.0 g of the target product was obtained. m, p, = 98-99°C Synthesis Example 2 Synthesis of Compound (2) The same procedure as Synthesis Example 1 was used except that 7.6 g of parachlorophenol was used instead of 6.9 g of para-cresol used in Synthesis Example 1. 10.4 g of the target product was obtained.

m, I), = 103-'104°C Example 1 20 g of 3-diethylamino-6-methyl-7-anilinofluorane was dispersed with 1% polyvinyl alcohol aqueous solution 809 in a ball mill. Separately, 50 g of 4.4'-isopropylidene diphenol was dispersed with 200 g of a 1% aqueous polyvinyl alcohol solution in a ball mill, and 50 g of compound (1) was mixed with 200 g of a 1% aqueous polyvinyl alcohol solution.
00g was similarly dispersed.

After mixing these three types of dispersions, 250 g of a 40% dispersion of calci carbonate and rum was added, and then a 25% dispersion of zinc stearate 40S? , 9.4% poly. 490 g of vinyl alcohol aqueous solution was added and thoroughly stirred to obtain a coating liquid. The coating liquid was applied to a base paper having a basis weight of 55 g/rd so that the solid content coating amount was 7 g/m, 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 compound (2) was used instead of compound (1) in Example 1.

Comparative Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the dispersion of compound (1) in Example 1 was omitted.

Comparative Example 2 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 the compound (1) in Example 1.

Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that benzyl hydroxybenzoic acid ester was used in place of 4,4'-isopropylidene diphenol.

Example 4 A heat-sensitive recording material was obtained in the same manner as in Example 3 except that compound (2) was used instead of compound (1) in Example 3.

Comparative Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 3 except that the dispersion of compound (1) in Example 3 was omitted.

The thermal recording materials obtained in Evaluation Examples 1 to 4 and Comparative Examples 1 to 3 were printed under the conditions of 16.00 volts, 1.5 milliseconds, 2.0 milliseconds, and 2.5 milliseconds. The optical density of the colored image was measured using Macbeth RD918.

The results are shown in the table.

(F) As shown in the effect table of the invention, the heat-sensitive recording material using the sensitizer according to the invention has excellent thermal responsiveness and high sensitivity.

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 an alkyl group, halogen, alkoxy group, acyloxy group, or acyl group. n represents an integer of 0, 1, or 2. )