JPS61263793A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having excellent preservation stability of developed color images and high sensitivity, by incorporating a specified compound as a sensitizer. CONSTITUTION:A compound of formula I, wherein R<1> is cynnamoyl, phenylacetyl or phenoxyacetyl, and R<2> is alkyl, is incorporated as a sensitizer in a thermal recording material 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, to obtain a thermal recording material having excellent preservation stability of developed color images and high sensitivity. The sensitizer is ordinarily added in an amount of not less than 5wt% based on the amount of the color developer, preferably, 10-400wt%. The dye precursor is a compound based on triphenylmethane, fluoran, diphenylmethane, thiazine, spiropyran or the like, and the color developer is an acidic substance generally used for a thermal recording paper. Although a paper is mainly used as a base, the base may be a nonwoven fabric, a plastic film, a synthetic paper, a metallic foil or the like or a composite sheet thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a highly sensitive heat-sensitive recording material with excellent thermal responsiveness.

03) Conventional heat-sensitive recording materials are generally those in which a heat-sensitive recording layer is provided on a support, and the heat-sensitive recording layer is composed mainly of a colorless or light-colored dye precursor that is generously donating and an electron-accepting monochromatic agent. , a dye precursor and a color developer instantaneously react by heating with a thermal pen, laser light, etc., and a recorded image is obtained, and is disclosed in Japanese Patent Publication No. 43-4160, Japanese Patent Publication No. 45-14039, etc. has been done. 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 such as terminals, labels, and automatic ticket vending machines such as 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 receive and send standard A4 documents in 10 to 20 seconds, the current that flows through the facsimile's thermal circuit 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. The sensitizer has the function of promoting the color reaction by dissolving or encapsulating the pupil itself, the dye precursor and color developer in the vicinity, which are melted by the transferred thermal energy. 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
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 Naphthol Visitor Association, JP 57-64592, JP 57-185187, JP 57-191089, JP 58-1102
No. 89 discloses naphthoic acid derivatives in % JP-A-57-12
No. 8592 and JP-A-57-182483 disclose the addition of a benzoic acid ester enzyme conductor.

However, heat-sensitive recording materials produced using these methods are still insufficient in terms of color density, storage stability of the resulting colored images, and staining of unprinted devices (background) over time. .

(Q. Purpose of the Invention The present inventors further investigated various sensitizers with the aim of obtaining a highly sensitive heat-sensitive recording material with excellent storage stability of colored images.

0 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 upon heating to cause the dye precursor to develop a color, a compound represented by the following general formula is included as a sensitizer. Therefore, we were able to obtain a highly sensitive heat-sensitive recording material with excellent storage stability for colored images.

General formula (where R is a cinnamoyl group, a phenylacetyl group,
or phenoxyacetyl group 't-represents, mata, R2 represents alkyl:4. ) Specific examples of the compound represented by the above general formula include those shown below.

Compound (1) m, p, = 88-88.5°C Compound (2) m, p, = 109.5-110°C Compound (3) m-n- = 1119-1 n 9 r% r
Compound (4) m, p, = 75-75.5°C Compound (5) m, I), = 123.5-124.5°C The compound of the above general formula can be easily obtained by a known method.

The sensitizer according to the invention is usually added in an amount of 5 parts or more to the kA colorant. Preferably 't is 10-400% by weight, particularly preferably 20-300% by weight, and the amount added is 5% by weight.
If the weight is less than 400 f, the sensitivity improvement effect will not be sufficient.
Addition of more than qb 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, crystal violet lactone, 3-diethylamino-7-methylfluorane, 3-diethylamine-6-chloro-7-methylfluorane, 3-diethylamine-6-methyl-7-chlorofluorane, 3-diethylamine-7- Anilinofluoran, 3-diethylamino-7-(2-/roloanilino)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-butylphenol, p-phenylphenol, naphthol, p-hydroxyacetophenone, 2゜2'-dihydroxydiphenol, 4.4'-isopropylidene (2-t-butylphenol), 4.4'-isopropylidene diphenol, 4.4'-cyclohexylidene diphenol, bis(4-hydroxyphenyl) sulfone, novolac type phenolic resin, benzoin acid, p-t-butylbenzoic acid, p
-hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid methyl ester, and the like.

As a binder, starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, volivite alcohol sf
a Polyt;'yl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, etc.
water-soluble binder, styrene-butadiene copolymer,
Examples include latex-based water-soluble binders such as acrylonitrile-butadiene copolymer, acrylic acid, methyl chloride-butadiene copolymer, and the like.

Examples of pigments include diatomaceous earth, talc, carbon dioxide, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like.

(7) Other ICs, 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 for the purpose of preventing head wear and sticking. In addition, dispersants such as dioctyl sulfosuccinate (sodium), ultraviolet absorbers such as benzophenone type and benzo 177 sol type, surfactants, fluorescent dyes and the like can be mentioned.

Although paper is mainly used as the support for the heat-sensitive recording material according to the present invention, any combination of combed nonwoven fabric, plastic film, synthetic paper, metal foil, etc. or a composite sheet made of a combination of these may be used.

(2) 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) Methyl parahydroxybenzoate (11.3 ft) was dissolved in 80 m of acetone, and 27 sodium hydroxide aqueous solution (12);
3 ff added. To this system, 11.6 t'efit of phenylacetyl chloride was added dropwise over 3 minutes while stirring, and stirring was then continued for 24 minutes. Thereafter, benzene and water were added to separate the layers, and the organic layer was washed with an aqueous solution of IJ and hydrogen carbonate and dried over anhydrous potassium carbonate. The solvent was distilled off and the residue was treated with n-hexane and benzene to obtain crystals of the desired product. This was recrystallized with a mixed solvent of n-hexane and benzene to obtain the desired product 11.4 f
I got it.

m, p, = 88-88.5°C Synthesis Example 2 Synthesis of Compound (2) Same as Synthesis Example 1 except that 12.59% of t-cinnamoyl chloride was used for the phenylacetyl chloride D used in Synthesis Example 1. Similarly, compound (2) 14.3f'lf
Obtained. m, p, = 109.5-110℃0℃ synthesis
Synthesis of Compound (3) Except that 12.5 ft of t-cinnamoyl chloride was used as the phenylacetyl chloride base used in Synthesis Example 1, and 12.5 ft of ethyl hydroxybenzoate was used as the base of methyl hydroxybenzoate. Compound (3) 1'y, 1t was obtained in the same manner as in Synthesis Example 1. m,
p, = 102-102.5°C Synthesis Example 4 Compound (4)
Synthesis Synthesis except that 12.5f of t-cinnamoyl chloride was used as the base of phenylacetyl chloride used in Synthesis Example 1, and 13.5f of rose hydroxybenzoin flln-globil was used as the base of methyl parahydroxybenzoate. In the same manner as in Example 1, 19.6 ft of compound (4) was obtained.
m, p, = 75-75.5°C Synthesis Example 5 Compound (5
) Synthesis of phenylacetyl chloride glue used in Synthesis Example 1 9
6.6 ff of compound (5) was obtained in the same manner as in Synthesis Example 1 except that 2.8 t of phenylacetyl chloride was used.

m, p, = 123.5 124.5°C Example 1 2-anilino-3-methyl-6-dinithylaminofluorane 10 ff 2% polyvinyl alcohol aqueous solution 30 f
At the same time, it was dispersed in a ball mill for 24 hours. On the other hand 2.2-
Bis(p-hydroxyphenyl)furopane 25ff2'
4 and 75f of a 2% polyvinyl alcohol aqueous solution in a ball mill for 24 hours, and further dispersed in a ball mill for 24 hours with 25ff of p-cinnamoyloxybenzoic acid methyl ester (compound 2) and 75f of a 2% polyvinyl alcohol aqueous solution. After mixing these 3m dispersions, add 100fQ of a 50% dispersion of calcium carbonate, further add 25fQ of a 20% dispersion of zinc stearate, 230f of a 110% polyvinyl alcohol aqueous solution, and 165f'i of water and stir thoroughly to form a coating liquid. did.

The coating liquid has a basis weight of 55f/n? The amount of hard coating applied to the base paper is 6.
f/I? The mixture was coated and dried, and treated with a supercalender to obtain a heat-sensitive recording material.

Comparative Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that N-methylolstearylamide was used in place of Compound 2 used in Example 1.

Example 2 Bis(4-hydroxyphenyl)sulfone was used as the 2,2-bis(p-hydroxyphenyl)propane glue 9 used in Example 1, and p-cinnamoyloxybenzoic acid was used as the glue for compound 2. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that ethyl ester (compound 3) was used. Comparative Example 2 Except that hemethylolstearylamide was used in place of compound 3 used in Example 2. A thermosensitive recording material was obtained in the same manner as in Example 2.

Example 3 Practical M In place of 2,2-bis(p-hydroxyphenyl)propane used in Example 1, p-hydroxybenzoic acid benzyl ester was used, and compound 2 or bi) Kp-benzylcarbonyloxybenzoic acid methyl ester was added. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that (Compound 1) was used.

Comparative Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 3 except that N-methylolsterylamide was used as the base of Compound 1 used in Example 3.

The heat-sensitive recording materials obtained in Evaluation Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated as follows, and the results are shown in the 'fc table.

(1) Color density: Printing was performed using a thermal facsimile, Facom Fax 621C, and the optical density of the color image was measured using Macbeth RD918.

(2) Image storage stability: Colored images are stored at 40°C and relative humidity 9.
It was stored for 24 hours under a zero temperature environment. Optical density f before and after storage: measurement, image retention rate was determined from the following formula.

(31ff1lb Skin Capri; Optical densities of unprinted areas after being stored in an environment of 60°C for 24 hours were added.

As shown in the effect table of the invention, by adding one of the compounds of the present invention, high-sensitivity heat-sensitive recording materials with excellent storage stability of colored images and low background capri were obtained.

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 ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R^1 represents a cinnamoyl group, phenylacetyl group, or phenoxyacetyl group. Also, R^2
represents an alkyl group. )