JPH0374917B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to the improvement of a heat-sensitive recording material whose main components are a colorless or light-colored organic dye generally called a leuco compound and an organic acid such as a phenol compound that develops a color by reacting with the leuco compound. It is something. [Prior Art] A thermosensitive recording paper containing a leuco compound and an organic acid is already known, for example, from Japanese Patent Publication No. 14039/1983. This recording paper is based on the principle that thermal energy is applied to the recording layer to soften or melt the leuco compound, organic acid, and binder, and the two coloring components are brought into contact to cause a coloring reaction. It is used in fields such as Although the recording characteristics of the recording paper differ depending on the use, for example, in order to increase the recording speed, it is necessary to improve the recording apparatus and to promote the color development of the recording paper itself. A commonly used method for promoting color development is to include a low melting point substance in the recording layer. As low melting point substances, i.e. color accelerators or sensitizers, urea, phthalic anhydride,
Acetanilide, paraffin wax, carnauba wax, beeswax, wood wax, higher fatty acids, higher fatty acid esters are used in JP-A-48-19231, and salicylic acid, anisic acid,
Phthalic acid monophenyl ester, phthalic acid monobenzyl ester, and fatty acid amide have recently been widely used as color accelerators. Specifically, Japanese Patent Publication No. 51-27599 describes the sensitizing effect of fatty acid amide by combining paraffin or microwax with fatty acid amide.
No. 139740 also describes the sensitizing effect of fatty acid amides such as stearamide and oleic acid amide, and is well known. [Problems to be Solved by the Invention] The inventors of the present invention confirmed the effects of these known color accelerators, and as a result of wide and deep studies in order to find substances with even better properties, they have found that they have remarkable effects. We have discovered a novel color development accelerator having the following characteristics, and based on this knowledge, we have accomplished the present invention. [Means for Solving the Problems] That is, the present invention provides a heat-sensitive recording material mainly composed of a leuco compound and an organic acid that develops a color by reacting with the leuco compound, in which the heat-sensitive recording layer contains a compound having the following general formula. The present invention relates to a heat-sensitive recording material containing at least one of the compounds shown below. (In the formula, m and n represent integers from 1 to 10.) The compound of the above general formula is excellent in the effect of promoting color development, and also has other properties as a heat-sensitive recording material, such as background density and background texture after storage. It also has properties such as fogging and fading that cause no problems in practical use. Further, the object of the present invention can be achieved when the content of the compound of the above general formula is 1 to 40% by weight of the total solid content of the heat-sensitive recording layer. Next, the substances used in the present invention will be described. (1) Leuco compounds Colorless or light-colored substances that develop color by reacting with organic acids, such as triphenylmethane, triphenylmethanephthalide, fluoran, leucoolamine, diphenylmethane, phenothiazine, phenoxazine, Various derivatives such as spiropyran derivatives, indoline derivatives, and indigo derivatives may be mentioned, but are not particularly limited, and the following may be exemplified. Crystal violet lactone (blue),
3-diethylamino-6-methyl-7-anilinofluorane (black), 3-(N-ethyl-P-
toluideino)-6-methyl-7-anilinofluorane (black), 3-diethylamino-6-
Methyl-7-(ortho, p-dimethylanilino)fluoran (black), 3-pyrrolidino-
6-methyl-7-anilinofluorane (black),
3-piperidino-6-methyl-7-anilinofluorane (black), 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluorane (black), 3-diethylamino-7 -(ortho-chloroanilino)fluoran (black), 3-diethylamino-7-(meta-trifluoromethylanilino)fluoran (black), 3-diethylamino-6-methyl-chlorofluoran (red), 3-diethylamino-
6-Methyl-fluorane (red), 3-cyclohexylamino-6-chlorofluorane (orange), 3-(N-isoamyl-N-ethylamino)-6-methyl-7-anilinofluorane (black). (2) Organic acid A substance that is solid at room temperature, melts when heated, and becomes a color developer when it comes into contact with a leuco compound.
There are various phenolic substances, fatty acids, aromatic carboxylic acids, etc. Examples include gallic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, o-
Hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-p-toluic acid, 3,5
-xylenol, thymol, p-tert-butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-
Naphthol, catechol, resorcinol, hydroquinone, 4-tert-octylcatechol, 4,
4'-sec-butylidenephenol, 2,2'-dihydroxydiphenyl, 2,2'-methylenebis(4-methyl-6-tert-butylphenol),
2,2'-bis(4'-hydroxyphenyl)propane (also known as bisphenol A), 4,4'-isopropylidene-bis(2-tert-butylphenol), pyrogallol, phloroglucin, phloroglucin carboxylic acid , p-methylphenol, p-phenylphenol, 4,4'-cyclohexylidene diphenol, 4,4'-(1-methyl-n-hexylidene) diphenol, 4,
4'-isopropylidene dicatechol, 4,4'-
Benzylidene diphenol, 4,4'-isopropylidene bis(2-chlorophenol), 3-
Phenylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 1-oxy-2-naphthoic acid, gallic acid ester, salicylic acid ester, p-hydroxybenzoic acid ester, 4-hydroxyphthalic acid ester, 2-(4- hydroxyphenyl)-2-(2'-hydroxyphenyl)propane, 4,4'-dihydroxy-3,
Examples include 3'-diisopropyldiphenyl-2,2-propane. (3) Binder A water-soluble binder is mainly used to isolate and fix the coloring agent dispersed in fine particles from each other, such as polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, and casein. , gelatin, starch and their derivatives. (4) Other additives The heat-sensitive recording material of the present invention may contain other additives in the heat-sensitive layer as necessary, such as inorganic or organic pigments such as clay, calcium carbonate, aluminum hydroxide, talc, titanium oxide, zinc oxide, etc. , waxes, antioxidants for storage stability, ultraviolet absorbers, various fatty acid metal salts to prevent staining, water resistance agents to improve water resistance, phenolic resins, surfactants, etc. can also be added. It is. Further, in combination with the color development accelerator according to the present invention, a known color development accelerator can be added and contained in the recording layer. (5) Substrate The substrate used in the present invention is generally paper such as high-quality paper, medium-quality paper, or coated paper, but other substrates such as glass fiber sheets, plastic sheets, and film laminated paper are also used. It can be used as [Example] Below, the effects of the present invention will be explained in more detail with reference to Examples. Example 1 (a) Production of heat-sensitive recording material Liquids A and B having the following compositions were separately dispersed in a paint shaker (manufactured by Toyo Seiki) for 10 hours. Solution A: Leuco dye 3-(N-cyclohexyl-N-
Methyl)-amino-6-methyl-7-anilinofluorane 5g 4,4'bis(hydroxyethyl)bisphenol A 8g Aluminum hydroxide 20g Zinc stearate 5g Polyvinyl alcohol 12% solution 35g Water 52g Part B: Bisphenol A 15g Kaolin 20g Zinc stearate 3g Polyvinyl alcohol 12% liquid 35g Water 52g Next, add 125g of Part A, 125g of Part B, 50g of 12% polyvinyl alcohol, and 40g of water, mix and stir to adjust, and make a coating liquid. This coating liquid was applied onto the surface of a 50 g/m ² high-quality paper using a Meyer bar so that the coating amount after drying was 8 g/m ² and dried to obtain heat-sensitive recording paper. Example 2 The formulation of Solution A used in Example 1 was the same as Example 1 except that 3-(N-isoamyl-N-ethyl)amino-6-methyl-7-anilinofluorane was used as the leuco dye. A thermosensitive recording paper was obtained in the same manner. Example 3 Same as Example 1 except that 4,4'bis(hydroxybutyl)bisphenol A was used in place of 4,4'bis(hydroxyethyl)bisphenol A in the liquid A formulation used in Example 1. A thermosensitive recording paper was obtained in the same manner. Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except for 4,4'bis(hydroxyethyl)bisphenol A in the formulation of liquid A used in Example 1. Comparative Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that stearamide was used in place of 4,4'bis(hydroxyethyl)bisphenol A in the A liquid formulation used in Example 1. . The heat-sensitive recording papers obtained in the Examples and Comparative Examples above were surface-treated with a test super calender so that the recording surface had a Bekk smoothness of 500 seconds. Next, regarding the thermal recording paper obtained by surface treatment, the commercially available G facsimile machine FACOM FAX
621C (manufactured by Fujitsu Ltd.) under the conditions of recording power 0.96w/dot, energization time 0.45msec, cycle approximately 5msec/, and the image density and background density at the time of printing were measured using a Macbeth densitometer. did. Storage stability was determined by the concentration after 24 hours of storage in a constant temperature room at 60°C in a dry state. Table results were obtained for Examples and Comparative Examples.

[Table] [Effects of the Invention] As described above, it has been demonstrated that the heat-sensitive recording material of the present invention has excellent characteristics in terms of sensitivity and storage stability.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material mainly composed of a leuco compound and an organic acid that develops a color by reacting with the leuco compound, which contains at least one compound represented by the following general formula in the heat-sensitive recording layer. A heat-sensitive recording material characterized by the following properties. (In the formula, m and n represent integers from 1 to 10.)