JPH021031B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a colorless or light-colored leuco dye, an organic acid that causes the leuco dye to develop color when heated, and/or a colorless or light-colored leuco dye.
The present invention also relates to an improved heat-sensitive recording material using a phenolic substance or a phenolic substance. BACKGROUND ART Various heat-sensitive recording materials have been known in which a heat-sensitive coloring layer is provided on a support such as paper, synthetic paper, or resin film, and is capable of recording an image by developing color when heated.
Compared to other recording materials, this material can be used as a computer output because it does not require complicated phenomena or processes such as fixing, records can be obtained in a relatively short time, does not generate noise, and is low in cost. It is widely used as a recording material for computer printers, facsimile machines, telex machines, various information devices, medical devices, various measuring devices, automatic ticket vending machines, etc. However, these conventional recording materials have several drawbacks and have not yet been satisfactory. In particular, there is a strong demand for higher speed output machines, and there are no machines that have sufficient thermal sensitivity to meet this demand. For this reason, it has been proposed to add various sensitizers. For example, JP-A-53-
No. 39139, JP-A-53-26139, JP-A-53-5636
No. 53-11036, etc., various waxes, fatty acid amides, alkylated biphenyls,
These include substituted biphenylsylalkanes, coumarin compounds, and diphenylamines. Further, surface treatments have been applied to increase the smoothness of the heat-sensitive layer to increase heat sensitivity, but the effect has been insufficient. Also, it melts due to heating during recording and adheres to the thermal head, etc., causing residue and sticking phenomenon.
Since this problem significantly impairs running performance and image clarity, a further solution is strongly desired. The purpose of the present invention is to solve the above-mentioned conventional drawbacks, and in particular, it is possible to record high-density, clear colored images with low thermal energy, and to use high heat that does not impede the running performance of the thermal head due to adhesion of residue, sticking, etc. The object of the present invention is to provide a sensitive heat-sensitive recording material. As a result of repeated research aimed at the purpose of the present invention, it has been found that a heat-sensitive recording material having a heat-sensitive coloring layer containing a colorless or light-colored leuco dye and an organic acid or phenolic substance that causes the leuco dye to develop color when heated,
It has been found that the above-mentioned conventional drawbacks can be significantly solved by incorporating a compound represented by the following structural formula into the heat-sensitive coloring layer, and the present invention has been achieved. general formula (In the formula, X means a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a phenylene group, or a direct bond; R ₁ and R ₂ may be the same;
Indicates a phenyl group or an alkyl-substituted phenyl group. ) Examples of such compounds include benzyl (mp95°C), 1,1-dibenzoylmethane (m.p.
p.95℃), 1,2-dibenzoylethane (mp144
°C), 1,3-dibenzoylpropane (mp67.5
℃), 1,4-dibenzoylbutane (mp112℃),
1,5-dibenzoylpentane (mp68℃), 1,
6-dibenzoylhexane (mp84℃), 1,7
-Dibenzoylheptane (mp57℃), 1,8-
Dibenzoyl octane (mp 89℃), benzoylacetone (mp 59℃), 4-t-butyl dibenzoylmethane (mp 100℃), stearoyl benzoylmethane (mp 70℃), 1,2-dibenzoylbenzene (mp 146℃), 1,3-dibenzoylbenzene (mp100℃), 1,4-dibenzoylbenzene (mp164℃), 1,4-diacetylbenzene (mp114℃), cuminyl (mp84℃), trans-1,2-dibenzoyl Ethylene (mp134
°C, cis-1,2-dibenzoylethylene (m.
p.111℃), stearylbenzoylmethane (mp67
~70℃) etc. Since the above-mentioned compound exhibits an extremely large effect on the thermal sensitivity of the thermosensitive recording material, it can provide a colored image with high density with lower thermal energy than in the past. On top of that,
Since the coloring start temperature shows a sharp rise in the coloring temperature-coloring density characteristic curve, a clear image with high density can be quickly obtained without coloring the surrounding areas of the colored image. Furthermore, the compound used in the present invention is less likely to cause residue adhesion or sticking during recording, thereby impeding the running performance of the thermal head, and can withstand long-term recording. In the present invention, conventionally known leuco dyes, organic acids, or phenolic substances constituting the heat-sensitive coloring layer are used, and examples thereof are shown below. Examples of leuco dyes include triphenylmethane phthalide series, fluoran series, phenothiazine series, indolyl phthalide series, spiropyran series, leuco auramine series, rhodamine lactam series, triphenylmethane series, triazene series, naphtholactam series, and spironolan. It is a substance selected from the group of xanthenes, azomethines, benzopyrans, hydroxyphthalanes, and leukoolamines, and organic acids include stearic acid, oxalic acid, maleic acid, tartaric acid, citric acid, and benzoic acid. acid, naphthoic acid, 4-t-butylphenol, 4
- solid organic acids such as phenylphenol, 2,2'-dihydroxydiphenyl, 4,4'-isopropylidene diphenol, naphthol, 4-hydroxyamotophenone, methyl-4-hydroxybenzoate, salicylic acid, or together with formalin; acidic polymer with, phenol-aldehyde polymer, phenol-acetylene polymer, rosin-modified maleic acid resin, styrene-maleic anhydride copolymer hydrolyzate, carboxypolyethylene polymer hydrolyzate, vinyl ethyl ether-maleic anhydride The substance is selected from the group of acid copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, and the like. This will be explained below using examples. Examples and Comparative Examples Mixtures having the following compositions were each dispersed for 24 hours using a ball mill, and then mixed after preparation to prepare a thermosensitive color forming layer forming liquid. Solution A 3-cyclohexyl-methyl amino-6
Methyl 7-anilino fluoran 20 parts Polyvinyl alcohol (10% aqueous solution) 30 parts Water 50 parts Solution B Bisphenol A 14 parts Polyvinyl alcohol (10% aqueous solution) 33 parts Calcium carbonate 20 parts Water 33 parts Wax liquid C, which is a sensitizing agent, is prepared as follows. Liquid C Stearamide 20 parts Sodium dodecylbenzenesulfonate 2 parts Water 78 parts In place of the liquid C, liquids D to F having the following compositions were prepared and used in the recording material forming liquid of the present invention. Solution D 1,1-dibenzoylmethane 20 parts Methylcellulose (5% aqueous solution) 40 parts Water 40 parts Solution E 1,4-dibenzoylbenzene 20 parts Methylcellulose (5% aqueous solution) 40 parts Water 40 parts Solution F 4-t-Butyldibenzoylmethane 20 parts Methylcellulose (5% aqueous solution) 40 parts Water 40 parts Example 1 10 parts of solution A, 30 parts of solution B, 20 parts of solution D and 10 parts of polyvinyl alcohol (10% aqueous solution) A coating solution prepared by mixing the above was coated and dried on the surface of high-quality paper using a wire bar so that the coating weight after drying was 6 g/m ² to prepare thermal paper. Example 2 10 parts of liquid A, 30 parts of liquid B, 20 parts of liquid E and 10 parts of polyvinyl alcohol (10% aqueous solution) were mixed, and Example 1 was prepared.
I did the same thing. Example 3 10 parts of liquid A, 30 parts of liquid B, 20 parts of liquid F and 10 parts of polyvinyl alcohol (10% aqueous solution) were mixed, and Example 1 was prepared.
I did the same thing. Comparative Example 1 The same procedure as in Example 1 was carried out by mixing 10 parts of liquid A, 30 parts of liquid B, and 10 parts of polyvinyl alcohol (10% aqueous solution). Comparative Example 2 10 parts of liquid A, 30 parts of liquid B, 20 parts of liquid C and 10 parts of polyvinyl alcohol (10% aqueous solution) were mixed, and Example 1 was prepared.
I did the same thing. The temperature coefficient γ value of the color density curve due to heating of the thermal paper produced above is shown in the table. The coloring density D is a function of the coloring temperature T, and there is a linear relationship between the density and temperature between the coloring start temperature and the temperature at which the coloring density is almost saturated. The temperature coefficient of this color density (γ
value) is the slope of the straight line with respect to the temperature axis (αD/
αT). From the table, it can be seen that Examples 1, 2, and 3 showed a rise in concentration higher than that of Comparative Examples 1 and 2, indicating that the thermal sensitivity of the heat-sensitive layer was significantly improved. Furthermore, when the heat-sensitive recording material obtained in this manner was printed on a thermal printer equipped with a built-in thermal head, a black image with high density was obtained, and there was hardly any scum adhesion to the thermal head or the sticking phenomenon. It was recognized that the running properties were better than those of Comparative Examples 1 and 2. 【table】

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material having a heat-sensitive coloring layer containing a combination of a colorless or light-colored basic dye and an organic acid and/or a phenolic substance as a heat-sensitive coloring component, wherein the coloring layer contains the following general formula: A heat-sensitive recording material characterized by containing a compound represented by: general formula (In the formula, X means a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a phenylene group, or a direct bond; R ₁ and R ₂ may be the same;
Indicates a phenyl group or an alkyl-substituted phenyl group. )