JPH0259795B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording sheet with excellent thermal responsiveness. A heat-sensitive recording sheet generally has 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 developer. When heated with light, the dye precursor and developer react instantly, resulting in a recorded image.
No. 45-14039, etc.
This type of heat-sensitive recording sheet has the advantages of being able to record with a relatively simple device, being easy to maintain, and not generating noise.
It is used in a wide range of fields, including facsimiles, printers, computer terminals, labels, and automatic ticket vending machines. In recent years, the speed of printing and recording has been increasing, and as the speed of recording devices themselves has increased, recording sheets that can cope with this speed, namely thermal recording sheets with excellent thermal responsiveness that can produce high-density colored images with low thermal energy, have been developed. Development is desired. In order to improve the thermal responsiveness of a thermosensitive recording sheet, it is necessary to lower the melting point of the color developer and improve its compatibility with the dye precursor. In the past, various color developers have been studied in order to obtain high-density colored images, and
No. 155059 and No. 55-27253 contain alkylidene bisphenols, and JP-A-57-128594 and No. 57-
No. 129787 discloses monohydroxybenzoic acid esters. However, the thermal response is poor,
There are drawbacks such as not being able to obtain a sufficient density, or even if a high density image is obtained, the storage stability is poor, so that no satisfactory image has been obtained. As a result of various studies on color developers in order to obtain heat-sensitive recording sheets with excellent thermal responsiveness, the inventors of the present invention found that in heat-sensitive recording sheets containing a color developer that develops color from normally colorless or light-colored dye precursors, the color developer By adding a compound represented by the following general formula [] as an agent, a heat-sensitive recording sheet with excellent properties could be obtained. (However, R represents an aralkyl group) As the compound represented by the above general formula [] used in the present invention, 2-(4-hydroxyphenyl)-2-(4-phenethyloxyphenyl)propane , 2-(4-hydroxyphenyl)-2-(4
-benzyloxyphenyl)propane, etc. The main components used in the heat-sensitive recording sheet of the present invention will be specifically explained, but the present invention is not limited thereto unless it exceeds the gist of the present invention. As a dye precursor, triphenylmethane type,
Examples include fluoran-based, diphenylmethane-based, thiazine-based, and spiropyran-based compounds. For example, crystal violet lactone, 3-diethylamino-7-methylfluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7 -anilinofluorane, 3-diethylamino-7-(2-
chloroanilino)fluoran, 3-dibutylamino-7-(2-chloroanilino)fluoran, 3
-diethylamino-7-(3-chloroanilino)
Fluoran, 3-diethylamino-6-methyl-
7-anilinofluorane, 3-(N-ethyl-P
-toluidino)-6-methyl-7-anilinofluorane, 3-(N-methylcyclohexylamino)
-6-methyl-7-anilinofluorane, 3-piperidino-3-methyl-7-anilinofluorane, and the like. As binders, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol,
Styrene-maleic anhydride copolymer, ethylene/
Examples include water-soluble binders such as maleic anhydride copolymers, latex-based water-soluble binders such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and methyl acrylate-butadiene copolymers. Pigments include diatomaceous earth, talc, kaolin,
Examples include 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, paraffin oxide, polyethylene, polyethylene oxide, stearic acid amide, and castor wax are used to prevent head wear and staking. , a dispersant such as sodium dioctyl sulfosuccinate, and a sensitivity improver,
Examples include ultraviolet absorbers and surfactants. Although paper is mainly used as the support for the heat-sensitive recording sheet of the present invention, various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of a combination of these can also be used as desired. EXAMPLES The present invention will be explained in more detail by way of Examples below, but the present invention is not limited to these Examples. Example 1 3-(N-methyl-N-cyclohexylamino)
-20g of -6-methyl-7-anilinofluorane
% polyvinyl alcohol aqueous solution for 24 hours using a ball mill. On the other hand, 50 g of 2-(4-hydroxyphenyl)-2-(4-benzyloxyphenyl)propane was dispersed in a ball mill for 24 hours with 75 g of a 2% polyvinyl alcohol aqueous solution. Mix these dispersions, add 100g of a 50% dispersion of calcium carbonate, and add 20g of a 50% dispersion of calcium carbonate.
% dispersion 50g, 12% polyvinyl alcohol aqueous solution
250 g and 200 g of water were added and mixed and stirred to obtain a coating liquid. Next, this coating liquid was applied to a base paper having a basis weight of 50 g/m ² so that the amount of the dye precursor was 0.5 g/m ² and dried, and then treated with a supercalender to obtain a heat-sensitive recording sheet. Example 2 A heat-sensitive recording sheet was obtained in the same manner as in Example 1, except that 50 g of a 20% dispersion of stearic acid amide was added to the coating solution of Example 1. Comparative Example 1 2-(4-hydroxyphenyl)-2 of Example 1
- In the same manner as in Example 1 except that 2,2-bis(4-hydroxyphenylpropane) was used instead of (4-benzyloxyphenyl)propane,
A thermosensitive recording sheet was obtained. Comparative Example 2 A heat-sensitive recording sheet was obtained in the same manner as in Comparative Example 1, except that 50 g of a 20% dispersion of stearic acid amide was added to the coating solution of Comparative Example 1. Test Printed using Fujitsu's Huacom Fax 621C.
After obtaining a colored image, the density of the colored image was measured. The results are shown in Table 1.

[Table] As is clear from Table 1, by using the color developer according to the present invention, a heat-sensitive recording sheet with improved color density and excellent thermal responsiveness was obtained.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording sheet containing a color developer that reacts with a normally colorless or light-colored dye precursor upon heating to cause the dye precursor to develop a color, wherein the color developer is represented by the following general formula. A heat-sensitive recording sheet characterized by being a compound that causes general formula (However, R represents an aralkyl group)