JPH0259784B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermal recording paper with excellent water resistance of recorded images. Thermal recording paper, which utilizes a heated color-forming reaction between a so-called basic colorless dye, which is normally colorless or light-colored, and an organic color developer such as phenols or organic acids, was published in Japanese Patent Publication No. 43-4160.
It was published in Japanese Patent Publication No. 45-14039, Japanese Patent Application Laid-open No. 48-27736, etc., and has been widely put into practical use. Thermal recording paper can be used for various types of tickets such as train tickets, admission tickets, etc.
It has come to be used for product price tags, labels, etc., and as these uses have expanded, there have been cases where the water resistance of recorded images has become a problem. However, thermal recording paper is generally unstable against moisture and high-humidity environments, and the density of the colored image may decrease or the colored image itself may disappear due to adhesion of water droplets. As described above, the lack of stability against water is a major hindrance to expanding the field of use of thermal recording paper. Even with bisphenol A, which has the longest history of use and is widely used in the field of thermal recording paper, the above-mentioned drawbacks are noticeable, and even when used in combination with a wax such as stearamide,
Stability against water cannot be expected. An object of the present invention is to provide a heat-sensitive recording paper which has extremely high water resistance such that the colored image does not disappear even when immersed in water. As a result of studying the field of organic color developers, the present inventors discovered that 1,3-di[2-(4-hydroxyphenyl)]
It has been found that a coloring layer obtained with -2-propyl]-benzene provides an image that is relatively stable against water. This 1,3-di[2-(4-hydroxyphenyl)-2-propyl]-benzene is a new bisphenol-type color developer consisting of three benzene nuclei, and Phenol A and P
- It is characterized by less sublimation than hydroxybenzoic acid esters, and high image stability as a color developer. As a green substance of 1,3-di[2-(4-hydroxyphenyl)-2-propyl]-benzene, 1,3-di[2-(4-hydroxyphenyl)-2-propyl]-benzene is
alkylphenyl)-2-propyl]-benzene,
1,3-di[2-(2,4-dihydroxyphenyl)-2-propyl]-benzene, 1,3-di[2
-(2-hydroxy-5-methylphenyl)2-
Propyl]-benzene, etc. can be mentioned, but
These compounds do not have a color developing ability comparable to that of 1,3-di[2-(4-hydroxyphenyl)-2-propyl]-benzene. The present invention provides at least one water-insoluble heated melt having two or more benzene nuclei for the 1,3-di[2-(4-hydroxyphenyl)-2-propyl]-benzene. It is characterized in that it is used in combination, wherein the heated melt used is selected from di(P-tolyl) carbonate, dibenzyl terephthalate, benzyl P-benzyloxybenzoate and benzyl diphenyl. By using these heated melts, image density can be significantly improved and stability against water can be increased. Various dyes are well known as the normally colorless to light-colored basic colorless dye used in the present invention, and examples thereof include, but are not limited to, the following. 3-(N-ethyl-isoamyl)amino-6-methyl-7-anilinofluorane (black),
3-dibutylamino-6-methyl-7-anilinofluorane (black), 3-diethylamino-6-
Methyl-7-anilinofluorane (black), 3-
(N-ethyl-P-toluideino)-6-methyl-
7-anilinofluorane (black), 3-diethylamino-6-methyl-7-(ortho, para-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-(meta-trifluoromethylanilino)fluoran (black), 3-dibutylamino-7-(ortho-chloroanilino)fluoran (black), 3
-diethylamino-6-methyl-chlorofluorane (red), 3-diethylamino-6-methyl-
Fluoran (red), 3-cyclohexylamino-6-chlorofluoran (orange), crystal
Violet lactone (blue). The above-mentioned organic color developer, basic colorless dye, and water-soluble heated melt are atomized to a particle size of several microns or less using a grinder such as a ball mill, attritor, or sand grinder, or a suitable emulsifying device. Depending on the purpose, various additive materials are added to make a coating liquid. This coating fluid usually contains polyvinyl alcohol, modified polyvinyl alcohol,
Binders such as hydroxyethyl cellulose, methyl cellulose, starches, styrene-maleic anhydride copolymer, vinyl acetate maleic anhydride copolymer, styrene-butadiene copolymer, as well as kaolin, calcined kaolin, diatomaceous earth, talc,
Inorganic or organic fillers such as titanium oxide, calcium carbonate, magnesium carbonate, and aluminum hydroxide are added, but in addition, mold release agents such as fatty acid metal salts, lubricants such as waxes, and ultraviolet absorbers such as benzophenones and triazoles are added. A water-proofing agent, a dispersing agent, an antifoaming agent, etc. can be used. By applying this coating liquid to paper and various films, the desired thermosensitive recording paper can be obtained. The types and amounts of various components used in the present invention are determined according to the required performance and recording suitability, and are not particularly limited, but usually 1,3- Di[2-(4-hydroxyphenyl)-2-propyl]-benzene 3~
10 parts, di(P-tolyl) carbonate, dibenzyl terephthalate and other heated melts are used in an amount of 3 to 12 parts, a filler is used in an amount of 1 to 20 parts, and a binder is used in an amount of 10 to 25 parts in total solid content.
section is appropriate. Further, by coating a water-soluble binder on the coloring layer, an oil resistance effect can be obtained, so that both water resistance and oil resistance requirements can be satisfied. In this case, the water-soluble binder includes polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acrylamide-modified polyvinyl alcohol,
Hydroxyethyl cellulose, carboxymethyl cellulose, styrene-maleic acid copolymer, etc. are used, but by using a waterproofing agent in combination, a more robust thermosensitive recording paper can be obtained. Images recorded using the thermal recording paper according to the present invention have a high degree of water resistance, so that they can withstand use in environments where water droplets are likely to splash or under high humidity conditions. Not only that, but it also has excellent high-speed recording suitability and ground color stability. For example, in a typical thermal recording paper that uses conventional bisphenol A as a color developer and fatty acid amide, the color develops at a temperature of 60 to 80°C in order to support higher speeds, and the storage of the thermal recording paper However, the thermal recording paper of the present invention does not reduce the whiteness of the background color under temperature conditions of 60 to 80 degrees Celsius, and also maintains high color density even during high-speed recording. An image is obtained. Next, the present invention will be specifically explained using examples. Example liquid A (dye dispersion) 3-(N-ethyl-isoamyl)amino-6-
Methyl-7-anilinofluorane 1.5 parts 10% polyvinyl alcohol aqueous solution 3.4 parts Water 1.9 parts Solution B (developer dispersion) Bisphenol A 6 parts 10% polyvinyl alcohol aqueous solution 15 parts Water 9 parts Solution C (developer dispersion) (1,3-di[2-(4-hydroxyphenyl)
-2-propyl]-benzene 6 parts 10% polyvinyl alcohol aqueous solution 15 parts water 9 parts D-liquid stearamide 5 parts 10% polyvinyl alcohol aqueous solution 12.5 parts water 7.5 parts Furthermore, the above-mentioned D stearamide was added to P- Dispersions in which benzyl benzyloxybenzoate, dibenzyl terephthalate, di(P-tolyl) carbonate, and benzyl diphenyl are substituted are designated as solutions E, F, G, and H, respectively. Each liquid of the above composition was ground in a ball mill to a particle size of 3 microns. Next, the dispersion liquids were mixed in the proportions shown in Table 1 to prepare a coating liquid.

[Table] Coating amount of each coating liquid is 6.0 on one side of 50g/ ^m2 base paper.
The sheet was coated and dried to give a smoothness of 200 to 300 seconds using a ^{supercalender} . Table 2 shows the results of a quality performance test performed on the obtained thermal recording paper.

[Table] As is clear from Table 2, 1,3-di[2-
(4-Hydroxyphenyl)-2-propyl]-benzene mixed with di(P-tolyl)carbonate, benzyldiphenyl, benzyl P-benzyloxybenzoate, or dibenzyl terephthalate, when immersed in water. Also, a thermosensitive recording paper with such good water resistance that the image density hardly decreases can be obtained.
A comparison with the comparative example shows that this water resistance is characteristic of the combination of the present invention. Further, the thermal recording paper of the present invention has high color density during high-speed recording and excellent stability of the ground color. In particular, di(P-
The effect of combined use with tolyl) carbonate is remarkable.

Claims (1)

[Scope of Claims] 1. A thermosensitive recording paper provided with a coloring layer containing a basic colorless dye and an organic color developer, wherein 1,3-di[2-(4-hydroxyphenyl)-2-propyl]
- In the coloring layer using benzene as an organic color developer,
1. A thermosensitive recording paper containing at least one selected from di(P-tolyl) carbonate, dibenzyl terephthalate, benzyl P-benzyloxybenzoic acid ester, and benzyl diphenyl.