JPS59199286A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To prevent decolorization of a developed color image and a reverse recording phenomenon from occurring, by using a parahydroxybenzoic acid ester and a specified glycol parahydroxybenzoate as a color developer. CONSTITUTION:A color forming layer comprising a colorless or light-colored leuco dye, a parahydroxybenzoic acid ester and a glycol bisparahydroxybenzoate of formula I , wherein R is 2-12C alkylene group, or formula II, wherein R' is 2-5C alkylene group and n is an integer of not smaller than 2, is provided. The thus obtained thermal recording paper has adaptability to high-speed recording, decolorization of a recorded image and reverse recording are improved, and excellent performance is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording paper which has excellent color development, suitability for high-speed recording, and background stability, and which has improved stability of recorded images.

A color reaction caused by contact between a colorless or light-colored leuco dye and a phenol compound has been known for a long time, and its application to recording materials is also known. (Refer to Japanese Patent Publications No. 43-4160 and No. 45-14039). Thermal recording paper is made by grinding a color developer such as a leuco dye and a phenolic compound into fine particles, then mixing them with auxiliary agents such as a binder, lubricant, and sensitizer, and then forming them into a support such as paper or film. When heated, the developer dissolves and comes into contact with the leuco dye, producing a recorded image.

In recent years, advances in electronics have led to remarkable advances in recording devices, with thermal pen recorders for various measuring instruments, thermal printers for computers, thermal automatic ticket vending machines, and facsimile machines becoming widespread.

Information-related devices such as facsimiles are particularly required to have high-speed recording performance, and the thermal paper used therein must also have the ability to quickly produce dense recorded images. For this purpose, it is necessary for the color developer to dissolve in the hot summer of JS to cause a color reaction, and it is desired that the color develop at a temperature of 70 to 120°C. Among poly(phenol compounds), parahydroxybenzoic acid ester, especially parahydroxybenzoic acid benzyl ester, is known as a color developer suitable for such high-speed thermal recording (Japanese Patent Application Laid-Open No. 140486/1986, No. 56-144.193,
(See Publications No. 57-82089 and No. 57-107883).

The melting point of parahydroxybenzoic acid benzyl ester is 11
0°C, which is thermally advantageous compared to other color developers such as bisphenol, which have a melting point of 156°C.

Thermal recording paper made of benzyl parahydroxybenzoic acid ester and a certain type of fluoran dye has many features such as good coloring performance, high density and clear recording, and little background fog. However, the stability of recording after color development is not necessarily sufficient, and slight fading of color and white spots in color recording have been pointed out as points that require improvement.

The present inventors completed the present invention as a result of intensive research in order to improve the recording stability without impairing the advantages of thermal recording paper using rose hydroxybenzoic acid ester.

The present invention relates to a colorless to light-colored leuco dye, a parahydroxybenzoic acid ester, and the following formula (in the formula, R represents an alkylene group of 02 to C12) or (in the formula, R' represents an alkylene group of C2 to C6). , n is an integer of 2 or more).

The reason why the stability of recording is improved by the present invention is not necessarily clear, but parahydroxybenzoic acid ester is separated from the charge transfer complex of leuco 1 dye and nokurahydroxybenzoic acid ester and crystallized, causing discoloration or white spots. This phenomenon is thought to occur because glycol-bis-parahydroxybenzoic acid ester prevents this crystallization and also functions as a color developer.

The glycol-bis-parahydroxybenzoic acid ester used in the present invention has the general formula (wherein R is 02 to C
12 alkylene group) or (in the formula, R/ means an alkylene group of 02 to C6, and n is an integer of 2 or more) is used.

Examples of compounds of general formula (■) include ethylene glycol-
Examples include bis-halahydroxybenzoate, propylene glycol-pisubarahydroxybenzoate, butanediol-bisnoclahindroxybenzoate, hexa-Δdiol-bis-parahydroxybenzoate, and the like. General formula ■
Examples of compounds include diethylene glycol-bis-
Examples include parahydroxybenzene-1, triethylene glycol bis-parahydroxybenzoate, and the like.

Examples of parahydroxybenzoic acid esters that serve as main color developers include methyl/, -ethyl parahydroxybenzoate,
Examples include -propyl, -isopropyl, -butyl, -inbutyl, -hexyl, -benzyl, -phenethyl/, -phenyl, -naphthyl, and the like.

Colorless to light-colored leuco dyes include phthalide-based and fluoran-based dyes, such as crystal violet lactone, benzoyl leucomethylene blue, ro-diethylamine-6-methyl-7-anilinofluoran, 6-
diethyl) raremino-6-methyl-7-chlorofluorane, 3-(N-cyclohexyl-N-methylamine)-6
-Methyl-7-anilinofluorane, ro-diethylamine-7-(ortho-chloroanilino)fluorane, 3-
(N-ethyl-paratoluidino)-6-methyl-7-anilinofluorane, 6-diethylamine-7-[meth-
(trifluoromethyl)anilinofluorane, 6-diethylamine-6-methyl-7-(ortho-, para-dimethylanilino)fluorane, 6-pyrrolidino-6-methyl-anilinofluorane, 3-piperisino6- Methyl-7-anilinofluorane, 6-diethylamine-
Examples include 6-methyl-f-chlorofluoran, 6-diethylami/-6-methylfluoran, and 6-cyclohexylamino-6-chlorofluoran.

When producing the thermal recording paper of the present invention, a leuco dye, a parahydroxybenzoic acid ester, and a glycol-bis-parahydroxybenzoic acid ester are blended.

The blending ratio is preferably 100 to 10 parts by weight of parahydroxybenzoic acid ester per 100 parts by weight of the leuco dye.
00 parts by weight. Glycol-bis-parahydroxybenzoic acid-11-styv of formula (1) or H, 1 to 200% per 100 weight of ester of glycol-bis-parahydroxybenzoic acid
It is preferable to mix parts by weight.

These materials are atomized using water as a medium using a grinder such as a ball mill, attritor, or sand grinder, or a suitable emulsifying device, and various additive materials are added depending on the purpose to form a coating liquid.

This coating typically contains binders such as polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, starches, styrene-maleic anhydride copolymers, vinyl acetate-maleic anhydride copolymers, and styrene-butadiene copolymers. as well as kaolin, diatomaceous earth, talc, titanium oxide,
Preferably, fillers such as calcium carbonate, magnesium carbonate, aluminum hydroxide are added. In addition, excipients such as fatty acid metal salts, lubricants such as waxes, benzophenone-based or triazole-based ultraviolet absorbers, water-resistant agents such as glyoxal, dispersants, antifoaming agents, etc. can also be added. The thermosensitive recording paper of the present invention can be obtained by applying this coating liquid to a substrate such as paper or film.

The heat-sensitive recording paper of the present invention is suitable for high-speed recording, and exhibits excellent performance with improved fading and white spots in recorded images.

Example 1 Solution A (dye dispersion) Ro-diethylamino-7-(ortho-chloroanilino)
Fluoran 4.0 parts 10% polyvinyl alcohol aqueous solution 9.1 parts water
5.0 parts Liquid B (color developer dispersion) 6.0 parts halahydroxybenzoic acid benzyl ester 0.6 parts halahydroxybenzoate in ethylene glycol bis 30.0 parts 10% polyvinyl alcohol aqueous solution Grind and mix using a ball mill.

Next, 1.0 part of liquid A and 4.0 parts of liquid B were mixed to prepare a coating liquid, and this coating liquid was applied to high-quality paper using a wire bar to obtain thermal recording paper (coating amount: 6F/ 7772
).

Example 2 Diethylene glycol-bis-parahydroxybenzoate was used as a substitute for ethylene glycol-bis-parahydroxybenzoate in Example 10B solution,
A thermosensitive recording paper was obtained in the same manner as in Example 1 in other respects.

Example 6 Instead of ethylene glycol-bis-parahydroxybenzoate in Solution B of Example 1, )! A thermosensitive recording paper was obtained in the same manner as in Example 1 except that J ethylene glycol benzene (hydroxybenzoate-1) was used.

Example 4 A thermosensitive recording paper was obtained in 1- in the same manner as in Example 1, except that hexanediol-bis-parahydroxybenzoate was used instead of ethylene glycol-his-parahydroxybenzoate in Example 10B solution.

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that ethylene glycol bis-parahydroxybenzoate was not used in the Example 10B solution.

The image density when color was developed was measured using a Macbeth densitometer. In addition, heat-sensitive recording paper after color development is 400C1 humidity 90%.
or 60° C.) for 24 hours, and changes in background density and image density were measured. The results are shown in the table below.

As is clear from this result, the thermal recording paper of the present invention has
Compared to the case of only benzyl rose hydroxybenzoate,
It is known that the image storage stability has been improved by several orders of magnitude, and that the advantages of benzyl parahydroxybenzoate, such as color development performance and good texture, are maintained unchanged.

Applicant: Ueno Pharmaceutical Application Research Institute Co., Ltd. Attorney: Masao Hayashi

Claims (1)

[Scope of Claims] A colorless to light-colored leuco dye, a parahydroxybenzoic acid ester, and the following formula (wherein R means a C2-C1□ alkylene group) or (wherein R' means a 02-C6 alkylene group) 1. A thermosensitive recording paper having a coloring layer containing a glycol-bis-parahydroxybenzoic acid ester represented by \, where n is an integer of 2 or more.