JPS6239280A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance light resistance, by providing an overcoat layer comprising a phenol antioxidant having a specified composition on a thermal color forming layer comprising a leuco dye and a color developer. CONSTITUTION:An overcoat layer comprising a phenol antioxidant of formula I, wherein each of R1, R2 and R3 is independently 1-5C alkyl, is provided on a thermal color forming layer, in a thermal recording material which comprises a thermal color forming layer comprising a leuco dye and a color developer on a base. The antioxidant may be 1,1-bis(2'-methyl-4'-hydroxy-5'-t-butylphenyl) butane, 1,1-bis(2'-ethyl-4'-hydroxy-5'-t-butylphenyl)butane or the like. The leuco dye may be based on triphenylmethane, fluoran, phenothiazine or the like. The color developer may be based on phenol, a sulfur-containing compound, an ester, a carboxylic acid or the like. The material has excellent light resistance in addition to excellent heat resistance and moisture resistance, and capable of providing a recorded image with favorable preservability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording sheet, and more specifically, the present invention relates to a heat-sensitive recording sheet, and more specifically, a color-forming component comprising a normally colorless or slightly light-colored leuco dye and a color developer that reacts with the leuco dye under heat to develop a color. This invention relates to an improvement in a heat-sensitive recording material in which a heat-sensitive coloring layer containing a heat-sensitive color forming layer is formed on a support.

[Prior art]

Thermosensitive recording materials generally consist of a support such as paper, synthetic paper, or plastic film provided with a thermosensitive coloring layer containing a thermochromic composition as a main component. A colored image can be obtained by heating with, etc. Compared to other recording materials, this type of recording material can record in a short time with a relatively simple device without complex processes such as development and fixing, produces less noise and pollutes the environment, and is inexpensive. Due to its advantages such as being cheap,
In addition to being used for copying books, documents, etc., it is also widely used as a recording material in a wide variety of applications, including electronic computers, facsimile machines, ticket vending machines, labels, and recorders.

In recent years, product information, sales management, corresponding product systemization, and PO5 (Point of 5ale) systems have advanced in particular, and thermosensitive recording materials have been used as recording materials.

Thermochromic compositions used in such heat-sensitive recording materials generally include a color former and a color developer that causes the color former to develop color when heated. Examples of the color former include lactones, lactams, Colorless or light-colored leuco dyes containing a spiropyran ring have been used, and organic acids, phenolic acid substances, and the like have been used as color developers.

However, this type of recording material has significant light resistance in the image area and the background area, that is, when exposed to fluorescent lights or sunlight for a long time, the density of the image area decreases significantly, and the background area changes color, especially for tags in POS systems. It is not fully satisfactory for this purpose. Conventionally, it has been proposed to incorporate ultraviolet absorbers such as benzophenone, benzotriazole, and salicylate into the heat-sensitive coloring layer as a method to improve the light resistance. Sex is not obtained. As a result of repeated research aimed at improving the light resistance of heat-sensitive recording materials, the present inventors discovered that phenolic antioxidants provide excellent light resistance. It has been found that it easily reacts with the color-forming ingredients inside, causing background fog, and has poor heat resistance and moisture resistance.

〔the purpose〕

An object of the present invention is to provide a heat-sensitive recording material that has excellent light resistance, that is, very little image fading or background discoloration when exposed to fluorescent lamps or sunlight for a long period of time, and has excellent moisture resistance and heat resistance. There is a particular thing.

〔composition〕

According to the present invention, in a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer is provided on a support, the following general formula (wherein R1, R2 and R3 are , each independently representing an alkyl group having 1 to 5 carbon atoms.

In the present invention, the phenolic antioxidant represented by the above general formula to be contained in the overcoat layer is specifically 1,1-bis(2'-methyl-47-hydroxy-s'-t-butyl phenyl)butane, 1,1-
bis(2'-ethyl-4'-hydroxy-5'-t-
Examples thereof include, but are not limited to, butylphenyl)butane, 1,1-bis(2'-butyl-4'-hydroxy-5'-7-butylphenyl)butane, and the like.

The overcoat layer typically contains a water-soluble binder, such as polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, or alkali salts of isobutylene/maleic anhydride copolymers. In addition, latex such as polyurethane, styrene/butadiene copolymer, polyacrylic acid ester, starch and its derivatives, and casein.

Examples include styrene-maleic acid copolymer.

Furthermore, in order to improve water resistance and matching properties with the thermal head, the overcoat layer contains a water-resistant agent, a filler such as a thermosetting organic filler, a higher fatty acid or its ester, an amide or a metal salt, and a lubricant such as wax. may be included. Additionally, a surfactant or the like may be included as appropriate.

As the leuco dye used in the present invention, those commonly used in this type of heat-sensitive recording material, such as triphenylmethane type, fluoran type, phenothiazine type, auramine type, and spiropyran type, are applicable. ,
As a particularly preferred leuco dye, a fluoran compound represented by the following general formula is used.

In the formula, R4 and R5 are each an alkyl group or a cyclohexyl group, R6 is an alkyl group, a haloalkyl group, or a halogen atom, R7 is a hydrogen atom or a halogen atom, and R
8 is a hydrogen atom or an alkyl group. As the alkyl group, one having 1 to 8 carbon atoms is usually used.

Examples of the fluoran compound represented by the above general formula include 3-diethylamino-7-o-chloro-anilinofluoran, 3-diethylamino-7-m-chloro-anilinofluoran, and 3-di-n-butyl. Amino-7-chloroanilinofluorane, 2-(N-3'-trifluoromethylphenyl)amino-6-dinithylaminofluorane, 2-(N-3'-trifluoromethylphenyl-N-methyl) Examples include amino-6-dinithylaminofluoran, 3-diethylamino-7-(3'-trifluoromethyl-4'-chlorophenyl)aminofluoran, and the like.

The color developers used in the present invention include those commonly used in this type of heat-sensitive recording material, such as phenol-based, sulfur-containing, ester-based, carboxylic acid-based, metal salt-based, and amine-based developers. things apply, but
As a particularly preferred color developer, a phenylthiourea compound represented by the following general formula is preferably used.

In the formula, X and Y are each a halogen atom, an alkyl group, or a haloalkyl group, and m and n are each an integer of θ to 3.

Specific examples of such phenylthiourea derivatives include:
For example, diphenylthiourea, 4,4'-diethylphenylthiourea, 4,4'-dibutylphenylthiourea, 4,4'-dichlorophenylthiourea, 3
,3'-dichlorophenylthiourea, 3.3'-
Examples include dimethylphenylthiourea, 3,3'-ditrichloromethylphenylthiourea, but the present invention is not limited to these.

The thermosensitive coloring layer may further contain a binder, a thermofusible substance, a filler, a lubricant, and the like. As a binder,
Water-soluble polymers are preferably used. In this case, water-soluble polymers include polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, isobutylene-maleic anhydride copolymer alkali salt, as well as polyurethane, styrene/butadiene copolymer, polyacrylic acid ester, etc. Latex etc. can be used. Fillers include inorganic substances such as calcium carbonate, silica, titanium oxide, aluminum hydroxide, clay, and talc, as well as urea-formalin resin.

An organic filler made of fine particles of polystyrene or the like can be used. Furthermore, if necessary, a surfactant, a lubricant, etc. can be included in the heat-sensitive coloring layer.

As a lubricant, higher fatty acids or their esters, amides,
In addition to metal salts, various wax-like substances can be used.

To make the above heat-sensitive recording material, an aqueous solution containing a leuco dye, a color developer, and a binder as main components is coated on a support such as paper or synthetic paper and dried, and then a water-soluble resin, a water-soluble resin, A coating liquid containing a filler and a phenolic antioxidant represented by the above general formula as main components is applied and dried. Here, the appropriate amounts of the leuco dye, color developer and binder used in the heat-sensitive coloring layer are 5 to 30% by weight, 40 to 80% by weight, and 2 to 20% by weight, respectively, and the phenolic antioxidant The amount used is preferably 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight, per 1 part by weight of the leuco dye.

In the heat-sensitive recording material of the present invention, an undercoat layer can be provided between the support and the heat-sensitive coloring layer and adjacent to the heat-sensitive coloring layer, thereby improving sensitivity, whiteness, coating suitability, and even matching. It can also improve your sexuality. The undercoat layer can be formed from a water-soluble polymer binder, a filler, a lubricant, a surfactant, and the like. As these materials, those exemplified above for the heat-sensitive coloring layer are used.

〔effect〕

The heat-sensitive recording material of the present invention has extremely excellent light resistance,
Furthermore, it has excellent heat resistance and moisture resistance, and provides recorded images with extremely good storage stability. 1. The heat-sensitive recording material of the present invention utilizes such characteristics to be used for labeling, CAD, etc., which require light resistance quality.
Advantageously applied to labels etc.

〔Example〕

Examples of the present invention are shown below. Note that all parts and percentages shown below are based on weight.

Example 1 [Liquid A] 3-di-n-butylamino-7-o-chloroanilinofluorane 10 parts Polyvinyl alcohol 10% aqueous solution 1 part Water
301F
[Liquid B] 3.3'-dichlorophenylthiourea 3.5 parts Calcium carbonate 4 10% polyvinyl alcohol aqueous solution 5.5 Water
17〃〔
Solution C] Octadecylcarbamoylbenzene 10 parts Polyvinyl alcohol 10% aqueous solution 1o Water
3o〃
[Liquid D] 1.1-bis(2'-methyl-41-hydroxy-5
'-1-Butylphenyl)butane 10 parts Polyvinyl alcohol 10% aqueous solution 1 IQtt bottle 1 O22 water
30
The above compositions were pulverized and dispersed in a ball mill so that the average particle size was 5 μm or less to obtain solutions (A) to (D).

10 parts of [Liquid A] thus obtained, 30 parts of [Liquid B] and 30 parts of [Liquid C] were mixed, and the basis weight of the mixed solution was 5゜g/rrr.
[
[Liquid D] on the above heat-sensitive coloring layer with a dry adhesion amount of 4g1rd.
The heat-sensitive recording material of the present invention was obtained by coating with a wire bar so as to obtain the following.

Example 2.3 In Example 1, the antioxidant in [Liquid D] was replaced with 1,1-bis(2'-ethyl-4'-hydroxy-5'-7-butylphenyl)butane (Example 2) and 1,1-bis(
A heat-sensitive recording material of the present invention was obtained in the same manner except that 2'-butyl-4'-hydroxy-5'-butylphenyl)butane (Example 3) was used instead.

Comparative Example 1 A comparative sample was obtained in the same manner as in Example 1, except that the phenolic antioxidant was removed from [Liquid D] and an overcoat layer containing no antioxidant was provided.

Comparative example 2 [Liquid E] having the following composition was prepared in the same manner as in Example 1.

[E liquid]

Octadecylcarbamoylbenzene 10 parts 1.1
-bis(2'-methyl-4'-hydroxy-5'-
Butylphenyl)butane lo〃Polyvinyl alcohol 10% aqueous solution IQn water
3o Next, 10 parts of [Liquid A], 30 parts of (Liquid B), and 30 parts of [Liquid E].
This mixed solution was coated and dried using a wire bar on a high-quality paper having a basis weight of 50 g1rd so that the dry weight was 0.5 g/rrr in terms of leuco dye, to obtain a heat-sensitive recording material.

Next, various tests shown below were conducted on each of the heat-sensitive recording materials obtained above, and the results are shown in Table 1.

Heat resistance: The colored part and the background part, which were colored at 110°C using a thermal gradient tester, were placed in a dry atmosphere at 60°C for 2 days.
It was left to stand for 4 hours, and the density change in the image area and the density change in the background area at that time was measured using a Macbeth densitometer.

Moisture resistance: Using a thermal gradient tester, the colored area and background area that were developed at 110°C were left in an atmosphere of 40°C and 90% RH for 24 hours, and the density change in the image area at that time was measured. ,
Concentration changes in the skin were measured using a Macbeth densitometer.

Sunlight fading resistance: 110°C using a thermal gradient tester
The colored area and background area were exposed to sunlight for 30 hours, and the density changes in the image area and the background area were measured using a Macbeth densitometer.

Fluorescent light fading resistance: 110° using a thermal gradient tester
The colored area and background area colored with C were exposed to 5000 Lux fluorescent lamp light for 240 hours, and the density changes in the image area and the background area at that time were measured using a Macbeth densitometer.

Procedural amendment Written on January 28, 1985 by Michibe Uga, Commissioner of the Patent Office1, Indication of the case, Patent Application No. 179376 filed in 19852, Name of the invention, Heat-sensitive recording material3, Person making the amendment. Related Patent Applicant Address 1-3-6 Nakamagome, Ota-ku, Tokyo Name
(674) Ricoh Co., Ltd. - Representative Hama 1) Hiro 4, Agent 〒151 Address 1-58-10-5 Yoyogi, Shibuya-ku, Tokyo
Date of amendment order: 6, Number of inventions increased by amendment: 07, Subject of amendment: 8, Contents of amendment: The following amendments will be made in the specification of the present application. (1) The scope of claims will be corrected as shown in the attached document. Masu.

``Claim 1 (1) A heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer is provided on a support, wherein the following general formula (wherein R□, R2 and R3 each independently represent an alkyl group having 1 to 5 carbon atoms. A heat-sensitive recording material comprising an overcoat layer containing a phenolic antioxidant represented by:

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive coloring layer containing a leuco dye and a color developer is provided on a support, the following general formula ▲mathematical formula, chemical formula, table, etc. is provided on the heat-sensitive coloring layer▼ (in the formula , R_1, R_2 and R_3 are each independently,
A heat-sensitive recording material comprising a cover coat layer containing a phenolic antioxidant represented by the formula (representing an alkyl group having 1 to 5 carbon atoms).