JPS6239281A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material showing extremely little image fading or ground discoloration and having excellent resistance to moisture and heat, by providing an undercoat layer comprising a specified phenol antioxidant between a thermal color forming layer and a base adjacently to the color forming layer. CONSTITUTION:An undercoat layer comprising a phenol antioxidant of the formula, wherein each of R1, R2 and R3 is independently 1-5C alkyl, is provided between a thermal color forming layer and a base adjacently to the 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, 1, 1-bis(2'-butyl-4'-hydroxy-5'-t-butylphe nyl)butane or the like.

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 Fiveale) systems have progressed in particular, and thermosensitive recording materials have been used as recording materials.

Thermochromic compositions used in such heat-sensitive recording materials generally consist of 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, etc. 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〕

The 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 light or sunlight for a long time, and has low moisture resistance and heat resistance. It is about providing.

〔composition〕

According to the present invention, 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 is provided between the heat-sensitive coloring layer and the support, adjacent to the heat-sensitive coloring layer: It is characterized by being provided with an overcoat layer containing a phenolic antioxidant represented by the general formula (wherein R1, 112 and R3 each independently represent an alkyl group having 1 to 5 carbon atoms). A thermosensitive recording material is provided.

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

The undercoat layer further contains a water-soluble polymer binder,
It can contain fillers. In this case, water-soluble polymers include polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, alkali salts of isobutylene/maleic anhydride copolymers, and other water-soluble resins, as well as polyurethane, styrene/butadiene copolymers, and polyacrylic acid esters. Latex such as can be used.

As the filler, in addition to inorganic substances such as calcium carbonate, silica, titanium oxide, aluminum hydroxide, clay, and talc, organic fillers made of fine particles of urea-formalin resin, polystyrene, etc. can be used. Furthermore, if necessary, a surfactant, a lubricant, etc. can be included in the undercoat layer. As the lubricant, in addition to higher fatty acids or their esters, amides, and metal salts, various wax-like substances can be used.

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 R8 is a hydrogen atom or an alkyl group. As the alkyl group, an alkyl group 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-(1-3'-trifluoromethylphenyl-N-methyl) Examples include amino-6-dinithylaminofluoran, 3-diethylamino-7-(3'-)-lifluoromethyl-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 0 to 3.

Specific examples of such phenylthiourea derivatives include:
For example, diphenylthiourea, 4,4'-diethylphenylthiourea, 4,4'-dibutylphenylthiourea, 4,4'-dichlorophenylthiourea, 3,3
Examples include '-dichlorophenylthiourea, 3,3'-dimethylphenylthiourea, and 3,3'-ditrichloromethylphenylthiourea, but are not limited to those with coarse grains.

In addition to a binder and a thermofusible substance, the thermosensitive coloring layer also contains a binder, a thermofusible substance,
Fillers, lubricants, etc. as described above may be contained. As the binder, the water-soluble polymer described above is preferably used.

To make the above-mentioned heat-sensitive recording material, an undercoat coating liquid containing a phenolic antioxidant and a binder as main components is applied and dried on a support such as paper or synthetic paper, and then a leuco dye, a leuco dye, A coating liquid containing a color developer and a binder as main components is applied and dried. Here, the amounts of the leuco dye, color developer, and binder used in the heat-sensitive coloring layer are 5 to 30% by weight and 40 to 80% by weight, respectively.
, 2 to 20% by weight, and the amount of the phenolic antioxidant 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. Furthermore, for the purpose of improving oil resistance, a water-soluble polymer protective layer can be provided on the thermosensitive coloring layer. As water-soluble polymers, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxyl methyl cellulose, starch and its derivatives, casein, sodium alginate, polyacrylamide, styrene-maleic acid copolymer, etc. are preferably used. Ru. This protective layer may also contain fillers and waxes as described above, as well as waterproofing agents and the like. The thickness of the overcoat layer is usually 1 to 10 microns, preferably 2 to 5 microns.

〔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. The heat-sensitive recording material of the present invention utilizes such characteristics to be used for tags, CAD, etc. that require light-fast 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] 1.1-bis(2'-methyl-4'-hydroxy-5
'-butylphenyl)butane 10 parts Polyvinyl alcohol 10% aqueous solution IQu calcium carbonate 10! I water
307
F [Liquid B] 3-di-n-butylamino-7-o-chloroanilinofluorane 10 parts Polyvinyl alcohol 10% aqueous solution 101! water
30//
[Liquid C] 3.3'-dichlorophenylthiourea 3.5 parts Calcium carbonate 4 10% polyvinyl alcohol aqueous solution 5.5 Water
1711
[Liquid D] Octadecylcarbamoylbenzene 10 parts Polyvinyl alcohol 10% aqueous solution 10 Water
301
I The above compositions were pulverized and dispersed in a ball mill so that the average particle size was 5 μm or less to obtain liquids (A) to (D).

The thus obtained liquid (A) was coated on a high-quality paper with a basis weight of 50 g/rrr using a wire bar and dried to form an undercoat layer so that the dry adhesion amount was 4 g/m.

Next, (Liquid B) 10 parts, [Liquid C] 30 parts, and [Liquid D] 3
The heat-sensitive recording material of the present invention was obtained by coating this mixed solution on the above-mentioned undercoat layer with a wire bar so that the dry adhesion amount was 0.5 g/I in terms of leuco dye. .

Example 2.3 In Example 1, the antioxidant in [Liquid A] was changed to 1.1-
bis(2'-ethyl-4'-hydroxy-5'-
The heat-sensitive recording material of the present invention was prepared in the same manner except that butane (butylphenyl)butane and 1,1-bis(2'-butyl-4'-hydroxy-5'=butylphenyl)butane (Example 3) were used. Created.

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 A) and an undercoat 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.

cE liquid] Octadecylcarbamoylbenzene 10 parts 1.1
-Bis(2'-methyl-4'-hydroxy-5'-butylphenyl)butane 10//Polyvinyl alcohol 10% aqueous solution IQu water
30〃
Next, 10 parts of [liquid B], 30 parts of [liquid C] and 3 parts of [liquid E]
0 parts, and the mixed solution was adjusted to have a basis weight of 50 g/rr so that the weight after drying would be 0.5 g/rd in terms of leuco dye. Apply on high-quality paper using a wire bar and let dry.

A heat-sensitive recording material without an undercoat layer was obtained.

Next, for each heat-sensitive recording material obtained above.

Perform the various tests listed below. The results are shown in Table-1.

Heat resistance: Colored areas and background areas that were colored at 110°C using a thermal gradient tester were placed in a 60'Cdry atmosphere.
It was left to stand for 24 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 190% RH for 24 hours, and the density change in the image area at that time, Concentration changes in the skin were measured using a Macbeth densitometer.

Sunlight fading resistance: The colored area and background area that were developed at 110℃ using a thermal gradient tester were exposed to sunlight for 30 hours, and the density change in the image area and the density change in the background area at that time was measured. Measured with 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.

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 ▲ There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1, R_2 and R_3 are each independently,
1. A heat-sensitive recording material comprising an undercoat layer containing a phenolic antioxidant (representing an alkyl group having 1 to 5 carbon atoms).