JPH08282100A - Thermal recording material - Google Patents

Abstract

PURPOSE: To enhance the preservability of a recording image part and the storage stability of a ground color, in a two-component type thermal recording material utilizing the thermal color forming reaction of a colorless or light- colored basic dye and a coupler in a thermal recording layer, by adding an epoxy compd. and a specific chelating agent to the thermal recording layer. CONSTITUTION: In a two-component type thermal recording material utilizing the thermal color forming reaction of a colorless or light-colored basic dye and a coupler being principal components of the thermal recording layer formed on a support, a chelating agent having chelating ligand represented by EDTA (ethylenediaminetetraacetic acid) represented by formula and an expoxy compd. are added to the thermal recording layer. As the chelating agent, at least one of ethyenediamine-N,N,N',N'-tetraacetic acid, ethylenediamine-N,N,N',N'- tetraacetic acid, disodium ethylenediamine-N,N,N',N'-tetraacetic acid, 4-sodium ethylenediamine-N,N,N',N'-tetraacetic acid is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material which is a main component of a heat-sensitive recording layer formed on a support such as paper, synthetic paper or film, and is particularly excellent in color developability and other recording characteristics and is obtained by recording. The present invention relates to a heat-sensitive recording material having good image storage stability and background color (non-image portion) storage stability.

[0002]

2. Description of the Related Art A two-component type heat-sensitive recording material using an electron-donating color-forming dye such as a colorless or light-colored basic dye and an electron-accepting color developing agent which makes the dye develop color when heated. JP-B-43-4160, JP-B-45-140
It is described in Japanese Unexamined Patent Publication No. 39, etc. and is widely put into practical use. Normal,
The two-component heat-sensitive recording material is composed of two components, a basic dye and a developer which is a phenolic compound, separately mixed with a binder, a dispersant, etc., and wet-milled with a sand mill, etc. (Basic dye and developer) are mixed, and auxiliary agents such as binders, fillers, lubricants, etc. are further added to make a heat-sensitive coating liquid, which is used as support paper, synthetic paper, film, etc. It is applied. The basic dye and the color developer in the heat-sensitive recording layer formed on the support are melted and brought into contact with each other when heated, and a color is developed by a chemical reaction to obtain a recorded image.

Thermal energy of the thermal recording system is supplied from a thermal head or the like, and a thermal recording image can be obtained by a printer or a facsimile having a built-in thermal head. The characteristics of such a thermal recording system are as follows: (1) Almost no noise is generated during recording. (2) Maintenance-free, with no need for developer or toner. (3) The machine is relatively inexpensive and easy to make compact. (4) No running cost is required. In recent years, it has been widely used in the fields of conventional facsimile machines, computer printouts, medical analysis recorders / word processors, calculators and other OA-related machines, vending machines, and label printers.

However, in such a two-component heat-sensitive recording method using a basic dye and a phenol-based color developer, the fastness of the color-developing dye produced is weak, so that it may come into contact with chemicals such as plasticizers, oils and fats and solvents. Then, there is a defect that the recorded image portion is discolored or erased. Various antioxidants and storage stabilizers have been used to solve this problem, but the use of an antioxidant that greatly improves the fastness of the color forming dye, and the heat-sensitivity generated by the use of the antioxidant In some cases, secondary problems such as deterioration of the ground color of the recording sheet (ground fog) and deterioration of pot life in the heat-sensitive coating liquid phase (liquid fog) occur, and the recording sheet cannot be used.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide a color-forming dye in a two-component heat-sensitive recording material containing a basic dye and a phenol-based developer. Of the heat-sensitive recording sheet caused by the use of an antioxidant that greatly improves the fastness of the ink, and the deterioration of the pot life in the heat-sensitive coating liquid stage (liquid fog). By preventing the above), it is intended to provide a heat-sensitive recording material which is excellent in the preservability of the recorded image portion and in the preservation stability of the background color.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a two-component system heat-sensitive method utilizing a color development reaction at the time of coloring with a colorless or light-colored basic dye which is a main component of a heat-sensitive recording layer formed on a support. In the recording material, at least one epoxy compound is contained in the thermosensitive recording layer, whereby the fastness of the color-forming dye is remarkably improved, and the storage stability of the thermosensitive image area is made excellent. The background color is not deteriorated by including at least one chelating agent in the heat-sensitive recording layer at the same time as the epoxy compound. It has been found that the chelating agent is added at the stage of coating liquid, and according to the present invention, the pot life of the coating liquid is also improved. Further, the recording material of the present invention may have an undercoat layer between the support and the heat-sensitive recording layer, and may have an overcoat layer on the upper surface of the heat-sensitive recording layer. include.

In the present invention, the following are used as various known colorless or pale basic dyes which are one of the main components of the heat-sensitive recording layer formed on the support and which are colored by a phenolic developer. . (1) Crystal violet lactone (2) 3-diethylamino-5-methyl-7-anilinofluorane (3) 3-dibutylamino-6-methyl-7-anilinofluorane (4) 3- (N-methyl) Cyclohexylamino) -6-
Methyl-7-anilinofluorane (5) [2-anilino-6- (N-ethyl-N-isopentylamino) -3-methyl] xanthene-9-spiro-1 '-(3'-isobenzofuranone ) (6) 3-Nn-propylmethylamino-6-methyl-7-phenylaminofluorane (7) 3-pyrrolidino-6-methyl-7-anilinofluorane (8) 3-piperidino-7- Cyclohexylaminofluorane (9) 3-Diethylamino-7- (m-trifluoromethylanilino) fluorane (10) 3-Diethylamino-6-methyl-7-chlorofluorane (11) 3- (N-ethyl-P -Toluidino) -6-methyl-7- (P-toluidino) fluorane (12) 3- (N-ethyl-Nn-hexyl) amino-6-methyl-7-phenylami Fluoran These basic dyes can be used in combination of two or more as necessary.

In the present invention, typical examples of the phenol-based color developing agent, which is one of the main components of the heat-sensitive recording layer formed on the support and is colored by contact with the basic dye, are shown below. (1) 2,2'-bis (4'-oxyphenyl) propane (2) Bis (4-hydroxyphenyl) sulfone (3) 4-Hydroxy-4'-isopropyloxydiphenyl sulfone (4) Parabenzyloxybenzoic acid (5) Parahydroxybenzoic acid benzyl ester (6) 4,4'-Cyclohexylidenediphenyl (7) 4,4'-Benzylidenediphenyl (8) 4,4'-Cyclohexylidenebis (2-methylphenol) (9) 4,4'-thiobis (6-tert-butyl-
3-methylphenol) (10) 4,4'-isopropylidene bis (2-methylphenol) (11) 3-benzylsalicylic acid (12) 3-chloro-5- (α-methylbenzyl) salicylic acid

The present invention relates to a two-component heat-sensitive recording material utilizing a color-developing reaction at the time of color development with a colorless or light basic dye which is a main component of a heat-sensitive recording layer formed on a support. It is an important feature that the heat-sensitive recording layer contains at least one epoxy compound and at least one chelating agent. The epoxy compound used in the present invention has the general formula

Typical examples of the chelating agent used in the present invention are shown below. (1) Ethylenediamine-N, N, N ', N'-tetraacetic acid (2) Gindium ethylenediamine-N, N, N',
N'-tetraacetic acid (3) 4-sodium ethylenediamine-N, N, N ',
N'-tetraacetic acid (4) 3-sodium-N-hydroxyethylethylenediamine-N, N ', N' triacetate (5) 5-sodium diethylenetriamine pentaacetate

Although the amount of the epoxy compound used in the present invention is not necessarily limited, it is generally 5 to 500 parts by weight, preferably 20 to 200 parts by weight per 100 parts by weight of the color developer. Is desirable. To prepare a coating liquid containing these substances, water is generally used as a dispersion medium and stirring with a ball mill, attritor, sand mill, etc.
It is adjusted by a pulverizer together with a color-forming dye, a color-developing agent, a sensitizer or the like, or by dispersing them separately. In such a coating solution, starches, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, maleic anhydride copolymer salt, styrene maleic anhydride copolymer salt, styrene-acryl are usually used as binders in the coating liquid. Copolymer salts, styrene / butadiene copolymer emulsions, urea resins, amide resins and the like are used in an amount of 10 to 100% by weight, preferably 15 to 50% by weight, based on the total solid content.

Further, various auxiliary agents can be added to the coating liquid, for example, dispersants such as lauryl alcohol sulfate / fatty acid metal salt, ultraviolet absorbers such as triazoles, other defoaming agents and fluorescent dyes. , Coloring dyes and the like. If necessary, waxes such as zinc stearate, calcium stearate, polyethylene wax, paraffin wax, and inorganic pigments such as kaolin, clay, calcined clay, calcium carbide, titanium oxide, and fine particulate anhydrous silica may be added. it can.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and the recording layer can be formed according to a conventionally known technique. For example, an air knife coater, a blade coater, a rod coater or the like is used. After coating and drying, a recording layer is formed. The coating amount of the coating liquid is not particularly limited, and is usually 1 to 15 g / m ² , preferably ^{2 to} 10 g / m ² in terms of dry weight.
² is common.

[0014]

EXAMPLES Specific examples of the present invention will be described below with reference to examples, but the present invention is not limited to these ranges. Further, “parts” and “%” in the examples represent “parts by weight” and “% by weight”, respectively, unless otherwise specified. (Example 1) Liquid A preparation 3-Dibrylamino-6-methyl-7-anilinofluorane 10 parts Polyvinyl alcohol 10% aqueous solution 20 parts Water 10 parts Liquid B preparation 2,2'-bis (4'-oxyphenyl) ) Propane 20 parts Polyvinyl alcohol 10% aqueous solution 20 parts Water 10 parts C liquid preparation NTZ-95 (Nippon Soda, epoxy compound) 20 parts Polyvinyl alcohol 10% aqueous solution 20 parts Water 10 parts A, B, C Various compositions are sand mill averaged. The particles were pulverized until the particles became 2 μm or less.

Formation of Recording Layer Liquid A 50 parts, liquid B 90 parts, liquid C 50 parts, 15% polyvinyl alcohol aqueous solution 50 parts, light calcium carbonate (oil absorption 20 cc / 100 g) 30 parts ethylenediaminetetraacetic acid 5 parts, water 20 The parts were mixed and stirred to obtain a coating liquid. Coating amount after drying the resulting coating solution base paper 50 g / m ² is coated by Meyer bar so as to be 7 g / m ^2, to obtain a heat-sensitive recording material.

(Example 2) NTZ-9 in the preparation of C liquid
A thermosensitive recording material was obtained in the same manner as in Example 1 except that TGE-13 (manufactured by Nippon Kayaku Co., Ltd.) was used instead of 5. (Example 3) A thermosensitive recording material was obtained in the same manner as in Example 1 except that disodium ethylenediaminetetraacetic acid was used instead of ethylenediaminetetraacetic acid in the formation of the recording layer.

(Comparative Example 1) NTZ-9 in preparation of C liquid
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 1,1 ', 3-tris (2-methyl-4hydroxy-5-t-butylphenyl) butane was used in place of 5. (Comparative Example 2) A thermosensitive recording material was obtained in the same manner as in Example 1 except that water was used instead of ethylenediaminetetraacetic acid in the formation of the recording layer.

The five types of heat-sensitive recording materials thus obtained were used as heat-sensitive word processors (Toshiba Lupo JW-90HX
Type), and the recording density (D ₁ ) and the recording density (D ₂ ) after the preservative test treatment are measured using a reflection densitometer (DM-400 type) manufactured by Dainippon Screen Mfg. Co. did. Furthermore, a Hunter whiteness meter (Amber filter) was used to measure the whiteness before and after the storage stability test. (Preservation test method) Recording density → The recording surface of the recorded heat-sensitive recording material was coated with a mixed solution of 80% castor oil and 20% ethanol at ² cc / m ² under the conditions of a temperature of 40 ° C. and a humidity of 90%. Leave for 24 hours. Whiteness → Left for 24 hours under conditions of temperature 60 ° C. and humidity 85%.

The results of these storage stability tests are shown in Table 1.

[Table 1]

[0020]

As can be seen from the above description, the present invention utilizes the color development reaction under heat of a color developing agent and a colorless or light basic dye which is a main component of the thermosensitive recording layer formed on the support. In a two-component heat-sensitive recording material, since the heat-sensitive recording material contains a chelating agent and an epoxy compound at the same time in the heat-sensitive recording layer, the fastness of the color-forming dye can be extremely improved by including the epoxy compound. Also, deterioration of the ground color of the thermal recording sheet (ground fog) and deterioration of the pot life at the heat-sensitive coating liquid stage (liquid fog) caused by the use of an epoxy compound include a chelating agent in the thermal recording layer at the same time as the epoxy compound. It is possible to obtain a heat-sensitive recording material which can be prevented by making the recording image portion excellent and has excellent storage stability of the recorded image portion and storage stability of the background color.

As is clear from the results shown in Table 1, all of the heat-sensitive recording materials of the present invention are excellent in recording suitability, oil and fat resistance, chemical resistance, and storage stability in the blank area. Is.

Claims (4)

[Claims] 1. A two-component heat-sensitive recording material utilizing a color development reaction at the time of color development with a colorless or light-colored basic dye which is a main component of a heat-sensitive recording layer formed on a support, wherein the heat-sensitive recording is carried out. EDTA (ethylenediaminetetraacetic acid) in the layer A heat-sensitive recording material comprising a chelating agent having a chelate ligand represented by 1 and an epoxy compound at the same time. 2. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer contains at least one chelating agent and at least one epoxy compound. 3. A chelating agent is (1) ethylenediamine-N, N, N ', N'-tetraacetic acid (2) gindium ethylenediamine-N, N, N',
N'-tetraacetic acid (3) 4-sodium ethylenediamine-N, N, N ',
N'-tetraacetic acid (4) 3-sodium-N-hydroxyethylethylenediamine-N, N ', N' triacetate (5) 5-sodium diethylenetriamine pentaacetate At least one kind is used. The heat-sensitive recording material according to claim 1. 4. The epoxy compound has the general formula