JPS61134292A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve the durability and fasteness to light, heat resistance of thermal recording material by conaining pigments or dyes having photoabsorption in a specific range of light wavelengths into a heat sensitive layer and/or a heat sensitive film layer. CONSTITUTION:Pigments or dyes having photoabsorption in the range of light wavelengths 400-600nm on a heat sensitive layer and/or a coated layer containing an acid substance which colors leuco dye when heated are provided as additives to leuco dye. This improves the fastness to light remarkably. The acceptable pigments or dyes should have high photoabsorption within the range of light wavelengths 400-600nm. In addition, they are allowed to have photoabsorption of sch light wavlengths and those other than the former. When the fastness to light is enhanced, the introduction of the above-mentioned materials into the protection layer instead of the heat sensitive layer is more effective. If they are introduced into the scattering system, their particle diameter should preferably be smaller. Further, the simultaneous use of ultraviolet ray absorbent or antioxidant as a photo-stabilizer with the pigment or dye used will contritube toward an improvement of the fastness to light.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a heat-sensitive recording material, and more specifically, to improving the fastness, particularly the light and heat resistance, of a heat-sensitive recording material containing a leuco dye and an acidic substance that causes the dye to develop color when heated. This invention relates to a heat-sensitive recording material.

<Prior Art> In general, heat-sensitive recording materials whose coloring components are a flit-colored or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated, have a lower temperature than other heat-sensitive recording materials that have been put to practical use in the past.
Because the resulting colored images are very clear, it is widely used as recording paper for computer output, facsimiles, recorders, etc., and also for tickets, cards, etc. However, when a recording sheet using this heat-sensitive recording material is exposed to sunlight, fluorescent light, etc. for a long period of time, color fading occurs in colored areas and discoloration occurs in uncolored areas, and improvements are needed.

-This is said to be due to the decomposition of leuco dyes by ultraviolet rays, and to prevent this phenomenon, ultraviolet absorbers such as benzophenone and benzotriazole derivatives are added to the heat-sensitive layer containing leuco dyes and acidic substances. Method (special u
11 Showa 50-104650, Showa 55-55891, Showa 5
5-93492, 58-87093), a method of incorporating an antioxidant (JP-A-49-54040, JP-A-49-511-
18752>, and a method of incorporating an anti-aging agent (Japanese Patent Application Laid-Open No. 149353/1983), but a sufficient light and heat resistance effect has not yet been obtained.

<Problems to be Solved by the Invention> In view of the above problems, an object of the present invention is to improve the light resistance of a heat-sensitive recording material containing a leuco dye and an acidic substance that causes the leuco dye to develop color when heated.

<Means for solving the problems> The present invention provides a heat-sensitive recording material comprising a heat-sensitive layer containing a leuco dye and an acidic substance that causes the leuco dye to develop color when heated, or a coating layer on the heat-sensitive layer. The present invention was completed based on the discovery that a significant improvement in light resistance can be obtained by incorporating a pigment or dye that absorbs light in the wavelength range of 400 to 600 nm into the coating layer. That is,
Photodeterioration of the heat-sensitive recording material is caused not only by light wavelengths in the ultraviolet region below 400 nm but also by light wavelengths in the range of 400 to 600 r+m. For this purpose, we not only need to block ultraviolet light wavelengths by adding ultraviolet absorbers, etc., but also
By blocking light in the range of 600°C, a significant improvement in the optical properties of the heat-sensitive recording material can be obtained.

The pigment or dye used in the present invention has a light wavelength of 400 to 600
Any material may be used as long as it has strong light absorption in the 0r+n+ range (or it may be a material that includes this light wavelength and has light absorption at other light wavelengths as well. Specific examples include yellow lead, zinc yellow, barium chromate, cadmium yellow, yellow iron oxide, yellow ocher, titanium yellow, lead cyanamide, calcium leadate, naphthol yellow, Hanzaie 0-10G, Reza Yellow 5G, /1
Nzaiero 7l-3G, Hansa Yellow G, Hansa Yellow GR, Hansa Yellow A, Hensa Yellow RN.

Hansa Yellow R1 Pigment Yellow Upper 1 Henshin Yellow, Henjin Yellow G1 Benzi Diene Yellow GR, Non-permanent Yellow NCG, Palcan Fast Yellow 5G, ] 1 Lucan Fast Yellow R1
Tartrazine Lake, Quinoline Yellow Lake, Anthragen Yellow 6GL, Permanent Yellow F G
L, Permanent Yellow HIOG, Permanent Yellow)-IR.

Single or mixtures of pigments or dyes such as anthrapyrimidiene yellow, heta-carotene, azulene, coronene, naphthacene, perylene, henzoquinone, ferrocene, 1,2-naphthoquinone, 1,4-naphthoquine, nitroazulene, and azobenzene can be used. However, it is not limited to these.

Furthermore, when using these substances to improve light resistance, it is more effective to introduce these substances into the protective layer than into the heat-sensitive layer, and when introducing them in a dispersion system, it is better to use smaller particle sizes. is preferred.

In addition, the pigment or dye used in the present invention may be used in combination with a light stabilizer such as an ultraviolet absorber, an antioxidant, or an energy quencher, and when used in combination, light resistance can be further improved. .

Examples of typical leuco dyes used in the present invention include crystal violet lactone, 3-indolino-3-p-
Dimethylaminophenyl-6-cynotylaminophthalide, 3-diethylamino-7-chlorofluoran, 3-diethylamine-5-methyl-7-t-butylfluoran, 3-diethylamino-6-methyl-7-anilino Fluoran, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-diethylamino-7-sibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6- Methyl-7-xylidinofluorane, 2-anilino-3-
Methyl-6-(N-ethyl-p-toluidino)fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolisino-7-cyclohexylaminofluorane, 3-piperidino-6-methyl-7- Toluidinofluorane, 3-pyrrolidino-6-methyl-7-(ρ-
toluidino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-N-methylcyclohexylamino-6-methyl-7-anilinofluorane, 3
-diethylamino-? Examples include, but are not limited to, -(+n-trifluoromethylanilihafluorane).

In addition, examples of acidic substances that develop color by reacting with the leuco dye under heat include 4-phenylphenol, 4-hydroxyace1-phenone, 2,2'-dihydroxydiphenyl, 2,2'-
Methylenehis (4-chlorophenol), 2.2'-
Methylenebis(4-methyl-6-t-butylphenol), 4.4'-isopropylidenebis(2-methylphenol), 4.4'-ethylenebis(2-methylphenol), 1.1'-bis(4 '-Hydroxyphenyl)-cyclohexane, 2,2'-bis(4-hydroxyphenyl)propane, 4,4'-cyclohexylidenebis(2-isopropylphenol), novolak type phenolic resin, 3-5-di-1-butyl salicylic acid,
Examples include, but are limited to, 3-5-di-α-methylbenzylsalicylic acid, 3-methyl-5-t-butylsalicylic acid, phthalic acid monoanilide barethoxyamic acid, and 4-hydroxybenzoic acid ester. It is not something that will be done.

Furthermore, as components for forming the heat-sensitive layer of the present invention, inorganic and organic pigments such as aluminum hydroxide, heavy and light calcium carbonate, titanium oxide, tMH barium, silica gel, activated clay,
Talc, clay, °su''tin white, kaolinite,
Calcined kaolinite, diatomaceous earth, synthetic kaolinite, polyolefin particles, polystyrene particles, urea-formalin resin particles, etc., and as Ii5 enhancers such as stearamide, balmitic acid amide, oleic acid amide, lauric acid amide, ethylene bis Stearoamide, methylene bisstearoamide, methylolstearoamide, paraffin wax, higher alcohol, higher resin acid, etc. may be added.

The above-mentioned heat-sensitive components of the present invention are used as a binder to form a heat-sensitive layer on a support such as paper, synthetic paper, resin film, or a composite thereof, using a water-soluble or water-insoluble resin binder. Adhesives can be used, but water-soluble resins are preferred, such as casein, gelatin, polyvinyl alcohol, modified 11 polyvinyl alcohol, polyvinylpyrrolidone, starch,
Modified starch, isobutylene-maleic anhydride resin, diisobutylene-maleic anhydride resin, styrene-maleic anhydride resin, polyacrylamide, modified polyacrylamide, carboxymethylcellulose, methyl vinyl ether-maleic acid copolymer, methylcellulose,
Hydroxyethyl cellulose, hydroxypropyl cellulose, and as a water-soluble emulsion, vinyl acetate, polystyrene, acrylic ester, vinyl chloride-vinyl acetate copolymer, etc. are used alone or in combination with gamma.

Furthermore, if necessary, a curing agent may be added to harden these binders to improve water resistance and chemical resistance.

The above-mentioned water-soluble binders can also be used as a binder in the film formation 11 of the coating layer provided on the heat-sensitive layer of the present invention.

Further, the above-mentioned pigments, lubricants, etc. may be added to this coating layer, if necessary, for the purpose of preventing sticking with the thermal head, adhesion of residue, etc.

<Examples> The present invention will be explained in detail below using examples. Hereinafter, parts refer to parts by weight.

A-G solutions were prepared by grinding and dispersing mixtures having the following formulations in a ball mill for one day. Solutions E and F are dispersions of substances having strong light absorption in the light wavelength range of 400 to 600 nm according to the present invention, and Solution G is a dispersion of an ultraviolet absorber used in comparative examples.

Solution A 3-N-methylcyclohexylamino-6-methyl-7
-Azulitsufluoran 25 parts 5% hydroxyethyl cellulose aqueous solution 50 parts Water 25 parts Solution B 4, ll'-isopropylidene diphenyl 15 parts 5
% hydroxyethylcellulose aqueous solution 60 parts Stearamide 15ffH water 10 children Iζ
C liquid light calcium carbonate 110 parts 109
≦Polyvinyl alcohol aqueous solution 40flζ water
20 le 5D1
Zinc stearate 25 parts lO% methylcellulose aqueous solution 25 parts water
50 parts E liquid ferrocene (absorption wavelength: 440rIIll) 40 parts 10
% polyvinyl alcohol 40 parts water
20 parts F liquid permanent yellow I-IR (absorption wavelength: 430 nm
) 40 parts 10% polyvinyl alcohol aqueous solution 40 parts water
20th part C! Night 2.4-dihydroxybenzophenone 40 parts lO% polyvinyl alcohol aqueous solution 40 parts water
20 copies Example 1 Above (7) AKll OflH1BYff133.3 copies, C? r! 9 parts of L40R1E liquid, 30 parts of 10% polyvinyl alcohol aqueous solution, and 3 parts of water were mixed to obtain a heat-sensitive recording paint.

The coating solution was coated on high-quality paper so that the coated amount after drying was 6 g/J and dried to form a heat-sensitive layer.

Furthermore, 40 parts of 10% polyvinyl alcohol aqueous solution, 2 parts of E liquid
．． 5 parts of C1r (33.3 parts) and 9 parts of water were mixed to obtain a coating layer application liquid to be provided on the heat-sensitive layer. After drying this coating liquid, the outside of the dmi cloth was adjusted to 4 g/at. A heat-sensitive recording paper having a coating layer was obtained by coating and drying.

Example 2 A thermosensitive recording paper was produced in exactly the same manner as in Example 1, except that Liquid E in Example 1 was replaced with Liquid F.

Example 3 A heat-sensitive layer was prepared in exactly the same manner as in Example 1 except that the amount of liquid E was changed to 49 parts and Ei was removed.Furthermore, the liquid for coating layer was changed to 24.3 parts of liquid E, and E A membrane-ruptured layer was provided on the heat-sensitive layer in the same manner as above except that 9 parts of the liquid was newly added to obtain a heat-sensitive recording paper.

Example 4 A thermosensitive recording paper was obtained in exactly the same manner as in Example 3 except that liquid E was replaced with liquid F.

Comparative Example 1 A heat-sensitive recording paper was obtained by producing a heat-sensitive layer and a coating layer in exactly the same manner as in Example [, except that the amount of liquid E was changed to 49 parts and liquid E was omitted.

Comparative Example 2 A thermosensitive recording paper was prepared in the same manner as in Example 1 except that Liquid E in Example I was replaced with Liquid G.

The parts of these heat-sensitive recording papers that had been colored with a hot plate at 120 DEG C. were placed in a weather meter and exposed in a dry state for 3 days to determine the photofading rate of all parts.

The results are shown in the table.

Density of colored area (black) before surface exposure <Effects of the invention> As shown in the table, pigments or dyes having light absorption in the light wavelength range of 400 to 600 nun are applied to the heat-sensitive layer and/or the heat-sensitive layer. It has been found that by including it in the coating layer, the light resistance is significantly improved compared to when it is not included.

Claims (1)

[Claims] In a heat-sensitive recording material in which a heat-sensitive layer containing a leuco dye and an acidic substance that causes the leuco dye to develop color when heated on a support, or a coating layer provided on the heat-sensitive layer, the heat-sensitive layer and/or the coating layer is provided with a light wavelength. A heat-sensitive recording material characterized by containing a pigment or dye having light absorption in the range of 400 to 600 nm.