JPS6021552B2 - heat sensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a heat-sensitive recording material using a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated. The present invention relates to a heat-sensitive recording material which contains a heat-sensitive recording material to prevent color development due to rubbing or pressure of the heat-sensitive recording material.

A thermosensitive recording material is one in which a so-called thermosensitive coloring layer that develops color is formed on the surface of a support such as paper or a plastic film by heating, and a Samal printer with a built-in Samal head or the like is used for heating.
The thermal recording method using the above-mentioned recording materials is used not only to copy books and documents, but also to record the output of computers, facsimile machines, measuring instruments, etc. The recording materials used include lactones, fuctams, A recording material in which a heat-sensitive coloring layer containing a colorless or light-colored leuco dye having residual spiropyran and an acidic substance such as an organic acid or a ferrolytic substance is formed on a support has a clear color tone;
It is attracting attention because it has the advantage of having little fog. However, such heat-sensitive recording materials have the disadvantage that they easily develop color when scratched, rubbed or under pressure. The present invention aims to prevent this rubbing and color development due to pressure, and to improve the clarity of recorded images.
The present inventors coated the heat-sensitive coloring layer containing a leuco dye and an acidic substance with a polymer substance, and then
It has been found that these defects can be significantly reduced by incorporating particles of a solid substance having a color erasing effect (hereinafter referred to as a color erasing agent) into the hardened coloring system.

Conventionally, decolorizing agents suppress color development of low-temperature-sensitive V thermochromic images at high coloring temperatures when low-temperature and high-temperature thermochromic layers are laminated on the same support for multicolor thermosensitive recording materials of two or three colors. This was used for the purpose of improving the clarity of each colored image, but in the present invention, a solid decoloring agent coated with a polymeric substance and then hardened is added to the heat-sensitive coloring layer to create a monochrome heat-sensitive recording. It is possible to prevent the material from rubbing and color development under pressure, and to obtain sufficient color density during thermal printing.

It is unclear in detail why such an effect is obtained, but it is probably because the decoloring agent, which has been coated with a polymeric material and then hardened, is partially exposed to the polymeric material by rubbing or applying pressure. It is thought that the color decoloring agent was exposed in the heat-sensitive coloring layer due to the destruction of the coloring agent, and the effect of preventing coloration was obtained.

The present invention has been made based on this knowledge.

That is, the present invention provides a heat-sensitive recording material having a heat-sensitive coloring layer containing a heat-sensitive coloring system consisting of a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated. It is characterized by containing solid decolorizing agent particles that have been hardened after coating. Examples of decolorizing agents include the following.

1 Alcohols (Japanese Patent Publication No. 50-17865) For example, cetyl alcohol, stearyl alcohol, mericyl alcohol, crotyl alcohol, polyethylene glycol, polypropylene glycol, 1,8-octadiol 2,4-dimethyl-2-3-4 -Bentatorio-'Re 2
．． 4-Dimethyl-2-3-4-hexatriole, etc., group alcohol 2 Derivatives of polyether or polyethylene glycol, (Samurai Publication No. 17866/1983) For example, polyether derivative 10 (C ratio) represented by n-○chix Polyethylene oxide, polyoxydecamethylene, trimethylene oxide polymers, etc.

Polyoxymethylene represented by Len etc.

Polymers of 1,3-dioxolane represented by 10(CH2)n-OCH20nax, etc.

The above n is 1 to 10, x is 10 to loo0, and R is an alkyl group or hydrogen.

(b) Polyethylene glycol derivatives: polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, etc. represented by R-○-(CH2C string 0)nH.

Polyethylene glycol monostearate, polyethylene glycol beef tallow, fatty acid ester, etc. represented by R-○-(CH2C ratio ○)nH.

represented by polyoxyethylene alkyl allyl ether, etc.

The point represented by such as lyoxyethylene alkylamide.

oxy represented by such as ethylene alkylamines.

The above n and m are 10 to 10,000, and R is an alkyl group or hydrogen.

3. Compounds having nitrogen in the molecule such as nitro group or amino group (Tokukan Sho 49-65241), such as acetamide, stearamide, phthalonitrile, m-nitroaniline, B-naphthylamine.

4 Alkylene oxide adducts of bisphenols (Patent Application No. 1983-46689) where A is methylene or alkylidene 5 Long chain 1,2-glycol (Patent Application No. 99563) 6 Ethylene oxide adducts of terephthalic acid (Patent Application No. 99563) (Gan Shobou-96666) Examples of polymeric substances that coat the decolorizing agent particles include methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, acetylcellulose,
Celluloses such as nitrocellulose, corn starch, corn starch, wheat starch, oxidized starch, acetyl starch, methyl starch, dialdehyde starch and other starches, gelatin, casein, sodium alginate, polypinyl alcohol, Polyacrylonitrile, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, styrene-maleic anhydride copolymer, acrylic monomer and maleic anhydride copolymer, isobutylene. Maleic anhydride copolymer, styrene
Any water-soluble or organic solvent-soluble polymeric material can be used, such as acrylic acid copolymers, melamine, and aminoblasts initial integrators.

In the case of water-repellent polymeric substances, it is preferable to subject the surface of the coating to a hardening treatment to make it water-insoluble. Examples of the coating method include a melt-grinding method in which a decolorizing agent and a polymeric substance are mixed and dissolved in an organic solvent, the solvent is removed, solidified, and finely ground, or fine particles of a decolorizing agent are mixed and dissolved in the air. The so-called fluid coating method involves floating and suspending a polymeric substance in the suspension and spray-drying it through a nozzle, and the other is by mixing and dispersing a polymeric substance in which fine particles of a decolorizing agent are dissolved in an aqueous solution. After hardening, there is a method of separating and covering.

Particles obtained by the methods described above also exhibit the desired effects of the present invention.

Therefore, in the present invention, solid decolorizing agent particles J that have been coated with a polymeric substance and subjected to a hardening process are defined as ``solid decolorizing agent particles J that have been coated with a polymeric substance and subjected to a hardening process. The amount of the polymeric substance to be coated is 0.05 to 5 parts by weight per 1 part by weight of the decolorizing agent, and the amount of the polymeric substance to be coated is 0.05 to 5 parts by weight, and The coated decolorizer is preferably classified into particle sizes of approximately 0.5 to 10 grains, and more preferably has a particle size of approximately 0.5 to 5R. The amount of the coloring agent added is such that the amount of decoloring agent is contained in the thermosensitive coloring layer at a ratio of 0.1 to 5.0 parts by weight per 1 part by weight of the leuco dye contained in the thermosensitive coloring layer. It is preferable to

If the amount is less than 0.1 part by weight, the effect of preventing color development due to rubbing or pressure will be poor. If the amount is more than 1 part by weight, the density of the colored image will be low. In the present invention, conventionally known leuco dyes, acidic substances (organic acids, phenolic substances) and binders constituting the heat-sensitive coloring layer are used, and examples thereof are shown below.

1 Leuco dye 3,3-bis(P-dimethylaminophenyl)-phthalide, 3,3-bis(P-dimethylaminophenyl)-6
-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis(P-dimethylaminophenyl)-6-diethylaminophthalide, 3,3-bis(
P-dimethylaminophenyl)-6-chlorophthalide,
Triphenylmethane series such as 3,3-bis(P-diptylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 31-(N,N-diethylamino)-151-methyl-71 (N,N-dibenzylamino)
Leuco base of fluoran dyes such as fluoran, 3-dimethylamino-5,7-dimethylfluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7,8-benzfluoran, 3-diethylamino- 6-methyl-7-chlorofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-{N-
Fluoran dyes such as (3'-trifluoromethylphenyl)amino}-6-diethylaminofluorane, 2-{3,6-bis(diethylamino)-9-(0-chloranilino)xanthylbenzoic acid lactam}, 3 One (2'
-hydroxy-4'-dimethylaminophenyl)-31(2'-methoxy-5'-chlorophenyl)phthalide, 31(2'-hydroxy-4'-dimethylaminophenyl)131(2-methoxy-5- nitrophenyl)phthalide, 3-(2-hydroxy-4'-diethylaminophenyl)-31(2'-methoxy-5-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-31 (2'-Hydroxy-4'-chloro-5-methylphenyl)phthalide 2 Organic acids: boric acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, benzoic acid, stearic acid, gallic acid, saccharic acid, 1- Hydroxy-2-naphthoic acid, 0-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-P-toluic acid.

3 Phenolic substances: 3,5-xylenol, thymol, t-butylphenol, 4-hydroxyphenol, methyl-4
-Hydroxybesoate, 4-hydroxyacetophenone, Q naphthol, 8-naphthol, catechol,
Resorcinol, hydroquinone, 4-ten-octylcatechol, 4,4'-sec-butylidenephenol, 2
, 2-dihydroxydiphenyl, 2,2-methylenebis(4-methyl-6-ten-butylphenol), 2,
2'-bis(4'-hydroxyphenyl)propane, 4
, 4'-isopropylidene-bis(2-ten-butylphenol), 4,4-sec-butylidene diphenol, pyrogallol, phloroglucin, phloroglucin carboxylic acid.

4 Binders Water-removable materials such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, hydroxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, gelatin, etc.
Alternatively, aqueous emulsions such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. can be used as the binder.

In the heat-sensitive recording material of the present invention, fine powders such as calcium carbonate, silica, alumina, magnesia, talc, barium sulfate, and aluminum stearate are added to the heat-sensitive coloring layer to improve the clarity of the colored image. Furthermore, the runnability of the Samar head can be further improved by adding a lubricant such as linseed oil, tung oil, wax, paraffin, polyethylene wax, or chlorinated paraffin.

The heat-sensitive coloring layer of the present invention may be provided on a support such as ordinary paper, plastic film, metal-deposited paper, etc. by means such as coating or pasting to form a heat-sensitive recording material.

Furthermore, a thin colorless or colored transparent polymer material is formed on this heat-sensitive coloring layer. A protective layer can also be provided. In some cases, it is also possible to use a self-supporting substance as a binder for the heat-sensitive coloring layer to produce a recording material without a support. The present invention will be explained below using examples.

Example 1 Dispersions A and B were prepared by mixing the following components for 1q hours using a ball mill, and then dispersions A and B were further mixed to prepare a thermosensitive coloring layer forming liquid.

(Components of dispersion A) (Parts by weight) Crystal violet lactone 5.2 10% aqueous solution of polyvinyl alcohol 25.0 Water
14.8 (Components of dispersion B) Bisphenol 20.0 Oxidized starch 2.5
Water 22.5 (Coating with polymer substance as coloring agent) Cellulose Diacetate 15
Part by weight was dissolved in 150 parts by weight of a mixed solution of ethyl acetate and hexane, 5 parts by weight of jetyl phthalate was added as a plasticizer to this solution, and the mixture was uniformly dissolved to completely dissolve. By using an ethylene oxide adduct of bisphenol A, suspended in the air using a spirocoater (manufactured by Okada Seiko), and spraying the cellulose and diacetate solution from a spray nozzle to perform coating. Fine particles of decolorizer were coated with cellulose and diacetate.

(The coating amount was 0.5 parts by weight per 1 part by weight of the decolorizing agent. 1 part by weight of the coated decolorizing agent was added to and mixed with the thermosensitive coloring layer forming liquid prepared above. The prepared thermosensitive coloring layer forming liquid was coated on high-quality paper (5M/
A heat-sensitive recording material was obtained by coating on the surface of the film and drying to form a heat-sensitive coloring layer with an adhesion amount of 5.8%.

When the recording material thus obtained was printed with a thermal printer at a temperature of 100° C., a clear blue image was obtained. A heat-sensitive recording material for comparison was prepared using the same procedure as above except that the erasing agent coated with cellulose diacetate was not included, and when printed at 100°C in the same manner as above, a blue image was formed. Although no difference was observed between the heat-sensitive recording material of the present invention and the heat-sensitive recording material of the present invention, in the color development test by applying pressure, that is, rubbing or rubbing, almost no color development was observed with the recording material of the present invention. The comparative recording material exhibited remarkable color development, demonstrating the superiority of the recording material of the present invention.

Example 2 A thermosensitive color forming layer forming liquid was prepared by mixing dispersions A and B similar to Example 1.

(Coating of decolorizing agent with polymeric substance) As a decolorizing agent, a casein aqueous solution (3 parts casein, 5 parts water) in which 1.2 parts by weight of glycol of fine powder with a particle size of 0.5 to 5 mm is dissolved. The above-mentioned dispersion was thoroughly mixed and dispersed in 10 parts by weight of methanol prepared separately, and the above-mentioned dispersion was added while stirring to form a precipitate of long-chain 1,2-glycol coated with casein. After separating the material, add magnesium chloride and 1 part water as a hardening treatment.
50. The above precipitate was added to the above magnesium chloride solution and subjected to hardening treatment, and the decolorizing agent coated with the hardened casein film was separated.

8.5 parts by weight of the coated decolorizing agent thus obtained was added to and mixed with the thermosensitive color forming layer forming liquid prepared above.

Claims (1)

[Claims] 1. In a heat-sensitive recording material having a heat-sensitive coloring layer containing a heat-sensitive coloring system consisting of a colorless or light-colored leuco dye and an acidic substance that causes the leuco dye to develop color when heated, after the heat-sensitive coloring layer is coated with a polymeric substance. . A heat-sensitive recording material, characterized in that it contains particles of a solid substance that has a color erasing effect on the hardened heat-sensitive coloring system.