JPH089266B2 - Thermal recording material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having excellent storability of a color image.

2. Description of the Related Art A heat-sensitive recording material using a colorless or light-colored coloring substance and a color-developing substance capable of coloring the coloring substance under heat is disclosed in Japanese Patent Publication No.
−4160 and Japanese Patent Publication No. 45-14039 have been widely put into practical use. In general, a heat-sensitive recording material is prepared by separately dispersing a leuco dye and a color developing agent such as a phenolic substance in the form of fine particles, and then mixing the two with an additive such as a binder, a sensitizer, a filler and a lubricant. Is added as a coating liquid to a support such as paper, film, synthetic paper, etc., and when heated, one or both of the leuco dye and the developer melt, and color recording is achieved by a chemical reaction caused by contact. Usually, a sheet-shaped heat-sensitive recording material is prepared. A thermal printer or the like having a built-in thermal head is used for color development of such a thermal recording sheet. Compared with other recording methods, this thermal recording method (1) produces no noise during recording. (2) No need for development and fixing, (3) Maintenance-free, (4) Machines are relatively inexpensive, so it can be used in the field of facsimiles, computer output, printers such as calculators, and medical measurement. It is widely used in the fields of recorders, vending machines, thermal recording labels, etc.

Among these fields of use, labels are increasing with the expansion of POS systems at retail stores, supermarkets, etc., and the use of station automation systems for tickets is increasing. A problem with these applications is that the colored image disappears or fades due to contact with plastic sheets or water leakage. Of the above, the phenomenon of decoloring and / or fading of the colored image due to contact with plastic sheets is due to the volatile agent contained in the plastics, but the thermosensitive recording method is similar to price label or ticket. As it is used for a short period of time and is extended to a long-term use such as commuter passes and various cards, the conventional method of increasing plastics resistance (resistance to solvating agents) is becoming insufficient. It was

Problems to be Solved by the Invention An object of the present invention is to solve the above-mentioned drawbacks of the prior art. That is, it is to provide a heat-sensitive recording material having a so-called highly reversible solubilizing property, which does not cause discoloration or discoloration of a color image due to long-term contact with plastic sheets or the like.

Means for Solving the Problems The present inventors have completed the present invention as a result of various studies to achieve the above object.

That is, the present invention relates to a thermosensitive recording material comprising a color-forming substance and a thermosensitive coloring layer mainly composed of a color-developing substance capable of developing a color when the coloring substance is heated on a support, wherein isobutylene is contained in the thermosensitive coloring layer. Provided is a heat-sensitive recording material containing an alkali salt of an N-phenylmaleimide-maleic anhydride copolymer and a water-soluble epoxy compound.

Isobutylene-N used in the thermal recording material of the present invention
-Phenylmaleimide-maleic anhydride is, for example, copolymerized with isobutylene, N-phenylmaleimide and maleic anhydride in a weight ratio of isobutyne: N-phenylmaleimide: maleic anhydride = 50: 45-20: 5-30. The product having a molecular weight of 20,000 to 80,000 is usually produced. In the heat-sensitive material of the present invention, the alkali salt of such a copolymer can be used as it is. Examples of the alkali salt of this copolymer include soda salt and ammonium salt.

In the present invention, a water-soluble epoxy compound, which is a water-soluble epoxy compound, is not preferable because it causes fog and innumerable point-like color development on the background of the heat-sensitive recording color-forming layer. Examples of water-soluble epoxy compounds include polyamide epoxy resin, ethylene polyethylene glycol diglycidyl ether, propylene polypropylene glycol diglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, phenol glycidyl ether, and lauryl alcohol glycidyl ether. It is considered that these water-soluble epoxy compounds act as a cross-linking agent for the copolymer, and the cross-linked copolymer acts as a binder.

The amount of the alkali salt of the isobutylene-N-phenylmaleimide-maleic anhydride copolymer used in the present invention is preferably 5 to 50% by weight, more preferably 5 to 20% by weight based on the weight of the heat-sensitive recording coloring layer. The amount of the water-soluble epoxy compound used is preferably 5 to 100% by weight, more preferably 20 to 50% by weight, based on the weight of the copolymer.

In the thermosensitive coloring layer of the thermosensitive recording material of the present invention, in addition to an alkali salt of isobutylene-N.phenylmaleimide-maleic anhydride copolymer and a water-soluble epoxy compound, a water-soluble high-functioning binder that acts as shown below is used. It may also contain molecules.

In this case, the use ratio of the alkali salt of the copolymer is at least 20% by weight and preferably 50% by weight or more based on the total amount of the copolymer and the water-soluble polymer used.

In the present invention, examples of the water-soluble polymer (binder) that can be used in combination with the alkali salt of the copolymer include polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and its derivatives, casein, alginate, Examples thereof include polyvinylpyrrolidone and polyacrylic amide.

The heat-sensitive recording material of the present invention comprises an alkali salt of isobutylene-N-phenylmaleimide-maleic anhydride copolymer and a water-soluble epoxy resin (A) a color-forming compound (B) a color-developing compound and others. It can be obtained by containing it in the heat-sensitive recording color-forming layer together with a binder, a filler, a heat-fusible compound, a surfactant and the like, if necessary.

(A) Chromogenic Compound Rhodamine-β-anilinolactam, Rhodamine (p-nitroanilino) lactam, 2-dibenzylamino-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylamino as xanthene compounds −
Fluoran, 2-anilino-3-methyl-6-cyclohexylmethylaminofluorane, 2-anilino-3-methyl-6-isopentylethylaminofluorane, 2-
Anilino-3-methyl-6-dibutylaminofluorane, 2-p-chloroanilino-3-methyl-6-diethylaminofluorane, 2-p-fluoroanilino-3-
Methyl-6-diethylaminofluorane, 2-p-fluoroanilino-3-methyl-6-dibutylaminofluorane, 2-Alinino-3-methyl-6- (p-toluidinoethyl) aminofluorane, 2-p- Triuzino-3
-Methyl-6-diethylaminofluorane, 2-o-chloroanilino-6-diethylaminofluorane, 2-o
-Chloroanilino-6-dibutylaminofluorane, 2
-O-fluoroanilino-6-diethylaminofluorane, 2-o-fluoroaniline-6-dibutylaminofluorane, 2-m-chloroanilino-6-diethylaminofluorane, 2-alinino-3-methyl-6-pi Peridinofluorane, 2-Alinino-3-methyl-6-pyrrolidinofluorane, 2-m-trifluoromethylanilino-6-diethylaminofluorane, 2-dihexylamino-6-aminofluorane, 2-butyl Amino-3-
Chloro-6-diethylaminofluorane, 2-ethoxyethylamino-3-chloro-6-diethylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-diphenylamino-6-diethylaminofluorane, 2- Anilino-3-methyl-6-diphenylaminofluorane, 2-phenyl-6-diethylaminofluorane, 2-chloro-3-methyl-6-diethylaminofluorane, 2-chloro-6-diethylaminofluorane, 2- Methyl-6-diethylaminofluorane, 6-diethylamino-1,2-benzofluorane, etc.,
3,3-Bis (p- as a traarylmethane compound
Dimethylaminophenyl) -6-dimethylaminophthalide (also known as Crystal Violet Lactone), 3,3-
Bis (p-dimethylaminophenyl) phthalide, 3-
(P-Dimethylaminophenyl) -3- (1,2-dimethylaminoindol-3-yl) phthalide, 3- (p-
Dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, chromenes and the like, 3-methyl-3-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-as spirolane compounds. Naphtho- (3-methoxy-benzo) spiropyran, 3
-Propyl-spiro-dibenzopyran, 1,3,3-trimethyl-6'-nitro-8'-methoxyspiro (indoline-2,2'-benzopyran), 1,3,3-trimethyl-6 '
-Nitrospiro (indoline-2,2'-benzopyran)
4,4'-bis- as a diphenylmethane compound
Dimethylaminobenzhydrin benzyl ether, N-
Halophenyl-leuco olamine, N-2,4,5-trichlorophenyl leuco olamine, and the like, benzoyl leuco methylene blue, p-nitrobenzyl leuco methylene blue, and the like as thiazine compounds, and other bis-3,
3- [bis-1,1- (p-dimethylaminophenyl) ethyleno-2] phthalide, bis-3,3- [bis-1,1- (p-
Dimethylaminophenyl) ethyleno-2] -4,5,6,7-
Tetrachlorophthalide, bis-3,3- [bis-1,1- (p
-Diethylaminophenyl) ethyleno-2] -4,5,6,7
-Tetrachlorophthalide, bis-3,3- [bis-1,1-
(P-Dimethylaminophenyl) ethyleno-2] -4
(Or 7) -Dinitro group-containing phthalide derivative such as nitrophthalide, 3,6-bis (dimethylamino) fluorenspyrro (9,3 ')-6'-dimethylaminophthalide, 3,6
-Bis (diethylamino) fluorene spiro (9,3 ')
Fluorene-based compounds such as -6'-diethylaminophthalide can also be used.

These color forming compounds may be used alone or as a mixture.

(B) Color-developing compound α-naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, pt-butylphenol, p-phenylphenol, 1,1′-bis (p-hydroxy) Phenyl) propane, 2,2'-bis (p-hydroxyphenyl) propane, 2,2'-bis (p-hydroxyphenyl) butane, 1,1'-bis (p
-Hydroxyphenyl) cyclohexane, 4,4'-thiobisphenol, 4,4'-cyclo-hexylidenediphenol, 4,4'-sulfonyldiphenol, 4,4'-sulfonyl-bis (2-allylphenol) ), 2,2'-bis (2,5-dibromo-4-hydroxyphenyl) propane, 4,4'-isopropylidenebis (2-t-butylphenol), 2,2'-methylenebis (4-chloro) A phenolic compound such as phenol), benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-t. -Butylsalicylic acid, aromatic carboxylic acid derivatives such as 3,5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids or polyvalent metal salts thereof, etc. .

The heat-sensitive recording material of the present invention is prepared by using the above-mentioned materials by the following method, for example. That is, by a conventional method, a color-developing compound and a color-developing compound are separately separated from each other separately with water or other additives, protective colloid substances such as polyvinyl alcohol, surfactants, etc., such as a ball mill, attritor, and sand mill. It was pulverized and dispersed by a disperser.

Another isobutylene-N-phenylmaleimide-maleic anhydride copolymer is added to water with an alkali compound such as caustic alkali or aqueous ammonia and dissolved by heating to obtain an aqueous solution of an alkali salt of the copolymer.

Then, a pulverized dispersion of a color-forming compound and a color-developing compound, an aqueous solution of an isobutylene-N-phenylmaleimide-maleic acid anhydride copolymer salt and a water-soluble epoxy compound are mixed to prepare a heat-sensitive color-developing coating solution, which is prepared on paper. , Coated on a support such as plastic sheet or synthetic paper with a bar coater or the like so as to be 5 to 40 g / m ² (the ratio of the color-forming compound and the color-developing compound is usually 1: 1 to 1:10 by dry weight ratio). The dried thermosensitive recording material of the present invention is obtained.

If necessary, an overcoat layer such as PVA may be provided between the thermosensitive coloring layer and the support (intermediate layer) or on the thermosensitive coloring layer.

The heat-sensitive recording material of the present invention containing a water-soluble epoxy compound and an isobutylene-N-phenylmaleimide-maleic anhydride copolymer has remarkably excellent resistance to solubilizing agents in color images as compared with the conventionally known materials.

Examples The present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. "Part" in the examples
Indicates parts by weight.

Example 1 Liquids [A] and [B] were prepared from a mixture having the following composition using a sand grinder.

Another mixture of the following compositions was dissolved by stirring at 90 ° C for about 2 hours to prepare a [° C] solution.

Next, the above [A] liquid: [B] liquid: [C] liquid = 58 parts: 27.
5 parts: mixed at a ratio of 16 parts, and 1.2 parts of polyethylene glycol glycine dil ether (molecular weight of about 420) was further added to prepare a thermosensitive color developing layer coating solution, and the basis weight was 50 g / m ²
Apply to 30 g / m ² and dry, then add 10% PV on the layer.
The aqueous solution A was applied so that the coating amount after drying was 2 g / m ^2, and dried to obtain a heat-sensitive recording material of the present invention.

Example 2 A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the amount of the liquid [C] was 30 parts.

Practical example 3 A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the amount of polyethylene glycol glycine dil ether used in Example 1 was 0.6 part.

Example 4 Instead of the solution [A] in Example 1, [D] having the following pulverization composition was used.
liquid A thermal recording material of the present invention was obtained in the same manner as in Example 1 except that was used.

Example 5 A mixture having the following composition was used with a sand grinder [E].
Solution, [F] solution was prepared.

[E] solution: [F] solution: [C] solution = 6 parts: 74 parts: 16 parts, and 1.2 parts of polyethylene glycol glycine diether (molecular weight about 420) is further added to apply a thermosensitive color developing layer. A liquid is prepared, coated on a high-quality paper having a basis weight of 50 g / m ^{2 so} as to have a liquid amount of 30 g / m ² , dried, and a coating amount after drying a 10% PVA aqueous solution on the layer is 3 g / m ^2. To obtain the heat-sensitive recording material of the present invention.

Example 6 A thermosensitive recording material of the present invention was obtained in the same manner as in Example 5 except that phenol glycidyl ether was used instead of polyethylene glycol glycine dil ether.

Example 7 A thermosensitive recording material of the present invention was obtained in the same manner as in Example 5, except that a 15% polyamide epoxy resin aqueous solution was used in place of polyethylene glycol glycine dil ether.

Example 8 A mixture having the following composition was used in place of the liquid [C] in Example 5:
Liquid [G] dissolved by stirring for about 2 hours at ℃ A thermal recording material of the present invention was obtained in the same manner as in Example 5 except that was used.

Comparative Example 1 A thermal recording material for comparison was obtained in the same manner as in Example 1 except that polyethylene glycol glycine dil ether was not used.

Comparative Example 2 Carboxylation in Example 1 instead of the liquid [C]
A thermal recording material for comparison was obtained in the same manner as in Example 1 except that 4.8 parts of SB latex (solid content 50%) was used.

As can be seen from the table, the heat-sensitive recording material of the present invention containing a water-soluble epoxy compound and an isobutylene-N-phenylmaleimide-maleic anhydride copolymer is superior to the conventionally known materials in the color image, and is resistant to the solvent. Is remarkably excellent. Further, it has a feature that it shows sufficient whiteness even on the background.

EFFECTS OF THE INVENTION A heat-sensitive recording material having remarkably excellent resistance to soaking was obtained.

Claims (1)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer comprising a coloring material and a coloring material capable of coloring the coloring material when heated as a main component, wherein isobutylene is contained in the thermosensitive coloring layer. A heat-sensitive recording material comprising an alkali salt of an N-phenylmaleimide-maleic anhydride copolymer and a water-soluble epoxy compound.