JPH04164685A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material improved in the preservability of a recording image, especially, in the plasticizer resistance and oil resistance thereof, generating no background fog and enhanced in recording density and recording sensitivity by adding at least one kind of a compound having an epoxy group and a specific compound. CONSTITUTION:A thermal recording material utilizes the color reaction of a colorless or light-colored basic dye and a developer capable of forming a color upon the contact with said dye and contains at least one kind of a compound having an epoxy group and a compound represented by general formula (I). The compound having an epoxy group is selected from a novolac type epoxy resin, a bisphenol A type epoxy resin and a diphenylsulfonic acid derivative having an epoxy group. The compound represented by the general formula (I) is usually added to a thermal recording layer and, concretely, dibenzyl oxalate is pref. The use amount of the compound represented by the general formula (I) is about 10-1000 pts.wt., pref., 50-500 pts.wt. per 100 pts.wt. of the basic dye.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a heat-sensitive recording medium, and particularly to a heat-sensitive recording medium that has a high recording density and excellent storage stability of recorded images.

``Prior art'' Heat-sensitive recording materials that utilize a color reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to obtain a recorded image by bringing both coloring substances into contact with heat are well known. Are known.

Such heat-sensitive recording media are relatively inexpensive, and because the recording device is compact and easy to maintain, they are used not only as recording media for facsimile machines and various computers, but also in a wide range of fields.

For example, a retail store's POS (point of 5)
Ales) With the expansion of systemization, the number of cases in which they are used as heat-sensitive recording labels is increasing.

However, when a POS system is introduced in a supermarket, etc., the labels often come into contact with water, lamps, oil, etc., and as a result, the recorded image on the thermal recording label (
A defect in which the print (printing) fades is observed. Therefore, heat-sensitive recording materials are required to have storage properties such as water resistance, plasticizer resistance, and oil resistance.

Conventionally, in order to improve the storage stability of recorded images, there has been a method of coating an aqueous emulsion of a resin with film-forming ability and chemical resistance on the heat-sensitive recording layer (Japanese Patent Application Laid-open No. 128347/1983), and a method of coating polyvinyl alcohol. A method of applying a water-soluble polymer compound such as (Japanese Utility Model Application Publication No. 125354/1983) has been proposed. Methods of adding various storage improvers to the heat-sensitive recording layer have also been proposed, but in each case new drawbacks accompany the improvement, and satisfactory effects are not always obtained. is the current situation.

In addition, in recent years, printers used for recording have become faster and more compact, and the number of devices that require less energy from the thermal head is increasing.As a result, thermal recording materials are required to have higher density and higher sensitivity. There is.

- [Problems to be Solved by the Invention] The present invention provides a thermosensitive material that significantly improves the storage stability of recorded images, especially plasticizer resistance and oil resistance, does not cause background capri, and has high recording density and recording sensitivity. The purpose is to provide a record.

Means for Solving the Problems The present invention provides a thermal recording material that utilizes a coloring reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color upon contact with the dye. The thermosensitive recording material is characterized in that it contains at least one compound having an epoxy group and also contains a compound represented by the following general formula (1).

[R represents a hydrogen atom, a halogen atom, an alkyl group, or an alkoxyl group. ] The present invention provides that the above-mentioned epoxy group-containing compound is a novolac type epoxy resin, a glycidyl ether compound having a benzene ring as its core, a glycidyl ester compound of aromatic carboxylic acid, a bisphenol A type epoxy resin, and a diphenyl sulfone derivative having an epoxy group. Disclosed is a thermosensitive recording material that is at least one selected from the following.

The present invention discloses the above heat-sensitive recording material in which the coloring agent contains a compound represented by the following general formula (II).

(Rz, Rs, and R- may be the same or different and each represents a hydrogen atom, an alkyl group, or an allyl group.) Also disclosed is a heat-sensitive recording material having a protective layer on the uppermost layer of the recording surface of the heat-sensitive recording material.

"Function" The compound represented by the above general formula (1) is usually contained in the heat-sensitive recording layer, and specific examples thereof include dibenzyl oxalate, di(p-chlorobenzyl oxalate), ) ester, oxalic acid di(p-methylbenzyl) ester, oxalic acid di(p-ethoxybenzyl) ester
Examples include esters, among which oxalic acid dibenzyl ester is preferred.

When R1 is an alkyl group, the number of carbon atoms is preferably about 01 to C3, and C1 is particularly preferred.

When R1 is an alkoxyl group, the number of carbon atoms is C3 to CIO
degree is preferred.

Two or more of these compounds may be used in combination.

The amount of the compound represented by the general formula (1) is not particularly limited, but 1 part by weight of the basic dye
It is used in an amount of about 0 to 1000 parts by weight, preferably about 50 to 500 parts by weight.

The compound having an epoxy group is not particularly limited, but it is usually preferable to include it in the raging heat recording layer.

Specific examples thereof include the following.

(A) Novolak-type epoxy resin As the novolak-type epoxy resin used in the present invention, a compound represented by general formula (III) can be exemplified.

[In the formula, X represents a methyl group or a hydrogen atom, and Y represents a halogen atom. In addition, a represents an integer from 0 to 3, and b represents an integer from 0 to 2.
Indicates an integer of 0. [For example, phenol novolac type epoxy resin, brominated phenol novolac type epoxy resin, etc. are phenol novolak, which is a reaction product of phenol and formaldehyde, or brominated phenol novolak, which is a reaction product of phenol, formaldehyde, and bromine, and epichlorohydrin, respectively. These include those obtained by reaction. Preferably, b is a mixture of resins in the range of 2 to 7 or the average value of b is 2 to 7, and a solid novolac type epoxy resin having a softening point of about 60 to 100°C is preferably used.

Orthocresol novolak type epoxy resin is obtained by reacting orthocresol novolac, which is a reaction product of orthocresol and formaldehyde, with epichlorohydrin, and b=2 to 7 or the average value of b is 2 to 7. A mixture is preferred, with a softening point of 60-14
A solid novolak type epoxy resin at about 0°C is preferred.

(a) Examples of glycidyl ether compounds having a benzene ring as a core and glycidyl ester compounds of aromatic carboxylic acids are as follows.

[In the formula, R,, R, are each a hydrogen atom, provided that R,, R
, cannot become hydrogen atoms at the same time. m, n, p, q, r
, s each represent an integer of 1 to 5. Further, Z represents a halogen atom, an alkyl group of 01 to C4, or an alkoxyl group of CI""' Ca, and h represents 0 or an integer of 1 to 4. ] Specific examples of the compound represented by the above general formula (IV) include 1,4-di(glycidyloxy)benzene, 1
, 4-di(glycidyloxy)-3゜6-dibromobenzene, 1,4-di(glycidyloxy)-3,6-dichlorobenzene, 1,4-di(glycidyloxy)-3-
Methylbenzene, 1,4-di(glycidyloxy)-3
-methoxybenzene, 1,4-di(2-glycidyloxyethoxy)benzene, 1,4-di(4-glycidyloxybutoxy)benzene, 1,4-di(2-glycidyloxyethoxy)-3,6-dibromo Benzene, 1.4
-di(2-glycidyloxyethoxy)-3,6-dichlorobenzene, 1,4-di(2-glycidyloxyethoxy)-3-methylbenzene, 1,4-diglycidyl phthalate, 1゜4-diglycidyl-3 -methyl phthalate, 1゜4-diglycidyl-3-methoxyphthalate,
Examples include 1°4-diglycidyl-3-ethoxyphthalate and 1°4-di(2-glycidyloxyethyl)phthalate.

Examples of the monoglycidyl compound include glycidyloxybenzene, monoglycidyl phthalate, and monoglycidyl terephthalate.

In addition, as ether compounds other than the above general formula, 1-phenoxy-14glycidyloxy-3,6゜9.12-
Examples include tetraoxatetradecane.

It is preferable in terms of plasticizer properties and background fog.

(1) Bisphenol A type epoxy resin [In the formula, W represents a halogen atom, C represents an integer of 0 to 4, and d represents an integer of 1 to 23. ] The bisphenol A type epoxy resin represented by the general formula (V) includes a compound obtained by a condensation reaction of bisphenol A obtained by reacting phenol with acetone and epichlorohydrin, and a compound obtained by a condensation reaction of bisphenol A obtained by reacting phenol with acetone, and tetrabromobisphenol A.
For example, a flame-retardant epoxy resin obtained by reacting tetrabromobisphenol A with a bisphenol A type epoxy resin is exemplified.

By changing the reaction conditions and the blending amounts of bisphenol A and epichlorohydrin, various epoxy resins having different average molecular weights can be obtained.

Furthermore, they are broadly classified into low halogen types and high halogen types depending on the halogen content, and a large number of types are known for each type based on differences in average molecular weight, halogen content, etc.

The bisphenol A type epoxy resin used in the present invention is not particularly limited, but is a solid type having an epoxy equivalent, which indicates the average molecular weight per epoxy group, of 500 or more and a softening point of 60°C to 140''. Epoxy resins of grade C are preferably used.

That is, liquid bisphenol A type epoxy resin,
A solid epoxy resin with a low softening point may reduce the whiteness of the recording medium or worsen background fog, and if the softening point is too high, the effect of improving storage stability may be reduced.

(1) Diphenylsulfone derivative having an epoxy group υ -0-(CHz)r-CHCHRz or \
1 However, Ro. + R11+ LX each represents a hydrogen atom or an alkyl group, e and f are each 0 or 1 to 5
represents an integer of 1 to 5, and g and i each represent an integer of 1 to 5.

Further, Ri and Rq each represent a halogen atom, an alkyl group, or an alkoxyl group, t represents O or 1, U represents 0 or an integer of 1 to 5, and ■ represents 0 or an integer of 1 to 4, respectively. ] Specific examples of the diphenylsulfone derivative having an epoxy group represented by the above general formula (Vl) include the following.

4-(1,2-epoxyethyl)diphenylsulfone,
4-glycidyldiphenylsulfone, 4-(3,4-epoxybutyl)diphenylsulfone, 4-(2,3-epoxybutyl)diphenylsulfone, 4-(1,2-epoxyethyloxy)diphenylsulfone, 4-glycidyloxy Diphenylsulfone, 4-(3,4-epoxybutyloxy)diphenylsulfone, 4-(2,3-
Epoxybutyloxy)diphenylsulfone, 4-glycidyloxy-4'-chlorodiphenylsulfone, 4-
glycidyloxy-4'-bromodiphenyl sulfone,
4-glycidyloxy-4'-methyldiphenylsulfone, 4-glycidyloxy-4'-ethyldiphenylsulfone, 4-glycidyloxy-2', 4'-dimethyldiphenylsulfone, 4-glycidyloxy-2', 4
'-Dichlorodiphenylsulfone, 4-glycidyloxy-4'-(n-propyl)diphenylsulfone, 4-
Glycidyloxy-4'-isopropyldiphenylsulfone, 4-glycidyloxy-4' (tert-
butyl) diphenylsulfone, 4-glycidyloxy-
4'-isoamyldiphenylsulfone, 4-glycidyloxy-4'-methoxydiphenylsulfone, 4-glycidyloxy-4'-ethoxydiphenylsulfone, 4
-Glycidyloxy-4'-isopropyloxydiphenylsulfone, 4-glycidyloxy-4'-n-pentyloxydiphenylsulfone, 4-glycidyloxy-2',4'-dimethoxydiphenylsulfone, 4.4
'-Diglycidyloxydiphenyl sulfone, 4.4'
-diglycidyloxy-3,3'-dichlorodiphenylsulfone, 4゜4'-diglycidyloxy-2,2'
-dibromodiphenylsulfone, 4.4'-diglycidyloxy-3,3',5.5'-tetrabromodiphenylsulfone, 4.4'-bis(2-7'lycidyloxyethoxy)diphenylsulfone, 4. 4'-bis(2-
glycidyloxyethoxy)-3゜3',5.5'-tetrabromodiphenylsulfone, 4.4'-bis(2-
glycidyloxyethoxy)-3,3',5,5'-tetrachlorodiphenylsulfone, 4,4'-bis(2-
glycidyloxyethoxy)-3,3',5.5'-
Tetramethyldiphenylsulfone, 4,4'-bis(3
, 4-epoxybutyloxy)diphenylsulfone, etc.

Among the diphenylsulfone derivatives represented by the above general formula (Vl), compounds in which t is 1 are particularly preferred in terms of the effect of improving print storage stability.

On the other hand, diphenylsulfone derivatives having a monoglycidyl group include those represented by the formula -i (■), which are particularly preferably used.

It [In the formula, R13 represents a hydrogen atom, an alkyl group, or an allyl group, and R14 represents a hydrogen atom, an alkyl group, an allyl group, an aryl group that may be substituted with an alkyl group or an allyl group, or an alkyl group or an allyl group. Indicates an optionally substituted aralkyl group. ] For example, 4-[(2,3-epoxy-2methyl)propyloxyphphenyl-4'-(hensyloxy)phenylsulfone, 4-((2,3epoxy)propyloxyphphenyl-4'-(4-methyl Hensyloxy)
Phenylsulfone, 4-((2,3-epoxy-2ethyl)propyloxyphenyl-4'-(benzyloxy)phenylsulfone, 4-((2,3-epoxy)
Propyloxyphphenyl-4'-(4-ethylbenzyloxy)phenylsulfone, 4-((2゜3epoxy)propyloxy]phenyl-4'-benzyloxyphenylsulfone, 4-[(2゜3epoxy)propyloxy Pphenyl-4'-methoxyphenylsulfone, 4-[(2,3epoxy-2-methyl)propyloxy]phenyl-4'-ethoxyphenylsulfone, 4-((2,3epoxy-2-methyl)propyl Oxyphenyl-3'-methoxyphenyl sulfone, 4
-[(2,3epoxy)propyloxy]phenyl-4
'-Hydroxyphenylsulfone, 4-((2,3epoxy-2-methyl)propyloxy]phenyl-3'
-Hydroxyphenylsulfone, 4-((2,3epoxy-2-methyl)propyloxy]phenyl-3'-
Phenethyloxyphenylsulfone, 4-((2,3
Epoxy-2-propyl)propyloxyphphenyl-
4'-(benzyloxy)phenylsulfone, 4-
((2,3epoxy-2-methyl)propyloxyphphenyl-3'-(hensyloxy)phenylsulfone, 4-((2,3epoxy)propyloxyphphenyl-4'-(m-methylbenzyloxy)phenyl Examples include sulfone, 3-((2°3epoxy)propyloxyphenyl-3'-(p-methylbenzyloxy)phenylsulfone, etc.).

Furthermore, in the epoxy compound represented by the general formula (■), [where j represents 0 or an integer of 1 to 5, h represents O or 1 to 5]
Indicates an integer of 4. Z represents a halogen atom, an alkyl group of 01 to C1, and an alkoxyl group of C, -C4. ] 1.4-di(1,2-epoxyethyl)benzene, 1.
Examples include 4-diglycidylbenzene.

The amount of these epoxy group-containing compounds to be used is not particularly limited, but based on 100 parts by weight of the coloring agent,
It is used in an amount of about 0.1 to 500 parts by weight, preferably 1 to 200 parts by weight.

The coloring agent is contained in the heat-sensitive recording layer, and typical examples include activated clay, acid clay, attapulgite, bentonite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butylphenol, 4-Hydroxyfunoxide, α-naphthol, β
-Naphthol, 4-hydroxyacetophenol, 4-
tert-octylcatechol, 2,2"-dihydroxydiphenol, 2.2"-methylenebis(4-methyl-6-tert-isobutylphenol), 4.4
'-isopropylidene bis(2-tert-butylphenol), 4.4"-5ec-butylidene diphenol, 4-phenylphenol, 4.4"-isopropylidene diphenol, 2,2"-methylenebis(4-chlorophenol) ), hydroquinone, 4゜4''-cyclohebocylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroxymonobenzyl ether, 4.4'-(1,3-dimethylbutylidene) bisphenol , 4.4"-(1-phenylethylidene)bisphenol, 4,4"-(p-phenylenediisopropylidene)diphenol, 4.4"
-(m-phenylene diisopropylidene) diphenol, phenolic compounds such as phenol polymers, benzoic acid, p, -tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3.5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isobrobylsalicylic acid, 3-te
rt-butylsalicylic acid, 3-benzylsalicylic acid, 3
-(α-methylhensyl)salicylic acid, 3-chloro-5
-(α-methylbenzylsalicylic acid, 3,5-di-te
rt-Butylsalicylic acid, 3-phenyl-5-(α.

α-dimethylbenzyl)salicylic acid, 3. 5-C α
- aromatic carboxylic acids such as methylbenzylsalicylic acid,
and these phenolic compounds, salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, and also zinc, magnesium, aluminum,
Examples include organic acidic substances such as complex compounds of polyvalent metal salts such as calcium, titanium, manganese, tin, and nickel and organic compounds such as antipyrine, pyridine, and demethylaminoantipyrine.

Among them, the compound represented by the general formula (II) is particularly preferred, and specific examples include bis-(4-hydroxyphenyl)sulfone, bis-(3-allyl-4-hydroxyphenyl)sulfone, 2.4 '-dihydroxydiphenylsulfone, 2-hydroxy-5-t-butylphenyl-4'-hydroxyphenylsulfone, 2-
Hydroxy-5-t-amylphenyl-4'-hydroxyphenylsulfone, 2-hydroxy-5-isopropylphenyl-4'-hydroxyphenylsulfone,
2-Hydroxy-5-t-butylphenyl-3'-methyl-4''-hydroxyphenylsulfone, 2-hydroxy-5-t-butylphenyl-3'-isopropyl-
4'-hydroxyphenylsulfone, 2-hydroxy-5-t-butylphenyl-2'-methyl-4-hydroxyphenylsulfone, 4-hydroxy-4'isopropoxydiphenylsulfone, 4-hydroxy-4'
Examples include methoxydiphenyl sulfone.

The amount of these coloring agents used is not necessarily limited, but is 100 to 7 parts by weight per 100 parts by weight of the basic dye.
00 parts by weight, more preferably 150 to 400 parts by weight of a coloring agent. In addition, two or more types of coloring agents may be used in combination as necessary.

In the heat-sensitive recording material of the present invention, various types of colorless to light-colored basic dyes constituting the recording layer are known, and the following are exemplified.

3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2 -dimethylindol-3-yl)phthalide, 3-(P-dimethylaminophenyl")
-3-(2-methylindol-3-yl)phthalide,
3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1°2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide, 3.3-
Triallyl such as bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-P-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, etc. Methane dye, 4,4
'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,
4,5-) Diphenylmethane dyes such as dichlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and P-nitrobensoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3
Spiro dyes such as -ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzobilane , lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (0-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran,
3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-
6-Methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-ethyl-
p-Toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluoran Oran, 3-diethylamino-7-N-methyl-N-
Benzylaminofluorane, 3-diethylamino-7-
N-chloroethyl-N-methylaminofluorane, 3-
Diethylamino-7-diethylaminofluorane, 3-
(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-)luidino)-6-methyl-7-(p-toluidino)fluorane, 3-dimethyl Amino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-
7-phenylaminofluorane, 3-cyptylamino-
6-methyl-7-phenylaminofluorane, 3-di-
n-pentylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluorane, 3-(N-cyclohexyl-N-methylamino)-6-methyl- 7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6
-Methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3
-diethylamino-7-(0-chlorophenylamino)
Fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-P-butylphenylaminofluoran, 3-diethylamino-7-(0-fluorophenylamino)fluoran,゛3-dibutylamino-7-(0-fluorophenylamino)fluorane, 3-(N-methyl-N-
n-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-n-amyl)amino-6-methyl-7-phenylaminofluorane, 3-
(N-ethyl-N-isoamyl)amino-6-methyl-
7-phenylaminofluorane, 3-(N-methyl-N
-n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-Nn-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl -N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluorane, 3-(
N-ethyl-N-cyclopentyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
N-tetrahydrofurfuryl)amino-6-methyl-7
Examples include fluoran dyes such as -phenylaminofluorane.

Coating liquids for heat-sensitive recording layers containing these substances are generally prepared by using water as a dispersion medium and dispersing them using a stirring/pulverizing machine such as a ball mill or a sand mill.

The thermosensitive recording layer usually contains binders, such as starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic,
Polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, styrene/maleic anhydride M copolymer salt, ethylene/acrylic acid copolymer salt , styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, urea resin, melamine resin, amide resin, etc. The binder is preferably 5 to 40% by weight, more preferably 10 to 40% by weight based on the total solid content of the recording layer.
It is blended in an amount of about 30% by weight.

Furthermore, various auxiliary agents can be added to the coating liquid as necessary, such as dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt,
Dispersants such as lauryl alcohol sulfate/sodium salt and fatty acid metal salts, ultraviolet absorbers such as benzophenone, other antifoaming agents, fluorescent dyes, coloring dyes, etc. are added as appropriate.

In addition, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, It is also possible to add inorganic pigments such as activated clay, and various sensitizers can also be used in combination depending on the purpose as long as they do not interfere with the present invention.

The method of forming the recording layer is not particularly limited, and the heat-sensitive recording layer coating solution may be formed by an appropriate coating method such as air knife coating, varibur blade coating, rod blade coating, pure blade coating, short dwell coating, curtain coating, or die coating. It is formed by a method such as coating and drying on a support. The amount of the coating liquid to be applied is not particularly limited, and is usually adjusted in the range of about 2 to 12 g/rrf, preferably about 3 to 10 g/rrf, in terms of dry weight.

In the heat-sensitive recording material of the present invention, by providing a protective layer on the heat-sensitive recording layer, the storage stability of recorded prints can be further improved.

The protective layer contains a water-soluble or water-dispersible polymer. Examples of such polymers include the various binders mentioned above, but among them, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are particularly preferred because they exhibit excellent effects. Preferably used.

In addition, to further improve water resistance, glyoxal, polarmarine, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, dialdehyde starch, melamine resin polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde resin,
A curing agent such as borax, boric acid, ammonium zirconium carbonate, or an epoxy compound can also be included in the protective layer or in an adjacent layer such as the heat-sensitive recording layer.

Pigments can be added to the protective layer as necessary to further improve printability and sticking. Specific examples include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, and silicon dioxide. , aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, inorganic pigments such as colloidal silica, styrene microspheres, nylon powder, polyethylene powder, urea/formalin resin filler,
Examples include organic pigments such as raw starch particles.

It is generally desirable to adjust the amount of pigment to be used in a range of 5 to 500 parts by weight based on 100 parts by weight of the binder.

Furthermore, in the coating liquid that forms the protective layer, lubricants such as zinc stearate, calcium stearate polyethylene wax, carnauba wax, paraffin wax, and ester wax, and surfactants (dispersants, lubricants, etc.) such as sodium dioctyl sulfosuccinate, etc. Various auxiliary agents such as antifoaming agents) and antifoaming agents can also be added as appropriate.

The coating solution forming the protective layer is generally prepared using water as a dispersion medium.

The coating liquid for the protective layer thus prepared is applied onto the heat-sensitive recording layer using a suitable coating device, but if the coating amount is too large, the recording sensitivity of the heat-sensitive recording medium may decrease, so the coating liquid is generally 0.1 ~20g/M or so, preferably 0.5~10g
Adjust within the range of /rd.

Note that, if necessary, it is also possible to further improve the storage stability by providing a protective layer on the back side of the heat-sensitive recording material. Furthermore, various known techniques in the field of heat-sensitive recording material manufacturing may be added as necessary, such as providing an undercoat layer on the support, applying an adhesive treatment to the back surface of the recording material, and processing it into an adhesive label.

As the support, paper, plastic film, synthetic paper, etc. can be used, and paper is preferably used in terms of cost, coatability, etc.

“Examples” The present invention will be explained in more detail with reference to Examples below, but it is of course not limited to these examples.
"Parts" and "%" refer to "parts by weight" and "% by weight," respectively, unless otherwise specified.

Example 1 ■ Preparation of liquid A 3-dibutylamino-6-methyl-7-phenylaminofluorane 10 parts Methyl cellulose 5% aqueous solution 5 parts water
40 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Preparation of B solution 4.4”-(L 3-dimethylbutylidene)bisphenol 30 parts Methylcellulose 5% aqueous solution 5 parts water
80 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ C-wave preparation oxalic acid dibenzyl ester 20 parts Methyl cellulose 5% aqueous solution 5 parts water
55 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Preparation of Solution D Orthocresol novolac type epoxy resin (general formula (
In III), a mixture where b is 2 to 7, a=0, X is a methyl group, softening point 97°C) 20 parts methylcellulose 5% aqueous solution 5 parts water
55 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Formation of recording layer 55 parts of liquid A, 115 parts of liquid B, 80 parts of liquid C, 24 parts of liquid D,
A coating liquid obtained by mixing and stirring 80 parts of a 10% polyvinyl alcohol aqueous solution, 35 parts of calcium carbonate, and 25 parts of a 30% zinc stearate dispersion was applied to a base paper of 50 g/rrf, and the coating amount after drying was 6 g/rrr. A heat-sensitive recording material was obtained by coating and drying as described above.

Example 2 The same procedure as in Example 1 was carried out except that 4-hydroxy-4'-isopropoxydiphenylsulfone was used instead of 4.4'-(1,3-dimethylbutylidene)bisphenol in preparing Solution B. A thermosensitive recording medium was obtained.

Example 3 A thermosensitive recording material was obtained in the same manner as in Example 2, except that 1.4-4 diυ゛lycidyloxy)benzene was used in place of the ortho-cresol novolak type epoxy resin in preparing Liquid D.

Example 4 In the preparation of liquid D, 1,4-diglycidyl phthalate was used instead of the ortho-cresol novolac type epoxy resin, and in the preparation of wave C, di(p-methylbenzyl oxalate was used instead of dibenzyl oxalate). ) A thermosensitive recording material was obtained in the same manner as in Example 1 except that ester was used.

Example 5 In place of 4-hydroxy-4'-isopropoxydiphenylsulfone in the preparation of Solution B.

A thermosensitive recording material was obtained in the same manner as in Example 3 except that bis-(4-hydroxyphenyl)sulfone was used.

Example 6 A thermosensitive recording material was obtained in the same manner as in Example 3, except that 2,4'-dihydroxydiphenylsulfone was used in place of 4-hydroxy-4'-isopropoxydiphenyl in the preparation of liquid B.

Example 7 In the preparation of Solution B, 2.4'-dihydroxydiphenylsulfone was replaced with bis-(3-allyl-4-hydroxyphenyl)sulfone, and in the preparation of Solution D, 1.
4-[ instead of 4-(diglycidyloxy)benzene
A thermosensitive recording material was obtained in the same manner as in Example 6 except that (2,3epoxy-2-methyl)propoxy]phenyl-4'-(benzyloxy)phenylsulfone was used.

Example 8 A thermosensitive recording material was obtained in the same manner as in Example 6, except that a bisphenol A type epoxy resin (epoxy equivalent: 650 to 850) was used in place of 1,4-(diglycidyloxy)benzene in the preparation of Liquid D.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 2, except that liquid C was not added in the formation of the recording layer in Example 1.

Comparative Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1 except that stearic acid amide was used instead of oxalic acid dibenzyl ester in the C wave preparation.

Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 2 except that liquid C and D were omitted in the formation of the thermosensitive recording material.

Comparative Example 4 In the preparation of liquid B, 4.4'-isopropylidene diphenol was used instead of 4.4'-(1,3 dimethylbutylidene) bisphenol, and in the preparation of wave C, stearic acid was used instead of dibenzyl oxalate. A thermosensitive recording material was obtained in the same manner as in Example 1 except that amide was used. The following evaluation tests were conducted on the 12 types of heat-sensitive recording bodies thus obtained, and the results are listed in Table 1.

[Whiteness]

In order to evaluate the degree of color fog, the whiteness of the recording layer was measured using a Hunter whiteness meter.

[Color density]

Thermal printer (Texas Instruments, PC)
The color density of the recorded image obtained by printing with a Macbeth densitometer (manufactured by Macbeth Co., Ltd.) was measured using a Macbeth densitometer (Macbeth Co., Ltd.).

RD-100R model).

[Plasticizer resistance]

A vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemical Co., Ltd.) is wrapped three times around a polypropylene pipe (40 gamφ pipe), and a heat-sensitive recording material with colored print is placed on top of it so that the colored side of the print is facing outward. A vinyl chloride wrap film was wrapped three times on top, and the plasticizer resistance was evaluated from the print density after being left at 20° C. for 24 hours.

Table 1 Example 9 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 2.

■ Formation of protective layer 10% aqueous solution of acetoacetylated polyvinyl alcohol 1
0 parts, 20 parts of kaolin clay, and 50 parts of water were mixed and stirred, and the coating liquid was applied onto the recording layer of the above-mentioned heat-sensitive recording material so that the coating amount after drying was 4 g/nf. Obtained a record.

Example 10 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 3.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

Example 11 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 5.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

Example 12 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 6.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

Example 13 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 7.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

Example 14 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 8.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

Comparative example 5 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Comparative Example 1.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

Comparative example 6 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Comparative Example 2.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

Comparative example 7 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Comparative Example 3.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

Comparative example 8 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Comparative Example 4.

(2) Formation of protective layer A thermosensitive recording material having a protective layer was obtained in the same manner as in Example 9 except that the above thermosensitive recording material was used.

The ten types of heat-sensitive recording materials thus obtained were subjected to the same evaluation tests as described above, except that the plasticizer resistance and water plasticizer resistance were evaluated using the following methods, and the results are listed in Table 2.

[Plasticizer resistance]

Wrap vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemicals) three times around a polypropylene pipe (40mφ pipe).
A heat-sensitive recording material with colored prints is placed on top of it with the printed colored side facing outward, and a vinyl chloride wrap film is then wrapped three times over it. Plasticizer properties were evaluated.

[Water resistance to plasticizers]

After lightly moistening the colored printed heat-sensitive recording material with water, it was evaluated in the same manner as the plasticizer resistance above, and the results of Water Resistance Plasticizer Table 2 "Effect" are clear from the results of Tables 1 and 2. All of the heat-sensitive recording materials had excellent storage stability after recording and were free from background fog.

Claims (4)

[Claims] (1) A thermosensitive recording material that utilizes a coloring reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color upon contact with the dye, wherein the thermosensitive recording material contains at least one compound having an epoxy group. and a compound represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [R_1 represents a hydrogen atom, a halogen atom, an alkyl group, or an alkoxyl group. ] (2) The compound having an epoxy group is selected from a novolac type epoxy resin, a glycidyl ether compound having a benzene ring as its core, a glycidyl ester compound of aromatic carboxylic acid, a bisphenol A type epoxy resin, and a diphenyl sulfone derivative having an epoxy group. at least 1
The heat-sensitive recording material according to claim (1), which is a seed. (3) The heat-sensitive recording material according to claim (1) or (2), wherein the coloring agent contains a compound represented by the following general formula (II). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) [R_2, R_3, and R_4 may be the same or different,
Each represents a hydrogen atom, an alkyl group, or an allyl group. ] (4) The heat-sensitive recording material according to claim 1, (2), or (3), further comprising a protective layer on the uppermost layer of the recording surface of the heat-sensitive recording material.