JPH04214384A - Thermal recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a heat-sensitive recording medium, which has excellent storage stability of recorded images, high initial whiteness, and less whiteness deterioration due to aging (background fog). .

0002

[Prior Art] A thermosensitive recording material that utilizes a color reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent, and obtains a recorded image by reacting both coloring substances with heat, is well known. Are known. Such thermosensitive recording materials are relatively inexpensive;
Furthermore, since the recording device is compact and easy to maintain, it is used not only as a recording medium for facsimiles and various computers, but also in a wide range of fields.

[0003] For example, as one of its fields of use, with the expansion of POS (point of sales) systems in retail stores, the number of cases in which it is used as labels is increasing. However, POS at supermarkets etc.
When a system is introduced, labels often come into contact with water, plastic wrap, oil, etc., and as a result, defects such as fading of the recorded image (print) on the heat-sensitive label are observed. Therefore, thermal recording materials are required to have preservability such as water resistance, plasticizer resistance, and oil resistance.

Conventionally, in order to improve the storage stability of recorded images,
A method of coating an aqueous emulsion of a chemically resistant resin with film-forming ability on a heat-sensitive recording layer (Japanese Patent Laid-Open No. 55-1
28347), a method of applying a water-soluble polymer compound such as polyvinyl alcohol (Japanese Utility Model Publication No. 56-12535)
Publication No. 4) etc. have been proposed. Also, methods have been proposed in which various storage improvers are added to the heat-sensitive recording layer.
In either case, new drawbacks accompany improvements, and at present, satisfactory effects are not necessarily obtained.

[0005] In view of the actual situation, the applicant has previously published Japanese Patent Application Laid-Open Nos. 2-194994, 2-215589, 220885 and 2-227.
In Japanese Patent No. 282, etc., excellent preservability is achieved by containing a compound having a specific epoxy group in the recording layer, a protective layer provided on the recording layer, or an intermediate layer between the support and the recording layer. A method for obtaining a heat-sensitive recording material having the following characteristics was proposed.

However, especially when a compound having an epoxy group is contained in the recording layer, there is no change for a while after the recording layer is formed, but the basic colorless dye, which is a coloring agent, and the epoxy compound gradually react, and the epoxy compound changes over time. It has become clear that fog (background fog) occurs in the blank areas of the recording layer, resulting in a decrease in whiteness, and there is an urgent need to solve this phenomenon.

[0007]

[Problems to be Solved by the Invention] The present invention provides an excellent heat-sensitive recording material in which the storage stability of recorded images, particularly the plasticity resistance, is significantly improved, and not only the initial whiteness but also the background fog over time is extremely low. There is a particular thing.

[0008]

[Means for Solving the Problems] The present invention provides, on a support,
In a heat-sensitive recording material provided with a recording layer that utilizes a coloring reaction between a colorless or light-colored basic dye and a coloring agent that can react with the dye to develop a color, the recording layer contains particles with an average particle diameter of 0. .5μm
The heat-sensitive recording material described above is characterized in that it contains one or more compounds having a water-insoluble epoxy group of less than 3.0 μm.

[0009]

[Function] By the way, as mentioned above, in the present invention, a compound having an epoxy group is contained in the recording layer as a preservability improving agent, but the compound is gradually mixed with the basic dye used together in the recording layer. It has the disadvantage that it reacts to the skin and causes background fogging over time.

[0010] In order to eliminate such drawbacks, the inventors of the present invention have made intensive studies and found that the particle size of the compound containing an epoxy group contained in the recording layer improves the whiteness, especially the above-mentioned background fog over time. It was found that this had a significant impact. That is, if the average particle size is less than 0.5 μm, it is extremely difficult to prevent not only initial whiteness but also background fogging over time, and a particle size of 1.0 μm or more is preferable. They also discovered that when the average particle size is 3.0 μm or more, the shelf life improvement effect is not sufficient, but when the average particle size is 2.5 μm or less, and even 2.0 μm or less, the shelf life improvement effect is significantly improved. It is something. In other words, the average particle diameter is within a specific range, 0.5μm or more, 3.0μm or more.
When the thickness is less than m, preferably from 1.0 μm to 2.5 μm, more preferably from 1.0 μm to 2.0 μm, the desired effects of the present invention are fully exhibited. In addition, the average particle diameter in the present invention is determined by Coulter Multisizer (CO
(manufactured by LTER COUNTER).

The compound having an epoxy group used in the present invention is not particularly limited, but includes, for example, a novolak type epoxy resin, a glycidyl ether or glycidyl ester compound having a benzene ring as its core, a bisphenol A type epoxy resin, or Diphenylsulfone derivatives having an epoxy group are preferred. Incidentally, specific examples of the above-mentioned compound having an epoxy group include 1,4-
Di(1,2-epoxyethyl)benzene, 1,4-diglycidylbenzene, 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-dibromobenzene, 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, 1,4-diglycidyl-3-ethoxyphthalate, 1,4-di(2-glycidyloxyethyl)phthalate, glycidyloxybenzene, monoglycidyl phthalate, monoglycidyl terephthalate, 1-phenoxy-1,4-glycidyl Oxy-3,6,9,12-
Tetraoxatetradecane, phenol novolac type epoxy resin, orthocresol novolac type epoxy resin, bisphenol A type epoxy resin obtained by condensing bisphenol A and epichlorohydrin or tetrabromobisphenol A and epichlorohydrin, 4-
(1,2-epoxyethyl)diphenylsulfone, 4-
Glycidyl diphenyl sulfone, 4-(3,4-epoxybutyl) diphenyl sulfone, 4-(2,3-epoxybutyl) diphenyl sulfone, 4-(1,2-epoxyethyloxy) diphenyl sulfone, 4-glycidyloxydiphenyl sulfone , 4-(3,4-epoxybutyloxy)diphenylsulfone, 4-(2,3-epoxybutyloxy)diphenylsulfone, 4-glycidyloxy-4'-chlorodiphenylsulfone, 4-glycidyloxy-4'-bromo Diphenylsulfone, 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-glycidyl Oxy-2',
4'-dimethoxydiphenylsulfone, 4,4'-diglycidyloxydiphenylsulfone, 4,4'-diglycidyloxy-3,3'-dichlorodiphenylsulfone, 4,4'-diglycidyloxy-2,2'- Dibromodiphenyl sulfone, 4,4'-diglycidyloxy-
3,3',5,5'-tetrabromodiphenylsulfone, 4,4'-bis(2-glycidyloxyethoxy)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-glycidyloxy) ethoxy)-3,3',5,5'-tetramethyldiphenylsulfone, 4,4'-bis(3,4-epoxybutyloxy)diphenylsulfone, 4-[(2,3-
Epoxy-2methyl)propyloxy]phenyl-4'
-(benzyloxy)phenylsulfone, 4-[(2
,3epoxy)propyloxy]phenyl-4'-(4
-methylbenzyloxy)phenylsulfone, 4-[
(2,3-epoxy-2ethyl)propyloxy]phenyl-4'-(benzyloxy)phenylsulfone,
4-[(2,3epoxy)propyloxy]phenyl-
4'-(4-ethylbenzyloxy)phenylsulfone, 4-[(2,3epoxy)propyloxy]phenyl-4'-benzyloxyphenylsulfone, 4-[
(2,3epoxy)propyloxy]phenyl-4'-
Methoxyphenylsulfone, 4-[(2,3epoxy-2-methyl)propyloxy]phenyl-4'-ethoxyphenylsulfone, 4-[(2,3epoxy-2-methyl)
-methyl)propyloxy]phenyl-3'-methoxyphenylsulfone, 4-[(2,3epoxy)propyloxy]phenyl-4'-hydroxyphenylsulfone, 4-[(2,3epoxy-2-methyl)propyl Oxy]phenyl-3'-hydroxyphenylsulfone, 4-[(2,3epoxy-2-methyl)propyloxy]phenyl-3'-phenethyloxyphenylsulfone, 4-[(2,3epoxy-2-propyl) Propyloxy]phenyl-4'-(benzyloxy)phenylsulfone, 4-[(2,3epoxy-2-methyl)propyloxy]phenyl-3'-(benzyloxy)phenylsulfone, 4-[(2,3 epoxy)propyloxy]phenyl-4'-(m-methylbenzyloxy)phenylsulfone, 3-[(2,3epoxy)
Examples include propyloxy]phenyl-3'-(p-methylbenzyloxy)phenylsulfone. Among them, 1,4-di(glycidyloxy)benzene, 1,4-
Diglycidyl phthalate is particularly preferred in terms of plasticizer resistance and whiteness.

The amount of these epoxy group-containing compounds used is not particularly limited, but is 0.1 to 500 parts by weight, preferably 1 to 200 parts by weight, based on 100 parts by weight of the coloring agent.
Approximately parts by weight are used. Further, in the present invention, various known coloring agents can be used in combination, and examples thereof include the following. Inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2 ,2'-
Dihydroxydiphenol, 4,4'-isopropylidene bis(2-tert-butylphenol), 4,4'
-sec -butylidenediphenol, 4-phenylphenol, 4-acetylphenol, 4-tert-octylphenol, 4-phenylphenol, 4,4'
-dihydroxydiphenylmethane, 4,4'-isopropylidene diphenol (bisphenol A), hydroquinone, 4,4'-cyclohexylidene diphenol,
4,4'-[1,4-phenylenebis(1-methylethylidene)]bisphenol, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisphenol, 4,4'-(1, 3-dimethylbutylidene)bisphenol, 2,2-bis(4-hydroxyphenyl)-4
-Methyl-pentane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(6-tert-
butyl-3-methylphenol), 1,3-di[2-(
4-hydroxyphenyl)-2-propyl]benzene,
Hydroquinone monobenzyl ether, bis(4-hydroxyphenyl)acetic acid butyl ester, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone,
2,4,4'-trihydroxybenzophenone, 2,2
',4,4'-tetrahydroxybenzophenone, 4-
Dimethyl hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-sec
-Butyl, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, 4-hydroxybenzoate phenethyl acid,
p-chlorobenzyl 4-hydroxybenzoate, p-methoxybenzyl 4-hydroxybenzoate, bis(4-
hydroxyphenyl)acetic acid-2-phenoxyethyl ester, P-hydroxy-N-(2-phenoxyethyl)
Benzene sulfonamide, dimethyl 4-hydroxyphthalate, 1,5-bis(4-hydroxyphenylthio)-
3-oxa-pentane, 1,7-bis(4-hydroxyphenylthio)-3,5-dioxaheptane, 1,8
-Bis(4-hydroxyphenylthio)-3,6-dioxa-octane, (4-hydroxyphenylthio)acetic acid-2-(4-hydroxyphenylthio)ethyl ester, novolak type phenolic resin, phenol polymer, etc. benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-s
ec -butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3
, 5-di-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid,
3-chloro-5-(α-methylbenzyl)salicylic acid,
3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-di-α-methylbenzylsalicylic acid,
4-(2-P-methoxyphenoxyethoxy)salicylic acid, 4-(3-P-tolylsulfonylpropyloxy)
Organic acidic substances such as aromatic carboxylic acids such as salicylic acid, their phenolic compounds, and salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel. etc.

However, in the present invention, as a coloring agent used in combination with a compound having an epoxy group, the following general formula [Chemical formula 1]
A diphenolsulfone compound represented by is a particularly preferred compound from the viewpoint of storage stability.

[0014]

[Chemical formula 1]

[In the formula, R1, R2, and R3 may be the same or different and represent a hydrogen atom, an alkyl group, or an allyl group. ]

In particular, among the diphenolsulfone compounds represented by the above general formula [Formula 1], particularly preferred examples include bis-(4-hydroxyphenyl)sulfone, bis-(3-allyl-4- hydroxyphenyl) sulfone, 2,4'-dihydroxydiphenyl sulfone, 2-hydroxy-5-t-butylphenyl-
4'-hydroxyphenylsulfone, 2-hydroxy-5-t-amylphenyl-4'-hydroxyphenylsulfone, 2-hydroxy-5-isopropylphenyl-4'-hydroxyphenylsulfone, 2-hydroxy-5-t-butyl Phenyl-3'-methyl-4'-
Hydroxyphenylsulfone, 2-hydroxy-5-
t-Butylphenyl-3'-isopropyl-4'-hydroxyphenylsulfone, 2-hydroxy-5-t-
Examples include butylphenyl-2'-methyl-4-hydroxyphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, and 4-hydroxy-4'-methoxydiphenylsulfone. Of course, the coloring agent is not limited to these coloring agents, and two or more of these coloring agents may be used in combination.

The proportion of the coloring agent to be used is not necessarily limited, but is 100 to 700 parts by weight, more preferably 150 to 4 parts by weight, per 100 parts by weight of the basic dye.
00 parts by weight of coloring agent is blended.

In the heat-sensitive recording medium of the present invention, there are various known colorless to light-colored basic dyes constituting the recording layer, including the following. 3,3
-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(4-dimethylaminophenyl)-3-(4-diethylamino-2- methylphenyl)
-6-dimethylaminophthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole-
3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindole-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-bis(2-phenylindol-3-yl)-
6-dimethylaminophthalide, 3-(p-dimethylaminophenyl)-3-(1-methylpyrrol-3-yl)
-6-dimethylaminophthalide, 3-(p-dibenzylaminophenyl)-3-(1,2-dimethylindol-3-yl)-7-azaphthalide, 3-(4-diethylamino-2-ethoxyphenyl) -3-(1-ethyl-
2-methylindol-3-yl)-7-azaphthalide, 3,3-bis(1-ethyl-2-methylindole-
3-yl)phthalide, N-butyl-3-{bis[4-(
Triarylmethane dyes such as N-methylanilino)phenyl]methyl}carbazole, 4,4'-bis(dimethylamino)benzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2,4,5-tri Chlorophenyl leuko auramine, diphenylmethane dyes such as 4,4'-bis(dimethylamino)benzhydryl-p-toluenesulfinic acid ester, 3,3-bis[1,1-bis(4-pyrrolidinophenyl)ethylene-2 -yl]-4,5,6,7-tetrabromophthalide, 3,3-bis[1-(4-methoxyphenyl)-1-
(4-dimethylaminophenyl)ethylene-2-yl]
-4,5,6,7-tetrachlorophthalide, 3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6 ,7
- Divinylphthalide dyes such as tetrachlorophthalide,
3,7-bis(diethylamino)-10-benzoylphenoxazine, benzoylleucomethylene blue, p
- Thiazine dyes such as nitrobenzoylleucomethylene blue, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-phenylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho(6'- Spiro dyes such as methoxybenzo)spiropyran, 3-propylspirodibenzopyran, di-β-naphthospiropyran, 3-methyl-di-β-naphthospiropyran, rhodamine-B-anilinolactam, rhodamine(p-nitroanilino)lactam , rhodamine (
Lactam dyes such as o-chloroanilino)lactam, 3
-diethylamino-6-methylfluorane, 3-dimethylamino-7-methoxyfluorane, 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-methylamino)fluoran, 3-diethylamino-7-N-methylamino)fluoran, 3
-diethylamino-7-dibenzylaminofluorane,
3-diethylamino-7-(N-methyl-N-benzylamino)fluoran, 3-diethylamino-7-(N-
β-chloroethyl-N-methylamino)fluorane, 3
-diethylamino-7-diethylaminofluorane, 4
-benzylamino-8-diethylaminobenzo[a]fluorane, 3-[4-(4-dimethylaminoanilino)
Anilino]-7-chloro-6-methylfluorane, 8-
[4-(4-dimethylaminoanilino)anilino]benzo[a]fluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3
-(N-ethyl-p-toluidino)-6-methyl-7-
(p-toluidino)fluoran, 3-diethylamino-
6-Methyl-7-phenylaminofluorane, 3-dimethylamino-6-methyl-7-phenylaminofluorane 3-dibutylamino-6-methyl-7-phenylaminofluorane, 3-dipentylamino-6-methyl -7
-phenylaminofluorane, 3-diethylamino-7
-(2-Carbomethoxy-phenylamino)fluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-phenylaminofluorane, 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-(o-chlorophenylamino)
Fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-phenylaminofluoran, 3-(N-methyl- N-propylamino)-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-(N-ethyl-N-isobutylamino)-6- Methyl-7-phenylaminofluorane, 3-(N-methyl-N-n-hexylamino)-
6-Methyl-7-phenylaminofluorane, 3-(N
-ethyl-N-n-hexylamino)-6-methyl-7
-phenylaminofluorane, 3-(N-ethyl-N-
cyclopentylamino)-6-methyl-7-phenylaminofluorane, 3-[N-(3-ethoxypropyl)
-N-methylamino]-6-methyl-7-phenylaminofluorane, 3-[N-ethyl-N-(3-ethoxypropyl)amino]-6-methyl-7-phenylaminofluorane, 3-diethylamino -7-[m-(trifluoromethyl)phenylamino]fluorane, 3-diethylamino-7-(o-fluorophenylamino)fluorane, 3-dibutylamino-7-(o-fluorophenylamino)fluorane, 3-diethylamino -6-chloro-7-phenylaminofluorane, 3-(N-ethyl-N-p-tolylamino)-7-methylfluorane,
3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-(N-
cyclopentyl-N-ethylamino)-6-methyl-7
-anilinofluorane, 3-(N-ethyl-N-p-tolylamino)-6-methyl-7-anilinofluorane,
2,2-bis{4-[6'-(N-cyclohexyl-N
-methylamino)-3'-methylspiro[phthalide-3
,9'-xanthene]-2'-ylamino]fail}
Fluorane dyes such as propane, 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3-diethylamino-6-(
N-allyl-N-methylaminofluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3,6-
Bis(dimethylamino)-spiro[fluorene-9,6
'-6'H-chromeno(4,3-b)indole], 3
,6-bis(dimethylamino)-3'-methyl-spiro[fluorene-9,6'-6'H-chromeno(4,3-
b) Indole], 3,6-bis(diethylamino)-
3'-Methyl-spiro[fluorene-9,6'-6'H
-chromeno(4,3-b)indole] and other fluorene dyes. Of course, the dyes are not limited to these dyes, and it is also possible to use two or more dyes in combination.

Furthermore, various known sensitizers can be used in combination as required, and examples include the following compounds. Caproic acid amide, capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, linolenic acid amide, N
-Methylstearamide, stearanilide,
N-methyl oleic acid amide, benzanilide, linoleic acid anilide, N-ethyl capric acid amide, N-butyl lauric acid amide, N-octadecyl acetamide,
Fatty acid amides such as N-oleacetamide, N-oleylbenzamide, N-stearylcyclohexylamide, polyethylene glycol, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, stearic acid methylene bisamide, coconut fatty acid amide, 2,2'-
Methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(6-tert-
butyl-3-methylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol)
, 2,4-di-tert-butyl-3-methylphenol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3
-Tris(5-cyclohexyl-4-hydroxy-2-
methylphenyl)butane, 1,3,5-tris(4-t
Hindered phenols such as ert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid, sodium-2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, 2-( 2'-
UV absorbers such as hydroxy-5'-methylphenyl)benzotriazole, 2-hydroxy-4-benzyloxybenzophenone, 1,2-di(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 1-phenoxy -2-(4-methylphenoxy)ethane, 1-(2
-methylphenoxy)-2-(4-methoxyphenoxy)ethane, parabenzylbiphenyl, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether, 1-hydroxy-2-naphthoic acid phenyl ester,
1 -Hydroxynaphthoic acid phenyl ester and various known thermofusible substances.

Among them, 1,2-di(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 1-phenoxy-2-(4-methylphenoxy)ethane, oxalic acid dibenzyl ester, oxalic acid di- p-methylbenzyl ester is particularly preferred in terms of sensitizing effect. Further, the amount of the sensitizer to be used is not particularly limited, but it is generally desirable to adjust the amount to about 4 parts by weight or less per 1 part by weight of the coloring agent.

[0021] A method for preparing a coating liquid for a heat-sensitive recording layer containing these substances is generally a method in which water is used as a dispersion medium, various compounds are dissolved with heat and a solvent, and then dispersed in water to form an emulsion. , a wet grinding method using an attritor, a ball mill, a sand grinder, etc. However, as a method for adjusting the particle size of the compound having a specific epoxy group of the present invention to a specific particle size, the above-mentioned wet pulverization method is preferable.

Various dispersants can be used in the dispersion liquid for wet grinding, such as polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, vinyl acetate resin containing sulfonic acid groups, starches, polyacrylic Examples include dispersants such as sodium acid, sodium polysulfonate, sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and metal salts of fatty acids.

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 copolymer salt, ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, styrene/
Examples include butadiene copolymer emulsion, urea resin, melamine resin, amide resin, and the like. The binder is preferably blended in an amount of about 5 to 40% by weight, more preferably about 10 to 30% by weight, based on the total solid content of the recording layer.

Furthermore, various known pigments can be used in the heat-sensitive recording layer as long as they do not impede the desired effects of the present invention, such as magnesium carbonate, calcite-based light calcium carbonate, aragonite-based light calcium carbonate, and heavy pigments. Calcium carbonate, basic calcium carbonate, calcium sulfoaluminate, aluminum hydroxide, alkali-modified silica,
Inorganic pigments such as kaolin, clay, talc, calcined kaolin, titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay, etc., and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea/formalin resin filler, raw starch particles, etc. etc.

It is also possible to add waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, if necessary.

[0026] Furthermore, various auxiliaries can be added to the coating liquid constituting the recording layer as necessary, such as dioctyl sulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt, lauryl alcohol sulfate ester, - Dispersants such as sodium salts and fatty acid metal salts, ultraviolet absorbers such as benzophenone, other antifoaming agents, fluorescent dyes, coloring dyes, etc. are added as appropriate.

The method for forming the recording layer is not particularly limited, and may be any suitable coating method such as air knife coating, variver blade coating, rod blade coating, pure blade coating, short dwell coating, curtain coating, die coating, etc. It is formed by applying a heat-sensitive recording layer coating liquid onto a support and drying it. The amount of the coating liquid to be applied is also not particularly limited, and is usually adjusted within the range of about 2 to 12 g/m2, preferably about 3 to 10 g/m2 in terms of dry weight.

In the heat-sensitive recording material of the present invention, it is possible to further improve the whiteness and the recorded image by providing an intermediate layer between the heat-sensitive recording layer and the support.

Furthermore, in the heat-sensitive recording material of the present invention, by providing a protective layer mainly composed of a polymer compound on the heat-sensitive recording layer, the storage stability of recorded prints can be further improved. Examples of polymer compounds include the various binders used in the recording layer as described above, among which carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol exhibit excellent effects. Therefore, it is particularly preferably used.

In order to further improve water resistance, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, dialdehyde starch, melamine resin, polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde resin, boron A water-soluble curing agent such as sand, boric acid, ammonium zirconium carbonate, or an epoxy compound can also be used in combination.

[0031] Furthermore, various pigments may be appropriately added to the protective layer as necessary in order to further improve printability and sticking. Specific examples include zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide,
Barium sulfate, zinc sulfate, talc, kaolin, clay,
Examples include inorganic pigments such as calcined kaolin, colloidal silica, and magnesium carbonate, and organic pigments such as styrene microspheres, nylon powder, polyethylene powder, urea/formalin resin filler, and raw starch particles. Generally, the amount of each of these pigments used is desirably adjusted within a range of about 5 to 500 parts by weight per 100 parts by weight of the binder.

Furthermore, zinc stearate, calcium stearate,
Lubricants such as polyethylene wax, carnauba wax, paraffin wax, and ester wax, surfactants (dispersants, lubricants) such as dioctyl sodium sulfosuccinate, etc.
, various auxiliary agents such as antifoaming agents can also be added as appropriate.

The above-mentioned coating liquid for the protective layer 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 it is generally applied in a coating amount of 0. About 1 to 20 g/m2, preferably 0.5 to 1
Adjust within the range of 0g/m2. Note that as the support, paper, plastic film, synthetic paper, etc. can be used as appropriate. In addition, if necessary, we can provide a protective layer on the back side of the heat-sensitive recording material to further increase its shelf life, or apply adhesive treatment to the back surface of the recording material to process it into adhesive labels. Various known techniques can be added as necessary.

[0034]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is of course not limited to these. Note that "parts" and "%" in the examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 ■ Preparation of liquid A 3-Dibutylamino-6-methyl-7-phenylaminofluorane 10 parts Methylcellulose 5
% aqueous solution
5 parts water


40 parts of this composition was ground in a sand mill until the average particle size was 1.0 μm.

■ Preparation of B solution 4-hydroxy-4'-isopropoxydiphenylsulfon 30 parts Methyl cellulose
5% aqueous solution
5 parts water


80 parts of this composition was ground in a sand mill until the average particle size was 1.8 μm.

■ Preparation of liquid C 1,2-di(3-methylphenoxy)ethane
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 2 μm.

■ D-liquid preparation orthocresol novolac type epoxy resin
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 1.2 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,
50 g/m2 of a coating liquid obtained by mixing and stirring 80 parts of a 10% polyvinyl alcohol aqueous solution and 35 parts of calcium carbonate.
A heat-sensitive recording material was obtained by coating and drying the mixture on a base paper so that the coating amount after drying was 6 g/m2.

Example 2 In the preparation of Solution D, 1,4-di(glycidyloxy) was used instead of the orthocresol novolac type epoxy resin.
A thermosensitive recording material was obtained in the same manner as in Example 1 except that benzene (manufactured by Nagase Kasei Co., Ltd., trade name: EX-203) was used.

Example 3 In the preparation of liquid B in Example 2, 4-hydroxy-4'-
2, instead of isopropoxydiphenyl sulfone
Using 4'-dihydroxydiphenylsulfone, D
In the liquid preparation, 4-[(2,3-epoxy-2-methyl)propyloxy]phenyl- A thermosensitive recording material was obtained in the same manner as in Example 2, except that 4'-(benzoxy)phenylsulfone was used and the particle size was 0.7 μm.

Example 4 A thermosensitive recording material was obtained in the same manner as in Example 2 except that the particle size was changed to 0.68 μm in the preparation of liquid D.

Example 5 A thermosensitive recording material was obtained in the same manner as in Example 2 except that the particle size was changed to 1.8 μm in the preparation of liquid D.

Example 6 A thermosensitive recording material was obtained in the same manner as in Example 2, except that the particle size was changed to 2.2 μm in the preparation of liquid D.

Example 7 A thermosensitive recording material was obtained in the same manner as in Example 2 except that the particle size was changed to 2.7 μm in the preparation of liquid D.

Example 8 In the preparation of Solution D in Example 2, a bisphenol A type epoxy resin (epoxy equivalent: 650 to 850 ) A thermosensitive recording material was obtained in the same manner as in Example 2 except that the following was used.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that liquid D 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 2 except that the particle size was changed to 3.5 μm in the preparation of liquid D.

Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 2 except that the particle size was changed to 0.35 μm in the preparation of liquid D.

The initial whiteness, whiteness after aging (background fog), color density, and plasticizer resistance of the 11 types of recording media thus obtained were evaluated and summarized in [Table 1].

[Initial Whiteness] Immediately after forming the recording material, the whiteness of the recording layer was measured using a Hunter whiteness meter.

[Whiteness after aging] The white paper portion was left at room temperature for 14 days, and the whiteness thereafter was measured using a Hunter whiteness meter.

[Color density] Thermal printer (manufactured by Texas Instruments, PC
The color density of the recorded image obtained by printing with a Macbeth densitometer (manufactured by Macbeth Co., Ltd., model RD-100R) was measured.

[Plasticizer resistance] A vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemical Co., Ltd.) was wrapped three times around a polypropylene pipe (40 mm φ pipe), and a heat-sensitive recording material with colored print was placed on top of the polypropylene pipe (40 mmφ pipe) so that the printed color-forming side The plasticizer resistance was evaluated from the print density after sandwiching the paper so that it was facing outward, wrapping a vinyl chloride wrap film three times over it, and leaving it for 48 hours at 15°C.

[0055]

[Table 1]

Example 9 (1) Formation of recording layer A heat-sensitive recording layer was formed in the same manner as in Example 1. ■ Formation of protective layer 10% aqueous solution of acetoacetylated polyvinyl alcohol 1
00 parts, 20 parts of kaolin clay, and 50 parts of water were mixed and stirred, and the coating liquid was applied onto the heat-sensitive recording layer so that the coating amount after drying was 4 g/m.
2 and dried to obtain a heat-sensitive recording material having a protective layer.

Examples 10 to 16 The protective layer prepared in Example 9 was coated and dried in the same manner as in Example 9 on each of the recording layers of the recording bodies of Examples 2 to 8 to obtain examples with protective layers. 10 to 16 thermosensitive recording bodies were obtained. Incidentally, Example 10: Using the recording medium of Example 2, Example 11
: Using the recording body of Example 3, Example 12: Using the recording body of Example 4, Example 13: Using the recording body of Example 5, Example 14: Using the recording body of Example 6, Implementation Example 15: The recording body of Example 7 was used. Example 16: The recording body of Example 8 was used.

Comparative Examples 4 to 6 The protective layer prepared in Example 9 was coated and dried on each recording layer of the recording bodies of Comparative Examples 1 to 3 in the same manner as in Example 9, and the protective layer was provided. 4 to 6 thermosensitive recording bodies were obtained. Incidentally,
Comparative Example 4: The recording body of Comparative Example 1 was used. Comparative Example 5: The recording body of Comparative Example 2 was used. Comparative Example 6: The recording body of Comparative Example 3 was used.

The 11 types of heat-sensitive recording bodies thus obtained were evaluated in the same way as for the recording bodies without a protective layer, and the results are listed in Table 2.

[0060]

[Table 2]

[0061]

Effects of the Invention As is clear from the results in [Table 1] and [Table 2], the heat-sensitive recording material of the present invention has excellent storage stability after recording, and has no background fog over time. It was a heat-sensitive recording medium.

Claims (1)

[Scope of Claims] [Claim 1] A recording layer is provided on a support, which utilizes a color reaction between a colorless or light-colored basic dye and a coloring agent capable of forming a color by reacting with the dye. 1. A heat-sensitive recording material, characterized in that the recording layer contains one or more compounds having a water-insoluble epoxy group with an average particle diameter of 0.5 μm or more and less than 3.0 μm. Claim 2: The average particle diameter is 1.0 to 2.5 μm.
The heat-sensitive recording medium according to claim 1. 3. The compound having an epoxy group is at least one selected from a novolak type epoxy resin, a glycidyl ether having a benzene ring as its core, a glycidyl ester compound, a bisphenol A type epoxy resin, and a bisphenol sulfone derivative having an epoxy group. A thermosensitive recording material according to any one of claims 1 and 2.