JPH0532047A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a high sensitivity thermal recording material imparting a recording image excellent in storage stability, especially excellent in chemical resistance and reduced in the background fog of its blank part. CONSTITUTION:In a thermal recording material utilizing the color forming reaction of a colorless or light-colored basic dye and a developer, at least one kind of an oxazoline derivative is added to at least one of the intermediate layer provided between a support and a recording layer, the recording layer and the protective layer provided on the recording layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material which is excellent in storage stability of recorded images, has less background fog and is excellent in color development.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a color or color reaction between a colorless or pale basic dye and an organic or inorganic coloring agent is used to bring a recording image by contacting both coloring substances with heat. Has been. Such thermal recording materials are used in various fields and forms in association with the remarkable progress of thermal recording systems, and are used not only as recording media for thermal facsimiles and thermal printers but also as POS (Point of Sales) labels. The use for new applications is also rapidly increasing.

However, such a heat-sensitive recording material generally has insufficient storage stability of a recorded image and has a drawback of fading over time. In particular, if it is exposed to high humidity or high temperature conditions, or if it comes into contact with plasticizers, cosmetics, or chemicals such as alcohol contained in the vinyl chloride film, the recorded image will disappear in a relatively short time. Therefore, the improvement is strongly requested.

Therefore, for the purpose of improving the storage stability of a recorded image, a thermal recording material to which various storability improving agents are added has been proposed, but no sufficient effect can be obtained or the thermal recording material is improved. Therefore, satisfactory results have not always been obtained because new defects such as a decrease in whiteness are accompanied.

[0005]

In view of the above situation, the inventors of the present invention have conducted various studies on techniques for improving the preservation of recorded images, and as a result, when an oxazoline derivative is used as a preservation improving agent, the recorded images are improved. It was found that a heat-sensitive recording material having excellent storage stability, particularly chemical resistance, less background fog, and excellent color development can be obtained, and the present invention has been completed.

[0006]

The present invention provides a thermosensitive recording medium utilizing a color reaction between a colorless or light-colored basic dye and a color developing agent, an intermediate layer provided between a support and a recording layer, A thermosensitive recording medium characterized in that at least one of an oxazoline derivative is contained in at least one of a recording layer or a protective layer provided on the recording layer.

[0007]

In the present invention, an oxazoline derivative is used as a preservative improving agent, and among these derivatives, a derivative represented by the following general formula [Chemical formula 1] or [Chemical formula 2] is preferably used.

[0008]

[Chemical 1]

[Wherein, X is a C ₁ -C ₂₀ alkyl group, C
₇ aralkyl group ~C _9, C ₁ ~C ₂₀ alkoxy group, aralkyloxy group C ₇ -C _9, phenoxy alkoxyl group C ₇ -C _12, phenyl group, a phenoxy group,
Indicates a halogen atom or a hydroxyl group. Also, p
Represents 0 or an integer of 1 to 5. ]

[0010]

[Chemical 2]

[Wherein R is a C ₁ -C ₅ alkyl group, C
₁ -C ₅ alkoxyl group or a phenylene group which may be substituted by a halogen atom; C ₁ -C ₅ alkyl group, C ₁ -C ₅ alkoxyl group or a naphthylene group which may be substituted by a halogen atom; C ₁ -C alkyl group _5, C ₁ ~C ₅ alkoxyl group or a xylylene group optionally substituted with a halogen atom; or an [Formula 3].

[0012]

[Chemical 3]

Here, Y is a direct bond, -O-, -S-,
--SO _2- , or C optionally having an ether bond
_{1 to} C _{12 is} an alkylene group, R ₁ and R ₂ are each a C _{1 to} C ₅ alkyl group, a C _{1 to} C ₅ alkoxyl group, or a halogen atom, and m and n are 0 or 1 respectively. Indicates an integer of 4. ]

Specific examples of the oxazoline derivative that can be used in the present invention include the following. 2-phenyloxazoline, 2-p-tolyloxazoline, 2-
(P-tert-butylphenyl) oxazoline, 2- (p
-N-octylphenyl) oxazoline, 2- (pn)
-Dodecylphenyl) oxazoline, 2- (pn-octadecylphenyl) oxazoline, 2- (p-α, α
-Dimethylbenzylphenyl) oxazoline, 2- (p
-Methoxyphenyl) oxazoline, 2- (m-methoxyphenyl) oxazoline, 2- (o-methoxyphenyl) oxazoline, 2- (p-ethoxyphenyl) oxazoline, 2- (p-isopropoxyphenyl) oxazoline, 2- ( p-tert-butoxyphenyl) oxazoline, 2- (pn-dodecyloxyphenyl) oxazoline, 2- (p-benzyloxyphenyl) oxazoline, 2- (p-phenethyloxyphenyl) oxazoline, 2- (p-phenoxy) Ethoxyphenyl) oxazoline, 2- (p-phenoxyphenyl) oxazoline, 2- (o-phenoxyphenyl) oxazoline, 2
-(P-biphenyl) oxazoline, 2- (o-biphenyl) oxazoline, 2- (p-chlorophenyl) oxazoline, 2- (p-bromophenyl) oxazoline,
2- (p-hydroxyphenyl) oxazoline, 2-
(O-hydroxyphenyl) oxazoline, 2- (m-
Hydroxyphenyl) oxazoline, 2- (5-chloro-2-hydroxyphenyl) oxazoline, 2- (3,
5-dichloro-2-hydroxyphenyl) oxazoline, 2- (3,5-dibromo-2-hydroxyphenyl) oxazoline, 2- (2-naphthyl) oxazoline, 2- (1-naphthyl) oxazoline, 2- (3- Hydroxy-2-naphthyl) oxazoline, 2- (2-hydroxy-1-naphthyl) oxazoline, 1,4-bis (4,5-dihydro-oxazol-2-yl) benzene, 1,2-bis (4,5) -Dihydro-oxazole-
2-yl) benzene, 1,3-bis (4,5-dihydro-oxazol-2-yl) benzene, 1,4-bis (4,5-dihydro-oxazol-2-yl) -2-
Methylbenzene, 1,4-bis (4,5-dihydro-oxazol-2-yl) -2-methoxybenzene, 1,
4-bis (4,5-dihydro-oxazol-2-yl) -2-chlorobenzene, 1,4-bis (4,5-dihydro-oxazol-2-yl) naphthalene, 2,6
-Bis (4,5-dihydro-oxazol-2-yl)
Naphthalene, 1,4-bis [(4,5-dihydro-oxazol-2-yl) methyl] benzene, 1,3-bis [(4,5-dihydro-oxazol-2-yl) methyl] benzene, 4, 4'-bis (4,5-dihydro-oxazol-2-yl) biphenyl, bis [4- (4,4
5-dihydro-oxazol-2-yl) phenyl]-
Ether, bis [4- (4,5-dihydro-oxazol-2-yl) phenyl] -thioether, bis [4-
(4,5-Dihydro-oxazol-2-yl) phenyl] sulfone, bis [4- (4,5-dihydro-oxazol-2-yl) phenyl] methane, 1,2-bis [4- (4,5) -Dihydro-oxazol-2-yl)
Phenyl] ethane, 2,2-bis [4- (4,5-dihydro-oxazol-2-yl) phenyl] propane,
1,2-bis [4- (4,5-dihydro-oxazol-2-yl) phenoxy] ethane, 1,3-bis [4-
(4,5-dihydro-oxazol-2-yl) phenoxy] propane, 1,6-bis [4- (4,5-dihydro-oxazol-2-yl) phenoxy] hexane,
1,8-bis [4- (4,5-dihydro-oxazol-2-yl) phenoxy] octane, 1,12-bis [4- (4,5-dihydro-oxazol-2-yl)
Phenoxy] dodecane, 1,5-bis [4- (4,5-
Dihydro-oxazol-2-yl) phenoxy] -3
-Oxa-pentane, bis [4- (4,5-dihydro-
Oxazol-2-yl) -3,5-dichlorophenyl] methane, bis [4- (4,5-dihydro-oxazol-2-yl) -3,5-di-tert-butylphenyl] methane and the like. Of course, the present invention is not limited to these, and two or more kinds can be used in combination as required.

In the present invention, these oxazoline derivatives exert their effects even when added to any of the intermediate layer provided between the support and the recording layer, the recording layer, and the protective layer provided on the recording layer. However, especially when added to the recording layer, a particularly remarkable preservation improving effect is exhibited, which is preferable. The amount of the derivative used is not necessarily limited, but is generally about 5 to 500 parts by weight, preferably 10 to 100 parts by weight of the basic dye.
It is desirable to adjust the amount within the range of about 200 parts by weight.

In the present invention, various known basic dyes can be used as the colorless or light-colored basic dye constituting the recording layer. However, the dye having a lactone ring in the molecule exerts a particularly remarkable effect, and thus is more preferable. It is preferably used. Specific examples of such dyes include the following. Three
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-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-ethylcarbazole-3-) Yl) -6-dimethylaminophthalide,
3,3-bis (2-phenylindol-3-yl)-
6-Dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6
-Triarylmethane dyes such as dimethylaminophthalide, 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]-
Divinylphthalide dyes such as 4,5,6,7-tetrachlorophthalide, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane Three
-Diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N
-Ethyl-p-toluidino) -7-methylfluorane,
3-Dimethylamino-7- (N-acetyl-N-methylamino) fluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-
(N-methyl-N-benzylamino) fluorane, 3-
Diethylamino-7- (N-chloroethyl-N-methylamino) fluorane, 3-diethylamino-7-diethylaminofluorane, 4-benzylamino-8-diethylamino-benzo [a] fluorane, 3- [4- (4-
Dimethylaminoanilino) anilino] -7-chloro-6
-Methylfluorane, 3- [4- (4-phenylanilino) 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) fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3
-Di-n-butylamino-6-methyl-7-phenylaminofluorane, 3-di-n-pentylamino-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) fluorane, 3-di-n-butylamino-7
-(O-chlorophenylamino) fluorane, 3- (N
-Ethyl-N-tetrahydrofurfuryl) amino-6-
Methyl-7-phenylaminofluorane, 3- (N-methyl-Nn-propylamino) -6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylamino Fluoran, 3- (N
-Methyl-N-n-propyl) amino-6-methyl-7
-Phenylaminofluorane, 3- (N-ethyl-N-
Isobutylamino) -6-methyl-7-phenylaminofluorane, 3- (N-methyl-Nn-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-di-n-butylamino-7- (o
-Fluorophenylamino) fluorane, 3-diethylamino-6-chloro-7-phenylaminofluorane,
3- (N-ethyl-N-isoamylamino) -7- (o
-Chlorophenylamino) fluorane, 3- (N-ethyl-Nn-hexylamino) -7- (o-chlorophenylamino) fluorane and other fluorane dyes, 3,6
-Bis (dimethylamino) fluorene-9-spiro-
3 '-(6'-Dimethylamino) phthalide, 3-diethylamino-6- (N-allyl-N-methylamino) fluorene-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'-6H-
Chromene (4,3-b) indole], 3,6-bis (diethylamino) -3′-methyl-spiro [fluorene-9,6′-6H-chromeno (4,3-b) indole] and other fluorene-based compounds Dyes, etc. Of course, the dyes are not limited to these dyes, and two or more dyes may be used in combination as required.

Various known compounds can be used as the color former used in the present invention, and specific examples thereof include the following. 4-tert-butylphenol, α-naphthol, β-naphthol, 4-acetylphenol, 4-te
rt-octylphenol, 4,4'-sec-butylidene diphenol, 4-phenylphenol, 4,4'-dihydroxy-diphenylmethane, 4,4'-isopropylidenediphenol, hydroquinone, 4,4'-cyclohexylidenediphenol 4.4 '-(1,3-dimethylbutylidene) bisphenol, 2,2-bis (4
-Hydroxyphenyl) -4-methyl-pentane, 4,
4'-dihydroxydiphenyl sulfide, 4,4'-
Dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-methoxyphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy -3 ',
4'-trimethylene diphenyl sulfone, 4-hydroxy-3 ', 4'-tetramethylene diphenyl sulfone,
3,4-dihydroxy-4'-methyldiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 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, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-
Hydroxybenzoic acid-sec-butyl, 4-hydroxybenzoic acid pentyl, 4-hydroxybenzoic acid phenyl, 4
-Benzyl hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, 4
-Phenylpropyl hydroxybenzoate, phenethyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p-
Chlorobenzyl, 4-hydroxybenzoic acid-p-methoxybenzyl, bis (4-hydroxyphenyl) acetic acid-2
-Phenoxyethyl ester, p-hydroxy-N-
(2-phenoxyethyl) benzenesulfonamide, 4
-Dimethyl hydroxyphthalate, 1,5-bis (4-hydroxyphenylthio) -3-oxa-pentane, 1,
7-bis (4-hydroxyphenylthio) -3,5-dioxa-heptane, 1,8-bis (4-hydroxyphenylthio) -3,6-dioxa-octane, (4-hydroxyphenylthio) acetic acid-2 -(4-hydroxyphenylthio) ethyl ester, novolac type phenol resin,
Phenolic compounds such as phenolic polymers, benzoic acid,
p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-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-
Benzyl salicylic 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 -Methylbenzyl salicylic acid, 4- (2-p-methoxyphenoxyethoxy)
Aromatic carboxylic acids such as salicylic acid, 4- (3-p-tolylsulfonylpropyloxy) salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and phenolic compounds and aromatic carboxylic acids thereof. And organic acidic substances such as salts with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel, and metal complex compounds such as antipyrine complex of zinc thiocyanate. Two or more of these colorants can be used in combination, if necessary.

The ratio of the basic dye to the coloring agent used is not particularly limited, but in general, the basic dye 100 is used.
100 to 700 parts by weight, preferably 15 parts by weight
About 0 to 400 parts by weight of a coloring agent is used. In the heat-sensitive recording material of the present invention, a recording sensitivity improving agent can be added to the recording layer for the purpose of obtaining high speed recording suitability. Examples of the recording sensitivity improving agent 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-methylstearic acid amide, stearic acid anilide, N-methyloleic acid amide, Benzanilide,
Linoleic acid anilide, N-ethylcapric acid amide, N
-Butyllauric acid amide, N-octadecylacetamide, N-oleinacetamide, N-oleylbenzamide, N-stearylcyclohexylamide, polyethylene glycol, 1-benzyloxynaphthalene, 2
-Benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, 1,2-diphenoxyethane,
1,4-diphenoxybutane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4-methoxyphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1- Phenoxy-2- (4-methoxyphenoxy) ethane, 1- (2-methylphenoxy) -2- (4-methoxyphenoxy) ethane, terephthalic acid dibenzyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methyl) Benzyl) ester, p-
Benzyloxybenzoic acid benzyl ester, p-benzylbiphenyl, 1,5-bis (p-methoxyphenoxy) -3-oxa-pentane, 1,4-bis (2-vinyloxyethoxy) benzene, p-biphenyl-p- Trilyl ether, benzyl-p-methylthiophenyl ether, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxy-4-benzyloxybenzophenone and the like. The amount of the recording sensitivity improver to be used is not particularly limited, but it is generally adjusted in the range of 50 to 1000 parts by weight, preferably 100 to 500 parts by weight with respect to 100 parts by weight of the basic dye. desirable.

The coating liquid containing these is generally a dispersion medium of water, and a basic dye, a coloring agent, a basic dye, a coloring agent, by a stirrer / pulverizer such as a ball mill, an attritor, or a vertical or horizontal sand mill.
It is prepared by dispersing oxazoline derivatives or the like together or separately. In such coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxyethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, etc. are usually used as a binder.
Styrene / maleic anhydride copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, etc. are added in an amount of about 2 to 40% by weight, preferably about 5 to 25% by weight, based on the total solid content. .

Furthermore, various auxiliaries can be added to the coating liquid, for example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts, Other examples include defoaming agents, fluorescent dyes, and coloring dyes. Further, in order to improve the adhesion of dust to the recording head, it is possible to add an inorganic pigment such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, and activated clay. It is also possible to add a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax or the like so that sticking does not occur due to contact with the recording head.

The method for forming the heat-sensitive recording layer is not particularly limited, and the heat-sensitive recording layer can be formed in accordance with well-known and commonly used techniques. For example, a coating solution for the heat-sensitive recording layer can be formed by an air knife coater, a blade coater or a bar coater. ,
It is formed by a method such as coating on a support using an appropriate coating device such as a gravure coater or a curtain coater.
Also, the coating amount is not particularly limited,
Generally, the dry weight is about 1 to 12 g / m ² , preferably 2
It is adjusted within the range of about 10 g / m ² . As the support, paper, plastic film, synthetic paper or the like is appropriately selected and used.

In the present invention, a protective layer may be provided on the thermosensitive recording layer for the purpose of protecting the recording layer, or an intermediate layer may be provided between the support and the recording layer. Various publicly known techniques in the field of manufacturing a thermosensitive recording medium, such as providing a protective layer on the backside of the body and applying an adhesive process to the backside of the recording medium, can be appropriately added.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, parts and% are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 Preparation of liquid A 10 parts of 3-di-n-butylamino-6-methyl-7-phenylaminofluorane, 25 parts of 1,2-bis (3-methylphenoxy) ethane, 5% of methylcellulose A composition consisting of 5 parts of an aqueous solution and 50 parts of water was pulverized with a horizontal sand mill until the average particle size became 1.0 μm. Solution B Preparation 4,4'-isopropylidenediphenol 20 parts, a 5% aqueous solution of methyl cellulose 5 parts, and a composition comprising 55 parts of water, average particle size 1.5m in a horizontal sand mill
It was crushed until it became.

Liquid C Preparation A composition consisting of 10 parts of 2- (p-methoxyphenyl) oxazoline, 5 parts of a 5% aqueous solution of methyl cellulose, and 35 parts of water was used to obtain an average particle size of 1.5 μm in a horizontal sand mill.
It was crushed until it became. Formation of thermosensitive recording layer 90 parts of liquid A, 80 parts of liquid B, 20 parts of liquid C, 7 parts of silicon oxide pigment (oil absorption: 180 ml / 100 g), 8 parts of light calcium carbonate (oil absorption: 90 ml / 100 g), 20% A coating solution was obtained by mixing and stirring 50 parts of an aqueous polyvinyl alcohol solution, 15 parts of a 30% zinc stearate aqueous dispersion, and 10 parts of water.
The coating amount of obtained dried coating liquid on a base paper of 45 g / m ² was obtained a heat-sensitive recording paper by coating and drying so that 3 g / m ^2.

Examples 2 to 7 Six kinds of heat-sensitive recording were carried out in the same manner as in Example 1 except that the following compounds were used in place of 2- (p-methoxyphenyl) oxazoline in the preparation of the liquid C of Example 1. Got the paper. Example 2: 2- (p-chlorophenyl) oxazoline Example 3: 2- (p-benzyloxyphenyl) oxazoline Example 4: 2- (p-biphenyl) oxazoline Example 5: 1,4-bis (4,4) 5-dihydro-oxazol-2-yl) benzene Example 6: Bis [4- (4,5-dihydro-oxazol-2-yl) phenyl] methane Example 7: 1,3-bis [4- (4,4 5-dihydro-oxazol-2-yl) phenoxy] propane

Examples 8 to 9 Two kinds of heat-sensitive recordings were carried out in the same manner as in Example 1 except that the following compounds were used in place of 4,4'-isopropylidenediphenol in the preparation of the liquid B of Example 1. Got the paper. Example 8: 2,4'-Dihydroxydiphenylsulfone Example 9: 4-Hydroxy-4'-isopropoxydiphenylsulfone

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the liquid C was not used in forming the thermosensitive recording layer.

Comparative Example 2 In the preparation of the liquid C of Example 1, 4,4'-thiobis (3 was used instead of 2- (p-methoxyphenyl) oxazoline.
-Methyl-6-tert-butylphenol) was used to obtain a thermosensitive recording paper in the same manner as in Example 1.

The 11 kinds of heat-sensitive recording papers thus obtained were recorded by a heat-sensitive facsimile (Hitachi HIFAX-400 type), and the density of the recorded image and the blank area was measured by a Macbeth densitometer (RD).
-100R type, using amber filter),
The results are shown in Table 1. Further, after recording, the thermosensitive recording paper is left under conditions of 40 ° C. and 70% RH for 24 hours (weather resistance test), or after being overlaid with a vinyl chloride film containing a plasticizer on the coloring surface and left at room temperature for 24 hours ( (Plasticizer resistance test), and the densities of the recorded image and the blank area were measured again with a Macbeth densitometer, and the results are shown in Table 1.

[0031]

[Table 1]

[0032]

As is clear from the results shown in Table 1, the thermosensitive recording medium of the present invention is excellent in storage stability of recorded images, particularly in chemical resistance, and has excellent high-sensitivity thermosensitive recording with little background fog in the blank area. It was a body.

Claims (3)

[Claims] 1. A thermosensitive recording medium utilizing a color reaction between a colorless or light-colored basic dye and a color developing agent, wherein an intermediate layer, a recording layer or a recording layer provided between a support and a recording layer. A thermosensitive recording medium, characterized in that at least one of the protective layers provided contains at least one oxazoline derivative. 2. An oxazoline derivative is represented by the following general formula:
Alternatively, the thermosensitive recording medium according to claim 1, which is a compound represented by [Chemical Formula 2]. [Chemical 1] [In the formula, X is a C _{1 to} C ₂₀ alkyl group, a C _{7 to} C ₉ aralkyl group, a C _{1 to} C ₂₀ alkoxyl group, and a C _{7 to} C ₉
Aralkyloxy group, C _{7 to} C ₁₂ phenoxyalkoxyl group, phenyl group, phenoxy group, halogen atom,
Alternatively, it represents a hydroxyl group. In addition, p is 0 or 1 to 5
Indicates an integer. ] [Chemical 2] [In the formula, R is a C _{1 to} C ₅ alkyl group, a C _{1 to} C ₅ alkoxyl group, or a phenylene group optionally substituted with a halogen atom; a C _{1 to} C ₅ alkyl group, C _{1 to} C ₅
Alkoxyl group or naphthylene group optionally substituted with a halogen atom; C ₁ -C ₅ alkyl group, C _1-
A C ₅ alkoxyl group or a xylylene group optionally substituted with a halogen atom; or [Chemical Formula 3] is shown. [Chemical 3] Here, Y is a direct bond, -O -, - S -, - SO 2 -,
Or, it represents a C ₁ -C ₁₂ alkylene group which may have an ether bond, and R ₁ and R ₂ are each a C ₁ -C ₅ alkyl group, a C ₁ -C ₅ alkoxyl group, or a halogen atom. , M and n each represent 0 or an integer of 1 to 4. ] 3. The thermosensitive recording medium according to claim 1, wherein the oxazoline derivative is contained in the recording layer.