JP2895591B2 - Thermal recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermosensitive recording medium, and more particularly to a thermosensitive recording medium having excellent storage stability of a recorded image.

`` Prior art '' A heat-sensitive recording material using a colorless reaction of a colorless or light-colored basic dye and an organic or inorganic colorant, and contacting both color-forming substances by heat to obtain a recorded image is good. Are known. Such a thermosensitive recording medium is relatively inexpensive, and the recording apparatus is compact and easy to maintain, so that it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

For example, POS (p.
oint of sales) With the expansion of systemization, the cases used as labels are increasing.

However, when a POS system is introduced in a supermarket or the like, the label often comes into contact with water, wraps, oil, and the like, and as a result, there has been a problem that the recorded image (printing) of the heat-sensitive label fades. Therefore, it is required that the heat-sensitive recording medium has storage properties such as water resistance, plasticizer resistance, and oil resistance.

Conventionally, in order to improve the preservability of a recorded image, a method of applying an aqueous emulsion of a resin having a film forming ability and chemical resistance on a heat-sensitive recording layer (JP-A-54-128347), polyvinyl alcohol, etc. (Japanese Utility Model Application Laid-Open No. 56-125354) has been proposed. Further, a method of adding various storability improvers to the heat-sensitive recording layer has also been proposed, but all of them have new disadvantages such as a decrease in recording density with the improvement and a decrease in whiteness of the heat-sensitive recording layer. At present, it is not always possible to obtain satisfactory effects.

In particular, satisfactory results have not been obtained for the water-resistant plasticizer, which requires water resistance and plasticizer resistance at the same time.

"Problems to be Solved by the Invention" The present invention solves the above-mentioned problems, and preserves recorded images,
In particular, to provide a heat-sensitive recording material that has improved plasticizer resistance, oil resistance, water resistance, and water-resistant plasticizer resistance and does not cause background fog and decrease in whiteness even when exposed to a high-temperature environment. With the goal.

[Means for Solving the Problems] The present invention relates to a thermosensitive recording medium utilizing a reaction between a colorless or pale-colored basic dye and a colorant capable of forming a color upon contact with the dye, and comprises a compound represented by the following general formula (I) ) Containing at least one selected from diphenol sulfone compounds represented by
The thermosensitive recording medium further comprises a novolak type epoxy resin.

[Wherein R ₁ , R ₂ , R ₃ and R ₄ represent a hydrogen atom, an alkyl group or an allyl group. In the present invention, the novolak epoxy resin is preferably at least one selected from phenol novolak epoxy resin, halogen-substituted phenol novolak epoxy resin, and ortho-cresol novolak epoxy resin.

Further, in the present invention, it is preferable that the novolak epoxy resin is at least one selected from novolak epoxy resins represented by the following general formulas (II) and (III).

Wherein X represents a halogen atom, and a represents an integer of 0 to 4. N represents an integer of 0 to 20. ] [M represents an integer of 0 to 20. The present invention also discloses a thermosensitive recording medium having a protective layer on the uppermost layer on the recording surface side.

"Action" The diphenol sulfone-based compound represented by the general formula (I) is a color former and is usually contained in the heat-sensitive recording layer. The following are examples of the compound represented by the general formula (I).

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-tert-butylphenyl-3'-isopropyl-4'-hydroxyphenylsulfone, 2-hydroxy-5-tert-butylphenyl-2 '-Methyl-4'-hydroxyphenylsulfone and the like. In general formula (I), when it has an alkyl group, it preferably has about 1 to 10 carbon atoms. Of these, 2,4'-dihydroxydiphenylsulfone is particularly preferred in terms of color development and background fog. Other colorants can be used in the heat-sensitive recording layer as long as the effects of the present invention are not impaired.

Examples of the novolak type epoxy resin used in the present invention include the compounds represented by the general formulas (II) and (III) and mixtures thereof.

The resin represented by the general formula (II) is a phenol novolak type epoxy resin, a brominated phenol novolak type epoxy resin, or the like, and is a reaction product of phenol and formaldehyde, or a reaction product of phenol, formaldehyde and bromine. And those obtained by reacting brominated phenol novolak with epichlorohydrin. In the general formula (II), n is preferably in the range of 2 to 7 or a mixture thereof, and a softening point is preferably 60 to 140 ° C, more preferably about 60 to 100 ° C. Can be In the general formula (II), a is an integer of 0 to 4, preferably 0 to 3.

The compound represented by the general formula (III) is an ortho-cresol novolak-type epoxy resin, which is obtained by reacting ortho-cresol novolac, which is a reaction product of ortho-cresol and formaldehyde, with epichlorohydrin. In the general formula (III), m is preferably in the range of 2 to 7 or a mixture thereof, and a solid novolak type epoxy resin having a softening point of about 60 to 140 ° C. is preferable.

If the softening point is too low, the whiteness of the recording medium may decrease, and if it is too high, the storage stability improving effect may decrease.

The novolak-type epoxy resin can be contained in the protective layer or the like, but is usually contained in the heat-sensitive recording layer from the viewpoint of device characteristics and the like. According to the present invention, a heat-sensitive recording medium having improved recording preservability such as plasticizer resistance and oil resistance and free from background fog can be obtained.

The amount of these novolak type epoxy resins is not particularly limited, but is preferably 0.1 to 500 parts by weight based on 100 parts by weight of the coloring agent.
It is used in an amount of about 1 part by weight, preferably 1 to 200 parts by weight.

Examples of the basic dye used in the present invention include various colorless or light-colored basic dyes. For example, 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-bis (2-phenylindole-3-
Triallylmethane-based dyes such as yl) -6-dimethylaminophthalide and 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide; 4,4'- Diphenylmethane dyes such as bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, thiazines such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue Dyes, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) spiropyran, 3-propyl-spiro-
Spiro dyes such as dibenzopyran, rhodamine-B anilino lactam, lactam dyes such as rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino -6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3
-Diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluoran, 3- (N-
Ethyl-p-toluidino) -7-methylfluoran, 3
-Diethylamino-7-N-acetyl-N-methylaminofluoran, 3-diethylamino-7-N-methylaminofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-N-methyl -N-benzylaminofluoran, 3-diethylamino-7-N-chloroethyl-N-methylaminofluoran, 3-diethylamino-7-N-diethylaminofluoran, 3- (N-ethyl-p-toluidino) -6 -Methyl-7-phenylaminofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-methyl-
7-phenylaminofluoran, 3-diethylamino-
7- (2-carbomethoxy-phenylamino) fluoran, 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-phenylaminofluoran, 3-pyrrolidino-6-methyl-7-phenylaminofluoran,
3-piperidino-6-methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7- (o-chlorophenylamino) fluoran, 3-dibutylamino-
7- (o-chlorophenylamino) fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3-diethylamino-7- (o-fluorophenylamino) fluoran, 3-dibutylamino-7
-(O-fluorophenylamino) fluoran, 3-dibutylamino-6-methyl-7-phenylaminofluoran, 3- (N-methyl-NNn-amyl) amino-6
-Methyl-7-phenylaminofluoran, 3- (N-
Ethyl-N-n-amyl) amino-6-methyl-7-phenylaminofluoran, 3- (N-ethyl-N-iso
-Amyl) amino-6-methyl-7-phenylaminofluoran, 3- (N-methyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluoran, 3-
(N-ethyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluoran, 3- (N-ethyl-
Fluorane dyes such as (N-β-ethylhexyl) amino-6-methyl-7-phenylaminofluoran. In addition, these basic dyes can be used in combination of two or more as necessary.

The use ratio of the basic dye and the colorant represented by the general formula (I) is appropriately selected depending on the type of the basic dye and the colorant used, and is not particularly limited. Generally, 0.1 to 50 parts by weight, preferably about 1 to 10 parts by weight, of a coloring agent is used per 1 part by weight of the basic dye.

A coating solution for a heat-sensitive recording layer containing these substances is generally prepared by using water as a dispersion medium and dispersing the mixture with a stirring / pulverizer such as a ball mill or a sand mill.

In the heat-sensitive recording layer, binders are usually contained, and examples of the binders include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and 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 / butadiene copolymer emulsion, urea resin, melamine resin, amide resin, and the like. 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.
About 30% by weight is blended.

Furthermore, various auxiliaries can be added to the coating liquid as needed, such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, sodium salt, fatty acid metal salt, etc. Agents, ultraviolet absorbers such as benzophenones, other antifoaming agents, fluorescent dyes, coloring dyes, and the like are appropriately added.

Also, if necessary, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, waxes such as ester wax,
It is also possible to add inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, diatomaceous earth, fine anhydrous silica, activated clay, etc., and it is also possible to use a sensitizer in combination according to the purpose. it can.

Specific examples of sensitizers include, for example, stearic acid amide,
Methylene bisamide stearate, amide oleate,
Fatty acid amides such as palmitic acid amide and coconut fatty acid amide; 2,2'-methylenebis (4-methyl-6-tert-
Butylphenol), 4,4'-butylidenebis (6-ter
t-butyl-3-methylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol),
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-tert-butyl-3-hydroxy-
Hindered phenols such as 2,6-dimethylbenzyl) isocyanuric acid, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxy-4
Ultraviolet absorbers such as benzyloxybenzophenone, 1,
2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, parabenzylbiphenyl, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether, 1 -Hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid-di-p-
Methylbenzyl, di-p-chlorobenzyl oxalate,
Examples include dimethyl terephthalate, dibutyl terephthalate, dibenzyl terephthalate, dibutyl isophthalate, phenyl 1-hydroxynaphthoate, and various known heat-fusible substances.

Among them, 1,2-di (3-methylphenoxy) ethane, 1,2
-Diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane are particularly preferred.

The use amount of the sensitizer is not particularly limited, but it is generally desirable to adjust the sensitizer within a range of about 4 parts by weight or less based on 1 part by weight of the color former.

The method for forming the recording layer is not particularly limited. For example, the coating solution for the heat-sensitive recording layer is applied to the support by an appropriate application method such as air knife coating, barber blade coating, rod blade coating, pure blade coating, or short dwell coating. It is formed by a method such as drying. The coating amount of the coating liquid is not particularly limited, 2~12g / m ² at normal dry weight, preferably 3 to 10 g / m ²
It is adjusted within a range.

In the thermosensitive recording medium of the present invention, by providing a protective layer on the thermosensitive recording layer, the storability of the recorded print can be further improved.

The protective layer contains a water-soluble or water-dispersible polymer. Examples of such a polymer include various binders as described above. Among them, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are particularly preferable because they exhibit excellent effects. It is 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, borax, boric acid, zirconium ammonium carbonate,
A curing agent such as an epoxy compound can be used in combination.

In the protective layer, a pigment can be added as needed in order to further improve printability and sticking. Specific examples thereof include casium carbonate, zinc oxide,
Inorganic pigments such as aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder,
Organic pigments such as polyethylene powder, urea / formalin resin filler, raw starch particles, and the like. In general, it is desirable to adjust the amount of the pigment to be used in the range of about 5 to 500 parts by weight based on 100 parts by weight of the binder.

Further, a surfactant such as a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, or ester wax, or a surfactant such as sodium dioctyl sulfosuccinate may be contained in the coating liquid for forming the protective layer, if necessary. Various auxiliaries such as a lubricant) and an antifoaming agent can be added as appropriate.

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

The protective layer coating solution thus prepared is applied onto the heat-sensitive recording layer by an appropriate coating device.However, if the coating amount is too large, the recording sensitivity of the heat-sensitive recording medium may be reduced. / m ² , preferably in the range of 0.5 to 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storage stability. Furthermore, various known techniques in the field of heat-sensitive recording material production can be added as necessary, such as providing an undercoat layer on the support, applying a pressure-sensitive adhesive treatment to the back surface of the recording material, and processing it into a pressure-sensitive adhesive label.

As the support, paper, plastic film, synthetic paper and the like are used, but paper is preferably used in terms of price, applicability and the like.

"Examples" Hereinafter, the present invention will be described more specifically with reference to examples, but is not limited thereto. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 Preparation of Solution A 3-Dibutylamino-6-methyl-7-phenylaminofluoran 10 parts Methylcellulose 5% aqueous solution 5 parts Water 40 parts This composition was pulverized with a sand mill until the average particle diameter became 0.8 μm.

Preparation of Solution B Bis- (4-hydroxyphenyl) sulfone 30 parts Methylcellulose 5% aqueous solution 5 parts Water 80 parts This composition was pulverized with a sand mill until the average particle diameter became 1.2 μm.

Preparation of Solution C 1,2-di (3-methylphenoxy) ethane 20 parts Methylcellulose 5% aqueous solution 5 parts Water 55 parts This composition was pulverized by a sand mill until the average particle diameter became 1.2 μm.

Preparation of Solution D Orthocresol novolak type epoxy resin (manufactured by Asahi Kasei Corporation, trade name: ECN-299, softening point 97 ° C, compound represented by the general formula (III), m is a mixture of 2 to 7) 20 parts methylcellulose 5% aqueous solution 5 parts Water 55 parts This composition was pulverized with a sand mill until the average particle size became 2.1 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, 80 parts of a 10% aqueous solution of polyvinyl alcohol, and 35 parts of calcium carbonate were mixed and stirred to obtain a coating liquid of 50 g / m2. ^The heat-sensitive recording material was obtained by applying and drying the base paper of No. ² so that the coating amount after drying was 6 g / m ² .

Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 2,4'-dihydroxydiphenylsulfone was used instead of bis- (4-hydroxyphenyl) sulfone in the preparation of solution B.

Example 3 In preparing solution B, bis- (3-allyl-4-) was used instead of bis- (4-hydroxyphenyl) sulfone.
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that (hydroxyphenyl) sulfone was used.

Example 4 In the preparation of solution B, heat was applied in the same manner as in Example 1 except that 2-hydroxy-5-isopropylphenyl-4'-hydroxyphenylsulfone was used instead of bis- (4-hydroxyphenyl) sulfone. A recording was obtained.

Example 5 In the preparation of solution D, an ortho-cresol novolak type epoxy resin (trade name: ECN-285, trade name: ECN-285, softening point 86) was used instead of an ortho-cresol novolak type epoxy resin (trade name: ECN-299). ° C, general formula (III)
And m was a mixture of 2 to 7), except that a thermosensitive recording medium was obtained in the same manner as in Example 2.

Example 6 In the preparation of solution D, an ortho-cresol novolak-type epoxy resin (trade name: EX-695, manufactured by Nagase Kasei Kogyo Co., Ltd., softening point) was used instead of an ortho-cresol novolak-type epoxy resin (trade name: ECN-299). 93 ℃, general formula (I
A heat-sensitive recording material was obtained in the same manner as in Example 2 except that the compound represented by II) and m was a mixture of 2 to 7).

Example 7 In the preparation of solution D, phenol novolak type epoxy resin (manufactured by Dow Chemical Company, trade name: XD-7855, softening point 73) was used instead of orthocresol novolak type epoxy resin (manufactured by Asahi Kasei Kogyo Co., Ltd., trade name: ECN-299). A thermosensitive recording medium was obtained in the same manner as in Example 2 except that the compound represented by the general formula (II), a = 0, and n was a mixture of 2 to 7) was used.

Example 8 In the preparation of solution D, a brominated phenol novolak-type epoxy resin (softening point 90 ° C., represented by the general formula (II)) was used instead of the ortho-cresol novolak-type epoxy resin (trade name: ECN-299, manufactured by Asahi Kasei Kogyo). Compound, a = 1, n is 2
-7) was obtained in the same manner as in Example 2 except that the mixture of Comparative Examples 1 to 7 was used.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that the solution D was not added in forming the recording layer of Example 1.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 2, except that the solution D was not added in forming the recording layer of Example 2.

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 4,4'-isopropylidenediphenol was used instead of bis- (4-hydroxyphenyl) sulfone in the preparation of solution B.

Comparative Example 4 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 4-hydroxy-4'-isopropoxydiphenylsulfone was used instead of bis- (4-hydroxyphenyl) sulfone in the preparation of solution B. Was.

The following evaluation tests were performed on the 12 types of thermal recording media thus obtained, and the results are shown in Table 1.

(Whiteness)

 The whiteness of the recording layer was measured with a Hunter whiteness meter.

[Surface fog]

After treating the heat-sensitive recording material at 50 ° C. for 15 hours, the whiteness of the recording layer was measured with a Hunter whiteness meter.

(Coloring density)

Thermal printer (Texas Instruments, PC
The color density of a recorded image obtained by printing with a -100A type was measured with a Macbeth densitometer (RD-100R type, manufactured by Macbeth).

(Plasticizer resistance)

A vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemicals, Inc.) is wound three times on a polypropylene pipe (40 mmφ tube), and a thermosensitive recording material having a printed color is sandwiched thereon so that the printed color surface is outside, Further, a vinyl chloride wrap film was wound three times from above, and the plasticizer resistance was evaluated from the print density after being left at 30 ° C. for 24 hours.

Example 9 Formation of recording layer A thermosensitive recording medium was obtained in the same manner as in Example 1.

Formation of protective layer Acetacetylated polyvinyl alcohol 10% aqueous solution 80
Part, partially saponified polyvinyl alcohol (trade name; PVA-217,
20 parts of 10% aqueous solution, 20 parts of calcium carbonate, 50 parts of water
The parts were mixed and stirred, and the coating liquid was applied and dried on the recording layer of the above-mentioned thermosensitive recording medium so that the coating amount after drying was 6 g / m ² , to obtain a thermosensitive recording medium having a protective layer.

Example 10 Formation of recording layer A thermosensitive recording medium was obtained in the same manner as in Example 2.

Formation of Protective Layer A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 9 except that the above-described thermosensitive recording medium was used.

Example 11 Formation of Recording Layer A thermosensitive recording medium was obtained in the same manner as in Example 6.

Formation of Protective Layer A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 9 except that the above-described thermosensitive recording medium was used.

Example 12 Formation of recording layer A thermosensitive recording medium was obtained in the same manner as in Example 7.

Formation of Protective Layer A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 9 except that the above-described thermosensitive recording medium was used.

Example 13 Formation of Undercoat Layer 100 parts of calcined clay (trade name; manufactured by Ansilex, Engelhard Co.), 20 parts of magnesium carbonate, ethylene / butadiene copolymer latex (trade name: Dow-1571, manufactured by Asahi Kasei Corporation, 48%) Aqueous dispersion) 15 parts, polyvinyl alcohol 12
A 25% aqueous solution and 200 parts of water were mixed and stirred,
The coating was dried on a base paper of 0 g / m ² so that the coating amount after drying was 6 g / m ² , to obtain a support for a thermosensitive recording medium.

Formation of Recording Layer A heat-sensitive recording medium was obtained in the same manner as in Example 2, except that the above-mentioned support for a heat-sensitive recording medium was used.

Formation of Protective Layer A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 9 except that the above-described thermosensitive recording medium was used.

Comparative Example 5 Formation of Recording Layer A thermosensitive recording medium was obtained in the same manner as in Comparative Example 1.

Formation of Protective Layer A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 9 except that the above-described thermosensitive recording medium was used.

Comparative Example 6 Formation of Recording Layer A thermosensitive recording medium was obtained in the same manner as in Comparative Example 2.

Formation of Protective Layer A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 9 except that the above-described thermosensitive recording medium was used.

Comparative Example 7 Formation of Recording Layer A thermosensitive recording medium was obtained in the same manner as in Comparative Example 3.

Formation of Protective Layer A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 9 except that the above-described thermosensitive recording medium was used.

Comparative Example 8 Formation of Recording Layer A thermosensitive recording medium was obtained in the same manner as in Comparative Example 4.

Formation of Protective Layer A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 9 except that the above-described thermosensitive recording medium was used.

The nine types of heat-sensitive recording materials thus obtained were subjected to the same evaluation test as described above except that the plasticizer resistance and the water-resistant plasticizer resistance were evaluated by the following methods, and the results are shown in Table 2.

(Plasticizer resistance)

A vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemicals, Inc.) is wound three times on a polypropylene pipe (40 mmφ tube), and a thermosensitive recording material having a printed color is sandwiched thereon so that the printed color surface is outside, Furthermore, a vinyl chloride wrap film was wound three times from above, and the plasticizer resistance was evaluated based on the print density after leaving at 40 ° C. for 24 hours.

(Water resistant plasticizer)

After the printed heat-sensitive recording medium was lightly wetted with water, it was evaluated in the same manner as the above-mentioned plasticizer resistance to obtain a water-resistant plasticizer resistance.

"Effects" As is clear from the results of Tables 1 and 2, the heat-sensitive recording materials of the present invention were all excellent in storage stability after recording, and were excellent heat-sensitive recording materials without background fog. .

Continuation of front page (56) References JP-A-2-17883 (JP, A) JP-A-60-219088 (JP, A) JP-A-3-26590 (JP, A) JP-A-2-289378 (JP) , A) (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (4)

(57) [Claims] 1. A heat-sensitive recording material utilizing a reaction between a colorless or light-colored basic dye and a colorant capable of forming a color upon contact with said dye, comprising a diphenol sulfone represented by the following general formula (I): Containing at least one selected from the series compounds,
A thermosensitive recording medium comprising a novolak type epoxy resin. [Wherein R ₁ , R ₂ , R ₃ and R ₄ represent a hydrogen atom, an alkyl group or an allyl group. ] 2. The thermosensitive recording medium according to claim 1, wherein the novolak type epoxy resin is at least one selected from a phenol novolak type epoxy resin, a halogen-substituted phenol novolak type epoxy resin, and an orthocresol novolak type epoxy resin. 3. The thermosensitive recording medium according to claim 1, wherein the novolak type epoxy resin is at least one selected from novolak type epoxy resins represented by the following general formulas (II) and (III). Wherein X represents a halogen atom, and a represents an integer of 0 to 4. N represents an integer of 0 to 20. ] [M represents an integer of 0 to 20. ] 4. The thermosensitive recording medium according to claim 1, wherein the thermosensitive recording medium has a protective layer on the uppermost layer on the recording surface side.