JPH04103386A - Heat-sensitive recording body - Google Patents

Abstract

PURPOSE:To improve the shelf stability, particularly plasticizer resistance, oil resistance, water resistance, and water-resistant plasticizer resistance, and also prevent whiteness due to generation of base blushing from decreasing even when being exposed under a high temperature environment by containing one type which is selected among specific diphenol sulfonic compounds, and also containing a novolak type epoxy resin. CONSTITUTION:A diphenol sulfonic compound shown by the formula is a chromogenic agent, and it is normally contained in a heat-sensitive recording layer. As a compound shown by the formula, bis-(4-hydroxyphenyl) sulfone, etc. can be given. When an alkyl group is contained in the formula, it is desirable that the carbon number is approximately l-10. While being at the middle of these, 2,4'-dihydroxy-diphenyl sulfone is especially desirable because of the coloring characteristics and base blushing. Although a novolak type epoxy resin can be contained in a protective layer, etc., it is normally contained in a heat-sensitive recording layer because of equipment characteristics, etc. In the formula, R1, R2, R3, R4 show hydrogen atom, alkyl group or aryl group.

Description

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

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

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

For example, one of the fields of use is POS at retail stores, etc.
(Point of 5ales) With the expansion of systemization, the number of cases in which they are used as labels is increasing.

However, when a POS system is introduced in a supermarket or the like, the labels often come into contact with water, plastic wrap, oil, etc., and as a result, there is a problem in that the recorded image (print) on the heat-sensitive label fades.

Therefore, heat-sensitive recording materials are required to have storage properties such as water resistance, plasticizer resistance, and oil resistance.

Conventionally, in order to improve the storage stability of recorded images, methods such as coating an aqueous emulsion of a resin having film-forming ability and chemical resistance on the heat-sensitive recording layer (Japanese Patent Application Laid-open No. 128347/1982), polyvinyl alcohol, etc. A method of coating a water-soluble polymer compound (Utility Model Application Publication No. 56-125354) has been proposed. In addition, methods of adding various preservability improvers to the heat-sensitive recording layer have been proposed, but all of these methods have new drawbacks such as a decrease in recording density and a decrease in the whiteness of the heat-sensitive recording layer. The current situation is that the results are not always satisfactory.

In particular, satisfactory results have not been obtained regarding water and plasticizer resistance, which requires both water resistance and plasticizer resistance.

"Problems to be Solved by the Invention" The present invention solves the above problems, improves the storage stability of recorded images, especially plasticizer resistance, oil resistance, water resistance, and water plasticizer resistance, and also improves the storage properties of recorded images in high temperature environments. To provide a heat-sensitive recording material which does not cause background fogging and does not reduce its whiteness even when exposed to sunlight.

"Means for Solving the Problems" The present invention provides a heat-sensitive recording material using the reaction between a colorless or light-colored basic dye and a coloring agent capable of forming a color when it comes into contact with the dye. ) The heat-sensitive recording material is characterized in that it contains at least one diphenolsulfone compound represented by the following formula, and also contains a novolac type epoxy resin.

[In the formula, R1, Rz, R3, and Ra 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 novolac epoxy resins, halogen-substituted phenol novolac epoxy resins, and orthocresol novolac epoxy resins.

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

[In the formula, X represents a halogen atom, and a represents an integer of O to 4. Moreover, n represents an integer of 0 to 20. ] [m represents an integer of θ to 20. ] The present invention also discloses a heat-sensitive recording material having a protective layer on the uppermost layer on the side of the recording surface.

"Function" The diphenolsulfone compound represented by general 2N) above is a coloring agent and is usually contained in the heat-sensitive recording layer.

Examples of the compound represented by the general formula (1) include the following.

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-butylphenyl-3'-methyl-4'-hydroxyphenylsulfone, 2-hydroxy-5-t-butylphenyl-
Examples include 3'-isopropyl-4'-hydroxyphenylsulfone, 2-hydroxy-5-t-butylphenyl-2'-methyl-4'-hydroxyphenylsulfone, and the like.

When the general formula (1) has an alkyl group, it preferably has about 1 to 10 carbon atoms. Furthermore, among these, 2,4
-Dihydroxydiphenylsulfone is particularly preferred in terms of color development and background fog.

Other coloring agents may also be used in the heat-sensitive recording layer as long as they do not impede the effects of the present invention.

Examples of the novolac type epoxy resin used in the present invention include compounds represented by the above general formula (II) and general formula (III), and mixtures thereof.

-1t=The resin represented by the formula (II) is a phenol novolac type epoxy resin, a brominated phenol novolac type epoxy resin, etc., and is a phenol novolak which is a reaction product of phenol and formaldehyde, or a reaction product of phenol, formaldehyde and bromine. These are those obtained by reacting the product brominated phenol novolac with epichlorohydrin. and the general formula (I
In I), preferably n=2 to 7 or a mixture thereof, and the softening point is preferably 60 to 140°C
More preferably, a solid novolac type epoxy resin having a temperature of about 60 to 100°C is used. Moreover, in general formula (II), a is an integer of 0 to 4, preferably 0 to 3.

The compound represented by general formula (II) is an orthocresol novolak type epoxy resin, which is obtained by reacting orthocresol novolak, which is a reaction product of orthocresol and formaldehyde, with epichlorohydrin. In general formula (III), m is preferably in the range of 2 to 7 or a mixture thereof, and has a softening point of 60 to 140.
A solid novolac type epoxy resin having a temperature of about 10°C is preferred.

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

Although it is possible to include the novolac type epoxy resin in the protective layer, etc., it is usually included in the heat-sensitive recording layer from the viewpoint of device characteristics and the like. According to the present invention, a heat-sensitive recording material can be obtained which has improved recording storage properties such as plasticizer resistance and oil resistance, and which does not cause background fog.

The amount of these novolac type epoxy resins used is not particularly limited, but is 0.1 to 0.1 to 100 parts by weight of the coloring agent.
About 500 parts by weight, preferably 1 to 200 parts by weight, is used.

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-(
12-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-phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylvirol-3-yl)- Triallylmethane dyes such as 6-dimethylaminophthalide, 4,4'bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenylleucoauramine, etc. diphenylmethane dyes, thiazine dyes such as benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, 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 anilinolactam, rhodamine (
Lactam dyes such as P-nitroanilino)lactam and rhodamine(0-chloroanilino)lactam, 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-)luidino)
-7-methylfluorane, 3-diethylamine-7-N
-Acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-? -N-methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-
7-N-diethylaminofluorane 1.3-(N-ethyl-p-)luidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-)luidino)-
6-Methyl-7-(p-)luidino)fluoran, 3-
Diethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluorane, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7 -phenylaminofluorane, 3-pyrrolidino-6-methyl-7
-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-
7-P-butylphenylaminofluoran, 3-diethylamino-7-(0-fluorophenylamino)fluoran, 3-dibutylamino-7-(0-fluorophenylamino)fluoran, 3-dibutylamino-6-methyl- 7-phenylaminofluorane, 3-(N-methyl-Nn-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-Nn-amyl)amino-6- Methyl-7-phenylaminofluorane, 3-(N-ethyl-N-iso-amyl)amino-6
-Methyl-7-phenylaminofluorane, 3-(N-
Methyl-Nn-hexyl)amino-6-methyl-7-
Phenylaminofluorane, 3-(N-ethyl-N-n
-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluorane, and other fluoran dyes. . In addition, two or more types of these basic dyes can be used in combination as necessary.

The usage ratio of the basic dye and the coloring agent represented by the general formula CI) is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited.
Generally, 0.1 to 50 parts by weight, preferably 1 to 10 parts by weight, of room coloring agents are used per 1 part by weight of basic dye.

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

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

Furthermore, various auxiliaries can be added to the coating liquid as necessary, such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, etc. Dispersants, UV absorbers such as benzophenone,
Other antifoaming agents, fluorescent dyes, coloring dyes, etc. may be added as appropriate.

In addition, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, It is also possible to add inorganic pigments such as activated clay, and a sensitizer can also be used in combination depending on the purpose.

Specific examples of the sensitizer include stearic acid amide, stearic acid methylene bisamide, oleic acid amide, valmitic acid amide, fatty acid amide such as coconut fatty acid amide, 2,2'-methylenebis(4-methyl-5-ter
t-butylphenol), 4,4'-butylidene bis(
6-tert-butyl-3-methylphenol), 2.
2'-methylenebis(4-ethyl-5-tert-butylphenol), 2,4-di-tert-butyl-
3-methylphenol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)
Butane, 11.3-tris(5-cyclohexyl-4-
Hydroxy-2-methylphenyl)butane, 1.35-
Tris(4-tert-butyl-3-hydroxy-2,
Hindered phenols such as 6-dimethylbenzyl)isocyanuric acid, 2-(2'-hydroxy-5'-methylphenyl)pendutriazole, 2-hydroxy-4
- Ultraviolet absorber 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, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, dimethyl terephthalate, dibutyl terephthalate, dibenzyl terephthalate Examples include ester, dibutyl isophthalate, phenyl 1-hydroxynaphthoate, and various known thermofusible substances.

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

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

The method for forming the recording layer is not particularly limited; for example, the heat-sensitive recording layer coating liquid may be applied to the support by an appropriate coating method such as air knife coating, varibur blade coating, rod blade coating, pure blade coating, sheet-dwell coating, etc. It is formed by methods such as drying. The amount of coating liquid applied is not particularly limited either, and is usually 2 to 12 g/rr in terms of dry weight. , preferably 3~
It is adjusted within a range of about 10g/bo.

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

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

In 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, A curing agent such as boric acid, ammonium zirconium carbonate, or an epoxy compound can also be used in combination.

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

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

Furthermore, in the coating solution forming the protective layer, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, and surfactants such as sodium dioctyl sulfosuccinate (dispersed Various auxiliary agents such as a lubricant) and an antifoaming agent can also be added as appropriate.

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

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

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

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

``Example J'' The present invention will be described in more detail with reference to Examples below, but the present invention is of course not limited to these.

In addition, "parts" and "%" in the examples indicate "parts by weight" and "wt% J, respectively, unless otherwise specified.

Example 1 ■ Preparation of liquid A 3-dibutylamino-6-methyl-7-phenylaminofluoran methylcellulose 5% aqueous solution water 4
This composition was ground with a sand mill until the average particle diameter was 0°.

■ Preparation of Solution B Bis-(4-hydroxyphenyl)sulfone 30 parts Methylcellulose 5% aqueous solution 5 parts Water
80 parts of this composition was ground in a sand mill until the average particle diameter was 2 μm, 0 parts, 5 parts, and 8 μm.

■ C-wave preparation 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 1.2 μm.

■ Preparation of Solution D Orthocresol novolac type epoxy resin (manufactured by Asahi Kasei Kogyo, trade name: ECN-299, softening point: 97°C, compound represented by general formula (1), m is a mixture of 2 to 7) 20 parts Methyl cellulose 5% aqueous solution 5 parts water
55 parts of this composition was ground in a sand mill until the average particle size was 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,
A coating solution obtained by mixing and stirring 80 parts of 10% polyvinyl alcohol water tS solution and 35 parts of calcium carbonate is applied onto a 50 g/board base paper so that the coating amount after drying is 6 g/rrr, and then dried to produce thermal recording. I got a body.

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

Example 3 A thermosensitive recording material was prepared in the same manner as in Example 1, except that bis-(3-allyl-4-hydroxyphenyl) sulfone was used instead of bis-(4-hydroxyphenyl) sulfone in BWL preparation. Obtained.

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

Example 5 Orthocresol novolak type epoxy resin (manufactured by Asahi Kasei Industries, trade name: ECN-299) manufactured by DIll
Orthocresol novolak type epoxy resin (
Manufactured by Asahi Kasei Industries, product name: ECN-285, softening point 86°
A thermosensitive recording material was obtained in the same manner as in Example 2 except that a compound represented by the C2 general formula (1) (m is a mixture of 2 to 7) was used.

Example 6 In the preparation of liquid B, orthocresol novolac type epoxy resin (manufactured by Asahi Kasei Kogyo, trade name 2ECN-299) was replaced with orthocresol novolac type epoxy resin
Manufactured by Nagase Chemical Industries, product name: EX-695, softening point 93
°C2 Compound 2m of general formula (III) is 2-7
A thermosensitive recording material was obtained in the same manner as in Example 2, except that a mixture of the following was used.

Example 7 Orthocresol novola type epoxy resin manufactured by Dial (manufactured by Asahi Kasei Industries, trade name 2ECN-299)
Instead, use phenol novolac type epoxy resin (manufactured by Dow Chemical Company, product name: xD-7855, softening point 73°C)
, a compound represented by the general formula (If), a=0. n is 2~
A heat-sensitive recording material was obtained in the same manner as in Example 2 except that a mixture of Example 7) was used.

Example 8 In the preparation of liquid B, a brominated phenol novolak type epoxy resin (softening point: 90° C1 represented by the general formula (■) compound, a
=1. A thermosensitive recording material was obtained in the same manner as in Example 2, except that n was a mixture of 2 to 7).

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 liquid D was not added in the formation of the recording layer in Example 2.

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

Comparative Example 4 In preparing liquid B, bis-(4-hydroxyphenyl)
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 4-hydroxy-4''-isopropoxydiphenyl sulfone was used instead of sulfone.

The following evaluation tests were conducted on the 12 types of heat-sensitive recording bodies thus obtained, and the results are listed in Table 1.

(whiteness) The whiteness of the recording layer was measured using a Hunter whiteness meter.

[Skin fog]

After the heat-sensitive recording material was treated at 50° C. for 15 hours, the whiteness of the recording layer 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.) was measured using a Macbeth densitometer (Macbeth Co., Ltd.).

RD-100R model).

[Plasticizer resistance]

Wrap vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemicals) three times around a polypropylene vibe (40mφ pipe).
A heat-sensitive recording material with colored print is placed on top of it so that the colored side of the print is facing out, and then a vinyl chloride wrap film is wrapped three times over it, and the print density after being left at 30°C for 24 hours is determined by the plasticity resistance. The drug properties were evaluated.

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

■ Formation of protective layer 10% aqueous solution of acetoacetylated polyvinyl alcohol 8
0 parts, partially saponified polyvinyl alcohol (trade name, PVA
-217, manufactured by Kuraray) 20 parts of a 10% aqueous solution, 20 parts of calcium carbonate, and 50 parts of water were mixed and stirred, and the coating liquid was applied onto the recording layer of the heat-sensitive recording material so that the coating amount of dry tU1t was 6 g/%. The mixture was coated and dried to obtain a heat-sensitive recording material having an iJ retention layer.

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

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

Example 11 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 6.

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

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

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

Example 13 ■ Formation of undercoat layer 100 parts of baked clay (trade name: Ansilex, manufactured by Engelhard), 20 parts of magnesium carbonate, ethylene.
Butadiene copolymer latex (product name: Dow-15
71, manufactured by Asahi Kasei Co., Ltd., 15 parts of 48% aqueous dispersion), 25 parts of 12% polyvinyl alcohol aqueous solution, and 200 parts of water were mixed and stirred, and the resulting coating liquid was applied to 50 g/board of base paper with a dry coating amount of 6. 'g/nT and dried to obtain a support for a heat-sensitive recording material.

■ Formation of recording layer Example 2 except that the above support for heat-sensitive recording material was used.
A thermosensitive recording material was obtained in the same manner as above.

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

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

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

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

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

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

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

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

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

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

[Plasticizer resistance]

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

C Water Resistance to Plasticizers] After the heat-sensitive recording material with colored prints was lightly wetted with water, it was evaluated in the same manner as the plasticizer resistance described above to determine its water resistance to plasticizers.

It was an excellent heat-sensitive recording material with a second appearance and no background fog.

Claims (4)

[Claims] (1) A diphenolsulfone compound represented by the following general formula (I) in a thermosensitive recording material that utilizes the reaction between a colorless or light-colored basic dye and a coloring agent that can change color when it comes into contact with the dye. 1. A heat-sensitive recording material comprising at least one selected from the following, and a novolac type epoxy resin. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [In the formula, R_1, R_2, R_3, and R_4 represent a hydrogen atom, an alkyl group, or an allyl group. ] (2) Claim (1) wherein the novolac type epoxy resin is at least one selected from phenol novolac type epoxy resin, halogen-substituted phenol novolac type epoxy resin, and orthocresol novolac type epoxy resin.
The heat-sensitive recording medium described above. (3) The heat-sensitive recording material according to claim (1), wherein the novolac type epoxy resin is at least one type selected from novolac type epoxy resins represented by the following general formula (II) and general formula (III). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (II) [In the formula, X represents a halogen atom, and a represents an integer from 0 to 4. Moreover, n represents an integer of 0 to 20. ] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (III) [m represents an integer from 0 to 20. ] (4) The heat-sensitive recording material according to claim (1), (2) or (3), wherein the heat-sensitive recording material has a protective layer on the uppermost layer on the side of the recording surface.