JPH1058834A - Thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording material which has high coloring sensitivity, high texture whiteness, and is almost free from the blushing of a printed part and is of high recorded image conservation stability, that is, improved resistance against humidity and plasticizer. SOLUTION: In the thermosensitive recording material containing leuco dye and a developer, at least, one type of β-sulfoketone compound expressed by the formula is added as sensitivity improver. In the formula, R1 is a 1-6C lower alkyl group, R2 , R3 and R4 are independently hydrogen atom, an alkyl group, an aryl group, a halogen atom, an alkoxy group or a nitro group; (1) is 1 or 2; and (m) is an integer of 1-3. R4 may be R1 -SO2 -(CH2 -CO)1 -. The leuco dye used as a color former is colorless or pale at normal temperatures and is such a material as develops color through a chemical reaction with a developer under heat. Various dyes such as triaryl methane dye, e.g. 3,3'-bis(p- dimethylaminophenyl)-6-dimethylamino phthalide and diphenyl methane dye, e.g. 4,4'-bisdimethylamino benzhydride benzyl ether are pointed out as the leuco dye. Either of these color formers or a combination of two types or more of these color formers may be used.

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 has excellent coloring sensitivity, high background whiteness, little whitening of a printed area, and storage stability of a recorded image, that is, moisture resistance, The present invention relates to a thermosensitive recording material having improved plasticizer properties.

[0002]

2. Description of the Related Art In recent years, the amount of information has increased along with the diversification of information. In the field of information recording for recording such information, various recording methods and recording materials have been studied and put to practical use. I have. Above all, the thermal recording method is (1) hardware is inexpensive and compact, (2) a recorded image can be obtained by simply heating a thermal recording material, and a complicated developing step is not required; ) Production and storage management of thermal recording materials are easier and less expensive than other recording materials. (4) Inexpensive paper is often used as a support for thermal recording materials. Has the advantage that the obtained recording material feels like that of plain paper, and it has many advantages, such as computer output, printers such as calculators, recorders for various measuring instruments, facsimile machines, automatic ticketing machines, thermal copiers, and labels. Has been adopted in the field.

In particular, recently, heat-sensitive recording materials have been used for labels, cards, receipts, and the like, and high functions different from conventional functions have been demanded. Conventionally, phenol compounds, for example, bisphenol A, bisphenol S derivatives, hydroxybenzoic acid esters, and the like have been widely used as color developers for developing leuco dyes. A thermosensitive recording material using these developers is called PO
When used for labels and receipts in the S system, etc., especially labels used in supermarkets, etc.
Receipts often come in contact with water, wrap films and oils, and have the disadvantage that the recorded image is significantly discolored.

[0004] In order to solve such a problem in the conventional heat-sensitive recording material, Japanese Patent Publication No. Sho 63
JP-A-46067, JP-A-63-176181 and JP-B-3-39474 disclose a method of incorporating a diphenylsulfone derivative having a phenol skeleton as a color developing agent. JP-A-7-96674 discloses a method in which a benzoic acid derivative is contained as a color developer. JP-A-62-82070 and JP-A-2-122977 contain a salicylic acid derivative as a color developer. The method disclosed in
JP-A No. 32061, JP-A-5-147357 and JP-A-5-148220 disclose a method of incorporating a sulfonylaminocarbonylamino derivative as a color developing agent, and JP-A-62-164579 discloses a phenol. JP-A-59-73990 and JP-A-61-160 further employ a method in which an epoxy compound is used in combination with a system developer.
No. 292 and JP-A-4-37589 propose to stabilize the storage by incorporating a sulfonic acid ester derivative as a sensitivity improver.

[0005] However, although the storage stability is improved by any of the methods, it is not satisfactory in terms of the color sensitivity, the storage stability of the background, the storage stability of the printed area, the whitening of the printed area, and the like. We cannot say that we pull out enough. In particular, heat-sensitive recording materials having high storage stability often have the disadvantage of relatively low sensitivity because somewhat special coloring materials and additives have to be used. As an attempt to improve this, JP-A-5-169836 discloses that a sulfonylaminocarbonylamino derivative is contained as a color developer and a compound such as p-toluenesulfonic acid phenyl ester is contained as a sensitivity improver. There has been proposed a method for improving color sensitivity. However, with this technique, storage stability and sensitivity are remarkably improved, but problems such as whitening of a printed portion are caused, and it is not satisfactory in aspects other than storage stability and color sensitivity.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such a viewpoint.
An object of the present invention is to provide a heat-sensitive recording material which has excellent coloring sensitivity, high background whiteness, little whitening of a printed portion, and improved storage stability of a recorded image, that is, improved moisture resistance and plasticizer resistance.

[0007]

That is, the present invention relates to a heat-sensitive coloring layer containing a colorless or pale-colored leuco dye at room temperature and a color developer which reacts with the leuco dye by heating to form a color. Wherein at least one β-sulfoketone compound represented by the following general formula (1) is contained as a sensitivity improver.

[0008]

Embedded image

Wherein R ₁ represents a lower alkyl group having 1 to 6 carbon atoms, and R ₁ , R ₂ and R ₃ each independently represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, an alkoxy group or Represents a nitro group, 1 is 1 or 2, m is 1-3
Represents an integer. However, R ₄ is R ₁ —SO ₂ — (CH ₂
—CO) _l −)

In the present invention, the leuco dye used as a color former is a substance which is colorless or pale at room temperature and which reacts with a developer under heating to develop a color.
Triallylmethane dyes such as bis (p-dimethylaminophenyl) -6-dimethylaminophthalide;
Diphenylmethane dyes such as -bisdimethylaminobenzhydride benzyl ether, thiazine dyes such as benzoylleucomethylene blue, spiro dyes such as 3-methylspirodinaphthopyran, and fluoran dyes;
Other leuco auramine-based, indoline-based, indigo-based dyes and the like can be mentioned. These color formers may be used alone or in combination of two or more.

In the present invention, at least one β-sulfoketone compound represented by the general formula (1) is used as a sensitivity enhancer for the purpose of improving color sensitivity and improving storage stability of a color image. It is. In the general formula (1), R ₄ is R ₁ —SO ₂ — (CH ₂ —C
O) _l - a may be, but in this case, up to four R ₁ -SO ₂ per molecule - will have a - (CH ₂ -CO) _l. And a β-sulfoketone compound having a melting point of 60 to 160 ° C. is preferable. Compounds with a melting point below 60 ° C.
A coloring reaction may occur during the production of the heat-sensitive recording material, or the stability of the whiteness of the background of the heat-sensitive recording material may decrease. Further, a compound having a melting point exceeding 160 ° C.
It becomes difficult to obtain a thermosensitive recording material with high sensitivity.

The [0012] Preferred β- Suruhoketon compounds, in the general formula (1), R ₁ is a methyl group, an ethyl group, a propyl group, a lower alkyl group having 1 to 3 carbon atoms such as isopropyl group, R _2, R ₃ and R ₄ are each independently a hydrogen atom, a halogen atom, a lower alkyl group having 1 to 3 carbon atoms, an aryl group such as a phenyl group or a toluyl group, an alkoxy group such as a methoxy group or an ethoxy group, or a nitro group; Is 1 or 2, and m is 1 or 2. Specifically, for example, the following (Compound 1) to
(Compound 15) and the like, but are not limited thereto.

(Compound 1)

Embedded image (Compound 2)

Embedded image (Compound 3)

Embedded image (Compound 4)

Embedded image (Compound 5)

Embedded image (Compound 6)

Embedded image (Compound 7)

Embedded image (Compound 8)

Embedded image (Compound 9)

Embedded image (Compound 10)

Embedded image (Compound 11)

Embedded image (Compound 12)

Embedded image (Compound 13)

Embedded image (Compound 14)

Embedded image (Compound 15)

Embedded image

The β-sulfoketone compound represented by the general formula (1) can be obtained by reacting a methyl sulfone derivative with an aromatic ester in various solvents in the presence of a base. For example, after dispersing potassium t-butoxide in a dimethylacetamide solution in which dimethylsulfone is dissolved, 2-methylsulfonylacetophenone (compound 1) is added by dropping ethyl benzoate.
Can be obtained.

At least one β-sulfoketone compound represented by the general formula (1) may be used alone, or may be used as a mixture with another sensitivity improver. Examples of such a sensitivity improver include stearic acid amide,
Nitrogen-containing compounds such as palmitic acid amide, oleic acid amide, capric acid amide, linoleic acid amide, atearic acid anilide, 4-hydroxybenzoic acid benzyl ester, 4-benzyloxybenzoic acid benzyl ester, 2
-Phenyl naphthoate, benzyl 2-naphthoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di (4-methylbenzyl) oxalate, dibenzyl terephthalate, isophthalic acid n-butyl ester, p
Ester compounds such as phenyl toluenesulfonic acid ester, 4-benzylbiphenyl, m-terphenyl,
Fluorene, fluoranthene, 2,6-diisopropylnaphthalene, 3-benzylacenaphthene, 1,2-bis (3,4-dimethylphenyl) ethane, 1,2-bis (2,4-dimethylphenyl) ethane, 1,2 Aromatic hydrocarbon compounds such as -bis (2,4,5-trimethylphenyl) ethane, 2-benzyloxynaphthalene,
1,4-diethoxynaphthalene, 1,2-diphenoxyethane, 1,2-bis (3′-methylphenoxy) ethane, 1,2-diphenoxybenzene, 1,4-diphenoxybenzene, 4- (4 Ether compounds such as' -methylphenoxy) biphenyl, diphenylsulfone, 4,4'-diisopropoxydiphenylsulfone, 4,4'-diphenoxydiphenylthioether, and benzyl-4-methylthiophenyl ether; and sulfur-containing compounds. be able to.

Further, in the present invention in which at least one β-sulfoketone compound represented by the general formula (1) is used as a sensitivity improver, the developer used together with the leuco dye is brought into contact with the leuco dye by heating. It is a substance that forms a leuco dye, and phenol derivatives such as 4-tert-butylphenol and 4-phenylphenol,
Naphthol derivatives such as 1-naphthol and 2-naphthol, 2,2'-dihydroxybiphenyl, 2,2-bis (4'-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, and 2,4'-dihydroxy Diphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (4-hydroxyphenyl) sulfoxide, bis (3-allyl-4-hydroxyphenyl) sulfoxide, 4-hydroxy-
4'-isopropoxydiphenyl sulfoxide, bis (4-hydroxyphenyl) sulfide, bis (3-allyl-4-hydroxyphenyl) sulfide, bis (3
-Methyl-4-hydroxyphenyl) sulfide, 4-
Hydroxy-4'-isopropoxydiphenyl sulfide, 1,7-bis (4-hydroxyphenylthio)-
Bisphenol derivatives such as 3,5-dioxaheptane; hydroxybenzoic acid ester derivatives such as 4-hydroxybenzoic acid benzyl ester and 4-hydroxyphenethyl ester; 3-isopropylsalicylic acid;
Salicylic acid derivatives such as di-tert-butylsalicylic acid or metal salts thereof, and benzoic acid derivatives such as benzyl 2-carboxy-benzoate, benzyl 4-carboxy-benzoate, 4-nitrobenzoic acid, 4-chlorobenzoic acid or the like Metal salts, urea derivatives such as diphenylurea and diphenylthiourea, and inorganic developers such as acid clay, activated clay, aluminum chloride, zinc chloride and zinc bromide can be used.

Further, in the present invention using at least one β-sulfoketone compound represented by the general formula (1) as a sensitivity improver, a preferred color developer is represented by the following general formula (2) Compounds.

[0018]

Embedded image

Wherein X represents an oxygen or sulfur atom;
Represents an unsubstituted aromatic group or an aromatic group substituted with a lower alkyl group or a halogen atom, A represents a group having a valence of 2 or more, and n represents an integer of 2 or more. )

Examples of such compounds include bis (p-toluenesulfonylaminocarbonylamino) ketone, 1,2-bis (p-toluenesulfonylaminocarbonylamino) ethane, and 1,3-bis (p-toluenesulfonylamino) Carbonylamino) benzene, 1,3
-Bis (o-toluenesulfonylaminocarbonylamino) benzene, 1,4-bis (p-toluenesulfonylaminocarbonylamino) benzene, 1,4-bis (o
-Toluenesulfonylaminocarbonylamino) benzene, 4,4'-bis (benzenesulfonylaminocarbonylamino) diphenylmethane, 4,4'-bis (p-
Toluenesulfonylaminocarbonylamino) diphenylmethane, 4,4'-bis (o-toluenesulfonylaminocarbonylamino) diphenylmethane, 4,4'-
Bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone and the like can be mentioned.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION When a sensitivity enhancer represented by the general formula (1) and a developer represented by the general formula (2) are combined, a commercially available sensitivity enhancer such as p-benzylbiphenyl and m-terphenyl is used. Sensitivity is further improved than in the case, whitening of the printing part is suppressed,
In addition, the storage stability of the color image can be improved.

In addition, these compounds are added for the purpose of improving the storage stability of the colored portion, and include epoxy compounds,
Additives such as epoxy resin, zinc stearate, iron stearate, and zinc salicylate may be used in combination.

Further, various additives can be added to the heat-sensitive recording material of the present invention depending on the use. As such an additive, a binder for fixing the leuco dye and the electron-accepting substance dispersed on the fine particles while being isolated from each other, for example, polyvinyl alcohol, latex,
Methylcellulose, carboxymethylcellulose, casein polyacrylate, gelatin, starch and derivatives thereof and the like, the whiteness of the thermosensitive coloring layer, the slipperiness of writing instruments,
White pigments for improving sticking and the like, for example, calcium carbonate, silica, kaolin, clay, talc, titanium oxide and the like can be mentioned. These additives are mixed or separately applied to a support such as paper or film to form a thermosensitive coloring layer. Further, the thermosensitive coloring layer may have another layer such as a protective layer.

In the heat-sensitive recording material of the present invention, when the leuco dye constituting the heat-sensitive coloring layer is colored by a developer, β represented by the general formula (1) contained in the heat-sensitive coloring layer is used. -It is believed that the sulfoketone compound causes the fastness of the printed image.

[0025]

The present invention will be specifically described below based on examples and comparative examples.

Example 1 (1) Preparation of Solution A (Compound 1) 11.5 parts by weight of bisphenol A11.
5 parts by weight, 10% by weight polyvinyl alcohol aqueous solution 46
Parts by weight and 46 parts by weight of water were pulverized, mixed and dispersed using a sand mill to prepare a liquid A having an average particle size of about 1 μm.

(2) Preparation of Solution B 5.5 parts by weight of 7'-anilino-3 '-(dibutylamino) -6'-methylfluorane and 49.5 parts by weight of a 10% by weight aqueous solution of polyvinyl alcohol were put on a paint shaker. The mixture was pulverized, mixed and dispersed to prepare a liquid B having an average particle diameter of 1 μm.

(3) Preparation of thermal recording paper 20 parts by weight of liquid A, 10 parts by weight of liquid B, 1 part by weight of paraffin wax emulsion (manufactured by Chukyo Yushi: Hydrin Z-7), paraffin wax emulsion (manufactured by Chukyo Yushi: Hydrin P) -7) A coating liquid is prepared by mixing 4 parts by weight, 10 parts by weight of a 50% calcium carbonate dispersion and 11.5 parts by weight of a 10% by weight aqueous solution of polyvinyl alcohol, and this coating liquid is applied on a base paper and dried. Then, a thermosensitive recording paper having a coating amount after drying of 6 g / m ² was prepared.

(4) Color Test A dynamic color test was performed on the thus prepared heat-sensitive recording paper using a printing tester (manufactured by Okura Electric Co., Ltd.). Printing was performed at 0.0 ms, and printing was performed at 27 V and 1.9 ms for a plasticizer resistance test. Simultaneously, the color density of the background was measured. The color density was measured using a Macbeth reflection densitometer RD-914.

(5) Humidity resistance test Thermal recording paper (24 V, 1.0 m) printed under the above conditions
s) was stored in a thermo-hygrostat (40 ° C., relative humidity 90%) for 10 hours, and then the color density of the printed portion was measured using a Macbeth reflection densitometer RD-914. The residual ratio was calculated by the following equation (1). Table 1 shows the results of the color density of the printed portion and the background portion before the test, the color density of the printed portion and the background portion after the test, and the remaining ratio of the printed portion. Residual rate = (AB) / C (1) (where A represents the density of the printed portion after the humidity resistance test, and
Indicates the value obtained by subtracting the color density of the background before the humidity resistance test from the color density of the background after the humidity resistance test, and C indicates the color density printed under the conditions of 24 V and 1.0 ms before the humidity resistance test. Show)

(6) Plasticizer resistance test Thermal recording paper (27 V, 1.9 m) printed under the above conditions
s), a vinyl chloride wrap was brought into close contact with the entire printing surface and stored in a dryer (50 degrees) for 10 hours. Thereafter, the color density of the printing portion was measured using a Macbeth reflection densitometer RD-914. . The residual ratio was calculated by the following equation (2). Table 2 shows the results of the color density of the printed portion and the background portion before the test, the color density of the printed portion and the background portion after the test, and the remaining ratio of the printed portion. Residual rate = (DE) / F (2) (where D represents the density of the printed portion after the plasticizer resistance test,
E shows a value obtained by subtracting the color density of the background before the plasticizer resistance test from the color density of the background after the plasticizer resistance test, and C shows printing at 27 V and 1.9 ms before the plasticizer resistance test. Color density)

(7) Whitening test After the heat-sensitive recording paper obtained above was colored at 200 ° C,
After leaving at room temperature for 3 days, the degree of whitening of the printed portion was observed. Table 3 shows the observation results. Printing was performed using an iron tester manufactured by Daiei Kagaku Seiki.

Example 2 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 2) was used in place of (Compound 1) in the preparation of Solution A of Example 1. As in Example 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 1, 2 and 3, respectively.

Example 3 A heat-sensitive recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 3) was used in place of (Compound 1) in the preparation of Solution A of Example 1. As in Example 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 1, 2 and 3, respectively.

Example 4 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 5) was used in place of (Compound 1) in the preparation of Solution A of Example 1. As in Example 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 1, 2 and 3, respectively.

Example 5 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 8) was used in place of (Compound 1) in the preparation of Solution A of Example 1. As in Example 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 1, 2 and 3, respectively.

Example 6 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 12) was used instead of (Compound 1) in the preparation of Solution A of Example 1. As in Example 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 1, 2 and 3, respectively.

Example 7 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 13) was used in place of (Compound 1) in the preparation of Solution A of Example 1. As in Example 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 1, 2 and 3, respectively.

Example 8 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that (Compound 14) was used in place of (Compound 1) in the preparation of Solution A of Example 1. As in Example 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 1, 2 and 3, respectively.

Example 9 In preparing the solution A of Example 1, (Compound 3) was used in place of (Compound 1), and 4-hydroxy-4'-isopropoxydiphenyl sulfone was used in place of bisphenol A. A heat-sensitive recording paper was prepared in exactly the same manner as in Example 1 except for the fact that the heat-resistant recording paper was subjected to a humidity resistance test, a plasticizer resistance test and a whitening test in the same manner as in Example 1. The results are shown in Tables 1, 2 and 3, respectively.

Comparative Example 1 In preparing the solution A of Example 1, p was used instead of (Compound 1).
A heat-sensitive recording paper was prepared in exactly the same manner as in Example 1 except that -benzylbiphenyl was used, and a humidity resistance test, a plasticizer resistance test, and a whitening test were performed in the same manner as in Example 1. The results are shown in Tables 1, 2 and 3, respectively.

Comparative Example 2 In the preparation of the solution A in Example 1, p was used instead of (Compound 1).
A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that -benzylbiphenyl was used and 4-hydroxy-4'-isopropoxydiphenylsulfone was used instead of bisphenol A. Humidity resistance test,
A plasticizer resistance test and a whitening test were performed. The results are shown in Tables 1, 2 and 3, respectively.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

Example 10 Except for using 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane in place of bisphenol A in preparing the solution A of Example 1, it was completely the same as Example 1. In the same manner, a thermosensitive recording paper was prepared, and a humidity resistance test, a plasticizer resistance test, and a whitening test were performed in the same manner as in Example 1. The results are shown in Tables 4, 5 and 6, respectively.

Example 11 In preparing the solution A of Example 1, (Compound 3) was used in place of (Compound 1), and 4,4 was used in place of bisphenol A.
A heat-sensitive recording paper was prepared in exactly the same manner as in Example 1 except that 4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane was used. And a whitening test. The results are shown in Tables 4, 5 and 6, respectively.

Example 12 In preparing the solution A of Example 1, (Compound 5) was used instead of (Compound 1), and 4,4 was used instead of bisphenol A.
A heat-sensitive recording paper was prepared in exactly the same manner as in Example 1 except that 4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane was used. And a whitening test. The results are shown in Tables 4, 5 and 6, respectively.

Comparative Example 3 In preparing the solution A of Example 1, p was used instead of (Compound 1).
A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that -benzylbiphenyl was used and 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane was used instead of bisphenol A. Similarly to 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 4, 5 and 6, respectively.

Comparative Example 4 In preparing the solution A of Example 1, p was replaced with (compound 1).
A heat-sensitive recording paper was prepared in exactly the same manner as in Example 1 except that toluene sulfonic acid phenyl ester was used and 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane was used instead of bisphenol A. In the same manner as in Example 1, a humidity resistance test, a plasticizer resistance test, and a whitening test were performed. The results are shown in Tables 4, 5 and 6, respectively.

[0051]

[Table 4]

[0052]

[Table 5]

[0053]

[Table 6]

[0054]

According to the present invention, by using at least one β-sulfoketone compound represented by the general formula (1) as a sensitivity improver, excellent color sensitivity, high background whiteness, and whitening of a printed portion can be obtained. Less storage stability of recorded images,
That is, moisture resistance and plasticizer resistance can be improved.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Matsumoto 1618 Ida, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, within the Technology Development Division of Nippon Steel Corporation

Claims (2)

[Claims] 1. A thermosensitive recording material comprising a support having thereon a thermosensitive coloring layer containing a colorless or pale-colored leuco dye at room temperature and a developer which reacts with the leuco dye to form a color when heated. A heat-sensitive recording material comprising, as an enhancer, at least one β-sulfoketone compound represented by the following general formula (1). Embedded image (Wherein, R ₁ represents a lower alkyl group having 1 to 6 carbon atoms, and R ₂ , R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, an alkoxy group or a nitro group. Represents 1 or 2 and m represents an integer of 1 to 3, provided that R ₄ is R ₁ —SO ₂ — (CH ₂ —CO) ₁
-) 2. The method according to claim 1, wherein the developer contains at least one compound represented by the following general formula (2).
The heat-sensitive recording material as described. Embedded image (Wherein X represents an oxygen or sulfur atom, R represents an unsubstituted aromatic group or an aromatic group substituted with a lower alkyl group or a halogen atom, and A represents a divalent or higher valent group. And n represents an integer of 2 or more)