JPH11268421A - Thermal recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To render the preservability of images excellent in the recording part by the use of a specific compound having a phenylsulfamoyl group and urea structure or thiourea structure as the developer of a thermal recording body. SOLUTION: The compound shown by formula is so-called a nonphenol developing agent having no hydroxy group in the molecule; however, having a developing ability to color a dye precursor, and a compound having respectively one of a phenylsulfamoyl group and urea or thiourea structure. A thermal recording body manufactured by using this is extremely raised in the preservability of oil resistance, water resistance, or the like in the recording part. Namely, such a compound having urea or thiourea structure is not subjected to elusion even if it is exposed by virtue of being indissoluble to oil or plasticizer and each kind of a solvent. In the formula, R<1> , R<2> , R<3> express respectively an alkyl group, an alcoxy group, and an electron attracting property, (m) shows integers of 0-5, (n) shows integers of 0-4, and (o) shows integers of 0-5 respectively. X shows an oxygen atom or a sulfur atom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium having excellent image storability in a recording section.

[0002]

2. Description of the Related Art In general, a thermosensitive recording medium is prepared by grinding and dispersing a colorless or light-colored dye precursor as an electron donating compound and a developer as an electron accepting compound into fine particles. Mix, binder, filler, sensitizer,
A coating solution obtained by adding a lubricant and other auxiliaries is applied to a support such as paper, synthetic paper, film, plastic, etc., and develops color by an instantaneous chemical reaction caused by heating with a thermal head, hot stamp, laser light, etc. Get the record. These heat-sensitive recording materials are applied to a wide range of fields such as measuring recorders, computer terminal printers, facsimile machines, automatic ticket vending machines, and barcode labels.

However, with the recent diversification of recording devices for thermosensitive recording media and the development of higher performance, the quality required for thermosensitive recording media has become higher. In addition, with the spread of plain paper recording methods such as the electrophotographic method and the ink jet method, the thermal recording method has more opportunities to be compared with these plain paper recording methods. Therefore, for example, it is required that the stability of the recording portion (image) or the stability of the non-recording portion (ground color) of the thermal recording medium approach the same level as that of the plain paper recording method. In particular, from the viewpoint of storage stability of a recorded image, a heat-sensitive recording medium having excellent light resistance, oil resistance, water resistance, and plasticizer resistance has been required.

Particularly, in order to improve oil resistance and plasticizer resistance, an epoxy compound described in JP-A-4-97887, an aziridine compound described in JP-A-4-113888, and JP-A-63-163 in a thermosensitive coloring layer. Examples including various metal salts described in JP-A--22683 are known. However, the effect is insufficient.

Also, instead of the conventionally used phenolic color developer, a so-called non-phenolic color developer having an acidic atmosphere capable of coloring a dye precursor without a hydroxy group has been developed. I have. Until now, examples using urea, thiourea, phosphoric acid, phosphoric acid ester, amide, urethane, etc. as a non-phenolic color developer have been disclosed,
When these are used as a color developer, it is known that the image storability of the recording portion is improved as compared with a conventional phenol-based color developer.

For example, carbonyl sulfonamide compounds described in JP-A-4-282291, JP-A-6-99
No. 666, and the like. One of the causes of decolorization of the color image is the dissociation of the dye and the developer, but the non-phenolic developer is less soluble in water, oil, plasticizer, etc. than the conventional phenolic developer, It is considered that the image storability is improved. However, with some effect, the degree is still not enough.

[0007] Further, many examples of using a urea or thiourea compound as a color developing agent have been filed, such as Japanese Patent Application Laid-Open No. 58-21496, and a color developing agent more effective for image preservation has been filed. Urea and thiourea derivatives are being searched for development. For example, JP-A-59-
Phenylurea or phenylthiourea compounds described in JP-A-184694, thiourea dimer compounds described in JP-A-60-145883, halogen-introduced diphenylthiourea compounds described in JP-A-61-211085, And a benzylthiourea compound described in Japanese Patent No. 185739. However, when thermal recording paper is made using these materials, the effect of short-term plasticizer resistance and oil resistance test is effective, but the long-term test shows image disappearance, and the effect of improving image storability is insufficient. is there. Further, Japanese Unexamined Patent Publication No.
No. 147357 discloses an example using a sulfonylurea compound as a color developer. Although this shows excellent image storability, it has a problem of ground color development in a plasticizer resistance test and a drawback that water resistance is rather weak.

Further, there is an example in which a sulphonamide group is introduced into a urea or thiourea compound.
7 and JP-A-8-59603, JP-A-8-25810
And diphenylthiourea sulfonamide compounds described in JP-A-8-132939. Although they exhibit excellent image storability, they have the disadvantage of developing ground color in heat resistance tests.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermosensitive recording medium having improved image storability in a recording section.

[0010]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a compound having a phenylsulfamoyl group (PhNHSO _2- ) and a urea structure or a thiourea structure was found to be heat-sensitive. The inventors have found that they exhibit excellent functions as a developer for a recording medium, and have completed the present invention. That is, the present invention relates to a thermosensitive recording medium using a compound represented by the following general formula (1).

[0011]

Embedded image (Where R ¹ , R ² , and R ³ each represent an alkyl group, an alkoxy group, or an electron-withdrawing group; m represents an integer of 0 to 5; n represents an integer of 0 to 4; Represents an integer of 5. X represents an oxygen atom or a sulfur atom.)

Here, R ¹ , R ² , and R ³ may be any substituents which do not inhibit color development and image storability when the compound is used as a developer. Among them, from the viewpoint of stability of color developing ability and color sensitivity, an alkyl group having 1 to 4 carbon atoms,
As the alkoxy group 4 and the electron-withdrawing group, a halogen atom such as chlorine, bromine and fluorine, and a nitro group are preferable.

The compound of the present invention is a so-called non-phenol type developer which has no hydroxy group in the molecule but has a color developing ability to form a dye precursor, and has a phenylsulfamoyl group and a urea or thiol group in the molecule. Each urea structure is 1
The compound is characterized in that it is a compound having two or more compounds. The thermosensitive recording medium produced by using this greatly improves the image storage properties such as oil resistance and water resistance of the recording part. The reason is not clear, but is presumed as follows.

In general, compounds having a urea or thiourea structure are hardly soluble in oils, plasticizers, and various solvents, and therefore do not elute even when exposed to these compounds. There is a tendency that good image storability is obtained without causing image disappearance due to dissociation. On the other hand, the present inventors have found that the phenylsulfamoyl group also has an effect of improving image storability, and as a result of earnest study, the compounds of the present invention can achieve better image storability. It was obtained that it was a developer.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The compound of the present invention can be synthesized by the following method. First, an acetamidobenzenesulfonyl chloride compound and an aniline compound are reacted to synthesize an acetamido-N-phenylbenzenesulfonamide compound. Next, an acetyl group is eliminated by a hydrolysis reaction to lead to an amino-N-phenylbenzenesulfonamide compound. Furthermore, the amino-N-phenylbenzenesulfonamide compound was prepared by a conventionally known method (for example, New Experimental Chemistry Course 14 Synthesis and Reaction of Organic Compounds [III] P.163)
1, 1633) to produce urea or thiourea. Specifically, phenylisocyanate or phenylthioisocyanate dissolved in an inert solvent such as acetone or THF is mixed with amino-
The desired compound can be synthesized by mixing N-phenylbenzenesulfonamide under an inert gas atmosphere and stirring for several minutes to several hours at room temperature or while heating.

The following compounds are illustrated as specific examples of the compound used in the present invention, but the present invention is not limited to these compounds.

[0017]

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[0018]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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In order to produce the thermosensitive recording medium of the present invention, conventionally known various production methods can be used. Specifically, it can be produced by the following method. That is,
The compound of the present invention, the dye precursor, and the sensitizer are each atomized by a pulverizer or an emulsifier such as a ball mill, an attritor, and a sand grinder, and various fillers and various additives are added, and dispersed in an aqueous solution of a water-soluble binder. Paint
When this is applied to an arbitrary support with various coaters such as an air knife coater, a blade coater and a roll coater, a heat-sensitive recording material is obtained. The compounds of the present invention may be used alone or in combination of two or more.

As the dye precursor used in the thermal recording medium of the present invention, conventionally known dye precursors can be used. The dye precursor is illustrated below, but the present invention is not limited thereto, and two or more of these may be used in combination.

3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide <Trade name: CVL
>, 3-diethylamino-6-methyl-7-anilinofluoran <ODB>, 3-dibutylamino-6-methyl-7-anilinofluoran <ODB-2>, 3- (N-
Isoamyl-N-ethylamino) -6-methyl-7-anilinofluoran <S-205>, 3-diethylamino-7-m-trifluoromethylanilinofluoran <B
rack-100>, 3-dibutylamino-7-o-chloroanilinofluoran <TH-107>, 3- (N-
Cyclohexyl-N-methylamino) -6-methyl-7
-Anilinofluoran <PSD-150>, 3-diethylamino-7-anilinofluoran <Green-2
>, 3,3-bis (4-dimethylaminophenyl) phthalide <MGL>, tris [4- (dimethylamino) phenyl] methane <LCV>, 3,3-bis (1-ethyl-
2-methylindol-3-yl) phthalide <indolyl red>, 3-cyclohexylamino-6-chlorofluoran <OR-55>, 3,3-bis [2- (p-dimethylaminophenyl) -2- (P-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide <NIR-Black>, 1,1,5,5-tetrakis (p-dimethylaminophenyl) -3-methoxy-
1,4-pentadiene, 1,1,5,5-tetrakis (p-dimethylaminophenyl) -3- (p-dimethylaminophenyl) -1,4-pentadiene.

In the present invention, the compound of the present invention may be used in combination with one or more known developers which have been conventionally used. The following are examples of color developers, but the present invention is not limited to these.

4,4'-isopropylidene diphenol, 1,7-di (4-hydroxyphenylthio) -3,
Bisphenols such as 5-dioxaheptane and 4,4′-cyclohexylidenediphenol, benzyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate,
-4-hydroxybenzoic acid esters such as normal propyl hydroxybenzoate, isopropyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, diisopropyl 4-hydroxyphthalate, dibenzyl 4-hydroxyphthalate , 4-
4-hydroxyphthalic acid diesters such as dihexyl hydroxyphthalate, monobenzyl phthalate,
Monoesters of phthalic acid such as monocyclohexyl phthalate, monophenyl phthalate, and monomethylphenyl phthalate, bis (4-hydroxy-3-tert-butyl-6-methylphenyl) sulfide, bis (4-hydroxy- 2,5-dimethylphenyl) sulfide, bis (4-hydroxy-2-methyl-)
Bishydroxyphenyl sulfides such as 5-ethylphenyl) sulfide, 4-hydroxy-4′-isopropoxydiphenyl sulfone, 4-hydroxy-4′-
4-hydroxyphenylarylsulfones such as methyldiphenylsulfone, 4-hydroxy-4′-normalpropoxydiphenylsulfone, 4-hydroxyphenylbenzenesulfonate, 4-hydroxyphenyl-
p-tolylsulfonate, 4-hydroxyphenyl-p
4-hydroxyphenylarylsulfonates such as -chlorobenzenesulfonate; 1,3-di [2- (4
-Hydroxyphenyl) -2-propyl] benzene,
1,3-di [2- such as 1,3-di [2- (4-hydroxy-3-methylphenyl) -2-propyl] benzene
(Hydroxyphenyl) -2-propyl] benzenes,
Benzyl 4-hydroxybenzoyloxybenzoate, 4
Methyl-hydroxybenzoyloxybenzoate, ethyl 4-hydroxybenzoyloxybenzoate, normal propyl 4-hydroxybenzoyloxybenzoate, 4-
Isopropyl hydroxybenzoyloxybenzoate, 4
4 such as butyl hydroxybenzoyloxybenzoate;
-Hydroxybenzoyloxybenzoates, bis (3-tert-butyl-4-hydroxy-6-methylphenyl) sulfone, bis (3-ethyl-4-hydroxyphenyl) sulfone, bis (3-propyl-4-hydroxy) Phenyl) sulfone, bis (3-isopropyl-4-hydroxyphenyl) sulfone, bis (3-ethyl-4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfone, 2-hydroxyphenyl-4′-hydroxyphenylsulfone Bishydroxyphenylsulfones such as bis (3-chloro-4-hydroxyphenyl) sulfone, bis (3-bromo-4-hydroxyphenyl) sulfone, p-tert-butylphenol, p-phenylphenol, p-benzylphenol, 1-naft Phenols such as phenol, 2-naphthol, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3, Metal salts of aromatic carboxylic acids such as 5-dimethyl-4-hydroxybenzoic acid, terephthalic acid, salicylic acid, 3-isopropylsalicylic acid, and 3-tert-butylsalicylic acid.

In a thermosensitive recording medium containing a dye precursor and a color developer as a color-forming component, a sensitizer is usually used in order to increase the color-forming sensitivity. Examples of the sensitizer are shown below, but the present invention is not limited to these, and two or more of these may be used in combination.

Stearic acid, stearic acid amide, palmitic acid amide, oleic acid amide, behenic acid, ethylene bisstearamide, coco fatty acid amide, montan wax, polyethylene wax, phenyl-α-naphthyl carbonate, di-p-tolyl Carbonate, diphenyl carbonate, 4-biphenyl-p-tolyl ether, p-benzylbiphenyl, m-terphenyl, triphenylmethane, 1,1,3-tris (2-methyl-
4-hydroxy-5-tert-butylphenyl) butane, 1,2-bis (3-methylphenoxy) ethane,
1,2-bisphenoxyethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-bisphenoxybutane, 1,4-bisphenoxybutene, 2-naphthylbenzyl ether, 1,4-di Ethoxynaphthalene, 1,4
-Dimethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid methyl ester, 2-naphthoic acid phenyl ester,
benzyl p-benzyloxybenzoate, dibenzyl terephthalate, dimethyl terephthalate, 1,1-diphenylethanol, 1,1-diphenyl-2-propanol,
1,3-diphenoxy-2-propanol, p- (benzyloxy) benzyl alcohol, normal octadecylcarbamoyl-p-methoxycarbonylbenzene, normal octadecylcarbamoylbenzene.

In the present invention, various auxiliaries may be added in order to improve the stability of the recorded image. The auxiliaries are exemplified below, but the present invention is not limited to these.

Zinc stearate, aluminum stearate, calcium stearate, zinc palmitate, zinc behenate, metal salts of p-chlorobenzoate (Zn, C
a), p-nitrobenzoic acid metal salt (Zn, Ca), phthalic acid monobenzyl ester metal salt (Zn, Ca), 4,
4'-isopropylidene-bis (3-methyl-6-te
rt-butyl) phenol.

As the binder used in the heat-sensitive recording medium of the present invention, those known in the field of heat-sensitive recording can be used. Examples of the binder are shown below, but the present invention is not limited thereto.

A completely saponified polyvinyl alcohol having a degree of polymerization of 2000 or less, a partially saponified polyvinyl alcohol, a carboxy-modified polyvinyl alcohol, an amide-modified polyvinyl alcohol, a sulfonic acid-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxy Ethyl cellulose, methyl cellulose,
Cellulose derivatives such as carboxymethylcellulose and acetylcellulose, casein, gelatin, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, polymers and copolymers such as styrene, vinyl acetate, acrylamide and acrylate, polyamide Resins, silicone resins, petroleum resins, terpene resins, ketone resins, coumarone resins, and others can be mentioned. These natural and synthetic polymer substances can be used by dissolving them in water or an organic solvent such as alcohol, or can be used in a state of being emulsified or dispersed in a paste form in a medium such as water. Also, two or more of these can be used.

The filler used in the thermosensitive recording medium of the present invention includes clay, calcined clay, diatomaceous earth, talc, kaolin, calcium carbonate, basic magnesium carbonate, barium sulfate, barium carbonate, aluminum hydroxide, zinc oxide, silica , Magnesium hydroxide, titanium oxide, urea
Formalin resin, polystyrene resin, phenol resin,
Other natural or synthetic inorganic or organic fillers may be mentioned, but are not limited thereto. Two or more of these can be used.

As additives, ultraviolet absorbers, defoamers,
Examples include a fluorescent whitening agent, a waterproofing agent, a lubricant and the like, but the present invention is not limited to these.

The amounts of the dye precursor and the developer used in the thermosensitive recording medium of the present invention and the types and amounts of other various components are determined according to the required performance and recording suitability, and are not particularly limited. Usually, with respect to 1 part of the dye precursor,
The developer is preferably 1 to 8 parts and the filler is preferably 1 to 20 parts, and the binder is preferably 10 to 25% of the total solid content.

As the support used in the thermal recording medium of the present invention, paper such as high quality paper, medium quality paper, coated paper, synthetic paper,
Although a plastic film etc. can be mentioned, this invention is not limited to these.

For the purpose of further improving the storability, an overcoat layer of a polymer substance or the like can be provided on the thermosensitive coloring layer. Further, for the purpose of enhancing the storage stability and sensitivity, an undercoat layer containing an organic filler or an inorganic filler may be provided between the color-forming layer and the support.

[0041]

The present invention will be specifically described below by way of examples of synthesis of the compounds of the present invention and production examples of thermosensitive recording materials using them as a color developer. In addition, the reactants and other components used are shown as representative examples, and various modifications can be made as described above within the scope of the present invention.

-Synthesis of Compound of the Invention- [Synthesis Example of Starting Material] Synthesis of 4-amino-N-phenylbenzenesulfonamide 4-acetamidobenzenesulfonyl chloride
0 g of methyl ethyl ketone 250 ml, water 300 ml,
18.6 g of sodium carbonate was added and dissolved. 13.6 g of aniline was added thereto and reacted at room temperature for 1 hour. After that, 4N-sodium hydroxide aqueous solution 170ml
Was added and heated under reflux for 16 hours to cause a reaction. The solvent was distilled off using an evaporator, and the residue was acidified by adding 6N-hydrochloric acid, and the resulting solid was collected by filtration. This was recrystallized from ethyl acetate to obtain 29.4 g (yield 81%) of 4-amino-N-phenylbenzenesulfonamide as a white solid. <IR spectrum> (KBr tablet method, cm ^-1 ) 3420,3349,3294,3246,1638,1596,1495,1465,1435,1394,
1319,1301,1220,1152,1093,1072,918,891,831,751,691,
561 ^<1 H-NMR _{spectrum> (300MHz, DMSO-d 6} , δ / ppm, TMS) 5.92 (2H, s, NH 2), 6.52 (2H, d, J = 9Hz, ArH), 6.96 (1H, t , J = 7H
z, ArH), 7.06 (2H, d, J = 8Hz, ArH), 7.18 (2H, t, J = 8Hz, ArH),
7.38 (2H, d, J = 8Hz, ArH), 9.82 (1H, s, NH) <13 C-NMR _{spectrum> (75MHz, DMSO-d 6} , δ / ppm, TMS) 112.50,119.36,123.18,124.43, 128.62,128.83,138.44,1
52.73 <MS spectrum> (FAB-MS (M / Z)) 249 (M + H) ⁺

[Synthesis Example 1] Synthesis of 4-phenylsulfamoyl-N, N'-diphenylurea (A-01) 4-amino-N-phenylbenzenesulfonamide
17 g was dissolved in 40 ml of THF. Under a nitrogen atmosphere, 1.83 ml of phenyl isocyanate was added thereto,
The mixture was reacted by heating under reflux for 6 hours. After the completion of the reaction, the solvent was distilled off using an evaporator, and the residue was recrystallized from ethyl acetate to give 3.95 g (yield) of 4-phenylsulfamoyl-N, N'-diphenylurea (A-01) as a white solid. Rate 6
4%). <Melting point> 223-224 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3348,3281,1665,1592,1548,1496,1443,1404,1316,1232,
1156,1097,933,752,695,600,557 ^<1 H-NMR _{spectrum> (300MHz, DMSO-d 6} , δ / ppm, TMS) 6.97 (2H, t, J = 7Hz, ArH), 7.11 (4H, d, J = 8Hz, ArH ), 7.18 (4H,
t, J = 8Hz, ArH), 7.25 (4H, t, J = 8Hz, ArH), 7.43 (4H, d, J = 8Hz,
ArH), 7.55 (4H, d, J = 9Hz, ArH), 7.65 (4H, d, J = 9Hz, ArH), 8.0
9 (2H, t, J = 8Hz, ArH), 8.64 (1H, s, NH), 8.95 (1H, s, NH), 9.97
(1H, s, NHSO ₂ ) < ¹³ C-NMR spectrum> (75 MHz, DMSO-d ₆ , δ / ppm, TMS) 116.99,117.08,118.18,119.69,121.92,123.39,127.69,1
28.36,128.54,131.54,143.52,151.81,177.72 <MS spectrum> (FAB-MS (M / Z)) 368 (M + H) ⁺

[Synthesis Example 2] Synthesis of 4-phenylsulfamoyl-N, N'-diphenylthiourea (A-25) 4-amino-N-phenylbenzenesulfonamide
00 g was dissolved in 40 ml of THF. Under a nitrogen atmosphere, 2.99 g of phenylisothiocyanate was added, and the mixture was heated and refluxed for 8 hours to cause a reaction. After completion of the reaction, the solvent was distilled off using an evaporator, and the residue was recrystallized from ethyl acetate to obtain 3.58 g of 4-phenylsulfamoyl-N, N'-diphenylthiourea (A-25) as a white solid.
(47% yield). <Melting point> 171-172 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3298,3192,1592,1545,1497,1405,1333,1293,1263,1229,
1157,1088,917,745,690,636,609,557,496 ^<1 H-NMR _{spectrum> (300MHz, DMSO-d 6} , δ / ppm, TMS) 7.00 (1H, t, J = 7Hz, ArH), 7.10-7.15 (3H, m, ArH), 7.21 (2H,
t, J = 8Hz, ArH), 7.32 (2H, t, J = 8Hz, ArH), 7.46 (2H, d, J = 8Hz,
ArH), 7.67-7.74 (4H, m , ArH), 10.09 (3H, br) <13 C-NMR _{spectrum> (75MHz, DMSO-d 6} , δ / ppm, TMS) 119.64,121.85,123.56,123.67,124.62 , 127.20,128.36,1
28.95,133.82,137.78,138.97,143.63,179.18 <MS spectrum> (FAB-MS (M / Z)) 384 (M + H) ⁺

-Production of heat-sensitive recording material- [Examples 1 and 2] A heat-sensitive recording material comprising the following composition was prepared. That is, first, a dye dispersion (solution A) and a developer dispersion (solution B) having the following composition were each ground by a sand grinder to an average particle diameter of 1 μm. (Solution A: dye dispersion) 3-N, N-diethylamino-6-methyl-7-anilinofluoran 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.6 parts (Solution B: color development Agent dispersion) Compound of the present invention (see Table 1) 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts Then, the following mixture of solution A, solution B and kaolin clay is mixed. To obtain a heat-sensitive paint. Solution A: Dye dispersion 9.2 parts Solution B: developer dispersion 36.0 parts Kaolin clay (50% dispersion) 12.0 parts Amount of this heat-sensitive paint applied to one side of a 50 g / m ² base paper 6.
The sheet was coated and dried so as to have a thickness of 0 to 6.5 g / m ² , and this sheet was treated with a super calender so that the smoothness became 500 to 600 seconds, thereby producing a thermosensitive recording medium.

[Comparative Examples 1-2] In the same manner as in Examples 1-2, except that the following developer was used in place of the compound of the present invention in the developer dispersion (solution B), A recording medium was produced. 4-hydroxy-4'-isopropoxydiphenylsulfone (B-01) N, N'-diphenylurea (B-02) N, N'-diphenylthiourea (B-03)

-Evaluation of thermosensitive recording medium- [Coloring method]
01 (made by UBI) with an applied energy of 450 m
At j / mm ² , recording was performed on the produced thermosensitive recording medium. Next, the image density of the recording portion was measured using a Macbeth densitometer (RD-
914, using an amber filter).
Using this as a test sample, the following test was performed. [Oil resistance test]: The test sample was immersed in salad oil for 1 hour, the oil was wiped off, left at room temperature for 24 hours, and the residual image density of the recording portion was measured with a Macbeth densitometer. [Water resistance test]: The test sample was immersed in tap water for 24 hours, dried at 30 ° C. for 2 hours, and the image remaining density of the recording portion was measured with a Macbeth densitometer. Table 1 shows the results of the image storability test of the image recording unit.

[0048]

[Table 1] Image storage test results

As is evident from the results in Table 1, Examples 1 and 2 using the compound of the present invention as a developer were Comparative Examples 1 and 2 using a conventional phenolic developer and a phenylsulfamoyl group. Oil resistance and water resistance are remarkably improved as compared with Comparative Example 2 of a urea color developer having no phenylsulfamoyl group and Comparative Example 3 of a urea color developer having no phenylsulfamoyl group.

[0050]

The compounds of the present invention have sufficient ability to form a dye precursor. Further, a heat-sensitive recording material using this compound as a color developer is extremely useful because it has very excellent image storability in a recording portion.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiki Yoneshige 5-2-1-1, Oji, Kita-ku, Tokyo Nippon Paper Industries Central Research Laboratory (72) Inventor Hidetoshi Yoshioka 5-2-1-1, Oji, Kita-ku, Tokyo No. Nippon Paper Industries Central Research Laboratory

Claims (1)

[Claims] 1. A thermosensitive recording medium having a thermosensitive coloring layer containing a colorless or pale-colored dye precursor and a developer which reacts upon heating to form the dye precursor, wherein the developer is represented by the following general formula: A heat-sensitive recording material, which is a compound represented by (1). Embedded image (Where R ¹ , R ² , and R ³ each represent an alkyl group, an alkoxy group, or an electron-withdrawing group; m represents an integer of 0 to 5; n represents an integer of 0 to 4; Represents an integer of 5. X represents an oxygen atom or a sulfur atom.)