JPH10230681A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording medium having improved image persistence and heat resistant ground color stability. SOLUTION: The thermal recording medium uses sulfoneamide compound represented by a formula as a developer. In this case, the compound has sufficient color developability to color develop a dye precursor. As compared with phenol developer used heretofore, it exhibit excellent performances of image persistence of a recorded part and heat resistant ground color stability of a whit part. In the formula, R<1> indicates hydrogen atom, alkyl group, alkoxy group, halogen atom, or nitro group. X indicates a bivalent group, and m indicates integer of 1 to 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermosensitive recording medium using a sulfonamide compound as a color developer. The heat-sensitive recording material of the present invention is excellent in image storability of a recording portion and heat-resistant ground color stability of a blank portion, and is useful for applications requiring long-term storability of a recorded image and use at high temperatures.

[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. For example, JP-A-58-
Urea and thiourea compounds described in JP-A-21496, carbonylsulfonamide compounds described in JP-A-4-282291, and organic phosphoric acid compounds described in JP-A-6-99666 are exemplified. One of the causes of decolorization of a color-developed image is the dissociation of a dye and a developer, but the non-phenol-based developer is more water, oil, and
It is considered that it hardly dissolves in a plasticizer or the like, and the image storability improves. However, with some effect, the degree is still not enough.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material having improved image storability of a recording portion and heat-resistant ground color stability of a blank portion.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the sulfonamide compound exerts an excellent function as a developer for a thermosensitive recording medium. The present invention has been completed. That is,
The present invention relates to a thermosensitive recording material characterized by using sulfonamide compounds represented by the following general formula (1) or (2) or (3) alone or in combination of two or more thereof.

[0008]

Embedded image (However, R ¹ is a hydrogen atom, an alkyl group, an alkoxy group,
Represents a halogen atom or a nitro group. X represents a divalent group.
m represents an integer of 1 to 4. )

[0009]

Embedded image (However, R ² is a hydrogen atom, an alkyl group, an alkoxy group,
Represents a halogen atom or a nitro group. n represents an integer of 1 to 4. )

[0010]

Embedded image (However, R ³ is a hydrogen atom, an alkyl group, an alkoxy group,
Represents a halogen atom or a nitro group. One of R ⁴ and R ⁵ represents a hydrogen atom and the other represents a methyl group. o represents an integer of 1 to 4. )

In the sulfonamide compound represented by the general formula (1) of the present invention, X represents a divalent group. Representative examples of the group belonging to X are shown in the following formulas (4) and (5).
The present invention is not limited to these.

[0012]

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[0013]

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The compound of the present invention does not have a hydroxy group in the molecule but has the ability to develop a dye precursor.
It is a so-called non-phenol type developer. Until now, examples using urea, thiourea, phosphoric acid, phosphoric acid ester, amide, urethane and the like as a non-phenol type developer have been disclosed, and when these are used as a developer, a conventional phenol type developer is used. It is known that the image storability of the recording section is improved as compared with the colorant.

In particular, many examples of using a urea or thiourea compound as a color developer have been filed, such as in Japanese Patent Application Laid-Open No. 58-112496, and development of a color developer more effective in image preservation has been developed. Therefore, urea and thiourea derivatives are being searched for. For example, JP-A-59-18469
4, a phenylurea or phenylthiourea compound described in JP-A-60-145883, a thiourea dimer compound described in JP-A-60-145883, a halogen-introduced diphenylthiourea compound described in JP-A-61-211085, -2
No. 03381, an anilinothiourea compound described in JP-A-5-185739, and a benzylthiourea compound described in JP-A-5-187439. Further, JP-A-5-147357 and the like report examples using a sulfonylurea compound as a developer. Have been.

There is also an example in which a sulphonamide group is introduced into a urea or thiourea compound, as disclosed in JP-A-7-304723.
And diphenyl urea sulfonamide compounds described in JP-A-8-59603 and JP-A-8-25810 and JP-A-8-132939.

The compound of the present invention is a compound characterized in that the structure in which a sulphonamide group is introduced into urea is dimerized. This was achieved by finding that not only the ground color stability but also the image storability was greatly improved.

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.

[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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[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The sulfonamide compound of the present invention can be prepared by a conventionally known method (for example, a method described in New Experimental Chemistry Lecture 14, Synthesis of Organic Compounds and Reaction [III], page 1631).
Can be synthesized by Specifically, a diisocyanate dissolved in an inert solvent such as acetone or THF and aminobenzenesulfonamide are mixed under an inert gas atmosphere, and the mixture is stirred at room temperature for several minutes to several hours to synthesize a target compound. can do. In addition, diphenylmethane which is a raw material of the sulfonamide compound of the present invention
4,4'-diisocyanate <trade name: MDI> and toluylene-2,4-diisocyanate <2,4-TDI
>, Toluylene-2,6-diisocyanate <2,6-
TDI> is very easily and inexpensively available because it is industrially produced in large quantities as a raw material for paints, adhesives and polyurethane. Also, the production can be performed at a high yield without requiring any special equipment. Therefore, there is an advantage that the production cost of the color developer of the present invention is very low.

In order to produce the thermosensitive recording medium of the present invention, various known production methods can be used. Specifically, it can be produced by the following method. That is,
The sulfonamide compound, 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. A heat-sensitive recording material can be obtained by applying a coating material to an arbitrary support with an air knife coater, blade coater, roll coater, or other various coaters. The sulfonamide compounds may be used alone or as a mixture 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.

The sulfonamide compounds used as color developers in the present invention may be used alone or in combination of two or more.

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 main components are as follows.
Although it is determined according to the required performance and recording suitability and is not particularly limited, usually, 1 to 8 parts of a developer and 1 to 20 parts of a filler are preferable with respect to 1 part of a dye precursor, and a binder is all solids. 10 to 25% per minute is preferred.

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 sulfonamide compounds used in the present invention and production examples of thermosensitive recording materials using them as a color developer. The invention is not limited to these.

-Synthesis of Sulfonamide Compound- [Synthesis Example 1] Synthesis of 4,4'-bis (p-aminosulfonylphenylureido) diphenylmethane (A-01) 3.0 g of p-aminobenzenesulfonamide and 25 ml of anhydrous acetone Was dissolved. Here, under nitrogen atmosphere, MD
A solution of 2.0 g of I dissolved in 25 ml of anhydrous acetone was added dropwise, and the mixture was stirred at room temperature for 2 hours. After completion of the reaction, the resulting precipitate was separated by filtration, purified by recrystallization with acetone,
A white solid of 4,4′-bis (p-aminosulfonylphenylureido) diphenylmethane (A-01) was obtained in 4.2.
8 g (yield 90%) was obtained. <Decomposition point> 292-294 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3377,3328,3277,1654,1597,1541,1410,1327,1239,1159,
1099,905,819,696,639,606,543 ^<1 H-NMR _{spectrum> (300MHz, DMSO-d 6} , δ / ppm, TMS) 3.37 (s, 2H, CH 2), 7.12 (d, 4H, J = 8Hz, ArH), 7.16 (s , 4H, SO ₂ N
H ₂ ), 7.37 (d, 4H, J = 8Hz, ArH), 7.59 (d, 4H, J = 8Hz, ArH), 7.73
(d, 4H, J = 8Hz , ArH), 8.65 (s, 2H, NH), 8.95 (s, 1H, NH) <13 C-NMR _{spectrum> (75MHz, DMSO-d 6} , δ / ppm, TMS) 97.43,117.15,118.48,126.67,128.78,135.17,137.08,14
2.80,152.11,180.72 <MS spectrum> (FAB-MS (M / Z)) 595 (M + H) ⁺

[Synthesis Example 2] 4,4'-bis (m-aminosulfonylphenylureido) diphenylmethane (A-
Synthesis of 07) 4.52 g of m-aminobenzenesulfonamide was dissolved in 50 ml of anhydrous acetone. Here, under nitrogen atmosphere, M
A solution of 3.0 g of DI dissolved in 50 ml of anhydrous acetone was added dropwise, and the mixture was stirred at room temperature for 2 hours. After the reaction,
The resulting precipitate was separated by filtration, purified by recrystallization from acetone, and purified. 6.48 g (yield 91%) of 4,4'-bis (m-aminosulfonylphenylureido) diphenylmethane (A-07) white solid was obtained. Obtained. <Decomposition point> 274 ° C or higher <IR spectrum> (KBr tablet method, cm ^-1 ) 3362,3328,3271,1649,1594,1557,1483,1408,1340,1304,
1236,1160,685,628,603 ^<1 H-NMR _{spectrum> (300MHz, DMSO-d 6} , δ / ppm, TMS) 3.83 (s, 2H, CH 2) 7.11-7.43 (m, 16H, ArH), 7.55 (s, 2H, SO ₂ NH
_{2), 8.07 (s, 2H} , SO 2 NH 2), 8.61 (s, 2H, NH), 8.94 (s, 2H, NH) <13 C-NMR _{spectrum> (75MHz, DMSO-d 6} , δ / ppm , TMS) 114.97,118.47,118.67,120.85,128.83,129.15,135.14,1
37.26,140.18,144.61,152.32 <MS spectrum> (FAB-MS (M / Z)) 595 (M + H) ⁺

Synthesis Example 3 2,4-Bis (p-aminosulfonylphenylureido) -1-methylbenzene (A
Synthesis of -13) 4.35 g of p-aminobenzenesulfonamide was dissolved in 30 ml of anhydrous acetone. Here under a nitrogen atmosphere,
A solution of 2.0 g of 2,4-TDI dissolved in 10 ml of anhydrous acetone was added dropwise, and the mixture was stirred at room temperature for 2 hours. After completion of the reaction, the formed precipitate was separated by filtration, recrystallized from acetone and purified, and a white solid of 2,4-bis (p-aminosulfonylphenylureido) -1-methylbenzene (A-13) was obtained. 90 g (yield 82%) was obtained. <Decomposition point> 264-267 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3346,3230,2274,1697,1602,1539,1402,1317,1224,1155,
1099,904,837,544 ^<1 H- _{spectrum> (300MHz, DMSO-d 6} , δ / ppm, TMS) 3.36 (s, 3H, Me), 7.08 (s, 2H, SO 2 NH 2), 7.09 (s, 2H, SO ₂ NH ₂ ),
7.57-7.78 (m, 11H, ArH), 7.91 (s, 1H, NH), 7.98 (s, 1H, NH),
8.65 (s, 1H, NH) , 8.77 (s, 1H, NH) <13 C-NMR _{spectrum> (75MHz, DMSO-d 6} , δ / ppm, TMS) 17.12,95.56,110.90,112.38,112.83,116.93, 120.71,12
6.58,126.64,123.00,136.38,136.97,137.20,137.93,14
2.74,142.83,151.98,152.08 <MS spectrum> (FAB-MS (M / Z)) 519 (M + H) ⁺

[Synthesis Example 4] 2,4-bis (m-aminosulfonylphenylureido) -1-methylbenzene (A
Synthesis of -14) 5.28 g of m-aminobenzenesulfonamide was dissolved in 30 ml of anhydrous acetone. Here under a nitrogen atmosphere,
A solution of 2.43 g of 2,4-TDI dissolved in 20 ml of anhydrous acetone was added dropwise, and the mixture was stirred at room temperature for 2 hours.
After the completion of the reaction, the resulting precipitate was separated by filtration, recrystallized from acetone, and purified to obtain a white solid of 2,4-bis (m-aminosulfonylphenylureido) -1-methylbenzene (A-14). 63 g (yield 64%) was obtained. <Melting point> 210-212 ° C <IR spectrum> (KBr tablet method, cm ^-1 ) 3342,3280,1650,1594,1553,1478,1425,1337,1310,1233,
1155,877,786,682,597,584 ^<1 H-NMR _{spectrum> (300MHz, DMSO-d 6} , δ / ppm, TMS) 2.22 (s, 3H, Me), 7.03-7.54 (m, 11H, ArH), 7.86 (s, 2H, SO ₂ NH
₂ ), 8.11 (s, 2H, SO ₂ NH ₂ ), 8.19 (s, 1H, NH), 8.63 (s, 1H, NH),
8.72 (s, 1H, NH) , 8.31 (s, 1H, NH) <13 C-NMR _{spectrum> (75MHz, DMSO-d 6} , δ / ppm, TMS) 17.12,110.47,112.40,114.92,118.54,120.15, 120.40,12
0.61,128.81,128.93,129.96,137.19,137.43,140.08,14
0.14,144.48,144.50,152.08,152.20 <MS spectrum> (FAB-MS (M / Z)) 519 (M + H) ⁺

-Production of heat-sensitive recording medium- [Examples 1 to 4] A heat-sensitive recording medium 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 Tables 1 and 2) 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts water 11.2 parts Then, dispersion liquid of liquid A, liquid B and kaolin clay at the following ratios Was 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 Example Example 1 was repeated except that 4-hydroxy-4'-isopropoxydiphenyl sulfone (B-01) was used in place of the compound of the present invention in the developer dispersion (solution B). In the same manner as in Examples 4 to 4, a thermosensitive recording medium was prepared.

-Evaluation of thermal 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 and the blank portion was measured by a Macbeth densitometer (RD-914, using an amber filter). Using this as a test sample, the following test was performed. [Plasticizer resistance test]: The test sample was brought into contact with a vinyl chloride film (Dialup 300G, manufactured by Mitsubishi Plastics, Inc.), left at 40 ° C. for 24 hours, and the image remaining density of the recording portion was measured with a Macbeth densitometer. . [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. [Heat-resistant ground color test of blank portion]: The test sample was left at 100 ° C. for 30 minutes, and the density of the blank portion was measured with a Macbeth densitometer.

Table 1 shows the results of the image storability test of the image recording section.
Shown in The image remaining rate at that time was calculated from the following equation.
The larger the value, the better the image preservability. In addition, Table 2 shows the results of the heat resistant ground color test on the white paper portion.
The smaller the value, the better the stability of the heat resistant ground color.

[0050]

## EQU1 ## Image residual ratio (%) = (image density after test / image density before test) × 100

[0051]

[Table 1] Image storage test results

[0052]

[Table 2] Table 2. Results of heat resistant ground color test

As is clear from the results shown in Tables 1 and 2, Examples 1 to 4 using the compound of the present invention as a color developer exhibited higher oil resistance than Comparative Examples using a conventional phenolic color developer. In addition, the plasticizer resistance is remarkably improved, the water resistance is also good, and the heat resistant ground color stability of the white paper portion is also excellent.

[0054]

As described above, the sulfonamide compound of the present invention has a sufficient ability for coloring a dye precursor. Further, a heat-sensitive recording material using this compound as a color developer is extremely useful because it is very excellent in image storability of a recording portion and heat-resistant ground color stability of a blank portion.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hidetoshi Yoshioka 5-21-1, Oji, Kita-ku, Tokyo Nippon Paper Industries Central Research Laboratory

Claims (3)

[Claims] 1. A thermosensitive recording medium having a thermosensitive coloring layer containing a colorless or light-colored dye precursor and a developer that reacts upon heating to form the dye precursor, wherein the developer has the following general formula: A thermosensitive recording material, wherein the sulfonamide compound represented by (1) is used alone or in combination of two or more thereof. Embedded image (However, R ¹ is a hydrogen atom, an alkyl group, an alkoxy group,
Represents a halogen atom or a nitro group. X represents a divalent group.
m represents an integer of 1 to 4. ) 2. The thermosensitive recording medium according to claim 1, wherein the color developer is a sulfonamide compound represented by the following general formula (2). Embedded image (However, R ² is a hydrogen atom, an alkyl group, an alkoxy group,
Represents a halogen atom or a nitro group. n represents an integer of 1 to 4. ) 3. The heat-sensitive recording material according to claim 1, wherein the color developer is a sulfonamide compound represented by the following general formula (3). Embedded image (However, R ³ is a hydrogen atom, an alkyl group, an alkoxy group,
Represents a halogen atom or a nitro group. One of R ⁴ and R ⁵ represents a hydrogen atom and the other represents a methyl group. o represents an integer of 1 to 4. )