Sulfonyl compound and thermal-sensitive recording medium using the same

Abstract: A thermal recording medium comprising a as a developer a sulfonyl compound represented by general formula (1) or a polyvalent metal salt thereof. where X represents H or a lower alkyl group, R₁, R₂ and R₃ represent H, halogen atom, a hydroxyl group, a lower alkyl group or a cycloalkyl group, R₄, R₅ and R₆ represent H, halogen atom, a lower alkyl group or a cycloalkyl group, and R₇ represents H or where R₄, R₅ and R₆ are as defined above. The thermal recording medium has a high sensitivity and a lower background blush during storage, and also has excellent stability against heating, moisture and plasticizer.

Description: The present invention relates to a specific sulfonyl compound and a polyvalent metal salt thereof, and to the usage of the compounds, more particularly to specific a sulfonyl compound and a polyvalent metal salt thereof, which, when used as a developer, provide a thermal recording medium having less blushing on the background and storage stability of the recorded image especially under the humid condition, thermal resistance and durability against a plasticizer. Prior Art: EP-A-567 314 discloses color recording compounds related to the present compounds but differ in the Ar (arylene central core) grouping. Thermal recording media using a thermal developing reaction of a basic dye precursor and an electron receptive developer have heretofore been well known. As a developer for those media, 2,2-bis(4-hydroxyphenyl)propane and 4-hydroxy-4'isopropoxydiphenylsulfone have been well known (see JPB Hei 3-54655). However, the thermal recording media using the above developer has been recognized to be further improved in the storage stability of the recorded image especially under the humid condition, and also in the thermal resistance and durability against plasticizer. SUMMARY OF THE INVENTION It is an object of the present invention to provide a developer , which, when used as a developer, provides a thermal recording medium having less blushing on the background and storage stability of the recorded image especially under the humid condition, thermal resistance and durability against plasticizer. We have found that, as a result of evaluation to find out a developer having a higher sensitivity and durability of recorded image, specific sulfonyl compounds and polyvalent metal salts thereof represented by general formula (1) below can satisfy the above requirement. where X represents a hydrogen atom or a lower alkyl group, R 1 , R 2 and R 3 , which may be equal or different, represent a hydrogen atom, halogen atom, a hydroxyl group, a lower alkyl group or a cycloalkyl group, R 4 , R 5 and R 6 , which may be equal or different, represent a hydrogen atom, halogen atom, a lower alkyl group or a cycloalkyl group, and R 7 represents a hydrogen atom or where R 4 , R 5 and R 6 are as defined above. In the definition of general formula (1) the cycloalkyl group includes preferably 3-6 carbon atoms and is most preferably the cyclohexyl group. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an infrared absorption spectrum of the compound obtained in Example 1. Fig. 2 is an infrared absorption spectrum of the compound obtained in Example 2; Fig. 3 is an infrared absorption spectrum of the compound obtained in Example 3; Fig. 4 is an infrared absorption spectrum of the compound obtained in Example 4; Fig. 5 is an infrared absorption spectrum of the compound obtained in Example 5; Fig. 6 is an infrared absorption spectrum of the compound obtained in Example 6; Fig. 7 is an infrared absorption spectrum of the compound obtained in Example 7; Fig. 8 is an infrared absorption spectrum of the compound obtained in Example 8; Fig. 9 is an infrared absorption spectrum of the compound obtained in Example 9; Fig. 10 is an infrared absorption spectrum of the compound obtained in Example 10; Fig. 11 is an infrared absorption spectrum of the compound obtained in Example 11; Fig. 12 is an infrared absorption spectrum of the compound obtained in Example 12; Fig. 13 is an infrared absorption spectrum of the compound obtained in Example 13; Fig. 14 is an infrared absorption spectrum of the compound obtained in Example 14; Fig. 15 is an infrared absorption spectrum of the compound obtained in Example 15; and Fig. 16 is an infrared absorption spectrum of the compound obtained in Example 16. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording medium characterized by comprising the sulfonyl compounds or polyvalent metal salts thereof represented by general formula (1) as a developer. In general formula (1), the lower alkyl group has 1 to 4 carbon atoms. Specific examples of the compounds represented by general formula (1) may include the following: (1) 2,4-bis(phenylsulfonyl)phenol (2) 2,4-bis(2-methylphenylsulfonyl)phenol (3) 2,4-bis(4-ethylphenylsulfonyl)phenol (4) 2,4-bis(4-bromophenylsulfonyl)phenol (5) 2,4-bis(4-chlorophenylsulfonyl)phenol (6) 2,4-bis(2,4-dimethylphenylsulfonyl)phenol (7) 2,4-bis(3,4-dimethylphenylsulfonyl)phenol (8) 2,4-bis(2,5-dimethylphenylsulfonyl)phenol (9) 2,4-bis(2,4,6-trimethylphenylsulfonyl)phenol (10) 2,4-bis(4-ethylphenylsulfonyl)phenol (11) 2,4-bis(4-isopropylphenylsulfonyl)phenol (12) 2,4-bis(4-cyclohexylphenylsulfonyl)phenol (13) 2,4-bis(phenylsulfonyl)-5-methylphenol (14) 2,4-bis(2-methylphenylsulfonyl)-5-methylphenol (15) 2,4-bis(4-methylphenylsulfonyl)-5-methylphenol (16) 2,4-bis(4-isopropylphenylsulfonyl)-5-methylphenol (17) 2,4-bis(2,4-dimethylphenylsulfonyl)-5-methylphenol (18) 2,4-bis(2,5-dimethylphenylsulfonyl)-5-methylphenol (19) 2,4-bis(phenylsulfonyl)-5-ethylphenol (20) 2,4-bis(4-methylphenylsulfonyl)-5-ethylphenol (21) 2,4-bis(4-ethylphenylsulfonyl)-5-ethylphenol (22) 2,4-bis(2,4-dimethylphenylsulfonyl)-5-ethylphenol (23) 2,4-bis(2,5-dimethylphenylsulfonyl)-5-ethylphenol (24) 2,4-bis(phenylsulfonyl)-5-isopropylphenol (25) 2-(4-methylphenylsulfonyl)-4-(phenylsulfonyl)phenol (26) 2-(4-ethylphenylsulfonyl)-4-(phenylsulfonyl)phenol (27) 2-(4-isopropylphenylsulfonyl)-4-(phenylsulfonyl)phenol (28) 2-(2,5-dimethylphenylsulfonyl)-4-(phenylsulfonyl)phenol (29) 2-(2,4-dimethylphenylsulfonyl)-4-(phenylsulfonyl)phenol (30) 2-(3,4-dimethylphenylsulfonyl)-4-(phenylsulfonyl)phenol (31) 2-(4-chlorophenylsulfonyl)-4-(phenylsulfonyl)phenol (32) 2-(4-bromophenylsulfonyl)-4-(phenylsulfonyl)phenol (33) 2-(phenylsulfonyl)-4-(4-methylphenylsulfonyl)phenol (34) 2-(phenylsulfonyl)-4-(4-ethylphenylsulfonyl)phenol (35) 2-(phenylsulfonyl)-4-(4-isopropylphenylsulfonyl)phenol (36) 2-(phenylsulfonyl)-4-(2-methylphenylsulfonyl)phenol (37) 2-(phenylsulfonyl)-4-(2,5-dimethylphenylsulfonyl)phenol (38) 2-(phenylsulfonyl)-4-(2,4-dimethylphenylsulfonyl)phenol (39) 2-(phenylsulfonyl)-4-(3,4-dimethylphenylsulfonyl)phenol (40) 2-(phenylsulfonyl)-4-(4-chlorophenylsulfonyl)phenol (41) 2-(phenylsulfonyl)-4-(4-bromophenylsulfonyl)phenol (42) 2-(4-methylphenylsulfonyl)-4-(phenylsulfonyl)-5-methylphenol (43) 2-(4-chlorophenylsulfonyl)-4-(phenylsulfonyl)-5-methylphenol (44) 2-(4-bromophenylsulfonyl)-4-(phenylsulfonyl)-5-methylphenol (45) 2-(phenylsulfonyl)-4-(methylphenylsulfonyl)-5-methylphenol (46) 2-(phenylsulfonyl)-4-(4-chlorophenylsulfonyl)-5-methylphenol (47) 2-(phenylsulfonyl)-4-(4-bromophenylsulfonyl)-5-methylphenol (48) 2-(4-methylphenylsulfonyl)-4-(phenylsulfonyl)-5-ethylphenol (49) 2-(4-chlorophenylsulfonyl)-4-(phenylsulfonyl)-5-ethylphenol (50) 2-(4-bromophenylsulfonyl)-4-(phenylsulfonyl)-5-ethylphenol (51) 2-(phenylsulfonyl)-4-(4-methylphenylsulfonyl)-5-ethylphenol (52) 2-(phenylsulfonyl)-4-(4-chlorophenylsulfonyl)-5-ethylphenol (53) 2-(phenylsulfonyl)-4-(4-bromophenylsulfonyl)-5-ethylphenol (54) 2-(4-methylphenylsulfonyl)-4-(phenylsulfonyl)-5-isopropylphenol (55) 2-(phenylsulfonyl)-4-(4-methylphenylsulfonyl)-5-isopropylphenol (56) 4,4'-dihydroxy-5-(phenylsulfonyl)diphenylsulfone (57) 4,4'-dihydroxy-5,5'-bis(phenylsulfonyl)diphenylsulfone (58) 4,4'-dihydroxy-5-(4-chlorophenylsulfonyl)diphenylsulfone (59) 4,4'-dihydroxy-5,5'-bis(4-methylphenylsulfonyl)-diphenylsulfone (60) 4,4'-dihydroxy-5,5'-bis(4-chlorophenylsulfonyl)-diphenylsulfone (61) 4,4'-dihydroxy-5,5'-bis(4-bromophenylsulfonyl)-diphenylsulfone Of the sulfonyl compounds listed above, compounds (1), (3), (5)-(8), (10)-(11), (13), (15), (19), (25)-(26), (28)-(31), (33)-(34), (37)-(40), and (56)-(57) are of more preferable. Preferable examples of metals which are used to constitute a polyvalent salts with the above compounds include: zinc, magnesium, strontium, aluminum, iron, cobalt, nickel and titanium. The most preferable metals are zinc, magnesium, aluminum, iron, nickel and titanium. Referring now to the method of preparation of sulfonyl compound, the following three reactions conducted under the presence of the Friedel-Crafts catalyst are applicable: In general formula (3), Z represents a halogen atom, and X is as defined in general formula (1). In general formula (4), R 1 , R 2 and R 3 are as defined in general formula (1). In general formula (5), Z is as defined in general formula (3), and X, R 1 , R 2 and R 3 are as defined in general formula (1). When this method is used, in general formula (1), and are same, and R 7 is a hydrogen atom. In general formula (6), X is as defined in general formula (1). In general formula (7), R 1 , R 2 and R 3 are as defined in general formula (1). But, when this method is used, general formula (1) is as defined in method (I). In general formula (8), X, R 1 , R 2 and R 3 are as defined in general formula (1). In general formula (9), m represents 1 or 2, and R 4 , R 5 and R 6 are as defined in general formula (1). In this reaction, the catalyst is selected from the Friedel-Crafts catalysts. Preferable examples of such catalysts may include iron chloride, aluminum chloride, zinc chloride and magnesium chloride. As has been mentioned above, the thermal recording medium of the present invention is characterized by that, in a thermal recording medium comprising a substrate and a thermal recording layer containing an electron donative basic dye precursor, the thermal recording layer comprises an electron receptible developer and a sensitizer, a compound represented by general formula (1) or a polyvalent metal salt thereof alone or in any combination, and a combination of at least one of the developer and at least one of diphenyl derivatives represented by general formula (2) below: where R 8 and R 9 , which may be equal or different, represent a hydrogen atom, a lower alkyl group or a lower alkylene group, and R 10 represents a hydrogen atom or straight or branched lower alkyl group, Y represents sulfonyl group, a lower alkylene group or a lower alkylidene group, and n represents 0 or 1. In the definition of general formula (2), the lower alkyl group includes 1-4 carbon atoms, the lower alkylene group includes 1-4 carbon atoms, and the lower alkylidene group includes 1-5 carbon atoms. The diphenyl derivatives represented by general formula (2) may, for example, be 2,2-bis(4-hydroxyphenyl)propane, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4,4'-dihydoxydiphenylsulfone, bis(3-aryl-4-hydroxyphenyl)sulfone, 4-hydroxy-2'-5'-dimethyldiphenylsulfone, 2-methyl-4-hydroxydiphenylsulfone. Next, a suitable combination of the compound of the present invention as a developer will be described in more detail. (1) It is preferable that the number of the compounds used in combination is 2 or 3, because a larger number than this would cause handling difficult. (2) For achieving the purpose of the present invention, the sulfonyl compound represented by general formula (1) is essential. (3) The least content of each compound is 1 part by weight, preferably 5 parts by weight or more on the basis of 100 parts by weight of the total amount of the developer. (4) As a method of blending, either one of the following methods can be applied: (a) blending the desired compounds, which have previously been pulverized, in a desired ratio; (b) blending the compounds in a desired ratio and then pulverizing the blend; and (c) preparing a blend consisting of the compounds in a desired ratio by recrystallization and then pulverizing the blend. The polyvalent metal salts used as a developer may be prepared by reacting the compound represented by general formula (1) with a soluble salt of a polyvalent metal such as zinc, magnesium, strontium, aluminum, iron, cobalt, nickel and titanium. Alternatively, the polyvalent metal may be coexistent with the compound represented by general formula (1) in a thermal recording layer in the form of oxide, hydroxide, carbonate or sulfonate. When used as a developer, the total amount of the polyvalent metal salts may preferably be 50-600 parts, more preferably 100-400 parts by weight per 100 parts by weight of the basic dye. The basic dye and the sensitizer used in the recording medium of the present invention will be described below. Examples of the basic dye may include triaryl methanes, diaryl methanes, pyridines, spiro-series compounds, rhodamine-lactam compounds, fluoranes, indolylphthalides and fluolenes. Typical compounds of the above are 3-N,N-dibutylamino-6-methyl-7-anilinofluorane, 3-N,N-diethylamino-6-methyl-7-anilinofluorane, 3-(N-isopentyl-N-ethyl)-6-methyl-7-anilinofluorane, 3-(N-cyclohexyl-N-methyl)-6-methyl-7-anilinofluorane, and 3-N,N-diethyl-6-chloro-7-anilinofluorane. These basic dyes can be used alone or in any combination for the purpose of adjusting the color of the image or polychrome thermal recording media. Examples of the sensitizer may include esters, hydrocarbons, ethers and sulfones. Typical examples are beta-naphtylbenzylether, stearic amides, 4-benzyloxybenzoic benzyl ester, oxalic dibenzyl, oxalic-di-P-methylbenzyl, bis(4-methylphenyl)carbonate, 4-benzylbiphenyl, N-terphenyl, 1,2-bis(3-metylphenoxy)ethane, 1,2-bis(phenoxy)ethane, diphenylsulfone and 3,3',4,4'-tetramethyl-diphenylethane. These sensitizers can be used alone or in any combination. Further, the amount of the sensitizers is preferably 50-800 parts, more preferably 100-400 parts by weight per 100 parts by weight of the basic dye. The thermal recording medium can be manufactured in accordance with any well known process, and there is no need to use any special process. In general, a basic dye, a developer, a sensitizer, a pigment, a metal soap, a wax, a surfactant, an antifoaming agent are dispersed in an aqueous medium containing a water soluble binder and pulverized by means of a ball mill or a sand mill into usually 3µm or less, more preferably 1.5µm or less to obtain a coating liquid. Examples of pigments may include potassium carbonate, magnesium carbonate, titanium oxide, kaolin, silica, amorphous silica and zinc oxide. Examples of metal soaps may include zinc stearate and calcium stearate. Examples of waxes may include paraffine wax, micro-crystalline wax and polyethylene wax. Examples of surfactants may include alkali metal salts of sulfosuccinic acid, alkali metal salts of alkylbenzenesulfonic acid and sodium salts of lauryl alcohol sulfonic acid esters. In the thermal recording medium of the present inventhe thermal recording layer can be formed in any well known process, and there is no limitation for the forming process. For example, the coating liquid for the thermal recording layer may be applied by means of an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater and a wire bar, and then dried. There is no limitation for the amount of the coating liquid to be applied, but a preferable amount may be 0.5-12 g/m 2 , and more preferably be 1.0-8.0g/m 2 on dry basis. The substrate is preferably a paper sheet, a plastic sheet or a synthetic paper sheet. The present invention will be more clearly understood from the following specific examples. Example 1 A 2 liter reaction vessel was charged with 309g of 1-chloro-2,4-sulfonylbenzen dichloride, 20g of benzene and 2g of anhydrous ferric chloride. The charge was heated with stirring to 150°C in a nitrogen atmosphere, into which 150g of benzene was dropped over 20 hours at the same temperature. During the dropping crystals were formed. After completion of the dropping, the reaction mixture was allowed to stand for 2 hours at the same temperature for aging, and then 500g of benzene was poured slowly. The reaction mixture was then cooled to a room temperature, and the crystals formed therein was filtered out of the mixture. The crystals were washed with 1 liter of methanol to obtain 280g of white crystal powder having a melting point of 196°C. Next, 196g of the crystal powder and 600g of 10% aqueous sodium hydroxide solution were charged into an autoclave reactor, and heated at a temperature of 200°C under a pressure of 15kg/cm 2 for 5 hours for hydrolysis. After being cooled, an amount of 10% dilute sulfuric acid was slowly dropped with stirring to bring pH 6. The crystals thus formed were filtered out, and then purified by recrystallization in n-butanol to obtain 160g of white crystal powder having a melting point of 157°C. From the results of the IR analysis, NMR analysis and elementary analysis (Table 1), it was confirmed that the product was 2,4-bis(phenylsulfonyl)phenol. Elementary Analysis Value (%) C H S Measured Value 57.6 3.8 17.0 Calculated Value (as C 18 H 14 O 5 S 2 ) 57.7 3.8 17.1 (Potassium bromide method. Same method was used in all the following Examples.) The infrared absorption spectrum of the product is shown in Fig. 1. In Figs. 1-16, the cordinates represent a rate of transmission (%) and the abscissas represent a wave number (cm -1 ). Example 2 An 1 liter reaction vessel was charged with 94g of phenol and 1g of anhydrous ferric chloride. The charge was heated with stirring to 80°C and 379g of benzensulfonyl chloride was dropped into the charge over 2 hours at the same temperature. After completion of the dropping, the reaction mixture was allowed to stand at the same temperature for 5 hours, and then heated slowly to 150°C and kept at this temperature for 24 hours for completion of the reaction. Next, the reaction liquid thus obtained was poured into 1000g of 5% aqueous sodium hydroxide solution, and the mixture was heated at 95°C for 2 hours with stirring, and then filtered. The filtrate was then slowly dropped into 1000g of 6% dilute sulfuric acid kept at 90°C with stirring, thereby to obtain crystals. The crystals were filtered out, and after washed with 1 liter of water, dissolved in 1 liter of warm methylisobutylketone, and then 100ml of water was added to wash out an oily component. The oily component was separated out, and further washed with 100ml of water two times. Then, water in the oily component was removed by azeotropy, and the remaining component was subjected to decoloring by 3g of activated carbon and 1g of activated clay. The solution thus obtained was cooled to a room temperature to obtain 310g of white crystal powder having a melting point of 157°C. From the results of the IR analysis, NMR analysis and elementary analysis (Table 2), it was confirmed that the product was 2,4-bis(phenylsulfonyl)phenol. Elementary Analysis Value (%) C H S Measured Value 57.8 3.8 17.0 Calculated Value (as C 18 H 14 O 5 S 2 ) 57.7 3.8 17.1 The infrared absorption spectrum of the product is shown in Fig. 2. Examples 3-10 The procedure of Example 2 was repeated with the exception that the compounds listed in Table 3 below were used in the given amounts in place of phenol, benzensulfonyl chloride, and methylisobutylketone used in Example 2. The results are shown in Table 4. Ex. Compound of formula (1) (g) Compound of formula (7) (g) Solvent for Recrystallization (liter) 3 phenol (94) tosyl chloride (400) methylisobutylketone (1) 4 m-cresol (108) benzenesulfonyl chloride (370) n-buthanol (1) 5 m-cresol (108) 4-isopropylbenzenesulfonylchloride (460) toluene (1) 6 m-ethylphenol (122) benzenesulfonyl chloride (370) toluene (1) 7 m-ethylphenol (122) tosyl chloride (400) toluene (1) 8 phenol (94) 2,4-dimethylbenzenesulfonylchloride (435) toluene (1) 9 phenol (94) 4-chlorobenzenesulfonylchloride (440) toluene (1) 10 phenol (94) 2,5-dimethylbenzenesulfonylchloride (435) toluene (1) (R 7 =H) in general formula (1) Yield (g) m.p. (°C) Infrared Absorption Spectrum Ex. X R 1 , R 4 R 2 , R 5 R 3 , R 6 3 H H 4-CH 3 H 340 170 3 4 CH 3 H H H 330 189 4 5 CH 3 H 4-CH(CH 3 ) 2 H 400 176 5 6 C 2 H 5 H H H 335 166 6 7 C 2 H 5 H 4-CH 3 H 300 180 7 8 H 2-CH 3 4-CH 3 H 320 105 8 9 H H 4-Cl H 380 167 9 10 H 2-CH 3 H 5-CH 3 365 161 10 The infrared absorption spectrum of each of the products are shown in Figs. 3-10. Example 11 A 2 liter reaction vessel was charged with 234g of 4-(phenylsulfonyl)phenol, 60g of tosyl chloride and 1g of anhydrous ferric chloride. The charge was slowly heated with stirring to 100°C in a nitrogen atmosphere. Generation of hydrochloric gas was weakened after conducting reaction for 5 hours, and then 150g of tosyl chloride was dropped the same temperature for 5 hours. After that, the mixture was slowly heated to 150°C and kept at this temperature for 24 hours to continue the reaction. Next, the reaction mixture thus obtained was poured into 1000g of 5% aqueous sodium hydroxide solution, and the mixture was heated at 95°C for 2 hours with stirring, and then filtered. The filtrate was then slowly dropped into 1000g of 6% dilute sulfuric acid kept at 90°C with stirring, thereby to obtain crystals. The crystals were filtered out, and after washed with 1 liter of water, dissolved in 1 liter of warm toluene, and then 100ml of water was added to wash out an toluene oily component. The oily component was separated out, and further washed with 100ml of water two times. Then, water in the oily component was removed by azeotropy, and the remaining component was subjected to decoloring by 3g of activated carbon and 1g of activated clay. The solution thus obtained was cooled to a room temperature to obtain 300g of white crystal powder having a melting point of 158°C. From the results of the IR analysis, NMR analysis and elementary analysis (Table 5), it was confirmed that the product was 2-(4-methylsulfonyl)-4-(phenylsulfonyl)phenol. Elementary Analysis Value (%) C H S Measured Value 58.8 4.2 16.6 Calculated Value (as C 18 H 14 O 5 S 2 ) 58.7 4.2 16.5 The infrared absorption spectrum of the product is shown in Fig. 11. Example 12 An 1 liter reaction vessel was charged with 25g of 4,4'-dihydoxydiphenyl sulfone, 180g of benzenesulfonyl chloride and 0.1g of anhydrous ferric chloride. The charge was slowly heated with stirring to 120°C. Generation of hydrochloric gas was weakened after conducting reaction for 24 hours and crystals were produced. The crystals were filtered out, and subjected to slurry washing using 500ml of 5% aqueous sodium hydroxide solution and further washed with 1 liter of water. The crystals were recrystallized in 500ml of a mixed solution of methanol:water=98:2 (in volume ratio) to obtain 30g of white crystal powder having a melting point of 247°C. From the results of the IR analysis, NMR analysis and elementary analysis (Table 6), it was confirmed that the product was 4,4'-(dihydroxy-5,5'-bis(phenylsulfonyl)diphenylsulfone. Elementary Analysis Value (%) C H S Measured Value 54.4 3.4 17.9 Calculated Value (as C 18 H 14 O 5 S 2 ) 54.3 3.4 18.1 The infrared absorption spectrum of the product is shown in Fig. 12. Example 13 The procedure of Example 11 was repeated with the exception that 248g of 4-(4-methylphenylsulfonyl)phenol was used in place of 234g of 4-(phenylsulfonyl)phenol, 60g of benzenesulfonyl chloride in place of 60g of tosyl chloride, and 134g of benzenesulfonyl chloride in place of 150g of tosyl chloride. The yield of the final product was 310g, and its melting point was 155°C. The infrared absorption spectrum of the product is shown in Fig. 13. From the results of analysis, it was confirmed that the product was 2-(phenylsulfonyl)-4-(4-methylsulfonyl)phenol. Example 14 The procedure of Example 11 was repeated with the exception that 60g of 4-chlorobenzenesulfonylchloride in place of 60g of tosyl chloride, and 172g of 4-chlorobenzenesulfonylchloride in place of 150g of tosyl chloride. The yield of the final product was 330g, and its melting point was 135°C. The infrared absorption spectrum of the product is shown in Fig. 14. From the results of analysis, it was confirmed that the product was 2-(4-chlorophenylsulfonyl)-4-(phenylsulfonyl)phenol. Example 15 An 1 liter reaction vessel was charged with 50g of 2,4-bis(phenylsulfonyl)phenol, 500g of water and 107g of 5% aqueous sodium hydroxide solution. The charge was stirred for 5 hours at 60°C, and then 250g of 10% aqueous solution of zinc sulfonate (septohydrated) was dropped over 2 hours. After completion of the dropping, the mixture was kept at the same temperature for 2 hours for aging, and then the crystals were crystallized out. The crystals were washed with 1 liter of water, and then dried to obtain 52.5g of white crystal powder. The product did not melt up to 250°C. From the results of the IR analysis and atomic absorption analysis, it was confirmed that the product was zinc salt of 2,4-bis(phenylsulfonyl)phenol. The infrared absorption spectrum of the product is shown in Fig. 15. Example 16 An 1 liter reaction vessel was charged with 50g of 2,4-bis(phenylsulfonyl)-5-ethylphenol, 500g of water and 99g of 5% aqueous sodium hydroxide solution and the charge was stirred for 5 hours at 60°C, and then 100g of 10% aqueous solution of magnesium chloride was dropped over 2 hours. After completion of the dropping, the mixture was kept at the same temperature for 2 hours for aging, and then the crystals were crystallized out. The crystals were washed with 1 liter of water, and then dried to obtain 50g of white crystal powder having melting point of 220°C. From the results of the IR analysis and atomic absorption analysis, it was confirmed that the product was magnesium salt of 2,4-bis(phenylsulfonyl)-5-ethylphenol. The infrared absorption spectrum of the product is shown in Fig. 16. Example 17 (Preparation of Basic Dye Dispersion) 20g of 3-N,N-dibutylamino-6-methyl-7-anilinofluorane was mixed with 80g of 5% aqueous solution of polyvinyl alcohol (trade name "PVA-117", manufactured by Kurare Co., Ltd.) and finely pulverized in a ball mill for 20 hours, thereby to obtain a dispersion of the basic dye particles having an average particle size of 0.6µm. (Preparation of Developer-Sensitizer Dispersion) 20g of 2,4-bis(4-metylphenylsulfonyl)phenol and 20g of 1,2-bis(3-methylphonoxy)ethane were finely pulverized in 5% aqueous solution of polyvinyl alcohol ("PVA-117") using a ball mill for 20 hours, thereby to obtain a dispersion of the developer-sensitizer particles having an average particle size of 0.6µm. (Preparation of Pigment Dispersion) 30g of calcium carbonate (trade name "UNIBAR 70", manufactured by Shiraishi Kogyo Co., Ltd.), 70g of water and 1g of 40% aqueous solution of sodium hexamethaphosphate were mixed together in a homogenizer with a rotation speed of 15,000rpm for 15min to obtain a pigment dispersion. (Preparation of Coating Liquid for Thermal Recording Layer) 3g of the basic dye dispersion, 6g of the developer-sensitizer dispersion, 7g of the pigment dispersion, 1.0g of 30% HYDRIN Z-7 (trade name, manufactured by Chukyo Yushi Co., Ltd.) and 15g of water were mixed together to obtain a coating liquid for a thermal recording layer. (Preparation of Thermal Recording Paper) On a substrate paper sheet the coating liquid was applied to form a thermal recording layer at 5g/cm 2 on the dry basis using a wire bar, and dried in a oven at 60°C, and then calendared to have the smoothness of 200 (the Beck method). Examples 18-35 The procedure of Example 17 was repeated with the exception that various developers listed in Table 7 below were used in place of 20g of 2,4-bis(4-metylphenylsulfonyl)phenol. The kinds and the amounts used were given in Table 7. Ex. Developer Amout Used (g) 18 2,4-bis(phenylsulfonyl)phenol 20 19 2,4-bis(2,5-dimethylphenylsulfonyl)phenol 20 20 2,4-bis(phenylsulfonyl)-5-methylphenol 20 21 2,4-bis(phenylsulfonyl)-5-ethylphenol 20 22 2-(4-methylphenylsulfonyl)-4-(phenylsulfonyl)phenol 20 23 2-(4-chlorophenylsulfonyl)-4-(phenylsulfonyl)phenol 20 24 2-(phenylsulfonyl)-4-(4-methylphenylsulfonyl)phenol 20 25 2,4-bis(phenylsulfonyl)phenol 10 2,4-bis(phenylsulfonyl)-5-methylphenol 10 26 2,4-bis(phenylsulfonyl)-5-methylphenol 10 2,4-bis(4-ethylphenylsulfonyl)-5-ethylphenol 10 27 2,4-bis(2,5-dimethylphenylsulfonyl)phenol 10 2,4-bis(phenylsulfonyl)-5-methylphenol 10 28 2,4-bis(2,5-dimethylphenylsulfonyl)phenol 10 4,4'-dihydroxy-5-(phenylsulfonyl)diphenylsulfone 10 29 2,4-bis(2,5-dimethylphenylsulfonyl)phenol 10 4,4'-dihydroxy-5,5'-bis(phenylsulfonyl)diphenylsulfone 10 30 2,4-bis(phenylsulfonyl)-5-methylphenol 10 4-hydroxy-4'-isopropoxydiphenyl sulfone 10 31 2,4-bis(2,5-dimethylphenylsulfonyl)phenol 10 2,2-bis(4-hydroxyphenyl)propane 10 32 2,4-bis(phenylsulfonyl)-5-ethylphenol 10 bis(3-aryl-4-hydroxyphenyl)sulfone 10 33 2,4-bis(2,5-dimethylphenylsulfonyl)phenol 8 2,4-bis(phenylsulfonyl)-5-methylphenol 8 4-hydroxy-4'-isopropoxydiphenyl sulfone 4 34 2,4-bis(phenylsulfonyl)phenol 10 Zn salt of 2,4-bis(phenylsulfonyl)phenol 10 35 2,4-bis(2,4-dimethylphenylsulfonyl)phenol 10 Mg salt of 2,4-bis(phenylsulfonyl)-5-ethylphenol 10 Example 36 The procedure of Example 17 was repeated with the exception that a mixture of equal amount on the weight basis of developer-sensitizer dispersions obtained in Examples 17 and 20, respectively, was used. Example 37 The procedure of Example 17 was repeated with the exception that 20g of a mixture of 2,4-bis(4-metylphenylsulfonyl)phenol and 2,4-bis(phenylsulfonyl)-5-methylphenol in the ratio of 50:50 on the weight basis. Comparative Examples 1 The procedure of Example 17 was repeated with the exception that 20g of 2,2-bis(4-hydorxyphenyl)propane was used, in place of 20g of 2,4-bis(4-metylphenylsulfonyl)phenol. Comparative Examples 2 The procedure of Example 17 was repeated with the exception that 10g of 2,2-bis(4-hydorxyphenyl)propane and 10g of 4-hydroxy-4'-isopropoxydiphnylsulfone were used, in place of 20g of 2,4-bis(4-methylphenylsulfonyl)phenol. The thermal recording paper sheets obtained in Examples 17-37 and Comparative Examples 1-2 were subjected to a printing test using a facsimile sold under the trade name "FF1700RX" in its copy mode. Also, the following tests were conducted for evaluating ing the performance of the thermal recording paper sheets under the condition below: Print Density: measured by Macbeth Densitometer Thermal Resistance: Background: measured by the naked eye after 24 hours at 60°C according to the following criterion: O: no change Δ : slight coloring ×: significant coloring Printing: measure the percentage of the print density retention after 24 hours from printing at 60°C Print Density Retention (%) = {(Print Density after 24 hrs) / (Density immediately after printing)} x 100 Anti-humidity: Background: measuring background blush of the not printed sheets stored for 24 hrs in 90% humidity and represented according to the standards of the background blush test. Prints: measuring the percentage of the print density retention of the printed paper sheets stored for 24 hrs in 90% humidity. Anti-plasticizer Property: measured according to the percentage of the retention for the thermal resistance under the condition that the sheets were wound on the outer periphery of a glass bottle, wrapping the wound sheets with three layers of a wrap ("HIWRAP V-450" manufactured by Mitsui Toatsu Kagaku Co., Ltd.) and kept 24 hrs at 40'C. Heat Resistivity Anti-humidity Durability against Plasticizer (%) Ex. Density Background Stain Print Retention (%) Background Stain Print Retention (%) 17 1.32 ○ 92 ○ 99 68 18 1.35 ○ 98 ○ 99 82 19 1.32 ○ 93 ○ 99 74 20 1.33 ○ 89 ○ 96 70 21 1.33 ○ 96 ○ 99 76 22 1.35 ○ 99 ○ 99 81 23 1.30 ○ 92 ○ 95 70 24 1.35 ○ 99 ○ 99 80 25 1.34 ○ 99 ○ 99 78 26 1.34 ○ 99 ○ 99 75 27 1.35 ○ 99 ○ 99 72 28 1.30 ○ 99 ○ 99 85 29 1.30 ○ 99 ○ 99 95 30 1.32 ○ 95 ○ 95 68 31 1.32 ○ 92 ○ 94 60 32 1.32 ○ 99 ○ 99 72 33 1.36 ○ 99 ○ 99 70 34 1.30 ○ 99 ○ 99 94 35 1.30 ○ 99 ○ 99 93 36 1.34 ○ 99 ○ 99 75 37 1.34 ○ 99 ○ 99 75 Comparative Example 1 1.30 ▵ 63 ▵ 65 10 2 1.32 X 70 X 75 20 As clearly understood from Table 8, the thermal recording media of the present invention is superior in developing property, and has less background blush with lapse of time, the stability of retaining the recorded image under high temperature and/or high humidity condition, and also a high anti-plasticizer property.

Claims: A sulfonyl compound and a polyvalent metal salt thereof represented by general formula (1) below: where X represents a hydrogen atom or a lower C 1-4 alkyl group, R 1 , R 2 and R 3 , which may be equal or different, represent a hydrogen atom, halogen atom, a hydroxyl group, a lower C 1-4 alkyl group or a cycloalkyl group, R 4 , R 5 and R 6 , which may be equal or different, represent a hydrogen atom, halogen atom, a lower C 1-4 alkyl group or a cycloalkyl group, and R 7 represents a hydrogen atom or where R 4 , R 5 and R 6 are as defined above. The sulfonyl compound and a polyvalent metal salt thereof according to claim 1, which are any one selected from 2,4-bis(phenylsulfonyl)phenol, 2,4-bis(2-methylphenylsulfonyl)phenol, 2,4-bis(4-ethylphenylsulfpnyl)phenol, 2,4-bis(4-chlorophenilsulfonyl)phenol, 2,4-bis(2,4-dimethylphenylsulfonyl)phenol, 2,4-bis(3,4-dimethylphenylsulfonyl)phenol, 2,4-bis(2,5-dimethylphenylsulfonyl)phenol, 2,4-bis(4-isopropylphenylsulfonyl)phenol, 2,4-bis(phenylsulfonyl)-5-methylphenol, 2,4-bis(4-methylphenylsulfonyl)-5-methylphenol, 2,4-bis(phenylsulfonyl)-5-ethylphenol, 2,4-bis(4-methylphenylsulfonyl)-5-ethylphenol, 2-(4-methylphenylsulfonyl)-4-(phenylsulfonyl)phenol, 2-(4-ethylphenylsulfonyl)-4-(phenylsulfonyl)phenol, 2-(2,5-dimethylphenylsulfonyl)-4-(phenylsulfonyl)phenol, 2-(2,4-dimethylphenylsulfonyl)-4-(phenylsulfonyl)phenol, 2-(3,4-dimethylphenylsulfonyl)-4-(phenylsulfonyl)phenol, 2-(4-chlorophenylsulfonyl)-4-(phenylsulfonyl)phenol, 2-(phenylsulfonyl)-4-(4-methylphenylsulfonyl)phenol, 2-(phenylsulfonyl)-4-(4-ethylphenylsulfonyl)phenol, 2-(phenylsulfonyl)-4-(2,5-dimethylphenylsulfonyl)phenol, 2-(phenylsulfonyl)-4-(2,4-dimethylphenylsulfonyl)phenol, 2-(phenylsulfonyl)-4-(3,4-dimethylphenylsulfonyl)phenol, 2-(phenylsulfonyl)-4-(4-chlorophenylsulfonyl)phenol, 4,4'-dihydroxy-5-(phenylsulfonyl)diphenylsulfone and 4,4'-dihydroxy-5,5'-bis(phenylsulfonyl)diphenylsulfone. A developer for a thermal recording medium using a developing reaction of an electron donative basic dye precursor and an electron receptive developer, said developer comprising at least one selected from the sulfonyl compounds represented by general formula (1) and the polyvalent metal salts thereof. The thermal recording medium comprising a thermal developer layer containing therein the developer according to claim 3. A developer for a thermal recording medium using a developing reaction of an electron donative basic dye precursor and an electron receptive developer, said developer comprising at least one selected from the sulfonyl compounds represented by general formula (1) and the polyvalent metal salts thereof, and at least one selected from the diphenyl derivatives represented by general formula (2) below: where R 8 and R 9 , which may be equal or different, represent a hydrogen atom, a lower C 1-4 alkyl group or a lower alkylene group, and R 10 represents a hydrogen atom or straight or branched lower C 1-4 alkyl group, Y represents sulfonyl group, a lower C 1-4 alkylene group or a lower lower C 1-5 alkylidene group, and n represents 0 or 1. The developer for a thermal recording medium according to claim 5 wherein the diphenyl derivatives represented by general formula (2) is one selected from 2,2-bis(4-hydroxyphenyl)propane, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4,4'-dihydoxydiphenylsulfone, bis(3-aryl-4-hydroxyphenyl)sulfone, 4-hydroxy-2'-5'-dimethyldiphenylsulfone and 2-methyl-4-hydroxydiphenylsulfone. The thermal recording medium comprising a thermal developer layer containing therein the developer according to claim 5.

Inventors: KAWABATA EIJI, ODA SHIGERU, SAITO TORANOSUKE, KAWABATA, EIJI, ODA, SHIGERU, SAITO, TORANOSUKE, Kawabata, Eiji, c/o Sanko Kaihatsu Kagaku, Oda, Shigeru, c/o Sanko Kaihatsu Kagaku, Saito, Toranosuke, c/o Sanko Kaihatsu Kagaku
Applicants: SANKO KAIHATSU KAGAKU KENK, SANKO KAIHATSU KAGAKU KENKYUSHO
Application year: 1995
Main classification: C07C317
IPC codes: C07C317, B41M5