Novel urea (thiourea) derivative and thermal recording sheet using same

Abstract: Compounds of formula (I) : wherein A is hydrogen, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy or nitro; R₁, R₂, and R₃, which may be the same or different, are each hydrogen, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy or nitro, or R₁ and R₂ form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulphur or oxygen atom; and formula (II) : wherein B is hydrogen, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy or nitro; R₁, R₂, and R₃, which may be the same or different, are each hydrogen, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy or nitro, or R₁ and R₂ form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulphur of oxygen atom; are used in the color developing layer of a thermal recording sheet which comprises a basic colorless dye and an organic color developer.

Description: This invention relates to a novel urea (thiourea) derivative and a thermal recording sheet using the compound. In general, a thermal recording sheet is obtained by mixing a normally colorless or pale colored dye precursor and a color developer such as a phenolic compound, each dispersed to fine particles and mixed, adding a binder, a filler, a sensitizer, a slip agent, and other additives to form a coating color, and coating the coating color on a substrate such as paper, synthetic paper, films, or plastics. The sheet develops a color by a momentary chemical reaction caused by heating with a thermal head, a hot stamp, a thermal pen, laser light or the like to obtain a recorded image. Thermal recording sheets are useful in a wide variety of areas such as measuring recorders, terminal printers for coinputers, facsimiles, automatic ticket vendors, and bar code labels. However, with recent diversification of these recording devices and progress towards higher performance, the quality requirements for thermal recording sheets have become higher and more difficult to achieve. For example, for high-speed recording there is a demand for thermal recording sheets which can provide a high recording density and a sharp recorded image, even with a small thermal energy. On the other hand, in view of the storage stability of the recording sheet, the thermal recording sheet is required to be superior in light resistance, weather resistance, and oil resistance. Examples of conventional thermal recording sheets include, for example, the thermal recording materials disclosed in Japanese Patent Publications 43-4160 and 45-14039. However, such conventional thermal recording materials have a low thermal response and an insufficient colour developing density when used in high-speed recording. In order to eliminate such disadvantages, high-sensitivity dyestuffs have been developed. Examples include 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane (Japanese Patent Laid-open Publication (OPI) 49-109120) or 3-dibutylamino-6-methyl-7-anilinofluorane (Japanese OPI 59-190891) as a leuco dye and, as a colour developer, 1,7-bis(4-hydroxyphenylthio)-3,5-dioxaheptane (Japanese OPI 59-106456), 1,5-bis(4-hydroxyphenylthio)-3-oxaheptane (Japanese OPI 59-116262), or 4-hydroxy-4'-isopropoxydiphenylsulfone (Japanese Patent Publication 63-46067) to achieve high-speed recording and high sensitivity. However, although these thermal recording sheets have high sensitivity they have a problem in thermal resistance in that, when they are stored at high temperatures, there tends to be a reduction in image density. Further, the low storage stability of the recorded image means that these sheets have the additional disadvantage that a considerable decrease in the image density or discoloration occurs when water or sebaceous matter contacts the color image, or the image contacts with a plasticizer (DOP, DOA, or the like) contained in wrap films such as PVC films. An object of the present invention is therefore to provide a novel urea (thiourea) derivative and a thermal recording sheet with high sensitivity and superior thermal resistance, water resistance, and oil resistance. Accordingly, the present invention provides a compound of formula (I) wherein A is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro, R 1 , R 2 and R 3 , which may be the same or different, are each hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro, or R 1 and R 2 form together with the carbon atom to which they are attached an aromatic ring; and Y is a sulfur or oxygen atom. The invention further provides a compound of formula (II): wherein B is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro; R 1 , R 2 , and R 3 , which may be the same or different, are each hydrogen, C 1 -C 4 alkyl, hydroxy or nitro; or R 1 and R 2 form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulfur atom. A C 1 -C 4 alkyl group may be straight or branched. Examples include methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl and tert-butyl. A C 1 -C 4 alkoxy group may be straight or branched. Examples include methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, sec-butoxy and tert-butoxy. The compounds of the invention may be included in the thermal recording layer of a thermal recording material, e.g. a thermal recording sheet. The present invention therefore also provides a thermal recording sheet comprising a substrate having thereon a thermal color developing layer which comprises a colorless or pale colored basic dye and an organic color developer with which the dye reacts to develop a color, wherein the thermal color developing layer comprises a compound of formula (I) as defined above or a compound of formula (IIa): wherein B is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro; R 1 , R 2 , and R 3 , which may be the same or different, are each hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro, or R 1 and R 2 form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulphur or oxygen atom. In the thermal recording sheet of the invention, the compound of Formula (I) or (IIa) is used as an organic color developer to provide a superior color developing function. Since addition of the compound to a thermal recording layer together with another organic colour developer leads to a recorded image which is stable under extreme storage conditions, the compound can also be used as a stabilizer. The compounds of formulae (I), (II) and (IIa) can be obtained by the method described in US-A-2383874 in which the nitro group of N-arylsulfonyl-nitrobenzamide or N-acylnitrosulfamide is reduced to an amino group, and then condensed with an isocyanate or thiocyanate. Specifically, examples of compounds of formulae (I), (II) and (IIa) include the following compounds, which can be used alone or in combination of two or more. N-(benzenesulfonyl)-p-(phenylureilene)benzamide, N-(4-toluenesulfonyl)-p-(phenylureilene)benzamide, N-(4-ethylphenylsulfonyl)-p-(phenylureilene)benzamide, N-(4-n-propylphenylsulfonyl)-p-(phenylureilene)benzamide, N-(4-isopropylphenylsulfonyl)-p-(phenylureilene)benzamide, N-(4-t-butylphenylsulfonyl)-p-(phenylureilene)benzamide, N-(4-methoxyphenylsulfonyl)-p-(phenylureilene)benzamide, N-(4-ethoxyphenylsulfonyl)-p-(phenylureilene)benzamide, N-(4-hydroxyphenylsulfonyl)-p-(phenylureilene)benzamide, N-(2-hydroxyphenylsulfonyl)-p-(phenylureilene)benzamide, N-(4-nitrophenylsulfonyl)-p-(phenylureilene)benzamide, N-(benzenesulfonyl)-p-(4-tolylureilene)benzamide, N-(4-toluenesulfonyl)-p-(4-tolylureilene)benzamide, N-(4-ethylphenylsulfonyl)-p-(4-tolylureilene)benzamide, N-(4-isopropylsulfonyl)-p-(4-tolylureilene)benzamide, N-(4-butylphenylsulfonyl)-p-(4-tolylureilene)benzamide, N-(4-methoxyphenylsulfonyl)-p-(4-tolylureilene)benzamide, N-(4-hydroxyphenylsulfonyl)-p-(4-tolylureilene)benzamide, N-(2-hydroxyphenylsulfonyl)-p-(4-tolylureilene)benzamide, N-(4-nitrophenylsulfonyl)-p-(4-tolylureilene)benzamide, N-(benzenesulfonyl)-p-(2-naphthylureilene)benzamide, N-(4-toluenesulfonyl)-p-(2-naphthylureilene)benzamide, N-(4-isopropylsulfonyl)-p-(2-naphthylureilene)benzamide, N-(4-methoxyphenylsulfonyl)-p-(2-naphthylureilene)benzamide, N-(4-hydroxyphenylsulfonyl)-p-(2-naphthylureilene)benzamide, N-(4-nitrophenylsulfonyl)-p-(2-naphthylureilene)benzamide, N-(benzenesulfonyl)-p-(phenylthioureilene)benzamide, N-(4-toluenesulfonyl)-p-(phenylthioureilene)benzamide, N-(4-ethylphenylsulfonyl)-p-(phenylthioureilene)benzamide, N-(4-n-propylphenylsulfonyl)-p-(phenylthioureilene)benzamide, N-(4-isopropylphenylsulfonyl)-p-(phenylthioureilene) benzamide, N-(4-methoxyphenylsulfonyl)-p-(phenylthioureilene)benzamide, N-(4-ethoxyphenylsulfonyl)-p-(phenylthioureilene)benzamide, N-(4-hydroxyphenylsulfonyl)-p-(phenylthioureilene)benzamide, N-(2-hydroxyphenylsulfonyl)-p-(phenylthioureilene)benzamide, N-(4-nitrophenylsulfonyl)-p-(phenylthioureilene)benzamide, N-(benzenesulfonyl)-p-(4-tolylthioureilene)benzamide, N-(4-toluenesulfonyl)-p-(4-tolylthioureilene)benzamide, N-(4-n-propylphenylsulfonyl)-p-(4-tolylthioureilene)benzamide, N-(4-n-methoxyphenylsulfonyl)-p-(4-tolylthioureilene)benzamide, N-(4-methoxyphenylsulfonyl)-p-(4-methylphenylthioureilene) benzamide, N-(4-hydroxyphenylsulfonyl)-p-(4-tolylthioureilene)benzamide, N-(2-hydroxyphenylsulfonyl)-p-(4-methylphenylthioureilene)benzamide, N-(4-nitrophenylsulfonyl)-p-(4-methylphenylthioureilene) benzamide, N-(benzenesulfonyl)-p-(2-naphthylthioureilene) benzamide, N-(4-toluenesulfonyl)-p-(2-naphthylthioureilene) benzamide, N-(4-methoxyphenylsulfonyl)-p-(2-naphthylthioureilene)benzamide, N-(4-hydroxyphenylsulfonyl)-p-(2-naphthylthioureilene) benzamide, N-(2-hydroxyphenylsulfonyl)-p-(2-naphthylthioureilene)benzamide, N-(4-nitrophenylsulfonyl)-p-(2-naphthylthioureilene)benzamide, N-(phenyl)-N'-(p-benzoylaminosulfonyl)phenylurea, N-(phenyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylurea, N-(phenyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylurea, N-(phenyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylurea, N-(phenyl)-N'-{p-(2-hydroxybenzoylaminosulfonyl)}phenylurea, N-(phenyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)}phenylurea, N-(phenyl)-N'-{p-(4-ethoxybenzoylaminosulfonyl)}phenylurea, N-(phenyl)-N'-{p-(4-n-propoxybenzoylaminosulfonyl)} phenylurea, N-(phenyl)-N'-{p-(4-isopropoxybenzoylaminosulfonyl)}phenylurea, N-(phenyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylurea, N-(4-toluyl)-N'-{p-(benzoylaminosulfonyl)]phenylurea, N-(4-toluyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylurea, N-(4-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylurea, N-(3-toluyl)-N'-(p-benzoylaminosulfonyl)phenylurea, N-(3-toluyl)-N'-{p-(4-toluoylaminosulfonyl)phenylurea, N-(3-toluyl)-N'-{p-(3-toluoylaminosulfonyl)phenylurea, N-(3-toluyl)-N'-{p-(2-toluoylaminosulfonyl)phenylurea, N-(3-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)phenylurea, N-(4-toluyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylurea, N-(4-toluyl)-N'-{p-(2-hydroxybenzoylaminosulfonyl)} phenylurea, N-(4-toluyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)}phenylurea, N-(4-toluyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylurea, N-(phenyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea, N-(phenyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylthiourea, N-(phenyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)} phenylthiourea, N-(phenyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)}phenylthiourea, N-(phenyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylthiourea, N-(4-toluyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea, N-(4-toluyl)-N'-{p-(3-toluoylaminosulfonyl)}phenylthiourea, N-(4-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)} phenylthiourea, N-(3-toluyl)-N'-{p-(benzoylaminosulfonyl)}phenylthiourea, N-(3-toluyl)-N'-(p-benzoylaminosulfonyl)}phenylthiourea, N-(3-toluyl)-N'-{p-(3-toluoylaminosulfonyl)}phenylthiourea, N-(3-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)} phenylthiourea, N-(4-toluyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylthiourea, N-(4-toluyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)}phenylthiourea, N-(4-toluyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)} phenylthiourea. In the present invention, the compound of Formula (1) or (IIa) can of course be used as a color developer and, in this case, one or more types of other organic color developers can be used in combination as far as the advantages of the compound of the present invention are not impaired. Other organic color developers include the following bisphenols A, 4-hydroxybenzoic acid esters, 4-hydroxyphthalic acid diesters, phthalic acid monoesters, bis-(hydroxyphenyl) sulfides, 4-hydroxyphenylarylsulfones, 4-hydroxyphenylarylsulfonates, 1,3-di[2-(hydroxyphenyl)-2-propyl]-benzenes, 4-hydroxybenzoyloxybenzoic acid esters, and bisphenolsulfones. Further, in the present invention, the above-described other organic color developers can be used alone or in combination of two or more types, and the compound of Formula (I) or (IIa) can also be used as a stabilizer. Practical examples of other organic color developers are shown below: 〈Bisphenols A〉 4,4'-Isopropylidene-diphenol (Bisphenol A) 4,4'-Cyclohexylidene-diphenol p,p'-(1-Methyl-n-hexylidene)-diphenol 1,7-Di(4-hydroxyphenylthio)-3,5-dioxaheptane 〈4-Hydroxybenzoic acid esters〉 Benzyl 4-hydroxybenzoate Ethyl 4-hydroxybenzoate Propyl 4-hydroxybenzoate Isopropyl 4-hydroxybenzoate Butyl 4-hydroxybenzoate Isobutyl 4-hydroxybenzoate Methylbenzyl 4-hydroxybenzoate 〈4-Hydroxyphthalic acid diesters〉 Dimethyl 4-hydroxyphthalate Diisopropyl 4-hydroxyphthalate Dibenzyl 4-hydroxyphthalate Dihexyl 4-hydroxyphthalate 〈Phthalic acid monoesters〉 Monobenzyl phthalate Monocyclohexyl phthalate Monophenyl phthalate Monomethylphenyl phthalate Monoethylphenyl phthalate Monopropylbenzyl phthalate Monohalogenbenzyl phthalate Monoethoxybenzyl phthalate 〈Bis-(hydroxyphenyl)-sulfides〉 Bis-(4-hydroxy-3-tert-butyl-6-methylphenyl)sulfide Bis-(4-hydroxy-2,5-dimethylphenyl)sulfide Bis-(4-hydroxy-2-methyl-5-ethylphenyl)sulfide Bis-(4-hydroxy-2-methyl-5-isopropylphenyl)sulfide Bis-(4-hydroxy-2,3-dimethylphenyl)sulfide Bis-(4-hydroxy-2,5-dimethylphenyl)sulfide Bis-(4-hydroxy-2,5-diisopropylphenyl)sulfide Bis-(4-hydroxy-2,3,6-trimethylphenyl)sulfide Bis-(2,4,5-trihydroxyphenyl)sulfide Bis-(4-hydroxy-2-cyclohexyl-5-methylphenyl)sulfide Bis-(2,3,4-trihydroxyphenyl)sulfide Bis-(4,5-dihydroxy-2-tert-butylphenyl)sulfide Bis-(4-hydroxy-2,5-diphenylphenyl)sulfide Bis-(4-hydroxy-2-tert-octyl-5-methylphenyl)sulfide 〈4-Hydroxyphenylarylsulfones〉 4-Hydroxy-4'-isopropoxydiphenylsulfone 4-Hydroxy-4'-propoxydiphenylsulfone 4-Hydroxy-4'-n-butyloxydiphenylsulfone 4-Hydroxy-4'-n-propoxydiphenylsulfone 〈4-Hydroxyphenylarylsulfonates〉 4-Hydroxyphenylbenzenesulfonate 4-Hydroxyphenyl-p-tolylsulfonate 4-Hydroxyphenylmethylenesulfonate 4-Hydroxyphenyl-p-chlorobenzenesulfonate 4-Hydroxyphenyl-p-tert-butylbenzenesulfonate 4-Hydroxyphenyl-p-isopropoxybenzenesulfonate 4-Hydroxyphenyl-1'-naphthalenesulfonate 4-Hydroxyphenyl-2'-naphthalenesulfonate 〈1,3-Di[2-(hydroxyphenyl)-2-propyl]-benzenes〉 1,3-Di[2-(4-hydroxyphenyl)-2-propyl]-benzene 1,3-Di[2-(4-hydroxy-3-alkylphenyl-2-propyl]-benzene 1,3-Di[2-(2,4-dihydroxyphenyl)-2-propyl]-benzene 1,3-Di[2-(2-hydroxy-5-methylphenyl)-2-propyl]-benzene 〈Resorcinols〉 1,3-Dihydroxy-6(α,α-dimethylbenzyl)-benzene 〈4-Hydroxybenzoyloxybenzoic acid esters〉 Benzyl 4-hydroxybenzoyloxybenzoate Methyl 4-hydroxybenzoyloxybenzoate Ethyl 4-hydroxybenzoyloxybenzoate Propyl 4-hydroxybenzoyloxybenzoate Butyl 4-hydroxybenzdyloxybenzoate Isopropyl 4-hydroxybenzoyloxybenzoate tert-Butyl 4-hydroxybenzoyloxybenzoate Hexyl 4-hydroxybenzoyloxybenzoate Octyl 4-hydroxybenzoyloxybenzoate Nonyl 4-hydroxybenzoyloxybenzoate Cyclohexyl 4-hydroxybenzoyloxybenzoate β-Phenethyl 4-hydroxybenzoyloxybenzoate Phenyl 4-hydroxybenzoyloxybenzoate α-Naphthyl 4-hydroxybenzoyloxybenzoate β-Naphthyl 4-hydroxyhenzoyloxybenzoate sec-Butyl 4-hydroxybenzoyloxybenzoate 〈Bisphenolsulfones (I)〉 Bis-(3-1-butyl-4-hydroxy-6-methylphenyl)sulfone Bis-(3-ethyl-4-hydroxyphenyl)sulfone Bis-(3-propyl-4-hydroxyphenyl)sulfone Bis-(3-methyl-4-hydroxyphenyl)sulfone Bis-(3-isopropyl-4-hydroxyphenyl)sulfone Bis-(2-ethyl-4-hydroxyphenyl)sulfone Bis-(3-chloro-4-hydroxyphenyl)sulfone Bis-(2,3-dimethyl-4-hydroxyphenyl)sulfone Bis-(2,5-dimethyl-4-hydroxyphenyl)sulfone Bis-(3-methoxy-4-hydroxyphenyl)sulfone 4-Hydroxyphenyl-2'-ethyl-4'-hydroxyphenylsulfone 4-Hydroxyphenyl-2'-isopropyl-4'-hydroxyphenylsulfone 4-Hydroxyphenyl-3'-isopropyl-4'-hydroxyphenylsulfone 4-Hydroxyphenyl-3'-sec-butyl-4'-hydroxyphenylsulfone 3-Chloro-4-hyydroxyphenyl-3'-isopropyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-butylphenyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-aminophenyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-isopropylphenyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-octylphenyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-butylphenyl-3'-chloro-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-butylphenyl-3'-methyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-butylphenyl-3'-isopropyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-butylphenyl-3'-chloro-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-butylphenyl-3'-methyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-butylphenyl-3'-isopropyl-4'-hydroxyphenylsulfone 2-Hydroxy-5-t-butylphenyl-3'-methyl-4'-hydroxyphenylsulfone 〈Bisphenolsulfones (II)〉 4,4'-Sulfonyldiphenol 2,4'-Sulfonyldiphenol 3,3'-Dichloro-4,4'-sulfonyldiphenol 3,3'-Dibromo-4,4'-sulfonyldiphenol 3,3',5,5'-Tetrabromo-4,4'-sulfonyldiphenol 3,3'-Diamino-4,4'-sulfonyldiphenol 〈Others〉 p-tert-Butylphenol 2,4-Dihydroxybenzophenone Novolac type phenolic resin 4-Hydroxyacetophenone p-Phenylphenol Benzyl 4-hydroxyphenylacetate p-Benzylphenol The basic colorless dyes used in the present invention are not specifically limited, but triphenylmethane type compounds, fluorane type compounds, fluorene type compounds, and divinyl type compounds are preferable. Typical examples of these dyes are shown below. These dyes may be used alone or in combination of two or more types. 〈Triphenylmethane type leuco dyes〉 3,3-Bis(p-dimethylaminophenyl)-6-dimethylaminophthalide [Crystal Violet Lactone] 〈Fluorane type leuco dyes (I)〉 3-Diethylamino-6-methyl-7-anilinofluorane 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilino)fluorane 3-Diethylamino-6-methyl-7-(o,p-dimethylanilino)fluorane 3-Pyrrolidino-6-methyl-7-anilinofluorane 3-Piperidino-6-methyl-7-anilinofluorane 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluorane 3-Diethylamino-7-(m-trifluoromethylanilino)fluorane 3-N-n-dibutylamino-6-methyl-7-anilinofluorane 3-N-n-dibutylamino-7-(o-chloroanilino)fluorane 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane 3-Dibutylamino-6-methyl-7-(o,p-dimethylanilino)fluorane 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluorane 3-Diethylamino-6-chloro-7-anilinofluorane 3-Dibutylamino-7-(o-chloroanilino)fluorane 3-Diethylamino-7-(o-chloroanilino)fluorane 3-Diethylamino-6-methyl-chlorofluorane 3-Diethylamino-6-methyl-fluorane 3-Cyclohexylamino-6-chlorofluorane 3-Diethylamino-benzo[a]fluorane 3-n-Dipentylamino-6-methyl-7-anilinofluorane 2-(4-Oxo-hexyl)-3-dimethylamino-6-methyl-7-anilinofluorane 2-(4-Oxo-hexyl)-3-diethylamino-6-methyl-7-anilinofluorane 2-(4-Oxo-hexyl)-3-dipropylamino-6-methyl-7-anilinofluorane 〈Fluorene type leuco dyes〉 3,6,6'-Tris(dimethylamino)spiro[fluorene-9,3'-phthalide] 3,6,6'-Tris(diethylamino)spiro[fluorene-9,3'-phthalide] 〈Fluorane type leuco dyes (II)〉 2-Methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluorane 2-Methoxy-6-p-(p-dimethylaminophenyl)aminoanilinofluorane 2-Chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluorane 2-Chloro-6-p-(p-dimethylaminophenyl)aminoanilinofluorane 2-Nitro-6-p-(p-diethylaminophenyl)aminoanilinofluorane 2-Amino-6-p-(p-diethylaminophenyl)aminoanilinofluorane 2-Diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluorane 2-Phenyl-6-metyl-p-(p-phenylaminophenyl)aminoanilinofluorane 2-Benzyl-6-p-(p-phenylaminophenyl)aminoanilinofluorane 2-Hydroxy-6-p-(p-phenylaminophenyl)aminoanilinofluorane 3-Methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluorane 3-Diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluorane 3-Diethylamino-6-p-(p-dibutylaminophenyl)aminoanilinofluorane 〈Divinyl type leuco dyes〉 3,3-Bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl) ethenyl]-4,5,6,7-tetrabromophthalide 3,3-Bis-[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl) ethenyl]-4,5,6,7-tetrachlorophthalide 3,3-Bis-[1,1-bis(4-pyrrolidinophenyl)-2-(p-methoxyphenyl) ethylen-2-yl]-4,5,6,7-tetrabromophthalide 3,3-Bis-[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl) ethylen-2-yl]-4,5,6,7-tetrachlorophthalide 〈Others〉 1,1-Bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-dinitrileethane 1,1-Bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-naphthoyleethane 1,1-Bis-[2',2',2'',2''-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-diacetylethane Bis-[2,2,2',2'-tetrakis-(p-dimethylaminophenyl)-ethenyl]-methylmalonic acid dimethyl ester. Further, as a sensitizer, a fatty acid amide such as stearamide or palmitamide; ethylene-bisamide, montan wax, polyethylene wax, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolylcarbonate, p-benzylbiphenyl, phenyl-α-naphthylcarbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, 1,2-di-(3-methylphenoxy)ethane, di(p-methylbenzyl) oxalate, β-benzyloxynaphthalene, 4-biphenyl-p-tolylether, o-xylylene-bis-(phenylether), 4-(m-methylphenoxymethyl)biphenyl, or the like can be added. The binder used in the present invention includes completely-hydrolyzed polyvinylacohol having a polymerization degree of 200 to 1900, partially-hydrolyzed polyvinylalcohol, carboxy-modified polyvinylalcohol, amide-modified polyvinylalcohol, sulfonic acid-modified polyvinylalcohol, butyral-modified polyvinylalcohol, other modified polyvinylalcohols, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, styrene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, cellulose derivatives such as ethylcellulose and acetylcellulose, polyvinylchloride, polyvinylacetate, polyacrylamide, polyacrylic acid esters, polyvinylbutyral, polystyrene, and copolymers thereof, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and cumarone resins. These polymeric substances are used by dissolving in solvents such as water, alcohol, ketone, ester, and hydrocarbon, emulsifying or dispersing to a paste form in water or other solvents, and can be used in combination according to the quality requirements. In the present invention, it is also possible to add known stabilisers based on metal salts (Ca, Zn) of p-nitrobenzoic acid or metal salts (Ca, Zn) of phthalic acid monobenzyl ester, as much as the desired effect of the present invention is not hindered. Fillers that can be used in the present invention include inorganic or organic fillers such as such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, and titanium oxide. In addition to the above, it is also possible to use release agents such as fatty acid metal salts, slip agents such as waxes, benzophenone- or triazole-based ultraviolet absorbers, water resistant agents such as glyoxal, dispersants, defoamers, antioxidants, and the like. Preferably, the colour developing layer of the thermal recording sheet of the invention further comprises a sensitiser, a binder or a filler. The amounts of the colour developer and the basic colorless dye used in the present invention and the types and amounts of other constituents are determined according to the required properties and recording adaptability, and are not specifically limited, but when the compound of formula (I) or (IIa) is used as the colour developer, it is usually preferable to use from 1 to 8 parts of the compound of formula (I) or (IIa) based on 1 part of the basic colourless dye. When the compound of formula (I) or (IIa) is used as a stabilizer, it is preferable to use 0.25 to 3 parts of the compound of formula (I) or (IIa) based on 1 part of the basic colourless dye. In the latter case it is preferable to use 1 to 8 parts of the colour developer. When the compound of formula (I) or (IIa) is used as either stabilizer or developer, the binder is typically used in an amount of 10 to 25% of the total solid. The above composition is coated on any type of substrate such as paper, synthetic paper, plastic films, non-woven fabrics, or metal foils to obtain a thermal recording sheet. In one aspect the thermal recording sheet of the present invention further comprises an overcoating layer on the thermal colour developing layer. The overcoating layer typically comprises a polymeric substance, and serves to improve storage stability. In a second aspect the thermal recording sheet of the present invention further comprises an undercoating layer beneath the thermal recording layer. The undercoating layer typically contains an organic or inorganic filler and serves to enhance storage stability and sensitivity. The organic color developer, the basic colorless dye, and the materials which are added as necessary are finely divided by a grinding machine such as a ball mill, an attriter, or a sand grinder, or by an appropriate emulsifying apparatus, to a particle diameter of less than several microns, and mixed with the binder and various additives according to purpose to obtain a coating color. The reason for the high thermal resistance, water resistance, and oil resistance of the recorded image is explained as follows. In general, a thermal recording paper comprises a basic colorless dye as an electron donor, and an organic acid substance such as phenolic compound, aromatic carboxylic acid, or organic sulfonic acid as an electron acceptor. The heat melting reaction of the basic colorless dye and the color developer is an acid-base reaction based on the donation and acceptance of electron, which forms a metastable "charge transfer complex" to obtain a colored image. At this moment, since the compound of the present invention has a so-called acidified nitrogen atom having a reduced electron density adjacent to the electron attracting group in the molecule, the chemical binding force of acid and base is enhanced and, as a result, the recorded image is stabilized by a reaction of the color developer and the leuco dye during the heat melting reaction, and the stability of the color developed image is maintained even under an environment where the recorded image is exposed to water, oil, or heat. The present invention will be described with reference to the examples. In the description, part indicates part by weight unless otherwise noted. Synthesis Example 1 Synthesis of N-(benzenesulfonyl)-p-(phenylureilene)benzamide In a 300-ml reaction flask provided with a thermometer and a stirrer, 18.5 g of p-nitrobenzoyl chloride, 15.7 g of benzenesulfonamide, 100 g of toluene, and 8 g of pyridine were charged, and reacted at 100°C for 5 hours. After the reaction, the reaction mixture was cooled, was added, and the internal temperature was decreased to 30°C to sufficiently precipitate crystals. The solution was filtered to obtain 27.2 g of N-(benzenesulfonyl)-p-nitrobenzamide. 27.2 g of the thus obtained N-(benzenesulfonyl)-p-nitrobenzamide, 270 g of water, and 5.4 g of glacial acetic acid were charged in a 1,000-ml reaction flask, 54 g of iron powder was slowly added, and a reductive reaction was carried out for 12 hours. The reaction solution was made alkaline with sodium carbonate and filtered. The transparent filtrate was acidified with acetic acid to obtain 19.8 g of N-(benzenesulfonyl)-p-aminobenzamide. 19.8 g of N-(benzenesulfonyl)-p-aminobenzamide, 50 g of 1,2-dichloromethane, and 10 g of phenylisocyanate were charged in a 300-ml reaction flask, and reacted for 6 hours at room temperature. Then, 50-ml of water was added, stirred for 1 hour, and a crystal was filtered. The crystal was recrystallized from a water-methanol mixture to obtain 24.5 go of N-(benzenesulfonyl)-p-(phenylureilene)benzamide (Formula III). Synthesis Example 2 Synthesis of N-(4-toluenesulfonyl)-p-(phenylureilene)benzamide 18.5 Grams of p-nitrobenzoyl chloride, 17.1 g of 4-toluenesulfonamide, 100 g of toluene, and 8 g of pyridine were charged in a reaction vessel, and reacted using the same procedure as in Synthesis Example 1 to obtain 26.7 g of N-(4-toluenesulfonyl)-p-(phenylureilene)benzamide as a white crystal having a melting point of 223° (Formula IV). Synthesis Example 3 Synthesis of N-(benzenesulfonyl)-p-(phenylthioureilene) benzamide 20.0 Grams of N-(4-toluenesulfonyl)-p-nitrobenzamide synthesized by the method of Synthesis Example 1 and 80 g of N,N-dimethylformamide were charged in a 300-ml with a dropping funnel and thoroughly dissolved, 12 g of phenylisothiocyanate was dropped therein and reacted for 6 hours. Then, 150 g of water and 30 g of toluene were added and thoroughly stirred to precipitate a crystal. The crystal was filtered and dissolved in methanol at room temperature, and diluted with a small amount of water to precipitate 20.5 g crystal of N-(benzenesulfonyl)-p-(phenylthioureilene) benzamide having a melting point of 170°C (Formula V). Synthesis Example 4 Synthesis of N-(4-toluenesulfonyl)-p-(phenylthioureilene) benzamide Using the same procedure as in Synthesis Example 1, 20 g of N-(4-toluenesulfonyl)-p-nitrobenzamide obtained in Synthesis Example and 12 g of phenylisothiocyanate were charged and reacted using the same procedure as in Synthesis Example 3 to obtain 23.2 g of N-(4-toluenesulfonyl-p-(phenylthioureilene)benzamide having a melting point of 175°C (Formula VI). Synthesis Example 5 (Reference) Synthesis of N-(phenyl)-N'-{p-(benzoylaminosulfonyl)}phenylurea In a reaction flask with a thermometer and a stirrer, 25 g of p-nitrobenzenesulfonamide, 18 g of benzoylchloride, 1 g of copper powder, and 100 g of toluene were charged and refluxed until evolution of hydrogen chloride gas was completely ended. The reaction mixture was then cooled to room temperature to precipitate a crystal, which was filtered. The crystal was dissolved in an aqueous sodium carbonate solution and filtered. The filtrate was neutralized with hydrochloric acid to precipitate a crystal. The crystal was filtered to obtain 30.6 g of N-(4-nitrobenzenesulfonyl)benzamide. 30.6 Grams of the N-(4-nitrobenzenesulfonyl)benzamide was reduced using the same procedure as in Synthesis Example 1 to obtain 20.4 g of N-(4-aminobenzenesulfonyl)benzamide. Further, using the same procedure as in Synthesis Example 1, it is reacted with 10 g of phenylisocyanate to obtain 21.3 g of N-(phenyl)-N'-{p-(benzoylaminosulfonyl)}phenylurea having a melting point of 231.5°C (Formula VII). Synthesis Example 6 Synthesis of N-(phenyl)-N'-{p-(benzoylaminosulfonyl)} phenylthiourea 20.0 Grams of N-(4-aminobenzenesulfonyl)benzamide obtained according to Synthesis Example 5, 12.0 g of phenylisothiocyanate, and 80 g of N,N-dimethylformamide were charged in a reaction flask, and reacted using the same procedure as in Synthesis Example 3 to obtain 18.2 g of N-(phenyl)-N'-{p-(benzoylaminosulfonyl)}phenylthiourea having a melting point of 179°C (Formula VIII). Examples for producing a thermal recording sheet of the present invention will be described. Example 1 (Test Nos. 1-31) Liquid A (color developer dispersion) Color developer (see Tables 1 and 2) 6.0 parts 10% Aqueous polyvinylalcohol solution 18.8 Water 11.2 Liquid B (dye dispersion) 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane 2.0 parts 10% Aqueous polyvinylalcohol solution 4.6 Water 2.6 Liquid C (sensitizer dispersion) 4-Biphenyl-p-tolylether 4.0 parts 10% Aqueous polyvinylalcohol solution 5.0 Water 3.0 The liquids of the above compositions were milled by a sand grinder to an average particle diameter of 1 micron, and mixed in the following ratio to obtain a coating color. Liquid A 36.0 parts Liquid B 9.2 Liquid C 12.0 Kaolin clay (50% dispersion) 12.0 The coating color was coated on one side of a 50 g/m 2 base paper to a coating amount of 6.0 g/m 2 , dried, and supercalendered to a flatness of 500 to 600 seconds to obtain a thermal recording sheet. Comparative Example 1 (Test Nos. 32-37) Liquid D (color developer dispersion) Color developer (see Table 5) 6.0 parts 10% Aqueous polyvinylalcohol solution 18.8 Water 11.2 Liquid B (dye dispersion) 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane 2.0 parts 10% Aqueous polyvinylalcohol solution 4.6 Water 2.6 Liquid C (sensitizer dispersion) 4-Biphenyl-p-tolylether 4.0 parts 10% Aqueous polyvinylalcohol solution 5.0 Water 3.0 The liquids of the above compositions were milled by a sand grinder to an average particle diameter of 1 micron, mixed in the following ratio to obtain a coating color, and treated as in Example 1 to obtain a thermal recording sheet. Liquid D 36.0 parts Liquid B 9.2 Liquid C 12.0 Kaolin clay (50% dispersion) 12.0 Example 2 (Test Nos. 38-40) Liquid E (color developer dispersion) Color developer (see Table 7) 6.0 parts 10% Aqueous polyvinylalcohol solution 18.8 Water 11.2 Liquid B (dye dispersion) 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane 2.0 parts 10% Aqueous polyvinylalcohol solution 4.6 Water 2.6 Liquid C (sensitizer dispersion) 4-Biphenyl-p-tolylether 4.0 parts 10% Aqueous polyvinylalcohol solution 5.0 Water 3.0 Liquid F (stabilizer dispersion) Stabilizer (see Table 7) 2.0 parts 10% Aqueous polyvinylalcohol solution 2.5 Water 1.5 The liquids of the above compositions were milled by a sand grinder to an average particle diameter of 1 micron, mixed in the following ratio to obtain a coating color, and treated as in Example 1 to obtain a thermal recording sheet. Liquid E 36.0 parts Liquid B 9.2 Liquid C 12.0 Liquid F 6.0 Kaolin clay (50% dispersion) 12.0 The thermal recording sheets obtained in the above Examples and Comparative Example were subjected to quality evaluation tests. The tests results are shown in Tables 1-8. Quality test results Test No. Color developer Example 1 1 (Synth. Ex. 1) N-(benzenesulfonyl)-p-(phenylureilene)benzamide 2 (Synth. Ex. 2) N-(4-toluenesulfonyl)-p-(phenylureilene)benzamide 3 (Synth. Ex. 3) N-(benzenesulfonyl)-p-(phenylthioureilene)benzamide 4 (Synth. Ex. 4) N-(4-toluenesulfonyl)-p-(phenylthioureilene)benzamide 5 N-(4-methoxyphenylsulfonyl)-p-(phenylureilene)benzamide 6 N-(2-hydroxyphenylsulfonyl)-p-(phenylureilene)benzamide 7 N-(4-toluenesulfonyl)-p-(4-tolylureilene)benzamide 8 N-(n-butylphenylsulfonyl)-p-(4-tolylureilene)benzamide 9 N-(2-hydroxyphenylsulfonyl)-p-(4-tolylureilene)benzamide 10 N-(4-toluenesulfonyl)-p-(2-naphthylureilene)benzamide 11 N-(4-hydroxyphenylsulfonyl)-p-(2-naphthylureilene)benzamide 12 N-(4-isopropylphenylsulfonyl)-p-(phenylthioureilene)benzamide 13 N-(4-hydroxyphenylsulfonyl)-p-(phenylthioureilene)benzamide 14 N-(benzenesulfonyl)-p-(4-tolylthioureilene)benzamide 15 N-(4-methoxyphenylsulfonyl)-p-(4-methylphenylthioureilene)benzamide Quality test results Test No. Color developer Example 1 16 (Synth. Ex. 5) N-(phenyl)-N'-(p-benzoylaminosulfonyl)phenylurea 17 (Synth. Ex. 6) N-(phenyl)-N'-(p-benzoylaminosulfonyl)phenylthiourea 18 N-(phenyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylurea 19 N-(phenyl)-N'-{p-(4-ethoxybenzoylaminosulfonyl)}phenylurea 20 N-(phenyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylurea 21 N-(4-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylurea 22 N-(3-toluyl)-N'-{p-(3-toluoylaminosulfonyl)}phenylurea 23 N-(4-toluyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylurea 24 N-(4-toluyl)-N'-{p-(4-nitrobenzoylaminosulfonyl)}phenylurea 25 N-(phenyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea 26 N-(phenyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylthiourea 27 N-(phenyl)-N'-{p-(4-hydroxybenzoylaminosulfonyl)}phenylthiourea 28 N-(phenyl)-N'-{p-(4-methoxybenzoylaminosulfonyl)}phenylthiourea 29 N-(4-toluyl)-N'-{p-(2-naphthoylaminosulfonyl)}phenylurea 30 N-(3-toluyl)-N'-(p-benzoylaminosulfonyl)phenylthiourea 31 N-(3-toluyl)-N'-{p-(4-toluoylaminosulfonyl)}phenylthiourea Quality test results Test No. Color developer Comparative Example 1 32 4,4'-Isopropylidenediphenol 33 4-Hydroxy-4-isopropoxydiphenylsulfone 34 Bis(4-hydroxyphenyl)acetic acid butyl ester 35 4-Hydroxy-4'-n-propoxydiphenylsulfone 36 4-Hydroxy-β-naphthalenesulfonate 37 4-Hydroxy-4'-n-butoxydiphenylsulfone Quality test results Test No. Color developer Stabilizer Example 2 38 4,4'-Isopropylidenediphenol N-(benzenesulfonyl)-p-(phenylureilene) benzamide 39 4-Hydroxy-4'-isopropoxydiphenylsulfone N-(4-toluenesulfonyl)-p-(phenylureilene) benzamide 40 Bis(4-hydroxyphenyl)acetic acid butyl ester N-(benzenesulfonyl)-p-(phenylthioureilene) benzamide Note (1): Dynamic color density: The image density recorded using the Toshiba Thermal Facsimile KB-4800 at an applied voltage of 18.03V and a pulse width of 3.2 ms was measured by a Macbeth densitometer (RD-914, an amber filter used). Note (2): Heat resistance: The thermal recording paper sample dynamic-recorded by the method of (1) was allowed to stand under a dry condition at 60°C for 24 hours, and the recorded portion was measured by the Macbeth densitometer. The retention was calculated by the following equation. Retention = image density after heat treatment untreated image density x 100 (%). Note (3): Water resistance: The thermal recording paper sample dynamic-recorded by the method of (1) was immersed in 20°C water, dried, and the recorded portion was measured by the Macbeth densitometer. The retention was calculated by the following equation. Retention = image density after water treatment untreated image density x 100 (%). Note (4): Oil resistance: The thermal recording paper sample dynamic-recorded by the method of (1) was dropped thereon with salad oil, after 10 seconds the oil was wiped, allowed to stand at room temperature for 1 hour, and the image density was measured by the Macbeth densitometer. The retention was calculated by the following equation. Retention = image density after oil treatment untreated image density x 100 (%). The thermal recording sheet of the present invention has the following advantageous effects of storage stability of the recorded image. (1) The recorded image is stable at high temperatures (heat resistance). (2) The recorded image is stable and does not discolor when contacting with water (water resistance). (3) The recorded image is stable and does not discolor when contacting with plasticizers, salad oil, vinegar, or the like (oil resistance).

Claims: A compound of formula (I): wherein A is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro; R 1 , R 2 , and R 3 , which may be the same or different, are each hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro, or R 1 and R 2 form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulphur or oxygen atom. A compound of formula (II): wherein B is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro; R 1 , R 2 , and R 3 , which may be the same or different, are each hydrogen, C 1 -C 4 alkyl, hydroxy or nitro, or R 1 and R 2 form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulphur atom. A thermal recording sheet comprising a substrate having thereon a thermal color developing layer which comprises a colorless or pale colored basic dye and an organic color developer with which the dye reacts to develop a color, wherein the thermal color developing layer comprises a compound of formula (I) as defined in claim 1 or a compound of formula (IIa) : wherein B is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro; R 1 , R 2 , and R 3 , which may be the same or different, are each hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, hydroxy or nitro, or R 1 and R 2 form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulphur or oxygen atom. A thermal recording sheet according to claim 3, wherein the compound of formula (I) or (IIa) is present in an amount of from 1 to 8 parts based on 1 part of the basic colorless dye. A thermal recording sheet according to claim 3, wherein the compound of formula (I) or (IIa) is present in an amount of from 0.25 to 3 parts based on 1 part of the basic colorless dye. A thermal recording sheet according to any one of claims 3 to 5 wherein the dye comprises one or more compounds selected from triphenylmethane type compounds, fluorane type compounds, fluorene type compounds and divinyl type compounds. A thermal recording sheet according to any one of claims 3 to 6 wherein the color-developing layer further comprises a sensitiser, a binder or a filler. A thermal recording sheet according to any one of claims 3 to 7 which further comprises an overcoating layer on the thermal color developing layer. A thermal recording sheet according to any one of claims 3 to 8 which further comprises an undercoating layer beneath the thermal recording layer.

Inventors: HAMADA KAORU, KINISHI RYOICHI, MINAKAMI RYUZO, MINAMI TOSHIAKI, NAGAI TOMOAKI, SEKINE AKIO, HAMADA, KAORU, KINISHI, RYOICHI, MINAKAMI, RYUZO, MINAMI, TOSHIAKI, NAGAI, TOMOAKI, SEKINE, AKIO, Hamada, Kaoru, c/o Res. Lab. of Product Dev., Kinishi, Ryoichi, c/o Chemical Research Lab., Minakami, Ryuzo, c/o Chemical Research Lab., Minami, Toshiaki, c/o Res. Lab. of Product Dev., Nagai, Tomoaki, c/o Res. Lab. of Product Dev., Sekine, Akio, c/o Res. Lab. of Product Dev.
Applicants: JUJO PAPER CO LTD, YOSHITOMI PHARMACEUTICAL, NIPPON PAPER INDUSTRIES CO., LTD., YOSHITOMI PHARMACEUTICAL INDUSTRIES, LTD.
Application year: 1995
Main classification: C07C311
IPC codes: C07C335, C07C311, B41M5