Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1985-11-25
1987-09-15
Milestone, Norma S.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D49310
Patent
active
046940880
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE ART
The present invention relates to novel fluoran compounds. More particularly, the present invention relates to novel fluoran compounds characterized by containing a cyclohexylalkylamino group at the 6-position thereof which are useful as dye precursors used for heat-sensitive recording sheets, heat-sensitive recording sheets by applying an electric current and light-sensitive color forming recording sheets.
BACKGROUND OF THE INVENTION
Known fluoran compounds relating to the present invention are found in Examined Japanese Patent Publication No. 23204/76, No. 29180/76, No. 52759/81 and Unexamined Japanese Patent Publication No. 162690/81. The fluoran compounds disclosed in these gazettes are used as color formers (dye precursors) for heat-sensitive recording sheets, heat-sensitive recording sheets by applying an electric current, pressure-sensitive copying paper, etc.
However, the heat-sensitive recording sheets using these fluoran compounds as color formers requires a high temperature necessary to obtain a color density of 1.0, namely, requires a great consumption energy for attaining a practical color density. In addition, the fluoran compounds encounter disadvantages in moisture resistance, decolorization, oil resistance, resistance to fogging in the background, etc.
DISCLOSURE OF THE INVENTION
As a result of extensive investigations with an attempt to improve the above-described disadvantages, the present inventors have found that novel fluoran compounds having a cyclohexylalkylamino group at the 6-position thereof are colorless or pale color solids in the air but form colors of black hue upon contact with acidic substances and efficiencies as heat-sensitive recording sheets can be markedly improved by the use of these compounds.
That is, the present invention are directed to a fluoran compound represented by the following general formula (I): ##STR2## wherein R.sub.1 represents a straight or branched alkyl group having 1 to 8 carbon atoms, a cyclohexylalkyl group, a cyclic alkyl group, a phenyl group which may be substituted, an alkoxyalkyl group, a benzyl group which may be substituted or a hydrogen atom; R.sub.2 represents a hydrogen atom, a halogen atom, a lower alkyl group having 1 to 4 carbon atoms, a phenyl group which may be substituted, a benzyl group which may be substituted, a lower alkoxy group or a lower alkoxyalkyl group; R.sub.3 represents a hydrogen atom, a chlorine atom, a fluorine atom or a lower alkyl group having 1 to 4 carbon atoms; and n represents an integer of 1 to 3, which are characterized by containing a cyclohexylalkylamino group at the 6-position thereof.
The novel fluoran compounds shown by general formula (I) of the present invention may be prepared by the following process.
Diphenylamine derivatives represented by general formula: ##STR3## wherein R.sub.2 and R.sub.3 have the same significances as defined above and R.sub.4 represents a hydrogen atom, an acetyl group or a lower alkyl group, are reacted with benzophenone derivatives represented by general formula: ##STR4## wherein R.sub.1 and n have the same significances as defined above, at temperatures of 0.degree. to 80.degree. C. for several hours in the presence of sulfuric acid having a concentration of 80 to 100%. After completion of the reaction, the reaction mixture is poured into water and sodium hydroxide is added thereto to render pH 8 to 10. The precipitates are collected by filtration. Toluene and a 5 to 10% aqueous sodium hydroxide solution are added to the resulting cake. The mixture is stirred under reflux for 1 to 3 hours. The toluene layer is separated by fractionation. After washing with water, the system is concentrated. The precipitated crystals are collected by filtration. By drying the crystals, novel fluoran compounds which are slightly colored can be obtained in high purity and high yield. If necessary, the products are recrystallized from volatile organic solvents such as toluene, acetone, butyl acetate, hexane, etc.
As the condensing agents used in the present invention, t
REFERENCES:
patent: 4536220 (1985-08-01), Kondo et al.
Gonda Michihiro
Kanasugi Mikiko
Kaneko Kazuo
Suzuka Susumu
Hodogaya Chemical Co. Ltd.
Milestone Norma S.
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