Transition metal-spirobenzopyran complex, a production process therefor and a photochromic material comprising the complex
Patent 5288592 Issued on February 22, 1994. Estimated Expiration Date: 
November 12, 2012. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
November 12, 2012. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3299079 3510308 3923524 Synthesis of photochromic indolinespiropyrans Photosensitive compositions for direct positive color photography Color image forming method and particulate developer for developing electrostatic latent image Patent #: 5045420 InventorAssigneeApplicationNo. 938044 filed on 11/12/1992US Classes:430/345, Spiropyran dye or dye former252/586, Displaying color change430/962, RADIATION-CHROMIC COMPOUND548/402, Heavy metal or aluminum containing548/409Both rings which form the spiro are hetero ringsExaminersPrimary: Bowers, Charles L. Jr.Assistant: McPherson, John A. Attorney, Agent or FirmForeign Patent References
International ClassesG03C 001/735C07D 209/96 Foreign Application Priority Data1991-03-13 JPAbstractThe object of the invention is to provide a novel compound exhibiting stable photochromism.The invention is directed to a transition metal-spirobenzothiopyran complex of the general formula ##STR1## wherein R1 for example be C1-20 alkyl; R2, R3, R4, R5, R6, R7 and R8 independently may mean hydrogen; Y means O or S; M may for example be Cr, and a process for producing the complex.Other References
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