Patent ID: 8759540

Claim:
An optical filter, comprising a color tone correcting squarylium compound having general formula (2): wherein at least one of R 10 , R 11 , R 12 , and R 13 is a nitro group, an alkyl group having 1 to 4 carbon atom(s), a halogen-substituted alkyl group having 1 to 4 carbon atom(s), an alkoxy group having 1 to 4 carbon atom(s) or a halogen-substituted alkoxy group having 1 to 4 carbon atom(s), and other is/are each a hydrogen atom, at least one of R 14 , R 15 , R 16 , and R 17 is a nitro group, an alkyl group having 1 to 4 carbon atom(s), a halogen-substituted alkyl group having 1 to 4 carbon atom(s), an alkoxy group having 1 to 4 carbon atom(s) or a halogen-substituted alkoxy group having 1 to 4 carbon atom(s), and other is/are each a hydrogen atom, X 1 and X 2 each represents —CR 53 R 54 —, wherein R 53 and R 54 each represents an alkyl group having 1 to 20 carbon atom(s) optionally substituted by a hydroxyl group, a halogen atom, a cyano group or a nitro group, and Y 3 and Y 4 each represents a hydrogen atom, an alkyl group having 1 to 20 carbon atom(s) optionally substituted by a hydroxyl group, a halogen atom, a cyano group or a nitro group, an aryl group having 6 to 30 carbon atoms optionally substituted by a hydroxyl group, a halogen atom, a cyano group or a nitro group, or an arylalkyl group having 7 to 30 carbon atoms optionally substituted by a hydroxyl group, a halogen atom, a cyano group or a nitro group, wherein the methylene group(s) in the alkyl groups and arylalkyl groups in the Y 3 and Y 4 may be interrupted by —O—, —S—, —CO—, —COO—, —OCO—, —SO 2 —, —NH—, —CONH—, —NHCO—, —N═CH— or —CH═CH—.