Abstract: A photochromic compound featuring a large fading rate to prevent a change in the color tone at the time of fading, exhibiting little color after aged, and exhibiting good durability in the photochromic property. The photochromic compound is a novel chromene compound having a substituted phenyl group at the second position of the naphthopyrane ring and an alkyl group at the fifth position thereof, and is represented by, for example, the following formula, wherein R1 is an alkyl group, R2 and R3 are substituted phenyl groups, and R4 and R5 are substituents.

Abstract: A novel fulgimide compound in which the nitrogen atom of the imide ring is substituted by a phenyl group having an electron-attracting group at least at the meta position, which is represented by the following general formula (I): ##STR1## [wherein the group (a) of the following formula is a divalent aromatic hydrocarbon group or unsaturated heterocyclic group, each of which may have a substituent(s); ##STR2## the group (b) of the following formula is a norbornylidene, bicyclo[3.3.1]nonylidene or adamantylidene group, ##STR3## and R.sup.2 is an electron-attracting group] and its use as a photochromic material.The fulgimide compound of the present invention has a higher color density in a color-developed state than conventional photochromic compounds.

Abstract: The present invention relates to a novel chromene compound having favorable photochromic properties, developing a color of a high density, exhibiting a small degree of initial color and permitting the color to quickly fade.

Abstract: The present invention relates to a novel chromene compound having favorable photochromic properties, developing a color of a high density, exhibiting a small degree of initial color and permitting the color to quickly fade.

Abstract: A fulgide or fulgimide compound having a cyclopropyl group as a substituent. The compound has excellent durability which changes reversibly in color from a colorless form to a colored form by the action of light containing ultraviolet rays such as sunlight or the light from a mercury lamp. There are also provided processes for its production, a composition comprising it, and its use.

Abstract: A fulgimide compound which reversibly changes from a colorless state into a colored state upon the action of light including ultraviolet-rays, and a composition containing this compound. The fulgimide compound is represented by the following formula (I), ##STR1## wherein the following formula (a) ##STR2## represents a divalent aromatic hydrocarbon or a divalent unsaturated heterocyclic group which may have a substituent, respectively, R.sup.1 represents a monovalent hydrocarbon group or a monovalent heterocyclic group which may have a substituent, respectively, and the following formula (b), ##STR3## represents a norbornylidene group, bicyclo[3,3,1]nonylidene group or adamantylidene group which may have a substituent, respectively, and R.sup.