NOVELTY - A spirobenzopyran compound and its derivatives are new.    USE - The invention is useful for an article, e.g. display elements, photochromic filters, photo switches, photosensitive drums, recording elements, solar batteries, lenses, cosmetics, and fibers or optical elements (all claimed). It is also useful in paper money or cards for preventing counterfeit forgeries, decorative articles, light stabilizers, optical disks, or optical recording media.    ADVANTAGE - The invention exhibits fast color change by light as well as high thermal stability and processability.    DETAILED DESCRIPTION - A spirobenzopyran compound of formula (1) and its derivatives are new.    R1 = 1-22C alkyl or alkenyl, or Ph or phenylalkyl (where the alkyl, alkenyl and phenyl groups may be substituted with a functional group, e.g. hydroxyl, halide, glycidoxy (sic), amine, vinyl, epoxy (meth)acryl, amino or mercapto;    R2, R3 = H, halo, cyano, substituted amino, nitro, or 1-10C alkyl or alkoxy groups which may be substituted;    R4 = H, hydroxy, -R1 or -OR1 group, or -R5)n-Z;    R5 = 1-22C alkylene which may be substituted and may contain in its carbon chain hetero atom(s) from C, S or N;    Z = functional group, e.g. hydroxyl, halide, glycidoxy, amine, vinyl, epoxy, (meth)acryl, amino, or mercapto;    n = 0-20;    X = divalent linking group and -CO-, -S-, -SO2-, CC-, -O-, -C(R6)2-, -C(R6)=C(R6)-, -N=N- or NR5-; and    R6 = substituents defined for R1-R3    INDEPENDENT CLAIMS are included for:    (a) a method of preparing the spirobenzopyran compound (1) and its derivatives, comprising reacting a carbonyl salicyl aldehyde of formula (2) or its derivatives with an indoline of formula (3) or its derivatives, where the substituents have the same meanings as defined above;    (b) a spirobenzopyran group-containing polymer, comprising units of formula (1a) derived from the compound (1);    (c) a method of preparing the spirobenzopyran group-containing polymer, comprising polymerizing by either heat curing or light curing in the presence of an initiator and in the presence or absence of a solvent, a spirobenzopyran monomer of formula (1a) and as a comonomer, unsaturated functional group-containing monomer from compounds of formula (200): R1-C(C(R1)2)-C(O)-O-R4 or compounds of formula (300): R1-C(R3)=C(R1)2;    (d) a composition, comprising spirobenzopyran group-containing monomer(s) (1), a solvent or solvents, an optional polymer, or their mixtures;    (e) a thin film obtained by coating to a support the composition comprising spirobenzopyran group-containing monomer(s) (1); and    (f) a composition, comprising spirobenzopyran group-containing polymer(s) (1a), a solvent or solvents, an optional monomer, or their mixtures.    R4 (for formula (1a)) = 1-22C alkylene or alkyleneoxy which may contain in its carbon chain hetero atom(s) from O, S or N (where the alkylene portion is capable of being substituted with substituent(s) from 1-6C alkyl, alkenyl, hydroxyl, halide, glycidoxy, amine, vinyl, epoxy, (meth)acryl, amino or mercapto;    Z = OH, halide, or a group having unsaturated linkage; and    R1-R4, X, Z = as defined in formula (1a).