A polymerizable compound has a practical low melting point, excellent solubility in a general-purpose solvent, and can produce an optical film at low cost, exhibits low reflected luminance, and achieves uniform conversion of polarized light over a wide wavelength band, an optically anisotropic article. A carbonyl compound is useful as a raw material for producing the polymerizable compound. (In the formula (I), Y.sup.1 to Y.sup.8 represent C(O)O, G.sup.1 and G.sup.2 represent a C.sub.1-20 divalent linear aliphatic group, Z.sup.1 and Z.sup.2 represent a C.sub.2-10 alkenyl group that is unsubstituted, or substituted with a halogen atom, A.sup.x represents a C.sub.2-30 organic group with at least one aromatic ring, A.sup.y represents a hydrogen atom or C.sub.1-20 alkyl group, A.sup.1 represents a trivalent aromatic group, A.sup.2 and A.sup.3 represent a C.sub.3-30 divalent alicyclic hydrocarbon group, A.sup.4 and A.sup.5 represent a C.sub.6-30 divalent aromatic group or the like, and Q.sup.1 represents a hydrogen atom.) ##STR00001##

A monomer containing as a polymerizable group an acenaphthylene structure having an acid labile group of tertiary ester type attached thereto is provided as well as a polymer comprising repeat units derived from the monomer. A chemically amplified resist composition comprising the polymer has advantages including high sensitivity, high contrast, improved lithography properties, e.g., EL, LWR and profile, collapse resistance during fine pattern formation, and etch resistance after development.

A monomer containing as a polymerizable group an acenaphthylene structure having an acid labile group of tertiary ester type attached thereto is provided as well as a polymer comprising repeat units derived from the monomer. A chemically amplified resist composition comprising the polymer has advantages including high sensitivity, high contrast, improved lithography properties, e.g., EL, LWR and profile, collapse resistance during fine pattern formation, and etch resistance after development.

Provided are a vinylcyclopropane that exhibits volume expansion upon homopolymerization and that enables improved solvent solubility, a monomer composition that contains the vinylcyclopropane, a polymer of the vinylcyclopropane, a polymer composition that contains the polymer, and an article that is obtainable through curing of the monomer composition. The vinylcyclopropane is represented by general formula (I) shown below. ##STR00001##

Provided are a vinylcyclopropane that exhibits volume expansion upon homopolymerization and that enables improved solvent solubility, a monomer composition that contains the vinylcyclopropane, a polymer of the vinylcyclopropane, a polymer composition that contains the polymer, and an article that is obtainable through curing of the monomer composition. The vinylcyclopropane is represented by general formula (I) shown below. ##STR00001##

An onium salt monomer containing an aromatic sulfonic acid anion having a vinyl-substituted aromatic ring is provided as well as a polymer comprising repeat units derived from the monomer. A chemically amplified resist composition comprising the polymer has advantages including high sensitivity, high contrast, improved lithography properties, e.g., EL, LWR, CDU and DOF, collapse resistance during fine pattern formation, and etch resistance after development.

An onium salt monomer containing an aromatic sulfonic acid anion having a vinyl-substituted aromatic ring is provided as well as a polymer comprising repeat units derived from the monomer. A chemically amplified resist composition comprising the polymer has advantages including high sensitivity, high contrast, improved lithography properties, e.g., EL, LWR, CDU and DOF, collapse resistance during fine pattern formation, and etch resistance after development.

Provided are a vinylcyclopropane that exhibits volume expansion upon homopolymerization and that enables improved solvent solubility, a monomer composition that contains the vinylcyclopropane, a polymer of the vinylcyclopropane, a polymer composition that contains the polymer, and an article that is obtainable through curing of the monomer composition. The vinylcyclopropane is represented by general formula (I) shown below.

##STR00001##

Provided are a vinylcyclopropane that exhibits volume expansion upon homopolymerization and that enables improved solvent solubility, a monomer composition that contains the vinylcyclopropane, a polymer of the vinylcyclopropane, a polymer composition that contains the polymer, and an article that is obtainable through curing of the monomer composition. The vinylcyclopropane is represented by general formula (I) shown below.

##STR00001##

Provided is a positive photoresist composition excellent in terms of heat resistance. A radically curable compound is represented by a general formula (1) below (where R.sup.1, R.sup.2, and R.sup.3 each independently represent an alkyl group having 1 to 8 carbon atoms; m and n each independently represent an integer of 1 to 4; p represents an integer of 0 to 4; X, Y, and Z each independently represent an acryloyloxy group, a methacryloyloxy group, or a hydroxy group, and at least one of X, Y, and Z represents an acryloyloxy group or a methacryloyloxy group; and t represents 1 or 2). ##STR00001##