Abstract: A photopolymerization sensitizer may not cause problems of dusting or coloring of a cured product due to bleeding of additives such as the photopolymerization sensitizer on the surface, e.g., by blooming at the time of photo-curing or during storage of the cured product, and which provides a practically sufficient photo-curing rate. A 9,10-bis(alkoxycarbonylalkyleneoxy)anthracene compound having ester groups, of formula (I): wherein A is a C1-20 alkylene group, optionally branched by an alkyl group, R is a C1-20 alkyl group, optionally branched by the alkyl group, the C1-20 alkyl group optionally being a cycloalkyl group or a cycloalkylalkyl group, and X and Y are independently a hydrogen, a C1-8 alkyl group, or a halogen.

Abstract: Compactness is enhanced while retaining the performance, noise deadening characteristic and engine output. The ratio of the distance, a, from a gas outlet end, p, of an exhaust pipe to an inner wall of a rear partition wall to an inside diameter ∅A of the exhaust pipe is set in a relation of 0.6≦(a/∅A)<1.2, while the ratio of the distance, b, from a gas inlet end, q, of a tail pipe to an inner wall of a front partition wall to an inside diameter ∅B of the tail pipe is set in a relation of 0.4≦(b/∅B)<1.2, to afford a silencer having an optimum combination of engine output characteristic and compactness while retaining a noise deadening effect.