Piperidine derivatives

Disclosed is a piperidine derivatives of a formula: wherein: R indicates a hydrogen atom or a group where R is an alkyl, alkylene or arylene group capable of having 1 to 4 carboxylic group; R indicates a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an acyl group having 2 to 7 carbon atoms, or an arylalkyl group having 7 to 10 carbon atoms; R and R ' respectively indicate a hydrogen atom, or an alkyl group having 1 to 4 carbon atoms; R and R in combination indicate a group =CH-R , or R indicates a hydrogen atom and R indicates either -CH2-R wherein R is a substituted or non-substituted phenyl group or a substituted or non-substituted cyclohexyl group the substituent being an alkyl having 1 to 4 carbon atoms, or a 2-furyl group or a tetrahydrofuryl group; and n indicates an integer of 1 to 4. The piperidine derivatives are improved photostabilizer to various organic materials including poly- alpha -olefins with least breeding out tendency.