| 摘要 |
PURPOSE:To provide the titled material composed of a copolymer containing a specific recurring unit and having a reduced viscosity falling within a specific range, having excellent heat-resistance and mechanical strength and improved fluidity and photoelastic coefficient. CONSTITUTION:The objective material for optical instruments is composed of a copolymer containing the recurring unit of formula I (R<1> and R<2> are 1-5C alkyl, 1-5C alkoxy, aryl, aryloxy or halogen; X is 1-3C alkylene, 2-3C alkylidene, O, S, carbonyl, sufinyl or sulfonyl; l and m are 0-4; n is 0 or 1) and the recurring unit of formula II, and having a reduced viscosity [eta] of 0.3-1.5dl/g (at 20 deg.C as 0.5g/dl methylene chloride solution), wherein the molar fraction of the recurring unit of formula I is 5-50%. It can be produced e.g. by producing a polycarbonate oligomer by the reaction of the 2,2'-dihydroxy compound of formula III with bisphenol A and phosgene and carrying out the polycondensation of the oligomer in a solvent such as methylene chloride, in the presence of a catalyst, an alkali and a molecular weight regulator, etc.
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