Patent ID: 7357973

Claim:
A flat plate made of a cycloolefin polymer comprising at least 30% by weight, based on the cycloolefin polymer, of repeating units (A) having an alicyclic structure; said repeating units (A) comprising at least 30% by weight, based on the repeating units (A), of repeating units (A-i) having no norbornane structure and more than 0% but not more than 70% by weight of repeating units (A-ii) having a norbornane structure, represented by the following formula (4): wherein R 35 through R 48 are independently selected from the group consisting of a hydrogen atom, hydrocarbon, hydroxyl, ester, alkoxy, cyano, imido and silyl groups, a halogen atom, and hydrocarbon groups having a functional group as substituent selected from the group consisting of hydroxyl, ester, alkoxy, cyano, imido and silyl groups; e is an integer of 1 to 3; and the chemical symbol of in formula (4) represents a carbon-carbon single or double bond; and said cycloolefin polymer having a weight average molecular weight of 5,000 to 50,000, wherein the phase difference of the flat plate, as measured in the direction of the thickness of the plate, is not larger than 100 nm.