Patent ID: 7463417

Claim:
A polarizing beam splitter comprising: a first prism having a first surface and at least two outer surfaces, and a second prism having a first surface and at least two outer surfaces, wherein the prisms exhibit a birefringence of less than 1×10 −6 ; and an polarizing layer having a pass axis disposed between said first surfaces of the first and second prisms, wherein at least one prism comprises a cured composition comprising a) 50 to 99 parts by weight of an oligomer having a plurality of pendent, free-radically polymerizable functional groups and a T g of ≧20° C.; b) 1 to 50 parts by weight of a free-radically polymerizable crosslinking agent and/or a diluent monomer, and c) 0.001 to 5 parts by weight of a photoinitiator, based on 100 parts by weight of a) and b); wherein said oligomer comprises polymerized monomer units comprising: a) 50 to 99 parts by weight of (meth)acryloyl monomer units homopolymerizable to a polymer having a glass transition temperature ≧20° C., b) 1 to 50 parts by weight of monomer units having a pendent, free-radically polymerizable functional group; and c) less than 40 parts by weight of monomer units homopolymerizable to a polymer having a glass transition temperature <20° C., based on 100 parts by weight of a) and b).