Abstract: A non-crystalline ether-imide type high purity bismaleimide composition represented by formula (I): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each represent a hydrogen atom, a halogen atom, or an alkyl group having from 1 to 4 carbon atoms; R.sup.5 represents a hydrogen atom or a methyl group; and R.sup.6 represents a hydrogen atom, a methyl group or a phenyl group. The non-crystalline bismaleimide (I) has a purity of 95 wt % or higher, a melting point of not higher than 130.degree. C., and exhibits excellent solubility in a solvent.

Abstract: An optical resin consisting essentially of a radical polymerization polymer of an ethylenically unsaturated monomer, characterized in that at least a major part of the ethlenically unsaturated monomer is an ester of 1 mole of tricyclo[5,2,1,0.sup.2,6 ]decanedimethanol with 2 moles of a mixture of acrylic acid and metharcylic acid. Because the resin is a polymer obtained from the restricted monomer as specified above, the resin possesses high thermal resistance and high heat stability as well as low hygroscopic property. Dimethanol compounds from higher Diels-Alder adducts of cyclopentadine are also used in place of the tricyclo [5,2,1,0.sup.2,6 ]decanedimthanol which is a Diels-Alder adduct of two moles of cyclopentadiene.

Abstract: A method for producing a plastic substrate having Tg of 110.degree. C. or more is disclosed, which comprises radical polymerizing a polyfunctional (meth)acrylate compound in a mold by a cast molding method, removing the resulting substrate from the mold when the glass transition temperature of the substrate reaches 10.degree. to 100.degree. C., and then post-curing the substrate. The method of the present invention can provide high quality plastic substrates with high productivity.