TECHNOLOGY FOCUS - POLYMERS - Preferred Dimensional Change Limit: A plastic sheet preliminarily dipped in water of 40-99 degreesC and then left in air for at least one hour, should give a dimensional change of within minus 0.02% in a heating test, wherein the sheet is heated in air at 150 degreesC for 3 hours and left in air of 50% RH at 23 degreesC for an hour. Preferred Components: Said plastic sheet comprises (parts):(A) Alicyclic skeletoned bis(meth)acrylate of formula (1) (70-99);(B) Alicyclic skeletoned mono(meth)acrylate of formula (2) (1-30); and(C) Al least bifunctional mercapto compound (1-10).R1-R3 = H or methyl;m = 1 or 2;n = 0 or 1;p,q,r,s = 0, 1 or 2Preferred Properties: Tg of said sheet is at least 150 degreesC, and birefringence of up to 5nm, Plastic laminate comprises said plastic sheet and a gas barrier layer on at least one surface thereof. EXAMPLE - Example 1: (1) Plastic sheet was prepared by firstly mixing 94 parts of bis (hydroxymethyl) tricyclo (5.2.1.02.6) decane dimethacrylate, 6 parts of bis (hydroxymethyl) tricyclo (5.2.1.02.6) decane monomethacrylate, 6 parts of pentaerythritol tetraquis (beta-thiopropionate), 0.1 parts of photoinitiator 2,4,6- trimethyl benzoyl phenyl phosphine oxide, Rucilyn TPO (RTM) of BASF and 0.1 parts of benzophenone, and pouring the composition into a glass mold and irradiated with 80W/cm metal halide UV beam for 5 minutes. Then cured at 160 degreesC for 1 hour, then heat-treated at 170 degreesC for 3 hours to obtain a 0.5 mm thick sheet. Results: Light transmission = 92%. Birefringence = 1 nm. Heat resistance = 195 degreesC. (2) Formation of a gas barrier film: One side of the sheet was spattered to give 300 Angstrom thick SiOx. Oxygen permeability of the laminate = 0.4 cc/m2 per 24 hour-atm. (3) Oxide film formed by spin coating a composition of 20 parts of bis (hydroxymethyl) tricyclo (5.2.2.02.6)decane diacrylate, 2 parts of 2,4,6- trimethyl benzoyl diphenylphosphine oxide and 78 parts of a solvent propyleneglycol monomethylether acetate on the SiOx surface, then UV irradiated with 80W/cm metal halide lamp. Cured film gave: Pencil hardness = 4H. Film thickness = 2 microns. Dimensional change by heating = minus 0.005%. Dimensional change by warm water dipping = plus 0.009%. Comparative Example 1: Market available polycarbonate sheet gave: Dimensional change by heating = minus 0.085%. Dimensional change by warm water dipping = plus 0.042%.