Abstract: The essence of the present invention lies in an optical sheet made of transparent resin having a visible light transmittance of not less than 80%, a glass transition temperature of not lower than 150° C. and a thickness of from 0.2 to 1.5 mm, which exhibits a birefringence index of not higher than 15 nm, a surface roughness Ra of not more than 0.1 &mgr;m and an impact strength of not less than 600 gf·cm as calculated in terms of dropping ball breakdown energy determined by Du Pont process impact resistance test.

Abstract: A porous film or sheet including a resin composition mainly of an ultra-high molecular weight polyethylene having a viscosity-average molecular weight of not less than 500,000, and having a thickness of 10 to 100 .mu.m, an air permeability of 20 to 2,000 sec/100 cc, a porosity of 15 to 80%, a pin puncture strength (per 25 .mu.m of film thickness) of not less than 120 g, a thermal-shut down temperature of 90.degree. to 150.degree. C. and a heat puncture temperature of not less than 160.degree. C., and a process for producing the same.

Abstract: This invention provides an extensible film or sheet comprising 100 to 60 parts by weight of an ethylene copolymer having a density of less than 0.910 g/cm.sup.3 and 0 to 40 parts by weight of a linear polyethylene having a density of 0.910 to 0.945 g/cm.sup.3, specified by the following properties:1) film blocking as expressed by 180.degree. peel strength is 60 g/25 mm or less;2) tensile elongation is 750% or more;3) Elmendorf tear strength is 30 kg.cm/cm.sup.2 or more; and4) 1% secant modulus is 20 to 2,000 kg/cm.sup.2.The film or sheet of this invention has excellent extensibility and is free from blocking. It is also excellent in flexibility and hand and drape and can be preferably used as a film for gather of disposable diapers, etc., packing sheet for disposable diapers, and the like.