TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The inorganic oxide is alumina, silica, stannic oxide or magnesium oxide, and thickness of inorganic oxide thin film is 2-1000 nm.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The thermoplastic polymer is polytrimethylene terephthalate, blends of polytrimethylene terephthalate and polyethylene terephthalate, or polyethylene-vinyl acetate. The outer layers of polytrimethylene terephthalate and/or middle layer of polytrimethylene terephthalate have: a crystallinity of 30-50%; a glass transition temperature of 45-70 degrees C; a tensile strength of 60-70 MPa; a flexural modulus of 2.4-3 GPa; a notched impact strength of 40-55 J/m; a specific gravity of 1300-1400 kg/m3; and a 14-day moisture absorption rate of less than or equal to 0.15%. The outer layers of polytrimethylene terephthalate are made of a blend of polytrimethylene terephthalate with other thermoplastic polyesters. The content of the thermoplastic polyesters is the polytrimethylene terephthalate (less than 30 wt.%, preferably 8-15 wt.%). The thermoplastic polyesters are polyethylene terephthalate, polybutylene terephthalate, polyethylene 2,6-naphthalate, poly(1,4-cyclohexylene-dimethylene terephthalate), or polyethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate. The two outer layers of polytrimethylene terephthalate have the same or different thickness of 10-500 (preferably 20-200) microns. The middle layer is made of polytrimethylene terephthalate which is different from the polytrimethylene terephthalate in the outer layers, and the middle layer contains polyethylene terephthalate at 0-30 wt.% of the polytrimethylene terephthalate. (I) has a thin film of an inorganic oxide on the surface of the middle layer of polytrimethylene terephthalate and/or one or both of the outer layers of polytrimethylene terephthalate. In (I), at least one of the outer layers of polytrimethylene terephthalate and the middle layer contains: flame retardants, whiteners, UV absorbers or antistatic agents; and titanium dioxide comprising polytrimethylene terephthalate film (0.2-40 wt.%). The middle layer has a thickness of 10-500 microns. The middle layer between the two outer layers of polytrimethylene terephthalate is made of polyethylene-vinyl acetate, and the content of the vinyl acetate is 3-6 wt.% in the polyethylene-vinyl acetate.