Patent ID: 7041344

Claim:
A biaxially oriented polyester film for a light-diffusing plate, which film comprises: (1) an aromatic polyester whose main recurring unit is ethylene-2,6-naphthalene dicarboxylate, and has (2) a heat shrinkage in each of two directions perpendicular to each other along the surface of the film of not higher than 0.3% when heated under no load at 105° for 30 minutes, (3) a dimensional change in each of the two directions perpendicular to each other along the surface of the film, which is measured under a load of 0.37 MPa per the cross section of the film within a temperature range of 30 to 150° C., of not higher than 1.0%, (4) a density of not lower than 1.350 g/cm 3 , (5) a total light transmittance of not lower than 87%, (6) a haze value of lower than 1.5%, and (7) a thickness of 50 to 130 μm.