To provide a surface light diffusive polyester film which is superior in heat resistance, mechanical strength, thickness accuracy, etc., makes a total light transmittance compatible with light diffusivity, suppresses the occurrence of heating curling derived from its bimetal structure and the occurrence of moire and scintillation when used in a liquid crystal display, and is superior in post-processability.
In the surface light diffusive polyester film, nab is 0.015-0.060, (1) a light diffusion layer made of a mixed composition comprising 50-99 pts.mass of a crystalline polyester and 1-50 pts.mass of an additive non-compatible with the polyester is provided, (2) a plane orientation coefficient P is 0.08-0.16. (3) a surface haze is at least 15%, (4) an internal haze is below the surface haze, (5) tensile strength is at least 100 MPa, and (6) S (3) is at least 30% and below 50%, each ratio TS/TE between four-directional strength at break TS and elongation at break TE is at least 0.6 (MPa/%) and not exceeding 2.6 (MPa/%), and a difference in thermal shrinkage rate in the width direction (HS150) is 0.1% or below.
BABA SHUNICHIRO
MATSUOKA MIKIO
NOSE KATSUHIKO
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