| 摘要 |
<p>Disclosed is a polyester film having excellent optical properties, which is advantageous in cost. When the polyester film is used as a member for optical products, particularly as a base for a diffusion sheet, prism sheet, composite sheet or lens sheet of a backlight for an LCD, the film exhibits high luminance, and is capable of providing a bright and clear high-quality image, while being free from optical defects due to crystallized material. Specifically disclosed is a biaxially stretched polyester film which is characterized in that a polyester layer containing 1-20% by weight of a copolymerized polyester, wherein 75-90% by mole of the dicarboxylic acid content is composed of terephthalic acid, 10-25% by mole of the dicarboxylic acid content is composed of 2,6-naphthalene dicarboxylic acid, 20-50% by mole of the glycol content is composed of 1,4-butanediol and 50-80% by mole of the glycol content is composed of ethylene glycol, and 80-99% by weight of a polyethylene terephthalate is formed on both sides of another polyester layer.</p> |
