PURPOSE: To obtain a polyester sheet having a specific thickness, fast impact strength, dependence of fast impact strength on thickness and light transmittance, excellent in transparency, impact resistance, safety, solvent resistance, appearance, glare-proof property and cost performance and useful for window plate, illumination cover, lens, etc.

CONSTITUTION: This sheet has 0.5-30mm thickness (t), ≥1000N fast impact strength (FI), ≥50ON/mm dependence (FI/t) of fast impact strength on thickness and ≥60% light transmittance. The sheet is a polyester sheet, in which ≥80mol% of a recurring structure is composed of a ethylene terephthalate unit, having 110-2OO°C crystallization temperature in raising temperature or a polyester sheet containing 0.5-10wt.% cyclohexanedimethanol and 0.5-5.0wt.% diethylene glycol and having 0.6-1.1dl/g intrinsic viscosity.