Patent ID: 8197931
Filing Date: 2012-06-12
Classification: B32B,C08J,G02B,G02F,Y10T

Abstract:
1. A white polyester film containing voids, wherein a resin constituting the film has a layer (layer A) formed by using a polyester resin and a cyclic olefin copolymerized resin, and wherein a void ratio taken in a cross-section of the layer is more than 25% and 75% or less and the average particle size of the cyclic olefin copolymerized resin in the film is 0.1 μm more and 3 μm or less and a variation coefficient of particle size of the cyclic olefin copolymerized resin in said layer A is 1 or less, wherein a glass transition temperature of said cyclic olefin copolymerized resin is 120° C. or higher and 230° C. or lower, and wherein said layer A has a content of the polyester resin of 37% by weight or more and 76% by weight or less and a content of the cyclic olefin copolymerized resin of 12% by weight or more and 30% by weight or less, and said resin constituting the layer A contains a block copolymerized resin of polyalkylene glycol and polyester comprising an aliphatic diol component having 2 to 6 carbon atoms and phthalic acid in an amount of 0.05% by weight or more and 15% by weight or less, and said layer A contains a copolyester resin in which a diol component includes alicyclic glycol in an amount of 0.1 to 25% by weight.