Opaque polyester film as substrate with white coatings on both sides

Abstract

A polyester film having an opaque core layer having on both surfaces a white outer layer.

1 . A polyester film comprising an opaque core layer having an optical density greater than 2.0, having on both surfaces thereof, a white outer layer.  
     
     
         2 . A film according to  claim 1  wherein the core layer comprises in the range from 0.05% to 10% by weight of opacifying agent, based on the weight of the core layer polyester.  
     
     
         3 . A film according to  claim 2  wherein the opacifying agent comprises carbon black.  
     
     
         4 . A film according to any one of the preceding claims wherein the core layer comprises a whitening agent.  
     
     
         5 . A film according to any one of the preceding claims wherein the outer layers comprise in the range from 5% to 30% by weight of a whitening agent, based on the weight of the outer layer polyester.  
     
     
         6 . A film according to either one of claims  4  and  5  wherein the same whitening agent is present in both the core layer and the outer layers.  
     
     
         7 . A film according to any one of the preceding claims wherein the thickness of the opaque core layer is in the range from 20% to 65% of the thickness of the polyester film.  
     
     
         8  A film according to  claim 7  wherein the difference in the whiteness index for the two outer layers is in the range from 0 to 3%.  
     
     
         9 . A film according to any one of the preceding claims additionally comprising an ink-receptive layer suitable for ink-jet printing, on at least one surface of the outer layer.  
     
     
         10 . A method of producing a polyester film which comprises forming an opaque core layer having an optical density greater than 2.0, and applying on both surfaces thereof, a white outer layer.