Abstract: The present invention provides a polyester film for release film which makes it possible to conduct accurate inspections of polarizing plates by the crossed nicols method and can also inhibit transfer of the polyester oligomers into the adhesive layer. A polyester film for release film having a coating layer on at least one surface thereof with defects of not more than 50 per m2, which polyester film has such properties that the amount of polyester oligomers extracted from the surface of said coating layer after 10-minute heat treatment at 150° C. is not more than 0.3 mg/m2, and the inclination of the principal axis of orientation (angle of orientation) of the film is not more than 8°; a release film for polarizing plate comprising the above-said film and a release layer provided thereon; and a polyester film for polarizing plate protective film comprising the above-said film.

Abstract: An object of the present invention is provide a polyester film useful as base for release film according to which when a ceramic slurry is applied on the release film, formation of pinholes in the ceramic slurry layer is suppressed prominently, and also when a ceramic layer is provided on the release film, thickness variation of the ceramic layer is lessened, thus realizing excellent releasability of the release film. A polyester film for release film, which has a maximum height of projection (Rmax) in one surface (surface A) of said polyester film, of not more than 500 nm; and has a thickness variation of not more than 5%.

Abstract: The present invention relates to a polyester film for release film, which has a maximum height of projection (Rmax) in one surface (surface A) of said polyester film, of not more than 500 nm; and has a thickness variation defined by the following equation using the maximum, minimum and mean values of film thickness in the machine and transverse directions of said polyester film, of not more than 5%:

Abstract: The present invention relates to a biaxially oriented polyester film having at least one layer of a sea-island structure which satisfies the following formulae (1) and (2) at the same time, said film having a specific surface resistance of not more than 1×1015 &OHgr;: 50≦X/Y  (1) 5≦N≦200  (2) wherein X is the mean value of length (&mgr;m) of the islands in the longitudinal direction of the film; Y is the mean value of length (&mgr;m) of the islands in the width direction of the film; and N is the number (per &mgr;m2) of the islands existing in the section of the film in its width direction.

Abstract: The present invention relates to a biaxially oriented polyester film having at least one layer of a sea island structure which satisfies the following formulae (1) and (2) at the same time, said film having a specific surface resistance of not more than 1×1015 &OHgr;: