Abstract: A biaxially oriented film of a film-forming aromatic polyester derived from an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component, said film having surface properties such that(1) it has a surface flatness, R.sub.CLA, of from 0.001 to 0.016 micron,(2) it has a coefficient of travelling friction, .mu.k, of from 0.01 to 0.20, and(3) the following relation is established between R.sub.CLA and .mu.k,0.10.ltoreq.10.times.R.sub.CLA +.mu.k.ltoreq.0.31.Preferably, said film has many minute protrusions on its surface which are attributed to fine particles of titanium dioxide or of both titanium dioxide and calcium carbonate, and has such further surface property that(4) a distribution curve showing the relation between the heights of said many protrusions on the film surface and the numbers of the protrusions having the respective heights does not cross a straight line represented by the following equation (1)log.sub.10 y=-8.0x+4.

Abstract: A biaxially oriented film of a film-forming aromatic polyester derived from an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component, said film having surface properties such that(1) it has a surface flatness, R.sub.CLA, of from 0.001 to 0.016 micron,(2) it has a coefficient of travelling friction, .mu.k, of from 0.01 to 0.20, and(3) the following relation is established between R.sub.CLA and .mu.k,0.10.ltoreq.10.times.R.sub.CLA +.mu.k.ltoreq.0.31.Preferably, said film has many minute protrusions on its surface which are attributed to fine particles of titanium dioxide or of both titanium dioxide and calcium carbonate, and has such further surface property that(4) a distribution curve showing the relation between the heights of said many protrusions on the film surface and the numbers of the protrusions having the respective heights does not cross a straight line represented by the following equation (1)log.sub.10 y=-8.0.times.+4.