a process for producing a multi - layer opaque , biaxially oriented polymeric film structure . the film structure includes a thermoplastic polymer matrix core layer having a first surface and a second surface , within which is located a strata of voids , positioned at least substantially within a substantial number of the voids is at least one spherical void - initiating particle which is phase distinct and incompatible with the matrix material , the void space occupied by the particle being substantially less than the volume of the void , the population of the voids in the core being such as to cause a significant degree of opacity , a first thermoplastic polymer skin layer having a first surface and a second surface , the first surface of the first skin layer adhering to the first surface of the core layer , the first skin layer including up to about 12 % by weight of titanium dioxide contact pigment , and a second thermoplastic polymer skin layer having a first surface and a second surface , the first surface of the second skin layer adhering to the second surface of the core layer , the second skin layer including finely divided , uniformly dispersed inorganic material in an amount effective to impart antiblocking characteristics and decrease the inherent film - to - film coefficient of friction at the second surface of the second thermoplastic polymer skin layer .