Manufacturing process for coated polyester film

A biaxially oriented composite film comprising a polyester substrate supporting one or more coatings on one or both surfaces of said substrate, wherein said one or more coatings is/are derived from a coating composition selected from the group consisting of:

• (i) an organic coating composition comprising a low molecular weight reactive diluent;
• an unsaturated oligomer;
• a solvent;
• and a photoinitiator;
• (ii) an organic/inorganic hybrid coating composition comprising a low molecular weight reactive component and/or an unsaturated oligomeric component;
• a solvent;
• and inorganic particles, and optionally further comprising a photoinitiator;
• and
• (iii) a coating composition comprising a cross-linkable organic polymer selected from polyethylene imine (PEI), polyester and polyvinylalcohol (PVOH), and a cross-linking agent;
• wherein said polyester substrate is a heat-stabilised, heat-set, biaxially oriented film having a thickness in a range from 25 μm to 250 μm which exhibits one or more of:
• (i) a shrinkage at 30 mins at 230° C. of less than 1%;
• (ii) a residual dimensional change ΔLr measured at 25° C. before and after heating the heat-stabilised, heat-set, biaxially oriented film from 8° C. to 200° C. and then cooling to 8° C., of less than 0.75%;
• and/or
• (iii) a coefficient of linear thermal expansion (CLTE) within the temperature range from −40° C. to +100° C. of less than 40×106/° C.;
• wherein the biaxially oriented composite film has been annealed at a temperature Ta (° C.) above Tg where Tg<Ta≦Tg+100 (° C.) for a time t after thermal equilibrium where 1 hour≦t≦72 hours, and wherein the annealed composite film exhibits a haze value which is no more than a 10% increase on the initial haze value of the coated film before annealing.