Patent ID: 8802226

Claim:
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 ΔL r 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 40×10 6 /° C.; wherein the biaxially oriented composite film has been annealed at a temperature T a (° C.) above Tg where Tg<T a ≦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.