Light extraction film for organic light emitting diode display devices

A method for making an optical film for enhancing light extraction, comprising:

• coating a layer of an organic material having a first index of refraction onto a flexible substrate;
• imparting nanostructured features into the organic material to create a nanostructured surface;
• and
• applying a backfill layer to the nanostructured surface to form a planarizing layer on the nanostructured surface,
• wherein the backfill layer comprises a material having a second index of refraction different from the first index of refraction, and
• wherein a substantial portion of the nanostructured features are within an evanescent zone adjacent to a light emitting region of a self-emissive light source when the optical film is located against the self-emissive light source.

An organic light emitting diode (OLED) display device, comprising:

• an OLED display device comprising a self-emissive light source having at least one surface that outputs light from the device;
• and
• a light extraction film adjacent the at least one surface of the self-emissive light source, wherein the light extraction film comprises:
• a flexible substrate;
• a structured layer of extraction elements having a first index of refraction, wherein a substantial portion of the extraction elements are within an evanescent zone of the light output surface of the self-emissive light source;
• and
• a backfill layer comprising a material having a second index of refraction different from the first index of refraction, wherein the backfill layer forms a planarizing layer over the extraction elements,
• wherein the structured layer and backfill layer are in sufficient proximity to the light output surface of the self-emissive light source in order to at least partially enhance the extraction of light from that surface.