LIGHT EXTRACTION FILM FOR ORGANIC LIGHT EMITTING DIODE DISPLAY DEVICES

• US 20090015142A1
• Filed: 07/13/2007
• Published: 01/15/2009
• Est. Priority Date: 07/13/2007
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Smith, Terry L., McCormick, Fred B., Zhang, Jun-Ying, Wang, Ding, Wolk, Martin B., Bright, Clark I., Roehrig, Mark A., Tolbert, William A., Battiato, James M., Potts, John E.
• Application Number:
  US11/777,453
• Publication Number:
  US 20090015142A1
• Time in Patent Office: Days
• US Class Current: 313/504
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: G02B 5/20 Filters polarising elements G02B5/30
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 2202/36 Micro- or nanomaterials
• CPC Class Codes: H10K 2102/331 Nanoparticles used in non-emissive layers, e.g. in packaging layer
• CPC Class Codes: H10K 50/8445 multilayered coatings having a repetitive structure, e.g. having multiple organic-inorganic bilayers
• CPC Class Codes: H10K 50/854 comprising scattering means
• CPC Class Codes: H10K 50/858 comprising refractive means, e.g. lenses
• CPC Class Codes: H10K 59/8731 multilayered coatings having a repetitive structure, e.g. having multiple organic-inorganic bilayers
• CPC Class Codes: H10K 59/877 comprising scattering means
• CPC Class Codes: H10K 59/879 comprising refractive means, e.g. lenses

Abstract

A multifunctional optical film for enhancing light extraction includes a flexible substrate, a structured layer, and a backfill layer. The structured layer effectively uses microreplicated diffractive or scattering nanostructures located near enough to the light generation region to enable extraction of an evanescent wave from an organic light emitting diode (OLED) device. The backfill layer has a material having an index of refraction different from the index of refraction of the structured layer. The backfill layer also provides a planarizing layer over the structured layer in order to conform the light extraction film to a layer of an OLED display device. The film may have additional layers added to or incorporated within it to an emissive surface in order to effect additional functionalities beyond improvement of light extraction efficiency.

Claims

1. A multifunctional optical film for enhancing light extraction from a self-emissive light source, comprising:

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 adjacent to a light emitting region of the self-emissive light source when the optical film is located against 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.

2. The multifunctional optical film of claim 1, wherein the backfill layer has a lower index than the extraction elements and wherein the backfill layer has a thickness approximately equal to a thickness of the layer of the extraction elements.

3. The multifunctional optical film of claim 1, wherein the backfill layer has a higher index than the extraction elements.

4. The multifunctional optical film of claim 1, wherein the extraction elements comprise nanostructured features.

5. The multifunctional optical film of claim 4, wherein the nanostructured features comprise nanoparticles or replicated features.

6. The multifunctional optical film of claim 1, further comprising a coating having at least one of the following functions:

color filtering;

color shifting;

polarization modification;

antireflection;

light redirection;

diffusion;

or optical rotation.

7. The multifunctional optical film of claim 1, further comprising a coating applied to the substrate and having at least one of the following functions:

antiabrasion;

antismudge;

hydrophobicity;

or hydrophilicity.

8. The multifunctional optical film of claim 1, wherein the backfill layer material comprises one of the following:

an inorganic material;

an organic material;

or a nanoparticle filled polymer material.

9. The multifunctional optical film of claim 1, wherein the difference between the first and second indices of refraction is greater than or equal to 0.3.

10. The multifunctional optical film of claim 4, wherein the nanostructured features comprise one of the following:

a periodic or quasi-periodic array of features;

a random distribution of features;

or portions of periodic or quasi-periodic array of features interspersed within a different distribution of features.

11. The multifunctional optical film of claim 1, wherein the substrate comprises one of the following:

glass;

a polymer film;

a substantially optically transmissive material;

or a barrier material.

12. The multifunctional optical film of claim 1, further comprising a barrier layer.

13. The multifunctional optical film of claim 1, further comprising a layer applied to the backfill layer comprising a transparent electrically conductive material.

14. The multifunctional optical film of claim 1, wherein the backfill layer material functions as a barrier to moisture and oxygen.

15. The multifunctional optical film of claim 1, wherein the backfill layer material is transparent.

16. The multifunctional optical film of claim 1, wherein the backfill layer material is electrically conductive.

17. The multifunctional optical film of claim 1, wherein the extraction elements comprise particles having at least one dimension between 20 nanometers and 1000 nanometers.

18. The multifunctional optical film of claim 1, wherein the extraction elements comprise particles having at least one dimension between 30 nanometers and 300 nanometers.

19. The multifunctional optical film of claim 1, wherein the extraction elements comprise particles having at least one dimension between 60 nanometers and 300 nanometers.

20. 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.

21. The method of claim 20, further comprising curing the organic material having the nanostructured features.

22. The method of claim 20, wherein the imparting step comprises:

providing a master tool having nanostructured features; and

applying the flexible substrate with the layer of the organic material to the tool with the organic material applied against the tool to impart the nanostructures into the organic material.

23. The method of claim 20, wherein the imparting step comprises printing the nanostructured features onto the organic material.

24. The method of claim 20, wherein the imparting step comprises embossing the nanostructured features into the organic material.

25. The method of claim 20, further comprising using one of the following methods to apply the backfill layer to form the planarizing layer:

liquid coating;

vapor coating;

powder coating;

or lamination.

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

applying nanoparticles having a first index of refraction onto a flexible substrate, wherein a substantial portion of the nanoparticles 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; and

overcoating a backfill layer on the nanoparticles to form a planarizing layer over the nanoparticles, wherein the backfill layer comprises a material having a second index of refraction different from the first index of refraction.

27. The method of claim 26, wherein the applying step comprises:

coating the nanoparticles dispersed in a solvent onto the flexible substrate; and

allowing the solvent to evaporate before overcoating the backfill layer.

28. The method of claim 26, wherein the applying step comprises applying the nanoparticles in dry form to the flexible substrate.

29. The method of claim 26, wherein the applying step includes forming the nanoparticles as a monolayer on the flexible substrate.

30. The method of claim 26, wherein the substantial portion of the nanoparticles are in contact with the flexible substrate.

31. 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.

32. The device of claim 31, wherein the OLED display device comprises a bottom emitting OLED display device.

33. The device of claim 31, wherein the OLED display device comprises a top emitting OLED display device.