Light Extraction Films for Increasing Pixelated OLED Output with Reduced Blur

• US 20120099323A1
• Filed: 10/20/2010
• Published: 04/26/2012
• Est. Priority Date: 10/20/2010
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Thompson, David S.
• Granted Patent: US 8,469,551 B2
• Time in Patent Office: Days
• US Class Current: 362/257
• CPC Class Codes: B29C 2035/0822 using IR radiation
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 2035/0833 using actinic light
• CPC Class Codes: B29C 2035/0838 using laser
• CPC Class Codes: B29C 2035/0877 using electron radiation, e.g. beta-rays
• CPC Class Codes: B29C 35/02 Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mouldcold vulcanisation B29C35/18 ; vulcanising tyres, presses therefor B29D30/0601
• CPC Class Codes: B29C 35/0866 using particle radiation
• CPC Class Codes: B29C 59/046 for layered or coated substantially flat surfaces
• CPC Class Codes: H10K 50/858 comprising refractive means, e.g. lenses
• CPC Class Codes: H10K 59/879 comprising refractive means, e.g. lenses

Abstract

Optical films for enhancing light extraction from self-emissive pixelated OLEDs, without introducing significant pixel blur, are disclosed. The extraction films include a flexible carrier film, and a first and second layer carried by the carrier film. The first layer has a nanovoided morphology, includes a polymer binder, and may have a refractive index less than 1.35 or 1.3. An embedded structured surface of light extraction elements is formed between the first and second layers. The extraction film includes a major coupling surface for attachment to an outer surface of the light source. The film is configured such that a land portion between the structured surface and the major coupling surface is thinner than a specified amount, e.g., less than 50, 25, or 10 microns, or less than a thickness of the carrier film.

Claims

1. An optical extraction film for enhancing light extraction from a self-emissive pixelated light source that has an outer surface, the extraction film having a major coupling surface adapted to attach to the outer surface of the light source, the extraction film comprising:

a flexible carrier film; and

a first and second layer carried by the carrier film, the first and second layers defining therebetween an embedded interface that forms a structured surface of light extraction elements;

wherein the first layer has a nanovoided morphology and comprises a polymer binder, the first layer also being disposed between the second layer and the carrier film; and

wherein the second layer has a refractive index greater than that of the first layer, and the first layer has a refractive index less than 1.35.

2. The extraction film of claim 1, wherein the major coupling surface is a surface of the second layer opposite the structured surface, and wherein the second layer includes a land portion between the structured surface and the major coupling surface.

3. The extraction film of claim 2, wherein the land portion has a thickness less than 50 micrometers.

4. The extraction film of claim 3, wherein the land portion has a thickness less than 25 micrometers.

5. The extraction film of claim 4, wherein the land portion has a thickness less than 10 micrometers.

6. The extraction film of claim 2, wherein the land portion has a thickness in a range from 0.1 to 25 micrometers.

7. The extraction film of claim 2, wherein the land portion is thinner than the carrier film.

8. The extraction film of claim 1, wherein the first layer has a refractive index less than 1.3.

9. The extraction film of claim 1, wherein the second layer has a refractive index greater than 1.4.

10. The extraction film of claim 1, wherein a refractive index difference between the first and second layers is at least 0.3, or at least 0.4, or at least 0.5.

11. The extraction film of claim 1, wherein the second layer comprises a light transmissive polymer.

12. The extraction film of claim 11, wherein the polymer comprises a light transmissive viscoelastic material.

13. The extraction film of claim 1, further comprising a release liner or premask covering the major coupling surface.

14. The extraction film of claim 1, wherein the light extraction elements have a pitch greater than 1 micron.

15. The extraction film of claim 1 in combination with the self-emissive pixelated light source, wherein the light extraction film couples to the self-emissive pixelated light source to enhance light extraction therefrom.

16. The combination of claim 15, wherein the extraction film attaches to the outer surface of the light source with no air gap therebetween.

17. The combination of claim 15, wherein the structured surface is separated from the major coupling surface by a land portion having a thickness less than 50 micrometers.

18. The combination of claim 17, wherein the land portion has a thickness less than 25 micrometers.

19. The combination of claim 18, wherein the land portion has a thickness less than 10 micrometers.

20. The combination of claim 15, wherein the self-emissive pixelated light source includes an optical coupling layer that planarizes the pixelated light source, and wherein the outer surface of the light source is an outer surface of the optical coupling layer.

21. The combination of claim 20, wherein the optical coupling layer has a refractive index of at least 1.4.

22. The combination of claim 15, wherein the pixelated light source comprises pixels that have at least one transverse dimension of less than 25 microns.

23. The combination of claim 15, wherein the light extraction elements have a pitch greater than 1 micron.

24. A method of enhancing the light output of a self-emissive pixelated light source without substantially blurring pixels of the light source, comprising:

providing a self-emissive pixelated light source having an outer surface;

providing an optical extraction film having a major coupling surface, the extraction film including;

a flexible carrier film; and

a first and second layer carried by the carrier film, the first and second layers defining therebetween an embedded interface that forms a structured surface of light extraction elements;

wherein the first layer has a nanovoided morphology and comprises a polymer binder, the first layer also having a refractive index less than 1.35 and less than that of the second layer; and

attaching the major coupling surface of the extraction film to the outer surface of the self-emissive pixelated light source.

25. The method of claim 24, wherein the self-emissive pixelated light source includes an optical coupling layer that planarizes the pixelated light source, and wherein the outer surface of the light source is an outer surface of the optical coupling layer.

26. The method of claim 24, wherein the attaching is carried out such that a land portion is defined between the structured surface of the optical extraction film and the outer surface of the light source.

27. The method of claim 26, wherein the land portion has a thickness less than 50 microns.

28. The method of claim 27, wherein the land portion has a thickness less than 25 microns.

29. The method of claim 26, wherein the land portion has a thickness less than 10 microns.

30. The method of claim 26, wherein the land portion is thinner than the carrier film.