Illumination device comprising a film-based lightguide

• US 9,110,200 B2
• Filed: 04/15/2011
• Issued: 08/18/2015
• Est. Priority Date: 04/16/2010
• Status: Active Grant

• Current Assignee: FLEx Lighting II, LLC
• Original Assignee: FLEx Lighting II, LLC
• Inventors: Nichol, Anthony John, Coleman, Zane Arthur
• Primary Examiner(s): Hollweg, Thomas A
• Application Number:
  US13/088,231
• Publication Number:
  US 20110255303A1
• Time in Patent Office: 1,586 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/002 by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/006 to produce indicia, symbols, texts or the like
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/0088 of the light guide or other optical sheets in the package
• CPC Class Codes: G02F 1/133616 Front illuminating devices
• CPC Class Codes: G09F 13/18 Edge-illuminated signs
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

A light emitting device includes a film lightguide. The lightguide includes a lightguide region and an array of coupling lightguides continuous with the lightguide region, each terminating in a bounding edge and folded such that the bounding edges define a light input surface. A light source emits light into the light input surface. Light propagates within each coupling lightguide to the lightguide region, with light from each coupling lightguide combining with light from one or more other coupling lightguides and totally internally reflecting within the lightguide region. One or more light extraction features frustrate the totally internally reflected light such that light exits the lightguide in a light emitting region. Surface relief features on a surface of a low contact area cover are adjacent to a region of the lightguide with one or more of the surface relief features contacting the lightguide. A method of producing a device is disclosed.

Claims

1. A light emitting device comprising:

a lightguide formed from a film having a thickness not greater than 0.5 millimeters, the lightguide having a lightguide region and an array of coupling lightguides continuous with the lightguide region, wherein each coupling lightguide terminates in a bounding edge and each coupling lightguide is folded such that the bounding edges of the array of coupling lightguides form a stack defining a light input surface;

a light source configured to emit light into the light input surface, such that the light propagates within each coupling lightguide to the lightguide region, with light from each coupling lightguide combining with light from one or more, other coupling lightguides of the array of coupling lightguides and totally internally reflecting within the lightguide region;

one or more light extraction features operatively coupled to the lightguide and configured to frustrate the totally internally reflected light within the lightguide region such that the light exits the lightguide in a light emitting region defined within the lightguide region; and

a first low contact area cover comprising a surface having a plurality of first surface relief features adjacent to a first region of the lightguide including at least a portion of the array of coupling lightguides with one or more of the plurality of surface relief features contacting the lightguide, wherein an air gap is formed between the surface of the first low contact area cover and the first region.

2. The light emitting device of claim 1 wherein a percentage of a surface area of the lightguide contacting the one or more first surface relief features in the first region is less than 30% of the surface area in the first region.

3. The light emitting device of claim 2 wherein the first low contact area cover extracts a total of less than 30% of the light propagating within the lightguide out of the lightguide.

4. The light emitting device of claim 1 wherein a percentage of a surface area of the lightguide contacting the one or more first surface relief features in the first region is less than 10% of the surface area in the first region.

5. The light emitting device of claim 1 wherein the first low contact area cover comprises one of a film and a sheet.

6. The light emitting device of claim 1 wherein a combination of the first low contact area cover and the lightguide has a flexural modulus greater than 2 gigapascals when measured according to ASTM D790.

7. The light emitting device of claim 1 further comprising a second low contact area cover comprising a second surface having a plurality of second surface relief features adjacent to a second region of the lightguide wherein one or more of the plurality of second surface relief features contact the lightguide and the second region is disposed on an opposite side of the lightguide than the first region.

8. The light emitting device of claim 1 wherein the array of coupling lightguides are optically coupled to each other in at least 10% of a region where the coupling lightguides are adjacent each other.

9. The light emitting device of claim 1 wherein the coupling lightguides are optically coupled to each other by a natural surface adhesion between adjacent coupling lightguides.

10. The light emitting device of claim 1 wherein a first coupling lightguide of the array of coupling lightguides comprises the first region.

11. The light emitting device of claim 1 wherein the first low contact area cover wraps substantially around at least two sides of the stack of coupling lightguides.

12. The light emitting device of claim 1 wherein the first region of the lightguide includes at least a portion of the light emitting region of the lightguide.

13. The light emitting device of claim 12 wherein the low contact area cover has a diffuse reflectance measured in the d/0 geometry according to ASTM E 1164 greater than 70%.

14. The light emitting device of claim 1 wherein the lightguide further comprises a light mixing region disposed between folds in the coupling lightguides and the light emitting region, the light from each coupling lightguide combines and totally internally reflects within the light mixing region, and the first region of the lightguide includes at least a portion of the light mixing region.

15. The light emitting device of claim 1 wherein the low contact area cover is coupled to a rigid support with a flexural modulus greater than 2 gigapascals when measured according to ASTM D790.

16. The light emitting device of claim 1 further comprising a display wherein the light emitting device is a backlight for the display.

17. A light emitting device comprising:

a lightguide comprising a film having a thickness not greater than 0.5 millimeters, the lightguide having a lightguide region and an array of coupling lightguides continuous with the lightguide region, wherein each coupling lightguide terminates in a bounding edge and each coupling lightguide is folded such that the bounding edges of the array of coupling lightguides form a stack defining a light input surface;

a light source configured to emit light into the light input surface, such that the light propagates within each coupling lightguide to the lightguide region, with light from each coupling lightguide combining with light from one or more other coupling lightguides of the array of coupling lightguides and totally internally reflecting within the lightguide region;

a plurality of light extraction features operatively coupled to the lightguide and configured to frustrate the totally internally reflected light within the lightguide region such that the light exits the lightguide in a light emitting region defined within the lightguide region; and

a low contact area cover comprising a surface having a plurality of surface relief features adjacent a first region of the lightguide including at least a portion of the array of coupling lightguides with one or more of the plurality of surface relief features contacting the lightguide, an air gap formed between the surface of the low contact area cover and the first region, wherein the low contact area cover is configured to extract out of the lightguide a total of less than 30% of the light propagating within the lightguide.

18. The light emitting device of claim 17 wherein the film comprises a core material with a critical surface tension less than 32 mN/m.

19. The light emitting device of claim 18 wherein a surface of the film in the first region has a critical surface tension greater than 32 mN/m.

20. The light emitting device of claim 17 wherein a percentage of a surface area of the lightguide contacting the one or more surface relief features in the first region is less than 30% of the surface area in the first region.

21. A method of producing a light emitting device, said method comprising:

a. forming an array of coupling lightguides extending continuously from a lightguide region of a film, each coupling lightguide of the array of coupling lightguides having a bounding edge at the end thereof;

b. folding the array of coupling lightguides such that the bounding edges of the array of coupling lightguides form a stack defining a light input surface;

c. positioning a light source to direct light into the light input surface such that light from the light source propagates within each coupling lightguide and the lightguide region by total internal reflection;

d. forming one or more light extraction features on or within the film in a light emitting region of the lightguide region; and

e. positioning a low contact area cover comprising a surface having a plurality of surface relief features adjacent a first region of the film including at least a portion of the array of coupling lightguides to cover at least a portion of the stack, wherein an air gap is formed between the surface of the low contact area cover and the first region and the plurality of surface relief features contact the film in an area less than 30% of a surface area of the film in the first region.

22. The method of claim 21 wherein the first region of the film includes at least a portion of the light emitting region.

23. A light emitting device comprising:

a lightguide formed from a film having a thickness not greater than 0.5 millimeters, the lightguide having a lightguide region and an array of coupling lightguides continuous with the lightguide region, wherein each coupling lightguide terminates in a bounding edge and each coupling lightguide is folded such that the bounding edges of the array of coupling lightguides form a stack defining a light input surface;

a light source configured to emit light into the light input surface, such that the light propagates within each coupling lightguide to the lightguide region, with light from each coupling lightguide combining with light from one or more other coupling lightguides of the array of coupling lightguides and totally internally reflecting within the lightguide region;

one or more light extraction features operatively coupled to the lightguide and configured to frustrate the totally internally reflected light within the lightguide region such that the light exits the lightguide in a light emitting region defined within the lightguide region; and

a cover having a surface with a plurality of surface relief features contacting a first region of the lightguide, wherein a first region of the cover covers at least a portion of the stack to form an air gap between the surface of the cover and the first region of the lightguide and the first region of the cover is opaque, light absorbing, or light reflecting.

24. A light emitting device comprising:

a lightguide formed from a film having a thickness not greater than 0.5 millimeters, the lightguide having a lightguide region and an array of coupling lightguides continuous with the lightguide region, wherein each coupling lightguide terminates in a bounding edge and each coupling lightguide is folded such that the bounding edges of the array of coupling lightguides form a stack defining a light input surface;

a light source configured to emit light into the light input surface, such that the light propagates within each coupling lightguide to the lightguide region, with light from each coupling lightguide combining with light from one or more other coupling lightguides of the array of coupling lightguides and totally internally reflecting within the lightguide region;

one or more light extraction features operatively coupled to the lightguide and configured to frustrate the totally internally reflected light within the lightguide region such that the light exits the lightguide in a light emitting region defined within the lightguide region; and

a cover positioned about at least a portion of the stack, the cover comprising a first material having a first surface with a plurality of surface relief features on the first surface contacting an outer surface of a second material of the lightguide in a first region, wherein a gap is formed between the first surface and the outer surface of the lightguide, and the first material has a refractive index less than a refractive index of the second material.