Frontlit display

• US 20020149925A1
• Filed: 04/06/2001
• Published: 10/17/2002
• Est. Priority Date: 04/06/2001
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wenz, Robert P., Boyd, Gary T., Epstein, Kenneth A., Pankratz, Stephan J.
• Granted Patent: US 6,592,234 B2
• Time in Patent Office: Days
• US Class Current: 362/31
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide

Abstract

An illuminated frontlit display includes a front light guide having at least one light input face that supplies light to the guide, a viewing face, and a light output face opposite the viewing face, the light output face having a light extraction layer thereon, the extraction layer having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the guide through the light exit face to a reflective light valve and back through the viewing face of the guide to a viewer.

Claims

1. An illuminated display comprising:

a) at least one light source;

b) a front light guide having at least one light input face through which light from the source can be supplied to the guide, a viewing face, and a light output face opposite the viewing face, the light output face having a light extraction layer thereon, the extraction layer having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the guide through the light exit face; and

c) a reflective light valve that receives extracted light from the guide and returns at least some of that light through the viewing face.

2. A display according to claim 1, wherein the guide has a reflective face opposite the light input face, and some of the facets are inclined so that supplied light reflected from the reflective face is extracted from the guide via such inclined facets.

3. A display according to claim 1, wherein the guide comprises a tapered plastic sheet and the extraction layer comprises a structured surface that faces the guide and a smooth face that faces away from the guide.

4. A display according to claim 1, wherein the guide comprises a planar glass or plastic sheet and the extraction layer comprises a structured surface that faces the guide and a smooth face that faces away from the guide.

5. A display according to claim 1, wherein the extraction layer comprises a film having a structured surface comprising a plurality of projections that face the guide, and wherein pockets adjacent the facets and between the projections contain a medium having a lower refractive index than the material from which the film is made.

6. A display according to claim 5, wherein the projections have a generally trapezoidal shape.

7. A display according to claim 5, wherein the projections comprise the facets and further comprise risers and plateaus, and wherein supplied light passes from the light output face through a plateau and then is reflected from a facet through the light exit face.

8. A display according to claim 5, wherein lands separate the projections and wherein the pockets contain air.

9. A display according to claim 8, wherein the ratio of ratio of total plateau length to total land length is greater than 1:

1.

10. A display according to claim 9, wherein the ratio is greater than 3:

1.

11. A display according to claim 5, wherein the projections have dimensions, pitch and angular orientation such that supplied light is evenly distributed across the viewing face.

12. A display according to claim 5, wherein supplied light that is reflected from the exit face and refracted through a facet is recaptured by being refracted through a nearby facet and directed into the light extraction layer.

13. A display according to claim 5, wherein the projections are spaced at a relatively coarser pitch near the light input face and at a relatively finer pitch further from the light input face.

14. A display according to claim 5, wherein the projections have dimensions, pitch and angular orientation such that Moire patterns are not visible on the viewing face.

15. A display according to claim 1, wherein substantially all the facet area is accessible to the supplied light.

16. A display according to claim 1, further comprising an antireflection coating on the light exit face.

17. A display according to claim 16, further comprising an air gap between such coating and the light valve.

18. A cellular telephone, pager, personal digital assistant, clock, watch, calculator, laptop computer or transportation vehicle comprising a display according to claim 1.