Frontlit display

• US 6,592,234 B2
• Filed: 04/06/2001
• Issued: 07/15/2003
• Est. Priority Date: 04/06/2001
• Status: Expired due to Term

• 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.
• Primary Examiner(s): O'Shea, Sandra
• Assistant Examiner(s): Sawhney, Hargobind S.
• Application Number:
  US09/844,744
• Publication Number:
  US 20020149925A1
• Time in Patent Office: 830 Days
• Field of Search: 362/31, 362/26, 362/559, 362/561, 362/339, 349/63, 349/64, 349/65, 349/66, 349/67, 349/68
• US Class Current: 362/603
• 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 light guide, a viewing face, and a light output face opposite the viewing face, the light output face having a light extraction thereon, the extraction layer having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the light guide through the light exit face; and

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

wherein the facets have varied dimensions, pitch or angular orientation such that the supplied light is evenly distributed across the viewing face.

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

3. A display according to claim 1, wherein the extraction layer comprises a flexible film having a structured surface comprising a plurality of projections fastened to the light guide via a transparent adhesive, 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.

4. A display accordign to claim 3, wherein the projections have a generally trapezoidal shape.

5. A display according to claim 3, 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.

6. A display according to claim 3, wherein lands separate the projections and wherein the pockets contain air.

7. A display according to claim 3, wherein the light extraction layer has a width and the facets extend across that width.

8. A display according to claim 3, wherein the centroid of the supplied light extracted from the light guide has less than about a 50°

angle of incidence with respect to a normal to the light valve.

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

10. A display according to claim 1 selected from the group consisting of a cellular telephone, pager, personal digital assistant, clock, watch, calculator, laptop computer or transportation vehicle.

11. A display according to claim 1, wherein the light extraction layer has a width and the facets extend across that width.

12. A display according to claim 1, wherein the centroid of the supplied light extracted from the light guide has less than about a 50°

angle of incidence with respect to a normal to the light valve.

13. 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 light guide, a reflective face opposite the light input face that reflects supplied light back into the light 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 light guide through the light exit face, and wherein some of the facets are inclined so that supplied light reflected from the reflective face is extracted from the light guide via such inclined facets; and

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

wherein the facets have varied dimensions, pitch or angular orientation such that the supplied light is evenly distributed across the viewing face.

14. 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 light 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 light guide through the light exit face; and

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

wherein the light guide comprises a tapered plastic sheet and the extraction layer comprises a structured surface that faces the light guide and a smooth surface that faces away from the light guide.

15. A display according to claim 14, wherein the light extraction layer has a width and the facets extend across that width.

16. A display according to claim 15, wherein the centroid of the supplied light extracted from the light guide has a zero or near-zero angle of incidence with respect to the normal.

17. A display according to claim 14, wherein the centroid of the supplied light extracted from the light guide has less than about a 50°

angle of incidence with respect to a normal to the light valve.

18. 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 light guide, a viewing face, and a light output face opposite the viewing face, the light output face having a light extraction layer thereon comprising a film having a structured surface comprising a plurality of projections that face the light guide, the extraction layer having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the light guide through the light exit face and containing pockets adjacent the facets and between the projections containing air, wherein lands separate the projections, the projections further comprise plateaus, and the ratio of total plateau length to total land length is greater than 1;

1; and

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

19. A display according to claim 18, wherein the ratio is greater than 3:

1.

20. 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 light guide, a viewing face, and a light output face opposite the viewing face, the light output face having a light extraction layer thereon comprising a film having a structured surface comprising a plurality of projections that face the light guide, the extraction layer having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the light guide through the light exit face, 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; and

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

wherein the projections are spaced at a relatively coarser pitch of from about 0.06 to about 12 projections per mm near the light input face or faces to a relatively finer pitch of about 250 to about 1 projection per mm further from the light input face or faces such that supplied light is evenly distributed across the viewing face.

21. 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 light guide, a viewing face, and a light output face opposite the viewing face, the light output face having a light extraction layer thereon comprising a film having a structured surface comprising a plurality of projections that face the light guide, the extraction layer having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the light guide through the light exit face, 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; and

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

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.

22. 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 light guide, a viewing face, and a light output face opposite the viewing face, the light output face having a light extraction layer thereon comprising a film having a structured surface comprising a plurality of projections that face the light guide and that are spaced at a relatively coarser pitch near the light input face and at a relatively finer pitch further from the light input face, the extraction layer having a substantially flat light exit face, containing pockets adjacent the facets and between the projections containing a medium having a lower refractive index than the material from which the film is made and containing buried reflective facets that extract supplied light from the light guide through the light exit face; and

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

23. 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 light guide, a viewing face, and a light output face opposite the viewing face, the light output face having a light extraction layer thereon comprising a film having a structured surface comprising a plurality of projections that face the light guide, an extraction layer having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the light guide through the light exit face, 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; and

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

wherein the reflective light valve has pixels or other repeating elements having dimensions, pitch or angular orientation, and the projections have dimensions, pitch or angular orientation that are varied relative to the dimensions, pitch or angular orientation of the pixels or other repeating elements such that Moiré

patterns are not visible on the viewing face.

24. 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 light 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 with an antireflection coating on the light exit face, and containing buried reflective facets that extract supplied light from the light guide through the light exit face; and

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

25. A display according to claim 24, further comprising an air gap between such coating and the light valve.