Frontlit illuminated touch panel

• US 6,738,051 B2
• Filed: 04/06/2001
• Issued: 05/18/2004
• Est. Priority Date: 04/06/2001
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Pankratz, Stephan J., Boyd, Gary T.
• Primary Examiner(s): Liang, Regina
• Application Number:
  US09/827,732
• Publication Number:
  US 20020145593A1
• Time in Patent Office: 1,138 Days
• Field of Search: 345/173-178, 345/102, 178/18.01, 178/18.03, 178/18.09, 349/61, 349/62, 349/63, 349/64, 349/65, 360/31, 360/561
• US Class Current: 345/176
• CPC Class Codes: G02B 6/0023 provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133616 Front illuminating devices
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: G06F 3/043 using propagating acoustic waves
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A frontlit touch panel for use with a reflective light valve, comprising a front light guide having at least one light input face that supplies light to the guide, a viewing face, a light output face opposite the viewing face, and at least one component of a touch-sensitive transducer, the light output face having a light extraction layer thereon having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the guide through the light exit face. The touch panel can be used with a light source, reflective light valve and suitable control electronics to form a compact, efficient illuminated touch panel display assembly.

Claims

1. A frontlit touch panel for use with a reflective light valve, comprising a front light guide having at least one light input face that supplies light to the guide, a viewing face, a light output face opposite the viewing face, and at least one component of a touch-sensitive transducer, the light output face having a light extraction layer thereon having a substantially flat light exit face and containing buried facets that reflect and thereby extract supplied light from the guide through the light exit face, the facets having varied dimensions, pitch or angular orientation such that the supplied light is evenly distributed across the viewing face.

2. A touch panel 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 touch panel according to claim 1, wherein the guide comprises a planar glass sheet and the extraction layer comprises a flexible film having a structured surface that faces the guide and a smooth face that faces away from the guide.

4. A touch panel according to claim 1, wherein substantially all the facet area is accessible to the supplied light.

5. A touch panel according to claim 1, further comprising an antireflection coating on the light exit face.

6. A touch panel according to claim 1, wherein the touch-sensitive transducer comprises a resistive touch panel.

7. A touch panel according to claim 1, wherein the touch-sensitive transducer comprises a capacitive overlay, guided acoustic wave, surface acoustic wave or near field imaging touch panel.

8. A touch panel according to claim 7, wherein the component comprises a layer comprising indium tin oxide and the light extraction layer comprises a structured surface plastic film.

9. A touch panel according to claim 1, wherein application of the component to the front light guide requires temperatures or processing conditions that would destroy the light extraction layer.

10. A frontlit touch panel for use with a reflective light valve, comprising a front light guide having at least one light input face that supplies light to the guide, a viewing face, a light output face opposite the viewing face, and at least one component of a touch-sensitive transducer, the light output face having a light extraction layer thereon having a substantially flat light exit face and containing buried reflective facets that extract supplied light from the guide through the light exit face, wherein the extraction layer comprises a flexible film having a structured surface comprising a plurality of projections that face the guide, wherein the facets have varied dimensions, pitch or angular orientation such that the supplied light is evenly distributed across the viewing 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.

11. A touch panel according to claim 10, wherein the projections have a generally trapezoidal shape.

12. A touch panel according to claim 10, 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.

13. A touch panel according to claim 10, wherein lands separate the projections and wherein the pockets contain air.

14. A touch panel according to claim 13, wherein the ratio of ratio of total plateau length to total land length is greater than 1:

1.

15. A touch panel according to claim 14, wherein the ratio is greater than 3:

1.

16. A touch panel according to claim 10, wherein the projections have varied angular orientation.

17. A touch panel according to claim 10, 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.

18. A touch panel according to claim 10, 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.

19. A touch panel according to claim 10, wherein the projections have dimensions, pitch and angular orientation such that Moiré

patterns are not visible on the viewing face.

20. An illuminated touch panel 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, a light output face opposite the viewing face, and at least one component of a touch-sensitive transducer, the light output face having a light extraction layer thereon having a substantially flat light exit face and containing buried facets that reflect and thereby 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

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

21. A display according to claim 20, further comprising an antireflection coating on the light exit face and an air gap between such coating and the light valve.

22. A cellular telephone, pager, personal digital assistant, clock, watch, calculator, laptop computer or transportation vehicle comprising a display according to claim 20.

23. An illuminated touch panel 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, a light output face opposite the viewing face, and at least one component of a touch-sensitive transducer, the light output face having a light extraction layer thereon 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;

wherein the extraction layer comprises a flexible film having a structured surface comprising a plurality of projections that face the guide, wherein the facets have varied dimensions, pitch or angular orientation such that the supplied light is evenly distributed across the viewing 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.