Background lighting apparatus for liquid crystal display

• US 5,667,289 A
• Filed: 04/07/1992
• Issued: 09/16/1997
• Est. Priority Date: 05/18/1989
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Funamoto, Tatsuaki, Yagasaki, Tooru, Akahane, Fumiaki
• Primary Examiner(s): Yeung, James C.
• Assistant Examiner(s): CARIASO, ALAN B
• Application Number:
  US07/864,772
• Time in Patent Office: 1,988 Days
• Field of Search: 362/31, 362/26, 362/32, 362/227, 362/235, 362/236, 362/237, 362/307, 362/311, 362/330, 362/343, 362/27, 359/49, 359/50
• US Class Current: 362/614
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0071 with elongated shape, e.g. tube

Abstract

A background lighting apparatus includes a light entering edge surface around substantially the entire periphery of a highly internally reflecting transparent plate wherein light beams enter from peripheral light sources and travel toward the central portion of the plate and are dispersed and diffused by a diffusion system formed relative to the transparent plate. Uniformity of luminance provided from the background lighting apparatus is enhanced as a whole by increasing the incident quality of the input light beams into the transparent plate while easing the incident directivity of the light beams on the transparent plate with the overall substantial enhancement of luminance produced from the apparatus. Further, the temperature distribution on a liquid crystal panel positioned adjacent to the output surface of the background lighting apparatus is substantially uniform across the panel so that the transmission quality of the liquid crystal material, which is dependent upon ambient temperatures, is made substantially more uniform resulting in significantly higher levels of uniformity in luminance across the display as well as uniformity of displayed colors and gradations thereof emanating from the display panel.

Claims

1. A background lighting apparatus for an adjoining LCD panel having enhanced luminance and thermal uniformity thereacross comprising:

a transparent plate having two major surfaces providing a high level of internal reflection for light below a critical angle,

a peripheral edge surface around a perimeter of said plate functioning as a light input to the interior of said plate,

one of said major surfaces functioning as a light output from said apparatus for light above said critical angle,

a distributed diffusion system formed relative to at least the other of said major surfaces to diffuse and reflect light entering the interior of said plate and permit light at or above said critical angle to output through said one major surface, and

a fluorescent-type light source configured to uniformly follow said peripheral edge and provide a continuous light input uniformly along said the entire peripheral edge of said plate so that for a required light level input, the amount of light flux is reduced due to the continuity of said light source along said edge permitting the utilization of smaller light source and, correspondingly, providing a reduction in the overall light source heat generated as well as provide even heat transfer distribution across said plate wherein electrical operating characteristics of said adjoining LCD panel are affected evenly thereacross.

2. The background lighting apparatus of claim 1 wherein said transparent plate has a geometric shape which is substantially rectangular, circular or polygonal.

3. The background lighting apparatus of claim 1 wherein said diffusion system comprises a pattern of separate diffusion elements formed relative to said other major surface wherein an area ratio of size of said diffusion elements monotonically increases from said peripheral edge surface of said plate to the center of said plate wherein the area ratio of size of said elements is maximum.

4. The background lighting apparatus of claim 3 wherein the area ratio of size of said diffusion elements monotonically increases from said peripheral edge surface of said plate to the central region of said plate in a normal distribution pattern.

5. The background lighting apparatus of claim 3 wherein said transparent plate has a geometric shape which is substantially rectangular, circular or polygonal.

15. The background lighting apparatus of claim 1 employed with said adjoining LCD panel in a display apparatus.

18. The background lighting apparatus of claim 1 wherein said adjoining LCD panel is a color display.

6. A background lighting apparatus for an adjoining LCD panel comprising:

a transparent plate having two opposite major surfaces, one of said major surfaces including means to disperse, diffuse and otherwise redirect light in an interior portion of said plate and the other of said major surfaces functioning as an exit surface for light from said plate interior portion,

said plate having a peripheral edge functioning along its full length as a light input into said plate interior portion,

a plurality of elongated tubular fluorescent light sources positioned uniformly and continuously along and adjacent to said peripheral edge such that substantially the entire periphery thereof functions as a light source input wherein light is provided into said plate interior portion substantially along the entire periphery of said plate,

said light sources having a dimensional width equal to or less than the thickness of said plate,

said light sources providing a uniform light flux input along said peripheral edge permitting a reduction in the total amount of required light flux for said apparatus and correspondingly a reduction in the overall light source heat generated from such light sources so that both generated light and heat are uniformly distributed into the interior of and across the planar extent of said plate wherein electrical operating characteristics of said adjoining LCD panel are uniformly affected thereacross.

7. The background lighting apparatus of claim 6 wherein said transparent plate has a thickness in the range of 1 mm to 6 mm.

8. The background lighting apparatus of claim 7 wherein said light sources are elongated fluorescent lamps having a tube diameter in the range of 3 mm to 4 mm.

9. The background lighting apparatus of claim 8 wherein said plate is rectilinear or polygon shape, at least one of said elongated fluorescent lamps having a length and intermediate bent section to correspond along at least two angularly disposed edge surfaces of said plate peripheral edge.

16. The background lighting apparatus of claim 6 employed with said adjoining LCD panel in a display apparatus.

19. The background lighting apparatus of claim 6 wherein said adjoining LCD panel is a color display.

10. A background lighting apparatus comprising:

a transparent plate having two opposite major surfaces, one of said major surfaces including means to disperse, diffuse and otherwise redirect light in an interior portion of said plate and the other of said major surfaces functioning as an exit surface for light from said plate interior portion,

said plate having a peripheral edge functioning as a light input into said plate interior portion,

a plurality of elongated light sources formed continuously along and adjacent to said peripheral edge such that the entire periphery thereof provides a light source input wherein light is provided uniformly into said plate interior portion substantially along the entire periphery of said plate,

said light sources having a dimensional width equal to or less than the thickness of said plate,

said one major surface including a diffusion pattern that contains a plurality of separate light dispersing features wherein area ratio of size of said light dispersing features monotonically increase from said plate peripheral edge of said plate to a central region of said plate wherein the area ratio size of said features is maximum,

said other major surface including a diffusion means permitting transmission of light therethrough, renders said diffusion pattern visually indiscernible as viewed externally from said other major surface and causing light exiting therethrough to leave said plate in a lobar pattern formation.

11. The background lighting apparatus of claim 10 wherein said plate has a thickness in the range of 1 mm to 6 mm and said light dispersing features having a spatial pitch in the range of 0.5 mm to 2.0 mm.

12. The background lighting apparatus of claim 11 wherein said pitch is uniform across said diffusion pattern.

13. The background lighting apparatus of claim 10 wherein said light sources are elongated fluorescent lamps having a tube diameter in the range of 3 mm to 4 mm, said plate having a thickness in the range of 4 mm to 6 mm.

14. The background lighting apparatus of claim 13 wherein said plate is rectilinear or polygon shape, at least one of said elongated fluorescent lamps having a length and intermediate bent section to correspond along at least two angularly disposed edge surfaces of said plate peripheral edge.

17. The background lighting apparatus of claim 10 employed with an adjoining LCD panel in a display apparatus.

20. The background lighting apparatus of claim 10 employed with an adjoining LCD panel in a color display apparatus.