Background lighting apparatus for liquid crystal display

• US 5,931,555 A
• Filed: 02/03/1997
• Issued: 08/03/1999
• Est. Priority Date: 05/18/1989
• Status: Expired due to Fees

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Yagasaki, Tooru, Funamoto, Tatsuaki, Akahane, Fumiaki
• Primary Examiner(s): CARIASO, ALAN B
• Application Number:
  US08/794,652
• Time in Patent Office: 911 Days
• Field of Search: 349/62, 349/64, 349/65, 362/26, 362/27, 362/31, 362/216, 362/246
• US Class Current: 362/613
• 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 specular 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 comprising:

a transparent plate defining first and second major surfaces, said transparent plate terminating in a first edge, a second edge facing said first edge, a third edge and a fourth edge facing said third edge;

a plurality of light sources positioned so as to radiate light into said transparent plate from each of said edges; and

a pattern of geometrically-shaped diffusion elements formed on at least one of said first and said second surfaces, each diffusion element having a surface area, wherein the surface area of said diffusion elements gradually increases toward a first axis between said first and second edges, and gradually increases toward a second axis between said third and fourth edges so that the luminance distribution on the at least one of said first and second surfaces is substantially uniform.

2. The background lighting apparatus of claim 1, wherein each of said first and second major surfaces defines a plurality of corner regions, wherein the surface area of said diffusion elements reaches a minimum at at least one of said plurality of corner regions.

3. The background lighting apparatus of claim 1, wherein each of said first and second major surfaces defines a central region, wherein the surface area of said diffusion elements reaches a maximum at said central region.

4. The background lighting apparatus of claim 1, wherein said transparent plate is a rectangle.

5. The background lighting apparatus of claim 1, wherein said diffusion elements are uniformly disposed throughout at least one of said first and second major surfaces of said transparent plate.

6. A display apparatus comprising;

a LCD panel;

a background lighting apparatus adjoining said LCD panel comprising a transparent plate defining first and second major surfaces, said transparent plate terminating in a first edge, a second edge facing said first edge, a third edge and a fourth edge facing said third edge;

a plurality of light sources positioned so as to radiating light into said transparent plate from each of said edges; and

a pattern of geometrically-shaped diffusion elements formed on at least one of said first and said second surfaces, each diffusion element having a surface area, wherein the surface area of said diffusion elements gradually increases toward a first axis between said first and second edges, and gradually increases toward a second axis between said third and fourth edges so that the luminance distribution on the at least one of said first and second surfaces is substantially uniform.

7. The display apparatus of claim 6, wherein each of said first and second major surfaces defines a plurality of corner regions, wherein the surface area of said diffusion elements reaches a minimum at at least one of said plurality of corner regions.

8. The display apparatus of claim 6, wherein each of said first and second major surfaces defines a central region, wherein the surface area of said diffusion elements reaches a maximum at said central region.

9. The display apparatus of claim 6, wherein said transparent plate is a rectangle.

10. The display apparatus of claim 6, wherein said diffusion elements are uniformly disposed throughout at least one of said first and second major surfaces of said transparent plate.