Liquid crystal display

• US 6,104,454 A
• Filed: 11/20/1996
• Issued: 08/15/2000
• Est. Priority Date: 11/22/1995
• Status: Expired due to Term

• Current Assignee: Hitachi Displays Limited (Japan Display Incorporated), Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Kondo, Katsumi, Hiyama, Ikuo, Funahata, Katsuyuki
• Primary Examiner(s): Dang, Hung Xuan
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US08/752,795
• Time in Patent Office: 1,364 Days
• Field of Search: 349/61, 349/62, 349/64, 349/65, 349/70, 349/113, 349/96, 349/117, 362/19, 362/26, 362/31, 362/224, 362/331, 362/332, 359/487, 359/488, 359/494, 359/495, 359/498, 385/11, 385/129, 385/130, 385/131, 385/146, 385/901
• US Class Current: 349/65
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

A backlight device having a light source, a waveguide provided close to the light source, this waveguide being a wedge-shaped waveguide so constructed that the incident light from the light source can be greatly changed in its direction and made to exit therefrom, a polarizing beam splitter provided on the light-exiting side of the wedge-shaped waveguide, and a light converter disposed on the light-exiting side of the polarizing beam splitter. This backlight device is used for liquid crystal displays.

Claims

1. A liquid crystal display having a backlight device comprising:

a light source;

a waveguide provided close to said light source;

light converting means provided at said light source and said waveguide so that light from said light source can be made substantially parallel; and

polarizing means for causing polarized light from said waveguide to exit substantially perpendicularly to the direction in which said waveguide guides the light from said light converting means.

2. A liquid crystal display according to claim 1, wherein the degree of parallel of light exiting from said backlight device is within ±

10 degrees.

3. A liquid crystal display according to claim 1, wherein the degree of polarization of light exiting from said backlight device is 80% or above.

4. A liquid crystal display having a backlight device comprising:

a light source;

a waveguide provided close to said light source; and

light converting means provided at said light source and said waveguide so that light from said light source can be made substantially parallel, said waveguide for guiding the light from said light converting means having formed therein diagonally laminated transparent media and polarization eliminators of which the refractive indexes are different from that of said waveguide.

10. A liquid crystal display according to claim 4, wherein the refractive indexes of said waveguide and said transparent media and the angle at which said transparent media are tilted are determined to substantially meet Brewster angle to the light guided in said waveguide.

5. A liquid crystal display having a backlight device comprising:

a light source;

a waveguide provided close to said light source; and

light converting means provided at said light source and said waveguide so that light from said light source can be made substantially parallel, said waveguide for guiding the light from said light converting means having formed therein diagonally laminated transparent media and retardation films of which the refractive indexes are different from that of said waveguide.

6. A liquid crystal display according to claim 5, wherein the spacings of said laminated layers is decreased with the increase of the distance from said light source.

7. A liquid crystal display according to claim 5, wherein the film thickness of said transparent media is changed with the increase of the distance from said light source.

8. A liquid crystal display according to claim 5, wherein the refractive index difference between said transparent media and said waveguide, and the angle at which said transparent media are tilted are increased with the increase of the distance from said light source.

9. A liquid crystal display according to claim 8, wherein second light converting means for greatly changing light path with the increase of the distance from the light source is provided on the surface of said waveguide from which light exits substantially perpendicularly to said surface of said waveguide.

11. A liquid crystal display according to claim 5, wherein the refractive indexes of said waveguide and said transparent media and the angle at which said transparent media are tilted are determined to be substantially Brewster'"'"'s angle to the light guided in said waveguide.