Light guide apparatus, a backlight apparatus and a liquid crystal display apparatus

• US 6,867,828 B2
• Filed: 11/17/2003
• Issued: 03/15/2005
• Est. Priority Date: 10/08/1999
• Status: Expired due to Term

• Current Assignee: AU Optronics Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Yamada, Fumiaki, Taira, Yoichi, Nishikai, Akiko
• Primary Examiner(s): Dudek, James A.
• Application Number:
  US10/713,116
• Publication Number:
  US 20040105046A1
• Time in Patent Office: 484 Days
• Field of Search: 349/65, 362/31
• US Class Current: 349/65
• 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: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

A backlight apparatus (and light guide and liquid crystal display apparatus incorporating the same) includes a wedge-type light guide having a refractive index n1, and having a top surface, a bottom surface and a side surface, a light source for directing light to the side surface of the wedge-type light guide, a first light transmission layer having a refractive index n2, which is smaller than said refractive index n1, and having a top surface and a bottom surface, wherein the top surface of the first light transmission layer is attached to the bottom surface of the wedge-type light guide, and a light deflecting layer having a top surface attached to the bottom surface of the first light transmission layer for deflecting the incident light from the first light transmission layer toward the top surface of the wedge-type light guide.

Claims

1. A backlight apparatus comprising:

a wedge-type light guide comprising a refractive index n1, and comprising a top surface, a bottom surface and a side surface;

a light source for directing light to said side surface of said wedge-type light guide;

a light transmission layer comprising a refractive index n2, which is smaller than said refractive index n1, and comprising a top surface and a bottom surface, wherein said bottom surface of said light transmission layer is attached to said top surface of said wedge-type light guide; and

a plurality of prisms attached on said top surface of said light transmission layer for directing the incident light from said light transmission layer toward a light path along a direction of a normal line of said top surface of said light transmission layer and for controlling an angle spread of said incident light from the top said light-transmission layer.

2. The backlight apparatus according to claim 1, wherein the range of said refractive index n1 of said wedge-type light guide is substantially 1.4 through substantially 2.0, and the range of said refractive index n2 of said light transmission layer is substantially 1.2 through substantially 1.4.

3. The backlight apparatus according to claim 2, wherein said refractive index n1 of said wedge-type light guide is substantially 1.49, and said refractive index n2 of said light transmission layer is substantially 1.3.

8. The backlight apparatus according to claim 1, wherein said plurality of prisms for controlling said angle spread of said incident light from the top surface of said light-transmission layer narrow said angle spread of said incident light from the top surface of said light-transmission layer.

11. The backlight apparatus according to claim 1, further comprising a polarizer adjacent to said plurality of prisms,

wherein said incident light is emitted from said plurality of prisms in said direction of said normal line of said top surface of said light transmission layer to said polanzer.

4. A liquid crystal display (LCD) apparatus comprising:

an LCD panel including an upper transparent substrate, a lower transparent substrate, and a liquid crystal material filled between said upper transparent substrate and said lower transparent substrate;

a light diffusing layer adjacent to said upper transparent substrate; and

a backlight apparatus adjacent to said lower transparent substrate, wherein said backlight apparatus comprises;

a wedge-type light guide comprising a refractive index n1, and comprising a top surface, a bottom surface and a side surface;

a light source for directing light to said side surface of said wedge-type light guide;

a light transmission layer comprising a refractive index n2, which is smaller than said refractive index n1, and comprising a top surface and a bottom surface, wherein said bottom surface of said light transmission layer is attached to said top surface of said wedge-type light guide; and

a plurality of prisms attached on said top surface of said light transmission layer for directing the incident light from said light transmission layer toward a light path along a direction of a normal line of said top surface of said light transmission layer and for controlling an angle spread of said incident light from the top surface of said light-transmission layer.

5. The LCD apparatus according to claim 4, wherein the range of said refractive index n1 of said wedge-type light guide is substantially 1.4 through substantially 2.0, and the range of said refractive index n2 of said light transmission layer is substantially 1.2 through substantially 1.4.

6. The LCD apparatus according to claim 4, wherein said refractive index n1 of said wedge-type light guide is substantially 1.49, and said refractive index n2 of said light transmission layer is substantially 1.3.

9. The liquid crystal display (LCD) apparatus according to claim 4, wherein said plurality of prisms for controlling said angle spread of said incident light from the top surface of said light-transmission layer narrow said angle spread of said incident light from the top surface of said light-transmission layer.

12. The liquid crystal display (LCD) apparatus according to claim 4, further comprising a polarizer adjacent to said plurality of prisms,

wherein said incident light is emitted from said plurality of prisms in said direction of said normal line of said top surface of said light transmission layer to said polarizer.

7. A light guide apparatus comprising:

a wedge-type light guide comprising a refractive index n1, and comprising a top surface, a bottom surface and a side surface;

a light transmission layer comprising a refractive index n2, which is smaller than said refractive index n1, and comprising a top surface and a bottom surface, wherein said bottom surface of said light transmission layer is attached to said top surface of said wedge-type light guide; and

a plurality of prisms attached on said top surface of said light transmission layer for directing the incident light from said light transmission layer toward a light path along a direction of a normal line of said top surface of said light transmission layer and for controlling an angle spread of said incident light from the top surface of said light-transmission layer.

10. The light guide apparatus according to claim 7, wherein said plurality of prisms for controlling said angle spread of said incident light from the top surface of said light-transmission layer narrow said angle spread of said incident light from the top surface of said light-transmission layer.

13. The light guide apparatus according to claim 7, further comprising a polarizer adjacent to said plurality of prisms,

wherein said incident light is emitted from said plurality of prisms in said direction of said normal line of said top surface of said light transmission layer to said polarizer.

14. A backlight apparatus comprising:

a wedge-shaped light guide comprising a refractive index n1,

wherein said wedge-shaped light guide includes a top surface and a side surface, said side surface receiving light from a light source;

a light transmission layer comprising a refractive index n2 and includes a top surface and a bottom surface, said bottom surface being disposed directly on said top surface of said wedge-shaped light guide, and

wherein said refractive index n2 is less than said refractive index n1; and

means for directing the incident light from said light transmission layer toward a light path along a direction of a normal line of said top surface of said light transmission layer and for controlling an angle spread of said incident light from the top surface of said light-transmission layer,

wherein said means for directing and controlling is disposed directly on said top surface of said light transmission layer.