Liquid-crystal display device

• US 6,590,625 B1
• Filed: 05/23/2000
• Issued: 07/08/2003
• Est. Priority Date: 05/24/1999
• Status: Expired due to Fees

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Umemoto, Seiji, Yano, Shuuji
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US09/576,195
• Time in Patent Office: 1,141 Days
• Field of Search: 349/65, 349/114, 385/146, 362/556, 362/561, 362/554, 362/26, 362/31
• US Class Current: 349/65
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer

Abstract

A liquid-crystal display device has a light pipe, a light source, a reflection layer, a light diffusion layer, and a liquid-crystal shutter. The light pipe is provided with light output means formed on an upper surface thereof. The light source is disposed near to an incident side surface of the light pipe so that light incident on the light pipe from the light source is delivered from a lower surface of the light pipe through the light output means. The reflection layer is disposed on the lower surface of the light pipe so that reflected light of the output light is transmitted through the upper surface. The light diffusion layer has polarization-keeping characteristic. The liquid-crystal shutter is disposed on the upper surface of the light pipe through the light diffusion layer, the liquid-crystal shutter including liquid-crystal cells and at least one polarizing plate.

Claims

1. A liquid-crystal display device comprising:

a light pipe including light output means formed on an upper surface of said light pipe;

a light source disposed near to an incident side surface of said light pipe so that light incident on said light pipe from said light source is output from an upper surface of said light pipe through said light output means;

a reflection layer disposed on the lower surface of said light pipe so that light reflected from said light output means is made incident on and reflected by said reflection layer to travel toward said upper surface of said light pipe;

a light diffusion layer having polarization-keeping characteristic; and

a liquid-crystal shutter disposed on the upper surface of said light pipe through said light diffusion layer, said liquid-crystal shutter including liquid-crystal cells and at least one polarizing plate.

2. A liquid-crystal display device according to claim 1, wherein said light source can be switched on and off.

3. A liquid-crystal display device according to claim 1, wherein said light output means provided on the upper surface of said light pipe comprising:

slopes facing said incident side surface and inclined at an angle of from 35 to 45 degrees with respect to a reference plane of said lower surface; and

flat surfaces inclined at a crossing angle of not larger than 10 degrees with respect to said reference plane and provided so that projected area of said flat surfaces on said reference plane is not smaller than 8 times as large as projected area of said slopes on said reference plane.

4. A liquid-crystal display device according to claim 1, wherein said light output means on said upper surface of said light pipe has a repetition structure of continuous or discontinuous prism-like irregularities arranged at intervals of a pitch of from 50 μ

m to 1.5 mm, each of said prism-like irregularities comprising;

a short side surface constituted by slopes inclined downward from the incident side surface to an opposite end at an inclination angle of from 35 to 45 degrees with respect to said reference plane of said lower surface; and

a long side surface constituted by a slope inclined at an inclination angle in a range of from 0 to 10 degrees, exclusive of 0 degree, with respect to said reference plane so that the difference in the inclination angle among all of said slopes of the long side surface is within 5 degrees and the difference in the inclination angle between adjacent long side surfaces is within 1 degree,

wherein projected area of the long side surfaces on said reference plane is not smaller than 8 times as large as projected area of the short side surfaces on said reference plane.

5. A liquid-crystal display device according to claim 4, wherein the repetition pitch of said prism-like irregularities is constant.

6. A liquid-crystal display device according to claim 4, wherein a projected width of each of said short side surfaces on said reference plane is not larger than 40 μ

m.

7. A liquid-crystal display device according to claim 4, wherein a ridge line direction of said prism-like irregularities is within ±

35 degrees with respect to a reference plane of said incident side surface.

8. A liquid-crystal display device according to claim 1, wherein incident light from said lower surface is transmitted through said upper surface at total light-rays transmissivity of not lower than 90%.

9. A liquid-crystal display device according to claim 1, wherein said reflection layer is made of at least one selected from the group of consisting gold, silver, aluminum and a dielectric multilayer film.

10. A liquid-crystal display device according to claim 1, wherein said reflection layer is in close contact with said lower surface of said light pipe so as to be integrated therewith.

11. A liquid-crystal display device according to claim 1, wherein said reflection layer reflects light while diffusing said light.

12. A liquid-crystal display device according to claim 1, wherein said polarization-keeping light diffusion layer exhibits light transmissivity of not higher than 2% when said light diffusion layer is disposed between crossed-Nicol prisms.

13. A liquid-crystal display device according to claim 4, wherein said light source can be switched on and off.

14. A liquid-crystal display device according to claim 4, wherein incident light from said lower surface is transmitted through said upper surface at total light-rays transmissivity of not lower than 90%.

15. A liquid-crystal display device according to claim 4, wherein said reflection layer is made of at least one selected from the group of consisting gold, silver, aluminum and a dielectric multilayer film.

16. A liquid-crystal display device according to claim 4, wherein said reflection layer is in close contact with said lower surface of said light pipe so as to be integrated therewith.

17. A liquid-crystal display device according to claim 4, wherein said reflection layer reflects light while diffusing said light.

18. A liquid-crystal display device according to claim 4, wherein said polarization-keeping light diffusion layer exhibits light transmissivity of not higher than 2% when said light diffusion layer is disposed between crossed-Nicol prisms.