Back light unit including a diffuser with various diffusion effects

• US 6,861,789 B2
• Filed: 10/01/2002
• Issued: 03/01/2005
• Est. Priority Date: 02/07/2002
• Status: Expired due to Fees

• Current Assignee: InnoLux Corporation
• Original Assignee: CHI MEI Optoelectronics Corporation
• Inventors: Wei, Chung-Kuang
• Primary Examiner(s): Patel, Ashok
• Assistant Examiner(s): Roy, Sikha
• Application Number:
  US10/065,289
• Publication Number:
  US 20030146680A1
• Time in Patent Office: 882 Days
• Field of Search: 313/116, 313/113, 362/31, 362/330, 362/331, 362/339, 362/223, 362/355, 349/112, 349/113, 349/86, 349/61, 349/64, 359/615
• US Class Current: 313/116
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity

Abstract

A backlight unit is disposed beneath a display panel. The backlight unit includes an illumination means, which is used to provide a light source, and a diffuser positioned between the illumination means and the display panel, which is used to scatter the light generated by the illumination means. The diffuser, which is composed of liquid crystal particles and polymer, has a plurality of regions. The region thatis closer to the illumination means has greater scattering effect. In addition, the region with the greatest scattering effect has a shape corresponding to the illumination means.

Claims

1. A back light unit disposed under a display panel, the back light unit comprising:

a luminous means as a light source for providing light beams; and

a diffuser interposed between the luminous means and the display panel for diffusing the light beams to the display panel, wherein the diffuser is composed of liquid crystal molecules and polymers and comprises a plurality of regions with different diffusion effects;

wherein a region with greater diffusion effect is closer to the luminous means than that with smaller diffusion effect.

2. The back light unit of claim 1 wherein regions with different diffusion effects are formed of liquid crystal droplets with different sizes.

3. The back light unit of claim 1 wherein the region which is closer to the luminous means is composed of smaller liquid crystal droplets.

4. The back light unit of claim 1 wherein a location of the regions with greatest diffusion effect corresponds to a location of the luminous means.

5. The back light unit of claim 1 wherein a shape of the regions with greatest diffusion effect corresponds to a shape of the luminous means.

6. The back light unit of claim 1 wherein the diffusion effect of the diffuser changes according to an electric field applied thereon.

7. The back light unit of claim 6 wherein the back light unit further comprises at least one pair of electrode plates, with one plate disposed on each side of the diffuser for applying an electric field to the diffuser.

8. The back light unit of claim 7 wherein the electric field is according to a luminous intensity of the luminous means.

9. The back light unit of claim 1 wherein the diffuser is composed of polymer dispersed liquid crystal (PDLC) molecules.

10. The back light unit of claim 1 wherein the back light unit further comprises a reflective layer disposed under the luminous means for reflecting the light beams to the diffuser.