Light guide plate having orthogonal stresses or strains and backlight module therewith

• US 7,806,537 B2
• Filed: 07/17/2006
• Issued: 10/05/2010
• Est. Priority Date: 07/20/2005
• Status: Active Grant

• Current Assignee: Hon Hai Precision Industry Co., Ltd., Tsinghua University
• Original Assignee: Hon Hai Precision Industry Co., Ltd., Tsinghua University
• Inventors: Jin, Guo-Fan, Yang, Xing-Peng, Yan, Ying-Bai
• Primary Examiner(s): Lee; Jong-Suk (James)
• Assistant Examiner(s): SPINELLA, KEVIN
• Application Number:
  US11/309,236
• Publication Number:
  US 20070076432A1
• Time in Patent Office: 1,541 Days
• Field of Search: 362/19, 362/615, 362/617, 362/623, 362/626, 362/629
• US Class Current: 362/19
• 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 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements

Abstract

A backlight module includes a light guide plate (52), a light source (51), a reflecting sheet (53), a diffusion sheet (54), and a reflective polarizing beam splitter (57). The light guide plate includes a light input surface (521), a light output surface (522) adjacent to the light input surface, a reflecting surface (523) opposite the light output surface, and a number of microstructures (524) located on the reflecting surface. In the light guide plate, stress-induced birefringence is introduced to achieve a polarization state conversion, thereby facilitating efficient use of the light generated by the light source.

Claims

1. A light guide plate, comprising:

a light input surface, a light output surface adjacent to the light input surface, and a reflective surface opposite to the light output surface;

two orthogonal stresses or strains existing in the light guide plate, an angle in the range more than about 0 and less than about 90 degrees between one of the two orthogonal stresses or strains and the light input surface of the light guide plate, a stress or strain difference existing between the two orthogonal stresses or strains;

a phase retardation due to the stress or strain difference, the phase retardation being defined by the equations;

2. The light guide plate as defined in claim 1, wherein the angle between one stress or strain and the light input surface is about 45 degrees.

3. The light guide plate as defined in claim 1, wherein the stress or strain is defined by the minimum of an objective function:

4. The light guide plate as defined in claim 1, wherein a plurality of microstructures is formed on the reflective surface of the light guide plate.

5. The light guide plate as defined in claim 4, wherein at least one of the plurality of microstructures is in the shape of a V-shaped groove.

6. A light guide plate, comprising:

a light input surface configured for inputting light beams emitting from a light source;

a light output surface adjacent to the light input surface, and configured for outputting a plane light;

a reflective surface opposite to the light output surface, and configured for reflecting the light beams toward the light output surface; and

two orthogonal strains existing in the light guide plate,

wherein,

one of the two orthogonal strains and the light input surface of the light guide plate form an angle in a range of more than about 0 and less than about 90 degrees therebetween;

a strain difference exists between the two orthogonal strains; and

a phase retardation is achieved due to the strain difference, for making a S-polarized light passing through the light guide plate twice to be converted into a P-polarized light, the S-polarized light is input from the light output surface and reflected by the reflective surface.

7. The light guide plate as defined in claim 6, wherein the angle between one stress or strain and the light input surface is about 45 degrees.

8. The light guide plate as defined in claim 6, wherein a plurality of microstructures is formed on the reflective surface of the light guide plate.

9. The light guide plate as defined in claim 6, wherein polarization of the S-polarized light is perpendicular to polarization of the P-polarized light.