Liquid crystal display device with a backlight unit having a diffusion plate

• US 7,705,930 B2
• Filed: 06/29/2007
• Issued: 04/27/2010
• Est. Priority Date: 07/03/2006
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Hitachi Displays Limited (Japan Display Incorporated), IPS Alpha Technology Limited (Milliken & Company)
• Inventors: Sekiguchi, Yoshifumi, Hiyama, Ikuo, Imajo, Yoshihiro, Taniguchi, Hitoshi
• Primary Examiner(s): Ullah; Akm E
• Application Number:
  US11/819,906
• Publication Number:
  US 20080002098A1
• Time in Patent Office: 1,033 Days
• Field of Search: 349/65, 349/66, 349/70, 349/71, 349/64, 349/62, 362/29, 362/97
• US Class Current: 349/64
• CPC Class Codes: G02B 5/0263 with positional variation of the diffusing properties, e.g. gradient or patterned diffuser
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/0294 adapted to provide an additional optical effect, e.g. anti-reflection or filter
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity

Abstract

A liquid crystal display device having a direct backlight which uses a high-bright light source achieves both of a high efficiency and thin uniformity. In a liquid crystal display device which includes a liquid crystal panel, and a backlight unit which is arranged on a side of the liquid crystal panel opposite to a display screen of the liquid crystal panel, the backlight unit includes a housing, a plurality of light sources arranged in the inside of the housing, and a diffusion plate which is arranged between the plurality of light sources and the liquid crystal panel, the diffusion plate includes a plurality of light blocking regions at positions corresponding to the plurality of respective light sources, and the light blocking region at a center portion of the housing and the light blocking region at an edge portion of the housing exhibits transmissivities different from each other.

Claims

1. A liquid crystal display device comprising:

a liquid crystal panel; and

a backlight unit which is arranged on a side of the liquid crystal panel opposite to a display screen of the liquid crystal panel, wherein

the backlight unit includes;

a housing,

a plurality of light sources arranged in the inside of the housing;

a diffusion plate which is arranged between the plurality of light sources and the liquid crystal panel; and

an intermediate plate which is formed between the plurality of light sources and the diffusion plate, and

the intermediate plate includes a plurality of light blocking regions at positions corresponding to the plurality of respective light sources.

2. A liquid crystal display device according to claim 1, wherein the light source is a hot cathode fluorescent lamp (HCFL).

3. A liquid crystal display device according to claim 1, wherein respective widths of the plurality of light blocking regions are set larger than a radial width of the light sources.

4. A liquid crystal display device according to claim 1, wherein the transmissivity differs between the light blocking region at a center portion of the housing and the light blocking region at an edge portion of the housing.

5. A liquid crystal display device according to claim 1, wherein crest-like irregularities arranged parallel to the longitudinal direction of the light source are formed on the light blocking region.

6. A liquid crystal display device according to claim 5, wherein the crest shape of the light blocking region is a crest shape which has a narrow width at a center portion and a wide width at a peripheral portion.

7. A liquid crystal display device according to claim 5, wherein respective crests of the irregularities of the light blocking region have a long ridge at a center side and a short ridge at a peripheral side.

8. A liquid crystal display device according to claim 5, wherein a crest shape of the light blocking region at the edge portion of the housing is formed such that a housing-center-side shape and a housing-edge-side shape are formed in asymmetry providing the light source as a center, and the housing-edge-side exhibits the higher transmissivity.

9. A liquid crystal display device according to claim 1, wherein the plurality of light blocking regions form a plurality of rectangular reflection patterns, and an area for forming the reflection patterns is narrower in the light blocking region at the edge portion of the housing than in the light blocking region at the center portion of the housing.

10. A liquid crystal display device according to claim 1, wherein the light blocking region at the center portion of the housing and the light blocking region at the edge portion of the housing have the same transmissivity.

11. A liquid crystal display device according to claim 1, wherein a total light transmissivity of the intermediate plate except for the light blocking region is higher than a total light transmissivity of the diffusion plate.