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

• US 7,944,526 B2
• Filed: 03/09/2010
• Issued: 05/17/2011
• Est. Priority Date: 07/03/2006
• Status: Expired due to Fees

• Current Assignee: Hitachi Displays Limited (Japan Display Incorporated), Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi Displays Limited (Japan Display Incorporated), IPS Alpha Technology Limited (Panasonic Holdings Corporation)
• Inventors: Sekiguchi, Yoshifumi, Hiyama, Ikuo, Imajo, Yoshihiro, Taniguchi, Hitoshi
• Primary Examiner(s): Ullah; Akm E
• Application Number:
  US12/659,456
• Publication Number:
  US 20100165250A1
• Time in Patent Office: 434 Days
• Field of Search: 349/64, 349/65, 349/66, 349/70, 349/71, 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 linear-shaped light sources arranged in the inside of the housing; and

a diffusion plate which is arranged between the plurality of linear-shaped light sources and the liquid crystal panel, the diffusion plate including a plurality of light blocking regions at positions respectively corresponding to the plurality of linear-shaped light sources, the plurality of light blocking regions including a light blocking region at a center portion of the housing and a light blocking region at an edge portion of the housing that exhibit different transmissivities from each other.

2. A liquid crystal display device according to claim 1, wherein each of the linear-shaped light sources is a hot cathode fluorescent lamp (HCFL).

3. A liquid crystal display device according to claim 1, wherein each of the light blocking regions has a crest shape, the crest shape including crest-like irregularities and being arranged parallel to a longitudinal direction of the linear-shaped light sources.

4. A liquid crystal display device according to claim 3, wherein the crest shape has a narrow width at a center portion and a wide width at a peripheral portion.

5. A liquid crystal display device according to claim 3, wherein respective crests of the crest-like irregularities of the crest shape have a long ridge at a center side and a short ridge at a peripheral side.

6. A liquid crystal display device according to claim 3, wherein the 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 respectively corresponding linear-shaped light source as a center, and the housing-edge-side exhibits the higher transmissivity.

7. A liquid crystal display device according to claim 1, wherein the plurality of light blocking regions have a plurality of rectangular reflection patterns, and the reflection patterns are narrower in the light blocking region at the edge portion of the housing than the center portion of the housing.