Liquid crystal display device having high brightness and high contrast

• US 5,995,180 A
• Filed: 06/17/1998
• Issued: 11/30/1999
• Est. Priority Date: 07/07/1997
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Moriwaki, Hiroyuki, Ashida, Takeyuki, Yoshimura, Kazuya
• Primary Examiner(s): Dang, Hung Xuan
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US09/098,970
• Time in Patent Office: 531 Days
• Field of Search: 349/96, 349/112, 349/113, 349/117, 349/119, 359/485, 359/488, 359/490, 359/494, 359/495
• US Class Current: 349/96
• CPC Class Codes: G02F 1/133528 Polarisers

Abstract

A liquid crystal display having high brightness and high contrast and being able to achieve a paper-white appearance is provided. The liquid crystal cell is interposed between a pair of polarizing plates. The upper polarizing plate separates an incident light into a reflected light and a transmitted light. A light which would be absorbed when the dichroic polarizing plate is used, is utilized as a reflected light, so that a high brightness can be obtained. The lower polarizing plate partly transmits incident light and absorbs the remaining part. A reflected light from the lower polarizing plate is removed, so that the possible occurrence of a reduction in contrast attributed to the phenomenon that the reflected light is reflected on the upper polarizing plate is prevented. The upper polarizing plate has a flat spectral characteristic with regard to the reflected light and the transmitted light, and a* value and b* value of which plate are each smaller than 1. Therefore, no coloring occurs in the reflected light and the transmitted light at the upper polarizing plate, so that the paper-white appearance can be easily achieved.

Claims

1. A liquid crystal display device having a liquid crystal layer and a pair of polarizing layers between which the liquid crystal layer is interposed, wherein

one polarizing layer of the pair of polarizing layers, located on an observer side, is a polarizing layer which separates an incident light into a reflected light and a transmitted light, and

the other polarizing layer of the pair of polarizing layers is a polarizing layer which transmits part of the incident light and absorbs the remaining part.

2. A liquid crystal display device as claimed in claim 1, wherein

the one polarizing layer is a polarizing layer on which the reflected light has a roughly flat spectral characteristic.

3. A liquid crystal display device as claimed in claim 1, wherein

the one polarizing layer is a polarizing layer

in which chromaticness indices a* and b* in a CIELAB space have values expressed by a* #1 and b* #1 and

the transmitted light has a roughly flat spectral characteristic.

4. A liquid crystal display device as claimed in claim 1, wherein

the one polarizing layer separates the incident light into a linearly polarized reflected light and a linearly polarized transmitted light.

5. A liquid crystal display device as claimed in claim 1, wherein

the other polarizing layer is a dichroic polarizing plate.

6. A liquid crystal display device as claimed in claim 1, wherein

a light diffusing layer is laminated on the observer side of the one polarizing layer.

7. A liquid crystal display device as claimed in claim 1, wherein

a light reflecting layer is provided on a side opposite to the observer side of the other polarizing layer.

8. A liquid crystal display device as claimed in claim 7, wherein

the light reflecting layer has a directivity in a direction in which light is reflected.

9. A liquid crystal display device as claimed in claim 1, wherein

the one polarizing layer has no right-side up with regard to a transmitted light characteristic and a reflected light characteristic.