Liquid crystal display apparatus

• US 20030151712A1
• Filed: 12/27/2002
• Published: 08/14/2003
• Est. Priority Date: 12/28/2001
• Status: Abandoned Application

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Ogawa, Shinji, Inoue, Kazuhiro, Ishida, Satoshi, Yamada, Tsutomu, Yamashita, Tohru, Oda, Nobuhiko, Koma, Norio
• Application Number:
  US10/330,998
• Publication Number:
  US 20030151712A1
• Time in Patent Office: Days
• US Class Current: 349/139
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/136227 Through-hole connection of the pixel electrode to the active element through an insulation layer
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 2300/0456 with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes

Abstract

An LCD apparatus having a liquid crystal layer sealed between a first substrate having a first electrode and a second substrate having a second electrode, wherein the first substrate comprises a reflective layer formed only in a subregion within a pixel region, for reflecting light. A transparent conductive material is used for the first electrode and the first electrode made of the transparent conductive material is layered to cover a transmissive region within a pixel region and over the reflective layer in a reflective region within the pixel region to directly cover the reflective layer. Optimum cell gaps dr and dt are set in the reflective and the transmissive regions, respectively, based on a twist angle, which is a difference between the alignment directions of liquid crystal at the side of the first electrode and of liquid crystal at the side of the second electrode so that an optimum reflectivity and an optimum transmittance are realized in each region to allow enhancements in the quality of a transflective LCD. A configuration may be employed in which a switching element is formed over the first substrate and the reflective layer is placed in the reflective region of a pixel region on an insulating film which covers the switching element, the reflective layer being insulated from the switching element, the work functions for the first electrode and for the second electrode are similar.

Claims

1. A liquid crystal display apparatus having a liquid crystal layer sealed between a first substrate having a first electrode and a second substrate having a second electrode, wherein

the first substrate comprises a reflective layer formed only in a subregion within a pixel region, for reflecting light transmitted and incident through the second substrate and the second electrode to the liquid crystal layer;

a transparent conductive material is used for the first electrode;

the first electrode made of the transparent conductive material is layered to cover a transmissive region within a pixel region and over the reflective layer in a reflective region within the pixel region to directly cover the reflective layer;

a twist angle which is a difference between the alignment direction of liquid crystal at the side of the first electrode and the alignment direction of liquid crystal at the side of the second electrode is set to 60°

or greater; and

in a pixel region, a gap dr which is defined as a distance between the first electrode and the second electrode in the reflective region is approximately equal to a gap dt which is defined as a distance between the first electrode and the second electrode in the transmissive region.

2. A liquid crystal display apparatus according to claim 1, wherein a difference between a work function of the transparent conductive material for the first electrode and a work function of a transparent conductive material for the second electrode formed on the second substrate side over a surface facing the liquid crystal layer is 0.5 eV or less.

3. A liquid crystal display apparatus according to claim 1, wherein

a switching element is formed for each pixel over the first substrate;

the reflective layer is placed on an insulating film which covers the switching element, the reflective layer being insulated from the switching element; and

a connecting metal layer is formed within a contact hole formed in the insulating film covering the switching element and the switching element and the first electrode are electrically connected through the connecting metal layer.

4. A liquid crystal display apparatus according to claim 1, wherein the driving frequency of the liquid crystal layer for each pixel is 60 Hz or less.

5. A liquid crystal display apparatus having a liquid crystal layer sealed between a first substrate having a first electrode and a second substrate having a second electrode, wherein

the first substrate comprises a reflective layer formed only in a subregion within a pixel region, for reflecting light transmitted and incident through the second substrate and the second electrode to the liquid crystal layer;

a transparent conductive material is used for the first electrode;

the first electrode made of the transparent conductive material is layered to cover a transmissive region within a pixel region and over the reflective layer in a reflective region within the pixel region to directly cover the reflective layer;

a twist angle which is a difference between the alignment direction of liquid crystal at the side of the first electrode and the alignment direction of liquid crystal at the side of the second electrode is set to 80°

or less;

a gap adjustment layer is formed below the reflective layer formed in the reflective region; and

in a pixel region, a difference between a gap dr which is defined as a distance between the first electrode and the second electrode in the reflective region and a gap dt which is defined as a distance between the first electrode and the second electrode in the transmissive region is greater than the thickness of the reflective layer.

6. A liquid crystal display apparatus according to claim 5, wherein

when the twist angle is approximately 0°

, a gap dt which is defined as the distance between the first electrode and the second electrode in the transmissive region and a gap dr which is defined as the distance between the first electrode and the second electrode in the reflective region within the pixel region satisfy a condition that dr is approximately 0.4 times-0.6 times dt.

7. A liquid crystal display apparatus according to claim 5, wherein

a difference between a work function of the transparent conductive material for the first electrode and a work function of a transparent conductive material for the second electrode formed on the second substrate side over a surface facing the liquid crystal layer is 0.5 eV or less.

8. A liquid crystal display apparatus according to claim 5, wherein

a switching element is formed for each pixel over the first substrate;

the reflective layer is placed on an insulating film which covers the switching element, the reflective layer being insulated from the switching element; and

a connecting metal layer is formed within a contact hole formed in the insulating film covering the switching element and the switching element and the first electrode are electrically connected through the connecting metal layer.

9. A liquid crystal display apparatus according to claim 5, wherein the driving frequency of the liquid crystal layer for each pixel is 60 Hz or less.