Vertical alignment active matrix liquid crystal display device having particular reflection metal films

• US 7,787,092 B2
• Filed: 03/24/2009
• Issued: 08/31/2010
• Est. Priority Date: 09/30/2004
• Status: Active Grant

• Current Assignee: InterDigital Patent Holdings, Inc. (InterDigital, Inc.)
• Original Assignee: Casio Computer Company Limited
• Inventors: Morita, Hidehiro, Mizusako, Ryota
• Primary Examiner(s): QI, ZHI QIANG
• Application Number:
  US12/410,223
• Publication Number:
  US 20090185124A1
• Time in Patent Office: 525 Days
• Field of Search: 349142-144, 349/129, 349/130
• US Class Current: 349/142
• CPC Class Codes: G02F 1/133707 Structures for producing distorted electric fields, e.g. bumps, protrusions, recesses, slits in pixel electrodes
• CPC Class Codes: G02F 1/133742 for homeotropic alignment
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• CPC Class Codes: G02F 2201/128 field shaping

Abstract

A liquid crystal display device comprises a TFT substrate, a CF substrate, a liquid crystal with negative dielectric anisotropy filled between the substrates, a pixel electrode provided on the TFT substrate, and an auxiliary electrode formed around the pixel electrode. A slit for segmenting a pixel region into a plurality of sub-pixel regions is formed in the pixel electrode from the center portion of each pixel toward the periphery portion thereof. The auxiliary electrode has a transparent step film formed at a position corresponding to the slit of the pixel electrode in such a way as to overlie the auxiliary electrode. Molecules of the liquid crystal of each sub-pixel region are aligned toward center of the sub-pixel region from the circumference of the sub-pixel region by a horizontal electric filed applied between the pixel electrode and auxiliary electrode, and the shape of the end portion of the transparent step film.

Claims

1. A liquid crystal display device comprising:

a first substrate;

a second substrate arranged opposite to the first substrate;

a liquid crystal layer with a negative dielectric anisotropy filled between respective opposing surfaces of the first substrate and the second substrate;

wherein an opposing electrode is formed on the opposing surface of the first substrate, and a TFT device and a pixel electrode connected to a source electrode of the TFT device are formed on the opposing surface of the second substrate;

wherein an auxiliary electrode is arranged on a lower layer side of the pixel electrode via a first insulation film and is set to an electric potential that is equal to an electric potential of the opposing electrode, and a reflection metal film is deposited on an upper layer side of the pixel electrode via a second insulation film, wherein the lower layer side of the pixel electrode is the side of the pixel electrode where the second substrate is provided, and the upper layer side of the pixel electrode is the side of the pixel electrode where the first substrate is provided;

wherein the pixel electrode has a slit formed in a predetermined shape;

wherein the auxiliary electrode, the reflection metal film, and the second insulation film are formed in a shape corresponding to the predetermined shape of the slit with respective areas that are larger than an area of the slit, and the auxiliary electrode, the reflection metal film, and the second insulation film are arranged to overlap the slit; and

wherein the reflection metal film is formed on the second insulation film such that a step portion of the second insulation film is exposed.

2. The liquid crystal display device according to claim 1, wherein the step portion of the second insulation film is included with respect to the opposing surface of the second substrate.

3. The liquid crystal display device according to claim 1, wherein the slit is cross-shaped.

4. The liquid crystal display device according to claim 1, wherein liquid crystal molecules of the liquid crystal layer are arranged to be aligned perpendicularly with respect to the surfaces near where the molecules are provided when no voltage is applied between the pixel electrode and the opposing electrode.

5. The liquid crystal display device according to claim 1, wherein the pixel electrode is formed with a transparent material.

6. The liquid crystal display device according to claim 1, wherein a surface of the second insulation film contacting the reflection metal film is roughened.

7. The liquid crystal display device according to claim 1, wherein a region of the liquid crystal layer that corresponds to the pixel electrode includes a first region and a second region that is thinner than the first region, and the slit in the pixel electrode overlaps the second region.

8. A liquid crystal display device comprising:

a first substrate;

a second substrate arranged opposite to the first substrate;

a liquid crystal layer with a negative dielectric anisotropy filled between respective opposing surfaces of the first substrate and the second substrate;

wherein an opposing electrode is formed on the opposing surface of the first substrate, and a TFT device and a pixel electrode connected to a source electrode of the TFT device are formed on the opposing surface of the second substrate;

wherein an auxiliary electrode is arranged on a lower layer side of the pixel electrode via a first insulation film and is set to an electric potential that is equal to an electric potential of the opposing electrode, and a reflection metal film is deposited on an upper layer side of the pixel electrode via a second insulation film, wherein the lower layer side of the pixel electrode is the side of the pixel electrode where the second substrate is provided, and the upper layer side of the pixel electrode is the side of the pixel electrode where the first substrate is provided;

wherein the pixel electrode has a slit formed in a predetermined shape;

wherein the auxiliary electrode, the reflection metal film, and the second insulation film are formed in a shape corresponding to the predetermined shape of the slit with respective widths that are wider than a width of the slit, and the auxiliary electrode, the reflection metal film, and the second insulation film are arranged to overlap the slit; and

wherein the reflection metal film is formed on the second insulation film such that a step portion of the second insulation film is exposed.