Reflective plate structure provided in a reflective liquid crystal display having a thin film transistor

• US 6,545,735 B1
• Filed: 07/21/2000
• Issued: 04/08/2003
• Est. Priority Date: 07/22/1996
• Status: Expired due to Term

• Current Assignee: NLT Technologies, Ltd.
• Original Assignee: NEC Corporation
• Inventors: Koide, Shin, Noguchi, Kesao, Yamamori, Shuuki, Katou, Takuya
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US09/621,744
• Time in Patent Office: 991 Days
• Field of Search: 349/113, 349/122, 349/138, 349/43, 349/47
• US Class Current: 349/113
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence

Abstract

In a reflective liquid crystal display, source/drain electrodes are formed on an insulation substrate and separated from each other. A pixel electrode is provided which has an end portion unitary formed with the source electrode and the pixel electrode extending over the insulation substrate. A semiconductor layer extends over the insulation substrate in contact directly with a gap between the source/drain electrodes and also extends on at least respective parts of the source/drain electrodes for connecting the source/drain electrodes. A gate insulation film extends over entire parts of the semiconductor layer. A gate electrode extends on at least a part of the gate insulation film so that the gate electrode is positioned to cover the semiconductor layer and to be separated by the gate insulation film from the semiconductor layer for shielding the semiconductor layer from incident light. A reflective plate is formed over the pixel electrode so as to be separated from the gate electrode and from the semiconductor layer. An opposite electrode is supported on a surface of an opposite substrate so that the opposite electrode is separated by a space filled with a liquid crystal from the gate electrode and from the reflective plate and also that the opposite electrode faces to the gate electrode and the reflective plate.

Claims

1. A reflective plate structure provided in a reflective liquid crystal display having a thin film transistor, comprising:

a pixel electrode formed as a single layer with a source electrode of the thin film transistor, said pixel electrode being immediately adjacent to said source electrode; and

a reflective film extending over the pixel electrode and being separated from a gate electrode, said gate electrode being formed over a semiconductor layer of said thin film transistor.

2. The reflective plate structure as claimed in claim 1, wherein said reflective film comprises a single metal film having a flat top surface.

3. The reflective plate structure as claimed in claim 1, wherein said reflective plate structure comprises a single metal plate having a rough top surface.

4. The reflective plate structure as claimed in claim 1, wherein said reflective film is made of a metal selected from the group consisting of aluminum and aluminum-based alloys.

5. The reflective plate structure as claimed in claim 1, wherein said reflective film is made of a metal selected from the group consisting of platinum, silver, platinum-based alloys and silver-based alloys.

6. The reflective plate structure as claimed in claim 1, wherein said reflective film is electrically insulated from said pixel electrode.

7. The reflective plate structure as claimed in claim 1, wherein said reflective film is separated from said semiconductor layer.

8. The reflective plate structure of claim 1, further comprising:

a color filter over the reflective film.

9. The reflective plate structure of claim 1, further comprising:

a substrate; and

an inorganic film extending over an entire surface of the substrate and directly under said source electrode and said pixel electrode.

10. The reflective plate structure of claim 9, wherein said inorganic film is made of one of:

silicon oxide and silicon nitride.

11. The reflective plate structure of claim 1, further comprising:

a semiconductor layer extending over said pixel electrode.

12. The reflective plate structure of claim 11, further comprising:

a gate insulation layer formed over said semiconductor layer.

13. The reflective plate structure of claim 12, wherein said reflective film is formed on said gate insulation layer.

14. The reflective plate structure of claim 13, wherein said reflective film comprises a single layered structure of the same metal as said gate electrode.

15. The reflective plate structure of claim 13, wherein said reflective film comprises a double layered structure comprising a Cr-layer and an Al-layer discontinuously extending with gaps over said Cr-layer.

16. The reflective plate structure of claim 1, wherein said pixel electrode discontinuously extends with gaps over a substrate, and wherein the reflective plate structure further comprises:

a semiconductor layer discontinuously extending with gaps over said pixel electrode; and

a gate insulating film discontinuously extending with gaps over said semiconductor layer, said reflective film continuously extending over said gate insulating film, and filling said gaps so that said reflective film is in contact directly with said gate insulating film, said semiconductor layer, said pixel electrode and said substrate.

17. The reflective plate structure of claim 16, wherein said reflective film comprises a single layered structure of the same metal as said gate electrode.

18. The reflective plate structure of claim 1, wherein said reflective film is formed on said pixel electrode.

19. The reflective plate structure of claim 18, wherein said reflective film comprises a single layered structure of the same metal as said gate electrode.

20. The reflective plate structure of claim 1, wherein said reflective film and said gate electrode are made of the same metal.