Active matrix substrate with the double layered structure

• US 5,956,103 A
• Filed: 06/17/1997
• Issued: 09/21/1999
• Est. Priority Date: 06/19/1996
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ishiguro, Kenichi
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): KIM, JOANNE H
• Application Number:
  US08/877,520
• Time in Patent Office: 826 Days
• Field of Search: 349/111, 349/138, 349/42, 349/43, 349/38, 257/59, 257/72
• US Class Current: 349/38
• CPC Class Codes: G02F 1/136209 Light shielding layers, e.g. black matrix, incorporated in the active matrix substrate, e.g. structurally associated with the switching element
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode

Abstract

An active matrix substrate including: pixel electrodes provided in a matrix; a TFT composed essentially of a semiconductor layer; a scanning signal line; a data signal line; a conductive light-shielding film formed on a substrate; a first insulating film formed on the substrate so as to cover the conductive light-shielding film; a thin semiconductor film formed on the first insulating film, the thin semiconductor film being formed of the same material as the semiconductor layer composing the TFT; a second insulating film formed on the first insulating film so as to cover the thin semiconductor film; and a storage capacitance electrode formed on the second insulating film. The storage capacitance electrode is a thin metal film formed of the same material as the scanning signal line. The storage capacitance electrode is electrically coupled to the conductive light-shielding film. A first storage capacitance is formed between the conductive light-shielding film and the thin semiconductor film. A second storage capacitance is formed between the storage capacitance electrode and the thin semiconductor film. The storage capacitance electrode at least partially overlaps the data signal line.

Claims

1. An active matrix substrate opposed by a counter substrate with a liquid crystal layer interposed therebetween, the active matrix substrate comprising:

a substrate;

a plurality of pixel electrodes for display purposes, provided in a matrix on the substrate;

a TFT provided corresponding to each of the pixel electrodes and including a semiconductor layer;

a scanning signal line for controlling the TFT; and

a data signal line for supplying a data signal to each of the pixel electrodes via the TFT,

the active matrix substrate further comprising;

a conductive light-shielding film formed on the substrate;

a first insulating film formed on the substrate so as to cover the conductive light-shielding film;

a thin semiconductor film formed on the first insulating film, the thin semiconductor film being formed of the same material as a material of the semiconductor layer included in the TFT;

a second insulating film formed on the first insulating film so as to cover the thin semiconductor film; and

a storage capacitance electrode formed on the second insulating film,

wherein the storage capacitance electrode is a thin metal film formed of the same material as a material for the scanning signal line, the storage capacitance electrode being electrically coupled to the conductive light-shielding film,

a first storage capacitance being formed between conductive light-shielding film and the thin semiconductor film, and

a second storage capacitance being formed between the storage capacitance electrode and the thin semiconductor film, and

at least a portion of the storage capacitance electrode overlapping the data signal line.

2. An active matrix substrate according to claim 1, wherein the conductive light-shielding film functions as a black matrix.

3. An active matrix substrate according to claim 2, wherein the conductive light-shielding film is maintained at a constant potential.

4. An active matrix substrate according to claim 2, wherein the conductive light-shielding film is driven by the same voltage for driving a counter electrode formed on the counter substrate.

5. An active matrix substrate according to claim 1, wherein the conductive light-shielding film is maintained at a constant potential.

6. An active matrix substrate according to claim 1, wherein the conductive light-shielding film is driven by the same voltage for driving a counter electrode formed on the counter substrate.

7. A method for producing an active matrix substrate opposed by a counter substrate with a liquid crystal layer interposed therebetween, the active matrix substrate comprising:

a substrate;

a plurality of pixel electrodes for display purposes, provided in a matrix on the substrate;

a TFT provided corresponding to each of the pixel electrodes, the TFT having a semiconductor layer;

a scanning signal line for controlling the TFT;

a data signal line for supplying a data signal to each of the pixel electrodes via the TFT,

the method comprising the steps of;

forming a conductive light-shielding film on the substrate;

forming a first insulating film on the substrate so as to cover the conductive light-shielding film;

forming the semiconductor layer on the first insulating film so as to at least partially overlap the conductive light-shielding film;

forming a second insulating film on the first insulating film so as to cover the semiconductor layer;

forming a contact hole through the first and second insulating films, the contact hole reaching the conductive light-shielding film; and

forming and patterning a storage capacitance electrode and the scanning signal line of the same thin metal film, the storage capacitance electrode being electrically coupled to the conductive light-shielding film via the contact hole and overlapping the semiconductor layer via the second insulating film.

8. A method according to claim 7, wherein the step of forming the conductive light-shielding film is a step of forming the conductive light-shielding film so as to define a black matrix and to include a terminal for receiving an externally-supplied electrical signal.