LIGHT SHIELDING STRUCTURE OF A SUBSTRATE FOR A LIQUID CRYSTAL DEVICE, LIQUID CRYSTAL DEVICE AND PROJECTION TYPE DISPLAY DEVICE

• US 20020024622A1
• Filed: 04/05/2001
• Published: 02/28/2002
• Est. Priority Date: 10/16/1996
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Murade, Masao
• Granted Patent: US 6,388,721 B1
• Time in Patent Office: Days
• US Class Current: 349/44
• 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

Abstract

Placement of a first light shielding film (7) at least below the channel region (1c) of a TFT which drives a pixel, and of a second light shielding film (3) above the same prevents impingement of light coming from above or from below on that channel region (1c) Further, a second light shielding film (3) is formed to cover the channel region (1c) and the first light shielding film (7) thereby to prevent the surface of the first light shielding film (7) from direct exposure to light

Claims

1. A substrate for a liquid crystal device comprising:

a plurality of data lines formed on the substrate;

a plurality of scan lines crossing the plurality of data lines,

a plurality of thin film transistors connected to the plurality of data lines and the plurality scan lines; and

a plurality of pixel electrodes connected to the plurality of thin film transistors, wherein a first light shielding film is formed at least below channel region of the thin film transistors, and the junctions between the channel region and source/drain regions, and

a second light shielding film is formed above the channel region and its junctions between the channel region and the source/drain regions.

2. A substrate for a liquid crystal device as described in claim 1, wherein the first light shielding film is a metal film selected from the group consisting of a tungsten film, a titanium film, a chromium film, a tantalum film, a molybdenum film, or an alloy film thereof.

3. A substrate for a liquid crystal device as described in claims 1 or 2, wherein a first lead extending from the first light shielding film is electrically connected to a constant potential line outside a pixel display region.

4. A substrate for a liquid crystal device as described in any one of claims 1 to 3, wherein the first lead extending from the first light shielding film is formed along and beneath the scan line.

5. A substrate for a liquid crystal device as described in any one of claims 1 to 4, wherein a width of the first lead extending from the first light shielding film is less than a width of the scan line formed above it.

6. A substrate for a liquid crystal device as described in claim 5, wherein the first lead extending from the first light shielding film is covered by the scan line formed above it.

7. A substrate for a liquid crystal device as described in any one of claims 1 to 4, wherein a capacitance line which is formed on a same layer as that of the scan line to add a capacitance to the pixel is placed in parallel with the scan line, and has below it a second lead extending from the first light shielding film.

8. A substrate for a liquid crystal device as described in any one of claims 1 to 7, wherein a third lead extending from the first light shielding film is formed along and below the data line.

9. A substrate for a liquid crystal device as described in any one of claims 1 to 8, wherein the data line also acts as a second light shielding film, and is made of a metal film selected from the group consisting an aluminum film, a tungsten film, a titanium film, a chromium film, a tantalum film and a molybdenum film, or an alloy film thereof.

10. A substrate for a liquid crystal device as described in any one of claims 1 to 9, wherein a width of the third lead extending from the first light shielding film is less than a width of the data line.

11. A substrate for a liquid crystal device as described in any one of claims 1 to 10, wherein the channel region and the junctions the channel region forms with the source/drain regions are disposed below the data line, and the first light shielding film disposed below channel region and the junctions between the channel region and the source/drain regions is covered by the data line at least on the part underlying the channel region and the junctions between the channel region and the source/drain regions.

12. A substrate for a liquid crystal device as described in any one of claims 1 to 11, wherein LDD (lightly doped drain) regions are formed at the junctions of the channel region with the source/drain regions.

13. A substrate for a liquid crystal device as described in any one of claims 1 to 11, wherein the junctions of the channel region with the source/drain regions are formed as offset regions.

14. A substrate for a liquid crystal device as described in any one of claims 1 to 13, wherein the scan line is selected from the group consisting of a metal film selected from a tungsten film, a titanium film, a chromium film, a tantalum film and a molybdenum film, or a metal alloy film thereof.

15. A substrate for a liquid crystal device as-described in any one of claims 1 to 13, wherein a minimum distance L1 from the lateral edges of the first light shielding film to the channel region is 0.2 μ

m≦

L1≦

4 μ

m.

16. A substrate for a liquid crystal device as described in any one of claims 9 to 15, wherein a minimum distance L2 from the lateral edges of the second light shielding film to the lateral edges of the first light shielding film is 0.2 μ

m≦

L2.

17. A liquid crystal device as described in any one of claims 1 to 16, wherein the substrate for the liquid crystal device and an opposite substrate with an opposite electrode are placed with a specified interval in between, and that liquid crystal is injected into the space between the substrate for the liquid crystal device and the opposite substrate.

18. A liquid crystal device as described in claim 17, wherein a third light shielding film is formed on the opposite substrate.

19. A liquid crystal device as described in claim 17 or claim 18, wherein the third light shielding film covers at least the first light shielding film.

20. A liquid crystal device as described in any one of claims 17 to 19, wherein small lenses are arranged in the form of a matrix on the opposite substrate in correspondence with the plurality of pixel electrodes placed on the substrate for the liquid crystal display device.

21. A projection type display device comprising a light source, a liquid crystal device as described in any one of claims 17 to 20 to transmit or reflect light from the light source, after having modulated it, and a projection optical means which receives the modulated light from the liquid crystal device, and converges and enlarges it through projection.