Liquid crystal device with shorting ring and transistors for electrostatic discharge protection

• US 5,373,377 A
• Filed: 02/05/1993
• Issued: 12/13/1994
• Est. Priority Date: 02/21/1992
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation, Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: International Business Machines Corporation, Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kitahara, Hiroaki, Ichioka, Yoshikazu, Kimura, Shinichi, Suzuki, Kouhei, Ogawa, Meiko
• Primary Examiner(s): Gross, Anita Pellman
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US08/014,162
• Time in Patent Office: 676 Days
• Field of Search: 359/54, 359/55, 359/58, 359/59, 359/60, 359/87, 257/355, 257/356, 257/357, 257/358, 257/359, 257/360, 257/361, 257/362, 257/363
• US Class Current: 349/40
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G02F 1/136204 Arrangements to prevent high voltage or static electricity failures

Abstract

An active matrix type liquid crystal display device with a short-circuiting wire for mutually short-circuiting address wires and data wires through the medium of resistors made of a thin-film transistor is formed along the periphery of a display region on an insulating substrate. The short-circuiting wire is electrically connected inside a region in which the resistors made of a thin-film transistor are formed. In one embodiment, the transistors are surrounded by a portion of the shod circuiting wire. In another embodiment, they are partially surrounded by the wire with a gate electrode which is not protruding out. In another embodiment they are formed with two source and drain regions, one which has a lower breakdown voltage than the other.

Claims

1. A liquid crystal display device comprising:

an insulating substrate manifesting an insulating property at least on a surface thereof;

a plurality of address wires formed in a display region on said insulating substrate;

a plurality of data wires formed to intersect said address wires;

first thin-film transistors formed one each at points of intersection of said address wires and data wires and having gate electrodes electrically connected to said address wires and drain electrodes electrically connected to said data wires;

picture element electrodes formed one each near said points of intersection and electrically connected to the source electrodes of said first thin-film transistors; and

a short-circuiting wire formed along at least part of a periphery of the display region of said insulating substrate and adapted to short-circuit said address wires and data wires to each other through a first resistor made of a second thin-film transistor, said short-circuiting wire formed along at least part of the periphery of the display region of said insulating substrate and being electrically connected such that a portion of said short-circuiting wire surrounds the first resistor made of the second thin-film transistor, a part of the short-circuiting wire being formed inside of the first resistor.

2. A liquid crystal display device according to claim 1, wherein said short-circuiting wire is formed in a shape of a ladder along the periphery of said insulating substrate, and the first resistors made of the second thin-film transistor are formed as openings in the ladder shaped short-circuiting wire.

3. A liquid crystal display device according to claim 1, wherein a magnitude of resistance of said first resistor made of the second thin-film transistor is set in a range between 10 kΩ

and 100 MΩ

when a potential difference between opposite terminals of said first resistor is 20V.

4. A liquid crystal display device according to claim 1, further comprising an auxiliary capacitance.

5. A liquid crystal display device according to claim 4, wherein an auxiliary capacitance line for each auxiliary capacitance is connected to said short-circuiting wire through a second resistor made of a third thin-film transistor.

6. A liquid crystal display device comprising:

an insulating substrate manifesting an insulating property at least on a surface thereof;

a plurality of address wires formed in a display region on said insulating substrate;

a plurality of data wires formed to intersect said address wires;

first thin-film transistors formed one each at points of intersection of said address wires and data wires and having gate electrodes electrically connected to said address wires and drain electrodes electrically connected to said data wires;

picture element electrodes formed one each near said points of intersection and electrically connected to the source electrodes of said first thin-film transistors; and

a short-circuiting wire formed along at least part of a periphery of the display region of said insulating substrate and adapted to short-circuit said address wires and data wires to each other through a first resistor made of a second thin-film transistor;

wherein said second thin-film transistor has a first part of opposite source and drain electrodes and a second part of opposite source and drain electrodes distinct from said first part, the second part of opposite source and drain electrodes being more easily broken by static electricity than the first part of opposite source and drain electrode.

7. A liquid crystal display device according to claim 6, wherein said second thin-film transistors are comb-shaped having the first part of opposite source and drain electrodes as fingers and said short-circuiting wire is comb-shaped and interleaved with the comb-shaped second thin-film transistor.

8. A liquid crystal display device according to claim 7, wherein the fingers of said comb-shaped source electrodes and drain electrodes are electrically connected to a bus bar formed in a lower layer through separate through holes.

9. A liquid crystal display device according to claim 8, wherein a gate electrode of the first resistor made of the second thin-film transistor has a square shape and said gate electrode covers the fingers of said comb-shaped source electrodes and drain electrodes.

10. A liquid crystal display device according to claim 6, wherein a-Si is a component element of said first resistor made of the second thin-film transistor and has a rectangular shape.

11. A liquid crystal display device according to claim 6, wherein a magnitude of resistance of the first resistor made of the second thin-film transistor is set in a range between 10 kΩ

and 100 MΩ

when a potential difference between opposite terminals of said first resistor is 20V.

12. A liquid crystal display device according to claim 6, further comprising an auxiliary capacitance.

13. A liquid crystal display device according to claim 12, wherein an auxiliary capacitance wire for each auxiliary capacitance is connected to said short-circuiting wire through a second resistor made of a third thin-film transistor.

14. A liquid crystal display device comprising:

an insulating substrate manifesting an insulating property at least on a surface thereof;

a plurality of address wires formed in a display region on said insulating substrate;

a plurality of data wires formed to intersect said address wires;

first thin-film transistors formed one each at points of intersection of said address wires and data wires and having gate electrodes electrically connected to said address wires and drain electrodes electrically connected to said data wires;

picture element electrodes formed one each near said points of intersection and electrically connected to source electrodes of said first thin-film transistors; and

a short-circuiting wire formed along at least part of a periphery of the display region of said insulating substrate and adapted to short-circuit said address wires and data wires to each other through a first resistor made of a second thin-film transistor, wherein the short-circuiting wire surrounds the second thin-film transistor except that a gate-electrode of the second thin-film transistor protrudes outside the short-circuiting wire.

15. A liquid crystal display device according to claim 14, wherein the gate electrode of the second thin-film transistor is protruded from said short-circuiting wire by causing a part of said short-circuiting wire near the gate electrode to be formed in an inwardly depressed shape.

16. A liquid crystal display device according to claim 14, wherein said gate electrode of the second thin-film transistor is possessed of a constriction.

17. A liquid crystal display device according to claim 14, wherein the gate electrode of the second thin-film transistor is tapered.

18. A liquid crystal display device according to claim 14, wherein the gate electrode of the second thin-film transistor is connected to a ring made of a-Si outside said short-circuiting wire.

19. A liquid crystal display device according to claim 14, wherein a magnitude of resistance of said first resistor made of the second thin-film transistor is set in a range between 10 kΩ

and 100 MΩ

when a potential difference between opposite terminals of said first resistor is 20V.

20. A liquid crystal display device according to claim 14, further comprising an auxiliary capacitance.

21. A liquid crystal display device according to claim 20, wherein an auxiliary capacitance wire for each auxiliary capacity is connected to said short-circuiting wire through a second resistor made of a third thin-film transistor.