Forming an opaque metal layer in a liquid crystal display

• US 4,687,298 A
• Filed: 12/04/1985
• Issued: 08/18/1987
• Est. Priority Date: 04/11/1984
• Status: Expired due to Fees

• Current Assignee: Hosiden And Philips Display Corporation (Koninklijke Philips N.V.)
• Original Assignee: Hosiden Electronics Co. Ltd. (Hosiden Corporation)
• Inventors: Aoki, Shigeo, Miyake, Katsumi, Ugai, Yasuhiro, Okamoto, Kotaro
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/812,890
• Time in Patent Office: 622 Days
• Field of Search: 350/334, 357/24, 357/23.7, 357/30 L, 357/30 M, 357/339 R, 357/339 F
• US Class Current: 349/44
• CPC Class Codes: G02F 1/133514 Colour filters
• 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 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A liquid crystal display device is disclosed, which comprises first and second transparent substrates facing each other, a liquid crystal sealed between the transparent substrates, a plurality of display electrodes formed on the inner surface of the first transparent substrate, thin film transistors also formed on the first transparent substrate inner surface and each connected to each display electrode, and a transparent common electrode formed on the inner surface of the second transparent substrate, and in which the thin film transistors are selectively controlled to selectively drive the display electrodes for display. The resistance of semiconductor layers of the thin film transistors is reduced by external light to result in deterioration of the contrast of display. According to the invention, an opaque metal layer is formed between each thin film transistor and the first transparent substrate, and an insulating film is provided between the opaque metal layer and thin film transistor. Source buses of the same material as of and connected to the opaque metal layers are formed on the first transparent substrate.

Claims

1. A liquid crystal display device comprising first and second transparent substrates closely spaced apart and facing each other, a liquid crystal sealed between said transparent substrates, a plurality of transparent display electrodes provided on the inner surface of said first transparent substrate, thin film transistors formed on said first transparent substrates and each having a drain connected to each said display electrode, and a transparent common electrode formed substantially on the entire inner surface of said second transparent substrate,

said thin film transistors each including a semiconductor layer formed between corresponding display electrode and source electrode, a gate insulating film formed on said semiconductor layer on the side opposite said first transparent substrate, and a gate electrode formed on said gate insulating film,

an opaque metal layer being formed between each said thin film transistor and said first transparent substrate with an insulating layer provided between the thin film transistor and the opaque metal layer,

source buses of the same material as said opaque metal layer being formed integrally therewith on the side of said first transparent substrate to face said source electrodes thru said insulating layer, said source buses being connected to said source electrodes through holes formed in said insulating layer.

2. The liquid crystal display device according to claim 1, wherein second source buses of the same opaque metal as of said source electrodes are formed on the side of said insulating layer opposite said first transparent substrate and connected to said source electrodes, and each said second source bus and the corresponding source bus of said opaque metal layers are connected together at a source terminal.

3. The liquid crystal display device according to claim 1 or 2, wherein light-blocking layers of an opaque metal are formed on portions of said second transparent substrate corresponding to gaps between adjacent display electrodes.

4. The liquid crystal display device according to claim 3, wherein color filters are formed on said second transparent substrate such that they face said display electrodes.

5. The liquid crystal display device according to claim 4, wherein said light-blocking layers are formed between said common electrode and said second transparent substrate.

6. The liquid crystal display device according to claim 5, wherein said light-blocking layers partly overlie said color filters on the side opposite said second transparent substrate.

7. The liquid crystal display device according to claim 4, wherein said display electrodes are picture element electrodes arranged in a matrix array, said thin film transistors connected to the picture element electrodes in each column have their source electrodes connected to a common source bus, said thin film transistors connected to the picture element electrodes in each row of said matrix array have their gate electrodes connected to a common gate bus, and said color filters consist of a plurality of different color filters, which are substantially uniformly distributed.

8. The liquid crystal display device according to claim 1 or 2, wherein said display electrodes are picture element electrodes arranged in a matrix array, said thin film transistors connected to the picture element electrodes in each column have their source electrodes connected to a common source bus, and said thin film transistors connected to the picture element electrodes in each row of said matrix array have their gate electrodes connected to a common gate bus.

9. A method of manufacturing a liquid crystal display device by the steps of forming a plurality of transparent display electrodes and thin film transistors with their drains connected to said transparent display electrodes on one surface of a first transparent substrate, forming a transparent common electrode on and substantially over the entire surface of a second transparent substrate and sealing a liquid crystal between said first and second transparent substrates with said display electrodes and common electrode on the inner side, wherein:

opaque metal layers are formed on areas of one surface of said first transparent substrate where said thin film transistors are to be formed, together with source buses of the same material as and connected to said opaque metal layers;

an insulating layer is formed on said opaque metal layers and source buses;

holes are formed in said insulating layer at positions corresponding to said source buses prior to the formation of said thin film transistors on said opaque metal layers, the source electrodes of said thin film transistors being connected to said source buses through said holes.

10. The method of manufacturing a liquid crystal display device according to claim 9, wherein the source electrodes of said thin film transistors, said display electrodes and second source buses connected to said source electrodes are formed at a time from the same transparent metal in the formation of said thin film transistors, and at least one end of each said second source bus is connected to a corresponding end of the corresponding source bus of said opaque metal in an overlying relation thereto at a source terminal.

11. The method of manufacturing a liquid crystal display device according to claim 9 or 10, wherein said common electrode is formed after formation of color filters on portions of said second transparent substrate facing said display electrodes and metal light-blocking layers filling gaps between adjacent color filters.

12. The method of manufacturing a liquid crystal display device according to claim 11, wherein said light-blocking layers are formed after formation of said color filters.