Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-02-23
2003-09-30
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S143000, C349S147000
Reexamination Certificate
active
06628361
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display unit and a wiring structure of the liquid crystal display device, and particularly to an active matrix type liquid crystal display device (AM-LCD) which is driven by many thin-film transistors (TFT) and a wiring structure of the active matrix type liquid crystal display device.
In recent years, a thin-film transistor driving liquid crystal display device (TFT-LCD) is used as a liquid crystal display device which can be made thin in size, light in weight and high in definition, and the market of the thin-film transistor driving liquid crystal display device is gradually being expanded compared to that of the conventional display device using a cathode-ray tube.
The thin-film transistor driving liquid crystal display device is constructed by forming a plurality of parallel gate wires, a plurality of parallel data wires intersecting with the plurality of gate wires, a plurality of thin-film transistors each arranged near each of the intersections of the parallel gate wire and the parallel data wire, pixel electrodes each connected to each of the thin-film transistors, gate insulator films each covering a gate of each of the thin-film transistors and a protective film covering exposed portions of each of the thin-film transistor on a first substrate (a glass substrate); and by placing a second substrate (a glass substrate) opposite to the first substrate; and by putting a liquid crystal layer between the first substrate and the second substrate arranged opposite to each other. In regard to such a thin-film transistor drive liquid display device, as needs of large display screen and high definition are growing more in recent years, the requirements of specifications to the thin-film transistor drive liquid display device such as necessity of reducing resistance of the parallel gate wiring and the parallel data wiring, necessity of increasing the manufacturing yield at manufacturing the display devices and so on become severer.
In order to reduce the resistance of the parallel gate wiring and the parallel data wiring, it is necessary to employ a material having a low resistivity as the wiring material. As such a material, aluminum (Al), copper (Cu), silver (Ag) or an alloy containing any one of the above elements as a major constituent is known. However, as reported, for example, in Journal of the Electrochemical Society, 137 (1990), pp. 3928-3930, it is well known that these low-resistance wiring materials are large in contact resistance with indium-tin oxide (ITO) which is generally used for connecting terminals of the parallel gate wiring and the parallel data wiring, and accordingly, it is impractical to directly connect the low-resistance wire to the indium-tin oxide terminal. Therefore, a clad structure, in which the parallel gate wiring and the parallel data wiring made of the low-resistive wiring material are coated with the other metallic material, is formed so that the other material may bear the contact property with the indium-tin oxide and the low-resistive wiring material may bear the low resistive property of the parallel gate wiring and the parallel data wiring. Such a clad structure is disclosed, for example, in Japanese Patent application Laid-Open No.9-26602.
In general photolithography is used to form such a clad structure, and it is necessary to perform the two processes of photolithography in total, that is, one process for the low-resistive wiring material and the other process for the other metallic material, which makes the manufacturing process complicated. Therefore, in order to simplify the manufacturing process, a wiring pattern of the laminated structure is formed by a method of continuously forming a laminated layer of a film made of aluminum or aluminum alloy and a film made of the other metallic material through a single process of photolithography. The laminated structures formed through methods similar to the above are disclosed, for example, in Japanese Patent Application Laid-Open No.11-74537, Japanese Patent Application Laid-Open No.6-281954, Japanese Patent Application Laid-Open No.4-240824, Japanese Patent Application Laid-Open No.4-20930 and Japanese Patent Application Laid-Open No.10-240150.
The thin-film transistor drive liquid display device needs to use wiring materials having a low resistivity as the need of high definition is growing more. In such a case, in regard to the thin-film transistor drive liquid display device up to the definition of ultra extended graphics array (hereinafter, referred to as UXGA) (1600×1200), the thin-film transistor drive liquid display device without unevenness of color can be manufactured with a high manufacturing yield by using an aluminum group wiring material and setting the wires to an appropriate thickness (about 200 nm). However, in regard to the thin-film transistor drive liquid display device having a finer definition above quadrable extended graphics array (hereinafter, referred to as QXGA) (2048×1536), troubles such as unevenness of color or the like caused by the wiring resistance are occur when an aluminum group wiring material is used for the wiring material of the thin-film transistor drive liquid display device. In this case, if the thickness of the wiring is increased in order to reduce the wiring resistance, the coverage of the insulator film covering the wires is degraded and accordingly the manufacturing yield is decreased. In order to solve this problem, it is necessary to employ a metallic material having a resistivity lower than that of the aluminum group wiring material, for example, silver or an alloy containing silver as the major constituent.
Although the thin-film transistor drive liquid display device which uses silver for the low-resistive wiring material and has the clad structure of cladding the wiring with the other metallic material is known, as described above, it is required to perform two processes of photolithography in order to form the clad structure. As far as such a means is used, the manufacturing process becomes complicated, and the thin-film transistor drive liquid display devices cannot be manufactured in low cost, and accordingly low-cost thin-film transistor drive liquid display devices cannot be supplied to the market.
SUMMARY OF THE INVENTION
The present invention has been made from the viewpoint of the technical background described above, and an object of the present invention is to provide a wiring structure in which a laminated film composed of a film made of silver or an alloy containing silver as the major constituent and a film made of the other metallic material is formed, and a wiring pattern is formed through a single process of photolithography.
Another object of the present invention is to provide a liquid crystal display device which can be manufactured in low cost by forming the laminated film composed of a film made of silver or an alloy containing silver as the major constituent and a film made of the other metallic material and by forming a wiring pattern through a single process of photolithography.
In order to attain the object described above, the wiring structure in accordance with the present invention has a first structure which comprises a plurality of first parallel wires; a plurality of second parallel wires intersecting with the first parallel wires; and a plurality of active elements, each of the active elements being arranged at a position near an intersection of the first parallel wire and the second parallel wire and connected to the first parallel wire and the second parallel wire, wherein part or all of the first parallel wires and the second parallel wires are of a laminated structure of a layer made of silver or an alloy containing silver as a major constituent and a layer made of a metallic element having a standard electrode potential of dissolution reaction lower than the standard electrode potential of silver or an alloy containing said metallic element as a major constituent, and are formed through a single process of pho
Ikuta Isao
Onisawa Ken-ichi
Sakaki Yoichi
Takahashi Takuya
Tamura Katsumi
Antonelli Terry Stout & Kraus LLP
Chung David
Parker Kenneth
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