Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-05-24
2004-07-27
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S149000, C349S152000
Reexamination Certificate
active
06768533
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to liquid crystal devices which reduce wiring resistance, to manufacturing methods therefor, and to electronic apparatuses using the liquid crystal devices for display portions.
2. Description of the Related Art
As has been well known, since liquid crystal display devices have advantages in weight and electric power consumption compared to display devices using CRTs (cathode ray tubes), in particular, they are widely used for display portions of electronic apparatuses which are required to have portability.
Liquid crystal display devices generally have a structure in which two substrates are bonded to each other with a predetermined gap therebetween so that electrode forming surfaces thereof oppose each other, and liquid crystal is received in the gap; and when roughly classified in accordance with a driving mode, they can be classified into an active matrix type in which liquid crystal is driven by switching elements, and a passive matrix type in which liquid crystal is driven without using switching elements. In addition, the former, the active matrix type, can be further classified into a type which uses three-terminal elements, such as a thin-film transistor (TFT), as switching elements, and a type which uses two-terminal elements such as a thin-film diode (TFD).
The type which uses TFD elements as the switching elements among active matrix types and the simple passive matrix type have a structure in which scanning lines (common electrodes) are formed on one substrate and data lines (segment electrodes) are formed on the other substrate. Accordingly, in these types described above, since scanning signals (common signals) and data signals (segment signals) must be supplied by bonding an FPC substrate to each of the two substrates, problems of complicated bonding step and an increase in cost may arise. Accordingly, in the types described above, a technique has been proposed to bond one piece of FPC substrate to only one of the two substrates by using a structure in which all wirings or electrodes formed on the other substrate are connected to wirings formed on said one of the two substrates via conducting materials, that is, a structure is formed so that all wirings or electrodes formed on the other substrate are gathered on said one of the two substrates.
However, in the technique described above, the wirings formed on said one of the two substrates are composed of the same material as that used for transparent electrodes on said one of the two substrates, which apply a voltage to the liquid crystal. In this connection, as a material used for the transparent electrode mentioned above, ITO (Indium Tin Oxide) is generally used; however, the square resistivity of this transparent electrode material is high compared to that of a common metal. Accordingly, when the transparent electrode material described above is used for wirings for electrical connection in an area other than the display area, the resistance is naturally increased, and as a result, a problem may arise in that the image quality is adversely influenced.
In particular, recently, in order to reduce the number of connection points between a liquid crystal panel and a FPC substrate, driver ICs for driving the scanning lines (common electrodes) and the data lines (segment electrodes) are mounted on a glass substrate of the liquid crystal panel in some cases. In the case described above, various control signals and clock signals must be supplied to the driver ICs; however, when the transparent electrode material described above is used for wiring from the FPC substrate to the driver ICs, since the time constant is increased concomitant with an increase in wiring resistance, deformation of waveforms, a decrease in amplitude, and the like occur, and as a result, a problem may arise in that the operation margin is narrowed.
The present invention was made in view of the problems described above, and an object of the present invention is to provide a liquid crystal device which reduces resistance of wirings formed on a substrate, a manufacturing method therefor, and an electronic apparatus using the liquid crystal device for the display portion.
SUMMARY OF THE INVENTION
Accordingly, a liquid crystal device of one aspect of the present invention is a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a first transparent electrode provided on the first substrate; a first wiring provided on the second substrate; and a conductive material connecting the first transparent electrode and the first wiring; wherein the first wiring comprises a metal oxide film and a conductive film having a resistance lower than that of the metal oxide film. According to the structure described above, since the first wiring is a laminated film composed of a chemically stable metal oxide film and a chemically unstable conductive film having a resistance lower than that of the metal oxide film, compared a single layer composed of one of the two films described above, a lower resistance and improved stabilization of the wiring can be obtained.
In the structure described above, the conductive material is composed of nonconductive particles formed of, for example, a plastic covered with a metal such as gold (Au), and a metal oxide film generally has better adhesion with this covering metal. As a result, in the structure described above, the conductive film of the first wiring is preferably formed on an area other than the portion connecting with the conductive material.
In addition, preferably, the structure described above further comprises a driver IC provided on the second substrate for driving the liquid crystal, wherein the driver IC comprises an output side bump for supplying a signal, the output side bump is connected to the first wiring, and the conductive film is formed on an area other than the portion connecting with the driver IC. When the driver IC for driving the liquid crystal is mounted on the second substrate via the first wiring, the conductive material, and the first transparent electrode as described above, the number of connection points with the external can also be decreased. Furthermore, when the driver IC is bonded to the wiring, an adhesive having conductive particles dispersed therein is used, and similar to the conductive material described above, the conductive particles are formed of nonconductive particles such as a plastic covered with a metal such as gold (Au). Accordingly, when the conductive film is formed on an area other than the portion connecting with the driver IC, the metal oxide film and the covering metal contained in the conductive material are brought into contact with each other, and as a result, the adhesion therebetween is improved.
Furthermore, preferably, the structure described above further comprises a second wiring which is provided on the second substrate and which comprises a metal oxide film and a conductive film having a resistance lower than that of the metal oxide film; and a driver IC provided on the second substrate for driving the liquid crystal; wherein the driver IC comprises an input side bump for inputting a signal, the input side bump is connected to the second wiring, and the conductive film included in the second wiring is formed on an area other than the portion connecting with the driver IC. As a result, since the second wiring is a laminated film formed of a chemically stable metal oxide film and a chemically unstable conductive film having a resistance lower than that of the metal oxide film, compared to a single layer composed of one of the two films described above, a lower resistance of the wiring can be obtained. Accordingly, since the signals are supplied to the driver IC driving the liquid crystal via the second wiring having a lower resistance, the influence caused by voltage drop and the like can be suppressed to b
Hanakawa Manabu
Hinata Shoji
Dudek James A.
Harness & Dickey & Pierce P.L.C.
Seiko Epson Corporation
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