Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Patent
1997-01-14
1999-04-13
Sikes, William L.
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
349 49, 349187, G02F 1135, G02F 1136, G02F 113
Patent
active
058936211
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a liquid crystal display comprising MIM elements composed of metal-insulator-metal structures or metal-insulator-transparent and electrical conductor structures, and a method of manufacturing the same.
BACKGROUND TECHNOLOGY
Along with an advance in commercial application of liquid crystal displays, liquid crystal displays of an active matrix type capable of displaying images of excellent quality have come by now to occupy a position in the mainstream of the market.
The active matrix type liquid crystal display described above comprises thin-film transistors (TFTs), diodes, or nonlinear resistance elements of a metal-insulator-metal (referred to hereinafter as "MIM") structure composed of three layers consisting of metal-insulator-metal or metal-insulator-transparent and electrical conductor, as switching elements for each of liquid crystal display electrodes for displaying images.
The MIM elements described above is generally composed of a Ta-Ta.sub.2 O.sub.5 -Cr or Ta-Ta.sub.2 O.sub.5 -ITO structure. Herein, Ta refers to a tantalum film, Ta.sub.2 O.sub.5 a tantalum oxide film, Cr a chromium film, and ITO an indium tin oxide film.
With a liquid crystal display using MIM elements, images are displayed by switching on and off a liquid crystal layer connected in series with the MIM elements by taking advantage of a nonlinear voltage-current characteristic of the MIM elements.
Now referring to FIGS. 29 to 32, the structure of a conventional liquid crystal display panel having nonlinear resistance elements composed of the Ta-Ta.sub.2 O.sub.5 -ITO structure is described hereafter.
As shown clearly in FIG. 32, the MIM element comprises a tantalum (Ta) film as a lower electrode 103 formed on a first substrate 102, a tantalum oxide (Ta.sub.2 O.sub.5) film as an insulation film 104 formed on the lower electrode, and a transparent and electrically conductive film composed of an indium tin oxide (ITO) film as an upper electrode 105 formed on the insulation film, all these films together constituting a nonlinear resistance element.
In addition, the MIM element is provided with a display electrode 106 composed of an indium tin oxide film. Data signals dependent on the contents of display are applied on the display electrode 106 via the nonlinear resistance element by a signal electrode 107 composed of a tantalum film and a tantalum oxide film.
This liquid crystal display is provided with the first substrate 102 on which the nonlinear resistance elements are formed and a second substrate 109 (refer to FIG. 29) having opposite electrodes 110 (as indicated by phantom lines in FIG. 30) formed in such a way as to face the display electrodes 106 formed on the first substrate 102.
After applying liquid crystal-molecular alignment treatment to the surfaces of the first substrate 102 and the second substrate 109, the two substrates are bonded together with a sealing portion 108 such that the surfaces of the both substrates face each other at a predetermined spacing, and liquid crystals are sealed in a gap formed therebetween, thus forming a liquid crystal display. A region surrounded by a phantom line 118 as indicated in FIG. 29 and a solid line 118 as indicated in FIG. 30 represents a display region of the liquid crystal display.
However, the liquid crystal display having the conventional nonlinear resistance elements described above poses a problem of an after-image phenomenon occurring when an image displayed is changed in the course of driving the liquid crystal display.
Referring to FIG. 33, the after-image phenomenon is described. Herein, the liquid crystal display is assumed to display images in "normally white" mode.
FIG. 33 indicates variation in transmissivity of light when an applied voltage for a random pixel is varied for every 5 minutes. Specifically, a voltage (V1) for providing a display of 50% transmissivity is applied for first 5 minutes (unselect period: T1), then a voltage (V2) for providing a display of 10% transmissivity is applied for another 5 minutes (
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Citizen Watch Co. Ltd.
Sikes William L.
Ton Toan
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