Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Plasma excitation
Reexamination Certificate
2000-12-07
2003-06-10
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Plasma excitation
C349S123000, C349S093000
Reexamination Certificate
active
06577356
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device and a method for fabricating the same, and more particularly, to a plasma addressed liquid crystal display device and a method for fabricating the same.
Development of plasma addressed liquid crystal display (LCD) devices is in progress for realization of large and thin flat displays. Plasma addressed LCD devices are liquid crystal display devices using a plasma cell for switching respective pixels. Size increase of this type of devices is easier compared with active matrix LCD devices using thin film transistors (TFTs), and therefore fabrication at low cost is possible. Plasma addressed LCD devices are disclosed in Japanese Laid-Open Patent Publication No. 1-217396 and No. 4-265931, for example.
A large problem to be overcome on plasma addressed LCD devices is that long-time maintenance of display quality is difficult. Plasma addressed LCD devices display images in the following manner. Plasma channels arranged in row are filled with ionizable discharge gas. Discharge plasma is generated in the plasma channels, to scan the plasma channels line-sequentially. In synchronization with this scanning, a voltage is applied to signal electrodes arranged in columns. In general, a plasma addressed LCD device emits ultraviolet rays during generation of discharge plasma. The emitted ultraviolet rays may degrade organic materials constituting a liquid crystal cell, such as liquid crystal molecules and alignment layers. By this degradation, the voltage retention decreases, for example, causing troubles such as local display exudation (irreversible display failure, indicating that the contrast ratio changes) and afterimage (reversible display failure, also called “image burn-in”). This lowers the display quality of the LCD device.
In order to solve the above problem, Japanese Laid-Open Patent Publication No. 10-239671 discloses a plasma addressed LCD device that includes an ultraviolet transmission preventing layer formed on a sheet glass to prevent ultraviolet rays from a plasma cell from entering a liquid crystal cell.
There has been reported a technique of controlling the orientation of liquid crystal molecules by use of ultraviolet radiation for the purpose of improving the viewing angle characteristics of an LCD device. For example, Japanese Laid-Open Patent Publication No. 9-197384 discloses a plasma addressed LCD device of an axially symmetrically aligned micro-cell (ASM) mode that utilizes ultraviolet radiation during aligning processing. In the technique disclosed in this publication, ultraviolet rays including i-line (wavelength: 365 nm) are radiated from outside a plasma cell for stabilizing axially symmetrical orientation of liquid crystal molecules in the ASM mode LCD device.
Japanese Laid-Open Patent Publication No. 10-87859 discloses a technique of controlling the alignment direction (direction in which liquid crystal molecules are aligned) of an alignment film by irradiating the alignment film with linearly polarized ultraviolet rays. Japanese Laid-Open Patent Publication No. 10-148835 discloses a technique where a specific position of an alignment film is selectively irradiated with ultraviolet rays, to thereby selectively change the pretilt angle of liquid crystal molecules at the irradiated position and thus to widen the viewing angle.
SUMMARY OF THE INVENTION
The object of the present invention is providing a plasma addressed liquid crystal display device having wide viewing angle characteristics that can suppress or prevent deterioration in display quality due to ultraviolet rays from plasma channels and also can perform aligning processing using ultraviolet rays in a specific wavelength band, and a method for fabricating the plasma addressed liquid crystal display device.
The above object is attained by liquid crystal display devices of the first and second embodiments and the methods for fabricating the liquid crystal display devices, which are to be described below. The liquid crystal display device of the first embodiment of the invention includes: a substrate; a dielectric layer; a liquid crystal layer sandwiched by the substrate and the dielectric layer; a plurality of stripe-shaped electrodes formed on a surface of the substrate facing the liquid crystal layer to extend in parallel with a first direction; and a plurality of stripe-shaped plasma channels formed to face the plurality of electrodes with the liquid crystal layer and the dielectric layer therebetween to extend in parallel with a second direction different from the first direction, a plurality of pixel regions being formed in respective crossings of the plurality of electrodes and the plurality of plasma channels, wherein the dielectric layer selectively attenuates ultraviolet rays emitted from the plurality of plasma channels.
The dielectric layer of the LCD device of the first embodiment of the invention selectively attenuates ultraviolet rays emitted from the plurality of plasma channels. Accordingly, the dielectric layer can suppress or prevent organic materials such as liquid crystal molecules and alignment layers constituting a liquid crystal cell from degrading due to ultraviolet rays having a specific wavelength emitted by plasma discharge during use, and yet can transmit ultraviolet rays in other ranges. It is therefore possible to perform aligning processing and the like using ultraviolet rays allowed to pass through the dielectric layer.
Japanese Laid-Open Patent Publication No. 10-239671 mentioned above does not expect the case of positively utilizing ultraviolet rays, and thus does not disclose the idea of providing the ultraviolet transmission preventing layer with the function of transmitting ultraviolet rays in a specific wavelength range. Therefore, it is not possible to adopt the technique of controlling the alignment of liquid crystal molecules under ultraviolet radiation disclosed in Japanese Laid-Open Patent Publication No. 9-197384 mentioned above, for the fabrication of the plasma addressed LCD device having the ultraviolet transmission prevention layer disclosed in Japanese Laid-Open Patent Publication No. 10-239671 mentioned above.
The wavelength of the ultraviolet rays selectively attenuated by the dielectric layer is set depending on the plasma channels used. For example, it is set depending on the conditions of sealed discharge gas such as the kind and/or the pressure thereof. The wavelength of the ultraviolet rays allowed to pass through the dielectric layer may be appropriately set depending on the ultraviolet rays used in the fabrication process of the plasma addressed LCD device.
The expression of “attenuating ultraviolet rays” as used herein means attenuating the intensity of incident ultraviolet rays by “absorbing” or “scattering” the ultraviolet rays.
The dielectric layer may be formed of a single dielectric sheet having a property of selectively attenuating the ultraviolet rays. By adopting the dielectric layer formed of a single dielectric sheet having a property of selectively attenuating the ultraviolet rays emitted from the plasma channels, no separate ultraviolet-blocking layer is required for selective ultraviolet attenuation. This simplifies the fabrication process, that is, reduces the number of fabrication steps. This also prevents possible occurrence of peeling off at the interface between such a separate ultraviolet-blocking layer and the dielectric sheet. As a result, a reliable plasma addressed LCD device is provided.
The dielectric layer may include a dielectric sheet transmitting the ultraviolet rays and an ultraviolet-blocking layer formed on at least one surface of the dielectric sheet, and the ultraviolet-blocking layer may have a property of selectively attenuating the ultraviolet rays. Some ultraviolet-blocking materials may not be easily processed into a single dielectric sheet. Such ultraviolet-blocking materials are made usable by adopting the dielectric layer including a dielectric sheet such as a glass sheet transmitting the ultraviolet rays and an u
Miyazaki Aya
Onishi Noriaki
Duong Thoi V
Kim Robert H.
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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