Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-10-30
2002-01-15
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S130000, C349S106000
Reexamination Certificate
active
06339459
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a liquid crystal display device applicable to so-called one-chip full-color liquid crystal display panels such as microlens-integrated liquid crystal display devices without a color filter.
2. Related Background Art
The world of today is in the age of multimedia, and equipment for communication by image information is becoming more and more important. Among others, the liquid crystal display devices are drawing attention because of their slimness and low power consumption and have grown to one of basic industries comparable to the semiconductors. The liquid crystal display devices are mainly used for 10-inch notebook-size personal computers at present. It is expected that the liquid crystal display devices of larger screen sizes will be used not only for the personal computers, but also for workstations and televisions for home use in future. With increase in the screen size, however, manufacturing equipment becomes expensive and, in addition, electrically exacting characteristics are demanded for driving of such large screens. The manufacturing cost will thus increase abruptly in proportion to the square to cube of the size with increasing screen size.
Recently, attention is thus drawn to a projection method for preparing a compact liquid crystal display panel and optically enlarging a liquid-crystal image to display an enlarged image. This is because the microstructure tendency of semiconductors permits decrease in the size, improvement in the characteristics, and decrease in the cost, similar to the scaling rule to improve performance and cost. From these aspects, in the case of the liquid crystal display panel of the TFT type, TFTs have to be compact and have sufficient driving force, and transition is now occurring from the TFTs using amorphous Si to those using polycrystal Si. Video signals of the resolution level conforming to the NTSC system etc. used in the ordinary televisions do not require so quick processing.
This allows not only the TFTs but also peripheral driving circuits such as shift registers or decoders to be made of polycrystal Si, whereby the liquid crystal display devices can be constructed in monolithic structure of a display region and a peripheral driving circuit region. Polycrystal Si is inferior to single-crystal Si, however. For realizing high-definition televisions having the higher resolution level than the NTSC system or display of the XGA (extended Graphics Array) or SXGA (Super extended Graphics Array) class in the resolution standards for computers by polycrystal Si, a shift register needs to be composed of a plurality of segments. In this case, noise, called ghost, appears in the display region at portions corresponding to borders between the segments and there are desires for a solution to this problem in this field.
On the other hand, focus is also drawn to display devices using a single-crystal Si substrate, which can realize extremely higher driving force than the display devices of the monolithic structure of polycrystal Si. In this case, the transistors of the peripheral driving circuitry have sufficient driving force and thus the divisional driving described above is not necessary. This solves the problem of the noise and the like.
A microlens-integrated liquid crystal panel and a projection-type liquid crystal display device using it are disclosed in Japanese Laid-Open Patent Application No. 8-114780, for example. The microlens-integrated liquid crystal panel in this case is normally of the transmission type and it was constructed in the structure as illustrated in FIG.
13
. Specifically, illumination beams of the respective primary colors of R, G, and B are guided at mutually different angles onto the liquid crystal panel and then onto pixels
1318
different from each other by converging action of microlenses
1316
. This eliminated the need for the color filter and enabled to achieve high light utilization efficiency. The projection type display device of this type can project and display a bright full-color picture even by use of the one-chip liquid crystal panel which is a single liquid crystal panel capable of creating the colors R, G, B. Such projection type display devices are gradually becoming commercially available.
On the other hand, various attempts have been made to achieve operational modes of liquid crystal of the liquid crystal panel used in the liquid crystal display apparatus, and there are operational modes including a mode using ferroelectric liquid crystal, a TN mode using nematic liquid crystal, which is relatively popularly used, an STN mode, an IPS (In-Plain-Switching) mode, a polymer-dispersed liquid crystal mode, and an electrically controlled birefringence (ECB) mode for controlling birefringence of liquid crystal cell by application of an electric field. As for the ECB mode, there are three types of methods, among which the DAP (deformation of vertical aligned phase) type uses the nematic liquid crystal having negative dielectric anisotropy. Namely, the liquid crystal in the initial state is in vertical alignment (homeotropic alignment) and the liquid crystal molecules become inclined with application of voltage to change incident, linearly polarized light into elliptically polarized light by the birefringence effect, thereby achieving gradation display. This method has steep voltage-reflectance characteristics and black is easy to create in the normally black mode by use of orthogonal polarizers. Therefore, this method can implement high-contrast liquid crystal display.
For use of the liquid crystal apparatus of the DAP mode, it is important to uniformly align longitudinal axes of liquid crystal molecules with the vertical direction to the substrate in the initial stage and how uniformly and stably angles and directions of pretilt of the molecules are controlled would be a key to enhancing the contrast and in-plane uniformity which represent the performance of the liquid crystal display apparatus. A method known for implementing such vertical alignment is, for example, application of such an amphiphilic surface-active agent as lecithin or organic silane (Liquid crystal-applications, p61, coauthored by Koji Okano and Shunsuke Kobayashi, Baifukan).
A variety of oblique evaporation methods and rubbing methods are normally used as methods for controlling the pretilt angles of liquid crystal molecules at elevations of about 1 to 5 degrees relative to an alignment layer surface, and there is also a recent report to suggest a method for controlling alignment by irradiating the vertical alignment layer with ultraviolet rays. Among these the rubbing methods are techniques excellent in mass productivity and cost efficiency, which are often used in practice.
The vertical alignment layers, however, still have the problems that their wettability is poor, that it is hard to form the layers stably in uniform thickness and quality of film, and it is hard to implement reliable control of alignment. Particularly, there are some cases in which display characteristics are degraded considerably by disturbance of alignment caused by weakness of adhesion of the alignment layers at step portions of base layer in contact with the alignment layers. In particular there is a possibility that the problem becomes significant on the occasion of rubbing for the pretilt control.
Further, in the case of the microlens-integrated liquid crystal panels, say the conventional example described above (FIG.
13
), a projection display image thereof is an enlarged projection image of the pixels
1318
of R, G, and B on the screen and, therefore, the mosaic pattern of R, G, and B becomes prominent as illustrated in FIG.
14
. This could degrade the quality of display image.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid crystal display device that can be applied to the one-chip projection type liquid crystal display apparatus and that can display a full-color projec
Ichikawa Takeshi
Koyama Osamu
Kurematsu Katsumi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Ton Toan
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