Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-04-02
2001-08-14
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S156000, C349S110000, C349S106000
Reexamination Certificate
active
06275280
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a liquid crystal display element substrate which has a spacer function, and to a liquid crystal display device in which this is included.
2. Background Art
In order to maintain the liquid crystal layer thickness (the cell gap), in conventionally-employed liquid crystal display devices plastic beads, glass beads or glass fibres are generally interposed between two liquid crystal display element substrates and used as spacers. Here, the plastic beads or other such spacers are positioned by spraying, so the positions between the two liquid crystal display element substrates (the positions within the screen) where they are arranged cannot be controlled accurately. In other words, spacers are also present in the display regions (the light transmitting regions within the screen, other than the light screening regions) on the liquid crystal display element substrate. Consequently, there is the problem of a lowering of the display quality of the liquid crystal display device due to light scattering and transmission by the spacers. Furthermore, the spacers tend to be maldistributed, and the display quality in those parts where spacers are bunched is impaired and there are also problems in terms of the precise maintenance of the cell gap. Consequently, not only is there a need to control with a high degree of accuracy the process of evenly spreading the spacers and the particle size distribution of the spacers, but also the difficulty of obtaining a liquid crystal display device of stable display quality by a simple method needs to be addressed. In addition, there is also the following problem. Since the spacers are spherical or have a rod-like shape, and effect point-like or line-like contact at the time of the cell press bonding, there is the disadvantage that the alignment layer or the transparent electrodes are easily damaged and display faults produced. Moreover, there is also the dis-advantage that the liquid crystal is contaminated by the damage to the alignment layer or transparent electrodes, and the effective voltage applied to the liquid crystal tends to be lowered.
In order to maintain the cell gap, in Japanese Unexamined Patent Publication Nos 56-140324, 63-824054, 4-93924, 5-196946 and 7-318950, liquid crystal display devices have been proposed which employ, as spacers, structures produced by the lamination of the coloured layers for forming a colour filter. However, there have been cases where cell gap unevenness is produced and a lowering of the display quality occurs in the liquid crystal display devices actually obtained by such techniques. With liquid crystal display devices, it is not easy to stick together the two liquid crystal display element substrates at a uniform force and, when the perimeter of the elements is sealed, strains remain where even just a slight unevenness in force occurs. The cell gap may be changed due to such slight strains and a lowering of the display quality readily tends to arise.
Again, there have been cases where display faults occur when the liquid crystal display device is subject to a force or impact from the outside. In particular, where a force has been locally applied, display unevenness is noted and there is a lowering of the display quality. Furthermore, problems are also produced when there is a variation in the height of the spacers formed. At the time of the cell (panel) assembly, the two liquid crystal display element substrates are stuck together by applying a certain degree of force, but when the force imposed on the substrates is removed problems can arise in that the spacer heights recover to form an uneven state. As a result, the number of effectively functioning spacers is reduced and there is an increased possibility of display unevenness. Moreover, if it not possible to maintain the cell gap accurately, bubbles may be generated in the cell when at low temperatures. Such bubbles lower the display quality.
The objective of the present invention is to offer a liquid crystal display element substrate where a uniform cell gap is maintained within the screen, and where the display quality is not reduced when subjected to a force or impact from outside, or when a change in cell temperature occurs; together with a liquid crystal display device in which this is included.
DISCLOSURE OF THE INVENTION
As a result of a painstaking investigation into means for resolving the aforesaid problems, the present inventors have discovered that by setting, in a specified range, the compression displacement of the spacers in response to a load lying within a specified compression stress range, the aforesaid objective can be attained, and the present invention has been perfected based thereon.
Specifically, the present invention provides a liquid crystal display element substrate which is characterized in that it has spacers fixed in non-display regions on the liquid crystal display element substrate, and the load compression displacement of these spacers for a compression stress of 0.5 to 0.6 GPa is from 0.001 to 1 &mgr;m/mN. Furthermore, the present invention provides a liquid crystal display device which is characterized in that, in a liquid crystal display device where a liquid crystal layer is held between two liquid crystal display element substrates, at least one of these liquid crystal display element substrates is an aforesaid liquid crystal display element substrate of the present invention.
REFERENCES:
patent: 4678284 (1987-07-01), Tashiro
patent: 4682858 (1987-07-01), Kanbe et al.
patent: 5953087 (1999-09-01), Hoyt
patent: 0 113 064 (1984-07-01), None
H. Yamashita et al.: “P-48: Precise Cell-Thickness Control By Spacer-Ball-Free Structure and Its Application to Large-Size-TFT-LCDs”, Sid International Symposium, Digest of Technical Papers, San Diego, May 12-17, 1996, vol. 27, May 12, 1996, pp: 600-2, XP000621060, Society for Information Display.
Goto Tetsuya
Ido Hideo
Kajita Junji
Nomura Hideshi
Tsuda Keiji
Morrison & Foerster / LLP
Sikes William L.
Ton Toan
Toray Industries Inc.
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