Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-07-13
2004-01-13
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S156000, C349S157000
Reexamination Certificate
active
06678030
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device.
2. Background Art
Liquid crystal display devices have a vessel made of transparent substrates disposed in opposition to each other with a liquid crystal being interposed therebetween, and a display part made of multiple pixels arranged in the spreading direction of the liquid crystal.
Either one of the transparent substrates is secured to the other transparent substrate by a sealing material which also serves the function of sealing the liquid crystal, and the gap between the transparent substrates in the display is retained by spacers scattered in the liquid crystal.
A recently known example of the spacers is a resin layer which is formed in a columnar shape on either one of the transparent substrates by selective etching using a photolithography technique.
The spacers formed in this manner have the advantage of being able to be formed with high accuracy at predetermined positions in the display part as well as the advantage of being able to be made uniform in height.
However, it has been observed that when the temperature of such a liquid crystal display device reaches a high temperature owing to heat generated from a backlight or the like, the liquid crystal thermally expands and one of the transparent substrates separates from the spacers formed on the other. This is because the thermal expansion of the spacers cannot follow the thermal expansion of the liquid crystal.
As a result, the gap between the transparent substrates, that is, the layer thickness of the liquid crystal, cannot be made uniform, and a deflection occurs in at least either one of the transparent substrates.
Even when the temperature of the device returns to a normal temperature, the deflection of the transparent substrate does not easily disappear, and offers a problem which causes the irregular display image.
SUMMARY OF THE INVENTION
The invention has been made in view of the above-described problems, and provides a liquid crystal display device in which the gap between its transparent substrates can be made uniform irrespective of whether the temperature of the device is normal temperature or high temperature.
A representative aspect of the invention disclosed will be described below in brief.
A liquid crystal display device according to the invention includes transparent substrates disposed in opposition to each other with a liquid crystal being interposed therebetween, and plural spacers secured to one of the transparent substrates so as to support the other transparent substrate. The plural spacers include first spacers and second spacers, and the first spacers are formed of a material whose elasticity is higher than that of the second spacers, and are larger in height than the second spacers.
In the liquid crystal display device constructed in this manner, before the temperature of the device becomes high, the gap between the transparent substrates is retained according to the height of the second spacers. In this case, the first spacers are in the state of being shrunk owing to their elasticity.
When the temperature becomes high and the liquid crystal thermally expands, either one of the transparent substrates separates from the second spacers, but does not separate from the first spacers. This is because the first spacers are in the state of being expanded owing to their elasticity.
When the temperature returns to normal temperature, the first spacers are brought to the state of being shrunk owing to their elasticity, and the gap between the transparent substrates is retained according to the height of the second spacers.
Accordingly, a deflection does not occur in either of the transparent substrates, and the gap between the transparent substrates can be kept uniform irrespective of whether the temperature of the device is normal temperature or high temperature.
REFERENCES:
patent: 5381255 (1995-01-01), Ohnuma et al.
patent: 5812232 (1998-09-01), Shiroto et al.
patent: 5978061 (1999-11-01), Miyazaki et al.
patent: 6187440 (2001-02-01), Wu
Hasegawa Shinji
Imabayashi Makiko
Iwakabe Yasushi
Di Grazio Jeanne
Kim Robert H.
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