Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-07-07
2004-01-27
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06683671
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-196209, filed Jul. 9, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device and more particularly to a liquid crystal display device having columnar spacers that allow the cell gap formed between a pair of substrates to be made uniform.
In recent years, flat-panel display devices, typically liquid crystal display devices, have been used as display devices for personal computers and word processors because of their features of small thickness, light weight, and low power dissipation. Among them, active-matrix liquid crystal display devices in which a switching element is electrically connected to each pixel electrode have been intensively studied and developed because they provide good images with little crosstalk between adjacent pixels.
Such active-matrix liquid crystal display devices have spacers for forming a cell gap between a pair of substrates. For example, the spacers are provided on the counter substrate having red, green and blue color filter layers. That is, the spacers are formed by stacking color filter layers on a light shield layer that prevents wire pattern, such as scanning lines and signal lines around pixel electrodes, and switching elements from exposure to light.
Thus, if the spacers are formed on the light shield layer for concealing alignment failures due to differences in level around the switching elements and near the wire patterns, the alignment failures near the spacers are difficult to be exposed. For this reason, higher-quality images can be provided than in liquid crystal display devices in which the cell gap is formed by scattering spherical spacers on a substrate.
However, when the spacers are formed from stacked color filter layers on the light shield layer, counter electrode arranged on the color filter layers will cover the spacers as well. Such counter electrode protrude from the major surface of the counter substrate toward the array substrate side. For this reason, the counter electrode that cover the spacers become easy to be short-circuited to the pixel electrodes, wire patterns and switching elements on the array substrate side.
The color filter layers that form such a spacer are each set to a given thickness to allow light to pass through at a given transmission factor. Thus, the spacer formed by stacking the color filter layers can be formed only at a given height and hence suffers from a limitation on the freedom of its height. For this reason, it is difficult to apply spacers of such a structure to a liquid crystal display device with an arbitrary cell gap.
On the other hand, a liquid crystal display device having a columnar spacer formed of resin on color filter layers has been proposed. In such a liquid crystal display device, no color filter layer is located in the peripheral area around the display area, i.e., the outside area defined by a sealing material. If, therefore, columnar spacers of the same height as those in the display area are formed in the peripheral area, then the spacers in the peripheral area will fall the thickness of the color filter layers short of those in the display area. Therefore, local nonuniformity occurs in the cell gap. The nonuniformity of the gap also influences the display area and may cause image display failures.
In recent years, as the demand for small-sized display devices increases, the width of the peripheral area around the display area tends to decrease. With small-sized liquid crystal display devices, the gap nonuniformity in the peripheral area further significantly affects the display area.
Thus, the conventional spacer structure may result in reduced manufacturing yields because of short-circuiting between the counter substrate and the array substrate, the limited freedom of the spacer's height, and display failures due to the gap nonuniformity.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid crystal display device capable of permitting the manufacturing yield to be prevented from lowering and good images to be displayed.
Another object of the present invention is to provide a method of manufacturing a liquid crystal display device capable of permitting the manufacturing yield to be prevented from lowering and good images to be displayed.
According to the present invention there is provided a liquid crystal display device comprising: a first substrate having a plurality of pixel electrodes; a second substrate having a counter electrode which is opposed to the pixel electrodes; and an optical modulating layer sandwiched between the first and second substrates, wherein a display area for modulating light transmitted through the optical modulating layer to display images has color filter layers each of which allows a predetermined color of light to pass through, and a peripheral area around the display area has a color filter layer and a column-shaped spacer which is stacked on the color filter layer and forms a gap between the first and second substrates.
According to the present invention there is provided a method of manufacturing a liquid crystal display device comprising the step of forming a first substrate having pixel electrodes, the step of forming a second substrate having a counter electrode, and the step of sealing in an optical modulating layer between the first and second substrates, wherein the step of forming a second substrate includes a substep of forming color filter layers each of which allows a predetermined color of light to pass through on an insulating substrate, a substep of forming the counter electrode to cover the color filter layers in a display area adapted to display images by modulating light transmitted through the optical modulating layer, a substep of forming column-shaped spacers on the counter electrode, and a substep of forming a column-shaped spacer to cover a color filter layer formed in a peripheral area around the display area.
According to the liquid crystal display device of the present invention, the spacer in the peripheral area is formed on a dummy color filter layer, which allows the cell gap to be made uniform over the display area and the peripheral area.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5978061 (1999-11-01), Miyazaki et al.
Kabushiki Kaisha Toshiba
Kim Robert H.
Pillsbury & Winthrop LLP
Rude Timothy
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