Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-11-09
2004-04-20
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06724457
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-318820, filed Nov. 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 a method of manufacturing the same, particularly, to the construction of a columnar spacer for forming a predetermined gap between a pair of substrates and a method of manufacturing the columnar spacer.
A liquid crystal display device comprises a liquid crystal material held between a pair of an array substrate and a counter substrate each having an electrode. In order to maintain constant the gap between these two substrates, plastic beads having a uniform particle diameter are dispersed as a spacer between the two substrates.
In the manufacturing process of such a liquid crystal display device, the plastic beads used as a spacer are dispersed on the substrate, with the result that the spacer forms particles contaminating the manufacturing line so as to bring about a defect. Also, the spacer present in the pixel portion causes a poor alignment. Further, an agglomerated lump of the spacer and the nonuniformity in the dispersing density cause an inconvenience that the gap provided between the paired substrates is rendered nonuniform.
In order to overcome the difficulties described above, it is proposed to employ a photolithography process for forming a columnar spacer in a predetermined position on the array substrate.
However, in the manufacturing process of the array substrate, a material of an alignment film is formed after formation of a columnar spacer on the substrate, followed by applying an aligning treatment to the material of the alignment film. As a result, a problem is generated that the columnar spacer tends to be peeled off together with the alignment material formed into a film. Where the material of the alignment film is peeled off, the alignment of the liquid crystal molecules is disturbed in the vicinity of the columnar spacer, leading to deterioration in the display performance and to reduction in the manufacturing yield.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention, which has been achieved in an attempt to overcome the problems described above, is to provide a liquid crystal display device satisfactory in the display performance and capable of preventing the reduction in the manufacturing yield and to provide a method of manufacturing the particular liquid crystal display device.
According to a first aspect of the present invention, there is provided a liquid crystal display device, comprising:
a first substrate;
a columnar spacer formed on the first substrate and exhibiting light shielding properties;
an alignment film formed to cover at least a part of the columnar spacer;
a second substrate arranged to face the first substrate with a predetermined gap provided by the columnar spacer between the first and second substrates; and
a liquid crystal material arranged within the gap;
wherein the columnar spacer is tapered in the forward direction as viewed from the first substrate in that portion of the columnar spacer which is positioned closest to the second substrate and has the largest diameter portion in the region other than that region of the columnar spacer which is positioned closest to the first substrate.
According to a second aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, comprising:
a first step of forming a columnar spacer on a first substrate;
a second step of forming an alignment film on the first substrate on which the columnar spacer is formed;
a third step of applying a rubbing treatment to the alignment film; and
a fourth step of arranging the first substrate and the second substrate to face each other and arranging a liquid crystal material in a gap formed between the first and second substrates by the columnar spacer;
wherein the columnar spacer in the first step is tapered in the forward direction as viewed from the first substrate in that portion of the columnar spacer which is positioned closest to the second substrate and has the largest diameter portion in the region other than that region of the columnar spacer which is positioned closest to the first substrate.
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: 5499128 (1996-03-01), Hasegawa et al.
patent: 6238754 (2001-05-01), Shohara et al.
patent: 9-120075 (1997-05-01), None
Manabe Atsuyuki
Maya Natsuko
Nagata Hiroyuki
Sunohara Kazuyuki
Toriyama Akiko
Akkapeddi P. R.
Chowdhury Tarifur R.
Kabushiki Kaisha Toshiba
Pillsbury & Winthrop LLP
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