Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-09-17
2004-10-05
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06801287
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to liquid crystal display device and also relates, for example, to a liquid crystal display device of the type employing the so-called lateral electric field scheme.
2. Description of Related Art
The liquid crystal display device of this type is such that a pixel electrode and an opposite or “counter” electrode which are disposed adjacent to each other are formed in a pixel region of a liquid crystal side surface of one substrate of respective substrates being disposed to oppose each other with a layer of liquid crystal material interposed therebetween, wherein components of an electric field created between these respective electrodes which are in parallel to the substrate are used to cause molecules of the liquid crystal material to take behavioral actions.
And, the one that applies this lateral electric field scheme to an active matrix type display device is arranged to use as pixel regions respective regions which are surrounded by a great number of parallel-provided gate signal lines extending on the liquid crystal side surface of one substrate in an “x” direction thereof and a great number of parallel-provided drain signal lines extending on the substrate surface in a “y” direction thereof and comprise in each of these pixel regions a thin-film transistor which is made active in response to receipt of a scan signal from a gate signal line and the aforesaid pixel electrode to which an image or video signal is supplied from a drain signal line through this thin-film transistor and also the counter electrode to which a signal is supplied which becomes a reference with respect to the image signal.
In addition, in view of the fact that the electric field for permitting liquid crystals to take behavioral actions is inherently weak and faint, the pixel electrode and the counter electrode are formed into band-like shapes respectively, at least one of which consists of a plurality of ones that becomes a comb-tooth like pattern while letting them be disposed alternately.
And, one is known in which the pixel electrode and the counter electrode are formed of different layers with a protective film sandwiched therebetween, wherein the protective film is comprised for example of an organic material layer which covers the thin-film transistor.
Due to this, an orientation film which determines the initial alignment of liquid crystal molecules is to be formed to cover the organic material layer for use as the protective film and one electrode of the above-noted pixel electrode and counter electrode.
SUMMARY OF THE INVENTION
However, it has been found that in the liquid crystal display device thus arranged in the way stated above, each of the following phenomena occurs due to unusual matter of the orientation film which is formed in direct contact with the liquid crystals.
More specifically, in cases where vibration shocks—in particular, vibrations at high-frequency waves—are applied to the liquid crystal display device, unwanted separation or peel-off takes place at the orientation film, causing bright points to generate on the entire surface of a display plane. The result of disassembling for investigation such liquid crystal display device has revealed that peel-off occurs at a portion of the orientation film overlying an electrode in a manner as shown in
FIG. 9
(this phenomenon will be referred to as “Mode
1
” hereinafter).
The bright points can also generate when the liquid crystal display device is continuously driven in a vibration-free state. As a result of disassembling for investigation this liquid crystal display device, it has been found that peel-off generates at part of the orientation film overlying the protective film as shown in
FIG. 10
(this phenomenon will be referred to hereinafter as “Mode
2
”).
In addition, the bright points can gradually generate even in the so-called temperature cycling test which recurrently changes an ambient temperature of the liquid crystal display device between low and high temperatures. As a result of disassembling for investigation such liquid crystal display device, it has been found that the orientation film overlying an electrode is liberated with respect to this electrode as shown in
FIG. 11A
(this phenomenon will be referred to hereinafter as “Mode
3
”). Note that
FIG. 11B
is a cross-sectional diagram as taken along line b—b of FIG.
11
A.
Additionally each view of
FIGS. 9
,
10
and
11
A is a drawing which corresponds to
FIG. 3
which will be later presented.
The present invention has been made in light of the above-discussed technical background, and one of the advantages of this invention is to provide a liquid crystal display device which comprises an orientation film(s) with increased reliability.
A brief explanation will be given of the summary of representative ones of the inventive concepts as disclosed herein.
(1) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, a silane coupling material be mixed into the orientation film at a specific mixture ratio which is equal to or more than 0.1% and yet less than or equal to 2% with respect to an orientation film solid content concentration.
(2) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, wherein the orientation film is formed with its temperature suppressed to less than or equal to 250° C. during firing or baking in the fabrication thereof.
(3) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, that the above-noted one electrode exhibits a zigzag-shaped pattern having a plurality of bent portions along the extending direction thereof, and that the other electrode is disposed in parallel to the above-mentioned electrode.
(4) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, and that the orientation film is designed so that its film thickness falls within a range of from 60 to 250 nanometers (nm).
(5) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface o
Kurahashi Nagatoshi
Nakayoshi Yoshiaki
Yanagawa Kazuhiko
Chowdhury Tarifur R.
Di Grazio Jeanne Andrea
Hitachi LTD
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