Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-03-22
2003-06-10
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06577373
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a liquid crystal display and a liquid crystal display manufacturing method.
BACKGROUND OF THE INVENTION
A liquid crystal display is widely used in a portable electronic device or the like. The liquid crystal display is generally constituted, as shown in
FIG. 27
, by putting a liquid crystal
7
between two substrates
1
each provided with a color filter
4
, a black matrix
5
, a linear transparent electrode
3
, an alignment film
9
and the like. It is spacers
8
that restrict the distance between said two substrates
1
and maintain the appropriate thickness of a liquid crystal layer.
According to the conventional method of manufacturing a liquid crystal display, since spacers are randomly, uniformly spread onto the substrate on which a pixel electrode is formed, they are arranged even onto the pixel electrode, i.e., the display section of the liquid crystal display. The spacers are generally formed of synthetic resin, glass or the like. If the spacers are arranged onto the pixel electrode, light leakage occurs to the spacer portions due to depolarization. Also, light void occurs due to the irregular orientation of the liquid crystal on the surfaces of the spacers, with the result that contrast and tone are lowered and display quality deteriorates.
Japanese Kokai Publication Sho-60-361 discloses a liquid crystal display cell which reduces the quantity of spacers arranged onto a display section compared with that of spacers arranged onto non-display sections by masking the display section at the time of spreading the spacers. The liquid crystal display cell disclose therein is, however, a simple display system such as a so-called seven-segment display system and spacers are not selectively arranged onto a black matrix portion.
The black matrix is provided to improve the display contrast of a liquid crystal display and to prevent the malfunction of elements due to external light in case of a TFT-type liquid crystal display. To solve the above-stated problems, spacers may be arranged only onto a black matrix portion serving as a light shielding film.
As a technique for arranging spacers only onto a black matrix portion, that is, a portion other than the pixel electrode of a liquid crystal display, Japanese Kokai Publication Hei-4-256925 discloses a method of maintaining the potential of a gate electrode to be the same as that of a drain electrode at the time of spreading spacers. Also, Japanese Kokai Publication Hei-5-53121 discloses a method of applying a voltage to a wiring electrode at the time of spreading spacers. Further, Japanese Kokai Publication Hei-5-61052 discloses a method of applying a positive voltage to a wiring electrode, negatively charging spacers and spreading the resultant spacers in dry condition.
All of the above methods are, however, arrangement-related techniques utilizing a wiring electrode and, therefore, intended for a TFT-type liquid crystal display. An STN-type liquid crystal display does not include an electrode corresponding to the wiring electrode and a pixel electrode is formed simply by making stripe electrodes perpendicular to one another on upper and lower substrates. Owing to this, the above-stated arrangement techniques cannot be applied to the STN-type liquid crystal display.
Furthermore, Japanese Kokai Publications Hei-3-293328 and Hei-4-204417 disclose a method of selectively arranging spacers in areas which are not provided with electrodes by charging one of insulating substrates and spreading spacers charged with the same polarity as that of the electrode onto the insulating substrates.
With this method, however, the spacers are charged with the same polarity as that of the electrode. Due to this, a repulsive force is generated between the spacer and the electrode. However, an attracting force for attracting the spacers to be positioned between the electrodes is not generated. This results in the following disadvantages. That is, only the repulsive force occurs to the spacers in the display area in which a group of electrodes charged with the same polarity as that of the spacers as well as its periphery and the spacers cannot be applied uniformly to areas in which the spacers are intended to be arranged (areas between electrodes) as a result that it is difficult to actively, selectively arrange the spacers.
Furthermore, Japanese Kokai Publication Hei-8-76132 discloses, as a method of arranging spacers with better selectivity than those of the above-stated methods, a method of arranging spacers with good selectivity by charging spacers either positively or negatively, by applying a potential opposite in polarity to that of the spacers to the first electrode provided in areas on an insulating substrate in which the spacers are to be arranged and by applying a potential in the same polarity as that of the spacers to the second electrode provided in areas on the insulating substrate in which the spacers are not to be arranged.
This method, however, has disadvantage in that contrast is decreased since the spacers are arranged on the electrodes. Besides, if this method is applied to a simple matrix liquid crystal display, an electrode for arranging the spacers other than a pixel electrode needs to be formed and numerical aperture thereby decreases.
As can be seen from the above, according to the conventional techniques, it is difficult to easily, efficiently obtain a liquid crystal display with excellent contrast and good display quality by removing spacers on a pixel electrode in a liquid crystal display comprising a substrate having stripe transparent electrodes.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the above problems, i.e., to provide a liquid crystal display exhibiting excellent display quality having good contrast which quality is not influenced by light leakage resulting from spacers due to the fact that most of the spacers are arranged under a black matrix, and to provide a method of manufacturing a liquid crystal display capable of preventing the spacers from being arranged onto pixel electrodes, arranging the spacers onto a black matrix portion and manufacturing a liquid crystal display having extremely high contrast without light leakage resulting from the spacers.
The first invention is a liquid crystal display having a liquid crystal injected into a gap between two substrates arranged to oppose each other through spacers, wherein at least one of said two substrates is a substrate on which a black matrix is formed; at least one of said two substrates is a substrate constituted by aligning a plurality of transparent electrodes; not less than 50% of the spacers are arranged just under a position of the black matrix; and the spacers arranged just under the position of the black matrix are arranged along said transparent electrodes.
The second invention is a method of manufacturing a liquid crystal display wherein spacers are spread onto at least one of a first substrate constituted by aligning a plurality of electrodes and a second substrate arranged on the first substrate to oppose the first substrate and a liquid crystal are injected into a gap between both substrates, which comprises the steps of charging and then spreading the spacers; applying voltages having two or more different voltage values to said plural electrodes; controlling an electric field generated above the transparent electrodes; and thereby selectively arranging the spacers only between predetermined transparent electrodes among the transparent electrodes adjacent each other.
The third invention is a method of manufacturing a liquid crystal display wherein spacers are spread onto a first substrate having a stripe transparent electrode constituted by aligning a plurality of linear transparent electrodes in parallel, a second substrate is arranged above the first substrate to oppose the first substrate and a liquid crystal are injected to a gap between the substrates, wherein spreading said spacers are carried out by applying voltages having different voltage values to
Ikesugi Daisuke
Kira Takatoshi
Nakahara Makoto
Nakatani Hiroyuki
Tateno Akihiko
Connolly Bove & Lodge & Hutz LLP
Nguyen Hoan
Sekisui Chemical Co. Ltd.
Ton Toan
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