Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-01-19
2004-07-27
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S002000, C349S144000
Reexamination Certificate
active
06768532
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a liquid crystal display panel forming a part of a liquid crystal display device, and more particularly, to a liquid crystal display panel suited for displaying patterns (characters, mark graphics, and so forth) in the shape as required in cloudy white or black, or in the form of a colored pattern against a transparent background.
DESCRIPTION OF THE RELATED ART
As liquid crystal display devices, using a liquid crystal display (LCD) panel, have advantages of low-profile shape, light weight, and further, very low power consumption, these devices have come to be used as display devices for a wide variety of equipment including various kinds of portable electronic equipment such as a tabletop calculator, cellular phone, wrist watch, camera, video camera, note-type personal computer, and so forth.
With such a liquid crystal display panel, a pair of transparent substrates are bonded together by a sealing section provided on the periphery of a display region with a given spacing provided therebetween, and a liquid crystal cell is made up by sealing a liquid crystal layer in-between the spacing. By applying a voltage to parts of the liquid crystal layer via signal electrodes and opposite electrodes formed on an opposed inner face of the two substrates, respectively, optical properties (twist of a polarization axis, birefringence, transmission/scattering, and so on) of the liquid crystal layer can be varied.
Accordingly, through a combination of a polarizing film disposed on both sides of the liquid crystal cell or by the use of the liquid crystal cell itself, parts of the liquid crystal layer where a voltage is applied come to differ from parts of the liquid crystal layer where no voltage is applied, in terms of transmission/absorption or scattering of light, or hue of light, thereby enabling a variety of displays to be effected.
Consequently, with this type of liquid crystal display panel, parts where the respective signal electrodes formed on one of the substrates are opposed to (or cross in the case of a dot-matrix type liquid crystal display panel) the respective opposite electrodes formed on the other of the substrates, with the liquid crystal layer interposed therebetween, perform functions of display portions (pixels).
In order to enable each of the display portions (pixels) to be driven independently, it is necessary to provide the periphery of the respective display portions with a gap where no electrode is installed.
For this reason, in the case of a liquid crystal display panel using, for example, twisted nematic (TN) liquid crystal in a liquid crystal layer, it has been possible to effect consistent display across the entire area of a display region in a condition wherein no voltage is applied to the liquid crystal layer, but impossible to do so in a condition wherein a voltage is applied thereto because the voltage cannot be applied to regions of the gaps where no electrode has been installed.
Further, in the case of a liquid crystal display panel for selectively displaying isolated patterns against a background in consistent display, there is a need of forming wiring electrodes for use in applying a voltage to electrodes constituting respective isolated pattern display portions, in such a way as to cross electrodes in a background region while providing a gap between the electrodes and the wiring electrodes. As with the case of the signal electrodes and the opposite electrodes, the wiring electrodes are formed of a transparent ant electrically conductive film, such as an indium tin oxide (ITO) film.
However, if, for effecting display at any of the pattern display portions, a voltage is intended to be applied to a signal electrode and an opposite electrode for the relevant pattern display portion, this will cause a problem that, because the voltage is applied via a wiring at connected to the signal electrode, the voltage will be applied to a portion of the liquid crystal layer between the wiring electrode and the opposite electrode as well, so that a region of the wiring electrode as well as the relevant pattern display portion is turned into a display state.
Accordingly, the wiring electrodes are rendered very thin in width so as to be inconspicuous. However, if the same are rendered too thin, this will increase electrical resistance, causing a problem of poor responsivity in display.
Also, in the case of a liquid crystal display panel for use in a viewfinder of a camera, and the like, it is important from the viewpoint of enhanced visibility from a viewer to have an even display across the entire area of a display region, and to have a transmittance as high as possible, except for necessary patterns such as a target pattern for auto focus, and the like.
In order to attain a high transmittance, a liquid crystal display panel using a liquid crystal layer capable of obtaining a high contrast ratio without use of polarizing films is promising.
For example, a liquid crystal display panel using a scattering-type liquid crystal layer with transparent solids made of organic polymers diffused in liquid crystal is in a milky white state causing incident light to scatter when no voltage is applied to the liquid crystal layer, but is turned into a transparent state having a high transmittance when a voltage is applied thereto.
It follows therefore that for effecting display only at necessary display portions such as a target pattern for auto focus, and the like, against a transparent background, no voltage may be applied to the liquid crystal layer only at display portions to be displayed while a voltage is applied to the entire region of the liquid crystal layer, other than regions of the display portions to be displayed.
However, when no voltage is applied to electrodes at the display portions, no voltage is applied to wiring electrodes connected thereto either, and consequently, no voltage is applied to a portion of the liquid crystal layer interposed between the wiring electrodes and the opposite electrodes, so that the portion of that liquid crystal layer is not turned into a transparent state. Consequently, it follows that the entire region of the liquid crystal layer, other than the regions of the necessary display portions, cannot be rendered transparent.
The present invention has been developed to solve such problems as described in the foregoing, and it is therefore an object of the invention to provide a liquid crystal display panel capable of displaying isolated patterns against a transparent background, wherein a consistently transparent state can be attained with ease across the entire area of a display region, other than regions of necessary pattern display portions, in a condition where a voltage is applied to a liquid crystal layer in a background region.
SUMMARY OF THE INVENTION
To attain the object as described above, a liquid crystal display panel according to the present invention is as follows.
A first substrate with signal electrodes formed on a face thereof is bonded to a second substrate with an opposite electrode formed on a face thereof at a given spacing provided by a peripheral sealing section interposed therebetween on the periphery of a display region such that the signal electrodes are opposed the opposite electrode, and a liquid crystal layer is installed in between the spacing.
The signal electrodes include a peripheral electrode formed substantially across the entire area of the display region, pattern electrodes formed in isolation within the peripheral electrode, and wiring electrodes formed across the peripheral electrode with a gap provided between the same and the peripheral electrode for selectively applying a voltage to the respective pattern electrodes.
The opposite electrode is installed over the entire area of the display region in such a way as to oppose the signal electrode.
With the liquid crystal display panel, the first substrate, second substrate, signal electrodes and opposite electrode are all transparent, the liquid crystal layer undergoes changes in optical properties dep
Citizen Watch Co. Ltd.
Nguyen Dung
Parker Kenneth
Westerman Hattori Daniels & Adrian LLP
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