JPH07168157A - Liquid crystal display - Google Patents

Abstract

PURPOSE:To provide a device capable of lessening light leakage at the time of a dark display and assuring a sufficient constant even in high time-division driving by matching and arranging a liquid crystal display element and a high polymer disper sion type liquid crystal shutter laid with counter electrodes facing scanning electrodes in such a manner that the respective scanning electrodes are synchronously driven on each other. CONSTITUTION:The high polymer dispersion type liquid crystal shutter 13 is arranged relative to the liquid crystal display element 1 in such a manner that the scanning electrodes thereof overlap spatially on the scanning electrodes of the liquid crystal element 1. The high polymer dispersion type liquid crystal shutter 13 is time-division driven in synchronization with the liquid crystal display element 1 by the driving circuit. At this time, light is transmitted in regions corresponding to the scanning electrodes impressed with the scanning signals of the high polymer dispersion type liquid crystal shutter 13 and the light is scattered in the regions corresponding to the scanning electrodes to which the light signals are not impressed. Then, the light is not made incident in the regions corresponding to the scanning electrodes to which the scanning signals on the liquid crystal display element 1 side are not impressed even if the on signal is applied thereon and, therefore, the light is not transmitted in these regions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix display type liquid crystal display device.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device of this type has a plurality of first transparent substrates out of two transparent substrates which face each other with a liquid crystal layer in which liquid crystal molecules are twist-aligned in a predetermined direction. A liquid crystal display device having a plurality of signal electrodes having scanning electrodes and intersecting the scanning electrodes substantially at right angles on a second transparent substrate; and a backlight device for illuminating the liquid crystal display devices from the back side. The scanning electrodes of the liquid crystal display device are time-divisionally driven to display an image in a matrix.

[0003]

However, in such a time division drive type liquid crystal display device, there are selection timing and non-selection timing, and a certain voltage is applied even at non-display (off) timing. Therefore, there is a problem that light leakage occurs in the dark display and a decrease in contrast occurs regardless of whether the system is normally white or normally black. In particular, the contrast was significantly reduced in the mode in which the duty was large and the response speed was fast.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal display device capable of reducing light leakage during dark display and ensuring a sufficient contrast even in high time division driving. That is.

[0005]

In order to solve the above-mentioned problems, the present invention provides a first of two transparent substrates which face each other with a liquid crystal layer in which liquid crystal molecules are twist-aligned in a predetermined direction sandwiched therebetween.
A liquid crystal display element having a plurality of scanning electrodes on the transparent substrate and a plurality of signal electrodes on the second transparent substrate intersecting the scanning electrodes at a substantially right angle, and a polymer between a pair of transparent substrates arranged opposite to each other. A polymer dispersed liquid crystal layer is formed by mixing regions in which liquid crystal is present in the material in a dispersed state, and a plurality of scanning electrodes are laid on the opposing surface of one transparent substrate in correspondence with the scanning electrodes of the liquid crystal display element. , A polymer dispersion type liquid crystal shutter in which counter electrodes facing the plurality of scan electrodes are laid on the opposite surface of the other transparent substrate, and the polymer electrodes are aligned with each other so that the scan electrodes overlap each other, and the scan electrodes Are driven synchronously.

[0006]

In the present invention, when the polymer dispersion type liquid crystal shutter provided on the light incident side or the light emission side of the liquid crystal display element is driven in time division in synchronization with the liquid crystal display element, the scanning of the polymer dispersion type liquid crystal shutter is performed. The region corresponding to the scanning electrode to which the signal is applied transmits the light, and the region corresponding to the scanning electrode to which the scanning signal is not applied scatters the light. Therefore, even if an ON signal is applied to the signal electrode in a region corresponding to the scan electrode to which the scan signal on the liquid crystal display element side is not applied, no light is incident and no leakage light is generated in dark display. To be done.

[0007]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of a liquid crystal display device according to an embodiment of the present invention. This liquid crystal display device is a TN (twisted nematic) type liquid crystal display element 1
And a backlight device 10 for illuminating the liquid crystal display element 1 from the back side, and a polymer dispersion type liquid crystal shutter 1 arranged between the backlight device 10 and the liquid crystal display element 1.
3 and 3.

As shown in FIG. 2, the TN type liquid crystal display element 1 includes a liquid crystal layer 2 in which liquid crystal molecules are arranged at a twist angle of 90 °, and a transparent substrate 3, which faces each other with the liquid crystal layer 2 interposed therebetween. 4 and polarizing plates 5 and 6 facing each other with the transparent substrates 3 and 4 interposed therebetween, and the surface of the transparent substrate 3 on the side in contact with the liquid crystal layer 2 is made of a transparent conductive material such as ITO. A plurality of scanning electrodes 7a, 7b, 7c, 7d, 7e, 7f, 7
g, 7h are formed, and a plurality of signal electrodes 8 made of a transparent conductive material such as ITO are formed on the surface of the transparent substrate 4 which is in contact with the liquid crystal layer 2 as scanning electrodes 7a, 7b, 7c, 7d, 7
It is formed so as to intersect with e, 7f, 7g, and 7h at a substantially right angle. That is, each electrode is arranged in a simple matrix type. An alignment film 9 made of polyimide or the like is provided on the transparent electrodes 3 and 4 on the scanning electrodes 7a to 7h and the signal electrode 8.
Is provided so as to cover the entire surface of the.

As shown in FIG. 1, the backlight unit 10 is composed of a light source lamp 11 and a reflection plate 12 for reflecting the light generated by the light source lamp 11 toward the liquid crystal display element 1.

As shown in FIGS. 3 and 4, the polymer dispersion type liquid crystal shutter 13 includes, for example, a liquid crystal layer 16 in which a liquid crystal 15 is dispersed in an epoxy-based polymer material 14, and the liquid crystal layer 16. A flat plate-shaped electrode 1 made of a transparent conductive material such as ITO is provided on the surface of the transparent substrate 17 facing the liquid crystal layer 16 with the transparent substrates 17 and 18 facing each other.
9 is formed on the entire surface of the transparent substrate 17, and the transparent substrate 1
8 has a plurality of scanning electrodes 20a, 20b made of a transparent conductive material such as ITO on the surface in contact with the liquid crystal layer 16.
20c, 20d, 20e, 20f, 20g and 20h are formed corresponding to the scanning electrodes 7a to 7h of the liquid crystal display element. Further, the polymer dispersed liquid crystal shutter configured as described above has the scanning electrodes 20a, 20b, 20
c, 20d, 20e, 20f, 20g and 20h are scan electrodes 7a, 7b, 7c, 7d, 7e and 7 of the liquid crystal display element 1.
Liquid crystal display element 1 so as to spatially overlap with f, 7g, and 7h.
The polymer-dispersed liquid crystal shutter 13 is provided for
Are driven in a time division manner in synchronization with the liquid crystal display element 1 by a drive circuit (not shown).

FIG. 5 shows the scanning electrodes 7a of the liquid crystal display element 1,
Scan signals applied to 7b, 7c, 7d, 7e, 7f, 7g and 7h and scan electrodes 20a, 20b, 20c, 20d, 20e, 20f and 2 of the polymer dispersed liquid crystal shutter 13.
FIG. 3 is a waveform diagram of scanning signals applied to 0 g and 20 h. When the polymer dispersed liquid crystal shutter 13 is driven in time division in synchronization with the liquid crystal display element 1 as shown in FIG. Since light is transmitted through the selected scan line and scattered through the non-selected scan line, light is not incident on the region corresponding to the non-selected scan electrode of the liquid crystal display element 1, so that the signal electrode 8 is turned on. Even when a voltage is applied, light does not pass therethrough, light leakage during dark display can be prevented, and contrast can be improved.

Although the polymer dispersion type liquid crystal shutter 13 is provided on the light incident side of the liquid crystal display element 1 in the above-mentioned embodiment, the polymer dispersion type liquid crystal shutter 13 is provided on the light emission side of the liquid crystal display element 1. Is also good.

Although the TN type liquid crystal display device has been described in the above embodiments, the present invention can be applied to an STN type liquid crystal display device. Further, in the above-described embodiment, the scanning electrodes of the liquid crystal display element and the polymer dispersion type liquid shutter are selected in synchronization with each other at a ratio of 1: 1. However, the present invention is not limited to this. The n-1, n, and n + 1 scan electrodes on the polymer dispersed shutter side may be simultaneously selected.

[0014]

As described above, according to the present invention, a plurality of transparent substrates, which are opposed to each other with a liquid crystal layer in which liquid crystal molecules are aligned at a predetermined twist angle, are sandwiched between a plurality of first transparent substrates. Liquid crystal is present in a polymer material between a liquid crystal display element having scan electrodes and a plurality of signal electrodes crossing the scan electrodes at substantially right angles on a second transparent substrate, and a pair of transparent substrates facing each other. A polymer-dispersed liquid crystal layer in which regions are mixed in a dispersed state is formed, and a plurality of scanning electrodes are laid on the opposing surface of one transparent substrate so as to correspond to the scanning electrodes of the liquid crystal display element, and the other transparent substrate is opposed. A polymer dispersion type liquid crystal shutter formed by laying a counter electrode facing the plurality of scan electrodes on the surface, and arranged in alignment so that each scan electrode overlaps,
It is characterized in that the respective scan electrodes are synchronously driven. Therefore, light is transmitted in the area corresponding to the scanning electrode of the polymer dispersed liquid crystal shutter to which the scanning signal is applied, and light is transmitted in the area corresponding to the scanning electrode of the polymer dispersed liquid crystal shutter to which the scanning signal is not applied. Since the light is scattered, the light does not enter the area corresponding to the scan electrode to which the scan signal of the liquid crystal display element is not applied. Therefore, the light does not pass through even if the ON voltage is applied to the signal electrode. A liquid crystal display device capable of preventing leakage and improving contrast can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a liquid crystal display element in the same device.

FIG. 3 is a cross-sectional view of a polymer dispersed liquid crystal shutter in the same device.

FIG. 4 is a diagram showing a configuration of a liquid crystal layer of a polymer dispersed liquid crystal shutter.

FIG. 5 is a waveform diagram of a scanning signal applied to a scanning electrode of a liquid crystal display element and a scanning signal applied to a scanning electrode of a polymer dispersed liquid crystal shutter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 2 ... Liquid crystal layer 3, 4 ... Transparent substrate 7a-7h ... Scan electrode 8 ... Signal electrode 10 ... Backlight device 13 ... Polymer dispersion type liquid crystal shutter

Claims (1)

[Claims] 1. A first transparent substrate having a plurality of scanning electrodes among two transparent substrates facing each other with a liquid crystal layer formed by orienting liquid crystal molecules at a predetermined twist angle interposed therebetween, and A liquid crystal display element having a plurality of signal electrodes crossing at a substantially right angle on a second transparent substrate and a region in which liquid crystal is present in a polymer material in a dispersed state mixed between a pair of transparent substrates facing each other. A molecular dispersed liquid crystal layer is formed, a plurality of scanning electrodes are laid on the facing surface of one transparent substrate so as to correspond to the scanning electrodes of the liquid crystal display element, and the plurality of scanning electrodes are opposed to the facing surface of the other transparent substrate. And a polymer dispersion type liquid crystal shutter in which opposite electrodes are laid, and the scanning electrodes are aligned so as to overlap each other, and the scanning electrodes are synchronously driven.