JP2001228460A - Liquid crystal panel using liquid crystal exhibiting smectic layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal panel bringing about no residual image phenomenon even when an identical display is carried out for a long time and carrying out an excellent display in the liquid crystal panel exhibiting a smectic layer. SOLUTION: A driving waveform and a layer structure controlling waveform are arbitrarily selected and outputted from a driving circuit connected to the liquid crystal cell. Consequently, even when the identical display is carried out for a long time, later, by applying the layer structure controlling waveform to the liquid crystal cell for a specified period, the layer structures of all the pixels are made identical so as to bring about no after image phenomenon and carry out an excellent display.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal panel such as a liquid crystal display panel or a liquid crystal optical shutter array in which a liquid crystal showing a smectic layer is used as a liquid crystal layer.

[0002]

2. Description of the Related Art An example of a liquid crystal showing a smectic layer is an antiferroelectric liquid crystal, which will be described below. A liquid crystal panel using an antiferroelectric liquid crystal is disclosed in Japanese Patent Application Laid-Open No. 2-173724 of Nippon Denso Co., Ltd. and Showa Shell Sekiyu KK, having a wide viewing angle, capable of high-speed response, multiplex. Since the report of good properties has been reported, intensive research has been made.

As shown in FIG. 3, an antiferroelectric liquid crystal has a quantity of transmitted light minus
It has a hysteresis in the voltage characteristic. From this, when a certain pulse wave is applied to the liquid crystal molecules, when the product of the pulse width and the voltage value exceeds a threshold value, the first stable state (ferroelectric State) is selected, and a second stable state (ferroelectric state) is selected according to the difference in polarity of the applied voltage.
From the first state and the second state, when the absolute value of the product of the pulse width and the voltage value is lower than a certain threshold, the third stable state (antiferroelectric state) is selected. . FIG. 4 shows an electrode configuration of a matrix type liquid crystal panel. A selection voltage is sequentially and periodically applied to the scan electrodes Y1 to Y128, and a predetermined information signal is applied to the signal electrodes X1 to X160 in synchronization with the scan electrode signal in parallel to display the liquid crystal molecules of the selected pixel. A time-division drive that switches according to information is employed.

Various methods have been proposed as a method of time division driving. FIG. 5 and FIG.
In order to write one screen with the driving method shown in the issue,
The writing of two frames is performed, and the voltage values of the waveforms of the first frame and the second frame have a symmetrical relationship with each other with respect to the voltage value of 0V. I have. FIG. 5 shows the ON state, and FIG. 6 shows the change in the voltage waveform and the transmittance of the pixel when the OFF state is set. The signal applied to the scanning electrode has three phases as shown in FIG. 5, and is always reset to the OFF state (antiferroelectric state) once in the first phase, and
In the phase, the state in the first phase is maintained, and ON in the third phase
Select whether to set to the state (ferroelectric state). In the case of FIG. 5, the third phase exceeds the threshold voltage for setting the ferroelectric state, so that it is set to the ON state (ferroelectric state). In the case of FIG. To keep the OFF state (anti-ferroelectric state).

The antiferroelectric liquid crystal has several layer structures for the smectic layer as shown in FIG. In the antiferroelectric liquid crystal state before the voltage is applied, the substrate normal and the layer normal are not perpendicular to each other in the cell, and the layer has a chevron structure in which the layer is bent in the shape of "ku". (A) When a voltage is applied and the liquid crystal enters a ferroelectric liquid crystal state,
As shown in the figure, a bookshelf type layer structure is formed in which the substrate normal and the layer normal are substantially perpendicular to each other (b), and when the liquid crystal re-enters the antiferroelectric liquid crystal state, the initial antiferroelectric The difference (c) from the layer structure in the liquid crystal state is reported in the literature (applied physics, VOL.59, NO.10).

Therefore, if the same display is performed for a long time by the driving method as in the prior art, some pixels are in a ferroelectric liquid crystal state and some pixels are not in a ferroelectric liquid crystal state at all. Come. For this reason, when these pixels are switched to the antiferroelectric liquid crystal state again, there is a difference in the liquid crystal layer structure for each pixel. That is, each pixel has a different layer structure as shown in FIGS. 7A and 7C. This causes a difference in light transmittance, which is visually recognized as an afterimage phenomenon.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a liquid crystal panel using a liquid crystal exhibiting a smectic layer having a plurality of pixels. Even if the same display is performed for a long time, the layer structure of the liquid crystal is different for each pixel. Therefore, it is an object of the present invention to provide a liquid crystal panel capable of performing a good display by eliminating the afterimage phenomenon that occurs.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a liquid crystal panel having pixels, in which a liquid crystal showing a smectic layer is sandwiched between a pair of substrates having electrodes, and comprising a pixel. Is characterized by having a control circuit in which the liquid crystal showing the smectic layer has the same layer structure at the same time. The liquid crystal panel has two circuits, a display drive waveform output circuit for displaying a display pattern and a layer structure control output circuit for controlling the layer structure of the liquid crystal. The output can be arbitrarily selected,
When the output circuit for controlling the layer structure is selected, the liquid crystal showing the smectic layers of all the pixel portions has the same layer structure at the same time.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, in order to keep all pixels in the same layer structure state for a certain period irrespective of display data, a layer structure control circuit is provided.
A means for simultaneously performing a reset period for forcibly setting the same layer structure state in one writing period was performed.

Therefore, even if the same screen is displayed for a long time,
The layer structure of all pixels can always be in the same state, and even if another screen is displayed, the transmittance of light transmitted through the liquid crystal layer does not change for each pixel, and the previous display remains as an afterimage Nothing.

[0011]

Embodiment 1 An embodiment of the present invention will be described below in detail with reference to the drawings.
FIG. 8 is a diagram showing the cell structure of the liquid crystal panel used in this embodiment. The liquid crystal panel used in this embodiment is composed of a pair of glass substrates 83 having an antiferroelectric liquid crystal layer 86 as a liquid crystal showing a smectic layer having a thickness of about 2 μm. An electrode 84 is formed on the opposite surface of the glass substrate, and an alignment film 85 is applied thereon, and an alignment process is performed. Further, a first polarizing plate 81 is provided outside one of the glass substrates so that the polarization axis and the orientation axis of the polarizing plate are parallel to each other, and the first polarizing plate is provided outside the other glass substrate. The direction of the polarization axis of the second polarizing plate is set so as to be 90 ° different from the direction of the polarization axis of 81.

FIG. 1 is a configuration diagram of a liquid crystal panel showing an embodiment of the present invention. In the liquid crystal panel used in this embodiment, the scanning side drive circuit 12 and the signal side drive circuit 13 are electrically connected to the liquid crystal cell 16, and this drive circuit outputs two different waveforms. For this purpose, a display drive waveform output circuit 14 for displaying a display pattern and a layer structure control output circuit 15 for controlling a smectic layer in a cell are provided. Therefore, it is possible to arbitrarily select which output is performed. As a result, all the pixels were brought into the ferroelectric liquid crystal state, that is, the same bookshelf type layer structure state by applying a waveform for controlling the layer structure to the liquid crystal cell for several seconds after performing the same display for a long time. After applying the voltage, the layer structure of all the pixels is in the same state, so that the afterimage phenomenon caused by the difference in the layer structure can be prevented.

Embodiment 2 FIGS. 2 and 4 show a driving waveform diagram and an electrode configuration when the liquid crystal panel of the present invention is actually driven. As shown in FIG. 4, a liquid crystal cell having 128 electrodes on the scanning side and 160 electrodes on the signal side and having the structure shown in FIG. 8 was used. Y in FIG.
Reference numerals 1 and Y2 correspond to the scan electrodes Y1 and Y2 in FIG. In the driving waveform according to the present invention, one selection period includes two pulses. One scan is composed of two scan periods, and the first scan period and the second scan period have voltage values symmetric with respect to 0V. With respect to the scan electrodes, the voltage value at the first phase of the selection period of the first scanning period is 0 V, the voltage value of the second phase is 30 V, the two phases before the next selection period are the reset period of 30 V, and the remaining non-voltages are 30 V In the selection period, a voltage waveform of 10 V is applied, the first phase of the selection period of the second scanning period is 0 V, the voltage value of the second phase is −30 V, and the two phases before the next selection period are the reset period. Then, a voltage waveform of −30 V is applied during the remaining non-selection period, and a voltage waveform of −10 V is applied. In addition, a voltage waveform of 0V is applied to the signal electrode side in the first phase and 6V is applied to the second phase in the ON state in synchronization with the scanning electrode side. In the OFF state, the first phase is 0V, and the second phase is -6V.
Is applied. Frame frequency is about 60ms
The drive was performed as follows.

Embodiment 1 of the present invention using the electrode configuration of Embodiment 2
By using such a driving circuit, all the pixels are always reset to the ferroelectric liquid crystal state at the same time, and the liquid crystal in the pixel portion is reset to have the same layer structure state. Then ON for the selected period
Select whether to turn off or turn off. For this reason, even if the same display is performed for a long time, the layer structure does not differ for each pixel, so that the afterimage phenomenon does not occur even when a new display is written.

[0015]

As described in the above embodiments, by driving with the liquid crystal panel configuration and the driving method of the present invention, even when the same display is performed for a long time, a new screen is written when a new screen is written. Good display can be performed without an afterimage on the screen.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a liquid crystal display of the present invention.

FIG. 2 is a diagram showing signal waveforms in the driving method of the present invention.

FIG. 3 is a diagram showing a hysteresis curve showing characteristics of an antiferroelectric liquid crystal.

FIG. 4 is a diagram showing a matrix electrode structure of the liquid crystal cell of the present invention.

FIG. 5 is a diagram showing a conventional driving method.

FIG. 6 is a diagram showing a conventional driving method.

FIG. 7 is a diagram showing a layer structure of an antiferroelectric liquid crystal.

FIG. 8 is a configuration diagram of a liquid crystal cell of the present invention.

[Explanation of symbols]

 81 Polarizing plate 83 Glass substrate 84 Electrode 85 Alignment film 86 Antiferroelectric liquid crystal X1 to X160 Signal electrode Y1 to Y128 Scanning electrode A1, A128 Pixel

Claims (7)

[Claims] In a liquid crystal panel having a plurality of pixels, a liquid crystal exhibiting a smectic layer of all pixels has the same layer structure at the same time in a liquid crystal panel having a plurality of pixels. A liquid crystal panel, comprising: a control circuit for: 2. The control circuit outputs an output waveform to all pixels from which a liquid crystal showing a smectic layer has the same layer structure after the liquid crystal panel performs the same display for a long time. Item 2. The liquid crystal panel according to item 1. 3. The control circuit outputs an output waveform to all pixels from which a liquid crystal showing a smectic layer has the same layer structure before the liquid crystal panel writes a new display. 2. The liquid crystal panel according to 1. 4. In a liquid crystal panel having a plurality of pixels sandwiching a liquid crystal exhibiting a smectic layer between a pair of substrates having electrodes, the liquid crystal panel has a display driving waveform for displaying a display pattern. An output circuit, and an output circuit for controlling a layer structure of a liquid crystal showing a smectic layer; and an output circuit for controlling a layer structure. An output from the two circuits can be arbitrarily selected. A liquid crystal panel characterized in that, when the structure control output circuit is selected, the liquid crystal showing the smectic layer of all the pixel portions has the same layer structure at the same time. 5. The liquid crystal panel according to claim 4, wherein the output from the layer structure control output circuit is selected after the liquid crystal panel performs the same display for a long time. 6. The liquid crystal panel according to claim 4, wherein an output from a layer structure control output circuit is selected before the liquid crystal panel writes a new display. 7. The liquid crystal panel has a scanning electrode and a signal electrode, a scanning driver circuit for outputting a voltage waveform to the scanning electrode, and a signal driver circuit for outputting a voltage waveform to the signal electrode. 5. The liquid crystal panel according to claim 4, wherein each of the side drive circuit and the signal side drive circuit includes a display drive waveform output circuit and a layer structure control output circuit.