JPH06202078A - Antiferroelectric liquid crystal display - Google Patents

Abstract

PURPOSE:To eliminate the after-image phenomenon generated by a difference in the laminar structure of a liquid layer by each of picture elements even if the same display is made over a long period of time and to make good display by making all the picture elements be in an antiferroelectric liquid crystal state for a certain period without depending on display patterns. CONSTITUTION:A scanning side driving circuit 12 and a signal driving circuit 13 are electrically connected to an antiferroelectric liquid crystal panel 16. Further, these driving circuits 12, 13 are constituted of a driving waveform output circuit for display 14 which displays the display patterns and an output circuit 15 for controlling the layer structure which controls a smectic layer within the cell in order to output two different outputs. An output selector switch 11 is attached to the output sections for both waveforms and can arbitrarily select, the section which from the outputting is to be executed. As a result, all the picture elements are put into the antiferroelectric liquid crystal state by impressing the waveform for controlling the layer structure to the liquid crystal cell for several seconds after the same display is made for a long period of time. The layer structures of all the picture elements can be made to be the same after applying the voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an antiferroelectric liquid crystal panel such as a liquid crystal display panel having a matrix of pixels having an antiferroelectric liquid crystal as a liquid crystal layer or a liquid crystal optical shutter array. is there.

[0002]

2. Description of the Related Art A liquid crystal panel using an antiferroelectric liquid crystal is
JP-A-2 of Nippon Denso Co., Ltd. and Showa Shell Sekiyu Co., Ltd.
Since the publication of 173724 discloses that it has a wide viewing angle, that it can respond at high speed, and that it has good multiplex characteristics, it has been actively researched.

As shown in FIG. 3, the antiferroelectric liquid crystal has a hysteresis in the transmitted light quantity-voltage characteristic. Therefore, when a pulse wave is applied to the liquid crystal molecules, the product of the pulse width and the voltage value is obtained. Is a threshold value or more, the first stable state (ferroelectric state) is selected, and the second stable state (ferroelectric state) is selected depending on the polarity of the applied voltage.
From the first state and the second state, the third stable state (antiferroelectric state) is selected when the absolute value of the product of the pulse width and the voltage value is lower than a certain threshold value. . FIG. 4 shows an electrode structure of a matrix type liquid crystal panel including the antiferroelectric liquid crystal. Scan electrodes Y1 to Y12
8, a selection voltage is sequentially and cyclically applied to the signal electrodes X1 to X
The time-division driving is adopted in 160 in which a predetermined information signal is applied in parallel in synchronization with the scan electrode signal and the liquid crystal molecules of the selected pixel are switched according to the display information.

Various methods have been proposed as time-division driving methods. 5 and 6 are shown in Japanese Patent Application Laid-Open No. 2-173724.
In order to write one screen with the driving method shown in No.
Two frames are written, and the voltage values of the respective waveforms in the first frame and the second frame are symmetrical with respect to the voltage value of 0 V. Therefore, by writing two frames, alternating current is achieved. There is. FIG. 5 shows the ON state, and FIG. 6 shows changes in the voltage waveform and the pixel transmittance when the OFF state is set. The signal applied to the scan electrodes has three phases as shown in FIG. 5, and is always reset to the OFF state (antiferroelectric state) once in the first phase,
In the phase, the state of the first phase is retained, and the state of the third phase is ON
Select whether to set the state (ferroelectric state). In the case of FIG. 5, since the third phase exceeds the threshold voltage for setting the ferroelectric state, it is set to the ON state (ferroelectric state), and in the case of FIG. 6, the threshold voltage is set. The OFF state (antiferroelectric state) is maintained in order not to exceed.

Further, the antiferroelectric liquid crystal has a layer structure for the smectic layer as shown in FIG. 7, and in the antiferroelectric liquid crystal state before applying a voltage, the substrate normal and the layer normal are perpendicular to each other in the cell. The cell has a chevron structure in which the layers are bent in a square shape in the cell (a). When a voltage is applied and the ferroelectric liquid crystal state is reached, the substrate normal and layer A bookshelf type layered structure is formed in which the normals are vertical (b), and when the antiferroelectric liquid crystal state is restored again, the layer structure is different from the initial antiferroelectric liquid crystal state. Thing (c) is a document (Applied Physics, VOL.5).
9, NO. 10).

Therefore, when the same display is performed for a long time by the driving method as in the prior art, some pixels may be in the ferroelectric liquid crystal state and some pixels may never be in the ferroelectric liquid crystal state. Come on. Therefore, when these pixels are switched to the antiferroelectric liquid crystal state again, a difference in the liquid crystal layer structure can be seen from pixel to 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]

DISCLOSURE OF THE INVENTION The present invention occurs in an antiferroelectric liquid crystal panel having pixels in a matrix because the liquid crystal layer structure is different for each pixel even when the same display is performed for a long time. It is an object of the present invention to provide a liquid crystal panel which eliminates the afterimage phenomenon and can perform good display.

[0008]

In order to achieve the above object, the present invention has a matrix-like structure in which an antiferroelectric liquid crystal is sandwiched between a pair of substrates each having a plurality of scanning electrodes and signal electrodes on opposite surfaces. In an anti-ferroelectric liquid crystal panel having pixels, all the pixels are in a ferroelectric liquid crystal state for a certain period regardless of the display pattern.

Here, a layer structure control circuit is provided in order to make all the pixels in the ferroelectric liquid crystal state for a certain period regardless of the display data, or the ferroelectric liquid crystal is formed in one writing period without depending on the display data. The means to set a reset period to force the state.

[0010]

[Effect] 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 pixel has the same transmittance as that of light transmitted through the liquid crystal layer. It does not change from time to time, and the previous display does not remain as an afterimage.

[0011]

【Example】

Embodiment 1 An embodiment of the present invention will be described in detail below with reference to the drawings.
FIG. 8 is a cell structure diagram of the liquid crystal panel used in this example. The liquid crystal panel used in this embodiment is a pair of glass substrates 83a and 83b having an antiferroelectric liquid crystal 86 having a thickness of about 2μ.
It consists of An electrode 84 is provided on the opposite surface of the glass substrate.
a and 84b are formed on the polymer alignment film 8
5a and 85b are applied and a rubbing process is performed. Further, a first polarizing plate 81a is installed on the outside of one glass substrate so that the polarization axis of the polarizing plate and the rubbing axis are parallel to each other, and the first polarizing plate 81a is installed on the outside of the other glass substrate. The second polarizing plate 81b is installed so as to be different from the polarization axis of the above by 90 °.

FIG. 1 is a block diagram of a liquid crystal panel showing a first embodiment according to claim 2 of the present invention. In the liquid crystal panel used in this embodiment, the scanning side driving circuit 12 and the signal side driving circuit 13 are electrically connected to the antiferroelectric liquid crystal panel 16, and the driving circuit has two different waveforms. In order to output, a display drive waveform output circuit 14 for displaying a display pattern and a layer structure control output circuit 15 for controlling the smectic layer in a cell are provided. 11 is attached, and it is possible to arbitrarily select from which the output is performed. As a result, by applying the waveform for controlling the layer structure to the liquid crystal cell for a few seconds after the same display is performed for a long time, all the pixels are made into a ferroelectric liquid crystal state, and after applying the voltage, the layer structure of all the pixels is the same. Therefore, the afterimage phenomenon caused by the difference in the layer structure can be prevented.

Embodiment 2 FIG. 2 is a drive waveform diagram executed in relation to claim 3. As shown in FIG. 6, the number of scanning side electrodes is 128, and the number of signal side electrodes is 1
A liquid crystal cell having 60 electrodes and having a structure shown in FIG. 8 was used. Y1 and Y2 in FIG. 2 correspond to the scan electrodes Y1 and Y2 in FIG. In the drive waveform of the present invention, one selection period is composed of two pulses. Further, one scan is composed of two scan periods, and the first scan period and the second scan period are 0 V each other.
The voltage value is symmetrical with respect to. The first phase of the selection period of the first scanning period applied to the scan electrodes is 0V, the second phase is
The voltage value of the phase is 30V, the two phases before the next selection period are reset periods, 30V, and the remaining non-selection period is 10V.
Voltage waveform of the second scanning period is applied to the first scanning period of the selection period of the second scanning period.
A voltage waveform of 0V for the second phase, −30V for the second phase, −30V for the two phases before the next selection period is the reset period, and −10V for the rest of the non-selection periods. In addition, a voltage waveform of 0 V for the first phase and 6 V for the second phase is applied to the signal electrode side in the ON state in synchronization with the scan electrode side. Further, in the OFF state, a voltage waveform of 0 V for the first phase and −6 V for the second phase is applied. The driving was performed with a frame frequency of about 60 ms.

The liquid crystal of the pixel portion is always reset to the ferroelectric liquid crystal state once during the reset period, regardless of the ON or OFF state of the signal electrode, and is then turned on or off during the selection period. Select. 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 if the same display is displayed for a long time, a new screen can be written. There is no afterimage on the screen, and good display is possible.

[Brief description of 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 a 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 electrodes X1 to X160 signal electrodes Y1 to Y128 scanning electrodes

Claims (3)

[Claims] 1. An antiferroelectric liquid crystal is sandwiched between a pair of substrates each having a plurality of scanning electrodes and signal electrodes on opposite surfaces,
An antiferroelectric liquid crystal display, characterized in that, in an antiferroelectric liquid crystal panel having pixels in a matrix, the antiferroelectric liquid crystal in all pixel portions is brought into a ferroelectric liquid crystal state for a certain period. 2. A drive circuit electrically connected to the anti-ferroelectric liquid crystal panel controls a display drive waveform output circuit for displaying a display pattern and a layer structure of a smectic layer in a cell. 2. The antiferroelectric liquid crystal display according to claim 1, wherein the antiferroelectric liquid crystal display is composed of two circuits of a layer structure control output circuit for controlling the output, and outputs from the two circuits are arbitrarily selected. 3. In the antiferroelectric liquid crystal panel, at least two scanning periods are provided within a period for writing all scanning electrodes, and at least one scanning period is provided during the scanning period.
The antiferroelectric liquid crystal display according to claim 1, wherein a driving method is used in which a reset period is provided so that all pixels are always in a ferroelectric liquid crystal state.