JP3171713B2 - Antiferroelectric liquid crystal display - Google Patents

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 and a liquid crystal optical shutter array, using an antiferroelectric liquid crystal as a liquid crystal layer. is there.

[0002]

2. Description of the Related Art A liquid crystal panel using an antiferroelectric liquid crystal,
Japanese Patent Application Laid-Open No. 2 by Nippondenso Co., Ltd. and Showa Shell Sekiyu KK
Since 173724 reports that it has a wide viewing angle, that high-speed response is possible, and that multiplex characteristics are good, intensive studies have been made.

As shown in FIG. 3, an antiferroelectric liquid crystal has a hysteresis in transmitted light quantity-voltage characteristics, and when a pulse wave is applied to liquid crystal molecules, the value of the product of the pulse width and the voltage value is obtained. Takes a value equal to or greater than a threshold, a first stable state (ferroelectric state) is selected, and a second stable state (ferroelectric state) is selected depending on the 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, a third stable state (antiferroelectric state) is selected. . FIG. 4 shows an electrode configuration of a matrix type liquid crystal panel including the antiferroelectric liquid crystal. Scan electrodes Y1 to Y12
8 are sequentially and periodically applied with a selection voltage, and the signal electrodes X1 to X
160 employs a time-division drive in which a predetermined information signal is applied in parallel in synchronization with the scanning electrode signal, and the liquid crystal molecules of the selected pixel are switched according to the display information.

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 a layer structure for the smectic layer as shown in FIG. 7, and in the antiferroelectric liquid crystal state before voltage is applied, the substrate normal and the layer normal are perpendicular to each other in the cell. The cell has a chevron structure in which the layer is bent in a square in the cell (a), and when a voltage is applied to the ferroelectric liquid crystal state, the substrate normal and the layer When a bookshelf-type layer structure is formed so that the normal line is vertical (b), and then the antiferroelectric liquid crystal state is again formed, the layer structure is different from that in the initial antiferroelectric liquid crystal state. The thing (c) is a document (applied physics, VOL.5)
9, 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]

The present invention arises in an antiferroelectric liquid crystal panel having pixels in a matrix even if the same display is performed for a long time because the layer structure of the liquid crystal is different for each pixel. It is an object of the present invention to provide a liquid crystal panel capable of performing good display by eliminating the afterimage phenomenon.

[0008]

In order to achieve the above object, the present invention provides an antiferroelectric liquid crystal panel having pixels by sandwiching an antiferroelectric liquid crystal between a pair of substrates having electrodes. In addition, 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 pixels in a ferroelectric liquid crystal state for one period irrespective of display data, or a ferroelectric liquid crystal is formed in one writing period independently of display data. Means were provided to set a reset period to force the state.

[0010]

[Function] Therefore, even if the same screen is displayed for a long time, the layer structure of all the pixels can always be kept in the same state, and even if another screen is displayed, the transmittance of the light transmitted through the liquid crystal layer is changed to the pixel. And the previous display does not remain as an afterimage.

[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 having a thickness of about 2 μ. An electrode 84 is formed on the opposite surface of the glass substrate, and a polymer alignment film 85 is applied thereon, and a rubbing process is performed. Is further first polarizing plate 81 is placed so the outside of the 1-way glass substrate and the polarization axis and the rubbing axis of the polarizing plate to be parallel, the outside of the other glass substrate and the first polarizer 81 The second polarizing plate is installed so as to be different from the polarization axis of the second polarizing plate 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 anti-ferroelectric liquid crystal panel 16 is electrically connected to the scanning side driving circuit 12 and the signal side driving circuit 13, and the driving circuit has two different waveforms. And a layer structure control output circuit 15 for controlling the smectic layer in the cell, and an output switch for both waveforms. 11 is attached, and the output from which can be arbitrarily selected. By applying the same waveform for controlling the layer structure to the liquid crystal cell for several seconds after performing the same display for a long time, all the pixels are brought into the ferroelectric liquid crystal state, and after applying the voltage, the layer structure of all the pixels is the same. The afterimage phenomenon caused by the difference in the layer structure can be prevented.

Embodiment 2 FIG. 2 is a driving waveform diagram implemented according to the present invention . FIG.
As shown in the figure, the number of scanning side electrodes is 128 and the number of signal side electrodes is 16.
A liquid crystal cell having zero electrodes and having the 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 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 are 0 V each other.
Symmetrical voltage values. The first phase in the selection period of the first scanning period applied to the scanning electrode is 0 V,
The voltage value of the phase is 30 V, the two phases before the next selection period are 30 V as a reset period, and 10 V in the remaining non-selection period.
Is applied, and the first waveform in the selection period of the second scanning period is applied.
A voltage waveform of 0 V is applied for the phase, a voltage value of -30 V for the second phase, a voltage of -30 V for a reset period for the two phases before the next selection period, and a voltage waveform of -10 V for the remaining non-selection period. In addition, a voltage waveform of 0V is applied to the signal electrode side in a first phase and 6V is applied to a second phase in an ON state in synchronization with the scanning electrode side. In the OFF state, a voltage waveform of 0V is applied to the first phase and a voltage waveform of -6V is applied to the second phase. 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 signal electrodes in the ON state and the OFF state. 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 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 X1 to X160 signal electrode Y1 to Y128 scanning electrode

Claims (3)

(57) [Claims] 1. A an antiferroelectric liquid crystal between a pair of substrates having an electrode sandwiched, in the antiferroelectric liquid crystal display having a pixel intensity of the anti-ferroelectric liquid crystal for a period all pixel portions Invitation
An antiferroelectric liquid crystal display characterized by being in an electric state . 2. An antiferroelectric material between a pair of substrates having electrodes.
An antiferroelectric liquid crystal display having pixels and holding a liquid crystal
After writing to the pixel in (a), the next writing
The ferroelectric liquid crystal to the ferroelectric state before
Drive to provide a reset period for
Characterized antiferroelectric liquid crystal display. 3. The display device according to claim 1, wherein the antiferroelectric liquid crystal panel is a display pattern.
A display drive waveform output circuit for displaying the down, and outputs a waveform for an antiferroelectric liquid crystal in a ferroelectric state control
It has two circuits with the control output circuit.
2. The method according to claim 1, wherein said output is arbitrarily selected.
An antiferroelectric liquid crystal display according to claim 2.