JP3171833B2 - Antiferroelectric liquid crystal panel - 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 of driving an antiferroelectric liquid crystal panel such as a liquid crystal display panel or a liquid crystal optical shutter array using an antiferroelectric liquid crystal as a liquid crystal layer.

[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 greater than or equal to 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, the 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, a selection voltage is sequentially and periodically applied to 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 several layer structures for the smectic layer as shown in FIG. In the antiferroelectric liquid crystal state before voltage is applied, the substrate normal and the layer normal are not perpendicular to each other in the cell, and the layer in the cell has a chevron structure that bends in the shape of a square. (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 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 liquid crystal layer structure 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 an afterimage phenomenon.

[0008]

In order to achieve the above object, the present invention provides an antiferroelectric liquid crystal panel in which an antiferroelectric liquid crystal is sandwiched between a pair of substrates having electrodes. Regardless, the antiferroelectric liquid crystal of all pixels
It is characterized by having a control circuit with one layer structure.
You. In addition, the antiferroelectric liquid crystal panel displays the display pattern
Display drive waveform output circuit for causing
And a layer structure control output circuit for controlling the crystal layer structure.
Circuit, and arbitrarily select the output from these two circuits.
When the output circuit for controlling the layer structure is selected,
Means that the anti-ferroelectric liquid crystal of all pixels has the same layer structure at the same time.
It is characterized by becoming.

[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 setting 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 includes 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 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 polarizing axis and the orientation axis of the polarizing plate are parallel to each other, and the first polarizing plate 81 is provided outside the other glass substrate. 90 ° different from the polarization axis of
Polarizing plate is installed.

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. To this end, 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 the cell are provided. , From which output is performed can be arbitrarily selected. 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 FIG. 2 is a driving waveform diagram used in the present invention. 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. 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 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 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, the first phase is 0V, and the second phase is -6V.
Is applied. Frame frequency is about 60ms
The drive was performed as follows.

[0014] The electrode configuration of the second embodiment is similar to that of the first embodiment.
By using a simple driving circuit,
The liquid crystal of all the pixel portions is reset to the liquid crystal state, and has the same layer structure state. After that, the user selects whether to turn on or off during the selection period. 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)

(57) [Claims] An anti-ferroelectric liquid crystal is sandwiched between a pair of substrates having electrodes. In an anti-ferroelectric liquid crystal panel having a plurality of pixels, anti-ferroelectric liquid crystals in all pixels are simultaneously formed. Same
Having a control circuit for forming a layer structure
Antiferroelectric liquid crystal panel. 2. The antiferroelectric liquid crystal panel is the same for a long time.
After displaying, the antiferroelectric liquid crystal has the same layer structure.
Output from the control circuit to all pixels.
2. The antiferroelectric liquid crystal panel according to claim 1, wherein
Le. 3. The display device according to claim 1, wherein said antiferroelectric liquid crystal panel is a new display.
Before writing, the antiferroelectric liquid crystal has the same layer structure
Output from the control circuit to all pixels
The anti-ferroelectric liquid crystal panel according to claim 1, wherein: 4. An antiferroelectric liquid crystal panel having a plurality of pixels by sandwiching an antiferroelectric liquid crystal between a pair of substrates having electrodes, wherein the antiferroelectric liquid crystal panel has a display pattern.
Drive waveform output circuit for displaying
With an output circuit for controlling the layer structure of the conductive liquid crystal
It has two circuits, and the output from these two circuits is arbitrarily
Select the output circuit for controlling the layer structure
The antiferroelectric liquid crystal of all pixels
An antiferroelectric liquid crystal panel having a layer structure. 5. The antiferroelectric liquid crystal panel is the same for a long time.
After displaying, the output from the layer structure control output circuit is
5. The antiferroelectric material according to claim 4, wherein said antiferroelectricity is selected.
LCD panel. 6. The anti-ferroelectric liquid crystal panel according to claim 1, further comprising :
Select the output from the layer structure control output circuit before writing
5. The antiferroelectric liquid according to claim 4, wherein the liquid is selected.
Crystal panel. 7. An antiferroelectric liquid crystal panel includes a scanning electrode and a signal.
Scan side drive that has electrodes and outputs a voltage waveform to the scan electrodes
Circuit and signal-side drive circuit that outputs voltage waveforms to signal electrodes
And a scanning side driving circuit and a signal side driving circuit.
In addition, display drive waveform output circuit and layer structure control output circuit
The repulsion according to claim 4, characterized by comprising:
Dielectric liquid crystal panel.