JPH06118384A - Ferroelectric liquid crystal panel - Google Patents

Abstract

PURPOSE:To provide a ferroelectric liquid crystal panel in which 'burning' or 'ghost' is not generated. CONSTITUTION:Between a transparent electrode 2 and a transparent electrode 5, an AC low frequency high voltage of a frequency by which an electro-optical response of a ferroelectric liquid crystal 9 is saturated enough by a sufficiently high voltage for varying a layer structure of the ferroelectric liquid crystal 9, in this example, a square wave of 500Hz and + or -50V is impressed for one minute, and thereafter, an AC high frequency high voltage of a frequency which the electro-optical response of the ferroelectric liquid crystal 9 cannot follow by a sufficiently high voltage for varying the layer structure of the ferroelectric liquid crystal 9, in this example, a square wave of 5kHz and + or -50V is impressed for ten seconds, and bistability of the ferroelectric liquid crystal at the time when no electric field is applied and a memory property in one side direction are obviated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric liquid crystal panel.

[0002]

2. Description of the Related Art Conventionally, in a ferroelectric liquid crystal panel using a ferroelectric liquid crystal, it is general to use the bistability of the ferroelectric liquid crystal to drive it. FIG. 4 is a diagram showing an electro-optical response characteristic of a ferroelectric liquid crystal panel with respect to a drive pulse. In the figure, 4a indicates a drive pulse, and 4b indicates an electro-optical response characteristic (light transmission characteristic).

However, since it is not easy to orient the ferroelectric liquid crystal uniformly and at the same time to have the bistability and maintain its characteristics, the ferroelectric liquid crystal having a negative dielectric anisotropy is used. In addition, there is also a technique of forcibly providing a memory property by applying a high-voltage high frequency in which the direction of the electric field changes at a period sufficiently faster than the switching speed at the time of driving, that is, a technique called AC stabilization.

[0004]

However, if one of the above is left in one of the switching states, that is, the memory state, that state has an advantage over the other state as shown in FIG. That is, the one-sided stable state is achieved (in FIG. 4, the stable state when a negative drive voltage is applied has a superiority.) There is a problem that a phenomenon called “burn-in” or “ghost” occurs. Was there. The above problem is that the direction of spontaneous polarization of the ferroelectric liquid crystal is 1
It has been pointed out that this is an essential problem of the ferroelectric liquid crystal that is caused by the formation of an electric double layer by the movement of ionic impurities due to the internal electric field generated due to the alignment in the directions. When a ferroelectric liquid crystal panel is driven, this phenomenon is caused by the asymmetry that only one side has a memory property, resulting in a decrease in contrast, a difference in response speed between two memory states, and when it worsens, switching disappears at the drive voltage level. However, there is a problem that the operation becomes unstable even when driven by the AC stabilization method.

An object of the present invention is to provide a ferroelectric liquid crystal panel free from "burn-in" or "ghost".

[0006]

According to the present invention, electrodes are formed on opposite surfaces of two substrates, and an alignment film is provided on each of the electrodes. The ferroelectric film is provided between the alignment films. In a ferroelectric liquid crystal panel in which a liquid crystalline liquid crystal is present, a high frequency of a frequency at which the electro-optical response of the ferroelectric liquid crystal cannot follow the electrodes at a voltage high enough to change the layer structure of the ferroelectric liquid crystal. By applying a high voltage,
The above object is achieved by eliminating the bistability of the ferroelectric liquid crystal and the memory property in one direction when no electric field is applied.

A low-frequency high voltage having a frequency at which the electro-optical response of the ferroelectric liquid crystal is sufficiently saturated is applied to each of the electrodes at a voltage high enough to change the layer structure of the ferroelectric liquid crystal. After that, by applying a high frequency high voltage having a frequency at which the electro-optical response of the ferroelectric liquid crystal cannot follow at a voltage high enough to change the layer structure of the ferroelectric liquid crystal, The above object is achieved by eliminating the bistability of the dielectric liquid crystal and the memory property in one direction.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on an embodiment shown in the drawings.

In FIG. 1, a transparent electrode 2 made of ITO (tin oxide-doped indium oxide) is selectively formed on one surface of a substrate 1 made of glass or the like. An orientation film 3 formed by oblique vapor deposition of SiO ₂ is selectively provided.

A transparent electrode 5 made of ITO is selectively formed on the opposite surface of the substrate 1 of a substrate 4 made of glass or the like, and SiO ₂ is formed on the transparent electrode 5 by oblique vapor deposition. An alignment film 6 is selectively provided.

A spacer 7 holds the substrate 1 and the substrate 4 at a predetermined interval. In this example, the thickness is 2.5μ
m spacers 7 are used. Then, the substrate 1 and the substrate 4
The outer peripheral portions of and are fixed by a sealant 8. In this example, an acrylic thermosetting adhesive is used as the sealant 8.

Ferroelectric liquid crystal 9 is enclosed in a portion surrounded by the substrates 1 and 4, the sealant 8 and the like. In this example, as the ferroelectric liquid crystal 9, ferroelectric liquid crystal SKC102 manufactured by Chisso Petrochemical Co., Ltd. is used.

The electro-optical response of the ferroelectric liquid crystal 9 is sufficiently saturated at a voltage high enough to change the layer structure of the ferroelectric liquid crystal 9 between the transparent electrode 2 and the transparent electrode 5 of this ferroelectric liquid crystal panel. AC low frequency high voltage with a frequency of
After applying a square wave of 0 Hz, ± 50 V for 1 minute, a high frequency of alternating current with a frequency at which the electro-optical response of the ferroelectric liquid crystal 9 cannot follow at a voltage high enough to change the layer structure of the ferroelectric liquid crystal 9. A square wave having a voltage of 5 kHz and ± 50 V in this example is applied for 10 seconds. First, the liquid crystal molecules are aligned by the above low frequency and high voltage to make the alignment state uniform. Subsequently, the direction of spontaneous polarization is dispersed with respect to the substrate vertical direction by the high-frequency high voltage to erase the memory property when no electric field is applied.

FIG. 2 is a diagram showing the transmitted light amount b with respect to the applied voltage a under crossed Nicols of the ferroelectric liquid crystal panel to which the alternating low frequency high voltage and high frequency high voltage are applied as described above. Thus, the amount of transmitted light c when no electric field is applied is
It is an intermediate value between the two transmitted light amounts at the time of switching, that is, the transmitted light amount at bright d and the transmitted light amount at dark e. That is, it has no memory property when no electric field is applied.

The above liquid crystal panel has a uniform alignment state in the pixel and has no extinction position under crossed Nicols. This indicates that the directions of the spontaneous polarization are not aligned in the direction perpendicular to the substrate. Therefore, the internal electric field created by the spontaneous polarization is reduced, image sticking is less likely to occur, and high contrast can be obtained.

FIG. 3 shows a ferroelectric liquid crystal panel having no memory property as described above, which is formed by the AC stabilization method.
It shows the optical response characteristics when the digit multiplex drive is performed.

In the figure, f is an applied voltage waveform applied to the transparent electrode (segment electrode) 2, g is an applied voltage waveform applied to the transparent electrode (common electrode) 5, and h is the above ferroelectric liquid crystal panel. Shows the amount of light transmission of.

In this example, one driving cycle is divided into four, first initialized to a dark state, then written to a desired response state, and then the written state is held (non-selected) by AC stabilization. 1/4 of each cycle for each digit
The multiplex drive is performed by shifting the cycle.

As described above, the ferroelectric liquid crystal panel of the present invention can obtain stable operation even when it is driven by the AC stabilization method, can reduce the driving voltage, and can stably drive multi-digits. Can be done. Moreover, since the ferroelectric liquid crystal is used, a fast electro-optical response can be obtained.

In the above example, the low frequency high voltage of 500 Hz is a frequency at which the electro-optical response of the ferroelectric liquid crystal 9 is sufficiently saturated at a voltage high enough to change the layer structure of the ferroelectric liquid crystal 9. , ± 50 V square wave was used, but the low frequency high voltage is not limited to this, and can be appropriately changed depending on the type of ferroelectric liquid crystal used. Similarly, a square wave of 5 kHz and ± 50 V is used as a high frequency high voltage of a frequency at which the electro-optical response of the ferroelectric liquid crystal 9 cannot follow at a voltage high enough to change the layer structure of the ferroelectric liquid crystal 9. However, similar to the above, the present invention is not limited to this, and can be appropriately changed.

In the above example, the alignment film formed by oblique vapor deposition of SiO ₂ is used, but the same effect as above can be obtained by using the alignment film which has been subjected to the alignment treatment by the rubbing method or the like.

Also, in the above, after applying a low frequency high voltage of a frequency at which the electro-optical response of the ferroelectric liquid crystal 9 is sufficiently saturated at a voltage high enough to change the layer structure of the ferroelectric liquid crystal 9, An example of applying a high frequency high voltage having a frequency at which the electro-optical response of the ferroelectric liquid crystal 9 cannot follow at a voltage high enough to change the layer structure of the dielectric liquid crystal 9 has been described. Baking can be eliminated by simply applying the high frequency high voltage without applying the voltage. However, it is preferable to apply the low frequency high voltage because the alignment state can be made more uniform.

The ferroelectric liquid crystal panel configured as described above can be widely used for a liquid crystal shutter of an optical printer, a display device and the like.

[0024]

According to the present invention, electrodes are formed on the opposite surfaces of two substrates, and an alignment film is provided on each of the electrodes. A ferroelectric liquid crystal is interposed between the alignment films. In the ferroelectric liquid crystal panel, a high frequency high voltage having a frequency at which the electro-optical response of the ferroelectric liquid crystal cannot follow is applied to each of the electrodes at a voltage high enough to change the layer structure of the ferroelectric liquid crystal. Then, by eliminating the bistability of the above-mentioned ferroelectric liquid crystal and the memory property in one direction when no electric field is applied, it is possible to eliminate the image sticking, and it is stable even when driven by the AC stabilizer method, for example. The above operation can be obtained, the driving voltage can be reduced, and more multi-digit driving can be stably performed. Moreover, since the ferroelectric liquid crystal is used, a fast electro-optical response can be obtained. Further, since the alignment of the ferroelectric liquid crystal in the pixel is uniform and there is no defect, high contrast can be obtained.

Before applying a high-frequency high voltage to each of the electrodes, a low frequency at which the electro-optical response of the ferroelectric liquid crystal is sufficiently saturated at a voltage high enough to change the layer structure of the ferroelectric liquid crystal. By applying a high frequency voltage, the alignment state can be made more uniform, image sticking can be eliminated in the same manner as above, and a higher contrast than the above can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an optical response characteristic of a ferroelectric liquid crystal panel according to the present invention to an applied voltage under crossed Nicols.

FIG. 3 is an explanatory diagram showing an example of a drive waveform of a ferroelectric liquid crystal panel according to the present invention by an AC stabilization method and an optical response characteristic at that time.

FIG. 4 is an explanatory diagram showing an electro-optical response characteristic of a conventional ferroelectric liquid crystal panel with respect to a drive pulse.

FIG. 5 is an explanatory diagram showing an electro-optical response characteristic of a conventional ferroelectric liquid crystal panel with respect to a drive pulse.

[Explanation of symbols]

 1 Substrate 2 Electrode 3 Alignment Film 4 Substrate 5 Electrode 6 Alignment Film 9 Ferroelectric Liquid Crystal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Fujita 4-1-1 Taihei, Sumida-ku, Tokyo Inside Seikosha Co., Ltd.

Claims (2)

[Claims] 1. Ferroelectricity in which electrodes are formed on opposite surfaces of two substrates, alignment films are provided on the electrodes, and a ferroelectric liquid crystal is interposed between the alignment films. In the liquid crystal panel, by applying to each of the electrodes a high frequency high voltage having a frequency at which the electro-optical response of the ferroelectric liquid crystal cannot follow at a voltage high enough to change the layer structure of the ferroelectric liquid crystal, A ferroelectric liquid crystal panel characterized by eliminating the bistability of the ferroelectric liquid crystal and the memory property in one direction when no electric field is applied. 2. Ferroelectricity in which electrodes are formed on opposite surfaces of two substrates, alignment films are respectively provided on the electrodes, and a ferroelectric liquid crystal is interposed between the alignment films. In the liquid crystal panel, after applying a low-frequency high voltage of a frequency at which the electro-optical response of the ferroelectric liquid crystal is sufficiently saturated at a voltage high enough to change the layer structure of the ferroelectric liquid crystal, to each electrode. , By applying a high frequency high voltage of a frequency at which the electro-optical response of the ferroelectric liquid crystal cannot follow at a voltage high enough to change the layer structure of the ferroelectric liquid crystal, A ferroelectric liquid crystal panel characterized by eliminating the bistability of a liquid crystal and the memory property in one direction.