JPH0527717A - Ferroelectric liquid crystal device - Google Patents

Abstract

PURPOSE:To improve reliability and durability by alternately impressing electric fields for putting the ferroelectric liquid crystals of non-display parts into stable states to the liquid crystals and setting the voltage crest values of non-display part driving signals at the voltage crest values of information electrode signals or below. CONSTITUTION:A non-display part driving means 113 impresses the electric fields exceeding the 1st and 2nd threshold values sufficient for putting the ferroelectric liquid crystals existing in the non-display parts 105, 107 into the 1st and 2nd stable states to the liquid crystals by alternating the electric fields in the prescribed periods. The bright state and the dark state are, therefore, repeated in these periods. Then, the non-display parts 105, 107 are held at the prescribed brightness between the substantially bright state and dark state. The voltage crest values VH, VL of the non-display part driving signals are set at the voltage crest values V3, V4 of the information electrode signals or below. The time until a liquid crystal gap part is generated between the display part 103 and the non-display parts 105, 107 parallel with an information electrode group is, therefore, prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device, and in particular,
The present invention relates to a liquid crystal device that uses a ferroelectric liquid crystal (hereinafter, also referred to as FLC) for displaying.

[0002]

2. Description of the Related Art Conventionally, in a display device using liquid crystal, a liquid crystal panel unit is usually constructed by mounting a liquid crystal panel using a cosmetic case.

[0003]

However, when the liquid crystal panel is mounted by using the cosmetic case, the height of the cosmetic case is higher than the surface of the liquid crystal panel, and the display portion cannot be visually recognized when viewed obliquely. Therefore, the width 5 to the adjacent portion outside the display unit
A non-display portion of about 10 mm is provided to improve the visibility of the display.

However, when a liquid crystal element having bistability is used, it is necessary to apply some electric signal to the non-display section so that the non-display section has a uniform display state. Therefore, an object of the present invention is to provide a means for controlling the display state of the non-display portion to be uniform, and further to provide a display device having high durability and high reliability. ..

[0005]

In order to achieve the above object, a ferroelectric liquid crystal device of the present invention has first and second stable states between two substrates each having a scanning electrode group and an information electrode group. A liquid crystal element that holds a ferroelectric liquid crystal and has a matrix-shaped display portion formed by the intersections of the scanning electrode group and the information electrode group, and a drive that applies scanning electrode signals and information electrode signals to these electrode groups, respectively. A signal applying unit, at least one polarizer that optically distinguishes the first and second stable states of the ferroelectric liquid crystal into a bright state and a dark state, and a non-polarizer provided outside the display unit of the liquid crystal element. A display part driving electrode and a non-display part driving signal having a voltage peak value less than or equal to the voltage peak value of the information electrode signal, and an electric field sufficient to bring the ferroelectric liquid crystal into the first and second stable states. Alternates in a predetermined cycle and exists in the non-display area The non-display portion driving signal applied to the ferroelectric liquid crystal comprises a non-display section drive means for applying to the non-display section driving electrodes.

The non-display section drive signals applied to the non-display section parallel to the scanning electrode group and the information electrode group are
Have the same frequency and are in phase with each other from 1/8 to 7 /
It is desirable that the deviation is within the range of 8. Also, year alternating period is desirably at least 30H _Z.

[0007]

In this structure, the non-display portion driving means exceeds the first and second threshold values sufficient to bring the ferroelectric liquid crystal existing in the non-display portion into the first and second stable states. Since the electric field is alternately applied in a predetermined cycle, the bright state and the dark state are repeated in that cycle. Therefore, the non-display portion is maintained at a predetermined brightness substantially between the bright state and the dark state. Further, since the voltage peak value of the non-display portion drive signal is less than or equal to the voltage peak value of the information electrode signal, the time until the liquid crystal void portion is generated between the display portion and the non-display portion parallel to the information electrode group Is dramatically extended, and the reliability and durability of the device are improved.

[0008]

1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention. This device is 640 (information line)
The FLC panel 101 having the number of pixels of × 480 (scan line) is provided, and the non-display area adjacent to the display section 103 has a common non-display section 105 and a segment non-display section 10.
7 are formed by the scanning electrodes and the signal electrodes. Further, the display panel drive voltage power supply 111, the non-display section drive voltage power supply 126, the non-display section drive waveform control section 113, which includes the FLC panel controller 109, are provided.
The logic control unit 115 and the logic control power supply 117 set drive conditions such as drive waveforms and drive voltages, and segment and common drive driver groups 119 and 121.
Control, communication between the data generator 123 and the driver groups 119 and 121, control of drive waveforms in the non-display part, etc.
It controls all of the panel 101. Then, VH and VL, which will be described later, are used as the drive waveform voltage of the non-display portion.

FIG. 2 shows drive waveforms for drawing a desired pattern on the display section 103. As shown in the figure, when the information signal m is applied to the scanning signals n to n + 2, (n,
The (m) pixel is in the dark state, and the (n + 1, m) and (n + 2, m) pixels are in the bright state. Driving conditions for good drawing are V1 = 15V, V2 = −15V, V at room temperature.
3 = 6V, V4 = -6V and one horizontal scanning period = 80 μ
There is sec. However, each voltage value is a potential difference from Vc.

FIG. 3A is a waveform diagram of drive waveforms Wc and Ws applied to the scan electrodes of the common non-display area 105 and the information electrodes of the segment non-display area 107, respectively. The voltage level is a simple square wave with VH and VL. The frequency of the rectangular wave is a rectangular wave having a period Tc, Ts (Tc = Ts) sufficient to switch between the bright and dark states, and the switching is set to a frequency that cannot be recognized by human eyes. , It is necessary to suppress flicker. As a result of examination by the present inventors, it has been clarified that flicker can be suppressed at a practically no problem level if the frequency of the non-display portion drive waveform is 30 Hz or more (the cycle is 33.3 msec or less). Therefore, here, the frequency of the non-display section drive waveform is set to 50 Hz (1 cycle = 2
0 msec). Further, although the common and segment sides have the same period, the phases are shifted from each other by 1/4. The reason is that a sufficient voltage is applied to the non-display electrode intersections 125 at the four corners. That is, for example, when the voltages are applied in the same phase, the electric field is not applied to the non-display electrode intersection portion 125, and control cannot be performed. As a result of examination by the present inventors, it has been found that by shifting the phase from ⅛ to 7/8, uniform control with no difference in hue can be performed. FIG. 3B shows a waveform (Wc-Ws) applied as a result to the non-display electrode intersection portion 125 when the phase is shifted by 1/4. By driving the liquid crystal panel 101 under the conditions as described above, it is possible to control the display unit and the non-display unit to have a uniform display state.

In this configuration, each peak value (potential difference from Vc) of the driving waveform shown in FIG. 2 is a value under the above-mentioned favorable driving condition, that is, V1 = 15V, V2 = -15V,
When V3 = 6V, V4 = -6V, and the driving waveform voltage of the non-display portion is set to VH = -VL = 2 to 10V, and a certain driving time elapses, as shown in FIG. A defect that a liquid crystal void 401 was generated between the portion 103 and the non-display portion 107 was recognized. Then, the relationship between the drive time until the occurrence of this defect and the drive waveform voltages VH and VL of the non-display portion, which is obtained at that time, is VH
And VL are within the range VH = −VL ≦ 6V (crest value of the information electrode signal) of the present invention, 2, 4, 5 and 6V.
Table 1 shows the cases of Examples 1 to 4 and Comparative Examples 1 and 2 at 8 V and 10 V, which are out of the scope of the present invention.

As can be seen from Table 1, the non-display portion drive voltage peak value (VH, VL) is the information signal voltage peak value (V3,
It was confirmed that in the cases of Examples 1 to 4 which are V4) or less, the durability reliability is remarkably improved as compared with Comparative Examples 1 and 2.

Such voids are generated because the ferroelectric liquid crystal layer having a thickness of several microns or less is subjected to a strong electric field of more than 20 volt, and the stress due to the deformation of the layer structure peculiar to the FLC element is generated. It is presumed that this is because the difference between (1) and (2) occurs between the non-display portion and the display portion, which causes some liquid crystal movement within the panel. Therefore, as in the case of the comparative example, when the above electric field in the display unit is applied to the non-display unit and the period of the drive waveform of the non-display unit is lower than the period of the drive waveform of the display unit by about two digits, a defect is generated. It is thought to be encouraged. However, details such as the torque generation mechanism of liquid crystal movement are not clear.

[0014]

[Table 1]

[0015]

As described above, according to the present invention, the first and second threshold values sufficient to bring the ferroelectric liquid crystal existing in the non-display portion into the first and second stable states. Since the electric field exceeding 10 is alternately applied at a predetermined cycle, the non-display portion can be maintained at a predetermined brightness substantially between the bright state and the dark state. Further, since the voltage peak value of the non-display portion drive signal is less than or equal to the voltage peak value of the information electrode signal, the time until the liquid crystal void portion is generated between the display portion and the non-display portion parallel to the information electrode group Can be dramatically extended, and the reliability and durability of the device can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing drive waveforms for drawing a desired pattern on the display unit of the apparatus shown in FIG.

FIG. 3 is a waveform diagram showing drive waveforms of a non-display section of the device of FIG.

FIG. 4 is a schematic view showing a void portion of liquid crystal generated between a display portion and a non-display portion of the device of FIG.

[Explanation of symbols]

101: FLC panel, 103: display unit, 105: common non-display unit, 107: segment non-display unit, 109: F
LC panel controller, 119: segment driver group, 121: common driver group, 123: data generating section, 401: void section

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Osamu Yuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazunori Katakura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (1)

Claim: What is claimed is: 1. A ferroelectric liquid crystal having first and second stable states is held between two substrates each having a scanning electrode group and an information electrode group. A liquid crystal element in which a matrix-shaped display portion is formed by intersections with the information electrode group, drive signal applying means for applying a scanning electrode signal and an information electrode signal to the electrode group, and first and second ferroelectric liquid crystals. 2. At least one polarizer that optically distinguishes the stable state of 2 into a bright state and a dark state; a non-display portion driving electrode provided around the display portion of the liquid crystal element; A non-display portion drive signal having a voltage peak value of the electrode signal or less, which is present in the non-display portion by alternating an electric field sufficient for causing the ferroelectric liquid crystal to be in the first and second stable states in a predetermined cycle. The non-display part drive signal applied to the ferroelectric liquid crystal is Ferroelectric liquid crystal device characterized by comprising a non-display section drive means for applying to the display unit driving electrode.