JPH0412320A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To decrease the number of times of rise and fall of applied pulses and then to improve the display quality without being affected with a ripple by making the timing of information signals applied to information signal lines shift between adjacent information signal lines. CONSTITUTION:This element is provided with a means which shifts the information signals applied to the information signal lines in timing between adjacent information signal lines. Image information which is sent from an image information generating means 41 through a controller 43 has odd-numbered (ODD) and even-numbered (EVEN) data read out by S/Rs 47 and 48 for segments in synchronism with clocks phi1 and phi1, and those data are sent out to a multiplexer 51 through line memories 49 and 50 in synchronism with clocks phi1' and phi2' and multiplexed. At this time, the timing of the clocks phi1' and phi2' is so set that only the even-numbered data is delayed by sigmat. Consequently, a flicker on a screen due to a ripple generated on a common signal line is eliminated to improve the display quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display element using ferroelectric liquid crystal.

[Prior art] Regarding display elements using ferroelectric liquid crystal, Japanese Patent Application Laid-Open No. 1986-9
As shown in Publication No. 4023, a liquid crystal cell is constructed by facing two glass substrates with transparent electrodes formed on opposing surfaces and subjected to alignment treatment, with a cell gap of about 1 to 3 microns maintained. However, it is known that a ferroelectric liquid crystal is injected into this.

The characteristics of the above display element using ferroelectric liquid crystal are that the ferroelectric liquid crystal has spontaneous polarization, so the coupling force between an external electric field and the spontaneous polarization can be used for switching, and the long sleeve direction of the ferroelectric liquid crystal molecules is Since there is a one-to-one correspondence with the polarization direction, switching can be performed depending on the polarity of the external electric field. Since chiral smectic liquid crystals (SmC*, SmH*) are generally used as ferroelectric liquid crystals,
In the bulk state, the long axes of liquid crystal molecules exhibit a twisted orientation;
By placing it in a cell with a cell gap of about 1 to 3 microns as described above, it is possible to eliminate the twist of the long axis of the liquid crystal molecules (N, A: CLARK et al.
, MCLC, 1983, Vol. 194. P213-P
234).

The actual structure of a ferroelectric liquid crystal cell uses a simple matrix substrate as shown in FIG. In other words, the same figure (a
) is a cross-sectional view of a cell, each of which is made of ITO.
A liquid crystal 26 is placed between upper and lower glass substrates 21 on which a stripe electrode 22, an SiO2 insulating film 23, and a polyimide alignment film 24 are formed in this order, and this is sealed with a sealing member 25. FIG. 2B shows an example of the pattern of each ITO stripe electrode 22, in which the upper and lower electrodes 22 are arranged so as to intersect with each other.

[Problems to be Solved by the Invention] However, in the above conventional example, when line sequential scanning is performed, information signal waveforms having the same information content are the same and the write timing is also the same, so the following It has the following drawbacks.

■As liquid crystal display elements become larger and more precise, the wiring resistance of scanning signal lines (hereinafter also referred to as common lines) and information signal lines (hereinafter also referred to as segment lines) increases, and the wiring resistance on the electrode lines increases. The delay in waveform ledger is increasing.

■Furthermore, when using a ferroelectric liquid crystal (hereinafter referred to as FLC), good bistability cannot be obtained unless the cell thickness is maintained at 1 to 2 μm, and the drive voltage becomes high and retardation Therefore, the cell thickness must be kept thin (about 1 to 2 μm), and the capacitance of the liquid crystal layer becomes large (approximately 6 times that of a conventional TN type element).

- Also, due to mass production constraints, it is difficult to reduce the on-resistance of the drive IC to less than about 1Ω.

Due to these causes, a phenomenon occurs in which the driving waveform applied to the liquid crystal layer becomes dull. This phenomenon causes a situation in which the switching margin is reduced, such as an intra-cell distribution of FLC switching thresholds, and also has a large impact on non-selected pixels.

In non-selected pixels, a reference voltage is applied to the common line, and an information signal for the selected pixel is applied to the segment line. Under these circumstances, the display contents shown in Figure 2 (
If you draw a white circle W after making all pixels black as shown in a), most of the information signals in one frame will be "black".
((b) in the same figure), differential waveform ripples ((C) in the same figure) corresponding to the rising and falling edges of the information signal occur on the common line. The peak value of this ripple depends on the information content; for example, in the case of a checkered pattern for each bit, there is almost no ripple. This is because the positive and negative input voltages of adjacent segment lines are reversed and have the same peak value, so no ripple appears on the common line.

However, when there are many "black" screens as shown in FIG. 2(a), a pull occurs when the screen corresponds to a "black" information signal (FIG. 2(C)). At that time, if the information signal drawn by the white circle ((d) in the same figure) has a reverse phase shape, it will be strengthened by the ripple, and the "black" signal will not be strengthened by the ripple and will only become dull. A difference occurs in the influence exerted on non-selected pixels between the "white" signal strengthened by the pull and the "white" signal. This results in the phenomenon of screen flickering, which significantly reduces display quality.

In other words, as shown in Fig. 2(a), the information signal when drawing the tool part is common to the entire screen, but when drawing the white circle part W, the segment line that outputs the white signal and the black signal are used. This means that the actual shape of the information signal (the amount of ripple) becomes distorted due to the segment line that outputs the .

In view of the problems of the prior art, an object of the present invention is to
The object of the present invention is to improve display quality in a ferroelectric liquid crystal cell by eliminating screen flickering caused by ripples occurring on a common signal line.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a strong signal between a pair of electrode substrates each having a scanning signal line group and an information signal line group and disposed facing each other so that these lines intersect. Dielectric liquid crystal (
In a matrix-type strong electrostatic liquid crystal display element formed by sandwiching a chiral smectic liquid crystal (chiral smectic liquid crystal), a means is provided for shifting the timing of an information signal applied to an information signal line between adjacent information signal lines.

[Function] In this configuration, by shifting the timing of the information signal applied to the information signal line between adjacent information signal lines, the number of rises and falls of the applied pulse is reduced compared to the case of the conventional technology, and the pull The display is performed without being affected by the

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows drive waveforms according to an embodiment of the present invention.

In the same figure (a), S is the waveform of the scanning signal, and V
It is composed of three voltage pulses: I + v2 r v3. Reference numerals 11 and 12 indicate information signals input to two adjacent segment lines, respectively, which display the same information content. The signal I2 is delayed in timing from the signal 11 by δ. Signals 1' and 12' are information signals having the same information content that are similarly applied to adjacent segment lines, but are for displaying other information content different from signals I, , I2. These information signals are composed of voltage pulses of V, , v4. Signal engineer, and ■1', signal ■2 and I2'
are respectively applied on the same segment line.

FIG. 1(b) shows the scanning signal S and each information signal 1, +I1', I2+12' applied to the pixel.
Signal 5-It, S It , S I
2,5-I2' is shown. As can be seen from the figure, the half selection signal S-I applied to one segment and the other segment, and the selection signal S
-I+' and S-I2',
The efficacy of FLC on switching remains largely unchanged. Furthermore, there was no change in actual driving under the following cell conditions.

The cell to which this drive waveform is applied is as shown in FIG.
On the ITO stripe electrodes 22 patterned on the upper and lower glass substrates 21, a sputtered SiO film of about 1,000 layers is formed as an insulating film 23, and on top of that, about 400 layers of polyimide LP-64 manufactured by Toshi Co., Ltd. is formed as an alignment film 24. It was formed to the thickness of a human being and then subjected to a rubbing process. The rubbing directions of the upper and lower substrates in the cell state were aligned in the same direction, and the cell thickness was set to about 1.5 μm. One of the upper and lower electrodes 22 is a scanning signal line group, and the other is an information signal line group.

FIG. 4 is a block diagram of a circuit for driving the liquid crystal cell 41 constructed in this manner. 42 is an image information generating means, and the scanning signal information from the image information generating means 42 is
The signal is supplied as a scanning signal to the scanning signal line group of the liquid crystal cell 41 via the controller 43, common S/R, decoder 45, and analog switch 46.

On the other hand, in the image information sent from the image information generating means 42 via the controller 43, odd numbered (0DD) and even numbered (EVEN) data are clocked φ1 and φ1 by the segment S/Rs 47 and 48, respectively.
are read out at the timing of each line memory 49.
and 50 to the multiplexer 51 at the timing of clocks φ1' and φ2', and are combined again.

At this time, the timings of clocks φ1' and φ2' are set so that even-numbered data is delayed by δt. The image information signal synthesized by the multiplexer 51 is applied to the information signal line group of the liquid crystal cell 41 via the decoder 52 and the analog switch 41.

In this configuration, C5-1014 manufactured by Chisso Corporation was injected into the cell 41 as a liquid crystal, the temperature was raised to 40°C, and the above drive waveform was applied to measure the Δ
T: Matrix driving could be performed in 50 μs. However, ■, = 9■/μm, V2 = 9V/μm
, Vs=4V/μm, and V4=-4V/μm.

Here, as shown in FIG. 1(a), times H1 and H2 are the selection times for one scanning line, but the signal applied to the signal line and I2, and between I2 and I2' are There is a difference of δt due to clocks φ1' and φ2',
All segment lines are divided into two types, one signal I+ is selected during time H1, and the other signal I2 is selected during time H2.
selected during the period. That is, times H1 and H2 have the same duration, but time H2 starts later than Hl by δt,
Signal 2 lags I by δt.

According to this, the information signal is the same information (for example, "white")
Even when continuous application of
As shown in Figure (a), the scanning time can be shortened and at the same time the selection time is fixed for all segment lines (Figure 3).
Compared to the conventional example b), the number of rises and falls of the pulse is reduced, making it less susceptible to pull effects. Therefore, the display quality of FLC can be greatly improved.

[Other Embodiments] FIG. 6 is a time chart showing drive waveforms according to another embodiment of the present invention. The device configuration is the same as that of the above embodiment.

This drive waveform is created by making the selection time difference δt between the segment lines equal to the selection time H1 of the signal ■1.
During the period t, a voltage pulse that cancels the ripple caused by the signal 1 is applied by the signal 2, and in the next period H2, a pulse that cancels the ripple caused by the information waveform on the signal I2 is applied by the signal 2. 4 is applied. ΔT,V,,v2. The values of v and v4 are the same as in the above embodiment.

[Effects of the Invention] As explained above, according to the present invention, since the writing timing of adjacent segment lines is shifted, the scanning time can be shortened, and ripples occurring on the common line can be reduced to improve the display of FLC. Quality can be improved.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are timing charts showing drive waveforms according to an example of the present invention, and FIGS. 2(a) to (d)
3(a) and (b) are timing charts showing a comparison between the conventional example and the embodiment shown in FIG. 1, and FIG. is the first
5(a) and 5(b) are a cross-sectional view and a plan view of an electrode pattern illustrating the configuration of a liquid crystal cell, and FIG. 6 is a block diagram of a circuit that generates the drive waveform shown in FIG. 3 is a timing chart showing drive waveforms according to the embodiment. 44: S/R for common, 45, 52: Decoder, 46.
53: Analog switch, 47.48: S for segment
/R, 49, 50 line memory, 51: multiplexer. Patent applicant: Canon Co., Ltd.

Claims (2)

[Claims] (1) In a matrix type liquid crystal element in which a liquid crystal is sandwiched between a pair of electrode substrates that are arranged facing each other so that the scanning signal line group and the information signal line group are intersected, the information signal line 1. A liquid crystal device comprising means for shifting the timing of applied information signals between adjacent information signal lines. (2) The liquid crystal element according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal.