JPH02116822A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To suppress the generation of the flickers occurring in scanning driving of a low frame frequency by providing the 1st driving means which executes one-screen scanning with plural times of one perpendicular scanning and the 2nd driving means which impress voltage signals generating the other orientation state in a ferroelectric liquid crystal in information electrodes. CONSTITUTION:The information electrode groups 11A, 11B and scanning electrode groups C12 are so constituted as to constitute the matrix with each other and are respectively formed on glass substrates 13 and 14. The liquid crystal device is constituted by inserting an FLC material 15 between these substrates. One picture element is constituted of, for example, a region E where the scanning electrode C2 and the information electrodes A2 and B2 overlap. Scanning selection signals are jump-impressed to the scanning electrodes at every five other pieces so that the scanning selection signals are impressed to the scanning electrodes which are not adjacent to each other in the continuous six fields. The scanning selection period is set long at the time of low temp. in this way and the generation of the flickers occurring in the scanning driving of the low- frame frequency is eventually suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display device using ferroelectric liquid crystal, and particularly to a display device suitable for gradation display in which flicker is not noticeable.

[Conventional technology]

Conventionally, liquid crystal display elements are well known in which a scanning electrode group and a signal electrode group are configured in a matrix, and a liquid crystal compound is filled between the electrodes to form a large number of pixels to display images or information. . The driving method for this display element is time-division driving, in which an address signal is selectively and periodically applied to a group of scanning electrodes, and a predetermined information signal is selectively applied in parallel to a group of signal electrodes in synchronization with the address signal. It has been adopted.

Most of these were put to practical use, for example, in “Applied Physics Letters” (“Applied Phys Letters”).
sics Letters”) 1971, 18 (
4) M, Shut (M, published in issue 127-128)
S c h a d and W, Helfrich (W, H
e1f rich) Co-author of “Voltage Dependant Optical Activity of a Twisted Nematic Liquid Crystal”
(Voltage Dependent Optica
l Activity of a Twisted N
TN (TwistedN e m a ti
c) type liquid crystal.

In recent years, the use of bistable liquid crystal elements as an improved version of conventional liquid crystal elements has been proposed by both C1ark and Lagerwall in Japanese Unexamined Patent Publication No. 5
This method has been proposed in Japanese Patent No. 6-107216, US Pat. No. 4,367,924, and the like. Bistable liquid crystals are generally chiral smectic C phase (SmC*) or H phase (
A ferroelectric liquid crystal having a ferroelectric liquid crystal (SmH*) is used, and in these states, it changes to either a first optically stable state or a second optically stable state in response to an applied electric field;
It also has the property of maintaining its state when no electric field is applied, that is, it has bistability, and it also responds quickly to changes in the electric field, so it is expected to be widely used in fields such as high-speed and memory-type display devices. .

However, the above-mentioned ferroelectric liquid crystal device has a problem in that flicker occurs when driving the multiplexed screen. In particular, in European Publication No. 149899, an alternating current voltage is applied with the phase of the scanning selection signal reversed for each write frame, and as shown in FIG. set on)
A multiplex puff drive method is disclosed in which selective writing is performed in the following frame, and in the subsequent frame, selective writing is performed in black (crossed nicols are arranged so as to be in a dark state). In addition to the driving method described above, driving methods disclosed in US Pat. No. 4,548,476 and US Pat. No. 4,655,561 are known.

In such a driving method, during black selective writing after white selective writing, the white pixel that was selectively written in the previous frame becomes half-selected, and a smaller but effective voltage than the writing voltage is applied. Therefore, in this multiplex leg driving method, when writing black selection, the half selection voltage is uniformly applied to the white selection pixels, which are the background of black characters, for 172 frame periods (one frame scanning time is one screen). In the white selected pixel to which the half selection voltage is applied, the optical characteristics thereof change every 1/2 frame period. Therefore, in the case of a display in which black characters are written on a white background, the number of pixels that select white is overwhelmingly larger than the pixels that select black, and the white background appears to flicker. Further, in contrast to the above-mentioned display in which black characters are written on a white background, flickering is also observed in the case of a display in which white characters are written on black characters. When the normal frame frequency is 30 Hz, the half-select voltage described above is applied at 15 Hz, which is the 1/2 frame frequency, which is perceived by the viewer as flickering, which significantly impairs display quality.

In particular, when driving a ferroelectric liquid crystal at low temperatures, compared to, for example, scanning driving at a 15 Hz frame frequency at high temperatures,
It is necessary to lengthen the drive pulse (scan selection period), and therefore it is necessary to use scan drive at a low frame frequency such as 5 to 10 Hz. Therefore, when driving at low temperatures, flicker occurs due to scan driving at a low frame frequency.

[Summary of the invention]

An object of the present invention is to provide a liquid crystal device that suppresses the occurrence of flicker caused by scanning drive at a low frame frequency, and another object of the present invention is to provide a liquid crystal device that realizes gradation display without flicker. There is a particular thing.

Another object of the present invention is to provide a liquid crystal device that prevents image deletion from occurring.

The present invention provides, firstly, a) a liquid crystal element having a matrix electrode formed of a scan electrode and an information electrode and a ferroelectric liquid crystal, and b) a scan electrode that is not selected during one vertical scan period. a first driving means that applies scan selection signals having one polarity voltage and the other polarity voltage in an interlaced manner every two or more lines based on the voltage applied to the electrode, and scans one screen in one vertical scan a plurality of times; A voltage signal is applied to the selected information electrode to provide a voltage that produces one orientation state of the ferroelectric liquid crystal by combining with the voltage of one polarity of the scan selection signal, and the voltage signal of the other polarity of the scan selection signal is applied to the other information electrode. A liquid crystal device having a driving means having a second driving means for applying a voltage signal that provides a voltage that causes the other orientation state of the ferroelectric liquid crystal by combination with a polar voltage has a first feature, and a second feature is provided. , a, has a scanning electrode and an information electrode, and the plurality of electrodes constituting at least one of the scanning electrode and the information electrode are at least two
A matrix electrode wired with two different electrode widths, a liquid crystal element having a ferroelectric liquid crystal, and (b) scan electrodes are applied with reference to the voltage applied to the unselected scan electrodes within one vertical scan period. , - and the other polarity voltages are applied in an interlaced manner every two or more lines, and the first driving means scans one screen in one vertical scan a plurality of times, and scans the selected information electrode. A voltage signal is applied that provides a voltage that causes one orientation state of the ferroelectric liquid crystal by combining with the voltage of one polarity of the selection signal, and a voltage signal that gives a voltage that causes one orientation state of the ferroelectric liquid crystal is applied to the other information electrode by combining the voltage of the other polarity of the scanning selection signal. The liquid crystal device has a second feature, the liquid crystal device having a second drive means for applying a voltage signal that provides a voltage that causes the other distribution state of the liquid crystal, and thirdly, a. a liquid crystal element having a matrix electrode formed with an electrode and a ferroelectric liquid crystal, and (b) scanning having one and the other polarity voltages with reference to the voltage applied to an unselected scanning electrode within one vertical scanning period. A first driving means that performs one-screen scanning by serially applying a selection signal to non-adjacent scanning electrodes, and a ferroelectric liquid crystal that is applied to a selected information electrode by combining the scanning selection signal with one polarity voltage. A voltage signal that provides a voltage that causes one orientation state of the ferroelectric liquid crystal is applied, and a voltage that provides a voltage that creates the other orientation state of the ferroelectric liquid crystal by combining with the other polarity voltage of the scan selection signal is applied to the other information electrode. the second to apply the signal
The liquid crystal device having the driving means has a third feature.

[Detailed description of aspects of the invention]

An embodiment of the present invention will be described using a ferroelectric liquid crystal (hereinafter referred to as FLC).

FIG. 1 shows a first embodiment of the present invention (FIG. 2 shows A-A in FIG. 1).
A' is a sectional view), and the upper electrode group 11A and I
IB (hereinafter referred to as information electrode group) and lower electrode group 12 (lower scanning electrode group C) are configured to form a matrix with each other, and are formed on glass substrates 13 and 14, respectively, with FLC material 15 interposed between them. It has a closed structure. Further, as shown in the figure, the scanning electrode group C is made of Co, C,, C2, .
, the information electrode groups are A (A,, A2゜A3...) and B
(B l+ I32.133.I34...), and one pixel is an area E (electrode line width A>
B), i.e., for example, scanning electrode C2 and information electrode A2 and B
It consists of an area E where 2 overlap each other.

At this time, the electrode line width is AG8. Each scanning electrode group C
and information electrode groups A-B are connected to the power supply unit (
), and the SW is also connected to its 0N1
It is connected to a controller circuit (not shown) that controls 0FF. With the second configuration, under the control from the controller circuit, for example, grayscale representation at pixel E is performed as follows. When the common electrode C2 is being scanned, white (hereinafter referred to as W) is A2. When a signal that becomes W is applied to B2, Gray 1 (hereinafter referred to as Grayl) gives W1 to A2.
When a signal that becomes black (hereinafter referred to as B) is given to B2, gray 2
(hereinafter referred to as Gray 2), when A2 is given a B signal and B2 is given a W signal, black is A2. When a signal that becomes B is applied to B2, FIG. 3 shows the above-mentioned W and Grayl.

It shows the halftone expression of Gray2 and B.

With such a simple configuration, it is possible to express a four-value gray scale on a binary expression FLC.

In a preferred embodiment of the present invention, the plurality of intersections constituting one pixel E are configured with different intersection areas, and in particular, the different intersection areas are 2:
The ratio is preferably 4:8:16:-:2' (n=number of intersections in one pixel E).

In the present invention, the scanning electrode is divided into two parts, and when the electrode line width C=H, 8 gray scale levels are possible, and when COD, 16 gray scale levels are possible.

Furthermore, when only the information electrode side is divided, the electrode line width A=B, and color filters are provided on A and B so that they have a complementary color relationship, thereby making it possible to display four colors. For example, [A-yellow; B=nibble-, [A=magenta: B=
By arranging the complementary colors such as nibreen or [A=cyan:B=nirerad], four-color display of white, black, color A, and color B becomes possible.

Further, the polarizers 16A and 16B shown in FIG. 2 are arranged with their polarization axes intersecting, and a black display is made in a dark state, and a white display is made in a bright state.

Although the matrix electrode shown in FIG. 1 is driven by the driving example described above, the present invention can also be applied to a matrix electrode formed of a scanning electrode and an information electrode having the same electrode width.

FIG. 4(A) shows the scanning selection signal Ss and the scanning non-selection signal S.
N represents white information signals ① to V and black information signal I8. FIG. 4(B) shows the voltage (
Iw Ss) is applied),
The voltage waveform applied to the non-selected pixel (voltage (Is Ss) is applied at the pixel to which the black information signal ■8 is applied) on the same scanning selection electrode and the scanning non-selection electrode to which the scanning non-selection signal is applied. The voltage waveforms applied to the top two types of pixels are shown. According to FIGS. 4(A) and (B), the phase t,
At the non-selected pixels on the scan selection electrode, there is a voltage -(v) which is a voltage exceeding one threshold voltage of the ferroelectric liquid crystal.

+v3) is applied to produce one orientation/state of the ferroelectric liquid crystal, thereby creating a dark state and performing black writing. At this time, at phase t1, the selected pixel on the scanning selection electrode is applied with a voltage (-
V, +V3) is applied, and no change occurs in the alignment state of the ferroelectric liquid crystal. At phase t2, a voltage (V2+v3) that exceeds the other threshold voltage of the ferroelectric liquid crystal is applied to the selected pixel on the scan selection electrode, and the ferroelectric liquid crystal is aligned to the other alignment state. This produces a bright state,
written in white. Further, at phase t2, a voltage (V2V3) which is a voltage below the threshold of the ferroelectric liquid crystal is applied to the non-selected pixels on the scanning selection electrode, and the voltage (V2V3) is applied to the non-selected pixels on the scanning selection electrode.

does not change the orientation state of the On the other hand, a voltage ±v3, which is a voltage below the threshold voltage of the ferroelectric liquid crystal, is applied to the pixels on the scanning non-selected electrodes at phases t1 and t2. For this reason,
In this example, even if a pixel on the scanning electrode selected in phase T1 is written in white or black and then a scanning non-selection signal is applied, the writing state at the previous writing is unchanged. It will remain as is.

Further, in this example, at phase T2, a voltage of opposite polarity to the information signal at write phase T is applied from the information electrode. Therefore, as shown in FIG. 4(C), an alternating current voltage is applied to the pixels when scanning is not selected, and the threshold characteristics of the ferroelectric liquid crystal can be improved.

FIG. 4(C) shows a timing chart of voltage waveforms for producing the display state shown in FIG. 5. In this example, the scan selection signal is applied to every five scan electrodes in an intermittent manner, and the scan selection signal is applied to non-adjacent scan electrodes in six consecutive fields. In this example, by selecting every five scanning electrodes and scanning one frame (single screen scanning) in six field scans, the scanning selection period (TI+T2) is set to be long at low temperatures.
As a result, low frame frequency scan drives (e.g. 5-10
Hz), it is possible to significantly suppress the occurrence of flicker caused by low frame frequency scan driving, and furthermore, it is possible to select scan electrodes that are not adjacent to each other in six consecutive field scans. Image deletion could be effectively eliminated by applying a scan selection signal to.

FIG. 4(D) is an example using the drive waveform of FIG. 4(A). In this example, every two scanning electrodes are selected in an interlaced manner, and adjacent scanning electrodes are selected in two successive field scans. A scan selection signal was applied to select the scan electrodes that were not present.

FIGS. 6A and 6B show another driving example used in the present invention. According to FIGS. 6A and 6B, black writing is performed at phase t1, and white writing is performed at phase t4. Further, the phase T2 is an auxiliary signal applied from the information signal so that an AC voltage is applied to the pixel when scanning is not selected, as in the previous example. Such an auxiliary signal can produce effects similar to those disclosed in US Pat. No. 4,655,561 and the like.

FIG. 6(C) is an application timing chart of the scan selection signal when the drive waveforms of FIGS. 6(A) and 6(B) are used. According to the driving example shown in FIG. 6(C), the scan selection signal is applied to the scan electrodes in an interlaced manner every seventh field, and one frame scan is completed by eight field scans.

Also in this example, scan selection signals are applied to non-adjacent scan electrodes in eight consecutive field scans.

The present invention is not limited to the above-mentioned example, and in particular, the scan selection signal can be applied to the scan electrodes every four or more scan electrodes, preferably every five to twenty scan electrodes. In addition, in the present invention, the peak values of the voltage signals V, , -V and ±■3 are set to lV.
+ l=l V21>l±V3 preferably lV+l
=l V2 l>, preferably set to II±v31. Furthermore, the pulse width of these voltage signals is generally 1 μsec.
~1 msec, preferably 10 μsec ~1
It is better to set the pulse width at low temperature to be longer than the pulse width at high temperature.

In the present invention, various types of ferroelectric liquid crystal elements can be used. Specifically, 5SFLC disclosed by Clark et al. in U.S. Patent No. 4,367,924, etc.
and Isogai et al. in U.S. Pat. No. 4,586,791, or a ferroelectric liquid crystal device in an aligned state with a helical residue as disclosed in British Publication No. 2,159,635. Can be used.

FIG. 7 is a configuration diagram showing an example of a display device of the present invention. 7
01 is a display panel, which has scanning electrodes 702 and information electrodes 703.
and a ferroelectric liquid crystal filled between them, and at the intersection of a matrix made up of a scanning electrode 702 and an information electrode 703, the orientation of the ferroelectric liquid crystal is caused by an electric field caused by a voltage applied to the electrode. controlled.

704 is an information electrode drive circuit, and a video data shift register 7041.704 stores serial video data from the video information signal line 706. Video data shift register 7041
Line memory 7 that stores parallel video data from
042, an information electrode driver 7043 for applying a voltage to the information electrode 703 according to the video data stored in the line memory 7042, and a voltage V to be applied to the information electrode 703; , 0 and -vD by a signal from the switching control line 711.

705 is a scan electrode drive circuit, which connects the scan address data line 7.
Decoder 7051 and decoder 70 for receiving a signal from 07 and instructing one scanning electrode among all scanning electrodes.
a scan electrode driver 7052 for applying a voltage to the scan electrode 702 in response to a signal from the scan electrode 702;
Voltage applied to V5.02. A scanning side power switch 7 that switches between O and -V5 by a signal from a switch control line 711
It has 053.

A CPU 708 receives clock pulses from an oscillator 709 to control an image memory 710 and a video information signal line 706.
．． Scanning address data line 707. The switching control line 711 controls signal transfer.

〔Effect of the invention〕

According to the present invention, it is possible to effectively suppress the occurrence of flicker caused by scanning drive at a low frame frequency such as 2 Hz = 15 Hz, and especially during a long scan selection period at low temperatures. Also, there is no flicker, and a high-quality display screen can be obtained over a substantially wide temperature range. Further, according to the present invention, image distortion can be effectively prevented, and in this sense, a high-quality display screen can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a matrix electrode used in the present invention. Figure 2 shows the A-
A' is a sectional view. FIG. 3 is an explanatory diagram schematically showing halftones. FIGS. 4(A) to 4(D) are waveform diagrams showing examples of drive waveforms used in the present invention. FIG. 5 is an explanatory diagram schematically showing the display state of the matrix electrode. 6th
Figures (A) to (C) are waveform diagrams showing other drive waveform examples used in the present invention. FIG. 7 is a block diagram of the present invention. Fig. 74 (△) 11 Depressed Crow 3g t I t2 Ding C Ding (■? Fig. 6 (A) Kaidou Nonbenki Shi'eup No. sAJ High School 6 Fig. (B) 1゜ Ding 2

Claims (8)

[Claims] (1) A. A liquid crystal element having a matrix electrode formed by a scanning electrode and an information electrode and a ferroelectric liquid crystal, and b. A voltage applied to a scanning electrode that is not selected within one vertical scanning period. a first driving means for scanning one screen in one vertical scan a plurality of times by interlacingly applying scan selection signals having one and the other polarity voltages at every two or more lines, and a selected information electrode; A voltage signal is applied to the other information electrode to provide a voltage that causes one orientation state of the ferroelectric liquid crystal by combining with the voltage of one polarity of the scanning selection signal, and a voltage signal of combining with the voltage of the other polarity of the scanning selection signal is applied to the other information electrode. A liquid crystal device having a driving means having a second driving means for applying a voltage signal that provides a voltage that causes the other orientation state of the ferroelectric liquid crystal to occur. (2) The liquid crystal device according to claim 1, wherein the first driving means includes means for applying a scan selection signal to the scan electrodes in an interlaced manner every fourth or more times within one vertical scanning period. (3) The liquid crystal device according to claim 1, wherein the first driving means includes means for applying a scan selection signal to the scan electrodes in an interlaced manner every 5 to 20 scan electrodes within one vertical scanning period. (4) The first driving means interlacely applies a scan selection signal to the scan electrode every N (N=an integer of 2, 3, 4, ...) within one vertical scanning period, and (N+1) 2. The liquid crystal device according to claim 1, further comprising means for scanning one screen in one vertical scan. (5) A. A liquid crystal element having a matrix electrode formed by a scanning electrode and an information electrode and a ferroelectric liquid crystal, and b. A voltage applied to a scanning electrode that is not selected within one vertical scanning period. Scan selection signals having one and the other polarity voltages are applied in an interlaced manner every two or more lines, one screen scan is performed in one vertical scan multiple times, and the scan selection signal is applied in at least two consecutive one vertical scans. A first driving means for applying a signal to non-adjacent scan electrodes and a selected information electrode are provided with a voltage that causes one orientation state of the ferroelectric liquid crystal by combining with one polarity voltage of the scan selection signal. a second driving means for applying a voltage signal to the other information electrode, and applying a voltage signal to the other information electrode to generate the other orientation state of the ferroelectric liquid crystal by combining with the other polarity voltage of the scan selection signal; A liquid crystal device having a driving means. (6)a, a matrix electrode having a scanning electrode and an information electrode, in which a plurality of electrodes constituting at least one of the scanning electrode and the information electrode are wired with at least two different electrode widths, and ferroelectric A liquid crystal element having a liquid crystal, and (b) a scan selection signal having one polarity voltage and the other polarity voltage is applied to the scan electrodes every two or more lines within one vertical scan period, with reference to the voltage applied to the unselected scan electrodes. A first driving means performs one screen scan in multiple vertical scans by applying an intermittent voltage to the selected information electrode. Applying a voltage signal that provides a voltage that causes an orientation state, and applying a voltage signal that provides a voltage that causes the other orientation state of the ferroelectric liquid crystal by combining with the other polarity voltage of the scanning selection signal to the other information electrode. A liquid crystal device having a driving means having a second driving means. (7)a, a matrix electrode having a scanning electrode and an information electrode, in which a plurality of electrodes constituting at least one of the scanning electrode and the information electrode are wired with at least two different electrode widths, and a ferroelectric A liquid crystal element having a liquid crystal, and (b) a scan selection signal having one polarity voltage and the other polarity voltage is applied to the scan electrodes every two or more lines within one vertical scan period, with reference to the voltage applied to the unselected scan electrodes. a first driving means that performs one screen scan in one vertical scan a plurality of times, and applies a scan selection signal to non-adjacent scan electrodes in at least two consecutive one vertical scans; A voltage signal that provides a voltage that causes one orientation state of the ferroelectric liquid crystal is applied to the information electrode, and the voltage signal of the other polarity of the scan selection signal is applied to the other information electrode. A liquid crystal device comprising a second driving means for applying a voltage signal that provides a voltage that causes the other orientation state of the ferroelectric liquid crystal to be synthesized with the ferroelectric liquid crystal. (8) a. A liquid crystal element having a matrix electrode formed by a scanning electrode and an information electrode and a ferroelectric liquid crystal, and b. A voltage applied to an unselected scanning electrode within one vertical scanning period as a reference. , a first driving means for performing one-screen scanning by serially applying scan selection signals having one and the other polarity voltages to non-adjacent scan electrodes; A voltage signal is applied to the other information electrode to provide a voltage that causes one orientation state of the ferroelectric liquid crystal when combined with the voltage, and the other information electrode is applied to the other information electrode when combined with the other polarity voltage of the scan selection signal. A liquid crystal device having a driving means having a second driving means for applying a voltage signal that provides a voltage that causes an alignment state.