JPS6298330A - Driving method for liquid crystal matrix display panel - Google Patents

Abstract

PURPOSE:To improve the quantity of liquid crystal display on a liquid crystal display panel in which an electric field is applied to X-axial electrode and Y-axial electrodes by making the potential of the X-axial electrodes opposite in polarity with four AC signals which have four different waveforms. CONSTITUTION:The liquid crystal panel is constituted by arranging plural X-axial and Y-axial electrode lines in crossing relation. Then, an electric field is applied to the Y-axial electrodes at every horizontal scanning period of the X-axial electrodes with a frame signal to display information. Further, the X-axial electrodes are made opposite in polarity periodically with a specific AC signal so that the 1st potential H and the 2nd potential L are obtained. This AC signal is so varied as to have (a): the 1st waveform phi0 which has the potential H for the Nth (N: natural integer) time and the potential L for the (H+1)th - the (H+3)th times, (b): the 2nd waveform phi1 which has the potential L for the Nth, (N+1)th, (N+3)th times and the potential H for the (N+2)th time, (c): the waveform phi2 obtained by inverting the waveform phi0, and (d): the waveform phi3 obtained by inverting the waveform phi1. Thus, the X-axial electrodes are made opposite in polarity with the AC signal, so the liquid crystal display is unchanged with the effective value of an applied voltage and an irregularity in density is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a liquid crystal matrix display panel, and particularly to a method for converting the same into AC.

[Conventional technology]

There are two conventionally well-known driving systems for liquid crystal IJ display panels, as described in Japanese Patent Publication No. 44438/1983.

Figure 4 shows the voltage applied to the liquid crystal by a drive waveform called the so-called A waveform, which inverts the voltage applied to the liquid crystal once in one horizontal scanning period (hereinafter abbreviated as IH). It is a diagram.

Figure 5 is a diagram showing the voltage applied to the liquid crystal using the so-called B waveform, which inverts the voltage applied to the liquid crystal every frame, and Figure 5 (a) shows the display pattern of each dot on the liquid crystal belonging to the Y axis. If is a repetition of black, white, and white, then Figure 5 (b)
is the case where the display pattern is all dots.

FIG. 6 is a diagram illustrating the liquid crystal display panel and drive system.

In FIG. 6, 2 is a liquid crystal matrix display panel, Y
Axis electrode wire ¥1~Y64o and X-axis electrode wire X.

~X,. A 1/100 duty, 640 x 200 dot display is performed by a so-called simple matrix up-and-down method in which the upper surface and the Y-axis electrode line \1 and 0 are formed.

4.6 are the Y-axis electrode wires (Y, ~Y640), respectively;
8.10 are the X moving electrode wires (Xx ~ X+oo
), 12 is a controller that receives necessary information from a microcomputer or the like and sends driving signals to the common driver 8.10 and segment driver 4.6, and 14 is a power supply circuit that provides the voltage necessary for driving.

From the controller 12, display data for the upper side DAT
AI, lower screen display data DATA2 is sent,
The data is sequentially input into a shift register in the segment driver 4.6 by clock pulses CP. 640 clock pulses CP are output and one row's worth of D AT A IJ' is output to the shift register in the segment driver.
- When the alignment is completed, a LOAD signal is output as shown in FIG. 7(a), and the DATA signal is stored in the memory in the segment driver by this signal. The segment driver outputs the output terminals O1 to 064o based on the stored data.
Outputs liquid crystal and drive signals from. The time of 640 clocks, that is, the period of the LOAD signal is one horizontal scanning period I
It is H. The common driver 8.10 is given the FRAME signal shown in FIG. 7(b) instead of the data signal, and reads this signal using the LOAD signal as a clock pulse. Then the output is O3-O7°. The period in which the selection waveforms appear one after another and the selection of the display spring active electrode line goes around is one frame. M
The signal is an alternating current signal for reversing the electric field applied to the liquid crystal, and as shown in Figure 5 (b), when the potential of the M signal changes every frame, the drive waveform becomes the B waveform mentioned above, and the M signal becomes 1. If it changes every /2H, it becomes a human waveform.

[Problem that the invention seeks to solve]

In Figures 4 and 5, the waveform is rounded in consideration of the increase in liquid crystal capacity due to the increase in density of IJ display panels and the increase in electrode resistance within the liquid crystal cell. It is. Since the AC frequency of the liquid crystal is high in the human waveform, both the charging and discharging current of the liquid crystal and the current consumption of the drive IC are large.The selected waveform that appears at the timing shown at t in Figure 4 is reversed in the IH. Therefore, receiving the influence of waveform rounding twice will lead to a decrease in the drive margin, and since the waveform rounding will affect the entire waveform strongly, the effective value of the applied voltage will decrease and the voltage for driving will increase, which will cause the drive IC to High-density liquid crystal panels are rarely used because they have drawbacks such as exceeding the breakdown voltage.

Currently, most of the liquid crystal matrix display channels for display terminals are driven by the B waveform.
A very troubling problem has arisen in the channel of the X200 dot configuration. This is because the effective values of the applied voltages are clearly different between the waveforms (a) and (b) in FIG. In case (a), the effective value of the applied voltage decreases significantly due to the rounding of the waveform due to the large number of voltage changes at the non-selection timing 12:00, whereas (
In the case of b), since the entire column has the same pattern, there is no fluctuation in the waveform and there is no decrease in the effective value of the applied voltage. As a result, when the F patterns shown in Figure 8 are displayed vertically, columns 5E02 to 40 are thin because there are many changes in black and white, and S
The EG50 column is displayed darkly because there is no change. Thus, noticeable vertical stripes are observed on the background surface of the display, which should be uniform.

Figure 9 shows the voltage V applied to the liquid crystal when using the B waveform.
This is an example in which the display pattern on the Y axis of the liquid crystal display panel is a repetition of 1001 (1: black, 0: white).The waveform at the non-selection timing t2 of Vtcn is It is determined by the display pattern of other dots on the same Y-axis, and the difference in the number of state changes at the t2 timing becomes the difference in the effective value of the voltage applied to the liquid crystal, causing unevenness in display density.

For example, the display pattern for the dot on the adjacent Y axis is 101.
If 0 is repeated, the number of state changes of the VLqo waveform in FIG. 8 will be doubled, and the display of the dots on the adjacent Y-axis will be lighter.

The polarity of VLeD when it is not selected is determined by the display pattern and the potential of the alternating current signal M. In Fig. 9, when M is H, the applied voltage when selecting Lc+ is positive, and when it is L, it is negative. If the display is 0, it is negative; if it is 1, it is positive; if M is L and the display is O, it is positive; if it is 1, it is negative.

Therefore, the waveform of the VLCD in the non-selected state shown in FIG. 9 has inverted polarity at time t2 when the AC conversion signal M is H and at time 127 when it is L.

As a proposal to solve this problem of uneven display shading, "sID Japan Display '83
-The 3rd International
DisplayRe5earchConter
ence Po5t-Deadline Paper
There is a sPD5 j.

This proposal attempts to remove the display pattern dependence of the effective voltage applied to the liquid crystal by inverting the polarity of the voltage applied to the liquid crystal every multiple horizontal scanning periods, using the average value over multiple frame periods. Fig. 1 shows a table in which the AC is reversed every 3H. However, although AC reversal every 3 H has a considerable averaging effect, there are still problems that display pattern dependence cannot be completely removed and that the time required for averaging is a little too long. There is. Note that a comparison between this proposal and the present invention will be made in detail in the later explanation.

An object of the present invention is to provide a fixed liquid crystal matrix display panel system that enables high quality display by eliminating the dependence of the effective value of the voltage applied to the liquid crystal on the display pattern.

[Means for solving problems]

In the present invention, the above-mentioned problem is solved by using a novel alternating current signal.

According to the present invention, the first potential (hereinafter abbreviated as ■) is applied to the alternating signal in the Nth horizontal scanning period from the lal frame signal, and N+1, N+
In the 2nd, N+3rd horizontal scanning period, the second potential (abbreviated as below) is taken and the period is 4 horizontal scanning periods.The first waveform state (N is a natural number) (Nth from the bl frame signal, L during the N+1st and N+3rd horizontal scanning periods.
a second waveform state in which the potential is taken as the I-I potential in the N1,022 horizontal scanning period, and the period is four horizontal scanning periods, and a third waveform state in which the fcl is an inverted state of the first waveform. and (d) a fourth waveform state that is an inverted state of the second waveform, and the four waveform states have a 4m frame period (m is a natural number).
By arranging the display to appear m times each, the unevenness of shading in the display described above is eliminated.

[Effect]

FIG. 10 is a diagram showing four states of the alternating current signal, from the Nth (N is a natural number) horizontal scanning period TN11 to N +
At the timing of moving to the first horizontal scanning period, S,
is the first state in which the first potential H is maintained; S2 is the second state in which the potential is shifted from the first potential H to the second potential; S3 is the state in which the potential is shifted from the second potential H to the first potential T The third state, S4, is a fourth state in which the second potential is maintained. As shown in FIG. 8, the conventional B waveform is configured such that the first state S and the fourth state S4 appear alternately every frame period.

FIG. 11 shows the effect of a configuration in which the four states s, s2, s, , s appear sequentially and periodically for equal frame periods.

Figure 11 shows the Nth and N+ poles on the Y axis of the liquid crystal display panel.
The display pattern of the first dot is 00.01.10.1
In each case of 1, the four states of the alternating signal s, , s,
, s, , the voltage VLCI+ applied to the liquid crystal by s4
FIG. 3 is a diagram showing what the waveform looks like when not selected. That is, this is a diagram showing how the waveforms of the Nth and N+1st horizontal scanning periods of the non-selection period indicated by t2.12/ of the VLCD in FIG. 8 change depending on the display pattern and the alternating current signal.

As shown in FIG. 11, when the display pattern is OO, when the alternating current signal is in the state of 81, the VLCD maintains -V, , and when it is in the state of S2, it changes from -vL to +v, and S When the state is , it changes from +VL to -vL,
+■ when in S4 state.

maintain the state of Therefore, if the states S, , S, , Sl, and S4 appear for the same number of frames, the time to take -VL and the time to take 10V, , when each of the above states are in order, will match. There are no problems with alternating current, and state changes occur once every two times. (
When looking at the VLCD waveform at the timing of transition from the N-th horizontal scanning period to the N+1-th horizontal scanning period, a state change occurs once every two frame periods.

) In the case of display pattern 01.10.11, wash S1~
When the state of S4 is in order, alternating current is complete and a state change occurs once every two times.

In other words, what is the pattern of display dots next to each other (
(Even if this happens, the number of state changes will be equal when the states of S1 to S are in order.

Therefore, counting from the beginning of the frame, Nth to N+1
All timings of transition to the th horizontal scanning period,
In other words, if the configuration is such that an equal number of states S, ~S, appear at the transition timing of all horizontal scanning periods as in the present invention, no matter what the display pattern on the Y-axis pole is, The number of state changes when the VLCD is not selected is equal. The present invention provides an alternating current signal that realizes such a configuration.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 2 shows four waveform states of the alternating current signal according to the present invention, where N in the claims is 1, φ. is the first waveform state, and φ1, φ2, and φ3 are the 2nd and 3rd waveform states, respectively.
．． 40 waveform state.

From the first horizontal scanning period to the second horizontal scanning period indicated by the dotted line in Figure 2.
φ at the timing of moving to the th horizontal scanning period. is the 10th
The first state Sl, φ3 shown in the figure is the second state S2, φ
, is the third state 33% φ2 is the fourth state S4 and φ.

~φ3 reveals all the states of S and ~S4. As is clear from FIG. 2, φ also occurs at the timing of changes in other horizontal scanning periods. ~φ, reveals all states of S1 to S4. Therefore, φ in FIG. If the waveform states of .about.φ3 are made to appear periodically and sequentially for equal frame periods, an even display that does not depend on the display pattern can be realized.

FIG. 1 is a diagram showing the alternating current signal N1 according to the present invention, and in the 4th M frame, φ. The waveform state of 4M+1, 4th
In the M+2 and 4th M+3 frames, φ1, φ2,
The waveform state of φ is φ. This is an example in which the waveform states of ~φ are sequentially and periodically displayed for each frame period.

φ. ~φ.

For example, the order in which the waveform states of φ8, φ2, φ1 appear is
,φ. It may be in this order or in any other order.

FIG. 3 shows the waveforms of vt and co at 12 o'clock (i.e., non-selected) in FIG. 8 for one period for each waveform state of the alternating current signal when the alternating current signal of the present invention is used. .

Since the cycle of the alternating current signal in this system is 4H, it is sufficient to examine the waveforms applied to the liquid crystal for all display patterns of four connected dots. In this method, four waveform states of the alternating current signal are selected at equal intervals, so if the sum of the number of state changes of the liquid crystal applied waveform in each waveform state is equal, there will be no difference in the effective value of the applied voltage. become.

As is clear from FIG. 3, the sum of the number of waveform state changes is equal for all display patterns.

Particularly noteworthy is the display pattern 0100.1110
．． Between the waveforms of the alternating current signals at 0001.1011,
This means that a correction effect occurs in the number of state changes in the liquid crystal applied waveform. Such a correction effect is unique to this method.

FIG. 12 shows a trial case in which a method similar to the present method was used to invert the polarity every 3H. In the case of every 3H, there are six possible phases of the alternating current signal, but the remaining three phases are inverted forms of the three phases shown in FIG. 12, so here, φ shown in the figure is used. , φ1, and φ2 will be investigated.

As is clear from the figure, in the case of the display pattern 111 and 11, the sum of the number of state changes in the three phases is 6 times, while in the case of the display pattern 010101, it is doubled to 12 times. That is, when the polarity of the electric field applied to the liquid crystal is reversed every 3H, a considerable averaging effect is observed when compared with the B waveform, but the dependence of the effective value of the liquid crystal applied voltage on the display pattern has not yet been removed.

The method of reversing every 3H shown in Fig. 12 is <prior art>
This method is the same as the method described in the SID JAPAN document mentioned in the section. The method in the SID document uses a normal signal and an inverted signal of the AC converting signal of one type of phase, but since the number of lines is 8 and the cycle of the AC converting signal is 6 days, the frame signal and the AC converting signal are As a result, when looking at the frame signal in sequence, all six phase states of the alternating current signal appear.

What happens in the case of an alternating current signal with a period of 4H like in this method? Since the number of lines is 8, which is divisible by the period 4, even if the alternating current signal is periodically inverted, there are two different phases. Only the state will appear. If only two phase states are used for every 2H inversion, φ in Figure 9
. It is sufficient to examine the phase of the number of state changes of only and φ2, or only φ and φ. Then, as is clear from FIG. 11, the display butter 71100.0110,0011°1001
When , the number of state changes is different. Therefore, when displaying a pattern in which black and white are repeated in two vertical dots, display unevenness will occur. Generally, liquid crystal matrix display panels are often constructed with a number of lines divisible by 4, so it is difficult to completely eliminate display unevenness using the method described in the above document.

Furthermore, the method in the above document requires 6 frames for averaging. This becomes a problem when using a liquid crystal material with a fast response time of about 100 m5ec.

On the other hand, since this method is configured to select the waveform state, the required time for averaging can be freely selected. In this embodiment, the waveform is shown when averaging over four frames, but this method does not cause any practical problems.

Note that when driving a liquid crystal panel at a duty of 1/100, the B waveform is inverted every 100 rows, whereas in this method, it is inverted every 2 rows, and as the frequency increases, the power consumption of the liquid crystal panel and the drive circuit increases.

Therefore, the power supply circuit shown in FIG. 4 14 uses an operational amplifier to lower the impedance of the output as shown in FIG. 13, and it is also necessary to provide a capacitor of 1 μF or more at the operational amplifier output.

The alternating current signal according to the present invention shown in FIG. 1 can be produced relatively easily by ordinary logic circuit techniques from signals normally used in liquid crystal display piles.

In addition, many controller ICs for liquid crystal display panels output the B waveform as an AC signal, but the 14th waveform
As shown in the figure, by providing an alternating current signal generation circuit 18 between the controller 12 and the LCD module 116 for generating an alternating current signal according to the present invention, the LCD module can be easily operated by the driving method of the present invention. I can do it.

Note that φ shown in FIG. ～φ3 waveform state in FRAM
A waveform state as shown in FIG. 15 in which the F signal is shifted by one horizontal scanning period has the same effect, and such a waveform state also falls within the scope of the present invention.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, since the effective value of the voltage applied to the liquid crystal does not change depending on the display pattern, it is possible to realize a display without unevenness in density.

[Brief explanation of drawings]

1, 2, and 15 are waveform diagrams showing AC signals according to the present invention; FIGS. 3, 10, and 11 are waveform diagrams corresponding to each display state of the present invention; and FIG. 4. , Figure 5, Figure 7,
9 and 12 are waveform diagrams in the prior art, FIG. 8 is a display pattern diagram in the prior art, and FIG. 6 is in the prior art. The rigid circuit diagrams shown in FIGS. 13 and 14 are circuit diagrams of main parts for realizing the driving method according to the present invention. φ. ...First waveform state, φ1...Second waveform state, φ2...Third waveform state, φ,...Fourth waveform situation.゛・λ, 14,2・ Tofu Σ Figure 3 Figure 4 Figure 5 (A) Figure 7 (B) (A) Figure 8 Rororororo 1 ■ - Shingou 1 Rorororo 11 ■■ Mouth ■ Rorororo Rororororororororo Intestines Rororororororororo No. 9 Figure FRAME Top-11111-8 Code-1 + 001100110011001100 It 0
0th figure 10th figure 12 mouth 111111-1 ``-yu-rL]-ichi-o10
101]”-u-kneefhi”-lower “]”001100
-Lower fLf 7 7 000111 -EngJlfna14 Figure vJ13 Prisoner

Claims (2)

[Claims] (1) A liquid crystal that has a plurality of X-axis electrode lines, a plurality of Y-axis electrode lines that intersect with the X-axis electrode lines, and a liquid crystal that is narrowed by the X-axis electrode line and the Y-axis electrode line. Using a display panel, the plurality of X-axis electrodes are sequentially selected for each horizontal scanning period in response to a frame signal instructing the start of a frame period on the liquid crystal display panel, and the Y-axis electrodes are selected according to data to be displayed. A voltage is applied to connect the X-axis electrode and the Y-axis electrode.
A method for driving a liquid crystal matrix display panel in which information is displayed by applying an electric field to a liquid crystal using an axial electrode, and the polarity of the electric field is reversed at a predetermined period to drive the liquid crystal with alternating current. The alternating signal is a periodic signal having a first potential and a second potential, and the electric field applied to the liquid crystal driven by the selected X-axis electrode is controlled by the alternating signal. The configuration is such that the polarity is opposite when the first potential is taken and when the second potential is taken, and the following [a], [b], [c], [d] are added to the alternating current signal.
[a] The first potential is taken during the Nth horizontal scanning period from the frame signal, and the second potential is taken during the N+1st, N+2nd, and N+3rd horizontal scanning periods from the frame signal. A first waveform state in which the scanning period is four horizontal scanning periods. (N is a natural number) [b] The second potential is taken during the N-th, N+1-th, and N+3-th horizontal scanning periods from the frame signal, and the first potential is taken during the N+2-th horizontal scanning period and the period is changed. A second waveform state with four horizontal scanning periods. [c] A third waveform state that is an inversion state of the first waveform. [d] A fourth waveform state that is an inversion of the second waveform. The four waveform states have a 4m frame period (m is a natural number)
A method for driving a liquid crystal matrix display panel, characterized in that the display panel is configured to appear m times each. (2) The method for driving a liquid crystal matrix display panel according to claim 1, wherein m is 1.