JPH03167521A - Method for driving liquid crystal panel - Google Patents

Abstract

PURPOSE:To suppress the unequal luminance of liquid crystal cells and to average the burden of a power source by executing the polarity inversion of the voltage to be impressed to the respective liquid crystal cells of a simple matrix at equal intervals for each of two lines. CONSTITUTION:A frequency dividing circuit 55 divides down a polarity inversion signal (f) by two at the rise of the pulse thereof and outputs the signal (h) to a logical inversion circuit 56. The logical inversion circuit 56 makes the exclusive OR of the signal (g) and the signal (h), the output of which is a signal (i). A frequency dividing circuit 57 divides down the scanning data clock signal (a) by n at the rise of the pulse thereof, the output of which is (j). The logical inversion circuit 58 makes the exclusive OR of the signal (i) and the signal (j), the output of which is (k). The (k) inverts at every two line and is the signal which is deviated in phase by 90 deg. each per frame and is deviated in phase by 180 deg. per n-line scanning. The burden of a power source is flattened and the generation of flickers is suppressed. In addition, the generation of the unequal luminance is suppressed.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for driving a liquid crystal panel with a simple matrix structure, the purpose of this method is to suppress the occurrence of brightness unevenness in a simple matrix IJ drive liquid crystal display device. In the positive voltage application mode of the matrix type liquid crystal panel, which is provided in such a way that they alternately intersect with each other, ■ is applied to the selected data side electrode, O is applied to the scan side electrode, and O is applied to the unselected data side electrode. (1 - 2/a) V is applied to the unselected scan side electrode, (1 - 1/a) V is applied to the unselected scan side electrode, and in the negative voltage application mode, 0 is applied to the selected data side electrode, and 0 is applied to the scan side electrode. 2V/a is applied to the unselected data side electrodes, and V/a is applied to the unselected scan side electrodes.
In a driving method that applies a voltage, a positive polarity period driven in a positive voltage application mode and a negative polarity period driven in a negative voltage application mode are reversed every two lines scanned, and the polarity is reversed every two lines scanned. The phase is shifted by 90 degrees for each frame to start, and the phase is shifted by 180 degrees every n line scans.

[Industrial application field]

The present invention relates to a method for driving a liquid crystal panel having a simple matrix structure.

In recent years, with the spread of personal computers, word processors, etc., liquid crystal display devices, which are lightweight, thin, and can be powered by batteries, have been increasingly adopted as display devices in place of large, power-consuming CRTs. Driving methods for liquid crystal display devices are broadly divided into simple matrix type and active matrix type.The active matrix type requires a nonlinear element for each pixel that makes up the matrix, making it difficult to manufacture. A simple matrix structure is generally adopted for large capacity liquid crystal display devices.

However, in liquid crystal display devices with a simple matrix structure, as the display capacity is increased, brightness unevenness (crosstalk) occurs in the display pattern due to its characteristics and the display condition deteriorates, so it is desired to eliminate this brightness unevenness. There is.

[Conventional technology]

FIG. 8 shows the liquid crystal panel with the simple matrix structure shown in FIG.
), and r-dark'' writing (liquid crystal display is ●). In the figure (
a) is the data side voltage, the bold line is X, column characteristics, and the dotted line is X
The characteristics are in two columns, (b) and (C) are the Y1 and Y2 characteristics of the scan side voltage, and (d) is the drive voltage waveform of cell α (thick line) and the drive voltage waveform of cell β (dotted line). .

In addition, conventional driving methods employ the voltage averaging method shown in FIG. 7, in which the l-th period is selected during one frame period and the second period is selected in the next frame, A device that switches between the first cycle and the cycle shown in Figure 2 every few lines has been put into practical use, and a high-reliability drive that prevents direct current from being applied to the liquid crystal cell and does not deteriorate the liquid crystal panel characteristics has been realized. has been done. This switching between the first cycle and the second cycle is called polarity inversion, and the control signal for this is called a polarity inversion signal. By the way, in the conventional liquid crystal driving method as described above, as shown in FIG. I'll think about it. At this time, cell X. of row y1 and column X1. ．． The voltage application waveforms of the cells Y1 and X in the r+ column and the cell Z in the column are as shown in FIG. As can be seen from this figure, when the cell applied voltage is reversed from positive to negative or from negative to positive, the cell waveform becomes dull, and the number of times the cell waveform becomes dull varies depending on the display pattern. Since the liquid crystal has an effective value response, there is a problem in that the more the waveform is rounded, the more the effective voltage differs, resulting in display unevenness (brightness unevenness) depending on the display pattern. That is, to describe the display pattern in FIG. 9, cell X is the brightest, cell Z is the darkest, and the brighter the cells in the row with more stripes, the darker the cells become.

Therefore, the present applicant has already proposed a method for driving a liquid crystal display device in which the number of inversions of the voltage applied to all cells can be made the same (Japanese Patent Application No. 63-268300). This method is applied to the data side electrode to which a certain liquid crystal cell belongs, the scan side electrode, and the drive waveform of the cell when performing "bright" writing on the entire surface of a simple matrix type liquid crystal panel equipped with a data side electrode and a scan side electrode. This will be explained using FIG. I1. still,
The drive voltage for this liquid crystal panel is performed by alternating positive and negative voltages. In the positive voltage application mode, when the data side electrode is selected, V is set, when it is not selected, (1-2/a) V is set, and when the scan side electrode is selected, it is set to O. However, when not selected, (1-1/
a) When V is applied and in the negative voltage application mode, O is applied when the data side electrode is selected, 2V/a is applied when it is not selected, V is applied when the scan side electrode is selected, and V/a is applied when it is not selected.
Assume that a is applied. In this method, frame A
In frame C and frame C, frame inversion driving is performed to invert the polarity of the applied voltage for the entire frame, and in frame B and D, in addition to the above-described frame inversion, line inversion driving is performed to invert the polarity of the applied voltage line by line.

[Problem to be solved by the invention]

However, in the method proposed by the present applicant, when the entire surface is displayed in bright light, one line of all cells is selected in the second frame (B frame), as can be seen from the cell applied waveform in FIG. Since the voltage applied to the cell changes each time, there is a problem in that it places a large burden on the power supply. Furthermore, since a periodic waveform is applied on a frame-by-frame basis, problems such as flicker occur.

The present invention is a method for driving a liquid crystal display device in which the number of times the voltage applied to all cells is reversed from positive to negative or from negative to positive is the same, which averages out the burden on the power supply and suppresses the occurrence of flicker. It is an object of the present invention to provide a simple matrix-driven liquid crystal display method that can also suppress the occurrence of uneven brightness.

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the method of the present invention. In the method of the present invention, in a positive voltage application mode of a matrix type liquid crystal panel in which data side electrodes and scan side electrodes are provided in an alternating manner, V is applied to the selected data side electrode and V is applied to the scan side electrode. 0 is applied, (1 2/a) V is applied to the unselected data side electrode, (1-1/a) V is applied to the unselected scan side electrode, and in the negative voltage application mode, the selected Apply 0 to the selected data side electrode, V to the scan side electrode, 2V/a to the unselected data side electrode,
V/a is applied to unselected scan side electrodes. Then, the positive polarity period driven in the positive voltage application mode and the negative polarity period driven in the negative voltage application mode are inverted every two lines scanned by the scan data shift clock, and
90% polarity reversal performed every line scan at the end of each frame
The liquid crystal display device is driven by starting with a phase shift of 180 degrees every scan of n lines (n=6 in the figure).

(Function) According to the method for driving a liquid crystal display device of the present invention, the polarity of the voltage applied to each liquid crystal cell in a simple matrix is inverted at equal intervals every two lines, so that uneven brightness of the liquid crystal cells can be suppressed. At the same time, the load on the power source is evened out. In addition, in polarity reversal mode, each frame is shifted by 90 degrees, and by shifting the phase by 180 degrees every n lines, no matter what pattern is displayed, periodic waveforms will not be applied frame by frame. , flicker no longer occurs.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a schematic diagram of an apparatus for carrying out the method of the present invention. The liquid crystal panel 1 includes a data-side driver 2 that controls data-side electrodes of a liquid crystal cell, and a scan-side driver 3 that controls scan-side electrodes. A signal generator 4 is connected to the data side driver 2 and the scanning side driver 3, and the data side driver 2 receives a voltage v, (1 2/a) from a power supply circuit built in the signal generator 4. V, 2 V/
A, and O potentials are applied to the scanning side driver 3.
From the same power supply circuit, V, (1-1/a) V, V/a
- and 0 potentials are applied.

Further, the signal generator 4 supplies X data, which is liquid crystal panel display data, and Y data, which is scanning data, to the data side driver 2 and the scanning side driver 3 in response to commands from a control device such as a personal computer. and,
The data side driver 2 and the scanning side driver 3 control the liquid crystal panel 1 according to the X data and Y data from the signal generator 4.
One of the voltages from the power supply circuit described above is selectively applied to each data side electrode and each scanning side electrode.

That is, in the positive voltage application mode in which the liquid crystal panel l is driven with a positive voltage, the data side driver 2 applies V to the selected data side electrode and (1-) to the unselected data side electrode based on the X data. 2/a) V is applied, while the scan side driver 3 applies O to the selected scan side electrodes and (1-1/a) V to the unselected scan side electrodes based on the Y data. Apply. Similarly, in the negative voltage application mode in which the liquid crystal panel l is driven with a negative voltage, the data side driver 2 applies 0 when the data side electrode is selected and 2V/a when it is not selected, and the scanning side driver 3 applies 0 V/a when the data side electrode is selected. When selecting the electrode, set V,
When not selected, apply V/a. Further, a polarity conversion circuit 5 is connected to the signal generator 4, and the polarity conversion circuit 5 includes an inverter 50, four pulse frequency dividing circuits 51, 52, 53, 55, 57, and a switching circuit 54.
, and logic inversion circuits 56 and 58. The scanning data clock signal a from the signal generator 4 is transmitted to a frequency dividing circuit 51.
．． 57, and the polarity inversion signal f is input to the switching circuit 54 and the frequency dividing circuit 55. To explain the operation of the polarity conversion circuit 5, one frame consists of four
The case where the lines are structured will be explained using Figure 3. The frequency dividing circuit 5l divides the frequency of the scanning data shift clock signal a by 2 at the falling edge of the pulse, and the output of the frequency division by 2 is directly input to the frequency dividing circuit 52 as a signal b.
The signal C is input to the frequency dividing circuit 53 via the inverter 50 as an inverted signal C. These frequency dividers 52, 53 are
The manually inputted signals b and c are frequency-divided by two at the rising edge of the pulse and outputted to the switching circuit 54 as signals d and e.

The polarity inversion signal r is a signal whose polarity is inverted every frame, and the switching circuit 54 to which this polarity inversion signal f is input changes the signal d to the output signal g when the signal f is at a high level "H#".
When the signal f is at a low level "L", the signal e is outputted to the logic inversion circuit 56 as an output signal g.

Further, the frequency dividing circuit 55 divides the polarity inversion signal f by two at the rising edge of the pulse, and outputs the divided signal to the logic inversion circuit 56 as a signal h. The logic inversion circuit 56 performs an exclusive OR (EOR) of the signal g and the signal h, and this output is the signal i.
becomes. The frequency dividing circuit 57 divides the scanning data clock signal a by n (n=6 in the figure) at the falling edge of the pulse, and its output becomes j. The logic inversion circuit 58 outputs the signal i and the signal j.
The exclusive OR (EOR) is performed with k, and this output becomes k. As shown in FIG. 3, this signal k is inverted every two lines, and the phase is shifted by 90'' every frame.
Furthermore, the signal has a phase shift of 180° every n line scans. By manually inputting this signal k to the data-side driver 2 and scanning-side driver 3 as shown in Fig. 2, the ``dark'' display can be reduced to stripes while suppressing the unbalanced load on the power supply circuit and display flicker. It is possible to suppress uneven brightness of a liquid crystal cell displaying bright 1 in a column.

Figure 4 shows the state of the voltage waveform applied to the liquid crystal cell in the first row by the method of the present invention for each frame when all columns are displayed. This figure shows the driving waveform of the liquid crystal cell α according to the method of the present invention (the waveform according to the conventional method is shown in FIG. 7(a)). As can be seen from this figure, the polarity of the applied voltage is reversed every two lines, the phase is shifted by 90° every frame, and
The phase is shifted by 180 degrees for each line scan, and the drive waveform has no periodicity of more than one frame, so flicker does not occur. Here, in the pattern in which r light j display is performed on the entire surface of the liquid crystal panel shown in FIG. ．． X,
FIG. 5 shows the voltage application waveforms of the cell Y1 in the column and the cell Z in the X5 column according to the method of the present invention.

In this example, n=7 was set. As can be seen from this figure, even if the cell waveform becomes dull when the cell applied voltage is reversed from positive to negative or from negative to positive, according to the method of the present invention, it is possible to ) will be the same regardless of the display pattern. Therefore, in the present invention, display unevenness (brightness unevenness) does not occur due to the display pattern, and cell
, Y, and Z all have the same brightness.

As described above, according to the driving method of the present invention, in addition to suppressing brightness unevenness, flicker is also suppressed.
Display quality can be further improved.

〔Effect of the invention〕

As explained above, according to the present invention, in a simple matrix-driven liquid crystal display device, the load on the power supply is averaged,
It is possible to suppress the occurrence of flicker and also to suppress the occurrence of uneven brightness, which has the effect of improving display quality.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the method of driving a liquid crystal panel of the present invention;
FIG. 2 is a circuit diagram showing the configuration of an embodiment of an apparatus for implementing the method of the present invention, FIG. 3 is a waveform diagram showing waveforms of each part of FIG. 2, and FIG. The drive waveform diagram when driving the cell α in the figure, FIG.
Driving waveform diagram when driving cells X, Y, and Z in the figure, Figure 6 is a diagram showing an example of a display pattern of a liquid crystal cell, and Figure 7 is a diagram showing a voltage averaging method used when driving a liquid crystal panel. , 8th
The figure shows a driving voltage waveform diagram of cells α and β in FIG. 6 according to the conventional driving method, FIG. 9 shows an example of a display pattern of a 5×8 dot liquid crystal panel, and FIG. Cell X,
FIG. 11, which is a diagram showing drive waveforms when Y and Z are driven by a conventional drive method, is an explanatory diagram of a drive method that can make the polarity inversions of the voltages the same number, which has already been proposed. 1...Liquid crystal panel, 2...Data side dryer, 3.
... Scanning side driver, 4... Signal generator, 5... Polarity conversion circuit, 51, 52, 53, 55.57... Frequency dividing circuit, 54... Switching circuit, 56.58...・Logic inversion circuit.

Claims (1)

[Claims] In a positive voltage application mode of a matrix type liquid crystal panel in which data side electrodes and scan side electrodes are provided in an alternating manner,
Apply V to the selected data side electrode, 0 to the scan side electrode, and (1-2/a) to the unselected data side electrode.
V, (1-1/a) V is applied to the unselected scan side electrode, and in the negative voltage application mode, 0 is applied to the selected data side electrode, V is applied to the scan side electrode, In a driving method that applies 2V/a to unselected data side electrodes and V/a to unselected scan side electrodes, the positive polarity period is driven in positive voltage application mode and the negative electrode is driven in negative voltage application mode. At the same time, the polarity reversal performed every two lines is started with a phase shift of 90° for each frame, and the phase is shifted by 180° every n line scans. Characteristic LCD panel driving method.