JP2820160B2 - Driving method of liquid crystal panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method of driving a liquid crystal panel having a simple matrix structure, in which a data side electrode and a scan side electrode are alternately arranged in order to suppress the occurrence of uneven brightness in a liquid crystal display device driven by a simple matrix. In the matrix-type liquid crystal panel provided to intersect with V, in the positive voltage application mode, V is applied to the selected data side electrode, 0 is applied to the scan side electrode, and (1- 2 /
a) V is applied to the non-selected scan-side electrode, and (1-1 / a) V is applied. In the negative voltage application mode, 0 is applied to the selected data-side electrode, and V is applied to the scan-side electrode. 2 V / a for the unselected data side electrode, and 2 V / a for the unselected scan side electrode.
In the driving method of applying V / a, the positive period driven in the positive voltage application mode and the negative period driven in the negative voltage application mode are inverted every two lines, and
The polarity inversion performed every line scan is started by shifting the phase by 90 ° every frame, and the phase is shifted by 180 ° every n line scans.

[Industrial applications]

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

2. Description of the Related Art In recent years, with the spread of personal computers, word processors, and the like, liquid crystal display devices that are lightweight, thin, and can be driven by batteries have become remarkable as display devices instead of large-sized, large-power-consumption CRTs. The driving method of the liquid crystal display device is roughly classified into a simple matrix type and an active matrix type. However, the active matrix type is difficult to manufacture because a non-linear element is required for each pixel constituting the matrix, and currently the display is performed. In general, a liquid crystal display device having a large capacity employs a simple matrix structure.

However, in a liquid crystal display device having a simple matrix structure,
As the display capacity increases, uneven brightness (crosstalk) occurs in the display pattern due to its characteristics, and the display state deteriorates. Therefore, it is desired to eliminate the uneven brightness.

[Conventional technology]

In FIG. 8 is a liquid crystal panel of simple matrix structure shown in FIG. 6, when the "bright" write one column all the liquid crystal display device like that X ₁ row and X ₂ rows (display of the liquid crystal ○) , And when writing "dark" (LCD display is ●)
3 shows a liquid crystal panel drive waveform. (A) is a data-side voltage in the figure, characteristics of the thick line X ₁ column, dotted line X ₂
A characteristic of a column, with (b) and (c) Y ₁ properties and Y ₂ Characteristics of the scan-side voltage, (d) the drive voltage waveform of the cell alpha (thick line), the driving voltage waveform of the cell beta (dotted line) is there.

Note that the conventional driving method employs the voltage averaging method shown in FIG. 7, in which the first cycle is selected during one frame period and the second cycle is selected in the next frame. The one that switches between the first period and the period of FIG. 2 every few lines has been put to practical use, and a high-reliability drive that does not deteriorate the liquid crystal panel characteristics by preventing a DC component from being applied to the liquid crystal cell has been realized. I have. Switching between the first cycle and the second cycle is called polarity inversion, and the control signal is called a polarity inversion signal.

By the way, in the conventional liquid crystal driving method as described above, a case where "bright" display is performed on the entire surface of the liquid crystal panel as shown in FIG. I'll think about it. In this case, cell X of x ₁ column of _one row y, cell Y, and the voltage waveform applied cell Z of x ₅ columns x ₃ rows as shown in Figure 10. As can be seen from this figure, when the cell applied voltage is inverted from positive to negative or from negative to positive, the cell waveform is distorted, and the rounding depends 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 becomes different, and the display pattern causes display unevenness (luminance unevenness). That is, in the case of the display pattern shown in FIG. 9, there is a problem that the cell X is the brightest, the cell Z is the darkest, and the “bright” cells in the row with many stripes become darker.

Therefore, the present applicant has already proposed a driving method of 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. 62-268300). In this method, when "bright" writing is performed on the entire surface of a simple matrix type liquid crystal panel having a data side electrode and a scan side electrode, a drive waveform of a data side electrode to which a certain liquid crystal cell belongs and a scan side electrode and a cell are used. This will be described with reference to FIG. The driving voltage of the liquid crystal panel is controlled by a positive / negative alternating voltage. In the positive voltage application mode, V is selected when the data side electrode is selected.
However, when not selected, (1-2 / a) V is applied, when the scan side electrode is selected, 0 is applied. When not selected, (1-1 / a) V is applied. In the negative voltage application mode, the data side electrode is selected. In some cases, 0 is applied, 2 V / a is applied when not selected, V is applied when the scan side electrode is selected, and V / a is applied when not selected.
In this method, a frame inversion drive for inverting the polarity of the applied voltage of the entire frame is performed in the frames A and C, and the polarity of the applied voltage is inverted for each line in the frames B and D in addition to the above-described frame inversion. Perform line inversion driving.

[Problems to be solved by the invention]

However, in the method proposed by the present applicant,
When the display is performed, as shown in FIG. 11, the voltage applied to the cells changes every time one cell is selected in the second frame (B frame), as can be seen from FIG. However, there is a problem that a large burden is imposed on the power supply. In addition, since a periodic waveform is applied in a frame unit, a problem such as flicker occurs.

The present invention provides a method for driving a liquid crystal display device in which the number of times that voltages applied to all cells are changed from positive to negative, or from negative to positive, can be equalized. It is an object of the present invention to provide a simple matrix drive liquid crystal display method that can also suppress the occurrence of luminance unevenness.

[Means for solving the problem]

FIG. 1 is a diagram for explaining the principle of the method of the present invention. According to the method of the present invention, V is applied to the selected data-side electrode and V is applied to the scan-side electrode of the matrix-type liquid crystal panel provided with the data-side electrodes and the scan-side electrodes alternately intersecting in the positive voltage application mode. 0 is applied, (1-2 / a) V is applied to the unselected data side electrode, and (1/2) V is applied to the unselected scan side electrode.
−1 / a) V, and in the negative voltage application mode, 0 is applied to the selected data side electrode, V is applied to the scan side electrode, 2 V / a is applied to the unselected data side electrode, V / a is applied to unselected scan-side electrodes. The positive period driven in the positive voltage application mode and the negative period driven in the negative voltage application mode are inverted each time two lines are scanned by the scan data shift clock, and the polarity is inverted every two lines scanned. The phase is shifted by 90 ° at the end of each frame, and is shifted by 18 ° every n lines (n = 6 in the figure).
The liquid crystal display is driven so as to shift the phase by 0 °.

[Action]

According to the driving method of the liquid crystal display device of the present invention, the polarity inversion of the voltage applied to each liquid crystal cell of the simple matrix is performed at equal intervals every two lines, so that the luminance unevenness of the liquid crystal cell can be suppressed and the power supply can be reduced. Burden is averaged. In addition, the polarity inversion mode is shifted by 90 ° for each frame, and further, by shifting the phase by 180 ° for every n lines, a periodic waveform is not applied for each frame regardless of what pattern is displayed. And flicker does not occur.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram of an apparatus for implementing the method of the present invention. The liquid crystal panel 1 has a data side driver 2 for controlling a data side electrode of the liquid crystal cell and a scanning side driver 3 for controlling a scanning side electrode. A signal generator 4 is connected to the data driver 2 and the scanning driver 3.
The data side driver 2 receives a voltage V, (1-2 / a) V, 2V / a, and 0 from a power supply circuit built in the signal generator 4.
, And potentials of V, (1-1 / a) V, V / a, and 0 are supplied to the scanning driver 3 from the same power supply circuit.

Further, the signal generator 4 supplies X data as liquid crystal panel display data and Y data as scanning data to the data side driver 2 and the scanning side driver 3 in response to a command from a control device such as a personal computer. The data-side driver 2 and the scanning-side driver 3 supply the data-side electrodes and the scanning-side electrodes of the liquid crystal panel 1 with the X data and the Y data from the signal generator 4 among the voltages from the power supply circuit. Is given.

That is, in the positive voltage application mode in which the liquid crystal panel 1 is driven with a positive voltage, the data driver 2 based on the X data is used.
Applies V to the selected data side electrode and (1-2 / a) V to the non-selected data side electrode, while the scanning side driver 3 applies the selected scanning side based on the Y data. 0 is applied to the electrodes, and (1-1 / a) V is applied to the non-selected scanning electrodes. Similarly, in the negative voltage application mode in which the liquid crystal panel 1 is driven with a negative voltage, the data driver 2 applies 0 when the data electrode is selected, and applies 2 V / a when the data electrode is not selected. V is applied when an electrode is selected, and V / a is applied when it is not selected.

Further, a polarity conversion circuit 5 is connected to the signal generator 4, and the polarity conversion circuit 5 has an inverter 50, four pulse frequency dividing circuits 51, 52, 53, 55, 57, a switching circuit 54, and a logical inversion. There are circuits 56 and 58. The scanning data clock signal a from the signal generator 4 is input to the frequency dividing circuits 51 and 57, and the polarity inversion signal f is input to the switching circuit 54 and the frequency dividing circuit 55.

The operation of the polarity conversion circuit 5 will be described with reference to FIG. 3 in the case where one frame is composed of four lines for the sake of explanation. The dividing circuit 51 divides the scanning data shift clock signal a by 2 at the falling edge of the pulse, and the divided output is directly input to the dividing circuit 52 as a signal b. It is input as an inverted signal c via 50. These frequency dividers 52 and 53 divide the input signals b and c by two at the rise of the pulse, and output the signals d and e.
To the switching circuit 54.

The polarity inversion signal f is a signal for inverting the polarity every frame, and the switching circuit 54 to which the polarity inversion signal f is input outputs the signal d when the signal f is at the high level “H”.
And outputs the signal e as an output signal g to the logic inversion circuit 56 when the signal f is at the low level “L”. Further, the frequency dividing circuit 55 divides the polarity inversion signal f by 2 at the rise of the pulse, and outputs the result 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 the output thereof becomes the signal i. The frequency divider 57 divides the scan data clock signal a by n (n = 6 in the figure) at the falling edge of the pulse, and the output becomes j. The logic inverting circuit 58 performs an exclusive OR (EOR) of the signal i and the signal j, and the output is k. As shown in FIG. 3, this signal k is inverted every two lines, and the phase is shifted by 90 ° for each frame, and further shifted by 180 ° every n-line scanning.

This signal k is transmitted to the data side driver 2 as shown in FIG.
To the scanning side driver 3 to suppress the biased load on the power supply circuit and the flicker of the display,
It is possible to suppress the brightness unevenness of the liquid crystal cell of “bright” display in the striped display. FIG. 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 the "column" display is performed for all columns, and is shown in FIG. FIG. 7D shows a driving waveform of the liquid crystal cell α according to the method of the present invention (a waveform according to the conventional method is shown in FIG. 7D). As can be seen from the figure, the polarity of the applied voltage is inverted every two lines, the phase is shifted by 90 ° for each frame, and further, the phase is shifted by 180 ° for every n lines, and the driving waveform is more than one frame. And the flicker does not occur.

Here, complete the "bright" displayed on the entire surface of the liquid crystal panel shown in FIG. 9 described above, the cell X of the "dark" x ₁ column of y ₁ line in the pattern that displays stripes stepwise therein, of x ₃ rows cell Y, and x ₅ columns cell Z of the voltage application waveform according to the method of the present invention shown in FIG. 5. In this example, n = 7. As can be seen from this figure, when the cell applied voltage reverses from positive to negative or from negative to positive, even if the cell waveform is distorted, according to the method of the present invention, the number of rounding (the number in the figure is changed). Is the same regardless of the display pattern. Therefore, in the present invention, display unevenness (luminance unevenness) does not occur due to the display pattern, and the cells X, Y, and Z all have the same brightness.

As described above, according to the driving method of the present invention, in addition to suppressing the luminance unevenness, the flicker is suppressed, so that the display quality can be further improved.

〔The invention's effect〕

As described above, according to the present invention, in a liquid crystal display device driven by a simple matrix, the load on the power supply is averaged, the occurrence of flicker can be suppressed, and the occurrence of luminance unevenness can be suppressed. There is an effect of improving.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of a method for driving a liquid crystal panel according to the present invention;
FIG. 2 is a circuit diagram showing the configuration of an embodiment of an apparatus for carrying out the method of the present invention, FIG. 3 is a waveform diagram showing the waveform of each part in FIG. 2, and FIG. FIG. 5 is a driving waveform diagram when driving the cell α shown in FIG.
FIG. 6 is a diagram showing an example of a display pattern of a liquid crystal cell, and FIG. 7 is a diagram showing a voltage averaging method used when driving a liquid crystal panel. 8, FIG. 8 shows a driving voltage waveform diagram of the conventional driving method of the cells α and β of FIG. 6, FIG. 9 shows an example of a display pattern of a 5 × 8 dot liquid crystal panel, and FIG. FIG. 9 is a diagram showing driving waveforms when cells X, Y, and Z of FIG. 9 are driven by a conventional driving method.
The figure is an explanatory diagram of a driving method that can make the number of polarity inversions of a voltage already proposed equal. 1 ... LCD panel, 2 ... Data side driver, 3 ... Scan side driver, 4 ... Signal generator, 5 ... Polarity conversion circuit, 51,52,53,55,57 ... Division circuit, 54 ...... Switching circuit, 5
6,58 ... Logic inversion circuit.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Murakami 1015 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Hisashi Yamaguchi 1015 Kamikodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited ( 56) References JP-A-2-275988 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/133 545

Claims (1)

(57) [Claims] In a matrix type liquid crystal panel provided with data electrodes and scan electrodes alternately intersecting with each other, V is applied to selected data electrodes and 0 is applied to scan electrodes in a positive voltage application mode. Is applied, (1-2 / a) V is applied to the unselected data side electrode, and (1-1-1) V is applied to the unselected scan side electrode.
/ a) V is applied, and in the negative voltage application mode, 0 is applied to the selected data side electrode, and V is applied to the scan side electrode,
In the driving method of applying 2 V / a to the unselected data side electrode and applying V / a to the unselected scan side electrode, the positive period driven in the positive voltage application mode and the negative period driven in the negative voltage application mode The polarity period is inverted every two line scans, the polarity inversion performed every two line scans is started by shifting the phase by 90 ° every frame, and the phase is shifted by 180 ° every n line scans. Characteristic liquid crystal panel driving method.