JPH026921A - Method for driving liquid crystal display device - Google Patents

Abstract

PURPOSE:To eliminate the variance of an effective voltage applied to liquid crystal cells and to improve the display quality by providing a period wherein the applied voltage of the liquid crystal cells is 0V for each scan period and driving the liquid crystal cell. CONSTITUTION:At every scan period, 0V is applied to the liquid crystal cells 4-11 to 4-nm, so even when the polarity of the applied voltage is not inverted, the voltage is boosted and lowered at every scan period and the polarity is inverted equivalently. The applied voltage of the respective liquid crystal cells 4-1 to 4-nm has no variance in effective value depending upon a display pattern. Consequently, even when a simple matrix type large-screen display panel 1 is used, its display quality can be improved.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for driving a liquid crystal display device having a simple matrix type liquid crystal display panel, the present invention aims to improve display quality by reducing variations in effective voltage applied to liquid crystal cells. , simple ma) IJ
A liquid crystal display that performs display by applying a voltage that is a combination of a scanning voltage from a scanning driver and a data voltage from a data driver to a liquid crystal cell at the intersection of a scanning electrode and a data electrode of a box-shaped liquid crystal display panel. In the method of driving the device,
A period in which the voltage applied to the liquid crystal cell is 0.times. is provided for each scanning period, so that display according to the display data is performed.

[Industrial application field]

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

A simple matrix type liquid crystal display panel has a simpler structure than an active matrix type liquid crystal display panel, which has a switching element such as a thin film transistor in each liquid crystal cell, so it is relatively easy to produce a large screen configuration. It becomes possible to do so.

However, as the size increases, brightness unevenness may occur due to the display pattern, resulting in a decrease in display quality. Therefore, it is not affected by 1 display pattern.)
V-drive is required.

[Conventional technology]

FIG. 6 is an explanatory diagram of a conventional example, in which 31 is a simple matrix type liquid crystal display panel, 32-1 to 3211 are scanning electrodes,
33-1 to 33-m are data electrodes 34-11 to 34-n
m is a liquid crystal cell, 35 is a scan driver, 36 is a data driver, and 37 is a display control section. host computer (
(not shown) etc. is applied to the display control unit 37, the display control unit 37 outputs display data XD and shift clock pulses XCP, ! =1 code pulse L
P and a polarity inversion signal DF are applied to the data driver 36, and a scanning signal YD and a shift 1 clock pulse YCP are applied.
and a polarity inversion signal DF are applied to the scan driver 35.

FIG. 7 is an explanatory diagram of the operation, in which the serial display data XD for one scanning electrode shown in (a) and the shift clock pulse XCP for one scanning electrode shown in (b) are sent to the data driver 3G. When the display data XI] is added and the display data
is applied to the data driver 36, and the shifted display data is applied to the output side of the data driver 36.
data voltage for one scanning electrode is applied in parallel to data electrodes 3:1-1 to 33-m. Then, as shown in (d)-=.(gl) from the scan driver 35, sequential scan voltages are applied to the scan electrodes 32-1 to 32-n, so line sequential writing is performed. The applied voltages of the upper liquid crystal cells have the same polarity or opposite polarity depending on the relationship of the applied voltages to the liquid crystal cells of the same data electrode, as shown in fll.

FIG. 8 is an explanatory diagram of applied voltage waveforms in a conventional example, and is a liquid crystal cell A in the case of the display pattern shown in FIG.

The applied voltage waveform of B is shown. In the display pattern of FIG. 9, the liquid crystal cells at the intersections of the de--electrode DI and the scanning electrode S1=-S4 are all selected cells indicated by white circles.)! -ta electrode D2
The liquid crystal cell at the intersection of -84 to scanning electrode S1 is a case where selected cells indicated by white circles and non-selected cells indicated by black circles are arranged alternately.

Therefore, in the case of frame reversal in which the applied voltage polarity is reversed every frame, the liquid crystal cell A at the intersection of the day electrode D1 and the scan electrode S1 has the voltage shown in the eighth VAl. A voltage is applied. That is, after the voltage of ■o is applied, corresponding to the voltage applied to other liquid crystal cells on the data electrode D1,
If the bias ratio is a, a voltage of Vo/a is applied. Then, in the next frame, the polarity is reversed.

Also, the liquid crystal cell B at the intersection of the data electrode D2 and the scanning electrode S1
1, a voltage shown at VBI in FIG. 8 is applied. That is, after the voltage ①o is applied, the voltage V corresponding to the voltage applied to the other liquid crystal cells of the data electrode D2j-. /a and -'
A voltage of J o/a is applied, and the polarity is reversed in the next frame.

In the case of line inversion, VA2. of FIG. 8 is applied to liquid crystal cells A and H within one frame. A voltage indicated by VB2 is applied. That is, +Vo and 1■ are in the selected cell. A pair of voltages are applied to the half-selected cell, 10 ■. /a and -V
A voltage set with o/a is applied.

[Problem to be solved by the invention]

In the simple 7 trix type liquid crystal display panel 31, scanning electrodes 32-1 to 32-n and data electrodes 33-1 to 33
-m and the capacitance of the liquid crystal cells 3411 to 34-nrn, the waveforms of the voltages applied from the scan driver 35 and data driver 3G become blunt.

FIG. 10 is an explanatory diagram of changes in the voltage applied to the liquid crystal cell. In the case of frame reversal, the applied voltages VA and VB of the liquid crystal cells A and B in FIG. The falling edge is slowed down by the resistance of the electrode and the capacitance of the liquid crystal cell. For example, if the bias ratio is a, the time constant of the liquid crystal cell is , and the scanning period is T, then as time t elapses, the voltage VA applied to the liquid crystal cell rises as follows. Further, the fall of the applied voltage VA is aa.

Similarly, the rise and fall of the voltage VB applied to the liquid crystal cell B are as shown in the figure.

When such waveform distortion becomes large, the effective value of the voltage applied to the liquid crystal cell becomes low, and the display brightness decreases. If the display brightness decrease occurs uniformly, it can be corrected by brightness adjustment, but if brightness unevenness occurs due to the display pattern, it cannot be corrected by brightness adjustment. That is, compared to the applied voltage VA of liquid crystal cell A, the applied voltage VB of liquid crystal cell B has a larger number of polarity reversals, so its effective value is lower. Since the display brightness becomes low, brightness unevenness occurs.

In this way, in frame inversion, when selected cells and non-selected cells on the same data electrode are arranged alternately, the number of polarity inversions of the voltage applied to the liquid crystal cell on that data electrode is When selected cells or non-selected cells are arranged consecutively, the number of polarity reversals of the voltage applied to the liquid crystal cell on the data electrode is small, so the display brightness of the liquid crystal cell on both data electrodes is different. become. That is,
This results in uneven brightness. Also, in the case of line reversal,
As shown in FIG. 8, the number of times the applied voltage polarity is reversed is opposite to that in the case of frame reversal.

FIG. 11 is an explanatory diagram of the influence of the number of applied voltage polarity reversals,
The horizontal axis is the ratio of the time constant of the liquid crystal cell to the scanning period T (k/
T), and the vertical axis shows the effective voltage ratio [%] and the rate of decrease in transmittance [%]. Further, curve (a) shows the case where the number of polarity inversions is small, and curve (b) shows the case where the number of polarity inversions is large.

For example, when k/T is set to 0.03, the effective voltage ratio when the number of polarity inversions is small, that is, about 98.8% of the effective voltage when there is no polarity inversion.

On the other hand, when the number of polarity inversions is large, the effective voltage ratio is approximately 98.4. That is, as the number of polarity inversions increases, the effective voltage decreases. Also, the rate of decrease in transmittance is
Corresponds to the effective voltage ratio, and if the number of polarity reversals is small, it is approximately 1
The reduction will be 8%, but if there are many polarity reversals, the reduction will be approximately 23%.
% decrease, resulting in uneven brightness. especially,
As the time constant k of the liquid crystal cell increases, the rate of decrease in transmittance due to the difference in the number of polarity inversions increases, resulting in a disadvantage that the display quality deteriorates due to the influence of the display pattern.

An object of the present invention is to improve display quality by reducing variations in effective voltage applied to liquid crystal cells.

[Means for Solving the Problems] The method for driving a liquid crystal display device of the present invention removes the influence of the display pattern by temporarily setting the voltage applied to the liquid crystal cell to OV every scanning period. This will be explained with reference to FIG.

Scanning electrode 2-1 of simple matrix type liquid crystal display panel 1
A composite voltage of the scan voltage from the scan driver 5 and the data voltage from the data driver 6 is applied to the liquid crystal cells 4-11 to 4-nm at the intersections of ~2-n and the data electrodes 3-1 to 3-m. In a method for driving a liquid crystal display device that performs display according to display data, the liquid crystal cell 4 is
The device is driven by providing a period in which the applied voltage of -11 to 4 nm becomes OV.

[Effect]

Since the voltage applied to the liquid crystal cells 4-11 to 4-nm is set to Ov for each scanning period, even if the polarity of the applied voltage is not reversed, the rising and falling edges of the applied voltage are different from each other during each scanning period. This is equivalent to polarity reversal. Therefore, variations in the effective value of the applied voltage of each liquid crystal cell 4-11 to 4-nm due to the display pattern do not occur.

That is, display quality can be improved.

〔Example〕

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

FIG. 2 is a block diagram of an embodiment of the present invention, in which 11 is a simple matrix type liquid crystal display panel, 12-1 to 12-n
are scanning electrodes, 13-1 to 13-m are data electrodes, l4
-11 to 14-nm is a liquid crystal cell, 15 is a scan driver,
16 is a data driver 17 which is a display control section, and 18 is a monomultipiperator. From the display control unit 17'l,
Display data
and Law Dovals 1. P and a polarity inversion signal DF are applied to the decoder driver 1G, and a polarity inversion signal DF, a scanning signal YD, and a shift clock pulse YCP are applied to the scanning driver 15. Also, a load pulse LP is applied to the multivibrator 18, and its output signal is applied as an enable signal EN to the driver 16 and the scan driver 15.

Figure 3 is an explanation of the operation. As with the conventional example, +, X':
, not shown in (a), serial display Y-ta for one scanning electrode X l
') and the shift clock pulse x c p shown in (b)
, = is de~.

When the display data XI) for C11 scanning electrodes is shifted, a load pulse LP shown in FIG. 1C is applied and loaded to the output section of the data driver 16. Also, mono multivibe 17-ta 18 is
Triggered by load pulse 1, P shown in tel, (
(As shown in 11, the enable signal EN for a period shorter than one scan period is sent to the scan driver 15 and the data driver 1.
Add to 6.

The scanning driver 15 and the data driver 16a receive the input signal 1. when the input signal EN from the monomagnetic driver 1, data driver 18 is "0". ’”Output OV2, “1”
4, which outputs the scanning voltage and the data voltage at the time of 4, and as shown in (e)-([1), the scanning voltage is sequentially output from the scanning driver 15 and applied to the scanning electrode, and the data driver 15 outputs the scanning voltage and the data voltage. 16, a data voltage according to the display Y-YXD is applied to the data electrodes 13-1- and 13-m. Therefore, the voltage applied to the liquid crystal cell of the data electrode E is (1
) is controlled to be 0■ in each scanning period, as shown in (3). That is, regardless of the display pattern, the applied voltage of each liquid crystal cell 14-11 to 14-nm0 has a period in which it becomes 0 in every scanning period, regardless of the presence or absence of polarity reversal, and the applied voltage expires. The variation in values is reduced.

In the above embodiment, the period in which the voltage applied to the liquid crystal cell is set to OV is formed using a mono-multivibrator, but it is also possible to form it using other configurations. . For example, shift clock pulse XCP
It is also possible to count the period with a counter and determine the period during which it is 0■.

FIG. 4 is an explanatory diagram of a seventh embodiment applied to line inversion, in which the scanning voltage applied to the selected scanning electrode and the data voltage applied to the selected data electrode are applied at different times.

Therefore, the voltage applied to the synthesized liquid crystal cell is
(It consists of the voltages -Vo and -Vo, and includes a period in which the voltage is 0.

Also, the scanning voltage applied to the non-selected scanning electrodes is (■).

/a and (11/a)Vo, and the data voltage applied to the non-selected data electrodes is (2/a)VO and (
12/a) voltage of Vo, respectively OV
Therefore, the applied voltage of unselected cells is
+(2/a)V.

and 1. It consists of the voltages OV, -(2/a)Vo, and OV, and the voltage applied to the half-selected cell is →-(1/a)V(
The voltage between 1, OV, (1/a) Vo and 0■,
Or →-(1-2/a)Vo, OV and (12/a)V
It consists of the voltages o and OV.

As mentioned above, every scan period. Including the period of 0■
Therefore, regardless of the display pattern, the number of times the voltage applied to the liquid crystal cell becomes 0, that is, the number of rising and falling times is the same, and brightness unevenness can be reduced.

FIG. 5 is an explanatory diagram of an embodiment applied to frame inversion, and the scanning voltage applied to the scanning electrode S1 in FIG.
S 1 , the data voltage applied to the data electrode D1 is V
The voltage applied to Dl and data electrode D2 is YD2, and the voltages applied to liquid crystal cells A and B are shown as VA and VB. Also, for DF, “0” is used to invert the polarity every frame.
The polarity inversion signal of "1" and YD are the scanning signals.

The scanning voltage is applied to the scanning (scanning driver 1 in synchronization with the δ number YD).
Scanning electrodes 12-1 to 12-n! Please apply. By providing a period of 0 for each of the scanning voltage VSI and the data voltages D1 and YD2, the liquid crystal cell A,
A period of 0 is also formed for the applied voltages VA and VB of B, and the number of times that the applied voltages VA and VB fall to OV and rise from OV is the same regardless of the display pattern. Therefore, variations in the effective value of the voltage applied to the liquid crystal cell are reduced, and display quality can be improved.

The above-mentioned period of 0■ is due to the time constant of the liquid crystal cell or the scanning period T.
This O
As the period of V becomes longer, the effective value of the applied voltage becomes lower, so approximately 10% of the scanning period T is appropriate.

〔Effect of the invention〕

As explained above, the present invention provides liquid crystal cells 4-11 to 4
-nm applied voltage with a period of OV for each scanning period, regardless of the display pattern,
Since the number of rising and falling times of the applied voltage of the liquid crystal cells 4-11 to 4-nm is the same, thereby eliminating variations in the effective value of the applied voltage, when a simple matrix type large-screen liquid crystal display panel 1 is used. However, it has the advantage of improving display quality.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the operation of an embodiment of the present invention.
Fig. 4 is an explanatory diagram of an embodiment applicable to line inversion, Fig. 5 is an explanatory diagram of an embodiment applied to frame inversion, Fig. 6 is an explanatory diagram of a conventional example, and Fig. 7 is an explanatory diagram of the operation of the conventional example. , FIG. 8 is an explanatory diagram of the applied voltage waveform of the conventional example, FIG. 9 is an explanatory diagram of the display pattern, and FIG. 10 is an explanatory diagram of changes in the applied voltage of the liquid crystal cell.
FIG. 11 is a diagram illustrating the influence of the number of applied voltage polarity reversals. ■ is a liquid crystal display panel, 2-1 to 2-n are scanning electrodes, 3-
1 to 3-m are data electrodes, 4-11 to 4-nm are liquid crystal cells, 5 is a scan driver, and 6 is a data driver.

Claims (1)

[Claims] Scanning electrodes (
The scanning voltage from the scanning driver (5) and the data driver ( In the method for driving a liquid crystal display device that performs display according to display data by applying a composite voltage with the data voltage from 6), the liquid crystal cells (4-11 to 4-4) are applied for each scanning period. nm)
A method for driving a liquid crystal display device, characterized in that a period in which an applied voltage is 0 V is provided to perform display according to the display data.