JPH02244024A - Method for driving liquid crystal display device - Google Patents

Abstract

PURPOSE:To nearly uniformize a voltage over the entire part of a screen so as to eliminate display unequalness by impressing the data voltages controlled in the direction where the attenuation component of a scanning voltage is compensated the further from a driving circuit for supplying the scanning voltage to scanning electrodes. CONSTITUTION:The scanning voltage Vs in display cells A, B and C, D near the driving circuit 11 maintains the voltage waveform applied from the driving circuit 11, but the scanning voltage Vs is display cells E, F and G, H farther from the circuit 11 is dulled by the resistance of the scanning electrodes and is dropped below the intrinsic voltage Vs0. The data voltages Vd1 to Vd640 to be applied to the data electrodes D1 to D640 are, therefore, decreased by as much as the attenuation component of the scanning voltage when the scanning voltage Vs to be impressed to the respective scanning electrodes is of a positive value. The brightness unequalness in the panel is eliminated in this way and the display of the excellent display quality is possible.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a method for driving a liquid crystal display device, particularly regarding how to apply a data voltage to compensate for attenuation of the scan voltage caused by scan electrode resistance. In order to eliminate display unevenness by making the voltage applied to the liquid crystal layer almost uniform over the entire screen, the opposing surfaces of a pair of insulating substrates are placed opposite each other with the liquid crystal layer in between. A plurality of data electrodes made of a transparent conductive film are arranged on one side, a plurality of scan electrodes made of a transparent conductive film are arranged on the other side so as to be perpendicular to the data electrodes, and a scanning voltage is applied to the scanning electrodes. When driving a simple matrix type liquid crystal display device in which a driving circuit to be supplied is arranged at one end of a scanning electrode, the data voltage applied to each data electrode is connected to a connecting portion between the scanning electrode and the driving circuit. The voltage is corrected to remove fluctuations in the difference voltage between the scanning voltage and the data voltage due to attenuation of the scanning voltage depending on the distance.

[Industrial application field]

The present invention relates to a method of driving a liquid crystal display device, and more particularly to a method of applying a data voltage to compensate for attenuation of scan voltage caused by scan electrode resistance.

Liquid crystal display devices, which are often used as display devices in office automation equipment and the like due to their thinness, include a simple matrix type and an active matrix type in which each pixel is driven by a switching element.

Among these, the simple matrix type has a pair of glass substrates facing each other with a liquid crystal in between, and a plurality of striped transparent electrodes are arranged in parallel on the opposing surfaces of each substrate, and these two sets of electrode groups are arranged in parallel. They are arranged perpendicular to each other,
The intersection of the picture electrodes constitutes a display cell.

The above-mentioned simple matrix type liquid crystal display device has the advantage of a simple structure, but when driving, the driving voltage decreases toward the end of the electrode stripe due to the relatively high resistance of the transparent electrode. There is a problem with doing so.

In order to increase the display capacity of a simple matrix liquid crystal display device, it is essential to solve this problem.

[Conventional technology]

In a simple matrix type liquid crystal display device, as shown in FIG. 2(a), the drive circuit 11 for the scan electrode S
On one side of the data electrode, driving circuits 12 and 12' are provided both above and below the data electrode, as shown, to supply a scanning voltage and a data voltage, respectively.

The reason why conventionally two drive circuits 12 and 12' were provided for the data electrodes was because the screen became larger and the number of scanning lines increased to 400.
However, in the case of liquid crystal display devices, the drive duty ratio cannot be made very large, so the screen is divided into 200 lines each on the top and bottom.
In order to supply data voltage separately for each,
Independent drive circuits 12 and 12' are provided on the upper and lower sides.

On the other hand, in order to keep the overall size of the device as small as possible, the driving circuit 11 for the scanning electrode S has to be arranged only on one side of the scanning electrode S. There is a problem in that the scanning voltage becomes slower as it goes to the display cell farther away from the extraction section.

The reason for this is that the transparent electrode (I
Due to the high sheet resistance of To), even if a pulse voltage with a waveform as shown in Fig. 2(b) is applied from the scanning electrode, the actual voltage applied to the display cell far from the electrode extraction part is This results in a dull waveform as shown in (C).

(Problem to be Solved by the Invention) Since the voltage applied to the liquid crystal is the difference between the scanning voltage and the data voltage, when the scanning voltage is attenuated in this way, the voltage applied to the liquid crystal becomes smaller. Therefore, display unevenness occurs in the simple matrix liquid crystal display device.

For example, S
In a yellow mode, blue mode, black and white mode, etc. liquid crystal display device that is composed of a TN type liquid crystal panel and a pair of polarizing plates, such attenuation of the scanning voltage appears as uneven brightness or uneven display color.

The present invention compensates for the attenuation of the scanning voltage so that the voltage applied to the liquid crystal layer is approximately uniform across the entire screen.
The purpose is to eliminate display unevenness.

[Means to solve the problem]

In the present invention, the data voltage is applied in a direction that compensates for the attenuation valve of the scan voltage as the distance from the drive circuit that supplies the scan voltage to the scan electrode increases.

[For production]

By compensating the attenuation of the scan voltage with the data voltage, the difference voltage between the scan voltage and the data voltage,
That is, since the voltage applied to the liquid crystal layer can be made substantially uniform, uneven brightness can be eliminated.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1(a) is a plan view of the above embodiment, and FIG. 1(b) is a waveform diagram for explaining the operation of this embodiment.

The liquid crystal display device of this embodiment shown in FIG. 1(a) is a normal simple matrix type liquid crystal display device, and there is no particular difference in structure.

In the circle shown by ■ in FIG.
, St, and the display cell A-D at the intersection of the leftmost data electrodes D+ and Dz on the right. ,
That is, the rightmost data electrode D & 4° on the screen, the data electrode to the left of it, 3°, and the uppermost scanning electrode S,
, S shows the positional relationship of display cells E-H at the intersection with ,S.

The display cells A to D are located closest to the connection between the drive circuit 11 and the scan electrode S, and the display cells E to H are located farthest from each other. [Hereinafter, to simplify the explanation, it will simply be described as being near or far from the drive circuit 11. ] In this embodiment, the liquid crystal display device is driven by a commonly used voltage averaging driving method.

In order to select the first scan electrode, that is, the topmost scan electrode S1 in the figure, the drive circuit 11 applies the scan voltage Vso to the scan electrode S1, and applies the above Vs to the next scan electrode S2, which is a non-selected scan electrode. (Applies a voltage Vsl lower than 1 to lower the voltage of all non-selected display cells. Drive circuit 11
In display cells A, B, C, and D that are close to each other, the scanning voltage Vs maintains the voltage waveform applied from the drive circuit 11, as shown in Figure 1), but in display cells that are far from the drive circuit 11, E.

At F, G, and H, the scanning voltage Vs is blunted by the resistance of the scanning electrode, and as shown by the solid line in the figure, becomes lower than the original voltage VSO shown by the dotted line.

Therefore, in this embodiment, the data voltages Vdt to Vd, . . . are applied to the data voltages Fix D+ to D64°. is made smaller by the attenuation of the scanning voltage when the scanning voltage Vs applied to each scanning electrode is a positive value. That is, the data voltages Vd, , Vd2 applied to the data electrodes D, D, near the drive circuit 11 remain at the normal voltage OV, but the data voltages V applied to the data electrodes D&391D&46 far from the drive circuit 11 are changed.
d639. Vd, 4° (display cell E.

The data voltage applied to F] is a voltage lowered by the attenuation of the scanning voltage as shown in the figure.

When the scanning voltage Vs is OV, no voltage attenuation occurs, so there is no need to change the data voltage Vd depending on the distance from the drive circuit . Therefore, the data voltages applied to display cells A and E, and B and F may be the same.

In the illustrated example, display cells A and E are selected points, and display cells B and F are half-selected points, and if there is no attenuation of the scanning voltage, the data voltage is determined depending on whether it is a selected point or a half-selected point. It is something that does not need to be changed depending on its location.

However, since the scanning voltage is attenuated by the resistance component of the scanning electrode S, in this embodiment, the attenuation of the scanning voltage is compensated for by controlling the data voltage as described above. The applied voltage, that is, the difference voltage between the scanning voltage Vs and the data voltage Vd, is applied to the drive circuit 11.
Irrespective of the distance from the selection point, the display cells A and E are in a negative line, and the half-selected point, and the display cells B and F are also in a negative line, so that uneven brightness does not occur.

On the other hand, the scanning voltage for non-selected points is Vs as shown in the figure.
l and Vs+" are applied. Vs, and Vs," are both smaller than the scanning voltage Vs6 for the selected point and V3
They are symmetrical with respect to 0/2, the voltages are both positive values, and never become OV. Therefore, these attenuate as the distance from the drive circuit 11 increases.

While the scanning voltage applied to the non-selected point is Vs,
Since the scanning voltage Vs6 is applied to the selected point,
As described above, a voltage that compensates for the attenuation is applied to the data voltage. Therefore, display cells E and 02 and display cells F and H have the same data electrodes D6, 9 and D64, respectively.
Since the voltage applied to the liquid crystal layer is above the display cell C,
It is the same between display cells D and H, and the voltage applied to the liquid crystal layer is compensated even at a non-selected point, regardless of the distance from the drive circuit 11.

However, when the scanning voltage for the selected point is O■, the data voltage is not compensated for depending on the distance from the drive circuit 11, so the display cells C and D near the drive circuit 11 and the display cells G and H far away In this case, slightly different voltages will be applied to the liquid crystal layer.

However, since this difference is a slight difference in the non-selected state, it is not visually noticeable and causes no problem in terms of display.

As described above, there is no difficulty in the circuit configuration or method for controlling the data voltage for each data electrode, and therefore there is no need to be particularly limited.

For example, by using an analog data driver, the voltage waveform input to the data electrodes can be made higher as the distance from the drive circuit 11 for the scan electrodes increases.

〔Effect of the invention〕

As explained above, according to the present invention, the uneven brightness within the panel, which has been a problem in the past, is eliminated, and display with excellent display quality becomes possible.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are detailed explanatory diagrams of the present invention, and FIG.
Figures (a) to (C) are explanatory views of conventional problems. In the figure, S, S, , S are scanning electrodes, and D. D + + Dt r D&! ? r Dha. is a data electrode, 11 is a scanning electrode drive circuit, 12.12' is a data electrode drive circuit, Vs+Vso+Vsl,
Vsl' indicates a scanning voltage, and Vd indicates a data voltage. bt (C) Figure 1 Dependency/1 town problem αθn Figure 2

Claims (1)

[Claims] A plurality of data electrodes (D) made of a transparent conductive film are disposed on one of the opposing surfaces of a pair of insulating substrates that are placed opposite to each other with a liquid crystal layer in between, and a plurality of data electrodes (D) made of a transparent conductive film are provided on the other side. A simple method in which a plurality of scan electrodes (S) made of conductive films are disposed perpendicular to the data electrodes, and a drive circuit (11) for supplying a scan voltage to the scan electrodes is disposed at one end of the scan electrodes. When driving a matrix type liquid crystal display device, a data voltage (Vd) is applied to each data electrode (D).
, removes fluctuations in the differential voltage (Vs-Vd) between the scan voltage and the data voltage due to attenuation of the scan voltage (Vs) depending on the distance from the connection between the scan electrode (S) and the drive circuit (11). A method for driving a liquid crystal display device, characterized in that the voltage is corrected to compensate for the voltage.