JPS6355590A - Driving of liquid crystal display device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an active matrix type liquid crystal display device in which each pixel is provided with a switching element.

(Prior Art) In recent years, flat displays have been actively developed. Among these, active matrix type liquid crystal display devices, in which each pixel is equipped with an active element for switching, are capable of ■capable of displaying moving images, ■obtaining halftones, and ■achieving high-quality display with little crosstalk between pixels. can. □It has many advantages, such as □Full-color display is possible by using color filters, and is expected to be used in the future.

By the way, when driving a liquid crystal, AC driving is generally used in order to prevent the characteristics of the liquid crystal from deteriorating. Therefore, in order to display a television image, for example, the voltage applied to the liquid crystal pixels is inverted for each field or frame in accordance with the current standard television system.

Especially now that the degree of integration of liquid crystal pixels is increasing.

It is conceivable that interlaced driving may be adopted for liquid crystal display devices, and in this case, polarity reversal cannot be performed unless the period is one frame.

When driving a liquid crystal with alternating current, the display contrast can be maintained constant even if the polarity is reversed as long as the voltage is the same. However, in active matrix liquid crystal display devices,
Is it per pixel for the purpose of simplifying the structure? Since no 7-product capacitor is provided, the voltage applied to the liquid crystal is partially attenuated in one frame period.

Furthermore, due to parasitic capacitance between the address line and the pixel electrode (including the transistor electrode), the pixel voltage may change due to a voltage change on the address line. For this reason.

AC drive, where the magnitude of the voltage is constant and only the polarity is reversed, becomes difficult. If the magnitude of the voltage changes each time the polarity is reversed in this way, the magnitude of the voltage applied to the liquid crystal will change every frame period, and the contrast will change every twice the frame period. Therefore 15)1
There was a problem in that the flicker of the z signal was noticeable.

(Problem to be solved by the invention) The present invention was made based on this problem.

The object of the present invention is to provide a method for driving a liquid crystal display device that can display a flicker-free, high-quality image even in a liquid crystal display device having a large capacity of pixels.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides for controlling the polarity of the voltage applied to each pixel in a temporal manner when driving an active matrix type liquid crystal display device in which each of a plurality of pixels is provided with a switching element. It is characterized by sending a signal to invert the polarity for each data line so that the polarity is inverted at a constant period and also spatially inverted between adjacent pixels.

(Function) In the active matrix method, it is possible to increase the degree of pixel integration, and it is also possible to realize a display device with a pixel count comparable to or greater than the resolution of television broadcasting. As described above, if the degree of integration is high, it becomes difficult for the human eye to separate pixels, and contrast differences between adjacent pixels do not pose much of a problem.

According to the present invention, in addition to inverting the polarity of the voltage applied to each pixel in one field period or one frame period, the polarity of the voltage applied to each pixel is also inverted spatially for each adjacent data line, that is, pixels connected to that data line. Since the polarity of the applied voltage is reversed, the contrast difference due to the difference in polarity is made uniform as a whole, and there is no difference in contrast between fields or frames.

Therefore, according to the present invention, it is possible to provide a part of an active matrix type 4 type liquid crystal display device that is capable of displaying high-quality images without blur or glare.

(Example) Hereinafter, an example of the present invention will be described with reference to the negative side.

FIG. 1 shows a block diagram of a liquid crystal display device according to the invention.

In FIG. 1, address lines ADI of the liquid crystal panel 10,
AD2. ... is a line that selects pixels in the horizontal direction,
Data lines DI, D2. ... is a line for selecting pixels in the vertical direction. Odd address line AD of this liquid crystal panel 10
I.

AD3. The first address line drive circuit 11 is connected to the same even address aAD2 . AD4. A second address input line driver WJJ circuit I2 is connected to the odd data lines Di, D3 . ... is connected to the first sample hold circuit 21, and the same even number data @D2,04
．． ... are connected to a second sample and hold circuit 22. Shift registers 23 and 24 are connected to each sample and hold circuit: 1.22. The polarity inversion signal forming circuits 25 and 26 output the polarity inversion signal S' and a polarity inversion circuit 10' having an opposite phase to the polarity inversion signal S' to the sample and hold circuits 21 and 22, respectively. Polarity inversion signal forming circuit 25.2
6 is composed of, for example, a polarity inversion circuit and a level shift circuit.

The liquid crystal panel 10 is an active matrix type panel as shown in FIG. 2, and has opposing ff! +1ic and data lines DI, D2. A switching transistor 17 is connected in series to each liquid crystal pixel 16 provided between the respective liquid crystal pixels 16, and the gate electrode of each transistor 17 is connected to each address line ADI, AD2, . It is configured by connecting to...

In such a configuration, a driving method using a non-interlace method and a driving method using an interlace method can be considered.

First, the case of non-interlaced method will be described. When a video signal S as shown in FIG. 3 is input to the polarity inversion signal forming circuits 25 and 26, the polarity inversion signal forming circuit 25
first generates a signal that inverts this video signal every frame period around the 0 level, and then shifts the O level, which is the center of inversion of the obtained signal, to generate a polarity inversion signal S. The amount of shift at this time is given so that the polarity inversion signal S' is always positive. On the other hand, the opposite phase extreme pressure inversion signal forming circuit 26 generates an opposite phase polarity inversion signal 10' which is further inverted with respect to the center of inversion of the extreme pressure inversion signal S'.

These extreme pressure inversion signals S' and 10' are input to sample and hold circuits 21 and 22, respectively. In the sample and hold circuits 21 and 22, the data lines Di and D of the liquid crystal panel IO are
The data signal to be supplied to 2 is sampled and generated.

Address lines ADI, AD2. . . are sequentially driven every horizontal scanning period (LH period) as shown in FIG.

This turns on the transistor 17 connected to the selected address line, and the LCD screen connected to that address line? A signal obtained by sampling the polarity inverted signals S' and 116 is applied to the electrode on the data line side. As mentioned above, the polarity inversion signals s' and s' are always positive potential signals, but the common electrode (counter electrode) C of the liquid crystal panel 10
By setting the voltage to a level at the center of 1 inversion, a voltage whose polarity is inverted will be applied to each adjacent liquid crystal pixel 16 with respect to one dress line 7. Here, to simplify the explanation, we ignore the drop in pixel voltage due to the overlap capacitance between the address line and the pixel electrode (including the source and drain electrodes of the transistor), but when this is taken into account, the voltage of the counter electrode C is reversed. It will be set smaller than the center level.

FIG. 4 shows the spatial arrangement of the polarities of the voltages applied to each liquid crystal pixel immediately after one frame of scanning.

That is, in a particular frame, as shown in FIG. A positive voltage is applied to the liquid crystal pixels connected to the even data lines D2 . D4.・
A negative voltage is applied to the liquid crystal pixels connected to ....

On the other hand, in the next frame, odd number data aD1. D3. A negative voltage is applied to the liquid crystal pixels connected to the even data aDz, D4 . A positive voltage is applied to the liquid crystal pixels connected to... According to such a driving method, the polarity of the voltage applied to each pixel can be reversed every frame, and in addition, the polarity of the voltage can be reversed between horizontally adjacent pixels. Can be done. Therefore, differences in contrast due to different polarities are made uniform throughout, and an image with less flicker can be obtained. Furthermore, since the period in which the polarity inversion signal forming circuit switches the inversion signal is only one frame period, CMO5
Circuits using this lead to power savings. Furthermore, it is sufficient to switch during the vertical retrace period, so there is plenty of time, and there is no need for a circuit that takes special care in response.

In this embodiment, since the polarity inversion signals S' and 10' are always positive signals, there is no need to signal two power supplies with different polarities in the sample and hold circuits 25 and 26, and the configuration of the sample and hold circuits 25 and 26 is can be simplified.

Next, in the same liquid crystal display device having the configuration shown in FIG.
An interlaced drive method will be described. With non-interlaced driving, when dealing with normal television signals, when increasing the response speed of the liquid crystal, and when pixels are attenuated after writing, for example, flicker is noticeable at a frame period of 1130 seconds, so interlace driving is required. Mold drive is advantageous.

In this case, as shown in FIG. 5, in odd fields, odd address lines ADI, AD3 . . . . In the even field, the pulse is applied only to the even address AD2. AD4. It is only necessary to apply a pulse to...

FIG. 6 shows the polarity arrangement of pixel voltages in an interlaced driving method, and thin arrows in the figure indicate horizontal pixel columns to be accessed. First, in an odd field of a certain frame shown in al, odd address lines are accessed, and for each address line, the pixels connected to the odd data line are exactly
Pixels connected to even data lines become negative. At this time, the even address lines retain the state of the previous field, so
As can be seen from b2 in the figure, the polarity array in the horizontal direction is opposite to that of the pixels accessed in this field. In the even field of the same frame, as shown in a2, the pixels connected to the odd data line are positive, so the extreme pressures are aligned in the vertical direction.In the 0th order frame, the polarity of each data line is reversed. For,
The polar arrangement shown in bl, bl is realized.

In this way, even with interlaced driving, the voltage applied to each pixel can be reversed for each field, and the polarity of the voltage can be reversed between adjacent pixels for each address line. . Therefore, differences in contrast due to different polarities are made uniform throughout, and an image with less flicker can be obtained.

Although the polarity is reversed for each frame in FIG. 5, the polarity may be reversed between the odd field and even field of each frame. In this case, the polarity at 82 in FIG.
Alternatively, bl is the polar array of odd fields of each frame, and bl and at are the polar arrays of even fields.

In each of the embodiments described above, a sample and hold circuit is used, but if each pixel is driven point-sequentially, the sample and hold circuit can be omitted.

Also, although the data lines were drawn out to two opposing sides of the liquid crystal panel, there was no problem even if they were drawn out to the - side, and even though every other line sent signals of the same polarity.

For example, the same effect can be obtained by forming pairs of two and reversing the polarity for each adjacent pair. Furthermore, the polarity may be reversed for each address line, or the polarity distribution may be in opposite phases above and below the center of both surfaces, for example.

As described above, the present invention can be implemented with various modifications without departing from the spirit thereof.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a liquid crystal display device with less flicker even if the number of pixels increases.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a partial configuration of a liquid crystal panel of the device, and FIG. 3 explains the operation of the device. Figure 4 is a waveform diagram showing the polarity of the voltage applied to each pixel of the device, Figure 5 is a waveform diagram to explain another driving method, and Figure 6 is a diagram showing the polarity of the voltage applied to each pixel of the device. FIG. 3 is a diagram showing the polarity of voltage applied to each pixel realized by the driving method. 10...Liquid crystal panel, 11.12...Address line drive circuit, 21.22...Sample hold circuit, 25
...Polarity inversion signal forming circuit, 16...Liquid crystal pixel, 1
7... Transistor, 26... Opposite phase polarity inversion signal forming circuit. Agent Patent Attorney Yudo Nori Chika Kikuo Takehana D2 Figure 2 Figure 3 (a) (6) Figure 4

Claims (2)

[Claims] (1) Driving a liquid crystal display device characterized in that when driving an active matrix type liquid crystal display device, a signal is sent to invert each data line in order to spatially invert the polarity of the voltage applied to the pixel. Method. (2) Every other data line is drawn out to one end of the display section, and a signal of the same polarity is applied to each side, and a signal of opposite polarity is applied to the opposite sides. A method for driving a liquid crystal display device according to claim 1.