JPH0488770A - Drive method for display device - Google Patents

Abstract

PURPOSE:To realize video display with high picture quality without causing a stripe pattern between lines of picture elements by differentiating the polarity of a signal voltage applied to picture elements of one line from columns of picture elements. CONSTITUTION:One row drive circuit 36a of row drive circuits 36a, 36b in pairs is connected to an odd numbered order scanning signal line 32 counted from an upper side of a liquid crystal panel 31 and the other row drive circuit 36b connects to an even order numbered scanning signal line 32. A timing control circuit 38 operates simultaneously the two row drive circuits 36a, 36b for one field in two fields forming one frame and the even numbered order row drive circuit 36b is started with a delay by one horizontal scanning period from the odd numbered order row drive circuit 36a.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for driving a display device such as a matrix type liquid crystal display device used as a color television receiver.

Conventional technology Figure 7 shows an active matrix drive type liquid crystal panel 1.
FIG. 8 is a block diagram schematically showing a conventional liquid crystal display device using the at, and FIG. 8 is a diagram showing a partial configuration of the liquid crystal panel 1.

The liquid crystal panel 1 has a plurality of scanning signal lines 2 arranged in parallel to each other and a plurality of data signal lines 3 arranged in parallel to each other so as to intersect with the scanning signal lines 2, and includes a scanning signal i12 and a data signal. At each intersection with the line 3, an independent picture element 4 is formed. Now, if the number of scanning signal lines 2 is N and the number of data signals 113 is M, then
A total of MXN picture elements 4 are arranged in a matrix on this liquid crystal panel 1.

Each picture element 4 is connected to a scanning signal line 2 and a data signal line 3 through a switching element 5, and a selection signal for selecting driving the picture element 4 to a display state is applied from the scanning signal line 2. A signal voltage corresponding to display data is applied to the picture element 4 from the signal line 4 .

A row drive circuit 6 is connected to the scanning signal line 2, and a column drive circuit 7 is connected to the data signal line 3. The row drive circuit 6 outputs the selection signal, and the column drive circuit 7 outputs the signal voltage.

The upper E row drive circuit 6 includes a shift register (not shown) that performs a shift operation in synchronization with the horizontal scanning period of the input video signal, and is driven by the operation of the shift register.

The column drive circuit 7 also includes a similar shift register (not shown), and has an operation of sampling the video signal in synchronization with the same horizontal scanning period, shifting the sampled signal, and outputting it to the corresponding data signal line 4. It will be done.

That is, when the row drive circuit 6 outputs a selection signal to a certain scanning signal line 2, M×N picture elements 4
In the liquid crystal panel 1 including the above, M signal voltages corresponding to video signals for one scanning period are applied to the column drive circuit for one row of M picture elements 4 connected to the scanning signal line 2. 7 through each data signal line 3, and one line of video signals is displayed on one row of picture elements 4. This operation is sequentially repeated N times in accordance with the arrangement order of the scanning signal lines 2 in each horizontal scanning period, thereby displaying one screen of video.

The timing control circuit 8 controls the row drive circuit 6 based on the synchronization signal input through the synchronization signal line 9.
, a circuit for controlling the operations of the column drive circuit 7 and the polarity inversion circuit 10.

The polarity inversion circuit 10 is a circuit for inverting the polarity of the video signal input from the video signal line 11 for the purpose of AC driving the liquid crystal panel 1.

The polarity-inverted video signal is input to the column drive circuit 7, and the column drive circuit 7 outputs an alternating current data signal.
As a result, AC driving of the liquid crystal panel 1 is performed.

The above-mentioned liquid crystal display device is an example in which the number of scanning signal lines 2 is set to the number (220 to 240) corresponding to the number of effective scanning lines for one field of television signal according to the Japanese domestic standard NTSC system. Since the display device lacks the number of scanning signal lines, its vertical resolution is inferior to that of a television receiver using a cathode ray tube.

Therefore, as an alternative to this, a liquid crystal display device using a liquid crystal panel in which the number of scanning signal lines has been increased to the number of effective scanning lines (440 to 480 lines) for one frame of television signal according to the Japanese domestic standard NTSC system has been proposed. There is.

In this liquid crystal display device, as a method of driving the scanning signal line,
A method is adopted in which a selection signal is simultaneously applied to two adjacent scanning signal lines, scanning is performed every two scanning signal lines, and the combination of the two scanning signal lines is changed for each field.

9 and 10 are timing charts showing the scanning signal line selection operation in the driving method, of which FIG. 9 shows the timing chart for the odd field.
FIG. 10 shows timing charts for even fields.

In Figures 9 and 10, Figures 9 (1) and 10
Figure (1) shows the waveform of the horizontal synchronizing signal H5ync, and for example, Figures 9 (2) and 10 (2) show the waveform of the selection signal OGI applied to the first scanning signal line counting from the top side of the liquid crystal panel. The waveforms are shown in Figure 9 (3) to Figure 9 (9).
), FIG. 10(3) to FIG. 10(9) respectively show the waveforms of selection signals OG2 to OG8 applied to the second to eighth scanning signal lines.

By employing such a scanning method, the signals of each line in the original video signal and the positions on the liquid crystal panel where these signals are displayed have a relationship as shown in FIG. 11.

That is, in the odd field, line numbers 1, 1, 2, 2, 3, 34, 4, . ... signals are displayed, and in even fields, line number 1
,2,2.3,3,4°4.5. ... signals are displayed respectively.

As is clear from FIG. 11, the display position in the even field is shifted by one scanning signal line from the odd field, so that the display appears to be threaded between the lines displayed in the odd field. As a result, display is performed in accordance with the original interlace, and vertical resolution equivalent to that achieved when using a cathode ray tube is achieved.

By the way, in this liquid crystal display device, in order to reduce flickering on the screen, a method is used in which the polarity of the voltage applied to the video signal supplied to the data signal line is reversed every horizontal scanning period. The time transition of the polarity of the applied signal voltage is shown in either FIG. 12 or FIG. 13.

That is, each picture element has 2 fields (1 frame).
A signal whose polarity is inverted each time is given.

As a result, although the intensity of the liquid crystal transmitted light of each picture element fluctuates by 15H2, when multiple lines are viewed as a unit of display area, there are four
There is a phase light intensity fluctuation, and these light intensities cancel each other out, and the fundamental frequency of the light intensity fluctuation is 60H.
It becomes z. In other words, the appearance is good, the frequency of light intensity fluctuations is improved four times as much as when focusing on individual picture elements, and flicker is almost invisible.

Problems to be Solved by the Invention However, in the conventional liquid crystal display device described above,
Since a signal voltage of the same polarity is always applied to a group of picture elements in a row, the phase of light intensity fluctuations for that one row will be aligned, resulting in subtle differences in brightness between multiple picture element rows. will be visually recognized as a horizontal striped pattern. Furthermore, since the striped pattern appears to flow from top to bottom or from bottom to top, there is a problem in that the image quality is significantly degraded.

Therefore, an object of the present invention is to provide a method for driving a display device that does not cause striped image quality disturbance and has excellent vertical resolution.

Means for Solving the Problems In the present invention, in an odd field, a screen in which a plurality of picture elements are arranged in a matrix is divided into two adjacent rows of picture elements.
The picture elements are grouped into a plurality of groups, and signal voltages with polarities reversed between the front and rear groups are applied to the picture elements according to the arrangement order of the groups. One frame is displayed by grouping two adjacent rows of picture elements into multiple groups, and applying signal voltages whose polarities are inverted between the front and rear groups to the picture elements according to the arrangement order of the groups. In a method for driving a display device in which the polarity of the signal voltage is reversed in the next frame and the picture elements are AC driven, the polarity of the signal voltage applied to one group of picture elements is This is a method for driving a display device characterized in that the polarity is also made different between columns of picture elements within a group.

According to the present invention, the polarity of the signal voltage applied to one row of picture elements differs between columns of picture elements, so that striped patterns do not occur between rows of picture elements. Good video display without striped interference can be obtained.

Embodiment FIG. 1 is a block diagram showing a schematic configuration of a display device to which a driving method according to an embodiment of the present invention is applied, and FIG. 2 shows signal lines 32 and 33 in a liquid crystal panel 31 of the display device.
FIG. 3 is a diagram showing the arrangement of a part of the liquid crystal panel 31. FIG.

The display device in this case is an active matrix drive type liquid crystal display device, which has a plurality of picture elements 34 arranged in a matrix.
A pair of row drive circuits 36a, 36 that line-sequentially apply selection signals to the scanning signal lines 32 arranged parallel to each other along each row of the picture elements 34.
b, a pair of column drive ports 137a and 37b that apply signal voltages to the data signal lines 33 arranged parallel to each other along each column of the picture elements 34, and an image input through the video signal line 41. a polarity inversion circuit 40a that inverts the polarity of the signal at a constant cycle and supplies it to the one-column drive circuits 37a and 37b;
40b, and a timing control circuit 38 that controls the operations of the row drive circuits 36a, 36b, column drive circuits 37a, 37b, and polarity inversion circuits 40a, 40b based on a synchronization signal input through the synchronization signal line 39.

Each picture element 34 of the liquid crystal panel 31 is provided with a thin film transistor (ThinFils Tr) as a switching element.
(hereinafter abbreviated as TFT) 35 are arranged in correspondence, and the picture element 34 is connected to the data signal line 33 via the TFT 35, while the gate electrode of the TFT 35 is connected to the corresponding scanning signal line 32. The TFT 35 is turned on by a selection signal applied to the scanning signal line 32, and a signal voltage from the data signal line 33 is applied to the picture element 34 through the TFT 35.

Each picture element 34 is constructed with a liquid crystal layer interposed between the picture element ti and the counter electrode, and the drain electrode of the TFT 35 is connected to the picture element electrode, and the source electrode of the TFT 35 is connected to the corresponding data signal line 33. has been done. The signal voltage ' is applied to the picture element electrode, and the state of the liquid crystal layer constituting the picture element 35 changes depending on the voltage applied between the picture element electrode and the counter electrode, and the amount of light transmitted through the picture element 35 changes. is controlled.

Specifically, when a selection signal is applied to a certain scanning signal line 32, that is, when the voltage level of a certain scanning signal line 32 becomes sufficiently high, the TF connected to that scanning signal line 32
T35 is turned on, current flows between its source electrode and drain electrode, and charge is stored in the picture element electrode. after that,
When the voltage level of the same scanning signal line 32 returns to its original low value, the TFT 35 is turned off, and the resistance between the source and drain becomes high, and the charge stored in the picture element electrode is retained as it is. A potential difference between the potential of the picture element electrode and the counter signal potential applied from the counter electrode line 49 to the counter electrode is applied to the liquid crystal layer of the picture element 35 for a period until the TFT 35 is turned on again. By repeating this operation according to the arrangement order of the picture element rows, an image is displayed on the liquid crystal panel 31.

Among the pair of row drive circuits 36a and 36b described above,
One row drive circuit 36a is connected to odd-numbered scanning signal lines 32 counting from the upper side of the liquid crystal panel 31, and the other row drive circuit 36b is connected to even-numbered scanning signal lines 32. That is, one row drive circuit 36a is a circuit for driving odd-numbered scanning signals 1132, and the other row drive circuit 36b is a circuit for driving even-numbered scanning signal lines 32.

These row drive circuits 36a and 36b each include a shift register, and are configured to output a selection signal in accordance with a shift operation synchronized with the horizontal scanning period.

In the timing control circuit 38, the two row drive circuits 36a and 36b are operated simultaneously in one of the two fields constituting one frame, and in the other field, the even-numbered row drive circuit 36b is operated simultaneously. Control is performed to start the row drive circuit 36a for odd numbers one horizontal scanning period later than the row drive circuit 36a for odd numbers.

That is, in an odd field, two adjacent rows of picture elements are grouped into multiple groups, and selection signals are sequentially applied according to the arrangement order of the groups.
An operation is performed in which picture elements in two adjacent rows spanning the group are grouped into a plurality of groups, and selection signals are sequentially applied in accordance with the arrangement order of the groups.

Regarding the above-mentioned pair of column drive circuits 37a and 37b, one of the column drive circuits 37a is connected to the liquid crystal panel 3.
The other column drive circuit 37b is connected to the odd-numbered data signal line 33 counting from the left side of 1, and the other column drive circuit 37b is connected to the even-numbered data signal line 33. That is, one column drive circuit 37a is a circuit for driving odd-numbered data signal lines 33, and the other column drive circuit 37b is a circuit for driving even-numbered data signal lines 33.

These column drive circuits 37a and 37b also have the function of repeating sampling, internal transfer, and output operations of video signals in synchronization with the horizontal scanning period, similar to column drive circuits in conventional liquid crystal display devices.

These column drive circuits 37a and 37b are supplied with video signals whose voltages have opposite polarities from respective polarity inversion circuits 40a and 40b.

The operation is achieved by the timing control circuit 38 controlling each polarity inverting circuit 40a, 40b.

FIG. 4 is a block diagram showing an example of a reference signal generation circuit 42 incorporated in the timing control circuit 38 for inverting the polarity of a data signal.

The synchronization separation circuit 43 is a circuit for separating the synchronization signal input from the synchronization signal line 39 into a horizontal synchronization signal, a vertical synchronization signal, and a field signal for determining odd and even fields. The flip-flop 44 is a circuit that frequency-divides the horizontal synchronization signal output from the synchronization separation circuit 43 to generate a signal whose polarity is inverted every horizontal scanning period. This circuit divides the frequency of the vertical synchronizing signal output from 43 twice to generate a signal whose polarity is inverted every frame. The two signals thus generated are input to the next-stage exclusive OR gate 47, and a signal that is inverted every horizontal scanning period and every frame is generated. This signal and a signal obtained by inverting this signal by an inverter 48 are input to two systems of polarity inverting circuits 40a and 40b, and thereby the voltage polarity of the video signal input to the odd number column drive circuit 37a and the even number The voltage polarities of the video signals input to the column drive circuit 37b for the number are inverted with respect to each other.

FIGS. 5 and 6 are diagrams showing the time transition of the polarity of the signal voltage applied to each picture element during display driving by the liquid crystal display device.

That is, each picture element has 2 fields (1 frame).
A signal whose polarity is inverted each time is given.

The screen of each field is grouped with two adjacent picture elements as one group. Within one group, the polarity of the signal voltage is the same between the upper and lower rows, but the polarity of the signal voltage is the same between the odd and even fields. The alignment is shifted by one line. These are the same as in the case of a conventional liquid crystal display device, but here, the polarities of the signal voltages applied are different between picture elements in even-numbered columns and picture elements in odd-numbered columns in the same group.

As a result, image quality interference in the form of horizontal stripes does not occur between picture elements, and a good image display can be obtained.

Although the embodiment described above is applied to an active matrix drive type liquid crystal display device, the present invention can be similarly applied to a dynamic drive type liquid crystal display device.

Effects of the Invention As described above, according to the method for driving a display device of the present invention,
The polarity of the signal voltage applied to each row of picture elements is made to differ between rows of picture elements, which eliminates striped patterns between rows of picture elements and enables high-quality video display. can do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a liquid crystal display device to which a driving method according to an embodiment of the present invention is applied, FIG. 2 is a diagram showing the arrangement of signal lines in the liquid crystal display device, and FIG. 3 is a diagram showing the arrangement of signal lines in the liquid crystal display device. A diagram showing a partial configuration of a liquid crystal panel in a liquid crystal display device, FIG. 4 is a block diagram showing a configuration of a reference signal generation circuit in the liquid crystal display device, and FIGS. 5 and 6 each show a picture element of the liquid crystal display device. 7 is a block diagram showing the configuration of a liquid crystal display device to which a conventional driving method is applied, and FIG. 8 is a diagram showing one of the liquid crystal panels in the liquid crystal display device. 9 and 10 are timing charts showing the scanning timing in each field of the liquid crystal display device, and FIG. 11 shows the display position of the original video signal on the liquid crystal panel of the liquid crystal display device. 12 and 13 are diagrams showing the time transition of the polarity of the signal voltage applied to the picture elements of the liquid crystal display device, respectively. 31...Liquid crystal panel, 32...Scanning signal line, 33...
...Data signal line, 34...Picture element, 35...TFT
, 36a, 36b... row drive circuit, 37a, 37b□-
・Column drive circuit, 38... Timing control circuit, 40a, 40b... Polarity inversion circuit, 42... Reference signal generation circuit Agent Patent attorney Number of strokes Keiichi Figure 1 (1) H5ync Figure 10 Figure 2] Cause

Claims (1)

[Claims] In an odd field, a screen in which a plurality of picture elements are arranged in a matrix is grouped into a plurality of groups with two adjacent rows of picture elements as one group, and the polarity is changed between the preceding and succeeding groups. Signal voltages that are inverted with each other are applied to the picture elements according to the arrangement order of the groups, and in the even field, the screen is divided into multiple groups, with two adjacent rows of picture elements as one group, spanning two adjacent groups in the odd field. The display of one frame is completed by applying signal voltages whose polarities are inverted between the groups before and after the pixels to the picture elements in accordance with the arrangement order of the groups, and in the next frame, the polarity of the signal voltages is In a method for driving a display device in which the picture elements are driven with alternating current by inverting the polarity of the picture element, the polarity of the signal voltage applied to the picture elements of one group may be different between columns of picture elements within the group. A method for driving a display device, characterized in that: