JP2546332Y2 - Drive circuit for liquid crystal display - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal display device which has high contrast, has little flicker, and has few defects.

[0002]

2. Description of the Related Art Even when the number of pixels is increased by increasing the number of rows of a color matrix liquid crystal display from, for example, 250 to 500, and the resolution is improved, flicker on the screen due to AC driving of the liquid crystal is made inconspicuous. There has been a method of driving a liquid crystal display device (Japanese Patent Application Laid-Open No. 62-113129).

FIG. 7 shows a pixel signal diagram according to the position of a liquid crystal display device in which two frames are defined as one cycle by sampling video signals of different fields for each row.

FIG. 7A shows a video signal 1 forming one frame by odd and even fields.

FIG. 7B shows a pixel signal 2 applied to a pixel electrode of the liquid crystal display device, which is selected once at a selection point 3 in one frame, and is inverted for each frame of a video signal. As a result, the polarity is inverted in one frame.

Referring to FIG. 7B, the pixel signal below (b) is (c), and the pixel signal on the right of (b) is (d).
Thus, the pixel signals obliquely below (b) can be expressed as (e).

In the above driving method, as shown in FIG. 7, two adjacent rows have the same polarity in the interlaced field, and have the opposite polarity in the next field, as shown in FIG. I was

Although the resistance of the liquid crystal in the liquid crystal display device is usually large, a certain amount of leak current flows, so that the driving method of FIG. 7 for holding a selected one field signal for one frame is a low resistance liquid crystal. In a liquid crystal display device using a material, the contrast was sometimes reduced.

On the other hand, there has been a structure in which a plurality of scanning lines or video signal lines are simultaneously driven to reduce the density of pixels, thereby reducing the cost of the TFT substrate (Japanese Patent Application Laid-Open No. 2-130524).

FIG. 8 shows a display diagram when adjacent scanning lines or image lines (video signal lines) are connected two by two and driven simultaneously.

FIG. 8A shows an original signal 4 as a liquid crystal display before connection, and FIG. 8B shows a display when two adjacent scanning lines are connected. (C) shows a display when two adjacent scanning lines and video signal lines are connected.

As is clear from FIG. 8, if the simultaneous selection is fixed, the original signal may not be faithfully reproduced on the screen of the liquid crystal display device.

[0013] NTSC signals and HDTV signals are transmitted to a television receiver in an interlace system.

While a row of the interface signal is selected, a scanning line of another row which is not selected is also continuously selected.
There has been a driving circuit of a liquid crystal display device which supplies an interpolation signal to a pixel electrode in another row from a video signal line and displays an image in a non-interlaced manner by double-speed line sequential scanning in order to improve the image quality (Japanese Patent Laid-Open No. Hei 2 (1994)). -65577).

FIG. 9 shows a drive circuit diagram of a liquid crystal display device which performs double-speed line sequential scanning on an input video signal of an interface system by using an interpolation signal.

In FIG. 9, the video signal 1 is held by the horizontal scanning period holding circuit 5 with the number of video signals corresponding to the number of columns.

The field discriminating circuit 6 discriminates between odd and even fields of the video signal 1.

The adder 7 adds the video signals of the adjacent fields and makes the amplitude about half by the amplifier 8 to obtain the average value (interpolation signal) of the video signals.

The mixing circuit 9 works to shift the timing of the interpolation signal and the video signal, and is then compressed by half the time by the double speed conversion circuit 10 to perform double speed line sequential scanning.

However, the above circuit has a disadvantage that a large amount of memory and a high-speed and complicated signal processing are required.

It has also been proposed that two lines selected in simultaneous driving of the scanning lines are made variable for each field.

However, according to this driving method, there is a problem that flicker occurs because the driving frequency is lowered.

[0023]

SUMMARY OF THE INVENTION An object of the present invention is to provide a driving circuit for a simple flickerless liquid crystal display device which does not require a memory and has a high degree of reproduction of an original signal and a high contrast.

[0024]

According to the present invention, a pixel electrode is provided near an intersection between a scanning line of M rows and a video signal line of N columns (M and N are integers). A driving circuit for a liquid crystal display device having electrodes, comprising: a synchronization control circuit for supplying different timing signals to left and right scanning line driving circuits; and an inversion circuit for inverting a video signal in one frame and one horizontal scanning period. M rows of scanning lines are simultaneously selected two by two, and the scanning start row is made different for each field of the video signal. The polarity of the other set of pixel electrodes in the row and column is different from the polarity of the counter electrode, and the polarity of the other set of pixel electrodes in the adjacent row is different from the polarity of the other set of pixel electrodes in each field of the video signal. Drive circuit of liquid crystal display device showing reverse polarity It was.

[0025]

[Action] image quality of the display device pattern interferes with the original image and reducing the flicker - seems exhausted to reduce the emissions.

The former is called flicker and is caused by inversion of a signal which is inevitably required in a liquid crystal display device.

It has been proposed that the flicker can be reduced by shortening the inversion period Tinv to a period equal to or less than the period that can be perceived by the human eye (Japanese Patent Laid-Open No. 2-177679).

The latter is known under the name of moire or various types of interference, and occurs when a certain pattern is recognized by the human eye as a pattern other than the original signal.

In the present invention, if the latter is referred to as pattern disturbance, as one idea, the pattern disturbance only needs to have a complicated inversion pattern. Specifically, the number Ni of the inversion pattern is Ni.
It is preferable that nv be large and the entire period T be long.

From the above two ideas, the image quality Q is determined by the inversion period T
inv, the number of inversion patterns Ninv, and the entire period T.

Q∝T * Ninv / Tinv In the present invention, T is two frames, Ninv is four, and a video signal is selected for each field. Device.

[0032]

1 is a circuit diagram showing a driving circuit of the liquid crystal display device according to the present invention.

In FIG. 1, the video signal 1 is inverted by an inverting circuit A11 for inverting at a period of one frame (1F) and one horizontal scanning period (1H). A signal sent to the sample hold A13 connected to the video signal line and an inverting circuit B which always inverts the signal midway
The signal is branched by 14 into a signal of the opposite polarity which is sent to a sample hold B15 connected to the video signal lines of the even-numbered column below the liquid crystal panel.

The vertical synchronizing signal 16 and the horizontal synchronizing signal 17 are sent to a synchronizing control circuit 18 and are converted into various control signals by the synchronizing control circuit.

The synchronization control circuit supplies the start timing to the STVR 20 for measuring the start timing to the right scanning line shift register A19 for scanning the even-numbered scanning lines and the left scanning line shift register B21 for scanning the odd-numbered scanning lines. ST to measure
Send out VL22.

The timing signal ST for starting the scanning of the scanning line
The VR 20 and the STVL 22 alternate between the same timing and different timings for each field.

The synchronization control circuit transmits a signal corresponding to one row of the liquid crystal panel and a signal corresponding to one field of the liquid crystal panel to the video signal shift register A23 and the video signal shift register B24.

Of the pixel electrodes of the liquid crystal panel 12, a, b, a, b,
Called c, d, e, f, g, h.

The synchronization control circuit 18 is connected to the STVR 20 and the STV
The pixel electrodes a, b, c,
When d and d are selected simultaneously and a and c of the same polarity are positive (+), b and d of the same polarity are negative (-), e of the same polarity,
Control is performed so that g is negative (−) and f and h of the same polarity are positive (+).

Subsequently, in the next field, the pixel electrodes c, d,
e and f are simultaneously selected to have opposite polarities in columns adjacent to each other.

FIG. 2 is a block diagram of a synchronization control circuit used in the driving circuit of the liquid crystal display device according to the present invention.

In FIG. 2, the signal generating circuit 25 receives the vertical synchronizing signal 16 and the horizontal synchronizing signal 17 as inputs and outputs the timing signal ST to the scan line shift register B as an output.
VL22 , a vertical shift clock 26 and a field signal 27 are output.

[0043] Fi - multiplexor 28 by field signal 27 is operated, one Fi - timing signal STV R20 for each field is STV L or become the same signal as STV L
And the timing is shifted.

The difference in timing between STVL and STVR is achieved by delaying by the delay circuit 29 to the STV L22 is vertical shift clock 26 is inputted.

FIG. 3 shows waveform diagrams of various signals of the synchronization control circuit of the drive circuit of the liquid crystal display device of the present invention.

FIG. 3A shows the vertical synchronizing signal 16.
FIG. 3B shows the horizontal synchronizing signal 17, and FIG.
Is S which determines the scanning start timing of the even-numbered row of the liquid crystal panel.
FIG. 3D shows an STVL 22 for determining the scanning start timing of an odd-numbered row of the liquid crystal panel, and FIG. 3E shows a vertical shift clock 26 referred to by a delay circuit.

When comparing (c) and (d) of FIG. 3, the timing of STVR and STVL coincides in a certain field, and the timing of STVR and STVL does not coincide in the next field. I understand.

FIG. 4 shows the selected points and polarities of the waveforms of the pixel signals applied to the pixel electrodes in the eight pixel electrodes of FIG.

4A to 4H correspond to the pixel signals of the pixel electrodes a to h in the four rows and two columns of FIG. 1, respectively.

In FIG. 4A, the pixel signal 2 has a positive polarity (+) from the selection point 3 of the odd field (o), and then has a positive polarity again at the selection point 3 of the even field (e). (+),
From the selected point 3 of the odd field (o) of the next frame, the negative polarity (-) is obtained, and then the even field (e) becomes negative (-) again.

The polarity of the pixel signal 2 in FIG. 4B is always different from the polarity of the pixel signal of the adjacent pixel electrode a by the inverting circuit B.

In order to drive two scanning lines simultaneously, FIG.
4 (a) and FIG. 4 (c), and FIG. 4 (b) and FIG. 4 (d) have the same waveform.

The pixel signal 2 in FIG. 4E has a period T with respect to the pixel signal in FIG.
Are shifted by 90 °.

Since the pixel signal by the driving circuit of the liquid crystal display device of the present invention is selected twice during one frame, the contrast can be maintained high even when the liquid crystal resistance of the liquid crystal display device is low and the leak current is large. .

FIG. 5 shows the selection state of the scanning line for each field by the driving circuit of the liquid crystal display device of the present invention and the polarity of the pixel signal applied to the pixel electrode.

In FIG. 5, the scanning lines 30 are selected two by two in a certain row and are scanned from the top to the bottom of the liquid crystal panel.

Signals STVR, STV from synchronous control circuit
The combination of two scanning lines selected for each field differs depending on L.

Focusing on one row of the liquid crystal display device, the polarity of the pixel signal is repeated for four pixel electrodes in the direction of the video signal line with one unit of ++-in one field, and the next field is repeated. And the polarity of the pixel electrode is + in the direction of the video signal line.
+++ is repeated as one unit, the polarity of the pixel electrode is repeated in the following field in the direction of the video signal line in the direction of the video signal line, and the polarity of the pixel electrode in the subsequent field is reduced in the direction of the video signal line in the subsequent field. −−− is repeated as one unit.

As shown in FIG. 5, the pixel signals applied to the adjacent pixel electrodes in the row direction are opposite to each other with the two pixel electrodes in two rows and one column as one unit, and the pixels adjacent in the column direction are opposite to each other. One of two consecutive field periods of the pixel signal applied to the electrode has the opposite phase, and the other has the same phase.

The image quality Q of the driving circuit of the liquid crystal display device of the present invention.
FIG. 5 shows that the number Ninv of the inverted N turns is four, the total period T is two frames, and the normally used Ninv is two, and the total period is one frame compared to the image quality Q of one frame. Are better.

FIG. 6 shows an operation diagram of the driving circuit of the liquid crystal display device of the present invention in the case of a television signal.

In FIG. 6, the original signal 4 is represented by a white part 31 in five rows and n columns and a black part 32 indicated by oblique lines.

In FIG. 6, when the conventional display 33 in the first field of the liquid crystal display device has a point defect, the same display as in the first field is performed in the conventional display 35 in the second field. The disadvantages are very noticeable.

The hatched portion on the outside of the conventional display of FIG. 6 shows a black frame 36 unique to the display device, and makes the display portion stand out.

In FIG. 6, reference numeral 37 denotes the display of the invention in the first field. In the display of the invention in the second field, since the signals of the adjacent rows are input, the point defect 34 becomes almost inconspicuous on average.

In this embodiment, two rows are always selected.
Two odd-numbered fields and one even-numbered field are selected (this is indicated by [2, 1]), and the inverting circuit A is selected.
Is one frame and one field inversion, the number Ninv of inversion N turns is four and the total period T is two frames.
It becomes.

If one odd field and two even fields are selected ([1, 2]) and the configuration of the inverting circuit A is one frame inversion, the number Ninv of inverted N turns is obtained. Are four, and the entire period T is two frames.

Two odd fields, one even field and one next odd field are selected ([2,1,1]). If frame inversion and one-field inversion are used, the number N of inversion N turns is Ni.
nv is four, and the total period T is six frames.

One is selected for the odd field, two for the even field, and one for the next odd field ([1, 2, 1]). In the case of frame inversion, the number Ninv of inversion N turns is four, and the total period T is six frames.

[0070]

As described above, according to the present invention, a driving circuit for a liquid crystal display device for a television can be provided which has a simple circuit configuration, in which the contrast is hardly reduced by discharge and the points and defects are substantially compensated.

Further, since the number of inversion patterns within a certain period is large, human eyes cannot catch up with the period of the luminance change, flickers which disturb the original display are eliminated, and a liquid crystal display device which is easy to see can be constructed.

[Brief description of the drawings]

FIG. 1 is a driving circuit diagram of the liquid crystal display device of the present invention.

FIG. 2 is a synchronous control circuit diagram of the liquid crystal display device of the present invention.

FIG. 3 is a waveform diagram of a synchronization control signal of the liquid crystal display device of the present invention.

FIG. 4 is a waveform diagram of a pixel signal of the liquid crystal display device of the present invention.

FIG. 5 is a distribution diagram of polarities of pixel signals of the liquid crystal display device of the present invention.

FIG. 6 is an operation diagram of the driving circuit of the liquid crystal display device of the present invention.

FIG. 7 is a driving waveform diagram of the liquid crystal display device.

FIG. 8 is a liquid crystal display diagram by conventional simultaneous driving.

FIG. 9 is a drive circuit diagram of a conventional liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 video signal 2 pixel signal 3 selection point 4 original signal 5 horizontal scanning period holding circuit 6 field discriminating circuit 7 adder 8 amplifier 9 mixing circuit 10 double speed conversion circuit 11 inverting circuit A 12 liquid crystal panel 13 sample hold A 14 Inverting circuit B 15 Sample hold B 16 Vertical synchronization signal 17 Horizontal synchronization signal 18 Synchronization control circuit 19 Scan line shift register A 20 STVR 21 Scan line shift register B 22 STVL 23 Video signal shift register A 24 For video signal Shift register B 25 Signal generation circuit 26 Vertical shift clock 27 Field signal 28 Multiplexer 29 Delay circuit 30 Scan line 31 White part 32 Black part 33 Conventional display of first field 34 point defect 35 Conventional display of second field 36 Black frame 37 Device of the first field Display 38 Display of the device of the second field

Claims (1)

(57) [Scope of request for utility model registration] 1. A liquid crystal display comprising a pixel electrode near an intersection between an M-row scanning line and an N-column (M and N are integers) video signal lines, and a counter electrode facing the pixel electrode with a liquid crystal interposed therebetween. In the driving circuit of the device, a synchronization control circuit for supplying different timing signals for each field to the left and right scanning line driving circuits of the liquid crystal display device in which the scanning lines are alternately connected to the left and right, and one frame and one video signal. A first inverting circuit that inverts in one horizontal scanning period, and a second that always supplies video signals of opposite polarities to upper and lower video signal line driving circuits of a liquid crystal display device to which video signal lines are alternately connected vertically. With an inverting circuit,
Two adjacent scanning lines of the liquid crystal display device are simultaneously selected two by two out of the scanning lines in the row, and the left and right scanning lines of the liquid crystal display device are selected for each field of the video signal by the timing signal of the synchronization control circuit. The scanning timing of the driving circuit is made different so that the polarity of one set of pixel electrodes in two rows and one column with respect to the counter electrode is different from the polarity of the other set of pixel electrodes in two rows and one column of the adjacent column with respect to the counter electrode, and the adjacent row is different. A driving circuit for a liquid crystal display device, which shows the same polarity and the opposite polarity for each field of the video signal with respect to the polarity of the other set of pixel electrodes with respect to the counter electrode in two rows and one column.