JPH04355717A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the high-brightness and high-quality liquid crystal display device capable of displaying a half-tone with fine gradations by controlling a signal supplied to a liquid crystal panel, shortening an image update period and reducing the discharge of a liquid crystal cell, and reducing brightness unevenness between an upper and a lower part on a screen and differences in brightness between odd-numbered and even-numbered lines. CONSTITUTION:The signal supplied to the liquid crystal cell is divided into a display signal Vs and a brightness signal Vb, which are supplied alternately in each signal update period Tr. At this time, the brightness signal Vb with saw-tooth waveform which is large at the large-discharge part of the liquid crystal cell and small at the small-discharge part is used. When a period wherein the display signal Vs is updated is the signal update period Tr, the image update period of the liquid crystal cell is reduced to a half as long as before, the discharge period of charges is shortened to a half, and a decrease in brightness is drastically reduced. Consequently, the brightness differences between upper and lower parts on the screen, and odd-numbered and even- numbered lines are reduced and the brightness unevenness between the upper and lower parts on the screen and the differences in brightness between the odd-numbered and even-numbered lines are drastically reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device that uses liquid crystal to display images in general television signals, such as NTSC signals and high-quality television signals.

0002

2. Description of the Related Art As an example of a conventional liquid crystal display device, an example of an active matrix is shown in Japanese Patent Application No. 84012/1983. Further, FIG. 5 is a block diagram showing the configuration of a panel peripheral drive circuit of a conventional interlace drive liquid crystal display device. In FIG. 5, 101 is a liquid crystal panel, 102 is one picture element, and 103 is each picture element. A switching transistor (generally a thin film transistor made of amorphous silicon etc., hereinafter referred to as TFT [Thin Film Transistor])
), 104 is a liquid crystal cell, 105 is a picture element electrode connected to the drain electrode of TFT 103, 106 is a counter electrode common to all picture elements, 107 is a scanning electrode connected to gate electrode G of TFT 103, 108 is a signal electrode connected to the source electrode S of the TFT 103, 109 is a scanning start signal Sv input terminal to which the scanning start signal Sv is input, and 110 is a horizontal synchronizing signal f to which the horizontal synchronizing signal fH is input.
H input terminal, 111 is a control signal G1 input terminal that controls the signals of the scan electrodes in odd rows, 112 is a control signal G2 input terminal that controls the signals of the even rows scan electrodes, 113 is a TFT
Scan electrode voltage (+Vg) to turn on 103
The scanning electrode voltage (+Vg) input terminal 114 inputs the scanning electrode voltage (-Vg) for turning off the TFT 103.
) scanning electrode voltage (-Vg) input terminal, 115
are i/2 shift register circuits, 116 is i gate circuits, 117 is a vertical signal switching circuit that switches between scan electrode voltage (+Vg) and scan electrode voltage (-Vg), and 118 is an interlace TFT 103 of each picture element. 119 is a vertical scanning circuit that outputs a driving signal; 119 is a liquid crystal driving signal input terminal that inputs a liquid crystal driving signal whose polarity is inverted from a video signal every vertical scanning period in order to AC drive the liquid crystal; A clock CK input terminal 121 which inputs a clock CK for sampling indicates a horizontal scanning circuit that samples a liquid crystal drive signal using a clock CK and drives the liquid crystal drive signal line-sequentially every horizontal scanning period Th. The output of the horizontal scanning circuit 121 is column j from Y1 to Yj, and the output of the vertical scanning circuit 118 is column i from X1 to Xi.
There are rows for each, and the screen is composed of i rows and j columns.

FIGS. 6A to 6N show signal waveform diagrams of this conventional liquid crystal display device. Here, to simplify the diagram, a white raster signal is used as the video signal. In FIG. 6, Sv shown in (a) is a scanning start signal, and (b)
fH shown in (c) is a horizontal synchronizing signal, G1 shown in (c) is a control signal that controls the scanning signal of the odd field, G2 shown in (d) is a control signal that controls the scanning signal of the even field,
Vg-U1 shown in (e) is a scan electrode signal at the scan electrodes in odd-numbered rows at the top of the screen, Vg-U2 shown in (f) is a scan electrode signal at the scan electrodes in even-numbered rows at the top of the screen, and Vg-L1 shown in (g). Vg-L2 shown in (h) is a scan electrode signal in the scan electrodes in odd-numbered rows at the bottom of the screen, Vs shown in (i) is a signal output from the horizontal scanning circuit 121. Electrode signal, (j)
Vc shown in is a counter electrode signal supplied to the counter electrode 106,
Vd-U1 shown in (k) is a picture element electrode signal at the scanning electrodes in odd-numbered rows at the top of the screen, Vd-U2 shown in (l) is a picture-element electrode signal at the scanning electrodes in even-numbered rows at the top of the screen, and Vd shown in (m). -L1 indicates a picture element electrode signal at the scan electrodes in odd rows at the bottom of the screen, and Vd-L2 shown in (n) indicates a picture element electrode signal at the scan electrodes at even rows at the bottom of the screen.

FIG. 7 is a block diagram showing the configuration of a one-pixel equivalent circuit in a conventional liquid crystal display device when the TFT is off. In FIG. 7, 701 is the off resistance Ro of the TFT 103.
ff, 702 is the equivalent capacitance CLc of the liquid crystal cell 104, 70
3 indicates the equivalent resistance RLc of the liquid crystal cell 104, respectively.

FIG. 8 is a characteristic diagram showing the normally black mode (black display without voltage application) effective voltage-transmittance characteristic of a conventional liquid crystal display device. In FIG. 8, the horizontal axis represents the effective voltage (Vrms) applied to the liquid crystal cell 104, and the vertical axis represents the transmittance (%) through the liquid crystal panel.

The operation of the conventional liquid crystal display device configured as described above is shown in FIGS. 5 and 6(a) to (n) below.
, will be explained in conjunction with FIGS. 7 and 8.

In FIG. 5, when a liquid crystal drive signal is input to the horizontal scanning circuit 121, each signal electrode 108 is
) is supplied with the signal electrode signal Vs shown in FIG. Then, the counter electrode signal Vc shown in FIG. 6(j) is input to the counter electrode 106. In the vertical scanning circuit 118, the scanning start signal Sv shown in FIG.
The horizontal synchronization signal fH shown in (b) is inputted, the control signal G1 shown in FIG. 6(c) is inputted to the control signal G1 input terminal 111, and the control signal G2 shown in FIG. 6(d) is inputted to the control signal G2 input terminal 112. do.

First, the scanning electrodes in odd-numbered rows at the top of the screen will be explained. In an odd field, the scanning electrode signal V shown in FIG. 6(e) with a pulse width of one horizontal scanning period Th
g-U1 is output. Then, the TFT 103 is turned on, the signal electrode signal Vs shown in FIG. 6(i) is supplied to the picture element electrode 105, and the pixel electrode 105 is charged with electric charge. Then, after one horizontal scanning period Th, the TFT 103 is turned off, and the charged charge is transferred to the off-resistance Roff of the TFT shown in FIG. 7 for one frame period (k
) is held as shown in the picture element electrode signal Vd-U1. Then, in the odd field of the next frame, the pulse width is again one horizontal scanning period Th as shown in FIG. 6(e).
A scanning electrode signal Vg-U1 shown in is output. Then,
The TFT 103 is turned on again, and the signal electrode signal Vs shown in FIG. 6(i) is supplied to the picture element electrode 105. After one horizontal scanning period Th, the TFT 103 turns off and then turns on for one frame period as shown in FIG. 6(k).
The picture element electrode signal Vd-U1 shown in FIG. Then, the shaded portion in FIG. 6 is applied as an effective value to the liquid crystal cell 104, and an image corresponding to this effective value is displayed. Thereafter, similar operations are performed on the odd-numbered rows at the top of the screen and the scanning electrodes at the bottom of the screen to display images.

[0009]

However, in the above configuration, during the period when the signal electrode signal Vs and the pixel electrode signal Vd have the same polarity, there is almost no voltage difference between both ends of the off-resistance Roff701 of the TFT; During the period when the polarity is different, the voltage difference increases, and a large amount of the charge stored in the liquid crystal cell is discharged through the off-resistance Roff701 of the TFT.

As a result, in the odd-numbered rows at the top of the screen, the period in which the signal electrode signal Vs and the picture element electrode signal Vd-U1 have the same polarity is long, so there is little discharge, but in the even-numbered rows at the bottom of the screen, the signal electrode signal Vs and the picture element electrode signal Since the period in which the electrode signals Vd-L2 have the same polarity is short and the period in which they have different polarities is long, the amount of discharge increases. The even-numbered rows at the top of the screen and the odd-numbered rows at the bottom of the screen are located between them. For this reason, Fig. 6(k) to (n)
As shown by the effective voltage indicated by the shaded area, there is a difference in brightness between the top and bottom of the screen, so-called uneven brightness between the top and bottom of the screen, which makes it impossible to display fine halftones.

[0011] Furthermore, there is a difference in brightness between the odd-numbered rows and the even-numbered rows, and in reality, a horizontal striped pattern is created with vertically scrolling stripes, resulting in a problem that the displayed image is significantly degraded. For these reasons, the TFT's off resistance Rof
I had to make the f701 larger.

Furthermore, since interlaced driving is used, the image update period is every frame, and the equivalent resistance RLc 703 of the liquid crystal causes the charge stored in the liquid crystal cell to be greatly discharged until it is updated, causing the screen to change. Another problem was that the display brightness became extremely dark.

On the other hand, as shown in the characteristic diagram of FIG. 8, when the effective voltage is low, the transmittance hardly changes and is low. In actual driving, when displaying an image, by using the B period shown in FIG.
When displaying black, the effective voltage for period A shown in FIG. 8 must be constantly applied, and a problem arises in that a signal with a larger amplitude than the original image signal must be supplied. This also has the problem that, for example, when digital processing is used for image signals, full bits cannot be allocated to the image processing portion, resulting in wasted portions.

In view of the above, the present invention provides a high-brightness, high-quality liquid crystal display that reduces unevenness in brightness at the top and bottom of the screen and the difference in brightness between odd and even lines, provides fine halftone display, and provides a high-brightness, high-quality liquid crystal display. The purpose is to provide equipment.

[0015]

[Means for Solving the Problems] The present invention has a liquid crystal sandwiched between two transparent substrates, and on the first transparent substrate, i scanning electrodes and j signal electrodes are arranged in i rows and j columns, A picture element consisting of a three-terminal switching element and a liquid crystal cell is constructed at each intersection.
A drain electrode of the three-terminal switching element in each picture element is connected to a first electrode of the liquid crystal cell, a gate electrode is connected to the scanning electrode, and a source electrode is connected to the signal electrode. a liquid crystal panel in which the electrode is connected to a counter electrode common to all picture elements on a second transparent substrate;
The control signal Gb divides one horizontal scanning period Th into a signal supply period Ts and a brightness supply period Tb, and the signal supply period Ts
includes a horizontal circuit that supplies a display signal Vs for displaying an image to the signal electrodes during the luminance supply period Tb, and a horizontal circuit that supplies the display signal Vs for displaying an image to the signal electrodes during the luminance supply period Tb; The scan electrode voltage (+Vg) for supplying the voltage to the liquid crystal cell and the brightness supply period Tb
and a vertical circuit that switches a scan electrode voltage (+Vg) for supplying the luminance signal Vb to the liquid crystal cell every signal update period Tr and supplies the brightness signal Vb to the scan electrode, respectively. It is.

[0016]

[Operation] According to the present invention, with the above-described configuration, when the period for supplying a signal to the liquid crystal cell becomes the signal update period Tr, the image update period of the liquid crystal cell becomes 1/2 of the conventional one, and the charge discharge period becomes 1/2. 2, and the decrease in brightness is significantly reduced. Therefore, the uneven brightness between the top and bottom of the screen and the difference in brightness between odd and even rows are significantly reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the configuration of a panel peripheral drive circuit of a liquid crystal display device according to a first embodiment of the present invention. An object of the present invention is to reduce uneven brightness at the top and bottom of the screen and the difference in brightness between odd and even lines using the same liquid crystal panel as the conventional one, and to obtain a halftone display with fine gradations.

In FIG. 1, 101 is a liquid crystal panel;
2 is a picture element, 103 is a TFT, 104 is a liquid crystal cell, 105
is a picture element electrode connected to the drain electrode of TFT103,
106 is a counter electrode common to all picture elements, 107 is a TF
Scanning electrode 108 connected to gate electrode G of T103
is a signal electrode connected to the source electrode S of the TFT 103,
109 is a scan start signal Sv input terminal for inputting a scan start signal Sv, 110 is a horizontal synchronization signal fH input terminal for inputting a horizontal synchronization signal fH, 111 is a control signal G1 input terminal for controlling the signals of scan electrodes in odd rows, Reference numeral 112 indicates a control signal G2 input terminal for controlling the signals of the scan electrodes in even rows, 113 indicates a scan electrode voltage (+Vg) input terminal for inputting the scan electrode voltage (+Vg) for turning on the TFT 103, and 114 indicates for turning off the TFT 103. This is a scan electrode voltage (-Vg) input terminal for inputting the scan electrode voltage (-Vg) for.

115 is i/2 shift register circuits;
116 is i gate circuit, 117 is scanning electrode voltage (+
118 is a vertical scanning circuit that outputs a signal for interlace driving the TFT 103 of each picture element;
Reference numeral 9 indicates a liquid crystal drive signal input terminal to which a liquid crystal drive signal whose polarity is inverted from a video signal every vertical scanning period is input in order to AC drive the liquid crystal, and 120 indicates a clock CK input terminal to which a clock CK for sampling the liquid crystal drive signal is input. terminal, 1
21 samples the liquid crystal drive signal with the clock CK and outputs 1
Horizontal scanning circuits that are driven line-sequentially every horizontal scanning period Th are shown.

The configuration up to this point is the same as the block diagram of FIG. 6 showing the configuration of the panel peripheral drive circuit of a conventional liquid crystal display device.

The difference from the conventional method is that a horizontal signal switching circuit 122 is provided at the output of the horizontal scanning circuit 121. The configuration of the horizontal signal switching circuit 122 includes a control signal Gb input terminal 123 to which a control signal Gb is input, and a brightness supply signal Vb input terminal 124 to which a brightness supply signal Vb is input. The output of the horizontal signal switching circuit 122 is from Y1 to Yj in column j, and the output of the vertical scanning circuit 118 is from X1 to X.
There are i rows up to i, and the screen is composed of i rows and j columns.

FIGS. 2A to 2O show signal waveform diagrams of the liquid crystal display device according to the first embodiment of the present invention. Here, a white raster is used for the video signal to simplify the diagram. In FIG. 2, Sv shown in (a) is a scanning start signal, fH shown in (b) is a horizontal synchronization signal, and (c
G1 shown in ) is a control signal that controls a scanning electrode signal whose period is one horizontal scanning period Th and whose pulse width is signal supply period Ts in odd fields and brightness supply period Tb in even fields, and G2 shown in (d) is the period. is one horizontal scanning period Th
A control signal that controls the scan electrode signal whose pulse width is the brightness supply period Tb in odd-numbered fields and the signal supply period Ts in even-numbered fields. , Vg-U2 shown in (f) is the scan electrode signal for the scan electrodes in even-numbered rows at the top of the screen, Vg-L1 shown in (g) is the scan electrode signal for the scan electrodes in odd-numbered rows at the bottom of the screen, and Vg- shown in (h). L
2 is a scan electrode signal for scan electrodes in even-numbered rows at the bottom of the screen.

Vs shown in (i) is the signal electrode signal output from the horizontal scanning circuit 121, Vcom shown in (j) is the counter electrode signal supplied to the counter electrode 106, and Vs shown in (k) is the signal electrode signal output from the horizontal scanning circuit 121.
d-U1 is a pixel electrode signal at the scanning electrodes in odd-numbered rows at the top of the screen, Vd-U2 shown in (l) is a pixel electrode signal at the scanning electrodes in even-numbered rows at the top of the screen, and Vd-L1 shown in (m) is at the bottom of the screen. The picture element electrode signal in the scanning electrodes of odd rows, (n
Vd-L2 shown in ) controls the pixel electrode signal in the scanning electrodes in even-numbered rows at the bottom of the screen, and Gb shown in (o) controls the signal electrode signal whose period is one horizontal scanning period Th and whose pulse width is the brightness supply period Tb. The control signal, Vb shown in (p), is a sawtooth waveform signal that is 90 degrees out of phase with the signal electrode signal Vs shown in (i), and is a brightness supply signal for supplying brightness to the information written in the picture element, ( Vs shown in q) indicates the signal electrode signals output from the horizontal signal switching circuit 122, respectively.

The operation of the liquid crystal display device according to the first embodiment of the present invention constructed as described above will be explained below with reference to FIGS. 1 and 2(a) to 2(q).

In FIG. 1, a liquid crystal drive signal is input to the horizontal scanning circuit 121, and the control signal Gb input terminal is inputted as shown in FIG.
The control signal Gb shown in FIG. 2(p) is input to the brightness supply signal Vb input terminal. Then, each signal electrode 108 is supplied with the signal electrode signal Vs shown in FIG. 2(q). Then, the counter electrode 106 is
A counter electrode signal Vc shown in (j) is input. In the vertical scanning circuit 118, the scan start signal Sv shown in FIG. 2(a) is input to the scan start signal Sv input terminal 109, and the horizontal synchronization signal fH shown in FIG. The control signal G1 input terminal 111 shown in FIG.
The control signal G1 shown in c) is input to the control signal G2 input terminal 11.
2, the control signal G2 shown in FIG. 2(d) is inputted to each of them.

First, the scanning electrodes in odd-numbered rows at the top of the screen will be explained. In the odd field, the scanning electrode signal Vg- shown in FIG. 2(e) whose pulse width is the signal supply period Ts
U1 is output. Then, the TFT 103 is turned on, and the signal electrode signal Vs of the signal supply period Ts shown in FIG. 2(q) is supplied to the picture element electrode 105. After the signal supply period Ts, the TFT 103 is turned off and the period until the next turn on is the picture element electrode signal Vd shown in FIG. 2(k).
-The voltage will be maintained as shown at U1. Next, in the even field, the scan electrode signal Vg-U1 shown in FIG. 2E, whose pulse width is the brightness supply period Tb, is output. Then, the TFT 103 becomes on state, and as shown in FIG.
The signal electrode signal Vs of the brightness supply period Tb shown in (q) is supplied to the picture element electrode 105.

After the brightness supply period Tb, the TFT 103
Fig. 2
The brightness supply signal voltage Vb is held as shown in the picture element electrode signal Vd-U1 shown in (k). Here, the shaded portion is applied to the liquid crystal cell 104 as an effective value,
An image corresponding to this effective value will be displayed.

Next, the scanning electrodes in even-numbered rows at the top of the screen will be explained. In the even field, the scanning electrode signal Vg-U shown in FIG. 2(f) whose pulse width is the signal supply period Ts
2 is output. Then, the TFT 103 is turned on, and the signal electrode signal Vs of the signal supply period Ts shown in FIG. 2(q) is supplied to the picture element electrode 105. After the signal supply period Ts, the TFT 103 is turned off and the picture element electrode signal Vd shown in FIG.
-The voltage will be maintained as shown at U2. Next, in the odd field, the scan electrode signal Vg-U2 shown in FIG. 2(f) whose pulse width is the brightness supply period Tb is output. Then, the TFT 103 becomes on state, and as shown in FIG.
The signal electrode signal Vs of the brightness supply period Tb shown in (q) is supplied to the picture element electrode 105.

After the brightness supply period Tb, the TFT 103
Figure 2 shows the period from which the is off to the next on.
The brightness supply signal voltage Vb is held as shown in the picture element electrode signal Vd-U2 shown in 1). Here, the shaded portion is applied to the liquid crystal cell 104 as an effective value, and an image corresponding to this effective value is displayed. Here, as shown in FIG. 2(p), the brightness supply signal Vb has a slope for each frame. As a result, the brightness supply signal for the odd-numbered rows at the top of the screen is small, and the brightness supply signal for the even-numbered rows is larger than that for the odd-numbered rows.

[0030] Similarly, scanning electrodes in odd-numbered rows and even-numbered rows at the bottom of the screen are used to display images. Here, as in the upper part of the screen, the brightness supply signal is small for the odd-numbered rows at the bottom of the screen, and is larger for the even-numbered rows than for the odd-numbered rows.

These steps are repeated to display an image on the entire screen. As described above, according to this embodiment, with the same liquid crystal panel configuration as the conventional one, the signal supplied to the signal electrodes is divided into the display signal Vs and the brightness supply signal Vb, and the output of the vertical scanning circuit is controlled. By constantly supplying the brightness supply signal Vb to the liquid crystal cell 104 every field of the signal update period Tr after writing the signal Vs into the liquid crystal cell, charges are replenished before the discharge of the liquid crystal cell becomes large. In addition, by replenishing areas where conventional discharge was large and filling areas where discharge was small with a smaller size, an image with less difference in brightness can be obtained. This is because conventionally there was a large difference in brightness between the top and bottom of the screen and between odd and even rows, but these effects have been reduced, resulting in high-quality images without uneven brightness at the top and bottom of the screen and no difference in brightness between odd and even rows. You can get the display. Furthermore, when image processing is performed digitally, full bits can be used for the image signal portion, making it possible to display fine halftones.

On the other hand, by changing the amplitude and slope of the brightness supply signal Vb, the effective voltage applied to the liquid crystal cell 104 can be changed.

FIG. 3 is a block diagram showing the configuration of a panel peripheral drive circuit of a liquid crystal display device according to a second embodiment of the present invention. An object of the present invention is to display high-quality images without uneven brightness between the top and bottom of the screen and without differences in brightness between odd and even rows using the same drive circuit as the conventional one.

In FIG. 3, 301 is a brightness supply signal Vb
302 is a luminance supply signal input terminal for supplying a luminance supply signal to the liquid crystal cell 104 of each picture element.
FT is shown respectively. Components having the same configuration as in the first embodiment are denoted by the same numbers, and the description thereof will be omitted here.

FIGS. 4A to 4O show signal waveform diagrams of a liquid crystal display device according to a second embodiment of the present invention. Here, as in the first embodiment, a white raster is used for the video signal to simplify the diagram. In the same figure, (
Sv shown in a) is a scanning start signal, fH shown in (b)
is a horizontal synchronization signal, G1 shown in (c) is a control signal, (d)
G2 shown in (e) is a scan electrode signal for the scan electrodes in odd-numbered rows at the top of the screen, Vg-U2 shown in (f) is a scan electrode signal for the scan electrodes in even-numbered rows at the top of the screen, ( Vg-L1 shown in g) is the scan electrode signal of the scan electrodes in odd rows at the bottom of the screen, and Vg-L1 shown in (h)
L2 is a scan electrode signal for scan electrodes in even-numbered rows at the bottom of the screen. Vs shown in (i) is the signal electrode signal output from the horizontal scanning circuit 121, Vcom shown in (j) is the counter electrode signal supplied to the counter electrode 106, and Vd- shown in (k)
U1 is the picture element electrode signal at the scanning electrodes in the odd rows at the top of the screen, Vd-U2 shown in (l) is the picture element electrode signal at the scanning electrodes at the even rows at the top of the screen, and Vd-L1 shown in (m) is the odd rows at the bottom of the screen. Vd-L2 shown in (n) is the picture element electrode signal at the scan electrodes in even-numbered rows at the bottom of the screen, and Vb shown in (o) is 90 degrees from the signal electrode signal Vs shown in (i). These are sawtooth waveform signals with different phases, and each shows a brightness supply signal for supplying brightness to information written in a picture element.

The operation of the liquid crystal display device according to the second embodiment of the present invention constructed as described above will be explained below with reference to FIGS. 3 and 4(a) to 4(o).

In FIG. 3, a liquid crystal drive signal is input to the horizontal scanning circuit 121. Then, each signal electrode 108 is supplied with the signal electrode signal Vs shown in FIG. 4(i). Then, the counter electrode signal Vc shown in FIG. 4(j) is applied to the counter electrode 106.
Enter. In the vertical scanning circuit 118, the scanning start signal Sv shown in FIG.
The horizontal synchronizing signal fH shown in FIG. 4(b) is
The control signal G1 shown in FIG. 4(c) is applied to the input terminal 111, the control signal G2 shown in FIG. 4(d) is applied to the control signal G2 input terminal 112, and the control signal G2 shown in FIG.
The brightness supply signals Vb shown in are respectively input.

First, the scanning electrodes in odd-numbered rows at the top of the screen will be explained. In odd fields, the pulse width is 1
The scanning electrode signal Vg shown in FIG. 4(e) during the horizontal scanning period Th
-U1 is output. Then, the TFT 103 is turned on, and the signal electrode signal Vs shown in FIG. 4(i) is supplied to the picture element electrode 105. After one horizontal scanning period Th, T
The FT 103 maintains a voltage as shown in the picture element electrode signal Vd-U1 shown in FIG. 4(k) during a period from when the FT 103 is turned off to when it is next turned on. Next, in an even field, a scan electrode signal Vg-U2 shown in FIG. 4F having a pulse width of one horizontal scan period Th is output to the scan electrodes in even rows. Then, the brightness supply TFT 301 is turned on, and the brightness supply signal Vb shown in FIG. 4(o) is supplied to the liquid crystal cell 104. After that, the brightness supply TFT301
Figure 4
The voltage is held as the picture element electrode signal Vd-U1 shown in (k). Here, the shaded portion is applied to the liquid crystal cell 104 as an effective value, and an image corresponding to this effective value is displayed.

Next, the scanning electrodes in even-numbered rows at the top of the screen will be explained. In an even field, the scanning electrode signal Vg-U shown in FIG. 4(f) with a pulse width of one horizontal scanning period Th
2 is output. Then, the TFT 103 is turned on, and the signal electrode signal Vs shown in FIG. 4(i) is applied to the picture element electrode 10.
5. After one horizontal scanning period Th, the TFT
The voltage 103 is held as the picture element electrode signal Vd-U2 shown in FIG. 4(l) during the period from when it is turned off until it is turned on. Next, in an odd field, a scan electrode signal Vg-L1 shown in FIG. 4G having a pulse width of one horizontal scan period Th is output to the scan electrodes in odd rows. Then, the brightness supply TFT 301 is turned on,
A brightness supply signal Vb shown in FIG. 4(o) is supplied to the liquid crystal cell 104. Then, after one horizontal scanning period Th, the brightness supply TFT 301 turns off and holds the voltage as the picture element electrode signal Vd-U2 shown in FIG. 4(l) until the next turn on. . Here, the shaded portion is applied to the liquid crystal cell 104 as an effective value, and an image corresponding to this effective value is displayed. Here, Figure 4
As shown in (o), the brightness supply signal Vb has a slope for each frame. As a result, the brightness supply signal for the odd-numbered rows at the top of the screen is small, and the brightness supply signal for the even-numbered rows is larger than that for the odd-numbered rows.

[0040] Similarly, scanning electrodes in odd-numbered rows and even-numbered rows at the bottom of the screen are used to display images. Here, as in the upper part of the screen, the brightness supply signal is small for the odd-numbered rows at the bottom of the screen, and is larger for the even-numbered rows than for the odd-numbered rows.

These steps are repeated to display the image on the entire screen. As described above, according to this embodiment, with the same liquid crystal panel configuration as the conventional one, the signal supplied to the signal electrodes is divided into the display signal Vs and the brightness supply signal Vb, and the output of the vertical scanning circuit is controlled. By constantly supplying the brightness supply signal Vb to the liquid crystal cell 104 every field of the signal update period Tr after writing the signal Vs into the liquid crystal cell, charges are replenished before the discharge of the liquid crystal cell becomes large. In addition, by replenishing areas where conventional discharge was large and filling areas where discharge was small with a smaller size, an image with less difference in brightness can be obtained. This is because conventionally there was a large difference in brightness between the top and bottom of the screen and between odd and even rows, but these effects have been reduced, resulting in high-quality images without uneven brightness at the top and bottom of the screen and no difference in brightness between odd and even rows. You can get the display. Furthermore, when image processing is performed digitally, full bits can be used for the image signal portion, making it possible to display fine halftones.

In the first and second embodiments, the effective voltage applied to the liquid crystal cell 104 can be changed by changing the amplitude and slope of the brightness supply signal Vb. This allows the overall brightness of image display to be changed.

Furthermore, in the first embodiment, the case of interlaced driving has been described, but non-interlaced driving may also be used. At that time, the signal update period Tr is 1
/2, and the decrease in brightness is smaller.

[0044]

As described above, according to the first invention, it is possible to display high-quality images without uneven brightness between the top and bottom of the screen and without differences in brightness between odd and even rows using the same liquid crystal panel configuration as before. Obtainable.

According to the second aspect of the present invention, it is possible to obtain a high-quality image display with no uneven brightness between the top and bottom of the screen and no difference in brightness between odd and even rows with the same drive circuit configuration as the conventional one.

Furthermore, in manufacturing the TFT, it is not necessary to increase the off-resistance of the TFT, and the practical effects thereof are great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a drive circuit of a liquid crystal display device in a first embodiment of the present invention.

[Figure 2] Operation waveform diagram of the same example

FIG. 3 is a block diagram showing the configuration of a drive circuit of a liquid crystal display device according to a second embodiment of the present invention.

[Figure 4] Operation waveform diagram of the same example

[Figure 5] Block diagram showing the configuration of a drive circuit of a conventional liquid crystal display device

[Figure 6] Conventional operation waveform diagram

[Figure 7] Equivalent circuit diagram showing the configuration of one conventional pixel

[Figure 8] Conventional effective voltage-transmittance characteristic diagram

[Explanation of symbols]

101 Liquid crystal panel 102 Picture element 103 TFT 104 Liquid crystal cell 105 Picture element electrode 106 Counter electrode 107 Scan electrode 108 Signal electrode 109 Scan start signal Sv input terminal 110 Horizontal synchronization signal fH input terminal 111 Control signal G1 input terminal 112 Control signal G2 input terminal 113 Scan electrode voltage (+Vg) input terminal 114
Scanning electrode voltage (-Vg) input terminal 115 Shift register circuit 116 Gate circuit 117 Vertical signal switching circuit 118 Vertical scanning circuit 119 Liquid crystal drive signal input terminal 120 Clock CK input terminal 121 Horizontal scanning circuit 122 Horizontal signal switching circuit 123 Control signal Gb input Terminal 124 Brightness supply signal Vb input terminal

Claims (5)

[Claims] Claim 1: A liquid crystal is sandwiched between two transparent substrates, and on the first transparent substrate, i scanning electrodes and j signal electrodes are arranged in i rows and j columns, and a three-terminal switching element is arranged at each intersection. and a liquid crystal cell, the drain electrode of the three-terminal switching element in each picture element is the first electrode of the liquid crystal cell, the gate electrode is the scanning electrode, and the source electrode is the signal electrode. and a liquid crystal panel in which the second electrode of the liquid crystal cell is connected to a counter electrode common to all picture elements on a second transparent substrate, and one horizontal scanning period Th is controlled by a control signal Gb during a signal supply period Ts. and a luminance supply period Tb, and during the signal supply period Ts, a display signal Vs for displaying an image is supplied to the signal electrode, and during the luminance supply period Tb, a luminance signal Vb for displaying luminance is supplied to the signal electrode. a horizontal circuit, and the display signal V during the signal supply period Ts.
The scanning electrode voltage (+V
g) and a vertical circuit that switches a scanning electrode voltage (+Vg) for supplying the luminance signal Vb to the liquid crystal cell during each signal update period Tr and supplies the luminance signal Vb to the scanning electrode during the luminance supply period Tb. A liquid crystal display device characterized by: 2. The signal update period Tr is one field period, and the vertical circuit includes i/2 shift register circuits that shift signals every horizontal scanning period Th, and an output period of the shift register circuit. It is composed of i gate circuits that control the gate circuits, and a vertical signal switching circuit that switches between two types of scan electrode voltage (+Vg) and scan electrode voltage (-Vg) according to the output of the gate circuit, and the output of each of the shift register circuits. A first input of the odd-numbered gate circuit and a first input of the even-numbered gate circuit are respectively connected, a first control signal G1 is connected to a second input of the odd-numbered gate circuit, and a second control signal G1 is connected to a second input of the odd-numbered gate circuit. is connected to the second input of the even-numbered gate circuit, and the first control signal G1 is such that the output of the odd-numbered row of the vertical circuit is the scanning electrode voltage ( +Vg), and the output of the even rows of the vertical circuit becomes the scan electrode voltage (+Vg) during the brightness supply period Tb of the even field, and the second control signal G2 is the signal that causes the brightness supply of the odd field. In the period Tb, the output of the scan electrodes in even rows of the vertical circuit is a signal that becomes the scan electrode voltage (+Vg), and in the signal supply period Ts of the even field, the output of the scan electrodes in the even rows of the vertical circuit becomes the scan electrode voltage. (+
2. The liquid crystal display device according to claim 1, wherein the signal is Vg). 3. The brightness supply signal Vb is 90% lower than the display signal Vs.
2. The liquid crystal display device according to claim 1, wherein the slope and amplitude of a tail-tooth waveform with a delayed slope can be adjusted to arbitrary values. 4. A liquid crystal is sandwiched between two transparent substrates, and on the first transparent substrate, one common electrode, i scanning electrodes, and j signal electrodes are arranged in i rows and j columns, and each intersection point is A picture element is composed of two three-terminal switching elements and a liquid crystal cell, and the drain electrode of the first three-terminal switching element in each picture element is connected to the first electrode of the liquid crystal cell, and the gate electrode is connected to the first electrode of the liquid crystal cell. A scanning electrode is connected to a source electrode, a source electrode is connected to the signal electrode, a second electrode of the liquid crystal cell is connected to a counter electrode common to all picture elements on a second transparent substrate, and a second The drain electrode of the three-terminal switching element is connected to the first electrode of the liquid crystal cell, the gate electrode is connected to the scan electrode adjacent to the scan electrode, and the source electrode is connected to the common electrode. a liquid crystal panel connected to each electrode, i/2 shift register circuits that shift a signal every horizontal scanning period Th, i gate circuits that control the output period of the shift register circuit, and the A vertical signal switching circuit that switches between two types of scanning electrode voltages (+Vg) and (-Vg) based on the output of the gate circuit, and a display signal Vsig for driving the liquid crystal.
and a horizontal scanning circuit that supplies a first control signal, and connects the output of each shift register circuit to a first input of a gate circuit in an odd row and a first input of a gate circuit in an even row, respectively. G1 is connected to a second input of the gate circuit in the odd row, a second control signal G2 is connected to a second input of the gate circuit in the even row, and the first control signal G1 is connected to the second input of the gate circuit in the odd row. The second control signal G2 is a signal in which the output of the scan electrodes in the odd rows of the vertical signal switching circuit becomes the scan electrode voltage (+Vg) only during the even field period. A liquid crystal display device characterized in that the output of the scanning electrode is a signal that corresponds to the scanning electrode voltage (+Vg). 5. The brightness supply signal Vb is 90% lower than the display signal Vs.
5. The liquid crystal display device according to claim 4, wherein the slope and amplitude can be adjusted to arbitrary values using a tail-tooth waveform with a delayed slope.