JPH03235989A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve linearity and reduce an offset and to obtain the liquid crystal display device of high picture quality by charging or discharging signal lines of a liquid crystal panel to a constant potential before a video signal is impressed. CONSTITUTION:The signal lines 12 of the display panel 125 are charged or discharged to the specific constant potential before the video signal is impressed from a horizontal driving circuit 24 to drive the signal lines 12. Namely, the signal lines 12 of the liquid crystal panel 125 are connected to a constant potential point through switching transistors (TR) 16 respectively and when the switching TRs 16 are turned on, the respective signal lines 12 are charged or discharged to the constant potential V1. In this case, only a voltage corresponding to the variation of the video signal needs to be supplied from the horizontal driving circuit 24, so the input/output amplitude of the horizontal driving circuit 24 is reducible. Consequently, the linearity, offset, etc., of the video signal are improved and a video display of high picture quality is made.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a liquid crystal display device that displays images using a liquid crystal panel, and particularly to a drive circuit for a liquid crystal panel.

(Prior Art) Liquid crystal display devices have recently begun to be used in portable liquid crystal TVs because of their low power consumption and thinness. FIG. 16 shows a general configuration of a liquid crystal TV.

In FIG. 16, a video demodulation circuit 1120 demodulates a luminance signal and a color difference signal from a video signal voltage input via a tuner 1100 and a video intermediate frequency amplifier 1110, and further converts it into R, G, and B primary color signals. Ru. The R, G, and B color signals are switched by the color switching circuit 1150 according to the color filter arrangement of each pixel of the liquid crystal panel 1250, and further converted by the polarity switching circuit into signals that are more positive or negative than the reference potential, and then sent to the horizontal drive circuit 1210. is supplied to On the other hand, horizontal and vertical synchronization signals are separated and extracted by the synchronization separation circuit 1130, and from these synchronization signals, the pulse generation circuit 1140 generates a clock to be supplied to the vertical scanning circuit 1200, a clock to be supplied to the horizontal drive circuit 1210, and the like.

A specific example of the liquid crystal panel 1220, vertical scanning circuit 1200, and horizontal drive circuit 1210 is shown in FIG. As shown in FIG. 17, the liquid crystal panel 1220 has an intersection between zero address lines 11 extending in the horizontal direction (horizontal scanning direction) and m signal lines 12 extending in the vertical direction (vertical scanning direction). , Xn liquid crystal display elements (hereinafter referred to as pixels) C++,
..., Gmn are arranged in a matrix. Each of these pixels G11. ..., G, 7 are each TPT
It has a switching transistor 13 made of a thin film transistor (thin film transistor), a capacitor 14, and a liquid crystal cell 15. The vertical scanning circuit 1210 outputs gate pulses VVI, VV2 . VV3. ...V
VN is output to the liquid crystal panel 220. Horizontal drive circuit 1
210 is a video signal DOI, DO2, DO3, . . . DO
N is output to the liquid crystal panel 1220.

As shown in FIG. 18, the horizontal drive circuit 1210 is composed of an m-stage shift register 1300, m sample-and-hold circuits 1301 connected to the outputs Q1 to Q1 of each stage, and an output buffer (amplifier) 1302. Ru.

The operations shown in FIGS. 17 and 18 will be explained with reference to FIG. 19. When clock pulse Cp and data D are input to shift register 1800 in FIG. 18, Q, ~Q,
A sample pulse is output. The sample and hold circuit 18 inches samples the input video signal VIN using a sample pulse, and the held signal is sent to the output buffer 1.
Video signals 001 to DOM are applied to the signal line 12 via 802. On the other hand, from the vertical scanning circuit 1200
Pulses VVI to VVN corresponding to H (horizontal scanning period) are output. As a result, for example, the transistor 13 in the pixel Gll is turned on, and the voltage of the video signal DOI-DOM held by the sample and hold circuit 1301 is held in the capacitor 14 via the transistor 13. Pixel G
The transmittance of the liquid crystal cell 15 in I changes according to the video signal voltage held in the capacitor 14, and displays a video.

Similarly, the video signal DO2 is sent from the horizontal drive circuit 1210.
, DO3, . . . DON are sequentially output, a plurality of pixels G11 . ..., Gmn
Among them, the video signal 002. D03. ...DOM output timing and gate pulse VV1. VV2. ...VV
Pixels corresponding to N output timings operate sequentially. Through the above series of operations, an image corresponding to the input video signal VIN is displayed on the liquid crystal panel 1220.

As is well known, alternating current driving is generally used in such liquid crystal display devices in order to improve reliability and extend life. For example, when displaying television images, a video signal whose polarity is inverted every frame or field is input to the input video signal VI.
Used as N. FIG. 19 shows the waveform of the video signal in which the polarity of the second field is inverted. Further, FIG. 20 shows an example of applied voltage-transmittance characteristics of liquid crystal.

In this case, due to the resistance when the switching transistor of each pixel is turned off, the jumping of gate pulses VVL to VVN, and the interference between surrounding pixels, there is a difference between when a positive polarity video signal is supplied and when a negative polarity video signal is supplied. The effective voltage of the video signal applied to each pixel differs depending on the time. For example, if the polarity is reversed at 60 Hz for each field, Hz flicker will occur due to the difference between positive and negative effective voltages. 30
Since Hz flicker is visually very noticeable, in order to remove it, there are various methods to remove it, such as a method of inverting the polarity of the input video signal VIN at high speed, that is, a method of inverting the polarity of each scanning line, a method of inverting the polarity of each signal line, or a method of inverting the polarity of each pixel. Various methods have also been proposed, such as a method in which the image is reversed.

However, if the polarity of the input video signal VIN is reversed,
As is clear from FIG. 19, the input amplitude of the horizontal drive circuit is doubled, and the sample hold circuit 130 of FIG.
The amplitude of the video signal Dot-DOM output from 1 is also required to be doubled. Therefore, it is necessary to increase the power supply voltage of the horizontal drive circuit 1210, and the sample and hold circuit 18
01 and the dynamic range of the output buffer 1302 is 2.
This makes it difficult to ensure linearity and reduce offset. Errors in linearity and offset appear as level differences between the video signals DOI to DOM supplied to each signal line 12, resulting in vertical stripe interference on the screen, significantly degrading the image quality.

(Problem to be Solved by the Invention) As mentioned above, in conventional liquid crystal display devices, when the polarity of the input video signal is periodically reversed to realize AC drive, the amplitude doubles, so horizontal drive is difficult. Not only is it necessary to increase the power supply voltage of the circuit, but also the dynamic range of the circuit is required to be doubled, which increases errors in linearity and offset, and causes a difference in the level of the video signal between the signal lines, causing the screen to become distorted. There was a problem in that vertical stripe interference occurred on the top, significantly degrading the image quality.

The present invention has been made in view of the above points, and it is possible to lower the power supply voltage of the horizontal drive circuit when AC driving a liquid crystal cell, and to reduce the periodic noise caused by the difference in video signal level between signal lines. An object of the present invention is to provide a liquid crystal display device that can display high-quality images without causing interference such as vertical stripes.

[Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, the liquid crystal display device of the present invention applies video signals from a horizontal drive circuit to a plurality of signal lines in a display panel to control the signal lines. It is characterized by comprising means for charging or discharging the signal line to a predetermined constant potential before driving.

Here, if there is a threshold value in the voltage-transmittance characteristic of the liquid crystal cell, the reference potential of the liquid crystal panel, that is, the predetermined constant potential obtained by adding the threshold value to the common electrode potential of the liquid crystal cell, is set before driving the signal line. so that the signal line is charged or discharged.

In addition, when actually applying a video signal to the signal line from the horizontal drive circuit, by applying only the amount of change in the video signal with respect to a predetermined constant potential, a voltage equal to the amount of change in the constant potential is applied to each pixel. Make it.

(Function) In the present invention, when applying a video signal to each pixel, the signal line is charged or discharged to a constant potential, and then the video signal voltage is supplied to the signal line as a change from the constant potential. A voltage corresponding to a constant potential change is applied to the pixel.

If this constant potential is used as the potential of the common electrode (counter electrode) of the liquid crystal cell, alternating current driving of the liquid crystal cell can be easily realized by alternately supplying video signals of positive and negative polarity as changes. In this case, since it is necessary to supply only the voltage corresponding to the change in the video signal from the horizontal drive circuit, the input/output amplitude of the horizontal drive circuit can be 172 or less than the conventional one.

Also, when there is a threshold value in the voltage-transmittance characteristic of the liquid crystal cell, after charging or discharging the signal line to a constant potential that is higher than the common electrode potential of the liquid crystal cell by the threshold value, only the change in the video signal is supplied. By supplying the horizontal drive circuit to the signal line, the amplitude of the video signal supplied from the horizontal drive circuit to the signal line is further reduced.

By reducing the output amplitude of the horizontal drive circuit in this way, it is possible to reduce the power consumption of the horizontal drive circuit, and by reducing the dynamic range, the linearity and offset of the video signal applied from the horizontal drive circuit to the signal line can be reduced. etc., and the level difference between signal lines becomes smaller.
This enables high-quality video display without interference such as vertical stripes.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a liquid crystal television as a liquid crystal display device according to an embodiment of the present invention. The NTSC composite video signal supplied to the input terminal IN is sent to the A/D converter 1.
11, the frame memory 11
Written to 2. The video signal read from the frame memory 112 is separated into a luminance signal and a color difference signal by a Y-C separation circuit 113. Since the current NTSC system uses an interlace system, in order to facilitate display on the liquid crystal panel 125, the separated luminance signal and color difference signal are converted to 525 scanning lines and a frame frequency of 80H by a non-interlace conversion circuit 114.
z signal. As is well known, this interlace to non-interlace conversion is performed by scanning line interpolation when the movement is large, and by field interpolation when the movement is small. The luminance signal and color difference signal converted by the non-interlace conversion circuit 114 are further converted into R, G, B conversion circuit 115 configured using a matrix circuit.
It is converted into lG and B signals. The R, G, and B signals are periodically switched between positive and negative by a polarity switching circuit 116 in order to AC drive the liquid crystal panel 125, and then converted back to analog signals by a D/A converter 117 before being horizontally driven. is supplied to circuit 124.

On the other hand, synchronization components such as horizontal synchronization, vertical synchronization, and color burst are separated from the input NTSC composite video signal 2 by a synchronization separation circuit 118, and horizontal and vertical timing clocks, etc. are generated by a timing generator 119 based on these synchronization components. Furthermore, a drive pulse for driving the vertical scanning circuit 123 and the horizontal drive circuit 124 is created by the drive pulse generator 120 based on the timing clock. The drive pulse generator 120 further supplies a timing signal of any one of the field period, frame period, horizontal scanning period, or one pixel period to the polarity switching signal generator 121. The polarity switching signal generator 121 uses this timing signal to generate a pulse that alternately becomes "1" and "0" for each field or frame, or a pulse that alternately repeats "1m" and "0" for every horizontal scanning line. Alternatively, a polarity switching signal consisting of pulses of "1" and "0" is generated for each pixel, and the polarity switching circuit 116
supply to.

FIG. 2 is a diagram showing the vertical scanning circuit 123, horizontal drive circuit 3 124, and liquid crystal panel 125 in detail. The liquid crystal panel 125 has Xn liquid crystal display elements arranged at intersections between n address lines 11 extending in the horizontal direction (horizontal scanning direction) and m signal lines 12 extending in the vertical direction (vertical scanning direction). G-th (hereinafter referred to as pixels), . . . HGmn are arranged in a matrix. Each of these pixels G1
1゜... Gm, , are the switching transistors 13 made of TPT (thin film transistor), and
It has a capacitor 14 and a liquid crystal cell 15.

As shown in FIG. 8, the liquid crystal cell 15 has an individual electrode (also called a pixel electrode) formed separately for each pixel and a common electrode (also called a counter electrode) formed in common for each pixel. The individual electrodes are connected to the switch transistor 13 and the capacitor 14, and the common electrode is connected in common to all pixels and has a constant potential V. is maintained. Vertical scanning circuit 1
23 are gate pulses VV with mutually different output timings.
I, VV2. VV3. - Output VVN to the liquid crystal panel 125. The horizontal drive circuit 124 receives video 4 signals Dot, D02. DO3, . . . output DOM to the liquid crystal panel 125.

The signal lines 12 of the liquid crystal panel 125 are each connected to a constant potential point (in this example, a point at the common electrode potential V of the liquid crystal cell 15) via a switching transistor (TPT) 16. When the switching transistor 16 is turned on by applying a gate pulse PSW to the switching transistor 16, each signal line 12 is at a constant potential, in this case, the common electrode potential V. charged or discharged.

The capacitor 17 is a stray capacitance of the signal line 12, but a separate capacitor connected to the signal line 12 may be used.

FIG. 3 is a diagram showing a portion of the horizontal drive circuit 124 and the liquid crystal panel 125 in detail in order to explain an example of the drive method of the present invention. The operation shown in FIG. 3 will be explained using the timing chart shown in FIG. The horizontal drive circuit 124 has two
It has a stage sample and hold circuit. Horizontal drive circuit 12
The video signal (luminance signal or R, G, B signal, etc.) input to 4 is processed by a switch 1241 in the first stage sample hold circuit into a sample nox signal whose phase matches the position of the pixel in the horizontal scanning direction. It is sampled at φ1 and held in a capacitor 1242. When the input video signal is of positive polarity, by turning on the switch 1245 with the pulse φ3 at the beginning of the horizontal blanking period, the output terminal potential v4 of the second stage sample and hold circuit is changed to the potential ■ applied to the switch 1245. Set it to 1. A gate pulse PSW is input with the same phase as this pulse φ3, turning on the transistor 16, and the potential V of the signal line 12 becomes the common electrode potential V of the liquid crystal cell 15. It is discharged to the same potential as.

Next, in the second-stage sample-and-hold circuit, a switch 1243 performs a sample using the sample pulse φ2, and the charge in the capacitor 1242 in the first-stage sample-and-hold circuit is transferred to a capacitor 1244. As a result, the output terminal potential V of the second stage sample and hold circuit
4 is φ1 in the first stage sample and hold circuit.
6 The potential of the sampled video signal becomes higher than vl by the potential v5+. At this time, the transistor 16 is off, so the output voltage (v
s+-Vl) is supplied to the signal line 12 via an output buffer 1247 and a capacitor 1248, and the potentials of the signal line 12 are V and -V. +(Vs+V+). Next, the switching transistor 13 of the pixel receives the gate pulse VV.
When turned on by I, the individual electrode potential v of the liquid crystal cell 15
6 has the same potential as approximately V, and even after the transistor 13 is turned off, the capacitor 14 maintains v6 at approximately V.

When the input video signal of the horizontal drive circuit 124 is of negative polarity, the input video signal has a potential based on v max as shown in FIG. 4, and the capacitor 1242 has (V l1lax V s- ) is held.

Then, by turning on the switch 1246 with a pulse φ4 at the beginning of horizontal blanking, the output terminal potential v4 of the second-stage sample-and-hold circuit is set to the potential v2 applied to the switch 1245.

At the same time, the gate pulse PSW is input with the same phase as the pulse φ4 and the transistor 16 is turned on, so that the potential V5 of the signal line 12 is changed to the common electrode potential of the liquid crystal cell 15.
. It is discharged to the same potential as. Hereinafter, similarly to the case where the input video signal is of positive polarity, the switch 1243 is used to generate the sample pulse φ in the second stage sample hold circuit.
2, the signal line 12 has V
2- (V max -V s-) is supplied, and the potential of the signal line 12 is V, -VO+ (V max -V
s-V2). Further, the individual electrode potential V6 is also approximately V,
The potential is the same as that of

Here, if v1=0, V2=VmaX,
The individual electrode potential v6 is V when the input video signal is of positive polarity. 10V5+, V for negative polarity. -V5-.

On the other hand, the common electrode potential V. is always constant. Therefore, positive and negative voltages +vs+, -V, and - are applied alternately to the liquid crystal cell 15, and AC driving is achieved.

8 By the way, the applied voltage-transmittance characteristic of the liquid crystal cell 15 is the fifth
As shown in the figure, when the threshold value vth is present, the applied voltage is V.

During +vth, the transmittance of the liquid crystal cell 15 does not change. In such a case, the amplitude of the input video signal to the horizontal drive circuit 124 can be reduced by vth as shown in the figure. Specifically, switch 1245.12413 in FIG.
The potentials V, , V2 applied to Vl--V
Th.

It may be set as V2-Viax+Vth. In this way, the individual electrode potential V6 is V when the input video signal is of positive polarity. +vs +v th, V in case of negative polarity
o (Vs-+Vth). At this time, the liquid crystal cell 15 has Vs, +Vth, -(Vs-+Vth
) is applied. Therefore, horizontal drive circuit 124
The amplitude of the input video signal only needs to be a voltage corresponding to a change that actually contributes to the response of the liquid crystal after subtracting Vth, which is 1/2 to 1/3 of that in the conventional case.

FIG. 6 shows switches 1241, 1243.
An example is shown in which the 1245 and 1246 are configured with CMOS analog switches, and the output buffer (amplifier) is configured with MOS) rungs. Output buffer is N channel M
The OS transistor 1250 is used as a source follower, and a bias VB is applied to the gate of the N-channel MO8I transistor 1251. In this way, the output terminal potential of the second stage sample and hold circuit is set to Vl or V2 by the pulse φ3 or φ4, and the change due to the input video signal is supplied to the signal line 12 with the output of the source follower at that time as a reference. By doing so, it is possible to prevent the influence of the output offset of the source follower from appearing on the signal line 12.

In an actual liquid crystal panel, the stray capacitance of each signal line 12 is several tens of pF to several hundred pP, so in order to accurately transmit the video signal voltage to the signal line 12, the capacitor 124 is
8 is preferably as large as possible; for example, several thousand pP is sometimes desired. In this case, assuming that the horizontal drive circuit 124 is implemented as an IC, a capacitance of several thousand pP can be applied to the IC.
Since it is difficult to form the capacitor 124B on-chip, the capacitor 124B may be attached externally to the IC and configured as shown in FIG.

0 FIG. 8 shows an example of mounting the horizontal drive circuit 124 and liquid crystal panel 125 in FIG. 7. A chip capacitor is inserted as a capacitor 1248 in the middle of the lead 1250 of the signal line 12 in the liquid crystal panel 125, and this is connected to the IC of the horizontal drive circuit 124.

Figure 9 shows two sample and hold circuits installed in parallel,
This is an embodiment in which the input video signal is switched and output every H (horizontal scanning period), and its operation is shown in the timing chart of FIG. For example, in the 1st H, switch 1
241 samples the input video signal with sample pulse φ1, and switches 1245 during the horizontal blanking period.
Accordingly, the output terminal potential v4 of the sample and hold circuit is set to Vl by the pulse φ, and the output terminal potential of the output buffer 1247 is also set to approximately v1. At the same time, the switching transistor 16 is turned on by the gate pulse PSW, and the potential of the signal line 12 is set to V. Charge (discharge) to. Next, in the second H, by turning on the switch 1243 with the transfer pulse φ2, the sampled and held value VS+ of the input video signal is transmitted to v4, and the potential of the signal line 12 becomes Vo + (Vs+
-Vl). Similarly, the 2nd H-th video signal is sampled by the switch 1251 using the sample pulse φ1, and is outputted at the 3rd H-th by turning on the switch 1253 with the transfer pulse φ2. Similarly, when a negative polarity video signal is input, the potential of V4 is set to V2 by the pulse φ4 using the switch 1246, so that the liquid crystal panel 125
transmits video signals to.

In addition, in the example so far, each pixel Gl of the liquid crystal panel 125
l～G□. The switch transistor 13 has been considered to be an ideal switch, but in reality, as shown in FIG. 11, there is a gate overlap capacitor 18 between the gate and drain of the transistor, so as shown in FIG. When the gate pulses (VVI, VV2, . . . ) are turned off, the individual electrode potential of each pixel changes in proportion to the amplitude of the gate pulse PSW. Therefore, the individual electrode potential of each pixel slightly deviates from the voltage value of the input video signal. This voltage deviation can be corrected by selecting the potentials V, V2 applied to the switches 1245 and 1246. For example, when the input video signal has positive polarity as described above, the potential v5 of the signal line 12 is V o + (V s + V
l), so if the potential V1 is set equal to the potential drop ΔV due to the gate overlap capacitor 18, then
Individual electrode potential is V. 10V5+, which is a value that exactly corresponds to the input video signal.

Another method for correcting this voltage drop ΔV is to set the charging (discharging) voltage of the signal line 12 to V.

Instead, it may be set to (VO+ΔV).

FIG. 13 shows a horizontal drive circuit 1 in another embodiment of the present invention.
24 and a part of the liquid crystal panel 125 in detail, and when a threshold value Vth exists in the applied voltage-transmittance characteristic of the liquid crystal cell 15 as shown in FIG. 5, the output of the horizontal drive circuit 124 This allows the amplitude to be reduced. In FIG. 13, the signal line 123 is connected to the common electrode potential V via the switch 16. V through switch 16 and changeover switch 19 without connecting to
01-V o + V th, V 02-Vo -
It is configured to be selectively connected to a point of potential Vth.

That is, instead of charging (discharging) the signal line 12 to the common electrode potential VO of the liquid crystal cell 15 before applying the video signal to the signal line 12 as in the previous embodiments, As shown in the timing chart in the figure, when the input video signal is of positive polarity, the switch 19 is set to Vo1 side, and when it is of negative polarity, it is set to V. 2 side, common electrode potential V
. The configuration is such that charging (or discharging) is performed to a potential obtained by adding a threshold value vth to the potential. In this way, the output of the horizontal drive circuit 124 only needs to be the change in the video signal, Vs+ or Vt, and does not need to include the threshold value vth, so its amplitude becomes even smaller.

In this embodiment as well, the gate overlap capacitor 1
To correct the voltage drop ΔV due to 8, Vo + vth + Δv - VollVo
-Vth+Δv-Vo2 may be used.

FIG. 15 shows another embodiment of the horizontal drive circuit 124, in which the output buffer 1247 is constructed using both an N-channel MOS transistor source follower and a P-channel MOS transistor source follower.

In addition, the present invention can be modified and implemented without departing from the scope of the invention.

[Effects of the Invention] As explained above, according to the present invention, by charging or discharging the signal line of a liquid crystal panel to a constant potential before applying a video signal, a video signal can be supplied to the signal line even in the case of AC drive. It becomes possible to reduce the input amplitude of the horizontal drive circuit to 172 or less.

In addition, if the applied voltage-transmittance characteristic of the liquid crystal cell has a threshold value, the output amplitude of the horizontal drive circuit can be adjusted by setting the charging or discharging potential of the signal line to the common electrode potential of the liquid crystal cell plus the threshold value. It can be made even smaller.

5 This makes it possible to lower the power supply voltage of the horizontal drive circuit, achieving low power consumption, and reducing the dynamic range of amplifiers such as output buffers in the horizontal drive circuit, improving linearity and reducing offset. It is possible to realize a liquid crystal display device with high image quality by reducing the amount of image.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a diagram showing details of the configuration of the vertical scanning circuit, horizontal drive circuit, and liquid crystal panel in FIG. 1, and FIG. 3 is a horizontal drive circuit diagram. A diagram showing a part of the circuit and the liquid crystal panel in more detail, FIG. 4 is a timing chart showing the operation of FIG. A diagram showing the relationship between voltages of video signals. Figure 6 is a diagram showing details of the horizontal drive circuit and part of the liquid crystal panel when the horizontal drive circuit in Figure 3 is configured with MOS analog switches. Figure 7 is a diagram showing the horizontal drive circuit in Figure 3 and a part of the liquid crystal panel. 6. A diagram showing in detail the configuration of a vertical scanning circuit, a horizontal drive circuit, and a liquid crystal panel when the output capacitor in the drive circuit is externally attached,
FIG. 8 is a cross-sectional view showing an example of a mounting structure of a horizontal drive circuit, a capacitor, and a liquid crystal panel, FIG. 9 is a diagram showing another embodiment of the horizontal drive circuit according to the present invention, and FIG. 10 is an operation of FIG. 9. FIG. 11 is a diagram showing a horizontal drive circuit and part of the liquid crystal panel to explain errors occurring in the liquid crystal panel. FIG. 12 is a timing chart showing the operation of FIG. 11. FIG. 13 is a timing chart showing the operation of FIG. 14 is a timing chart showing the operation of FIG. 13, and FIG. 15 is a diagram showing a part of the horizontal drive circuit and liquid crystal panel in another embodiment of the present invention. 16 is a block diagram of a conventional general liquid crystal television; FIG. 17 is a diagram showing a liquid crystal panel, vertical scanning circuit, and horizontal drive circuit in a conventional liquid crystal display device; FIG. 18 is a block diagram of a conventional general LCD television. Figure 1 shows the horizontal drive circuit in detail.
FIG. 9 is a timing chart showing the operations of FIGS. 17 and 18, and FIG. 20 is a diagram showing an example of the applied voltage 7 transmittance characteristics of the liquid crystal cell. 11...Address line, 12...Signal line, G11~G
mn... Pixel (liquid crystal display element), 13... Switching transistor, 14... Capacitor, 15...
・Liquid crystal cell, 16... Switching transistor, 1
23... Vertical scanning circuit, 124... Horizontal drive circuit,
125...Liquid crystal panel.

Claims (3)

[Claims] (1) A liquid crystal panel in which a plurality of liquid crystal display elements are respectively connected to the intersections of a plurality of address lines along the horizontal scanning direction and a plurality of signal lines along the vertical scanning direction, and the plurality of address lines are sequentially scanned. scanning means for driving the plurality of signal lines with video signals in synchronization with the scanning of the address lines by the scanning means; 1. A liquid crystal display device comprising means for charging or discharging the battery to a predetermined constant potential. (2) A configuration in which multiple liquid crystal display elements including liquid crystal cells each having a common electrode and individual electrodes are connected to the intersections of multiple address lines along the horizontal scanning direction and multiple signal lines along the vertical scanning direction. a liquid crystal panel in which the transmittance of the liquid crystal cell changes when a voltage equal to or higher than a predetermined threshold is applied to the liquid crystal cell; a scanning means for sequentially scanning the plurality of address lines; and a scanning means for scanning the address lines by the scanning means. a driving means for synchronously driving the plurality of signal lines with a video signal; and before driving the plurality of signal lines by the driving means,
A liquid crystal display device comprising means for charging or discharging the signal line to a constant potential obtained by adding the threshold value to the common electrode potential of the liquid crystal cell. (3) The liquid crystal display device according to claim 1 or 2, wherein the driving means applies only a change in the video signal with respect to the constant potential to the signal line.