JP2002358052A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which deviation in the voltages being held in pixels is reduced to thus obtain good display quality. SOLUTION: Changes in gate line driving voltages are reduced by changing the gate line driving voltage for turning off a pixel driving transistor from a voltage for turning on a gate to a voltage for turning off a first gate, and deviation 49 in image signal voltages to be held in pixels is made smaller compared with the deviation in a conventional case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a driving circuit for a liquid crystal display using thin film transistors.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional liquid crystal display using thin film transistors. Reference numeral 1 denotes an N-channel transistor which drives a pixel of the liquid crystal display device. Reference numeral 2 denotes a storage capacity of a pixel, and reference numeral 3 denotes a liquid crystal, which is a capacitive load. 4 is a counter electrode. A constant voltage is applied to the counter electrode. Reference numeral 5 denotes a source line connected to the source terminal of the pixel transistor 1, reference numeral 6 denotes a gate line connected to the gate of the pixel transistor 1, and reference numeral 7 denotes a storage capacitor line connected to the storage capacitor 2.

[0005] Reference numeral 8 denotes a gate line driving circuit for driving a gate line. 9 is a source line drive circuit for driving the source line 5. 10 is a gate line drive circuit 8, a source line drive circuit 9
2 shows a control signal and image data input to the CPU. A transistor 11 switches an output signal of the source line driving circuit 9.

The gate drive circuit sequentially scans the gate electrode, applies a voltage for turning on the pixel transistor on the same gate electrode to the gate line, and the source drive circuit multiplexes an image signal voltage corresponding to image data to be displayed. Using the drive, outputs are sequentially output in chronological order. The switch circuit controls the control signal 12 of the switch circuit input to the gate of the transistor constituting the switch circuit, and the source drive circuit outputs the signal by closing each switch circuit. The image signal voltage is charged according to the capacitance of the source line by charging the image signal voltage to be applied and opening the switch circuit. This operation is sequentially performed for each source line to be multiplex-driven, so that each source line is charged to a desired image signal voltage. Further, the storage capacitor and the liquid crystal are charged to a desired image signal voltage via the pixel transistor.

Next, a voltage for turning off the pixel transistor on the same gate line is applied to the gate electrode, the pixel transistor is turned off, and the storage capacitor and the image signal voltage applied to the liquid crystal are held.

Next, by changing the drive voltage of the storage capacitor line from the voltage applied during the period when the gate line is turned on, a bias voltage corresponding to the difference voltage of the changed drive voltage is obtained. The voltage is superimposed and applied. The application of the drive voltage to the storage capacitor lines is sequentially performed on each storage capacitor line in accordance with the scanning of the gate line, and the entire screen is displayed. Also, in the next screen display, the bias voltage is applied in the reverse direction by applying the drive voltage so that the direction in which the previous drive voltage changes is the opposite direction. By applying a voltage of the opposite polarity to that of the previous screen display in advance,
The voltage applied to the liquid crystal is converted to AC and driven. At this time, the counter voltage is adjusted so that no DC voltage is applied to the liquid crystal.

FIG. 4 is a timing chart of a conventional driving circuit. Reference numeral 41 denotes a drive waveform applied to the gate line. The pixel drive transistor is turned on when it is at a high level, and turned off when it is at a low level. The gate lines are sequentially scanned, and the scanning is sequentially repeated for each screen display frame. The high level of the driving waveform of the gate is set so that the storage capacitor and the liquid crystal are sufficiently charged by using a pixel transistor for the image signal voltage applied to the source, and a voltage of about 10 V is generally applied. On the other hand, the voltage for turning off the gate is set so that the pixel transistor is turned off with respect to the held voltage of each pixel so that the voltage held in each pixel does not change. In general, a voltage of about -5 V is applied. I do.

Reference numeral 42 denotes a driving waveform applied to the storage capacitor line. The drive waveform of the storage capacitor line changes after the gate line is turned on, and is driven such that its polarity changes for each display frame. The values of the high level and the low level of the drive voltage applied to the storage capacitor line are generally set to about 10 V and about 0 V, and the ratio of the liquid crystal capacitor to the storage capacitor is set so that a voltage of about 5 V is transmitted as a bias voltage transmitted to the pixel. Is set when designing the mask.

Reference numeral 45 denotes a control signal for opening and closing the switch circuit. The control signal 45 holds the output signals of the source drive circuit output by multiplex driving in the source line in order. The high level of this control signal is set so that the capacitance of the source line is sufficiently charged using the transistor of the switch circuit to the image signal voltage applied to the source, while the low level is set when the switch circuit is turned off. Also, the switch transistor is set to be turned off with respect to the held voltage of each source line so that the voltage held in each source line does not change. In general, the high level of the control signal for opening and closing the switch circuit is set to +10 V and the low level is set to -5 V in many cases in common with the gate line driving circuit.

Reference numeral 46 denotes an output signal of the source line drive circuit, showing how the image signal voltage is multiplexed and output. The voltage level of the image signal voltage is generally a high level of about 5V and a low level of about 0V.
47 indicates a voltage waveform applied to the pixel. Regarding the voltage applied to the pixel, first, an on-voltage is applied to the gate line to turn on the pixel driving transistor, and the voltage of the source line is applied.

Next, by turning on the control signal of the switch circuit, each source line is charged with the image signal voltage output from the multiplexed source line drive circuit, and the control signal of the switch circuit is turned off. The image signal voltage is held in each source line, and the image signal voltage of each source line is applied to the storage capacitor and the liquid crystal through the pixel driving transistor.

However, when the switch circuit is turned off, a control signal for controlling the switch circuit is superimposed on the basis of the ratio of the gate capacitance of the transistor constituting the switch circuit to the capacitance of the source line, and the image signal voltage held in the source line is held. Is generated. The deviation 48 of the image signal voltage held in the source line is proportional to the amplitude of the control signal for controlling the switch circuit.

Next, when an off-voltage is applied to the gate line, the image signal voltage held in the source line is held in the storage capacitor and the liquid crystal when the pixel driving transistor is turned off.

However, when the pixel transistor is turned off, the gate drive voltage is superimposed due to the ratio of the gate capacity of the pixel drive transistor to the storage capacity and the liquid crystal capacity, and a shift 49 occurs in the image signal voltage held in the pixel. Let it. The deviation 49 of the image signal voltage held in the pixel is proportional to the amplitude of the gate line driving voltage.

Next, after a voltage for turning off the pixel transistor is applied to the gate line, the storage capacitor line drive voltage is changed, so that the pixel voltage becomes a bias voltage corresponding to the difference voltage of the changed drive voltage. , And is applied until the next frame. In a normal design, the ratio between the liquid crystal capacitance and the storage capacitance is set at the time of mask design so that a voltage of about 5 V is transmitted as a bias voltage. In the next frame, a bias voltage of the opposite polarity is applied for the alternating current of the liquid crystal.

As described above, the image signal voltage, which is the output signal of the source line drive circuit, is applied to the pixel voltage during the period from when the gate line is turned on to when the drive waveform of the storage capacitor line changes. Its voltage ranges between about 0V and about 5V. In addition, during the period from when the drive waveform of the storage capacitor line changes to when the gate line turns on next, the image signal voltage is maintained at a voltage obtained by adding a bias voltage according to the changed voltage of the drive waveform of the storage capacitor line. Is done. The voltages are in the range of about 7.5V and about -2.5V.

[0017]

However, in the conventional liquid crystal display device, as described above, the deviation 48 of the image signal voltage held in the source line or the image signal voltage held in the pixel is reduced. This causes a shift 49, which does not cause much problem in the case of normal display, but causes a problem such as generation of flicker at the time of displaying a specific pattern such as a display pattern which is inverted for each line. This is due to the fact that the alternating of the liquid crystal has not been sufficiently performed due to the above-mentioned deviation of the holding voltage, and there has been a problem in stabilizing the characteristics in manufacturing the liquid crystal display device, such as variation in each liquid crystal display device. . As a countermeasure, if countermeasures such as adjusting the opposing voltage to correct the alternating current of the liquid crystal are individually adjusted for each liquid crystal display device, the number of steps in manufacturing the liquid crystal display device increases, and there is a problem. .

In the conventional liquid crystal display device, the time for charging the source line is shortened when using the multiplex drive, and the number of multiplexes is increased to reduce the number of outputs of the source drive circuit. There is a problem that the shortage occurs and a problem such as a decrease in contrast of a displayed image occurs.

[0019]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device which reduces the problems of flickering and lowering the contrast in the liquid crystal display device of the present invention. In order to achieve the above object, in a liquid crystal display device of the present invention, in a liquid crystal display device, a pixel driving transistor formed by a display pixel, a thin film transistor driving the display pixel, and a source line connected to a source terminal of the pixel driving transistor A source line driving circuit for applying an image signal voltage to the pixel, a gate line driving circuit for driving a gate line connected to a gate terminal of the pixel driving transistor, and a circuit between the display pixel and the pixel driving transistor. And a storage capacitor line driving circuit for driving a storage capacitor line connected to the storage capacitor element,
The driving method is to apply a predetermined compensation voltage to the storage capacitor line, and the compensation voltage is applied after an ON voltage for turning on the pixel driving transistor is applied to a gate line. After applying a predetermined voltage until a predetermined off voltage for turning off the pixel transistor is applied to the gate line, by switching to a voltage different from the predetermined voltage, the voltage of the display pixel and the image signal voltage An active matrix type liquid crystal display device which superimposes and applies a compensation voltage, wherein a predetermined off-state voltage applied to a gate line for turning off the pixel transistor comprises first and second off-state voltages, The off voltage is applied to the gate line during a period from when the pixel transistor is turned off to when the compensation voltage is switched, and the second off voltage is the compensation voltage. After changing switches, is applied to the gate line in the period leading up to the next gate line is turned on, the first
Is the voltage between the on-voltage and the second off-voltage, and during the period in which the first off-voltage is applied, the first off-voltage is a voltage that further turns off the pixel driving transistor. There is a feature.

According to this structure, the gate line driving voltage when the pixel driving transistor is turned off is changed from the voltage for turning on the gate to the voltage for turning off the first gate, thereby changing the gate line driving voltage. And the deviation 49 of the image signal voltage held in the pixel can be reduced as compared with the conventional one. Therefore, it is possible to realize a liquid crystal display device that suppresses flicker and its flicker.

Further, the gate line driving circuit or the storage capacitor line driving circuit is formed by an integrated circuit using a thin film transistor, and is formed on the same substrate by using the same process for forming a pixel driving transistor. Features. According to this configuration, the gate line driving circuit can be formed on the same substrate at the same time as the process of manufacturing the pixel driving transistor, so that an inexpensive liquid crystal display device can be realized.

Also, a pixel driving transistor formed by a display pixel and a thin film transistor for driving the display pixel, and a source line drive for applying an image signal voltage to a source line connected to a source terminal of the pixel driving transistor A circuit, a gate line driving circuit driving a gate line connected to a gate terminal of the pixel driving transistor, a storage capacitor element formed between the display pixel and the pixel driving transistor, and a storage capacitor A storage capacitor line driving circuit for driving a storage capacitor line connected to the element,
The driving method is to apply a predetermined compensation voltage to the storage capacitor line, and the compensation voltage is applied after an ON voltage for turning on the pixel driving transistor is applied to a gate line. After applying a predetermined voltage until a predetermined off voltage for turning off the pixel transistor is applied to the gate line, by switching to a voltage different from the predetermined voltage, the voltage of the display pixel and the image signal voltage A compensating voltage is superimposed and applied, and the image signal voltage is multiplexed and provided by the source line driving circuit. A switching circuit including a transistor is provided between the source line driving circuit and the source line, and the switching circuit is turned on. An active matrix that charges a source line to the image signal voltage, turns off a switch circuit, and holds the image signal voltage on the source line There the liquid crystal display device, characterized in that said upper limit voltage or more of the image signal voltage a voltage for turning off the switching circuit composed of transistors or below the lower limit voltage.

According to this structure, the voltage at which the transistor constituting the switch circuit is turned off is set as described above, and the voltage that changes from the voltage for turning on the switch circuit to the voltage for turning off is minimized to control the switch. Therefore, the change 48 in the image signal voltage held in the source line can be reduced as compared with the conventional one. Therefore, it is possible to realize a liquid crystal display device that suppresses flicker and its flicker.

Further, the switch circuit is formed by an integrated circuit using a thin film transistor, and is formed on the same substrate by using the same process for forming a pixel driving transistor.

According to this configuration, the switch circuit can be simultaneously formed on the same substrate in the process of manufacturing the pixel driving transistor, so that an inexpensive liquid crystal display device can be realized.

Also, a pixel driving transistor formed by a display pixel and a thin film transistor for driving the display pixel, and a source line drive for applying an image signal voltage to a source line connected to a source terminal of the pixel driving transistor A circuit, a gate line driving circuit driving a gate line connected to a gate terminal of the pixel driving transistor, a storage capacitor element formed between the display pixel and the pixel driving transistor, and a storage capacitor A storage capacitor line driving circuit for driving a storage capacitor line connected to the element,
The driving method is to apply a predetermined compensation voltage to the storage capacitor line, and the compensation voltage is applied after an ON voltage for turning on the pixel driving transistor is applied to a gate line. After applying a predetermined voltage until a predetermined off voltage for turning off the pixel transistor is applied to the gate line, by switching to a voltage different from the predetermined voltage, the voltage of the display pixel and the image signal voltage A compensating voltage is superimposed and applied, and the image signal voltage is multiplexed and provided by the source line driving circuit. A switching circuit including a transistor is provided between the source line driving circuit and the source line, and the switching circuit is turned on. An active matrix that charges a source line to the image signal voltage, turns off a switch circuit, and holds the image signal voltage on the source line In the liquid crystal display device, a precharge circuit including a transistor is provided between the source line and a predetermined drive voltage, and the switch circuit is provided for the purpose of reducing a time required for the source line drive circuit to charge the source line. Before the source line drive circuit charges the image signal voltage to the source line, the precharge circuit charges the source line to a predetermined voltage.

According to this structure, the potential of the source line is charged to a predetermined potential by the precharge circuit in advance, so that the time required for the source line driving circuit to charge the source line can be reduced, and the number of multiplex signals can be reduced. It is possible to realize a liquid crystal display device without lowering the contrast that occurs when the number increases.

Further, the predetermined drive voltage of the precharge circuit is approximately half the voltage of the image signal voltage. According to this configuration, the time required for the source line drive circuit to charge the source line can be substantially minimized.

Further, the precharge circuit is formed of an integrated circuit using thin film transistors, and is formed on the same substrate by using the same process for forming a pixel driving transistor.

According to this configuration, a precharge circuit can be simultaneously formed on the same substrate in the process of manufacturing the pixel driving transistor, so that an inexpensive liquid crystal display device can be realized.

[0031]

Embodiments of the present invention will be described below.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a structure of a liquid crystal display device according to the present invention (Embodiment 1). Hereinafter, FIG. 1 will be described. The same components as those in FIG. 3 showing the conventional driving circuit are denoted by the same reference numerals, and description thereof will be omitted.
In FIG. 1, the configuration of the liquid crystal display device according to the first embodiment of the present invention is different from the conventional example in that a precharge circuit 11 composed of a thin film transistor is provided for each source line separately from a switch circuit 13 composed of a thin film transistor.
Is provided. Reference numeral 14 denotes an input terminal of a precharge voltage commonly input to a control signal for commonly controlling a transistor which is a precharge circuit provided for each source line.

FIG. 2 is a timing chart of the liquid crystal display device according to the present invention (Embodiment 1), and its operation will be described. Hereinafter, FIG. 2 will be described. 2 which shows a timing chart of a conventional liquid crystal display device and which is the same as that in FIG.

Referring to FIG. 2, (Embodiment 1) of the present invention
The difference between the timing chart of the liquid crystal display device and the conventional example in the first example is the gate line driving waveform. Reference numeral 21 denotes a drive waveform applied to the gate line according to the first embodiment of the present invention, and the gate line is sequentially scanned as in the conventional example. The pixel driving transistor is turned on when the highest voltage is output, and the storage capacitor and the liquid crystal are set to be sufficiently charged using the pixel transistor for the image signal voltage applied to the source. Voltage of the order of magnitude. The voltages of the pixel and the source line are approximately the same as the image signal voltage. The output signal of the source line driving circuit has a high level of about 5 V and a low level of 0 V as in the conventional example.
The image signal voltage is multiplexed and output at about the same voltage.

Next, a first off voltage for turning off the pixel transistor is applied to the gate line. The voltage at this time was set to about 0 V so that the pixel transistor was turned off because the voltage of the pixel and the source line were in the range of about 0 V to 5 V. Since the pixel transistor is an N-channel thin film transistor of an enhancement type and has a threshold voltage of about 2 V, the pixel transistor can be sufficiently turned off by applying the aforementioned 0 V to the gate.

Reference numeral 42 denotes a drive waveform applied to the storage capacitor line as in the conventional example. The drive waveform of the storage capacitor line changes after the gate line is turned on, and is driven such that its polarity changes for each display frame. The high-level and low-level values of the drive voltage applied to the storage capacitor line are 10
The ratio between the liquid crystal capacitance and the storage capacitance was set at the time of mask design so that V was set to a value of about 0 V and a voltage of about 5 V was transmitted as a bias voltage transmitted to the pixel.

Reference numeral 24 denotes a control signal for opening / closing the switch circuit. The output signal of the source drive circuit, which is output by multiplex driving in the same manner as in the prior art, is sequentially held in the source line.
The high level of the control signal is set to +10 V so that the capacity of the source line is sufficiently charged using the transistor of the switch circuit to the image signal voltage applied to the source as in the conventional example.

However, the low level is sufficient if the voltage held in each source line or the voltage held in the pixel does not change even if the switch circuit is turned off, so that the gate line is turned on. At the timing, the voltage of the source line or the pixel is set to a voltage of about 0 V, paying attention to the fact that the voltage of the pixel is substantially in the range of 0 V to 5 V which is substantially equal to the image signal voltage. The thin-film transistor constituting the switch is an N-channel thin-film transistor formed in the same process as the pixel and is an enhancement type, and its threshold voltage is about 2 V, which is equivalent to that of the pixel transistor. , The switch circuit can be sufficiently turned off.

Reference numeral 25 denotes a control signal for controlling the precharge circuit, which is controlled at the same control signal level as that of the switch circuit. Also, a half voltage of the image signal voltage is prepared and supplied as the input voltage of the precharge circuit. The input voltage of the precharge circuit functions even when the same power supply that supplies a counter voltage is used.

Reference numeral 25 denotes a voltage waveform applied to the pixel.
Regarding the voltage applied to the pixel, first, an on-voltage is applied to the gate line to turn on the pixel driving transistor, and the voltage of the source line is applied. Next, when the control signal of the precharge circuit is turned on, the potential of each source line is charged to the input voltage of the precharge circuit. next,
By turning on the control signal of the switch circuit, each source line is charged to the image signal voltage which is the output of the multiplexed source line drive circuit, and by turning off the control signal of the switch circuit, each image signal voltage is changed. The image signal voltage of each source line is applied to the storage capacitor and the liquid crystal via the pixel driving transistor while being held at the source line.

By using a precharge circuit,
When the source line voltage is once charged to half the image signal voltage, the switch circuit is closed again, and the source line driving circuit is charged to a predetermined image signal voltage, so that the precharge circuit is not used. It is possible to charge up to a predetermined image signal in a shorter time than in the case of.

By setting the level at which the control circuit of the switch circuit and the precharge signal are turned off to about 0 V, the voltage difference of 15 V between the on level and the off level of the control signal of the conventional example can be reduced according to the present invention. In the invention of 1), the voltage difference between the ON level and the OFF level of the control signal is 10
V, and when the switch circuit is turned off, a control signal for controlling the switch circuit is superimposed by the ratio of the gate capacitance of the transistor forming the switch circuit to the capacitance of the source line, and is held in the source line. The occurrence of the deviation 48 in the image signal voltage can be reduced to 2/3 in proportion to the amplitude of the control signal for controlling the switch circuit.

The off level of the control signal for controlling the switch is set to 0 V this time. However, in order to reduce the deviation of the image signal voltage held in the source line, the off level is set to about the threshold voltage of the transistor constituting the switch. The voltage may be set, or a negative voltage of about several volts may be used to turn off the switch transistor. In the first embodiment of the present invention, the off-level value is reduced to suppress the deviation of the image signal held in the source line. However, when the switch circuit is turned off, the waveform of the control signal is turned off. While recharging the gate voltage of the transistors that make up the switch circuit,
By turning off, it goes without saying that the deviation of the image signal voltage held in the source line is further reduced in combination with the first embodiment of the present invention.

Next, when the first off-voltage is applied to the gate line, the image signal voltage held in the source line is held in the storage capacitor and the liquid crystal when the pixel driving transistor is turned off.

As described above, since the voltages of the pixel and the source line are in the range of about 0 V to 5 V, the first
By applying 0 V to the gate as an off voltage of
The pixel transistor can be sufficiently turned off. By applying a first off-voltage for turning off the pixel transistor to the gate line, a voltage difference of 15 V between the on-level and the off-level of the drive voltage of the gate line in the conventional example can be reduced by the invention of the first embodiment of the present invention. In the above, the voltage difference between the ON level and the OFF level of the drive voltage of the gate line can be reduced to 10 V,
When the pixel transistor is turned off, the gate line driving voltage applied to the pixel transistor is superimposed due to the ratio of the gate capacitance of the pixel transistor to the storage capacitance and the capacitance of the liquid crystal, and a shift 49 occurs in the image signal voltage held in the pixel. Can be reduced to 2/3 in proportion to the amplitude of the gate line drive voltage for controlling the pixel transistor.

Although the first off voltage for turning off the pixel transistor was set to 0 V this time, in order to reduce the deviation of the image signal voltage held in the pixel, the first off voltage was set to about the threshold voltage of the transistor constituting the switch. The voltage may be set, or a negative voltage of about several volts may be used to turn off the switch transistor.

In the first embodiment of the present invention, a voltage for turning off the first gate line of the gate line is provided to suppress the deviation of the image signal held in the pixel, but the pixel transistor is turned off. In this case, the waveform of the drive voltage of the gate line, which is the control signal, is blunted or switched stepwise so that the gate voltage of the pixel transistor is turned off while being recharged. Form 1)
In addition, it goes without saying that the deviation of the image signal voltage held in the pixel is further reduced.

Next, after a first off voltage for turning off the pixel transistor is applied to the gate line, the voltage applied to the gate line is switched to the second off voltage. The second off-state voltage must be set so that the pixel transistor is turned off with respect to the voltage held in the pixel. Since the voltage held in the pixel is about 7.5 V to about -2.5 V, the voltage is set to -5 V similarly to the off-state voltage of the conventional example.

Next, by changing the storage capacitor line driving voltage, the pixel voltage is applied with a bias voltage corresponding to the difference voltage of the changed driving voltage superimposed on the pixel voltage and held until the next frame. You. As in the conventional design, the ratio between the liquid crystal capacitance and the storage capacitance was set at the time of mask design so that a voltage of about 5 V was transmitted as a bias voltage.

In the next frame, the driving waveform of the storage capacitor line is inverted so that a bias voltage of the opposite polarity is applied in order to make the liquid crystal AC. As described above, the image signal voltage, which is the output signal of the source line driving circuit, is applied to the pixel voltage during the period from when the gate line is turned on to when the driving waveform of the storage capacitor line changes. Its voltage is about 0V and about 5
V range. At this time, the first off-state voltage of 0 V was applied to the gate line so that the deviation of the voltage held in the pixel was reduced.

In the period from when the drive waveform of the storage capacitor line changes to when the gate line turns on next, a bias voltage corresponding to the changed voltage of the storage capacitor line drive waveform is applied to the image signal voltage. It is held at voltage. The voltages are in the range of about 7.5V and about -2.5V. At this time, the second off voltage of −5 V was applied to the gate line to turn off the pixel transistor so that the voltage held in the pixel did not leak.

In the first embodiment of the present invention, as described above, the gate line driving circuit, the storage capacitor line driving circuit,
The switch circuit and the precharge circuit are formed by an integrated circuit using thin film transistors, and are collectively formed over the same substrate by using the same process for forming a pixel driving transistor.

(Embodiment 2) The liquid crystal display device described in (Embodiment 1) of the present invention has the same configuration, and the pixel transistors and the transistors used in the driving circuit are P channel transistors. Mode 1) The same effect was obtained.

[0054]

As described above, by using the liquid crystal display device of the present invention, the shift 48 in the image signal voltage held in the source line and the shift 4 in the image signal voltage held in the pixel.
9 can be reduced, flicker and its variation can be improved, and a liquid crystal display device that achieves good display quality can be realized.
In addition, the insufficiency of the source line charging capability when the number of multiplexes is increased can be improved by using a precharge circuit, and a liquid crystal display device that achieves good display quality without a decrease in contrast of a displayed image can be realized. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a drive circuit according to an embodiment of the present invention.

FIG. 2 is a timing chart showing an operation of a driving circuit according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional liquid crystal display device.

FIG. 4 is a timing chart showing the operation of a drive circuit in a conventional liquid crystal display device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 pixel drive transistor 2 storage capacitor 3 liquid crystal 4 counter electrode 5 source line 6 gate line 7 storage capacitor line 8 gate drive circuit 9 source drive circuit 10 control signal and image data 11 thin film transistor switch circuit 12 signal for controlling switch circuit 13 Precharge circuit by thin film transistor 14 Signal for controlling precharge circuit and drive voltage input to precharge circuit 21 Gate line drive waveform of liquid crystal display device of the present invention 24 Signal waveform for controlling switch circuit of liquid crystal display device of the present invention 24 25 Pixel voltage waveform of liquid crystal display device of the present invention 41 Gate line drive waveform of conventional liquid crystal display device 42 Storage capacitor line drive waveform of conventional liquid crystal display device 45 Signal waveform for controlling switch circuit of conventional liquid crystal display device 46 Source Multiplex drive with output of drive circuit The image signal voltage waveform 47 pixel voltage waveform of a conventional liquid crystal display device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 622 G09G 3/20 622C 622D 624 624B 642 642A F-term (Reference) 2H093 NA32 NC09 NC58 NC59 NC67 ND07 ND10 ND33 5C006 AC27 AF46 AF50 BB16 BC03 BC06 BC12 BC20 EB05 FA22 FA23 5C080 AA10 BB05 DD05 DD06 EE28 FF11 JJ02 JJ04

Claims (7)

[Claims] 1. A pixel driving transistor formed by a display pixel and a thin film transistor driving the display pixel, and a source line driving for applying an image signal voltage to a source line connected to a source terminal of the pixel driving transistor. A circuit, a gate line driving circuit driving a gate line connected to a gate terminal of the pixel driving transistor, a storage capacitor element formed between the display pixel and the pixel driving transistor, and a storage capacitor A storage capacitor line driving circuit for driving a storage capacitor line connected to an element, wherein the driving method applies a predetermined compensation voltage to the storage capacitor line, and the compensation voltage After an on-voltage for turning on the driving transistor is applied to the gate line, a predetermined off-voltage for turning off the pixel transistor is applied to the gate line. An active matrix type liquid crystal that applies a predetermined voltage until it is applied to the gate line and then switches the voltage of the display pixel to a voltage different from the predetermined voltage by superimposing the image signal voltage and the compensation voltage. In the display device, the predetermined off-state voltage applied to a gate line for turning off the pixel transistor includes first and second off-state voltages, and the first off-state voltage is obtained after the pixel transistor is turned off. The second off-voltage is applied to the gate line during a period until the next gate line is turned on after the compensation voltage is switched, and the second off-voltage is applied to the gate line during the period until the compensation voltage is switched. The first off-voltage is a voltage between the on-voltage and the second off-voltage, and the first off-voltage is the first off-voltage during the period in which the first off-voltage is applied.
Wherein the off-voltage is a voltage that further turns off the pixel driving transistor. 2. The method according to claim 1, wherein the gate line driving circuit or the storage capacitor line driving circuit is formed by an integrated circuit using a thin film transistor, and is formed on the same substrate by using the same process for forming a pixel driving transistor. 2. The liquid crystal display device according to claim 1, wherein: 3. A pixel driving transistor formed by a display pixel, a thin film transistor driving the display pixel, and a source line driving circuit for applying an image signal voltage to a source line connected to a source terminal of the pixel driving transistor. A circuit, a gate line driving circuit driving a gate line connected to a gate terminal of the pixel driving transistor, a storage capacitor element formed between the display pixel and the pixel driving transistor, and a storage capacitor A storage capacitor line driving circuit that drives a storage capacitor line connected to an element, wherein the driving method applies a predetermined compensation voltage to the storage capacitor line, and the compensation voltage is After an on-voltage for turning on the driving transistor is applied to the gate line, a predetermined off-voltage for turning off the pixel transistor is applied to the gate line. After a predetermined voltage is applied until the voltage is applied to the gate line, the voltage is switched to a voltage different from the predetermined voltage, so that the voltage of the display pixel is applied by superimposing an image signal voltage and a compensation voltage, and the image signal is applied. The voltage is multiplexed by the source line drive circuit, and a switch circuit including a transistor is provided between the source line drive circuit and the source line. The switch circuit is turned on to charge the source line to the image signal voltage. An active matrix type liquid crystal display device in which a switch circuit is turned off and the image signal voltage is held in a source line, wherein a voltage for turning off a switch circuit including the transistor is set to a voltage higher than or equal to an upper limit voltage of the image signal voltage, or a lower limit. A liquid crystal display device having the following voltages. 4. The liquid crystal according to claim 3, wherein said switch circuit is formed by an integrated circuit using a thin film transistor, and is formed on the same substrate by using the same process for forming a pixel driving transistor. Display device. 5. A pixel driving transistor formed by a display pixel, a thin film transistor for driving the display pixel, and a source line driving circuit for applying an image signal voltage to a source line connected to a source terminal of the pixel driving transistor. A circuit, a gate line driving circuit driving a gate line connected to a gate terminal of the pixel driving transistor, a storage capacitor element formed between the display pixel and the pixel driving transistor, and a storage capacitor A storage capacitor line driving circuit for driving a storage capacitor line connected to an element, wherein the driving method applies a predetermined compensation voltage to the storage capacitor line, and the compensation voltage After an on-voltage for turning on the driving transistor is applied to the gate line, a predetermined off-voltage for turning off the pixel transistor is applied to the gate line. After a predetermined voltage is applied until the voltage is applied to the gate line, the voltage is switched to a voltage different from the predetermined voltage, so that the voltage of the display pixel is applied by superimposing an image signal voltage and a compensation voltage, and the image signal is applied. The voltage is multiplexed by the source line drive circuit, and a switch circuit including a transistor is provided between the source line drive circuit and the source line. The switch circuit is turned on to charge the source line to the image signal voltage. An active matrix type liquid crystal display device which turns off a switch circuit and holds the image signal voltage on a source line, wherein a precharge circuit comprising a transistor is provided between the source line and a predetermined drive voltage; The switch circuit allows the source line drive circuit to reduce the time required for the drive circuit to charge the source line. The liquid crystal display device before charging the pressure source line, by the precharge circuit, characterized by charging the source line to a predetermined voltage. 6. The liquid crystal display device according to claim 5, wherein the predetermined drive voltage of the precharge circuit is approximately half the voltage of the image signal voltage. 7. The precharge circuit according to claim 5, wherein the precharge circuit is formed of an integrated circuit using a thin film transistor, and is formed on the same substrate by using the same process for forming a pixel driving transistor. Liquid crystal display.