JP3754056B2 - Display device and display method - Google Patents

Description

  The present invention relates to a display device such as a matrix liquid crystal display device and a display method, and more particularly to a display device and a display method such as a liquid crystal display device in which, for example, a thin film transistor is provided as a switching element for each display pixel.

  Liquid crystal display devices are actively used as display elements for televisions and graphic displays. Among them, in particular, a liquid crystal display device in which a switching element such as a thin film transistor (hereinafter referred to as TFT) is provided for each display pixel causes crosstalk between adjacent display pixels even when the number of display pixels increases. It has attracted particular attention because it can provide a superior display image.

  As shown in FIG. 9, the liquid crystal display device includes a liquid crystal display panel 1 and a driving circuit unit, and the liquid crystal display panel includes a liquid crystal composition held between a pair of electrode substrates. A polarizing plate is attached to the outer surface of each electrode substrate.

  A TFT array substrate, which is one electrode substrate, has a plurality of signal lines S (1), S (2), ... S (i), ... S (N) on a transparent insulating substrate 100 such as glass. Scanning signal lines G (1), G (2)... G (j),... G (M) are formed in a matrix. A switch element 102 made of a TFT connected to the pixel electrode 103 is formed at each intersection of the signal line and the scanning signal line, and an alignment film is provided so as to cover almost the entire surface thereof. Thus, a TFT array substrate is formed.

  On the other hand, the counter substrate, which is another electrode substrate, is formed by sequentially laminating the counter electrode 101 and the alignment film over the entire surface on a transparent insulating substrate such as glass like the TFT array substrate. The scanning signal line driving circuit 300 connected to each scanning signal line of the liquid crystal display panel thus configured, the signal line driving circuit 200 connected to each signal line, and the counter electrode connected to the counter electrode The drive circuit unit is configured by the drive circuit COM.

  For example, as shown in FIG. 10, the scanning signal line driving circuit (gate driver) 300 includes a shift register unit 3 a including M flip-flops connected in cascade, and a selection switch that switches according to an output from each flip-flop. 3b.

  A gate-on voltage Vgh sufficient to turn on the TFT 102 (see FIG. 9) is input to one input terminal VD1 of each selection switch 3b, and sufficient to turn the TFT 102 off to the other input terminal VD2. A valid gate-off voltage Vgl is input. Therefore, the data signal (GSP) is sequentially transferred through the flip-flops by the clock signal (SCK) and is sequentially output to the selection switch 3b. In response to this, the selection switch 3b selects the Vgh voltage for turning on the TFT for one scanning period (TH) and outputs it to the scanning signal line 105, and then the Vgl for turning off the TFT on the scanning signal line 105. Output each voltage. With this operation, the video signal output from the signal line driver circuit 200 to each signal line 104 (see FIG. 9) can be written to each corresponding pixel.

  FIG. 11 shows an equivalent circuit of one display pixel P (i, j) having a configuration in which the pixel capacitor C1c and the auxiliary capacitor Cs are connected in parallel to the counter potential VCOM of the counter electrode drive circuit COM. In the figure, Cgd represents the parasitic capacitance between the gate and the drain of the TFT.

  FIG. 12 shows a drive waveform diagram of a conventional liquid crystal display device. In FIG. 12, Vg represents the waveform of one scanning signal line, Vs represents the waveform of one signal line, and Vd represents the drain waveform.

  Here, a conventional driving method will be described with reference to FIGS. 9, 11, and 12. Note that it is widely known that liquid crystals require AC drive to prevent burn-in afterimages and display deterioration, and the conventional drive method described below also uses frame inversion drive, which is one type of AC drive described above. explain.

  As shown in FIG. 12, from the scanning signal line driving circuit 300 to the gate electrode g (i, j) (see FIG. 9) of the TFT of one display pixel P (i, j) in the first field (TF1). As shown, when the scanning voltage Vgh is applied, the TFT is turned on, and the video signal voltage Vsp from the signal line driving circuit 200 is written to the pixel electrode through the source electrode and the drain electrode of the TFT, and the next field The pixel electrode holds the pixel potential Vdp as shown in FIG. 12 until the scanning voltage Vgh is applied at (TF2). Since the counter electrode is set to a predetermined counter potential VCOM by the counter electrode drive circuit COM, the liquid crystal composition held by the pixel electrode and the counter electrode is in accordance with the potential difference between the pixel potential Vdp and the counter potential VCOM. In response, the image is displayed.

  Similarly, a scanning voltage Vgh is applied from the scanning signal line driving circuit 300 to the gate electrode g (i, j) of the TFT of one display pixel P (i, j) in the second field (TF2) as shown in FIG. Then, the TFT is turned on, the video signal voltage Vsn from the signal line driver circuit 200 is written to the pixel electrode, and the pixel potential Vdn is held. The liquid crystal composition has a potential difference between the pixel potential Vdn and the counter potential VCOM. In response, image display is performed, and liquid crystal AC driving is realized.

Further, as shown in FIG. 11, since a parasitic capacitance Cgd is inevitably formed between the gate and drain of the TFT, as shown in FIG. 12, when the scanning voltage Vgh falls, the pixel A level shift ΔVd caused by the parasitic capacitance Cgd occurs in the potential Vd. As described above, the level shift ΔVd generated in the pixel potential Vd due to the parasitic capacitance Cgd inevitably formed in the TFT is as follows. When the non-scanning voltage of the scanning signal (TFT off voltage) is Vgl,
ΔVd = Cgd · (Vgh−Vgl) / (C1c + Cs + Cgd)
This causes problems such as flicker and display deterioration in the display image, which is not preferable for a liquid crystal display device that is oriented toward higher definition and higher quality.

  Therefore, conventionally, for example, it is considered to bias the counter electrode to the counter potential VCOM so as to reduce the level shift ΔVd caused by the parasitic capacitance Cgd in advance.

  However, in the above conventional technique, as shown in FIG. 9, the scanning signal lines G (1), G (2),... G (j),. M) is a signal delay path that is difficult to form with an ideal wiring having no signal delay propagation and causes a signal propagation delay to some extent.

  FIG. 14 is a propagation equivalent circuit when attention is paid to the signal propagation delay of one scanning signal line G (j). In FIG. 14, rg1, rg2, rg3,... RgN mainly indicate the resistance component of the wiring material forming the scanning signal line, and the resistance component due to the wiring width and the wiring length. In addition, cg1, cg2, cg3,... CgN indicate various parasitic capacitances that are capacitively coupled to the scanning signal lines in terms of configuration, and are constituted by, for example, cross capacitance generated by crossing the signal lines. . In this way, the scanning signal line is a distributed constant type signal delay propagation path.

  FIG. 15 shows how the scanning signal VG (j) input from the scanning signal line driving circuit 300 to the scanning signal line is distorted inside the panel due to the signal delay propagation characteristic of the scanning signal line. . In FIG. 15, a waveform Vg (1, j) is a waveform near g (1, j) immediately after the output of the scanning signal line driving circuit 300, and there is almost no waveform rounding. On the other hand, the waveform Vg (N, j) in the figure is a waveform near the scanning signal line termination portion g (N, j), and the waveform is rounded due to the signal delay propagation characteristics of the scanning signal line. Due to the waveform rounding, a change amount SyN per unit time is generated.

  Further, the TFT is not a complete ON / OFF switch, but has a VI characteristic (gate voltage-drain current characteristic) as shown in FIG. In FIG. 13, the horizontal axis represents the voltage applied to the gate of the TFT, and the vertical axis represents the drain current. Normally, the scan pulse is composed of two voltage levels, a voltage level Vgh sufficient to turn on the TFT and a Vgl sufficient to turn off the TFT. An intermediate ON region (linear region) exists from the threshold value VT to the Vgh level.

  Therefore, as shown in FIG. 15, in the pixel located at g (1, j) immediately after the output of the scanning signal line driving circuit 300, the falling edge of the scanning signal from Vgh to Vgl falls instantaneously. The level shift ΔVd (1) generated in the pixel potential Vd (1, j) due to the parasitic capacitance Cgd is not affected by the above-described linear region characteristics, and ΔVd (1) = Cgd · (Vgh− Vgl) / (C1c + Cs + Cgd).

  However, since the falling edge of the scanning signal is lost in the pixel located in the vicinity of the scanning signal line terminal end g (N, j), the characteristics of the linear region of the TFT influences, and the scanning signal is changed from Vgh to the threshold of the TFT. While the TFT falls to the vicinity of the value level VT, the TFT is turned on in a linear state, so that no level shift occurs in the pixel potential Vd due to the parasitic capacitance Cgd, and the scanning signal further changes from near the threshold level VT to Vgl. In the region, a level shift ΔVd (N) that occurs in the pixel potential Vd (N, j) due to the parasitic capacitance Cgd described above occurs. Therefore, the level shift ΔVd (N) satisfies ΔVd (N) <Cgd · (Vgh−Vgl) / (C1c + Cs + Cgd), and satisfies ΔVd (1)> ΔVd (N).

  As described above, the deviation of the level shift ΔVd caused in the pixel potential Vd due to the parasitic capacitance Cgd in the panel is not uniform within the display surface, and cannot be ignored due to the increase in size and definition of the screen. Accordingly, the conventional method of biasing the counter voltage cannot absorb the level shift non-uniformity in the display surface, and each pixel cannot be optimally AC driven, resulting in problems such as flickering and burn-in afterimages due to DC component application. Will do.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to sufficiently reduce the occurrence of flicker or the like due to fluctuations in pixel potential caused by parasitic capacitance, thereby achieving high definition and high quality. It is an object of the present invention to provide a display device and a display method capable of obtaining a correct display image.

  Another object of the present invention is that a wiring formed on a transparent insulating substrate such as glass is not an ideal wiring path having no signal delay but a signal delay path in which a signal delay occurs to some extent. It is an object to provide a display device and a display method capable of canceling the display non-uniformity caused by the above and making the level shift caused in the pixel potential due to the parasitic capacitance small and uniform and obtaining a high-quality display image.

  In order to solve the above problem, a display device according to a first aspect of the present invention provides a plurality of pixels, a video signal line for supplying a data signal to the pixels, and a scanning signal provided so as to cross the video signal line. And a drive circuit that drives the scan signal line by outputting a scan signal to the scan signal line, and the drive circuit is accompanied by a voltage level change in which the voltage level decreases so as to incline When the voltage level change ends, the voltage starts to rise vertically from the decrease end level toward the voltage level equal to or higher than the decrease end level, and has a length of one scanning period. The waveform is characterized by having a period and a period in which the voltage level decreases so as to incline one by one in one period.

  According to the above invention, the drive circuit can use the voltage level change that decreases so that the voltage level is inclined to generate the falling slope of the scanning signal, so that the scanning signal does not fall sharply. It becomes possible to control to. As a result, the level shift of the pixel potential caused by the parasitic capacitor is reduced, so that it is possible to avoid occurrence of flicker and display deterioration (including display defects such as burn-in afterimages) in the display image. As a result, it is possible to provide a display device capable of obtaining a high-definition and high-quality display image.

  In addition, it is possible to provide a display device that can cancel display non-uniformity caused by signal delay, make a level shift generated in a pixel potential due to parasitic capacitance small and uniform, and obtain a high-quality display image.

  According to a second aspect of the present invention, in order to solve the above problem, in the display device according to the first aspect, the driving circuit is configured so that one cycle of the voltage in a scanning period is applied to each scanning signal line. Minute waveform is output, and the scanning signal is supplied by outputting a voltage level equal to or lower than the decrease end level of the voltage level change outside the scanning period.

According to a third aspect of the present invention, in order to solve the above problem, in the display device according to the first or second aspect, the period accompanied by the voltage level change is from the direct current level after the direct current level period. It is characterized in that it is a period in which the voltage level decreases while inclining .

According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, a data signal is supplied to a plurality of pixels via a video signal line, and a scanning signal line provided so as to cross the video signal line is provided. In a display method in which a scanning signal is supplied from a driving circuit to drive the scanning signal line, a voltage having a waveform having a period with a voltage level change that decreases so that the voltage level is inclined is input to the driving circuit, At the end of the decrease in the voltage level change, the voltage starts to rise vertically from the decrease end level to a voltage level equal to or higher than the decrease end level, and has a period of one scanning period, and the voltage level is inclined. Thus, the waveform is characterized by having a waveform that includes one period of decrease in one period.

  According to the above invention, the drive circuit can use the voltage level change that decreases so that the voltage level is inclined to generate the falling slope of the scanning signal, so that the scanning signal does not fall sharply. It becomes possible to control to. As a result, the level shift of the pixel potential caused by the parasitic capacitor is reduced, so that it is possible to avoid occurrence of flicker and display deterioration (including display defects such as burn-in afterimages) in the display image. As a result, it is possible to provide a display method capable of obtaining a high-definition and high-quality display image.

  Further, it is possible to provide a display method capable of canceling display non-uniformity caused by signal delay and making the level shift caused in the pixel potential due to parasitic capacitance small and uniform and obtaining a high-quality display image.

In a display method according to a fifth aspect of the present invention, in order to solve the above problem, in the display method according to the fourth aspect of the present invention, the driving circuit performs one cycle of the voltage in the scanning period for each scanning signal line. Minute waveform is output, and the scanning signal is supplied by outputting a voltage level equal to or lower than the decrease end level of the voltage level change outside the scanning period .

In order to solve the above problem, the display method according to claim 6 is the display method according to claim 4 or 5 , wherein the voltage level change is between a high level and a low level of the scanning signal. It is for tilting a part of the change.

  As described above, the display device according to the first aspect of the present invention includes a plurality of pixels, a video signal line for supplying a data signal to the pixels, a scanning signal line provided so as to intersect the video signal line, In a display device including a driving circuit that outputs a scanning signal to the scanning signal line to drive the scanning signal line, the waveform having a period with a voltage level change that decreases so that the voltage level is inclined in the driving circuit. The voltage starts to rise vertically from the lower end level toward the voltage level equal to or higher than the lower end level at the end of the decrease in the voltage level change, and has a period of one scanning period. In this configuration, the period in which the voltage level decreases so as to incline is included in one cycle.

  Therefore, the drive circuit can use the voltage level change that decreases so that the voltage level is inclined to generate the falling slope of the scanning signal, so that the scanning signal is controlled not to fall sharply. Is possible. As a result, the level shift of the pixel potential caused by the parasitic capacitor is reduced, so that it is possible to avoid occurrence of flicker and display deterioration (including display defects such as burn-in afterimages) in the display image. As a result, it is possible to provide a display device capable of obtaining a high-definition and high-quality display image.

  In addition, the display non-uniformity caused by the signal delay is canceled, and the level shift caused in the pixel potential due to the parasitic capacitance is made small and uniform, and a display device capable of obtaining a high-quality display image can be provided.

In the display method of the invention according to claim 4 , as described above, the data signal is supplied to the plurality of pixels via the video signal line, and the scanning signal line provided so as to cross the video signal line is supplied from the drive circuit. In a display method of supplying a scanning signal to drive the scanning signal line, a voltage having a waveform having a period with a voltage level change that decreases so that the voltage level is inclined is input to the driving circuit, and the voltage is At the end of the voltage level change decrease, the voltage level starts to rise vertically from the decrease end level to a voltage level equal to or higher than the decrease end level, and has a period of one scanning period, and the voltage level decreases. It is the structure which makes it the waveform which contains the period to carry out one by one in 1 period.

  Therefore, the drive circuit can use the voltage level change that decreases so that the voltage level is inclined to generate the falling slope of the scanning signal, so that the scanning signal is controlled not to fall sharply. Is possible. As a result, the level shift of the pixel potential caused by the parasitic capacitor is reduced, so that it is possible to avoid occurrence of flicker and display deterioration (including display defects such as burn-in afterimages) in the display image. As a result, it is possible to provide a display method capable of obtaining a high-definition and high-quality display image.

  In addition, it is possible to provide a display method capable of canceling display non-uniformity caused by signal delay and making level shift caused in pixel potential due to parasitic capacitance small and uniform and obtaining a high-quality display image.

  The present invention inputs an input signal that changes so that wiring formed on a transparent insulating substrate such as glass is not affected by parasitic signal delay propagation characteristics in a display device such as a liquid crystal display device. In particular, this is based on the fact that it is possible to obtain a waveform equivalent to the input waveform at an arbitrary location on the wiring, and the influence of the signal change is the same.

  In addition, according to the present invention, depending on the ON / OFF characteristics of a switch element such as a thin film transistor connected to the wiring, if the change in the waveform of the input waveform and the waveform at any place on the wiring becomes gradual, This is based on the fact that the magnitude of the level shift that occurs can be reduced.

  1 and 2 will be described below. In FIG. 1, GCK represents a clock signal.

  1 and 2 show the output waveforms VG (j−1), VG (j), VG (j + 1) of the scanning signal line driving circuit according to the present embodiment, and the scanning waveform Vg (1, j), a scanning signal line waveform Vg (N, j) near the end of the scanning signal line, and pixel potentials Vd (1, j) and Vd (N, j), respectively. In the output waveform VG (j) of the scanning signal line drive circuit, the falling waveform from the scanning voltage Vgh to the non-scanning voltage Vgl has a slope (inclination) of the change amount Sx per unit time as shown in FIG. Change.

  According to this embodiment, a data signal is supplied to a plurality of pixel electrodes via a video signal line, and a scanning signal is supplied via a scanning signal line intersecting with the video signal line to drive and display the data. In the display method, the fall of the scanning signal is controlled at the time of driving, but this fall can be achieved by arbitrarily setting the change amount Sx.

  By appropriately setting the amount of change Sx as described above, the amount of change Sx1 and SxN of the falling waveform near the input and end of the scanning signal line can be obtained from the scanning signal line waveform Vg (1, j), And Vg (N, j), which are almost the same without being affected by the signal delay propagation characteristic that the scanning signal line has parasitically (see FIGS. 1 and 2). As a result, the level shift that occurs in the pixel potential Vd due to the parasitic capacitance Cgd that exists parasitically in the scanning signal line becomes substantially uniform within the display surface. Accordingly, for example, the flicker is sufficiently reduced by a conventional method such as biasing the counter potential VCOM to the counter electrode so as to reduce the level shift ΔVd caused by the parasitic capacitance Cgd in advance, and there is no display defect such as a burn-in afterimage. A display device was realized.

  As described above, in order to make the change amounts Sx1 and SxN of the falling waveform substantially the same regardless of the position on the scanning line, the falling control is performed based on the signal delay transmission characteristic of the scanning signal line. It's fine. By controlling in this way, it is possible to make the slopes of the falling edges of the scanning signal substantially the same anywhere on the scanning signal line, so that the level shift of each pixel potential becomes substantially uniform.

  Instead of controlling the fall based on the signal delay propagation characteristics, the fall slope of the scanning signal may be controlled based on the gate voltage-drain current characteristics of the thin film transistor. When a voltage in the range from the threshold voltage to the on voltage is applied to the gate of the thin film transistor, the drain current (on resistance) of the thin film transistor changes linearly depending on the gate voltage (that is, a binary state). The thin film transistor is in an intermediate on state (in other words, the drain current is changed in analog by the gate voltage).

  In this case, when the falling edge of the scanning signal is steep as in the prior art, the level shift of the pixel potential due to the parasitic capacitance capacitor occurs as described above regardless of the gate voltage-drain current characteristics of the thin film transistor. However, according to the present embodiment, it is possible to control the falling slope of the scanning signal so as to be affected by the linearly changing region of the thin film transistor. By controlling in this way, the falling edge of the scanning signal is inclined, and the state change from on to off of the thin film transistor also changes linearly based on the voltage-current characteristics. Therefore, the pixel potential caused by the parasitic capacitance capacitor is changed. Level shift is reliably reduced.

  It is more preferable to control the falling slope of the scanning signal based on both the signal delay propagation characteristic and the gate voltage-drain current characteristic of the thin film transistor. In this case, since it is possible to make the slopes of the falling edges of the scanning signal substantially the same anywhere on the scanning signal line, the level shift of each pixel potential becomes substantially uniform and the level shift itself is small. Become.

  The voltage level VT in FIG. 2 is the threshold voltage of the TFT shown in FIG. 13, but the TFT is on during the period when the scanning signal falls from the scanning voltage Vgh to the threshold voltage VT of the TFT, and the parasitic capacitance Cgd The level shift due to the above is hardly generated, and the level shift due to the parasitic capacitance Cgd occurs due to the influence of the scanning signal line change amount (VT−Vgl) at which the TFT is turned off.

  According to the present embodiment, since VT−Vgl <Vgh−Vgl, not only the level shift non-uniformity in the display surface caused by the parasitic capacitance Cgd is canceled, but also the level shift amount caused by the parasitic capacitance Cgd It became possible to make itself smaller.

  Here, the level shift amount generated in the pixel potential Vd due to the parasitic capacitance Cgd of the pixel in the vicinity of the scanning signal line driving circuit in the prior art is ΔVd (1), and the level shift amount of the pixel in the vicinity of the terminal is ΔVd (N ), The level shift amount of the pixel in the vicinity of the scanning signal line driving circuit according to this embodiment is ΔVdx (1), and the level shift amount of the pixel in the vicinity of the terminal is ΔVdx (N). In this case, as described above, the falling waveform variation amounts Sx1 and SxN are substantially the same without being affected by the signal delay propagation characteristics that the scanning signal line has parasitically, and therefore exist in a parasitic manner. The level shift generated in the pixel potential Vd due to the parasitic capacitance Cgd is substantially uniform within the display surface, and the relationship ΔVdx (1) = ΔVdx (N) <ΔVd (N) <ΔVd (1) Satisfied.

  Therefore, for example, the bias level can be reduced by using a conventional method such as biasing the counter electrode to the counter potential VCOM so as to reduce the level shift caused by the parasitic capacitance Cgd in advance. It is possible to solve the problem and realize a display device with low power consumption.

  Next, FIG. 3 will be described below. For convenience of explanation, members having the same functions as those shown in FIG.

  3 includes M flip-flops (F1, F2,..., Fj,..., FM) connected in cascade as in the conventional scanning signal line drive circuit shown in FIG. It has a shift register unit 3a and a selection switch 3b that switches according to the output from each flip-flop. One input terminal VD1 of each selection switch 3b receives a gate-on voltage Vgh sufficient to turn the TFT on, and the other input terminal VD2 receives a gate-off voltage Vgl sufficient to turn the TFT off. Has been. The common terminal of each switch 3 b is connected to the scanning signal line 105.

  Accordingly, the data signal GSP is sequentially transferred through the flip-flop by the clock signal GCK, and is sequentially output through the selection switch 3b. In response to this, the selection switch 3b selects the Vgh voltage for turning on the TFT for one scanning period (TH) and outputs it to the scanning signal line 105, and then the Vgl for turning off the TFT on the scanning signal line 105. Output each voltage.

  In FIG. 3, a slew rate control element SC (gradient control unit) that can control the falling speed of the output signal (gate off voltage Vgl) is added to the output stage of the conventional gate driver. Similarly, the falling slope of the scanning signal output to each scanning signal line can be controlled.

  The slew rate control circuit SC provided between each selection switch 3b and the input terminal VD2 is equivalently an output impedance control element that controls the impedance of each output of the gate driver, and is output to the scanning signal line. The output impedance is increased only at the falling edge of the gate-off voltage (hereinafter referred to as the falling edge of the scanning signal line), the output waveform of the gate driver itself is smoothed, and the waveform is rounded due to the transfer characteristics of the scanning signal line itself. By canceling the difference in the falling speed in the display panel surface, the generation of the level shift ΔV due to the influence of the parasitic capacitance Cgd described above is suppressed, and the level shift amount is made the same over the entire display panel. Is possible.

  The slew rate control circuit SC is not particularly limited as long as the output impedance can be varied and the falling speed can be varied. For example, the general control for adjusting the impedance by controlling the gate voltage of the MOS transistor element is possible. It may be realized with technology.

  In FIG. 3, the output impedance is increased only when the scanning signal line falls, and only the falling waveform is smoothed. However, depending on the panel structure used, the gate-off voltage Vgl during the output period after the scanning signal line falls may be used. If another display problem such as crosstalk does not occur even when the impedance is high, the output impedance may be increased not only when the scanning signal line falls.

  In FIG. 3, the case where the slew rate control element SC for controlling the falling speed (tilt) of the scanning signal is added to the conventional configuration in the scanning signal line driving circuit (gate driver) has been described. However, in this case, it is necessary to separately provide a slew rate control element SC in the gate driver, and a conventional general inexpensive gate driver cannot be used as it is, which is not economical.

  Therefore, the case where a conventional inexpensive general-purpose gate driver is used will be described below with reference to FIGS.

  As described above with reference to FIG. 10, the conventional gate driver receives the gate-on voltage Vgh and the gate-off voltage Vgl, and sequentially selects the scan-on voltage Vgh for one scan period (TH) by the clock signal GCK. After being output to the scanning signal line 105, a Vgl voltage for turning off the TFT is output to the scanning signal line 105, respectively. On the other hand, in the circuit shown in FIG. 4, the output of the circuit is used as the Vgh voltage of the scanning signal line driving circuit.

  4 mainly includes resistors Rcnt and Ccnt for charging / discharging, an inverter INV for controlling the charging / discharging, and a switch SW1 and a switch SW2 for switching charging / discharging. It consists of and.

  A signal voltage Vdd is applied to one terminal of the switch SW1. This signal voltage Vdd is a DC voltage having a level Vgh sufficient to turn on the TFT. The other terminal of the switch SW1 is connected to one end of the resistor Rcnt and also connected to one end of the capacitor Ccnt. The other end of the resistor Rcnt is grounded via the switch SW2. The opening / closing control of the switch SW2 is performed based on the Stc signal (see FIG. 5) input via the inverter INV. This Stc signal is synchronized with one scanning period, and also performs opening / closing control of the switch SW1. As shown in FIG. 5, the Stc signal may be formed so as to be synchronized with the clock signal (GCK), and can be configured using, for example, a mono multivibrator or the like (not shown).

  The opening / closing operation of the switches SW1 and SW2 will be described later. When the Stc signal is at a high level, the switch SW1 is closed. At this time, a low level is applied to the switch SW2 via the inverter INV. SW2 is in an open state. On the other hand, when the Stc signal is at a low level (discharge control signal), the switch SW1 is opened. At this time, a high level is applied to the switch SW2 via the inverter INV, so that the switch SW2 is in the closed state. Become. That is, in the configuration of FIG. 4, the switches SW1 and SW2 are high-active elements.

  The output signal VD1a generated by this circuit is connected to the input terminal VD1 of the scanning signal line driving circuit 300 shown in FIG. As shown in FIG. 5, the Stc signal is a timing signal for controlling the gate falling period, and is a signal having the same cycle as that of one scanning period (TH).

  According to the above configuration, since the switch SW1 is closed and the switch SW2 is opened while the Stc signal is at a high level, the output signal VD1a is a level Vgh voltage as shown in FIG. 300 is output to the input terminal VD1. In contrast, while the Stc signal is at a low level, the switch SW1 is opened and the switch SW2 is closed, and the electric charge stored in Ccnt is discharged via Rcnt, and the voltage level gradually decreases. . As a result, the output signal VD1a has a sawtooth waveform as shown in FIG.

  When the output signal VD1a (see FIG. 5) generated by the circuit of FIG. 4 is sent to the input terminal VD1 of the scanning signal line driving circuit 300, the falling edge of the scanning signal line is inclined as shown by VG (j) of FIG. It is possible to easily generate a waveform having The inclination time of the inclination waveform is adjusted in the L period of the Stc signal, and the inclination amount Vslope is possible by changing the resistance Rcnt and the capacitor Ccnt in FIG. 4 and adjusting the time constant thereof. You can optimize it.

  FIG. 6 shows the measurement result for the position on the scanning line of the level shift caused by the parasitic capacitance Cgd when the present embodiment is applied to a diagonal 13.3 inch XGA (resolution 1024 * RGB * 768). As is apparent from FIG. 6, according to the present embodiment, the slope distribution (nonuniformity) of the level shift ΔVd in the display panel is completely eliminated, and the size of ΔVd itself is also reduced. I understand that.

  As shown in FIG. 5, in VG (j), the falling waveform does not need to be inclined at the falling of all levels from Vgh to Vgl. That is, FIG. 6 shows that the gate falling slope in the on region of the TFT is important for the variation of the level shift ΔVd in the display surface. In other words, once the TFT enters the off region, it does not depend on the gate falling speed. Therefore, a sufficient effect can be obtained by forming such a slight falling waveform.

  In the above-described configuration, the falling time of the scanning signal line is adjusted in the L period of the Stc signal, and the amount of inclination Vslope changes the resistance Rcnt and the capacitor Ccnt to adjust the time constant thereof, thereby reducing the falling speed. Controlled. However, in the case of a larger display device, the magnitude of the charge held on the scanning signal line differs depending on the parasitic capacitance and display state at each intersection of the scanning signal line and the signal line. In addition to the original purpose, new problems such as the generation of display noise may occur. The following configuration solves such a problem. This will be described in detail below.

  FIG. 7 shows a main part of a scanning signal line drive circuit having another configuration, and FIG. 8 shows waveforms of main parts thereof. A signal Stc in FIG. 7 is an inclination period control signal (a charge control signal and a discharge control signal), and performs opening / closing control of the switch SW3 connected in parallel to the capacitor Cct. The constant current source Ict is connected to one end of the capacitor Cct via the resistor Rct, and the other end of the capacitor Cct is grounded. The voltage Vct across the capacitor Cct is connected to the inverting input terminal of the operational amplifier OP via the resistor R3. A resistor R4 is connected between the inverting input terminal and the output terminal of the operational amplifier OP.

  The Stc signal may be formed so as to be synchronized with the clock signal (GCK) as shown in FIG. 5, and can be configured using, for example, a mono multivibrator or the like (not shown). The switch SW3 is closed during the high level period of the Stc signal, and is open during the low level period.

  On the other hand, one end of a resistor R2 and a resistor R1 is connected to the non-inverting input terminal of the operational amplifier OP. The other end of the resistor R2 is grounded, and the signal voltage Vdd is applied to the other end of the resistor R1. This signal voltage Vdd is a DC voltage having a level Vgh sufficient to turn on the TFT. From the output terminal of the operational amplifier OP, the output signal VD1b is sent as a scanning signal to the input terminal VD1 of the scanning signal line driving circuit 300 shown in FIG.

  The operational amplifier OP and the resistors R1, R2, R3, and R4 constitute a subtracting unit. In this subtraction unit, the following subtraction process is performed.

VD1b = Vdd ・ (R2 / (R1 + R2)) ・ (1+ (R4 / R3)) − (R4 / R3) ・ Vct
Here, when R1 = R4, R2 = R3, and A = R4 / R3, VD1b = Vdd−A · Vct.

  The operation of the circuit shown in FIG. 7 will be described below with reference to FIG.

  While the Stc signal is at a low level, the switch SW3 is opened, so that the capacitor Cct is charged from the constant current source Ict via the resistor Rct, and the voltage Vct changes in a sawtooth waveform as shown in FIG. . In the subtracting unit, the voltage Vct multiplied by A (= R4 / R3) is subtracted from the signal voltage Vdd and output as the output signal VD1b (decreasing from Vgh to Vslope) as shown in FIG. Therefore, by changing A, the output signal VD1b can be lowered at an arbitrary Vslope.

  On the other hand, since the switch SW3 is closed during the period when the Stc signal is high, the charge charged in the capacitor Cct is discharged through the switch SW3, and the voltage Vct across the capacitor Cct is It becomes zero as shown in FIG. In the subtracting unit, the signal voltage Vdd multiplied by A (= R4 / R3) is subtracted from the signal voltage Vdd. However, since the voltage Vct is zero, the signal voltage Vdd is the output signal VD1b as shown in FIG. Is output as

  As described above, with the control of the signal Stc, the voltage Vct becomes a sawtooth wave having a maximum amplitude of Vct, and the output signal VD1b has a waveform of the inclination period Ts1ope and the inclination amount Vslope. The inclination amount Vslope is Vslope. = Vcth · (R4 / R3), which can be easily adjusted by setting the resistors R4 and R3. Moreover, since the output signal VD1b is the output of the operational amplifier OP, the impedance is low (impedance when the operational amplifier OP is viewed from the next stage is small).

  According to the configurations of FIGS. 7 and 8, it is possible to create a scan signal slope waveform having an optimum falling characteristic suitable for each device in any liquid crystal display device. .

  In order to make the amount of change in the falling waveform substantially the same regardless of the position on the scanning line as described above, the control of the falling edge is performed based on the signal delay transmission characteristic of the scanning signal line. Is preferred. Further, instead of performing the fall control based on the signal delay propagation characteristics, the slope of the scan signal fall may be controlled based on the gate voltage-drain current characteristics of the thin film transistor. Furthermore, it is more preferable to control the falling slope of the scanning signal based on both the signal delay propagation characteristic and the gate voltage-drain current characteristic of the thin film transistor.

  As described above, the display device is connected to the scanning signal line, the thin film transistor having the gate electrode connected to the scanning signal line, the video signal line connected to the source electrode of the thin film transistor, and the drain electrode of the thin film transistor. In a pixel comprising a pixel electrode, an additional capacitance element formed between the pixel electrode and the scanning signal line, and a liquid crystal capacitance element formed between the drain electrode and the counter electrode, the scanning signal line It is characterized in that the state change from the scanning level of the writing pulse to the non-scanning level is arbitrarily inclined and gentle. In this case, it is preferable that the state change from the scanning level of the writing pulse to the non-scanning level is an arbitrary inclination considering the signal delay transmission characteristic of the scanning signal line.

  In the display device, it is preferable that the state change of the writing pulse from the scanning level to the non-scanning level is gentle with an arbitrary inclination in consideration of the VI characteristic of the thin film transistor.

  In the above configuration, the state change from the scanning level of the writing pulse to the non-scanning level has a gentle slope with an arbitrary inclination in consideration of both the signal delay transmission characteristic of the scanning signal line and the VI characteristic of the thin film transistor. It is preferable that

  In addition, another display device includes a plurality of pixel electrodes, a video signal line for supplying a data signal to the corresponding pixel electrode, and a scanning signal line orthogonal thereto, and a switching element is provided at each intersection. A display device for supplying a data signal to the pixel electrode by a scanning signal for controlling a switch element supplied to the scanning signal line, wherein the scanning signal of the scanning signal is changed from a scanning level to a non-scanning level. The change is characterized by an arbitrary slope and gradual.

  The signal transmission path from the scanning line driving circuit to the plurality of switch elements preferably has a signal delay transmission characteristic. The switch characteristics of the plurality of switch elements preferably have an intermediate conduction state rather than a complete on / off binary characteristic.

  Still another display device drives a plurality of pixel electrodes, video signal lines for supplying data signals to the corresponding pixel electrodes, scanning signal lines orthogonal thereto, and the scanning signal lines. And a scanning line driving circuit having a function capable of arbitrarily adjusting the speed of change in the output state of the scanning signal. It is said.

  In this case, it is preferable that the speed of the level change of the scanning signal takes into account the signal delay transmission characteristic of the scanning signal line. It is also preferable that the speed of the level change of the scanning signal takes into account the VI characteristic of the thin film transistor. More preferably, the speed of the level change of the scanning signal takes into account both the signal delay transmission characteristic of the scanning signal and the VI characteristic of the thin film transistor.

  Further, the other display device includes a plurality of pixel electrodes, a video signal line for supplying a data signal to the corresponding pixel electrode, a scanning signal line orthogonal to the video signal line, and a drive for driving the scanning signal. A display device including a scanning signal line driver circuit and a thin film transistor formed at an intersection of the scanning signal line driver circuit, wherein a voltage input to the scanning line driver circuit is a sawtooth waveform.

  In this case, it is preferable that the voltage input to the scanning line driving circuit has an intermittent sawtooth waveform. It is preferable that the slope of the sawtooth voltage takes into account the signal delay transmission characteristics of the scanning signal line. The sawtooth voltage gradient preferably takes into account the VI characteristics of the thin film transistor, and takes into account both the signal delay transmission characteristic of the scanning signal line and the VI characteristic of the thin film transistor. It is more preferable.

  According to the above configuration, the falling waveform of the scanning signal of the scanning line driving circuit can be apparently reduced by the influence of the signal delay propagation characteristic of the scanning line to be output, and the falling speed at each location on the scanning line is the same. Thus, the level shift ΔVd generated in the pixel potential Vd due to the parasitic capacitance Cgd can be made uniform in the display surface.

  Furthermore, since the falling waveform of the scanning signal is gentle, the linear on-region characteristics of the TFT can be used effectively, and the level shift ΔVd generated in the pixel potential Vd due to the parasitic capacitance Cgd itself can be reduced. As a result, the level shift that occurs parasitically in the pixel potential can be uniformly reduced in the plane, and the occurrence of flicker, burn-in afterimage, etc. can be sufficiently reduced, and a high-definition and high-quality display device can be obtained.

  As described above, according to the present invention, the level shift amount generated in the pixel potential due to the parasitic capacitance coming from the structure of the liquid crystal display device is made uniform in the plane and / or the level shift amount itself is reduced. Therefore, it is possible to realize a display device with low power consumption that is free from flicker and has no afterimage. That is, a display device and a display method with much improved display quality and reliability can be realized, and the effect obtained by the present invention is extremely large.

In addition, there are various types of AC driving of liquid crystal display devices, such as frame inversion driving for switching the polarity of signal lines for each frame, line inversion driving for switching for each horizontal signal, and dot inversion driving for switching for each pixel. Needless to say, is effective for each driving method without depending on these driving methods.
(1) The display device includes a plurality of pixel electrodes, a switch element connected to each of the pixel electrodes, a video signal line for supplying a data signal to the pixel electrode via the switch element, and the video signal. A plurality of scanning signal lines provided across the line and connected to the switch element, and a scanning signal for determining an ON state and an OFF state of the switch element are output to the scanning signal line so as to be supplied to the switch element. And a driving circuit for driving the scanning signal line, wherein the driving circuit controls a falling edge of the scanning signal and finishes the falling edge within one horizontal period. can do.

  According to the above configuration, the scanning signal is output to the scanning signal line by the driving circuit. At this time, the falling edge of the scanning signal is controlled by the driving circuit.

  In general, a parasitic capacitor is formed between the gate and drain of a thin film transistor, which is one of the switch elements, because of its configuration. At this time, if the scanning signal falls sharply as in the prior art, the thin film transistor is turned off instantaneously, and the influence of the parasitic capacitance capacitor is caused by the amount of falling of the scanning signal (subtraction of the non-scanning voltage from the scanning voltage). Since the potential of the receiving pixel electrode is lowered by that amount, a serious level shift occurs in the potential of the pixel electrode (hereinafter referred to as pixel potential). Thus, when a level shift occurs in the pixel potential, flicker and display deterioration are caused in the display image.

  However, according to the display device, since the falling edge of the scanning signal is controlled, the scanning signal can be controlled so as not to fall sharply. Thereby, the level shift of the pixel potential due to the parasitic capacitance capacitor is reduced.

  (2) In the display device according to (1), the drive circuit may be configured so that the scanning signal is substantially independent of a position on the scanning signal line based on a signal delay transmission characteristic of the scanning signal line. It can be configured to control to fall at the same inclination.

  According to the above configuration, in addition to the operation of the display device of (1), the falling edge of the scanning signal is controlled by the driving circuit based on the signal delay transmission characteristic of the scanning signal line. As a result of this control, the scanning signal falls with substantially the same inclination regardless of the position on the scanning signal line.

  When the scanning signal falls steeply as in the prior art, the falling slope changes depending on the position on the scanning signal line due to the signal delay transmission characteristic of the scanning signal line. The level shift of the pixel potential increases near the start edge of the scanning signal line having a steep fall, whereas the level shift of the pixel potential decreases near the end of the scanning line where the fall ends. As described above, generally, the level shift in the pixel potential is not uniform on the scanning signal line (in the display surface). The non-uniformity of the level shift cannot be ignored particularly when a large screen and high definition are required.

  However, according to the above configuration, the slope of the falling edge of the scanning signal can be made almost the same anywhere on the scanning signal line, so that the signal delay transmission characteristic of the scanning signal line can be ignored, The level shift amount distribution does not occur in the display surface, and the level shift of each pixel potential becomes substantially uniform.

  (3) In the display device according to (1), the switch element is a thin film transistor in which a gate is connected to the scanning signal line, a source is connected to the video signal line, and a drain is connected to the pixel electrode. In addition, the drive circuit may be configured to control a falling slope of the scanning signal based on a gate voltage-drain current characteristic of the thin film transistor.

  According to the above configuration, in addition to the operation of the display device of (1), the falling slope of the scanning signal is controlled by the driving circuit based on the voltage-current characteristics of the thin film transistor.

  By the way, the thin film transistor is turned on when a threshold voltage is applied to the gate, and is stably turned on when a predetermined on voltage higher than the threshold voltage is applied. When it falls below, it shifts to the off state. In addition, when a voltage in the range from the threshold voltage to the on-voltage is applied to the gate, the drain current (on-resistance) of the thin film transistor depends on the gate voltage and changes linearly (that is, The thin film transistor is not in the on state in the binary state, but is in an intermediate on state (the drain current changes in analog terms by the gate voltage).

  When the scanning signal falls steeply as in the prior art, the level shift of the pixel potential caused by the parasitic capacitance capacitor occurs as described above regardless of the gate voltage-drain current characteristics of the thin film transistor.

  However, according to the above configuration, it is possible to control the falling slope of the scanning signal so as to be influenced by the linearly changing region of the thin film transistor. By controlling in this way, the falling edge of the scanning signal is inclined, and the state change from on to off of the thin film transistor also changes linearly based on the voltage-current characteristics. Therefore, the pixel potential caused by the parasitic capacitance capacitor is changed. Level shift is reliably reduced.

  As described above, during the initial period when the scan signal falls, the thin film transistor is in an intermediate on state that is not yet off, and the signal from the source can be transmitted to the pixel electrode through the thin film transistor, causing a level shift of the pixel potential. do not do. When the scanning signal falls, a level shift of the pixel potential occurs only for the latter half of the change, but the amount is small.

  (4) In the display device according to (2), the switch element is a thin film transistor in which a gate is connected to the scanning signal line, a source is connected to the video signal line, and a drain is connected to the pixel electrode. In addition, the driving circuit may further control a falling slope of the scanning signal based on a gate voltage-drain current characteristic of the thin film transistor.

  According to the above configuration, in addition to the operation related to the display device of (2), the scanning is performed so as to be influenced by the linearly changing region of the thin film transistor as in the operation related to the display device of (3). It is possible to control the slope of the falling edge of the signal. With this control, the falling edge of the scanning signal slopes, and the state change of the thin film transistor from on to off is linear based on the voltage-current characteristics. Therefore, the level shift of the pixel potential due to the parasitic capacitor is reliably reduced.

  That is, according to the display device of (4), the slopes of the falling edges of the scanning signals can be made substantially the same anywhere on the scanning signal lines, so that the level shift of each pixel potential is substantially uniform. At the same time, the level shift itself becomes smaller.

  As described above, the level shift of the pixel potential occurs only with respect to the change in the latter half of the fall of the scanning signal.

  (5) In the display device according to any one of (1) to (4), the switch element includes a gate serving as the scanning signal line, a source serving as the video signal line, and a drain serving as the pixel electrode. Each of the thin film transistors is connected, and the scanning signal includes a gate-on voltage for turning on the thin film transistor and a gate-off voltage for turning off the thin film transistor. The driving circuits are cascade-connected and the data signal is input. A shift register unit composed of a plurality of flip-flops, a slope control unit that controls the slope of the fall of the gate-off voltage, and a switch unit that switches between the gate-on voltage and the gate-off voltage according to the output from each flip-flop It can consist of.

  According to the above configuration, when a data signal is input to the shift register unit, a signal switching signal is output from each flip-flop based on a predetermined clock signal. Based on this output signal, the switch unit switches between the gate-on voltage and the gate-off voltage and outputs it. At this time, after the falling of the gate-off voltage is controlled by the slope control unit, the switch unit is used as the gate-off voltage. Is output from. As described above, according to the above configuration, the effects of the display devices (1) to (4) can be obtained only by adding the tilt control unit to the conventional drive circuit (gate driver).

  (6) In the display device according to any one of (1) to (4), the switch element includes a gate serving as the scanning signal line, a source serving as the video signal line, and a drain serving as the pixel electrode. Each of the thin film transistors is connected, and the scanning signal includes a gate-on voltage for turning on the thin film transistor and a gate-off voltage for turning off the thin film transistor, and the driving circuit outputs a discharge control signal synchronized with one scanning period. And a drive voltage generation unit that generates the gate-on voltage and discharges the gate-on voltage when receiving the discharge control signal.

  According to the above configuration, the gate-on voltage is generated and controlled as follows. That is, the discharge control signal synchronized with one scanning period is output to the drive voltage generation unit by the control unit. Normally, the gate-on voltage is generated (when the discharge control signal is inactive). When this gate-on voltage is applied to the scanning signal line, the thin film transistor is turned on.

  On the other hand, when the discharge control signal is received, the drive voltage generator discharges the gate-on voltage only during that period. With this discharge, the gate-on voltage decreases.

  As described above, it is possible to output a scanning signal having an arbitrary falling slope by controlling the discharge timing and the discharge amount for each scanning period.

  (7) In the display device according to any one of (1) to (4), the switch element includes a gate as the scanning signal line, a source as the video signal line, and a drain as the pixel electrode. The scanning signal includes a gate-on voltage for turning on the thin film transistor and a gate-off voltage for turning off the thin film transistor, and the driving circuit performs a charge control signal and discharge synchronized with one scanning period. A control unit that outputs a control signal; and a ramp voltage control unit that, when receiving the charge control signal, charges and outputs a ramp control voltage, while receiving the discharge control signal, sets the ramp control voltage to zero by discharging. In addition, when subtracting the slope control voltage from the gate-on voltage at the time of charging is output as the gate-on voltage, while at the time of discharging Can be assumed that a subtraction unit which outputs the gate-on voltage as it is.

  According to the above configuration, the gate-on voltage, which is a scanning signal, is generated and controlled as follows. That is, the charge control signal and the discharge control signal synchronized with one scanning period are output to the ramp voltage control unit by the control unit. When receiving the discharge control signal, the ramp voltage control unit stops the charging operation and makes the ramp control voltage zero by discharging. Along with this discharge, the gate-on voltage is applied to the scanning signal line as it is without being subtracted from the subtracting section, and the thin film transistor is turned on.

  On the other hand, when the charge control signal is received, the ramp voltage control unit performs a charging operation until the next discharge control signal is received, and outputs the ramp control voltage to the subtraction unit. Along with this charging, a value obtained by subtracting the slope control voltage from the gate-on voltage is applied to the scanning signal line from the subtracting unit. When the applied voltage becomes lower than the above threshold voltage, the thin film transistor is turned off.

  As described above, by controlling the timing of charging and discharging and the amount of discharge for each scanning period, it is possible to output a scanning signal having an arbitrary falling slope.

  (8) Further, in the display method, a data signal is supplied to a plurality of pixel electrodes via a video signal line, a scanning signal is supplied via a scanning signal line crossing the video signal line, and the display is driven. In the display method to be performed, the falling edge of the scanning signal is controlled at the time of driving, and the falling edge can be finished within one horizontal period.

  According to the above configuration, the scanning signal is output to the scanning signal line and driven. At this time, the falling edge of the scanning signal is controlled.

  In general, a parasitic capacitor is a problem during driving. At this time, if the scanning signal line falls sharply as in the prior art, the thin film transistor is turned off instantaneously, and the falling edge of the scanning signal (subtraction of the non-scanning voltage from the scanning voltage) affects the parasitic capacitance capacitor. As a result, the potential of the pixel electrode decreases by that amount, so that a level shift occurs in the pixel potential. Thus, when a level shift occurs in the pixel potential, flicker and display deterioration are caused in the display image.

  However, according to the above display method, since the falling edge of the scanning signal is controlled, the scanning signal can be controlled so as not to fall sharply. Thereby, the level shift of the pixel potential due to the parasitic capacitance capacitor is reduced.

  (9) In the display method according to (8), the scanning signal is independent of the position on the scanning signal line based on the signal delay transmission characteristic of the scanning signal line during the driving. It can control to fall at substantially the same inclination.

  According to the above configuration, in addition to the operation related to the display method of (8), at the time of driving, the falling edge of the scanning signal is controlled based on the signal delay transmission characteristic of the scanning signal line. As a result of this control, the scanning signal falls with substantially the same inclination regardless of the position on the scanning signal line.

  In general, the level shift in the pixel potential is not uniform on the scanning signal line (in the display surface). The non-uniformity of the level shift cannot be ignored particularly when a large screen and high definition are required.

  However, according to the above configuration, the slope of the falling edge of the scanning signal can be made substantially the same anywhere on the scanning signal line, so that the level shift of each pixel potential becomes substantially uniform.

  (10) In addition, in the display method according to (8), in the display method, the gate voltage-drain current characteristics of a plurality of thin film transistors provided at intersections of the video signal and the scanning signal line at the time of driving. Based on this, the falling slope of the scanning signal can be controlled.

  According to the above configuration, in addition to the operation related to the display method of (8), the slope of the fall of the scanning signal is controlled based on the voltage-current characteristics of the thin film transistor during driving.

  By the way, the thin film transistor is turned on when a threshold voltage is applied to the gate, and is stably turned on when a predetermined on voltage higher than the threshold voltage is applied. When it falls below, it shifts to the off state. In addition, when a voltage in the range from the threshold voltage to the on-voltage is applied to the gate, the drain current (on-resistance) of the thin film transistor depends on the gate voltage and changes linearly (that is, The thin film transistor is not in the on state in the binary state, but is in an intermediate on state (the drain current changes in analog terms by the gate voltage).

  When the scanning signal falls steeply as in the prior art, the level shift of the pixel potential caused by the parasitic capacitance capacitor occurs as described above regardless of the gate voltage-drain current characteristics of the thin film transistor.

  However, according to the above configuration, it is possible to control the falling slope of the scanning signal so as to be influenced by the linearly changing region of the thin film transistor. By controlling in this way, the falling edge of the scanning signal is inclined, and the state change from on to off of the thin film transistor also changes linearly based on the voltage-current characteristics. Therefore, the pixel potential caused by the parasitic capacitance capacitor is changed. Level shift is reliably reduced.

  (11) Further, in the display method of (9), the display method further includes gate voltages-drain currents of a plurality of thin film transistors provided at intersections of the video signal and the scanning signal line during the driving. Based on the characteristics, the slope of the falling edge of the scanning signal can be controlled.

  According to the above configuration, in addition to the operation related to the display method of (9), the scanning is performed so as to be influenced by the linearly changing region of the thin film transistor as in the operation related to the display method of (10). It is possible to control the slope of the falling edge of the signal. With this control, the falling edge of the scanning signal slopes, and the state change of the thin film transistor from on to off is linear based on the voltage-current characteristics. Therefore, the level shift of the pixel potential caused by the parasitic capacitor is reliably reduced.

  That is, according to the display method of (11), the slopes of the falling edges of the scanning signals can be made substantially the same anywhere on the scanning signal lines, so that the level shift of each pixel potential is substantially uniform. At the same time, the level shift becomes smaller.

  (12) Further, in each of the display methods (8) to (11), the display method can change the falling waveform of the supplied scanning signal with a constant change amount of inclination.

  (13) Further, in the display method according to (12), the slope of the falling waveform of the scanning signal in the vicinity of the input of the scanning signal line and the slope of the falling waveform of the scanning signal in the vicinity of the terminal are substantially the same. It can be the same slope.

It is a wave form diagram which shows each part output waveform of the scanning signal line drive circuit which concerns on embodiment of this invention. FIG. 2 is a waveform diagram showing a scanning waveform in the vicinity of the scanning signal line input, a scanning signal line waveform in the vicinity of the scanning signal line end, and each pixel potential in FIG. It is explanatory drawing which shows the comparative structural example of the scanning signal line drive circuit which concerns on embodiment of this invention. FIG. 3 is a block diagram illustrating a configuration example of a scanning signal line driving circuit according to an embodiment of the present invention. It is a wave form diagram of the principal part of FIG. It is explanatory drawing which shows the result of having compared the characteristic of the level shift resulting from the parasitic capacitance Cgd at the time of applying the structure of FIG. 4 to diagonal 13.3 inches XGA (resolution 1024 * RGB * 768) with the conventional structure. It is a circuit diagram which shows the other structural example of the scanning signal line drive circuit which concerns on embodiment of this invention. It is a wave form diagram of the principal part in the structure of FIG. It is explanatory drawing which shows the structure of the conventional liquid crystal display device. It is explanatory drawing which shows the structural example of the conventional scanning signal line drive circuit. FIG. 3 is an equivalent circuit diagram of one display pixel in a configuration in which a pixel capacitor and an auxiliary capacitor are connected in parallel to a counter potential of a counter electrode drive circuit. It is a drive waveform diagram of a conventional liquid crystal display device. It is explanatory drawing used for both this invention and a prior art, and is explanatory drawing which shows that a thin film transistor has a linear gate voltage-drain current characteristic instead of a perfect ON / OFF switch. This is a propagation equivalent circuit when attention is paid to the signal propagation delay of one scanning signal line. It is explanatory drawing which shows a mode that the scanning signal input into the scanning signal line from the said scanning signal line drive circuit is curled inside a panel by the signal delay propagation characteristic of a scanning signal line.

Explanation of symbols

GCK clock signal GSP data signal VD1 input terminal VD2 input terminal 3a shift register section 3b selection switch (switch section)
SC slew rate control element (tilt control unit)
105 scanning signal line 200 scanning signal line driving circuit (driving circuit)
SW1 switch SW2 switch SW3 switch Ict constant current source OP operational amplifier (subtraction unit)
VG Scan signal VD1a Output signal (voltage)
VD1b output signal (voltage)

Claims (6)

A plurality of pixels, a video signal line for supplying a data signal to the pixel, a scanning signal line provided to intersect the video signal line, a scanning signal output to the scanning signal line, and the scanning signal line In a display device comprising a drive circuit for driving,
A voltage having a waveform having a period with a voltage level change that decreases so that the voltage level is inclined is input to the drive circuit,
The voltage starts to rise vertically from the decrease end level toward the voltage level equal to or higher than the decrease end level at the end of the decrease in the voltage level change, and has a period of one scanning period, and the voltage level is inclined. The display device is characterized in that the waveform includes one period that falls in a cycle.   The driving circuit outputs, for each scanning signal line, a waveform corresponding to one cycle of the voltage during a scanning period, and outputs a voltage level equal to or lower than the decrease end level of the voltage level change outside the scanning period. The display device according to claim 1, wherein the scanning signal is supplied.   3. The display device according to claim 1, wherein the period accompanied by the voltage level change is a period in which the voltage level decreases while being inclined from the direct current level after the direct current level period. In a display method for driving a scanning signal line by supplying a data signal to a plurality of pixels via a video signal line and supplying a scanning signal from a driving circuit to a scanning signal line provided to intersect the video signal line ,
  A voltage having a waveform having a period with a voltage level change that decreases so that the voltage level is inclined is input to the drive circuit;
  At the end of the decrease in the voltage level change, the voltage starts to rise vertically from the decrease end level to a voltage level equal to or higher than the decrease end level, and has a period of one scanning period, and the voltage level is inclined A display method characterized by having a waveform that includes one period that falls in a cycle. The driving circuit outputs, for each scanning signal line, a waveform corresponding to one cycle of the voltage during a scanning period, and outputs a voltage level equal to or lower than the decrease end level of the voltage level change outside the scanning period. The display method according to claim 4, wherein the scanning signal is supplied. 6. The display method according to claim 4, wherein the voltage level change is for tilting a part of a change between a high level and a low level of the scanning signal.

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