JP2003066920A - Display device and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce both the cost and a flicker of a display device. SOLUTION: Related to an active matrix liquid-crystal display device which is capacity-coupled-driven by allowing a common electrode potential to assume two potential levels, a voltage for resetting display is written before a video signal is written in a pixel electrode. Thus, the liquid-crystal capacity at writing of video signal can be made constant independent of display gradation, and a flicker caused by anisotropy in dielectric constant of a liquid-crystal can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor display for a personal computer, a display device used as a display screen of a portable terminal, a display device such as a liquid crystal television, a liquid crystal projector and the like and a driving method thereof.

[0002]

2. Description of the Related Art A display device using liquid crystal as a display medium is widely used as a thin and lightweight flat display for display devices of various electronic devices. Among them, active matrix type liquid crystal display devices using switching elements such as thin film transistors are widely applied to monitor displays for personal computers and liquid crystal televisions due to their excellent image characteristics.

There are various configurations of the active matrix type display device, and an example thereof is shown in FIG. The display device 101 is roughly divided into a scan signal drive circuit 102, a video signal drive circuit 103, a common electrode potential control circuit 109, and a display element 106.

The display element 106 includes a plurality of pixel electrodes 108 arranged in a matrix, a plurality of switching elements 107 arranged corresponding to the pixel electrodes 108, and a row direction (horizontal direction) corresponding to the matrix arrangement of the pixel electrodes. Direction), the plurality of scanning electrodes 104 and the common electrode 110, and the plurality of video signal electrodes 105 arranged in the column direction (vertical direction).
Is the main component. The video signal electrode 105 is electrically connected to the pixel electrode 108 via the switching element 107. A counter electrode (not shown) is provided so as to face the pixel electrode 108, and a display medium (liquid crystal) is inserted between the pixel electrode and the counter electrode. The switching element 107 is mainly a thin film transistor (TF).
T) is used.

The video signal drive circuit 103 includes a display element 10
6 is a drive circuit for applying a video signal voltage to the plurality of video signal electrodes 105. In addition, the scanning signal drive circuit 102
The drive circuit applies a scanning signal voltage for controlling conduction of the switching element 107 to the plurality of scanning electrodes 104 of the display element 106. The common electrode potential control circuit 109 is a circuit that controls the potential of the common electrode 110.

As one driving method of such an active matrix type display device, there is a driving method disclosed in Japanese Unexamined Patent Publication No. 5-143021. This is to form a storage capacitor between the common electrode and the pixel electrode, vary the potential of the common electrode in synchronization with the potential of the scanning electrode, and superimpose a capacitive coupling voltage on the pixel electrode potential via the storage capacitor. is there. Due to the effect of this voltage superposition, the video signal voltage (source voltage)
The effects of lowering the voltage, reducing drive power, improving response speed, and improving drive reliability are obtained.

The driving method will be described in detail below.

FIG. 17 shows a common electrode 110 and a pixel electrode 108.
2 shows an equivalent circuit of one pixel of a display device in which a storage capacitor 111 (represented by Cst) is formed between the two. This corresponds to the part surrounded by the broken line in FIG. In FIG. 17, Cgd is a gate-drain capacitance (also referred to as a scanning electrode-pixel electrode capacitance. Cgd does not necessarily have to be intentionally added, but even in such a case, it exists as a stray capacitance. ), Clc is a capacitance between the pixel electrode and the counter electrode formed between the pixel electrode and the counter electrode that is opposed to the display medium with the display medium sandwiched between the pixel electrode and the counter electrode.
There is also a capacitive component generated by electrically adding another medium in series or in parallel. Alternatively, such a capacity may be added intentionally), and Vg
(N) is the potential of the scanning electrode, Vs is the video signal potential, Vd is the pixel electrode potential, Vf is the counter electrode potential, and Vc (n) is the common electrode potential. Note that the pixel arrangement is arranged in a matrix, and the subscript n is particularly added to Vg and Vc in the sense that attention is paid to the n-th row.

FIG. 18 is for explaining the potential of each part when the display device shown in FIGS. 16 and 17 is driven. In the odd frame, the video signal voltage is Vs
It is assumed that the value is ig (-). Scan electrode potential Vg
When (n) becomes the ON level Vgon, the TFT becomes conductive (ON state) and the pixel electrode potential Vd becomes Vsig.
It is charged to (-). At this time, the potential of the common electrode is Vc
The value is (+). Then, the scan electrode potential Vg
(N) is set to the off level Vgoff to put the TFT in a non-conducting state (OFF state). After that, the potential of the common electrode is set to V
When changing downward from c (+) to Vcoff, a coupling voltage proportional to this voltage difference is superimposed downward on the pixel electrode potential Vd (arrow in the figure).

In an even frame, the video signal voltage is V
It is assumed that the value is sig (+). Pixel electrode potential Vd
Is charged to Vsig (+), the potential of the common electrode is set to Vc (-) this time. After the charging is completed and the scan electrode potential falls, the common electrode potential is set to Vc.
The value is changed upward from (-) to Vcoff. A coupling voltage proportional to this voltage difference is superposed upward on the pixel electrode potential Vd.

In any case, even when the scanning electrode potential changes, the pixel electrode potential Vd slightly changes due to the coupling voltage via the gate-drain capacitance Cgd (this is generally a penetration or feedthrough). be called).

As a result of the above, while the video signal electrodes are applied with voltages of small amplitudes (Vsig (+) and Vsig (-)), the pixel electrodes have larger amplitudes (Vdo (+) and Vdo (-)). Can be applied (effect of increasing video signal amplitude). For example, by using a video signal IC with an output voltage width of 5 V, the voltage width applied to the liquid crystal can be expanded to 10 V or 15 V, and while using a low withstand voltage IC,
It becomes possible to drive the liquid crystal with a voltage higher than the withstand voltage.

In this driving method, the common electrode potential control circuit 109 outputs three different values (Vc (+), Vc (-), and Vcoff) to the common electrode 110. Among these, Vc (+) and Vc (-) are called common electrode compensation voltage (compensation potential).

Now, in order for the common electrode potential control circuit to output three kinds of voltage values, three kinds of power supplies (power supply circuits) corresponding to these voltage values are necessary, which causes a problem that the cost is slightly high. there were. Therefore, a driving method has been devised in which only two types of power supplies are required (thus, the cost is reduced) and the above-described effect of increasing the amplitude of the video signal can be obtained. This is shown in FIG. As can be seen from FIG. 19, the common electrode potential control circuit has Vc1 and Vc2 (Vc1
Only two voltage values <Vc2) are output.
Then, in the odd frame, the common electrode potential is set to Vc2.
When changing from → Vc1 to Vc1 → Vc2 in an even frame, the coupling voltage via the storage capacitor is superimposed on the pixel electrode potential Vd. That is, the effect of increasing the amplitude of the video signal is obtained as in the case of FIG.

Next, another configuration example of the active matrix type display device is shown in FIG. The display device 101 is roughly divided into a scan signal drive circuit 102, a video signal drive circuit 103, and a display element 106. The basic configuration is the same as that of FIG. 16 except that the common electrode potential control circuit and the common electrode are not provided.

One of the active matrix type display devices
As one driving method, Japanese Unexamined Patent Publication No. 2-913 and AM-LCD 95 (AM-LCD95) 59-
There is a capacitive coupling drive method disclosed on page 62. In this technique, a storage capacitor is formed between the scan electrode and the pixel electrode in the previous stage or the subsequent stage, the potential of the scan electrode is changed stepwise, and the capacitive coupling voltage is superimposed on the pixel electrode potential via the storage capacitor. . Due to the effect of the voltage superposition, the effect of lowering the video signal voltage (source voltage), reducing the driving power, improving the response speed, and improving the driving reliability can be obtained.

Hereinafter, this driving method will be described in detail.

FIG. 21 shows an equivalent circuit of one pixel of a display device in which a storage capacitor 111 (represented by Cst) is formed between the scan electrode 112 and the pixel electrode 108 in the previous stage (hereinafter, pay attention to this point. The scan electrode 112 in the previous stage connected to the existing pixel electrode via the storage capacitor is called a compensation scan electrode). This corresponds to the part surrounded by the broken line in FIG. This FIG. 21 is almost the same as FIG. 17, except that the connection destination of the storage capacitor is the compensation scan electrode 112.
Note that Vg (n-1) indicates the potential of the compensation scan electrode.

FIG. 22 is for explaining the potential of each part when the display device shown in FIGS. 20 and 21 is driven. In the odd frame, the video signal voltage is Vs
It is assumed that the value is ig (-). When the scanning electrode potential Vg (n) at this stage becomes the on level Vgon, the TFT becomes conductive (ON state) and the pixel electrode potential Vd becomes Vsi.
It is charged to g (-). At this time, the potential of the compensation scan electrode has a value of Vge (+). Next, the scanning electrode potential Vg (n) of this stage is set to the off level, and the TFT is turned off (OFF state). After that, when the potential of the compensation scan electrode is changed downward from Vge (+) to Vgoff, a coupling voltage proportional to this voltage difference is downwardly superimposed on the pixel electrode potential Vd (arrow in the figure). .

In an even frame, the video signal voltage is V
It is assumed that the value is sig (+). Pixel electrode potential Vd
Is charged to Vsig (+), the potential of the compensation scan electrode is set to Vge (-) this time. After the charging is completed and the scan electrode potential of this stage falls, the potential of the compensation scan electrode is changed upward from Vge (−) to Vgoff. A coupling voltage proportional to this voltage difference is superposed upward on the pixel electrode potential Vd.

In any case, even when the scanning electrode potential at this stage changes, the pixel electrode potential Vd slightly changes due to the coupling voltage via the gate-drain capacitance Cgd (this is generally the case). , Or called feedthrough).

As a result of the above, while the video signal electrodes are applied with voltages of small amplitudes (Vsig (+) and Vsig (-)), larger amplitudes (Vdo (+) and Vdo (-)) are applied to the pixel electrodes. Can be applied (effect of increasing video signal amplitude). For example, by using a video signal IC with an output voltage width of 5 V, the voltage width applied to the liquid crystal can be expanded to 10 V or 15 V, and while using a low withstand voltage IC,
It becomes possible to drive the liquid crystal with a voltage higher than the withstand voltage.

In the present driving method, the scanning signal driving circuit 1
Reference numeral 02 denotes three different values (Vge) other than the voltage Vgon for turning on the TFT with respect to the scanning electrode 104.
(+), Vge (-), and Vgoff) are output. Among these, Vge (+) and Vge (-) are referred to as scan electrode compensation voltage (compensation potential).

In order for the scanning signal drive circuit to output four kinds of voltage values including Vgon, four kinds of power supplies (power supply circuits) corresponding to these voltage values are required, and the cost is slightly increased. There was a problem. Therefore, the power source is 3
A driving method has also been devised in which only the types (two types except Vgon) are required (therefore, the cost is reduced) and the above-described effect of increasing the amplitude of the video signal can be obtained. This is shown in FIG.
As can be seen from FIG. 23, the scan signal driving circuit has Vgon, Vgoff1 and Vgoff2 for the scan electrodes.
Only three types of voltage values (Vgoff1 <Vgoff2) are output. In the even-numbered frame, the compensation scan electrode potential does not change and no voltage superimposition occurs, but in the odd-numbered frame, the compensation scan electrode potential is Vgo.
When changing from ff2 to Vgoff1, the coupling voltage via the storage capacitor is superimposed on the pixel electrode potential Vd. That is, the effect of increasing the amplitude of the video signal is obtained only by the coupling voltage in the odd frames.

Next, color display on the display device will be described.

There are various methods for displaying a color image in a display device, but the mainstream of the direct-view type liquid crystal display panel at present is to provide a color filter for each pixel by providing red, green and blue color filters. This is a display method (color filter method). On the other hand, what is attracting attention as a color display system for the next-generation display is a system (field sequential system) for performing color display by lighting a plurality of light sources having different spectrums in a time division manner.

FIG. 24A shows an example of a concrete structure of a display device using the field sequential system.
The lighting profile of the light source at this time is shown in (b). One display cycle (one frame) of video as shown in FIG.
Is divided into, for example, three subframes (also referred to as fields and unit intervals), and red, green, and blue light sources 201r, 201g, and 201b are provided in each subframe.
Light up. Then, in synchronization with this, each color component of a desired image is presented on the display unit 202 using a display medium (liquid crystal). Here, the display control is performed by the display control unit 205 including an active matrix array or the like. The observer 204 observes the output light 203 transmitted through the display unit 202 and output at this time. If the switching of each color light source is sufficiently fast, the presented image is recognized as a color image by the observer 204 due to the visual integration effect.

In the color filter system, when the light from the light source passes through the color filter, only a specific wavelength spectrum component is selectively transmitted and other wavelength spectrum components are absorbed, so that the light utilization efficiency is low. There were challenges. On the other hand, in the field sequential method, the light from each color light source can be used as it is without passing through a color filter, so that high light utilization efficiency can be obtained, and thus low power consumption can be achieved. There are advantages. Furthermore, since a red, green, or blue light emitting diode (LED) having a sharp emission spectrum (that is, high color purity) or the like can be used as a light source, there is an advantage that an image with high color reproducibility can be obtained. Further, in the color filter system, three pixels each provided with a red, green, and blue filter are one display unit, but in the field sequential system, one pixel is one display unit, so high definition is possible. There is also an advantage that Further, there is also an advantage that the cost can be reduced because the color filter is not used.

The display control unit 205 is generally composed of an active matrix array in many cases, and the driving of this active matrix array is performed by the above-mentioned FIG. 18 and FIG.
9, or the method described with reference to FIGS. 22 and 23, or the most general driving method in which the coupling voltage is not applied from other electrodes. For example, in FIG.
When a pixel equivalent circuit is given and driving as shown in FIG. 25 is performed (in that case, the common electrode potential control circuit shown in FIG. 16 is not necessarily required), or the equivalent circuit of one pixel shown in FIG. This is the case when the driving is performed as shown in FIG. Hereinafter, such a case will be considered.

When scanning is performed in a field sequential system in a display device (a general example. For example, Shunsuke Kobayashi Responsible Editing Series Advanced Display Technology 3
Details of "Next Generation Liquid Crystal Display" (described in Chapter 8 of Kyoritsu Shuppan Co., Ltd.) will be described with reference to FIG. FIG. 27 shows changes in the scanning electrode potential in the upper part, the center part, and the lower part of the display area, the transmissivity response of the liquid crystal in each part at that time, and the timing of the lighting luminance of each light source. As described above, one frame is divided into three subframes corresponding to each color. Here, they are referred to as a red subframe, a green subframe, and a blue subframe, respectively. Then, each subframe is further divided into a writing period and a reading period.

First, in the writing period, the display region is scanned from the upper part to the lower part, and the scan electrode potentials are sequentially selected. In response to this, the pixel switching elements in each row are turned on, and the video signal voltage is sequentially applied from the video signal drive circuit to the pixel electrodes in each row via the video signal electrodes and held. At this time, the transmittance of the liquid crystal shows a value corresponding to the video signal voltage, but it takes some time to reach the target transmittance due to the viscosity of the liquid crystal, and as shown in FIG. The waveform changes gently. In the next reading period, scanning is not particularly performed, and the video signal voltage is held in each pixel electrode, but each light source is turned on in this period. As a result, the two-dimensional image information written in the liquid crystal (in this case, the two-dimensional distribution of transmittance) is read. This is red, green,
A color image can be obtained as a moving image by repeating each of the blue and blue sub-frames and repeating this for each frame.

[0032]

First, the method of obtaining the effect of increasing the amplitude of the video signal by using the common electrode potential control circuit in the configuration of FIG. 16 will be explained. Especially, if the driving method as shown in FIG. It has been shown that the output potential level of the electrode potential control circuit can be reduced to two and the cost can be reduced. However, when this drive is applied to an actual display device, flicker (flicker) is noticeable.

Generally, flicker is caused by the difference in brightness between even frames and odd frames (for example, when the display device is driven at a frame frequency of 60 Hz, the flickering frequency is 30 Hz, which is recognized by human eyes. Will be done). Therefore, the potential Vf of the counter electrode
By adjusting, it is possible to balance the voltage applied to the liquid crystal between even and odd frames (that is, between positive and negative polarities) and suppress flicker.

However, in the case of this configuration, even if the potential of the counter electrode is adjusted so that the flicker becomes minimum with respect to a certain video signal level, when the video signal level is changed to another, the flicker appears or the black level is reduced. The phenomenon that it floated and the contrast did not appear appeared.

Secondly, a method for obtaining the effect of increasing the amplitude of the video signal with the configuration of FIG. 20 will be described. Particularly, if the driving method as shown in FIG. 23 is used, the output potential level of the scanning signal driving circuit is reduced to three. It is possible to reduce the cost. However, when this drive was applied to an actual display device, flicker (flickering) was still noticeable.

Also in this case, as in the first case, even if the potential of the counter electrode is adjusted so that the flicker becomes minimum for a certain video signal level, the flicker appears at another video signal level. I was surprised, and the black level floated and the contrast did not come out.

Thirdly, the field sequential system has been described with the configuration of FIG. 24, and it has been shown that color display can be obtained by the driving of FIG. However, when this drive is applied to an actual display device, the color reproducibility of the output image is not so high. In addition, a phenomenon was observed in which the output image did not have the desired color and color shift occurred.

According to the present invention, (1) the flicker in the first and second configurations is improved, and (2) the color reproducibility in the third configuration is improved and the color shift is suppressed. With regard to the solution.

[0039]

A first display device of the present invention for solving the above-mentioned problem (1) includes a display element,
A display device comprising a video signal drive circuit, a scanning signal drive circuit, and a common electrode potential control circuit, wherein the display element includes a display medium, a plurality of pixel electrodes arranged in a matrix, and connected to the display medium. The switching element, the scan electrode, the video signal electrode, and the common electrode, and the storage capacitor is provided between the pixel electrode and the common electrode. The video signal driving circuit outputs two different voltage values to the electrodes, and superimposes the coupling voltage via the storage capacitor on the potential of the pixel electrode. The display device is characterized in that, in addition to the video signal voltage, a voltage for resetting the display is output to the signal electrode.

Here, it is desirable that the voltage for resetting the display is written just before the video signal voltage is written to the pixel electrode.

Further, voltages of both positive and negative polarities are applied to the display medium, and two kinds of voltages output to the common electrode by the common electrode potential control circuit are respectively Vc1 and Vc2 (Vc1 <
Vc2), the common electrode potential control circuit writes the video signal voltage for applying a positive voltage to the display medium to the pixel electrode and then sets the potential of the common electrode to Vc2).
After changing from c1 to Vc2 and writing a video signal voltage for applying a negative voltage to the display medium to the pixel electrode, the potential of the common electrode is changed from Vc2 to Vc.
It is desirable to change it to 1.

Alternatively, the common electrode potential control circuit is
In order to change the potential of the common electrode from Vc1 to Vc2 after writing a video signal voltage for applying a positive voltage to the display medium and to apply a negative voltage to the display medium The potential of the common electrode may not be changed immediately after writing the video signal voltage of No. 2 to the pixel electrode.

Alternatively, the common electrode potential control circuit does not change the potential of the common electrode immediately after writing a video signal voltage for applying a positive voltage to the display medium to the pixel electrode, and The potential of the common electrode may be changed from Vc2 to Vc1 after writing a video signal voltage for applying a negative voltage to the display medium to the pixel electrode.

Further, let ε // be the permittivity sensitive to the electric field applied in the direction of the long axis of the molecule of the display medium, and let ε⊥ be the permittivity sensitive to the electric field in the direction perpendicular to it.
When ε // − ε⊥ is set, the value of | Δε | / ε⊥ is 1.1.
It is preferably 5 or more.

A second display device of the present invention for solving the problem (1) is a display device including a display element, a video signal drive circuit, and a scanning signal drive circuit. The element has a display medium, a plurality of pixel electrodes arranged in a matrix, a switching element connected to the pixel electrode, a scanning electrode, and a video signal electrode, and includes the pixel electrode and the scanning electrode. The scan signal driving circuit has two kinds of different voltages other than the voltage value for bringing the switching element into a conductive state with respect to the scan electrodes. Outputting a value and superimposing a coupling voltage via the storage capacitor on the potential of the pixel electrode, wherein the video signal drive circuit applies a video signal voltage to the video signal electrode. In addition to the It is a display device characterized by the voltage for bets output.

Here, it is desirable that the voltage for resetting the display is written just before the video signal voltage is written to the pixel electrode.

Further, voltages of both positive and negative polarities are applied to the display medium, and the scanning signal drive circuit outputs to the scanning electrodes two types of voltages other than the voltage value for making the switching element conductive, Vgoff1. , Vgoff2
When (Vgoff1 <Vgoff2) and the scanning electrodes other than the current stage which are connected to a certain pixel electrode via the storage capacitor are called compensation scanning electrodes, the scanning signal drive circuit
After writing a video signal voltage for applying a positive voltage to the display medium to the pixel electrode, the potential of the compensation scan electrode is changed from Vgoff1 to Vgoff2, and
It is preferable that the potential of the compensation scan electrode is not changed immediately after the video signal voltage for applying the negative voltage to the display medium is written in the pixel electrode.

Alternatively, the scan signal drive circuit does not change the potential of the compensation scan electrode immediately after writing a video signal voltage for applying a positive voltage to the display medium to the pixel electrode, and After writing a video signal voltage for applying a negative voltage to the display medium to the pixel electrode, the potential of the compensation scan electrode is changed from Vgoff2 to Vg.
It may be changed to off1.

Further, it is desirable that the display medium is a normally white type, and the voltage amplitude of the signal for resetting the display is equal to or larger than the maximum amplitude of the video signal voltage for the display.

Alternatively, the display medium is a normally black type, and the voltage amplitude of the signal for resetting the display is
It may be less than the minimum amplitude of the video signal voltage for display.

The display medium is preferably liquid crystal, and more preferably OCB mode liquid crystal.

Further, a third display device of the present invention for solving the problem (2) is a display provided with a display element, a video signal drive circuit, a scanning signal drive circuit and a common electrode potential control circuit. A display device for performing color display by lighting a plurality of light sources having different spectrums in a time division manner, wherein the display element includes a display medium and a plurality of display elements arranged in a matrix. Pixel electrode of
It has a switching element connected to it, a scanning electrode, a video signal electrode, and a common electrode, and has a storage capacitance between the pixel electrode and the common electrode. The video signal voltage applied from the video signal drive circuit to the video signal electrode in a certain subframe is superimposed on the potential of the pixel electrode via the storage capacitor. In the display device, the display medium is corrected according to the capacity of the display medium.

Here, the absolute value of the video signal voltage applied from the video signal drive circuit to the video signal electrode in a certain sub-frame is smaller than that in the case where the absolute value of the applied voltage to the display medium in the previous sub-frame is the minimum. It is preferable that the absolute value of the voltage applied to the display medium in the previous subframe is corrected so that the absolute value is smaller.

Then, ΔQcc = CgdΔVg + CstΔV, where ΔVg is the potential change of the scanning electrode at this stage after writing the video signal voltage, ΔVc is the potential change of the common electrode, Cst is the storage capacitance, and Cgd is the capacitance between the scanning electrode and the pixel electrode.
c, when a certain gray level of a certain sub-frame is to be displayed, the applied voltage to the display medium for achieving that gray level is Vlc, and the sum of the capacitances electrically connected to the pixel electrodes is the display medium. The value when the applied voltage to Vlc is Cto
t, of the total capacitance electrically connected to the pixel electrode,
When the value in the previous sub-frame is Ctot ', the video signal voltage given to the video signal by the video signal drive circuit is approximately [Ct based on the potential on the opposite side of the display medium.
It is preferably given by otVlc−ΔQcc] / Ctot ′.

A fourth display device of the present invention for solving the problem (2) is a display device including a display element, a video signal drive circuit, and a scanning signal drive circuit, and is different. In the display device for performing color display by lighting a plurality of light sources having a spectral spectrum in a time division manner, the display element includes a display medium, a plurality of pixel electrodes arranged in a matrix, and A switching element connected to the scanning electrode, a scanning electrode, and a video signal electrode, and a storage capacitor between the pixel electrode and one of the scanning electrodes excluding the scanning electrode at the current stage, The scanning signal drive circuit superimposes the coupling voltage via the storage capacitor on the potential of the pixel electrode, and the video signal voltage applied from the video signal drive circuit to the video signal electrode in a certain subframe is So A display device which is characterized in that having been corrected according to the capacity of said display medium at a previous sub-frame.

Here, the absolute value of the video signal voltage applied from the video signal drive circuit to the video signal electrode in a certain sub-frame is smaller than the absolute value of the voltage applied to the display medium in the previous sub-frame. It is preferable that the absolute value of the voltage applied to the display medium in the previous subframe is corrected so that the absolute value is smaller.

Further, the potential change of the scan electrodes of the present stage after writing the video signal voltage is ΔVg, the potential change of the scan electrodes of other stages connected via the storage capacitor is ΔVgp, the storage capacitance is Cst, and The capacitance between the scanning electrode and the pixel electrode of the step is Cg
When ΔQcc = CgdΔVg + CstΔVgp is set as d, and when a gray scale which is a certain subframe is to be displayed, the voltage applied to the display medium for attaining the grayscale is Vl.
c, the sum of the capacitances electrically connected to the pixel electrodes when the applied voltage to the display medium is Vlc is Ctot,
When the value of the total capacitance electrically connected to the pixel electrodes in the previous subframe is Ctot ′, the video signal voltage applied to the video signal by the video signal drive circuit is the potential on the opposite side of the display medium. As a reference, the outline [CtotVl
It is desirable to be given by c−ΔQcc] / Ctot ′.

In the third and fourth display devices, the display medium is preferably liquid crystal, and OC
B-mode liquid crystal is more preferable.

The fifth display device of the present invention for solving the problem (2) is a display device including a display element, a video signal drive circuit, and a scanning signal drive circuit, and is different. In the display device for performing color display by lighting a plurality of light sources having a spectral spectrum in a time division manner, the display element includes a display medium, a plurality of pixel electrodes arranged in a matrix, and Has a switching element connected to, a scanning electrode, and a video signal electrode, and has a permittivity ε // sensed by an electric field applied in the molecular long axis direction of the display medium, and a direction perpendicular to the permittivity. Let ε ⊥ be the dielectric constant that is sensitive to the electric field of Δε = ε //-ε
When ⊥ is set, the value of | Δε | / ε⊥ is 1.2 or more, and the video signal drive circuit causes the video signal electrode to reset the display before writing the video signal voltage. Is a display device.

In addition, the driving method corresponding to each of the above-mentioned display devices can also be mentioned as means for solving (1) or (2).

[0061]

BEST MODE FOR CARRYING OUT THE INVENTION (Analysis of Flicker Occurrence Phenomenon in First Configuration) First, the cause of flicker occurring in the first configuration was analyzed. As a result, it has been clarified that the flicker is caused by the dielectric anisotropy of the display medium, that is, the liquid crystal. This will be explained below.

The liquid crystal molecules are represented by a slender rod-shaped model as shown in FIG. 28 (a). Generally, the dielectric constant ε // which is sensitive to the electric field applied in the long axis direction of the molecule and the Dielectric constants ε⊥ that are sensitive to the electric field applied in the direction are different. Such a property is called dielectric anisotropy. When Δε = ε / −− ε⊥ is set, Δε may be positive or negative, which are called positive dielectric anisotropy and negative dielectric anisotropy, respectively.

As an example of the case where Δε is positive, Twisted Nematic (T)
N) There is a liquid crystal. In general, the TN liquid crystal is arranged in a twisted state as shown in FIG. 28B when no electric field is applied between the electrodes of the two substrates (the upper interface is lateral in the plane of the paper, and the lower interface is Arranged in the direction perpendicular to the paper). In this case, the liquid crystal molecules are oriented in a direction parallel to the substrate surface at any position between the upper and lower substrates, so when a voltage is applied between the two substrates, the dielectric constant ε⊥ is sensed and the liquid crystal between the two substrates is sensed. Capacity is Clc ⊥ = ε ⊥ × (area of liquid crystal layer) /
(Thickness of liquid crystal layer). Next, when the applied voltage between the electrodes is increased, the liquid crystal gradually faces the direction perpendicular to the substrate surface as shown in FIG. 28 (c). Then, the part that senses the dielectric constant ε // between the two substrates gradually increases, and the liquid crystal capacitance ultimately becomes Clc // = ε // × (area of liquid crystal layer) / (thickness of liquid crystal layer). Approaching. Therefore, the liquid crystal capacitance changes according to the applied voltage, as shown in FIG. Since we are now considering the case of ε /> ε⊥, the capacitance increases with the applied voltage.
Actually, even if the applied voltage is 0, some liquid crystal molecules are oriented in a direction slightly deviated from the plane perpendicular to the substrate surface, or the orientation of the liquid crystal near the interface remains fixed even when a large voltage is applied. The capacitance value is always Clc⊥ at 0 voltage and Clc /// at sufficiently high voltage.
However, the capacitance increases at least with the applied voltage.

Regardless of whether the voltage applied to the liquid crystal is positive or negative, if the absolute values are the same, the alignment state is almost the same (strictly speaking, the difference in the electrode materials at both interfaces and the residual ion). It may be asymmetrical due to influence or flexo electric effect,
In the following, we will ignore these and assume positive and negative symmetry). Therefore, it can be considered that the horizontal axis in FIG. 29 is the absolute value of the liquid crystal applied voltage.

A typical example of a liquid crystal in which Δε is negative is a vertical alignment (V).
A) Liquid crystal. In this case, the liquid crystal molecules are oriented so as to be substantially perpendicular to the substrate surface without applying a voltage (FIG. 28 (d)), and the liquid crystal capacitance becomes minimum. As the voltage is applied, the liquid crystal molecules gradually face the direction perpendicular to the substrate surface (FIG. 28 (e)), and the liquid crystal capacitance gradually increases.

Therefore, the capacitance increases with the applied voltage regardless of whether Δε is positive or negative, and the dependency of the liquid crystal capacitance on the applied voltage (absolute value) can be expressed as shown in FIG.

Although the TN liquid crystal and the VA liquid crystal have been described above, other than these, in-plane switching (In Pla
ne Switching (IPS) liquid crystal, MVA (multi-domain VA) liquid crystal, PVA (Patterned)
VA) liquid crystal and OCB (optically comp)
optical Bend) Liquid crystal or S
TN (Super Twisted Nematic)
EC including liquid crystal, ASV liquid crystal, homogeneous alignment liquid crystal, etc.
B (electric field control birefringence) type liquid crystal and GH (guest host)
It can be said that the capacity of liquid crystals, polymer-dispersed liquid crystals, discotech liquid crystals, etc. increases with applied voltage.

Next, let us consider the condition where the flicker becomes minimum when the driving of FIG. 18 is performed with the pixel structure of FIG. 17 to display a uniform still image (the driving of FIG. 19 will be described later). . The flicker is minimized when the alignment state of the liquid crystal is the same over the even and odd frames, that is, when the absolute value of the voltage applied to the liquid crystal is the same. In this case, the liquid crystal capacitance also has a constant value over even and odd frames, so that the liquid crystal capacitance can be treated as a constant value under this condition.

Here, as the video signal voltage, the central value Vs
When a signal of c and an amplitude of Vsp is given, the video signal voltages Vsig (-) and Vsig (+) in the odd frame and the even frame can be written as in (Equation 1).

[0070]

[Equation 1]

Under this video signal voltage, it is assumed that the minimum flicker condition can be realized when the counter electrode potential is Vf. Then, the pixel electrode holding potentials Vdo (−) and Vdo (+) can be written as in (Equation 2).

[0072]

[Equation 2]

This Vdp is the absolute value of the voltage applied to the liquid crystal,
It is an unknown value at this moment.

In addition, the amount of charge accumulated in the pixel electrode must be the same when the pixel electrode is completely charged in FIG. 18 and when the pixel electrode is held thereafter (charge conservation law). Therefore, the relational expression of (Equation 3) is obtained.

[0075]

[Equation 3]

This can be summarized as shown in (Equation 4).

[0077]

[Equation 4]

However, the value Ctot when the voltage applied to the display medium is Vlc is given by (Equation 5).

[0079]

[Equation 5]

Now, by adding the two equations of (Equation 4) to each other and dividing them by 2 to obtain (Equation 1) and (Equation 2), (Equation 6) is obtained.

[0081]

[Equation 6]

Further, if the difference between the two expressions of (Equation 4) is taken and divided by 2, (Equation 1) and (Equation 2) are considered, (Equation 7) is obtained.

[0083]

[Equation 7]

That is, the minimum flicker counter electrode potential Vf value and the absolute value of the liquid crystal applied voltage at that time were derived from (Equation 6) and (Equation 7).

Next, the same thing will be considered in the case of the driving shown in FIG. In this case, the charge conservation equation corresponding to the above (Equation 3) is given by (Equation 8).

[0086]

[Equation 8]

This is organized as shown in (Equation 9).

[0088]

[Equation 9]

Therefore, by combining (Equation 1) and (Equation 2), (Equation 10) and (Equation 11) are obtained.

[0090]

[Equation 10]

[0091]

[Equation 11]

Now, let us compare the equation (Equation 6) of the value of the minimum flicker counter electrode potential Vf in FIG. 18 with the equation (Equation 10) in FIG. First, paying attention to the equation (Equation 10) in the case of FIG. 19, the liquid crystal capacitance Clc is Ctot.
Included in. Since the gate-drain capacitance Cgd and (Vgon-Vgoff) are not 0, the minimum flicker counter electrode potential Vf changes depending on the liquid crystal capacitance Clc. The liquid crystal capacitance Clc depends on the liquid crystal applied voltage Vdp as shown in FIG. 29.
As can be seen from 1), since it depends on the video signal amplitude Vsp, the minimum flicker counter electrode potential Vf eventually changes depending on the amplitude Vsp of the input video signal. Therefore, it can be understood that even if the counter electrode potential is adjusted so as to minimize the flicker with respect to a certain video signal level, a phenomenon occurs in which the flicker appears at another video signal level. Further, the problem that the black level floats and the contrast does not appear is essentially the same, and the minimum flicker counter electrode potential Vf at a certain gradation level and the counter electrode potential at which the black level sinks most (that is, black display). It is nothing but because it does not match the counter electrode potential) at which the liquid crystal applied voltage becomes positive and negative symmetrical.

Next, in the case of (Equation 6) corresponding to the driving in FIG. 18, the flicker minimum counter electrode potential Vf also depends on Ctot in this case as well, so a similar problem appears at first glance. Seems to be. However, it is assumed that the condition such as (Equation 12) is satisfied in this equation.

[0094]

[Equation 12]

Then, the second and third terms of (Equation 6) cancel each other out, and eventually Vf = Vsc, and the minimum flicker counter electrode potential Vf value does not depend on the liquid crystal capacitance Clc. Even if the condition of (Equation 12) is not strictly met, at least [(Vc (+) + Vc (-)) / 2-V
coff] is a negative value, the second and third terms on the right side of (Equation 6) have opposite signs, and thus the deviation of the minimum flicker counter electrode potential Vf is smaller than that in the driving of FIG. In fact, also in FIG. 18, [(Vc (+) + Vc (−)) / 2−V
coff] is negative.

From the above, it can be understood that the flicker is not noticeable in the drive of FIG. 18, but the flicker is increased by the drive of FIG.

In the expressions (Equation 4) and (Equation 9) of the pixel electrode holding potential corresponding to the driving in FIGS. 18 and 19, the third term on the right side corresponds to the coupling voltage given from the common electrode in each of the even and odd frames. is doing. 18 in the case of the drive of FIG.
Types of potentials Vc (+), Vc (-), and Vcoff
By appropriately changing, the positive and negative coupling voltages can be independently changed, and the center of the video signal voltage and the center of the pixel electrode holding potential can be adjusted to be equal. However, in the case of the driving in FIG. 19, there are only two kinds of potentials Vc1 and Vc2, and no matter how these values are changed, the positive and negative coupling voltages always have the same absolute value, which is the center of the video signal voltage. The center of the pixel electrode holding potential cannot be made equal. That is, it is considered that the flicker appears as a side effect of reducing the potential level of the common electrode by one.

(Principle 1 of the Present Invention) After performing the above analysis, in the display device of FIG. 16 having the pixel structure of FIG. 17, using only two values as the common electrode potential level,
Moreover, the inventors have found a means for eliminating flicker that occurs depending on the video signal voltage amplitude. That is the content of the present invention, in which the reset voltage is written before the video signal voltage is charged. The principle will be described below.

FIG. 1 shows an example of the drive voltage waveform of the present invention. The scanning signal pulses indicated by [b] and [d] in the figure correspond to the timing when the video signal is written from the video signal drive circuit to the pixel electrode via the video signal electrode, and [a]
Similarly, the scanning signal pulse shown by [c] corresponds to the timing when the reset signal is written from the video signal drive circuit to the pixel electrode via the video signal electrode. It is assumed that the negative video signal voltage Vsig (-) is written in [b] and the positive video signal voltage Vsig (+) is written in [d]. Further, it is assumed that the positive reset voltage Vres (+) is written in [a] and the negative reset voltage Vres (−) is written in [c]. These reset voltages are for resetting the display written in [b] and [d], and are always at a constant level regardless of the video signal voltage.

The period from [a] to [b] or the period from [c] to [d] is the reset period,
A period from [b] to [c] or a period from [d] to [a] will be referred to as a video signal writing period.

The common electrode potential waveforms are Vc1 and Vc2.
It is assumed that there are only two levels (Vc1 <Vc2) (that is, the common electrode potential control circuit outputs two different voltage values Vc1 and Vc2). After writing the positive video signal voltage or the reset voltage to the pixel electrode, the common electrode potential is changed from Vc1 to Vc1.
After changing to c2 and writing a negative video signal voltage or a reset voltage to the pixel electrode, the common electrode potential is Vc.
The waveform is such that it changes from 2 to Vc1. Then, when the common electrode potential changes, the change in the pixel electrode potential Vd due to the coupling voltage via the storage capacitor Cst becomes as shown in FIG. 1, and the pixel electrode holding potential with respect to both the video signal voltage and the reset voltage becomes The effect of increasing the amplitude of is obtained.

Now, in the case of the present driving method, the alignment state of the liquid crystal changes with time, and the liquid crystal capacitance also changes. At the end of each video signal writing period for each positive and negative polarity and the reset period, the response of the liquid crystal is sufficiently stable, and as shown in FIG. 1, Clc (sig, +), C
lc (sig,-), and Clc (res, +), C
It is assumed that the capacitance value is lc (res, −). Also,
The pixel electrode potentials at that time are Vdo (sig,
+), Vdo (sig, −), and Vdo (res,
+) And Vdo (res,-). The counter electrode potential is Vf. Then, the equation for storing electric charges in the video signal writing period is as shown in (Equation 13).

[0103]

[Equation 13]

However, it is assumed that the charge pulse width of the scan electrode is sufficiently shorter than the response time of the liquid crystal, and the alignment state of the liquid crystal does not change during the charge period, and the capacitance at the end of the previous period (reset period) is changed. It is assumed that the battery is charged. By rearranging (Equation 13), (Equation 14) is obtained.

[0105]

[Equation 14]

However, this equation is rewritten by substituting (Equation 1) for giving a signal of the central value Vsc and the amplitude Vsp as the video signal voltage.

Now, in both equations (Equation 14), C is set on the right side.
Capacitances of lc (res, +) and Clc (res,-) appear, but if the same charge conservation law as in (Equation 13) is considered in the reset period, the period before that, that is, at the end of the video signal writing period. It should depend on the liquid crystal capacity. However, it is assumed that a sufficiently large voltage is applied to the liquid crystal during the reset period in FIG. 1, and the absolute value of the applied voltage at that time | Vdo (re
s, +)-Vf | and | Vdo (res,-)-Vf
Assuming that the liquid crystal capacitance for | is in a sufficiently saturated region in the graph of FIG. 29, the pixel electrode potentials Vdo (res, +) and Vdo (r) in the reset period are assumed.
Even if es, −) slightly changes depending on the liquid crystal capacitance in the previous video signal writing period, Clc (re
s, +) and Clc (res,-) can be considered to be constant with little change (this just means that the display is reset). This constant capacity value is represented as Clc (H) according to FIG. Then, (Equation 14) can be rewritten as (Equation 15).

[0108]

[Equation 15]

Now, let us consider the condition where the flicker becomes minimum. This is because the alignment state of the liquid crystal in the even-odd frame (that is, in the positive and negative polarity video signal writing period) is the same as that described in (Analysis of flicker occurrence phenomenon in the first configuration) in FIG. 18 and FIG. In the same case, that is, when the absolute value of the voltage applied to the liquid crystal is the same, the capacitance of the liquid crystal also becomes the same value in the even and odd frames.

Now, assuming that the flicker is minimized at the counter electrode potential Vf, the same equation (Equation 16) as in the case of (Equation 2) is established with the absolute value of the liquid crystal applied voltage being Vdp.

[0111]

[Equation 16]

Then, the liquid crystal capacities become equal over the even and odd frames, and Clc (sig, +) = Clc (si
If g,-) [= Clc (sig) is set], (Equation 17) is derived from (Equation 15) and (Equation 16).

[0113]

[Equation 17]

(Equation 18) is obtained by adding the two equations of (Equation 17) side by side and slightly deforming, and (Equation 19) is obtained by subtraction.

[0115]

[Equation 18]

[0116]

[Formula 19]

(Equation 18) and (Equation 19) are equations (Equation 6) and (Equation 7) in the case of driving in FIG. 18, or FIG.
It corresponds to the equations (Equation 10) and (Equation 11) in the case of the drive of 9.

Now, in (Equation 18), Clc (H) is contained as the capacitance of the liquid crystal, which is due to the video signal amplitude V
It is a constant capacitance value irrelevant to sp. Therefore, the minimum flicker counter electrode potential Vf has a constant value regardless of the video signal amplitude. In other words, if the counter electrode potential is set to the voltage value given by (Equation 18), flicker does not occur at any gradation level.

When the equation (Equation 18) of the minimum flicker counter electrode potential Vf in the present invention is compared with the equation (Equation 10) in the case of driving in FIG. 19, the equations are very similar. However, in (Equation 10), Cl appears through (Equation 5)
Although c is the liquid crystal capacitance at the display gradation level at that time, Clc (H) in (Equation 18) is largely different in that it is the liquid crystal capacitance after reset is applied in the reset period. By providing the reset period immediately before the video signal writing period, flicker can be eliminated for the first time.

In the case of the method of the present invention, the counter electrode potential at which the black level sinks most (that is, the counter electrode potential at which the liquid crystal applied voltage is positive and negative symmetrical in black display) (equation 1)
Since it is given in 8), the contrast reduction due to the floating of the black level is also improved.

(Principle 2 of the Present Invention) FIG. 2 shows a second drive waveform for the display device of FIG. 16 having the pixel structure of FIG.
Shown in. This is almost the same as the drive waveform of FIG. 1 described in (Principle 1 of the present invention), but the polarity of the reset period before the video signal writing period is opposite to that in FIG. That is, in FIG. 1, the negative polarity video signal writing period precedes the positive polarity reset period, and the positive polarity video signal writing period precedes the negative polarity reset period.
In FIG. 2, the opposite is the case. A negative polarity reset period precedes the negative polarity video signal writing period, and a positive polarity reset period precedes the positive polarity video signal writing period.

The common electrode potential waveform is V as in the case of FIG.
It has only two levels of c1 and Vc2 (Vc1 <Vc2) (that is, the common electrode potential control circuit outputs two different voltage values Vc1 and Vc2). Although the shape of the waveform itself is different from that of FIG. 1, the common electrode potential is from Vc1 to Vc after the positive video signal voltage or the reset voltage is written in the pixel electrode.
2 and the common electrode potential is Vc2 after the negative video signal voltage or the reset voltage is written in the pixel electrode.
It is the same as in the case of FIG. 1 that the waveform changes from Vc1 to Vc1. Therefore, as in the case of FIG.
An effect of increasing the amplitude of the pixel electrode holding potential can be obtained for both the video signal voltage and the reset voltage.

In this case, the formula for charge storage during the video writing period is the one in which Clc (res, +) and Clc (res,-) are exchanged in (Equation 13),
As described in (Principle 1 of the present invention), if a sufficiently large voltage is applied to the liquid crystal during the reset period, Cl
c (res, +) = Clc (res,-) = Clc
Since it can be set to (H), exactly the same formula as (Formula 15) is obtained, and the flicker minimum counter electrode potential Vf is expressed by the same formula as (Formula 18). Therefore, the minimum flicker counter electrode potential Vf has a constant value regardless of the video signal amplitude, and if the counter electrode potential is set to a voltage value given by (Equation 18), flicker does not occur at any gradation level. I understand.

(Principle 3 of the Present Invention) FIG. 3 shows a third drive waveform for the display device of FIG. 16 having the pixel structure of FIG.
Shown in. This is similar to FIG. 1 in that the reset voltage is written before charging the video signal voltage, but the common electrode potential waveform is slightly different from that in FIG. That is, Vc
1 and Vc2 (Vc1 <Vc2), but the common electrode potential changes from Vc1 to Vc2 after the positive video signal voltage or the reset voltage is written to the pixel electrode. The waveform of the common electrode potential does not change after the negative video signal voltage or the reset voltage is written in the pixel electrode. In this case, the coupling voltage via the storage capacitor Cst is superimposed after writing the positive polarity video signal voltage or the reset voltage, but such a coupling voltage is superimposed after writing the negative polarity video signal voltage or the reset voltage. Not done. However, even if the coupling voltage is superimposed only on one side, at least the effect of increasing the amplitude of the pixel electrode holding potential can be obtained as compared with the case where no coupling voltage is applied.

Now, in the case of the main drive waveform, the equation of charge conservation corresponding to (Equation 13) is given by (Equation 20).

[0126]

[Equation 20]

Compared with (Equation 13), this means that Vc1 is Vc in the first term (term relating to Cst) on the right side of the first equation.
The only difference is that it is 2. By rearranging (Equation 20), (Equation 21) is obtained.

[0128]

[Equation 21]

However, this equation is rewritten by substituting (Equation 1) for giving a signal having a center value Vsc and an amplitude Vsp as a video signal voltage, as in the case of (Equation 14).

Here, assuming that a sufficiently large voltage is applied to the liquid crystal in the reset period, Clc (res, +) = Clc as in the case of (Principle 1 of the present invention).
(Res,-) = Clc (H) can be set. If the flicker is minimized at the counter electrode potential Vf, Clc (sig, +) is further calculated using (Equation 16).
By setting = Clc (sig, −) = Clc (sig), (Equation 22) is obtained.

[0131]

[Equation 22]

Therefore, (Equation 23) can be obtained by adding the two equations of (Equation 22) to each other and slightly modifying them, and (Equation 24) can be obtained by subtracting them.

[0133]

[Equation 23]

[0134]

[Equation 24]

(Equation 23) and (Equation 24) correspond to the equations (Equation 18) and (Equation 19) in the case of driving in FIG. The expression of (Equation 23) is slightly different from that of (Equation 18), but the fact that the right side has a constant capacitance value irrelevant to the video signal amplitude Vsp is the same as the case of (Equation 18). Therefore, the minimum flicker counter electrode potential Vf has a constant value regardless of the video signal amplitude, and if the counter electrode potential is set to the voltage value given by (Equation 23), flicker does not occur at any gradation level.

Note that, unlike (Equation 19), (Equation 24) is preceded by a coefficient of 1/2 before the term relating to Cst on the right side, but this is about half in the main drive compared to the case of the drive in FIG. It is shown that the effect of increasing the image amplitude can be obtained.

For reference, consider what happens if the reset period is not provided in the main drive waveform. In this case, it is possible to explain in the same flow as the explanation given for the driving in FIG. 19 in (Analysis of flicker occurrence phenomenon in the first configuration). However, in the charge conservation equation of (Equation 8), the first term (term relating to Cst) on the right side of the first equation is Vc1.
Instead of Vc2. Then, when the expression of the minimum flicker counter electrode potential Vf corresponding to (Equation 10) is obtained (Equation 2)
It becomes 5).

[0138]

[Equation 25]

Here, pay attention to the part [] on the rightmost side of (Equation 25). In general, in a liquid crystal display device, Cgd (gate-drain capacitance) is often sufficiently smaller than the storage capacitance Cst. In fact, Cgd is rarely formed intentionally in particular, and in most cases, it is unavoidable as a parasitic capacitance. Generally, Cgd / Cs
The value of t is about 0.1, and even if it is large, it is at most 0.4.
It is a degree. If Cgd is smaller than Cst by about one digit, and (Vgon-Vgoff) and (Vc2-Vc1) are about the same value, | Cgd (Vgon-Vg
off) | value is | (1/2) Cst (Vc2-Vc
1) It is smaller than |. Then, it is unlikely that the rightmost [] in (Equation 25) becomes zero. Therefore, the minimum flicker counter electrode potential Vf of (Equation 25) depends on the liquid crystal capacitance Clc at the display gradation level. Therefore, the minimum counter flicker electrode potential Vf changes depending on the video signal amplitude Vsp, and gradation-dependent flicker and black level floating occur as in the case of the driving in FIG. Moreover, as described above, | (1/2) Cst (Vc2-Vc1) | is | Cg
d (Vgon-Vgoff) | is larger than d (Vgon-Vgoff) |
It is considered that it will be more prominent than in the case of.

In other words, the gradation dependent flicker and the floating of the black level, which are conspicuous in the conventional configuration without the reset period, can be completely removed by providing the reset period as in the present invention. Is that
It can be said that the effect of the present invention is extremely large.

In FIG. 3, the common electrode potential is Vc2 which remains unchanged after the negative video signal voltage or the reset voltage is written in the pixel electrode. However, Vc1 remains unchanged. It does not matter if you formulate and formulate the formula for charge conservation (equation 21).

(Principle 4 of the Present Invention) FIG. 4 shows a fourth drive waveform for the display device of FIG. 16 having the pixel structure of FIG.
Shown in. This is also to write the reset voltage before charging the video signal voltage, but the method of applying the coupling voltage from the common electrode is opposite to that in FIG. That is, Vc
1 and Vc2 (Vc1 <Vc2), but the common electrode potential does not change after writing the positive video signal voltage or the reset voltage to the pixel electrode, and the negative polarity. After the video signal voltage or the reset voltage is written in the pixel electrode, the common electrode potential has a waveform that changes from Vc2 to Vc1. In this case, the coupling voltage via the storage capacitor Cst is superimposed after writing the negative polarity video signal voltage or the reset voltage, but such a coupling voltage is superimposed after writing the positive polarity video signal voltage or the reset voltage. Not done. However, at least the effect of increasing the amplitude of the pixel electrode holding potential is obtained as in the case of FIG.

The case of the main drive waveform can be considered in exactly the same way as in FIG. 3, and the minimum flicker counter electrode potential Vf becomes a constant value regardless of the video signal amplitude, and the counter electrode potential is a voltage given by (Equation 26). The value indicates that flicker does not occur for any gradation level.

[0144]

[Equation 26]

For reference, the charge conservation equation in FIG. 4 is obtained by replacing Vc2 appearing in the first term (term relating to Cst) on the right side of the second equation with Vc1 in (Equation 13). is there. (Equation 26) is derived from the equation of the law of conservation of charge. Comparing (Expression 26) with the expression (Expression 23) in the case of FIG. 3, it can be seen that the sign of the third term on the right side (the term relating to Cst) is reversed. This is a natural consequence of the fact that the method of applying the capacitive coupling voltage is opposite to that in the case of FIG.

(Specific Embodiment 1) An example in which the present invention is applied to a display device having the structure of FIG. 16 which actually has the pixel structure of FIG. 17 will be described. In the pixel structure of FIG. 17, it is assumed that Cst = 0.70 pF and Cgd = 0.12 pF. Then, the capacitance Clc of the liquid crystal shown in FIG.
(L) and Clc (H) are respectively Clc (L) =
0.60 pF and Clc (H) = 0.90 pF (these capacitances may be obtained by actual measurement or simulation).

Consider, for example, the case of performing the driving shown in FIG. 1 (Principle 1 of the present invention). Here, the driving condition is Vgon = 1
2V, Vgoff = -8V, Vsc = 3V, Vc1 = 0
It is assumed that V and Vc2 = 12V (Vsc is a video signal voltage amplitude). And one frame period is 16.67 mse
c (corresponding to a frame frequency of 60 Hz), and the width of the reset period is 1/10 of that (that is, 1.667 msec).
And set.

First, when Vf is calculated by (Equation 10) in the case where the conventional driving (driving in FIG. 19) without the reset period is performed, when Clc is equal to Clc (L) (absolute voltage applied to liquid crystal is absolute). Vf = 1.310V when the value is a small gradation level, and Vf = 1.605V when Clc is equal to Clc (H) (when the absolute value of the voltage applied to the liquid crystal is sufficiently large). . That is,
The flicker minimum counter electrode potential Vf value has a difference of 0.295V.

Further, the flicker level was measured when only Vf was changed while keeping the driving conditions other than the minimum flicker counter electrode potential Vf constant (fixing the video signal voltage center value Vsc and the amplitude Vsp to a certain value). , A graph as shown in FIG. 5 is obtained. Here, the flicker level on the vertical axis is a value expressed in dB by taking the ratio of the two-frame period component (30 Hz component) of the output light luminance to the DC component. If the permissible limit of the flicker level is set to -35 dB, then V which makes the flicker level below the permissible limit is obtained.
The allowable change range of f was 0.15V.

According to this, the width of the minimum flicker counter electrode potential Vf value of 0.295 V exceeds the permissible range of 0.15 V, and the flicker cannot be set to the permissible limit or less for all gradations.

On the other hand, when the reset period is provided as in the present invention, the minimum flicker counter electrode potential Vf value is calculated by (Equation 18) regardless of the gradation level, and becomes a constant value Vf = 1.605V. This means that the width of the minimum flicker counter electrode potential Vf value is substantially 0 V. For example, the video signal voltage center value Vsc is appropriately adjusted to Vf.
Is made to match the minimum flicker state (Vfm) in FIG. 5, it becomes possible to sufficiently reduce the flicker for any gradation level.

In order to obtain the above effect, it is desirable to apply a voltage of sufficient amplitude to the liquid crystal in the reset period, but in reality Vres (+) = 6V,
If Vres (−) = 0V (video signal voltage amplitude with respect to reset voltage = 3V), that condition was sufficiently achieved. By the way, if the absolute value of the liquid crystal applied voltage related to the reset voltage is calculated by using (Equation 7) for convenience, it is about 7.8 V at the least, and it can be said that a sufficient voltage is applied to the liquid crystal. .

The parameters used in the above embodiments are numerical values as typical examples, and the present invention is by no means limited to the above parameters.

The drive shown in (Principle 2 of the present invention),
In other words, the drive shown in FIG. 2 can be considered in exactly the same way.

(Relationship between Dielectric Anisotropy and Flicker)
It is estimated that the gradation-dependent flicker that appears in the driving of FIG. 19 of the conventional technique becomes more significant as the absolute value of the dielectric anisotropy | Δε | of the display medium increases. In fact, when | Δε | is large, it is considered that the difference between Clc (H) and Clc (L) in FIG. 29 becomes large, and the variation width of the minimum flicker counter electrode potential Vf in (Equation 10) becomes large. To be

Now, (Clc (H) -Clc (L)) /
Pay attention to the amount of Clc (L). Δε for simplicity
Consider the case of> 0. If the applied voltage to the liquid crystal is 0, the liquid crystal molecules are all oriented in the direction parallel to the substrate surface, and the applied voltage to the liquid crystal is sufficiently large. Are all perpendicular to the substrate surface, Clc (L) = Clc⊥ = ε⊥ × as described in (Analysis of flicker occurrence phenomenon in the first configuration) above.
(Area of liquid crystal layer) / (thickness of liquid crystal layer), Clc (H) =
Clc // = ε // × (area of liquid crystal layer) / (thickness of liquid crystal layer) becomes (Clc (H) -Clc (L)) / Clc
(L) = (ε / −− ε⊥) / ε⊥ = Δε / ε⊥.
However, in practice, even if the applied voltage is 0, some liquid crystal molecules are oriented in a direction slightly deviated from the plane perpendicular to the substrate surface, or even if a large voltage is applied, the alignment of the liquid crystal near the interface is fixed. Since it may remain, (Clc
(H) -Clc (L)) / Clc (L) becomes a value smaller than Δε / ε⊥. Actually, the capacitance values Clc (H) and Clc (L) of liquid crystal materials having various values of Δε (including various modes such as TN mode, OCB mode, and VA mode) are measured, and then (Clc (H )
-Clc (L)) / Clc (L) value and | Δε | / ε⊥
FIG. 6 shows the relationship between the values of. according to this,
Although the value of (Clc (H) -Clc (L)) / Clc (L) is smaller than | Δε | / ε⊥, it is almost proportional to | Δε | / ε⊥, and the proportional constant is 0. 20 (for example, ε⊥ = 3.8, ε // = 11.5, that is, the measured Clc (H) and Clc (in the OCB liquid crystal material such that | Δε | /ε⊥=2.03). The ratio of L) is 1
It is about 0: 7, and [(Clc (H) -Clc (L))
/ Clc (L)] / [| Δε | / ε⊥] ≈ [(10-
7) / 7] /2.03=0.21).

Now, as described in the above (Specific Embodiment 1), Cst = 0.70 pF, C as a representative value.
gd = 0.12pF, Vgon = 12V, Vgoff =
Set to -8V. Then, the minimum flicker counter electrode potential Vf
A condition is obtained in which the range of change in value exceeds 0.15 V in FIG. Now, for simplicity, Clc (L) = 0.60p
If it is fixed to F, the condition is expressed by (Equation 27) based on (Equation 10).

[0158]

[Equation 27]

However, the unit of Clc (H) is represented by pF. Solving this, Clc (H) ≧ 0.738
We obtain the condition of pF. That is, (Clc (H) -C
If expressed by lc (L)) / Clc (L), (Clc (H))
-Clc (L)) / Clc (L) ≥ (0.738-0.
60) /0.60=0.23. (Clc (H) -Clc (L)) / Clc (L) and | Δ as shown in FIG.
Using the proportional relationship of ε | / ε⊥ and rewriting the conditions for | Δε | / ε⊥, | Δε | /ε⊥≧0.23/0.2
0 = 1.15.

By the way, the flicker reduction effect by driving as described in (Principle 1 of the present invention) can be obtained regardless of the value of | Δε | / ε⊥. But especially | Δ
For liquid crystals with ε | / ε⊥ larger than 1.15,
In the conventional driving method such as No. 9, flicker occurs beyond the allowable limit, but the effect of the present invention is particularly advantageous in that the flicker can be eliminated by adopting the drive of (Principle 1 of the present invention). Can be said to be effective (| Δε |
Is large, there are also side effects such as faster response speed of the liquid crystal).

In FIG. 5, the permissible change width of the minimum flicker counter electrode potential Vf is set to 0.15 V. However, if this is loosened slightly to 0.20 V, the condition for generating flicker is (Clc (H)). -Clc (L)) / Clc (L) ≧
0.318, and | Δε | /ε⊥≧0.318/0.
20 = 1.59. Alternatively, if it is further loosened and the allowable change width of the minimum flicker counter electrode potential Vf is set to 0.25 V, (Clc (H) -Clc (L)) / Clc (L) ≧
0.411, and | Δε | /ε⊥≧0.411/0.
20 = 2.05. That is, | Δε | / ε⊥ ≧
In the case of 1.15, the effect of the present invention is remarkably obtained, and especially |
If Δε | /ε⊥≧1.59, the effect of the present invention can be obtained more remarkably, and if | Δε | /ε⊥≧2.05, the effect of the present invention can be obtained more remarkably. .

(Specific Embodiment 2) Next, the drive shown in (Principle 3 of the present invention), that is, the drive shown in FIG. 3 will be considered. As the parameters, the values shown in (Specific Embodiment 1) are used.

First, in the case of the conventional driving in which the reset period is not provided, the flicker minimum counter electrode potential Vf is calculated as follows.
According to (Equation 25), when Clc is equal to Clc (L) (when the absolute value of the voltage applied to the liquid crystal is a small gradation level)
Is Vf = 4.268V, and when Clc is equal to Clc (H) (at a gradation level where the absolute value of the voltage applied to the liquid crystal is sufficiently large), Vf = 4.047V. That is, the minimum flicker counter electrode potential Vf value has a difference of 0.221V. Therefore, the permissible range of Vf change does not fall within 0.15 V, and flicker cannot be eliminated for all gradations. On the other hand, when the reset period is provided as in the present invention, the minimum flicker counter electrode potential Vf is (Equation 23).
Thus, Vf = 4.047V is calculated for all gradations. Therefore, this value is the minimum flicker state Vf in FIG.
Flicker can be eliminated by adjusting so as to match m.

In the case of this configuration, the capacitive coupling voltage is given only in the case of the positive polarity, and therefore the effect of increasing the amplitude of the video signal is about half that of the specific embodiment 1. However, if the video signal voltage amplitude related to the reset voltage is set to be slightly larger than that in (Specific Embodiment 1), it is possible to apply a voltage of sufficient amplitude to the liquid crystal during the reset period.

The drive shown in FIG. 4 can be considered in exactly the same way.

(Analysis of Flicker Generation Phenomenon in Second Configuration) Next, the cause of flicker produced in the configuration of FIG. 20 having the pixel structure of FIG. 21 was analyzed. Basically, it is the same as in the case of the first configuration, and it is also due to the dielectric anisotropy. Hereinafter, description will be made based on the case of (analysis of flicker occurrence phenomenon in the first configuration).

First, let us consider the condition where the flicker becomes minimum when a uniform still image is displayed by performing the driving shown in FIG. 22 with the pixel structure shown in FIG. The concept is exactly the same as that described in the case of performing the driving of FIG. 18 with the pixel structure of FIG. 17 in (Analysis of flicker occurrence phenomenon in the first configuration), and may be based on the law of conservation of charge.

When the driving shown in FIG. 22 is performed with the pixel structure shown in FIG. 21, the formula for storing charges is given by (Equation 28).

[0169]

[Equation 28]

This is the same as Vc in the equation (equation 3) of charge storage when the driving of FIG. 18 is performed in the pixel structure of FIG.
(+) → Vge (+), Vc (−) → Vge (−), V
It is nothing but a replacement of coff → Vgoff.
Therefore, the minimum flicker counter electrode potential Vf value is the same as the replacement in (Equation 6), (Equation 29).
Given in.

[0171]

[Equation 29]

Next, the same equation for storing electric charges is similarly written in the case of driving in FIG. 23, as shown in (Equation 30).

[0173]

[Equation 30]

This is organized as shown in (Equation 31).

[0175]

[Equation 31]

Therefore, by combining (Equation 1) and (Equation 2), (Equation 32) is obtained as the voltage value of the minimum flicker counter electrode potential Vf.

[0177]

[Equation 32]

Here, in (Principle 3 of the present invention), (Equation 25)
For the same reason as described above, it is unlikely that the value of [] on the rightmost side of (Equation 32) becomes zero. Therefore,
The flicker minimum counter electrode potential Vf is the liquid crystal capacitance C of (Equation 5).
Since it depends on the video signal amplitude Vsp via lc, even if the counter electrode potential is optimally adjusted at a certain display gray level, it will be different from the problem described in (Problems to be solved by the invention). It can be understood that the display gradation level of causes the problem of flicker.
The same applies to the problem that the black level floats and the contrast does not appear.

On the other hand, in the equation (Equation 29) in the case of driving in FIG. 22, if the relation of (Equation 33) (corresponding to (Equation 12) in driving in FIG. 18) is satisfied, Vf = Vsc, and flicker occurs. The voltage value of the minimum counter electrode potential Vf does not depend on the liquid crystal capacitance Clc.

[0180]

[Expression 33]

Even if the condition of (Equation 33) is not strictly satisfied,
At least [(Vge (+) + Vge (-)) / 2-V
goff] is a negative value, the second and third terms on the right side of (Equation 29) have opposite signs, and thus the deviation of the minimum flicker counter electrode potential Vf is smaller than that in the driving of FIG. In fact
Also in FIG. 22, [(Vge (+) + Vge (−)) /
2-Vgoff] is negative.

Therefore, it can be understood that the flicker is not noticeable in the driving of FIG. 22, but the flicker is increased by the driving of FIG.

As described above at the end of (Analysis of flicker occurrence phenomenon in the first configuration),
It is considered to be a side effect of reducing the level of the scan electrode potential by one.

(Principle 5 of the Present Invention) After performing the above analysis, in the display device of FIG. 20 having the pixel structure of FIG. 21, there are two potentials other than the potential Vgon that makes the TFT conductive as the scan electrode potential level. We have found a means for eliminating flicker that occurs by using only the value and depending on the video signal voltage amplitude. That is the content of the present invention, in which the reset voltage is written before the video signal voltage is charged. The principle of the present invention will be described in detail below, although it may be a bit redundant with the description in (Principle 1 of the present invention).

FIG. 7 shows an example of the fifth drive voltage waveform of the present invention. The scanning signal pulses shown by [b] and [d] in the figure correspond to the timing when the video signal is written from the video signal drive circuit to the pixel electrode through the video signal electrode, and [a]
Similarly, the scanning signal pulse shown by [c] corresponds to the timing when the reset signal is written from the video signal drive circuit to the pixel electrode via the video signal electrode. It is assumed that the negative video signal voltage Vsig (-) is written in [b] and the positive video signal voltage Vsig (+) is written in [d]. Further, it is assumed that the positive reset voltage Vres (+) is written in [a] and the negative reset voltage Vres (−) is written in [c]. These reset voltages are for resetting the display written in [b] and [d], and are always at a constant level regardless of the video signal voltage. In addition,
The period from [a] to [b], or the period from [c] to [d] is the reset period, the period from [b] to [c], or the period from [d] to [a]. It is called a signal writing period.

The scanning signal drive waveform is V except Vgon.
goff1 and Vgoff2 (Vgoff1 <Vgo
ff2) only (that is, the scanning signal drive circuit outputs two different voltage values Vgoff1 and Vgoff2 in addition to the voltage for turning on the TFT). Then, after writing the positive video signal voltage or the reset voltage to the pixel electrode, the scan electrode potential Vg (n−1) of the preceding stage is Vgoff.
It remains at 1, and has a waveform such that Vg (n-1) changes from Vgoff2 to Vgoff1 after the negative video signal voltage or the reset voltage is written in the pixel electrode. Then, when the scan electrode potential changes, the change in the pixel electrode potential Vd due to the coupling voltage via the storage capacitor Cst becomes as shown in FIG. 7, and the pixel electrode holding potential with respect to both the video signal voltage and the reset voltage. The effect of increasing the amplitude of is obtained.

In FIG. 7, in addition to Vgon, Vgoff1 and Vgo are also included in the scanning electrode potential waveform Vg (n) at this stage.
Although there is a level of ff2, this is to similarly give the effect of increasing the amplitude of the pixel electrode holding potential to the pixel scanned next to the pixel of interest. FIG. 7 illustrates the case where the polarity of the next pixel is opposite to the pixel of interest (line inversion drive, dot inversion drive, etc.), but when the same polarity (frame inversion drive or column inversion drive) is used, The waveform will be slightly different. However, even in that case, the transition of the potential of the pixel electrode of interest does not essentially change (in FIG. 7, the scan electrode potential at this stage is V
The capacitive coupling voltage for the target pixel when changing from goff2 to Vgoff1 is omitted because it is small).

In the case of this driving method, the alignment state of the liquid crystal changes with time and the liquid crystal capacitance also changes. At the end of each video signal writing period for each positive and negative polarity and the reset period, the response of the liquid crystal is sufficiently stable, and as shown in FIG. 7, Clc (sig, +), C
lc (sig,-), and Clc (res, +), C
It is assumed that the capacitance value is lc (res, −). Also,
The pixel electrode potentials at that time are Vdo (sig,
+), Vdo (sig, −), and Vdo (res,
+) And Vdo (res,-). The counter electrode potential is Vf. Then, the equation for storing electric charges in the video signal writing period is as shown in (Equation 34).

[0189]

[Equation 34]

However, this formula assumes that the charge pulse width of the scan electrode is sufficiently shorter than the response time of the liquid crystal, the alignment state of the liquid crystal does not change during the charge period, and the end of the previous period (reset period). It is assumed that the charging is performed for the capacity in. By rearranging (Equation 34), (Equation 35) is obtained.

[0191]

[Equation 35]

However, this equation is rewritten by substituting (Equation 1) for giving a signal having the center value Vsc and the amplitude Vsp as the video signal voltage.

Here, although capacitances Clc (res, +) and Clc (res,-) appear on the right side of both equations (35), it is assumed that a sufficiently large voltage is applied to the liquid crystal during the reset period. Then, it can be regarded as a constant value for the reason described in (Principle 1 of the present invention). This is represented as Clc (H) according to FIG. Then, (Equation 35) can be rewritten as (Equation 36).

[0194]

[Equation 36]

Now, let us consider the condition where the flicker is minimized. This is because the alignment state of the liquid crystal in the even-odd frame (that is, in the positive and negative polarity video signal writing period) is the same as that described in (Analysis of flicker occurrence phenomenon in the first configuration) in FIG. 18 and FIG. In the same case, that is, when the absolute value of the voltage applied to the liquid crystal is the same, the capacitance of the liquid crystal also becomes the same value in the even and odd frames.

Now, assuming that the flicker is minimized at the counter electrode potential Vf, the equation (Equation 16) similar to the case of (Equation 2) is established with the absolute value of the liquid crystal applied voltage being Vdp. And the capacity of the liquid crystal becomes equal over even and odd frames,
Clc (sig, +) = Clc (sig,-) [= Cl
[C (sig)]], (Equation 37) is derived from (Equation 36) and (Equation 16).

[0197]

[Equation 37]

(Expression 38) is obtained by adding the two expressions of Expression (37) side by side and slightly modifying them, and (Expression 39) is obtained by subtraction.

[0199]

[Equation 38]

[0200]

[Formula 39]

Now, in (Equation 38), Clc (H) is contained as the capacitance of the liquid crystal.
It is a constant capacitance value irrelevant to sp. Therefore, the minimum flicker counter electrode potential Vf has a constant value regardless of the video signal amplitude. In other words, if the counter electrode potential is set to the voltage value given by (Equation 38), flicker does not occur at any gradation level.

When the equation (Equation 38) for the minimum flicker counter electrode potential Vf in the present invention is compared with the equation (Equation 32) for driving in FIG. 23, the equations are very similar. However, in (Equation 32), Cl that appears through (Equation 5)
Although c is the liquid crystal capacitance at the display gradation level at that time, Clc (H) in (Equation 38) is largely different in that it is the liquid crystal capacitance after reset is applied in the reset period. By providing the reset period immediately before the video signal writing period, flicker can be eliminated for the first time.

In the case of the method of the present invention, the counter electrode potential at which the black level sinks most (that is, the counter electrode potential at which the voltage applied to the liquid crystal is positive / negative symmetrical in black display) is also given by (Equation 3).
Since it is given in 8), the contrast reduction due to the floating of the black level is also improved.

In FIG. 7, the scan electrode potential Vg (n-1) of the preceding stage remains unchanged at Vgoff1 after writing the positive video signal voltage or the reset voltage to the pixel electrode, but Vgoff2 is different. It does not matter if it remains unchanged (if you formulate and formulate the charge conservation formula, it will be the same as (Equation 35) after all).

(Principle 6 of the Present Invention) FIG. 8 shows a sixth drive waveform for the display device of FIG. 20 having the pixel structure of FIG.
Shown in. This is almost the same as the drive waveform of FIG. 7 described in (Principle 5 of the present invention), but the polarity of the reset period before the video signal writing period is opposite to that in the case of FIG. 7. That is, in FIG. 7, the negative polarity video signal writing period precedes the positive polarity reset period, and the positive polarity video signal writing period precedes the negative polarity reset period.
In FIG. 8, the opposite is the case. A negative polarity reset period precedes the negative polarity video signal writing period, and a positive polarity reset period precedes the positive polarity video signal writing period.

The scan electrode potential waveform is V as in the case of FIG.
Vgoff1 and Vgoff2 (V
goff1 <Vgoff2) (that is, the scanning signal drive circuit has two different voltage values Vgo other than the voltage for turning on the TFT).
ff1 and Vgoff2 are output). Although the waveform shape itself is different from that of FIG. 7, Vg (n-1) remains Vgoff1 after writing the positive video signal voltage or the reset voltage to the pixel electrode, and thus the negative video signal voltage. Alternatively, after writing the reset voltage to the pixel electrode, Vg (n-1) is changed from Vgoff2 to Vgoff2.
The fact that the waveform changes to off1 is shown in FIG.
Is the same as in. Therefore, as in the case of FIG. 7, the effect of increasing the amplitude of the pixel electrode holding potential can be obtained for both the video signal voltage and the reset voltage.

In this case, the formula for charge storage during the video writing period is the one in which Clc (res, +) and Clc (res,-) are interchanged in (Equation 34),
As described in (Principle 1 of the present invention), if a sufficiently large voltage is applied to the liquid crystal during the reset period, Cl
c (res, +) = Clc (res,-) = Clc
Since it can be set to (H), exactly the same formula as (Formula 36) is obtained, and the minimum flicker counter electrode potential Vf is expressed by the same formula as (Formula 38). Therefore, the minimum flicker counter electrode potential Vf has a constant value regardless of the video signal amplitude, and if the counter electrode potential is set to a voltage value given by (Equation 38), flicker does not occur at any gradation level. I understand.

(Principle 7 of the Present Invention) FIG. 9 shows a seventh drive waveform for the display device of FIG. 20 having the pixel structure of FIG.
Shown in. This is also to write the reset voltage before charging the video signal voltage, but the method of applying the coupling voltage from the scan electrode in the previous stage is opposite to that in FIG. 7. That is, Vgoff1 and Vgoff2 (Vgoff1 <
Vgoff2), but the common electrode potential changes from Vgoff1 to Vgoff2 after writing a positive polarity video signal voltage or a reset voltage to the pixel electrode, and a negative polarity video signal. The waveform is such that the common electrode potential does not change after the voltage or reset voltage is written to the pixel electrode. In this case, the coupling voltage via the storage capacitor Cst is superimposed after writing the positive polarity video signal voltage or the reset voltage, but such a coupling voltage is superimposed after writing the negative polarity video signal voltage or the reset voltage. Not done. However, at least the effect of increasing the amplitude of the pixel electrode holding potential is obtained as in the case of FIG. 7.

The case of the main drive waveform can be considered in exactly the same manner as in FIG. 7, and the minimum flicker counter electrode potential Vf becomes a constant value regardless of the video signal amplitude, and the counter electrode potential is a voltage given by (Equation 40). The value indicates that flicker does not occur for any gradation level.

[0210]

[Formula 40]

Comparing (Formula 40) with the formula (Formula 38) in the case of FIG. 7, it can be seen that the sign of the third term on the right side (the term relating to Cst) is reversed. This is a natural consequence of the fact that the method of applying the capacitive coupling voltage is opposite to that in the case of FIG. In addition, the second term in (Equation 40) (term relating to Cgd)
The factor (Vgoff1 + Vgoff2) / 2 is included in the above, because the final value of the potential of the scanning electrode at this stage in the video signal readout period is different between positive and negative polarities (in the case of positive polarity, Vgoff1, In the case of negative polarity, since Vgoff2, the arithmetic mean (Vgoff1 + Vgoff2) / 2 of these is included in (Equation 40).

(Specific Embodiment 3) Actually, FIG.
In the display device having the structure of FIG. 20 having the pixel structure of
An example to which the present invention is applied will be described. In the pixel structure of FIG. 21, Cst = 0.70 pF, Cgd = 0.12 pF
Suppose Then, the capacitance Cl of the liquid crystal shown in FIG.
c (L) and Clc (H) are respectively Clc (L) =
0.60 pF and Clc (H) = 0.90 pF (these capacitances may be obtained by actual measurement or simulation).

Consider, for example, the case of performing the driving shown in FIG. 7 (Principle 5 of the present invention). Here, the driving condition is Vgon = 1
2V, Vgoff1 = -14V, Vgoff2 = -4
It is assumed that V and Vsc = 3V (Vsc is a video signal voltage amplitude). And one frame period is 16.67 msec
(Corresponding to a frame frequency of 60 Hz), and the width of the reset period is set to 1/10 thereof (that is, 1.667 msec).

First, when the conventional flicker minimum counter electrode potential Vf is calculated by (Equation 32) in the case where the conventional driving (driving in FIG. 23) without the reset period is performed, the liquid crystal capacitance Clc is equal to Clc (L). (When the absolute value of the voltage applied to the liquid crystal is a small gradation level), Vf = -1.6
62 V, Vc when Clc is equal to Clc (H) (when the absolute value of the voltage applied to the liquid crystal is a sufficiently large gradation level)
= -0.849V. That is, there is a difference of 0.813 V in the minimum flicker counter electrode potential Vf value.

This is an allowable range of 0.1 obtained from FIG.
The voltage exceeds 5V, and the flicker cannot be made lower than the allowable limit in all gradations.

On the other hand, when the reset period is provided as in the present invention, the minimum flicker counter electrode potential Vf value is calculated by (Equation 38) regardless of the gradation level, and becomes a constant value Vf = −0.849V. . This means that the width of the minimum flicker counter electrode potential Vf value is substantially 0V,
For example, the central value Vsc of the video signal voltage is appropriately adjusted to V
If f is made to coincide with the minimum flicker state (Vfm) in FIG. 5, it is possible to sufficiently reduce the flicker for any gradation level.

In order to obtain the above effect, it is desirable to apply a voltage of sufficient amplitude to the liquid crystal during the reset period, but in reality Vres (+) = 6V,
If Vres (−) = 0V (video signal voltage amplitude with respect to reset voltage = 3V), that condition was sufficiently achieved.

The parameters used in the above embodiments are only numerical values as representative examples, and the present invention is by no means limited to the above parameters.

The driving shown in (Principle 6 of the present invention) and (Principle 7 of the present invention), that is, the driving shown in FIGS. 8 and 9 can be considered in exactly the same manner.

(Supplemental Information) Incidentally, FIG. 2 shows the drive in FIG. 1 in which the polarities in the reset period are exchanged.
It is of course possible to switch the polarities in the reset period in the same manner for FIGS. 3 and 4. Even so,
The same effect can be obtained in FIG. 3 or FIG. Further, although the polarities in the reset period are exchanged for the drive of FIG. 7 in FIG. 8, the polarities of the reset period can be exchanged for the drive of FIG. 9 as well.
Even if it does so, the same effect can be obtained in FIG.

In the display device of FIG. 16, the storage capacitors may be connected to the common electrode Vc (n) of this stage for all pixels, but this is not always necessary. 5 and 13 of Japanese Patent Application No. 12-181101, for example.
As described above, every other column may be connected to different common electrodes. By doing so, the present invention can be applied not only to frame inversion and line inversion but also to column inversion and dot inversion drive. The same applies to the display device of FIG. 20, and the storage capacitors of all the pixels may be connected to the scan electrode Vg (n−1) of the preceding stage, but this is not necessarily the case. For example, Japanese Patent Application No. 1
The scan electrodes may be connected to different scan electrodes every other column as in FIGS. By doing so, the present invention can be applied not only to frame inversion and line inversion but also to column inversion and dot inversion drive.

Further, in the display device of FIG. 20, it goes without saying that the storage capacitors may be connected to the scanning electrodes in the subsequent stage for all the pixels.

In all of the above examples, n-channel TFTs (on-state with positive gate voltage and off-state with negative gate voltage) are assumed, but of course p-channel type TFTs (negative It goes without saying that the present invention can be applied even in the case where the ON state is brought about by the gate voltage and the OFF state is brought about by the positive gate voltage.

The TFT may be amorphous Si or polycrystalline Si, or may be a MOSFET (metal-oxide film-semiconductor type field effect transistor) using crystalline Si. . Alternatively, it may be a MOSFET using an SOI (silicon-on-insulator) type semiconductor, or may be a TFT made of Ge, an organic material, or the like, not limited to Si, as a matter of course.

The liquid crystal has a normally white type (in which the absolute value of the applied voltage increases and the output light brightness decreases) and a normally black type (in which the absolute value of the applied voltage increases and the output light brightness increases. Any of). By the way, TN liquid crystals and OCB liquid crystals belong to the former, and IPS liquid crystals belong to the latter.

In the above examples, the absolute value of the voltage applied to the liquid crystal in the reset period is set to the region where the liquid crystal capacitance reaches a sufficiently saturated state in FIG. However, in the region before the steep rise near the applied voltage 0 (the region where the liquid crystal capacitance is approximately Clc (L)), the change in the capacitance value with respect to the change in the absolute value of the liquid crystal applied voltage is small, and the display is reset using this region. It is also possible to do so.

However, in the case of normally white type liquid crystal, if the region of Clc (L) is used at the time of resetting, white display will be performed there and the contrast will be lowered. Therefore, it is preferable to use the region where the liquid crystal capacitance is Clc (H). For that purpose, it is desirable that the voltage amplitude of the signal for resetting the display be equal to or larger than the maximum value of the amplitude of the video signal for displaying. On the other hand, in the case of the normally black type, it is preferable to use the region of Clc (L) for the same reason. For that purpose, it is desirable to make the voltage amplitude of the signal for resetting the display equal to or more than the minimum value of the amplitude of the video signal for displaying (of course, for example, by using a stroboscopic light emission type backlight, the light source is As long as it does not emit light, there is no reduction in contrast, and there is no limitation mentioned above).

Although various kinds of display media can be considered, liquid crystal is the cheapest and it is preferable to use this. Among them, many liquid crystals in a nematic phase have an applied voltage-capacitance characteristic as shown in FIG. 29 and are particularly suitable for the present invention (for example, a liquid crystal that is not a nematic phase like a ferroelectric liquid crystal or an antiferroelectric liquid crystal). Does not necessarily have the characteristics shown in FIG. 29). Among them, it is desirable to use various liquid crystals (modes) as described in (Analysis of flicker occurrence phenomenon in the first configuration).

Among them, the OCB liquid crystal is particularly suitable for use in the structure of the present invention because it has a relatively fast response speed and sufficiently responds even if the reset period is short (to obtain the reset effect. It is desirable that the liquid crystal response be fully completed within the reset period). Further, since OCB liquid crystal is generally used in a state in which a sufficiently large voltage is applied and the splay alignment state is changed to the bend alignment state, black display is intermittently performed in order to prevent the reverse transition from the bend state to the splay alignment state. However, the reset period in the present invention can also serve as such reverse transition prevention, which is highly desirable.

Of course, the display medium does not necessarily have to be liquid crystal. For example, an electro-optic crystal such as BSO (bismuth silicon oxide) may be used. Further, it may be an electrochromic material, a self-luminous diode, a laser, an electroluminescent material, or the like. Alternatively, DMD (Deformable Mi)
error device) or the like. In these cases, the present invention can be applied when the capacitance can be changed by the applied voltage as shown in FIG. 29 regardless of the degree.

By providing the reset period as in the present invention, it is possible to obtain a secondary effect such that blurring of a moving image can be reduced.

The effect of eliminating the flicker depending on the gradation by providing the reset period as described above is (to obtain the effect of increasing the amplitude of the video signal and further reduce the cost). ) In the configuration of FIG. 16, there are two types of common electrode potential levels,
It is emphasized that this is obtained only when the potential level of the scanning electrode is set to two types except the voltage for turning on the TFT in the configuration of 0.
In other words, the effect of increasing the amplitude of the video signal (the effect of lowering the voltage of the video signal drive circuit and reducing the cost of the video signal drive circuit) and the reduction of the number of potential levels can be achieved only by the configuration of the present invention. That is, further cost reduction) and flicker reduction can be realized at the same time.

(Analysis of Color Reproducibility Degradation and Color Misregistration in Third Configuration) Next, the cause of the color reproducibility degradation and color misregistration occurring in the third configuration was analyzed. As a result, it became clear that these are also caused by the dielectric anisotropy of the display medium, that is, the liquid crystal. This will be described below.

FIG. 30 shows the relationship between the capacitance and transmittance of the liquid crystal and the absolute value of the applied voltage. In addition, FIG. 31 shows a third configuration, that is, a change in pixel electrode potential in each sub-frame and a response of liquid crystal capacitance and transmittance in the field sequential driving. Note that FIG. 30 shows the case where the transmittance decreases with the applied voltage, that is, the case of a normally white type.

Now, considering the case where there are subframes in the order of red, green, and blue as shown in FIG. 31, a bright state (white) is displayed in the red subframe and a dark state (black) is displayed in the green subframe. Then, consider the behavior before and after the green sub-frame charging (the portion of the scan electrode potential pulse shown by [A] in the figure).
First, according to FIG. 30, the absolute value of the voltage applied to the liquid crystal is a small value, and the liquid crystal capacitance at that time is almost Clc (L), because it is in a bright state in the red sub-frame holding period. Next, at the time of charging the green sub-frame, if the charging pulse width is sufficiently shorter than the response time of the liquid crystal, the liquid crystal is charged assuming that the capacitance is Clc (L). Then, during the green subframe period after charging, the liquid crystal responds toward the dark state, at which time the capacitance of the liquid crystal becomes Cl.
It changes toward c (H). At this time, the amount of charge accumulated in the pixel electrode is saved, so that the voltage applied to the liquid crystal is slightly reduced in inverse proportion to the increase in capacitance. Therefore, according to FIG. 30, the dark state is slightly floated, and the light output of the green subframe is slightly generated. Therefore, although originally only the red light output in the red sub-frame is desired, the green light output is mixed. The above is the reason why the color purity is lowered and the color reproducibility is deteriorated.

The cause of the color shift can be similarly explained. Now, in FIG. 32, (a) a case where a dark state is displayed in the red sub-frame and an intermediate state is displayed in the green sub-frame,
(B) Changes in pixel electrode potential and changes in liquid crystal capacitance and transmittance when displaying a bright state in the red subframe and an intermediate state in the green subframe are shown. In FIG. 32, pay attention to the charging shown in [A]. In the case of (a), the liquid crystal capacitance is charged as Clc (H), and in the case of (b), it is charged as Clc (L). Therefore, even when both are charged with the same video signal voltage, The amount of charge accumulated in the pixel electrode is different. Then, in the holding period of the green sub-frame, in the case of (a), the capacitance goes from Clc (H) to an intermediate value in accordance with the response of the liquid crystal, and in the case of (b), the capacity is changed from Clc (L) to the intermediate value. The pixel electrode potential increases in the former case and decreases in the latter case because it changes toward the value of. Therefore, the pixel electrode potential becomes different according to the preceding sub-frame, and the liquid crystal transmittance also becomes different according to FIG. This indicates that color shift occurs.

(Principle 8 of the Present Invention) After performing the above analysis, a means for eliminating the deterioration of color purity and color shift in the display device of FIG. 16 having the pixel structure of FIG. 17 was found. That is the content of the present invention, in which the video signal voltage output from the video signal drive circuit to the video signal electrode in a certain subframe is corrected according to the capacitance of the liquid crystal in the preceding subframe. is there. The principle will be described below.

FIG. 10 shows the potential waveform of each part in the case where the display device of FIG. 16 superimposes the coupling voltage from the common electrode via the storage capacitor. Here, each subframe has a positive polarity, and after charging the pixel electrode, the potential of the common electrode is changed from Vca to Vcb to give a positive coupling voltage to the pixel electrode (Vca < Vcb).
The potential of the scanning electrode when the TFT is turned on is V
gon, the scanning electrode potential when the non-conduction state is set to Vgo
It is as ff. The counter electrode potential is Vf.

Now, it is assumed that the capacitance of the liquid crystal before charging [A] (the end of the red sub-frame) is Clc ′, and that the potential Vsig is charged from the video signal electrode during charging [A]. Then, the pixel electrode holding potential in the green subframe becomes Vdo = Vf + Vlc (Vlc is a voltage applied to the liquid crystal), and the liquid crystal capacitance at that time is Clc.
Let's say. At this time, the following equation of charge conservation holds.

[0240]

[Formula 41]

This can be rearranged into (Equation 42).

[0242]

[Equation 42]

However, ΔQcc is (Equation 43), and Cto
t and Ctot 'are given by (Equation 44).

[0244]

[Equation 43]

[0245]

[Equation 44]

In these equations, Ctot is the sum of the capacitances electrically connected to the pixel electrodes when the target subframe is held, and is the value determined by the absolute value of the liquid crystal applied voltage, that is, | Vlc |. . Also, Ct
ot 'is a value in the preceding subframe. Also,
ΔVg and ΔVc correspond to the potential changes of the scanning electrode and the common electrode at this stage after writing the video signal voltage, respectively.

Now, what kind of video signal voltage should be applied to the video signal electrodes when it is desired to display a certain gradation will be considered. Now, the liquid crystal applied voltage required to obtain a desired gradation is Vlc, and the liquid crystal capacitance at that time is Clc.
And | Vlc | is a value obtained by back-calculating the absolute value of the voltage applied to the liquid crystal from the transmittance corresponding to the desired gradation in the lower graph of FIG. 30, and Clc is | Vlc | in the graph above it.
It can be considered as the capacity corresponding to. The video signal voltage to be applied at that time is Vsi that satisfies (Equation 42).
It is nothing but g, that is, (Equation 42) is solved for Vsig. That is, it is given by (Equation 45).

[0248]

[Equation 45]

Each symbol in this equation is Morochin (Equation 43),
And (Equation 44). Since the liquid crystal capacitance Clc 'is included in this equation, it is corrected according to the liquid crystal capacitance in the previous frame.

Although the case of positive polarity has been considered above,
The same can be considered for the negative polarity. Figure 1
FIG. 1 shows a diagram of potential change of each part in the case of negative polarity. Here, each subframe has a negative polarity, and after charging the pixel electrode, the potential of the common electrode is changed from Vcc to Vcd to give a negative coupling voltage to the pixel electrode (Vcc> Vcd). Also in this case, the video signal voltage to be applied is given by (Equation 46) in consideration of the equation for charge storage as in the case of the positive polarity.

[0251]

[Equation 46]

However, ΔQcc, Ctot and Cto
t'is given by (Equation 47) and (Equation 48).

[0253]

[Equation 47]

[0254]

[Equation 48]

Comparing these expressions with the case of positive polarity,
Except that the expression of ΔVc is different, it is exactly the same as the case of positive polarity. Further, although ΔVc is also different in expression, it is still the potential change of the common electrode after writing the video signal voltage.

From the above, in order to prevent color shift and increase color purity, [CtotVlc-ΔQcc] with reference to the potential of the counter electrode regardless of whether the polarity is positive or negative.
It was shown that a value of / Ctot 'should be given to the image electrode (however, in general, the value of ΔQcc differs depending on the positive and negative polarities).

By the way, Vsig of (Equation 45) or (Equation 46)
However, it is rewritten as (Equation 49).

[0258]

[Equation 49]

In this equation, the liquid crystal capacitance Clc 'in the previous subframe depends on the denominator, and | Cto
Since tVlc-ΔQcc | is positive, the value of | Vsig-Vf | may be made smaller as Clc 'is larger in order to obtain a constant gradation in the target subframe. By the way, as described above in (Analysis of flicker occurrence phenomenon in the first configuration), the capacitance of the liquid crystal increases as the absolute value of the liquid crystal applied voltage increases. Therefore, as the absolute value of the voltage applied to the liquid crystal increases, | Vsig
It suffices to make a correction such that −Vf | becomes smaller.

Note that it is most desirable to perform correction according to (Equation 46) or (Equation 45) regardless of the value of the liquid crystal capacitance in the previous sub-frame. However, even if this is not always the case, for example, considering the case where the absolute value of the liquid crystal applied voltage in the previous sub-frame is the maximum and the case where the absolute value is the minimum, the former has | Vsig−Vf | If the correction is made smaller, at least some degree of color misregistration reduction and color purity improvement effects can be obtained.

Now, regarding the method of applying the coupling voltage from the common electrode potential, for example, in the case of the conventional driving as shown in FIG. 18, Vca = Vc (−), Vcb = Vco.
It may be considered that ff, Vcc = Vc (+), and Vcd = Vcoff. Similarly, in the case of driving as shown in FIG. 19 in the conventional technique, Vca = Vc1, Vcb = Vc2,
It can be considered that Vcc = Vc2 and Vcd = Vc1. Besides, for example, as in the case of FIG. 3 or FIG. 4, the same idea can be applied to the drive in which the capacitive coupling voltage is superposed only with one of the positive and negative polarities. In either case, ΔVc remains the potential change of the common electrode after writing the video signal voltage.

Now, let us consider a case where the common electrode potential is always constant and no capacitive coupling voltage is applied from the common electrode as shown in FIG. In this case, Vca = Vcb
= Vcc = Vcd, that is, ΔVc = 0 in both positive and negative polarities, formally applying (Equation 45) and (Equation 46) to correct the video signal voltage to cause color shift or color It is possible to prevent a decrease in purity.
However, when the correction is performed by (Equation 45) and (Equation 46) in the drive in which the capacitive coupling voltage is applied from the common electrode as in the present invention, a further effect is obtained. This will be explained below.

Now, in (Equation 45) or (Equation 46), what is the correction range, that is, a certain gradation level (the liquid crystal applied voltage is Vlc, and the capacitance at that time is Clc)? When trying to display, when the liquid crystal capacity is the smallest in the previous sub-frame (Clc
Calculate how much the value of Vsig differs between (L)) and (Clc (H)). If the absolute value of this difference is ΔVsig, ΔVsig is given by (Equation 50).

[0264]

[Equation 50]

However, Ctot (L) and Ctot
(H) is given by (Equation 51).

[0266]

[Equation 51]

Therefore, if the maximum value and the minimum value of the liquid crystal capacitance are the same, ΔVsig is | CtotVlc-ΔQcc |
Will be proportional to.

As described above, since the gate-drain capacitance Cgd is sufficiently smaller than the storage capacitance Cst, the Cgd term is neglected in the expression of ΔQcc in (Equation 43) or (Equation 47). And approximately ΔQcc = Cst
You can think of it as ΔVc. Then, in the case of driving without capacitive coupling, ΔQcc becomes almost 0, and the part of the absolute value symbol on the right side of (Equation 50) can be regarded as | CtotVlc |. On the other hand, in the case of driving which gives capacitive coupling as in the present invention, in general, when Vlc is positive (at the time of positive polarity)
ΔQcc is positive, and when Vlc is negative (negative polarity), ΔQcc is negative. Therefore, in the part of the absolute value symbol on the right side of (Equation 50), CtotVlc and ΔQcc cancel each other out, and have a smaller value than in the case where no capacitive coupling voltage is applied. That is, when capacitive coupling is applied as in the present invention, ΔVsig can be made smaller than when capacitive coupling is not applied, and therefore, a circuit for correcting a video signal can have a simpler configuration. The cost can be reduced. For example, when the correction processing of the video signal is performed by digital signal processing, | CtotVlc-Δ
If the value of Qcc | can be reduced to half of | CtotVlc |, the range of correction can be halved, and the number of bits for signal processing can be reduced by one.
Processing can be performed at high speed, and the circuit scale can be small.

(Principle 9 of the Present Invention) In the above (Principle 8 of the present invention), the display device of FIG. 16 having the pixel structure of FIG. 17 was used. The video signal voltage output from the signal drive circuit to the video signal electrode is corrected according to the capacitance of the liquid crystal in the previous sub-frame) in the display device of FIG. 20 having the pixel structure of FIG. It can also be applied to.

FIG. 12 shows the potential waveform of each part in the case where the coupling voltage via the storage capacitor is superposed from the scan electrode of the previous stage in the display device of FIG. Although each sub-frame has a positive polarity here, the potential of the preceding scan electrode is changed from Vgoffa to Vgoffb after charging the pixel electrode potential.
To a positive coupling voltage (Vgoffa <Vgoffb). In this case, if the scan electrode in the previous stage is considered in the same manner as the common electrode in (Principle 9 of the present invention), the signal voltage Vsig to be applied is (Equation 4)
In the exact same formula as 5), Vca → Vgoffa, V
It is nothing but a replacement of cb → Vgoffb. That is, it is given by (Equation 52).

[0271]

[Equation 52]

In the case of a negative polarity, for example, when the potential of the preceding scan electrode changes from Vgoffc to Vgoffd after charging the pixel electrode (FIG. 13, Vgoffc>
Vgoffd) is the same, and the signal Vsig to be given to the pixel electrode is given by (Equation 53).

[0273]

[Equation 53]

In (Equation 52) and (Equation 53), Δ
It can be said that Vgp is a potential change of the scan electrodes other than the current stage connected via the storage capacitor.

As described above, similar to (Principle 8 of the present invention), the value of [CtotVlc-ΔQcc] / Ctot 'with the potential of the counter electrode as a reference (however, in general, the value of ΔQcc is (Different in positive and negative polarity)
It was shown that the color deviation can be prevented and the color purity can be increased by applying the above to the image electrode.

It should be noted that the correction may be made so that | Vsig-Vf | becomes smaller as the absolute value of the voltage applied to the liquid crystal becomes larger, which is exactly the same as (Principle 8 of the present invention).

As a representative point, consider the case where the absolute value of the liquid crystal applied voltage in the previous sub-frame is the maximum and the case where the absolute value is the minimum.
If the former is corrected so that | Vsig−Vf | is smaller than the latter, at least some degree of color misregistration reduction and color purity improvement effects can be obtained (principle 8 of the present invention). It is the same.

In equations (52) and (53), the value of Vgoff appears in the equation of ΔVg, which is the value when the potential of the scanning electrode at this stage is held (thus ΔVg is the video signal voltage). It means that the potential change of the scanning electrode at this stage after writing. Vgoffa, V
While goffb, Vgoffc, and Vgoffd are values relating to the scan electrodes in the preceding stage of the pixel of interest, Voff
goff is a value related to the scanning electrode at this stage.

For example, in the case of the conventional driving of FIG. 22, Vgoffa = Vge (-), Vgoffb = Vg
off, Vgoffc = Vge (+), Vgoffd =
Vgoff, and the above Vgoff is also Vgoff in FIG. Further, for example, in the case of the driving of FIG. 23 of the conventional technique or the driving of FIG. 7 or 8 of the present invention, Vgoffa = Vgoff1 and Vgoffb = V
goff1, Vgoffc = Vgoff2, Vgoff
d = Vgoff1 and Vgoff = Vgoff1. The same can be considered for the drive shown in FIG. 9 of the present invention.

By the way, as shown in FIG. 26, Vgoffa = Vgoffb = Vgoff formally even in the case of driving in which the coupling voltage is not applied from the scan electrodes of the other stages.
Given that c = Vgoffd = Vgoff, it is possible to apply the principles of the present invention. However, in the case of the capacitive coupling type drive as described in the present invention, the circuit for correcting the video signal has a simpler structure for the same reason as described in (Principle 8 of the present invention). It is possible,
The effect is that the cost can be reduced.

(Principle 10 of the Present Invention) (Principle 1 of the Present Invention), (Principle 2 of the Present Invention), (Principle 3 of the Present Invention), (Principle 4 of the Present Invention), (Principle 5 of the Present Invention) ), (Principle 6 of the present invention), or (Principle 7 of the present invention) and the like, the voltage for resetting the display before writing the video signal voltage to the pixel electrode in each subframe. It is also possible to correct the color misregistration and suppress the deterioration of the color purity also by writing. FIG. 14 shows an example of such a driving method. The scanning signal pulse [B] for writing the reset signal is provided before the scanning signal pulse [A] for writing the video signal. In this way, the charge conservation equation becomes Clc 'instead of Clc' in (Equation 41).
(H) is given, and Vsig may be given as in the following (Equation 54), and correction according to the signal in the previous subframe is certainly unnecessary.

[0282]

[Equation 54]

Therefore, it is possible to prevent color misregistration and color purity deterioration without providing an extra correction circuit.

Note that such an effect (that color misregistration and color purity reduction can be prevented without providing an extra correction circuit) is effective for driving in which no coupling voltage is applied from the common electrode or the scanning electrodes of other stages. You can get it.

By the way, it is considered that the color shift and the decrease in color purity in the driving of the conventional technique as shown in FIGS. 31 and 32 become particularly remarkable when the dielectric anisotropy of the display medium (liquid crystal) is large.

Now, various dielectric anisotropies Δε are actually used.
A display device was manufactured using a liquid crystal material having the above, and was driven by a driving method (FIG. 32) in the related art to display a moving image. Then, a large number of observers were made to observe the image, and a subjective evaluation was made as to whether or not the observer feels the color shift of the image at that time. The display device used has the pixel structure shown in FIG. 17, and Cst = 0.70.
pF and Cgd = 0.12 pF. The driving conditions were Vgon = 12V and Vgoff = -8V. FIG. 15 shows an experimental result of the relationship between the value of | Δε | / ε⊥ of the liquid crystal material and the ratio of the number of people who perceive color shift among a large number of observers at this time. According to this, | Δε | / ε⊥
When the value of exceeds 1.2, more than half of the people feel color shift,
It can be seen that when it exceeds 1.8, three or more out of four feel color shift. A certain parameter (in this case, | Δε |
/ Ε⊥) is called the detection limit, which is a limit condition that half of the observers feel color shift when changing. In this case, the detection limit of color shift is | Δε | / ε⊥ = 1 .2.

For reference, FIG. 15 also shows a similar evaluation result in the case of driving for writing a signal for resetting the display before writing the video signal voltage to the pixel electrode in each sub-frame as in the present invention. . In this case, there were almost no people who felt the color shift.

The color misregistration improving effect by adopting the driving method of the present invention can be obtained regardless of the value of | Δε | / ε⊥. However, especially | Δε | / ε⊥ is 1.2
In the case of a larger liquid crystal, the color shift is recognized by more than half of the people by the conventional driving method, but by adopting the driving method of the present invention, it is possible to eliminate the proportion of people who eliminate the color shift. In that sense, the effect of the present invention can be more effectively realized (when | Δε | is large,
There are also side effects such as faster response speed of the liquid crystal). Further, particularly when | Δε | / ε⊥ is larger than 1.8, the effect of the present invention is more effectively realized in the sense that the proportion of people who feel color misregistration can be reduced from 75% to almost 0%. .

(Supplemental Information) Although the polarities of the subframes in one frame are the same in FIGS. 10, 11, 12, 13 and the like, they need not be the same. For example, when there are red, green, and blue subframes, the driving may be such that red and blue have the same polarity and only green has the opposite polarity.

It is desirable that the light source has three colors of red, green and blue, but it is not always necessary to use these three colors. For example,
It may be three colors of yellow, magenta and cyan. However, three colors of red, green, and blue are usually used to perform natural color display. Also, it does not necessarily have to be three colors, and two colors (for example, red and green) or four or more colors (for example, red,
The configurations of the invention apply exactly the same for the cases of green, blue and white). In any case, any light source may be used as long as the light sources have different spectral spectra.

Needless to say, some of the plurality of light sources may have the same spectrum. For example, the effect of the present invention can be obtained even if there are six light sources, that is, two red light sources, two green light sources, and two blue light sources.

Each color may have a wavelength close to a single wavelength like laser light, or may have a wide wavelength range such as a color filter inserted in a white light source. A light source that can be turned on / off at high speed is desirable, and in that sense, a light emitting diode or an electroluminescence (EL) light source is suitable. The electroluminescent light source includes an inorganic EL light source and an organic EL light source. Of course, laser light may be used.

The light source may be a light source / non-light emitting switching device itself like the above-mentioned light sources. For example, a light source that is always lit may be an optical shutter or a rotary color filter. (A circular filter is divided into three fan-shaped parts, each of which is provided with a red-blue-green filter and is used while being rotated in synchronization with a frame.
Japanese Patent No. 163985 discloses an example of a projection type display device using a rotary filter. Of course, it does not matter if a light source is turned on / off in a pseudo manner by inserting () or the like. In this case, a combination of the light source and the optical shutter or the rotary color filter may be regarded as a blinking light source. The former is preferable from the viewpoint of light utilization efficiency (or power consumption).

When operating with the three colors of red, green and blue,
It is not always necessary to configure the subframes in the order of red, green and blue. For example, red-blue-green, green-blue-red, etc. may be used in any order. Alternatively, it is of course possible to provide a plurality of subframes for one color such as red green blue green.

In all of the above examples, n-channel TFTs (on-state with positive gate voltage and on-state with negative gate voltage) are assumed, but of course p-channel TFTs (negative It goes without saying that the present invention can be applied even in the case where the ON state is brought about by the gate voltage and the OFF state is brought about by the positive gate voltage.

The TFT may be amorphous Si or polycrystalline Si, or may be a MOSFET (metal-oxide film-semiconductor type field effect transistor) using crystalline Si. . Alternatively, it may be a MOSFET using an SOI (silicon-on-insulator) type semiconductor, or may be a TFT made of Ge, an organic material, or the like, not limited to Si, as a matter of course.

The liquid crystal is normally white type (one in which the absolute value of the applied voltage increases and the output light brightness decreases), and one in the normally black type (the absolute value of the applied voltage increases and the output light brightness increases. Any of). By the way, TN liquid crystals and OCB liquid crystals belong to the former, and IPS liquid crystals belong to the latter.

Various display media can be considered, but liquid crystal is the cheapest and it is preferable to use this. Among them, many liquid crystals in a nematic phase have an applied voltage-capacitance characteristic as shown in FIG. 29 and are particularly suitable for the present invention (for example, a liquid crystal that is not a nematic phase like a ferroelectric liquid crystal or an antiferroelectric liquid crystal). Does not necessarily have the characteristics shown in FIG. 29). Among them, it is desirable to use various liquid crystals (modes) as described in (Analysis of flicker occurrence phenomenon in the first configuration).

Among them, OCB liquid crystal is particularly suitable for use in the structure of the present invention because it has a relatively high response speed (for example, a field sequential driving method in which one frame is composed of three subframes). In that case, it is desirable to have a response speed three times higher than that of the color filter method).

Since OCB liquid crystals are generally used in a state in which a sufficiently large voltage is applied to cause a transition from the splay alignment state to the bend alignment state, the OCB liquid crystal is intermittently prevented in order to prevent the reverse transition from the bend state to the splay alignment state. A voltage for black display may be applied, but in particular (the principle 1 of the present invention 1
When 0) is adopted, the reset period can also serve as such reverse transition prevention, which is very desirable.

Of course, the display medium does not necessarily have to be liquid crystal. For example, an electro-optic crystal such as BSO (bismuth silicon oxide) may be used. Further, it may be an electrochromic material, a self-luminous diode, a laser, an electroluminescent material, or the like. Alternatively, DMD (Deformable Mi)
error device) or the like. In these cases, the present invention can be applied when the capacitance can be changed by the applied voltage as shown in FIG. 29 regardless of the degree.

The display device or the driving method thereof according to the present invention is applicable to personal computer monitors, televisions, portable terminals,
It can be used for various things such as mobile phone screens, micro displays, head mounted displays and projectors.

[0303]

As described above, according to the display device and the driving method thereof of the present invention, firstly, in a display device mainly using a liquid crystal, the video signal drive circuit is lowered in voltage and the voltage level is kept low. By reducing the cost, the cost can be reduced, and flicker that occurs as a side effect can be eliminated. Secondly, in a field-sequential display device using liquid crystal, it is possible to improve color misregistration and decrease in color purity.

Further, according to the present invention, the power consumption can be reduced by lowering the voltage of the video signal drive circuit.
It will also be friendly to the global environment and space environment.

As described above, the industrial value of the present invention is extremely large.

[Brief description of drawings]

FIG. 1 is a drive voltage waveform diagram of a display device of the present invention having a common electrode potential.

FIG. 2 is a second display device of the present invention having a common electrode potential.
Drive voltage waveform diagram

FIG. 3 is a third display device of the present invention having a common electrode potential.
Drive voltage waveform diagram

FIG. 4 is a fourth display device of the present invention having a common electrode potential.
Drive voltage waveform diagram

FIG. 5 is a diagram showing a relationship between a counter electrode potential and a flicker level.

FIG. 6 is a diagram showing a relationship between liquid crystal capacitance and dielectric anisotropy.

FIG. 7 is a fifth drive voltage waveform diagram of a display device of the present invention of a type in which a storage capacitor is connected to a scan electrode in a preceding stage.

FIG. 8 is a sixth drive voltage waveform diagram of the display device of the present invention of the type in which the storage capacitor is connected to the scan electrode in the preceding stage.

FIG. 9 is a seventh drive voltage waveform chart of the display device of the present invention of the type in which the storage capacitor is connected to the scan electrode in the preceding stage.

FIG. 10 is a waveform diagram for explaining an eighth driving method of the field-sequential display device of the present invention.

FIG. 11 is a waveform diagram for explaining a ninth driving method of the field-sequential display device of the present invention.

FIG. 12 is a waveform diagram for explaining a tenth driving method of the field-sequential display device of the present invention.

FIG. 13 is a waveform diagram for explaining an eleventh driving method of the field-sequential display device of the present invention.

FIG. 14 is a waveform diagram for explaining a twelfth driving method of the field-sequential display device of the present invention.

FIG. 15 is a diagram showing the results of evaluating the relationship between the dielectric anisotropy of liquid crystal and the degree of color shift.

FIG. 16 is a configuration diagram of a display device having a common electrode potential.

17 is an equivalent circuit diagram of one pixel of the display device of FIG.

FIG. 18 is a drive waveform diagram of the display device of FIG. 16 in the related art.

FIG. 19 is another drive waveform diagram of the conventional display device of FIG.

FIG. 20 is a configuration diagram of a display device of a type in which a storage capacitor is connected to a preceding scan electrode.

21 is an equivalent circuit diagram of one pixel of the display device of FIG.

22 is a drive waveform diagram of the display device of FIG. 20 in the related art.

23 is another drive waveform diagram of the conventional display device of FIG. 20.

FIG. 24 is a configuration diagram of a field-sequential display device and a light source emission timing diagram.

25 is a drive waveform diagram of the display device of FIG. 24.

26 is another drive waveform diagram of the display device of FIG. 24.

FIG. 27 is a drive voltage waveform diagram of a field sequential display device.

FIG. 28 is a diagram for explaining the dielectric anisotropy of liquid crystal molecules.

FIG. 29 is a diagram showing the relationship between the absolute value of the voltage applied to the liquid crystal and the liquid crystal capacitance.

FIG. 30 is a diagram showing the relationship between liquid crystal capacitance and transmittance and the absolute value of liquid crystal applied voltage.

FIG. 31 is a waveform diagram for explaining that color reproducibility is reduced in a field sequential display device.

FIG. 32 is a waveform diagram for explaining that color misregistration occurs in a field-sequential display device.

[Explanation of symbols]

101 display device 102 scan signal drive circuit 103 Video signal drive circuit 104 scanning electrodes 105 video signal electrode 106 display element 107 switching element 108 pixel electrode 109 common electrode potential control circuit 110 common electrode 111 storage capacity 112 Pre-stage scan electrode (compensation scan electrode)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 641 G09G 3/20 641E 642 642L (72) Inventor Takashi Okada 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Katsuhiko Kumagawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H093 NA16 NA64 NC02 NC16 NC43 NC44 ND10 NH03 NH12 NH18 5C006 AA01 AA14 AA22 AC25 BB16 BC03 BC12 BC20 FA23 FA51 FA56 5C080 AA10 BB05 CC03 DD06 EE29 EE30 FF11 JJ02 JJ04 JJ05

Claims (28)

[Claims] 1. A display device comprising a display element, a video signal drive circuit, a scanning signal drive circuit, and a common electrode potential control circuit, wherein the display element is arranged in a matrix with a display medium. A plurality of pixel electrodes, a switching element connected thereto, a scan electrode, a video signal electrode, and a common electrode, and a storage capacitor between the pixel electrode and the common electrode,
The common electrode potential control circuit has two
Outputting a different kind of voltage value, and superimposing a coupling voltage via the storage capacitor on the potential of the pixel electrode, the video signal drive circuit, with respect to the video signal electrode ,
A display device, which outputs a voltage for resetting the display in addition to the video signal voltage. 2. The display device according to claim 1, wherein the voltage for resetting the display is written just before the video signal voltage is written to the pixel electrode. 3. A display medium is applied with voltages of both positive and negative polarities, and two types of voltages output from the common electrode potential control circuit to the common electrode are Vc1 and Vc2 (Vc1 <Vc2), respectively.
In this case, the common electrode potential control circuit changes the potential of the common electrode from Vc1 to Vc2 after writing a video signal voltage for applying a positive voltage to the display medium to the pixel electrode, and The video signal voltage for applying a negative voltage to the display medium is written in the pixel electrode, and then the potential of the common electrode is changed from Vc2 to Vc1. Display device. 4. The display medium is applied with a voltage having both positive and negative polarities, and two types of voltages output from the common electrode potential control circuit to the common electrode are Vc1 and Vc2 (Vc1 <Vc2), respectively.
In this case, the common electrode potential control circuit changes the potential of the common electrode from Vc1 to Vc2 after writing a video signal voltage for applying a positive voltage to the display medium to the pixel electrode, and The display according to claim 2, wherein the potential of the common electrode is not changed immediately after writing a video signal voltage for applying a negative voltage to the display medium to the pixel electrode. apparatus. 5. A display medium is applied with a voltage having both positive and negative polarities, and two types of voltages output from the common electrode potential control circuit to the common electrode are Vc1 and Vc2 (Vc1 <Vc2), respectively.
When, the common electrode potential control circuit does not change the potential of the common electrode immediately after writing a video signal voltage for applying a positive voltage to the display medium to the pixel electrode, and
The video signal voltage for applying a negative voltage to the display medium is written in the pixel electrode, and then the potential of the common electrode is changed from Vc2 to Vc1. Display device. 6. A dielectric constant sensitive to an electric field applied in the direction of the major axis of the display medium is ε //, and a dielectric constant sensitive to an electric field in a direction perpendicular thereto is ε⊥, and Δε = ε /
The display device according to claim 2, wherein the value of | Δε | / ε⊥ is 1.15 or more, where / −ε⊥. 7. A display device comprising a display element, a video signal drive circuit, and a scanning signal drive circuit, wherein the display element comprises a display medium, a plurality of pixel electrodes arranged in a matrix, and the display medium. A switching element connected to the scanning electrode, a scanning electrode, and a video signal electrode, and a storage capacitor between the pixel electrode and one of the scanning electrodes excluding the scanning electrode at the current stage, The scan signal drive circuit outputs two different voltage values to the scan electrode in addition to the voltage value for making the switching element conductive, and the potential of the pixel electrode has the storage capacitance. Characterized in that the video signal drive circuit outputs a voltage for resetting the display to the video signal electrodes, in addition to the video signal voltage. Display device. 8. The display device according to claim 7, wherein a voltage for resetting the display is written just before the video signal voltage is written to the pixel electrode. 9. A display medium is applied with a voltage having both positive and negative polarities, and a scanning signal drive circuit outputs two types of voltages to the scanning electrodes, in addition to the voltage value for making the switching element conductive, Vgoff1. , Vgoff2 (Vgof
f1 <Vgoff2), and when a scan electrode other than the current stage connected to a certain pixel electrode via a storage capacitor is called a compensation scan electrode, the scan signal drive circuit applies a positive voltage to the display medium. After writing the video signal voltage to be applied to the pixel electrode, the potential of the compensation scan electrode is changed from Vgoff1 to Vgo.
The potential of the compensation scan electrode is not changed immediately after the video signal voltage for applying a negative voltage to the display medium is written in the pixel electrode. The display device according to claim 8. 10. A voltage having both positive and negative polarities is applied to the display medium, and the scanning signal drive circuit outputs two types of voltages to the scanning electrodes other than the voltage value for making the switching element conductive, Vgoff1. , Vgoff2 (Vgof
f1 <Vgoff2), and when a scan electrode other than the current stage connected to a certain pixel electrode via a storage capacitor is called a compensation scan electrode, the scan signal drive circuit applies a positive voltage to the display medium. Immediately after writing the video signal voltage to be applied to the pixel electrode, the potential of the compensation scan electrode is not changed, and
9. The video signal voltage for applying a negative voltage to the display medium is written to the pixel electrode, and then the potential of the compensation scan electrode is changed from Vgoff2 to Vgoff1. Display device described. 11. The display medium according to claim 2, wherein the display medium is a normally white type, and the voltage amplitude of the signal for resetting the display is not less than the maximum amplitude of the video signal voltage for the display. 8. The display device according to item 8. 12. The display medium according to claim 2, wherein the display medium is a normally black type, and the voltage amplitude of the signal for resetting the display is less than or equal to the minimum amplitude of the video signal voltage for displaying. 8. The display device according to item 8. 13. The display device according to claim 2, wherein the display medium is liquid crystal. 14. The display device according to claim 13, wherein the liquid crystal is an OCB mode liquid crystal. 15. A display device comprising a display element, a video signal drive circuit, a scanning signal drive circuit, and a common electrode potential control circuit, wherein a plurality of light sources having different spectrums are turned on in a time division manner. In the display device for performing color display by making the display element, the display element includes a display medium, a plurality of pixel electrodes arranged in a matrix, switching elements connected to the pixel electrode, scanning electrodes, and a video signal. An electrode and a common electrode, and a storage capacitor between the pixel electrode and the common electrode, wherein the common electrode potential control circuit applies a coupling voltage to the potential of the pixel electrode via the storage capacitor. The video signal voltage applied to the video signal electrode from the video signal drive circuit in a certain subframe is determined according to the capacitance of the display medium in the preceding subframe. Characterized in that it is an Tadashisa display device. 16. The absolute value of the video signal voltage applied to the video signal electrode from the video signal drive circuit in a certain sub-frame is smaller than that in the case where the absolute value of the applied voltage to the display medium in the previous sub-frame is the minimum. 16. The correction is made so that the absolute value of the applied voltage to the display medium in the previous sub-frame is maximum when the absolute value is smaller.
Display device according to. 17. The potential change of the scanning electrode at the stage after writing the video signal voltage is ΔVg, and the potential change of the common electrode is ΔVg.
Letting Vc, the storage capacitance be Cst, and the capacitance between the scanning electrode and the pixel electrode be Cgd, ΔQcc = CgdΔVg + CstΔVc is set, and when a gradation that is a certain subframe is to be displayed,
The applied voltage to the display medium for setting the gradation is Vlc,
Let Ctot be the value of the sum of the capacitances electrically connected to the pixel electrodes when the applied voltage to the display medium is Vlc, and let the value of the sum of the capacitances electrically connected to the pixel electrodes in the previous subframe be When Ctot ′, the video signal voltage applied to the video signal by the video signal drive circuit is approximately [CtotVlc−, with reference to the potential on the opposite side of the display medium.
16. The display device according to claim 15, wherein the display device is given by ΔQcc] / Ctot ′. 18. A display device comprising a display element, a video signal drive circuit, and a scanning signal drive circuit, wherein color display is performed by lighting a plurality of light sources having different spectral spectra in a time division manner. In the display device to be performed, the display element includes a display medium, a plurality of pixel electrodes arranged in a matrix, a switching element connected thereto, a scanning electrode, and a video signal electrode. A storage capacitor is provided between the pixel electrode and one of the scan electrodes excluding the scan electrode at the current stage, The video signal voltage applied to the video signal electrodes from the video signal drive circuit in a certain subframe is corrected according to the capacitance of the display medium in the preceding subframe. And characterized in that the display device. 19. The absolute value of the video signal voltage applied to the video signal electrode from the video signal drive circuit in a certain sub-frame is smaller than that in the case where the absolute value of the voltage applied to the display medium in the previous sub-frame is minimum. 19. The correction is performed so that the absolute value of the voltage applied to the display medium in the previous sub-frame has a maximum value that is smaller.
Display device according to. 20. The potential change of the scan electrode of this stage after writing the video signal voltage is ΔVg, the potential change of the scan electrodes of other stages connected via the storage capacitor is ΔVgp, the storage capacitance is Cst, and The capacitance between the scanning electrode and the pixel electrode of the stage is Cgd
As ΔQcc = CgdΔVg + CstΔVgp, when a gradation that is a certain subframe is to be displayed,
The applied voltage to the display medium for setting the gradation is Vlc,
Let Ctot be the value of the total capacitance electrically connected to the pixel electrodes when the applied voltage to the display medium is Vlc, and let the value of the total capacitance electrically connected to the pixel electrodes in the previous subframe be When Ctot ′, the video signal voltage applied to the video signal by the video signal drive circuit is approximately [CtotVlc−
19. The display device according to claim 18, wherein the display device is given by ΔQcc] / Ctot ′. 21. The display device according to claim 15, wherein the display medium is liquid crystal. 22. The display device according to claim 21, wherein the liquid crystal is an OCB mode liquid crystal. 23. A display device comprising a display element, a video signal drive circuit, and a scanning signal drive circuit, wherein color display is performed by lighting a plurality of light sources having different spectral spectra in a time division manner. In the display device, the display element includes a display medium, a plurality of pixel electrodes arranged in a matrix, a switching element connected to the pixel electrode, a scanning electrode, and a video signal electrode. Δε = ε // −, where ε // is the permittivity sensitive to the electric field applied in the direction of the major axis of the display medium and ε⊥ When ε⊥ is set, the value of | Δε | / ε⊥ is 1.2 or more, and the video signal drive circuit
A display device, which outputs a voltage for resetting a display before writing a video signal voltage. 24. A driving method of a display device comprising a display element, a video signal drive circuit, a scanning signal drive circuit, and a common electrode potential control circuit, wherein the display element is in a matrix with a display medium. It has a plurality of pixel electrodes arranged, a switching element connected thereto, a scanning electrode, a video signal electrode, and a common electrode, and a storage capacitor between the pixel electrode and the common electrode. However, the common electrode potential control circuit has
Outputting a different kind of voltage value, and superimposing a coupling voltage via the storage capacitor on the potential of the pixel electrode, the video signal drive circuit, with respect to the video signal electrode ,
A method for driving a display device, which outputs a voltage for resetting a display in addition to a video signal voltage. 25. A method of driving a display device comprising a display element, a video signal drive circuit, and a scanning signal drive circuit, wherein the display element comprises a display medium and a plurality of pixels arranged in a matrix. An electrode, a switching element connected to the electrode, a scan electrode, and a video signal electrode are provided, and a storage capacitor is provided between the pixel electrode and one of the scan electrodes excluding the scan electrode at the stage. The scan signal driving circuit outputs two different voltage values to the scan electrode, in addition to the voltage value for turning on the switching element, and the potential of the pixel electrode. Is to superimpose the coupling voltage via the storage capacitor, the video signal drive circuit, to the video signal electrode,
A method for driving a display device, which outputs a voltage for resetting a display in addition to a video signal voltage. 26. A driving method of a display device comprising a display element, a video signal drive circuit, a scanning signal drive circuit, and a common electrode potential control circuit, wherein a plurality of light sources having different spectrums are time-divided. In the driving method of the display device for performing color display by selectively lighting, the display element, a display medium, a plurality of pixel electrodes arranged in a matrix, and a switching element connected thereto, A scan electrode, a video signal electrode, and a common electrode, and a storage capacitor between the pixel electrode and the common electrode, wherein the common electrode potential control circuit stores the potential at the pixel electrode. The video signal voltage applied from the video signal drive circuit to the video signal electrode in a certain subframe is superimposed on the coupling voltage through the capacitor. Characterized in that it is one that is corrected in accordance with the capacity of the medium, the driving method of the display device. 27. A driving method of a display device comprising a display element, a video signal drive circuit, and a scanning signal drive circuit, wherein a plurality of light sources having different spectrums are turned on in a time division manner. A driving method of the display device for performing color display, wherein the display element includes a display medium, a plurality of pixel electrodes arranged in a matrix, switching elements connected to the pixel electrode, scanning electrodes, and a video signal. An electrode, and has a storage capacitor between the pixel electrode and one of the scanning electrodes excluding the scanning electrode at the current stage, and the scanning signal drive circuit stores the voltage at the potential of the pixel electrode. A video signal voltage applied to the video signal electrodes from the video signal driving circuit in a certain subframe is superimposed on the coupling voltage via a capacitor. Characterized in that it is one that is corrected in accordance with the capacity, the driving method of the display device. 28. A method of driving a display device comprising a display element, a video signal drive circuit, and a scanning signal drive circuit, wherein a plurality of light sources having different spectrums are turned on in a time division manner. A driving method of the display device for performing color display, wherein the display element includes a display medium, a plurality of pixel electrodes arranged in a matrix, switching elements connected to the pixel electrode, scanning electrodes, and a video signal. The electrode has an electrode, and the permittivity which is sensitive to an electric field applied in the molecular long axis direction of the display medium is ε //, and the permittivity which is sensitive to an electric field in a direction perpendicular thereto is ε⊥, When Δε = ε // − ε⊥ is set, the value of | Δε | / ε⊥ is 1.2 or more, and the video signal drive circuit, with respect to the video signal electrode,
A method for driving a display device, comprising outputting a voltage for resetting a display before writing a video signal voltage.