JP2010102217A - Electrooptical device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrooptical device and electronic apparatus capable of improving the quality of display. <P>SOLUTION: The electrooptical device includes a data line selection circuit 40 having a switching circuit 41 which selects data lines 114 made a block for every predetermined number of data lines (RGB) in order, and also supplies a video signal Video to the selected data lines 114. The electrooptical device supplies pre-charge voltage (voltage equivalent to gradation voltage of a subpixel of B) set individually for every data lines 114 made a block in a non-effective display period before performing writing in the subpixel in the order of RGB in an effective display period. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electro-optical device such as a liquid crystal display device and an electronic apparatus including the electro-optical device.

Conventionally, electro-optical devices such as liquid crystal display devices have been widely used as display devices for displaying images. The liquid crystal display device includes an element substrate, a counter substrate disposed opposite to the element substrate, and a liquid crystal provided between the element substrate and the counter substrate.
As such a liquid crystal display device, a control circuit that supplies a voltage VCOML and a voltage VCOMH alternately to a common electrode as a common (COM) potential, a scanning line driving circuit that sequentially supplies a selection voltage to a plurality of scanning lines, and a scanning line A data line driving circuit that alternately supplies a positive polarity image signal having a higher potential than the voltage VCOML and a negative polarity image signal having a lower potential than the voltage VCOMH to a plurality of data lines. Is known (for example, see Patent Document 1).

Here, the common electrode is divided for each horizontal line, and so-called common electrode division driving (COM division driving) is performed in which the voltage VCOML or the voltage VCOMH is supplied from the control circuit to each common electrode, and pixel writing in each row is performed. The polarity of the common electrode is sequentially reversed for each row at the timing immediately before the execution. By adopting this common electrode division driving (COM division driving), it is possible to suppress the deterioration of display quality.
JP 2008-33247 A

However, when the COM division driving method is employed as in the liquid crystal display device described in Patent Document 1, the common electrode is made of a transparent conductive material such as ITO (Indium Tin Oxide), and is formed by an elongated linear electrode. In the pixel region far from the common potential supply source (COM potential supply source), the wiring resistance increases, and the common potential waveform distortion (COM waveform distortion) generated when the potential of the pixel and the drain line changes completely returns within a predetermined time. Due to the disappearance, the display quality such as crosstalk may be affected.
As a method of reducing the remaining COM waveform distortion, the same specific potential is simultaneously written to all the signal lines at the beginning of one horizontal scanning period or the horizontal blanking period, and the potential for actually writing to the pixels thereafter is set to the signal line. In general, so-called precharge is employed so that the change in potential of the signal line when applied to is minimized. However, in this method, since the precharge potential cannot be made the same as the potential for actually writing to the pixels for every display image, the potential change of the signal line always occurs when each signal line is selected. End up.

In particular, the data line driving circuit includes a plurality of demultiplexers that have one input terminal and n plurality of output terminals, and sequentially select the plurality of output terminals by a switching element and connect to the input terminals. When writing n sets of signal line groups divided into n periods within one horizontal scanning period, the last nth selected signal line group and the pixels connected to them The time that can be used to alleviate the COM waveform distortion that occurs when the potential changes is from the time point when the nth signal line group selection switch is turned on to the time point when the gate is turned off. For this reason, in such an electro-optical device, the COM waveform distortion is not sufficiently relieved, and the display quality is deteriorated.
SUMMARY An advantage of some aspects of the invention is that it provides an electro-optical device and an electronic apparatus that can improve display quality.

  In order to solve the above problem, an electro-optical device according to the present invention is provided corresponding to a plurality of scanning lines, a plurality of data lines, and an intersection of the plurality of scanning lines and the plurality of data lines. An electro-optical device including a plurality of sub-pixels, wherein the plurality of data lines are blocked for each predetermined number, and the plurality of sub-pixels include a pair of substrates opposed to each other with a liquid crystal layer interposed therebetween. A scanning line driving circuit configured by a common electrode and a pixel electrode for driving liquid crystal molecules of the liquid crystal layer, wherein the common electrode is divided into a plurality of parts and supplies a selection voltage to the scanning lines in a predetermined order; A data line selection circuit that sequentially selects the predetermined number of blocked data lines and supplies a video signal to the selected data lines in an effective display period in one horizontal scanning period; a first voltage; From the first voltage A control circuit for supplying any one of the second voltages having a high potential to the common electrode, and data blocked for the plurality of data lines in an ineffective display period in one horizontal scanning period. A precharge voltage is individually supplied for each line, and the precharge voltage is set equal to the gradation voltage of the sub-pixel corresponding to the data line selected at the end of the effective display period among the blocked data lines. It is characterized by being.

  As a result, a voltage equal to the gradation voltage of the pixel corresponding to the data line last selected in the effective display period can be supplied to the data lines belonging to the same block by the precharge in the ineffective display period. Therefore, the gradation voltage can be written in advance to each pixel when the gate is turned on. Therefore, when writing to the pixel corresponding to the data line selected last in the effective display period, the potential change of the pixel can be minimized, and finally the timing at which the COM potential greatly varies is displayed in the effective display period. It can be close to the first half. Therefore, even when a so-called COM waveform distortion in which the COM potential deviates from the original potential due to the potential change of the pixel electrode occurs, the time until the COM potential completely returns to the original potential (relaxation time). The remaining distortion of the COM waveform at the end of one horizontal scanning period can be reduced, and the display quality can be prevented from deteriorating.

Moreover, since the common electrode is divided into a plurality of parts and the COM divided drive for supplying the first voltage or the second voltage for each common electrode is adopted, for example, the first voltage and the second voltage are alternately arranged for each horizontal line. While supplying to the common electrode, a positive image signal and a negative image signal can be alternately supplied for each horizontal line with respect to the voltage of the common electrode. As a result, the flicker between pixels can be offset and the deterioration of display quality can be suppressed.
Furthermore, the common electrode is composed of elongated linear electrodes such as ITO, and even when the time constant is large in the pixel region far from the COM potential supply source, the COM waveform distortion relaxation time is sufficiently secured. Thus, it is possible to suppress the occurrence of crosstalk due to the COM waveform distortion and suppress the deterioration of display quality.

Furthermore, in the electro-optical device according to the invention, in the above, the data line selection circuit includes a switching circuit that is a switching element group including a plurality of switching elements, and the video signal is supplied to one selected data line. It functions as a demultiplexer for distribution.
In this way, the data line selection circuit can function as a demultiplexer, so that it is possible to cope with higher definition of the display image.
In the electro-optical device according to the aspect of the invention, the precharge voltage is configured to be supplied to the plurality of data lines by controlling a switching element of the switching circuit. It is characterized by.
As a result, the data line selection circuit can have the function of a precharge circuit, so that it is not necessary to provide a separate precharge switch and the circuit area can be reduced.

Furthermore, the electro-optical device according to the present invention is arranged in the above-described manner on the opposite side of the switching element group or in parallel with the switching element group via the data line, and the precharge voltage supply source and each data line And a precharge circuit including a switch for connecting the two.
As described above, since the precharge switch and the pixel writing switch are separately provided, precharge and pixel writing can be performed without requiring complicated control by the driver IC.

Still further, in the electro-optical device according to the invention, in the above, a plurality of sub-pixels adjacent in the extending direction of the scanning line constitute one pixel, and the predetermined number corresponds to one pixel. It is characterized by the number of data lines.
Thereby, it is possible to reduce the COM waveform distortion while preventing the occurrence of flicker, and to further improve the display quality.
The electro-optical device according to the invention is characterized in that, in the above, the common electrode and the pixel electrode are formed on one of the pair of substrates.
Thereby, a lateral electric field drive system such as IPS or FFS can be employed.
In addition, an electronic apparatus according to the present invention includes any one of the above electro-optical devices.
Thereby, it can be set as the electronic device which implement | achieved the improvement of display quality.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating an overall configuration of an electro-optical device 1 according to the present embodiment.
As shown in this figure, the electro-optical device 1 has a display area 100, and around this display area 100, a Y driver (scanning line driving circuit) 20, a driver IC 30, and a data line selection circuit. 40 and a COM driver (control circuit) 50 are arranged. Although not particularly shown, the display panel is configured such that the element substrate and the counter substrate are bonded together with a certain gap so that the electrode formation surfaces face each other, and liquid crystal is sealed in the gap.

In the display area 100 of the display panel, a plurality of scanning lines 112 are provided so as to extend in the row (X) direction, and a plurality of data lines 114 are extended in the column (Y) direction. In addition, each scanning line 112 is provided so as to be electrically insulated from each other. Sub-pixels 110 are arranged corresponding to the intersections between the scanning lines 112 and the data lines 114, respectively. A plurality of sub-pixels 110 constitute one pixel.
A color filter or the like is formed on the counter substrate of the display panel, thereby enabling color display. Here, the color filter has a colored region in which a primary color is applied corresponding to each pixel. The color filter according to the present embodiment has three colored regions of R (red), G (green), and B (blue), and three sub-pixels are arranged in the order of RGB in the row direction. In addition, it is assumed that the pixel arrangement is a stripe type in which sub-pixels of the same color are arranged in the column direction. In this case, one pixel is composed of three sub-pixels corresponding to the three colors of RGB.

In this embodiment, the so-called full-color WVGA in which the sub-pixels 110 are arranged in a matrix in the display region 100 in 480 rows × 2400 columns (3 × 800 = 2400 including 3 colors of RGB). However, it is not intended that the present invention be limited to this arrangement.
The 2400 data lines 114 are divided into blocks every predetermined number (in this embodiment, every three lines). That is, the 2400 data lines 114 are divided into M blocks (2400/3 = 800 in this embodiment).

Next, a detailed configuration of the sub-pixel 110 will be described.
FIG. 2 is a diagram illustrating a configuration of the sub-pixel 110. Here, a configuration for a total of three sub-pixels corresponding to the intersection of n rows and (3m−2) to 3m columns is shown. Note that m is an integer from 1 to M.
As shown in FIG. 2, each subpixel 110 is provided with an n-channel thin film transistor (hereinafter referred to as TFT) 116 that functions as a pixel switching element, a pixel electrode 118, and the pixel electrode 118. Common electrode 108 and storage capacitor 130.

Since the sub-pixels 110 have the same configuration, the sub-pixels 110 located in n rows (3m−2) columns will be described as representative. In the sub-pixels 110 in the n rows (3m−2) columns, the gate electrode of the TFT 116 is The source electrode is connected to the (3m-2) -th column data line 114 and the drain electrode is connected to the pixel electrode 118 while being connected to the n-th scanning line 112.
The common electrode 108 is divided for each horizontal line corresponding to the scanning line 112, is made of a transparent conductive material such as ITO (Indium Tin Oxide), and is provided along the scanning line 112. The common electrode 108 is alternately supplied with the voltage VCOML (first voltage) and the voltage VCOMH (second voltage) having a higher potential than the voltage VCOML as the common signal Z from the COM driver 50. It has become.

Since the common electrode 108 is made of a transparent conductive material such as ITO (Indium Tin Oxide), the common electrode wiring made of the same material as the scanning line 112 is divided into a plurality of divided common electrodes 108 in order to reduce resistance. It may be provided and connected.
The pixel capacitor 120 has a structure in which a liquid crystal which is a kind of dielectric is sandwiched between the pixel electrode 118 and the common electrode 108, and holds a differential voltage between the pixel electrode 118 and the common electrode 108. In this configuration, in the pixel capacitor 120, the amount of transmitted light changes according to the effective value of the holding voltage.
In the present embodiment, for convenience of explanation, the black voltage is displayed when the effective voltage value held in the pixel capacitor 120 is close to zero, while the normally black mode in which the white color is displayed as the effective voltage value increases. It shall be.

In this embodiment, the pixel electrode 118 and the common electrode 108 are formed on the same substrate (element substrate), and the liquid crystal of the electro-optical device 1 operates in the FFS (Fringe Field Switching) mode of the lateral electric field drive method. It shall be.
In FIG. 1, the Y driver 20 applies scanning signals G1, G2, G3,..., G480 corresponding to the selection voltage over one vertical scanning period (one frame period) according to control by a control circuit (not shown). ,..., 480 are supplied to the scanning line 112 in the 480th row. That is, the Y driver 20 selects the scanning line 112 in the order of 1, 2, 3,..., 480th row, sets the scanning signal to the selected scanning line 112 to the H level corresponding to the selection voltage, and the others. The scanning signal to the scanning line 112 is set to the L level corresponding to the non-selection voltage (ground potential Gnd). At this time, all TFTs 116 connected to the selected scanning line 112 are turned on (conductive state).

Specifically, the Y driver 20 outputs the scanning signals G1, G2, G3,..., G480 by sequentially shifting the start pulse VSP supplied from the control circuit in accordance with the clock signal VCK.
The driver IC 30 outputs data signals D1 to DM having voltages corresponding to the gradation of the sub-pixel 110 corresponding to the intersection of the selected scanning line 112 and each data line 114 to the data line selection circuit 40. It is. Each data signal D1 to DM is a video signal for each block, and signals to be supplied to the three data lines 114 in the block are time-division multiplexed. Note that, in the case where the data signal corresponding to each block is generally described without specifying the block number, it is expressed as Dm using m described above.

The data line selection circuit 40 includes a plurality of switching circuits 41 each having three switching elements and switches 42R, 42G, and 42B. One end of each of the three data lines 114 belonging to one block is connected to an output terminal of each switch. Are connected to each other.
Specifically, the output end of the switch 42R in the first (leftmost in FIG. 1) switching circuit 41 of the data line selection circuit 40 is connected to one end of the data line 114 in the first column, and the first switching circuit. 41, the output terminal of the switch 42G is connected to one end of the data line 114 in the second column, and the output terminal of the switch 42B in the first switching circuit 41 is connected to one end of the data line 114 in the third column. The data signals D1 corresponding to the three data lines to which the first block belongs are commonly supplied to the input ends of the switches 42R, 42G, and 42B.

In the data line selection circuit 40, a plurality (three in this case) of signal supply lines LineR, LineG, and LineB are arranged along the switching circuit 41 in the arrangement direction of the switching circuit 41 (direction orthogonal to the data line 114). One end thereof is connected to an output end of a driver IC 30 which is a signal supply source of selection signals SEL_R, SEL_G, and SEL_B.
Each switch 42R is commonly supplied with a selection signal SEL_R via a signal supply line LineR, and each switch 42G is commonly supplied with a selection signal SEL_G via a signal supply line LineG, and is supplied to each switch 42B. Are commonly supplied with a selection signal SEL_B via a signal supply line LineB. Here, the selection signals SEL_R, SEL_G, and SEL_B are signals that become H level in a predetermined order in one horizontal scanning period.

The switch 42R is in a conductive (ON) state only when the selection signal SEL_R becomes H level. Similarly, the switches 42G and 42B are in a conductive state only when the selection signals SEL_G and SEL_B become H level, respectively. It becomes a state.
With this configuration, for example, in the first block, the data signal D1 is separated into signals corresponding to RGB colors in one horizontal scanning period, and supplied to the data lines 114 from the first column to the third column, respectively. Can do.
Although the case where the switches 42R, 42G, and 42B of the switching circuit 41 are configured with TFTs has been described here, it may be configured with electronic elements such as a transmission gate.

In the present embodiment, a positive polarity data signal having a higher potential than the voltage of the common electrode 108 is supplied to the data line 114, and an image voltage based on the positive polarity data signal is written to the pixel electrode 118. And negative writing that supplies a negative data signal having a potential lower than the voltage of the common electrode 108 to the data line 114 and writes an image voltage based on the negative data signal to the pixel electrode 118. Alternately every horizontal line.
The COM driver 50 supplies the voltage VCOML or the voltage VCOMH as the common signals Z1 to Z480 to the common electrodes 108, respectively. Here, it is assumed that the common signal Zn is supplied to the n-th common electrode 108 before the scanning signal Gn is supplied to the n-th scanning line 112.

Further, the voltage VCOML and the voltage VCOMH are alternately supplied to each common electrode 108 every frame period. For example, when the voltage VCOML is supplied to the common electrode 108 in the nth row in a certain one frame period, the voltage VCOMH is supplied in the next one frame period.
Further, different voltages are supplied to adjacent common electrodes 108. For example, when the voltage VCOML is supplied to the common electrode 108 in the nth row in a certain frame period, the common electrode 108 in the (n−1) th row and the common electrode in the (n + 1) th row in the same one frame period. The voltage VCOMH is supplied to 108.

Next, the operation of the electro-optical device 1 configured as described above will be described.
FIG. 3 is a timing chart showing the operation of the electro-optical device 1. Here, a writing operation (in the case of white display) to the sub-pixel 110 corresponding to the n-th scanning line 112 will be described. In the case of white display, all of the RGB video signals Video are High.
First, in the horizontal blanking period (within the ineffective display period) before the scanning signal Gn is supplied from the Y driver 20 to the n-th scanning line 112, the driver IC 30 is set to the H level for a predetermined period from the time t1. The selection signals SEL_R, SEL_G, and SEL_B are supplied to the data line selection circuit 40 at the same time. As a result, the switches 42R, 42G, and 42B of each switching circuit 41 are all turned on, and the data signal Dm set to a predetermined precharge voltage is supplied to each data line 114.

Here, the driver IC 30 obtains in advance pixel data of a group (B in the present embodiment) that is selected last in the effective display period from the RGB 3 groups of data line groups, and a potential corresponding to this (actually, The potential to be written) is set as a precharge voltage that is individually supplied to each of the blocked data lines.
Next, at time t2, the Y driver 20 supplies the scanning signal Gn to the scanning line 112 in the nth row. As a result, all the TFTs 116 connected to the n-th scanning line 112 are turned on, and all the sub-pixels 110 related to the n-th scanning line 112 are selected. At this time, the precharge voltage is written to the pixel electrodes 118 of all the sub-pixels 110 related to the n-th scanning line 112, and each pixel potential (Rpixel, Gpixel, Bpixel) changes toward the precharge voltage. . Here, since white display is performed, all of RGB approaches a desired potential (potentially written potential).

At this time t2, the potentials of all the pixel electrodes 118 in the nth row change. When the potential of the pixel electrode 118 is greatly changed, the COM potential is largely deviated from the original potential due to capacitive coupling between the pixel electrode 118 and the common electrode 108. Since the COM potential is constantly supplied from the COM potential supply source, it tries to return to the original potential with a predetermined time constant even if the potential shift occurs.
Here, when the common electrode 108 is formed of ITO as in the present embodiment, the time constant is large in the pixel region away from the COM potential supply source. Therefore, since the COM potential tends to return to the original potential relatively slowly, it takes time until the COM potential returns to the original potential.

When the selection signal SEL_R that becomes H level is supplied by the driver IC 30 to the data line selection circuit 40 at time t3 before the COM potential returns to the original potential, the switch 42R of each switching circuit 41 is turned on. Thus, the video signal Video is supplied to the data line 114 corresponding to the red (R) sub-pixel, and the image data is written to the R pixel electrode 118. Therefore, the R pixel voltage Rpixel changes toward a pixel voltage corresponding to the gradation (here, a voltage corresponding to white display).
At this time, since the pixel voltage Rpixel is close to a desired potential due to the precharge, the variation of the pixel potential Rpixel is suppressed to be small. Therefore, the fluctuation of the COM potential at the time t3 can be suppressed to a small level.

Next, at time t <b> 4, the driver IC 30 supplies the selection signal SEL_G that becomes H level to the data line selection circuit 40. As a result, the switch 42G of each switching circuit 41 is turned on, the video signal Video is supplied to the data line 114 corresponding to the green (G) sub-pixel, and the image data is written to the G pixel electrode 118. Therefore, the G pixel voltage Gpixel changes toward a pixel voltage corresponding to the gradation (here, a voltage corresponding to white display).
Also in this case, since the pixel voltage Gpixel is close to a desired potential due to the precharge, the variation of the pixel potential Gpixel is suppressed to be small. Therefore, the fluctuation of the COM potential at time t4 can be suppressed to a small level.

After that, when the selection signal SEL_B at which the driver IC 30 becomes H level is supplied to the data line selection circuit 40 at time t5, the switch 42B of each switching circuit 41 is turned on, and the data line corresponding to the blue (B) sub-pixel. The video signal Video is supplied to 114 and image data is written to the B pixel electrode 118. Therefore, the B pixel voltage Bpixel changes toward a pixel voltage corresponding to the gradation (here, a voltage corresponding to white display).
Also in this case, since the pixel voltage Bpixel approaches the desired potential due to the precharge, the variation in the pixel potential Bpixel is suppressed to a small value. Therefore, the fluctuation of the COM potential at time t5 can be suppressed to a small level.
At time t6, the Y driver 20 finishes supplying the scanning signal Gn to the n-th scanning line 112, thereby turning off all the TFTs 116 connected to the n-th scanning line 112.

In this way, in the non-effective display period in one horizontal scanning period, a precharge voltage corresponding to the gradation voltage of the B sub-pixel selected last in the effective display period is supplied to each data line. In particular, in the case of white display, during the effective display period, there is almost no change in the COM potential when the video signal Video corresponding to the gradation is sequentially supplied to the RGB sub-pixels.
That is, the COM potential gradually returns to the original potential with a predetermined time constant from the time t2 when the last large potential fluctuation occurs. The period from when the last large potential fluctuation occurs until the TFT 116 is turned off is hereinafter referred to as “COM waveform distortion relaxation time”.
Therefore, when white display is performed, the gradation voltage of the B sub-pixel is set to the precharge voltage, so that the fluctuation of the COM potential can be suppressed not only when writing the B pixel but also when writing the R and G pixels. And the relaxation time can be taken long enough.

Next, the case of yellow display will be described.
FIG. 4 is a timing chart showing the operation of the electro-optical device 1 in the case of yellow display. In the case of yellow display, the R and G video signals Video are High, and the B video signals Video are Low.
First, in the horizontal blanking period (within the ineffective display period) before the scanning signal Gn is supplied from the Y driver 20 to the n-th scanning line 112, the driver IC 30 is at the H level for a predetermined period from the time t11. The selection signals SEL_R, SEL_G, and SEL_B are supplied to the data line selection circuit 40 at the same time. As a result, the switches 42R, 42G, and 42B of each switching circuit 41 are all turned on, and the data signal Dm set to a potential corresponding to the gradation voltage of the B sub-pixel is supplied to each data line 114.

Next, at time t12, the Y driver 20 supplies the scanning signal Gn to the scanning line 112 in the nth row. As a result, all the TFTs 116 connected to the n-th scanning line 112 are turned on, and all the sub-pixels 110 related to the n-th scanning line 112 are selected. At this time, the precharge voltage is written to the pixel electrodes 118 of all the sub-pixels 110 related to the n-th scanning line 112, and each pixel potential (Rpixel, Gpixel, Bpixel) changes toward the precharge voltage. .
At this time t12, the potentials of all the pixel electrodes 118 in the n-th row change, but since the precharge voltage level is low, the variation in each pixel potential is relatively small and the variation in the COM potential is not so large. .

At time t13, when the selection signal SEL_R that becomes H level is supplied to the data line selection circuit 40 by the driver IC 30, the switch 42R of each switching circuit 41 is turned on, corresponding to the red (R) sub-pixel. A video signal Video is supplied to the data line 114, and image data is written to the R pixel electrode 118. Therefore, the R pixel voltage Rpixel changes toward a pixel voltage corresponding to the gradation (here, a voltage corresponding to yellow display).
At this time, since there is a large difference between the precharge voltage and the desired voltage of the R subpixel, a large potential change occurs in the pixel voltage Rpixel at time t13, and the COM potential also varies greatly.

Next, at time t <b> 14, the driver IC 30 supplies the selection signal SEL_G that becomes the H level to the data line selection circuit 40. As a result, the switch 42G of each switching circuit 41 is turned on, the video signal Video is supplied to the data line 114 corresponding to the green (G) sub-pixel, and the image data is written to the G pixel electrode 118. For this reason, the G pixel voltage Gpixel changes toward a pixel voltage (here, a voltage corresponding to yellow display) corresponding to the gradation.
Also in this case, since there is a large difference between the precharge voltage and the desired voltage of the G sub-pixel, a large potential change occurs in the pixel voltage Gpixel even at time t14, and the COM potential varies greatly.

After that, when the selection signal SEL_B at which the driver IC 30 becomes H level is supplied to the data line selection circuit 40 at time t15, the switch 42B of each switching circuit 41 is turned on, and the data line corresponding to the blue (B) sub-pixel. The video signal Video is supplied to 114 and image data is written to the B pixel electrode 118. Therefore, the B pixel voltage Bpixel changes toward the pixel voltage corresponding to the gradation (here, the voltage corresponding to yellow display).
At this time, since the pixel voltage Bpixel is close to a desired potential due to the precharge, the variation of the pixel potential Bpixel is suppressed to be small. Therefore, the fluctuation of the COM potential at time t15 can be suppressed to a small value.

At time t16, the Y driver 20 ends the supply of the scanning signal Gn to the n-th scanning line 112, thereby turning off all the TFTs 116 connected to the n-th scanning line 112.
As described above, when yellow display is performed, the gradation voltage of the B subpixel is set to the precharge voltage, so that the fluctuation of the COM potential at the time of writing the B pixel can be suppressed. That is, the COM potential gradually returns to the original potential with a predetermined time constant from the time t14 when the last large potential fluctuation occurs, and the period from the time t14 to the time t16 becomes the relaxation time of the COM waveform distortion. .

FIG. 5 is a timing chart showing the operation of a general electro-optical device. This general electro-optical device has a circuit configuration similar to that of the electro-optical device 1 of the present embodiment shown in FIG.
First, at time t <b> 21, the driver IC 30 supplies selection signals SEL_R, SEL_G, and SEL_B that become H level simultaneously to the data line selection circuit 40, and supplies a data signal Dm set to a predetermined precharge voltage to each data line 114. . Here, it is assumed that the precharge voltage is set to the center voltage of the amplitude of the video voltage.

Next, at time t <b> 22, the Y driver 20 supplies the scanning signal Gn to the n-th scanning line 112 and selects all the sub-pixels 110 related to the n-th scanning line 112. At this time, the precharge voltage is written to the pixel electrodes 118 of all the sub-pixels 110 related to the scanning line 112 in the n-th row, and each pixel potential (Rpixel, Gpixel, Bpixel) changes toward the intermediate voltage.
At this time t22, the potentials of all the pixel electrodes 118 in the n-th row change, and thereby the COM potential greatly deviates from the original potential.

Thereafter, the image data is written to the R pixel electrode 118 at time t23, the image data is written to the G pixel electrode 118 at time t24, and the image data is written to the B pixel electrode 118 at time t25. When writing to the sub-pixel is performed by selecting each of these data lines 114, the COM potential also varies according to the variation of the pixel voltage.
At time t26, when the Y driver 20 finishes supplying the scanning signal Gn to the n-th scanning line 112, all the TFTs 116 connected to the n-th scanning line 112 are turned off.

As described above, in the general electro-optical device, the COM waveform distortion is relatively short after the writing to the B sub-pixel at time t25 until the TFT 116 is turned off at time t26. It becomes relaxation time.
Here, since the precharge voltage is set to the center voltage of the amplitude of the video voltage, when halftone display is performed as shown by the broken line in FIG. 5, each pixel voltage is desired by precharge at time t21. Therefore, even if the relaxation time is relatively short, the remaining distortion of the COM waveform at time t26 can be suppressed. Does not occur.

On the other hand, as shown by the solid line in FIG. 5, when white display is performed, the potential of each pixel greatly varies when writing to each sub-pixel, and the COM potential also varies greatly accordingly. Therefore, in this case, if the relaxation time is short, the COM potential does not fully return to the original potential at time t26, and distortion remains.
The precharge potential may be set to a black potential or a white potential in addition to the intermediate potential, but both have advantages and disadvantages. For example, when the precharge potential is a black potential, if the display image is a black raster, the potential change during pixel writing after the precharge is small and the COM waveform distortion can be suppressed. However, if the display image is a white raster, the precharge potential is precharged. The potential change during the subsequent pixel writing is large, and the COM potential greatly fluctuates. This also occurs when the precharge potential is a white potential.

If the pixel electrode potential is determined in a state where the COM potential deviates from the original potential in this way, the liquid crystal applied voltage in the row is held in a state different from the intended level. Since the amount of change in the COM potential at the time of pixel writing depends on the display gradation of the row, it causes horizontal crosstalk and leads to deterioration of display quality.
On the other hand, in the present embodiment, the precharge potential is set to a potential corresponding to the gradation potential of the B sub-pixel, so that the potential change at the time of B pixel writing after precharge is minimized. For example, when yellow display is performed as shown in FIG. 4, the potential change at the time of writing the previous G pixel becomes the final large COM waveform distortion factor, so the COM waveform distortion relaxation time is shown in FIG. Compared to the method, the length can be increased up to about twice.

  As described above, in this embodiment, the precharge in the ineffective display period causes the data lines belonging to the same block to be equal to the gradation voltage of the sub-pixel corresponding to the data line last selected in the effective display period. Since the voltage is supplied, the gradation voltage can be written to each sub-pixel when the gate is turned on. Therefore, when writing to the sub-pixel corresponding to the data line selected last in the effective display period, the potential change of the sub-pixel can be minimized, and the timing at which the COM potential greatly varies last is effective. It can be close to the first half of the display period.

Therefore, even when a so-called COM waveform distortion in which the COM potential deviates from the original potential due to the potential change of the pixel electrode occurs, the time until the COM potential completely returns to the original potential (relaxation time). Can be ensured, and the remaining distortion of the COM waveform at the end of one horizontal scanning period can be reduced, thereby suppressing deterioration in display quality.
In addition, since the data line selection circuit functions as a demultiplexer that distributes the video signal to one selected data line among the plurality of blocked data lines, it is possible to cope with high definition of the display image. .
Further, since the number of data lines to be blocked is set to the number of data lines corresponding to one pixel forming one dot, the remaining distortion of the COM waveform is reduced while preventing occurrence of flicker. Display quality can be improved.

Furthermore, since the pixel write switches (42R, 42G, 42B) are used as precharge switches and the driver IC 30 and the data line selection circuit 40 have a function as a precharge circuit, a separate precharge circuit is provided. There is no need to provide the circuit area, and the circuit area can be reduced.
Further, after the voltage VCOML is supplied to the common electrode 108 by the COM driver 50, the scanning signal Gn is supplied to the scanning line 112 by the scanning line driving circuit 20A or 20B, and then the positive image signal is converted to the data by the data line driving circuit 30. Supply to line 114. Further, after the voltage VCOMH is supplied to the common electrode 108 by the COM driver 50, the scanning signal Gn is supplied to the scanning line 112 by the scanning line driving circuit 20A or 20B, and then the negative image signal is supplied to the data line driving circuit 30 by the data line driving circuit 30. Supply to line 114.

As described above, the voltage VCOML and the voltage VCOMH are alternately supplied to the common electrode 108 for each horizontal line, and a positive image signal and a negative image signal are 1 for the voltage of the common electrode 108. Since the alternating supply is performed for each horizontal line, the flicker between pixels can be offset and the deterioration of display quality can be further suppressed.
Further, since the voltage of the common electrode 108 is changed to the voltage VCOML or the voltage VCOMH, it is not necessary to change the voltage of one electrode of the storage capacitor 130 with a voltage different from that of the pixel electrode 118 and the common electrode 108. Therefore, the storage capacitor and the pixel capacitor can be formed integrally.
Furthermore, the common electrode is composed of elongated linear electrodes such as ITO, and even when the time constant is large in the pixel region far from the COM potential supply source, the COM waveform distortion relaxation time is sufficiently secured. Thus, it is possible to suppress the occurrence of crosstalk due to the COM waveform distortion and suppress the deterioration of display quality.

  In the above embodiment, the case where the precharge voltage is supplied to each data line 114 by turning on the switches 42R, 42G, and 42B of the data line selection circuit 40 in the horizontal blanking period has been described. A precharge switch (precharge circuit) connected between the supply source of the precharge voltage and the data line 114 may be provided separately. In this case, the precharge switch can be provided on the opposite side of the data line 114 to the side where the switches 42R, 42G, and 42B are connected, or in parallel with the switches 42R, 42G, and 42B. Thus, by providing a precharge switch separately, the pixel writing function and the precharge function can be separated, and the control by the driver IC 30 can be simplified.

In the above-described embodiment, the case where the RGB color filters are used has been described. However, four color filters such as RGBC (cyan) and RGBW (white) may be used.
Furthermore, in the above-described embodiment, the common electrode is divided into a plurality of parts, and the common electrode division driving (COM division driving) for supplying the first voltage or the second voltage for each common electrode has been described. It is good also as a structure which does not drive (a common electrode is not divided | segmented).
In each of the above embodiments, the case where the FFS method is employed as the liquid crystal driving method has been described. However, a TN method, an IPS method, or the like may be employed.

Furthermore, in each of the above embodiments, the case where the present invention is applied to a liquid crystal display device has been described. However, the present invention is applied to a display device using an electro-optical material other than liquid crystal, for example, a display device using organic EL or plasma discharge. It can also be applied.
In addition, the electro-optical device of each of the above embodiments can be used as a display device mounted on an electronic apparatus. Specific examples of the electronic device include a monitor, a TV, a notebook computer, a PDA, a digital camera, a video camera, a mobile phone, a mobile photo viewer, a mobile video player, a mobile DVD player, and a mobile audio player.

1 is a block diagram illustrating an overall configuration of an electro-optical device according to an embodiment. It is a figure which shows the structure of a sub pixel. 6 is a timing chart illustrating an operation of the electro-optical device according to the present embodiment. 6 is a timing chart illustrating an operation of the electro-optical device according to the present embodiment. 10 is a timing chart showing the operation of a conventional electro-optical device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electro-optical apparatus, 20 ... Y driver, 30 ... Driver IC, 40 ... Data line selection circuit, 41 ... Switching circuit, 42R, 42G, 42B ... Switch, 50 ... COM driver, 100 ... Display area, 108 ... Common electrode , 110 ... subpixels, 112 ... scanning lines, 114 ... data lines, 116 ... TFTs, 118 ... pixel electrodes, 120 ... pixel capacitors, 130 ... storage capacitors

Claims (7)

An electro-optical device comprising a plurality of scanning lines, a plurality of data lines, and a plurality of sub-pixels provided corresponding to intersections of the plurality of scanning lines and the plurality of data lines,
The plurality of data lines are divided into blocks every predetermined number,
The plurality of sub-pixels includes a pair of substrates facing each other with a liquid crystal layer interposed therebetween, and a common electrode and a pixel electrode that drive liquid crystal molecules in the liquid crystal layer, and the common electrode is divided into a plurality of portions.
A scanning line driving circuit for supplying a selection voltage to the scanning lines in a predetermined order;
A data line selection circuit for sequentially selecting the predetermined number of data lines blocked in an effective display period in one horizontal scanning period and supplying a video signal to the selected data lines;
A control circuit that supplies either the first voltage or a second voltage having a higher potential than the first voltage to the common electrode;
In a non-effective display period in one horizontal scanning period, a precharge voltage is individually supplied to each of the plurality of data lines for each of the blocked data lines, and the precharge voltage is applied to each of the blocked data lines. Among these, the electro-optical device is set to be equal to the gradation voltage of the sub-pixel corresponding to the data line selected at the end of the effective display period.   The data line selection circuit includes a switching circuit that is a group of switching elements including a plurality of switching elements, and functions as a demultiplexer that distributes the video signal to one selected data line. 2. The electro-optical device according to 1.   The electro-optical device according to claim 2, wherein the precharge voltage is configured to be supplied to the plurality of data lines by controlling a switching element of the switching circuit.   A precharge circuit including a switch that is disposed on the opposite side of the switching element group or in parallel with the switching element group via the data line and that connects the source of the precharge voltage and the data lines; The electro-optical device according to claim 2. A plurality of subpixels adjacent in the direction in which the scanning line extends constitutes one pixel,
The electro-optical device according to claim 1, wherein the predetermined number is the number of data lines corresponding to one pixel.   The electro-optical device according to claim 1, wherein the common electrode and the pixel electrode are formed on one of the pair of substrates.   An electronic apparatus comprising the electro-optical device according to claim 1.

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