JP2008304660A - Display device and display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically adjust the value of the common electrode voltage of a liquid crystal display. <P>SOLUTION: The potential of a pixel electrode (electrode connected to a TFT) of a liquid crystal cell in a dummy pixel region is input voltage VCOM_ OUT of an analog buffer 71 of a common voltage adjusting circuit 63. The output voltage via the analog buffer 71 and a path capacitor 72 is supplied as common voltage potential VCOM_IN of a liquid crystal panel 61. When an opening part 91 is constructed with the whole pixels of a single row to be taken as a dummy pixel region, the size of the liquid crystal panel 61 is utilized most effectively to secure the number of dummy pixels, and the effective pixel region in the liquid crystal panel 61 can be made rectangular. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device and a display method, and more particularly to a display device and a display method that are suitable for use when channel capacity-induced feedthrough occurs.

  A general liquid crystal display device will be described with reference to FIGS.

  The active matrix type liquid crystal display device 1 has a matrix (matrix shape) corresponding to scanning (gate) lines arranged in rows, signal lines arranged in columns, and intersections of the scanning lines and signal lines. ), A horizontal driving circuit that activates the elements in the row every horizontal period (1H), and a scanning line in the row in the active state are sequentially scanned to scan the pixels. A vertical driving circuit that selects and drives each row (each line), writes a video signal for each horizontal period to pixels in each selected row, and outputs a video signal for one frame (or one field) Hold.

  As shown in FIG. 1, the liquid crystal display device 1 includes a liquid crystal panel 11, a signal line drive circuit 12 that is a horizontal drive circuit, a gate line drive circuit 13 that is a vertical drive circuit, and a controller 14.

  The liquid crystal panel 11 is a matrix-driven pixel-type display, and displays an image by changing the amount of transmitted light by controlling the arrangement of liquid crystals inside the liquid crystal cell, which is a pixel, on the screen. .

  The signal line driving circuit 12 and the gate line driving circuit 13 drive each pixel of the liquid crystal panel 11 in a matrix manner based on a control signal supplied from the controller 14.

  In the liquid crystal panel 11, liquid crystal cells as pixels are arranged from 1 row 1 column to n rows m columns. Specifically, as shown in FIG. 2, the liquid crystal cell 31-is arranged in the B column (1 ≦ B <m) of the A row (1 ≦ A ≦ n) of the pixels up to n rows and m columns. A set of A-B, TFT (Thin Film Transistor) 32-A-B, and capacitor 33-A-B is arranged, and the liquid crystal cell 31-A- (B + 1) is arranged in the (B + 1) -th column of the A-th row. ), TFT 32-A- (B + 1), and capacitor 33-A- (B + 1).

  Hereinafter, the liquid crystal cells 31-1-1 to 31-nm are simply referred to as a liquid crystal cell 31 when it is not necessary to distinguish them individually. Hereinafter, when it is not necessary to individually distinguish the TFTs 32-1-1 to 32-n-m, they are simply referred to as TFTs 32. Hereinafter, when it is not necessary to distinguish the capacitors 33-1-33 to 33 -n-m individually, they are simply referred to as capacitors 33.

  The gate electrode of the TFT 32 is connected to the gate line from the gate line driving circuit 13, the source electrode (or signal electrode) of the TFT 32 is connected to the signal line from the signal line driving circuit 12, and the drain electrode of the TFT 32 is It is connected to the liquid crystal cell 31 and the capacitor 33, and is hereinafter also referred to as a pixel electrode.

  The liquid crystal cell 31 stores liquid crystal, and the transmittance of the liquid crystal is changed by the pixel electrode voltage applied by the TFT 32. Therefore, the amount of light transmitted through the backlight (not shown) is changed. A common voltage is applied to the counter electrode of the liquid crystal cell 31 (the electrode on the side not connected to the TFT 32).

  The TFT 32 drives the liquid crystal cell 31 by applying a voltage to the liquid crystal cell 31. That is, the TFT 32 drives the liquid crystal cell 31 based on the signal voltage when the corresponding gate signal is ON.

  The capacitor 33 is provided in parallel with the liquid crystal cell 31 and holds a voltage applied to the liquid crystal cell 31 in a period of one frame. The counter electrode of the capacitor 33 (the electrode not connected to the TFT 32) is connected to the counter electrode, or the median value of the signal potential is applied.

  The life of the liquid crystal stored in the liquid crystal cell 31 is shortened when a DC voltage is applied. Therefore, in a general liquid crystal display device, the voltage applied to the pixel electrode of the liquid crystal cell 31 is changed between the positive voltage side and the negative voltage side at regular intervals with reference to the voltage applied to the common electrode. Thus, the life of the liquid crystal is prevented from being shortened.

  When the TFT 32 is configured by an NMOS (Negative Channel Metal Oxide Semiconductor), as shown in FIG. 3, the feedthrough of the pixel (Pix) potential is caused by the influence of the gate-Pix capacitance and the channel capacitance of the pixel TFT. Occurs, and the held pixel potential decreases. In a display device that performs positive polarity writing and negative polarity writing, such as the liquid crystal display device 1, the counter common voltage potential is set so that the potential effectively applied to the liquid crystal cell 31 is equivalent in consideration of this feedthrough. Need to be set. However, the feedthrough due to the channel capacitance greatly varies due to variations in the characteristics of the TFT 32, and it is necessary to adjust the common voltage value (common electrode potential) that is optimal for each liquid crystal panel 11.

  Conventionally, in order to adjust an optimum common voltage value for each liquid crystal panel, a dummy pixel is provided in the liquid crystal panel, and a gradation voltage having a maximum gradation of different polarity is written in the first dummy pixel and the second dummy pixel. There is a technique for adjusting the common electrode potential based on the potential difference between each pixel electrode potential and the common electrode potential (see, for example, Patent Document 1).

JP 2002-264677 A

  However, in the technique described in Patent Document 1, based on the potential difference between the pixel electrode potential and the common electrode potential of each of the first dummy pixel and the second dummy pixel to which the gradation voltage of the maximum gradation of different polarity is written. In order to obtain a common electrode potential suitable for the liquid crystal panel, a plurality of operational amplifiers and a common voltage generation circuit are required.

  On the other hand, it is required to adjust the common electrode potential more easily and to reduce the circuit scale necessary for the adjustment.

  The present invention has been made in view of such circumstances, and can use a simple circuit to automatically adjust the common voltage value of a liquid crystal display device in which feedthrough due to channel capacitance occurs. To do.

  A display device according to one aspect of the present invention is a display device that displays an image by changing the transmittance of liquid crystal, and includes at least the liquid crystal and a switching element, and displays each pixel corresponding to the displayed image. The image display means, the adjustment means for adjusting the counter electrode voltage potential of the liquid crystal included in the image display means, and the liquid crystal that the liquid crystal possesses by itself includes the same configuration as the portion corresponding to each pixel of the image display means A reference voltage supply means for supplying the pixel electrode potential as a reference voltage value to the adjustment means, and a first drive means for controlling on / off of the switching element included in the image display means and the reference voltage supply means; A second driving means for controlling a voltage applied to a signal electrode of the switching element included in the image display means and the reference voltage supply means; Control means for controlling the first drive means and the second drive means, and the control means is included in the image display means in a predetermined period before the display of the image on the image display means is started. The switching element included in the reference voltage supply means is turned on, and a median value of bipolar signal voltages is applied to the signal electrode of the switching element included in the reference voltage supply means. The first driving unit and the second driving unit are controlled so as to cause the first driving unit and the second driving unit to operate.

  The adjustment means adds a predetermined voltage based on the wiring resistance when the pixel electrode potential of the liquid crystal is supplied from the reference voltage supply means to the pixel electrode potential of the liquid crystal supplied from the reference voltage supply means. Then, the counter electrode voltage potential of the liquid crystal included in the image display means can be supplied.

  The reference voltage supply means may have a configuration corresponding to a plurality of pixels of the image display means, and each pixel electrode may be connected.

  The reference voltage supply means may have a configuration corresponding to a plurality of pixels for one row of the image display means, and each pixel electrode may be connected.

  The adjusting means supplies the pixel electrode potential of the liquid crystal supplied from the reference voltage supply means as the counter electrode voltage potential of the liquid crystal included in the image display means via an analog buffer. Can do.

  The adjustment means includes the liquid crystal pixel electrode potential supplied from the reference voltage supply means via an analog buffer, and further via a pass capacitor to the liquid crystal counter electrode included in the image display means. It can be supplied as a voltage potential.

  A display method according to one aspect of the present invention is a display method for a display device that includes an adjustment unit that adjusts a counter electrode voltage potential of a liquid crystal, and displays an image by changing the transmittance of the liquid crystal. In a predetermined period before starting display of an image on the image display unit including the liquid crystal and the switching element, the switching element included in the image display unit is turned off, and in each pixel of the image display unit in the predetermined period The switching element included in the reference voltage supply unit in the predetermined period includes the same configuration as the corresponding part, turns on the switching element included in the reference voltage supply unit that supplies the adjustment unit as a reference voltage value Before applying the median value of the bipolar signal voltage to the liquid crystal of the reference voltage supply unit in the predetermined period. A pixel electrode potential is supplied to the adjustment unit. In the adjustment unit, a counter electrode potential of the liquid crystal based on the supplied pixel electrode potential is output, supplied to the image display unit, and supplied to the image display unit. Driving the liquid crystal included to display the image.

  In one aspect of the present invention, the switching element included in the image display unit is turned off in a predetermined period before starting image display, and the reference voltage supply unit supplies the adjustment unit as a reference voltage value in the predetermined period. The switching element included is turned on, and the median value of the bipolar signal voltages is applied to the signal electrode of the switching element included in the reference voltage supply unit in a predetermined period, and the liquid crystal included in the reference voltage supply unit is applied in the predetermined period. The applied pixel electrode potential is supplied to the adjustment unit. In the adjustment unit, the counter electrode potential of the liquid crystal based on the supplied pixel electrode potential is output and supplied to the image display unit, and the liquid crystal included in the image display unit Is driven and an image is displayed.

  The display device may be an independent device or a block that performs display processing of the information processing device.

  As described above, according to one aspect of the present invention, an image can be displayed, and in particular, the counter electrode potential can be automatically adjusted.

  Embodiments of the present invention will be described below. Correspondences between constituent elements of the present invention and the embodiments described in the specification or the drawings are exemplified as follows. This description is intended to confirm that the embodiments supporting the present invention are described in the specification or the drawings. Therefore, even if there is an embodiment which is described in the specification or the drawings but is not described here as an embodiment corresponding to the constituent elements of the present invention, that is not the case. It does not mean that the form does not correspond to the constituent requirements. Conversely, even if an embodiment is described here as corresponding to a configuration requirement, that means that the embodiment does not correspond to a configuration requirement other than the configuration requirement. It's not something to do.

  A display device according to one aspect of the present invention is a display device that displays an image by changing the transmittance of liquid crystal, and includes at least the liquid crystal and a switching element, and displays each pixel corresponding to the displayed image. Image display means (for example, the liquid crystal cell 31, TFT 32, and capacitor 33 in the opening 91) and adjustment means for adjusting the counter electrode voltage potential of the liquid crystal included in the image display means (for example, the common voltage in FIG. 4) An adjustment circuit 63) and a pixel electrode potential of the liquid crystal included in the adjustment circuit 63) which is identical to a portion corresponding to each pixel of the image display means, and supplies the liquid crystal pixel electrode potential to the adjustment means as a reference voltage value (for example, VCOM_OUT) Reference voltage supply means (for example, the liquid crystal cell 31, TFT 32 and capacitor 33 in the dummy pixel region), the image display means and the base First driving means for controlling on / off of the switching element included in the voltage supply means (for example, the gate line driving circuit 13 in FIG. 4), and the switching element included in the image display means and the reference voltage supply means Second driving means (for example, the signal line driving circuit 12 in FIG. 4) for controlling the voltage applied to the signal electrodes, and control means for controlling the first driving means and the second driving means (for example, 4 and the controller 62), the control means in a predetermined period (for example, the start-up period or V blanking period in FIG. 9) before starting the display of the image on the image display means, The switching element included in the image display means is turned OFF, the switching element included in the reference voltage supply means is turned ON, and included in the reference voltage supply means The first drive means and the second drive means are controlled so that a median value of bipolar signal voltages is applied to the signal electrode of the switching element.

  The reference voltage supply means has a configuration corresponding to a plurality of pixels of the image display means, and each pixel electrode is connected (for example, the configuration shown in FIG. 6, FIG. 7, or FIG. 8). Can be.

  The reference voltage supply means has a configuration corresponding to a plurality of pixels for one row of the image display means, and each pixel electrode is connected (for example, the configuration shown in FIG. 8). it can.

  The adjustment means uses the pixel electrode potential of the liquid crystal supplied from the reference voltage supply means as a counter electrode voltage potential of the liquid crystal included in the image display means via an analog buffer (for example, the analog buffer 71). Can be supplied.

  The adjustment means includes the pixel electrode potential of the liquid crystal supplied from the reference voltage supply means via the analog buffer, and further to the image display means via a pass capacitor (for example, a pass capacitor 72). The counter electrode voltage potential of the liquid crystal can be supplied.

  The display method according to one aspect of the present invention includes an adjustment unit (for example, the common voltage adjustment circuit 63 in FIG. 4) that adjusts the counter electrode voltage potential of the liquid crystal, and displays an image by changing the transmittance of the liquid crystal. The display method of the display device is a predetermined method before starting display of an image on an image display unit (for example, the liquid crystal cell 31, the TFT 32, and the capacitor 33 in the opening 91) including at least the liquid crystal and the switching element. In the period (for example, the startup period or the V blanking period in FIG. 9), the switching element included in the image display unit is turned off (for example, the process in step S2 or step S5 in FIG. 10). A reference that includes the same configuration as the portion corresponding to each pixel of the image display unit, and supplies the reference voltage value (for example, VCOM_OUT) to the adjustment unit The switching element included in the pressure supply unit (for example, the liquid crystal cell 31, the TFT 32, and the capacitor 33 in the dummy pixel region) is turned on (for example, the process of step S2 or step S5 in FIG. 10), and in the predetermined period, A median value of bipolar signal voltages is applied to the signal electrode of the switching element included in the reference voltage supply unit (for example, step S3 or step S6 in FIG. 10), and the reference voltage is applied during the predetermined period. The pixel electrode potential applied to the liquid crystal included in the supply unit is supplied to the adjustment unit, and the adjustment unit outputs a counter electrode potential of the liquid crystal based on the supplied pixel electrode potential, and the image The liquid crystal supplied to the display unit and driven in the image display unit is driven to display the image (for example, the step of FIG. 10). Step S4 or step S7).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 4 shows the configuration of the liquid crystal display device 51.

  In addition, the same code | symbol is attached | subjected to the part corresponding to the conventional case, The description is abbreviate | omitted suitably.

  That is, the liquid crystal display device 51 of FIG. 4 includes a liquid crystal panel 61 instead of the liquid crystal panel 11, a controller 62 instead of the controller 14, and a new common voltage adjustment circuit 63. Except for the above, it basically has the same configuration as that of the conventional liquid crystal display device 1. Similarly to the liquid crystal display device 1, the liquid crystal display device 51 performs positive polarity writing and negative polarity writing.

  The liquid crystal panel 61 is provided with a dummy pixel region that is not used for display, that is, not opened, apart from an effective pixel region that is used for display, that is, opened and is in a visible state. .

  The controller 62 controls the timing of applying a voltage to the liquid crystal cell 31 by the signal line driving circuit 12 and the gate line driving circuit 13 and the voltage value to be applied in order to display a predetermined image on the liquid crystal panel 61. In the start-up section before the first frame (or one field, hereinafter the same) is displayed on the liquid crystal panel 61 and the vertical blanking section (V_blank) between frames, the common voltage adjustment circuit 63 Thus, the timing of applying the voltage to the liquid crystal cell 31 by the signal line driving circuit 12 and the gate line driving circuit 13 and the voltage value to be applied are controlled so that the common voltage is adjusted correctly. Details of processing in the start-up section and the vertical blanking section will be described later with reference to FIG.

  The common voltage adjustment circuit 63 includes an analog buffer 71 and a pass capacitor 72. The pixel electrode voltage in the dummy pixel region is supplied to the analog buffer 71 as VCOM_IN, and an output voltage via the analog buffer 71 and the pass capacitor 72 is a liquid crystal. The panel 61 is connected to the liquid crystal panel 61 so as to have the common electrode potential VCOM_OUT.

  Then, the controller 62 controls the gate line driving circuit 13 so that only the gates of the dummy pixels are turned on (active state) before drawing the image of each frame, and the signal line voltage potential in the dummy pixel region. The signal line driver circuit 12 is controlled so that the potential of Vsig_center is written. At that time, the pixel electrode potential obtained in the dummy pixel is supplied to the analog buffer 71 as VCOM_IN.

  The dummy pixel region that is not opened will be described with reference to FIG.

  Due to the characteristics of the TFT 32, the effective applied voltage Vsig_center of the liquid crystal, that is, the median value of the applied voltage at the time of positive polarity writing and the negative polarity writing, due to the influence of the feedthrough, that is, the fluctuation of the signal line voltage that occurs when the gate voltage of the TFT 32 falls. Will shift. For this reason, it is necessary to adjust the optimal common voltage value (common electrode potential).

  In FIG. 5, it is composed of one pixel in the A row (B + 1) column, that is, a liquid crystal cell 31-A- (B + 1), a TFT 32-A- (B + 1), and a capacitor 33-A- (B + 1). This portion is a dummy pixel region.

  The potential of the pixel electrode of the liquid crystal cell 31 in the dummy pixel region (the electrode connected to the TFT 32-A- (B + 1)) is the input voltage VOCM_OUT of the analog buffer 71 of the common voltage adjustment circuit 63. Then, the output voltage via the analog buffer 71 and the pass capacitor 72 is supplied as the common electrode potential VCOM_IN of the liquid crystal panel 61.

  Although the capacitor 33 and the common electrode of the liquid crystal cell 31 are not common in FIG. 5, the capacitor 33 and the common electrode of the liquid crystal cell 31 may be common.

  Here, the analog buffer 71 is interposed when the pixel electrode of the liquid crystal cell 31 in the dummy pixel region is directly connected to the common electrode, the parasitic capacitance is increased, and the feedthrough potential is, for example, A row B in FIG. This is because it is greatly different from the effective pixel portion such as the column. The reason why the pass capacitor 72 is connected after the analog buffer 71 is to stabilize the common electrode potential.

  Further, the dummy pixel region may be a plurality of pixels of one pixel or more.

  Specifically, for example, as shown in FIG. 6, the pixel electrode of the liquid crystal cell 31-A-B in the dummy pixel region and the pixel electrode of the liquid crystal cell 31-A- (B + 1) are connected, and a common voltage adjustment circuit 63 as the input voltage VOCM_OUT of the analog buffer 71, and as shown in FIG. 7, the liquid crystal cell 31-A- (B-1) in the dummy pixel region, the pixel electrode of the liquid crystal cell 31-A-B, and Alternatively, the pixel electrodes of the liquid crystal cell 31-A- (B + 1) may be connected and used as the input voltage VOCM_OUT of the analog buffer 71 of the common voltage adjustment circuit 63.

  6 and 7, the pixel electrodes of a plurality of dummy pixels in the same column are connected to be used as the input voltage VOCM_OUT of the analog buffer 71 of the common voltage adjustment circuit 63. However, in FIG. The pixel electrodes of a plurality of dummy pixels may be connected to obtain the input voltage VOCM_OUT of the analog buffer 71 of the common voltage adjustment circuit 63, or the common voltage adjustment may be performed by connecting the pixel electrodes of a plurality of rows of dummy pixels in a plurality of columns. The input voltage VOCM_OUT of the analog buffer 71 of the circuit 63 may be used.

  In this way, by connecting the pixel electrodes of a plurality of dummy pixels to the input voltage VOCM_OUT of the analog buffer 71 of the common voltage adjustment circuit 63, a larger storage capacitor can be used, and the parasitic capacitance can be reduced. This is preferable because the influence is reduced.

  Further, it is preferable to connect the pixel electrodes of a plurality of dummy pixels to obtain the input voltage VOCM_OUT of the analog buffer 71 of the common voltage adjusting circuit 63. Since the dummy pixel region is not opened, for example, as shown in FIG. When the opening 91 is configured by using the entire pixel of one row as a dummy pixel region, the size of the liquid crystal panel 61 is most effectively used to secure the number of dummy pixels and The effective pixel area can be rectangular, which is preferable.

  In FIG. 8, each capacitor 33 and the common electrode of the liquid crystal cell 31 are assumed to be common. However, the capacitor 33 is not common to the common electrode of the liquid crystal cell 31, for example. You may connect the voltage potential of the median value of a common voltage.

  In FIG. 8, the entire pixels in one row are used as dummy pixel regions, but it goes without saying that two or more rows may be used as dummy pixel regions. The number of pixels in the dummy pixel region is determined experimentally or empirically depending on the balance between the storage capacity of the dummy pixel region and the aperture ratio required in the liquid crystal panel 61. That's fine.

  Even in such a configuration, the optimum VCOM and VCOM_OUT output may differ due to the influence of the wiring resistance of the output wiring from the dummy pixel. In particular, when the number of dummy pixels is small, since the storage capacitance is small, the influence of the parasitic capacitance becomes large, and the possibility that the optimum VCOM and VCOM_OUT outputs are different increases. In such a case, the analog buffer 71 may have a circuit configuration capable of adding or subtracting a constant voltage to the VCOM_OUT output. At this time, if the design of the output wiring is the same, the capacity of the output wiring is not greatly different for each liquid crystal panel 11, so the voltage to be added and subtracted may be a constant value, and it is necessary to adjust for each liquid crystal panel 11. Absent.

  With reference to FIG. 9, the voltage potential applied to the liquid crystal cell 31 by the signal line driving circuit 12 and the gate line driving circuit 13 and the timing thereof under the control of the controller 62 will be described.

  If the potential of the dummy pixel group is indeterminate when the power is turned on, the output of the analog buffer becomes unstable, causing liquid crystal burn-in. Therefore, the controller 62 controls the gate line driving circuit 13 so that only the gate of the dummy pixel region is turned ON (TFT 32 is in an active state) during the start-up period after the power is turned on, and the signal line voltage of the dummy pixel region. The signal line driver circuit 12 is controlled so as to write the potential of Vsig_center as the potential. Then, the output voltage VCOM_IN of the analog buffer 71 at this time becomes the counter common voltage potential supplied to the common electrodes of all the liquid crystal cells 31 after the start-up period ends.

  After that, the controller 62 controls the gate line driving circuit 13 so that only the gates of the dummy pixels are ON (TFT 32 is in an active state) during the V blank period for each frame even when the normal operation is started. In this startup period, the signal line drive circuit 12 is controlled so that the potential of Vsig_center is written as the signal line voltage potential of the dummy pixel region. Thus, the VCOM potential is refreshed every time one frame of image is written.

  With such a configuration, it is not necessary to set the optimum VCOM value generated for each panel because the effective applied voltage Vsig_center of the liquid crystal shifts due to the influence of feedthrough.

  Next, the operation of the liquid crystal display device 51 will be described with reference to the flowchart of FIG.

  In step S1, the controller 62 determines whether the power is turned on. If it is determined in step S1 that the power is not turned on, the process of step S1 is repeated until it is determined that the power is turned on.

  If it is determined in step S1 that the power is turned on, in step S2, the controller 62 controls the gate line driving circuit 13 so that the potential of the gate electrode of the TFT 32 is turned on only for the dummy pixels and the others are turned off. To do.

  In step S3, the controller 62 controls the signal line driving circuit 12 so that the signal electrode potentials are all set to the median value for a certain period of time (the rising period described with reference to FIG. 9).

  The gate line driving circuit 13 is controlled so that only the gates of the dummy pixels are turned on (active state) by the processing of step S2 and step S3, and the potential of Vsig_center is written as the signal line voltage potential of the dummy pixel region. Thus, since the signal line driver circuit 12 is controlled, the pixel electrode potential obtained in the dummy pixel at that time is supplied to the analog buffer 71 as VCOM_OUT. Then, the output voltage via the analog buffer 71 and the pass capacitor 72 is supplied to each pixel as the common electrode potential VCOM_IN of the liquid crystal panel 61.

  In step S4, the controller 62 controls the signal line driving circuit 12 and the gate line driving circuit 13 so as to draw image data for one frame.

  After the drawing of one frame of image data is completed, in step S5, the controller 62 controls the gate line driving circuit 13 so that only the dummy pixels are turned on and the others are turned off.

  In step S6, the controller 62 controls the signal line driving circuit 12 so that the signal electrode potentials are all set to the median value for a certain time (the V blanking period described with reference to FIG. 9).

  The gate line driving circuit 13 is controlled by the processing of step S5 and step S6 so that only the gate of the dummy pixel is turned on (active state), as in the above-described start-up section, and the dummy pixel region Since the signal line drive circuit 12 is controlled so that the signal line voltage potential of Vsig_center is written as the signal line voltage potential, the pixel electrode potential obtained in the dummy pixel at that time is supplied to the analog buffer 71 as VCOM_OUT.

  Since the output voltage via the analog buffer 71 and the pass capacitor 72 is supplied to each pixel as the common electrode potential VCOM_IN of the liquid crystal panel 61, the optimum common electrode potential base is also used in the drawing period of the next frame. Then, image drawing is executed.

  In step S7, the controller 62 controls the signal line driving circuit 12 and the gate line driving circuit 13 so as to draw image data for one frame.

  After the drawing of one frame of image data is completed, in step S8, the controller 62 determines whether there is data for the next frame.

  If it is determined in step S8 that there is data for the next frame, the process returns to step S5, and the subsequent processes are repeated. If it is determined in step S8 that there is no data for the next frame, the process is terminated.

  By performing such a process, in a predetermined time (a start-up period and a vertical blanking period described with reference to FIG. 9) before applying a predetermined charge to the liquid crystal cell in the opening 91 and drawing an image. As a signal line voltage potential, the pixel electrode voltage in the dummy pixel region in which the potential of Vsig_center is written is supplied to the analog buffer 71 of the common voltage adjustment circuit 63 as VCOM_OUT, and the output voltage via the analog buffer 71 and the pass capacitor 72 is , And supplied as the common electrode potential VCOM_IN of the liquid crystal panel 61.

  Therefore, in the liquid crystal display device 51, it is not necessary to set the optimal VCOM value generated for each panel because the effective applied voltage Vsig_center of the liquid crystal shifts due to the influence of feedthrough. Therefore, the VCOM value adjustment process can be omitted from the manufacturing process of the conventional liquid crystal display device, which leads to cost reduction.

  In the above description, an NMOS transistor is assumed as the pixel TFT, and it is assumed that the held pixel potential is lowered due to the influence of feedthrough when the transistor is OFF. However, the pixel TFT is not an NMOS but a PMOS. Good. At this time, the pixel potential held by the influence of the feedthrough rises. However, even in this case, the common electrode potential is automatically set before drawing the image of each frame by using the common voltage adjustment circuit 63. Adjusted to

  Also, when a CMOS switch using both NMOS and PMOS is used in a liquid crystal display device, the influence of feedthrough is reduced, but it is not completely eliminated. Similarly, by applying the present invention, VCOM The quality can be improved while omitting the process of adjusting the value of.

  In addition, in this specification, each step for executing processing is executed in parallel or individually even if processing is not necessarily performed in time series, as well as processing performed in time series in the order described. It also includes the processing.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

It is a block diagram which shows the structure of the conventional liquid crystal display device. It is a figure which shows the structure of each pixel in a liquid crystal panel. It is a figure explaining generation | occurrence | production of a feedthrough electric potential. It is a block diagram which shows the structure of the liquid crystal display device of this invention. It is a figure shown about the connection of a common voltage adjustment circuit and each element of a dummy pixel. It is a figure shown about the connection of a common voltage adjustment circuit and each element of a dummy pixel. It is a figure shown about the connection of a common voltage adjustment circuit and each element of a dummy pixel. It is a figure which shows the example of arrangement | positioning of a dummy pixel and an opening part. It is a timing chart which shows the electric potential applied by a gate line and an honor line. It is a flowchart for demonstrating the process which the liquid crystal display device of this invention performs.

Explanation of symbols

  12 signal line drive circuit, 13 gate line drive circuit, 31 liquid crystal cell, 32 TFT, 33 capacitor, 51 liquid crystal display device, 61 liquid crystal panel, 62 controller, 63 common voltage adjustment circuit, 71 analog buffer, 72 pass capacitor, 91 opening Part

Claims (7)

In a display device that displays an image by changing the transmittance of liquid crystal,
Image display means including at least the liquid crystal and the switching element, and displaying each pixel corresponding to a displayed image;
Adjusting means for adjusting the counter electrode voltage potential of the liquid crystal included in the image display means;
Reference voltage supply means that includes the same configuration as the portion corresponding to each pixel of the image display means, and supplies the liquid crystal pixel electrode potential as a reference voltage value to the adjustment means;
First driving means for controlling on / off of the switching elements included in the image display means and the reference voltage supply means;
Second driving means for controlling a voltage applied to a signal electrode of the switching element included in the image display means and the reference voltage supply means;
Control means for controlling the first drive means and the second drive means,
The control means turns off the switching element included in the image display means and turns on the switching element included in the reference voltage supply means in a predetermined period before starting display of an image on the image display means. And controlling the first driving means and the second driving means so that a median value of the bipolar signal voltages is applied to the signal electrodes of the switching elements included in the reference voltage supply means. apparatus. The adjusting means adds a predetermined voltage based on a wiring resistance when the pixel electrode potential of the liquid crystal is supplied from the reference voltage supply means to the pixel electrode potential of the liquid crystal supplied from the reference voltage supply means. The display device according to claim 1, wherein the voltage is supplied as a counter electrode voltage potential of the liquid crystal included in the image display unit. The display device according to claim 1, wherein the reference voltage supply unit has a configuration corresponding to a plurality of pixels of the image display unit, and each pixel electrode is connected. The display device according to claim 1, wherein the reference voltage supply unit has a configuration corresponding to a plurality of pixels for one row of the image display unit, and each pixel electrode is connected. The adjustment unit supplies the pixel electrode potential of the liquid crystal supplied from the reference voltage supply unit as a counter electrode voltage potential of the liquid crystal included in the image display unit via an analog buffer. Display device. The adjustment means, after passing the pixel electrode potential of the liquid crystal supplied from the reference voltage supply means through an analog buffer, and further via a pass capacitor, the counter electrode voltage of the liquid crystal included in the image display means The display device according to claim 5, wherein the display device is supplied as a potential. In a display method of a display device that has an adjustment unit that adjusts the counter electrode voltage potential of the liquid crystal and displays an image by changing the transmittance of the liquid crystal,
In a predetermined period before starting display of an image on the image display unit including at least the liquid crystal and the switching element, the switching element included in the image display unit is turned off,
In the predetermined period, including the same configuration as the portion corresponding to each pixel of the image display unit, turning on the switching element included in a reference voltage supply unit that supplies the adjustment unit as a reference voltage value,
In the predetermined period, a median value of bipolar signal voltages is applied to the signal electrodes of the switching elements included in the reference voltage supply unit,
In the predetermined period, the pixel electrode potential applied to the liquid crystal of the reference voltage supply unit is supplied to the adjustment unit,
In the adjustment unit, the counter electrode potential of the liquid crystal based on the supplied pixel electrode potential is output and supplied to the image display unit,
An image display method including the step of displaying the image by driving the liquid crystal included in the image display unit.

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