Display device having built-in touch sensor and driving method of the same

Abstract

To provide an AC drive system display device having built-in touch sensor, capable of preventing display defect from occurring, such as bright spot defect, even when device characteristics are slightly changed due to secular change and operation environment, etc.SOLUTION: A liquid crystal display device having built-in touch sensor is provided in which a common voltage signal Vcom including a sensor drive signal as AC signal is applied to a plurality of segment electrodes composing a common electrode in a touch detection period Tsen provided for touch position detection. During the touch detection period Tsen, the sensor drive signal is superimposed on each scan signal G(i) while the sensor drive signal is also superimposed on a data signal D(j). The sensor drive signal is thus superimposed on not only a gate voltage Vg but also a source voltage Vs in each pixel TFT during the touch detection period Tsen. Therefore, reduction in off-margin of the pixel TFT caused by superposition of the sensor drive signal on the gate voltage Vg is suppressed.SELECTED DRAWING: Figure 12A

Description

[Technical Field]

[0001] The following disclosure relates to an AC-driven display device with a built-in touch sensor and a driving method thereof, for example, a liquid crystal display device with a built-in touch sensor and a driving method thereof. [Background technology]

[0002] Active matrix liquid crystal display devices have been known in the past, each having a display section including a plurality of data signal lines (also called "source bus lines"), a plurality of scanning signal lines (also called "gate bus lines") intersecting the plurality of data signal lines, and a plurality of pixel formation sections arranged in a matrix along the plurality of data signal lines and the plurality of scanning signal lines. Such active matrix liquid crystal display devices include a data signal line drive circuit (also called a "data driver" or "source driver") for driving the plurality of data signal lines and a scanning signal line drive circuit (also called a "gate driver") for driving the plurality of scanning signal lines. The scanning signal line drive circuit applies a plurality of scanning signals to the plurality of scanning signal lines so that the plurality of scanning signal lines are sequentially selected during each frame period. The data signal line drive circuit applies a plurality of data signals representing an image signal to be displayed to the plurality of data signal lines in conjunction with this sequential selection of the plurality of scanning signal lines. This provides a plurality of pixel data constituting image data representing an image to be displayed to the plurality of pixel formation sections, respectively.

[0003] Meanwhile, active matrix liquid crystal display devices have increasingly been equipped with touch panels that detect touch positions with fingers, pens, and the like. In-cell touch panels, which incorporate touch sensor functionality into the liquid crystal panel, have been actively developed as touch panels for such active matrix liquid crystal display devices. These in-cell touch panels use, for example, rectangular electrodes segmented into multiple rows and multiple columns. These rectangular electrodes are used as common electrodes for image display and also as sensor electrodes for detecting touch positions using a capacitive touch method. This configuration enables devices to be made thinner and lighter.

[0004] In relation to the present case, Japanese Patent Application Laid-Open No. 2002-40993 discloses an invention aimed at reducing vertical crosstalk in a liquid crystal display device regardless of the type of display pattern. The liquid crystal display device according to this invention is configured so that the potential of the image signal wiring during the vertical blanking period is maintained at the potential of the opposing electrode (common electrode). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-40993 Summary of the Invention [Problem to be solved by the invention]

[0006] In an in-cell touch panel in which the common electrode for image display is also used as a sensor electrode for detecting a touch position as described above, a common voltage signal including an AC signal (a rectangular wave or sine wave signal) having a certain amplitude is supplied to the common electrode during a period set aside for detecting a touch position (hereinafter referred to as the "touch detection period") (the AC signal is a signal that causes the common electrode to function as a sensor electrode, and is hereinafter referred to as the "sensor drive signal").

[0007] However, the inventors of the present application have confirmed that in AC-driven display devices with built-in touch sensors, such as liquid crystal display devices equipped with in-cell touch panels, if the element characteristics change slightly due to changes over time or the operating environment, display defects such as the appearance of bright spots that are not included in the original display image may occur due to the common voltage signal including the sensor drive signal being applied to the common electrode as described above.

[0008] Therefore, it is desirable that such AC-driven display devices with built-in touch sensors as described above do not cause display defects such as bright spot defects even if the element characteristics change slightly over time or due to the operating environment. [Means for solving the problem]

[0009] (1) A display device according to some embodiments of the present invention is a display device including a display panel with a built-in touch sensor, the display panel including a plurality of data signal lines, a plurality of scanning signal lines, a plurality of pixel formation portions provided along the plurality of data signal lines and the plurality of scanning signal lines, and a common electrode provided in common to the plurality of pixel formation portions, a data signal line driving circuit that drives the plurality of data signal lines so that the polarities of the voltages of the plurality of data signal lines relative to the voltage of the common electrode are inverted every predetermined period; a scanning signal line driving circuit that drives a plurality of scanning signal lines; a sensor drive circuit that drives the common electrode with a signal including a sensor drive signal that is an AC signal of a predetermined amplitude during a touch detection period provided for detecting a touch position; Equipped with each of the plurality of pixel formation portions includes a pixel electrode; a display element that is AC-driven by a voltage applied between the pixel electrode and the common electrode; and a pixel transistor that has a first conduction terminal connected to one of the plurality of data signal lines, a second conduction terminal connected to the pixel electrode, and a control terminal connected to one of the plurality of scanning signal lines; the common electrode includes a plurality of segment electrodes; The sensor drive circuit generating and applying a signal including the sensor drive signal to each of the plurality of segment electrodes during the touch detection period; applying a common voltage, which is a voltage common to the plurality of pixel formation portions, to the plurality of segment electrodes as a reference for a voltage to be applied to the display element for image display during a period other than the touch detection period; The scanning signal line driving circuit In a period other than the touch detection period, active signals are sequentially applied to the plurality of scanning signal lines to turn on the pixel transistors so that voltages of the plurality of data signal lines are applied to the pixel electrodes of the plurality of pixel formation portions; During the touch detection period, a signal obtained by superimposing an AC signal corresponding to the sensor drive signal on an inactive signal that turns off the pixel transistor is applied to the plurality of scanning signal lines as a sensor drive corresponding scanning signal; The data signal line drive circuit drives the plurality of data signal lines so that a decrease in the absolute value of the voltage between the first conduction terminal and the control terminal of the pixel transistor caused by superimposing the sensor drive signal on the inactive signal applied to the one scanning signal line is reduced, at least during a same polarity period in which the voltage polarity based on the common voltage matches the voltage of the inactive signal and the voltage of any one of the plurality of data signal lines.

[0010] (2) Furthermore, a display device according to some embodiments of the present invention includes the configuration of (1) above, The data signal line drive circuit superimposes an AC signal corresponding to the sensor drive signal on the voltages of the plurality of data signal lines during the touch detection period at least in the same polarity period.

[0011] (3) Furthermore, a display device according to some embodiments of the present invention includes the configuration of (2) above, The data signal line driving circuit includes: a superposition circuit for generating a signal by superimposing an AC signal corresponding to the sensor drive signal on a data signal to be applied to each data signal line; During periods other than the touch detection period, the data signals to be applied to each data signal line are output to the respective data signal lines, and at least during the same polarity period, the signal generated by the superposition circuit from the data signals to be applied to each data signal line is output to the respective data signal line.

[0012] (4) Furthermore, a display device according to some embodiments of the present invention includes the configuration of (1) above, The data signal line drive circuit shifts the voltage levels of the plurality of data signal lines in a direction away from the voltage level of the inactive signal by an amount corresponding to the amplitude of the sensor drive signal during the touch detection period, at least during the same polarity period.

[0013] (5) Furthermore, a display device according to some embodiments of the present invention includes the configuration of (1) above, The data signal line drive circuit electrically disconnects the plurality of data signal lines from the data signal line drive circuit during the touch detection period at least in the same polarity period.

[0014] (6) Furthermore, a display device according to some embodiments of the present invention includes the configuration of (1), (2), (3), or (5) above, the pixel transistor is an N-channel transistor, The same polarity period is a negative polarity period in which the polarity of the voltage of any one of the plurality of data signal lines is negative with respect to the common voltage.

[0015] (7) Furthermore, a display device according to some embodiments of the present invention includes the configuration of (4) above, the pixel transistor is an N-channel transistor, the same polarity period is a negative polarity period in which the polarity of the voltage of any one of the plurality of data signal lines is negative with respect to the common voltage; The data signal line drive circuit shifts the voltage levels of the plurality of data signal lines in the positive direction by an amount corresponding to the amplitude of the sensor drive signal during the touch detection period, at least in the negative polarity period.

[0016] (8) Furthermore, a display device according to some embodiments of the present invention is a display device including a display panel with a built-in touch sensor, the display panel including a plurality of data signal lines, a plurality of scanning signal lines, a plurality of pixel formation portions provided along the plurality of data signal lines and the plurality of scanning signal lines, and a common electrode provided in common to the plurality of pixel formation portions, a data signal line driving circuit that drives the plurality of data signal lines so that the polarities of the voltages of the plurality of data signal lines relative to the voltage of the common electrode are inverted every predetermined period; a scanning signal line driving circuit that drives a plurality of scanning signal lines; a sensor drive circuit that drives the common electrode with a signal including a sensor drive signal that is an AC signal of a predetermined amplitude during a touch detection period provided for detecting a touch position; Equipped with Each of the plurality of pixel formation portions A pixel electrode; a display element that is AC-driven by a voltage applied between the pixel electrode and the common electrode; a pixel transistor having a first conductive terminal connected to one of the plurality of data signal lines, a second conductive terminal connected to the pixel electrode, and a control terminal connected to one of the plurality of scanning signal lines, the common electrode includes a plurality of segment electrodes; The sensor drive circuit generating and applying a signal including the sensor drive signal to each of the plurality of segment electrodes during the touch detection period; applying a common voltage, which is a voltage common to the plurality of pixel formation portions, to the plurality of segment electrodes as a reference for a voltage to be applied to the display element for image display during a period other than the touch detection period; The scanning signal line driving circuit In a period other than the touch detection period, active signals are sequentially applied to the plurality of scanning signal lines to turn on the pixel transistors so that voltages of the plurality of data signal lines are applied to the pixel electrodes of the plurality of pixel formation portions; During the touch detection period, voltage levels of the plurality of scanning signal lines are shifted from a voltage level of an inactive signal that turns off the pixel transistors to a direction approaching the level of the common voltage by an amount corresponding to an amplitude of the sensor drive signal; During at least a same polarity period, which is a period in which the voltage polarity based on the common voltage matches the voltage of the inactive signal and the voltage of any of the plurality of data signal lines, the data signal line drive circuit shifts the voltage levels of the plurality of data signal lines in a direction away from the voltage level of the inactive signal by an amount corresponding to the amplitude of the sensor drive signal during the touch detection period.

[0017] (9) Furthermore, a method for driving a display device according to some embodiments of the present invention is a method for driving a display device including a display panel with a built-in touch sensor, the display panel including a plurality of data signal lines, a plurality of scanning signal lines, a plurality of pixel formation portions provided along the plurality of data signal lines and the plurality of scanning signal lines, and a common electrode provided in common to the plurality of pixel formation portions, a data signal line driving step of driving the plurality of data signal lines so that polarities of voltages of the plurality of data signal lines relative to the voltage of the common electrode are inverted every predetermined period; a scanning signal line driving step of driving a plurality of scanning signal lines; a sensor driving step of driving the common electrode with a signal including a sensor driving signal that is an AC signal of a predetermined amplitude during a touch detection period provided for detecting a touch position; Equipped with each of the plurality of pixel formation portions includes a pixel electrode; a display element that is AC-driven by a voltage applied between the pixel electrode and the common electrode; and a pixel transistor that has a first conduction terminal connected to one of the plurality of data signal lines, a second conduction terminal connected to the pixel electrode, and a control terminal connected to one of the plurality of scanning signal lines; the common electrode includes a plurality of segment electrodes; The sensor driving step includes: generating and applying a signal including the sensor drive signal to each of the plurality of segment electrodes during the touch detection period; applying a common voltage, which is a voltage common to the plurality of pixel formation portions, to the plurality of segment electrodes as a reference for voltages to be applied to the display elements of the plurality of pixel formation portions for image display during a period other than the touch detection period; The scanning signal line driving step sequentially applying active signals to the plurality of scanning signal lines to turn on the pixel transistors so that voltages of the plurality of data signal lines are applied to the pixel electrodes in the plurality of pixel formation portions during a period other than the touch detection period; applying, to the plurality of scanning signal lines, as a sensor drive corresponding scanning signal, a signal obtained by superimposing an AC signal corresponding to the sensor drive signal on an inactive signal that turns off the pixel transistor during the touch detection period; The data signal line driving step drives the plurality of data signal lines so that a decrease in the absolute value of the voltage between the first conduction terminal and the control terminal of the pixel transistor caused by superimposing the sensor drive signal on the inactive signal applied to the one scanning signal line in each pixel formation portion is reduced, at least during a same polarity period in which the voltage polarity based on the common voltage matches the voltage of the inactive signal and the voltage of any one of the plurality of data signal lines. [Effects of the Invention]

[0018] In some of the above embodiments of the present invention, in a display device including a display panel with a built-in touch sensor, the display panel includes a plurality of data signal lines, a plurality of scanning signal lines, a plurality of pixel formation portions provided along the plurality of data signal lines and the plurality of scanning signal lines, and a common electrode provided in common to the plurality of pixel formation portions, the plurality of data signal lines are driven so that the polarity of the voltage of the plurality of data signal lines is inverted every predetermined period with respect to a voltage of the common electrode (common voltage). Also, during a touch detection period provided for detecting a touch position, a signal including a sensor drive signal that is an AC signal of a predetermined amplitude is generated and applied to each of a plurality of segment electrodes constituting the common electrode, and during the touch detection period, the plurality of scanning signal lines are applied with a signal in which an AC signal corresponding to the sensor drive signal is superimposed on an inactive signal that turns off a pixel transistor. At least during a same polarity period during which the voltage polarity, relative to the common voltage, of the inactive signal of the scanning signal line is the same as that of any of the plurality of data signal lines, the plurality of data signal lines are driven so that a decrease in the absolute value of the voltage between the first conduction terminal and the control terminal of the pixel transistor due to the superposition of the sensor drive signal on the inactive signal of the scanning signal line is reduced. For this purpose, for example, an AC signal corresponding to the sensor drive signal is superimposed on the data signal to be applied to each data signal line. Therefore, the superimposition of the AC signal corresponding to the sensor drive signal on the inactive signal of the scanning signal line during the touch detection period not only prevents an increase in leakage current when the pixel transistor is off due to application of a signal including the sensor drive signal to each segment electrode as a common electrode element, but also reduces a decrease in the absolute value of the voltage between the first conduction terminal and the control terminal of the pixel transistor due to the superimposition of the AC signal corresponding to the sensor drive signal on the inactive signal of the scanning signal line, thereby suppressing a decrease in the off margin of the pixel transistor during the touch detection period and suppressing the occurrence of display defects such as bright spot defects even if the characteristics of the pixel transistor are shifted in the negative direction.

[0019] Furthermore, in some other embodiments of the present invention, in a display device including a display panel having a built-in touch sensor, the display panel including a plurality of data signal lines, a plurality of scanning signal lines, a plurality of pixel formation portions provided along the plurality of data signal lines and the plurality of scanning signal lines, and a common electrode provided in common to the plurality of pixel formation portions, the plurality of data signal lines are driven so that the polarity of the voltage of the plurality of data signal lines is inverted every predetermined period with reference to the voltage of the common electrode (common voltage), and during a touch detection period provided to detect a touch position, a signal including a sensor drive signal which is an AC signal of a predetermined amplitude is generated and applied to each of a plurality of segment electrodes constituting the common electrode, and the plurality of scanning signal lines are driven so that the voltage levels of the plurality of scanning signal lines are shifted in a direction approaching the level of the common voltage by an amount corresponding to the amplitude of the sensor drive signal from the voltage level of an inactive signal that turns off pixel transistors during the touch detection period. The plurality of data signal lines are driven such that, at least during a same-polarity period, which is a period during which the voltage polarity, relative to a common voltage, of the inactive signals of the scanning signal lines matches that of any of the voltages of the plurality of data signal lines, the voltage levels of the plurality of data signal lines are shifted in a direction away from the voltage level of the inactive signals by an amount corresponding to the amplitude of the sensor drive signal during the touch detection period. Therefore, by shifting the voltage levels of the inactive signals of the scanning signal lines in the touch detection period in a direction toward the level of the common voltage by an amount corresponding to the amplitude of the sensor drive signal, not only is an increase in leakage current when the pixel transistors are turned off due to application of signals including the sensor drive signal to each segment electrode as a common electrode element prevented, but also, by shifting the voltage levels of the plurality of data signal lines in a direction away from the voltage level of the inactive signals by an amount corresponding to the amplitude of the sensor drive signal during the touch detection period at least during the same-polarity period, the decrease in the off margin of the pixel transistors during the touch detection period is suppressed, and the occurrence of display defects such as bright spot defects is suppressed even if the characteristics of the pixel transistors are shifted in a negative direction. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a block diagram showing an overall configuration of a display device with a built-in touch sensor according to an embodiment; [Figure 2] FIG. 3 is a circuit diagram showing an electrical configuration of a pixel formation portion in the embodiment. [Figure 3] 3A to 3C are schematic diagrams for explaining a configuration example of a touch sensor in the embodiment. [Figure 4] FIG. 2 is a block diagram showing a configuration of a sensor drive circuit in the embodiment. [Figure 5] FIG. 2 is a block diagram showing a configuration related to touch position detection in the scanning signal line driving circuit in the embodiment. [Figure 6] FIG. 2 is a block diagram showing a configuration related to touch position detection in the data signal line driving circuit in the embodiment. [Figure 7] 4 is a signal waveform diagram showing a drive signal for a display unit in the touch sensor-embedded display device according to the embodiment. FIG. [Figure 8A] FIG. 10 is a waveform diagram showing a voltage waveform for driving a pixel of interest in a display device with a built-in touch sensor as a comparative example. [Figure 8B] FIG. 10 is a circuit diagram showing an electrical configuration of a pixel of interest in the comparative example. [Figure 9A] FIG. 10 is a voltage waveform diagram for explaining the influence of a sensor drive signal on the circuit operation of a pixel of interest in the comparative example. [Figure 9B] FIG. 10 is a characteristic diagram of a pixel TFT for explaining the problem in the comparative example. [Figure 10A] FIG. 10 is a voltage waveform diagram for explaining the influence of a sensor drive signal on the circuit operation of a pixel of interest in a display device with a built-in touch sensor as an improved example. [Figure 10B] FIG. 10 is a characteristic diagram of the pixel TFT of the pixel of interest in the improved example. [Figure 11A] FIG. 10 is a voltage waveform diagram for explaining a problem in the above-described improved example. [Figure 11B] FIG. 10 is a circuit diagram showing the electrical configuration of a pixel of interest for explaining a display defect in the improved example. [Figure 11C] 10 is a diagram showing the characteristics of a pixel TFT in a pixel of interest for explaining the occurrence of a display defect (bright spot defect) in the above-mentioned improved example. FIG. [Figure 11D] 10A and 10B are diagrams showing display defects (bright spot defects) in the above-mentioned improved example. [Figure 12A] FIG. 10 is a voltage waveform diagram for explaining the influence of a sensor drive signal on the circuit operation of a pixel of interest in the embodiment. [Figure 12B] FIG. 2 is a circuit diagram showing an electrical configuration of the pixel of interest in the embodiment. [Figure 12C] 5A and 5B are diagrams illustrating the characteristics of a pixel TFT in the pixel of interest in the embodiment. [Figure 12D] FIG. 10 is a diagram for explaining the effects of the embodiment. [Figure 13] FIG. 10 is a waveform diagram showing a voltage waveform for driving a pixel of interest in a first modified example of the embodiment. [Figure 14] FIG. 10 is a waveform diagram showing a voltage waveform for driving a pixel of interest in a second modified example of the embodiment. [Figure 15] FIG. 10 is a block diagram showing a configuration of a data signal line driving circuit according to a third modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments will be described with reference to the accompanying drawings. In each transistor described below, the gate terminal corresponds to the control terminal, one of the drain terminal and the source terminal corresponds to the first conduction terminal, and the other corresponds to the second conduction terminal. Although all transistors in this embodiment are N-channel, the present invention is not limited to this. In an N-channel transistor, the higher-potential of the two conduction terminals is the drain terminal and the lower-potential is the source terminal. In this specification, even if the potentials of the two conduction terminals are reversed during operation, one of the two conduction terminals will be referred to as the "drain terminal" and the other as the "source terminal." In this specification, unless otherwise specified, "connection" means "electrical connection," and includes not only direct connection but also indirect connection via another element, within the scope of the present invention.

[0022] <1. Embodiment> <1.1 Overall configuration and operation overview> FIG. 1 is a block diagram showing the overall configuration of a display device with a built-in touch sensor according to one embodiment. This display device is an active matrix liquid crystal display device, and as shown in FIG. 1, includes a display control circuit 100, a scanning signal line driving circuit 200, a data signal line driving circuit 300, and a display unit 500 constituting a liquid crystal panel. In this embodiment, the scanning signal line driving circuit 200 and the display unit 500 are formed on the same substrate (on an active matrix substrate, which is one of two substrates included in the liquid crystal panel). That is, the scanning signal line driving circuit 200 is a monolithic gate driver (GDM circuit). Furthermore, the display unit 500 has a built-in touch sensor, and a liquid crystal panel 600 serving as the display panel is integrated with the touch panel. That is, the display device according to this embodiment is a liquid crystal display device equipped with an in-cell touch panel. Furthermore, the display device according to this embodiment includes a sensor driving circuit 400 that drives a sensor electrode (described later) for detecting a touch position on the display unit 500 of the liquid crystal panel integrated with the touch panel. In this embodiment, as shown in FIG. 1, the data signal line driving circuit 300 is realized by a data driver IC 310, and the data driver IC 310 has a sensor driving circuit 400 built therein.

[0023] 1, a plurality of data signal lines DL and a plurality of scanning signal lines GL intersecting the plurality of data signal lines DL are arranged in the display unit 500. The display unit 500 also has a plurality of pixel formation portions arranged in a matrix along the plurality of data signal lines DL and the plurality of scanning signal lines GL, and each pixel formation portion corresponds to one of the plurality of data signal lines DL and one of the plurality of scanning signal lines GL.

[0024] FIG. 2 is a circuit diagram showing the electrical configuration of one pixel formation portion 50. The pixel formation portion 50 includes a pixel TFT 51, which is a thin-film transistor serving as a switching element, having a gate terminal connected to a corresponding scanning signal line GL and a source terminal connected to a corresponding data signal line DL; a pixel electrode 53 connected to the drain terminal of the pixel TFT 51; and a common electrode 55 provided in common to a plurality of pixel formation portions 50 formed in the display unit 500. Liquid crystal is filled between the plurality of pixel electrodes 53 and the common electrode 55, and a liquid crystal capacitance is formed as a pixel capacitance Cp by the pixel electrode 53 and the common electrode 55. Note that the configuration of the pixel formation portion 50 is not limited to the configuration shown in FIG. 2, and an auxiliary capacitance may be provided in parallel with the pixel capacitance Cp serving as the liquid crystal capacitance. As described below, the common electrode 55 is also used as an electrode for touch position detection, and is therefore divided into a plurality of segment-like electrodes (see FIG. 3 described below).

[0025] The TFTs 51 in the pixel formation section 50 are typically thin film transistors having an oxide semiconductor layer (hereinafter referred to as "oxide TFTs"). Employing oxide TFTs can reduce off-leakage. For example, the oxide TFT may be a thin film transistor having an oxide semiconductor layer containing an In-Ga-Zn-O-based semiconductor (e.g., indium gallium zinc oxide). Note that a TFT other than an oxide TFT, such as a thin film transistor using low-temperature polysilicon in the semiconductor layer (LTPS-TFT), may also be employed as the TFTs 51 in the pixel formation section 50.

[0026] An outline of the operation of the display device according to this embodiment, configured as shown in Fig. 1, will be described below. The display control circuit 100 receives an image signal DAT and a timing control signal TG sent from the outside, and outputs a digital video signal DV, a scanning-side control signal GCTL for controlling the operation of the scanning signal line driving circuit 200, and a data-side control signal DCTL for controlling the operation of the data signal line driving circuit 300. The scanning-side control signal GCTL includes a gate start pulse signal, a gate clock signal, a touch detection control signal CTS (described later), and the like. The data-side control signal DCTL includes a data start pulse signal, a data clock signal, and a latch strobe signal. The touch detection control signal CTS included in the scanning-side control signal GCTL is also included in the data-side control signal DCTL.

[0027] The scanning signal line driving circuit 200 sequentially applies active scanning signals to the multiple scanning signal lines GL in the display unit 500 based on the scanning side control signal GCTL sent from the display control circuit 100, and repeats the application of the active scanning signal to each scanning signal line GL once every frame period (one vertical scanning period). That is, the scanning signal line driving circuit 200 scans the scanning signal lines GL. During this scanning operation, inactive scanning signals are applied to scanning signal lines other than the scanning signal lines to which the active scanning signals are applied. The active scanning signals are signals that turn the pixel TFTs 51 on, and the inactive scanning signals are signals that turn the pixel TFTs 51 off.

[0028] The touch detection control signal CTS included in the scanning-side control signal GCTL is a signal that is active during a touch detection period Tsen provided for detecting a touch position and is inactive during periods other than the touch detection period. During the touch detection period Tsen, the common electrode 55 is used as a sensor electrode, and therefore scanning of the scanning signal lines GL cannot be performed (details will be described later). However, in this embodiment, as will be described later, the touch detection control signal CTS is generated as a signal that is active (high level) only during a vertical blanking period Tbl. However, instead of this, as in a modified example described later, the touch detection control signal CTS may be active during periods other than the vertical blanking period Tbl. In this case, scanning of the scanning signal lines GL is stopped during the touch detection period Tsen.

[0029] The data signal line driving circuit 300 applies a data signal as a driving video signal to the data signal line DL based on the digital video signal DV and the data-side control signal DCTL sent from the display control circuit 100. At this time, the data signal line driving circuit 300 sequentially holds the digital video signal DV indicating the voltage to be applied to each data signal line DL at the timing when a pulse of the data clock signal is generated. Then, at the timing when a pulse of the latch strobe signal is generated, the held digital video signal DV for one pixel row is converted to an analog voltage. The converted analog voltage is simultaneously applied to all data signal lines DL in the display unit 500 as a data signal for one pixel row. The voltage of each data signal line DL (the voltage of the data signal D(i) applied to the data signal line DL) is applied to the pixel electrode 53 of the pixel formation portion corresponding to the scanning signal line to which an active scanning signal is applied, and is written as a data voltage (pixel data) to the pixel capacitance Cp.

[0030] In this manner, by applying a scanning signal to the scanning signal line GL and a data signal to the data signal line DL, the voltage of the data signal line DL is written as a data voltage into the pixel capacitance Cp in each pixel formation portion 50, and an image corresponding to the image signal DAT sent from outside is displayed on the display portion 500.

[0031] 1.2 Configuration and operation for touch position detection Next, with reference to FIGS. 3 to 8, a configuration and operation for detecting a touch position on a display unit 500 in a touch sensor-embedded display device according to this embodiment will be described, referring to driving of the display unit 500 for display operation. Note that hereinafter, the plurality of scanning signal lines GL in the display unit 500 will be referred to as "scanning signal lines GL1 to GLn" when distinguished from one another, and the plurality of data signal lines DL in the display unit 500 will be referred to as "data signal lines DL1 to DLm" when distinguished from one another. Furthermore, the scanning signal line driving circuit 200 generates a plurality of scanning signals G(1) to G(n) and applies them to the plurality of scanning signal lines GL1 to GLn, respectively, to selectively drive the plurality of scanning signal lines GL1 to GLn, and the data signal line driving circuit 300 generates a plurality of data signals D(1) to D(m) and applies them to the plurality of data signal lines DL1 to DLm, respectively, to drive the plurality of data signal lines DL1 to DLn.

[0032] FIG. 3 is a schematic diagram illustrating a configuration example of a touch sensor 510 according to this embodiment. The liquid crystal panel 600 according to this embodiment is composed of an active matrix substrate (also called a "TFT array substrate") 610, which are two glass substrates arranged facing each other with liquid crystal sandwiched therebetween, and a counter substrate. The active matrix substrate is formed with the plurality of pixel formation portions 50 constituting the display unit 500, a plurality (m) of data signal lines DL1 to DLm, a plurality (n) of scanning signal lines GL1 to GLn intersecting the plurality of data signal lines DL1 to DLm, and a scanning signal line drive circuit 200, and the like, and a color filter is formed on the counter substrate. A common electrode 55, which is a component common to the plurality of pixel formation portions 50, is composed of a plurality of rectangular common electrode elements 511 arranged in a matrix on the active matrix substrate 610. That is, in this embodiment, the common electrode 55 is segmented into a plurality of common electrode elements 511 to detect a touch position (hereinafter, each common electrode element is also referred to as a "segment electrode"), and during the touch detection period Tsen, scanning of the scanning signal lines GL for display is stopped, and a common voltage signal Vcom including a sensor drive signal Ssen (described later) (as an AC component) is applied to the common electrode 55, causing the common electrode 55 to function as a sensor electrode. Note that one common electrode element (segment electrode) 511 is, for example, a substantially square with one side measuring several millimeters, and is larger than the pixel electrode 53.

[0033] A data driver IC (also referred to as a "source driver IC") 310 is mounted in the frame region of the active matrix substrate 610. This data driver IC 310 not only functions as the data signal line driving circuit 300 in this embodiment but also includes a sensor driving circuit 400 for implementing the touch sensor function. The active matrix substrate 610 is also provided with a plurality of sensor signal lines SL that correspond one-to-one to the plurality of segment electrodes (common electrode elements) 511 and extend parallel to the data signal lines DL. Each segment electrode 511 is electrically connected to its corresponding sensor signal line SL via several contact holes 513 and is connected to the sensor driving circuit 400 via the corresponding sensor signal line SL. Each segment electrode 511 is used to apply a voltage for image display between itself and the pixel electrode 53 and is also used to form a capacitance for detecting a touch position.

[0034] 4 is a block diagram showing the configuration of a sensor drive circuit 400 in this embodiment. The sensor drive circuit 400 includes a common voltage source 60 that generates a common voltage VCOM, which is a fixed voltage to be applied to the common electrode 55 (each segment electrode 511) for display operation, and a sensor drive signal generator 40 that generates a sensor drive signal Ssen for obtaining an individual sensor drive signal Ssl to be applied as the common voltage signal Vcom to each segment electrode 511 during a touch detection period Tsen for touch position detection. The sensor drive circuit 400 also includes a plurality of sensor drive unit circuits 45 corresponding to the plurality of sensor signal lines SL, respectively, and a position detection processing circuit 47 that identifies the touch position based on a touch detection result signal Std (described later) obtained by applying the individual sensor drive signal Ssl to each segment electrode 511.

[0035] As shown in FIG. 4, each sensor driving unit circuit 45 includes a driving signal output circuit 41, a touch detection circuit 42, and a switching circuit 43. The driving signal output circuit 41 outputs a signal including the sensor driving signal Ssen generated by the sensor driving signal generator 40 as an individual sensor driving signal Ssl to a sensor signal line SL corresponding to the sensor driving unit circuit 45 (hereinafter, when focusing on one sensor driving unit circuit 45, this will be referred to as the "corresponding sensor signal line") during the touch detection period Tsen. This individual sensor driving signal Ssl corresponds to the common voltage signal Vcom during the touch detection period Tsen and is a signal equivalent to the sensor driving signal Ssen in terms of AC, but its DC component is set to a value corresponding to the level of the common voltage VCOM as a fixed voltage. In this embodiment, the DC component of this individual sensor driving signal Ssl is set so that its minimum value coincides with the level of the common voltage VCOM as a fixed voltage. However, instead, the DC component may be set so that its central value coincides with the level of the common voltage VCOM. The switching circuit 43 is a circuit for switching the output from the sensor drive unit circuit 45, i.e., the voltage or signal to be output to the corresponding sensor signal line SL, between the common voltage VCOM and the individual sensor drive signal Ssl, based on the touch detection control signal CTS included in the data-side control signal DCTL, and outputs the common voltage VCOM to the corresponding sensor signal line SL when the touch detection control signal CTS is inactive, and outputs the individual sensor drive signal Ssl to the corresponding sensor signal line SL when the touch detection control signal CTS is active. As a result, the common voltage VCOM as a fixed voltage is applied as the common voltage signal Vcom to each segment electrode 511 constituting the common electrode 55 except during the touch detection period Tsen, and the individual sensor drive signal Ssl including the sensor drive signal Ssen as an AC component is applied during the touch detection period Tsen.

[0036] The drive signal output circuit 41 sets the output impedance to an appropriate value when the individual sensor drive signal Ssl is output to the corresponding sensor signal line SL, and also functions as a buffer circuit to prevent the input side of the individual sensor drive signal Ssl from being affected by the output side (the output current) of the drive signal output circuit 41. The touch detection circuit 42 is configured to sense a change in capacitance of the segment electrode connected to the corresponding sensor signal line SL when the touch detection control signal CTS is active (during the touch detection period Tsen) based on a change in the output voltage of the touch detection circuit 42 that is based on the current flowing through the corresponding sensor signal line SL. With this configuration, the presence or absence of a touch at the position of the segment electrode 511 connected to the corresponding sensor signal line SL is detected, and a touch detection result signal Std indicating the detection result is output from the touch detection circuit 42.

[0037] As described above, a touch detection result signal Std indicating whether or not a touch has occurred at the position of each segment electrode 511 on the display unit 500 is output from the touch detection circuit 42 connected to that segment electrode 511. When a touch operation is performed on any position on the display unit 500, the position detection processing circuit 47 in the sensor drive circuit 400 identifies the touch position based on the touch detection result signal Std output from each touch detection circuit 42, and generates a touch position signal Stp indicating the touch position. This touch position signal Stp is sent to the display control circuit 100 as shown in FIG. 1, and the display control circuit 100 performs processing in accordance with the touch position signal Stp (such as transferring information indicating the touch position to a host computer of the display device).

[0038] 1.2.1 Configuration related to touch position detection in the scanning signal line driving circuit The sensor drive signal Ssen generated by the sensor drive signal generator 40 as described above is output from the sensor drive circuit 400 and is also provided to the scanning signal line drive circuit 200 and the data signal line drive circuit 300, as shown in FIG.

[0039] 5 is a block diagram showing a configuration for generating scan signals G(1) to G(n) on which the sensor drive signal Ssen is superimposed based on the sensor drive signal Ssen during the touch detection period Tsen in which the touch detection control signal CTS is active in the scan signal line drive circuit 200. As shown in FIG. 5, the scan signal line drive circuit 200 in this embodiment includes a scan signal generation circuit 250 that generates normal scan signals Go(1) to Go(n) necessary for scanning for display operation, as well as a superimposing circuit 21 and n switching circuits 23 corresponding to the n scan signal lines GL1 to GLn formed in the display unit 500, respectively.

[0040] The superimposing circuit 21 receives the sensor drive signal Ssen and a low-level voltage (hereinafter referred to as a "gate low voltage") Vgl of the scan signal Go(i) (i = 1 to n) (hereinafter referred to as an "original scan signal" to distinguish it from the scan signal output from the scan signal line drive circuit 200) generated by the scan signal generation circuit 250, and generates a signal by superimposing the sensor drive signal on the gate low voltage Vgl as the sensor drive-compatible scan signal Gsen. The switching circuit 23 is a circuit for switching the scan signal G(i) to be applied to each scan signal line GLi between the original scan signal Go(i) and the sensor drive-compatible scan signal Gsen based on the touch detection control signal CTS included in the scan-side control signal GCTL. When the touch detection control signal CTS is inactive, the switching circuit 23 outputs the original scan signal Go(i) as the scan signal G(i) to the scan signal line GLi, and when the touch detection control signal CTS is active, the switching circuit 23 outputs the sensor drive-compatible scan signal Gsen as the scan signal G(i) to the scan signal line GLi (i = 1 to n).

[0041] 7 is a signal waveform diagram showing signals for driving the display unit 500 in the touch sensor-embedded display device according to this embodiment. In this embodiment, a frame inversion driving method is adopted to drive the liquid crystal panel 600. In FIG. 7, "Tf(positive)" indicates a frame period in which a positive data signal D(j) is applied to the data signal line DLj (hereinafter referred to as a "positive frame period"), "Tf(negative)" indicates a frame period in which a negative data signal D(j) is applied to the data signal line DLj (hereinafter referred to as a "negative frame period") (j = 1 to m), and "Tbl" indicates a vertical blanking period. Here, the polarity of the data signal D(j) refers to the voltage polarity of the data signal D(j) relative to the common voltage VCOM, and corresponds to the polarity of the voltage applied to the liquid crystal by the pixel electrode 53 and the common electrode 55 relative to the common voltage VCOM. Fig. 7(D) exemplarily shows a general waveform of such a data signal D(j), and Fig. 7(E) shows the waveform of the data signal D(j) when a black and white screen (described later) is displayed (see Fig. 11(D) and Fig. 12(D)). In this embodiment, the touch detection control signal CTS is generated by the display control circuit 100 as a signal that becomes active (high level) only during a touch detection period Tsen provided in a vertical blanking period Tbl.

[0042] According to the above configuration as shown in FIG. 5, as shown in FIG. 7, scanning signals G(1) to G(n) on which the sensor drive signal Ssen is superimposed are generated only while the touch detection control signal CTS is active (high level), and these scanning signals G(1) to G(n) are applied to the scanning signal lines GL1 to GLn, respectively.

[0043] <1.2.2 Configuration related to touch position detection in the data signal line driving circuit> 6 is a block diagram showing a configuration for generating data signals D(1) to D(m) on which the sensor drive signal Ssen is superimposed in the data signal line drive circuit 300 during a touch detection period Tsen in which the touch detection control signal CTS is active, based on the sensor drive signal Ssen. As shown in FIG. 6, the data signal line drive circuit 300 in this embodiment includes a data signal generation circuit 350 that generates normal data signals Do(1) to Do(m) representing an image to be displayed (hereinafter referred to as "original data signals" to distinguish them from data signals output from the data signal line drive circuit 300), as well as m unit output circuits 35 corresponding to m data signal lines DL1 to DLm formed in the display unit 500. Each unit output circuit 35 outputs a data signal D(j) (j=1 to m) to a corresponding data signal line DLj (hereinafter referred to as a "corresponding data signal line" when focusing on one unit circuit).

[0044] 6, each unit output circuit 35 includes a superposition circuit 31 and a switching circuit 33. The superposition circuit 31 generates a signal by superimposing a sensor drive signal Ssen on an original data signal Do(j) corresponding to a corresponding data signal line as a test signal superimposed data signal Ds(j) (j = 1 to m). In each unit output circuit 35, the switching circuit 33 is a circuit for switching the data signal D(j) to be applied to the corresponding data signal line DLj between the original data signal Do(i) and the test signal superimposed data signal Ds(j) based on a touch detection control signal CTS included in the data-side control signal DCTL. When the touch detection control signal CTS is inactive, the switching circuit 33 outputs the original data signal D(j) to the corresponding data signal line DLj as the data signal D(j), and when the touch detection control signal CTS is active, the switching circuit 33 outputs the test signal superimposed data signal Ds(j) to the corresponding data signal line DLj as the data signal D(j) (j = 1 to m).

[0045] According to the above configuration as shown in FIG. 6, as shown in FIG. 7, data signals D(1) to D(m) on which the sensor drive signal Ssen is superimposed are generated only while the touch detection control signal CTS is active (high level), and these data signals D(1) to D(m) are applied to the data signal lines DL1 to DLm, respectively.

[0046] 1.3 Influence of sensor drive signals on circuit operation in pixel formation area Hereinafter, focusing on one pixel formation portion 50 in the display unit 500 (hereinafter, the pixel formation portion 50 of interest will be referred to as the "pixel of interest" and denoted by the symbol "PixA"), the influence of the sensor drive signal Ssen on the circuit operation of the pixel of interest PixA will be described. Note that, for convenience of explanation, the liquid crystal panel 600 will be assumed to be a normally black type, but it may also be a normally white type.

[0047] In this embodiment, as described above, during the touch detection period Tsen when the touch detection control signal CTS is active, a common voltage signal Vcom including the sensor drive signal Ssen, which is an AC signal (voltage signal) with a predetermined amplitude Vx, is applied as an individual sensor drive signal Ssl to each segment electrode (each common electrode element) 511. During the touch detection period Tsen, an AC signal corresponding to the sensor drive signal Ssen is superimposed on each scanning signal G(i) and each data signal D(j) ( FIG. 7 ). Here, the amplitude Vx of the AC signal refers to the difference between the maximum and minimum values ​​of the AC signal. Before describing the influence of the sensor drive signal Ssen on the circuit operation of the pixel of interest PixA in this embodiment, we will first describe the influence of the sensor drive signal Ssen on the circuit operation of the pixel of interest PixA in a touch-sensor-embedded display device (hereinafter referred to as a “comparative example”) in which an AC signal corresponding to the sensor drive signal Ssen is not superimposed on any scanning signal G(i) or any data signal D(j). Note that the same reference numerals are used to designate parts of this comparative example that are the same as or correspond to those of this embodiment.

[0048] <1.3.1 Influence on circuit operation of the pixel of interest in the comparative example> 8A is a waveform diagram showing the voltage Vg at the gate terminal of the pixel TFT 51 (hereinafter referred to as the "gate voltage") applied by the scanning signal G(i), the voltage Vs at the source terminal of the pixel TFT 51 (hereinafter referred to as the "source voltage") applied by the data signal D(j), and the common voltage signal Vcom applied to the common electrode 55 connected to the drain terminal (pixel electrode) of the pixel TFT 51 via the pixel capacitance Cp to drive the pixel of interest PixA in this comparative example. Note that a circuit diagram showing the electrical configuration of the pixel of interest PixA is shown in FIG. 8B.

[0049] FIG. 8A shows the waveforms of the gate voltage Vg, source voltage Vs, and common voltage signal Vcom at a pixel of interest PixA during an nth frame period Tfn (positive polarity frame period Tf) and an n+1th frame period Tfn+1 (negative polarity frame period Tf). In FIG. 8A, a thick solid line indicates the waveform of the gate voltage Vg based on a scanning signal G(i), a thick dotted line indicates the waveform of the common voltage signal Vcom, and a thick dashed-dotted line indicates the waveform of the source voltage Vs based on a data signal D(j). The common voltage signal Vcom corresponds to the individual sensor drive signal Ssl, which includes the sensor drive signal Ssen, a square-wave or sinusoidal voltage signal with a predetermined amplitude Vx as shown in FIG. 8A, during a touch detection period Tsen. These points also apply to FIGS. 9A, 10A, 11A, and 12A, which will be described later.

[0050] Fig. 9A is a voltage waveform diagram illustrating the influence on the circuit operation of the pixel of interest PixA in this comparative example. In Fig. 9A, the thin solid line indicates the waveform of the voltage Vd (hereinafter referred to as "drain voltage") at the drain terminal of the pixel TFT 51 included in the pixel of interest PixA, i.e., the pixel voltage Vp, which also applies to Figs. 10A, 11A, and 12A described below. Fig. 9B is a characteristic diagram of the pixel TFT 51 in the pixel of interest PixA.

[0051] 9A, the touch detection period Tsen is provided within the vertical blanking period Tbl, and the pixel electrode 53 connected to the drain terminal of the pixel TFT 51 is in a floating state during the touch detection period Tsen. Therefore, the individual sensor drive signal Ssl serving as the common voltage signal Vcom during the touch detection period Tsen is superimposed on the drain voltage Vd (=pixel voltage Vp) via the pixel capacitance Cp. As a result, as shown in FIG. 9A, the off-bias Voff_S+=Vgl-Vd of the pixel TFT 51 during the touch detection period Tsen is deeper by the amplitude Vx of the sensor drive signal Ssen (individual sensor drive signal Ssl) than the off-bias Voff_NS+=Vgl-Vd of the pixel TFT 51 during periods other than the touch detection period Tsen. Since the liquid crystal panel 600 is a normally black type, when white is displayed, the off bias Voff_S+=Vgl-Vd (white) during the touch detection period Tsen becomes particularly deep. As a result, as shown in FIG. 9B, the leakage current Id(off) in the pixel TFT 51 when it is off increases, and the holding voltage in the pixel capacitance Cp becomes prone to decrease.

[0052] <1.3.2 Impact on circuit operation of the pixel of interest in the improvement example> To address this problem in the comparative example, it is conceivable to suppress deepening of the off-bias of the pixel TFT 51 by superimposing a sensor drive signal Ssen on each scanning signal G(i) during the touch detection period Tsen. The following describes the influence of the sensor drive signal Ssen on the circuit operation of the pixel of interest Pix_A in a touch sensor-embedded display device having such a configuration (hereinafter referred to as the "improved example"). Note that the same reference numerals are used to designate parts of the improved example that are the same as or correspond to those of the present embodiment. To superimpose the sensor drive signal Ssen on each scanning signal G(i) during the touch detection period Tsen, for example, a scanning signal line drive circuit 200 configured as shown in FIG. 5 may be used in the improved example.

[0053] FIG. 10A is a voltage waveform diagram illustrating the influence of the sensor drive signal Ssen (individual sensor drive signal Ssl) on the circuit operation of the pixel of interest PixA in this improved example. FIG. 10B is a characteristic diagram of the pixel TFT 51 in the pixel of interest PixA. As shown in FIG. 10A, during the touch detection period Tsen, the drain voltage Vd increases according to the amplitude Vx of the sensor drive signal Ssen (individual sensor drive signal Ssl), and the scan signal G(i) also increases according to the amplitude Vx of the sensor drive signal Ssen. Therefore, the off-bias Voff_S+=Vgl-Vd of the pixel TFT 51 during the touch detection period Tsen is equal to the off-bias Voff_NS+=Vgl-Vd of the pixel TFT 51 during periods other than the touch detection period Tsen. As a result, as shown in FIG. 10B, the leakage current Id(off) of the pixel TFT 51 during the touch detection period Tsen is small, similar to the leakage current Id(off) of the pixel TFT 51 during the off-state during periods other than the touch detection period Tsen.

[0054] However, in this improved example, when a specific display is performed (for example, when a screen with a black upper portion and a white lower portion (hereinafter referred to as a "black and white screen") is displayed), bright spots that are not included in the original display may appear. Hereinafter, the occurrence of such bright spot defects in this improved example will be described with reference to Figures 11A to 11D.

[0055] 11A is a voltage waveform diagram illustrating the effect of the sensor drive signal Ssen (individual sensor drive signal Ssl) on the circuit operation of the pixel TFT 51 included in the pixel of interest PixA when a black and white screen is displayed in this improved example. Here, the pixel of interest PixA is assumed to display black. FIG. 11B is a circuit diagram showing the electrical configuration of the pixel of interest PixA, FIG. 11C is a characteristic diagram of the pixel TFT 51 in the pixel of interest PixA, and FIG. 11D is a diagram showing a bright spot defect that occurs when a black and white screen is displayed in this improved example.

[0056] 11A, the pixel of interest PixA displays black, and therefore a small positive or negative voltage is held in its pixel capacitance Cp. On the other hand, in this improved example, the sensor drive signal Ssen is superimposed on the gate voltage Vg based on the scanning signal G(i), and therefore, during the negative frame period Tf (negative), the off-bias Voff_S+=Vgl-Vs of the pixel TFT51 during the touch detection period Tsen is smaller than the off-bias Voff_NS+=Vgl-Vs of the pixel TFT51 during periods other than the touch detection period Tsen. Therefore, if the characteristics of the pixel TFT51 of the pixel of interest PixA shift in the negative direction due to changes over time, characteristic variations, or some kind of charge (electrostatic charge), i.e., if the characteristics shift from those shown by the solid line in Figure 11C to those shown by the dotted line, even if the pixel TFT51 is in the off state due to the off bias Voff_NS+ during periods other than the touch detection period Tsen (non-sensing), it may be in the on state due to the off bias Voff_S+ during the touch detection period Tsen (sensing), as described below.

[0057] During the negative frame period Tf (negative), at the start of the touch detection period Tsen, the pixel voltage Vp is a negative voltage (-Vb) for black display due to the holding voltage of the pixel capacitance Cp. However, the source voltage Vs, which is the voltage of the data signal line DLj connected to the source terminal of the pixel TFT51, is a negative voltage (-Vw) for white display. Therefore, when the pixel TFT51 is turned on (or half-on) due to a negative shift in the characteristics (FIG. 11C), the pixel voltage Vp cannot maintain the negative voltage (-Vb) for black display. Instead, the pixel capacitance Cp is charged by the voltage of the data signal line DLj, causing the pixel voltage Vp to become a negative voltage (-Vw) for white display, resulting in the pixel PixA of interest appearing as a bright spot. As a result, as shown in FIG. 11D, in a black-and-white screen display, the area around the pixel PixA of interest is displayed in black, and the pixel PixA of interest appears as a very noticeable bright spot defect.

[0058] <1.3.3 Influence on circuit operation of pixel of interest in the embodiment> In contrast, in this embodiment, in order to prevent display defects due to such bright spot defects, the data signal line driving circuit 300 has the above-described configuration shown in FIG. 6 in order to superimpose the sensor driving signal Ssen on each data signal D(j) during the touch detection period Tsen.

[0059] Fig. 12A is a voltage waveform diagram illustrating the influence of the sensor drive signal Ssen on the drain voltage Vd, i.e., pixel voltage Vp, of the pixel TFT 51 included in the pixel of interest PixA when a black and white screen is displayed in this embodiment. Here, too, the pixel of interest PixA is assumed to display black. Fig. 12B is a circuit diagram showing the electrical configuration of the pixel of interest PixA, Fig. 12C is a characteristic diagram of the pixel TFT 51 in the pixel of interest PixA, and Fig. 12D is a diagram illustrating the effect of this embodiment (showing that no bright spot defects occur when a black and white screen is displayed).

[0060] In this embodiment, when a black and white screen is displayed, a small positive or negative voltage is held in the pixel capacitance Cp of the pixel of interest PixA, but during the touch detection period Tsen provided within the vertical blanking period Tbl, the voltage of the data signal line DLj connected to the source terminal of the pixel TFT51 is a positive or negative voltage for white display. Therefore, during the negative frame period Tf (negative), for the pixel TFT51, the difference between the gate voltage Vg based on the scanning signal G(i) and the negative voltage −Vw for white display, which is the source voltage Vs based on the data signal D(j), is relatively small, and during the touch detection period Tsen, the difference between the gate voltage Vg and the negative voltage −Vw for white display becomes even smaller because the sensor drive signal Ssen is superimposed on the scanning signal G(i). However, in this embodiment, as shown in FIG. 12A , the sensor drive signal Ssen is also superimposed on the data signal D(j) during the touch detection period Tsen. Therefore, the off-bias Voff_S+=Vgl-Vs of the pixel TFT 51 during the touch detection period Tsen is maintained at the same value as the off-bias Voff_NS+=Vgl-Vs of the pixel TFT 51 during periods other than the touch detection period Tsen. Therefore, even if the characteristics of the pixel TFT 51 of the pixel PixA of interest shift negatively due to aging or characteristic variations, i.e., even if the characteristics shift from the solid line to the dashed-dotted line in FIG. 12C , the pixel TFT 51 is likely to be maintained in the off state during the touch detection period Tsen. In this way, the same off-margin can be ensured for the TFT 51 during the touch detection period Tsen as during periods other than the touch detection period Tsen. As a result, even if the characteristics of the pixel TFT 51 shift negatively, as shown in FIG. 12D , display defects such as bright spot defects are suppressed in a black-and-white screen display.

[0061] <1.4 Effects> According to the present embodiment described above, in a liquid crystal display device with an integrated touch sensor, during a touch detection period Tsen, the sensor drive signal Ssen, which is an AC component of the individual sensor drive signal Ssl applied as a common voltage signal Vcom to each segment electrode 511 serving as a common electrode element, is superimposed not only on each scan signal G(i) but also on each data signal D(j). This not only prevents an increase in the leakage current Id(off) when the pixel TFT 51 is off due to the application of the individual sensor drive signal Ssl to the common electrode 55, but also suppresses the occurrence of display defects such as bright spot defects in a black and white screen display even if the characteristics of the pixel TFT 51 are shifted in the negative direction.

[0062] <2. Modifications> The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

[0063] For example, in the above embodiment, the scanning signal line drive circuit 200 has a configuration as shown in Fig. 5 including a configuration related to touch position detection, but the configuration of the scanning signal line drive circuit 200 is not limited to the configuration shown in Fig. 5 and may have other configurations (i = 1 to n) as long as the voltage of the scanning signal G(i), i.e., the voltage of the scanning signal line GLi (= gate voltage Vg), has a waveform as shown in Fig. 7 and Fig. 12A. Also, in the above embodiment, the data signal line drive circuit 300 has a configuration as shown in Fig. 6 including a configuration related to touch position detection, but the configuration of the data signal line drive circuit 300 is not limited to the configuration shown in Fig. 6 and may have other configurations (j = 1 to m) as long as the voltage of the data signal D(j), i.e., the voltage of the data signal line DLj (= source voltage Vs), has a waveform as shown in Fig. 7 and Fig. 12A. 5, the sensor drive signal Ssen is superimposed on the inactive scan signal (Vgl), but instead of this, an AC signal having the same frequency and phase as the sensor drive signal Ssen but a different amplitude, i.e., an AC signal corresponding to the sensor drive signal Ssen, may be superimposed. Also, in the data signal line drive circuit 300 shown in FIG. 6, the sensor drive signal Ssen is superimposed on each original data signal Do(j), but instead of this, an AC signal having the same frequency and phase as the sensor drive signal Ssen but a different amplitude, i.e., an AC signal corresponding to the sensor drive signal Ssen, may be superimposed.

[0064] 12A, during the touch detection period Tsen, the sensor drive signal Ssen is superimposed on each scanning signal G(i) and data signal D(j). Alternatively, as shown in FIG. 13, during the touch detection period Tsen, the voltage of each scanning signal G(i), i.e., the voltage level of each scanning signal line GLi, and the voltage of the data signal D(j), i.e., the voltage level of each data signal line DLj, may be shifted in the positive direction by an amount corresponding to the amplitude Vx of the sensor drive signal Ssen (a display device configured in this manner is referred to as a "first modified example"). Such a configuration can be realized by replacing the superimposing circuit 21 shown in FIG. 5 with a circuit that converts the level of the gate low voltage Vgl into a voltage level shifted in the positive direction by an amount corresponding to the amplitude Vx, and by replacing the superimposing circuit 31 shown in FIG. 6 with a circuit that converts the level of the voltage of the original data signal Do(j) into a voltage level shifted in the positive direction by an amount corresponding to the amplitude Vx (j=1 to m). In this case, during the touch detection period Tsen, the voltage levels of the scanning signal lines GL1 to GLn shift in the positive direction, i.e., in a direction approaching the level of the common voltage VCOM, from the voltage level (Vgl) of the inactive scanning signal by an amount corresponding to the amplitude Vx of the sensor drive signal Ssen, and the voltage levels of the data signal lines DL1 to DLm shift in the positive direction, i.e., in a direction away from the voltage level (Vgl) of the inactive scanning signal, by an amount corresponding to the amplitude Vx of the sensor drive signal Ssen.

[0065] In the above embodiment, the voltage of each scanning signal G(i) during the touch detection period Tsen is the gate low voltage Vgl. Therefore, instead of superimposing the sensor drive signal Ssen on each scanning signal G(i) during the touch detection period Tsen, the gate low voltage signal Vgl_sen may be generated by superimposing the sensor drive signal Ssen on the gate low voltage Vgl used in the scanning signal line drive circuit 200 during the touch detection period Tsen, or by shifting the level of the gate low voltage Vgl used in the scanning signal line drive circuit 200 in the positive direction by an amount corresponding to the amplitude Vx of the sensor drive signal Ssen during the touch detection period Tsen, and each scanning signal G(i) may be generated using the gate low voltage signal Vgl_sen instead of the gate low voltage Vgl corresponding to non-selection of the scanning signal line GLi in a normal scanning signal line drive circuit (for example, the scanning signal line drive circuit in the above comparative example).

[0066] 11A, in the above-described improved example, when the characteristics of the pixel TFT 51 shift in the negative direction due to changes over time, characteristic variations, or the like, a bright spot defect occurs in the display of a black and white screen (see FIGS. 11C and 11D). This is because, during the negative frame period Tf (negative), the sensor drive signal Ssen is superimposed on the inactive scanning signal during the touch detection period Tsen, reducing the off margin of the pixel TFT 51 of the pixel formation portion (pixel of interest) in the black display state, causing the pixel TFT to enter an on state (or a half-on state). Therefore, in the above-described embodiment, as shown in FIG. 14, the sensor drive signal Ssen may be superimposed on each data signal D(j) during the touch detection period Tsen only during the negative frame period Tf (negative), or the voltage of each data signal D(j) may be shifted in the positive direction by an amount corresponding to the amplitude Vx of the sensor drive signal Ssen during the touch detection period Tsen (a display device configured in this manner is referred to as a "second modified example").

[0067] As shown in FIG. 2 , in the above embodiment, an N-channel transistor is used as the pixel TFT 51 in each pixel formation portion 50. However, instead, a P-channel transistor such as an LTPS-TFT may be used as the pixel TFT 51. In this case, when scanning the scanning signal lines GL (GL1 to GLn), a gate low voltage Vgl is sequentially applied as an active scanning signal to the n scanning signal lines GL1 to GLn, and a gate high voltage Vgh is applied as an inactive scanning signal to the scanning signal lines other than the scanning signal lines to which the active scanning signal is applied. Therefore, unlike the above-described improved example (see FIGS. 11A to 11D ), the off-margin of the pixel TFT 51 is reduced by superimposing the sensor drive signal Ssen on the inactive scanning signal during the touch detection period Tsen during the positive frame period Tf (positive) rather than the negative frame period Tf (negative), which may result in the generation of bright spots that are not included in the intended display image. This is because the relationship between the level difference between the voltage of the inactive scan signal and the voltage of the data signal, and the positive frame period Tf (positive) and the negative frame period Tf (negative), differs depending on whether the pixel TFT 51 is an N-channel or P-channel type. That is, when an N-channel transistor is used as the pixel TFT 51, the voltage polarity, relative to the common voltage VCOM, differs between the gate low voltage Vgl as the inactive scan signal G(i) and the voltage (source voltage Vs) of the data signal D(j) during the positive frame period Tf (positive), but matches during the negative frame period Tf (negative), resulting in a small level difference. In contrast, when a P-channel transistor is used as the pixel TFT 51, the voltage polarity, relative to the common voltage VCOM, differs between the gate high voltage Vgh as the inactive scan signal G(i) and the voltage (source voltage Vs) of the data signal D(j) during the negative frame period Tf (negative), but matches during the positive frame period Tf (positive), resulting in a small level difference.Therefore, to prevent the occurrence of the above-mentioned bright spots due to a decrease in the off margin of the pixel TFT 51 caused by the superposition of the sensor drive signal Ssen on the inactive scanning signal during the touch detection period Tsen, more generally, at least during the period in which the voltage polarity based on the common voltage VCOM matches between the voltage of the inactive scanning signal G(i) and the voltage of any of the data signals D(j), the sensor drive signal Ssen can be superimposed on the voltage of any of the data signals D(j), i.e., the voltage of the data signal line DLj, during the touch detection period Tsen, or the voltage of any of the data signals D(j), i.e., the voltage of the data signal line DLj, can be shifted in a direction away from the voltage level of the inactive scanning signal (in a direction approaching the level of the common voltage VCOM) by an amount corresponding to the amplitude Vx of the sensor drive signal Ssen during the touch detection period Tsen.

[0068] In a liquid crystal display device such as the above embodiment, a predetermined capacitance generally exists between each data signal line DLj and the common electrode 55 (plurality of segment electrodes 511) in the display unit 500. For this reason, it is conceivable to float each data signal line DLj during the touch detection period Tsen, thereby varying the voltage of each data signal line DLj in response to the sensor drive signal Ssen (hereinafter, a display device configured in this manner will be referred to as a "third modified example"). For example, a display device of the third modified example can be realized by changing the data signal line drive circuit 300 in the above embodiment to the configuration shown in FIG. 15 instead of the configuration shown in FIG. 6. The data signal line drive circuit 300 shown in FIG. 15 includes a data signal generation circuit 350 similar to the data signal line drive circuit 300 in the above embodiment shown in FIG. 6, and also includes m open / close switches 37 corresponding to the m data signal lines DL1 to DLm formed in the display unit 500, respectively. The data signal generation circuit 350 has m output terminals that output data signals Do(1) to Do(m) that represent an image to be displayed, and these m output terminals are connected to m data signal lines DL1 to DLm in the display unit 500 via m open / close switches 37, respectively. Each open / close switch 37 is in an on state when a touch detection control signal CTS included in the data-side control signal DCTL is inactive, and is in an off state when the touch detection control signal CTS is active. Therefore, during periods other than the touch detection period Tsen, each original data signal Do(j) is applied to the data signal line DLj as a data signal D(j) via the open / close switch 37 that is in an on state. During the touch detection period Tsen, all of the m open / close switches 37 are in an off state, so that all of the m data signal lines DL1 to DLm are in a floating state. With this configuration, the voltage of each data signal line DLj in a floating state can be varied in response to the sensor drive signal Ssen during the touch detection period Tsen.However, unlike the data signal line drive circuit 300 (FIG. 6) in the above embodiment, the sensor drive signal Ssen is not configured to be superimposed on each data signal D(j) during the touch detection period Tsen, and therefore the amount of fluctuation (amplitude) of the voltage of the data signal line DLj during the touch detection period Tsen in this modification may be smaller than the amplitude of the common voltage signal Vcom during the touch detection period Tsen, i.e., the amplitude Vx of the sensor drive signal Ssen. However, compared to when the voltage of each data signal line DLj (the source voltage Vs based on the data signal D(j)) is fixed during the touch detection period Tsen (see FIGS. 9A and 11A), it is possible to reduce the decrease in the off margin of the pixel TFT 51 during the touch detection period Tsen.

[0069] Furthermore, in the above embodiment, a frame inversion driving method is adopted to drive the liquid crystal display device, but the present invention is also applicable to cases where other driving methods such as a line inversion driving method, a dot inversion driving method, or a source inversion driving method are adopted.

[0070] Furthermore, in the above embodiment, the touch detection period Tsen is provided within the vertical blanking period Tbl, but instead, the touch detection period Tsen may be provided by stopping the scanning of the scanning signal lines GL1 to GLn midway during each frame period. The present invention is also applicable to such a configuration.

[0071] Furthermore, although the above description has been given using a liquid crystal display device as an example of an embodiment, the present invention is not limited to this and can be applied to any display device that employs an AC drive system in which the polarity of the drive voltage applied to the display elements in the display section by the pixel electrodes and common electrodes is reversed every predetermined period.

[0072] It should be noted that the features of the display devices according to the above-described embodiments and their modifications can be arbitrarily combined to form display devices according to various modifications, provided that the combination does not contradict the nature of the display devices. [Explanation of symbols]

[0073] 21, 31 ... Superposition circuit 23, 33 ... Switching circuit 37...Open / close switch 40...Sensor drive signal generator 41...Drive signal output circuit 42 ... Touch detection circuit 43...Switching circuit 47... Position detection processing circuit 50...pixel formation section 51...pixel TFT 53...pixel electrode 55…Common electrode 100...Display control circuit 200 ...scanning signal line driving circuit 300...Data signal line driving circuit 400...Sensor drive circuit 500...Display section 510...Touch sensor 511 ... Segment electrode (common electrode element) 600...LCD panel 610 ... Active matrix substrate Cp: ​​pixel capacitance SL: Sensor signal line GLi...scanning signal line (i=1~n) DLj ... Data signal line (j=1~m) G(i) ... scanning signal (i = 1 to n) D(j) ... Data signal (j=1~m) Ssen: Sensor drive signal Ssl: Individual sensor drive signal CTS: Touch detection control signal Gsen: Sensor drive compatible scanning signal VCOM...Common voltage Vcom...common voltage signal Vgl: Gate low voltage Vgh: Gate high voltage Tsen: Touch detection period

Claims

1. A display device including a display panel with a built-in touch sensor, the display panel including a plurality of data signal lines, a plurality of scanning signal lines, a plurality of pixel formation portions provided along the plurality of data signal lines and the plurality of scanning signal lines, and a common electrode provided in common to the plurality of pixel formation portions, a data signal line driving circuit that drives the plurality of data signal lines so that the polarities of the voltages of the plurality of data signal lines relative to the voltage of the common electrode are inverted every predetermined period; a scanning signal line driving circuit that drives a plurality of scanning signal lines; a sensor drive circuit that drives the common electrode with a signal including a sensor drive signal that is an AC signal of a predetermined amplitude during a touch detection period provided for detecting a touch position; Equipped with Each of the plurality of pixel formation portions A pixel electrode; a display element that is AC-driven by a voltage applied between the pixel electrode and the common electrode; a pixel transistor having a first conductive terminal connected to one of the plurality of data signal lines, a second conductive terminal connected to the pixel electrode, and a control terminal connected to one of the plurality of scanning signal lines, the common electrode includes a plurality of segment electrodes; The sensor drive circuit generating and applying a signal including the sensor drive signal to each of the plurality of segment electrodes during the touch detection period; applying a common voltage, which is a voltage common to the plurality of pixel formation portions, to the plurality of segment electrodes as a reference for a voltage to be applied to the display element for image display during a period other than the touch detection period; The scanning signal line driving circuit In a period other than the touch detection period, active signals are sequentially applied to the plurality of scanning signal lines to turn on the pixel transistors so that voltages of the plurality of data signal lines are applied to the pixel electrodes of the plurality of pixel formation portions; During the touch detection period, a signal obtained by superimposing an AC signal corresponding to the sensor drive signal on an inactive signal that turns off the pixel transistor is applied to the plurality of scanning signal lines; the data signal line drive circuit drives the plurality of data signal lines so as to reduce a decrease in the absolute value of the voltage between the first conduction terminal and the control terminal of the pixel transistor caused by superimposing an AC signal corresponding to the sensor drive signal on the inactive signal applied to the one scanning signal line, at least during a same polarity period in which the voltage polarity based on the common voltage matches that of the voltage of the inactive signal and any one of the voltages of the plurality of data signal lines.

2. The display device according to claim 1 , wherein the data signal line drive circuit superimposes an AC signal corresponding to the sensor drive signal on the voltages of the plurality of data signal lines during the touch detection period at least in the same polarity period.

3. The data signal line driving circuit a superposition circuit for generating a signal by superimposing an AC signal corresponding to the sensor drive signal on a data signal to be applied to each data signal line; 3. The display device according to claim 2, further comprising: a switching circuit that switches signals to be output to each data signal line so that, during periods other than the touch detection period, data signals to be applied to each data signal line are output to the respective data signal lines, and at least during the same polarity period, the signals generated by the superposition circuit from the data signals to be applied to each data signal line are output to the respective data signal lines.

4. 2. The display device according to claim 1, wherein the data signal line drive circuit shifts voltage levels of the plurality of data signal lines in a direction away from a voltage level of the inactive signal by an amount corresponding to an amplitude of the sensor drive signal during the touch detection period, at least in the same polarity period.

5. The display device according to claim 1 , wherein the data signal line driving circuit electrically disconnects the plurality of data signal lines from the data signal line driving circuit during the touch detection period at least in the same polarity period.

6. the pixel transistor is an N-channel transistor, 6. The display device according to claim 1, wherein the same polarity period is a negative polarity period in which the polarity of the voltage of any one of the plurality of data signal lines is negative relative to the common voltage.

7. the pixel transistor is an N-channel transistor, the same polarity period is a negative polarity period in which the polarity of the voltage of any one of the plurality of data signal lines is negative with respect to the common voltage; 2. The display device according to claim 1, wherein the data signal line drive circuit shifts voltage levels of the plurality of data signal lines in a positive direction by an amount corresponding to an amplitude of the sensor drive signal during the touch detection period, at least in the negative polarity period.

8. A display device including a display panel with a built-in touch sensor, the display panel including a plurality of data signal lines, a plurality of scanning signal lines, a plurality of pixel formation portions provided along the plurality of data signal lines and the plurality of scanning signal lines, and a common electrode provided in common to the plurality of pixel formation portions, a data signal line driving circuit that drives the plurality of data signal lines so that the polarities of the voltages of the plurality of data signal lines relative to the voltage of the common electrode are inverted every predetermined period; a scanning signal line driving circuit that drives a plurality of scanning signal lines; a sensor drive circuit that drives the common electrode with a signal including a sensor drive signal that is an AC signal of a predetermined amplitude during a touch detection period provided for detecting a touch position; Equipped with Each of the plurality of pixel formation portions A pixel electrode; a display element that is AC-driven by a voltage applied between the pixel electrode and the common electrode; a pixel transistor having a first conductive terminal connected to one of the plurality of data signal lines, a second conductive terminal connected to the pixel electrode, and a control terminal connected to one of the plurality of scanning signal lines, the common electrode includes a plurality of segment electrodes; The sensor drive circuit generating and applying a signal including the sensor drive signal to each of the plurality of segment electrodes during the touch detection period; applying a common voltage, which is a voltage common to the plurality of pixel formation portions, to the plurality of segment electrodes as a reference for a voltage to be applied to the display element for image display during a period other than the touch detection period; The scanning signal line driving circuit In a period other than the touch detection period, active signals are sequentially applied to the plurality of scanning signal lines to turn on the pixel transistors so that voltages of the plurality of data signal lines are applied to the pixel electrodes of the plurality of pixel formation portions; During the touch detection period, voltage levels of the plurality of scanning signal lines are shifted from a voltage level of an inactive signal that turns off the pixel transistors to a direction approaching the level of the common voltage by an amount corresponding to an amplitude of the sensor drive signal; the data signal line driving circuit shifts the voltage levels of the plurality of data signal lines in a direction away from the voltage level of the inactive signal by an amount corresponding to the amplitude of the sensor driving signal during the touch detection period, at least during a same polarity period in which the voltage polarity based on the common voltage matches the voltage of the inactive signal and the voltage of any one of the plurality of data signal lines.

9. A method for driving a display device including a display panel with a built-in touch sensor, the display panel including a plurality of data signal lines, a plurality of scanning signal lines, a plurality of pixel formation portions provided along the plurality of data signal lines and the plurality of scanning signal lines, and a common electrode provided in common to the plurality of pixel formation portions, a data signal line driving step of driving the plurality of data signal lines so that polarities of voltages of the plurality of data signal lines relative to the voltage of the common electrode are inverted every predetermined period; a scanning signal line driving step of driving a plurality of scanning signal lines; a sensor driving step of driving the common electrode with a signal including a sensor driving signal that is an AC signal of a predetermined amplitude during a touch detection period provided for detecting a touch position; Equipped with each of the plurality of pixel formation portions includes a pixel electrode; a display element that is AC-driven by a voltage applied between the pixel electrode and the common electrode; and a pixel transistor that has a first conduction terminal connected to one of the plurality of data signal lines, a second conduction terminal connected to the pixel electrode, and a control terminal connected to one of the plurality of scanning signal lines; the common electrode includes a plurality of segment electrodes; The sensor driving step includes: generating and applying a signal including the sensor drive signal to each of the plurality of segment electrodes during the touch detection period; applying a common voltage, which is a voltage common to the plurality of pixel formation portions, to the plurality of segment electrodes as a reference for voltages to be applied to the display elements of the plurality of pixel formation portions for image display during a period other than the touch detection period; The scanning signal line driving step sequentially applying active signals to the plurality of scanning signal lines to turn on the pixel transistors so that voltages of the plurality of data signal lines are applied to the pixel electrodes in the plurality of pixel formation portions during a period other than the touch detection period; applying, to the plurality of scanning signal lines, a signal obtained by superimposing an AC signal corresponding to the sensor drive signal on an inactive signal that turns off the pixel transistor during the touch detection period; the data signal line driving step drives the plurality of data signal lines so as to reduce a decrease in the absolute value of the voltage between the first conduction terminal and the control terminal of the pixel transistor caused by superimposing an AC signal corresponding to the sensor drive signal on the inactive signal applied to the one scanning signal line, at least during a same polarity period in which the voltage polarity based on the common voltage matches that of the voltage of the inactive signal and that of any one of the plurality of data signal lines.

10. 10. The driving method according to claim 9, wherein the data signal line driving step superimposes an AC signal corresponding to the sensor drive signal on voltages of the plurality of data signal lines during the touch detection period at least in the same polarity period.

11. 10. The driving method according to claim 9, wherein the data signal line driving step shifts voltage levels of the plurality of data signal lines in a direction away from a voltage level of the inactive signal by an amount corresponding to an amplitude of the sensor drive signal during the touch detection period, at least in the same polarity period.

12. The driving method according to claim 9 , wherein the data signal line driving step electrically disconnects the plurality of data signal lines from the data signal line driving circuit during the touch detection period at least in the same polarity period.

Images