Liquid crystal display device having touch panel and driving method therefor

Abstract

To achieve a liquid crystal display device capable of combining excellent display quality and highly accurate touch detection.SOLUTION: After a start of each horizontal scanning period, a source driver maintains a source bus line arranged in a display unit in a high impedance state for a predetermined period. A sensor electrode potential control IC varies a potential VCOM of a sensor electrode (a common electrode) during a period in which the source bus line is maintained in the high impedance state. A touch detection circuit acquires a touch detection signal from the sensor electrode and processes the touch detection signal during a period in which the potential VCOM of the sensor electrode varies. After the source driver releases the high impedance state of the source bus line, a video signal is written to a liquid crystal capacitance in a pixel formation portion corresponding to a gate bus line in a selection state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The following disclosure relates to a liquid crystal display device, and more particularly to a liquid crystal display device equipped with an in-cell touch panel and a driving method thereof. [Background technology]

[0002] Touch panels have traditionally been used as input devices for operating computer systems and the like. For example, in capacitive touch panels, the position of an object to be detected, such as an operator's finger or a touch pen, is detected based on changes in capacitance. An increasing number of liquid crystal display devices are also equipped with such touch panels.

[0003] There are several types of touch panels, but in recent years, in-cell touch panels have become mainstream on the market. In-cell touch panels are touch panels in which sensor electrodes are provided inside the two glass substrates that make up the display panel. In-cell touch panels use, for example, multiple rectangular sensor electrodes arranged in a matrix, and perform touch detection (detection of the touched position on the touch panel) using a self-capacitance method. The multiple sensor electrodes are shared with a common electrode that is used to display images. In other words, one electrode is used both as a sensor electrode for touch detection and as a common electrode for image display. This configuration enables devices to be made thinner and lighter.

[0004] In a liquid crystal display device equipped with an in-cell touch panel, as described above, one electrode is used both as a sensor electrode for touch detection and as a common electrode for image display. Therefore, a period for image display (hereinafter referred to as a "display period") and a period for touch detection (hereinafter referred to as a "touch detection period") must be provided in a time-division manner. That is, a time-division driving method is required in which image display driving and touch detection driving are performed in different periods. For example, in each frame period (each vertical scanning period), vertical scanning (sequential scanning of the gate bus lines in the display unit one by one) is temporarily stopped every time a video signal is written to a liquid crystal capacitance corresponding to a certain number of gate bus lines (scanning signal lines) (i.e., every time image display driving is performed for an area corresponding to a certain number of gate bus lines), and touch detection driving is performed during the vertical scanning stop period. In this example, as shown in FIG. 11, a display period and a touch detection period are repeated within one frame period.

[0005] FIG. 12 is a signal waveform diagram for explaining a method for driving a liquid crystal display device equipped with an in-cell touch panel. FIG. 12 shows changes in the potential (source potential) VS of the source bus line (video signal line), the potential VCOM of the sensor electrode (common electrode), and the potentials (gate potentials) G(n-1) to G(n+1) of the gate bus lines from the (n-1)th row to the (n+1)th row. The period indicated by the arrow with the symbol T91 is the display period, and the period indicated by the arrow with the symbol T92 is the touch detection period. During the display period T91, the potential VCOM of the sensor electrode is maintained at a constant level. In this state, the gate bus lines are sequentially selected one by one. During each horizontal scanning period within the display period T91, the source potential VS changes according to the target display image. Through the above operations, during the display period T91, a video signal according to the target display image is written to the liquid crystal capacitance corresponding to the selected gate bus line. During the touch detection period T92, while the source potential and gate potential are maintained at a constant level, the potential VCOM of the sensor electrode fluctuates as shown by the part marked with reference numeral 9 in Fig. 12. This allows the determination of whether or not a touch has occurred and, if a touch has occurred, the touch position to be identified.

[0006] According to the time-division driving method described above, as can be seen from FIG. 11, it is necessary to provide a touch detection period within a frame period. This inevitably shortens the time required to write a video signal to each liquid crystal capacitor (hereinafter referred to as "write time"), which can lead to a deterioration in display quality due to insufficient charging. Furthermore, high-speed driving increases power consumption. This deterioration in display quality and increase in power consumption are particularly noticeable in liquid crystal display devices with high resolution and a high refresh rate.

[0007] Therefore, Japanese Patent Application Laid-Open No. 2015-232601 discloses, as a comparative example, a method of performing a display operation (driving for image display) and a touch detection operation (driving for touch detection) within a horizontal scanning period. Note that in this method, the display operation and the touch detection operation are performed on different display lines in each horizontal scanning period. According to the method disclosed in Japanese Patent Application Laid-Open No. 2015-232601, the touch detection period is included in the display period, and there is no need to provide a touch detection period separate from the display period in each frame period. Therefore, unlike the case of performing the above-mentioned time-division driving, a sufficiently long write time can be ensured. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-232601 Summary of the Invention [Problem to be solved by the invention]

[0009] According to the technique disclosed in Japanese Patent Application Laid-Open No. 2015-232601, touch detection is performed during periods when the video voltage (source potential) and the scanning voltage (gate potential) are not fluctuating. This is because parasitic capacitance exists between the source bus line and the sensor electrode (common electrode) and between the gate bus line and the sensor electrode (common electrode). If touch detection is performed during fluctuations in the video voltage or the scanning voltage, noise generated during fluctuations in the video voltage or the scanning voltage will affect the touch detection (i.e., the accuracy of touch detection will decrease). In this regard, to perform touch detection during periods when the video voltage and the scanning voltage are not fluctuating, sufficient margins are required between the point in time when the video voltage changes and the touch detection period, and between the point in time when the scanning voltage changes and the touch detection period. However, because timing control is difficult, the margins may not be sufficiently secured, which may result in a decrease in display quality or accuracy of touch detection.

[0010] Therefore, the following disclosure aims to realize a liquid crystal display device that can achieve both good display quality and highly accurate touch detection. [Means for solving the problem]

[0011] (1) A liquid crystal display device according to some embodiments of the present invention is a liquid crystal display device including a touch panel including a plurality of sensor electrodes provided for detecting a touch position, a plurality of video signal lines for transmitting video signals; a plurality of scanning signal lines intersecting the plurality of video signal lines; a plurality of pixel formation portions provided corresponding to intersections of the plurality of video signal lines and the plurality of scanning signal lines; a video signal line drive circuit that applies the video signals to the plurality of video signal lines; a scanning signal line driving circuit that selectively drives the plurality of scanning signal lines; a sensor electrode potential control circuit for controlling the potentials of the plurality of sensor electrodes; a touch detection circuit for acquiring touch detection signals for detecting a touch position from the plurality of sensor electrodes and processing the touch detection signals; a touch control circuit that controls an operation of the sensor electrode potential control circuit and an operation of the touch detection circuit; a timing control circuit that controls an operation of the video signal line drive circuit, an operation of the scanning signal line drive circuit, and an operation of the touch control circuit; Equipped with the plurality of sensor electrodes and the plurality of pixel formation portions are in a 1:n correspondence, where n is an integer of 2 or more; Each of the plurality of pixel formation portions A pixel electrode; a pixel transistor having a control terminal connected to a corresponding scanning signal line, a first conduction terminal connected to a corresponding video signal line, and a second conduction terminal connected to the pixel electrode; a liquid crystal capacitance formed by the corresponding sensor electrode and the pixel electrode; Including, the video signal line drive circuit maintains the plurality of video signal lines in a high impedance state during a first period before the video signals are written to the liquid crystal capacitance during a horizontal scanning period during which the scanning signal lines are driven; the touch control circuit controls the operation of the sensor electrode potential control circuit based on a synchronization signal provided from the timing control circuit, whereby potentials of the plurality of sensor electrodes fluctuate during a second period included in the first period, and potentials of the plurality of sensor electrodes are maintained at a constant level during periods other than the second period; The touch control circuit controls the operation of the touch detection circuit based on a synchronization signal provided from the timing control circuit, whereby the touch detection circuit acquires and processes the touch detection signal during the second period.

[0012] (2) Furthermore, a liquid crystal display device according to some embodiments of the present invention includes the configuration of (1) above, The start point of the first period is the start point of a horizontal scanning period.

[0013] (3) Furthermore, a liquid crystal display device according to some embodiments of the present invention includes the configuration of (1) above, The video signal line driving circuit an output buffer for outputting the video signal; a changeover switch for switching each video signal line between a state where it is connected to the output terminal of the output buffer and a high impedance state; Includes.

[0014] (4) Furthermore, a liquid crystal display device according to some embodiments of the present invention includes any one of the configurations (1) to (3) above, the video signal line drive circuit maintains the video signal lines in a high impedance state during the first period in all horizontal scanning periods included in each vertical scanning period; In all horizontal scanning periods included in each vertical scanning period, the potentials of the plurality of sensor electrodes fluctuate in the second period.

[0015] (5) Furthermore, a driving method according to some embodiments of the present invention is a driving method for a liquid crystal display device having a touch panel including a plurality of sensor electrodes provided for detecting a touch position, the driving method comprising: The liquid crystal display device comprises: a plurality of video signal lines for transmitting video signals; a plurality of scanning signal lines intersecting the plurality of video signal lines; a plurality of pixel formation portions provided corresponding to intersections of the plurality of video signal lines and the plurality of scanning signal lines; a sensor electrode potential control circuit for controlling the potentials of the plurality of sensor electrodes; a touch detection circuit for acquiring touch detection signals for detecting a touch position from the plurality of sensor electrodes and processing the touch detection signals; a touch control circuit that controls an operation of the sensor electrode potential control circuit and an operation of the touch detection circuit; a timing control circuit for controlling the operation of the touch control circuit; Equipped with the plurality of sensor electrodes and the plurality of pixel formation portions are in a 1:n correspondence, where n is an integer of 2 or more; Each of the plurality of pixel formation portions A pixel electrode; a pixel transistor having a control terminal connected to a corresponding scanning signal line, a first conduction terminal connected to a corresponding video signal line, and a second conduction terminal connected to the pixel electrode; a liquid crystal capacitance formed by the corresponding sensor electrode and the pixel electrode; Including, The driving method includes: a video signal line high impedance setting step of setting the plurality of video signal lines to a high impedance state at a first time point before the video signal is written to the liquid crystal capacitance during a horizontal scanning period in which scanning signal lines are driven; a video signal line high impedance canceling step of canceling the high impedance state of the plurality of video signal lines at a second time point during the horizontal scanning period that is a time point before the video signal is written to the liquid crystal capacitance and that is a time point after the first time point; a touch detection step in which the touch control circuit controls an operation of the sensor electrode potential control circuit and an operation of the touch detection circuit based on a synchronization signal provided from the timing control circuit so that potentials of the plurality of sensor electrodes fluctuate and the touch detection circuit acquires and processes the touch detection signal during a period between the first time point and the second time point; Includes. [Effects of the Invention]

[0016] In some embodiments of the liquid crystal display device according to the present invention, a sensor electrode potential control circuit varies the potential of the sensor electrode during a portion of the horizontal scanning period, and during this period, a touch detection circuit acquires and processes a touch detection signal from the sensor electrode. That is, touch detection drive is performed during a portion of the horizontal scanning period. Since a separate period for touch detection drive is not provided in addition to a period for image display drive, the write time for writing a video signal to the liquid crystal capacitor is longer than conventionally. Furthermore, when varying the potential of the sensor electrode for touch detection, each video signal line is maintained in a high-impedance state. Therefore, fluctuations in the potential of the sensor electrode do not affect the display. As a result, good display quality is maintained. Furthermore, a configuration is adopted in which the touch control circuit controls the operation of the sensor electrode potential control circuit and the touch detection circuit based on a synchronization signal provided by the timing control circuit, facilitating timing control. Therefore, there is no degradation in touch detection accuracy due to noise contamination, etc. As described above, a liquid crystal display device capable of achieving both good display quality and high-precision touch detection is realized. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a signal waveform diagram for explaining a method of driving a liquid crystal display device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a configuration of the liquid crystal display device according to the embodiment. [Figure 3] FIG. 2 is a block diagram showing a schematic configuration of a drive unit in the embodiment. [Figure 4] FIG. 2 is a diagram for explaining components for image display among components in the liquid crystal touch panel in the embodiment. [Figure 5] FIG. 2 is a diagram for explaining components for touch detection among components in the liquid crystal touch panel in the embodiment. [Figure 6] 10 is a diagram for describing details of a touch detection circuit in the embodiment. FIG. [Figure 7] 3 is a diagram showing a configuration of an output section of a source driver IC in the embodiment. FIG. [Figure 8] FIG. 10 is a signal waveform diagram for explaining details of a method for driving the liquid crystal display device in the embodiment. [Figure 9] 10A and 10B are diagrams for explaining the difference between the above embodiment and a conventional example. [Figure 10] 10A and 10B are diagrams for explaining the difference between the above embodiment and a conventional example. [Figure 11] FIG. 10 is a diagram for explaining time-division driving in a conventional example. [Figure 12] FIG. 10 is a signal waveform diagram for explaining a method of driving a liquid crystal display device having an in-cell touch panel according to a conventional example. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0019] <1. Configuration of Liquid Crystal Display Device> 2 is a block diagram showing the configuration of a liquid crystal display device according to one embodiment of the present invention. This liquid crystal display device is composed of a liquid crystal touch panel 10 and a PCB (printed circuit board) 20 on which various ICs and the like are mounted. The liquid crystal touch panel 10 is composed of two glass substrates, a TFT array substrate and a color filter substrate, facing each other, and the PCB 20 is provided on the back surface of the liquid crystal touch panel 10, for example.

[0020] The LCD touch panel 10 has two functionalities: an image display function and a touch detection function. In the LCD touch panel 10, a driving unit 100 that drives components for image display and components for touch detection is provided in an area outside an active area 190, which is the effective display area. As shown in FIG. 3, the driving unit 100 includes a source driver 110 that applies video signals to each source bus line, and a touch detection circuit 120 that acquires and processes touch detection signals to identify the presence or absence of a touch and the touch position. The driving unit 100 is realized, for example, by TDDI (Touch Display Driver Integration).

[0021] The PCB 20 includes a composite power supply IC 210, a timing controller (timing control circuit) 220, a level shifter IC 230, a touch controller (touch control circuit) 240, and a sensor electrode potential control IC (sensor electrode potential control circuit) 250. The composite power supply IC 210 supplies the necessary power supply voltages to each of the timing controller 220, the level shifter IC 230, the touch controller 240, and the sensor electrode potential control IC 250.

[0022] The timing controller 220 receives image data DAT sent from the outside, and outputs a digital video signal DV, a source control signal SCTL that controls the operation of the source driver 110, a timing signal TS that is the source of a gate control signal GCTL that controls the operation of a gate driver (described later), and a synchronization signal Sync that controls the operation of the touch controller 240. In other words, the timing controller 220 controls the operation of the source driver 110, the operation of the gate driver, and the operation of the touch controller 240. For example, P2P (peer-to-peer) communication is employed for transmitting the digital video signal DV from the timing controller 220 to the source driver 110. The source control signal SCTL includes a source start pulse signal, a source clock signal, a latch strobe signal, etc.

[0023] The level shifter IC 230 generates and outputs a gate control signal GCTL by converting the voltage level (potential) of the timing signal TS provided by the timing controller 220. The gate control signal GCTL includes a gate start pulse signal, a gate clock signal, etc.

[0024] The touch controller 240 outputs a sensor electrode potential control signal VCTL that controls the operation of the sensor electrode potential control IC 250 and a touch control signal TCTL that controls the operation of the touch detection circuit 120, based on a synchronization signal Sync provided by the timing controller 220. In other words, the touch controller 240 controls the operation of the sensor electrode potential control IC 250 and the operation of the touch detection circuit 120. The touch controller 240 also determines whether or not a touch has occurred and identifies the touch position, based on a touch detection signal DS sent from the drive unit 100.

[0025] The sensor electrode potential control IC 250 controls the potential VCOM of the sensor electrode (common electrode) based on the sensor electrode potential control signal VCTL provided from the touch controller 240. In the following, the magnitude of the constant potential to be provided to the sensor electrode during the period when the video signal is written to the liquid crystal capacitance is referred to as the "normal level."

[0026] 4 is a diagram illustrating components for image display among the components in the liquid crystal touch panel 10. The liquid crystal touch panel 10 includes a display unit 101, a source driver (video signal line drive circuit) 110, and a gate driver (scanning signal line drive circuit) 130.

[0027] The display unit 101 displays an image under the control of a source driver 110 and a gate driver 130. A plurality of source bus lines (video signal lines) SL and a plurality of gate bus lines (scanning signal lines) GL are arranged in the display unit 101. Pixel formation portions 14 that form pixels are provided at each intersection of the source bus lines SL and the gate bus lines GL. That is, the display unit 101 includes a plurality of pixel formation portions 14 (however, only one pixel formation portion 14 is shown in FIG. 4). The plurality of pixel formation portions 14 form a pixel matrix. Each pixel formation portion 14 includes a pixel TFT (pixel transistor) 140, which is a thin-film transistor having a gate terminal (control terminal) connected to a gate bus line GL passing through the corresponding intersection and a source terminal (first conduction terminal) connected to a source bus line SL passing through the intersection, a pixel electrode 141 connected to the drain terminal (second conduction terminal) of the pixel TFT 140, a sensor electrode (common electrode) 144 functioning as an electrode for touch detection and an electrode for image display, an auxiliary capacitance electrode 145 provided in common to the plurality of pixel formation portions 14, a liquid crystal capacitance 142 formed by the pixel electrode 141 and the sensor electrode 144, and an auxiliary capacitance 143 formed by the pixel electrode 141 and the auxiliary capacitance electrode 145. The liquid crystal capacitance 142 and the auxiliary capacitance 143 form a pixel capacitance 146. Note that a configuration without the auxiliary capacitance 143 (i.e., a configuration without the auxiliary capacitance electrode 145) may also be employed.

[0028] The pixel TFT 140 may be, for example, a thin-film transistor (oxide semiconductor TFT) using an oxide semiconductor for the semiconductor layer. More specifically, a TFT (hereinafter referred to as an "IGZO-TFT") having a channel layer formed of In-Ga-Zn-O (indium gallium zinc oxide), an oxide semiconductor primarily composed of indium (In), gallium (Ga), zinc (Zn), and oxygen (O), may be used as the pixel TFT 140. Because oxide semiconductors have high electron mobility, using an oxide semiconductor TFT such as an IGZO-TFT enables the pixel TFT 140 to be miniaturized, which is advantageous in terms of achieving high definition and a high aperture ratio. Furthermore, the reduced leakage current is advantageous in terms of reducing power consumption. Furthermore, the voltage retention rate of the pixel capacitor 146 is improved.

[0029] The source driver 110 applies a driving video signal to each source bus line SL based on the digital video signal DV and source control signal SCTL sent from the timing controller 220. At this time, the source driver 110 sequentially holds the digital video signal DV indicating the voltage to be applied to each source bus line SL at the timing when a pulse of the source clock signal is generated. Then, the held digital video signal DV is converted into an analog voltage at the timing when a pulse of the latch strobe signal is generated. The converted analog voltage is applied simultaneously to all source bus lines SL as a driving video signal. The source driver 110 is realized by, for example, four ICs (source driver ICs) 112.

[0030] The gate driver 130 repeatedly applies an active scanning signal to each gate bus line GL in a cycle of one vertical scanning period based on the gate control signal GCTL output from the level shifter IC 230. The gate driver 130 is formed directly on the TFT array substrate.

[0031] In this manner, video signals are applied to the source bus lines SL and scanning signals are applied to the gate bus lines GL, whereby an image based on image data DAT sent from the outside is displayed on the display unit 101.

[0032] 5 is a diagram illustrating components for touch detection among the components in the liquid crystal touch panel 10. As described above, the liquid crystal touch panel 10 in this embodiment is composed of two glass substrates facing each other, a TFT array substrate and a color filter substrate, and the components for touch detection are provided on the TFT array substrate of the two glass substrates.

[0033] The liquid crystal touch panel 10 includes a plurality of rectangular sensor electrodes 144, a touch detection circuit 120, and a plurality of sensing lines SNL. One end of each sensing line SNL is connected to a contact portion 147 formed on the corresponding sensor electrode 144, and the other end of each sensing line SNL is connected to the touch detection circuit 120. In this embodiment, the plurality of sensor electrodes 144 are formed by dividing a conventional common electrode into a matrix as shown in FIG. 5. In this regard, as an example, a conventional common electrode is divided into 18 portions in the horizontal direction (the direction in which the gate bus lines GL extend) and into 32 portions in the vertical direction (the direction in which the source bus lines SL extend). In this case, 576 sensor electrodes 144 are formed in the liquid crystal touch panel 10. As described above, the plurality of sensor electrodes 144 function as electrodes for touch detection and electrodes for image display. As described above, the liquid crystal display device according to this embodiment is a liquid crystal display device equipped with an in-cell touch panel. Touch detection is performed by a self-capacitance method.

[0034] 6 is a diagram for explaining the details of the touch detection circuit 120. The touch detection circuit 120 is provided with one AFE (analog front end) 122 for each of a plurality of sensing lines SNL. The AFE 122 is an IC that processes the touch detection signal obtained from the sensing line SNL (for example, performs noise removal and signal component amplification), and is configured with, for example, an operational amplifier, an AD converter, etc. In this embodiment, the AFE 122 outputs a touch detection signal DS after AD conversion, and the touch detection signal DS is sent to the touch controller 240. Note that FIG. 6 shows only the components corresponding to one AFE 122.

[0035] As shown in FIG. 6, the touch detection circuit 120 includes a switch group 121G consisting of a plurality of switches 121. The on / off of each switch 121 is controlled by a touch control signal TCTL sent from the touch controller 240. When a switch 121 is turned on, the corresponding sensing line SNL is connected to the AFE 122. As a result, the AFE 122 processes the touch detection signal obtained from the corresponding sensing line SNL. In this embodiment, all the switches 121 are turned off during periods other than when touch detection is to be performed, and one of the plurality of switches 121 included in the switch group 121G is turned on during when touch detection is to be performed. The plurality of switches 121 included in each switch group 121G are turned on sequentially, so that the AFE 122 processes the touch detection signals obtained from all the sensing lines SNL.

[0036] As will be described later, in this embodiment, the source bus lines SL are maintained in a high-impedance state for a certain period of time. A configuration for achieving this will be described. FIG. 7 is a diagram showing the configuration of the output unit 160 of the source driver IC 112. However, FIG. 7 shows only a portion corresponding to one source bus line SL. As shown in FIG. 7, the output unit 160 includes an output buffer 161 and a changeover switch 162. The operation of the changeover switch 162 is controlled by an output control signal OCTL included in the source control signal SCTL. When the terminals 1621 and 1622 are connected, the video signal V is applied to the source bus lines SL via the output buffer 161. When the terminals 1621 and 1623 are connected, the source bus lines SL are in a high-impedance state. As described above, in this embodiment, the source driver 110 includes a changeover switch 162 that switches each source bus line SL between a state where it is connected to the output terminal of the output buffer 161 that outputs the video signal V and a high-impedance state. This makes it possible to place the source bus lines SL in a high-impedance state.

[0037] <2. Drive method> The driving method of this embodiment will be described with reference to Figures 1 and 8. Figures 1 and 8 show changes in the potential (source potential) VS of the source bus line SL, the potential VCOM of the sensor electrode (common electrode) 144, and the potentials (gate potentials) G(n-1) to G(n+1) of the gate bus lines GL from the (n-1)th row to the (n+1)th row.

[0038] As shown in FIG. 1, each horizontal scanning period includes a period during which the potential VCOM of the sensor electrode 144 fluctuates and a period during which the potential VCOM of the sensor electrode 144 is maintained at the normal level. During the period during which the potential VCOM of the sensor electrode 144 fluctuates, the touch detection circuit 120 acquires a touch detection signal. This allows touch detection to be performed during each horizontal scanning period. Regarding the waveforms of the source potential VS in FIGS. 1 and 8, the source bus lines SL are in a high-impedance state in the shaded areas. Therefore, in this embodiment, touch detection is performed by fluctuating the potential VCOM of the sensor electrode 144 during the period during which the source bus lines SL are maintained in a high-impedance state. During each horizontal scanning period, during the period during which the potential VCOM of the sensor electrode 144 is maintained at the normal level, a video signal is written to the liquid crystal capacitor 142 in the pixel formation unit 14 corresponding to the selected gate bus line GL.

[0039] FIG. 8 is an enlarged view of a portion indicated by an arrow with reference numeral 50 in FIG. 1. Referring to FIG. 8, the operation of one horizontal scanning period will be described. At time t1, the potential G(n-1) of the gate bus line GL in the (n-1)th row drops from the gate high potential VGH to the gate low potential VGL, and the potential G(n) of the gate bus line GL in the nth row rises from the gate low potential VGL to the gate high potential VGH. This starts a horizontal scanning period for writing a video signal to the liquid crystal capacitor 142 in the pixel formation portion 14 corresponding to the gate bus line GL in the nth row. At time t1, a video signal is applied to each source bus line SL from the source driver IC 112, and the potential VCOM of the sensor electrode 144 is at a normal level. At time t1, in the touch detection circuit 120 (see FIG. 6), all of the switches 121 included in each switch group 121G are in the off state.

[0040] At time t2, in the output section 160 (see FIG. 7) in the source driver IC 112, the changeover switch 162 operates based on the output control signal OCTL, causing a change from a state in which the terminals 1621 and 1622 are connected to a state in which the terminals 1621 and 1623 are connected. As a result, each source bus line SL enters a high impedance state. Note that it is also possible to employ a configuration in which each source bus line SL enters a high impedance state at time t1 (i.e., at the start of the horizontal scanning period).

[0041] At time t3, the sensor electrode potential control IC 250 varies the potential VCOM of the sensor electrode 144 by a predetermined amplitude based on the sensor electrode potential control signal VCTL provided from the touch controller 240. Also at time t3, in the touch detection circuit 120, each switch group 121G operates based on the touch control signal TCTL, thereby turning on one of the multiple switches 121 included in each switch group 121G. As a result, the AFE 122 processes the touch detection signal obtained from the sensing line SNL connected to the switch 121 that has turned on.

[0042] At time t4, the sensor electrode potential control IC 250 stops the fluctuation of the potential VCOM of the sensor electrode 144 based on the sensor electrode potential control signal VCTL provided from the touch controller 240. That is, the potential VCOM of the sensor electrode 144 returns to the normal level. Also, at time t4, in the touch detection circuit 120, each switch group 121G operates based on the touch control signal TCTL, and all the switches 121 included in each switch group 121G are turned off.

[0043] At time t5, in the output section 160 in the source driver IC 112, the changeover switch 162 operates based on the output control signal OCTL, causing the state in which the terminals 1621 and 1623 are connected to change to the state in which the terminals 1621 and 1622 are connected. This releases the high impedance state of each source bus line SL, and a video signal is applied to each source bus line SL via the output buffer 161. Then, the source potential VS changes according to the target display image, and the video signal is written to the liquid crystal capacitance 142 in the pixel formation section 14 corresponding to the n-th gate bus line GL.

[0044] At time t6, the potential G(n) of the nth gate bus line GL drops from the gate high potential VGH to the gate low potential VGL, and the potential G(n+1) of the (n+1)th gate bus line GL rises from the gate low potential VGL to the gate high potential VGH, thereby completing the horizontal scanning period for writing a video signal to the liquid crystal capacitance 142 in the pixel formation portion 14 corresponding to the nth gate bus line GL.

[0045] As described above, in the present embodiment, in all horizontal scanning periods included in each frame period (each vertical scanning period), each source bus line SL is maintained in a high impedance state from time t2 to time t5, and the potential VCOM of each sensor electrode 144 fluctuates from time t3 to time t4. Under these conditions, the AFE 122 processes the touch detection signal obtained from the sensing line SNL from time t3 to time t4.

[0046] Meanwhile, during the period from time t3 to time t4, the potential VCOM of the sensor electrode 144 fluctuates due to touch detection. At this time, in the pixel formation portions 14 corresponding to the gate bus lines GL other than the n-th row, the pixel TFTs 140 are maintained in the off state, so the potential of the pixel electrodes 141 also fluctuates in response to the fluctuation of the potential VCOM of the sensor electrode 144. In the pixel formation portion 14 corresponding to the n-th row gate bus line GL, the pixel TFTs 140 are in the on state, but as described above, the source bus line SL is in a high-impedance state. Therefore, in the pixel formation portion 14 corresponding to the n-th row gate bus line GL, the potential of the pixel electrode 141 also fluctuates in response to the fluctuation of the potential VCOM of the sensor electrode 144. As described above, the fluctuation of the potential VCOM of the sensor electrode 144 does not affect the display.

[0047] In this embodiment, the video signal line high-impedance step is realized by the operation at time t2, the video signal line high-impedance release step is realized by the operation at time t5, and the touch detection step is realized by the operation from time t3 to time t4. Also, the period from time t2 to time t5 realizes a first period, the period from time t3 to time t4 realizes a second period, the first point in time is realized by time t2, and the second point in time is realized by time t5.

[0048] <3. Comparison between the conventional example and this embodiment> FIG. 9 compares one frame period in a conventional example with one frame period in this embodiment. In the conventional example, a touch detection period is provided separately from the display period. In contrast, in this embodiment, touch detection is performed during each horizontal scanning period. That is, the touch detection period is not provided separately from the display period, but is included in the display period. Therefore, as can be seen from FIG. 9 , the display period is longer in this embodiment than in the conventional example. Due to the difference in the length of the display period in one frame period between the conventional example and this embodiment, the transmission rate of the digital video signal DV (transmission rate per source driver IC) also differs between the conventional example and this embodiment, as shown in FIG. 10 . For example, focusing on the row indicated by the arrow labeled 6 in FIG. 10 , assuming a resolution of 3840 × 2160, a source driver 110 consisting of four source driver ICs 112, and a refresh rate of 120 Hz, the transmission rate is 5.1 Gbps in the conventional example, but 3.6 Gbps in this embodiment. As such, the transmission rate in this embodiment is significantly lower than that of the conventional example. Specifically, in the example shown in Fig. 10, the transmission rate in this embodiment is approximately 70% of the transmission rate in the conventional example. As a result, according to this embodiment, power consumption is also reduced compared to the conventional example.

[0049] <4. Effects> According to this embodiment, the sensor electrode potential control IC 250 varies the potential VCOM of the sensor electrode 144 during a portion of each horizontal scanning period, and during this period, the touch detection circuit 120 acquires and processes a touch detection signal from the sensor electrode 144. That is, as shown in FIG. 1 , driving for touch detection is performed during a portion of each horizontal scanning period. Because a period for driving for touch detection is not provided separately from a period for driving for image display, the writing time (the time for writing a video signal to the liquid crystal capacitor 142) is longer than in the conventional example. Furthermore, when varying the potential VCOM of the sensor electrode 144 for touch detection, each source bus line SL is maintained in a high-impedance state. Therefore, fluctuations in the potential VCOM of the sensor electrode 144 do not affect the display. As a result, good display quality is maintained. Furthermore, a configuration is adopted in which the touch controller 240 controls the operation of the sensor electrode potential control IC 250 and the operation of the touch detection circuit 120 based on a synchronization signal Sync provided by the timing controller 220, facilitating timing control. Therefore, the accuracy of touch detection does not decrease due to the inclusion of noise, etc. As described above, according to this embodiment, a liquid crystal display device that can achieve both good display quality and highly accurate touch detection is realized.

[0050] <5.Other> The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, touch detection driving is performed in all horizontal scanning periods included in each frame period (each vertical scanning period), but the present invention is not limited to this, and there may be a horizontal scanning period in each frame period in which touch detection driving is not performed. [Explanation of symbols]

[0051] 10...LCD touch panel 20...PCB 100...Drive unit 101...Display section 110...Source driver 112...Source driver IC 120...Touch detection circuit 130...Gate driver 144...Sensor electrode 210…Combined power supply IC 220...Timing controller 230...Level shifter IC 240...Touch controller 250...Sensor electrode potential control IC GL: Gate bus line SL...Source bus line SNL…Sensing Line

Claims

1. A liquid crystal display device having a touch panel including a plurality of sensor electrodes provided for detecting a touch position, a plurality of video signal lines for transmitting video signals; a plurality of scanning signal lines intersecting the plurality of video signal lines; a plurality of pixel formation portions provided corresponding to intersections of the plurality of video signal lines and the plurality of scanning signal lines; a video signal line drive circuit that applies the video signals to the plurality of video signal lines; a scanning signal line driving circuit that selectively drives the plurality of scanning signal lines; a sensor electrode potential control circuit for controlling the potentials of the plurality of sensor electrodes; a touch detection circuit for acquiring touch detection signals for detecting a touch position from the plurality of sensor electrodes and processing the touch detection signals; a touch control circuit that controls an operation of the sensor electrode potential control circuit and an operation of the touch detection circuit; a timing control circuit that controls an operation of the video signal line drive circuit, an operation of the scanning signal line drive circuit, and an operation of the touch control circuit; Equipped with the plurality of sensor electrodes and the plurality of pixel formation portions are in a one-to-n correspondence, where n is an integer of 2 or more; Each of the plurality of pixel formation portions A pixel electrode; a pixel transistor having a control terminal connected to a corresponding scanning signal line, a first conduction terminal connected to a corresponding video signal line, and a second conduction terminal connected to the pixel electrode; a liquid crystal capacitance formed by the corresponding sensor electrode and the pixel electrode; Including, the video signal line drive circuit maintains the plurality of video signal lines in a high impedance state during a first period before the video signals are written to the liquid crystal capacitance during a horizontal scanning period during which the scanning signal lines are driven; the touch control circuit controls the operation of the sensor electrode potential control circuit based on a synchronization signal provided from the timing control circuit, whereby potentials of the plurality of sensor electrodes fluctuate during a second period included in the first period, and potentials of the plurality of sensor electrodes are maintained at a constant level during periods other than the second period; a touch control circuit that controls the operation of the touch detection circuit based on a synchronization signal provided from the timing control circuit, thereby causing the touch detection circuit to acquire and process the touch detection signal during the second period.

2. The liquid crystal display device according to claim 1 , wherein the start point of the first period is the start point of a horizontal scanning period.

3. The video signal line driving circuit an output buffer for outputting the video signal; a changeover switch for switching each video signal line between a state where it is connected to the output terminal of the output buffer and a high impedance state; The liquid crystal display device according to claim 1 , comprising:

4. the video signal line drive circuit maintains the video signal lines in a high impedance state during the first period in all horizontal scanning periods included in each vertical scanning period; 4. The liquid crystal display device according to claim 1, wherein the potentials of the plurality of sensor electrodes fluctuate in the second period in all horizontal scanning periods included in each vertical scanning period.

5. A method for driving a liquid crystal display device having a touch panel including a plurality of sensor electrodes provided for detecting a touch position, comprising: The liquid crystal display device comprises: a plurality of video signal lines for transmitting video signals; a plurality of scanning signal lines intersecting the plurality of video signal lines; a plurality of pixel formation portions provided corresponding to intersections of the plurality of video signal lines and the plurality of scanning signal lines; a sensor electrode potential control circuit for controlling the potentials of the plurality of sensor electrodes; a touch detection circuit for acquiring touch detection signals for detecting a touch position from the plurality of sensor electrodes and processing the touch detection signals; a touch control circuit that controls an operation of the sensor electrode potential control circuit and an operation of the touch detection circuit; a timing control circuit for controlling the operation of the touch control circuit; Equipped with the plurality of sensor electrodes and the plurality of pixel formation portions are in a one-to-n correspondence, where n is an integer of 2 or more; Each of the plurality of pixel formation portions A pixel electrode; a pixel transistor having a control terminal connected to a corresponding scanning signal line, a first conduction terminal connected to a corresponding video signal line, and a second conduction terminal connected to the pixel electrode; a liquid crystal capacitance formed by the corresponding sensor electrode and the pixel electrode; Including, The driving method includes: a video signal line high impedance setting step of setting the plurality of video signal lines to a high impedance state at a first time point before the video signal is written to the liquid crystal capacitance during a horizontal scanning period in which scanning signal lines are driven; a video signal line high impedance canceling step of canceling the high impedance state of the plurality of video signal lines at a second time point during the horizontal scanning period that is a time point before the video signal is written to the liquid crystal capacitance and that is a time point after the first time point; a touch detection step in which the touch control circuit controls an operation of the sensor electrode potential control circuit and an operation of the touch detection circuit based on a synchronization signal provided from the timing control circuit so that potentials of the plurality of sensor electrodes fluctuate and the touch detection circuit acquires and processes the touch detection signal during a period between the first time point and the second time point; A driving method comprising:

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