Display device and control method for display device

Abstract

To provide a display device with improved display quality at low ambient temperatures. [Solution] A display device comprising a plurality of pixel electrodes, a plurality of drive electrodes, and a drive circuit for driving at least one of the plurality of drive electrodes, wherein the drive circuit alternately drives at least one of the plurality of pixel electrodes in a display mode for image display and drives at least one of the plurality of drive electrodes in a touch mode for touch sensing, and in the nth drive in touch mode, it supplies a pulsed touch drive signal to at least one of the plurality of drive electrodes, and in the (n+1)th drive in touch mode, it supplies a pulsed touch drive signal to at least one of the plurality of drive electrodes that has the opposite sign to the pulsed touch drive signal of the nth drive, where n is a natural number.

Description

Technical Field

[0004] , , , , ,

[0005] , , , , ,

[0001] The present technology relates to a display device and a method for controlling the display device.

Background Art

[0002] There is known a so-called in-cell type touch display in which part or all of a touch panel structure is incorporated inside a display device (see, for example, Patent Documents 1 and 2). In an in-cell type touch display, a display driving electrode is used as one sensor, and a common electrode arranged to face the display driving electrode is used as the other sensor. This in-cell type touch display has an advantage in that it can realize a display with higher brightness, thinner thickness, and lighter weight because there is no need to provide a touch panel structure on the display screen of the display compared with an on-cell type.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an in-cell type display device having a touch sensor function, a driving display driving period for driving the display and a touch driving period for exerting the touch sensor function are executed within one frame period. Here, in the touch driving period, a pulsed touch driving signal is supplied to a touch wiring to which a touch electrode is connected to detect the presence or absence of a touch and the position of the touch. However, according to this pulsed touch driving signal, there is a problem that electromagnetic interference noise (EMI) is likely to occur.

[0005] This technology was developed in view of the above-mentioned problems, and its purpose is to reduce electromagnetic interference noise during touch operation in a display device having a touch sensor function. [Means for solving the problem]

[0006] This technology discloses a display device comprising any combination of the following configurations 1 to 12, or a program comprising the following configuration 13, or a control method for a display device corresponding thereto. [Configuration 1] Multiple pixel electrodes, Multiple drive electrodes, A drive circuit that drives at least one of the plurality of drive electrodes, Prepare, The aforementioned drive circuit is At least one of the plurality of pixel electrodes is driven in display mode for image display, At least one of the plurality of drive electrodes is driven in touch mode for touch sensing, Perform these alternately, During the nth drive in the touch mode, a pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes. During the (n+1)th touch mode drive, a pulsed touch drive signal with the opposite polarity to the nth pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes, where n is a natural number. The display device is configured as follows.

[0007] [Configuration 2] The display device according to configuration 1, comprising a plurality of gate wirings and a plurality of source wirings, wherein each of the plurality of pixel electrodes is connected to the plurality of gate wirings and the plurality of source wirings via a switch element and arranged in a matrix.

[0008] [Configuration 3] The display device according to configuration 1 or 2, wherein the plurality of drive electrodes are common electrodes that provide a common potential in display mode.

[0009] [Structure 4] The display device according to any one of the above configurations 1 to 3, wherein the drive circuit includes a detection circuit that outputs a pulsed touch drive signal for driving at least one of the plurality of drive electrodes to detect the presence or absence of a touch or the position of a touch.

[0010] [Composition 5] The display device according to any one of the above configurations 1 to 4, wherein the drive circuit includes a detection circuit that outputs the pulsed touch drive signal to detect the presence or absence of a touch or the position of the touch.

[0011] [Composition 6] The detection circuit includes a sensing generator that generates a pulsed touch drive signal, and a switching circuit that switches between a positive voltage and a negative voltage of the power supply for the sensing generator. The display device according to configuration 5 above, including the above configuration.

[0012] [Composition 7] A method for driving a display device comprising a plurality of pixel electrodes and a plurality of drive electrodes, the method comprising alternating between driving at least one of the plurality of pixel electrodes in a display mode for image display and driving at least one of the plurality of drive electrodes in a touch mode for touch sensing, wherein in the nth drive in touch mode, a pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes, where n is a natural number, and in the (n+1)th drive in touch mode, a pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes, having the opposite sign to the pulsed touch drive signal of the nth drive. [Brief explanation of the drawing]

[0013] [Figure 1]It is a diagram showing a schematic system configuration of a display device according to an embodiment. [Figure 2] It is a diagram schematically showing a part of a cross-sectional structure along a source wiring of a display device according to an embodiment. [Figure 3] It is a diagram schematically showing a part of a partial structure along a gate wiring of a display device according to an embodiment. [Figure 4] It is a plan view schematically showing a configuration related to touch sensing of a display device according to an embodiment. [Figure 5] It is a diagram conceptually showing signal waveforms applied to a source wiring, a gate wiring, and a common electrode according to a driving mode in a conventional display device. [Figure 6] It is a diagram conceptually showing signal waveforms applied to a source wiring, a gate wiring, and a common electrode according to a driving mode in a display device according to an embodiment. [Figure 7] It is a diagram conceptually showing the direction of current flowing through a common electrode during a touch driving period in a display device according to an embodiment. [Figure 8] It is a diagram schematically showing a detection circuit for a reset phase during a touch driving period of a display device according to an embodiment. [Figure 9] It is a diagram schematically showing a detection circuit in a sensing phase during a touch driving period of a display device according to an embodiment. [Figure 10] It is a diagram showing a structure for applying a signal to a touch wiring of a display device according to an embodiment. [Figure 11] It is a diagram schematically showing a part of a partial structure along a gate wiring of a display device according to another embodiment.

Embodiments for Carrying Out the Invention

[0014] The following describes a display device according to one embodiment, with reference to the drawings as appropriate. In the following, an in-cell type touch display (hereinafter sometimes simply referred to as "display device") is given as an example of an embodiment of the display device, but this technology is not limited to this. In some of the drawings, arrows X, Y, and Z indicate directions that intersect each other (for example, orthogonal), and correspond to the long side direction, short side direction, and thickness direction (normal direction of the display surface) of the display device, respectively.

[0015] [Display device configuration] Figure 1 is a schematic plan view showing the configuration of a display device 1 according to one embodiment. The display device 1 of this embodiment is generally a flat, rectangular plate and includes a display panel 10 which is the main component of the display device 1. The display panel 10 displays an image based on image information and can also electrically rewrite the displayed image. The display device 1 includes a plurality of source wirings SL and a plurality of gate wirings GL, and includes a source drive unit SD that drives the plurality of source wirings SL, a gate drive unit GD that drives the plurality of gate wirings GL, and a control circuit CTR that controls the source drive unit SD and the gate drive unit GD.

[0016] Furthermore, the display device 1 of this embodiment is configured to operate as a touch panel having a touch sensor function. Specifically, the display panel 10 is equipped with a plurality of touch electrodes (see, for example, Figure 4). Such plurality of touch electrodes may be dedicated touch mode electrodes to which a touch drive signal is applied only when the drive mode is touch mode, or they may be shared electrodes to which a display drive signal (including, for example, a common voltage) for displaying an image is applied in display mode, and a touch drive signal is applied in touch mode.

[0017] Here, for example, when multiple touch electrodes are used as a shared electrode, a conventional common electrode that is continuously formed over almost the entire display area can be divided into multiple matrix-shaped common electrodes (CE: Common Electrode) and used as multiple touch electrodes. In this way, the touch electrodes may be common with the common electrode CE to which a common voltage (Common Voltage: Vcom) common to all pixels is applied for image display.

[0018] In this case, the multiple touch electrodes, which are also multiple common electrodes CE provided on the display panel 10, are, for example, subjected to a common voltage as a display drive signal in display mode, and when driven in touch mode, a touch drive signal is applied to at least one of them.

[0019] If the display device 1 is, for example, a liquid crystal display (LCD) with an in-cell type touch sensor function, the multiple common electrodes CE provided on the display panel 10 can be common electrodes to which a common voltage Vcom is applied in order to form an electric field corresponding to each pixel electrode to which a pixel voltage is applied.

[0020] In the following explanation, for the sake of clarity, this technology will be described using the example of a display device 1 equipped with a common electrode CE as a touch electrode. In this display device 1, a common electrode CE to which a common voltage Vcom can be applied for image display is used as a touch electrode. Hereafter, without distinguishing any particular function, the touch electrode will sometimes be referred to as the common electrode CE.

[0021] As shown in Figure 1, the display device 1 of this embodiment is equipped with a backlight device BL on the back side of the display panel 10. The display panel 10 is capable of displaying an image using illumination light emitted from the backlight device BL, for example. The display panel 10 includes a display area (active area) AA on which the display image can be displayed, and a non-display area (non-active area) NA on which the display image is not displayed.

[0022] Figure 2 is a schematic diagram showing a part of the cross-sectional structure along the source wiring SL of a display device according to one embodiment. Figure 3 is a schematic diagram showing a part of the cross-sectional structure along the gate wiring GL of a display device according to one embodiment. The display device 1 of this embodiment is a liquid crystal display device with a touch sensor. The display panel 10 includes, for example, an array substrate 20 provided with a display circuit for displaying images, a counter substrate 30 positioned opposite the array substrate 20, and a liquid crystal layer 40 positioned between the array substrate 20 and the counter substrate 30, as shown in Figures 2 and 3. The display panel 10 can control the amount of light transmitted from the backlight device BL by controlling the orientation state of the liquid crystal with a drive circuit.

[0023] The array substrate 20 and the opposing substrate 30 are equipped with nearly transparent (highly visible light transmittance (e.g., 90% or more)) glass substrates 21 and 31, and display circuits are provided on the inner surfaces (opposing surfaces) of these glass substrates 21 and 31. The drive circuit DC is composed of various layers formed by lamination, for example, photolithography. The array substrate 20 extends beyond the opposing substrate 30 in the Y direction, for example, and the drive circuit DC (e.g., gate driver GD, source driver SD, common electrode drive circuit CD) and a control board (e.g., control circuit CTR) via a flexible wiring board (not shown) are mounted on this extended portion to supply various signals related to display functions and touch panel functions.

[0024] The array substrate 20, on the display surface side of the glass substrate 21, includes, as described above, a plurality of gate wirings GL extending along the long side direction X and a plurality of source wirings SL extending along the short side direction Y. The display panel 10 is divided into a plurality of pixel regions by these gate wirings GL and source wirings SL. Each pixel region corresponds to, for example, a subpixel. A switching element (e.g., a thin-film transistor: TFT) is provided in each pixel region. In the switching element, for example, the gate electrode of the TFT is connected to the gate wiring GL, the source electrode to the source wiring SL, and the drain electrode to the transparent pixel electrode PE. The pixel electrode PE has a shape corresponding to each pixel region (in this case, a subpixel). The display region AA is occupied by, for example, a plurality of pixel regions arranged in a matrix.

[0025] The TFT is driven (ON) based on a high-potential scanning signal (GateH) supplied by the gate drive unit GD to the gate wiring GL. This drive causes the source electrode and drain electrode to conduct, and the source drive unit SD supplies an image signal (Source) to the source wiring SL, thereby charging the pixel electrode PE to a potential based on the image signal. The gate drive unit GD sequentially supplies scanning signals to multiple gate wirings GL, and the source drive unit SD supplies an image signal to the driven pixel electrode so that it reaches a pixel potential corresponding to the displayed image.

[0026] The array substrate 20 is provided with a common electrode CE that forms an electric field with the pixel electrode PE when a common potential (reference potential) is supplied. In other words, the display panel 10 according to this embodiment is set to FFS (Fringe Field Switching) mode, and both the pixel electrode PE and the common electrode CE are provided on the array substrate 20 side, and these pixel electrode PE and common electrode CE are arranged on different layers. The pixel electrode PE is provided with slits SLp that extend diagonally along the X-axis and Y-axis directions when viewed in a plane, spaced apart. When a potential difference occurs between the common electrode CE and the pixel electrode PE, which are arranged on different layers, a fringe electric field (diagonal electric field) is applied, which includes a component along the surface of the array substrate 20 as well as a component normal to the surface of the array substrate 20. This fringe electric field can then be used to appropriately switch the orientation state of the liquid crystal molecules contained in the liquid crystal layer 40.

[0027] Figure 4 is a schematic plan view showing the configuration of the touch sensor function of the display device 1 according to one embodiment. The array substrate 20 is equipped with multiple touch electrodes (common electrodes CE) for performing touch sensor functions. The touch sensor function realized in this embodiment is, for example, based on a projected capacitance method, and its detection method is a self-capacitance method. The common electrodes CE are arranged within the layers of the display panel 10, as shown in Figures 2 and 3. The common electrodes CE are arranged in a matrix in the display area AA of the display panel 10. The display area AA of the display panel 10 roughly coincides with the touch sensor area where the input position can be detected. Therefore, when a user brings a conductive input object, such as the user's finger or a stylus, close to the surface (display surface) of the display panel 10 based on an image displayed in the display area AA of the display panel 10, a capacitance is formed between the input object and the common electrodes CE. The capacitance detected at the common electrodes CE changes with the distance as the input object approaches, and becomes different from the capacitance of the common electrodes CE that are far from the input object. Based on this difference in capacitance, the detection circuit described later can detect the input position.

[0028] Multiple common electrodes CE are arranged across almost the entire display area AA of the array substrate 20 and are divided into individual common electrodes CE via, for example, roughly grid-like slits SLc. The common electrodes CE are much larger in size when viewed in a plane than the pixel electrodes PE, and can have a size that spans multiple (tens to hundreds) pixel electrodes PE in the X and Y directions.

[0029] Multiple touch wirings TL are provided on the array substrate 20 along the Y direction. Each touch wiring TL extends along the Y direction, crossing all of the common electrodes CE arranged in a line along the Y direction. Each touch wiring TL is connected to a specific common electrode CE among the multiple common electrodes CE it crosses. In Figure 4, the connection points (contact holes) of the touch wiring TL to the common electrodes CE are shown as black circles. Depending on the number of touch wirings TL installed, only one touch wiring TL may be connected to one common electrode CE, or multiple touch wiring TLs may be connected to one common electrode CE. The number of touch wirings TL connected to one common electrode CE may also vary depending on the position of the common electrode CE. In that case, although not limited to this, it is preferable to have more touch wirings TL connected to common electrode CEs far from the common electrode drive circuit CD than to touch wirings TL connected to common electrode CEs close to the common electrode drive circuit CD.

[0030] One end of the touch wiring TL in the Y-axis direction is connected to the common electrode drive circuit CD in the non-display area NA. The touch wiring TL may extend beyond the common electrode CE to which it is connected, on the opposite side from the common electrode drive circuit CD (upper side of Figure 4). The touch wiring TL may also be connected to an inspection circuit or electrostatic discharge protection element (not shown) located in the non-display area NA on the opposite side from the common electrode drive circuit CD (upper side of Figure 4). Furthermore, the touch wiring TL is connected to a detection circuit. The detection circuit may be provided in the common electrode drive circuit CD, or it may be provided outside the display panel 10 via a flexible substrate (not shown).

[0031] Other configurations of the display device 1 as a liquid crystal display device will be described. As shown in Figures 2 and 3, the array substrate 20 has the following layers stacked on it, from the bottom layer side (glass substrate 21 side): a first conductive film, a first insulating film (gate insulating film 23), a semiconductor film, a second conductive film, a second insulating film 24, a planarization film (insulating film) 25, a third conductive film, a third insulating film 26, a first transparent electrode film, a fourth insulating film 27, and a second transparent electrode film.

[0032] The first conductive film constitutes a part of the gate wiring GL, the gate electrode 22A of the TFT22, and so on. The second conductive film constitutes a portion of the gate wiring GL, the source electrode 22B and drain electrode 22C of the TFT 22, and so on. The third conductive film constitutes the source wiring SL, touch wiring TL, etc. The first conductive film, the second conductive film, and the third conductive film are each single-layer films or multilayer films or alloys made of different types of metal materials, selected from copper, titanium, aluminum, molybdenum, tungsten, etc., and possess conductivity and light-shielding properties.

[0033] The semiconductor film constitutes the semiconductor portion 22D in the TFT22. The semiconductor film is composed of semiconductor materials such as oxide semiconductors and amorphous silicon. The first transparent electrode film constitutes the common electrode CE (touch electrode), etc. The second transparent electrode film constitutes the pixel electrode PE, etc. The first and second transparent electrode films are made of transparent electrode material (for example, ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide), etc.).

[0034] The liquid crystal layer 40 (medium layer) contains liquid crystal molecules, which are substances whose optical properties change when an electric field is applied. The liquid crystal layer 40 is placed between a pair of substrates 20 and 30. The inner surfaces of the array substrate 20 and the opposing substrate 30 are each provided with alignment films (not shown) for aligning the liquid crystal molecules contained in the liquid crystal layer 40. The outer surfaces of the array substrate 20 and the opposing substrate 30 are each provided with polarizing plates (not shown).

[0035] On the inner surface of the glass substrate 31 of the opposing substrate 30, a translucent color filter 32 of different colors is provided in the display area AA. The color filter 32 exhibits three colors, for example, blue (B), green (G), and red (R), and is arranged side by side between multiple source wirings SL so as to be adjacent to each other. In other words, the color filter 32 is arranged along the extending direction (generally the X-axis direction) of the gate wiring GL. Thus, the multiple color filters 32 as a whole are arranged in a horizontal stripe pattern. These color filters 32 are arranged so as to overlap with each pixel electrode PE on the array substrate 20 side when viewed in a plane. The overlapping color filters 32 and the pixel electrode PE constitute a pixel (subpixel), which is the display unit. The boundaries (color boundaries) of the color filters 32 of different colors are positioned to overlap with the gate wiring GL. Furthermore, an overcoat film 34 is provided on the upper side (liquid crystal layer 40 side) of the color filter 32, which is laid in a solid shape over almost the entire surface of the opposing substrate 30 in order to flatten it.

[0036] Furthermore, a light-shielding portion 33 and a spacer 35 are formed on the opposing substrate 30 side. The light-shielding portion 33 shields light between adjacent pixel electrodes PE. It also shields light between adjacent color filters 32 of different colors. The light-shielding portion 33 has a roughly grid-like planar shape so as to overlap with adjacent pixel electrodes PE, and has pixel openings 33A such that, when viewed in a planar view, it does not overlap with most of the pixel electrodes PE. These pixel openings 33A allow the transmitted light from the pixel electrodes PE to be emitted to the outside of the display panel 10. The light-shielding portion 33 is positioned so as to overlap, when viewed in a planar view, with at least the TFT 22, gate wiring GL, source wiring SL, and touch wiring TL on the array substrate 20 side.

[0037] Spacer 35 is an element that maintains the distance between a pair of substrates 20 and 30. For example, the spacer 35 has a planar shape that is approximately circular. Spacer 35 is positioned near the intersection of gate wiring GL and source wiring SL on the array substrate 20. Spacer 35 has a height equal to the cell thickness (the distance between the array substrate 20 and the opposing substrate 30, i.e., the thickness of the liquid crystal layer 40) and functions to maintain the cell thickness evenly. There are also sub-spacers that are a certain amount shorter in height than the main spacers and have the function of supporting the cell when a load is applied from outside. Figure 3 shows an example where spacer 35 is a sub-spacer, but spacer 35 may also be a main spacer.

[0038] [Drive method] In general, a display device supplies power to the TFT (Thin Film Display) each time it displays one frame (one image). However, some display devices can, for example, not continuously supply power to the TFT during the duration of one frame, but instead provide power intermittently during "pause periods" to drive the TFT. This pause period can then be used to enable touch sensing using touch electrodes incorporated within the display device.

[0039] Figure 5 is a typical timing diagram of control signals for voltages applied to gate wiring GL, touch wiring TL, and source wiring SL in a conventional touch display, illustrated for illustrative purposes. As shown in Figure 5, the display device operates alternately between a display mode for displaying images and a touch mode for touch sensing within the display period of one frame. In other words, with respect to the common electrode CE (touch electrode), a common potential signal related to the image display function and a touch drive signal (position detection signal) related to the touch panel function are supplied from the common electrode drive circuit CD in a time-divided manner. The period during which the display device operates in display mode is called the display drive period. The period during which the display device operates in touch mode is called the touch drive period.

[0040] <Display operating time> In the diagram, "GateH" indicates the timing at which a predetermined high-potential signal is sent to the gate wiring GL. During the display driving period, a signal with a voltage level sufficient to turn on the gate of the TFT is sent to the gate wiring GL. "GateL" indicates the timing for sending a predetermined low-potential signal to the gate wiring GL. During the display drive period, no low-potential signal is sent to the gate wiring GL, and outside of the display drive period (i.e., during the touch drive period), the low-potential signal described later is sent. These high-potential and low-potential signals are supplied sequentially (scanned), for example, to one gate trace at a time GL.

[0041] "Source" indicates the timing for sending data signals to the source wiring SL. During the display driving period, for example, data signals corresponding to the display content are sent to the source wiring SL. The data signals transmit potential data signals corresponding to the display content of the gate wiring GL (pixel) whose gate has been turned ON, in accordance with the scanning of the gate wiring GL.

[0042] "Vcom" indicates the timing for sending a predetermined potential signal to the touch wiring TL. During the display drive period, for example, a common potential signal related to the image display function can be sent to the touch wiring TL. This common potential signal is sent to all touch wiring TL at the same timing (display period), for example. As a result, all common electrodes CE become reference potentials based on the common potential signal and function as common electrodes CE. However, it is not always necessary to apply a common potential to the common electrodes CE during the display drive period; for example, in the timing diagram shown in Figure 5, no common potential signal is sent during the display drive period.

[0043] <Conventional: Touch operation period> During the touch drive period, a pulsed touch drive signal (e.g., Vcom) is sent from the common electrode drive circuit CD to the touch wiring TL. The common electrode drive circuit CD can, for example, modulate a common voltage matched to the display drive with a pulsed pattern to create a touch drive signal (reference signal) for touch detection. The common electrode drive circuit CD supplies a pulsed touch drive signal for position detection to at least one touch wiring TL. Typically, the common electrode drive circuit CD sequentially supplies pulsed touch drive signals for position detection to multiple touch wiring TLs. The waveform of the touch drive signal is not particularly limited, but can be, for example, a square wave, triangle wave, or sine wave. The frequency of the touch drive signal is also not particularly limited, but can be, for example, a predetermined frequency of several tens of kHz to several hundred kHz.

[0044] The common electrode drive circuit CD may simultaneously supply pulse signals for pulsed position detection to multiple touch wirings TL. Regardless of whether the common electrode CE is driven sequentially or simultaneously, the common electrode drive circuit CD can perform sensing processing to sense (detect) the presence or absence of a touch and / or the location of a touch by utilizing the signal received from at least one of the multiple touch electrodes (TE).

[0045] Furthermore, to prevent abnormal potential differences from occurring within the display panel 10 during the touch drive period, the gate driver GD and source driver SD can also send gate potential signals and source potential signals synchronized with Vcom sent to the touch wiring TL to the gate wiring GL and source wiring SL. The gate potential signals and source potential signals supplied to the gate wiring GL and source wiring SL, respectively, may, for example, be the same as the position detection signal Vcom sent to the touch wiring TL, or they may be different. The gate potential signals and source potential signals supplied to the gate wiring GL and source wiring SL, respectively, during the touch drive period should, for example, have at least one of the voltage width and phase identical to the position detection signal Vcom sent to the touch wiring TL. The gate potential signals and source potential signals can be supplied to some or all of the multiple source wirings SL and multiple gate wirings GL. When supplied to some, the wiring should be located at a position corresponding to the common electrode CE to which the touch drive signal (TDS) is applied.

[0046] However, such position detection signals Vcom are relatively high-frequency pulse signals with steep rising and falling edges, which presents a challenge in that they can exacerbate electromagnetic interference (EMI) noise.

[0047] <Embodiment: Touch operation period> Figure 6 is a general timing diagram of the control signals for the voltages applied to the gate wiring GL, touch wiring TL, and source wiring SL in a display device 1 according to one embodiment. In Figure 6, the control signal for the display driving period is the same as in the conventional example in Figure 5. Therefore, a description of the common configuration and effects will be omitted.

[0048] In contrast, in the control signal for the touch drive period, the common potential signal Vcom sent to the touch wiring TL in the (n+1)th frame has its sign reversed compared to the common potential signal Vcom sent to the touch wiring TL in the nth frame. That is, in the (n+1)th frame, the common electrode drive circuit CD sends a position detection signal Vcom to the touch wiring TL, which is a predetermined common voltage matched to the drive of the display, modulated into a pulse-like pattern with the opposite sign to that of the nth frame. Here, n is a natural number, and for example, n can be any natural number. Also, n can be a sequence of natural numbers such as n=1,2,3... or a natural number that can be expressed as any function (for example, an arithmetic sequence such as n=3,7,11... (4k-1, k=1,2,3...)).

[0049] Figure 7 is a diagram conceptually showing the direction of the current flowing through the common electrode CE during the touch drive period in a display device according to one embodiment. In this process, as shown in Figure 7, a pulsed voltage applied to the common electrode CE in the nth frame generates a current in the common electrode CE. This current also causes a magnetic flux to spread around the common electrode CE. For example, at the rising edge of the pulsed voltage, the magnetic flux spreads outward from the common electrode CE, and at the falling edge of the pulsed voltage, the magnetic flux converges towards the common electrode CE, with the phase of the magnetic flux reversing between the rising and falling edges of the voltage. Since the strength of the magnetic flux is proportional to the rate of change of the current, a strong magnetic flux is generated at the rising and falling edges of the voltage. Furthermore, the direction and density of the magnetic flux change periodically as the voltage changes periodically. These factors can be the cause of EMI. In conventional touch driving methods, such EMI can occur every time the touch is driven.

[0050] In contrast, this technology reverses the sign of the pulsed voltage applied to the common electrode CE in the (n+1)th frame. As a result, the direction of the current flowing through the common electrode CE due to the application of the pulsed voltage is reversed compared to the previous nth frame. Consequently, the phase of the magnetic flux generated from the common electrode CE is reversed. That is, the magnetic fluxes cancel each other out between the nth frame and the (n+1)th frame. This reduces the EMI of the display device 1 as a whole.

[0051] The nth frame touch drive period, which outputs a relatively positive pulsed touch drive signal (positive touch drive signal), is referred to as the positive touch drive period, and the (n+1)th frame touch drive period, which outputs a relatively negative pulsed touch drive signal (negative touch drive signal), is referred to as the negative touch drive period. The negative touch drive period is provided after the positive touch drive period via the display drive period. In other words, after the positive touch drive period, which outputs a positive touch drive signal, there is a negative touch drive period, which outputs a negative touch drive signal via the display drive period. The common electrode drive circuit CD outputs a negative touch drive signal in the touch drive period following the positive touch drive period, which outputs a negative touch drive signal.

[0052] Such a combination of positive and negative touch drive periods, when performed at least once, contributes to reducing EMI originating from magnetic flux fluctuations. The combination of positive and negative touch drive periods may be performed, for example, at predetermined frame counts (e.g., 1000 frames) or predetermined time intervals (e.g., 1 minute). The combination of positive and negative touch drive periods may be repeated for all frames, for example. For example, a positive touch drive period may be included in the 2m frame, where a positive touch drive signal is output, and a negative touch drive period may be included in the (2m+1) frame, where a negative touch drive signal is output. In other words, the common electrode drive circuit CD may, for example, output a positive touch drive signal in the 2m frame and a negative touch drive signal in the (2m+1) frame. Of course, a negative touch drive period may also be included in the 2m frame, where a negative touch drive signal is output, and a positive touch drive period may be included in the (2m+1) frame, where a positive touch drive signal is output. In other words, the common electrode drive circuit CD may, for example, output a negative touch drive signal on the 2m frame and a positive touch drive signal on the (2m+1) frame. This allows the magnetic flux generated from the common electrode CE to be canceled out every frame. As a result, the overall EMI of the display device 1 can be effectively reduced.

[0053] [Sense Circuit] This section describes how to drive the touch electrodes (supply the touch drive voltage) when the drive mode is touch mode. Figure 8 is a schematic diagram showing the detection circuit for the reset phase during the touch drive period of the display device 1 according to one embodiment. Figure 9 is a schematic diagram showing the detection circuit for the sensing phase during the touch drive period of the display device 1 according to one embodiment.

[0054] Figures 8 and 9 schematically show the configuration of a touch wiring TL connected to an arbitrary (e.g., the nth) touch wiring TL and its detection circuit (single-ended charge integrator). The main components of the circuit and their corresponding reference numerals in Figures 8 and 9 are shown below.

[0055] The non-inverting input terminal of the operational amplifier is connected to the touch drive power supply V. The output of the operational amplifier is connected to the inverting input terminal via a feedback capacitor Cint and a reset switch S1 in parallel with this feedback capacitor Cint. The detection electrode Rx is also connected to the inverting input terminal of the operational amplifier in a single-ended manner via an input selector switch S2. The detection electrode Rx has parasitic capacitance Ct (capacitance) due to touching the common electrode CE, and parasitic capacitance Cp between it and the pixel electrode PE, gate wiring GL, source wiring SL, etc. A signal line that can be connected to GND or the touch drive power supply V is connected between the inverting input terminal and the input selector switch S2 via a bias capacitor Cb. This operational amplifier functions as a charge integrator, integrating and amplifying the minute signal input to the sense line to detect the change in capacitance due to touching the common electrode CE as a voltage.

[0056] Input section Ct: Capacitance (parasitic capacitance) due to touch Cp: ​​Parasitic capacitance between the common electrode CE and gate wiring GL or source wiring SL, etc. Rx: Detection electrode

[0057] Feedback Department Cint: Feedback capacitance (integral capacitance) S1: Reset switch Switching section S2, S3: Input selector switch Cb: Bias capacitor

[0058] Amplification section op-amp Vso: Output voltage P1: First connection point (potential: GRD or V) P2: Second connection point (potential: V)

[0059] This detection circuit is controlled by, for example, the control circuit CTR as follows: In the "reset phase," as shown in Figure 8, the reset switch S1, input selector switch S3 are set to ON, and input selector switch S2 is set to OFF. The first potential of the first connection point P1 is connected to GND, and the second connection point P2 is connected to the touch drive power supply V. This discharges the feedback capacitance Cint and charges the bias capacitor Cb to the input voltage V of the second contact, thereby initializing the circuit. The charge amount Q of the bias capacitor Cb is expressed by the formula: Q = Cb × V.

[0060] In the "sensing phase," as shown in Figure 9, the reset switch S1, input selector switch S3: OFF, and input selector switch S2: ON are switched. Here, the input voltage of the first connection point P1 is connected to the same voltage V as the input voltage of the second connection point P2. This allows the input voltage V to be applied to the detection electrode Rx. At this time, the charge amount Q that was charged in the bias capacitor Cb is redistributed to each capacitance of the detection circuit. Here, if there is a position input object such as a finger near the common electrode CE, the capacitance Ct, which is the capacitance to ground, increases, and the proportion of the charge amount Q distributed to the feedback capacitance Cint decreases. The detection circuit detects this decrease in charge amount Q as the output voltage Vso.

[0061] Conventionally, in addition to the parasitic capacitance Cp between the common electrode CE and the gate wiring GL and source wiring SL, EMI due to the supply of the touch drive input voltage V was introduced into the touch system via parasitic capacitance. As a result, the parasitic capacitance Cp increased, and even when a position input object such as a finger was present near the common electrode CE, the proportion of the charge amount Q distributed to the feedback capacitance Cint (i.e., the change in the capacitance Ct of the common electrode CE due to touch) became so small that it may not be detectable or the effects of noise could not be ignored.

[0062] In contrast, this technology switches the polarity of the input voltage (position detection signal Vcom) supplied to the common electrode CE during the touch driving period. Therefore, the effects of EMI can be reduced. For example, by switching the polarity of the position detection signal Vcom supplied to the common electrode CE every frame during the touch driving period, the parasitic capacitance Cp can be canceled (made invisible). As a result, the charge amount Q of the bias capacitor Cb is redistributed to only two components: the feedback capacitance Cint and the capacitance Ct due to the touch. This suppresses the effects of EMI and parasitic capacitance Cp, enabling accurate detection of the touch driving signal.

[0063] [Additional Circuitry] The configuration for switching the polarity of the input voltage V supplied to the common electrode CE during the touch drive period, as described above, will now be explained.

[0064] Figure 10 schematically shows the power supply circuit that is input to the detection circuit. The unconnected terminals P11 and P12 in Figure 10 can be connected to the first connection point P1 and the second connection point P2 in Figures 8 and 9. In Figure 10, the oscillator 101, touch logic circuit 102, and sensing generator 103, located on the right side, are generally similar in configuration to the touch drive power supply found in conventional detection circuits. In this technology, the power supply circuit further includes a T flip-flop 104 and a multiplexer 105, enclosed by a dotted line in the figure. Each element will be described below.

[0065] The oscillator 101 generates periodic timing signals, for example, in the form of a square wave or pulse signal. The oscillator 101 provides, for example, the clock signal or timing signal necessary for the entire display device 1 to operate. This allows the detection circuit, drive circuit, etc., of the display device 1 to be synchronized.

[0066] The touch logic circuit 102 is the central element for controlling the touch sensor function. The touch logic circuit 102 controls the timing of various operations based on a reference clock signal from the oscillator 101, for example. These operations include, for example, sensing, sampling, reset (switch switching), and synchronization with the display drive. The touch logic circuit 102 also instructs the subsequent sensing generator 103 to generate a pulsed touch drive signal so that touch driving can be suitably performed on the display device 1.

[0067] The sensing generator 103 generates a pulsed touch drive voltage to drive the touch electrode. In other words, the sensing generator 103 generates a drive voltage for sensing. The sensing generator 103 receives instructions from the touch logic circuit 102 and generates a voltage in a form and timing corresponding to the instructions. The sensing generator 103 receives instructions from the T flip-flop 104 and generates a voltage in a form and timing corresponding to the instructions. The sensing generator 103 may be, for example, a signal generator.

[0068] The T flip-flop 104 is a type of flip-flop circuit that can hold one of two states, with its output inverting in response to a change in the value of one input. This T flip-flop 104 has, for example, an input terminal T for inputting the operating power supply VCC and a terminal CLK for inputting the clock signal, and inverts the output Q each time the CLK signal is input. By inputting a vertical synchronization signal Vsync, which indicates the start and end timing of the touch drive period in, for example, Low Voltage Differential Signaling (LVDS), to terminal CLK, the output Q switches alternately between "0" and "1" each time the vertical synchronization signal Vsync is input. This allows the selection voltage to be controlled, for example, depending on whether the count of the vertical synchronization signal Vsync is even (e.g., 2m) or odd (e.g., 2m+1). The output Q of the T flip-flop 104 is sent to the subsequent multiplexer 105 as a selection signal S.

[0069] The multiplexer 105, also known as a multiplexer, multiplexer, multiplexing device, or multiplexer, outputs two or more inputs as a single signal. The multiplexer 105 has two input terminals: the first input terminal is Pos-V and the second input terminal is Neg-V, which indicate the power supply to the sensing generator 103. The multiplexer 105 uses the output Q of the T flip-flop 104 as a selection signal S, and accordingly selects and outputs one of the first input: Pos-V and the second input: Neg-V. For example, when the output Q from the T flip-flop 104 (selection signal S) is "0", the multiplexer 105 can output the first input: Pos-V as the power supply for the sensing generator 103, and when the output Q is "1", it can output the second input: Neg-V positive voltage. This multiplexer 105 allows the positive and negative polarity of the output voltage V generated by the sensing generator 103 to be alternately switched each time the vertical synchronization signal Vsync is generated.

[0070] In the above embodiment, a display device 1 is provided, comprising a plurality of pixel electrodes PE, a plurality of common electrodes CE (an example of drive electrodes), and a drive circuit (e.g., a common electrode drive circuit) for driving at least one of the plurality of common electrodes CE. This common electrode drive circuit CD alternately drives at least one of the plurality of pixel electrodes PE in a display mode for image display and drives at least one of the plurality of common electrodes CE in a touch mode for touch sensing. In the nth touch mode drive, a pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes. In the (n+1)th touch mode drive, a pulsed touch drive signal with the opposite polarity to the nth pulsed touch drive signal is supplied to at least one (typically all) of the plurality of common electrodes CE.

[0071] With this configuration, the magnetic flux formed on the common electrode CE during the nth touch mode drive is canceled out by the reverse magnetic flux formed by the supply of a pulsed touch drive signal with the opposite sign during the (n+1)th drive. As a result, the apparent magnetic flux disappears, and EMI is reduced. Furthermore, this configuration can be realized simply by adding a mechanism to a conventional touch mode drive device that reverses the sign of the supplied power.

[0072] The embodiments relating to this technology have been specifically described above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above. For example, the embodiments described above are described in detail to make the present invention easy to understand, and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace a part of the configuration of one embodiment with another, and it is also possible to add other configurations to the configuration of one embodiment. In addition, it is possible to add, delete, or replace other configurations for a part of the configuration of each embodiment.

[0073] (1) In the above embodiment, a display device was described that employs a self-capacitance method as a touch sensor method, for example, a method that detects the change in capacitance between a finger (position input body) and a touch electrode (common electrode CE). This technology is not limited to being applied to a display device 1 equipped with a touch sensor function that detects using a self-capacitance method. The display device 1 may be, for example, a display device equipped with a touch sensor function using a mutual-capacitance method that detects the change in capacitance between two touch electrodes. In a mutual-capacitance display device 1, a drive electrode (transmitting electrode) to which a touch drive signal is applied and a receiving electrode corresponding to this drive electrode are used to detect the change in capacitance between two touch electrodes (drive electrode, receiving electrode) to detect the presence or absence of a touch and / or the touch position. In a display device equipped with such a mutual-capacitance detection method touch sensor function, the drive electrode to which the touch drive signal (TDS) is applied is equivalent to the common electrode CE to which a pulsed drive signal is applied in this technology.

[0074] (2) In the above embodiment, the common electrode CE, which serves as a touch electrode, is connected to the touch wiring TL provided on the array substrate 20. The detection circuit for detecting changes in capacitance in the common electrode CE is also connected to the touch wiring TL. However, the method of detecting changes in capacitance is not limited to this. For example, as shown in Figure 11, the common electrode CE may be provided on the array substrate 20, and a detection electrode Rx for detecting changes in capacitance may be provided on the opposing substrate 30. In this case, the common electrode drive circuit CD may supply pulsed drive signals to the common electrode CE and the detection electrode Rx. The detection circuit can then detect the presence and location of a touch in relation to changes in parasitic capacitance between the common electrode CE and the detection electrode Rx.

[0075] (3) In the above embodiment, during the touch drive period when the display device 1 is operating in touch mode, a touch drive signal was sent to the common electrode CE (touch electrode) via a touch wiring TL arranged along the source wiring SL. The touch wiring TL was selectively connected to one common electrode CE. However, the touch wiring TL may be connected to multiple common electrode CEs. For example, during the touch drive period when the display device 1 is operating in touch mode, the detection circuit can detect the presence or absence of a touch or the location of a touch by outputting a pulsed touch drive signal that drives at least one of a plurality of touch electrodes (TE) electrically connected through the source wiring SL.

[0076] The detection circuit may, for example, sequentially drive at least one of the multiple touch electrodes, or it may drive all of the touch electrodes simultaneously. Whether the touch electrodes are driven sequentially or all simultaneously, the detection circuit can use the signals received from at least one of the multiple touch electrodes to detect the presence or absence of a touch and the location of the touch. The detection circuit can also detect changes in capacitance and determine the presence or absence of a touch and the location of the touch based on the detected changes in capacitance.

[0077] In the case of a self-capacitance type touch sensor function, a touch drive signal is applied to the touch electrode (common electrode CE), and the change in capacitance is detected by the touch electrode (common electrode CE) to which the touch drive signal is applied. Therefore, it can be said that this self-capacitance type touch electrode (common electrode CE) plays the role of both the drive electrode and the receiving electrode in a mutual capacitive type.

[0078] (4) In the above embodiment, the case in which the display device 1 is a liquid crystal display device having an in-cell type touch sensor function was described. However, the display device 1 is not limited to a liquid crystal display device. If the display device 1 is, for example, an electronic paper display device having an in-cell type touch sensor function, the multiple common electrodes CE provided on the display panel 10 may be common electrodes to which a common voltage Vcom is applied in order to form an electric field (electric field) corresponding to each pixel electrode (back electrode) of the electronic paper unit to which a pixel voltage is applied.

[0079] As another example, if the display device 1 is an organic light-emitting display (OLED) equipped with an in-cell type touch sensor function, the multiple common electrodes CE provided on the display panel 10 may be cathode electrodes (common electrodes) of organic light-emitting diodes corresponding to the anode electrodes (pixel electrodes) of the organic light-emitting diodes.

[0080] (5) In the detection circuit of the above embodiment, Vso output from the operational amplifier was used as the output voltage. However, in order to distinguish between the capacitance (change) signal due to touch and noise, the capacitance detection operation may be performed multiple times, and the average value of the multiple detected capacitances may be used as the output voltage.

[0081] (6) In Embodiment 1, one frame time included one set of display drive period and touch drive period. However, one frame time may be divided into one or more display drive periods and one or more touch drive periods. [Explanation of Symbols]

[0082] 1…Display device, 10…Display panel, 20…Array substrate, 22…TFT, 22A…Gate electrode, 22B…Source electrode, 22C…Drain electrode, 22D…Semiconductor part, PE…Pixel electrode, 30…Opposite substrate, 40…Liquid crystal layer, BL…Backlight device, GL…Gate wiring, GD…Gate drive unit (gate driver), SL…Source wiring, SD…Source drive unit (source driver), TL…Touch wiring, CE…Common electrode, CD…Common electrode drive circuit, CTR…Control circuit, DC…Drive circuit, AA…Display area, NA…Non-display area, Rx…Detection electrode

Claims

1. Multiple pixel electrodes, Multiple drive electrodes, A drive circuit that drives at least one of the plurality of drive electrodes, Prepare, The aforementioned drive circuit is At least one of the plurality of pixel electrodes is driven in display mode for image display, At least one of the plurality of drive electrodes is driven in touch mode for touch sensing, Perform these alternately, During the nth drive in the touch mode, a pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes. In the (n+1)th touch mode drive, a pulsed touch drive signal with the opposite polarity to the nth pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes, where n is a natural number. A display device configured in such a way.

2. Equipped with multiple gate wires and multiple source wires, Each of the plurality of pixel electrodes is connected to the plurality of gate wirings and the plurality of source wirings via a switch element and arranged in a matrix. The display device according to claim 1.

3. The aforementioned plurality of drive electrodes are common electrodes that provide a common potential in display mode. The display device according to claim 1.

4. The drive circuit includes a detection circuit that outputs a pulsed touch drive signal to drive at least one of the plurality of drive electrodes to detect the presence or absence of a touch or the location of the touch. The display device according to claim 1.

5. The drive circuit includes a detection circuit that outputs the pulsed touch drive signal to detect whether or not a touch is present or the location of the touch. The display device according to claim 1.

6. The detection circuit is a sensing generator that generates pulsed touch drive signals. And a switching circuit that switches between the positive and negative voltages of the power supply for the sensing generator, The display device according to claim 5, including the following:

7. Multiple pixel electrodes, Multiple drive electrodes, A control method for a display device, At least one of the plurality of pixel electrodes is driven in display mode for image display, At least one of the plurality of drive electrodes is driven in touch mode for touch sensing, It includes them alternately, During the nth drive in the touch mode, a pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes, where n is a natural number. In the (n+1)th drive in the touch mode, a pulsed touch drive signal is supplied to at least one of the plurality of drive electrodes, the pulsed touch drive signal having the opposite polarity to the nth pulsed touch drive signal. A method for controlling a display device.

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