Touch sensor and display device

Abstract

Disclosed is a touch sensor which is low in manufacturing cost and is driven with low power consumption. A touch sensor according to one embodiment of the present invention is provided with: a first detection conductor comprising a divided electrode having a plurality of electrode portions electrically insulated from each other; the second detection conductor is insulated from the first detection conductor or is connected with the first detection conductor in a high-impedance manner by a resistor of more than 10 kilohms; and a control unit that extracts a commercial power band signal from the signals detected by the first detection conductor with the second detection conductor as a reference potential, and detects a touch position using the commercial power band signal.

Description

Technical Field

[0001] This invention relates to a touch sensor and a display device. Background Technology

[0002] Touch panels are widely used in small portable devices and various terminals. Typically, a touch panel includes: a sensor that detects the position coordinates of a finger, pen, or other pointing action; and a surface display device such as an LCD.

[0003] As detection methods for such sensors, known methods include surface electrostatic capacitance, resistive film, infrared, ultrasonic surface acoustic wave, and electromagnetic induction. For example, Patent Document 1 discloses a sensor using the surface electrostatic capacitance method.

[0004] A surface-mount capacitive sensor comprises a laminate consisting of an insulating substrate, a uniform conductive layer formed on its surface, and a thin insulating layer (protective layer) formed on its upper surface. The sensor operates as follows: 1) An alternating current voltage is applied to the four corners of the conductive layer, creating a uniform electric field. 2) When a finger touches the conductive layer, a weak current flows through the finger via the electrostatic capacitance formed by the conductive layer and the finger. 3) This current flows from the four corners of the conductive layer to the point where the finger touches (contacts) the sensor. 4) The signal processing circuit then measures the ratio of the current at each of the four corner terminals, thereby calculating the coordinates of the finger's touch position.

[0005] Surface-mount capacitive sensors have a simple structure, can be manufactured at low cost, and are easy to scale up, so they are widely used in touch panels.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2010-262626 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, surface-mount capacitive sensors detect touch locations by applying an AC voltage to generate a weak electric field on the substrate surface and using four electrodes to capture changes in electrostatic capacitance caused by touch. Therefore, it is difficult to further reduce circuit costs and power consumption.

[0011] Therefore, it is desirable to develop a new type of touch sensor that is simple in structure, simplifies the processing circuit for the detection signal, and has low power consumption for driving the sensor.

[0012] In view of the above, the present invention aims to provide a touch sensor that is low in manufacturing cost and driven by low power consumption.

[0013] Solution for solving the problem

[0014] One aspect of the present invention provides a touch sensor comprising: a first detection conductor comprising segmented electrodes having multiple electrode portions electrically insulated from each other; a second detection conductor insulated from the first detection conductor or connected with a high impedance of 10kΩ or more; and a control unit that uses the second detection conductor as a reference potential, extracts a signal from a commercial power supply frequency band from a signal detected by the first detection conductor, and uses the signal from the commercial power supply frequency band to detect a touch position.

[0015] Invention Effects

[0016] According to one aspect of the present invention, a touch sensor with low manufacturing cost and low power consumption can be provided. Attached Figure Description

[0017] Figure 1 This is a perspective view of an exemplary touch sensor display device having one embodiment of the present invention.

[0018] Figure 2A This is a side sectional view of an exemplary display device according to this embodiment.

[0019] Figure 2B This is a side sectional view of an exemplary display device, a variation of this embodiment.

[0020] Figure 3 This is an explanatory diagram illustrating the structure of an exemplary display device for illustrating this embodiment.

[0021] Figure 4 This is an explanatory diagram illustrating an example of the processing of the signal processing unit of an exemplary display device according to this embodiment.

[0022] Figure 5 This is a diagram illustrating an example of the filtering frequency characteristics of a filter used by an exemplary display device of this embodiment to extract the signal of the commercial power supply frequency band component.

[0023] Figure 6 This is a diagram illustrating an example of a digital signal generated after the signal processing unit processes the signal detected from the electrode touched by a finger.

[0024] Figure 7 This diagram illustrates an example of a digital signal obtained after the signal processing unit processes signals detected from electrodes adjacent to the electrodes touched by the finger but not touched by the finger.

[0025] Figure 8 It is Figure 6 and Figure 7 A graph showing the horizontal axis of each signal-B in terms of time.

[0026] Figure 9 It is a display that will Figure 8 A graph of the signal after performing a Fast Fourier Transform (FFT) on the interval from 1.00 seconds to 1.25 seconds. Detailed Implementation

[0027] (The process of completing this invention)

[0028] We are surrounded by electrical noise from AC power lines and electronic devices. One type of electrical noise is AC noise (humming noise). AC noise is generated when electromagnetic waves produced by the amplitude of commercial AC power collide with conductors, becoming current, and is thus detected as electrical noise.

[0029] Alternating current noise is a noise component that depends on the frequency of commercial power supplies, and is known to be mixed in, for example, when measuring minute bioelectrical signals from electrodes worn on the surface of the human body.

[0030] Here, commercial power frequency refers to the frequency of AC power supplied as commercial power. Commercial power frequencies can vary by country and region; for example, in Japan, the commercial power frequency is 50Hz or 60Hz. AC noise can be referred to as commercial power frequency noise, or noise dependent on the commercial power frequency, etc.

[0031] The inventors conducted in-depth research and discovered that the presence or absence of finger touch can be detected by utilizing AC noise. Therefore, an implementation method for detecting touch location using AC noise will be described below.

[0032] (Related technologies)

[0033] Before describing the embodiments of the present invention, related technologies will be described below. As related technologies, a touch sensor utilizing AC sound was disclosed in "Xia Zixuan et al., "Single-touch calibration of HumTouch touch sensor using AC sound", 22nd System Integration Division Seminar (SI2021) (December 15-17, 2021)".

[0034] The touch position detection method of this touch sensor is similar to the position detection method of the surface-type electrostatic capacitive sensor described above. Specifically, this method arranges electrodes around the panel and detects the touch position based on the difference in voltage detected by each electrode.

[0035] If this method is used, the difference in voltage signals detected by each electrode will decrease if the resistance of the touch panel is too low, potentially reducing the accuracy of position detection. On the other hand, if the resistance is too high, the AC noise is a weak current, making it difficult to detect the signal at each electrode.

[0036] Furthermore, in the disclosed touch panel, the resistance becomes uneven depending on the location due to the inhomogeneity of the material, and consequently, the noise generation varies due to individual differences in the human body. Therefore, the accuracy of position detection may not be guaranteed in this method.

[0037] Hereinafter, embodiments of the present invention will be described in detail with appropriate reference to the accompanying drawings. However, sometimes unnecessary detailed descriptions will be omitted. For example, detailed descriptions of matters already known, or repeated descriptions of substantially the same structures, may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0038] It should be noted that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the invention, and are not intended to limit the subject matter of the claims. It should also be noted that the elements shown in the various drawings are not necessarily drawn to scale.

[0039] (Implementation Method)

[0040] Figure 1 This is a perspective view of an exemplary display device having a touch sensor according to one embodiment of the present invention. Examples of the aforementioned display devices include various devices such as mobile personal computers (PCs), tablet terminals, smartphones, and digital cameras with touch detection capabilities.

[0041] like Figure 1 As shown, the display device 1 includes a housing 10 with a generally rectangular parallelepiped shape. The housing 10 has an opening on its surface side (the front side in the Z direction). It should be noted that in this specification and accompanying drawings, the width direction (lateral direction) of the housing 10 is defined as the X direction, the length direction (longitudinal direction) as the Y direction, and the thickness direction as the Z direction (the X, Y, and Z axes are orthogonal to each other). In this embodiment, the case where the length of the housing 10 in the X direction is shorter than the length of the housing 10 in the Y direction is shown. However, the length in the X direction can be the same as the length in the Y direction, or the length in the X direction can be longer than the length in the Y direction.

[0042] Figure 2A This is a side cross-sectional view of an exemplary display device of this embodiment, taken with the A-A' plane parallel to the XZ plane cut off.

[0043] like Figure 2AAs shown, the housing 10 contains stacked bodies 201 to 205 constituting the touch sensor 20, various circuits 40, and a display panel 30. These are arranged sequentially along the Z-direction from the opening (display surface) side (positive Z-axis side) of the housing 10, in the order of stacked bodies 201 to 205, display panel 30, and various circuits 40. The touch sensor 20 can also be referred to as a touch input device. All or part of the circuits 40 can also be referred to as a control unit or control circuit.

[0044] like Figure 2A As shown, the touch sensor 20 includes: a protective film (protective layer) 201, a substrate 202, a first detection conductor 203, an insulating film 204, and a second detection conductor 205. In this embodiment, in order to detect the touch position with higher sensitivity, the first detection conductor 203 is disposed on the opening side of the housing 10 (i.e., closer to the surface touched by the finger), and the second detection conductor 205 is disposed on the side further in the negative Z-axis direction than the first detection conductor 203, so as to detect greater commercial power supply frequency noise.

[0045] The protective film 201 is made of glass, has insulating properties, and is approximately 1 mm thick (1.1 mm in this embodiment). The protective film 201 is present on the outermost layer of the opening surface, and is disposed on approximately the entire surface of the opening side of the housing 10 of the substrate 202. The protective film 201 serves as the operating surface for the display device 1 and the touch sensor (touch input device). It should be noted that the protective film 201 can be made of transparent organic materials such as epoxy resin, inorganic materials such as glass, or a mixture of these materials.

[0046] The substrate 202 is disposed on approximately the entire surface of the protective film 201 on the side opposite to the opening surface of the substrate 202. The substrate 202 is a rectangular flat insulating material made of a transparent material. In this embodiment, the substrate 202 is made of polyethylene terephthalate (PET). It should be noted that known transparent films can be used as the substrate, and there is no particular limitation, but PET, polycarbonate, and cyclic olefin polymers (COP) are preferred.

[0047] The first detection conductor 203 is disposed on the side of the substrate 202 opposite to the side that abuts against the protective film 201. (See reference...) Figure 3As explained, the first detection conductor 203 is composed of multiple electrodes. These electrodes are arranged in a matrix, spaced apart along the X and Y directions. The first detection conductor 203 is connected to a measurement circuit (composed of an amplification unit 401, a multiplexer 402, an analog-to-digital (AD) converter 403, and a signal processing unit 404, described later). When a human body comes into direct contact with or approaches the first detection conductor 203 (electrodes), AC noise can be detected.

[0048] The first detection conductor 203 uses an electrode with PET film as the substrate and indium tin oxide (ITO) as the main component. It should be noted that, in addition to ITO, inorganic electrodes such as zinc oxide (ZnO), silver nanowires, carbon nanotubes, and graphene, as well as organic electrodes with polythiophene and polyaniline as the main components, can also be used. By using these materials, highly transparent conductor patterns can be formed.

[0049] The insulating film 204 is a rectangular plate with approximately the same dimensions as the substrate 202, and is disposed on the side of the first detection conductor 203 opposite to the opening side of the housing 10. It should be noted that the insulating film 204 is preferably made of PET, PC, or COP, but it can also be made of glass, epoxy resin, etc.

[0050] The second detection conductor 205 is a rectangular plate with approximately the same dimensions as the substrate 202 and the insulating film 204, and is disposed on approximately the entire surface of the insulating film 204 opposite to the opening side of the housing 10. It should be noted that the shape and area of ​​the second detection conductor 205 can be set as needed. Furthermore, the position of the second detection conductor 205 is not particularly limited as long as it functions as a reference potential.

[0051] The second detection conductor 205 is composed of an ITO electrode.

[0052] Ideally, the second detection conductor 205 is connected to the ground potential of the measurement circuit board, or a fixed potential with a certain offset voltage from the ground potential, and serves as a reference potential (for example, it can also be used as the ground of the display device 1). In this way, by using the second detection conductor 205 as the reference potential, the detection signal output via the first detection conductor 203 and the second detection conductor 205 is used for touch position detection.

[0053] It should be noted that the structure of the stacked body constituting the touch sensor 20 is not limited to Figure 2A The structure shown is described below. A modified example of the laminate constituting the touch sensor 20 will be described below.

[0054] Figure 2BThis is a side sectional view of an exemplary display device 1, a variation of this embodiment. In this variation, as... Figure 2B As shown, the touch sensor 20 includes: a protective film (protective layer) 201, a first detection conductor 203, a substrate (insulating film) 206, and a second detection conductor 205. The first detection conductor 203 can also be implemented by forming a conductor pattern on the substrate 206. Thus, it can also be implemented by... Figure 2A The arrangement of the substrate 202 and the first detection conductor 203 shown is swapped, thereby making it into Figure 2B The substrate 206 and the first detection conductor 203 are arranged as shown. In other words, in the Z direction, the first detection conductor 203 can also be arranged on the positive side and the substrate 206 on the negative side. In this case, as... Figure 2B As shown, it is a reasonable structure to use substrate 206 as an insulating film.

[0055] In addition, the first detection conductor 203 can also be implemented by forming a conductor pattern on a protective film 201 such as glass.

[0056] In this variation, the distance between the finger and the first detection conductor 203 is shortened, thus enabling higher sensitivity and accuracy in detecting the touch position.

[0057] The laminate formed by stacking the protective film 201, the substrate 202, the first detection conductor 203, the insulating film 204, and the second detection conductor 205 (located on the side closer to the positive Z-axis direction than the display panel 30) can have a total light transmittance of more than 80%.

[0058] When an operator's finger touches the operating surface of the display device 1, the signal from the electrode constituting the first detection conductor 203 corresponding to the touch position includes commercial power frequency noise accompanying the finger's approach to the electrode. Therefore, by identifying the commercial power frequency noise, the position of the electrode that generates the noise (signal) can be detected as the touch position.

[0059] The display panel 30 is a flat panel display having a liquid crystal display element (not shown). The display panel 30 includes a liquid crystal panel, a surface polarizer, a back polarizer, and a backlight (all not shown). The surface polarizer and the back polarizer are arranged to hold the liquid crystal panel in place. The backlight is positioned on the opposite side of the liquid crystal panel, separated by the back polarizer. The display panel 30 displays images overlapping with the touch sensor 20 (touch input device). It should be noted that the display panel 30 is not limited to the above structure and can be any display panel, such as a flat panel display having an organic EL (Electro-Luminescence) element.

[0060] For reference Figure 3As described, the various circuits 40 include an amplification unit 401 (amplifier circuit), a multiplexer 402, an AD conversion unit 403 (AD converter, AD conversion circuit), a signal processing unit 404 (signal processing circuit), and a controller 405. They also include a driving unit (driving circuit; not shown) for controlling the liquid crystal display elements and driving the display panel 30. The various circuits 40 are disposed on the back side of the display panel 30. For example, a mounting substrate (not shown) is disposed in the space on the back side of the display panel 30 within the housing 10, and the various circuits 40 are mounted on this mounting substrate. All or part of the various circuits 40 (e.g., the signal processing unit 404, the controller 405) may also be referred to as a control unit or control circuit.

[0061] Figure 3 This is an explanatory diagram illustrating the structure of an exemplary display device for illustrating this embodiment.

[0062] As described above, the first detection conductor 203 is composed of multiple electrodes, which are arranged in a segmented manner. It should be noted that, in this embodiment, the number of electrodes is E. (1) Electrode E (2) Electrode E (n) These n.

[0063] When viewed from the Z direction, multiple electrodes E (1) ~Electrode E (n) They are arranged in a matrix along the X and Y directions. As described above, electrode E (1) ~Electrode E (n) Each electrode is, for example, a rectangular electrode of 30mm x 30mm made of ITO with PET film as the substrate. However, the size, position, and shape of the electrode are not limited to this. For example, the shape of the electrode can be hexagonal. Furthermore, for example, in the case of a flat touch panel touched by a finger, the first detection conductor 203 is composed of segmented electrodes having multiple electrode portions that are electrically insulated from each other. If it is arranged in a way that completely covers the entire panel, the finger can (indirectly) touch (approach) more than one electrode, thus determining its position.

[0064] Multiple electrodes E (1) ~Electrode E (n) The analog signals are output (sent) to the amplification unit 401 respectively.

[0065] Amplification unit 401 will output from electrode E (1) ~Electrode E (n) The received analog signals are amplified to a measurable amplitude range (0–3.3V in this embodiment) and output to the multiplexer 402. The number of amplification units 401 is equal to the number of electrodes.

[0066] Multiplexer 402 multiplexes the analog signal input from electrode E via multiplexer 402. Multiplexer 402, based on the selection signal input from controller 405, repeats the input signal from electrode E at regular intervals (periods) (i.e., periodically). (1) Amplified analog signal AS (1) From electrode E (2) Amplified analog signal AS (2) ... from electrode E (n) Amplified analog signal AS (n) The outputs are sequentially sent to the AD conversion unit 403.

[0067] The AD converter 403 receives the (amplified) analog signal AS input from the multiplexer 402. (1) ~Analog signal AS (n) Converted into digital signals DS respectively (1) ~Digital signal DS (n) and the digital signal DS (1) ~Digital signal DS (n) The signals are sequentially output to the signal processing unit 404. Here, the digital signal output from the AD converter 403 to the signal processing unit 404 is used to obtain the digital signal DS. (1) To digital signal DS (n) The output up to this point is one cycle, and the output repeats continuously and periodically at a certain period (e.g., 5 milliseconds). It should be noted that the sampling frequency during AD conversion is at least twice the commercial power supply frequency.

[0068] The signal processing unit 404 performs the following processing (bandpass filtering, envelope detection, and touch detection) on the digital signal input from the AD conversion unit 403 at regular intervals (periods) (i.e., repeating periodically) based on the selection signal input from the controller 405. Hereinafter, appropriate references will be made. Figure 4 The processing of the signal processing unit 404 will be explained below. It should be noted that the processing performed by the signal processing unit 404 (or controller 405) described below can be implemented in hardware, in software, or in a combination of hardware and software.

[0069] [Bandpass Filtering]

[0070] Before bandpass filtering, the signal processing unit 404 first performs offset adjustment on the digital signal input from the AD conversion unit 403. The signal processing unit 404 uses a commercial power supply frequency bandpass filter (e.g., one with...). Figure 5The filter (shown for its frequency characteristics) extracts the commercial power frequency component (signal) B from the (offset-adjusted) digital signal A input to the AD converter 403. Through bandpass filtering, high-frequency noise and other noise can be removed, thus enabling higher accuracy detection of the signal used for touch position detection.

[0071] [Envelope detection processing]

[0072] Signal processing unit 404 processes the signal B, which is the commercial power frequency component extracted as described above. Figure 4 The envelope signal C is calculated by performing envelope detection processing on the waveform shown. It should be noted that known techniques such as the Hilbert transform can be used to obtain the envelope signal C.

[0073] [Touch detection processing]

[0074] Since the value of the envelope signal C from the touched electrode is larger than that from the untouched electrode, the signal processing unit 404 can determine whether there is a touch for each electrode based on a preset threshold. Figure 4 (The touch detection process shown). For example, for each electrode, the signal processing unit 404 determines that a period during which the value of the envelope signal C exceeds a predetermined threshold is a touch, and outputs a signal (indicating a touch) that is high only during the period during which a touch is determined to be a touch to the controller 405.

[0075] In the signal processing unit 404, a touch detection process using envelope detection is shown, but the same touch detection process can be performed by performing a Fourier transform on the obtained signal. By continuously capturing the signal B, which is a component of the commercial power supply frequency, at a certain interval (frame), and performing a Fourier transform on the frames, a spectrum of the piezoelectric signal intensity relative to the frequency can be obtained. In this spectrum, the intensity at the commercial power supply frequency of the touched electrode is greater than that of the untouched electrode, so it is possible to determine whether or not each electrode has been touched. For example, if the intensity at the commercial power supply frequency of a certain electrode exceeds a predetermined threshold, it can be determined that the electrode was touched at the measurement time point.

[0076] The controller 405 outputs a selection signal for sequentially outputting the amplified analog signals from each electrode to the AD converter 403 to the multiplexer 402. The controller 405 also outputs a selection signal for performing the aforementioned signal processing on each digital signal input from the AD converter 403 to the signal processing unit 404.

[0077] The controller 405 detects the touch position in real time based on the signal input from the signal processing unit 404. Specifically, the controller 405 can determine (i.e. detect) the touch position based on the electrode corresponding to the signal input from the signal processing unit 404 representing the touch determination processing result, and the position information (e.g., position coordinates) of the electrode pre-stored in the storage unit.

[0078] According to the above embodiment, since no AC voltage needs to be applied, it has a very simple structure, thus enabling miniaturization (thinning) and providing a touch sensor and display device that can perform touch position detection at low cost and low power consumption. Furthermore, since position detection is performed using segmented electrodes, weak signals of AC noise can be accurately detected, and accurate position detection can be performed regardless of the inhomogeneity of the detection conductor or individual differences.

[0079] <Variation Example>

[0080] In the above embodiment, the first detection conductor 203 and the second detection conductor 205 are insulated from each other by the insulating film 204. However, the same effect as the above embodiment can also be obtained by connecting the first detection conductor 203 and the second detection conductor 205 with a high impedance. In this case, the first detection conductor 203 and the second detection conductor 205 are preferably connected with a high impedance of 10kΩ or more, and more preferably with a high impedance of 100kΩ or more.

[0081] In the above embodiment, it was described that the signal processing unit 404 uses a bandpass filter to extract the signal of the commercial power frequency component. However, the signal processing unit 404 can also achieve the same effect by using a notch filter (band-cut filter or band-stop filter) to extract the signal of the commercial power frequency component. In this case, the signal processing unit 404 separates the (offset-adjusted) digital signal input from the AD conversion unit 403 into the commercial power frequency component that does not pass through the filter and frequency components other than the commercial power frequency component that pass through the filter. Furthermore, the signal processing unit 404 can extract the signal of the commercial power frequency component by subtracting the frequency components other than the commercial power frequency component from the (offset-adjusted) digital signal.

[0082] In the above embodiments, a bandpass filter is used as a digital filter after digital signal conversion to realize signal processing. However, even if an analog filter is used instead of a digital filter, the same function can be achieved.

[0083] In the above embodiment, it is described that the controller 405 determines the touch position based on the touch determination processing result of the signal processing unit 404, but the signal processing unit 404 may also determine the touch position based on the touch determination processing result and the position information of the electrodes stored in the storage unit in advance.

[0084] In the above embodiments, the first detection conductor 203 and the second detection conductor 205 are illustrated to have the shape of parallel plates, but the shapes of the first detection conductor 203 and the second detection conductor 205 are not limited to the shapes described above.

[0085] <Touch Position Detection Evaluation>

[0086] The inventors fabricated the touch sensor according to this embodiment and evaluated the touch position detection. In this touch sensor, 12 rectangular electrodes (electrodes E) are arranged in a mutually insulated manner. (1) ~Electrode E (12) The first detection conductor 203 constitutes the total transmittance of the stacked body constituting the touch sensor, which is above 80%. Light from electrodes E... (1) ~Electrode E (12) Analog signal AS (1) ~Analog signal AS (12) Set to one cycle, the signal output from the multiplexer 402 at a sampling frequency of 200Hz is converted from the analog signal AS by the AD converter 403. (1) ~Analog signal AS (12) Converted into digital signals DS respectively (1) ~Digital signal DS (12) The digital signal DS after AD conversion (1) ~Digital signal DS (12) It is input to the signal processing unit 404.

[0087] Figure 6 This diagram illustrates an example of a digital signal processed by the signal processing unit 404 after processing the signal detected from the electrode touched by a finger. Figure 6 In this context, signal B (“signal-B”) is the signal obtained from the offset-adjusted digital signal of the signal processing unit 404 after passing through a commercial power frequency bandpass filter for extracting the commercial power frequency (50Hz). Signal C (“signal-C”) is the envelope signal obtained by performing envelope detection processing on the commercial power frequency component B (signal B).

[0088] exist Figure 6 In the graph shown, the horizontal axis represents the number of samples n when sampling at a period of 5 milliseconds, and the vertical axis represents the voltage signal strength (strength 1 is equivalent to 0.8 millivolts).

[0089] The envelope signal C of the rectangular electrode touched by a finger is larger than the envelope signal of the rectangular electrode not touched by a finger (see below). Figure 7Therefore, the signal processing unit 404 can determine whether there is a touch for each rectangular electrode by performing a threshold determination on the value of the envelope signal C. In this evaluation, the signal processing unit 404 determines that the period when the value of the envelope signal C exceeds the threshold 100 ("threshold") is a touch, and outputs a signal D ("signal-D") that is high only during the touch period.

[0090] Figure 7 This diagram illustrates an example of a digital signal processed by the signal processing unit 404 after processing a signal detected from an electrode adjacent to the electrode touched by the finger but not touched by the finger. Figure 7 In this context, signal B (“Signal-B”) is the signal obtained from the offset-adjusted digital signal of signal processing unit 404 after passing through a commercial power frequency bandpass filter for extracting the commercial power frequency (50Hz). Signal C (“Signal-C”) is the envelope signal obtained by performing envelope detection processing on the commercial power frequency component B (Signal B). Figure 7 Since almost no signal of commercial power frequency was detected and there was no period during which the value of envelope signal C exceeded the threshold 100 ("threshold"), the signal processing unit 404 determined that the finger was not touched during the measurement period.

[0091] In this way, the signal processing unit 404 periodically acquires information about the rectangular electrode touched by the finger and the rectangular electrode not touched by the finger and outputs it to the controller 405. As a result, the controller 405 can determine (i.e. detect) the touch position by referring to the position information of the rectangular electrode stored in the storage unit.

[0092] The controller 405 can detect the touch position in real time based on the information input from the signal processing unit 404.

[0093] Figure 8 It is Figure 6 and Figure 7 The graph shows the horizontal axis of each signal-B in time (in seconds). The signal of the electrode that is being touched is called signal-6T, and the signal of the electrode that is not being touched is called signal-7T.

[0094] Figure 9 It is a display that will Figure 8 The graph shows the signal after performing a Fast Fourier Transform (FFT) on the interval from 1.00 seconds to 1.25 seconds, with the horizontal axis representing frequency (unit: Hz). The signal after performing a FET on signal -6T is labeled as signal -6F, and the signal after performing a FET on signal -7T is labeled as signal -7F. There is no particular limitation on the sampling width used for the Fourier Transform. A shorter sampling width results in faster detection speed, but due to the reduced number of detection points, there is a tendency for lower detection accuracy.

[0095] In signal -6F from the touched electrode, a strong signal originating from pressing was observed in the commercial power supply band (50Hz). On the other hand, in signal -7F from the untouched electrode, the signal was not observed in the same commercial power supply band. Therefore, it can be seen that if the intensity threshold is appropriately set (set to 300 in Figure 10B) for determination, it is possible to determine whether or not the electrode has been touched.

[0096] <Effects of the Implementation Method>

[0097] A touch sensor 20 included in a display device 1 according to one embodiment of the present invention comprises a first detection conductor 203, a second detection conductor 205, a signal processing unit 404, and a controller 405. The first detection conductor 203 is composed of segmented electrodes having multiple electrode portions that are electrically insulated from each other. The second detection conductor 205 is insulated from the first detection conductor 203 or connected with a high impedance of 10kΩ or more. The signal processing unit 404 and the controller 405 extract a signal (AC noise) in the commercial power supply frequency band from the signal detected by the first detection conductor 203, using the second detection conductor 205 as a reference potential. The signal processing unit 404 and the controller 405 use the extracted signal in the commercial power supply frequency band to detect the touch position on the touch sensor 20.

[0098] Based on the above structure, since no AC voltage needs to be applied, it is a very simple structure, thus enabling miniaturization (thinning) and touch position detection at low cost and low power consumption. Furthermore, because position detection uses segmented electrodes, it can accurately detect weak signals of AC noise and is unaffected by the non-uniformity of the detection conductor or individual differences in position detection.

[0099] <Summary of Implementation Methods>

[0100] One aspect of the present invention provides a touch sensor comprising: a first detection conductor comprising segmented electrodes having multiple electrode portions electrically insulated from each other; a second detection conductor insulated from the first detection conductor or connected with a high impedance of 10kΩ or more; and a control unit that uses the second detection conductor as a reference potential, extracts a signal from a commercial power supply frequency band from a signal detected by the first detection conductor, and uses the signal from the commercial power supply frequency band to detect a touch position.

[0101] In one example, the control unit calculates the envelope signal of the signal in the commercial power supply band, and if the value of the envelope signal exceeds a threshold, detects the position of the segmented electrode corresponding to the envelope signal as the touch position.

[0102] In one example, the first detection conductor is configured to be closer to the finger-touchable surface of the touch sensor than the second detection conductor.

[0103] In one example, the control unit uses a bandpass filter that allows the commercial power supply band to pass through to extract the signal from the signal.

[0104] In one example, the control unit uses a band-stop filter that allows frequency bands outside the commercial power band to pass through to extract the signal from the signal in the commercial power band.

[0105] In one example, the total light transmittance of the stack of the touch sensor, which includes the first detection conductor and the second detection conductor, is above 80%.

[0106] One aspect of the present invention provides a display device comprising: the touch sensor; a display panel for displaying an image overlapping the surface of the laminate disposed on the side opposite to the surface of the touch sensor to be touched by a finger; and a driving unit for driving the display panel.

[0107] According to one aspect of the present invention, a touch sensor with low manufacturing cost and low power consumption can be provided.

[0108] The embodiments have been described above with reference to the accompanying drawings, but the present invention is not limited to the examples described above. Those skilled in the art will obviously be able to conceive of various modifications or alterations within the scope of the claims. It should be understood that such modifications or alterations also fall within the technical scope of the present invention. Furthermore, the constituent elements in the embodiments can be arbitrarily combined without departing from the spirit of the present invention.

[0109] This application claims priority based on Japanese Patent Application No. 2023-070741, filed on April 24, 2023. The contents of that application's specification and drawings are incorporated herein by reference in their entirety.

[0110] Industrial availability

[0111] One aspect of the present invention is suitable as a touch sensor.

[0112] Explanation of reference numerals in the attached figures

[0113] 1: Display device;

[0114] 10: Shell;

[0115] 20: Touch sensor;

[0116] 201: Protective film;

[0117] 202: Substrate;

[0118] 203: First detection conductor;

[0119] 204: Insulating film;

[0120] 205: Second detection conductor;

[0121] 206: Substrate (insulating film);

[0122] 30: Display panel;

[0123] 40: Circuit;

[0124] 401: Enlarged section;

[0125] 402: Multiplexer;

[0126] 403: AD conversion unit;

[0127] 404: Signal Processing Department;

[0128] 405: Controller.

Claims

1. A touch sensor, the touch sensor comprising: The first detection conductor is composed of segmented electrodes having multiple electrode portions that are electrically insulated from each other; The second detection conductor is insulated from the first detection conductor or connected with a high impedance of 10kΩ or more; and The control unit uses the second detection conductor as a reference potential, extracts a signal from the commercial power supply frequency band from the signal detected by the first detection conductor, and uses the signal from the commercial power supply frequency band to detect the touch position.

2. The touch sensor according to claim 1, wherein, The control unit calculates the envelope signal of the signal in the commercial power supply frequency band, and if the value of the envelope signal exceeds a threshold, it detects the position of the segmented electrode corresponding to the envelope signal as the touch position.

3. The touch sensor according to claim 1 or 2, wherein, The first detection conductor is configured to be closer to the finger-touchable surface of the touch sensor than the second detection conductor.

4. The touch sensor according to any one of claims 1 to 3, wherein, The control unit uses a bandpass filter that allows the commercial power supply frequency band to pass through to extract the signal from the signal.

5. The touch sensor according to any one of claims 1 to 3, wherein, The control unit uses a band-stop filter that allows frequency bands outside the commercial power supply frequency band to pass through, to extract the signal from the signal in the commercial power supply frequency band.

6. The touch sensor according to any one of claims 1 to 5, wherein, The total light transmittance of the stack of the touch sensor, including the first detection conductor and the second detection conductor, is 80% or more.

7. A display device, the display device comprising: The touch sensor according to claim 6; The display panel displays an image overlapping the surface of the laminate disposed on the side of the touch sensor opposite to the surface touched by the finger; and The driving unit drives the display panel.

Images