JP2011243081A - Touch panel device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce occurrence frequency of migration and attain a high speed of a touch position detection without causing increase in manufacturing cost and deterioration of convenience.SOLUTION: A touch panel device comprises an IV conversion unit 31 for converting a charge/discharge current signal from a reception electrode 3 into a voltage signal by applying a predetermined reference potential Vref, and when a reception electrode of interest is selected, the reception electrode of interest is electrically connected to the IV conversion unit so that the reception electrode of interest is applied with a selection potential Vra that is the same as the reference potential, and this selection potential is set to be approximately the same as a non-selection potential Vrb applied to the reception electrode of interest when the reception electrode of interest is not selected. In addition, a non-selection potential Vsb applied to a transmission electrode 2 of interest when the transmission electrode of interest is not selected is set to be approximately the same as the selection potential and the non-selection potential of the reception electrode of interest. In particular, the selection potential and the non-selection potential of the reception electrode of interest, and the non-selection potential of the transmission electrode of interest are set to be a ground potential.

Description

  The present invention relates to a capacitive touch panel device in which electrodes are arranged in a grid pattern and detects a touch position based on a change in an output signal of the electrode accompanying a change in capacitance according to a touch operation, in particular, a transmission electrode The present invention relates to a mutual capacitance type touch panel device that applies a driving signal while selecting one by one and receives a charging / discharging current signal in response to the driving signal while selecting receiving electrodes one by one.

  There are various types of touch panel devices that differ in the principle of detecting the touch position. In the case of a configuration in which a large number of electrodes are arranged in the panel, such as a resistive film type or a capacitance type, a bias is applied between the electrodes. When a voltage is applied for a long period of time, a phenomenon in which current flows due to an electrolysis phenomenon in the vicinity of the electrode, so-called migration, occurs. Effective migration countermeasures are desired because it reduces the reliability of the system.

  In particular, in a capacitive touch panel device that detects a touch position based on a change in an output signal of an electrode accompanying a change in capacitance according to a touch operation, a transmission electrode and a reception electrode are provided on the front and back of an insulating support sheet. In the case of the arrangement, migration may occur between the transmission electrode and the reception electrode on the front and back sides of the support sheet due to pinholes or the like existing in the support sheet.

  With respect to migration countermeasures related to such a touch panel device, conventionally, in a resistive film type touch panel device, a technique is known in which a bias voltage causing migration is applied when a touch operation is detected by a mechanical switch (patent). Reference 1). In addition, in a resistive touch panel device, a technique is known in which a touch position detection process is stopped when a use environment is in a state where migration occurs (see Patent Document 2).

JP 2000-284911 A JP 2006-39927 A

  By the way, touch panel devices are widely used in the field of personal computers and personal digital assistants, but this touch panel device can be used in presentations and lectures for a large number of people by combining it with a large screen display device. It can be used as a so-called interactive whiteboard.

  However, in the configuration in which the touch operation is detected by the mechanical switch as in the conventional technology, when the touch panel device is enlarged, it becomes difficult to realize a mechanism for detecting the touch operation by the mechanical switch, and the manufacturing cost is significantly increased. The problem of doing.

  On the other hand, in the configuration in which the touch position detection process is stopped according to the use environment as in the conventional technique, the migration itself cannot be suppressed, and the touch position detection process is sufficient to suppress the migration sufficiently. If the environmental conditions permitting the above are narrowly limited, unusable situations frequently occur, which hinders the user's use, resulting in a problem of reduced convenience.

  Also, in the touch panel device, for example, a line is drawn along the locus of the finger when the user moves the finger in the drawing mode, but the movement of the finger is too early and the detection of the touch position follows the movement of the finger. If this is not possible, there will be a problem that the line is drawn in a broken state, which reduces usability. For this reason, even if a user moves a finger | toe quickly, the structure which can detect a touch position at high speed so that a detection of a touch position can be made to follow a motion of a finger is desired.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to suppress the occurrence of migration without causing an increase in manufacturing cost or a decrease in convenience. In addition, an object of the present invention is to provide a touch panel device configured so as to increase the speed of touch position detection.

  The touch panel device of the present invention includes a panel body having a touch surface, a plurality of transmission electrodes that run parallel to each other, and a plurality of reception electrodes that run parallel to each other arranged in a grid, and electrodes to be transmitted from the plurality of transmission electrodes A transmission unit that selects and applies a drive signal, selects an electrode to be received from the plurality of reception electrodes, receives a charge / discharge current signal in response to the drive signal, and outputs a level signal for each electrode intersection A receiving unit; and a control unit that detects a touch position based on a level signal output from the receiving unit and controls operations of the transmitting unit and the receiving unit, and the receiving unit has a predetermined reference An IV converter that converts a charging / discharging current signal from the receiving electrode into a voltage signal by applying a potential; and when the receiving electrode is selected, the IV converter is energized and the reference potential is applied to the receiving electrode. same Given a choice period potential, the selection time potential, a configuration that was set to be unselected potential supplied and substantially the same in the reception electrode at the time of non-selection of the receiving electrodes.

  According to the present invention, since the selection potential and the non-selection potential of the reception electrode are substantially the same, there is a large potential difference between the reception electrode in the selected state and the reception electrode in the non-selection state adjacent thereto. Since it does not occur, the occurrence of migration can be suppressed. In addition, since the potential when the receiving electrode is selected and the potential when the receiving electrode is not substantially the same, a large potential difference does not occur in the receiving electrode when switching the selection state of the receiving electrode. It is possible to increase the speed of the selection switching operation of the receiving electrode while keeping it small. As a result, it is possible to suppress the occurrence of migration and increase the speed of touch position detection without causing an increase in manufacturing cost or a decrease in convenience.

Overall configuration diagram showing a touch panel device according to the present invention Schematic configuration diagram of the transmission unit shown in FIG. Schematic configuration diagram of the receiver shown in FIG. Schematic configuration diagram of the received signal processing unit shown in FIG. 4 is a circuit diagram showing the configuration of the IV converter shown in FIG. The figure which shows the electric potential in the selection state of a transmission electrode and a reception electrode shown in FIG. 1, and a non-selection state 1 is a waveform diagram showing a drive signal applied to the transmission electrode shown in FIG. 1, an output signal after IV conversion in the reception unit, and a control signal that defines processing timing in the reception unit. The schematic diagram which shows the condition of the electric potential of the transmission electrode and reception electrode which were shown in FIG.

  A first invention made to solve the above problems includes a panel main body having a touch surface, in which a plurality of transmitting electrodes that run in parallel with each other and a plurality of receiving electrodes that run in parallel with each other are arranged in a grid pattern, A transmitting unit that selects an electrode to be transmitted from a plurality of transmitting electrodes and applies a driving signal; and an electrode that receives a charge / discharge current signal in response to the driving signal by selecting an electrode to be received from the plurality of receiving electrodes A receiving unit that outputs a level signal for each intersection; and a control unit that detects the touch position based on the level signal output from the receiving unit and controls the operation of the transmitting unit and the receiving unit; The reception unit includes an IV conversion unit that converts a charge / discharge current signal from the reception electrode into a voltage signal by applying a predetermined reference potential, and is energized with the IV conversion unit when the reception electrode is selected. Its receiving electrode The reference potential is the same selected period potential given and, the selection time potential, a configuration that was set to be unselected potential supplied and substantially the same in the reception electrode at the time of non-selection of the receiving electrodes.

  According to this, since the selection potential and the non-selection potential of the reception electrode are substantially the same, a large potential difference does not occur between the reception electrode in the selected state and the reception electrode in the non-selection state adjacent thereto. Therefore, occurrence of migration can be suppressed. In addition, since the potential when the receiving electrode is selected and the potential when the receiving electrode is not substantially the same, a large potential difference does not occur in the receiving electrode when switching the selection state of the receiving electrode. It is possible to increase the speed of the selection switching operation of the receiving electrode while keeping it small. As a result, it is possible to suppress the occurrence of migration and increase the speed of touch position detection without causing an increase in manufacturing cost or a decrease in convenience.

  Further, according to a second aspect, in the first aspect, the non-selection potential applied to the transmission electrode when the transmission electrode is not selected is substantially the same as the selection potential and the non-selection potential of the reception electrode. The configuration is as follows.

  According to this, since the non-selection potential of the transmission electrode is substantially the same as the reception potential and non-selection potential of the reception electrode, the transmission electrode is not selected between the transmission electrode and the reception electrode during the non-selection period. In the period when the transmission electrode is in the selected state, there is a potential difference between the transmission electrode and the reception electrode and between the adjacent transmission electrodes, but this period is extremely short, The occurrence of migration can be greatly suppressed.

  According to a third aspect of the present invention, the selection potential and non-selection potential of the receiving electrode and the non-selection potential of the transmission electrode are both ground potentials in the second invention.

  According to this, since it is only necessary to ground the required terminals of the transmission unit and the reception unit, the configuration can be simplified.

  According to a fourth aspect of the present invention, in the first to third aspects of the invention, the IV converter has a dual power supply type operational amplifier, and a ground potential is applied to the operational amplifier as the reference potential.

  According to this, by setting the reference potential to the ground potential, it is possible to obtain a voltage signal that swings positively and negatively around 0V.

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

  FIG. 1 is an overall configuration diagram showing a touch panel device according to the present invention. The touch panel device 1 includes a panel body 4 in which a plurality of transmission electrodes 2 that run parallel to each other and a plurality of reception electrodes 3 that run parallel to each other are arranged in a grid pattern, and drive signals (pulse signals) to the transmission electrodes 2. Level signal for each electrode intersection where the transmission electrode 2 and the reception electrode 3 intersect each other by receiving the charge / discharge current signal of the reception electrode 3 in response to the drive signal applied to the transmission electrode 2 And a control unit 7 that detects the touch position based on the level signal output from the reception unit 6 and controls the operations of the transmission unit 5 and the reception unit 6.

  The touch panel device 1 is used as a so-called interactive whiteboard that can be used for presentations and lectures by being combined with a large-screen display device. In particular, the touch panel device 1 is used in combination with a projector device. The touch surface of 1 serves as a projector screen.

  Touch position information output from the touch panel device 1 is input to an external device 8 such as a personal computer, and is projected and displayed on the touch surface of the touch panel device 1 by the projector device 9 based on display screen data output from the external device 8. On the display screen, an image corresponding to the touch operation performed by the user with the pointing object (conductor such as the user's fingertip and stylus or pointer) on the touch surface of the touch panel device 1 is displayed, and the touch surface of the touch panel device is displayed. It is possible to display a required image in the same manner as when directly drawing with a marker, and it is possible to operate buttons and the like displayed on the display screen. Furthermore, an eraser that erases an image drawn by a touch operation can be used.

  The transmission electrode 2 and the reception electrode 3 are arranged at the same arrangement pitch (for example, 10 mm), and the number thereof varies depending on the aspect ratio of the panel body 4. For example, the transmission electrode 2 is 120 and the reception electrode 3 is 186, for example. Book placed.

  The transmission electrode 2 and the reception electrode 3 intersect in an overlapping manner with an insulating layer (support sheet) interposed therebetween, and a capacitor is formed at an electrode intersection where the transmission electrode 2 and the reception electrode 3 intersect. When a touch operation is performed with an indicator, the presence or absence of the touch operation can be detected by substantially reducing the capacitance at the electrode intersection in accordance with this.

  In particular, here, the mutual capacitance method is adopted, and when a drive signal is applied to the transmission electrode 2, a charge / discharge current flows to the reception electrode 3 in response to this, and at this time, according to the touch operation of the user, When the capacitance changes, the charging / discharging current of the receiving electrode 3 changes, and the amount of change of the charging / discharging current is converted into a level signal (digital signal) for each electrode intersection by the receiving unit 6 and output to the control unit 7. In the control unit 7, the touch position is calculated based on the level signal for each electrode intersection. This mutual capacitance method enables so-called multi-touch (multi-point detection) in which a plurality of touch positions are detected simultaneously.

  The control unit 7 obtains the touch position (center coordinate of the touch area) from the level signal for each electrode intersection output from the receiving unit 6 by a predetermined calculation process. In the calculation of the touch position, from the level signals at a plurality of (for example, 4 × 4) electrode intersections adjacent in the X direction (extension direction of the transmission electrode 2) and the Y direction (extension direction of the reception electrode 3), respectively. The touch position is obtained using a required interpolation method (for example, the center of gravity method). Thereby, the touch position can be detected with a resolution (for example, 1 mm or less) higher than the arrangement pitch (10 mm) of the transmission electrode 2 and the reception electrode 3.

  FIG. 2 is a schematic configuration diagram of the transmission unit 5 shown in FIG. The transmission unit 5 includes a drive signal generation unit 11 and an electrode selection unit 12. The drive signal generation unit 11 generates a drive signal (pulse signal) in synchronization with the timing signal output from the control unit 7. The electrode selection unit 12 selects the transmission electrodes 2 one by one, and sequentially applies the drive signals output from the drive signal generation unit 11 to the transmission electrodes 2.

  When the transmission electrode 2 is selected, a selection potential Vsa by a pulse wave of a maximum value Vp (for example, 5 V) as a drive signal is given to the transmission electrode 2, and the potential of the transmission electrode 2 is between 0 V and the maximum value Vp. Change. On the other hand, when the transmission electrode 2 is not selected, the non-selection potential Vsb (0 V), which is a ground potential, is applied to the transmission electrode 2.

  FIG. 3 is a schematic configuration diagram of the receiving unit 6 shown in FIG. The reception unit 6 includes an electrode selection unit 21 and a reception signal processing unit 22. In the electrode selection unit 21, a switching element SW is connected to each reception electrode 3, and the reception electrode 3 is selected one by one while applying a drive signal to one transmission electrode 2. Are sequentially input to the reception signal processing unit 22. Thereby, the charge / discharge current signal for every electrode intersection can be taken out. Each switching element SW is individually switched and controlled in accordance with a drive signal from the control unit 7.

  The switching element SW of the electrode selection unit 21 has a selection state in which one of the two contacts is connected to the reception signal processing unit 22, the other is grounded, and the reception electrode 3 is connected to the reception signal processing unit 22, It is switched between a non-selected state in which the electrode 3 is grounded. In the selected state, the receiving electrode 3 is supplied with the selection potential Vra, and in the non-selected state, the receiving electrode 3 becomes the ground potential in the non-selection potential Vrb (0 V). ) Is given. The selection potential Vra will be described in detail later.

  The receiving electrodes 3 and the switching elements SW of the electrode selection unit 21 are grouped by a predetermined number (for example, 24), and switching elements SW belonging to each group corresponding to each other are switched and controlled in parallel. A reception signal processing unit 22 is provided for each group. In each group, the switching elements SW are controlled so that the receiving electrodes 3 are sequentially selected one by one, and the remaining switching elements SW are controlled to be in a non-selected state. The charge / discharge current signal is input to the reception signal processing unit 22.

  As described above, since the switching operation of the switching element SW is performed in parallel among a plurality of groups, the time required to receive the charge / discharge current signals of all the reception electrodes 3 can be shortened. Moreover, since the process of the charging / discharging current signal in the receiving unit 6 can be divided and performed for each group, an increase in the size of the hardware configuration can be suppressed.

  In the grouping of the reception electrodes 3, the number of reception electrodes 3 belonging to each group does not need to be the same. For example, when the number of reception electrodes 3 is 186, seven groups A to G are set to 24, and the last What is necessary is just to make 18 groups H.

  FIG. 4 is a schematic configuration diagram of the received signal processing unit 22 shown in FIG. The reception signal processing unit 22 includes an IV conversion unit 31, a band pass filter 32, an absolute value detection unit 33, an integration unit 34, a sample hold unit 35, and an AD conversion unit 36.

  In the IV conversion unit 31, the charge / discharge current signal (analog signal) of the reception electrode 3 input via the electrode selection unit 21 is converted into a voltage signal. In the band pass filter 32, a process for removing a signal having a frequency component other than the frequency of the drive signal applied to the transmission electrode 2 is performed on the output signal of the IV conversion unit 31. The absolute value detection unit (rectification unit) 33 performs full-wave rectification on the output signal of the bandpass filter 32. The integration unit 34 performs processing for integrating the output signal of the absolute value detection unit 33 in the time axis direction. In the sample hold unit 35, a process of sampling the output signal of the integration unit 34 at a predetermined timing is performed. The AD converter 36 AD-converts the output signal from the sample hold unit 35 and outputs a level signal (digital signal).

  FIG. 5 is a circuit diagram showing a configuration of the IV conversion unit 31 shown in FIG. The IV converter 31 includes a feedback circuit between the inverting input terminal and the output terminal of the operational amplifier OPA, and includes a resistance component (feedback resistor) R and a capacitance component (phase compensation capacitor) C connected in parallel to each other. Yes, a weak current can be converted into a current-voltage with high sensitivity.

  The operational amplifier OPA is of a dual power supply system, and positive and negative voltages (+ V, −V) supplied from the power supply circuit 15 are applied. The charge / discharge current signal from the reception electrode 3 is input to the inverting input terminal of the operational amplifier OPA via the electrode selection unit 21. The reference potential Vref is applied to the non-inverting input terminal of the operational amplifier OPA. In particular, here, the non-inverting input terminal is grounded, and the reference potential Vref becomes the ground potential (0 V). As a result, a voltage signal having positive and negative amplitudes around 0V can be obtained.

  In this operational amplifier OPA, due to an imaginary short, the inverting input terminal connected to the receiving electrode 3 via the electrode selector 21 has the same potential as the grounded non-inverting input terminal. For this reason, when the receiving electrode 3 is selected, the receiving electrode 3 is energized with the IV converter 31, so that the selection potential Vra (0 V) which is the ground potential is applied to the receiving electrode 3.

  FIG. 6 is a diagram showing potentials in the selected state and the non-selected state of the transmission electrode 2 and the reception electrode 3 shown in FIG. As described above, the selection potential Vsa applied to the transmission electrode 2 when the transmission electrode 2 is selected varies between 0 V and the maximum value Vp, and the non-selection applied to the transmission electrode 2 when the transmission electrode 2 is not selected. The hourly potential Vsb is 0 V that is the ground potential.

  On the other hand, the selection-time potential Vra applied to the reception electrode 3 when the reception electrode 3 is selected becomes 0 V, which is the ground potential, when the operational amplifier OPA of the reception signal processing unit 22 is energized. The non-selection potential Vrb applied to 3 is also 0 V, which is the ground potential, and there is no potential difference between when the receiving electrode 3 is selected and when it is not selected.

  FIG. 7 is a waveform diagram illustrating a drive signal applied to the transmission electrode 2 illustrated in FIG. 1, an output signal after IV conversion in the reception unit 6, and a control signal that defines processing timing in the reception unit 6. . The transmission unit 5 selects the transmission electrodes 2 one by one and applies a drive signal (pulse signal) to the transmission electrodes 2, and the reception unit 6 applies the drive signal to one of the transmission electrodes 2. The receiving electrode 3 is selected one by one, and the charge / discharge current signal of the receiving electrode 3 is received and IV-converted. At this time, the transmitting electrode 2 receives a plurality of (12 in this case) pulse waves at one electrode intersection. Applied.

  The electrode selection unit 21 of the reception unit 6 switches the selection of the reception electrode 3 based on the control signal output from the control unit 7, and the switching element SW is switched at the timing when the control signal changes from low to high. The receiving electrode 3 is selected. In addition, the integration unit 34 performs integration processing based on the control signal, starts integration processing when the control signal changes from high to low, and ends integration processing when the control signal changes from low to high. To do.

  FIG. 7A shows an embodiment according to the present invention. Here, as described above, the selection potential Vra and the non-selection potential Vrb of the receiving electrode 3 are the same, and the ground potential (0 V) is applied to the receiving electrode 3 regardless of whether or not it is selected. Almost no switching noise is generated when the electrode 3 is switched. For this reason, the waiting time until the switching noise is settled (integration stop period) can be shortened, and the selection switching of the receiving electrode 3 can be performed at high speed.

  FIG. 7B shows a comparative example in which a single power supply type operational amplifier is used for the IV converter 31. In a single power supply type operational amplifier, it is necessary to set the reference potential (operating potential of the operational amplifier) to a positive potential in order to obtain a voltage signal with positive and negative amplitude centering on 0V. The selection potential Vra applied to the reception electrode 3 when the electrode 3 is selected is the same positive potential (for example, 2 V) as the reference potential of the operational amplifier.

  On the other hand, when the receiving electrode 3 is not selected, a non-selection potential Vrb (0 V) that is a ground potential is applied. Therefore, since a large potential difference is generated between the selection and non-selection of the reception electrode 3, a large switching noise is generated when the reception electrode 3 is switched. If this switching noise is included in the integral value, an erroneous touch position is generated. Invite detection. Therefore, it is necessary to ensure a long waiting time (integration stop period) until the switching noise is settled, and this takes time to switch the receiving electrode 3, so that the detection of the touch position becomes slow.

  FIG. 8 is a schematic diagram showing the state of the potentials of the transmission electrode 2 and the reception electrode 3 shown in FIG. As described above, the selection potential Vra and the non-selection potential Vrb of the receiving electrode 3 are both the ground potential (0 V). Therefore, there is no potential difference between the receiving electrode 3 in the selected state and the receiving electrode 3 in the non-selected state adjacent thereto, so that migration does not cause a problem.

  The non-selection potential Vsb of the transmission electrode 2 is the same ground potential (0 V) as the selection potential Vra and the non-selection potential Vrb of the reception electrode 3. Therefore, during the period in which the transmission electrode 2 is in a non-selected state, no potential difference is generated between the transmission electrode 2 and the reception electrode 3, so that migration does not cause a problem.

  On the other hand, since the selection potential Vsa of the transmission electrode 2 changes between 0 V and the maximum value Vp, there is a potential difference between the transmission electrode 2 and the reception electrode 3 during the period in which the transmission electrode 2 is in the selected state. Therefore, migration becomes a problem around the electrode intersection where the transmission electrode 2 and the reception electrode 3 intersect. Further, since a potential difference is generated between the transmitting electrode 2 in the selected state and the transmitting electrode 2 in the non-selected state adjacent thereto, migration between the transmitting electrodes becomes a problem.

  However, if the number of transmission electrodes 2 is 120 as described above, the transmission electrode 2 is selected only at a ratio (duty ratio) of 1/120, which is the reciprocal number thereof, as shown in FIG. Therefore, a potential difference is generated between the transmission electrode 2 and the reception electrode 3, and a period in which the potential difference is generated between the adjacent transmission electrodes 2 is extremely short. For this reason, generation | occurrence | production of migration can be suppressed significantly.

  In the above example, the selection potential Vra and the non-selection potential Vrb of the reception electrode 3 and the non-selection potential Vsb of the transmission electrode 2 are the same. However, these potentials do not need to be exactly the same. . If these potentials are sufficiently close, the occurrence of migration can be suppressed, and if the selection potential Vra and the non-selection potential Vrb of the reception electrode 3 are sufficiently close, switching noise can be reduced. Can do.

  The touch panel device according to the present invention has an effect of suppressing the occurrence of migration and increasing the speed of touch position detection without causing an increase in manufacturing cost or a decrease in convenience. In particular, it is useful as a touch panel device that detects a touch position by a mutual capacitance method.

DESCRIPTION OF SYMBOLS 1 Touch panel apparatus 2 Transmission electrode 3 Reception electrode 4 Panel main body 5 Transmission part 6 Reception part 7 Control part 11 Drive signal generation part 12 Electrode selection part 21 Electrode selection part 22 Reception signal processing part 31 IV conversion part Vsa Potential at the time of selection of a transmission electrode Vsb Transmission electrode non-selection potential Vra Reception electrode selection potential Vrb Reception electrode non-selection potential Vref Reference potential

Claims (4)

A panel body having a touch surface, a plurality of transmitting electrodes that run parallel to each other and a plurality of receiving electrodes that run parallel to each other are arranged in a grid pattern;
A transmission unit that selects an electrode to be transmitted from the plurality of transmission electrodes and applies a drive signal;
A receiving unit that selects an electrode to be received from the plurality of receiving electrodes, receives a charge / discharge current signal in response to the drive signal, and outputs a level signal for each electrode intersection;
A control unit that detects a touch position based on a level signal output from the reception unit and controls operations of the transmission unit and the reception unit;
The reception unit includes an IV conversion unit that converts a charge / discharge current signal from the reception electrode into a voltage signal by applying a predetermined reference potential, and is energized with the IV conversion unit when the reception electrode is selected. The receiving electrode is given the same selection potential as the reference potential, and the selection potential is substantially the same as the non-selection potential given to the receiving electrode when the receiving electrode is not selected. A featured touch panel device.   2. The non-selection potential applied to the transmission electrode when the transmission electrode is not selected, and the selection potential and non-selection potential of the reception electrode are substantially the same. Touch panel device.   The touch panel device according to claim 2, wherein the selection potential and non-selection potential of the reception electrode and the non-selection potential of the transmission electrode are both ground potential.   4. The touch panel device according to claim 1, wherein the IV conversion unit includes a dual power supply type operational amplifier, and a ground potential is applied to the operational amplifier as the reference potential. 5.

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