JP2010282462A - Capacity type touch panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacity type touch panel which can detect an input operation position accurately even if an input operation surface is upsized and resistances of a detection electrode pattern and its wiring pattern are changed. <P>SOLUTION: A detection resister connected to a detection electrode pattern in series and a stray capacity of the detection electrode pattern form a high-pass filter through which a common mode noise generated in an input operation body passes. As an input operation body comes closer and the stray capacity of the detection electrode pattern becomes larger, a level of the common mode noise passing through the high-pass filter rises, so that an input operation position is detected from an arrangement position of the detection electrode pattern at which the level of the common mode noise rises. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a capacitive touch panel that detects an input operation position on an input operation surface of an insulating panel from a change in stray capacitance at the input operation position.

  As a pointing device for pointing and inputting icons displayed on the display of electronic devices, the input operation position is detected in a non-contact manner using the change in capacitance caused by bringing an input operation body such as a finger close to the input operation surface. Thus, a capacitive touch panel that allows input operation even when arranged on the back side of the display is used.

  A change in capacitance due to an input operation is such that a detection electrode pattern in which a detection resistor R is connected in series is arranged on the input operation surface, and the capacitance (floating capacitance) C of the detection electrode pattern and the detection resistor R are on one side. By applying a predetermined voltage Vcc, it can be detected from a change in charge time or discharge time depending on the time constant RC.

  However, in a touch panel in which the size of the input operation surface is expanded to, for example, 4 inches or more, each detection electrode is caused by a manufacturing error or a temperature change of the thickness or width of the detection electrode pattern itself or the extraction electrode pattern connected thereto. There is a problem that an input operation is erroneously detected because the resistance value for each pattern is not stable and the time constant is different from the design value. Therefore, a capacitive touch panel with a large input operation surface has conventionally formed a uniform resistance layer on the surface of the input operation surface, so that an AC signal flowing to the operator can be input via the floating capacitance at the input operation position. The input operation position is detected by detecting at the four corners of the surface and comparing the signal levels at the four corners (Patent Document 1).

Further, in the detection method using the change in the time constant described above, the stray capacitance when the finger is brought close to the detection electrode pattern is only about 10 pF, so even if a 1 MΩ detection resistor is connected in series, The constant only changes about 10 ⁻⁵ seconds, and it is extremely difficult to detect an input operation to the detection electrode pattern directly from the comparison of the charging time and the discharging time. In order to solve this problem, a charge transfer type capacitance detection method has been proposed in which a capacitor with a larger capacity is prepared, the charge of the stray capacitance is repeatedly transferred to this capacitor, and the capacitor charge times are compared. (Patent Document 2).

  Hereinafter, a charge transfer type capacitance detection method will be described with reference to FIGS. A capacitor C1 shown in FIG. 6 is a small-capacitance c1 capacitor that attempts to detect a change in capacitance. One side of the capacitor C1 is grounded via the operator, and is charged with the charging voltage Vcc while the other side SW1 is ON. In addition, a capacitor C2 having a capacity c2 that is sufficiently larger than the capacitance of the capacitor C1 is connected in parallel with the capacitor C1 through SW2.

  In the detection circuit configured as described above, SW1 is turned on and SW2 is turned off in the first step, the capacitor C1 is charged with the charging voltage Vcc, and after charging, both SW1 and SW2 are turned off in the second step. . In this second step, the voltage V1 of the capacitor C1 is Vcc. Subsequently, in the third step, SW1 is turned off and SW2 is turned on, and a part of the charge of the capacitor C1 is transferred to the capacitor C2. Then, in the fourth step, both SW1 and SW2 are turned off again. In this fourth step, the voltage V1 of the capacitor C1 is equal to the voltage V2 of the capacitor C2.

The voltage V2 of the capacitor C2 when the processing from the first step to the fourth step is repeated N times is expressed as V2 = Vcc × (1−c2 / (c1 + c2) ^N ), and the charging voltage Vcc and the capacitance of the capacitor C2 Since c2 is known, if the number N of times that the voltage V2 of the capacitor C2 is achieved up to Vref set to ½ of the charging voltage Vcc shown in FIG. 7 is obtained, the capacitance c1 of the capacitor C1 to be detected is obtained. It is done.

  As shown in FIG. 7, as the capacitance c1 increases, the number of repetitions N reaching Vref becomes shorter. Therefore, in a sufficient capacitance type touch panel that can detect only the approach of the input operation body to the detection electrode pattern, When the threshold Nref of the number of repetitions is set to 1100 in the figure, for example, when Vref is reached with the number of repetitions shorter than the threshold value Nref, the input operation finger approaches and stray capacitance of 10 pF or more is generated. As an input operation to the detection electrode pattern is detected.

JP 2000-76014 A JP 2006-78292 A

  The capacitance-type touch panel disclosed in Patent Document 1 cannot detect a so-called multi-touch input operation position in which the input operation body is brought close to two or more positions on the input operation surface. The larger the operation surface, the larger the detection error simply by comparing the signal levels at the four corners, and the more accurate input operation position cannot be detected.

  Further, in the capacitive touch panel using the charge transfer capacitive detection method described in Patent Document 2, two types of switches SW1, SW2 and charging means and control means for the switches SW1, SW2 are provided for each detection electrode pattern. In the example described in Patent Document 2, unless the processing from step 1 to step 4 is repeated about 1000 times, the change in capacitance cannot be detected, and the input operation can be detected within the time that can be detected. Since it must be detected, the switches SW1 and SW2 are switched and controlled at a high speed with a period of 2 μsec in each step. Further, as the touch panel becomes larger, the detection electrode pattern becomes longer, so that the resistance of the pattern increases, and the time constant with the stray capacitance capacitor indicated by C1 in FIG. In some cases, the stray capacitance capacitor is insufficiently charged, and the input operation is erroneously detected.

  In this type of touch panel, when the input operation position is detected by two-dimensional plane coordinates, the processing from step 1 to step 4 is performed for each of a large number of row detection electrode patterns and a large number of column detection electrode patterns arranged in a grid pattern. The switches SW1 and SW2 must be simultaneously controlled at high speed, and the overall structure becomes complicated, and detection of an input operation in a short time is extremely difficult.

  Accordingly, there is a demand for a capacitive touch panel that can detect an input operation on a large-area input operation surface without misdetection, and can accurately detect the input operation position with high accuracy. Even a capacitive touch panel could not be realized.

  In addition, since any capacitive touch panel requires an AC signal to be applied to the input operation surface or a charge / discharge process, power is consumed even during a standby time for waiting for an input operation, and the battery is consumed. Due to the intense nature, it was unsuitable for mounting on mobile devices.

  The present invention has been made in consideration of such conventional problems, and even when the input operation surface is enlarged and the resistance value of the detection electrode pattern and its wiring pattern fluctuates, the input operation position is accurate. It is an object of the present invention to provide a capacitive touch panel capable of detecting the above.

  It is another object of the present invention to provide a capacitive touch panel that can quickly detect an input operation for a large number of detection electrode patterns without performing high-speed circuit opening / closing control for each detection electrode pattern.

  In addition, there is no need to generate a detection signal for detecting a change in stray capacitance or to charge a capacitor generated between the detection electrode pattern and the input operation body. It is an object of the present invention to provide a capacitive touch panel that can be used.

In order to achieve the above-described object, the capacitive touch panel according to claim 1 is connected to a plurality of detection electrode patterns disposed on one surface of the insulating panel so as to be insulated from each other, and to the plurality of detection electrode patterns. A plurality of capacitance detection means for outputting a capacitance change signal that changes in accordance with the stray capacitance of the detection electrode pattern to be detected, when the capacitance change signal output from one or more capacitance detection means changes. A capacitive touch panel that detects the input operation position from the position of the detection electrode pattern, assuming that the input operation body approaches the detection electrode pattern connected to the capacitance detection means that outputs the change signal and the floating capacitance rises. Because
Each capacitance detection unit is connected between a connection portion maintained at a ground potential or a stable potential and the detection electrode pattern, and constitutes a high-pass filter through which common mode noise passes with the stray capacitance of the detection electrode pattern. A detection resistor and an impedance conversion unit in which the detection electrode pattern is connected to an input having a high input impedance, and the common mode noise output from the impedance conversion unit of the capacitance detection unit is a capacitance change signal, When the level of common mode noise output from two or more capacitance detection means exceeds a predetermined threshold value, the input operation position is detected from the arrangement position of the detection electrode pattern to which the capacitance detection means is connected. Features.

  In the vicinity where the commercial AC power line is wired, common mode noise in which the potential fluctuates at the commercial AC power supply frequency is generated in the input operation body regarded as a part of the operator with reference to the detection electrode pattern. The common mode noise generated in the input operation body passes through the high-pass filter and is output as a capacitance change signal from the impedance conversion means having a high input impedance. Since the level of the capacitance change signal increases as the input operating body approaches the detection electrode pattern and the stray capacitance of the detection electrode pattern increases, the capacitance change signal is compared with a predetermined threshold value. Then, it can be determined that the input operation body has approached the detection electrode pattern, and the input operation position is detected from the arrangement position of one surface of the insulating panel of the detection electrode pattern.

  The input impedance of the impedance converting means is extremely higher than the output impedance, and the weak common mode noise output from the high-pass filter can be output as a capacitance change signal without being affected by other noise.

  The capacitive touch panel according to claim 2 is characterized in that a shield electrode pattern having a ground potential or a stable potential is arranged in parallel with the detection electrode pattern between adjacent detection electrode patterns on one surface of the insulating panel. To do.

  On one surface of the insulating panel, the detection electrode pattern is sandwiched and shielded between shield electrode patterns having a ground potential or a stable potential, and noise other than the common mode noise input from the input operation body does not easily enter the detection electrode pattern.

  The capacitive touch panel according to claim 3 is characterized in that a shield plate having a ground potential or a stable potential is laminated on the other surface of the insulating panel so as to cover the entire other surface of the insulating panel.

  Since the entire other surface of the insulation panel is covered with a shield plate having a ground potential or a stable potential, each detection electrode pattern is shielded on the other surface side by a shield plate, and other than the common mode noise input from the input operation body on the one surface side. Noise hardly penetrates into the detection electrode pattern.

  The capacitive touch panel according to claim 4, wherein a plurality of row detection electrode patterns are arranged along the X direction in a Y direction that intersects the row detection electrode patterns in a grid pattern with a first insulating panel disposed on one surface. A plurality of column detection electrode patterns are stacked on a second insulating panel disposed on one surface that insulates from one surface of the first insulating panel, and an input operation position on the XY plane is detected. .

  The stray capacitance of the row detection electrode pattern and the column detection electrode pattern intersecting in the vicinity of the input operation position by the input operation body increases, and the level of the capacitance change signal increases, so that the capacitance that has output a capacitance change signal exceeding the threshold value An input operation position on the XY plane is detected from each arrangement position of the row detection electrode pattern and the column detection electrode pattern of the detection means.

  The capacitive touch panel according to claim 5 is characterized in that the resistance value of the detection resistor is 1 MΩ or more by adding the resistance value of the detection electrode pattern connected in series.

  The level of the common mode noise is about 30 V. When the stray capacitance that changes by about 10 pF by the input operation and the resistance value of the detection resistor constituting the high pass filter is 1 MΩ or more, the level change of the capacitance change signal is It becomes 100 mV or more that can be detected.

  According to the first aspect of the present invention, in order to detect a change in the stray capacitance between the input operation body and the detection electrode pattern, the stray capacitance is not charged, or a separately generated detection signal is not sent to the stray capacitance. Since the naturally occurring common mode noise is used as the detection signal, the input operation position can be detected from the change in the stray capacitance at high speed with a simple circuit.

  Since changes in the stray capacitances of a plurality of detection electrode patterns arranged on one surface of the insulating panel can be detected simultaneously, it can be detected even when there are a plurality of input operation positions.

  Even if the input operation surface becomes larger and the resistance value of the detection electrode pattern or its wiring pattern fluctuates, the resistance value of the detection resistor can be adjusted to such a level that the fluctuation amount of the resistance value can be ignored. It hardly affects the level of the change signal and does not erroneously detect an input operation.

  In addition, since there is no capacitor charging process or detection signal generation circuit, it is possible to wait for an input operation with low power consumption.

  According to the second and third aspects of the invention, noise other than the common mode noise is difficult to be superimposed on the capacitance change signal, and the detection accuracy of the input operation position is improved.

  According to the invention of claim 4, the input operation position on the XY plane can be detected with high accuracy.

  According to the invention of claim 5, since the resistance value of the detection resistor is 1 MΩ or more by adding the resistance value of the detection electrode pattern, even if the stray capacitance is a minute change of about 10 pF by the input operation, the detection circuit Can detect the change.

  The resistance value of the detection electrode pattern is several tens of kΩ or less even when the input operation surface is expanded to 5 inches or more, and the resistance value of the detection resistor including the resistance value of the detection electrode pattern is 1 MΩ or more. Even if the resistance value of the electrode pattern fluctuates, it has a negligible size, does not affect the level of the capacitance change signal, and does not erroneously detect an input operation even if the input operation surface is enlarged.

It is a block diagram which shows the determination circuit 15 of the capacitive touch panel 1 which concerns on 1st Embodiment of this invention. The relationship between the input operation position of the capacitive touch panel 1 and the capacitance change signal is shown, (a) is a partial plan view of the insulating panel 2, and (b) is the envelope of the output signal B of the high-pass filter 4 and the capacitance change signal. 4 is a waveform diagram of a line waveform C. FIG. 6 is a waveform diagram showing the relationship between the resistance value Ri of the detection resistor 3 and the frequency characteristic of the high-pass filter 4. FIG. It is a wave form diagram which shows the relationship between the input-output ratio of the high pass filter 4, and the resistance value Ri of the detection resistance 3 about the electrostatic capacitance c of a different floating capacitance. It is a block diagram of the capacitive touch panel 20 according to the second embodiment. It is a block diagram which shows the capacitance detection method of the conventional charge transfer system. It is a wave form diagram which shows the relationship between the frequency | count N of charge by the electrostatic capacitance detection method shown in FIG. 6, and the voltage V2 of the capacitor | condenser C2.

  Hereinafter, a capacitive touch panel (hereinafter referred to as a touch panel) 1 according to an embodiment of the present invention will be described with reference to FIGS. The touch panel 1 has an input operation surface 2a on the surface of the insulating panel 2. As shown in FIG. 2A, x1, x2, x3, x4 along one direction on the input operation surface 2a. ... A plurality of detection electrode patterns 5 made of a conductive material such as ITO are formed in parallel to each other at positions at equal intervals of xn.

  Between each detection electrode pattern 5, a linear shield electrode pattern 12 connected to the ground is formed in parallel with the detection electrode pattern 5, and is input to the detection electrode pattern 5 along the surface of the insulating panel 2. Noise is cut off. In the present embodiment, the shield electrode pattern 12 is grounded. However, as long as the shield electrode pattern 12 is kept at a stable potential, the shield electrode pattern 12 does not necessarily have to be a ground potential.

  The detection resistor 3 is connected in series to one side of each detection electrode pattern 5, and the other side of the detection resistor 3 is grounded. As shown in FIG. 1, each detection electrode pattern 5 has a stray capacitance Cf that increases when an operator's finger as the input operation body 6 approaches, and the detection resistor 3 is detected on one side of the stray capacitance Cf. By connecting between the electrode pattern 5 and the ground, the high-pass filter 4 for the input from the finger 6 is configured.

  When the touch panel 1 is mounted on an electronic device operating with a commercial AC power source or a commercial AC power line is wired around the space where the touch panel 1 is used, as shown in FIG. 1, the touch panel 1 is in contact with the ground plane. The operator's finger 6 varies in potential at the commercial AC power frequency with reference to the detection electrode pattern 5, and common mode noise A having a commercial AC power frequency f of, for example, 50 Hz is generated on the finger 6.

で表される。 The output level passing through the high-pass filter 4 is | Vo |, the level of the common mode noise A is | Vi |, the frequency of the common mode noise A (commercial AC power supply frequency f * 2π) is ω, the stray capacitance is Cf, and the detection resistor If the resistance value of 3 is Ri,

It is represented by

  That is, as the operator's finger 6 approaches the specific detection electrode pattern 5, the stray capacitance Cf generated in the detection electrode pattern 5 increases, and the output level | Vo | of the common mode noise passing through the high-pass filter 4 also increases. To do.

Here, since the stray capacitance when the finger 6 is brought close to the detection electrode pattern 5 is about 10 pF, the stray capacitance Cf is 10 pF and the resistance value Ri of the detection resistor 3 is 1 GΩ and 100 MΩ in the equation (1). FIG. 3 shows the frequency characteristics of | Vo | / | Vi | when 10 MΩ and 1 MΩ are set, | Vo | / | Vi | increases as the frequency ω increases. The level of the common mode noise A generated by the operator is about 30 V. If the level at which the output level | Vo | can be detected by the subsequent circuit is 100 mV or more, at least the gain (| Vo | / | Vi | ) is 3 × 10 ^-3 or more is required, the frequency of the common mode noise a (commercial AC power supply frequency f) is assumed to be 50 Hz, the resistance value Ri of the detection resistor 3, in addition to the resistance value of the detection electrode pattern 5 At least 1 MΩ or more.

Also, in equation (1), when the stray capacitance Cf is 100 pF, 10 pF, and 1 pF, | Vo | / | Vi | with respect to the resistance value Ri of the detection resistor 3 increases the resistance value Ri as shown in FIG. When a circuit capable of detecting an output level | Vo | of 100 mV or more is detected, a gain (| Vo | / | Vi |) of 3 × 10 ⁻³ or more is detected. Therefore, it is necessary to connect the detection resistor 3 having a resistance value Ri of 10 MΩ or more. Here, the resistance value Ri of the detection resistor 3 shown in FIG. 1 is set to 10 MΩ.

  Even if the input operation surface 2a is enlarged and the resistance value of the detection electrode pattern 5 and its wiring pattern fluctuates, the amount of change in the resistance value is about 40 KΩ, and the resistance value Ri of the detection resistor 3 is at least 1 MΩ or more. Since the amount of change is negligible in comparison, it does not affect the determination of the level of a capacitance change signal, which will be described later, that passes through the high-pass filter 4, and the input operation is not erroneously detected.

  When the resistance value Ri of the detection resistor 3 is 1 GΩ or more, even if the stray capacitance Cf is very small, external noise passes through the high-pass filter 4 and external noise and common mode noise level fluctuations cause malfunction. The resistance value Ri is preferably less than 1 GΩ.

The output side of the high pass filter 4 is connected to the cathode of the diode 7 whose anode is grounded, so that the common mode noise output from the high pass filter 4 is clamped to the ground level as shown by the waveform shown in FIG. To do. This is because the polarity of the common mode noise, which is an AC signal, is matched to facilitate comparison between a voltage threshold V _TH described later and a voltage level.

  The output side of the high-pass filter 4 is further connected to the input of a unity gain amplifier 8 that acts as a voltage follower that is an impedance conversion means. The unity gain amplifier 8 has an input impedance that is sufficiently higher than the output impedance from the high-pass filter 4 and converts it into an output impedance of several hundred ohms. Can be output as Further, the unity gain amplifier 8 does not pass AC signals such as noise and clock from the output side circuit of the unity gain amplifier 8 to the capacitance detection circuit 9 from the high pass filter 4 to the unity gain amplifier 8 and separates them from the output side. Therefore, common mode noise can be detected without being affected by the internal circuit of the touch panel 1.

The output of the unity gain amplifier 8 is connected to a low-pass filter 10 composed of a resistor R ₁ connected in series and a capacitor C ₁ connected between the output of the resistor R ₁ and the ground terminal. The low-pass filter 10 cuts off the high-frequency component of the capacitance change signal shown by the waveform B in FIG. 1 output from the unity gain amplifier 8, and the comparator 11 connected to the subsequent stage makes its envelope easy to compare. Waveform shaping to a C waveform approximating a line.

The comparator 11 compares the level of the C waveform capacitance change signal input to the non-inverting input from the low-pass filter 10 with a voltage threshold V _TH set to a predetermined voltage, and outputs the comparison result in binary. As described above, since the level of the capacitance change signal increases as the detection electrode pattern 5 is approached, the voltage threshold V _TH is, for example, that the finger 6 approaches the detection electrode pattern 5 and the stray capacitance Cf is 10 pF. When this is the case, the level of the capacitance change signal input to the non-inverting input is set. As a result, as shown by the waveform D in FIG. 1, the comparator 11 does not perform an input operation on the detection electrode pattern 5, and thus the input level of the non-inverted input is the voltage threshold value V _TH . the "L", when the finger 6 to perform an input operation close to the detection electrode pattern 5, the input level of the non-inverting input exceeds the voltage threshold V _TH, outputs a binary output CMPo "H" To do.

  The input operation determination circuit 15 described above is provided for each detection electrode pattern 5, and the binary output CMPo output from each comparator 11 is output to each input port of a microcomputer (not shown) that detects the input operation position. . In the microcomputer, when an input determination signal of “H” is input to any one or two or more input ports, the detection electrode pattern 5 of the determination circuit that outputs “H” is placed at the position on the insulating panel 2. The input operation position is detected on the assumption that the finger 6 of the input operation has approached.

As shown in FIG. 2A, the finger 6 that performs an input operation in the direction from x1 to xn moves along the input operation surface 2a of the touch panel 1 configured in this manner, and the detection electrode pattern 5 at x1 is moved. the a finger 6 passes, from the high-pass filter 4 constituting the detection electrode patterns 5 of x1, the common mode noise shown by B ₁ in the waveform is output to the comparator 11 of the determination circuit 15, a voltage shown in C ₁ the level of the waveform exceeding the threshold V _TH are inputted. As a result, the binary output CMPo of “H” is output from the comparator 11, and the input operation position of x1 is detected from the arrangement position of the detection electrode pattern 5 of the determination circuit 15 that outputs “H”.

Similarly, from the high-pass filter 4 in which the detection electrode patterns 5 positions the finger 6 has passed constitutes, it is the common mode noise of each _{B 2,} B 3, _{B 4} of the waveform output, the comparator _11, C 2, _{C 3} , A waveform having a level exceeding the voltage threshold V _TH shown in C ₄ is input. As a result, the binary output CMPo of “H” is output from the comparator 11, and the input operation of x2, x3, x4,... Xn is performed from the position of the detection electrode pattern 5 of the determination circuit 15 that output “H”. The position is detected in order.

  Next, the capacitive touch panel 20 according to the second embodiment of the present invention will be described with reference to FIG. In FIG. 5, the same reference numerals are given to configurations that operate in the same or the same manner as in the first embodiment, and detailed description thereof is omitted.

  The touch panel 20 detects an input operation position on a two-dimensional plane of the input operation surface 2a, and has a three-layer structure in which an X-side insulating panel 22 and a Y-side insulating panel 23 are stacked on a shield plate 21. ing. The touch panel 20 according to the present embodiment is mounted on the surface side of a display element such as a liquid crystal display of an electronic device, so that an operator can perform an input operation while checking the display on the display element. The shield plate 21, the X-side insulating panel 22, and the Y-side insulating panel 23 are each formed of a transparent insulating film.

  On the surface of the X-side insulating panel 22, a plurality of detection electrode patterns 24X made of a transparent conductive material such as ITO are formed in parallel to each other along the Y direction at equal intervals in the X direction shown in the figure. The detection resistor 3 having the other side grounded is connected in series to one side of each detection electrode pattern 24X.

  Further, on the surface of the Y-side insulating panel 23, a plurality of detection electrode patterns 24Y made of a transparent conductive material such as ITO along the X direction are arranged in parallel with each other at equal intervals in the Y direction shown in the figure. A detection resistor 3 formed and grounded on the other side is also connected in series to one side of each detection electrode pattern 24Y. Therefore, with the XY plane as the input operation surface 2a, a large number of detection electrode patterns 24X and detection electrode patterns 24Y intersect in a lattice pattern on the back side of the input operation surface 2a.

  Between the detection electrode patterns 24X and 24Y of the X-side insulating panel 22 and the Y-side insulating panel 23, a linear shield electrode pattern 12 is formed in parallel with the detection electrode patterns 24X and 24Y. Further, the X-side insulating panel Since the shield plate 21 on which the transparent conductive pattern layer connected to the ground is formed on the entire surface is laminated on the back side of the surface 22, the detection electrode patterns 24X and 24Y are shield electrodes in directions other than the direction above the input operation surface 2a. It is shielded by the pattern 12 and the shield plate 21, and noise other than the common mode noise of the finger 6 does not enter. The shield plate 21 is not necessarily grounded as long as it is kept at a stable potential.

  The other side of each detection electrode pattern 24X to which the detection resistor 3 is connected is clamped to the ground level by the diode 7, connected to the input of the unity gain amplifier 8, and an input side circuit having the detection electrode pattern 24X and its output side To be separated. The output of the unity gain amplifier 8 connected to each detection electrode pattern 24X is connected to the input of the X side multiplexer 26 whose connection is switched by the CPU 25, and is output from the unity gain amplifier 8 selectively connected by the X side multiplexer 26. A capacitance change signal is input to the A / D converter 27.

  Similarly to the detection electrode pattern 24X, the other side to which the detection resistor 3 of each detection electrode pattern 24Y is connected is clamped to the ground level by the diode 7 and the connection is switched by the CPU 25 via the unity gain amplifier 8. Each is connected to 28 inputs. Accordingly, the capacitance change signal output from the unity gain amplifier 8 selectively connected by the Y-side multiplexer 28 is input to the A / D converter 27.

In the first embodiment, the level of the envelope of the capacitance change signal is compared with the voltage threshold V _TH and the input operation to the specific detection electrode pattern 5 is detected. However, in this embodiment, the capacitance The change signal is binarized by the A / D converter 27, and the CPU 25 connected to the output of the A / D converter 27 detects the input operation position from the binarized capacity change signal level.

  Hereinafter, a method of detecting the input operation position with the touch panel 20 configured as described above will be described on the assumption that there has been an input operation in which the finger 6 approaches the position of the XY coordinates (Xn, Yn) on the input operation surface 2a. . The CPU 25 scans the detection electrode patterns 24X and 24Y by switching and controlling all inputs of the X-side multiplexer 26 and the Y-side multiplexer 28 at a cycle shorter than at least the input operation time for causing the finger 6 to approach the input operation surface 2a. .

  That is, capacitance change signals representing the floating capacitances Cf of the multiple detection electrode patterns 24X on the X-side insulation panel 22 and the multiple detection electrode patterns 24Y on the Y-side insulation panel 23 are sequentially sent to the A / D converter 27. Entered. When the finger 6 approaches the XY coordinates (Xn, Yn), the detection electrode pattern 24X (Xn) and the unity gain amplifier 8 connected to the detection electrode pattern 24Y (Yn) are input to the A / D converter 27. The level of the capacitance change signal rises, and the CPU 25 detects that the level of the binarized capacitance change signal repeatedly exceeds the threshold value a predetermined number of times at the timing of connection to the output of these unity gain amplifiers 8. A position (Xn, Yn) ′ where the electrode pattern 24X (Xn) and the detection electrode pattern 24Y (Yn) intersect is detected as an input operation position.

  In addition, when the level of the capacitance change signal of the plurality of detection electrode patterns 24X and 24Y adjacent in the same direction exceeds the threshold value within the same scanning period, the level of each capacitance change signal is compared and an input operation is performed. Find the position. For example, output from the unity gain amplifier 8 connected to the detection electrode patterns 24X (Xn-1), 24X (Xn), 24X (Xn + 1) arranged in Xn-1, Xn, Xn + 1 in the X direction within the same scanning period. When the level of the capacitance change signal to be repeated exceeds the threshold value a predetermined number of times, the center of gravity position calculated by weighting the level of the capacitance change signal to each arrangement position is set as the input operation position in the X direction. And Thereby, the input operation position in the XY directions can be detected with a resolution higher than the number of wires of the plurality of detection electrode patterns 24X and 24Y.

  The CPU 25 outputs the input operation position thus truly detected to a microcomputer that controls cursor movement control on the display screen and the operation of the electronic device, and executes predetermined processing according to the input operation position.

  In the first and second embodiments described above, the detection resistor 3 is connected to the other side of the detection electrode patterns 5, 24X, 24Y to which the unity gain amplifier 8 is connected, but the high-pass filter 4 is formed. For example, it may be connected to the connection side of the unity gain amplifier 8.

  The unity gain amplifier 8 may be an amplifier that also serves as voltage amplification as long as the impedance conversion element has an input impedance that is extremely higher than the output impedance.

  Although one side of the detection resistor 3 is grounded, it may be connected to a terminal having a stable potential, and is clamped by a diode 7 in order to change the common mode noise with the same polarity. As long as the level of common mode noise can be measured, the diode 7 is not necessarily interposed.

  Furthermore, although the input operation body 6 has been described with the operator's finger, it may be an operation body different from the operator, such as a dedicated input pen held by the operator.

  The present invention is suitable for a capacitive touch panel having a large input operation surface.

DESCRIPTION OF SYMBOLS 1 Capacitance type touch panel which concerns on 1st Embodiment 2 Insulation panel 3 Detection resistance 4 High pass filter 5 Detection electrode pattern 6 Input operation body (finger)
8 Impedance conversion means (Unity gain amplifier)
9 Capacitance detection means (capacitance detection circuit)
DESCRIPTION OF SYMBOLS 12 Shield electrode pattern 20 The electrostatic capacitance type touch panel which concerns on 2nd Embodiment 21 Shield board 22 X side insulation panel 23 Y side insulation panel 24X Detection electrode pattern 24Y Detection electrode pattern

Claims (5)

A plurality of detection electrode patterns that are insulated from each other on one surface of the insulating panel, and a plurality of detection electrode patterns that are connected to the plurality of detection electrode patterns and that output capacitance change signals that change according to the stray capacitance of the connected detection electrode patterns When the capacitance change signal output from one or more capacitance detection means changes, the input operating body is connected to the detection electrode pattern connected to the capacitance detection means that outputs the capacitance change signal. It is a capacitive touch panel that detects the input operation position from the arrangement position of the detection electrode pattern, assuming that the stray capacitance has increased by approaching,
Each capacity detection means
A detection resistor that is connected between a connection portion that is maintained at a ground potential or a stable potential and the detection electrode pattern, and that constitutes a high-pass filter through which common mode noise passes with the stray capacitance of the detection electrode pattern;
Impedance conversion means having the detection electrode pattern connected to an input having a high input impedance;
When the common mode noise output from the impedance conversion means of the capacitance detection means is used as a capacitance change signal, and the level of the common mode noise output from any one or more of the capacitance detection means exceeds a predetermined threshold value An electrostatic capacity type touch panel, wherein an input operation position is detected from an arrangement position of a detection electrode pattern to which the capacitance detection means is connected. The electrostatic capacitance method according to claim 2, wherein a shield electrode pattern having a ground potential or a stable potential is disposed in parallel with the detection electrode pattern between adjacent detection electrode patterns on one surface of the insulating panel. Touch panel. 3. The capacitive touch panel according to claim 1, wherein a shield plate having a ground potential or a stable potential is laminated on the other surface of the insulating panel so as to cover the entire other surface of the insulating panel. A plurality of row detection electrode patterns along the X direction, the first insulating panel disposed on one surface, and a plurality of column detection electrode patterns along the Y direction intersecting the row detection electrode pattern in a lattice shape, A first insulating panel and a second insulating panel disposed on one surface for insulation are laminated;
The capacitive touch panel according to any one of claims 1 to 3, wherein an input operation position on an XY plane is detected. 5. The capacitive touch panel according to claim 1, wherein the resistance value of the detection resistor is 1 MΩ or more by adding the resistance value of the detection electrode patterns connected in series.

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