JP5605577B2 - Capacitive touch sensor - Google Patents

Description

  The present invention relates to a capacitive touch sensor that monitors changes in capacitance and detects the approach or contact of a test object.

  A capacitance sensor that detects an operation using capacitance between a capacitance detection electrode and a human body is used in, for example, a touch panel and a touch pad. The touch panel is mounted on, for example, an LCD screen and is widely used because the switch can be arranged flexibly as compared with a conventional mechanical switch.

  In such a capacitance type switch, as a method of detecting the object to be detected, a method of detecting by directly measuring the impedance of the detection electrode and detecting the capacitance, or the capacitance detected by the detection electrode is a voltage. A method of measuring the oscillation frequency by configuring an oscillation circuit to be converted and input, a method of configuring an RC charge / discharge circuit and measuring the discharge time, and a capacitor having a known capacitance charged with a known voltage There are known a method of measuring the time during which the capacitor having the known capacity is charged to a predetermined voltage, or a method of repeatedly charging and discharging the capacitor having the known capacity and counting the number of times.

  In addition, a plurality of electrodes are arranged on the dielectric layer, a capacitor is formed between the electrodes and the conductive operation body approaching the plurality of electrodes, and the capacitance of which electrode of the plurality of electrodes is close to the conductive operation body A capacitance sensor that can prevent erroneous operation when a conductive operating body approaches a wiring line has been devised (see Patent Document 1).

  In addition, one of the two or more detection electrodes is connected to the capacitance detection circuit, and the other detection electrodes are connected to the same potential output means so that the detection electrodes other than the measurement target function as a shield, and malfunction due to disturbance. An electrostatic capacity sensor that can prevent the above has been devised (see Patent Document 2).

  In addition, a touch panel has been devised in which a plurality of through holes are formed in a substrate and wiring between the substrate front surface and the substrate back surface is connected without passing through the end surface of the substrate, thereby reliably preventing disconnection in the wiring ( (See Patent Document 3).

JP 2010-086385 A JP 2007-303895 A Japanese Patent Application Laid-Open No. 60-200425

  The configuration of Patent Document 1 requires the formation of a foamed layer that prevents erroneous operation, and thus the configuration is complicated and the cost increases accordingly.

  Since the configuration of Patent Document 2 requires a switching device, there is a problem that the configuration becomes complicated and the cost increases accordingly.

  The configuration of Patent Document 3 does not include a configuration that prevents a user's erroneous operation.

  With the above problem as a background, an object of the present invention is to provide a capacitive touch sensor that can accurately detect a user's operation.

Means for Solving the Problems and Effects of the Invention

A capacitive touch sensor for solving the above-described problems is provided by insulating a plurality of electrodes arranged in a row on the surface of a plate-like insulator and generating capacitance when a test object approaches. A plurality of wiring lines that are arranged at predetermined intervals on the back surface of the body so as to face the electrodes with an insulator interposed therebetween, and that are output ends that output the capacitance generated at one end, and a plurality of electrodes A connection portion that connects one of the plurality of wiring lines and one of the plurality of wiring lines at a predetermined position of the wiring line, and the connection portion is located below the periphery of the electrode or from the periphery of the electrode. The electrode is located at a predetermined distance, the electrode is located between the connecting portion and the output end, and the wiring line is a peripheral edge of the electrode far from the output end and a peripheral edge near the output end. intersects the, this is formed to reach the output end of the connecting portion The features.

  The present invention changes the arrangement of the wiring lines by focusing on the fact that the above-mentioned problem is caused by the fact that the erroneous determination of the capacitance change in the wiring lines is caused by the wiring lines being wired on the same plane as the electrodes. It solves by. In the conventional configuration, the wiring line connected to the electrode is often wired on the same plane on the top, bottom, left, and right of the electrode. However, in the present invention, the wiring passes through the lower side of the electrode and is fixed to the electrode with an insulator in between. By arranging so as to keep the distance, it becomes possible to prevent malfunction when the object to be measured comes close to the electrostatic touch panel (electrode).

  Moreover, the connection part in the capacitive touch sensor of the present invention connects the other end of the wiring line.

  Even with the above configuration, it is possible to prevent malfunction when a test object such as a user's finger approaches the electrostatic touch panel (electrode). Further, since the wiring line extends from the electrode to the output end, the length of the wiring line can be shortened.

  In addition, the capacitance type touch sensor of the present invention is a wiring line in which the capacitance generated in the electrode that the test object approaches is connected to the electrode that the test object approaches and the electrode that the test object does not approach The thickness of the insulator is determined so as to be larger than the capacitance generated between the two.

  The value of the capacitance C is represented by C = ε0 × εr × S / L. That is, it is determined by the area S of the metal plates, the distance L between the metal plates, and the relative dielectric constant εr of the insulator between the metal plates (ε0 is the vacuum dielectric constant, minus 8 12 of 8.854 × 10). In the configuration of the present invention, the thickness of the insulator corresponds to the distance L, and the area of the surface facing the electrode of the wiring line corresponds to the area S. When the area S cannot be reduced due to the limitation of the wiring space, if the distance L is increased, the capacitance generated between the electrode approaching the test object and the wiring line connected to the electrode not approaching the test object is reduced. can do. With the above configuration, it is possible to accurately determine the electrode that the test object has approached.

  In addition, the capacitance type touch sensor of the present invention is configured such that the capacitance generated at the electrode approaching the test object is connected to the wiring line connected to the electrode approaching the test object and the electrode not approaching the test object The spacing between the wiring lines is determined so as to be larger than the capacitance generated between the wiring lines connected to the.

  According to the calculation formula of the capacitance C described above, if the interval between these wiring lines is large, the wiring line connected to the electrode that the test object approaches and the wiring that is connected to the electrode that the test object does not approach Capacitance generated between the lines can be reduced. Also with the above configuration, it is possible to accurately determine the electrode that the test object has approached.

  In the capacitive touch sensor of the present invention, the wiring line is covered with an insulator.

  With the above configuration, the dielectric constant between adjacent wiring lines is constant (that is, the dielectric constant of the insulator) as compared to the state where the wiring lines are exposed (that is, in contact with air). When the user's finger (that is, the test object) approaches the electrode, it is possible to suppress a change in capacitance that occurs between adjacent wiring lines.

The figure which shows the structure of the electrostatic capacitance type touch sensor by a prior art. The figure which shows the output voltage of each electrode at the time of the test object approach in the structure of FIG. The figure which shows the structure of the electrostatic capacitance type touch sensor of this invention. X-X 'sectional drawing of FIG. FIG. 4 is a Y-Y ′ cross-sectional view of FIG. 3. The figure which shows another example of a structure of the electrostatic capacitance type touch sensor of this invention. X-X 'sectional drawing of FIG. The figure which shows another example of the Y-Y 'cross section of FIG. 3 or FIG. The figure which shows another example of the Y-Y 'cross section of FIG. 3 or FIG. The figure which shows the output voltage of each electrode at the time of the test object approach in the structure of FIG. 3 or FIG. The figure which shows the output voltage of each electrode at the time of the test object approach in all the electrodes in the structure of FIG. 3 or FIG. The figure which shows another example of a structure of the electrostatic capacitance type touch sensor of this invention. X-X 'sectional drawing of FIG. The figure which shows the output voltage of each electrode at the time of a test object approach in the structure of FIG. The figure which shows another example of arrangement | positioning of an electrode. The figure which shows another example of arrangement | positioning of an electrode.

  Hereinafter, the capacitive touch sensor of the present invention will be described with reference to the drawings. First, FIG. 1 shows an example of the configuration of a capacitive touch sensor according to the prior art. The capacitive touch sensor 2 includes electrodes 10, 20, 30, 40, a switching circuit 5, and a signal processing circuit 6 mounted on a substrate 4 such as a printed circuit board. Further, the electrodes 10, 20, 30, 40 and the switching circuit 5 are connected by wiring lines 11a, 21a, 31a, 41a formed as wiring patterns on the surface of the substrate 4 where the electrodes are arranged, respectively. .

  The switching circuit 5 selects one of the electrodes 10, 20, 30, and 40 based on the control command of the signal processing circuit 6 and outputs the state.

  The signal processing circuit 6 includes a capacitor for accumulating capacitance generated in the electrodes, an amplifier including a known operational amplifier, an AD converter, a microcomputer, a ROM, a RAM, and peripheral circuits. Is done. The microcomputer executes a control program stored in the ROM to perform various operations as the capacitive touch sensor 2.

  Note that the switching circuit 5 and the signal processing circuit 6 may not be mounted on the substrate. That is, the substrate 4 may be included in a different substrate or apparatus. Further, the switching circuit 5 and the signal processing circuit 6 may be configured not to be included in the present invention.

  With the configuration described above, the capacitive touch sensor 2 selects one of the four electrodes by the switching circuit 5 in accordance with a control instruction from the signal processing circuit 6 (for example, a microcomputer), and applies a predetermined voltage to the electrode. Apply. For example, when the user's finger F (test object) approaches (or comes into contact with) the electrode, electric charge corresponding to the capacitance between the electrode and the user and the capacitance between the user and GND is accumulated in the electrode. Is done. The electric charge accumulated in this electrode is transferred to a capacitor included in the signal processing circuit 6. Then, after repeating the accumulation and transfer of these charges for a predetermined period, the voltage of the capacitor generated according to the amount of charge is amplified and AD converted, and in the microcomputer, the voltage value or the change in the voltage value is Determine whether it is due to approach or contact. As this determination method, a charge transfer method is known.

  In the configuration of FIG. 1, when the user's finger F approaches the capacitive touch sensor 2, there is no problem as long as the user's finger F approaches the electrode, but when the user's finger F approaches the wiring line, the user's finger F and the wiring line Capacitance is generated between The capacitance value is not constant depending on the approaching state of the user's finger F, and may cause erroneous detection.

  For example, when the user's finger F approaches as shown in FIG. 1, the voltage value of each electrode detected by the signal processing circuit 6 is the detection level of the electrode 20 (in this case, the wiring line 21) as shown in FIG. Among the four electrodes, the largest value V1 is obtained. At this time, when the threshold value of the voltage for determining the approach of the user's finger F is set between V1 and V2, the user's finger F approaches the electrode 20 even though it does not approach the electrode 20. It may be determined that the user does not intend to perform the operation.

  Further, when the above threshold value is set between V3 and V4, there arises a problem that it cannot be determined whether the signal is a normal signal or a signal of a malfunction factor that is not intended to be accepted as an input.

  Next, the capacitive touch sensor of the present invention will be described with reference to FIGS. In addition, about the structure similar to FIG. 1, detailed description here is omitted. 3 is a top view of the capacitive touch sensor 1, FIG. 4 is a cross-sectional view taken along the line X-X ′ of FIG. 3, and FIG. 5 is a cross-sectional view taken along the line Y-Y ′ of FIG.

  The capacitive touch sensor 1 includes electrodes 10, 20, 30, and 40, a switching circuit 5, and a signal processing circuit 6 that are mounted in a row on the surface of the substrate 4. Further, the electrodes 10, 20, 30, 40 and the switching circuit 5 are connected by wiring lines 11, 21, 31, 41 formed as wiring patterns on the back surface of the substrate 4, respectively.

  Each wiring line (11, 21, 31, 41) is wired at a predetermined interval (L2) so as to be substantially equidistant, for example, so as to face the electrode with the substrate 4 being an insulator interposed therebetween. ing. The ends (16, 26, 36, 46) connected to the wiring line switching circuit 5 are output ends.

  The board | substrate 4 may be comprised with an insulator instead of a printed wiring board, for example, and is good also as an air layer. However, the configuration using an insulator rather than the air layer has an advantage that the variation in capacitance generated between each electrode and each wiring line is small.

  Through holes (also referred to as through holes) 15, 25, 35, 45 are formed at the ends of the substrate 4 far from the switching circuit 5 of the electrodes (10, 20, 30, 40). , 21, 31, 41) are connected to the electrodes through the corresponding through holes and via the wiring patterns (12, 22, 32, 42) on the surface of the substrate 4. The through hole and the wiring pattern correspond to the connection portion of the present invention.

  The electrodes (10, 20, 30, 40) are substantially rectangular, but may be polygonal or circular as long as the following conditions are satisfied. However, since it is desirable that the capacitance generated between the electrode and the wiring line of the other electrode is uniform, a substantially rectangular shape is suitable for the electrode.

  In FIG. 5, the thickness L1 of the substrate 4, the interval L2 between the wiring lines, and the width L3 of the wiring lines are determined so as to satisfy the following conditions, for example. Of course, the area of the electrode is also determined so as to satisfy the following conditions.

When the user's finger F approaches the electrode, the capacitance generated in the electrode that the user's finger F approaches is generated between the electrode that the user's finger F approaches and the wiring line of another electrode. At least one of the thickness L1 of the substrate 4 and the width L3 of the wiring line is determined so as to be larger than the electrostatic capacitance (floating capacitance).

-When the user's finger F approaches the electrode, the capacitance generated in the electrode that the user's finger F approaches is between the wiring line of the electrode that the user's finger F approaches and the wiring line of another electrode. The thickness L1 of the substrate 4 and the interval L2 between the wiring lines are determined so as to be larger than the electrostatic capacitance (floating capacitance) generated in step (b).

When the user's finger F approaches the electrode, electrostatic capacitance (floating capacitance) generated between the wiring line of the electrode that the user's finger F approaches and the wiring line that passes under the electrode that the user's finger F approaches ) Is larger than the capacitance (floating capacitance) generated between the wiring line of the electrode that the user's finger F approaches and the wiring line that does not pass under the electrode that the user's finger F approaches. 4 is determined (for example, L2 = 2 × L1).

  Another example of the capacitive touch sensor 1 will be described with reference to FIGS. Since this configuration example is a modification of FIGS. 3 and 4, only the differences between FIGS. 3 and 4 will be described. 6 shows a top view of the capacitive touch sensor 1, and FIG. 7 shows a cross-sectional view taken along the line X-X 'of FIG. 6 is the same as that of FIG.

  6 and 7, there is no wiring pattern (12, 22, 32, 42) on the surface of the substrate 4, and the through holes (15, 25, 35, 45) are formed on the electrodes (10, 20, 30, 40). ) On the side far from the switching circuit 5. The position of the through hole may be formed below the periphery (15a in the wiring line 11) on the side closer to the switching circuit 5 (capacitance signal output side), or may be formed at any position of 15 to 15a. . At this time, each wiring line is disposed only between the switching circuit 5 and the through hole.

  8 and 9 show other examples of FIGS. 8 and 9, the wiring lines (11, 21, 31, 41) are covered with a member made of the same material as the substrate 4 or another insulator 4a (FIG. 8), or the wiring lines are formed on the substrate 4. It is what was arrange | positioned inside (FIG. 9).

  8 and 9, the cross-sectional shapes of the wiring lines are rectangular and circular, respectively (polygonal shapes may be used), and either may be used, but the rectangular shape is between adjacent wiring lines. The generated capacitance is stabilized.

  FIG. 10 shows an output voltage (detection level) corresponding to the capacitance generated in each electrode when the user's finger F approaches the electrode 30 in the configurations of FIGS. The detection level of the electrode 30 is based on the capacitance generated between the user's finger F and is V11. The detection levels of the electrodes 10 and 20 are based on the electrostatic capacitance generated between the electrode 30 and the wiring lines 11 and 21, and have substantially the same value (V21). The detection level of the electrode 40 is based on the capacitance generated between the wiring line 31 and the wiring line 41, and is a value (V31) that is sufficiently smaller than V21.

  FIG. 11 shows the detection level of each electrode when the test object approaches in all the electrodes in the configurations of FIGS. In the example of FIGS. 10 and 11, if the threshold value 1 is set between V11 to V21 and the threshold value 2 is set between V21 to V31, the state of the output voltage of each electrode can be grasped, and the user's finger F approaches Can be accurately identified.

  Another example of the capacitive touch sensor 1 will be described with reference to FIGS. Since this configuration example is a modification of FIGS. 6 and 7, only the differences between FIGS. 6 and 7 will be described. FIG. 12 is a top view of the capacitive touch sensor 1, and FIG. 13 is a cross-sectional view taken along the line X-X 'of FIG. 12 is the same as FIG. 5 (or FIG. 8, FIG. 9).

  12 and 13, each wiring line is extended from the respective through holes (25, 35, 45) of the electrodes 20, 30, 40 toward the periphery of the electrode 10 on the side far from the switching circuit 5. The wiring line 11 is also extended to the side far from the switching circuit 5. The extended part (13, 23, 33, 43) of the wiring line may extend beyond the above-mentioned peripheral edge or may extend to the bottom of the electrode 10.

  FIG. 14 shows the output voltage (detection level) of each electrode when the user's finger (not shown) approaches the electrode 30 in the configuration of FIGS. The detection level from the electrode 30 is based on the capacitance generated between the user's finger and is V12. The detection levels from the electrodes 10, 20, 40 are based on the capacitance generated between the electrode 30 and the extended portion 43 of the wiring lines 11, 21, 41, and have substantially the same value (V22). .

  In other words, in this configuration, the output voltages from the electrodes that the user's finger does not approach all have almost the same value, so by setting one threshold value between V12 and V22, the electrode that the user's finger approaches It can be determined accurately. The thickness L1 of the substrate 4, the interval L2 between the wiring lines, and the width L3 of the wiring lines are determined so that V12 and V22 can be distinguished.

  Further, as shown in FIG. 15, in the above-described configuration, the sizes of the electrodes are not necessarily the same. Further, the electrode arrangement may be an arrangement that does not face the adjacent electrode 30 like the electrode 20. Further, as shown in FIG. 16, the electrodes may be formed in an oblique straight line shape or in an arc shape. It is sufficient that the wiring line can be arranged so as to pass through the back surface of the other electrode.

  Although the embodiments of the present invention have been described above, these are merely examples, and the present invention is not limited to these embodiments, and the knowledge of those skilled in the art can be used without departing from the spirit of the claims. Various modifications based on this are possible.

DESCRIPTION OF SYMBOLS 1 Capacitive touch sensor 4 Board | substrate 5 Switching circuit 6 Signal processing circuit 10, 20, 30, 40 Electrode 11, 21, 31, 41 Wire line 12, 22, 32, 42 Wiring pattern (connection part)
13, 23, 33, 43 Extension part of wiring line 15, 25, 35, 45 Through hole (connection part)
16, 26, 36, 46 Output terminal

Claims (5)

A plurality of electrodes arranged in a row on the surface of the plate-like insulator, and generating a capacitance when the test object approaches,
A plurality of wiring lines that are arranged at predetermined intervals on the back surface of the insulator so as to face the electrode across the insulator, and that are output ends for outputting the capacitance generated at one end. ,
A connection portion that connects one of the plurality of electrodes and one of the plurality of wiring lines at a predetermined position of the wiring line;
With
The connecting portion is formed below the periphery of the electrode or at a predetermined distance from the periphery of the electrode,
The electrode is located between the connection portion and the output end ,
The wiring line is formed so as to intersect the peripheral edge of the electrode far from the output end and the peripheral edge close to the output end so as to reach the output end from the connection portion. Capacitive touch sensor.   The capacitive touch sensor according to claim 1, wherein the other end of the wiring line is connected to the connection portion.   The capacitance generated at the electrode approached by the test object is determined by the capacitance generated between the electrode at which the test object approaches and the wiring line connected to the electrode at which the test object does not approach. The capacitive touch sensor according to claim 1, wherein a thickness of the insulator is determined so as to be larger.   The capacitance generated at the electrode approaching the test object is between the wiring line connected to the electrode approaching the test object and the wiring line connected to the electrode not approaching the test object. The capacitive touch sensor according to any one of claims 1 to 3, wherein an interval between wiring lines is determined to be larger than a generated capacitance.   The capacitive touch sensor according to claim 1, wherein the wiring line is covered with the insulator.

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