JP5293577B2 - Touch panel input device, touch panel drive device, touch panel drive method, and system display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent false touch detection due to electric noise in a touch area in a capacitive coupling type touch panel. <P>SOLUTION: A touch panel input device 6 is provided with: a plurality of capacitors C<SB>11</SB>to C<SB>mn</SB>two-dimensionally arranged in a touch area to be touched by a contact body; selection circuits 7 and 8 for sequentially selecting each of the plurality of capacitors; a charging circuit 94 for charging the capacitor selected by the selection circuit; a charging time measurement circuit 95 for measuring a charging time between when charging by the charging circuit is started and when the charging voltage of the capacitor reaches a predetermined upper threshold; a discharging circuit 93 for discharging the capacitor after the charging voltage reaches the predetermined upper threshold; and a discharging time measurement circuit 96 for measuring the discharging time between when discharging by the discharging circuit is started and when the charging voltage reaches a lower threshold which is less than the upper threshold. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a touch panel input device using a capacitive coupling method, a touch panel drive device, a touch panel drive method, and a system display including the touch panel input device.

  In a conventional capacitively coupled touch panel, the presence or absence of a touch is determined by detecting a change in capacitance that occurs in the touch area. Specifically, a plurality of X coordinate electrodes (X1 to X6) are provided on the surface of the substrate of the touch panel. A plurality of Y coordinate electrodes (Y1 to Y8) are provided so as to be orthogonal to the X coordinate electrodes via an insulating film. One end of each X coordinate electrode and each Y coordinate electrode is connected to the capacitance detection circuit (401), and the other end is grounded. When the control circuit (6) turns on one switch (403) and the other switch (404), the current source (402) is connected to either the X coordinate electrode or the Y coordinate electrode. For example, when one X coordinate electrode is connected to a current source, a capacitance (Cs) is generated between the X electrode and the surrounding Y electrode. Then, electric charges are charged in the capacitance, and the voltage of the electrode rises. When the voltage of the electrode reaches a predetermined value, the comparator (406) outputs a signal to the switch and the time required for charging is measured. Then, the switch (404) is turned on and the switch (403) is turned off, and the charge charged in the capacitance is discharged. This series of operations is repeated while sequentially selecting the electrodes to be connected.

  When the touch panel is driven, if the touch area is touched with a finger, an electric charge flows from the electrode to the finger. And it will be in the same state as the new electrostatic capacitance having arisen between the X coordinate electrode and the Y coordinate electrode and the finger. For this reason, more electric charge flows into the electrode passing under the finger than when the touch is not performed. And the charge time until the voltage of an electrode reaches a predetermined value becomes long. The presence or absence of a touch is determined by detecting the longer charging time with the control circuit (7) (see Patent Document 1).

JP 2009-089442 A

By the way, this type of touch panel is easily affected by external electrical noise. Therefore, for example, when the touch panel is stacked on the liquid crystal display device, the charging time detected by the control circuit is different from the actual charging time due to the influence of electrical noise from the liquid crystal display device. There is. Then, although the touch panel is not touched, the touch may be erroneously detected.
Therefore, a problem to be solved by the present invention is to prevent erroneous detection of touch due to electrical noise in a touch area in a capacitively coupled touch panel.

In order to solve the above problems, according to one aspect of the present invention,
A plurality of capacitors two-dimensionally arranged in a touch area touched by a contact body;
A selection circuit for sequentially selecting each of the plurality of capacitors;
A charging circuit for charging the capacitor selected by the selection circuit;
A charging time measuring circuit for measuring a charging time from the start of charging by the charging circuit until the charging voltage of the capacitor reaches a predetermined upper threshold; and
A discharge circuit for discharging the capacitor after the charge voltage reaches the predetermined upper threshold;
There is provided a touch panel input device comprising: a discharge time measurement circuit that measures a discharge time from when discharge by the discharge circuit is started until the charge voltage becomes a lower threshold value that is lower than the upper threshold value. The

Preferably, a control for determining a charge / discharge time ratio including a ratio of the charge time and the discharge time for each of the plurality of capacitors and determining whether the value of the charge / discharge time ratio is included in a predetermined range. Provide a circuit.
Preferably, the control circuit is configured such that a total time of the charging time and the discharging time for any one of the plurality of capacitors is larger than a predetermined reference value, and the charge / discharge time ratio is included in the predetermined range. The detection signal for detecting that the contact body is touched on the capacitor formation region in the touch region is output, and in other cases, the detection signal is not output.
Preferably, at the time of charging by the charging circuit, when the charging voltage reaches the upper threshold, charging by the charging circuit is terminated, timing by the charging time measuring circuit is terminated, and by the discharging circuit When the charging voltage reaches the lower threshold during discharging by the first determination circuit for starting discharging and the discharging circuit, the discharging by the discharging circuit is terminated and the timing by the discharging time measuring circuit is terminated. A second determination circuit.

According to another aspect of the invention,
In a touch panel drive device for driving a touch panel having a touch area touched by a contact body and having a plurality of capacitors two-dimensionally arranged in the touch area,
A selection circuit for sequentially selecting each of the plurality of capacitors;
A charging circuit for charging the capacitor selected by the selection circuit;
A charging time measuring circuit for measuring a charging time from the start of charging by the charging circuit until the charging voltage of the capacitor reaches a predetermined upper threshold; and
A discharge circuit for discharging the capacitor after the charge voltage reaches the predetermined upper threshold;
A touch panel drive device comprising: a discharge time measurement circuit that measures a discharge time from when discharge by the discharge circuit is started until the charge voltage becomes a lower threshold value that is lower than the upper threshold value. Is done.

Preferably, a charge / discharge time ratio including a ratio of the charge time and the discharge time for each of the plurality of capacitors of the touch panel is obtained, and whether or not the value of the charge / discharge time ratio is included in a predetermined range. A control circuit for determining is provided.
Preferably, the control circuit is configured such that a total time of the charging time and the discharging time for any one of the plurality of capacitors of the touch panel is larger than a predetermined reference value, and the charge / discharge time ratio is in the predetermined range. A detection signal for detecting that the contact body is touched on the capacitor formation region of the touch region is output, and in other cases, the detection signal is not output.
Preferably, at the time of charging by the charging circuit, when the charging voltage reaches the upper threshold, charging by the charging circuit is terminated, timing by the charging time measuring circuit is terminated, and by the discharging circuit When the charging voltage reaches the lower threshold during discharging by the first determination circuit for starting discharging and the discharging circuit, the discharging by the discharging circuit is terminated and the timing by the discharging time measuring circuit is terminated. A second determination circuit.

According to another aspect of the invention,
In a touch panel driving method for driving a touch panel having a touch area touched by a contact body and having a plurality of capacitors two-dimensionally arranged in the touch area,
Sequentially selecting each of the plurality of capacitors;
Start charging the selected capacitor,
Measure the charging time from the start of charging the capacitor until the capacitor charging voltage reaches a predetermined upper threshold,
After the charging voltage reaches the predetermined upper threshold, start discharging the capacitor,
There is provided a method for driving a touch panel, characterized by measuring a discharge time from the start of discharging of the capacitor until the charging voltage becomes a lower threshold value lower than the upper threshold value.

Preferably, a charge / discharge time ratio including a ratio of the charge time and the discharge time for any one of the plurality of capacitors of the touch panel is obtained, and a total time of the charge time and the discharge time is a predetermined reference value. If it is larger and the charge / discharge time ratio is included in the predetermined range, it is determined that the contact body is touched on the capacitor formation region of the touch region, and otherwise the contact is performed. Does not determine that the body has been touched.
Preferably, at the time of charging the capacitor, if the charging voltage reaches the upper threshold, the charging of the capacitor is terminated, the timing of the charging time is terminated, and the discharging of the capacitor is started. If the charging voltage reaches the lower threshold during the discharging of the capacitor, the discharging of the capacitor is terminated and the timing of the discharging time is terminated.

According to another aspect of the invention,
A display panel;
A touch panel having a touch area touched by the contact body, having a plurality of capacitors two-dimensionally arranged in the touch area, and provided on the display surface side of the display panel;
A drive device for driving the touch panel,
The drive device
A selection circuit for sequentially selecting each of the plurality of capacitors of the touch panel;
A charging circuit for charging the capacitor selected by the selection circuit;
A charging time measuring circuit for measuring a charging time from the start of charging by the charging circuit until the charging voltage of the capacitor reaches a predetermined upper threshold; and
A discharge circuit for discharging the capacitor after the charge voltage reaches the predetermined upper threshold;
There is provided a system display comprising: a discharge time measuring circuit for measuring a discharge time from when the discharge by the discharge circuit is started until the charge voltage becomes a lower threshold value lower than the upper threshold value. .

Preferably, a charge / discharge time ratio including a ratio of the charge time and the discharge time for each of the plurality of capacitors of the touch panel is obtained, and whether or not the value of the charge / discharge time ratio is included in a predetermined range. A control circuit for determining is provided.
Preferably, the control circuit is configured such that a total time of the charging time and the discharging time for any one of the plurality of capacitors of the touch panel is larger than a predetermined reference value, and the charge / discharge time ratio is in the predetermined range. If included, the detection signal for detecting that the contact body is touched on the capacitor formation region of the touch region is output. In other cases, the detection signal is not output.
Preferably, when the charging voltage reaches the upper threshold during charging by the charging circuit, the driving device ends charging by the charging circuit, ends timing by the charging time measuring circuit, and A first determination circuit for starting discharge by the discharge circuit; and when the charge voltage reaches the lower threshold during the discharge by the discharge circuit, the discharge by the discharge circuit is terminated and the discharge time measurement And a second determination circuit that terminates timing by the circuit.

  According to the present invention, it is possible to prevent erroneous touch detection due to electrical noise in a touch area in a capacitively coupled touch panel.

It is the disassembled perspective view which showed the system display in embodiment of this invention. It is the schematic block diagram which showed the touchscreen input device in the same embodiment. It is the front view which showed the touchscreen input device in the same embodiment. It is IV-IV sectional drawing of FIG. FIG. 3 is a circuit diagram illustrating a first scanning circuit in the same embodiment. FIG. 6 is a circuit diagram showing a second scanning circuit in the same embodiment. It is the circuit diagram which showed the electrostatic capacitance detection circuit in the same embodiment. It is a timing chart of the touch panel input device in the embodiment. It is a timing chart of the touch panel input device in the embodiment. It is the graph which showed the change of the voltage input into the inverting input terminal of the 1st comparator in the embodiment.

  Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

First, the configuration of the system display 1 will be described.
FIG. 1 is an exploded perspective view of an example of a system display 1. As shown in FIG. 1, the system display 1 includes an upper case 2, a lower case 3, a liquid crystal display panel 4, a backlight 5, a touch panel input device 6, and the like. Hereinafter, the configuration in a state where the system display 1 is assembled will be specifically described.

  The lower case 3 is assembled in a nested manner with respect to the upper case 2. A rectangular display window 22 is opened in the top plate 21 of the upper case 2. A rectangular window 32 is opened in the bottom plate 31 of the lower case 3.

  A liquid crystal display panel 4 and a touch panel input device 6 are provided inside the upper case 2 and the lower case 3. The liquid crystal display panel 4 is mounted on the bottom plate 31 of the lower case 3. The liquid crystal display panel 4 is configured as follows.

  The liquid crystal display panel 4 is of an active matrix drive system, for example. In the liquid crystal display panel 4, the upper substrate 42 faces the lower substrate 41. A sealing material is provided in a frame shape along the edge portion of the upper substrate 42, the sealing material is sandwiched between the upper substrate 42 and the lower substrate 41, and the upper substrate 42 and the lower substrate 41 are bonded by the sealing material. ing. Liquid crystal is sealed between the lower substrate 41 and the upper substrate 42 and inside the sealing material. Since the size of the lower substrate 41 is larger than the size of the upper substrate 42, a part of the lower substrate 41 protrudes from the edge of the upper substrate 42. A portion where the lower substrate 41 and the upper substrate 42 overlap is a display area. On the upper surface in the display area of the lower substrate 41, a plurality of scanning lines are provided so as to extend in the horizontal direction in parallel with each other, and a plurality of signal lines extend in the vertical direction in parallel with each other. Is provided. A thin film transistor is formed at each intersection of the scanning line and the signal line. The gate electrode of the thin film transistor is connected to the scanning line, one of the source electrode and the drain electrode of the thin film transistor is connected to the signal line, and the other is connected to the transparent pixel electrode. A plurality of pixel electrodes are arranged in a matrix on the surface of the lower substrate 41. On the other hand, a transparent common electrode is formed on the surface of the upper substrate 42 facing the lower substrate 41. Alignment films are formed on the surfaces of the pixel electrode and the common electrode, respectively. Further, a color filter is formed on the upper substrate 42. A polarizing plate 43 is stuck on the upper substrate 42.

  One end portion of the FPC 44 is joined to the non-display area 41 a that protrudes from the edge of the upper substrate 42 in the lower substrate 41. An IC chip 45 is surface-mounted on the non-display area 41a. The IC chip 45 includes a driver that drives the liquid crystal display panel 4. A plurality of output terminals of the IC chip 45 are connected to scanning lines and signal lines extending from the display area. The plurality of input terminals of the IC chip 45 are connected to a plurality of lead wirings formed on the non-display area 41a, and these lead wirings are formed from one end portion to the other end portion of the FPC 44. Each is connected to the wiring. A terminal formed at the other end of the FPC 44 is inserted into an electronic board (not shown).

  The backlight 5 is disposed on the lower side of the lower case 3 so as to face the lower surface of the liquid crystal display panel 4 through the window 32. Specifically, the backlight 5 faces the lower substrate 41 of the liquid crystal display panel 4. The backlight 5 is a surface light emitting device and emits light toward the liquid crystal display panel 4. The backlight 5 is, for example, an array of point light emitting elements such as LEDs arranged in a matrix, a combination of point light emitting elements such as LEDs arranged and a light guide plate, a linear light emitting element such as a cold cathode tube, and a light guide plate Or a surface light emitting element such as an electroluminescence element. An FPC 51 is connected to the backlight 5. The FPC 51 is connected to an electric board (not shown).

  The touch panel input device 6 includes a touch panel 6a, a flexible circuit sheet (hereinafter referred to as FPC) 65, and an IC chip 66. The IC chip 66 is surface-mounted on the touch panel 6a by a COG (Chip On Glass) method. The FPC 65 is bonded to the touch panel 6a. A touch panel 6 a is accommodated inside the upper case 2 and the lower case 3. The touch panel 6 a is overlaid on the display surface of the liquid crystal display panel 4. That is, the touch panel 6 a has a touch area 61 a and is overlaid on the polarizing plate 43 of the liquid crystal display panel 4. The upper case 2 is put on the touch panel 6a. The touch panel 6a faces the display window 22 of the upper case 2, and the display window 22 is blocked by the touch panel 6a.

  In the above description, the touch panel 6a is attached to the display surface of the liquid crystal display panel 4, but may be attached to the display surface of a display other than the liquid crystal display panel 4. For example, the touch panel 6a may be attached to the display surface of an organic electroluminescence display, a plasma display, an inorganic electroluminescence display, a light emitting diode display, a field emission display, a vacuum fluorescent display, a cathode ray tube, or electronic paper. The display may be a dot matrix display type display or a segment display. The display may be a self-luminous display, a transmissive display, or a reflective display. When the display is a self-luminous or reflective display, the backlight 5 may not be provided.

  Hereinafter, the touch panel input device 6 will be described in detail. 2 is a schematic configuration diagram of the touch panel input device 6, FIG. 3 is a front view of the touch panel input device 6, and FIG. 4 is a sectional view taken along the line IV-IV in FIG.

  The touch panel 6a is of a capacitive coupling type. In the touch panel 6a, the rectangular upper substrate 62 faces the rectangular lower substrate 61 as shown in FIG. The length of the lower substrate 61 in the short direction is equal to the length of the upper substrate 62 in the short direction, and the length of the lower substrate 61 in the longitudinal direction is longer than that of the upper substrate 62. Therefore, in a state where one short side of the lower substrate 61 and one short side of the upper substrate 62 are aligned and overlapped, a part of the lower substrate 61 protrudes from the edge of the upper substrate 62. A portion where the lower substrate 61 and the upper substrate 62 overlap is a touch region 61a.

As shown in FIG. 3, a plurality of Y electrodes Y _{1 to} Y _{n that} are _first electrodes are provided on the upper surface of the touch region 61 a of the lower substrate 61. Specifically, n (n− = 2 or more natural numbers) Y electrodes Y _{1 to} Y _n are formed to be parallel to each other and extend along the short direction of the touch region 61a. Further, the upper surface of the touch area 61a, a plurality of X electrodes _X 1 to X _m is provided as a second electrode. Specifically, m (m− = 2 or more natural number) X electrodes X _{1 to} X _m are provided so as to extend in a direction perpendicular to the Y electrodes Y _{1 to} Y _n .

Each of the Y electrodes Y _{1 to} Y _n has a plurality of electrode patterns Y ₁ a to Y _n a and a plurality of connecting portions Y ₁ b to Y _n b. The electrode patterns _Y 1 to Y _n a and the coupling portion _Y 1 _{b~Y n} b is formed of a transparent conductive material such as indium tin oxide (ITO). Specifically, the electrode patterns Y ₁ to Y n _a having a substantially square shape is formed in a matrix in the touch area 61a a on the lower substrate 61. Between the electrode patterns _{Y 1} a and _Y 1 a to both electrode patterns adjacent in the lateral direction of the touch area 61a _{Y n} a and _{Y n} a, coupling portion _Y 1 _{b~Y n} b is the electrode pattern _Y 1 a to It is formed integrally with Y _na . Then, the electrode pattern _{Y 1} a and _Y 1 a to the electrode pattern _{Y n} a and _{Y n} a is conductive, respectively.

X electrodes _X 1 to X _m has a plurality of electrode patterns _X 1 A to X _m a and a plurality of bridges _X 1 _{b~X m} b. Specifically, electrode patterns X ₁ a to X _m a having a substantially square shape are arranged in a matrix. The electrode patterns _X 1 _{a~X m} a is formed of a transparent conductive material such as ITO similarly to the Y electrodes _Y 1 to Y _n. The electrode patterns _X 1 _{a~X m} a is formed on the same plane and the Y electrode _Y 1 to Y _n. Further, the electrode patterns _X 1 _{a~X m} a, the connecting portions adjacent in the longitudinal direction of the touch area 61a _{Y 1} b and _Y 2 B to connecting portion _{Y (n-1)} b and _{Y n} b respectively between the positioned. A pair of corners X ₁ c of each electrode pattern X ₁ a to X _m a is directed to both short sides of the lower substrate 61. Then, the electrode pattern _{X 1} a and _X 1 a to the electrode pattern _{X m} and _{X m} adjacent in the longitudinal direction of the touch area 61a is spaced so as not to touch the connecting portion _Y 1 _{b~Y n} b, together and facing the corner _{X 1} c and _X 1 _{c~X m} c and _{X m} c. Further, another pair of corner _X 1 _{d~X m} d of each electrode pattern _X 1 _{a~X m} a is oriented in a direction in both long sides of the lower substrate 61, respectively. Then, the electrode patterns X ₁ a and X ₂ a to X _(m−1) a and X _m a that are adjacent to each other in the short direction of the touch area 61 a are slightly spaced from each other at their angles X ₁ d and X _2. d~ angle _{X (m-1)} are facing the d and _{X m} d.

On the Y electrodes _Y 1 to Y _n and the electrode pattern _X 1 A to X _m a is the insulating film 63 as shown in FIG. 4 is deposited on Betaichimen, Y electrodes _Y 1 to Y _n and the electrode pattern X _{1 a to} X _m a are covered with an insulating film 63. Metal bridge _X 1 _{b~X m} b is provided from the upper surface of the insulating film 63 over the electrode pattern _X 1 _{a~X m} a. Specifically, one end of the bridge _X 1 _{b~X m} b formed in a U-shape, as well as through the insulating film 63, the electrode pattern _{X 1} adjacent in the longitudinal direction of the touch area 61a a and _X 1 a We are in contact with - the electrode pattern _{X m} a and _{X m} one at the corner of a _X 1 c~X _m c. The other end of the bridge _X 1 _{b~X m} b makes contact with the adjacent electrode patterns _{X 1} a and _X 1 a to the electrode pattern _{X m} a and _{X m} a while the corners _X 1 _{c~X m} c of ing. Then, the electrode pattern _{X 1} a and _X 1 a to the electrode pattern _{X m} a and _{X m} a is conductive, respectively. The X electrodes _X 1 to X _m are provided in this way.

Each bridge X ₁ b of the X electrode X ₁ crosses over the connecting portions Y ₁ b to Y _n b and intersects with the Y electrodes Y _{1 to} Y _n , respectively. Also, another bridge _X 2 _{b~X m} b, straddle over the connecting portion _Y 1 _{b~Y n} b, intersect respectively and the Y electrode _Y 1 to Y _n. Then, the insulating film 64 so as to cover the bridge _X 1 _{b~X m} b is deposited Betaichimen. An adhesive is applied on the insulating film 64, and the upper substrate 62 is bonded. In this way, the touch panel 6a is configured. In touch area 61a of the touch panel 6a, since a plurality of electrode patterns _X 1 _{a~X m} a and a plurality of electrode patterns _Y 1 to Y _n a is provided adjacent to each other, the capacitive component between the electrodes Is formed. The capacitive component becomes a form which is connected to the respective electrode patterns _Y 1 to Y _n a and the electrode patterns _X 1 _{a~X m} a, when it was used as a capacitor _C 11 _{-C mn,} FIG as an equivalent circuit It becomes the form shown in 2. These capacitors C _{11 to} C _mn are two-dimensionally arranged on the same plane.

Capacitor C _b shown in FIG. 2, of the X electrodes X ₁ to X _m, a capacitance component is formed between the adjacent. Here, when a contact body such as a finger contacts the upper substrate 62, a capacitor C _f is formed between the electrode pattern X _i a and the electrode pattern Y _j a in the vicinity of the contact portion. For example, as shown in FIG. 2, between the contact body comes into contact with the upper substrate 62 in the top of the near intersections between the X electrode X ₂ and the Y electrodes Y _2, an electrode pattern X ₂ a and the electrode pattern Y ₂ a , i.e. the capacitor _{C f} is formed between the X electrode _{X 2} and the Y electrodes _{Y 2.}

  As shown in FIGS. 1 and 3, the FPC 65 is connected to the touch panel 6a. Specifically, one end portion of the FPC 65 is bonded to the non-touch area 61 b that protrudes from the edge of the upper substrate 62 in the lower substrate 61. The FPC 65 extends from the inside of the upper case 2 and the lower case 3 to the outside of the upper case 2 and the lower case 3. Wiring for supplying power to the IC chip 66 and transmitting signals is formed from one end portion of the FPC 65 to the other end portion. A terminal is formed at the tip of the FPC 65.

An IC chip 66 is surface-mounted on the touch panel 6a. Specifically, the IC chip 66 is surface-mounted on the non-touch area 61 b that protrudes from the edge of the upper substrate 62 in the lower substrate 61. The plurality of output terminals of the IC chip 66, X electrodes ₁ to X exiting extending from the touch area 61a _m and Y electrodes _Y 1 to Y _n are connected. The plurality of input terminals of the IC chip 66 are connected to a plurality of routing wirings formed on the non-touch area 61b, and these routing wirings are a plurality of wirings of the FPC 65 bonded on the non-touch area 61b. Are connected to each. The terminals of the FPC 65 are inserted into an electronic board (not shown).

  The IC chip 66 includes a drive device 6b. As shown in FIG. 2, the driving device 6b includes a first scanning circuit 7, a second scanning circuit 8, a capacitance detection circuit 9, a control circuit 10, and the like.

The control circuit 10 operates the first scanning circuit 7, the second scanning circuit 8, and the capacitance detection circuit 9.
First scanning circuit 7 is a selection circuit for sequentially selecting the Y electrodes _Y 1 to Y _n. A selected _{one of the} Y electrodes Y _{1 to} Y _n is grounded (becomes a reference potential), and an unselected one is electrically floated.
The second scanning circuit 8 is a selection circuit that sequentially selects the X electrodes X _{1 to} X _m when the Y electrodes Y _{1 to} Y _n are selected by the first scanning circuit 7.
The electrostatic capacitance detection circuit 9, as selected by the first scanning circuit 7 of the Y electrodes Y ₁ to Y _n, as selected by the second scanning circuit 8 of the X electrodes X ₁ to X _m The capacitance of the capacitor formed between is detected. The capacitance detection circuit 9 outputs a signal representing the detected capacitance.
Control circuit 10 determines the selected ones of the Y electrodes Y ₁ to Y _n, the presence or absence of the intersection touch in the vicinity of the selected ones of the X electrodes X ₁ to X _m. That is, the control circuit 10 determines the presence / absence of a touch based on the signal input from the capacitance detection circuit 9 and outputs a signal representing the determination result. For example, if the signal output from the control circuit 10 is 1 bit, the signal output from the control circuit 10 is “1” when there is a touch, and the control circuit 10 when there is no touch. The signal output from is “0”. Here, when the Y electrode Y ₁ and the X electrode X ₁ are selected by the first scanning circuit 7 and the second scanning circuit 8, the Y electrode Y ₁ is selected by the first scanning circuit 7 and the second scanning circuit 8. Until _n and the X electrode _Xm are selected, the signal output from the control circuit 10 represents the coordinates of the touch position.

As shown in FIG. 5, the first scanning circuit 7 includes a shift register 71, switches SW_Y1 to SW_Yn, and the like.
Y electrodes Y _{1 to} Y _n are connected to a reference potential (ground) via switches SW_Y _{1 to} SW_Yn, respectively. Switch SW_Y1~SW_Yn, respectively, to open and close between the Y electrodes _Y 1 to Y _n and the reference potential (on-off). For example, the switches SW_Y1 to SW_Yn are in a closed state (on state) when a signal input from the shift register 71 is at a high level, and are in an open state (off) when the signal is low.
The shift register 71 has n output terminals. Switches SW_Y1 to SW_Yn are connected to the respective output terminals. The shift register 71 in synchronization with the input of the set signal ST _2, to select a switch SW_Y1～SW_Yn. For example, every time the set signal ST ₂ of a high level is input to the shift register 71, by the output terminal for outputting a high level signal is gradually shifted to sequentially neighboring switch SW_Y1~SW_Yn are sequentially selected .
The shift register 71, until the next set signal ST ₂ is input from the input of the set signal ST _2, and holds the selected state.
Which selected ones of the switches SW_Y1~SW_Yn is selected among the closed state (ON state), Y electrodes _Y 1 to Y _n is the reference potential. Meanwhile, those that are not selected among the switches SW_Y1~SW_Yn is opened (OFF state), those that are not selected among the Y electrodes Y ₁ to Y _n is electrically floating.
Set signal ST ₂ is output by the control circuit 10. Further, the control circuit 10 outputs the clock signal CK ₁ to the shift register 71, and the shift register 71 operates based on the clock signal CK ₁ .

As shown in FIG. 6, the second scanning circuit 8 includes a shift register 83, changeover switches SW_X1 to SW_Xm, and the like.
X electrodes _X 1 to X _m are respectively connected to a reference potential (ground) via a changeover switch SW_X1～SW_Xm. Furthermore, the X electrodes X _{1 to} X _m are connected to the wiring 84 via the changeover switches SW_X 1 to SW_Xm, respectively. Selector switch SW_X1~SW_Xm, respectively, to open and close between the X electrodes _X 1 to X _m and the reference potential. The switching switch SW_X1~SW_Xm, respectively, to open and close between the X electrodes _X 1 to X _m and the wiring 84. Here, the changeover switch SW_X1 causes alternatively conducting the X electrodes _{X 1} and the wiring 84 and the reference potential. The same applies to the changeover switches SW_X2 to SW_Xm.
The shift register 83 has m output terminals. The switches SW_X1 to SW_Xm are connected to the output terminals, respectively. The shift register 83 in synchronization with the input of the set signal ST _3, selects the changeover switch SW_X1～SW_Xm. For example, every time the set signal ST ₃ of a high level is input, by an output terminal a high level signal is output shifts to sequentially next, the changeover switch SW_X1~SW_Xm are sequentially selected.
The shift register 83, until the next set signal ST ₃ from the input of the set signal ST ₃ is input, and holds the selected state.
The selected one of the changeover switches SW_X1 to SW_Xm closes the wiring 84 and opens the reference potential. As a result, a selected _one of the X electrodes X _{1 to} X _m conducts to the wiring 84 and is grounded. On the other hand, an unselected switch among the switches SW_X1 to SW_Xm opens between the wiring 84 and closes with the reference potential. Thereby, the unselected X electrodes X _{1 to} X _m are disconnected from the wiring 84 and grounded.
Set signal ST ₃ is output by the control circuit 10. Further, the control circuit 10 outputs the clock signal CK ₂ to the shift register 83.

As shown in FIG. 7, the capacitance detection circuit 9 includes a first determination circuit 91, a second determination circuit 92, a charging circuit 94, a charging time measuring circuit 95, a discharging circuit 93, a discharging time measuring circuit 96, and the like.
The set signal ST ₁ output from the control circuit 10 is input to the charging circuit 94 and the charging time measuring circuit 95.
When the set signal ST ₁ is input, the charging circuit 94 starts charging via the wiring 84. Specifically, the charging circuit 94 charges a capacitor formed between a selected _one of the Y electrodes Y _{1 to} Y _{n and} a selected one of the X electrodes X _{1 to} X _m .
First judging circuit 91, when the charging by the charging circuit 94, the voltage of the wiring 84 (the voltage of the wiring 84 corresponds to a voltage of a selected one of the X electrodes X ₁ to X _m. The same applies hereinafter.) Is When the upper threshold value V _th H is reached, the reset signal R ₁ is output. Charging circuit 94, the reset signal R ₁ is input, terminates the charging.
Charging time measuring circuit 95 starts counting by the set signal ST ₁ is input, terminates the time counting by the reset signal R ₁ is input. Charging time measuring circuit 95 measures the time from the set signal ST ₁ is inputted to the reset signal R ₁ is input. The charging time measuring circuit 95 outputs a signal representing the measured time to the control circuit 10. The time measured by the charging time measuring circuit 95 is the static capacitance of the capacitor formed between the selected _one of the Y electrodes Y _{1 to} Y _{n and} the selected one of the X electrodes X _{1 to} X _m. It corresponds to the capacitance value.
Discharge circuit 93, the reset signal R ₁ is input as a set signal, begins to discharge through the line 84. Specifically, the discharge circuit 93 discharges a capacitor formed between a selected _one of the Y electrodes Y _{1 to} Y _{n and} a selected one of the X electrodes X _{1 to} X _m .
The second determination circuit 92 outputs the reset signal R ₂ when the voltage of the wiring 84 becomes the lower threshold value V _th L during discharge by the discharge circuit 93. Discharge circuit 93, the reset signal R ₂ is input to end the discharge.
Discharge time measuring circuit 96 starts counting by the reset signal R ₁ is input, terminates the time counting by the reset signal R ₂ is input. Discharge time measuring circuit 96 measures the time from the input of the reset signal R ₁ until the reset signal R ₂ is input. The discharge time measuring circuit 96 outputs a signal representing the measured time to the control circuit 10. Time measured by the discharge time measuring circuit 96, Y electrodes Y ₁ and selected ones of to Y _n, electrostatic capacitor formed between the selected ones of the X electrodes X ₁ to X _m It corresponds to the capacitance value.
The control circuit 10, each time the reset signal _{R 2} is input, and outputs a set signal ST _1.

The charging circuit 94 includes a constant current source 94a, a flip-flop 94b, a switch 94c, and the like.
The constant current source 94a generates a constant current. The constant current source 94a is connected to the capacitor 94d and the wiring 84 through the switch 94c. The switch 94c opens and closes the wiring 84 and the capacitor 94d and the constant current source 94a. The switch 94c is connected to the output terminal of the flip-flop 94b that is the first holding circuit. Flip-flop 94b, when the set signal ST ₁ to the set terminal is input closes the switch 94c, maintaining thereafter the closed state of the switch 94c to the reset signal R ₁ to the reset terminal is input. Flip-flop 94b, when the reset signal R ₁ is input to the reset terminal is opened the switch 94c, remain open switch 94c to thereafter set signal ST ₁ to the set terminal is input. Specifically, the flip-flop 94b outputs a high-level signal to the switch 94c when a high-level signal is input to the set terminal while a low-level signal is input to the reset terminal. As a result, the switch 94c is closed. Thereafter, the flip-flop 94b continues to output a high level signal until a high level signal is input to the reset terminal. Thereby, the closed state of the switch 94c continues. The flip-flop 94b outputs a low-level signal when a high-level signal is input to the reset terminal while a low-level signal is input to the set terminal. This opens the switch 94c. Thereafter, the flip-flop 94b continues to output a high level signal until a high level signal is input to the set terminal. Thereby, the open state of the switch 94c continues.
When the switch 94c is in the closed state (ON state), charges in selected ones of the X electrodes X ₁ to X _m is charged, its voltage increases. That is, the selected ones of the X electrodes X ₁ to X _m, a capacitor formed between the selected ones of the Y electrodes Y ₁ to Y _n are charged.

The capacitor 94d has a larger capacitance C _sum than the capacitors C _{11 to} C _mn . The capacitor 94d is connected between the wiring 84 and the reference potential.

The first determination circuit 91 includes a first comparator 91a and a first inverter 91b. The charging time measuring circuit 95 includes a first AND gate 95a, a first counter 95b, and the like.
The wiring 84 is connected to the inverting input (−) terminal of the first comparator 91a. A voltage source whose voltage value is set to the upper threshold V _th H is connected to the non-inverting input (+) terminal of the first comparator 91a. The first comparator 91a compares the voltage of the wiring 84 with the upper threshold value V _th H. The first comparator 91a outputs the comparison result to the first AND gate 95a. Specifically, in the first comparator 91a, when the voltage of the wiring 84 is lower than the upper threshold V _th H, the output of the first comparator 91a is at a high level, and the voltage of the wiring 84 is equal to or higher than the upper threshold V _th H. In this case, the output of the first comparator 91a is at a low level.
The output of the first comparator 91a is input to the first AND gate 95a. The clock signal CK ₃ output by the control circuit 10, is input to the 1AND gate 95a. The 1AND gate 95a outputs the output and logical multiplication of the clock signal CK ₃ of the first comparator 91a in the first counter 95b. Accordingly, when the output of the first comparator 91a is at a high level, the output of the first AND gate 95a becomes a clock signal.
The control circuit set signal ST ₁ of a high level output by 10 is input to the start terminal and preset terminal of the first counter 95b.
The inverter 91b inverts the output of the first comparator 91a. Signal output is inverted in the first comparator 91a is a reset signal R ₁ through the inverter 91b. Reset signal R ₁ of the high-level low-level signal outputted by the first comparator 91a is inverted by the inverter 91b is input to the stop terminal of the first counter 95b.
First counter 95b, when the set signal ST ₁ is input as the start signal and the preset signal, the preset count value and starts counting of the clock signal input from the first 1AND gate 95a. First counter 95b is a period from the set signal ST ₁ is inputted to the reset signal _{R 1} is input, counts the clock of the output of the 1AND gate 95a. The first counter 95 b stops counting and outputs the count value N ₁ to the control circuit 10 when the high-level reset signal R ₁ is input as a stop signal.

The second determination circuit 92 includes a second comparator 92a and a second inverter 92b. The discharge time measuring circuit 96 includes a second AND gate 96a, a second counter 96b, and the like.
The wiring 84 is connected to the non-inverting input (+) terminal of the second comparator 92a. A voltage source whose voltage value is the lower threshold value V _th L is connected to the inverting input (−) terminal of the second comparator 92a. The lower threshold value V _th L is lower than the upper threshold value V _th H. The second comparator 91a compares the voltage of the wiring 84 with the lower threshold value V _th L. The second comparator 91a outputs the comparison result to the second AND gate 96a. Specifically, when the voltage of the wiring 84 is higher than the lower threshold value V _th L, the output of the second comparator 92a is at a high level, and when the voltage of the non-inverting input terminal is lower than the lower threshold value V _th L, 2 The output of the comparator 92a is at a low level.
The output of the second comparator 92a is input to the second AND gate 96a. The clock signal CK ₃ output by the control circuit 10, is input to the 2AND gate 96a. The 2AND gate 96a outputs the output and logical multiplication of the clock signal CK ₃ of the first comparator 92a to the second counter 96b. Therefore, when the output of the second comparator 92a is at a high level, the output of the second AND gate 95a becomes a clock signal.
The inverter 92b inverts the output of the second comparator 91a. Signal output is inverted in the second comparator 92a is a reset signal R ₂ via the inverter 92b. Low-level signal outputted by the second comparator 92a is reset signal R ₂ of high-level inverted by the inverter 92b, is input to the stop terminal of the second counter 96b. Further, the reset signal R ₁ of the high-level low-level signal outputted by the first comparator 91a is inverted by the inverter 91b is input to the start terminal and preset terminal of the second counter 96b.
The second counter 96b is reset signal R ₁ of a high level is input as the start signal and the preset signal, starts counting the clock input from the 2AND gate 96a. The second counter 96b is between from the input of the reset signal _{R 1} until the reset signal _{R 2} is input, counts the clock of the output of the 2AND gate 96a. Further, when the reset signal R ₂ is input, the second counter 96 b stops counting and outputs the count value N ₂ to the control circuit 10.

The discharge circuit 93 includes a flip-flop 93a, a switch 93b, a resistor 93c, and the like.
A switch 93b and a resistor 93c are connected in series between the wiring 84 and the reference potential. The switch 93b opens and closes between the wiring 84 and the reference potential. The switch 93b is connected to the output terminal of the flip-flop 94b that is the second holding circuit. Flip-flop 93a is reset signal R ₁ is input as a set signal to the set terminal closes the switch 93b, it is maintained then a closed switch 93b until the reset signal R ₂ to the reset terminal is input. Flip-flop 93a is reset signal R ₂ is input to the reset terminal is opened the switch 93b, it is maintained thereafter set terminal of the opened switch 93b until the reset signal R ₂ is input as a set signal. Specifically, the flip-flop 93a outputs a high level signal when a high level signal is input to the set terminal while a low level signal is input to the reset terminal. As a result, the switch 93b is closed. The flip-flop 93a continues to output a high level signal until a new high level signal is input to the reset terminal. As a result, the switch 93b is kept closed. The flip-flop 93a outputs a low-level signal when a high-level signal is input to the reset terminal while a low-level signal is input to the set terminal. Thereby, the switch 93b is opened. The flip-flop 93a continues to output a low level signal until a new high level signal is input to the set terminal. As a result, the switch 93b is kept open.
Here, the reference potential is equal to the lower threshold value V _{th L,} or is set to a slightly lower potential than the lower threshold value V _{th L.}
When the switch 93b is in the closed state (ON state), the charge of a selected one of the X electrodes X ₁ to X _m is discharged, its voltage decreases. That is, the capacitor formed between the selected _{one of} the X electrodes X _{1 to} X _{m and} the selected one of the Y electrodes Y _{1 to} Y _n is discharged.

As shown in FIG. 2, the control circuit 10 includes a relay circuit 10a, a first oscillation circuit 10b, a second oscillation circuit 10c, a third oscillation circuit 10d, and an arithmetic unit 10e.
First oscillation circuit 10b generates a clock signal CK _1. The first oscillation circuit 10 b outputs the clock signal CK ₁ to the shift register 71.
Second oscillation circuit 10c generates a clock signal CK _2. The second oscillation circuit 10 c outputs the clock signal CK ₂ to the shift register 83.
Third oscillator circuit 10d generates a clock signal CK _3. Third oscillator circuit 10d outputs a clock signal CK ₃ to the 1AND gate 95a and the 2AND gate 96a.
FIG. 8 is a timing chart showing input / output of the relay circuit 10a. 8, (a) is an output to the shift register 71, (b) is an output to the shift register 83, (c) is an output to the flip-flop 94b and the first counter 95b, and (d) is an output of the relay circuit 10a. Indicates each input. As shown in FIG. 8, the relay circuit 10 a outputs a set signal ST ₂ to the shift register 71 and outputs a set signal ST ₃ to the shift register 83. Then, the relay circuit 10a outputs a set signal ST ₁ to the flip-flop 94b and the first counter 95b. Then, the relay circuit 10a each time the reset signal _{R 2} is input, and outputs a set signal ST _3, and outputs a set signal ST ₁ at a time later. Further, the relay circuit 10a each time the reset signal _{R 2} is input m (X number of electrode) times, and outputs a set signal ST _2.
The arithmetic device 10e includes a CPU, a RAM, a ROM, and the like, and performs various processes based on a program recorded in the ROM.
Arithmetic unit 10e compares a predetermined reference value stored count value N ₁ input from the first counter 95b in the ROM.
On the other hand, the arithmetic unit 10e calculates the ratio _N 1 / _{N 2} of the count value _{N 1} and the count value _{N 2.} The arithmetic device 10e determines whether or not the ratio N ₁ / N ₂ is within a predetermined range. Specifically, the arithmetic unit 10e compares the predetermined upper reference value and lower reference value stored in the ROM. The predetermined range is determined by the upper reference value and the lower reference value.
The arithmetic device 10e outputs the result of these comparisons. Specifically, the count value N ₁ is greater than a predetermined reference value, and, when the ratio N _{1 /} N ₂ is within a predetermined range, the output is high level computing unit 10e (true: "1") and , That is the detection signal. On the other hand, if the count value N ₁ is less than a predetermined reference value, or, when the ratio N _{1 /} N ₂ is outside of the predetermined range, the output of the arithmetic unit 10e is low (false: "0") becomes .

Although the arithmetic device 10e functions as described above by executing a program, the functions of the arithmetic device 10e as described above may be realized by a logic circuit. Specifically, the arithmetic unit 10e includes a comparison circuit, a division circuit, a determination circuit, an AND circuit, and the like. Comparison circuit compares the count value N ₁ with a predetermined reference value. Division circuit divides the count value _{N 1} and the count value _{N 2.} The determination circuit compares the output (ratio N ₁ / N ₂ ) of the division circuit with a predetermined upper reference value and a lower reference value. The AND circuit outputs a logical product of the output of the comparison circuit and the output of the division circuit.

Next, the operation of the touch panel input device 6 will be described with reference to FIGS. Here, FIG. 9 is a timing chart showing input / output and the like of the capacitance detection circuit 9. FIG. 9 shows a timing chart of a period from when any _{one of} the X electrodes X _{1 to} X _m is selected to when the next one of the X electrodes X _{1 to} X _m is selected.
In the touch panel input device 6, an oscillation circuit 10b, 10c, the 10d, the clock signal CK ₁ to the shift register 71, a clock signal CK ₂ to the shift register 83, a clock signal CK ₃ to the 1AND gate 95a and the 2AND gate 96a Are output respectively. On the other hand, as shown in FIG. 8, the relay circuit 10a is a set signal ST ₂ at a high level to the shift register 71, and outputs each of the high level set signal ST ₃ to the shift register 83. Accordingly, the shift register 71 outputs a high level signal to the switch SW_Y1, and the shift register 83 outputs a high level signal to the changeover switch SW_X1. Thus the switch SW_Y1 is turned ON, Y electrodes _{Y 1} is connected to a reference potential. Further, by switching the switch SW_X1, X electrodes _{X 1} is electrically connected to the wiring 84. On the other hand, the switch SW_Y2~SW_Yn is turned OFF, Y electrodes _Y 2 to Y _n is an electrically floating state. The selector switch SW_X2~SW_Xm, X electrodes _X 2 to X _m is connected to a reference potential. Thereafter, the shift register 71, until entering the next set signal ST _2, to hold the switch SW_Y1 the ON state. Shift register 83, until entering the next set signal ST _3, holds the state of the changeover switch SW_X1.

Subsequently, as shown in FIG. 9, the control circuit 10 outputs a set signal ST ₁ at a high level to the stop pin, the preset terminal of the set terminal and a first counter 95b of the flip-flop 94b. Then, the first counter 95b is preset and starts counting. On the other hand, the output of the flip-flop 94b becomes high level, and the switch 94c is switched ON. Then, X electrodes _{X 1} and the capacitor 94d is connected to the constant current source 94a. Thereby, the capacitor 94d is charged. The charge to the X electrodes _{X 1} is charged, the capacitor _{C 11} formed between the X electrodes _{X 1} and Y electrodes _{Y 1} is charged. The capacitor C _b formed between the X electrode X ₂ adjacent thereto and the X electrodes X ₁ is charged. Furthermore, if the contact is the contact body near the intersection between the X electrodes X ₁ and Y electrodes Y _1, capacitor C _f is charged. When the capacitor 94d and the capacitors C ₁₁ , C _b , and C _f are charged, the voltage of the X electrode X ₁ and the wiring 84 increases.

Here, since the capacitances of the capacitors C ₁₁ , C _b , and C _f are small, there is a risk that the voltage rising speed of the X electrode X ₁ and the wiring 84 is increased. However, the capacitor _{C 11,} C b, since large capacitors 94d of capacity than _{C f} is connected in parallel to the capacitor _{C 11, C b, C f} , suppress the rate of rise of the voltage of the X electrode _{X 1} and the wiring 84 be able to.
Further, when the capacitor C _f is formed and when the capacitor C _f is not formed, the rising speed of the voltage of the X electrode X ₁ and the wiring 84 is different.

While the voltage of the X electrode _{X 1} is raised, since the voltage of the X electrode _{X 1} and the wiring 84 is less than the upper threshold value _{V th} H, the output of the first comparator 91a is at a high level. At this time, the control circuit 10 is outputting a clock signal CK ₃ to the 1AND gate 95a. Therefore, the output of the 1AND gate 95a is a clock synchronized with the clock signal CK _3. The first counter 95b counts the clock input from the first AND gate 95a. Incidentally, while the voltage of the X electrodes X ₁ is rising, the output of the second comparator 92a is at a high level.

Thereafter, when the voltage of the X electrode _{X 1} and the wiring 84 reaches the upper threshold value _{V th} H, the output of the first comparator 91a becomes the low level. Therefore, the output of the first AND gate 95a becomes a low level, and the clock composed of the output of the first AND gate 95a is stopped.

On the other hand, the reset signal _{R 1} of the high-level low-level signal output from the first comparator 91a is inverted by the first inverter 91b is first counter 95b, the second counter 96b and a flip-flop 93a, the input to the 94b Is done. First counter 95b, by the reset signal R ₁ is input to the stop terminal, to stop the counting. The first counter 95b outputs a count value N ₁ counted during a period from the set signal ST ₁ is inputted to the reset signal R ₁ of a high level is input to the arithmetic unit 10e of the control circuit 10. The count value N ₁ represents the time from when the set signal ST ₁ is input until the voltage of the X electrode X ₁ and the wiring 84 reaches the upper threshold V _th H.
Further, by the reset signal R ₁ of a high level is input to the reset terminal of the flip-flop 94b, the output of the flip-flop 94b becomes low level, the switch 94c is switched to OFF. Therefore, a state where the wiring 84, X electrodes _{X 1} and the capacitor 94d is blocked from the constant current source 94a is held.

Further, when the reset signal R ₁ of a high level is input to the start terminal preset terminal of the second counter 96b, together with the first counter 96b is preset, it begins counting.
On the other hand, when the reset signal R ₁ of a high level is input to the set terminal of the flip-flop 93a as a set signal, the output of the flip-flop 93a goes high, the switch 93b is switched to ON. Then, X electrodes _{X 1} and the capacitor 94d is connected to the reference potential. Thus, the charge stored in the X electrodes _{X 1} is discharged, the capacitor 94d and a capacitor _C 11, _{C b} is discharged. Furthermore, if the contact body near the intersection between the X electrodes X ₁ and Y electrodes Y ₁ are in contact, the capacitor C _f is discharged. Accordingly, the voltage of the X electrode _{X 1} and the wiring 84 is reduced. And if the capacitor C _f is formed, in the case where the capacitor C _f is not formed, the rate of decrease in the voltage of the X electrode X ₁ and the wiring 84 are different.
When the voltage of the X electrode _{X 1} and the wiring 84 is below the upper threshold value _{V th} H, the output becomes high level again in the first comparator 91a.

While the voltage of the X electrodes _{X 1} is lowered, since the voltage of the X electrode _{X 1} and the wiring 84 is below the threshold value _{V th} L or more, the output of the second comparator 92a is at a high level. At this time, the control circuit 10 outputs a clock signal CK ₃ to the 2AND gate 96a. Therefore, the output of the 2AND gate 96a is a clock synchronized with the clock signal CK _3. The second counter 96b counts the clock output from the second AND gate. Incidentally, while the voltage of the X electrode X ₁ and the wiring 84 is decreased, the output of the first comparator 91a is a high level.

Thereafter, when the voltage of the X electrodes _{X 1} is reduced to below the threshold _{V th} L, the output of the second comparator 92a becomes the low level. Therefore, the output of the second AND gate 96a becomes a low level, and the clock of the output of the second AND gate 96a is stopped.

On the other hand, a low-level signal output from the second comparator 92a is reset signal R ₂ of high level which is inverted, is input to the second counter 96b, a second flip-flop 93a and relay circuit 10a by the second inverter 92b . When the reset signal R ₂ of a high level is input to the stop terminal of the second counter 96b, the second counter 96b stops counting. Furthermore, the second counter 96b is counted value N ₂ the calculation unit counted during a period from the reset signal R ₁ of the high level from the first inverter 91b is input to the reset signal R ₂ of a high level is input To 10e. The count value N ₂ represents the time from when the reset signal R ₁ is input until the voltage of the X electrode X ₁ and the wiring 84 reaches the lower threshold value V _th L.
Further, when the reset signal R ₂ of a high level is input to the reset terminal of the flip-flop 93a, the output of the flip-flop 93a goes low, switch 93b is switched to OFF. Therefore, a state where the wiring 84, X electrodes X ₁ and the capacitor 94d is cut off from the reference potential is held.

When the reset signal R ₂ is input to the relay circuit 10a of the control circuit 10 outputs a set signal ST ₃ at a high level to the shift register 83 relay circuit 10a again, the set of high level to the set terminal of the flip-flop 94b and outputs a signal ST _1. Thus, the changeover switch SW_X2 and the X electrode _{X 2} is selected, the X electrode _{X 2} is connected to the wiring 84, the switch 94c is opened again. Thus, even with respect to the X electrodes X _2, as in the case of X electrodes X _1, charging and discharging are performed.

Accordingly, as shown in FIG. 8, each time the reset signal _{R 2} is input to the relay circuit 10a of the control circuit 10, the X electrode _X 2 to X _m are sequentially selected, the charging-related X electrodes _X 2 to X _m Discharging is performed sequentially. Then, the relay circuit 10a, the reset signal _{R 2} to each input of m times, and outputs a set signal ST ₂ at a high level to the shift register 71 again. Therefore, it switches SW_Y2~SW_Yn and Y electrodes _Y 2 to Y _n are sequentially selected. The selection of the switches SW_Yn and Y electrodes _{Y n} are made, the changeover switch SW_X1~SW_Xm and X electrodes _X 1 to X _m are sequentially selected, it ends the discharge in the X electrode _{X m,} relay circuit 10a reset signal R ₂ is input. Then, the relay circuit 10a is a set signal ST ₂ at a high level to the shift register 71, and outputs each of the high level set signal ST ₃ to the shift register 83. Therefore, the switch SW_Y1 and Y electrodes _{Y 1} is selected, the changeover switch SW_X1 and X electrodes _{X 1} is selected. Thus, a series of operations are repeated.

Arithmetic unit 10e of the control circuit 10, each time the reset signal R ₂ is input, the following processing is performed. That is, the arithmetic unit 10e compares the count value N ₁ input from the first counter 95b with a predetermined reference value. On the other hand, the arithmetic unit 10e is the ratio _N 1 / _{N 2} of the count value _{N 1} and the count value _{N 2} was calculated, the ratio _N 1 / _{N 2} is determined whether or not within a predetermined range. Then, the arithmetic device 10e outputs these comparison results. Specifically, the count value N ₁ is greater than a predetermined reference value, and, when the ratio N _{1 /} N ₂ is within a predetermined range, the output of the arithmetic unit 10e becomes a high level. On the other hand, if the count value N ₁ is less than a predetermined reference value, or, when the ratio N _{1 /} N ₂ is outside of the predetermined range, the output of the arithmetic unit 10e becomes a low level.

As described above, in the present embodiment, not only the count value N ₁ indicating the charging time but also the count value N ₂ indicating the discharging time is measured, so that it is possible to prevent erroneous detection of the touch of the contact body. This will be specifically described below.
FIG. 10 is a graph showing the relationship between the voltage V input to the inverting input terminal of the first comparator 91a and the elapsed time t. FIG. 10A shows a case where the touch panel 6a is not touched with a finger or the like, and FIG. This shows a case where 6a is touched with a finger. Voltage input to the inverting input terminal of the first comparator 91a indicates one of the voltage of the X electrode X ₁ to X _m, which is connected at that time. When the charging time (count value N ₁ ) of each of the capacitors C _{11 to} C _mn when the finger or the like is not touched on the touch panel 6a is t _c and the discharge time (count value N ₂ ) is t _d , the capacitor C The time from the start of charging at one of _{11 to} C _{mn to} the end of discharging (period T) is t _c + t _d , and the ratio of charging time to discharging time (charge / discharge time ratio) is t _c / t _d Become.

When touched with a finger or the like (in the vicinity of the capacitor C ₂₂ in this case) some point on the upper substrate 62 of the touch panel 6a, the X electrode X ₂ passing under the finger or the like is connected to the constant current source 94a, X electrodes through the upper substrate 62 from the X ₂ charge of minute flows into the finger. Then, X electrode _{X 2} and the finger, a capacitor _{C f} between the Y electrode _{Y 2} and the finger or the like occurs. As a result, the capacitance of the X electrode _{X 2} is increased. If the capacity has increased α times, the charging time (count value N ₁ ) of each of the capacitors C _{11 to} C _mn when the finger or the like is touched on the touch panel 6a is αt _c . The discharge time (count value N ₂ ) also increases α times to αt _d . The time (cycle T) from the start of charging with one of the capacitors C _{11 to} C _{mn to} the end of discharging is α (t _c + t _d ). On the other hand, the ratio between the charging time and the discharging time is αt _c / αt _d = t _c / t _d , and the value does not change when the touch panel 6 a is touched with a finger or the like.

By the way, in this touch panel input device 6, static electricity is charged in the touch area 61 a and electrical noise may be generated, or electrical noise from the liquid crystal display panel 4 may enter. Then, the electrical noise, touch panel 6a to may change the value of the count value N ₁ even without the touch with a finger or the like. For example, the potential of the X electrode that is in conduction with the constant current source 94a increases (or decreases), and the time from when charging starts until the upper threshold value V _th H is reached may be shortened (or increased). On the other hand, when discharging, since electrical noise flows to the power source side of the reference potential, the amount of charge discharged from the capacitors C _{11 to} C _mn is the same as when no electrical noise is generated. Therefore, the ratio N ₁ / N ₂ is different depending on whether or not electrical noise is generated.

According to the present embodiment, not only the count value N ₁ indicating the charging time but also the count value N ₂ indicating the discharge time can be measured. Since the ratio of the count value N ₁ and the count value N ₂ when the electrical noise is not generated becomes constant value, even an increase in the charging time by checking the ratio by those or electrical noise due to the touch Can be determined. Therefore, there is an effect that erroneous detection of touch can be prevented.
Further, by providing the control circuit 10, the effect is also Kanade that can be easily compared with the operation and the predetermined value of the ratio N _{1 /} N _2.

In the above-described embodiment, scanning is performed by the second scanning circuit 8, but such scanning may not be performed. Specifically, the electrostatic capacitance detection circuit 9 is provided for each X electrode _X 1 to X _m, between the X electrodes _X 1 to X _m is the switch 94c and the switch 93b of each of the electrostatic capacitance detection circuit 9 Each may be connected. In this case, after the relay circuit 10a of the control circuit 10 outputs a set signal ST ₃ to the first scanning circuit 7, one of the Y electrodes Y ₁ to Y _n is selected by the first scanning circuit 7, the relay circuit 10a outputs a set signal ST ₁ to all of the electrostatic capacitance detection circuit 9. The relay circuit 10 a outputs the set signal ST ₃ to the first scanning circuit 7 every time the reset signal R ₂ is input from all the capacitance detection circuits 9. By doing so, scanning is performed by the first scanning circuit 7.

1 system display 6 touch panel input device 6a touch panel _{Y 1} -Y _n Y electrodes (first electrode)
X ₁ -X _m X electrode (second electrode)
6b Driving device 7 First scanning circuit (selection circuit)
8 Second scanning circuit (selection circuit)
9 electrostatic capacitance detection circuit 91 first determination circuit 91a first comparator 92 second determination circuit 92a second comparator 93 discharge circuit 93a flip-flop (second holding circuit)
94 charging circuit 94a constant current source 94b flip-flop (first holding circuit)
95 charging time measuring circuit 95b first counter 96 discharging time measuring circuit 96b second counter 10 control circuit

Claims (15)

A plurality of capacitors two-dimensionally arranged in a touch area touched by a contact body;
A selection circuit for sequentially selecting each of the plurality of capacitors;
A charging circuit for charging the capacitor selected by the selection circuit;
A charging time measuring circuit for measuring a charging time from the start of charging by the charging circuit until the charging voltage of the capacitor reaches a predetermined upper threshold; and
A discharge circuit for discharging the capacitor after the charge voltage reaches the predetermined upper threshold;
A touch panel input device comprising: a discharge time measurement circuit that measures a discharge time from when discharge by the discharge circuit is started until the charge voltage becomes a lower threshold value that is lower than the upper threshold value.   A control circuit is provided for determining a charge / discharge time ratio including a ratio of the charge time and the discharge time for each of the plurality of capacitors and determining whether the value of the charge / discharge time ratio is included in a predetermined range. The touch panel input device according to claim 1.   The control circuit, when the total time of the charging time and the discharging time for any one of the plurality of capacitors is larger than a predetermined reference value, and the charge / discharge time ratio is included in the predetermined range. The detection signal for detecting that the contact body is touched on the capacitor formation region of the touch region is output, and otherwise the detection signal is not output. The touch panel input device described. When the charging voltage reaches the upper threshold during charging by the charging circuit, charging by the charging circuit is terminated, timing by the charging time measuring circuit is terminated, and discharging by the discharging circuit is started. A first determination circuit for causing
A second determination circuit that terminates the discharge by the discharge circuit and the timing by the discharge time measurement circuit when the charge voltage reaches the lower threshold during the discharge by the discharge circuit. The touch panel input device according to claim 1, wherein the touch panel input device is a touch panel input device. In a touch panel drive device for driving a touch panel having a touch area touched by a contact body and having a plurality of capacitors two-dimensionally arranged in the touch area,
A selection circuit for sequentially selecting each of the plurality of capacitors;
A charging circuit for charging the capacitor selected by the selection circuit;
A charging time measuring circuit for measuring a charging time from the start of charging by the charging circuit until the charging voltage of the capacitor reaches a predetermined upper threshold; and
A discharge circuit for discharging the capacitor after the charge voltage reaches the predetermined upper threshold;
A touch panel drive device comprising: a discharge time measurement circuit that measures a discharge time from when discharge by the discharge circuit is started until the charge voltage becomes a lower threshold value lower than the upper threshold value.   Control which calculates | requires the charge / discharge time ratio which consists of ratio of the said charge time with respect to each of the said several capacitor of the said touch panel, and the said discharge time, and the value of the said charge / discharge time ratio is contained in a predetermined range The touch panel drive device according to claim 5, further comprising a circuit.   In the control circuit, a total time of the charging time and the discharging time for any one of the plurality of capacitors of the touch panel is larger than a predetermined reference value, and the charge / discharge time ratio is included in the predetermined range. The detection signal for detecting that the contact body is touched on the capacitor formation region of the touch region is output, and in other cases, the detection signal is not output. Item 7. The touch panel drive device according to Item 6. When the charging voltage reaches the upper threshold during charging by the charging circuit, charging by the charging circuit is terminated, timing by the charging time measuring circuit is terminated, and discharging by the discharging circuit is started. A first determination circuit for causing
A second determination circuit that terminates the discharge by the discharge circuit and the timing by the discharge time measurement circuit when the charge voltage reaches the lower threshold during the discharge by the discharge circuit. The touch panel drive device according to claim 5, wherein the touch panel drive device is a touch panel. In a touch panel driving method for driving a touch panel having a touch area touched by a contact body and having a plurality of capacitors two-dimensionally arranged in the touch area,
Sequentially selecting each of the plurality of capacitors;
Start charging the selected capacitor,
Measure the charging time from the start of charging the capacitor until the capacitor charging voltage reaches a predetermined upper threshold,
After the charging voltage reaches the predetermined upper threshold, start discharging the capacitor,
A method for driving a touch panel, comprising: measuring a discharge time from the start of discharging of the capacitor until the charge voltage reaches a lower threshold value lower than the upper threshold value. Obtaining a charge / discharge time ratio consisting of a ratio of the charge time and the discharge time for any one of the plurality of capacitors of the touch panel;
When the total time of the charging time and the discharging time is larger than a predetermined reference value and the charging / discharging time ratio is included in the predetermined range, the contact body is formed on the capacitor formation region of the touch region. The touch panel driving method according to claim 9, wherein the touch panel is determined to be touched, and otherwise the touch body is not determined to be touched. During charging of the capacitor, if the charging voltage reaches the upper threshold, the charging of the capacitor is terminated, the timing of the charging time is terminated, and discharging of the capacitor is started,
The discharge time of the capacitor and the time measurement of the discharge time are ended when the charge voltage reaches the lower threshold during the discharge of the capacitor. Touch panel drive method. A display panel;
A touch panel having a touch area touched by the contact body, having a plurality of capacitors two-dimensionally arranged in the touch area, and provided on the display surface side of the display panel;
A drive device for driving the touch panel,
The drive device
A selection circuit for sequentially selecting each of the plurality of capacitors of the touch panel;
A charging circuit for charging the capacitor selected by the selection circuit;
A charging time measuring circuit for measuring a charging time from the start of charging by the charging circuit until the charging voltage of the capacitor reaches a predetermined upper threshold; and
A discharge circuit for discharging the capacitor after the charge voltage reaches the predetermined upper threshold;
A system display, comprising: a discharge time measurement circuit that measures a discharge time from when discharge by the discharge circuit is started until the charge voltage becomes a lower threshold value lower than the upper threshold value.   Control which calculates | requires the charge / discharge time ratio which consists of ratio of the said charge time with respect to each of the said several capacitor of the said touch panel, and the said discharge time, and the value of the said charge / discharge time ratio is contained in a predetermined range The system display of claim 12, comprising a circuit.   In the control circuit, a total time of the charging time and the discharging time for any one of the plurality of capacitors of the touch panel is larger than a predetermined reference value, and the charge / discharge time ratio is included in the predetermined range. The detection signal for detecting that the contact body is touched on the capacitor formation region of the touch region is output, and in other cases, the detection signal is not output. Item 14. The system display according to Item 13. The drive device
When the charging voltage reaches the upper threshold during charging by the charging circuit, charging by the charging circuit is terminated, timing by the charging time measuring circuit is terminated, and discharging by the discharging circuit is started. A first determination circuit for causing
A second determination circuit that terminates the discharge by the discharge circuit and terminates the time measurement by the discharge time measurement circuit when the charge voltage reaches the lower threshold during the discharge by the discharge circuit. 15. A system display according to any one of claims 12 to 14, characterized by:

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