JP5354546B2 - Sensing device and electronic device - Google Patents

Description

  The present invention relates to a technique for detecting whether or not an indicator (such as a finger or a pen) is in contact with a screen and a contact position of the indicator with respect to a screen.

  For example, in Patent Document 1, an ITO film for shielding is provided between the touch panel and the organic EL display unit, or the ITO film is grounded so that the touch panel does not malfunction due to noise from the organic EL display device. And improving the shielding effect.

JP 2003-99193 A

However, even if an ITO film for shielding is provided or the ITO film is grounded, noise from the display device cannot be completely blocked.
The present invention has been made in view of the above-described problems, can reduce the influence of noise from the display device, and can detect the presence or absence of contact of the indicator and the contact position of the indicator with higher accuracy. It is an object to provide a sensing device and an electronic device using the sensing device.

  In order to solve the above problems, a sensing device according to a first aspect of the present invention includes a touch panel having a first electrode for detecting contact of an indicator, and the touch panel and a screen of a display device between the touch panel and the display device. Using a second electrode provided so as to cover all or part of the screen, a measurement unit for measuring the capacitance value of the first electrode and the capacitance value of the second electrode, and the capacitance value of the second electrode A correction unit that corrects the capacitance value of the first electrode, and a detection unit that detects presence or absence of contact of the indicator based on the capacitance value corrected by the correction unit.

  According to this configuration, the second electrode functions as a shield for preventing noise propagating from the display device to the touch panel, and also functions as an electrode for measuring noise from the display device. The correction unit corrects the capacitance value of the first electrode using the capacitance value of the second electrode. Therefore, the noise from the display device that cannot be prevented by the second electrode (shield) is removed by correcting the capacitance value of the first electrode in the correction unit. That is, since the contact detection of the indicator is performed based on the capacitance value of the first electrode from which the influence of noise from the display device is removed by the shielding effect of the second electrode and the correction in the correction unit, it is more accurate than the conventional case The presence or absence of contact of the indicator can be detected.

Further, in the sensing device according to the first aspect described above, the correction unit specifies and specifies a capacitance value induced in the first electrode by noise from the display device from a capacitance value of the second electrode. The capacitance value may be subtracted from the capacitance value of the first electrode.
That is, the capacitance value induced in the first electrode by noise that could not be prevented by the second electrode (shield) is specified from the capacitance value of the second electrode measured by the measurement unit, and the specified capacitance value is determined by the measurement unit. The structure which subtracts from the measured capacitance value of the 1st electrode may be sufficient.

The sensing device according to the first aspect described above further includes a storage unit that stores the capacitance value of the second electrode measured by the measurement unit, and the correction unit is stored in the storage unit. The average value of a plurality of capacitance values may be calculated, and the capacitance value of the first electrode may be corrected using the average value.
According to this configuration, the capacitance value of the first electrode can be corrected using the average value of the capacitance values (plurality) of the second electrode stored in the storage unit.

In the sensing device described above, the correction unit calculates an average value of a maximum value and a minimum value among a plurality of capacitance values stored in the storage unit, and uses the average value to calculate the first value. The configuration may be such that the capacitance value of the electrode is corrected.
According to this configuration, the capacitance value of the first electrode can be corrected using the average value of the maximum value and the minimum value among the capacitance values (plurality) of the second electrode stored in the storage unit.

  Moreover, the sensing device according to the second aspect of the present invention provides a touch panel having a plurality of first electrodes for detecting contact of an indicator, and all or one of the screens between the touch panel and the screen of the display device. A second electrode provided so as to cover the portion, a measuring unit that measures the capacitance value of each of the plurality of first electrodes and the capacitance value of the second electrode, and the capacitance value of the second electrode A correction unit that corrects the capacitance value of each of the plurality of first electrodes, and detection that detects the presence or absence of contact of the indicator or the contact position of the indicator based on each capacitance value corrected by the correction unit And a section.

  Even in this configuration, the noise that cannot be prevented by the second electrode (shield) in the noise from the display device is removed by correcting the capacitance value of each first electrode in the correction unit. Therefore, based on the shielding effect of the second electrode and the capacitance value of each first electrode from which the influence of noise from the display device has been eliminated by correction in the correction unit, contact detection of the pointer and contact position of the pointer are detected. be able to. Therefore, it is possible to detect the presence or absence of contact with the indicator and the contact position of the indicator with higher accuracy than in the past.

  In the sensing device according to the second aspect as well, the correction unit specifies the capacitance value induced in each of the plurality of first electrodes by the noise from the display device from the capacitance value of the second electrode. The specified capacitance value may be subtracted from the capacitance value of each of the plurality of first electrodes. The sensing device according to the second aspect further includes a storage unit that stores a capacitance value of the second electrode measured by the measurement unit, and the correction unit includes a plurality of storage units stored in the storage unit. The average value of the capacitance value may be calculated, and the capacitance value of each of the plurality of first electrodes may be corrected using the average value. In addition, the correction unit calculates an average value of the maximum value and the minimum value among the plurality of capacitance values stored in the storage unit, and uses the average value for each of the plurality of first electrodes. It may be configured to correct the capacitance value.

Further, in the sensing device according to the first or second aspect described above, the second electrode is connected to the measurement unit in a measurement period in which the capacitance value of the second electrode is measured, and in the period other than the measurement period, The structure which further has the switching part which earth | grounds a 2nd electrode may be sufficient.
According to this configuration, since the second electrode is grounded in a period other than the measurement period, the shielding effect of the second electrode can be enhanced.

Further, in the sensing device according to the first or second aspect described above, the second electrode is connected to the measurement unit in a measurement period in which the capacitance value of the second electrode is measured, and in the period other than the measurement period, The structure further provided with the switching part which connects a 2nd electrode to AC power supply may be sufficient.
Also in this configuration, the shielding effect of the second electrode can be enhanced in a period other than the measurement period.

  Moreover, the structure currently formed in the surface at the side of the said display apparatus among the said touch panels may be sufficient as the said 2nd electrode in the sensing apparatus which concerns on the 1st or 2nd aspect mentioned above. In the sensing device according to the first or second aspect described above, the first electrode and the second electrode may be formed of a light-transmitting conductive material.

  An electronic apparatus according to the present invention includes any one of the sensing devices described above. Examples of the electronic device include a personal computer, a mobile phone, and an information portable terminal.

4 is an exploded perspective view showing a configuration of a liquid crystal device D. FIG. 4 is a cross-sectional view showing a structure of a liquid crystal device D. FIG. 4 is a plan view showing the shape and arrangement of an X direction electrode 40 and a Y direction electrode 50. FIG. 4 is a block diagram showing an electrical configuration of a liquid crystal device D. FIG. 4 is a flowchart showing the operation of the touch detection unit 100. FIG. 11 is a block diagram showing an electrical configuration of a liquid crystal device D ′ according to Modification Example 1. It is a figure which shows the data structure of the correction table 112 which concerns on the modification 2. It is a perspective view which shows the specific example (personal computer) of an electronic device. It is a perspective view which shows the specific example (cellular phone) of an electronic device. It is a perspective view which shows the specific example (portable information terminal) of an electronic device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the scale of each layer and each member is appropriately different from the actual one.
<1. Embodiment>
FIG. 1 is an exploded perspective view showing a configuration of a liquid crystal device D equipped with a sensing device according to the present invention. The liquid crystal device D is a liquid crystal display device having a capacitive touch panel, and has a function of displaying an image by an optical action of the liquid crystal and a contact of an indicator (finger or pen) to the screen of the liquid crystal device D. It has a function of detecting presence / absence and its contact position according to a change in capacitance. As shown in the figure, the liquid crystal device D includes a touch panel 10, a noise electrode 20, and a liquid crystal panel 30. The liquid crystal panel 30 has a structure in which liquid crystal is sealed between two substrates facing each other. The two substrates are formed of a light-transmitting material such as glass, quartz, or plastic. For example, a thin film transistor as a switching element, a plurality of scanning lines, data lines, pixel electrodes, and the like are formed on the opposing surface of the substrate located on the lower side in the drawing of the two substrates, and the other substrate is opposed to the other substrate. A counter electrode or the like is formed on the surface. Further, the noise electrode 20 and the touch panel 10 are laminated so as to cover at least the entire display area (screen) on which an image is displayed on the upper surface (observation side) of the liquid crystal panel 30. In FIG. 1, illustration of a polarizing plate and a backlight is omitted.

  FIG. 2 is a cross-sectional view showing the structure of the liquid crystal device D. On the upper surface of the liquid crystal panel 30, a touch panel 10 having a noise electrode 20 formed on the back surface is laminated via an air gap (or adhesive layer). Note that the back surface of the touch panel 10 is the surface of the touch panel 10 opposite to the observation side. The noise electrode 20 is formed of a transparent conductive material such as ITO (indium tin oxide), ZnO (zinc oxide), or IZO (indium zinc oxide). The noise electrode 20 functions as a shield for preventing noise propagating from the liquid crystal panel 30 to the touch panel 10 and also functions as an electrode for measuring noise from the liquid crystal panel 30.

  The touch panel 10 includes a transparent substrate 12 made of a light transmissive material such as glass. An electrode layer 14 is formed on the upper surface of the transparent substrate 12. The electrode layer 14 includes a plurality of touch detection electrodes (hereinafter referred to as “detection electrodes”). The plurality of detection electrodes are formed of a transparent conductive material such as ITO, ZnO, or IZO. Although details will be described later, a plurality of X-direction electrodes and a plurality of Y-direction electrodes are formed on the electrode layer 14 as detection electrodes. A protective layer 18 is bonded to the upper surface of the electrode layer 14 by an adhesive layer 16. The protective layer 18 protects the electrode layer 14 and is formed of, for example, a transparent curable resin such as an epoxy resin or glass. The adhesive layer 16 is made of, for example, an epoxy-based transparent adhesive.

  FIG. 3 is a plan view showing the shape and arrangement of the X direction electrode 40 and the Y direction electrode 50. FIG. 3 is a plan view of the electrode layer 14 as viewed from above (observation side) in FIG. As shown in the figure, one X direction electrode 40 includes a rhombus electrode 42 having a rhombus shape in plan view, and a connection wiring 44 penetrating a plurality of the rhombus electrodes 42 in the horizontal direction (X direction) in the figure. The plurality of rhombus electrodes 42 and the connection wiring 44 are electrically connected to each other and are manufactured as the same conductive film. Further, X-direction electrodes 40 are repeatedly arranged on the surface of the transparent substrate 12 in the vertical direction (Y direction) in the figure. Thus, the X direction electrode 40 is a long conductive film arranged in parallel in the Y direction, and is used to detect the position of the indicator in the Y direction.

  On the other hand, one Y-direction electrode 50 includes a plurality of rhombus electrodes 52 and connection wirings 54 penetrating them in the vertical direction (Y direction) in the drawing. Similarly to the X-direction electrode 40, the Y-direction electrode 50 is also manufactured as the same conductive film by electrically connecting the plurality of rhombus electrodes 52 and the connection wiring 54 to each other. Further, Y-direction electrodes 50 are repeatedly arranged in the vertical direction (X direction) in the figure on the surface of the transparent substrate 12. Thus, the Y-direction electrode 50 is a long conductive film arranged in parallel in the X direction, and is used for detecting the position of the indicator in the X direction. In the present embodiment, it is assumed that m X-direction electrodes 40 and n Y-direction electrodes 50 are formed on the touch panel 10 (m and n are natural numbers).

  Further, as shown in the figure, each rhombus electrode 42 for the X direction electrode 40 and each rhombus electrode 52 for the Y direction electrode 50 are arranged in a matrix so as not to overlap each other. Although not shown, an insulating film is interposed at each portion where the m connection wirings 44 and the n connection wirings 54 intersect. That is, in the case of the configuration shown in the figure, n Y-direction electrodes 50 are first formed on the surface of the transparent substrate 12. Next, when m X-direction electrodes 40 are formed, an insulating film is formed on each portion (m × n) where the m connection wirings 44 and the n connection wirings 54 will intersect, and thereafter , M X-direction electrodes 40 are formed. Therefore, each X direction electrode 40 and each Y direction electrode 50 are electrically insulated.

  The X direction electrode 40 and the Y direction electrode 50 are opposed to the pixel electrodes of the liquid crystal panel 30. For this reason, parasitic capacitance accompanies between the X direction electrode 40 and the pixel electrode and between the Y direction electrode 50 and the pixel electrode. A voltage corresponding to the gradation to be displayed is supplied to the pixel electrode. However, since the X-direction electrode 40 and the Y-direction electrode 50 are capacitively coupled to the pixel electrode by parasitic capacitance, the potential of the pixel electrode changes. The potentials of the X direction electrode 40 and the Y direction electrode 50 change, and this becomes noise. That is, the change in the potential of the pixel electrode becomes noise and is superimposed on the potential of the X direction electrode 40 and the Y direction electrode 50. In particular, in the case of the liquid crystal panel 30 that does not have a counter electrode as in the IPS (in-plane switching) method, the counter electrode cannot function as a shield, so noise from the liquid crystal panel 30 increases. Although the noise electrode 20 functions as a shield, the noise propagating from the liquid crystal panel 30 to the touch panel 10 cannot be completely blocked because it only covers the facing surface of the touch panel 10 and the liquid crystal panel 30.

  FIG. 4 is a block diagram showing an electrical configuration of the liquid crystal device D. The sensing device according to the present invention is configured by the touch panel 10, the noise electrode 20, and the touch detection unit 100 shown in FIG. The driving circuit 302 supplies a scanning line driving circuit that outputs a scanning signal for sequentially selecting a plurality of scanning lines provided in the liquid crystal panel 30 and a voltage corresponding to the gradation to be displayed on the plurality of data lines provided in the liquid crystal panel 30. A data line driving circuit is provided. The display control circuit 304 performs image processing on the input image data Din to generate output image data Dout, and supplies this to the drive circuit 304 (data line drive circuit). Further, the display control circuit 304 supplies various timing signals to the drive circuit 302. The timing signal includes, for example, a Y clock signal for driving the scanning line driving circuit and a Y transfer start pulse for instructing start of transfer in the Y direction, an X clock signal for driving the data line driving circuit, and the X direction. X transfer start pulse for instructing the start of transfer. Further, part or all of these timing signals are also supplied to the touch detection unit 100.

  The touch detection unit 100 includes a drive circuit 102, a capacitance detection unit 104, a correction unit 106, and a position detection unit 108. The drive circuit 102 sequentially selects m + n detection electrodes one by one, and applies an initialization potential to the selected detection electrodes. When the detection electrode selected in the drive circuit 102 is a detection electrode i (i = 1 to m + n), the capacitance detection unit 104 connects the detection electrode i to a resistor whose one end is grounded to detect the detection electrode i. By discharging the charge accumulated in the electrode for i through a resistor, the capacitance of the electrode for detection i is obtained from the time constant at that time.

  Since each detection electrode is accompanied by a parasitic capacitance, a time constant at the time of discharge is determined by the capacitance value and the resistance (resistance value) connected in the capacitance detection unit 104. When the indicator is positioned above the detection electrode i, a capacitor is formed between the detection electrode i and the indicator to generate a new capacitance. For this reason, the capacitance associated with the detection electrode i increases, and the time constant during discharge increases. When the period in which the initialization potential is applied to the detection electrode is an initialization period and the subsequent period is a detection period, the capacitance detection unit 104 measures each time constant during discharge in the detection period by measuring each time constant. The capacitance (capacitance value) of the detection electrode is detected. For example, when the indicator touches the broken line circle FR shown in FIG. 3 on the touch panel 10, for the X direction electrode 40, the capacitance value of the first X direction electrode 40 counted from the top in FIG. It becomes larger than the capacitance value of the direction electrode 40. For the Y-direction electrode 50, the capacitance value of the fourth Y-direction electrode 50 counted from the left in the drawing is larger than the capacitance values of the other Y-direction electrodes 50.

  The drive circuit 102 and the capacitance detection unit 104 measure the capacitance value CE of each detection electrode in this way, and measure the time constant during discharge for the noise electrode 20 as in the case of the detection electrode. As a result, the capacitance value CN is measured. The drive circuit 102 and the capacitance detection unit 104 constitute a measurement unit that measures the capacitance value CE (m + n) of each detection electrode and the capacitance value CN (1) of the noise electrode 20. Further, the capacitance value CE of each detection electrode and the capacitance value CN of the noise electrode 20 thus measured are output to the correction unit 106.

The correction unit 106 corrects the capacitance value CE (m + n) of each detection electrode using the capacitance value CN of the noise electrode 20. Here, the capacitance induced by each detection electrode due to noise from the liquid crystal panel 30, that is, the capacitance due to noise that could not be prevented by the noise electrode 20 (shield) is corrected. For example, the capacitance value of the detection electrode i (i = 1 to m + n) measured by the drive circuit 102 and the capacitance detection unit 104 is CE (i), and the corrected capacitance value of the detection electrode i is CE ′. When (i) is assumed, the correction unit 106 corrects the capacitance value CE of each detection electrode using [Expression 1] shown below. Further, the correction unit 106 outputs the corrected capacitance value CE ′ (m + n) of each detection electrode to the position detection unit 108.
CE (i) ′ = CE (i) −α × CN (Formula 1)

  In addition, the α × CN portion in [Expression 1] is a capacitance induced in the detection electrode by noise that could not be prevented by the noise electrode 20 (shield). In other words, the correction unit 106 multiplies the measured capacitance value CN of the noise electrode 20 by the coefficient α (α <1) to induce the detection electrode by noise that could not be prevented by the noise electrode 20. By specifying the capacitance value (α × CN) and subtracting this capacitance value from the capacitance value CE of each detection electrode, the influence of the noise is removed.

  The value of the coefficient α is obtained by actually measuring the relationship between the capacitance value CN of the noise electrode 20 and the capacitance value induced in the detection electrode by noise that cannot be prevented by the noise electrode 20 (shield). Determined by The area of the noise electrode 20 is much larger than the area of each detection electrode, and since the noise electrode 20 functions as a shield, the noise received by the noise electrode 20 is received by each detection electrode. Since it is much larger than noise, the value of the coefficient α is at least less than 1.

The correction unit 106 may be configured to correct the capacitance value CE of each detection electrode using [Equation 2] shown below. In this case, the touch detection unit 100 includes a memory (not shown), and stores the measured capacitance value CN of the noise electrode 20 in the memory. The correction unit 106 obtains an average value of a plurality of capacitance values CN stored in the memory, and corrects the capacitance value CE of each detection electrode using the average value.
CE (i) ′ = CE (i) −α × ΣCN / number of samplings [Equation 2]

The correction unit 106 may be configured to correct the capacitance value CE of each detection electrode using [Equation 3] shown below. In this case, the correction unit 106 obtains an average value of the maximum value and the minimum value among the plurality of capacitance values CN stored in the memory, and corrects the capacitance value CE of each detection electrode using the average value. .
CE (i) ′ = CE (i) −α × {(CN _MAX + CN _MIN ) / 2} [Equation 3]

  The position detection unit 108 detects the presence or absence of contact of the indicator and the contact position based on the corrected capacitance value CE ′ (m + n) of each detection electrode. Here, first, the presence / absence of contact of the indicator is detected based on the capacitance value CE ′ of each detection electrode. When the indicator is in contact, the contact position of the indicator is detected based on the capacitance value CE ′ of each detection electrode. For example, the position detection unit 108 calculates an X coordinate value PX and a Y coordinate value PY indicating the contact position by centroid calculation.

  As shown in FIG. 3, the X-direction electrode 40 and the Y-direction electrode 50 are arranged so as to form a lattice in plan view. Therefore, when the indicator touches the touch panel 10, the indicator touches the touch position and its vicinity. The capacitance value of the X direction electrode 40 and the Y direction electrode 50 which are located increases. For example, when the indicator touches the broken line circle FR shown in FIG. 3 on the touch panel 10, the X-direction electrode 40 has the capacitance value of the first X-direction electrode 40 and the second X-direction electrode 40 counted from the top in the figure. The capacitance value of the direction electrode 40 increases. As for the Y-direction electrode 50, the capacitance value of the third Y-direction electrode 50 and the capacitance value of the fourth Y-direction electrode 50 increase from the left in the figure.

  At this time, if the corrected capacitance value CE ′ of each X-direction electrode 40 is 5.8, 4.0, 3.4, 3.4,... The change amount of the capacitance value CE ′ with respect to is 2.4, 0.6, 0, 0,... Sequentially from the top in the figure. Further, the corrected capacitance value CE ′ of each Y-direction electrode 50 is 3.4, 3.4, 4.3, 5.5, 3.4, 3.4,. Then, the change amount of the capacitance value CE ′ for each Y-direction electrode 50 becomes 0, 0, 0.9, 2.1, 0, 0,... In order from the left in the figure. Therefore, by performing the centroid calculation, the X coordinate value PX is obtained as {(1 × 0) + (2 × 0) + (3 × 0.9) + (4 × 2.1) + (5 × 0) + (6 × 0) +...} / (0 + 0 + 0.9 + 2.1 + 0 + 0 +...) = 3.7. The Y coordinate value PY is {(1 × 2.4) + (2 × 0.6) + (3 × 0) + (4 × 0) +...} / (2.4 + 0.6 + 0 + 0 +...) = 1 .2.

  The X coordinate value PX and the Y coordinate value PY calculated in this way are output from the position detection unit 108 as position information indicating the contact position of the indicator. The position detector 108 may specify the X coordinate value PX and the Y coordinate value PY from the X direction electrode 40 and the Y direction electrode 50 having the maximum capacitance value CE ′. In this case, in the above-described example, the X coordinate value PX is “4” and the Y coordinate value PY is “1”. Further, when the indicator is not in contact, the position detection unit 108 outputs a signal indicating non-contact instead of the X coordinate value PX and the Y coordinate value PY.

  FIG. 5 is a flowchart showing the operation of the touch detection unit 100. As shown in the figure, after completing the initial process (step S101), the touch detection unit 100 determines whether or not it is a touch detection start timing (step S102). For example, when touch detection is performed at a rate of once per frame in synchronization with the display control of the liquid crystal panel 30, the touch detection unit 100 generates a new frame based on the timing signal supplied from the display control circuit 304. When it is detected that the transition has been made, it is determined that it is a touch detection start timing (step S102: YES), and the process proceeds to step S103. Note that the timing for starting touch detection and the cycle for performing touch detection are not limited to the above example and can be arbitrarily determined.

  When the touch detection is started, first, the drive circuit 102 and the capacitance detection unit 104 measure the capacitance value CE (m + n) of each detection electrode (step S103). Further, the measured capacitance value CE of each detection electrode is stored in a memory (not shown) (step S104). Next, the drive circuit 102 and the capacitance detection unit 104 measure the capacitance value CN (one) of the noise electrode 20 (step S105), and the measured capacitance value CN is stored in the memory (step S106). ).

  Thereafter, the correction unit 106 corrects the capacitance value CE (m + n) of each detection electrode using [Expression 1] described above (step S107). Of course, the correction unit 106 may be configured to perform correction using [Expression 2] or [Expression 3] described above. In the present embodiment, all the capacitance values CE of m + n are corrected using the single capacitance value CN measured in step S105, but the capacitance value CE (i) of one detection electrode is corrected. Even when the capacitance value CN (i) of the noise electrode 20 is measured each time measurement is performed, the capacitance value CE (i) of each detection electrode is corrected using the corresponding capacitance value CN (i). Good. With this configuration, the influence of noise can be more accurately removed.

  Next, the position detection unit 108 detects the presence / absence of the pointer and the contact position based on the corrected capacitance value CE ′ (m + n) of each detection electrode (step S108). When the indicator is in contact, the position detection unit 108 specifies the X coordinate value PX and the Y coordinate value PY indicating the contact position, and outputs them. When the indicator is not in contact, the position detection unit 108 outputs a signal indicating non-contact instead of the X coordinate value PX and the Y coordinate value PY. In step S108, it is not always necessary to detect both the presence / absence of the indicator and the contact position of the indicator, and it may be configured to detect only the presence / absence of the indicator.

  As described above, according to the present embodiment, the noise electrode 20 functions as a shield for preventing noise propagating from the liquid crystal panel 30 to the touch panel 10 and also functions as an electrode for measuring noise from the liquid crystal panel 30. To do. Further, the correction unit 106 corrects the capacitance induced in each detection electrode by noise that could not be prevented by the noise electrode 20 (shield). Therefore, based on the capacitance value CE ′ of each detection electrode from which the influence of noise from the liquid crystal panel 30 is removed by the shielding effect of the noise electrode 20 and correction by the correction unit 106, the presence or absence of contact of the indicator and the contact position thereof. Is detected. Therefore, it is possible to detect the presence or absence of contact of the indicator and the contact position thereof with higher accuracy than in the past.

<2. Modification>
The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. Also, two or more modifications shown below can be combined as appropriate.

(Modification 1)
FIG. 6 is a block diagram showing an electrical configuration of the liquid crystal device D ′ according to the first modification. The liquid crystal device D ′ shown in the figure is different from the liquid crystal device D in the above-described embodiment in that a switching control unit 110 and a switch SW are added. The switching control unit 110 outputs a switching signal for switching the switch SW on and off. For example, the switch SW is turned off when the signal level of the switching signal is Low, and turned on when the signal level of the switching signal is Hi. The switching control unit 110 sets the signal level of the switching signal to Low in the measurement period in which the capacitance value CN of the noise electrode 20 is measured, and sets the signal level of the switching signal to Hi in a period other than the measurement period. Thereby, in the measurement period, the switch SW is turned off, and the noise electrode 20 is connected to the drive circuit 102 and the capacitance detection unit 104. In a period other than the measurement period, the switch SW is turned on, and the noise electrode 20 is connected to GND. Thus, in the period when the capacitance value CN of the noise electrode 20 is not measured, the shielding effect may be enhanced by grounding the noise electrode 20.
Further, during the period when the capacitance value CN of the noise electrode 20 is not measured, the noise electrode 20 is connected to an AC power source instead of GND, and the noise electrode 20 is AC driven to enhance its shielding effect. Also good.
When the configuration in which the noise electrode 20 is grounded or AC driven as described above is adopted, the shielding effect of the noise electrode 20 is increased when measuring the capacitance value CE (m + n) of each detection electrode. Compared to the case of the above-described embodiment, it is necessary to reduce the value of the coefficient α in [Expression 1] to [Expression 3].

(Modification 2)
In the above-described embodiment, the case where the capacitance value CE of each detection electrode is corrected using a calculation formula has been described. However, the correction unit 106 refers to the correction table 112 illustrated in FIG. It may be configured to correct the value CE. As shown in FIG. 7, the correction table 112 stores a correction capacitance value CL in association with each division obtained by dividing the range of the capacitance value CN of the noise electrode 20 into a plurality of divisions. Has been. The correction capacitance value CL in the correction table 112 corresponds to α × CN in [Expression 1] described above. The correction unit 106 refers to the correction table 112, reads the correction capacitance value CL corresponding to the measured capacitance value CN of the noise electrode 20, and uses the read correction capacitance value CL as the capacitance value CE of each detection electrode. Subtract from

(Modification 3)
The detection electrodes (X-direction electrode 40 and Y-direction electrode 50) are not limited to the configuration shown in FIG. For example, a plurality of X direction electrodes and a plurality of Y direction electrodes may be arranged to face each other with an insulating film interposed therebetween. In this case, the shape of the X direction electrode or the Y direction electrode may be a strip shape. Further, rectangular detection electrodes may be arranged in a matrix.

(Modification 4)
There may be one detection electrode instead of a plurality. In this case, the capacitance value CE measured by the drive circuit 102 and the capacitance detection unit 104 is one. Further, the correction unit 106 corrects one capacitance value CE. In addition, the position detection unit 108 functions as a contact detection unit, and detects the presence or absence of contact of the indicator based on one corrected capacitance value CE ′.

(Modification 5)
The installation location of the noise electrode 20 is not limited to the back surface of the touch panel 10. For example, the noise electrode 20 may be formed on the upper surface of the liquid crystal panel 30. Alternatively, the noise electrode 20 may be formed on the surface of a transparent substrate different from the touch panel 10, and the transparent substrate may be provided between the touch panel 10 and the liquid crystal panel 30. The noise electrode 20 may be configured to cover a part of the display area of the liquid crystal panel 30 instead of the entire display area. As described above, the noise electrode 20 may be provided between the touch panel 10 and the liquid crystal panel 30 so as to cover all or part of the display area of the liquid crystal panel 30. The display device is not limited to a liquid crystal display device, and may be, for example, an organic EL display, a plasma display, a CRT (Cathode Ray Tube) display, or the like.

<3. Application example>
Next, an electronic device equipped with the sensing device according to the present invention will be described. 8 to 10 illustrate an electronic device on which the liquid crystal device 500 according to any one of the above-described forms is mounted.
FIG. 8 is a perspective view showing a configuration of a mobile personal computer 2000 equipped with the liquid crystal device 500. The personal computer 2000 includes a liquid crystal device 500 serving as a display unit and a touch input unit, and a main body 2010 provided with a power switch 2001 and a keyboard 2002.
FIG. 9 is a perspective view showing a configuration of a mobile phone 3000 on which the liquid crystal device 500 is mounted. The cellular phone 3000 includes a liquid crystal device 500 as a display unit and a touch input unit, and a plurality of operation buttons 3001 and scroll buttons 3002. By operating the scroll button 3002, an image displayed on the liquid crystal device 500 is scrolled.
FIG. 10 is a perspective view showing a configuration of an information portable terminal 4000 (PDA: Personal Digital Assistants) on which the liquid crystal device 500 is mounted. The portable information terminal 4000 includes a liquid crystal device 500 as a display unit and a touch input unit, and a plurality of operation buttons 4001 and a power switch 4002. When the operation button 4001 is operated, various types of information such as an address book and a schedule book are displayed on the liquid crystal device 500.
In addition, as an electronic device in which the liquid crystal device 500 is mounted, in addition to the devices illustrated in FIG. 8 to FIG. Examples include printers, scanners, copiers, video players, and electronic paper.

D, D ', 500 ... Liquid crystal device, 10 ... Touch panel, 12 ... Transparent substrate, 14 ... Electrode layer, 16 ... Adhesive layer, 18 ... Protective layer, 20 ... Noise electrode, 30 ... Liquid crystal panel, 40 ... X direction electrode 42 ... Diamond electrode, 44 ... Connection wiring, 50 ... Y direction electrode, 52 ... Diamond electrode, 54 ... Connection wiring, 100, 100 '... Touch detection unit, 102 ... Drive circuit, 104 ... Capacitance detection unit, 106 ... correction unit 108 ... position detection unit CE ... capacitance value of each detection electrode, CN ... capacitance value of noise electrode, CE '... capacitance value of each detection electrode after correction, PX ... X coordinate value, PY ... Y coordinate value, 110 ... switch control unit, SW ... switch, 112 ... correction table, CL ... correction capacitance value, 302 ... drive circuit, 304 ... display control circuit, Din ... input image data, Dout ... output image data, 2000 ... Personal Pewter, 2001 ... power switch, 2002 ... keyboard, 2010 ... the main body portion, 3000 ... mobile phone, 3001 ... operation button, 3002 ... scroll button, 4000 ... portable information terminal, 4001 ... operation button, 4002 ... power switch.

Claims (10)

A touch panel having a first electrode for detecting contact of the indicator;
A second electrode provided so as to cover all or part of the screen between the touch panel and the screen of the display device;
A measuring unit for measuring the capacitance value of the first electrode and the capacitance value of the second electrode;
A correction unit that corrects the capacitance value of the first electrode using the capacitance value of the second electrode;
Based on the capacitance value corrected by the correction unit, a detection unit that detects the presence or absence of contact of the indicator,
A sensing device comprising: The correction unit specifies a capacitance value induced in the first electrode by noise from the display device from a capacitance value of the second electrode, and subtracts the specified capacitance value from the capacitance value of the first electrode. The sensing device according to claim 1. A storage unit for storing the capacitance value of the second electrode measured by the measurement unit;
The correction unit calculates an average value of a plurality of capacitance values stored in the storage unit, and corrects the capacitance value of the first electrode using the average value. The sensing device described in 1. The correction unit calculates an average value of a maximum value and a minimum value among a plurality of capacitance values stored in the storage unit, and corrects the capacitance value of the first electrode using the average value. The sensing device according to claim 3. A touch panel having a plurality of first electrodes for detecting contact of an indicator;
A second electrode provided so as to cover all or part of the screen between the touch panel and the screen of the display device;
A measuring unit that measures the capacitance value of each of the plurality of first electrodes and the capacitance value of the second electrode;
A correction unit that corrects the capacitance value of each of the plurality of first electrodes using the capacitance value of the second electrode;
Based on each capacitance value corrected by the correction unit, a detection unit for detecting presence or absence of contact of the indicator or a contact position of the indicator;
A sensing device comprising: The apparatus further comprises a switching unit that connects the second electrode to the measurement unit in a measurement period in which the capacitance value of the second electrode is measured, and grounds the second electrode in a period other than the measurement period. The sensing device according to any one of Items 1 to 5. A switching unit that connects the second electrode to the measurement unit in a measurement period in which the capacitance value of the second electrode is measured, and connects the second electrode to an AC power supply in a period other than the measurement period. The sensing device according to any one of claims 1 to 5. The sensing device according to any one of claims 1 to 7, wherein the second electrode is formed on a surface of the touch panel on the display device side. The sensing device according to any one of claims 1 to 8, wherein the first electrode and the second electrode are made of a light-transmitting conductive material. An electronic apparatus comprising the sensing device according to claim 1.

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