JP2005275934A - Position detecting device for touch panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detecting device for a touch panel which enhances precision in detecting a contact point position. <P>SOLUTION: The position detecting device is the device for the touch panel including a first conductive film 2b, having a uniform resistance distribution; and a second conductive film 2a which is slightly separated from the first conductive film 2b, arranged so as to superimpose on the first film 2b, and brought into local contact with the first film 2b by pressure. The device especially comprises: first and second electrodes 9a, 9b mutually facing and connected to the outer edge of the first conductive film 2b; an electric current supply part 12 for supplying a current to the second conductive film 2a; electric current detecting circuits 11a, 11b for measuring a first current which flows in the first conductive film 2b from the contact point of the first and second conductive films 2b, 2a toward the first electrode 9a and a second current which flows from the contact point of the first and second conductive films 2b, 2a toward the second electrode 9b; and a processing circuit 8 for performing a processing to specify the position of the contact point, based on the measurement values of the first and second electric currents. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a touch panel disposed, for example, on a display screen, and more particularly to a position detection device for a touch panel that detects the position of a contact point obtained on a touch panel by contact of a pointer member such as a stylus pen.

  A flat display device typified by a liquid crystal display is widely used as a monitor display of a portable information device such as a notebook personal computer or a PDA (Personal Digital Assistance).

  In recent years, an input tool called a touch panel (or tablet) is provided in a portable information device to perform handwritten input of characters and figures and menu selection instead of a keyboard and a mouse pointer. For example, a transmissive touch panel is configured to transmit an image displayed on a liquid crystal display of a portable information device, and a user performs an input operation by bringing a pointer member into contact with the touch panel while viewing the image.

  FIG. 19 shows a cross-sectional structure of a conventional transmissive touch panel. The touch panel includes a pair of transparent substrates 1a and 1b and transparent conductive films 2a and 2b formed on the transparent substrates 1a and 1b (see, for example, Non-Patent Document 1). The transparent conductive films 2a and 2b are each a resistor having a uniform resistance distribution. The transparent substrates 1a and 1b are bonded to each other so that the transparent conductive films 2a and 2b are slightly spaced apart from each other by a sealing material 5a disposed along the outer edge. A space surrounded by the sealing material 5a between the transparent substrates 1a and 1b is filled with, for example, an inert gas 5b (or liquid). Further, the gap material 5c is sprayed in this space in order to maintain the transparent conductive films 2a and 2b in a non-contact state except for a portion pressed by the pointer member 6. In this pressure portion, the transparent conductive film 2a is curved together with the transparent substrate 1a and locally contacts the transparent conductive film 2b. In FIG. 19, 4a and 4b are electrodes respectively connected to both ends of the transparent conductive film 2b in the horizontal axis (X-axis) direction of the liquid crystal display, and 3a and 3b are respectively connected to both ends of the transparent conductive film 2a in the X-axis direction. Each is a connected electrode.

  In the touch panel described above, when the position coordinates of the contact points of the transparent conductive films 2a and 2b obtained with the contact of the pointer member 6 are detected in the X-axis direction, the power supply voltage E1 is between the electrodes 4a and 4b as shown in FIG. The voltage detector 7 is connected to the transparent conductive film 2a via the electrode 3b in order to measure the voltage Vp at the contact point of the transparent conductive films 2a and 2b. This voltage Vp is a value obtained by dividing the power supply voltage E1 by the resistance value Rx1 between the electrode 4a and the contact and the resistance value Rx2 between the electrode 4b and the contact.

  The X coordinate of the contact point of the transparent conductive films 2a and 2b is equal to the distance X1 from the left end of the transparent conductive film 2b where the X coordinate X = 0, and is obtained by substituting the measured value of the voltage Vp into the following equation 1.

X1 = (1-Vp / E1) Lx (Formula 1)
Here, Lx is the distance between the electrodes 4a and 4b, that is, the total length of the transparent conductive film 2b in the X-axis direction.

When detecting the position coordinates of the contact points of the transparent conductive films 2a and 2b in the Y-axis direction, two electrodes connected to both ends of the transparent conductive film 2b in the vertical axis (Y-axis) direction of the liquid crystal display are used. . In this case, the power supply voltage E1 is applied between these two electrodes, and the voltage detector 7 is connected to the transparent conductive film 2a via the electrode 3b in order to measure the voltage Vp at the contact point of the transparent conductive films 2a and 2b. Subsequently, the Y coordinate of the contact point of the transparent conductive films 2a and 2b is obtained in the same manner as in the case of the X coordinate based on the measured value of the voltage Vp.
Masatoshi Tokoro, “7-Wire Analog Resistive Touch Panel”, Monthly Display, Techno Times, Inc., November 2001, P.23-26

  By the way, in the measurement of the voltage Vp, the sheet resistance of the transparent conductive film 2a is set to be sufficiently large. However, a slight current flows from the contact point of the first and second transparent conductive films 2a and 2b toward the voltage detection unit 7 described above. Flows. This causes a voltage drop in the transparent conductive film 2a and the wiring of the voltage detection unit 7 and causes the measurement result of the voltage Vp to fluctuate.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a position detection device for a touch panel that can improve the detection accuracy of a contact position.

  According to the present invention, the first conductive film having a uniform resistance distribution and the first conductive film are disposed so as to be slightly spaced from the first conductive film and overlap the first conductive film, and locally by pressurization. A position detecting device for a touch panel having a second conductive film in contact with the first and second electrodes facing each other and connected to the outer edge of the first conductive film, and a current for supplying a current to the second conductive film A first current flowing through the first conductive film from the contact point of the supply unit to the first electrode and a second current flowing from the contact point of the first and second conductive films toward the second electrode; A position detection device for a touch panel is provided, which includes a current detection circuit that measures current and a processing circuit that performs processing for specifying the position of the contact based on the measured values of the first and second currents.

  In this touch panel position detection device, the contact positions of the first and second conductive films are obtained by performing processing based on the first and second currents in the direction in which the first and second electrodes face each other. In this case, the current flowing out from the contact point of the first and second conductive films to the first conductive film side is always equal to the sum of the first current and the second current. For this reason, even if a voltage drop depending on at least the resistance value of the second conductive film 2 occurs, this does not affect the detection result of the contact position. In other words, the influence of the voltage drop in the second conductive film can be eliminated from the detection result of the contact position. Therefore, the contact position detection accuracy can be improved.

  Hereinafter, a touch panel according to a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a cross-sectional structure of the touch panel TP. This touch panel TP has a pair of first and second transparent substrates 1a and 1b and first and second transparent conductive films 2a and 2b formed on the transparent substrates 1a and 1b, as in the conventional case. The transparent conductive films 2a and 2b are resistors such as ITO (Indium Tin Oxide) having a uniform resistance distribution. The transparent substrates 1a and 1b are bonded to each other so that the transparent conductive films 2a and 2b are slightly spaced apart from each other by a sealing material 5a disposed along the outer edge. A space surrounded by the sealing material 5a between the transparent substrates 1a and 1b is filled with, for example, an inert gas 5b (or liquid). Further, the gap material 5c is sprayed in this space in order to maintain the transparent conductive films 2a and 2b in a non-contact state except for a portion pressed by the pointer member 6. Here, the transparent conductive films 2a and 2b are set to have a resistance value different from the conventional relationship. That is, the sheet resistance of the transparent conductive film 2a is about 10 ohms per unit area, and the sheet resistance of the transparent conductive film 2b is about 500 ohms per unit area.

  FIG. 2 shows a planar structure on the transparent substrate 1a side shown in FIG. The transparent conductive film 2a is formed on the transparent substrate 1a so as to be a rectangle having an aspect ratio of, for example, length: width = 3: 4. The striped electrodes 10a and 10b are made of a metal film such as silver, and are, for example, along the two short sides, which are both ends of the transparent conductive film 2a in the horizontal axis (X-axis) direction, and connected to these two short sides, respectively. Formed on 1a. Here, the constant current source 12 is connected to one of the electrodes 10a and 10b, for example, the electrode 10b, in order to supply the constant current Io to the transparent conductive film 2a.

  FIG. 3 shows a planar structure on the transparent substrate 1b side shown in FIG. Similar to the transparent conductive film 2a, the transparent conductive film 2b is formed on the transparent substrate 1b so as to be a rectangle having an aspect ratio of length: width = 3: 4. The striped electrodes 9a and 9b are made of a metal film such as silver, and are along the two short sides, which are both ends of the transparent conductive film 2b in the horizontal axis (X-axis) direction, and are connected to these two short sides, respectively. Formed on top. The striped electrodes 13a and 13b are made of a metal film such as silver, and are transparent along the two long sides that are both ends of the transparent conductive film 2b in the vertical axis (Y-axis) direction. It is formed on the substrate 1b. Two current detectors 11a and 11b are provided for the electrodes 9a and 13a and the electrodes 9b and 13b, respectively. The changeover switch Sa connects one of the electrode 9a and the electrode 13a to the current detection unit 11a by the control of the mode control signal SWC from the arithmetic processing circuit 8, and the changeover switch Sb controls the electrodes 9b and 13b by the control of the mode control signal SWC. One is connected to the current detector 11b. For example, when the X-axis direction mode is set by the mode control signal SWC, the current detection units 11a and 11b measure currents supplied from the electrodes 9a and 9b via the changeover switches Sa and Sb, respectively. On the other hand, when the Y-axis direction mode is set by the mode control signal SWC, the current detectors 11a and 11b measure currents supplied from the electrodes 13a and 13b via the changeover switches Sa and Sb, respectively. These measurement results are supplied to the arithmetic processing circuit 8. Note that peripheral circuits such as the arithmetic processing circuit 8, the current detection units 11a and 11b, and the changeover switches Sa and Sb are disposed outside the seal material 5a in the touch panel TP. When these peripheral circuits are arranged on the transparent substrate 1b, for example, a peripheral circuit forming region is provided on the transparent substrate 1b outside the sealing material 5a.

  FIG. 4 shows a liquid crystal display LCD integrated with the touch panel TP described above. This liquid crystal display LCD is used as a monitor display of a portable information device in which the aspect ratio of the screen is set to vertical: horizontal = 3: 4, and the liquid crystal layer LQ is sandwiched between a pair of electrode substrates AR and CT. Have The electrode substrate AR includes a plurality of pixel electrodes arranged in a matrix and a drive circuit for driving these pixel electrodes, and the electrode substrate CT includes a common electrode facing the plurality of pixel electrodes on the electrode substrate AR side. The liquid crystal layer LQ is set to a transmittance according to the potential difference between the pixel electrode and the counter electrode. In this liquid crystal display LCD, backlight light incident from the electrode substrate AR side is optically modulated by the liquid crystal layer LQ and displayed as an image on a display region on the electrode substrate CT side corresponding to an array of a plurality of pixel electrodes. The touch panel TP is light transmissive at least in the display area, and is configured such that the user can perform an input operation on the portable information device by bringing the pointer member 6 into contact with the touch panel TP while viewing the image.

  FIG. 5 shows a state in which the pointer member 6 is in contact with the touch panel TP, and FIG. 6 shows an equivalent circuit of the touch panel TP obtained when the X-axis direction mode is set in this state. At the portion where the pointer member 6 is brought into contact, the transparent conductive film 2a is curved together with the transparent substrate 1a and locally contacts the transparent conductive film 2b. As a result, the constant current Io flows from the constant current source 12 to the transparent conductive film 2a via the electrode 10b, and flows out from the contact points of the transparent conductive films 2a and 2b to the transparent conductive film 2b side. In the transparent conductive film 2b, the constant current Io is divided into a current Ix1 directed to the electrode 9a and a current Ix2 directed to the electrode 9b, and these currents Ix1 and Ix2 are measured by the current detectors 11a and 11b, respectively.

  The X coordinate of the contact point of the transparent conductive films 2a and 2b is equal to the distance X1 from the left end of the transparent conductive film 2b where the X coordinate X = 0 as shown in FIG. The arithmetic processing circuit 8 shown in FIG. 3 calculates the X coordinates of the contacts of the transparent conductive films 2a and 2b by substituting the measured values of the currents Ix1 and Ix2 into the following equation 1 and performing arithmetic processing.

X1 = {Ix2 / (Ix1 + Ix2)} Lx (Formula 2)
Here, Lx is the distance (X1 + X2) between the electrodes 9a and 9b, that is, the total length of the transparent conductive film 2b in the X-axis direction.

  When the Y-axis direction mode is set to obtain the Y coordinate of the contact point of the transparent conductive films 2a and 2b, the constant current Io flows from the constant current source 12 to the transparent conductive film 2a via the electrode 10b, and the transparent conductive film It flows out from the contact point of the films 2a and 2b to the transparent conductive film 2b side. In the transparent conductive film 2b, the constant current Io is divided into a current Iy1 directed to the electrode 13a and a current Iy2 directed to the electrode 13b, and these currents Iy1 and Iy2 are measured by the current detectors 11a and 11b, respectively.

  The Y coordinate of the contact point of the transparent conductive films 2a and 2b is equal to the distance Y1 from the lower end of the transparent conductive film 2b where the Y coordinate Y = 0. The arithmetic processing circuit 8 shown in FIG. 3 obtains the Y coordinate of the contacts of the transparent conductive films 2a and 2b by substituting the measured values of the currents Iy1 and Iy2 into the following expression 3 and performing arithmetic processing.

Y1 = {Iy2 / (Iy1 + Iy2)} Ly (Formula 3)
Here, Ly is the distance (Y1 + Y2) between the electrodes 13a and 13b, that is, the total length of the transparent conductive film 2b in the Y-axis direction. Y2 is the distance from the contact point of the transparent conductive films 2a and 2b to the upper end of the transparent conductive film 2b.

  In the present embodiment, the contact positions of the transparent conductive films 2a and 2b are obtained by performing arithmetic processing based on the measured values of the currents Ix1 and Ix2 in the X-axis direction, and are based on the measured values of the currents Iy1 and Iy2 in the Y-axis direction. It is obtained by performing arithmetic processing. In this case, the current flowing out from the contact point of the transparent conductive films 2a and 2b toward the transparent conductive film 2b is always the sum of the currents Ix1 and Ix2, or the sum of the currents Iy1 and Iy2, and is equal to the current Io from the constant current source 12. For this reason, even if a voltage drop depending on the resistance values of the transparent conductive film 2a and the wiring occurs, this does not affect the detection result of the contact position. In other words, the influence of the voltage drop in the transparent conductive film 2a and the wiring can be eliminated from the contact position detection result. Therefore, the contact position detection accuracy can be improved.

  Further, in the above-described structure, the sheet resistance of the transparent conductive film 2a is not involved in the detection of the contact position, and thus is set to a value sufficiently smaller than the sheet resistance of the transparent conductive film 2b of about 10 ohms per unit area. This is because an unnecessary electromagnetic wave leaking from the portable information device generates an eddy current when the transparent conductive film 2a is transmitted and attenuates electromagnetic wave energy. Thus, since the electromagnetic wave is effectively absorbed by the transparent conductive film 2a, a good shielding effect against the electromagnetic wave can be obtained.

  FIG. 7 shows a first modification in which the planar structure on the transparent substrate 1a side shown in FIG. 2 is modified. In this modification, the single electrode 10 shown in FIG. 7 is used instead of the electrodes 10a and 10b shown in FIG. The electrode 10 surrounds the transparent conductive film 2a as a whole, is formed on the transparent substrate 1a, and is connected to the transparent conductive film 2a. The constant current source 12 is connected to an arbitrary point of the electrode 10 in order to supply a constant current Io to the transparent conductive film 2a.

  According to the first modified example, since the in-plane current of the transparent conductive film 2a becomes uniform, the responsiveness is improved.

  FIG. 8 shows a second modification in which the planar structure on the transparent substrate 1a side shown in FIG. 2 is modified. In this modification, the single electrode 16 shown in FIG. 8 is used instead of the electrodes 10a and 10b shown in FIG. The electrode 16 is formed on the transparent substrate 1a so as to entirely surround the transparent conductive film 2a except for the vicinity of the power feeding ends 17a and 17b, and is connected to the transparent conductive film 2a. The changeover switch STa connects the power supply end 17a to one of the constant current source 12 and the transceiver unit TR of the portable information terminal by controlling the switch signal RFC from the arithmetic processing circuit 8, and the changeover switch STb supplies power by controlling the switch signal RFC. The end 17b is connected to one of the constant current source 12 and the transceiver unit TR of the portable information terminal. When detecting the contact positions of the transparent conductive films 2a and 2b, the constant current source 12 is connected to the power supply terminals 17a and 17b via the changeover switches STa and STB. When transmission / reception is performed by the transceiver unit TR, the transceiver unit TR is connected to the power supply terminals 17a and 17b via the changeover switches STa and STB. In this case, the electrode 16 functions as a loop antenna.

  According to the second modification, the electrode 16 can be used not only as an electrode for supplying the constant current Io from the constant current source 12 to the transparent conductive film 2a but also as a loop antenna. Accordingly, an antenna provided independently for the transceiver unit TR to communicate with the outside in the portable information terminal can be eliminated.

  FIG. 9 shows a third modification in which the planar structure on the transparent substrate 1a side shown in FIG. 2 is modified. In this modification, the electrodes 18 and 19 shown in FIG. 9 are used instead of the electrodes 10a and 10b shown in FIG. The electrode 18 is formed on the transparent substrate 1a so as to entirely surround the transparent conductive film 2a except for the vicinity of the power feeding ends 20a and 20b, and is connected to the transparent conductive film 2a. Here, the power supply ends 20a and 20b are provided close to the right end of the transparent conductive film 2a, and the changeover switches STa and STb are provided so as to function in the same manner as in the second modification. The electrode 19 is provided for capacitively coupling with the electrode 18 functioning as a loop antenna to change the directivity of the loop antenna. Further, the transceiver unit TR may be connected to one end 20c of the electrode 19 in order to perform transmission / reception while the constant current source 12 detects a contact position using the electrode 10. In this case, the electrode 19 functions as a rod antenna. Further, one end 20c of the electrode 19 may be used as a power feeding end connected to a second transceiver unit TR provided in the portable information terminal independently to perform transmission / reception in a frequency band different from the transceiver unit TR, for example. Good.

  According to the third modification, when the electrode 18 is used not only as an electrode for supplying the constant current Io from the constant current source 12 to the transparent conductive film 2a but also as a loop antenna, it cooperates with this electrode 18. By providing the electrode 19, the application range as an antenna can be expanded.

  FIG. 10 shows a fourth modification in which the current detection structure on the transparent substrate 1b side shown in FIG. 3 is modified. In this modification, the electrodes 9a, 9b, 13a, and 13b are connected to the current detection units 11a, 11b, 11c, and 11d via the external connection terminals P1, P2, P3, and P4, respectively. The current detection unit 11a measures a current Iy2 flowing through the transparent conductive film 2b from the contact point of the transparent conductive films 2a and 2b toward the electrode 13b, and the current detection unit 11b moves from the contact point of the transparent conductive films 2a and 2b to the electrode 9b. The current Ix2 flowing through the transparent conductive film 2b is measured, the current detector 11c measures the current Iy1 flowing through the transparent conductive film 2b from the contact point of the transparent conductive films 2a and 2b toward the electrode 13a, and the current detector 11d is transparent conductive A current Ix1 flowing through the transparent conductive film 2b from the contact point between the films 2a and 2b toward the electrode 9a is measured. The measured values of these currents Ix1, Ix2, Iy1, and Iy2 are supplied from the current detection units 11a to 11d to the arithmetic processing circuit 8. The arithmetic processing circuit 8 converts the measured values of the currents Ix1, Ix2, Iy1, and Iy2 into an arithmetic expression that defines the relationship between the X coordinates of the contacts with these four currents and an arithmetic expression that defines the relationship between these four currents and the Y coordinates of the contacts. The X coordinate and the Y coordinate of the contact points of the transparent conductive films 2a and 2b are obtained by performing the calculation process by substituting each.

  According to the fourth modification, measured values of the currents Ix1, Ix2, Iy1, and Iy2 are obtained simultaneously from the current detection units 11a to 11d. Therefore, the changeover switches Sa and Sb and the mode control signal SWC generated from the arithmetic processing circuit 8 as shown in FIG.

  FIG. 11 shows a fifth modification in which the planar structure and the current detection structure on the transparent substrate 1b side shown in FIG. 3 are modified. In this modification, the transparent conductive film 2b is formed on the transparent substrate 1b in a shape in which four sides of a rectangle having an aspect ratio of vertical: horizontal = 3: 4 are warped inward as shown in FIG. 11, and the electrodes 23a, 23b are formed. , 23c and 23d are connected to the outer edge of the transparent conductive film 2b so as to face each other instead of the electrodes 9a, 9b, 13a and 13b shown in FIG. Here, the electrodes 23a and 23c are arranged extending from the two diagonals of the transparent conductive film 2b facing each other on the first diagonal line to the vicinity of the center of the two adjacent sides, and facing each other on the second diagonal line of the electrodes 23b and 23d. The transparent conductive film 2b is disposed so as to extend from the two diagonals to the vicinity of the center of two adjacent sides. The transparent conductive film 2b includes a high resistance region 22 having a sheet resistance of about 500 ohm per unit area and a low resistance region 24 having a sheet resistance of about 10 ohm per unit area. The low resistance region 24 is a band shape surrounding the high resistance region as the outer edge of the transparent conductive film 2b, and is provided to reduce the contact resistance between the transparent conductive film 2b and the electrodes 23a, 23b, 23c, and 23d. As shown in FIG. 10, the shape of the transparent conductive film 2b is such that the in-plane potential distribution of the effective position detection range 21 which is a rectangle inscribed in the low resistance region 24 is made uniform, and the electrodes 23a, 23b, 23c, It is used to reduce interference between 23d.

  The electrodes 23a, 23b, 23c, and 23d are connected to the current detection units 11a, 11b, 11c, and 11d through the external connection terminals P1, P2, P3, and P4, respectively. The current detection unit 11a measures a current flowing through the transparent conductive film 2b from the contact point of the transparent conductive films 2a and 2b toward the electrode 23a, and the current detection unit 11b is transparent from the contact point of the transparent conductive films 2a and 2b to the electrode 23b. The current flowing through the conductive film 2b is measured, the current detection unit 11c measures the current flowing through the transparent conductive film 2b from the contact points of the transparent conductive films 2a and 2b toward the electrode 23c, and the current detection unit 11d receives the transparent conductive film 2a, The current flowing through the transparent conductive film 2b from the contact 2b toward the electrode 23d is measured. The measured values of these four currents are supplied from the current detectors 11a to 11d to the arithmetic processing circuit 8. The arithmetic processing circuit 8 calculates the measurement values of the four currents from the current detectors 11a to 11d, the arithmetic expression defining the relationship between the X coordinates of the contacts with these four currents, and the calculation defining the relationship between these four currents and the Y coordinate of the contact The X and Y coordinates of the contact points of the transparent conductive films 2a and 2b are obtained by substituting each into the equation and performing arithmetic processing.

  According to the fifth modification, four current measurement values are obtained simultaneously from the current detectors 11a to 11d. Therefore, the changeover switches Sa and Sb and the mode control signal SWC generated from the arithmetic processing circuit 8 as shown in FIG. Further, since the transparent conductive film 2b is set to the shape shown in FIG. 11, it is possible to reduce the contact position detection error that occurs in the simultaneous measurement of four currents.

  When the effective position detection range 21 is a horizontally long rectangle, d1 and d2 shown in FIG. 12 are set in a relationship of d2> d1 in order to reduce contact position detection errors, and w1 shown in FIG. , W2 are preferably in a relationship of w2> w1. Here, d1 is the distance from the long side of the virtual rectangle circumscribing the transparent conductive film 2b to the high resistance region 22, and d2 is from the short side of the virtual rectangle circumscribing the transparent conductive film 2b to the high resistance region. It is the distance to 22. Further, w1 is the width of the low resistance region 24 provided on the short side of the virtual rectangle circumscribing the transparent conductive film 2b, and w1 is provided on the long side of the virtual rectangle circumscribing the transparent conductive film 2b. This is the width of the low resistance region 24 to be formed. However, the relationship of d2> d1 and the relationship of w2> w1 may be satisfied only for at least one of them.

  FIG. 14 shows a sixth modification in which the planar structure on the transparent substrate 1b side shown in FIG. 11 is further modified. In this modification, the transparent conductive film 2b consists of only the high resistance region 22, and the electrodes 26a, 26b, 26c, and 26d are provided instead of the electrodes 23a, 23b, 23c, and 23d. These electrodes 26a, 26b, 26c, and 26d are metal films such as silver formed on the outer edge of the transparent conductive film 2b so as to serve as the low resistance region 24 shown in FIG.

  According to the sixth modification, since the low resistance region 24 shown in FIG. 11 is not required, the manufacturing process can be simplified.

  Here, a method of obtaining the shape of the transparent conductive film 2b used in the fifth and sixth modifications will be described with reference to FIG. The transparent conductive film 2b is formed in a shape in which four sides of a rectangle having an aspect ratio of vertical: horizontal = 3: 4 are warped inward. In FIG. 15, 25 indicates this rectangle. In this case, an ellipse having an aspect ratio of short axis: major axis = 3: 4 common to the aspect ratio of the rectangle 25 is overlapped on the rectangle 25 as shown in FIG. 15, and the short side and the long side of the rectangle 25 are bent inward. What is necessary is just to obtain the shape. This amount of warpage is set within an allowable range depending on the frame width of the liquid crystal display LCD. In FIGS. 11 and 14, the amount of warpage is drawn very large, but the actual value is, for example, about 1 mm.

  Hereinafter, a touch panel according to a second embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 16 shows the circuit structure of the touch panel TP. This touch panel TP is the same as that of the first embodiment except that the connection destination of the constant current source 12 is switched as shown in FIG. 16 and the contact position is detected in the X-axis direction or the Y-axis direction. . For this reason, in FIG. 16, the same part as 1st Embodiment is represented by the same referential mark, and detailed description is abbreviate | omitted. The transparent conductive films 2a and 2b are respectively formed on the pair of transparent substrates 1a and 1b shown in FIG. 1, but these transparent substrates 1a and 1b are omitted in FIG.

  The transparent conductive films 2a and 2b are resistors such as ITO (Indium Tin Oxide) having a uniform resistance distribution. The sheet resistances of the transparent conductive films 2a and 2b are both about 500 ohms per unit area.

  The striped electrodes 10a, 10b, 13a, 13b are made of a metal film such as silver. The electrodes 10a and 10b are formed on a transparent substrate 1a (not shown) along the two short sides which are both ends of the transparent conductive film 2a in the horizontal axis (X-axis) direction and connected to the two short sides, respectively. The electrodes 10a and 10b are formed on a transparent substrate 1b (not shown) along the two long sides which are both ends of the transparent conductive film 2b in the direction of the vertical axis (Y axis) and connected to the two long sides. The

Two current detectors 11a and 11b are provided for the electrodes 10a and 13a and the electrodes 10b and 13b, respectively. The changeover switch Sa connects one of the electrode 10a and the electrode 13a to the current detection unit 11a by the control of the mode control signal SWC from the arithmetic processing circuit 8, and the changeover switch Sb controls the electrodes 10b and 13b by the control of the mode control signal SWC. One is connected to the current detector 11b. A changeover switch Sc is provided to connect the constant current source 12 to one of the electrodes 10b and 13b under the control of the mode control signal SWC.

  For example, when the X-axis direction mode is set by the mode control signal SWC, the constant current source 12 is connected to 13b via the changeover switch Sc, and the current detection units 11a and 11b change the changeover switches Sa and Sb from the electrodes 10a and 10b. The current supplied through each is measured. On the other hand, when the Y-axis direction mode is set by the mode control signal SWC, the constant current source 12 is connected to 10b via the changeover switch Sc, and the current detectors 11a and 11b are changed from the electrodes 13a and 13b to the changeover switches Sa and Sb. Each of the currents supplied through each is measured. These measurement results are supplied to the arithmetic processing circuit 8. Note that peripheral circuits such as the arithmetic processing circuit 8, the current detection units 11a and 11b, and the changeover switches Sa, Sb, and Sc are arranged outside the sealing material 5a in the touch panel TP. When these peripheral circuits are arranged on the transparent substrate 1b, for example, a peripheral circuit forming region is provided on the transparent substrate 1b outside the sealing material 5a.

  When the pointer member 6 is actually contacted in the X-axis direction mode, the constant current Io flows from the constant current source 12 to the transparent conductive film 2a through the electrode 13b, and from the contact points of the transparent conductive films 2a and 2b to the transparent conductive film 2a side. Flows out. In the transparent conductive film 2a, the constant current Io is divided into a current Ix1 directed to the electrode 10a and a current Ix2 directed to the electrode 10b, and these currents Ix1 and Ix2 are measured by the current detectors 11a and 11b, respectively. The arithmetic processing circuit 8 substitutes the measured values of the currents Ix1 and Ix2 into the above-described equation 2 and performs arithmetic processing to obtain the X coordinate of the contact points of the transparent conductive films 2a and 2b. However, in this case, Lx is the distance (X1 + X2) between the electrodes 10a and 10b, that is, the total length of the transparent conductive film 2a in the X-axis direction.

  Further, when the pointer member 6 is actually brought into contact in the Y-axis direction mode, the constant current Io flows from the constant current source 12 into the transparent conductive film 2a through the electrode 10b, and from the contact points of the transparent conductive films 2a and 2b. It flows out to the 2b side. In the transparent conductive film 2b, the constant current Io is divided into a current Iy1 directed to the electrode 13a and a current Iy2 directed to the electrode 13b, and these currents Iy1 and Iy2 are measured by the current detectors 11a and 11b, respectively. The arithmetic processing circuit 8 calculates the Y coordinates of the contacts of the transparent conductive films 2a and 2b by substituting the measured values of the currents Iy1 and Iy2 into the above equation 3 and performing arithmetic processing.

  In the present embodiment, as in the first embodiment, the contact positions of the transparent conductive films 2a and 2b are obtained by performing arithmetic processing based on the measured values of the currents Ix1 and Ix2 in the X-axis direction, and the current in the Y-axis direction. It is obtained by performing arithmetic processing based on the measured values of Iy1 and Iy2. In this case, the current flowing out from the contact point of the transparent conductive films 2a and 2b to the transparent conductive film 2a side is always equal to the sum of the currents Ix1 and Ix2, and the current flowing out to the transparent electrode 2b side is equal to the sum of the currents Iy1 and Iy2. For this reason, even if a voltage drop at least depending on the transparent conductive film 2b in the X-axis direction mode and the transparent conductive film 2a in the Y-axis direction mode occurs, this does not affect the detection result of the contact position. In other words, the influence of such a voltage drop can be eliminated from the detection result of the contact position. Further, there is little interference between the electrodes 10a and 10b and the electrodes 13a and 13b. Therefore, the contact position detection accuracy can be improved with certainty.

  Hereinafter, a touch panel according to a third embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 17 shows an equivalent circuit obtained with the pointer member in contact with the touch panel TP, and FIG. 18 shows the equivalent circuit in an easy-to-understand manner. The touch panel TP is the same as that of the first embodiment except that the touch panel TP is configured to detect the position of the contact without using the constant current source 12 shown in FIG. For this reason, in FIG. 17, the same part as 1st Embodiment is represented with the same referential mark, and detailed description is abbreviate | omitted. Further, peripheral circuits having the same configuration are omitted in FIG.

  In this embodiment, a constant voltage source 14 such as a battery that outputs a voltage E2 is used instead of the constant current source 12, and is connected to the electrodes 10a and 10b on the transparent substrate 1a side. In this case, the current flowing out from the contact point of the transparent conductive films 2a and 2b to the transparent conductive film 2b varies depending on the wiring resistance of the transparent conductive films 2a and 2b and the peripheral circuit.

  For example, when the X-axis direction mode is set to obtain the X coordinate of the contact of the transparent conductive films 2a and 2b, the current flowing from the contact corresponds to the ratio of the resistances Rx1 and Rx2 to the currents Ix1 directed to the electrodes 9a and 9b, respectively. And Ix2.

  The X coordinate of the contact point of the transparent conductive films 2a and 2b is equal to the distance X1 from the left end of the transparent conductive film 2b where the X coordinate X = 0 as shown in FIG. Therefore, an arithmetic processing circuit similar to that in FIG. 3 can obtain the X coordinate of the contact point of the transparent conductive films 2a and 2b by substituting the measured values of the currents Ix1 and Ix2 into the above equation 2 and performing arithmetic processing.

  Further, when the Y-axis direction mode is set to obtain the Y coordinate of the contact points of the transparent conductive films 2a and 2b, the current flowing from the contact points to the electrodes 13a and 13b corresponding to the ratio of the resistances Ry1 and Ry2, respectively. Shunt to Iy1 and Iy2. Here, Ry1 is the resistance between the electrode 13a and the contact, and Ry2 is the resistance between the contact and the electrode 13b.

  The Y coordinate of the contact point of the transparent conductive films 2a and 2b is equal to the distance Y1 from the lower end of the transparent conductive film 2b where the Y coordinate Y = 0. Therefore, an arithmetic processing circuit similar to that shown in FIG. 3 can obtain the Y coordinate of the contact points of the transparent conductive films 2a and 2b by substituting the measured values of the currents Iy1 and Iy2 into the above-described equation 3 and performing arithmetic processing.

  In the present embodiment, as in the first embodiment, the contact positions of the transparent conductive films 2a and 2b are obtained by performing arithmetic processing based on the measured values of the currents Ix1 and Ix2 in the X-axis direction, and the current in the Y-axis direction. It is obtained by performing arithmetic processing based on the measured values of Iy1 and Iy2. In this case, the current flowing from the contact point of the transparent conductive films 2a and 2b to the transparent conductive film 2b side changes, but the position coordinates of the contact point can be specified from the ratio of the currents Ix1 and Ix2 or the ratio of the currents Iy1 and Iy2. Therefore, the contact position detection accuracy can be improved without requiring a constant current source.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the summary, it can change variously. Moreover, you may combine the above-mentioned modification arbitrarily.

  In the above-described embodiment, the two-dimensional coordinates of the contacts of the transparent conductive films 2a and 2b are detected as the contact positions. However, the one-dimensional coordinates may only be detected as the contact positions.

  8 and 9, the transceiver unit TR that performs transmission and reception is connected to the electrode 16 as a wireless communication circuit. However, at least one of a transmission circuit that performs only transmission and a reception circuit that performs only reception is wirelessly communicated. What is necessary is just to connect to the electrode 16 as a circuit. In addition, although the single electrode 19 is formed adjacent to the electrode 16, a plurality of electrodes may be formed adjacent to the electrode 16 as an antenna of an arbitrary wireless communication circuit.

  Further, the arithmetic processing circuit 8 shown in FIGS. 3, 10, 11, and 16 is configured to obtain the two-dimensional position coordinates of the contact by substituting each current measurement value into the arithmetic expression. You may comprise using the table memory which outputs the two-dimensional position coordinate of a contact with respect to a measured value.

  Furthermore, although the above-mentioned embodiment demonstrated the transmissive touch panel, this invention is applicable also to a non-transmissive touch panel.

It is a figure which shows the cross-sectional structure of the touchscreen which concerns on 1st Embodiment of this invention. It is a figure which shows the planar structure by the side of the 1st transparent substrate shown in FIG. It is a figure which shows the planar structure by the side of the 2nd transparent substrate shown in FIG. It is a figure which shows the liquid crystal display integrated with the touch panel shown in FIG. It is a figure which shows the state which made the pointer member contact the touch panel shown in FIG. It is a figure which shows the equivalent circuit of the touchscreen obtained when the X-axis direction mode is set in the state shown in FIG. It is a figure which shows the 1st modification which deform | transformed the planar structure by the side of the 1st transparent substrate shown in FIG. It is a figure which shows the 2nd modification which deform | transformed the planar structure by the side of the 1st transparent substrate shown in FIG. It is a figure which shows the 3rd modification which deform | transformed the planar structure by the side of the 1st transparent substrate shown in FIG. It is a figure which shows the 4th modification which deform | transformed the electric current detection structure by the side of the 2nd transparent substrate shown in FIG. It is a figure which shows the 5th modification which deform | transformed the planar structure and electric current detection structure by the side of the 2nd transparent substrate shown in FIG. It is a figure for demonstrating the optimal dimension of the high resistance area | region shown in FIG. It is a figure for demonstrating the optimal dimension of the low resistance area | region shown in FIG. It is a figure which shows the 5th modification which further deform | transformed the planar structure by the side of the 2nd transparent substrate shown in FIG. It is a figure for demonstrating the method to obtain the shape of the 2nd transparent conductive film used by the 5th and 6th modification shown in FIG. 11 and FIG. It is a figure which shows the circuit structure of the touchscreen which concerns on 2nd Embodiment of this invention. It is a figure which shows the equivalent circuit obtained in the state which made the pointer member contact the touchscreen which concerns on 3rd Embodiment of this invention. FIG. 18 is a diagram showing the equivalent circuit shown in FIG. 17 in an easy-to-understand manner. It is a figure which shows the cross-section of the conventional transmissive touch panel. It is a figure which shows the equivalent circuit obtained in the state which made the pointer member contact the touch panel shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a, 1b ... 1st and 2nd transparent substrate, 2a, 2b ... 1st and 2nd transparent conductive film, 6 ... Pointer member, 9a, 9b, 10a, 10b, 13a, 13b ... Electrode, 8 ... Arithmetic processing circuit, 11a, 11b ... current detector, 12 ... constant current source, Sa, Sb ... changeover switch, TP ... touch panel.

Claims (20)

The first conductive film having a uniform resistance distribution and the first conductive film are disposed so as to be slightly separated from the first conductive film and overlap the first conductive film, and locally contact the first conductive film by pressurization. A position detection device for a touch panel having a second conductive film, the first and second electrodes facing each other and connected to the outer edge of the first conductive film, and a current supply for supplying a current to the second conductive film And a first current flowing through the first conductive film from the contact point of the first and second conductive films toward the first electrode and a contact point of the first and second conductive films toward the second electrode A position detection device for a touch panel, comprising: a current detection circuit that measures a flowing second current; and a processing circuit that performs a process of specifying a position of the contact based on the measured values of the first and second currents. . Furthermore, the current detection circuit further includes third and fourth electrodes connected to the outer edge of the second conductive film so as to face each other in a direction different from the first and second electrodes, and the current detection circuit further includes a current from the current supply unit. Is switched from the second conductive film to the first conductive film, whereby the third current flowing through the second conductive film from the contact point of the first and second conductive films toward the third electrode, and A fourth current flowing through the second conductive film from a contact point of the first and second conductive films toward the fourth electrode; and the processing circuit is configured to measure the first and second currents in the processing. One of the two-dimensional position coordinates of the contact is obtained based on the measured value, and the other of the two-dimensional position coordinates of the contact is obtained based on the measured values of the third and fourth currents. To claim 1 Position detecting device for the touch panel. The first conductive film having a uniform resistance distribution and the first conductive film are disposed so as to be slightly separated from the first conductive film and overlap the first conductive film, and locally contact the first conductive film by pressurization. A position detecting device for a touch panel having a second conductive film, wherein the first and second electrodes are opposed to each other and connected to the outer edge of the first conductive film, and the first and second electrodes are in different directions. Third and fourth electrodes that face each other and are connected to the outer edge of the first conductive film, a current supply unit that supplies current to the second conductive film, and a contact point between the first and second conductive films, respectively. A current detection circuit for measuring first, second, third, and fourth currents flowing through the first conductive film toward the first electrode, the second electrode, the third electrode, and the fourth electrode; And the two-dimensional position of the contact based on the measured value of the second current A touch panel position detecting device comprising: a processing circuit that specifies one of the marks and performs processing for specifying the other of the two-dimensional position coordinates of the contact point based on the measured values of the third and fourth currents. . The touch panel position detecting device according to claim 3, wherein the second conductive film has a resistance distribution that is uniformly lower than that of the first conductive film. The touch panel position detecting device according to claim 3, wherein the current supply unit is connected to the second conductive film via a second conductive film electrode. The position detecting device for a touch panel according to claim 5, wherein the second conductive film electrode has a shape surrounding the second conductive film in a plane. The first and second conductive films have a rectangular shape, the first and second electrodes are disposed on two sides of the first conductive film facing in the first direction, and the third and fourth electrodes are The touch panel position detecting device according to claim 3, wherein the touch panel position detecting device is disposed on two sides of the first conductive film facing each other in a second direction perpendicular to the first direction. The current detection circuit includes first and second current detection units that are selectively connected to the first and second electrodes and the third and fourth electrodes, respectively. Position detector for touch panels. The current detection circuit includes first, second, third, and fourth current detection units connected to the first, second, third, and fourth electrodes, respectively. Touch panel position detector. The first conductive film has a shape in which four sides of a horizontally long rectangle are bent inward, and the first and second electrodes are adjacent to each other from two diagonals of the first conductive film facing each other on a first diagonal line. The third and fourth electrodes are arranged so as to extend from the two diagonals of the first conductive film facing each other on the second diagonal line to the vicinity of the centers of the two adjacent sides. The position detection device for a touch panel according to claim 3. The touch panel position detecting device according to claim 10, wherein the first conductive film is warped along an ellipse having an aspect ratio common to the rectangle. The position detection device for a touch panel according to claim 10, wherein the first conductive film includes a high resistance region and a low resistance region surrounding the high resistance region as the outer edge. The position detection device for a touch panel according to claim 12, wherein a distance from the short side of the rectangle to the high resistance region is larger than a distance from the long side of the rectangle to the high resistance region. The position detection device for a touch panel according to claim 12 or 13, wherein the width of the low resistance region on the long side of the rectangle is larger than the width of the low resistance region on the short side of the rectangle. The position detection device for a touch panel according to claim 10, wherein the first, second, third, and fourth electrodes are metal films formed on an outer edge of the first conductive film. The position detection device for a touch panel according to claim 6, wherein the second conductive film electrode also serves as an antenna of a wireless communication circuit, and is connected to the wireless communication circuit instead of the current supply unit by a switch unit. The touch panel position detecting apparatus according to claim 16, wherein at least one antenna electrode is formed adjacent to the second conductive film electrode. 4. The touch panel position detecting device according to claim 1, wherein the current supply unit is a constant current source. The touch panel position detection device according to claim 1, wherein the current supply unit is a voltage source. The touch panel position detecting device according to claim 1, wherein the first and second conductive films are transparent.

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