Touch panel

A touch panel includes an upper electrode substrate having a rectangular shape and having an upper conductive film formed thereon, a lower electrode substrate having a rectangular shape and having a lower conductive film formed thereon, a first power feeding terminal, a second power feeding terminal, a third power feeding terminal, and a fourth power feeding terminal disposed on the lower conductive film at four respective corners of the lower electrode substrate, a first potential detecting unit configured to detect a potential of the second power feeding terminal, a second potential detecting unit configured to detect a potential of the fourth power feeding terminal, and a third potential detecting unit configured to detect a potential of the third power feeding terminal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosures herein relate to a touch panel.

2. Description of the Related Art

A touch panel (i.e., touchscreen panel) is an input device that allows input to be directly entered into a display, and is placed in front of the display. Touch panels are widely used in various applications because of their capability of allowing direct inputting based on visual information provided by the display.

A resistive-type touch panel is widely known in the art. The resistive-type touch panel includes an upper electrode substrate and a lower electrode substrate having respective transparent conductive films. These substrates are arranged such that the corresponding transparent conductive films face each other. When pressure is applied to a point on the upper electrode substrate, the transparent conductive films are brought into contact with each other, thereby allowing the position of the pressed point to be detected.

The resistive-type touch panel is classified into a four-wire-type and a five-wire-type. In the four-wire-type, X-axis electrodes are disposed on one of the upper electrode substrate and the lower electrode substrate, and Y-axis electrodes are disposed on the other substrate (see Patent Document 1, for example). In the five-wire-type, X-axis electrodes and Y-axis electrodes are both disposed on the lower electrode substrate while the upper electrode substrate serves as a probe for detecting voltage (see Patent Document 2, for example).

The four-wire-type touch panels include those which allow multiple points of contact to be detected (see Patent Document 4, for example).

There is no five-wire-type touch panel that allows multiple points of contact to be readily detected.

Accordingly, it may be desirable to provide a five-wire-type touch panel that allows multiple points of contact to be readily detected.

[Patent Document 7] Japanese National Publication of International Patent Application No. 2005-505065

[Patent Document 8] Japanese National Publication of International Patent Application No. 2011-502314

SUMMARY OF THE INVENTION

According to an embodiment, a touch panel includes an upper electrode substrate having a rectangular shape and having an upper conductive film formed thereon, a lower electrode substrate having a rectangular shape and having a lower conductive film formed thereon, a first power feeding terminal, a second power feeding terminal, a third power feeding terminal, and a fourth power feeding terminal disposed on the lower conductive film at four respective corners of the lower electrode substrate, a first switch situated between the second power feeding terminal and a ground potential, a second switch situated between the third power feeding terminal and the ground potential, a first resistor and a third switch that are series-connected between the second power feeding terminal and a power supply potential, a first potential detecting unit configured to detect a potential of the second power feeding terminal, a second resistor and a fourth switch that are series-connected between the fourth power feeding terminal and the power supply potential, a second potential detecting unit configured to detect a potential of the fourth power feeding terminal, a third resistor and a fifth switch that are series-connected between the third power feeding terminal and the power supply potential, and a third potential detecting unit configured to detect a potential of the third power feeding terminal.

According to an embodiment, a touch panel includes an upper electrode substrate having a rectangular shape and having an upper conductive film formed thereon, a lower electrode substrate having a rectangular shape and having a lower conductive film formed thereon, a first power feeding terminal, a second power feeding terminal, a third power feeding terminal, and a fourth power feeding terminal disposed on the lower conductive film at four respective corners of the lower electrode substrate, a first switch situated between the second power feeding terminal and a ground potential, a second switch situated between the third power feeding terminal and the ground potential, a third switch having a first terminal thereof coupled to the second power feeding terminal, a fourth switch having a first terminal thereof coupled to the fourth power feeding terminal, a first resistor having a first end thereof coupled to a second terminal of the third switch and to a second terminal of the fourth switch, a first potential detecting unit configured to detect a potential at a point between the first end of the first resistor and both the second terminal of the third switch and the second terminal of the fourth switch, a fifth switch having a first terminal thereof coupled to the fourth power feeding terminal, a sixth switch having a first terminal thereof coupled to the third power feeding terminal, a second resistor having a first end thereof coupled to a second terminal of the fifth switch and to a second terminal of the sixth switch, and a second potential detecting unit configured to detect a potential at a point between the first end of the second resistor and both the second terminal of the fifth switch and the second terminal of the sixth switch, wherein a second terminal of the first resistor and a second terminal of the second resistor are coupled to a power supply potential.

According to an embodiment, a touch panel includes an upper electrode substrate having a rectangular shape and having an upper conductive film formed thereon, a lower electrode substrate having a rectangular shape and having a lower conductive film formed thereon, a first power feeding terminal, a second power feeding terminal, a third power feeding terminal, and a fourth power feeding terminal disposed on the lower conductive film at four respective corners of the lower electrode substrate, a first potential detecting unit configured to detect at least one of a potential of the third power feeding terminal and a potential of the fourth power feeding terminal when the third and fourth power feeding terminals are coupled to a first potential, and the first and second power feeding terminals are coupled to a second potential, a second potential detecting unit configured to detect at least one of a potential of the second power feeding terminal and a potential of the fourth power feeding terminal when the second and fourth power feeding terminals are coupled to the first potential, and the first and third power feeding terminals are coupled to the second potential, and a third potential detecting unit configured to detect a potential of the upper conductive film.

According to at least one embodiment, a five-wire-type touch panel is provided that allows multiple points of contact to be readily detected.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments will be described by referring to the accompanying drawings. The same or similar elements are referred to by the same or similar numerals.

First Embodiment

In the following, a description will be given of a touch panel according to a first embodiment. This embodiment is directed to a five-wire-type touch panel that is capable of detecting two contact points.

With reference toFIG. 1, a description will be given of a touch panel according to the present embodiment. The touch panel of the present embodiment includes an upper electrode substrate10and a lower electrode substrate20. The upper electrode substrate10is a rectangular substrate made of glass or transparent resin material that has a transparent conductive film11made of ITO (Indium Tin Oxide) or the like formed thereon to serve as an upper conductive film. The lower electrode substrate20is a rectangular substrate made of glass or transparent resin material that has a transparent conductive film21made of ITO (Indium Tin Oxide) or the like formed thereon to serve as a lower conductive film. The upper electrode substrate10and the lower electrode substrate20are placed such that the transparent conductive film11and the transparent conductive film21face each other.

The four corners of the lower electrode substrate20have a first power feeding terminal31, a second power feeding terminal32, a third power feeding terminal33, and a fourth power feeding terminal34formed on the transparent conductive film21. In the present embodiment, the straight line connecting between the first power feeding terminal31and the second power feeding terminal32and the straight line connecting between the third power feeding terminal33and the fourth power feeding terminal34are both parallel to the Y axis. Further, the straight line connecting between the first power feeding terminal31and the third power feeding terminal33and the straight line connecting between the second power feeding terminal32and the fourth power feeding terminal34are both parallel to the X axis.

The first power feeding terminal31is coupled to the ground, and receives a voltage of 0 V. The second power feeding terminal32is coupled to a first terminal of a first switch SW1, and a second terminal of the first switch SW1is coupled to the ground potential. The third power feeding terminal33is coupled to a first terminal of a second switch SW2, and a second terminal of the second switch SW2is coupled to the ground potential.

The second power feeding terminal32is coupled to the power supply potential through a third switch SW3and a first resistor41that are series-connected. The third power feeding terminal33is coupled to the power supply potential through a sixth switch SW6and a second resistor42that are series-connected. The fourth power feeding terminal34is coupled to the power supply potential through a fourth switch SW4and the first resistor41that are series-connected. The fourth power feeding terminal34is further coupled to the power supply potential through a fifth switch SW5and the second resistor42that are series-connected.

Namely, the second power feeding terminal32is coupled to a first terminal of the third switch SW3, and the fourth power feeding terminal34is coupled to a first terminal of the fourth switch SW4, with a second terminal of the third switch SW3and a second terminal of the fourth switch SW4being coupled to each other. Further, the second terminal of the third switch SW3and the second terminal of the fourth switch SW4are coupled to one end of the first resistor41, and the other end of the first resistor41is coupled to the power supply potential. Moreover, a first potential detecting unit51is coupled to a connection point between the second terminal of the third switch SW3, the second terminal of the fourth switch SW4, and the above-noted one end of the first resistor41.

The third power feeding terminal33is coupled to a first terminal of the sixth switch SW6, and the fourth power feeding terminal34is coupled to a first terminal of the fifth switch SW5, with a second terminal of the sixth switch SW6and a second terminal of the fifth switch SW5being coupled to each other. Further, the second terminal of the sixth switch SW6and the second terminal of the fifth switch SW5are coupled to one end of the second resistor42, and the other end of the second resistor42is coupled to the power supply potential. Moreover, a second potential detecting unit52is coupled to a connection point between the second terminal of the sixth switch SW6, the second terminal of the fifth switch SW5, and the above-noted one end of the second resistor42.

In order to perform a measurement in the X-axis direction in the touch panel of the present embodiment, the first switch SW1is closed, and the second switch SW2is open, with the third switch SW3and the fourth switch SW4being open, and the fifth switch SW5and the sixth switch SW6being closed. With this arrangement, as illustrated inFIG. 2, the first power feeding terminal31and the second power feeding terminal32are coupled to the ground, and the third power feeding terminal33and the fourth power feeding terminal34are coupled to the power supply potential through the second resistor42. As a result, the transparent conductive film21of the lower electrode substrate20has a potential gradient in the X-axis direction.

In order to perform a measurement in the Y-axis direction in the touch panel of the present embodiment, the first switch SW1is open, and the second switch SW2is closed, with the third switch SW3and the fourth switch SW4being closed, and the fifth switch SW5and the sixth switch SW6being open. With this arrangement, as illustrated inFIG. 3, the first power feeding terminal31and the third power feeding terminal33are coupled to the ground, and the second power feeding terminal32and the fourth power feeding terminal34are coupled to the power supply potential through the first resistor41. As a result, the transparent conductive film21of the lower electrode substrate20has a potential gradient in the Y-axis direction.

In the touch panel of the present embodiment, as illustrated inFIG. 2, a potential gradient is generated in the X-axis direction, and the second potential detecting unit52is used to detect a voltage divided by the second resistor42and the resistance of the touch panel. With the resistance of the second resistor42being known, the resistance of the touch panel is derived from the detected divided voltage. The resistance of the touch panel is the resistance of the transparent conductive film21in the X-axis direction between the pair of the third power feeding terminal33and the fourth power feeding terminal34and the pair of the first power feeding terminal31and the second power feeding terminal32when there is no touch or when there is a single point of touch. It may be noted that in the case of pressure being applied at a single point on the upper electrode substrate10, the transparent conductive film11and the transparent conductive film21come in contact with each other only at this single point of touch. The resistance of the touch panel as measured by the above-noted configuration is not affected by the presence of such a single point touch.

In the case of pressure being applied at two points on the upper electrode substrate10, on the other hand, the transparent conductive film11and the transparent conductive film21come in contact with each other at these two points of touch, between which a portion of the transparent conductive film11and a portion of the transparent conductive film21are parallel-connected to form parallel-connected resistances. The resistance of the touch panel as measured by the above-noted configuration thus involves such parallel-connected resistances, and is responsive to the distance between the two points of touch.

Further, as illustrated inFIG. 3, a potential gradient is generated in the Y-axis direction, and the first potential detecting unit51is used to detect a voltage divided by the first resistor41and the resistance of the touch panel. With the resistance of the first resistor41being known, the resistance of the touch panel is derived from the detected divided voltage. The resistance of the touch panel is the resistance of the transparent conductive film21in the Y-axis direction between the pair of the second power feeding terminal32and the fourth power feeding terminal34and the pair of the first power feeding terminal31and the third power feeding terminal33when there is no touch or when there is a single point of touch. The resistance of the touch panel as measured by the above-noted configuration is not affected by the presence of a single point touch.

In the case of pressure being applied at two points on the upper electrode substrate10, on the other hand, the transparent conductive film11and the transparent conductive film21come in contact with each other at these two points of touch, between which a portion of the transparent conductive film11and a portion of the transparent conductive film21are parallel-connected to form parallel-connected resistances. The resistance of the touch panel as measured by the above-noted configuration thus involves such parallel-connected resistances, and is responsive to the distance between the two points of touch.

With the above-described arrangement, the distance as well as a change in the distance between two points of contact such as points A and B illustrated inFIG. 4andFIG. 5, for example, are detectable based on the resistance between the point A and the point B. This arrangement thus enables the detection of a multi-touch operation.FIG. 4illustrates a case in which the second potential detecting unit52detects a potential when a potential gradient in the X-axis direction is generated as illustrated inFIG. 2.FIG. 5illustrates a case in which the first potential detecting unit51detects a potential when a potential gradient in the Y-axis direction is generated as illustrated inFIG. 3.

Second Embodiment

In the following, a description will be given of a touch panel according to a second embodiment. This embodiment is directed to a five-wire-type touch panel which includes the upper electrode substrate10and the lower electrode substrate20, and which enables the detection of positions of two contact points when there are two points of touch on the touch panel. With this arrangement, multi-touch gestures can be identified when there are two points of touch on the touch panel.

With reference toFIG. 6, a description will be given of a touch panel according to the present embodiment. In the touch panel of the present embodiment, the upper electrode substrate10is a rectangular substrate made of glass or transparent resin material that has a transparent conductive film11made of ITO or the like formed thereon to serve as an upper conductive film. The lower electrode substrate20is a rectangular substrate made of glass or transparent resin material that has a transparent conductive film21made of ITO (Indium Tin Oxide) or the like formed thereon to serve as a lower conductive film. The upper electrode substrate10and the lower electrode substrate20are placed such that the transparent conductive film11and the transparent conductive film21face each other.

The four corners of the lower electrode substrate20have a first power feeding terminal31, a second power feeding terminal32, a third power feeding terminal33, and a fourth power feeding terminal34formed on the transparent conductive film21. In the present embodiment, the straight line connecting between the first power feeding terminal31and the second power feeding terminal32and the straight line connecting between the third power feeding terminal33and the fourth power feeding terminal34are both parallel to the Y axis. Further, the straight line connecting between the first power feeding terminal31and the third power feeding terminal33and the straight line connecting between the second power feeding terminal32and the fourth power feeding terminal34are both parallel to the X axis.

The first power feeding terminal31is coupled to the ground, and receives a voltage of 0 V. The second power feeding terminal32is coupled to a first terminal of a first switch SW1, and a second terminal of the first switch SW1is coupled to the ground potential. The third power feeding terminal33is coupled to a first terminal of a second switch SW2, and a second terminal of the second switch SW2is coupled to the ground potential.

The second power feeding terminal32is coupled to the power supply potential through a first resistor141and a third switch SW13that are series-connected. The third power feeding terminal33is coupled to the power supply potential through a fourth resistor144and a sixth switch SW16that are series-connected. The fourth power feeding terminal34is coupled to the power supply potential through a second resistor142and a fourth switch SW14that are series-connected. The fourth power feeding terminal34is also coupled to the power supply potential through a third resistor143and a fifth switch SW15that are series-connected.

Namely, the second power feeding terminal32is coupled to one end of the first resistor141, and the other end of the first resistor141is coupled to a first terminal of the third switch SW13, with a second terminal of the third switch SW13being coupled to the power supply potential. Further, a connection point between the second power feeding terminal32and the above-noted one end of the first resistor141is coupled to a first potential detecting unit151. With this arrangement, the first potential detecting unit151detects the potential of the second power feeding terminal32.

Moreover, the third power feeding terminal33is coupled to one end of the fourth resistor144, and the other end of the fourth resistor144is coupled to a first terminal of the sixth switch SW16, with a second terminal of the sixth switch SW16being coupled to the power supply potential. Further, a connection point between the third power feeding terminal33and the above-noted one end of the fourth resistor144is coupled to a fourth potential detecting unit154. With this arrangement, the fourth potential detecting unit154detects the potential of the third power feeding terminal33.

Moreover, the fourth power feeding terminal34is coupled to one end of the second resistor142, and the other end of the second resistor142is coupled to a first terminal of the fourth switch SW14, with a second terminal of the fourth switch SW14being coupled to the power supply potential. Further, a connection point between the fourth power feeding terminal34and the above-noted one end of the second resistor142is coupled to a second potential detecting unit152. With this arrangement, the second potential detecting unit152detects the potential of the fourth power feeding terminal34.

Moreover, the fourth power feeding terminal34is coupled to one end of the third resistor143, and the other end of the third resistor143is coupled to a first terminal of the fifth switch SW15, with a second terminal of the fifth switch SW15being coupled to the power supply potential. Further, a connection point between the fourth power feeding terminal34and the above-noted one end of the third resistor143is coupled to a third potential detecting unit153. With this arrangement, the third potential detecting unit153detects the potential of the fourth power feeding terminal34.

In order to perform a measurement in the X-axis direction in the present embodiment, the first switch SW1is closed, and the second switch SW2is open, with the third switch SW13and the fourth switch SW14being open, and the fifth switch SW15and the sixth switch SW16being closed. With this arrangement, as illustrated inFIG. 7, the first power feeding terminal31and the second power feeding terminal32are coupled to the ground, with the third power feeding terminal33being coupled to the power supply potential through the fourth resistor144, and the fourth power feeding terminal34being coupled to the power supply potential through the third resistor143. As a result, the transparent conductive film21of the lower electrode substrate20has a potential gradient in the X-axis direction. In this state, the third potential detecting unit153and the fourth potential detecting unit154perform potential detections.

In order to perform a measurement in the Y-axis direction, the first switch SW1is open, and the second switch SW2is closed, with the third switch SW13and the fourth switch SW14being closed, and the fifth switch SW15and the sixth switch SW16being open. With this arrangement, as illustrated inFIG. 8, the first power feeding terminal31and the third power feeding terminal33are coupled to the ground, with the second power feeding terminal32being coupled to the power supply potential through the first resistor141, and the fourth power feeding terminal34being coupled to the power supply potential through the second resistor142. As a result, the transparent conductive film21of the lower electrode substrate20has a potential gradient in the Y-axis direction. In this state, the first potential detecting unit151and the second potential detecting unit152perform potential detections.

Subsequently, the coordinate positions of two points of touch on the touch panel are calculated based on the respective potentials detected by the third potential detecting unit153and the fourth potential detecting unit154and the respective potentials detected by the first potential detecting unit151and the second potential detecting unit152. With this arrangement, multi-touch gestures can be identified when there are two points of touch.

In the present embodiment, the first resistor141may have a resistance equal to the resistance between the second power feeding terminal32and the first power feeding terminal31, and the second resistor142may have a resistance equal to the resistance between the fourth power feeding terminal34and the third power feeding terminal33. Further, the third resistor143may have a resistance equal to the resistance between the fourth power feeding terminal34and the second power feeding terminal32, and the fourth resistor144may have a resistance equal to the resistance between the third power feeding terminal33and the first power feeding terminal31.

Third Embodiment

In the following, a description will be given of a touch panel according to a third embodiment. The touch panel of this embodiment is directed to a configuration in which the numbers of resistors, potential detecting units, and switches are reduced compared with the touch panel of the second embodiment. The present embodiment thus provides a touch panel having the same or similar functions as the touch panel of the second embodiment at a lower cost.

With reference toFIG. 9, a description will be given of the touch panel according to the present embodiment. In the touch panel of the present embodiment, the first power feeding terminal31is coupled to the ground, and receives a voltage of 0 V. The second power feeding terminal32is coupled to a first terminal of a first switch SW1, and a second terminal of the first switch SW1is coupled to the ground potential. The third power feeding terminal33is coupled to a first terminal of a second switch SW2, and a second terminal of the second switch SW2is coupled to the ground potential.

The second power feeding terminal32is coupled to the power supply potential through a first resistor241and a third switch SW23that are series-connected. The third power feeding terminal33is also coupled to the power supply potential through a third resistor243and a fifth switch SW25that are series-connected. The fourth power feeding terminal34is coupled to the power supply potential through a second resistor242and a fourth switch SW24that are series-connected.

Namely, the second power feeding terminal32is coupled to one end of the first resistor241, and the other end of the first resistor241is coupled to a first terminal of the third switch SW23, with a second terminal of the third switch SW23being coupled to the power supply potential. Further, a connection point between the second power feeding terminal32and the above-noted one end of the first resistor241is coupled to a first potential detecting unit251. With this arrangement, the first potential detecting unit251detects the potential of the second power feeding terminal32.

Moreover, the third power feeding terminal33is coupled to one end of the third resistor243, and the other end of the third resistor243is coupled to a first terminal of the fifth switch SW25, with a second terminal of the fifth switch SW25being coupled to the power supply potential. Further, a connection point between the third power feeding terminal33and the above-noted one end of the third resistor243is coupled to a third potential detecting unit253. With this arrangement, the third potential detecting unit253detects the potential of the third power feeding terminal33.

Moreover, the fourth power feeding terminal34is coupled to one end of the second resistor242, and the other end of the second resistor242is coupled to a first terminal of the fourth switch SW24, with a second terminal of the fourth switch SW24being coupled to the power supply potential. Further, a connection point between the fourth power feeding terminal34and the above-noted one end of the second resistor242is coupled to a second potential detecting unit252. With this arrangement, the second potential detecting unit252detects the potential of the fourth power feeding terminal34.

In other words, the present embodiment uses the second potential detecting unit252that serves the functions of both the second potential detecting unit152and the third potential detecting unit153of the second embodiment. Further, the second resistor242serves the functions of both the second resistor142and the third resistor143of the second embodiment. The fourth switch SW24serves the functions of both the fourth switch SW14and the fifth switch SW15of the second embodiment.

In the present embodiment, the first resistor241may have a resistance equal to the resistance between the second power feeding terminal32and the first power feeding terminal31, and the second resistor242may have a resistance equal to the resistance between the fourth power feeding terminal34and the third power feeding terminal33. Further, the third resistor243may have a resistance equal to the resistance between the fourth power feeding terminal34and the second power feeding terminal32, or may have a resistance equal to the resistance between the third power feeding terminal33and the first power feeding terminal31.

Further, the first resistor241of the present embodiment corresponds to the first resistor141of the second embodiment, and the third resistor243corresponds to the fourth resistor144of the second embodiment. Further, the third switch SW23of the present embodiment corresponds to the third switch SW13of the second embodiment, and the fifth switch SW25corresponds to the sixth switch SW16of the second embodiment. Further, the first potential detecting unit251of the present embodiment corresponds to the first potential detecting unit151of the second embodiment, and the third potential detecting unit253corresponds to the fourth potential detecting unit154of the second embodiment.

In the present embodiment, the second resistor242serves the functions of both the second resistor142and the third resistor143of the touch panel of the second embodiment. The second potential detecting unit252serves the functions of both the second potential detecting unit152and the third potential detecting unit153of the touch panel of the second embodiment. Further, the fourth switch SW24serves the functions of both the fourth switch SW14and the fifth switch SW15of the touch panel of the second embodiment.

Configurations other than those described above are the same as or similar to those of the second embodiment.

Fourth Embodiment

In a typical five-wire-type touch panel, a low resistance pattern is formed on the perimeter of the transparent conductive film21on the surface thereof facing toward the glass, thereby providing a homogeneous potential distribution. When pressure is applied to the touch panel at two points of touch, the transparent conductive film11and the transparent conductive film21form parallel-connected resistances whose combined resistance varies in response to the positions of the two points of touch. A change in the combined resistance is detected by an external apparatus by measuring a total resistance including the resistance of the low resistance pattern, so that the magnitude of the detected change is very small and may be smaller than a few ohms. It may be noted that the panel resistance ranges from tens of ohms to hundreds of ohms.

Detecting such a small resistance change as a change in the voltage divided by a potential divider using a fixed resistance may be difficult because the divided voltage may exhibit a change of only a few millivolts at the maximum. Accordingly, there is a need to amplify the divided voltage to a detectable range. When the ratio of the fixed resistance to the panel resistance is 1 to 1, the divided voltage is 2.5 V in the case of a power supply voltage of 5 V. Amplifying such a voltage in a straightforward manner would produce a voltage ranging from tens of voltages to hundreds of voltages, which is difficult to handle. In consideration of this, a voltage of 2.5 V is maintained as a reference voltage, and only a change from this reference voltage is obtained by use of a differential amplifier. Further, a divided voltage of 2.5 V, which varies due to variation in the panel resistance or the fixed resistance, is sampled and held in a given environment by use of a sample and hold circuit.

In the following, a fourth embodiment will be described. The touch panel of this embodiment employs a sample and hold circuit and a differential amplifier situated between a power feeding terminal and a resistor, and further employs a potential detecting unit to measure the output of the differential amplifier. This arrangement enables the accurate detection of the positions of touch as well as the types of gestures by amplifying a detected minute potential change.

With reference toFIG. 10, a description will be given of the touch panel according to the present embodiment. A description of the present embodiment will be given by referring to an example in which the sample and hold circuit and the differential amplifier are employed in the touch panel of the second embodiment. This is not a limiting example, and the configuration of the present embodiment is also applicable to the touch panels of the first and third embodiments.FIG. 10illustrates an example in which the sample and hold circuit and the differential amplifier are situated between the first resistor141and the second power feeding terminal32disposed on the lower electrode substrate20. The same or similar configuration is also employed with respect to the path between third power feeding terminal33and the fourth resistor144, the path between the fourth power feeding terminal34and the second resistor142, and the path between the fourth power feeding terminal34and the third resistor143.

In the present embodiment, an input terminal of a sample and hold circuit360and one of the input terminals of a differential amplifier370are connected to the path between the first resistor141and the second power feeding terminal32disposed on the lower electrode substrate20. The sample and hold circuit360includes a sample and hold switch361. A sample and hold control unit362situated in a controller or the like controls the operation of the sample and hold switch361. The sample and hold circuit360serves to sample and hold a potential that is observed when there is no touch on the touch panel by a finger or the like. Namely, the sample and hold switch361is closed when the touch panel is free of touch by a finger or the like, so that the sample and hold circuit360samples a potential as observed at the input terminal thereof in such a state. With this arrangement, the sample and hold circuit360samples and holds the potential as observed when the touch panel is free of touch by a finger or the like. Subsequently, the sample and hold switch361is opened. Operations on the touch panel are performed in the state in which the sample and hold switch361is open. In this state, the output terminal of the sample and hold circuit360provides the potential as observed when there is no touch on the touch panel by a finger or the like.

The output terminal of the sample and hold circuit360is connected to one of the input terminals of the differential amplifier370, and the other one of the input terminals of the differential amplifier370receives a potential observed at a point between the first resistor141and the second power feeding terminal32. The differential amplifier370amplifies a difference between the potentials input into the respective input terminals to produce an amplified difference at the output terminal of the differential amplifier370. The signal output from the output terminal of the differential amplifier370is supplied to the first potential detecting unit151.

In the present embodiment, the signal output from the output terminal of the differential amplifier370is a result of amplifying a difference between the potentials input into the respective input terminals of the differential amplifier370. Accordingly, the first potential detecting unit151detects a signal exhibiting a large change obtained by amplifying a change in the potentials. With this arrangement, the positions of touch points and the types of gestures are detected with improved accuracy even when there are multiple touch points on the touch panel.

In the present embodiment, another sample and hold circuit and another differential amplifier are also situated between the third power feeding terminal33and the fourth resistor144. The output of this differential amplifier situated between the third power feeding terminal33and the fourth resistor144is supplied to the fourth potential detecting unit154. Further, another sample and hold circuit and another differential amplifier are also situated between the fourth power feeding terminal34and the second resistor142. The output of this differential amplifier situated between the fourth power feeding terminal34and the second resistor142is supplied to the second potential detecting unit152. Moreover, another sample and hold circuit and another differential amplifier are also situated between the fourth power feeding terminal34and the third resistor143. The output of this differential amplifier situated between the fourth power feeding terminal34and the third resistor143is supplied to the third potential detecting unit153.

Fifth Embodiment

In the following, a fifth embodiment will be described. A touch panel of the present embodiment is directed to a configuration that has the function to detect a single point of touch on the touch panel of the second embodiment. The present embodiment will be described by referring to the touch panel of the second embodiment as an example. This is not a limiting example, and the present embodiment is also applicable to the touch panels of the first and third embodiments.

The touch panel of the present embodiment includes a multi-touch detecting circuit401for detecting two or more points of touch and a single-touch detecting circuit402for detecting a single point of touch. The multi-touch detecting circuit401of the present embodiment is the same as or similar to the configuration employed in the touch panel of the second embodiment.

The single-touch detecting circuit402includes a seventh switch SW47, an eighth switch SW48, a ninth switch SW49, and a tenth switch SW50.

Specifically, the second power feeding terminal32on the lower electrode substrate20is coupled to a first terminal of the seventh switch SW47, and a second terminal of the seventh switch SW47is coupled to the power supply potential. The first terminal of the first switch SW1and the first terminal of the seventh switch SW47are coupled to each other. The first switch SW1and the seventh switch SW47are series-connected between the ground potential and the power supply potential.

The third power feeding terminal33is coupled to a first terminal of the eighth switch SW48, and a second terminal of the eighth switch SW48is coupled to the power supply potential. The first terminal of the second switch SW2and the first terminal of the eighth switch SW48are coupled to each other. The second switch SW2and the eighth switch SW48are series-connected between the ground potential and the power supply potential.

The fourth power feeding terminal34is coupled to a first terminal of the ninth switch SW49, and a second terminal of the ninth switch SW49is coupled to the power supply potential. The first power feeding terminal31is coupled to a first terminal of the tenth switch SW50, and a second terminal of the tenth switch SW50is coupled to the ground potential.

A description will be given of position detection in the touch panel of the present embodiment with reference toFIGS. 12A through 12C.

A description will first be given of position detection in the case of multi-touch by referring toFIG. 12A. In this case, the seventh switch SW47, the eighth switch SW48, and the ninth switch SW49are open, and the tenth switch SW50is closed.

In order to perform a measurement in the X-axis direction in the this case, the first switch SW1is closed, and the second switch SW2is open, with the third switch SW13and the fourth switch SW14being open, and the fifth switch SW15and the sixth switch SW16being closed.

In order to perform a measurement in the Y-axis direction, the first switch SW1is open, and the second switch SW2is closed, with the third switch SW13and the fourth switch SW14being closed, and the fifth switch SW15and the sixth switch SW16being open.

A description will next be given of the position detection of a single point of touch and the position detection of a midpoint between two points of touch by referring toFIG. 12B. In this case, the third switch SW13, the fourth switch SW14, and the fifth switch SW15, and the sixth switch SW16are open.

In order to perform a measurement in the X-axis direction in the this case, the first switch SW1is closed, and the second switch SW2is open, with the seventh switch SW47being open, the eighth switch SW48and the ninth switch SW49being closed, and the tenth switch SW50being closed. With the switches being in the above-noted states, the third power feeding terminal33and the fourth power feeding terminal34are set to the power supply potential, and the first power feeding terminal31and the second power feeding terminal32are set to the ground potential, so that a potential gradient in the X-axis direction is formed in the transparent conductive film21. When pressure is applied to the touch panel, the transparent conductive film11comes in contact with the transparent conductive film21. A detecting unit200connected to the transparent conductive film11detects a potential generated by such contact with the transparent conductive film21that is responsive to the position(s) of contact in the X-axis direction.

In order to perform a measurement in the Y-axis direction, the first switch SW1is open, and the second switch SW2is closed, with the seventh switch SW47being closed, the eighth switch SW48being open, and the ninth switch SW49and the tenth switch SW50being closed. With the switches being in the above-noted states, the second power feeding terminal32and the fourth power feeding terminal34are set to the power supply potential, and the first power feeding terminal31and the third power feeding terminal33are set to the ground potential, so that a potential gradient in the Y-axis direction is formed in the transparent conductive film21. When pressure is applied to the touch panel, the transparent conductive film11comes in contact with the transparent conductive film21. The detecting unit200connected to the transparent conductive film11detects a potential generated by such contact with the transparent conductive film21that is responsive to the position(s) of contact in the Y-axis direction.

A description will further be given of the sampling and holding of a potential when the touch panel of the fourth embodiment is free of touch by a finger or the like by referring toFIG. 12C. In this case, the switches are set in the same manner as in the case of detecting the positions of multi-touch points. That is, the seventh switch SW47, the eighth switch SW48, and the ninth switch SW49are open, and the tenth switch SW50is closed.

In order to perform a sample-and-hold operation in the X-axis direction in the this case, the first switch SW1is closed, and the second switch SW2is open, with the third switch SW13and the fourth switch SW14being open, and the fifth switch SW15and the sixth switch SW16being closed.

In order to perform a sample-and-hold operation in the Y-axis direction, the first switch SW1is open, and the second switch SW2is closed, with the third switch SW13and the fourth switch SW14being closed, and the fifth switch SW15and the sixth switch SW16being, open.

The present application is based on Japanese priority application No. 2014-034476 filed on Feb. 25, 2014, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.