Touch panel

A touch panel includes an upper electrode substrate having a transparent conductive film formed thereon, a lower electrode substrate having a transparent conductive film formed thereon, two electrodes formed on the transparent conductive film of the upper electrode substrate, two electrodes formed on the transparent conductive film of the lower electrode substrate, an adhesive sheet bonding the upper electrode substrate and the lower electrode substrate to each other such that the transparent conductive films face each other, a film removed area formed on the upper electrode substrate by removing part of the transparent conductive film, the film removed area enclosing the two electrodes on the transparent conductive film of the upper electrode substrate, and an outer rim electrode formed on the transparent conductive film of the upper electrode substrate in such a manner as to surround the film removed area, wherein the film removed area forms a closed loop.

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 generally placed in front of the display. Touch panels are widely used in various applications because of their capability of allowing direct input 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, a five-wire type, and a diode type. In the four-wire type, an X-axis electrode is disposed on one of the upper electrode substrate and the lower electrode substrate, and a Y-axis electrode is disposed on the other substrate (see Patent Document 1, for example). In the five-wire type, an X-axis electrode and a Y-axis electrode 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).

A touch panel as described above is operated by a finger or the like coming into contact with the touch panel. The finger that is used to operate the touch panel may also come in contact with various other objects. Upon touching an object with static charge, the finger may be charged with static electricity. Operating a touch panel with the finger charged with static electricity results in the static charge of the finger flowing into the touch panel, thereby destroying a semiconductor device such as an integrated circuit chip used in the touch panel. As a result, the touch panel may be broken.

As a preventive measure, an anti-electrostatic sheet may be attached to the surface of a touch panel. Alternatively, the finger may be brought into contact with a highly conductive object prior to operating a touch panel, which serves to remove static charge from the finger. Then, the touch panel may be operated by the use of the finger.

The measures described above are associated with problems. For example, a complex process may become necessary to manufacture the touch panel, resulting in a cost increase. It may otherwise be burdensome to operate a touch panel, and, also, a mistake made with respect to the order of operations may cause the destruction of the touch panel. Further, these measures may not be sufficient as an anti-electrostatic measure.

Accordingly, there may be a need for a touch panel provided with a sufficient anti-electrostatic measure, which neither causes a cost increase nor requires cumbersome operating steps.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide a touch panel that substantially obviates one or more problems caused by the limitations and disadvantages of the related art.

According to an embodiment, a touch panel includes an upper electrode substrate having a transparent conductive film formed thereon, a lower electrode substrate having a transparent conductive film formed thereon, two electrodes formed on the transparent conductive film of the upper electrode substrate, two electrodes formed on the transparent conductive film of the lower electrode substrate, an adhesive sheet bonding the upper electrode substrate and the lower electrode substrate to each other such that the transparent conductive film of the upper electrode substrate and the transparent conductive film of the lower electrode substrate face each other, a transparent conductive film removed area formed on the upper electrode substrate by removing part of the transparent conductive film of the upper electrode substrate, the transparent conductive film removed area enclosing the two electrodes on the transparent conductive film of the upper electrode substrate, and an outer rim electrode formed on the transparent conductive film of the upper electrode substrate in such a manner as to surround the transparent conductive film removed area, wherein the transparent conductive film removed area forms a closed loop.

According to at least one embodiment, a sufficient anti-electrostatic measure can be taken at low cost.

DESCRIPTION OF THE PREFERRED 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.

A four-wire touch panel according to the present embodiment will be described with reference toFIG. 1andFIG. 2. The touch panel of the present embodiment includes an upper electrode substrate10, a lower electrode substrate20, an adhesive sheet30, and a flexible substrate40. The upper electrode substrate10and the lower electrode substrate20have a rectangular shape, and have a size of 15 cm by 20 cm, for example. InFIG. 1and similar figures, the upper electrode substrate10is illustrated as being transparent.

The upper electrode substrate10is formed based on a rectangular transparent substrate such as a transparent film or glass. A surface of the upper electrode substrate10(i.e., the lower surface inFIG. 1) has a transparent conductive film11made of ITO (i.e., tin-doped indium oxide) or the like formed thereon. The transparent conductive film11of the upper electrode substrate10has two electrodes12and13formed thereon that extend in the X-axis direction. The electrodes12and13are formed near the opposite sides, respectively, of the upper electrode substrate10extending in the X-axis direction. The two electrodes12and13are formed by screen printing using silver paste. One end of the electrode12has an electrode terminal part12aformed thereat. One end of the electrode13has an electrode terminal part13aformed thereat. The electrodes12and13serve to generate a potential distribution in the Y-axis direction on the upper electrode substrate10, and are also used as a potential detector for the purpose of detecting a coordinate point in the X-axis direction via the transparent conductive film11.

The transparent conductive film11on the upper electrode substrate10has a portion thereof removed that is a strip of 1-mm width along the perimeter of a rectangular area enclosing the electrodes12and13. The void generated by such removal constitutes a transparent conductive film removed area14. The transparent conductive film11remains on both the inner side and the outer side of the transparent conductive film removed area14. The transparent conductive film removed area14forms a closed loop that is made by removing the transparent conductive film11along the perimeter of the rectangular area enclosing the electrodes12and13. An outer rim electrode15is disposed on the transparent conductive film11outside the transparent conductive film removed area14, and has a rectangular shape surrounding the transparent conductive film removed area14. The outer rim electrode15is formed by screen printing using silver paste as a countermeasure against ESD (i.e., electrostatic discharge). In the present embodiment described above, the transparent conductive film removed area14forms a closed loop extending along the perimeter of a rectangular area enclosing the two electrodes12and13. The outer rim electrode15forms a closed loop having a rectangular shape surrounding the transparent conductive film removed area14. The transparent conductive film removed area14serves to isolate the transparent conductive film11inside the transparent conductive film removed area14and the transparent conductive film11outside the transparent conductive film removed area14from each other.

The lower electrode substrate20is formed based on a rectangular transparent substrate such as a transparent film or glass. A surface of the lower electrode substrate20(i.e., the upper surface inFIG. 1) has a transparent conductive film21made of ITO or the like formed thereon. The transparent conductive film21of the lower electrode substrate20has two electrodes22and23formed thereon that extend in the Y-axis direction. The electrodes22and23are formed near the opposite sides, respectively, of the lower electrode substrate20extending in the Y-axis direction. The electrodes22and23are formed by screen printing using silver paste. The electrodes22and23serve to generate a potential distribution in the X-axis direction on the lower electrode substrate20, and are also used as a potential detector for the purpose of detecting a coordinate point in the Y-axis direction via the transparent conductive film21.

The electrode22is coupled to an interconnection part22athat is formed to extend toward one of the two opposite sides of the lower electrode substrate20extending in the Y-axis direction. The electrode23is connected to an interconnection part23athat extends, along a side of the lower electrode substrate20extending in the X-axis direction, from one of the two opposite sides of the lower electrode substrate20extending in the Y-axis direction to the other one of the two opposite sides. The transparent conductive film21of the lower electrode substrate20has interconnection parts24and25formed thereon extending toward one of the two opposite sides of the lower electrode substrate20extending in the Y-axis direction. The interconnection parts24and25are coupled to the electrodes12and13, respectively, formed on the upper electrode substrate10. The interconnection parts22a,23a,24and25are formed by screen printing using silver paste.

The upper electrode substrate10and the lower electrode substrate20are attached to each other via the adhesive sheet30such that the transparent conductive film11of the upper electrode substrate10and the transparent conductive film21of the lower electrode substrate20face each other. The adhesive sheet30may be a double-faced tape having a thickness of 60 micrometers with adhesive layers formed on both faces thereof, and has a rectangular opening30aat the center thereof for the purpose of allowing functioning as a touch panel. Through holes30band30care formed through the adhesive sheet30near one of the two opposite sides of the adhesive sheet30extending in the Y-axis direction, thereby allowing respective couplings between the electrode terminal parts12aand13aof the electrodes12and13on the upper electrode substrate10and the interconnection parts24and25on the lower electrode substrate20.

As illustrated inFIG. 2, the flexible substrate40has an electrode terminal41formed on a first surface thereof coupled to the outer rim electrode15formed on the upper electrode substrate10, and has a plurality of electrode terminals42formed on a second surface thereof coupled to the respective interconnection parts22a,23a,24and25formed on the lower electrode substrate20. The electrode terminal41disposed on the first surface of the flexible substrate40and the outer rim electrode15disposed on the upper electrode substrate10are electrically coupled to each other via an anisotropic conductive film51. The electrode terminals42disposed on the second surface of the flexible substrate40and the interconnection parts22a,23a,24and25disposed on the lower electrode substrate20are electrically coupled to each other, respectively, via anisotropic conductive films52.

Further, the electrode terminal part12aof the electrode12disposed on the upper electrode substrate10and the interconnection part24disposed on the lower electrode substrate20are electrically coupled to each other via an electrically conductive adhesive that fills the through hole30bof the adhesive sheet30. Similarly, the electrode terminal part13aof the electrode13disposed on the upper electrode substrate10and the interconnection part25disposed on the lower electrode substrate20are electrically coupled to each other via an electrically conductive adhesive31that fills the through hole30cof the adhesive sheet30. These conductive adhesives serve as electrodes formed inside the through holes30band30c. In the present embodiment, the electrodes formed of the conductive adhesive31may sometimes be referred to as through electrodes.

In the present embodiment, the electrode terminal41on the first surface of the flexible substrate40is electrically coupled to the outer rim electrode15formed for anti-ESD purposes. Further, the electrode terminals42on the second surface of the flexible substrate40are electrically coupled to the interconnection parts22a,23a,24and25, respectively.

The interconnection part22ais part of the electrode22, and the interconnection part23ais part of the electrode23.

A description of the present embodiment has been given with respect to the case in which the conductive adhesive31is used. Alternatively, conductive paste containing minute metal particles made of Ag (silver), Au—C (gold-carbon), or the like may be used.

The above description has been directed to the case in which the electrode terminal41and the electrode terminals42are disposed on both surfaces of the flexible substrate40, respectively. Alternatively, the touch panel of the present embodiment may use two flexible substrates which have one or more electrode terminals formed on only one surface thereof. More specifically, as illustrated inFIG. 3, a flexible substrate40ahaving the electrode terminal41formed on one surface thereof and a flexible substrate40bhaving the electrode terminals42formed on one surface thereof may be used. Similarly to the previous case, the electrode terminal41formed on the surface of the flexible substrate40ais electrically coupled to the outer rim electrode15via the anisotropic conductive film51, and the electrode terminals42formed on the surface of the flexible substrate40bare electrically coupled to the interconnection parts22a,23a,24and25via the anisotropic conductive films52, respectively.

In the following, an advantage of the touch panel according to the present embodiment will be described.FIG. 4Ais an oblique perspective view of the upper electrode substrate10of the touch panel according to the present embodiment.FIG. 4Bis an oblique perspective view of an upper electrode substrate910of a touch panel that is illustrated for comparison purposes.

The upper electrode substrate910of the touch panel illustrated inFIG. 9Bhas a transparent conductive film911formed thereon similarly to the upper electrode substrate10of the present embodiment. The transparent conductive film911has two electrodes912and913formed thereon extending in the X-axis direction and situated near the two opposite sides, respectively, of the upper electrode substrate910extending in the X-axis direction. The two electrodes912and913are formed by screen printing using silver paste similarly to the touch panel of the present embodiment. An electrode interconnection part912ais formed at one end of the electrode912situated toward the positive X-axis direction, and extends toward one of the two opposite sides of the upper electrode substrate910extending in the Y-axis direction. An electrode interconnection part913ais formed at one end of the electrode913situated toward the positive X-axis direction, and extends toward one of the two opposite sides of the upper electrode substrate910extending in the Y-axis direction.

The transparent conductive film911on the upper electrode substrate910has a portion thereof removed that is a strip of 1-mm width along the perimeter of a rectangular area enclosing the electrodes912and913, thereby creating a transparent conductive film removed area914. In the example illustrated inFIG. 4B, however, the transparent conductive film removed area914has open ends914a, which create a gap through which the electrode interconnection parts912aand913aof the two electrodes912and913extend toward a side of the upper electrode substrate910.

An outer rim electrode915is disposed on the transparent conductive film911outside the transparent conductive film removed area914in such a manner as to surround the transparent conductive film removed area914. Similarly to the outer rim electrode15of the present embodiment, the outer rim electrode915is formed by screen printing using silver paste for anti-ESD purposes. The outer rim electrode915is formed in such a manner as to surround the transparent conductive film removed area914. Since the transparent conductive film removed area914extends toward a side of the upper electrode substrate910extending in the Y-axis direction, however, the outer rim electrode915has open ends at the points where the outer rim electrode915abuts on the ends914aof the transparent conductive film removed area914.

Due to the gap created by the open ends of the transparent conductive film removed area914in the touch panel illustrated inFIG. 4B, static electricity may flow into the touch panel along the two electrodes912and913through the gap of the transparent conductive film removed area914situated at one side of the upper electrode substrate910. Inflow of static electricity into the touch panel along the electrodes912and913may end up destroying the touch panel.

On the other hand, the transparent conductive film removed area14in the touch panel of the present embodiment as illustrated inFIG. 4Aforms a closed loop. With this configuration, the inner part of the transparent conductive film11having the electrodes12and13formed thereon is isolated by the transparent conductive film removed area14from the outer part of the transparent conductive film11having the outer rim electrode15formed thereon. This ensures that the transparent conductive film removed area14blocks static electricity. Static electricity flows along the outer rim electrode15without flowing into the two electrodes12and13from a side of the upper electrode substrate10, so that the effect of static electricity entering from a side of the touch panel is removed.

Accordingly, the touch panel of the present embodiment provides a highly effective anti-electrostatic measure at low cost.

The present application is based on and claims the benefit of priority of Japanese priority application No. 2014-005433 filed on Jan. 15, 2014, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.