Electronic device and touch panel for same

An electronic device includes a shell and a touch panel located in the shell. The touch panel includes a touch sensing unit, a signal transmitting circuit, a signal guiding circuit, a protection unit, and a driving unit. The signal transmitting circuit is electrically connected to the touch sensing unit and the driving unit. The signal guiding circuit surrounds the touch sensing unit and the signal transmitting circuit. The protection unit is electrically connected to the signal guiding circuit and ground. At least one switch signal is outputted from the driving unit and transmitted to the signal transmitting circuit and the signal guiding circuit. An external interference signal is received by the signal guiding circuit and guided to ground via the protection unit.

BACKGROUND

1. Technical Field

The disclosure relates to an electronic device and a touch panel.

2. Description of Related Art

In touch panels, the signal for determining a touch may be susceptible to interference by static electricity or other signals which reduces the quality of the touch-sensitivity of the touch panel.

DETAILED DESCRIPTION

Reference will now be made to the drawings to describe various embodiments of the present disclosure in detail, wherein like numerals refer to like elements throughout.

FIG. 1shows one embodiment of an electronic device10. The electronic device10includes a shell11and a touch panel12located in the shell11. The electronic device can be a mobile communication device with touch function. In the embodiment, the shell11consists of a cover110and a bottom112.

FIG. 2shows that the touch panel12includes a touch sensing unit121, a signal transmitting circuit122, a signal guiding circuit123, a protection unit124, and a driving unit125. The touch panel12can be a capacitive, resistance, or an optical type touch panel.

The touch sensing unit121may include a conductive film, a conductive glass, or an optical element, such as an infrared transceiver.

The signal transmitting circuit122is electrically connected to the touch sensing unit121and the driving unit125. The signal guiding circuit123surrounds the signal transmitting circuit and electrically connected to the driving unit125. The signal transmitting circuit122and the signal guiding circuit123can be a printed circuit that is located or formed on the substrate.

In one embodiment, the impedance of the signal guiding circuit123is smaller than the impedance of the signal transmitting circuit122. The line width of the signal guiding circuit123is greater than the line width of the signal transmitting circuit122to reduce the impedance. In the circuit, electrons will be passed via a low impedance path, most of the external interference signal than can be easily guided by the signal guiding circuit123directed to the protection unit124. In addition, the material of the signal guiding circuit123can be a low impedance material, for example, copper, silver, or graphene.

The signal transmitting circuit122further includes a plurality of electrodes122ain contact with the touch sensing unit121. Its detailed description will be described hereinafter.

The protection unit124is electrically connected to the signal guiding circuit123and ground126. The external interference signal is guided to ground via the protection unit124to avoid external interference signal affecting the functionality of the touch panel. The protection unit124may include at least one high-level trigger element, which can be an overvoltage protection element. The overvoltage protection element is such as a zener diode, a transient voltage suppressor (TVS), a varistor, or a multilayer varistor. These components will be turned on if the signal level on the circuit has a factory preset level.

The driving unit125outputs at least one switching signal delivered to the signal transmitting circuit122and the signal guiding circuit123. In the embodiment, the switching signal can be a pulse signal. The switching signal transmitted on the signal transmitting circuit122and the switching signal transmitted on the signal guiding circuit123are the signal with the similar phase and amplitude, that are showing inFIGS. 3A and 3B. The kind of switching signal can reduce the capacitance effect generated between the signal transmitting circuit122and the signal guiding circuit123, thereby reducing the capacitive load of the signal transmitting circuit122. The capacitive load reduction can also reduce the load on the driving unit125, and thus save energy.

When the electronic device10is used close to the external interference signal (e.g., static electricity or high-level voltage), the external interference signal may enter into the electronic device10via the edge of the housing11. In one embodiment, the signal guiding circuit123is located on the periphery of the signal transmitting circuit122and the touch sensing unit121. The signal guiding circuit123guides most of the external interfering signal to the ground via the protection unit124to eliminate external interference signals causing functional impact of the electronic device10.

In general, the external interference signal is a high-level signal which can turn on the protection unit124and be guided to ground126via the protection unit124when the external interference signal is received by the signal guiding circuit123.

In one embodiment, the touch sensing unit121is a capacitive touch sensing unit and includes structural characteristics as shown inFIGS. 4, 5A and 5B.

FIG. 4shows a cross-sectional diagram of a surface capacitive touch panel ofFIG. 2. Referring toFIGS. 2 and 4, the surface capacitive touch panel includes a substrate121aand a conductive thin film121blocated on the substrate121a. The substrate121amay be glass or a flexible substrate. The conductive film121bhas anisotropic impedance, which means that the conductive film121bhas a different impedance characteristic in two different directions, a low impedance direction and a high impedance direction. In the embodiment, the direction of the low impedance and high impedance direction are substantially perpendicular to each other.

The conductive film121bincludes a carbon nanotube (CNT) film. The manufacturing process of the CNT films begins with forming the carbon nanotubes first. The carbon nanotubes are pulled one by one according to well known stretching technologies. Further substantially parallel alignment of conductive structures can occur because the front end and the back end of each carbon nanotube are attracted to each other due to van der Waals force. The impedance of the CNT films in the stretched direction is less than the impedance substantially perpendicular to the stretched direction, thereby forming an anisotropic impedance characteristic. The CNTs are pulled out and adhered to the substrate121aby a light-curing adhesive to form the CNT film.

FIG. 2shows that the electrode122ais located on two opposite sides of the conductive film121balong the high impedance direction. A signal input to the conductive film121bor received from the conductive film121bof each electrode122ais transmitted along the low impedance direction.

FIGS. 5A and 5Bare the structural diagrams showing another touch sensing unit of a touch panel of the embodiment.

FIG. 5Ais a top view of a projected capacitive touch panel.FIG. 5Bis an exploded view of the projected capacitive touch panel. The projected capacitive touch panel includes a first conductive film121dand a second conductive film121e, wherein the first conductive film121dhas a low impedance direction and a high impedance direction, thus the first conductive film121dhas anisotropic impedance.

The second conductive film121eincludes a patterned plurality of conductive structures substantially parallel and separated from each other by a preset distance. The conducting direction of the conductive structures of the second conductive film121eis substantially perpendicular to the low impedance direction of the first conductive film121d. In the embodiment, the second conductive film121ecan be a patterned indium tin oxide (ITO) film.

An insulating layer (not shown) is located between the first conductive film121dand the second conductive film121e, whereby the three elements constitute a capacitor structure.

The electrodes located on the first conductive film121dand the second conductive film121ecan be electrically connected to the same driving unit, or electrically connected to a different driving unit. In addition, the signal guiding circuit (not shown) is located around the touch sensing unit and the signal transmitting circuit.

In summary, the signal guiding circuit is located on a peripheral of the touch sensing unit and the signal transmitting circuit, and the similar signals are provided to the signal guiding circuit and the signal transmitting unit to reduce the generation of capacitive loading effect. In addition, the external interference signal is guided to the protection unit via the signal guiding circuit to avoid external interference signal affect the functionality of the touch panel.