Mutual capacitive touch panel with double-layer electrodes

This application claims benefit of U.S. Provisional Patent Application No. 62/678,998, filed May 31, 2018, the entire contents of which are incorporated herein by reference.

1. Field of the Invention

The present invention relates to a mutual capacitive touch panel with double-layer electrodes, and more particularly, to a mutual capacitive touch panel with double-layer electrodes which edges are spaced apart by a certain spacing.

2. Description of the Prior Art

A touch display device formed of a display and a touch panel has characteristic of human-machine interaction because of providing both touch and display functions and thus is widely applied in various electronic products including smart phones, GPS navigator systems, tablet computers and laptop computers. In various touch display devices, mutual capacitive touch panels have become main touch technology used in this art due to the advantages of great accuracy, multi-touch, long endurance and high touch resolution.

Mutual capacitive touch technology can be grouped into two types in structural design: a single-layer electrode structure and a double-layer electrode structure. In the structure design and control algorithm, the double-layer electrode structure is simpler than the single-layer electrode structure, so the double-layer electrode structure is widely used in middle-level and high-level consumer electronic products. In the conventional double-layer electrode structure design, the sensing string is fabricated on one glass substrate, and the driving string is fabricated on another glass substrate. The glass substrate with the sensing string and the glass substrate with the driving string can be bonded to each other by an optical adhesive and then adhered to a display device or other electronic devices. Each sensing string and each driving string cross each other, and sensing units are formed at the intersecting positions. The position of the finger can be identified by detecting the variation in sensing capacitances before and after the finger touches or approaches the touch panel. In the conventional design, one of the glass substrates serves as an insulating layer between the driving strings and the sensing strings and has a thickness of at least 0.55 mm. Therefore, when the finger has not touched or approached yet, the background capacitance between the sensing string and the driving string is still within the required range for detection.

However, as the thickness of the touch panel becomes thinner and thinner, the dielectric layer of the background capacitor between the driving string and the sensing string becomes thinner and thinner, such that the background capacitance is forced to increase. When the larger the background capacitance is, the more obvious the loading effect on the same driving string is. For example, the driving signals received by the sensing unit adjacent to the driving string signal input end (near end) and by the sensing unit far from the signal input end (far end) are obviously different due to the loading effect, thereby causing the far-end sensing unit to become smaller and affecting the detecting quality of touch panel. Furthermore, when the background capacitance is larger, the output of the amplifier for amplifying the sensing signal from the sensing string is easily saturated without attenuation of the driving signal, so that the difference between sensing capacitances cannot be determined, thereby affecting the detecting quality.

It is an objective of the present invention is to provide a mutual capacitive touch panel to reduce background capacitance and raising capacitance variation amount and detecting quality by the electrode width and arranging rule of the double-layer electrode layers.

According to an embodiment of the present invention, a mutual capacitive touch panel is disclosed and includes a first electrode layer, an insulating layer, and a second electrode layer. The first electrode layer includes a plurality of electrode strings extending along a first direction, and each electrode string has an outer side. The insulating layer is disposed on the first electrode layer. The second electrode layer is disposed on the insulating layer and includes a plurality of electrode strips extending along a second direction, in which one of the electrode strips includes a plurality of electrode portions connected in series, one of the electrode portions includes a first main part and at least one first branch part, the first main part crosses a corresponding one of the electrode strings, the first branch part is connected to a side of the first main part, and no branch part is disposed between the at least one first branch part and the outer side. Also, the first branch part has a first side adjacent to the outer side, and a spacing between the first side and the outer side is greater than twice a width of the at least one first branch.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

FIG. 1 is a schematic diagram illustrating a sectional view of a mutual capacitive touch panel according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating an enlarged top view of a single sensing unit according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a sectional view of a stack structure formed by the first electrode layer C 11 , the insulating layer IN 1 and the second electrode layer C 12 taken along a sectional line A-A′ of FIG. 2 .

FIG. 5 is a schematic diagram illustrating a relation between the size of the spacing and the capacitance variation rate.

FIG. 6 is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a second embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a third embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a fourth embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a fifth embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a sixth embodiment of the present invention.

FIG. 11 is a schematic diagram illustrating a sectional view of a mutual capacitive touch panel according to a seventh embodiment of the present invention.

FIG. 12 is a schematic diagram illustrating a sectional view of a mutual capacitive touch panel according to an eighth embodiment of the present invention.

In order to enable those skilled in the art to further understand the present invention, preferred embodiments of the present invention are listed below, and the composition and intended effects of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the drawings are simplified schematic diagrams, therefore, only the components and combination relationships related to the present invention are shown to provide a clearer description of the basic architecture or implementation method of the present invention, while the actual components and layout may be more complicated. In addition, for convenience of explanation, the elements shown in the various drawings of the present invention are not drawn to the actual number, shape and size, and the detailed scale can be adjusted according to the design requirements.

Please refer to FIG. 1 , which is a schematic diagram illustrating a sectional view of a mutual capacitive touch panel according to a first embodiment of the present invention. The mutual capacitive touch panel 100 is used for detecting a touch position of a touch object and includes a first electrode layer C 11 , a second electrode layer C 12 and an insulating layer IN 1 , in which the insulating layer IN 1 is disposed on the first electrode layer C 11 , the second electrode layer C 12 is disposed on the insulating layer IN 1 , and the first electrode layer C 11 and the second electrode layer C 12 can be electrically insulated from each other by the insulating layer IN 1 disposed therebetween, such that the first electrode layer C 11 , the insulating layer IN 1 and the second electrode layer C 12 can form a capacitor structure, and the insulating layer IN 1 serves as a dielectric layer of the capacitor structure. In some embodiments, the second electrode layer C 12 is closer to the touch object for inputting the command than the first electrode layer C 11 . The touch object may be, for example, a finger or a stylus pen. The first electrode layer C 11 and the second electrode layer C 12 may be formed of a transparent conductive material, which may include, for example, indium tin oxide (ITO), indium zinc oxide (IZO), antimony tin oxide (ATO), antimony zinc oxide (AZO), nano-silver, or other suitable transparent conductive materials. The thickness of the first electrode layer C 11 and thickness of the second electrode layer C 12 may be less than 1 micron.

In this embodiment, the mutual capacitive touch panel 100 may include a film 102 , and the first electrode layer C 11 and the second electrode layer C 12 may be respectively formed on a bottom surface and a top surface of the same film 102 . In other words, the film 102 may be the insulating layer IN 1 that isolates the first electrode layer C 11 from the second electrode layer C 12 , which serves as a dielectric layer of a coupling capacitor between the first electrode layer C 11 and the second electrode layer C 12 . In this embodiment, the film 102 may be, for example, a flexible substrate such as polyimide (PI), polyethylene terephthalate (PET), or thin glass. For example, the thickness of the film 102 may be 45 microns (μm), so as compared with the conventional touch panel, the thickness of the insulating layer IN 1 of the mutual capacitive touch panel 100 of this embodiment is greatly reduced. In some embodiments, the mutual capacitive touch panel 100 may further include an adhesive layer 104 and a cover plate 106 , in which the cover plate 106 is adhered to the second electrode layer C 12 by the adhesive layer 104 to form the mutual capacitive touch panel 100 . In some embodiments, the mutual capacitive touch panel 100 may be adhered to the display device 110 through an adhesive layer 108 , but the present invention is not limited thereto.

Please refer to FIGS. 2 and 3 . FIG. 2 is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to the first embodiment of the present invention. FIG. 3 is a schematic diagram illustrating an enlarged top view of a single sensing unit according to the first embodiment of the present invention. In the mutual capacitive touch panel 100 provided in this embodiment, the first electrode layer C 11 includes a plurality of electrode strings ES 1 separated and insulated from each other and extending along a first direction D 1 , and the second electrode layer C 12 includes a plurality of electrode strips EL 1 extending along a second direction D 2 and crossing the electrode strings ES 1 . A plurality of sensing units SU arranged in an array formation can be formed by the electrode strips EL 1 crossing the electrode strings ES 1 and used for detecting the touch position of the touch object. In this embodiment, each the electrode string ES 1 can be used as a sensing electrode and each electrode strip EL 1 can be used as a driving electrode, but the present invention is not limited to this, and vice versa.

In this embodiment, each electrode string ES 1 is a strip-shaped electrode, but is not limited thereto. In some embodiments, the design of the top-view pattern of each electrode string ES 1 can be adjusted according to real requirements. In some embodiments, each electrode string can also be formed by alternately connecting a plurality of electrodes and a plurality of connecting lines in series, in which each electrode corresponds to one corresponding sensing unit, but is not limited thereto. In this embodiment, each electrode string ES 1 may have a first outer side OS 1 and a second outer side OS 2 that are opposite to each other and extend along the first direction D 1 , and a first end side ESN 1 and a second end side ESN 2 opposite to each other and extending along the second direction D 2 , in which the first end side ESN 1 and the second end side ESN 2 are located between the first outer side OS 1 and the second outer side OS 2 . The terms “outer side” and “end side” used herein refer to the side of the corresponding electrode string ES 1 facing outward (i.e., a part of a profile of the electrode string ES 1 in a top view direction V) rather than the side of the opening of the corresponding electrode string ES 1 . The number and shape of the outer sides of each electrode string ES 1 of the present invention are not limited to this, but can be adjusted according to the pattern of the top-view profile of each electrode string ES 1 .

In addition, each electrode strip EL 1 is divided into a plurality of electrode portions EP 1 connected in series with each other, and each electrode portion EP 1 corresponds to one of the electrode strings ES 1 , so that each electrode portion EP 1 and the corresponding electrode string ES 1 form a sensing unit SU. Referring to FIG. 3 , one of the electrode portions EP 1 includes a first main part MP 1 and at least one first branch part BP 1 , in which the first main part MP 1 extends along the second direction D 2 and crosses the corresponding electrode string ES 1 , and the first branch part BP 1 is connected to one side of the first main part MP 1 . The first branch part BP 1 has a first side S 11 adjacent to the first outer side OS 1 , and a spacing G 11 between the first side S 11 and the first outer side OS 1 is greater than twice a width W 1 of the first branch part BP 1 . In this embodiment, each electrode portion EP 1 may include the first main part MP 1 and a plurality of the first branch parts BP 1 , in which each first branch part BP 1 is connected to the same side of the first main part MP 1 . The first branch part BP 1 having the first side S 11 is one of the first branch parts BP 1 closest to the first outer side OS 1 . That is, no other branch part is disposed between the first branch part BP 1 having the first side S 11 and the first outer side OS 1 . In some embodiments, a spacing G 12 between two adjacent first branch parts BP 1 may be greater than twice the width W 1 of the first branch parts BP 1 . Similarly, the first branch part BP 1 closest to the second outer side OS 2 may have another first side S 12 facing the second outer side OS 2 , and a spacing G 13 between the first side S 12 and the second outer side OS 2 may be greater than twice the width W 1 of the first branch part BP 1 . For example, the width W 1 of the first branch part BP 1 may be less than 0.5 mm, and the spacings G 11 , G 12 , G 13 may be greater than 0.6 mm, preferably greater than 0.75 mm. In some embodiments, a width W 2 of the first main part MP 1 may be the same as the width W 1 of the first branch part BP 1 , for example, less than 0.5 mm. In other embodiments, each electrode portion EP 1 may have only a single first branch part BP 1 .

In this embodiment, the electrode portion EP 1 may optionally further include a second main part MP 2 adjacent to the first main part MP 1 and crossing the corresponding electrode string ES 1 . For example, the second main part MP 2 may be parallel to the first main part MP 1 and have the same width as the first main part MP 1 , but is not limited thereto. Also, a spacing GM between the first main part MP 1 and the second main part MP 2 may be greater than the width W 2 of the first main part MP 1 or twice a width W 3 of the second main part MP 2 . The first main part MP 1 may have the same width as the second main part MP 2 , such as less than 0.5 mm, and the spacing GM may be, for example, greater than 0.6 mm, preferably greater than 0.75 mm.

Each electrode portion EP 1 may optionally further include at least one second branch part BP 2 located between the first main part MP 1 and the second main part MP 2 , in which the first branch part BP 1 is located on one side of the first main part MP 1 opposite to the second main part MP 2 , the second branch part BP 2 has a second side S 21 adjacent to the first outer side OS 1 , and a spacing G 21 between the second side S 21 and the first outer side OS 1 is greater than twice a width W 4 of the second branch part BP 2 . In this embodiment, each electrode portion EP 1 may include a plurality of second branch parts BP 2 . For example, each second branch part BP 2 may be aligned with a corresponding first branch part BP 1 in the first direction D 1 . In this embodiment, the second branch part BP 2 having the second side S 21 is the second branch part BP 2 closest to the first outside OS 1 . That is, no other branch part is disposed between the second branch part BP 2 having the second side S 21 and the first outside side OS 1 . In some embodiments, a spacing G 22 between two adjacent second branch parts BP 2 may be greater than twice the width W 4 of each second branch part BP 2 . Similarly, the second branch part BP 2 closest to the second outer side OS 2 may have another second side S 22 facing the second outer side OS 2 , and a spacing G 23 between the second side S 22 and the second outer side OS 2 may be greater than twice the width W 4 of each second branch part BP 2 . The width W 4 of each second branch part BP 2 may be the same as that of each first branch part BP 1 . For example, when the width W 4 is less than 0.5 mm, the spacings G 21 , G 22 , G 23 may be greater than 0.6 mm, preferably greater than 0.75 mm.

Each electrode portion EP 1 may optionally further include at least one third branch part BP 3 located on one side of the second main part MP 2 opposite to the first main part BP 1 , the third branch part BP 3 having a third side S 31 adjacent to the first outer side OS 1 , and a spacing G 31 between the third side S 31 and the first outer side OS 1 is greater than twice a width W 5 of the third branch part BP 3 . In this embodiment, each electrode portion EP 1 may include a plurality of third branch parts BP 3 . For example, each third branch part BP 3 may be aligned with a corresponding second branch BP 2 in the first direction D 1 . In this embodiment, the third branch part BP 3 having the third side S 31 is the third branch BP 3 closest to the first outside OS 1 . That is, no other branch part is disposed between the third branch BP 3 having the third side S 31 and the first outer side OS 1 . In some embodiments, a spacing G 32 between two adjacent third branch parts BP 3 may be greater than twice the width W 5 of each third branch part BP 3 . Similarly, the third branch part BP 3 closest to the second outer side OS 2 may have another third side S 32 facing the second outer side OS 2 , and a spacing G 33 between the third side S 32 and the second outer side OS 2 may be greater than twice the width W 5 of each third branch part BP 3 . The width W 5 of each third branch part BP 3 may be the same as that of each first branch part BP 1 , for example, when the width W 5 is less than 0.5 mm, and the spacings G 31 , G 32 , G 33 may be greater than 0.6 mm, preferably greater than 0.75 mm.

Referring to FIG. 2 , in this embodiment, in the electrode strip EL 1 closest to the first end side ESN 1 , each first branch part BP 1 located between the first main part MP 1 and the first end side ESN 1 is the part closest to the first end side ESN 1 and has a first end EN 1 , and a spacing G 4 between each first end EN 1 and the first end side ESN 1 (i.e., the shortest distance between the electrode strip EL 1 closest first end side ESN 1 and the first end side ESN 1 ) may be greater than twice the width W 1 of each first branch part BP 1 . Similarly, in the electrode strip EL 1 closest to the second end side ESN 2 , each third branch part BP 3 located between the second main part MP 2 and the second end side ESN 2 is the part closest to the second end side ESN 2 and has a second end EN 2 , and a spacing G 5 between the second end EN 2 and the second end side ESN 2 (that is, the shortest distance between the electrode strip EL 1 closest to the second end side ESN 2 and the second end side ESN 2 ) is greater than twice the width W 4 of each third branch part BP 3 . In some embodiments, the shortest spacing G 6 between two adjacent electrode strips EL 1 (i.e., a spacing between the endpoints of the third branch part BP 3 and the first branch part BP 1 adjacent to each other in two adjacent electrode strips EL 1 ) may be greater than the width of each first branch part BP 1 or the width of each third branch part BP 3 .

In this embodiment, since the electrode string ES 1 does not have an opening, the spacings G 11 , G 12 , G 13 , G 21 , G 22 , G 23 , G 31 , G 32 , G 33 , GM, G 4 , G 5 , G 6 are the widths of the electrode string ES 1 exposed in the corresponding regions in the top view direction V. It should be noted that by means of designing the spacings G 11 , G 12 , G 13 , G 21 , G 22 , G 23 , G 31 , G 32 , G 33 , GM, G 4 , G 5 , G 6 to be greater than twice the width of the corresponding part, the number of lines of electric force extending from the electrode strip EL 1 to the electrode string ES 1 can be increased during operation of the mutual capacitive touch panel 100 . For example, as compared with the spacing G 1 less than twice the width W 1 of the first branch part BP 1 , when the spacing G 1 is greater than twice the width W 1 of the first branch part BP 1 , the number of lines of electric force between the electrode string ES 1 between the first branch part BP 1 and the first outer side OS 1 and the first branch part BP 1 can be increased during the operation of the mutual capacitive touch panel 100 , so that when a finger approaches or touches the mutual capacitive touch panel 100 , more lines of electric force changes, thereby increasing the capacitance variation amount at the position between the electrode string ES 1 and the first branch part BP 1 . Specifically, please refer to FIG. 4 and FIG. 5 . FIG. 4 is a schematic diagram illustrating a sectional view of a stack structure formed by the first electrode layer C 11 , the insulating layer IN 1 and the second electrode layer C 12 taken along a sectional line A-A′ of FIG. 2 , and FIG. 5 is a schematic diagram illustrating a relation between the size of the spacing and the capacitance variation rate. For convenience of explanation, FIG. 4 only shows regions corresponding to one first branch part BP 1 and the electrode string ES 1 exposed on two sides of the first branch part BP 1 , but is not limited thereto. As can be seen from FIG. 4 , the width of the electrode string ES 1 not covered by the second electrode layer C 12 is the spacing G, and lines EF of electric force are generated between the top surface of the first branch part BP 1 and the electrode string ES 1 located on two sides of the first branch part BP 1 and not covered by the second electrode layer C 12 . Moreover, since the approach or touch of the finger on the mutual capacitive touch panel 100 mainly changes the lines of electric force located on the second electrode layer C 12 without changing the lines of electric force located directly below the second electrode layer C 12 , the lines of electric force described herein is for the lines of electric force extending onto the second electrode layer C 12 . Since the number of lines of electric force between the first branch part BP 1 and the electrode string ES 1 depends on the spacing G and the width of the branch part, the width of each branch part is 0.3 mm and the spacings G 11 , G 12 , G 13 , G 21 , G 22 , G 23 , G 31 , G 32 , G 33 are all the same (represented by the spacing G) as an example in FIG. 5 , but is not limited thereto. A curve C shows the relation between the measured spacing and the capacitance variation rate, in which the measured spacing is obtained based on the capacitance variation measured when the width of the branch part is 0.3 mm and the spacing G is 2.25 mm. As can be seen from FIG. 5 , when the spacing G is greater than 0.6 mm, the capacitance variation rate may be greater than 80%. In particular, when the spacing G is greater than 0.75 mm, the capacitance variation rate may be greater than 90%. Therefore, with the increase of the spacing G, the capacitance variation rate is also increased, thereby improving the signal attenuation problem in the far-end sensing unit due to loading effect and increasing the detecting quality.

Generally, the size of the sensing unit is limited to a certain size to effectively detect the position of the finger, for example, the width of the sensing unit is limited to 4.5 mm or less than 5 mm. Since the increase of the spacing G limits the total side length of the electrode portion in the sensing unit (i.e., the sum of the lengths of the sides), the above design of increasing the spacing G to raise the capacitance variation amount is different from the conventional concept of increasing the capacitance variation amount by increasing the total side length of the electrode portion, and they are in conflict with each other. In other words, the capacitance variation amount can be effectively increased not only by continuously increasing the total side length of the electrode portion, but also by considering the size of the spacing G (more than twice the width of the branch part). Therefore, in a fixed area, the capacitance variation amount can be effectively increased by simultaneously optimizing the total side length of the electrode portion and the spacing G. In this way, in addition to the increase of the capacitance variation amount, the area of the electrode portion will not be excessively increased, such that the background capacitance between the electrode string and the electrode portion can be reduced, and the coupling capacitance between the electrode portion and the finger can also be reduced when the finger approaches or touches the touch panel. Accordingly, the output of the amplifier for amplifying the sensing signal is not easily saturated under the condition that the driving signal is not attenuated, so as to improve the touch accuracy of the mutual capacitive touch panel 100 . In this embodiment, although the thickness of the insulating layer IN 1 is greatly reduced to increase the background capacitance, the above design can increase the capacitance variation amount and reduce the background capacitance to improve the detecting quality of the mutual capacitive touch panel 100 .

The mutual capacitive touch panel of the present invention is not limited to the above embodiment. In order to compare the differences between the first embodiment and other embodiments and simplify the description, same symbols are used to label same elements, and the differences between the first embodiment and other embodiments are mainly described in the other embodiments below. The repeated parts will not be redundantly detailed.

Please refer to FIG. 6 , which is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a second embodiment of the present invention. The difference between the mutual capacitive touch panel 200 of this embodiment and the first embodiment is that each electrode portion EP 2 of each electrode strip EL 2 of this embodiment is #-shaped. Specifically, the numbers of the first branch parts BP 1 , the second branch parts BP 2 , and the third branch parts BP 3 of each electrode portion EP 2 may be two, so that the first branch parts BP 1 , the second branch parts BP 2 , the third branch parts BP 3 , the first main part MP 1 , and the second main part MP 2 may form the “#” shape. In this embodiment, the spacing between each branch part and the corresponding outer side, the spacing between two adjacent branch parts, the spacing between two adjacent main parts, the spacing between two adjacent electrode strips EL 2 , and the shortest spacing between the electrode strip EL 2 and the end side may be the same as those in the above embodiment, and will not be redundantly detailed.

In some embodiments, one of the electrode strings ES 2 may optionally include an opening OP 2 corresponding to an electrode portion EP 2 . For example, each electrode string ES 2 may include a plurality of openings OP 2 , and each opening OP 2 corresponds to one of the electrode portions EP 2 . In addition, each opening OP 2 may have the same shape as the corresponding electrode portion EP 2 , such as the “#” shape, and most part of each electrode portion EP 2 is located in the corresponding opening OP 2 in the top view direction V. In other words, through the design of the openings OP 2 , the overlapping area of each electrode portion EP 2 and each electrode string ES 2 in the top view direction V can be reduced, thereby reducing the coupling capacitance between each electrode portion EP 2 and each electrode string ES 2 . Specifically, the opening OP 2 may have a first main opening MOP 1 corresponding to the first main part MP 1 and two first branch openings BOP 1 respectively corresponding to the first branch parts BP 1 . The first main opening MOP 1 does not penetrate the corresponding electrode string ES 2 . In some embodiments, the width of the first main opening MOP 1 is greater than the width W 2 of the first main part MP 1 , and the width of each first branch opening BOP 1 is greater than the width W 1 of the corresponding first branch part BP 1 , so that most part of the first main part MP 1 may be located in the first main opening MOP 1 , and each first branch part BP 1 may be completely located in the first main opening MOP 1 and the corresponding first branch opening BOP 1 in the top view direction V. A spacing G 7 between the side of the first main opening MOP 1 and the side of the corresponding first main part MP 1 and a spacing G 8 between the side of the first branch opening BOP 1 and the side of the corresponding first branch part BP 1 may be, for example, substantially greater than or equal to 0.2 mm while taking process tolerances into account. Similarly, the opening OP 2 may also have a second main opening MOP 2 corresponding to the second main part MP 2 , two second branch openings BOP 2 respectively corresponding to the second branch parts BP 2 , and two third branch openings BOP 3 respectively corresponding to the third branch parts BP 3 , so that most part of the second main part MP 2 , the second branch parts BP 2 , and the third branch parts BP 3 may be completely located in the opening OP 2 in the top view direction V. The second main opening MOP 2 does not penetrate through the electrode string ES 2 . The spacing between the side of the second main part MP 2 and the side of the corresponding second main opening MOP 2 , the spacing between the side of one of the second branch parts BP 2 and the side of the corresponding second branch opening BOP 2 , and the spacing between the side of one of the third branch parts BP 3 and the side of the corresponding third branch opening BOP 2 may also be, for example, substantially greater than or equal to 0.2 mm while taking process tolerances into account. It is noted that since the spacing between each branch part and the outer side and the spacing between two adjacent branch parts may be greater than twice the width of each branch part, when the electrode string ES 2 is designed to have the openings OP 2 , the width of the electrode string ES 2 located on two sides of each branch part are not too small, thereby avoiding breaking risk.

It should be noted that since the overlapping part of the electrode string ES 2 and the electrode portion EP 2 is located directly below the electrode portion EP 2 , the lines of electric force between the overlapping part and the electrode portion EP 2 will not change when a finger approaches or touches the touch panel, and thus the background capacitance can be effectively reduced by removing the overlapping part of the electrode string ES 2 and the electrode portion EP 2 , thereby reducing the difference between the driving signals received by the near-end and far-end sensing units and avoiding the output saturation of the amplifier for enlarging the sensing signals. In addition, a ratio of the capacitance variation amount to the background capacitance of each sensing unit SU can be increased accordingly, such that the detecting quality of the mutual capacitive touch panel 200 can be improved. In other embodiments, the electrode portion may be string-shaped (‡), i.e., the electrode portion may include only one first branch part, only one second branch part, and only one third branch part, so that the first branch part, the second branch part, the third branch part, the first main part, and the second main part may form the string shape. In such situation, when the electrode string has the opening, the opening may have the string shape.

Please refer to FIG. 7 , which is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a third embodiment of the present invention. The difference between the mutual capacitive touch panel 300 of this embodiment and the second embodiment shown in FIG. 6 is that the electrode portion EP 3 of this embodiment is I-shaped. Specifically, the electrode portion EP 3 of this embodiment only has a single first branch part BP 13 located between the first main part MP 1 and the second main part MP 2 besides the first main part MP 1 and the second main part MP 2 . Moreover, the electrode portion EP 3 does not have the second branch parts and the third branch parts. Therefore, the first main part MP 1 , the second main part MP 2 , and the first branch part BP 13 may form the “I” shape. In some embodiments, the electrode string ES 3 may also have a plurality of openings OP 3 corresponding to the electrode portions EP 3 respectively, and each opening OP 3 may have the “I” shape. In this embodiment, the spacing between the branch part and the outer side, the spacing between two adjacent main parts, the spacing between two adjacent electrode strips EL 3 , and the shortest spacing between the electrode strips EL 3 and the end side can be the same as those in the above embodiment, so they will not be described herein. In some embodiments, the width of the main opening may be greater than the width of the main part, and the width of the branch opening is greater than the width of the branch part. For example, the spacing between the side of the main opening and the side of the corresponding main part, and the spacing between the side of the branch opening and the side of the corresponding branch part may be, for example, substantially greater than or equal to 0.2 mm, while taking process tolerances into account.

Please refer to FIG. 8 , which is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a fourth embodiment of the present invention. The difference between the mutual capacitive touch panel 400 of this embodiment and the second embodiment shown in FIG. 6 is that the electrode portion EP 4 of this embodiment is fence-shaped ( ). Specifically, the electrode portion EP 4 of this embodiment only has a single first main part MP 1 , and the first branch parts BP 1 and the second branch parts BP 2 are located on two sides of the first main part MP 1 , respectively, so the electrode portion EP 4 does not have the second main part and the third branch parts. Thus, the first main part MP 1 , the first branch parts BP 1 , and the second branch parts BP 2 may form the fence shape. In some embodiments, the electrode string ES 4 may also have a plurality of openings OP 4 corresponding to the electrode portions EP 4 respectively, and each opening OP 4 may have the fence shape. In this embodiment, the spacing between one of the branch parts and the outer side, the spacing between two adjacent branch parts, the spacing between two adjacent electrode strips EL 4 , and the shortest spacing between the electrode strips EL 4 and the end side can be the same as those in the above embodiment, so they will not be described herein. In some embodiments, the width of the main opening may be greater than the width of the main part, and the width of the branch opening may be greater than the width of the branch part. For example, the spacing between the side of the main opening and the side of the corresponding main part, and the spacing between the side of the branch opening and the side of the corresponding branch part may be, for example, substantially greater than or equal to 0.2 mm, while taking process tolerances into account.

Please refer to FIG. 9 , which is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a fifth embodiment of the present invention. The difference between the mutual capacitive touch panel 500 of this embodiment and the fourth embodiment shown in FIG. 8 is that the electrode portion EP 5 of this embodiment is cross-shaped (+). Specifically, the electrode portion EP 5 of this embodiment only has a single first branch part BP 1 and a single second branch part BP 2 , so the first main part MP 1 , the first branch part BP 1 , and the second branch part BP 2 may form the cross shape. In some embodiments, the electrode string ES 5 may also have a plurality of openings OP 5 corresponding to the electrode portions EP 5 respectively, and each opening OP 5 may have the cross shape. In this embodiment, the spacing between one of the branch parts and the outer side, the spacing between two adjacent electrode strips EL 5 , and the shortest spacing between the electrode strips EL 5 and the end side can be the same as those in the above embodiment, so they will not be described herein. In some embodiments, the width of the main opening may be greater than the width of the main part, and the width of the branch opening may be greater than the width of the branch part. For example, the spacing between the side of the main opening and the side of the corresponding main part, and the spacing between the side of the branch opening and the side of the corresponding branch part may be, for example, substantially greater than or equal to 0.2 mm, while taking process tolerances into account.

Please refer to FIG. 10 , which is a schematic diagram illustrating a top view of a mutual capacitive touch panel according to a sixth embodiment of the present invention. The difference between the mutual capacitive touch panel 600 of this embodiment and the second embodiment shown in FIG. 6 is that the mutual capacitive touch panel 600 of this embodiment is a narrow border type. For example, the first electrode layer C 61 includes a plurality of first electrode strings ES 61 spaced apart and insulated from each other and a plurality of second electrode strings ES 62 spaced apart and insulated from each other, and the first electrode strings ES 61 and the second electrode strings E 62 extend along the first direction D 1 . Moreover, each first electrode string ES 61 includes a plurality of first electrodes E 61 and a plurality of first connecting segments CS 61 , and each second electrode string ES 62 includes a plurality of second electrodes E 62 and a plurality of second connecting segments CS 62 . The first electrodes E 61 and the second electrodes E 62 are arranged in an array, in which the first electrodes E 61 are located in odd rows and the second electrodes E 62 are located in even rows, so in each column of the array, each first electrode E 61 and each second electrode E 62 are alternately arranged in sequence. In addition, the first electrodes E 61 in the same column are serially connected with each other through the first connecting segments CS 61 to form a first electrode string ES 61 , and the second electrodes E 62 in the same column are serially connected with each other through the second connecting segments CS 62 to form a second electrode string ES 62 . In this embodiment, the column direction of the array may be the first direction D 1 and the row direction of the array may be the second direction D 2 , but is not limited thereto. In this embodiment, the electrode strips EL 6 of the second electrode layer C 62 includes a plurality of shielding portions SP besides the electrode portions EP 6 , and each electrode portion EP 6 is disposed between two adjacent shielding portions SP, so that each shielding portion SP can be disposed on the corresponding first connecting segment C 61 and the corresponding second connecting segment CS 62 . Accordingly, the detected touch position can be prevented from being influenced by the lines of electric force generated between the electrode portion EP 6 and the first connecting segment C 61 and between the electrode portion EP 6 and the second connecting segment CS 62 . In some embodiments, two adjacent electrode strips EL 6 may be electrically connected to each other to form an electrode strip set ELM. In addition, the first electrodes E 61 of the same row and the second electrodes E 62 of the same row overlap two adjacent electrode strip sets ELM in the top view direction V, and each electrode strip set ELM overlaps the first electrodes E 61 and the second electrodes E 62 of two adjacent rows in the top view direction V, thereby effectively improving the touch accuracy in the first direction D 1 . In addition, the width of each first electrode E 61 of a first row in the first direction D 1 is smaller than the width of each first electrode E 61 of the other rows in the first direction D 1 , and the width of each second electrode E 62 of the last row in the first direction D 1 is smaller than the width of each second electrode E 62 of the other rows in the first direction D 1 . In this embodiment, the electrode portion EP 6 has the string shape, but is not limited thereto. In some embodiments, the first electrodes E 61 and the second electrodes E 62 may have the string-shaped openings OP 6 , and each opening OP 6 corresponds to one electrode portion EP 6 . In other embodiments, the electrode portions EP 6 may have the shape of any one of the above embodiments. In other embodiments, the spacing and opening conditions mentioned above may also be applied to other touch panel of the narrow border type. In this embodiment, the spacing between one of the branch parts and the outer side, the spacing between two adjacent main parts, the spacing between two adjacent electrode strips EL 6 , and the shortest spacing between the electrode strips EL 6 and the end side can be the same as those in the above embodiment, so they will not be described herein. In some embodiments, the width of the main opening may be greater than the width of the main part, and the width of the branch opening is greater than the width of the branch part. For example, the spacing between the side of the main opening and the side of the corresponding main part, and the spacing between the side of the branch opening and the side of the corresponding branch may be, for example, substantially greater than or equal to 0.2 mm, while taking process tolerances into account.

The stack structure of the mutual capacitive touch panel of the present invention is not limited thereto. Please refer to FIG. 11 , which is a schematic diagram illustrating a sectional view of a mutual capacitive touch panel according to a seventh embodiment of the present invention. The difference between the mutual capacitive touch panel 700 provided in this embodiment and the first embodiment shown in FIG. 1 is that the mutual capacitive touch panel 100 of this embodiment includes two films 702 , 704 and an adhesive layer 706 , and the first electrode layer C 71 and the second electrode layer C 72 may be formed on the films 702 , 704 , respectively, and the film 702 with the first electrode layer C 71 and the film 704 with the second electrode layer C 72 are bonded to each other by the adhesive layer 706 . In this embodiment, the film 704 and the adhesive layer 706 disposed between the first electrode layer C 71 and the second electrode layer C 72 form an insulating layer IN 2 for isolating the first electrode layer C 71 from the second electrode layer C 72 , i.e., serve as a dielectric layer of a capacitor structure. The thickness of the adhesive layer 706 may be, for example, 20 microns (μm), and the thickness of the film 704 may be, for example, 25 microns. In some embodiments, the design of using the film 704 and the adhesive layer 706 as the stack structure of the dielectric layer of the coupling capacitor between the first electrode layer C 71 and the second electrode layer C 72 can also be applied to the mutual capacitive touch panel of the first to sixth embodiments mentioned above.

Please refer to FIG. 12 , which is a schematic diagram illustrating a sectional view of a mutual capacitive touch panel according to an eighth embodiment of the present invention. The difference between the mutual capacitive touch panel 800 provided in this embodiment and the first embodiment shown in FIG. 1 is that the insulating layer IN 3 of this embodiment may be formed of, for example, silicon oxide, silicon nitride or other suitable insulating materials. The thickness of the insulating layer IN 3 may, for example, range from 1.2 to 30 microns. Since the first electrode layer C 81 and the second electrode layer C 82 in this embodiment can be in contact with the bottom surface and the top surface of the insulating layer IN 3 respectively, the insulating layer IN 3 can serve as a dielectric layer of the coupling capacitor between the first electrode layer C 81 and the second electrode layer C 82 . As compared with the dielectric layer composed of the film, the thickness of the insulating layer IN 3 of this embodiment can be thinner, thus reducing the spacing between the second electrode layer C 82 and the first electrode layer C 81 . Accordingly, the mutual capacitive touch panel 800 of this embodiment may be used as a flexible type touch panel, such as a folding or rolling type. In this embodiment, the mutual capacitive touch panel 800 may include a film 802 and a protecting layer 804 , and the first electrode layer C 81 , the insulating layer IN 3 , the second electrode layer C 82 and the protecting layer 804 are sequentially formed on the same first side of the film 802 . In another embodiment, the first electrode layer C 81 , the insulating layer IN 3 , and the second electrode layer C 82 may be directly formed on the display surface of the display device in sequence, such as a color filter substrate of a liquid crystal display panel or a package plate of an organic light emitting display panel, and a cover plate may be disposed on the second electrode layer C 82 . In some embodiments, the design of using the insulating layer IN 3 formed of silicon oxide, silicon nitride or other suitable insulating materials as the stack structure of the dielectric layer of the coupling capacitor between the first electrode layer C 81 and the second electrode layer C 82 may also be applied to the mutual capacitive touch panel of the first to sixth embodiments mentioned above.

In summary, in the mutual capacitive touch panel of the present invention, the spacing between one of the branch parts and the outer side, the spacing between two adjacent branch parts, the spacing between two adjacent main parts, the spacing between two adjacent electrode strips, and the shortest distance between the electrode strips and the end side may be greater than twice the width of each branch part or twice the width of each main part, so that the number of lines of electric force extending from the electrode strips onto the electrode strings can be increased to raise the capacitance variation amount and relatively reduce the area of the electrode portions. Accordingly, the coupling capacitance between the finger and the electrode portion can be reduced. Furthermore, by means of disposing the openings corresponding to the electrode portions in the electrode strings, the background capacitance of the sensing unit can be effectively reduced to decrease the difference between driving signals received by the near-end and far-end sensing units. Therefore, through this design, the output of the amplifier can be prevented from saturation, thereby improving the detecting quality of the mutual capacitive touch panel.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.