Patent Publication Number: US-2015061700-A1

Title: Capacitive sensor

Description:
The current application claims a foreign priority to the patent application of Taiwan No. 102216012 filed on Aug. 27, 2013. 
     FIELD OF THE INVENTION 
     The present invention relates to capacitive sensors for use with capacitive touch panels, and more particularly, to a capacitive sensor comprising electrodes made from fine metallic wires. 
     BACKGROUND OF THE INVENTION 
     A conventional touch panel is characterized in that virtual electrodes are formed between sensing electrodes arranged in a row and electrically insulated rather than electrically connected with the sensing electrodes to thereby reduce parasitic capacitance between the sensing electrodes and preclude a short circuit between two adjacent ones of the sensing electrodes driven at high frequency. 
     The virtual electrodes must have plenty of interrupted portions which are totally different from the continuous (uninterrupted) wire pattern of the sensing electrodes. When light rays from a backlight source pass through the virtual electrodes and the sensing electrodes, the light rays are hidden by the virtual electrodes and the sensing electrodes to different degrees, thereby resulting in uneven brightness of the display frame watched by naked eyes. 
     In view of the shortcomings of the conventional touch panel, the inventor of the present invention conducted extensive researches and experiments and finally developed a capacitive sensor to overcome the aforesaid shortcomings. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a capacitive sensor conducive to enhancement of uniformity of brightness of the display frame of a capacitive touch panel. 
     In order to achieve the above and other objectives, the present invention provides a capacitive sensor, applicable to a capacitive touch panel, comprising: a plurality of first electrodes each having a first wire portion; a plurality of second electrodes disposed beneath the first electrodes, insulated from the first electrodes, and crossing the first electrodes, the second electrodes each having a second wire portion; and a plurality of virtual electrodes each disposed between two adjacent ones of the first electrodes to space apart the two adjacent ones of the first electrodes, the virtual electrodes each comprising a plurality of continuous portions and a plurality of interrupted portions, wherein the interrupted portions each overlap a corresponding one of the second wire portions of the second electrodes, and a width of each of the interrupted portions is less than or equal to a width of the corresponding second wire portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Technical features and advantages of the present invention are hereunder illustrated with preferred embodiments in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic view of the structure of a capacitive sensor according to the present invention; 
         FIG. 2  is a schematic view of the structure of second electrodes and virtual electrodes of the capacitive sensor according to the present invention; and 
         FIG. 3  is a partial enlarged view of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to  FIG. 1  through  FIG. 3 , a capacitive sensor  10  of the present invention is for use with a capacitive touch panel. The capacitive sensor  10  comprises a plurality of first electrodes  11 , a plurality of second electrodes  13 , and a plurality of virtual electrodes  15 , which are described below. The first electrodes  11 , the second electrodes  13 , and the virtual electrodes  15  are disposed at a transparent substrate  17 . For example, the first electrodes  11  and the virtual electrodes  15  are formed on the upper surface of the transparent substrate  17 , whereas the second electrodes  13  are formed on the lower surface of the transparent substrate  17 . With the transparent substrate  17  being made of an electrically insulating material, not only are the first electrodes  11  insulated from the second electrodes  13 , but the virtual electrodes  15  are also insulated from the second electrodes  13 . 
     In an embodiment of the present invention, the first electrodes  11  each have a first wire portion  11   a.  The first wire portions  11   a  come in the form of reticular electrically conductive fine metallic wires. The second electrodes  13  are each disposed beneath the first electrodes  11  and insulated therefrom. The second electrodes  13  each have a second wire portion  13   a.  In an embodiment, the second wire portions  13   a  come in the form of reticular electrically conductive fine metallic wires. The first electrodes  11  each run in a first direction of the transparent substrate  17 . The second electrodes  13  each run in a second direction of the transparent substrate  17 . The first direction and the second direction are not parallel. Hence, the first electrodes  11  are each insulated from the second electrodes  13  and cross the second electrodes  13 . For example, the first direction and the second direction are perpendicular to each other, and thus the first electrodes  11  are each insulated from the second electrodes  13  and perpendicular thereto. Both the first wire portions  11   a  and the second wire portions  13   a  are reticular electrically conductive fine metallic wires. 
     The reticular electrically conductive fine metallic wires of the first wire portions  11   a  and the second wire portions  13   a  are made of copper, aluminum, nickel, iron, gold, silver, stainless steel, tungsten, chromium, titanium, or an alloy thereof. The linear shape of the reticular electrically conductive fine metallic wires is straight or arcuate. 
     The virtual electrodes  15  are each disposed between two adjacent ones of the first electrodes  11  to space apart the two adjacent ones of the first electrodes  11 . The virtual electrodes  15  each comprise a plurality of continuous portions  15   a  and a plurality of interrupted portions  15   b.  In an embodiment, the continuous portions  15   a  are two electrically conductive fine metallic wires which cross each other and thus are cruciform or X-shaped. The two electrically conductive fine metallic wires which cross each other are made of copper, aluminum, nickel, iron, gold, silver, stainless steel, tungsten, chromium, titanium, or an alloy thereof. The linear shape of the two electrically conductive fine metallic wires which cross each other is linear or arcuate. 
     The interrupted portions  15   b  each overlap a corresponding one of the second wire portions  13   a  of the second electrodes  13 . The width W 1  of each of the interrupted portions  15   b  is less than or equal to the width W 2  of the corresponding second wire portion  13   a.  With each said interrupted portion  15   b  being hidden by the corresponding second wire portion  13   a  below, the light rays from the backlight source of the capacitive touch panel are blocked by the second wire portion  13   a  and thus cannot pass through each of the interrupted portions  15   b,  thereby enhancing the uniformity of brightness of the display frame of the capacitive touch panel. 
     Both the vertically adjacent ones of the continuous portions  15   a  and the horizontally adjacent ones of the continuous portions  15   a  are separated by the interrupted portions  15   b  and spaced apart by a predetermined distance. The interrupted portions  15   b  can be directly formed from the transparent substrate  17 , such that none of the continuous portions  15   a  is connected to two vertically adjacent ones of the continuous portions  15   a  and two horizontally adjacent ones of the continuous portions  15   a.    
     The capacitive sensor  10  of the present invention is advantageously characterized in that: the virtual electrodes  15  are improved in a manner that the interrupted portions  15   b  are each hidden by the second wire portion  13   a  of the second electrodes  13  below to thereby enhance the uniformity of brightness of the display frame of the capacitive touch panel. 
     The present invention is disclosed above by preferred embodiments. However, persons skilled in the art should understand that the preferred embodiments are illustrative of the present invention only, but should not be interpreted as restrictive of the scope of the present invention. Hence, all equivalent changes and modifications made in accordance with the claims and the specification of the present invention to the aforesaid embodiments should fall within the scope of the present invention.