Patent Publication Number: US-2011050605-A1

Title: Touch Sensing Module, Display Apparatus and Manufacturing Method Thereof

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATION 
     This patent application is based on Taiwan, R.O.C. patent application No. 098129589 filed on Sep. 2, 2009. 
     FIELD OF THE INVENTION 
     The present invention relates to a touch sensing module, a display apparatus and a manufacturing method thereof, and more particularly, to a double-layer electrode touch sensing module, a display apparatus and a manufacturing method thereof. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  shows a schematic diagram of a conventional capacitive touch module comprising a first sensing layer  110 , a second sensing layer  120 , and a shielding layer  130 . The first sensing layer  110  and the second sensing layer  120  are coupled to a sensing circuit  100 , and are for detecting a position of a touched point to output a position signal. 
       FIG. 2  shows a top view of the first sensing layer  110  and the second sensing layer  120  in  FIG. 1 . The first sensing layer  110  has a plurality of first sensing electrodes  111  horizontally arranged along an X direction, and the second sensing layer  120  has a plurality of second sensing electrodes  121  vertically arranged along a Y direction. The first electrodes  111  and the second electrodes  121  are connected to the sensing circuit  100  in  FIG. 1  via a plurality of first traces  112  and a plurality of second traces  122 , respectively. As shown in  FIG. 2 , gaps between two sensing electrodes  111  and the gaps between two sensing electrodes  121  of the prior art are equal, such that similar level of sensing effects are resulted for the X and Y directions. An equivalent capacitor is provided at each intersection of the sensing electrodes  111  and  121 . More specifically, when a user touches the capacitive touch panel, the equivalent capacitance at the touched point is changed to allow the sensing circuit  100  to detect an actual position of the touched point and to output a position signal. 
     The shielding layer  130  in  FIG. 1  is mainly for isolating panel control signals from sensing signals so that sensing signals are not affected by noise from the control signals. Another source of noise imposed on the sensing signals is common voltage signals (Vcom). The common voltage signals are generated by an integrated display controller (not shown) to control the inversion of liquid crystals of a liquid crystal display (LCD). Since the amplitude of the common voltage signals ranges from 3V to 5V, without a shielding layer  130 , transitions between high and low levels of the common voltage signals cause noise and the noise is often coupled to the sensing signals thereby hindering the sensing circuit  100  from generating accurate position signals. 
     Further, the conventional three-layer capacitive touch module having the shielding layer is more costly. Therefore, there is a need for a touch sensing module capable of eliminating noise interference as well as having reduced space and cost. 
     SUMMARY OF THE INVENTION 
     A touch sensing module is provided by the invention. The touch sensing module comprises a first sensing layer having a plurality of first sensing electrodes, and a second sensing layer having a plurality of second sensing electrodes. The plurality of second electrodes have gaps far smaller than a width thereof. 
     A touch sensing display apparatus is further provided by the invention. The touch sensing display apparatus comprises: a touch sensing module, comprising a first sensing layer having a plurality of first sensing electrodes, and a second sensing layer having a plurality of second sensing electrodes; a sensing circuit, coupled to the plurality of first sensing electrodes and the plurality of second sensing electrodes; and an LCD module. The second sensing layer is situated between the first sensing layer and the LCD module, and the second sensing electrodes have gaps that are far smaller than a width thereof. 
     A manufacturing method for a touch sensing module is also provided by the invention. The manufacturing method comprises placing a plurality of first sensing electrodes at a first sensing layer, placing a plurality of second sensing electrodes at a second sensing in a way that the second sensing electrodes have gaps that are far smaller than a width thereof, and driving the second sensing electrodes to render the second sensing electrodes in a low-impedance state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
         FIG. 1  is a schematic diagram of a conventional capacitance touch sensing module; 
         FIG. 2  is a top view of the first sensing layer and the second sensing layer in  FIG. 1 ; 
         FIG. 3  is a top view of a structure of a touch sensing module according to an embodiment of the invention; 
         FIG. 4  is a partial enlarged view of  FIG. 3 ; 
         FIG. 5  is a schematic diagram of a touch sensing display apparatus according to an embodiment of the invention; and 
         FIG. 6  is a flowchart of a manufacturing method for a touch sensing module according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 3  shows a top view of a structure of a touch sensing module  300  according to an embodiment of the invention. The touch sensing module  300  comprises a plurality of first sensing electrodes horizontally arranged along an X direction at a first sensing layer, and a plurality of second sensing electrodes vertically arranged along a Y direction at a second sensing layer. The first sensing layer is disposed on the second sensing layer. To apply the touch sensing module  300  to a touch sensor display, the sensing electrodes need be optically transparent and conductive, and may be made of indium tin oxide (ITO), for example. It is to be noted that, the embodiment is also suitable for a touch sensing module without display capabilities, e.g., a touch sensing panel below a keyboard of a laptop computer, so that the touch sensing panel needs not be a transparent material in this case. The first sensing electrodes  311  and the second sensing electrodes  321  are connected to a sensing circuit (not shown) via a plurality of first trace lines  312  and a plurality of second trace lines  322 , respectively. The trace lines are conductive but not necessarily transparent. Via the trace lines  312  and  322 , the sensing circuit detects variations of equivalent capacitance between the sensing electrodes  311  and  321  caused by a touch, so as to obtain a position of the touch point. 
       FIG. 4  shows a partial enlarged view of  FIG. 3 . According to an embodiment of the invention, the first sensing electrodes  311  are arranged in the Y direction. Each of the first sensing electrodes  311  has a first width WidthY of 0.5 mm, and a first gap GapY of 4 mm is formed between every two of the first sensing electrodes  311 . The second sensing electrodes  321  are arranged in the X direction. Each of the second sensing electrodes  321  has a second width WidthX of 4 mm, and a second gap GapX of 0.2 mm is formed between every two of the second sensing electrodes  321 . As shown in  FIG. 4 , second width WidthX of each of the second sensing electrodes  321  is far greater than the second gap GapX, and also far greater than the first width WidthY of the first sensing electrodes  311 . That is, the second sensing electrodes  321  have second gap GapX far smaller than first gap GapY of the first sensing electrodes  311 . Thus, in the particular embodiment depicted in  FIG. 4 , the WidthY is at least 10 times, and preferably at least 20 times, greater than GapY. Also, GapY is at least 10 times, and preferably 20 times, smaller than GapX. In still other embodiments, WidthY may be greater than GapY by more than 20 times. 
       FIG. 5  shows a schematic diagram of a touch sensing display apparatus  500  according to an embodiment of the invention. The touch sensing display apparatus  500  comprises a touch sensing module  530 , an LCD module  540 , a sensing circuit  550  and a display controller  560 . The touch sensing module  530  comprises a first sensing layer  510  having a plurality of first sensing electrodes  511 , and a second sensing layer  520  having a plurality of second sensing electrodes  521 . As shown in  FIG. 5 , each of the second sensing electrodes  521  has a width, and a gap is formed between every two second sensing electrodes  521 . Similar to the embodiment shown in  FIG. 4 , the width of each of the second sensing electrodes  521  is far greater than the gap between every two of the second sensing electrodes  521 . The area formed by the second sensing electrodes  521  occupies a major part of the area of the second sensing layer  520 . The display controller  560  outputs a common voltage signal Vcom with an amplitude ranging from 3V to 5V to the LCD module  540 . Preferably, the sensing circuit  550  renders the second sensing electrodes  521  at a low-impedance state by using an internal driving circuit (not shown), such that the signal of the second sensing electrodes  521  does not shift along with variations of the common voltage signal Vcom. Since the gaps do exist between the second sensing electrodes  521 , electric force lines generated from a constant voltage used for the sensing circuit  550  to drive the second sensing electrodes  521  are present in the gaps. The electric force lines are emitted from one side of the second sensing electrodes  521 , and the electric force lines near edges of the second sensing electrodes  521  exit at the other side of the second sensing electrodes  521 . When the second sensing electrodes  521  have gaps far smaller than their width, it is difficult for the common voltage Vcom to penetrate through the electric field at the gaps of the second sensing electrodes  521  to further affect the electric potential of the first sensing electrodes  511 . Therefore, when the second sensing electrodes  521  are voltage driven, a shielding effect is formed by shielding the first sensing layer  510  against the common voltage signal outputted by the display controller  560  to the LCD module  540 , thereby enhancing quality of sensing signals of the touch module  530 . 
       FIG. 6  shows a flowchart of a manufacturing method for a touch sensor module according to an embodiment of the invention. The flow starts at Step  600 . Step  610  provides disposing a plurality of first sensing electrodes at a first sensing layer. Step  620  provides disposing a plurality of second sensing electrodes at a second sensing layer. The second sensing electrodes have a gap, in between each other, far smaller than their width, such that the second electrodes occupy a major part of the area of the second sensing layer. The first sensing layer is disposed parallel to the second sensing layer, and the first sensing electrodes are substantially arranged perpendicular to the second sensing electrodes. The first and second sensing electrodes may be made of an optically transparent and conductive material, e.g., ITO, for applications to a touch sensing display module. Alternatively, the first and second sensing electrodes are not necessarily a transparent material when applied to a non-display-oriented touch sensing panel, e.g., a touch sensing panel below a keyboard of a laptop computer. Step  630  provides coupling the first and second sensing electrodes to a sensing circuit to detect a sensing signal. Step  640  provides applying a voltage to the second sensing electrodes to render the second sensing electrodes at a low-impedance state with an internal driving circuit of the sensing circuit, so as to shield the first sensing layer from noise interference. The flow ends at Step  650 . 
     Therefore, according to the touch sensor apparatus of the invention, no additional shielding layer is needed to shield against interference. More specifically, when manufacturing the second sensing layer, etched patterns on the ITO are modified, such that the second sensing electrodes have gaps that are far smaller than their width, and thus occupy a major part of the area of the second sensing layer. A driving voltage is applied to render the second sensing electrodes at a low-impedance state so that the second sensing electrodes become capable of shielding noise interference coming from below the second electrodes. 
     With the description of the embodiments above, it is easily appreciated for a person skilled in the art that, when the touch sensing module is applied to a touch sensing display, the sensing electrodes are made of an optical transparent and conductive material in order to shield against interference imposed on a sensing signal by the common voltage signal Vcom outputted from the display controller to the LCD module; when the touch sensor module is applied to a touch sensing panel below a keyboard of a laptop computer, the shielding layer is also needed to prevent the control signal from coupling to the sensing signal since the control circuit that generates noise interference is present below the sensing layer. Therefore, for accommodating different applications, the sensing electrodes according to the invention may be a transparent and conductive material, and a non-transparent and conductive material. 
     Therefore, the invention is capable of eliminating the shielding layer of the prior art and/or improving signal quality. Advantages of eliminating the shielding layer are that not only a portable device is made more compact for better mobility but also a display panel on the portable device is provided with a better transmittance, so as to achieve objects of reducing space and cost. 
     A touch sensor module according to the disclosure comprises a first sensing layer having a plurality of first sensing electrodes, and a second sensing layer having a plurality of second sensing electrodes. The plurality of second electrodes have gaps far smaller than a width thereof. 
     A touch sensing display apparatus according to the disclosure comprises a touch sensor module including a first sensing layer having a plurality of first sensing electrodes and a second sensing layer having a plurality of second sensing electrodes; a sensing circuit, coupled to the plurality of first sensing electrodes and the plurality of second sensing electrodes; and an LCD module. The second sensing layer is situated between the first sensing layer and the LCD module, and the second sensing electrodes have gaps that are far smaller than a width thereof. 
     A manufacturing method for a touch sensing module according to the disclosure comprises placing a plurality of first sensing electrodes at a first sensing layer, placing a plurality of second sensing electrodes at a second sensing layer in a way that the second sensing electrodes have gaps that are far smaller than a width thereof, and driving the second sensing electrodes to render the second sensing electrodes in a low-impedance state. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not to be limited to the above embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.