Patent Publication Number: US-2018052542-A1

Title: Touch panel and method of fabricating the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of capacitive sensing techniques, and more particularly, to a touch panel using capacitive sensing components and a method of fabricating the touch panel. 
     2. Description of the Prior Art 
     Liquid crystal displays show vivid colors while keeping a low power consumption and flicker rate, and thus have become mainstream in displays, being widely applied in electronic devices such as mobile phones, cameras, computer screens, and televisions. 
     Touch panels are sturdy, durable, and space saving. They react fast and are easy to interact with. Via touch panel technology, users may operate electronic devices by simply touching an icon or a text on a touch screen. This direct way of human-machine interaction has brought revolutionized convenience to users who are not so good at conventional computer operation. 
     Nowadays many electronic devices have screens manufactured via both liquid crystal display technology and touch panel technology. These liquid crystal touch panels, born with advantages from both technologies, are a great market success. However, due to structural facts of conventional liquid crystal displays, conventional liquid crystal touch panels have their sensing electrodes, which realize the touch function, set under pixel electrodes of liquid crystal displays. This lays difficulty for sensing electrodes to sense user touch, and thus decreases sensitivity of touch panels. 
     A conventional capacitive sensing component where a first transparent conductive line and a second transparent conductive line are mutually overlapped. The first conductive line and the second conductive line are connected to a driving line arranged horizontally and a sensing line arranged vertically, respectively. But parasitic capacitance often occurs at the crossing of the driving line and the sensing line. The parasitic capacitance has an influence on the aperture ratio of the pixel. Also, the bezel of the display near the active area has to be widened since a lot of driving lines are arranged, which contradicts modern displays with narrow bezels. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to propose an in-cell touch panel for resolving the aforementioned technical problem. The in-cell touch panel is an integration of a capacitive touch panel and an in plane switching (IPS) panel. 
     According to the present invention, a touch panel comprises: a substrate; a first metallic layer, arranged on the substrate, for forming a gate of a thin-film transistor (TFT) and a driving line, and the driving line used for transmitting a driving signal and a common voltage; a gate insulating layer, arranged on the first metallic layer; a second metallic layer, arranged on the gate insulating layer, for forming a source of the TFT and a drain of the TFT; an isolation layer, arranged on the second metallic layer, penetrated by a first hole and by a second hole, the second hole also penetrating the gate insulating layer, the first hole aiming at the source or the drain, and the second hole aiming at the driving line; a pixel electrode, connected to the source or the drain through the first hole; a driving electrode, connected to the driving line through the second hole; and a sensing electrode, for transmitting a sensing signal and the common voltage. The driving electrode and the sensing electrode are used as common electrode layers. 
     In one aspect of the present invention, the pixel electrode, the sensing electrode, and the driving electrode are formed by an identical conductive layer. 
     In another aspect of the present invention, the conductive layer is made of indium tin oxide (ITO) or metal. 
     In still another aspect of the present invention, the second metallic layer further comprises a data line, and the data line is used for transmitting a data voltage to the pixel electrode through the TFT. 
     In still another aspect of the present invention, the data line is used for transmitting the data voltage to the pixel electrode through the TFT when the driving line transmits the common voltage to the driving electrode. 
     In yet another aspect of the present invention, the data line stops transmitting the data voltage to the pixel electrode when the driving line transmits the driving signal to the driving electrode. 
     According to the present invention, a method of fabricating a touch panel comprises: forming a first metallic layer on a substrate; etching the first metallic layer for forming a gate of a thin-film transistor (TFT) and a driving line; forming a gate insulating layer on the gate of the TFT and the driving line; forming a second metallic layer on the gate insulating layer; etching the second metallic layer for forming a source of the TFT and a drain of the TFT; forming an isolation layer on the source of the TFT and the drain of the TFT; forming a first hole penetrating the isolation layer, a second hole penetrating the isolation layer and the gate insulating layer, aiming the first hole at the source or the drain, and aiming the second hole at the driving line; depositing a conductive layer on the isolation layer, the source, or the drain; and etching the conductive layer for forming a pixel electrode, a driving electrode, and a sensing electrode, the pixel electrode connected to the source or the drain through the first hole, the driving electrode connected to the driving line through the second hole, the sensing electrode used for transmitting a sensing signal and the common voltage, and the driving electrode and the sensing electrode used as common electrode layers at the same time. 
     In one aspect of the present invention, the conductive layer is made of indium tin oxide (ITO) or metal. 
     In another aspect of the present invention, the step of etching the second metallic layer for forming the source of the TFT and the drain of the TFT comprises: etching the second metallic layer for a data line, and the data line used for transmitting a data voltage to the pixel electrode through the TFT. 
     In yet another aspect of the present invention, before the step of forming the second metallic layer on the gate insulating layer, the method further comprises: forming an amorphous (a-Si) layer on the gate insulating layer; and etching the a-Si layer for forming a semiconductor layer of the TFT. 
     Compared with the conventional technology, the driving line arranged in the array substrate of the touch panel in the present invention can transmit common voltage and driving signals without adding extra driving signal lines for transmitting driving signals. According to the present invention, the bezel of the touch panel is not widened even though driving signal lines are arranged in the touch panel. Because the driving electrode, the sensing electrode, and the pixel electrode are formed on the same conductive layer, the processes of fabrication are simplified, and the costs are reduced. Also, parasitic capacitance does not easily occur even if extra driving signal lines are arranged in the touch panel. Touch sensitivity improves as well because the driving electrode, the sensing electrode, and the pixel electrode are fabricated from indium tin oxide (ITO) or metal. In addition, the driving lines are fabricated from the third metallic layer, so parasitic capacitance does not easily occur even though extra driving signal lines are arranged. 
     These and other features, aspects and advantages of the present disclosure will become understood with reference to the following description, appended claims and accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a display device according to one preferred embodiment of the present invention. 
         FIG. 2  is a schematic diagram of distribution of a touch capacitor in a touch area in a display device according to the embodiment of the present invention. 
         FIG. 3  is a cross-sectional view of the touch panel according to a first embodiment of the present invention. 
         FIG. 4  through  FIG. 9  are schematic diagrams of the array substrate in the touch panel as shown in the working drawing  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. 
     Please to refer to  FIG. 1  and  FIG. 2 .  FIG. 1  is a schematic diagram of a display device  10  according to one preferred embodiment of the present invention.  FIG. 2  is a schematic diagram of distribution of a touch capacitor in a touch area  50  in a display device  10  according to the embodiment of the present invention. The display device  10  comprises a touch panel  100 . The touch panel  100  is a liquid crystal panel with a touch function. The touch panel  100  comprises a display area  30  and a touch area  50 . The display area  30  is used for showing images. The touch area  50  is used for sensing where a human&#39;s finger touches. The display device  10  comprises a gate driver  12 , a controller  14 , and a source driver  16 . A plurality of pixels arranged in a matrix are disposed in the display area  30 . Each of the plurality of pixels comprises three pixel units  20 . Theses three pixel units  20  are the primary colors—red (R), green (G), and blue (B). The gate driver  12  outputs a scanning signal at regular intervals for turning on transistors  22  on each row successively. Meanwhile, the source driver  16  outputs a corresponding data signal to all of the pixel units  20  on one column so that all of the pixel units  20  on the column can be fully charged for showing diverse grayscales based on the difference of voltage between the data signal and the common voltage Vcom. When all of the pixel units  20  on the same row are fully charged, the scanning signal for the row is turned off by the gate driver  12 . Then, the gate driver  12  outputs a scanning signal again to turn on the transistors  22  on the next row. The source driver  16  charges and discharges the pixel units  20  on the next row. According to the step, all of the pixel units  20  are fully charged in the end. Subsequently, the pixel units  20  on the first row are charged again. 
     Please refer to  FIG. 2 . The touch area  50  comprises a plurality of capacitive driving electrodes  521 , a plurality of sensing electrodes  522  (touch electrode layers  52 ), a driving lines  53 , and a sensing line  54 . The plurality of capacitive driving electrodes  521  and the plurality of sensing electrodes  522  are mutually insulated. The plurality of capacitive driving electrodes  521  and sensing electrodes  522  are distributed in arrays. Each of the plurality of capacitive driving electrodes  521  can be shaped as round, triangle, or any other kind of shape. Each of the plurality of sensing electrodes  522  can be shaped as round, triangle, or any other kind of shape as well. 
     Each of the plurality of driving electrodes  521  is connected to a corresponding driving line  53 . The controller  14  comprises a driving signal unit  14   a . The driving signal unit  14   a  outputs a driving signal to the driving electrode  521  through the driving line  53 . Each of the plurality of sensing electrodes  522  is connected to a corresponding sensing line  54 . The sensed sensing signal is transmitted to a driving signal unit  14   b  of the controller  14 . The driving signal unit  14   a  outputs the driving signal to each of the plurality of driving electrodes  521  periodically. The capacitor between the driving electrode  521  and the sensing electrode  522  is a fixed value before a human&#39;s finger touches the monitor. When the human&#39;s finger touches the monitor, for example, operating functions on the monitor, the capacitance between the driving electrode  521  and the sensing electrode  522  which the touched position on the monitor corresponds to is subject to the human body and varies accordingly. So a sensing signal sent back by the sensing electrode  522  near the touched position is different from a sensing signal sent back by the sensing electrode  522  far away from the touched position. It implies that variations of capacitive values tell where a human&#39;s finger touches after the controller  14  senses, which implements the touch function. 
     Please refer to  FIG. 3 .  FIG. 3  is a cross-sectional view of the touch panel  100  according to a first embodiment of the present invention. The touch panel  100  comprises an array substrate  200 , a color film substrate  202 , and a liquid crystal layer  204 . A plurality of pixel electrodes  112 , a thin-film transistor (TFT)  22 , and a driving electrode  52  are disposed on the array substrate  200 . A glass substrate  102 , a first metallic layer  104 , a gate insulating layer  106 , a second metallic layer  108 , an isolation layer  110 , a pixel electrode  112 , a driving electrode  521 , and a sensing electrode  522  are arranged on the array substrate  200 . The first metallic layer  104  is arranged on the glass substrate  102  for forming a gate  22   g  of the TFT  22  and a driving line  53 . The driving line  53  is used for transmitting a driving signal generated by the controller  14  and a common voltage Vcom. The gate insulating layer  106  is arranged on the first metallic layer  104 . The second metallic layer  108  is arranged on the gate insulating layer  106  for forming a source  22   s  of the TFT  22  and a drain  22   d  of the TFT  22 . The isolation layer  110  is arranged on the second metallic layer  108 . The pixel electrode  112  is connected to the source  22   s  or the drain  22   d  through a first hole  141 . The driving electrode  521  is connected to the driving line  53  through a second hole  142 . The driving electrode  521 , the sensing electrode  522 , and the pixel electrode  112  are formed by an identical conductive layer. 
     The driving electrode  521  and the sensing electrode  522  are used as the common electrodes layer in this embodiment. On one hand, the source driver  16  transmits data voltage to the pixel electrode  112  through the TFT  22  when the controller  14  transmits the common voltage Vcom to the driving electrode  521  through the driving line  53 . The difference between the data voltage imposed on the pixel electrode  112  and the common voltage imposed on the driving electrode  521  (or the sensing electrode  522 ) pushes the liquid crystal molecules in the liquid crystal layer  204  between the pixel electrode  112  and the driving electrode  52  to rotate for showing diverse grayscales. On the other hand, the data line  114  stops transmitting the data voltage to the pixel electrode  112  when the controller  14  transmits the driving signal to the driving electrode  521  through the data line  53 . At this time, the sensing electrode  522  transmits the sensed sensing signal to the controller  54 . The liquid crystal molecules between the pixel electrode  112  and the driving electrode  521  (or the sensing electrode  522 ) keep the same rotating state. In other words, the driving electrode  521  and the sensing electrode  522  are used as the common electrodes for receiving the common voltage at the stage of image display and are used for sensing a touched and pressed position at the stage of touch and sense. 
     The color film substrate  202  comprises a color filter layer  116 , a black matrix layer  118 , and a glass substrate  120 . The color filter layer  116  is used for filtering out light with different colors. The black matrix layer  118  is used for blocking light leakage. A spacer  116  is used for making room between the array substrate  200  and the color film substrate  202  for accommodating the liquid crystal layer  204 . The driving line  53  is arranged in the vertical projecting area on the array substrate  200  on the black matrix layer  118  on the color film substrate  202  so as to reduce the influence of the driving line  53  on the aperture ratio. 
     Please refer to  FIG. 4  through  FIG. 9 .  FIG. 4  through  FIG. 9  are schematic diagrams of the array substrate  200  in the touch panel  100  as shown in the working drawing  FIG. 3 . As shown in  FIG. 4 , a glass substrate  102  is used. A deposition process for a metallic thin film is conducted. A first metallic layer (not shown) is formed on the surface of the glass substrate  102 . Also, a first lithography etching is conducted using a first mask. The gate  22   g  of the TFT  22 , the driving line  53 , and a scanning line (not shown) are formed after the first lithography etching. Although no scanning lines are shown in  FIG. 4 , the people skilled in this field are supposed to realize that the gate  22   g  is part of the scanning line. 
     Please refer to  FIG. 5 . The gate insulating layer  106  made of SiN x  is deposited. The gate insulating layer  106  covers the gate  22   g  and the driving line  53 . 
     Please refer to  FIG. 6 . An amorphous Si (a-Si) layer is deposited on the gate insulating layer  106  over the gate  22   g . Subsequently, the a-Si layer is etched using a second mask for forming a semiconductor layer  22   e . The semiconductor layer  22   c  is used as a semiconductor layer of the TFT  22 . 
     Please refer to  FIG. 7 . A second metallic layer (not shown) is formed on the surface of the gate insulating layer  106 . Also, the lithography etching is conducted using a third mask. The source  22   s  of the TFT  22 , the drain  22   d  of the TFT  22 , and the data line (not shown) are formed after the second lithography etching. The data line is directly to the source  22   s . The people skilled in this field are supposed to realize that the source  22   s  is part of the data line. In addition, the source  22   s  and the drain  22   d  can be switched. 
     Please refer to  FIG. 8 . The isolation layer  110  made of soluble polyfluoroalkoxy (PFA) is deposited. The isolation layer  110  covers the source  22   s , the drain  22   d , and the driving line  53 . The isolation layer  110  is etched using a fourth mask. Part of the isolation layer  110  on the drain  22   d , part of the isolation layer  110  on the driving line  53 , and the gate insulating layer  106  are removed for showing the surface of the drain  22   d  and the surface of the driving line  53 . The first hole  141  is formed on the drain  22   d . The second hole  142  is formed on the driving line  53 . In other words, the first hole  141  aims at the drain  22   d , and the second hole  142  aims at the driving line  53 . 
     Please refer to  FIG. 9 . A conductive layer (not shown) made of indium tin oxide (ITO), graphene, or metal is formed on the isolation layer  110 . Subsequently, the insulating layer is etched using a fifth mask for forming the pixel electrode  112 , the driving electrode  521 , and the sensing electrode  522  simultaneously. The pixel electrode  112  is electrically connected to the drain  22   d  of the TFT  22  through the formed first hole  141 . The driving electrode  521  is connected to the driving line  53  through the formed second hole  142 . A plurality of pixel electrodes  112  are formed. A plurality of pixel electrodes  112 , a plurality of driving electrodes  521 , and a plurality of sensing electrodes  522  are alternatively formed on the isolation layer  110 . 
     At this time, the array substrate  200  is finished completely. The combination of the color film substrate  202  and the liquid crystal layer  204  forms the touch panel  100  proposed by this embodiment. 
     At this time, the array substrate  200  is finished completely. The combination of the color film substrate  202  and the liquid crystal layer  204  forms the touch panel  100  proposed by this embodiment. 
     Further, the touch panel  100  can be an organic light-emitting diode (OLED) display panel with a touch function or other kinds of display panels in other embodiments. 
     Compared with the conventional technology, the driving line arranged in the array substrate of the touch panel in the present invention can transmit common voltage and driving signals without adding extra driving signal lines for transmitting driving signals. According to the present invention, the bezel of the touch panel is not widened even though driving signal lines are arranged in the touch panel. Because the driving electrode, the sensing electrode, and the pixel electrode are formed on the same conductive layer, the processes of fabrication are simplified, and the costs are reduced. Also, parasitic capacitance does not easily occur even if extra driving signal lines are arranged in the touch panel. Touch sensitivity improves as well because the driving electrode, the sensing electrode, and the pixel electrode are fabricated from indium tin oxide (ITO) or metal. In addition, the driving lines are fabricated from the third metallic layer, so parasitic capacitance does not easily occur even though extra driving signal lines are arranged. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements made without departing from the scope of the broadest interpretation of the appended claims.