Patent Publication Number: US-2015062468-A1

Title: Touch screen structure

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to a display device, and particularly to a touch screen structure. 
     BACKGROUND OF THE INVENTION 
     With rapid development of touch sensing technology, many electronic apparatuses such as mobile phones, notebook computers or tablet computers take advantage of touch devices to provide intuitive operation and easy human-machine interface. These electronic apparatuses hugely enter modern lives and great business opportunities are created. There are two known touch sensing technologies, i.e. capacitive sensing and resistive sensing. 
     For capacitive sensing, when the touch device is touched with a human finger or a conductive object, a capacitor is temporarily formed on the electrode corresponding to the touched position. Therefore, equivalent capacitance of the corresponding electrode changes. A sensor circuit can determine the touched position on the touch device according to the equivalent capacitance change of the corresponding electrode. 
     For resistive sensing, when an object such a finger or a stylus presses down onto a surface of the touch device, the upper electrode and the lower electrode are electrically connected at the pressed position so that the electrodes behave as a voltage divider circuit. Therefore, the sensor circuit can determine the pressed position on the touch device according to the voltage change of the upper electrode and the lower electrode. 
     Since large-area flat-panel display gains popularity now and touch sensing technology is widely used as a most friendly human-machine interface, there is an increased demand for large-area touch screen these days. In a conventional manufacturing process of the touch screen, a touch module and a display module are produced separately, and then the touch module is tightly attached to or laminated on the display module. However, large area of the touch screen usually leads to several problems such as misalignment of the touch module in the lamination or attachment procedure. Therefore, a touch screen structure which can avoid the problems is desired. 
     SUMMARY OF THE INVENTION 
     An aspect of the present disclosure provides a touch screen structure. The touch screen structure includes a display module, a transparent conductive member and a control circuit. The display module has a transparent substrate. The transparent conductive member is formed on a surface of the transparent substrate for providing a single layer capacitive touch panel having sensor pads. A space between two adjacent sensor pads is greater than or equal to 100 μm. The control circuit is electrically connected to the sensor pads for controlling the single layer capacitive touch panel. 
     In an embodiment, the single capacitive touch panel includes a connecting element electrically connected to the sensor pads and the control circuit. 
     In an embodiment, the connecting element includes connecting traces formed from the transparent conductive member for electrically connecting the sensor pads and the control circuit. Spacing between the connecting traces is greater than or equal to 100 μm. 
     In an embodiment, the touch screen structure includes a cover lens. The transparent conductive member is disposed between the cover lens and the transparent substrate. Air or a dielectric material exists in a gap between the cover lens and the transparent conductive member. 
     In an embodiment, the gap between the cover lens and the transparent conductive member has a thickness of 0.1 mm-5 mm. 
     In an embodiment, the transparent substrate is a glass substrate and the transparent conductive member is made of an indium tin oxide material, a transparent conductive oxide material, a conductive polymer material, a conductive ink or a conductive liquid material. 
     In an embodiment, the touch screen structure includes a polarizing layer covering the transparent conductive member. 
     Another aspect of the present disclosure provides a touch screen structure. The touch screen structure includes a display module, a transparent conductive member and a control circuit. The display module has a transparent substrate. The transparent conductive member is formed on a surface of the transparent substrate for providing a single layer capacitive touch panel having sensor pads and connecting traces. The connecting traces are electrically connected to the sensor pads. A space between two adjacent sensor pads is greater than or equal to 100 μm. The control circuit is electrically connected to the sensor pads for controlling the single layer capacitive touch panel. 
     In an embodiment, spacing between the connecting traces is greater than or equal to 100 μm. 
     Another aspect of the present disclosure provides a touch screen structure. The touch screen structure includes a display module, a transparent conductive member and a control circuit. The display module has a transparent substrate including an extending region. The transparent conductive member is formed on a surface of the transparent substrate for providing a single layer capacitive touch panel having sensor pads and connecting traces, which extend to the extending region. The control circuit is disposed at the extending region and electrically connected to the sensor pads through the connecting traces for controlling the single layer capacitive touch panel. 
     Another aspect of the present disclosure provides a touch screen structure. The touch screen structure includes a display module, a single layer capacitive touch panel and a control circuit. The display module has pixel units and a shielding area disposed between any two adjacent pixel units. The single layer capacitive touch panel has sensor pads and a connecting element on a specific surface. The connecting element is electrically connected to the sensor pads. The control circuit is electrically connected to the sensor pads for controlling the single layer capacitive touch panel. Edges of the sensor pads and/or the connecting element are arranged in the shielding area. 
     In an embodiment, the sensor pads and the connecting element are formed from a transparent conductive member. 
     Another aspect of the present disclosure provides a touch screen structure. The touch screen structure includes a backlight module, a display module, a conductive member and a control circuit. The display module is disposed relative to the backlight module. The conductive member is formed on a surface of the backlight module for providing a portion of a capacitive touch panel. The control circuit is electrically connected to the capacitive touch panel for controlling the capacitive touch panel. 
     In an embodiment, the conductive member is a transparent conductive member disposed between the backlight module and the display module. 
     In an embodiment, the conductive member is an opaque conductive member, and the backlight module is disposed between the conductive member and the display module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages of the present disclosure 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 illustrating a touch screen structure according to an embodiment of the present invention; 
         FIG. 2  is a schematic diagram illustrating a single layer capacitive touch panel of the touch screen structure; 
         FIG. 3  is a top view illustrating arrangement of sensor pads and connecting traces of the single layer capacitive touch panel; 
         FIG. 4  is a schematic diagram illustrating a touch screen structure according to another embodiment of the present invention; 
         FIGS. 5A-5C  illustrate another single layer capacitive touch panel of the touch screen structure according to the present disclosure; 
         FIG. 6  is a schematic diagram illustrating dimensions of a sensing cell and a capacitor of the single layer capacitive touch panel in  FIGS. 5A-5C ; and 
         FIGS. 7A and 7B  illustrate portions of a further single layer capacitive touch panel of the touch screen structure according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present disclosure will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
     Please refer to  FIG. 1 , a schematic diagram illustrating a touch screen structure according to an embodiment of the present invention. The touch screen structure  1  is a flat-panel display (e.g. LCD display) with touch sensing function. The touch screen structure  1  includes a display module  10 , a transparent conductive member  11 , a control circuit  12  and a capacitive touch panel (as shown in  FIG. 2 ). The display module  10  includes a transparent substrate  100 . In the embodiment, the transparent substrate  100  includes a lower glass substrate  101  and an upper glass substrate  102 . There are thin film transistors (TFT)  103  formed on a surface  1010  of the lower glass substrate  101 . In addition, color filters  104  are formed on a surface of the upper glass substrate  102 . 
     For example, the transparent conductive member  11  is formed on another surface of the upper glass substrate  102  by a semiconductor process such as a photolithography and etching process. A single layer capacitive touch panel  13  having many sensor pads  132  which is formed by such semiconductor process is shown in  FIG. 2 . In an embodiment, the transparent conductive member  11  may be a transparent conductive layer made of metal, nonmetal, nanomaterial, whisker material, etc. In other embodiments, the transparent conductive member  11  is formed by a screen printing method with low cost. Two screen printing methods are given here for illustration purpose. In the first screen printing method, at first, a transparent conductive material such as an indium tin oxide (ITO) material or a transparent conductive oxide (TCO) material is formed on the upper glass substrate  102 . Then, an etching paste with patterns is transferred onto the transparent conductive material. Reaction between the etching paste and the transparent conductive material occurs. Finally, the etching paste and the reacted transparent conductive material are washed out, and the left transparent conductive material (e.g. ITO material or TCO material) forms the transparent conductive member  11 . In general, the smallest line width of the transparent conductive member  11  reaches 100 μm-150 μm when the etching paste is used in the screen printing method. In the second screen printing method, a conductive polymer material, a conductive ink or a conductive liquid material is directly printed onto the upper glass substrate  102  to form a pattern of the transparent conductive member  11 . The smallest line width of the transparent conductive member  11  is determined according to the printed material, for example, 100 μm-150 μm for a conductive polymer material. 
     Although the transparent conductive member  11  of the single layer capacitive touch panel  13  is formed on the upper glass substrate  102 , it is not intended to limit thereto. For example, the transparent conductive member  11  may be formed on a surface  1011  of the lower glass substrate  101 . 
     Please refer to  FIG. 2 , a schematic diagram illustrating a single layer capacitive touch panel of the touch screen structure. The single capacitive touch panel  13  includes many sensor pads  132  and a connecting element  130  on the upper glass substrate  102 . The sensor pads  132  are separately disposed on the upper glass substrate  102  and electrically isolated from one other. Some of the sensor pads  132  are hexagonal or regular hexagonal sensor pads. For some hexagonal sensor pads  133 , each of them is surrounded by six nearby sensor pads  132 . In  FIG. 2 , the hexagonal sensor pads  132  are regularly arranged. The sensor pads  132  at edges of the upper glass substrate  102  are not entirely surrounded by other sensor pads  132  and there are less than six nearby sensor pads  132 . The space between any two adjacent sensor pads  132  may be greater than or equal to 100 μm. Low cost screen printing method is sufficient to form the transparent conductive member  11 , and it is not required to take advantage of precision photolithography and etching process to form fine space. Increasing an area of the sensor pads  132  or grouping the sensor pads  132  can increase a sensible distance for floating touch between the single layer capacitive touch panel  13  and the human finger, palm or conductive object. 
     Please refer to  FIG. 1  and  FIG. 2  again. The connecting element  130  is electrically connected to the sensor pads  132  and the control circuit  12 . The connecting element  130  may include, but is not limited to, connecting traces, a flexible printed circuit (FPC), a flexible printed circuit assembly (FPCA) or a combination thereof. In an embodiment, the connecting element  130  includes several connecting traces electrically connected to respective sensor pads  132 . In another embodiment, the connecting element  130  further includes a flexible printed circuit or a flexible printed circuit assembly to replace and omit several connecting traces. 
     In an embodiment as shown in  FIG. 2 , the connecting element  130  is implemented by connecting traces  131  disposed on the upper glass substrate  102 . Each connecting trace  131  is electrically connected to a corresponding sensor pad  132 . There is one-to-one correspondence between the connecting traces  131  and the sensor pads  132 . The sensor pads  132  and the corresponding connecting traces  131  may be made of the same material through the same formation process. In another embodiment, the sensor pads  132  and the corresponding connecting traces  131  are made of different materials or formed through different formation processes. As described above, the connecting traces  131  and the sensor pads  132  may be formed by a screen printing method and the spacing between the connecting traces  131  is greater than or equal to 100 μm. 
     Please refer back to  FIG. 1 , the upper glass substrate  102  of the transparent substrate  100  may have an extending region  1021  more than the lower glass substrate  101 . The control circuit  12  is disposed at the extending region  1021  and electrically connected to the sensor pads  132  through the connecting element  130  which extends to the extending region  1021 . 
     The touch screen structure  1  may further include a cover lens  14 . The material of the cover lens  14  may be, but is not limited to, glass material. According to this design, the transparent conductive member  11  is disposed between the cover lens  14  and the upper glass substrate  102  of the transparent substrate  100 . A gap  2  between the cover lens  14  and the upper glass substrate  102  of the transparent substrate  100  is filled with air or other dielectric material. The gap  2  has a thickness about 0.1 mm-5 mm. The user may touch the cover lens  14  to perform a control action through proximity sensing. Since the cover lens  14  configured to protect the transparent conductive member  11  is not tightly attached to/laminated on or even does not touch the upper glass substrate  102 , the problems such as misalignment of the touch module occurring in the attachment or lamination procedure are avoided so that the production yield of the touch screen structure  1  is highly improved, especially for large-area display. 
     In an embodiment, the touch screen structure  1  may further include a polarizing layer  15  with a thickness about 1.5 μm-2 μm covering the transparent conductive member  11 . The polarizing layer  15  is formed on the transparent conductive member  11  before assembly of the cover lens  14 . Air or other dielectric material exists in the gap  2  between the cover lens  14  and the polarizing layer  15 . 
     Please refer to  FIG. 3 , a top view illustrating arrangement of sensor pads and connecting traces of the single layer capacitive touch panel. The upper glass substrate  102  of the display module  10  includes pixel units  32  and a shielding area  31 . Since tilt angles of the liquid crystal molecules at edges of the pixel units  32  can not be well controlled, the shielding area  31  is set to hide the liquid crystal molecules at the edges of the pixel units  32 . The shielding area  31  is usually located between two adjacent pixel units  32 . In this example, the shielding area  31  includes a black matrix for shielding light. In an embodiment, edges of the sensor pads  132  and the connecting element  130  are also arranged in the shielding area  31  to prevent from being seen. 
     For example, the edges of the sensor pads  132  and the connecting traces  131  are arranged at an area covered by the black matrix. As shown in  FIG. 3 , the edges of the sensor pads  132  and the connecting traces  131  are aligned with central lines (e.g. line A-A′ or line B-B′) of shielding parts of the shielding area  31  wherein each shielding part is defined by two adjacent sensor pads  132 . Layout of the sensor pads  132 , the connecting traces  131  and relative wiring can be designed according to the arrangement of the pixel units  32 . In fact, it is not necessary that the edges of the sensor pads  132  and the connecting traces  131  are aligned with the central lines of the shielding parts of the shielding area  31 , and their positions can be adjusted in different applications. Thus, light passing the edges of the sensor pads  132  and the connecting traces  131  is minimized to prevent the viewers from recognizing the sensor pads  132  and the connecting traces  131 . 
     As described above, in the touch screen structure  1  of the present disclosure, the transparent conductive member  11  is directly formed on the surface of the transparent substrate  10  to function as a single layer capacitive touch panel  13  including sensor pads  132 . The problems such as misalignment of the touch module occurring in the attachment or lamination procedure are avoided. Furthermore, since air or other dielectric material is provided in the gap  2  between the cover lens  14  and the transparent conductive member  11 , the cover lens  14  for protecting the sensor pads  132  is not tightly attached to/laminated on the upper glass substrate  102  so that the production yield of the touch screen structure  1  is improved. 
     According to the present disclosure, it is to be noted that the transparent conductive member is not limited to be formed on the surface of the upper glass substrate. Please refer to  FIG. 4 , a schematic diagram illustrating a touch screen structure according to another embodiment of the present invention. The touch screen structure  4  includes a display module  10 , a backlight module  40 , a conductive member  41 , a back plate  44 , a capacitive touch panel (not shown) and a control circuit (not shown). In the embodiment, the conductive member  41  is formed on a surface of the backlight module  40 . The backlight module  40  is disposed between the conductive member  41  and the display module  10 . The conductive member  41  forms a single layer capacitive touch panel (not shown) including many sensor pads  42  and a connecting element  43 . The structure of the capacitive touch panel and the arrangement of the control circuit are similar to those described with reference to  FIG. 1  and  FIG. 2 . 
     In this embodiment, since the sensor pads  42  and the connecting element  43  are disposed on a back surface of the backlight module  40 , the material of the sensor pads  42  and the connecting element  43  may be made of opaque material, e.g. better conductive material such as metal. Increasing an area of the sensor pads  42  or grouping the sensor pads  42  can increase a sensible distance for floating touch between the single layer capacitive touch panel and the human finger, palm or conductive object. By this method, even if user&#39;s finger or the conductive object does not directly touch the sensor pads  42 , or the sensor pads  42  are located under the display module  10  and the backlight module  40 , the touch sensing function is still operable. Please refer to US 2014/0083834 and US 2014/0035865 for the relative description. However, it is not intended to limit the conductive member  41  to be made of the opaque conductive material. If the conductive member  41  is made of a transparent conductive material, the conductive member  41  may be formed on a front surface (a surface near the display module  10 ) of the backlight module  40  rather than a back surface (a surface far from the display module  10 ) of the backlight module  40 . In other words, the conductive member  41  is disposed between the backlight module  40  and the display module  10 . 
     Furthermore, the present disclosure can be applied to other capacitive touch panel instead of the single layer capacitive touch panel. For example, for a two dimensional or a 1.5 dimensional (1.5D) capacitive touch panel (not shown), entire capacitor electrodes or a portion of capacitor electrodes of the capacitive touch panel and corresponding signal input/output lines may be formed on either the front surface or the back surface of the backlight module  40 . The 1.5 dimensional structure will be described in detail in the following paragraphs. 
     It is to be noted that although the touch screen structure  4  includes a cover lens  14  at the front side as shown in  FIG. 4 , it is not necessary to provide the cover lens. Alternatively, the user may touch the back plate  44  of the touch screen structure  4  for touch sensing. Therefore, the design flexibility of the touch screen structure is increased. 
     Please refer to  FIGS. 5A-5C  illustrating another single layer capacitive touch panel of the touch screen structure according to the present disclosure. In this embodiment, a 1.5 dimensional (1.5D) structure is shown. In  FIG. 5A , there are M*N sensing cells  900  on the substrate  90 , and they are arranged in an M*N matrix (e.g. M=9 and N=13). Each of the sensing cells  900  has a corresponding capacitor  93 . Most of the capacitors  93  have a smaller area than the sensing cells  900 . For example, the area fraction of the capacitors  93  to the sensing cells  900  is about ½-⅓. 
       FIGS. 5B and 5C  only illustrate portions, i.e. sensing cells  900  at four corners of the single layer capacitive touch panel. Each sensing cell  900  has a first capacitor electrode  901 , total M*N first capacitor electrodes  901  (e.g. 9*13 first capacitor electrodes  901 ) in the capacitive touch panel. The first capacitor electrodes  901  are formed on a surface of the substrate  90 . For the same column in the M*N matrix, M first capacitor electrodes  901  are connected to respective signal lines  911 - 91 M, which form a signal line group. Hence, for N columns in the capacitive touch panel, there are total N signal line groups. Further, the signal lines  911 - 91 M with the same serial number (i.e. the signal lines for the first capacitor electrodes  901  in the same row) are electrically connected in parallel (not shown) so that N signal lines for the N first capacitor electrodes in the same row is integrated to a first signal input/output terminal. Hence, for M rows, there are M first signal input/output terminals  1911 - 191 M. 
     Furthermore, M*N second electrodes  902  are formed on the same surface of the substrate  90 . For the same column, M second electrodes  902  are electrically connected to a second signal input/output terminal. Hence, for N columns, there are N second signal input/output terminals  921 - 92 N. According to this arrangement, every one of the first capacitor electrodes  901  and adjacent second capacitor electrode  902  forms a capacitor  93 , total M*N capacitors  93  in the capacitive touch panel. The M first signal input/output terminals  1911 - 191 M and the N second signal input/output terminals  921 - 92 N may be connected to signal input lines and signal output lines, respectively, or vice versa. 
     In the embodiment as shown in  FIGS. 5B and 5C , each first capacitor electrode  901  and each second capacitor electrode  902  have first sub-electrodes and second sub-electrodes, respectively. The first sub-electrodes and the second sub-electrodes have a zigzag pattern and they are alternately arranged. Compared with conventional capacitors having two big electrode plates, such arrangement can increase capacitance of the capacitors  93 . No dielectric layer is required to be sandwiched between the first capacitor electrodes  901  and the second capacitor electrodes  902 . Therefore, the first capacitor electrodes  901  and the second capacitor electrodes  902  are provided in a single layer and the formation steps can be reduced. 
     The applicant has provided new sensing methods in other patent applications (e.g. U.S. patent application Ser. No. 14/162,004 and Taiwanese Patent Application No. 102145721) to increase sensing resolution, double along one axis and quadruple for area sensing resolution. By adopting these sensing methods, even though the capacitors are not arranged as close as before, the same sensing quality of the touch screen structure can be reached. Please refer to  FIG. 6 , a width W 1  of the sensing cell  900  is designed as twice as a width of a touch area of a touch object. If the touch object is a human finger, the width of the touch area is about 4 mm. Therefore, the width W 1  of the sensing cell  900 , usually designed in a shape of rectangle or a square, may be 8 mm, but is not limited to this value. The width W 1  of the sensing cell  900  may range from 6 mm to 13 mm, and the width W 2  of the capacitor  93  may range from 4 mm to 8 mm. The ratio of the width W 2  to the width W 1  is about 8/13 to 2/3. Therefore, in this example, the width W 3  of the routing region for various signal lines or connecting traces ranges from 2 mm to 5 mm. In this embodiment, the M signal lines  911 - 91 M connected to the first capacitor electrodes  901  in the same column pass the routing region. Larger routing region can accommodate wider lines or traces to avoid high resistance of the lines or traces due to small sectional area. However, it is to be noted that since the routing region is not an effective touch region, the width W 3  of the routing region is designed to be similar to the width of the touch area so that the routing region will not affect sensing accuracy. It is acceptable that the width W 3  is 1/2-4/5 of the width of the touch area. 
     For example, if the width of the touch area of the human finger is 4mm, the width W 3  of the routing region may range from 2 mm to 5 mm. An area of the capacitor  93  is 64/169-16/36 of an area of the sensing cell  900 , roughly speaking, about 1/3-1/2. 
     If the touch object is a stylus and the width of the touch area is about 1 mm-2 mm, the width W 1  of the sensing cell  900  is about 6 mm and the width W 2  of the capacitor  93  is about 5 mm-4.5 mm. Thus, the width W 3  of the routing region is about 1 mm-1.5 mm and less than the range is disadvantageous to form the lines or traces. In another case, if the touch object is a human palm and the width of the touch area is about 20 mm, the width W 1  of the sensing cell  900  is about 40 mm and the width W 2  of the capacitor  93  is about 20 mm in an example. Thus, the width W 3  of the routing region is about 20 mm-30 mm. In brief, the width W 2  of the capacitor  93  is similar to the width of the touch area of the touch object or 0.5-4.5 times wider than the touch area of the touch object. The width W 3  of the routing region is similar to, may be 1/2-3/2 of the width of the touch area. The width W 1  of the sensing cell  900  is twice as the width of the touch area, or 1.5-2.5 times wider than the width of the touch area. 
     Similar to the sensor pads  42  and the connecting traces  43  in the previous embodiment, the capacitor electrodes and the signal lines can be implemented by a transparent conductive member so as to be integrated into the touch screen structure. Furthermore, dummy transparent conductive lines  99  can be disposed in an empty region where no capacitor electrodes or signal lines are formed ( FIGS. 7A and 7B ) to avoid visual nonuniformity. 
     In an embodiment, these transparent electrodes and signal lines are patterned and formed through a photolithography and etching process. Alternatively, if wider spacing between the capacitor electrodes/signal lines is acceptable, greater than 100 μm for example, the low coat screen printing method rather than the etching process can be utilized to form the capacitor electrodes and the signal lines. In other embodiments, the capacitor electrodes and the signal lines may be made of opaque material (e.g., better conductive material such as metal) through the screen printing method if the single layer capacitive touch panel is disposed in an invisible region. Thus, no dummy transparent conductive lines are required to save the conductive material usage. Other modifications such as edges of the capacitor electrodes and/or signal lines being arranged in the shielding area are also applicable. 
     In conclusion, the conductive member is directly formed on a surface of the transparent substrate or the surface of the backlight module to provide the single layer or other dimensional capacitive panel having sensor pads. The problems such as misalignment of the touch module occurring in the attachment or lamination procedure are avoided so that the production yield of the touch screen structure is highly improved. Furthermore, the conductive member may be optionally formed on different surfaces according to different applications so as to increase the design flexibility of the touch screen structure. 
     While the disclosure 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 be limited to the disclosed embodiment. 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.