PATENT DOCUMENT

Publication Number: US-10198123-B2
Application Number: US-201415306054-A
Country: US
Kind Code: B2

Title: Mitigating noise in capacitive sensor

Abstract:
The disclosed embodiments relate to forming an area on a touchscreen which electrically isolates a portion of the viewable area of the touchscreen from a capacitive sensor associated with the touchscreen.

Claims:
What is claimed is: 
     
       1. A touchscreen comprising:
 a liquid crystal display having an upper surface area and a lower surface area; 
 a capacitive array adjacent said lower surface area; 
 an optically transparent electrically conductive layer deposited between said lower surface area and said capacitive array, said layer including:
 a first area electrically isolating said liquid crystal display and said capacitive array, said first area including less than said upper surface area, and a second area permitting electrical transmission between said upper surface area and said capacitive array. 
 
 
     
     
       2. The touchscreen of  claim 1  wherein said optically transparent electrically conductive layer includes indium tin oxide. 
     
     
       3. The touchscreen of  claim 1  wherein said optically transparent electrically conductive layer includes silver nanowire matrix. 
     
     
       4. The touchscreen of  claim 1  wherein said optically transparent electrically conductive layer is deposited on a thin film transistor layer in said liquid crystal display. 
     
     
       5. The touchscreen of  claim 1  wherein said optically transparent electrically conductive layer is deposited on a transparent substrate between said liquid crystal display and said capacitive array. 
     
     
       6. The touchscreen of  claim 1  wherein said first area and said second area are separated by an interface area formed on said optically transparent electrically conductive layer. 
     
     
       7. The touchscreen of  claim 1  wherein said second area is electromagnetically connected to a processor, thereby facilitating detection of an object adjacent the liquid crystal display and above the second area. 
     
     
       8. An electronic device comprising:
 a housing; 
 a touchscreen in said housing, said touchscreen including: a liquid crystal display having an upper surface area and a lower surface area; 
 a capacitive array beneath said lower surface area; 
 an optically transparent electrically conductive layer deposited between said lower surface area and said capacitive array, said layer including: a first area less in size than said upper surface area, and a second area electrically isolated from the first area, the second area operative to capacitively sense an object adjacent the touchscreen. 
 
     
     
       9. The electronic device of  claim 8  wherein said optically transparent electrically conductive layer includes one of indium tin oxide and silver nanowire. 
     
     
       10. The electronic device of  claim 8  wherein said optically transparent electrically conductive layer is deposited on a thin film transistor layer in said liquid crystal display. 
     
     
       11. The electronic device of  claim 8  wherein said optically transparent electrically conductive layer is deposited on a transparent substrate between said liquid crystal display and said capacitive array. 
     
     
       12. The electronic device of  claim 8  wherein said first area is approximately centered within said second area. 
     
     
       13. The electronic device of  claim 8  wherein said first area is offset within said second area. 
     
     
       14. The electronic device of  claim 8  wherein said first area and said second area are separated by an interface area formed on said optically transparent electrically conductive layer.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a 35 U.S.C. § 371 application of PCT/US2014/034817, filed on Apr. 21, 2014, and entitled “Mitigating Noise in Capacitive Sensor,” which is incorporated by reference as if fully disclosed herein. 
     FIELD 
     The described embodiments relate generally to touchscreens and touch-sensitive devices. More particularly, the present embodiments relate to forming an area on a touchscreen which electrically isolates a portion of the viewable area of the touchscreen such that a user may use a portion of the screen as a touchscreen and another portion for viewing without electrical interference between the two portions. 
     BACKGROUND 
     A touchscreen is an electronic visual display that the user can control through simple or multi-touch gestures by touching the screen with one or more fingers. Some touchscreens can also be manipulated with other implements detect such as a stylus or ordinary or specially coated gloves. The user can use the touchscreen to react to what is displayed and to control how it is displayed (for example by zooming the text size). The touchscreen enables the user to interact directly with what is displayed, rather than using a mouse, touchpad, or any other intermediate device other than the optional stylus. 
     Touchscreens are common in devices such as game consoles, all-in-one computers, tablet computers, and smartphones. They can also be attached to computers or, as terminals, to networks. They also play a prominent role in the design of digital appliances such as personal digital assistants (PDAs), satellite navigation devices, mobile phones, and video games and some books. The popularity of smartphones, tablets, and many types of information appliances is driving the demand and acceptance of common touchscreens for portable and functional electronics. Touchscreens are found in the medical field and in heavy industry, as well as for automated teller machines (ATMs), and kiosks such as museum displays or room automation, where keyboard and mouse systems do not allow a suitably intuitive, rapid, or accurate interaction by the user with the display&#39;s content. 
     A capacitive touchscreen panel consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (ITO). As the human body is also an electrical conductor, touching the surface of the screen results in a distortion of the screen&#39;s electrostatic field, measurable as a change in capacitance. When a user touches the surface, the system records the change in the electrical current that flows through the display. Different technologies may be used to determine the location of the touch. The location is then sent to the controller for processing. The controller interprets the command that the touch represents and communicates the command to the appropriate application in the electronic device. 
     SUMMARY 
     An embodiment is disclosed that includes an area on a touchscreen which is electrically isolated from a portion of the viewable area of the touchscreen such that the capacitive sensor associated with the touchscreen does not detect a change in capacitance generated when a user touches a portion of a non-sensing region of the touchscreen but does detect a change in capacitance generated when a user touches a reference plane portion of the touchscreen. In one embodiment the reference plane and viewable areas are formed on a surface of the liquid crystal display associated with the touchscreen. In another embodiment, the reference plane and viewable areas are formed on a surface of a transparent layer which may be affixed between a liquid crystal display and a capacitive array. In another embodiment, an electronic device including the touchscreen is disclosed. 
     An embodiment is disclosed including a method for making a touchscreen which includes depositing an optically transparent electrically conductive layer of material on the thin film transistor (TFT) layer of an LCD. A portion of the deposited layer is then removed, to electromagnetically isolate a reference plane area and a non-sensing region on the TFT layer. The reference plane area is electrically connected to the system such that the reference plane area is active and a user&#39;s touch may be sensed by the capacitive array. The liquid crystal display is affixed to a capacitive array to complete the touchscreen. 
     In another embodiment, a method is disclosed depositing an optically transparent electrically conductive layer of material on an optically transparent separate layer. A portion of the optically transparent electrically conductive layer of material is then removed to define a reference plane area and a non-sensing region as in the embodiment above. The reference plane area is electromagnetically connected to the system such that the reference plane area is active and a user&#39;s touch may be sensed by the capacitive array. The optically transparent layer is sandwiched between the LCD and the capacitive array to form the touchscreen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  shows a perspective view of a various layers of a conventional Liquid Crystal Display (LCD); 
         FIG. 2  shows a front view of a conventional capacitive array; 
         FIG. 3  shows a tablet computer held by a user; 
         FIG. 4  shows a perspective view of a tablet including a touchscreen; 
         FIG. 5  shows a tablet with touchscreen including viewable and reference plane areas on the touchscreen; 
         FIG. 6  shows a side view of an LCD including one embodiment of an optically transparent electrically conductive layer on a thin film transistor layer of the LCD; 
         FIG. 7  shows one embodiment of a non-sensing region and reference plane area on a touchscreen; 
         FIG. 8  shows a side view of an alternate embodiment including a transparent layer having an optically transparent electrically conductive surface on the rear surface of an LCD; 
         FIG. 9  shows a perspective view of an alternate embodiment including a transparent layer sandwiched between an LCD and a capacitive array; 
         FIG. 10  shows an alternate embodiment configuration of a non-sensing region and reference plane area on a touchscreen; 
         FIG. 11  is a flow chart illustrating the touchscreen manufacturing steps according to one embodiment; and 
         FIG. 12  is a flow chart illustrating the touchscreen manufacturing steps according to an alternate embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. The embodiments are discussed below with reference to  FIGS. 1-12 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these Figures is for explanatory purposes only and are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     Referring to  FIG. 1 , the various layers forming a conventional Liquid Crystal Display (LCD) are shown in exploded view. A polarizing filter film  11  with a vertical axis to polarize light as it enters is shown adjacent to glass substrate  12  with Indium Tin Oxide (ITO) electrodes deposited thereon. Indium Tin Oxide is a useful transparent conducting oxide because it has two desirable properties, electrical conductivity and optical transparency. It can easily be deposited as a thin film by physical vapor deposition, electron beam evaporation or a variety of sputter deposition or other techniques. 
     When certain of the ITO electrodes in  FIG. 1  are activated, they may determine the shapes that will appear on the LCD. In  FIG. 1 , the numbers  888  appear on layer  12  representing the activation of those corresponding electrodes when LCD is assembled and activated. Vertical ridges etched on the surface of  12  are parallel with the vertical polarizing layer  11 . A liquid crystal layer  13  includes liquid crystals sandwiched between glass substrates  12  and  14 . Glass substrate  14  includes common electrode film (ITO) with horizontal ridges to line up with a polarizing filter film  15 , which has an orientation to block/pass light along a horizontal axis. A reflective surface  16  may be included to reflect light back to a viewer. In a backlit LCD, this layer  16  is replaced with a light source. Layers  11  through  16  may be affixed one to another to form a conventional liquid crystal display. Other LCD constructions may also be used in various embodiments of this disclosure. 
     In LCD operation, each pixel of the LCD consists of a layer of liquid crystal molecules aligned between two transparent electrode layers ( 12  and  14  in  FIG. 1 ), and two polarizing filters. The axes of optical transmission of layers  11  and  15  are perpendicular to each other. Without the liquid crystal layer between the polarizing filters, light passing through the first filter may be blocked by the second (crossed) polarizer. 
     Liquid crystals do not allow light to pass uniformly along both axes of the crystals. Grooves are formed on the surface of both pieces of glass  12  and  14  at 90 degrees to one another. The molecules in liquid crystal layer  13  in-between line up in a helix. When light from the backlight or reflective layer  16  passes through the first polarizer and enters the sandwich it&#39;s rotated by the liquid crystals so as to allow it to pass through the second polarizer and emerge out the front of the screen. This is known as the normally white mode. Applying an electric field across the sandwich causes the crystals to line up lengthwise. The light that passes through the first polarizer is not rotated by the crystals and can no longer pass through the front of the screen which is referred to as black mode. By controlling the voltage between these transparent electrodes the intensity of the light that passes through can be controlled. By adding a color filter array layer, the transmitted light may be controlled so as to appear in various color wavelengths. 
     Many touchscreens include a capacitive sensing array to sense changes in electrostatic fields caused by movement of an electrical conductor from one sensor to another in the array. Typically, a mutual-capacitance capacitive sensing array includes two layers or sets of traces/lines formed from a conductive coating, which may be transparent (such as indium tin oxide). In some embodiments, the layers of the array may be formed on opposing surfaces with the layers separated by an adhesive spacer. In a mutual capacitance array there is a capacitor at every intersection of each row and column of the array. A voltage is applied to the rows and columns and by bringing a finger or a conductive stylus close to the surface of the array the local field changes which alters the mutual capacitance. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location by measuring the voltage in the other axis. Mutual capacitance allows multi-touch operation where multiple fingers, palms or styli can be accurately tracked at the same time. Referring to  FIG. 2  a capacitive array  10  is shown with intersecting conductive tracks  20  in a grid like arrangement with capacitors at the intersection of tracks  20 . 
     Certain embodiments may use a mutual capacitance sensing array to correlate changes in capacitance to an input force, thereby sensing force in a non-binary fashion, in addition to or instead of sensing a touch. For example, a force exerted on a cover glass or other portion of a touchscreen  19  may cause local deformation of the touchscreen, thereby moving the upper and lower portions of the capacitive array closer to one another. This motion may generate a corresponding change in capacitance, insofar as a smaller distance separates the elements of the capacitive array and capacitance between two elements varies inversely with the square of the distance between the elements. Thus, a sensed change in capacitance may be indicative of, or correlated to, a force exerted on the touchscreen. The exact location of the force may be determined through the use of multiple force sensors spaced apart from one another, each of which may output a different change in capacitance in response to a force exerted in a local area. As one example, sensors closer to the location of a touch may detect a higher change in capacitance than sensors further away from the location of the touch. Alternately, a touch-sensing array may be used in addition to a force-sensing array in order to relatively precisely place the location of a touch. 
     Further, although capacitive sensing arrays described herein (such as the active reference planes discussed below) may be described in terms of mutual capacitance, the embodiments and concepts disclosed herein may operate equally with self-capacitive sensors. 
     Referring to  FIG. 3 , an electronic device, one example of which is a tablet  17 , is shown held by a user  18 . Tablet  17  includes a touchscreen  19  which may include a liquid crystal display as will be described below. User  18  may activate various applications or functions on touchscreen  19  by moving or touching finger  21  on appropriate portions of touchscreen  19 . Thus, user  18  may be able to control the functions of tablet  17  without any additional equipment and without using his or her other hand. Alternatively, user  18  could hold tablet  17  with one hand and use fingers from his or her other hand to select functions or applications on touchscreen  19 . Additional sample electronic devices that may incorporate a touchscreen and embodiments described herein include mobile telephones, computing displays, touch screens for appliances and/or home automation, in-vehicle displays, and so on. Further, embodiments may take the form of other touch-sensitive devices, such as track pads and other suitable input devices, and descriptions and disclosure herein may apply to such embodiments. 
     Referring to  FIG. 4 , tablet  17  includes touchscreen  19  as described above. Tablet  17  includes housing  22  which contains touchscreen  19 . Touchscreen  19  may include a liquid crystal display, a cover glass overlying the display, and a capacitive array (not shown) behind the liquid crystal display. Various icons  23  appear on touchscreen  19  representing various applications or functions that may be accessed on tablet  17 . The human body is an electrical conductor and by touching or moving finger  21  over icons  23 , a touch may be measured as a change in capacitance detected by capacitor arrays located behind and in close proximity to the LCD and under the active viewing area of the LCD. The location of the user&#39;s finger  21  touch is sent to the controller (not shown) in tablet  17  for processing. The processor may thus determine which icon, and thus which application or function, user  18  has selected. 
     As stated above, the capacitive array is located in close proximity to and under the LCD. Capacitive array is also located adjacent to other electrical components in the electronic device. As such capacitive array is subject to exposure to electrical noise that could distort electrostatic fields, or capacitive measurements thereof, employed to sense a touch location. Similarly, the electrostatic fields generated by the capacitive array may distort the signals in liquid crystal display, which may result in visual artifacts visible to the user on touchscreen  19 . It may be desirable to define and/or pattern various regions on, beneath, or related to the touchscreen  19  such that the signals from the capacitive array associated with the liquid crystal display and the signals from the display itself do not interfere with each other so as to distort the visual image to a user or to introduce errors into the location determination of the capacitive array. 
     Thus, in many applications of tablet  17 , it may be advantageous to use only selected areas of touchscreen  19  as an active touch-sensing, or force-sensing, area. Referring to  FIG. 5 , tablet  17  is shown including touchscreen  19 . Touchscreen  19  is mounted in housing  22 . In one embodiment, touchscreen  19  includes a non-sensing region  24  surrounded by a capacitive sensing area  25  that is part of an active reference plane  26 . (It should be noted that the demarcation of the capacitive sensing area  25  is shown in the figure for clarity, but such demarcation may not be visible on an electronic device; further, the capacitive sensing area  25  may be a portion of the touchscreen  19  in some embodiments.) That is, in this embodiment, non-sensing region  24  is electrically isolated from capacitive array behind the LCD screen such that the visual display on non-sensing region  24  does not include optical artifacts introduced by electrical interference from the capacitive array behind the LCD. 
     By limiting the area on touchscreen  19  on which the capacitive array senses a user&#39;s touch, force, or other input, certain economies may be achieved. For example, providing power to the entire viewable area of the LCD raises additional issues including higher resistance and increased coupling of display noise. By isolating non-sensing region  24 , only the smaller area of the reference plane  26  requires power for the corresponding area of the capacitive array behind the screen. In addition, by limiting the areas of touchscreen  19  which serves as an “active” touchscreen area, certain aesthetic appeal is also achieved in that the displayed icons  23  do not interfere with the non-sensing region  24  and fingerprints or other residue left by user&#39;s finger  21  on the non-sensing region  24  may be reduced or eliminated. 
     In the embodiment shown in  FIG. 5  user  18  may activate icons  23  on capacitive sensing area  25  around the perimeter of touchscreen  19 . That is, icons  23  are only visible on area  25  and are not present on non-sensing region  24 . If a user&#39;s finger  21  contacts non-sensing region  24  the capacitance of the finger is shielded from the capacitive array behind non-sensing region  24  and such contacts are thus not detected by the capacitive array; alternately, the finger may capacitively couple to the capacitive array but the array may not be electrically active, and thus may not generate any output. In capacitive sensing area  25  surrounding non-sensing region  24  there is no electrical shielding such that the capacitive load of the user&#39;s finger  21  contacting the force and/or touch capacitive sensing area  25  on touchscreen  19  is sensed by the capacitive array as described above. 
     Referring again to  FIG. 5 , the capacitive sensing area  25  is part of an active reference plane  26  (e.g., an active sensing region) that is generated by the electrical isolation of non-sensing region  24  from the capacitive array. The reference plane  26  is created from an optically transparent yet electrically conductive material as, for example, ITO or a silver nano wire matrix. Because available conductive materials create optical artifacts including but not limited to transmissive loss, color shift and reflection, the creation of the reference plane area  26  may be done with a uniform covering of the conductive material in the non-sensing region  24  of the LCD such that perceptible optical defects are not introduced and visible to the user  18  in the non-sensing region  24 . 
     The portion of the non-sensing region excluding the active reference plane (e.g., the non-sensing region  24 ) may be patterned in a fashion similar to, or identical to, the patterning of the active reference plane but is typically electrically isolated from the active reference plane. Thus, this non-sensing region  24  may not be electrically powered even when the active reference plane  26  is powered. 
     The creation of the active reference plane area  26  and the non-sensing region  24  on touchscreen  19  results in an interface area  27  which is the boundary between reference plane area  26  and non-sensing region  24 . The interface area  27  between non-sensing region  24  and active reference plane  26  may be made small enough to prevent artifacts that may otherwise be visible to a user  18  on touchscreen  19  in the interface area  27 . In another embodiment, this interface area  27  may be designed such that, while visible artifacts are present, the entire screen is populated with regular artifacts such that the overall appearance of touchscreen  19  remains uniform to user  18 . In another embodiment, interface area  27  could be designed so as to be decorative or definitive to provide a clear visual delineation between non-sensing region  24  and active reference plane  26 . Likewise, the interface area  27  and its boundaries may not be visible from the exterior of the device and the shape of the interface area may vary from what is shown. 
     Referring to  FIG. 5 , the delineation of the interface area  27  between non-sensing region  24  and active reference plane  26  is shown. The active reference plane areas  26  of the conductive material behind the LCD display which are actively powered for use in the capacitive sensor array are electrically isolated from adjacent areas of conductive material under viewable area  24 . In one embodiment, the patterned conductive layer may be a layer of ITO or other conductive material located between LCD and the capacitive array. 
     Referring to  FIG. 6 , in one embodiment a side view of an LCD assembly is shown, such as may be assembled in or incorporated into a suitable electronic device (although the device housing is omitted for simplicity). It should be appreciated that the relative sizes, shapes and positions of the various layers may vary between embodiments; thus, illustrated side views and/or cross-sectional views in the figures are examples only. A layer of ITO  28  may be located on the back exterior surface of thin film transistor glass layer  29  and between glass layer  29  and the rear polarizing layer  31  in the LCD panel. Referring to  FIG. 1 , ITO layer  28  may be deposited between glass layer  14  and polarizing filter film  15 . In  FIG. 6 , color filter array  32  is also shown adjacent to thin film transistor layer  29 . The active portion of the layer of indium tin oxide  28  which is deposited on the back of thin film transistor layer  29  defines a reference plane or region, as will be described below, and is electrically connected to a controller  33  in an electronic device. 
     Referring to  FIG. 7 , once ITO layer  28  is deposited on the surface of glass layer  29 , interface area  27  may be generated. That is, the portion of layer  28  which will correspond to non-sensing region  24  may be electrically isolated from the portion of layer  28  which corresponds to reference plane area  26 . Interface area  27  may be created by sputtering, photolithography, masking, laser etching, chemical etching, or any other combination of deposition, masking or material ablation or removal. While indium tin oxide (ITO) has been disclosed in one embodiment, layer  28  may be silver nanowire or any other electrically conductive optically transparent material known in the art. 
     Referring to  FIG. 8 , a side view of an alternate embodiment of an LCD assembly is shown. In this embodiment, the patterned conductive ITO layer  28  may be deposited on a separate layer  34  made of polymer, glass or other transparent material. Layer  34  may then be affixed to the outside of rear polarizing layer  31  on the LCD panel. This rear polarizing layer  31  may correspond to polarizing film layer  15  in  FIG. 1 . Thus, in this embodiment, layer  34  may be affixed to the rear of the LCD panel. The LCD panel assembly in  FIG. 8  also includes thin film transistor glass layer  29  in the LCD panel and color filter array  32  shown adjacent to thin film transistor layer  29 . Front polarizing layer  11  is shown adjacent to color filter array layer  32 . Referring to  FIG. 1 , in this embodiment, ITO layer  28  is deposited on glass layer  34  and layer  34  is affixed to the rear of LCD panel behind reflective layer  16  and in front of the capacitive array as will be described below. Reference plane outer ring area  26  is connected to controller  33  as previously described. 
     Referring to  FIG. 9 , a perspective view of touchscreen  19  is shown including an LCD panel  35  and a capacitive array  36 . LCD panel  35  may be the LCD panel shown in  FIG. 1  and capacitive array  36  may be the array described in  FIG. 2 , depending upon the embodiment. That is, as discussed above with respect to  FIGS. 6 and 8 , conductive ITO layer  28  may be positioned on a separate layer  32  between conventional LCD panel  35  and conventional capacitive array  36  as in  FIG. 8  or it may be deposited onto thin film transistor layer  29  in the modified LCD panel as described in  FIG. 6 . Both embodiments are illustrated in  FIG. 9  although it can be appreciated that only one of these embodiments is employed at any one time. In either embodiment, ITO layer provides electrical isolation for an area of LCD panel  35  from the electrostatic fields generated within capacitive array  36  due to the changes in capacitance generated by movement of user finger  21  or other device on the screen of LCD panel  35 . 
     Referring to  FIG. 10 , tablet  17  is shown including touchscreen  19 . Touchscreen  19  is mounted in housing  22 . In one embodiment, touchscreen  19  includes a non-sensing region  37  surrounded by a capacitive sensing area  38  that is part of an active reference plane  39 . That is, in this embodiment, non-sensing region  37  is electrically isolated from capacitive array behind the LCD screen such that the visual display on non-sensing region  37  does not include optical artifacts introduced by electrical interference from the capacitive array behind LCD. This embodiment differs from that shown in  FIG. 5  in that non-sensing region  37  is not centered on touchscreen  19 . The portion  41  of capacitive sensing area  38  below the non-sensing region  37  is larger than the portion  42  of capacitive sensing area  38  above non-sensing region  37 . In this embodiment, the larger area  41  allows the inclusion of additional icons  23  as opposed to the embodiment shown in  FIG. 5 . That is, area  41  provides a larger active working area while permitting the viewable screen portion to remain approximately the same size as in  FIG. 5 . As with other embodiments, the delineation between the non-sensing region  37  and capacitive sensing area  38  si shown for purposes of illustration and may not be visible in a physical device. 
     In the embodiment shown in  FIG. 10 , user  18  may activate icons  23  on capacitive sensing area  38 / 41  of touchscreen  19 ; the icon activation may be determined through either touch sensing or localized force sensing. As with the embodiment shown in  FIG. 5 , icons  23  are only present on area  38 / 41  and are not present on non-sensing region  37 . If a user&#39;s finger  21  contacts non-sensing region  37  the capacitance of the user&#39;s finger  21  may couple to the capacitive array behind non-sensing region  37 , but that array is not powered and so does not output any signal to indicate a touch or force. Further, in some embodiments, the user&#39;s finger may be electrically shielded from the array in the non-sensing region  37 . 
     By contrast, in capacitive sensing area  38  surrounding non-sensing region  37  there is no electrical shielding and the sensing array is active (e.g., powered), such that the capacitance of the user&#39;s finger  21  contacting the capacitive sensing area  38  on touchscreen  19  is sensed by the capacitive array as described above. Capacitive sensing area  38  is part of an active reference plane  39  that is defined by the electrical isolation of non-sensing region  37  from the capacitive array. 
     The creation of the active reference plane area  39  and the non-sensing region  37  on touchscreen  19  results in an interface area  43  which is the boundary between reference plane area  39  and non-sensing region  37  as was described above with reference to  FIG. 5 . As with the embodiment described in  FIG. 5 , the active reference plane areas  39  of the conductive material behind the LCD display which are actively powered for use in the capacitive sensor array are electrically isolated from adjacent areas of conductive material under viewable area  37 . The ITO layer  28 , which is deposited on the back of thin film transistor layer  29  in  FIG. 6  or on glass layer  34  in the embodiment shown in  FIG. 8 , is the same. However, as with the embodiment described in  FIG. 7 , once ITO layer  28  is deposited on the surface of glass layer  29  or glass layer  34 , the interface area  43  may be generated. That is, the portion of ITO layer  28  which will correspond to non-sensing region  37  may be electrically isolated from the portion of layer  28  that corresponds to reference plane area  39 . Interface area  43  may be created by sputtering, photolithography, masking, laser etching, chemical etching, or any other combination of deposition, masking or material ablation or removal. 
     Referring to  FIG. 11 , a flow chart is shown illustrating the steps for manufacturing a touchscreen according to one embodiment. Referring to  FIG. 11 , Liquid Crystal Display (LCD) is provided at step  44 . An optically transparent electrically conductive layer of material, which may be Indium Tin Oxide (ITO) in one embodiment, is deposited on the thin film transistor (TFT) layer of the LCD in step  45 . In step  46 , a portion of the ITO layer is then removed, etched, ablated, or the like, as described above, to electromagnetically isolate a reference plane area and a non-sensing region on the TFT layer. Step  46  results in electromagnetically isolating the reference plane area from the non-sensing region on the TFT layer. In step  47 , the reference plane area is electrically connected to the controller in the electronic device system such that the reference plane area is active and a user&#39;s touch may be sensed by the capacitive array. In step  48 , the LCD is affixed to a capacitive array to complete the touchscreen. As described above, step  46  may result in a centered viewable area as described in  FIGS. 5 and 7  or it may result in an offset viewable area as described in the embodiment described in  FIG. 10 . 
     Referring to  FIG. 12 , a flow chart is shown illustrating the steps for manufacturing a touchscreen according to another embodiment. Referring to  FIG. 12 , Liquid Crystal Display (LCD) is provided at step  49 . An optically transparent electrically conductive layer of material, which may be Indium Tin Oxide (ITO) in one embodiment, is deposited on an optically transparent separate layer made of polymer, glass or other transparent material as described above. In step  52 , a portion of the ITO layer is then removed, etched, ablated, etc. as described above to define a reference plane area and a non-sensing region on the layer as was described in step  46  above. This results in electromagnetically isolating the reference plane area from the non-sensing region on the transparent layer. As described above, step  52  may result in a centered viewable area as described in  FIGS. 5 and 7  or it may result in an offset viewable area as described in the embodiment described in  FIG. 10 . In step  53 , the reference plane area is electromagnetically connected to the controller in the electronic device such that the reference plane area is active and a user&#39;s touch may be sensed by the capacitive array. In step  54 , the optically transparent layer is sandwiched between the LCD and the capacitive array to complete the touchscreen. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not target to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20140421
Publication Date: 20190205
Grant Date: 20190205
Priority Date: 20140421
Inventors: CHEN, CHENG
UTTERMANN, ERIK A.
GIBBS, KEVIN D.
AGARWAL, MANU
GRUNTHANER, MARTIN P.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/0418", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F2001/133302", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133528", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1368", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2201/121", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13439", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133514", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0414", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133302", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13439", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133514", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133528", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1368", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2201/121", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 50792582