PATENT DOCUMENT

Publication Number: US-12197684-B2
Application Number: US-202318393367-A
Country: US
Kind Code: B2

Title: Ultra-thin touch sensors

Abstract:
Touch screens with ultra-thin stack-ups can provide for a lower profile device, can improve the optical image on the display by reducing the display to cover glass distance, and can reduce the weight of the device. In some examples, the thickness of the touch screen stack-up can be reduced and/or the border region reduced, by removing the flex circuit connection from the stack-up. A flexible substrate can be used to enable routing of touch electrodes to touch circuitry. In some examples including a shield layer, the thickness of the touch screen stack-up can be reduced by routing the shield layer to a shield electrode on the touch sensor panel. The shield layer can then be routed to touch sensing circuitry via the flexible substrate. In some examples, the touch sensor panel or a portion of thereof can be integrated with the polarizer.

Claims:
The invention claimed is: 
     
       1. A touch screen comprising:
 a display; and 
 a touch sensor panel disposed on the display, the touch sensor panel comprising:
 a substrate formed from a flexible material including a first portion and a second portion; 
 a plurality of first touch electrodes formed on a first surface of the substrate; 
 a plurality of first conductive traces disposed on the first surface of the substrate configured to route the plurality of first touch electrodes to touch sensing circuitry; and 
 a first protective layer disposed on the plurality of first conductive traces; 
 wherein:
 the first portion of the substrate including the plurality of first touch electrodes is planar, 
 the second portion of the substrate including the plurality of first conductive traces is non-planar such that the substrate extends beyond a first dimension of the display, and 
 the second portion of the substrate wraps around from the touch sensor panel to a different layer in the touch screen, the different layer separated from the touch sensor panel by the display. 
 
 
 
     
     
       2. The touch screen of  claim 1 , further comprising a first coating layer disposed on the first surface of the substrate, wherein the plurality of first touch electrodes formed on the first surface of the substrate are disposed on the first coating layer. 
     
     
       3. The touch screen of  claim 2 , further comprising a second protective layer disposed on the first coating layer, wherein the plurality of first touch electrodes formed on the first surface of the substrate are disposed on the second protective layer. 
     
     
       4. The touch screen of  claim 1 , wherein the second portion of the substrate is separated from the display such that a gap is formed between the second portion of the substrate and the display. 
     
     
       5. The touch screen of  claim 1 , wherein the substrate wraps around from the touch sensor panel to a different layer in the touch screen on a first side of the touch screen without the substrate wrapping around to the different layer in the touch screen on a second side of the touch screen, different than the first side of the touch screen. 
     
     
       6. The touch screen of  claim 1 , wherein the plurality of first touch electrodes are formed from indium tin oxide and the plurality of first conductive traces are formed without indium tin oxide. 
     
     
       7. The touch screen of  claim 1 , wherein the plurality of first touch electrodes are formed from silver nanowire and the plurality of first conductive traces are formed from silver nanowire. 
     
     
       8. The touch screen of  claim 1 , wherein the first portion of the substrate is coterminous with the display. 
     
     
       9. The touch screen of  claim 1 , wherein a third portion of the substrate is planar and separated from the first portion of the substrate by the display, the third portion including at least part of the plurality of first conductive traces. 
     
     
       10. The touch screen of  claim 1 , wherein the first protective layer is further disposed on the plurality of first touch electrodes. 
     
     
       11. A touch screen comprising:
 a display; and 
 a touch sensor panel disposed on the display, the touch sensor panel comprising:
 a substrate formed from a flexible material including a first portion and a second portion; 
 a plurality of first touch electrodes formed on a first surface of the substrate; 
 a plurality of first conductive traces disposed on the first surface of the substrate configured to route the plurality of first touch electrodes to touch sensing circuitry; 
 a first protective layer disposed on the plurality of first conductive traces; 
 a plurality of second touch electrodes formed on a second surface of the substrate opposite the first surface of the substrate; 
 a plurality of second conductive traces disposed on the second surface of the substrate configured to route the plurality of second touch electrodes to the touch sensing circuitry; and 
 a second protective layer disposed on the plurality of second conductive traces; 
 wherein:
 the first portion of the substrate including the plurality of first touch electrodes is planar, 
 the second portion of the substrate including the plurality of first conductive traces is non-planar such that the substrate extends beyond a first dimension of the display, 
 the first portion of the substrate that is planar includes the plurality of second touch electrodes, and 
 a third portion of the substrate including the plurality of second conductive traces is non-planar such that the substrate extends beyond a second dimension of the display, different than the first dimension of the display. 
 
 
 
     
     
       12. The touch screen of  claim 11 , wherein the third portion of the substrate wraps around from the touch sensor panel to a different layer in the touch screen. 
     
     
       13. The touch screen of  claim 11 , wherein the third portion of the substrate is planar and separated from the first portion of the substrate by the display, the third portion including at least part of the plurality of second conductive traces. 
     
     
       14. The touch screen of  claim 11 , further comprising a first coating layer disposed on the second surface of the substrate, wherein the plurality of second touch electrodes formed on the second surface of the substrate are disposed on the first coating layer. 
     
     
       15. The touch screen of  claim 14 , further comprising a third protective layer disposed on the first coating layer, wherein the plurality of second touch electrodes formed on the second surface of the substrate are disposed on the third protective layer. 
     
     
       16. The touch screen of  claim 11 , wherein the third portion of the substrate is separated from the display such that a gap is formed between the third portion of the substrate and the display. 
     
     
       17. The touch screen of  claim 11 , wherein the plurality of second touch electrodes are formed from indium tin oxide and the plurality of second conductive traces are formed without indium tin oxide. 
     
     
       18. The touch screen of  claim 11 , wherein the plurality of second touch electrodes are formed from silver nanowire and the plurality of second conductive traces are formed from silver nanowire. 
     
     
       19. The touch screen of  claim 11 , wherein a fourth portion of the substrate is planar and separated from the first portion of the substrate by the display, the fourth portion including at least part of the plurality of second conductive traces. 
     
     
       20. The touch screen of  claim 11 , further comprising a first coating layer disposed on the first surface of the substrate, wherein the plurality of first touch electrodes formed on the first surface of the substrate are disposed on the first coating layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/712,339, filed Dec. 12, 2019, and published on Jun. 25, 2020 as U.S. Publication No. 2020-0201482, which claims the benefit under 35 USC 119(e) of U.S. Provisional Patent Application No. 62/782,264, filed Dec. 19, 2018, the contents of which are incorporated herein by reference in their entirety for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     This relates generally to touch screens, and more particularly, to touch screens with ultra-thin stack-ups. 
     BACKGROUND OF THE DISCLOSURE 
     Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD), light emitting diode (LED) display or organic light emitting diode (OLED) display that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch and the position of the touch on the touch sensor panel, and the computing system can then interpret the touch in accordance with the display appearing at the time of the touch, and thereafter can perform one or more actions based on the touch. In the case of some touch sensing systems, a physical touch on the display is not needed to detect a touch. For example, in some capacitive-type touch sensing systems, fringing electrical fields used to detect touch can extend beyond the surface of the display, and objects approaching near the surface may be detected near the surface without actually touching the surface. 
     Capacitive touch sensor panels can be formed by a matrix of partially or fully transparent or non-transparent conductive plates (e.g., touch electrodes) made of materials such as Indium Tin Oxide (ITO). It is due in part to their substantial transparency that some capacitive touch sensor panels can be overlaid on a display to form a touch screen, as described above. Some touch screens can be formed by at least partially integrating touch sensing circuitry into a display pixel stack-up (i.e., the stacked material layers forming the display pixels). 
     SUMMARY OF THE DISCLOSURE 
     This relates to touch screens with ultra-thin stack-ups. Reducing the thickness of the touch screen can provide for a lower profile device, can improve the optical image on the display by reducing the display to cover glass distance, and can reduce the weight of the device. In some examples, the thickness of the touch screen stack-up can be reduced and/or the border region reduced, by removing the flex circuit connection from the stack-up. A flexible substrate can be used to enable routing of touch electrodes to touch circuitry. In some examples, the touch screen stack-up can include a shield layer between the touch sensor panel and the display. In some examples, the thickness of the touch screen stack-up including a shield layer can be reduced by routing the shield layer to a shield electrode on the touch sensor panel. The shield layer can then be routed to touch sensing circuitry via the flexible substrate. Additionally, or alternatively, in some examples, as described herein, the touch sensor panel or a portion of thereof can be integrated with the polarizer. Integrating the touch sensor panel with the polarizer can reduce the thickness of the touch screen stack-up because one substrate can be used for the touch sensor panel and polarizer in place of separate substrates for each of the touch sensor panel and the polarizer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A- 1 E  illustrate example systems that can include touch screens with ultra-thin stack-ups according to examples of the disclosure. 
         FIG.  2    illustrates an example computing system including a touch screen according to examples of the disclosure. 
         FIG.  3 A  illustrates an exemplary touch sensor circuit corresponding to a self-capacitance measurement of a touch node electrode and sensing circuit according to examples of the disclosure. 
         FIG.  3 B  illustrates an exemplary touch sensor circuit corresponding to a mutual-capacitance drive line and sense line and sensing circuit according to examples of the disclosure. 
         FIG.  4 A  illustrates a touch screen with touch electrodes arranged in rows and columns according to examples of the disclosure. 
         FIG.  4 B  illustrates a touch screen with touch node electrodes arranged in a pixelated touch node electrode configuration according to examples of the disclosure. 
         FIG.  5 A  illustrates an exemplary touch screen that can be used in a touch sensitive device according to examples of the disclosure. 
         FIG.  5 B  illustrates an exemplary polarizer stack-up according to examples of the disclosure. 
         FIGS.  6 A- 6 D  illustrate examples of touch screen stack-ups with a flexible substrate according to examples of the disclosure. 
         FIGS.  7 A- 7 J  illustrate examples of flexible substrates and routing according to examples of the disclosure. 
         FIGS.  8 A- 8 B  illustrate an example of touch screen stack-up with a shield layer routed to the touch sensor panel examples of the disclosure. 
         FIGS.  9  and  10    illustrate examples of an integrated touch sensor panel and polarizer according to examples of the disclosure. 
         FIG.  11    illustrates an exemplary process for forming an integrated touch sensor panel and polarizer according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the disclosed examples. 
     This relates to touch screens with ultra-thin stack-ups. Reducing the thickness of the touch screen can provide for a lower profile device, can improve the optical image on the display by reducing the display to cover glass distance, and can reduce the weight of the device. In some examples, the thickness of the touch screen stack-up can be reduced and/or the border region reduced, by removing the flex circuit connection from the stack-up. A flexible substrate can be used to enable routing of touch electrodes to touch circuitry. 
     In some examples, the touch screen stack-up can include a shield layer between the touch sensor panel and the display. In some examples, the thickness of the touch screen stack-up including a shield layer can be reduced by routing the shield layer to a shield electrode on the touch sensor panel. The shield layer can then be routed to touch sensing circuitry via the flexible substrate. 
     Additionally, or alternatively, in some examples, as described herein, the touch sensor panel or a portion of thereof can be integrated with the polarizer. Integrating the touch sensor panel with the polarizer can reduce the thickness of the touch screen stack-up because one substrate can be used for the touch sensor panel and polarizer in place of separate substrates for each of the touch sensor panel and the polarizer. 
       FIGS.  1 A- 1 E  illustrate example systems that can include touch screens with ultra-thin stack-ups according to examples of the disclosure.  FIG.  1 A  illustrates an example mobile telephone  136  that includes a touch screen  124  that can be implemented with ultra-thin stack-ups according to examples of the disclosure.  FIG.  1 B  illustrates an example digital media player  140  that includes a touch screen  126  that can be implemented with ultra-thin stack-ups according to examples of the disclosure.  FIG.  1 C  illustrates an example personal computer  144  that includes a touch screen  128  that can be implemented with ultra-thin stack-ups according to examples of the disclosure.  FIG.  1 D  illustrates an example tablet computing device  148  that includes a touch screen  130  that can be implemented with ultra-thin stack-ups according to examples of the disclosure.  FIG.  1 E  illustrates an example wearable device  150  that includes a touch screen  132  and can be attached to a user using a strap  152  and that can be implemented with ultra-thin stack-ups according to examples of the disclosure. It is understood that a touch screen with ultra-thin stack-ups can be implemented in other devices as well. 
     In some examples, touch screens  124 ,  126 ,  128 ,  130  and  132  can be based on self-capacitance. A self-capacitance based touch system can include a matrix of small, individual plates of conductive material or groups of individual plates of conductive material forming larger conductive regions that can be referred to as touch electrodes or as touch node electrodes (as described below with reference to  FIG.  4 B ). For example, a touch screen can include a plurality of individual touch electrodes, each touch electrode identifying or representing a unique location (e.g., a touch node) on the touch screen at which touch or proximity is to be sensed, and each touch node electrode being electrically isolated from the other touch node electrodes in the touch screen/panel. Such a touch screen can be referred to as a pixelated self-capacitance touch screen, though it is understood that in some examples, the touch node electrodes on the touch screen can be used to perform scans other than self-capacitance scans on the touch screen (e.g., mutual capacitance scans). During operation, a touch node electrode can be stimulated with an alternating current (AC) waveform, and the self-capacitance to ground of the touch node electrode can be measured. As an object approaches the touch node electrode, the self-capacitance to ground of the touch node electrode can change (e.g., increase). This change in the self-capacitance of the touch node electrode can be detected and measured by the touch sensing system to determine the positions of multiple objects when they touch, or come in proximity to, the touch screen. In some examples, the touch node electrodes of a self-capacitance based touch system can be formed from rows and columns of conductive material, and changes in the self-capacitance to ground of the rows and columns can be detected, similar to above. In some examples, a touch screen can be multi-touch, single touch, projection scan, full-imaging multi-touch, capacitive touch, etc. 
     In some examples, touch screens  124 ,  126 ,  128 ,  130  and  132  can be based on mutual capacitance. A mutual capacitance based touch system can include electrodes arranged as drive and sense lines that may cross over each other on different layers (in a double-sided configuration), or may be adjacent to each other on the same layer (e.g., as described below with reference to  FIG.  4 A ). The crossing or adjacent locations can form touch nodes. During operation, the drive line can be stimulated with an AC waveform and the mutual capacitance of the touch node can be measured. As an object approaches the touch node, the mutual capacitance of the touch node can change (e.g., decrease). This change in the mutual capacitance of the touch node can be detected and measured by the touch sensing system to determine the positions of multiple objects when they touch, or come in proximity to, the touch screen. As described herein, in some examples, a mutual capacitance based touch system can form touch nodes from a matrix of small, individual plates of conductive material. 
     In some examples, touch screens  124 ,  126 ,  128 ,  130  and  132  can be based on mutual capacitance and/or self-capacitance. The electrodes can be arranged as a matrix of small, individual plates of conductive material (e.g., as in touch node electrodes  408  in touch screen  402  in  FIG.  4 B ) or as drive lines and sense lines (e.g., as in row touch electrodes  404  and column touch electrodes  406  in touch screen  400  in  FIG.  4 A ), or in another pattern. The electrodes can be configurable for mutual capacitance or self-capacitance sensing or a combination of mutual and self-capacitance sensing. For example, in one mode of operation electrodes can be configured to sense mutual capacitance between electrodes and in a different mode of operation electrodes can be configured to sense self-capacitance of electrodes. In some examples, some of the electrodes can be configured to sense mutual capacitance therebetween and some of the electrodes can be configured to sense self-capacitance thereof. 
       FIG.  2    illustrates an example computing system including a touch screen according to examples of the disclosure, although it should be understood that the illustrated touch screen  220  (which includes a touch sensor panel) could instead be only a touch sensor panel. Computing system  200  can be included in, for example, a mobile phone, tablet, touchpad, portable or desktop computer, portable media player, wearable device or any mobile or non-mobile computing device that includes a touch screen or touch sensor panel. Computing system  200  can include a touch sensing system including one or more touch processors  202 , peripherals  204 , a touch controller  206 , and touch sensing circuitry (described in more detail below). Peripherals  204  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. Touch controller  206  can include, but is not limited to, one or more sense channels  208 , channel scan logic  210  and driver logic  214 . Channel scan logic  210  can access RAM  212 , autonomously read data from the sense channels and provide control for the sense channels. In addition, channel scan logic  210  can control driver logic  214  to generate stimulation signals  216  at various frequencies and/or phases that can be selectively applied to drive regions of the touch sensing circuitry of touch screen  220 , as described in more detail below. In some examples, touch controller  206 , touch processor  202  and peripherals  204  can be integrated into a single application specific integrated circuit (ASIC), and in some examples can be integrated with touch screen  220  itself. 
     It should be apparent that the architecture shown in  FIG.  2    is only one example architecture of computing system  200 , and that the system could have more or fewer components than shown, or a different configuration of components. The various components shown in  FIG.  2    can be implemented in hardware, software, firmware or any combination thereof, including one or more signal processing and/or application specific integrated circuits. 
     Computing system  200  can include a host processor  228  for receiving outputs from touch processor  202  and performing actions based on the outputs. For example, host processor  228  can be connected to program storage  232  and a display controller, such as a Liquid-Crystal Display (LCD) driver or more generally, display driver  234 . It is understood that although some examples of the disclosure are described with reference to LCD displays, the scope of the disclosure is not so limited and can extend to other types of displays, such as Light-Emitting Diode (LED) displays, including Organic LED (OLED), Active-Matrix Organic LED (AMOLED) and Passive-Matrix Organic LED (PMOLED) displays. The display driver  234  can provide voltages on select (e.g., gate) lines to each pixel transistor and can provide data signals along data lines to these same transistors to control the pixel display image. 
     Host processor  228  can use display driver  234  to generate a display image on touch screen  220 , such as a display image of a user interface (UI), and can use touch processor  202  and touch controller  206  to detect a touch on or near touch screen  220 , such as a touch input to the displayed UI. The touch input can be used by computer programs stored in program storage  232  to perform actions that can include, but are not limited to, moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device, answering a telephone call, placing a telephone call, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. Host processor  228  can also perform additional functions that may not be related to touch processing. 
     Note that one or more of the functions described herein can be performed by firmware stored in memory (e.g., one of the peripherals  204  in  FIG.  2   ) and executed by touch processor  202 , or stored in program storage  232  and executed by host processor  228 . The firmware can also be stored and/or transported within any non-transitory computer-readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer-readable storage medium” can be any medium (excluding signals) that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. In some examples, RAM  212  or program storage  232  (or both) can be a non-transitory computer readable storage medium. One or both of RAM  212  and program storage  232  can have stored therein instructions, which when executed by touch processor  202  or host processor  228  or both, can cause the device including computing system  200  to perform one or more functions and methods of one or more examples of this disclosure. The computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like. 
     The firmware can also be propagated within any transport medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “transport medium” can be any medium that can communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
     Touch screen  220  can be used to derive touch information at multiple discrete locations of the touch screen, referred to herein as touch nodes. Touch screen  220  can include touch sensing circuitry that can include a capacitive sensing medium having a plurality of drive lines  222  and a plurality of sense lines  223 . It should be noted that the term “lines” is sometimes used herein to mean simply conductive pathways, as one skilled in the art will readily understand, and is not limited to elements that are strictly linear, but includes pathways that change direction, and includes pathways of different size, shape, materials, etc. Drive lines  222  can be driven by stimulation signals  216  from driver logic  214  through a drive interface  224 , and resulting sense signals  217  generated in sense lines  223  can be transmitted through a sense interface  225  to sense channels  208  in touch controller  206 . In this way, drive lines and sense lines can be part of the touch sensing circuitry that can interact to form capacitive sensing nodes, which can be thought of as touch picture elements (touch pixels) and referred to herein as touch nodes, such as touch nodes  226  and  227 . This way of understanding can be particularly useful when touch screen  220  is viewed as capturing an “image” of touch (“touch image”). In other words, after touch controller  206  has determined whether a touch has been detected at each touch nodes in the touch screen, the pattern of touch nodes in the touch screen at which a touch occurred can be thought of as an “image” of touch (e.g., a pattern of fingers touching the touch screen). As used herein, an electrical component “coupled to” or “connected to” another electrical component encompasses a direct or indirect connection providing electrical path for communication or operation between the coupled components. Thus, for example, drive lines  222  may be directly connected to driver logic  214  or indirectly connected to drive logic  214  via drive interface  224  and sense lines  223  may be directly connected to sense channels  208  or indirectly connected to sense channels  208  via sense interface  225 . In either case an electrical path for driving and/or sensing the touch nodes can be provided. 
       FIG.  3 A  illustrates an exemplary touch sensor circuit  300  corresponding to a self-capacitance measurement of a touch node electrode  302  and sensing circuit  314  (e.g., corresponding to a sense channel  208 ) according to examples of the disclosure. Touch node electrode  302  can correspond to a touch electrode  404  or  406  of touch screen  400  or a touch node electrode  408  of touch screen  402 . Touch node electrode  302  can have an inherent self-capacitance to ground associated with it, and also an additional self-capacitance to ground that is formed when an object, such as finger  305 , is in proximity to or touching the electrode. The total self-capacitance to ground of touch node electrode  302  can be illustrated as capacitance  304 . Touch node electrode  302  can be coupled to sensing circuit  314 . Sensing circuit  314  can include an operational amplifier  308 , feedback resistor  312  and feedback capacitor  310 , although other configurations can be employed. For example, feedback resistor  312  can be replaced by a switched capacitor resistor in order to minimize a parasitic capacitance effect that can be caused by a variable feedback resistor. Touch node electrode  302  can be coupled to the inverting input (−) of operational amplifier  308 . An AC voltage source  306  (V ac ) can be coupled to the non-inverting input (+) of operational amplifier  308 . Touch sensor circuit  300  can be configured to sense changes (e.g., increases) in the total self-capacitance  304  of the touch node electrode  302  induced by a finger or object either touching or in proximity to the touch sensor panel. Output  320  can be used by a processor to determine the presence of a proximity or touch event, or the output can be inputted into a discrete logic network to determine the presence of a proximity or touch event. 
       FIG.  3 B  illustrates an exemplary touch sensor circuit  350  corresponding to a mutual-capacitance drive line  322  and sense line  326  and sensing circuit  314  (e.g., corresponding to a sense channel  208 ) according to examples of the disclosure. Drive line  322  can be stimulated by stimulation signal  306  (e.g., an AC voltage signal). Stimulation signal  306  can be capacitively coupled to sense line  326  through mutual capacitance  324  between drive line  322  and the sense line. When a finger or object  305  approaches the touch node created by the intersection of drive line  322  and sense line  326 , mutual capacitance  324  can change (e.g., decrease). This change in mutual capacitance  324  can be detected to indicate a touch or proximity event at the touch node, as described herein. The sense signal coupled onto sense line  326  can be received by sensing circuit  314 . Sensing circuit  314  can include operational amplifier  308  and at least one of a feedback resistor  312  and a feedback capacitor  310 .  FIG.  3 B  illustrates a general case in which both resistive and capacitive feedback elements are utilized. The sense signal (referred to as Vin) can be inputted into the inverting input of operational amplifier  308 , and the non-inverting input of the operational amplifier can be coupled to a reference voltage V ref . Operational amplifier  308  can drive its output to voltage V o  to keep V in  substantially equal to V ref , and can therefore maintain V in  constant or virtually grounded. A person of skill in the art would understand that in this context, equal can include deviations of up to 15%. Therefore, the gain of sensing circuit  314  can be mostly a function of the ratio of mutual capacitance  324  and the feedback impedance, comprised of resistor  312  and/or capacitor  310 . The output of sensing circuit  314  Vo can be filtered and heterodyned or homodyned by being fed into multiplier  328 , where Vo can be multiplied with local oscillator  330  to produce V detect . V detect  can be inputted into filter  332 . One skilled in the art will recognize that the placement of filter  332  can be varied; thus, the filter can be placed after multiplier  328 , as illustrated, or two filters can be employed: one before the multiplier and one after the multiplier. In some examples, there can be no filter at all. The direct current (DC) portion of V detect  can be used to determine if a touch or proximity event has occurred. Note that while  FIGS.  3 A- 3 B  indicate the demodulation at multiplier  328  occurs in the analog domain, output Vo may be digitized by an analog-to-digital converter (ADC), and blocks  328 ,  332  and  330  may be implemented in a digital fashion (e.g.,  328  can be a digital demodulator,  332  can be a digital filter, and  330  can be a digital NCO (Numerical Controlled Oscillator). 
     Referring back to  FIG.  2   , in some examples, touch screen  220  can be an integrated touch screen in which touch sensing circuit elements of the touch sensing system can be integrated into the display pixel stack-ups of a display. The circuit elements in touch screen  220  can include, for example, elements that can exist in LCD or other displays (LED display, OLED display, etc.), such as one or more pixel transistors (e.g., thin film transistors (TFTs)), gate lines, data lines, pixel electrodes and common electrodes. In a given display pixel, a voltage between a pixel electrode and a common electrode can control a luminance of the display pixel. The voltage on the pixel electrode can be supplied by a data line through a pixel transistor, which can be controlled by a gate line. It is noted that circuit elements are not limited to whole circuit components, such as a whole capacitor, a whole transistor, etc., but can include portions of circuitry, such as only one of the two plates of a parallel plate capacitor. 
       FIG.  4 A  illustrates touch screen  400  with touch electrodes  404  and  406  arranged in rows and columns according to examples of the disclosure. Specifically, touch screen  400  can include a plurality of touch electrodes  404  disposed as rows, and a plurality of touch electrodes  406  disposed as columns. Touch electrodes  404  and touch electrodes  406  can be on the same or different material layers on touch screen  400 , and can intersect with each other, as illustrated in  FIG.  4 A . In some examples, the electrodes can be formed on opposite sides of a transparent (partially or fully) substrate and from a transparent (partially or fully) semiconductor material, such as ITO, though other materials are possible. In some examples, the conductive plates can be formed from other materials including conductive polymers, metal mesh, graphene, nanowires (e.g., silver nanowires) or nanotubes (e.g., carbon nanotubes). Electrodes displayed on layers on different sides of the substrate can be referred to herein as a double-sided sensor. In some examples, touch screen  400  can sense the self-capacitance of touch electrodes  404  and  406  to detect touch and/or proximity activity on touch screen  400 , and in some examples, touch screen  400  can sense the mutual capacitance between touch electrodes  404  and  406  to detect touch and/or proximity activity on touch screen  400 . 
       FIG.  4 B  illustrates touch screen  402  with touch node electrodes  408  arranged in a pixelated touch node electrode configuration according to examples of the disclosure. Specifically, touch screen  402  can include a plurality of individual touch node electrodes  408 , each touch node electrode identifying or representing a unique location on the touch screen at which touch or proximity (i.e., a touch or proximity event) is to be sensed, and each touch node electrode being electrically isolated from the other touch node electrodes in the touch screen/panel, as previously described. Touch node electrodes  408  can be on the same or different material layers on touch screen  402 . In some examples, touch screen  402  can sense the self-capacitance of touch node electrodes  408  to detect touch and/or proximity activity on touch screen  402 , and in some examples, touch screen  402  can sense the mutual capacitance between touch node electrodes  408  to detect touch and/or proximity activity on touch screen  402 . 
       FIG.  5 A  illustrates an exemplary touch screen that can be used in a touch sensitive device, such as a mobile phone, tablet, touchpad, portable computer, portable media player, wearable device or the like, according to examples of the disclosure. Touch screen  500  can include a stack-up including a display  502 , a polarizer  504 , a touch sensor panel  520  and a cover glass  508  (also referred to as front crystal). Display  502  can generate an image on the touch screen. Polarizer  504  can be used to control the brightness of light emitted from the display  502 . Cover glass  508  can be used as the outermost layer of the touch screen to protect components of the touch screen. Touch sensor panel  520  can be formed from rows and columns of transparent conductive material  512  (touch electrodes) patterned on opposite sides of a dielectric, such as transparent plastic substrate  506 . It should be understood that although the representation of conductive material  512  gives an appearance in a cross-sectional view of  FIG.  5 A  of electrodes having the same orientation on both sides of substrate  506  (for simplicity of illustration), that the rows and columns on opposite sides of substrate  506  can be perpendicular in a row-column pattern (e.g., as described above with respect to  FIG.  4 B ). Touch sensor panel  520  can also include passivation layers  516  disposed over the transparent conductive material  512 . The transparent plastic substrate  506  can act as a dielectric layer between the rows and columns of transparent conducting material  512 . The crossing points between rows and columns of conductive material, separated by the dielectric, can form sensing regions or nodes (e.g., as described above with respect to  FIG.  4 A ). Although a double-sided row-column pattern is shown in  FIG.  5 A , other patterning is possible. For example, the electrodes can be patterned on one side in a row-column pattern using bridges or in a pixelated pattern (e.g., as described above with respect to  FIG.  4 B ). The transparent plastic substrate can be made from different materials such as cylco olefin polymer (COP), polyethylene terephthalate (PET), polycarbonate (PC), clear polyimide (CPI) or the like. The transparent conducting material can be indium tin oxide (ITO) or silver nanowire (AgNW), for example. Display  502 , polarizer  504 , touch sensor panel  520  and cover glass  508  can be coupled (e.g., laminated together) by optically clear adhesive (OCA) layers  510 . 
       FIG.  5 B  illustrates an exemplary polarizer stack-up according to examples of the disclosure. Polarizer  504  can include a polarizing layer, such as a polyvinyl alcohol (PVA) film  530  doped with iodine. Although examples in the disclosure refer to PVA film doped with iodine, it should be understood that polarizing layer is not limited to PVA film doped with iodine, and any suitable polarizing material can be used. The polarizer PVA film  530  can be disposed between substrate layers  532 ,  534  to protect the PVA film  530 . The substrate layers can be made from materials including COP, PC, acrylic, triacetyl cellulose (TAC) or the like. Polarizer  504  can also include additional protective layers including a hard coat layer  536  disposed on substrate  532 , and one or more wave plate (retarder) coating layers, such as a half wave plate and/or a quarter wave plate (not shown). The PVA film, the various substrates, protective layers and wave plate layers can be coupled via a lamination process using adhesives (not shown). In some examples, the PVA film  530  can be 5-35 lam and the substrate layers can be between 15-50 μm. 
     Referring back to  FIG.  5 A , in some examples, the touch electrodes (conductive material  512 ) can be routed to touch sensing circuitry (e.g., touch controller  206 ) outside the visible area of the touch screen (e.g., disposed beneath display  502 ). For example,  FIG.  5 A  illustrates a flexible printed circuit (FPC)  550  (also referred to herein as “flex circuit”) that can be coupled to touch sensor panel  520 . In some examples, the coupling can be via a bonding pad or conductive film  514  (e.g., anisotropic conductive film (ACF)). As shown in  FIG.  5 A  the flex circuit  550  can include one or multiple tabs to couple to one or more different sides of the touch sensor panel  520 . The number of tabs can depend on the pattern of conductive material forming the touch electrodes and on the routing of the touch electrodes to the edges of substrate  506 . In some examples, the touch electrodes on one side of substrate  506  (e.g., rows) can be routed to one side of the touch sensor panel and touch electrodes on another side of substrate  506  (e.g., columns) can be routed to a different side of the touch sensor panel. In such an example, two flex circuit tabs may be used. In some examples, more or fewer flex circuits may be used. 
     The flex circuit  550  connection to touch sensor panel  520 , however, can increase the thickness of touch screen stack-up  500 . Additionally, connecting the flex circuit  550  to touch sensor panel  520  can require a border region around the active touch and display region of the touch screen that may not be used for display and/or touch sensing. In some examples, as described herein, the thickness of the touch screen stack-up can be reduced and/or the border region reduced, by removing the flex circuit from the stack-up. Instead, in some examples, the touch sensor panel can be formed using a flexible substrate (e.g., replacing a single-layer rigid substrate in the stack-up with a flexible substrate). The touch electrodes can be routed from the touch sensor panel to the touch sensing circuitry using the flexible substrate rather than a flexible printed circuit. Reducing the thickness of the touch screen can provide for a lower profile device and can reduce the weight of the device. Additionally, reducing the display to cover glass distance can improve the optical image on the display and/or can reduce mechanical strain during bending of the touch screen. 
     Although not illustrated in  FIG.  5 A , in some examples, a touch screen stack-up can include a shield layer between the touch sensor panel and the display to reduce interference between the touch and display systems. In some examples, routing the shield layer can also require a flex circuit (or another tab of an existing flex circuit). In some examples, as described herein, the thickness of the touch screen stack-up including a shield layer can be reduced by routing the shield layer to a shield electrode on the touch sensor panel. The shield layer (via the shield electrode) can then be routed to touch sensing circuitry (e.g., touch controller  206 ) via the flexible substrate of the touch sensor panel. 
     Additionally or alternatively, in some examples, as described herein, the touch sensor panel  520  or a portion of thereof can be integrated with polarizer  504 . Integrating the touch sensor panel  520  with the polarizer  504  can reduce the thickness of the touch screen stack-up because one substrate can be used in place of transparent plastic substrate  506  of the touch sensor panel and substrate  532  of the polarizer. Reducing the thickness of the touch screen also provides the added benefit of reducing the weight of the device. Additionally, reducing the display to cover glass distance can improve the optical image on the display and/or can reduce mechanical strain during bending of the touch screen. 
       FIGS.  6 A- 6 D  illustrate examples of touch screen stack-ups with a flexible substrate according to examples of the disclosure. In some examples, as shown in  FIGS.  6 A- 6 C , the stack-up can include a flexible substrate configured to flex from the touch sensor panel around to an opposite side of the display (wrap-around). In some examples, the stack-up may not include a full wrap-around, but may include a flexible substrate which extends, at least partially, beyond the visual area of the touch screen (beyond the display/touch electrode area of the stack-up). For example,  FIG.  6 D  shows a short tab extending from the stack-up for connection to a flex circuit. The latter implementation can remove the flex circuit from the stack-up (thereby reducing the height of the stack-up) without requiring as much flexibility from the substrate as a full wrap-around shown in  FIGS.  6 A- 6 C . 
       FIG.  6 A  illustrates touch screen  600  can include a display  602 , a polarizer  604 , a touch sensor panel  620  (e.g., including touch electrodes  612 , passivation layers  616  disposed on substrate  606 ), a cover glass  608  and one or more adhesive layers  610 . Touch screen  600  can be similar to touch screen  500 , and some differences will be described below for ease of description. Unlike  FIG.  5 A  with a rigid/planar substrate  606  in the stack-up and a flex circuit  550  to connect touch sensor panel  520  with touch sensing circuitry, touch sensor panel  620  can connect with touch sensing circuitry without including a flex circuit connection in the stack-up. Instead, touch sensor panel  620  of touch screen  600  can include a substrate  606  formed with a flexible material. A portion of the substrate within the stack-up (labeled  606 A in  FIG.  6 B ) can be planar due to its placement within the stack-up (which may include other rigid layers). A portion of the substrate outside of the stack-up (labeled  606 B in  FIG.  6 B ) can be non-planar and flexible to bend from the touch sensor panel  620  to below the display  602 . In some examples, a portion of the substrate (labeled  606 C in  FIG.  6 B ) can be planar due to its placement below display  602 . The flexible substrate  606  can route the touch electrodes of touch screen  620  to touch sensing circuitry below display  602  (e.g., on a printed circuit board (PCB)  648 ). Although  FIG.  6 A  shows the polarizer below the touch sensor panel, in some examples, the polarizer can be disposed above the touch sensor panel. 
       FIG.  6 B  illustrates additional details of the example of the wrap-around flexible substrate of touch screen  600  of  FIG.  6 A . The substrate illustrated in  FIG.  6 B  can be formed of a flexible material such as CPI, COP (e.g., partially crystallized and partially amorphous), or PET. The flexibility provided by flexible materials can enable bending of the substrate (e.g., portion  606 B of the substrate). In some examples, as shown in  FIGS.  6 A- 6 B , for example, the bending of portion  606 B of the substrate can provide for 180 degrees of bending between substantially planar portions  606 A and  606 C of the substrate. The planar portion  606 A can include touch electrodes  612  of the touch sensor panel and can be disposed above the display of the touch screen. The planar portion  606 A can also include a passivation layer  662  (e.g., corresponding to passivation layer  616 ) above touch electrodes  612 . In some examples, to reduce the stack-up thickness, passivation layer  662  can be formed using a material with both adhesive and passivation properties such that the stack-up does not need to include both the adhesive layer above the touch sensor panel (e.g., corresponding to adhesive layer  610 ) and a separate passivation layer (e.g., corresponding to passivation layer  616 ). The planar portion  606 C can be disposed below the display of the touch screen (outside the visible area). In some examples, the substrate can include a protective coating (e.g., hard coating  660 ) which can improve performance for bending of the substrate. In some examples, hard coating  660  may be replaced (or augmented) with a coating layer (not necessarily hard) to provide for improved adhesion and/or for chemical compatibility for deposition of touch electrodes. 
     As described above with respect to  FIG.  6 A , the flexible substrate  606  can route the touch electrodes of touch screen  620  to touch sensing circuitry below display  602 . For example, the flexible substrate can include routing  644  to route touch electrodes  612  from the touch sensor panel  620  to the touch sensing circuitry. As shown in  FIG.  6 B , the routing  644  can be flexible and can be disposed on portion  606 B of the substrate. The routing  644  can be electrically coupled to touch electrodes  612  at a first interconnection interface (e.g., on portion  606 A of the substrate). The routing  644  can be electrically coupled to the touch sensing circuitry (not shown) via a second interconnection interface (e.g., on portion  606 C of the substrate). Additionally, a protective coating  642  can be included to prevent corrosion and/or to provide mechanical stability for routing  644  and the flexible substrate  606 . 
     For ease of description,  FIG.  6 B  illustrates touch electrodes  612  on one side of substrate  606 A, but it is understood that for double-sided touch sensor panels (e.g., such as the double-sided touch sensor panel  620  in  FIG.  6 A ), additional touch electrodes  612  can be disposed and routed via the flexible substrate. For example, touch electrodes  612  on the opposite side of the flexible substrate (shown in  FIG.  6 A , but not shown in  FIG.  6 B ) can be routed from portion  606 A to  606 B to  606 C of the substrate (e.g., along the inner portion of the flexible substrate in portion  606 B shown in  FIG.  6 B ). In some examples, the touch electrodes  612 , hard coating  660 , routing trace  644  and/or protective layer  642  can be mirrored on the second side of substrate  606  for such a stack-up. 
     In some examples, the touch electrodes on the second, opposite side of the substrate can be routed via a wrap-around bend at another edge of the touch sensor panel. For example,  FIG.  6 C  illustrates additional details of an example of the flexible substrate of touch screen  600  of  FIG.  6 A  including a double-sided touch sensor panel and wrapping around multiple different edges of the touch sensor panel. The substrate of  FIG.  6 C  can be formed of a flexible material such as CPI, COP, or PET. The flexibility provided by flexible materials can enable bending of the substrate (e.g., portions  606 B/ 606 B′ of the substrate). In some examples, as shown in  FIG.  6 C , for example, the bending of portion  606 B on a first side of the substrate can provide for 180 degrees of bending between substantially planar portions  606 A and  606 C of the substrate, and the bending of portion  606 B′ on a second side of the substrate (different from the first side of the substrate) can be provide for 180 degrees of bending between substantially planar portions  606 A and  606 C of the substrate. In some examples, the first side and the second side of the substrate at which bending occurs can be on opposite sides as illustrated in  FIG.  6 C  (for simplicity of illustration). In some examples, the first side and the second side of the substrate at which bending occurs can be on adjacent sides. Although bending is illustrated at two sides of the substrate in  FIG.  6 C , it should be understood that the bending can occur at fewer or more sides of the substrate. Additionally, the bending described herein can occur along the entire side of the substrate (e.g., to reduce the border region around the touch screen) or only for a portion of the substrate (e.g., to reduce the border region proximate to another component (e.g., a camera or other sensor or circuitry). 
     The planar portion  606 A can include touch electrodes  612  of the touch sensor panel and can be disposed above the display of the touch screen (e.g., the touch electrodes and/or planar portion  606 A can be coterminous with the display). In double-sided touch sensor panels, the touch electrodes  612  can include electrodes on opposite sides of the substrate (e.g., in a row-column pattern, as described with respect to  FIG.  6 A ). In some examples, the substrate can include a protective coating (e.g., hard coating  660 ) which can improve performance for bending of the substrate. In some examples, hard coating  660  may be replaced (or augmented) with a coating layer (not necessarily hard) to provide for improved adhesion and/or for chemical compatibility for deposition of touch electrodes. The planar portion  606 A can also include one or more layers above touch electrodes  612  (e.g., on both sides of the substrate). In some examples, the one or more layers can include a passivation layer (e.g., corresponding to passivation layer  616 ) and adhesive layer (e.g., corresponding to adhesive layer  610 ) over touch electrodes  612  on both sides of the substrate. In some examples, to reduce the stack-up thickness, protective/adhesive layer  672  can be formed using a material with both adhesive and passivation properties such that the stack-up does not need to include both the adhesive layer (e.g., corresponding to adhesive layer  610 ) and a separate passivation layer (e.g., corresponding to passivation layer  616 ). The planar portion  606 C can be disposed below the display of the touch screen (outside the visible area). 
     The flexible substrate can route the touch electrodes  612  of touch screen  600  to touch sensing circuitry below display  602 . For example, the flexible substrate can include routing  644  on a first side of the flexible substrate to route touch electrodes  612  from one side of the touch sensor panel  620  to the touch sensing circuitry. Likewise, the flexible substrate can include routing  644 ′ on a second side of the flexible substrate to route touch electrodes  612  from the second, opposite side of the touch sensor panel  620  to the touch sensing circuitry. As shown in  FIG.  6 C , the routing  644 ,  644 ′ can be flexible and can be disposed on portions  606 B,  606 B′ of the substrate. The routing  644 ,  644 ′ can be electrically coupled to touch electrodes  612  at first interconnection interfaces (e.g., on two ends of portion  606 A of the substrate). The routing  644 ,  644 ′ can be electrically coupled to the touch sensing circuitry (not shown) via second interconnection interfaces (e.g., on portions  606 C,  606 C′ of the substrate). In some examples, protective/adhesive layer  672  can extend from portion  606 A to portions  606 B,  606 B′,  606 C,  606 C′ to provide protection from corrosion and/or provide mechanical stability for routing  644 ,  644 ′ and the flexible substrate  606 . In some examples, a separate protective coating (e.g., corresponding to protective coating  642  in  FIG.  6 B ) can be included to prevent corrosion and/or to provide mechanical stability for routing  644 ,  644 ′ and the flexible substrate  606 . 
     As discussed above, the routing in the flexed portion  606 B (bending area of portion  606 B) of the substrate can be flexible for reliability.  FIGS.  7 A- 7 J  illustrate examples of flexible substrates and routing according to examples of the disclosure.  FIGS.  7 A- 7 J  illustrate a planar substrate  706  prior to bending. For simplicity of illustration and description, routing of one touch electrode (e.g., touch electrode  712 ) is shown, but it is understood that routing can be included for additional touch electrodes.  FIG.  7 A  illustrates an example with touch electrodes  712  formed from ITO and with copper terminated ITO routing forming an extended bond pad across substrate  706  (from portion  706 A to  706 C) for an interconnect to touch sensing circuitry via the copper terminated bond pad. The touch electrode  712  can be connected the copper terminated ITO in portion  706 A by a routing trace formed of ITO, for example. 
     In some examples, the flexibility of routing can be improved by selecting materials with improved flexibility compared with ITO. For example, the copper terminated ITO in the bending area of portion  706 B can be replaced with a flexible conductor, such as a silver (or copper) paste.  FIG.  7 B  illustrates an example with a copper terminated ITO bond pad in portion  706 C (and a copper terminated ITO bond pad in portion  706 A that can be coupled to touch electrodes  712  in portion  706 A by a routing trace formed of ITO, for example), but without the ITO (and copper) in the bending area of portion  706 B. Instead, a silver paste can be used for routing in portion  706 B. In some examples, copper can be omitted from the bond pads as well. For example,  FIG.  7 C  illustrates an example with ITO bond pads without copper termination. In some examples, for example as illustrated in  FIG.  7 D , the silver paste can form the bond pads (without ITO and/or copper). 
     In some examples, as illustrated in  FIG.  7 E , rather than using a silver (or copper) paste, the routing from the touch electrodes  712  can be via sputtered copper or silver across substrate  706  (from portion  706 A to  706 C) for an interconnect to touch sensing circuitry via the sputtered copper or silver bond pad. In a similar manner as described above with respect to  FIGS.  7 A- 7 B , the touch electrode  712  formed of ITO can be connected the ITO in portion  706 A by a routing trace formed of ITO, for example, in  FIGS.  7 C- 7 E . 
     Although  FIGS.  7 A- 7 E  refer to touch electrodes  712  formed from ITO, it should be understood that touch electrodes can be formed from other materials (e.g., silver nanowire). For example,  FIGS.  7 F- 7 J  illustrate a flexible substrate  706  that can include touch electrodes  712  that can be formed of silver nanowire. The touch electrode  712  represented in  FIGS.  7 F -FJ can be connected to the silver nanowire material in portion  706 A by a routing trace formed of silver nanowire, for example. In some examples, the silver nanowire touch electrodes can be routed via silver (or copper) paste (e.g., as described with respect to  FIG.  7 D ). In some examples, the silver nanowire touch electrodes can be routed via copper or silver traces (e.g. sputtered silver or copper, or printed silver ink), as illustrated in  FIG.  7 F . The copper or silver can form the bond pads for interconnection in portion  706 C. In some examples, silver nanowire can be used in portion  706 B for flexible routing, as shown in  FIG.  7 G . Additionally or alternatively, as shown in  FIG.  7 G , the bond pad for interconnection in portion  706 C can be formed of copper or a silver paste (or ink). In some examples, the silver nanowire in portions  706 A- 706 C can be overlaid with silver paste or ink, as illustrated, for example in  FIG.  7 H  (e.g., to improve the conductivity of the routing). 
     In some examples, the routing in the bending area (portion  706 B) can be silver (or copper) paste or ink (or other sputtered silver or copper), as illustrated in  FIG.  7 I . Thus,  FIG.  7 I  can be similar to  FIGS.  7 D- 7 E , but using a silver nanowire touch electrode rather than an ITO touch electrode. In some examples, the routing can be formed of both silver nanowire and silver paste (or ink or sputtered silver or copper) in portions  706 A- 706 C, with the silver nanowire overlaying silver paste or ink as illustrated, for example, in  FIG.  7 J  (as opposed to silver nanowire overlaid with silver paste or ink as in  FIG.  7 H ). 
     It should be understood that  FIGS.  7 A- 7 J  illustrate exemplary options for routing for a flexible substrate (and for touch electrodes and bond pads), but other materials and options can be implemented for flexible routing between the touch electrodes and touch sensing circuitry. 
     As described above, in some examples, the flexible substrate may not fully wrap-around from the touch sensor panel to touch sensing circuitry (e.g., disposed behind the display). In some examples, the touch screen may include a flexible substrate which extends, at least partially, beyond the visual area of the touch screen. For example,  FIG.  6 D  shows a short flexible tab extending from the stack-up for connection to a flex circuit (and subsequently to the touch sensing circuitry, not shown).  FIG.  6 D  illustrates touch screen  630  that can be similar to touch screen  600  of  FIG.  6 A , and some differences will be described below for ease of description. Unlike  FIG.  6 A  with a flexible substrate  606  wrapping around from the touch sensor panel  620  to behind the display  602 , in  FIG.  6 D  the flexible substrate  606  can include a tab  606 D extending from the stack-up and a flex circuit  650  coupled to tab  606 D to route the touch electrodes  612  of touch sensor panel  620  to touch sensing circuitry. Connecting the flex circuit  650  to tab  606 D outside of the stack-up can reduce the height of the stack-up relative to  FIG.  5 A  where the flexible circuit is coupled within the stack-up. Although  FIG.  6 D  shows one short flexible tab and one flex circuit, it should be understood that additional flexible tabs (and corresponding flex circuits) can be implemented on additional side of the substrate, in some examples. 
     Although primarily illustrated in  FIG.  6 A- 6 D  as a planar touch screen, it should be understood that the flexible substrate described herein can also include touch electrodes and other flexible circuitry to enable curved, flexible or foldable touch sensors. 
     As mentioned above, in some examples, a touch screen stack-up can include a shield layer between the touch sensor panel and the display to reduce interference between the touch and display systems. The thickness of the touch screen stack-up including a shield layer can be reduced by routing the shield layer to a shield electrode on the touch sensor panel. The shield layer can then be routed to touch sensing circuitry (e.g., touch controller  206 ) via the flexible substrate. In some examples that use flex circuits rather than a flexible substrate, routing the shield layer to the touch sensing layer can reduce the number of flex circuits (or tabs), which can reduce the thickness of the stack-up. 
       FIGS.  8 A- 8 B  illustrate an example of touch screen stack-up with a shield layer routed to the touch sensor panel examples of the disclosure.  FIG.  8 A  illustrates touch screen  800  can include a display  802 , a polarizer  804 , a touch sensor panel  820  (e.g., including touch electrodes  812  patterned on one side of substrate  806 , passivation/adhesive layer  816  disposed on substrate  806 ), a cover glass  608  and one or more adhesive layers  810 . Touch screen  800  can be similar to touch screen  600 , and some differences will be described below for ease of description. Unlike  FIG.  6 A , touch screen  800  can include a shield layer  870  between its touch sensor panel  820  (illustrated as a single-sided touch electrode pattern) and display  802  (and/or polarizer  804 ). In some examples, shield layer  870  can be formed of a partially or fully transparent material such as ITO, silver nanowire, etc. The shield layer  870  can reduce interference between the touch sensor panel  820  and the display  802 . 
     The shield layer  870  can be separated from the touch electrodes  812  by at least substrate  806 , such that the touch electrodes  812  can be disposed on a first side of substrate  806  and shield layer  870  can be disposed on a second side, opposite the first side. In some examples, the shield layer can be formed on the substrate  806  (on the second side for a one-sided touch electrode pattern). In some examples, the shield layer can be formed on a different substrate in the stack-up than substrate  806  upon which the touch electrodes  812  are formed. In such examples, the shield layer  870  can be further separated from touch sensor panel  820  by an adhesive layer. In some examples, the different substrate can be a substrate of polarizer  804 . Using a substrate of polarizer  804  can reduce the thickness of the stack-up. 
     Touch screen  800  also includes a conductive bridge  880  to electrically couple the shield layer  870  from the second side of substrate  806  to the first side of substrate  806  of touch sensor panel  820 . For example, a silver (or copper) paste can wrap around substrate  806  to the side of the substrate including the touch electrodes. It is understood that other suitable materials (e.g., conductive films, etc.) can be used to form a bridge between the shield layer  870  and the touch sensor panel  820 . The conductive bridge  880  can connect to an electrode (“shield electrode”)  882  on the first side of substrate  806  of touch sensor panel  820 . In some examples, shield electrode  882  can be formed of ITO, though other materials are possible (e.g., silver nanowire, etc.). The shield electrode  882  can then be routed to touch sensing circuitry (e.g., to drive the shield with a voltage, such as the touch sensing stimulation voltage). For example, as shown in  FIG.  8 A , the wraparound of conductive bridge  880  can wrap around the edge of substrate  806 , opposite the edge of the stack-up from which flexible substrate  806  extends. The shield layer  870 , via conductive bridge  880  and shield electrode  882 , can therefore be routed to the touch sensing circuitry via the flexible substrate to the touch sensing circuitry (e.g., on PCB  848 ). In some examples, the conductive bridge can be used in a stack-up that does not include a flexible substrate. Instead, the shield electrode can be routed to touch sensing circuitry via a flex circuit. Whether a flexible substrate or flex circuit is used, the conductive bridge  880  can reduce the thickness of the stack-up because a separate flex circuit does not need to be used to connect the shield layer to the touch sensing circuitry. 
       FIG.  8 B  illustrates another view of touch screen  800  including some additional details according to examples of the disclosure. For example,  FIG.  8 B  illustrates additional details regarding the flexible substrate  806  of touch sensor panel  820  to enable connection of touch sensor panel  820  to touch sensing circuitry (not shown) without a flex connector. The planar portion of substrate  806  can include touch electrodes  812 . The planar portion of substrate  806  can also include a passivation layer  817  (with separate adhesive layer  810 , together corresponding to passivation/adhesive layer  816 ) above touch electrodes  612 . In some examples, the substrate can include a protective coating (e.g., hard coating  860 ) which can improve performance for bending of the substrate. In some examples, hard coating  860  may be replaced (or augmented) with a coating layer (not necessarily hard) to provide for improved adhesion and/or for chemical compatibility for deposition of touch electrodes. An index matching layer can be disposed between hard coating  860  and conductive layers (e.g., touch electrodes  812 , shield layer  870 , shield electrode  882 ) for matching optical properties (e.g., to reduce the index of refraction change between two materials with different indexes of refraction). The flexible substrate  806  can also include routing  844  to route touch electrodes  812  from the touch sensor panel  820  to the touch sensing circuitry. Additionally, a protective coating  842  can be included to prevent corrosion and/or to provide mechanical stability for routing  844  and the flexible substrate  806 . 
     Conductive bridge  880  can be coupled to shield layer  870  and shield electrode  882  as illustrated by interconnections. For example, on the side of the stack-up including conductive bridge  880 , display  802 , polarizer  804  and shield layer  882  can be wider than touch sensor panel  820  to enable the conductive bridge  880  to be bonded to shield layer  870  (e.g., within the stack-up). Conductive bridge  880  can then wrap around substrate  806  to a bond pad corresponding to shield electrode  882  on the opposite side of substrate  806  from shield layer  870 . 
     Although  FIGS.  8 A- 8 B  illustrate shield layer  870  disposed on top of polarizer  804 , in some examples, the shield layer  870  can be disposed on a different layer of polarizer  804 . For example, the shield layer could be disposed on the opposite side of polarizer  804  (e.g., between polarizer  804  and display  802 ). In such a case, the polarizer can be narrowed within the stack-up to enable conductive bridge  880  to be bonded to shield layer  870 . In some examples, shield layer  870  can be disposed on display  802  and coupled to driving circuitry via a flex circuit for display  802  (not shown). 
     Additionally, or alternatively, in some examples, as described herein, the touch sensor panel or a portion of thereof can be integrated with polarizer. Integrating the touch sensor panel with the polarizer can reduce the thickness of the touch screen stack-up because fewer substrates can be used. 
       FIGS.  9  and  10    illustrate examples of an integrated touch sensor panel and polarizer according to examples of the disclosure.  FIG.  9    illustrates an integrated touch sensor panel and polarizer  900  in which a double-sided touch sensor panel  910  is formed using the polarizer substrate according to examples of the disclosure. An example polarizer (e.g., corresponding to polarizer  504  from  FIG.  5 B ) without an integrated touch sensor panel is reproduced on the left-hand side of  FIG.  9   , which includes a substrate (labeled “COP”). In some examples, the same substrate can be shared by the touch sensor panel  910  and the polarizer layers for an integrated touch sensor panel and polarizer  900 . For example, as illustrated in  FIG.  9   , prior to forming the polarizer layers (e.g., PVA film, TAC, etc.) on the substrate, touch electrodes  904  can be disposed on both sides of substrate  902 . Although touch electrodes  904  are shown on both sides of substrate  902 , it should be understood that in some examples the touch electrodes can be disposed on one side of the substrate (e.g., for a pixelated touch electrode pattern shown in  FIG.  4 B  or a single-sided row-column touch electrode pattern using bridges). Touch electrodes  904  can be formed from ITO, or other suitable materials (e.g., silver nanowire, etc.). A passivation layer  906  can be disposed on touch electrodes  904 . Forming the touch electrodes on the substrate prior to forming the polarizer layers can enable high-temperature processing steps for touch electrodes (e.g., for ITO deposition and annealing) that may damage polarizer layers. After forming sensor panel  910 , the remaining polarizer layers (e.g., hard coat, PVA film, TAC layer, etc.) can be formed on touch sensor panel  910  to form integrated touch sensor panel and polarizer  900 . 
       FIG.  10    illustrates an integrated touch sensor panel and polarizer  1000  in which a single-sided touch sensor panel  1010  is formed using the polarizer substrate according to examples of the disclosure. An example polarizer (e.g., corresponding to polarizer  504  from  FIG.  5 B ) without an integrated touch sensor panel is reproduced on the left-hand side of  FIG.  10   , which includes a substrate (labeled “COP”). In some examples, the same substrate can be shared by the touch sensor panel  1010  and the polarizer layers for an integrated touch sensor panel and polarizer  1000 . For example, as illustrated in  FIG.  10   , before or after forming the polarizer layers (e.g., PVA film, TAC, etc.) on the substrate, touch electrodes  1004  can be disposed on the hard coat layer  1008  on substrate  1002 . Touch electrodes  1004  can be formed from ITO, or other suitable materials (e.g., silver nanowire, etc.). Although not shown in  FIG.  10   , in some examples, a passivation layer can be disposed on touch electrodes  1004 . 
     Additionally, in some examples, integrated touch sensor panel and polarizer  1000  can include a shield layer  1022 . The shield layer can be formed of ITO or other suitable materials (e.g., silver nanowire), and can be formed on a second substrate  1020 , which can serve as the bottom substrate of integrated touch sensor panel and polarizer  1000 . In some examples, a passivation layer  1024  can be disposed on shield layer  1022 . In some examples, the shield layer  1022  can be coupled to the layer including touch electrodes  1004  via a conductive bridge (e.g., as described above with respect to shield layer  870 , conductive bridge  880 , and shield electrode  882 ). Substrate  1020 , shield layer  1022  and passivation layer  1024  can be coupled (e.g., via adhesive, lamination) to the rest of integrated touch sensor panel and polarizer  1000 . 
     In some examples, forming the touch electrodes on the substrate/hard coat prior to forming the polarizer layers can enable high-temperature processing steps for touch electrodes (e.g., for ITO deposition and annealing) that may damage polarizer layers. After forming sensor panel  1010 , the remaining polarizer layers (e.g., PVA film, TAC layer, etc.) can be formed on touch sensor panel  1010  to form integrated touch sensor panel and polarizer  1000 . In some examples, the touch electrodes can be formed on the substrate/hard coat after forming the polarizer layers using lower-temperature processing steps for touch electrodes (e.g., silver nanowire) that may be performed without damaging polarizer layers. 
       FIG.  11    illustrates an exemplary process  1100  for forming an integrated touch sensor panel and polarizer according to examples of the disclosure. At  1105 , a first substrate can be formed. The first substrate can be formed from a glass or a transparent polymer (e.g., COP). At  1110 , a touch sensor panel can be formed on the substrate. For example, as described above with respect to  FIG.  9   , touch electrodes can be deposited on one or both sides of the substrate to form the touch sensor panel  910 . In some examples, the touch electrodes can be formed of ITO via deposition and annealing. Additionally, in some examples, a passivation layer can be deposited over the touch electrodes to protect the touch electrodes and/or to planarize the touch sensor panel. At  1115 , the polarizer layers can be formed on the touch sensor panel. For example, the polarizer layers can include, as described herein, one or more hard coat layers, one or more adhesive layers, one or more optical retarder layers (e.g., HWP, QWP), a polyvinyl alcohol layer (e.g., PVA film layer), and a tri-acetyl cellulose layer. In some examples, the integrated touch sensor panel and polarizer can include a shield layer to reduce interference between the touch sensor panel and the display. For example, at  1120 , the shield layer can be formed on a second substrate. The shield layer can be formed of ITO or other suitable materials (e.g., silver nanowire). A passivation layer can be disposed on the shield layer as well. At  1125 , the second substrate (and the shield layer) can be coupled to the polarizer layers (e.g., via an adhesive layer and lamination process). 
     It should be understood that  FIG.  11    describes an example process for forming an integrated touch sensor panel and polarizer according to examples of the disclosure. For example, the integrated touch sensor panel and polarizer of  FIG.  11    can be formed without the shield layer (omitting  1120  and  1125 ). In some examples, touch electrodes can be formed on one side of the substrate at  1110 , and additional touch electrodes can be formed on one side of a second substrate. The second substrate and touch electrodes can be coupled instead of the shield layer at  1125 . In some examples, the touch sensor panel may include touch electrodes formed on only one side (e.g., pixelated touch electrodes). In such examples, the touch electrodes can be formed on the hard coat of the substrate. In some examples, the polarizer can first be formed on the substrate and subsequently the touch electrodes can be formed on the polarizer (e.g., as described above with respect to  FIG.  10   ). 
     Therefore, according to the above, some examples of the disclosure are directed to a touch screen comprising: a display and a touch sensor panel disposed on the display. The touch sensor panel can comprise a substrate formed from a flexible material and touch electrodes formed on one or more surfaces of the substrate. A first portion of the substrate including the touch electrodes can be planar and a second portion of the substrate can be non-planar such that the substrate extends beyond a dimension of the display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second portion of the substrate can be a tab. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second portion of the substrate can wrap around from the touch sensor panel to a different layer in the touch screen. The different layer can be separated from the touch sensor panel by the display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise a flex circuit coupled to the second portion of the substrate outside the dimensions of the display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise conductive traces disposed on the second portion of the substrate configured to route the touch electrodes disposed on the first portion of the substrate to touch sensing circuitry. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the conductive traces disposed on the second portion of the substrate can comprise first conductive traces disposed on a first side of the substrate in the second portion of the substrate and second conductive traces disposed on a second side of the substrate in the second portion of the substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first conductive traces can be disposed between an inner coating layer disposed on the first side of the substrate and an outer coating layer disposed over the first conductive traces. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second conductive traces can be disposed between an inner coating layer disposed on the second side of the substrate and an outer coating layer disposed over the second conductive traces. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch electrodes can be formed from indium tin oxide and the conductive traces disposed on the second portion of the substrate can be formed without indium tin oxide. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch electrodes can be formed from silver nanowire and the conductive traces disposed on the second portion of the substrate can be formed from silver nanowire. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first portion of the substrate can be coterminous with the display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, a third portion of the substrate can be planar and separated from the first portion of the substrate by the display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise a bonding pad disposed on the third portion of the substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise a coating layer disposed on the one or more surfaces of the substrate. The touch electrodes formed on the one or more surfaces of the substrate can be disposed on the coating layer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise a protective layer disposed on the one or more surfaces of the substrate. The touch electrodes can be formed on the one or more surfaces of the substrate can be disposed on the protective layer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second portion of the substrate can be separated from the display such that a gap can be formed between the second portion of the substrate and the display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the substrate can wrap around from the touch sensor panel to a different layer in the touch screen on a first side of the touch screen without the substrate wrapping around to the different layer in the touch screen on a second side of the touch screen different than the first side of the touch screen. Additionally or alternatively to one or more of the examples disclosed above, in some examples, a fourth portion of the substrate (e.g.,  606 B′) can be non-planar such that the substrate can extend beyond a second dimension of the display different than the first dimension of the display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the fourth portion of the substrate can wrap around from the touch sensor panel to the different layer in the touch screen. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise first conductive traces disposed on a first side of the substrate in the second portion of the substrate and second conductive traces disposed on a second side of the substrate opposite the first side of the substrate in the fourth portion of the substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first conductive traces can be configured to route first touch electrodes of the touch electrodes on a first side of the substrate to touch sensing circuitry and the second conductive traces can be configured to route second touch electrodes of the touch electrodes on a second side of the substrate to the touch sensing circuitry. 
     Some examples of the disclosure are directed to a touch screen comprising a touch sensor panel, a shield layer and conductive routing. The touch sensor panel can comprise a first substrate and touch electrodes formed on a first surface of the first substrate. The first substrate can separate the touch electrodes from the shield layer. The conductive routing can be configured to route the shield layer around a first edge of the first substrate to the first side of the first substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the shield layer can be disposed on a second substrate different from the first substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise a polarizer comprising the second substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the polarizer can further comprise the first substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise an adhesive layer disposed between the touch sensor panel and the shield layer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise an index matching layer disposed between the touch sensor panel and the shield layer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the shield layer can be disposed on a second side of the first substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the shield layer can comprise indium tin oxide or silver nanowire. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the conductive routing can comprise silver paste. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch sensor panel can further comprise: a shield electrode on the first side of the first substrate separate from the touch electrodes. The conductive routing can electrically couple the shield layer to the electrode on the first side of the first substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the shield electrode can comprise indium tin oxide or silver nanowire. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch screen can further comprise a flexible connector disposed on a second edge of the first substrate. The flexible connector can be configured to route the touch electrodes and the shield layer from the first side of the first substrate to touch sensing circuitry. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the shield layer can extend beyond the first edge of the first substrate such that the conductive routing can be disposed on the shield layer without extending beyond a length of a display of the touch screen. 
     Some examples of the disclosure are directed to a touch screen. The touch screen can be prepared by a process comprising: forming a substrate; forming a touch sensor panel on the substrate; and forming polarizer layers on the touch sensor panel. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the substrate can have a thickness less than 50 μm. Additionally or alternatively to one or more of the examples disclosed above, in some examples, forming the touch sensor panel on the substrate can comprise depositing touch electrodes on both sides of the substrate. Additionally or alternatively to one or more of the examples disclosed above, in some examples, forming the touch sensor panel on the substrate can comprise depositing a passivation layer over the touch electrodes. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the substrate can be formed from a transparent polymer and the touch electrodes are formed from indium tin oxide. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the polarizer layers can include a polyvinyl alcohol layer, a tri-acetyl cellulose layer, and one or more optical retarder layers. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the process can further comprise forming a shield layer on a second substrate; and coupling the second substrate to the polarizer layers. Additionally or alternatively to one or more of the examples disclosed above, in some examples, each of the substrate and the second substrate can have a thickness of 25 μm or less. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the shield layer can be formed from indium tin oxide or silver nanowire. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second substrate can be coupled to the polarizer layers via an adhesive layer and lamination. 
     Some examples of the disclosure are directed to a method of forming a touch screen. The method can comprise forming a substrate; forming a touch sensor panel on the substrate; and forming polarizer layers on the touch sensor panel. 
     Although the disclosed examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosed examples as defined by the appended claims.

Metadata:
Filing Date: 20231221
Publication Date: 20250114
Grant Date: 20250114
Priority Date: 20181219
Inventors: WEISSE, JEFFREY M.
TUNG, CHUN-HAO
CHOI, JI HUN
DAI, Wenqing
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01B1/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01B1/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04164", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0416", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 70969942