PATENT DOCUMENT

Publication Number: US-9158143-B2
Application Number: US-201113230331-A
Country: US
Kind Code: B2

Title: Dual purpose touch sensor panel and optical retarder

Abstract:
When a user operates a touch sensor panel having an LCD device outdoors or in a bright environment, light reflecting off the device can create glare. In order to reduce glare, a user can view the device through polarized filters such as polarized sunglasses. Doing so can reduce the visibility of the image displayed on the LCD. A quarter-wave retardation film can be added to the touch sensor panel&#39;s LCD device to mitigate these effects by producing circularly polarized light. However, adding a separate quarter-wave retardation film can increase the thickness and cost of manufacturing the touch sensor panel. Embodiments of the present disclosure are directed to a touch sensor panel constructed from a base film having quarter-wave retardation properties that can produce circularly polarized light. Because the base film has the desired optical properties, a separate quarter-wave retardation film may not be needed.

Claims:
What is claimed is: 
     
       1. A device, comprising:
 a touch sensor panel disposed on a substrate; and 
 a display that emits linearly polarized light towards the touch sensor panel, 
 wherein the substrate introduces optical retardation to the light as it passes through the touch sensor panel and the touch sensor panel is oriented with respect to the display such that a 45°±30° or 135°±30° angle is formed between the optical axis in the substrate of the touch sensor panel and a polarization axis of the light emitted from the display. 
 
     
     
       2. The device of  claim 1 , wherein the substrate is configured such that a total amount of optical retardation introduced by the substrate is substantially equal to one-quarter of the wavelength of the light or substantially equal to an odd number multiple of one-quarter of the wavelength of the light. 
     
     
       3. The device of  claim 2 , wherein the total amount of optical retardation introduced by the substrate converts the linearly polarized light from the display into circularly polarized light. 
     
     
       4. The device of  claim 1 , wherein the substrate of the touch sensor panel is made from a material, the material selected from a group consisting of polycarbonate (PC), cyclo-olefin polymer (COP), cyclo-olefin copolymer (COC), polymethyl methacrylate (PMMA), and cellulose triacetate (TAC). 
     
     
       5. The device of  claim 1 , wherein the substrate of the touch sensor panel is formed by a controlled stretch of the substrate, the controlled stretch selected from a group consisting of a machine direction stretch, a transverse direction stretch, and a diagonal direction stretch. 
     
     
       6. The device of  claim 5 , wherein the machine direction stretch yields an optical axis in the substrate oriented along the direction of the stretch or in a direction perpendicular to the direction of the stretch. 
     
     
       7. The device of  claim 5 , wherein the transverse direction stretch yields an optical axis in the substrate oriented in a direction perpendicular to the direction of the stretch. 
     
     
       8. The device of  claim 5 , wherein the diagonal direction stretch includes a machine direction stretch component and a transverse direction stretch component, the diagonal direction stretch yielding an optical axis in the substrate oriented at an angle substantially equal to 45° with respect to the machine direction stretch. 
     
     
       9. The device of  claim 1 , wherein the display is selected from a group consisting of a liquid crystal display (LCD) and an OLED (organic light emitting diode) display that includes a polarizer. 
     
     
       10. A method for converting linearly polarized light into circularly polarized light in a device having a display and a touch sensor panel, the touch sensor panel having a substrate, the method comprising:
 emitting linearly polarized light from the display towards the touch sensor panel; 
 orienting the touch sensor panel with respect to the display such that a 45°±30° or 135°±30° angle is formed between an optical axis in the substrate of the touch sensor panel and a polarization axis of the light emitted from the display; and 
 introducing optical retardation to the light using the substrate as the light passes through the touch sensor panel, 
 wherein the substrate of the touch sensor panel introduces the optical retardation. 
 
     
     
       11. The method of  claim 10 , wherein the total amount of optical retardation introduced by the substrate is substantially equal to one-quarter of the wavelength of the light or substantially equal to an odd number multiple of one-quarter of the wavelength of the light. 
     
     
       12. The method of  claim 10 , wherein the substrate of the touch sensor panel is made from a material, the material selected from a group consisting of polycarbonate (PC), cyclo-olefin polymer (COP), cyclo-olefin copolymer (COC), polymethyl methacrylate (PMMA), and cellulose triacetate (TAC). 
     
     
       13. The method of  claim 10 , wherein the touch sensor panel is formed by cutting the touch sensor panel from the substrate. 
     
     
       14. The method of  claim 13 , wherein the substrate of the touch sensor panel is formed by a controlled stretch of the substrate, the controlled stretch selected from a group consisting of a machine direction stretch, a transverse direction stretch, and a diagonal direction stretch. 
     
     
       15. The method of  claim 14 , wherein the machine direction stretch yields an optical axis in the substrate oriented along the direction of the stretch or in a direction perpendicular to the direction of the stretch. 
     
     
       16. The method of  claim 14 , wherein the transverse direction stretch yields an optical axis in the substrate oriented in a direction perpendicular to the direction of the stretch. 
     
     
       17. The method of  claim 14 , wherein the diagonal direction stretch includes a machine direction stretch component and a transverse direction stretch component, the diagonal direction stretch yielding an optical axis in the substrate oriented at an angle substantially equal to 45° with respect to the machine direction stretch. 
     
     
       18. The method of  claim 13 , wherein the controlled stretch is performed during roll-to-roll processing of the substrate.

Description:
FIELD OF THE DISCLOSURE 
     This relates generally to a touch sensor panel and, more particularly, to the construction of a touch sensor panel display that can be viewed by a user wearing linearly polarized filters such as polarized sunglasses. 
     BACKGROUND OF THE DISCLOSURE 
     Display screens of various types of technologies, such as liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, etc., can be used as screens or displays for a wide variety of electronic devices, including such consumer electronics as televisions, computers, and handheld devices (e.g., cellular telephones, audio and video players, gaming systems, and so forth). LCD devices, for example, typically provide a flat display in a relatively thin package that is suitable for use in a variety of electronic goods including touch sensor panels. LCD technology is based on polarization optics and typically employs a linear polarizer on the front surface that emits linearly polarized light. Linearly polarized light has an electric field that vibrates in only one particular direction. 
     When a user operates a touch sensor panel having an LCD device outdoors or in a bright environment, light reflecting off the device can create glare. Polarized sunglasses can be worn to reduce the effects of glare by only allowing the passage of light that vibrates in a given direction (e.g., in a vertical direction). Depending on the angle that the touch sensor panel is held or oriented, the display image produced from the LCD device can appear clear, completely dark, or somewhere in between to a user wearing polarized sunglasses. 
     SUMMARY 
     When a user operates a touch sensor panel having an LCD device outdoors or in a bright environment, light reflecting off the device can create glare. In order to reduce this glare, a user can view the device through polarized filters. These polarized filters can be, for example, polarized sunglasses. Doing so, however, can reduce the visibility of the image displayed on the LCD. A quarter-wave retardation film can be added to the touch sensor panel&#39;s LCD device to mitigate these effects by producing circularly polarized light. However, the addition of a separate quarter-wave retardation film can increase the thickness and cost of manufacturing the touch sensor panel. 
     Various embodiments of the present disclosure are directed to a touch sensor panel constructed from a base film having quarter-wave retardation properties that can produce circularly polarized light. Because the base film has the desired optical properties, a separate quarter-wave retardation film may not be needed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates an example mobile telephone according to embodiments of the disclosure. 
         FIG. 1B  illustrates an example digital media player according to embodiments of the disclosure. 
         FIG. 1C  illustrates an example personal computer according to embodiments of the disclosure. 
         FIG. 1D  illustrates an example tablet computer according to embodiments of the disclosure 
         FIG. 2  illustrates an example quarter-wave retardation film according to embodiments of the disclosure. 
         FIG. 3  illustrates an example cross sectional view of an LCD device and quarter-wave retardation film according to embodiments of the disclosure. 
         FIG. 4  illustrates an example system stack-up having a touch sensor panel that can act as an optical retarder according to embodiments of the disclosure. 
         FIG. 5  illustrates an example roll-to-roll manufacturing process according to embodiments of the disclosure. 
         FIG. 6A  illustrates the example use of a machine direction stretch during roll-to-roll processing according to embodiments of the disclosure. 
         FIG. 6B  illustrates an example enlarged view of a base film as it is stretched in the machine direction according to embodiments of the disclosure. 
         FIG. 6C  illustrates an example system stack-up having a touch sensor panel and display according to embodiments of the disclosure. 
         FIG. 7A  illustrates example touch sensor panels that have been stretched in the machine direction and arranged in a diamond configuration according to embodiments of the disclosure. 
         FIG. 7B  illustrates an example system stack-up having a touch sensor panel and display according to embodiments of the disclosure. 
         FIG. 8A  illustrates the example use of a transverse direction stretch during roll-to-roll processing according to embodiments of the disclosure. 
         FIG. 8B  illustrates an example enlarged view of a base film as it is stretched in the transverse direction according to embodiments of the disclosure. 
         FIG. 8C  illustrates an example system stack-up having a touch sensor panel and display according to embodiments of the disclosure. 
         FIG. 9A  illustrates example touch sensor panels that have been stretched in the transverse direction and arranged in a diamond configuration according to embodiments of the disclosure. 
         FIG. 9B  illustrates an example system stack-up having a touch sensor panel and display according to embodiments of the disclosure. 
         FIG. 10A  illustrates the use of an example diagonal direction stretch during roll-to-roll processing according to embodiments of the disclosure. 
         FIG. 10B  illustrates an enlarged view of an example base film as it is stretched in the diagonal direction according to embodiments of the disclosure. 
         FIG. 10C  illustrates an example system stack-up having a touch sensor panel and display according to embodiments of the disclosure. 
         FIG. 11  illustrates an exemplary computing system utilizing a touch sensor panel that can act as an optical retarder according to embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific embodiments that can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the embodiments of this disclosure. 
     Embodiments of the disclosure relate to a touch sensor panel having an LCD or other device that displays an image that can be viewed through polarized filters at various angles without a significant reduction in display image quality. These polarized filters can be, for example, polarized sunglasses. LCD devices can emit linearly polarized light. When used outdoors or in a bright environment, a device housing the touch sensor panel and LCD device can reflect light and create glare. Although a user can wear polarized sunglasses to reduce the effects of glare, the visibility of the image displayed on the LCD may also be reduced. A quarter-wave retardation film can be added to the touch sensor panel&#39;s LCD device to mitigate these effects. The addition of a quarter-wave retardation film can convert the uni-directionally polarized light from the display device into circularly polarized light. However, the addition of a separate quarter-wave retardation film can increase the thickness and cost of manufacturing the touch sensor panel. In order to avoid adding a separate quarter-wave retardation film, embodiments of the disclosure are directed to a touch sensor panel constructed from a base film having quarter-wave retardation properties that can produce circularly polarized light. Because the base film has the desired optical properties, a separate quarter-wave retardation film may not be needed. 
       FIGS. 1A-1C  show example systems in which display screens according to embodiments of the disclosure may be implemented.  FIG. 1A  illustrates an example mobile telephone  136  that includes a display screen  124 .  FIG. 1B  illustrates an example digital media player  140  that includes a display screen  126 .  FIG. 1C  illustrates an example personal computer  144  that includes a display screen  128 .  FIG. 1D  illustrates an example tablet computer  150  that includes a display screen  154 . In some embodiments, display screens  124 ,  126 ,  128 , and  154  can be LCD based touch screens in which touch sensing circuitry can be integrated into the display pixels to form a touch sensor panel. In other embodiments, display screens  124 ,  126 ,  128 , and  154  can be OLED displays that include a polarizer and touch sensing circuitry. Touch sensing can be based on, for example, self capacitance or mutual capacitance, or another touch sensing technology. In some embodiments, a touch screen can be multi-touch, single touch, projection scan, full-imaging multi-touch, or any other type of capacitive touch sensing mechanism. 
     The LCD display screens in the handheld devices of  FIGS. 1A-1C  can emit linearly polarized light. When viewed through polarized sunglasses, the image displayed on the display screen can appear clear, completely dark, or somewhere in between. The variation in image quality can result from the use of polarized sunglasses. Polarized sunglasses only allow through light with an electric field that vibrates in a single direction (e.g., a vertical direction). As such, the quality of the image seen through polarized sunglasses can vary as the handheld device is oriented at different angles. A user wearing polarized sunglasses can perceive a deteriorated image on the display screen. This deterioration can, for example, result in the appearance of color and gray shade artifacts which can lead to a reduced or complete loss of readability. In other circumstances, a user wearing polarized sunglasses may perceive a variation in image quality as the device is rotated or tilted. 
     A quarter-wave retardation plate or film can be added to an LCD device to reduce the above described loss in image quality. Examples of such a quarter-wave retardation film are disclosed in U.S. Patent Publication Nos. 2010/0118235 and 2011/0124260, the contents of which are incorporated by reference herein in their entirety for all purposes. 
     A quarter-wave retardation film is an optical element that can alter the polarization state of a light wave traveling through it. A quarter-wave retardation film can have a higher refractive index in one direction, called the optical axis, than in the direction perpendicular to the optical axis. Light passing through the quarter-wave retardation film can vibrate along either direction. However, due to the difference in refractive indices, light polarized along the optical axis can travel through the film at a different speed than light traveling in the perpendicular direction. This difference in speed can create a phase difference. Depending on the thickness of the film, light with polarization components along both axes can emerge from the plate in a different polarization state. 
       FIG. 2  illustrates a quarter-wave retardation film  200  with film thickness D  206 . The refractive index n1  202  in the direction of the optical axis can be larger than the refractive index n2  204  in a direction perpendicular to the optical axis. As light passes from the bottom of retardation film  200  through the film&#39;s top surface, the total phase shift can be substantially equal to or close to one-quarter (or substantially equal to or close to an odd number multiple of one-quarter) of the wavelength of light such that the following relationship is satisfied: 
     
       
         
           
             
               
                 ( 
                 
                   
                     n 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   - 
                   
                     n 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                 
                 ) 
               
               ⁢ 
               D 
             
             = 
             
               
                 ( 
                 
                   
                     2 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     k 
                   
                   - 
                   1 
                 
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               ⁢ 
               
                 λ 
                 4 
               
             
           
         
       
     
     In the above equation, n1, n2, and D can correspond to refractive index  202 , refractive index  204 , and film thickness  206 , respectively, as described above. λ can be the wavelength of light, preferably between 380 nm and 800 nm; and k can be any integer, preferably less than 3 in order to minimize potential artifacts caused by high retardation films. These artifacts can include, for example, a color shift or the appearance of Newton rings. 
     By using retardation film  200 , light emitted from the top surface of film  200  can be circularly polarized. Because circularly polarized light has no angular dependence, the light and its corresponding image can remain visible even when viewed at different angles through polarized filters (e.g., sunglasses). 
       FIG. 3  illustrates a cross sectional view of an LCD device and quarter-wave film. The device can have a front polarizer  302 , a bottom polarizer  310 , and liquid crystal  306  sandwiched between two glass layers  308 . Quarter-wave retardation film  300  can be placed on top of front polarizer  302 . Additional display components  312  can be added depending on the type of display used and may include, for example, circuitry to control the transparency of the liquid crystal layer or a backlight that generates light that passes through the display device. The LCD device can also be integrated with an overlying touch sensor panel (not shown). 
     The addition of quarter-wave retardation film  300  to the LCD device can increase the cost of manufacturing the device. This cost can increase as the size of the film needed for a large LCD increases. Moreover, the addition of a separate quarter-wave retardation film  300  can increase the thickness of the device. In order to remedy these issues, embodiments of the disclosure are directed to a touch sensor panel made from a base film that can act as a quarter-wave optical retarder. Because this base film already has the desired optical properties, it can emit circularly polarized light. As such, a separate quarter-wave retardation film may not be needed. 
       FIG. 4  illustrates the stack-up of a system having a touch sensor panel that can act as an optical retarder. This system can be any of the systems illustrated in  FIGS. 1A-1C , and may include a touch sensor panel integrated with a display. The stack-up can have a cover glass  406  and an adhesive or air gap  404 . Touch sensor panel  402  can lie below adhesive or air gap  404 . Touch sensor panel  402  can be composed of a non-conducting substrate, conducting electrodes, and other electronics as known in the art. Although the touch sensor panel can have multiple layers of substrates, at least one of these layers can be made from a base film that can act as a quarter-wave optical retarder. Display  400  can lie below touch sensor panel  402 . Additional structure (not shown) may lie between any of these components. 
     Display  400  can be an LCD, an OLED display that includes a polarizer, or other display device. As previously explained, light emitted from an LCD device can be linearly polarized. As linearly polarized light vibrates or passes from the LCD device and through the touch sensor panel&#39;s base film, a phase shift can occur because the base film can act as an optical retarder. This phase shift can convert the linearly polarized light emitted from display  400  into circularly polarized light after it passes through the base film. Because the base film of touch sensor panel  402  can act as an optical retarder, a separate quarter-wave retardation film may not be needed. Although the above touch sensor panel is described as having a single substrate layer made from a base film that can act as a quarter-wave optical retarder, other variations are possible. In other exemplary embodiments, the touch sensor panel can have multiple layers of substrates made with a base film that can act as an optical retarder. In these embodiments, the multiple substrate layers can have a total optical retardation substantially equal to or close to one quarter-wavelength of light or substantially equal to or close to an odd number multiple of one quarter-wavelength of light. 
     The base film of touch sensor panel  402  can be made from the same materials used to make a quarter-wave retardation film. Typically, a touch sensor panel and quarter-wave retardation film can be made from a variety of plastics including, for example, polycarbonate (PC), cyclo-olefin polymer (COP), cyclo-olefin copolymer (COC), polymethyl methacrylate (PMMA), or cellulose triacetate (TAC). Because the same materials are used in both films, PC, COP, COC, PMMA, and TAC can also be used to manufacture a dual purpose base film having quarter-wave retardation properties. Polyethylene terephthalate (PET) can also be used to manufacture this dual purpose base film. However, PET may not be as desirable as PC, COP, COC, PMMA, and TAC because it can exhibit a large variation in the direction of the optical axis which, in turn, can affect the amount of optical retardation. 
     The amount of optical retardation exhibited by the base film can be affected by the orientation of the base film&#39;s optical axis relative to the polarization axis of light emitted from display  400 . This orientation can depend on the type of display used. For example, when an in-plane switching (IPS) display or fringe field switching (FFS) display is used, the light emitted from the display can be linearly polarized either along a horizontal or vertical direction with respect to the touch sensor panel&#39;s edge. In order to produce circularly polarized light, the optical axis of the base film should be positioned such that it lies 45°±30° or 135°±30° from the polarization axis of the light emitted from the display. If, however, a different type of display is used (e.g., a twisted nematic LCD), then the light emitted from the display may already be polarized at a 45° or 135° angle with respect to the touch sensor panel&#39;s edge. Although any type of display may be used, the following embodiments are described with respect to an IPS or FFS display. The base film may, in some embodiments, maintain a relatively constant retardation over the entire visible spectrum of light (e.g., 380 nm-800 nm for each individual wavelength). 
       FIG. 5  illustrates an exemplary roll-to-roll manufacturing process that can be used to make the dual purpose base film of touch sensor panel  402 . Roll-to-roll processing can create electronic devices from a roll of raw material  500 . This raw material can, for example, be a flexible plastic like PC, COP, COC, PMMA, or TAC as described above. As raw material  500  is unwound at roller  502  and wound by roller  504 , multiple touch sensor panels  506  can be formed by deposition processing, patterning circuits onto the roll, and packaging the circuits as known in the art. Once touch sensor panels  506  are formed, individual touch sensor panels can be cut out from the roll. 
     Manufacturing a touch sensor panel using standard roll-to-roll processing as described above, however, does not inherently create a base film having the desired quarter-wave retardation properties. According to an exemplary embodiment of the disclosure, an extra processing step may be added to impart the desired optical characteristics on the base film. As the base film is rolled out, a controlled stretch can be performed on the base film to generate the desired optical axis and the desired retardation value in the base film. The following paragraphs describe the use of a machine direction stretch, a transverse direction stretch, and a diagonal direction stretch during roll-to-roll processing to form a touch sensor panel having a base film that can act as a quarter-wave optical retarder. Although only three types of stretches are described, a person of ordinary skill in the art would recognize that other stretches may be used. 
       FIG. 6A  illustrates the use of a machine direction stretch during roll-to-roll processing. As base film  600  is rolled out from roller  604  and onto roller  602 , roller  602  can operate at a higher speed than roller  604 . The difference in roller speed can stretch film  600  in the machine direction. Depending on the material used in the base film, this stretch can yield an optical axis that runs either along the direction of the stretch or in a direction perpendicular to the stretch. For example, when the base film is made from PC or COP, the machine direction stretch can generate an optical axis  606  in base film  600  that runs in the direction of the stretch. It should be noted that stretching mechanisms other than the roller embodiment of  FIG. 6A  are also contemplated. 
       FIG. 6B  illustrates an enlarged view of base film  600  as it is stretched in the machine direction. After base film  600  undergoes deposition processing, patterning, and packaging, individual touch sensor panels  608  can be cut out of the base film. Each of these touch sensor panels can have an optical axis  606  that runs in the machine direction. In this exemplary embodiment, there are two rows of touch sensor panels. In each row, the top edges of the touch sensor panels are substantially aligned with each other. Similarly, in each row, the bottom edges of the touch sensor panels are substantially aligned with each other. Although this exemplary embodiment illustrates two rows of touch sensor panels, any number of rows of touch sensor panels may be formed on base film  600 . 
       FIG. 6C  illustrates a stack-up that pairs touch sensor panel  608  with display  610 . Display  610  can lie below touch sensor panel  608 . If display  610  is an LCD, then the light emitted from the display can be linearly polarized with a polarization axis  612 . When the linearly polarized light vibrates or passes through the base film of touch sensor panel  608 , an angle  614  can form between the polarization axis  612  of the emitted light and optical axis  606  of the base film. As previously explained, the optical axis of the base film should be 45°±30° or 135°±30° from the polarization axis of the emitted light in order to produce circularly polarized light. In this exemplary embodiment, angle  614  formed by polarization axis  612  and optical axis  606  may not fall within the 45°±30° or 135°±30° range and, consequently, may not produce circularly polarized light. Because light passing from touch sensor panel  608  may not be circularly polarized, a user viewing the device through polarized sunglasses may perceive color and gray shade artifacts which can lead to a reduced or complete loss of readability. 
     In order to form the desired angle between the polarization axis of the light emitted from the display and the optical axis of the base film, the touch sensor panels can be rotated on the base film before they are cut. In an exemplary embodiment, these touch sensor panels can be rotated to form the diamond configuration of  FIG. 7A . Each touch sensor panel can, for example, be rotated clockwise or counter-clockwise by 45° or 135°. Rotating the touch sensor panel may not affect the direction of the base film&#39;s optical axis  704  which runs along the direction of the machine stretch. In this exemplary embodiment, there are two rows of touch sensor panels. Unlike the configuration of  FIG. 6B , the top edges of the touch sensor panels in a given row may not be substantially aligned. Similarly, the bottom edges of the touch sensor panels in a given row may not be substantially aligned. Although this exemplary embodiment illustrates two rows of touch sensor panels, any number of rows of touch sensor panels may be formed on base film  700 . 
       FIG. 7B  illustrates a stack-up that pairs display  706  with touch sensor panel  702  after the touch sensor panel has been removed from base film  700 . Display  706  can be rotated in the same manner as touch sensor panel  702  such that both components lie over each other. If display  706  is an LCD, then the light emitted from the display can be linearly polarized with a polarization axis  708  that can run either along the horizontal or vertical direction with respect to the edge of display  706 . When the linearly polarized light vibrates or passes through the base film of touch sensor panel  702 , an angle  710  can form between the polarization axis  708  of the emitted light and optical axis  704  of the base film. Because angle  710  can fall within the desired 45°±30° or 135°±30° range in this exemplary embodiment, the base film of touch sensor panel  702  can act as a quarter-wave optical retarder that produces circularly polarized light. 
       FIG. 8A  illustrates another exemplary embodiment that utilizes a transverse direction stretch. As base film  800  is unwound at roller  804  and wound by roller  802 , clips or other attachment mechanisms  808  can stretch material  800  in the transverse direction. This transverse direction stretch can yield an optical axis  806  in base film  800 . Optical axis  806  can be perpendicular to the optical axis of a material stretched in the machine direction. It should be noted that stretching mechanisms other than the roller and clip embodiment of  FIG. 8A  are also contemplated. 
       FIG. 8B  illustrates an enlarged view of stretched base film  800  after deposition processing, patterning, and packaging. Individual touch sensor panels  810  can be cut out of base film  800 . Each of these touch sensor panels can have an optical axis  806  that runs in the transverse direction. In this exemplary embodiment, there are two rows of touch sensor panels. In each row, the touch sensor panels&#39; top edges are substantially aligned with each other, and the touch sensor panels&#39; bottom edges are substantially aligned with each other. Although this exemplary embodiment illustrates two rows of touch sensor panels, any number of rows of touch sensor panels may be formed on base film  800 . 
       FIG. 8C  illustrates a stack-up that pairs touch sensor panel  810  with display  812 . This configuration is similar to the configuration of  FIG. 6C . If display  812  is an LCD, then the light emitted from the display can be linearly polarized with a polarization axis  814 . When the linearly polarized light vibrates through the base film of touch sensor panel  810 , an angle  816  can form between polarization axis  814  of the emitted light and optical axis  806  of the base film. Because angle  816  may not fall within the 45°±30° or 135°±30° range in this exemplary embodiment, the configuration of  FIG. 8C  may not produce circularly polarized light for reasons similar to those discussed above with respect to  FIG. 6C . 
     As illustrated in  FIGS. 9A and 9B , touch sensor panels  902  can be rotated and cut from base film  900  in a diamond configuration in order to yield the desired angle between the polarization axis of the light emitted from a LCD and the optical axis of the base film. The configuration of  FIG. 9A  is similar to the diamond configuration of  FIG. 7A . Each touch sensor panel can, for example, be rotated clockwise or counter-clockwise by 45° or 135°. Each touch sensor panel  902  has an optical axis  904  that runs along the direction of the transverse stretch. Although this exemplary embodiment illustrates two rows of touch sensor panels, any number of rows of touch sensor panels may be formed on base film  900 . 
       FIG. 9B  illustrates a stack-up that pairs touch sensor panel  902  with display  906 . Display  906  can be rotated in the same manner as touch sensor panel  902  such that both components lie over each other. If display  906  is an LCD, then the light emitted from the display can be linearly polarized with a polarization axis  908 . When the linearly polarized light vibrates through the base film of touch sensor panel  902 , a 45°±30° or 135°±30° angle  910  can form between the polarization axis  908  of the emitted light and optical axis  904  of the base film. This configuration can produce circularly polarized light in a manner similar to  FIG. 7B . 
     Although the diamond configuration of  FIGS. 7A ,  7 B,  9 A, and  9 B can produce circularly polarized light, this diamond pattern can yield various inefficiencies. As illustrated in these figures, the top edge of each touch sensor panel in a given row may not be substantially aligned with each other. The same may also apply to each bottom edge. In order to cut touch sensor panels from a base film using this diamond configuration, the base film should be cut at an angle. Doing so, however, can result in wasted base film. If the diamonds are cut as illustrated in  FIGS. 7A and 9A , the left-over material between diamonds may not be used. 
     In another exemplary embodiment, a diagonal direction stretch can be used to reduce the amount of wasted material.  FIG. 10A  illustrates the use of a diagonal direction stretch during roll-to-roll processing of base film  1000 . A diagonal direction stretch can utilize a machine direction stretch in combination with a transverse direction stretch. Examples of producing a diagonal direction stretch are disclosed in Japanese Patent Publication No. 2010201659, the contents of which are incorporated by reference herein in its entirety for all purposes. With regard to the machine direction stretch, roller  1002  can operate at a higher speed than roller  1004  to stretch base film  1000  towards roller  1002 . Arrow  1006  can represent the machine direction stretch component. With regard to the transverse direction stretch, some or all of clips or other attachment mechanisms  1009  can stretch base film  1000  in the transverse direction as the base film is rolled out. Arrow  1007  can represent the transverse direction stretch component. It should be noted that stretching mechanisms other than the roller and clip embodiment of  FIG. 10A  are also contemplated. 
       FIG. 10B  illustrates an enlarged view of stretched base film  1000  after it has undergone roll-to-roll processing. The diagonal direction stretch can produce an optical axis  1008  that lies at an angle substantially equal to 45° with respect to the machine direction stretch. As previously explained, the optical axis should form a 45°±30° or 135°±30° angle with the polarization axis of light emitted from a display in order to produce circularly polarized light. As illustrated in  FIG. 10C , an LCD display  1012  can be placed below the cut-out touch sensor panel. Because the polarization axis of light emitted from an LCD can run along the horizontal or vertical direction of the display&#39;s edge, the desired angle can be formed by cutting touch sensor panels  1010  in rows using the configuration of  FIG. 10B . Although this exemplary embodiment illustrates two rows of touch sensor panels, any number of rows of touch sensor panels may be formed on base film  1000 . 
       FIG. 10C  illustrates the resulting angle between the optical axis of touch sensor panel  1010  and the polarization axis of light emitted from display  1012  with more detail. If display  1012  is an LCD display, then polarization axis  1014  can form an angle  1016  with optical axis  1008 . Because angle  1016  can fall within the 45°±30° or 135°±30° range, the base film of touch sensor panel  1010  can act as an optical retarder that can produce circularly polarized light. 
     The configuration of  FIG. 10B  can waste less material than the configurations of  FIGS. 7A and 9A . By cutting the touch sensor panels  1010  from the base film as illustrated in  FIG. 10B , the touch sensor panels can be positioned close to each other along base film  1000  before they are cut. This may be possible because the top edge of each touch sensor panel in a given row are substantially aligned with each other, and the bottom edge of each touch sensor panel in a given row are substantially aligned with each other. In contrast, more unused material may remain between the touch sensor panels when the touch sensor panels are cut along an angle using the diamond configuration of  FIGS. 7A and 9A . 
       FIG. 11  illustrates exemplary computing system  1100  that can include one or more of the embodiments described above. Computing system  1100  can include one or more panel processors  1102  and peripherals  1104 , and panel subsystem  1106 . Peripherals  1104  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. Panel subsystem  1106  can include, but is not limited to, one or more sense channels  1108 , channel scan logic  1110  and driver logic  1114 . Channel scan logic  1110  can access RAM  1112 , autonomously read data from the sense channels and provide control for the sense channels. In addition, channel scan logic  1110  can control driver logic  1114  to generate stimulation signals  1116  at various frequencies and phases that can be selectively applied to drive lines of touch sensor panel  1124 . In some embodiments, panel subsystem  1106 , panel processor  1102  and peripherals  1104  can be integrated into a single application specific integrated circuit (ASIC). 
     Touch sensor panel  1124  can be composed of multiple layers of substrates. These substrate layers can be made from a base film that can act as an optical retarder. As explained above, at least one of these layers should exhibit quarter-wave retardation properties. If more than one layer acts as an optical retarder, the total optical retardation should be one-quarter of the wavelength of light or an odd number multiple of one-quarter of the wavelength of light. Touch sensor panel  1124  can include a capacitive sensing medium having a plurality of drive lines and a plurality of sense lines, although other sensing media can also be used. Each intersection of drive and sense lines can represent a capacitive sensing node and can be viewed as picture element (pixel)  1126 , which can be particularly useful when touch sensor panel  1124  is viewed as capturing an “image” of touch. After panel subsystem  1106  has determined whether a touch event has been detected at each touch sensor in the touch sensor panel, the pattern of touch sensors in the multi-touch panel at which a touch event occurred can be viewed as an “image” of touch (e.g. a pattern of fingers touching the panel). Each sense line of touch sensor panel  1124  can drive sense channel  1108  (also referred to herein as an event detection and demodulation circuit) in panel subsystem  1106 . 
     Although the disclosed embodiments 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 embodiments as defined by the appended claims.

Metadata:
Filing Date: 20110912
Publication Date: 20151013
Grant Date: 20151013
Priority Date: 20110912
Inventors: CHEN CHENG
MOHAPATRA SIDDHARTH
HUANG LILI
ZHONG JOHN Z.
KUWABARA MASATO
Assignee: APPLE INC
CPC Classifications: [{"code": "H04N9/3105", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N9/3197", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13363", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F2001/133635", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/042", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2001/133638", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133634", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133638", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133635", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133638", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133635", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N9/3197", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N9/3105", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133634", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/042", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13363", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/042", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/1333", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 46970391