Abstract:
An apparatus and method is provided for removing smudges ( 506, 706, 806, 906 ) including oils and dust from portable electronic displays. The apparatus comprises a display device ( 110, 150, 500, 700, 800, 900, 1000 ) positioned within a housing ( 102, 104, 808 ), comprising a transparent cover ( 302, 502, 702, 802, 902, 1002 ) having a surface ( 508, 908 ) viewable through an opening in the housing ( 102, 104, 808 ) and a susceptibility to receiving contaminants ( 506, 706, 806, 906 ). A vibration device ( 504, 704, 804, 904, 1004 ) is positioned against the transparent cover ( 302, 502, 702, 802, 902, 1002 ) to provide motion ( 510 ) in a direction parallel to the surface, thereby causing the contaminants to move ( 708 ) across the surface ( 508, 908 ). The contaminants ( 506, 706, 806, 906 ) may then be hidden by the housing ( 102, 104, 808 ) or ejected by a motion ( 912 ) perpendicular to the surface by another vibrating device ( 911 ). Electronic circuitry ( 505 ) is provided for activating the vibration device ( 504, 704, 804, 904, 1004 ) either during normal operation of the electronic device or as selected by the user.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to portable electronic device displays and more particularly to an apparatus and method for removing smudges including oils and dust therefrom. 
       BACKGROUND OF THE INVENTION 
       [0002]    In many portable electronic devices, such as mobile communication devices, displays present information to a user. For example, polymer-dispersed liquid crystal (PDLC) display technology can display video and text information. These optical displays, especially touch panel displays, typically comprise a transparent or a high gloss reflective surface thermoplastic or glass layer. While these transparent layers have excellent transparency and are physically strong, they suffer both aesthetic and functional degradation due to the build up of oils and other contaminants during use. This is particularly true for the display components of products which receive significant handling, such as persona data assistants (PDAs) and cell phones. For these displays, any type of fouling is especially undesirable as it tends to be very noticeable to the user and can result in a less than satisfactory viewing experience. 
         [0003]    While screen protectors are available for many of these products, they do not offer an optimal solution. Most are based on anti-fouling coatings that reduce but do not eliminate smudges. Furthermore, the screen protectors often become scratched or otherwise degraded, necessitating that the consumer periodically replace them. For example, see U.S. Pat. No. 6,660,388 and European patent application EP 1 712 531 A2. 
         [0004]    Accordingly, it is desirable to provide an apparatus and method for removing smudges including oils and dust from portable electronic devices. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    An apparatus and method are provided for removing smudges including oils and dust from displays of a portable electronic device. The electronic device includes a display positioned within a housing. A transparent cover of the display has a surface viewable outside of the housing and is susceptible to receiving a smudge. A vibration device is coupled to the transparent cover to provide motion in a direction parallel to the surface, thereby causing the smudges to migrate from a viewing area of the display. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
           [0007]      FIG. 1  is a front view of a mobile communication device having a touch screen in accordance with an exemplary embodiment; 
           [0008]      FIG. 2  is a partial cross-section of a conventional touch screen taken along line  2 - 2  of  FIG. 1 ; 
           [0009]      FIG. 3  is a cross sectional diagram of a conventional TN/PDLC touch screen; 
           [0010]      FIG. 4  is a timing diagram for a display driver and a capacitive sensor operating the touch screen of  FIG. 2  in a conventional manner; 
           [0011]      FIG. 5  is a partial cross-section of a display screen in accordance with a first exemplary embodiment; 
           [0012]      FIG. 6  is a partial cross-section of the display screen of  FIG. 5  after a vibratory motion has been activated; 
           [0013]      FIG. 7  is a partial cross-section of a display screen in accordance with a second exemplary embodiment; 
           [0014]      FIG. 8  is a partial cross-section of a display screen in accordance with a third exemplary embodiment; 
           [0015]      FIG. 9  is a partial cross-section of a display screen in accordance with a fourth exemplary embodiment; 
           [0016]      FIG. 10  is a partial cross-section of a display screen in accordance with a fifth exemplary embodiment; and 
           [0017]      FIG. 11  is a bottom view of the display screen of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention. 
         [0019]    An integrated solution that maintains the cleanliness of display surfaces without user intervention incorporates acoustic, ultrasonic, or other types of vibrational actuators coupled to the display. Vibration of the display causes droplets of oil, fatty acids, and other contaminants to migrate across the surface resulting in a clean viewing area. Asymmetric vibrations may be generated from the edges of the display screen or cover. This approach may be particularly suitable to cell phones as haptic devices providing feedback to the user may also be connected to the display to cause migration of the contaminants by causing a spatial displacement of the display. Therefore, rather than having to incorporate a vibration device specifically to generate acoustic waves on the face of the display, an existing element may be adapted to serve a dual role. 
         [0020]    An alternative approach is to incorporate piezoelectric thin films onto the display. While it would be preferred to cover the entire surface of the display with such films, the piezoelectric thin films may cover only a portion of the display, e.g., the edges or periphery of the display. Surface acoustic wave filters can actuate droplet motion with very small amplitudes. Furthermore, the display cover material, thickness, tapering, and shape may be tailored to achieve optimum contaminant migration. 
         [0021]    As the contaminants build up in peripheral areas, they can be hidden under a portion of the device housing, moved via capillary or self driven flow effects to areas less noticeable, or pooled into areas where removal is can be efficiently done by methods such as ejection by additional vibratory motion in a direction perpendicular to the screen or wiping by holster elements. 
         [0022]    Although the apparatus and method described herein may be used with an exposed display surface for any type of electronic device, the exemplary embodiment as shown in  FIG. 1  comprises a mobile communication device  100  implementing a touchscreen. While the electronic device shown is a mobile communication device  100 , such as a flip-style cellular telephone, the touchscreen can also be implemented in cellular telephones with other housing styles, personal digital assistants, television remote controls, video cassette players, household appliances, automobile dashboards, billboards, point-of-sale displays, landline telephones, and other electronic devices. 
         [0023]    The mobile communication device  100  has a first housing  102  and a second housing  104  movably connected by a hinge  106 . The first housing  102  and the second housing  104  pivot between an open position and a closed position. An antenna  108  transmits and receives radio frequency (RF) signals for communicating with a complementary communication device such as a cellular base station. A display  110  positioned on the first housing  102  can be used for functions such as displaying names, telephone numbers, transmitted and received information, user interface commands, scrolled menus, and other information. A microphone  112  receives sound for transmission, and an audio speaker  114  transmits audio signals to a user. 
         [0024]    A keyless input device  150  is carried by the second housing  104 . The keyless input device  150  is implemented as a touchscreen with a display. A main image  151  represents a standard, twelve-key telephone keypad. Along the bottom of the keyless input device  150 , images  152 ,  153 ,  154 ,  156  represent an on/off button, a function button, a handwriting recognition mode button, and a telephone mode button. Along the top of the keyless input device  150 , images  157 ,  158 ,  159  represent a “clear” button, a phonebook mode button, and an “OK” button. Additional or different images, buttons or icons representing modes, and command buttons can be implemented using the keyless input device. Each image  151 ,  152 ,  153 ,  154 ,  156 ,  157 ,  158 ,  159  is a direct driven pixel, and this keyless input device uses a display with aligned optical shutter and backlight cells to selectively reveal one or more images and provide contrast for the revealed images in both low-light and bright-light conditions. 
         [0025]    Referring to  FIG. 2 , a cross section of a conventional touchscreen  200  is depicted that is usable for either the display  110  or the keyless input device  150  with the cross-section, for example, being a portion of a view taken along line  2 - 2  of  FIG. 1 . The conventional display  200  is a stack with a user-viewable and user-accessible face  201  and multiple layers below the face  201 , including a transparent cover  202 , a thin transparent conductive coating  204 , a substrate  206 , and an imaging device  208 . The transparent cover  202  provides an upper layer viewable to and touchable by a user and may provide some glare reduction. The transparent cover  202  also provides scratch and abrasion protection to the layers  204 ,  206 ,  208  contained below. 
         [0026]    The substrate  206  protects the imaging device  208  and typically comprises plastic, e.g., polycarbonate or polyethylene terephthalate, or glass, but may comprise any type of material generally used in the industry. The thin transparent conductive coating  204  is formed over the substrate  206  and typically comprises a metal or an alloy such as indium tin oxide or a conductive polymer. 
         [0027]    Referring to  FIG. 3 , a cross section of a conventional display  300  is depicted with aligned optical shutter and backlight cells and is usable for the display  110  of  FIG. 1  with the cross-section being a portion of a view taken along line  3 - 3  of  FIG. 1 . The conventional display  300  is a stack with a user-viewable and user-accessible face  301  and multiple layers below the face  301 , including a transparent cover  302  and a capacitive sensor layer  304  with an indium-tin oxide (ITO) electrode  305 . The transparent cover  302  provides an upper layer viewable to and touchable by a user and may provide some glare reduction. The capacitive sensor layer  304  senses touchscreen inputs on the transparent cover  302  of the display  300 . Beneath the capacitive sensor layer  304  is a twisted nematic (TN) stack layer  306  including a TN backplane electrode  310  and TN segment electrodes  308  between two substrates  312 ,  314  for providing the optical shutter operation of the display  300 . The TN backplane electrode  310  and TN segment electrodes  308  are formed of indium-tin oxide (ITO) material to provide both transparency and electrical conductivity for operation of the TN stack. Also, while the TN backplane electrode  310  is depicted above the TN segment electrodes  308 , a TN stack layer  306  having the TN backplane electrode  310  below the TN segment electrodes  308  would function similarly. 
         [0028]    The TN stack layer  306  utilizes, for example, twisted nematic (TN) liquid crystal (TNLC) display technology employing TN optical shutter material in an optical shutter layer  313  and the TN segment electrodes  308  to provide optical shutter operation. While TNLC technology is described herein for the optical shuttering operation, the optical shutter layer  313 , sandwiched between the TN backplane electrodes  310  and the TN polymer segment electrodes  308 , can alternatively be made using nematic liquid crystal technology (such as twisted nematic or super twisted nematic liquid crystals), polymer-dispersed liquid crystal technology (PDLC), ferro-electric liquid crystal technology, electrically-controlled birefringent technology, optically-compensated bend mode technology, guest-host technology, and other types of light modulating techniques which use optical shutter material  313  such as TN polymer material, PDLC material, cholesteric material, or electro-optical material. The electric field created by the electrodes  308 ,  310  alter the light transmission properties of the TNLC optical shutter material  313 , and the pattern of the TN segment electrode layer  308  defines pixels of the display. These pixels lay over the images  151 ,  152 ,  153 ,  154 ,  156 ,  157 ,  158 ,  159  shown in  FIG. 1 . In the absence of the electric field, the liquid crystal material and dichroic dye in the TNLC material  313  are randomly aligned and absorb most incident light. In the presence of the electric field, the liquid crystal material and dichroic dye align in the direction of the applied field and transmit substantial amounts of incident light. In this manner, a pixel of the TNLC cell can be switched from a relatively non-transparent state to a relatively transparent state. Each pixel can be independently controlled to be closed-shuttered or open-shuttered, depending on the application of an electric field, and the pixels act as “windows” with optical shutters that can be opened or closed, to reveal images underneath (e.g. images  151 ,  152 ,  153 ,  154 ,  156 ,  157 ,  158 ,  159 ). 
         [0029]    Beneath the TN stack layer  306  is an electroluminescent (EL) stack layer  316  separated from the TN stack layer  306  by an ITO ground layer  318 . The EL stack layer  316  includes a backplane and electrodes which provide backlight for operation of the display  300  in both ambient light and low light conditions by alternately applying a high voltage level, such as one hundred volts, to the backplane and electrode. The ITO ground layer  318  is coupled to ground and provides an ITO ground plane  318  for reducing the effect on the capacitive sensor layer  304  of any electrical noise generated by the operation of the EL stack layer  316  or other lower layers within the display  300 . Beneath the EL stack layer  316  is a base layer  320  which may include one or more layers such as a force sensing switch layer and/or a flex base layer. The various layers  302 ,  304 ,  306 ,  318 ,  316  and  320  are adhered together by adhesive layers applied therebetween. 
         [0030]    Conventional operation of the display  300  is illustrated in  FIG. 4 , wherein the charge  402  from the capacitive sensor layer  304 , the voltage  404  of the TN backplane  310  and the voltages  406 ,  408  of first and second portions of the TN segment electrodes  308  are depicted. To perform capacitive sensing during a period  410 , a charging voltage is provided to the ITO electrode  305  of the capacitive sensor layer  304  for a first portion  422  of the period  410 . After the charging voltage is removed from the electrode  305 , the charge  402  has two different decay profiles  412 ,  414  depending on whether a user&#39;s touch is detected on the display  300 . In an electrically noisy environment, the signal-to-noise ratio (SNR) of the capacitive sensing (i.e., of the voltage of the detectable charge), where the charge is the multiple of the capacitance (determined from a distance of user&#39;s finger from the face  301 ) times the voltage thereof, is small, thereby complicating detection of touchscreen inputs. The ITO ground plane layer  318  provides some isolation between the high voltage EL backlight layer  316  and the low voltage TN stack layer  306 , thereby increasing the SNR of the capacitive sensing. 
         [0031]    During the same time period  410 , the voltages  404 ,  406 ,  408  supplied to the TN backplane  310  and the TN segment electrodes  308  are switched between a positive voltage, typically about five volts, and zero volts. The voltage  406  of the portion of the TN segment electrodes  308  that are turned “on” to render corresponding portions of the display  300  over such portion of the TN segment electrodes  308  relatively transparent are switched opposite to the voltage  404  of the TN backplane  310  (i.e., when the voltage  304  of the TN backplane is high, the voltage  406  of the “on” portion of the TN segment electrodes  308  is low). Conversely, the voltage  408  of the portion of the TN segment electrodes  308  that are turned “off” optically shutter corresponding portions of the display  300  over such portion of the TN segment electrodes  308  because their voltage is switched in the same manner as the voltage  404  of the TN backplane  310 . It can be seen from  FIG. 4  that during period  410 , the voltages  406 ,  408  supplied to the TN segment electrodes  308  and the TN backplane  310  are high approximately fifty per cent of the time period  410 . 
         [0032]    Those skilled in the art will appreciate that other types of imaging devices  200 ,  300  may be utilized as exemplary embodiments, including, for example, transmissive, reflective or transflective liquid crystal displays, cathode ray tubes, micromirror arrays, and printed panels. 
         [0033]    Referring to  FIG. 5  and in accordance with a first exemplary embodiment, a display device  500  includes a vibration device  504  attached to a transparent cover  502 . The transparent cover  502  may comprise a cover on any type of display, for example, the transparent covers  202  of  FIG. 2  and the transparent cover  302  of  FIG. 3 . The vibration device  504  may comprise, for example, a piezo electric transducer, and may comprise a haptic element that is otherwise used in an electronic device to provide information to the user, including for example, feedback relating to key activation. The vibration device  504  is coupled to electronic circuitry  505  within the electronic device for selectively activation. An optional layer  507  comprising an antistatic coating may be formed on the transparent cover  502  that repels contaminants  506  such as dust. 
         [0034]    During use of the display device  500 , contaminants  506  from, for example, dust and oils from the user&#39;s touch, accumulate on the viewing surface  508  as shown in  FIG. 6 . These contaminants  506  impede the ability of the user to view the information presented through the transparent cover  502 . The activation of the vibration device  504  may be accomplished routinely during operation of the electronic device or as selected by the user. Activation of the vibration device  504  causes the transparent cover  502  to move in a direction  510  (See  FIG. 6 ) that is parallel with the viewing surface  508 . This motion of the transparent cover  502  causes the contaminants  506  to migrate to the periphery  512  of the viewing surface  510  and away from the area viewed by the user. This migration of the contaminants  506  may be assisted by other forces such as gravity. 
         [0035]    A second exemplary embodiment is shown in  FIG. 7  and comprises an electronic device  700  having a transparent cover  702  coupled to a vibration device  704 . In this case, the vibration device is coupled or mounted in such a way as to induce vibration of the lense in the out of plane direction. The tapering of the transparent cover  702  leads to an asymmetry in vibrational amplitudes which causes migration of the contaminants  706  in a direction  708  away from the smaller end  710  of the transparent cover  702 . It should be noted that vibrational asymmetry may be created by using vibrational device(s) which generate surface waves asymetrically or by a physical grading of layer  702  by varying the density of a piece of uniform thickness or tapering the dimensions of the layer  702 . An optional layer may be included to enhance motion. It may also comprise a smudge resistant layer such as a fluoropolymer based coating which would also minimize friction. 
         [0036]    Once the contaminants  506 ,  706  have migrated to the periphery, the contaminants  506 ,  706  may be hidden or eliminated by removal from the transparent cover  502 ,  702 . For example, as shown in  FIG. 8 , the electronic device  800  includes a housing  808  that extends over the periphery  810  and covers or hides the contaminants  806  that have migrated across the transparent cover  802 .  FIG. 8  further shows multiple vibration devices  804  may be connected to the transparent cover  802  to enhance the movement thereof. 
         [0037]      FIG. 9  shows a fourth embodiment wherein the contaminants  906  are ejected from the transparent cover  902  by a vibration device  911  connected to the transparent cover  902  and imparts a motion  912  perpendicular to the surface  908  of the transparent cover  902 . Preferably, the vibration device  904  has caused the contaminants  906  to migrate to the periphery  910  prior to activation of the vibration device  911  that flicks or ejects the contaminants  906  from the transparent cover  902 ; however, the vibration devices  904  and  911  may operate simultaneously. 
         [0038]      FIGS. 10  (partial cross-sectional view) and  11  (bottom view) show how one or more thin piezoelectric layers  1004  may be attached to the top or bottom of the transparent cover  1002  in a very space efficient manner. Piezoelectric plate-like elements could be bonded with one or two-part epoxy. Curing of the epoxy could be at elevated or ambient temperatures depending on epoxy specification and preferred stress loading on piezoelectric elements. Other adhesive materials, for example, pressure sensitive adhesives, may also applicable. 
         [0039]    While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.