Abstract:
A device includes a liquid crystal display panel, a compression pad, and a bottom chassis. The bottom chassis supports the liquid crystal display panel. The compression pad has a first surface facing the liquid crystal display panel and a second surface opposite the first surface. The second surface faces away from the liquid crystal display panel. The compression pad substantially fills a volume between the liquid crystal display panel and the bottom chassis. Also, a method of assembling a device includes providing a liquid crystal display panel having a display module reflector, aligning a compression pad assembly with the liquid crystal display panel, and removing a compression pad liner from the compression pad. The compression pad assembly includes the compression pad and the compression pad liner.

Description:
FIELD 
       [0001]    The disclosure relates generally to the liquid crystal displays (LCDs) for mobile devices, and more specifically to devices and methods for LCDs that do not include a bezel. 
       BACKGROUND 
       [0002]    In the world of smartphones, the bezel functions acts as a shield and protects the back of the phone display. In the early days, cellphones were almost entirely bezel—screens were tiny, and because they lacked touchscreen interaction, that was fine. Once we began to poke and swipe at our screens, though, they got bigger—and the frame that was structurally necessary to keep them stable began to get smaller and smaller. 
         [0003]    It follows, by some logic, that the next evolutionary step would be to get rid of the bezel altogether. However, removing a bezel is not without difficulties. As provided above, the bezel offers structural support to smartphones. The bezel is often form fitted to the display screen of a phone, wrapping around the edge and extending beneath the display screen or main lens of the phone. Without bezel protection, the display is more susceptible to any point load or line load to the backside of the display screen, causing visual defects. These permanent and dynamic visual defects are often referred to as dynamic bloom, white/dark/blue spots and edge glow, but may be referred to collectively as “pressure marks.” 
       SUMMARY 
       [0004]    Accordingly, there are provided herein devices and methods that allow for bloom or pressure mark protection for a thin liquid crystal display (LCD) product without a formed metal bezel. 
         [0005]    In a first aspect, a device is disclosed. The device includes: a liquid crystal display panel; a compression pad having a first surface facing the liquid crystal display panel and a second surface opposite the first surface, the second surface facing away from the liquid crystal display panel, the compression pad substantially filling a volume between the liquid crystal display panel and a bottom chassis; and a bottom chassis that supports the liquid crystal display panel. 
         [0006]    In a second aspect, a method of assembling a device is disclosed. The method includes: providing a liquid crystal display panel having a display module reflector; aligning a compression pad assembly with the liquid crystal display panel, the compression pad assembly including a compression pad and a compression pad liner; and removing the compression pad liner from the compression pad. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The details of the present disclosure, both as to its structure and operation, may be understood in part by study of the accompanying drawings, in which like reference numerals refer to like parts. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the disclosure. 
           [0008]      FIG. 1  is a perspective view of an example mobile device with a display bezel. 
           [0009]      FIG. 2  is a perspective view of an example mobile device without a display bezel. 
           [0010]      FIG. 3  is a perspective view an example mobile device with a compression pad in accordance with an embodiment. 
           [0011]      FIG. 4  is an example graph showing the compression load (N/cm 2 ) versus the compression ratio (%) for a compression pad in accordance with an embodiment. 
           [0012]      FIG. 5A  is a perspective exploded view of an example mobile device with a compression pad in accordance with an embodiment. 
           [0013]      FIG. 5B  is a front top view of an example mobile device in a first assembly position in accordance with an embodiment. 
           [0014]      FIG. 5C  is a front top view of an example mobile device in a second assembly position in accordance with an embodiment. 
           [0015]      FIG. 5D  is a close up of a top portion of  FIG. 5C . 
           [0016]      FIG. 5E  is a front top view of an example mobile device in a third assembly position in accordance with an embodiment. 
           [0017]      FIG. 6A  is a perspective exploded view of an example mobile device in a first assembly position in accordance with an embodiment. 
           [0018]      FIG. 6B  is a top view showing a general front side and backside of an LCD module for the example mobile device of  FIG. 6A . 
           [0019]      FIG. 6C  is a perspective exploded view of an example mobile device in a second assembly position in accordance with an embodiment. 
           [0020]      FIG. 6D  is a perspective exploded view of an example mobile device in a third assembly position in accordance with an embodiment. 
           [0021]      FIG. 7  is a perspective view of an example mobile device showing gaps in the mobile device. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The present disclosure describes methods and systems for that allow for bloom or pressure mark protection for a thin LCD product without a formed metal bezel. In some embodiments, the LCD product includes a low compression force pad proximate to the back of a display module reflector, between the display and chassis, to distribute point loads, thereby reducing the occurrence of pressure marks. 
         [0023]      FIG. 1  is a perspective view of an example mobile device with a display bezel. As shown, mobile device is not an entire mobile device, but rather a liquid crystal display (LCD) module  100 . LCD module  100  includes a metal bezel  110 , a reflector  130  and a light guide frame (LGF)  140 . Metal bezel  110  is connected to reflector  130  via adhesive  120 . LGF  140  is configured to hold LCD module  100  together by means of mechanical features and adhesives. Adhesive  120  may be made of any suitable adhesive material, including for example, glues and/or epoxies. Reflector  130  may be a multilayered plastic film that functions as a mirror. 
         [0024]    In some embodiments, the metal bezel  110  has a thickness of approximately 0.150 mm. Reflector  130  may have a thickness of around 0.082 mm. Adhesive  120  has a thickness of approximately 0.03 mm to approximately 0.08 mm. 
         [0025]    As shown, metal bezel  110  does not effectively solve bloom issues or pressure marks associated with LCD module  100 . This is because point or edge loads translate through the thin metal bezel  110  and into the LCD module  100  with minimal load distribution. When the load is minimally distributed, the applied pressure is higher through the LCD module  100  (e.g., Pressure=Force/Area). The higher pressure results in more deflection through the layers of the LCD module  100  and reduces the gap between the front and back glass prisms  146 ,  148  containing the liquid crystal. The effect is bloom. 
         [0026]    LCD module  100  also includes a light guide  142 , a diffuser film  144 , a lower prism  146 , and an upper prism  148 . In some embodiments, the light guide  142  is constructed from plastic and distributes light from light emitting diodes (LEDs) throughout LCD module  100 . In some embodiments, diffuser film  144  is constructed from plastic and spreads light throughout the display. In some embodiments, the lower prism  146  and upper prism  148  are constructed from plastic and are brightness enhancement films that focus light. One prism  146  or  148  focuses light in the horizontal direction and the other prism  146  or  148  focuses light in the vertical direction. Also shown is a rim adhesive  150  that allows the prisms  146 ,  148  to be secured to LFG  140 . 
         [0027]    In some embodiments, light guide  142  has a thickness of approximately 0.45 to 0.56 mm. Diffuser film  144  may have a thickness of around 0.05 mm. Lower prism  146  may have a thickness of approximately 0.065 mm and upper prism  148  may have a thickness of approximately 0.095 mm. 
         [0028]    LCD module  100  also includes a back polarizer  160 , a lower prism  170 , an upper prism  180 , and a front polarizer  190 . In some embodiments, the back polarizer  160  is constructed from plastic and allows light to pass at a specific polarization. In some embodiments, lower prism  170  is constructed from glass and holds a thin film transistor (TFT), which carries electrical current to the liquid crystal and forces it to either block or omit light. In some embodiments, the liquid crystal (not shown) is located between lower prism  170  and upper prism  180 . In some embodiments, upper prism  180  is constructed from glass and includes a color filter for red, green, and blue (RGB). Each RGB filter is associated with a transistor that defines the color that will be visible (e.g., a pixel). In some embodiments, front polarizer  190  is constructed from plastic and allows light to pass at a specific polarization. 
         [0029]      FIG. 2  is a perspective view of an example mobile device without a display bezel. As shown, mobile device is not an entire mobile device, but rather an LCD module  200 . LCD module  200  includes a reflector  210  and a light guide frame (LGF)  240 . LGF  240  is configured to hold LCD module  200  together by means of mechanical features and adhesives. Reflector  210  may be a multilayered plastic film that functions as a mirror. 
         [0030]    LCD module  200  also includes a light guide  242 , a diffuser film  244 , a lower prism  246 , and an upper prism  248 . In some embodiments, the light guide  242  is constructed from plastic and distributes light from light emitting diodes (LEDs) throughout LCD module  200 . In some embodiments, diffuser film  244  is constructed from plastic and spreads light throughout the display. In some embodiments, the lower prism  246  and upper prism  248  are constructed from plastic and are brightness enhancement films that focus light. One prism  246  or  248  focuses light in the horizontal direction and the other prism  246  or  248  focuses light in the vertical direction. Also shown is a rim adhesive  250  that allows the prisms  246 ,  248  to be secured to LFG  240 . 
         [0031]    LCD module  200  also includes a back polarizer  260 , a lower prism  270 , an upper prism  280 , and a front polarizer  290 . In some embodiments, the back polarizer  260  is constructed from plastic and allows light to pass at a specific polarization. In some embodiments, lower prism  270  is constructed from glass and holds a thin film transistor (TFT), which carries electrical current to the liquid crystal and forces it to either block or omit light. In some embodiments, the liquid crystal (not shown) is located between lower prism  270  and upper prism  280 . In some embodiments, upper prism  280  is constructed from glass and includes a color filter for red, green, and blue (RGB). Each RGB filter is associated with a transistor that defines the color that will be visible (e.g., a pixel). In some embodiments, front polarizer  290  is constructed from plastic and allows light to pass at a specific polarization. 
         [0032]    A main difference between  FIG. 1  and  FIG. 2  is that  FIG. 1  includes a bezel  110  and adhesive  120  to secure it to the LCD module  110 . Generally, the sizes (e.g., thicknesses) of like components are similar. However, the overall thickness of mobile device  100  is greater than mobile device  200  due to including the bezel  110 . 
         [0033]      FIG. 3  is a perspective view an example mobile device  300  with a compression pad in accordance with an embodiment. Unlike in  FIG. 1  and  FIG. 2 ,  FIG. 3  shows a mobile device  300  including an LCD module  310  and additional components, making a more complete phone. It should be appreciated that for purposes of discussion, LCD module  310  may include similar components to LCD module  200 . 
         [0034]    Mobile device  300  also includes a main lens  320 , which may be constructed of a transparent material such as glass. Main lens  320  may be secured to the LCD module  310  via an optically clear adhesive (OCA)  330 . OCA  330  may be approximately 0.15 thick and made from any suitable adhesive. 
         [0035]    Also shown are front housing  340 , which is secured to main lens  320  via main lens adhesive  350 . In some embodiments, front housing is constructed from aluminum die cast and over-molded PC plastic. Main lens adhesive  350  may be any suitable adhesive and is approximately 0.25 mm thick. Proximate to and beneath LCD module  310  is compression pad  360 . As shown, compression pad  360  is in contact with a reflector or reflector film (not shown) of LCD module  360 . Beneath compression pad  360  is a chassis  370 . As shown, chassis  370  is generally a bottom structure of mobile device  300 , however in some embodiments, it may be a printed circuit board (not shown) of other internal phone component that is located beneath the LCD module  310 . 
         [0036]    In some embodiments, compression pad  360  substantially fills a volume between the LCD module  310  and chassis  370 . In some embodiments, compression pad  360  effectively minimizes or removes any gaps in mobile device  300  between LCD module  310  and chassis  370 . Thus, compression pad  360  is at least partially compressed between LCD module  310  and chassis  370 . 
         [0037]    The compression force on the compression pad  360  is important, because if compression force is too high, it may overstress the lens bond between main lens  320  and LCD module  330 . Too much force from the compression pad  360  may force the main lens  320  to detach from the phone. If compression force is too low, the compression pad  360  may not be effective to distribute point and/or line loads. 
         [0038]    Material properties for suitable compression pads  360  are provided in Tables 1 and 2. In some embodiments, compression pad  360  has a thickness of approximately 0.3 mm to 0.4 mm. However, it is appreciated that the thickness of the compression pad  360  may vary, depending on the size of a gap between the LCD module  310  and chassis  370 . Additionally, the width and length of compression pad  360  will vary according to the display size. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Compression Pad Dimensions 
               
             
          
           
               
                 Thickness (mm) 
                 Width (mm) 
                 Length (mm) 
               
               
                   
               
               
                 0.3-0.4 
                 36 
                 117 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Compression Pad General Properties 
               
             
          
           
               
                   
                 Property 
                 Unit 
                 Values 
                 Test Method 
               
               
                   
                   
               
             
          
           
               
                   
                 Density 
                 g/cm 3   
                 0.045 
                 JIS K 6767 
               
               
                   
                 50% Compression Load 
                 N/cm 2   
                 1.4 
                 JIS K 6767 
               
               
                   
                   
               
             
          
         
       
     
         [0039]    In some embodiments, compression pad  360  is constructed from a compressible or pliable material such as polypropylene, polyethylene terephthalate, silicone, thermoplastic urethane, or other suitable porous materials. In some embodiments, compression pad  360  has a density of approximately 0.02 to 2.3 g/cm 3 . The range of densities may be dependent on the material of compression pad  360 . For example, a compression pad  360  having a density of 0.02 g/cm 3  to 1 g/cm 3  is a highly porous compressible pad  360  and a compression pad  360  having a density of 1 g/cm 3  to 2.3 g/cm 3  is a nonporous compressible pad  360  such as silicone rubber. In some embodiments, compression pad  360  has a 50% compression load of approximately 0.5 to 5 N/cm 2 . 
         [0040]      FIG. 4  is an example graph showing the compression load (N/cm 2 ) versus the compression ratio (%) for a suitable compression pad material. 
         [0041]      FIG. 5A  is a perspective exploded view of an example mobile device with a compression pad in accordance with an embodiment. In  FIG. 5A , mobile device  500  includes a main lens and a display assembly  510  or LCD module. Also included in display assembly  510  is a display flex  520 , which includes a processor chip and supporting circuitry. The display flex  520  connects to the phone&#39;s main printed circuit board (PCB). 
         [0042]    Also shown in  FIG. 5A  are a compression pad  530  and a compression pad liner  540 . Compression pad  530  includes one or more adhesive strips  550  that run the length of the compression pad  530 . The adhesive strips  550  are located on the underside of compression pad  530 , proximate to display assembly  510 , and are used to secure the compression pad  530  to the display assembly  510 . 
         [0043]      FIG. 5B  is a front top view of an example mobile device in a first assembly position in accordance with an embodiment. In  FIG. 5B , mobile device  500  is shown with compression pad liner  540  and compression pad  530  unattached to display assembly  510 . 
         [0044]      FIG. 5C  is a front top view of an example mobile device in a second assembly position in accordance with an embodiment. In  FIG. 5C , mobile device  500  is shown with compression pad liner  540  and compression pad  530  placed on top of display assembly  510 . A top portion  570  of mobile device  500  is also shown, where the compression pad liner  540  is aligned to a top edge of the display assembly  510  in order to properly position the compression pad  530  on the display assembly  510 . 
         [0045]      FIG. 5D  is a close up of a top portion of  FIG. 5C . In top portion  570 , two corners  542 ,  544  of compression pad liner  540  are shown which align with two corners of the display assembly  510 . In some embodiments, the compression pad liner  540  aligns with the display reflector of display assembly  510 . 
         [0046]      FIG. 5E  is a front top view of an example mobile device in a third assembly position in accordance with an embodiment. In  FIG. 5E , the compression pad liner  540  has been removed after placing the compression pad  530  in its correct position. As provided above, the compression pad  530  is secured to display assembly  510  with adhesive strips  550 . 
         [0047]      FIG. 6A  is a perspective exploded view of an example mobile device in a first assembly position in accordance with an embodiment. In  FIG. 6A , an example mobile device  600  includes a main lens  610 , OCA  620  and LCD module  630 , which when placed together form partial device  650 . Main lens  610  bonds to the LCD module  630  via OCA  620 . 
         [0048]      FIG. 6B  is a top view showing a general front side and backside of an LCD module for the example mobile device of  FIG. 6A . Partial device  650  is shown with a front side showing main lens  610  and backside showing LCD module  630 . On LCD module  630  is a display flex  632  and touch flex  634 . In some embodiments, the display flex  632  connects to the touch flex  634 , which controls the capacitive touch on module  634 . The display flex  632  connects to the mobile device&#39;s  600  main printed circuit board (PCB) (not shown). 
         [0049]      FIG. 6C  is a perspective exploded view of an example mobile device in a second assembly position in accordance with an embodiment. A compression pad  640  is shown as assembled to the back of partial device  650  (which is LCD module  630  from  FIG. 6B ), resulting in main lens assembly  660 . In some embodiments, fixtures can be used during assembly to ensure proper alignment. 
         [0050]      FIG. 6D  is a perspective exploded view of an example mobile device in a third assembly position in accordance with an embodiment. As provided, main lens assembly  660  is secured to front housing  670  to form a top half  680  of a mobile device. 
         [0051]      FIG. 7  is a perspective view of an example mobile device without a compression pad or display bezel. A mobile device  700  is shown having a LCD module  710 , main lens  720 , OCA  730 , front housing  740  and mains lens adhesive  750 . Also shown are an X-gap  770  and a Z-gap  760 . A Y-gap is also present and identical to the X-gap, but is not shown. In some embodiments, using a compression pad reduces the X-gap  770  and Z-gap  760  and Y-gap (not shown). For example, the X-gap  770  may be reduced by approximately 0.27 mm for each side of the mobile device, the Y-gap (not shown) may be reduced by approximately 0.27 mm for each side of the mobile device, and the Z-gap  760  may be reduced by approximately 0.25 mm. 
         [0052]    The reduction in mobile device thickness is provided in Tables 3-5. In Table 3, the mobile device thickness for a device with a display bezel is shown. Gap  2  in Table 3 provides a minimum distance used to prevent bloom or pressure marks in the mobile device using a bezel. Table 4 provides the mobile device thickness for a device without a bezel or compression pad. The Gap in Table 4 provides a minimum distance used to prevent bloom or pressure marks in the mobile device without a bezel or compression pad. Table 5 provides the mobile device thickness for a device with a compression pad. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Mobile Device Thickness for Device with Display Bezel 
               
               
                 Stack Through Display 
               
             
          
           
               
                   
                 Description of Layer 
                 Size (mm) 
               
               
                   
                   
               
               
                   
                 Main Lens 
                 0.600 
               
               
                   
                 OCA 
                 0.150 
               
               
                   
                 Display 
                 1.400 
               
               
                   
                 Gap 1 
                 0.050 
               
               
                   
                 Display Bezel 
                 0.150 
               
               
                   
                 Gap 2 
                 0.250 
               
               
                   
                 Chassis 
                 0.500 
               
               
                   
                 Total Thickness 
                 3.100 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Mobile Device Thickness for Device without Bezel 
               
               
                 Stack Through Display 
               
             
          
           
               
                   
                 Description of Layer 
                 Size (mm) 
               
               
                   
                   
               
               
                   
                 Main Lens 
                 0.600 
               
               
                   
                 OCA 
                 0.150 
               
               
                   
                 Display 
                 1.400 
               
               
                   
                 Gap 
                 0.350 
               
               
                   
                 Chassis 
                 0.500 
               
               
                   
                 Total Thickness 
                 3.000 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Mobile Device Thickness for Device with Compression Pad 
               
               
                 Stack Through Display 
               
             
          
           
               
                   
                 Description of Layer 
                 Size (mm) 
               
               
                   
                   
               
               
                   
                 Main Lens 
                 0.600 
               
               
                   
                 OCA 
                 0.150 
               
               
                   
                 Display 
                 1.400 
               
               
                   
                 Gap 
                 0.200 
               
               
                   
                 Chassis 
                 0.500 
               
               
                   
                 Total Thickness 
                 2.850 
               
               
                   
                   
               
             
          
         
       
     
         [0053]    In some embodiments, adding a pad behind a display distributes point or edge loads over an area, which results in less pressure translating through the liquid crystal layer. As the equation (Pressure=Force/Area) shows, at constant force pressure decreased if the area of applied force is increased. The reduction in pressure reduces the deflection between films and the liquid crystal layer between the two glass prisms. By reducing the deflections, light paths are less interrupted resulting in less cosmetic defects such as bloom. 
         [0054]    Benefits associated with using a compression pad in a mobile device assembly may include:
       The compression pad distributes point and line load and conforms to a gap between an LCD module display reflector and device housing.   The compression pad reduces the x-y-z device package, allowing thinner devices with a greater screen to size ratio.
           For example, using a compression pad may reduce the device by approximately 0.5 mm in both x and y directions, and may reduce the device by approximately 0.2 mm in the z direction.   The compression pad allows the use of an LCD panel without a protective bezel while maintaining visual performance. This translates into opportunities in cost and weight savings for the device.   For example, the device weight may be reduced by approximately 5 g by using a compression pad.   The aspect ratio of the display active area to the size of the screen may be improved because the compression pad sits behind the display, whereas the metal bezel wraps around the display.   
               
 
         [0061]    Accordingly, the present disclosure is not limited to only those implementations described above. Those of skill in the art will appreciate that the various illustrative modules and method steps described in connection with the above described figures and the implementations disclosed herein can often be implemented as electronic hardware, software, firmware or combinations of the foregoing. To clearly illustrate this interchangeability of hardware and software, various illustrative modules and method steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled persons can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure. In addition, the grouping of functions within a module or step is for ease of description. Specific functions can be moved from one module or step to another without departing from the disclosure. 
         [0062]    The various illustrative modules and method steps described in connection with the implementations disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (“DSP”), an application specific integrated circuit (“ASIC”), a field programmable gate array (“FPGA”) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any processor, controller, or microcontroller. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
         [0063]    Additionally, the steps of a method or algorithm described in connection with the implementations disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in computer or machine-readable storage media such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium including a network storage medium. An example storage medium can be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can also reside in an ASIC.