Abstract:
A keypad assembly includes a pressing surface layer, a pattern layer, an elastic layer, a light guiding layer, and a pressing bottom layer. The pattern layer is under the pressing surface layer. The elastic layer is located between and interlocks the pattern layer and the light guiding layer by adhesive. The pressing bottom layer adheres to the light guiding layer. The keypad assembly has an ideal appearance by lights collection of the light guiding layer. User can feel comfortable when pressing the keypad assembly because of the elastic layer&#39;s buffering effect.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to keypad assemblies, specifically to a keypad assembly for an electronic device, such as a mobile phone. 
         [0003]    2. Description of Related Art 
         [0004]    A typical keypad assembly for a given electronic device includes an upper shell and a keypad. The upper shell defines a plurality of holes therethrough. The keypad has a plurality of keys formed on a top surface thereof and a plurality of switch points on a bottom surface thereof. Each switch point corresponds to a key of the keypad. The keypad is mounted under the upper shell and each key is exposed through a corresponding hole of the upper shell. However, the keys of the keypad are typically made of stiff material and the switch points are made of metal. When a user presses the key, a finger of the user may feel uncomfortable due to the hardness of the keys and switch points. 
         [0005]    Currently, a thin keypad assembly for an electronic device may include a pressing surface layer and a pressing bottom layer. The pressing surface layer is made of transparent elastic rubber and the pressing bottom layer is made of hard polycarbonate. The pressing surface layer and the pressing bottom layer are made integral by adhesive or hot press molding. Patterns on the keypad assembly are formed on the pressing bottom layer by printing before adhesive or hot press molding. However, the thickness of the keypad assembly may be so thin that the user may feel uncomfortable when pressing the keypad assembly. Also, because collecting the light rays under the pressing bottom layer can be difficult in the area of the patterns, it is difficult to achieve ideal vision effect. Also, if the thin keypad assembly cannot eliminate static electricity, the static electricity may generate undesirable influence for the electronic device. 
         [0006]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present keypad assembly can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present keypad assembly. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is an exploded, isometric view of a keypad assembly, in accordance with an exemplary embodiment. 
           [0009]      FIG. 2  is similar to  FIG. 1 , but viewed from another aspect. 
           [0010]      FIG. 3  is an assembled, isometric view of the keypad assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0011]    The present keypad assembly is suitable for electronic devices, such as mobile phones, personal digital assistants (PDAs), and etc. 
         [0012]    Referring to  FIGS. 1 and 2 , a keypad assembly  100  includes a pressing surface layer  10 , a pattern layer  20 , a first adhesive layer  30 , an elastic layer  40 , a second adhesive layer  50 , a light guiding layer  60 , a third adhesive layer  70  and a pressing bottom layer  80 . 
         [0013]    The pressing surface layer  10  can be made of transparent and elastic thermoplastic macromolecule materials such as rubber, thermoplastic polyurethane or a combination thereof. A thickness of the pressing surface layer  10  is in the range of about 0.1-about 0.2 mm (millimeter) and is preferably about 0.2 mm. The pressing surface layer  10  has a top surface  12  and an opposite bottom surface  14 . The top surface  12  has a plurality of key profiles  122  formed thereon. The profiles  122  may protrude from the top surface  12  or may be recessed in top surface  12 . In the exemplary embodiment, the profiles  122  protrude from the top surface  12 . Each profile  122  can be substantially ring-shaped. A thickness of the profile  122  is in the range of about 0.2-about 0.3 mm and is preferably about 0.2 mm. The profiles  122  can be formed by hot press molding. The location of the profiles  122  on the pressing surface layer  10  identify the locations of keys formed on the keypad assembly  100 . 
         [0014]    The pattern layer  20  includes a hard layer  22 , and a printing ink layer  24  formed on one surface of the hard layer  22 . The hard layer  22  is a transparent and can be made of thermoplastic macromolecule material such as polycarbonate, polyethylene terephthalate or a combination thereof. The printing ink layer  24  has a plurality of icons  26  formed thereon. In this exemplary embodiment, the printing ink layer  24  has a background color printed or applied thereon and the icons  26  are printed on or applied thereto in a contrasting color. Each icon  26  corresponds to a profile  122 . The hard layer  22  contacts the bottom surface  14  of the pressing surface layer  10  after the pattern layer  20  is assembled to the pressing surface layer  10 . A thickness of the pattern layer  20  is in the range of about 0.1-about 0.2 mm and is preferably about 0.125 mm. 
         [0015]    The first adhesive layer  30  is transparent double-face adhesive layer and substantially rectangular. The first adhesive layer  30  has a thickness in the range of about 0.1-about 0.2 mm and is preferably about 0.1 mm. The shape of the first adhesive  30  is similar with the shape of the pattern layer  20 , and the size of the first adhesive layer  30  is smaller than the size the pattern layer  20 . The first adhesive layer  30  adheres the pattern layer  20  to the elastic layer  40 . 
         [0016]    The elastic layer  40  can be made of transparent and elastic thermoplastic macromolecule materials such as rubber, thermoplastic polyurethane or a combination thereof. The surface size of the elastic layer  40  is same as the surface size of the first adhesive layer  30 . A thickness of the elastic layer  40  is in the range of about 0.1-about 0.2 mm and is preferably about 0.2 mm. A bottom surface of the elastic layer  40  has a plurality of columns  42  formed thereon. The thickness of a column  42  is in the range of about 0.2-about 0.3 mm and is preferably about 0.25 mm. Each column  42  can be formed by hot press molding the elastic layer  40 . Each column  42  corresponds to an icon  26  after the elastic layer  40  is affixed to the pattern layer  20  by the first adhesive layer  30 . 
         [0017]    The second adhesive layer  50  is a transparent double-face adhesive layer and is a substantially hollow rectangular frame. The shape of the second adhesive layer  50  corresponds to a peripheral edge of the pattern layer  20 . The thickness of the second adhesive layer  50  is in the range of about 0.1-about 0.2 mm and is preferably about 0.1 mm. The second adhesive layer  50  interconnects the pattern layer  20  and a housing (not shown) of an electronic device together. 
         [0018]    The light guiding layer  60  is made of transparent and plastic macromolecule material such as polyimide. A surface size of the light guiding layer  60  is the same as the surface size of the elastic layer  40 . A thickness of the light guiding layer  60  is in the range of about 0.1-about 0.2 mm and is preferably about 0.125 mm. The light guiding layer  60  is associated with a light source (not shown) contained within the electronic device and has a plurality of focusing areas  62  formed thereon. Each focusing area  62  corresponds to an icon  26  of the pattern layer  20  and is formed by printing. In this exemplary embodiment, the focusing areas  62  are in circular shapes and printed on the light guiding layer  60  by white printing ink. Light rays from the light source (neither shown) inside of electronic device will be collected in the focusing areas  62  and directed towards the icons  26 , thereby increasing the brightness of the icon  26 . 
         [0019]    The third adhesive layer  70  is a transparent double-faced adhesive layer. The third adhesive layer  70  includes glue pieces  72 . A thickness of the glue piece  72  is in the range of about 0.1-about 0.2 mm and is preferably about 0.1 mm. The third adhesive layer  70  interconnects the pressing bottom layer  80  and the light guiding layer  60  together. 
         [0020]    The pressing bottom layer  80  can be made of a transparent and thermoplastic macromolecule material such as polycarbonate, polyethylene terephthalate or a combination thereof. The pressing bottom layer  80  has a plurality of protrusions  82  formed on a first surface thereof and a plurality of concaves  84  formed on opposite second surface thereof corresponding to the protrusions  82 . The protrusions  82  and the concaves  84  can be formed by hot press molding. The first surface of the pressing bottom layer  80  has a metal mesh  83  printed thereon. A wire  86  formed at a side of the pressing bottom layer  80  is electronically connected at one end to the metal mesh  83  and the other end is connected to the grounded circuit (not shown) of the electronic device. The wire  86  can remove the static electricity formed in the keypad assembly  100 . The second surface of the pressing bottom layer  80  has a plurality metal domes  88  mounted in the concaves  84 . The metal domes  88  protrude from the concave  84 . The metal domes  88  are used for resisting the switches (not shown) formed on a circuit board of the electronic device. 
         [0021]    In assembly, the pressing surface layer  10  and the pattern layer  20  are connected and stacked together by hot pressing molding, each profile  122  of the pressing surface layer  10  corresponds to an icon  26 . The pattern layer  20  is adhered to the elastic layer  40  by the first adhesive layer  30 , with the peripheral edge of the pattern layer  20  exposed from the elastic layer  40  and each icon  26  corresponding to a column  42 . The second adhesive layer  50  is adhered to the peripheral edge of the pattern layer  20  and the housing of electronic device. The guiding layer  60  is adhered to the first surface of the pressing bottom layer  80  by the glue pieces  72 , each focusing area  62  corresponds to a protrusion  82 . The guiding layer  60  together with the pressing bottom layer  80  are clamped between the elastic layer  40  and the circuit board of the electronic device. Each column  42  corresponds to a focusing area  62 , the metal domes  88  of the pressing bottom layer  80  contacts the switches of the circuit board. 
         [0022]    When using the keypad assembly  100 , a desired profile  122  is pressed to further press the columns  42  of the elastic layer  40  such that the columns  42  resist the protrusions  82 . Because the column  42  is elastic, the column  42  has a buffering effect when pressed. Accordingly, the user will not feel the obvious resisting force, so the user can feel more comfortable when pressing. The light guiding layer  60  has a plurality of focusing areas  62 , the focusing areas  62  can collect light rays under the pressing bottom layer  80  to make the appearance of the icons  26  brighter. The wire  86  connects the metal mesh  83  and the grounded circuit of the electronic device to effectively eliminate static electricity. 
         [0023]    It should be understood that the icons  26  may be formed on the bottom surface  14  of the pressing surface layer  10 . 
         [0024]    It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.