Abstract:
A key top member used in an input device includes a base sheet, a lower colored layer coated on the base sheet and coated with a transparent protecting layer thereon, an upper layer coated on the protecting layer, and a top layer coated on the upper layer. The top layer and the upper colored layer are pierced with open indicating an displaying symbol.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to a key top member for a push button switch structure suitable for usage in mobile communication equipment such as a mobile phone or a car phone, a home telephone, an electronic notebook, a measuring instrument, a vehicle mounted-switch, a remote control, a computer, a personal computer, or the like (collectively, named as input device), more particularly to a key top member for a push button switch structure which permits a display section such as a symbol, a letter, a pattern or the like printed on a sheet to exhibit enhanced design characteristics and durability and is used for a back-lighted push button switch structure as well. 
         [0003]    2. Description of the Prior Art 
         [0004]    In general, a push button switch structure is so constructed that a key top member or a cover having key top elements arranged thereon is mounted on a circuit board received in a casing of the equipment, to thereby function as a switch structure for carrying an ON-OFF operation of a circuit of the equipment. Such a push button switch structure typically has a key top member incorporated therein, which is formed of thermoplastic resin into a predetermined configuration by injection molding. Recently, it has been demanded to apply a variety of designs such as a symbol, a pattern and the like to the key top by printing. The symbol or/and pattern can be formed on the key top member by laser&#39;s irradiation. After completion of irradiation, the key top member with irradiated symbols and patterns are then assembled in the casing of mobile phone. The symbols and the patterns on the key top members of the mobile phones are specified in response to languages and custom of a predetermined country the mobile phone will sell in. 
         [0005]    It will be happened that mobile phones originally planed to launch in one country might overstock in said one country. The key top member can no longer used. So, a key top member without any symbol and pattern after it is assembled to the casing of the mobile phone, is desired. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    Therefore, an object of the present invention is to provide a key top member without any symbols and patterns after assembled in an input device, such as mobile phones. 
         [0007]    To fulfill the above-mentioned object, a key top member used in an input device comprises a base sheet, a lower colored layer coated on the base sheet and coated with a transparent protecting layer thereon, an upper layer coated on the protecting layer, and a top layer coated on the upper layer. The top layer and the upper colored layer are pierced with opens indicating a displaying symbol. 
         [0008]    Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The foregoing summary, as well as the following detailed description of the embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. As should be understood, however, the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
           [0010]      FIG. 1  is a top perspective view of a key top member made in accordance with the present invention; 
           [0011]      FIG. 2  is a schematic cross sectional view of the key top member without any symbols and patterns thereon; 
           [0012]      FIG. 3  is a schematic cross sectional view of the key top member, wherein symbols and patterns are formed by laser&#39;s irradiation; 
           [0013]      FIG. 4  is a top plan view of a mobile phone in which the key top member without any symbols and patterns is assembled; and 
           [0014]      FIG. 5  is a top plan view of the mobile phone of  FIG. 4  which is irradiated with symbols and patters. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    Reference will now be made in detail to the preferred embodiment of the present invention. 
         [0016]    With reference to  FIGS. 1 ,  4  and  5 , an embodiment of a key top member  1  for a push button switch structure according to the present invention is illustrated to be used at a mobile phone  2 . The key top member  1  of the illustrated embodiment is completed without any symbols and pattern or the like as shown in  FIG. 1 . The blank key top member  1  is assembled to the mobile phone  2  as shown in  FIG. 4  and then the key top member  1  is deposited with symbols and pattern or the like such as numerals  1 ˜ 9  and symbols #, * and so on, as shown in  FIG. 5 , collectively, named as displaying symbols. 
         [0017]      FIGS. 2 and 3  shows a laminate of the key top member  1 . The key top member  1  includes a base sheet  10 , a lower colored layer  20 , a protecting layer  30 , an upper colored layer  40  and a top layer  50 . Said each former layer is superimposed above each latter layer in turn, to constitute the key top member  1 . The base sheet  10  is the lowest layer confronting with a circuit board (not shown), which generally is made from soft and elastic material such as thermoplastic resin and silicone rubber. The base sheet  10  can be transparent or semitransparent. As shown in  FIG. 1 , a key unit is constituted of specified arrayed keys. 
         [0018]    The lower colored layer  20  is coated on a top surface of the base sheet  10 . The lower colored layer  20  is formed by spraying colored paint or printing colored ink on the base sheet  10 . The color for the lower colored layer  20  is selected by manufacturer according to overall design of the mobile phone  2 . 
         [0019]    The protecting layer  30  is coated on a top surface of the lower colored layer  20 , which is formed by transparent painting. The lower colored layer  20  displays through the protecting layer  30  at the top surface of the lower colored layer  20 . 
         [0020]    The upper colored layer  40  is coated on a top surface of the protecting layer  30 . The upper colored layer  40  also is formed by spraying colored paint or printing colored ink. The upper and lower colored layers  20 ,  40  are be colored paint or colored ink. 
         [0021]    The top layer  50  made form UV (ultraviolet-cured resin), is coated on a top face of the upper colored layer  40 . After irradiation of ultraviolet beans, the upper colored layer  50  is harden to attach on the upper colored layer  40 . The top layer  50  is different from the lower colored layer  20  in color. 
         [0022]    The completed laminate of the key top member  1  without any symbols and patterns or the like is assembled together as a key unit as shown in  FIG. 1  and then the key unit is assembled in the mobile phone  2 . Please notes, the base sheets  10  of the array of the key can be discrete and separate from each other, or make from a single piece of silicon rubber. After determination of which country the mobile phone  2  will be sold, the key top member  1  is deposited with displaying symbols. As shown in  FIG. 3 , a laser bean is irradiated on the top layer  60 , thereby etching and piercing the top layer  50  and the upper colored layer  40  to form three-dimensional opens  60  and expose the color of the lower colored layer  20  through these opens and the transparent protecting layer  30 . Each open  60  indicates one designed display symbols. The transparent protecting layer  30  is used to prevent the lower colored layer  20  from etching by the laser beans and missing colors. The different color between the top layer  50  and the lower colored layer  20  benefit user observe displaying symbols, even in a circumstance without any back-light. 
         [0023]    It is to be understood, however, that even though numerous, characteristics and advantages of the present invention have been set fourth in the foregoing description, together with details of the structure and function of the invention, the disclosed 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.