Abstract:
A backlight button assemblage includes an opaque button, a light-guiding element, and a light-emitting element. The light-emitting element is disposed under the button and light emitted from the light-emitting element is guided to the front side of the button via the light-guiding element surrounding the button. Light can therefore be evenly distributed over the light-guiding element, and uniformity of light achieved, so that partial dazzling spots are avoided, the quantity of light-emitting elements is reduced, and fabrication costs are saved.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a structure of backlight button, particularly to a backlight button assemblage, which has an improved light-guiding structure. 
   BACKGROUND OF THE INVENTION 
   With the progress of science and technology, the utility and popularity of the electronic product grow obviously. In some places, such as conference room, interior of car or airplane, as light is dim, an operation of keyboard is difficult when a user operates electronic products, such as a computer, PDA, projector, mobile phone, etc. 
   To solve the above-mentioned problem, Taiwanese Utility Model Patent Publication No. M248011 discloses a backlight button. The backlight button includes a button body and a guiding element. The button body is transparent and the guiding element is extended from at least one side of the button body. A light-emitting element is disposed in a position of a printed circuit board (PCB), which corresponds to the button body, and an inching switch is disposed in the portion of the PCB, which corresponds to the guiding element. When a user presses the button, the guiding element actuates the inching switch to turn on the light-emitting element, and the light from the light-emitting element directly projects onto the button body, and thus, the button also emits light. 
   However, the transparent button results in the light projecting directly into the user&#39;s eyes, which incurs the discomfort for the user. Referring to  FIG. 1 , another conventional design of a backlight button includes an opaque button  10 , a transparent light-guiding element  11  disposed along a perimeter of the button  10 , and a light-emitting element  12  disposed under the light-guiding element  11 . Via a light-guiding ability of the light-guiding element  11 , the perimeter of the button  10  has a ring of backlight. But the design of installing the light-emitting element  12  under the light-guiding element  11  still results in dazzling spots on a light-exiting surface of the light-guiding element  11  and light non-uniformity. To lessen the light non-uniformity, it is necessary to evenly install more light-emitting elements  12  along the perimeter of the button  10  to achieve light uniformity. However, utilizing more light-emitting elements  12  results in more fabrication cost and power consumption. 
   SUMMARY OF THE INVENTION 
   An objective of the present invention is to provide a backlight button assemblage that can provide a light uniformity and can also avoid an appearing of partial dazzling spots and a light directly projecting into user&#39;s eyes. 
   Another objective of the present invention is to provide the backlight button assemblage that reduces a quantity of the light-emitting elements. 
   To achieve the aforementioned objectives, in one embodiment of the present invention, a backlight button assemblage includes an opaque button, a light-guiding element disposed along a perimeter of the button, and the light-emitting element disposed under the button. The light emitted from the light-emitting element is transmitted through a direct or a reflective path to the light-guiding element surrounding the perimeter of the button, and via a light-guiding ability of the light-guiding element, the light inside the light-guiding element is guided toward a front side of the button and transmits out. Thus, the light is evenly distributed over the light-guiding element to achieve the light uniformity and to avoid the partial dazzling spots, and the quantity of the light-emitting elements can be reduced, and the fabrication cost is saved. 
   Further scope of the applicability of the present invention will become apparent from the detailed description givin hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various chances and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
       FIG. 1  is the section view of a conventional backlight button. 
       FIG. 2  is a structural diagram showing a backlight button assemblage of the present invention on a printed circuit board. 
       FIG. 3  is a section view along the line  3 - 3  in  FIG. 4 . 
       FIG. 4  is the schematic diagram showing a disposal of the light-emitting elements of the backlight button assemblage in a first embodiment of the present invention. 
       FIG. 5  is the schematic diagram showing another disposal of the light-emitting elements of the backlight button assemblage in the first embodiment of the present invention. 
       FIG. 6  is the section view of the backlight button assemblage in the second embodiment of the present invention. 
       FIG. 7  is the section view of the backlight button assemblage in the third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As shown in  FIG. 2  and  FIG. 3 , according to the first embodiment of the present invention, a backlight button assemblage  30  includes a button  31 , a light-guiding element  40 , and at least one light-emitting element  50 . 
   The button  31  is opaque and disposed above a switch  32 . A bottom of the button  31  usually has a protrusion  311 , which is used to press a contact end  321  of the switch  32 . In a normal state, the button  31  is supported by support elements, such as a spring (not shown), or directly supported by the contact end  321  of the switch  32 . 
   The light-guiding element  40  is transparent. The shape of light-guiding element  40  matched a contour of the button  31  and is disposed along the perimeter of the button  31 , The light-guiding element  40  can not interfere with a movement of the button  31 . The light-guiding element  40  is annular, and is fixed to or stands on the surface of a printed circuit board (PCB)  20 . The light-guiding element  40  guides a light and is made of a transparent material, such as Polycarbonate (PC) or Acrylic, and Polycarbonate has higher transparency than Acrylic. 
   The light-emitting element  50  is disposed on the PCB  20  and in a rear of the button  31 . The light-emitting element  50  is surrounded by the light-guiding element  40  and a directionless light emitting diode (LED) is a better choice of the light-emitting element  50 . When the light-emitting element  50  is directionless, one portion of the light directly illuminates the light-guiding element  40 , and the other portion of the light is reflected by the opaque button  31  and then enters the light-guiding element  40 . Via a light-guiding ability of light-guiding element  40 , the light inside the light-guiding element  40  is guided toward a front side of the button  31  and transmits out. Thus, the light can be uniformly distributed over the light-guiding element  40  to achieve the light uniformity and to avoid the partial dazzling spots. It is better to dispose the light-emitting element  50  in symmetric positions of which symmetric center is a central point of the button  31 . For example, as shown in  FIG. 4 , two light-emitting elements  50  can be installed on an upper and a lower side of the central point of the button  31 , or as shown in  FIG. 5 , four light-emitting elements  50  can be installed on four sides of the central point of the button  31 . The number of the light-emitting elements  50  can be adjusted according to a brightness requirement of the backlight button assemblage  30 . 
   The switch  32  is disposed below the button  31 . In fact, the switch  32  is embodied in many ways. For example, a conventional switch is composed of a button cap, an elastic element, and a membrane circuit. The elastic element is coupled to an underneath of the button cap having a protrusion that is spaced out from the membrane circuit by a gap. The membrane circuit has a first electrical conductive portion and a second electrical conductive portion. In a normal state, a space between the first electrical conductive portion and the second electrical conductive portion is formed to keep them from contacting to each other. When the button cap is pressed down, the protrusion of the elastic element contacts the membrane circuit, which enables the first electrical conductive portion to contact the second electrical conductive portion, and thus, the circuit becomes electrical conductive. Further, Taiwanese Patent Publication No. I223295 discloses a space saving and a cost saving button switch. The first electrical conductive portion is installed on the elastic element and the second electrical conductive portion is installed on the membrane circuit. Via pressing the button cap, the first electrical conductive portion contacts the second electrical conductive portion to conduct electricity. Those mentioned above are only the supplementary description of the switch and not intended to represent the characteristics of the present invention, and each person skilled in the art should be able to understand and utilize those conventional technologies easily. 
   Refer to  FIG. 6 , which discloses the backlight button assemblage in the second embodiment of the present invention, a directional light-emitting element  50   a  is adopted. In this embodiment, the objectives of the present invention are achieved via a modification of the shape of the light-guiding element and the position of the light-emitting element  50   a . In this embodiment, the light-guiding element  40   a  is a transparent structure and has a L-shaped section, which has at least one corner  41 . Two ends of the L-shaped transparent structure are a light incident surface  42  and a light-emitting surface  43  respectively. The light-emitting surface  43  surrounds the perimeter of the button  31 . The light incident surface  42  is near and perpendicular to a surface of the PCB  20 . The light-emitting element  50   a  is disposed in front of the light incident surface  42 , and the light-emitting direction (indicated by the arrow B in  FIG. 6 ) is parallel to the surface of the PCB  20 . The light-emitting direction of a light emitted from light-emitting element  50   a  is parallel to a normal direction of said light incident surface  42 . The light emitted from the light-emitting element  50   a  directly enters through the light incident surface  42  into the light-guiding element  40   a . The corner  41  of the light-guiding element  40   a  has a reflective surface, which reflects the light from the light incident surface  42  to the light-emitting surface  43  where the light transmits out. Thus, the light from the light-emitting element  50   a  does not directly project into the user&#39;s eyes, and the light has been uniformly dispersed inside the light-guiding element  40   a  before the light transmits out. 
     FIG. 7  discloses the backlight button assemblage in a third embodiment of the present invention. In contrast to only one corner  41  in the second embodiment, in this embodiment, the light-guiding element  40   b  has two corners  41   a  and  41   b . Each corner  41   a  and  41   b  has a reflective surface. The light-emitting element  50   a  stands vertically on the surface of the PCB  20  and below the light incident surface  42   a . The light-emitting element  50   a  emits the light upward through the light incident surface  42   a  into the light-guiding element  40   b . Then, the light is reflected twice by the reflective surfaces on the corner  41   a  and corner  41   b  respectively and thereafter projected from light-emitting surface  43   a . The light-emitting direction of a light emitted from light-emitting element  50   a  is parallel to a normal direction of said light incident surface  42   a . Thus, a uniform illumination is provided for the button  31 . 
   In summary, the present invention adopts the opaque button, and the light-guiding element is disposed along the perimeter of the button; further, the light-emitting elements are disposed in the positions where the light-emitting element can not been directly seen from the exterior of the button, such as the position rear of the button or the lateral side of light-emitting surface of the light-guiding element, in order to avoid the partial dazzling spots resulting from the unevenly dispersed light or the light emitted from the light-emitting element directly projected into the user&#39;s eyes. The light emitted from the light-emitting element is projected to the light-guiding element surrounding the button via the direct or reflective path, and the light is evenly dispersed and guided to transmit out from the front of the button via the light-guiding ability of the light-guiding element. Thus, the objective of light uniformity is achieved, and the partial dazzling spots are avoided. 
   The preferred embodiments mentioned above are only to clarify the present invention and not intended to limit the scope of the present invention, and any modification or variation made by the person skilled in the art according to the spirit of the present invention is to be included within the scope of the present invention.