Abstract:
A keypad apparatus for an electronic device permits a thinner construction. The keypad apparatus includes a first light guide plate having key buttons molded in one body attached onto the first light guide plate, a second light guide plate disposed under the first light guide plate, a first light source disposed at one side of the first light guide plate, a second light source disposed at one side of the second light guide plate, and key input switches associated with the key buttons.

Description:
CLAIM OF PRIORITY 
     This application claims the benefit under 35 U.S.C. §119(a) from a Korean Patent Application filed in the Korean Intellectual Property Office on Nov. 25, 2008 and assigned Serial No. 10-2008-0117609, the entire disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a keypad apparatus used for an electronic device. More particularly, the present invention relates to a keypad apparatus using a Light Guide Plate (LGP) to provide a thinner and simpler structure. 
     2. Description of the Related Art 
       FIG. 1  is a cross-sectional view illustrating a conventional LGP keypad apparatus. Referring now to  FIG. 1 , a light guide plate (LGP)  50  including a plurality of reflector patterns  90  is disposed over a Printed Circuit Board (PCB)  70  and a dome sheet  60 , and a rubber sheet  30  having pressing protrusions  40  is disposed over the LGP  50 . A film sheet  20  covers the top of the rubber sheet  30 , and key buttons  10  are adhered to the film sheet  20 . A light source  80  for irradiating light to the light guide plate  50  is disposed on the PCB  70 , facing one side of the LGP  50 . 
       FIGS. 3A and 3B  illustrate a conventional portable wireless terminal which is slidable in a horizontal or vertical direction. As shown in the example in  FIG. 3A , if a keypad  220  is open by pushing up a display unit  210  having its longest surface in the horizontal direction, a keypad with alphabet letters such as ‘U’, ‘I’, ‘O’ and ‘P’ printed thereon appears. As shown in  FIG. 3B , if the keypad  220  is open in the vertical direction, a keypad  225  with Arabic numerals printed thereon appears. An LGP keypad shown in  FIG. 2  is conventionally used to realize the above keypad. The LGP keypad apparatus of  FIG. 2  is also manufactured as follows. A second light guide plate  140  having pressing protrusions  150  including reflector patterns  145  and a first light guide plate  130  with a plurality of reflector patterns  135  are disposed over a PCB  170  and a dome sheet  160 , and a rubber sheet  120  and a film sheet  115  are disposed over the top of the first light guide plate  130 . Key buttons  110  are adhered to the film sheet  115 . A first light source  180  irradiates light only to the first light guide plate  130 , and a second light source  190  irradiates light only to the second light guide plate  140 . In this structure, by selectively activating the first light source  180  or the second light source  190 , the alphabet letters, for example, ‘I’, ‘O’ and ‘P’ printed on the first light guide plate  130  can be displayed on the keypad, or the Arabic numerals, for example, ‘3’, ‘6’ and ‘9’ printed on the second light guide plate  140  can be displayed on the keypad. Since this conventional keypad apparatus for an electronic device is complex in structure, it is thick and has a large number of parts, causing an increase in manufacturing cost and processing time. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is to provide a keypad apparatus for an electronic device capable of reducing manufacturing cost, processing time and keypad thickness by decreasing the number of parts. According to an exemplary aspect of the invention, a keypad apparatus using a Light Guide Plate (LGP) (hereinafter referred to as an LGP keypad apparatus), includes a key button unit that is directly molded on the light guide plate by Ultraviolet (UV) molding thereby to enable a slimmer and simpler structure. 
     According to another exemplary aspect of the present invention, there is provided a keypad apparatus for an electronic device, including a light guide plate having key buttons molded in one (unitary) body; a light source disposed at one side of the light guide plate; and key input switches associated with the key buttons. 
     According to still another exemplary aspect of the present invention, there is provided a keypad apparatus for an electronic device, including a first light guide plate having key buttons molded in one body; a second light guide plate disposed under the first light guide plate; a first light source disposed at one side of the first light guide plate; a second light source disposed at one side of the second light guide plate; and key input switches associated with the key buttons. 
     Other exemplary aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other exemplary aspects, features and advantages of certain examples of the present invention presented herein will become more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional view illustrating a conventional LGP keypad apparatus; 
         FIG. 2  is a cross-sectional view illustrating another conventional LGP keypad apparatus; 
         FIG. 3A  is a view illustrating a horizontal/vertical sliding portable terminal with the LGP keypad apparatus of  FIG. 2 , with a display being open in a horizontal direction; 
         FIG. 3B  is a view illustrating a horizontal/vertical sliding portable terminal with the LGP keypad apparatus of  FIG. 2 , with a display being open in a vertical direction; 
         FIG. 4  is a cross-sectional view illustrating an LGP keypad apparatus according to a first exemplary embodiment of the present invention; 
         FIG. 5  is a cross-sectional view illustrating an LGP keypad apparatus according to a second exemplary embodiment of the present invention; 
         FIG. 6A  is a cross-sectional view illustrating an LGP keypad apparatus according to a third exemplary embodiment of the present invention; 
         FIG. 6B  is a plane view illustrating a top surface of a light guide plate with notches formed therein according to the third exemplary embodiment of the present invention; and 
         FIG. 7  is a flow diagram illustrating an UV molding process of an LGP keypad apparatus according to an exemplary embodiment of the present invention. 
     
    
    
     Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features and structures. 
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary and illustrative in nature. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the examples described herein can be made without departing from the scope and spirit of the claimed invention. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness when their inclusion could obscure appreciation of the subject matter of the present invention by a person of ordinary skill in the art. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purposes only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
       FIG. 4  is a cross-sectional view illustrating an LGP keypad according to a first exemplary embodiment of the present invention. Referring now to  FIG. 4 , key input switches  430  are mounted on a PCB  440 , and a light guide plate  420  with pressing protrusions  425  formed thereon is disposed over the top of the key input switches  430 . Key buttons  410  are molded on the light guide plate  420  in one body by UV molding. The UV molding is a method for molding an embossed product from a transparent film and an intaglio-processed mold  615  using a UV solidified resin. 
     A UV molding process according to an exemplary embodiment of the present invention will now be described with reference to  FIG. 7 . In step S 1 , an intaglio mold  615  is prepared. In step S 2 , an appropriate amount of UV resin  625  is put in the mold  615  in such a manner that no bubbles are generated. In step S 3 , the entire surface is covered with a light guide plate  635  and then uniformly pressed to remove any bubbles that might exist in the UV resin  625 . In step S 4 , UV is irradiated to the UV resin  625  with wavelength and irradiation dosage specific to the solidified UV resin  625 . Finally, in step S 5 , the light guide plate  635  with the solidified UV resin  625  attached thereto is separated from the mold  615 . 
     In this manner, it is possible to manufacture a keypad with key buttons molded on the light guide plate in one body. The light guide plate  420  of  FIG. 4  can be molded by this UV molding process (shown in  FIG. 7 ), and have pressing protrusions  425  on a lower end, for readily pressing the key input switches  430 . In addition, reflection patterns  435  are formed on partial regions of the light guide plate  420 , which are associated with the key buttons  410 , to refract, diffract, reflect or diffuse light irradiated from a light source  450  in a direction of the key buttons  410 . Letters and numerals may be printed on the top surfaces of the key buttons  410 , and the letters and numerals may be recognized as being brighter by a user due to the light irradiated through the reflection patterns  435 . As a result, the rubber sheet and the film sheet used in the conventional keypad apparatus can be removed, contributing to a reduction in the thickness and the number of parts. 
       FIG. 5  is a cross-sectional view illustrating an LGP keypad apparatus according to a second exemplary embodiment of the present invention. The LGP keypad apparatus is a preferred example to be used as a keypad of the conventional portable wireless terminal shown in  FIGS. 3A and 3B . 
     Referring now to  FIG. 5 , key input switches  540 , such as in this example being a dome sheet, are disposed over a PCB  550 , and a second light guide plate  530  with pressing protrusions  535  formed on the bottom and a first light guide plate  520  with key buttons  510  molded thereon on the top in one body by UV molding are disposed over the key input switches  540 . Reflection patterns  525  and  545  are formed on specific regions associated with the key buttons  510 , in the first light guide plate  520  and the second light guide plate  530 , respectively, and serve to direct light irradiated from a first light source  560  and a second light source  570  in a direction of the key buttons  510 . In addition, the first light source  560  and the second light source  570  are disposed along opposite ends of the PCB  550 , facing one side or the other side of the first and second light guide plates  520  and  530 , respectively. In this example, light irradiated from the first light source  560  is input to one side of the first light guide plate  520 , and a light incidence preventing film  522  is formed on the other side to prevent light irradiated from the second light source  570  from being incident on the other end. Similarly, light irradiated from the second light source  570  is input to one side of the second light guide plate  530 , and a light incidence preventing film  532  is formed on the other side to prevent light irradiated from the first light source  560  from being incident on the other end. Also, the light incidence preventing film can be formed all around the side surfaces except for the parts on which light to the light guide plate is incident, thereby preventing undesired light incidence or light leakage. A person of ordinary skill in the art understands and appreciates that while the first light source  560  in this example is input to one side of the first light guide plate  520  and the second light source  570  is input to the second light guide plate  530 , it is within the sprit of the invention and the scope of the appended claims that the light sources could be arranged to the first light source is input to the second light guide plate, and vice versa. The first and second light sources may be operated independently of each other. Assuming that letters are printed and/or arranged on the top of the first light guide plate  520  and numerals are printed and/or arranged on the top of the second light guide plate  530 , if only the first light source  560  irradiates light, the light is input only to the first light guide plate  520  and propagates in a direction of the key buttons  510  through the reflection patterns  525 , so that the user can see the letters (not shown) printed on the first light guide plate  520 . On the contrary, if the first light source  560  is turned off and only the second light source  570  irradiates light, the light is input only to the second light guide plate  530  and propagates in a direction of the key buttons  510  through the reflection patterns  545 , so that the user can see the numerals (not shown) printed on the second light guide plate  530 . That is, it is possible to selectively display letters and/or numerals on the keypad by selectively turning On/Off the first light source  560  and/or the second light source  570 . Under certain lighting conditions, such selective usage of the light sources can be desirable, enhancing visibility for the desired keys. 
     The key buttons  510  may be separately UV-molded on the first light guide plate  520  as shown in  FIG. 5 , or the key buttons  410  may be collectively UV-molded on the light guide plate  420  in one body as shown in  FIG. 4 . It should be apparent to those skilled in the art that various modifications are possible to the key buttons (more than one body but not individual attachment of the key buttons, etc.). 
     As a result, a slim LGP keypad apparatus is possible, even though it uses two or more light guide plates. 
       FIG. 6A  is a cross-sectional view illustrating an LGP keypad apparatus according to a third exemplary embodiment of the present invention. Referring now to  FIG. 6A , a series of notches are carved in a light guide plate so that key buttons may be more softly pressed by reducing the overall mass of the light guide plate. Specifically, V-shaped notches  610  are formed on the first light guide plate  520  and the second light guide plate  530 . The notches  610  are formed around the key buttons  510  so that the key buttons  510  may be pressed down more smoothly. In case of an LGP keypad apparatus using two light guide plates, since its thickness is increased when compared to the single light guide plate arrangement, the notches may provide softer key press feeling, i.e., improved click feeling. 
       FIG. 6B  is a plan view illustrating a top surface of a light guide plate with notches  610  formed therein according to the third exemplary embodiment of the present invention. 
     Although the examples above include key buttons are molded on the light guide plate in one body by UV molding in exemplary embodiments of the present invention, various molding methods other than UV molding are available. While molding is clearly preferred, it is possible and within the spirit and scope of the claimed invention that the key buttons could be bonded or attached in other ways to the light guide plate(s). 
     While the invention has been shown and described with reference to a certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.