Abstract:
A keypad assembly for a portable terminal according to the present invention includes: a keypad having pad portions with a plurality of key buttons placed thereon, light guide plates disposed between the pad portions, and reflection units disposed on the light guide plates to direct the light toward the key buttons; light sources for providing the light toward the reflection units; a plurality of spacers disposed below the light guide plates for separating the light guide plate from a substrate and for supporting the light guide plates; switches disposed below the pad portions under the key buttons for applying signal to the substrate; and a casing for enclosing the keypad.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims priority to an application entitled “Keypad Assembly for Mobile Phone,” filed with the Korean Intellectual Property Office on Jun. 28, 2005 and assigned Serial No. 2005-56494, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a portable terminal such as cellular phones, Personal Digital Assistants (PDA), Personal Communication System (PCS), game phones, camera phones, Digital Multimedia Broadcasting (DMB) phones, and more particularly to a portable terminal having a lighting function to enable a user to dial another user at night.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, “a portable terminal” implies an electronic device that a user can carry for communication with another user wirelessly. In consideration of portability, the design of such a portable terminal focuses not only toward a compactness, slimness, and lightness, but also toward providing multimedia capabilities to allow the user to enjoy a wider variety of functions. Thus, future portable terminals will be used in a multimedia environment to provide the Internet access and its related functions globally.  
         [0006]     Currently, a conventional portable communication terminal allows a voice communication as well as a high-speed data communication. Further, as consumer&#39;s demands have increased, various services have been provided using a wireless communication technology for transmitting and receiving data at a high speed. Most portable terminals are now equipped with an embedded or an external camera lens to transmit image signals and the like.  
         [0007]     The portable terminal typically includes data input and output units, data transmitting and receiving units, an antenna unit and the like. The data input unit includes a keypad assembly or a touch screen to input data. The keypad assembly is constructed with key buttons, silicon rubber, dome switches and the like. A well-known liquid crystal display unit is generally used as data output unit.  
         [0008]     Moreover, the portable terminal has a lighting device for lighting the keypad and may include a plurality of light emitting diodes arranged on a printed substrate, or an inorganic electro luminescent body inserted in an elastic pad disposed on the printed substrate.  FIG. 1  shows such a conventional keypad assembly  100 , which includes a switch substrate  120 , a plurality of light emitting diode  122 , and a keypad  110 .  
         [0009]     The keypad  110  is made from an elastic material, i.e., silicon and other material made from the combination of silicone and a poly urethane film. The keypad  110  includes a plate-shaped elastic layer  111 , a plurality of key buttons  112  having characters printed thereon and mounted on the elastic layer  111 , and a plurality of protuberances  111   a  formed at a lower surface of the key pad  110 . The key buttons  112  and the protuberances  111   a  are vertically aligned to each other.  
         [0010]     The switch substrate  120  includes a plate-shaped printed substrate  120   a  and a plurality of switches  121  facing the protuberance  111   a  of the keypad  110 . Each of the switches  121  is provided with a conductive contact and a metal dome entirely covering the conductive contact. The light emitting diodes  122  are disposed at predetermined positions on the printed substrate  120   a.    
         [0011]     However, in order to guarantee the operation of the switch  121 , the light emitting diodes  122  are disposed on the printed substrate  120   a,  each of which is not vertically aligned to the corresponding key button  112 . That is, the light emitting diodes  122  are disposed between the switches  121 . As a result, the light emitted toward the respective key button  112  from the light emitting diode  122  diverges in all directions, so that the illumination of the key buttons  112  becomes non-uniform and dark. That is, as the light emitted from the light emitting diode is shed through the side of each key button, the number or characters printed on the respective key button cannot be displayed with a uniform brightness.  
         [0012]     Therefore, in order to overcome the above-mentioned problems, it is necessary to use a larger number of light emitting diodes for lighting the key buttons, which increases the cost for assembling the light emitting diodes as well as electric power consumption of the light emitting diodes, thereby causing the manufacture of the keypad assembly to be economically inefficient.  
       SUMMARY OF THE INVENTION  
       [0013]     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art and provides additional advantages, by providing a keypad assembly for a portable terminal, which can be illuminated with a uniform brightness for the entire keypad.  
         [0014]     One aspect of the present invention is to provide a keypad assembly for a portable terminal, which has a local light source for key buttons disposed at the edge of the keypad, thereby providing a uniform surface light source for the entire keypad.  
         [0015]     Another aspect of the present invention is to provide a keypad assembly for a portable terminal, which has a light source consuming minimum electric power.  
         [0016]     Still another aspect of the present invention is to provide a keypad assembly for a portable terminal, which has a top view-type light source instead of the side view-type light source, so that it can provide a uniform brightness.  
         [0017]     In one embodiment, there is provided a keypad assembly for a portable terminal includes: a keypad including pad portions having key buttons placed thereon, light guide plates disposed between the pad portions, and reflection units disposed on the light guide plates to direct the light toward the key buttons; light sources for providing the light toward the reflection units; a plurality of spacers disposed below the light guide plates for separating the light guide plate from a substrate and supporting the light guide plates; switches disposed below the pad portions under the key buttons for applying signal to the substrate; and a casing for enclosing the keypad. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The above features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0019]      FIG. 1  is a sectional view of a conventional keypad assembly of a portable terminal;  
         [0020]      FIG. 2  is a perspective of a portable terminal having a keypad assembly according to an embodiment of the present invention;  
         [0021]      FIG. 3  is a sectional view of a keypad assembly for a portable terminal according to an embodiment of the present invention;  
         [0022]      FIG. 4  is a sectional view of a keypad assembly for a portable terminal according to an embodiment of the present invention, in which a pad portion has the same thickness as that of a light guide plate;  
         [0023]      FIG. 5  is a sectional view of a keypad assembly for a portable terminal according to an embodiment of the present invention, in which the light guide plate has a tapered portion;  
         [0024]      FIG. 6  is a sectional view of a reflection unit in a keypad assembly for a portable terminal according to another embodiment of the present invention;  
         [0025]      FIG. 7  is a sectional view of a keypad assembly for a portable terminal according to another embodiment of the present invention, in which a pad portion has the same thickness as that of a light guide plate; and  
         [0026]      FIG. 8  is a sectional view of a keypad assembly, which is enclosed by a casing, according to the embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0027]     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. For the purposes of clarity and simplicity, a detailed description of known functions and configurations incorporated herein is omitted to avoid making the subject matter of the present invention unclear.  
         [0028]      FIG. 2  shows a portable terminal  300  having a keypad assembly according to the present invention. The portable terminal  300  includes a speaker  310 , a display unit  320 , a keypad assembly having a plurality of key buttons  330 , and a microphone  340 , which are arranged on an upper surface of the portable terminal  300 . The key buttons  330  are protruding out of a casing  301  so that the top of each key button  330  is exposed. Therefore, a user can touch and push the top of the key button  330  to input data or activate the phone.  
         [0029]     Referring to  FIG. 3 , the structure of a keypad assembly  200  according to the present invention will be described. As shown in  FIG. 3 , the keypad assembly  200  according to the present invention includes a keypad, a light source  230 , spacers  225 , switch portions  240 , and a casing  250  (see  FIG. 8 ).  
         [0030]     More specifically, the keypad includes pad portions  210  provided with a plurality of key buttons K, a light guide plate  220  disposed between and in parallel with the pad portions  210 , and a reflection unit  260  which directs light transmitted from the light source  230  toward each key button K. The pad portions  210  are made from materials having a high elasticity. The light guide plate  220  is preferably made of materials having a good transmittance in the visible ray region. The light guide plate  220  is made of the same material as that of the pad portion  210 , and preferably is made of elastic silicon materials so that the light guide plate  220  can play the role as a part of the pad portion  210 .  
         [0031]     The reflection units  260  are disposed on an upper surface of the light guide plate  220 , specifically, on portions corresponding to the key buttons arranged on the substrate. The positions of the reflection units  260  are determined based on the relative positions of the arranged key buttons K. This configuration causes the reflection units  260  to reflect the light to the pad portion  210  so as to give an entirely uniform brightness to the keypad. That is, the positions of the reflection units  260  are determined depending on the arrangement of the key buttons K deployed in the portable terminal. However, it is possible to locate the reflection units  260  at other positions that are not dependent on the arrangement of the key buttons K. For example, it is possible to locate the reflection units  260  at positions at which the reflection units  260  can direct a sufficient light toward the key buttons at the edge portions, which are relatively dark.  
         [0032]     The respective reflection unit  260  may include a reflection mirror or a unit having a reflective coating layer with a high reflectance. The unit having the reflective coating layer may include a metallic material and a reflective coating layer coated on the metallic material. It is unnecessary to limit the reflection unit  260  to the reflective coating layer made of the metallic material, thus the reflection unit  260  may be made by preparing an inclined structure on the light guide plate and then coating a suitable material on the incline structure. The suitable materials include materials having a higher refractive index than the light guide plate. Each of the reflection units  260  has a triangular shape in section, which includes at least one inclined surface. That is,  FIG. 2  shows a cross section of the reflection units  260 , but the reflection unit is a conical shape. Accordingly, a light emitted from the light source  230  is transmitted by the conical reflection units in all directions. The reflection unit  260  has a reflective coating layer formed on the inclined surface facing the light source  230 .  
         [0033]     The light source  230  is disposed vertically below the reflection unit  260  and between the spacers  225  or between the key buttons K to emit the light toward the reflection unit  260  so as to give an entirely uniform brightness to the keypad. Of course, the light source  230  is locally disposed in a dark region of the keypad. It is preferred that a light emitting diode is used as the light source  230  in consideration of the lifetime and the environment. The dome switches  240  are metal dome switches, which apply electric signals to a processor as the user presses a key.  
         [0034]     The pad portion  210  having the key buttons K further includes protuberances  212  to activate the dome switches  240 . Each of the protuberances  212  includes a reflection pattern  214  to locally guide the light reflected by the reflection unit  260  toward each of the key buttons K. The region of the reflection pattern corresponds to the width of the respective key button K in order to transmit the reflected light to the key button K as much as possible.  
         [0035]     The spacers  225  is disposed below the light guide plate  220  in order to support the light guide plate  220  spaced apart from the substrate B. The spacers  225  are made of the same material as that of the light guide plate  220 . More specially, it is economical to integrate the spacers  225  with the light guide plate  220  using silicon material. However, some structure does not include the spacer  225  and can be separated from the guide plate  220 . The spacers  225  supporting the light guide plate  220  may be used to adjust the height of the light guide plate  220  with respect to the pad portions  210 . Thus, the size of the spacers may be changed according to its purpose. Further, the spacers  225  may be disposed near the dome switches  240 , for example, below the pad portion  210  as well as the light guide plate  220 .  
         [0036]     The reflection unit  260  as shown in FIGS.  3  to  5  has an isosceles triangular shape in a cross section, particularly a conical shape, which is comprised of a reflective mirror that a reflective layer is disposed on its surface. The FIGS.  3  to  5  show a cross section of the reflection unit with the first and second inclined surfaces  261  and  262 .  
         [0037]     The first and second inclined surfaces  261  and  262  are symmetric to each other and serve to direct the light from the light source  230  toward the key button K. However, it should be noted that the shape of the reflection unit  260  may have different shapes other than the triangular shape, specifically a conical shape. The reflection unit  260  may be formed in convex or concave shape having a certain curvature. Here, it is important that the reflection unit  260  must have a surface shape capable of preventing the light from the light source  230  from leaking out of the keypad and transmitting the light to the key button K as much as possible.  
         [0038]     The light guide plate  220 - 1  shown in  FIG. 4  has the same thickness as the pad portion  210  in the portion in contact with the pad portion  210 .  
         [0039]     Meanwhile, it should be noted that the light guide plate does not have to have the same thickness as the pad portion. Preferably, the light guide plate  220  is thicker than the pad portion  210  in order to prevent the light guided from the light source through the light guide plate  220  from leaking and transmit it to the pad portion  210  as much as possible.  
         [0040]      FIG. 5  shows a light guide plate  220 - 2  having a tapered portion  224 . In the case in which the light from the light source  230  is directed toward the pad portion  210  by way of the reflection unit  260 , it is possible to transmit a large quantity of light when the light guide plate  220  is thicker than the pad portion  210  as described above. However, in this case, a discontinuity occurs at the connecting point between the pad portion  210  and the light guide plate  220 , so it is necessary to prevent the loss of the light in advance. For this reason, the tapered portion  224  is provided to the light guide plate  220 - 2 . That is, the tapered portion  224  can prevent the loss of the light in the discontinuity region due to a difference in the thickness between the light guide plate  220  and the pad portion  210 .  
         [0041]     Preferably, the above-mentioned light guide plate  220  may be formed integrally with the pad portion  210  and may be made of materials having low hardness, high elastic coefficient, high elastic recovery force, and high permeability, for example, silicon material or polyurethane material in order to play a role as the pad portion  210 .  
         [0042]     In the keypad assembly having a plurality of key buttons K employed in the portable terminal, as shown in  FIG. 6 , the key buttons K- 1  placed at the outer edge of the keypad may possibly darker during operation due to distance. Thus, it is desirable for the reflection unit  260 - 1  to reflect the light in only one direction for such key buttons. To address this problem, the reflection unit  260 - 1  having a right triangular shape in a cross section, specifically a semi-conical shape, with a single inclined surface  263  may be provided according to anther embodiment of the present invention. The  FIG. 6  shows a cross section of the reflection unit having the right triangular shape. The single inclined surface  263  directs the light from the light source  230  toward the key buttons K- 1 . It should be noted that other functions, such as pad portion, switches, light guide plate, and light source, shown in  FIG. 6  is omitted to avoid redundancy as they are already described with reference to  FIG. 3 .  
         [0043]     The reflection unit  260 - 1  is disposed on the light guide plate  220 - 2 , and more specifically is aligned vertically above the light source  230 . Although  FIG. 6  shows the light guide plate  220  and the pad portion  210  having different thicknesses from each other, it is possible that the light guide plate has the same thickness as the pad portion at the portion at which the light guide plate is in contact with the pad portion.  FIG. 7  shows the light guide plate  220  and the pad portion  210  having the same thickness. In the case in which the light guide plate has a different thickness from the pad portion, the tapered portion as shown in  FIG. 5  can be adopted for the light guide plate to minimize the light loss.  
         [0044]     Referring to  FIG. 8 , a casing  250  encloses and separates the keypad assembly from its outer environment. The casing  250  includes a protuberance  252  normally extending downward from an inner surface of the casing  250 . The casing  250  may be integrally formed with the protuberance  252  by injection molding while the reflection unit  260  is attached to the protuberance  252  of the casing  250 . Otherwise, the protuberance  252  and the reflection unit  260  may be independently made and then assembled in an assembling process.  
         [0045]     Referring back to  FIG. 3 , an operation of the lighting unit provided to the keypad assembly according to the teachings of the present invention will be described hereinafter.  
         [0046]     As shown in  FIG. 3 , the light from the light source  230  is mostly transmitted in a vertical direction of the light guide plate  220 - 2 , while hardly transmitted in a horizontal direction of the light guide plate  220 - 2 . Then, the light transmitted from the light source  230  is directed by means of the reflection unit  260  to the light guide plate  220 - 2 , which in turn horizontally transmits the light toward the key buttons K. The light introduced to the light guide plate  220 - 2  in this way is subjected to a total reflection at the boundary between the light guide plate  220 - 2  and the reflection unit  260 , so that almost all of the light is transmitted through the light guide plate  220 - 2 . When the light reflected by the reflection unit  260  reaches the reflection pattern  214 , the transmission angle of the light exceeds the critical angle, so the light is refracted upward and emitted out of the pad portion  210 . Here, the reflection patterns  214  are coarsely formed at a site adjacent to the light source  230 , while closely formed at a site far from the light source  230 . Thereby, it is possible to ensure the entirely uniform brightness to the keypad.  
         [0047]     As described above, the present invention can provide a keypad for a portable terminal with a uniform illumination. In addition, the present invention is provided with the reflection pattern to locally emit light to the key button. The light guide plate has the same thickness as the pad portion in the connecting region of the pad portion and the light guide plate, so as to minimize the light loss. As a result, the present invention allows the keypad assembly to have a small number of light emitting diodes (LEDs), resulting in a decrease in the numbers of the LED and in the reduction of manufacturing cost. Furthermore, the present invention can be applied to the region of the key buttons which are arranged at a side or at the edge of the pad portion having a relative darker area during operation, so as to provide a uniform illumination through out the key button regions mainly.  
         [0048]     While the invention has been shown and described with reference to certain preferred 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.