Patent Publication Number: US-2011051455-A1

Title: Illumination panel

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-203043 filed on Sep. 2, 2009, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to an illumination panel. 
     BACKGROUND 
     With the technological advancement in light-emitting diodes (referred to as “LEDs” hereinafter), many types of electronic apparatuses are provided with LEDs as radiation sections that perform illuminated display. For example, in a portable terminal apparatus, such as a portable telephone, a part of a housing thereof is sometimes provided with a radiation section that displays various kinds of light colors or patterns for informing the user of an incoming call or for improving the design of the apparatus. The radiation section is mainly formed of an illumination panel on a surface of the housing. Light emitted from a light source, such as an LED, arranged inside the housing is projected onto the illumination panel so as to achieve an illuminated display of various kinds of light colors or patterns. 
     If the radiation section has a relatively small area, a single LED is often used as the light source. However, for improving visibility or design, it is desirable to give the radiation section a relatively large area. When the radiation section has a relatively large area, the light emitted from the single LED cannot reach the entire radiation section. Therefore, when the radiation section extends over a wide area, a structural design, such as providing a plurality of LEDs as light sources, is required. 
     A configuration example of a radiation section of a portable terminal apparatus is shown in  FIG. 10 .  FIG. 10  is a cross-sectional view of the radiation section and its surrounding area in the portable terminal apparatus. As shown in  FIG. 10 , four LEDs  10   a  to  10   d  are arranged on a substrate, and light emitted from the LEDs  10   a  to  10   d  is displayed on an illumination panel  30 . Although the illumination panel  30  is held by a nontransparent holding member  20 , the holding member  20  has window holes  20   a  to  20   d  formed at positions corresponding to the LEDs  10   a  to  10   d . Therefore, the light emitted from the LEDs  10   a  to  10   d  passes through the window holes  20   a  to  20   d  so as to be projected onto the illumination panel  30 . As a result, an illuminated display can be achieved over a relatively wide area of the illumination panel  30 . 
     Japanese Laid-open Patent Publication No. 2001-324937 is an example of related art. 
     SUMMARY 
     However, when performing illuminated display over a wide area, there is a problem in that the number of components, such as LEDs, is increased, resulting in a complicated assembly process and an increased cost. For example, in the above-described example, four LEDs are used as light sources, meaning that the number of components is increased as compared with when a single LED is used. This results in a complicated assembly process since each of the LEDs needs to be mounted onto a substrate, as well as an increased cost for manufacturing the portable terminal apparatus. 
     Furthermore, when the portable terminal apparatus has waterproof performance, for example, an increased number of components can sometimes lead to deterioration of the waterproof performance. Specifically, an increased number of components means increased joint sections between components, which can lead to a higher possibility of formation of gaps between the components due to an error at the time of manufacture. Therefore, there is a higher risk of water penetration in the portable terminal apparatus, leading to deterioration of the waterproof performance. At the same time, the formation of gaps between the components due to an increased number of components can also result in reduced strength of the portable terminal apparatus. 
     According to an aspect of the embodiment, an illumination panel includes: a light-collecting section for collecting light emitted from a light source; an optical guide for optically guiding the light collected by the light-collecting section in a direction away from the light source; and a radiation section for radiating the light optically guided by the optical guide; wherein the optical guide has a plurality of grooves for reflecting the light optically guided by the optical guide to the radiation section. 
     The object and advantages of the embodiment will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating the exterior appearance of a front-face side of a portable terminal apparatus according to an embodiment; 
         FIG. 2  is a perspective view illustrating the exterior appearance of a rear-face side of the portable terminal apparatus according to the embodiment; 
         FIG. 3  is an exploded perspective view illustrating the configuration of a movable housing according to the embodiment; 
         FIG. 4  is a plan view illustrating the configuration of the reverse side of a rear casing according to the embodiment; 
         FIG. 5  is an enlarged view illustrating a part of the rear casing according to the embodiment; 
         FIGS. 6A and 6B  are diagrams for explaining an optical guide through which light emitted from an LED travels; 
         FIG. 7  is a perspective view illustrating the movable housing of the portable terminal apparatus according to the embodiment; 
         FIG. 8  is a schematic cross-sectional view taken along line VIII-VIII in  FIG. 7 ; 
         FIG. 9  is a schematic cross-sectional view taken along line IX-IX in  FIG. 7 ; and 
         FIG. 10  is a cross-sectional view illustrating a configuration example of a radiation section. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An illumination panel and a light-emitting device according to an embodiment disclosed by the present application will be described below with reference to the drawings. The following embodiment will be described with reference to a portable terminal apparatus equipped with the light-emitting device as an example. It should be noted that the present invention is not to be limited by this embodiment. 
       FIG. 1  is a perspective view illustrating the exterior appearance of the portable terminal apparatus according to this embodiment. As shown in  FIG. 1 , the portable terminal apparatus according to this embodiment is a folding-type portable telephone having a movable housing  100  and a stationary housing  200 . The movable housing  100  is rotatably attached to the stationary housing  200 . The movable housing  100  has a display section  101  and an opening  102 . The stationary housing  200  has an operating key section  201  and an opening  202 . The surfaces on which the display section  101  and the operating key section  201  shown in  FIG. 1  are provided are surfaces with which a user comes into contact when making a telephone call, and these surfaces will each be referred to as “front face” hereinafter. On the other hand, the surfaces opposite the surfaces provided with the display section  101  and the operating key section  201  will each be referred to as “rear face” hereinafter. 
     The display section  101  includes, for example, a liquid-crystal panel. The display section  101  displays various kinds of information. In detail, the display section  101  displays, for example, a telephone number input by operating the operating key section  201 . 
     The opening  102  is a through-hole that connects to a receiver provided inside the movable housing  100 . Specifically, a receiver that produces the sound of received audio is provided inside the movable housing  100 . The sound produced by the receiver can be heard through the opening  102 . 
     The operating key section  201  accepts input operation performed by the user. In detail, the operating key section  201  accepts, for example, input operation of a telephone number that the user may desire to call, or accepts input operation for commencing or ending a telephone call. 
     The opening  202  is a through-hole that connects to a microphone provided inside the stationary housing  200  at the front-face side thereof. Verbal sound released by the user enters the interior of the stationary housing  200  through the opening  202  and is picked up by the microphone provided at the front-face side. The portable terminal apparatus according to this embodiment has a double microphone structure and is equipped with two microphones at the front-face side and the rear-face side, respectively. With such a double microphone structure, ambient noise can be reduced during, for example, a telephone call. 
       FIG. 2  is a perspective view illustrating the exterior appearance of the rear-face side of the portable terminal apparatus according to this embodiment. As shown in  FIG. 2 , the rear face of the movable housing  100  is provided with a radiation section  103 . On the other hand, a camera section  203 , a fingerprint sensor section  204 , and an opening  205  are arranged on the rear face of the stationary housing  200 . 
     As will be described later, the radiation section  103  is formed in a transparent rear casing that partly constitutes the movable housing  100 . The radiation section  103  is illuminated with light emitted from an LED provided inside the movable housing  100 . For example, when receiving an incoming call, the radiation section  103  displays a predetermined light color or a predetermined pattern for informing the user of the incoming call. 
     The camera section  203  includes a camera for image acquisition. The camera section  203  acquires an image in response to user&#39;s operation performed via the operating key section  201 . The fingerprint sensor section  204  includes a fingerprint sensor for user authentication. The fingerprint sensor section  204  identifies the user by reading the user&#39;s fingerprint and determines whether or not to permit the use of the portable terminal apparatus. 
     The opening  205  is a through-hole that connects to the microphone provided inside the stationary housing  200  at the rear-face side thereof. Verbal sound released by the user enters the interior of the stationary housing  200  not only through the aforementioned opening  202  but also through the opening  205 , and is picked up by the microphone provided at the rear-face side. 
       FIG. 3  is an exploded perspective view illustrating the configuration of the movable housing  100 . As shown in  FIG. 3 , a surface of the movable housing  100  is constituted of a front casing  110 , a rear casing  120 , a first exterior panel  130 , and a second exterior panel  140 . 
     The front casing  110  secures a substrate  111  in position. An LED  112  is arranged in the substrate  111 . The LED  112  is a light source for emitting light. The display section  101  and the opening  102  shown in  FIG. 1  are formed on the front-face side (not shown) of the front casing  110 . 
     The rear casing  120  functions as an illumination panel made of a transparent material. The rear casing  120  is joined to the front casing  110  such that the substrate  111  equipped with the LED  112  is housed between the rear casing  120  and the front casing  110 . When joined to the front casing  110 , the rear casing  120  is provided with the radiation section  103  that extends longitudinally from a position near the LED  112 . The radiation section  103  extends in the longitudinal direction of the rear casing  120 . The substrate  111  has a single LED  112  arranged therein. As will be described later, in this embodiment, an optical guide that allows light emitted from the LED  112  to efficiently reach the entire radiation section  103  is formed on the reverse side of the rear casing  120 . 
     The first exterior panel  130  and the second exterior panel  140  are resinous panels with different colors. The exterior panels  130  and  140  are fixed to the rear face of the rear casing  120 . In this embodiment, the exterior panels  130  and  140  are attached to the rear casing  120  such that the radiation section  103  is exposed through a gap between an edge  131  of the first exterior panel  130  and an edge  141  of the second exterior panel  140 . 
       FIG. 4  is a plan view illustrating the configuration of the reverse side of the rear casing  120 . As shown in  FIG. 4 , the reverse side of the rear casing  120  is provided with an optical guide  121  formed along the radiation section  103 , and a light-collecting section  122  is provided at a position of the optical guide  121  that corresponds to the LED  112 . The optical guide  121  has a plurality of reflective grooves  123  extending slantwise relative to the traveling direction of light entering the optical guide  121  from the light-collecting section  122 . 
     The optical guide  121  extends along the radiation section  103  in a direction away from the LED  112 . The light from the LED  112  enters the optical guide  121  via the light-collecting section  122  formed at one end of the optical guide  121  so as to be projected onto the entire radiation section  103 . The optical guide  121  optically guides the light from the LED  112  in the extending direction of the radiation section  103 . The reflective grooves  123  in the optical guide  121  reflect a portion of the light toward the radiation section  103 . With the reflected light, an illuminated display is achieved in the radiation section  103 . The optical guide  121  has a shape that is wide near the light-collecting section  122  and tapers with increasing distance from the light-collecting section  122  arranged at the position corresponding to the LED  112 . Thus, the light entering the optical guide  121  from the light-collecting section  122  becomes concentrated in a narrower region as the light travels toward a terminal end of the optical guide  121 , thereby compensating for a reduction of light intensity caused by attenuation. 
     The light-collecting section  122  protrudes from the reverse side of the rear casing  120  so as to cover the light emission range of the LED  112  when the front casing  110  and the rear casing  120  are joined to each other. The protruding portion of the light-collecting section  122  collects the light from the LED  112  and makes the light enter the optical guide  121 . Because the light-collecting section  122  covers the light emission range of the LED  112 , the light emitted from the LED  112  serving as a light source is prevented from being scattered outward from the optical guide  121 , thereby preventing a loss of light. 
     The reflective grooves  123  formed in the optical guide  121  are substantially parallel to each other. The reflective grooves  123  reflect the light entering the optical guide  121  from the light-collecting section  122  and project the light onto the radiation section  103 . The reflective grooves  123  are depressions formed in the reverse side of the rear casing  120 . A portion of the light traveling through the optical guide  121  is reflected toward the radiation section  103  by being incident on the reflective grooves  123 . Because the reflective grooves  123  are formed substantially parallel to each other, the reflected light traveling toward the radiation section  103  can be made uniform. Furthermore, the reflective grooves  123  extend slantwise and away from the light-collecting section  122  as they approach the radiation section  103  so that the light reflected by the reflective grooves  123  is made to travel toward the radiation section  103 . An angle formed between the traveling direction of the light optically guided by the optical guide  121  and the extending direction of the reflective grooves  123  is equal to an angle formed between the traveling direction of the light reflected by the reflective grooves  123  and the extending direction of the reflective grooves  123 . Consequently, the light traveling through the optical guide  121  is reflected by the reflective grooves  123  by a reflection angle that is equal to an incidence angle of the light, before being projected onto the radiation section  103 . 
     The reflective grooves  123  can be deeper with increasing distance from the light-collecting section  122 . The deeper the reflective groove, the larger the amount of the reflection of light is. The further from the light-collecting section  122 , the larger the amount of attenuation of light is. The amount of the light reflected to the radiation section  103  can be adjusted by changing the depth of the reflective groove in accordance with the distance from the light-collecting section  122 . 
     Next, the configuration of the light-collecting section  122  will be described in more detail with reference to  FIG. 5  and  FIGS. 6A and 6B .  FIG. 5  is an enlarged view illustrating a part of the rear casing  120 . As shown in  FIG. 5 , the light-collecting section  122  includes a light-collecting surface  122   a  that protrudes from the reverse side of the rear casing  120  and that is formed to cover the light emission range of the LED  112 . Furthermore, in plan view, the light-collecting section  122  has a trapezoidal shape that becomes wider with increasing distance from the light-collecting surface  122   a . The light-collecting section  122  allows the light emitted from the LED  112  to enter the optical guide  121  via the light-collecting  surface  122   a.    
       FIGS. 6A and 6B  are diagrams for explaining an optical guide through which light emitted from an LED travels.  FIG. 6A  illustrates a configuration for introducing the light emitted from the LED directly to the radiation section. As shown in  FIG. 6A , in the configuration for introducing the light emitted from the LED directly to the radiation section, the light emitted from the LED is scattered to regions  301  other than the radiation section, resulting in a loss of light projected onto the radiation section. Although a light-emitting surface of the LED emits light to a certain light emission range, the light traveling toward the regions  301  cannot be utilized for illuminated display especially when the radiation section has a small width, resulting in a loss of light. 
       FIG. 6B  illustrates a configuration for introducing the light emitted from the LED  112  to the light-collecting section  122  in this embodiment. As shown in  FIG. 6B , the light-collecting section  122  has the light-collecting surface  122   a  that covers the light emission range of the LED  112 . The light-collecting surface  122   a  collects the entire light emitted from the LED  112  without scattering the light. The light collected by the light-collecting surface  122   a  is projected onto the radiation section  103  via the reflective grooves  123 . Consequently, the light emitted from the LED  112  serving as a light source is efficiently projected onto the radiation section  103 , thereby preventing a loss of light. 
     Next, a cross-sectional structure of the radiation section  103  and its surrounding area in the portable terminal apparatus according to this embodiment will be described with reference to  FIG. 7  to  FIG. 9 .  FIG. 7  is a perspective view illustrating the movable housing  100  according to this embodiment. As shown in  FIG. 7 , the rear face of the movable housing  100  is mainly constituted of the first exterior panel  130  and the second exterior panel  140 . The radiation section  103  provided in the rear casing  120  is exposed through the gap between the first exterior panel  130  and the second exterior panel  140 . 
       FIG. 8  is a schematic cross-sectional view taken along line VIII-VIII in  FIG. 7 .  FIG. 8  illustrates the cross section of the movable housing  100  taken along line VIII-VIII through the radiation section  103 . As shown in  FIG. 8 , in the cross section taken along line VIII-VIII, the front casing  110  as well as the radiation section  103  and the first exterior panel  130  of the rear casing  120  constitute an outer shell of the movable housing  100 . The movable housing  100  has the substrate  111  therein. Although not shown in  FIG. 8 , a reflective film that reflects light may be attached to the surface of the rear casing  120  that faces the substrate  111  so as to prevent a leakage of light from areas other than the radiation section  103 . 
     In this embodiment, the LED  112  is not arranged at a position on the substrate  111  that faces the radiation section  103 . The radiation section  103  displays the light emitted from the LED  112  (not shown in  FIG. 8 ) and projected from the optical guide  121 . The illuminated display in the radiation section  103  can be changed to various forms in accordance with the color and the pattern of the light emitted from the LED  112 . 
       FIG. 9  is a schematic cross-sectional view taken along line IX-IX in  FIG. 7 .  FIG. 9  illustrates the cross section of the movable housing  100  taken along line IX-IX through the optical guide  121 . As shown in  FIG. 9 , in the cross section taken along line IX-IX, the front casing  110  as well as the first exterior panel  130  and the second exterior panel  140  constitute the outer shell of the movable housing  100 . The substrate  111  arranged inside the movable housing  100  has the LED  112 . 
     The rear casing  120  is attached to the reverse side of the first exterior panel  130  and the second exterior panel  140 . The rear casing  120  forms the optical guide  121 . The light-collecting section  122  that collects the light emitted from the LED  112  is formed adjacent to the LED  112 . The optical guide  121  that optically guides the collected light toward the radiation section  103  extends from the light-collecting section  122 . In the light-collecting section  122 , the light-collecting surface  122   a  protrudes from the reverse side of the rear casing  120  and faces the LED  112 . The light-collecting surface  122   a  collects the light emitted from the LED  112  without scattering the light. 
     The optical guide  121  is provided with the reflective grooves  123  formed as depressions in the reverse side of the rear casing  120 . The reflective grooves  123  extend slantwise relative to the course of light traveling through the optical guide  121 . By reflecting a portion of the light traveling through the optical guide  121 , the reflective grooves  123  project the light toward the radiation section  103  in the cross section taken along line VIII-VIII. As mentioned above, a reflective film may be attached to the surface of the rear casing  120  that faces the substrate  111 . Moreover, regarding the surface of the rear casing  120  that is in contact with the first exterior panel  130  and the second exterior panel  140 , a reflective film may similarly be attached to an area of the surface other than the radiation section  103 . In this manner, since light traveling outward from the optical guide  121  can be returned to the interior of the optical guide  121  by the reflective films, a light leakage can be prevented, thereby minimizing a loss of light. 
     Accordingly, in this embodiment, the light-collecting section  122  that collects the light from the LED  112 , the optical guide  121  that optically guides the collected light, and the radiation section  103  that displays the optically guided light are all formed in the rear casing  120 . Therefore, an illuminated display can be achieved by providing a layer for the rear casing  120  in the movable housing  100 , thus preventing an increase of the number of components required for the illuminated display. As a result, a risk of, for example, water penetration between components is reduced, thereby preventing deterioration of waterproof performance of the portable terminal apparatus as well as increasing the strength thereof. Furthermore, since the light emitted from the LED  112  is optically guided by the optical guide  121  and is projected onto the radiation section  103  via the reflective grooves  123 , light from a single light source can be displayed over a relatively wide area. Therefore, the number of LEDs can be minimized, thereby preventing a complicated assembly process and an increased cost of the portable terminal apparatus. 
     According to this embodiment, the rear casing made of a transparent material is configured to collect the light from the light source, optically guide the collected light in the direction in which the radiation section extends, and reflect a portion of the light by using the reflective grooves extending slantwise relative to the traveling direction of the light, thereby achieving an illuminated display. Therefore, the light emitted from a single light source can be efficiently displayed over a wide area, and the number of components used for the illuminated display is not increased. In other words, a wide-area illuminated display can be achieved while an increase of the number of components is prevented. 
     Although the above-described embodiment is directed to a description of an illuminated display in a movable housing of a folding-type portable telephone, the above-described advantages can be achieved with respect to an illuminated display in various electronic apparatuses by providing an illumination panel having a similar configuration to that of the aforementioned rear casing. Specifically, by providing an illumination panel having a similar configuration to that of the aforementioned rear casing in, for example, a light-emitting device provided in a housing of a notebook-size personal computer, an increase of the number of components in the notebook-size personal computer can be prevented and the strength of the housing can be increased. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.