Abstract:
A surface light source device includes a plurality of light guide plates spliced together side by side and forming a plurality of jointing interfaces. A plurality of LEDs is attached to a side face of each of the light guide plates. The LEDs are arranged in a linear LED array along the side face of each of the light guide plates. At most one linear LED array is arranged at the jointing interface between each two neighboring light guide plates.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to surface light source devices, and particularly to a surface light source device with light emitting diodes (LEDs). 
     2. Description of related art 
     With features of long-term reliability, small size, environment friendliness and low power consumption, presently, LEDs are widely used as backlight source of liquid crystal display (LCD) devices, automobiles lights, and common luminous sources and so on. 
     LEDs are generally used in a surface light source device as a backlight source in an LCD device. The surface light source device comprises a light guide plate and a plurality of LEDs attached to the light guide plate. According to positions where the LEDs are mounted on the light guide plate, the surface light source devices are generally categorized to edge lighting mode and bottom lighting mode. In the edge lighting mode, the LEDs are attached to an edge of the light guide plate. In the bottom lighting mode, the LEDs are attached to a bottom of the light guide plate. With the development of electronic industry, large area light source with large light guide plate is needed. However, the surface light source device with the edge lighting mode is not suitable for large light guide plate to provide sufficient light. The surface light source device with the bottom lighting mode suit for large light guide plate to provide sufficient light, but in this mode, more LEDs are needed to emit light, which inevitably increase cost thereof. 
     What is needed, therefore, is a surface light source device with LEDs having a large light area and a low cost. 
     SUMMARY OF THE INVENTION 
     A surface light source device in accordance with a first embodiment of the present invention comprises a plurality of light guide plates spliced together side by side and forming a plurality of jointing interfaces. A plurality of LEDs is attached to a side face of each of the light guide plates. The LEDs are arranged in a linear LED array along the side face of each of the light guide plates. At most one linear LED array is arranged at the jointing interface between each two neighboring light guide plates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present surface light source device with LEDs can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present performance testing apparatus for heat pipes. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a plan view of a surface light source device in accordance with a first embodiment of the present invention. 
         FIG. 2  shows a light source unit of the surface light source device of  FIG. 1 . 
         FIG. 3  is a plan view of a light guide plate of the light source unit of  FIG. 2 . 
         FIG. 4  is a section view of an alternative light guide plate taking along a line III-III of  FIG. 2 . 
         FIG. 5  is a section view of an additional light guide plate taking along the line III-III of  FIG. 2 . 
         FIG. 6  is a section view of the light source unit taking along the line III-III of  FIG. 2 . 
         FIG. 7  is a plan view of a surface light source device in accordance with a second embodiment of the present invention. 
         FIG. 8  is a plan view of a surface light source device in accordance with a third embodiment of the present invention. 
         FIG. 9  is a plan view of a surface light source device in accordance with a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-3  and  6 , a surface light source device  100  in accordance with a first embodiment is shown. The device  100  comprises four light source units  120  splicing together. 
     Each light source unit comprises a light guide plate  122  and a plurality of LEDs  124  attached to the light guide plate  122 . 
     The light guide plate  122  comprises a light emitting face  1222 , a bottom face  1224  opposite to the light emitting face  1222 , and a side face  1223  interconnecting the light emitting face  1222  and the bottom face  1224 . In  FIG. 1 , the light guide plate  122  is a rectangular plate. The side face  1223  comprises four interconnecting portions: two parallel opposite splicing faces  1223   a  and two opposite mounting faces  1223   b . Each splicing face  1223   a  is a flat face. Each mounting face  1223   b  is a flat face, and therein evenly defines three concaves  123  toward a center of the light guide plate  122 . Each concave  1223   b  is defined in a position where the mounting face  1223   b  joints the bottom face  1224 , in this manner, a dark zone formed at a joint of two adjacent mounting faces  1223   b  of the surface light source device  100  is eliminated. 
     Each light guide plate  122  can be made of polymethyl methacrylate, polycarbonate, polyacrylate, glass, silicone, quartz, epoxy and other transparent materials. The light guide plate  122  forms a plurality of micro-structures to realize a uniformity of light emitted from the LEDs  124 . In  FIG. 3 , the micros-structures are a plurality of mini protrudes  1225  evenly distributed on the light emitting face  1222  of the light guide plate  122 . In  FIG. 4 , the micro-structures are a plurality of particulates  1226 , with a refractive index different from that of the light guide plate  122 , adulterated in the light guide plate  122 . The particulates  1226  are selected from titanium dioxide (TiO 2 ), aluminum oxide (AL 2 O 3 ), silicon dioxide (SiO 2 ), zine oxide (ZnO 2 ), or other dielectric materials. Alternatively, in  FIG. 4 , the micro-structures consist of a plurality of material defects  1226 , with a refractive index different from that of the light guide plate  122 , formed in the light guide plate  122  by laser or other high power electromagnetic waves. In  FIG. 5 , the micro-structures are a plurality of cavities  1227  formed in the light guide plate  122 . 
     The LEDs  124  are received in the concaves  123  of the light guide plates  122 , respectively, by adhesive or other means. The LEDs on each mounting face  1223   b  forms a linear array thereon. Each LED array has a light emitting face facing to the light guide plate  122 . The light emitting faces of the two LED arrays of each light source unit  120  have normal thereof opposite and parallel to each other. In this embodiment, the LEDs  124  are side emitting LEDs, thereby producing a light coupling into the light guide plate  122 . 
     In the surface light source device  100 , the four light source units  120  are splicing together via one of the splicing faces  1223   a  of each light source unit  120  splicing with one of the mounting faces  1223   b  of an adjacent one of the four light source units  120 . A jointing position is formed between two adjacent light source units  120 . In this manner, only one LED array is located at the jointing position between two adjacent light source units  120 , which facilitates heat dissipation from the jointing positions to avoid heat accumulation at the jointing positions of the surface light source devices  100 . 
     Referring to  FIG. 7 , a surface light source device  200  in accordance with a second embodiment of the present invention is shown. The device  200  has a configuration similar to that of the device  100  of the first embodiment, a difference therebetween is that a light guide plate  222  of each light source unit  220  of the device  200  has two adjacent mounting faces  2223   b  and two adjacent splicing faces  2223   a . The LEDs  124  are attached to the mounting faces  2223   b  of the light guide plates  222 . The LEDs  124  on each mounting face  2223   b  form a linear array thereon. Each LED array has a light emitting face facing to the light guide plate  222 . The light emitting faces of the two LED arrays of each light source unit  220  have normal thereof crossed with each other, for example, two normal of the two LED arrays are perpendicular to each other. 
     Referring to  FIG. 8 , a surface light source device  300  in accordance with a third embodiment of the present invention is shown. The device  300  has a configuration similar to that of the device  100  of the first embodiment, a difference therebetween is that a light guide plate  322  of each light source unit  320  of the device  300  has a mounting face  3223   b  and three splicing faces  3223   a . The LEDs  124  are attached to the mounting face  3223   b  of the light guide plates  322 . The LEDs  124  on each mounting face  3223   b  form a linear array thereon. In the device  300 , the four light source units  320  are splicing together via one of the splicing faces  3223   a  of each light source unit  320  splicing with the mounting face  3223   b  or one of the splicing faces  3223   a  of an adjacent one of the four light source units  320 . In this embodiment, only one or no LED array is located at the jointing position between two adjacent light source units  320 . 
     Referring to  FIG. 9 , a surface light source device  400  in accordance with a fourth embodiment of the present invention is shown. The device  400  has a configuration similar to that of the device  100  of the first embodiment, a difference therebetween is that a light guide plate  422  of each light source unit  420  of the device  400  has three mounting faces  4223   b  and a splicing face  4223   a . The LEDs  124  are attached to the mounting faces  4223   b  of the light guide plates  422 . The LEDs  124  on each mounting face  4223   b  form a linear array thereon. Each LED array has a light emitting face facing to the light guide plate  422 . Two of the three light emitting faces of the three LED arrays of each light source unit  420  have normal thereof opposite and parallel to each other and crossed with a normal of another of the three light emitting faces. In the device  400 , the four light source units  420  are splicing together via each splicing faces  4223   a  of each light source unit  420  splicing with one of the mounting faces  4223   b  of an adjacent one of the four light source units  420 . 
     It is believed that the present invention and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.