Abstract:
A light guide device ( 21 ) includes an incident surface ( 211 ), an emitting surface ( 212 ) and a plurality of protrusions ( 212   a ). The incident surface is configured so as to allow an incident light to pass therethrough. The emitting surface is adjoining the incident surface and configured so as to allow the light to emit out of the light guide device. The protrusions are formed on at least a portion of the emitting surface. The protrusions are configured for concentrating light that emits out from said portion of the emitting surface. The present application is also concerned to a backlight module ( 2 ) including a light source ( 22 ) and the light guide device.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to light guide devices and backlight modules and, particularly, to a light guide device and backlight module for use in, e.g., a liquid crystal display (LCD).  
       BACKGROUND  
       [0002]     In a liquid crystal display (LCD) device, a liquid crystal is a substance that does not itself illuminate light. Instead, the liquid crystal relies on receiving light from a light source, thereby displaying images and data. In the case of a typical liquid crystal display device, a backlight module powered by electricity supplies the needed light. Generally, a bottom-lighting type backlight module and/or an edge-lighting type backlight module are/is provided.  
         [0003]     Generally, a bottom-lighting type backlight module has two or more light sources, thus making the overall LCD big, heavy, and energy inefficient. Therefore, bottom-lighting type backlight modules are usually employed in LCDs or LCD televisions where portability, mass, and volume are negligible factors.  
         [0004]      FIG. 1  represents a typical edge-lighting type backlight module  1 . The backlight module  1  includes a light guide plate  11 , a light source  12 , a reflector  13 , and a plurality of optical elements  14 ,  15 , and  16 . The light guide device  11  is wedge-shaped. The optical elements include a reflective sheet  14 , a diffusion sheet  15 , and two prism sheets  16 . The light source  12  generally includes a cold cathode fluorescent lamp (CCFL). The reflective sheet  14  is positioned under the light guide plate  11  and is configured for reflecting light back into the light guide plate  11 . The diffusion sheet  15  is located above the light guide plate  11  and is configured for uniformly diffusing the emitted light. The prism sheets  16  are positioned above the diffusion sheet  15  and are configured for collimating the emitted light, thereby improving the brightness of light illumination.  
         [0005]     Also referring to  FIG. 2 , two ends of the light source  12 , i.e. two electrodes  121  that do not emit light results in that few light enters into two corners of the light guide plate  11  adjacent to the two electrodes  121 . Thus, two dark corners  18  are formed. The light source  12  may be configured to extend or displace farther out from the light guide plate  11  to solve the above problem. However, it makes little effect and instead will enlarge the volume of the backlight module  1 .  
         [0006]     What is needed, therefore, is a light guide device and a backlight module using the same which overcome the above-described problem.  
       SUMMARY  
       [0007]     A light guide device according to an embodiment includes an incident surface, an emitting surface and a plurality of protrusions. The incident surface is configured so as to allow an incident light to pass therethrough. The emitting surface is adjoining the incident surface and configured so as to allow the light to emit out of the light guide device. The protrusions are formed on at least a portion of the emitting surface. The protrusions are configured for concentrating light that emits out from said portion of the emitting surface.  
         [0008]     A backlight module according to a preferred embodiment includes a light source and an above-described light guide device.  
         [0009]     Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     Many aspects of the light guide device and related backlight module having the same can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
         [0011]      FIG. 1  is a schematic, perspective view of a conventional backlight module;  
         [0012]      FIG. 2  is a top view of the conventional backlight module of  FIG. 1 ;  
         [0013]      FIG. 3  is a schematic, perspective view of a light guide device according to a first preferred embodiment;  
         [0014]      FIG. 4  is an enlarged view of an incident surface of the light guide device of  FIG. 3 ;  
         [0015]      FIG. 5  is an enlarged view of a second protrusion of the light guide device of  FIG. 3 ;  
         [0016]      FIG. 6  is a partially schematic view of a light path when light beams pass the first protrusion of the light guide device of  FIG. 3 ;  
         [0017]      FIG. 7  is a top view of an emitting surface of the light guide device of  FIG. 3 ;  
         [0018]      FIG. 8  is a schematic, perspective view of a light guide device according to a second preferred embodiment;  
         [0019]      FIG. 9  is a top view of an emitting surface of the light guide device of  FIG. 8 ; and  
         [0020]      FIG. 10  is a schematic, perspective view of a backlight module according to a third preferred embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Reference will now be made to the drawings to describe preferred embodiments of the present light guide device and backlight module, in detail.  
         [0022]     Referring to  FIG. 3 , a light guide device  21 , in accordance with a first preferred embodiment is shown. The light guide device  21  is a rectangular sheet, or alternatively may be generally cuneiform. The light guide device  21  includes an incident surface  211  formed on one side surface thereof, an emitting surface  212  adjacent to the incident surface  211 , and a bottom surface  213  opposite to the emitting surface  212 . A plurality of first protrusions  211   a  is formed on two ends of the incident surface  211 . A plurality of second protrusions  212   a  is formed on two corners of the emitting surface  212  corresponding to the adjacent incident surface  211 . The bottom surface  213  is configured to reflect light by defining a plurality of microstructures (not shown) thereof such as protrusions, recesses or dots. It is to be understood that the microstructures may also be omitted.  
         [0023]     Referring to  FIG. 4 , a length of the incident surface  211  is represented by “L”. The first protrusions  211   a  are formed on each end of the incident surface  211  along a length of “L 1 ”. The length of “L 1 ” is configured to be less than a quarter of “L”. Each first protrusion  211   a  is in a shape of triangular prism. Each first protrusion  211   a  has a triangular cross-section taken along a direction perpendicular to the incident surface  211  and parallel to the emitting surface  212 . Each triangular cross-section of the first protrusions  211   a  defines a vertex angle A 1 . The vertex angle A 1  progressively increase with increasing distance from the two ends of the incident surface  211  toward a middle of the incident surface  211 . The vertex angle A 1  is configured to be larger than or equal to 60 degrees and less than or equal to 150 degrees.  
         [0024]     Referring to  FIG. 6 , an incident light  1   a  enters the light guide device  21  through an outside substance (i.e., atmosphere). An incident angle of the incident beam  1   a  is defined as “α”, and an angle of refraction of a refractive beam  2   a  is defined as “β”. “n1” represents a refractive index of the atmosphere and “n2” represents a refractive index of the light guide device  21 . Furthermore, “n1” is less than the “n2”. A formula of refraction law is defined as: n1*sin α=n2*sin β. Therefore α is larger than β. Thus, any incident light parallel to the incident light  1   a  is diffused.  
         [0025]     Referring to  FIG. 5 , the second protrusions  212   a  are in a shape of an elongated tetrahedron. Each second protrusion  212   a  has a base surface parallel to the emitting surface  212  and a side surface perpendicularly adjacent to the emitting surface  212 . Each side surface of the second protrusions  212   a  defines a vertex angle A 2  where “A 2 ” is larger than or equal to 45 degrees and less than or equal to 175 degrees.  
         [0026]     Referring also to  FIG. 7 , the emitting surface  212  has a length of “L” and a width of “W”. The second protrusions  212   a  extend out of the emitting surface  212  at regular intervals along the width of the emitting surface  212 . A length of the longest second protrusion  212   a  “L 2 ” is less than a quarter of “L”. The second protrusions  212   a  is disposed within an area with width “W 2 ” that is less than one third of “W”. Lengths of the second protrusions  212   a  progressively decrease with increasing distance between the incident surface  211  and the second protrusion  212   a.    
         [0027]     When the light guide device  21  is in use, light passes through the light incidence surface  211  and enters the light guide device  21 . Light is reflected and refracted inside the light guide device  21  before finally outputted from the light guide device  21  via the emitting surface  212 .  
         [0028]     The first protrusions  211   a  refract part of the incident light toward the corners of the light guide device  21  so that more light enters the corners. Light is diffused evenly throughout the light guide device  21  by the first protrusions  211   a . Thus, the first protrusions  211   a  makes more light rays incident the light guide device  21  via two ends of the incident surface  211 . Contrary, when the light is emitted out of the emitting surface  212  via the corners thereof, the second protrusions  212   a  serve to concentrate light so as to increase the emitting light in the corners of the emitting surface  212  adjacent to the two ends of the incident surface  211 . Thereby, a luminance of the corners of the emitting surface  212  is higher. In conclusion, the light guide device  21  has good emitting luminance and uniformity.  
         [0029]     In alternative embodiment, the first protrusion  211   a  may also be a shape of hexahedron having a quadrangular cross-section such as trapezoidal cross-section. A certain optional non-protruding flat interval may also be arranged between every two first protrusions  211   a . The second protrusion  212   a  may also be polyhedron having a polygonal cross-section. The first and second protrusions  211   a ,  212   a  are either manufactured together with the light guide device  21  or formed by a method of V-cutting.  
         [0030]      FIG. 8  shows a second embodiment light guide device  31 . The light guide device  31  in accordance with the second preferred embodiment of the present application is the same as the first embodiment, except that a number of third protrusions  312   b  are formed on the emitting surface  312 . The light guide device  31  has a same number of first and second protrusions  311   a  and  312   a  as the first and second protrusions  211   a  and  212   a  of the light guide device  21  of the first embodiment. The third protrusions  312   b  are arranged symmetrical to the second protrusions  312   a . A shape of the third protrusion  312   b  is the same as the second protrusion  312   a.    
         [0031]     Referring also to  FIG. 9 , the emitting surface  312  has a length of “L′” and a width of “W′”. The second protrusions  312   a  and the third protrusions  312   b  extend out of the emitting surface  312  at regular intervals along the width of the emitting surface  312  and parallel to each other. A length of the longest second protrusion  312   a  “L 2 ′” and a length of the longest third protrusion  312   b  “L 3 ” are both less than a quarter of “L′”. The second protrusions  312   a  is disposed within an area with width “W 2 ” and the third protrusions  312   b  is disposed within an area with width “W 3 ” that are both less than one third of “W′”.  
         [0032]     Similar to the second protrusions  212   a  in the first embodiment, the third protrusions  312   b  results in that light emitting from the other two corners of the emitting surface  312  adjacent to two ends of the incident surface  311  increases.  
         [0033]     In other exemplary embodiments, the third protrusion  312   b  may also be polyhedrons having a polygonal cross-section. The third protrusions  312   b  are either manufactured together with the light guide device  31  or formed by a method of V-cutting.  
         [0034]     Referring to  FIG. 10 , a backlight module  2  of a third preferred embodiment is similar to that of the first embodiment, except that a light source  22  is provided, i.e. the backlight module  2  includes the light guide device  21  and the light source  22 . Facing and being opposite to the incident surface  211  of the light guide device  21 , the light source  22  is mounted besides the light guide device  21 . The light source  22  generally is a CCFL. The light guide device  21  employed in the backlight module  2  is alternative with the light guide device  31 .  
         [0035]     Finally, while the present invention has been described with reference to particular embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Therefore, various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.