Abstract:
A light guide plate includes a plurality of micro dots. The micro dots are provided uniformly on one side of the light guide plate and are integrated with the light guide plate. Each dot is coated by a fluorescent layer, and the fluorescent layer emits light when excited by an ultraviolet light.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to light guide plates, and particularly to a light guide plate and a backlight module employing the light guide plate, the backlight module typically being part of an LCD (liquid crystal display). 
     2. Description of Related Art 
     LCD devices are thin, light in weight, and drivable by a low voltage, and thereby extensively employed in various electronic devices. 
     In an LCD device, usually a backlight module having a light source and a light guiding device is used to provide the needed illumination. The light source emits light beams to the light guiding device, which then transmits the light beams to illuminate liquid crystal molecules in a liquid crystal panel. It is important that the light guiding device transmits light beams to the liquid crystal panel uniformly. However, conventional backlight modules are not always able to provide uniform illumination, and may be unduly thick and heavy. 
     Therefore, there is room for improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with references 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 light guide plate and the backlight module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, in which: 
         FIG. 1  is an isometric view of an exemplary backlight module; 
         FIG. 2  is a schematic view of the exemplary light guide plate shown in  FIG. 1 ; and 
         FIG. 3  is a partially, cross-sectional view of the exemplary light guide plate along III-III line shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an exemplary backlight module  100  includes a light source  10 , a light guide plate  20 , a diffusing plate  40 , a first prism plate  50  and a second prism plate  60 . The light source  10 , the light guide plate  20 , the diffusing plate  40 , the first prism plate  50  and the second prism plate  60 , are received in a housing  30 . In an exemplary embodiment, the housing  30  is an LCD housing. 
     The light source  10  may be an ultraviolet light source, and providean ultraviolet beam. A light source cover  11  is positioned at one side of the light source  10 , and surrounds the side of the light source  10 . The light source cover  11  functions mainly as a reflection element, to ensure that most of the light beams emitted from the light source  10  enter the light guide plate  20 . 
     Referring to  FIGS. 2 and 3 , the light guide plate  20  is made of a transparent material such as glass or plastic. The plastic material can be any of acrylic, polyvinylchloride resin (PVC), polycarbonate (PC), polystyrene (PS), polypropylene (PP). The light guide plate  20  includes a bottom surface  202  and an emitting surface  204 . The bottom surface  202  further includes a plurality of micro dots  23 . The micro dots  23  are arranged in a uniform matrix formation. The micro dots  23  are generally frustum-shaped, and are formed by etching. The micro dots  23  on the bottom surface  202  of the transparent plate  20  can scatter and reflect incident light beams, as to almost completely eliminate internal reflection of the light beams and make the light beams more uniformly emit from the emitting surface  204 . A largest diameter of each micro dot  23  is in the range from  20  micron to  40  micron. An orthogonal cross-section of each micro dot  23  is trapezium-shape, and subtends an angle in the range from about 20 to about 70 degrees. 
     Each micro dot  23  has a fluorescent layer  25  formed by electrostatic spraying. The material forming the fluorescent layer  25  has red (R), green (G), and blue (B) colors. The red fluorescent material may be zinc sulfide mixed with copper. The green fluorescent material may be sodium fluorescein. The red fluorescent material may be rhodamine, yttrium aluminium garnet. The ultraviolet light from the light source  10  will excite the fluorescent layer  25  to emit light. 
     The diffusing plate  40  includes a base  41  and a plurality of diffusing protrusions  43 . The base  41  is made of polyethylene terephthalate (PET). The diffusing protrusions  43  are uniformly distributed on the base  41 , and are integrally formed with the base  41 . In general, the diffusing protrusions  43  are made of an organic material such as PMMA, polycarbonate or MCOC (metallocene Cyclic Olefin Copolymer). The diffusing protrusions  43  are hemispherical or sub-hemispherical, and can diffuse the light beams emitting from the emitting surface  204  of the transparent plate  20 , in order to achieve a plane light source having uniform brightness. Since the base  41  and the diffusing protrusions  43  are of different materials, the brightness uniformity of the diffusing plate  40  is greatly improved. 
     The first prism plate  50  and the second prism plate  60  are made of transparent acrylics having a cross section of a right angled triangle. The emitted light beams eventually penetrate the first prism plate  50  and the second prism plate  60 . 
     In use, the ultraviolet light source  10  excites the fluorescent layer  25  to emit light. The emitted light is guided by the light guide plate  20  to the diffuser plate  40 , and then, the light is diffused by the diffuser plate  40  to penetrate through the first prism plate  50  and the second prism plate  60 . The light source  10  can be light emitting diodes (LED) emitting blue-ray or ultraviolet-ray. The light emitted by the blue-ray or ultraviolet-ray LED can enhance the energy-transition efficiency of the fluorescent layer  25  and can also promote the illumination obviously. Moreover, the mirco dots  23  on the bottom surface  202  of the transparent plate  20  can scatter and reflect incident light beams, to almost completely eliminate internal reflection of light beams and make the light beams uniformly emit from the emitting surface. 
     It is to be understood that the micro dots  23  may be cylindrical, hemispherical, sub-hemispherical, parallelepiped-shaped. 
     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that different 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.