Abstract:
A light guide plate ( 300 ) includes a light incidence surface ( 310 ) for receiving light beams, a light-emitting surface ( 320 ) for guiding light beams out of the light guide plate, and a bottom surface ( 330 ) reflecting and scattering light beams in directions toward the light-emitting surface. The bottom surface includes scattering-dots ( 341 ), and a predetermined region of the bottom surface also includes sub-scattering-dots ( 342 ). At least one sub-scattering-dot is disposed around each scattering-dot. The sub-scattering-dots are smaller than the scattering-dots. With this micro-configuration, intensities of light beams output from the light guide plate are uniform and bright.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to light guide plates, and particularly to a light guide plate used for a liquid crystal display. 
   2. The Prior Art 
   In a typical liquid crystal display, a backlight module provides a surface light source for illuminating the liquid crystal display. Generally, the backlight module includes a light guide plate and a light source arranged adjacent to one side of the light guide plate. The light guide plate changes light beams received from the light source into surface light beams, and directs the surface light beams to a liquid crystal panel of the liquid crystal display. 
     FIG. 8  shows a conventional backlight module  100 . The backlight module  100  comprises a light source  110 , a light guide plate  120 , a diffuser  130 , and a prism sheet module  140 . The light guide plate  120  includes a light incidence surface  121 , a light-emitting surface  122 , and a bottom surface  123 . 
   Referring to  FIG. 9 , a distribution of scattering-dots  124  on the bottom surface  123  of the light guide plate  120  is shown. To improve the uniformity of the surface light beams of the backlight module  100 , the scattering-dots  124  are evenly arranged on the bottom surface  123  of the light guide plate  120 . 
   With this configuration, when light beams from the light source  110  enter the light guide plate  120  from the light incidence surface  121 , the scattering-dots  124  reflect and diffract the light beams. The light beams are thus changed into uniform surface light beams, which are output from the light-emitting surface  122  of the light guide plate  120 . However, in one or more predetermined regions of the light guide plate  120 , especially one or more small regions, it is difficult to control and micro-adjust the configuration of the scattering-dots  124  to ensure uniformity and brightness of the output light beams. 
     FIG. 10  is a simplified view of a plurality of scattering-dots  230  on a bottom surface  210  of another conventional light guide plate  200 . Sizes of the scattering-dots  230  progressively increase with increasing distance away from a light incidence surface  220 . With this configuration, the uniformity and brightness of light beams output from a light-emitting surface (not shown) can be improved overall. However, in one or more predetermined regions of the light guide plate  200 , especially one or more small regions, it is difficult to control and micro-adjust the configuration of the scattering-dots  230  to ensure uniformity and brightness of the output light beams. 
   A new light guide plate with a new distribution of scattering-dots on a bottom surface thereof is desired in order to overcome the above-described problems. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a light guide plate which is micro-configured in one or more predetermined regions thereof to ensure that intensities of light beams output from the light guide plate are uniform and bright. 
   In order to achieve the object set out above, a light guide plate according to the present invention comprises a light incidence surface for receiving light beams, a light-emitting surface for guiding light beams out of the light guide plate, and a bottom surface reflecting and scattering light beams in directions toward the light-emitting surface. The bottom surface comprises a plurality of scattering-dots thereon, and a predetermined region of the bottom surface also comprises a plurality of sub-scattering-dots thereon. At least one sub-scatteriug-dot is disposed around each scattering-dot symmetrically along an imaginary ring closely surrounding each scattering-dot, and the at least one sub-scattering-dot is smaller than the scattering-dot. 
   The light guide plate has the following advantages. In one aspect according to the invention, by the utilization of the sub-scattering-dots with a smaller size cooperating with the scattering-dots in the predetermined region, it is easier to provide a configuration that yields high uniformity and brightness of light beams exiting the light-emitting surface. This is especially the case where appropriate micro-configuration is needed in small parts of the predetermined region. In another aspect according to the invention, the utilization of the sub-scattering-dots can compensate for micro differences in the light manipulation effects of the scattering-dots affecting the whole light-emitting surface, thereby providing improved uniformity and luminance of light beams exiting the whole light-emitting surface. 
   Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a simplified, side view of a light guide plate according to a first embodiment of the present invention; 
       FIG. 2  is a simplified, plan view of a bottom of the light guide plate of  FIG. 1 , showing a distribution of scattering-dots on a bottom surface of the light guide plate; 
       FIG. 3  is an enlarged view of a circled portion III of  FIG. 2 ; 
       FIG. 4  is a simplified, plan view of a bottom of a light guide plate according to a second embodiment of the present invention, showing a distribution of scattering-dots on a bottom surface of the light guide plate; 
       FIG. 5  is an enlarged view of a circled portion V of  FIG. 4 ; 
       FIG. 6  is a simplified, plan view of a bottom of a light guide plate according to a third embodiment of the present invention, showing a distribution of scattering-dots on a bottom surface of the light guide plate; 
       FIG. 7  is a simplified, plan view of a bottom of a light guide plate according to a fourth embodiment of the present invention, showing a distribution of scattering-dots on a bottom surface of the light guide plate; 
       FIG. 8  is an exploded, isometric view of a conventional backlight module; 
       FIG. 9  is a simplified, plan view of a bottom of a light guide plate of the module of  FIG. 8 , showing a distribution of scattering-dots on a bottom surface of the light guide plate; and 
       FIG. 10  is a simplified, plan view of a bottom of another conventional light guide plate, showing a distribution of scattering-dots on a bottom surface of the light guide plate. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As shown in  FIGS. 1 to 3 , a plate-like light guide member  300  of the first embodiment of the present invention includes a light incidence surface  310 , a light-emitting surface  320  connecting with the light incidence surface  310 , and a bottom surface  330  opposite to the light-emitting surface  320 . 
   The bottom surface  330  has a plurality of scattering-dots  341  distributed thereon as a first scattering element, for eliminating total internal reflection of light beams in the light guide plate  300 . That is, light beams incident on the bottom surface  330  are reflected and scattered at the scattering-dots  341  in directions toward the light-emitting surface  320 . The scattering-dots  341  have a same size and are uniformly arranged as an array on the bottom surface  330 . Furthermore, in a predetermined region of the bottom surface  330 , a plurality of sub-scattering-dots  342  as a second scattering element are disposed at peripheries of the scattering-dots  341 . The sub-scattering-dots  342  have the same function as the scattering-dots  341 . At least one sub-scattering-dot  342  is located at the periphery of each scattering-dot  341  in the predetermined region, i.e., symmetrically distributed along the ring-like predetermined region closely surrounding each scattering-dot  341 . The sub-scattering-dots  342  are smaller than the scattering-dots  341 . Preferably, a diameter of each sub-scattering-dot  342  is less than 10 μm, or is equal to a tenth of the size of each scattering-dot  341 . 
   In operation, when light beams from a light source (not shown) enter the light guide plate  300  via the light incidence surface  310 , the light beams are reflected and diffused by the scattering-dots  341  of the bottom surface  330  in directions toward the light-emitting surface  320 . Further, in the predetermined region, certain of the light beams are reflected and diffused by the scattering-dots  341  and the sub-scattering-dots  342  of the bottom surface  330  in directions toward the light-emitting surface  320 . The number and sizes of the sub-scattering-dots  342  within different parts of the predetermined region can vary, to account for differences in uniformity and intensity of the light beams reaching the different parts of the predetermined region. Thus, the light beams are uniformly transmitted out from the light-emitting surface  320  in a direction roughly perpendicular to the light-emitting surface  320 . 
   The dots  341 ,  342  are formed by using the so-called LIGA process (in German: Lithographie, Galvanoformung, Abformung). LIGA includes three basic steps: lithography, electroforming, and micro molding. Firstly, a light guide plate body is formed by injection molding, the body including the light incidence surface  310 , the bottom surface  330  and the light-emitting surface  320  opposite to the bottom surface  330 . Secondly, a mold with a plurality of printing-dots is formed by LIGA. Finally, the light guide plate  300  with the plurality of scattering-dots  341  and sub-scattering-dots  342  is formed by hot pressing the bottom surface  330  with the mold. 
   A light guide plate  400  according to the second embodiment of the present invention is shown in  FIGS. 4 and 5 . The light guide plate  400  has a structure similar to the light guide plate  300 . A plurality of scattering-dots  431  and sub-scattering-dots  432  are distributed on a bottom surface  420  of the light guide plate  400 . The sub-scattering-dots  432  are located at peripheries of scattering-dots  431  that are in a predetermined region of the bottom surface  420 , i.e., symmetrically distributed along the ring-like predetermined region closely surrounding each scattering-dot  431 . At least one sub-scattering-dot  432  is located at the periphery of each scattering-dot  431  in the predetermined region. The scattering-dots  431  have a same size. A distribution density of the scattering-dots  431  progressively increases with increasing distance away from a light incidence surface  410  of the light guide plate  400 . The number and sizes of the sub-scattering-dots  432  within different parts of the predetermined region can vary, to account for differences in uniformity and intensity of the light beams reaching the different parts of the predetermined region, and/or to account for differences in the light manipulation effects of the scatteringdots  431  in the different parts of the predetermined region. 
     FIG. 6  shows a light guide plate  500  according to the third embodiment of the present invention. The light guide plate  500  has a structure similar to the light guide plate  300 . A plurality of scattering-dots  531  and sub-scattering-dots (not shown) are disposed on a bottom surface  520  of the light guide plate  500 . The sub-scattering-dots are located at peripheries of scattering-dots  531  that are in a predetermined region of the bottom surface  520 . At least one sub-scattering-dot is located at the periphery of each scattering-dot  531  in the predetermined region. The scattering-dots  531  are uniformly arranged on the bottom surface  520 . Sizes of the scattering-dots  531  progressively increase with increasing distance away from a light incidence surface  510  of the light guide plate  500 . The number and sizes of the sub-scattering-dots within different parts of the predetermined region can vary, to account for differences in uniformity and intensity of the light beams reaching the different parts of the predetermined region, and/or to account for differences in the light manipulation effects of the scattering-dots  531  in the different parts of the predetermined region. 
     FIG. 7  shows a light guide plate  600  according to the fourth embodiment of the present invention. In the light guide plate  600 , a plurality of scattering-dots  631  and sub-scattering-dots (not shown) are distributed on a bottom surface  620  of the light guide plate  600 . The sub-scattering-dots are located at peripheries of scattering-dots  631  that are in a predetermined region of the bottom surface  620 . At least one sub-scattering-dot is located at the periphery of each scattering-dot  631  in the predetermined region. A distribution density and sizes of the scattering-dots  631  both progressively increase with increasing distance away from a light incident surface  610  of the light guide plate  600 . The number and sizes of the sub-scattering-dots within different parts of the predetermined region can vary, to account for differences in uniformity and intensity of the light beams reaching the different parts of the predetermined region, and/or to account for differences in the light manipulation effects of the scattering-dots  631  in the different parts of the predetermined region. 
   In summary, the light guide plate  300  has the following advantages. In one aspect according to the present invention, by the utilization of the sub-scattering-dots  342  with a smaller size cooperating with the scattering-dots  341  in the predetermined region, it is easier to provide a configuration that yields high uniformity and brightness of light beams exiting the light-emitting surface  320 . This is especially the case where appropriate micro-configuration is needed in small parts of the predetermined region. In another aspect according to the invention, the utilization of the sub-scattering-dots  342  can compensate for micro differences in the light manipulation effects of the scattering-dots  341  affecting the whole light-emitting surface  320 , thereby providing improved uniformity and luminance of light beams exiting the whole light-emitting surface  320 . 
   Furthermore, a plurality of scattering-dots and sub-scattering-dots can be arranged selectively on the light-emitting surface  310  of the light guide plate  300 . In any of the above-described embodiments, the scattering-dots and the sub-scattering-dots can be hemispherical, sub-hemispherical, pyramidal, or any suitable combination of these shapes. 
   Further, it is to be understood that even though numerous characteristics and advantages of the present invention have been set out in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.