Abstract:
A light guide plate having micro-reflectors is to increase luminance of the light guide plate by changing light route. The light guide plate includes an incidence plane, an illuminating plane, and a bottom. Each of the micro-reflectors is disposed at the bottom and intersected with the light guide plate in a direction heading for a recess provided at the bottom of the light guide plate, and comprises a light reflection plane located between the incidence plane and the illuminating plane to define an angle θ. The light reflection plane is an arc quadrilateral or a sector when observed from top of the illuminating plane. The arc quadrilateral has two concentric arc sides parallel with each other.

Description:
BACKGROUND OF THE INVENTION 
   (a) Field of the Invention 
   The present invention relates to a light guide plate having micro-reflectors applied on the backlight module of a liquid crystal display, and more particularly, to one that has an arc or sectorial recess at the bottom of the light guide plate to increase luminance of the light guide plate. 
   (b) Description of the Prior Art 
   Referring to  FIG. 1  of the accompanying drawings for a schematic view of a micro-reflector  2  of a light guide plate  1  of the prior art, the micro-reflector  2  with rough surface is created by using the etching method on a bottom  12  of the smooth light guide plate  1 . Rays of light  50  continuing to convey through the surface of the micro-reflector  2  create reflected rays  51  or refracted rays  52  of light in scattering fashion. The reflected rays  51  of light pass through an illuminating plane  11  of the light guide plate  1  when the angle of incidence of the reflected rays  51  is smaller than the critical angle; or are fully reflected back into the light guide plate  1  to continue passing on if the angle of incidence is greater than the critical angle. 
     FIG. 2  interprets coordinates illustrated in  FIG. 3(   a ).  FIG. 3(   a ) is a radar view of illuminating intensity of the rays of light leaving the illuminating plane  11  of the light guide plate  1  of the prior art. Wherein, the abscissa indicates a horizontal angle (HA) with the movement of angle turns from a normal direction  13  of the illuminating plane  11  into a direction  14  vertical to a light source  4 ; meanwhile, the ordinate indicates a vertical angle (VA). The movement of angle turns from the normal direction  13  of the illuminating plane  11  into a direction  15  in parallel with the light source  4 . In  FIG. 3(   a ), each closed curve represents a value of the illuminating intensity, which is defined as a luminous flux of each unit of a solid angle. There are ten closed curves as illustrated in  FIG. 3(   a ), representing ten grades of illuminating intensity. As shown in  FIG. 3(   a ), the distribution of the illuminating intensity from the light guide plate  1  of the prior art approximates the Lambertian distribution, i.e., the illuminating intensity indicates cosine distribution. When the illuminating intensity is converted into luminance value, the luminance value is equal in each direction. 
   Now referring to  FIG. 3(   b ) for a perspective view of the illuminating intensity from the illuminating plane  11  of the light guide plate  1 , the distribution of the illuminating intensity approximates spherical one, i.e., it resembles the Lambertian distribution to permit the observation changes of the illuminating intensity in angle or direction. 
   Furthermore, each of light guide plates as disclosed in Taiwan Patent Publication No. 575759, U.S. Pat. Nos. 6,629,764 and 6,755,545 is adapted with a linear light source. Each illuminating plane of the latter US patents makes in a wave form while each micro-reflector disclosed in all three citations is originated from a conic form of concave disposed on the bottom of the light guide plate. The micro-reflector of Taiwan Patent Publication No. 575759 is a semi-spherical or triangle cone, and a triangle when viewed sideways; the micro-reflector of U.S. Pat. No. 6,629,764, as indicated in its side view, is two consecutive triangles, similar to a capitalized letter M. The bottom of the light guide plate in the disclosed embodiment includes a slope. The micro-reflector in U.S. Pat. No. 6,755,545 is a single cone. 
   In general, rays of light reflected from the hollow inside of a conic form of the micro-reflector of a light guide plate are prone to scatter and prevent from easy concentration. 
   SUMMARY OF THE INVENTION 
   The primary purpose of the present invention is to provide a light guide plate having micro-reflectors. Each of the micro-reflectors is disposed in an arc quadrilateral or a sector recess on the bottom of the light guide plate so to promote rays of light to radiate towards an illuminating plane of the light guide plate for increasing luminance of the light guide plate. 
   To achieve the purpose, the light guide plate includes an incidence plan, an illuminating plane, and a bottom. Light from a light source enters into the light guide plate from the incidence plane and leaves from the illuminating plane. The bottom is located on the opposite side of the illuminating plane, and the micro-reflectors are disposed on the bottom. Each of the micro-reflectors is a recess in the light guide plate intersected with the light guide plate and includes a light reflection plane that is located between the incidence plane and the illuminating plane to define an angle θ with the bottom of the light guide plate. The shape of the micro-reflector when viewed from top of the illuminating plane is an arc quadrilateral or a sector. The arc quadrilateral has two arc sides concentrically in parallel with each other. 
   Furthermore, each of the micro-reflectors includes a rear light pervious plane, two light pervious side planes, and a hollowed plane. The rear light pervious plane is abutted to the light reflection plane and farther from the incidence plane of the light guide plate in relation to the light reflection plane, and is vertical to the bottom of the light guide plate. Both light pervious side planes are respectively abutted to both sides of the light reflection plane and vertical to the bottom of the light guide plate. The hollowed plane is the recess on the bottom of the light guide plate. 
   The light reflection plane of the arc quadrilateral is cut from a sectional cone or an elliptic cone having a wide upper part and a narrow lower part with its center located at where nearer to the incidence plane. The cut is made for an angle β from the center of the sectional cone or the elliptic cone to come up with a light reflection plane with β as its central angle. 
   Alternatively, the light reflection plane of the arc quadrilateral is cut from a sectional cone or an elliptic cone having a narrow upper part and a wide lower part with its center located at where nearer to the rear light pervious plane. The cut is made for an angle β from the center of the sectional cone or the elliptic cone to come up with a light reflection plane with β as its central angle. 
   The light reflection plane of the sector is cut from a cone or an elliptic cone having a wide upper part and a narrow lower part with its center located at where nearer to the incidence plane. The cut is made for an angle β from the center of the cone or the elliptic cone to come up with a light reflection plane with β as its central angle. 
   Alternatively, the light reflection plane of the sector is cut from a cone or an elliptic cone having a narrow upper part and a wide lower part with its center located at where nearer to the rear light pervious plane. The cut is made for an angle β from the center of the cone or the elliptic cone to come up with a light reflection plane with β as its central angle. 
   Wherein, the side sectional shape of the light reflection plane is selected from a straight line, a concave curve, or a convex curve. It is to be noted that the micro-reflector of the light guide plate in each preferred embodiment of the present invention is capable of reflecting and locally focusing the light to effectively promote the luminance of the light guide plate. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of a light guide plate having micro-reflectors of the prior art. 
       FIG. 2  is a schematic view of light emitted from an illuminating plane of the light guide plate of the prior art (describing the coordinates illustrated in  FIG. 3 ). 
       FIG. 3  ( a ) is a radar view of the illumination intensity from the illuminating plane of the light guide plate of the prior art 
       FIG. 3  ( b ) is a perspective view of the illumination intensity from the illuminating plane of the light guide plate of the prior art. 
       FIG. 4  is a schematic view of micro-reflectors of a preferred embodiment of the present invention applied in a light guide plate. 
       FIG. 5  ( a ) is a schematic view showing a construction of the micro-reflector of the first preferred embodiment of the present invention. 
       FIG. 5  ( b ) is a top view showing the construction of the micro-reflector of the first preferred embodiment of the present invention. 
       FIG. 5  ( c ) is a sectional view showing the construction of the micro-reflector of the first preferred embodiment of the present invention. 
       FIG. 6  ( a ) is schematic view showing a light reflection plane cut from a sectional conic plane for supplementary explanation of the present invention. 
       FIG. 6  ( b ) is a side view showing the light reflection plane cut from a sectional conic plane for supplementary explanation of the present invention. 
       FIG. 7  is a schematic view showing a rear light pervious plane cut from a cylindrical surface for supplementary explanation of the present invention. 
       FIG. 8  ( a ) is a schematic view showing a light transport behavior in the micro-reflector. 
       FIG. 8  ( b ) is a side view of a light transport behavior in the micro-reflector. 
       FIG. 8  ( c ) is a side view of another light transport behavior in the micro-reflector. 
       FIG. 8  ( d ) is a side view of another light transport behavior yet in the micro-reflector. 
       FIG. 8  ( e ) is a front view of another light transport behavior yet in the micro-reflector. 
       FIG. 9  ( a ) is a radar view of the illuminating intensity of the light emitted from the light guide plate of the first preferred embodiment of the present invention. 
       FIG. 9  ( b ) is a perspective view of the illuminating intensity of the light emitted from the light guide plate of the first preferred embodiment of the present invention. 
       FIG. 10  is a schematic view showing a micro-reflector of a second preferred embodiment of the present invention. 
       FIG. 11  is a schematic view showing a micro-reflector of a third preferred embodiment of the present invention. 
       FIG. 12  is a schematic view showing a micro-reflector of a fourth preferred embodiment of the present invention. 
       FIG. 13  is a top view of a micro-reflector of a fifth preferred embodiment of the present invention. 
       FIG. 14  is a side view of a micro-reflector of a sixth preferred embodiment of the present invention. 
       FIG. 15  is a side view of a micro-reflector of a seventh preferred embodiment of the present invention. 
       FIGS. 16 ,  17 ,  18 ,  19 ,  20 , and  21  are top views of the distributions of the micro-reflectors on the light guide plate of the first preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 4  for a schematic view of a distribution of micro-reflectors  6  of a first preferred embodiment of the present invention on a light guide plate  1 A, rays of light emitting from a light source  4  radiate into an incidence plane  10 A of the light guide plate  1 A. Each micro-reflectors  6  is disposed in an arc recess on a bottom  12 A of the light guide plate  1 A to admit the rays of light to leave an illuminating plane  11 A to increase luminance of the light guide plate  1 A. 
   Now referring to  FIGS. 5(   a ) through  5 ( c ) for a perspective view, a side view and a sectional view of the micro-reflector  6 , the micro-reflector  6  is an arc recess and comprises a light reflection plane  601 , a rear light pervious plane  602 , two light pervious side planes  603 ,  604 , and a hollowed plane  605 . The light reflection plane  601  is a sectorial camber, cut along two cutting lines  702 ,  703  from a sectional conic plane as illustrated in  FIG. 6 . Radii and the height of the sectional cone are respectively designated by r 1  and r 2 , and h. As illustrated in  FIG. 5  ( b ), the cutting range commences from a sectional conic center “O” for an angle β with both cutting lines  702 ,  703  are in symmetrical to a central line  701  of the micro-reflector  6 , i.e., the cutting angle β is dichotomized by the central line  701 . The direction of the central line  701  toward the light reflection plane  601  is referred as a designated direction  8  for the micro-reflector  6 . Both light pervious side planes  603 ,  604  are sections cut by the cutting lines  702 ,  703 . The rear light pervious plane  602  is an arc camber. As illustrated in  FIG. 7 , the rear light pervious plane  602  is an arc camber cut along the two cutting lines  702 ,  703  from a cylindrical surface in radius r 2  and height h, wherein, the center of the cylinder and the conic center are located at the same position. The hollowed plane  605  is an arc and where the micro-reflector  6  creates the recess on the bottom  12 A of the light guide plate  1 A. As illustrated in  FIG. 5  ( b ), the sectional view of the micro-reflector  6  in  FIG. 5  ( c ) can be observed either viewed from a-a tangent plane, a′-a′, or a″-a″. Whereas the light reflection plane  601  is taken from a part of sectional conic plane, and the rear light pervious plane  602  is taken from a part of the cylindrical plane, all three sectional views are identical. An angle θ is defined by the light reflection plane  601  and the bottom  12 A (i.e., the hollowed plane  605  as illustrated) of the light guide plate  1 A. The angle θ controls variation of the light reflection plane  601  and affects the light transport behavior in the micro-reflector  6 . 
   As illustrated in  FIGS. 8(   a ) through  8 ( e ) for schematic views showing light transports in the micro-reflector  6 . The light may transport in any direction in the micro-reflector  6 . That&#39;s why the micro-reflector  6  is made in an arc shape so that there won&#39;t be too significant difference in the directions of rays of light radiate through the micro-reflector  6 . When an incidence light  50  travels in a direction closer to a line  704  between the conic center “O” and the incidence point, the incidence light  50  arrives at the light reflection plane  601  of the micro-reflector  6 , an incidence angle α is greater than 42°, a critical angle of the light guide plate  1 A (the refraction ratio of the light guide plate is 1.49) to reflect the incidence light to where above the reflection plane  601 , thus to increase the intensity of the illuminating light in a normal direction  13  as illustrated in  FIGS. 8  ( a ) and  8  ( b ). When the incidence angle α is less than the critical angle 42° of the light guide plate  1 A as illustrated in  FIG. 8  ( c ), the light will pass through a first micro-reflector  6  and arrive at a second micro-reflector  61  through the rear light pervious plane  602 , where the light is reflected to become reflection light  51  or passes through the second micro-reflector  61 . In either case, both light transport behavior are sufficient to increase the intensity of the illuminating light in HA direction. 
   Now referring to  FIGS. 8  ( d ) and  8  ( e ), when the direction of the incidence light  50  is away from the direction of the line  704  between the conic center “O” and the incidence point, the incidence light  50  upon arriving on the light reflection plane  601  will bounce back sideways to become the reflection light  51 , thus to increase the intensity of the illuminating light in VA direction. 
     FIGS. 9(   a ) and  9 ( b ) are a radar view and a perspective view of the illuminating light from the light guide plate  1 A having the micro-reflectors  6  of the first preferred embodiment. The light enters from the light source  4  into the light guide plate  1 A provided with the micro-reflectors  6  to contact the micro-reflectors  6  and transport in the direction  13  of the illuminating light at an angle essentially concentrating at HA=25° and VA=3°. The angle θ of elevation of the micro-reflector changes the illuminating angle and distribution of the light in HA direction and the central angle β controls the illuminating distribution of the light in VA direction. 
   In a second preferred embodiment as illustrated in  FIG. 10 , a micro-reflector  6 A is a sector and includes a light reflection plane  601 A, a rear light pervious plane  602 A, two light pervious side planes  603 A,  604 A, and a hollowed plane  605 A. The light reflection plane  601 A is a sectorial camber taken from a cone. 
     FIG. 11  shows a construction of a micro-reflector  6 B of a third preferred embodiment of the present invention. The micro-reflector  6 B is an arc recess and includes a light reflection plane  601 B, a rear light pervious plane  602 B, two light pervious side planes  603 B,  604 B, and a hollowed plane  605 B. The light reflection plane  601 B is an arc camber and protrudes towards a light guide plate  1 C. When viewed from the light guide plate  1 C toward the direction of the hollowed plane  605 B, the light reflection plane  601  B of the third preferred embodiment is taken from the sectional conic plane having a narrow upper part and a wide lower part, while the light reflection plane  601  of the micro-reflector  6  of the first preferred embodiment is taken from the sectional conic plane having a wide upper part and a narrow lower part. 
   In a fourth preferred embodiment of the present invention as illustrated in  FIG. 12 , a micro-reflector  6 C is a sectorial construction including a light reflection plane  601 C, two light pervious side planes  603 C,  604 C, and a hollowed plane  605 C. The light reflection plane  601 C is a sectorial camber protruding toward a light guide plate  1 D and does not have a rear light pervious plane since it is taken from a sharp cone. 
     FIG. 13  is a top view of a micro-reflector  6 D of a fifth preferred embodiment of the present invention. A light reflection plane  601 D indicates an elliptic arc or sector. Two light pervious side planes  603 D,  604 D are plotted by two cutting lines  702 D,  703 D from an elliptic focus outwardly, and are vertical to tangents of the elliptic lines. 
   As illustrated in  FIG. 14  for a side view of a micro-reflector  6 E of a sixth preferred embodiment of the present invention, a light reflection plane  601 E when observed sideways indicates a convex curve. As illustrated in  FIG. 15  for a side view of a micro-reflector  6 F of a seventh preferred embodiment of the present invention, a light reflection plane  601 F when observed sideways indicates a concave curve. 
   When comparing the second through the seventh preferred embodiments with the first preferred embodiment, light transport distribution varies depending on the camber taken for each of the light reflection planes  601 , and  601 A˜ 601 F. In general, all the behaviors of light transport among the micro-reflectors  6 , and  6 A˜ 6 F are similar to contribute to promote luminance and consistence of the light guide plate. 
     FIGS. 16 through 21  are top views of the distribution of the micro-reflectors of the first preferred embodiment on the light guide plate.  FIG. 16  is a top view taken from  FIG. 4 . The micro-reflectors  6  indicate regular distribution on the light guide plate  1 A and head in the same direction  8  that faces the light source  4  to facilitate incidence of light to radiate into the micro-reflectors to increase luminance. 
   The micro-reflectors  6  also indicate regular distribution on a light guide plate  1 A 1  as illustrated in  FIG. 17 . Though they don&#39;t point at the same direction  8 , they in generally tend to face in the direction of the light source  4  to achieve the same purpose of increasing luminance. 
   In  FIG. 18 , the micro-reflectors  6  are distributed at random on a light guide plate  1 A 2  heading for the same direction  8  toward the light source  4  to facilitate incidence of light to radiate into the micro-reflectors to increase luminance. 
   The micro-reflectors  6  also indicate distribution at random on a light guide plate  1 A 3  as illustrated in  FIG. 19 . Though they don&#39;t point at the same direction  8 , they in generally tend to face in the direction of the light source  4  to achieve the same purpose of increasing luminance. 
   As illustrated in  FIG. 20 , the micro-reflectors  6  indicate regular distribution on a light guide plate  1 A 4  and the direction  8  of all or certain parts of the micro-reflectors  6  head for point-like light sources  41  to facilitate incidence of light to radiate into the micro-reflector to increase luminance. 
   The micro-reflectors  6  indicate distribution at random on a light guide plate  1 A 5 , as illustrated in  FIG. 21 , and the direction  8  of all or certain parts of the micro-reflectors  6  head for point-like light sources  41  to facilitate incidence of light to radiate into the micro-reflectors to increase luminance. 
   In  FIGS. 16˜21 , the micro-reflectors  6  may be any single or combination of those preferred embodiments. Any distribution of the micro-reflectors facilitates incidence of light to radiate into the micro-reflectors to increase luminance and the light guide plate to produce highly consistent light illuminating of plane type. 
   The present invention by promoting luminance and consistence of the light guide plate improves performance of LCD and helps LCD save power consumption. It is to be noted that any change, substitute and replacement may be made without departing from the scope and teaching of the present invention as defined by the claims to be claimed in this application.