Patent Publication Number: US-2007097710-A1

Title: Light guide plate having micro-reflectors

Description:
BACKGROUND OF THE INVENTION  
      (a) Field of the Invention  
      The present invention relates to a light guide plate having micro-reflectors, and more particularly, to a micro-reflector shaped like a pyramid 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 conventional light guide plate  1 , the micro-reflector  2  with rough surface is created by using an etching method on a bottom  12  of the smooth light guide plate  1 . The 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 surface  11  of the light guide plate  1  when the angle of incidence of the reflected rays  51  is smaller than the critical angle; or the reflected rays  51  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. 3 ( a ) is a radar view of illuminating intensity of the rays of light leaving the illuminating surface  11  of the light guide plate  1 , and  FIG. 2  interprets those coordinates appearing in  FIG. 3 ( a ). Wherein, the abscissa indicates a horizontal angle (HA) with the movement of angle turns from a normal direction  13  of the illuminating surface  11  into a direction  14  vertical to a light source  4 ; meanwhile, the ordinate indicates a vertical angle (VA) with the movement of angle turns from the normal direction  13  of the illuminating surface  11  into a direction  15  in parallel with the light source  4 .  
      As illustrated in  FIG. 3 ( a ), each closed curve represents the illuminating intensity defined as the luminous flux of unit solid angle. There are ten closed curves illustrated in  FIG. 3 ( a ) representing ten grades of illuminating intensity. The distribution of the illuminating intensity from the light guide plate  1 , as shown in  FIG. 3 ( a ), approximates a Lambertian distribution; that is, closed curves in circles are produced with the illuminating intensity showing 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 surface  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 both micro-reflectors disclosed in U.S. Pat. Nos. 6,746,129 and 6,894,740 is shaped like a quadrangle-pyramid with the front two inclined planes abutted to each other of the quadrangle-pyramid facing the light source and the incident light continues to reflect on both abutted inclined planes to illuminate. Wherein, as taught in U.S. Pat. No. 6,746,129 a point-like light source is adapted and the micro-reflector is distributed at the light guide plate; and in U.S. Pat. No. 6,894,740, a linear light source is adapted with its both ends respectively provided with a point-like light source.  
      In general, the quadrangle-pyramid structure is comparatively more complicated; and in practice, those two abutted inclined planes among four abutted four inclined planes give insignificant illuminating results.  
     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 shaped like a pyramid externally protruding from the bottom of the light guide plate to effectively increase the rays of light emitting toward an illuminating surface of the light guide plate and the luminance of the light guide plate.  
      To achieve the purpose, each of the micro-reflectors of the light guide plate of a preferred embodiment of the present invention is shaped like a pyramid disposed on and externally protruding from the bottom of the light guide plate. The pyramid includes a transparent plane and two reflection plans. The transparent plane is disposed at right angle to the bottom of the light guide plate, facing and comparatively nearer to the light source. The reflection planes are disposed at a certain inclination to the bottom of the light guide plate, facing the illuminating surface of the light guide plate and comparatively farther from the light source.  
      Both reflection planes cut each other with the cutting line referred to their direction on the light guide plate that is in parallel with the direction of the rays of light emitting from the light source. Alternatively, the cutting line of both reflection planes cutting each other tends to but not exactly in parallel with that of the rays of light emitting from the light source.  
      The micro-reflectors are regularly arranged on the light guide plate or at random.  
      The micro-reflectors are arranged on the light guide plate at random.  
      The structure of the micro-reflectors of the present invention is simple and the light guide direction is exact, allowing simulation and design roadmap in advance, and easier cost and quality control.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic view showing a micro-reflector of a conventional light guide plate.  
       FIG. 2  is a schematic view showing the illuminating light from an illuminating surface of the conventional light guide plate (that also explains the coordinates given in  FIGS. 3 ).  
       FIG. 3 ( a ) is a radar view of the illumination intensity from the illuminating surface of the conventional light guide plate.  
       FIG. 3 ( b ) is a perspective view of the illumination intensity from the illuminating surface of the conventional light guide plate.  
       FIG. 4 ( a ) is a side view of micro-reflectors of a preferred embodiment of the present invention applied in a light guide plate.  
       FIG. 4 ( b ) is an upward view of the micro-reflectors of the preferred embodiment of the present invention applied in the light guide plate (also as a first preferred embodiment of the present invention showing the distribution of the micro-reflectors of the present invention applied in the light guide plate).  
       FIG. 5 ( a ) is a perspective view of the micro-reflector of the preferred embodiment of the present invention.  
       FIG. 5 ( b ) is an upward view of the micro-reflector of the preferred embodiment of the present invention.  
       FIG. 5 ( c ) is a top view of the micro-reflector of the preferred embodiment of the present invention.  
       FIG. 5 ( d ) is a side view of the micro-reflector of the preferred embodiment of the present invention.  
       FIG. 6 ( a ) is a perspective view of the conveyance behavior of the light through the micro-reflector of the preferred embodiment of the present invention  
       FIG. 6 ( b ) is a top view of the conveyance behavior of the light through the micro-reflector of the preferred embodiment of the present invention  
       FIG. 6 ( c ) is a side view of the conveyance behavior of the light through the micro-reflector of the preferred embodiment of the present invention.  
       FIG. 7  is a radar view of the distribution of the illuminating intensity of those rays of light emitting through the micro-reflectors of the preferred embodiment of the present invention with angles β and θ as the parameters.  
       FIG. 8  is a perspective view of the illuminating intensity of those rays of light emitting through the micro-reflectors of the preferred embodiment of the present invention with angles β=50° and θ=30° as the parameters.  
       FIG. 9  is a perspective view of the illuminating intensity of those rays of light emitting through the micro-reflectors of the preferred embodiment of the present invention with angles β=40° and θ=10° as the parameters.  
       FIG. 10  is a perspective view of the illuminating intensity of those rays of light emitting through the micro-reflectors of the preferred embodiment of the present invention with angles β=60° and θ=20° as the parameters.  
       FIG. 11  is a view of a second preferred embodiment of the present invention showing the distribution of the micro-reflectors on the light guide plate.  
       FIG. 12  is a view of a third preferred embodiment of the present invention showing the distribution of the micro-reflectors on the light guide plate.  
       FIG. 13  is a view of a fourth preferred embodiment of the present invention showing the distribution of the micro-reflectors on the light guide plate.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 4 ( a ) is a schematic view of micro-reflectors  6  of a first preferred embodiment of the present invention applied in a light guide plate  1 A. The light guide plate  1 A comprises a plurality of micro-reflectors  6  disposed on a bottom  12 A of the light guide plate  1 A. Each micro-reflector  6  is shaped like a pyramid externally protruding from the bottom  12 A of the light guide plate  1 A to effective upgrade rays of light emitting from an illuminating surface  11 A of the light guide plate  1 A to increase its luminance.  
       FIG. 4 ( b ) is a view of the first preferred embodiment showing the distribution of the micro-reflectors  6  on the light guide plate  1 A. The micro-reflectors  6  are arranged in regular while all the micro-reflectors  6  indicate a direction  7  completely in parallel with the rays of light emitted from a linear light source  4 . Rays of light emitted from the linear light source  4  enter into the light guide plate  1 A to generate highly consistent of luminance in plane fashion.  
      Referring to FIGS.  5 ( a ) through  5 ( d ) respectively for a perspective view, an upward view, a top view and a side view of the micro-reflector  6  of the preferred embodiment of the present invention, the micro-reflector  6  is shaped like a pyramid and comprises a transparent plane  601 , and two reflection planes  602 ,  603 . The transparent plane  601  is disposed at right angle to the bottom  12 A of the light guide plate  1 A, facing and comparatively nearer to the light source  4 . Both the reflection planes  602 ,  603  are inclined to the bottom  12 A of the light guide plate  1 A, facing the illuminating surface  11 A of the light guide plate  1 A and comparatively farther from the light source  4 . Both the reflection planes  602 ,  603  are capable of changing the forward direction of the rays of light on the light guide plate  1 A. Once rays of light enter into the micro-reflectors  6 , both the reflection planes  602 ,  603  reflect them upward to increase the luminance of the light guide plate  1 A.  
      As illustrated in FIGS.  5 ( c ) and  5 ( d ), an angle β defined by two bases  611 ,  612  where both the reflection planes  602 ,  603  connect to the bottom  12 A of the light guide plate  1 A, and an angle θ defined by a sharp edge  613  where both the reflection planes  602 ,  603  meet are capable of changing the inclination of both the reflection planes  602 ,  603  that affects most the distribution of intensity of rays of light emitting upward. The sharp edge  613  where both the reflection planes  602 ,  603  meet points out the direction  7  of the micro-reflectors  6  as illustrated in  FIG. 4 ( b ).  
      As illustrated in FIGS.  6 ( a ) through  6 ( c ) for a schematic view of the conveyance of rays of light  5  through the micro-reflectors  6 , rays of light  5  upon entering into the reflection plane  602  are reflected to another reflection plane  603 , where rays of light  5  emit upward. Similarly, rays of light  5  upon entering into the reflection plane  603  emit upward through the reflection plane  602 . Angle θ affects the longitudinal inclination (in the direction of Z-axis) of each of the reflection planes  602 ,  603  to affect the variation of the light intensity on the HA while angle β affects the inclination in lateral direction of the reflection planes  602 ,  603  (in the direction of Y-axis) to affect the variation of the light intensity on the VA.  
       FIG. 7  shows a radar view of the distribution of the illuminating intensity after rays of light having entered into the micro-reflectors  6  with angles β and θ as the parameters. The inventor of the present invention has located on a model designed with the preferred embodiment of the present invention the optimal combinations of angles β and θ that yield the distribution of high illuminating intensity. In the group of design parameters, angle β respectively relates to 30°, 40°, 50°, and 60° while that of angle θ, 10°, 20°, 30°, and 40°. This inventor using ASAP optical software to simulate those parameters has solved that the distribution of high illuminating intensity takes place when angle β is of 50° or 60° and angle θ is of 30°. As illustrated in  Fig. 8 , rays of light collectively emit in the direction  13 , meaning the maximal illuminating intensity is measured in the direction  13  of the normal (VA=0° and HA=0°). When angle θ=10°, rays of light collect at where VA=60° as illustrated in  FIG. 9 . When angle θ=20°, rays of light collect at where VA=60°, and fork distribution of the illuminating intensity is observed in the vicinity of HA=±30˜40° as illustrated in  FIG. 10 . Accordingly, variations in angles β and θ affect the illuminating intensity distribution on the illuminating surface  11 A of the light guide plate  1 A.  
      Now referring to  FIG. 4 ( b ) for the array of the micro-reflectors  6  of the present invention on the light guide plate  1 A, in the first preferred embodiment of the distribution, the micro-reflectors  6  distributed on the light guide plate  1 A are arranged regularly with the direction  7  of the micro-reflectors  6  is in parallel with that of rays of light emitted from the linear light source  4 . Rays of light when emitted by the linear light source  4  enter into the light guide plate  1 A and produce a plane light source with highly consistent luminance.  
      As illustrated in  FIG. 11  for a second preferred embodiment of the micro-reflectors  6  of the present invention distributed on a light guide plate  1 B, the micro-reflectors  6  are also regularly arranged but the direction  7  is not exactly in parallel with that of rays of light emitted from the linear light source  4 ; however, in generally, the direction  7  of the micro-reflectors  6  tends to be in parallel with that of rays of light emitted from the linear light source  4 . Rays of light emitted from the linear light source  4  enter into the light guide plate  1 B and produce a plane light source with highly consistent luminance.  
      In a third preferred embodiment of the present invention as illustrated in  FIG. 12 , the micro-reflectors  6  are distributed at random on a light guide plate  1 C to indicate the direction  7  in parallel with that of rays of light emitted from the linear light source  4 . Rays of light emitted from the linear light source  4  enter into the light guide plate  1 C and produce a plane light source with highly consistent luminance.  
      In a fourth preferred embodiment of the present invention as illustrated in  FIG. 13 , the micro-reflectors  6  are also distributed at random on a light guide plate  1 D to indicate the direction  7  not exactly in parallel with that of rays of light emitted from the linear light source  4 . However, in generally, the direction  7  of the micro-reflectors  6  tends to be in parallel with that of rays of light emitted from the linear light source  4 . Rays of light emitted from the linear light source  4  enter into the light guide plate  1 D and produce a plane light source with highly consistent luminance.  
      Other than the linear light source, e.g., cold cathode tube, applied for those four preferred embodiments described above, multiple point-like light sources, e.g., light emitting diodes may be used as the light source for the arrangement and direction similar to any of those preferred embodiments.