Abstract:
A light emitting diode (LED) device comprises a substrate, an LED chip and an encapsulation body. The LED chip is mounted on the substrate, and the encapsulation body is overlaid on the LED chip and the substrate. The encapsulation body includes a light output surface. The light output surface can uniformly diffuse emission light over a wide angle in a first direction and concentrate the emission light in a second direction perpendicular to the first direction.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a light emitting diode device and a backlight module, and relates more particularly to a light emitting diode device with improved light emission distribution and a backlight module using the same. 
         [0003]    2. Description of the Related Art 
         [0004]    Because light emitting diodes (LED) have characteristics such as low power consumption, high conversion efficiency and extended lifetimes, and they can exhibit excellent color performance when used in backlight modules, the application of light emitting diodes in display devices has become a focus of much research in recent years. 
         [0005]    Backlight modules are categorized according to the position of the module, including direct-lit backlight modules and edge-lit backlight modules. At present, the major apparatuses using liquid crystal displays are notebook computers and other liquid crystal display screens, and the requirements of the backlight modules used in these apparatuses are light weight, small volume, and thin profile. Of the two types of modules, the edge-lit backlight modules can best meet these requirements. 
         [0006]      FIG. 1  is a cross sectional view showing a light emitting diode package disclosed in Taiwan Patent Publication No. 200733425. The LED package  10  includes a housing  10  and a seating recess  11  formed on the upper portion of the housing  10 ; an LED  12  seated on the bottom of the seating recess  11 ; and a lens  13  disposed on the upper side of the seating recess  11 . The light emitted from the LED  12  passes through the lens  13  having a convex surface that can redirect light over large angles so that the redirected light can laterally emit. However, such an LED  12  is suitable for direct-lit backlight modules, not for edge-lit backlight modules. 
         [0007]    In addition, as shown in  FIG. 2 , Taiwan Patent Publication No. 200512500 discloses an LED package suitable for an edge-lit backlight module. The LED package  20  includes a base  21 , a light emitting diode  22 , and an encapsulation resin  23 . The encapsulation resin  23  encases the light emitting diode  22  and is formed to have a light output surface (not shown) similar to a hemispherical surface, and a diffraction grating  24  including a plurality of grooves is disposed on the light output surface to similarly increase the refraction angle of emitted light. Although such a hemispherical light output surface can distribute light uniformly, the hemispherical light output surface cannot concentrate light in the thickness-wise direction (i.e. the direction perpendicular to the light output surface) to meet the requirements of an edge-lit backlight module, and therefore light beams having a large emitting angle relative to a central axis cannot be directed into the interior of the backlight from the side thereof. Further, the groove structure of the diffraction grating  24  is unfavorable to a press-molding process. Specifically, melt molding material cannot easily fill the grooves completely, and during the demolding operation, the protruding portions between the grooves can easily be damaged. 
         [0008]    Taiwan Patent No. 1287126 provides an LED package for a direct-lit backlight module, and a light guide plate mated with the LED package and having a concavity formed on a bottom surface, for accommodating the LED package. The point light source of the LED package is received within the concavity, and a semi-transparent and semi-reflective film is further disposed between the light guide plate and the point light source. With the characteristics of the penetration ratio of light of the semi-transparent and semi-reflective film that is inversely proportional to the distance between the point light source and the film, the light entering into the light guide plate can be diffused as uniformly as possible. However, such a semi-transparent and semi-reflective film is not easy to manufacture, and it may absorb a portion of passing light so as to lower light utilization efficiency. 
         [0009]    U.S. Pat. No. 6,953,952 proposes a semiconductor device adapted for edge-lit backlight module and packaged using a lead-frame. Although the semiconductor device is shaped to be tightly embedded into a side of a light guide plate, the process using a lead-frame to package a semiconductor device is complex and results in higher manufacturing cost. Furthermore, the lengths of light paths in different directions are significantly different so that light passing through different paths may encounter different amounts of phosphorous particles. Consequently, the uniformity of light from the light output surface may be poor. 
         [0010]    In summary, the manufacture of a light emitting diode having improved light emission efficiency remains an urgent research target in the lighting industry. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention proposes a light emitting diode device and a backlight module. The light emitting diode device has an outline configuration that can improve light emission distribution, and that can uniformly diffuse over a wide angle and concentrate emission light along two perpendicular directions. Furthermore, in a backlight module, light entering the light guiding plate of the backlight module increases such that the non-uniformity of light distribution at the light entrance side of the light guiding plate can be eliminated. 
         [0012]    To solve the prior art issues, the present invention provides the following solution: a light emitting diode device comprises a substrate, a light emitting diode chip and an encapsulation body. The light emitting diode chip is mounted upon a surface of the substrate. The encapsulation body is coated on the light emitting diode chip and the substrate. The encapsulation body includes a light output surface, wherein the light output surface is parallel to the surface of the substrate, and the light output surface can uniformly diffuse emission light over a wide angle in a first direction and concentrate the emission light in a second direction perpendicular to the first direction, wherein the two directions perpendicular to the surface of the substrate. 
         [0013]    The encapsulation body includes two shoulder portions respectively disposed on two ends of the light output surface. 
         [0014]    The light output surface comprises at least one curved surface, and the curved surface is a semi-cylindrical surface, or the light output surface may comprise a plurality of continuously connected curved surfaces. 
         [0015]    The light output surface includes a plurality of planes. The light output surface is a triangular prism with two adjacent inclines. 
         [0016]    The distances between each position on the light output surface and the light emitting diode chip are approximately equal. 
         [0017]    The light emitting diode device further comprises two end surfaces adjacent to the light output surface, and the two end surfaces are perpendicular to the surface of the substrate. 
         [0018]    The light emitting diode device further comprises reflecting layers disposed on the two end surfaces. 
         [0019]    The present invention provides a backlight module, which comprises a light emitting diode device and a light guiding plate. The light emitting diode device comprises a substrate, a light emitting diode chip and an encapsulation body. The light emitting diode chip is mounted upon a surface of the substrate. The encapsulation body is coated on the light emitting diode chip and the substrate. The encapsulation body includes a light output surface, wherein the light output surface is parallel to the surface of the substrate, and the light output surface can uniformly diffuse emission light over a wide angle in a first direction and concentrate the emission light in a second direction perpendicular to the first direction, wherein the two directions perpendicular to the surface of the substrate. A lateral side of the light guide plate includes at least one recess, wherein the recess can engage with the light output surface. 
         [0020]    The light emitting diode device further comprises two shoulder portions respectively disposed on two ends of the light output surface. 
         [0021]    The shape of the recess is complementary to the shape of the light output surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The invention will be described according to the appended drawings in which: 
           [0023]      FIG. 1  is a cross sectional view showing a light emitting diode package disclosed in Taiwan Patent Publication No. 200733425; 
           [0024]      FIG. 2  shows an LED package suitable for an edge-lit backlight module disclosed in Taiwan Patent Publication No. 200512500; 
           [0025]      FIG. 3A  is a perspective view showing a light emitting diode device according to the first embodiment of the present invention; 
           [0026]      FIG. 3B  is a cross section taken along line A-A in  FIG. 3A ; 
           [0027]      FIG. 3C  is a cross section taken along line B-B in  FIG. 3A ; 
           [0028]      FIG. 4A  is a perspective view showing a light emitting diode device according to the second embodiment of the present invention; 
           [0029]      FIG. 4B  is a cross section taken along line C-C in  FIG. 4A ; 
           [0030]      FIG. 4C  is a cross section taken along line D-D in  FIG. 4A ; 
           [0031]      FIG. 5A  is a perspective view showing a backlight module according to one embodiment of the present invention; 
           [0032]      FIG. 5B  is a perspective view showing a backlight module according to another embodiment of the present invention; 
           [0033]      FIG. 6  is a perspective view of a light emitting diode chip according to the third embodiment of the present invention; 
           [0034]      FIG. 7A  is a perspective view of a light emitting diode chip according to the fourth embodiment of the present invention; 
           [0035]      FIG. 7B  is a perspective view of a light emitting diode chip according to the fifth embodiment of the present invention; 
           [0036]      FIG. 8A  is a perspective view of a light emitting diode chip according to the sixth embodiment of the present invention; 
           [0037]      FIG. 8B  is a perspective view of a light emitting diode chip according to the seventh embodiment of the present invention; 
           [0038]      FIG. 9A  is a perspective view of a light emitting diode chip according to the eighth embodiment of the present invention; 
           [0039]      FIG. 9B  is a perspective view of a light emitting diode chip according to the ninth embodiment of the present invention; and 
           [0040]      FIGS. 10A and 10B  show angular distributions of scattered light from a light emitting diode chip according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    Referring to  FIG. 3A , according to one embodiment of the present invention, the light emitting diode device  30  comprises a substrate  31  and an encapsulation body  32 . The encapsulation body  32  has an upper surface that includes a non-planar light output surface  321 . As shown in  FIG. 3A , the semi-cylindrical light output surface  321  may tend to scatter emitted light at larger angles. In other words, light emitted from the light output surface  321  may become more uniform. Cross-sections of the encapsulation body  32  along the Y-axis direction parallel to the XZ plane are substantially identical, and two end surfaces of the encapsulation body  32  are also parallel to the XZ plane. Therefore, emission light is concentrated within a specified angle in the Y-axis direction. 
         [0042]      FIG. 3B  is a cross section taken along line A-A in  FIG. 3A . The light emitting diode device  30  further comprises a light emitting diode chip  33  and at least one metal wire  34 . The light emitting diode chip  33  is mounted on the surface of the substrate  31 , and the encapsulation body  32  covers the light emitting diode chip  33  and the substrate  31 . The metal wire  34  is configured to electrically connect the light emitting diode chip  33  to the substrate  31 . In the encapsulation body  32 , phosphorus particles  36  are evenly mixed. Light, emitted from a light-emitting region on the surface of the light emitting diode chip  33 , penetrating through the light output surface  321  passes through paths having similar lengths in different directions such that the light propagating through each light path may encounter similar amounts of phosphorus particles. The semi-cylindrical light output surface  321  of the present invention can result in uniform light distribution. More specifically, the distance from every position on the light output surface  321  to the central position of the light emitting diode chip  33  is approximately equal. 
         [0043]      FIG. 3C  is a cross section taken along line B-B in  FIG. 3A . The two end surfaces of the encapsulation body  32  can be coated with a reflective layer  35 . Because the two end surfaces are planes perpendicular to the surface of the substrate  31 , the view angle of the light emitted from the light emitting diode chip  33  along the Y direction can be further constrained. 
         [0044]    As shown in  FIG. 4A , according to one embodiment of the present invention, the light emitting diode device  40  comprises a substrate  31  and an encapsulation body  42 . The encapsulation body  42  has an upper surface that includes a non-planar light output surface  421 . As shown in  FIG. 4A , the light output surface  421  on the configuration of a semi-elliptical cylinder may tend to scatter emitted light at larger angles. In other words, light emitted from the light output surface  421  may become more uniform. Cross-sections of the encapsulation body  42  along the Y-axis direction parallel to the XZ plane are substantially identical, and two end surfaces of the encapsulation body  42  are also parallel to the XZ plane. Therefore, emission light is concentrated within a specified angle in the Y-axis direction. The encapsulation body  42  includes two shoulder portions  422  disposed on the two sides thereof respectively and configured to provide support for installation. 
         [0045]      FIG. 4B  is a cross section taken along line C-C in  FIG. 4A . The light emitting diode device  40  further comprises a light emitting diode chip  33  and at least one metal wire  34 . The light emitting diode chip  33  is mounted on the surface of the substrate  31 , and the encapsulation body  42  covers the light emitting diode chip  33  and the substrate  31 . The metal wire  34  is configured to electrically connect the light emitting diode chip  33  to the substrate  31 . In the encapsulation body  42 , phosphorus particles  36  are evenly mixed. Light, emitted from a light-emitting region on the surface of the light emitting diode chip  33 , penetrating through the light output surface  421  passes through paths having similar lengths in different directions such that the light propagating through each light path may encounter similar amounts of phosphorus particles. The non-planar light output surface  421  of the present invention can result in uniform light distribution. More specifically, the distance from every position on the light output surface  421  to the central position of the light emitting diode chip  33  is approximately equal. 
         [0046]      FIG. 4C  is a cross section taken along line D-D in  FIG. 4A . The two end surfaces of the encapsulation body  42  can be coated with a reflective layer  45 . Because the two end surfaces are planes perpendicular to the surface of the substrate  31 , the view angle of the light emitted from the light emitting diode chip  33  along the Y direction can be further constrained. 
         [0047]      FIG. 5A  is a perspective view showing a backlight module according to one embodiment of the present invention. The backlight module  50  comprises a plurality of light emitting devices  30  and a light guide plate  51 , one lateral side  511  of which includes a plurality of recesses  512  each having a configuration complementarily mated with the outline of the light output surface  321  on an encapsulation body  32 . Namely, the light output surface  321  can remain close to the interior of the respective recess  512  and the substrate  31  may also be firmly placed against the lateral side  511  at the same time. 
         [0048]      FIG. 5B  is a perspective view showing a backlight module according to another embodiment of the present invention. The backlight module  50 ′ comprises a plurality of light emitting devices  40  and a light guide plate  51 ′, one lateral side  511 ′ of which includes a plurality of recesses  512 ′ each having a configuration complementarily mated with the outline of the light output surface  421  and the shoulder portions  422  of an encapsulation body  42 . Namely, the light output surface  421  and the shoulder portions  422  can remain close to the configuration of the respective recess  512 ′. 
         [0049]      FIG. 6  is a perspective view of a light emitting diode chip according to another embodiment of the present invention. The light emitting diode chip  60  comprises a substrate  31  and an encapsulation body  62 . The encapsulation body  62  has an upper surface that includes a non-planar light output surface  621 . As shown in  FIG. 6 , the semi-cylindrical light output surface  621  may tend to scatter emitted light at larger angles. In other words, light emitted from the light output surface  621  may become more uniform. Two shoulder portions  622  with respective inclines are disposed correspondingly on the two sides of the encapsulation body  62  and are configured to provide support for installation. 
         [0050]    Compared to the embodiments in  FIGS. 3A and 6 , the light output surfaces  721  of the encapsulation body  72  of the light emitting diode chip  70  in  FIG. 7A  define a triangular prism-like shape, which has two inclines causing uniform distribution of emitted light. The encapsulation body  72  is attached to the surface of the substrate  31 . 
         [0051]    Referring to  FIG. 7B , the light output surfaces  721 ′ of the light emitting diode chip  70 ′ define a triangular prism-like shape, and the two sides of the encapsulation body  72 ′ are disposed respectively with shoulder portions  722 ′. The encapsulation body  72 ′ is attached to the surface of the substrate  31 . 
         [0052]      FIG. 8A  is a perspective view of a light emitting diode chip according to the sixth embodiment of the present invention. The contour of the light emitting output surface  821  of the encapsulation body  82  of the light emitting diode chip  80  shown in the figure is composed of a plurality of continuously connected circular arcs, and the circular arc-shaped curve surfaces can uniformly distribute light over forward angles. The encapsulation body  82  is attached to the surface of the substrate  31 . 
         [0053]    Moreover, referring to  FIG. 8B , the contour of the light emitting output surface  821 ′ of the light emitting diode chip  80 ′ is composed of a plurality of continuously connected circular arcs, and the two sides of the encapsulation body  82 ′ are respectively disposed with right-angle shoulder portions  822 ′, which are configured to provide support for installation. The encapsulation body  82 ′ is attached to the surface of the substrate  31 . 
         [0054]      FIG. 9A  is a perspective view of a light emitting diode chip according to the eighth embodiment of the present invention. The contour of the light emitting output surface  921  of the encapsulation body  92  of the light emitting diode chip  90  shown in the figure is composed of a plurality of continuously connected planes, the planes each having different inclined angles that can uniformly distribute light over forward angles. The encapsulation body  92  is attached to the surface of the substrate  31 . 
         [0055]    Referring to  FIG. 9B , the contour of the light emitting output surface  921 ′ of the light emitting diode chip  90 ′ is composed of a plurality of continuously connected planes. The two sides of the encapsulation body  92 ′ are respectively disposed with right-angle shoulder portions  922 ′, which are configured to provide support for installation. The encapsulation body  92 ′ is attached to the surface of the substrate  31 . 
         [0056]      FIGS. 10A and 10B  show angular distributions of scattered light from a light emitting diode chip according to one embodiment of the present invention. As shown in the figures, the light beam  91  passing through the light output surface  321  travels over a wider angle (about 90 degrees to 180 degrees), and the observed light distribution is uniform at every degree of angle. Compared to the curved surface in  FIG. 10A , the light, as shown in  FIG. 10B , emitted from the light output surface travels over a constrained angle (less than about 60 degrees). 
         [0057]    The above-described embodiments of the present invention are intended to be illustrative only. Numerous alternative embodiments may be devised by persons skilled in the art without departing from the scope of the following claims.