Patent Document

[0001]    This application is a continuation application of pending U.S. patent application Ser. No. 12/003,880 filed Jan. 3, 2008 (of which the entire disclosure of the pending, prior application is hereby incorporated by reference). 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a light-emitting device, and more particularly to a side emitting light-emitting device and the application thereof. 
       REFERENCE TO RELATED APPLICATION 
       [0003]    This application claims the right of priority based on TW application Ser. No. 096100867, filed Jan. 9, 2007; and TW application Ser. No. 096112300, filed Apr. 4, 2007, and the contents of which are hereby incorporated by reference. 
       DESCRIPTION OF BACKGROUND ART 
       [0004]      FIG. 10  illustrates a lateral cross section of a known side view light-emitting diode  50 , including a base  51 , a chip  53  mounted on the base  51 , a upper sidewall  52 A and a bottom sidewall  52 B for blocking and/or reflecting light from the chip  53  (some types of light-emitting diodes have right and left sidewalls), and filling material  54 . 
         [0005]    Light striking the sidewalls  52 A and  52 B at about 90 degree (as shown by the arrow) likely moves back and forth between the chip  53  and the upper sidewall  52 A, and/or the chip  53  and bottom sidewall  52 B, and accordingly is confined within the light-emitting diode. Furthermore, due to the miniaturizing light-emitting diode  50 , the light penetrating the decreasing thickness may result in a leakage. In practice, by above reason or others, the light extraction efficiency of a packaged chip likely drops 40% in comparison with a bare chip. 
         [0006]    Moreover, the decreasing spacing between the sidewalls of the miniaturizing light-emitting diode also causes the difficulty in filling the space with the filling material  54  and generates voids accordingly. Therefore, the light may be trapped inside the voids, and the light extraction efficiency is reduced. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    A light-emitting device according to the present invention includes a light channel formed on a base, and a light-emitting unit, wherein the light channel includes an upper surface, a lower surface opposite to the upper surface, an inner surface intersecting with the upper surface and the lower surface at different intersecting angles, and a light output surface opposite the inner surface; and the light-emitting unit is on the inner surface and emits light to propagate inside the light channel towards the light output surface. 
         [0008]    The light-emitting device according to the present invention further includes a first reflecting layer covering the inner surface, a conducting layer covering the first reflecting layer and electrically connecting to the light-emitting unit, and a second reflecting layer on a side opposite to the lower surface. The preferable embodiment further discloses an insulating layer between the first reflecting layer and the conducting layer. The light channel can be filled with a filling material. 
         [0009]    In one embodiment, the light output surface is substantially parallel to the inner surface, or perpendicular to at least one of the upper surface and the lower surface, or intersects with the upper surface and the lower surface at different intersecting angles. The light output surface may be a curved surface. Optionally, the upper surface is substantially parallel to the lower surface. In addition, at least a portion of the inner surface or the lower surface may be a curved surface. A cut is formed on the fringe of the upper surface in order to avoid metallic residuals generated during wafer cutting, or the sidewall of the light-emitting unit being polluted by the overflowed solder. 
         [0010]    In another embodiment, the conducting layer includes a first conducting layer and a second conducting layer. The light-emitting unit has electrodes electrically connecting to the first conducting layer and the second conducting layer respectively. 
         [0011]    Furthermore, the light-emitting unit emits two or more colors of lights, or red, blue and green lights. The light-emitting device further includes a wavelength converting material for receiving light from the light-emitting unit and generating excited light. In one embodiment, the wavelength converting material overlays directly on the light-emitting unit. 
         [0012]    The light-emitting device of the present invention can be coupled to a display, and a light guide plate is used to receive light from the light-emitting unit and change its direction. The contour of the light input surface of the light guide plate corresponds preferably to that of the light output surface. Specifically speaking, the light-emitting device further includes a reflecting layer on a side of the light guide plate for reflecting light, an optical film, and a liquid crystal layer, wherein the optical film and the liquid crystal layer are on the other side of the light guide plate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  illustrates a light emitting device according to an embodiment of the present invention. 
           [0014]      FIGS. 2A and 2B  illustrate a perspective view of a part of a light emitting device according to a preferable embodiment of the present invention. 
           [0015]      FIGS. 3A and 3B  illustrate a drawing of light path according to an embodiment of the present invention. 
           [0016]      FIGS. 4A˜4G  illustrate a light-emitting device according to another embodiment of the present invention. 
           [0017]      FIGS. 5A˜5C  illustrates a light-emitting device according to a further embodiment of the present invention. 
           [0018]      FIG. 6  illustrates a light-emitting device according to an embodiment of the present invention. 
           [0019]      FIGS. 7A and 7B  illustrate a display using a light-emitting device according to the present invention. 
           [0020]      FIGS. 8A˜8I  illustrate a process flow according to a preferable embodiment of the present invention. 
           [0021]      FIGS. 9A˜9F  illustrate a process flow according to another preferable embodiment of the present invention. 
           [0022]      FIG. 10  illustrates a side cross section of a known side view light-emitting diode. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0023]    As shown in  FIG. 1A , a light-emitting device includes a base  11 , a first reflecting layer  12 , a first insulating layer  13 , a conducting layer  14 , a light-emitting unit  16 , a filling material  17 , a wavelength converting material  17 A, a second insulating layer  18 , and a second reflecting layer  19 . 
         [0024]    In one embodiment, the base  11  is made of silicon, and has an upper terrace  111 , an incline  112 , and a lower terrace  113 . The first reflecting layer  12 , the first insulating layer  13 , and the conducting layer  14  are sequentially formed on the incline  112 , wherein the first reflecting layer  12  and the first insulating layer  13  overlay the upper terrace  111 , incline  112 , and the lower terrace  113 . The conducting layer  14  overlays the upper terrace  111  and the incline  112 . The light-emitting unit  16 , such as a light-emitting diode chip, is mounted on the conducting layer  14 . The second insulating layer  18  and the second reflecting layer  19  are formed on a side of the light channel opposite to the lower terrace  113 . The filling material  17  is formed between the first insulating layer  13  and the second insulating layer  18 . 
         [0025]    The first reflecting layer  12  and the second reflecting layer  19  are capable of reflecting or/and scattering light, and the material thereof includes but not limited to Au, Ag, Cu, Ti, an alloy of aforementioned materials, a stacking layer of aforementioned materials, and a distributed Bragg reflector (DBR). The material of the first insulating layer  13  and the second insulating layer  18  includes but not limited to SiO 2 , epoxy, benzocyclobutene (BCB), and Si x N y . The insulating layer preferably has a thickness that the light can pass through and reach the reflecting layer. The material of the conducting layer  14  includes but not limited to Au, Ag, Al, Cu, W, Sn, and Ni. 
         [0026]    The filling material  17  includes but not limited to expoy, acrylic resin, COC, PMMA, PC, polyetherimide, fluorocarbon polymer, and silicone. 
         [0027]    The filling material  17  may also includes the wavelength converting material  17 A, such as phosphor, which can be excited by the light from the light-emitting unit  16  and generates light with a different wavelength. As shown in  FIG. 1B , the phosphor layer can overlay directly on any light output surface of the light-emitting unit  16 . The phosphor layer thickness may be identical or varied on each of the light output surfaces according to the required light field or color. Applicant&#39;s Taiwan patent application, SN. 093126439, which discloses related technology, is incorporated herein by reference. 
         [0028]    The light-emitting unit  16  can be a horizontal or vertical type light-emitting diode or chip. A horizontal type light-emitting diode has a p-electrode and an n-electrode formed on the same side of a substrate or a carrying layer for carrying the p- and n-electrodes. A vertical type light-emitting diode has a p-electrode and an n-electrode formed on the opposite sides of a substrate or a carrying layer. 
         [0029]    The details of the conducting layers of the present invention are shown in  FIG. 2A . The conducting layers  14 A and  14 B are formed on the insulating layer  13 , and electrically connected to the p- and n-electrodes respectively. In detail, one of the p- and n-electrodes of the vertical type light-emitting diode is coupled to the conducting layer  14 A, and the other is electrically connected to the conducting layer  14 B via a wire or other connecting means. The p- and n-electrodes of the horizontal type light-emitting diode are respectively coupled to the conducting layers  14 A and  14 B, i.e. mounted to the conducting layer in a flip-chip fashion. When the horizontal type light-emitting diode is carried by an insulating substrate, the insulating substrate can be directly put on one of the conducting layer  14 A and  14 B, or span the two conducting layers, and the p- and n-electrodes are electrically connected to the conducting layer  14 A and  14 B by wiring or other connecting means respectively. The light-emitting diode or chip having an insulating substrate can also be disposed directly on the incline  112 , the first reflecting layer  12 , or the insulating layer  13 . As shown in  FIG. 2B , the reflecting layer  12  is made of conducting material(s) and connected to a wiring  16 A, i.e. the light-emitting unit  16  is electrically connected to an outer circuit through the reflecting layer  12 . The covering area of the first reflecting layer  12  and/or the insulating layer  13  can be adjusted in view of the requirement. 
         [0030]    As shown in  FIG. 3A , according to an embodiment of the present invention, parts of the light from the lateral side of the light-emitting unit  16  strike the first reflecting layer  12  and the second reflecting layer  19  respectively. Because the conducting layer  14  on the incline  112  intersects with the first conducting layer  12  and the second reflecting layer  19  at different intersecting angles, the light is reflected to different directions. In one embodiment, the intersecting angle D 1  between the inclines  112  and the lower terrace  113  is 120 degree, and the intersecting angle between the inclined portion of the conducting layer  14  and the first reflecting layer  12  is D 1 . The light R 1  shooting to the second reflecting layer  19  leaves the light-emitting device  10  after two reflections. The light R 2  shooting to the first reflecting layer  12  leaves the light-emitting device  10  after one time reflection or reflection(s) between the first reflecting layer  12  and the second reflecting layer  19 . As shown in  FIG. 3B , the portion between incline  112  and the lower terrace  113  is such as a curved surface, which has an intersecting angle D 1 . The curved surface has a constant curvature, or a varying curvature, which is a space function of two or three dimensions. According to the design of the present invention, the light confined in the package structure is released, and the light extraction efficiency is hence improved. 
         [0031]    As shown in  FIG. 4A , the light output surface  20  of the light emitting device  10  is parallel to the incline  112 , or inclines relative to the lower terrace  113  by D 2  degree. The light is refracted after passing through the inclined light output surface  20 , and changes the direction; therefore, the light can be directed to a predetermined direction under a properly set degree. In another embodiment, assuming degree D 2 =60°, the light field or the light R 3  moves downward. As shown in  FIGS. 4B and 4C , the light output surface  20  of the light-emitting device  10  is a curved surface; the curved surface has a constant curvature, or a varying curvature, which is a 2D or 3D space function. The curved surface may result in various light fields. Under a properly designed curved surface, even without the second insulating layer  18  and the second reflecting layer  19 , the light also leaves out the light output surface  20  after one or many times of total reflections on the boundary between the curved surface and the environmental medium. 
         [0032]    As shown in  FIG. 4D , in another embodiment of the present invention, the light-emitting device  10  has several light output surfaces  20 . The neighboring surfaces intersect respectively with a reference plane, such as the lower terrace  113 , at different angles; therefore, the light incident at the same angle is refracted out of the several light output surfaces at different angles. Moreover, when the angle between the light output surface  20  and the lower terrace  113  becomes smaller, the light field tends to move downward, and on the contrary, the light field tends to move upward. The contour of the light output surfaces may be a part of a polyhedron. In other embodiments, at least part of the light output surface  20 , or several light output surfaces  20  is/are constructed in a formation including a curved surface, a rough surface, and a lens, as shown in  FIGS. 4E-4G . The overall light field of the light-emitting device  10  can be controlled by combining different angles and types of light output surfaces. 
         [0033]    The light output surface  20  of aforementioned embodiments further include two or more micro lenses  201 . As shown in  FIG. 5A , lenses  201  are laterally arranged on the light output surface  20 . The light leaves the light output surface  20  of the light-emitting device via the guidance of the lenses  201 . By using the lenses  201 , the light-emitting device  10  can display a light field with a larger angle or well-mixed colors of lights. Provided two or more colors of lights are emitted by the light-emitting unit  16  of the light-emitting device  10 , the color lights can be well mixed by the lenses  201 . In addition, the lenses  201  also facilitate the mixture of a plurality of light rays. However, the lenses may be vertically arranged according to the requirement. The lens  201  can be a convex or a concave. The radius of the lens  201  is between 50 μm˜60 μm. 
         [0034]    Furthermore,  FIG. 5B  illustrates a top view of a light-emitting device  10 , as shown in  FIG. 4C , having lenses  201 . The radius of the lens  201  changes along an extending path. In the present case, the radius of the lens  201  increases from top to down. In addition, as shown in  FIG. 5C , in the light-emitting device  10  having an array of lens  201 , the inner surface  117  of the light channel may be a vertical surface and is not limited to an incline. 
         [0035]    In the present invention, the light-emitting unit  16  of the light-emitting device  10  is not limited to be disposed on a single side of the light channel, but on any side of the light channel. As shown in  FIG. 6 , the light channel includes two or more inclines  112  on different sides thereof. Arbitrary quantity of the light-emitting unit  16  can be disposed on the incline  112 . Provided two inclines  112  is disposed opposite to each other, the reflecting layer formed on the incline  112  can reflect the light from the opposite side upward. Provided each side of the light channel includes an incline  112 , and the reflecting layer is formed on the incline  112  and the lower terrace  113 , the light from the light-emitting unit  16  on each of the incline  112  is reflected upward by the reflecting layer on the incline  112 . 
         [0036]    According to another embodiment of the present invention, the light-emitting device  10  includes two or more light-emitting units  16  which can emit colorful light having a single color, multi-colors, non-visible wavelength, or a combination of the aforementioned lights. The arrangement of the light-emitting unit  16  is determined by the electrode design of an individual light-emitting unit  16 , which is described in detail in the description of  FIG. 2B . White light can be mixed up by using red, blue, and green light-emitting units  16 , or two light-emitting units  16  having complementary colors. 
         [0037]    The aforementioned design is beneficial to apply the light-emitting unit to a product requiring a particular light field, such as a backlight module of a liquid crystal display. As shown in  FIG. 7A , an edge type liquid crystal display essentially includes a light guide plate  30 , a reflecting film  31 , an optical film  32 , and a liquid crystal layer  33 . The light input surface of the light guide plate  30  has a geometry changing with the light output surface  20  of the light-emitting device  10 , In present case, the contours of the light input surface and the light output surface are identical, but the present invention is not limited to such implementation, other disposition well adapted to the light-emitting device is acceptable. The light from light-emitting unit  16 , which is refracted at the light input surface and then moves to the bottom of light guide plate, is reflected to the optical film  32  and liquid crystal layer  33  by the reflecting film  31 . In the present embodiment, the angle of the light output surface  20  is different from that disclosed in above embodiments in order to fit the design of the display. 
         [0038]    The light output angle of the light-emitting device  10  can be adjusted by tuning the inclined angle of the light output angle relative to a reference plane. The horizontal incident light can reach a farther position through a light output surface having a larger inclined angle; on the contrary, the light through the light output surface having a smaller inclined angle can only reach a closer position. As shown in  FIG. 7B , two light output surfaces  20 A and  20 B having different angles are arranged on the same side of the reflector  34 , wherein, the two light output surfaces  20 A and  20 B can be formed on a single or separate light-emitting device  10 . The light (light field) R 5  through a larger angle light output surface  20 A is refracted to a position distant from the light output surface; while the light (light field) R 6  through a smaller angle light output surface  20 B is refracted to a position near the light output surface. The light is reflected by the reflector  34  to a direction leaving away the reflector. By the design, a uniform light distribution can be realized on a predetermined region, even without using the light guide plate of  FIG. 7A . The light output surfaces having different light output angles can be designed into several or individual light-emitting device(s). Moreover, the light-emitting device can be disposed on one or two or more edges of the reflector. 
         [0039]    In addition, the surface of the reflector  34  can be a rough surface, which has protrusions and depressions. The light striking the roughing surface is scattered in an arbitrary direction. In one embodiment, the distribution density of the protrusions and depressions is higher in the position leaving away the light output surface. However, the protrusions and depressions can also distribute uniformly or randomly on the surface  35 . The protrusion and depression can be formed in a formation including dot, stripe, hole, or the combination thereof. 
         [0040]    The manufacture process of present invention is described below. 
         [0041]    Firstly, as shown in  FIG. 8A , a silicon substrate  11  is prepared. As shown in  FIGS. 8B-8E , a trench  114  having an upper terrace  111 , an incline  112 , and lower terrace  113 , is then formed by performing an anisotropic-etching on the silicon substrate  11  assisted by an oxide mask (not shown) and KOH etchant. A first reflecting layer  12  and a first insulating layer  13  are sequentially overlaid on the upper terrace  111 , the incline  112 , and the lower terrace  113 . Conducting layers  14  and  15  are then overlaid on the area of the first insulating layer above the upper terrace  111  and the incline  112 . The light-emitting unit  16  is mounted on the conducting layer  14  and/or  15 , and a wire is bonded thereto according to the requirement. A filling material  17  is filled into the trench  114 , and a second insulating layer  18  and a second reflecting layer  19  are sequentially overlaid thereon, as shown in  FIGS. 8F and 8G . Finally, after cutting the silicon substrate  11 , a separate light-emitting device  10  is obtained. In addition, a cut  115  (the adjacent light-emitting device is shown in dotted lines) is formed before cutting in order to avoid short circuit caused by metallic residuals or the sidewall of the light-emitting unit  16  being polluted by the solder, as shown in  FIGS. 8H and 8I . The cut  115  can be also formed before overlaying the first insulating layer  13 , i.e. the first insulating layer  13  is covered on the cut  115 . In the above description, the thickness of each layer can be identical or varying in view of the manufacture conditions of design requirements. 
         [0042]    An alternative manufacture process can be used in present invention. As shown in  FIGS. 9A and 9B , for example, a Si 3 N 4  film  116  is firstly formed on a surface of the silicon substrate  11 , and then etched to form a pattern. In the case, to provide an easy manufacture process, the Si 3 N 4  film  116  can be formed simultaneously on the other surfaces of the substrate  11 . By adapting the pattern as a mask, the KOH solution is used to etch the substrate  11  to form the trench  114  and the cut  115 . The Si 3 N 4  film  116  is then removed by dry etching. A reaction gas, such as oxygen, is introduced to cause the surface of the silicon substrate  11  to become a silica layer  13 . The steps after  FIG. 5D  are repeated to complete the light-emitting device  10 . 
         [0043]    The foregoing description has been directed to the specific embodiments of this invention. It will be apparent; however, that other variations and modifications may be made to the embodiments without escaping the spirit and scope of the invention.

Technology Category: 4