Abstract:
A light source module includes a bottom circuit board, a plurality of LED chips disposed on the bottom circuit board, and a sealant covering the LED chips. Each LED chip includes a light-emitting structure and at least a patterned reflecting layer disposed on the light-emitting structure. The patterned reflecting layer can appropriately enhance the brightness of the lateral surface of the LED chip. Thus, the diffuser particles included in the sealant can diffuse light so that the light beams emitted from the lateral surfaces of the LED chips can exit from the light-exiting surface of the light source module. Accordingly, a uniform light distribution of the light source module can be provided.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a light source module, especially to the light source module employing a light-emitting diode (LED) as a light source. 
       REFERENCE TO RELATED APPLICATION 
       [0002]    This application claims the right of priority based on TW application Ser. No. 097120199, filed “May 30, 2008”, entitled “LIGHT SOURCE MODULE, RELATED LIGHT BAR AND RELATED LIQUID CRYSTAL DISPLAY” and the contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0003]    A light source module can be applied to various kinds of displays and illuminative devices. Taking a Back-Light Unit (BLU) of the display for example, the conventional BLU employs Cold Cathode Fluorescent Lamp (CCFL) as a light source. Referring to  FIG. 1  which is a cross-sectional view of a conventional BLU  20 , the BLU  20  is located under a display panel  10  and includes a shell  12 , a plurality of lamps  14 , a diffuser  16 , and a reflector  18 . The plurality of lamps  14  are parallely arranged in a chamber  22  defined by the shell  12 . The reflector  18  reflects light generated from the plurality of lamps  14  upward to enhance the utilization efficiency of light. The diffuser  16  further diffuses the reflected light uniformly. In addition, another diffuser  24  can be located between the BLU  20  and the display panel  10  to enhance light uniformity. 
         [0004]    However, CCFL includes several drawbacks like poor color rendering index, high forward voltage, mercury contained, having a spectrum with in ultraviolet region, slow starting speed, a cracky tube, the difficulty in controlling the chromaticity, and so on. Therefore, an LED package has been applied in BLU as a light source recently. The LED package basically includes a cup and an LED chip mounted on the cup. The cup includes two inward connective ends which electrically connect with the LED chip, and two outward connective ends which electrically connect with a controlling device outside. Because the LED package has advantages like small volume, low electricity consumption, high brightness, high color performance, fast reaction speed (operation in high frequency), environmental protection (shock-endurable, uncracky, and recyclable), and fitness for thin products, it is popular in small-dimension liquid crystal displays (LCDs). 
         [0005]    Nevertheless, because light-emitting profile of the LED package is close to that of a point light source, the screen where is close to the LED package is brighter and results in non-uniform brightness of the image. To solve the problem mentioned above, the thickness of the BLU is usually increased to provide space for light mixing, or more optical films are added in displays for light mixing and complement. Therefore, not only is the volume of the display increased, but also the cost of manufacturing is increased. 
         [0006]    As the idea of using LED as a light source becomes popular, the related technology of applying LED in various sizes of BLU and LED light bar (LB) is getting more important. Accordingly, it is an important issue to provide an LED light source module with great optical efficiency and slim structure. 
       SUMMARY 
       [0007]    The present application provides a light source module applicable to LCD and LB. The light source module includes good optical efficiency, slim structure, and uniform brightness to solve aforementioned problems. 
         [0008]    To achieve aforementioned purposes, the present application provides a light source module including a first print circuit board (PCB), a plurality of LED chips, and a sealant covering the plurality of LED chips. The plurality of LED chips are located on a top surface of the first PCB and electrically connected with the first PCB. Each of the plurality of LED chips includes a light-emitting structure and at least a patterned reflective layer on the light-emitting structure, wherein the patterned reflective layer includes at least an opening and a reflective region. The sealant includes a top surface to become a main surface of light extraction, and a plurality of diffusing particles to diffuse light generated from the LED chips. 
         [0009]    To make the aforementioned purposes, characteristics, and advantages easy to be understood, the following description provides preferable embodiments associated with the attached drawings for explanation. However, the following preferable embodiments and drawings are provided for reference and explanation only, not for limiting the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a cross-sectional view of a conventional BLU. 
           [0011]      FIG. 2  shows a side view of an LED chip of a first embodiment of the present application. 
           [0012]      FIG. 3  and  FIG. 4  show schematic views of a patterned reflective layer in accordance one embodiment of the present application. 
           [0013]      FIG. 5  and  FIG. 6  show side views of the LED chip of a second embodiment and a third embodiment of the present application. 
           [0014]      FIG. 7  shows a side view of an LCD of a forth embodiment of the present application. 
           [0015]      FIG. 8  shows a schematic view of a BLU of  FIG. 7 . 
           [0016]      FIG. 9  shows a side view of the BLU of a fifth embodiment of the present application. 
           [0017]      FIG. 10  and  FIG. 11  show schematic views of electrical connection of different kinds of the LED chips adopted in the embodiments of the present application. 
           [0018]      FIG. 12  shows a schematic view of an LB of a six embodiment of the present application. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring to  FIG. 2  which is a side view of an LED chip  330  of a first embodiment, the LED chip  330  includes a light-emitting structure  334 , a reflective layer  318 , a first electrode  314 , a second electrode  316 , and a patterned reflective layer  318 . The light-emitting structure  334  can include a substrate and a light-emitting stacked layer (not shown), wherein the light-emitting stacked layers at least include an active layer. The first electrode  314  and the second electrode  316  can include conductive materials like metal or alloy. When applying forward voltage to the LED chip  330 , the light-emitting structure  334  can emit light to surrounding areas. The reflective layer  318  is located between the light-emitting structure  334  and the second electrode  316 . The light originally emitting to the second electrode  316  can be reflected by the reflective layer  318  toward upside or lateral surfaces  330   a  of the LED chip  330  to enhance brightness of the LED chip  330 . In another aspect, lateral light generated from the light-emitting structure  334  can emit toward the lateral surfaces  330   a  without passing the reflective layer  318  or the patterned reflective layer  332 . 
         [0020]    The patterned reflective layer  332  includes reflective materials and a plurality of openings  333  which are pervious to light. A portion of the light generated from the light-emitting structure  334  can emit upward through the plurality of openings  333 , and another portion of that can be reflected by the patterned reflective layer  332  to emit toward the lateral surfaces  330   a . In a preferable embodiment of the present application, the patterned reflective layer  332  preferably allows 5%˜10% of the light of the LED chip  330  to emit outside through the plurality of openings  333 , and makes 95%˜90% of that emit outside through the lateral surfaces  330   a  so as to enable the lateral surfaces  330   a  to become a main light-emitting surface. In this embodiment, the first electrode  314  and the patterned reflective layer  332  are located on the same horizontal plane, wherein they can be made of the same or different materials. When the first electrode  314  includes opaque materials, it can be deemed as a portion of the patterned reflective layer  332 . 
         [0021]    Because the brightness of the upside of the conventional LED package is brighter than that of the lateral sides of the conventional LED package, it easily results in non-uniform brightness of the image. Therefore, the present application employs the patterned reflective layer  332  to reflect the light originally emitting toward the upside of the LED chip  330  to the lateral sides thereof. The intensity of the light received at each view angle around the periphery of the LED chip  330  is close so brightness of the upside of the LED chip  330  is not brighter than that of the lateral sides of the LED chip  330  and the LED chip  330  has much uniform brightness. Therefore, when the LED chip  330  is applied to the light source module, it can solve the problem of non-uniform brightness of the light source module without increasing space of the light source module for promoting uniformity of brightness. 
         [0022]    In the present application, materials, patterns, and locations of the patterned reflective layer  332  are not limited by the LED chip  330  as shown in  FIG. 2  and can be modified in accordance with the needs of various products. For example, the material of the patterned reflective layer  332  can be In, Sn, Al, Au, Pt, Zn, Ag, Ti, Pb, Ge, Cu, Ni, AuBe, AuGe, AuZn, PbSn, the combination thereof, or Distributed Bragg Reflector (DBR). In a schematic view, a pattern of the patterned reflective layer preferably includes openings distributed uniformly as shown in  FIG. 3  and  FIG. 4 . Referring to  FIG. 3 , the patterned reflective layer  270  at least includes a reflective region  272  and a plurality of circle openings  274  which are pervious to light. Referring to  FIG. 4 , the patterned reflective layer  276  includes a plurality of reflective regions  278  and at least a grid opening  280 . In the schematic views, the area of the patterned reflective layer  270  occupied by a light-pervious region of the patterned reflective layer  270  is 5% to 20%, preferably 5% to 10%. Namely, the ratio of the area occupied by the reflective region  272  to that occupied by the plurality of light-pervious circle openings is about 19 to 4. So is the ratio of the area occupied by the plurality of reflective regions  278  to that occupied by the grid opening  280 . Therefore, the lateral surfaces of the LED chip can become main light-emitting lateral surfaces. 
         [0023]    In other embodiments, the patterned reflective layer can be formed between the first electrode and the light-emitting structure.  FIG. 5  and  FIG. 6  are side views of the LED chips  300  and  310  of a second embodiment and a third embodiment of the present application respectively. The LED chip  300  can include a light-emitting structure  336 , a reflective layer  318 , a first electrode  338 , a second electrode  316 , and a patterned reflective layer  340 . The light-emitting structure  336  includes a transparent substrate  320  and a light-emitting stacked layer  321 , wherein the light-emitting stacked layer  321  at least includes an active layer. The reflective layer  318  is located between the second electrode  316  and the transparent substrate  320 . Light of the LED chip  300  can emit out from the light-emitting stacked layer  321 . A portion of the light can penetrate the transparent substrate  320  and be reflected out. Therefore, all lateral sides of the light-emitting structure  336  can emit light. In addition, the patterned reflective layer  340  is located between the first electrode  338  and the light-emitting structure  336 , and can allow a portion of light emitting upward through the patterned reflective layer  340 . The patterned reflective layer  340  can reflect a portion of light generated from the light-emitting structure  336  to balance light-emitting intensity of a top surface and lateral surfaces of the LED chip  300 . 
         [0024]    Referring to  FIG. 6 , an LED chip  310  can include a light-emitting stacked layer  337 , an opaque substrate  322 , a reflective layer  318 , a first electrode  338 , a second electrode  316 , and a patterned reflective layer  340 , wherein the light-emitting stacked layer  337  at least includes an active layer. The reflective layer  318  is located between the opaque substrate  322  and the light-emitting stacked layer  337  so light-emitting profile of the LED chip  310  is different from that of the LED chip  300 . When light generated from the light-emitting stacked layer  337  emits outside, the light emitting to downside does not penetrate the opaque substrate  322  and is reflected by the reflective layer  318 . Therefore, the light of the LED chip  310  gathers on the lateral sides of the light-emitting stacked layer  337  and emits outside. 
         [0025]    In the second and third embodiments, when the first electrode  338  is a transparent layer, the first electrode  338  and the second electrode  316  can substantially cover all the top surfaces or bottom surfaces of the LED chips  300  or  310 . Otherwise, the first electrode  338  also can include the same pattern as the patterned reflective layer  340  so a portion of light can penetrate the patterned reflective layer  340  and the first electrode  338  and emits outside. Because the first electrode  338  and the second electrode  316  can be distributed on all top surfaces and bottom surfaces, the current can spread uniformly, the wiring is easier, and the angle of light extraction of the LED chip  300  and  310  can be controlled easily. 
         [0026]    A light source module formed by the LED chips of the present application can be applied to various kinds of displays, illumination devices, and light-emitting devices, like the LB or the BLU of LCD. Referring to  FIG. 7  and  FIG. 8 ,  FIG. 7  is a side view of an LCD  100  of a forth embodiment and  FIG. 8  is a schematic view of a BLU  120  shown in  FIG. 7 . The LCD  100  includes a frame  102 , an LCD panel  110 , and a BLU  120 , wherein the BLU  120  is a direct-type BLU located under the LCD panel  110 . A surface of light extraction  122  of the BLU  120  is set to associate with a display region  112  of the LCD panel  110  for providing light employed by the LCD panel  110  for displaying image. 
         [0027]    Referring to  FIG. 7  and  FIG. 8 , the BLU  120  can include a first PCB  124 , a second PCB  126  which is transparent, a plurality of LED chips  128 , and an sealant  130  covering the plurality of LED chips  128 . Each of the plurality of LED chips  128  can include a first electrode  132  and a second electrode  134  located on a top surface  136  and a bottom surface  134  of each of the plurality of LED chips  128  respectively. The second PCB  126  and the first PCB  124  are located on a top end and a bottom end of the LED chips  128  for controlling the switch thereof. The first electrode  132  and the second electrode  134  of each LED chip  128  are adjacent to and connect with a first connective end  126   a  of the second PCB  126  and a second connective end  124   a  of the first PCB  124  respectively by, for example, employing conductive glue for die mount and electrical connection, or direct contact with the circuit boards for electrical connection. 
         [0028]    The LED chip  128  is located on the top surface of the first PCB  124  and at least includes a main light-emitting lateral surface  142 . In this embodiment, the LED chip  128  can be the aforementioned LED chip including the patterned reflective layer or a side-emitting type LED. The main light-emitting lateral surface  142  of the LED chip  128  is perpendicular to the surface of light extraction  122  of the BLU  120 . The top surface  136  of the LED chip  128  is located on the position facing the surface of light extraction  122 . There is weaker light intensity or no light at the top surface  136  of the LED chip  128 . 
         [0029]    The sealant  130  can include any insulating materials which are transparent, solidifying, and moisture-proof, like epoxy. In addition, the sealant  130  can include a plurality of diffusing particles  146  which can change direction of the light to make the light emitted from the LED chip  128  out of the surface of light extraction  122  (same as the top surface of the sealant  130 ) of the BLU  120  uniformly. 
         [0030]    Generally, an LED package is located on the lateral sides of a side-emitting LED type BLU. A light guide plate guides light to a surface of light extraction of the BLU. For the side-emitting LED type BLU, two ends of the BLU are brighter than the central part thereof because light sources are located on the lateral sides. Therefore, only the central part of the BLU can correspond to the LCD panel. The region providing light of the side-emitting LED type BLU occupies only 70% to 80% of the area of the BLU so the volume of the LCD can not be reduced effectively. The present application discloses a chip-scaled packaged module which the LED chip  128  is directly mounted on the first PCB  124  and the second PCB  126 ; not mounted the LED package on the circuit boards, the space of the package element like a cup, and the thickness of the BLU can be reduced sufficiently. For example, the thickness of the BLU  120  of the present application is about equal to the sum of the thicknesses of the first PCB  124 , the second PCB  126 , and the LED chip  128 . Because of the reduced thickness of the BLU  120 , the BLU  120  itself can be a planar light source so the chance of light consumed on the lateral surfaces of the BLU  120  can be reduced. Moreover, because the BLU  120  does not have to employ the package element like the cup, it can avoid absorbing or blocking the light by the cup and provide better optical performance. 
         [0031]    In another aspect, the brightness of the lateral surfaces of the light-emitting device (the LED chip  128 ) is larger than that of the top surface thereof. The plurality of diffusing particles  146  of the sealant  130  can change the light emitting sideward to emit to the surface of light extraction  122  uniformly and penetrate the surface of light extraction  122 . Therefore, the brightnesses of the periphery and the upside of the LED light source are about close. The problem of non-uniform brightness of the LED type BLU can be improved effectively, and there is enough light to be provided to the LCD panel  110 . 
         [0032]    It is noted that the first PCB  124  and the second PCB  126  can include various kinds of circuit board structures, preferably a soft PCB like a flexible PCB. Consequently, the present application can provide a flexible BLU to form more different kinds of displays. Besides, the first PCB  124  can support the LED chips  128  immediately. The surfaces of the first PCB  124  can include highly reflective materials like light color materials or metal materials to reflect light. Otherwise, the first PCB  124  can be transparent and has a reflector (not shown) located underneath to enhance the optical performance of the BLU  120 . Furthermore, the LCD  100  can optionally include different kinds of optical film  101  based on the specification of the products. For example, a prism or a diffuser can be provided between the LCD panel  110  and the BLU  120  or a reflective layer can be provided in the frame  102  to further promote the display performance of the LCD  100 . 
         [0033]    In addition, associating with different type LED chips, the present application can also employ other BLU structures. Referring to  FIG. 9  which is a side view of a BLU  220  of a fifth embodiment of the present application, a first electrode  232  and a second electrode  234  of an LED chip  228  are located on a top surface  236  thereof. After fixing the LED chip  228  on a top surface of a first PCB  224 , the first electrode  232  and the second electrode  234  can electrically connect with a first connective end  224   a  and a second connective end  224   b  of the first PCB  224  via a wire  229  respectively. Then, the sealant  130  having a plurality of diffusing particles  146  can cover each LED chip  228  to form a surface of light extraction  222  of the BLU  220 . 
         [0034]    In this embodiment, similarly, each LED chip  228  primarily emits light through a main light-emitting lateral surfaces  242  perpendicular to the surface of light extraction  222 . The light of weaker intensity or no light can emit from a top surface  236  of the LED chip  228  facing the surface of light extraction  222 . For example, the LED chip  228  can include the aforementioned patterned reflective layer. However, it is noted that the application of the light-emitting devices of the present application are not limited to the aforementioned BLUs. Referring to  FIG. 10  and  FIG. 11  which show schematic views of the electrical connection of different kinds of the LED chips of the present application, when a first electrode  252  and a second electrode  254  of an LED chip  250  are located on the same side thereof, the first electrode  252  can be adjacent to and electrically connect with a first connective end  410   a  of a first PCB  254 , and the second electrode  254  can be adjacent to and electrically connect with a second connective end  410   b  of the first PCB  254 . Bumps or the conductive glue can be employed to form connection between the first electrode  252  and the first connective end  410   a  or the second electrode  254  and the second connective end  410   b . Otherwise, direct contact can also be employed to form electrical connection therebetween. In this embodiment, the LED chip  250  can employ a transparent substrate and a patterned reflective layer located on a side of the transparent substrate close to or far away from the first electrode  252  and the second electrode  254 . Therefore, a portion of the light of the LED  250  can penetrate the transparent substrate and emit to the upside of the LED chip  250 . Most light emits toward the lateral surfaces of the LED chip  250 . 
         [0035]    Referring to  FIG. 11 , when a first electrode  262  and a second electrode  264  of an LED chip  260  are located on a top surface  266  and a bottom surface  268  thereof, the first electrode  262  can employ a wire  269  to electrically connect with a first connective end  412   a  of a first PCB  412  and the second electrode  264  can directly connect with a second connective end  412   b  of the first PCB  412 . 
         [0036]    Referring to  FIG. 12  which shows a schematic view of an LB  420  of a sixth embodiment of the present application, a light source module of the LB  420  includes a similar structure of the aforementioned BLU  120 . The LB  420  can include a strip type of PCB  324 , a second PCB  326  which is transparent, the plurality of LED chips  128 , and the sealant  130  covering the plurality of LED chips  128 . The first electrode and the second electrode of the LED chip  128  are adjacent to and connect with the first connective end of a second PCB  326  and a second connective end (not shown) of the strip type of PCB  324  respectively. The main light-emitting lateral surfaces  142  of the LED chip  128  are perpendicular to a main surface of light extraction  422  of the LB  420 , and the top surface of the LED chip  128  includes the patterned reflective layer (not shown) located on the position facing the main surface of light extraction  422 . The open region of the patterned reflective layer allows light to penetrate and the reflective region thereof can reflect light to enhance lateral light-emitting of the LED chip  128  so the upside and the lateral sides thereof have uniform brightness. 
         [0037]    The sealant  130  can protect the LED chips  128  and include the plurality of diffusing particles  146  additionally for a more uniform brightness thereof. As a result, the light generated from the LED chip  128  can uniformly emit to and penetrate through the main surface of light extraction  422  and the lateral surfaces of the LB  420 . The light source module of the present application includes not only a slim structure but also a uniform brightness. It is noted that the light source module of the LB  420  can also adopt other package types, other methods of allocating the LED chips, and other methods of electrical connection, without limitation of the structure of the LB  420 . 
         [0038]    The LED chip of the present application primarily emits light through the lateral surfaces. The LED chip can emit the light of weaker intensity or no light through the top surface thereof. The sealant and the diffusing particles thereof can change the direction of light to make the light of the lateral sides of the LED chip penetrate the main surface of light extraction of the light source module. Therefore, the uniformity of the brightness of the light source module can be promoted. In addition, the present application also provides package of module in chip stage to largely reduce the volume of the light module. 
         [0039]    It should be noted that the proposed various embodiments are not for the purpose to limit the scope of the application. Any possible modifications without departing from the spirit of the application may be made and should be covered by the application.