Abstract:
A lighting device and a back light module therewith are disclosed. The back light module includes a light-guiding structure and a lighting device. The light-guiding structure includes two light-guiding parts and a reflection sheet disposed therebetween. The lighting device is disposed close to the light-guiding structure and includes an insulation carrier and two light sources disposed on the insulation carrier. The insulation carrier includes a positioning groove structure where an edge of the reflection sheet is disposed such that the two light sources correspond to the two light-guiding parts respectively and light emitted by the two light sources is capable of entering the corresponding light-guiding parts. Thereby, the invention uses the single-structure lighting device to simultaneously provide required light to the two light-guiding parts respectively, and uses the positioning structure formed on the lighting device to improve the assembly preciseness of the light-guiding structure with the lighting device.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a lighting device and a back light module, and especially relates to a lighting device capable of providing two light sources and a back light module having the lighting device for providing two back lights. 
         [0003]    2. Description of the Prior Art 
         [0004]    As use customs of users become various, there is a displaying apparatus capable of providing a forward screen and a backward screen by a single apparatus configuration on the market. For current back light modules with dual screens, some are designed to use a single lighting device to provide light to two light-guiding plates simultaneously. Some are designed to use a single lighting device to provide light to a light-guiding plate and use a semi-transmitting and semi-reflecting structure to guide the light in the light-guiding plate to another light-guiding plate. Still some are designed to use two lighting devices to provide light to corresponding light-guiding plates respectively. In the above configurations, each of the light-guiding plates is used for providing light to a corresponding liquid crystal panel. 
         [0005]    In the above first configuration, it is not easy to precisely align the lighting device with the light-guiding plate, leading to an unpredictable intensity of light into each light-guiding plate. In the above second configuration, the preciseness of the assembly for the lighting device with the light-guiding plates can be controlled precisely. The light for the second light-guiding plate is from the first light-guiding plate, so it is difficult to enhance the intensity of the light into the second light-guiding plate so that the application scope of the liquid crystal panel corresponding to the second light-guiding plate is limited. In the above third configuration, in logic, the back light module consists of two independent liquid crystal stacked. The preciseness of the assembly therefor can also be controlled precisely. The intensity of the back light therefor can be controlled independently. But it is obviously difficult to decrease the volume of the whole displaying apparatus. 
       SUMMARY OF THE INVENTION 
       [0006]    An objective of the invention is to provide a lighting device, using a positioning structure between two light sources for disposing a reflection sheet therein such that after assembled, the lighting device is capable of precisely providing required light to light-guiding parts. 
         [0007]    The lighting device of the invention includes an insulation carrier, a first light source, and a second light source. The insulation carrier has a package space and a light-out side. The light-out side thereon defines a first light-out area and a second light-out area. The insulation carrier includes a positioning groove structure for positioning a reflection sheet such that the reflection sheet divides the light-out side into the first light-out area and the second light-out area. The first light source is disposed in the package space corresponding to the first light-out area. Light emitted from the first light source emits through the first light-out area out of the lighting device. The second light source is disposed in the package space corresponding to the second light-out area. Light emitted from the second light source emits through the second light-out area out of the lighting device. Thereby, when the reflection sheet is disposed in the positioning groove structure, light-guiding parts at two opposite sides of the reflection sheet can be disposed corresponding to the first light-out area and the second light-out area precisely, and the intensity of the light into the light-guiding parts can be easily controlled by use of the first light source and the second light source. 
         [0008]    Another objective of the invention is to provide a back light module having the lighting device of the invention. The back light module uses a single-structure lighting device to provide required light to two light-guiding parts simultaneously and uses a positioning structure formed on the lighting device to improve the assembly preciseness of the light-guiding structure and the lighting device. 
         [0009]    The back light module includes a light-guiding structure and a lighting device. The light-guiding structure has a light-in side and includes a first light-guiding part, a second light-guiding part, and a reflection sheet. The lighting device is disposed close to the light-in side and contacts an edge of the reflection sheet. The lighting device includes an insulation carrier, a first light source, and a second light source. The insulation carrier has a package space and a light-out side. The light-out side is opposite to the light-in side. The light-out side thereon defines a first light-out area and a second light-out area. The insulation carrier includes a positioning groove structure. The edge of the reflection sheet is disposed in the positioning groove structure to divide the light-out side into the first light-out area and the second light-out area such that the first light-out area and the second light-out area are opposite to the first light-guiding part and the second light-guiding part respectively. The first light source is disposed in the package space corresponding to the first light-out area. Light emitted from the first light source emits through the first light-out area out of the lighting device to enter the first light-guiding part through the light-in side. The second light source is disposed in the package space corresponding to the second light-out area. Light emitted from the second light source emits through the second light-out area out of the lighting device to enter the second light-guiding part through the light-in side. Thereby, the back light module uses only the single-structure lighting device to precisely provide required light to the two light-guiding parts, which is conducive to reduction of a volume of an apparatus using the back light module. 
         [0010]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic diagram illustrating a lighting device of a preferred embodiment according to the invention. 
           [0012]      FIG. 2  is a sectional view of the lighting device in  FIG. 1  along the line X-X. 
           [0013]      FIG. 3  is a sectional view of a lighting device according to another embodiment. 
           [0014]      FIG. 4  is a top view of the lighting device in  FIG. 1 . 
           [0015]      FIG. 5  is a top view of a lighting device according to another embodiment. 
           [0016]      FIG. 6  is a top view of a lighting device according to another embodiment. 
           [0017]      FIG. 7  is a sectional view of aback light module of a preferred embodiment according to the invention. 
           [0018]      FIG. 8  is a sectional view of a back light module according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Please refer to  FIG. 1  and  FIG. 2 .  FIG. 1  is a schematic diagram illustrating a lighting device  1  of a preferred embodiment according to the invention.  FIG. 2  is a sectional view of the lighting device  1  in  FIG. 1  along the line X-X. The lighting device  1  includes an insulation carrier  12 , a first light source  14 , and a second light source  16 . The insulation carrier  12  has a package space  122  and a light-out side  124 . The light-out side  124  thereon defines a first light-out area  124   a  and a second light-out area  124   b  (shown by hatched lines in  FIG. 1 ). The insulation carrier  12  includes a positioning groove structure  126  for a reflection sheet  2  (shown by dashed lines in  FIG. 2 ) to be positioned thereon such that the reflection sheet  2  divides the light-out side  124  into the first light-out area  124   a  and the second light-out area  124   b . The first light source  14  is disposed in the package space  122  corresponding to the first light-out area  124   a . The second light source  16  is disposed in the package space  122  corresponding to the second light-out area  124   b.    
         [0020]    Thereby, light emitted from the first light source  14  emitting through the first light-out area  124   a  out of the lighting device  1 ; light emitted from the second light source  16  emitting through the second light-out area  124   b  out of the lighting device  1 . Therein, bold lines with arrow show the primary light paths. In other words, in logic, the light passing through the two side of the reflection sheet  2  comes mainly from the first light source  14  and the second light source  16  respectively. Therefore, in practice, the light-out quantity by the lighting device  1  for each side of the reflection sheet  2  depends on the light-out quantity of either the first light source  14  or the second light source  16  correspondingly. It is added that, in practice, light emitted by the first light source  14  travels in a plurality of directions, so it is possible that a very few portion of the light may emit through the second light-out area  124   b  out of the lighting device  1 . However, the light-out quantity of the portion of the light is obviously much less than the light-out quantity of the light emitting through the first light-out area  124   a  out of the lighting device  1 , so the light-out quantity of the portion of the light can be regarded as being with an allowable tolerance so as to be ignored in practice. Furthermore, if the first light source  14  is designed properly in structure for convergence of the divergence angle of the first light source  14 , the extent of the light from the first light source  14  emitting through the second light-out area  124   b  out of the lighting device  1  can be reduced effectively. The above explanation is also applicable to the second light source  16 , which will be not repeated. 
         [0021]    In the embodiment, the insulation carrier  12  includes an insulation cup  128 , a lead frame  130  embedded in the insulation cup  128 , and a sealing gel  132  accommodated in the package space  122 . The positioning groove structure  126  is formed on the cup rim of the insulation cup  128 . The first light source  14  and the second light source  16  are disposed on the lead frame  130 . The sealing gel  132  covers the first light source  14  and the second light source  16 . Therein, the lead frame  130  can include electrode frames and a heat-conduction structure required for the first light source  14  and the second light source  16 . In practice, the positioning groove structure  126  is formed for example by cutting, after the first light source  14  and the second light source  16  are packaged by the sealing gel  132 , but the invention is not limited thereto. For example, the insulation cup  128  with the positioning groove structure  126  is directly formed by injection. Furthermore, in the embodiment, the positioning groove structure  126  includes two indentations disposed oppositely on the cup rim of the insulation cup  128 . The bottom of the indentation is coplanar with the top surface of the sealing gel  132 . But the invention is not limited thereto. For example, in a manufacturing design of forming the positioning groove structure  126  by a secondary working, the positioning groove structure  126  can be formed also on the sealing gel  132 , as shown by  FIG. 3 . In this case, the reflection sheet  2  can further extend into the sealing gel  132  for separating the light emitted by the first light source  14  and the second light source  16  more effectively. 
         [0022]    Please also refer to  FIG. 4 .  FIG. 4  is a top view of the lighting device  1 ; therein, the positions of the first light source  14  and the second light source  16  are indicated by dashed lines, and the first light-out area  124   a  and the second light-out area  124   b  are still shown by hatched lines. In the embodiment, the lighting device  1  shows a rectangular solid appearance; that is, the insulation cup  128  has a rectangular profile at the light-out side  124 . The first light source  14  and the second light source  16  are disposed in a short side direction of the rectangular profile. In practice, each of the first light source  14  and the second light source  16  includes at least one light-emitting diode chip, but the invention is not limited thereto. In a common case, the first light source  14  and the second light source  16  usually use light-emitting diode chips in same size and light-emitting efficiency, so for simple illustration in the description, the ratio of the light-out quantity of the light-emitting diode chips of the first light source  14  to that of the second light source  16  is directly indicated by the ratio of the size of the rectangle by dashed lines for the first light source  14  to that for the second light source  16 . In other words, the above ratio also indicates the ratio of the light-emitting power of the first light source  14  to that of the second light source  16 , as well as the ratio of the light-out quantity of the first light source  14  to that of the second light source  16 . In the embodiment, the first light source  14  is equivalent to the second light source  16 . 
         [0023]    Please refer to  FIG. 5 , which is a top view of a lighting device according to another embodiment. The lighting device  3  is substantially identical in structure to the lighting device  1 . Except for the difference, the lighting device  3  still uses the same denomination as the lighting device  1 . The main difference between the lighting device  3  and the lighting device  1  is the disposition of the first light source  34  and the second light source  36  of the lighting device  3 . As shown by  FIG. 5 , the light-emitting power of the first light source  34  is larger than the light-emitting power of the second light source  36 , so the light-out quantity from the first light-out area  324   a  is larger than the light-out quantity from the second light-out area  324   b . It is added that if the first light source  34  and the second light source  36  are disposed in the same disposition of light-emitting diode chips (for example, in disposition density), the light-emitting power of the first light source  34  and the second light source  36  can be reflected by the sizes of the areas of the first light-out area  324   a  and the second light-out area  324   b  respectively. For example, in the embodiment, the area of the first light-out area  324   a  corresponding to the first light source is larger than the area of the second light-out area  324   b  corresponding to the second light source  36 . For other description about the lighting device  3 , please refer to the relevant description of the lighting device  1 . It will not be repeated. 
         [0024]    Please refer to  FIG. 6 , which is a top view of a lighting device according to another embodiment. The lighting device  4  is substantially identical in structure to the lighting device  1 . Except for the difference, the lighting device  4  still uses the same denomination as the lighting device  1 . The main difference between the lighting device  4  and the lighting device  1  is the disposition of the first light source  44  and the second light source  46  of the lighting device  4 . As shown by  FIG. 6 , the first light source  44  and the second light source  46  are disposed in a long side direction of the rectangular profile. The light-emitting power of the first light source  44  is larger than the light-emitting power of the second light source  46 , so the light-out quantity from the first light-out area  424   a  is larger than the light-out quantity from the second light-out area  424   b . For other description about the lighting device  4 , please refer to the relevant description of the lighting devices  1  and  3 . It will not be repeated. 
         [0025]    It is added that, in the above embodiments, the lighting devices  1 ,  3  and  4  are illustrated to be with a top-view rectangular profile, but the invention is not limited thereto. For example, a top-view square profile, a top-view circular profile, and other top-view profiles are applicable to the invention, which will not be repeated. 
         [0026]    Please refer to  FIG. 7 , which is a sectional view of a back light module  5 , which has a lighting device of the invention, of a preferred embodiment according to the invention. Therein, for simple illustration, the components are shown by magnifying. The back light module  5  includes a frame  52 , a light-guiding structure  54 , and a first lighting device  56  and a second lighting device  58  disposed at two sides of the light-guiding structure  54 . For simple explanation, the embodiment uses the abovementioned lighting device  1  as the first lighting device  56  and the second lighting device  58 . Thus, the denomination for the first lighting device  56  and the second lighting device  58  directly follows the denomination of the lighting device  1 , and the relevant description of the lighting device  1  is also applicable herein and is not repeated herein. The light-guiding structure  54  includes a first light-guiding part  542 , a second light-guiding part  544  disposed opposite to the first light-guiding part  542 , and a reflection sheet  546  disposed between the first light-guiding part  542  and the second light-guiding part  544 . The light-guiding structure  54  has a first light-in side  54   a  and a second light-in side  54   b  opposite to each other. The first lighting device  56  is disposed close to the first light-in side  54   a . A first edge  546   a  of the reflection sheet  546  contacts the positioning groove structure  126  of the first lighting device  56  to divide the light-out side  124  into the first light-out area  124   a  and the second light-out area  124   b  of the first lighting device  56 , such that the first light-out area  124   a  and the second light-out area  124   b  are opposite to the first light-guiding part  542  and the second light-guiding part  544  respectively. Therefore, light emitted by the first light source  14  emitting through the first light-out area  124   a  out of the first lighting device  56  to enter the first light-guiding part  542  through the first light-in side  54   a ; light emitted by the second light source  16  emitting through the second light-out area  124   b  out of the second lighting device  58  to enter the second light-guiding part  544  through the second light-in side  54   b . Similarly, the second lighting device  58  is disposed opposite to the first lighting device  56  and close to the second light-in side  54   b , such that a second edge  546   b  of the reflection sheet  546  contacts the positioning groove structure  126  of the second lighting device  58  to divide the light-out side  124  into the first light-out area  124   a  and the second light-out area  124   b  of the second lighting device  58 . Other detailed disposition of the second lighting device  58  is the same as the first lighting device  56 , which will not be repeated. 
         [0027]    In the embodiment, the back light module  5  is applied to a bi-directional display apparatus, so in  FIG. 7 , each of the first light-guiding part  542  and the second light-guiding part  544  thereon disposes a liquid crystal panel  72  and  74 . Each of the first light-guiding part  542  and the second light-guiding part  544  is a light-guiding plate for providing required back light to the liquid crystal panels  72  and  74  correspondingly. The first light-guiding part  542 , the second light-guiding part  544 , and the reflection sheet  546  are stacked in a sandwich structure. It is added that, in practice, the back light module  5  includes a plurality of the lighting devices  56  and  58  at the first light-in side  54   a  and the second light-in side  54   b  respectively. Each group of the lighting devices  56  and the lighting devices  58  is arranged and soldered in a row on a circuit board  60  and  62  to form a bar light source module. Furthermore, in the above embodiment, the back light module  5  uses the first lighting device  56  and the second lighting device  58  disposed opposite to each other; that is, the first light-in side  54   a  is opposite to the second light-in side  54   b . The light-out uniformity of the first light-guiding part  542  and the second light-guiding part  544  is therefore improved. However, the invention is not limited thereto. For example, if the intensity of the back light provided by the first lighting devices  56  is sufficient, the second lighting devices  58  can be omitted; in practice, the first light-in side  54   a  and the second light-in side  54   b  can be disposed to be adjacent; even lighting devices can be disposed at several sides of the light-guiding structure  54 . In addition, in the embodiment, the back light module  5  includes reflection plates  64  and  66  at the lighting devices  56  and  58  respectively, which provides effect of fixing the lighting devices  56  and  58  and the light-guiding structure  54  and preventing light leakage thereby. The frame  52  can directly support the liquid crystal panels  72  and  74 ; the reflection plates  64  and  66  support the light-guiding structure  54  and the lighting devices  56  and  58 . 
         [0028]    In the above embodiments, each of the first light-guiding part  542  and the second light-guiding part  544  is a flat plate, but the invention is not limited thereto. Please refer to  FIG. 8 , which is a sectional view of a back light module  8  according to another embodiment. The back light module  8  is substantially identical in structure to the back light module  5 . Except for the difference, the back light module  8  still uses the same denomination as the back light module  5 . The main difference between the back light module  8  and the back light module  5  is that each of the first light-guiding part  842  and the second light-guiding part  844  of the first light-guiding part  842  of the light-guiding structure  84  of the back light module  8  is a wedge light-guiding plate, which is conducive to the light-out uniformity of the first light-guiding part  842  and the second light-guiding part  844 , so the back light module  8  is provided with the lighting device  56  only at one side of the light-guiding structure  84 . 
         [0029]    In addition, it is added that the lighting device of the invention can provide different light-out quantities; that is, the back light module provides different the light-out quantities by different light-guiding parts, so the back light intensity provided by the first light-guiding part and the second light-guiding part can be controlled by way of designing the light-out quantities provided by the lighting device through the first light-out area and the second light-out area respectively, so as to be adapted to different requirements of different products. For an example of a foldable mobile phone with dual screens, the outside screen thereof is usually small and used for indication display, so the back light intensity therefor is usually not high and the back light-out quantity is less. For this case, the lighting device  3  in  FIG. 5  is applicable. 
         [0030]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.