Patent Publication Number: US-2020292749-A1

Title: Backlight Module and Electronic Device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application is a continuation application of International (PCT) Patent Application No. PCT/CN2018/120028, filed on Dec. 10, 2018, which claims priority to Chinese Patent Application No. 201810106256.9, filed on Jan. 31, 2018 and Chinese Patent Application No. 201820181747.5, filed on Jan. 31, 2018, the entire contents of all of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of electronic devices, and in particular to a backlight module and an electronic device. 
     BACKGROUND 
     A backlight module of an electronic device may include an optical assembly and a backlight source. During assembling, a distance between a light guide plate of the optical assembly and the backlight source may be too large, such that the light guide plate may not be able to receive light emitted from the backlight source completely, and a backlight effect of the light guide plate may be reduced. 
     SUMMARY 
     According to a first aspect of the present disclosure, a backlight module is provided and includes: a back frame, an optical assembly, a backlight source, and a positioning member. The back frame includes a side wall and a bottom wall, and the side wall and the bottom wall are connected to each other and define a receiving space. The optical assembly is arranged on the bottom wall and received in the receiving space, and includes a light guide plate. The light guide plate defines a recess. The backlight source includes a lamp and a flexible circuit board and is arranged on a side of the light guide plate close to the side wall. The positioning member is arranged to connect to the back frame and at least partially received in the receiving space. The positioning member comprises a positioning portion. The positioning portion is engaged into the recess, such that a distance between the light guide plate and the backlight source is less than or equal to a threshold. The positioning portion is arranged to protrude from the positioning member, and a protruding direction of the positioning portion is parallel to an extending direction of the backlight source. 
     According to a second aspect of the present disclosure, a backlight module is provided and includes: a back frame, an optical assembly, a backlight source, and a positioning member. The back frame includes a side wall and a bottom wall, and the side wall and the bottom wall are connected to each other and define a receiving space. The optical assembly is arranged on the bottom wall and received in the receiving space, and includes a light guide plate. The light guide plate defines a recess. The backlight source comprises a lamp and a flexible circuit board. The lamp is arranged on and extends along a side of the light guide plate close to the side wall. The positioning member is arranged to connect to the back frame and at least partially received in the receiving space. The positioning member comprises a positioning portion. The f positioning portion is engaged into the recess, such that a distance between the light guide plate and the backlight source is less than or equal to a threshold. 
     According to a third aspect of the present disclosure, an electronic device is provided and includes a display module and a backlight module. The display module is arranged to stack above the backlight module, and the backlight module includes: a back frame, an optical assembly, a backlight source, and a positioning member. The back frame includes a side wall and a bottom wall, and the side wall and the bottom wall are connected to each other and define a receiving space. The optical assembly is arranged on the bottom wall and received in the receiving space, and includes a light guide plate. The light guide plate defines a recess. The backlight source is arranged on a side of the light guide plate close to the side wall. The positioning member is arranged to connect to the back frame and at least partially received in the receiving space. The positioning member comprises a positioning portion, and the positioning portion is engaged into the recess, enabling a distance between the light guide plate and the backlight source to be less than or equal to a threshold. The threshold is less than or equal to 0.1 mm. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       In order to illustrate technical solutions of embodiments of the present disclosure in details, drawings required for illustrating the embodiments will be described in brief. Obviously, the following drawings illustrate only some embodiments of the present disclosure, and to any one of skill in the related art, other drawings may be obtained based on the following drawings without any creative work. 
         FIG. 1  is a structural schematic view of a backlight module according to a first embodiment of the present disclosure. 
         FIG. 2  is a schematic view of a cross section of the embodiment shown in  FIG. 1 , taken along a line of II-II. 
         FIG. 3  is a schematic view of a cross section of the embodiment shown in  FIG. 1 , taken along a line of 
         FIG. 4  is an assembly schematic view of a light-shielding tape and a back frame according to an embodiment of the present disclosure. 
         FIG. 5  is a cross-sectional view of a backlight module according to a second embodiment of the present disclosure. 
         FIG. 6  is a schematic view of the back frame shown in  FIG. 5  of the present disclosure. 
         FIG. 7  is a schematic view of an electronic device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will be further illustrated in details by referring to drawings and embodiments. Specifically, following embodiments are for the purpose of illustrating the present disclosure, but do not limit the scope of the present disclosure. Similarly, the following embodiments are only a part of, but not all of, the embodiments of the present disclosure. Any other embodiment obtained by any one of skill in the art without performing creative work should be within the scope of the present disclosure. 
     The term “embodiment” indicates that specific characteristics, structures, or properties described in an embodiment may be included in at least one embodiment of the present disclosure. The expression “embodiment” appearing in various sections of the present specification may not indicate a same embodiment, and may not indicate an independent or alternative embodiment mutually exclusive of other embodiments. Any one of skill in the art should implicitly and explicitly understand that the embodiments described herein can be combined with other embodiments. 
     According to a first aspect of the present disclosure, a backlight module is provided and includes: a back frame, an optical assembly, a backlight source, and a positioning member. The back frame includes a side wall and a bottom wall, and the side wall and the bottom wall are connected to each other and define a receiving space. The optical assembly is arranged on the bottom wall and received in the receiving space, and includes a light guide plate. The light guide plate defines a recess. The backlight source includes an array of light emitting elements and a flexible circuit board, wherein the light emitting elements are arranged on a side of the light guide plate close to the side wall along a row direction and a column direction, the row direction is parallel to an extending direction of the side of the light guide plate arranged with the light emitting elements. The positioning member is arranged to connect to the back frame and at least partially received in the receiving space. The positioning member comprises a positioning portion. The positioning portion is engaged into the recess, such that a distance between the light guide plate and the backlight source is less than or equal to a threshold. The positioning portion is arranged to protrude from the positioning member, and a protruding direction of the positioning portion is parallel to the row direction of the light emitting elements. 
     In some embodiments, the positioning member includes a body portion and an extension portion. The body portion is connected to the back frame, and the extension portion is arranged to extend from the body portion towards the receiving space. The positioning portion is arranged to perpendicularly protrude from an end of the extension portion away from the body portion. 
     In some embodiments, At least two side walls are arranged and connected to each other. The body portion is arranged at a position at which the at least two side walls connect to each other, and the extension portion is arranged to extend from the body portion towards a position between another side of the light guide plate without the backlight source arranged and at least one of the at least two side walls. 
     According to a second aspect of the present disclosure, a backlight module is provided and includes: a back frame, an optical assembly, a backlight source, and a positioning member. The back frame includes a side wall and a bottom wall, and the side wall and the bottom wall are connected to each other and define a receiving space. The optical assembly is arranged on the bottom wall and received in the receiving space, and includes a light guide plate. The light guide plate defines a recess. The backlight source comprises a lamp and a flexible circuit board. The lamp is arranged on and extends along a side of the light guide plate close to the side wall. The positioning member is arranged to connect to the back frame and at least partially received in the receiving space. The positioning member comprises a positioning portion. The f positioning portion is engaged into the recess, and an extending direction of the positioning portion is parallel to an extending direction of the lamp, such that a distance between the light guide plate and the backlight source is less than or equal to a threshold. 
     In some embodiments, the positioning member includes a body portion and an extension portion. The body portion is arranged to connect to the back frame, and the extension portion is arranged to extend from the body portion towards the receiving space. The second positioning portion is arranged on the extension portion. 
     In some embodiments, at least two side walls are arranged and connected to each other. The body portion is arranged at a position at which the at least two side walls are connected to each other, and the extension portion is arranged to extend from the body portion towards a position between the light guide plate and at least one of the at least two side walls. 
     In some embodiment, the lamp is a plurality of light emitting elements arranged in a row, the positioning portion is arranged to perpendicularly protrude from an end of the extension portion away from the body portion, and a protruding direction of the positioning portion is parallel to a direction of the row. 
     In some embodiments, the back frame further includes a top wall. The top wall and an end of the side wall away from the bottom wall are connected to each other. The top wall, the side wall, and the bottom wall cooperatively define the receiving space. The positioning member is arranged on a side of the top wall away from the receiving space and is arranged to align with the top wall. 
     In some embodiments, the threshold is less than or equal to 0.1 mm. 
     In some embodiments, the flexible circuit board is adhered to a side of the lamp 
     (YB: 01050581 .DOCX away from the light guide plate. 
     In some embodiments, the light guide plate includes a light incidence surface and a light emitting surface. The lamp is arranged on the light incidence surface of the light guide plate and at an optimized position for light emitting. 
     In some embodiments, the optimized position for light emitting is an optimized position of the lamp in height and in distance relative to the light guide plate, such that emitted light may be completely received by the light guide plate. 
     In some embodiments, a first adhesion member is arranged between the lamp and the bottom wall, and the lamp is adhered to the bottom wall via the first adhesion member, such that the lamp is arranged at the optimized position in height relative to the light guide plate by providing the first adhesion member in an appropriate thickness. 
     In some embodiments, a second adhesion member is arranged between the lamp and the side wall, and the lamp is adhered to the side wall via the second adhesion member, such that the lamp is arranged at the optimized position in distance relative to the light guide plate by providing the second adhesion member in an appropriate thickness. 
     In some embodiments, the receiving space includes a first space and a second space communicating with each other, the first space and the second space are sequentially defined along a direction facing towards the side wall. The optical assembly is received in the first space. An area of a cross section of the second space taken along the direction facing towards the side wall is greater than that of the first space taken along the facing towards the side wall, and the lamp is received in the second space. 
     In some embodiments, the optical assembly further includes an optical film assembly arranged on the light emitting surface of the light guide plate. The backlight module further includes a light-shielding tape, and the light-shielding tape is arranged on a side of the top wall away from the receiving space and adhered to the top wall and the optical film assembly. 
     In some embodiments, the light-shielding tape is further arranged on a side of the side wall away from the receiving space and adhered to the side wall. 
     According to a third aspect of the present disclosure, an electronic device is provided and includes a display module and a backlight module. The display module is arranged to stack above the backlight module, and the backlight module includes: a back frame, an optical assembly, a backlight source, and a positioning member. The back frame includes a side wall and a bottom wall, and the side wall and the bottom wall are connected to each other and define a receiving space. The optical assembly is arranged on the bottom wall and received in the receiving space, and includes a light guide plate. The light guide plate defines a recess. The backlight source is arranged on a side of the light guide plate close to the side wall. The positioning member is arranged to connect to the back frame and at least partially received in the receiving space. The positioning member comprises a positioning portion, and the positioning portion is engaged into the recess, enabling a distance between the light guide plate and the backlight source to be less than or equal to a threshold. The threshold is less than or equal to 0.1 mm. 
     In some embodiments, the positioning member further includes a body portion and an extension portion, the body portion is connected to the back frame, and the extension portion is arranged to extend from the body portion towards a position between another side of the light guide plate without the backlight source arranged and the side wall. 
     In some embodiments, the backlight source includes a lamp extending along the side of the light guide plate close to the side wall, the positioning portion is arranged to perpendicularly protrude from an end of the extension portion away from the body portion, and a protruding direction of the positioning portion is parallel to an extending direction of the lamp. 
     As shown in  FIG. 1 , a structural schematic view of a backlight module  10  according to a first embodiment is provided. The backlight module  10  of the present embodiment may include a back frame  11 , an optical assembly  12 , a backlight source  13 , and a positioning member  14 . 
     As shown in  FIG. 1  and  FIG. 2 , the back frame  11  may include a side wall  111  and a bottom wall  112 , and the side wall  111  and the bottom wall  112  may be bent to connect to each other and define a receiving space  101 . 
     Alternatively, at least two side walls  111  may be arranged, and the at least two side walls  111  may be bent to connect to each other. 
     Alternatively, the back frame  11  may further include a top wall  113 . The top wall  113  and an end of the side wall  111  away from the bottom wall  112  may be bent to connect to each other. The top wall  113 , the side wall  111 , and the bottom wall  112  may cooperatively define the receiving space  101 . The top wall  113  may be arranged to carry a display module when the backlight module  10  is assembled with the display module of an electronic device. 
     Further, as shown in  FIG. 1 , the back frame  11  may define an opening  1111  communicating with the receiving space  101 . 
     Alternatively, the back frame  11  may be a metal back frame. 
     The optical assembly  12  may be received in the receiving space  101  and arranged on the bottom wall  112 . 
     The optical assembly  12  may include a light guide plate  121 . The light guide plate  121  may include a light incidence surface  1211  and a light emitting surface  1212 . The light incidence surface  1211  may be a surface of the light guide plate  121  close to the side wall  111 , and the light emitting surface  1212  may be a surface of the light guide plate  121  away from the bottom wall  112 . As shown in  FIG. 1 , the light guide plate  121  may be arranged with a first positioning portion  1213 . 
     Alternatively, the first positioning portion  1213  may be a recess. 
     Further, the optical assembly  12  may further include an optical film assembly  122  and a reflection sheet  123 . The optical film assembly  122  may be arranged on the light guide plate  121  and may specifically be on the light emitting surface  1212  of the light guide plate  121 . The reflection sheet  123  may be arranged on the bottom wall  112 , facing towards a side of the light guide plate  121  away from the light emitting surface  1212 . 
     The optical film assembly  122  may include a diffusion film  122   a , a lower transmission increasing film  122   b , and an upper transmission increasing film  122   c  sequentially stacked along a direction away from the light guide plate  121 . 
     The backlight source  13  may be arranged on a side of the light guide plate  121  close to the side wall  111 . Specifically, the backlight source  13  may be arranged on a side of the light guide plate  121  close to one of the at least two side walls  111 . 
     In the present embodiment, the backlight source  13  may include a lamp  131 , serving as a light source, and a flexible circuit board  132 . 
     The lamp  131  may be arranged on the side of the light guide plate  121  close to the side wall  111 . Specifically, the lamp  131  may be arranged on the light incidence surface  1211  of the light guide plate  121  and emit light to the light guide plate  121  through the light incidence surface  1211 . 
     The lamp  131  may include a printed circuit board (PCB)  131   a , an encapsulation member  131   b , and a light emitting element  131   c . The PCB  131   a  may be arranged on the side of the light guide plate  121  close to the side wall  111 . The encapsulation member  131   b  may be arranged on a side of the PCB  131   a  close to the light guide plate  121  and connected to the PCB  131   a . The encapsulation member  131   b  may define an encapsulation groove  1311 . The light emitting element  131   c  may be adhered to the PCB  131   a  and may be received in the encapsulation groove  1311 . The light emitting element  131   c  may emit the light to the light guide plate  121  through the encapsulation groove  1311 . In some embodiments, the lamp  131  may include an array of light emitting elements  131   c  arranged on the PCB  131   a  along a row direction and a column direction. The PCB  131   a  may be arranged on the side of the light guide plate  121  close to the side wall  111 . The row direction may be parallel to an extending direction of side of the light guide plate  121  arranged with the PCB  131   a , and the column direction may be perpendicular to the row direction. 
     Alternatively, the light emitting element  131   c  may be an LED chip. 
     Further, the lamp  131  may be arranged at an optimized position for light emitting relative to the light guide plate  121 . 
     The optimized position for light emitting may be a position of the lamp  131  from which the light emitted by the lamp  131  may be completely received by the light guide plate  121 . The optimized position may be an optimized position in height and in distance. It may be understood that, when the lamp  131  is arranged at a position being too high or too low along a direction perpendicular to the bottom wall  112 , the light guide plate  121  may be unable to receive the light emitted from the lamp  131  completely. When a distance between the lamp  131  and the light guide plate  121  is too long, the light emitted from the lamp  131  may escape from the light guide plate  121 , and therefore, the light may not be completely received by the light guide plate  121 , such that utilization of the light  131  and the backlight effect of the light guide plate  121  may be reduced. 
     Alternatively, the light emitting element  131   c  of the lamp  131  may be arranged on a central line of the light guide plate  121 . 
     Alternatively, a first adhesion member  15  may be arranged between the lamp  131  and the bottom wall  112 . The lamp  131  may be adhered to the bottom wall  112  via the first adhesion member  15 , enabling the lamp  131  to be arranged at an optimized height relative to the light guide plate  121 . That is, in the present embodiment, when the lamp  131  is adhered on the bottom wall  112  and fixed relative to the bottom wall  112  via the first adhesion member  15 , a thickness of the first adhesion member  15  may be adjusted to enable the light emitting element  131   c  of the lamp  131  to be arranged at the optimized height relative to the light guide plate  121  (i.e., arranged to align with the central line of the light guide plate  121 ), such that utilization of the light source  131  and the backlight effect of the light guide plate  121  may be improved. 
     Alternatively, the first adhesion member  15  may be a double-sided tape. 
     Alternatively, a second adhesion member  16  may be arranged between the lamp  131  and the side wall  111 . The lamp  131  may be adhered to the side wall  111  via the second adhesion member  16 , enabling the lamp  131  to be arranged at an optimized distance relative to the light guide plate  121 . That is, in the present embodiment, when the lamp  131  is adhered on the side wall  111  and fixed relative to the side wall  111  via the second adhesion member  16 , a thickness of the second adhesion member  16  may be adjusted to enable the lamp  131  to be arranged at the optimized distance relative to the light guide plate  121 , such that utilization of the light source  131  and the backlight effect of the light guide plate  121  may be improved. 
     As shown in  FIG. 1 ,  FIG. 2 , and  FIG. 3 , the flexible circuit board  132  may be arranged to adhere to the lamp  131  on a side of the lamp  131  away from the light guide plate  121 , such that a space for soldering the flexible circuit board  132  with the lamp  131  may not be required along a direction facing towards the side wall  111 . Therefore, the space may be saved along a direction perpendicular to the side wall  111 , a width of the backlight module  10  along the direction perpendicular to the side wall  111  may be reduced, and a narrow-sided backlight module maybe achieved. 
     Specifically, the flexible circuit board  132  may be adhered to a side of the PCB  131   a  away from the light emitting element  131   c . As shown in  FIG. 1 , the flexible circuit board may extend through the opening  1111  to reach a side of the back frame  11  away from the receiving space  101 . 
     The flexible circuit board  132  and the second adhesion member  15  may both be adhered to the PCB  131   a.    
     The positioning member  14  may be connected to the back frame  11  and at least partially received in the receiving space  101 . 
     Specifically, the positioning member  14  may include a body portion  14   a  and an extension portion  14   b . The body portion  14   a  may be connected to the back frame  11 . The extension portion  14   b  may extend from the body portion  14   a  towards the receiving space  101 . In 
       FIG. 1 , the body portion  14   a  may be at least partially received in the receiving space  101  and connect to the back frame  11 . The extension portion  14   b  may extend from a part of the body portion  14   a  received in the receiving space  101 . 
     Alternatively, the body portion  14   a  may be arranged at a position of which the at least two side walls  111  are bent and connected. The extension portion  14   b  may extend from the body portion  14   a  towards a position between the light guide plate  121  and at least one of the at least two side walls  111 . In the present embodiment, the extension portion  14   b  may extend from the body portion  14   a  towards a position between the light guide plate  121  and one of the at least two side walls  111  without the backlight source  13 . That is, the backlight source  13  may be arranged between a side of the light guide plate  121  and one of the at least two side walls  111 , whereas the extension portion  14   b  may be arranged between another side of the light guide plate  121  and another one of the at least two side walls  111 . 
     Alternatively, the positioning member  14  may be aligned with a side of the top wall  113  away from the receiving space  101 , such that the positioning member  14  and the top wall  113  may cooperatively carry the display module of the electronic device. In the present embodiment, the body portion  14   a  may be aligned with the side of the top wall  113  away from the receiving space  101 . 
     Further, the positioning member  14  may be arranged with a second positioning portion  141 , and the second positioning portion  141  may be engaged with the first positioning portion  1213 , such that the distance between the light guide plate  121  and the backlight source  13  may be less than or equal to a threshold. 
     It may be understood, during assembling the backlight module  10 , the backlight source  13  may be disposed into the receiving space  101  of the back frame  11  firstly, and the optical assembly  12  may subsequently be disposed into the receiving space  101 . At this point, an assembly gap may be reserved between the light guide plate  121  of the optical assembly  12  and the backlight source  13 . That is, after disposing the optical assembly  12  into the receiving space  101 , a gap may be defined between the light guide plate  121  and the backlight source  13 . However, during an actual assembling process, after the optical assembly  12  being disposed into the receiving space  101 , the gap between the light guide plate  121  and the backlight source  13  may be too large, such that the light guide plate  121  may not be able to receive the light emitted from the backlight source  13  completely, reducing the backlight effect of the light guide plate  121 . In the present embodiment, the second positioning portion  141  of the positioning member  14  may be arranged to engage with the first positioning portion  1213  of the light guide portion  121 . During engagement, the optical assembly  12  may disposed into the receiving space  101  by means of engaging the first positioning portion  1213  with the second positioning portion  141 , such that the distance between the light guide plate  121  and the backlight source  13  is less than or equal to the threshold. A situation of the distance between the light guide plate  121  and the backlight source  13  being too long may be avoided during the assembling, assembly precision may be improved, and a difficulty of assembling may be reduced. 
     Alternatively, the second positioning portion  141  may be a protrusion engaged with the first positioning portion  1213  (such as the recess in the present embodiments), and a direction of the protrusion protruding towards the recess may be parallel to an extending direction of the backlight source  13 . Specifically, the lamp  131  of the backlight source  13  may extend along the side of the light guide plate close to the side wall  111 , and the second positioning portion  141  may perpendicularly protrude from an end of the extension portion  14   b  away from the body portion  14   a . The protruding direction may be perpendicular to an extending direction of the extension portion  14   b  but parallel to the extending direction of the lamp  131 . A side of the light guide plate  121  without the lamp  131  arranged may be recessed inwardly to define the recess, i.e., the first positioning portion  1213 , and a direction of recessing may be parallel to the protruding direction of the second positioning portion  141 . The protrusion may be in a shape of an arc, and the recess may also be in the shape of the arc. In such a way, the first positioning portion  141  may be engaged into the recess. In some embodiment, the lamp  131  may include an array of light emitting elements  131   c  arranged on the PCB  131   a  long a row direction and a column direction. The PCB  131   a  may be arranged on the side of the light guide plate  121  close to the side wall  111 . The row direction may be parallel to an extending direction of side of the light guide plate  121  arranged with the PCB  131   a , and the column direction may be perpendicular to the row direction. The protruding direction of the second positioning portion  141  may be parallel to the row direction. 
     Alternatively, the threshold may be less than or equal to 0.1 mm. 
     Further, in the present embodiment, the backlight module  10  may further include a light-shielding tape  17 . The light-shielding tape  17  may be arranged on the side of the top wall  113  away from the receiving space  101  and may be adhered to the top wall  113  and the optical film assembly  122 . In such a way, when the backlight source  13  is emitting light, and the light is transmitting through the light guide plate  121  to reach the optical film assembly  122 , the light may not be escaped from the optical film assembly  122 . 
     Specifically, the light-shielding tape  17  may be arranged on the side of the top wall  113  away from the receiving space  101 , and may be adhered to the tope wall  113  and upper transmission increasing film  122   c  of the optical film assembly  122 . 
     As shown in  FIG. 4 , in other embodiments, the light-shielding tape  17  may be adhered to a side of the side wall  111  away from the receiving space  101  to increase an adhesion area between the light-shielding tape  17  and the back frame  11 , such that an adhesive force between the light-shielding tape  17  and the back frame  11  may be improved. 
     According to the backlight module provided in the present embodiment, the light guide plate may be arranged with the first positioning portion, and the positioning member may be arranged with the second positioning portion engaged with the first positioning portion, such that, during assembling the optical assembly, the first positioning portion and the second positioning portion may be engaged to achieve positioning, and the optical assembly may be disposed into the receiving space, such that the distance between the light guide plate and the backlight source may be less than or equal to the threshold. In such a way, during assembling, a situation of the distance between the light guide plate and the backlight source being too long may be avoided, and the light guide plate unable to completely receive the light emitted from the backlight source may be avoided, improving the backlight effect of the light guide plate, improving the assembly accuracy, and reducing the difficulty of assembling. 
     As shown in  FIG. 5 , a cross-sectional view of the backlight module  20  according to the second embodiment is provided. The backlight module  20  may include a back frame  21 , an optical assembly  12 , a backlight source  13 , and a positioning member  14 . 
     As shown in  FIG. 5  and  FIG. 6 , the back frame  21  may include a side wall  111  and a bottom wall  212 . The side wall  111  and the bottom wall  212  may be bent and connected to each other to define a receiving space  201 . 
     Alternatively, at least two the side walls  111  may be arranged, and the at least two side walls  111  may be bent and connected to each other. 
     Alternatively, the back frame  21  may further include a top wall  113 , and the top wall  113  and an end of the side wall  111  away from the bottom wall  212  may be bent and connected to each other. The top wall  113 , the side wall  111 , and the bottom wall  212  may cooperatively define the receiving space  201 . The top wall  113  may be arranged to support a display module while assembling the backlight module  10  with the display module of the electronic device. 
     The receiving space  201  may include a first space  2011  and a second space  2012  communicating with each other, and the first space  2011  and the second space  2012  may be defined sequentially along a direction facing towards the side wall  111 . An area of a cross section of the second space  2012  taken along a direction facing the side wall  111  is greater than that of the first space  2011  taken along a direction facing the side wall  111 . 
     Specifically, the bottom wall  212  may include a first bottom wall  2121  and a second bottom wall  2122 . The first bottom wall  2121  and the second bottom wall  2122  are connected to each other and arranged sequentially along a direction facing towards the side wall  111 . As shown in  FIG. 6 , a vertical distance between the second bottom wall  2122  and the top wall  113  may be greater than a vertical distance between the first bottom wall  2121  and the top wall  113 . In such a way, when the receiving space  201  is defined, cross sections of the first and the second spaces may be taken along the direction facing towards the side wall  111 , the area of the cross section of the second space  2012  defined by the second side wall  2122  may be greater than that of the first space  2011  defined by the first side wall  2121 . 
     Further, the back frame  21  may define an opening  1111  communicating with the receiving space  201 . 
     Alternatively, the back frame  21  may be a metal back frame. 
     The optical assembly  12  may be received in the receiving space  201  and may be arranged on the bottom wall  212 . 
     Specifically, the optical assembly  12  may be received in the first space  2011  of the receiving space  201 . 
     The optical assembly  12  may include a light guide plate  121 . The light guide plate  121  may include a light incidence surface  1211  and a light emitting surface  1212 . The light incidence surface  1211  may be a side of the light guide plate  121  close to the side wall  111 , and the light emitting surface  1212  may be a side of the light guide plate  121  away from the bottom wall  212 . Further, the light guide plate  121  may be arranged with a first positioning portion  1213 . 
     Alternatively, the first positioning portion may be a recess. 
     Further, the optical assembly  12  may further include an optical film assembly  122  and a reflection sheet  123 . The optical film assembly  122  may be arranged on the light guide plate  121  and may specifically be on the light emitting surface  1212  of the light guide plate  121 . The reflection sheet  123  may be arranged on the bottom wall  212  facing towards a side of the light guide plate  121  away from the light emitting surface  1212 . 
     The optical film assembly  122  may include a diffusion film  122   a , a lower transmission increasing film  122   b , and an upper transmission increasing film  122   c  sequentially stacked along a direction away from the light guide plate  121 . 
     The backlight source  13  may be arranged on the side of the light guide plate  121  close to the side wall  111 . Specifically, the backlight source  13  may be arranged on the side of the light guide plate  121  close to one of the at least two side walls  111 . 
     The backlight source  13  may include a lamp  131  and a flexible circuit board  132 . 
     The lamp  131  may be arranged on the side of the light guide plate  121  close to the side wall  111 . Specifically, the lamp  131  may be arranged on the light incidence surface  1211  of the light guide plate  121  to emit light to the light guide plate  121  through the light incidence surface  1211 . 
     Further, the light source  131  may be received in the second space  2012 . 
     The lamp  131  may include a PCB  131   a , an encapsulation member  131   b , and a light emitting element  131   c . The PCB  131   a  may be arranged on the side of the light guide plate  121  close to the side wall  111 . The encapsulation member  131   b  may be arranged on a side of the PCB  131   a  close to the light guide plate  121  and connected to the PCB  131   a . The encapsulation member  131   b  may define an encapsulation groove  1311 . The light emitting element  131   c  may be adhered to the PCB  131   a  and may be received in the encapsulation groove  1311 . The light emitting element  131   c  may emit the light to the light guide plate  121  through the encapsulation groove  1311 . 
     Alternatively, the light emitting element  131   c  may be an LED chip. 
     Further, the lamp  131  may be arranged at an optimized position for light emitting relative to the light guide plate  121 . 
     The optimized position for light emitting may be a position of the lamp  131  from which the light emitted may be completely received by the guide plate  121 . The optimized position may be an optimized position in height and in distance. It may be understood that, when the lamp  131  is arranged at a position being too high or too low along a direction perpendicular to the bottom wall  212 , the light guide plate  121  may be unable to receive the light emitted from the lamp  131  completely. When a distance between the lamp  131  and the light guide plate  121  is too long, the light emitted from the lamp  131  may escape from the light guide plate  121 , and therefore, the light may not be completely received by the light guide plate  121 , such that utilization of the light source  131  and the backlight effect of the light guide plate  121  may be reduced. 
     Alternatively, the light emitting element  131   c  of the lamp  131  may be arranged on a central line of the light guide plate  121 . 
     Alternatively, a first adhesion member  15  may be arranged between the lamp  131  and the bottom wall  212 . The lamp  131  may be adhered to the bottom wall  212  via the first adhesion member  15 , enabling the lamp  131  to be arranged at the optimized position in height relative to the light guide plate  121 . That is, in the present embodiment, when the lamp  131  is adhered on the bottom wall  212  and fixed relative to the bottom wall  212  via the first adhesion member  15 , a thickness of the first adhesion member  15  may be adjusted to enable the lamp  131  to be arranged at the optimized position in height relative to the light guide plate  121 , such that utilization of the light source  131  and the backlight effect of the light guide plate  121  may be improved. 
     Further, as the light  131  may be received in the second space  2012 , and the area of the cross section of the second space  2012  taken along the direction perpendicular to the side wall  111  is greater than that of the first space  2011  taken along the direction perpendicular to the side wall  111 , when a height of the light  131  relative to the light guide plate  121  is adjusted, an enough space for adjustment may be defined. A situation of defining insufficient space for adjustment may be avoided. When the space for adjustment is insufficient, a thickness of the first adhesion member  15  may be reduced, a small thickness of the first adhesion member  15  may reduce an adhesive force between the light  131  and the bottom wall  212 . Alternatively, under such the situation of insufficient space for adjustment, the light  131  may not be arranged at the optimized position to prevent the thickness of the first adhesion member  15  from being too small, reducing the backlight effect of the light guide plate  121 . 
     Alternatively, the first adhesion member  15  may be a double-sided tape. 
     Alternatively, a second adhesion member  16  may be arranged between the lamp  131  and the side wall  111 . The lamp  131  may be adhered to the side wall  111  via the second adhesion member  16 , enabling the lamp  131  to be arranged at the optimized position in distance relative to the light guide plate  121 . That is, in the present embodiment, when the lamp  131  is adhered on the side wall  111  and fixed relative to the side wall  111  via the second adhesion member  16 , a thickness of the second adhesion member  16  may be adjusted to enable the lamp  131  to be arranged at the optimized distance relative to the light guide plate  121 , such that utilization of the light  131  and the backlight effect of the light guide plate  121  may be improved. 
     The flexible circuit board  132  may be arranged to adhere to a side of the lamp  131  away from the light guide plate  121 , such that a space for soldering the flexible circuit board  132  with the lamp  131  may not be required along a direction facing towards the side wall  111 . Therefore, the space may be saved along the direction perpendicular to the side wall  111 , a width of the backlight module  10  along the direction perpendicular to the side wall  111  may be reduced, and the backlight module having a narrow side maybe achieved. 
     Specifically, the flexible circuit board  132  may be adhered to a side of the PCB  131   a  away from the light emitting element  131   c . The flexible circuit board may extend through the opening  1111  to reach a side of the back frame  11  away from the receiving space  101 . 
     The flexible circuit board  132  and the second adhesion member  15  may both be adhered to the PCB  131   a.    
     The positioning member  14  may be connected to the back frame  11  and at least partially received in the receiving space  201 . 
     Specifically, the positioning member  14  may include a body portion  14   a  and an extension portion  14   b . The body portion  14   a  may be connected to the back frame  11 . The extension portion  14   b  may extend from the body portion  14   a  towards the receiving space  201 . The positioning member  14  in the second embodiment is similar to that in the first embodiment, and by referring to  FIG. 1 , the body portion  14   a  may be at least partially received in the receiving space  201  and may connect to the back frame  11 . The extension portion  14   b  may extend from a part of the body portion  14   a  received in the receiving space  201 . 
     Alternatively, the body portion  14   a  may be arranged at a position of which the at least two side walls  111  are bent and connected. The extension portion  14   b  may extend from the body portion  14   a  towards a position between the light guide plate  121  and at least one of the at least two side walls  111 . In the present embodiment, the extension portion  14   b  may extend from the body portion  14   a  towards a position between the light guide plate  121  and one of the at least two side walls  111  without the backlight source  13 . That is, the backlight source  13  may be arranged between a side of the light guide plate  121  and one of the at least two side walls  111 , whereas the extension portion  14   b  may be arranged between another side of the light guide plate  121  and another one of the at least two side walls  111 . 
     Alternatively, the positioning member  14  may be aligned with the side of the top wall  113  away from the receiving space  201 , such that the positioning member  14  and the top wall  113  may cooperatively carry the display module of the electronic device. In the present embodiment, the body portion  14   a  may be aligned with the side of the top wall  113  away from the receiving space  201 . 
     Further, the positioning member  14  may be arranged with a second positioning portion  141 , and the second positioning portion  141  may be engaged with the first positioning portion  1213 , such that the distance between the light guide plate  121  and the backlight source  13  may be less than or equal to a threshold. 
     It may be understood, during assembling the backlight module  10 , the backlight  13  may be disposed into the receiving space  201  of the back frame  11  first, and the optical assembly  12  may subsequently be disposed into the receiving space  201 . At this point, an assembly gap may be reserved between the light guide plate  121  of the optical assembly  12  and the backlight  13 . That is, after disposing the optical assembly  12  into the receiving space  201 , a gap may be defined between the light guide plate  121  and the backlight source  13 . However, during an actual assembling process, after the optical assembly  12  being disposed into the receiving space  201 , the gap between the light guide plate  121  and the backlight  13  may be too large, such that the light guide plate  121  may not be able to receive the light emitted from the backlight source  13  completely, reducing the backlight effect of the light guide plate  121 . In the present embodiment, the second positioning portion  141  of the positioning member  14  may be arranged to engage with the first positioning portion  1213  of the light guide portion  121 . During engagement, the optical assembly  12  may disposed into the receiving space  101  by means of engaging the first positioning portion  1213  with the second positioning portion  141 , such that the distance between the light guide plate  121  and the backlight source  13  is less than or equal to the threshold. A situation of the distance between the light guide plate  121  and the backlight source  13  being too long may be avoided during the assembling, assembly precision may be improved, and a difficulty of assembling may be reduced. 
     Alternatively, the second positioning portion  141  may be a protrusion engaged with the recess of the first positioning portion  1213 , and a direction the protrusion protruding towards the recess may be parallel to an extending direction of the backlight source  13 . Specifically, the lamp  131  of the backlight source  13  may extend along the side of the light guide plate close to the side wall  111 , and the second positioning portion  141  may perpendicularly protrude from an end of the extension portion  14   b  away from the body portion  14   a . The protruding direction may be perpendicular to an extending direction of the extension portion  14   b  but parallel to the extending direction of the lamp  131 . A side of the light guide plate  121  without the lamp  131  arranged may be recessed inwardly to define the recess, i.e., the first positioning portion  1213 , and a direction of recessing may be parallel to the protruding direction of the second positioning portion  141 . The protrusion may be in a shape of an arc, and the recess may also be in the shape of the arc. In such a way, the first positioning portion  141  may be engaged into the recess. 
     Alternatively, the threshold may be less than or equal to 0.1 mm. 
     Further, in the present embodiment, the backlight module  20  may further include a light-shielding tape  17 . The light-shielding tape  17  may be arranged on the side of the top wall  113  away from the receiving space  201  and may be adhered to the top wall  113  and the optical film assembly  122 . In such a way, when backlight source  13  is emitting light, and the light is transmitting through the light guide plate  121  reaching the optical film assembly  122 , the light may not be escaped from the optical film assembly  122 . 
     Specifically, the light-shielding tape  17  may be arranged on the side of the top wall  113  away from the receiving space  201 , and may be adhered to the tope wall  113  and upper transmission increasing film  122   c  of the optical film assembly  12 . 
     Alternatively, in other embodiments, the light-shielding tape  17  may be adhered to a side of the side wall  111  away from the receiving space  201  to increase an adhesion area between the light-shielding tape  17  and the back frame  11 , such that an adhesive force between the light-shielding tape  17  and the back frame  11  may be improved. 
     According to the backlight module provided in the present embodiment, the light guide plate may be arranged with the first positioning portion, and the positioning member may be arranged with the second positioning portion engaged with the first positioning portion, such that, during assembling the optical assembly, the first positioning portion and the second positioning portion may be engaged to achieve positioning. The optical assembly may be disposed into the receiving space, such that the distance between the light guide plate and the backlight source may be less than or equal to the threshold. In such a way, during assembling, a situation of the distance between the light guide plate and the backlight source being too long may be avoided, and the light guide plate unable to receive the light emitted from the backlight source may be avoided, improving the backlight effect of the light guide plate, improving the assembly accuracy, and reducing the difficulty of assembling. Further, the lamp may be disposed in the second space, the area of the cross section of the second space taken along the direction facing towards the side wall is greater than that of the first space taken along the direction facing towards the side wall. When the height of the lamp relative to the bottom wall is adjusted, sufficient space may be defined. A situation of insufficient space for adjustment may be avoided, and reducing the thickness of the first adhesion member resulting in reduction of the adhesive force between the lamp and the bottom wall may be prevented. Alternatively, a situation of arranging the adhesion member in a proper thickness but resulting in the lamp missing the optimized position in height and reducing the backlight effect may be prevented. 
     As shown in  FIG. 7 , a structural diagram of an electronic device  30  is provided according to an embodiment. The electronic device in the present embodiment may be any device having functions of communication and storage, such as a tablet computer, a mobile phone, an electronic reader, a network television, a wearable device, and other intelligent devices able to connect to the network. 
     The electronic device  30  may include the backlight module  31  as described in any one of the above-mentioned embodiments and a display module  32 . The backlight module  31  may refer to detailed description of any one of the above-mentioned embodiments, and will not be repeatedly described hereinafter. The backlight module  20  described in the second embodiment may be shown in the figure of the present embodiment. 
     The display module  32  may be arranged to stack above the backlight module  31 . 
     Further, the display module  32  may be carried by the top wall  113 . 
     Only a part of embodiments are described in the above, and should not limit the scope of the present disclosure. Any equivalent apparatus and equivalent process transformation based on the drawings and the specification of the present disclosure, applied directly or indirectly in other related art, should be within the scope of the present disclosure.