Patent Publication Number: US-2022214579-A1

Title: Display apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of PCT PCT/CN2021/081821, filed on Mar. 19, 2021, which claims priorities to Chinese patent application No. 202010221021.1 filed on Mar. 25, 2020, No. 202010351591.2 filed on Apr. 28, 2020, No. 202020687645.8 filed on Apr. 28, 2020, No. 202010453658.3 filed on May 26, 2020, No. 202010522067.7 filed on Jun. 10, 2020, No. 202010468356.3 filed on May 28, 2020, No. 202010855892.9 filed on Aug. 24, 2020, No. 202010791424.X filed on Aug. 7, 2020, No. 202010791451.7 filed on Aug. 7, 2020, and No. 202011508504.6 filed on Dec. 18, 2020, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present application relates to display technology, in particular to a display apparatus. 
     BACKGROUND 
     As the mainstream display screen at present, a liquid crystal display screen has the advantages of low power consumption, small size, low radiation and the like. A liquid crystal panel is not self-lit panel, and needs to be used together with a backlight module. 
     In direct backlight module, a diffusion plate is usually required, and a certain distance generally exists between light sources and the diffusion plate to guarantee full light mixing between the light sources and improve the brightness uniformity of backlight display. 
     In order to optimize an emitting angle of backlight and the backlight uniformity, in a direct backlight module, functional films will be added under the diffusion plate. A diffusion plate support is in direct contact with the functional films, the functional films are soft, and if the diffusion plate has relative motions, the diffusion plate support will unavoidably scratch the functional films, causing failure of required optical performances of the functional films, leading poor display and the like. 
     SUMMARY 
     A display apparatus according to some embodiments of the present application includes: a panel, configured to display an image; a light source on an incident side of the panel, configured to provide backlight for the panel; a diffusion plate on a light emitting side of the light source; a functional layer on a side of the diffusion plate facing the light source; a support between the light source and the functional layer and configured to support the diffusion plate; and a cushion portion between the support and the functional layer and configured to contact the support and the functional layer so as to mitigate pressure of the support for the functional layer. 
     In some embodiments of the present application, the cushion portion is on a surface of a side of the support facing the functional layer; or the cushion portion is on a surface of a side of the functional layer facing the support. 
     In some embodiments of the present application, an area of a cross section of the cushion portion parallel to the functional layer is greater than an area of a cross section of the support parallel to the functional layer and close to the functional layer. 
     In some embodiments of the present application, the cushion portion is of a shape of a sphere, a hemisphere or an ellipsoid; and the support is of a shape of a tetrahedron, a pyramid, a cone, a cuboid, a cube or a cylinder. 
     In some embodiments of the present application, the cushion portion is made of silica gel or epoxy resin. 
     In some embodiments of the present application, the light source is a micro light emitting diode light board, and a height of the cushion portion and a height of the support meet a following relationship: 0.2≤(H1+H2−ΔH)/p≤0.8; wherein H1 represents a height of the support, H2 represents an original height of cushion portion, ΔH represents a deformation of the cushion portion, and p represents a distance between every two adjacent micro light emitting diodes in the micro light emitting diode light board. 
     In some embodiments of the present application, the height of the support is smaller than 6 mm. 
     In some embodiments of the present application, the support is fixed to the micro light emitting diode light board through buckles, screws or adhesive. 
     In some embodiments of the present application, the micro light emitting diode light board includes: a circuit board, configured to provide a driving signal; at least one micro light emitting diodes on the circuit board in an array; an packaging layer on a surface of a side of the micro light emitting diode away from the circuit board; and a reflective sheet on a surface of a side of the circuit board facing the micro light emitting diode, wherein the reflective sheet is provided with openings for exposing the at least one micro light emitting diodes; wherein the support is fixed at interval area among the at least one micro light emitting diodes. 
     In some embodiments of the present application, the packaging layer covers surfaces of the micro light emitting diodes as a whole layer; or the packaging layer covers the surfaces of the micro light emitting diodes, and the packaging layer has individual dot patterns; or the packaging layer covers micro light emitting diode rows or micro light emitting diode columns, and the packaging layer has individual strip-shaped patterns. 
     In some embodiments of the present application, a thickness of the diffusion plate is 1.5 mm to 3 mm. 
     In some embodiments of the present application, the diffusion plate has scattering particle materials inside. 
     In some embodiments of the present application, the functional layer is configured to reflect light rays with small incident angles emitted from the light source and transmit light rays with large incident angles emitted from the light source. 
     In some embodiments of the present application, the functional layer includes film layers with different refraction indexes and arranged in a laminated mode. 
     In some embodiments of the present application, the support is distributed at interval area among the micro light emitting diodes. 
     In some embodiments of the present application, the support is fixed to the micro light emitting diode light board through a limiting sheet, an auxiliary column and a buckle. 
     In some embodiments of the present application, the limiting sheet and the buckle are at two ends of the auxiliary column respectively. 
     In some embodiments of the present application, the display apparatus further includes a group of films on a side of the diffusion plate away from the light source. 
     In some embodiments of the present application, the group of films includes a quantum dot layer or a fluorescent layer. 
     In some embodiments of the present application, the group of films includes a prism sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a display apparatus according to an embodiment of the present application. 
         FIG. 2  is a first schematic cross-sectional view of a backlight module according to an embodiment of the present application. 
         FIG. 3  is a second schematic cross-sectional view of a backlight module according to an embodiment of the present application. 
         FIG. 4  is a schematic top view of a micro light emitting diode light board in  FIG. 3 . 
         FIG. 5  is a first schematic top view of a micro light emitting diode light board according to an embodiment of the present application. 
         FIG. 6  is a second schematic top view of a micro light emitting diode light board according to an embodiment of the present application. 
         FIG. 7  is a third schematic cross-sectional view of a backlight module according to an embodiment of the present application. 
         FIG. 8  is a schematic diagram of film interference according to an embodiment of the present application. 
         FIG. 9  is a schematic cross-sectional view of a backlight module according to an embodiment of the present application. 
         FIG. 10  is a schematic cross-sectional view of a backlight module according to an embodiment of the present application. 
         FIG. 11  is a schematic top view of a micro light emitting diode light board in  FIG. 10 . 
         FIG. 12  is a schematic cross-sectional view of a backlight module according to an embodiment of the present application. 
         FIG. 13  is a schematic top view of a micro light emitting diode light board according to an embodiment of the present application. 
         FIG. 14  is a schematic top view of a micro light emitting diode light board according to an embodiment of the present application. 
         FIG. 15  is a schematic diagram of a connection relationship between supports and a micro light emitting diode light board according to an embodiment of the present application. 
         FIG. 16  is a schematic diagram of a connection relationship between supports and a micro light emitting diode light board according to an embodiment of the present application. 
         FIG. 17  is a schematic diagram of a connection relationship between supports and a micro light emitting diode light board according to an embodiment of the present application. 
     
    
    
       100 —backlight module,  200 —panel,  11 —back plate,  12 —light source and micro light emitting diode light board,  13 —diffusion layer,  14 —first functional layer,  15 —support,  16 —transparent substrate,  17 —wavelength conversion layer,  18 —second functional layer,  19 —optical film,  121 —circuit board,  122 —micro light emitting diode,  123 —reflective layer, and  124 —packaging layer. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In order to make the objectives, features and advantages of the present application more obvious, the present application will be further described below in combination with the accompanying drawings and embodiments. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the implementations set forth herein. 
     A liquid crystal display apparatus is mainly includes a backlight module and a liquid crystal panel. The liquid crystal panel does not emit light itself, and needs to use a light source provided by the backlight module to achieve brightness display. 
     The work principle of the liquid crystal display apparatus is that liquid crystals are placed between two pieces of conductive glass, the electric field effect which is driven by an electric field between two electrodes causes distortion of liquid crystal molecules, so as to control transmission or shielding for light emitting from a backlight source, thereby displaying images. If color light filters are added, color images may be displayed. 
       FIG. 1  is a schematic cross-sectional view of a display apparatus according to an embodiment of the present application. 
     Referring to  FIG. 1 , the display apparatus includes: a backlight module  100  and a panel  200 . The backlight module  100  is configured to provide a backlight source for the panel  200 , and the panel  200  is configured to display images. 
     The backlight module  100  is usually located at the bottom of the display apparatus, with its shape and size being adaptive to those of the display apparatus. When applied to devices such as a television or a mobile terminal, the backlight module is usually in a rectangular shape. 
     The backlight module in the embodiments of the present application adopts a direct backlight module which is configured to uniformly emit light rays in a whole light emitting surface to provide light rays full in brightness and uniform in distribution for the panel, so that the panel can normally display images. 
     The panel  200  is located on a light emitting side of the backlight module  100 , and a shape and size of the panel are usually matched with those of the backlight module. Usually, the panel  200  may be rectangular, including a top side, a bottom side, a left side and a right side. The top side and the bottom side are opposite, the left side and the right side are opposite, the top side is connected with one end of the left side and one end of the right side, and the bottom side is connected with the other end of the left side and the other end of the right side. 
     The panel  200  is a panel which is able to transmit light and adjust transmittance of light, but the panel does not emit light itself. The panel  200  has a plurality of pixel units arranged in an array, and each pixel unit may independently control a transmittance and color of light rays entering the pixel unit from the backlight module  100  to make light rays transmitted through all the pixel units form a displayed image. 
       FIG. 2  is a first schematic cross-sectional view of the backlight module according to an embodiment of the present application. 
     Referring to  FIG. 2 , the backlight module according to the embodiment of the present application includes: a back plate  11 , a light source  12 , a diffusion layer  13 , a first functional layer  14 , a support  15  and a transparent substrate 16 . 
     The back plate  11  is located at the bottom of the backlight module and configured for supporting. Usually, the back plate  11  is of a square or rectangular structure, and when the back plate is applied to a special-shaped display apparatus, a shape of the back plate is adaptive to a shape of the display apparatus. 
     The back plate  11  includes a top side, a bottom side, a left side and a right side. The top side and the bottom side are opposite, the left side and the right side are opposite, the top side is connected with one end of the left side and one end of the right side, and the bottom side is connected with the other end of the left side and the other end of the right side. 
     A material of the back plate  11  is aluminum, iron, aluminum alloy or iron alloy. The back plate  11  is configured to fix the light source  12  and support and fix edge areas of components such as an optical film and a diffusion plate, and the back plate  11  also has an effect of dissipating heat for the light source  12 . 
     In the embodiments of the present application, the backlight module is a direct backlight module, and the light source  12  is located on the back plate  11 . Usually, the light source  12  may be a light bar or a light board. 
     The light bar or the light board is provided with point light sources, and the point light sources may be light emitting diodes or micro light emitting diodes. As a backlight source, compared with traditional light emitting diodes, the micro light emitting diodes have a smaller size and can achieve finer dynamic control and improve dynamic contrast of the display apparatus. 
     In the embodiments of the present application, the light source  12  may be a micro light emitting diode light board ( 12 ), and the whole micro light emitting diode light board ( 12 ) may be square or rectangular, with a length of 200 mm to 800 mm and a width of 100 mm to 500 mm. 
     A plurality of micro light emitting diode light boards ( 12 ) may be arranged according to a size of the display apparatus, and the micro light emitting diode light boards ( 12 ) are spliced to collectively provide backlight. In order to avoid optical problems caused by splicing of the micro light emitting diode light boards ( 12 ), splicing seams between the adjacent micro light emitting diode light boards ( 12 ) are made as small as possible, and even seamless splicing is achieved. 
     Referring to  FIG. 2 , the micro light emitting diode light board ( 12 ) includes: a circuit board  121 , micro light emitting diodes  122 , a reflective layer  123  and a packaging layer  124 . 
     The micro light emitting diode light board may be formed through two surface mounting manners: POB and COB. POB is short for package on board, and means that LED chips are packaged (large-size bonding pad) and then mounted to a circuit board; and COB is short for chip on board, and means that LED chips are directly mounted on a circuit board. 
     The two mounting manners can both apply to the micro light emitting diode light board in the present application. 
     In the embodiments of the present application, the micro light emitting diodes adopt micro light emitting diode chips of a micron size. 
     Next, a structure of the micro light emitting diode light board formed through a COB manner is taken as an example for discussion in detail. 
     In some embodiments, the micro light emitting diode light board  12  is a mini-LED light board. 
     The circuit board  121  is located on the back plate  11 , and a shape of the circuit board  121  is substantially same as an overall shape of the micro light emitting diode light board ( 12 ). Usually, the circuit board  121  is in a plate shape and is rectangular or square as a whole. The circuit board  121  has a length of 200 mm to 800 mm and a width of 100 mm to 500 mm. 
     In the embodiments of the present application, the circuit board  121  may be a printed circuit board (PCB), the PCB includes an electronic circuit and an insulating layer, and the insulating layer exposes one or more bonding pads in the electronic circuit for welding the micro light emitting diodes and covers remaining parts in the electronic circuit. 
     Or, the circuit board  121  may also be an array substrate formed by manufacturing a thin film transistor driving circuit on a base substrate, and a surface of the array substrate has electrodes connected to the thin film transistor driving circuit for welding the micro light emitting diodes. 
     A base or substrate of the circuit board  121  may be made of materials such as FR4 or glass, or a base or base substrate of the circuit board  121  may be made of a flexible material to form a flexible display apparatus. 
     The circuit board  121  is configured to provide a driving electric signal for the micro light emitting diodes  122 . The micro light emitting diodes  122  and the circuit board  121  are separately manufactured, a surface of the circuit board  121  includes a plurality of bonding pads for welding the micro light emitting diodes  122 , the micro light emitting diodes  122  are transferred above the bonding pads after being manufactured, the micro light emitting diodes  122  are welded to the circuit board  121  through processes such as reflow soldering, and thus the micro light emitting diodes  122  may be driven to emit light by controlling an input signal of the circuit board  121 . 
     The micro light emitting diodes  122  are located on the circuit board. Electrodes of the micro light emitting diodes  122  are welded to the bonding pads exposed on the circuit board  121  to achieve electric connection therebetween. 
     The micro light emitting diodes  122  are different from ordinary light emitting diodes, and specifically refer to micro light emitting diode chips. Since the micro light emitting diodes  122  have small sizes, dynamic light emitting of the backlight module can be controlled to smaller partitions, which contributes to improve picture contrast. In the embodiments of the present application, the size of the micro light emitting diodes  122  is 50 μm to 300 μm. 
     The micro light emitting diode light board ( 12 ) may only include micro light emitting diodes  122  of one color, or micro light emitting diodes  122  of various colors, which is not limited here. 
     The reflective layer  123  is located on a surface of a side of the circuit board  121  close to the micro light emitting diodes  122 . The reflective layer  123  and the circuit board  121  are substantially same in shape, and the reflective layer  123  includes a plurality of openings for exposing the micro light emitting diodes  122 . 
     The reflective layer  123  is a protective layer located above the circuit board and is configured for protecting the circuit board and performing diffuse reflection on the incident light rays. In the embodiments of the present application, the reflective layer  123  may be formed in the way that the surface of the circuit board  121  is coated with white oil or other materials having light reflecting properties and then the areas of the bonding pads for welding the micro light emitting diodes  122  are exposed through processes such as etching. 
     The reflective layer  123  has light reflecting property, so that when the light rays emitted from the micro light emitting diode light board  122  are reflected to one side of the back plate by elements in the backlight module, the light rays may be reflected to the light emitting side again by the reflective layer  123 , thereby improving the use efficiency of the light source. 
     The packaging layer  124  is located on surfaces of a side of the micro light emitting diodes  122  away from the circuit board  121 . The packaging layer  124  may be arranged individually or as a whole layer. When being arranged individually, the packaging layer  124  only covers the surfaces of the micro light emitting diodes  122 , while no pattern is arranged in other regions of the circuit board; and when being arranged as the whole layer, the packaging layer  124  covers the whole circuit board  121  and the surfaces of the micro light emitting diodes  122 . 
     The packaging layer  124  is configured to protect the micro light emitting diodes  122  and prevent foreign items from entering the micro light emitting diodes  122 . In the embodiment of the present application, the packaging layer  124  may be made of a transparent material, such as silica gel or epoxy resin. The packaging layer  124  may be manufactured in a point coating or whole-face coating mode. 
     Referring to  FIG. 2 , the whole packaging layer  124  may cover the surfaces of the micro light emitting diodes  122 , and the surfaces of the micro light emitting diodes  122  and the surface of the circuit board  121  are coated with one packaging layer  124  in a spot-coated mode, so packaging efficiency is high. 
       FIG. 3  is a schematic cross-sectional view of the backlight module according to an embodiment of the present application.  FIG. 4  is a schematic top view of the micro light emitting diode light board in  FIG. 3 . 
     Referring to  FIG. 3  and  FIG. 4 , the whole packaging layer  124  may cover the surfaces of the micro light emitting diodes  122 , and only the surfaces of the micro light emitting diodes  122  are coated with the packaging layer  124  in the spot-coated mode, so that the packaging layer  124  has individual dot array patterns. Forming the packaging layer  124  in the spot-coated mode may save materials and lower the packaging cost. 
       FIG. 5  is a schematic top view of the micro light emitting diode light board according to an embodiment of the present application.  FIG. 6  is a schematic top view of the micro light emitting diode light board according to an embodiment of the present application. 
     Referring to  FIG. 5 , the packaging layer  124  may be formed by whole-row coating in a direction of micro light emitting diode rows, or, referring to  FIG. 6 , the packaging layer  124  may also be formed by whole-column coating in a direction of micro light emitting diode columns, so that the packaging layer  124  has individual strip-shaped patterns. The packaging layer  124  formed in a whole-row/column coated mode has high packaging efficiency, and materials of packaging glue may be saved as well. 
     The diffusion layer  13  is located on a light emitting side of the light source  12 . The diffusion layer  13  is arranged as a whole layer, and a shape of the diffusion layer  13  is substantially same as the shape of the back plate  11 . Usually, the diffusion layer  13  may be rectangular or square. 
     The diffusion layer  13  is configured to scatter the incident light rays to make the light rays passing the diffusion layer  13  more uniform. Scattering particle materials are arranged in the diffusion layer  13 , and the light rays will be refracted and reflected continuously after entering the scattering particle materials, so that the effect of scattering the light rays is realized to achieve the effect of light uniformizing. 
     The diffusion layer  13  may adopt two forms, a diffusion plate or a diffusion sheet. The diffusion plate may be used for a large display apparatus such as a television; while the diffusion sheet may be used for a small display apparatus such as a mobile phone and a smart watch. 
     A thickness of the diffusion plate is larger than that of the diffusion sheet and is 1.5 mm to 3 mm. The diffusion plate has larger haze and better uniformizing effect, and usually may be processed through an extrusion process. A material for the diffusion plate is generally selected from at least one of polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS) or polypropylene (PP). 
     A thickness of the diffusion sheet is 0.3 mm or below, and the diffusion sheet is relatively thin and more suitable for small and light display apparatuses. According to the diffusion sheet, a base material is usually coated with diffusion particles, the base material may be polyethylene terephthalate (PET) or glass, and the diffusion particles may be titanium dioxide, zinc oxide, calcium oxide and the like. 
     The first functional layer  14  is located on a side of the diffusion layer  13  facing the light source  12 . The first functional layer  14  is arranged as a whole layer with a shape being substantially same as the shape of the diffusion layer  13 , which may be square or rectangular usually. 
     When the light source adopts the micro light emitting diode light board, energy distribution of emitting light of the micro light emitting diodes  122  in the micro light emitting diode light board meets Lamber distribution, and most light energy is concentrated within a small angle range over the micro light emitting diodes  122 , causing that the areas over the micro light emitting diodes  122  are bright, junction areas of the adjacent micro light emitting diodes  122  are dark, and the emitting light is not uniformly distributed. 
     The first functional layer  14  is configured to uniformize the emitting light of the light source  12 . The first functional layer  14  may reflect light rays with small incident angles and transmit light rays with large incident angles, in this way, most of light rays with small incident angles emitted from the micro light emitting diodes are reflected when entering the first functional layer  14  because an incident angle is small, while most of light rays with large angles emitted from the micro light emitting diodes are transmitted when entering the first functional layer  14  because an incident angle is large, and thus a brightness difference between light emitting centers and edge areas of the micro light emitting diodes  122  is balanced, thereby solving the problems that the areas over the micro light emitting diodes are too bright and the junction areas of the adjacent micro light emitting diodes are too dark. By arranging the first functional layer  14  on the light emitting side of the micro light emitting diode light board, the uniformity of the emitting light of the micro light emitting diode light board may be improved, so that the quantity of the micro light emitting diodes  122  used may be reduced to achieve backlight thinning design. 
     In some embodiments of the present application, the first functional layer is an angle selection layer. The angle selection layer is configured that: the larger the angle of the incident light rays, the smaller a reflectivity to the incident light rays; and the larger the angle of the incident light rays, the larger a transmittance to the incident light rays. The angle selection layer is configured to reflect light rays with a first incident angle range and transmit light rays with a second incident angle range. An incident angle value corresponding to the first incident angle range is smaller than an incident angle value corresponding to the second incident angle range. 
     The first functional layer  14  is usually made of a soft polymer material, and the first functional layer  14  may be attached to a surface of a side of the diffusion layer  13  facing the light source  12 . 
     In the embodiments of the present application, a certain distance needs to be formed between the light source  12  and the diffusion layer  13 , to guarantee full light mixing between the micro light emitting diodes  122  so as to guarantee the brightness uniformity of the backlight module. 
     To prevent deformation of the diffusion layer  13  and keep consistency of the distance between the light source  12  and the diffusion layer  13 , a plurality of supports  15  need to be arranged on the back plate to support the diffusion layer  13 . 
     The supports  15  are arranged at interval areas among the micro light emitting diodes  122  and are uniformly distributed. The supports  15  are fixed to the back plate through buckles, screws or pasting. 
     The supports  15  usually adopt a light transmitting material to prevent the supports  15  from shielding the emitting light of the light source. 
     The supports  15  may be made of hard materials such as polymethyl methacrylate (PMMA). Ends, close to the diffusion layer  13 , of the supports  15  are sharp. The first functional layer  14  is arranged on a side of the diffusion layer  13  facing the light source  12 . The material of the first functional layer  14  is soft. Thus the sharp ends of the supports  15  easily puncture the first functional layer  14 . When the diffusion layer  13  moves, the supports  15  will unavoidably scratch the first functional layer  14 , causing failure of required optical performances of the first functional layer  14 , leading poor display and the like. 
     In the embodiments of the present application, in view of the above issue, the transparent substrate  16  is arranged on a side of the first functional layer  14  facing the light source  12 . 
     The transparent substrate  16  is arranged as a whole layer, a size and a shape of the transparent substrate  16  are substantially same as those of the first functional layer  14 , and the shape usually may be a square or a rectangle. 
     The transparent substrate  16  may be made of light transmitting material with a high transmittance such as polymethyl methacrylate (PMMA) or glass. 
     The transparent substrate  16  is arranged between the first functional layer  14  and the supports  15  to avoid direct contact between the sharp ends of the supports  15  and the first functional layer  14 , so that the first functional layer  14  may be prevented from being damaged and scratched. At the same time, the transparent substrate  16  may further achieve an effect of supporting the first functional layer  14  and the diffusion layer  13 , so that two sides of the first functional layer  14  are both supported by plates, and the higher reliability is achieved. 
     The transparent substrate  16  is usually a parallel flat plate with its upper surface close to the first functional layer  14  and lower surface close to the supports  15 , and the upper surface and the lower surface of the transparent substrate  16  are parallel to each other. 
     The transparent substrate  16  is made of light transmitting material uniform in refraction, a refraction index of the material may have a difference with that of air, the refraction index of the material of the transparent substrate  16  is generally greater than that of air, and the light rays emitted from the light source will be deflected when entering the transparent substrate  16 . However, the transparent substrate  16  has no scattering effect or the like for the light rays, and if the upper surface and the lower surface of the transparent substrate  16  are both in contact with air, a propagating direction of the light rays cannot be changed after the light rays pass the transparent substrate  16 . 
     When the light rays emitted from the light source enter the transparent substrate  16  from air, an emitting angle will be reduced accordingly, and in order to avoid the problem that a coverage range of the emitting light of the micro light emitting diodes is shrunk due to the fact that the transparent substrate  16  is too thick, in the embodiments of the present application, a thickness of the transparent substrate  16  may be set in a range of 0.3 mm to 1 mm, so that a good support effect of the transparent substrate  16  is guaranteed, and diffusion of the light rays is not affected. 
     In the embodiments of the present application, when the light source adopts the micro light emitting diode light board, the micro light emitting diodes  122  may be blue-light micro light emitting diodes to emit blue light, and a wavelength of light rays emitted from the blue-light micro light emitting diodes is 440 nm to 450 nm. 
     As shown in  FIG. 2  and  FIG. 3 , the backlight module according to the embodiment of the present application further includes: a wavelength conversion layer  17 . 
     The wavelength conversion layer  17  is located on a side of the diffusion layer  13  away from the first functional layer  14 . The wavelength conversion layer  17  is arranged as a whole layer with a shape being substantially same as the shape of the back plate  11 , which may be square or rectangular usually. 
     The wavelength conversion layer  17  includes a red light conversion material and a green light conversion material, and under irradiation of the blue light, the red light conversion material is excited to emit red light (620 nm to 640 nm) and the green light conversion material is excited to emit green light (520 nm to 545 nm). Therefore, the wavelength conversion layer  17  is excited by the emitting light of the blue-light micro light emitting diodes to emit the red light and the green light, and the blue light, the red light and the green light are mixed to form white light so as to provide backlight for the panel. 
     In some embodiments of the present application, the wavelength conversion layer  17  may be a quantum dot layer, the quantum dot layer includes a red quantum dot material and a green quantum dot material, the red quantum dot material is excited by the blue light to emit red light, the green quantum dot material is excited by the blue light to emit green light, and the red light and the green light which are emitted by excitation and the transmitted blue light are mixed to form white light to be emitted. 
     In other embodiments of the present application, the wavelength conversion layer  17  may be a fluorescent layer, the fluorescent layer includes a red light conversion material and a green light conversion material, the red light conversion material is excited by the blue light to emit red light, the green light conversion material is excited by the blue light to emit green light, and the red light and the green light which are emitted by excitation and the transmitted blue light are mixed to form white light to be emitted. 
       FIG. 7  is a schematic cross-sectional view of the backlight module according to an embodiment of the present application. 
     Referring to  FIG. 7 , the backlight module according to the embodiment of the present application further includes: a second functional layer  18 . 
     The second functional layer  18  is located between the wavelength conversion layer  17  and the diffusion layer  13 . The second functional layer  18  is arranged as a whole layer with a shape being substantially same as the shape of the wavelength conversion layer  17 , which may be square or rectangular usually. 
     The second functional layer  18  is configured to transmit light emitted from the light source  12  and reflect excited light emitted from the wavelength conversion layer  17 . 
     The red light and the green light emitted from the wavelength conversion layer  17  by excitation are not only emitted to the light emitting side of the backlight module, but also emitted to one side of the back plate  11 . In order to improve use efficiency of the excited light, the second functional layer  18  is arranged between the wavelength conversion layer  17  and the diffusion layer  13 , and in this way, the excited light emitted from the wavelength conversion layer  17  to one side of the back plate will enter the second functional layer  18 , and this part of exciting light is reflected again by the second functional layer  18  to the light emitting side of the backlight module, so that use efficiency of the light rays is improved. 
     As shown in  FIG. 2 ,  FIG. 3  and  FIG. 7 , the backlight module according to the embodiments of the present application further includes: an optical film  19  located on a side of the wavelength conversion layer  17  away from the diffusion layer  13 . 
     The optical film  19  is arranged as a whole layer, and a shape of the optical film  19  is substantially same as that of the wavelength conversion layer  17  and usually may be a rectangle or a square. 
     Arranging the optical film  19  may make the backlight module adaptive to various practical applications. 
     The optical film  19  may include a prism sheet, and the prism sheet may change an emitting angle of light rays to change a viewing angle of the display apparatus. The prism sheet usually may converge light rays into a front view angle direction, thereby increasing front view angle brightness. 
     The optical film  19  may further include a reflective polarizer. As a brightness enhancement sheet, the reflective polarizer may increase the brightness of the backlight module, improve use efficiency of light rays, and make emitting light rays have a polarizing property, so a polarizer may be omitted in the liquid crystal panel. 
     When the light source is the micro light emitting diode light board, in the embodiments of the present application, the first functional layer  14  is configured to reflect the light rays with small angles emitted from the micro light emitting diodes  122  and transmit the light rays with large angles emitted from the micro light emitting diodes  122 . A reflectivity of the first functional layer  14  to the incident light rays is decreased with increasing of the angle of the incident light rays. 
     When the light rays with large angles emitted from the micro light emitting diodes  122  enter the first functional layer  14 , the incident angle is large, and most of the light rays are transmitted by the first functional layer  14 ; while when the light rays with small angles emitted from the micro light emitting diodes  122  enter the first functional layer  14 , the incident angle is small, and most of the light rays are reflected by the first functional layer  14 , and the reflected light rays are subjected to scattering or diffuse reflection after entering the reflective layer on the micro light emitting diode light board, so that light rays with large emitting angles are generated again to be reflected to the first functional layer  14  so as to be transmitted by the first functional layer  14 . By means of the above reflection for several times, the energy of the light rays emitted from the micro light emitting diodes  122  may be not concentrated in the small emitting angle any more, so that the light rays emitted from the micro light emitting diodes  122  are relatively uniform. 
     A transmittance of the first functional layer  14  to the light rays with an incident angle range of 0° to 70° is gradually increased in a range from 10% to 90%, and a reflectivity to the light rays with an incident angle range of 70° to 90° is less than 10%. 
     The second functional layer  18  may transmit the light rays with small angles emitted from the micro light emitting diode light board, and meanwhile, reflect the light rays with small angles emitted from the wavelength conversion layer  17  to the light emitting side of the backlight module. In this way, the light rays with small angles emitted from the micro light emitting diode light board may be transmitted by the second functional layer  18 , after the light rays with small angles enter the wavelength conversion layer  17 , a part of the light rays with small emitting angles in the light rays excited by the wavelength conversion layer  17  will be emitted to one side of the light source, this part of light rays will enter the second functional layer  18  to be reflected by the second functional layer  18  towards the light emitting side of the backlight module, and thus the light rays with small emitting angles emitted from the micro light emitting diode light board and the light rays with small angles excited by the wavelength conversion layer  17  both have good convergence, and the display contrast is improved. 
     In some embodiments of the present application, the second functional layer is configured to transmit activating light emitted from the light source and reflect exciting light emitted from the wavelength conversion layer. The second functional layer may transmit the small-angle activating light, and at the same time, reflect the small-angle exciting light emitted from the wavelength conversion layer to the light emitting side of the backlight module. 
     In the embodiment of the present application, the first functional layer  14  and the second functional layer  18  are both arranged by utilizing the principle of film interference. In specific implementations, the first functional layer  14  and the second functional layer  18  each include a plurality of film layers arranged in a laminated mode, and every two adjacent film layers have different refraction indexes. The refraction indexes and thicknesses of the film layers meet film interference conditions. 
       FIG. 8  is a schematic diagram of film interference according to the embodiment of the present application. 
     Referring to  FIG. 8 , when light rays enter a surface of a thin film with a refraction index being n 2  from a medium with a refraction index being n 1  with an incident angle of i, light reflection and refraction occur at an interface between two media n 1  and n 2 , a reflection angle and the incident angle are equal and are still i, and a refraction angle is γ; and when refracted light rays enter a lower surface of the thin film, light reflection and refraction also occur on the lower surface, wherein reflected light rays will pass an upper surface of the thin film to be refracted in the medium n 1 , and thus two beams of reflected light rays (1) and (2) are formed on the upper surface and the lower surface of the thin film. An optical path difference δ′ between the reflected light ray (1) and the reflected light ray (2) is: 
     
       
         
           
             
               δ 
               ′ 
             
             = 
             
               
                 
                   n 
                   2 
                 
                 ⁡ 
                 
                   ( 
                   
                     
                       AB 
                       _ 
                     
                     + 
                     
                       BC 
                       _ 
                     
                   
                   ) 
                 
               
               - 
               
                 
                   n 
                   1 
                 
                 ⁢ 
                 
                   
                     AD 
                     _ 
                   
                   . 
                 
               
             
           
         
       
     
     If a thickness of the thin film with the refraction index being n 2  is d and the thickness of the thin film is uniform, due to  AB = BC =d/cos γ and  AD = AC  sin i=2d tan γ×sin i, the following may be obtained: 
     
       
         
           
             
               δ 
               ′ 
             
             = 
             
               
                 
                   
                     n 
                     2 
                   
                   ⁢ 
                   2 
                   ⁢ 
                   
                     AB 
                     _ 
                   
                 
                 - 
                 
                   
                     n 
                     1 
                   
                   ⁢ 
                   
                     AD 
                     _ 
                   
                 
               
               = 
               
                 
                   
                     
                       2 
                       ⁢ 
                       
                         n 
                         2 
                       
                       ⁢ 
                       d 
                     
                     
                       cos 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       γ 
                     
                   
                   - 
                   
                     2 
                     ⁢ 
                     
                       n 
                       1 
                     
                     ⁢ 
                     d 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     tan 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     γ 
                     × 
                     sin 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     i 
                   
                 
                 = 
                 
                   
                     
                       2 
                       ⁢ 
                       d 
                     
                     
                       cos 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       γ 
                     
                   
                   ⁢ 
                   
                     
                       ( 
                       
                         
                           n 
                           2 
                         
                         - 
                         
                           
                             n 
                             1 
                           
                           ⁢ 
                           sin 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           i 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           sin 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           γ 
                         
                       
                       ) 
                     
                     . 
                   
                 
               
             
           
         
       
     
     It can be known from the refraction law that: 
     
       
         
           
             
               
                 
                   n 
                   1 
                 
                 ⁢ 
                 sin 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 i 
               
               = 
               
                 
                   n 
                   2 
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 sin 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 γ 
               
             
             ; 
           
         
       
       
         
           
             so: 
           
         
       
       
         
           
             
               δ 
               ′ 
             
             = 
             
               
                 
                   
                     2 
                     ⁢ 
                     d 
                     ⁢ 
                     
                       n 
                       2 
                     
                   
                   
                     cos 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     r 
                   
                 
                 ⁢ 
                 
                   ( 
                   
                     1 
                     - 
                     
                       
                         sin 
                         2 
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       γ 
                     
                   
                   ) 
                 
               
               = 
               
                 
                   
                     
                       2 
                       ⁢ 
                       
                         n 
                         2 
                       
                       ⁢ 
                       d 
                     
                     
                       cos 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       γ 
                     
                   
                   ⁢ 
                   
                     cos 
                     2 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   γ 
                 
                 = 
                 
                   
                     2 
                     ⁢ 
                     
                       n 
                       2 
                     
                     ⁢ 
                     d 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     cos 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     γ 
                   
                   = 
                   
                     
                       2 
                       ⁢ 
                       
                         n 
                         2 
                       
                       ⁢ 
                       d 
                       ⁢ 
                       
                         
                           1 
                           - 
                           
                             
                               sin 
                               2 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             γ 
                           
                         
                       
                     
                     = 
                     
                       2 
                       ⁢ 
                       d 
                       ⁢ 
                       
                         
                           
                             
                               n 
                               2 
                               2 
                             
                             - 
                             
                               
                                 n 
                                 1 
                                 2 
                               
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 sin 
                                 2 
                               
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               i 
                             
                           
                         
                         . 
                       
                     
                   
                 
               
             
           
         
       
     
     It can be seen from the above formula that, if a multi-layer film structure is arranged, an optical path difference between reflected light of the light rays on the upper and lower surfaces of each layer of medium is only related to a refraction index and a thickness of this layer and an incident angle. In practical applications, light rays usually enter a thin film from an air medium, light reflection occurs on an upper surface and a lower surface of the thin film, that is, the refraction index in the above formula is n 1 =1, and thus the above formula may be simplified as: 
     
       
         
           
             
               δ 
               ′ 
             
             = 
             
               
                 2 
                 ⁢ 
                 d 
                 ⁢ 
                 
                   
                     
                       n 
                       2 
                       2 
                     
                     - 
                     
                       
                         n 
                         1 
                         2 
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         sin 
                         2 
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       i 
                     
                   
                 
               
               = 
               
                 2 
                 ⁢ 
                 d 
                 ⁢ 
                 
                   
                     
                       
                         n 
                         2 
                         2 
                       
                       - 
                       
                         s 
                         ⁢ 
                         i 
                         ⁢ 
                         
                           n 
                           2 
                         
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         i 
                       
                     
                   
                   . 
                 
               
             
           
         
       
     
     It can be known from the principle of film interference that, when the optical path difference between the reflected light rays on the upper surface and the lower surface of the thin film is integer times of a wavelength, the two beams of light rays are coherently added; and when the optical path difference between the reflected light rays on the upper surface and the lower surface is odd times of a half-wavelength, the two beams of light rays are coherently subtracted. According to the principle of energy conservation, if the reflected light is coherently added, energy of the reflected light is enhanced, and energy of transmission light is weakened; and if the reflected light is coherently subtracted, the energy of the reflected light is weakened, and the energy of the transmission light is enhanced. 
     When the above principle is applied to the embodiment of the present application, for any film layer in the first functional layer  14  and the second functional layer  18 , an incident angle of reflection enhancement is set as θ 1  and an incident angle of anti-reflection is set as θ 2 , and by utilizing the above principle, a proper film layer material may be selected, so that the refraction index and the thickness of the film layer meet reflection enhancement to light rays with the incident angle θ 1  and anti-reflection of light rays with the incident angle θ 2 . 
     The present application further provides a structure of a backlight module. 
       FIG. 9  is a first schematic cross-sectional view of the backlight module according to an embodiment of the present application. 
     Referring to  FIG. 9 , the backlight module includes: a back plate  21 , a micro light emitting diode light board  22 , a diffusion plate  23  and a functional layer  24 . 
     The back plate  21  is located at the bottom of the backlight module and configured for support. Usually, the back plate  21  is of a square structure, and when the back plate is applied to a special-shaped display apparatus, a shape of the back plate is adaptive to a shape of the display apparatus. The back plate  21  includes a top side, a bottom side, a left side and a right side. The top side and the bottom side are opposite, the left side and the right side are opposite, the top side is connected with one end of the left side and one end of the right side, and the bottom side is connected with the other end of the left side and the other end of the right side. 
     The back plate  21  is made of aluminum, iron, aluminum alloy or iron alloy. The back plate  21  is configured to fix the micro light emitting diode light board  22  and support and fix edge areas of components such as an optical film and the diffusion plate, and the back plate  21  also has an effect of dissipating heat for the micro light emitting diode light board  22 . 
     In the embodiment of the present application, the backlight module is a direct backlight module, and the micro light emitting diode light board  22  is located on the back plate  21 . Usually, the whole micro light emitting diode light board  22  may be square or rectangular, with a length of 200 mm to 800 mm and a width of 100 mm to 500 mm. 
     A plurality of micro light emitting diode light boards  22  may be arranged according to a size of the display apparatus, and the micro light emitting diode light boards  22  are spliced to jointly provide backlight. In order to avoid optical problems caused by splicing of the micro light emitting diode light boards  22 , splicing seams between the adjacent micro light emitting diode light boards  22  are made as small as possible, and even seamless splicing is achieved. 
     As a backlight source, compared with a traditional light emitting diode, the micro light emitting diode light board  22  has a smaller size and can achieve finer dynamic control and improve dynamic contrast of the display apparatus. 
     The micro light emitting diode light board  22  includes: a circuit board  221 , micro light emitting diodes  222 , a reflective layer  223  and an packaging layer  224 . 
     The circuit board  221  is located on the back plate  21 , and a shape of the circuit board  221  is substantially same as an overall shape of the micro light emitting diode light board  22 . Usually, the circuit board  221  is in a plate shape and is rectangular or square as a whole. The circuit board  221  has a length of 200 mm to 800 mm and a width of 100 mm to 500 mm. 
     In the embodiment of the present application, the circuit board  221  may be a printed circuit board (PCB), the PCB includes an electronic circuit and an insulating layer, and the insulating layer exposes at least one bonding pad in the electronic circuit for welding the micro light emitting diodes  222  and covers remaining parts in the electronic circuit. 
     Or, the circuit board  221  may also be an array substrate formed by manufacturing a thin film transistor driving circuit on a base substrate, and a surface of the array substrate has electrodes connected to the thin film transistor driving circuit for welding the micro light emitting diodes  222 . 
     A base or substrate of the circuit board  221  may be made of materials such as FR4 or glass. Or, the base or a base substrate of the above circuit board  221  may be made of a flexible material to form a flexible circuit board. 
     The circuit board  221  is configured to provide a driving electric signal for the micro light emitting diodes  222 . The micro light emitting diodes  222  and the circuit board  221  are separately manufactured, a surface of the circuit board  221  includes a plurality of bonding pads for welding the micro light emitting diodes  222 , the micro light emitting diodes  222  are transferred above the bonding pads after being manufactured, the micro light emitting diodes  222  are welded to the circuit board  221  through processes such as reflow soldering, and thus the micro light emitting diodes  222  may be driven to emit light by controlling an input signal of the circuit board  221 . 
     The micro light emitting diodes  222  are located on the circuit board. Electrodes of the micro light emitting diodes  222  are welded to the bonding pads exposed on the circuit board  221  to achieve electric connection therebetween. 
     The micro light emitting diodes  222  are different from ordinary light emitting diodes, and specifically refer to micro light emitting diode chips without packaging supports. Since the micro light emitting diodes  222  have small sizes, dynamic light emitting of the backlight module can be controlled to smaller partitions, which facilitates increase of picture contrast. In the embodiment of the present application, the size of the micro light emitting diodes  222  is 500 μm or below. 
     The micro light emitting diode light board  22  may only include micro light emitting diodes  222  of one color, or micro light emitting diodes of various colors, which is not limited here. 
     The reflective layer  223  is located on a surface of a side of the circuit board  221  facing the micro light emitting diodes  222 . The reflective layer  223  and the circuit board  221  are substantially same in shape, and the reflective layer  223  includes a plurality of openings for exposing the micro light emitting diodes  222 . 
     The reflective layer  223  is a protective layer on the surface of the circuit board  221  and has an effect of diffuse reflection to incident light rays, and when the light rays emitted from the micro light emitting diodes  222  are reflected to one side of the back plate by elements in the backlight module, the light rays may be reflected to the light emitting side again by the reflective layer  223 , thereby improving the efficiency of the light source. 
     The reflective layer  223  may be formed by coating the surface of the circuit board  221  with white oil with a high reflectivity. 
     The packaging layer  224  is located on a surface of a side of the micro light emitting diodes  222  away from the circuit board  221 . The packaging layer  224  may be arranged individually or as a whole layer. When being arranged individually, the packaging layer  224  only covers the surfaces of the micro light emitting diodes  222 , while no pattern is arranged in other regions of the circuit board; and when being arranged as the whole layer, the packaging layer  224  covers the whole circuit board  221  and the surfaces of the micro light emitting diodes  222 . 
     The packaging layer  224  is configured to protect the micro light emitting diodes  222  and prevent foreign items from entering the micro light emitting diodes  222 . In the embodiment of the present application, the packaging layer  224  may be made of a transparent material, such as silica gel or epoxy resin. The packaging layer  224  may be manufactured in a point coating or whole-face coating. 
     Referring to  FIG. 9 , the whole packaging layer  224  may cover the surfaces of the micro light emitting diodes  222 , and the surfaces of the micro light emitting diodes  222  and the surface of the circuit board  221  are coated with one packaging layer  224  in a spot-coated mode, so packaging efficiency is high. 
       FIG. 10  is a second schematic cross-sectional view of the backlight module according to an embodiment of the present application.  FIG. 11  is a schematic top view of the micro light emitting diode light board in  FIG. 10 . 
     Referring to  FIG. 10  and  FIG. 11 , the whole packaging layer  224  may cover the surfaces of the micro light emitting diodes  222 , and only the surfaces of the micro light emitting diodes  222  are coated with the packaging layer  224  in the spot-coated mode, so that the packaging layer  224  has mutually discrete dot patterns. Forming the packaging layer  224  in the spot-coated mode may save materials and lower the packaging cost. 
       FIG. 12  is a third schematic cross-sectional view of the backlight module according to the embodiment of the present application. 
     Referring to  FIG. 12 , in order to improve the use efficiency of the light rays, a reflective sheet  223 ′ is further arranged on a side of the circuit board  221  facing the micro light emitting diodes  222 . The reflective sheet  223 ′ is provided with openings for exposing the micro light emitting diodes  222  and the packaging layer  224  above the micro light emitting diodes, and is configured to reflect light rays emitted from the micro light emitting diodes  222  to one side of the back plate to the light emitting side again, thereby improving the use efficiency of the light rays. 
       FIG. 13  is a first schematic top view of the micro light emitting diode light board according to an embodiment of the present application.  FIG. 14  is a second schematic top view of the micro light emitting diode light board according to an embodiment of the present application. 
     Referring to  FIG. 13  and  FIG. 14 , the packaging layer  224  may cover micro light emitting diode rows or micro light emitting diode columns. Referring to  FIG. 13 , the packaging layer  224  is formed by whole-row coating in a direction of the micro light emitting diode rows, or, referring to  FIG. 14 , the packaging layer  224  is formed by whole-column coating in a direction of the micro light emitting diode columns, so that the packaging layer  224  has mutually discrete strip-shaped patterns. The packaging layer  224  formed in a whole-row/column coated mode has high packaging efficiency, and materials of packaging glue may be saved at the same time. 
     The diffusion plate  23  is located on the light emitting side of the micro light emitting diode light board  22 . A shape of the diffusion plate  23  is substantially same as that of the micro light emitting diode light board  22 . Usually, the diffusion plate  23  may be rectangular or square. A thickness of the diffusion plate  23  is 1.5 mm to 3 mm. 
     The diffusion plate  23  is configured to scatter incident light rays to make the light rays passing the diffusion plate  23  more uniform. Scattering particle materials are arranged in the diffusion plate  23 , and the light rays will be refracted and reflected continuously after entering the scattering particle materials, so that the effect of scattering the light rays is achieved to contribute to light uniformizing. 
     The diffusion plate  23  usually has the larger haze and the more obvious uniformizing effect, and usually may be processed through an extrusion process. A material for the diffusion plate  23  is generally selected from at least one of polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS) or polypropylene (PP). 
     In the embodiment of the present application, a certain distance needs to be set between the micro light emitting diode light board  22  and the diffusion plate  23 , to guarantee full light mixing between light sources so as to guarantee the brightness uniformity of the backlight module. 
     The functional layer  24  is located on a side of the diffusion plate  23  facing the micro light emitting diode light board  22 . The functional layer  24  and the diffusion plate  23  are attached. 
     In the embodiment of the present application, the functional layer  24  is a special optical film and is configured to reflect light rays with small incident angles emitted from the micro light emitting diode light board  22  and transmit light rays with large incident angles emitted from the micro light emitting diode light board  22  to balance a brightness difference between light emitting centers and edge areas of the micro light emitting diodes  222 , thereby solving the problems that areas over the micro light emitting diodes are too bright while junction areas of the adjacent micro light emitting diodes are too dark. By arranging the functional layer  24  on the light emitting side of the micro light emitting diode light board  22 , the uniformity of emitting brightness is improved, and the quantity of the micro light emitting diodes is reduced to achieve backlight thinning design. 
     The functional layer  24  usually includes film layers which have different refraction indexes and arranged in a laminated mode, thicknesses of the film layers are at a nanometer order, and the film layers are usually made of soft polymer materials. 
     The backlight module according to an embodiment of the present application further includes supports  25  for supporting the diffusion plate  23 . Referring to  FIG. 9 ,  FIG. 10  and  FIG. 12 , the supports  25  are distributed between the micro light emitting diode light board  22  and the functional layer  24 . 
     The supports  25  are distributed at interval areas among the micro light emitting diodes  222  to avoid affecting light emitting from the micro light emitting diodes  222 . The supports  25  are fixed to the micro light emitting diode light board through buckles, screws or pasting. 
       FIG. 15  to  FIG. 17  are schematic diagrams of connection relationships between the supports and the micro light emitting diode light board according to an embodiment of the present application. 
     Referring to  FIG. 15 , the support  25  is fixed to the micro light emitting diode light board  22  through a limiting sheet  31 , an auxiliary column  32  and a buckle  33 . The limiting sheet  31  and the buckle  33  are located at two ends of the auxiliary column  32  respectively. After the buckle  33  is closed, the limiting sheet  31  and the buckle  33  clamp the micro light emitting diode light board  22  to fix the support  25  to the micro light emitting diode light board  22 . 
     Referring to  FIG. 16 , the support  25  is connected with base  34 . The base  34  is fixed to the micro light emitting diode light board  22  through a screw  35 , and the support  25  may be dismantled by rotating the screw  35 . 
     Referring to  FIG. 17 , the support  25  is directly attached to a surface of the micro light emitting diode light board  22  through glue  36  (e.g., double-sided glue, solid glue or liquid glue). 
     The supports  25  may be made of hard materials such as polymethyl methacrylate (PMMA). Ends, close to the functional layer  24 , of the supports  25  are sharp, while the material of the functional layer  24  is soft, and thus the sharp ends of the supports  25  will puncture the functional layer  24  easily, causing damage or displacement of the functional layer  24 , and leading to failure of required optical performances. 
     In view of this, in the embodiment of the present application, a cushion portion  26  is arranged between the support  25  and the functional layer  24 . The cushion portion  26  is in contact with the support  25  and the functional layer  24  respectively. The cushion portion  26  achieves an effect of mitigate or reduce pressure of the supports  25  on the functional layer  24  to prevent the sharp ends of the support  25  from damaging the functional layer  24  so as to guarantee that the optical performances of the functional layer  24  are achieved. 
     The cushion portion  26  adopts elastic materials such as silica gel or epoxy resin, in this way, after being placed on the diffusion plate  23 , the cushion portion  26  has a certain deformation to relieve the pressure of the supports  25  on the functional layer  24  so as to achieve an effect of protecting the functional layer  24 . 
     In the embodiment of the present application, the cushion portion  26  may be located on a surface of a side of the support  25  facing the functional layer  24  or a surface of a side of the functional layer  24  facing the supports  25 . 
     The cushion portion  26  is formed by dispensing. When the cushion portion  26  is located on the surface of the side of the support  25  facing the functional layer  24 , the cushion portion  26  may be formed at top end of the support  25  in a dispensing mode and then the diffusion plate  23  with the functional layer  24  attached is placed on the support  25 . When the cushion portion  26  is located on the surface of the side of the functional layer  24  facing the support  25 , the cushion portion  26  may be formed at areas, corresponding to the support  25 , of the functional layer  24  in a dispensing mode and then the diffusion plate  23  with the functional layer  24  attached is placed on the supports 25  in an aligned mode. 
     Referring to  FIG. 9 ,  FIG. 10  and  FIG. 12 , an area of a cross section parallel to the functional layer  24  of the cushion portion  26  is greater than an area of a cross section parallel to the functional layer  24  of one ends of the support  25  close to the functional layer  24 . When a size of the cushion portion  26  is set to be greater than a size of the top end of the support  25 , it may be guaranteed that the top end of the supports  25  and the cushion portion  26  have good contact and the support  25  cannot be in direct contact with the functional layer  24 . 
     In the embodiment of the present application, a shape of the cushion portion  26  may be set as a sphere, a hemisphere or an ellipsoid, and a shape of the support  25  may be set as a tetrahedron, a pyramid, a cone, a cuboid, a cube or a cylinder, which are not limited here. 
     The supports  25  is configured to guarantee a set distance between the micro light emitting diode light board  22  and the diffusion plate  23 , however, too high support  25  will affect an overall thickness of the backlight module, not meeting a thinning design requirement of the micro light emitting diode light board, and thus a height of the support  25  is set to be less than 6 mm. 
     The height of the support  25  may be designed according to combination of the optical films in the backlight module, the haze and thickness of the diffusion plate  23  and other requirements. A ratio H/p of an optical distance to a distance between every two adjacent micro light emitting diodes usually may reflect the overall thickness of the backlight module and a quantity of the micro light emitting diodes used in the backlight module. The smaller the H/p value, the smaller the optical distance, and the thinner the whole device; and the larger the distance between the adjacent micro light emitting diodes, the fewer micro light emitting diodes required, so the cost is lowered. 
     In the embodiment of the present application, the height of the support  25  and the height of the cushion portion  26  meet a following relationship: 
     
       
         
           
             
               0 
               . 
               2 
             
             ≤ 
             
               
                 ( 
                 
                   
                     H 
                     ⁢ 
                     1 
                   
                   + 
                   
                     H 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   - 
                   
                     Δ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     H 
                   
                 
                 ) 
               
               / 
               p 
             
             ≤ 
             
               0 
               . 
               8 
               . 
             
           
         
       
     
     H1 represents the height of the support  25 , H2 represents an original height of the cushion portion  26 , ΔH represents a deformation of the cushion portion  26 , and p represents the distance between every two adjacent micro light emitting diodes  222 . 
     The optical distance refers to a vertical distance from the micro light emitting diodes  222  to the diffusion plate  23 . In the embodiment of the present application, the support  25  and the cushion portion  26  further needs to be arranged between the diffusion plate  23  and the micro light emitting diode light board  22 , and the cushion portion  26  will be extruded in a mounting process to generate a deformation. Therefore, a sum of the height H1 of the support  25 , the height H2 of the cushion portion  26  and the deformation ΔH of the cushion portion  26  may reflect the optical distance, while the ratio of the optical distance to the distance between every two adjacent micro light emitting diodes may reflect the overall thickness of the backlight module and the quantity of the micro light emitting diodes used. Setting 0.2≤(H1+H2−ΔH)/p≤0.8 may meet design requirements of various backlight modules. 
     If the optical distance needs to be relatively large, the height of the support  25  may be correspondingly increased if not changing other element structures of the backlight module. If the optical distance needs to be relatively small, the height of the supports  25  may be correspondingly decreased if not changing other element structures of the backlight module. Therefore, the (H1+H2−ΔH)/p value of the backlight module may be flexibly set. 
     In order to optimize light emitting of the backlight module, the backlight module according to an embodiment of the present application further includes a group of films  27  located on a side of the diffusion plate  23  away from the micro light emitting diode light board  22 . 
     The group of films  27  is arranged as a whole layer with a shape being substantially same as that of the micro light emitting diode light board  22 , which usually may be a rectangle or a square. 
     Arranging the group of films  27  may allow the backlight module adaptive to various practical applications. 
     When the micro light emitting diodes  222  in the micro light emitting diode light board  22  adopt blue-light micro light emitting diodes, the group of films  27  includes a quantum dot layer or a fluorescent layer. 
     The quantum dot layer includes a red quantum dot material and a green quantum dot material, the red quantum dot material is excited by blue light to emit red light, the green quantum dot material is excited by the blue light to emit green light, and the red light and the green light which are emitted by excitation and the transmitted blue light are mixed to form white light to be emitted. 
     The fluorescent layer includes a fluorescent material which is excited to emit red light and green light, and the red light and the green light which are emitted by excitation and the transmitted blue light are mixed to form white light to be emitted. 
     Besides, the group of films  27  may further include a prism sheet, and the prism sheet may change an emitting angle of light rays to change a view angle of the display apparatus. 
     The group of films  27  may further include a reflective polarizer. As a brightness enhancement sheet, the reflective polarizer may increase the brightness of the backlight module, improve use efficiency of light rays, and make emitting light rays have a polarizing property, so a polarizer may be omitted in the liquid crystal panel. 
     The functional layer  24  in the embodiment of the present application may be at least one of the first functional layer or the second functional layer, and may also be a functional layer with other functions. 
     Apparently, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. These modifications and variations of the present application shall fall within the scope of the claims of the present application.