Patent Publication Number: US-2023152499-A1

Title: Design method for composite membrane and composite membrane

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to the technical field of backlight modules, and more particularly, to a design method for a composite membrane and the composite membrane. 
     BACKGROUND 
     Due to a limitation of lens technology and a trend requirement of cost reduction, for a backlight module having a same size, a number of a plurality of LED light sources used is becoming less and less, while a space between the LED light sources increases accordingly, which makes both a direct-lit backlight module and a side-lit backlight module have a problem of an uneven visual effect. For the direct-lit backlight module, a poor light mixing may appear in the visual effect, which is shown as a light spot phenomenon including a plurality of bright spots or a plurality of dark spots on a lamp; for the side-lit backlight module, it is shown as a lamp bead shadow problem including a plurality of bright lights and a plurality of dark lights alternating in the visual effect. 
     Therefore, the present technology needs to be improved and developed 
     BRIEF SUMMARY OF THE DISCLOSURE 
     A technical problem to be solved by the present disclosure is that, in view of the defects described above in the prior art, providing a design method for a composite membrane and the composite membrane, aimed at improving the phenomenon of uneven visual effect of the backlight module. 
     The technical solutions of the present disclosure are as follows: 
     A design method for a composite membrane, wherein comprising a plurality of steps: 
     arranging a test board on a light-emitting surface of a plurality of LED light sources, and turning on the LED light sources; 
     establishing a rectangular test area corresponding to each of the LED light sources on the test board, and detecting a brightness uniformity on each of the rectangular test areas; 
     comparing the brightness uniformity with a preset value, defining a rectangular test area having the brightness uniformity less than the preset value as a lamp bead shadow area; and defining both a rectangular test area having the brightness uniformity greater than the preset value, and a plurality of areas on the test board other than the rectangular test areas, as a non-lamp bead shadow area; 
     arranging a base plate on a light-emitting surface of the plurality of LED light sources, and arranging a plurality of dispersive prism areas and a plurality of diffusion plates on a light-emitting surface of the base plate respectively, while making the dispersive prism areas correspond to the lamp bead shadow areas, and making the diffusion plates correspond to the non-lamp bead shadow areas. 
     The design method for the composite membrane, wherein the step of establishing the rectangular test area corresponding to each of the LED light sources on the test board, and detecting the brightness uniformity on each of the rectangular test areas, comprises specifically: 
     establishing a rectangular test area corresponding to each of the LED light sources on the test board; 
     selecting nine test points arranged in three rows and three columns in the rectangular test area, and detecting a brightness of the nine test points respectively; 
     calculating a ratio of a sum of the brightness of the nine test points except for a middle test point to the brightness of the middle test point, and obtaining the brightness uniformity of the rectangular test area. 
     The design method for the composite membrane, wherein a test point in middle of the nine test points is corresponding to a center of the LED light source. 
     The design method for the composite membrane, wherein the test point in middle of the nine test points locates at a center of the rectangular test area, a space between every two adjacent rows of the LED light sources is equal, and a space between every two adjacent columns of the LED light sources is equal. 
     The design method for the composite membrane, wherein the step of arranging the base plate on the light-emitting surface of the plurality of LED light sources, and arranging the plurality of dispersive prism areas and the plurality of diffusion plates on the light-emitting surface of the base plate respectively, while making the dispersive prism areas correspond to the lamp bead shadow areas, and the diffusion plates correspond to the non-lamp bead shadow areas, comprises specifically: 
     arranging the base plate on the light-emitting surface of the plurality of LED light sources, fixing a first quadrangular surface of a plurality of dispersive prisms to the light-emitting surface of the base plate, and arranging the plurality of dispersive prisms into a dispersive prism matrix corresponding to an area and a position according to the areas and the positions of the lamp bead shadow; 
     arranging a coating layer with an equal area on a light-emitting surface of the base plate at a position corresponding to the non-lamp bead shadow, and arranging a plurality of diffusion particles on the coating layer, while the plurality of diffusion particles are arranged in a matrix. 
     The design method for the composite membrane, wherein further comprises a plurality of steps of: 
     fixing a plurality of first diffusion particles on both the second quadrangular surface and the third quadrangular surface of the dispersive prisms; 
     arranging a coating layer on a light incidence surface of the base plate; 
     arranging a plurality of second diffusion particles on a surface of the coating layer against the base plate. 
     The design method for the composite membrane, wherein the dispersive prism area comprises a plurality of first dispersive prisms and a plurality of second dispersive prisms, a height of the second dispersive prisms is smaller than a height of the first dispersive prisms, the first dispersive prisms and the second dispersive prisms are arranged alternately. 
     A composite membrane, wherein comprising a base plate, the base plate is applied to corresponding to a light source, a light-emitting surface of the base plate has a plurality of dispersive prism areas and a plurality of diffusion plates arranged, while the dispersive prism areas are corresponding to the lamp bead shadow areas, and the diffusion plates are corresponding to the non-lamp bead shadow areas. 
     The composite membrane, wherein the base plate is a PET base plate. 
     The composite membrane, wherein the diffusion plate comprises a coating layer arranged on the light-emitting surface of the base plate, and a plurality of diffusion particles arranged on a surface of the coating layer against the base plate. 
     The composite membrane, wherein the coating layer is a UV photosensitive adhesive coating layer. 
     The composite membrane, wherein the dispersive prism area comprises a plurality of dispersive prisms arranged in a matrix, a first quadrangular surface of the dispersive prism attaches to the base plate, a surface against the base plate of a second quadrangular surface and a third quadrangular surface of the dispersive prism has a plurality of first diffusion particles arranged. 
     The composite membrane, wherein the first diffusion particles are hemispherical shaped, while the second quadrangular surface and the third quadrangular surface of the dispersive prism are in contact with a plane of the first diffusion particle, correspondingly and respectively. 
     The composite membrane, wherein the dispersive prism area comprises a plurality of first dispersive prisms and a plurality of second dispersive prisms, a height of the second dispersive prism is smaller than a height of the first dispersive prism, while the first dispersive prism and the second dispersive prism are arranged alternately. 
     The composite membrane, wherein a distance from a top of the first dispersive prism and a top of the second dispersive prism is 30 μm-50 μm. 
     Benefits: The present disclosure arranges a plurality of dispersive prism areas and a plurality of diffusion plates on the light-emitting surface of the base plate, while the dispersive prism areas are corresponding to the lamp bead shadow areas, and the diffusion plates are corresponding to the non-lamp bead shadow areas. Arranging the dispersive prism areas in an area with an uneven light energy distribution, while laying out the diffusion plates only in an area with an even light energy distribution, without any needs to lay the dispersive prisms, so as to improve a phenomenon of uneven visual effects and reduce a production cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a flowchart on a design method for the composite membrane in the present disclosure; 
         FIG.  2    illustrates a schematic structural diagram on a direct-lit backlight module in the present disclosure; 
         FIG.  3    illustrates a schematic diagram on a distribution of a lamp bead shadow areas and a non-lamp bead shadow areas on a test board of the direct-lit backlight module in the present disclosure. 
         FIG.  4    illustrates a schematic diagram on a distribution of a plurality of dispersive prism areas and a diffusion plates on the composite membrane corresponding to the direct-lit backlight module in the present disclosure. 
         FIG.  5    illustrates a schematic structural diagram on a side-lit backlight module in the present disclosure; 
         FIG.  6    illustrates a schematic diagram on a distribution of the lamp bead shadow areas and the non-lamp bead shadow areas on the test board of the side-lit backlight module in the present disclosure. 
         FIG.  7    illustrates a schematic diagram on a distribution of the dispersive prism areas and the diffusion plates on the composite membrane corresponding to the side-lit backlight module in the present disclosure. 
         FIG.  8    illustrates a schematic diagram on a distribution of the nine test points in the rectangular test area of the present disclosure. 
         FIG.  9    illustrates a schematic structural diagram on the composite membrane in a preferred embodiment of the present disclosure. 
         FIG.  10    illustrates a schematic structural diagram on the composite membrane in another preferred embodiment of the present disclosure. 
         FIG.  11    illustrates a schematic diagram on a partial enlargement at point A in  FIG.  10   . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In order to make the purposes technical solutions, and effects of the present disclosure clearer and more specific, the present disclosure will be described in further details below. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not intended to limit the present disclosure. 
     Referencing to  FIGS.  1 - 11   , wherein a plurality of arrows in  FIG.  2    and  FIG.  5    illustrates a light emitting direction. 
     Embodiment 1 
     The present disclosure provides a design method for a composite membrane, shown as  FIG.  1   , comprising a plurality of steps below: 
     S 100 , arranging a test board  1  on a light-emitting surface of a plurality of LED light sources  10 , and turning on the LED light sources  10 . 
     In a preferred embodiment, as shown in  FIG.  2    and  FIG.  5   , the composite membrane is suitable for both a direct-lit backlight module and a side-lit backlight module; for the direct-lit backlight module, the test board  1  in the present disclosure is a diffusion plate; for the side-lit backlight module, the test board  1  in the present disclosure is a light guide plate. In the direct-lit backlight module, the plurality of LED light sources  10  are arranged in a matrix on a back plate, and a total rectangular area covered by the plurality of LED light sources  10  on the back plate has an area smaller than an area of a surface of the test board  1  facing toward the LED light source  10 , and the area of the surface of the test board  1  facing toward the LED light source  10  increases following a distance increase between the test board  1  and the LED light source  10 , that is, the smaller a distance between the test board  1  and the LED light source  10  is, the smaller an area of the test board  1  needed is; the bigger the distance between the test board  1  and the LED light source  10  is, the bigger the area of the test board  1  needed is. 
     S 200 , establishing a rectangular test area corresponding to each of the LED light sources  10  on the test board  1 , and detecting a brightness uniformity on each of the rectangular test areas. 
     The step S 200  comprises specifically: 
     S 201 , establishing a rectangular test area corresponding to each of the LED light sources  10  on the test board  1 ; 
     specifically, establishing a rectangular test area correspondingly on the test board  1  for each LED light source  10 , and by checking a brightness uniformity of each rectangular test area, it is decided that whether the rectangular test area belongs to a lamp bead shadow area  2  (a non-uniform visual effect area) or a non-lamp bead shadow area  3  (a uniform visual effect area), so as to determine whether setting a dispersive prism area  4  correspondingly or setting a diffusing plate  5  correspondingly according to a position and an area of the rectangular test area. 
     The rectangular test area faces to the LED light source  10  directly, and the rectangular test area covers completely an area where the LED light source  10  generates a light shadow on the test board  1 ; preferably, a center point of the rectangular test area corresponds to a center point of the LED light source  10 , a length of the rectangular test area is L, and a width thereof is H. 
     S 202 , selecting nine test points arranged in three rows and three columns in the rectangular test area, and detecting a brightness of the nine test points respectively. 
     Specifically, shown as  FIG.  8   , selecting nine test points in the rectangular test area: L 1 , L 2 , L 3 , L 4 , L 5 , L 6 , L 7 , L 8 , and L 9 , while the nine test points are arranged in three rows and three columns, a space between every two adjacent rows is equal, and a space between every two adjacent columns is equal. That is, a distance between L 1  and L 2  equals to a distance between L 2  and L 3 , a distance between L 1  and L 4  equals to a distance between L 4  and L 7 . A test point locates in middle of the nine test points is L 5 , a center of the LED light source  10  corresponding to the rectangular test area is against the L 5 , and L 5  also locates at a center of the rectangular test area. 
     The rectangular test area comprises a first side a 1 , a second side a 2 , a third side a 3 , and a fourth side a 4  connecting end to end in a sequence, wherein a length of the first side al is L, a length of the second side a 2  is H. A row that L 1 , L 2 , L 3  locates is parallel to the first side a 1 , a column that L 1 , L 4 , L 7  locates is parallel to the second side a 2 . While a distance between L 1  and the first side al equals to a distance between L 7  and the third side a 3 , and a distance between L 1  and the fourth side a 4  equals to a distance between L 3  and the second side a 2 . 
     In an embodiment, the distance between L 1  and the first side a 1  is H/10, a distance between L 1  and L 2  is 0.4 L, the distance between L 1  and the fourth side a 4  is L/10, both a distance between L 2  and the second side a 2  and a distance between L 2  and the fourth side a 4  is L/2, both a distance between L 5  and the first side al and a distance between L 5  and the third side a 3  is H/2; detecting a brightness at each of the test points according to a position of the nine test points, wherein, a brightness of the test point L 1  is A1, a brightness of the test point L 2  is A2, a brightness of the test point L 3  is A3, a brightness of the test point L 4  is A4, a brightness of the test point L 5  is A5, a brightness of the test point L 6  is A6, a brightness of the test point L 7  is A7, a brightness of the test point L 8  is A8. 
     S 203 , calculating a ratio of a sum of the brightness of the nine test points except for a middle test point to the brightness of the middle test point, and obtaining the brightness uniformity of the rectangular test area. 
     Specifically, after obtaining the brightness of each test point, calculating the sum of the brightness of all the test points except for the middle test point, taking the middle test point as L 5 , that is, calculating a sum S of the A1, A2, A3, A4, A6, A7, A8 and A9; followed by calculating the ratio of S to the brightness of the test point L 5 , that is, by calculating S/A5, the brightness uniformity of the rectangular test area will be obtained. 
     S 300 , comparing the brightness uniformity with a preset value, defining a rectangular test area having the brightness uniformity less than the preset value as the lamp bead shadow area  2 ; and defining the rectangular test area having the brightness uniformity greater than the preset value, and the plurality of areas on the test board  1  other than the rectangular test areas as the non-lamp bead shadow area  3 ; 
     Specifically, comparing the brightness uniformity of each rectangular test area with the preset value, to determine whether the rectangular test area is the lamp bead shadow area or the non-lamp bead shadow area. Preferably, the preset value is 80%, when the brightness uniformity is less than 80%, the rectangular test area corresponding to the brightness uniformity is the lamp bead shadow area  2 , a light energy is unevenly distributed, and it is needed to set the dispersive prism area  4 ; when the brightness uniformity is greater than 80%, the rectangular test area corresponding to the brightness uniformity is the non-lamp bead shadow area  3 , the light energy distributes evenly, and only the diffusion plates  5  are needed to lay to improve the light energy uniformity in this area, without a need to lay a dispersive prism, thus a production cost is reduced, while improving a phenomenon of an uneven visual effect at a same time; a plurality of areas on the test board  1  other than all of the rectangular test areas are the non-lamp bead shadow areas  3 . 
     S 400 , arranging a base plate  100  on a light-emitting surface of the plurality of LED light sources  10 , and arranging a plurality of dispersive prism areas  4  and a plurality of diffusion plates  5  on a light-emitting surface of the base plate  100  respectively, while making the dispersive prism areas  4  correspond to the lamp bead shadow areas  2 , and the diffusion plates  5  correspond to the non-lamp bead shadow areas  3 . 
     The step S 400  comprises specifically: 
     S 401 , arranging the base plate  100  on the light-emitting surface of the plurality of LED light sources  10 , fixing a first quadrangular surface of a plurality of dispersive prisms to the light-emitting surface of the base plate  100 , and arranging the plurality of dispersive prisms into a dispersive prism matrix corresponding to an area and a position according to the areas and the positions of the lamp bead shadow; 
     S 402 , arranging a coating layer  105  with an equal area on the light-emitting surface of the base plate at a position corresponding to the non-lamp bead shadow, and arranging a plurality of diffusion particles  102  on the coating layer  105 , while the plurality of diffusion particles  102  are arranged in a matrix. 
     Specifically, an area of the base plate  100  equals to an area of the test board  1 , the base plate  100  is arranged on a light-emitting surface of the LED light source  10 ; the dispersive prism area  4  and the diffusion plate  5  are arranged on a light-emitting surface of the base plate  100 , that is, the surface of the base plate  100  against the LED light source  10 ; as shown in  FIGS.  4  and  7   , according to a position of the lamp bead shadow area  2 , arranging a dispersive prism area  4  correspondingly on the base plate  100 , and an area that the dispersive prism area  4  covers on the base plate  100  equals to an area of the rectangular test area. The dispersive prism comprises three quadrangular surfaces (a first quadrangular surface, a second quadrangular surface and a third quadrangular surface, respectively) and two triangular surfaces, while the first quadrangular surface of the dispersive prism is stuck by an adhesive on the base plate  100 , a plurality of dispersive prisms are arranged in a matrix, and two adjacent dispersive prisms are in contact. 
     Based on a position of the non-lamp bead shadow area  3 , arranging a plurality of diffusion plates  5  at a plurality of positions on the based board  100  accordingly, an area that the diffusion plates  5  covers on the base plate  100  equals to the area of the rectangular test area. The diffusion plate  5  comprises a coating layer  105  and a plurality of diffusion particles  102 , placing a coating layer  105  with an area equals to the rectangular test area at a position of the base plate  100  corresponding to the non-lamp bead shadow area  3 , and arranging a plurality of diffusion particles  102  on a surface of the coating layer  105  against the base plate  100 , while the plurality of diffusion particles  102  are arranged in a matrix, with a space between two of the diffusion particles  102  in adjacent, and the diffusion particles  102  is sphere shaped. 
     Embodiment 2 
     The design method further comprises a plurality of steps: 
     fixing a plurality of first diffusion particles  103  on both a second quadrangular surface and a third quadrangular surface of the dispersive prisms; 
     arranging a coating layer  105  on a light incidence surface of the base plate  100 ; 
     arranging a plurality of second diffusion particles  104  on a surface of the coating layer  105  against the base plate  100 . 
     Specifically, the first diffusion particles  103  are hemispherical shaped, while a plane of the first diffusion particle  103  contacts with the second quadrangular surface and the third quadrangular surface of the dispersive prism, so as to facilitate a fixing and installation of the first diffusion particles  103  onto the dispersive prism. A diameter of the first diffusion particles  103  is 3 μm to 5 μm, the first diffusion particles  103  on the second quadrangular surface and the third quadrangular surface are all far away from the base plate  100 , that is, the plurality of first diffusion particles  103  are distributed at a tip of the dispersive prism, and a height of a coverage area of the plurality of first diffusion particles  103  on the dispersive prism is ⅓ of a height of the dispersive prism, so as to increase a diffusion of a light output from the dispersive prism, and decrease a phenomenon of glare or rainbow pattern of the light emitted by the dispersive prism. 
     In a preferred embodiment of the embodiment, as shown in  FIG.  9   , a size and a structure of the dispersive prisms  101  distributed in the dispersive prisms area  4  are same, a height of the dispersive prism  101  is 30 μm, and a vertex angle of the dispersive prism  101  is 90°. 
     In another preferred implementation of the embodiment, as shown in  FIGS.  10  and  11   , the sizes of the dispersive prisms  101  distributed in the dispersive prism area  4  are not completely same, the dispersive prism area  4  comprises a plurality of first dispersive prisms  106  and a plurality of second dispersive prisms  107 , a height of the second dispersive prisms  107  is smaller than a height of the first dispersive prisms  106 , the first dispersive prism  106  and the second dispersive prism  107  are arranged alternately, and adjacent two dispersive prisms of the first dispersive prisms  106  and the second dispersive prism  107  are in contact, making the dispersive prisms in the dispersive prism area  4  are arranged in a dithering way, which further destroys a uniformity of the dispersive prisms emitting light and increases the diffusivity of the light emitted by the dispersive prisms, so as to weaken the glare and the rainbow patterns. Preferably, a distance between the top of the first dispersive prism  106  and the top of the second dispersive prism  107  is 30 μm to 50 μm, both apex angles of the first dispersive prism  106  and the second dispersive prism  107  are 90°, the height of the second dispersive prism  107  is 20 μm, and the height of the first dispersive prism  106  is 30 μm. 
     coating a coating layer  105  on a light incidence surface of the base plate  100 , arranging the coating layer  105  completely covering the light incidence surface of the substrate plate  100 , and arranging a plurality of second diffusion particles  104  on a surface of the coating layer  105  against the base plate  100 , to increase a foggy feeling and a wear resistance of the light incidence surface of the base plate  100 . The plurality of second diffusion particles  104  are arranged in a matrix, with a gap between two adjacent second diffusion particles  104 ; a structure of the second diffusion particles  104  is as same as the structure of the diffusion particles  102 . Preferably, the base plate  100  is a PET base plate, the coating layer  105  is a UV photosensitive adhesive coating layer, and a diameter of both the diffusion particles  102  and the second diffusion particles  104  is 2 μm to 8 μm. 
     Taking the direct-lit backlight module as an example, as shown in  FIGS.  3  and  4   , according to a division of the rectangular test area and a calculation of the brightness uniformity, both the lamp bead shadow area  2  and the non-lamp bead shadow area  3  are obtained. Arranging a diffusion plate between the base plate  100  and the LED light sources  10 , and on the base plate  100 , the dispersive prisms areas  4  and lamp bead shadow areas  2  are corresponding to each other, and the diffusion pate  5  are corresponding to the non-lamp bead shadow area  3 . 
     Taking the side-lit backlight module as an example, as shown in  FIGS.  6  and  7   , according to a division of the rectangular test area and a calculation of the brightness uniformity, both the lamp bead shadow area  2  and the non-lamp bead shadow area  3  are obtained. Arranging a diffusion plate between the base plate  100  and the LED light sources  10 , and on the base plate  100 , the dispersive prisms areas  4  and lamp bead shadow areas  2  are corresponding to each other and the diffusion pate  5  are corresponding to the non-lamp bead shadow area  3 . 
     Embodiment 3 
     The present disclosure further provides a composite membrane, wherein comprising a base plate  100 , the base plate  100  is applied to corresponding to a light source, a light-emitting surface of the base plate  100  has a plurality of dispersive prism areas  4  and a plurality of diffusion plates  5  arranged, while the dispersive prism areas  4  are corresponding to the lamp bead shadow areas  2 , and the diffusion plates  5  are corresponding to the non-lamp bead shadow areas  3 . 
     In a preferred embodiment, shown as  FIG.  9   , the dispersive prism area  4  comprises a plurality of dispersive prisms  101  arranged in a matrix, a first quadrangular surface of the dispersive prism  101  attaches to the base plate, a surface against the base plate  100  of a second quadrangular surface and a third quadrangular surface of the dispersive prism  101  has a plurality of first diffusion particles  103  arranged. The first diffusion particles  103  are hemispherical shaped, while a plane of the first diffusion particle  103  is in contact with the second quadrangular surface and the third quadrangular surface of the dispersive prism  101 . A diameter of the first diffusion particles  103  is 3 μm to 5 μm, the first diffusion particles  103  on the second quadrangular surface and the third quadrangular surface are all far away from the base plate  100 , that is, the plurality of first diffusion particles  103  are distributed at a tip of the dispersive prism, and a height of a coverage area of the plurality of first diffusion particles  103  on the dispersive prism is ⅓ of a height of the dispersive prism, so as to increase a diffusion of a light output from the dispersive prism  101 , and decrease a phenomenon of glare or rainbow pattern of the light emitted by the dispersive prism  101 . 
     The diffusion plate  5  comprises a coating layer  105  arranged on the light-emitting surface of the base plate  100  and a plurality of diffusion particles  102  arranged on a surface of the coating layer  105  against the base plate  100 , the plurality of diffusion particles  102  are arranged in a matrix, and the diffusion particles  102  is sphere shaped. 
     In a preferred embodiment, shown as  FIG.  10   , the dispersive prism area  4  comprises a plurality of first dispersive prisms  106  and a plurality of second dispersive prisms  107 , a height of the second dispersive prisms  107  is smaller than a height of the first dispersive prisms  106 , the first dispersive prism  106  and the second dispersive prism  107  are arranged alternately. Preferably, a distance between the top of the first dispersive prism  106  and the top of the second dispersive prism  107  is 30 μm to 50 μm, both apex angles of the first dispersive prism  106  and the second dispersive prism  107  are 90°, the height of the second dispersive prism  107  is 20 μm, and the height of the first dispersive prism  106  is 30 μm. 
     Arranging a coating layer  105  on a light incidence surface of the base plate  100 , and arranging a plurality of second diffusion particles  104  into a matrix on a surface of the coating layer  105  against the base plate  100 , a shape of the second diffusion particles is a sphere, the base plate  100  is a PET base plate, the coating layer  105  is a UV photosensitive adhesive coating layer, and a diameter of both the diffusion particles  102  and the second diffusion particles  104  is 2 μm to 8 μm. 
     All above, the present disclosure provides a design method for a composite membrane and a composite membrane, comprising a plurality of steps: arranging a test board on a light-emitting surface of a plurality of LED light sources, and turning on the LED light sources; establishing a rectangular test area corresponding to each of the LED light sources on the test board, and detecting a brightness uniformity on each of the rectangular test areas; comparing the brightness uniformity with a preset value, defining a rectangular test area having the brightness uniformity less than the preset value as a lamp bead shadow area; and defining a rectangular test area having the brightness uniformity greater than the preset value, and a plurality of areas on the test board other than the rectangular test areas as a non-lamp bead shadow area; arranging a base plate on a light-emitting surface of the plurality of LED light sources, and arranging a plurality of dispersive prism areas and a plurality of diffusion plates on a light-emitting surface of the base plate respectively, while making an area of the dispersive prism areas correspond to that of the lamp bead shadow areas, and an area and a position of the diffusion plates area correspond to the non-lamp bead shadow areas, improving a visual effects while reducing a production cost. 
     It should be understood that the application of the present disclosure is not limited to the above examples. For those skilled in the art, improvements or changes can be made according to the above description, and all such improvements and changes should fall within the protection scope of the appended claims of the present disclosure. 
     Industrial Applicability 
     The present disclosure provides a design method for a composite membrane and a composite membrane, by arranging a plurality of dispersive prism areas and a plurality of diffusion plates on the light-emitting surface of the base plate, while making the dispersive prism areas correspond to the lamp bead shadow areas, and the diffusion plates correspond to the non-lamp bead shadow areas. Arranging the dispersive prism areas in an area with an uneven light energy distribution, while laying out the diffusion plates only in an area with an even light energy distribution, without any needs to lay the dispersive prisms, so as to improve a phenomenon of uneven visual effects and reduce a production cost.