Multilayer light diffusing plate and method for making same

Abstract

The present application discloses a kind of multilayer light diffusion plate and its preparation method.The multilayer light diffusion plate includes a main layer and a half-transmission half-reflection layer.The light exit surface of the multilayer light diffusion plate is the top surface of the main layer, and the light entrance surface is the bottom surface of the half-transmission half-reflection layer.The half-transmission half-reflection layer is located below the main layer and is composed of a plurality of first substrate layers and a plurality of second substrate layers stacked alternately.The materials of the first substrate layers and the second substrate layers have different refractive indices.The light entrance surface of the light diffusion plate is provided with a half-transmission half-reflection layer, which can partially transmit and partially reflect the linear light source intensity of the LED light source module below, thereby reducing the bright-dark band between LEDs and achieving the effect of uniform light.In addition, the half-transmission half-reflection layer composed of a plurality of first substrate layers and second substrate layers with different refractive indices stacked alternately is provided on the light entrance surface of the light diffusion plate by extrusion molding, which is relatively simple and low in cost.

Description

Technical Field

[0001] This invention relates to a multilayer light diffuser plate for use in direct-lit backlight modules and its manufacturing method, particularly to a multilayer light diffuser plate having a semi-transparent, semi-reflective layer formed by alternating stacking of a plurality of first substrate layers and second substrate layers with different refractive indices on the light incident surface of the light diffuser plate. Background Technology

[0002] Currently, an increasing number of LCD display devices are using direct-lit backlight modules to provide the light source for their LCD panels. Existing direct-lit backlight modules generally use light-emitting diode (LED) light source modules located on their bottom side to provide the light source, and use a light diffuser plate to homogenize the light emitted by the LEDs before it is emitted upwards from the light-emitting surface located on the top side, in order to improve the bright-dark band (MURA) phenomenon between the LEDs on the light-emitting surface of the light diffuser plate.

[0003] Existing light diffusion plates mainly provide light diffusion functionality in the following ways:

[0004] (i) Add numerous tiny diffusion particles inside the light diffusion plate. By utilizing the different refractive indices of the diffusion particles and the light diffusion plate, the light is refracted, reflected, or scattered, thereby diffusing the light. However, to achieve a good light uniformity effect, it is necessary to increase the amount of diffusion particles added, thereby reducing the light transmittance, or to increase the distance between the light diffusion plate and the LED light source module. These approaches will reduce the light utilization rate or increase the overall thickness of the light diffusion plate.

[0005] (ii) Add numerous microstructures to the surface of the light diffusion plate. These surface microstructures are used to alter the direction of light travel, thereby providing the function of light diffusion. However, due to the use of an extrusion process, a good transfer rate cannot be achieved, thus reducing the effectiveness of the microstructures in altering the light direction.

[0006] (iii) Printing halftone dots on the surface of the light diffuser plate. Surface printing halftone dots is used to diffuse / mask different locations on the light diffuser plate surface, thereby reducing the bright and dark band phenomenon between the light-emitting surfaces and LEDs. However, printing halftone dots requires multiple processing steps and presents assembly alignment issues.

[0007] As mentioned above, current light diffusion plate technologies mainly achieve light diffusion effects by adding light-diffusing particles to a light diffusion plate made of thermoplastic material, extruding surface microstructures using rollers, or printing dots on the surface of the light diffusion plate. However, these methods have limited diffusion effects and each has the following drawbacks: they require increasing the thickness of the diffusion plate, reducing the transmittance of the diffusion plate, increasing the distance between the LED and the diffusion plate, or requiring multiple processing steps and assembly alignment issues, etc., and still require further improvement.

[0008] This invention provides a semi-transparent, semi-reflective layer on the surface of a light diffuser plate, allowing some of the intensity of a linear light source above the LEDs to pass through and partially reflect, thereby reducing bright and dark bands between LEDs and achieving a uniform light effect. Existing semi-transparent, semi-reflective layers can be obtained through coating / electroplating, but this requires subsequent processing, which is complex and costly. In contrast, this invention uses an extrusion process to create a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser plate, consisting of multiple alternating stacked first and second substrate layers with different refractive indices. This overcomes the drawbacks of traditional coating / electroplating methods for creating semi-transparent, semi-reflective layers, which are complex and costly. Summary of the Invention

[0009] The main objective of this invention is to provide a multilayer light diffuser. This multilayer light diffuser includes a main layer and a semi-transparent, semi-reflective layer. The light-emitting surface of the multilayer light diffuser is the top surface of the main layer, while the light-incident surface is the bottom surface of the semi-transparent, semi-reflective layer. The semi-transparent, semi-reflective layer is located below the main layer and is composed of alternatingly stacked first substrate layers and second substrate layers. The materials constituting the first substrate layers and the second substrate layers have different refractive indices. This invention provides a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser, allowing the linear light intensity of the LED light source module below to pass through and partially reflect, thereby reducing the bright and dark bands between LEDs and achieving a uniform light effect. Furthermore, this invention, through extrusion fabrication, provides a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser, composed of alternatingly stacked first substrate layers and second substrate layers with different refractive indices, which has advantages such as simpler manufacturing process and lower cost.

[0010] To achieve the above objectives, the present invention discloses a multilayer light diffuser plate, which can be assembled on top of a light source module. The multilayer light diffuser plate has a light-incident surface and a light-exit surface that are parallel to each other, and a thickness perpendicular to the light-incident surface and the light-exit surface. The light-incident surface is adjacent to the light source module, allowing light emitted from the light source module to enter the multilayer light diffuser plate via the light-incident surface and travel approximately along the thickness direction. Furthermore, the multilayer light diffuser plate includes: a main layer, with the light-exit surface located on a top surface of the main layer; and a semi-transparent semi-reflective layer located below the main layer, with the light-incident surface located on a bottom surface of the semi-transparent semi-reflective layer. The semi-transparent semi-reflective layer is composed of a plurality of alternating stacked first substrate layers and a plurality of second substrate layers; at least one of the upper and lower sides of each first substrate layer is adjacent to a second substrate layer, and at least one of the upper and lower sides of each second substrate layer is adjacent to a first substrate layer; the materials constituting the first substrate layer and the second substrate layer have different refractive indices.

[0011] In one embodiment, both the main layer and the semi-transparent and semi-reflective layer are made of amorphous or semi-crystalline plasticized materials; the thickness ratio of the main layer and the semi-transparent and semi-reflective layer is between 9:1 and 7:3; the number of layers of the semi-transparent and semi-reflective layer, that is, the sum of the number of the first substrate layer and the second substrate layer, is between 50 and 400; and the thickness ratio of the first substrate layer and the second substrate layer is between 3:1 and 1:3.

[0012] In one embodiment, the main layer and the semi-transparent and semi-reflective layer are made of one of the following materials: polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA, commonly known as acrylic), polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET); the number of layers of the semi-transparent and semi-reflective layer is between 100 and 400.

[0013] In one embodiment, the main layer is made of polycarbonate (PC); the first substrate layer is made of polycarbonate (PC); the second substrate layer is made of polymethyl methacrylate (PMMA); the first substrate layer and the second substrate layer have the same thickness, that is, the thickness ratio of the first substrate layer and the second substrate layer is 1:1; the light source module is an LED light source module comprising a plurality of light-emitting diodes (LEDs) arranged in an array; the thickness of the multilayer light diffuser plate ranges from 1.0 mm to 3.0 mm.

[0014] In one embodiment, the multilayer light diffuser plate is formed by foam extrusion, and the main layer contains a plurality of microbubbles and a plurality of diffuser particles; the material of the plurality of diffuser particles is one of the following: calcium carbonate, silicon dioxide, titanium dioxide, organosilicon resin microparticles, polymethyl methacrylate microparticles; the weight percentage of the plurality of diffuser particles in the main layer is 0.1%-10%; the plurality of microbubbles are dispersed in the main layer and can perform at least one of the following functions on the light in the main layer: reflection, refraction, or scattering, so as to improve the uniform light output effect. The weight reduction rate of the plurality of microbubbles to the main layer is between 15% and 25%, and the average size of the plurality of microbubbles is between 60 and 800 μm. The formula for calculating the weight reduction rate is:

[0015] Weight loss rate (%) = (W1-W2) / W2*100%;

[0016] W1 = H * (L1 * L2 * D);

[0017] in:

[0018] H is the average thickness (mm) of the main layer;

[0019] L1 is the length (mm) of the main layer;

[0020] L2 is the width (mm) of the main layer;

[0021] D is the raw material specific gravity of the main layer (g / mm 3 );

[0022] W1 is the theoretical weight (g) of the main layer, that is, the weight without including a plurality of the microbubbles;

[0023] W2 is the actual weight (g) of the main layer, that is, the actual weight of the main layer containing a plurality of the microbubbles actually measured with a weighing scale.

[0024] In one embodiment, the multi-layer light diffusing plate further includes a quantum dot layer and a water and gas barrier layer. A plurality of microstructures are provided on the light-emitting surface, and are arranged in an array on the light-emitting surface of the multi-layer light diffusing plate; the plurality of microstructures form a plurality of convex portions and a plurality of concave portions on the light-emitting surface of the multi-layer light diffusing plate; the plurality of concave portions are separated by the plurality of convex portions, so the plurality of concave portions are independent and not connected to each other. The quantum dot layer is provided at the plurality of concave portions on the light-emitting surface of the multi-layer light diffusing plate; wherein, the thickness of the quantum dot layer is t1, the distance from the top of one of the plurality of convex portions to the bottom of one of the plurality of concave portions is t2, and t1 < t2. The water and gas barrier layer is provided on the light-emitting surface of the multi-layer light diffusing plate and covers the plurality of convex portions and the quantum dot layer. The quantum dot layer contains a plurality of quantum dots (Quantum Dot; abbreviated as QD); the plurality of quantum dots are a kind of nanocrystal semiconductor material composed of II-VI, III-V or IV-VI group elements, and the grain diameter of each quantum dot is between 2 and 10 nm; wherein, the plurality of quantum dots include a plurality of green quantum dots with a light-emitting wavelength of 520-530 nm and a plurality of red quantum dots with a light-emitting wavelength of 620-630 nm. The light source module is a blue light LED light source module composed of a plurality of blue light emitting diodes (LED) arranged in an array.

[0025] In one embodiment, the plurality of microstructures include a plurality of N-sided pyramids, where N is a positive integer greater than or equal to three; t2 is between 6 and 200 μm; the maximum width of the convex portion is between 50 and 500 μm, and the distance between two adjacent convex portions is between 50 and 1000 μm. The thickness of the water and gas barrier layer is t3, and t3 is between 5 and 100 μm. The blue light LED light source module is a submillimeter light emitting diode (Mini LED) array module that can emit the blue light; the wavelength of the blue light is between 430-500 nm.

[0026] In one embodiment, a plurality of microstructures are provided on the light-incident surface and arranged in an array on the light-incident surface of the multilayer light diffuser; the plurality of microstructures form a plurality of protrusions and a plurality of recesses on the light-incident surface of the multilayer light diffuser.

[0027] To achieve the above objectives, this invention discloses a method for manufacturing a multilayer light diffusion plate, comprising the following steps:

[0028] Feeding step: At least one first substrate, one second substrate, and one foaming agent constituting the multilayer light diffusion plate are fed into a foaming extrusion process equipment through a feed port; the first substrate and the second substrate have different refractive indices;

[0029] Heating and mixing step: The foaming and extrusion process equipment is used to uniformly mix and foam the materials at a general processing temperature suitable for polycarbonate; the first substrate and the second substrate are heated and mixed separately and are not mixed.

[0030] The splitter step: The first substrate and the second substrate after heating and mixing enter a splitter. The splitter splits the first substrate into a main layer and a plurality of first substrate layers, and splits the second substrate into a plurality of second substrate layers. The plurality of first substrate layers and the plurality of second substrate layers are alternately stacked to form a semi-transparent semi-reflective layer, and the semi-transparent semi-reflective layer is superimposed on the main layer.

[0031] T-die step: The main layer and the semi-transparent and semi-reflective layer, which have been uniformly mixed, foamed and stacked from the distributor, are co-extruded into a multi-layer board through a T-die of the foaming extrusion process equipment.

[0032] Roll forming step: The sheet material is rolled and cooled using a roller module; and

[0033] Discharge step: The cooled multilayer light diffusion plate is discharged from one of the discharge ports of the foaming extrusion process equipment;

[0034] The multilayer light diffusion plate discharged from the discharge port has a light-incident surface and a light-exit surface that are parallel to each other, and a thickness that is perpendicular to the light-incident surface and the light-exit surface; and the multilayer light diffusion plate includes the main layer and the semi-transparent and semi-reflective layer; the light-exit surface is located on the top surface of the main layer, the semi-transparent and semi-reflective layer is located below the main layer, and the light-incident surface is located on the bottom surface of the semi-transparent and semi-reflective layer;

[0035] Among them, the semi-transmissive semi-reflective layer is formed by alternately stacking a plurality of first substrate layers and a plurality of second substrate layers; at least one side of the upper and lower sides of each of the first substrate layers is adjacent to one of the second substrate layers, and at least one side of the upper and lower sides of each of the second substrate layers is adjacent to one of the first substrate layers; the materials constituting the first substrate layer and the second substrate layer have different refractive indexes.

[0036] In an embodiment, in the rolling step, the roller module rolls on the light-emitting surface of the multi-layer light diffusing plate to form a plurality of microstructures, which are arranged in an array on the light-emitting surface of the multi-layer light diffusing plate; the plurality of microstructures form a plurality of convex portions and a plurality of concave portions on the light-emitting surface of the multi-layer light diffusing plate; the plurality of concave portions are separated by the plurality of convex portions, so the plurality of concave portions are independent and not interconnected with each other. Among them, the following steps are further included between the rolling step and the discharging step: coating a quantum dot layer on the plurality of concave portions on the light-emitting surface of the multi-layer light diffusing plate through a coating process; wherein, the thickness of the quantum dot layer is t1, the distance from the top of one of the plurality of convex portions to the bottom of one of the plurality of concave portions is t2, and t1 < t2; and through a pasting process, a water and gas barrier layer is pasted on the light-emitting surface of the multi-layer light diffusing plate and covers the plurality of convex portions and the quantum dot layer; wherein, the quantum dot layer contains a plurality of quantum dots (Quantum Dot; abbreviated as QD); wherein, the light source module is a blue light LED light source module composed of a plurality of blue light emitting diodes (LED) arranged in an array. Brief Description of the Drawings

[0037] Figure 1 It is a side view schematic diagram of a preferred embodiment of a multi-layer light diffusing plate (Diffuser Plate) of the present invention combined with a light emitting diode (LED) light source module to form a white light backlight module (Backlight Module) and is disposed below a liquid crystal display panel (LCD Panel).

[0038] Figure 2 It is a partially enlarged side view schematic diagram of a preferred embodiment of the multi-layer light diffusing plate of the present invention.

[0039] Figure 3A and Figure 3B They are respectively a partially enlarged side view schematic diagram of another preferred embodiment of the multi-layer light diffusing plate of the present invention, and a three-dimensional exploded schematic diagram of an embodiment in which the multi-layer light diffusing plate is disposed on the LED light source module.

[0040] Figure 4 It is a partially enlarged side view schematic diagram of another preferred embodiment of the multi-layer light diffusing plate of the present invention.

[0041] Figure 5 This is a flowchart of a preferred embodiment of the manufacturing method of the multilayer light diffusion plate of the present invention.

[0042] Figure 6 A graph showing the light output brightness at different positions between LEDs for a light diffusion plate with different numbers of semi-transparent and semi-reflective layers.

[0043] Figure 7 A light diffusion plate with a semi-transparent and semi-reflective layer, showing the light output brightness at different positions between LEDs when the thickness ratio of the alternately stacked first substrate layer and the second substrate layer is different.

[0044] Figure 8 The graph shows the transmittance curves of light diffuser samples A, B, C, and D with semi-transparent and semi-reflective layers at different light wavelengths.

[0045] Figure 9 For example Figure 8 The chart shown compares the tastes of samples A, B, C, and D as displayed in the test.

[0046] Explanation of reference numerals in the attached figures: 10-Light diffusion plate; 11-Main layer; 111-Light emitting surface; 112-Microstructure; 113-Microbubble; 114-Diffuse particles; 12-Semi-transparent and semi-reflective layer; 120-Light incident surface; 121-First substrate layer; 122-Second substrate layer; 13-Quantum dot layer; 131-Quantum dot; 14-Water and gas barrier layer; 21-26-Steps; 91-Circuit board; 92-Light emitting diode; 93-Liquid crystal display panel. Detailed Implementation

[0047] This invention relates to a multilayer light diffuser plate and its manufacturing method. The multilayer light diffuser plate includes a main layer and a semi-transparent, semi-reflective layer. The light-emitting surface of the multilayer light diffuser plate is the top surface of the main layer, while the light-incident surface is the bottom surface of the semi-transparent, semi-reflective layer. The semi-transparent, semi-reflective layer is located below the main layer and is composed of alternatingly stacked first substrate layers and second substrate layers. The materials constituting the first substrate layers and the second substrate layers have different refractive indices. This invention provides a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser plate, allowing the linear light intensity of the LED light source module below to pass through and partially reflect, thereby reducing the bright and dark bands between LEDs and achieving a uniform light effect. Furthermore, this invention, through extrusion fabrication, provides a semi-transparent, semi-reflective layer composed of alternatingly stacked first substrate layers and second substrate layers with different refractive indices on the light-incident surface of the light diffuser plate, which has advantages such as simpler manufacturing process and lower cost.

[0048] To more clearly describe the multilayer light diffusion plate and its manufacturing method proposed in this invention, the following detailed description will be provided in conjunction with the accompanying drawings.

[0049] Please see Figure 1 and Figure 2 The images shown are, respectively, a side view schematic diagram of a preferred embodiment of the present invention, in which a multilayer diffuser plate is combined with a light-emitting diode (LED) light source module to form a white light backlight module, and is disposed below a liquid crystal display panel, and an enlarged side view schematic diagram of the multilayer diffuser plate.

[0050] like Figure 1 and Figure 2 As shown, the multilayer light diffuser 10, the LED light source module located below the multilayer light diffuser 10, and the liquid crystal display panel 93 located above the multilayer light diffuser 10 constitute an LCD display module. The multilayer light diffuser 10 and the LED light source module below it together form a white light backlight module, which provides white light to the liquid crystal display panel 93 above it, and is therefore a direct-light backlight module. The multilayer light diffuser 10 mainly provides the functions of converting the light emitted by the LED light source module into white light, making the light output uniform, and / or expanding the color gamut of the output light.

[0051] In this invention, the LED light source module is a sub-millimeter light-emitting diode (MiniLED) array module capable of emitting white or blue light, comprising a circuit board 91 and a plurality of sub-millimeter light-emitting diodes 92 arranged in an array on the upper surface of the circuit board 91. Figure 1 and Figure 2 In the embodiment shown, the LED light source module comprises a plurality of white sub-millimeter light-emitting diodes 92. However, in another embodiment of the invention, which will be described later, the LED light source module comprises a plurality of blue sub-millimeter light-emitting diodes 92, wherein the wavelength of the blue light emitted by each sub-millimeter light-emitting diode 92 is between 430-500 nm, and its grain size is approximately between 100-200 μm.

[0052] The multilayer light diffuser plate 10 has a relatively large length and width area and a light-incident surface 120 and a light-exit surface 111 that are parallel to each other, as well as a relatively small thickness that is perpendicular to the light-incident surface 120 and the light-exit surface 111. The light-incident surface 120 is adjacent to or near the light source module, so that the light emitted upward from the light source module can enter the multilayer light diffuser plate 10 through the light-incident surface 120 and travel approximately along the direction of the thickness, and then be emitted upward from the light-exit surface 111.

[0053] The multilayer light diffuser 10 includes a main layer 11 and a semi-transparent, semi-reflective layer 12. The light-emitting surface 111 is located on the top surface of the main layer 11. The semi-transparent, semi-reflective layer 12 is located below the main layer 11, and the light-incident surface 120 is located on the bottom surface of the semi-transparent, semi-reflective layer 12. Figure 2 As shown, the semi-transparent, semi-reflective layer 12 is composed of a plurality of first substrate layers 121 and a plurality of second substrate layers 122 stacked alternately; at least one of the upper or lower sides of each first substrate layer 121 is adjacent to a second substrate layer 122, and at least one of the upper or lower sides of each second substrate layer 122 is adjacent to a first substrate layer 121. The materials constituting the first substrate layer 121 and the second substrate layer 122 have different refractive indices.

[0054] The substrates of the main layer 11 and the semi-transparent and semi-reflective layer 12 of the multilayer light diffuser plate 10 of the present invention can be amorphous or semi-crystalline plasticized materials, such as polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA, commonly known as acrylic), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), etc. The thickness of the multilayer light diffuser plate 10 can range from 1.0 mm to 3.0 mm, with a preferred thickness range of 1.2 mm to 2.0 mm. The thickness ratio between the main layer 11 and the semi-transparent and semi-reflective layer 12 ranges from 9:1 to 7:3. The number of stacked layers of the semi-transparent and semi-reflective layer 12, that is, the sum of the number of the first substrate layer 121 and the second substrate layer 122, can be between 50 and 400 layers in some embodiments, and between 100 and 400 layers in some preferred embodiments. The thickness ratio of the first substrate layer 121 to the second substrate layer 122 is between 3:1 and 1:3. In this embodiment, the main layer 11 is made of polycarbonate (PC); the first substrate layer 121 is made of polycarbonate (PC); and the second substrate layer 122 is made of polymethyl methacrylate (PMMA). The preferred embodiment is that the first substrate layer 121 and the second substrate layer 122 have the same thickness, that is, the thickness ratio of the first substrate layer 121 to the second substrate layer 122 is approximately 1:1. Because the refractive indices of the first substrate layer 121 and the second substrate layer 122 are different, alternating stacking of one hundred or more layers of the first substrate layer 121 and the second substrate layer 122 can provide partial transmission and partial reflection of light from the underlying light source module. By combining the light-reflecting layer disposed on the upper surface of the circuit board 91, the light rays reflected downward by the semi-transparent semi-reflective layer 12 can be reflected again and directed to the light-incident surface of the semi-transparent semi-reflective layer 12, thereby achieving a uniform light effect that reduces the bright-dark patch (MURA) phenomenon.

[0055] In the other embodiments of the present invention described below, since the structure, material and function of most components are the same or similar to those in the foregoing embodiments, the same or similar components will be given the same component name and their structure, material and function will not be described again.

[0056] Please see Figure 3A and Figure 3B These are, respectively, an enlarged side view of another preferred embodiment of the multilayer light diffusion plate of the present invention, and a three-dimensional exploded view of an embodiment in which the multilayer light diffusion plate is disposed on an LED light source module.

[0057] like Figure 3A and Figure 3B As shown, another preferred embodiment of the multilayer light diffuser plate 10 of the present invention also includes: a main layer 11, a light-emitting surface 111 located on the top surface of the main layer 11, a semi-transparent and semi-reflective layer 12, and a light-incident surface 120 located on the bottom surface of the semi-transparent and semi-reflective layer 12. The light-incident surface 120 of the multilayer light diffuser plate 10 is also adjacent to or adjacent to the light-emitting diode 92 of the LED light source module. The semi-transparent and semi-reflective layer 12 also includes at least 50 layers (preferably at least 100 layers) of alternately stacked first substrate layer 121 and second substrate layer 122. This preferred embodiment is similar to the one described above. Figure 1 and Figure 2 The difference in the illustrated embodiment is that, Figure 3A and Figure 3B The multilayer light diffusion plate 10 of the preferred embodiment shown also includes the following technical contents.

[0058] In this embodiment, the multilayer light diffusion plate 10 is manufactured by foam extrusion molding, and the main layer 11 contains a plurality of microbubbles 113 and a plurality of diffusion particles 114. The materials of the plurality of diffusion particles 114 are one of the following: calcium carbonate, silicon dioxide, titanium dioxide, silicone resin microparticles, and polymethyl methacrylate microparticles. Due to the difference in refractive index between the diffusion particles 114 and the main layer 111, light traveling within the main layer 11 can be refracted, reflected, or scattered, thereby improving the uniform light output effect. The plurality of diffusion particles 114 account for 0.1%-10% of the weight percentage of the main layer. The plurality of microbubbles 113 are dispersed within the main layer 11. Due to the difference in refractive index between the air within the microbubbles 113 and the material of the main layer 11, light within the main layer 11 can perform at least one of the following functions: reflection, refraction, or scattering, thereby improving the uniform light output effect.

[0059] In this preferred embodiment, the weight reduction rate of the plurality of microbubbles 113 relative to the main layer 11 is between 15% and 25%, and the average size of the plurality of microbubbles 113 is between 60 and 800 μm; wherein, the formula for calculating the weight reduction rate is:

[0060] Weight loss rate (%) = (W1-W2) / W2*100%;

[0061] W1 = H * (L1 * L2 * D);

[0062] in:

[0063] H is the average thickness (mm) of the main layer;

[0064] L1 is the length (mm) of the main layer;

[0065] L2 is the width of the main layer (mm);

[0066] D is the specific gravity of the raw material in the main layer (g / mm²). 3 );

[0067] W1 is the theoretical weight (g) of the main layer, which is the weight without the presence of multiple microbubbles.

[0068] W2 is the actual weight (g) of the main layer, which is the actual weight of the main layer containing multiple microbubbles as measured by a scale.

[0069] A plurality of microbubbles 113 are generated by adding an appropriate amount of a foaming agent and a nucleating agent during the foaming extrusion molding process of the main layer 11. In this invention, the foaming agent used is a commercially available high-temperature foaming agent, such as (but not limited to): 5-benzyltetrazole (5-PT), or azodicarbonamide (also known as azodicarbonamide), etc. The nucleating agent comprises at least one of the following: calcium carbonate, silica, or calcium oxide. The weight percentage of the added nucleating agent can be in the range of 0.01%-5%, but is preferably in the range of 0.1%-0.5%. The weight loss rate of the microbubbles 113 can be controlled by the amount of foaming agent added, and the bubble size of the microbubbles 113 can be controlled by adding the nucleating agent and adjusting the process temperature. Based on the content (weight reduction rate between 15% and 25%) and size (between 60 and 800 μm) of microbubbles 113 in the main layer 11 described in this embodiment, a relatively optimal uniform light emission effect can be achieved.

[0070] In this embodiment, the light source module is a blue LED light source module consisting of a plurality of blue light-emitting diodes (LEDs) 92 arranged in an array on a circuit board 91; and the multilayer light diffusion plate 10 also includes a quantum dot layer 13, a water-blocking and gas-blocking layer 14, and a plurality of microstructures 112.

[0071] like Figure 3A and Figure 3BAs shown, at the light-emitting surface 111 of the multi-layer light diffusion plate 10, there are a plurality of microstructures 112, which are arranged in an array form on the light-emitting surface 111 of the multi-layer light diffusion plate 10. The plurality of microstructures 112 form a plurality of convex portions and a plurality of concave portions on the light-emitting surface 111 of the multi-layer light diffusion plate 10. The plurality of concave portions are separated by the plurality of convex portions, so the plurality of concave portions are independent of each other and do not communicate with each other. The quantum dot layer 13 is disposed at the plurality of concave portions of the plurality of microstructures 112 of the multi-layer light diffusion plate 10; there is no quantum dot layer 13 disposed at the top ends of the plurality of convex portions. Among them, the thickness of the quantum dot layer 13 is t1, and the distance from the top of one of the plurality of convex portions to the bottom of one of the plurality of concave portions is t2, and t1 < t2. In other words, the height t2 of the convex portion of the microstructure 112 is greater than the thickness t1 of the quantum dot layer 13, so that the quantum dot layers 13 located in different concave portions are blocked by the convex portions and do not communicate with each other or contact each other. The water and gas barrier layer 14 is disposed on the entire light-emitting surface 111 of the multi-layer light diffusion plate 10 and closely covers the top ends of the plurality of convex portions and the quantum dot layer 13. Through the water and gas barrier layer 14, it is possible to isolate and prevent external water vapor and oxygen from invading the upper surface of the quantum dot layer 13. The thickness of the water and gas barrier layer 14 is t3, and it can be selected from commercially available water and gas barrier films and directly adhered to the convex portions of the plurality of microstructures 112 and the quantum dot layer 13 on the top surface of the multi-layer light diffusion plate 10.

[0072] In this preferred embodiment, the plurality of microstructures 112 include a plurality of N-sided pyramids, where N is a positive integer greater than or equal to three. The plurality of microstructures can be composed of pyramids of a single shape or a combination of two or more different shapes of pyramids. Pyramids are called differently according to the shape of the bottom surface, depending on the bottom polygon; for example, a pyramid with a triangular bottom surface is called a triangular pyramid, and a pyramid with a square bottom surface is called a square pyramid, etc. As Figure 3BAs shown, a plurality of microstructures 112 include a plurality of pyramids with square bottoms, that is, N = 4. In the present invention, the thickness t1 of the quantum dot layer 13 can be implemented in the range of 5 to 150 μm, but the preferred implementation range is when t1 is between 10 and 40 μm; the distance from the top of the convex part to the bottom of the concave part of the microstructures 112 (or the height of the convex part) t2 can be implemented in the range of 6 to 200 μm, but the preferred implementation range is when t2 is between 25 and 50 μm; and, t1 < t2. The thickness t3 of the water and gas barrier layer 14 can be implemented in the range of 5 to 100 μm, but the preferred implementation range is when t3 is between 10 and 30 μm. The maximum width d1 of the convex part is between 50 and 500 μm. The distance d2 between two adjacent convex parts can be implemented in the range of 50 to 1000 μm, but the preferred implementation range is when d2 is between 250 and 500 μm. The blue light LED light source module is a submillimeter light emitting diode (Mini LED) array module that can emit blue light; the wavelength of the blue light is between 430 - 500 nm.

[0073] The quantum dot layer 13 contains a plurality of quantum dots 131 (Quantum Dot; abbreviated as QD). The plurality of quantum dots 131 are a kind of nanocrystal semiconductor material composed of II-VI, III-V or IV-VI group elements, and the grain diameter of each quantum dot 131 is between 2 and 10 nm. Among them, the emission wavelength of the plurality of quantum dots 131 in the quantum dot layer 13 can be between 490 and 650 nm; in this preferred embodiment, the plurality of quantum dots 131 include a plurality of green quantum dots with an emission wavelength of 520 - 530 nm and a plurality of red quantum dots with an emission wavelength of 620 - 630 nm. The blue light emitted upward by the submillimeter light emitting diode 92 of the blue light LED light source module can be mixed into white light after passing through the quantum dot layer 13 and then emitted upward from the light emitting surface 111 of the multi-layer light diffusion plate 10. The quantum dot layer 13 requires a consistent blue light intensity to convert red / green light and mix it into uniform white light; due to the lower light intensity around the display than the central intensity, there is an insufficient conversion of red / green light, resulting in a blue light phenomenon around the display. The multi-layer light diffusion plate 10 of the present invention is formed by foam extrusion, and includes a plurality of microbubbles 113 and diffusion particles 114 in the main layer 111, a plurality of microstructures 112 are provided on the light emitting surface 111, and a unique semi-transmissive and semi-reflective layer 12 is provided on the light incident surface 120 of the multi-layer light diffusion plate 10, which can have a better light diffusion effect, increase the light intensity in the surrounding area of the display, and thus improve the problems of blue light leakage and MURA (Mura).

[0074] Please refer to Figure 4 , which is a partially enlarged side view schematic diagram of another preferred embodiment of the multi-layer light diffusion plate of the present invention. As Figure 4As shown, another preferred embodiment of the multilayer light diffusion plate 10 of the present invention also includes: a main layer 11, a light-emitting surface 111 located on the top surface of the main layer 11, a semi-transparent and semi-reflective layer 12, and a light-incident surface 120 located on the bottom surface of the semi-transparent and semi-reflective layer 12. The semi-transparent and semi-reflective layer 12 also includes at least 50 layers (preferably at least 100 layers) of alternately stacked first substrate layer 121 and second substrate layer 122. This preferred embodiment is similar to the one described above. Figure 1 and Figure 2 The difference in the illustrated embodiment is that, Figure 4 In the preferred embodiment shown, a plurality of microstructures 112 are respectively disposed on the light-incident surface 120 and the light-exit surface 111 of the multilayer light diffuser 10. These microstructures are also arranged in an array on the light-incident surface 120 and the light-exit surface 111 of the multilayer light diffuser 10. Each of the microstructures 112 forms a plurality of protrusions and a plurality of recesses on the light-incident surface 120 and the light-exit surface 111 of the multilayer light diffuser. Furthermore, the main layer 111 contains a plurality of microbubbles 113 and a plurality of diffusion particles 114. Through the semi-transparent and semi-reflective layer 12 located on the light-incident surface 120, combined with the plurality of microbubbles 113 and diffusion particles 114 contained in the main layer 111, and the plurality of microstructures 112 disposed on the light-incident surface 120 and the light-exit surface 111, a relatively optimal light diffusion effect can be provided. When the multilayer light diffusion plate 10 of the present invention is used with a white LED light source module, or when it is used with a blue LED light source module but an additional quantum dot film is provided or a light color conversion material or phosphor is added to the main layer, the multilayer light diffusion plate 10 itself does not need to be provided with a quantum dot layer.

[0075] Please see Figure 5 This is a flowchart illustrating a preferred embodiment of the manufacturing method of the multilayer light diffusion plate of the present invention. In this embodiment, the manufacturing process of the multilayer light diffusion plate includes the following steps:

[0076] Feeding step 21: At least one first substrate, one second substrate, one foaming agent, and one diffusion particle, which constitute the multilayer light diffusion plate, are fed into a foaming extrusion process equipment through a feed port; the first substrate and the second substrate have different refractive indices.

[0077] Heating and mixing step 22: The foaming and extrusion process equipment is used to uniformly mix and foam the materials at a general processing temperature suitable for polycarbonate; the first substrate and the second substrate are heated and mixed separately and are not mixed.

[0078] Step 23 of the splitter: The first substrate and the second substrate after heating and mixing enter a splitter. The first substrate is split into a main layer and a plurality of first substrate layers, and the second substrate is split into a plurality of second substrate layers. The plurality of first substrate layers and the plurality of second substrate layers are alternately stacked to form a semi-transparent semi-reflective layer, and the semi-transparent semi-reflective layer is superimposed on the main layer.

[0079] Step 24: The main layer and the semi-transparent and semi-reflective layer, which have been uniformly mixed, foamed and stacked from the distributor, are co-extruded into a multi-layer board through a T-die of the foaming extrusion process equipment.

[0080] Rolling step 25: The plate is rolled and cooled by a roller module; in rolling step 25, the roller module rolls and forms a plurality of microstructures on the light-emitting surface of the multilayer light diffuser plate, so that the plurality of microstructures are arranged in an array on the light-emitting surface of the multilayer light diffuser plate; the plurality of microstructures form a plurality of protrusions and a plurality of concave portions on the light-emitting surface of the multilayer light diffuser plate; the plurality of concave portions are separated by the plurality of protrusions, so the plurality of concave portions are independent and not interconnected;

[0081] Discharge step 26: The cooled multilayer light diffusion plate is discharged from one of the discharge ports of the foaming extrusion process equipment.

[0082] The multilayer light diffuser plate discharged from the outlet has a parallel light-incident surface and a light-exit surface, and a thickness perpendicular to the light-incident surface and the light-exit surface. The multilayer light diffuser plate includes a main layer and a semi-transparent, semi-reflective layer. The light-exit surface is located on the top surface of the main layer, the semi-transparent, semi-reflective layer is located below the main layer, and the light-incident surface is located on the bottom surface of the semi-transparent, semi-reflective layer. The semi-transparent, semi-reflective layer is composed of a plurality of alternating stacked first substrate layers and a plurality of second substrate layers. At least one side of the upper or lower portion of each first substrate layer is adjacent to a second substrate layer, and at least one side of the upper or lower portion of each second substrate layer is adjacent to a first substrate layer. The materials constituting the first substrate layer and the second substrate layer have different refractive indices.

[0083] In a preferred embodiment, the following steps are further included between the rolling step 25 and the discharging step 26: coating a quantum dot layer on a plurality of the concave portions on the light-emitting surface of the multi-layer light diffusing plate through a coating process; wherein, the thickness of the quantum dot layer is t1, the distance from the top of one of the plurality of convex portions to the bottom of one of the plurality of concave portions is t2, and t1 < t2; thereafter, through an adhesion process, a water and gas barrier layer is adhered to the light-emitting surface of the multi-layer light diffusing plate and covers the plurality of convex portions and the quantum dot layer; wherein, a plurality of quantum dots (Quantum Dot; abbreviated as QD) are included in the quantum dot layer; wherein, the multi-layer light diffusing plate is used in combination with a blue light source module; the blue light source module is a blue mini light-emitting diode light source module composed of a plurality of blue mini light-emitting diodes (Mini LED) arranged in an array form.

[0084] The applicant has respectively used different light diffusion technologies such as "diffusion particles", "surface microstructure", and "semi-transmissive semi-reflective layer" in multiple different light diffusing plate samples (prior art comparative examples 1 to 3 and embodiment 1 of the present invention shown in Table 1 below), and then observed the optical effects such as "light diffusing plate transmittance", "luminance", and "optical taste (5 is the best, 1 is the lowest)" of each light diffusing plate sample in combination with the light source module. The test results are shown in Table 1 below. Among them, only the light diffusing plate of embodiment 1 uses the technology of the present invention of setting a semi-transmissive semi-reflective layer on the light-incident surface of the light diffusing plate, and the other comparative examples 1 to 3 do not set a semi-transmissive semi-reflective layer; correspondingly, the specific structure of the light diffusing plate of embodiment 1 can be referred to Figure 1 and Figure 2 the structure of the multi-layer light diffusing plate 10 shown. The multi-layer light diffusing plate does not include "diffusion particles" and "surface microstructure". As can be seen from Table 1, because embodiment 1 uses the technology and structure of the present invention of "setting a semi-transmissive semi-reflective layer on the light-incident surface of the light diffusing plate", even though embodiment 1 does not include "diffusion particles" and "surface microstructure", compared with other light diffusing plates (comparative examples 1 to 3) that only use "diffusion particles" or / and "surface microstructure", embodiment 1 still has relatively the best luminance and taste optical performance, and relatively good transmittance optical performance.

[0085] Table 1: Comparative table of optical effects of the present invention of setting a semi-transmissive semi-reflective layer on the light-incident surface of the light diffusing plate relative to other existing light diffusion technologies

[0086]

[0087]

[0088] Please refer to Table 2 below, which is a comparison table similar to Table 1. However, except that Example 1 has a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser, but no diffusion particles or surface microstructures are added, Example 2 and Example 3 are also added to Table 2. Furthermore, the distance between the diffuser and the LED was reduced to 0 mm during the test. Example 2 also has a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser and 2% diffusion particles, but no surface microstructures. Example 3 also has a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser, 2% diffusion particles, and surface microstructures. Comparative Examples 1-3 in Table 2 have the same structure as those shown in Table 1. As shown in Table 2, not only are the optical performance (brightness and luster) of the light diffusion plates of Examples 1-3 using the semi-transparent and semi-reflective layer technology of the present invention significantly better than that of Comparative Examples 1-3 without the technology of the present invention, but Example 3, in addition to having a semi-transparent and semi-reflective layer on the light-incident surface, also incorporates light diffusion technology with the addition of 2% diffusion particles and the setting of surface microstructures. Therefore, the optical performance (brightness and luster) of Example 3 is the best among all samples, and its transmittance optical performance is also relatively good. Furthermore, Table 2 shows that when the distance between the diffuser plate and the LED is reduced to 0 mm, the luster of Comparative Examples 1-3 without the technology of the present invention using a semi-transparent and semi-reflective layer on the light-incident surface decreases significantly, meaning the MURA problem becomes very serious. In contrast, the luster reduction of Examples 1-3 is not as significant, indicating that the technology of the present invention can provide relatively optimal light diffusion effect. In particular, Embodiment 3 of the present invention (in addition to providing a semi-transparent and semi-reflective layer on the light-incident surface, it also incorporates 2% diffusion particles and surface microstructures) can still achieve good optical performance in terms of brightness, clarity, and transmittance, even when the bottom surface of the diffuser plate is directly attached to the LED (i.e., the distance between the diffuser plate and the LED is 0mm). This structure can significantly reduce the overall thickness of the direct-lit backlight module, making the product thinner and more portable.

[0089] Table 2: Comparison of the optical effects of the present invention, which involves setting a semi-transparent and semi-reflective layer on the light incident surface of the light diffusion plate, compared with other existing light diffusion technologies.

[0090]

[0091]

[0092] Please see Table 3 below, which is a comparison table similar to Tables 1 and 2, except that it compares the newly added Examples 7 and 8 with the aforementioned Comparative Example 3. In Example 7, in addition to providing a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser, microbubbles are generated during the mixing process of the main layer of the light diffuser. In Example 8, in addition to providing a semi-transparent, semi-reflective layer on the light-incident surface of the light diffuser and generating microbubbles during the mixing process of the main layer of the light diffuser, a color-conversion material that can convert blue light to white light is added to the main layer. As shown in Table 3, the generation of microbubbles and the addition of color-conversion material in the main layer of the light diffuser in Examples 7 and 8 only slightly reduce the light transmittance and luminance, but further improve the quality. Even when the bottom surface of the diffuser plate is directly attached to the LED (i.e., the distance between the diffuser plate and the LED is 0mm), good brightness and luster, as well as acceptable transmittance, can still be achieved. This structure can significantly reduce the overall thickness of the direct-lit backlight module, making the product thinner and more portable.

[0093] Table 3: Comparison of the optical effects of the present invention, which involves setting a semi-transparent and semi-reflective layer on the light-incident surface of the light-diffusing plate and foaming or adding a light color conversion material, compared with other existing light diffusion technologies.

[0094]

[0095] Please see Figure 6 This is a graph showing the light output brightness at different positions between LEDs for a light diffuser plate with different numbers of semi-transparent and semi-reflective layers. Figure 6 The horizontal axis represents the position of the light diffuser in the horizontal direction (distance in cm), and the vertical axis represents the illuminance value (in lux). Figure 6 It is known that diffusers generally exhibit severe bright and dark banding because they do not have a semi-transparent and semi-reflective layer on the light-incident surface. When a diffuser has a semi-transparent and semi-reflective layer on the light-incident surface, the difference between bright and dark bands in the LEDs is still slightly noticeable when there are only 25 layers, but the difference can be homogenized when there are 100 layers.

[0096] Please see Figure 7 This is a graph showing the light output brightness at different positions between LEDs when the thickness ratio of the alternately stacked first and second substrate layers of a light diffuser plate with a semi-transparent and semi-reflective layer is different. Figure 7 The horizontal axis represents the position of the light diffuser in the horizontal direction (distance in cm), and the vertical axis represents the illuminance value (in lux). Figure 7 It can be seen that when the thickness ratio of the first substrate layer to the second substrate layer is 1:1, the relatively optimal light uniformity effect can be obtained.

[0097] Please see Figure 8 and Figure 9 ,in, Figure 8 The graph shows the transmittance curves of light diffuser samples A, B, C, and D with semi-transparent and semi-reflective layers at different light wavelengths. Figure 9 For example Figure 8 The chart shown compares the tastes of samples A, B, C, and D as displayed in the test. Among them, Figure 8 The horizontal axis represents the wavelength of light (in nm), and the vertical axis represents the transmittance (%). From Figure 8 and Figure 9 It can be seen that when a light diffusion plate with a semi-transparent and semi-reflective layer is set, and its transmittance at 400nm is in the range of 30-60% and its reflectance is in the range of 60-30%, that is, for samples B and C, the MURA problem is the least obvious, so the best taste can be obtained.

[0098] The embodiments described above should not be used to limit the scope of application of the present invention. The scope of protection of the present invention should be based on the technical spirit defined by the claims and the scope of its equivalent variations. That is, all equivalent variations and modifications made in accordance with the claims of the present invention will not lose the essence of the present invention, nor will they depart from the spirit and scope of the present invention, and therefore should be regarded as further implementations of the present invention.

Claims

1. A multilayer light diffusion plate for assembly above a light source module; characterized in that, The multi-layer light diffusing plate has a light incident surface and a light emitting surface that are parallel to each other, and a thickness that is perpendicular to the light incident surface and the light emitting surface; the light incident surface is adjacent to the light source module, so that the light emitted by the light source module enters the multi-layer light diffusing plate through the light incident surface and travels substantially along the direction of the thickness; and, the multi-layer light diffusing plate includes: A main layer, the light emitting surface is located on a top surface of the main layer; a plurality of microstructures are provided on the light emitting surface, and are arranged in an array form on the light emitting surface of the multi-layer light diffusing plate; the plurality of microstructures form a plurality of convex portions and a plurality of concave portions on the light emitting surface of the multi-layer light diffusing plate; the plurality of concave portions are separated by the plurality of convex portions, so the plurality of concave portions are independent of each other and do not communicate with each other; A semi-transmissive semi-reflective layer, located below the main layer, and the light incident surface is located on a bottom surface of the semi-transmissive semi-reflective layer; A quantum dot layer, the quantum dot layer is provided at the plurality of concave portions on the light emitting surface of the multi-layer light diffusing plate; wherein, the thickness of the quantum dot layer is t1, and the distance from a top of the plurality of convex portions to a bottom of the plurality of concave portions is t2, and, t1 < t2; and, A water and gas barrier layer, the water and gas barrier layer is provided on the light emitting surface of the multi-layer light diffusing plate and covers the plurality of convex portions and the quantum dot layer; Wherein, The semi-transmissive semi-reflective layer is composed of a plurality of first substrate layers and a plurality of second substrate layers stacked alternately; at least one of the upper and lower sides of each of the first substrate layers is adjacent to one of the second substrate layers, and at least one of the upper and lower sides of each of the second substrate layers is adjacent to one of the first substrate layers; the materials constituting the first substrate layer and the second substrate layer have different refractive indices; The materials of the main layer and the semi-transmissive semi-reflective layer are non-crystalline or semi-crystalline plasticized materials; The thickness ratio range between the main layer and the semi-transmissive semi-reflective layer is between 9:1 and 7:3; The number of layers of the semi-transmissive semi-reflective layer, that is, the sum of the number of layers of the first substrate layer and the second substrate layer, is between 50 layers and 400 layers; The thickness ratio range between the first substrate layer and the second substrate layer is between 3:1 and 1:3; The quantum dot layer contains a plurality of quantum dots; the plurality of quantum dots are a kind of nano microcrystalline semiconductor material, composed of elements of II-VI, III-V or IV-VI groups, and the grain diameter of each of the quantum dots is between 2 and 10 nm; wherein, the plurality of quantum dots contain a plurality of green quantum dots with a light emitting wavelength of 520 - 530 nm and a plurality of red quantum dots with a light emitting wavelength of 620 - 630 nm; The light source module is a blue LED light source module composed of a plurality of blue light emitting diodes arranged in an array form.

2. The multi-layer light diffusing plate according to claim 1, wherein: The materials of the main layer and the semi-transmissive semi-reflective layer are respectively selected from one of the following: polycarbonate, polystyrene, polymethyl methacrylate, polyethylene, polypropylene, polyethylene terephthalate; The number of layers of the semi-transmissive semi-reflective layer is between 100 layers and 400 layers.

3. The multilayer light diffusion plate as described in claim 2, characterized in that: The main layer is made of polycarbonate; the first substrate layer is made of polycarbonate; the second substrate layer is made of polymethyl methacrylate. The first substrate layer and the second substrate layer have the same thickness, that is, the thickness ratio of the first substrate layer and the second substrate layer is 1:

1. The light source module is an LED light source module consisting of a plurality of light-emitting diodes arranged in an array. The thickness of this multilayer light diffusion plate ranges from 1.0mm to 3.0mm.

4. The multilayer light diffusion plate as described in claim 1, characterized in that: This multilayer light diffuser is formed by foam extrusion, and the main layer contains a plurality of microbubbles and a plurality of diffuser particles; the material of the plurality of diffuser particles is one of the following: calcium carbonate, silicon dioxide, titanium dioxide, organosilicon resin microparticles, polymethyl methacrylate microparticles; the weight percentage of the plurality of diffuser particles in the main layer is 0.1%-10%; the plurality of microbubbles are dispersed in the main layer and perform at least one of the following functions on the light in the main layer: reflection, refraction, or scattering, so as to improve the uniform light output effect; The weight reduction rate of the plurality of these microbubbles to the main layer is between 15% and 25%, and the average size of the plurality of these microbubbles is between 60 and 800 μm; The formula for calculating this weight loss rate is as follows: Weight loss rate = (W1 - W2) / W2 * 100% W1 = H * (L1 * L2 * D); in: H is the average thickness of the main layer; L1 is the length of the main layer; L2 is the width of the main layer; D is the specific gravity of the raw material in the main layer; W1 is the theoretical weight of the main layer, which is the weight without including multiple of these microbubbles; W2 is the actual weight of the main layer, which is the actual weight of the main layer containing multiple of the microbubbles, as measured by a scale.

5. The multilayer light diffusion plate as described in claim 1, characterized in that: The plurality of such microstructures comprises a plurality of N-sided pyramids, where N is a positive integer greater than or equal to three; t2 is between 6 and 200 μm; the maximum width of the protrusion is between 50 and 500 μm, and the distance between two adjacent protrusions is between 50 and 1000 μm; The thickness of the water- and gas-barrier layer is t3, which is between 5 and 100 μm. The blue LED light source module is a sub-millimeter light-emitting diode array module that emits the blue light; the wavelength of the blue light is between 430-500nm.

6. The multilayer light diffusion plate as described in claim 1, characterized in that, A plurality of microstructures are provided on the light-incident surface and arranged in an array on the light-incident surface of the multilayer light diffuser plate; the plurality of microstructures form a plurality of protrusions and a plurality of recesses on the light-incident surface of the multilayer light diffuser plate.

7. A method for manufacturing a multilayer light diffusion plate, characterized in that, Including: Feeding step: At least one first substrate, one second substrate, and one foaming agent constituting the multilayer light diffusion plate are fed into a foaming extrusion process equipment through a feed port; the first substrate and the second substrate have different refractive indices; Heating and mixing step: The foaming and extrusion process equipment is used to uniformly mix and foam the materials at a general processing temperature suitable for polycarbonate; the first substrate and the second substrate are heated and mixed separately and are not mixed. The splitter step: The first substrate and the second substrate after heating and mixing enter a splitter. The splitter splits the first substrate into a main layer and a plurality of first substrate layers, and splits the second substrate into a plurality of second substrate layers. The plurality of first substrate layers and the plurality of second substrate layers are alternately stacked to form a semi-transparent semi-reflective layer, and the semi-transparent semi-reflective layer is superimposed on the main layer. T-die step: The main layer and the semi-transparent and semi-reflective layer, which have been uniformly mixed, foamed and stacked from the distributor, are co-extruded into a multi-layer board through a T-die of the foaming extrusion process equipment. Roll forming step: The sheet material is rolled and cooled using a roller module; and Discharge step: The cooled multilayer light diffusion plate is discharged from one of the discharge ports of the foaming extrusion process equipment; The multilayer light diffusion plate discharged from the discharge port has a light-incident surface and a light-exit surface that are parallel to each other, and a thickness that is perpendicular to the light-incident surface and the light-exit surface; and the multilayer light diffusion plate includes the main layer and the semi-transparent and semi-reflective layer; the light-exit surface is located on the top surface of the main layer, the semi-transparent and semi-reflective layer is located below the main layer, and the light-incident surface is located on the bottom surface of the semi-transparent and semi-reflective layer; The semi-transparent and semi-reflective layer is composed of a plurality of first substrate layers and a plurality of second substrate layers stacked alternately; at least one of the upper and lower sides of each first substrate layer is adjacent to a second substrate layer, and at least one of the upper and lower sides of each second substrate layer is adjacent to a first substrate layer; the materials constituting the first substrate layer and the second substrate layer have different refractive indices.

8. The method for manufacturing a multilayer light diffusion plate as described in claim 7, characterized in that: Both the main layer and the semi-transparent and semi-reflective layer are made of non-crystalline or semi-crystalline plasticized materials. The thickness ratio between the main layer and the semi-transparent and semi-reflective layer is between 9:1 and 7:

3. The number of layers of the semi-transparent and semi-reflective layer, which is the sum of the number of layers of the first substrate layer and the second substrate layer, is between 50 and 400 layers. The thickness ratio between the first substrate layer and the second substrate layer is between 3:1 and 1:

3.

9. The method for manufacturing a multilayer light diffusion plate as described in claim 8, characterized in that: The main layer and the semi-transparent and semi-reflective layer are each made of one of the following materials: polycarbonate, polystyrene, polymethyl methacrylate, polyethylene, polypropylene, or polyethylene terephthalate. The number of semi-transparent and semi-reflective layers is between 100 and 400.

10. The method for manufacturing a multilayer light diffusion plate as described in claim 9, characterized in that: The main layer is made of polycarbonate; the first substrate layer is made of polycarbonate; the second substrate layer is made of polymethyl methacrylate. The thicknesses of the first substrate layer and the second substrate layer are the same. That is, the thickness ratio of the first substrate layer to the second substrate layer is 1:

1. The multi-layer light diffusing plate is for being assembled above a light source module, and the light source module is an LED light source module composed of a plurality of light emitting diodes arranged in an array. The thickness range of the multi-layer light diffusing plate is 1.0 mm to 3.0 mm.

11. The manufacturing method of the multi-layer light diffusing plate as claimed in claim 8, wherein: The multi-layer light diffusing plate is formed by foam extrusion, and a plurality of microbubbles and a plurality of diffusion particles are included in the main layer; the materials of the plurality of diffusion particles are one of the following: calcium carbonate, silicon dioxide, titanium dioxide, silicone resin microparticles, polymethyl methacrylate microparticles; the weight percentage of the plurality of diffusion particles in the main layer is 0.1% - 10%; the plurality of microbubbles are dispersed in the main layer to perform at least one of the following functions on the light in the main layer: reflection, refraction or scattering, so as to improve the effect of uniform light emission. The weight reduction rate of the plurality of microbubbles with respect to the main layer is between 15 and 25%, and the average size of the plurality of microbubbles is between 60 and 800 μm. Wherein, the calculation formula of the weight reduction rate is: Weight reduction rate = (W1 - W2) / W2 * 100%; W1 = H * (L1 * L2 * D); Wherein: H is the average thickness of the main layer; L1 is the length of the main layer; L2 is the width of the main layer; D is the raw material specific gravity of the main layer; W1 is the theoretical weight of the main layer, that is, the weight when not including the plurality of microbubbles; W2 is the actual weight of the main layer, that is, the actual weight of the main layer including the plurality of microbubbles weighed by a weighing scale.

12. The method for manufacturing a multilayer light diffusion plate as described in claim 8, characterized in that, In the rolling step, the roller module rolls on the light emitting surface of the multi-layer light diffusing plate to form a plurality of microstructures, which are arranged in an array on the light emitting surface of the multi-layer light diffusing plate; the plurality of microstructures form a plurality of convex portions and a plurality of concave portions on the light emitting surface of the multi-layer light diffusing plate; the plurality of concave portions are separated by the plurality of convex portions, so the plurality of concave portions are independent and do not communicate with each other. Wherein, between the rolling step and the discharging step, the following steps are further included: Coating a quantum dot layer at the plurality of concave portions on the light emitting surface of the multi-layer light diffusing plate through a coating process; wherein, the thickness of the quantum dot layer is t1, the distance from the top of one of the plurality of convex portions to the bottom of one of the plurality of concave portions is t2, and t1 < t2; and Covering a water and gas barrier layer on the light emitting surface of the multi-layer light diffusing plate and covering the plurality of convex portions and the quantum dot layer through a pasting process. Wherein, a plurality of quantum dots are included in the quantum dot layer. The multi-layer light diffusing plate is for being assembled above a light source module, and the light source module is a blue light LED light source module composed of a plurality of blue light emitting diodes arranged in an array.

13. The manufacturing method of the multi-layer light diffusing plate as claimed in claim 12, wherein: The plurality of quantum dots is a nanocrystalline semiconductor material composed of group II-VI, III-V or IV-VI elements, and the grain diameter of each quantum dot is between 2 and 10 nm; wherein, the plurality of quantum dots includes a plurality of green quantum dots with an emission wavelength of 520-530 nm and a plurality of red quantum dots with an emission wavelength of 620-630 nm; The plurality of such microstructures comprises a plurality of N-sided pyramids, where N is a positive integer greater than or equal to three; t2 is between 6 and 200 μm; the maximum width of the protrusion is between 50 and 500 μm, and the distance between two adjacent protrusions is between 50 and 1000 μm; The thickness of the water- and gas-barrier layer is t3, which is between 5 and 100 μm. The blue LED light source module is a sub-millimeter light-emitting diode array module that emits the blue light; the wavelength of the blue light is between 430-500nm.

14. The method for manufacturing a multilayer light diffusion plate as described in claim 8, characterized in that, A plurality of microstructures are provided on the light-incident surface and arranged in an array on the light-incident surface of the multilayer light diffuser plate; the plurality of microstructures form a plurality of protrusions and a plurality of recesses on the light-incident surface of the multilayer light diffuser plate.

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