TWI870301B - Multilayer light diffuser plate - Google Patents

Abstract

A multilayer light diffuser plate comprises a main layer and a partially-transmissive and partially-reflective layer. The light-emitting surface of the multilayer light diffusion plate is the top surface of the main layer, and the light-incident surface is the bottom surface of the partially-transmissive and partially-reflective layer. The partially-transmissive and partially-reflective layer is located under the main layer and is composed of a plurality of first base material layers and a plurality of second base material layers stacked alternately. The materials of the first base material layer and the second base material layer have different refractive indices. The light-incident surface of the light diffuser plate is provided with the partially-transmissive and partially-reflective layer, which can partially penetrate and partially reflect the intensity of the linear light source of the LED light source module below, thereby reducing the bright and dark bands (MURA) between the LEDs and achieving the effect of uniform light. In addition, the partially-transmissive and partially-reflective layer formed by alternately stacking a plurality of first base material layers and second base material layers with different refractive indices is arranged on the light-incident surface of the light diffuser plate by means of extrusion, which is simpler and less expensive to manufacture.

Description

Multi-layer light diffusion plate

The present invention relates to a multi-layer light diffuser plate used in a direct-type backlight module, and in particular to a multi-layer light diffuser plate having a half-transmitting and half-reflecting layer composed of a plurality of first substrate layers and second substrate layers with different refractive indices stacked alternately arranged on the light incident surface of the light diffuser plate.

Currently, more and more LCD display devices use direct-type backlight modules to provide light for their LCD panels. Existing direct-type backlight modules generally use a light-emitting diode (LED) light source module installed on the bottom to provide light, and use a light diffuser to even out the light emitted by the LED and then emit it upward from the light-emitting surface located on the top, so as to improve the light-dark band (MURA) phenomenon between each LED on the light-emitting surface of the light diffuser.

The known light diffuser plates mainly provide light diffusion function in the following ways:

(1) Add a large number of tiny diffusion particles inside the light diffusion plate. The different refractive indices of the diffusion particles and the light diffusion plate are used to refract, reflect or scatter the light, thereby diffusing the light. In order to achieve a good uniform light effect, it is necessary to increase the amount of diffusion particles added to reduce the light transmittance, or increase the distance between the light diffusion plate and the LED light source module. These practices will reduce the light utilization rate or increase the overall thickness of the light diffusion plate.

(ii) Add a large number of microstructures on the surface of the light diffuser. Use surface microstructures to change the direction of light travel, thereby providing the function of diffusing light. Due to the use of extrusion process, it is impossible to obtain a good transfer rate, thereby reducing the effect of the microstructure in changing the direction of light.

(iii) Print dots on the surface of the light diffuser. Use surface printed dots to diffuse/shield different locations on the surface of the light diffuser, thereby reducing the bright and dark band phenomenon between each LED on the light-emitting surface. However, printing dots requires adding multiple processing steps and there are assembly alignment issues.

As can be seen from the above, the currently known light diffusion plate technology mainly achieves the light diffusion effect by adding light diffusion particles to the light diffusion plate made of thermoplastic material, extruding the surface microstructure by roller, or printing dots on the surface of the light diffusion plate. However, these methods have limited diffusion effects and have the following disadvantages: the thickness of the diffusion plate needs to be increased, or the penetration of the diffusion plate is reduced, or the distance between the LED and the diffusion plate is increased, or multiple processing steps are required and there are assembly alignment problems... etc., which still need to be further improved.

The present invention sets a semi-transmissive and semi-reflective layer on the surface of the light diffusion plate, partially penetrating and partially reflecting the intensity of the straight light source above the LED, thereby reducing the bright and dark bands between the LEDs and achieving a uniform light effect. The semi-transmissive and semi-reflective layer of the conventional technology can be obtained by coating/electroplating, but it requires subsequent processing, and the process is relatively complicated and costly. In contrast, the present invention sets a semi-transmissive and semi-reflective layer composed of a plurality of first substrate layers and second substrate layers with different refractive indices alternately stacked on the light incident surface of the light diffusion plate by extrusion production, which can solve the shortcomings of the traditional coating/electroplating method for producing semi-transmissive and semi-reflective layers, such as complicated process and high cost.

The main purpose of the present invention is to provide a multi-layer light diffusing plate. The multi-layer light diffusing plate includes a main layer and a semi-transmissive and semi-reflective layer. The light-emitting surface of the multi-layer light diffusing plate is the top surface of the main layer, and the light-incident surface of the multi-layer light diffusing plate is the bottom surface of the semi-transmissive and semi-reflective layer. The semi-transmissive and semi-reflective 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 constituting the first substrate layer and the second substrate layer have different refractive indices. The present invention sets a semi-transmissive and semi-reflective layer on the light-incident surface of the light diffusing plate to partially penetrate and partially reflect the linear light intensity of the LED light source module below, thereby reducing the bright and dark bands between LEDs and achieving a uniform light effect. In addition, the present invention uses an extrusion manufacturing method to set a semi-transmissive and semi-reflective layer composed of a plurality of first substrate layers and second substrate layers with different refractive indices alternately stacked on the light incident surface of the light diffusion plate, which has the advantages of simpler manufacturing process and lower cost.

To achieve the above-mentioned purpose, the present invention discloses a multi-layer light diffusion plate that can be assembled on top of a light source module. The multi-layer light diffusion plate has a light input surface and a light output surface that are parallel to each other, and a thickness that is perpendicular to the light input surface and the light output surface. The light input surface is adjacent to the light source module, so that the light emitted by the light source module can enter the multi-layer light diffusion plate through the light input surface and travel roughly along the direction of the thickness. In addition, the multi-layer light diffusion plate includes: a main layer, the light output surface is located on a top surface of the main layer; and a semi-transmissive and semi-reflective layer, which is located below the main layer, and the light input surface is located on a bottom surface of the semi-transmissive and semi-reflective layer. The semi-transmissive 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 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.

In one embodiment, the materials of the main layer and the semi-transmissive and semi-reflective layer are non-crystalline or semi-crystalline plasticized materials; the thickness ratio of the main layer and the semi-transmissive and semi-reflective layer is between 9:1 and 7:3; the number of layers of the semi-transmissive and 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 and 400 layers; the thickness ratio of the first substrate layer and the second substrate layer is between 3:1 and 1:3.

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

In one embodiment, the material of the main layer is polycarbonate (PC); the material of the first substrate layer is polycarbonate (PC); the material of the second substrate layer is polymethyl methacrylate (PMMA); the thickness of the first substrate layer and the second substrate layer are the same, 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 composed of a plurality of light emitting diodes (LEDs) arranged in an array; the thickness of the multi-layer light diffusion plate ranges from 1.0 mm to 3.0 mm.

In one embodiment, the multi-layer light diffusion plate is formed by foaming extrusion, and contains a plurality of microbubbles and a plurality of diffusion particles in the main layer; the material of the plurality of diffusion particles is one of the following: calcium carbonate, silicon dioxide, titanium dioxide, organic silicone resin particles, polymethyl methacrylate particles; 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, 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 effect of uniform light emission. 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 weight loss rate is calculated as follows: weight loss rate (%) = (W1-W2)/W2*100%; W1 = H*(L1*L2*D); wherein: H is the average thickness of the main layer (mm); L1 is the length of the main layer (mm); L2 is the width of the main layer (mm); D is the specific gravity of the material of the main layer (g/ ^mm3 ); W1 is the theoretical weight of the main layer (g), that is, the weight without the plurality of microbubbles; W2 is the actual weight of the main layer (g), that is, the actual weight of the main layer containing the plurality of microbubbles measured by a scale.

In one embodiment, the multi-layer light diffusing plate further includes a quantum dot layer and a water- and gas-blocking layer. A plurality of microstructures are arranged on the light-emitting surface of the multi-layer light diffusing plate in an array form; 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 not interconnected. The quantum dot layer is arranged 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 a top of the plurality of convex portions to a bottom of the plurality of concave portions is t2, and t1<t2. The water- and gas-blocking layer is disposed on the light-emitting surface of the multi-layer light diffusion plate and covers the plurality of protrusions and the quantum dot layer. The quantum dot layer includes a plurality of quantum dots (QD for short); the plurality of quantum dots are a 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 emission wavelength of 520 to 530 nm and a plurality of red quantum dots with a light emission wavelength of 620 to 630 nm. The light source module is a blue light LED light source module composed of a plurality of blue light emitting diodes (LEDs) arranged in an array.

In one embodiment, the plurality of microstructures include a plurality of N-sided pyramids, wherein 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-blocking layer is t3, and t3 is between 5 and 100 μm. The blue light LED light source module is a sub-millimeter light-emitting diode (Mini LED) array module that can emit the blue light; the wavelength of the blue light is between 430 and 500 nm.

In one embodiment, a plurality of microstructures are disposed on the light incident surface, and are disposed in an array on the light incident surface of the multi-layer light diffuser plate; the plurality of microstructures form a plurality of convex portions and a plurality of concave portions on the light incident surface of the multi-layer light diffuser plate.

To achieve the above-mentioned object, the present invention discloses a method for manufacturing a multi-layer light diffusion plate, comprising the following steps: a feeding step: feeding at least a first substrate, a second substrate, and a foaming agent constituting the multi-layer light diffusion plate into a foaming extrusion process equipment through a feeding port; the first substrate and the second substrate have different refractive indices; a heating and kneading step: uniformly mixing and foaming at a general processing temperature suitable for polycarbonate in the foaming extrusion process equipment; the first substrate and the second substrate are heated and kneaded separately, and the two are not mixed; a split flow step: The first substrate and the second substrate after heating and mixing enter a diverter, and the first substrate is diverted into a main layer and a plurality of first substrate layers, and the second substrate is diverted into a plurality of second substrate layers by the diverter, and the plurality of first substrate layers and the plurality of second substrate layers are alternately stacked to form a semi-transmissive and semi-reflective layer, and the semi-transmissive and semi-reflective layer is superimposed on the main layer; T-die step: The uniformly mixed, foamed and superimposed substrate from the diverter is passed through a T-die of the foam extrusion process equipment. The main layer and the semi-transmissive and semi-reflective layer are co-extruded into a multi-layer plate; a rolling step: the plate is rolled and formed by a roller module and cooled; and a discharging step: the multi-layer light diffusing plate after cooling is sent out from a discharging port of the foam extrusion process equipment; wherein the multi-layer light diffusing plate sent out from the discharging port has a light input surface and a light output surface parallel to each other, and a thickness perpendicular to the light input surface and the light output surface; and the multi-layer light diffusing plate includes the main layer and the semi-transmissive and semi-reflective layer; the light output surface is located at A top surface of the main layer, a semi-transmissive semi-reflective layer is located below the main layer, and the light incident surface is located at a bottom surface of the semi-transmissive semi-reflective 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.

In one embodiment, in the rolling step, the roller module rolls and presses a plurality of microstructures on the light-emitting surface of the multi-layer light diffusing plate, and the microstructures 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 of each other and are not connected to each other. The method further comprises the following steps between the rolling step and the discharging step: coating a quantum dot layer on the plurality of concave portions of the light-emitting surface of the multi-layer light diffusing plate by a coating process; wherein the thickness of the quantum dot layer is t1, 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 pasting a water- and gas-blocking 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 by a pasting process; wherein the quantum dot layer comprises 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 (LEDs) arranged in an array.

10: Light diffusion plate

11: Main floor

111: Bright surface

112: Microstructure

113: Microbubbles

114: Diffuse particles

12: Semi-transmissive and semi-reflective layer

120: Light-entering surface

121: First substrate layer

122: Second substrate layer

13: Quantum dot layer

131: Quantum dots

14: Water and air barrier layer

21~26: Steps

91: Circuit board

92: LED

93: LCD panel

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

Figure 2 is an enlarged schematic diagram of a side view of a preferred embodiment of the multi-layer light diffusion plate of the present invention.

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

Figure 4 is an enlarged schematic diagram of a side view of another preferred embodiment of the multi-layer light diffusion plate of the present invention.

Figure 5 is a flow chart of a preferred embodiment of the method for manufacturing the multi-layer light diffusion plate of the present invention.

Figure 6 is a graph showing the brightness of light emitted by a light diffuser with different numbers of semi-transmissive and semi-reflective layers at different positions between LEDs.

Figure 7 is a graph showing the brightness of light at different positions between LEDs when the thickness ratio of the alternately stacked first substrate layer and the second substrate layer is different for a light diffusion plate with a semi-transmissive and semi-reflective layer.

Figure 8 shows the curves of the transmittance of the light diffuser samples A, B, C, and D with a semi-transmissive and semi-reflective layer at different light wavelengths.

Figure 9 is a comparison of the tastes of samples A, B, C, and D shown in Figure 8 during the test.

The present invention relates to a multi-layer light diffusing plate and a method for manufacturing the same. The multi-layer light diffusing plate includes a main layer and a semi-transmissive and semi-reflective layer. The light-emitting surface of the multi-layer light diffusing plate is the top surface of the main layer, and the light-incident surface of the multi-layer light diffusing plate is the bottom surface of the semi-transmissive and semi-reflective layer. The semi-transmissive and semi-reflective 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 constituting the first substrate layer and the second substrate layer have different refractive indices. The present invention sets a semi-transmissive and semi-reflective layer on the light-incident surface of the light diffusing plate to partially penetrate and partially reflect the linear light intensity of the LED light source module below, thereby reducing the bright and dark bands between the LEDs and achieving a uniform light effect. In addition, the present invention uses an extrusion manufacturing method to set a semi-transmissive and semi-reflective layer composed of a plurality of first substrate layers and second substrate layers with different refractive indices alternately stacked on the light incident surface of the light diffusion plate, which has the advantages of simpler manufacturing process and lower cost.

In order to more clearly describe the multi-layer light diffuser plate and its manufacturing method proposed by the present invention, the following will be described in detail with the help of diagrams.

Please refer to Figures 1 and 2, which are respectively a side view schematic diagram of a preferred embodiment of the invention in which a multi-layer light diffuser plate (Diffuser Plate) is combined with a light emitting diode (LED) light source module to form a white light backlight module (Backlight Module) and is disposed under a liquid crystal display panel (LCD Panel), and a side view partial enlarged schematic diagram of the multi-layer light diffuser plate.

As shown in Figures 1 and 2, the multi-layer light diffusion plate 10, the LED light source module located below the multi-layer light diffusion plate 10, and the liquid crystal display panel 93 located above the multi-layer light diffusion plate 10 constitute an LCD display module. The multi-layer light diffusion plate 10 and the LED light source module located below constitute a white light backlight module, which is used to provide white light to the liquid crystal display panel 93 located above, so it belongs to a direct light backlight module. The multi-layer light diffusion plate 10 mainly provides the function of converting the light emitted by the LED light source module into white light, making the light output uniform, or/and increasing the color gamut of the light output.

In the present invention, the LED light source module is a sub-millimeter light emitting diode (Mini LED) array module that can emit white light or blue light, which includes 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. In the present embodiment shown in Figures 1 and 2, the LED light source module includes a plurality of white light sub-millimeter light emitting diodes 92. However, in another embodiment of the present invention to be introduced later, the LED light source module includes a plurality of blue light sub-millimeter light emitting diodes 92, and the wavelength of the blue light emitted by each of the sub-millimeter light emitting diodes 92 is between 430-500nm, and the grain size is approximately between 100-200μm.

The multi-layer light diffusion plate 10 has a light incident surface 120 and a light emitting surface 111 with relatively large length and width areas and parallel to each other, and a relatively small thickness which is perpendicular to the light incident surface 120 and the light emitting surface 111. The light incident surface 120 is adjacent to or close to the light source module, so that the light emitted upward by the light source module can enter the multi-layer light diffusion plate 10 through the light incident surface 120 and travel roughly along the direction of the thickness, and then be emitted upward from the light emitting surface 111.

The multi-layer light diffusion plate 10 includes a main layer 11 and a semi-transmissive semi-reflective layer 12. The light emitting surface 111 is located on a top surface of the main layer 11. The semi-transmissive semi-reflective layer 12 is located below the main layer 11, and the light incident surface 120 is located on a bottom surface of the semi-transmissive semi-reflective layer 12. As shown in FIG. 2, the semi-transmissive 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 and lower sides of each of the first substrate layers 121 is adjacent to one of the second substrate layers 122, and at least one of the upper and lower sides of each of the second substrate layers 122 is adjacent to one of the first substrate layers 121. The materials constituting the first substrate layer 121 and the second substrate layer 122 have different refractive indices.

The substrates of the main layer 11 and the semi-transmissive and semi-reflective layer 12 of the multi-layer light diffusing plate 10 of the present invention can be non-crystalline or semi-crystalline plastic 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 multi-layer light diffusing plate 10 can be implemented in the range of 1.0mm~3.0mm, and the preferred thickness range is 1.2mm~2.0mm. The thickness ratio of the main layer 11 and the semi-transmissive and semi-reflective layer 12 is between 9:1 and 7:3. The number of stacked layers of the semi-transmissive and semi-reflective layer 12, that is, the number of layers of the first substrate layer 121 and the second substrate layer 122 added together, can be between 50 and 400 layers in an embodiment, and between 100 and 400 layers in a preferred embodiment. The thickness ratio of the first substrate layer 121 and the second substrate layer 122 ranges from 3:1 to 1:3. In this embodiment, the material of the main layer 11 is polycarbonate (PC); the material of the first substrate layer 121 is polycarbonate (PC); and the material of the second substrate layer 122 is polymethyl methacrylate (PMMA). The first substrate layer 121 and the second substrate layer 122 have the same thickness, which is the best embodiment. That is, the thickness ratio of the first substrate layer 121 and the second substrate layer 122 is approximately 1:1. Since the refractive index of the first substrate layer 121 and the second substrate layer 122 is different, the alternating stacking of one hundred or more layers of the first substrate layer 121 and the second substrate layer 122 can provide partial penetration and partial reflection of the light from the lower light source module. In combination with the light reflection layer disposed on the upper surface of the circuit board 91, the light reflected downward by the semi-transmissive semi-reflective layer 12 can be reflected again and directed toward the light incident surface of the semi-transmissive semi-reflective layer 12, thereby achieving a uniform light effect that reduces the light-dark block (MURA) phenomenon.

In the other embodiments of the present invention described below, since the structures, materials and functions of most components are the same or similar to those of the aforementioned embodiments, the same or similar components will be given the same component names and their structures, materials and functions will not be described in detail.

Please refer to Figure 3A and Figure 3B, which are respectively a side view of another preferred embodiment of the multi-layer light diffusion plate of the present invention, and a three-dimensional exploded schematic diagram of an embodiment in which the multi-layer light diffusion plate is arranged on an LED light source module.

As shown in FIG. 3A and FIG. 3B, another preferred embodiment of the multi-layer light diffusing 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-transmissive semi-reflective layer 12, and a light incident surface 120 located on the bottom surface of the semi-transmissive semi-reflective layer 12. The light incident surface 120 of the multi-layer light diffusing plate 10 is also adjacent to or adjacent to the light emitting diode 92 of the LED light source module. The semi-transmissive semi-reflective layer 12 also includes at least 50 layers (preferably at least 100 layers) of alternately stacked first substrate layers 121 and second substrate layers 122. The difference between this preferred embodiment and the embodiments shown in the aforementioned Figures 1 and 2 is that the multi-layer light diffusion plate 10 of this preferred embodiment shown in Figures 3A and 3B further includes the following technical contents.

In this embodiment, the multi-layer light diffusion plate 10 is made by foam extrusion molding, and contains a plurality of micro bubbles 113 and a plurality of diffusion particles 114 in the main layer 11. The material of the plurality of diffusion particles 114 is one of the following: calcium carbonate, silicon dioxide, titanium dioxide, organic silicone resin particles, polymethyl methacrylate particles. Due to the different refractive indexes of the diffusion particles 114 and the main layer 11, the light traveling in the main layer 11 can be refracted, reflected or scattered to improve the effect of uniform light emission. The weight percentage of the plurality of diffusion particles 114 in the main layer is 0.1%-10%. The plurality of microbubbles 113 are dispersed in the main layer 11. Due to the different refractive indices between the air in the microbubbles 113 and the material of the main layer 11, the light in the main layer 11 can be subjected to at least one of the following functions: reflection, refraction or scattering, so as to improve the effect of uniform light emission.

In the preferred embodiment, the weight loss rate of the plurality of microbubbles 113 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 weight loss rate is calculated as follows: weight loss rate (%) = (W1-W2)/W2*100%; W1 = H*(L1*L2*D); wherein: H is the average thickness of the main layer length (mm); L1 is the length of the main layer (mm); L2 is the width of the main layer (mm); D is the specific gravity of the raw material of the main layer (g/mm3); W1 is the theoretical weight of the main layer (g), that is, the weight without the multiple microbubbles; W2 is the actual weight of the main layer (g), that is, the actual weight of the main layer containing the multiple microbubbles measured by a scale.

The plurality of microbubbles 113 are generated by adding a foaming agent and a nucleating agent in appropriate amounts during the foaming extrusion molding process of the main layer 11. In the present invention, the foaming agent used is selected from the known high-temperature foaming agent available on the market, such as (but not limited to): 5-phenyltetrazolyl (5-PT), or azodicarbonamide (Azodicarbonamide; also known as azodicarbonamide)... etc. The nucleating agent includes at least one of the following: calcium carbonate, silicon dioxide, calcium oxide. The weight percentage of the added nucleating agent can be implemented in the range of 0.01%-5%, but the preferred range is 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 diameter of the microbubbles 113 can be controlled by adding a nucleating agent and adjusting the process temperature. According to the content of the microbubbles 113 in the main layer 11 described in this embodiment (weight loss rate between 15~25%) and size (between 60~800μm), the best uniform light emission effect can be achieved.

In this embodiment, the light source module is a blue LED light source module composed of a plurality of blue light emitting diodes (LEDs) 92 arranged in an array and disposed on a circuit board 91; and the multi-layer light diffusion plate 10 further includes a quantum dot layer 13, a water- and gas-blocking layer 14, and a plurality of micro-structures 112 (Micro-Structures).

As shown in FIG. 3A and FIG. 3B , the light-emitting surface 111 of the multi-layer light diffusing plate 10 includes a plurality of microstructures 112, which are arranged in an array on the light-emitting surface 111 of the multi-layer light diffusing 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 diffusing plate 10. The plurality of concave portions are separated by the plurality of convex portions, so the plurality of concave portions are independent and not interconnected. The quantum dot layer 13 is arranged at the plurality of concave portions of the plurality of microstructures 112 of the multi-layer light diffusing plate 10; the quantum dot layer 13 is not arranged at the top of the plurality of convex portions. The thickness of the quantum dot layer 13 is t1, the distance from a top of the plurality of protrusions to a bottom of the plurality of concave portions is t2, and t1<t2. In other words, the height t2 of the protrusions 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 not connected or in contact with each other due to the obstruction of the protrusions. The water- and gas-blocking layer 14 is disposed on the entire light-emitting surface 111 of the multi-layer light diffusion plate 10 and is closely covered on the tops of the plurality of protrusions and the quantum dot layer 13. The water- and gas-blocking layer 14 can 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-blocking layer 14 is t3, and it can be selected from existing commercially available water- and gas-blocking films and directly bonded to the convex parts of the plurality of microstructures 112 on the top surface of the multi-layer light diffusion plate 10 and the quantum dot layer 13.

In the 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 pyramids of two or more different shapes. The pyramids are called differently depending on the shape of the bottom surface, depending on the polygon of the bottom surface; for example, a pyramid with a triangular bottom surface is called a triple pyramid, a pyramid with a square bottom surface is called a square pyramid, and so on. As shown in FIG. 3B , the plurality of microstructures 112 include a plurality of pyramids with a square bottom surface, that is, N=4. In the present invention, the thickness t1 of the quantum dot layer 13 can be implemented in a range of 5 to 150 μm, but t1 is preferably implemented in a range of 10 to 40 μm; the distance t2 from the top of the convex portion to the bottom of the concave portion of the microstructure 112 can be implemented in a range of 6 to 200 μm, but t2 is preferably implemented in a range of 25 to 50 μm; and t1<t2. The thickness t3 of the water- and gas-blocking layer 14 can be implemented in a range of 5 to 100 μm, but t3 is preferably implemented in a range of 10 to 30 μm. The maximum width d1 of the convex portion is between 50 and 500 μm. The practical range of the distance d2 between two adjacent protrusions is between 50 and 1000 μm, but the preferred practical range is d2 between 250 and 500 μm. The blue LED light source module is a sub-millimeter light-emitting diode (Mini LED) array module that can emit blue light; the wavelength of the blue light is between 430 and 500 nm.

The quantum dot layer 13 includes a plurality of quantum dots 131 (Quantum Dot, referred to as QD). The plurality of quantum dots 131 are a 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. The luminescence wavelength of the plurality of quantum dots 131 in the quantum dot layer 13 may be between 490 and 650 nm; in the preferred embodiment, the plurality of quantum dots 131 include a plurality of green quantum dots with a luminescence wavelength of 520 to 530 nm and a plurality of red quantum dots with a luminescence wavelength of 620 to 630 nm. The blue light emitted upward by the blue sub-millimeter 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 consistent blue light intensity to convert red/green light and mix them into uniform white light; because the peripheral light intensity of the display is lower than the central intensity, it is easy to have insufficient red/green light conversion, 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 contains a plurality of micro bubbles 113 and diffusion particles 114 in the main layer 11, a plurality of micro structures 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, improve the light intensity of the surrounding area of the display, and thus improve the problems of blue light and bright dark area (MURA).

Please refer to FIG. 4, which is a partially enlarged schematic diagram of a side view of another preferred embodiment of the multi-layer light diffusing plate of the present invention. As shown in FIG. 4, another preferred embodiment of the multi-layer light diffusing 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-transmissive semi-reflective layer 12, and a light incident surface 120 located on the bottom surface of the semi-transmissive semi-reflective layer 12. The semi-transmissive semi-reflective layer 12 also includes at least 50 layers (preferably at least 100 layers) of alternately stacked first substrate layers 121 and second substrate layers 122. The difference between the preferred embodiment and the embodiment shown in FIG. 1 and FIG. 2 is that the preferred embodiment shown in FIG. 4 has a plurality of microstructures 112 disposed on the light incident surface 120 and the light emitting surface 111 of the multi-layer light diffusing plate 10, respectively; the plurality of microstructures are also disposed in an array on the light incident surface 120 and the light emitting surface 111 of the multi-layer light diffusing plate 10; the plurality of microstructures 112 form a plurality of convex portions and a plurality of concave portions on the light incident surface 120 and the light emitting surface 111 of the multi-layer light diffusing plate, respectively. In addition, the main layer 11 includes a plurality of microbubbles 113 and a plurality of diffusion particles 114. The semi-transmissive and semi-reflective layer 12 located on the light incident surface 120, in combination with the plurality of microbubbles 113 and diffusion particles 114 contained in the main layer 11, and the plurality of microstructures 112 disposed on the light incident surface 120 and the light emitting surface 111, can provide a relatively optimal light diffusion effect. When the multi-layer light diffusion plate 10 of the present invention is used in combination with a white light LED light source module, or, although it is used in combination with a blue light LED light source module but an additional quantum dot film is provided or a light color conversion material or fluorescent powder is added to the main layer, the multi-layer light diffusion plate 10 itself does not need to be provided with a quantum dot layer.

Please refer to Figure 5, which is a flow chart of a preferred embodiment of the method for manufacturing the multi-layer light diffusing plate of the present invention. In this embodiment, the manufacturing process of the multi-layer light diffusing plate includes the following steps: Feeding step 21: feeding at least a first substrate, a second substrate, a foaming agent, and a diffusion particle constituting the multi-layer light diffusing plate into a foaming extrusion process equipment through a feed inlet; the first substrate and the second substrate have different refractive indices; heating and mixing step 22: uniformly mixing at a general processing temperature suitable for polycarbonate in the foaming extrusion process equipment The first substrate and the second substrate are heated and mixed separately, and the two are not mixed; the splitter step 23: the first substrate and the second substrate after heating and mixing enter a splitter, and 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, and the plurality of first substrate layers and the plurality of second substrate layers are alternately stacked to form a half-transmitting and half-reflecting layer. , and the semi-transmissive and semi-reflective layer is superimposed on the main layer; T-die step 24: the main layer and the semi-transmissive and semi-reflective layer which have been uniformly mixed, foamed and superimposed from the diverter are co-extruded into a multi-layer plate through a T-die (T-die) of the foam extrusion process equipment; rolling step 25: the plate is roll-formed by a roller module and cooled; in the rolling step 25, the roller module is on the multi-layer light diffusion plate The light-emitting surface is rolled to form a plurality of microstructures, so that the plurality of microstructures 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 of each other and not interconnected; discharging step 26: the multi-layer light diffusing plate after cooling is sent out from a discharging port of the foaming extrusion process equipment.

The multi-layer light diffusion plate sent out from the discharge port has a light incident surface and a light emitting surface parallel to each other, and a thickness perpendicular to the light incident surface and the light emitting surface; and the multi-layer light diffusion plate includes the main layer and the semi-transmissive and semi-reflective layer; the light emitting surface is located on a top surface of the main layer, the semi-transmissive and semi-reflective layer is located below the main layer, and the light incident surface is located on a bottom surface of the semi-transmissive and semi-reflective layer. The semi-transmissive 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 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.

In a preferred embodiment, the following steps are further included between the rolling step 25 and the discharging step 26: a quantum dot layer is coated on the plurality of concave portions of the light-emitting surface of the multi-layer light diffusing plate by a coating process; wherein the thickness of the quantum dot layer is t1, the distance from a top of the plurality of protrusions to a bottom of the plurality of concave portions is t2, and t1<t2; thereafter, a water- and gas-blocking layer is pasted on the light-emitting surface of the multi-layer light diffusing plate and covers the plurality of protrusions and the quantum dot layer by a pasting process; wherein the quantum dot layer includes a plurality of quantum dots (Quantum Dot; referred to as QD); wherein the multi-layer light diffusion plate is used in conjunction with a blue light source module; the blue light source module is a blue sub-millimeter light emitting diode light source module composed of a plurality of blue sub-millimeter light emitting diodes (Mini LED) arranged in an array.

The applicant used different light diffusion technologies such as "diffusing particles", "surface microstructures", and "semi-transmissive and semi-reflective layers" in a plurality of different light diffusion plate samples (as shown in Table 1 below, namely, comparative examples 1 to 3 of the prior art and embodiment 1 of the present invention), and then observed the optical effects such as "light diffusion plate transmittance", "brightness", and "optical quality (5 is the best, 1 is the lowest)" of each light diffusion plate sample in combination with a light source module. The test results are shown in Table 1 below. Among them, only the light diffusion plate of Example 1 uses the technology of the present invention to set a semi-transmissive and semi-reflective layer on the light incident surface of the light diffusion plate, and the other comparative examples 1 to 3 do not set a semi-transmissive and semi-reflective layer; in contrast, the specific structure of the light diffusion plate of Example 1 can refer to the structure of the multi-layer light diffusion plate 10 shown in Figures 1 and 2, and the multi-layer light diffusion plate does not include "diffusing particles" and "surface microstructures". As can be seen from Table 1, Example 1 uses the technology and structure of "setting a semi-transmissive and semi-reflective layer on the light-incident surface of the light diffuser plate" of the present invention. Therefore, even though Example 1 does not include "diffusing particles" and "surface microstructures", compared with other light diffusers that only use "diffusing particles" or/and "surface microstructures" (Comparison Examples 1 to 3), Example 1 still has relatively optimal brightness and quality optical performance, as well as relatively good transmittance optical performance.

Please see the following Table 2, which is a comparison table similar to Table 1, except that in Example 1, a semi-transmissive and semi-reflective layer is set on the light-entering surface of the light diffusion plate, but no diffusion particles are added and no surface microstructure is set. In addition, in Table 2, the distance between the diffusion plate and the LED is reduced to 0mm. Among them, Example 2 also has a semi-transmissive and semi-reflective layer set on the light-entering surface of the light diffusion plate, and 2% diffusion particles are added, but no surface microstructure is set; while Example 3 also has a semi-transmissive and semi-reflective layer set on the light-entering surface of the light diffusion plate, and 2% diffusion particles are added, and surface microstructure is also set. As for Comparative Examples 1 to 3 in Table 2, their structures are the same as those shown in Table 1. As can be seen from Table 2, not only the optical performance (brightness and quality) of Examples 1 to 3 of the light diffusing plate using the technology of setting a semi-transmissive and semi-reflective layer on the light incident surface of the present invention is significantly better than that of Comparative Examples 1 to 3 which do not use the technology of the present invention, but also, because Example 3 not only has a semi-transmissive and semi-reflective layer on the light incident surface, but also uses the light diffusing technology of adding 2% diffusing particles and setting a surface microstructure, the optical performance (brightness and quality) of Example 3 is the best among all samples, and its transmittance optical performance is relatively good. In addition, it can be found from Table 2 that when the distance between the diffuser and the LED is reduced to 0mm, the quality of Comparative Examples 1 to 3 which do not use the technology of setting a semi-transmissive and semi-reflective layer on the light incident surface of the present invention will be greatly reduced, that is, the MURA problem becomes very serious. In contrast, the reduction in quality of Examples 1 to 3 is not so obvious, which shows that the technology of the present invention can provide a relatively optimal light diffusion effect. In particular, Example 3 of the present invention (in addition to setting a semi-transmissive and semi-reflective layer on the light-entering surface, it also adds 2% diffusion particles and sets a surface microstructure), even when the bottom surface of the diffusion plate is directly attached to the LED (that is, the distance between the diffusion plate and the LED is 0mm), it can still achieve good optical performance of brightness, quality, and transmittance: This structure can greatly reduce the overall thickness of the direct-type backlight module, making the product thinner and more convenient to carry.

Please see Table 3 below, which is a comparison table similar to Table 1 and Table 2, except that newly added Examples 7 and 8 are used to compare with the aforementioned Comparative Example 3. In Example 7, in addition to setting a semi-transmissive and semi-reflective layer on the light-entering surface of the light-diffusing plate, foaming is performed during the mixing process of the main layer of the light-diffusing plate to generate micro-bubbles. In Example 8, in addition to setting a semi-transmissive and semi-reflective layer on the light-entering surface of the light-diffusing plate, foaming is performed during the mixing process of the main layer of the light-diffusing plate to generate micro-bubbles, and a light color conversion material that can convert blue light into white light is added to the main layer. As shown in Table 3, the samples of Examples 7 and 8 generate microbubbles and add light color conversion materials in the main layer of the light diffusion plate, which only slightly reduces the light transmittance and brightness, but can further improve the taste. Even when the bottom surface of the diffusion plate is directly attached to the LED (that is, the distance between the diffusion plate and the LED is 0mm), good brightness and taste, as well as acceptable optical performance of transmittance can still be achieved; this structure can greatly reduce the overall thickness of the direct-type backlight module, making the product thinner and more convenient to carry.

Please refer to Figure 6, which is a curve diagram of the light output brightness at different positions between LEDs for a light diffuser with different numbers of semi-transmissive and semi-reflective layers. The horizontal axis of Figure 6 is the horizontal position of the light diffuser (distance unit is cm), and the vertical axis is the illuminance value (unit is lux). As can be seen from Figure 6, the phenomenon of bright and dark blocks is extremely serious because the general diffuser does not have a semi-transmissive and semi-reflective layer on the light incident surface. When the light incident surface of the diffuser is provided with a semi-transmissive and semi-reflective layer, the number of layers stacked with different refractive indices is only 25 layers, and the light and dark bands of the LED are still slightly obvious, but when the number of layers reaches 100 layers, the difference between light and dark can be equalized.

Please refer to Figure 7, which is a curve diagram of the light brightness at different positions between LEDs when the thickness ratio of the alternately stacked first substrate layer and the second substrate layer of the light diffuser with a semi-transmissive and semi-reflective layer is different. The horizontal axis of Figure 7 is the horizontal position of the light diffuser (the distance unit is cm), and the vertical axis is the illuminance value (the unit is lux). It can be seen from Figure 7 that when the thickness ratio of the first substrate layer to the second substrate layer is 1:1, the best uniform light effect can be obtained.

Please refer to Figure 8 and Figure 9. Figure 8 is a curve diagram of the transmittance of the light diffuser samples A, B, C, and D with a semi-transmissive and semi-reflective layer at different light wavelengths; Figure 9 is a comparison diagram of the quality of samples A, B, C, and D shown in Figure 8 during the test. The horizontal axis of Figure 8 is the wavelength of light (in nm), and the vertical axis is the transmittance (%). It can be seen from Figures 8 and 9 that when the light diffuser with a semi-transmissive and semi-reflective layer is set, its transmittance at 400nm is in the range of 30~60% and the reflectance is in the range of 60~30%, that is, samples B and C, its MURA problem is relatively the least obvious, so the relatively best quality can be obtained.

However, the above-mentioned embodiments should not be used to limit the scope of application of the present invention. The protection scope of the present invention should be based on the technical spirit defined by the scope of the patent application of the present invention and the scope of its equivalent changes. That is, all equivalent changes and modifications made according to the scope of the patent application of the present invention will not lose the essence of the present invention, nor will they deviate from the spirit and scope of the present invention, so they should be regarded as further implementation of the present invention.

10: Light diffusion plate

11: Main floor

111: Bright surface

112: Microstructure

113: Microbubbles

114: Diffuse particles

12: Semi-transmissive and semi-reflective layer

120: Light-entering surface

121: First substrate layer

122: Second substrate layer

13: Quantum dot layer

131: Quantum dots

14: Water and air barrier layer

Claims (6)

A multi-layer light diffusion plate can be assembled on the top of a light source module; the multi-layer light diffusion plate has a light incident surface and a light exit surface which are parallel to each other, and a thickness which is perpendicular to the light incident surface and the light exit surface; the light incident surface is adjacent to the light source module, so that the light emitted by the light source module can enter the multi-layer light diffusion plate through the light incident surface and travel roughly along the direction of the thickness; and the multi-layer light diffusion plate includes: a main layer, the light exit surface The light-emitting surface is provided with a plurality of microstructures, which are arranged in an array on the light-emitting surface of the multi-layer light diffusion 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 diffusion 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 are not connected to each other; the half-transmitting semi-reflecting layer is located below the main layer, and the light-incident surface is located on the half A bottom surface of the semi-transmissive semi-reflective layer; a quantum dot layer, arranged at the plurality of concave portions of the light-emitting surface of the multi-layer light diffusion plate; wherein the thickness of the quantum dot layer is t1, 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-blocking layer, arranged on the light-emitting surface of the multi-layer light diffusion plate and covering the plurality of convex portions and the quantum dot layer; wherein: the semi-transmissive semi-reflective layer The radiation 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 quantum dot layer includes a plurality of quantum dots (Quantum Dot; referred to as QD); the plurality of quantum dots are a 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 luminescent wavelength of 520 to 530 nm and a plurality of red quantum dots with a luminescent wavelength of 620 to 630 nm; the light source module is a blue light LED light source module composed of a plurality of blue light emitting diodes (LEDs) arranged in an array. A multi-layer light diffusion plate as claimed in claim 1, wherein: the materials of the main layer, the first substrate layer and the second substrate layer are plasticized materials; the thickness ratio of the main layer to the semi-transmissive and semi-reflective layer is between 9:1 and 7:3; the number of layers of the semi-transmissive and 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 and 400 layers; the thickness ratio of the first substrate layer to the second substrate layer is between 3:1 and 1:3. The multi-layer light diffuser plate of claim 1, wherein: the materials of the main layer, the first substrate layer and the second substrate layer are selected from one of the following: polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA, commonly known as acrylic), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET); and the materials of the first substrate layer and the second substrate layer are different; the number of layers of the semi-transmissive and semi-reflective layer, that is, the sum of the number of layers of the first substrate layer and the second substrate layer, is between 100 and 400 layers. The multi-layer light diffuser plate of claim 1, wherein: the material of the main layer is polycarbonate (PC); the material of the first substrate layer is polycarbonate (PC); the material of the second substrate layer is polymethyl methacrylate (PMMA); the thickness 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 thickness range of the multi-layer light diffuser plate is 1.0 mm to 3.0 mm. A multi-layer light diffusion plate as claimed in claim 1, wherein: the plurality of microstructures include a plurality of N-sided pyramids, wherein 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 sub-millimeter light-emitting diode (Mini LED) array module that can emit the blue light; the wavelength of the blue light is between 430 and 500 nm. As in claim 1, a multi-layer light diffuser plate is provided on the light incident surface, wherein a plurality of microstructures are arranged in an array on the light incident surface of the multi-layer light diffuser plate; the plurality of microstructures form a plurality of convex portions and a plurality of concave portions on the light incident surface of the multi-layer light diffuser plate.

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