Diffusion angle variable diffusion sheet based on refractive index regulation and control and preparation method thereof

Abstract

The invention belongs to the technical field of optical diffusion devices, provides a variable diffusion angle diffusion sheet based on refractive index regulation and control and a preparation method thereof, and is widely applied to an illumination system, a three-dimensional measurement system, light field regulation and control, a backlight module and a display and imaging system. A transparent optical adhesive layer with a controllable refractive index is tightly attached to a scattering surface of a traditional rough surface type diffusion sheet (such as ground glass, sand blasting glass and the like), and refraction paths of light rays between the scattering surface and the adhesive layer and between the adhesive layer and an air interface can be effectively changed by changing the refractive index of the adhesive layer, so that regulation and control of overall emergent angle distribution are realized; on one hand, the angle-variable diffusion sheet has the advantages of being simple in structure, low in cost, simple in process, high in stability and the like; on the other hand, compared with an existing adjustable diffusion technology depending on an electric control liquid crystal or a complex variable structure lens, the key problems of high cost, high manufacturing difficulty, limited optical power tolerance and the like are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical diffusion devices, and specifically provides a variable diffusion angle diffusion sheet based on refractive index regulation and a preparation method thereof, which is widely applicable in lighting systems, three-dimensional measurement systems, optical field regulation, backlight modules, display and imaging systems. BACKGROUND

[0002] Optical diffusion sheets have wide applications in fields such as illumination homogenization, light spot shaping, viewing angle adjustment, and three-dimensional imaging systems. The core mechanism is to diffuse incident light (usually parallel light or small-angle divergent light) into outgoing light with a large angular distribution through scattering or refraction effects, thereby improving spatial light uniformity or achieving precise angle regulation.

[0003] Currently, diffusion devices are mainly divided into the following four categories: 1) rough surface diffusion sheets, such as ground glass and sandblasted glass, which utilize irregular microscopic rough structures on the surface to achieve multi-angle scattering of light. The advantages of this type of device are low cost and simple manufacturing process, but the diffusion performance is limited by the stability of the surface topography and the discontinuity of the refractive index, resulting in limited angle regulation capability; 2) microstructure array diffusion films, such as microlens arrays, sawtooth structure arrays, and surface holographic structures, which achieve precise control of light scattering direction and distribution through regular microstructure design, with high engineering design flexibility. However, the angle distribution characteristics are fixed at the manufacturing stage and cannot be adjusted later; 3) bulk scattering diffusion sheets, such as PMMA, PC, or PET substrates doped with high refractive index particles such as TiO2, BaSO4, or the introduction of air bubbles. This type of device has strong scattering ability, but the diffusion angle mainly depends on the matching relationship between the density, size of the scattering particles (or air bubbles) and the refractive index of the substrate. Once prepared, its characteristics cannot be changed; 4) electrically controllable adjustable diffusion devices, such as devices based on liquid crystals (LC), polymer dispersed liquid crystals (PDLC), or deformable optical structures, which achieve dynamic regulation of diffusion angle or intensity by applying voltage, suitable for dynamic light field scenarios. However, such devices generally have significant drawbacks such as high cost, limited lifespan, complex manufacturing process, and sensitivity to environmental temperature.

[0004] The common bottleneck of current technology is the fixed nature of the diffusion angle. The diffusion intensity and angle distribution characteristics are pre-set at the manufacturing stage and cannot be dynamically adjusted in later use, which severely restricts their application in adaptive optical systems, variable viewing angle displays, intelligent lighting, and other application scenarios that require flexible regulation. Based on this, the present application proposes a variable diffusion angle diffusion sheet based on refractive index regulation and a preparation method thereof. SUMMARY

[0005] The application aims to provide a variable-angle diffuser based on refractive index regulation and a preparation method thereof, by closely adhering a transparent optical glue layer with controllable refractive index on the scattering surface of a traditional rough surface type diffuser (such as frosted glass, sandblasted glass, etc.), the refractive path of light at the scattering surface and the glue layer, the glue layer and the air interface can be effectively changed by changing the refractive index of the glue layer, so as to realize the regulation of the overall exit angle distribution; on the one hand, the variable-angle diffuser provided by the application has the advantages of simple structure, low cost, simple and stable process; on the other hand, compared with the existing adjustable diffusion technology relying on electrically controlled liquid crystal or complex variable structure lens, the application effectively overcomes the key problems of high cost, great manufacturing difficulty and limited light power tolerance.

[0006] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0007] A variable-angle diffuser based on refractive index regulation, characterized in that it comprises a base diffuser 1 and a transparent optical glue layer 2; wherein the transparent optical glue layer is adhered to the scattering surface (exit surface) of the base diffuser, the refractive index of the base diffuser is , the refractive index of the transparent optical glue layer is , and .

[0008] Further, the scattering surface of the base diffuser has a random micro-rough structure, which scatters incident light to form exit light with Gaussian angle distribution, and the transparent optical glue layer fills the random micro-rough structure and forms an optically uniform interface.

[0009] Further, the thickness of the transparent optical glue layer is 10-100 μm, which is used to completely fill the micro-rough structure of the scattering surface and form an optically uniform interface.

[0010] Further, the base diffuser adopts frosted glass, frosted PMMA plate or optical-grade PET micro-structure film.

[0011] Further, the transparent optical glue layer adopts ultraviolet curing glue, hydrogel or silicone glue.

[0012] Further, the refractive indices of the base diffuser and the transparent optical glue layer satisfy:

[0013] ,

[0014] ,

[0015] wherein, is the target diffusion angle of the variable-angle diffuser, is the refractive index of air.

[0016] Further, the preparation method of the variable diffusion angle diffusion sheet based on refractive index regulation comprises the following steps.

[0017] Firstly, the scattering surface of the base diffusion sheet is cleaned to remove dust, oil stains and impurities;

[0018] Then, the transparent optical glue with the target refractive index is uniformly coated on the scattering surface of the base diffusion sheet by spin coating, drop coating or roll coating process, and uniform spreading and bubble removal are realized by pressing or vacuum bonding process;

[0019] Finally, the transparent optical glue layer after coating is cured to tightly adhere to the base diffusion sheet.

[0020] Further, the curing process adopts ultraviolet curing, thermal curing or natural curing, and the curing method is matched with the transparent optical glue.

[0021] From the working principle:

[0022] The variable diffusion angle regulation effect of the present application is derived from the interface refraction regulation mechanism caused by the refractive index difference between the refractive index n1 of the base diffusion sheet and the refractive index n2 of the optical glue layer; the scattering surface of the base diffusion sheet (such as ground glass, frosted polymer sheet, etc.) has a random micro-rough structure, when parallel light is incident, the normal direction of each micro-surface has a statistical distribution, according to Snell's law of refraction, the light can produce different refraction directions, thereby forming a scattered light field with a specific angle distribution (which can be approximately approximated as a Gaussian angle distribution);

[0023] When the transparent optical glue layer is uniformly and closely adhered to the scattering surface of the base diffusion sheet, a composite structure of "diffusion sheet-glue layer" is formed, and the light will be refracted twice at the "scattering surface-glue layer" interface and the "glue layer-air" interface. This structure is different from the traditional diffusion sheet which only refracts at the scattering surface-air interface, so that the overall exit angle distribution can be systematically adjusted by changing the refractive index n2 of the optical glue layer;

[0024] Theoretically, the diffusion angle of the scattered light after the first refraction ("scattering surface-glue layer" interface) is linearly related to the refractive index difference , which can be expressed as:

[0025] ,

[0026] wherein, is the intrinsic diffusion angle of the base diffusion sheet when used in air; is the refractive index of the base diffusion sheet material, which is a priori known constant value when the base diffusion sheet is selected; is the refractive index of the transparent optical glue layer. nair = 1; is the diffusion angle distribution of the scattered light after the first refraction;

[0027] On this basis, the final overall diffusion angle distribution can be obtained in combination with the second refraction of the light at the "adhesive layer-air" interface; in particular, the above expression must pass through the following two points:

[0028] (1) When , at this time, the scattering surface and the adhesive layer interface refractive index are completely matched, and the refraction does not change the direction of the light, the composite structure is equivalent to an optical flat, and does not have a diffusion function, and the overall exit light is approximately collimated;

[0029] (2) When , at this time, the angle modulation of the light by the adhesive layer is equivalent to the refraction of the air layer, and the intrinsic diffusion angle of the scattering surface is completely preserved, and the overall diffusion angle is consistent with the original diffusion angle of the base layer diffusion sheet.

[0030] In addition, after the scattered light passes through the first refraction at the "scattering surface-adhesive layer" interface, it will propagate in the adhesive layer in a new direction; when the light reaches the "adhesive layer-air" interface, the refractive index difference between the optical adhesive layer and the air refractive index will cause refraction again according to Snell's law of refraction, and the relationship is:

[0031] ,

[0032] wherein, is the diffusion angle distribution of the light after the first refraction, is the final exit angle distribution;

[0033] The second refraction has a further modulation effect on the overall diffusion angle, and generally, when , the light enters a low refractive index medium from a high refractive index medium, and the exit angle is greater than the incident angle, so that the angle distribution formed after the first refraction is amplified, thereby increasing the overall diffusion angle;

[0034] In summary, under the small-angle approximation, the superposition of the two refractions makes the final diffusion angle and maintain an approximately linear relationship, thereby realizing the adjustable diffusion angle function of the present application; the present application discards the traditional fixed diffusion angle design idea and no longer relies on complex electrical control components, and creatively proposes a composite structure of a base layer diffusion sheet and a controllable refractive index adhesive layer, which utilizes the interface refraction principle to achieve discrete multi-level angle control when the refractive index of the adhesive layer is switched between different values; when the refractive index is continuously variable, the continuous variable control of the diffusion angle is realized.

[0035] Based on the above technical solution and working principle, the beneficial effects of the present invention are as follows:

[0036] This invention provides a variable diffusion angle diffuser based on refractive index control. It employs a composite structure of a base diffuser and a controllable refractive index adhesive layer. Utilizing the principle of interfacial refraction, the diffusion angle is continuously controlled by adjusting (or replacing) the refractive index of the optical adhesive layer. It features a simple structure, low cost, and suitability for industrial production, showing broad application prospects in 3D measurement systems, backlights, imaging systems, and AR displays. Furthermore, this invention provides a method for preparing this variable diffusion angle diffuser, which is simple, low-cost, and conducive to industrial production. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the variable diffusion angle diffuser based on refractive index control in this invention, wherein 1 is the base diffuser and 2 is the transparent optical adhesive layer.

[0038] Figure 2 This is a process flow diagram of the fabrication process of the variable diffusion angle diffuser based on refractive index control in this invention.

[0039] Figure 3 This is a comparison diagram of the emission angle distribution of the variable diffusion angle diffuser and the base layer diffuser in Embodiment 1 of the present invention.

[0040] Figure 4 This is a comparison diagram of the emission angle distribution of variable diffusion angle diffusers using transparent optical adhesive layers with different refractive indices in Embodiment 2 of the present invention.

[0041] Figure 5 The refractive index of the variable diffusion angle diffuser and the transparent optical adhesive layer in Embodiment 2 of the present invention is ( The fitted curve of ). Detailed Implementation

[0042] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0043] Example 1

[0044] This embodiment provides a variable diffusion angle diffuser based on refractive index control, the structure of which is as follows: Figure 1 As shown, it specifically includes: a base diffuser sheet 1 and a transparent optical adhesive layer 2, wherein the base diffuser sheet 1 is frosted PMMA with a refractive index of [missing information]. , thickness of 2.0 mm, the bottom surface is an optical smooth surface, the top surface is a random micro-rough structure (scattering surface) formed by a sandblasting process, and the surface has a random distribution of micro-rough structures, and because the surface normal directions are different, the scattered light forms a specific angular distribution, which is approximately a Gaussian angular distribution with a half-width angle of 23.55°; the transparent optical adhesive layer 2 is an ultraviolet-cured optical adhesive, and the cured refractive index The transparent optical adhesive layer 2 forms a bubble-free, optically uniform permanent bond on the scattering surface of the base diffuser sheet 1, wherein the bonding thickness of the optical adhesive layer is about 50 um, which can ensure that the adhesive layer can completely fill the microstructure on the scattering surface, and can also avoid excessive thickness of the adhesive layer, which leads to a decrease in overall light transmittance.

[0045] Further, as shown in Figure 2 , the variable diffusion angle diffuser based on refractive index regulation is prepared by the following steps:

[0046] Step 1. Select a diffuser substrate with a random micro-rough structure, specifically a frosted PMMA plate, whose surface rough structure is used to achieve light scattering;

[0047] Step 2. Clean the scattering surface of the diffuser substrate to remove surface dust, oil stains and impurities to ensure the optical contact quality of the subsequent transparent optical adhesive layer and the substrate interface;

[0048] Step 3. Select a transparent optical adhesive with a target refractive index, specifically an ultraviolet-cured adhesive;

[0049] Step 4. Use spin coating, drop coating or roll coating to uniformly coat the optical adhesive on the scattering surface of the diffuser, and use pressing or vacuum bonding process to achieve uniform spreading and bubble removal, thereby forming an optically uniform interface;

[0050] Step 5. Perform ultraviolet curing treatment on the coated optical adhesive layer to firmly bond it with the diffuser substrate, forming a variable diffusion angle diffuser with complete structure and bubble-free interface.

[0051] As shown in Figure 3 , the comparison chart of the exit angle distribution of the variable diffusion angle diffuser and its base diffuser in this embodiment shows that the half-width of the exit light angle distribution of the variable diffusion angle diffuser (the composite structure of the base diffuser and the transparent optical adhesive layer) is reduced from 23.55° to 4°, indicating that this embodiment can achieve nearly 6 times angle compression capability without changing the scattering layer structure.

[0052] Example 2

[0053] The embodiment provides a variable diffusion angle diffusion sheet based on refractive index regulation, the base layer diffusion sheet is the same as that in the embodiment 1, and the difference is that the transparent optical glue layer 2 is composed of two kinds of optical UV glues in proportion, the refractive index of the first kind of optical UV glue is 1.5, the refractive index of the second kind of optical UV glue is 1.64, and the optical glue with the refractive index distributed between 1.5 and 1.64 can be obtained by mixing the two kinds of optical UV glues in different proportions.

[0054] In the embodiment, a series of adjustable refractive index liquid glue type diffusion sheets with different diffusion angles are obtained by mixing a plurality of proportions, the mixing proportions of the two kinds of optical UV glues are 1:1, 1:2, 2:1, 1:5, 5:1, 1:10 and 10:1, respectively, the refractive index of the mixed optical glue and the half width of the exit angle distribution of the corresponding diffusion sheet are shown in Table 1, the exit angle distribution of the variable diffusion angle diffusion sheet with the transparent optical glue layer with different refractive indexes is shown in Figure 4 , further, the data are fitted, the fitting curve of the variable diffusion angle diffusion sheet and the refractive index of the transparent optical glue layer is shown in , and the fitting curve of the variable diffusion angle diffusion sheet and the refractive index of the transparent optical glue layer is shown in Figure 5 It can be seen that the exit angle distribution of the variable diffusion angle diffusion sheet is proportional to , the refractive index of the base layer diffusion sheet material is , the refractive index of the transparent optical glue layer is , the refractive index of the transparent optical glue layer can be adjusted by changing the mixing proportion of the two kinds of optical glues, and different exit angle distributions are realized.

[0055] Table 1

[0056]

[0057] The above describes only a specific embodiment of the present application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose alternative features unless specifically described, and all features disclosed or all steps in the method or process can be combined in any way except that the features and / or steps are mutually exclusive.

Claims

1. A variable diffusion angle diffuser based on refractive index modulation, characterized by, The scattering surface of the base diffusion sheet has a random micro-rough structure, which scatters incident light to form outgoing light with a Gaussian angular distribution, and the transparent optical adhesive layer fills the random micro-rough structure and forms an optically uniform interface. The base diffusion sheet (1) and the transparent optical adhesive layer (2); wherein the transparent optical adhesive layer is attached to the scattering surface of the base diffusion sheet, the refractive index of the base diffusion sheet is , the refractive index of the transparent optical adhesive layer is , and .

2. The variable diffusion angle diffuser based on refractive index modulation according to claim 1, wherein, The thickness of the transparent optical adhesive layer is 10-100 μm.

3. The variable diffusion angle diffuser based on refractive index modulation according to claim 1, wherein, The base diffusion sheet is made of ground glass, frosted PMMA plate or optical-grade PET microstructure film.

4. The variable diffusion angle diffuser based on refractive index modulation according to claim 1, wherein, The transparent optical adhesive layer is made of ultraviolet-cured adhesive, hydrogel or silicone.

5. The variable diffusion angle diffuser based on refractive index modulation according to claim 1, wherein, The refractive indices of the base diffusion sheet and the transparent optical adhesive layer satisfy:

6. The variable diffusion angle diffuser based on refractive index modulation according to claim 1, wherein, The method comprises the following steps: ， ， wherein, is the target diffusion angle of the variable diffusion angle diffuser, is the air refractive index.

7. The method of claim 1, wherein the method further comprises the step of: First, clean the scattering surface of the base diffusion sheet to remove dust, oil stains and impurities; ​ Then, use spin coating, drop coating or roll coating process to uniformly coat the transparent optical adhesive with the target refractive index on the scattering surface of the base diffusion sheet, and realize uniform spreading and bubble removal through pressing or vacuum lamination process; Finally, cure the transparent optical adhesive layer after coating to make it tightly adhere to the base diffusion sheet. The curing process is ultraviolet curing, thermal curing or natural curing.

8. The method of claim 7, wherein the method further comprises the step of: ​ ​

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