LED light therapy device adaptive light output film structure and preparation method

Abstract

The application discloses an LED phototherapy instrument self-adaptive light-emitting film structure and a preparation method thereof. The self-adaptive light-emitting film structure comprises a substrate layer, a microlens array layer and a thermochromic layer. The microlens array layer is arranged on the light-emitting side surface of the substrate layer and comprises a plurality of array-arranged microlens units. The thermochromic layer covers the light-emitting surface of the microlens array layer and comprises a plurality of thermoresponsive microcapsules dispersed in a transparent matrix. The thermoresponsive microcapsules are in a transparent state to allow the transmission of therapeutic light when the temperature is lower than a threshold temperature, and are converted into an opaque state to block the therapeutic light when the temperature reaches or exceeds the threshold temperature. The LED divergent light is converged into a directional light beam through the microlens array layer, thereby improving the light energy utilization rate. Meanwhile, the temperature response characteristics of the thermoresponsive microcapsules in the thermochromic layer realize point-by-point sensing of the local skin temperature and automatic adjustment of the therapeutic light output, so that passive automatic protection against local overheating can be realized without electronic sensors and control circuits.

Description

Technical Field

[0001] This application relates to the field of LED phototherapy equipment technology, specifically to an adaptive light-emitting film structure and preparation method for an LED phototherapy device. Background Technology

[0002] LEDs possess advantages such as high electro-optical conversion efficiency, small size, long lifespan, low power consumption, good monochromaticity, and easy array integration, leading to their widespread application in phototherapy fields such as medical aesthetics, dermatological treatment, and rehabilitation therapy. With the continuous development of phototherapy technology, people have higher expectations for the performance and effects of LED phototherapy equipment, and the application scope of LED phototherapy devices continues to expand, playing an important role in improving skin condition and promoting wound healing.

[0003] In existing technologies, LED phototherapy devices commonly use planar light-transmitting plates or diffusion films as light-emitting components. Planar light-transmitting plates are simple in structure and low in cost, making them a common choice. They allow light to pass through, achieving basic illumination. Diffuse films, on the other hand, can distribute light more evenly, avoiding the problem of excessive light concentration to some extent. However, these conventional methods have some limitations in practical applications.

[0004] Existing light-emitting components have several shortcomings. LED light sources are typically Lambertian-type emitters, lacking directional constraint, resulting in significant light scattering towards non-treatment areas and substantial energy loss. Furthermore, the light-emitting membrane cannot sense the real-time temperature of the irradiated skin, failing to autonomously respond to and protect against localized overheating. In clinical phototherapy, differences in pigmentation, blood perfusion, and tissue water content across different skin areas lead to significant temperature variations under the same light intensity, potentially causing burns. Moreover, existing temperature protection solutions rely on electronic temperature sensors and control circuits, resulting in complex and costly systems. The spatial distance between the sensors and the skin prevents accurate real-time reflection of the true temperature distribution within the irradiated area. Additionally, existing light-emitting membranes suffer from light leakage at edges and in non-target areas, potentially irradiating normal tissue and reducing treatment safety. Uneven light intensity distribution on the emitting surface and inconsistent light power density across the treatment area also negatively impact clinical efficacy. Summary of the Invention

[0005] The purpose of this application is to provide an adaptive light-emitting film structure and preparation method for an LED phototherapy device, so as to solve the technical problems of existing LED phototherapy devices that the light-emitting components cannot autonomously sense skin temperature, cannot automatically protect against local overheating, have severe light diffusion, and have low light energy utilization.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] An adaptive light-emitting membrane structure for an LED phototherapy device includes the following components arranged sequentially from the light source side to the light-emitting side:

[0008] A base layer, the base layer being made of a light-transmitting material;

[0009] A microlens array layer is disposed on the light-emitting side surface of the substrate layer, comprising multiple arrayed microlens units for converging incident light into a directional beam;

[0010] A thermochromic layer is applied to the light-emitting surface of the microlens array layer. The thermochromic layer contains multiple thermoresponsive microcapsules dispersed in a transparent matrix. The thermoresponsive microcapsules have the characteristic of reversibly switching between a transparent state and an opaque state with temperature changes. The thermoresponsive microcapsules are transparent when the temperature is below a threshold temperature to allow the therapeutic light to pass through, and become opaque when the temperature reaches or exceeds the threshold temperature to block the therapeutic light. The thickness of the thermochromic layer is 3-10 μm, such that the self-absorption heat effect of the LED therapeutic light passing through the thermochromic layer is insufficient to raise the temperature of the thermochromic layer itself to the threshold temperature.

[0011] A method for preparing an adaptive light-emitting film structure for an LED phototherapy device, comprising the following steps:

[0012] Step 1, fabricating a microlens array mold: multiple micro-dimples are formed on the surface of the mold substrate. The shape of the micro-dimples is complementary to the convex surface of the microlens unit, serving as the negative structure of the microlens unit.

[0013] Step 2, prepare the light-shielding partition: fill the recessed partition area of ​​the mold with opaque composite material and pre-cur it to form a light-shielding partition;

[0014] Step 3, forming the base layer and microlens array layer: pour a light-transmitting base material into the mold, and demold it after curing to obtain a base layer with a microlens array layer and a light-shielding partition on one side surface;

[0015] Step 4, forming a thermochromic layer: The thermo-responsive microcapsules are dispersed in a solution of a transparent matrix material to prepare a coating solution. The coating solution is then applied to the light-emitting surface of the microlens array layer and cured into a film at a temperature lower than the threshold temperature of the thermo-responsive microcapsules to form a thermochromic layer.

[0016] In summary, this application includes at least one of the following beneficial technical effects:

[0017] 1. By setting a thermochromic layer containing thermally responsive microcapsules on the light-emitting surface of the microlens array layer, and utilizing the reversible switching between transparent and opaque states of the thermally responsive microcapsules with temperature changes, the light-emitting film can sense skin temperature point by point based on the material's own thermal response characteristics without the need for electronic sensors and control circuits. When the local temperature reaches or exceeds the threshold temperature, it automatically blocks the therapeutic light output in that area, achieving passive local overheat protection. Since the thickness of the thermochromic layer is only 3-10μm, its heat capacity is extremely small. The self-absorption heat generated when the LED therapeutic light passes through this thin layer is far from enough to raise the temperature of the thermochromic layer itself to the threshold temperature. Therefore, there is no problem of LED self-heating and false triggering of light blocking. The temperature change of the thermochromic layer is entirely driven by heat conduction and / or heat radiation from the skin surface.

[0018] 2. By setting a selectively reflective layer with an angle-selective reflective structure on the light-emitting side of the thermochromic layer, the therapeutic light that is scattered by the opaque thermal response microcapsules in the overheated area and propagates at a large angle is reflected back to the direction of the thermochromic layer. The reflected light propagates along the film surface direction (i.e., parallel to the film plane) in the thermochromic layer to the adjacent room temperature area and then exits in a direction close to the normal. This redistributes the light energy blocked in the overheated area to the room temperature area for treatment, reducing light energy waste.

[0019] 3. By arranging multiple microlens units in the microlens array layer, the Lambertian divergent light emitted by the LED light source is focused into a directional beam. In conjunction with the light-shielding partitions set between adjacent microlens units to prevent light crosstalk, the therapeutic light is concentrated and projected onto the treatment area, reducing scattering loss to non-treatment areas. This allows the emitted beams from each microlens unit to form a uniformly distributed light spot array on the treatment surface, improving the light energy utilization rate and the consistency of the light power density distribution in the treatment area. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the LED phototherapy device of this application.

[0021] Figure 2 This is a schematic diagram of the adaptive light-emitting film of this application.

[0022] Figure 3 This is a top view of the microlens array layer in this application.

[0023] Figure 4 This is a schematic diagram illustrating the structure and working principle of the thermally responsive microcapsules of this application.

[0024] Figure 5 This is a schematic diagram of the adaptive working process of the light-emitting film in this application.

[0025] Figure 6 This is a schematic flowchart of the method for preparing the light-emitting film of this application.

[0026] Figure reference numerals: 100, light-emitting membrane; 101, base; 102, support rod; 103, transverse cantilever; 104, caster; 105, control panel; 106, display screen; 107, operation buttons; 108, irradiation head; 1, base layer; 2, microlens array layer; 21, microlens unit; 22, light-shielding partition; 3, thermochromic layer; 31, thermoresponsive microcapsule; 311, thermosensitive polymer shell; 312, high refractive index nanoparticles; 313, water molecules; 32, transparent matrix; 4, selective reflection layer; 41, high refractive index dielectric film; 42, low refractive index dielectric film; 5, LED light source; 6, skin surface; 61, normal temperature area; 62, overheated area; 7, treatment beam; 8, infrared thermal radiation; 9, reflected and recovered light. Detailed Implementation

[0027] The technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. The embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] Example 1

[0029] Please refer to Figure 1 The LED phototherapy device provided in this embodiment includes a base 101, a support rod 102, a transverse cantilever 103, and an irradiation head 108. Casters 104 are provided at the bottom of the base 101 for easy movement of the device. The support rod 102 is longitudinally mounted on the base 101, and the transverse cantilever 103 is hinged to the top of the support rod 102. The irradiation head 108 is connected to the front end of the transverse cantilever 103. The transverse distance between the irradiation head 108 and the irradiated skin surface 6 can be adjusted via the transverse cantilever 103, and the longitudinal height of the irradiation head 108 can be adjusted via the longitudinal extension and retraction of the support rod 102. A control panel 105 is also provided on the base 101, which includes a display screen 106 and operation buttons 107 for displaying and adjusting therapy parameters. An LED light source 5 is provided inside the irradiation head 108, and the light-emitting film 100 of this application is installed at the light outlet of the irradiation head 108. The light-emitting film 100 is detachably installed at the light-emitting port of the irradiation head 108 housing by means of a snap or magnetic attachment, which facilitates replacement and cleaning / disinfection.

[0030] Please refer to Figure 1 and Figure 2This application provides an adaptive light-emitting film structure for an LED phototherapy device, namely a light-emitting film 100. The light-emitting film 100 is disposed between the LED light source 5 and the skin surface 6, and includes a base layer 1, a microlens array layer 2, and a thermochromic layer 3 arranged sequentially from the light source side to the light-emitting side. The base layer 1 is located on the side closest to the light source, the microlens array layer 2 is disposed on the light-emitting surface of the base layer 1, and the thermochromic layer 3 covers the light-emitting surface of the microlens array layer 2. This structural layout allows light emitted from the light source to pass sequentially through the base layer 1, the microlens array layer 2, and the thermochromic layer 3, ultimately achieving the functions of directional beam focusing, uniform light emission, and automatic protection against local overheating.

[0031] Specifically, the base layer 1 is made of a light-transmitting material, such as high-transmittance medical-grade silicone, optical-grade epoxy resin, or optical-grade polycarbonate. In this embodiment, the base layer 1 is made of high-transmittance medical-grade silicone with a thickness of 0.8 mm and a transmittance of more than 95% for the therapeutic wavelength (633 nm red light). The function of the base layer 1 is to provide support for the subsequent microlens array layer 2 while ensuring that light can pass through smoothly. The base layer 1 has good flexibility and biocompatibility, and appropriate materials can be selected according to the specific application scenario of the phototherapy device.

[0032] Please refer to Figure 2 and Figure 3The microlens array layer 2 includes multiple arrayed microlens units 21 and light-shielding partitions 22. The microlens units 21 can be spherical or aspherical convex lens structures. Spherical convex lens structures are relatively simple to manufacture, while aspherical convex lens structures can better correct aberrations and improve image quality. Multiple microlens units 21 are arranged in a hexagonal close-packed configuration with a fill factor greater than 90%, maximizing space utilization and improving light convergence. The diameter of the microlens units 21 ranges from 50 to 500 μm; different diameters can be selected to suit different treatment scenarios. In this embodiment, the microlens unit 21 is a spherical convex lens structure with a diameter of 200 μm, a radius of curvature of 150 μm, a center distance of 210 μm, and a fill factor of approximately 92%. Each microlens unit 21 can receive divergent light from the LED light source 5 (receiving half-angle ±60°) and converge it into a directional therapeutic beam 7 with an output half-angle less than ±20°, thereby reducing light scattering to non-treatment areas and improving light energy utilization. A light-shielding partition 22 is disposed in the gap between adjacent microlens units 21 and extends along the optical axis of the microlens unit 21. It is formed by doping an opaque filler into a transparent matrix material; the opaque filler can be carbon black particles and / or metal oxide particles. The height of the light-shielding partition 22 is 10-50 μm, and the width is 5-20 μm, not exceeding the width of the gap between adjacent microlens units 21. In this embodiment, the height of the light-shielding partition 22 is 30 μm, the width is 10 μm, and it is made of an opaque composite material formed by doping carbon black particles (10% carbon black by mass) into a silicone matrix. The function of the light-shielding partition 22 is to prevent optical crosstalk between adjacent microlens units 21, achieve pixel-level optical isolation, prevent non-directional scattered light from leaking from the gaps between microlenses, enhance the spatial resolution of the light-emitting film 100, make the boundary of the treatment area corresponding to each microlens unit 21 clear, and improve the directionality of light. The opaque filler in the light-shielding partition 22 can also be metal oxide particles such as Fe3O4 particles, which have a light-shielding effect comparable to carbon black and have better chemical stability.

[0033] Please refer to Figure 2 and Figure 4A thermochromic layer 3, with a thickness of 5 μm, covers the light-emitting surface of the microlens array layer 2 and contains multiple thermoresponsive microcapsules 31 dispersed in a transparent matrix 32. In this application, the thermochromic layer 3 is of the reverse thermochromic type, meaning that the transparency of the thermoresponsive microcapsules 31 decreases when heated (changing from a transparent state to an opaque state) and recovers when cooled (returning from an opaque state to a transparent state). The transparent matrix 32 is made of medical-grade polyurethane hydrogel with a water content of 30-50 wt% and a transmittance of more than 93% for 633 nm red light. The volume fraction of the thermoresponsive microcapsules 31 in the transparent matrix 32 is 35%. The water in the transparent matrix 32 provides the necessary water source for the reversible volume phase change of the thermoresponsive microcapsules 31—water molecules 313 discharged from the thermosensitive polymer shell 311 during heating enter the transparent matrix 32 for temporary storage, and water molecules 313 are reabsorbed from the transparent matrix 32 during cooling, thereby achieving a reversible cycle. The transparent matrix 32 acts as a buffer for water molecules 313, ensuring the complete reversibility of the entire adaptive response process.

[0034] Analysis of the impact of LED self-heating on the thermochromic layer: The thickness of the thermochromic layer 3 is only 5μm. Using polyurethane hydrogel (40wt% water content) as the transparent matrix 32 and thermally responsive microcapsules 31 with a volume fraction of 35%, the equivalent density of the thermochromic layer 3 is approximately 1.1 g / cm³, the equivalent specific heat capacity is approximately 3.2 J / (g·K), and the heat capacity per unit area is C = ρ·c·d = 1.1 × 3.2 × 5 × 10⁻ 4 =1.76×10⁻³ J / (cm²·K). Under typical LED phototherapy device operating conditions (light power density 50mW / cm²), even assuming the thermochromic layer 3 has an absorption rate of 5% for the 633nm therapeutic light (actual transmittance is greater than 93%, and the absorption rate is much lower than 5%), the light power density absorbed by the thermochromic layer 3 is 50×5%=2.5 mW / cm². Considering that both sides of the thermochromic layer 3 are in contact with air or other layers, and there is heat conduction and heat dissipation, under steady-state conditions, the temperature rise of the thermochromic layer 3 due to self-absorption does not exceed 0.5℃, which is far lower than the 15℃ temperature rise required from the ambient temperature (about 25℃) to the threshold temperature (40℃). Therefore, the self-heating effect of the LED therapeutic light will not cause the thermochromic layer 3 to be falsely triggered to change color; the temperature change of the thermochromic layer 3 is entirely driven by heat conduction and / or heat radiation from the skin surface.

[0035] like Figure 2 As shown, Figure 2 Hollow circles represent thermally responsive microcapsules 31 in a transparent state, while solid circles represent thermally responsive microcapsules 31 in an opaque state.

[0036] Please refer to Figure 4The thermoresponsive microcapsules 31 have a core-shell structure, comprising a thermosensitive polymer shell 311 and high-refractive-index nanoparticles 312 dispersed within a cross-linked polymer network of the thermosensitive polymer shell 311. The particle size of the thermoresponsive microcapsules 31 is 3-5 μm, and the thickness of the thermosensitive polymer shell 311 is 0.5-1 μm. The thermosensitive polymer shell 311 is a copolymer of poly(N-isopropylacrylamide) (PNIPAM) with hydrophilic and / or hydrophobic comonomers. The hydrophilic comonomers include acrylamide or hydroxyethyl methacrylate, and the hydrophobic comonomers include N-tert-butylacrylamide. The lower critical solution temperature (LCST) is adjusted to the range of 38℃-42℃ by the type and ratio of comonomers. In this embodiment, the molar ratio of N-isopropylacrylamide (NIPAM) to acrylamide is 90:10, and the molar ratio of crosslinking agent BIS is 3%. Through this copolymerization ratio, the LCST of the thermosensitive polymer shell 311 is adjusted to 40°C, matching the skin's safe temperature threshold. Introducing the hydrophobic comonomer N-tert-butylacrylamide can lower the LCST, while introducing more hydrophilic comonomer acrylamide can increase the LCST. The high-refractive-index nanoparticles 312 are nanoparticles with a refractive index of not less than 2.0. In this embodiment, titanium dioxide nanoparticles with a particle size of 20-100 nm are selected. In this embodiment, the high-refractive-index nanoparticles 312 are TiO2 nanoparticles with a particle size of 50 nm and a refractive index of approximately 2.5. The mass fraction of TiO2 nanoparticles in the thermoresponsive microcapsule 31 is 25%.

[0037] like Figure 4 As shown on the left, below the lower critical dissolution temperature, the thermosensitive polymer shell 311 absorbs liquid and swells. The amide groups in the polymer network of shell 311 form hydrogen bonds with water molecules 313, and a large number of water molecules 313 are absorbed into the polymer network. The water content of shell 311 can reach 10-20 times its own dry weight, resulting in volume expansion. Due to the high water content, the refractive index of shell 311 is close to that of water (n≈1.33), with little difference from the refractive index of the surrounding transparent matrix 32 (n≈1.45-1.50). Simultaneously, the high-refractive-index nanoparticles 312 are loosely distributed in the swollen polymer network, with interparticle spacing much larger than the wavelength of light, resulting in weak scattering effects. The thermoresponsive microcapsule 311 is generally transparent, allowing normal transmission of therapeutic light. Figure 4As shown on the right, when the low critical dissolution temperature is reached or exceeded, the thermosensitive polymer shell 311 undergoes a volume phase transition—the hydrophobic interactions between hydrophobic groups such as isopropyl groups on the polymer chains are enhanced, exceeding the hydrogen bonding forces between the amide groups and water molecules 313. The polymer chains collapse and shrink from the extended state, expelling the internal water molecules 313 from the shell 311 and temporarily storing them in the transparent matrix 32. The volume of the shell 311 shrinks drastically to 1 / 10 or even less of its swollen state. The polymer network of the shrunken shell 311 becomes denser, forming numerous tiny polymer-water interfaces and polymer-polymer interfaces. These interfaces themselves generate strong light scattering, causing the entire shell 311 to become milky white and opaque. At the same time, high refractive index nanoparticles 312 densely aggregate in the shrunken polymer network to form scattering centers, significantly increasing the number of scattering centers per unit volume and further enhancing the scattering effect. The overall opacity of the shell 311 and the dense scattering of the high-refractive-index nanoparticles 312 work together to make the thermally responsive microcapsule 31 opaque in the whole. No matter which direction the light is incident from, it cannot penetrate the thermally responsive microcapsule 31, effectively blocking the therapeutic light.

[0038] Quantitative explanation of the opaque state shading rate: In this embodiment, the thickness of the thermochromic layer 3 is 5 μm, the volume fraction of the thermally responsive microcapsules 31 is 35%, and the particle size is 3-5 μm. When all the thermally responsive microcapsules 31 are transformed into the opaque state, there are an average of about 1-2 layers of thermally responsive microcapsules 31 along the light propagation direction (perpendicular to the film surface). The extinction efficiency factor Q_ext≈2 of a single opaque thermally responsive microcapsule 31 (based on Mie scattering theory, for strongly scattering particles with a particle size much larger than the wavelength), then the shading rate (i.e., 1 minus the transmittance) of the thermochromic layer 3 for 633nm therapeutic light in the opaque state is not less than 80%. This shading rate is sufficient to reduce the therapeutic light power density in the overheated area to a safe level, effectively preventing thermal damage to the skin. If it is necessary to further improve the shading rate, the volume fraction of the thermally responsive microcapsules 31 can be increased or the thickness of the thermochromic layer 3 can be appropriately increased.

[0039] like Figure 4 As indicated by the arrow at the bottom, when the temperature drops below the LCST again, the hydrophobic interactions on the polymer chains weaken, and the amide groups are re-exposed, forming hydrogen bonds with the surrounding water molecules 313. The water molecules 313, previously relegated to the outside of the shell 311 and temporarily stored in the transparent matrix 32, re-permeate back into the shell 311 under the drive of hydrogen bonding. The shell 311 reabsorbs water and swells, its volume recovers, the scattering interfaces in the polymer network disappear, the shell 311 returns to its transparent state, and the therapeutic light resumes its transmission. This phase transition process is completely reversible; the water molecules 313 migrate back and forth between the shell 311 and the transparent matrix 32 over a distance only on the order of micrometers, exhibiting a fast response speed (response time on the order of seconds) and good reversible cycle stability.

[0040] The implementation principle of this embodiment is as follows: When light is emitted from the LED light source 5, it first passes through the base layer 1, which provides support for subsequent structures and ensures light transmission. Then, the light enters the microlens array layer 2, where the microlens units 21 converge the incident light into a directional beam, improving light energy utilization and reducing light scattering towards non-treatment areas. The light-shielding partition 22 prevents crosstalk and leakage between adjacent microlens units 21, further improving the directionality of the light. The light then passes through the thermochromic layer 3. When the skin temperature is normal, the thermally responsive microcapsules 31 are transparent, allowing the treatment light to pass through smoothly; when the local skin temperature reaches or exceeds a threshold temperature, the thermally responsive microcapsules 31 become opaque, blocking the treatment light and preventing skin burns. Each microlens unit 21 corresponds to an independent thermochromic region, achieving point-by-point temperature response. The spatial resolution is comparable to the size of the microlens unit 21 (approximately 200 μm in this embodiment), far exceeding the spatial resolution of traditional electronic temperature sensors. The entire process requires no electronic control system, operating completely autonomously, passively, and in real-time, with a response time in the order of seconds. It is important to note that the thermochromic layer 3 is only 5μm thick, and it absorbs very little heat generated by the LED treatment light. This prevents the thermochromic layer 3 from reaching its threshold temperature and triggering false light blocking. The temperature change of the thermochromic layer 3 is entirely driven by heat conduction and / or heat radiation from the skin surface. This multi-layered design effectively solves the problems of existing LED phototherapy devices, such as the inability of the light-emitting components to autonomously sense skin temperature, the inability to automatically protect against local overheating, severe light diffusion, and low light energy utilization, thus improving the safety and effectiveness of the treatment.

[0041] In practical use, the distance between the light-emitting surface of the light-emitting film 100 and the skin surface 6 depends on the specific phototherapy device model and treatment needs. The thermochromic layer 3 senses skin temperature in the following ways: when the light-emitting film 100 is close to or in contact with the skin surface 6, the temperature of the thermochromic layer 3 follows the change in skin surface temperature mainly through heat conduction; when there is a certain distance between the light-emitting film 100 and the skin surface 6, the thermochromic layer 3 senses temperature changes through the combined effect of infrared thermal radiation from the skin surface and air convection heat transfer.

[0042] Please refer to Figure 2 and Figure 5In a preferred embodiment, the adaptive light-emitting film structure of the LED phototherapy device provided in this application further includes a selective reflection layer 4, disposed on the light-emitting side surface of the thermochromic layer 3 (i.e., the outermost layer, facing the skin surface 6). The selective reflection layer 4 is an angle-selective reflection structure, configured to have a transmittance of not less than 85% for therapeutic light with a wavelength of λt incident at an incident angle less than a preset critical angle, a reflectance of not less than 85% for therapeutic light with a wavelength of λt incident at an incident angle greater than the preset critical angle, and a transmittance of not less than 70% for infrared radiation with a wavelength greater than 3 μm. The preset critical angle is 25°-45°. The wavelength λt of the therapeutic light is a specific single wavelength value, determined according to the peak emission wavelength of the LED light source used in the LED phototherapy device; in this embodiment, λt = 633 nm.

[0043] Please refer to Figure 2 The selective reflective layer 4 is a multilayer film structure composed of alternating stacks of high refractive index dielectric film 41 and low refractive index dielectric film 42, with an alternation period of no less than 5 periods. Figure 2 The multilayer film structure is illustrated by alternating solid and dashed lines. In this embodiment, the high-refractive-index dielectric film 41 is made of TiO2 (refractive index n1≈2.4), and the low-refractive-index dielectric film 42 is made of SiO2 (refractive index n2≈1.46). The material of the selective reflective layer 4 can also be other combinations of high-refractive-index / low-refractive-index dielectric materials such as Ge / ZnS or Si / SiO2. The optical thickness of both the high-refractive-index dielectric film 41 and the low-refractive-index dielectric film 42 is equal to one-quarter of the center wavelength λ0 of the reflection peak when incident perpendicularly. That is, the physical thickness d1 of the high-refractive-index dielectric film 41 satisfies d1=λ0 / (4n1), and the physical thickness d2 of the low-refractive-index dielectric film 42 satisfies d2=λ0 / (4n2), where n1 is the refractive index of the high-refractive-index dielectric film 41 and n2 is the refractive index of the low-refractive-index dielectric film 42. When the light is incident perpendicularly, the center wavelength λ0 of the reflection peak is greater than the wavelength λt of the therapeutic light, so that the wavelength of the therapeutic light is in the high transmittance range of the multilayer film structure when the light is incident perpendicularly. When the incident angle increases to the preset critical angle θc, the center wavelength of the reflection peak shifts to be equal to the wavelength λt of the therapeutic light due to the blue shift effect. When the incident angle further increases to be greater than the preset critical angle θc, the center wavelength of the reflection peak further blue shifts to be less than the wavelength λt of the therapeutic light, so that the wavelength of the therapeutic light falls into the reflection band of the multilayer film structure and is reflected efficiently. Among them, the center wavelength λ0 of the reflection peak, the wavelength λt of the therapeutic light, and the preset critical angle θc satisfy the relationship λ0=λt / cosθc when the light is incident perpendicularly.

[0044] The core design principle of the selective reflection layer 4 is to utilize the blue shift effect of the reflection peak of the multilayer dielectric film to achieve selective transmission and reflection of the therapeutic light wavelength. The relationship between the center wavelength of the reflection peak of the multilayer dielectric film and the incident angle θ is: λ(θ) = λ0·cosθ, where λ0 is the center wavelength of the reflection peak when incident perpendicularly (θ = 0°). In this embodiment, the wavelength of the therapeutic light λt = 633nm, and the preset critical angle θc = 32°. According to the design requirements of angle-selective reflection, the center wavelength of the reflection peak when incident perpendicularly is designed as: λ0 = λt / cosθc = 633 / cos32° ≈ 746nm, and λ0 = 750nm is selected. Therefore: the physical thickness of the TiO2 layer is d1 = λ0 / (4n1) = 750 / (4×2.4) ≈ 78nm; the physical thickness of the SiO2 layer is d2 = λ0 / (4n2) = 750 / (4×1.46) ≈ 128nm. The total number of cycles is 10, which is 20 thin films.

[0045] It should be noted that the total physical thickness of the selective reflective layer 4 is approximately (78+128)×10=2060nm≈2μm, which is much smaller than the wavelength of mid-infrared radiation (3-15μm). For mid-infrared radiation with wavelengths much larger than the periodic structure size of the film layer, the Bragg reflection condition of the multilayer film structure is not satisfied, and mid-infrared radiation mainly passes through the selective reflective layer 4 via transmission. Furthermore, with the total film thickness of this embodiment (approximately 2μm), the absorption loss of TiO2 and SiO2 materials in the 3-15μm band is limited, and the transmittance of mid-infrared radiation is not less than 70%. In applications requiring higher mid-infrared transmittance, a combination of dielectric materials such as ZnS / BaF2, which are more transparent to mid-infrared radiation, can be used to replace TiO2 / SiO2.

[0046] The angle-selective reflection function of selective reflection layer 4 is as follows:

[0047] (1) For 633nm therapeutic light incident perpendicularly (θ=0°): the center wavelength of the reflection peak is 750nm, and 633nm is far from the reflection peak and is in the high transmittance range with a transmittance greater than 90%. Therefore, the therapeutic beam 7, which is converged from the microlens array layer 2 and emitted in a direction close to the normal, can efficiently pass through the selective reflection layer 4 and normally irradiate the skin surface 6 without affecting the phototherapy effect.

[0048] (2) For 633nm light with an incident angle that is exactly equal to the preset critical angle θc=32°: the center wavelength of the reflection peak is blue-shifted to λ0·cos32°=750×0.848≈636nm, which is exactly equal to the wavelength of the therapeutic light 633nm (considering the bandwidth of the reflection peak). 633nm begins to enter the edge of the reflection band, and the reflectivity begins to increase.

[0049] (3) For 633nm scattered light with an incident angle greater than the preset critical angle (θ>32°): the center wavelength of the reflection peak is further blue-shifted to less than 636nm, and 633nm completely falls within the reflection band, with a reflectivity greater than 90%. Therefore, the therapeutic light that is scattered by the opaque thermal response microcapsule 31 of the overheated region 62 and reaches the selective reflection layer 4 at a large angle is efficiently reflected back to the direction of the thermochromic layer 3, forming the reflected recovery light 9.

[0050] (4) For mid-infrared radiation with wavelengths greater than 3 μm: the far-infrared wavelength is much greater than the reflection peak wavelength of 750 nm, and is not within the reflection band of the multilayer film, with a transmittance of not less than 70%. Therefore, the infrared thermal radiation 8 from the skin surface 6 can pass through the selective reflective layer 4 to reach the thermochromic layer 3, assisting in triggering the temperature response.

[0051] The preset critical angle θc can be selected within the range of 25°-45°. The smaller θc is, the stronger the angle selectivity but the narrower the range of normal transmission angles. The larger θc is, the more relaxed the angle selectivity but the lower the reflection and recovery efficiency. It needs to be determined comprehensively based on the divergence angle of the emitted beam of the microlens array layer 2 and the actual application requirements. In other embodiments, when the wavelength of the therapeutic light is 460nm blue light, the design value of λ0 can be adjusted accordingly (e.g., λ0=460 / cos32°≈542nm), and the thickness of each thin film layer can be adjusted accordingly to match the blue light wavelength.

[0052] Please refer to Figure 5 The adaptive working process of the light-emitting film 100 will be described in detail below.

[0053] The therapeutic light emitted by the LED light source 5 is converged by the microlens units 21 in the microlens array layer 2 to form a directional therapeutic beam 7 with an exit half-angle of less than ±20°. The therapeutic beam 7 passes through the thermochromic layer 3, which is transparent at room temperature, in a near-normal direction, and then enters the selective reflection layer 4 in a near-normal direction (the incident angle is less than 20°, much smaller than the preset critical angle of 32°). The 633nm wavelength is in the high transmittance range of the selective reflection layer 4, so it efficiently passes through the selective reflection layer 4 and irradiates the skin surface 6. Figure 5 The propagation path of the treatment beam 7 is represented by a long dashed line with an arrowhead.

[0054] After the skin surface absorbs light energy, the local temperature rises, generating infrared thermal radiation. Figure 5 The dotted line with an arrow indicates that infrared thermal radiation 8 propagates from the skin surface 6 towards the light-emitting film 100. The wavelength of infrared thermal radiation 8 is much greater than 3 μm, outside the reflection band of the selective reflective layer 4, and therefore can penetrate the selective reflective layer 4 to reach the thermochromic layer 3. Simultaneously, when the light-emitting film 100 is close to the skin surface 6, the skin's heat is also directly transferred to the thermochromic layer 3 via thermal conduction. Both thermal conduction and thermal radiation jointly drive the temperature response of the thermochromic layer 3.

[0055] like Figure 5 As shown, for the normal temperature region 61 (temperature <40℃) of the skin surface 6, the corresponding thermally responsive microcapsule 31 remains transparent. Figure 5 (Represented by a hollow circle in the center), the treatment beam 7 passes through normally, and phototherapy continues.

[0056] For the overheated region 62 (temperature ≥40℃) on the skin surface 6, the heat in this region (through thermal conduction and / or infrared thermal radiation) raises the temperature of the thermochromic layer 3 at the corresponding location to above LCST. The PNIPAM shell 311 of the thermally responsive microcapsule 31 contracts, and the entire shell 311 becomes opaque. The dense arrangement of TiO2 nanoparticles 312 further enhances scattering, and the entire thermally responsive microcapsule 31 becomes an opaque scattering state. Figure 5 (Represented by a solid circle in the center), automatically blocking the therapeutic light output in that area.

[0057] Of the light scattered by the opaque thermoresponsive microcapsules 31, the portion that propagates at a large angle (greater than the preset critical angle of 32°) towards the light-emitting side reaches the selective reflection layer 4. Because the incident angle is greater than 32°, the center wavelength of the reflection peak blue-shifts to less than 636nm, with 633nm falling within the reflection band and being efficiently reflected back to the thermochromic layer 3. The reflected light propagates along the film surface direction (i.e., parallel to the film plane) within the thermochromic layer 3. When it reaches the adjacent room-temperature region 61, the thermoresponsive microcapsules 31 in this region are in a transparent state. The light passes through the transparent thermoresponsive microcapsules 31 and reaches the selective reflection layer 4 at a near-normal direction (less than 32°). At this point, the center wavelength of the reflection peak is still around 750nm, and 633nm is in the high-transmittance range, efficiently passing through the selective reflection layer 4 and finally reaching the skin surface 6 corresponding to the room-temperature region 61, forming reflected and recovered light 9. Figure 5 The dashed line with an arrowhead represents the complete return path of the reflected and recovered light 9.

[0058] The complete optical path of the reflected and recovered light 9 is as follows: the therapeutic light from the LED light source 5 is converged through the microlens array layer 2 and reaches the thermochromic layer 3 of the overheated region 62 → it is scattered by the opaque thermally responsive microcapsules 31 → the portion of the scattered light propagating at a large angle (>32°) towards the light-emitting side reaches the selective reflection layer 4 → 633nm falls into the reflection band and is efficiently reflected → the reflected light returns to the direction of the thermochromic layer 3 → propagates along the film surface direction in the thermochromic layer 3 → reaches the adjacent normal temperature region 61 → passes through the transparent thermally responsive microcapsules 31 in this region → reaches the selective reflection layer 4 at a near-normal direction (<32°) → 633nm is in the high transmittance range and is efficiently transmitted → reaches the skin surface 6 corresponding to the normal temperature region 61. Through this optical path of "scattering → angle-selective reflection → propagation along the film surface direction → normal direction exit", the light energy originally irradiating the overheated region 62 is redistributed to the adjacent normal temperature region 61, which avoids thermal damage to the overheated region and improves the light energy utilization rate. During this process, the water molecules 313 discharged from the thermally responsive microcapsule 31 corresponding to the overheated region 62 are temporarily stored in the transparent matrix 32; when the temperature of this region decreases, the water molecules 313 flow back from the transparent matrix 32 to the interior of the shell 311, and the thermally responsive microcapsule 31 returns to the transparent state.

[0059] When the skin temperature in the overheated area 62 drops below 40°C due to the cessation of light exposure, the corresponding thermally responsive microcapsule 31 returns to a transparent state, and the therapeutic light output resumes. The entire process requires no electronic control system and is completely autonomous, passive, and real-time responsive.

[0060] The implementation principle of this embodiment is as follows: the selective reflective layer 4 further optimizes the performance of the light-emitting film 100. For light of therapeutic wavelengths with an incident angle less than a preset critical angle, it can transmit at high speed, ensuring the light intensity in the treatment area; while for light incident at an angle greater than the preset critical angle, it can reflect efficiently, reflecting the light that has been scattered by the opaque thermally responsive microcapsules 31 of the overheated region 62 and reaches the selective reflective layer 4 at a large angle back to the thermochromic layer 3, allowing it to propagate along the film surface to the adjacent room temperature region 61 and then exit in a direction close to the normal, realizing the redistribution of light energy from the overheated region 62 to the room temperature region 61, reducing light energy waste. At the same time, it has a transmittance of not less than 70% for infrared radiation with a wavelength greater than 3μm, allowing the infrared thermal radiation 8 of the skin surface 6 to pass through the selective reflective layer 4 to reach the thermochromic layer 3, ensuring that the thermochromic layer 3 can sense changes in skin temperature. This structure combines the preceding base layer 1, microlens array layer 2, and thermochromic layer 3, enabling the adaptive light-emitting film structure of the LED phototherapy device to further improve light utilization efficiency and treatment safety, building upon beam directional focusing, light uniformity, and automatic protection against local overheating. All functional layers are integrated into the light-emitting film 100, which has a total thickness of less than 2mm, without increasing the size of the phototherapy device, and can directly replace the light-emitting components of existing phototherapy devices.

[0061] Example 2

[0062] Please refer to Figure 6 This application provides a method for preparing an adaptive light-emitting film structure for an LED phototherapy device, comprising the following steps:

[0063] S1, Fabrication of the microlens array mold: Multiple micro-pits are formed on the surface of the mold substrate. The surface of the micro-pits is complementary to the convex surface of the microlens unit 21, serving as the negative structure of the microlens unit 21. In this embodiment, a hexagonal close-packed micro-pit array is fabricated on the silicon wafer mold using femtosecond laser direct writing technology. The pit diameter is 200 μm, the pit depth is 40 μm, and the hexagonal close-packed arrangement has a center-to-center distance of 210 μm. Alternatively, the mold can be fabricated using photolithography-thermal reflow technology: First, a photoresist cylindrical array is formed on the silicon wafer by photolithography. Then, it is heated to above the photoresist softening temperature, causing it to reflow under surface tension to form spherical protrusions. These protrusions serve as the positive mold for the microlens, and the negative mold is obtained by PDMS molding.

[0064] S2, Preparation of the light-shielding partition 22: Fill the recessed partition area (i.e., the ridge between the recesses) of the mold with a carbon black / silicone mixture (10% carbon black by mass), smooth it with a scraper so that the mixture is only retained in the ridge area, and pre-cur it (80℃, 30min) to form an opaque partition layer. In step S2, the light-shielding partition material is only pre-cured (semi-cured state) so that it can be co-cured and bonded with the substrate material in the subsequent step S3.

[0065] S3, Molding the base layer 1 and the microlens array layer 2: A light-transmitting base material is poured into the mold on which the light-shielding partition 22 has been formed. After curing, the mold is demolded to obtain a base layer 1 with a microlens array layer 2 and a light-shielding partition 22 on one side surface. In this embodiment, medical-grade high-transmittance silicone is poured into the mold and subjected to vacuum degassing treatment (vacuum degree less than 100 Pa, time 20 min), and then thermo-cured at 130°C for 1.5 h. During this thermo-curing process, the pre-cured light-shielding partition 22 in step S2 and the poured light-transmitting silicone are simultaneously cured to achieve final curing, and the light-shielding partition 22 is integrated with the base layer 1 and the microlens array layer 2 through co-curing. After demolding, a silicone substrate with a hexagonal close-packed microlens array and a light-shielding partition 22 on the upper surface is obtained, namely the base layer 1 and the microlens array layer 2.

[0066] S4, Forming the thermochromic layer 3: A coating solution is prepared by dispersing thermoresponsive microcapsules 31 in a solution of a transparent matrix material. This coating solution is then applied to the light-emitting surface of the microlens array layer 2 and cured into a film at a temperature below the threshold temperature of the thermoresponsive microcapsules 31, forming the thermochromic layer 3. In this embodiment, the thermoresponsive microcapsules 31 are dispersed in a medical-grade polyurethane hydrogel precursor solution (polyurethane dissolved in an ethyl acetate / water mixed solvent, concentration 15 wt%), with a volume fraction of 35% for the thermoresponsive microcapsules 31. The solution is stirred until homogeneous to prepare the coating solution. The coating solution is applied to the light-emitting surface of the microlens array layer 2 using either a spraying or spin coating process. When using a spin coating process, the spin coating speed is 2000 rpm, the time is 30 s, and the coating thickness is controlled to be 5 μm. Since the light-emitting surface of the microlens array layer 2 is a curved structure formed by the microlens units 21, in scenarios requiring high coating uniformity, a spraying process is preferred. Multiple thin-layer sprays are applied to accumulate to the target thickness to ensure the uniformity of the coating thickness on the curved surface. The film is cured by natural drying at 25℃ for 24 hours, forming a thermochromic layer 3 with a water content of 30-50wt%. The ambient temperature during the coating process must be strictly controlled below 30℃ to avoid triggering the color change of the thermal response microcapsules 31, which would affect the coating uniformity.

[0067] The implementation principle of this embodiment is as follows: by first preparing a microlens array mold, then preparing a light-shielding partition 22, then using the mold to form the base layer 1 and the microlens array layer 2, and finally forming the thermochromic layer 3, an adaptive light-emitting film structure for LED phototherapy devices with specific structure and performance can be precisely manufactured. This preparation method is relatively simple to operate and can ensure the quality and performance of the light-emitting film structure.

[0068] Please refer to Figure 4 and Figure 6 Specifically, the thermally responsive microcapsules 31 are prepared through the following steps:

[0069] Step a: N-isopropylacrylamide monomer, comonomer, and crosslinking agent are mixed and dissolved in a solvent, and a thermosensitive polymer microgel with a target low critical solution temperature is synthesized through free radical polymerization. In this embodiment, N-isopropylacrylamide (NIPAM) monomer and acrylamide are mixed at a molar ratio of 90:10, and crosslinking agent BIS (3% molar ratio) is added, dissolved in deionized water to prepare a solution with a total monomer concentration of 5 wt%. Ammonium persulfate (APS, 0.5% molar ratio) is added as an initiator, and a free radical precipitation polymerization reaction is carried out at 70°C under nitrogen protection for 3 h. After the reaction, the PNIPAM copolymer microgel particles are obtained by centrifugation and washing, with a particle size of 3-5 μm and an LCST of 40°C.

[0070] Step b involves swelling the thermosensitive polymer microgel at a temperature below the target lower critical dissolution temperature, then adding a liquid dispersion of high-refractive-index nanoparticles 312 to allow the high-refractive-index nanoparticles 312 to adsorb into the swollen polymer network. In this embodiment, TiO2 nanoparticles (50 nm in diameter) are dispersed in deionized water and ultrasonically dispersed for 30 min to prepare a dispersion with a concentration of 5 wt%. The PNIPAM microgel particles obtained in step a are dispersed in water at 25°C (below LCST) to allow them to fully swell, and the TiO2 dispersion is added, followed by stirring and adsorption for 2 h.

[0071] Step c involves heating to above the target lower critical melting temperature (LCST) to shrink the thermosensitive polymer microgel, thus fixing the high-refractive-index nanoparticles 312 within the shrunken polymer network. In this embodiment, the temperature is raised to 45°C (above the LCST) to shrink the microgel, encapsulating the TiO2 nanoparticles inside. After cooling to 25°C, the microgel re-swells. Steps b and c can be repeated once or multiple times to increase the loading of the high-refractive-index nanoparticles 312. In this embodiment, the loading operation is repeated twice to increase the TiO2 content to 25 wt%.

[0072] Step d, microcapsule surface modification: Thermoresponsive microcapsules 31 loaded with TiO2 were dispersed in an ethanol / water mixed solution (volume ratio 1:1), and silane coupling agent KH-570 (mass fraction 2%) was added. The mixture was stirred at 60℃ for 1 h to perform surface modification treatment, thereby improving the interfacial compatibility between the thermoresponsive microcapsules 31 and the transparent matrix 32. After centrifugation, washing, and drying, the microcapsules were ready for use.

[0073] In this embodiment, this preparation method allows for precise control of the performance of the thermally responsive microcapsules 31, enabling them to reversibly switch between transparent and opaque states with temperature changes. By repeatedly performing steps b and c, the loading of high-refractive-index nanoparticles 312 can be increased, enhancing the performance of the thermally responsive microcapsules 31 and thus improving the performance of the thermochromic layer 3. This further ensures the automatic overheat protection function of the adaptive light-emitting film structure of the LED phototherapy device.

[0074] Specifically, after step S4, the following is also included:

[0075] Step S5, Deposition of Selective Reflection Layer 4: On the light-emitting surface of the thermochromic layer 3, a high-refractive-index dielectric film 41 and a low-refractive-index dielectric film 42 are alternately deposited by electron beam evaporation or magnetron sputtering to form the selective reflection layer 4. The center wavelength λ0 of the reflection peak at perpendicular incidence is determined according to λ0 = λt / cosθc, where λt is the wavelength of the therapeutic light and θc is a preset critical angle. The physical thickness d1 of the high-refractive-index dielectric film 41 is determined according to d1 = λ0 / (4n1), and the physical thickness d2 of the low-refractive-index dielectric film 42 is determined according to d2 = λ0 / (4n2), where n1 is the refractive index of the high-refractive-index dielectric film 41 and n2 is the refractive index of the low-refractive-index dielectric film 42. The substrate temperature during the deposition process is lower than the threshold temperature of the thermally responsive microcapsule 31. In this embodiment, electron beam evaporation is used to alternately deposit TiO2 thin films (78 nm thick) and SiO2 thin films (128 nm thick) on the light-emitting surface of the thermochromic layer 3, for a total of 10 cycles (20 layers). During deposition, the substrate temperature is controlled below 35°C (lower than the LCST of the thermally responsive microcapsules 31, which is 40°C) to avoid damage to the thermochromic layer 3. The deposition rate is controlled at 0.1-0.5 nm / s to ensure film thickness uniformity and interface quality. Magnetron sputtering can also be used instead of electron beam evaporation, but the substrate temperature must be controlled similarly. It should be noted that the thermochromic layer 3 is a polyurethane hydrogel with a water content of 30-50 wt%, and there may be a risk of moisture evaporation in the vacuum deposition environment. Therefore, a 50-100 nm thick SiO2 protective layer (prepared by low-temperature sol-gel method) can be pre-coated on the surface of the thermochromic layer 3 before deposition. This protective layer serves both as a water vapor barrier to prevent hydrogel dehydration under vacuum and as a transition layer to improve film adhesion for subsequent multilayer film deposition. After deposition, the SiO2 protective layer becomes part of the selective reflective layer 4 and does not affect optical performance.

[0076] In this embodiment, by depositing a selective reflective layer 4 on the light-emitting surface of the thermochromic layer 3, the performance of the adaptive light-emitting film structure of the LED phototherapy device can be further optimized. Electron beam evaporation and magnetron sputtering are commonly used thin film deposition methods that can precisely control the thickness and performance of the thin film. By determining the center wavelength of the reflection peak and the film thickness according to the wavelength of the therapeutic light and the preset critical angle, the selective reflective layer 4 can achieve selective reflection of incident light at different angles, improving the utilization efficiency of light and the safety of treatment. At the same time, controlling the substrate temperature during the deposition process to be lower than the threshold temperature of the thermally responsive microcapsules 31 ensures that the performance of the thermochromic layer 3 is not affected.

[0077] Step S6, Encapsulation and Protection: Medical-grade silicone sealant is applied to the edge of the light-emitting membrane 100 to form a complete edge-sealed structure, preventing the evaporation and loss of moisture in the transparent matrix 32. Moisture in the transparent matrix 32 is a necessary condition for the reversible volume phase change of the thermally responsive microcapsules 31—if moisture is lost, the shell layer 311 cannot reabsorb water and swell after cooling, leading to a loss of reversibility. Therefore, edge sealing is a key process step to ensure the long-term reliable operation of the light-emitting membrane 100. The outermost layer is covered with a 0.3μm thick medical-grade fluorinated silicone protective film, providing biocompatibility and abrasion resistance. This protective film also has low water vapor permeability, further preventing moisture loss. After encapsulation, the light-emitting membrane 100 can be installed at the light outlet of the LED phototherapy head 108 via a snap-on or magnetic attachment, achieving plug-and-play functionality. The light-emitting membrane 100 can be repeatedly cleaned and disinfected, or it can be supplied separately as a disposable consumable. In practical applications, the light-emitting membrane 100 of this application can be used in various LED phototherapy devices, including but not limited to facial LED photon skin rejuvenation devices, dermatological red / blue light therapy devices, wound repair phototherapy devices, and rehabilitation physiotherapy phototherapy devices. The wavelength, threshold temperature, and other parameters of the therapeutic light of the light-emitting membrane 100 can be customized according to specific clinical needs. The phototherapy device can also be equipped with an electronic temperature sensor as an auxiliary monitoring method, forming a dual safety guarantee with the passive adaptive protection of the light-emitting membrane 100.

[0078] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be included within the scope of protection of this application. The specific embodiments of this application described above do not constitute a limitation on the scope of protection of this application. Any other corresponding changes and modifications made based on the technical concept of this application should be included within the scope of protection of this application.

Claims

1. An adaptive light-emitting film structure for an LED phototherapy device, characterized in that, Including those arranged sequentially from the light source side to the light emission side: A base layer (1) is made of a light-transmitting material; The microlens array layer (2) is disposed on the light-emitting side surface of the substrate layer (1) and includes multiple arrayed microlens units (21) for converging incident light into a directional beam. A thermochromic layer (3) is covered on the light-emitting surface of the microlens array layer (2). The thermochromic layer (3) contains a plurality of thermally responsive microcapsules (31) dispersed in a transparent matrix (32). The thermally responsive microcapsules (31) have the characteristic of reversibly switching between a transparent state and an opaque state with temperature change. The thermally responsive microcapsules (31) are transparent when the temperature is below a threshold temperature to allow the therapeutic light to pass through, and become opaque when the temperature reaches or exceeds the threshold temperature to block the therapeutic light. The thickness of the thermochromic layer (3) is 3-10 μm, so that the self-absorption heat effect when the LED therapeutic light passes through the thermochromic layer (3) is insufficient to raise the temperature of the thermochromic layer (3) itself to the threshold temperature.

2. The adaptive light-emitting film structure of the LED phototherapy device according to claim 1, characterized in that, It also includes a selective reflective layer (4) disposed on the light-emitting side surface of the thermochromic layer (3). The selective reflective layer (4) is an angle-selective reflective structure and is configured to have a transmittance of not less than 85% for light of the therapeutic wavelength used by the LED phototherapy device that is incident at an incident angle less than a preset critical angle, a reflectance of not less than 85% for light of the therapeutic wavelength that is incident at an incident angle greater than a preset critical angle, and a transmittance of not less than 70% for infrared radiation with a wavelength greater than 3 μm; wherein the preset critical angle is 25°-45°.

3. The adaptive light-emitting film structure of the LED phototherapy device according to claim 1, characterized in that, The microlens array layer (2) further includes a light-shielding partition (22), which is disposed in the gap between adjacent microlens units (21) and extends along the optical axis of the microlens unit (21). The light-shielding partition (22) is formed by doping opaque fillers into a light-transmitting matrix material.

4. The adaptive light-emitting film structure of the LED phototherapy device according to claim 1, characterized in that, The thermoresponsive microcapsule (31) comprises a thermosensitive polymer shell (311) and high-refractive-index nanoparticles (312) dispersed in a cross-linked polymer network within the thermosensitive polymer shell (311). The thermosensitive polymer shell (311) has a low critical dissolution temperature, which is the threshold temperature. Below the low critical dissolution temperature, the thermosensitive polymer shell (311) absorbs liquid and swells, and the high-refractive-index nanoparticles (312) are loosely distributed in the swollen polymer network, making the thermoresponsive microcapsule (31) transparent overall. When the low critical dissolution temperature is reached or exceeded, the thermosensitive polymer shell (311) dehydrates and shrinks, and the high-refractive-index nanoparticles (312) densely aggregate in the shrinking polymer network to form scattering centers, making the thermoresponsive microcapsule (31) opaque overall. In the opaque state, the thermoresponsive microcapsule (31) has a light-blocking rate of not less than 80% for the therapeutic light.

5. The adaptive light-emitting film structure of the LED phototherapy device according to claim 4, characterized in that, The material of the thermosensitive polymer shell (311) is a copolymer of poly(N-isopropylacrylamide) with a hydrophilic comonomer and / or a hydrophobic comonomer, wherein the hydrophilic comonomer includes acrylamide or hydroxyethyl methacrylate, and the hydrophobic comonomer includes N-tert-butylacrylamide. The low critical dissolution temperature is adjusted to the range of 38°C-42°C by the type and ratio of the comonomer. The high refractive index nanoparticles (312) are nanoparticles with a refractive index of not less than 2.0 and a particle size of 20-100 nm.

6. The adaptive light-emitting film structure of the LED phototherapy device according to claim 2, characterized in that, The selective reflective layer (4) is a multilayer film structure composed of alternating stacks of high refractive index dielectric film (41) and low refractive index dielectric film (42), with an alternation period of not less than 5 periods; The optical thickness of both the high-refractive-index dielectric film (41) and the low-refractive-index dielectric film (42) is equal to one-quarter of the center wavelength λ0 of the reflection peak when incident perpendicularly. That is, the physical thickness d1 of the high-refractive-index dielectric film (41) satisfies d1=λ0 / (4n1), and the physical thickness d2 of the low-refractive-index dielectric film (42) satisfies d2=λ0 / (4n2), where n1 is the refractive index of the high-refractive-index dielectric film (41) and n2 is the refractive index of the low-refractive-index dielectric film (42). The center wavelength λ0 of the reflection peak when incident perpendicularly is greater than the wavelength λt of the therapeutic light, making the therapeutic light... When the light is incident perpendicularly, the wavelength is within the high transmittance range of the multilayer film structure. When the incident angle increases to the preset critical angle θc, the center wavelength of the reflection peak shifts to be equal to the wavelength λt of the therapeutic light due to the blue shift effect. When the incident angle further increases to be greater than the preset critical angle θc, the center wavelength of the reflection peak further blue shifts to be less than the wavelength λt of the therapeutic light, so that the wavelength of the therapeutic light falls within the reflection band of the multilayer film structure and is efficiently reflected. The center wavelength λ0 of the reflection peak at perpendicular incidence satisfies the relationship λ0 = λt / cosθc with the wavelength λt of the therapeutic light and the preset critical angle θc.

7. The adaptive light-emitting film structure of the LED phototherapy device according to claim 3, characterized in that, The microlens unit (21) is a spherical convex lens structure or an aspherical convex lens structure with a diameter of 50-500μm; multiple microlens units (21) are arranged in a hexagonal close-packed manner with a fill factor greater than 90%; the height of the light-shielding partition (22) is 10-50μm, the width is 5-20μm and not greater than the width of the gap between adjacent microlens units (21), and the opaque filler is carbon black particles and / or metal oxide particles.

8. A method for preparing an adaptive light-emitting film structure for a phototherapy device, used to prepare the adaptive light-emitting film structure for an LED phototherapy device as described in claim 1, characterized in that, Includes the following steps: Step 1, prepare microlens array mold: process multiple micro-dimples on the surface of the mold substrate, the shape of the micro-dimples is complementary to the convex surface of the microlens unit (21), and serves as the negative structure of the microlens unit (21); Step 2, prepare the light-shielding partition: fill the recessed partition area of ​​the mold with opaque composite material and pre-cur it to form a light-shielding partition (22). Step 3, forming the base layer and microlens array layer: pour the light-transmitting base material into the mold, and demold after curing to obtain a base layer (1) with a microlens array layer (2) and a light-shielding partition (22) on one side surface. Step 4, forming a thermochromic layer: The thermo-responsive microcapsules (31) are dispersed in a solution of a transparent matrix material to prepare a coating liquid. The coating liquid is then coated on the light-emitting surface of the microlens array layer (2) and cured into a film at a temperature lower than the threshold temperature of the thermo-responsive microcapsules (31) to form a thermochromic layer (3).

9. The method for preparing the adaptive light-emitting film structure of the LED phototherapy device according to claim 8, characterized in that, The thermally responsive microcapsules (31) are prepared by the following steps: Step a: N-isopropylacrylamide monomer, comonomer, and crosslinking agent are mixed and dissolved in a solvent, and a thermosensitive polymer microgel with a target low critical dissolution temperature is synthesized by free radical polymerization. Step b: The thermosensitive polymer microgel is swollen at a temperature below the target low critical dissolution temperature, and a liquid dispersion of high refractive index nanoparticles (312) is added to allow the high refractive index nanoparticles (312) to be adsorbed into the swollen polymer network. Step c: Heat the temperature to above the target low critical melting temperature to shrink the thermosensitive polymer microgel and fix the high refractive index nanoparticles (312) inside the shrunken polymer network; Steps b and c can be repeated once or multiple times to increase the loading of the high-refractive-index nanoparticles (312).

10. The preparation method according to claim 8, characterized in that, Following step four, the following is also included: Step 5, Deposition of selective reflection layer: On the light-emitting surface of the thermochromic layer (3), a high refractive index dielectric film (41) and a low refractive index dielectric film (42) are alternately deposited by electron beam evaporation or magnetron sputtering to form a selective reflection layer (4); wherein, the center wavelength λ0 of the reflection peak when incident perpendicularly is determined according to λ0=λt / cosθc, λt is the wavelength of the therapeutic light, and θc is the preset critical angle; the physical thickness d1 of the high refractive index dielectric film (41) is determined according to d1=λ0 / (4n1), and the physical thickness d2 of the low refractive index dielectric film (42) is determined according to d2=λ0 / (4n2), wherein n1 is the refractive index of the high refractive index dielectric film (41), and n2 is the refractive index of the low refractive index dielectric film (42); the substrate temperature during the deposition process is lower than the threshold temperature of the thermally responsive microcapsule (31).

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