Multi-layer fusion type plane optical lens structure and integrated forming method

Abstract

The invention discloses a multi-layer fusion type plane optical lens structure and an integrated forming method, and belongs to the technical field of sampling devices. A gradient refractive index transition layer; a microstructure functional layer; a stress self-compensating intermediate layer; a transparent hard protective layer; the gradient refractive index transition layer, the microstructure function layer, the stress self-compensation intermediate layer and the transparent hard protection layer realize interface fusion through chemical bonding or an interpenetrating polymer network structure. Optical matching and mechanical buffering are achieved through the gradient refractive index transition layer, active stress balance is achieved through the stress self-compensation middle layer, multi-layer fusion is achieved through a chemical bonding interface, and high-precision and high-efficiency manufacturing is achieved through the integrated forming technology. The interface reflection loss is eliminated, and the light energy utilization efficiency is remarkably improved; wavefront distortion caused by stress is eliminated, and the imaging definition is remarkably improved; the interface bonding strength is improved, and the stripping risk is eliminated.

Description

Technical Field

[0001] This invention relates to the field of optical lens technology, specifically to a multi-layer fusion planar optical lens structure and an integrated molding method. Background Technology

[0002] Optical lenses based on diffractive optical elements or Fresnel microstructures utilize surface microstructures to achieve optical power, thereby compressing the lens body into a thin sheet structure, theoretically enabling a completely planar appearance. However, such solutions still face the following systemic technical challenges in practical industrial applications: 1. Exposed microstructure layers are susceptible to wear and contamination: Fresnel microstructures have feature sizes in the micrometer or even submicrometer range, with structural depths typically ranging from 0.5 to 30 μm and feature periods from 2 to 200 μm. When the microstructure is located on or near the lens surface, everyday activities such as wiping, scratching, dust accumulation, and sweat corrosion can lead to edge damage, groove blockage, a sharp decrease in diffraction efficiency, and severe stray light problems. Although existing technologies include coating the microstructure surface with a protective layer, a refractive index difference usually exists between the protective layer and the microstructure layer, introducing additional phase errors and compromising the optical design accuracy of the microstructure.

[0003] 2. Stress Mismatch and Optical Distortion Caused by Multilayer Bonding: To protect microstructures, current technologies often employ multilayer bonding, combining functional and protective layers with optical adhesives. However, differences in refractive index, coefficient of thermal expansion (CTE), elastic modulus, and curing shrinkage between different layers introduce complex residual stress distributions at the interlayer interfaces and within the layers. This stress mismatch leads to warping, optical center shift, aberration introduction, and interface delamination.

[0004] 3. Insufficient interfacial bonding reliability and low manufacturing yield: Existing processes mostly adopt a step-by-step bonding method, where each layer is formed independently and then assembled with optical adhesive. This process path has the following inherent defects: poor alignment accuracy, accumulation of errors from multi-layer stacking, and difficulty in controlling the deviation between the optical center and the geometric center; interfacial bubbles and contaminants are difficult to completely eliminate, forming scattering centers.

[0005] 4. Optical losses caused by abrupt changes in refractive index: In multilayer structures, abrupt changes in refractive index between any two adjacent layers result in Fresnel reflection losses. In the visible light band, the reflectivity of a single interface is approximately 4%. For 3-4 layer structures, the total transmittance loss can reach 10%-15%, severely impacting light energy utilization. Furthermore, multiple reflections can create stray light on the image plane, reducing image contrast.

[0006] In summary, there is an urgent need for a lens structure and its manufacturing method that can achieve an ultra-thin planar shape while possessing high optical efficiency, high mechanical stability, no risk of interface peeling, adjustable stress, and suitability for mass production. Summary of the Invention

[0007] To address the aforementioned technical shortcomings, the present invention aims to provide a multi-layered fusion planar optical lens structure and an integrated molding method. A gradient refractive index transition layer achieves optical matching and mechanical buffering; a stress-compensating intermediate layer achieves active stress balance; a chemically bonded interface enables multi-layer fusion; and an integrated molding process achieves high-precision and high-efficiency manufacturing. The gradient refractive index transition layer eliminates interface reflection loss, significantly improving light energy utilization efficiency. The stress-compensating intermediate layer eliminates stress-induced wavefront distortion, significantly improving image clarity. The transparent hard protective layer enhances interface bonding strength and eliminates the risk of peeling. This invention solves the technical problems mentioned in the background art.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The present invention provides a multi-layer fusion planar optical lens structure, comprising sequentially stacked components: Substrate bearing layer; A gradient refractive index transition layer has a refractive index that changes continuously along the thickness direction, ranging from 0.05 to 0.35; a chemically bonded interface is formed between the transition layer and the substrate support layer; The microstructure functional layer is provided with diffraction or Fresnel microstructures to achieve the prescription optical power; the depth of the microstructure is 0.5μm~30μm, and the characteristic period is 2μm~500μm; The stress-compensating intermediate layer has a thermal expansion coefficient between the microstructure functional layer and the transparent hard protective layer, and an elastic modulus between the microstructure functional layer and the transparent hard protective layer. The residual stress formed after curing is balanced with the residual stress of the microstructure functional layer and the substrate bearing layer, so that the overall warpage of the lens is ≤0.05mm. Transparent hard protective layer, pencil hardness ≥6H; The gradient refractive index transition layer, microstructure functional layer, stress self-compensating intermediate layer, and transparent hard protective layer are fused together through chemical bonding or interpenetrating polymer network structure, without independent adhesive layers.

[0009] Preferably, the gradient refractive index transition layer is formed by gradient coating or micro-layer co-extrusion of at least two photocurable resin materials with different refractive indices. The refractive index distribution curve along the thickness direction is selected from one of linear distribution, exponential distribution, S-shaped distribution or multi-segment distribution, and the thickness of the transition layer is 15μm~8μm.

[0010] Preferably, in the gradient refractive index transition layer, the low refractive index component is one or more of perfluoroalkyl acrylate, perfluoropolyether acrylate, trifluoroethyl methacrylate, and organosilicon acrylate, with a refractive index of 1.38~1.48; the high refractive index component is selected from sulfur-containing acrylate, fluorene-containing acrylate, bromine-containing acrylate, or acrylate doped with TiO2, ZrO2, Nb2O5, or ZnS nanoparticles; the nanoparticles have a particle size of 5~25 nm, a mass fraction of 10%~60%, and a refractive index of 1.65~1.85.

[0011] Preferably, the stress-compensating intermediate layer has a thermal expansion coefficient of 50~120 ppm / ℃, an elastic modulus of 0.5~2.5 GPa, a thickness of 10μm~30μm, a curing shrinkage rate of 1.5%~4.0%, and a shrinkage stress of 0.5~5MPa after curing.

[0012] Preferably, the stress-compensating intermediate layer material is one or more blends of polyurethane acrylate, polyether acrylate, and epoxy acrylate, with 5% to 25% by mass of flexible segments added, wherein the flexible segments are one of polyethylene glycol, polycaprolactone, or polytetrahydrofuran.

[0013] Preferably, the transparent hard protective layer is one of an organic-inorganic hybrid resin, a siloxane hard coating, a diamond-like carbon film, a silicon nitride film, or an alumina film, with a thickness of 10 μm to 100 μm (organic-inorganic hybrid) or 50 nm to 500 nm (inorganic film); the transparent hard protective layer and the stress self-compensating intermediate layer are fused together through covalent bonding or chemical bonding of the undercoat layer to form an interface.

[0014] Preferably, it further includes one or more of the following: a first stress buffer sublayer disposed between the substrate bearing layer and the gradient refractive index transition layer; a second stress buffer sublayer disposed between the gradient refractive index transition layer and the microstructure functional layer; and a third stress buffer sublayer disposed between the stress self-compensating intermediate layer and the transparent hard protective layer; wherein the stress buffer sublayer has a thickness of 2μm to 12μm and an elastic modulus of 0.3 to 3.0 GPa. An integrated molding method for a multi-layer fusion planar optical lens structure includes the following steps: Step 1: Perform surface activation treatment on the substrate support layer to increase the surface energy to 45~75 mN / m and introduce active functional groups that can participate in the photocuring reaction; Step 2: Form a gradient refractive index transition layer with a continuously changing refractive index on the substrate support layer by gradient coating or micro-layer co-extrusion, and then cure it with ultraviolet light to form a chemical bond between the transition layer and the substrate support layer; Step 3: Form a microstructure functional layer on the transition layer by ultraviolet nanoimprinting, with a replication accuracy deviation of ≤±30nm; Step 4: Form a stress-compensating intermediate layer on the microstructure functional layer, and control its curing stress by segmented illumination and temperature gradient to balance the shrinkage stress generated in the intermediate layer with the residual stress in the lower layer. Step 5: A transparent hard protective layer is integrally formed on the stress self-compensating intermediate layer, and a cross-linking reaction occurs at the interface between the protective layer and the intermediate layer to form chemical bonds; In steps two through five above, chemical bonding interfaces are achieved between adjacent layers through cross-linking reactions of active functional groups, forming an integrated structure.

[0015] Preferably, the segmented illumination and temperature gradient control in step four includes: First stage: light intensity 5~15 mW / cm², temperature 40~50℃, curing time 30~90s; Second stage: light intensity 30~60 mW / cm², temperature 60~90℃, curing time 60~180s; Curing parameters are adjusted in real time through online stress detection to control the overall warpage of the lens within ≤±0.05 mm.

[0016] Preferably, the online stress detection includes one or more combinations of laser triangulation to measure the radius of curvature, birefringence measurement to detect stress distribution, and Shaker-Hartmann wavefront sensor to measure transmission wavefront distortion. The detection data is fed back to the curing control system to dynamically adjust the light intensity and temperature, forming a closed-loop control.

[0017] Preferably, in step four, for progressive multifocal lenses or freeform lenses with uneven microstructure density distribution, digital micromirror devices or liquid crystal light valves are used to control the spatial distribution of light intensity, so that areas with higher microstructure density can obtain higher light intensity, thereby achieving regionalized stress matching, with regionalized light intensity differences of 20% to 50%.

[0018] Preferably, the materials of the gradient refractive index transition layer, the microstructure functional layer, the stress self-compensating intermediate layer, and the transparent hard protective layer all contain active functional groups that can participate in the photocuring crosslinking reaction. The active functional groups are selected from one or more of acrylate double bonds, methacrylate double bonds, epoxy groups, hydroxyl groups, and silanol groups.

[0019] Preferably, the gradient coating in step two uses a dual-channel or multi-channel slit coating head, and the mixing ratio of low refractive index component and high refractive index component changes with time by a precision metering pump. The thickness and refractive index distribution are monitored in real time during the coating process, and the thickness tolerance is ≤ ±2μm.

[0020] Preferably, the ultraviolet nanoimprinting in step three uses a nickel template or a quartz template, with a fluorosilane release layer coated on the template surface; the imprinting pressure is 0.5~3 bar, the release speed is 1~5 mm / s, and the curing light intensity is 30~100 mW / cm².

[0021] The beneficial effects of this invention are as follows: 1. The gradient refractive index transition layer of this invention achieves optical matching and mechanical buffering, active stress balance through a stress self-compensating intermediate layer, multi-layer fusion through a chemical bonding interface, and high-precision and high-efficiency manufacturing through an integrated molding process. The gradient refractive index transition layer eliminates interface reflection loss and significantly improves light energy utilization efficiency. The stress self-compensating intermediate layer eliminates stress-induced wavefront distortion and significantly improves imaging clarity. The transparent hard protective layer enhances interface bonding strength and eliminates the risk of peeling.

[0022] 2. This invention constructs layers sequentially from the substrate support layer to the protective layer, with continuous operation between each layer and integrated molding, improving manufacturing yield and significantly reducing production costs. The integrated molding employs precision coating methods such as spin coating and slot coating, resulting in high material utilization. By changing the embossing mold and adjusting the gradient refractive index distribution, various prescription lenses, including spherical, cylindrical, prism, progressive multifocal, and freeform lenses, can be produced, offering strong scalability and applicability to multiple prescription types. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A flowchart illustrating the integrated forming method of a multi-layer fusion planar optical lens structure provided in an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example: This invention provides a multilayer fusion planar optical lens structure, comprising: a substrate support layer; a gradient refractive index transition layer, the refractive index of which continuously varies along the thickness direction, ranging from 0.05 to 0.35; and a chemically bonded interface formed between the transition layer and the substrate support layer. In traditional multilayer stacked structures, abrupt changes in refractive index between every two adjacent layers result in Fresnel reflection loss. For lenses containing 3 to 4 layers, the single-interface reflectivity is approximately 4%, and the total transmittance loss can reach 10% to 15%. This application eliminates abrupt changes in refractive index between layers by setting a gradient refractive index transition layer, whose refractive index continuously varies along the thickness direction. Actual measurements show that the interfacial reflectivity between the transition layer and adjacent layers is reduced from approximately 4% to below 0.5%. The overall visible light transmittance of the lens reaches 92.5% to 93.8%, an improvement of 3 to 5 percentage points compared to traditional stacked and bonded structures, eliminating interfacial reflection loss and significantly improving light energy utilization efficiency.

[0027] The microstructure functional layer contains diffraction or Fresnel microstructures that achieve the prescribed optical power; the microstructure depth ranges from 0.5 μm to 30 μm, and the characteristic period ranges from 2 μm to 500 μm. When the microstructure layer is exposed or the refractive index of the protective layer is mismatched, multiple reflections will occur within the microstructure grooves, forming stray light. In this application, the microstructure functional layer is embedded under a stress-compensating intermediate layer and a transparent hard protective layer, and the gradient refractive index transition layer achieves optical matching, effectively suppressing parasitic reflections at the microstructure interface. The stray light intensity of the lens in this application is controlled at 2.0% to 2.5%, which is more than 60% lower than that of traditional structures, eliminating stray light and significantly improving image contrast.

[0028] The stress-compensating intermediate layer has a thermal expansion coefficient between that of the microstructure functional layer and the transparent rigid protective layer, and an elastic modulus between those of the same layer. Furthermore, the residual stress formed after curing balances the residual stresses of the microstructure functional layer and the substrate bearing layer, resulting in an overall lens warpage ≤0.05mm. In traditional adhesive structures, the mismatch in interlayer thermal expansion coefficients and differences in curing shrinkage introduce uneven residual stress within the lens, leading to localized refractive index changes through photoelasticity and unpredictable wavefront distortion. This application utilizes an active stress balancing mechanism in the stress-compensating intermediate layer to homogenize the overall residual stress distribution. The transmission wavefront distortion of the lens in this application is controlled within λ / 10, and the modulation transfer function reaches 0.80~0.83 at a spatial frequency of 50 lp / mm, an improvement of 10%~15% compared to traditional structures. This eliminates stress-induced wavefront distortion and significantly improves image clarity.

[0029] A transparent, rigid protective layer with a pencil hardness ≥6H is used. The gradient refractive index transition layer, microstructure functional layer, stress-compensating intermediate layer, and transparent rigid protective layer are chemically bonded or interpenetrating polymer network structures to achieve interfacial fusion, eliminating the need for a separate adhesive layer. Traditional optical adhesive bonding typically has an interfacial bond strength of 1-3 MPa, and is prone to interfacial delamination under environmental stresses such as damp heat aging and temperature cycling. In this application, each layer contains active functional groups that can participate in photocuring crosslinking reactions; adjacent layers undergo covalent bonding or form interpenetrating polymer networks during curing; there is no separate adhesive layer, and no material abrupt changes at the interface; the interfacial bond strength is improved, eliminating the risk of delamination.

[0030] In summary, this embodiment achieves optical matching and mechanical buffering through a gradient refractive index transition layer, active stress balance through a stress-compensating intermediate layer, multi-layer fusion through a chemical bonding interface, and high-precision, high-efficiency manufacturing through an integrated molding process. The gradient refractive index transition layer eliminates interface reflection loss, significantly improving light energy utilization efficiency. The stress-compensating intermediate layer eliminates stress-induced wavefront distortion, significantly improving imaging clarity. The transparent hard protective layer enhances interface bonding strength and eliminates the risk of peeling.

[0031] Furthermore, the gradient refractive index transition layer is formed by gradient coating or micro-layer co-extrusion of at least two photocurable resin materials with different refractive indices. The refractive index distribution curve along the thickness direction is selected from one of linear distribution, exponential distribution, S-type distribution or multi-segment distribution, and the thickness of the transition layer is 15μm~80μm; thus better eliminating the abrupt change in refractive index between layers.

[0032] Furthermore, in the gradient refractive index transition layer, the low refractive index component is one or more of perfluoroalkyl acrylate, perfluoropolyether acrylate, trifluoroethyl methacrylate, and organosilicon acrylate, with a refractive index of 1.38~1.48; the high refractive index component is selected from sulfur-containing acrylate, fluorene-containing acrylate, bromine-containing acrylate, or acrylate doped with TiO2, ZrO2, Nb2O5, or ZnS nanoparticles; the nanoparticles have a particle size of 5~25nm, a mass fraction of 10%~60%, and a refractive index of 1.65~1.85; and have excellent ultraviolet shielding ability.

[0033] Furthermore, the thermal expansion coefficient of the stress-compensating intermediate layer is 50~120 ppm / ℃, the elastic modulus is 0.5~2.5 GPa, the thickness is 10μm~30μm, the curing shrinkage rate is 1.5%~4.0%, and the shrinkage stress generated after curing is 0.5~5MPa, which effectively suppresses the accumulation of thermal stress.

[0034] Furthermore, the stress-compensating intermediate layer material is one or more blends of polyurethane acrylate, polyether acrylate, and epoxy acrylate, with 5% to 25% by mass of flexible segments added. The flexible segments are one of polyethylene glycol, polycaprolactone, or polytetrahydrofuran, which improves impact resistance.

[0035] Furthermore, the transparent hard protective layer is one of the following: organic-inorganic hybrid resin, siloxane hard coating, diamond-like carbon film, silicon nitride film, or alumina film, with a thickness of 10 μm to 100 μm (organic-inorganic hybrid) or 50 nm to 500 nm (inorganic film); the transparent hard protective layer and the stress self-compensating intermediate layer are fused together through covalent bonding or chemical bonding of the undercoat layer; it has excellent resistance to sweat, cosmetics, detergents, etc., and good chemical corrosion resistance.

[0036] Furthermore, the system includes one or more of the following: a first stress buffer sublayer disposed between the substrate bearing layer and the gradient refractive index transition layer; a second stress buffer sublayer disposed between the gradient refractive index transition layer and the microstructure functional layer; and a third stress buffer sublayer disposed between the stress self-compensating intermediate layer and the transparent hard protective layer. The stress buffer sublayer has a thickness of 2 μm to 12 μm and an elastic modulus of 0.3 to 3.0 GPa. The gradient refractive index transition layer and the stress buffer sublayer absorb impact energy, while the protective layer prevents surface cracking. Please see Figure 1 As shown, the integrated forming method for a multi-layer fusion planar optical lens structure includes the following steps: Step 1: Perform surface activation treatment on the substrate support layer to increase the surface energy to 45~75 mN / m and introduce active functional groups that can participate in the photocuring reaction; Step 2: Form a gradient refractive index transition layer with a continuously changing refractive index on the substrate support layer by gradient coating or micro-layer co-extrusion, and then cure it with ultraviolet light to form a chemical bond between the transition layer and the substrate support layer; Step 3: Form a microstructure functional layer on the transition layer by ultraviolet nanoimprinting, with a replication accuracy deviation of ≤±30nm; Step 4: Form a stress-compensating intermediate layer on the microstructure functional layer, and control its curing stress by segmented illumination and temperature gradient to balance the shrinkage stress generated in the intermediate layer with the residual stress in the lower layer. Step 5: A transparent hard protective layer is integrally formed on the stress self-compensating intermediate layer, and a cross-linking reaction occurs at the interface between the protective layer and the intermediate layer to form chemical bonds; In steps two through five above, adjacent layers achieve chemical bonding interfaces through cross-linking reactions of active functional groups, forming an integrated structure. In this embodiment, the structure is constructed layer by layer from the substrate support layer to the protective layer, with continuous operation between each layer, resulting in integrated molding, improved manufacturing yield, and significantly reduced production costs. It allows for continuous batch production, simplifying the process flow and shortening the production cycle. The integrated molding utilizes precision coating methods such as spin coating and slot coating, resulting in high material utilization. By changing the embossing mold and adjusting the gradient refractive index distribution, various prescription lenses, including spherical, cylindrical, prism, progressive multifocal, and freeform lenses, can be produced, as well as integrated functions such as blue light protection, photochromic, and polarization. It offers strong scalability and is suitable for various prescription types.

[0037] Furthermore, the segmented illumination and temperature gradient control described in step four includes: First stage: illumination intensity 5~15 mW / cm², temperature 40~50℃, curing time 30~90s; Second stage: illumination intensity 30~60 mW / cm², temperature 60~90℃, curing time 60~180s; Curing parameters are adjusted in real-time through online stress detection to control the overall lens warpage within ≤±0.05 mm. Through these two stages of illumination, the yellowing index ΔE ≤1.5, transmittance decrease ≤0.6%, and microstructure diffraction efficiency decrease ≤3%.

[0038] Furthermore, the online stress detection includes one or more combinations of laser triangulation to measure the radius of curvature, birefringence measurement to detect stress distribution, and Shaker-Hartmann wavefront sensor to measure transmission wavefront distortion. The detection data is fed back to the curing control system to dynamically adjust the light intensity and temperature, forming a closed-loop control.

[0039] Furthermore, in step four, for progressive multifocal lenses or freeform surface lenses with uneven microstructure density distribution, digital micromirror devices or liquid crystal light valves are used to control the spatial distribution of light intensity, so that areas with higher microstructure density receive higher light intensity, achieving regionalized stress matching. The regionalized light intensity difference is 20%~50%. The microstructure functional layer is located below the stress-compensating intermediate layer and the transparent hard protective layer, completely isolated from the external environment. The transparent hard protective layer uses organic-inorganic hybrid materials or diamond-like carbon films, with no obvious scratches on the surface and a haze increase value ≤0.5%.

[0040] Furthermore, the materials of the gradient refractive index transition layer, microstructure functional layer, stress self-compensating intermediate layer, and transparent hard protective layer all contain active functional groups that can participate in the photocuring crosslinking reaction. These active functional groups are selected from one or more of acrylate double bonds, methacrylate double bonds, epoxy groups, hydroxyl groups, and silanol groups. After a 90° peel test, the interfacial bonding strength of the lens of this application reaches 5-8 MPa, which is 2-4 times higher than that of traditional structures. Fracture analysis shows that the fracture occurs within the material rather than at the interface, proving that the interfacial bonding strength is higher than the material bulk strength.

[0041] Furthermore, in step two, the gradient coating uses a dual-channel or multi-channel slit coating head, and the mixing ratio of low-refractive-index components and high-refractive-index components is controlled by a precision metering pump to change over time. The thickness and refractive index distribution are monitored in real time during the coating process, and the thickness tolerance is ≤ ±2μm.

[0042] Furthermore, in step three, the ultraviolet nanoimprinting uses a nickel template or a quartz template, with a fluorosilane release layer coated on the template surface; the imprinting pressure is 0.5~3 bar, the release speed is 1~5 mm / s, and the curing light intensity is 30~100 mW / cm². The microstructure functional layer is directly formed on the transition layer via ultraviolet nanoimprinting, and the alignment accuracy between the optical center and the geometric center is ensured by the imprinting mold. Testing with an image measuring instrument shows that the optical center offset is controlled to ≤0.1 mm, an improvement of an order of magnitude compared to traditional processes, meeting the assembly accuracy requirements of high-end prescription lenses.

[0043] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A multi-layer fusion planar optical lens structure, characterized in that, Including those set up in a stacked manner: Substrate bearing layer; A gradient refractive index transition layer, wherein a chemically bonded interface is formed between the transition layer and the substrate support layer; The microstructure functional layer is provided with diffraction or Fresnel microstructures to achieve the prescription optical power; The stress-compensating intermediate layer has a thermal expansion coefficient between the microstructure functional layer and the transparent hard protective layer, and an elastic modulus between the microstructure functional layer and the transparent hard protective layer. The residual stress formed after curing is balanced with the residual stress of the microstructure functional layer and the substrate bearing layer, so that the overall warpage of the lens is ≤0.05 mm. Transparent hard protective layer; The gradient refractive index transition layer, microstructure functional layer, stress self-compensating intermediate layer, and transparent hard protective layer achieve interface fusion through chemical bonding or interpenetrating polymer network structure.

2. The multi-layer fusion planar optical lens structure as described in claim 1, characterized in that, The gradient refractive index transition layer is formed by at least two photocurable resin materials with different refractive indices through gradient coating or micro-layer co-extrusion. The refractive index distribution curve along the thickness direction is selected from one of linear distribution, exponential distribution, S-shaped distribution or multi-segment distribution.

3. The multi-layer fusion planar optical lens structure as described in claim 1, characterized in that, In the gradient refractive index transition layer, the low refractive index component is one or more of perfluoroalkyl acrylate, perfluoropolyether acrylate, trifluoroethyl methacrylate, and organosilicon acrylate; the high refractive index component is selected from sulfur-containing acrylate, fluorene-containing acrylate, bromine-containing acrylate, or acrylate doped with nanoparticles.

4. The multi-layer fusion planar optical lens structure as described in claim 1, characterized in that, The stress-compensating intermediate layer has a thermal expansion coefficient of 50~120 ppm / ℃, an elastic modulus of 0.5~2.5 GPa, a thickness of 10μm~30μm, a curing shrinkage rate of 1.5%~4.0%, and a shrinkage stress of 0.5~5MPa after curing.

5. The multi-layer fusion planar optical lens structure as described in claim 1, characterized in that, The stress-compensating intermediate layer material is one or more blends of polyurethane acrylate, polyether acrylate, and epoxy acrylate, with 5% to 25% by mass of flexible segments added, wherein the flexible segments are one of polyethylene glycol, polycaprolactone, or polytetrahydrofuran.

6. The multi-layer fusion planar optical lens structure as described in claim 1, characterized in that, The transparent hard protective layer is one of an organic-inorganic hybrid resin, a siloxane hard coating, a diamond-like carbon film, a silicon nitride film, or an aluminum oxide film. The transparent hard protective layer and the stress self-compensating intermediate layer are fused together through covalent bonding or chemical bonding of the undercoating layer.

7. The multi-layer fusion planar optical lens structure as described in claim 1, characterized in that, It also includes one or more of the following: a first stress buffer sublayer disposed between the substrate bearing layer and the gradient refractive index transition layer; a second stress buffer sublayer disposed between the gradient refractive index transition layer and the microstructure functional layer; and a third stress buffer sublayer disposed between the stress self-compensating intermediate layer and the transparent hard protective layer.

8. The integrated forming method for a multi-layer fusion planar optical lens structure as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Perform surface activation treatment on the substrate support layer to increase the surface energy to 45~75 mN / m and introduce active functional groups that can participate in the photocuring reaction; Step 2: Form a gradient refractive index transition layer with a continuously changing refractive index on the substrate support layer by gradient coating or micro-layer co-extrusion, and then cure it with ultraviolet light to form a chemical bond between the transition layer and the substrate support layer; Step 3: Form a microstructure functional layer on the transition layer using ultraviolet nanoimprinting; Step 4: Form a stress-compensating intermediate layer on the microstructure functional layer, and control its curing stress by segmented illumination and temperature gradient to balance the shrinkage stress generated in the intermediate layer with the residual stress in the lower layer. Step 5: A transparent hard protective layer is integrally formed on the stress self-compensating intermediate layer, and a cross-linking reaction occurs at the interface between the protective layer and the intermediate layer to form chemical bonds.

9. The integrated forming method for the multi-layer fusion planar optical lens structure as described in claim 8, characterized in that, Step four, which involves segmented illumination and temperature gradient control, includes: First stage: light intensity 5~15 mW / cm², temperature 40~50℃, curing time 30~90s; Second stage: light intensity 30~60 mW / cm², temperature 60~90℃, curing time 60~180s; curing parameters are adjusted in real time through online stress detection feedback.

10. The integrated forming method for the multi-layer fusion planar optical lens structure as described in claim 9, characterized in that, The online stress detection includes one or more combinations of laser triangulation to measure the radius of curvature, birefringence measurement to detect stress distribution, and Shaker-Hartmann wavefront sensor to measure transmission wavefront distortion. The detection data is fed back to the curing control system, which dynamically adjusts the light intensity and temperature to form a closed-loop control.

11. The integrated forming method for the multi-layer fusion planar optical lens structure as described in claim 8, characterized in that, In step four, for progressive multifocal lenses or freeform surface lenses with uneven microstructure density distribution, digital micromirror devices or liquid crystal light valves are used to control the spatial distribution of light intensity, so that areas with higher microstructure density can obtain higher light intensity.

12. The integrated forming method for the multi-layer fusion planar optical lens structure as described in claim 8, characterized in that, The materials of the gradient refractive index transition layer, the microstructure functional layer, the stress self-compensating intermediate layer, and the transparent hard protective layer all contain active functional groups that can participate in the photocuring crosslinking reaction. The active functional groups are selected from one or more of acrylate double bonds, methacrylate double bonds, epoxy groups, hydroxyl groups, and silanol groups.

13. The integrated forming method for the multi-layer fusion planar optical lens structure as described in claim 8, characterized in that, The gradient coating described in step two uses a dual-channel or multi-channel slit coating head. A precision metering pump controls the mixing ratio of low-refractive-index components to high-refractive-index components over time, and the thickness and refractive index distribution are monitored in real time during the coating process.

14. The integrated forming method for the multi-layer fusion planar optical lens structure as described in claim 8, characterized in that, The ultraviolet nanoimprinting described in step three uses a nickel template or a quartz template, with a fluorosilane release layer coated on the template surface.

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