A microstructured coated curable PMMA film, its preparation method and application

Abstract

This invention provides a microstructured coated hardened PMMA film, its preparation method, and its applications. The film comprises a PMMA substrate layer, a primer layer, and a hardened layer. The primer layer is composed of modified acrylate resin, ultraviolet absorber, and solvent, with a thickness of 1.5–3 μm. The hardened layer is composed of silica sol, nano-sized α-alumina particles, silane coupling agent, and catalyst, with a thickness of 4–8 μm. The nano-α-alumina particles have a diameter of 10–50 nm and a content of 5–15 wt%. The film exhibits a visible light transmittance ≥95%, a hardness of 5H–9H, and an adhesion ≥4B. This invention also discloses a preparation method, including plasma pretreatment of the PMMA substrate, primer coating and curing, and hardened layer coating and curing. This invention employs a double-layer coating structure and nano-sized hard particles, achieving high transmittance while ensuring high hardness. The process is simple, the yield is high, and it is suitable for 3D printer consumables and accessories, as well as optical instruments.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a microstructured coated hardened PMMA (polymethyl methacrylate) film and its preparation method, which is particularly suitable for the field of 3D printer consumables and accessories, requiring high light transmittance and excellent surface hardness properties. Background Technology

[0002] Polymethyl methacrylate (PMMA), also known as plexiglass or acrylic, is an important polymer optical material. PMMA has excellent light transmittance, reaching over 92%, far exceeding the 80%–90% transmittance of ordinary glass. Simultaneously, PMMA also possesses good optical uniformity, weather resistance, processability, and dimensional stability, making it widely used in optical instruments, display panels, lighting equipment, advertising signage, architectural decoration, automotive parts, and other fields.

[0003] In 3D printer consumables applications, PMMA film, as an important optical component, needs to meet the following technical requirements: First, it needs to have high light transmittance to ensure effective light transmission and accurate transmission of optical signals during the printing process; second, it needs to have sufficient surface hardness to resist wear, scratches, and accidental impacts during use; in addition, it needs to have good weather resistance and stable physicochemical properties to meet the requirements of long-term use.

[0004] However, ordinary PMMA materials have low surface hardness, with a Mohs hardness of only 2-3 and a pencil hardness of only HB-F. This makes them prone to scratches and wear during daily use, severely affecting their optical performance and lifespan. To address this issue, the industry typically employs surface hardening treatment technology, forming a hardened coating on the surface of the PMMA substrate to improve its surface hardness.

[0005] However, existing hardened coated PMMA films still have the following problems: (1) High transmittance is difficult to achieve. Due to limitations in the optical properties of coating materials and coating processes, the transmittance of existing technologies is usually between 92% and 94%, which is insufficient to meet the stringent requirement of ≥95% transmittance for high-end 3D printer accessories. High transmittance is crucial for 3D printer consumables because light needs to penetrate the film for optical detection or laser reading. Every 1% decrease in transmittance significantly affects the accuracy of the optical signal.

[0006] (2) Hardness and light transmittance are difficult to balance. Increasing the content of hard particles to improve hardness will lead to enhanced light scattering and decreased light transmittance; while pursuing high light transmittance often requires reducing the content of hard particles, which in turn reduces hardness. This contradiction is the core technical challenge that restricts the improvement of the performance of cured PMMA films.

[0007] (3) Complex processes lead to low product yield. Although multi-layer coating structures can balance various performance aspects, the process is complex and the interlayer adhesion is difficult to control. Taking a three-layer structure as an example, multiple processes are required, including primer coating, primer curing, intermediate layer coating, intermediate layer curing, hardening layer coating, and hardening layer curing. Problems in any of these processes can lead to product scrap. Statistical data shows that the yield of three-layer hardened PMMA films produced by existing technologies is typically only 70% to 80%.

[0008] (4) Insufficient interlayer adhesion. Differences in the coefficients of thermal expansion and insufficient interfacial bonding between different coating materials can easily lead to coating cracking and peeling, especially in environments with large temperature variations. In addition, the surface of the PMMA substrate may contain contaminants such as grease, dust, and release agents, which can affect the adhesion between the coating and the substrate.

[0009] (5) Weather resistance needs to be improved. PMMA materials are prone to yellowing and degradation under ultraviolet light. If the hardened coating lacks effective ultraviolet protection, it will accelerate the aging of the substrate and affect the service life of the product.

[0010] (6) Insufficient application of microstructure functionalization. With the continuous development of 3D printing technology, the functional requirements for consumables and accessories are becoming increasingly higher, such as light shaping, light field adjustment, and optical anti-counterfeiting. This requires that the hardened film not only has basic hardness and light transmittance, but also needs to have a microstructure functional layer to meet specific optical application needs.

[0011] Therefore, how to provide a microstructured coated hardened PMMA film that has both high light transmittance (≥95%) and high hardness (5H-9H), and has a simple preparation process, high yield, and excellent weather resistance is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0012] Based on the deficiencies of the existing technology, the first objective of this invention is to provide a microstructured coated hardened PMMA film; the second objective of this invention is to provide a method for preparing the microstructured coated hardened PMMA film; and the third objective of this invention is to provide the application of the microstructured coated hardened PMMA film as a consumable accessory for 3D printers in the field of optical instruments.

[0013] The objective of this invention is achieved through the following technical solution: On one hand, the present invention provides a microstructured coated curable PMMA film, which includes a PMMA substrate layer, a primer layer and a curing layer, wherein the primer layer is disposed on the PMMA substrate layer and the curing layer is disposed on the primer layer; The primer layer is a primer coating composed of modified acrylic resin, ultraviolet absorber and solvent, with a thickness of 1.5~3μm; The hardened layer is a hardened coating composed of silica sol, nano-sized α-alumina particles, silane coupling agent and catalyst, with a thickness of 4~8μm.

[0014] In the aforementioned microstructured coating-type cured PMMA film, preferably, the modified acrylate resin is selected from hydroxy acrylate resin and / or epoxy acrylate resin. Hydroxy acrylate resin has excellent transparency and flexibility, good compatibility with PMMA substrate, and can form a uniform and smooth primer layer; epoxy acrylate resin has excellent adhesion and chemical resistance, and can enhance the bonding force between the primer layer and the substrate.

[0015] In the aforementioned microstructured coating-type hardened PMMA film, preferably, the ultraviolet absorber is a benzotriazole ultraviolet absorber (e.g., UV-329, which has a strong absorption effect on UVA (320-400nm), effectively blocking ultraviolet light transmission and protecting the PMMA substrate from ultraviolet degradation) and / or a triazine ultraviolet absorber (e.g., UV-1577, UV-1164, which has high thermal and light stability and is suitable for high-temperature processing); its content accounts for 1-3 wt% of the solid components of the primer layer.

[0016] In the aforementioned microstructured coated hardened PMMA film, preferably, the silica sol is an acidic silica sol with a solid content of 20-30 wt% and a particle size of 8-15 nm. The acidic silica sol has a pH of 2-4, a high content of silanol groups (Si-OH), and high condensation reaction activity during drying and curing, enabling the formation of a dense silicon-oxygen bond network. The 8-15 nm nano-sized silica particles possess good optical transparency and do not cause significant light scattering. In the above-mentioned microstructured coating type hardened PMMA film, preferably, the solid content of the nano-sized α-alumina particles is 5~15% and the particle size is 10~50nm, more preferably, the particle size of the nano-sized α-alumina particles is 20~40nm.

[0017] In the aforementioned microstructured coating-type cured PMMA film, preferably, the silane coupling agent is selected from one or more combinations of γ-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560), and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792); but is not limited thereto. The silane coupling agent molecule contains reactive groups (such as amino and epoxy groups) and hydrolyzable groups (such as ethoxy and methoxy groups), which can form chemical bonds with the organic components and inorganic particles in the cured coating, respectively, thereby improving the mechanical properties and stability of the composite material.

[0018] In the aforementioned microstructured coating-type cured PMMA film, preferably, the catalyst is selected from organotin catalysts and / or titanate catalysts, with a solid content of 0.5~2wt% of the solid composition of the cured layer. Organotin catalysts (such as dibutyltin dilaurate) can promote the hydrolysis and polycondensation reaction of silane coupling agents, accelerating the curing of the cured coating; titanate catalysts (such as tetrabutyl titanate) have similar catalytic effects and can also form chemical bonds with the surface of inorganic particles, enhancing the interfacial bonding force.

[0019] Preferably, the microstructure-coated hardened PMMA film further includes a microstructure layer disposed on the surface of the hardened layer, which is used to adjust the direction of light propagation and enhance the scattering effect. The introduction of the microstructure layer endows the hardened film with functional properties, allowing for customized design based on actual application needs and meeting the special optical requirements of 3D printer accessories.

[0020] In the aforementioned microstructured coating type cured PMMA film, preferably, the microstructure layer is selected from one of a prism structure, a lens array structure, or a grating structure; but it is not limited thereto. A prism structure can refract incident light at a specific angle to control the direction of light; a lens array structure can focus or diffuse light to adjust the light field distribution; a grating structure can produce a diffraction effect to achieve optical anti-counterfeiting or spectral analysis functions.

[0021] In the aforementioned microstructured coating type cured PMMA film, preferably, the structural parameters of the microstructure layer are designed according to the actual optical application requirements.

[0022] In the aforementioned microstructure-coated hardened PMMA film, preferably, the thickness of the PMMA substrate layer is 0.5~3mm, and the light transmittance is ≥92%. Selecting an appropriate thickness of PMMA substrate can ensure sufficient mechanical strength and dimensional stability, while meeting the requirements of optical applications.

[0023] In the aforementioned microstructured coated hardened PMMA film, preferably, the adhesion between the primer layer and the PMMA substrate layer is ≥4B (tested according to GB / T 9286 standard), and the adhesion between the hardened layer and the primer layer is ≥4B. High adhesion is key to ensuring product durability; the coating should not exhibit cracking, peeling, or other problems during use.

[0024] Preferably, the microstructure-coated hardened PMMA film described above adopts a double-layer coating structure, and the yield rate is ≥90%.

[0025] Preferably, in the above-mentioned microstructure-coated hardened PMMA film, the visible light transmittance of the microstructure-coated hardened PMMA film is ≥95%, and the hardness reaches 5H-9H.

[0026] On the other hand, the present invention also provides a method for preparing the above-mentioned microstructured coated type cured PMMA film, the method comprising the following steps: Step 1, PMMA substrate pretreatment: The PMMA substrate is cleaned and subjected to plasma treatment to obtain a surface-activated PMMA substrate; Step 2, preparation of primer layer: The modified acrylic resin, ultraviolet absorber and solvent are mixed to obtain primer coating; the primer coating is applied to the surface of the PMMA substrate treated in step 1 by coating method, and dried and cured to obtain primer layer; Step 3, Preparation of the hardening layer: Silica sol, nano-sized α-alumina particles, silane coupling agent and catalyst are mixed to obtain a hardening coating; the hardening coating is applied to the surface of the primer layer by coating method, and dried and cured to obtain a hardening layer; finally, a microstructured coated type hardened PMMA film is prepared.

[0027] In the above preparation method, preferably, in step one, the plasma treatment power is 150~250W, the distance is 10~15mm, the treatment time is 0.2~0.5s, and the linear velocity is 10~20m / min. Plasma treatment can introduce polar functional groups such as hydroxyl (-OH) and carboxyl (-COOH) groups on the surface of the PMMA substrate, thereby increasing the surface energy and enhancing the wettability and adhesion between the coating and the substrate.

[0028] In the above preparation method, preferably, after plasma treatment, the surface tension of the PMMA substrate is increased to 50~60mN / m and the contact angle is reduced to below 30°.

[0029] In the above preparation method, preferably, in step two, the viscosity of the primer coating is 40-80 cps, the coating method is roller coating or spray coating, the drying temperature is 60-80℃, and the drying time is 5-15 min. Appropriate coating viscosity ensures a uniform coating thickness; roller coating and spray coating are commonly used coating methods in industrial production and are suitable for large-area production; the drying temperature and time should ensure sufficient solvent evaporation and resin curing.

[0030] In the above preparation method, preferably, in step three, the viscosity of the hardened coating is 55~150 cps, the coating method is roller coating or spray coating, the drying temperature is 80~120℃, and the drying time is 10~30 min. The viscosity of the hardened coating should be slightly higher than that of the primer coating to ensure that the hard particles can be uniformly dispersed in the coating.

[0031] In the above preparation method, preferably, the hardened coating is subjected to vacuum degassing treatment before coating, with a vacuum degree of -0.08 to ~0.1 MPa and a degassing time of 5 to 15 min. Vacuum degassing can remove air bubbles in the coating, avoid pinholes or air bubble defects after the coating is cured, and improve the optical uniformity and appearance quality of the coating.

[0032] In the above preparation method, preferably, the drying and curing process is carried out under nitrogen protection to prevent the agglomeration and oxidation of the nano-alumina particles. Nitrogen protection can eliminate the interference of oxygen and moisture in the air on the curing reaction, thereby improving the coating quality.

[0033] In the above preparation method, preferably, in steps two and three, the coating process adopts a continuous production line mode; the entire preparation process is carried out in a cleanroom with a cleanliness level of 10,000 or higher, and the concentration of dust particles in the environment is ≤3520 particles / m³. 3 .

[0034] In the above preparation method, preferably, the preparation method further includes step four: preparation of the microstructure layer: forming a microstructure layer on the surface of the hardened layer by hot pressing or ultraviolet nanoimprinting.

[0035] In the above preparation method, preferably, the temperature of the hot pressing molding method is 120~150℃, the pressure is 0.5~2MPa, and the time is 5~15min; the UV curing energy of the ultraviolet nanoimprinting method is 1000~3000mJ / cm². 2 Hot pressing and ultraviolet nanoimprinting are commonly used techniques for microstructure replication, capable of precisely replicating micron or nanometer-scale structures on mold surfaces.

[0036] In another aspect, the present invention also provides the application of the above-mentioned microstructure-coated hardened PMMA film as a consumable accessory for 3D printers in the field of optical instruments; the application is selected from display panels, optical lenses or lighting equipment.

[0037] The beneficial effects of this invention are: (1) The present invention adopts a double-layer coating structure (primer layer + hardening layer), which simplifies the process flow, reduces the number of coatings (compared to the three-layer structure), effectively improves the yield of finished products, and reduces production costs. Statistical data shows that the yield of finished products of the present invention reaches more than 90%, which is 10 to 15 percentage points higher than the existing three-layer structure technology.

[0038] (2) This invention uses nano-sized α-alumina particles as a hard filler with a particle size of only 10~50nm (far smaller than the 100~500nm particle size commonly used in the prior art), which can effectively reduce light scattering and achieve high transmittance (≥95%) while ensuring high hardness (5H-9H). The scattering cross-section of nano-sized particles is inversely proportional to the sixth power of the particle size. Therefore, reducing the particle size by one order of magnitude can reduce the scattering intensity by about 1 million times.

[0039] (3) The present invention adds an ultraviolet absorber to the primer layer, which effectively improves the weather resistance of the film. The ultraviolet absorber can absorb ultraviolet rays in the 280~400nm wavelength band and convert them into heat energy for dissipation, thereby avoiding photo-oxidative degradation and yellowing of the PMMA substrate and extending its service life.

[0040] (4) The present invention performs plasma pretreatment on PMMA substrate, which significantly improves the adhesion between the primer layer and the substrate. Plasma treatment can introduce active functional groups on the substrate surface, increasing the surface tension from the original 30~35mN / m to 50~60mN / m, significantly improving wettability and avoiding coating peeling problems.

[0041] (5) The present invention may optionally include a microstructure layer, which can adjust the direction of light propagation according to actual needs, thereby meeting the personalized optical requirements of 3D printer accessories. The introduction of the microstructure layer expands the application field of the product and increases its added value.

[0042] (6) The preparation method of the present invention is simple and easy to operate, and is suitable for large-scale industrial production. Compared with the three-layer structure, the double-layer structure reduces the coating and curing processes, shortens the production cycle by 20% to 30%, and reduces equipment investment and energy consumption accordingly.

[0043] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention will be described in detail below. Detailed Implementation

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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. The processes, conditions, reagents, experimental methods, etc., for implementing the present invention, except for the contents specifically mentioned below, are all common knowledge and general knowledge in the art, and the present invention does not have any special limitations.

[0045] Example 1: This embodiment provides a microstructured coated type of cured PMMA film, the preparation method of which includes the following steps: (1) PMMA substrate pretreatment: A PMMA substrate (PMMA particle injection molding) with a thickness of 1 mm and a light transmittance of 92.5% was cleaned with anhydrous ethanol and then subjected to plasma treatment. The treatment power was 200 W, the distance was 12 mm, the treatment time was 0.5 s, and the linear speed was 15 m / min to obtain a surface-activated PMMA substrate. After plasma treatment, the contact angle decreased from 52° to 28° and the surface tension increased from 34 mN / m to 54 mN / m.

[0046] (2) Preparation of primer layer: By weight percentage, 85% hydroxyl acrylate resin (solid content 50%, viscosity 500~800mPa·s), 2% benzotriazole ultraviolet absorber (UV-329) and 13% ethyl acetate were mixed and stirred evenly with a disperser to obtain primer coating with a viscosity of 58cps. The primer coating was applied to the surface of the PMMA substrate treated in step (1) by roller coating and dried in an oven at 80℃ for 10min to obtain a primer layer with a thickness of 2μm.

[0047] (3) Preparation of the hardened layer: By weight percentage, 70% acidic silica sol (solid content 25%, particle size 12nm, pH 2.5), 12% nano-sized α-alumina particles (particle size 30nm, purity 99.9%, purchased from Zhongke Jinyan), 15% γ-aminopropyltriethoxysilane (KH-550), and 3% organotin catalyst (dibutyltin dilaurate) were mixed and dispersed evenly using a high-speed disperser (speed 8000rpm, time 15min). Then, vacuum degassing treatment was performed (vacuum degree -0.09MPa, time 10min) to obtain a hardened coating with a viscosity of 85cps. The hardened coating was coated onto the surface of the primer layer using a roller coating method and dried in an oven at 100℃ for 20min to obtain a hardened layer with a thickness of 6μm.

[0048] Finally, a microstructured coated hardened PMMA film was prepared.

[0049] The following performance tests were performed on the microstructure-coated cured PMMA film prepared in this embodiment: Transmittance test: The transmittance of the film in the visible light wavelength range (400~700nm) was tested using a UV-Vis spectrophotometer (UV-2600, Shimadzu, Japan). The test results showed that the transmittance at a wavelength of 550nm was 95.3%, and the average transmittance across the entire spectrum was 95.1%.

[0050] Hardness test: The surface hardness was tested using the pencil hardness method (according to GB / T 6739-1996 standard). A Chinese pencil (6H) was used, and a load of 750g was applied. The test result was 6H, and there were no scratches on the coating surface.

[0051] Adhesion test: The coating adhesion was tested using the cross-cut test (according to GB / T 9286-1998 standard), and the test result was 5B, indicating no peeling of the coating.

[0052] Weather resistance test: Accelerated aging test was conducted using a xenon lamp aging test chamber (irradiation intensity 0.51W / m²). 2 At 340nm, 65℃, and 50% humidity, the transmittance decreased by only 0.8% after 1000 hours, and the surface showed no obvious yellowing.

[0053] Example 2: This embodiment provides a microstructured coated type of cured PMMA film, the preparation method of which includes the following steps: (1) PMMA substrate pretreatment: A PMMA substrate (PMMA particle injection molding) with a thickness of 1 mm and a light transmittance of 92.5% was cleaned with anhydrous ethanol and then subjected to plasma treatment. The treatment power was 200 W, the distance was 12 mm, the treatment time was 0.5 s, and the linear speed was 15 m / min to obtain a surface-activated PMMA substrate. After plasma treatment, the contact angle decreased from 52° to 28° and the surface tension increased from 34 mN / m to 54 mN / m.

[0054] (2) Preparation of primer layer: By weight percentage, 85% hydroxyl acrylate resin (solid content 50%, viscosity 500~800mPa·s), 2% benzotriazole ultraviolet absorber (UV-329) and 13% ethyl acetate were mixed and stirred evenly with a disperser to obtain primer coating with a viscosity of 58cps. The primer coating was applied to the surface of the PMMA substrate treated in step (1) by roller coating and dried in an oven at 80℃ for 10min to obtain a primer layer with a thickness of 2μm.

[0055] (3) Preparation of the hardened layer: By weight percentage, 70% acidic silica sol (solid content 25%, particle size 12nm, pH 2.5), 12% nano-sized α-alumina particles (particle size 30nm, purity 99.9%, purchased from Zhongke Jinyan), 15% γ-aminopropyltriethoxysilane (KH-550), and 3% organotin catalyst (dibutyltin dilaurate) were mixed and dispersed evenly using a high-speed disperser (speed 8000rpm, time 15min). Then, vacuum degassing treatment was performed (vacuum degree -0.09MPa, time 10min) to obtain a hardened coating with a viscosity of 85cps. The hardened coating was coated onto the surface of the primer layer using a roller coating method and dried in an oven at 100℃ for 20min to obtain a hardened layer with a thickness of 6μm.

[0056] (4) Preparation of microstructure layer: A prism structure microstructure layer is formed on the surface of the hardened layer by hot pressing. First, a nickel alloy mold with a prism shape is made (prism angle 60°, period 100μm, depth 50μm). Then, the hardened film is aligned with the mold, placed in a hot pressing machine, heated to 130℃, pressure 1MPa is applied, held for 10 minutes, and demolded after cooling.

[0057] Finally, a microstructured coated hardened PMMA film was prepared.

[0058] The following performance tests were performed on the microstructure-coated cured PMMA film prepared in this embodiment: Transmittance test: The average transmittance of visible light is 95.1%. Due to the directional refraction of the microstructure, the transmittance at a specific angle can reach more than 97%.

[0059] Hardness test: The hardness is 6H, and the microstructure layer did not affect the surface hardness.

[0060] Adhesion test: The adhesion between the hardened layer and the microstructure layer is 5B, indicating a strong bond.

[0061] Microstructure morphology: The surface of the microstructure layer was observed using an optical microscope. The prism structure was completely replicated with an angle error of ±1° and a surface roughness Ra<0.5μm.

[0062] Example 3: This embodiment provides a microstructured coated type of cured PMMA film, the preparation method of which includes the following steps: (1) PMMA substrate pretreatment: A PMMA substrate (PMMA particle injection molding) with a thickness of 1 mm and a light transmittance of 92.5% was cleaned with anhydrous ethanol and then subjected to plasma treatment. The treatment power was 200 W, the distance was 12 mm, the treatment time was 0.5 s, and the linear speed was 15 m / min to obtain a surface-activated PMMA substrate. After plasma treatment, the contact angle decreased from 52° to 28° and the surface tension increased from 34 mN / m to 54 mN / m.

[0063] (2) Preparation of primer layer: By weight percentage, 85% hydroxyl acrylate resin (solid content 50%, viscosity 500~800mPa·s), 2% benzotriazole ultraviolet absorber (UV-329) and 13% ethyl acetate were mixed and stirred evenly with a disperser to obtain primer coating with a viscosity of 58cps. The primer coating was applied to the surface of the PMMA substrate treated in step (1) by roller coating and dried in an oven at 80℃ for 10min to obtain a primer layer with a thickness of 2μm.

[0064] (3) Preparation of the hardened layer: By weight percentage, 65% acidic silica sol (solid content 25%, particle size 10nm, pH 2.0), 15% nano-sized α-alumina particles (particle size 20nm, purity 99.95%, purchased from Zhongke Jinyan), 16% γ-glycidyl etheroxypropyltrimethoxysilane (KH-560), and 4% titanate catalyst (tetrabutyl titanate) were mixed and dispersed evenly using a high-speed disperser (speed 10000rpm, time 20min). Then, vacuum degassing treatment was performed (vacuum degree -0.095MPa, time 12min) to obtain a hardened coating with a viscosity of 125cps. The hardened coating was applied to the surface of the primer layer by spraying and dried in an oven at 110℃ for 25min to obtain a hardened layer with a thickness of 7μm.

[0065] Finally, a microstructured coated hardened PMMA film was prepared.

[0066] The following performance tests were performed on the microstructure-coated cured PMMA film prepared in this embodiment: Transmittance test: The average transmittance of visible light was 95.8%, which is 0.7 percentage points higher than that of Example 1.

[0067] Hardness test: The hardness is 8H, which meets the highest level requirement.

[0068] Adhesion test: 5B, the coating is firmly bonded.

[0069] Abrasion resistance test: The abrasion tester (CS-10 wheel, 500g load, 500 rpm) was used. The mass loss was only 0.8mg, which is far lower than the industry standard requirement of 5mg.

[0070] Example 4: This embodiment provides a microstructured coated type of cured PMMA film, the preparation method of which includes the following steps: (1) PMMA substrate pretreatment: A PMMA substrate (PMMA particle injection molding) with a thickness of 1 mm and a light transmittance of 92.5% was cleaned with anhydrous ethanol and then subjected to plasma treatment. The treatment power was 200 W, the distance was 12 mm, the treatment time was 0.5 s, and the linear speed was 15 m / min to obtain a surface-activated PMMA substrate. After plasma treatment, the contact angle decreased from 52° to 28° and the surface tension increased from 34 mN / m to 54 mN / m.

[0071] (2) Preparation of primer layer: By weight percentage, 83% epoxy acrylate resin (solid content 55%, viscosity 600-900 mPa·s), 3% triazine ultraviolet absorber (UV-1577) and 14% ethyl acetate were mixed and stirred evenly with a disperser to obtain a primer coating with a viscosity of 65 cps. The primer coating was applied to the surface of the plasma-treated PMMA substrate by roller coating and dried in an oven at 75℃ for 12 min to obtain a primer layer with a thickness of 2.5 μm.

[0072] (3) Preparation of the hardened layer: By weight percentage, 70% acidic silica sol (solid content 25%, particle size 12nm, pH 2.5), 12% nano-sized α-alumina particles (particle size 30nm, purity 99.9%, purchased from Zhongke Jinyan), 15% γ-aminopropyltriethoxysilane (KH-550), and 3% organotin catalyst (dibutyltin dilaurate) were mixed and dispersed evenly using a high-speed disperser (speed 8000rpm, time 15min). Then, vacuum degassing treatment was performed (vacuum degree -0.09MPa, time 10min) to obtain a hardened coating with a viscosity of 85cps. The hardened coating was coated onto the surface of the primer layer using a roller coating method and dried in an oven at 100℃ for 20min to obtain a hardened layer with a thickness of 6μm.

[0073] Finally, a microstructured coated hardened PMMA film was prepared.

[0074] The following performance tests were performed on the microstructure-coated cured PMMA film prepared in this embodiment: Light transmittance test: The average transmittance of visible light is 95.2%.

[0075] Hardness test: Hardness is 6H.

[0076] Adhesion test: 5B, the adhesion between the primer layer and the substrate is particularly excellent, reaching the 5B level.

[0077] Weather resistance test: After 2000 hours of xenon lamp aging test, the light transmittance decreased by only 1.2%, and there was no obvious yellowing on the surface, further improving the weather resistance.

[0078] Example 5: This embodiment provides a microstructured coated type of cured PMMA film, the preparation method of which includes the following steps: (1) PMMA substrate pretreatment: A PMMA substrate (PMMA particle injection molding) with a thickness of 1 mm and a light transmittance of 92.5% was cleaned with anhydrous ethanol and then subjected to plasma treatment. The treatment power was 200 W, the distance was 12 mm, the treatment time was 0.5 s, and the linear speed was 15 m / min to obtain a surface-activated PMMA substrate. After plasma treatment, the contact angle decreased from 52° to 28° and the surface tension increased from 34 mN / m to 54 mN / m.

[0079] (2) Preparation of primer layer: By weight percentage, 85% hydroxyl acrylate resin (solid content 50%, viscosity 500~800mPa·s), 2% benzotriazole ultraviolet absorber (UV-329) and 13% ethyl acetate were mixed and stirred evenly with a disperser to obtain primer coating with a viscosity of 58cps. The primer coating was applied to the surface of the PMMA substrate treated in step (1) by roller coating and dried in an oven at 80℃ for 10min to obtain a primer layer with a thickness of 2μm.

[0080] (3) Preparation of the hardened layer: By weight percentage, 70% acidic silica sol (solid content 25%, particle size 12nm, pH 2.5), 12% nano-sized α-alumina particles (particle size 30nm, purity 99.9%, purchased from Zhongke Jinyan), 15% γ-aminopropyltriethoxysilane (KH-550), and 3% organotin catalyst (dibutyltin dilaurate) were mixed and dispersed evenly using a high-speed disperser (speed 8000rpm, time 15min). Then, vacuum degassing treatment was performed (vacuum degree -0.09MPa, time 10min) to obtain a hardened coating with a viscosity of 85cps. The hardened coating was coated onto the surface of the primer layer using a roller coating method and dried in an oven at 100℃ for 20min to obtain a hardened layer with a thickness of 6μm.

[0081] (4) Preparation of microstructure layer: A lens array microstructure layer was formed on the surface of the hardened layer using ultraviolet nanoimprinting. First, a layer of ultraviolet-curable resin (viscosity 20 mPa·s, curing shrinkage <3%) was coated on the surface of the hardened layer. Then, a silicone mold with a lens array shape (lens diameter 50 μm, height 25 μm, spacing 100 μm) was pressed onto the resin surface and cured by UV irradiation (UV curing energy 2000 mJ / cm²). 2 After curing, the material is demolded to obtain a lens array structure.

[0082] Finally, a microstructured coated hardened PMMA film was prepared.

[0083] The following performance tests were performed on the microstructure-coated cured PMMA film prepared in this embodiment: Light transmittance test: The average transmittance of visible light is 94.8%. Due to the focusing effect of the lens array, the light utilization rate is significantly improved.

[0084] Hardness test: The surface hardness remains 6H.

[0085] Optical performance testing: The lens array can focus the incident light to form a uniform light spot with a diameter of about 80μm and a uniformity of >95%, which is suitable for the optical inspection system of 3D printers.

[0086] Example 6: This embodiment provides a microstructured coated type of cured PMMA film, the preparation method of which includes the following steps: (1) PMMA substrate pretreatment: A PMMA substrate (PMMA particle injection molding) with a thickness of 0.5 mm and a light transmittance of 93% was taken, cleaned with anhydrous ethanol, and then subjected to plasma treatment. The treatment power was 200 W, the distance was 12 mm, the treatment time was 0.5 s, and the linear speed was 15 m / min to obtain a surface-activated PMMA substrate. After plasma treatment, the contact angle decreased from 52° to 28°, and the surface tension increased from 34 mN / m to 54 mN / m.

[0087] (2) Preparation of primer layer: By weight percentage, 85% hydroxyl acrylate resin (solid content 50%, viscosity 500~800mPa·s), 2% benzotriazole ultraviolet absorber (UV-329) and 13% ethyl acetate were mixed and stirred evenly with a disperser to obtain primer coating with a viscosity of 58cps. The primer coating was applied to the surface of the PMMA substrate treated in step (1) by roller coating and dried in an oven at 80℃ for 10min to obtain a primer layer with a thickness of 1.5μm.

[0088] (3) Preparation of the hardened layer: By weight percentage, 70% acidic silica sol (solid content 25%, particle size 12nm, pH 2.5), 12% nano-sized α-alumina particles (particle size 30nm, purity 99.9%, purchased from Zhongke Jinyan), 15% γ-aminopropyltriethoxysilane (KH-550), and 3% organotin catalyst (dibutyltin dilaurate) were mixed and dispersed evenly using a high-speed disperser (speed 8000rpm, time 15min). Then, vacuum degassing treatment was performed (vacuum degree -0.09MPa, time 10min) to obtain a hardened coating with a viscosity of 85cps. The hardened coating was coated onto the surface of the primer layer by roller coating and dried in an oven at 100℃ for 20min to obtain a hardened layer with a thickness of 4μm.

[0089] Finally, a microstructured coated hardened PMMA film was prepared.

[0090] The following performance tests were performed on the microstructure-coated cured PMMA film prepared in this embodiment: Transmittance test: The average visible light transmittance of the double-sided coated ultrathin film is 94.6%.

[0091] Hardness test: Surface hardness is 5H.

[0092] Flexibility test: The coating showed no cracking when the bending radius was 10mm, which meets the requirements for flexible applications.

[0093] Based on the above data, the following conclusions can be drawn: (1) Regarding light transmittance: The light transmittance of all embodiments of the present invention is ≥94.6%, with Embodiment 3 reaching 95.8%, which is significantly higher than the prior art (91.5%~93.2%). This is mainly due to the use of nano-sized α-alumina particles (particle size 10~50nm) in the present invention, which effectively reduces light scattering.

[0094] (2) Hardness: The hardness of all embodiments of the present invention is ≥5H, with Embodiment 3 reaching 8H, which is comparable to or better than the highest level of the prior art (7H). This is mainly due to the use of appropriate nanoparticle content (5%~15%) and optimized curing process in the present invention.

[0095] (3) Adhesion: The adhesion of all embodiments of the present invention is 5B, while that of the prior art is only 3-4B. This is mainly due to the plasma pretreatment and optimized primer formulation used in the present invention.

[0096] (4) In terms of process simplification: The present invention can achieve or exceed the performance level of a three-layer structure by using a two-layer structure, the production process is simpler, the yield of finished products is higher, and the production cost is lower.

[0097] Application example: The hardened PMMA film prepared in Example 1 of this invention was applied to 3D printer consumable accessories (consumable guide rail, optical inspection window) for practical application testing: (1) Application of consumable guide rail: The hardened PMMA film of this invention is used as the consumable guide rail material of FDM 3D printer. Test results: The guide rail surface is smooth and the friction coefficient is low (μ<0.2), and the consumable is transported smoothly; the high hardness surface is wear-resistant, and there is no obvious wear on the guide rail surface after 1000 hours of continuous printing; the high light transmittance makes it easy to observe the remaining amount of consumable and the printing progress.

[0098] (2) Application of optical inspection window: The hardened PMMA film of the present invention is used as the protective window of the optical inspection system of the 3D printer. The test results show that the high light transmittance (>95%) ensures the accurate transmission of optical signals; the high hardness surface is resistant to cleaning and wiping and is not easily scratched; the weather resistance is excellent and there is no yellowing after long-term use.

[0099] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A microstructured coated type cured PMMA film, characterized in that: The microstructured coating-type hardened PMMA film includes a PMMA substrate layer, a primer layer, and a hardening layer, wherein the primer layer is disposed on the PMMA substrate layer, and the hardening layer is disposed on the primer layer; The primer layer is a primer coating composed of modified acrylic resin, ultraviolet absorber and solvent, with a thickness of 1.5~3μm; The hardened layer is a hardened coating composed of silica sol, nano-sized α-alumina particles, silane coupling agent and catalyst, with a thickness of 4~8μm.

2. The microstructured coated type cured PMMA film according to claim 1, characterized in that: The modified acrylate resin is selected from hydroxy acrylate resins and / or epoxy acrylate resins; Preferably, the ultraviolet absorber is a benzotriazole ultraviolet absorber and / or a triazine ultraviolet absorber; its content accounts for 1-3 wt% of the solid components of the primer layer.

3. The microstructured coated type cured PMMA film according to claim 1, characterized in that: The silica sol is an acidic silica sol with a solid content of 20-30 wt% and a particle size of 8-15 nm. Preferably, the solid content of the nano-sized α-alumina particles is 5-15%, and the particle size is 10-50 nm, more preferably 20-40 nm; Preferably, the silane coupling agent is selected from one or more combinations of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane; Preferably, the catalyst is selected from organotin catalysts and / or titanate catalysts, and the solid content is 0.5~2wt% of the solid component of the hardened layer.

4. The microstructured coated type cured PMMA film according to any one of claims 1 to 3, characterized in that: The microstructured coating type cured PMMA film also includes a microstructured layer disposed on the surface of the cured layer; Preferably, the microstructure layer is selected from one of a prism structure, a lens array structure, or a grating structure; Preferably, the structural parameters of the microstructure layer are designed according to the actual optical application requirements.

5. The microstructured coated type cured PMMA film according to claim 1, characterized in that: The PMMA substrate layer has a thickness of 0.5~3mm and a light transmittance of ≥92%.

6. The microstructured coated type cured PMMA film according to claim 1, characterized in that: The adhesion between the primer layer and the PMMA substrate layer is ≥4B (tested according to GB / T 9286 standard), and the adhesion between the hardened layer and the primer layer is ≥4B; Preferably, the microstructure-coated hardened PMMA film adopts a double-layer coating structure, with a finished product yield of ≥90%; Preferably, the visible light transmittance of the microstructured coated hardened PMMA film is ≥95%, and the hardness reaches 5H-9H.

7. The method for preparing a microstructured coated type cured PMMA film according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: Step 1, PMMA substrate pretreatment: The PMMA substrate is cleaned and subjected to plasma treatment to obtain a surface-activated PMMA substrate; Step 2, preparation of primer layer: The modified acrylic resin, ultraviolet absorber and solvent are mixed to obtain primer coating; the primer coating is applied to the surface of the PMMA substrate treated in step 1 by coating method, and dried and cured to obtain primer layer; Step 3, Preparation of the hardening layer: Silica sol, nano-sized α-alumina particles, silane coupling agent and catalyst are mixed to obtain a hardening coating; the hardening coating is applied to the surface of the primer layer by coating method, and dried and cured to obtain a hardening layer; finally, a microstructured coated type hardened PMMA film is prepared.

8. The preparation method according to claim 7, characterized in that: In step one, the plasma treatment power is 150~250W, the distance is 10~15mm, the treatment time is 0.2~0.5s, and the linear speed is 10~20m / min; preferably, after the plasma treatment, the surface tension of the PMMA substrate increases to 50~60mN / m, and the contact angle decreases to below 30°. Preferably, in step two, the viscosity of the primer coating is 40~80 cps, the coating method is roller coating or spray coating, the drying temperature is 60~80℃, and the drying time is 5~15 min; Preferably, in step three, the viscosity of the hardened coating is 55~150 cps, the coating method is roller coating or spray coating, the drying temperature is 80~120℃, and the drying time is 10~30 min; Preferably, the hardened coating is subjected to vacuum degassing treatment before application, with a vacuum degree of -0.08 to ~0.1 MPa and a degassing time of 5 to 15 min; Preferably, the drying and curing process is carried out under nitrogen protection; Preferably, in steps two and three, the coating process is carried out using a continuous production line; the entire preparation process is conducted in a cleanroom with a cleanliness level of 10,000 or higher, where the concentration of dust particles in the environment is ≤3520 particles / m³. 3 .

9. The preparation method according to claim 7, characterized in that: The preparation method also includes step four: preparation of the microstructure layer: forming a microstructure layer on the surface of the hardened layer by hot pressing or ultraviolet nanoimprinting. Preferably, the hot pressing method uses a temperature of 120~150℃, a pressure of 0.5~2MPa, and a time of 5~15min; the UV curing energy of the ultraviolet nanoimprinting method is 1000~3000mJ / cm². 2 .

10. The microstructure-coated hardened PMMA film according to claims 1 to 6 or the microstructure-coated hardened PMMA film prepared by the preparation method according to any one of claims 7 to 9 is used as a consumable accessory for 3D printers in the field of optical instruments, preferably, the application is selected from display panels, optical lenses or lighting equipment.