A PVD composite coating for acrylic substrates, its preparation method and application

Abstract

This application discloses a PVD composite coating for acrylic substrates, its preparation method, and its application. The PVD composite coating includes a primer layer and a PVD coating layer. The primer layer comprises the following raw materials: 40-60 parts of aliphatic polyurethane acrylate, 10-20 parts of silicone polyurethane acrylate, 10-20 parts of reactive diluent monomer, 1-5 parts of photoinitiator, and 0.1-1 parts of additives. The aliphatic polyurethane acrylate comprises: 70-80 parts of polyether diol, 20-30 parts of polyether triol, 30-40 parts of isophorone diisocyanate, 20-30 parts of hydroxyl acrylate, 4-10 parts of hydroxyl phosphate, 0.1-0.2 parts of catalyst, and 0.05-0.1 parts of polymerization inhibitor. The primer layer of this application can effectively improve the plating properties and adhesion of PMMA and other imitation crystal substrates to the PVD coating layer, while ensuring the high light transmittance and flexibility of the primer layer.

Description

Technical Field

[0001] This application relates to the field of PVD coatings, and in particular to a PVD composite coating for acrylic substrates, its preparation method and application. Background Technology

[0002] As automotive interior design increasingly pursues a deep integration of luxury and technology, imitation crystal interior components, such as crystal buttons, knobs, gear shifters, and car logos, with their natural crystal-like luster, are gradually becoming important design elements for enhancing the quality of the cabin. These imitation crystal components typically use highly transparent plastics such as polymethyl methacrylate (PMMA) as the base material. Through precision injection molding and surface prism processing, an optical microstructure with multi-angle reflection and refraction is formed. A high-reflectivity physical vapor deposition (PVD) metal coating layer is then prepared on the bottom. When light passes through the transparent substrate and shines on the bottom coating, the metal coating efficiently reflects the light. Through multiple refractions and reflections via the prism surfaces, a crystal-clear, shimmering light and shadow visual effect is ultimately created.

[0003] However, PMMA, PC, and other imitation crystal substrates have low surface energy, weak polarity, and often high surface hardness, resulting in poor "coating uptake" of PVD coatings. Coating uptake refers to the ability of the substrate or primer surface to accept and firmly bond vapor-deposited metal atoms. Insufficient coating uptake makes it difficult for deposited metal atoms to nucleate and grow uniformly on the substrate surface, resulting in a loose, non-dense coating, and even defects such as incomplete coating or pinholes. This not only severely weakens the optical reflectivity of the metal coating, making the imitation crystal parts dull and hazy, failing to achieve the expected optical effect; more importantly, the loose coating has poor adhesion to the substrate, easily leading to coating peeling, cracking, and other failures, thus greatly limiting the reliable application of PVD technology in high-end automotive interior imitation crystal parts. Therefore, how to improve the coating uptake of PMMA and other imitation crystal plastic substrates for PVD coatings, while ensuring high adhesion between the coating and the substrate and good light transmittance of the coating, has become a pressing technical challenge in this field. Summary of the Invention

[0004] This application aims to improve the plating performance and adhesion of PMMA and other imitation crystal substrates to PVD coatings by using a primer layer, while ensuring the high light transmittance and flexibility of the primer layer.

[0005] In a first aspect, this application provides a PVD composite coating for acrylic substrates, comprising a primer layer and a PVD coating layer. The primer layer, by weight, comprises: 40-60 parts aliphatic polyurethane acrylate, 10-20 parts silicone polyurethane acrylate, 10-20 parts reactive diluent monomer, 1-5 parts photoinitiator, and 0.1-1 parts additives. The aliphatic polyurethane acrylate, by weight, comprises: 70-80 parts polyether diol, 20-30 parts polyether triol, 30-40 parts isophorone diisocyanate, 20-30 parts hydroxy acrylate, 4-10 parts hydroxyphosphate, 0.1-0.2 parts catalyst, and 0.05-0.1 parts polymerization inhibitor.

[0006] In any of the above technical solutions, the hydroxyphosphate is hydroxyethyl methacrylate phosphate and / or polyol phosphate.

[0007] In any of the above technical solutions, the hydroxyacrylate is selected from one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate.

[0008] In any of the above technical solutions, the reactive diluent monomer is one or more of 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, and polyethylene glycol dimethacrylate.

[0009] In any of the above technical solutions, the preparation method of the aliphatic polyurethane acrylate includes the following steps: Polyether diol, polyether triol and isophorone diisocyanate were subjected to a prepolymerization reaction in the presence of a catalyst and a polymerization inhibitor to obtain a polyurethane prepolymer with isocyanate-terminated groups. Hydroxyacrylate and hydroxyphosphate were added to the polyurethane prepolymer in step 1 for end-capping reaction to obtain aliphatic polyurethane acrylate.

[0010] In any of the above technical solutions, the catalyst is an organotin catalyst, preferably dibutyltin dilaurate.

[0011] In any of the above technical solutions, the polymerization inhibitor is p-hydroxyanisole.

[0012] The primer layer plays a role in connecting the acrylic substrate and the PVD coating layer in the composite coating. It needs to meet multiple performance requirements at the same time. It must have high adhesion to the acrylic substrate, excellent coating properties for the PVD coating layer, maintain high light transmittance to ensure that light can penetrate and reach the coating layer for reflection, and have good flexibility to prevent the coating layer from cracking and peeling due to internal stress.

[0013] This application uses aliphatic polyurethane acrylate as the main resin, employing a mixed system of polyether polyols, which forms a moderately cross-linked network structure after isocyanate chain extension. The polyether segments impart high flexibility and transparency to the coating, while the aliphatic structure avoids the yellowing problem caused by aromatic resins, thus ensuring high light transmittance and basic flexibility of the primer layer. Simultaneously, silicone polyurethane acrylate is introduced, whose silicone molecular chains exhibit significantly better flexibility than carbon-carbon backbones. The introduction of the polyurethane network effectively absorbs and dissipates the shrinkage stress caused by the difference in thermal expansion coefficients of the PVD coating layer, thereby improving the crack resistance of the primer layer.

[0014] However, the introduction of organosilicon segments reduces the surface energy of the coating, making it difficult for vapor-deposited metal atoms to uniformly nucleate and spread on the primer surface, thus weakening plating performance and adhesion. To compensate for this defect, this application introduces hydroxyphosphate monomers into the synthesis of aliphatic polyurethane acrylates, covalently linking the phosphate ester structure to the resin backbone. At the interface between the primer and the PMMA substrate, the phosphate ester groups can form hydrogen bonds and dipole-dipole interactions with the ester or carbonyl groups in the PMMA molecular chain, significantly improving the adhesion of the primer to the plastic substrate. More importantly, during PVD aluminum deposition, the oxygen atoms in the phosphate ester groups possess lone pairs of electrons, which can form stable coordination bonds with the newly deposited active aluminum atoms. These can act as anchoring sites to induce aluminum atoms to preferentially nucleate at these sites, thereby promoting the uniform and dense growth of the aluminum film and effectively compensating for the plating performance loss caused by the organosilicon components. In summary, the synergistic combination of aliphatic polyurethane acrylate and organosilicon polyurethane acrylate, along with the adhesion and coating enhancement effects of phosphate groups, achieves a simultaneous improvement in light transmittance, flexibility, adhesion, and coating performance.

[0015] In any of the above technical solutions, the raw materials of the organosilicon polyurethane acrylate, by weight, include: 100 parts of hydroxyl-terminated silicone oil, 55-65 parts of diisocyanate, 15-20 parts of hydroxy acrylate, 0.1-0.3 parts of catalyst, and 0.1-0.3 parts of polymerization inhibitor.

[0016] In any of the above technical solutions, the hydroxyl-terminated silicone oil is a hydroxyl-terminated vinyl silicone oil, and the raw material of the organosilicon polyurethane acrylate includes 5 to 8 parts of hydrosiloxane; the molecular structural formula of the hydroxyl-terminated vinyl silicone oil is shown below: .

[0017] In any of the above technical solutions, the hydrogen-based siloxane is selected from at least one of trimethoxysilane, triethoxysilane, methyldimethoxysilane, and ethyldimethoxysilane.

[0018] In any of the above technical solutions, the method for preparing the organosilicon polyurethane acrylate is as follows: A polyurethane prepolymer was prepared by reacting hydroxyl-terminated vinyl silicone oil with diisocyanate in the presence of a catalyst. Hydroxyacrylate is added to polyurethane prepolymer and a capping reaction is carried out to obtain polyurethane acrylate. Polyurethane acrylate is subjected to a hydrosilylation reaction with a hydrogen-based siloxane to obtain an organosilicon polyurethane acrylate.

[0019] In any of the above technical solutions, the hydrosilylation reaction is carried out under a platinum catalyst, which is selected from at least one of chloroplatinic acid, Karstedt catalyst (platinum-divinyltetramethyldisiloxane complex) or chloroplatinic acid-isopropanol complex, and the amount of platinum used is 5 to 20 ppm based on the total mass of the reactants.

[0020] The organosilicon polyurethane acrylate macromonomer of this application not only introduces organosilicon segments to improve flexibility, but also further enables the side chains or ends of the organosilicon polyurethane acrylate to carry hydrolyzable alkoxy groups through a hydrosilylation reaction. During coating formation, this monomer first undergoes free radical polymerization of the acrylate double bonds through UV curing, forming an organic crosslinked network. Subsequently, the alkoxysilane groups in the coating undergo hydrolysis under ambient moisture to generate silanol groups, and adjacent silanol groups condense to construct an inorganic siloxane crosslinked network. This inorganic network interpenetrates with the original organosilicon polyurethane acrylate network, forming an interpenetrating polymer network.

[0021] The aforementioned dual-network structure offers significant advantages. Firstly, the volume change of siloxane condensation induced by moisture is minimal, effectively offsetting the shrinkage stress generated by UV curing and significantly reducing the overall coating's curing shrinkage rate. Low shrinkage means reduced tensile stress on the PVD aluminum-coated film, further lowering the risk of cracking or peeling due to stress concentration. Secondly, the siloxane crosslinking network itself possesses excellent flexibility and thermal stability, and is physically entangled with the acrylate network rather than chemically bonded. This interpenetrating structure not only improves the overall crosslinking density and cohesive strength of the coating but also avoids the brittleness caused by excessive crosslinking of a single network. This allows the primer layer to maintain high hardness while significantly improving its elongation at break and fatigue resistance, providing the PVD coating with a stress-buffered layer that combines low shrinkage and high flexibility.

[0022] Secondly, this application provides a method for preparing a PVD composite coating, comprising the following steps: The aliphatic polyurethane acrylate, silicone polyurethane acrylate, reactive diluent monomer, photoinitiator and additives are mixed evenly and coated on the surface of an acrylic substrate. After curing, a primer layer is formed. A PVD coating layer is formed on the surface of the primer layer through physical vapor deposition.

[0023] In any of the above technical solutions, the thickness of the PVD coating layer is 50–200 nm.

[0024] In any of the above technical solutions, the thickness of the primer layer is 5 to 20 μm.

[0025] In any of the above technical solutions, the PVD coating layer is an aluminum coating layer or a chromium coating layer, preferably an aluminum coating layer, and the aluminum coating is performed by a vacuum evaporation process.

[0026] In any of the above technical solutions, the curing includes UV curing and moisture curing.

[0027] In any of the above technical solutions, the acrylic substrate is a crystal-like automotive interior part, selected from crystal gear levers, crystal knobs, crystal buttons, crystal seat adjusters, crystal ambient light strips, crystal car logos, or crystal car lights.

[0028] Thirdly, this application provides an application of the PVD composite coating for acrylic substrates described in any of the first aspects in automotive interior parts.

[0029] In summary, this application has the following beneficial effects: The primer layer of this application employs a synergistic combination of aliphatic polyurethane acrylate and silicone polyurethane acrylate. The former ensures high light transmittance and basic adhesion, while the latter provides excellent flexibility to buffer coating stress. By introducing phosphate groups into the aliphatic polyurethane acrylate, the hydrogen bonding with the PMMA substrate and the coordination anchoring effect on aluminum atoms are utilized to simultaneously enhance the primer's adhesion to the substrate and the coating's uptake. Furthermore, the hydrolyzable alkoxysilane grafted onto the silicone component can form a silicon-oxygen crosslinking network under humid conditions, constituting an interpenetrating structure with the UV-curing network, significantly reducing curing shrinkage and improving the coating's ductility. Ultimately, this composite coating makes the PVD coating of the imitation crystal interior parts less prone to cracking and peeling, while maintaining a high reflective gloss. Detailed Implementation

[0030] Preparation Example Preparation Example 1-1, aliphatic polyurethane acrylate, was prepared according to the following steps: Under nitrogen protection, 735g of polyether diol PPG-2000 (hydroxyl value approximately 51–62 mg KOH / g) and 265g of polyether triol PPG-3000 (hydroxyl value approximately 34–42 mg KOH / g), which had been dehydrated under reduced pressure at 120°C for 2 hours, were added to the reaction flask and stirred until homogeneous. Then, 375g of isophorone diisocyanate, 1.0g of dibutyltin dilaurate, and 0.45g of p-hydroxyanisole were added and stirred. The mixture was heated to 92°C and maintained at this temperature for 2.5 hours. Samples were taken every 30 minutes during the reaction, and the remaining -NCO content in the system was determined using the di-n-butylamine back titration method. The prepolymerization reaction was considered complete when the NCO content decreased below the theoretical value and remained stable (approximately 1.5–2.5%). The reaction system was then cooled to 52°C, and 235g of hydroxyethyl acrylate and 85g of 2-hydroxyethyl methacrylate phosphate were added sequentially. 0.45g of dibutyltin dilaurate catalyst was then added, and the temperature was raised to 85°C and maintained for 3 hours. The mixture was then cooled to below 50°C and filtered through a 400-mesh filter to obtain aliphatic polyurethane acrylate.

[0031] Preparation Examples 1-2: Aliphatic polyurethane acrylates were prepared according to the following steps: Under nitrogen protection, 710g of polyether diol PPG-2000 (hydroxyl value approximately 51–62 mg KOH / g) and 230g of polyether triol PPG-3000 (hydroxyl value approximately 34–42 mg KOH / g), which had been pre-dehydrated at 120°C under reduced pressure for 2 hours, were added to the reaction flask and stirred until homogeneous. Then, 355g of isophorone diisocyanate, 0.9g of dibutyltin dilaurate, and 0.35g of p-hydroxyanisole were added and stirred. The mixture was heated to 90°C and maintained at this temperature for 2 hours. Samples were taken every 30 minutes during the reaction, and the residual -NCO content in the system was determined using the di-n-butylamine back titration method. The prepolymerization reaction was considered complete when the NCO content was below 0.5% and remained stable. The reaction system was then cooled to 50°C, and 265g of hydroxyethyl acrylate and 42g of 2-hydroxyethyl methacrylate phosphate were added sequentially. 0.35g of dibutyltin dilaurate catalyst was then added, and the temperature was raised to 105°C and maintained for 3.5 hours. The mixture was then cooled to below 50°C and filtered through a 400-mesh filter to obtain aliphatic polyurethane acrylate.

[0032] Preparation Examples 1-3, aliphatic polyurethane acrylates, were prepared according to the following steps: Under nitrogen protection, 760g of polyether diol PPG-2000 (hydroxyl value approximately 51–62 mg KOH / g) and 290g of polyether triol PPG-3000 (hydroxyl value approximately 34–42 mg KOH / g), which had been pre-dehydrated at 120°C under reduced pressure for 2 hours, were added to a reaction flask and stirred until homogeneous. Then, 395g of isophorone diisocyanate, 1.1g of dibutyltin dilaurate, and 0.45g of p-hydroxyanisole were added and stirred. The mixture was heated to 95°C and maintained at this temperature for 3 hours. Samples were taken every 30 minutes during the reaction, and the residual -NCO content in the system was determined using a di-n-butylamine back titration method. The prepolymerization reaction was considered complete when the NCO content was below 0.5% and remained stable. The reaction system was then cooled to 55°C, and 295g of hydroxyethyl acrylate and 58g of 2-hydroxyethyl methacrylate phosphate were added sequentially. 0.45g of dibutyltin dilaurate catalyst was then added, and the temperature was raised to 115°C and maintained for 3 hours. After cooling to below 50°C, the mixture was filtered through a 400-mesh filter to obtain aliphatic polyurethane acrylate.

[0033] Preparation Examples 1-4, aliphatic polyurethane acrylates, differ from Preparation Example 1-1 in that an equal amount of hydroxyethyl acrylate is used instead of 2-hydroxyethyl methacrylate phosphate.

[0034] Preparation Example 2-1, organosilicon polyurethane acrylate, was prepared by the following steps: Under nitrogen protection, 1000g of hydroxyl-terminated vinyl silicone oil (IOTA 1203V) and 1000mL of toluene were added to a reaction flask and stirred until homogeneous. Then, 627g of isophorone diisocyanate, 2.0g of dibutyltin dilaurate, and 2.0g of p-hydroxyanisole were added. The mixture was heated to 75°C and reacted for 2.5 hours to obtain an isocyanate-terminated polyurethane prepolymer. Subsequently, the reaction system was cooled to 60°C, 225g of hydroxyethyl acrylate was added, and 0.6g of p-hydroxyanisole was added as a supplement. The temperature was raised to 85°C and reacted for 3 hours. The NCO content was monitored using a di-n-butylamine back titration method. When the NCO content was below 0.5%, the vinyl-terminated polyurethane acrylate was obtained. The system temperature was adjusted to 90℃, and 78g of trimethoxysilane was added. Under nitrogen protection, Karstedt catalyst solution (platinum content 12ppm based on total reactant mass) was added, and the temperature was raised to 115℃ and maintained for 5 hours. After the reaction was completed, the temperature was lowered to below 50℃, and toluene was removed by vacuum distillation. The product was then filtered through a 400-mesh filter to obtain organosilicon polyurethane acrylate.

[0035] Preparation Example 2-2, organosilicon polyurethane acrylate, was prepared by the following steps: Under nitrogen protection, 1000 g of hydroxyl-terminated vinyl silicone oil (IOTA 1203V) and 1000 mL of toluene were added to a reaction flask and stirred until homogeneous. 600 g of isophorone diisocyanate, 1.8 g of dibutyltin dilaurate, and 1.8 g of p-hydroxyanisole were added. The mixture was heated to 70°C and reacted for 2 hours to obtain an isocyanate-terminated polyurethane prepolymer. The reaction system was then cooled to 55°C, 200 g of hydroxyethyl acrylate was added, and 0.5 g of p-hydroxyanisole was added as a supplement. The temperature was raised to 80°C and reacted for 3 hours. The NCO content was monitored using a di-n-butylamine back titration method. When the NCO content was below 0.5%, vinyl-terminated polyurethane acrylate was obtained. The system temperature was adjusted to 90°C, 70 g of trimethoxysilane was added, and a Karstedt catalyst solution (platinum content 10 ppm based on the total mass of reactants) was added under nitrogen protection. The temperature was raised to 110°C and reacted for 6 hours. After the reaction was completed, the temperature was lowered to below 50°C, and toluene was removed by vacuum distillation. The product was then filtered through a 400-mesh filter to obtain organosilicon polyurethane acrylate.

[0036] Preparation Example 2-3, organosilicon polyurethane acrylate, was prepared by the following steps: Under nitrogen protection, 1000g of hydroxyl-terminated vinyl silicone oil (IOTA 1203V) and 1000mL of toluene were added to a reaction flask and stirred until homogeneous. 660g of isophorone diisocyanate, 2.2g of dibutyltin dilaurate, and 2.2g of p-hydroxyanisole were added. The mixture was heated to 80°C and reacted for 3 hours to obtain an isocyanate-terminated polyurethane prepolymer. The reaction system was then cooled to 65°C, 240g of hydroxyethyl acrylate was added, and 0.6g of p-hydroxyanisole was added as a supplement. The temperature was raised to 85°C and reacted for 4 hours. The NCO content was monitored using a di-n-butylamine back titration method. When the NCO content was below 0.5%, the vinyl-terminated polyurethane acrylate was obtained. The system temperature was adjusted to 100℃, and 85g of trimethoxysilane was added. Under nitrogen protection, Karstedt catalyst solution (platinum content 15ppm based on the total mass of reactants) was added, and the temperature was raised to 120℃ and maintained for 6 hours. After the reaction was completed, the temperature was lowered to below 50℃, and toluene was removed by vacuum distillation. The product was then filtered through a 400-mesh filter to obtain organosilicon polyurethane acrylate.

[0037] Preparation Example 2-4, an organosilicon polyurethane acrylate, differs from Preparation Example 2-1 in that trimethoxysilane was not added for the hydrosilylation reaction. The specific steps are as follows: Under nitrogen protection, 1000g of hydroxyl-terminated vinyl silicone oil (IOTA 1203V) and 1000mL of toluene were added to a reaction flask and stirred until homogeneous. 627g of isophorone diisocyanate, 2.0g of dibutyltin dilaurate, and 2.0g of p-hydroxyanisole were added. The mixture was heated to 75°C and reacted for 2.5 hours to obtain an isocyanate-terminated polyurethane prepolymer. The reaction system was then cooled to 60°C, 185g of hydroxyethyl acrylate was added, and 0.6g of p-hydroxyanisole was added as a supplement. The temperature was raised to 85°C and reacted for 3 hours. The NCO content was monitored using a di-n-butylamine back titration method. When the NCO content was below 0.5%, the mixture was cooled and discharged to obtain organosilicon polyurethane acrylate.

[0038] Example Example 1: A PVD composite coating for acrylic substrates, prepared by the following method: 520g of aliphatic polyurethane acrylate (Preparation Example 1-1), 150g of silicone polyurethane acrylate (Preparation Example 2-1), 95g of 1,6-hexanediol diacrylate, 85g of polyethylene glycol dimethacrylate (molecular weight approximately 600, acid value ≤5mgKOH / g), 12g of photoinitiator 1173, 8g of photoinitiator TPO, and 2.5g of leveling agent BYK-358N were sequentially added to a mixing tank. The mixture was stirred and dispersed at 800 rpm for 45 minutes. The mixture was then filtered through a 400-mesh filter and vacuum degassed for 15 minutes to obtain a primer composition. The obtained primer composition was applied to the surface of an acrylic substrate (PMMA injection molded sheet) using air spraying. The wet film was then leveled in an infrared oven at 65°C for 5 minutes, followed by UV curing using a high-pressure mercury lamp as the light source, with a curing energy of 900mJ / cm². 2 Light intensity 100mW / cm 2 The UV-cured product is then placed in a moisture curing device, with the temperature controlled at 60℃ and the relative humidity at 75%, and left for 8 hours. The thickness of the primer layer after curing is 12μm.

[0039] An acrylic substrate coated with primer is placed in a vacuum coating apparatus, and the vacuum chamber is evacuated to 2.0 × 10⁻⁶. - 2 The plasma was treated at 150W with argon gas as the working gas for 5 minutes. Aluminum was deposited using a vacuum evaporation process: a tungsten filament was used as the evaporation source, and a high-purity aluminum wire (≥99.99% purity) was placed on the evaporation source. Resistance heating was applied until the aluminum melted and evaporated. The substrate rotated at 25 rpm, and the deposition time was controlled to achieve a final aluminum layer thickness of 100 nm. After deposition, the substrate was naturally cooled to 55°C under vacuum conditions. Dry nitrogen was then introduced into the chamber to atmospheric pressure before removal, yielding the PVD composite coating product.

[0040] Example 2: A PVD composite coating for acrylic substrates, prepared by the following method: 420g of aliphatic polyurethane acrylate (Preparation Example 1-2), 110g of silicone polyurethane acrylate (Preparation Example 2-2), 70g of 1,6-hexanediol diacrylate, 60g of dipropylene glycol diacrylate, 11g of photoinitiator 1173, 6g of photoinitiator TPO, and 1.5g of leveling agent BYK-358N were sequentially added to a mixing tank and stirred and dispersed at 600 rpm for 30 minutes. The mixture was then filtered through a 400-mesh filter and vacuum degassed for 15 minutes to obtain a primer composition. The obtained primer composition was applied to the surface of an acrylic substrate (PMMA injection molded sheet) using air spraying. The wet film was then leveled in an infrared oven at 55°C for 5 minutes, followed by UV curing using a high-pressure mercury lamp as the light source, with a curing energy of 700 mJ / cm². 2 Light intensity 80mW / cm 2 The UV-cured product is then placed in a moisture curing device, with the temperature controlled at 50°C and the relative humidity at 65%, and left for 6 hours. The thickness of the primer layer after curing is 8μm.

[0041] An acrylic substrate coated with primer is placed in a vacuum coating apparatus, and the vacuum chamber is evacuated to 1.5 × 10⁻⁶. - 2 The plasma was treated at 120W with argon gas as the working gas for 4 minutes. Aluminum was deposited using a vacuum evaporation process: a tungsten filament was used as the evaporation source, and a high-purity aluminum wire (≥99.99% purity) was placed on the evaporation source. Resistance heating was applied until the aluminum melted and evaporated. The substrate rotated at 20 rpm, and the deposition time was controlled to achieve a final aluminum layer thickness of 80 nm. After deposition, the substrate was naturally cooled to 50°C under vacuum conditions. Dry nitrogen was then introduced into the chamber to atmospheric pressure before removal, yielding the PVD composite coating product.

[0042] Example 3: A PVD composite coating for acrylic substrates, prepared by the following method: 580g of aliphatic polyurethane acrylate (Preparation Examples 1-3), 190g of silicone polyurethane acrylate (Preparation Examples 2-3), 120g of 1,6-hexanediol diacrylate, 80g of polyethylene glycol dimethacrylate (molecular weight approximately 600, acid value ≤5mgKOH / g), 15g of photoinitiator 1173, 10g of photoinitiator TPO, and 3.5g of leveling agent BYK-358N were sequentially added to a mixing tank. The mixture was stirred and dispersed at 800 rpm for 55 minutes. The mixture was then filtered through a 400-mesh filter and vacuum degassed for 15 minutes to obtain a primer composition. The obtained primer composition was applied to the surface of an acrylic substrate (PMMA injection molded sheet) using air spraying. The wet film was then leveled in an infrared oven at 70°C for 6 minutes, followed by UV curing using a high-pressure mercury lamp as the light source, with a curing energy of 1100 mJ / cm². 2 Light intensity 130mW / cm 2 The UV-cured product is then placed in a moisture curing device, with the temperature controlled at 70℃ and the relative humidity at 85%, and left for 10 hours. The thickness of the primer layer after curing is 15μm.

[0043] An acrylic substrate coated with primer is placed in a vacuum coating apparatus, and the vacuum chamber is evacuated to 2.5 × 10⁻⁶. - 2 The plasma was treated at 180W with argon gas as the working gas for 6 minutes. Aluminum was deposited using a vacuum evaporation process: a tungsten filament was used as the evaporation source, and a high-purity aluminum wire (≥99.99% purity) was placed on the evaporation source. Resistance heating was applied until the aluminum melted and evaporated. The substrate rotated at 25 rpm, and the deposition time was controlled to achieve a final aluminum layer thickness of 120 nm. After deposition, the substrate was naturally cooled to 50°C under vacuum conditions. Dry nitrogen was then introduced into the chamber to atmospheric pressure before removal, yielding the PVD composite coating product.

[0044] Example 4, a PVD composite coating for acrylic substrate, differs from Example 1 in that an equal amount of silicone polyurethane acrylate prepared in Example 2-4 is used instead of the silicone polyurethane acrylate prepared in Example 2-1.

[0045] Comparative Example Comparative Example 1, a PVD composite coating for an acrylic substrate, differs from Example 1 in that an equal amount of aliphatic polyurethane acrylate from Preparation Example 1-1 is used instead of the silicone polyurethane acrylate from Preparation Example 2-1.

[0046] Comparative Example 2, a PVD composite coating for an acrylic substrate, differs from Example 1 in that an equal amount of silicone polyurethane acrylate from Preparation Example 2-1 is used instead of the aliphatic polyurethane acrylate from Preparation Example 1-1.

[0047] Comparative Example 3, a PVD composite coating for an acrylic substrate, differs from Example 1 in that an equal amount of aliphatic polyurethane acrylate from Preparation Examples 1-4 is used instead of the aliphatic polyurethane acrylate from Preparation Examples 1-1.

[0048] Comparative Example 4, a PVD coating for an acrylic substrate, differs from Example 1 in that it does not have a primer layer. The specific preparation steps are as follows: The acrylic substrate is placed in a vacuum coating equipment, and the vacuum chamber is evacuated to 2.0 × 10⁻⁶. -2 The plasma was treated at 150W with argon gas as the working gas for 5 minutes. Aluminum was deposited using a vacuum evaporation process: a tungsten filament was used as the evaporation source, and a high-purity aluminum wire (≥99.99% purity) was placed on the evaporation source. Resistance heating was applied until the aluminum melted and evaporated. The substrate rotated at 25 rpm, and the deposition time was controlled to achieve a final aluminum layer thickness of 100 nm. After deposition, the substrate was naturally cooled to 55°C under vacuum conditions. Dry nitrogen was then introduced into the chamber to atmospheric pressure before removal, yielding the PVD-coated product.

[0049] Performance testing Experiment 1: Light Reflection Performance Test Sample preparation: The PVD composite coating products (including PMMA injection molded sheets) obtained in the examples and comparative examples were cut into samples with a size of 50mm×50mm×3mm. Three parallel samples were prepared for each group, and the samples were cured for 24 hours at an environment with a temperature of 23±2℃ and a relative humidity of 50±5%.

[0050] Test Procedure: Place the sample in the incident port of the integrating sphere of a UV-Vis-NIR spectrophotometer (equipped with a 150mm integrating sphere attachment, wavelength range 250–2500nm), ensuring the back side of the PVD coating is flush with the port. Incident light should be perpendicularly incident from the PMMA side and reflected back to the integrating sphere from the coating surface. Using a spectrally pure BaSO4 white plate as the standard reflection reference, scan the spectral specular reflectance R(λ) of the sample in 2nm steps within the visible light wavelength range of 380–780nm. Based on the weighting factors of the D65 light source and 2° standard observer in ASTM E308—2022 "Standard Practice for Calculating the Color of Objects Using CIE Systems," calculate the visible light reflectance (lightness Y), i.e., specular reflectance (%), using the weighted orthogonal method specified in CIE 15:2018 "Colorimetry." Higher specular reflectance indicates a more uniform and dense PVD aluminum coating film formed after the aluminum plating layer and primer layer are improved by the coating properties, resulting in stronger optical reflectivity.

[0051] Experiment 2: PVD coating adhesion test Sample preparation: The PVD composite coating products (including PMMA injection molded sheets) obtained in the examples and comparative examples were cut into samples with a size of 100mm×100mm×3mm. Three parallel samples were prepared for each group, and the samples were cured for 24 hours under the conditions of temperature 23±2℃ and relative humidity 50±5%.

[0052] Test Procedure: Follow Method B, the multi-blade cross-cut test, in ASTM D3359-23, "Test Method for Assessing Adhesion by Tape Test." Place the sample on a horizontal, rigid surface. Using a multi-blade cross-cutting tool (1 mm blade spacing), cut two sets of mutually perpendicular parallel lines on the PVD coating surface with uniform pressure and speed (20–50 mm / s). Each set contains 6 lines, forming a 25-square (5×5) grid pattern. The cut depth should penetrate the PVD coating and primer layer to reach the PMMA substrate surface. Gently sweep away any debris generated during cutting along the diagonal of the grid using a soft brush. Take a standard pressure-sensitive tape approximately 75 mm long, align the center of the tape with the grid area, and apply it smoothly. Press firmly with your fingertips or an eraser to ensure full contact between the tape and the coating surface. Within 90 seconds of application, quickly peel the tape backward at an angle as close to 180° as possible. Visually inspect the coating peeling in the grid area using a 10x magnifying glass with built-in illumination to assess the adhesion level (5B is the highest, no peeling; 0B is the lowest, large-area peeling).

[0053] Experiment 3: Transmittance Test Sample Preparation: The test object in this experiment was the cured primer layer (excluding the PVD coating layer). The preparation method is as follows: The primer compositions prepared in the examples and comparative examples were applied to the surface of PMMA injection molded sheets (50mm×50mm×3mm) by air spraying. UV curing and moisture curing were performed according to the parameters corresponding to each example and comparative example. The thickness of the primer layer after curing was controlled at 8-15μm (consistent with the corresponding examples). Three parallel samples were prepared for each group.

[0054] Test Procedure: A haze meter (equipped with an integrating sphere) was used for measurement. Before measurement, the instrument was baseline-calibrated using a standard transparent reference plate. During measurement, the incident light was first calibrated by passing it through air (zero haze, 100% transmittance). Then, the primer layer of the sample was fixed in the measurement window with the integrating sphere orifice facing the sample. Using a C light source and 2° standard observer conditions (integrating sphere geometry as required by Procedure A of ASTM D1003-21 "Standard Test Method for Determination of Transmittance and Haze of Transparent Plastics"), the total visible light transmittance (%) of the sample (PMMA substrate + primer layer) was measured in the visible light wavelength range of 380–780 nm. The arithmetic mean of measurements was taken at three different locations for each sample.

[0055] Experiment 4: Flexibility Test Sample preparation: The primer compositions prepared in the examples and comparative examples were applied to the surface of PMMA injection molded sheets (150mm×25mm×2mm; PMMA at a thickness of 2mm can be bent around a mandrel of a certain diameter without cracking) by air spraying. UV curing and moisture curing were performed according to the parameters corresponding to each example and comparative example (the thickness of the cured primer layer was controlled at 8–15 μm). Aluminum was deposited on the primer layer surface using a vacuum evaporation process, with the thickness of the aluminum layer controlled according to the parameters corresponding to each example and comparative example. Multiple parallel samples were prepared for each group and cured for 24 hours at an environment of 23±2℃ and 50±5% relative humidity.

[0056] Test Procedure: The test was conducted according to the requirements of ASTM D6905-20(2025) "Standard Practice for Impact Flexibility of Organic Coatings". The specimen was fixed in the fixture of the impact testing machine with the coating facing outwards (away from the impact direction), so that the specimen was stretched rather than compressed under impact. A drop hammer impact device was used, with a drop hammer mass of 1 kg and an impact head diameter of 20 mm. The impact energy was controlled by adjusting the drop hammer height (gradual setting within the range of 0.3–1.0 m). Three specimens were tested at each impact energy. Immediately after impact, the PVD coating and primer layer were inspected under a standard light source using a 10x magnifying glass for cracks, peeling, or spalling. The lowest impact energy (J) at which the coating failed was recorded. The higher the lowest impact failure energy, the stronger the coating's resistance to impact cracking, i.e., the better the stress buffering effect of the primer layer on the PVD coating layer.

[0057] Table 1 Performance Test Results

[0058] Analysis of experimental results: Compared to Example 1, Example 4 did not introduce alkoxysilane, so it could not be moisture-cured to form a silicon-oxygen crosslinking network and construct an interpenetrating network structure. The curing shrinkage rate was relatively high, and the flexibility and reflectivity were slightly reduced.

[0059] Comparative Example 1 lacks organosilicon components, resulting in insufficient ductility and poor flexibility of the primer layer. This leads to high curing shrinkage of the coating, increased tensile stress on the PVD coating, and deterioration of coating performance. Comparative Example 2's raw material system lacks phosphate-modified polyurethane, causing the primer layer to lose its coordination and anchoring effect, resulting in uneven metal atom nucleation and a loose coating with decreased reflectivity. Simultaneously, the absence of hydrogen bonding / dipole interaction between the primer and PMMA further deteriorates adhesion. Similarly, the polyurethane backbone of Comparative Example 3 lacks phosphate functional groups, leading to a simultaneous decrease in coating performance and adhesion. In Comparative Example 4, the PVD layer, when directly deposited onto the acrylic surface, exhibits discontinuous film formation, poor density, and severely deteriorated reflectivity. The absence of a primer stress buffer layer results in extremely poor adhesion, severe coating peeling, and poor impact resistance.

[0060] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A PVD composite coating for acrylic substrates, characterized in that, Including the primer layer and the PVD coating layer; The raw materials of the primer layer, by weight, include: 40-60 parts of aliphatic polyurethane acrylate, 10-20 parts of silicone polyurethane acrylate, 10-20 parts of reactive diluent monomer, 1-5 parts of photoinitiator, and 0.1-1 parts of additives; the raw materials of the aliphatic polyurethane acrylate, by weight, include: 70-80 parts of polyether diol, 20-30 parts of polyether triol, 30-40 parts of isophorone diisocyanate, 20-30 parts of hydroxy acrylate, 4-10 parts of hydroxyphosphate, 0.1-0.2 parts of catalyst, and 0.05-0.1 parts of polymerization inhibitor.

2. The PVD composite coating according to claim 1, characterized in that, The hydroxyphosphate is hydroxyethyl methacrylate phosphate and / or polyol phosphate.

3. The PVD composite coating according to claim 1, characterized in that, The hydroxyacrylate is selected from one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate.

4. The PVD composite coating according to claim 1, characterized in that, The reactive diluent monomer is one or more of 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, and polyethylene glycol dimethacrylate.

5. The PVD composite coating according to claim 1, characterized in that, The raw materials for the organosilicon polyurethane acrylate, by weight, include: 100 parts of hydroxyl-terminated silicone oil, 55-65 parts of diisocyanate, 15-20 parts of hydroxy acrylate, 0.1-0.3 parts of catalyst, and 0.1-0.3 parts of polymerization inhibitor.

6. The PVD composite coating according to claim 5, characterized in that, The hydroxyl-terminated silicone oil is a hydroxyl-terminated vinyl silicone oil, and the raw material of the organosilicon polyurethane acrylate includes 5 to 8 parts of hydrogen-based siloxane.

7. The PVD composite coating according to claim 6, characterized in that, The hydrogen-based siloxane is selected from at least one of trimethoxysilane, triethoxysilane, methyldimethoxysilane, and ethyldimethoxysilane.

8. The PVD composite coating according to claim 6, characterized in that, The method for preparing the organosilicon polyurethane acrylate is as follows: A polyurethane prepolymer was prepared by reacting hydroxyl-terminated vinyl silicone oil with diisocyanate in the presence of a catalyst. Hydroxyacrylate is added to polyurethane prepolymer and a capping reaction is carried out to obtain polyurethane acrylate. Polyurethane acrylate is subjected to a hydrosilylation reaction with a hydrogen-based siloxane to obtain an organosilicon polyurethane acrylate.

9. The method for preparing the PVD composite coating according to any one of claims 1 to 8, characterized in that, Includes the following steps: The aliphatic polyurethane acrylate, silicone polyurethane acrylate, reactive diluent monomer, photoinitiator and additives are mixed evenly and coated on the surface of an acrylic substrate, and then cured to form a primer layer. A PVD coating layer is formed on the surface of the primer layer through physical vapor deposition.

10. The application of the PVD composite coating for acrylic substrates as described in any one of claims 1 to 8 in automotive interior parts.

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